1 . $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.86 2010/06/09 01:30:16 pdp Exp $
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.
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 . /////////////////////////////////////////////////////////////////////////////
17 . /////////////////////////////////////////////////////////////////////////////
18 . This outputs the standard DocBook boilerplate.
19 . /////////////////////////////////////////////////////////////////////////////
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
28 . /////////////////////////////////////////////////////////////////////////////
32 foot_right_recto="&chaptertitle; (&chapternumber;)"
33 foot_right_verso="&chaptertitle; (&chapternumber;)"
34 toc_chapter_blanks="yes,yes"
35 table_warn_overflow="overprint"
39 . /////////////////////////////////////////////////////////////////////////////
40 . This generate the outermost <book> element that wraps then entire document.
41 . /////////////////////////////////////////////////////////////////////////////
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 . /////////////////////////////////////////////////////////////////////////////
50 .set previousversion "4.71"
53 .set ACL "access control lists (ACLs)"
54 .set I " "
57 . /////////////////////////////////////////////////////////////////////////////
58 . Additional xfpt markup used by this document, over and above the default
59 . provided in the xfpt library.
60 . /////////////////////////////////////////////////////////////////////////////
62 . --- Override the &$ flag to automatically insert a $ with the variable name
64 .flag &$ $& "<varname>$" "</varname>"
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.
69 .flag &!! "</emphasis>†<emphasis>"
70 .flag &!? "</emphasis>‡<emphasis>"
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
84 .itable all 0 0 4 8* left 6* center 6* center 6* right
85 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
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.
93 .macro table2 196pt 254pt
94 .itable none 0 0 2 $1 left $2 left
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.
103 .row "&I;$1" "$2" "$3" "$4"
107 .row "&I;$1" "$2" "$3"
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.
121 &<indexterm role="concept">&
122 &<primary>&$1&</primary>&
124 &<secondary>&$2&</secondary>&
130 &<indexterm role="concept" id="$1" class="startofrange">&
131 &<primary>&$2&</primary>&
133 &<secondary>&$3&</secondary>&
139 &<indexterm role="concept" startref="$1" class="endofrange"/>&
143 &<indexterm role="option">&
144 &<primary>&$1&</primary>&
146 &<secondary>&$2&</secondary>&
152 &<indexterm role="variable">&
153 &<primary>&$1&</primary>&
155 &<secondary>&$2&</secondary>&
161 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
163 . ////////////////////////////////////////////////////////////////////////////
166 . ////////////////////////////////////////////////////////////////////////////
167 . The <bookinfo> element is removed from the XML before processing for Ascii
169 . ////////////////////////////////////////////////////////////////////////////
173 <title>Specification of the Exim Mail Transfer Agent</title>
174 <titleabbrev>The Exim MTA</titleabbrev>
175 <date>29 May 2010</date>
176 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
177 <authorinitials>EM</authorinitials>
178 <revhistory><revision>
179 <revnumber>4.72</revnumber>
180 <date>29 May 2010</date>
181 <authorinitials>EM</authorinitials>
182 </revision></revhistory>
183 <copyright><year>2009</year><holder>University of Cambridge</holder></copyright>
188 . /////////////////////////////////////////////////////////////////////////////
189 . This chunk of literal XML implements index entries of the form "x, see y" and
190 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
191 . at the top level, so we have to put the .chapter directive first.
192 . /////////////////////////////////////////////////////////////////////////////
194 .chapter "Introduction" "CHID1"
197 <indexterm role="variable">
198 <primary>$1, $2, etc.</primary>
199 <see><emphasis>numerical variables</emphasis></see>
201 <indexterm role="concept">
202 <primary>address</primary>
203 <secondary>rewriting</secondary>
204 <see><emphasis>rewriting</emphasis></see>
206 <indexterm role="concept">
207 <primary>Bounce Address Tag Validation</primary>
208 <see><emphasis>BATV</emphasis></see>
210 <indexterm role="concept">
211 <primary>Client SMTP Authorization</primary>
212 <see><emphasis>CSA</emphasis></see>
214 <indexterm role="concept">
215 <primary>CR character</primary>
216 <see><emphasis>carriage return</emphasis></see>
218 <indexterm role="concept">
219 <primary>CRL</primary>
220 <see><emphasis>certificate revocation list</emphasis></see>
222 <indexterm role="concept">
223 <primary>delivery</primary>
224 <secondary>failure report</secondary>
225 <see><emphasis>bounce message</emphasis></see>
227 <indexterm role="concept">
228 <primary>dialup</primary>
229 <see><emphasis>intermittently connected hosts</emphasis></see>
231 <indexterm role="concept">
232 <primary>exiscan</primary>
233 <see><emphasis>content scanning</emphasis></see>
235 <indexterm role="concept">
236 <primary>failover</primary>
237 <see><emphasis>fallback</emphasis></see>
239 <indexterm role="concept">
240 <primary>fallover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>filter</primary>
245 <secondary>Sieve</secondary>
246 <see><emphasis>Sieve filter</emphasis></see>
248 <indexterm role="concept">
249 <primary>ident</primary>
250 <see><emphasis>RFC 1413</emphasis></see>
252 <indexterm role="concept">
253 <primary>LF character</primary>
254 <see><emphasis>linefeed</emphasis></see>
256 <indexterm role="concept">
257 <primary>maximum</primary>
258 <seealso><emphasis>limit</emphasis></seealso>
260 <indexterm role="concept">
261 <primary>monitor</primary>
262 <see><emphasis>Exim monitor</emphasis></see>
264 <indexterm role="concept">
265 <primary>no_<emphasis>xxx</emphasis></primary>
266 <see>entry for xxx</see>
268 <indexterm role="concept">
269 <primary>NUL</primary>
270 <see><emphasis>binary zero</emphasis></see>
272 <indexterm role="concept">
273 <primary>passwd file</primary>
274 <see><emphasis>/etc/passwd</emphasis></see>
276 <indexterm role="concept">
277 <primary>process id</primary>
278 <see><emphasis>pid</emphasis></see>
280 <indexterm role="concept">
281 <primary>RBL</primary>
282 <see><emphasis>DNS list</emphasis></see>
284 <indexterm role="concept">
285 <primary>redirection</primary>
286 <see><emphasis>address redirection</emphasis></see>
288 <indexterm role="concept">
289 <primary>return path</primary>
290 <seealso><emphasis>envelope sender</emphasis></seealso>
292 <indexterm role="concept">
293 <primary>scanning</primary>
294 <see><emphasis>content scanning</emphasis></see>
296 <indexterm role="concept">
297 <primary>SSL</primary>
298 <see><emphasis>TLS</emphasis></see>
300 <indexterm role="concept">
301 <primary>string</primary>
302 <secondary>expansion</secondary>
303 <see><emphasis>expansion</emphasis></see>
305 <indexterm role="concept">
306 <primary>top bit</primary>
307 <see><emphasis>8-bit characters</emphasis></see>
309 <indexterm role="concept">
310 <primary>variables</primary>
311 <see><emphasis>expansion, variables</emphasis></see>
313 <indexterm role="concept">
314 <primary>zero, binary</primary>
315 <see><emphasis>binary zero</emphasis></see>
321 . /////////////////////////////////////////////////////////////////////////////
322 . This is the real start of the first chapter. See the comment above as to why
323 . we can't have the .chapter line here.
324 . chapter "Introduction"
325 . /////////////////////////////////////////////////////////////////////////////
327 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
328 Unix-like operating systems. It was designed on the assumption that it would be
329 run on hosts that are permanently connected to the Internet. However, it can be
330 used on intermittently connected hosts with suitable configuration adjustments.
332 Configuration files currently exist for the following operating systems: AIX,
333 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
334 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
335 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
336 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
337 Some of these operating systems are no longer current and cannot easily be
338 tested, so the configuration files may no longer work in practice.
340 There are also configuration files for compiling Exim in the Cygwin environment
341 that can be installed on systems running Windows. However, this document does
342 not contain any information about running Exim in the Cygwin environment.
344 The terms and conditions for the use and distribution of Exim are contained in
345 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
346 Public Licence, a copy of which may be found in the file &_LICENCE_&.
348 The use, supply or promotion of Exim for the purpose of sending bulk,
349 unsolicited electronic mail is incompatible with the basic aims of the program,
350 which revolve around the free provision of a service that enhances the quality
351 of personal communications. The author of Exim regards indiscriminate
352 mass-mailing as an antisocial, irresponsible abuse of the Internet.
354 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
355 experience of running and working on the Smail 3 code, I could never have
356 contemplated starting to write a new MTA. Many of the ideas and user interfaces
357 were originally taken from Smail 3, though the actual code of Exim is entirely
358 new, and has developed far beyond the initial concept.
360 Many people, both in Cambridge and around the world, have contributed to the
361 development and the testing of Exim, and to porting it to various operating
362 systems. I am grateful to them all. The distribution now contains a file called
363 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
367 .section "Exim documentation" "SECID1"
368 . Keep this example change bar when updating the documentation!
370 .cindex "documentation"
371 This edition of the Exim specification applies to version &version; of Exim.
372 Substantive changes from the &previousversion; edition are marked in some
373 renditions of the document; this paragraph is so marked if the rendition is
374 capable of showing a change indicator.
377 This document is very much a reference manual; it is not a tutorial. The reader
378 is expected to have some familiarity with the SMTP mail transfer protocol and
379 with general Unix system administration. Although there are some discussions
380 and examples in places, the information is mostly organized in a way that makes
381 it easy to look up, rather than in a natural order for sequential reading.
382 Furthermore, the manual aims to cover every aspect of Exim in detail, including
383 a number of rarely-used, special-purpose features that are unlikely to be of
386 .cindex "books about Exim"
387 An &"easier"& discussion of Exim which provides more in-depth explanatory,
388 introductory, and tutorial material can be found in a book entitled &'The Exim
389 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
390 (&url(http://www.uit.co.uk/exim-book/)).
392 This book also contains a chapter that gives a general introduction to SMTP and
393 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
394 with the latest release of Exim. (Note that the earlier book about Exim,
395 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
397 .cindex "Debian" "information sources"
398 If you are using a Debian distribution of Exim, you will find information about
399 Debian-specific features in the file
400 &_/usr/share/doc/exim4-base/README.Debian_&.
401 The command &(man update-exim.conf)& is another source of Debian-specific
404 .cindex "&_doc/NewStuff_&"
405 .cindex "&_doc/ChangeLog_&"
407 As the program develops, there may be features in newer versions that have not
408 yet made it into this document, which is updated only when the most significant
409 digit of the fractional part of the version number changes. Specifications of
410 new features that are not yet in this manual are placed in the file
411 &_doc/NewStuff_& in the Exim distribution.
413 Some features may be classified as &"experimental"&. These may change
414 incompatibly while they are developing, or even be withdrawn. For this reason,
415 they are not documented in this manual. Information about experimental features
416 can be found in the file &_doc/experimental.txt_&.
418 All changes to the program (whether new features, bug fixes, or other kinds of
419 change) are noted briefly in the file called &_doc/ChangeLog_&.
421 .cindex "&_doc/spec.txt_&"
422 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
423 that it can easily be searched with a text editor. Other files in the &_doc_&
427 .row &_OptionLists.txt_& "list of all options in alphabetical order"
428 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
429 .row &_exim.8_& "a man page of Exim's command line options"
430 .row &_experimental.txt_& "documentation of experimental features"
431 .row &_filter.txt_& "specification of the filter language"
432 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
433 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
436 The main specification and the specification of the filtering language are also
437 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
438 &<<SECTavail>>& below tells you how to get hold of these.
442 .section "FTP and web sites" "SECID2"
445 The primary site for Exim source distributions is currently the University of
446 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
447 distribution'& below. In addition, there is a web site and an FTP site at
448 &%exim.org%&. These are now also hosted at the University of Cambridge. The
449 &%exim.org%& site was previously hosted for a number of years by Energis
450 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
454 As well as Exim distribution tar files, the Exim web site contains a number of
455 differently formatted versions of the documentation. A recent addition to the
456 online information is the Exim wiki (&url(http://wiki.exim.org)),
457 which contains what used to be a separate FAQ, as well as various other
458 examples, tips, and know-how that have been contributed by Exim users.
461 An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
462 this to report bugs, and also to add items to the wish list. Please search
463 first to check that you are not duplicating a previous entry.
467 .section "Mailing lists" "SECID3"
468 .cindex "mailing lists" "for Exim users"
469 The following Exim mailing lists exist:
472 .row &'exim-users@exim.org'& "General discussion list"
473 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
474 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
475 .row &'exim-future@exim.org'& "Discussion of long-term development"
478 You can subscribe to these lists, change your existing subscriptions, and view
479 or search the archives via the mailing lists link on the Exim home page.
480 .cindex "Debian" "mailing list for"
481 If you are using a Debian distribution of Exim, you may wish to subscribe to
482 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
485 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
487 Please ask Debian-specific questions on this list and not on the general Exim
490 .section "Exim training" "SECID4"
491 .cindex "training courses"
492 Training courses in Cambridge (UK) used to be run annually by the author of
493 Exim, before he retired. At the time of writing, there are no plans to run
494 further Exim courses in Cambridge. However, if that changes, relevant
495 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
497 .section "Bug reports" "SECID5"
498 .cindex "bug reports"
499 .cindex "reporting bugs"
500 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
501 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
502 whether some behaviour is a bug or not, the best thing to do is to post a
503 message to the &'exim-dev'& mailing list and have it discussed.
507 .section "Where to find the Exim distribution" "SECTavail"
509 .cindex "distribution" "ftp site"
510 The master ftp site for the Exim distribution is
512 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
516 &*ftp://ftp.exim.org/pub/exim*&
518 The file references that follow are relative to the &_exim_& directories at
519 these sites. There are now quite a number of independent mirror sites around
520 the world. Those that I know about are listed in the file called &_Mirrors_&.
522 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
523 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
524 distributions), and &_Testing_& for testing versions. In the &_exim4_&
525 subdirectory, the current release can always be found in files called
528 &_exim-n.nn.tar.bz2_&
530 where &'n.nn'& is the highest such version number in the directory. The two
531 files contain identical data; the only difference is the type of compression.
532 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
534 .cindex "distribution" "signing details"
535 .cindex "distribution" "public key"
536 .cindex "public key for signed distribution"
537 The distributions are currently signed with Nigel Metheringham's GPG key. The
538 corresponding public key is available from a number of keyservers, and there is
539 also a copy in the file &_nigel-pubkey.asc_&. The signatures for the tar bundles are
542 &_exim-n.nn.tar.gz.asc_&
543 &_exim-n.nn.tar.bz2.asc_&
545 For each released version, the log of changes is made separately available in a
546 separate file in the directory &_ChangeLogs_& so that it is possible to
547 find out what has changed without having to download the entire distribution.
549 .cindex "documentation" "available formats"
550 The main distribution contains ASCII versions of this specification and other
551 documentation; other formats of the documents are available in separate files
552 inside the &_exim4_& directory of the FTP site:
554 &_exim-html-n.nn.tar.gz_&
555 &_exim-pdf-n.nn.tar.gz_&
556 &_exim-postscript-n.nn.tar.gz_&
557 &_exim-texinfo-n.nn.tar.gz_&
559 These tar files contain only the &_doc_& directory, not the complete
560 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
563 .section "Limitations" "SECID6"
565 .cindex "limitations of Exim"
566 .cindex "bang paths" "not handled by Exim"
567 Exim is designed for use as an Internet MTA, and therefore handles addresses in
568 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
569 simple two-component bang paths can be converted by a straightforward rewriting
570 configuration. This restriction does not prevent Exim from being interfaced to
571 UUCP as a transport mechanism, provided that domain addresses are used.
573 .cindex "domainless addresses"
574 .cindex "address" "without domain"
575 Exim insists that every address it handles has a domain attached. For incoming
576 local messages, domainless addresses are automatically qualified with a
577 configured domain value. Configuration options specify from which remote
578 systems unqualified addresses are acceptable. These are then qualified on
581 .cindex "transport" "external"
582 .cindex "external transports"
583 The only external transport mechanisms that are currently implemented are SMTP
584 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
585 transport is available, and there are facilities for writing messages to files
586 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
587 to send messages to other transport mechanisms such as UUCP, provided they can
588 handle domain-style addresses. Batched SMTP input is also catered for.
590 Exim is not designed for storing mail for dial-in hosts. When the volumes of
591 such mail are large, it is better to get the messages &"delivered"& into files
592 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
595 Although Exim does have basic facilities for scanning incoming messages, these
596 are not comprehensive enough to do full virus or spam scanning. Such operations
597 are best carried out using additional specialized software packages. If you
598 compile Exim with the content-scanning extension, straightforward interfaces to
599 a number of common scanners are provided.
603 .section "Run time configuration" "SECID7"
604 Exim's run time configuration is held in a single text file that is divided
605 into a number of sections. The entries in this file consist of keywords and
606 values, in the style of Smail 3 configuration files. A default configuration
607 file which is suitable for simple online installations is provided in the
608 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
611 .section "Calling interface" "SECID8"
612 .cindex "Sendmail compatibility" "command line interface"
613 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
614 can be a straight replacement for &_/usr/lib/sendmail_& or
615 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
616 about Sendmail in order to run Exim. For actions other than sending messages,
617 Sendmail-compatible options also exist, but those that produce output (for
618 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
619 format. There are also some additional options that are compatible with Smail
620 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
621 documents all Exim's command line options. This information is automatically
622 made into the man page that forms part of the Exim distribution.
624 Control of messages on the queue can be done via certain privileged command
625 line options. There is also an optional monitor program called &'eximon'&,
626 which displays current information in an X window, and which contains a menu
627 interface to Exim's command line administration options.
631 .section "Terminology" "SECID9"
632 .cindex "terminology definitions"
633 .cindex "body of message" "definition of"
634 The &'body'& of a message is the actual data that the sender wants to transmit.
635 It is the last part of a message, and is separated from the &'header'& (see
636 below) by a blank line.
638 .cindex "bounce message" "definition of"
639 When a message cannot be delivered, it is normally returned to the sender in a
640 delivery failure message or a &"non-delivery report"& (NDR). The term
641 &'bounce'& is commonly used for this action, and the error reports are often
642 called &'bounce messages'&. This is a convenient shorthand for &"delivery
643 failure error report"&. Such messages have an empty sender address in the
644 message's &'envelope'& (see below) to ensure that they cannot themselves give
645 rise to further bounce messages.
647 The term &'default'& appears frequently in this manual. It is used to qualify a
648 value which is used in the absence of any setting in the configuration. It may
649 also qualify an action which is taken unless a configuration setting specifies
652 The term &'defer'& is used when the delivery of a message to a specific
653 destination cannot immediately take place for some reason (a remote host may be
654 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
657 The word &'domain'& is sometimes used to mean all but the first component of a
658 host's name. It is &'not'& used in that sense here, where it normally refers to
659 the part of an email address following the @ sign.
661 .cindex "envelope, definition of"
662 .cindex "sender" "definition of"
663 A message in transit has an associated &'envelope'&, as well as a header and a
664 body. The envelope contains a sender address (to which bounce messages should
665 be delivered), and any number of recipient addresses. References to the
666 sender or the recipients of a message usually mean the addresses in the
667 envelope. An MTA uses these addresses for delivery, and for returning bounce
668 messages, not the addresses that appear in the header lines.
670 .cindex "message" "header, definition of"
671 .cindex "header section" "definition of"
672 The &'header'& of a message is the first part of a message's text, consisting
673 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
674 &'Subject:'&, etc. Long header lines can be split over several text lines by
675 indenting the continuations. The header is separated from the body by a blank
678 .cindex "local part" "definition of"
679 .cindex "domain" "definition of"
680 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
681 part of an email address that precedes the @ sign. The part that follows the
682 @ sign is called the &'domain'& or &'mail domain'&.
684 .cindex "local delivery" "definition of"
685 .cindex "remote delivery, definition of"
686 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
687 delivery to a file or a pipe on the local host from delivery by SMTP over
688 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
689 host it is running on are &'remote'&.
691 .cindex "return path" "definition of"
692 &'Return path'& is another name that is used for the sender address in a
695 .cindex "queue" "definition of"
696 The term &'queue'& is used to refer to the set of messages awaiting delivery,
697 because this term is in widespread use in the context of MTAs. However, in
698 Exim's case the reality is more like a pool than a queue, because there is
699 normally no ordering of waiting messages.
701 .cindex "queue runner" "definition of"
702 The term &'queue runner'& is used to describe a process that scans the queue
703 and attempts to deliver those messages whose retry times have come. This term
704 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
705 the waiting messages are normally processed in an unpredictable order.
707 .cindex "spool directory" "definition of"
708 The term &'spool directory'& is used for a directory in which Exim keeps the
709 messages on its queue &-- that is, those that it is in the process of
710 delivering. This should not be confused with the directory in which local
711 mailboxes are stored, which is called a &"spool directory"& by some people. In
712 the Exim documentation, &"spool"& is always used in the first sense.
719 . ////////////////////////////////////////////////////////////////////////////
720 . ////////////////////////////////////////////////////////////////////////////
722 .chapter "Incorporated code" "CHID2"
723 .cindex "incorporated code"
724 .cindex "regular expressions" "library"
726 A number of pieces of external code are included in the Exim distribution.
729 Regular expressions are supported in the main Exim program and in the
730 Exim monitor using the freely-distributable PCRE library, copyright
731 © University of Cambridge. The source to PCRE is no longer shipped with
732 Exim, so you will need to use the version of PCRE shipped with your system,
733 or obtain and install the full version of the library from
734 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
736 .cindex "cdb" "acknowledgment"
737 Support for the cdb (Constant DataBase) lookup method is provided by code
738 contributed by Nigel Metheringham of (at the time he contributed it) Planet
739 Online Ltd. The implementation is completely contained within the code of Exim.
740 It does not link against an external cdb library. The code contains the
741 following statements:
744 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
746 This program is free software; you can redistribute it and/or modify it under
747 the terms of the GNU General Public License as published by the Free Software
748 Foundation; either version 2 of the License, or (at your option) any later
750 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
751 the spec and sample code for cdb can be obtained from
752 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
753 some code from Dan Bernstein's implementation (which has no license
754 restrictions applied to it).
757 .cindex "SPA authentication"
758 .cindex "Samba project"
759 .cindex "Microsoft Secure Password Authentication"
760 Client support for Microsoft's &'Secure Password Authentication'& is provided
761 by code contributed by Marc Prud'hommeaux. Server support was contributed by
762 Tom Kistner. This includes code taken from the Samba project, which is released
766 .cindex "&'pwcheck'& daemon"
767 .cindex "&'pwauthd'& daemon"
768 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
769 by code taken from the Cyrus-SASL library and adapted by Alexander S.
770 Sabourenkov. The permission notice appears below, in accordance with the
771 conditions expressed therein.
774 Copyright © 2001 Carnegie Mellon University. All rights reserved.
776 Redistribution and use in source and binary forms, with or without
777 modification, are permitted provided that the following conditions
781 Redistributions of source code must retain the above copyright
782 notice, this list of conditions and the following disclaimer.
784 Redistributions in binary form must reproduce the above copyright
785 notice, this list of conditions and the following disclaimer in
786 the documentation and/or other materials provided with the
789 The name &"Carnegie Mellon University"& must not be used to
790 endorse or promote products derived from this software without
791 prior written permission. For permission or any other legal
792 details, please contact
794 Office of Technology Transfer
795 Carnegie Mellon University
797 Pittsburgh, PA 15213-3890
798 (412) 268-4387, fax: (412) 268-7395
799 tech-transfer@andrew.cmu.edu
802 Redistributions of any form whatsoever must retain the following
805 &"This product includes software developed by Computing Services
806 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
808 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
809 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
810 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
811 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
812 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
813 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
814 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
819 .cindex "Exim monitor" "acknowledgment"
822 The Exim Monitor program, which is an X-Window application, includes
823 modified versions of the Athena StripChart and TextPop widgets.
824 This code is copyright by DEC and MIT, and their permission notice appears
825 below, in accordance with the conditions expressed therein.
828 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
829 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
833 Permission to use, copy, modify, and distribute this software and its
834 documentation for any purpose and without fee is hereby granted,
835 provided that the above copyright notice appear in all copies and that
836 both that copyright notice and this permission notice appear in
837 supporting documentation, and that the names of Digital or MIT not be
838 used in advertising or publicity pertaining to distribution of the
839 software without specific, written prior permission.
841 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
842 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
843 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
844 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
845 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
846 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
851 Many people have contributed code fragments, some large, some small, that were
852 not covered by any specific licence requirements. It is assumed that the
853 contributors are happy to see their code incorporated into Exim under the GPL.
860 . ////////////////////////////////////////////////////////////////////////////
861 . ////////////////////////////////////////////////////////////////////////////
863 .chapter "How Exim receives and delivers mail" "CHID11" &&&
864 "Receiving and delivering mail"
867 .section "Overall philosophy" "SECID10"
868 .cindex "design philosophy"
869 Exim is designed to work efficiently on systems that are permanently connected
870 to the Internet and are handling a general mix of mail. In such circumstances,
871 most messages can be delivered immediately. Consequently, Exim does not
872 maintain independent queues of messages for specific domains or hosts, though
873 it does try to send several messages in a single SMTP connection after a host
874 has been down, and it also maintains per-host retry information.
877 .section "Policy control" "SECID11"
878 .cindex "policy control" "overview"
879 Policy controls are now an important feature of MTAs that are connected to the
880 Internet. Perhaps their most important job is to stop MTAs being abused as
881 &"open relays"& by misguided individuals who send out vast amounts of
882 unsolicited junk, and want to disguise its source. Exim provides flexible
883 facilities for specifying policy controls on incoming mail:
886 .cindex "&ACL;" "introduction"
887 Exim 4 (unlike previous versions of Exim) implements policy controls on
888 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
889 series of statements that may either grant or deny access. ACLs can be used at
890 several places in the SMTP dialogue while receiving a message from a remote
891 host. However, the most common places are after each RCPT command, and at the
892 very end of the message. The sysadmin can specify conditions for accepting or
893 rejecting individual recipients or the entire message, respectively, at these
894 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
897 An ACL is also available for locally generated, non-SMTP messages. In this
898 case, the only available actions are to accept or deny the entire message.
900 When Exim is compiled with the content-scanning extension, facilities are
901 provided in the ACL mechanism for passing the message to external virus and/or
902 spam scanning software. The result of such a scan is passed back to the ACL,
903 which can then use it to decide what to do with the message.
905 When a message has been received, either from a remote host or from the local
906 host, but before the final acknowledgment has been sent, a locally supplied C
907 function called &[local_scan()]& can be run to inspect the message and decide
908 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
909 is accepted, the list of recipients can be modified by the function.
911 Using the &[local_scan()]& mechanism is another way of calling external scanner
912 software. The &%SA-Exim%& add-on package works this way. It does not require
913 Exim to be compiled with the content-scanning extension.
915 After a message has been accepted, a further checking mechanism is available in
916 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
917 runs at the start of every delivery process.
922 .section "User filters" "SECID12"
923 .cindex "filter" "introduction"
924 .cindex "Sieve filter"
925 In a conventional Exim configuration, users are able to run private filters by
926 setting up appropriate &_.forward_& files in their home directories. See
927 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
928 configuration needed to support this, and the separate document entitled
929 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
930 of filtering are available:
933 Sieve filters are written in the standard filtering language that is defined
936 Exim filters are written in a syntax that is unique to Exim, but which is more
937 powerful than Sieve, which it pre-dates.
940 User filters are run as part of the routing process, described below.
944 .section "Message identification" "SECTmessiden"
945 .cindex "message ids" "details of format"
946 .cindex "format" "of message id"
947 .cindex "id of message"
952 Every message handled by Exim is given a &'message id'& which is sixteen
953 characters long. It is divided into three parts, separated by hyphens, for
954 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
955 normally encoding numbers in base 62. However, in the Darwin operating
956 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
957 (avoiding the use of lower case letters) is used instead, because the message
958 id is used to construct file names, and the names of files in those systems are
959 not always case-sensitive.
961 .cindex "pid (process id)" "re-use of"
962 The detail of the contents of the message id have changed as Exim has evolved.
963 Earlier versions relied on the operating system not re-using a process id (pid)
964 within one second. On modern operating systems, this assumption can no longer
965 be made, so the algorithm had to be changed. To retain backward compatibility,
966 the format of the message id was retained, which is why the following rules are
970 The first six characters of the message id are the time at which the message
971 started to be received, to a granularity of one second. That is, this field
972 contains the number of seconds since the start of the epoch (the normal Unix
973 way of representing the date and time of day).
975 After the first hyphen, the next six characters are the id of the process that
976 received the message.
978 There are two different possibilities for the final two characters:
980 .oindex "&%localhost_number%&"
981 If &%localhost_number%& is not set, this value is the fractional part of the
982 time of reception, normally in units of 1/2000 of a second, but for systems
983 that must use base 36 instead of base 62 (because of case-insensitive file
984 systems), the units are 1/1000 of a second.
986 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
987 the fractional part of the time, which in this case is in units of 1/200
992 After a message has been received, Exim waits for the clock to tick at the
993 appropriate resolution before proceeding, so that if another message is
994 received by the same process, or by another process with the same (re-used)
995 pid, it is guaranteed that the time will be different. In most cases, the clock
996 will already have ticked while the message was being received.
999 .section "Receiving mail" "SECID13"
1000 .cindex "receiving mail"
1001 .cindex "message" "reception"
1002 The only way Exim can receive mail from another host is using SMTP over
1003 TCP/IP, in which case the sender and recipient addresses are transferred using
1004 SMTP commands. However, from a locally running process (such as a user's MUA),
1005 there are several possibilities:
1008 If the process runs Exim with the &%-bm%& option, the message is read
1009 non-interactively (usually via a pipe), with the recipients taken from the
1010 command line, or from the body of the message if &%-t%& is also used.
1012 If the process runs Exim with the &%-bS%& option, the message is also read
1013 non-interactively, but in this case the recipients are listed at the start of
1014 the message in a series of SMTP RCPT commands, terminated by a DATA
1015 command. This is so-called &"batch SMTP"& format,
1016 but it isn't really SMTP. The SMTP commands are just another way of passing
1017 envelope addresses in a non-interactive submission.
1019 If the process runs Exim with the &%-bs%& option, the message is read
1020 interactively, using the SMTP protocol. A two-way pipe is normally used for
1021 passing data between the local process and the Exim process.
1022 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1023 example, the ACLs for SMTP commands are used for this form of submission.
1025 A local process may also make a TCP/IP call to the host's loopback address
1026 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1027 does not treat the loopback address specially. It treats all such connections
1028 in the same way as connections from other hosts.
1032 .cindex "message sender, constructed by Exim"
1033 .cindex "sender" "constructed by Exim"
1034 In the three cases that do not involve TCP/IP, the sender address is
1035 constructed from the login name of the user that called Exim and a default
1036 qualification domain (which can be set by the &%qualify_domain%& configuration
1037 option). For local or batch SMTP, a sender address that is passed using the
1038 SMTP MAIL command is ignored. However, the system administrator may allow
1039 certain users (&"trusted users"&) to specify a different sender address
1040 unconditionally, or all users to specify certain forms of different sender
1041 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1042 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1043 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1044 users to change sender addresses.
1046 Messages received by either of the non-interactive mechanisms are subject to
1047 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1048 (either over TCP/IP, or interacting with a local process) can be checked by a
1049 number of ACLs that operate at different times during the SMTP session. Either
1050 individual recipients, or the entire message, can be rejected if local policy
1051 requirements are not met. The &[local_scan()]& function (see chapter
1052 &<<CHAPlocalscan>>&) is run for all incoming messages.
1054 Exim can be configured not to start a delivery process when a message is
1055 received; this can be unconditional, or depend on the number of incoming SMTP
1056 connections or the system load. In these situations, new messages wait on the
1057 queue until a queue runner process picks them up. However, in standard
1058 configurations under normal conditions, delivery is started as soon as a
1059 message is received.
1065 .section "Handling an incoming message" "SECID14"
1066 .cindex "spool directory" "files that hold a message"
1067 .cindex "file" "how a message is held"
1068 When Exim accepts a message, it writes two files in its spool directory. The
1069 first contains the envelope information, the current status of the message, and
1070 the header lines, and the second contains the body of the message. The names of
1071 the two spool files consist of the message id, followed by &`-H`& for the
1072 file containing the envelope and header, and &`-D`& for the data file.
1074 .cindex "spool directory" "&_input_& sub-directory"
1075 By default all these message files are held in a single directory called
1076 &_input_& inside the general Exim spool directory. Some operating systems do
1077 not perform very well if the number of files in a directory gets large; to
1078 improve performance in such cases, the &%split_spool_directory%& option can be
1079 used. This causes Exim to split up the input files into 62 sub-directories
1080 whose names are single letters or digits. When this is done, the queue is
1081 processed one sub-directory at a time instead of all at once, which can improve
1082 overall performance even when there are not enough files in each directory to
1083 affect file system performance.
1085 The envelope information consists of the address of the message's sender and
1086 the addresses of the recipients. This information is entirely separate from
1087 any addresses contained in the header lines. The status of the message includes
1088 a list of recipients who have already received the message. The format of the
1089 first spool file is described in chapter &<<CHAPspool>>&.
1091 .cindex "rewriting" "addresses"
1092 Address rewriting that is specified in the rewrite section of the configuration
1093 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1094 both in the header lines and the envelope, at the time the message is accepted.
1095 If during the course of delivery additional addresses are generated (for
1096 example, via aliasing), these new addresses are rewritten as soon as they are
1097 generated. At the time a message is actually delivered (transported) further
1098 rewriting can take place; because this is a transport option, it can be
1099 different for different forms of delivery. It is also possible to specify the
1100 addition or removal of certain header lines at the time the message is
1101 delivered (see chapters &<<CHAProutergeneric>>& and
1102 &<<CHAPtransportgeneric>>&).
1106 .section "Life of a message" "SECID15"
1107 .cindex "message" "life of"
1108 .cindex "message" "frozen"
1109 A message remains in the spool directory until it is completely delivered to
1110 its recipients or to an error address, or until it is deleted by an
1111 administrator or by the user who originally created it. In cases when delivery
1112 cannot proceed &-- for example, when a message can neither be delivered to its
1113 recipients nor returned to its sender, the message is marked &"frozen"& on the
1114 spool, and no more deliveries are attempted.
1116 .cindex "frozen messages" "thawing"
1117 .cindex "message" "thawing frozen"
1118 An administrator can &"thaw"& such messages when the problem has been
1119 corrected, and can also freeze individual messages by hand if necessary. In
1120 addition, an administrator can force a delivery error, causing a bounce message
1123 .oindex "&%timeout_frozen_after%&"
1124 .oindex "&%ignore_bounce_errors_after%&"
1125 There are options called &%ignore_bounce_errors_after%& and
1126 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1127 The first applies only to frozen bounces, the second to any frozen messages.
1129 .cindex "message" "log file for"
1130 .cindex "log" "file for each message"
1131 While Exim is working on a message, it writes information about each delivery
1132 attempt to its main log file. This includes successful, unsuccessful, and
1133 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1134 lines are also written to a separate &'message log'& file for each message.
1135 These logs are solely for the benefit of the administrator, and are normally
1136 deleted along with the spool files when processing of a message is complete.
1137 The use of individual message logs can be disabled by setting
1138 &%no_message_logs%&; this might give an improvement in performance on very busy
1141 .cindex "journal file"
1142 .cindex "file" "journal"
1143 All the information Exim itself needs to set up a delivery is kept in the first
1144 spool file, along with the header lines. When a successful delivery occurs, the
1145 address is immediately written at the end of a journal file, whose name is the
1146 message id followed by &`-J`&. At the end of a delivery run, if there are some
1147 addresses left to be tried again later, the first spool file (the &`-H`& file)
1148 is updated to indicate which these are, and the journal file is then deleted.
1149 Updating the spool file is done by writing a new file and renaming it, to
1150 minimize the possibility of data loss.
1152 Should the system or the program crash after a successful delivery but before
1153 the spool file has been updated, the journal is left lying around. The next
1154 time Exim attempts to deliver the message, it reads the journal file and
1155 updates the spool file before proceeding. This minimizes the chances of double
1156 deliveries caused by crashes.
1160 .section "Processing an address for delivery" "SECTprocaddress"
1161 .cindex "drivers" "definition of"
1162 .cindex "router" "definition of"
1163 .cindex "transport" "definition of"
1164 The main delivery processing elements of Exim are called &'routers'& and
1165 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1166 number of them is provided in the source distribution, and compile-time options
1167 specify which ones are included in the binary. Run time options specify which
1168 ones are actually used for delivering messages.
1170 .cindex "drivers" "instance definition"
1171 Each driver that is specified in the run time configuration is an &'instance'&
1172 of that particular driver type. Multiple instances are allowed; for example,
1173 you can set up several different &(smtp)& transports, each with different
1174 option values that might specify different ports or different timeouts. Each
1175 instance has its own identifying name. In what follows we will normally use the
1176 instance name when discussing one particular instance (that is, one specific
1177 configuration of the driver), and the generic driver name when discussing
1178 the driver's features in general.
1180 A &'router'& is a driver that operates on an address, either determining how
1181 its delivery should happen, by assigning it to a specific transport, or
1182 converting the address into one or more new addresses (for example, via an
1183 alias file). A router may also explicitly choose to fail an address, causing it
1186 A &'transport'& is a driver that transmits a copy of the message from Exim's
1187 spool to some destination. There are two kinds of transport: for a &'local'&
1188 transport, the destination is a file or a pipe on the local host, whereas for a
1189 &'remote'& transport the destination is some other host. A message is passed
1190 to a specific transport as a result of successful routing. If a message has
1191 several recipients, it may be passed to a number of different transports.
1193 .cindex "preconditions" "definition of"
1194 An address is processed by passing it to each configured router instance in
1195 turn, subject to certain preconditions, until a router accepts the address or
1196 specifies that it should be bounced. We will describe this process in more
1197 detail shortly. First, as a simple example, we consider how each recipient
1198 address in a message is processed in a small configuration of three routers.
1200 To make this a more concrete example, it is described in terms of some actual
1201 routers, but remember, this is only an example. You can configure Exim's
1202 routers in many different ways, and there may be any number of routers in a
1205 The first router that is specified in a configuration is often one that handles
1206 addresses in domains that are not recognized specially by the local host. These
1207 are typically addresses for arbitrary domains on the Internet. A precondition
1208 is set up which looks for the special domains known to the host (for example,
1209 its own domain name), and the router is run for addresses that do &'not'&
1210 match. Typically, this is a router that looks up domains in the DNS in order to
1211 find the hosts to which this address routes. If it succeeds, the address is
1212 assigned to a suitable SMTP transport; if it does not succeed, the router is
1213 configured to fail the address.
1215 The second router is reached only when the domain is recognized as one that
1216 &"belongs"& to the local host. This router does redirection &-- also known as
1217 aliasing and forwarding. When it generates one or more new addresses from the
1218 original, each of them is routed independently from the start. Otherwise, the
1219 router may cause an address to fail, or it may simply decline to handle the
1220 address, in which case the address is passed to the next router.
1222 The final router in many configurations is one that checks to see if the
1223 address belongs to a local mailbox. The precondition may involve a check to
1224 see if the local part is the name of a login account, or it may look up the
1225 local part in a file or a database. If its preconditions are not met, or if
1226 the router declines, we have reached the end of the routers. When this happens,
1227 the address is bounced.
1231 .section "Processing an address for verification" "SECID16"
1232 .cindex "router" "for verification"
1233 .cindex "verifying address" "overview"
1234 As well as being used to decide how to deliver to an address, Exim's routers
1235 are also used for &'address verification'&. Verification can be requested as
1236 one of the checks to be performed in an ACL for incoming messages, on both
1237 sender and recipient addresses, and it can be tested using the &%-bv%& and
1238 &%-bvs%& command line options.
1240 When an address is being verified, the routers are run in &"verify mode"&. This
1241 does not affect the way the routers work, but it is a state that can be
1242 detected. By this means, a router can be skipped or made to behave differently
1243 when verifying. A common example is a configuration in which the first router
1244 sends all messages to a message-scanning program, unless they have been
1245 previously scanned. Thus, the first router accepts all addresses without any
1246 checking, making it useless for verifying. Normally, the &%no_verify%& option
1247 would be set for such a router, causing it to be skipped in verify mode.
1252 .section "Running an individual router" "SECTrunindrou"
1253 .cindex "router" "running details"
1254 .cindex "preconditions" "checking"
1255 .cindex "router" "result of running"
1256 As explained in the example above, a number of preconditions are checked before
1257 running a router. If any are not met, the router is skipped, and the address is
1258 passed to the next router. When all the preconditions on a router &'are'& met,
1259 the router is run. What happens next depends on the outcome, which is one of
1263 &'accept'&: The router accepts the address, and either assigns it to a
1264 transport, or generates one or more &"child"& addresses. Processing the
1265 original address ceases,
1266 .oindex "&%unseen%&"
1267 unless the &%unseen%& option is set on the router. This option
1268 can be used to set up multiple deliveries with different routing (for example,
1269 for keeping archive copies of messages). When &%unseen%& is set, the address is
1270 passed to the next router. Normally, however, an &'accept'& return marks the
1273 Any child addresses generated by the router are processed independently,
1274 starting with the first router by default. It is possible to change this by
1275 setting the &%redirect_router%& option to specify which router to start at for
1276 child addresses. Unlike &%pass_router%& (see below) the router specified by
1277 &%redirect_router%& may be anywhere in the router configuration.
1279 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1280 requests that the address be passed to another router. By default the address
1281 is passed to the next router, but this can be changed by setting the
1282 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1283 must be below the current router (to avoid loops).
1285 &'decline'&: The router declines to accept the address because it does not
1286 recognize it at all. By default, the address is passed to the next router, but
1287 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1288 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1289 &'decline'& into &'fail'&.
1291 &'fail'&: The router determines that the address should fail, and queues it for
1292 the generation of a bounce message. There is no further processing of the
1293 original address unless &%unseen%& is set on the router.
1295 &'defer'&: The router cannot handle the address at the present time. (A
1296 database may be offline, or a DNS lookup may have timed out.) No further
1297 processing of the address happens in this delivery attempt. It is tried again
1298 next time the message is considered for delivery.
1300 &'error'&: There is some error in the router (for example, a syntax error in
1301 its configuration). The action is as for defer.
1304 If an address reaches the end of the routers without having been accepted by
1305 any of them, it is bounced as unrouteable. The default error message in this
1306 situation is &"unrouteable address"&, but you can set your own message by
1307 making use of the &%cannot_route_message%& option. This can be set for any
1308 router; the value from the last router that &"saw"& the address is used.
1310 Sometimes while routing you want to fail a delivery when some conditions are
1311 met but others are not, instead of passing the address on for further routing.
1312 You can do this by having a second router that explicitly fails the delivery
1313 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1314 facility for this purpose.
1317 .section "Duplicate addresses" "SECID17"
1318 .cindex "case of local parts"
1319 .cindex "address duplicate, discarding"
1320 .cindex "duplicate addresses"
1321 Once routing is complete, Exim scans the addresses that are assigned to local
1322 and remote transports, and discards any duplicates that it finds. During this
1323 check, local parts are treated as case-sensitive. This happens only when
1324 actually delivering a message; when testing routers with &%-bt%&, all the
1325 routed addresses are shown.
1329 .section "Router preconditions" "SECTrouprecon"
1330 .cindex "router" "preconditions, order of processing"
1331 .cindex "preconditions" "order of processing"
1332 The preconditions that are tested for each router are listed below, in the
1333 order in which they are tested. The individual configuration options are
1334 described in more detail in chapter &<<CHAProutergeneric>>&.
1337 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1338 the local parts handled by the router may or must have certain prefixes and/or
1339 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1340 skipped. These conditions are tested first. When an affix is present, it is
1341 removed from the local part before further processing, including the evaluation
1342 of any other conditions.
1344 Routers can be designated for use only when not verifying an address, that is,
1345 only when routing it for delivery (or testing its delivery routing). If the
1346 &%verify%& option is set false, the router is skipped when Exim is verifying an
1348 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1349 &%verify_recipient%&, which independently control the use of the router for
1350 sender and recipient verification. You can set these options directly if
1351 you want a router to be used for only one type of verification.
1353 If the &%address_test%& option is set false, the router is skipped when Exim is
1354 run with the &%-bt%& option to test an address routing. This can be helpful
1355 when the first router sends all new messages to a scanner of some sort; it
1356 makes it possible to use &%-bt%& to test subsequent delivery routing without
1357 having to simulate the effect of the scanner.
1359 Routers can be designated for use only when verifying an address, as
1360 opposed to routing it for delivery. The &%verify_only%& option controls this.
1362 Individual routers can be explicitly skipped when running the routers to
1363 check an address given in the SMTP EXPN command (see the &%expn%& option).
1365 If the &%domains%& option is set, the domain of the address must be in the set
1366 of domains that it defines.
1368 .vindex "&$local_part_prefix$&"
1369 .vindex "&$local_part$&"
1370 .vindex "&$local_part_suffix$&"
1371 If the &%local_parts%& option is set, the local part of the address must be in
1372 the set of local parts that it defines. If &%local_part_prefix%& or
1373 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1374 part before this check. If you want to do precondition tests on local parts
1375 that include affixes, you can do so by using a &%condition%& option (see below)
1376 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1377 &$local_part_suffix$& as necessary.
1379 .vindex "&$local_user_uid$&"
1380 .vindex "&$local_user_gid$&"
1382 If the &%check_local_user%& option is set, the local part must be the name of
1383 an account on the local host. If this check succeeds, the uid and gid of the
1384 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1385 user's home directory is placed in &$home$&; these values can be used in the
1386 remaining preconditions.
1388 If the &%router_home_directory%& option is set, it is expanded at this point,
1389 because it overrides the value of &$home$&. If this expansion were left till
1390 later, the value of &$home$& as set by &%check_local_user%& would be used in
1391 subsequent tests. Having two different values of &$home$& in the same router
1392 could lead to confusion.
1394 If the &%senders%& option is set, the envelope sender address must be in the
1395 set of addresses that it defines.
1397 If the &%require_files%& option is set, the existence or non-existence of
1398 specified files is tested.
1400 .cindex "customizing" "precondition"
1401 If the &%condition%& option is set, it is evaluated and tested. This option
1402 uses an expanded string to allow you to set up your own custom preconditions.
1403 Expanded strings are described in chapter &<<CHAPexpand>>&.
1407 Note that &%require_files%& comes near the end of the list, so you cannot use
1408 it to check for the existence of a file in which to lookup up a domain, local
1409 part, or sender. However, as these options are all expanded, you can use the
1410 &%exists%& expansion condition to make such tests within each condition. The
1411 &%require_files%& option is intended for checking files that the router may be
1412 going to use internally, or which are needed by a specific transport (for
1413 example, &_.procmailrc_&).
1417 .section "Delivery in detail" "SECID18"
1418 .cindex "delivery" "in detail"
1419 When a message is to be delivered, the sequence of events is as follows:
1422 If a system-wide filter file is specified, the message is passed to it. The
1423 filter may add recipients to the message, replace the recipients, discard the
1424 message, cause a new message to be generated, or cause the message delivery to
1425 fail. The format of the system filter file is the same as for Exim user filter
1426 files, described in the separate document entitled &'Exim's interfaces to mail
1428 .cindex "Sieve filter" "not available for system filter"
1429 (&*Note*&: Sieve cannot be used for system filter files.)
1431 Some additional features are available in system filters &-- see chapter
1432 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1433 filter only once per delivery attempt, however many recipients it has. However,
1434 if there are several delivery attempts because one or more addresses could not
1435 be immediately delivered, the system filter is run each time. The filter
1436 condition &%first_delivery%& can be used to detect the first run of the system
1439 Each recipient address is offered to each configured router in turn, subject to
1440 its preconditions, until one is able to handle it. If no router can handle the
1441 address, that is, if they all decline, the address is failed. Because routers
1442 can be targeted at particular domains, several locally handled domains can be
1443 processed entirely independently of each other.
1445 .cindex "routing" "loops in"
1446 .cindex "loop" "while routing"
1447 A router that accepts an address may assign it to a local or a remote
1448 transport. However, the transport is not run at this time. Instead, the address
1449 is placed on a list for the particular transport, which will be run later.
1450 Alternatively, the router may generate one or more new addresses (typically
1451 from alias, forward, or filter files). New addresses are fed back into this
1452 process from the top, but in order to avoid loops, a router ignores any address
1453 which has an identically-named ancestor that was processed by itself.
1455 When all the routing has been done, addresses that have been successfully
1456 handled are passed to their assigned transports. When local transports are
1457 doing real local deliveries, they handle only one address at a time, but if a
1458 local transport is being used as a pseudo-remote transport (for example, to
1459 collect batched SMTP messages for transmission by some other means) multiple
1460 addresses can be handled. Remote transports can always handle more than one
1461 address at a time, but can be configured not to do so, or to restrict multiple
1462 addresses to the same domain.
1464 Each local delivery to a file or a pipe runs in a separate process under a
1465 non-privileged uid, and these deliveries are run one at a time. Remote
1466 deliveries also run in separate processes, normally under a uid that is private
1467 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1468 run in parallel. The maximum number of simultaneous remote deliveries for any
1469 one message is set by the &%remote_max_parallel%& option.
1470 The order in which deliveries are done is not defined, except that all local
1471 deliveries happen before any remote deliveries.
1473 .cindex "queue runner"
1474 When it encounters a local delivery during a queue run, Exim checks its retry
1475 database to see if there has been a previous temporary delivery failure for the
1476 address before running the local transport. If there was a previous failure,
1477 Exim does not attempt a new delivery until the retry time for the address is
1478 reached. However, this happens only for delivery attempts that are part of a
1479 queue run. Local deliveries are always attempted when delivery immediately
1480 follows message reception, even if retry times are set for them. This makes for
1481 better behaviour if one particular message is causing problems (for example,
1482 causing quota overflow, or provoking an error in a filter file).
1484 .cindex "delivery" "retry in remote transports"
1485 Remote transports do their own retry handling, since an address may be
1486 deliverable to one of a number of hosts, each of which may have a different
1487 retry time. If there have been previous temporary failures and no host has
1488 reached its retry time, no delivery is attempted, whether in a queue run or
1489 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1491 If there were any permanent errors, a bounce message is returned to an
1492 appropriate address (the sender in the common case), with details of the error
1493 for each failing address. Exim can be configured to send copies of bounce
1494 messages to other addresses.
1496 .cindex "delivery" "deferral"
1497 If one or more addresses suffered a temporary failure, the message is left on
1498 the queue, to be tried again later. Delivery of these addresses is said to be
1501 When all the recipient addresses have either been delivered or bounced,
1502 handling of the message is complete. The spool files and message log are
1503 deleted, though the message log can optionally be preserved if required.
1509 .section "Retry mechanism" "SECID19"
1510 .cindex "delivery" "retry mechanism"
1511 .cindex "retry" "description of mechanism"
1512 .cindex "queue runner"
1513 Exim's mechanism for retrying messages that fail to get delivered at the first
1514 attempt is the queue runner process. You must either run an Exim daemon that
1515 uses the &%-q%& option with a time interval to start queue runners at regular
1516 intervals, or use some other means (such as &'cron'&) to start them. If you do
1517 not arrange for queue runners to be run, messages that fail temporarily at the
1518 first attempt will remain on your queue for ever. A queue runner process works
1519 its way through the queue, one message at a time, trying each delivery that has
1520 passed its retry time.
1521 You can run several queue runners at once.
1523 Exim uses a set of configured rules to determine when next to retry the failing
1524 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1525 should give up trying to deliver to the address, at which point it generates a
1526 bounce message. If no retry rules are set for a particular host, address, and
1527 error combination, no retries are attempted, and temporary errors are treated
1532 .section "Temporary delivery failure" "SECID20"
1533 .cindex "delivery" "temporary failure"
1534 There are many reasons why a message may not be immediately deliverable to a
1535 particular address. Failure to connect to a remote machine (because it, or the
1536 connection to it, is down) is one of the most common. Temporary failures may be
1537 detected during routing as well as during the transport stage of delivery.
1538 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1539 is on a file system where the user is over quota. Exim can be configured to
1540 impose its own quotas on local mailboxes; where system quotas are set they will
1543 If a host is unreachable for a period of time, a number of messages may be
1544 waiting for it by the time it recovers, and sending them in a single SMTP
1545 connection is clearly beneficial. Whenever a delivery to a remote host is
1548 .cindex "hints database"
1549 Exim makes a note in its hints database, and whenever a successful
1550 SMTP delivery has happened, it looks to see if any other messages are waiting
1551 for the same host. If any are found, they are sent over the same SMTP
1552 connection, subject to a configuration limit as to the maximum number in any
1558 .section "Permanent delivery failure" "SECID21"
1559 .cindex "delivery" "permanent failure"
1560 .cindex "bounce message" "when generated"
1561 When a message cannot be delivered to some or all of its intended recipients, a
1562 bounce message is generated. Temporary delivery failures turn into permanent
1563 errors when their timeout expires. All the addresses that fail in a given
1564 delivery attempt are listed in a single message. If the original message has
1565 many recipients, it is possible for some addresses to fail in one delivery
1566 attempt and others to fail subsequently, giving rise to more than one bounce
1567 message. The wording of bounce messages can be customized by the administrator.
1568 See chapter &<<CHAPemsgcust>>& for details.
1570 .cindex "&'X-Failed-Recipients:'& header line"
1571 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1572 failed addresses, for the benefit of programs that try to analyse such messages
1575 .cindex "bounce message" "recipient of"
1576 A bounce message is normally sent to the sender of the original message, as
1577 obtained from the message's envelope. For incoming SMTP messages, this is the
1578 address given in the MAIL command. However, when an address is expanded via a
1579 forward or alias file, an alternative address can be specified for delivery
1580 failures of the generated addresses. For a mailing list expansion (see section
1581 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1586 .section "Failures to deliver bounce messages" "SECID22"
1587 .cindex "bounce message" "failure to deliver"
1588 If a bounce message (either locally generated or received from a remote host)
1589 itself suffers a permanent delivery failure, the message is left on the queue,
1590 but it is frozen, awaiting the attention of an administrator. There are options
1591 that can be used to make Exim discard such failed messages, or to keep them
1592 for only a short time (see &%timeout_frozen_after%& and
1593 &%ignore_bounce_errors_after%&).
1599 . ////////////////////////////////////////////////////////////////////////////
1600 . ////////////////////////////////////////////////////////////////////////////
1602 .chapter "Building and installing Exim" "CHID3"
1603 .scindex IIDbuex "building Exim"
1605 .section "Unpacking" "SECID23"
1606 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1607 creates a directory with the name of the current release (for example,
1608 &_exim-&version;_&) into which the following files are placed:
1611 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1612 .irow &_CHANGES_& "contains a reference to where changes are &&&
1614 .irow &_LICENCE_& "the GNU General Public Licence"
1615 .irow &_Makefile_& "top-level make file"
1616 .irow &_NOTICE_& "conditions for the use of Exim"
1617 .irow &_README_& "list of files, directories and simple build &&&
1621 Other files whose names begin with &_README_& may also be present. The
1622 following subdirectories are created:
1625 .irow &_Local_& "an empty directory for local configuration files"
1626 .irow &_OS_& "OS-specific files"
1627 .irow &_doc_& "documentation files"
1628 .irow &_exim_monitor_& "source files for the Exim monitor"
1629 .irow &_scripts_& "scripts used in the build process"
1630 .irow &_src_& "remaining source files"
1631 .irow &_util_& "independent utilities"
1634 The main utility programs are contained in the &_src_& directory, and are built
1635 with the Exim binary. The &_util_& directory contains a few optional scripts
1636 that may be useful to some sites.
1639 .section "Multiple machine architectures and operating systems" "SECID24"
1640 .cindex "building Exim" "multiple OS/architectures"
1641 The building process for Exim is arranged to make it easy to build binaries for
1642 a number of different architectures and operating systems from the same set of
1643 source files. Compilation does not take place in the &_src_& directory.
1644 Instead, a &'build directory'& is created for each architecture and operating
1646 .cindex "symbolic link" "to build directory"
1647 Symbolic links to the sources are installed in this directory, which is where
1648 the actual building takes place. In most cases, Exim can discover the machine
1649 architecture and operating system for itself, but the defaults can be
1650 overridden if necessary.
1653 .section "PCRE library" "SECTpcre"
1654 .cindex "PCRE library"
1655 Exim no longer has an embedded PCRE library as the vast majority of
1656 modern systems include PCRE as a system library, although you may need
1657 to install the PCRE or PCRE development package for your operating
1658 system. If your system has a normal PCRE installation the Exim build
1659 process will need no further configuration. If the library or the
1660 headers are in an unusual location you will need to set the PCRE_LIBS
1661 and INCLUDE directives appropriately. If your operating system has no
1662 PCRE support then you will need to obtain and build the current PCRE
1663 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1665 .section "DBM libraries" "SECTdb"
1666 .cindex "DBM libraries" "discussion of"
1667 .cindex "hints database" "DBM files used for"
1668 Even if you do not use any DBM files in your configuration, Exim still needs a
1669 DBM library in order to operate, because it uses indexed files for its hints
1670 databases. Unfortunately, there are a number of DBM libraries in existence, and
1671 different operating systems often have different ones installed.
1673 .cindex "Solaris" "DBM library for"
1674 .cindex "IRIX, DBM library for"
1675 .cindex "BSD, DBM library for"
1676 .cindex "Linux, DBM library for"
1677 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1678 Linux distribution, the DBM configuration should happen automatically, and you
1679 may be able to ignore this section. Otherwise, you may have to learn more than
1680 you would like about DBM libraries from what follows.
1682 .cindex "&'ndbm'& DBM library"
1683 Licensed versions of Unix normally contain a library of DBM functions operating
1684 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1685 versions of Unix seem to vary in what they contain as standard. In particular,
1686 some early versions of Linux have no default DBM library, and different
1687 distributors have chosen to bundle different libraries with their packaged
1688 versions. However, the more recent releases seem to have standardized on the
1689 Berkeley DB library.
1691 Different DBM libraries have different conventions for naming the files they
1692 use. When a program opens a file called &_dbmfile_&, there are several
1696 A traditional &'ndbm'& implementation, such as that supplied as part of
1697 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1699 .cindex "&'gdbm'& DBM library"
1700 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1701 compatibility interface it makes two different hard links to it with names
1702 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1703 file name is used unmodified.
1705 .cindex "Berkeley DB library"
1706 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1707 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1708 programmer exactly the same as the traditional &'ndbm'& implementation.
1710 If the Berkeley package is used in its native mode, it operates on a single
1711 file called &_dbmfile_&; the programmer's interface is somewhat different to
1712 the traditional &'ndbm'& interface.
1714 To complicate things further, there are several very different versions of the
1715 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1716 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1717 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1718 versions of Berkeley DB can be obtained from
1719 &url(http://www.sleepycat.com/).
1721 .cindex "&'tdb'& DBM library"
1722 Yet another DBM library, called &'tdb'&, is available from
1723 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1724 operates on a single file.
1728 .cindex "DBM libraries" "configuration for building"
1729 Exim and its utilities can be compiled to use any of these interfaces. In order
1730 to use any version of the Berkeley DB package in native mode, you must set
1731 USE_DB in an appropriate configuration file (typically
1732 &_Local/Makefile_&). For example:
1736 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1737 error is diagnosed if you set more than one of these.
1739 At the lowest level, the build-time configuration sets none of these options,
1740 thereby assuming an interface of type (1). However, some operating system
1741 configuration files (for example, those for the BSD operating systems and
1742 Linux) assume type (4) by setting USE_DB as their default, and the
1743 configuration files for Cygwin set USE_GDBM. Anything you set in
1744 &_Local/Makefile_&, however, overrides these system defaults.
1746 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1747 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1748 in one of these lines:
1753 Settings like that will work if the DBM library is installed in the standard
1754 place. Sometimes it is not, and the library's header file may also not be in
1755 the default path. You may need to set INCLUDE to specify where the header
1756 file is, and to specify the path to the library more fully in DBMLIB, as in
1759 INCLUDE=-I/usr/local/include/db-4.1
1760 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1762 There is further detailed discussion about the various DBM libraries in the
1763 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1767 .section "Pre-building configuration" "SECID25"
1768 .cindex "building Exim" "pre-building configuration"
1769 .cindex "configuration for building Exim"
1770 .cindex "&_Local/Makefile_&"
1771 .cindex "&_src/EDITME_&"
1772 Before building Exim, a local configuration file that specifies options
1773 independent of any operating system has to be created with the name
1774 &_Local/Makefile_&. A template for this file is supplied as the file
1775 &_src/EDITME_&, and it contains full descriptions of all the option settings
1776 therein. These descriptions are therefore not repeated here. If you are
1777 building Exim for the first time, the simplest thing to do is to copy
1778 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1780 There are three settings that you must supply, because Exim will not build
1781 without them. They are the location of the run time configuration file
1782 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1783 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1784 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1785 a colon-separated list of file names; Exim uses the first of them that exists.
1787 There are a few other parameters that can be specified either at build time or
1788 at run time, to enable the same binary to be used on a number of different
1789 machines. However, if the locations of Exim's spool directory and log file
1790 directory (if not within the spool directory) are fixed, it is recommended that
1791 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1792 detected early in Exim's execution (such as a malformed configuration file) can
1795 .cindex "content scanning" "specifying at build time"
1796 Exim's interfaces for calling virus and spam scanning software directly from
1797 access control lists are not compiled by default. If you want to include these
1798 facilities, you need to set
1800 WITH_CONTENT_SCAN=yes
1802 in your &_Local/Makefile_&. For details of the facilities themselves, see
1803 chapter &<<CHAPexiscan>>&.
1806 .cindex "&_Local/eximon.conf_&"
1807 .cindex "&_exim_monitor/EDITME_&"
1808 If you are going to build the Exim monitor, a similar configuration process is
1809 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1810 your installation and saved under the name &_Local/eximon.conf_&. If you are
1811 happy with the default settings described in &_exim_monitor/EDITME_&,
1812 &_Local/eximon.conf_& can be empty, but it must exist.
1814 This is all the configuration that is needed in straightforward cases for known
1815 operating systems. However, the building process is set up so that it is easy
1816 to override options that are set by default or by operating-system-specific
1817 configuration files, for example to change the name of the C compiler, which
1818 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1823 .section "Support for iconv()" "SECID26"
1824 .cindex "&[iconv()]& support"
1826 The contents of header lines in messages may be encoded according to the rules
1827 described RFC 2047. This makes it possible to transmit characters that are not
1828 in the ASCII character set, and to label them as being in a particular
1829 character set. When Exim is inspecting header lines by means of the &%$h_%&
1830 mechanism, it decodes them, and translates them into a specified character set
1831 (default ISO-8859-1). The translation is possible only if the operating system
1832 supports the &[iconv()]& function.
1834 However, some of the operating systems that supply &[iconv()]& do not support
1835 very many conversions. The GNU &%libiconv%& library (available from
1836 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1837 systems to remedy this deficiency, as well as on systems that do not supply
1838 &[iconv()]& at all. After installing &%libiconv%&, you should add
1842 to your &_Local/Makefile_& and rebuild Exim.
1846 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1847 .cindex "TLS" "including support for TLS"
1848 .cindex "encryption" "including support for"
1849 .cindex "SUPPORT_TLS"
1850 .cindex "OpenSSL" "building Exim with"
1851 .cindex "GnuTLS" "building Exim with"
1852 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1853 command as per RFC 2487. It can also support legacy clients that expect to
1854 start a TLS session immediately on connection to a non-standard port (see the
1855 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1858 If you want to build Exim with TLS support, you must first install either the
1859 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1862 If OpenSSL is installed, you should set
1865 TLS_LIBS=-lssl -lcrypto
1867 in &_Local/Makefile_&. You may also need to specify the locations of the
1868 OpenSSL library and include files. For example:
1871 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1872 TLS_INCLUDE=-I/usr/local/openssl/include/
1874 .cindex "USE_GNUTLS"
1875 If GnuTLS is installed, you should set
1879 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1881 in &_Local/Makefile_&, and again you may need to specify the locations of the
1882 library and include files. For example:
1886 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1887 TLS_INCLUDE=-I/usr/gnu/include
1889 You do not need to set TLS_INCLUDE if the relevant directory is already
1890 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1891 given in chapter &<<CHAPTLS>>&.
1896 .section "Use of tcpwrappers" "SECID27"
1897 .cindex "tcpwrappers, building Exim to support"
1898 .cindex "USE_TCP_WRAPPERS"
1899 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1900 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1901 alternative to Exim's own checking facilities for installations that are
1902 already making use of &'tcpwrappers'& for other purposes. To do this, you
1903 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1904 &_tcpd.h_& to be available at compile time, and also ensure that the library
1905 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1906 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1909 USE_TCP_WRAPPERS=yes
1910 CFLAGS=-O -I/usr/local/include
1911 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1913 in &_Local/Makefile_&. The name to use in the &'tcpwrappers'& control files is
1914 &"exim"&. For example, the line
1916 exim : LOCAL 192.168.1. .friendly.domain.example
1918 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1919 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1920 All other connections are denied. Consult the &'tcpwrappers'& documentation for
1925 .section "Including support for IPv6" "SECID28"
1926 .cindex "IPv6" "including support for"
1927 Exim contains code for use on systems that have IPv6 support. Setting
1928 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1929 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1930 where the IPv6 support is not fully integrated into the normal include and
1933 Two different types of DNS record for handling IPv6 addresses have been
1934 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1935 currently seen as the mainstream. Another record type called A6 was proposed
1936 as better than AAAA because it had more flexibility. However, it was felt to be
1937 over-complex, and its status was reduced to &"experimental"&. It is not known
1938 if anyone is actually using A6 records. Exim has support for A6 records, but
1939 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1940 support has not been tested for some time.
1944 .section "The building process" "SECID29"
1945 .cindex "build directory"
1946 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
1947 created, run &'make'& at the top level. It determines the architecture and
1948 operating system types, and creates a build directory if one does not exist.
1949 For example, on a Sun system running Solaris 8, the directory
1950 &_build-SunOS5-5.8-sparc_& is created.
1951 .cindex "symbolic link" "to source files"
1952 Symbolic links to relevant source files are installed in the build directory.
1954 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
1955 building process fails if it is set.
1957 If this is the first time &'make'& has been run, it calls a script that builds
1958 a make file inside the build directory, using the configuration files from the
1959 &_Local_& directory. The new make file is then passed to another instance of
1960 &'make'&. This does the real work, building a number of utility scripts, and
1961 then compiling and linking the binaries for the Exim monitor (if configured), a
1962 number of utility programs, and finally Exim itself. The command &`make
1963 makefile`& can be used to force a rebuild of the make file in the build
1964 directory, should this ever be necessary.
1966 If you have problems building Exim, check for any comments there may be in the
1967 &_README_& file concerning your operating system, and also take a look at the
1968 FAQ, where some common problems are covered.
1972 .section 'Output from &"make"&' "SECID283"
1973 The output produced by the &'make'& process for compile lines is often very
1974 unreadable, because these lines can be very long. For this reason, the normal
1975 output is suppressed by default, and instead output similar to that which
1976 appears when compiling the 2.6 Linux kernel is generated: just a short line for
1977 each module that is being compiled or linked. However, it is still possible to
1978 get the full output, by calling &'make'& like this:
1982 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
1983 command reflection in &'make'&. When you ask for the full output, it is
1984 given in addition to the short output.
1988 .section "Overriding build-time options for Exim" "SECToverride"
1989 .cindex "build-time options, overriding"
1990 The main make file that is created at the beginning of the building process
1991 consists of the concatenation of a number of files which set configuration
1992 values, followed by a fixed set of &'make'& instructions. If a value is set
1993 more than once, the last setting overrides any previous ones. This provides a
1994 convenient way of overriding defaults. The files that are concatenated are, in
1997 &_OS/Makefile-Default_&
1998 &_OS/Makefile-_&<&'ostype'&>
2000 &_Local/Makefile-_&<&'ostype'&>
2001 &_Local/Makefile-_&<&'archtype'&>
2002 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2003 &_OS/Makefile-Base_&
2005 .cindex "&_Local/Makefile_&"
2006 .cindex "building Exim" "operating system type"
2007 .cindex "building Exim" "architecture type"
2008 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2009 architecture type. &_Local/Makefile_& is required to exist, and the building
2010 process fails if it is absent. The other three &_Local_& files are optional,
2011 and are often not needed.
2013 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2014 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2015 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2016 values are used, thereby providing a means of forcing particular settings.
2017 Otherwise, the scripts try to get values from the &%uname%& command. If this
2018 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2019 of &'ad hoc'& transformations are then applied, to produce the standard names
2020 that Exim expects. You can run these scripts directly from the shell in order
2021 to find out what values are being used on your system.
2024 &_OS/Makefile-Default_& contains comments about the variables that are set
2025 therein. Some (but not all) are mentioned below. If there is something that
2026 needs changing, review the contents of this file and the contents of the make
2027 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2031 .cindex "building Exim" "overriding default settings"
2032 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2033 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2034 need to change the original files. Instead, you should make the changes by
2035 putting the new values in an appropriate &_Local_& file. For example,
2036 .cindex "Tru64-Unix build-time settings"
2037 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2038 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2039 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2040 called with the option &%-std1%&, to make it recognize some of the features of
2041 Standard C that Exim uses. (Most other compilers recognize Standard C by
2042 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2043 containing the lines
2048 If you are compiling for just one operating system, it may be easier to put
2049 these lines directly into &_Local/Makefile_&.
2051 Keeping all your local configuration settings separate from the distributed
2052 files makes it easy to transfer them to new versions of Exim simply by copying
2053 the contents of the &_Local_& directory.
2056 .cindex "NIS lookup type" "including support for"
2057 .cindex "NIS+ lookup type" "including support for"
2058 .cindex "LDAP" "including support for"
2059 .cindex "lookup" "inclusion in binary"
2060 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2061 lookup, but not all systems have these components installed, so the default is
2062 not to include the relevant code in the binary. All the different kinds of file
2063 and database lookup that Exim supports are implemented as separate code modules
2064 which are included only if the relevant compile-time options are set. In the
2065 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2071 and similar settings apply to the other lookup types. They are all listed in
2072 &_src/EDITME_&. In many cases the relevant include files and interface
2073 libraries need to be installed before compiling Exim.
2074 .cindex "cdb" "including support for"
2075 However, there are some optional lookup types (such as cdb) for which
2076 the code is entirely contained within Exim, and no external include
2077 files or libraries are required. When a lookup type is not included in the
2078 binary, attempts to configure Exim to use it cause run time configuration
2081 .cindex "Perl" "including support for"
2082 Exim can be linked with an embedded Perl interpreter, allowing Perl
2083 subroutines to be called during string expansion. To enable this facility,
2087 must be defined in &_Local/Makefile_&. Details of this facility are given in
2088 chapter &<<CHAPperl>>&.
2090 .cindex "X11 libraries, location of"
2091 The location of the X11 libraries is something that varies a lot between
2092 operating systems, and there may be different versions of X11 to cope
2093 with. Exim itself makes no use of X11, but if you are compiling the Exim
2094 monitor, the X11 libraries must be available.
2095 The following three variables are set in &_OS/Makefile-Default_&:
2098 XINCLUDE=-I$(X11)/include
2099 XLFLAGS=-L$(X11)/lib
2101 These are overridden in some of the operating-system configuration files. For
2102 example, in &_OS/Makefile-SunOS5_& there is
2105 XINCLUDE=-I$(X11)/include
2106 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2108 If you need to override the default setting for your operating system, place a
2109 definition of all three of these variables into your
2110 &_Local/Makefile-<ostype>_& file.
2113 If you need to add any extra libraries to the link steps, these can be put in a
2114 variable called EXTRALIBS, which appears in all the link commands, but by
2115 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2116 command for linking the main Exim binary, and not for any associated utilities.
2118 .cindex "DBM libraries" "configuration for building"
2119 There is also DBMLIB, which appears in the link commands for binaries that
2120 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2121 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2122 binary, and which can be used, for example, to include additional X11
2125 .cindex "configuration file" "editing"
2126 The make file copes with rebuilding Exim correctly if any of the configuration
2127 files are edited. However, if an optional configuration file is deleted, it is
2128 necessary to touch the associated non-optional file (that is,
2129 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2132 .section "OS-specific header files" "SECID30"
2134 .cindex "building Exim" "OS-specific C header files"
2135 The &_OS_& directory contains a number of files with names of the form
2136 &_os.h-<ostype>_&. These are system-specific C header files that should not
2137 normally need to be changed. There is a list of macro settings that are
2138 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2139 are porting Exim to a new operating system.
2143 .section "Overriding build-time options for the monitor" "SECID31"
2144 .cindex "building Eximon"
2145 A similar process is used for overriding things when building the Exim monitor,
2146 where the files that are involved are
2148 &_OS/eximon.conf-Default_&
2149 &_OS/eximon.conf-_&<&'ostype'&>
2150 &_Local/eximon.conf_&
2151 &_Local/eximon.conf-_&<&'ostype'&>
2152 &_Local/eximon.conf-_&<&'archtype'&>
2153 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2155 .cindex "&_Local/eximon.conf_&"
2156 As with Exim itself, the final three files need not exist, and in this case the
2157 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2158 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2159 variables of the same name, preceded by EXIMON_. For example, setting
2160 EXIMON_LOG_DEPTH in the environment overrides the value of
2161 LOG_DEPTH at run time.
2165 .section "Installing Exim binaries and scripts" "SECID32"
2166 .cindex "installing Exim"
2167 .cindex "BIN_DIRECTORY"
2168 The command &`make install`& runs the &(exim_install)& script with no
2169 arguments. The script copies binaries and utility scripts into the directory
2170 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2171 .cindex "setuid" "installing Exim with"
2172 The install script copies files only if they are newer than the files they are
2173 going to replace. The Exim binary is required to be owned by root and have the
2174 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2175 install`& as root so that it can set up the Exim binary in this way. However, in
2176 some special situations (for example, if a host is doing no local deliveries)
2177 it may be possible to run Exim without making the binary setuid root (see
2178 chapter &<<CHAPsecurity>>& for details).
2180 .cindex "CONFIGURE_FILE"
2181 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2182 in &_Local/Makefile_&. If this names a single file, and the file does not
2183 exist, the default configuration file &_src/configure.default_& is copied there
2184 by the installation script. If a run time configuration file already exists, it
2185 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2186 alternative files, no default is installed.
2188 .cindex "system aliases file"
2189 .cindex "&_/etc/aliases_&"
2190 One change is made to the default configuration file when it is installed: the
2191 default configuration contains a router that references a system aliases file.
2192 The path to this file is set to the value specified by
2193 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2194 If the system aliases file does not exist, the installation script creates it,
2195 and outputs a comment to the user.
2197 The created file contains no aliases, but it does contain comments about the
2198 aliases a site should normally have. Mail aliases have traditionally been
2199 kept in &_/etc/aliases_&. However, some operating systems are now using
2200 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2201 Exim's configuration if necessary.
2203 The default configuration uses the local host's name as the only local domain,
2204 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2205 running as the local user. System aliases and &_.forward_& files in users' home
2206 directories are supported, but no NIS or NIS+ support is configured. Domains
2207 other than the name of the local host are routed using the DNS, with delivery
2210 It is possible to install Exim for special purposes (such as building a binary
2211 distribution) in a private part of the file system. You can do this by a
2214 make DESTDIR=/some/directory/ install
2216 This has the effect of pre-pending the specified directory to all the file
2217 paths, except the name of the system aliases file that appears in the default
2218 configuration. (If a default alias file is created, its name &'is'& modified.)
2219 For backwards compatibility, ROOT is used if DESTDIR is not set,
2220 but this usage is deprecated.
2222 .cindex "installing Exim" "what is not installed"
2223 Running &'make install'& does not copy the Exim 4 conversion script
2224 &'convert4r4'&. You will probably run this only once if you are
2225 upgrading from Exim 3. None of the documentation files in the &_doc_&
2226 directory are copied, except for the info files when you have set
2227 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2229 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2230 to their names. The Exim binary itself, however, is handled differently. It is
2231 installed under a name that includes the version number and the compile number,
2232 for example &_exim-&version;-1_&. The script then arranges for a symbolic link
2233 called &_exim_& to point to the binary. If you are updating a previous version
2234 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2235 from the directory (as seen by other processes).
2237 .cindex "installing Exim" "testing the script"
2238 If you want to see what the &'make install'& will do before running it for
2239 real, you can pass the &%-n%& option to the installation script by this
2242 make INSTALL_ARG=-n install
2244 The contents of the variable INSTALL_ARG are passed to the installation
2245 script. You do not need to be root to run this test. Alternatively, you can run
2246 the installation script directly, but this must be from within the build
2247 directory. For example, from the top-level Exim directory you could use this
2250 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2252 .cindex "installing Exim" "install script options"
2253 There are two other options that can be supplied to the installation script.
2256 &%-no_chown%& bypasses the call to change the owner of the installed binary
2257 to root, and the call to make it a setuid binary.
2259 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2263 INSTALL_ARG can be used to pass these options to the script. For example:
2265 make INSTALL_ARG=-no_symlink install
2267 The installation script can also be given arguments specifying which files are
2268 to be copied. For example, to install just the Exim binary, and nothing else,
2269 without creating the symbolic link, you could use:
2271 make INSTALL_ARG='-no_symlink exim' install
2276 .section "Installing info documentation" "SECTinsinfdoc"
2277 .cindex "installing Exim" "&'info'& documentation"
2278 Not all systems use the GNU &'info'& system for documentation, and for this
2279 reason, the Texinfo source of Exim's documentation is not included in the main
2280 distribution. Instead it is available separately from the ftp site (see section
2283 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2284 source of the documentation is found in the source tree, running &`make
2285 install`& automatically builds the info files and installs them.
2289 .section "Setting up the spool directory" "SECID33"
2290 .cindex "spool directory" "creating"
2291 When it starts up, Exim tries to create its spool directory if it does not
2292 exist. The Exim uid and gid are used for the owner and group of the spool
2293 directory. Sub-directories are automatically created in the spool directory as
2299 .section "Testing" "SECID34"
2300 .cindex "testing" "installation"
2301 Having installed Exim, you can check that the run time configuration file is
2302 syntactically valid by running the following command, which assumes that the
2303 Exim binary directory is within your PATH environment variable:
2307 If there are any errors in the configuration file, Exim outputs error messages.
2308 Otherwise it outputs the version number and build date,
2309 the DBM library that is being used, and information about which drivers and
2310 other optional code modules are included in the binary.
2311 Some simple routing tests can be done by using the address testing option. For
2314 &`exim -bt`& <&'local username'&>
2316 should verify that it recognizes a local mailbox, and
2318 &`exim -bt`& <&'remote address'&>
2320 a remote one. Then try getting it to deliver mail, both locally and remotely.
2321 This can be done by passing messages directly to Exim, without going through a
2322 user agent. For example:
2324 exim -v postmaster@your.domain.example
2325 From: user@your.domain.example
2326 To: postmaster@your.domain.example
2327 Subject: Testing Exim
2329 This is a test message.
2332 The &%-v%& option causes Exim to output some verification of what it is doing.
2333 In this case you should see copies of three log lines, one for the message's
2334 arrival, one for its delivery, and one containing &"Completed"&.
2336 .cindex "delivery" "problems with"
2337 If you encounter problems, look at Exim's log files (&'mainlog'& and
2338 &'paniclog'&) to see if there is any relevant information there. Another source
2339 of information is running Exim with debugging turned on, by specifying the
2340 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2341 with debugging turned on by a command of the form
2343 &`exim -d -M`& <&'exim-message-id'&>
2345 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2346 produces rather a lot of output, but you can cut this down to specific areas.
2347 For example, if you use &%-d-all+route%& only the debugging information
2348 relevant to routing is included. (See the &%-d%& option in chapter
2349 &<<CHAPcommandline>>& for more details.)
2351 .cindex '&"sticky"& bit'
2352 .cindex "lock files"
2353 One specific problem that has shown up on some sites is the inability to do
2354 local deliveries into a shared mailbox directory, because it does not have the
2355 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2356 writing to a mailbox file, and if it cannot create the lock file, the delivery
2357 is deferred. You can get round this either by setting the &"sticky bit"& on the
2358 directory, or by setting a specific group for local deliveries and allowing
2359 that group to create files in the directory (see the comments above the
2360 &(local_delivery)& transport in the default configuration file). Another
2361 approach is to configure Exim not to use lock files, but just to rely on
2362 &[fcntl()]& locking instead. However, you should do this only if all user
2363 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2364 see chapter &<<CHAPappendfile>>&.
2366 One thing that cannot be tested on a system that is already running an MTA is
2367 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2368 &%-oX%& option can be used to run an Exim daemon that listens on some other
2369 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2370 &'exim_checkaccess'& utility can be used to check out policy controls on
2373 Testing a new version on a system that is already running Exim can most easily
2374 be done by building a binary with a different CONFIGURE_FILE setting. From
2375 within the run time configuration, all other file and directory names
2376 that Exim uses can be altered, in order to keep it entirely clear of the
2380 .section "Replacing another MTA with Exim" "SECID35"
2381 .cindex "replacing another MTA"
2382 Building and installing Exim for the first time does not of itself put it in
2383 general use. The name by which the system's MTA is called by mail user agents
2384 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2385 operating system), and it is necessary to make this name point to the &'exim'&
2386 binary in order to get the user agents to pass messages to Exim. This is
2387 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2388 or &_/usr/lib/sendmail_&
2389 .cindex "symbolic link" "to &'exim'& binary"
2390 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2391 privilege and executable status from the old MTA. It is then necessary to stop
2392 and restart the mailer daemon, if one is running.
2394 .cindex "FreeBSD, MTA indirection"
2395 .cindex "&_/etc/mail/mailer.conf_&"
2396 Some operating systems have introduced alternative ways of switching MTAs. For
2397 example, if you are running FreeBSD, you need to edit the file
2398 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2399 described. A typical example of the contents of this file for running Exim is
2402 sendmail /usr/exim/bin/exim
2403 send-mail /usr/exim/bin/exim
2404 mailq /usr/exim/bin/exim -bp
2405 newaliases /usr/bin/true
2407 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2408 your Exim installation is &"live"&. Check it by sending a message from your
2409 favourite user agent.
2411 You should consider what to tell your users about the change of MTA. Exim may
2412 have different capabilities to what was previously running, and there are
2413 various operational differences such as the text of messages produced by
2414 command line options and in bounce messages. If you allow your users to make
2415 use of Exim's filtering capabilities, you should make the document entitled
2416 &'Exim's interface to mail filtering'& available to them.
2420 .section "Upgrading Exim" "SECID36"
2421 .cindex "upgrading Exim"
2422 If you are already running Exim on your host, building and installing a new
2423 version automatically makes it available to MUAs, or any other programs that
2424 call the MTA directly. However, if you are running an Exim daemon, you do need
2425 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2426 new binary. You do not need to stop processing mail in order to install a new
2427 version of Exim. The install script does not modify an existing runtime
2433 .section "Stopping the Exim daemon on Solaris" "SECID37"
2434 .cindex "Solaris" "stopping Exim on"
2435 The standard command for stopping the mailer daemon on Solaris is
2437 /etc/init.d/sendmail stop
2439 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2440 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2441 for the text &"sendmail"&; this is not present because the actual program name
2442 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2443 solution is to replace the line that finds the process id with something like
2445 pid=`cat /var/spool/exim/exim-daemon.pid`
2447 to obtain the daemon's pid directly from the file that Exim saves it in.
2449 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2450 still be received from local processes, and if automatic delivery is configured
2451 (the normal case), deliveries will still occur.
2456 . ////////////////////////////////////////////////////////////////////////////
2457 . ////////////////////////////////////////////////////////////////////////////
2459 .chapter "The Exim command line" "CHAPcommandline"
2460 .scindex IIDclo1 "command line" "options"
2461 .scindex IIDclo2 "options" "command line"
2462 Exim's command line takes the standard Unix form of a sequence of options,
2463 each starting with a hyphen character, followed by a number of arguments. The
2464 options are compatible with the main options of Sendmail, and there are also
2465 some additional options, some of which are compatible with Smail 3. Certain
2466 combinations of options do not make sense, and provoke an error if used.
2467 The form of the arguments depends on which options are set.
2470 .section "Setting options by program name" "SECID38"
2472 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2473 were present before any other options.
2474 The &%-bp%& option requests a listing of the contents of the mail queue on the
2476 This feature is for compatibility with some systems that contain a command of
2477 that name in one of the standard libraries, symbolically linked to
2478 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2481 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2482 were present before any other options, for compatibility with Smail. The
2483 &%-bS%& option is used for reading in a number of messages in batched SMTP
2487 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2488 &%-oee%& options were present before any other options, for compatibility with
2489 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2492 .cindex "queue runner"
2493 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2494 were present before any other options, for compatibility with Smail. The &%-q%&
2495 option causes a single queue runner process to be started.
2497 .cindex "&'newaliases'&"
2498 .cindex "alias file" "building"
2499 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2500 If Exim is called under the name &'newaliases'& it behaves as if the option
2501 &%-bi%& were present before any other options, for compatibility with Sendmail.
2502 This option is used for rebuilding Sendmail's alias file. Exim does not have
2503 the concept of a single alias file, but can be configured to run a given
2504 command if called with the &%-bi%& option.
2507 .section "Trusted and admin users" "SECTtrustedadmin"
2508 Some Exim options are available only to &'trusted users'& and others are
2509 available only to &'admin users'&. In the description below, the phrases &"Exim
2510 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2511 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2512 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2515 .cindex "trusted users" "definition of"
2516 .cindex "user" "trusted definition of"
2517 The trusted users are root, the Exim user, any user listed in the
2518 &%trusted_users%& configuration option, and any user whose current group or any
2519 supplementary group is one of those listed in the &%trusted_groups%&
2520 configuration option. Note that the Exim group is not automatically trusted.
2522 .cindex '&"From"& line'
2523 .cindex "envelope sender"
2524 Trusted users are always permitted to use the &%-f%& option or a leading
2525 &"From&~"& line to specify the envelope sender of a message that is passed to
2526 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2527 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2528 users to set envelope senders.
2530 .cindex "&'From:'& header line"
2531 .cindex "&'Sender:'& header line"
2532 For a trusted user, there is never any check on the contents of the &'From:'&
2533 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2534 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2536 Trusted users may also specify a host name, host address, interface address,
2537 protocol name, ident value, and authentication data when submitting a message
2538 locally. Thus, they are able to insert messages into Exim's queue locally that
2539 have the characteristics of messages received from a remote host. Untrusted
2540 users may in some circumstances use &%-f%&, but can never set the other values
2541 that are available to trusted users.
2543 .cindex "user" "admin definition of"
2544 .cindex "admin user" "definition of"
2545 The admin users are root, the Exim user, and any user that is a member of the
2546 Exim group or of any group listed in the &%admin_groups%& configuration option.
2547 The current group does not have to be one of these groups.
2549 Admin users are permitted to list the queue, and to carry out certain
2550 operations on messages, for example, to force delivery failures. It is also
2551 necessary to be an admin user in order to see the full information provided by
2552 the Exim monitor, and full debugging output.
2554 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2555 Exim to attempt delivery of messages on its queue is restricted to admin users.
2556 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2557 option false (that is, specifying &%no_prod_requires_admin%&).
2559 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2560 is restricted to admin users unless &%queue_list_requires_admin%& is set
2565 &*Warning*&: If you configure your system so that admin users are able to
2566 edit Exim's configuration file, you are giving those users an easy way of
2567 getting root. There is further discussion of this issue at the start of chapter
2573 .section "Command line options" "SECID39"
2574 Exim's command line options are described in alphabetical order below. If none
2575 of the options that specifies a specific action (such as starting the daemon or
2576 a queue runner, or testing an address, or receiving a message in a specific
2577 format, or listing the queue) are present, and there is at least one argument
2578 on the command line, &%-bm%& (accept a local message on the standard input,
2579 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2580 outputs a brief message about itself and exits.
2582 . ////////////////////////////////////////////////////////////////////////////
2583 . Insert a stylized XML comment here, to identify the start of the command line
2584 . options. This is for the benefit of the Perl script that automatically
2585 . creates a man page for the options.
2586 . ////////////////////////////////////////////////////////////////////////////
2589 <!-- === Start of command line options === -->
2596 .cindex "options" "command line; terminating"
2597 This is a pseudo-option whose only purpose is to terminate the options and
2598 therefore to cause subsequent command line items to be treated as arguments
2599 rather than options, even if they begin with hyphens.
2602 .oindex "&%--help%&"
2603 This option causes Exim to output a few sentences stating what it is.
2604 The same output is generated if the Exim binary is called with no options and
2607 .vitem &%--version%&
2608 .oindex "&%--version%&"
2609 This option is an alias for &%-bV%& and causes version information to be
2612 .vitem &%-B%&<&'type'&>
2614 .cindex "8-bit characters"
2615 .cindex "Sendmail compatibility" "8-bit characters"
2616 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2617 clean; it ignores this option.
2622 .cindex "SMTP" "listener"
2623 .cindex "queue runner"
2624 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2625 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2626 that the daemon should also initiate periodic queue runs.
2628 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2629 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2630 disconnect from the controlling terminal. When running this way, it can be
2631 stopped by pressing ctrl-C.
2633 By default, Exim listens for incoming connections to the standard SMTP port on
2634 all the host's running interfaces. However, it is possible to listen on other
2635 ports, on multiple ports, and only on specific interfaces. Chapter
2636 &<<CHAPinterfaces>>& contains a description of the options that control this.
2638 When a listening daemon
2639 .cindex "daemon" "process id (pid)"
2640 .cindex "pid (process id)" "of daemon"
2641 is started without the use of &%-oX%& (that is, without overriding the normal
2642 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2643 in Exim's spool directory. This location can be overridden by setting
2644 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2647 When &%-oX%& is used on the command line to start a listening daemon, the
2648 process id is not written to the normal pid file path. However, &%-oP%& can be
2649 used to specify a path on the command line if a pid file is required.
2653 .cindex "daemon" "restarting"
2654 can be used to cause the daemon to re-execute itself. This should be done
2655 whenever Exim's configuration file, or any file that is incorporated into it by
2656 means of the &%.include%& facility, is changed, and also whenever a new version
2657 of Exim is installed. It is not necessary to do this when other files that are
2658 referenced from the configuration (for example, alias files) are changed,
2659 because these are reread each time they are used.
2663 This option has the same effect as &%-bd%& except that it never disconnects
2664 from the controlling terminal, even when no debugging is specified.
2668 .cindex "testing" "string expansion"
2669 .cindex "expansion" "testing"
2670 Run Exim in expansion testing mode. Exim discards its root privilege, to
2671 prevent ordinary users from using this mode to read otherwise inaccessible
2672 files. If no arguments are given, Exim runs interactively, prompting for lines
2673 of data. Otherwise, it processes each argument in turn.
2675 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2676 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2677 used without command line arguments. If successful, it uses the &[readline()]&
2678 function, which provides extensive line-editing facilities, for reading the
2679 test data. A line history is supported.
2681 Long expansion expressions can be split over several lines by using backslash
2682 continuations. As in Exim's run time configuration, white space at the start of
2683 continuation lines is ignored. Each argument or data line is passed through the
2684 string expansion mechanism, and the result is output. Variable values from the
2685 configuration file (for example, &$qualify_domain$&) are available, but no
2686 message-specific values (such as &$sender_domain$&) are set, because no message
2687 is being processed (but see &%-bem%& and &%-Mset%&).
2689 &*Note*&: If you use this mechanism to test lookups, and you change the data
2690 files or databases you are using, you must exit and restart Exim before trying
2691 the same lookup again. Otherwise, because each Exim process caches the results
2692 of lookups, you will just get the same result as before.
2694 .vitem &%-bem%&&~<&'filename'&>
2696 .cindex "testing" "string expansion"
2697 .cindex "expansion" "testing"
2698 This option operates like &%-be%& except that it must be followed by the name
2699 of a file. For example:
2701 exim -bem /tmp/testmessage
2703 The file is read as a message (as if receiving a locally-submitted non-SMTP
2704 message) before any of the test expansions are done. Thus, message-specific
2705 variables such as &$message_size$& and &$header_from:$& are available. However,
2706 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2707 recipients are read from the headers in the normal way, and are shown in the
2708 &$recipients$& variable. Note that recipients cannot be given on the command
2709 line, because further arguments are taken as strings to expand (just like
2712 .vitem &%-bF%&&~<&'filename'&>
2714 .cindex "system filter" "testing"
2715 .cindex "testing" "system filter"
2716 This option is the same as &%-bf%& except that it assumes that the filter being
2717 tested is a system filter. The additional commands that are available only in
2718 system filters are recognized.
2720 .vitem &%-bf%&&~<&'filename'&>
2722 .cindex "filter" "testing"
2723 .cindex "testing" "filter file"
2724 .cindex "forward file" "testing"
2725 .cindex "testing" "forward file"
2726 .cindex "Sieve filter" "testing"
2727 This option runs Exim in user filter testing mode; the file is the filter file
2728 to be tested, and a test message must be supplied on the standard input. If
2729 there are no message-dependent tests in the filter, an empty file can be
2732 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2733 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2734 filter and a user filter in the same run. For example:
2736 exim -bF /system/filter -bf /user/filter </test/message
2738 This is helpful when the system filter adds header lines or sets filter
2739 variables that are used by the user filter.
2741 If the test filter file does not begin with one of the special lines
2746 it is taken to be a normal &_.forward_& file, and is tested for validity under
2747 that interpretation. See sections &<<SECTitenonfilred>>& to
2748 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2751 The result of an Exim command that uses &%-bf%&, provided no errors are
2752 detected, is a list of the actions that Exim would try to take if presented
2753 with the message for real. More details of filter testing are given in the
2754 separate document entitled &'Exim's interfaces to mail filtering'&.
2756 When testing a filter file,
2757 .cindex "&""From""& line"
2758 .cindex "envelope sender"
2759 .oindex "&%-f%&" "for filter testing"
2760 the envelope sender can be set by the &%-f%& option,
2761 or by a &"From&~"& line at the start of the test message. Various parameters
2762 that would normally be taken from the envelope recipient address of the message
2763 can be set by means of additional command line options (see the next four
2766 .vitem &%-bfd%&&~<&'domain'&>
2768 .vindex "&$qualify_domain$&"
2769 This sets the domain of the recipient address when a filter file is being
2770 tested by means of the &%-bf%& option. The default is the value of
2773 .vitem &%-bfl%&&~<&'local&~part'&>
2775 This sets the local part of the recipient address when a filter file is being
2776 tested by means of the &%-bf%& option. The default is the username of the
2777 process that calls Exim. A local part should be specified with any prefix or
2778 suffix stripped, because that is how it appears to the filter when a message is
2779 actually being delivered.
2781 .vitem &%-bfp%&&~<&'prefix'&>
2783 This sets the prefix of the local part of the recipient address when a filter
2784 file is being tested by means of the &%-bf%& option. The default is an empty
2787 .vitem &%-bfs%&&~<&'suffix'&>
2789 This sets the suffix of the local part of the recipient address when a filter
2790 file is being tested by means of the &%-bf%& option. The default is an empty
2793 .vitem &%-bh%&&~<&'IP&~address'&>
2795 .cindex "testing" "incoming SMTP"
2796 .cindex "SMTP" "testing incoming"
2797 .cindex "testing" "relay control"
2798 .cindex "relaying" "testing configuration"
2799 .cindex "policy control" "testing"
2800 .cindex "debugging" "&%-bh%& option"
2801 This option runs a fake SMTP session as if from the given IP address, using the
2802 standard input and output. The IP address may include a port number at the end,
2803 after a full stop. For example:
2805 exim -bh 10.9.8.7.1234
2806 exim -bh fe80::a00:20ff:fe86:a061.5678
2808 When an IPv6 address is given, it is converted into canonical form. In the case
2809 of the second example above, the value of &$sender_host_address$& after
2810 conversion to the canonical form is
2811 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2813 Comments as to what is going on are written to the standard error file. These
2814 include lines beginning with &"LOG"& for anything that would have been logged.
2815 This facility is provided for testing configuration options for incoming
2816 messages, to make sure they implement the required policy. For example, you can
2817 test your relay controls using &%-bh%&.
2821 You can test features of the configuration that rely on ident (RFC 1413)
2822 information by using the &%-oMt%& option. However, Exim cannot actually perform
2823 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2826 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2827 are also skipped when testing using &%-bh%&. If you want these callouts to
2828 occur, use &%-bhc%& instead.
2830 Messages supplied during the testing session are discarded, and nothing is
2831 written to any of the real log files. There may be pauses when DNS (and other)
2832 lookups are taking place, and of course these may time out. The &%-oMi%& option
2833 can be used to specify a specific IP interface and port if this is important,
2834 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2835 session were authenticated.
2837 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2838 output just states whether a given recipient address from a given host is
2839 acceptable or not. See section &<<SECTcheckaccess>>&.
2841 Features such as authentication and encryption, where the client input is not
2842 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2843 specialized SMTP test program such as
2844 &url(http://jetmore.org/john/code/#swaks,swaks).
2846 .vitem &%-bhc%&&~<&'IP&~address'&>
2848 This option operates in the same way as &%-bh%&, except that address
2849 verification callouts are performed if required. This includes consulting and
2850 updating the callout cache database.
2854 .cindex "alias file" "building"
2855 .cindex "building alias file"
2856 .cindex "Sendmail compatibility" "&%-bi%& option"
2857 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2858 Exim does not have the concept of a single alias file, and so it cannot mimic
2859 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2860 tend to appear in various scripts such as NIS make files, so the option must be
2863 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2864 configuration option is run, under the uid and gid of the caller of Exim. If
2865 the &%-oA%& option is used, its value is passed to the command as an argument.
2866 The command set by &%bi_command%& may not contain arguments. The command can
2867 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2868 if this is required. If the &%bi_command%& option is not set, calling Exim with
2873 .cindex "local message reception"
2874 This option runs an Exim receiving process that accepts an incoming,
2875 locally-generated message on the current input. The recipients are given as the
2876 command arguments (except when &%-t%& is also present &-- see below). Each
2877 argument can be a comma-separated list of RFC 2822 addresses. This is the
2878 default option for selecting the overall action of an Exim call; it is assumed
2879 if no other conflicting option is present.
2881 If any addresses in the message are unqualified (have no domain), they are
2882 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
2883 options, as appropriate. The &%-bnq%& option (see below) provides a way of
2884 suppressing this for special cases.
2886 Policy checks on the contents of local messages can be enforced by means of
2887 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
2889 .cindex "return code" "for &%-bm%&"
2890 The return code is zero if the message is successfully accepted. Otherwise, the
2891 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
2894 .cindex "message" "format"
2895 .cindex "format" "message"
2896 .cindex "&""From""& line"
2897 .cindex "UUCP" "&""From""& line"
2898 .cindex "Sendmail compatibility" "&""From""& line"
2899 of the message must be as defined in RFC 2822, except that, for
2900 compatibility with Sendmail and Smail, a line in one of the forms
2902 From sender Fri Jan 5 12:55 GMT 1997
2903 From sender Fri, 5 Jan 97 12:55:01
2905 (with the weekday optional, and possibly with additional text after the date)
2906 is permitted to appear at the start of the message. There appears to be no
2907 authoritative specification of the format of this line. Exim recognizes it by
2908 matching against the regular expression defined by the &%uucp_from_pattern%&
2909 option, which can be changed if necessary.
2911 .oindex "&%-f%&" "overriding &""From""& line"
2912 The specified sender is treated as if it were given as the argument to the
2913 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
2914 preference to the address taken from the message. The caller of Exim must be a
2915 trusted user for the sender of a message to be set in this way.
2919 .cindex "address qualification, suppressing"
2920 By default, Exim automatically qualifies unqualified addresses (those
2921 without domains) that appear in messages that are submitted locally (that
2922 is, not over TCP/IP). This qualification applies both to addresses in
2923 envelopes, and addresses in header lines. Sender addresses are qualified using
2924 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
2925 defaults to the value of &%qualify_domain%&).
2927 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
2928 being used to re-submit messages that originally came from remote hosts after
2929 content scanning, you probably do not want to qualify unqualified addresses in
2930 header lines. (Such lines will be present only if you have not enabled a header
2931 syntax check in the appropriate ACL.)
2933 The &%-bnq%& option suppresses all qualification of unqualified addresses in
2934 messages that originate on the local host. When this is used, unqualified
2935 addresses in the envelope provoke errors (causing message rejection) and
2936 unqualified addresses in header lines are left alone.
2941 .cindex "configuration options" "extracting"
2942 .cindex "options" "configuration &-- extracting"
2943 If this option is given with no arguments, it causes the values of all Exim's
2944 main configuration options to be written to the standard output. The values
2945 of one or more specific options can be requested by giving their names as
2946 arguments, for example:
2948 exim -bP qualify_domain hold_domains
2950 .cindex "hiding configuration option values"
2951 .cindex "configuration options" "hiding value of"
2952 .cindex "options" "hiding value of"
2953 However, any option setting that is preceded by the word &"hide"& in the
2954 configuration file is not shown in full, except to an admin user. For other
2955 users, the output is as in this example:
2957 mysql_servers = <value not displayable>
2959 If &%configure_file%& is given as an argument, the name of the run time
2960 configuration file is output.
2961 If a list of configuration files was supplied, the value that is output here
2962 is the name of the file that was actually used.
2964 .cindex "daemon" "process id (pid)"
2965 .cindex "pid (process id)" "of daemon"
2966 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
2967 directories where log files and daemon pid files are written are output,
2968 respectively. If these values are unset, log files are written in a
2969 sub-directory of the spool directory called &%log%&, and the pid file is
2970 written directly into the spool directory.
2972 If &%-bP%& is followed by a name preceded by &`+`&, for example,
2974 exim -bP +local_domains
2976 it searches for a matching named list of any type (domain, host, address, or
2977 local part) and outputs what it finds.
2979 .cindex "options" "router &-- extracting"
2980 .cindex "options" "transport &-- extracting"
2981 .cindex "options" "authenticator &-- extracting"
2982 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
2983 followed by the name of an appropriate driver instance, the option settings for
2984 that driver are output. For example:
2986 exim -bP transport local_delivery
2988 The generic driver options are output first, followed by the driver's private
2989 options. A list of the names of drivers of a particular type can be obtained by
2990 using one of the words &%router_list%&, &%transport_list%&, or
2991 &%authenticator_list%&, and a complete list of all drivers with their option
2992 settings can be obtained by using &%routers%&, &%transports%&, or
2995 .cindex "options" "macro &-- extracting"
2996 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
2997 are available, similarly to the drivers. Because macros are sometimes used
2998 for storing passwords, this option is restricted.
2999 The output format is one item per line.
3003 .cindex "queue" "listing messages on"
3004 .cindex "listing" "messages on the queue"
3005 This option requests a listing of the contents of the mail queue on the
3006 standard output. If the &%-bp%& option is followed by a list of message ids,
3007 just those messages are listed. By default, this option can be used only by an
3008 admin user. However, the &%queue_list_requires_admin%& option can be set false
3009 to allow any user to see the queue.
3011 Each message on the queue is displayed as in the following example:
3013 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3014 red.king@looking-glass.fict.example
3017 .cindex "message" "size in queue listing"
3018 .cindex "size" "of message"
3019 The first line contains the length of time the message has been on the queue
3020 (in this case 25 minutes), the size of the message (2.9K), the unique local
3021 identifier for the message, and the message sender, as contained in the
3022 envelope. For bounce messages, the sender address is empty, and appears as
3023 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3024 the default sender address, the user's login name is shown in parentheses
3025 before the sender address.
3027 .cindex "frozen messages" "in queue listing"
3028 If the message is frozen (attempts to deliver it are suspended) then the text
3029 &"*** frozen ***"& is displayed at the end of this line.
3031 The recipients of the message (taken from the envelope, not the headers) are
3032 displayed on subsequent lines. Those addresses to which the message has already
3033 been delivered are marked with the letter D. If an original address gets
3034 expanded into several addresses via an alias or forward file, the original is
3035 displayed with a D only when deliveries for all of its child addresses are
3041 This option operates like &%-bp%&, but in addition it shows delivered addresses
3042 that were generated from the original top level address(es) in each message by
3043 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3049 .cindex "queue" "count of messages on"
3050 This option counts the number of messages on the queue, and writes the total
3051 to the standard output. It is restricted to admin users, unless
3052 &%queue_list_requires_admin%& is set false.
3057 This option operates like &%-bp%&, but the output is not sorted into
3058 chronological order of message arrival. This can speed it up when there are
3059 lots of messages on the queue, and is particularly useful if the output is
3060 going to be post-processed in a way that doesn't need the sorting.
3064 This option is a combination of &%-bpr%& and &%-bpa%&.
3068 This option is a combination of &%-bpr%& and &%-bpu%&.
3073 This option operates like &%-bp%& but shows only undelivered top-level
3074 addresses for each message displayed. Addresses generated by aliasing or
3075 forwarding are not shown, unless the message was deferred after processing by a
3076 router with the &%one_time%& option set.
3081 .cindex "testing" "retry configuration"
3082 .cindex "retry" "configuration testing"
3083 This option is for testing retry rules, and it must be followed by up to three
3084 arguments. It causes Exim to look for a retry rule that matches the values
3085 and to write it to the standard output. For example:
3087 exim -brt bach.comp.mus.example
3088 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3090 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3091 argument, which is required, can be a complete address in the form
3092 &'local_part@domain'&, or it can be just a domain name. If the second argument
3093 contains a dot, it is interpreted as an optional second domain name; if no
3094 retry rule is found for the first argument, the second is tried. This ties in
3095 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3096 rule is found that matches the host, one that matches the mail domain is
3097 sought. Finally, an argument that is the name of a specific delivery error, as
3098 used in setting up retry rules, can be given. For example:
3100 exim -brt haydn.comp.mus.example quota_3d
3101 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3106 .cindex "testing" "rewriting"
3107 .cindex "rewriting" "testing"
3108 This option is for testing address rewriting rules, and it must be followed by
3109 a single argument, consisting of either a local part without a domain, or a
3110 complete address with a fully qualified domain. Exim outputs how this address
3111 would be rewritten for each possible place it might appear. See chapter
3112 &<<CHAPrewrite>>& for further details.
3116 .cindex "SMTP" "batched incoming"
3117 .cindex "batched SMTP input"
3118 This option is used for batched SMTP input, which is an alternative interface
3119 for non-interactive local message submission. A number of messages can be
3120 submitted in a single run. However, despite its name, this is not really SMTP
3121 input. Exim reads each message's envelope from SMTP commands on the standard
3122 input, but generates no responses. If the caller is trusted, or
3123 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3124 believed; otherwise the sender is always the caller of Exim.
3126 The message itself is read from the standard input, in SMTP format (leading
3127 dots doubled), terminated by a line containing just a single dot. An error is
3128 provoked if the terminating dot is missing. A further message may then follow.
3130 As for other local message submissions, the contents of incoming batch SMTP
3131 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3132 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3133 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3135 Some other SMTP commands are recognized in the input. HELO and EHLO act
3136 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3137 QUIT quits, ignoring the rest of the standard input.
3139 .cindex "return code" "for &%-bS%&"
3140 If any error is encountered, reports are written to the standard output and
3141 error streams, and Exim gives up immediately. The return code is 0 if no error
3142 was detected; it is 1 if one or more messages were accepted before the error
3143 was detected; otherwise it is 2.
3145 More details of input using batched SMTP are given in section
3146 &<<SECTincomingbatchedSMTP>>&.
3150 .cindex "SMTP" "local input"
3151 .cindex "local SMTP input"
3152 This option causes Exim to accept one or more messages by reading SMTP commands
3153 on the standard input, and producing SMTP replies on the standard output. SMTP
3154 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3155 Some user agents use this interface as a way of passing locally-generated
3156 messages to the MTA.
3159 .cindex "sender" "source of"
3160 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3161 set, the senders of messages are taken from the SMTP MAIL commands.
3162 Otherwise the content of these commands is ignored and the sender is set up as
3163 the calling user. Unqualified addresses are automatically qualified using
3164 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3165 &%-bnq%& option is used.
3169 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3170 using a listening daemon. Exim can distinguish the two cases by checking
3171 whether the standard input is a TCP/IP socket. When Exim is called from
3172 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3173 above concerning senders and qualification do not apply. In this situation,
3174 Exim behaves in exactly the same way as it does when receiving a message via
3175 the listening daemon.
3177 .vitem &%-bmalware%&&~<&'filename'&>
3178 .oindex "&%-bmalware%&"
3179 .cindex "testing", "malware"
3180 .cindex "malware scan test"
3181 This debugging option causes Exim to scan the given file,
3182 using the malware scanning framework. The option of av_scanner influences
3183 this option, so if av_scanner's value is dependent upon an expansion then
3184 the expansion should have defaults which apply to this invocation. Exim will
3185 have changed working directory before resolving the filename, so using fully
3186 qualified pathnames is advisable. Exim will be running as the Exim user
3187 when it tries to open the file, rather than as the invoking user.
3188 This option requires admin privileges.
3190 The &%-bmalware%& option will not be extended to be more generally useful,
3191 there are better tools for file-scanning. This option exists to help
3192 administrators verify their Exim and AV scanner configuration.
3196 .cindex "testing" "addresses"
3197 .cindex "address" "testing"
3198 This option runs Exim in address testing mode, in which each argument is taken
3199 as a recipient address to be tested for deliverability. The results are
3200 written to the standard output. If a test fails, and the caller is not an admin
3201 user, no details of the failure are output, because these might contain
3202 sensitive information such as usernames and passwords for database lookups.
3204 If no arguments are given, Exim runs in an interactive manner, prompting with a
3205 right angle bracket for addresses to be tested.
3207 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3208 &[readline()]& function, because it is running as &'root'& and there are
3211 Each address is handled as if it were the recipient address of a message
3212 (compare the &%-bv%& option). It is passed to the routers and the result is
3213 written to the standard output. However, any router that has
3214 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3215 genuine routing tests if your first router passes everything to a scanner
3218 .cindex "return code" "for &%-bt%&"
3219 The return code is 2 if any address failed outright; it is 1 if no address
3220 failed outright but at least one could not be resolved for some reason. Return
3221 code 0 is given only when all addresses succeed.
3223 .cindex "duplicate addresses"
3224 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3225 addresses after routing is complete, so that only one delivery takes place.
3226 This does not happen when testing with &%-bt%&; the full results of routing are
3229 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3230 routers in the configuration makes any tests on the sender address of a
3232 .oindex "&%-f%&" "for address testing"
3233 you can use the &%-f%& option to set an appropriate sender when running
3234 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3235 default qualifying domain. However, if you have set up (for example) routers
3236 whose behaviour depends on the contents of an incoming message, you cannot test
3237 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3242 .cindex "version number of Exim"
3243 This option causes Exim to write the current version number, compilation
3244 number, and compilation date of the &'exim'& binary to the standard output.
3245 It also lists the DBM library this is being used, the optional modules (such as
3246 specific lookup types), the drivers that are included in the binary, and the
3247 name of the run time configuration file that is in use.
3249 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3250 configuration file. However, this is a static check only. It cannot check
3251 values that are to be expanded. For example, although a misspelt ACL verb is
3252 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3253 alone to discover (for example) all the typos in the configuration; some
3254 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3255 dynamic testing facilities.
3259 .cindex "verifying address" "using &%-bv%&"
3260 .cindex "address" "verification"
3261 This option runs Exim in address verification mode, in which each argument is
3262 taken as a recipient address to be verified by the routers. (This does
3263 not involve any verification callouts). During normal operation, verification
3264 happens mostly as a consequence processing a &%verify%& condition in an ACL
3265 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3266 including callouts, see the &%-bh%& and &%-bhc%& options.
3268 If verification fails, and the caller is not an admin user, no details of the
3269 failure are output, because these might contain sensitive information such as
3270 usernames and passwords for database lookups.
3272 If no arguments are given, Exim runs in an interactive manner, prompting with a
3273 right angle bracket for addresses to be verified.
3275 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3276 &[readline()]& function, because it is running as &'exim'& and there are
3279 Verification differs from address testing (the &%-bt%& option) in that routers
3280 that have &%no_verify%& set are skipped, and if the address is accepted by a
3281 router that has &%fail_verify%& set, verification fails. The address is
3282 verified as a recipient if &%-bv%& is used; to test verification for a sender
3283 address, &%-bvs%& should be used.
3285 If the &%-v%& option is not set, the output consists of a single line for each
3286 address, stating whether it was verified or not, and giving a reason in the
3287 latter case. Without &%-v%&, generating more than one address by redirection
3288 causes verification to end successfully, without considering the generated
3289 addresses. However, if just one address is generated, processing continues,
3290 and the generated address must verify successfully for the overall verification
3293 When &%-v%& is set, more details are given of how the address has been handled,
3294 and in the case of address redirection, all the generated addresses are also
3295 considered. Verification may succeed for some and fail for others.
3298 .cindex "return code" "for &%-bv%&"
3299 return code is 2 if any address failed outright; it is 1 if no address
3300 failed outright but at least one could not be resolved for some reason. Return
3301 code 0 is given only when all addresses succeed.
3303 If any of the routers in the configuration makes any tests on the sender
3304 address of a message, you should use the &%-f%& option to set an appropriate
3305 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3306 calling user at the default qualifying domain.
3310 This option acts like &%-bv%&, but verifies the address as a sender rather
3311 than a recipient address. This affects any rewriting and qualification that
3314 .vitem &%-C%&&~<&'filelist'&>
3316 .cindex "configuration file" "alternate"
3317 .cindex "CONFIGURE_FILE"
3318 .cindex "alternate configuration file"
3319 This option causes Exim to find the run time configuration file from the given
3320 list instead of from the list specified by the CONFIGURE_FILE
3321 compile-time setting. Usually, the list will consist of just a single file
3322 name, but it can be a colon-separated list of names. In this case, the first
3323 file that exists is used. Failure to open an existing file stops Exim from
3324 proceeding any further along the list, and an error is generated.
3326 When this option is used by a caller other than root or the Exim user, and the
3327 list is different from the compiled-in list, Exim gives up its root privilege
3328 immediately, and runs with the real and effective uid and gid set to those of
3329 the caller. However, if ALT_CONFIG_ROOT_ONLY is defined in
3330 &_Local/Makefile_&, root privilege is retained for &%-C%& only if the caller of
3333 That is, the Exim user is no longer privileged in this regard. This build-time
3334 option is not set by default in the Exim source distribution tarbundle.
3335 However, if you are using a &"packaged"& version of Exim (source or binary),
3336 the packagers might have enabled it.
3338 Setting ALT_CONFIG_ROOT_ONLY locks out the possibility of testing a
3339 configuration using &%-C%& right through message reception and delivery, even
3340 if the caller is root. The reception works, but by that time, Exim is running
3341 as the Exim user, so when it re-executes to regain privilege for the delivery,
3342 the use of &%-C%& causes privilege to be lost. However, root can test reception
3343 and delivery using two separate commands (one to put a message on the queue,
3344 using &%-odq%&, and another to do the delivery, using &%-M%&).
3346 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3347 prefix string with which any file named in a &%-C%& command line option
3348 must start. In addition, the file name must not contain the sequence &`/../`&.
3349 However, if the value of the &%-C%& option is identical to the value of
3350 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3351 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3352 unset, any file name can be used with &%-C%&.
3354 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3355 to a directory to which only root has access. This prevents someone who has
3356 broken into the Exim account from running a privileged Exim with an arbitrary
3359 The &%-C%& facility is useful for ensuring that configuration files are
3360 syntactically correct, but cannot be used for test deliveries, unless the
3361 caller is privileged, or unless it is an exotic configuration that does not
3362 require privilege. No check is made on the owner or group of the files
3363 specified by this option.
3365 .vitem &%-D%&<&'macro'&>=<&'value'&>
3367 .cindex "macro" "setting on command line"
3368 This option can be used to override macro definitions in the configuration file
3369 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3370 unprivileged caller, it causes Exim to give up its root privilege.
3371 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3372 completely disabled, and its use causes an immediate error exit.
3374 The entire option (including equals sign if present) must all be within one
3375 command line item. &%-D%& can be used to set the value of a macro to the empty
3376 string, in which case the equals sign is optional. These two commands are
3382 To include spaces in a macro definition item, quotes must be used. If you use
3383 quotes, spaces are permitted around the macro name and the equals sign. For
3386 exim '-D ABC = something' ...
3388 &%-D%& may be repeated up to 10 times on a command line.
3390 .vitem &%-d%&<&'debug&~options'&>
3392 .cindex "debugging" "list of selectors"
3393 .cindex "debugging" "&%-d%& option"
3394 This option causes debugging information to be written to the standard
3395 error stream. It is restricted to admin users because debugging output may show
3396 database queries that contain password information. Also, the details of users'
3397 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3398 writes an error message to the standard error stream and exits with a non-zero
3401 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3402 standard debugging data is output. This can be reduced, or increased to include
3403 some more rarely needed information, by directly following &%-d%& with a string
3404 made up of names preceded by plus or minus characters. These add or remove sets
3405 of debugging data, respectively. For example, &%-d+filter%& adds filter
3406 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3407 no spaces are allowed in the debug setting. The available debugging categories
3410 &`acl `& ACL interpretation
3411 &`auth `& authenticators
3412 &`deliver `& general delivery logic
3413 &`dns `& DNS lookups (see also resolver)
3414 &`dnsbl `& DNS black list (aka RBL) code
3415 &`exec `& arguments for &[execv()]& calls
3416 &`expand `& detailed debugging for string expansions
3417 &`filter `& filter handling
3418 &`hints_lookup `& hints data lookups
3419 &`host_lookup `& all types of name-to-IP address handling
3420 &`ident `& ident lookup
3421 &`interface `& lists of local interfaces
3422 &`lists `& matching things in lists
3423 &`load `& system load checks
3424 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3425 &<<CHAPlocalscan>>&)
3426 &`lookup `& general lookup code and all lookups
3427 &`memory `& memory handling
3428 &`pid `& add pid to debug output lines
3429 &`process_info `& setting info for the process log
3430 &`queue_run `& queue runs
3431 &`receive `& general message reception logic
3432 &`resolver `& turn on the DNS resolver's debugging output
3433 &`retry `& retry handling
3434 &`rewrite `& address rewriting
3435 &`route `& address routing
3436 &`timestamp `& add timestamp to debug output lines
3438 &`transport `& transports
3439 &`uid `& changes of uid/gid and looking up uid/gid
3440 &`verify `& address verification logic
3441 &`all `& almost all of the above (see below), and also &%-v%&
3443 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3444 for &`-all`&. The reason for this is that &`+all`& is something that people
3445 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3446 is included, an awful lot of output that is very rarely of interest is
3447 generated, so it now has to be explicitly requested. However, &`-all`& does
3448 turn everything off.
3450 .cindex "resolver, debugging output"
3451 .cindex "DNS resolver, debugging output"
3452 The &`resolver`& option produces output only if the DNS resolver was compiled
3453 with DEBUG enabled. This is not the case in some operating systems. Also,
3454 unfortunately, debugging output from the DNS resolver is written to stdout
3457 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3458 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3459 However, the &`pid`& selector is forced when debugging is turned on for a
3460 daemon, which then passes it on to any re-executed Exims. Exim also
3461 automatically adds the pid to debug lines when several remote deliveries are
3464 The &`timestamp`& selector causes the current time to be inserted at the start
3465 of all debug output lines. This can be useful when trying to track down delays
3468 If the &%debug_print%& option is set in any driver, it produces output whenever
3469 any debugging is selected, or if &%-v%& is used.
3471 .vitem &%-dd%&<&'debug&~options'&>
3473 This option behaves exactly like &%-d%& except when used on a command that
3474 starts a daemon process. In that case, debugging is turned off for the
3475 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3476 behaviour of the daemon without creating as much output as full debugging does.
3479 .oindex "&%-dropcr%&"
3480 This is an obsolete option that is now a no-op. It used to affect the way Exim
3481 handled CR and LF characters in incoming messages. What happens now is
3482 described in section &<<SECTlineendings>>&.
3486 .cindex "bounce message" "generating"
3487 This option specifies that an incoming message is a locally-generated delivery
3488 failure report. It is used internally by Exim when handling delivery failures
3489 and is not intended for external use. Its only effect is to stop Exim
3490 generating certain messages to the postmaster, as otherwise message cascades
3491 could occur in some situations. As part of the same option, a message id may
3492 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3493 new message contains the id, following &"R="&, as a cross-reference.
3496 .oindex "&%-e%&&'x'&"
3497 There are a number of Sendmail options starting with &%-oe%& which seem to be
3498 called by various programs without the leading &%o%& in the option. For
3499 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3500 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3502 .vitem &%-F%&&~<&'string'&>
3504 .cindex "sender" "name"
3505 .cindex "name" "of sender"
3506 This option sets the sender's full name for use when a locally-generated
3507 message is being accepted. In the absence of this option, the user's &'gecos'&
3508 entry from the password data is used. As users are generally permitted to alter
3509 their &'gecos'& entries, no security considerations are involved. White space
3510 between &%-F%& and the <&'string'&> is optional.
3512 .vitem &%-f%&&~<&'address'&>
3514 .cindex "sender" "address"
3515 .cindex "address" "sender"
3516 .cindex "trusted users"
3517 .cindex "envelope sender"
3518 .cindex "user" "trusted"
3519 This option sets the address of the envelope sender of a locally-generated
3520 message (also known as the return path). The option can normally be used only
3521 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3524 Processes running as root or the Exim user are always trusted. Other
3525 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3526 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3527 of a local message is set to the caller's login name at the default qualify
3530 There is one exception to the restriction on the use of &%-f%&: an empty sender
3531 can be specified by any user, trusted or not, to create a message that can
3532 never provoke a bounce. An empty sender can be specified either as an empty
3533 string, or as a pair of angle brackets with nothing between them, as in these
3534 examples of shell commands:
3536 exim -f '<>' user@domain
3537 exim -f "" user@domain
3539 In addition, the use of &%-f%& is not restricted when testing a filter file
3540 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3543 Allowing untrusted users to change the sender address does not of itself make
3544 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3545 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3546 though this can be overridden by setting &%no_local_from_check%&.
3549 .cindex "&""From""& line"
3550 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3551 given as two arguments or one combined argument). The sender of a
3552 locally-generated message can also be set (when permitted) by an initial
3553 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3554 if &%-f%& is also present, it overrides &"From&~"&.
3558 .cindex "Sendmail compatibility" "&%-G%& option ignored"
3559 This is a Sendmail option which is ignored by Exim.
3561 .vitem &%-h%&&~<&'number'&>
3563 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3564 This option is accepted for compatibility with Sendmail, but has no effect. (In
3565 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3570 .cindex "Solaris" "&'mail'& command"
3571 .cindex "dot" "in incoming non-SMTP message"
3572 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3573 line by itself should not terminate an incoming, non-SMTP message. I can find
3574 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3575 command in Solaris 2.4 uses it. See also &%-ti%&.
3577 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3579 .cindex "forcing delivery"
3580 .cindex "delivery" "forcing attempt"
3581 .cindex "frozen messages" "forcing delivery"
3582 This option requests Exim to run a delivery attempt on each message in turn. If
3583 any of the messages are frozen, they are automatically thawed before the
3584 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3585 and &%hold_domains%& are ignored.
3588 .cindex "hints database" "overriding retry hints"
3589 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3590 the normal retry time has not yet been reached. This option requires the caller
3591 to be an admin user. However, there is an option called &%prod_requires_admin%&
3592 which can be set false to relax this restriction (and also the same requirement
3593 for the &%-q%&, &%-R%&, and &%-S%& options).
3595 The deliveries happen synchronously, that is, the original Exim process does
3596 not terminate until all the delivery attempts have finished. No output is
3597 produced unless there is a serious error. If you want to see what is happening,
3598 use the &%-v%& option as well, or inspect Exim's main log.
3600 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3602 .cindex "message" "adding recipients"
3603 .cindex "recipient" "adding"
3604 This option requests Exim to add the addresses to the list of recipients of the
3605 message (&"ar"& for &"add recipients"&). The first argument must be a message
3606 id, and the remaining ones must be email addresses. However, if the message is
3607 active (in the middle of a delivery attempt), it is not altered. This option
3608 can be used only by an admin user.
3610 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3611 &~<&'message&~id'&>"
3613 .cindex "SMTP" "passed connection"
3614 .cindex "SMTP" "multiple deliveries"
3615 .cindex "multiple SMTP deliveries"
3616 This option is not intended for use by external callers. It is used internally
3617 by Exim to invoke another instance of itself to deliver a waiting message using
3618 an existing SMTP connection, which is passed as the standard input. Details are
3619 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3620 must be root or the Exim user in order to use it.
3624 This option is not intended for use by external callers. It is used internally
3625 by Exim in conjunction with the &%-MC%& option. It signifies that the
3626 connection to the remote host has been authenticated.
3630 This option is not intended for use by external callers. It is used internally
3631 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3632 which Exim is connected supports pipelining.
3634 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3636 This option is not intended for use by external callers. It is used internally
3637 by Exim in conjunction with the &%-MC%& option when the original delivery was
3638 started by a queue runner. It passes on the process id of the queue runner,
3639 together with the file descriptor number of an open pipe. Closure of the pipe
3640 signals the final completion of the sequence of processes that are passing
3641 messages through the same SMTP connection.
3645 This option is not intended for use by external callers. It is used internally
3646 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3647 SMTP SIZE option should be used on messages delivered down the existing
3652 This option is not intended for use by external callers. It is used internally
3653 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3654 host to which Exim is connected supports TLS encryption.
3656 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3658 .cindex "hints database" "not overridden by &%-Mc%&"
3659 .cindex "delivery" "manually started &-- not forced"
3660 This option requests Exim to run a delivery attempt on each message in turn,
3661 but unlike the &%-M%& option, it does check for retry hints, and respects any
3662 that are found. This option is not very useful to external callers. It is
3663 provided mainly for internal use by Exim when it needs to re-invoke itself in
3664 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3665 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3666 respects retry times and other options such as &%hold_domains%& that are
3667 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3668 If you want to run a specific delivery as if in a queue run, you should use
3669 &%-q%& with a message id argument. A distinction between queue run deliveries
3670 and other deliveries is made in one or two places.
3672 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3674 .cindex "message" "changing sender"
3675 .cindex "sender" "changing"
3676 This option requests Exim to change the sender address in the message to the
3677 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3678 &"edit sender"&). There must be exactly two arguments. The first argument must
3679 be a message id, and the second one an email address. However, if the message
3680 is active (in the middle of a delivery attempt), its status is not altered.
3681 This option can be used only by an admin user.
3683 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3685 .cindex "freezing messages"
3686 .cindex "message" "manually freezing"
3687 This option requests Exim to mark each listed message as &"frozen"&. This
3688 prevents any delivery attempts taking place until the message is &"thawed"&,
3689 either manually or as a result of the &%auto_thaw%& configuration option.
3690 However, if any of the messages are active (in the middle of a delivery
3691 attempt), their status is not altered. This option can be used only by an admin
3694 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3696 .cindex "giving up on messages"
3697 .cindex "message" "abandoning delivery attempts"
3698 .cindex "delivery" "abandoning further attempts"
3699 This option requests Exim to give up trying to deliver the listed messages,
3700 including any that are frozen. However, if any of the messages are active,
3701 their status is not altered. For non-bounce messages, a delivery error message
3702 is sent to the sender, containing the text &"cancelled by administrator"&.
3703 Bounce messages are just discarded. This option can be used only by an admin
3706 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3708 .cindex "delivery" "cancelling all"
3709 This option requests Exim to mark all the recipient addresses in the messages
3710 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3711 message is active (in the middle of a delivery attempt), its status is not
3712 altered. This option can be used only by an admin user.
3714 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3716 .cindex "delivery" "cancelling by address"
3717 .cindex "recipient" "removing"
3718 .cindex "removing recipients"
3719 This option requests Exim to mark the given addresses as already delivered
3720 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3721 the remaining ones must be email addresses. These are matched to recipient
3722 addresses in the message in a case-sensitive manner. If the message is active
3723 (in the middle of a delivery attempt), its status is not altered. This option
3724 can be used only by an admin user.
3726 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3728 .cindex "removing messages"
3729 .cindex "abandoning mail"
3730 .cindex "message" "manually discarding"
3731 This option requests Exim to remove the given messages from the queue. No
3732 bounce messages are sent; each message is simply forgotten. However, if any of
3733 the messages are active, their status is not altered. This option can be used
3734 only by an admin user or by the user who originally caused the message to be
3735 placed on the queue.
3737 .vitem &%-Mset%&&~<&'message&~id'&>
3739 .cindex "testing" "string expansion"
3740 .cindex "expansion" "testing"
3741 This option is useful only in conjunction with &%-be%& (that is, when testing
3742 string expansions). Exim loads the given message from its spool before doing
3743 the test expansions, thus setting message-specific variables such as
3744 &$message_size$& and the header variables. The &$recipients$& variable is made
3745 available. This feature is provided to make it easier to test expansions that
3746 make use of these variables. However, this option can be used only by an admin
3747 user. See also &%-bem%&.
3749 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3751 .cindex "thawing messages"
3752 .cindex "unfreezing messages"
3753 .cindex "frozen messages" "thawing"
3754 .cindex "message" "thawing frozen"
3755 This option requests Exim to &"thaw"& any of the listed messages that are
3756 &"frozen"&, so that delivery attempts can resume. However, if any of the
3757 messages are active, their status is not altered. This option can be used only
3760 .vitem &%-Mvb%&&~<&'message&~id'&>
3762 .cindex "listing" "message body"
3763 .cindex "message" "listing body of"
3764 This option causes the contents of the message body (-D) spool file to be
3765 written to the standard output. This option can be used only by an admin user.
3767 .vitem &%-Mvc%&&~<&'message&~id'&>
3769 .cindex "message" "listing in RFC 2822 format"
3770 .cindex "listing" "message in RFC 2822 format"
3771 This option causes a copy of the complete message (header lines plus body) to
3772 be written to the standard output in RFC 2822 format. This option can be used
3773 only by an admin user.
3775 .vitem &%-Mvh%&&~<&'message&~id'&>
3777 .cindex "listing" "message headers"
3778 .cindex "header lines" "listing"
3779 .cindex "message" "listing header lines"
3780 This option causes the contents of the message headers (-H) spool file to be
3781 written to the standard output. This option can be used only by an admin user.
3783 .vitem &%-Mvl%&&~<&'message&~id'&>
3785 .cindex "listing" "message log"
3786 .cindex "message" "listing message log"
3787 This option causes the contents of the message log spool file to be written to
3788 the standard output. This option can be used only by an admin user.
3792 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3793 treats it that way too.
3797 .cindex "debugging" "&%-N%& option"
3798 .cindex "debugging" "suppressing delivery"
3799 This is a debugging option that inhibits delivery of a message at the transport
3800 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3801 it just doesn't actually transport the message, but instead behaves as if it
3802 had successfully done so. However, it does not make any updates to the retry
3803 database, and the log entries for deliveries are flagged with &"*>"& rather
3806 Because &%-N%& discards any message to which it applies, only root or the Exim
3807 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3808 words, an ordinary user can use it only when supplying an incoming message to
3809 which it will apply. Although transportation never fails when &%-N%& is set, an
3810 address may be deferred because of a configuration problem on a transport, or a
3811 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3812 the message, and applies to any subsequent delivery attempts that may happen
3817 .cindex "Sendmail compatibility" "&%-n%& option ignored"
3818 This option is interpreted by Sendmail to mean &"no aliasing"&. It is ignored
3821 .vitem &%-O%&&~<&'data'&>
3823 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
3826 .vitem &%-oA%&&~<&'file&~name'&>
3828 .cindex "Sendmail compatibility" "&%-oA%& option"
3829 This option is used by Sendmail in conjunction with &%-bi%& to specify an
3830 alternative alias file name. Exim handles &%-bi%& differently; see the
3833 .vitem &%-oB%&&~<&'n'&>
3835 .cindex "SMTP" "passed connection"
3836 .cindex "SMTP" "multiple deliveries"
3837 .cindex "multiple SMTP deliveries"
3838 This is a debugging option which limits the maximum number of messages that can
3839 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
3840 transport. If <&'n'&> is omitted, the limit is set to 1.
3844 .cindex "background delivery"
3845 .cindex "delivery" "in the background"
3846 This option applies to all modes in which Exim accepts incoming messages,
3847 including the listening daemon. It requests &"background"& delivery of such
3848 messages, which means that the accepting process automatically starts a
3849 delivery process for each message received, but does not wait for the delivery
3850 processes to finish.
3852 When all the messages have been received, the reception process exits,
3853 leaving the delivery processes to finish in their own time. The standard output
3854 and error streams are closed at the start of each delivery process.
3855 This is the default action if none of the &%-od%& options are present.
3857 If one of the queueing options in the configuration file
3858 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
3859 overrides it if &%queue_only_override%& is set true, which is the default
3860 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
3864 .cindex "foreground delivery"
3865 .cindex "delivery" "in the foreground"
3866 This option requests &"foreground"& (synchronous) delivery when Exim has
3867 accepted a locally-generated message. (For the daemon it is exactly the same as
3868 &%-odb%&.) A delivery process is automatically started to deliver the message,
3869 and Exim waits for it to complete before proceeding.
3871 The original Exim reception process does not finish until the delivery
3872 process for the final message has ended. The standard error stream is left open
3875 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
3876 false and one of the queueing options in the configuration file is in effect.
3878 If there is a temporary delivery error during foreground delivery, the
3879 message is left on the queue for later delivery, and the original reception
3880 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
3881 restricted configuration that never queues messages.
3886 This option is synonymous with &%-odf%&. It is provided for compatibility with
3891 .cindex "non-immediate delivery"
3892 .cindex "delivery" "suppressing immediate"
3893 .cindex "queueing incoming messages"
3894 This option applies to all modes in which Exim accepts incoming messages,
3895 including the listening daemon. It specifies that the accepting process should
3896 not automatically start a delivery process for each message received. Messages
3897 are placed on the queue, and remain there until a subsequent queue runner
3898 process encounters them. There are several configuration options (such as
3899 &%queue_only%&) that can be used to queue incoming messages under certain
3900 conditions. This option overrides all of them and also &%-odqs%&. It always
3905 .cindex "SMTP" "delaying delivery"
3906 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
3907 However, like &%-odb%& and &%-odi%&, this option has no effect if
3908 &%queue_only_override%& is false and one of the queueing options in the
3909 configuration file is in effect.
3911 When &%-odqs%& does operate, a delivery process is started for each incoming
3912 message, in the background by default, but in the foreground if &%-odi%& is
3913 also present. The recipient addresses are routed, and local deliveries are done
3914 in the normal way. However, if any SMTP deliveries are required, they are not
3915 done at this time, so the message remains on the queue until a subsequent queue
3916 runner process encounters it. Because routing was done, Exim knows which
3917 messages are waiting for which hosts, and so a number of messages for the same
3918 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
3919 configuration option has the same effect for specific domains. See also the
3924 .cindex "error" "reporting"
3925 If an error is detected while a non-SMTP message is being received (for
3926 example, a malformed address), the error is reported to the sender in a mail
3929 .cindex "return code" "for &%-oee%&"
3931 this error message is successfully sent, the Exim receiving process
3932 exits with a return code of zero. If not, the return code is 2 if the problem
3933 is that the original message has no recipients, or 1 any other error. This is
3934 the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
3938 .cindex "error" "reporting"
3939 .cindex "return code" "for &%-oem%&"
3940 This is the same as &%-oee%&, except that Exim always exits with a non-zero
3941 return code, whether or not the error message was successfully sent.
3942 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
3946 .cindex "error" "reporting"
3947 If an error is detected while a non-SMTP message is being received, the
3948 error is reported by writing a message to the standard error file (stderr).
3949 .cindex "return code" "for &%-oep%&"
3950 The return code is 1 for all errors.
3954 .cindex "error" "reporting"
3955 This option is supported for compatibility with Sendmail, but has the same
3960 .cindex "error" "reporting"
3961 This option is supported for compatibility with Sendmail, but has the same
3966 .cindex "dot" "in incoming non-SMTP message"
3967 This option, which has the same effect as &%-i%&, specifies that a dot on a
3968 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
3969 single dot does terminate, though Exim does no special processing for other
3970 lines that start with a dot. This option is set by default if Exim is called as
3971 &'rmail'&. See also &%-ti%&.
3974 .oindex "&%-oitrue%&"
3975 This option is treated as synonymous with &%-oi%&.
3977 .vitem &%-oMa%&&~<&'host&~address'&>
3979 .cindex "sender" "host address, specifying for local message"
3980 A number of options starting with &%-oM%& can be used to set values associated
3981 with remote hosts on locally-submitted messages (that is, messages not received
3982 over TCP/IP). These options can be used by any caller in conjunction with the
3983 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
3984 other circumstances, they are ignored unless the caller is trusted.
3986 The &%-oMa%& option sets the sender host address. This may include a port
3987 number at the end, after a full stop (period). For example:
3989 exim -bs -oMa 10.9.8.7.1234
3991 An alternative syntax is to enclose the IP address in square brackets,
3992 followed by a colon and the port number:
3994 exim -bs -oMa [10.9.8.7]:1234
3996 The IP address is placed in the &$sender_host_address$& variable, and the
3997 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
3998 are present on the command line, the sender host IP address is taken from
3999 whichever one is last.
4001 .vitem &%-oMaa%&&~<&'name'&>
4003 .cindex "authentication" "name, specifying for local message"
4004 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4005 option sets the value of &$sender_host_authenticated$& (the authenticator
4006 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4007 This option can be used with &%-bh%& and &%-bs%& to set up an
4008 authenticated SMTP session without actually using the SMTP AUTH command.
4010 .vitem &%-oMai%&&~<&'string'&>
4012 .cindex "authentication" "id, specifying for local message"
4013 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4014 option sets the value of &$authenticated_id$& (the id that was authenticated).
4015 This overrides the default value (the caller's login id, except with &%-bh%&,
4016 where there is no default) for messages from local sources. See chapter
4017 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4019 .vitem &%-oMas%&&~<&'address'&>
4021 .cindex "authentication" "sender, specifying for local message"
4022 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4023 option sets the authenticated sender value in &$authenticated_sender$&. It
4024 overrides the sender address that is created from the caller's login id for
4025 messages from local sources, except when &%-bh%& is used, when there is no
4026 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4027 specified on a MAIL command overrides this value. See chapter
4028 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4030 .vitem &%-oMi%&&~<&'interface&~address'&>
4032 .cindex "interface" "address, specifying for local message"
4033 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4034 option sets the IP interface address value. A port number may be included,
4035 using the same syntax as for &%-oMa%&. The interface address is placed in
4036 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4038 .vitem &%-oMr%&&~<&'protocol&~name'&>
4040 .cindex "protocol, specifying for local message"
4041 .vindex "&$received_protocol$&"
4042 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4043 option sets the received protocol value that is stored in
4044 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4045 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4046 SMTP protocol names (see the description of &$received_protocol$& in section
4047 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4048 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4051 .vitem &%-oMs%&&~<&'host&~name'&>
4053 .cindex "sender" "host name, specifying for local message"
4054 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4055 option sets the sender host name in &$sender_host_name$&. When this option is
4056 present, Exim does not attempt to look up a host name from an IP address; it
4057 uses the name it is given.
4059 .vitem &%-oMt%&&~<&'ident&~string'&>
4061 .cindex "sender" "ident string, specifying for local message"
4062 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4063 option sets the sender ident value in &$sender_ident$&. The default setting for
4064 local callers is the login id of the calling process, except when &%-bh%& is
4065 used, when there is no default.
4069 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4070 In Sendmail, this option means &"me too"&, indicating that the sender of a
4071 message should receive a copy of the message if the sender appears in an alias
4072 expansion. Exim always does this, so the option does nothing.
4076 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4077 This option is ignored. In Sendmail it specifies &"old style headers"&,
4078 whatever that means.
4080 .vitem &%-oP%&&~<&'path'&>
4082 .cindex "pid (process id)" "of daemon"
4083 .cindex "daemon" "process id (pid)"
4084 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4085 value. The option specifies the file to which the process id of the daemon is
4086 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4087 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4088 because in those cases, the normal pid file is not used.
4090 .vitem &%-or%&&~<&'time'&>
4092 .cindex "timeout" "for non-SMTP input"
4093 This option sets a timeout value for incoming non-SMTP messages. If it is not
4094 set, Exim will wait forever for the standard input. The value can also be set
4095 by the &%receive_timeout%& option. The format used for specifying times is
4096 described in section &<<SECTtimeformat>>&.
4098 .vitem &%-os%&&~<&'time'&>
4100 .cindex "timeout" "for SMTP input"
4101 .cindex "SMTP" "input timeout"
4102 This option sets a timeout value for incoming SMTP messages. The timeout
4103 applies to each SMTP command and block of data. The value can also be set by
4104 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4105 for specifying times is described in section &<<SECTtimeformat>>&.
4109 This option has exactly the same effect as &%-v%&.
4111 .vitem &%-oX%&&~<&'number&~or&~string'&>
4113 .cindex "TCP/IP" "setting listening ports"
4114 .cindex "TCP/IP" "setting listening interfaces"
4115 .cindex "port" "receiving TCP/IP"
4116 This option is relevant only when the &%-bd%& (start listening daemon) option
4117 is also given. It controls which ports and interfaces the daemon uses. Details
4118 of the syntax, and how it interacts with configuration file options, are given
4119 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4120 file is written unless &%-oP%& is also present to specify a pid file name.
4124 .cindex "Perl" "starting the interpreter"
4125 This option applies when an embedded Perl interpreter is linked with Exim (see
4126 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4127 option, forcing the starting of the interpreter to be delayed until it is
4132 .cindex "Perl" "starting the interpreter"
4133 This option applies when an embedded Perl interpreter is linked with Exim (see
4134 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4135 option, forcing the starting of the interpreter to occur as soon as Exim is
4138 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4140 For compatibility with Sendmail, this option is equivalent to
4142 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4144 It sets the incoming protocol and host name (for trusted callers). The
4145 host name and its colon can be omitted when only the protocol is to be set.
4146 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4147 to embedded Perl. It is therefore impossible to set a protocol value of &`p`&
4148 or &`s`& using this option (but that does not seem a real limitation).
4152 .cindex "queue runner" "starting manually"
4153 This option is normally restricted to admin users. However, there is a
4154 configuration option called &%prod_requires_admin%& which can be set false to
4155 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4156 and &%-S%& options).
4158 .cindex "queue runner" "description of operation"
4159 The &%-q%& option starts one queue runner process. This scans the queue of
4160 waiting messages, and runs a delivery process for each one in turn. It waits
4161 for each delivery process to finish before starting the next one. A delivery
4162 process may not actually do any deliveries if the retry times for the addresses
4163 have not been reached. Use &%-qf%& (see below) if you want to override this.
4166 .cindex "SMTP" "passed connection"
4167 .cindex "SMTP" "multiple deliveries"
4168 .cindex "multiple SMTP deliveries"
4169 the delivery process spawns other processes to deliver other messages down
4170 passed SMTP connections, the queue runner waits for these to finish before
4173 When all the queued messages have been considered, the original queue runner
4174 process terminates. In other words, a single pass is made over the waiting
4175 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4176 this to be repeated periodically.
4178 Exim processes the waiting messages in an unpredictable order. It isn't very
4179 random, but it is likely to be different each time, which is all that matters.
4180 If one particular message screws up a remote MTA, other messages to the same
4181 MTA have a chance of getting through if they get tried first.
4183 It is possible to cause the messages to be processed in lexical message id
4184 order, which is essentially the order in which they arrived, by setting the
4185 &%queue_run_in_order%& option, but this is not recommended for normal use.
4187 .vitem &%-q%&<&'qflags'&>
4188 The &%-q%& option may be followed by one or more flag letters that change its
4189 behaviour. They are all optional, but if more than one is present, they must
4190 appear in the correct order. Each flag is described in a separate item below.
4194 .cindex "queue" "double scanning"
4195 .cindex "queue" "routing"
4196 .cindex "routing" "whole queue before delivery"
4197 An option starting with &%-qq%& requests a two-stage queue run. In the first
4198 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4199 every domain. Addresses are routed, local deliveries happen, but no remote
4202 .cindex "hints database" "remembering routing"
4203 The hints database that remembers which messages are waiting for specific hosts
4204 is updated, as if delivery to those hosts had been deferred. After this is
4205 complete, a second, normal queue scan happens, with routing and delivery taking
4206 place as normal. Messages that are routed to the same host should mostly be
4207 delivered down a single SMTP
4208 .cindex "SMTP" "passed connection"
4209 .cindex "SMTP" "multiple deliveries"
4210 .cindex "multiple SMTP deliveries"
4211 connection because of the hints that were set up during the first queue scan.
4212 This option may be useful for hosts that are connected to the Internet
4215 .vitem &%-q[q]i...%&
4217 .cindex "queue" "initial delivery"
4218 If the &'i'& flag is present, the queue runner runs delivery processes only for
4219 those messages that haven't previously been tried. (&'i'& stands for &"initial
4220 delivery"&.) This can be helpful if you are putting messages on the queue using
4221 &%-odq%& and want a queue runner just to process the new messages.
4223 .vitem &%-q[q][i]f...%&
4225 .cindex "queue" "forcing delivery"
4226 .cindex "delivery" "forcing in queue run"
4227 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4228 message, whereas without &'f'& only those non-frozen addresses that have passed
4229 their retry times are tried.
4231 .vitem &%-q[q][i]ff...%&
4233 .cindex "frozen messages" "forcing delivery"
4234 If &'ff'& is present, a delivery attempt is forced for every message, whether
4237 .vitem &%-q[q][i][f[f]]l%&
4239 .cindex "queue" "local deliveries only"
4240 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4241 be done. If a message requires any remote deliveries, it remains on the queue
4244 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4245 .cindex "queue" "delivering specific messages"
4246 When scanning the queue, Exim can be made to skip over messages whose ids are
4247 lexically less than a given value by following the &%-q%& option with a
4248 starting message id. For example:
4250 exim -q 0t5C6f-0000c8-00
4252 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4253 second message id is given, messages whose ids are lexically greater than it
4254 are also skipped. If the same id is given twice, for example,
4256 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4258 just one delivery process is started, for that message. This differs from
4259 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4260 that it counts as a delivery from a queue run. Note that the selection
4261 mechanism does not affect the order in which the messages are scanned. There
4262 are also other ways of selecting specific sets of messages for delivery in a
4263 queue run &-- see &%-R%& and &%-S%&.
4265 .vitem &%-q%&<&'qflags'&><&'time'&>
4266 .cindex "queue runner" "starting periodically"
4267 .cindex "periodic queue running"
4268 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4269 starting a queue runner process at intervals specified by the given time value
4270 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4271 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4272 single daemon process handles both functions. A common way of starting up a
4273 combined daemon at system boot time is to use a command such as
4275 /usr/exim/bin/exim -bd -q30m
4277 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4278 process every 30 minutes.
4280 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4281 pid file is written unless one is explicitly requested by the &%-oP%& option.
4283 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4285 This option is synonymous with &%-R%&. It is provided for Sendmail
4288 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4290 This option is synonymous with &%-S%&.
4292 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4294 .cindex "queue runner" "for specific recipients"
4295 .cindex "delivery" "to given domain"
4296 .cindex "domain" "delivery to"
4297 The <&'rsflags'&> may be empty, in which case the white space before the string
4298 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4299 which are the possible values for <&'rsflags'&>. White space is required if
4300 <&'rsflags'&> is not empty.
4302 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4303 perform a single queue run, except that, when scanning the messages on the
4304 queue, Exim processes only those that have at least one undelivered recipient
4305 address containing the given string, which is checked in a case-independent
4306 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4307 regular expression; otherwise it is a literal string.
4309 If you want to do periodic queue runs for messages with specific recipients,
4310 you can combine &%-R%& with &%-q%& and a time value. For example:
4312 exim -q25m -R @special.domain.example
4314 This example does a queue run for messages with recipients in the given domain
4315 every 25 minutes. Any additional flags that are specified with &%-q%& are
4316 applied to each queue run.
4318 Once a message is selected for delivery by this mechanism, all its addresses
4319 are processed. For the first selected message, Exim overrides any retry
4320 information and forces a delivery attempt for each undelivered address. This
4321 means that if delivery of any address in the first message is successful, any
4322 existing retry information is deleted, and so delivery attempts for that
4323 address in subsequently selected messages (which are processed without forcing)
4324 will run. However, if delivery of any address does not succeed, the retry
4325 information is updated, and in subsequently selected messages, the failing
4326 address will be skipped.
4328 .cindex "frozen messages" "forcing delivery"
4329 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4330 all selected messages, not just the first; frozen messages are included when
4333 The &%-R%& option makes it straightforward to initiate delivery of all messages
4334 to a given domain after a host has been down for some time. When the SMTP
4335 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4336 effect is to run Exim with the &%-R%& option, but it can be configured to run
4337 an arbitrary command instead.
4341 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4343 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4345 .cindex "delivery" "from given sender"
4346 .cindex "queue runner" "for specific senders"
4347 This option acts like &%-R%& except that it checks the string against each
4348 message's sender instead of against the recipients. If &%-R%& is also set, both
4349 conditions must be met for a message to be selected. If either of the options
4350 has &'f'& or &'ff'& in its flags, the associated action is taken.
4352 .vitem &%-Tqt%&&~<&'times'&>
4354 This an option that is exclusively for use by the Exim testing suite. It is not
4355 recognized when Exim is run normally. It allows for the setting up of explicit
4356 &"queue times"& so that various warning/retry features can be tested.
4360 .cindex "recipient" "extracting from header lines"
4361 .cindex "&'Bcc:'& header line"
4362 .cindex "&'Cc:'& header line"
4363 .cindex "&'To:'& header line"
4364 When Exim is receiving a locally-generated, non-SMTP message on its standard
4365 input, the &%-t%& option causes the recipients of the message to be obtained
4366 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4367 from the command arguments. The addresses are extracted before any rewriting
4368 takes place and the &'Bcc:'& header line, if present, is then removed.
4370 .cindex "Sendmail compatibility" "&%-t%& option"
4371 If the command has any arguments, they specify addresses to which the message
4372 is &'not'& to be delivered. That is, the argument addresses are removed from
4373 the recipients list obtained from the headers. This is compatible with Smail 3
4374 and in accordance with the documented behaviour of several versions of
4375 Sendmail, as described in man pages on a number of operating systems (e.g.
4376 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4377 argument addresses to those obtained from the headers, and the O'Reilly
4378 Sendmail book documents it that way. Exim can be made to add argument addresses
4379 instead of subtracting them by setting the option
4380 &%extract_addresses_remove_arguments%& false.
4382 .cindex "&%Resent-%& header lines" "with &%-t%&"
4383 If there are any &%Resent-%& header lines in the message, Exim extracts
4384 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4385 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4386 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4387 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4389 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4390 message is resent several times). The RFC also specifies that they should be
4391 added at the front of the message, and separated by &'Received:'& lines. It is
4392 not at all clear how &%-t%& should operate in the present of multiple sets,
4393 nor indeed exactly what constitutes a &"set"&.
4394 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4395 are often added at the end of the header, and if a message is resent more than
4396 once, it is common for the original set of &%Resent-%& headers to be renamed as
4397 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4401 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4402 compatibility with Sendmail.
4404 .vitem &%-tls-on-connect%&
4405 .oindex "&%-tls-on-connect%&"
4406 .cindex "TLS" "use without STARTTLS"
4407 .cindex "TLS" "automatic start"
4408 This option is available when Exim is compiled with TLS support. It forces all
4409 incoming SMTP connections to behave as if the incoming port is listed in the
4410 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4411 &<<CHAPTLS>>& for further details.
4416 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4417 Sendmail uses this option for &"initial message submission"&, and its
4418 documentation states that in future releases, it may complain about
4419 syntactically invalid messages rather than fixing them when this flag is not
4420 set. Exim ignores this option.
4424 This option causes Exim to write information to the standard error stream,
4425 describing what it is doing. In particular, it shows the log lines for
4426 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4427 dialogue is shown. Some of the log lines shown may not actually be written to
4428 the log if the setting of &%log_selector%& discards them. Any relevant
4429 selectors are shown with each log line. If none are shown, the logging is
4434 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4435 National Language Support extended characters in the body of the mail item"&).
4436 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4444 . ////////////////////////////////////////////////////////////////////////////
4445 . Insert a stylized DocBook comment here, to identify the end of the command
4446 . line options. This is for the benefit of the Perl script that automatically
4447 . creates a man page for the options.
4448 . ////////////////////////////////////////////////////////////////////////////
4451 <!-- === End of command line options === -->
4458 . ////////////////////////////////////////////////////////////////////////////
4459 . ////////////////////////////////////////////////////////////////////////////
4462 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4463 "The runtime configuration file"
4465 .cindex "run time configuration"
4466 .cindex "configuration file" "general description"
4467 .cindex "CONFIGURE_FILE"
4468 .cindex "configuration file" "errors in"
4469 .cindex "error" "in configuration file"
4470 .cindex "return code" "for bad configuration"
4471 Exim uses a single run time configuration file that is read whenever an Exim
4472 binary is executed. Note that in normal operation, this happens frequently,
4473 because Exim is designed to operate in a distributed manner, without central
4476 If a syntax error is detected while reading the configuration file, Exim
4477 writes a message on the standard error, and exits with a non-zero return code.
4478 The message is also written to the panic log. &*Note*&: Only simple syntax
4479 errors can be detected at this time. The values of any expanded options are
4480 not checked until the expansion happens, even when the expansion does not
4481 actually alter the string.
4483 The name of the configuration file is compiled into the binary for security
4484 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4485 most configurations, this specifies a single file. However, it is permitted to
4486 give a colon-separated list of file names, in which case Exim uses the first
4487 existing file in the list.
4490 .cindex "EXIM_GROUP"
4491 .cindex "CONFIGURE_OWNER"
4492 .cindex "CONFIGURE_GROUP"
4493 .cindex "configuration file" "ownership"
4494 .cindex "ownership" "configuration file"
4495 The run time configuration file must be owned by root or by the user that is
4496 specified at compile time by the EXIM_USER option, or by the user that is
4497 specified at compile time by the CONFIGURE_OWNER option (if set). The
4498 configuration file must not be world-writeable or group-writeable, unless its
4499 group is the one specified at compile time by the EXIM_GROUP option or by the
4500 CONFIGURE_GROUP option.
4502 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4503 to root, anybody who is able to edit the run time configuration file has an
4504 easy way to run commands as root. If you make your mail administrators members
4505 of the Exim group, but do not trust them with root, make sure that the run time
4506 configuration is not group writeable.
4508 A default configuration file, which will work correctly in simple situations,
4509 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4510 defines just one file name, the installation process copies the default
4511 configuration to a new file of that name if it did not previously exist. If
4512 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4513 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4518 .section "Using a different configuration file" "SECID40"
4519 .cindex "configuration file" "alternate"
4520 A one-off alternate configuration can be specified by the &%-C%& command line
4521 option, which may specify a single file or a list of files. However, when
4522 &%-C%& is used, Exim gives up its root privilege, unless called by root or the
4523 Exim user (or unless the argument for &%-C%& is identical to the built-in value
4524 from CONFIGURE_FILE). &%-C%& is useful mainly for checking the syntax of
4525 configuration files before installing them. No owner or group checks are done
4526 on a configuration file specified by &%-C%&.
4528 The privileged use of &%-C%& by the Exim user can be locked out by setting
4529 ALT_CONFIG_ROOT_ONLY in &_Local/Makefile_& when building Exim. However,
4530 if you do this, you also lock out the possibility of testing a
4531 configuration using &%-C%& right through message reception and delivery, even
4532 if the caller is root. The reception works, but by that time, Exim is running
4533 as the Exim user, so when it re-execs to regain privilege for the delivery, the
4534 use of &%-C%& causes privilege to be lost. However, root can test reception and
4535 delivery using two separate commands (one to put a message on the queue, using
4536 &%-odq%&, and another to do the delivery, using &%-M%&).
4538 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4539 prefix string with which any file named in a &%-C%& command line option must
4540 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4541 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4542 name can be used with &%-C%&.
4544 One-off changes to a configuration can be specified by the &%-D%& command line
4545 option, which defines and overrides values for macros used inside the
4546 configuration file. However, like &%-C%&, the use of this option by a
4547 non-privileged user causes Exim to discard its root privilege.
4548 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4549 completely disabled, and its use causes an immediate error exit.
4551 Some sites may wish to use the same Exim binary on different machines that
4552 share a file system, but to use different configuration files on each machine.
4553 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4554 looks for a file whose name is the configuration file name followed by a dot
4555 and the machine's node name, as obtained from the &[uname()]& function. If this
4556 file does not exist, the standard name is tried. This processing occurs for
4557 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4559 In some esoteric situations different versions of Exim may be run under
4560 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4561 help with this. See the comments in &_src/EDITME_& for details.
4565 .section "Configuration file format" "SECTconffilfor"
4566 .cindex "configuration file" "format of"
4567 .cindex "format" "configuration file"
4568 Exim's configuration file is divided into a number of different parts. General
4569 option settings must always appear at the start of the file. The other parts
4570 are all optional, and may appear in any order. Each part other than the first
4571 is introduced by the word &"begin"& followed by the name of the part. The
4575 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4578 .cindex "AUTH" "configuration"
4579 &'authenticators'&: Configuration settings for the authenticator drivers. These
4580 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4582 &'routers'&: Configuration settings for the router drivers. Routers process
4583 addresses and determine how the message is to be delivered (see chapters
4584 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4586 &'transports'&: Configuration settings for the transport drivers. Transports
4587 define mechanisms for copying messages to destinations (see chapters
4588 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4590 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4591 If there is no retry section, or if it is empty (that is, no retry rules are
4592 defined), Exim will not retry deliveries. In this situation, temporary errors
4593 are treated the same as permanent errors. Retry rules are discussed in chapter
4596 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4597 when new addresses are generated during delivery. Rewriting is discussed in
4598 chapter &<<CHAPrewrite>>&.
4600 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4601 want to use this feature, you must set
4603 LOCAL_SCAN_HAS_OPTIONS=yes
4605 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4606 facility are given in chapter &<<CHAPlocalscan>>&.
4609 .cindex "configuration file" "leading white space in"
4610 .cindex "configuration file" "trailing white space in"
4611 .cindex "white space" "in configuration file"
4612 Leading and trailing white space in configuration lines is always ignored.
4614 Blank lines in the file, and lines starting with a # character (ignoring
4615 leading white space) are treated as comments and are ignored. &*Note*&: A
4616 # character other than at the beginning of a line is not treated specially,
4617 and does not introduce a comment.
4619 Any non-comment line can be continued by ending it with a backslash. Note that
4620 the general rule for white space means that trailing white space after the
4621 backslash and leading white space at the start of continuation
4622 lines is ignored. Comment lines beginning with # (but not empty lines) may
4623 appear in the middle of a sequence of continuation lines.
4625 A convenient way to create a configuration file is to start from the
4626 default, which is supplied in &_src/configure.default_&, and add, delete, or
4627 change settings as required.
4629 The ACLs, retry rules, and rewriting rules have their own syntax which is
4630 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4631 respectively. The other parts of the configuration file have some syntactic
4632 items in common, and these are described below, from section &<<SECTcos>>&
4633 onwards. Before that, the inclusion, macro, and conditional facilities are
4638 .section "File inclusions in the configuration file" "SECID41"
4639 .cindex "inclusions in configuration file"
4640 .cindex "configuration file" "including other files"
4641 .cindex "&`.include`& in configuration file"
4642 .cindex "&`.include_if_exists`& in configuration file"
4643 You can include other files inside Exim's run time configuration file by
4646 &`.include`& <&'file name'&>
4647 &`.include_if_exists`& <&'file name'&>
4649 on a line by itself. Double quotes round the file name are optional. If you use
4650 the first form, a configuration error occurs if the file does not exist; the
4651 second form does nothing for non-existent files. In all cases, an absolute file
4654 Includes may be nested to any depth, but remember that Exim reads its
4655 configuration file often, so it is a good idea to keep them to a minimum.
4656 If you change the contents of an included file, you must HUP the daemon,
4657 because an included file is read only when the configuration itself is read.
4659 The processing of inclusions happens early, at a physical line level, so, like
4660 comment lines, an inclusion can be used in the middle of an option setting,
4663 hosts_lookup = a.b.c \
4666 Include processing happens after macro processing (see below). Its effect is to
4667 process the lines of the included file as if they occurred inline where the
4672 .section "Macros in the configuration file" "SECTmacrodefs"
4673 .cindex "macro" "description of"
4674 .cindex "configuration file" "macros"
4675 If a line in the main part of the configuration (that is, before the first
4676 &"begin"& line) begins with an upper case letter, it is taken as a macro
4677 definition, and must be of the form
4679 <&'name'&> = <&'rest of line'&>
4681 The name must consist of letters, digits, and underscores, and need not all be
4682 in upper case, though that is recommended. The rest of the line, including any
4683 continuations, is the replacement text, and has leading and trailing white
4684 space removed. Quotes are not removed. The replacement text can never end with
4685 a backslash character, but this doesn't seem to be a serious limitation.
4687 Macros may also be defined between router, transport, authenticator, or ACL
4688 definitions. They may not, however, be defined within an individual driver or
4689 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4691 .section "Macro substitution" "SECID42"
4692 Once a macro is defined, all subsequent lines in the file (and any included
4693 files) are scanned for the macro name; if there are several macros, the line is
4694 scanned for each in turn, in the order in which the macros are defined. The
4695 replacement text is not re-scanned for the current macro, though it is scanned
4696 for subsequently defined macros. For this reason, a macro name may not contain
4697 the name of a previously defined macro as a substring. You could, for example,
4700 &`ABCD_XYZ = `&<&'something'&>
4701 &`ABCD = `&<&'something else'&>
4703 but putting the definitions in the opposite order would provoke a configuration
4704 error. Macro expansion is applied to individual physical lines from the file,
4705 before checking for line continuation or file inclusion (see above). If a line
4706 consists solely of a macro name, and the expansion of the macro is empty, the
4707 line is ignored. A macro at the start of a line may turn the line into a
4708 comment line or a &`.include`& line.
4711 .section "Redefining macros" "SECID43"
4712 Once defined, the value of a macro can be redefined later in the configuration
4713 (or in an included file). Redefinition is specified by using &'=='& instead of
4718 MAC == updated value
4720 Redefinition does not alter the order in which the macros are applied to the
4721 subsequent lines of the configuration file. It is still the same order in which
4722 the macros were originally defined. All that changes is the macro's value.
4723 Redefinition makes it possible to accumulate values. For example:
4727 MAC == MAC and something added
4729 This can be helpful in situations where the configuration file is built
4730 from a number of other files.
4732 .section "Overriding macro values" "SECID44"
4733 The values set for macros in the configuration file can be overridden by the
4734 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4735 used, unless called by root or the Exim user. A definition on the command line
4736 using the &%-D%& option causes all definitions and redefinitions within the
4741 .section "Example of macro usage" "SECID45"
4742 As an example of macro usage, consider a configuration where aliases are looked
4743 up in a MySQL database. It helps to keep the file less cluttered if long
4744 strings such as SQL statements are defined separately as macros, for example:
4746 ALIAS_QUERY = select mailbox from user where \
4747 login='${quote_mysql:$local_part}';
4749 This can then be used in a &(redirect)& router setting like this:
4751 data = ${lookup mysql{ALIAS_QUERY}}
4753 In earlier versions of Exim macros were sometimes used for domain, host, or
4754 address lists. In Exim 4 these are handled better by named lists &-- see
4755 section &<<SECTnamedlists>>&.
4758 .section "Conditional skips in the configuration file" "SECID46"
4759 .cindex "configuration file" "conditional skips"
4760 .cindex "&`.ifdef`&"
4761 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4762 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4763 portions of the configuration file. The processing happens whenever the file is
4764 read (that is, when an Exim binary starts to run).
4766 The implementation is very simple. Instances of the first four directives must
4767 be followed by text that includes the names of one or macros. The condition
4768 that is tested is whether or not any macro substitution has taken place in the
4772 message_size_limit = 50M
4774 message_size_limit = 100M
4777 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
4778 otherwise. If there is more than one macro named on the line, the condition
4779 is true if any of them are defined. That is, it is an &"or"& condition. To
4780 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
4782 Although you can use a macro expansion to generate one of these directives,
4783 it is not very useful, because the condition &"there was a macro substitution
4784 in this line"& will always be true.
4786 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
4787 to clarify complicated nestings.
4791 .section "Common option syntax" "SECTcos"
4792 .cindex "common option syntax"
4793 .cindex "syntax of common options"
4794 .cindex "configuration file" "common option syntax"
4795 For the main set of options, driver options, and &[local_scan()]& options,
4796 each setting is on a line by itself, and starts with a name consisting of
4797 lower-case letters and underscores. Many options require a data value, and in
4798 these cases the name must be followed by an equals sign (with optional white
4799 space) and then the value. For example:
4801 qualify_domain = mydomain.example.com
4803 .cindex "hiding configuration option values"
4804 .cindex "configuration options" "hiding value of"
4805 .cindex "options" "hiding value of"
4806 Some option settings may contain sensitive data, for example, passwords for
4807 accessing databases. To stop non-admin users from using the &%-bP%& command
4808 line option to read these values, you can precede the option settings with the
4809 word &"hide"&. For example:
4811 hide mysql_servers = localhost/users/admin/secret-password
4813 For non-admin users, such options are displayed like this:
4815 mysql_servers = <value not displayable>
4817 If &"hide"& is used on a driver option, it hides the value of that option on
4818 all instances of the same driver.
4820 The following sections describe the syntax used for the different data types
4821 that are found in option settings.
4824 .section "Boolean options" "SECID47"
4825 .cindex "format" "boolean"
4826 .cindex "boolean configuration values"
4827 .oindex "&%no_%&&'xxx'&"
4828 .oindex "&%not_%&&'xxx'&"
4829 Options whose type is given as boolean are on/off switches. There are two
4830 different ways of specifying such options: with and without a data value. If
4831 the option name is specified on its own without data, the switch is turned on;
4832 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
4833 boolean options may be followed by an equals sign and one of the words
4834 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
4835 the following two settings have exactly the same effect:
4840 The following two lines also have the same (opposite) effect:
4845 You can use whichever syntax you prefer.
4850 .section "Integer values" "SECID48"
4851 .cindex "integer configuration values"
4852 .cindex "format" "integer"
4853 If an option's type is given as &"integer"&, the value can be given in decimal,
4854 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
4855 number is assumed. Otherwise, it is treated as an octal number unless it starts
4856 with the characters &"0x"&, in which case the remainder is interpreted as a
4859 If an integer value is followed by the letter K, it is multiplied by 1024; if
4860 it is followed by the letter M, it is multiplied by 1024x1024. When the values
4861 of integer option settings are output, values which are an exact multiple of
4862 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
4863 and M. The printing style is independent of the actual input format that was
4867 .section "Octal integer values" "SECID49"
4868 .cindex "integer format"
4869 .cindex "format" "octal integer"
4870 If an option's type is given as &"octal integer"&, its value is always
4871 interpreted as an octal number, whether or not it starts with the digit zero.
4872 Such options are always output in octal.
4875 .section "Fixed point numbers" "SECID50"
4876 .cindex "fixed point configuration values"
4877 .cindex "format" "fixed point"
4878 If an option's type is given as &"fixed-point"&, its value must be a decimal
4879 integer, optionally followed by a decimal point and up to three further digits.
4883 .section "Time intervals" "SECTtimeformat"
4884 .cindex "time interval" "specifying in configuration"
4885 .cindex "format" "time interval"
4886 A time interval is specified as a sequence of numbers, each followed by one of
4887 the following letters, with no intervening white space:
4897 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
4898 intervals are output in the same format. Exim does not restrict the values; it
4899 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
4903 .section "String values" "SECTstrings"
4904 .cindex "string" "format of configuration values"
4905 .cindex "format" "string"
4906 If an option's type is specified as &"string"&, the value can be specified with
4907 or without double-quotes. If it does not start with a double-quote, the value
4908 consists of the remainder of the line plus any continuation lines, starting at
4909 the first character after any leading white space, with trailing white space
4910 removed, and with no interpretation of the characters in the string. Because
4911 Exim removes comment lines (those beginning with #) at an early stage, they can
4912 appear in the middle of a multi-line string. The following two settings are
4913 therefore equivalent:
4915 trusted_users = uucp:mail
4916 trusted_users = uucp:\
4917 # This comment line is ignored
4920 .cindex "string" "quoted"
4921 .cindex "escape characters in quoted strings"
4922 If a string does start with a double-quote, it must end with a closing
4923 double-quote, and any backslash characters other than those used for line
4924 continuation are interpreted as escape characters, as follows:
4927 .irow &`\\`& "single backslash"
4928 .irow &`\n`& "newline"
4929 .irow &`\r`& "carriage return"
4931 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
4932 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
4936 If a backslash is followed by some other character, including a double-quote
4937 character, that character replaces the pair.
4939 Quoting is necessary only if you want to make use of the backslash escapes to
4940 insert special characters, or if you need to specify a value with leading or
4941 trailing spaces. These cases are rare, so quoting is almost never needed in
4942 current versions of Exim. In versions of Exim before 3.14, quoting was required
4943 in order to continue lines, so you may come across older configuration files
4944 and examples that apparently quote unnecessarily.
4947 .section "Expanded strings" "SECID51"
4948 .cindex "expansion" "definition of"
4949 Some strings in the configuration file are subjected to &'string expansion'&,
4950 by which means various parts of the string may be changed according to the
4951 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
4952 is as just described; in particular, the handling of backslashes in quoted
4953 strings is done as part of the input process, before expansion takes place.
4954 However, backslash is also an escape character for the expander, so any
4955 backslashes that are required for that reason must be doubled if they are
4956 within a quoted configuration string.
4959 .section "User and group names" "SECID52"
4960 .cindex "user name" "format of"
4961 .cindex "format" "user name"
4962 .cindex "groups" "name format"
4963 .cindex "format" "group name"
4964 User and group names are specified as strings, using the syntax described
4965 above, but the strings are interpreted specially. A user or group name must
4966 either consist entirely of digits, or be a name that can be looked up using the
4967 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
4970 .section "List construction" "SECTlistconstruct"
4971 .cindex "list" "syntax of in configuration"
4972 .cindex "format" "list item in configuration"
4973 .cindex "string" "list, definition of"
4974 The data for some configuration options is a list of items, with colon as the
4975 default separator. Many of these options are shown with type &"string list"& in
4976 the descriptions later in this document. Others are listed as &"domain list"&,
4977 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
4978 are all the same; however, those other than &"string list"& are subject to
4979 particular kinds of interpretation, as described in chapter
4980 &<<CHAPdomhosaddlists>>&.
4982 In all these cases, the entire list is treated as a single string as far as the
4983 input syntax is concerned. The &%trusted_users%& setting in section
4984 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
4985 in a list, it must be entered as two colons. Leading and trailing white space
4986 on each item in a list is ignored. This makes it possible to include items that
4987 start with a colon, and in particular, certain forms of IPv6 address. For
4990 local_interfaces = 127.0.0.1 : ::::1
4992 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
4994 &*Note*&: Although leading and trailing white space is ignored in individual
4995 list items, it is not ignored when parsing the list. The space after the first
4996 colon in the example above is necessary. If it were not there, the list would
4997 be interpreted as the two items 127.0.0.1:: and 1.
4999 .section "Changing list separators" "SECID53"
5000 .cindex "list separator" "changing"
5001 .cindex "IPv6" "addresses in lists"
5002 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5003 introduced to allow the separator character to be changed. If a list begins
5004 with a left angle bracket, followed by any punctuation character, that
5005 character is used instead of colon as the list separator. For example, the list
5006 above can be rewritten to use a semicolon separator like this:
5008 local_interfaces = <; 127.0.0.1 ; ::1
5010 This facility applies to all lists, with the exception of the list in
5011 &%log_file_path%&. It is recommended that the use of non-colon separators be
5012 confined to circumstances where they really are needed.
5014 .cindex "list separator" "newline as"
5015 .cindex "newline" "as list separator"
5016 It is also possible to use newline and other control characters (those with
5017 code values less than 32, plus DEL) as separators in lists. Such separators
5018 must be provided literally at the time the list is processed. For options that
5019 are string-expanded, you can write the separator using a normal escape
5020 sequence. This will be processed by the expander before the string is
5021 interpreted as a list. For example, if a newline-separated list of domains is
5022 generated by a lookup, you can process it directly by a line such as this:
5024 domains = <\n ${lookup mysql{.....}}
5026 This avoids having to change the list separator in such data. You are unlikely
5027 to want to use a control character as a separator in an option that is not
5028 expanded, because the value is literal text. However, it can be done by giving
5029 the value in quotes. For example:
5031 local_interfaces = "<\n 127.0.0.1 \n ::1"
5033 Unlike printing character separators, which can be included in list items by
5034 doubling, it is not possible to include a control character as data when it is
5035 set as the separator. Two such characters in succession are interpreted as
5036 enclosing an empty list item.
5040 .section "Empty items in lists" "SECTempitelis"
5041 .cindex "list" "empty item in"
5042 An empty item at the end of a list is always ignored. In other words, trailing
5043 separator characters are ignored. Thus, the list in
5045 senders = user@domain :
5047 contains only a single item. If you want to include an empty string as one item
5048 in a list, it must not be the last item. For example, this list contains three
5049 items, the second of which is empty:
5051 senders = user1@domain : : user2@domain
5053 &*Note*&: There must be white space between the two colons, as otherwise they
5054 are interpreted as representing a single colon data character (and the list
5055 would then contain just one item). If you want to specify a list that contains
5056 just one, empty item, you can do it as in this example:
5060 In this case, the first item is empty, and the second is discarded because it
5061 is at the end of the list.
5066 .section "Format of driver configurations" "SECTfordricon"
5067 .cindex "drivers" "configuration format"
5068 There are separate parts in the configuration for defining routers, transports,
5069 and authenticators. In each part, you are defining a number of driver
5070 instances, each with its own set of options. Each driver instance is defined by
5071 a sequence of lines like this:
5073 <&'instance name'&>:
5078 In the following example, the instance name is &(localuser)&, and it is
5079 followed by three options settings:
5084 transport = local_delivery
5086 For each driver instance, you specify which Exim code module it uses &-- by the
5087 setting of the &%driver%& option &-- and (optionally) some configuration
5088 settings. For example, in the case of transports, if you want a transport to
5089 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5090 a local file you would use the &(appendfile)& driver. Each of the drivers is
5091 described in detail in its own separate chapter later in this manual.
5093 You can have several routers, transports, or authenticators that are based on
5094 the same underlying driver (each must have a different instance name).
5096 The order in which routers are defined is important, because addresses are
5097 passed to individual routers one by one, in order. The order in which
5098 transports are defined does not matter at all. The order in which
5099 authenticators are defined is used only when Exim, as a client, is searching
5100 them to find one that matches an authentication mechanism offered by the
5103 .cindex "generic options"
5104 .cindex "options" "generic &-- definition of"
5105 Within a driver instance definition, there are two kinds of option: &'generic'&
5106 and &'private'&. The generic options are those that apply to all drivers of the
5107 same type (that is, all routers, all transports or all authenticators). The
5108 &%driver%& option is a generic option that must appear in every definition.
5109 .cindex "private options"
5110 The private options are special for each driver, and none need appear, because
5111 they all have default values.
5113 The options may appear in any order, except that the &%driver%& option must
5114 precede any private options, since these depend on the particular driver. For
5115 this reason, it is recommended that &%driver%& always be the first option.
5117 Driver instance names, which are used for reference in log entries and
5118 elsewhere, can be any sequence of letters, digits, and underscores (starting
5119 with a letter) and must be unique among drivers of the same type. A router and
5120 a transport (for example) can each have the same name, but no two router
5121 instances can have the same name. The name of a driver instance should not be
5122 confused with the name of the underlying driver module. For example, the
5123 configuration lines:
5128 create an instance of the &(smtp)& transport driver whose name is
5129 &(remote_smtp)&. The same driver code can be used more than once, with
5130 different instance names and different option settings each time. A second
5131 instance of the &(smtp)& transport, with different options, might be defined
5137 command_timeout = 10s
5139 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5140 these transport instances from routers, and these names would appear in log
5143 Comment lines may be present in the middle of driver specifications. The full
5144 list of option settings for any particular driver instance, including all the
5145 defaulted values, can be extracted by making use of the &%-bP%& command line
5153 . ////////////////////////////////////////////////////////////////////////////
5154 . ////////////////////////////////////////////////////////////////////////////
5156 .chapter "The default configuration file" "CHAPdefconfil"
5157 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5158 .cindex "default" "configuration file &""walk through""&"
5159 The default configuration file supplied with Exim as &_src/configure.default_&
5160 is sufficient for a host with simple mail requirements. As an introduction to
5161 the way Exim is configured, this chapter &"walks through"& the default
5162 configuration, giving brief explanations of the settings. Detailed descriptions
5163 of the options are given in subsequent chapters. The default configuration file
5164 itself contains extensive comments about ways you might want to modify the
5165 initial settings. However, note that there are many options that are not
5166 mentioned at all in the default configuration.
5170 .section "Main configuration settings" "SECTdefconfmain"
5171 The main (global) configuration option settings must always come first in the
5172 file. The first thing you'll see in the file, after some initial comments, is
5175 # primary_hostname =
5177 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5178 to know the official, fully qualified name of your host, and this is where you
5179 can specify it. However, in most cases you do not need to set this option. When
5180 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5182 The first three non-comment configuration lines are as follows:
5184 domainlist local_domains = @
5185 domainlist relay_to_domains =
5186 hostlist relay_from_hosts = 127.0.0.1
5188 These are not, in fact, option settings. They are definitions of two named
5189 domain lists and one named host list. Exim allows you to give names to lists of
5190 domains, hosts, and email addresses, in order to make it easier to manage the
5191 configuration file (see section &<<SECTnamedlists>>&).
5193 The first line defines a domain list called &'local_domains'&; this is used
5194 later in the configuration to identify domains that are to be delivered
5197 .cindex "@ in a domain list"
5198 There is just one item in this list, the string &"@"&. This is a special form
5199 of entry which means &"the name of the local host"&. Thus, if the local host is
5200 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5201 be delivered locally. Because the local host's name is referenced indirectly,
5202 the same configuration file can be used on different hosts.
5204 The second line defines a domain list called &'relay_to_domains'&, but the
5205 list itself is empty. Later in the configuration we will come to the part that
5206 controls mail relaying through the local host; it allows relaying to any
5207 domains in this list. By default, therefore, no relaying on the basis of a mail
5208 domain is permitted.
5210 The third line defines a host list called &'relay_from_hosts'&. This list is
5211 used later in the configuration to permit relaying from any host or IP address
5212 that matches the list. The default contains just the IP address of the IPv4
5213 loopback interface, which means that processes on the local host are able to
5214 submit mail for relaying by sending it over TCP/IP to that interface. No other
5215 hosts are permitted to submit messages for relaying.
5217 Just to be sure there's no misunderstanding: at this point in the configuration
5218 we aren't actually setting up any controls. We are just defining some domains
5219 and hosts that will be used in the controls that are specified later.
5221 The next two configuration lines are genuine option settings:
5223 acl_smtp_rcpt = acl_check_rcpt
5224 acl_smtp_data = acl_check_data
5226 These options specify &'Access Control Lists'& (ACLs) that are to be used
5227 during an incoming SMTP session for every recipient of a message (every RCPT
5228 command), and after the contents of the message have been received,
5229 respectively. The names of the lists are &'acl_check_rcpt'& and
5230 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5231 section of the configuration. The RCPT ACL controls which recipients are
5232 accepted for an incoming message &-- if a configuration does not provide an ACL
5233 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5234 contents of a message to be checked.
5236 Two commented-out option settings are next:
5238 # av_scanner = clamd:/tmp/clamd
5239 # spamd_address = 127.0.0.1 783
5241 These are example settings that can be used when Exim is compiled with the
5242 content-scanning extension. The first specifies the interface to the virus
5243 scanner, and the second specifies the interface to SpamAssassin. Further
5244 details are given in chapter &<<CHAPexiscan>>&.
5246 Three more commented-out option settings follow:
5248 # tls_advertise_hosts = *
5249 # tls_certificate = /etc/ssl/exim.crt
5250 # tls_privatekey = /etc/ssl/exim.pem
5252 These are example settings that can be used when Exim is compiled with
5253 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5254 first one specifies the list of clients that are allowed to use TLS when
5255 connecting to this server; in this case the wildcard means all clients. The
5256 other options specify where Exim should find its TLS certificate and private
5257 key, which together prove the server's identity to any clients that connect.
5258 More details are given in chapter &<<CHAPTLS>>&.
5260 Another two commented-out option settings follow:
5262 # daemon_smtp_ports = 25 : 465 : 587
5263 # tls_on_connect_ports = 465
5265 .cindex "port" "465 and 587"
5266 .cindex "port" "for message submission"
5267 .cindex "message" "submission, ports for"
5268 .cindex "ssmtp protocol"
5269 .cindex "smtps protocol"
5270 .cindex "SMTP" "ssmtp protocol"
5271 .cindex "SMTP" "smtps protocol"
5272 These options provide better support for roaming users who wish to use this
5273 server for message submission. They are not much use unless you have turned on
5274 TLS (as described in the previous paragraph) and authentication (about which
5275 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5276 on end-user networks, so RFC 4409 specifies that message submission should use
5277 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5278 configured to use port 587 correctly, so these settings also enable the
5279 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5280 &<<SECTsupobssmt>>&).
5282 Two more commented-out options settings follow:
5285 # qualify_recipient =
5287 The first of these specifies a domain that Exim uses when it constructs a
5288 complete email address from a local login name. This is often needed when Exim
5289 receives a message from a local process. If you do not set &%qualify_domain%&,
5290 the value of &%primary_hostname%& is used. If you set both of these options,
5291 you can have different qualification domains for sender and recipient
5292 addresses. If you set only the first one, its value is used in both cases.
5294 .cindex "domain literal" "recognizing format"
5295 The following line must be uncommented if you want Exim to recognize
5296 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5297 (an IP address within square brackets) instead of a named domain.
5299 # allow_domain_literals
5301 The RFCs still require this form, but many people think that in the modern
5302 Internet it makes little sense to permit mail to be sent to specific hosts by
5303 quoting their IP addresses. This ancient format has been used by people who
5304 try to abuse hosts by using them for unwanted relaying. However, some
5305 people believe there are circumstances (for example, messages addressed to
5306 &'postmaster'&) where domain literals are still useful.
5308 The next configuration line is a kind of trigger guard:
5312 It specifies that no delivery must ever be run as the root user. The normal
5313 convention is to set up &'root'& as an alias for the system administrator. This
5314 setting is a guard against slips in the configuration.
5315 The list of users specified by &%never_users%& is not, however, the complete
5316 list; the build-time configuration in &_Local/Makefile_& has an option called
5317 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5318 contents of &%never_users%& are added to this list. By default
5319 FIXED_NEVER_USERS also specifies root.
5321 When a remote host connects to Exim in order to send mail, the only information
5322 Exim has about the host's identity is its IP address. The next configuration
5327 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5328 in order to get a host name. This improves the quality of the logging
5329 information, but if you feel it is too expensive, you can remove it entirely,
5330 or restrict the lookup to hosts on &"nearby"& networks.
5331 Note that it is not always possible to find a host name from an IP address,
5332 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5335 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5336 1413 (hence their names):
5339 rfc1413_query_timeout = 5s
5341 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5342 You can limit the hosts to which these calls are made, or change the timeout
5343 that is used. If you set the timeout to zero, all ident calls are disabled.
5344 Although they are cheap and can provide useful information for tracing problem
5345 messages, some hosts and firewalls have problems with ident calls. This can
5346 result in a timeout instead of an immediate refused connection, leading to
5347 delays on starting up an incoming SMTP session.
5349 When Exim receives messages over SMTP connections, it expects all addresses to
5350 be fully qualified with a domain, as required by the SMTP definition. However,
5351 if you are running a server to which simple clients submit messages, you may
5352 find that they send unqualified addresses. The two commented-out options:
5354 # sender_unqualified_hosts =
5355 # recipient_unqualified_hosts =
5357 show how you can specify hosts that are permitted to send unqualified sender
5358 and recipient addresses, respectively.
5360 The &%percent_hack_domains%& option is also commented out:
5362 # percent_hack_domains =
5364 It provides a list of domains for which the &"percent hack"& is to operate.
5365 This is an almost obsolete form of explicit email routing. If you do not know
5366 anything about it, you can safely ignore this topic.
5368 The last two settings in the main part of the default configuration are
5369 concerned with messages that have been &"frozen"& on Exim's queue. When a
5370 message is frozen, Exim no longer continues to try to deliver it. Freezing
5371 occurs when a bounce message encounters a permanent failure because the sender
5372 address of the original message that caused the bounce is invalid, so the
5373 bounce cannot be delivered. This is probably the most common case, but there
5374 are also other conditions that cause freezing, and frozen messages are not
5375 always bounce messages.
5377 ignore_bounce_errors_after = 2d
5378 timeout_frozen_after = 7d
5380 The first of these options specifies that failing bounce messages are to be
5381 discarded after 2 days on the queue. The second specifies that any frozen
5382 message (whether a bounce message or not) is to be timed out (and discarded)
5383 after a week. In this configuration, the first setting ensures that no failing
5384 bounce message ever lasts a week.
5388 .section "ACL configuration" "SECID54"
5389 .cindex "default" "ACLs"
5390 .cindex "&ACL;" "default configuration"
5391 In the default configuration, the ACL section follows the main configuration.
5392 It starts with the line
5396 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5397 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5398 and &%acl_smtp_data%& above.
5400 .cindex "RCPT" "ACL for"
5401 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5402 RCPT command specifies one of the message's recipients. The ACL statements
5403 are considered in order, until the recipient address is either accepted or
5404 rejected. The RCPT command is then accepted or rejected, according to the
5405 result of the ACL processing.
5409 This line, consisting of a name terminated by a colon, marks the start of the
5414 This ACL statement accepts the recipient if the sending host matches the list.
5415 But what does that strange list mean? It doesn't actually contain any host
5416 names or IP addresses. The presence of the colon puts an empty item in the
5417 list; Exim matches this only if the incoming message did not come from a remote
5418 host, because in that case, the remote hostname is empty. The colon is
5419 important. Without it, the list itself is empty, and can never match anything.
5421 What this statement is doing is to accept unconditionally all recipients in
5422 messages that are submitted by SMTP from local processes using the standard
5423 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5426 deny message = Restricted characters in address
5427 domains = +local_domains
5428 local_parts = ^[.] : ^.*[@%!/|]
5430 deny message = Restricted characters in address
5431 domains = !+local_domains
5432 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5434 These statements are concerned with local parts that contain any of the
5435 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5436 Although these characters are entirely legal in local parts (in the case of
5437 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5438 in Internet mail addresses.
5440 The first three have in the past been associated with explicitly routed
5441 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5442 option). Addresses containing these characters are regularly tried by spammers
5443 in an attempt to bypass relaying restrictions, and also by open relay testing
5444 programs. Unless you really need them it is safest to reject these characters
5445 at this early stage. This configuration is heavy-handed in rejecting these
5446 characters for all messages it accepts from remote hosts. This is a deliberate
5447 policy of being as safe as possible.
5449 The first rule above is stricter, and is applied to messages that are addressed
5450 to one of the local domains handled by this host. This is implemented by the
5451 first condition, which restricts it to domains that are listed in the
5452 &'local_domains'& domain list. The &"+"& character is used to indicate a
5453 reference to a named list. In this configuration, there is just one domain in
5454 &'local_domains'&, but in general there may be many.
5456 The second condition on the first statement uses two regular expressions to
5457 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5458 or &"|"&. If you have local accounts that include these characters, you will
5459 have to modify this rule.
5461 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5462 allows them because they have been encountered in practice. (Consider the
5463 common convention of local parts constructed as
5464 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5465 the author of Exim, who has no second initial.) However, a local part starting
5466 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5467 file name (for example, for a mailing list). This is also true for local parts
5468 that contain slashes. A pipe symbol can also be troublesome if the local part
5469 is incorporated unthinkingly into a shell command line.
5471 The second rule above applies to all other domains, and is less strict. This
5472 allows your own users to send outgoing messages to sites that use slashes
5473 and vertical bars in their local parts. It blocks local parts that begin
5474 with a dot, slash, or vertical bar, but allows these characters within the
5475 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5476 and &"!"& is blocked, as before. The motivation here is to prevent your users
5477 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5479 accept local_parts = postmaster
5480 domains = +local_domains
5482 This statement, which has two conditions, accepts an incoming address if the
5483 local part is &'postmaster'& and the domain is one of those listed in the
5484 &'local_domains'& domain list. The &"+"& character is used to indicate a
5485 reference to a named list. In this configuration, there is just one domain in
5486 &'local_domains'&, but in general there may be many.
5488 The presence of this statement means that mail to postmaster is never blocked
5489 by any of the subsequent tests. This can be helpful while sorting out problems
5490 in cases where the subsequent tests are incorrectly denying access.
5492 require verify = sender
5494 This statement requires the sender address to be verified before any subsequent
5495 ACL statement can be used. If verification fails, the incoming recipient
5496 address is refused. Verification consists of trying to route the address, to
5497 see if a bounce message could be delivered to it. In the case of remote
5498 addresses, basic verification checks only the domain, but &'callouts'& can be
5499 used for more verification if required. Section &<<SECTaddressverification>>&
5500 discusses the details of address verification.
5502 accept hosts = +relay_from_hosts
5503 control = submission
5505 This statement accepts the address if the message is coming from one of the
5506 hosts that are defined as being allowed to relay through this host. Recipient
5507 verification is omitted here, because in many cases the clients are dumb MUAs
5508 that do not cope well with SMTP error responses. For the same reason, the
5509 second line specifies &"submission mode"& for messages that are accepted. This
5510 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5511 messages that are deficient in some way, for example, because they lack a
5512 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5513 probably add recipient verification here, and disable submission mode.
5515 accept authenticated = *
5516 control = submission
5518 This statement accepts the address if the client host has authenticated itself.
5519 Submission mode is again specified, on the grounds that such messages are most
5520 likely to come from MUAs. The default configuration does not define any
5521 authenticators, though it does include some nearly complete commented-out
5522 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5523 fact authenticate until you complete the authenticator definitions.
5525 require message = relay not permitted
5526 domains = +local_domains : +relay_domains
5528 This statement rejects the address if its domain is neither a local domain nor
5529 one of the domains for which this host is a relay.
5531 require verify = recipient
5533 This statement requires the recipient address to be verified; if verification
5534 fails, the address is rejected.
5536 # deny message = rejected because $sender_host_address \
5537 # is in a black list at $dnslist_domain\n\
5539 # dnslists = black.list.example
5541 # warn dnslists = black.list.example
5542 # add_header = X-Warning: $sender_host_address is in \
5543 # a black list at $dnslist_domain
5544 # log_message = found in $dnslist_domain
5546 These commented-out lines are examples of how you could configure Exim to check
5547 sending hosts against a DNS black list. The first statement rejects messages
5548 from blacklisted hosts, whereas the second just inserts a warning header
5551 # require verify = csa
5553 This commented-out line is an example of how you could turn on client SMTP
5554 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5559 The final statement in the first ACL unconditionally accepts any recipient
5560 address that has successfully passed all the previous tests.
5564 This line marks the start of the second ACL, and names it. Most of the contents
5565 of this ACL are commented out:
5568 # message = This message contains a virus \
5571 These lines are examples of how to arrange for messages to be scanned for
5572 viruses when Exim has been compiled with the content-scanning extension, and a
5573 suitable virus scanner is installed. If the message is found to contain a
5574 virus, it is rejected with the given custom error message.
5576 # warn spam = nobody
5577 # message = X-Spam_score: $spam_score\n\
5578 # X-Spam_score_int: $spam_score_int\n\
5579 # X-Spam_bar: $spam_bar\n\
5580 # X-Spam_report: $spam_report
5582 These lines are an example of how to arrange for messages to be scanned by
5583 SpamAssassin when Exim has been compiled with the content-scanning extension,
5584 and SpamAssassin has been installed. The SpamAssassin check is run with
5585 &`nobody`& as its user parameter, and the results are added to the message as a
5586 series of extra header line. In this case, the message is not rejected,
5587 whatever the spam score.
5591 This final line in the DATA ACL accepts the message unconditionally.
5594 .section "Router configuration" "SECID55"
5595 .cindex "default" "routers"
5596 .cindex "routers" "default"
5597 The router configuration comes next in the default configuration, introduced
5602 Routers are the modules in Exim that make decisions about where to send
5603 messages. An address is passed to each router in turn, until it is either
5604 accepted, or failed. This means that the order in which you define the routers
5605 matters. Each router is fully described in its own chapter later in this
5606 manual. Here we give only brief overviews.
5609 # driver = ipliteral
5610 # domains = !+local_domains
5611 # transport = remote_smtp
5613 .cindex "domain literal" "default router"
5614 This router is commented out because the majority of sites do not want to
5615 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5616 you uncomment this router, you also need to uncomment the setting of
5617 &%allow_domain_literals%& in the main part of the configuration.
5621 domains = ! +local_domains
5622 transport = remote_smtp
5623 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5626 The first uncommented router handles addresses that do not involve any local
5627 domains. This is specified by the line
5629 domains = ! +local_domains
5631 The &%domains%& option lists the domains to which this router applies, but the
5632 exclamation mark is a negation sign, so the router is used only for domains
5633 that are not in the domain list called &'local_domains'& (which was defined at
5634 the start of the configuration). The plus sign before &'local_domains'&
5635 indicates that it is referring to a named list. Addresses in other domains are
5636 passed on to the following routers.
5638 The name of the router driver is &(dnslookup)&,
5639 and is specified by the &%driver%& option. Do not be confused by the fact that
5640 the name of this router instance is the same as the name of the driver. The
5641 instance name is arbitrary, but the name set in the &%driver%& option must be
5642 one of the driver modules that is in the Exim binary.
5644 The &(dnslookup)& router routes addresses by looking up their domains in the
5645 DNS in order to obtain a list of hosts to which the address is routed. If the
5646 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5647 specified by the &%transport%& option. If the router does not find the domain
5648 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5649 the address fails and is bounced.
5651 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5652 be entirely ignored. This option is present because a number of cases have been
5653 encountered where MX records in the DNS point to host names
5654 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5655 Completely ignoring these IP addresses causes Exim to fail to route the
5656 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5657 continue to try to deliver the message periodically until the address timed
5664 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5666 file_transport = address_file
5667 pipe_transport = address_pipe
5669 Control reaches this and subsequent routers only for addresses in the local
5670 domains. This router checks to see whether the local part is defined as an
5671 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5672 data that it looks up from that file. If no data is found for the local part,
5673 the value of the &%data%& option is empty, causing the address to be passed to
5676 &_/etc/aliases_& is a conventional name for the system aliases file that is
5677 often used. That is why it is referenced by from the default configuration
5678 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5679 &_Local/Makefile_& before building Exim.
5684 # local_part_suffix = +* : -*
5685 # local_part_suffix_optional
5686 file = $home/.forward
5691 file_transport = address_file
5692 pipe_transport = address_pipe
5693 reply_transport = address_reply
5695 This is the most complicated router in the default configuration. It is another
5696 redirection router, but this time it is looking for forwarding data set up by
5697 individual users. The &%check_local_user%& setting specifies a check that the
5698 local part of the address is the login name of a local user. If it is not, the
5699 router is skipped. The two commented options that follow &%check_local_user%&,
5702 # local_part_suffix = +* : -*
5703 # local_part_suffix_optional
5705 .vindex "&$local_part_suffix$&"
5706 show how you can specify the recognition of local part suffixes. If the first
5707 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5708 by any sequence of characters, is removed from the local part and placed in the
5709 variable &$local_part_suffix$&. The second suffix option specifies that the
5710 presence of a suffix in the local part is optional. When a suffix is present,
5711 the check for a local login uses the local part with the suffix removed.
5713 When a local user account is found, the file called &_.forward_& in the user's
5714 home directory is consulted. If it does not exist, or is empty, the router
5715 declines. Otherwise, the contents of &_.forward_& are interpreted as
5716 redirection data (see chapter &<<CHAPredirect>>& for more details).
5718 .cindex "Sieve filter" "enabling in default router"
5719 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5720 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5721 is commented out by default), the contents of the file are interpreted as a set
5722 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5723 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5724 separate document entitled &'Exim's interfaces to mail filtering'&.
5726 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5727 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5728 There are two reasons for doing this:
5731 Whether or not a local user has a &_.forward_& file is not really relevant when
5732 checking an address for validity; it makes sense not to waste resources doing
5735 More importantly, when Exim is verifying addresses or handling an EXPN
5736 command during an SMTP session, it is running as the Exim user, not as root.
5737 The group is the Exim group, and no additional groups are set up.
5738 It may therefore not be possible for Exim to read users' &_.forward_& files at
5742 The setting of &%check_ancestor%& prevents the router from generating a new
5743 address that is the same as any previous address that was redirected. (This
5744 works round a problem concerning a bad interaction between aliasing and
5745 forwarding &-- see section &<<SECTredlocmai>>&).
5747 The final three option settings specify the transports that are to be used when
5748 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5749 auto-reply, respectively. For example, if a &_.forward_& file contains
5751 a.nother@elsewhere.example, /home/spqr/archive
5753 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5759 # local_part_suffix = +* : -*
5760 # local_part_suffix_optional
5761 transport = local_delivery
5763 The final router sets up delivery into local mailboxes, provided that the local
5764 part is the name of a local login, by accepting the address and assigning it to
5765 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5766 routers, so the address is bounced. The commented suffix settings fulfil the
5767 same purpose as they do for the &(userforward)& router.
5770 .section "Transport configuration" "SECID56"
5771 .cindex "default" "transports"
5772 .cindex "transports" "default"
5773 Transports define mechanisms for actually delivering messages. They operate
5774 only when referenced from routers, so the order in which they are defined does
5775 not matter. The transports section of the configuration starts with
5779 One remote transport and four local transports are defined.
5784 This transport is used for delivering messages over SMTP connections. All its
5785 options are defaulted. The list of remote hosts comes from the router.
5789 file = /var/mail/$local_part
5796 This &(appendfile)& transport is used for local delivery to user mailboxes in
5797 traditional BSD mailbox format. By default it runs under the uid and gid of the
5798 local user, which requires the sticky bit to be set on the &_/var/mail_&
5799 directory. Some systems use the alternative approach of running mail deliveries
5800 under a particular group instead of using the sticky bit. The commented options
5801 show how this can be done.
5803 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
5804 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
5805 similarly-named options above.
5811 This transport is used for handling deliveries to pipes that are generated by
5812 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
5813 option specifies that any output generated by the pipe is to be returned to the
5822 This transport is used for handling deliveries to files that are generated by
5823 redirection. The name of the file is not specified in this instance of
5824 &(appendfile)&, because it comes from the &(redirect)& router.
5829 This transport is used for handling automatic replies generated by users'
5834 .section "Default retry rule" "SECID57"
5835 .cindex "retry" "default rule"
5836 .cindex "default" "retry rule"
5837 The retry section of the configuration file contains rules which affect the way
5838 Exim retries deliveries that cannot be completed at the first attempt. It is
5839 introduced by the line
5843 In the default configuration, there is just one rule, which applies to all
5846 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5848 This causes any temporarily failing address to be retried every 15 minutes for
5849 2 hours, then at intervals starting at one hour and increasing by a factor of
5850 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5851 is not delivered after 4 days of temporary failure, it is bounced.
5853 If the retry section is removed from the configuration, or is empty (that is,
5854 if no retry rules are defined), Exim will not retry deliveries. This turns
5855 temporary errors into permanent errors.
5858 .section "Rewriting configuration" "SECID58"
5859 The rewriting section of the configuration, introduced by
5863 contains rules for rewriting addresses in messages as they arrive. There are no
5864 rewriting rules in the default configuration file.
5868 .section "Authenticators configuration" "SECTdefconfauth"
5869 .cindex "AUTH" "configuration"
5870 The authenticators section of the configuration, introduced by
5872 begin authenticators
5874 defines mechanisms for the use of the SMTP AUTH command. The default
5875 configuration file contains two commented-out example authenticators
5876 which support plaintext username/password authentication using the
5877 standard PLAIN mechanism and the traditional but non-standard LOGIN
5878 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
5879 to support most MUA software.
5881 The example PLAIN authenticator looks like this:
5884 # driver = plaintext
5885 # server_set_id = $auth2
5886 # server_prompts = :
5887 # server_condition = Authentication is not yet configured
5888 # server_advertise_condition = ${if def:tls_cipher }
5890 And the example LOGIN authenticator looks like this:
5893 # driver = plaintext
5894 # server_set_id = $auth1
5895 # server_prompts = <| Username: | Password:
5896 # server_condition = Authentication is not yet configured
5897 # server_advertise_condition = ${if def:tls_cipher }
5900 The &%server_set_id%& option makes Exim remember the authenticated username
5901 in &$authenticated_id$&, which can be used later in ACLs or routers. The
5902 &%server_prompts%& option configures the &(plaintext)& authenticator so
5903 that it implements the details of the specific authentication mechanism,
5904 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
5905 when Exim offers authentication to clients; in the examples, this is only
5906 when TLS or SSL has been started, so to enable the authenticators you also
5907 need to add support for TLS as described in &<<SECTdefconfmain>>&.
5909 The &%server_condition%& setting defines how to verify that the username and
5910 password are correct. In the examples it just produces an error message.
5911 To make the authenticators work, you can use a string expansion
5912 expression like one of the examples in &<<CHAPplaintext>>&.
5914 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
5915 usercode and password are in different positions. &<<CHAPplaintext>>&
5918 .ecindex IIDconfiwal
5922 . ////////////////////////////////////////////////////////////////////////////
5923 . ////////////////////////////////////////////////////////////////////////////
5925 .chapter "Regular expressions" "CHAPregexp"
5927 .cindex "regular expressions" "library"
5929 Exim supports the use of regular expressions in many of its options. It
5930 uses the PCRE regular expression library; this provides regular expression
5931 matching that is compatible with Perl 5. The syntax and semantics of
5932 regular expressions is discussed in many Perl reference books, and also in
5933 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
5934 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
5936 The documentation for the syntax and semantics of the regular expressions that
5937 are supported by PCRE is included in the PCRE distribution, and no further
5938 description is included here. The PCRE functions are called from Exim using
5939 the default option settings (that is, with no PCRE options set), except that
5940 the PCRE_CASELESS option is set when the matching is required to be
5943 In most cases, when a regular expression is required in an Exim configuration,
5944 it has to start with a circumflex, in order to distinguish it from plain text
5945 or an &"ends with"& wildcard. In this example of a configuration setting, the
5946 second item in the colon-separated list is a regular expression.
5948 domains = a.b.c : ^\\d{3} : *.y.z : ...
5950 The doubling of the backslash is required because of string expansion that
5951 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
5952 of this issue, and a way of avoiding the need for doubling backslashes. The
5953 regular expression that is eventually used in this example contains just one
5954 backslash. The circumflex is included in the regular expression, and has the
5955 normal effect of &"anchoring"& it to the start of the string that is being
5958 There are, however, two cases where a circumflex is not required for the
5959 recognition of a regular expression: these are the &%match%& condition in a
5960 string expansion, and the &%matches%& condition in an Exim filter file. In
5961 these cases, the relevant string is always treated as a regular expression; if
5962 it does not start with a circumflex, the expression is not anchored, and can
5963 match anywhere in the subject string.
5965 In all cases, if you want a regular expression to match at the end of a string,
5966 you must code the $ metacharacter to indicate this. For example:
5968 domains = ^\\d{3}\\.example
5970 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
5973 domains = ^\\d{3}\\.example\$
5975 if you want &'example'& to be the top-level domain. The backslash before the
5976 $ is needed because string expansion also interprets dollar characters.
5980 . ////////////////////////////////////////////////////////////////////////////
5981 . ////////////////////////////////////////////////////////////////////////////
5983 .chapter "File and database lookups" "CHAPfdlookup"
5984 .scindex IIDfidalo1 "file" "lookups"
5985 .scindex IIDfidalo2 "database" "lookups"
5986 .cindex "lookup" "description of"
5987 Exim can be configured to look up data in files or databases as it processes
5988 messages. Two different kinds of syntax are used:
5991 A string that is to be expanded may contain explicit lookup requests. These
5992 cause parts of the string to be replaced by data that is obtained from the
5993 lookup. Lookups of this type are conditional expansion items. Different results
5994 can be defined for the cases of lookup success and failure. See chapter
5995 &<<CHAPexpand>>&, where string expansions are described in detail.
5997 Lists of domains, hosts, and email addresses can contain lookup requests as a
5998 way of avoiding excessively long linear lists. In this case, the data that is
5999 returned by the lookup is often (but not always) discarded; whether the lookup
6000 succeeds or fails is what really counts. These kinds of list are described in
6001 chapter &<<CHAPdomhosaddlists>>&.
6004 String expansions, lists, and lookups interact with each other in such a way
6005 that there is no order in which to describe any one of them that does not
6006 involve references to the others. Each of these three chapters makes more sense
6007 if you have read the other two first. If you are reading this for the first
6008 time, be aware that some of it will make a lot more sense after you have read
6009 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6011 .section "Examples of different lookup syntax" "SECID60"
6012 It is easy to confuse the two different kinds of lookup, especially as the
6013 lists that may contain the second kind are always expanded before being
6014 processed as lists. Therefore, they may also contain lookups of the first kind.
6015 Be careful to distinguish between the following two examples:
6017 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6018 domains = lsearch;/some/file
6020 The first uses a string expansion, the result of which must be a domain list.
6021 No strings have been specified for a successful or a failing lookup; the
6022 defaults in this case are the looked-up data and an empty string, respectively.
6023 The expansion takes place before the string is processed as a list, and the
6024 file that is searched could contain lines like this:
6026 192.168.3.4: domain1:domain2:...
6027 192.168.1.9: domain3:domain4:...
6029 When the lookup succeeds, the result of the expansion is a list of domains (and
6030 possibly other types of item that are allowed in domain lists).
6032 In the second example, the lookup is a single item in a domain list. It causes
6033 Exim to use a lookup to see if the domain that is being processed can be found
6034 in the file. The file could contains lines like this:
6039 Any data that follows the keys is not relevant when checking that the domain
6040 matches the list item.
6042 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6043 Consider a file containing lines like this:
6045 192.168.5.6: lsearch;/another/file
6047 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6048 first &%domains%& setting above generates the second setting, which therefore
6049 causes a second lookup to occur.
6051 The rest of this chapter describes the different lookup types that are
6052 available. Any of them can be used in any part of the configuration where a
6053 lookup is permitted.
6056 .section "Lookup types" "SECID61"
6057 .cindex "lookup" "types of"
6058 .cindex "single-key lookup" "definition of"
6059 Two different types of data lookup are implemented:
6062 The &'single-key'& type requires the specification of a file in which to look,
6063 and a single key to search for. The key must be a non-empty string for the
6064 lookup to succeed. The lookup type determines how the file is searched.
6066 .cindex "query-style lookup" "definition of"
6067 The &'query-style'& type accepts a generalized database query. No particular
6068 key value is assumed by Exim for query-style lookups. You can use whichever
6069 Exim variables you need to construct the database query.
6072 The code for each lookup type is in a separate source file that is included in
6073 the binary of Exim only if the corresponding compile-time option is set. The
6074 default settings in &_src/EDITME_& are:
6079 which means that only linear searching and DBM lookups are included by default.
6080 For some types of lookup (e.g. SQL databases), you need to install appropriate
6081 libraries and header files before building Exim.
6086 .section "Single-key lookup types" "SECTsinglekeylookups"
6087 .cindex "lookup" "single-key types"
6088 .cindex "single-key lookup" "list of types"
6089 The following single-key lookup types are implemented:
6092 .cindex "cdb" "description of"
6093 .cindex "lookup" "cdb"
6094 .cindex "binary zero" "in lookup key"
6095 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6096 string without a terminating binary zero. The cdb format is designed for
6097 indexed files that are read frequently and never updated, except by total
6098 re-creation. As such, it is particularly suitable for large files containing
6099 aliases or other indexed data referenced by an MTA. Information about cdb can
6100 be found in several places:
6102 &url(http://www.pobox.com/~djb/cdb.html)
6103 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6104 &url(http://packages.debian.org/stable/utils/freecdb.html)
6106 A cdb distribution is not needed in order to build Exim with cdb support,
6107 because the code for reading cdb files is included directly in Exim itself.
6108 However, no means of building or testing cdb files is provided with Exim, so
6109 you need to obtain a cdb distribution in order to do this.
6111 .cindex "DBM" "lookup type"
6112 .cindex "lookup" "dbm"
6113 .cindex "binary zero" "in lookup key"
6114 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6115 DBM file by looking up the record with the given key. A terminating binary
6116 zero is included in the key that is passed to the DBM library. See section
6117 &<<SECTdb>>& for a discussion of DBM libraries.
6119 .cindex "Berkeley DB library" "file format"
6120 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6121 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6122 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6123 the DB_UNKNOWN option. This enables it to handle any of the types of database
6124 that the library supports, and can be useful for accessing DBM files created by
6125 other applications. (For earlier DB versions, DB_HASH is always used.)
6127 .cindex "lookup" "dbmnz"
6128 .cindex "lookup" "dbm &-- terminating zero"
6129 .cindex "binary zero" "in lookup key"
6131 .cindex "&_/etc/userdbshadow.dat_&"
6132 .cindex "dmbnz lookup type"
6133 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6134 is not included in the key that is passed to the DBM library. You may need this
6135 if you want to look up data in files that are created by or shared with some
6136 other application that does not use terminating zeros. For example, you need to
6137 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6138 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6139 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6140 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6142 .cindex "lookup" "dsearch"
6143 .cindex "dsearch lookup type"
6144 &(dsearch)&: The given file must be a directory; this is searched for an entry
6145 whose name is the key by calling the &[lstat()]& function. The key may not
6146 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6147 the lookup is the name of the entry, which may be a file, directory,
6148 symbolic link, or any other kind of directory entry. An example of how this
6149 lookup can be used to support virtual domains is given in section
6150 &<<SECTvirtualdomains>>&.
6152 .cindex "lookup" "iplsearch"
6153 .cindex "iplsearch lookup type"
6154 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6155 terminated by a colon or white space or the end of the line. The keys in the
6156 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6157 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6158 being interpreted as a key terminator. For example:
6160 1.2.3.4: data for 1.2.3.4
6161 192.168.0.0/16: data for 192.168.0.0/16
6162 "abcd::cdab": data for abcd::cdab
6163 "abcd:abcd::/32" data for abcd:abcd::/32
6165 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6166 file is searched linearly, using the CIDR masks where present, until a matching
6167 key is found. The first key that matches is used; there is no attempt to find a
6168 &"best"& match. Apart from the way the keys are matched, the processing for
6169 &(iplsearch)& is the same as for &(lsearch)&.
6171 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6172 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6173 lookup types support only literal keys.
6175 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6176 the implicit key is the host's IP address rather than its name (see section
6177 &<<SECThoslispatsikey>>&).
6179 .cindex "linear search"
6180 .cindex "lookup" "lsearch"
6181 .cindex "lsearch lookup type"
6182 .cindex "case sensitivity" "in lsearch lookup"
6183 &(lsearch)&: The given file is a text file that is searched linearly for a
6184 line beginning with the search key, terminated by a colon or white space or the
6185 end of the line. The search is case-insensitive; that is, upper and lower case
6186 letters are treated as the same. The first occurrence of the key that is found
6187 in the file is used.
6189 White space between the key and the colon is permitted. The remainder of the
6190 line, with leading and trailing white space removed, is the data. This can be
6191 continued onto subsequent lines by starting them with any amount of white
6192 space, but only a single space character is included in the data at such a
6193 junction. If the data begins with a colon, the key must be terminated by a
6198 Empty lines and lines beginning with # are ignored, even if they occur in the
6199 middle of an item. This is the traditional textual format of alias files. Note
6200 that the keys in an &(lsearch)& file are literal strings. There is no
6201 wildcarding of any kind.
6203 .cindex "lookup" "lsearch &-- colons in keys"
6204 .cindex "white space" "in lsearch key"
6205 In most &(lsearch)& files, keys are not required to contain colons or #
6206 characters, or white space. However, if you need this feature, it is available.
6207 If a key begins with a doublequote character, it is terminated only by a
6208 matching quote (or end of line), and the normal escaping rules apply to its
6209 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6210 quoted keys (exactly as for unquoted keys). There is no special handling of
6211 quotes for the data part of an &(lsearch)& line.
6214 .cindex "NIS lookup type"
6215 .cindex "lookup" "NIS"
6216 .cindex "binary zero" "in lookup key"
6217 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6218 the given key, without a terminating binary zero. There is a variant called
6219 &(nis0)& which does include the terminating binary zero in the key. This is
6220 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6221 aliases; the full map names must be used.
6224 .cindex "wildlsearch lookup type"
6225 .cindex "lookup" "wildlsearch"
6226 .cindex "nwildlsearch lookup type"
6227 .cindex "lookup" "nwildlsearch"
6228 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6229 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6230 the file may be wildcarded. The difference between these two lookup types is
6231 that for &(wildlsearch)&, each key in the file is string-expanded before being
6232 used, whereas for &(nwildlsearch)&, no expansion takes place.
6234 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6235 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6236 file that are regular expressions can be made case-sensitive by the use of
6237 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6239 . ==== As this is a nested list, any displays it contains must be indented
6240 . ==== as otherwise they are too far to the left.
6243 The string may begin with an asterisk to mean &"ends with"&. For example:
6245 *.a.b.c data for anything.a.b.c
6246 *fish data for anythingfish
6249 The string may begin with a circumflex to indicate a regular expression. For
6250 example, for &(wildlsearch)&:
6252 ^\N\d+\.a\.b\N data for <digits>.a.b
6254 Note the use of &`\N`& to disable expansion of the contents of the regular
6255 expression. If you are using &(nwildlsearch)&, where the keys are not
6256 string-expanded, the equivalent entry is:
6258 ^\d+\.a\.b data for <digits>.a.b
6260 The case-insensitive flag is set at the start of compiling the regular
6261 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6262 For example, to make the entire pattern case-sensitive:
6264 ^(?-i)\d+\.a\.b data for <digits>.a.b
6267 If the regular expression contains white space or colon characters, you must
6268 either quote it (see &(lsearch)& above), or represent these characters in other
6269 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6270 colon. This may be easier than quoting, because if you quote, you have to
6271 escape all the backslashes inside the quotes.
6273 &*Note*&: It is not possible to capture substrings in a regular expression
6274 match for later use, because the results of all lookups are cached. If a lookup
6275 is repeated, the result is taken from the cache, and no actual pattern matching
6276 takes place. The values of all the numeric variables are unset after a
6277 &((n)wildlsearch)& match.
6280 Although I cannot see it being of much use, the general matching function that
6281 is used to implement &((n)wildlsearch)& means that the string may begin with a
6282 lookup name terminated by a semicolon, and followed by lookup data. For
6285 cdb;/some/file data for keys that match the file
6287 The data that is obtained from the nested lookup is discarded.
6290 Keys that do not match any of these patterns are interpreted literally. The
6291 continuation rules for the data are the same as for &(lsearch)&, and keys may
6292 be followed by optional colons.
6294 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6295 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6296 lookup types support only literal keys.
6300 .section "Query-style lookup types" "SECID62"
6301 .cindex "lookup" "query-style types"
6302 .cindex "query-style lookup" "list of types"
6303 The supported query-style lookup types are listed below. Further details about
6304 many of them are given in later sections.
6307 .cindex "DNS" "as a lookup type"
6308 .cindex "lookup" "DNS"
6309 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6310 are given in the supplied query. The resulting data is the contents of the
6311 records. See section &<<SECTdnsdb>>&.
6313 .cindex "InterBase lookup type"
6314 .cindex "lookup" "InterBase"
6315 &(ibase)&: This does a lookup in an InterBase database.
6317 .cindex "LDAP" "lookup type"
6318 .cindex "lookup" "LDAP"
6319 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6320 returns attributes from a single entry. There is a variant called &(ldapm)&
6321 that permits values from multiple entries to be returned. A third variant
6322 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6323 any attribute values. See section &<<SECTldap>>&.
6325 .cindex "MySQL" "lookup type"
6326 .cindex "lookup" "MySQL"
6327 &(mysql)&: The format of the query is an SQL statement that is passed to a
6328 MySQL database. See section &<<SECTsql>>&.
6330 .cindex "NIS+ lookup type"
6331 .cindex "lookup" "NIS+"
6332 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6333 the field to be returned. See section &<<SECTnisplus>>&.
6335 .cindex "Oracle" "lookup type"
6336 .cindex "lookup" "Oracle"
6337 &(oracle)&: The format of the query is an SQL statement that is passed to an
6338 Oracle database. See section &<<SECTsql>>&.
6340 .cindex "lookup" "passwd"
6341 .cindex "passwd lookup type"
6342 .cindex "&_/etc/passwd_&"
6343 &(passwd)& is a query-style lookup with queries that are just user names. The
6344 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6345 success, the result string is the same as you would get from an &(lsearch)&
6346 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6347 password value. For example:
6349 *:42:42:King Rat:/home/kr:/bin/bash
6352 .cindex "PostgreSQL lookup type"
6353 .cindex "lookup" "PostgreSQL"
6354 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6355 PostgreSQL database. See section &<<SECTsql>>&.
6358 .cindex "sqlite lookup type"
6359 .cindex "lookup" "sqlite"
6360 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6361 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6364 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6365 not likely to be useful in normal operation.
6367 .cindex "whoson lookup type"
6368 .cindex "lookup" "whoson"
6369 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6370 allows a server to check whether a particular (dynamically allocated) IP
6371 address is currently allocated to a known (trusted) user and, optionally, to
6372 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6373 at one time for &"POP before SMTP"& authentication, but that approach has been
6374 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6375 &"POP before SMTP"& checking using ACL statements such as
6377 require condition = \
6378 ${lookup whoson {$sender_host_address}{yes}{no}}
6380 The query consists of a single IP address. The value returned is the name of
6381 the authenticated user, which is stored in the variable &$value$&. However, in
6382 this example, the data in &$value$& is not used; the result of the lookup is
6383 one of the fixed strings &"yes"& or &"no"&.
6388 .section "Temporary errors in lookups" "SECID63"
6389 .cindex "lookup" "temporary error in"
6390 Lookup functions can return temporary error codes if the lookup cannot be
6391 completed. For example, an SQL or LDAP database might be unavailable. For this
6392 reason, it is not advisable to use a lookup that might do this for critical
6393 options such as a list of local domains.
6395 When a lookup cannot be completed in a router or transport, delivery
6396 of the message (to the relevant address) is deferred, as for any other
6397 temporary error. In other circumstances Exim may assume the lookup has failed,
6398 or may give up altogether.
6402 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6403 .cindex "wildcard lookups"
6404 .cindex "lookup" "default values"
6405 .cindex "lookup" "wildcard"
6406 .cindex "lookup" "* added to type"
6407 .cindex "default" "in single-key lookups"
6408 In this context, a &"default value"& is a value specified by the administrator
6409 that is to be used if a lookup fails.
6411 &*Note:*& This section applies only to single-key lookups. For query-style
6412 lookups, the facilities of the query language must be used. An attempt to
6413 specify a default for a query-style lookup provokes an error.
6415 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6416 and the initial lookup fails, the key &"*"& is looked up in the file to
6417 provide a default value. See also the section on partial matching below.
6419 .cindex "*@ with single-key lookup"
6420 .cindex "lookup" "*@ added to type"
6421 .cindex "alias file" "per-domain default"
6422 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6423 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6424 character, a second lookup is done with everything before the last @ replaced
6425 by *. This makes it possible to provide per-domain defaults in alias files
6426 that include the domains in the keys. If the second lookup fails (or doesn't
6427 take place because there is no @ in the key), &"*"& is looked up.
6428 For example, a &(redirect)& router might contain:
6430 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6432 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6433 looks up these keys, in this order:
6439 The data is taken from whichever key it finds first. &*Note*&: In an
6440 &(lsearch)& file, this does not mean the first of these keys in the file. A
6441 complete scan is done for each key, and only if it is not found at all does
6442 Exim move on to try the next key.
6446 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6447 .cindex "partial matching"
6448 .cindex "wildcard lookups"
6449 .cindex "lookup" "partial matching"
6450 .cindex "lookup" "wildcard"
6451 .cindex "asterisk" "in search type"
6452 The normal operation of a single-key lookup is to search the file for an exact
6453 match with the given key. However, in a number of situations where domains are
6454 being looked up, it is useful to be able to do partial matching. In this case,
6455 information in the file that has a key starting with &"*."& is matched by any
6456 domain that ends with the components that follow the full stop. For example, if
6457 a key in a DBM file is
6459 *.dates.fict.example
6461 then when partial matching is enabled this is matched by (amongst others)
6462 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6463 by &'dates.fict.example'&, if that does not appear as a separate key in the
6466 &*Note*&: Partial matching is not available for query-style lookups. It is
6467 also not available for any lookup items in address lists (see section
6468 &<<SECTaddresslist>>&).
6470 Partial matching is implemented by doing a series of separate lookups using
6471 keys constructed by modifying the original subject key. This means that it can
6472 be used with any of the single-key lookup types, provided that
6473 partial matching keys
6474 beginning with a special prefix (default &"*."&) are included in the data file.
6475 Keys in the file that do not begin with the prefix are matched only by
6476 unmodified subject keys when partial matching is in use.
6478 Partial matching is requested by adding the string &"partial-"& to the front of
6479 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6480 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6481 is added at the start of the subject key, and it is looked up again. If that
6482 fails, further lookups are tried with dot-separated components removed from the
6483 start of the subject key, one-by-one, and &"*."& added on the front of what
6486 A minimum number of two non-* components are required. This can be adjusted
6487 by including a number before the hyphen in the search type. For example,
6488 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6489 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6490 subject key is &'2250.dates.fict.example'& then the following keys are looked
6491 up when the minimum number of non-* components is two:
6493 2250.dates.fict.example
6494 *.2250.dates.fict.example
6495 *.dates.fict.example
6498 As soon as one key in the sequence is successfully looked up, the lookup
6501 .cindex "lookup" "partial matching &-- changing prefix"
6502 .cindex "prefix" "for partial matching"
6503 The use of &"*."& as the partial matching prefix is a default that can be
6504 changed. The motivation for this feature is to allow Exim to operate with file
6505 formats that are used by other MTAs. A different prefix can be supplied in
6506 parentheses instead of the hyphen after &"partial"&. For example:
6508 domains = partial(.)lsearch;/some/file
6510 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6511 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6512 components is unchanged). The prefix may consist of any punctuation characters
6513 other than a closing parenthesis. It may be empty, for example:
6515 domains = partial1()cdb;/some/file
6517 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6518 &`a.b.c`&, &`b.c`&, and &`c`&.
6520 If &"partial0"& is specified, what happens at the end (when the lookup with
6521 just one non-wild component has failed, and the original key is shortened right
6522 down to the null string) depends on the prefix:
6525 If the prefix has zero length, the whole lookup fails.
6527 If the prefix has length 1, a lookup for just the prefix is done. For
6528 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6530 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6531 remainder is looked up. With the default prefix, therefore, the final lookup is
6532 for &"*"& on its own.
6534 Otherwise, the whole prefix is looked up.
6538 If the search type ends in &"*"& or &"*@"& (see section
6539 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6540 this implies happens after all partial lookups have failed. If &"partial0"& is
6541 specified, adding &"*"& to the search type has no effect with the default
6542 prefix, because the &"*"& key is already included in the sequence of partial
6543 lookups. However, there might be a use for lookup types such as
6544 &"partial0(.)lsearch*"&.
6546 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6547 in domain lists and the like. Partial matching works only in terms of
6548 dot-separated components; a key such as &`*fict.example`&
6549 in a database file is useless, because the asterisk in a partial matching
6550 subject key is always followed by a dot.
6555 .section "Lookup caching" "SECID64"
6556 .cindex "lookup" "caching"
6557 .cindex "caching" "lookup data"
6558 Exim caches all lookup results in order to avoid needless repetition of
6559 lookups. However, because (apart from the daemon) Exim operates as a collection
6560 of independent, short-lived processes, this caching applies only within a
6561 single Exim process. There is no inter-process lookup caching facility.
6563 For single-key lookups, Exim keeps the relevant files open in case there is
6564 another lookup that needs them. In some types of configuration this can lead to
6565 many files being kept open for messages with many recipients. To avoid hitting
6566 the operating system limit on the number of simultaneously open files, Exim
6567 closes the least recently used file when it needs to open more files than its
6568 own internal limit, which can be changed via the &%lookup_open_max%& option.
6570 The single-key lookup files are closed and the lookup caches are flushed at
6571 strategic points during delivery &-- for example, after all routing is
6577 .section "Quoting lookup data" "SECID65"
6578 .cindex "lookup" "quoting"
6579 .cindex "quoting" "in lookups"
6580 When data from an incoming message is included in a query-style lookup, there
6581 is the possibility of special characters in the data messing up the syntax of
6582 the query. For example, a NIS+ query that contains
6586 will be broken if the local part happens to contain a closing square bracket.
6587 For NIS+, data can be enclosed in double quotes like this:
6589 [name="$local_part"]
6591 but this still leaves the problem of a double quote in the data. The rule for
6592 NIS+ is that double quotes must be doubled. Other lookup types have different
6593 rules, and to cope with the differing requirements, an expansion operator
6594 of the following form is provided:
6596 ${quote_<lookup-type>:<string>}
6598 For example, the safest way to write the NIS+ query is
6600 [name="${quote_nisplus:$local_part}"]
6602 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6603 operator can be used for all lookup types, but has no effect for single-key
6604 lookups, since no quoting is ever needed in their key strings.
6609 .section "More about dnsdb" "SECTdnsdb"
6610 .cindex "dnsdb lookup"
6611 .cindex "lookup" "dnsdb"
6612 .cindex "DNS" "as a lookup type"
6613 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6614 of a record type and a domain name, separated by an equals sign. For example,
6615 an expansion string could contain:
6617 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6619 If the lookup succeeds, the result is placed in &$value$&, which in this case
6620 is used on its own as the result. If the lookup does not succeed, the
6621 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6622 &<<SECTforexpfai>>& for an explanation of what this means.
6624 The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and,
6625 when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6626 configured). If no type is given, TXT is assumed. When the type is PTR,
6627 the data can be an IP address, written as normal; inversion and the addition of
6628 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6630 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6632 If the data for a PTR record is not a syntactically valid IP address, it is not
6633 altered and nothing is added.
6635 .cindex "MX record" "in &(dnsdb)& lookup"
6636 .cindex "SRV record" "in &(dnsdb)& lookup"
6637 For an MX lookup, both the preference value and the host name are returned for
6638 each record, separated by a space. For an SRV lookup, the priority, weight,
6639 port, and host name are returned for each record, separated by spaces.
6641 For any record type, if multiple records are found (or, for A6 lookups, if a
6642 single record leads to multiple addresses), the data is returned as a
6643 concatenation, with newline as the default separator. The order, of course,
6644 depends on the DNS resolver. You can specify a different separator character
6645 between multiple records by putting a right angle-bracket followed immediately
6646 by the new separator at the start of the query. For example:
6648 ${lookup dnsdb{>: a=host1.example}}
6650 It is permitted to specify a space as the separator character. Further
6651 white space is ignored.
6654 .cindex "TXT record" "in &(dnsdb)& lookup"
6655 For TXT records with multiple items of data, only the first item is returned,
6656 unless a separator for them is specified using a comma after the separator
6657 character followed immediately by the TXT record item separator. To concatenate
6658 items without a separator, use a semicolon instead.
6660 ${lookup dnsdb{>\n,: txt=a.b.example}}
6661 ${lookup dnsdb{>\n; txt=a.b.example}}
6663 It is permitted to specify a space as the separator character. Further
6664 white space is ignored.
6667 .section "Pseudo dnsdb record types" "SECID66"
6668 .cindex "MX record" "in &(dnsdb)& lookup"
6669 By default, both the preference value and the host name are returned for
6670 each MX record, separated by a space. If you want only host names, you can use
6671 the pseudo-type MXH:
6673 ${lookup dnsdb{mxh=a.b.example}}
6675 In this case, the preference values are omitted, and just the host names are
6678 .cindex "name server for enclosing domain"
6679 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6680 records on the given domain, but if none are found, it removes the first
6681 component of the domain name, and tries again. This process continues until NS
6682 records are found or there are no more components left (or there is a DNS
6683 error). In other words, it may return the name servers for a top-level domain,
6684 but it never returns the root name servers. If there are no NS records for the
6685 top-level domain, the lookup fails. Consider these examples:
6687 ${lookup dnsdb{zns=xxx.quercite.com}}
6688 ${lookup dnsdb{zns=xxx.edu}}
6690 Assuming that in each case there are no NS records for the full domain name,
6691 the first returns the name servers for &%quercite.com%&, and the second returns
6692 the name servers for &%edu%&.
6694 You should be careful about how you use this lookup because, unless the
6695 top-level domain does not exist, the lookup always returns some host names. The
6696 sort of use to which this might be put is for seeing if the name servers for a
6697 given domain are on a blacklist. You can probably assume that the name servers
6698 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6701 .cindex "CSA" "in &(dnsdb)& lookup"
6702 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6703 records according to the CSA rules, which are described in section
6704 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6705 not sufficient because of the extra parent domain search behaviour of CSA. The
6706 result of a successful lookup such as:
6708 ${lookup dnsdb {csa=$sender_helo_name}}
6710 has two space-separated fields: an authorization code and a target host name.
6711 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6712 authorization required but absent, or &"?"& for unknown.
6715 .section "Multiple dnsdb lookups" "SECID67"
6716 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6717 However, you can specify a list of domains or IP addresses in a single
6718 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6719 the default separator, but with the ability to change this. For example:
6721 ${lookup dnsdb{one.domain.com:two.domain.com}}
6722 ${lookup dnsdb{a=one.host.com:two.host.com}}
6723 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6725 In order to retain backwards compatibility, there is one special case: if
6726 the lookup type is PTR and no change of separator is specified, Exim looks
6727 to see if the rest of the string is precisely one IPv6 address. In this
6728 case, it does not treat it as a list.
6730 The data from each lookup is concatenated, with newline separators by default,
6731 in the same way that multiple DNS records for a single item are handled. A
6732 different separator can be specified, as described above.
6734 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6735 temporary DNS error for any of them, the behaviour is controlled by
6736 an optional keyword followed by a comma that may appear before the record
6737 type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
6738 &"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
6739 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6740 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6741 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6742 error causes the whole lookup to defer only if none of the other lookups
6743 succeed. The default is &"lax"&, so the following lookups are equivalent:
6745 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6746 ${lookup dnsdb{a=one.host.com:two.host.com}}
6748 Thus, in the default case, as long as at least one of the DNS lookups
6749 yields some data, the lookup succeeds.
6754 .section "More about LDAP" "SECTldap"
6755 .cindex "LDAP" "lookup, more about"
6756 .cindex "lookup" "LDAP"
6757 .cindex "Solaris" "LDAP"
6758 The original LDAP implementation came from the University of Michigan; this has
6759 become &"Open LDAP"&, and there are now two different releases. Another
6760 implementation comes from Netscape, and Solaris 7 and subsequent releases
6761 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6762 the lookup function level, their error handling is different. For this reason
6763 it is necessary to set a compile-time variable when building Exim with LDAP, to
6764 indicate which LDAP library is in use. One of the following should appear in
6765 your &_Local/Makefile_&:
6767 LDAP_LIB_TYPE=UMICHIGAN
6768 LDAP_LIB_TYPE=OPENLDAP1
6769 LDAP_LIB_TYPE=OPENLDAP2
6770 LDAP_LIB_TYPE=NETSCAPE
6771 LDAP_LIB_TYPE=SOLARIS
6773 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
6774 same interface as the University of Michigan version.
6776 There are three LDAP lookup types in Exim. These behave slightly differently in
6777 the way they handle the results of a query:
6780 &(ldap)& requires the result to contain just one entry; if there are more, it
6783 &(ldapdn)& also requires the result to contain just one entry, but it is the
6784 Distinguished Name that is returned rather than any attribute values.
6786 &(ldapm)& permits the result to contain more than one entry; the attributes
6787 from all of them are returned.
6791 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
6792 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6793 the data returned by a successful lookup is described in the next section.
6794 First we explain how LDAP queries are coded.
6797 .section "Format of LDAP queries" "SECTforldaque"
6798 .cindex "LDAP" "query format"
6799 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6800 the configuration of a &(redirect)& router one might have this setting:
6802 data = ${lookup ldap \
6803 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6804 c=UK?mailbox?base?}}
6806 .cindex "LDAP" "with TLS"
6807 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
6808 secure (encrypted) LDAP connections. The second of these ensures that an
6809 encrypted TLS connection is used.
6812 .section "LDAP quoting" "SECID68"
6813 .cindex "LDAP" "quoting"
6814 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6815 and the second because the LDAP query is represented as a URL. Furthermore,
6816 within an LDAP query, two different kinds of quoting are required. For this
6817 reason, there are two different LDAP-specific quoting operators.
6819 The &%quote_ldap%& operator is designed for use on strings that are part of
6820 filter specifications. Conceptually, it first does the following conversions on
6828 in accordance with RFC 2254. The resulting string is then quoted according
6829 to the rules for URLs, that is, all non-alphanumeric characters except
6833 are converted to their hex values, preceded by a percent sign. For example:
6835 ${quote_ldap: a(bc)*, a<yz>; }
6839 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6841 Removing the URL quoting, this is (with a leading and a trailing space):
6843 a\28bc\29\2A, a<yz>;
6845 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
6846 base DN specifications in queries. Conceptually, it first converts the string
6847 by inserting a backslash in front of any of the following characters:
6851 It also inserts a backslash before any leading spaces or # characters, and
6852 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6853 is then quoted according to the rules for URLs. For example:
6855 ${quote_ldap_dn: a(bc)*, a<yz>; }
6859 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6861 Removing the URL quoting, this is (with a trailing space):
6863 \ a(bc)*\, a\<yz\>\;\
6865 There are some further comments about quoting in the section on LDAP
6866 authentication below.
6869 .section "LDAP connections" "SECID69"
6870 .cindex "LDAP" "connections"
6871 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6872 is in use, via a Unix domain socket. The example given above does not specify
6873 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6876 ldap://<hostname>:<port>/...
6878 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6879 used. When no server is specified in a query, a list of default servers is
6880 taken from the &%ldap_default_servers%& configuration option. This supplies a
6881 colon-separated list of servers which are tried in turn until one successfully
6882 handles a query, or there is a serious error. Successful handling either
6883 returns the requested data, or indicates that it does not exist. Serious errors
6884 are syntactical, or multiple values when only a single value is expected.
6885 Errors which cause the next server to be tried are connection failures, bind
6886 failures, and timeouts.
6888 For each server name in the list, a port number can be given. The standard way
6889 of specifying a host and port is to use a colon separator (RFC 1738). Because
6890 &%ldap_default_servers%& is a colon-separated list, such colons have to be
6891 doubled. For example
6893 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6895 If &%ldap_default_servers%& is unset, a URL with no server name is passed
6896 to the LDAP library with no server name, and the library's default (normally
6897 the local host) is used.
6899 If you are using the OpenLDAP library, you can connect to an LDAP server using
6900 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6901 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
6902 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6905 For this type of connection, instead of a host name for the server, a pathname
6906 for the socket is required, and the port number is not relevant. The pathname
6907 can be specified either as an item in &%ldap_default_servers%&, or inline in
6908 the query. In the former case, you can have settings such as
6910 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6912 When the pathname is given in the query, you have to escape the slashes as
6913 &`%2F`& to fit in with the LDAP URL syntax. For example:
6915 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6917 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
6918 a pathname, it uses the Unix domain socket code, even if the query actually
6919 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
6920 socket connection. This behaviour means that you can use a setting of
6921 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
6922 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
6923 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6926 If an explicit &`ldapi`& type is given in a query when a host name is
6927 specified, an error is diagnosed. However, if there are more items in
6928 &%ldap_default_servers%&, they are tried. In other words:
6931 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
6934 Using &`ldapi`& with a host name causes an error.
6938 Using &`ldapi`& with no host or path in the query, and no setting of
6939 &%ldap_default_servers%&, does whatever the library does by default.
6943 .section "LDAP authentication and control information" "SECID70"
6944 .cindex "LDAP" "authentication"
6945 The LDAP URL syntax provides no way of passing authentication and other control
6946 information to the server. To make this possible, the URL in an LDAP query may
6947 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
6948 spaces. If a value contains spaces it must be enclosed in double quotes, and
6949 when double quotes are used, backslash is interpreted in the usual way inside
6950 them. The following names are recognized:
6952 &`DEREFERENCE`& set the dereferencing parameter
6953 &`NETTIME `& set a timeout for a network operation
6954 &`USER `& set the DN, for authenticating the LDAP bind
6955 &`PASS `& set the password, likewise
6956 &`REFERRALS `& set the referrals parameter
6957 &`SIZE `& set the limit for the number of entries returned
6958 &`TIME `& set the maximum waiting time for a query
6960 The value of the DEREFERENCE parameter must be one of the words &"never"&,
6961 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
6962 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
6963 library from trying to follow referrals issued by the LDAP server.
6965 The name CONNECT is an obsolete name for NETTIME, retained for
6966 backwards compatibility. This timeout (specified as a number of seconds) is
6967 enforced from the client end for operations that can be carried out over a
6968 network. Specifically, it applies to network connections and calls to the
6969 &'ldap_result()'& function. If the value is greater than zero, it is used if
6970 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
6971 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
6972 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
6973 Netscape SDK; for OpenLDAP no action is taken.
6975 The TIME parameter (also a number of seconds) is passed to the server to
6976 set a server-side limit on the time taken to complete a search.
6979 Here is an example of an LDAP query in an Exim lookup that uses some of these
6980 values. This is a single line, folded to fit on the page:
6983 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6984 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6987 The encoding of spaces as &`%20`& is a URL thing which should not be done for
6988 any of the auxiliary data. Exim configuration settings that include lookups
6989 which contain password information should be preceded by &"hide"& to prevent
6990 non-admin users from using the &%-bP%& option to see their values.
6992 The auxiliary data items may be given in any order. The default is no
6993 connection timeout (the system timeout is used), no user or password, no limit
6994 on the number of entries returned, and no time limit on queries.
6996 When a DN is quoted in the USER= setting for LDAP authentication, Exim
6997 removes any URL quoting that it may contain before passing it LDAP. Apparently
6998 some libraries do this for themselves, but some do not. Removing the URL
6999 quoting has two advantages:
7002 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7003 DNs as with DNs inside actual queries.
7005 It permits spaces inside USER= DNs.
7008 For example, a setting such as
7010 USER=cn=${quote_ldap_dn:$1}
7012 should work even if &$1$& contains spaces.
7014 Expanded data for the PASS= value should be quoted using the &%quote%&
7015 expansion operator, rather than the LDAP quote operators. The only reason this
7016 field needs quoting is to ensure that it conforms to the Exim syntax, which
7017 does not allow unquoted spaces. For example:
7021 The LDAP authentication mechanism can be used to check passwords as part of
7022 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7027 .section "Format of data returned by LDAP" "SECID71"
7028 .cindex "LDAP" "returned data formats"
7029 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7030 as a sequence of values, for example
7032 cn=manager, o=University of Cambridge, c=UK
7034 The &(ldap)& lookup type generates an error if more than one entry matches the
7035 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7036 the result between the data from different entries. It is possible for multiple
7037 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7038 you know that whatever values are returned all came from a single entry in the
7041 In the common case where you specify a single attribute in your LDAP query, the
7042 result is not quoted, and does not contain the attribute name. If the attribute
7043 has multiple values, they are separated by commas.
7045 If you specify multiple attributes, the result contains space-separated, quoted
7046 strings, each preceded by the attribute name and an equals sign. Within the
7047 quotes, the quote character, backslash, and newline are escaped with
7048 backslashes, and commas are used to separate multiple values for the attribute.
7049 Apart from the escaping, the string within quotes takes the same form as the
7050 output when a single attribute is requested. Specifying no attributes is the
7051 same as specifying all of an entry's attributes.
7053 Here are some examples of the output format. The first line of each pair is an
7054 LDAP query, and the second is the data that is returned. The attribute called
7055 &%attr1%& has two values, whereas &%attr2%& has only one value:
7057 ldap:///o=base?attr1?sub?(uid=fred)
7060 ldap:///o=base?attr2?sub?(uid=fred)
7063 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7064 attr1="value1.1, value1.2" attr2="value two"
7066 ldap:///o=base??sub?(uid=fred)
7067 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
7069 The &%extract%& operator in string expansions can be used to pick out
7070 individual fields from data that consists of &'key'&=&'value'& pairs. You can
7071 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7072 results of LDAP lookups.
7077 .section "More about NIS+" "SECTnisplus"
7078 .cindex "NIS+ lookup type"
7079 .cindex "lookup" "NIS+"
7080 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7081 and field name. If this is given, the result of a successful query is the
7082 contents of the named field; otherwise the result consists of a concatenation
7083 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7084 values containing spaces are quoted. For example, the query
7086 [name=mg1456],passwd.org_dir
7088 might return the string
7090 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7091 home=/home/mg1456 shell=/bin/bash shadow=""
7093 (split over two lines here to fit on the page), whereas
7095 [name=mg1456],passwd.org_dir:gcos
7101 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7102 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7103 operator is to double any quote characters within the text.
7107 .section "SQL lookups" "SECTsql"
7108 .cindex "SQL lookup types"
7109 .cindex "MySQL" "lookup type"
7110 .cindex "PostgreSQL lookup type"
7111 .cindex "lookup" "MySQL"
7112 .cindex "lookup" "PostgreSQL"
7113 .cindex "Oracle" "lookup type"
7114 .cindex "lookup" "Oracle"
7115 .cindex "InterBase lookup type"
7116 .cindex "lookup" "InterBase"
7117 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7118 databases. Queries for these databases contain SQL statements, so an example
7121 ${lookup mysql{select mailbox from users where id='userx'}\
7124 If the result of the query contains more than one field, the data for each
7125 field in the row is returned, preceded by its name, so the result of
7127 ${lookup pgsql{select home,name from users where id='userx'}\
7132 home=/home/userx name="Mister X"
7134 Empty values and values containing spaces are double quoted, with embedded
7135 quotes escaped by a backslash. If the result of the query contains just one
7136 field, the value is passed back verbatim, without a field name, for example:
7140 If the result of the query yields more than one row, it is all concatenated,
7141 with a newline between the data for each row.
7144 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7145 .cindex "MySQL" "lookup type"
7146 .cindex "PostgreSQL lookup type"
7147 .cindex "lookup" "MySQL"
7148 .cindex "lookup" "PostgreSQL"
7149 .cindex "Oracle" "lookup type"
7150 .cindex "lookup" "Oracle"
7151 .cindex "InterBase lookup type"
7152 .cindex "lookup" "InterBase"
7153 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7154 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7155 option (as appropriate) must be set to a colon-separated list of server
7157 (For MySQL and PostgreSQL only, the global option need not be set if all
7158 queries contain their own server information &-- see section
7159 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7160 items: host name, database name, user name, and password. In the case of
7161 Oracle, the host name field is used for the &"service name"&, and the database
7162 name field is not used and should be empty. For example:
7164 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7166 Because password data is sensitive, you should always precede the setting with
7167 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7168 option. Here is an example where two MySQL servers are listed:
7170 hide mysql_servers = localhost/users/root/secret:\
7171 otherhost/users/root/othersecret
7173 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7174 because this is a colon-separated list, the colon has to be doubled. For each
7175 query, these parameter groups are tried in order until a connection is made and
7176 a query is successfully processed. The result of a query may be that no data is
7177 found, but that is still a successful query. In other words, the list of
7178 servers provides a backup facility, not a list of different places to look.
7180 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7181 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7182 respectively, and the characters single-quote, double-quote, and backslash
7183 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7184 addition, escapes the percent and underscore characters. This cannot be done
7185 for MySQL because these escapes are not recognized in contexts where these
7186 characters are not special.
7188 .section "Specifying the server in the query" "SECTspeserque"
7189 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7190 it is possible to specify a list of servers with an individual query. This is
7191 done by starting the query with
7193 &`servers=`&&'server1:server2:server3:...'&&`;`&
7195 Each item in the list may take one of two forms:
7197 If it contains no slashes it is assumed to be just a host name. The appropriate
7198 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7199 of the same name, and the remaining parameters (database, user, password) are
7202 If it contains any slashes, it is taken as a complete parameter set.
7204 The list of servers is used in exactly the same way as the global list.
7205 Once a connection to a server has happened and a query has been
7206 successfully executed, processing of the lookup ceases.
7208 This feature is intended for use in master/slave situations where updates
7209 are occurring and you want to update the master rather than a slave. If the
7210 master is in the list as a backup for reading, you might have a global setting
7213 mysql_servers = slave1/db/name/pw:\
7217 In an updating lookup, you could then write:
7219 ${lookup mysql{servers=master; UPDATE ...} }
7221 That query would then be sent only to the master server. If, on the other hand,
7222 the master is not to be used for reading, and so is not present in the global
7223 option, you can still update it by a query of this form:
7225 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7229 .section "Special MySQL features" "SECID73"
7230 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7231 causes a connection to the server on the local host by means of a Unix domain
7232 socket. An alternate socket can be specified in parentheses. The full syntax of
7233 each item in &%mysql_servers%& is:
7235 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7236 <&'user'&>/<&'password'&>
7238 Any of the three sub-parts of the first field can be omitted. For normal use on
7239 the local host it can be left blank or set to just &"localhost"&.
7241 No database need be supplied &-- but if it is absent here, it must be given in
7244 If a MySQL query is issued that does not request any data (an insert, update,
7245 or delete command), the result of the lookup is the number of rows affected.
7247 &*Warning*&: This can be misleading. If an update does not actually change
7248 anything (for example, setting a field to the value it already has), the result
7249 is zero because no rows are affected.
7252 .section "Special PostgreSQL features" "SECID74"
7253 PostgreSQL lookups can also use Unix domain socket connections to the database.
7254 This is usually faster and costs less CPU time than a TCP/IP connection.
7255 However it can be used only if the mail server runs on the same machine as the
7256 database server. A configuration line for PostgreSQL via Unix domain sockets
7259 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7261 In other words, instead of supplying a host name, a path to the socket is
7262 given. The path name is enclosed in parentheses so that its slashes aren't
7263 visually confused with the delimiters for the other server parameters.
7265 If a PostgreSQL query is issued that does not request any data (an insert,
7266 update, or delete command), the result of the lookup is the number of rows
7269 .section "More about SQLite" "SECTsqlite"
7270 .cindex "lookup" "SQLite"
7271 .cindex "sqlite lookup type"
7272 SQLite is different to the other SQL lookups because a file name is required in
7273 addition to the SQL query. An SQLite database is a single file, and there is no
7274 daemon as in the other SQL databases. The interface to Exim requires the name
7275 of the file, as an absolute path, to be given at the start of the query. It is
7276 separated from the query by white space. This means that the path name cannot
7277 contain white space. Here is a lookup expansion example:
7279 ${lookup sqlite {/some/thing/sqlitedb \
7280 select name from aliases where id='userx';}}
7282 In a list, the syntax is similar. For example:
7284 domainlist relay_domains = sqlite;/some/thing/sqlitedb \
7285 select * from relays where ip='$sender_host_address';
7287 The only character affected by the &%quote_sqlite%& operator is a single
7288 quote, which it doubles.
7290 The SQLite library handles multiple simultaneous accesses to the database
7291 internally. Multiple readers are permitted, but only one process can
7292 update at once. Attempts to access the database while it is being updated
7293 are rejected after a timeout period, during which the SQLite library
7294 waits for the lock to be released. In Exim, the default timeout is set
7295 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7301 . ////////////////////////////////////////////////////////////////////////////
7302 . ////////////////////////////////////////////////////////////////////////////
7304 .chapter "Domain, host, address, and local part lists" &&&
7305 "CHAPdomhosaddlists" &&&
7306 "Domain, host, and address lists"
7307 .scindex IIDdohoadli "lists of domains; hosts; etc."
7308 A number of Exim configuration options contain lists of domains, hosts,
7309 email addresses, or local parts. For example, the &%hold_domains%& option
7310 contains a list of domains whose delivery is currently suspended. These lists
7311 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7312 arguments to expansion conditions such as &%match_domain%&.
7314 Each item in one of these lists is a pattern to be matched against a domain,
7315 host, email address, or local part, respectively. In the sections below, the
7316 different types of pattern for each case are described, but first we cover some
7317 general facilities that apply to all four kinds of list.
7321 .section "Expansion of lists" "SECID75"
7322 .cindex "expansion" "of lists"
7323 Each list is expanded as a single string before it is used. The result of
7324 expansion must be a list, possibly containing empty items, which is split up
7325 into separate items for matching. By default, colon is the separator character,
7326 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7327 &<<SECTempitelis>>& for details of the list syntax; the second of these
7328 discusses the way to specify empty list items.
7331 If the string expansion is forced to fail, Exim behaves as if the item it is
7332 testing (domain, host, address, or local part) is not in the list. Other
7333 expansion failures cause temporary errors.
7335 If an item in a list is a regular expression, backslashes, dollars and possibly
7336 other special characters in the expression must be protected against
7337 misinterpretation by the string expander. The easiest way to do this is to use
7338 the &`\N`& expansion feature to indicate that the contents of the regular
7339 expression should not be expanded. For example, in an ACL you might have:
7341 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7342 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7344 The first item is a regular expression that is protected from expansion by
7345 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7346 senders based on the receiving domain.
7351 .section "Negated items in lists" "SECID76"
7352 .cindex "list" "negation"
7353 .cindex "negation" "in lists"
7354 Items in a list may be positive or negative. Negative items are indicated by a
7355 leading exclamation mark, which may be followed by optional white space. A list
7356 defines a set of items (domains, etc). When Exim processes one of these lists,
7357 it is trying to find out whether a domain, host, address, or local part
7358 (respectively) is in the set that is defined by the list. It works like this:
7360 The list is scanned from left to right. If a positive item is matched, the
7361 subject that is being checked is in the set; if a negative item is matched, the
7362 subject is not in the set. If the end of the list is reached without the
7363 subject having matched any of the patterns, it is in the set if the last item
7364 was a negative one, but not if it was a positive one. For example, the list in
7366 domainlist relay_domains = !a.b.c : *.b.c
7368 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7369 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7370 list is positive. However, if the setting were
7372 domainlist relay_domains = !a.b.c
7374 then all domains other than &'a.b.c'& would match because the last item in the
7375 list is negative. In other words, a list that ends with a negative item behaves
7376 as if it had an extra item &`:*`& on the end.
7378 Another way of thinking about positive and negative items in lists is to read
7379 the connector as &"or"& after a positive item and as &"and"& after a negative
7384 .section "File names in lists" "SECTfilnamlis"
7385 .cindex "list" "file name in"
7386 If an item in a domain, host, address, or local part list is an absolute file
7387 name (beginning with a slash character), each line of the file is read and
7388 processed as if it were an independent item in the list, except that further
7389 file names are not allowed,
7390 and no expansion of the data from the file takes place.
7391 Empty lines in the file are ignored, and the file may also contain comment
7395 For domain and host lists, if a # character appears anywhere in a line of the
7396 file, it and all following characters are ignored.
7398 Because local parts may legitimately contain # characters, a comment in an
7399 address list or local part list file is recognized only if # is preceded by
7400 white space or the start of the line. For example:
7402 not#comment@x.y.z # but this is a comment
7406 Putting a file name in a list has the same effect as inserting each line of the
7407 file as an item in the list (blank lines and comments excepted). However, there
7408 is one important difference: the file is read each time the list is processed,
7409 so if its contents vary over time, Exim's behaviour changes.
7411 If a file name is preceded by an exclamation mark, the sense of any match
7412 within the file is inverted. For example, if
7414 hold_domains = !/etc/nohold-domains
7416 and the file contains the lines
7421 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7422 any domain matching &`*.b.c`& is not.
7426 .section "An lsearch file is not an out-of-line list" "SECID77"
7427 As will be described in the sections that follow, lookups can be used in lists
7428 to provide indexed methods of checking list membership. There has been some
7429 confusion about the way &(lsearch)& lookups work in lists. Because
7430 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7431 sometimes thought that it is allowed to contain wild cards and other kinds of
7432 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7433 always fixed strings, just as for any other single-key lookup type.
7435 If you want to use a file to contain wild-card patterns that form part of a
7436 list, just give the file name on its own, without a search type, as described
7437 in the previous section. You could also use the &(wildlsearch)& or
7438 &(nwildlsearch)&, but there is no advantage in doing this.
7443 .section "Named lists" "SECTnamedlists"
7444 .cindex "named lists"
7445 .cindex "list" "named"
7446 A list of domains, hosts, email addresses, or local parts can be given a name
7447 which is then used to refer to the list elsewhere in the configuration. This is
7448 particularly convenient if the same list is required in several different
7449 places. It also allows lists to be given meaningful names, which can improve
7450 the readability of the configuration. For example, it is conventional to define
7451 a domain list called &'local_domains'& for all the domains that are handled
7452 locally on a host, using a configuration line such as
7454 domainlist local_domains = localhost:my.dom.example
7456 Named lists are referenced by giving their name preceded by a plus sign, so,
7457 for example, a router that is intended to handle local domains would be
7458 configured with the line
7460 domains = +local_domains
7462 The first router in a configuration is often one that handles all domains
7463 except the local ones, using a configuration with a negated item like this:
7467 domains = ! +local_domains
7468 transport = remote_smtp
7471 The four kinds of named list are created by configuration lines starting with
7472 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7473 respectively. Then there follows the name that you are defining, followed by an
7474 equals sign and the list itself. For example:
7476 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7477 addresslist bad_senders = cdb;/etc/badsenders
7479 A named list may refer to other named lists:
7481 domainlist dom1 = first.example : second.example
7482 domainlist dom2 = +dom1 : third.example
7483 domainlist dom3 = fourth.example : +dom2 : fifth.example
7485 &*Warning*&: If the last item in a referenced list is a negative one, the
7486 effect may not be what you intended, because the negation does not propagate
7487 out to the higher level. For example, consider:
7489 domainlist dom1 = !a.b
7490 domainlist dom2 = +dom1 : *.b
7492 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7493 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7494 means it matches the second list as well. The effect is not the same as
7496 domainlist dom2 = !a.b : *.b
7498 where &'x.y'& does not match. It's best to avoid negation altogether in
7499 referenced lists if you can.
7501 Named lists may have a performance advantage. When Exim is routing an
7502 address or checking an incoming message, it caches the result of tests on named
7503 lists. So, if you have a setting such as
7505 domains = +local_domains
7507 on several of your routers
7508 or in several ACL statements,
7509 the actual test is done only for the first one. However, the caching works only
7510 if there are no expansions within the list itself or any sublists that it
7511 references. In other words, caching happens only for lists that are known to be
7512 the same each time they are referenced.
7514 By default, there may be up to 16 named lists of each type. This limit can be
7515 extended by changing a compile-time variable. The use of domain and host lists
7516 is recommended for concepts such as local domains, relay domains, and relay
7517 hosts. The default configuration is set up like this.
7521 .section "Named lists compared with macros" "SECID78"
7522 .cindex "list" "named compared with macro"
7523 .cindex "macro" "compared with named list"
7524 At first sight, named lists might seem to be no different from macros in the
7525 configuration file. However, macros are just textual substitutions. If you
7528 ALIST = host1 : host2
7529 auth_advertise_hosts = !ALIST
7531 it probably won't do what you want, because that is exactly the same as
7533 auth_advertise_hosts = !host1 : host2
7535 Notice that the second host name is not negated. However, if you use a host
7538 hostlist alist = host1 : host2
7539 auth_advertise_hosts = ! +alist
7541 the negation applies to the whole list, and so that is equivalent to
7543 auth_advertise_hosts = !host1 : !host2
7547 .section "Named list caching" "SECID79"
7548 .cindex "list" "caching of named"
7549 .cindex "caching" "named lists"
7550 While processing a message, Exim caches the result of checking a named list if
7551 it is sure that the list is the same each time. In practice, this means that
7552 the cache operates only if the list contains no $ characters, which guarantees
7553 that it will not change when it is expanded. Sometimes, however, you may have
7554 an expanded list that you know will be the same each time within a given
7555 message. For example:
7557 domainlist special_domains = \
7558 ${lookup{$sender_host_address}cdb{/some/file}}
7560 This provides a list of domains that depends only on the sending host's IP
7561 address. If this domain list is referenced a number of times (for example,
7562 in several ACL lines, or in several routers) the result of the check is not
7563 cached by default, because Exim does not know that it is going to be the
7564 same list each time.
7566 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7567 cache the result anyway. For example:
7569 domainlist_cache special_domains = ${lookup{...
7571 If you do this, you should be absolutely sure that caching is going to do
7572 the right thing in all cases. When in doubt, leave it out.
7576 .section "Domain lists" "SECTdomainlist"
7577 .cindex "domain list" "patterns for"
7578 .cindex "list" "domain list"
7579 Domain lists contain patterns that are to be matched against a mail domain.
7580 The following types of item may appear in domain lists:
7583 .cindex "primary host name"
7584 .cindex "host name" "matched in domain list"
7585 .oindex "&%primary_hostname%&"
7586 .cindex "domain list" "matching primary host name"
7587 .cindex "@ in a domain list"
7588 If a pattern consists of a single @ character, it matches the local host name,
7589 as set by the &%primary_hostname%& option (or defaulted). This makes it
7590 possible to use the same configuration file on several different hosts that
7591 differ only in their names.
7593 .cindex "@[] in a domain list"
7594 .cindex "domain list" "matching local IP interfaces"
7595 .cindex "domain literal"
7596 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7597 in square brackets (as in an email address that contains a domain literal), but
7598 only if that IP address is recognized as local for email routing purposes. The
7599 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7600 control which of a host's several IP addresses are treated as local.
7601 In today's Internet, the use of domain literals is controversial.
7604 .cindex "@mx_primary"
7605 .cindex "@mx_secondary"
7606 .cindex "domain list" "matching MX pointers to local host"
7607 If a pattern consists of the string &`@mx_any`& it matches any domain that
7608 has an MX record pointing to the local host or to any host that is listed in
7609 .oindex "&%hosts_treat_as_local%&"
7610 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7611 are similar, except that the first matches only when a primary MX target is the
7612 local host, and the second only when no primary MX target is the local host,
7613 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7614 preference value &-- there may of course be more than one of them.
7616 The MX lookup that takes place when matching a pattern of this type is
7617 performed with the resolver options for widening names turned off. Thus, for
7618 example, a single-component domain will &'not'& be expanded by adding the
7619 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7620 options of the &(dnslookup)& router for a discussion of domain widening.
7622 Sometimes you may want to ignore certain IP addresses when using one of these
7623 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7624 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7625 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7626 on a router). For example:
7628 domains = @mx_any/ignore=127.0.0.1
7630 This example matches any domain that has an MX record pointing to one of
7631 the local host's IP addresses other than 127.0.0.1.
7633 The list of IP addresses is in fact processed by the same code that processes
7634 host lists, so it may contain CIDR-coded network specifications and it may also
7635 contain negative items.
7637 Because the list of IP addresses is a sublist within a domain list, you have to
7638 be careful about delimiters if there is more than one address. Like any other
7639 list, the default delimiter can be changed. Thus, you might have:
7641 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7642 an.other.domain : ...
7644 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7645 involved, it is easiest to change the delimiter for the main list as well:
7647 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7648 an.other.domain ? ...
7651 .cindex "asterisk" "in domain list"
7652 .cindex "domain list" "asterisk in"
7653 .cindex "domain list" "matching &""ends with""&"
7654 If a pattern starts with an asterisk, the remaining characters of the pattern
7655 are compared with the terminating characters of the domain. The use of &"*"& in
7656 domain lists differs from its use in partial matching lookups. In a domain
7657 list, the character following the asterisk need not be a dot, whereas partial
7658 matching works only in terms of dot-separated components. For example, a domain
7659 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7663 .cindex "regular expressions" "in domain list"
7664 .cindex "domain list" "matching regular expression"
7665 If a pattern starts with a circumflex character, it is treated as a regular
7666 expression, and matched against the domain using a regular expression matching
7667 function. The circumflex is treated as part of the regular expression.
7668 Email domains are case-independent, so this regular expression match is by
7669 default case-independent, but you can make it case-dependent by starting it
7670 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7671 are given in chapter &<<CHAPregexp>>&.
7673 &*Warning*&: Because domain lists are expanded before being processed, you
7674 must escape any backslash and dollar characters in the regular expression, or
7675 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7676 it is not to be expanded (unless you really do want to build a regular
7677 expression by expansion, of course).
7679 .cindex "lookup" "in domain list"
7680 .cindex "domain list" "matching by lookup"
7681 If a pattern starts with the name of a single-key lookup type followed by a
7682 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7683 must be a file name in a suitable format for the lookup type. For example, for
7684 &"cdb;"& it must be an absolute path:
7686 domains = cdb;/etc/mail/local_domains.cdb
7688 The appropriate type of lookup is done on the file using the domain name as the
7689 key. In most cases, the data that is looked up is not used; Exim is interested
7690 only in whether or not the key is present in the file. However, when a lookup
7691 is used for the &%domains%& option on a router
7692 or a &%domains%& condition in an ACL statement, the data is preserved in the
7693 &$domain_data$& variable and can be referred to in other router options or
7694 other statements in the same ACL.
7697 Any of the single-key lookup type names may be preceded by
7698 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7700 domains = partial-dbm;/partial/domains
7702 This causes partial matching logic to be invoked; a description of how this
7703 works is given in section &<<SECTpartiallookup>>&.
7706 .cindex "asterisk" "in lookup type"
7707 Any of the single-key lookup types may be followed by an asterisk. This causes
7708 a default lookup for a key consisting of a single asterisk to be done if the
7709 original lookup fails. This is not a useful feature when using a domain list to
7710 select particular domains (because any domain would match), but it might have
7711 value if the result of the lookup is being used via the &$domain_data$&
7714 If the pattern starts with the name of a query-style lookup type followed by a
7715 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
7716 pattern must be an appropriate query for the lookup type, as described in
7717 chapter &<<CHAPfdlookup>>&. For example:
7719 hold_domains = mysql;select domain from holdlist \
7720 where domain = '$domain';
7722 In most cases, the data that is looked up is not used (so for an SQL query, for
7723 example, it doesn't matter what field you select). Exim is interested only in
7724 whether or not the query succeeds. However, when a lookup is used for the
7725 &%domains%& option on a router, the data is preserved in the &$domain_data$&
7726 variable and can be referred to in other options.
7728 .cindex "domain list" "matching literal domain name"
7729 If none of the above cases apply, a caseless textual comparison is made
7730 between the pattern and the domain.
7733 Here is an example that uses several different kinds of pattern:
7735 domainlist funny_domains = \
7738 *.foundation.fict.example : \
7739 \N^[1-2]\d{3}\.fict\.example$\N : \
7740 partial-dbm;/opt/data/penguin/book : \
7741 nis;domains.byname : \
7742 nisplus;[name=$domain,status=local],domains.org_dir
7744 There are obvious processing trade-offs among the various matching modes. Using
7745 an asterisk is faster than a regular expression, and listing a few names
7746 explicitly probably is too. The use of a file or database lookup is expensive,
7747 but may be the only option if hundreds of names are required. Because the
7748 patterns are tested in order, it makes sense to put the most commonly matched
7753 .section "Host lists" "SECThostlist"
7754 .cindex "host list" "patterns in"
7755 .cindex "list" "host list"
7756 Host lists are used to control what remote hosts are allowed to do. For
7757 example, some hosts may be allowed to use the local host as a relay, and some
7758 may be permitted to use the SMTP ETRN command. Hosts can be identified in
7759 two different ways, by name or by IP address. In a host list, some types of
7760 pattern are matched to a host name, and some are matched to an IP address.
7761 You need to be particularly careful with this when single-key lookups are
7762 involved, to ensure that the right value is being used as the key.
7765 .section "Special host list patterns" "SECID80"
7766 .cindex "empty item in hosts list"
7767 .cindex "host list" "empty string in"
7768 If a host list item is the empty string, it matches only when no remote host is
7769 involved. This is the case when a message is being received from a local
7770 process using SMTP on the standard input, that is, when a TCP/IP connection is
7773 .cindex "asterisk" "in host list"
7774 The special pattern &"*"& in a host list matches any host or no host. Neither
7775 the IP address nor the name is actually inspected.
7779 .section "Host list patterns that match by IP address" "SECThoslispatip"
7780 .cindex "host list" "matching IP addresses"
7781 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7782 the incoming address actually appears in the IPv6 host as
7783 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
7784 list, it is converted into a traditional IPv4 address first. (Not all operating
7785 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7788 The following types of pattern in a host list check the remote host by
7789 inspecting its IP address:
7792 If the pattern is a plain domain name (not a regular expression, not starting
7793 with *, not a lookup of any kind), Exim calls the operating system function
7794 to find the associated IP address(es). Exim uses the newer
7795 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
7796 This typically causes a forward DNS lookup of the name. The result is compared
7797 with the IP address of the subject host.
7799 If there is a temporary problem (such as a DNS timeout) with the host name
7800 lookup, a temporary error occurs. For example, if the list is being used in an
7801 ACL condition, the ACL gives a &"defer"& response, usually leading to a
7802 temporary SMTP error code. If no IP address can be found for the host name,
7803 what happens is described in section &<<SECTbehipnot>>& below.
7806 .cindex "@ in a host list"
7807 If the pattern is &"@"&, the primary host name is substituted and used as a
7808 domain name, as just described.
7811 If the pattern is an IP address, it is matched against the IP address of the
7812 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
7813 IPv6 addresses can be given in colon-separated format, but the colons have to
7814 be doubled so as not to be taken as item separators when the default list
7815 separator is used. IPv6 addresses are recognized even when Exim is compiled
7816 without IPv6 support. This means that if they appear in a host list on an
7817 IPv4-only host, Exim will not treat them as host names. They are just addresses
7818 that can never match a client host.
7821 .cindex "@[] in a host list"
7822 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
7823 the local host. For example, if the local host is an IPv4 host with one
7824 interface address 10.45.23.56, these two ACL statements have the same effect:
7826 accept hosts = 127.0.0.1 : 10.45.23.56
7830 .cindex "CIDR notation"
7831 If the pattern is an IP address followed by a slash and a mask length (for
7832 example 10.11.42.0/24), it is matched against the IP address of the subject
7833 host under the given mask. This allows, an entire network of hosts to be
7834 included (or excluded) by a single item. The mask uses CIDR notation; it
7835 specifies the number of address bits that must match, starting from the most
7836 significant end of the address.
7838 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
7839 of a range of addresses. It is the number of bits in the network portion of the
7840 address. The above example specifies a 24-bit netmask, so it matches all 256
7841 addresses in the 10.11.42.0 network. An item such as
7845 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7846 32 for an IPv4 address is the same as no mask at all; just a single address
7849 Here is another example which shows an IPv4 and an IPv6 network:
7851 recipient_unqualified_hosts = 192.168.0.0/16: \
7852 3ffe::ffff::836f::::/48
7854 The doubling of list separator characters applies only when these items
7855 appear inline in a host list. It is not required when indirecting via a file.
7858 recipient_unqualified_hosts = /opt/exim/unqualnets
7860 could make use of a file containing
7865 to have exactly the same effect as the previous example. When listing IPv6
7866 addresses inline, it is usually more convenient to use the facility for
7867 changing separator characters. This list contains the same two networks:
7869 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7872 The separator is changed to semicolon by the leading &"<;"& at the start of the
7878 .section "Host list patterns for single-key lookups by host address" &&&
7879 "SECThoslispatsikey"
7880 .cindex "host list" "lookup of IP address"
7881 When a host is to be identified by a single-key lookup of its complete IP
7882 address, the pattern takes this form:
7884 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7888 hosts_lookup = net-cdb;/hosts-by-ip.db
7890 The text form of the IP address of the subject host is used as the lookup key.
7891 IPv6 addresses are converted to an unabbreviated form, using lower case
7892 letters, with dots as separators because colon is the key terminator in
7893 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
7894 quoting the keys, but this is a facility that was added later.] The data
7895 returned by the lookup is not used.
7897 .cindex "IP address" "masking"
7898 .cindex "host list" "masked IP address"
7899 Single-key lookups can also be performed using masked IP addresses, using
7900 patterns of this form:
7902 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7906 net24-dbm;/networks.db
7908 The IP address of the subject host is masked using <&'number'&> as the mask
7909 length. A textual string is constructed from the masked value, followed by the
7910 mask, and this is used as the lookup key. For example, if the host's IP address
7911 is 192.168.34.6, the key that is looked up for the above example is
7912 &"192.168.34.0/24"&.
7914 When an IPv6 address is converted to a string, dots are normally used instead
7915 of colons, so that keys in &(lsearch)& files need not contain colons (which
7916 terminate &(lsearch)& keys). This was implemented some time before the ability
7917 to quote keys was made available in &(lsearch)& files. However, the more
7918 recently implemented &(iplsearch)& files do require colons in IPv6 keys
7919 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
7920 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
7921 converted using colons and not dots. In all cases, full, unabbreviated IPv6
7922 addresses are always used.
7924 Ideally, it would be nice to tidy up this anomalous situation by changing to
7925 colons in all cases, given that quoting is now available for &(lsearch)&.
7926 However, this would be an incompatible change that might break some existing
7929 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
7930 IPv6 address) is not the same as specifying just &%net-%& without a number. In
7931 the former case the key strings include the mask value, whereas in the latter
7932 case the IP address is used on its own.
7936 .section "Host list patterns that match by host name" "SECThoslispatnam"
7937 .cindex "host" "lookup failures"
7938 .cindex "unknown host name"
7939 .cindex "host list" "matching host name"
7940 There are several types of pattern that require Exim to know the name of the
7941 remote host. These are either wildcard patterns or lookups by name. (If a
7942 complete hostname is given without any wildcarding, it is used to find an IP
7943 address to match against, as described in the section &<<SECThoslispatip>>&
7946 If the remote host name is not already known when Exim encounters one of these
7947 patterns, it has to be found from the IP address.
7948 Although many sites on the Internet are conscientious about maintaining reverse
7949 DNS data for their hosts, there are also many that do not do this.
7950 Consequently, a name cannot always be found, and this may lead to unwanted
7951 effects. Take care when configuring host lists with wildcarded name patterns.
7952 Consider what will happen if a name cannot be found.
7954 Because of the problems of determining host names from IP addresses, matching
7955 against host names is not as common as matching against IP addresses.
7957 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7958 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
7959 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
7960 are done can be changed by setting the &%host_lookup_order%& option. For
7961 security, once Exim has found one or more names, it looks up the IP addresses
7962 for these names and compares them with the IP address that it started with.
7963 Only those names whose IP addresses match are accepted. Any other names are
7964 discarded. If no names are left, Exim behaves as if the host name cannot be
7965 found. In the most common case there is only one name and one IP address.
7967 There are some options that control what happens if a host name cannot be
7968 found. These are described in section &<<SECTbehipnot>>& below.
7970 .cindex "host" "alias for"
7971 .cindex "alias for host"
7972 As a result of aliasing, hosts may have more than one name. When processing any
7973 of the following types of pattern, all the host's names are checked:
7976 .cindex "asterisk" "in host list"
7977 If a pattern starts with &"*"& the remainder of the item must match the end of
7978 the host name. For example, &`*.b.c`& matches all hosts whose names end in
7979 &'.b.c'&. This special simple form is provided because this is a very common
7980 requirement. Other kinds of wildcarding require the use of a regular
7983 .cindex "regular expressions" "in host list"
7984 .cindex "host list" "regular expression in"
7985 If the item starts with &"^"& it is taken to be a regular expression which is
7986 matched against the host name. Host names are case-independent, so this regular
7987 expression match is by default case-independent, but you can make it
7988 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
7989 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
7994 is a regular expression that matches either of the two hosts &'a.c.d'& or
7995 &'b.c.d'&. When a regular expression is used in a host list, you must take care
7996 that backslash and dollar characters are not misinterpreted as part of the
7997 string expansion. The simplest way to do this is to use &`\N`& to mark that
7998 part of the string as non-expandable. For example:
8000 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8002 &*Warning*&: If you want to match a complete host name, you must include the
8003 &`$`& terminating metacharacter in the regular expression, as in the above
8004 example. Without it, a match at the start of the host name is all that is
8011 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8012 .cindex "host" "lookup failures, permanent"
8013 While processing a host list, Exim may need to look up an IP address from a
8014 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8015 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8016 behaviour when it fails to find the information it is seeking is the same.
8018 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8019 apply to temporary DNS errors, whose handling is described in the next section.
8021 .cindex "&`+include_unknown`&"
8022 .cindex "&`+ignore_unknown`&"
8023 By default, Exim behaves as if the host does not match the list. This may not
8024 always be what you want to happen. To change Exim's behaviour, the special
8025 items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at
8026 top level &-- they are not recognized in an indirected file).
8029 If any item that follows &`+include_unknown`& requires information that
8030 cannot found, Exim behaves as if the host does match the list. For example,
8032 host_reject_connection = +include_unknown:*.enemy.ex
8034 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8035 any hosts whose name it cannot find.
8038 If any item that follows &`+ignore_unknown`& requires information that cannot
8039 be found, Exim ignores that item and proceeds to the rest of the list. For
8042 accept hosts = +ignore_unknown : friend.example : \
8045 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8046 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8047 name can be found for 192.168.4.5, it is rejected.
8050 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8051 list. The effect of each one lasts until the next, or until the end of the
8055 .section "Temporary DNS errors when looking up host information" &&&
8057 .cindex "host" "lookup failures, temporary"
8058 .cindex "&`+include_defer`&"
8059 .cindex "&`+ignore_defer`&"
8060 A temporary DNS lookup failure normally causes a defer action (except when
8061 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8062 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8063 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8064 section. These options should be used with care, probably only in non-critical
8065 host lists such as whitelists.
8069 .section "Host list patterns for single-key lookups by host name" &&&
8070 "SECThoslispatnamsk"
8071 .cindex "unknown host name"
8072 .cindex "host list" "matching host name"
8073 If a pattern is of the form
8075 <&'single-key-search-type'&>;<&'search-data'&>
8079 dbm;/host/accept/list
8081 a single-key lookup is performed, using the host name as its key. If the
8082 lookup succeeds, the host matches the item. The actual data that is looked up
8085 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8086 keys in the file, not IP addresses. If you want to do lookups based on IP
8087 addresses, you must precede the search type with &"net-"& (see section
8088 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8089 two items in the same list, one doing an address lookup and one doing a name
8090 lookup, both using the same file.
8094 .section "Host list patterns for query-style lookups" "SECID81"
8095 If a pattern is of the form
8097 <&'query-style-search-type'&>;<&'query'&>
8099 the query is obeyed, and if it succeeds, the host matches the item. The actual
8100 data that is looked up is not used. The variables &$sender_host_address$& and
8101 &$sender_host_name$& can be used in the query. For example:
8103 hosts_lookup = pgsql;\
8104 select ip from hostlist where ip='$sender_host_address'
8106 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8107 can use the &%sg%& expansion item to change this if you need to. If you want to
8108 use masked IP addresses in database queries, you can use the &%mask%& expansion
8111 If the query contains a reference to &$sender_host_name$&, Exim automatically
8112 looks up the host name if has not already done so. (See section
8113 &<<SECThoslispatnam>>& for comments on finding host names.)
8115 Historical note: prior to release 4.30, Exim would always attempt to find a
8116 host name before running the query, unless the search type was preceded by
8117 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8118 still recognized for query-style lookups, but its presence or absence has no
8119 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8120 See section &<<SECThoslispatsikey>>&.)
8124 .section "Mixing wildcarded host names and addresses in host lists" &&&
8126 .cindex "host list" "mixing names and addresses in"
8127 If you have name lookups or wildcarded host names and IP addresses in the same
8128 host list, you should normally put the IP addresses first. For example, in an
8131 accept hosts = 10.9.8.7 : *.friend.example
8133 The reason for this lies in the left-to-right way that Exim processes lists.
8134 It can test IP addresses without doing any DNS lookups, but when it reaches an
8135 item that requires a host name, it fails if it cannot find a host name to
8136 compare with the pattern. If the above list is given in the opposite order, the
8137 &%accept%& statement fails for a host whose name cannot be found, even if its
8138 IP address is 10.9.8.7.
8140 If you really do want to do the name check first, and still recognize the IP
8141 address, you can rewrite the ACL like this:
8143 accept hosts = *.friend.example
8144 accept hosts = 10.9.8.7
8146 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8147 &<<CHAPACL>>& for details of ACLs.
8153 .section "Address lists" "SECTaddresslist"
8154 .cindex "list" "address list"
8155 .cindex "address list" "empty item"
8156 .cindex "address list" "patterns"
8157 Address lists contain patterns that are matched against mail addresses. There
8158 is one special case to be considered: the sender address of a bounce message is
8159 always empty. You can test for this by providing an empty item in an address
8160 list. For example, you can set up a router to process bounce messages by
8161 using this option setting:
8165 The presence of the colon creates an empty item. If you do not provide any
8166 data, the list is empty and matches nothing. The empty sender can also be
8167 detected by a regular expression that matches an empty string,
8168 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8170 Non-empty items in an address list can be straightforward email addresses. For
8173 senders = jbc@askone.example : hs@anacreon.example
8175 A certain amount of wildcarding is permitted. If a pattern contains an @
8176 character, but is not a regular expression and does not begin with a
8177 semicolon-terminated lookup type (described below), the local part of the
8178 subject address is compared with the local part of the pattern, which may start
8179 with an asterisk. If the local parts match, the domain is checked in exactly
8180 the same way as for a pattern in a domain list. For example, the domain can be
8181 wildcarded, refer to a named list, or be a lookup:
8183 deny senders = *@*.spamming.site:\
8184 *@+hostile_domains:\
8185 bozo@partial-lsearch;/list/of/dodgy/sites:\
8186 *@dbm;/bad/domains.db
8188 .cindex "local part" "starting with !"
8189 .cindex "address list" "local part starting with !"
8190 If a local part that begins with an exclamation mark is required, it has to be
8191 specified using a regular expression, because otherwise the exclamation mark is
8192 treated as a sign of negation, as is standard in lists.
8194 If a non-empty pattern that is not a regular expression or a lookup does not
8195 contain an @ character, it is matched against the domain part of the subject
8196 address. The only two formats that are recognized this way are a literal
8197 domain, or a domain pattern that starts with *. In both these cases, the effect
8198 is the same as if &`*@`& preceded the pattern. For example:
8200 deny senders = enemy.domain : *.enemy.domain
8203 The following kinds of more complicated address list pattern can match any
8204 address, including the empty address that is characteristic of bounce message
8208 .cindex "regular expressions" "in address list"
8209 .cindex "address list" "regular expression in"
8210 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8211 done against the complete address, with the pattern as the regular expression.
8212 You must take care that backslash and dollar characters are not misinterpreted
8213 as part of the string expansion. The simplest way to do this is to use &`\N`&
8214 to mark that part of the string as non-expandable. For example:
8216 deny senders = \N^.*this.*@example\.com$\N : \
8217 \N^\d{8}.+@spamhaus.example$\N : ...
8219 The &`\N`& sequences are removed by the expansion, so these items do indeed
8220 start with &"^"& by the time they are being interpreted as address patterns.
8223 .cindex "address list" "lookup for complete address"
8224 Complete addresses can be looked up by using a pattern that starts with a
8225 lookup type terminated by a semicolon, followed by the data for the lookup. For
8228 deny senders = cdb;/etc/blocked.senders : \
8229 mysql;select address from blocked where \
8230 address='${quote_mysql:$sender_address}'
8232 Both query-style and single-key lookup types can be used. For a single-key
8233 lookup type, Exim uses the complete address as the key. However, empty keys are
8234 not supported for single-key lookups, so a match against the empty address
8235 always fails. This restriction does not apply to query-style lookups.
8237 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8238 cannot be used, and is ignored if specified, with an entry being written to the
8240 .cindex "*@ with single-key lookup"
8241 However, you can configure lookup defaults, as described in section
8242 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8243 default. For example, with this lookup:
8245 accept senders = lsearch*@;/some/file
8247 the file could contains lines like this:
8249 user1@domain1.example
8252 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8255 nimrod@jaeger.example
8259 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8260 would mean that every address matches, thus rendering the test useless.
8262 &*Warning 2*&: Do not confuse these two kinds of item:
8264 deny recipients = dbm*@;/some/file
8265 deny recipients = *@dbm;/some/file
8267 The first does a whole address lookup, with defaulting, as just described,
8268 because it starts with a lookup type. The second matches the local part and
8269 domain independently, as described in a bullet point below.
8273 The following kinds of address list pattern can match only non-empty addresses.
8274 If the subject address is empty, a match against any of these pattern types
8279 .cindex "@@ with single-key lookup"
8280 .cindex "address list" "@@ lookup type"
8281 .cindex "address list" "split local part and domain"
8282 If a pattern starts with &"@@"& followed by a single-key lookup item
8283 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8284 split into a local part and a domain. The domain is looked up in the file. If
8285 it is not found, there is no match. If it is found, the data that is looked up
8286 from the file is treated as a colon-separated list of local part patterns, each
8287 of which is matched against the subject local part in turn.
8289 .cindex "asterisk" "in address list"
8290 The lookup may be a partial one, and/or one involving a search for a default
8291 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8292 patterns that are looked up can be regular expressions or begin with &"*"&, or
8293 even be further lookups. They may also be independently negated. For example,
8296 deny senders = @@dbm;/etc/reject-by-domain
8298 the data from which the DBM file is built could contain lines like
8300 baddomain.com: !postmaster : *
8302 to reject all senders except &%postmaster%& from that domain.
8304 .cindex "local part" "starting with !"
8305 If a local part that actually begins with an exclamation mark is required, it
8306 has to be specified using a regular expression. In &(lsearch)& files, an entry
8307 may be split over several lines by indenting the second and subsequent lines,
8308 but the separating colon must still be included at line breaks. White space
8309 surrounding the colons is ignored. For example:
8311 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8314 As in all colon-separated lists in Exim, a colon can be included in an item by
8317 If the last item in the list starts with a right angle-bracket, the remainder
8318 of the item is taken as a new key to look up in order to obtain a continuation
8319 list of local parts. The new key can be any sequence of characters. Thus one
8320 might have entries like
8322 aol.com: spammer1 : spammer 2 : >*
8323 xyz.com: spammer3 : >*
8326 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8327 local parts for all domains, in addition to the specific local parts listed for
8328 each domain. Of course, using this feature costs another lookup each time a
8329 chain is followed, but the effort needed to maintain the data is reduced.
8331 .cindex "loop" "in lookups"
8332 It is possible to construct loops using this facility, and in order to catch
8333 them, the chains may be no more than fifty items long.
8336 The @@<&'lookup'&> style of item can also be used with a query-style
8337 lookup, but in this case, the chaining facility is not available. The lookup
8338 can only return a single list of local parts.
8341 &*Warning*&: There is an important difference between the address list items
8342 in these two examples:
8345 senders = *@+my_list
8347 In the first one, &`my_list`& is a named address list, whereas in the second
8348 example it is a named domain list.
8353 .section "Case of letters in address lists" "SECTcasletadd"
8354 .cindex "case of local parts"
8355 .cindex "address list" "case forcing"
8356 .cindex "case forcing in address lists"
8357 Domains in email addresses are always handled caselessly, but for local parts
8358 case may be significant on some systems (see &%caseful_local_part%& for how
8359 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8360 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8361 blocking lists should be done in a case-independent manner. Since most address
8362 lists in Exim are used for this kind of control, Exim attempts to do this by
8365 The domain portion of an address is always lowercased before matching it to an
8366 address list. The local part is lowercased by default, and any string
8367 comparisons that take place are done caselessly. This means that the data in
8368 the address list itself, in files included as plain file names, and in any file
8369 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8370 keys in files that are looked up by a search type other than &(lsearch)& (which
8371 works caselessly) must be in lower case, because these lookups are not
8374 .cindex "&`+caseful`&"
8375 To allow for the possibility of caseful address list matching, if an item in
8376 an address list is the string &"+caseful"&, the original case of the local
8377 part is restored for any comparisons that follow, and string comparisons are no
8378 longer case-independent. This does not affect the domain, which remains in
8379 lower case. However, although independent matches on the domain alone are still
8380 performed caselessly, regular expressions that match against an entire address
8381 become case-sensitive after &"+caseful"& has been seen.
8385 .section "Local part lists" "SECTlocparlis"
8386 .cindex "list" "local part list"
8387 .cindex "local part" "list"
8388 Case-sensitivity in local part lists is handled in the same way as for address
8389 lists, as just described. The &"+caseful"& item can be used if required. In a
8390 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8391 set false, the subject is lowercased and the matching is initially
8392 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8393 matching in the local part list, but not elsewhere in the router. If
8394 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8395 option is case-sensitive from the start.
8397 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8398 comments are handled in the same way as address lists &-- they are recognized
8399 only if the # is preceded by white space or the start of the line.
8400 Otherwise, local part lists are matched in the same way as domain lists, except
8401 that the special items that refer to the local host (&`@`&, &`@[]`&,
8402 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8403 Refer to section &<<SECTdomainlist>>& for details of the other available item
8405 .ecindex IIDdohoadli
8410 . ////////////////////////////////////////////////////////////////////////////
8411 . ////////////////////////////////////////////////////////////////////////////
8413 .chapter "String expansions" "CHAPexpand"
8414 .scindex IIDstrexp "expansion" "of strings"
8415 Many strings in Exim's run time configuration are expanded before use. Some of
8416 them are expanded every time they are used; others are expanded only once.
8418 When a string is being expanded it is copied verbatim from left to right except
8419 when a dollar or backslash character is encountered. A dollar specifies the
8420 start of a portion of the string that is interpreted and replaced as described
8421 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8422 escape character, as described in the following section.
8426 .section "Literal text in expanded strings" "SECTlittext"
8427 .cindex "expansion" "including literal text"
8428 An uninterpreted dollar can be included in an expanded string by putting a
8429 backslash in front of it. A backslash can be used to prevent any special
8430 character being treated specially in an expansion, including backslash itself.
8431 If the string appears in quotes in the configuration file, two backslashes are
8432 required because the quotes themselves cause interpretation of backslashes when
8433 the string is read in (see section &<<SECTstrings>>&).
8435 .cindex "expansion" "non-expandable substrings"
8436 A portion of the string can specified as non-expandable by placing it between
8437 two occurrences of &`\N`&. This is particularly useful for protecting regular
8438 expressions, which often contain backslashes and dollar signs. For example:
8440 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8442 On encountering the first &`\N`&, the expander copies subsequent characters
8443 without interpretation until it reaches the next &`\N`& or the end of the
8448 .section "Character escape sequences in expanded strings" "SECID82"
8449 .cindex "expansion" "escape sequences"
8450 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8451 expanded string is recognized as an escape sequence for the character newline,
8452 carriage return, or tab, respectively. A backslash followed by up to three
8453 octal digits is recognized as an octal encoding for a single character, and a
8454 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8457 These escape sequences are also recognized in quoted strings when they are read
8458 in. Their interpretation in expansions as well is useful for unquoted strings,
8459 and for other cases such as looked-up strings that are then expanded.
8462 .section "Testing string expansions" "SECID83"
8463 .cindex "expansion" "testing"
8464 .cindex "testing" "string expansion"
8466 Many expansions can be tested by calling Exim with the &%-be%& option. This
8467 takes the command arguments, or lines from the standard input if there are no
8468 arguments, runs them through the string expansion code, and writes the results
8469 to the standard output. Variables based on configuration values are set up, but
8470 since no message is being processed, variables such as &$local_part$& have no
8471 value. Nevertheless the &%-be%& option can be useful for checking out file and
8472 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8475 Exim gives up its root privilege when it is called with the &%-be%& option, and
8476 instead runs under the uid and gid it was called with, to prevent users from
8477 using &%-be%& for reading files to which they do not have access.
8480 If you want to test expansions that include variables whose values are taken
8481 from a message, there are two other options that can be used. The &%-bem%&
8482 option is like &%-be%& except that it is followed by a file name. The file is
8483 read as a message before doing the test expansions. For example:
8485 exim -bem /tmp/test.message '$h_subject:'
8487 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8488 Exim message identifier. For example:
8490 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8492 This loads the message from Exim's spool before doing the test expansions, and
8493 is therefore restricted to admin users.
8496 .section "Forced expansion failure" "SECTforexpfai"
8497 .cindex "expansion" "forced failure"
8498 A number of expansions that are described in the following section have
8499 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8500 (which are sometimes called &"curly brackets"&). Which of the two strings is
8501 used depends on some condition that is evaluated as part of the expansion. If,
8502 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8503 the entire string expansion fails in a way that can be detected by the code
8504 that requested the expansion. This is called &"forced expansion failure"&, and
8505 its consequences depend on the circumstances. In some cases it is no different
8506 from any other expansion failure, but in others a different action may be
8507 taken. Such variations are mentioned in the documentation of the option that is
8513 .section "Expansion items" "SECTexpansionitems"
8514 The following items are recognized in expanded strings. White space may be used
8515 between sub-items that are keywords or substrings enclosed in braces inside an
8516 outer set of braces, to improve readability. &*Warning*&: Within braces,
8517 white space is significant.
8520 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8521 .cindex "expansion" "variables"
8522 Substitute the contents of the named variable, for example:
8527 The second form can be used to separate the name from subsequent alphanumeric
8528 characters. This form (using braces) is available only for variables; it does
8529 &'not'& apply to message headers. The names of the variables are given in
8530 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8531 given, the expansion fails.
8533 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8534 .cindex "expansion" "operators"
8535 The string is first itself expanded, and then the operation specified by
8536 <&'op'&> is applied to it. For example:
8540 The string starts with the first character after the colon, which may be
8541 leading white space. A list of operators is given in section &<<SECTexpop>>&
8542 below. The operator notation is used for simple expansion items that have just
8543 one argument, because it reduces the number of braces and therefore makes the
8544 string easier to understand.
8546 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8547 This item inserts &"basic"& header lines. It is described with the &%header%&
8548 expansion item below.
8550 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8551 {*&<&'arg'&>&*}...}*&"
8553 This expansion dynamically loads and then calls a locally-written C function.
8554 This functionality is available only if Exim is compiled with
8558 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8559 object so that it doesn't reload the same object file in the same Exim process
8560 (but of course Exim does start new processes frequently).
8562 There may be from zero to eight arguments to the function. When compiling
8563 a local function that is to be called in this way, &_local_scan.h_& should be
8564 included. The Exim variables and functions that are defined by that API
8565 are also available for dynamically loaded functions. The function itself
8566 must have the following type:
8568 int dlfunction(uschar **yield, int argc, uschar *argv[])
8570 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8571 function should return one of the following values:
8573 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8574 into the expanded string that is being built.
8576 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8577 from &'yield'&, if it is set.
8579 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8580 taken from &'yield'& if it is set.
8582 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8584 When compiling a function that is to be used in this way with gcc,
8585 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8586 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8588 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8589 {*&<&'string3'&>&*}}*&"
8590 .cindex "expansion" "extracting substrings by key"
8591 .cindex "&%extract%&" "substrings by key"
8592 The key and <&'string1'&> are first expanded separately. Leading and trailing
8593 white space is removed from the key (but not from any of the strings). The key
8594 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8597 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8600 where the equals signs and spaces (but not both) are optional. If any of the
8601 values contain white space, they must be enclosed in double quotes, and any
8602 values that are enclosed in double quotes are subject to escape processing as
8603 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8604 for the value that corresponds to the key. The search is case-insensitive. If
8605 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8606 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8607 variable &$value$& contains the value that has been extracted. Afterwards, it
8608 is restored to any previous value it might have had.
8610 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8611 key is not found. If {<&'string2'&>} is also omitted, the value that was
8612 extracted is used. Thus, for example, these two expansions are identical, and
8615 ${extract{gid}{uid=1984 gid=2001}}
8616 ${extract{gid}{uid=1984 gid=2001}{$value}}
8618 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8619 appear, for example:
8621 ${extract{Z}{A=... B=...}{$value} fail }
8623 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8624 {<&'string2'&>} must be present for &"fail"& to be recognized.
8627 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8628 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8629 .cindex "expansion" "extracting substrings by number"
8630 .cindex "&%extract%&" "substrings by number"
8631 The <&'number'&> argument must consist entirely of decimal digits,
8632 apart from leading and trailing white space, which is ignored.
8633 This is what distinguishes this form of &%extract%& from the previous kind. It
8634 behaves in the same way, except that, instead of extracting a named field, it
8635 extracts from <&'string1'&> the field whose number is given as the first
8636 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8637 <&'string3'&> as before.
8639 The fields in the string are separated by any one of the characters in the
8640 separator string. These may include space or tab characters.
8641 The first field is numbered one. If the number is negative, the fields are
8642 counted from the end of the string, with the rightmost one numbered -1. If the
8643 number given is zero, the entire string is returned. If the modulus of the
8644 number is greater than the number of fields in the string, the result is the
8645 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8646 provided. For example:
8648 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8652 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8654 yields &"99"&. Two successive separators mean that the field between them is
8655 empty (for example, the fifth field above).
8658 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
8659 .cindex "list" "selecting by condition"
8660 .cindex "expansion" "selecting from list by condition"
8662 After expansion, <&'string'&> is interpreted as a list, colon-separated by
8663 default, but the separator can be changed in the usual way. For each item
8664 in this list, its value is place in &$item$&, and then the condition is
8665 evaluated. If the condition is true, &$item$& is added to the output as an
8666 item in a new list; if the condition is false, the item is discarded. The
8667 separator used for the output list is the same as the one used for the
8668 input, but a separator setting is not included in the output. For example:
8670 ${filter{a:b:c}{!eq{$item}{b}}
8672 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
8673 to what it was before. See also the &*map*& and &*reduce*& expansion items.
8676 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8677 .cindex "hash function" "textual"
8678 .cindex "expansion" "textual hash"
8679 This is a textual hashing function, and was the first to be implemented in
8680 early versions of Exim. In current releases, there are other hashing functions
8681 (numeric, MD5, and SHA-1), which are described below.
8683 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
8684 <&'n'&>. If you are using fixed values for these numbers, that is, if
8685 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
8686 use the simpler operator notation that avoids some of the braces:
8688 ${hash_<n>_<m>:<string>}
8690 The second number is optional (in both notations). If <&'n'&> is greater than
8691 or equal to the length of the string, the expansion item returns the string.
8692 Otherwise it computes a new string of length <&'n'&> by applying a hashing
8693 function to the string. The new string consists of characters taken from the
8694 first <&'m'&> characters of the string
8696 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8698 If <&'m'&> is not present the value 26 is used, so that only lower case
8699 letters appear. For example:
8701 &`$hash{3}{monty}} `& yields &`jmg`&
8702 &`$hash{5}{monty}} `& yields &`monty`&
8703 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
8706 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
8707 &*$h_*&<&'header&~name'&>&*:*&" &&&
8708 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8709 &*$bh_*&<&'header&~name'&>&*:*&" &&&
8710 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8711 &*$rh_*&<&'header&~name'&>&*:*&"
8712 .cindex "expansion" "header insertion"
8713 .vindex "&$header_$&"
8714 .vindex "&$bheader_$&"
8715 .vindex "&$rheader_$&"
8716 .cindex "header lines" "in expansion strings"
8717 .cindex "header lines" "character sets"
8718 .cindex "header lines" "decoding"
8719 Substitute the contents of the named message header line, for example
8723 The newline that terminates a header line is not included in the expansion, but
8724 internal newlines (caused by splitting the header line over several physical
8725 lines) may be present.
8727 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
8728 the data in the header line is interpreted.
8731 .cindex "white space" "in header lines"
8732 &%rheader%& gives the original &"raw"& content of the header line, with no
8733 processing at all, and without the removal of leading and trailing white space.
8736 .cindex "base64 encoding" "in header lines"
8737 &%bheader%& removes leading and trailing white space, and then decodes base64
8738 or quoted-printable MIME &"words"& within the header text, but does no
8739 character set translation. If decoding of what looks superficially like a MIME
8740 &"word"& fails, the raw string is returned. If decoding
8741 .cindex "binary zero" "in header line"
8742 produces a binary zero character, it is replaced by a question mark &-- this is
8743 what Exim does for binary zeros that are actually received in header lines.
8746 &%header%& tries to translate the string as decoded by &%bheader%& to a
8747 standard character set. This is an attempt to produce the same string as would
8748 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
8749 returned. Translation is attempted only on operating systems that support the
8750 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
8751 a system Makefile or in &_Local/Makefile_&.
8754 In a filter file, the target character set for &%header%& can be specified by a
8755 command of the following form:
8757 headers charset "UTF-8"
8759 This command affects all references to &$h_$& (or &$header_$&) expansions in
8760 subsequently obeyed filter commands. In the absence of this command, the target
8761 character set in a filter is taken from the setting of the &%headers_charset%&
8762 option in the runtime configuration. The value of this option defaults to the
8763 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
8766 Header names follow the syntax of RFC 2822, which states that they may contain
8767 any printing characters except space and colon. Consequently, curly brackets
8768 &'do not'& terminate header names, and should not be used to enclose them as
8769 if they were variables. Attempting to do so causes a syntax error.
8771 Only header lines that are common to all copies of a message are visible to
8772 this mechanism. These are the original header lines that are received with the
8773 message, and any that are added by an ACL statement or by a system
8774 filter. Header lines that are added to a particular copy of a message by a
8775 router or transport are not accessible.
8777 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8778 before the DATA ACL, because the header structure is not set up until the
8779 message is received. Header lines that are added in a RCPT ACL (for example)
8780 are saved until the message's incoming header lines are available, at which
8781 point they are added. When a DATA ACL is running, however, header lines added
8782 by earlier ACLs are visible.
8784 Upper case and lower case letters are synonymous in header names. If the
8785 following character is white space, the terminating colon may be omitted, but
8786 this is not recommended, because you may then forget it when it is needed. When
8787 white space terminates the header name, it is included in the expanded string.
8788 If the message does not contain the given header, the expansion item is
8789 replaced by an empty string. (See the &%def%& condition in section
8790 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
8792 If there is more than one header with the same name, they are all concatenated
8793 to form the substitution string, up to a maximum length of 64K. Unless
8794 &%rheader%& is being used, leading and trailing white space is removed from
8795 each header before concatenation, and a completely empty header is ignored. A
8796 newline character is then inserted between non-empty headers, but there is no
8797 newline at the very end. For the &%header%& and &%bheader%& expansion, for
8798 those headers that contain lists of addresses, a comma is also inserted at the
8799 junctions between headers. This does not happen for the &%rheader%& expansion.
8802 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
8803 .cindex "expansion" "hmac hashing"
8805 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
8806 shared secret and some text into a message authentication code, as specified in
8807 RFC 2104. This differs from &`${md5:secret_text...}`& or
8808 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
8809 cryptographic hash, allowing for authentication that is not possible with MD5
8810 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
8811 present. For example:
8813 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
8815 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
8818 dd97e3ba5d1a61b5006108f8c8252953
8820 As an example of how this might be used, you might put in the main part of
8821 an Exim configuration:
8823 SPAMSCAN_SECRET=cohgheeLei2thahw
8825 In a router or a transport you could then have:
8828 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
8829 ${hmac{md5}{SPAMSCAN_SECRET}\
8830 {${primary_hostname},${message_exim_id},$h_message-id:}}
8832 Then given a message, you can check where it was scanned by looking at the
8833 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
8834 this header line is authentic by recomputing the authentication code from the
8835 host name, message ID and the &'Message-id:'& header line. This can be done
8836 using Exim's &%-be%& option, or by other means, for example by using the
8837 &'hmac_md5_hex()'& function in Perl.
8840 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8841 .cindex "expansion" "conditional"
8842 .cindex "&%if%&, expansion item"
8843 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
8844 item; otherwise <&'string2'&> is used. The available conditions are described
8845 in section &<<SECTexpcond>>& below. For example:
8847 ${if eq {$local_part}{postmaster} {yes}{no} }
8849 The second string need not be present; if it is not and the condition is not
8850 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
8851 be present instead of the second string (without any curly brackets). In this
8852 case, the expansion is forced to fail if the condition is not true (see section
8853 &<<SECTforexpfai>>&).
8855 If both strings are omitted, the result is the string &`true`& if the condition
8856 is true, and the empty string if the condition is false. This makes it less
8857 cumbersome to write custom ACL and router conditions. For example, instead of
8859 condition = ${if >{$acl_m4}{3}{true}{false}}
8863 condition = ${if >{$acl_m4}{3}}
8866 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8867 .cindex "expansion" "string truncation"
8868 .cindex "&%length%& expansion item"
8869 The &%length%& item is used to extract the initial portion of a string. Both
8870 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
8871 you are using a fixed value for the number, that is, if <&'string1'&> does not
8872 change when expanded, you can use the simpler operator notation that avoids
8875 ${length_<n>:<string>}
8877 The result of this item is either the first <&'n'&> characters or the whole
8878 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
8879 &%strlen%&, which gives the length of a string.
8882 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
8883 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8884 This is the first of one of two different types of lookup item, which are both
8885 described in the next item.
8887 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
8888 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8889 .cindex "expansion" "lookup in"
8890 .cindex "file" "lookups"
8891 .cindex "lookup" "in expanded string"
8892 The two forms of lookup item specify data lookups in files and databases, as
8893 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
8894 lookups, and the second is used for query-style lookups. The <&'key'&>,
8895 <&'file'&>, and <&'query'&> strings are expanded before use.
8897 If there is any white space in a lookup item which is part of a filter command,
8898 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
8899 other place where white space is significant, the lookup item must be enclosed
8900 in double quotes. The use of data lookups in users' filter files may be locked
8901 out by the system administrator.
8904 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
8905 During its expansion, the variable &$value$& contains the data returned by the
8906 lookup. Afterwards it reverts to the value it had previously (at the outer
8907 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
8908 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
8909 string on failure. If <&'string2'&> is provided, it can itself be a nested
8910 lookup, thus providing a mechanism for looking up a default value when the
8911 original lookup fails.
8913 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
8914 data for the outer lookup while the parameters of the second lookup are
8915 expanded, and also while <&'string2'&> of the second lookup is expanded, should
8916 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
8917 appear, and in this case, if the lookup fails, the entire expansion is forced
8918 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
8919 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
8920 successful lookup, and nothing in the case of failure.
8922 For single-key lookups, the string &"partial"& is permitted to precede the
8923 search type in order to do partial matching, and * or *@ may follow a search
8924 type to request default lookups if the key does not match (see sections
8925 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
8927 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
8928 If a partial search is used, the variables &$1$& and &$2$& contain the wild
8929 and non-wild parts of the key during the expansion of the replacement text.
8930 They return to their previous values at the end of the lookup item.
8932 This example looks up the postmaster alias in the conventional alias file:
8934 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
8936 This example uses NIS+ to look up the full name of the user corresponding to
8937 the local part of an address, forcing the expansion to fail if it is not found:
8939 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8944 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8945 .cindex "expansion" "list creation"
8947 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
8948 default, but the separator can be changed in the usual way. For each item
8949 in this list, its value is place in &$item$&, and then <&'string2'&> is
8950 expanded and added to the output as an item in a new list. The separator used
8951 for the output list is the same as the one used for the input, but a separator
8952 setting is not included in the output. For example:
8954 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
8956 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
8957 value of &$item$& is restored to what it was before. See also the &*filter*&
8958 and &*reduce*& expansion items.
8960 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8961 .cindex "expansion" "numeric hash"
8962 .cindex "hash function" "numeric"
8963 The three strings are expanded; the first two must yield numbers. Call them
8964 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
8965 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
8966 can use the simpler operator notation that avoids some of the braces:
8968 ${nhash_<n>_<m>:<string>}
8970 The second number is optional (in both notations). If there is only one number,
8971 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
8972 processed by a div/mod hash function that returns two numbers, separated by a
8973 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
8976 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8978 returns the string &"6/33"&.
8982 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
8983 .cindex "Perl" "use in expanded string"
8984 .cindex "expansion" "calling Perl from"
8985 This item is available only if Exim has been built to include an embedded Perl
8986 interpreter. The subroutine name and the arguments are first separately
8987 expanded, and then the Perl subroutine is called with those arguments. No
8988 additional arguments need be given; the maximum number permitted, including the
8989 name of the subroutine, is nine.
8991 The return value of the subroutine is inserted into the expanded string, unless
8992 the return value is &%undef%&. In that case, the expansion fails in the same
8993 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
8994 Whatever you return is evaluated in a scalar context. For example, if you
8995 return the name of a Perl vector, the return value is the size of the vector,
8998 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
8999 with the error message that was passed to &%die%&. More details of the embedded
9000 Perl facility are given in chapter &<<CHAPperl>>&.
9002 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9003 out the use of this expansion item in filter files.
9006 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9007 .cindex "&%prvs%& expansion item"
9008 The first argument is a complete email address and the second is secret
9009 keystring. The third argument, specifying a key number, is optional. If absent,
9010 it defaults to 0. The result of the expansion is a prvs-signed email address,
9011 to be typically used with the &%return_path%& option on an &(smtp)& transport
9012 as part of a bounce address tag validation (BATV) scheme. For more discussion
9013 and an example, see section &<<SECTverifyPRVS>>&.
9015 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9016 {*&<&'string'&>&*}}*&"
9017 .cindex "&%prvscheck%& expansion item"
9018 This expansion item is the complement of the &%prvs%& item. It is used for
9019 checking prvs-signed addresses. If the expansion of the first argument does not
9020 yield a syntactically valid prvs-signed address, the whole item expands to the
9021 empty string. When the first argument does expand to a syntactically valid
9022 prvs-signed address, the second argument is expanded, with the prvs-decoded
9023 version of the address and the key number extracted from the address in the
9024 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9026 These two variables can be used in the expansion of the second argument to
9027 retrieve the secret. The validity of the prvs-signed address is then checked
9028 against the secret. The result is stored in the variable &$prvscheck_result$&,
9029 which is empty for failure or &"1"& for success.
9031 The third argument is optional; if it is missing, it defaults to an empty
9032 string. This argument is now expanded. If the result is an empty string, the
9033 result of the expansion is the decoded version of the address. This is the case
9034 whether or not the signature was valid. Otherwise, the result of the expansion
9035 is the expansion of the third argument.
9037 All three variables can be used in the expansion of the third argument.
9038 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9039 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9041 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9042 .cindex "expansion" "inserting an entire file"
9043 .cindex "file" "inserting into expansion"
9044 .cindex "&%readfile%& expansion item"
9045 The file name and end-of-line string are first expanded separately. The file is
9046 then read, and its contents replace the entire item. All newline characters in
9047 the file are replaced by the end-of-line string if it is present. Otherwise,
9048 newlines are left in the string.
9049 String expansion is not applied to the contents of the file. If you want this,
9050 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9051 the string expansion fails.
9053 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9054 locks out the use of this expansion item in filter files.
9058 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9059 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9060 .cindex "expansion" "inserting from a socket"
9061 .cindex "socket, use of in expansion"
9062 .cindex "&%readsocket%& expansion item"
9063 This item inserts data from a Unix domain or Internet socket into the expanded
9064 string. The minimal way of using it uses just two arguments, as in these
9067 ${readsocket{/socket/name}{request string}}
9068 ${readsocket{inet:some.host:1234}{request string}}
9070 For a Unix domain socket, the first substring must be the path to the socket.
9071 For an Internet socket, the first substring must contain &`inet:`& followed by
9072 a host name or IP address, followed by a colon and a port, which can be a
9073 number or the name of a TCP port in &_/etc/services_&. An IP address may
9074 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9077 ${readsocket{inet:[::1]:1234}{request string}}
9079 Only a single host name may be given, but if looking it up yields more than
9080 one IP address, they are each tried in turn until a connection is made. For
9081 both kinds of socket, Exim makes a connection, writes the request string
9082 (unless it is an empty string) and reads from the socket until an end-of-file
9083 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9084 extend what can be done. Firstly, you can vary the timeout. For example:
9086 ${readsocket{/socket/name}{request string}{3s}}
9088 A fourth argument allows you to change any newlines that are in the data
9089 that is read, in the same way as for &%readfile%& (see above). This example
9090 turns them into spaces:
9092 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9094 As with all expansions, the substrings are expanded before the processing
9095 happens. Errors in these sub-expansions cause the expansion to fail. In
9096 addition, the following errors can occur:
9099 Failure to create a socket file descriptor;
9101 Failure to connect the socket;
9103 Failure to write the request string;
9105 Timeout on reading from the socket.
9108 By default, any of these errors causes the expansion to fail. However, if
9109 you supply a fifth substring, it is expanded and used when any of the above
9110 errors occurs. For example:
9112 ${readsocket{/socket/name}{request string}{3s}{\n}\
9115 You can test for the existence of a Unix domain socket by wrapping this
9116 expansion in &`${if exists`&, but there is a race condition between that test
9117 and the actual opening of the socket, so it is safer to use the fifth argument
9118 if you want to be absolutely sure of avoiding an expansion error for a
9119 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9121 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9122 locks out the use of this expansion item in filter files.
9125 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9126 .cindex "expansion" "reducing a list to a scalar"
9127 .cindex "list" "reducing to a scalar"
9130 This operation reduces a list to a single, scalar string. After expansion,
9131 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9132 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9133 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9134 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9135 them. The result of that expansion is assigned to &$value$& before the next
9136 iteration. When the end of the list is reached, the final value of &$value$& is
9137 added to the expansion output. The &*reduce*& expansion item can be used in a
9138 number of ways. For example, to add up a list of numbers:
9140 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9142 The result of that expansion would be &`6`&. The maximum of a list of numbers
9145 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9147 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9148 restored to what they were before. See also the &*filter*& and &*map*&
9151 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9152 This item inserts &"raw"& header lines. It is described with the &%header%&
9153 expansion item above.
9155 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9156 {*&<&'string2'&>&*}}*&"
9157 .cindex "expansion" "running a command"
9158 .cindex "&%run%& expansion item"
9159 The command and its arguments are first expanded separately, and then the
9160 command is run in a separate process, but under the same uid and gid. As in
9161 other command executions from Exim, a shell is not used by default. If you want
9162 a shell, you must explicitly code it.
9164 The standard input for the command exists, but is empty. The standard output
9165 and standard error are set to the same file descriptor.
9166 .cindex "return code" "from &%run%& expansion"
9168 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9169 and replaces the entire item; during this expansion, the standard output/error
9170 from the command is in the variable &$value$&. If the command fails,
9171 <&'string2'&>, if present, is expanded and used. Once again, during the
9172 expansion, the standard output/error from the command is in the variable
9175 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9176 can be the word &"fail"& (not in braces) to force expansion failure if the
9177 command does not succeed. If both strings are omitted, the result is contents
9178 of the standard output/error on success, and nothing on failure.
9181 The return code from the command is put in the variable &$runrc$&, and this
9182 remains set afterwards, so in a filter file you can do things like this:
9184 if "${run{x y z}{}}$runrc" is 1 then ...
9185 elif $runrc is 2 then ...
9189 If execution of the command fails (for example, the command does not exist),
9190 the return code is 127 &-- the same code that shells use for non-existent
9193 &*Warning*&: In a router or transport, you cannot assume the order in which
9194 option values are expanded, except for those preconditions whose order of
9195 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9196 by the expansion of one option, and use it in another.
9198 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9199 out the use of this expansion item in filter files.
9202 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9203 .cindex "expansion" "string substitution"
9204 .cindex "&%sg%& expansion item"
9205 This item works like Perl's substitution operator (s) with the global (/g)
9206 option; hence its name. However, unlike the Perl equivalent, Exim does not
9207 modify the subject string; instead it returns the modified string for insertion
9208 into the overall expansion. The item takes three arguments: the subject string,
9209 a regular expression, and a substitution string. For example:
9211 ${sg{abcdefabcdef}{abc}{xyz}}
9213 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9214 if any $ or \ characters are required in the regular expression or in the
9215 substitution string, they have to be escaped. For example:
9217 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9219 yields &"defabc"&, and
9221 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9223 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9224 the regular expression from string expansion.
9228 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9229 .cindex "&%substr%& expansion item"
9230 .cindex "substring extraction"
9231 .cindex "expansion" "substring extraction"
9232 The three strings are expanded; the first two must yield numbers. Call them
9233 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9234 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9235 can use the simpler operator notation that avoids some of the braces:
9237 ${substr_<n>_<m>:<string>}
9239 The second number is optional (in both notations).
9240 If it is absent in the simpler format, the preceding underscore must also be
9243 The &%substr%& item can be used to extract more general substrings than
9244 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9245 length required. For example
9247 ${substr{3}{2}{$local_part}}
9249 If the starting offset is greater than the string length the result is the
9250 null string; if the length plus starting offset is greater than the string
9251 length, the result is the right-hand part of the string, starting from the
9252 given offset. The first character in the string has offset zero.
9254 The &%substr%& expansion item can take negative offset values to count
9255 from the right-hand end of its operand. The last character is offset -1, the
9256 second-last is offset -2, and so on. Thus, for example,
9258 ${substr{-5}{2}{1234567}}
9260 yields &"34"&. If the absolute value of a negative offset is greater than the
9261 length of the string, the substring starts at the beginning of the string, and
9262 the length is reduced by the amount of overshoot. Thus, for example,
9264 ${substr{-5}{2}{12}}
9266 yields an empty string, but
9268 ${substr{-3}{2}{12}}
9272 When the second number is omitted from &%substr%&, the remainder of the string
9273 is taken if the offset is positive. If it is negative, all characters in the
9274 string preceding the offset point are taken. For example, an offset of -1 and
9275 no length, as in these semantically identical examples:
9278 ${substr{-1}{abcde}}
9280 yields all but the last character of the string, that is, &"abcd"&.
9284 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9285 {*&<&'replacements'&>&*}}*&"
9286 .cindex "expansion" "character translation"
9287 .cindex "&%tr%& expansion item"
9288 This item does single-character translation on its subject string. The second
9289 argument is a list of characters to be translated in the subject string. Each
9290 matching character is replaced by the corresponding character from the
9291 replacement list. For example
9293 ${tr{abcdea}{ac}{13}}
9295 yields &`1b3de1`&. If there are duplicates in the second character string, the
9296 last occurrence is used. If the third string is shorter than the second, its
9297 last character is replicated. However, if it is empty, no translation takes
9303 .section "Expansion operators" "SECTexpop"
9304 .cindex "expansion" "operators"
9305 For expansion items that perform transformations on a single argument string,
9306 the &"operator"& notation is used because it is simpler and uses fewer braces.
9307 The substring is first expanded before the operation is applied to it. The
9308 following operations can be performed:
9311 .vitem &*${address:*&<&'string'&>&*}*&
9312 .cindex "expansion" "RFC 2822 address handling"
9313 .cindex "&%address%& expansion item"
9314 The string is interpreted as an RFC 2822 address, as it might appear in a
9315 header line, and the effective address is extracted from it. If the string does
9316 not parse successfully, the result is empty.
9319 .vitem &*${addresses:*&<&'string'&>&*}*&
9320 .cindex "expansion" "RFC 2822 address handling"
9321 .cindex "&%addresses%& expansion item"
9322 The string (after expansion) is interpreted as a list of addresses in RFC
9323 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9324 operative address (&'local-part@domain'&) is extracted from each item, and the
9325 result of the expansion is a colon-separated list, with appropriate
9326 doubling of colons should any happen to be present in the email addresses.
9327 Syntactically invalid RFC2822 address items are omitted from the output.
9329 It is possible to specify a character other than colon for the output
9330 separator by starting the string with > followed by the new separator
9331 character. For example:
9333 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9335 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9336 expansion item, which extracts the working address from a single RFC2822
9337 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9341 .vitem &*${base62:*&<&'digits'&>&*}*&
9342 .cindex "&%base62%& expansion item"
9343 .cindex "expansion" "conversion to base 62"
9344 The string must consist entirely of decimal digits. The number is converted to
9345 base 62 and output as a string of six characters, including leading zeros. In
9346 the few operating environments where Exim uses base 36 instead of base 62 for
9347 its message identifiers (because those systems do not have case-sensitive file
9348 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9349 be absolutely clear: this is &'not'& base64 encoding.
9351 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9352 .cindex "&%base62d%& expansion item"
9353 .cindex "expansion" "conversion to base 62"
9354 The string must consist entirely of base-62 digits, or, in operating
9355 environments where Exim uses base 36 instead of base 62 for its message
9356 identifiers, base-36 digits. The number is converted to decimal and output as a
9359 .vitem &*${domain:*&<&'string'&>&*}*&
9360 .cindex "domain" "extraction"
9361 .cindex "expansion" "domain extraction"
9362 The string is interpreted as an RFC 2822 address and the domain is extracted
9363 from it. If the string does not parse successfully, the result is empty.
9366 .vitem &*${escape:*&<&'string'&>&*}*&
9367 .cindex "expansion" "escaping non-printing characters"
9368 .cindex "&%escape%& expansion item"
9369 If the string contains any non-printing characters, they are converted to
9370 escape sequences starting with a backslash. Whether characters with the most
9371 significant bit set (so-called &"8-bit characters"&) count as printing or not
9372 is controlled by the &%print_topbitchars%& option.
9375 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9376 .cindex "expansion" "expression evaluation"
9377 .cindex "expansion" "arithmetic expression"
9378 .cindex "&%eval%& expansion item"
9379 These items supports simple arithmetic and bitwise logical operations in
9380 expansion strings. The string (after expansion) must be a conventional
9381 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9382 logical operators, and parentheses. All operations are carried out using
9383 integer arithmetic. The operator priorities are as follows (the same as in the
9384 C programming language):
9386 .irow &'highest:'& "not (~), negate (-)"
9387 .irow "" "multiply (*), divide (/), remainder (%)"
9388 .irow "" "plus (+), minus (-)"
9389 .irow "" "shift-left (<<), shift-right (>>)"
9392 .irow &'lowest:'& "or (|)"
9394 Binary operators with the same priority are evaluated from left to right. White
9395 space is permitted before or after operators.
9397 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9398 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9399 decimal, even if they start with a leading zero; hexadecimal numbers are not
9400 permitted. This can be useful when processing numbers extracted from dates or
9401 times, which often do have leading zeros.
9403 A number may be followed by &"K"& or &"M"& to multiply it by 1024 or 1024*1024,
9404 respectively. Negative numbers are supported. The result of the computation is
9405 a decimal representation of the answer (without &"K"& or &"M"&). For example:
9408 &`${eval:1+1} `& yields 2
9409 &`${eval:1+2*3} `& yields 7
9410 &`${eval:(1+2)*3} `& yields 9
9411 &`${eval:2+42%5} `& yields 4
9412 &`${eval:0xc&5} `& yields 4
9413 &`${eval:0xc|5} `& yields 13
9414 &`${eval:0xc^5} `& yields 9
9415 &`${eval:0xc>>1} `& yields 6
9416 &`${eval:0xc<<1} `& yields 24
9417 &`${eval:~255&0x1234} `& yields 4608
9418 &`${eval:-(~255&0x1234)} `& yields -4608
9421 As a more realistic example, in an ACL you might have
9423 deny message = Too many bad recipients
9426 {>{$rcpt_count}{10}} \
9429 {$recipients_count} \
9430 {${eval:$rcpt_count/2}} \
9434 The condition is true if there have been more than 10 RCPT commands and
9435 fewer than half of them have resulted in a valid recipient.
9438 .vitem &*${expand:*&<&'string'&>&*}*&
9439 .cindex "expansion" "re-expansion of substring"
9440 The &%expand%& operator causes a string to be expanded for a second time. For
9443 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9445 first looks up a string in a file while expanding the operand for &%expand%&,
9446 and then re-expands what it has found.
9449 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9451 .cindex "UTF-8" "conversion from"
9452 .cindex "expansion" "UTF-8 conversion"
9453 .cindex "&%from_utf8%& expansion item"
9454 The world is slowly moving towards Unicode, although there are no standards for
9455 email yet. However, other applications (including some databases) are starting
9456 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9457 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9458 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9459 the result is an undefined sequence of bytes.
9461 Unicode code points with values less than 256 are compatible with ASCII and
9462 ISO-8859-1 (also known as Latin-1).
9463 For example, character 169 is the copyright symbol in both cases, though the
9464 way it is encoded is different. In UTF-8, more than one byte is needed for
9465 characters with code values greater than 127, whereas ISO-8859-1 is a
9466 single-byte encoding (but thereby limited to 256 characters). This makes
9467 translation from UTF-8 to ISO-8859-1 straightforward.
9470 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9471 .cindex "hash function" "textual"
9472 .cindex "expansion" "textual hash"
9473 The &%hash%& operator is a simpler interface to the hashing function that can
9474 be used when the two parameters are fixed numbers (as opposed to strings that
9475 change when expanded). The effect is the same as
9477 ${hash{<n>}{<m>}{<string>}}
9479 See the description of the general &%hash%& item above for details. The
9480 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9484 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9485 .cindex "base64 encoding" "conversion from hex"
9486 .cindex "expansion" "hex to base64"
9487 .cindex "&%hex2b64%& expansion item"
9488 This operator converts a hex string into one that is base64 encoded. This can
9489 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9492 .vitem &*${lc:*&<&'string'&>&*}*&
9493 .cindex "case forcing in strings"
9494 .cindex "string" "case forcing"
9495 .cindex "lower casing"
9496 .cindex "expansion" "case forcing"
9497 .cindex "&%lc%& expansion item"
9498 This forces the letters in the string into lower-case, for example:
9503 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9504 .cindex "expansion" "string truncation"
9505 .cindex "&%length%& expansion item"
9506 The &%length%& operator is a simpler interface to the &%length%& function that
9507 can be used when the parameter is a fixed number (as opposed to a string that
9508 changes when expanded). The effect is the same as
9510 ${length{<number>}{<string>}}
9512 See the description of the general &%length%& item above for details. Note that
9513 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9514 when &%length%& is used as an operator.
9517 .vitem &*${local_part:*&<&'string'&>&*}*&
9518 .cindex "expansion" "local part extraction"
9519 .cindex "&%local_part%& expansion item"
9520 The string is interpreted as an RFC 2822 address and the local part is
9521 extracted from it. If the string does not parse successfully, the result is
9525 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9526 .cindex "masked IP address"
9527 .cindex "IP address" "masking"
9528 .cindex "CIDR notation"
9529 .cindex "expansion" "IP address masking"
9530 .cindex "&%mask%& expansion item"
9531 If the form of the string to be operated on is not an IP address followed by a
9532 slash and an integer (that is, a network address in CIDR notation), the
9533 expansion fails. Otherwise, this operator converts the IP address to binary,
9534 masks off the least significant bits according to the bit count, and converts
9535 the result back to text, with mask appended. For example,
9537 ${mask:10.111.131.206/28}
9539 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9540 be mostly used for looking up masked addresses in files, the result for an IPv6
9541 address uses dots to separate components instead of colons, because colon
9542 terminates a key string in lsearch files. So, for example,
9544 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9548 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9550 Letters in IPv6 addresses are always output in lower case.
9553 .vitem &*${md5:*&<&'string'&>&*}*&
9555 .cindex "expansion" "MD5 hash"
9556 .cindex "&%md5%& expansion item"
9557 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9558 as a 32-digit hexadecimal number, in which any letters are in lower case.
9561 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9562 .cindex "expansion" "numeric hash"
9563 .cindex "hash function" "numeric"
9564 The &%nhash%& operator is a simpler interface to the numeric hashing function
9565 that can be used when the two parameters are fixed numbers (as opposed to
9566 strings that change when expanded). The effect is the same as
9568 ${nhash{<n>}{<m>}{<string>}}
9570 See the description of the general &%nhash%& item above for details.
9573 .vitem &*${quote:*&<&'string'&>&*}*&
9574 .cindex "quoting" "in string expansions"
9575 .cindex "expansion" "quoting"
9576 .cindex "&%quote%& expansion item"
9577 The &%quote%& operator puts its argument into double quotes if it
9578 is an empty string or
9579 contains anything other than letters, digits, underscores, dots, and hyphens.
9580 Any occurrences of double quotes and backslashes are escaped with a backslash.
9581 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
9582 respectively For example,
9590 The place where this is useful is when the argument is a substitution from a
9591 variable or a message header.
9593 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
9594 .cindex "&%quote_local_part%& expansion item"
9595 This operator is like &%quote%&, except that it quotes the string only if
9596 required to do so by the rules of RFC 2822 for quoting local parts. For
9597 example, a plus sign would not cause quoting (but it would for &%quote%&).
9598 If you are creating a new email address from the contents of &$local_part$&
9599 (or any other unknown data), you should always use this operator.
9602 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
9603 .cindex "quoting" "lookup-specific"
9604 This operator applies lookup-specific quoting rules to the string. Each
9605 query-style lookup type has its own quoting rules which are described with
9606 the lookups in chapter &<<CHAPfdlookup>>&. For example,
9608 ${quote_ldap:two * two}
9614 For single-key lookup types, no quoting is ever necessary and this operator
9615 yields an unchanged string.
9618 .vitem &*${randint:*&<&'n'&>&*}*&
9619 .cindex "random number"
9620 This operator returns a somewhat random number which is less than the
9621 supplied number and is at least 0. The quality of this randomness depends
9622 on how Exim was built; the values are not suitable for keying material.
9623 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
9624 Otherwise, the implementation may be arc4random(), random() seeded by
9625 srandomdev() or srandom(), or a custom implementation even weaker than
9629 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
9630 .cindex "expansion" "IP address"
9631 This operator reverses an IP address; for IPv4 addresses, the result is in
9632 dotted-quad decimal form, while for IPv6 addreses the result is in
9633 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
9634 for DNS. For example,
9636 ${reverse_ip:192.0.2.4} and ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.3}
9640 4.2.0.192 and 3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
9644 .vitem &*${rfc2047:*&<&'string'&>&*}*&
9645 .cindex "expansion" "RFC 2047"
9646 .cindex "RFC 2047" "expansion operator"
9647 .cindex "&%rfc2047%& expansion item"
9648 This operator encodes text according to the rules of RFC 2047. This is an
9649 encoding that is used in header lines to encode non-ASCII characters. It is
9650 assumed that the input string is in the encoding specified by the
9651 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
9652 contains only characters in the range 33&--126, and no instances of the
9655 ? = ( ) < > @ , ; : \ " . [ ] _
9657 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
9658 string, using as many &"encoded words"& as necessary to encode all the
9662 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
9663 .cindex "expansion" "RFC 2047"
9664 .cindex "RFC 2047" "decoding"
9665 .cindex "&%rfc2047d%& expansion item"
9666 This operator decodes strings that are encoded as per RFC 2047. Binary zero
9667 bytes are replaced by question marks. Characters are converted into the
9668 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
9669 not recognized unless &%check_rfc2047_length%& is set false.
9671 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
9672 access a header line, RFC 2047 decoding is done automatically. You do not need
9673 to use this operator as well.
9677 .vitem &*${rxquote:*&<&'string'&>&*}*&
9678 .cindex "quoting" "in regular expressions"
9679 .cindex "regular expressions" "quoting"
9680 .cindex "&%rxquote%& expansion item"
9681 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
9682 characters in its argument. This is useful when substituting the values of
9683 variables or headers inside regular expressions.
9686 .vitem &*${sha1:*&<&'string'&>&*}*&
9687 .cindex "SHA-1 hash"
9688 .cindex "expansion" "SHA-1 hashing"
9689 .cindex "&%sha2%& expansion item"
9690 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
9691 it as a 40-digit hexadecimal number, in which any letters are in upper case.
9694 .vitem &*${stat:*&<&'string'&>&*}*&
9695 .cindex "expansion" "statting a file"
9696 .cindex "file" "extracting characteristics"
9697 .cindex "&%stat%& expansion item"
9698 The string, after expansion, must be a file path. A call to the &[stat()]&
9699 function is made for this path. If &[stat()]& fails, an error occurs and the
9700 expansion fails. If it succeeds, the data from the stat replaces the item, as a
9701 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
9702 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
9703 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
9704 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
9705 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
9706 can extract individual fields using the &%extract%& expansion item.
9708 The use of the &%stat%& expansion in users' filter files can be locked out by
9709 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
9710 systems for files larger than 2GB.
9712 .vitem &*${str2b64:*&<&'string'&>&*}*&
9713 .cindex "expansion" "base64 encoding"
9714 .cindex "base64 encoding" "in string expansion"
9715 .cindex "&%str2b64%& expansion item"
9716 This operator converts a string into one that is base64 encoded.
9720 .vitem &*${strlen:*&<&'string'&>&*}*&
9721 .cindex "expansion" "string length"
9722 .cindex "string" "length in expansion"
9723 .cindex "&%strlen%& expansion item"
9724 The item is replace by the length of the expanded string, expressed as a
9725 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
9728 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
9729 .cindex "&%substr%& expansion item"
9730 .cindex "substring extraction"
9731 .cindex "expansion" "substring expansion"
9732 The &%substr%& operator is a simpler interface to the &%substr%& function that
9733 can be used when the two parameters are fixed numbers (as opposed to strings
9734 that change when expanded). The effect is the same as
9736 ${substr{<start>}{<length>}{<string>}}
9738 See the description of the general &%substr%& item above for details. The
9739 abbreviation &%s%& can be used when &%substr%& is used as an operator.
9741 .vitem &*${time_eval:*&<&'string'&>&*}*&
9742 .cindex "&%time_eval%& expansion item"
9743 .cindex "time interval" "decoding"
9744 This item converts an Exim time interval such as &`2d4h5m`& into a number of
9747 .vitem &*${time_interval:*&<&'string'&>&*}*&
9748 .cindex "&%time_interval%& expansion item"
9749 .cindex "time interval" "formatting"
9750 The argument (after sub-expansion) must be a sequence of decimal digits that
9751 represents an interval of time as a number of seconds. It is converted into a
9752 number of larger units and output in Exim's normal time format, for example,
9755 .vitem &*${uc:*&<&'string'&>&*}*&
9756 .cindex "case forcing in strings"
9757 .cindex "string" "case forcing"
9758 .cindex "upper casing"
9759 .cindex "expansion" "case forcing"
9760 .cindex "&%uc%& expansion item"
9761 This forces the letters in the string into upper-case.
9769 .section "Expansion conditions" "SECTexpcond"
9770 .scindex IIDexpcond "expansion" "conditions"
9771 The following conditions are available for testing by the &%${if%& construct
9772 while expanding strings:
9775 .vitem &*!*&<&'condition'&>
9776 .cindex "expansion" "negating a condition"
9777 .cindex "negation" "in expansion condition"
9778 Preceding any condition with an exclamation mark negates the result of the
9781 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9782 .cindex "numeric comparison"
9783 .cindex "expansion" "numeric comparison"
9784 There are a number of symbolic operators for doing numeric comparisons. They
9790 &`>= `& greater or equal
9792 &`<= `& less or equal
9796 ${if >{$message_size}{10M} ...
9798 Note that the general negation operator provides for inequality testing. The
9799 two strings must take the form of optionally signed decimal integers,
9800 optionally followed by one of the letters &"K"& or &"M"& (in either upper or
9801 lower case), signifying multiplication by 1024 or 1024*1024, respectively.
9802 As a special case, the numerical value of an empty string is taken as
9805 .vitem &*bool&~{*&<&'string'&>&*}*&
9806 .cindex "expansion" "boolean parsing"
9807 .cindex "&%bool%& expansion condition"
9808 This condition turns a string holding a true or false representation into
9809 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
9810 (case-insensitively); also positive integer numbers map to true if non-zero,
9811 false if zero. Leading and trailing whitespace is ignored.
9812 All other string values will result in expansion failure.
9814 When combined with ACL variables, this expansion condition will let you
9815 make decisions in one place and act on those decisions in another place.
9818 ${if bool{$acl_m_privileged_sender} ...
9821 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
9822 .cindex "expansion" "boolean parsing"
9823 .cindex "&%bool_lax%& expansion condition"
9824 Like &%bool%&, this condition turns a string into a boolean state. But
9825 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
9826 loose definition that the Router &%condition%& option uses. The empty string
9827 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
9828 true. Leading and trailing whitespace is ignored.
9830 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
9832 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9833 .cindex "expansion" "encrypted comparison"
9834 .cindex "encrypted strings, comparing"
9835 .cindex "&%crypteq%& expansion condition"
9836 This condition is included in the Exim binary if it is built to support any
9837 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
9838 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
9839 included in the binary.
9841 The &%crypteq%& condition has two arguments. The first is encrypted and
9842 compared against the second, which is already encrypted. The second string may
9843 be in the LDAP form for storing encrypted strings, which starts with the
9844 encryption type in curly brackets, followed by the data. If the second string
9845 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
9846 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
9847 Typically this will be a field from a password file. An example of an encrypted
9848 string in LDAP form is:
9850 {md5}CY9rzUYh03PK3k6DJie09g==
9852 If such a string appears directly in an expansion, the curly brackets have to
9853 be quoted, because they are part of the expansion syntax. For example:
9855 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
9857 The following encryption types (whose names are matched case-independently) are
9862 .cindex "base64 encoding" "in encrypted password"
9863 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
9864 printable characters to compare with the remainder of the second string. If the
9865 length of the comparison string is 24, Exim assumes that it is base64 encoded
9866 (as in the above example). If the length is 32, Exim assumes that it is a
9867 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
9871 .cindex "SHA-1 hash"
9872 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
9873 printable characters to compare with the remainder of the second string. If the
9874 length of the comparison string is 28, Exim assumes that it is base64 encoded.
9875 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
9876 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
9879 .cindex "&[crypt()]&"
9880 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
9881 only the first eight characters of the password. However, in modern operating
9882 systems this is no longer true, and in many cases the entire password is used,
9883 whatever its length.
9886 .cindex "&[crypt16()]&"
9887 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
9888 use up to 16 characters of the password in some operating systems. Again, in
9889 modern operating systems, more characters may be used.
9891 Exim has its own version of &[crypt16()]&, which is just a double call to
9892 &[crypt()]&. For operating systems that have their own version, setting
9893 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
9894 operating system version instead of its own. This option is set by default in
9895 the OS-dependent &_Makefile_& for those operating systems that are known to
9896 support &[crypt16()]&.
9898 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
9899 it was not using the same algorithm as some operating systems' versions. It
9900 turns out that as well as &[crypt16()]& there is a function called
9901 &[bigcrypt()]& in some operating systems. This may or may not use the same
9902 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
9904 However, since there is now a move away from the traditional &[crypt()]&
9905 functions towards using SHA1 and other algorithms, tidying up this area of
9906 Exim is seen as very low priority.
9908 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
9909 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
9910 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
9911 default is &`{crypt}`&. Whatever the default, you can always use either
9912 function by specifying it explicitly in curly brackets.
9914 .vitem &*def:*&<&'variable&~name'&>
9915 .cindex "expansion" "checking for empty variable"
9916 .cindex "&%def%& expansion condition"
9917 The &%def%& condition must be followed by the name of one of the expansion
9918 variables defined in section &<<SECTexpvar>>&. The condition is true if the
9919 variable does not contain the empty string. For example:
9921 ${if def:sender_ident {from $sender_ident}}
9923 Note that the variable name is given without a leading &%$%& character. If the
9924 variable does not exist, the expansion fails.
9926 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
9927 &~&*def:h_*&<&'header&~name'&>&*:*&"
9928 .cindex "expansion" "checking header line existence"
9929 This condition is true if a message is being processed and the named header
9930 exists in the message. For example,
9932 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
9934 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
9935 the header name must be terminated by a colon if white space does not follow.
9937 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9938 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9939 .cindex "string" "comparison"
9940 .cindex "expansion" "string comparison"
9941 .cindex "&%eq%& expansion condition"
9942 .cindex "&%eqi%& expansion condition"
9943 The two substrings are first expanded. The condition is true if the two
9944 resulting strings are identical. For &%eq%& the comparison includes the case of
9945 letters, whereas for &%eqi%& the comparison is case-independent.
9947 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
9948 .cindex "expansion" "file existence test"
9949 .cindex "file" "existence test"
9950 .cindex "&%exists%&, expansion condition"
9951 The substring is first expanded and then interpreted as an absolute path. The
9952 condition is true if the named file (or directory) exists. The existence test
9953 is done by calling the &[stat()]& function. The use of the &%exists%& test in
9954 users' filter files may be locked out by the system administrator.
9956 .vitem &*first_delivery*&
9957 .cindex "delivery" "first"
9958 .cindex "first delivery"
9959 .cindex "expansion" "first delivery test"
9960 .cindex "&%first_delivery%& expansion condition"
9961 This condition, which has no data, is true during a message's first delivery
9962 attempt. It is false during any subsequent delivery attempts.
9965 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
9966 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
9967 .cindex "list" "iterative conditions"
9968 .cindex "expansion" "&*forall*& condition"
9969 .cindex "expansion" "&*forany*& condition"
9971 These conditions iterate over a list. The first argument is expanded to form
9972 the list. By default, the list separator is a colon, but it can be changed by
9973 the normal method. The second argument is interpreted as a condition that is to
9974 be applied to each item in the list in turn. During the interpretation of the
9975 condition, the current list item is placed in a variable called &$item$&.
9977 For &*forany*&, interpretation stops if the condition is true for any item, and
9978 the result of the whole condition is true. If the condition is false for all
9979 items in the list, the overall condition is false.
9981 For &*forall*&, interpretation stops if the condition is false for any item,
9982 and the result of the whole condition is false. If the condition is true for
9983 all items in the list, the overall condition is true.
9985 Note that negation of &*forany*& means that the condition must be false for all
9986 items for the overall condition to succeed, and negation of &*forall*& means
9987 that the condition must be false for at least one item. In this example, the
9988 list separator is changed to a comma:
9990 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
9992 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
9993 being processed, to enable these expansion items to be nested.
9996 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9997 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9998 .cindex "string" "comparison"
9999 .cindex "expansion" "string comparison"
10000 .cindex "&%ge%& expansion condition"
10001 .cindex "&%gei%& expansion condition"
10002 The two substrings are first expanded. The condition is true if the first
10003 string is lexically greater than or equal to the second string. For &%ge%& the
10004 comparison includes the case of letters, whereas for &%gei%& the comparison is
10007 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10008 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10009 .cindex "string" "comparison"
10010 .cindex "expansion" "string comparison"
10011 .cindex "&%gt%& expansion condition"
10012 .cindex "&%gti%& expansion condition"
10013 The two substrings are first expanded. The condition is true if the first
10014 string is lexically greater than the second string. For &%gt%& the comparison
10015 includes the case of letters, whereas for &%gti%& the comparison is
10018 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
10019 &*isip4&~{*&<&'string'&>&*}*& &&&
10020 &*isip6&~{*&<&'string'&>&*}*&
10021 .cindex "IP address" "testing string format"
10022 .cindex "string" "testing for IP address"
10023 .cindex "&%isip%& expansion condition"
10024 .cindex "&%isip4%& expansion condition"
10025 .cindex "&%isip6%& expansion condition"
10026 The substring is first expanded, and then tested to see if it has the form of
10027 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
10028 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
10030 For an IPv4 address, the test is for four dot-separated components, each of
10031 which consists of from one to three digits. For an IPv6 address, up to eight
10032 colon-separated components are permitted, each containing from one to four
10033 hexadecimal digits. There may be fewer than eight components if an empty
10034 component (adjacent colons) is present. Only one empty component is permitted.
10036 &*Note*&: The checks are just on the form of the address; actual numerical
10037 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
10038 check. The main use of these tests is to distinguish between IP addresses and
10039 host names, or between IPv4 and IPv6 addresses. For example, you could use
10041 ${if isip4{$sender_host_address}...
10043 to test which IP version an incoming SMTP connection is using.
10045 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
10046 .cindex "LDAP" "use for authentication"
10047 .cindex "expansion" "LDAP authentication test"
10048 .cindex "&%ldapauth%& expansion condition"
10049 This condition supports user authentication using LDAP. See section
10050 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
10051 queries. For this use, the query must contain a user name and password. The
10052 query itself is not used, and can be empty. The condition is true if the
10053 password is not empty, and the user name and password are accepted by the LDAP
10054 server. An empty password is rejected without calling LDAP because LDAP binds
10055 with an empty password are considered anonymous regardless of the username, and
10056 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
10057 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
10061 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10062 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10063 .cindex "string" "comparison"
10064 .cindex "expansion" "string comparison"
10065 .cindex "&%le%& expansion condition"
10066 .cindex "&%lei%& expansion condition"
10067 The two substrings are first expanded. The condition is true if the first
10068 string is lexically less than or equal to the second string. For &%le%& the
10069 comparison includes the case of letters, whereas for &%lei%& the comparison is
10072 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10073 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10074 .cindex "string" "comparison"
10075 .cindex "expansion" "string comparison"
10076 .cindex "&%lt%& expansion condition"
10077 .cindex "&%lti%& expansion condition"
10078 The two substrings are first expanded. The condition is true if the first
10079 string is lexically less than the second string. For &%lt%& the comparison
10080 includes the case of letters, whereas for &%lti%& the comparison is
10084 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10085 .cindex "expansion" "regular expression comparison"
10086 .cindex "regular expressions" "match in expanded string"
10087 .cindex "&%match%& expansion condition"
10088 The two substrings are first expanded. The second is then treated as a regular
10089 expression and applied to the first. Because of the pre-expansion, if the
10090 regular expression contains dollar, or backslash characters, they must be
10091 escaped. Care must also be taken if the regular expression contains braces
10092 (curly brackets). A closing brace must be escaped so that it is not taken as a
10093 premature termination of <&'string2'&>. The easiest approach is to use the
10094 &`\N`& feature to disable expansion of the regular expression.
10097 ${if match {$local_part}{\N^\d{3}\N} ...
10099 If the whole expansion string is in double quotes, further escaping of
10100 backslashes is also required.
10102 The condition is true if the regular expression match succeeds.
10103 The regular expression is not required to begin with a circumflex
10104 metacharacter, but if there is no circumflex, the expression is not anchored,
10105 and it may match anywhere in the subject, not just at the start. If you want
10106 the pattern to match at the end of the subject, you must include the &`$`&
10107 metacharacter at an appropriate point.
10109 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10110 At the start of an &%if%& expansion the values of the numeric variable
10111 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10112 succeeds causes them to be reset to the substrings of that condition and they
10113 will have these values during the expansion of the success string. At the end
10114 of the &%if%& expansion, the previous values are restored. After testing a
10115 combination of conditions using &%or%&, the subsequent values of the numeric
10116 variables are those of the condition that succeeded.
10118 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10119 .cindex "&%match_address%& expansion condition"
10120 See &*match_local_part*&.
10122 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10123 .cindex "&%match_domain%& expansion condition"
10124 See &*match_local_part*&.
10126 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10127 .cindex "&%match_ip%& expansion condition"
10128 This condition matches an IP address to a list of IP address patterns. It must
10129 be followed by two argument strings. The first (after expansion) must be an IP
10130 address or an empty string. The second (after expansion) is a restricted host
10131 list that can match only an IP address, not a host name. For example:
10133 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10135 The specific types of host list item that are permitted in the list are:
10138 An IP address, optionally with a CIDR mask.
10140 A single asterisk, which matches any IP address.
10142 An empty item, which matches only if the IP address is empty. This could be
10143 useful for testing for a locally submitted message or one from specific hosts
10144 in a single test such as
10145 . ==== As this is a nested list, any displays it contains must be indented
10146 . ==== as otherwise they are too far to the left. This comment applies to
10147 . ==== the use of xmlto plus fop. There's no problem when formatting with
10148 . ==== sdop, with or without the extra indent.
10150 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10152 where the first item in the list is the empty string.
10154 The item @[] matches any of the local host's interface addresses.
10156 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10157 even if &`net-`& is not specified. There is never any attempt to turn the IP
10158 address into a host name. The most common type of linear search for
10159 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10160 masks. For example:
10162 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10164 It is of course possible to use other kinds of lookup, and in such a case, you
10165 do need to specify the &`net-`& prefix if you want to specify a specific
10166 address mask, for example:
10168 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10170 However, unless you are combining a &%match_ip%& condition with others, it is
10171 just as easy to use the fact that a lookup is itself a condition, and write:
10173 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10177 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10179 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10180 .cindex "domain list" "in expansion condition"
10181 .cindex "address list" "in expansion condition"
10182 .cindex "local part" "list, in expansion condition"
10183 .cindex "&%match_local_part%& expansion condition"
10184 This condition, together with &%match_address%& and &%match_domain%&, make it
10185 possible to test domain, address, and local part lists within expansions. Each
10186 condition requires two arguments: an item and a list to match. A trivial
10189 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10191 In each case, the second argument may contain any of the allowable items for a
10192 list of the appropriate type. Also, because the second argument (after
10193 expansion) is a standard form of list, it is possible to refer to a named list.
10194 Thus, you can use conditions like this:
10196 ${if match_domain{$domain}{+local_domains}{...
10198 .cindex "&`+caseful`&"
10199 For address lists, the matching starts off caselessly, but the &`+caseful`&
10200 item can be used, as in all address lists, to cause subsequent items to
10201 have their local parts matched casefully. Domains are always matched
10204 &*Note*&: Host lists are &'not'& supported in this way. This is because
10205 hosts have two identities: a name and an IP address, and it is not clear
10206 how to specify cleanly how such a test would work. However, IP addresses can be
10207 matched using &%match_ip%&.
10209 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10210 .cindex "PAM authentication"
10211 .cindex "AUTH" "with PAM"
10212 .cindex "Solaris" "PAM support"
10213 .cindex "expansion" "PAM authentication test"
10214 .cindex "&%pam%& expansion condition"
10215 &'Pluggable Authentication Modules'&
10216 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10217 available in the latest releases of Solaris and in some GNU/Linux
10218 distributions. The Exim support, which is intended for use in conjunction with
10219 the SMTP AUTH command, is available only if Exim is compiled with
10223 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10224 in some releases of GNU/Linux &%-ldl%& is also needed.
10226 The argument string is first expanded, and the result must be a
10227 colon-separated list of strings. Leading and trailing white space is ignored.
10228 The PAM module is initialized with the service name &"exim"& and the user name
10229 taken from the first item in the colon-separated data string (<&'string1'&>).
10230 The remaining items in the data string are passed over in response to requests
10231 from the authentication function. In the simple case there will only be one
10232 request, for a password, so the data consists of just two strings.
10234 There can be problems if any of the strings are permitted to contain colon
10235 characters. In the usual way, these have to be doubled to avoid being taken as
10236 separators. If the data is being inserted from a variable, the &%sg%& expansion
10237 item can be used to double any existing colons. For example, the configuration
10238 of a LOGIN authenticator might contain this setting:
10240 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10242 For a PLAIN authenticator you could use:
10244 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10246 In some operating systems, PAM authentication can be done only from a process
10247 running as root. Since Exim is running as the Exim user when receiving
10248 messages, this means that PAM cannot be used directly in those systems.
10249 A patched version of the &'pam_unix'& module that comes with the
10250 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10251 The patched module allows one special uid/gid combination, in addition to root,
10252 to authenticate. If you build the patched module to allow the Exim user and
10253 group, PAM can then be used from an Exim authenticator.
10256 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10257 .cindex "&'pwcheck'& daemon"
10259 .cindex "expansion" "&'pwcheck'& authentication test"
10260 .cindex "&%pwcheck%& expansion condition"
10261 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10262 This is one way of making it possible for passwords to be checked by a process
10263 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10264 deprecated. Its replacement is &'saslauthd'& (see below).
10266 The pwcheck support is not included in Exim by default. You need to specify
10267 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10268 building Exim. For example:
10270 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10272 You do not need to install the full Cyrus software suite in order to use
10273 the pwcheck daemon. You can compile and install just the daemon alone
10274 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10275 access to the &_/var/pwcheck_& directory.
10277 The &%pwcheck%& condition takes one argument, which must be the user name and
10278 password, separated by a colon. For example, in a LOGIN authenticator
10279 configuration, you might have this:
10281 server_condition = ${if pwcheck{$auth1:$auth2}}
10283 Again, for a PLAIN authenticator configuration, this would be:
10285 server_condition = ${if pwcheck{$auth2:$auth3}}
10287 .vitem &*queue_running*&
10288 .cindex "queue runner" "detecting when delivering from"
10289 .cindex "expansion" "queue runner test"
10290 .cindex "&%queue_running%& expansion condition"
10291 This condition, which has no data, is true during delivery attempts that are
10292 initiated by queue runner processes, and false otherwise.
10295 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10297 .cindex "expansion" "Radius authentication"
10298 .cindex "&%radius%& expansion condition"
10299 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10300 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10301 the Radius client configuration file in order to build Exim with Radius
10304 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10305 library, using the original API. If you are using release 0.4.0 or later of
10306 this library, you need to set
10308 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10310 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10311 &%libradius%& library that comes with FreeBSD. To do this, set
10313 RADIUS_LIB_TYPE=RADLIB
10315 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10316 You may also have to supply a suitable setting in EXTRALIBS so that the
10317 Radius library can be found when Exim is linked.
10319 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10320 Radius client library, which calls the Radius server. The condition is true if
10321 the authentication is successful. For example:
10323 server_condition = ${if radius{<arguments>}}
10327 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10328 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10329 .cindex "&'saslauthd'& daemon"
10331 .cindex "expansion" "&'saslauthd'& authentication test"
10332 .cindex "&%saslauthd%& expansion condition"
10333 This condition supports user authentication using the Cyrus &'saslauthd'&
10334 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10335 Using this daemon is one way of making it possible for passwords to be checked
10336 by a process that is not running as root.
10338 The saslauthd support is not included in Exim by default. You need to specify
10339 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10340 building Exim. For example:
10342 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10344 You do not need to install the full Cyrus software suite in order to use
10345 the saslauthd daemon. You can compile and install just the daemon alone
10346 from the Cyrus SASL library.
10348 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10349 two are mandatory. For example:
10351 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10353 The service and the realm are optional (which is why the arguments are enclosed
10354 in their own set of braces). For details of the meaning of the service and
10355 realm, and how to run the daemon, consult the Cyrus documentation.
10360 .section "Combining expansion conditions" "SECID84"
10361 .cindex "expansion" "combining conditions"
10362 Several conditions can be tested at once by combining them using the &%and%&
10363 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10364 conditions on their own, and precede their lists of sub-conditions. Each
10365 sub-condition must be enclosed in braces within the overall braces that contain
10366 the list. No repetition of &%if%& is used.
10370 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10371 .cindex "&""or""& expansion condition"
10372 .cindex "expansion" "&""or""& of conditions"
10373 The sub-conditions are evaluated from left to right. The condition is true if
10374 any one of the sub-conditions is true.
10377 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
10379 When a true sub-condition is found, the following ones are parsed but not
10380 evaluated. If there are several &"match"& sub-conditions the values of the
10381 numeric variables afterwards are taken from the first one that succeeds.
10383 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10384 .cindex "&""and""& expansion condition"
10385 .cindex "expansion" "&""and""& of conditions"
10386 The sub-conditions are evaluated from left to right. The condition is true if
10387 all of the sub-conditions are true. If there are several &"match"&
10388 sub-conditions, the values of the numeric variables afterwards are taken from
10389 the last one. When a false sub-condition is found, the following ones are
10390 parsed but not evaluated.
10392 .ecindex IIDexpcond
10397 .section "Expansion variables" "SECTexpvar"
10398 .cindex "expansion" "variables, list of"
10399 This section contains an alphabetical list of all the expansion variables. Some
10400 of them are available only when Exim is compiled with specific options such as
10401 support for TLS or the content scanning extension.
10404 .vitem "&$0$&, &$1$&, etc"
10405 .cindex "numerical variables (&$1$& &$2$& etc)"
10406 When a &%match%& expansion condition succeeds, these variables contain the
10407 captured substrings identified by the regular expression during subsequent
10408 processing of the success string of the containing &%if%& expansion item.
10409 However, they do not retain their values afterwards; in fact, their previous
10410 values are restored at the end of processing an &%if%& item. The numerical
10411 variables may also be set externally by some other matching process which
10412 precedes the expansion of the string. For example, the commands available in
10413 Exim filter files include an &%if%& command with its own regular expression
10414 matching condition.
10416 .vitem "&$acl_c...$&"
10417 Values can be placed in these variables by the &%set%& modifier in an ACL. They
10418 can be given any name that starts with &$acl_c$& and is at least six characters
10419 long, but the sixth character must be either a digit or an underscore. For
10420 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
10421 variables persist throughout the lifetime of an SMTP connection. They can be
10422 used to pass information between ACLs and between different invocations of the
10423 same ACL. When a message is received, the values of these variables are saved
10424 with the message, and can be accessed by filters, routers, and transports
10425 during subsequent delivery.
10427 .vitem "&$acl_m...$&"
10428 These variables are like the &$acl_c...$& variables, except that their values
10429 are reset after a message has been received. Thus, if several messages are
10430 received in one SMTP connection, &$acl_m...$& values are not passed on from one
10431 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
10432 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
10433 message is received, the values of these variables are saved with the message,
10434 and can be accessed by filters, routers, and transports during subsequent
10437 .vitem &$acl_verify_message$&
10438 .vindex "&$acl_verify_message$&"
10439 After an address verification has failed, this variable contains the failure
10440 message. It retains its value for use in subsequent modifiers. The message can
10441 be preserved by coding like this:
10443 warn !verify = sender
10444 set acl_m0 = $acl_verify_message
10446 You can use &$acl_verify_message$& during the expansion of the &%message%& or
10447 &%log_message%& modifiers, to include information about the verification
10450 .vitem &$address_data$&
10451 .vindex "&$address_data$&"
10452 This variable is set by means of the &%address_data%& option in routers. The
10453 value then remains with the address while it is processed by subsequent routers
10454 and eventually a transport. If the transport is handling multiple addresses,
10455 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
10456 for more details. &*Note*&: The contents of &$address_data$& are visible in
10459 If &$address_data$& is set when the routers are called from an ACL to verify
10460 a recipient address, the final value is still in the variable for subsequent
10461 conditions and modifiers of the ACL statement. If routing the address caused it
10462 to be redirected to just one address, the child address is also routed as part
10463 of the verification, and in this case the final value of &$address_data$& is
10464 from the child's routing.
10466 If &$address_data$& is set when the routers are called from an ACL to verify a
10467 sender address, the final value is also preserved, but this time in
10468 &$sender_address_data$&, to distinguish it from data from a recipient
10471 In both cases (recipient and sender verification), the value does not persist
10472 after the end of the current ACL statement. If you want to preserve
10473 these values for longer, you can save them in ACL variables.
10475 .vitem &$address_file$&
10476 .vindex "&$address_file$&"
10477 When, as a result of aliasing, forwarding, or filtering, a message is directed
10478 to a specific file, this variable holds the name of the file when the transport
10479 is running. At other times, the variable is empty. For example, using the
10480 default configuration, if user &%r2d2%& has a &_.forward_& file containing
10482 /home/r2d2/savemail
10484 then when the &(address_file)& transport is running, &$address_file$&
10485 contains the text string &`/home/r2d2/savemail`&.
10486 .cindex "Sieve filter" "value of &$address_file$&"
10487 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
10488 then up to the transport configuration to generate an appropriate absolute path
10489 to the relevant file.
10491 .vitem &$address_pipe$&
10492 .vindex "&$address_pipe$&"
10493 When, as a result of aliasing or forwarding, a message is directed to a pipe,
10494 this variable holds the pipe command when the transport is running.
10496 .vitem "&$auth1$& &-- &$auth3$&"
10497 .vindex "&$auth1$&, &$auth2$&, etc"
10498 These variables are used in SMTP authenticators (see chapters
10499 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
10501 .vitem &$authenticated_id$&
10502 .cindex "authentication" "id"
10503 .vindex "&$authenticated_id$&"
10504 When a server successfully authenticates a client it may be configured to
10505 preserve some of the authentication information in the variable
10506 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
10507 user/password authenticator configuration might preserve the user name for use
10508 in the routers. Note that this is not the same information that is saved in
10509 &$sender_host_authenticated$&.
10510 When a message is submitted locally (that is, not over a TCP connection)
10511 the value of &$authenticated_id$& is normally the login name of the calling
10512 process. However, a trusted user can override this by means of the &%-oMai%&
10513 command line option.
10518 .vitem &$authenticated_sender$&
10519 .cindex "sender" "authenticated"
10520 .cindex "authentication" "sender"
10521 .cindex "AUTH" "on MAIL command"
10522 .vindex "&$authenticated_sender$&"
10523 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
10524 SMTP MAIL command if it believes the sender is sufficiently trusted, as
10525 described in section &<<SECTauthparamail>>&. Unless the data is the string
10526 &"<>"&, it is set as the authenticated sender of the message, and the value is
10527 available during delivery in the &$authenticated_sender$& variable. If the
10528 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
10530 .vindex "&$qualify_domain$&"
10531 When a message is submitted locally (that is, not over a TCP connection), the
10532 value of &$authenticated_sender$& is an address constructed from the login
10533 name of the calling process and &$qualify_domain$&, except that a trusted user
10534 can override this by means of the &%-oMas%& command line option.
10537 .vitem &$authentication_failed$&
10538 .cindex "authentication" "failure"
10539 .vindex "&$authentication_failed$&"
10540 This variable is set to &"1"& in an Exim server if a client issues an AUTH
10541 command that does not succeed. Otherwise it is set to &"0"&. This makes it
10542 possible to distinguish between &"did not try to authenticate"&
10543 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
10544 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
10545 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
10546 negative response to an AUTH command, including (for example) an attempt to use
10547 an undefined mechanism.
10549 .vitem &$body_linecount$&
10550 .cindex "message body" "line count"
10551 .cindex "body of message" "line count"
10552 .vindex "&$body_linecount$&"
10553 When a message is being received or delivered, this variable contains the
10554 number of lines in the message's body. See also &$message_linecount$&.
10556 .vitem &$body_zerocount$&
10557 .cindex "message body" "binary zero count"
10558 .cindex "body of message" "binary zero count"
10559 .cindex "binary zero" "in message body"
10560 .vindex "&$body_zerocount$&"
10561 When a message is being received or delivered, this variable contains the
10562 number of binary zero bytes in the message's body.
10564 .vitem &$bounce_recipient$&
10565 .vindex "&$bounce_recipient$&"
10566 This is set to the recipient address of a bounce message while Exim is creating
10567 it. It is useful if a customized bounce message text file is in use (see
10568 chapter &<<CHAPemsgcust>>&).
10570 .vitem &$bounce_return_size_limit$&
10571 .vindex "&$bounce_return_size_limit$&"
10572 This contains the value set in the &%bounce_return_size_limit%& option, rounded
10573 up to a multiple of 1000. It is useful when a customized error message text
10574 file is in use (see chapter &<<CHAPemsgcust>>&).
10576 .vitem &$caller_gid$&
10577 .cindex "gid (group id)" "caller"
10578 .vindex "&$caller_gid$&"
10579 The real group id under which the process that called Exim was running. This is
10580 not the same as the group id of the originator of a message (see
10581 &$originator_gid$&). If Exim re-execs itself, this variable in the new
10582 incarnation normally contains the Exim gid.
10584 .vitem &$caller_uid$&
10585 .cindex "uid (user id)" "caller"
10586 .vindex "&$caller_uid$&"
10587 The real user id under which the process that called Exim was running. This is
10588 not the same as the user id of the originator of a message (see
10589 &$originator_uid$&). If Exim re-execs itself, this variable in the new
10590 incarnation normally contains the Exim uid.
10592 .vitem &$compile_date$&
10593 .vindex "&$compile_date$&"
10594 The date on which the Exim binary was compiled.
10596 .vitem &$compile_number$&
10597 .vindex "&$compile_number$&"
10598 The building process for Exim keeps a count of the number
10599 of times it has been compiled. This serves to distinguish different
10600 compilations of the same version of the program.
10602 .vitem &$demime_errorlevel$&
10603 .vindex "&$demime_errorlevel$&"
10604 This variable is available when Exim is compiled with
10605 the content-scanning extension and the obsolete &%demime%& condition. For
10606 details, see section &<<SECTdemimecond>>&.
10608 .vitem &$demime_reason$&
10609 .vindex "&$demime_reason$&"
10610 This variable is available when Exim is compiled with the
10611 content-scanning extension and the obsolete &%demime%& condition. For details,
10612 see section &<<SECTdemimecond>>&.
10614 .vitem &$dnslist_domain$& &&&
10615 &$dnslist_matched$& &&&
10616 &$dnslist_text$& &&&
10618 .vindex "&$dnslist_domain$&"
10619 .vindex "&$dnslist_matched$&"
10620 .vindex "&$dnslist_text$&"
10621 .vindex "&$dnslist_value$&"
10622 .cindex "black list (DNS)"
10623 When a DNS (black) list lookup succeeds, these variables are set to contain
10624 the following data from the lookup: the list's domain name, the key that was
10625 looked up, the contents of any associated TXT record, and the value from the
10626 main A record. See section &<<SECID204>>& for more details.
10629 .vindex "&$domain$&"
10630 When an address is being routed, or delivered on its own, this variable
10631 contains the domain. Uppercase letters in the domain are converted into lower
10632 case for &$domain$&.
10634 Global address rewriting happens when a message is received, so the value of
10635 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
10636 is set during user filtering, but not during system filtering, because a
10637 message may have many recipients and the system filter is called just once.
10639 When more than one address is being delivered at once (for example, several
10640 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
10641 have the same domain. Transports can be restricted to handling only one domain
10642 at a time if the value of &$domain$& is required at transport time &-- this is
10643 the default for local transports. For further details of the environment in
10644 which local transports are run, see chapter &<<CHAPenvironment>>&.
10646 .oindex "&%delay_warning_condition%&"
10647 At the end of a delivery, if all deferred addresses have the same domain, it is
10648 set in &$domain$& during the expansion of &%delay_warning_condition%&.
10650 The &$domain$& variable is also used in some other circumstances:
10653 When an ACL is running for a RCPT command, &$domain$& contains the domain of
10654 the recipient address. The domain of the &'sender'& address is in
10655 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
10656 normally set during the running of the MAIL ACL. However, if the sender address
10657 is verified with a callout during the MAIL ACL, the sender domain is placed in
10658 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
10659 the &(smtp)& transport.
10662 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10663 &$domain$& contains the domain portion of the address that is being rewritten;
10664 it can be used in the expansion of the replacement address, for example, to
10665 rewrite domains by file lookup.
10668 With one important exception, whenever a domain list is being scanned,
10669 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
10670 a &%sender_domains%& condition in an ACL is being processed, the subject domain
10671 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
10672 that, in a RCPT ACL, the sender domain list can be dependent on the
10673 recipient domain (which is what is in &$domain$& at this time).
10676 .cindex "ETRN" "value of &$domain$&"
10677 .oindex "&%smtp_etrn_command%&"
10678 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
10679 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
10683 .vitem &$domain_data$&
10684 .vindex "&$domain_data$&"
10685 When the &%domains%& option on a router matches a domain by
10686 means of a lookup, the data read by the lookup is available during the running
10687 of the router as &$domain_data$&. In addition, if the driver routes the
10688 address to a transport, the value is available in that transport. If the
10689 transport is handling multiple addresses, the value from the first address is
10692 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
10693 domain by means of a lookup. The data read by the lookup is available during
10694 the rest of the ACL statement. In all other situations, this variable expands
10697 .vitem &$exim_gid$&
10698 .vindex "&$exim_gid$&"
10699 This variable contains the numerical value of the Exim group id.
10701 .vitem &$exim_path$&
10702 .vindex "&$exim_path$&"
10703 This variable contains the path to the Exim binary.
10705 .vitem &$exim_uid$&
10706 .vindex "&$exim_uid$&"
10707 This variable contains the numerical value of the Exim user id.
10709 .vitem &$found_extension$&
10710 .vindex "&$found_extension$&"
10711 This variable is available when Exim is compiled with the
10712 content-scanning extension and the obsolete &%demime%& condition. For details,
10713 see section &<<SECTdemimecond>>&.
10715 .vitem &$header_$&<&'name'&>
10716 This is not strictly an expansion variable. It is expansion syntax for
10717 inserting the message header line with the given name. Note that the name must
10718 be terminated by colon or white space, because it may contain a wide variety of
10719 characters. Note also that braces must &'not'& be used.
10723 When the &%check_local_user%& option is set for a router, the user's home
10724 directory is placed in &$home$& when the check succeeds. In particular, this
10725 means it is set during the running of users' filter files. A router may also
10726 explicitly set a home directory for use by a transport; this can be overridden
10727 by a setting on the transport itself.
10729 When running a filter test via the &%-bf%& option, &$home$& is set to the value
10730 of the environment variable HOME.
10734 If a router assigns an address to a transport (any transport), and passes a
10735 list of hosts with the address, the value of &$host$& when the transport starts
10736 to run is the name of the first host on the list. Note that this applies both
10737 to local and remote transports.
10739 .cindex "transport" "filter"
10740 .cindex "filter" "transport filter"
10741 For the &(smtp)& transport, if there is more than one host, the value of
10742 &$host$& changes as the transport works its way through the list. In
10743 particular, when the &(smtp)& transport is expanding its options for encryption
10744 using TLS, or for specifying a transport filter (see chapter
10745 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
10748 When used in the client part of an authenticator configuration (see chapter
10749 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
10750 client is connected.
10753 .vitem &$host_address$&
10754 .vindex "&$host_address$&"
10755 This variable is set to the remote host's IP address whenever &$host$& is set
10756 for a remote connection. It is also set to the IP address that is being checked
10757 when the &%ignore_target_hosts%& option is being processed.
10759 .vitem &$host_data$&
10760 .vindex "&$host_data$&"
10761 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
10762 result of the lookup is made available in the &$host_data$& variable. This
10763 allows you, for example, to do things like this:
10765 deny hosts = net-lsearch;/some/file
10766 message = $host_data
10768 .vitem &$host_lookup_deferred$&
10769 .cindex "host name" "lookup, failure of"
10770 .vindex "&$host_lookup_deferred$&"
10771 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
10772 message comes from a remote host and there is an attempt to look up the host's
10773 name from its IP address, and the attempt is not successful, one of these
10774 variables is set to &"1"&.
10777 If the lookup receives a definite negative response (for example, a DNS lookup
10778 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
10781 If there is any kind of problem during the lookup, such that Exim cannot
10782 tell whether or not the host name is defined (for example, a timeout for a DNS
10783 lookup), &$host_lookup_deferred$& is set to &"1"&.
10786 Looking up a host's name from its IP address consists of more than just a
10787 single reverse lookup. Exim checks that a forward lookup of at least one of the
10788 names it receives from a reverse lookup yields the original IP address. If this
10789 is not the case, Exim does not accept the looked up name(s), and
10790 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
10791 IP address (for example, the existence of a PTR record in the DNS) is not
10792 sufficient on its own for the success of a host name lookup. If the reverse
10793 lookup succeeds, but there is a lookup problem such as a timeout when checking
10794 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
10795 &"1"&. See also &$sender_host_name$&.
10797 .vitem &$host_lookup_failed$&
10798 .vindex "&$host_lookup_failed$&"
10799 See &$host_lookup_deferred$&.
10803 .vindex "&$inode$&"
10804 The only time this variable is set is while expanding the &%directory_file%&
10805 option in the &(appendfile)& transport. The variable contains the inode number
10806 of the temporary file which is about to be renamed. It can be used to construct
10807 a unique name for the file.
10809 .vitem &$interface_address$&
10810 .vindex "&$interface_address$&"
10811 This is an obsolete name for &$received_ip_address$&.
10813 .vitem &$interface_port$&
10814 .vindex "&$interface_port$&"
10815 This is an obsolete name for &$received_port$&.
10819 This variable is used during the expansion of &*forall*& and &*forany*&
10820 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
10821 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
10825 .vindex "&$ldap_dn$&"
10826 This variable, which is available only when Exim is compiled with LDAP support,
10827 contains the DN from the last entry in the most recently successful LDAP
10830 .vitem &$load_average$&
10831 .vindex "&$load_average$&"
10832 This variable contains the system load average, multiplied by 1000 so that it
10833 is an integer. For example, if the load average is 0.21, the value of the
10834 variable is 210. The value is recomputed every time the variable is referenced.
10836 .vitem &$local_part$&
10837 .vindex "&$local_part$&"
10838 When an address is being routed, or delivered on its own, this
10839 variable contains the local part. When a number of addresses are being
10840 delivered together (for example, multiple RCPT commands in an SMTP
10841 session), &$local_part$& is not set.
10843 Global address rewriting happens when a message is received, so the value of
10844 &$local_part$& during routing and delivery is the value after rewriting.
10845 &$local_part$& is set during user filtering, but not during system filtering,
10846 because a message may have many recipients and the system filter is called just
10849 .vindex "&$local_part_prefix$&"
10850 .vindex "&$local_part_suffix$&"
10851 If a local part prefix or suffix has been recognized, it is not included in the
10852 value of &$local_part$& during routing and subsequent delivery. The values of
10853 any prefix or suffix are in &$local_part_prefix$& and
10854 &$local_part_suffix$&, respectively.
10856 When a message is being delivered to a file, pipe, or autoreply transport as a
10857 result of aliasing or forwarding, &$local_part$& is set to the local part of
10858 the parent address, not to the file name or command (see &$address_file$& and
10861 When an ACL is running for a RCPT command, &$local_part$& contains the
10862 local part of the recipient address.
10864 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10865 &$local_part$& contains the local part of the address that is being rewritten;
10866 it can be used in the expansion of the replacement address, for example.
10868 In all cases, all quoting is removed from the local part. For example, for both
10871 "abc:xyz"@test.example
10872 abc\:xyz@test.example
10874 the value of &$local_part$& is
10878 If you use &$local_part$& to create another address, you should always wrap it
10879 inside a quoting operator. For example, in a &(redirect)& router you could
10882 data = ${quote_local_part:$local_part}@new.domain.example
10884 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
10885 to process local parts in a case-dependent manner in a router, you can set the
10886 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
10888 .vitem &$local_part_data$&
10889 .vindex "&$local_part_data$&"
10890 When the &%local_parts%& option on a router matches a local part by means of a
10891 lookup, the data read by the lookup is available during the running of the
10892 router as &$local_part_data$&. In addition, if the driver routes the address
10893 to a transport, the value is available in that transport. If the transport is
10894 handling multiple addresses, the value from the first address is used.
10896 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
10897 matches a local part by means of a lookup. The data read by the lookup is
10898 available during the rest of the ACL statement. In all other situations, this
10899 variable expands to nothing.
10901 .vitem &$local_part_prefix$&
10902 .vindex "&$local_part_prefix$&"
10903 When an address is being routed or delivered, and a
10904 specific prefix for the local part was recognized, it is available in this
10905 variable, having been removed from &$local_part$&.
10907 .vitem &$local_part_suffix$&
10908 .vindex "&$local_part_suffix$&"
10909 When an address is being routed or delivered, and a
10910 specific suffix for the local part was recognized, it is available in this
10911 variable, having been removed from &$local_part$&.
10913 .vitem &$local_scan_data$&
10914 .vindex "&$local_scan_data$&"
10915 This variable contains the text returned by the &[local_scan()]& function when
10916 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
10918 .vitem &$local_user_gid$&
10919 .vindex "&$local_user_gid$&"
10920 See &$local_user_uid$&.
10922 .vitem &$local_user_uid$&
10923 .vindex "&$local_user_uid$&"
10924 This variable and &$local_user_gid$& are set to the uid and gid after the
10925 &%check_local_user%& router precondition succeeds. This means that their values
10926 are available for the remaining preconditions (&%senders%&, &%require_files%&,
10927 and &%condition%&), for the &%address_data%& expansion, and for any
10928 router-specific expansions. At all other times, the values in these variables
10929 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
10931 .vitem &$localhost_number$&
10932 .vindex "&$localhost_number$&"
10933 This contains the expanded value of the
10934 &%localhost_number%& option. The expansion happens after the main options have
10937 .vitem &$log_inodes$&
10938 .vindex "&$log_inodes$&"
10939 The number of free inodes in the disk partition where Exim's
10940 log files are being written. The value is recalculated whenever the variable is
10941 referenced. If the relevant file system does not have the concept of inodes,
10942 the value of is -1. See also the &%check_log_inodes%& option.
10944 .vitem &$log_space$&
10945 .vindex "&$log_space$&"
10946 The amount of free space (as a number of kilobytes) in the disk
10947 partition where Exim's log files are being written. The value is recalculated
10948 whenever the variable is referenced. If the operating system does not have the
10949 ability to find the amount of free space (only true for experimental systems),
10950 the space value is -1. See also the &%check_log_space%& option.
10953 .vitem &$mailstore_basename$&
10954 .vindex "&$mailstore_basename$&"
10955 This variable is set only when doing deliveries in &"mailstore"& format in the
10956 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
10957 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
10958 contains the basename of the files that are being written, that is, the name
10959 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
10962 .vitem &$malware_name$&
10963 .vindex "&$malware_name$&"
10964 This variable is available when Exim is compiled with the
10965 content-scanning extension. It is set to the name of the virus that was found
10966 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
10968 .vitem &$max_received_linelength$&
10969 .vindex "&$max_received_linelength$&"
10970 .cindex "maximum" "line length"
10971 .cindex "line length" "maximum"
10972 This variable contains the number of bytes in the longest line that was
10973 received as part of the message, not counting the line termination
10976 .vitem &$message_age$&
10977 .cindex "message" "age of"
10978 .vindex "&$message_age$&"
10979 This variable is set at the start of a delivery attempt to contain the number
10980 of seconds since the message was received. It does not change during a single
10983 .vitem &$message_body$&
10984 .cindex "body of message" "expansion variable"
10985 .cindex "message body" "in expansion"
10986 .cindex "binary zero" "in message body"
10987 .vindex "&$message_body$&"
10988 .oindex "&%message_body_visible%&"
10989 This variable contains the initial portion of a message's body while it is
10990 being delivered, and is intended mainly for use in filter files. The maximum
10991 number of characters of the body that are put into the variable is set by the
10992 &%message_body_visible%& configuration option; the default is 500.
10994 .oindex "&%message_body_newlines%&"
10995 By default, newlines are converted into spaces in &$message_body$&, to make it
10996 easier to search for phrases that might be split over a line break. However,
10997 this can be disabled by setting &%message_body_newlines%& to be true. Binary
10998 zeros are always converted into spaces.
11000 .vitem &$message_body_end$&
11001 .cindex "body of message" "expansion variable"
11002 .cindex "message body" "in expansion"
11003 .vindex "&$message_body_end$&"
11004 This variable contains the final portion of a message's
11005 body while it is being delivered. The format and maximum size are as for
11008 .vitem &$message_body_size$&
11009 .cindex "body of message" "size"
11010 .cindex "message body" "size"
11011 .vindex "&$message_body_size$&"
11012 When a message is being delivered, this variable contains the size of the body
11013 in bytes. The count starts from the character after the blank line that
11014 separates the body from the header. Newlines are included in the count. See
11015 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
11017 .vitem &$message_exim_id$&
11018 .vindex "&$message_exim_id$&"
11019 When a message is being received or delivered, this variable contains the
11020 unique message id that is generated and used by Exim to identify the message.
11021 An id is not created for a message until after its header has been successfully
11022 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
11023 line; it is the local id that Exim assigns to the message, for example:
11024 &`1BXTIK-0001yO-VA`&.
11026 .vitem &$message_headers$&
11027 .vindex &$message_headers$&
11028 This variable contains a concatenation of all the header lines when a message
11029 is being processed, except for lines added by routers or transports. The header
11030 lines are separated by newline characters. Their contents are decoded in the
11031 same way as a header line that is inserted by &%bheader%&.
11033 .vitem &$message_headers_raw$&
11034 .vindex &$message_headers_raw$&
11035 This variable is like &$message_headers$& except that no processing of the
11036 contents of header lines is done.
11038 .vitem &$message_id$&
11039 This is an old name for &$message_exim_id$&, which is now deprecated.
11041 .vitem &$message_linecount$&
11042 .vindex "&$message_linecount$&"
11043 This variable contains the total number of lines in the header and body of the
11044 message. Compare &$body_linecount$&, which is the count for the body only.
11045 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
11046 number of lines received. Before delivery happens (that is, before filters,
11047 routers, and transports run) the count is increased to include the
11048 &'Received:'& header line that Exim standardly adds, and also any other header
11049 lines that are added by ACLs. The blank line that separates the message header
11050 from the body is not counted. Here is an example of the use of this variable in
11053 deny message = Too many lines in message header
11055 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
11057 In the MAIL and RCPT ACLs, the value is zero because at that stage the
11058 message has not yet been received.
11060 .vitem &$message_size$&
11061 .cindex "size" "of message"
11062 .cindex "message" "size"
11063 .vindex "&$message_size$&"
11064 When a message is being processed, this variable contains its size in bytes. In
11065 most cases, the size includes those headers that were received with the
11066 message, but not those (such as &'Envelope-to:'&) that are added to individual
11067 deliveries as they are written. However, there is one special case: during the
11068 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11069 doing a delivery in maildir format, the value of &$message_size$& is the
11070 precise size of the file that has been written. See also
11071 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11073 .cindex "RCPT" "value of &$message_size$&"
11074 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11075 contains the size supplied on the MAIL command, or -1 if no size was given. The
11076 value may not, of course, be truthful.
11078 .vitem &$mime_$&&'xxx'&
11079 A number of variables whose names start with &$mime$& are
11080 available when Exim is compiled with the content-scanning extension. For
11081 details, see section &<<SECTscanmimepart>>&.
11083 .vitem "&$n0$& &-- &$n9$&"
11084 These variables are counters that can be incremented by means
11085 of the &%add%& command in filter files.
11087 .vitem &$original_domain$&
11088 .vindex "&$domain$&"
11089 .vindex "&$original_domain$&"
11090 When a top-level address is being processed for delivery, this contains the
11091 same value as &$domain$&. However, if a &"child"& address (for example,
11092 generated by an alias, forward, or filter file) is being processed, this
11093 variable contains the domain of the original address (lower cased). This
11094 differs from &$parent_domain$& only when there is more than one level of
11095 aliasing or forwarding. When more than one address is being delivered in a
11096 single transport run, &$original_domain$& is not set.
11098 If a new address is created by means of a &%deliver%& command in a system
11099 filter, it is set up with an artificial &"parent"& address. This has the local
11100 part &'system-filter'& and the default qualify domain.
11102 .vitem &$original_local_part$&
11103 .vindex "&$local_part$&"
11104 .vindex "&$original_local_part$&"
11105 When a top-level address is being processed for delivery, this contains the
11106 same value as &$local_part$&, unless a prefix or suffix was removed from the
11107 local part, because &$original_local_part$& always contains the full local
11108 part. When a &"child"& address (for example, generated by an alias, forward, or
11109 filter file) is being processed, this variable contains the full local part of
11110 the original address.
11112 If the router that did the redirection processed the local part
11113 case-insensitively, the value in &$original_local_part$& is in lower case.
11114 This variable differs from &$parent_local_part$& only when there is more than
11115 one level of aliasing or forwarding. When more than one address is being
11116 delivered in a single transport run, &$original_local_part$& is not set.
11118 If a new address is created by means of a &%deliver%& command in a system
11119 filter, it is set up with an artificial &"parent"& address. This has the local
11120 part &'system-filter'& and the default qualify domain.
11122 .vitem &$originator_gid$&
11123 .cindex "gid (group id)" "of originating user"
11124 .cindex "sender" "gid"
11125 .vindex "&$caller_gid$&"
11126 .vindex "&$originator_gid$&"
11127 This variable contains the value of &$caller_gid$& that was set when the
11128 message was received. For messages received via the command line, this is the
11129 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11130 normally the gid of the Exim user.
11132 .vitem &$originator_uid$&
11133 .cindex "uid (user id)" "of originating user"
11134 .cindex "sender" "uid"
11135 .vindex "&$caller_uid$&"
11136 .vindex "&$originaltor_uid$&"
11137 The value of &$caller_uid$& that was set when the message was received. For
11138 messages received via the command line, this is the uid of the sending user.
11139 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11142 .vitem &$parent_domain$&
11143 .vindex "&$parent_domain$&"
11144 This variable is similar to &$original_domain$& (see
11145 above), except that it refers to the immediately preceding parent address.
11147 .vitem &$parent_local_part$&
11148 .vindex "&$parent_local_part$&"
11149 This variable is similar to &$original_local_part$&
11150 (see above), except that it refers to the immediately preceding parent address.
11153 .cindex "pid (process id)" "of current process"
11155 This variable contains the current process id.
11157 .vitem &$pipe_addresses$&
11158 .cindex "filter" "transport filter"
11159 .cindex "transport" "filter"
11160 .vindex "&$pipe_addresses$&"
11161 This is not an expansion variable, but is mentioned here because the string
11162 &`$pipe_addresses`& is handled specially in the command specification for the
11163 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11164 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11165 It cannot be used in general expansion strings, and provokes an &"unknown
11166 variable"& error if encountered.
11168 .vitem &$primary_hostname$&
11169 .vindex "&$primary_hostname$&"
11170 This variable contains the value set by &%primary_hostname%& in the
11171 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11172 a single-component name, Exim calls &[gethostbyname()]& (or
11173 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11174 qualified host name. See also &$smtp_active_hostname$&.
11177 .vitem &$prvscheck_address$&
11178 This variable is used in conjunction with the &%prvscheck%& expansion item,
11179 which is described in sections &<<SECTexpansionitems>>& and
11180 &<<SECTverifyPRVS>>&.
11182 .vitem &$prvscheck_keynum$&
11183 This variable is used in conjunction with the &%prvscheck%& expansion item,
11184 which is described in sections &<<SECTexpansionitems>>& and
11185 &<<SECTverifyPRVS>>&.
11187 .vitem &$prvscheck_result$&
11188 This variable is used in conjunction with the &%prvscheck%& expansion item,
11189 which is described in sections &<<SECTexpansionitems>>& and
11190 &<<SECTverifyPRVS>>&.
11192 .vitem &$qualify_domain$&
11193 .vindex "&$qualify_domain$&"
11194 The value set for the &%qualify_domain%& option in the configuration file.
11196 .vitem &$qualify_recipient$&
11197 .vindex "&$qualify_recipient$&"
11198 The value set for the &%qualify_recipient%& option in the configuration file,
11199 or if not set, the value of &$qualify_domain$&.
11201 .vitem &$rcpt_count$&
11202 .vindex "&$rcpt_count$&"
11203 When a message is being received by SMTP, this variable contains the number of
11204 RCPT commands received for the current message. If this variable is used in a
11205 RCPT ACL, its value includes the current command.
11207 .vitem &$rcpt_defer_count$&
11208 .vindex "&$rcpt_defer_count$&"
11209 .cindex "4&'xx'& responses" "count of"
11210 When a message is being received by SMTP, this variable contains the number of
11211 RCPT commands in the current message that have previously been rejected with a
11212 temporary (4&'xx'&) response.
11214 .vitem &$rcpt_fail_count$&
11215 .vindex "&$rcpt_fail_count$&"
11216 When a message is being received by SMTP, this variable contains the number of
11217 RCPT commands in the current message that have previously been rejected with a
11218 permanent (5&'xx'&) response.
11220 .vitem &$received_count$&
11221 .vindex "&$received_count$&"
11222 This variable contains the number of &'Received:'& header lines in the message,
11223 including the one added by Exim (so its value is always greater than zero). It
11224 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11227 .vitem &$received_for$&
11228 .vindex "&$received_for$&"
11229 If there is only a single recipient address in an incoming message, this
11230 variable contains that address when the &'Received:'& header line is being
11231 built. The value is copied after recipient rewriting has happened, but before
11232 the &[local_scan()]& function is run.
11234 .vitem &$received_ip_address$&
11235 .vindex "&$received_ip_address$&"
11236 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11237 variable is set to the address of the local IP interface, and &$received_port$&
11238 is set to the local port number. (The remote IP address and port are in
11239 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11240 the port value is -1 unless it has been set using the &%-oMi%& command line
11243 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11244 could be used, for example, to make the file name for a TLS certificate depend
11245 on which interface and/or port is being used for the incoming connection. The
11246 values of &$received_ip_address$& and &$received_port$& are saved with any
11247 messages that are received, thus making these variables available at delivery
11250 &*Note:*& There are no equivalent variables for outgoing connections, because
11251 the values are unknown (unless they are explicitly set by options of the
11252 &(smtp)& transport).
11254 .vitem &$received_port$&
11255 .vindex "&$received_port$&"
11256 See &$received_ip_address$&.
11258 .vitem &$received_protocol$&
11259 .vindex "&$received_protocol$&"
11260 When a message is being processed, this variable contains the name of the
11261 protocol by which it was received. Most of the names used by Exim are defined
11262 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11263 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11264 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11265 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11266 connection and the client was successfully authenticated.
11268 Exim uses the protocol name &"smtps"& for the case when encryption is
11269 automatically set up on connection without the use of STARTTLS (see
11270 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11271 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11272 where the client initially uses EHLO, sets up an encrypted connection using
11273 STARTTLS, and then uses HELO afterwards.
11275 The &%-oMr%& option provides a way of specifying a custom protocol name for
11276 messages that are injected locally by trusted callers. This is commonly used to
11277 identify messages that are being re-injected after some kind of scanning.
11279 .vitem &$received_time$&
11280 .vindex "&$received_time$&"
11281 This variable contains the date and time when the current message was received,
11282 as a number of seconds since the start of the Unix epoch.
11284 .vitem &$recipient_data$&
11285 .vindex "&$recipient_data$&"
11286 This variable is set after an indexing lookup success in an ACL &%recipients%&
11287 condition. It contains the data from the lookup, and the value remains set
11288 until the next &%recipients%& test. Thus, you can do things like this:
11290 &`require recipients = cdb*@;/some/file`&
11291 &`deny `&&'some further test involving'& &`$recipient_data`&
11293 &*Warning*&: This variable is set only when a lookup is used as an indexing
11294 method in the address list, using the semicolon syntax as in the example above.
11295 The variable is not set for a lookup that is used as part of the string
11296 expansion that all such lists undergo before being interpreted.
11298 .vitem &$recipient_verify_failure$&
11299 .vindex "&$recipient_verify_failure$&"
11300 In an ACL, when a recipient verification fails, this variable contains
11301 information about the failure. It is set to one of the following words:
11304 &"qualify"&: The address was unqualified (no domain), and the message
11305 was neither local nor came from an exempted host.
11308 &"route"&: Routing failed.
11311 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11312 or before the MAIL command (that is, on initial connection, HELO, or
11316 &"recipient"&: The RCPT command in a callout was rejected.
11319 &"postmaster"&: The postmaster check in a callout was rejected.
11322 The main use of this variable is expected to be to distinguish between
11323 rejections of MAIL and rejections of RCPT.
11325 .vitem &$recipients$&
11326 .vindex "&$recipients$&"
11327 This variable contains a list of envelope recipients for a message. A comma and
11328 a space separate the addresses in the replacement text. However, the variable
11329 is not generally available, to prevent exposure of Bcc recipients in
11330 unprivileged users' filter files. You can use &$recipients$& only in these
11334 In a system filter file.
11336 In the ACLs associated with the DATA command and with non-SMTP messages, that
11337 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
11338 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
11339 &%acl_not_smtp_mime%&.
11341 From within a &[local_scan()]& function.
11345 .vitem &$recipients_count$&
11346 .vindex "&$recipients_count$&"
11347 When a message is being processed, this variable contains the number of
11348 envelope recipients that came with the message. Duplicates are not excluded
11349 from the count. While a message is being received over SMTP, the number
11350 increases for each accepted recipient. It can be referenced in an ACL.
11353 .vitem &$regex_match_string$&
11354 .vindex "&$regex_match_string$&"
11355 This variable is set to contain the matching regular expression after a
11356 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
11359 .vitem &$reply_address$&
11360 .vindex "&$reply_address$&"
11361 When a message is being processed, this variable contains the contents of the
11362 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
11363 contents of the &'From:'& header line. Apart from the removal of leading
11364 white space, the value is not processed in any way. In particular, no RFC 2047
11365 decoding or character code translation takes place.
11367 .vitem &$return_path$&
11368 .vindex "&$return_path$&"
11369 When a message is being delivered, this variable contains the return path &--
11370 the sender field that will be sent as part of the envelope. It is not enclosed
11371 in <> characters. At the start of routing an address, &$return_path$& has the
11372 same value as &$sender_address$&, but if, for example, an incoming message to a
11373 mailing list has been expanded by a router which specifies a different address
11374 for bounce messages, &$return_path$& subsequently contains the new bounce
11375 address, whereas &$sender_address$& always contains the original sender address
11376 that was received with the message. In other words, &$sender_address$& contains
11377 the incoming envelope sender, and &$return_path$& contains the outgoing
11380 .vitem &$return_size_limit$&
11381 .vindex "&$return_size_limit$&"
11382 This is an obsolete name for &$bounce_return_size_limit$&.
11385 .cindex "return code" "from &%run%& expansion"
11386 .vindex "&$runrc$&"
11387 This variable contains the return code from a command that is run by the
11388 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
11389 assume the order in which option values are expanded, except for those
11390 preconditions whose order of testing is documented. Therefore, you cannot
11391 reliably expect to set &$runrc$& by the expansion of one option, and use it in
11394 .vitem &$self_hostname$&
11395 .oindex "&%self%&" "value of host name"
11396 .vindex "&$self_hostname$&"
11397 When an address is routed to a supposedly remote host that turns out to be the
11398 local host, what happens is controlled by the &%self%& generic router option.
11399 One of its values causes the address to be passed to another router. When this
11400 happens, &$self_hostname$& is set to the name of the local host that the
11401 original router encountered. In other circumstances its contents are null.
11403 .vitem &$sender_address$&
11404 .vindex "&$sender_address$&"
11405 When a message is being processed, this variable contains the sender's address
11406 that was received in the message's envelope. The case of letters in the address
11407 is retained, in both the local part and the domain. For bounce messages, the
11408 value of this variable is the empty string. See also &$return_path$&.
11410 .vitem &$sender_address_data$&
11411 .vindex "&$address_data$&"
11412 .vindex "&$sender_address_data$&"
11413 If &$address_data$& is set when the routers are called from an ACL to verify a
11414 sender address, the final value is preserved in &$sender_address_data$&, to
11415 distinguish it from data from a recipient address. The value does not persist
11416 after the end of the current ACL statement. If you want to preserve it for
11417 longer, you can save it in an ACL variable.
11419 .vitem &$sender_address_domain$&
11420 .vindex "&$sender_address_domain$&"
11421 The domain portion of &$sender_address$&.
11423 .vitem &$sender_address_local_part$&
11424 .vindex "&$sender_address_local_part$&"
11425 The local part portion of &$sender_address$&.
11427 .vitem &$sender_data$&
11428 .vindex "&$sender_data$&"
11429 This variable is set after a lookup success in an ACL &%senders%& condition or
11430 in a router &%senders%& option. It contains the data from the lookup, and the
11431 value remains set until the next &%senders%& test. Thus, you can do things like
11434 &`require senders = cdb*@;/some/file`&
11435 &`deny `&&'some further test involving'& &`$sender_data`&
11437 &*Warning*&: This variable is set only when a lookup is used as an indexing
11438 method in the address list, using the semicolon syntax as in the example above.
11439 The variable is not set for a lookup that is used as part of the string
11440 expansion that all such lists undergo before being interpreted.
11442 .vitem &$sender_fullhost$&
11443 .vindex "&$sender_fullhost$&"
11444 When a message is received from a remote host, this variable contains the host
11445 name and IP address in a single string. It ends with the IP address in square
11446 brackets, followed by a colon and a port number if the logging of ports is
11447 enabled. The format of the rest of the string depends on whether the host
11448 issued a HELO or EHLO SMTP command, and whether the host name was verified by
11449 looking up its IP address. (Looking up the IP address can be forced by the
11450 &%host_lookup%& option, independent of verification.) A plain host name at the
11451 start of the string is a verified host name; if this is not present,
11452 verification either failed or was not requested. A host name in parentheses is
11453 the argument of a HELO or EHLO command. This is omitted if it is identical to
11454 the verified host name or to the host's IP address in square brackets.
11456 .vitem &$sender_helo_name$&
11457 .vindex "&$sender_helo_name$&"
11458 When a message is received from a remote host that has issued a HELO or EHLO
11459 command, the argument of that command is placed in this variable. It is also
11460 set if HELO or EHLO is used when a message is received using SMTP locally via
11461 the &%-bs%& or &%-bS%& options.
11463 .vitem &$sender_host_address$&
11464 .vindex "&$sender_host_address$&"
11465 When a message is received from a remote host, this variable contains that
11466 host's IP address. For locally submitted messages, it is empty.
11468 .vitem &$sender_host_authenticated$&
11469 .vindex "&$sender_host_authenticated$&"
11470 This variable contains the name (not the public name) of the authenticator
11471 driver that successfully authenticated the client from which the message was
11472 received. It is empty if there was no successful authentication. See also
11473 &$authenticated_id$&.
11475 .vitem &$sender_host_name$&
11476 .vindex "&$sender_host_name$&"
11477 When a message is received from a remote host, this variable contains the
11478 host's name as obtained by looking up its IP address. For messages received by
11479 other means, this variable is empty.
11481 .vindex "&$host_lookup_failed$&"
11482 If the host name has not previously been looked up, a reference to
11483 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
11484 A looked up name is accepted only if it leads back to the original IP address
11485 via a forward lookup. If either the reverse or the forward lookup fails to find
11486 any data, or if the forward lookup does not yield the original IP address,
11487 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
11489 .vindex "&$host_lookup_deferred$&"
11490 However, if either of the lookups cannot be completed (for example, there is a
11491 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
11492 &$host_lookup_failed$& remains set to &"0"&.
11494 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
11495 host name again if there is a subsequent reference to &$sender_host_name$&
11496 in the same Exim process, but it does try again if &$host_lookup_deferred$&
11499 Exim does not automatically look up every calling host's name. If you want
11500 maximum efficiency, you should arrange your configuration so that it avoids
11501 these lookups altogether. The lookup happens only if one or more of the
11502 following are true:
11505 A string containing &$sender_host_name$& is expanded.
11507 The calling host matches the list in &%host_lookup%&. In the default
11508 configuration, this option is set to *, so it must be changed if lookups are
11509 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
11511 Exim needs the host name in order to test an item in a host list. The items
11512 that require this are described in sections &<<SECThoslispatnam>>& and
11513 &<<SECThoslispatnamsk>>&.
11515 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
11516 In this case, the host name is required to compare with the name quoted in any
11517 EHLO or HELO commands that the client issues.
11519 The remote host issues a EHLO or HELO command that quotes one of the
11520 domains in &%helo_lookup_domains%&. The default value of this option is
11521 . ==== As this is a nested list, any displays it contains must be indented
11522 . ==== as otherwise they are too far to the left.
11524 helo_lookup_domains = @ : @[]
11526 which causes a lookup if a remote host (incorrectly) gives the server's name or
11527 IP address in an EHLO or HELO command.
11531 .vitem &$sender_host_port$&
11532 .vindex "&$sender_host_port$&"
11533 When a message is received from a remote host, this variable contains the port
11534 number that was used on the remote host.
11536 .vitem &$sender_ident$&
11537 .vindex "&$sender_ident$&"
11538 When a message is received from a remote host, this variable contains the
11539 identification received in response to an RFC 1413 request. When a message has
11540 been received locally, this variable contains the login name of the user that
11543 .vitem &$sender_rate_$&&'xxx'&
11544 A number of variables whose names begin &$sender_rate_$& are set as part of the
11545 &%ratelimit%& ACL condition. Details are given in section
11546 &<<SECTratelimiting>>&.
11548 .vitem &$sender_rcvhost$&
11549 .cindex "DNS" "reverse lookup"
11550 .cindex "reverse DNS lookup"
11551 .vindex "&$sender_rcvhost$&"
11552 This is provided specifically for use in &'Received:'& headers. It starts with
11553 either the verified host name (as obtained from a reverse DNS lookup) or, if
11554 there is no verified host name, the IP address in square brackets. After that
11555 there may be text in parentheses. When the first item is a verified host name,
11556 the first thing in the parentheses is the IP address in square brackets,
11557 followed by a colon and a port number if port logging is enabled. When the
11558 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
11561 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
11562 was used and its argument was not identical to the real host name or IP
11563 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
11564 all three items are present in the parentheses, a newline and tab are inserted
11565 into the string, to improve the formatting of the &'Received:'& header.
11567 .vitem &$sender_verify_failure$&
11568 .vindex "&$sender_verify_failure$&"
11569 In an ACL, when a sender verification fails, this variable contains information
11570 about the failure. The details are the same as for
11571 &$recipient_verify_failure$&.
11573 .vitem &$sending_ip_address$&
11574 .vindex "&$sending_ip_address$&"
11575 This variable is set whenever an outgoing SMTP connection to another host has
11576 been set up. It contains the IP address of the local interface that is being
11577 used. This is useful if a host that has more than one IP address wants to take
11578 on different personalities depending on which one is being used. For incoming
11579 connections, see &$received_ip_address$&.
11581 .vitem &$sending_port$&
11582 .vindex "&$sending_port$&"
11583 This variable is set whenever an outgoing SMTP connection to another host has
11584 been set up. It contains the local port that is being used. For incoming
11585 connections, see &$received_port$&.
11587 .vitem &$smtp_active_hostname$&
11588 .vindex "&$smtp_active_hostname$&"
11589 During an incoming SMTP session, this variable contains the value of the active
11590 host name, as specified by the &%smtp_active_hostname%& option. The value of
11591 &$smtp_active_hostname$& is saved with any message that is received, so its
11592 value can be consulted during routing and delivery.
11594 .vitem &$smtp_command$&
11595 .vindex "&$smtp_command$&"
11596 During the processing of an incoming SMTP command, this variable contains the
11597 entire command. This makes it possible to distinguish between HELO and EHLO in
11598 the HELO ACL, and also to distinguish between commands such as these:
11603 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
11604 command, the address in &$smtp_command$& is the original address before any
11605 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
11606 the address after SMTP-time rewriting.
11608 .vitem &$smtp_command_argument$&
11609 .cindex "SMTP" "command, argument for"
11610 .vindex "&$smtp_command_argument$&"
11611 While an ACL is running to check an SMTP command, this variable contains the
11612 argument, that is, the text that follows the command name, with leading white
11613 space removed. Following the introduction of &$smtp_command$&, this variable is
11614 somewhat redundant, but is retained for backwards compatibility.
11616 .vitem &$smtp_count_at_connection_start$&
11617 .vindex "&$smtp_count_at_connection_start$&"
11618 This variable is set greater than zero only in processes spawned by the Exim
11619 daemon for handling incoming SMTP connections. The name is deliberately long,
11620 in order to emphasize what the contents are. When the daemon accepts a new
11621 connection, it increments this variable. A copy of the variable is passed to
11622 the child process that handles the connection, but its value is fixed, and
11623 never changes. It is only an approximation of how many incoming connections
11624 there actually are, because many other connections may come and go while a
11625 single connection is being processed. When a child process terminates, the
11626 daemon decrements its copy of the variable.
11628 .vitem "&$sn0$& &-- &$sn9$&"
11629 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
11630 that were current at the end of the system filter file. This allows a system
11631 filter file to set values that can be tested in users' filter files. For
11632 example, a system filter could set a value indicating how likely it is that a
11633 message is junk mail.
11635 .vitem &$spam_$&&'xxx'&
11636 A number of variables whose names start with &$spam$& are available when Exim
11637 is compiled with the content-scanning extension. For details, see section
11638 &<<SECTscanspamass>>&.
11641 .vitem &$spool_directory$&
11642 .vindex "&$spool_directory$&"
11643 The name of Exim's spool directory.
11645 .vitem &$spool_inodes$&
11646 .vindex "&$spool_inodes$&"
11647 The number of free inodes in the disk partition where Exim's spool files are
11648 being written. The value is recalculated whenever the variable is referenced.
11649 If the relevant file system does not have the concept of inodes, the value of
11650 is -1. See also the &%check_spool_inodes%& option.
11652 .vitem &$spool_space$&
11653 .vindex "&$spool_space$&"
11654 The amount of free space (as a number of kilobytes) in the disk partition where
11655 Exim's spool files are being written. The value is recalculated whenever the
11656 variable is referenced. If the operating system does not have the ability to
11657 find the amount of free space (only true for experimental systems), the space
11658 value is -1. For example, to check in an ACL that there is at least 50
11659 megabytes free on the spool, you could write:
11661 condition = ${if > {$spool_space}{50000}}
11663 See also the &%check_spool_space%& option.
11666 .vitem &$thisaddress$&
11667 .vindex "&$thisaddress$&"
11668 This variable is set only during the processing of the &%foranyaddress%&
11669 command in a filter file. Its use is explained in the description of that
11670 command, which can be found in the separate document entitled &'Exim's
11671 interfaces to mail filtering'&.
11673 .vitem &$tls_certificate_verified$&
11674 .vindex "&$tls_certificate_verified$&"
11675 This variable is set to &"1"& if a TLS certificate was verified when the
11676 message was received, and &"0"& otherwise.
11678 .vitem &$tls_cipher$&
11679 .vindex "&$tls_cipher$&"
11680 When a message is received from a remote host over an encrypted SMTP
11681 connection, this variable is set to the cipher suite that was negotiated, for
11682 example DES-CBC3-SHA. In other circumstances, in particular, for message
11683 received over unencrypted connections, the variable is empty. Testing
11684 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
11685 non-encrypted connections during ACL processing.
11687 The &$tls_cipher$& variable retains its value during message delivery, except
11688 when an outward SMTP delivery takes place via the &(smtp)& transport. In this
11689 case, &$tls_cipher$& is cleared before any outgoing SMTP connection is made,
11690 and then set to the outgoing cipher suite if one is negotiated. See chapter
11691 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
11692 details of the &(smtp)& transport.
11694 .vitem &$tls_peerdn$&
11695 .vindex "&$tls_peerdn$&"
11696 When a message is received from a remote host over an encrypted SMTP
11697 connection, and Exim is configured to request a certificate from the client,
11698 the value of the Distinguished Name of the certificate is made available in the
11699 &$tls_peerdn$& during subsequent processing. Like &$tls_cipher$&, the
11700 value is retained during message delivery, except during outbound SMTP
11703 .vitem &$tod_bsdinbox$&
11704 .vindex "&$tod_bsdinbox$&"
11705 The time of day and the date, in the format required for BSD-style mailbox
11706 files, for example: Thu Oct 17 17:14:09 1995.
11708 .vitem &$tod_epoch$&
11709 .vindex "&$tod_epoch$&"
11710 The time and date as a number of seconds since the start of the Unix epoch.
11712 .vitem &$tod_full$&
11713 .vindex "&$tod_full$&"
11714 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
11715 +0100. The timezone is always given as a numerical offset from UTC, with
11716 positive values used for timezones that are ahead (east) of UTC, and negative
11717 values for those that are behind (west).
11720 .vindex "&$tod_log$&"
11721 The time and date in the format used for writing Exim's log files, for example:
11722 1995-10-12 15:32:29, but without a timezone.
11724 .vitem &$tod_logfile$&
11725 .vindex "&$tod_logfile$&"
11726 This variable contains the date in the format yyyymmdd. This is the format that
11727 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
11730 .vitem &$tod_zone$&
11731 .vindex "&$tod_zone$&"
11732 This variable contains the numerical value of the local timezone, for example:
11735 .vitem &$tod_zulu$&
11736 .vindex "&$tod_zulu$&"
11737 This variable contains the UTC date and time in &"Zulu"& format, as specified
11738 by ISO 8601, for example: 20030221154023Z.
11741 .vindex "&$value$&"
11742 This variable contains the result of an expansion lookup, extraction operation,
11743 or external command, as described above. It is also used during a
11744 &*reduce*& expansion.
11746 .vitem &$version_number$&
11747 .vindex "&$version_number$&"
11748 The version number of Exim.
11750 .vitem &$warn_message_delay$&
11751 .vindex "&$warn_message_delay$&"
11752 This variable is set only during the creation of a message warning about a
11753 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11755 .vitem &$warn_message_recipients$&
11756 .vindex "&$warn_message_recipients$&"
11757 This variable is set only during the creation of a message warning about a
11758 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11764 . ////////////////////////////////////////////////////////////////////////////
11765 . ////////////////////////////////////////////////////////////////////////////
11767 .chapter "Embedded Perl" "CHAPperl"
11768 .scindex IIDperl "Perl" "calling from Exim"
11769 Exim can be built to include an embedded Perl interpreter. When this is done,
11770 Perl subroutines can be called as part of the string expansion process. To make
11771 use of the Perl support, you need version 5.004 or later of Perl installed on
11772 your system. To include the embedded interpreter in the Exim binary, include
11777 in your &_Local/Makefile_& and then build Exim in the normal way.
11780 .section "Setting up so Perl can be used" "SECID85"
11781 .oindex "&%perl_startup%&"
11782 Access to Perl subroutines is via a global configuration option called
11783 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
11784 no &%perl_startup%& option in the Exim configuration file then no Perl
11785 interpreter is started and there is almost no overhead for Exim (since none of
11786 the Perl library will be paged in unless used). If there is a &%perl_startup%&
11787 option then the associated value is taken to be Perl code which is executed in
11788 a newly created Perl interpreter.
11790 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
11791 need backslashes before any characters to escape special meanings. The option
11792 should usually be something like
11794 perl_startup = do '/etc/exim.pl'
11796 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
11797 use from Exim. Exim can be configured either to start up a Perl interpreter as
11798 soon as it is entered, or to wait until the first time it is needed. Starting
11799 the interpreter at the beginning ensures that it is done while Exim still has
11800 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
11801 fact used in a particular run. Also, note that this does not mean that Exim is
11802 necessarily running as root when Perl is called at a later time. By default,
11803 the interpreter is started only when it is needed, but this can be changed in
11807 .oindex "&%perl_at_start%&"
11808 Setting &%perl_at_start%& (a boolean option) in the configuration requests
11809 a startup when Exim is entered.
11811 The command line option &%-ps%& also requests a startup when Exim is entered,
11812 overriding the setting of &%perl_at_start%&.
11815 There is also a command line option &%-pd%& (for delay) which suppresses the
11816 initial startup, even if &%perl_at_start%& is set.
11819 .section "Calling Perl subroutines" "SECID86"
11820 When the configuration file includes a &%perl_startup%& option you can make use
11821 of the string expansion item to call the Perl subroutines that are defined
11822 by the &%perl_startup%& code. The operator is used in any of the following
11826 ${perl{foo}{argument}}
11827 ${perl{foo}{argument1}{argument2} ... }
11829 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
11830 arguments may be passed. Passing more than this results in an expansion failure
11831 with an error message of the form
11833 Too many arguments passed to Perl subroutine "foo" (max is 8)
11835 The return value of the Perl subroutine is evaluated in a scalar context before
11836 it is passed back to Exim to be inserted into the expanded string. If the
11837 return value is &'undef'&, the expansion is forced to fail in the same way as
11838 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
11839 by obeying Perl's &%die%& function, the expansion fails with the error message
11840 that was passed to &%die%&.
11843 .section "Calling Exim functions from Perl" "SECID87"
11844 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
11845 is available to call back into Exim's string expansion function. For example,
11848 my $lp = Exim::expand_string('$local_part');
11850 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
11851 Note those are single quotes and not double quotes to protect against
11852 &$local_part$& being interpolated as a Perl variable.
11854 If the string expansion is forced to fail by a &"fail"& item, the result of
11855 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
11856 expansion string, the Perl call from the original expansion string fails with
11857 an appropriate error message, in the same way as if &%die%& were used.
11859 .cindex "debugging" "from embedded Perl"
11860 .cindex "log" "writing from embedded Perl"
11861 Two other Exim functions are available for use from within Perl code.
11862 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
11863 debugging is enabled. If you want a newline at the end, you must supply it.
11864 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
11865 timestamp. In this case, you should not supply a terminating newline.
11868 .section "Use of standard output and error by Perl" "SECID88"
11869 .cindex "Perl" "standard output and error"
11870 You should not write to the standard error or output streams from within your
11871 Perl code, as it is not defined how these are set up. In versions of Exim
11872 before 4.50, it is possible for the standard output or error to refer to the
11873 SMTP connection during message reception via the daemon. Writing to this stream
11874 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
11875 error streams are connected to &_/dev/null_& in the daemon. The chaos is
11876 avoided, but the output is lost.
11878 .cindex "Perl" "use of &%warn%&"
11879 The Perl &%warn%& statement writes to the standard error stream by default.
11880 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
11881 you have no control. When Exim starts up the Perl interpreter, it arranges for
11882 output from the &%warn%& statement to be written to the Exim main log. You can
11883 change this by including appropriate Perl magic somewhere in your Perl code.
11884 For example, to discard &%warn%& output completely, you need this:
11886 $SIG{__WARN__} = sub { };
11888 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
11889 example, the code for the subroutine is empty, so it does nothing, but you can
11890 include any Perl code that you like. The text of the &%warn%& message is passed
11891 as the first subroutine argument.
11895 . ////////////////////////////////////////////////////////////////////////////
11896 . ////////////////////////////////////////////////////////////////////////////
11898 .chapter "Starting the daemon and the use of network interfaces" &&&
11899 "CHAPinterfaces" &&&
11900 "Starting the daemon"
11901 .cindex "daemon" "starting"
11902 .cindex "interface" "listening"
11903 .cindex "network interface"
11904 .cindex "interface" "network"
11905 .cindex "IP address" "for listening"
11906 .cindex "daemon" "listening IP addresses"
11907 .cindex "TCP/IP" "setting listening interfaces"
11908 .cindex "TCP/IP" "setting listening ports"
11909 A host that is connected to a TCP/IP network may have one or more physical
11910 hardware network interfaces. Each of these interfaces may be configured as one
11911 or more &"logical"& interfaces, which are the entities that a program actually
11912 works with. Each of these logical interfaces is associated with an IP address.
11913 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
11914 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
11915 knowledge about the host's interfaces for use in three different circumstances:
11918 When a listening daemon is started, Exim needs to know which interfaces
11919 and ports to listen on.
11921 When Exim is routing an address, it needs to know which IP addresses
11922 are associated with local interfaces. This is required for the correct
11923 processing of MX lists by removing the local host and others with the
11924 same or higher priority values. Also, Exim needs to detect cases
11925 when an address is routed to an IP address that in fact belongs to the
11926 local host. Unless the &%self%& router option or the &%allow_localhost%&
11927 option of the smtp transport is set (as appropriate), this is treated
11928 as an error situation.
11930 When Exim connects to a remote host, it may need to know which interface to use
11931 for the outgoing connection.
11935 Exim's default behaviour is likely to be appropriate in the vast majority
11936 of cases. If your host has only one interface, and you want all its IP
11937 addresses to be treated in the same way, and you are using only the
11938 standard SMTP port, you should not need to take any special action. The
11939 rest of this chapter does not apply to you.
11941 In a more complicated situation you may want to listen only on certain
11942 interfaces, or on different ports, and for this reason there are a number of
11943 options that can be used to influence Exim's behaviour. The rest of this
11944 chapter describes how they operate.
11946 When a message is received over TCP/IP, the interface and port that were
11947 actually used are set in &$received_ip_address$& and &$received_port$&.
11951 .section "Starting a listening daemon" "SECID89"
11952 When a listening daemon is started (by means of the &%-bd%& command line
11953 option), the interfaces and ports on which it listens are controlled by the
11957 &%daemon_smtp_ports%& contains a list of default ports. (For backward
11958 compatibility, this option can also be specified in the singular.)
11960 &%local_interfaces%& contains list of interface IP addresses on which to
11961 listen. Each item may optionally also specify a port.
11964 The default list separator in both cases is a colon, but this can be changed as
11965 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
11966 it is usually best to change the separator to avoid having to double all the
11967 colons. For example:
11969 local_interfaces = <; 127.0.0.1 ; \
11972 3ffe:ffff:836f::fe86:a061
11974 There are two different formats for specifying a port along with an IP address
11975 in &%local_interfaces%&:
11978 The port is added onto the address with a dot separator. For example, to listen
11979 on port 1234 on two different IP addresses:
11981 local_interfaces = <; 192.168.23.65.1234 ; \
11982 3ffe:ffff:836f::fe86:a061.1234
11985 The IP address is enclosed in square brackets, and the port is added
11986 with a colon separator, for example:
11988 local_interfaces = <; [192.168.23.65]:1234 ; \
11989 [3ffe:ffff:836f::fe86:a061]:1234
11993 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
11994 default setting contains just one port:
11996 daemon_smtp_ports = smtp
11998 If more than one port is listed, each interface that does not have its own port
11999 specified listens on all of them. Ports that are listed in
12000 &%daemon_smtp_ports%& can be identified either by name (defined in
12001 &_/etc/services_&) or by number. However, when ports are given with individual
12002 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
12006 .section "Special IP listening addresses" "SECID90"
12007 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
12008 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
12009 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
12010 instead of setting up separate listening sockets for each interface. The
12011 default value of &%local_interfaces%& is
12013 local_interfaces = 0.0.0.0
12015 when Exim is built without IPv6 support; otherwise it is:
12017 local_interfaces = <; ::0 ; 0.0.0.0
12019 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
12023 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
12024 The &%-oX%& command line option can be used to override the values of
12025 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
12026 instance. Another way of doing this would be to use macros and the &%-D%&
12027 option. However, &%-oX%& can be used by any admin user, whereas modification of
12028 the runtime configuration by &%-D%& is allowed only when the caller is root or
12031 The value of &%-oX%& is a list of items. The default colon separator can be
12032 changed in the usual way if required. If there are any items that do not
12033 contain dots or colons (that is, are not IP addresses), the value of
12034 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
12035 items that do contain dots or colons, the value of &%local_interfaces%& is
12036 replaced by those items. Thus, for example,
12040 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
12043 -oX 192.168.34.5.1125
12045 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
12046 (However, since &%local_interfaces%& now contains no items without ports, the
12047 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
12051 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
12052 .cindex "ssmtp protocol"
12053 .cindex "smtps protocol"
12054 .cindex "SMTP" "ssmtp protocol"
12055 .cindex "SMTP" "smtps protocol"
12056 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
12057 before the STARTTLS command was standardized for SMTP. Some legacy clients
12058 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
12059 list of port numbers, connections to those ports must use SSMTP. The most
12060 common use of this option is expected to be
12062 tls_on_connect_ports = 465
12064 because 465 is the usual port number used by the legacy clients. There is also
12065 a command line option &%-tls-on-connect%&, which forces all ports to behave in
12066 this way when a daemon is started.
12068 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
12069 daemon to listen on those ports. You must still specify them in
12070 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
12071 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
12072 connections via the daemon.)
12077 .section "IPv6 address scopes" "SECID92"
12078 .cindex "IPv6" "address scopes"
12079 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
12080 can, in principle, have the same link-local IPv6 address on different
12081 interfaces. Thus, additional information is needed, over and above the IP
12082 address, to distinguish individual interfaces. A convention of using a
12083 percent sign followed by something (often the interface name) has been
12084 adopted in some cases, leading to addresses like this:
12086 fe80::202:b3ff:fe03:45c1%eth0
12088 To accommodate this usage, a percent sign followed by an arbitrary string is
12089 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
12090 to convert a textual IPv6 address for actual use. This function recognizes the
12091 percent convention in operating systems that support it, and it processes the
12092 address appropriately. Unfortunately, some older libraries have problems with
12093 &[getaddrinfo()]&. If
12095 IPV6_USE_INET_PTON=yes
12097 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
12098 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
12099 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
12100 function.) Of course, this means that the additional functionality of
12101 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12103 .section "Disabling IPv6" "SECID93"
12104 .cindex "IPv6" "disabling"
12105 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12106 run on a host whose kernel does not support IPv6. The binary will fall back to
12107 using IPv4, but it may waste resources looking up AAAA records, and trying to
12108 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12109 .oindex "&%disable_ipv6%&"
12110 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12111 activities take place. AAAA records are never looked up, and any IPv6 addresses
12112 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12113 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12114 to handle IPv6 literal addresses.
12116 On the other hand, when IPv6 is in use, there may be times when you want to
12117 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12118 option to globally suppress the lookup of AAAA records for specified domains,
12119 and you can use the &%ignore_target_hosts%& generic router option to ignore
12120 IPv6 addresses in an individual router.
12124 .section "Examples of starting a listening daemon" "SECID94"
12125 The default case in an IPv6 environment is
12127 daemon_smtp_ports = smtp
12128 local_interfaces = <; ::0 ; 0.0.0.0
12130 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12131 Either one or two sockets may be used, depending on the characteristics of
12132 the TCP/IP stack. (This is complicated and messy; for more information,
12133 read the comments in the &_daemon.c_& source file.)
12135 To specify listening on ports 25 and 26 on all interfaces:
12137 daemon_smtp_ports = 25 : 26
12139 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
12141 local_interfaces = <; ::0.25 ; ::0.26 \
12142 0.0.0.0.25 ; 0.0.0.0.26
12144 To listen on the default port on all IPv4 interfaces, and on port 26 on the
12145 IPv4 loopback address only:
12147 local_interfaces = 0.0.0.0 : 127.0.0.1.26
12149 To specify listening on the default port on specific interfaces only:
12151 local_interfaces = 192.168.34.67 : 192.168.34.67
12153 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
12157 .section "Recognizing the local host" "SECTreclocipadd"
12158 The &%local_interfaces%& option is also used when Exim needs to determine
12159 whether or not an IP address refers to the local host. That is, the IP
12160 addresses of all the interfaces on which a daemon is listening are always
12163 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
12164 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
12165 available interfaces from the operating system, and extracts the relevant
12166 (that is, IPv4 or IPv6) addresses to use for checking.
12168 Some systems set up large numbers of virtual interfaces in order to provide
12169 many virtual web servers. In this situation, you may want to listen for
12170 email on only a few of the available interfaces, but nevertheless treat all
12171 interfaces as local when routing. You can do this by setting
12172 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
12173 &"all"& wildcard values. These addresses are recognized as local, but are not
12174 used for listening. Consider this example:
12176 local_interfaces = <; 127.0.0.1 ; ::1 ; \
12178 3ffe:2101:12:1:a00:20ff:fe86:a061
12180 extra_local_interfaces = <; ::0 ; 0.0.0.0
12182 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
12183 address, but all available interface addresses are treated as local when
12186 In some environments the local host name may be in an MX list, but with an IP
12187 address that is not assigned to any local interface. In other cases it may be
12188 desirable to treat other host names as if they referred to the local host. Both
12189 these cases can be handled by setting the &%hosts_treat_as_local%& option.
12190 This contains host names rather than IP addresses. When a host is referenced
12191 during routing, either via an MX record or directly, it is treated as the local
12192 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
12193 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
12197 .section "Delivering to a remote host" "SECID95"
12198 Delivery to a remote host is handled by the smtp transport. By default, it
12199 allows the system's TCP/IP functions to choose which interface to use (if
12200 there is more than one) when connecting to a remote host. However, the
12201 &%interface%& option can be set to specify which interface is used. See the
12202 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
12208 . ////////////////////////////////////////////////////////////////////////////
12209 . ////////////////////////////////////////////////////////////////////////////
12211 .chapter "Main configuration" "CHAPmainconfig"
12212 .scindex IIDconfima "configuration file" "main section"
12213 .scindex IIDmaiconf "main configuration"
12214 The first part of the run time configuration file contains three types of item:
12217 Macro definitions: These lines start with an upper case letter. See section
12218 &<<SECTmacrodefs>>& for details of macro processing.
12220 Named list definitions: These lines start with one of the words &"domainlist"&,
12221 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
12222 section &<<SECTnamedlists>>&.
12224 Main configuration settings: Each setting occupies one line of the file
12225 (with possible continuations). If any setting is preceded by the word
12226 &"hide"&, the &%-bP%& command line option displays its value to admin users
12227 only. See section &<<SECTcos>>& for a description of the syntax of these option
12231 This chapter specifies all the main configuration options, along with their
12232 types and default values. For ease of finding a particular option, they appear
12233 in alphabetical order in section &<<SECTalomo>>& below. However, because there
12234 are now so many options, they are first listed briefly in functional groups, as
12235 an aid to finding the name of the option you are looking for. Some options are
12236 listed in more than one group.
12238 .section "Miscellaneous" "SECID96"
12240 .row &%bi_command%& "to run for &%-bi%& command line option"
12241 .row &%disable_ipv6%& "do no IPv6 processing"
12242 .row &%keep_malformed%& "for broken files &-- should not happen"
12243 .row &%localhost_number%& "for unique message ids in clusters"
12244 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
12245 .row &%message_body_visible%& "how much to show in &$message_body$&"
12246 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
12247 .row &%print_topbitchars%& "top-bit characters are printing"
12248 .row &%timezone%& "force time zone"
12252 .section "Exim parameters" "SECID97"
12254 .row &%exim_group%& "override compiled-in value"
12255 .row &%exim_path%& "override compiled-in value"
12256 .row &%exim_user%& "override compiled-in value"
12257 .row &%primary_hostname%& "default from &[uname()]&"
12258 .row &%split_spool_directory%& "use multiple directories"
12259 .row &%spool_directory%& "override compiled-in value"
12264 .section "Privilege controls" "SECID98"
12266 .row &%admin_groups%& "groups that are Exim admin users"
12267 .row &%deliver_drop_privilege%& "drop root for delivery processes"
12268 .row &%local_from_check%& "insert &'Sender:'& if necessary"
12269 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
12270 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
12271 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
12272 .row &%never_users%& "do not run deliveries as these"
12273 .row &%prod_requires_admin%& "forced delivery requires admin user"
12274 .row &%queue_list_requires_admin%& "queue listing requires admin user"
12275 .row &%trusted_groups%& "groups that are trusted"
12276 .row &%trusted_users%& "users that are trusted"
12281 .section "Logging" "SECID99"
12283 .row &%hosts_connection_nolog%& "exemption from connect logging"
12284 .row &%log_file_path%& "override compiled-in value"
12285 .row &%log_selector%& "set/unset optional logging"
12286 .row &%log_timezone%& "add timezone to log lines"
12287 .row &%message_logs%& "create per-message logs"
12288 .row &%preserve_message_logs%& "after message completion"
12289 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
12290 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
12291 .row &%syslog_facility%& "set syslog &""facility""& field"
12292 .row &%syslog_processname%& "set syslog &""ident""& field"
12293 .row &%syslog_timestamp%& "timestamp syslog lines"
12294 .row &%write_rejectlog%& "control use of message log"
12299 .section "Frozen messages" "SECID100"
12301 .row &%auto_thaw%& "sets time for retrying frozen messages"
12302 .row &%freeze_tell%& "send message when freezing"
12303 .row &%move_frozen_messages%& "to another directory"
12304 .row &%timeout_frozen_after%& "keep frozen messages only so long"
12309 .section "Data lookups" "SECID101"
12311 .row &%ibase_servers%& "InterBase servers"
12312 .row &%ldap_default_servers%& "used if no server in query"
12313 .row &%ldap_version%& "set protocol version"
12314 .row &%lookup_open_max%& "lookup files held open"
12315 .row &%mysql_servers%& "default MySQL servers"
12316 .row &%oracle_servers%& "Oracle servers"
12317 .row &%pgsql_servers%& "default PostgreSQL servers"
12318 .row &%sqlite_lock_timeout%& "as it says"
12323 .section "Message ids" "SECID102"
12325 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
12326 .row &%message_id_header_text%& "ditto"
12331 .section "Embedded Perl Startup" "SECID103"
12333 .row &%perl_at_start%& "always start the interpreter"
12334 .row &%perl_startup%& "code to obey when starting Perl"
12339 .section "Daemon" "SECID104"
12341 .row &%daemon_smtp_ports%& "default ports"
12342 .row &%daemon_startup_retries%& "number of times to retry"
12343 .row &%daemon_startup_sleep%& "time to sleep between tries"
12344 .row &%extra_local_interfaces%& "not necessarily listened on"
12345 .row &%local_interfaces%& "on which to listen, with optional ports"
12346 .row &%pid_file_path%& "override compiled-in value"
12347 .row &%queue_run_max%& "maximum simultaneous queue runners"
12352 .section "Resource control" "SECID105"
12354 .row &%check_log_inodes%& "before accepting a message"
12355 .row &%check_log_space%& "before accepting a message"
12356 .row &%check_spool_inodes%& "before accepting a message"
12357 .row &%check_spool_space%& "before accepting a message"
12358 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
12359 .row &%queue_only_load%& "queue incoming if load high"
12360 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12361 .row &%queue_run_max%& "maximum simultaneous queue runners"
12362 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12363 .row &%smtp_accept_max%& "simultaneous incoming connections"
12364 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12365 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12366 .row &%smtp_accept_max_per_connection%& "messages per connection"
12367 .row &%smtp_accept_max_per_host%& "connections from one host"
12368 .row &%smtp_accept_queue%& "queue mail if more connections"
12369 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12371 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12372 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12373 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12374 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
12375 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12380 .section "Policy controls" "SECID106"
12382 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
12383 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
12384 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
12385 .row &%acl_smtp_auth%& "ACL for AUTH"
12386 .row &%acl_smtp_connect%& "ACL for connection"
12387 .row &%acl_smtp_data%& "ACL for DATA"
12388 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
12389 .row &%acl_smtp_etrn%& "ACL for ETRN"
12390 .row &%acl_smtp_expn%& "ACL for EXPN"
12391 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
12392 .row &%acl_smtp_mail%& "ACL for MAIL"
12393 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
12394 .row &%acl_smtp_mime%& "ACL for MIME parts"
12395 .row &%acl_smtp_predata%& "ACL for start of data"
12396 .row &%acl_smtp_quit%& "ACL for QUIT"
12397 .row &%acl_smtp_rcpt%& "ACL for RCPT"
12398 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
12399 .row &%acl_smtp_vrfy%& "ACL for VRFY"
12400 .row &%av_scanner%& "specify virus scanner"
12401 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12403 .row &%dns_csa_search_limit%& "control CSA parent search depth"
12404 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
12405 .row &%header_maxsize%& "total size of message header"
12406 .row &%header_line_maxsize%& "individual header line limit"
12407 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
12408 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
12409 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
12410 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
12411 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
12412 .row &%host_lookup%& "host name looked up for these hosts"
12413 .row &%host_lookup_order%& "order of DNS and local name lookups"
12414 .row &%host_reject_connection%& "reject connection from these hosts"
12415 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
12416 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
12417 .row &%message_size_limit%& "for all messages"
12418 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12419 .row &%spamd_address%& "set interface to SpamAssassin"
12420 .row &%strict_acl_vars%& "object to unset ACL variables"
12425 .section "Callout cache" "SECID107"
12427 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
12429 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
12431 .row &%callout_negative_expire%& "timeout for negative address cache item"
12432 .row &%callout_positive_expire%& "timeout for positive address cache item"
12433 .row &%callout_random_local_part%& "string to use for &""random""& testing"
12438 .section "TLS" "SECID108"
12440 .row &%gnutls_require_kx%& "control GnuTLS key exchanges"
12441 .row &%gnutls_require_mac%& "control GnuTLS MAC algorithms"
12442 .row &%gnutls_require_protocols%& "control GnuTLS protocols"
12443 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
12444 .row &%openssl_options%& "adjust OpenSSL compatibility options"
12445 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12446 .row &%tls_certificate%& "location of server certificate"
12447 .row &%tls_crl%& "certificate revocation list"
12448 .row &%tls_dhparam%& "DH parameters for server"
12449 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
12450 .row &%tls_privatekey%& "location of server private key"
12451 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
12452 .row &%tls_require_ciphers%& "specify acceptable ciphers"
12453 .row &%tls_try_verify_hosts%& "try to verify client certificate"
12454 .row &%tls_verify_certificates%& "expected client certificates"
12455 .row &%tls_verify_hosts%& "insist on client certificate verify"
12460 .section "Local user handling" "SECID109"
12462 .row &%finduser_retries%& "useful in NIS environments"
12463 .row &%gecos_name%& "used when creating &'Sender:'&"
12464 .row &%gecos_pattern%& "ditto"
12465 .row &%max_username_length%& "for systems that truncate"
12466 .row &%unknown_login%& "used when no login name found"
12467 .row &%unknown_username%& "ditto"
12468 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
12469 .row &%uucp_from_sender%& "ditto"
12474 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
12476 .row &%header_maxsize%& "total size of message header"
12477 .row &%header_line_maxsize%& "individual header line limit"
12478 .row &%message_size_limit%& "applies to all messages"
12479 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12480 .row &%received_header_text%& "expanded to make &'Received:'&"
12481 .row &%received_headers_max%& "for mail loop detection"
12482 .row &%recipients_max%& "limit per message"
12483 .row &%recipients_max_reject%& "permanently reject excess recipients"
12489 .section "Non-SMTP incoming messages" "SECID111"
12491 .row &%receive_timeout%& "for non-SMTP messages"
12498 .section "Incoming SMTP messages" "SECID112"
12499 See also the &'Policy controls'& section above.
12502 .row &%host_lookup%& "host name looked up for these hosts"
12503 .row &%host_lookup_order%& "order of DNS and local name lookups"
12504 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
12505 .row &%rfc1413_hosts%& "make ident calls to these hosts"
12506 .row &%rfc1413_query_timeout%& "zero disables ident calls"
12507 .row &%sender_unqualified_hosts%& "may send unqualified senders"
12508 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
12509 .row &%smtp_accept_max%& "simultaneous incoming connections"
12510 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12511 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12512 .row &%smtp_accept_max_per_connection%& "messages per connection"
12513 .row &%smtp_accept_max_per_host%& "connections from one host"
12514 .row &%smtp_accept_queue%& "queue mail if more connections"
12515 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12517 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12518 .row &%smtp_active_hostname%& "host name to use in messages"
12519 .row &%smtp_banner%& "text for welcome banner"
12520 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12521 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12522 .row &%smtp_enforce_sync%& "of SMTP command/responses"
12523 .row &%smtp_etrn_command%& "what to run for ETRN"
12524 .row &%smtp_etrn_serialize%& "only one at once"
12525 .row &%smtp_load_reserve%& "only reserve hosts if this load"
12526 .row &%smtp_max_unknown_commands%& "before dropping connection"
12527 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
12528 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
12529 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
12530 .row &%smtp_receive_timeout%& "per command or data line"
12531 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12532 .row &%smtp_return_error_details%& "give detail on rejections"
12537 .section "SMTP extensions" "SECID113"
12539 .row &%accept_8bitmime%& "advertise 8BITMIME"
12540 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
12541 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
12542 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
12543 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
12544 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12549 .section "Processing messages" "SECID114"
12551 .row &%allow_domain_literals%& "recognize domain literal syntax"
12552 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
12553 .row &%allow_utf8_domains%& "in addresses"
12554 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12556 .row &%delivery_date_remove%& "from incoming messages"
12557 .row &%envelope_to_remove%& "from incoming messages"
12558 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
12559 .row &%headers_charset%& "default for translations"
12560 .row &%qualify_domain%& "default for senders"
12561 .row &%qualify_recipient%& "default for recipients"
12562 .row &%return_path_remove%& "from incoming messages"
12563 .row &%strip_excess_angle_brackets%& "in addresses"
12564 .row &%strip_trailing_dot%& "at end of addresses"
12565 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
12570 .section "System filter" "SECID115"
12572 .row &%system_filter%& "locate system filter"
12573 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
12575 .row &%system_filter_file_transport%& "transport for delivery to a file"
12576 .row &%system_filter_group%& "group for filter running"
12577 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
12578 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
12579 .row &%system_filter_user%& "user for filter running"
12584 .section "Routing and delivery" "SECID116"
12586 .row &%disable_ipv6%& "do no IPv6 processing"
12587 .row &%dns_again_means_nonexist%& "for broken domains"
12588 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
12589 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
12590 .row &%dns_retrans%& "parameter for resolver"
12591 .row &%dns_retry%& "parameter for resolver"
12592 .row &%hold_domains%& "hold delivery for these domains"
12593 .row &%local_interfaces%& "for routing checks"
12594 .row &%queue_domains%& "no immediate delivery for these"
12595 .row &%queue_only%& "no immediate delivery at all"
12596 .row &%queue_only_file%& "no immediate delivery if file exists"
12597 .row &%queue_only_load%& "no immediate delivery if load is high"
12598 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12599 .row &%queue_only_override%& "allow command line to override"
12600 .row &%queue_run_in_order%& "order of arrival"
12601 .row &%queue_run_max%& "of simultaneous queue runners"
12602 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
12603 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12604 .row &%remote_sort_domains%& "order of remote deliveries"
12605 .row &%retry_data_expire%& "timeout for retry data"
12606 .row &%retry_interval_max%& "safety net for retry rules"
12611 .section "Bounce and warning messages" "SECID117"
12613 .row &%bounce_message_file%& "content of bounce"
12614 .row &%bounce_message_text%& "content of bounce"
12615 .row &%bounce_return_body%& "include body if returning message"
12616 .row &%bounce_return_message%& "include original message in bounce"
12617 .row &%bounce_return_size_limit%& "limit on returned message"
12618 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
12619 .row &%dsn_from%& "set &'From:'& contents in bounces"
12620 .row &%errors_copy%& "copy bounce messages"
12621 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
12622 .row &%delay_warning%& "time schedule"
12623 .row &%delay_warning_condition%& "condition for warning messages"
12624 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
12625 .row &%smtp_return_error_details%& "give detail on rejections"
12626 .row &%warn_message_file%& "content of warning message"
12631 .section "Alphabetical list of main options" "SECTalomo"
12632 Those options that undergo string expansion before use are marked with
12635 .option accept_8bitmime main boolean false
12637 .cindex "8-bit characters"
12638 This option causes Exim to send 8BITMIME in its response to an SMTP
12639 EHLO command, and to accept the BODY= parameter on MAIL commands.
12640 However, though Exim is 8-bit clean, it is not a protocol converter, and it
12641 takes no steps to do anything special with messages received by this route.
12642 Consequently, this option is turned off by default.
12644 .option acl_not_smtp main string&!! unset
12645 .cindex "&ACL;" "for non-SMTP messages"
12646 .cindex "non-SMTP messages" "ACLs for"
12647 This option defines the ACL that is run when a non-SMTP message has been
12648 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
12651 .option acl_not_smtp_mime main string&!! unset
12652 This option defines the ACL that is run for individual MIME parts of non-SMTP
12653 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
12656 .option acl_not_smtp_start main string&!! unset
12657 .cindex "&ACL;" "at start of non-SMTP message"
12658 .cindex "non-SMTP messages" "ACLs for"
12659 This option defines the ACL that is run before Exim starts reading a
12660 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
12662 .option acl_smtp_auth main string&!! unset
12663 .cindex "&ACL;" "setting up for SMTP commands"
12664 .cindex "AUTH" "ACL for"
12665 This option defines the ACL that is run when an SMTP AUTH command is
12666 received. See chapter &<<CHAPACL>>& for further details.
12668 .option acl_smtp_connect main string&!! unset
12669 .cindex "&ACL;" "on SMTP connection"
12670 This option defines the ACL that is run when an SMTP connection is received.
12671 See chapter &<<CHAPACL>>& for further details.
12673 .option acl_smtp_data main string&!! unset
12674 .cindex "DATA" "ACL for"
12675 This option defines the ACL that is run after an SMTP DATA command has been
12676 processed and the message itself has been received, but before the final
12677 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
12679 .option acl_smtp_etrn main string&!! unset
12680 .cindex "ETRN" "ACL for"
12681 This option defines the ACL that is run when an SMTP ETRN command is
12682 received. See chapter &<<CHAPACL>>& for further details.
12684 .option acl_smtp_expn main string&!! unset
12685 .cindex "EXPN" "ACL for"
12686 This option defines the ACL that is run when an SMTP EXPN command is
12687 received. See chapter &<<CHAPACL>>& for further details.
12689 .option acl_smtp_helo main string&!! unset
12690 .cindex "EHLO" "ACL for"
12691 .cindex "HELO" "ACL for"
12692 This option defines the ACL that is run when an SMTP EHLO or HELO
12693 command is received. See chapter &<<CHAPACL>>& for further details.
12696 .option acl_smtp_mail main string&!! unset
12697 .cindex "MAIL" "ACL for"
12698 This option defines the ACL that is run when an SMTP MAIL command is
12699 received. See chapter &<<CHAPACL>>& for further details.
12701 .option acl_smtp_mailauth main string&!! unset
12702 .cindex "AUTH" "on MAIL command"
12703 This option defines the ACL that is run when there is an AUTH parameter on
12704 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
12705 &<<CHAPSMTPAUTH>>& for details of authentication.
12707 .option acl_smtp_mime main string&!! unset
12708 .cindex "MIME content scanning" "ACL for"
12709 This option is available when Exim is built with the content-scanning
12710 extension. It defines the ACL that is run for each MIME part in a message. See
12711 section &<<SECTscanmimepart>>& for details.
12713 .option acl_smtp_predata main string&!! unset
12714 This option defines the ACL that is run when an SMTP DATA command is
12715 received, before the message itself is received. See chapter &<<CHAPACL>>& for
12718 .option acl_smtp_quit main string&!! unset
12719 .cindex "QUIT, ACL for"
12720 This option defines the ACL that is run when an SMTP QUIT command is
12721 received. See chapter &<<CHAPACL>>& for further details.
12723 .option acl_smtp_rcpt main string&!! unset
12724 .cindex "RCPT" "ACL for"
12725 This option defines the ACL that is run when an SMTP RCPT command is
12726 received. See chapter &<<CHAPACL>>& for further details.
12728 .option acl_smtp_starttls main string&!! unset
12729 .cindex "STARTTLS, ACL for"
12730 This option defines the ACL that is run when an SMTP STARTTLS command is
12731 received. See chapter &<<CHAPACL>>& for further details.
12733 .option acl_smtp_vrfy main string&!! unset
12734 .cindex "VRFY" "ACL for"
12735 This option defines the ACL that is run when an SMTP VRFY command is
12736 received. See chapter &<<CHAPACL>>& for further details.
12738 .option admin_groups main "string list&!!" unset
12739 .cindex "admin user"
12740 This option is expanded just once, at the start of Exim's processing. If the
12741 current group or any of the supplementary groups of an Exim caller is in this
12742 colon-separated list, the caller has admin privileges. If all your system
12743 programmers are in a specific group, for example, you can give them all Exim
12744 admin privileges by putting that group in &%admin_groups%&. However, this does
12745 not permit them to read Exim's spool files (whose group owner is the Exim gid).
12746 To permit this, you have to add individuals to the Exim group.
12748 .option allow_domain_literals main boolean false
12749 .cindex "domain literal"
12750 If this option is set, the RFC 2822 domain literal format is permitted in
12751 email addresses. The option is not set by default, because the domain literal
12752 format is not normally required these days, and few people know about it. It
12753 has, however, been exploited by mail abusers.
12755 Unfortunately, it seems that some DNS black list maintainers are using this
12756 format to report black listing to postmasters. If you want to accept messages
12757 addressed to your hosts by IP address, you need to set
12758 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
12759 domains (defined in the named domain list &%local_domains%& in the default
12760 configuration). This &"magic string"& matches the domain literal form of all
12761 the local host's IP addresses.
12764 .option allow_mx_to_ip main boolean false
12765 .cindex "MX record" "pointing to IP address"
12766 It appears that more and more DNS zone administrators are breaking the rules
12767 and putting domain names that look like IP addresses on the right hand side of
12768 MX records. Exim follows the rules and rejects this, giving an error message
12769 that explains the mis-configuration. However, some other MTAs support this
12770 practice, so to avoid &"Why can't Exim do this?"& complaints,
12771 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
12772 recommended, except when you have no other choice.
12774 .option allow_utf8_domains main boolean false
12775 .cindex "domain" "UTF-8 characters in"
12776 .cindex "UTF-8" "in domain name"
12777 Lots of discussion is going on about internationalized domain names. One
12778 camp is strongly in favour of just using UTF-8 characters, and it seems
12779 that at least two other MTAs permit this. This option allows Exim users to
12780 experiment if they wish.
12782 If it is set true, Exim's domain parsing function allows valid
12783 UTF-8 multicharacters to appear in domain name components, in addition to
12784 letters, digits, and hyphens. However, just setting this option is not
12785 enough; if you want to look up these domain names in the DNS, you must also
12786 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
12787 suitable setting is:
12789 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
12790 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
12792 Alternatively, you can just disable this feature by setting
12794 dns_check_names_pattern =
12796 That is, set the option to an empty string so that no check is done.
12799 .option auth_advertise_hosts main "host list&!!" *
12800 .cindex "authentication" "advertising"
12801 .cindex "AUTH" "advertising"
12802 If any server authentication mechanisms are configured, Exim advertises them in
12803 response to an EHLO command only if the calling host matches this list.
12804 Otherwise, Exim does not advertise AUTH.
12805 Exim does not accept AUTH commands from clients to which it has not
12806 advertised the availability of AUTH. The advertising of individual
12807 authentication mechanisms can be controlled by the use of the
12808 &%server_advertise_condition%& generic authenticator option on the individual
12809 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
12811 Certain mail clients (for example, Netscape) require the user to provide a name
12812 and password for authentication if AUTH is advertised, even though it may
12813 not be needed (the host may accept messages from hosts on its local LAN without
12814 authentication, for example). The &%auth_advertise_hosts%& option can be used
12815 to make these clients more friendly by excluding them from the set of hosts to
12816 which Exim advertises AUTH.
12818 .cindex "AUTH" "advertising when encrypted"
12819 If you want to advertise the availability of AUTH only when the connection
12820 is encrypted using TLS, you can make use of the fact that the value of this
12821 option is expanded, with a setting like this:
12823 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
12825 .vindex "&$tls_cipher$&"
12826 If &$tls_cipher$& is empty, the session is not encrypted, and the result of
12827 the expansion is empty, thus matching no hosts. Otherwise, the result of the
12828 expansion is *, which matches all hosts.
12831 .option auto_thaw main time 0s
12832 .cindex "thawing messages"
12833 .cindex "unfreezing messages"
12834 If this option is set to a time greater than zero, a queue runner will try a
12835 new delivery attempt on any frozen message, other than a bounce message, if
12836 this much time has passed since it was frozen. This may result in the message
12837 being re-frozen if nothing has changed since the last attempt. It is a way of
12838 saying &"keep on trying, even though there are big problems"&.
12840 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
12841 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
12842 thought to be very useful any more, and its use should probably be avoided.
12844 .option av_scanner main string "see below"
12845 This option is available if Exim is built with the content-scanning extension.
12846 It specifies which anti-virus scanner to use. The default value is:
12848 sophie:/var/run/sophie
12850 If the value of &%av_scanner%& starts with a dollar character, it is expanded
12851 before use. See section &<<SECTscanvirus>>& for further details.
12855 .option bi_command main string unset
12857 This option supplies the name of a command that is run when Exim is called with
12858 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
12859 just the command name, it is not a complete command line. If an argument is
12860 required, it must come from the &%-oA%& command line option.
12863 .option bounce_message_file main string unset
12864 .cindex "bounce message" "customizing"
12865 .cindex "customizing" "bounce message"
12866 This option defines a template file containing paragraphs of text to be used
12867 for constructing bounce messages. Details of the file's contents are given in
12868 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
12871 .option bounce_message_text main string unset
12872 When this option is set, its contents are included in the default bounce
12873 message immediately after &"This message was created automatically by mail
12874 delivery software."& It is not used if &%bounce_message_file%& is set.
12876 .option bounce_return_body main boolean true
12877 .cindex "bounce message" "including body"
12878 This option controls whether the body of an incoming message is included in a
12879 bounce message when &%bounce_return_message%& is true. The default setting
12880 causes the entire message, both header and body, to be returned (subject to the
12881 value of &%bounce_return_size_limit%&). If this option is false, only the
12882 message header is included. In the case of a non-SMTP message containing an
12883 error that is detected during reception, only those header lines preceding the
12884 point at which the error was detected are returned.
12885 .cindex "bounce message" "including original"
12887 .option bounce_return_message main boolean true
12888 If this option is set false, none of the original message is included in
12889 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
12890 &%bounce_return_body%&.
12893 .option bounce_return_size_limit main integer 100K
12894 .cindex "size" "of bounce, limit"
12895 .cindex "bounce message" "size limit"
12896 .cindex "limit" "bounce message size"
12897 This option sets a limit in bytes on the size of messages that are returned to
12898 senders as part of bounce messages when &%bounce_return_message%& is true. The
12899 limit should be less than the value of the global &%message_size_limit%& and of
12900 any &%message_size_limit%& settings on transports, to allow for the bounce text
12901 that Exim generates. If this option is set to zero there is no limit.
12903 When the body of any message that is to be included in a bounce message is
12904 greater than the limit, it is truncated, and a comment pointing this out is
12905 added at the top. The actual cutoff may be greater than the value given, owing
12906 to the use of buffering for transferring the message in chunks (typically 8K in
12907 size). The idea is to save bandwidth on those undeliverable 15-megabyte
12910 .option bounce_sender_authentication main string unset
12911 .cindex "bounce message" "sender authentication"
12912 .cindex "authentication" "bounce message"
12913 .cindex "AUTH" "on bounce message"
12914 This option provides an authenticated sender address that is sent with any
12915 bounce messages generated by Exim that are sent over an authenticated SMTP
12916 connection. A typical setting might be:
12918 bounce_sender_authentication = mailer-daemon@my.domain.example
12920 which would cause bounce messages to be sent using the SMTP command:
12922 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
12924 The value of &%bounce_sender_authentication%& must always be a complete email
12927 .option callout_domain_negative_expire main time 3h
12928 .cindex "caching" "callout timeouts"
12929 .cindex "callout" "caching timeouts"
12930 This option specifies the expiry time for negative callout cache data for a
12931 domain. See section &<<SECTcallver>>& for details of callout verification, and
12932 section &<<SECTcallvercache>>& for details of the caching.
12935 .option callout_domain_positive_expire main time 7d
12936 This option specifies the expiry time for positive callout cache data for a
12937 domain. See section &<<SECTcallver>>& for details of callout verification, and
12938 section &<<SECTcallvercache>>& for details of the caching.
12941 .option callout_negative_expire main time 2h
12942 This option specifies the expiry time for negative callout cache data for an
12943 address. See section &<<SECTcallver>>& for details of callout verification, and
12944 section &<<SECTcallvercache>>& for details of the caching.
12947 .option callout_positive_expire main time 24h
12948 This option specifies the expiry time for positive callout cache data for an
12949 address. See section &<<SECTcallver>>& for details of callout verification, and
12950 section &<<SECTcallvercache>>& for details of the caching.
12953 .option callout_random_local_part main string&!! "see below"
12954 This option defines the &"random"& local part that can be used as part of
12955 callout verification. The default value is
12957 $primary_host_name-$tod_epoch-testing
12959 See section &<<CALLaddparcall>>& for details of how this value is used.
12962 .option check_log_inodes main integer 0
12963 See &%check_spool_space%& below.
12966 .option check_log_space main integer 0
12967 See &%check_spool_space%& below.
12969 .oindex "&%check_rfc2047_length%&"
12970 .cindex "RFC 2047" "disabling length check"
12971 .option check_rfc2047_length main boolean true
12972 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
12973 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
12974 word; strings to be encoded that exceed this length are supposed to use
12975 multiple encoded words. By default, Exim does not recognize encoded words that
12976 exceed the maximum length. However, it seems that some software, in violation
12977 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
12978 set false, Exim recognizes encoded words of any length.
12981 .option check_spool_inodes main integer 0
12982 See &%check_spool_space%& below.
12985 .option check_spool_space main integer 0
12986 .cindex "checking disk space"
12987 .cindex "disk space, checking"
12988 .cindex "spool directory" "checking space"
12989 The four &%check_...%& options allow for checking of disk resources before a
12990 message is accepted.
12992 .vindex "&$log_inodes$&"
12993 .vindex "&$log_space$&"
12994 .vindex "&$spool_inodes$&"
12995 .vindex "&$spool_space$&"
12996 When any of these options are set, they apply to all incoming messages. If you
12997 want to apply different checks to different kinds of message, you can do so by
12998 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
12999 &$spool_space$& in an ACL with appropriate additional conditions.
13002 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
13003 either value is greater than zero, for example:
13005 check_spool_space = 10M
13006 check_spool_inodes = 100
13008 The spool partition is the one that contains the directory defined by
13009 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
13012 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
13013 files are written if either is greater than zero. These should be set only if
13014 &%log_file_path%& and &%spool_directory%& refer to different partitions.
13016 If there is less space or fewer inodes than requested, Exim refuses to accept
13017 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
13018 error response to the MAIL command. If ESMTP is in use and there was a
13019 SIZE parameter on the MAIL command, its value is added to the
13020 &%check_spool_space%& value, and the check is performed even if
13021 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
13023 The values for &%check_spool_space%& and &%check_log_space%& are held as a
13024 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
13026 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
13027 failure a message is written to stderr and Exim exits with a non-zero code, as
13028 it obviously cannot send an error message of any kind.
13030 .option daemon_smtp_ports main string &`smtp`&
13031 .cindex "port" "for daemon"
13032 .cindex "TCP/IP" "setting listening ports"
13033 This option specifies one or more default SMTP ports on which the Exim daemon
13034 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
13035 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
13037 .option daemon_startup_retries main integer 9
13038 .cindex "daemon startup, retrying"
13039 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
13040 the daemon at startup when it cannot immediately bind a listening socket
13041 (typically because the socket is already in use): &%daemon_startup_retries%&
13042 defines the number of retries after the first failure, and
13043 &%daemon_startup_sleep%& defines the length of time to wait between retries.
13045 .option daemon_startup_sleep main time 30s
13046 See &%daemon_startup_retries%&.
13048 .option delay_warning main "time list" 24h
13049 .cindex "warning of delay"
13050 .cindex "delay warning, specifying"
13051 When a message is delayed, Exim sends a warning message to the sender at
13052 intervals specified by this option. The data is a colon-separated list of times
13053 after which to send warning messages. If the value of the option is an empty
13054 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
13055 message has been on the queue for longer than the last time, the last interval
13056 between the times is used to compute subsequent warning times. For example,
13059 delay_warning = 4h:8h:24h
13061 the first message is sent after 4 hours, the second after 8 hours, and
13062 the third one after 24 hours. After that, messages are sent every 16 hours,
13063 because that is the interval between the last two times on the list. If you set
13064 just one time, it specifies the repeat interval. For example, with:
13068 messages are repeated every six hours. To stop warnings after a given time, set
13069 a very large time at the end of the list. For example:
13071 delay_warning = 2h:12h:99d
13074 .option delay_warning_condition main string&!! "see below"
13075 .vindex "&$domain$&"
13076 The string is expanded at the time a warning message might be sent. If all the
13077 deferred addresses have the same domain, it is set in &$domain$& during the
13078 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
13079 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
13080 &"false"& (the comparison being done caselessly) then the warning message is
13081 not sent. The default is:
13083 delay_warning_condition = ${if or {\
13084 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
13085 { match{$h_precedence:}{(?i)bulk|list|junk} }\
13086 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
13089 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
13090 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
13091 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
13092 &"auto-replied"& in an &'Auto-Submitted:'& header.
13094 .option deliver_drop_privilege main boolean false
13095 .cindex "unprivileged delivery"
13096 .cindex "delivery" "unprivileged"
13097 If this option is set true, Exim drops its root privilege at the start of a
13098 delivery process, and runs as the Exim user throughout. This severely restricts
13099 the kinds of local delivery that are possible, but is viable in certain types
13100 of configuration. There is a discussion about the use of root privilege in
13101 chapter &<<CHAPsecurity>>&.
13103 .option deliver_queue_load_max main fixed-point unset
13104 .cindex "load average"
13105 .cindex "queue runner" "abandoning"
13106 When this option is set, a queue run is abandoned if the system load average
13107 becomes greater than the value of the option. The option has no effect on
13108 ancient operating systems on which Exim cannot determine the load average.
13109 See also &%queue_only_load%& and &%smtp_load_reserve%&.
13112 .option delivery_date_remove main boolean true
13113 .cindex "&'Delivery-date:'& header line"
13114 Exim's transports have an option for adding a &'Delivery-date:'& header to a
13115 message when it is delivered, in exactly the same way as &'Return-path:'& is
13116 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
13117 should not be present in incoming messages, and this option causes them to be
13118 removed at the time the message is received, to avoid any problems that might
13119 occur when a delivered message is subsequently sent on to some other recipient.
13121 .option disable_fsync main boolean false
13122 .cindex "&[fsync()]&, disabling"
13123 This option is available only if Exim was built with the compile-time option
13124 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
13125 a runtime configuration generates an &"unknown option"& error. You should not
13126 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
13127 really, really, really understand what you are doing. &'No pre-compiled
13128 distributions of Exim should ever make this option available.'&
13130 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
13131 updated files' data to be written to disc before continuing. Unexpected events
13132 such as crashes and power outages may cause data to be lost or scrambled.
13133 Here be Dragons. &*Beware.*&
13136 .option disable_ipv6 main boolean false
13137 .cindex "IPv6" "disabling"
13138 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
13139 activities take place. AAAA records are never looked up, and any IPv6 addresses
13140 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
13141 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13142 to handle IPv6 literal addresses.
13145 .option dns_again_means_nonexist main "domain list&!!" unset
13146 .cindex "DNS" "&""try again""& response; overriding"
13147 DNS lookups give a &"try again"& response for the DNS errors
13148 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
13149 keep trying to deliver a message, or to give repeated temporary errors to
13150 incoming mail. Sometimes the effect is caused by a badly set up name server and
13151 may persist for a long time. If a domain which exhibits this problem matches
13152 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
13153 This option should be used with care. You can make it apply to reverse lookups
13154 by a setting such as this:
13156 dns_again_means_nonexist = *.in-addr.arpa
13158 This option applies to all DNS lookups that Exim does. It also applies when the
13159 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
13160 since these are most likely to be caused by DNS lookup problems. The
13161 &(dnslookup)& router has some options of its own for controlling what happens
13162 when lookups for MX or SRV records give temporary errors. These more specific
13163 options are applied after this global option.
13165 .option dns_check_names_pattern main string "see below"
13166 .cindex "DNS" "pre-check of name syntax"
13167 When this option is set to a non-empty string, it causes Exim to check domain
13168 names for characters that are not allowed in host names before handing them to
13169 the DNS resolver, because some resolvers give temporary errors for names that
13170 contain unusual characters. If a domain name contains any unwanted characters,
13171 a &"not found"& result is forced, and the resolver is not called. The check is
13172 done by matching the domain name against a regular expression, which is the
13173 value of this option. The default pattern is
13175 dns_check_names_pattern = \
13176 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
13178 which permits only letters, digits, slashes, and hyphens in components, but
13179 they must start and end with a letter or digit. Slashes are not, in fact,
13180 permitted in host names, but they are found in certain NS records (which can be
13181 accessed in Exim by using a &%dnsdb%& lookup). If you set
13182 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
13185 .option dns_csa_search_limit main integer 5
13186 This option controls the depth of parental searching for CSA SRV records in the
13187 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
13189 .option dns_csa_use_reverse main boolean true
13190 This option controls whether or not an IP address, given as a CSA domain, is
13191 reversed and looked up in the reverse DNS, as described in more detail in
13192 section &<<SECTverifyCSA>>&.
13194 .option dns_ipv4_lookup main "domain list&!!" unset
13195 .cindex "IPv6" "DNS lookup for AAAA records"
13196 .cindex "DNS" "IPv6 lookup for AAAA records"
13197 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
13198 looks for IPv6 address records (AAAA records) as well as IPv4 address records
13199 (A records) when trying to find IP addresses for hosts, unless the host's
13200 domain matches this list.
13202 This is a fudge to help with name servers that give big delays or otherwise do
13203 not work for the AAAA record type. In due course, when the world's name
13204 servers have all been upgraded, there should be no need for this option.
13207 .option dns_retrans main time 0s
13208 .cindex "DNS" "resolver options"
13209 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
13210 retransmission and retry parameters for DNS lookups. Values of zero (the
13211 defaults) leave the system default settings unchanged. The first value is the
13212 time between retries, and the second is the number of retries. It isn't
13213 totally clear exactly how these settings affect the total time a DNS lookup may
13214 take. I haven't found any documentation about timeouts on DNS lookups; these
13215 parameter values are available in the external resolver interface structure,
13216 but nowhere does it seem to describe how they are used or what you might want
13220 .option dns_retry main integer 0
13221 See &%dns_retrans%& above.
13224 .option drop_cr main boolean false
13225 This is an obsolete option that is now a no-op. It used to affect the way Exim
13226 handled CR and LF characters in incoming messages. What happens now is
13227 described in section &<<SECTlineendings>>&.
13229 .option dsn_from main "string&!!" "see below"
13230 .cindex "&'From:'& header line" "in bounces"
13231 .cindex "bounce messages" "&'From:'& line, specifying"
13232 This option can be used to vary the contents of &'From:'& header lines in
13233 bounces and other automatically generated messages (&"Delivery Status
13234 Notifications"& &-- hence the name of the option). The default setting is:
13236 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
13238 The value is expanded every time it is needed. If the expansion fails, a
13239 panic is logged, and the default value is used.
13241 .option envelope_to_remove main boolean true
13242 .cindex "&'Envelope-to:'& header line"
13243 Exim's transports have an option for adding an &'Envelope-to:'& header to a
13244 message when it is delivered, in exactly the same way as &'Return-path:'& is
13245 handled. &'Envelope-to:'& records the original recipient address from the
13246 messages's envelope that caused the delivery to happen. Such headers should not
13247 be present in incoming messages, and this option causes them to be removed at
13248 the time the message is received, to avoid any problems that might occur when a
13249 delivered message is subsequently sent on to some other recipient.
13252 .option errors_copy main "string list&!!" unset
13253 .cindex "bounce message" "copy to other address"
13254 .cindex "copy of bounce message"
13255 Setting this option causes Exim to send bcc copies of bounce messages that it
13256 generates to other addresses. &*Note*&: This does not apply to bounce messages
13257 coming from elsewhere. The value of the option is a colon-separated list of
13258 items. Each item consists of a pattern, terminated by white space, followed by
13259 a comma-separated list of email addresses. If a pattern contains spaces, it
13260 must be enclosed in double quotes.
13262 Each pattern is processed in the same way as a single item in an address list
13263 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
13264 the bounce message, the message is copied to the addresses on the list. The
13265 items are scanned in order, and once a matching one is found, no further items
13266 are examined. For example:
13268 errors_copy = spqr@mydomain postmaster@mydomain.example :\
13269 rqps@mydomain hostmaster@mydomain.example,\
13270 postmaster@mydomain.example
13272 .vindex "&$domain$&"
13273 .vindex "&$local_part$&"
13274 The address list is expanded before use. The expansion variables &$local_part$&
13275 and &$domain$& are set from the original recipient of the error message, and if
13276 there was any wildcard matching in the pattern, the expansion
13277 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
13278 variables &$0$&, &$1$&, etc. are set in the normal way.
13281 .option errors_reply_to main string unset
13282 .cindex "bounce message" "&'Reply-to:'& in"
13283 By default, Exim's bounce and delivery warning messages contain the header line
13285 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
13287 .oindex &%quota_warn_message%&
13288 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
13289 A warning message that is generated by the &%quota_warn_message%& option in an
13290 &(appendfile)& transport may contain its own &'From:'& header line that
13291 overrides the default.
13293 Experience shows that people reply to bounce messages. If the
13294 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
13295 and warning messages. For example:
13297 errors_reply_to = postmaster@my.domain.example
13299 The value of the option is not expanded. It must specify a valid RFC 2822
13300 address. However, if a warning message that is generated by the
13301 &%quota_warn_message%& option in an &(appendfile)& transport contain its
13302 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
13306 .option exim_group main string "compile-time configured"
13307 .cindex "gid (group id)" "Exim's own"
13308 .cindex "Exim group"
13309 This option changes the gid under which Exim runs when it gives up root
13310 privilege. The default value is compiled into the binary. The value of this
13311 option is used only when &%exim_user%& is also set. Unless it consists entirely
13312 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
13313 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
13317 .option exim_path main string "see below"
13318 .cindex "Exim binary, path name"
13319 This option specifies the path name of the Exim binary, which is used when Exim
13320 needs to re-exec itself. The default is set up to point to the file &'exim'& in
13321 the directory configured at compile time by the BIN_DIRECTORY setting. It
13322 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
13324 &*Warning*&: Do not use a macro to define the value of this option, because
13325 you will break those Exim utilities that scan the configuration file to find
13326 where the binary is. (They then use the &%-bP%& option to extract option
13327 settings such as the value of &%spool_directory%&.)
13330 .option exim_user main string "compile-time configured"
13331 .cindex "uid (user id)" "Exim's own"
13332 .cindex "Exim user"
13333 This option changes the uid under which Exim runs when it gives up root
13334 privilege. The default value is compiled into the binary. Ownership of the run
13335 time configuration file and the use of the &%-C%& and &%-D%& command line
13336 options is checked against the values in the binary, not what is set here.
13338 Unless it consists entirely of digits, the string is looked up using
13339 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
13340 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
13341 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
13344 .option extra_local_interfaces main "string list" unset
13345 This option defines network interfaces that are to be considered local when
13346 routing, but which are not used for listening by the daemon. See section
13347 &<<SECTreclocipadd>>& for details.
13350 . Allow this long option name to split; give it unsplit as a fifth argument
13351 . for the automatic .oindex that is generated by .option.
13353 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
13354 extract_addresses_remove_arguments
13356 .cindex "command line" "addresses with &%-t%&"
13357 .cindex "Sendmail compatibility" "&%-t%& option"
13358 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
13359 are present on the command line when the &%-t%& option is used to build an
13360 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
13361 line addresses are removed from the recipients list. This is also how Smail
13362 behaves. However, other Sendmail documentation (the O'Reilly book) states that
13363 command line addresses are added to those obtained from the header lines. When
13364 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
13365 argument headers. If it is set false, Exim adds rather than removes argument
13369 .option finduser_retries main integer 0
13370 .cindex "NIS, retrying user lookups"
13371 On systems running NIS or other schemes in which user and group information is
13372 distributed from a remote system, there can be times when &[getpwnam()]& and
13373 related functions fail, even when given valid data, because things time out.
13374 Unfortunately these failures cannot be distinguished from genuine &"not found"&
13375 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
13376 many extra times to find a user or a group, waiting for one second between
13379 .cindex "&_/etc/passwd_&" "multiple reading of"
13380 You should not set this option greater than zero if your user information is in
13381 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
13382 search the file multiple times for non-existent users, and also cause delay.
13386 .option freeze_tell main "string list, comma separated" unset
13387 .cindex "freezing messages" "sending a message when freezing"
13388 On encountering certain errors, or when configured to do so in a system filter,
13389 ACL, or special router, Exim freezes a message. This means that no further
13390 delivery attempts take place until an administrator thaws the message, or the
13391 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
13392 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
13393 warning message whenever it freezes something, unless the message it is
13394 freezing is a locally-generated bounce message. (Without this exception there
13395 is the possibility of looping.) The warning message is sent to the addresses
13396 supplied as the comma-separated value of this option. If several of the
13397 message's addresses cause freezing, only a single message is sent. If the
13398 freezing was automatic, the reason(s) for freezing can be found in the message
13399 log. If you configure freezing in a filter or ACL, you must arrange for any
13400 logging that you require.
13403 .option gecos_name main string&!! unset
13405 .cindex "&""gecos""& field, parsing"
13406 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
13407 password file to hold other information in addition to users' real names. Exim
13408 looks up this field for use when it is creating &'Sender:'& or &'From:'&
13409 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
13410 of the field are used unchanged, except that, if an ampersand is encountered,
13411 it is replaced by the user's login name with the first character forced to
13412 upper case, since this is a convention that is observed on many systems.
13414 When these options are set, &%gecos_pattern%& is treated as a regular
13415 expression that is to be applied to the field (again with && replaced by the
13416 login name), and if it matches, &%gecos_name%& is expanded and used as the
13419 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
13420 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
13421 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
13422 name terminates at the first comma, the following can be used:
13424 gecos_pattern = ([^,]*)
13428 .option gecos_pattern main string unset
13429 See &%gecos_name%& above.
13432 .option gnutls_require_kx main string unset
13433 This option controls the key exchange mechanisms when GnuTLS is used in an Exim
13434 server. For details, see section &<<SECTreqciphgnu>>&.
13436 .option gnutls_require_mac main string unset
13437 This option controls the MAC algorithms when GnuTLS is used in an Exim
13438 server. For details, see section &<<SECTreqciphgnu>>&.
13440 .option gnutls_require_protocols main string unset
13441 This option controls the protocols when GnuTLS is used in an Exim
13442 server. For details, see section &<<SECTreqciphgnu>>&.
13444 .option gnutls_compat_mode main boolean unset
13445 This option controls whether GnuTLS is used in compatibility mode in an Exim
13446 server. This reduces security slightly, but improves interworking with older
13447 implementations of TLS.
13449 .option headers_charset main string "see below"
13450 This option sets a default character set for translating from encoded MIME
13451 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
13452 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
13453 ultimate default is ISO-8859-1. For more details see the description of header
13454 insertions in section &<<SECTexpansionitems>>&.
13458 .option header_maxsize main integer "see below"
13459 .cindex "header section" "maximum size of"
13460 .cindex "limit" "size of message header section"
13461 This option controls the overall maximum size of a message's header
13462 section. The default is the value of HEADER_MAXSIZE in
13463 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
13464 sections are rejected.
13467 .option header_line_maxsize main integer 0
13468 .cindex "header lines" "maximum size of"
13469 .cindex "limit" "size of one header line"
13470 This option limits the length of any individual header line in a message, after
13471 all the continuations have been joined together. Messages with individual
13472 header lines that are longer than the limit are rejected. The default value of
13473 zero means &"no limit"&.
13478 .option helo_accept_junk_hosts main "host list&!!" unset
13479 .cindex "HELO" "accepting junk data"
13480 .cindex "EHLO" "accepting junk data"
13481 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
13482 mail, and gives an error response for invalid data. Unfortunately, there are
13483 some SMTP clients that send syntactic junk. They can be accommodated by setting
13484 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
13485 if you want to do semantic checking.
13486 See also &%helo_allow_chars%& for a way of extending the permitted character
13490 .option helo_allow_chars main string unset
13491 .cindex "HELO" "underscores in"
13492 .cindex "EHLO" "underscores in"
13493 .cindex "underscore in EHLO/HELO"
13494 This option can be set to a string of rogue characters that are permitted in
13495 all EHLO and HELO names in addition to the standard letters, digits,
13496 hyphens, and dots. If you really must allow underscores, you can set
13498 helo_allow_chars = _
13500 Note that the value is one string, not a list.
13503 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
13504 .cindex "HELO" "forcing reverse lookup"
13505 .cindex "EHLO" "forcing reverse lookup"
13506 If the domain given by a client in a HELO or EHLO command matches this
13507 list, a reverse lookup is done in order to establish the host's true name. The
13508 default forces a lookup if the client host gives the server's name or any of
13509 its IP addresses (in brackets), something that broken clients have been seen to
13513 .option helo_try_verify_hosts main "host list&!!" unset
13514 .cindex "HELO verifying" "optional"
13515 .cindex "EHLO" "verifying, optional"
13516 By default, Exim just checks the syntax of HELO and EHLO commands (see
13517 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
13518 to do more extensive checking of the data supplied by these commands. The ACL
13519 condition &`verify = helo`& is provided to make this possible.
13520 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
13521 to force the check to occur. From release 4.53 onwards, this is no longer
13522 necessary. If the check has not been done before &`verify = helo`& is
13523 encountered, it is done at that time. Consequently, this option is obsolete.
13524 Its specification is retained here for backwards compatibility.
13526 When an EHLO or HELO command is received, if the calling host matches
13527 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
13528 EHLO command either:
13531 is an IP literal matching the calling address of the host, or
13533 .cindex "DNS" "reverse lookup"
13534 .cindex "reverse DNS lookup"
13535 matches the host name that Exim obtains by doing a reverse lookup of the
13536 calling host address, or
13538 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
13539 available) yields the calling host address.
13542 However, the EHLO or HELO command is not rejected if any of the checks
13543 fail. Processing continues, but the result of the check is remembered, and can
13544 be detected later in an ACL by the &`verify = helo`& condition.
13546 .option helo_verify_hosts main "host list&!!" unset
13547 .cindex "HELO verifying" "mandatory"
13548 .cindex "EHLO" "verifying, mandatory"
13549 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
13550 backwards compatibility. For hosts that match this option, Exim checks the host
13551 name given in the HELO or EHLO in the same way as for
13552 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
13553 rejected with a 550 error, and entries are written to the main and reject logs.
13554 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
13557 .option hold_domains main "domain list&!!" unset
13558 .cindex "domain" "delaying delivery"
13559 .cindex "delivery" "delaying certain domains"
13560 This option allows mail for particular domains to be held on the queue
13561 manually. The option is overridden if a message delivery is forced with the
13562 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
13563 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
13564 item in &%hold_domains%&, no routing or delivery for that address is done, and
13565 it is deferred every time the message is looked at.
13567 This option is intended as a temporary operational measure for delaying the
13568 delivery of mail while some problem is being sorted out, or some new
13569 configuration tested. If you just want to delay the processing of some
13570 domains until a queue run occurs, you should use &%queue_domains%& or
13571 &%queue_smtp_domains%&, not &%hold_domains%&.
13573 A setting of &%hold_domains%& does not override Exim's code for removing
13574 messages from the queue if they have been there longer than the longest retry
13575 time in any retry rule. If you want to hold messages for longer than the normal
13576 retry times, insert a dummy retry rule with a long retry time.
13579 .option host_lookup main "host list&!!" unset
13580 .cindex "host name" "lookup, forcing"
13581 Exim does not look up the name of a calling host from its IP address unless it
13582 is required to compare against some host list, or the host matches
13583 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
13584 option (which normally contains IP addresses rather than host names). The
13585 default configuration file contains
13589 which causes a lookup to happen for all hosts. If the expense of these lookups
13590 is felt to be too great, the setting can be changed or removed.
13592 After a successful reverse lookup, Exim does a forward lookup on the name it
13593 has obtained, to verify that it yields the IP address that it started with. If
13594 this check fails, Exim behaves as if the name lookup failed.
13596 .vindex "&$host_lookup_failed$&"
13597 .vindex "&$sender_host_name$&"
13598 After any kind of failure, the host name (in &$sender_host_name$&) remains
13599 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
13600 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
13601 &`verify = reverse_host_lookup`& in ACLs.
13604 .option host_lookup_order main "string list" &`bydns:byaddr`&
13605 This option specifies the order of different lookup methods when Exim is trying
13606 to find a host name from an IP address. The default is to do a DNS lookup
13607 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
13608 if that fails. You can change the order of these lookups, or omit one entirely,
13611 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
13612 multiple PTR records in the DNS and the IP address is not listed in
13613 &_/etc/hosts_&. Different operating systems give different results in this
13614 case. That is why the default tries a DNS lookup first.
13618 .option host_reject_connection main "host list&!!" unset
13619 .cindex "host" "rejecting connections from"
13620 If this option is set, incoming SMTP calls from the hosts listed are rejected
13621 as soon as the connection is made.
13622 This option is obsolete, and retained only for backward compatibility, because
13623 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
13624 connections immediately.
13626 The ability to give an immediate rejection (either by this option or using an
13627 ACL) is provided for use in unusual cases. Many hosts will just try again,
13628 sometimes without much delay. Normally, it is better to use an ACL to reject
13629 incoming messages at a later stage, such as after RCPT commands. See
13630 chapter &<<CHAPACL>>&.
13633 .option hosts_connection_nolog main "host list&!!" unset
13634 .cindex "host" "not logging connections from"
13635 This option defines a list of hosts for which connection logging does not
13636 happen, even though the &%smtp_connection%& log selector is set. For example,
13637 you might want not to log SMTP connections from local processes, or from
13638 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
13639 the daemon; you should therefore strive to restrict its value to a short inline
13640 list of IP addresses and networks. To disable logging SMTP connections from
13641 local processes, you must create a host list with an empty item. For example:
13643 hosts_connection_nolog = :
13645 If the &%smtp_connection%& log selector is not set, this option has no effect.
13649 .option hosts_treat_as_local main "domain list&!!" unset
13650 .cindex "local host" "domains treated as"
13651 .cindex "host" "treated as local"
13652 If this option is set, any host names that match the domain list are treated as
13653 if they were the local host when Exim is scanning host lists obtained from MX
13655 or other sources. Note that the value of this option is a domain list, not a
13656 host list, because it is always used to check host names, not IP addresses.
13658 This option also applies when Exim is matching the special items
13659 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
13660 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
13661 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
13662 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
13663 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
13664 interfaces and recognizing the local host.
13667 .option ibase_servers main "string list" unset
13668 .cindex "InterBase" "server list"
13669 This option provides a list of InterBase servers and associated connection data,
13670 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
13671 The option is available only if Exim has been built with InterBase support.
13675 .option ignore_bounce_errors_after main time 10w
13676 .cindex "bounce message" "discarding"
13677 .cindex "discarding bounce message"
13678 This option affects the processing of bounce messages that cannot be delivered,
13679 that is, those that suffer a permanent delivery failure. (Bounce messages that
13680 suffer temporary delivery failures are of course retried in the usual way.)
13682 After a permanent delivery failure, bounce messages are frozen,
13683 because there is no sender to whom they can be returned. When a frozen bounce
13684 message has been on the queue for more than the given time, it is unfrozen at
13685 the next queue run, and a further delivery is attempted. If delivery fails
13686 again, the bounce message is discarded. This makes it possible to keep failed
13687 bounce messages around for a shorter time than the normal maximum retry time
13688 for frozen messages. For example,
13690 ignore_bounce_errors_after = 12h
13692 retries failed bounce message deliveries after 12 hours, discarding any further
13693 failures. If the value of this option is set to a zero time period, bounce
13694 failures are discarded immediately. Setting a very long time (as in the default
13695 value) has the effect of disabling this option. For ways of automatically
13696 dealing with other kinds of frozen message, see &%auto_thaw%& and
13697 &%timeout_frozen_after%&.
13700 .option ignore_fromline_hosts main "host list&!!" unset
13701 .cindex "&""From""& line"
13702 .cindex "UUCP" "&""From""& line"
13703 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
13704 the headers of a message. By default this is treated as the start of the
13705 message's body, which means that any following headers are not recognized as
13706 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
13707 match those hosts that insist on sending it. If the sender is actually a local
13708 process rather than a remote host, and is using &%-bs%& to inject the messages,
13709 &%ignore_fromline_local%& must be set to achieve this effect.
13712 .option ignore_fromline_local main boolean false
13713 See &%ignore_fromline_hosts%& above.
13716 .option keep_malformed main time 4d
13717 This option specifies the length of time to keep messages whose spool files
13718 have been corrupted in some way. This should, of course, never happen. At the
13719 next attempt to deliver such a message, it gets removed. The incident is
13723 .option ldap_default_servers main "string list" unset
13724 .cindex "LDAP" "default servers"
13725 This option provides a list of LDAP servers which are tried in turn when an
13726 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
13727 details of LDAP queries. This option is available only when Exim has been built
13731 .option ldap_version main integer unset
13732 .cindex "LDAP" "protocol version, forcing"
13733 This option can be used to force Exim to set a specific protocol version for
13734 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
13735 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
13736 the LDAP headers; otherwise it is 2. This option is available only when Exim
13737 has been built with LDAP support.
13741 .option local_from_check main boolean true
13742 .cindex "&'Sender:'& header line" "disabling addition of"
13743 .cindex "&'From:'& header line" "disabling checking of"
13744 When a message is submitted locally (that is, not over a TCP/IP connection) by
13745 an untrusted user, Exim removes any existing &'Sender:'& header line, and
13746 checks that the &'From:'& header line matches the login of the calling user and
13747 the domain specified by &%qualify_domain%&.
13749 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
13750 locally submitted message is automatically qualified by Exim, unless the
13751 &%-bnq%& command line option is used.
13753 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
13754 on the local part. If the &'From:'& header line does not match, Exim adds a
13755 &'Sender:'& header with an address constructed from the calling user's login
13756 and the default qualify domain.
13758 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
13759 and no &'Sender:'& header is ever added. If, in addition, you want to retain
13760 &'Sender:'& header lines supplied by untrusted users, you must also set
13761 &%local_sender_retain%& to be true.
13763 .cindex "envelope sender"
13764 These options affect only the header lines in the message. The envelope sender
13765 is still forced to be the login id at the qualify domain unless
13766 &%untrusted_set_sender%& permits the user to supply an envelope sender.
13768 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
13769 request similar header line checking. See section &<<SECTthesenhea>>&, which
13770 has more details about &'Sender:'& processing.
13775 .option local_from_prefix main string unset
13776 When Exim checks the &'From:'& header line of locally submitted messages for
13777 matching the login id (see &%local_from_check%& above), it can be configured to
13778 ignore certain prefixes and suffixes in the local part of the address. This is
13779 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
13780 appropriate lists, in the same form as the &%local_part_prefix%& and
13781 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
13784 local_from_prefix = *-
13786 is set, a &'From:'& line containing
13788 From: anything-user@your.domain.example
13790 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
13791 matches the actual sender address that is constructed from the login name and
13795 .option local_from_suffix main string unset
13796 See &%local_from_prefix%& above.
13799 .option local_interfaces main "string list" "see below"
13800 This option controls which network interfaces are used by the daemon for
13801 listening; they are also used to identify the local host when routing. Chapter
13802 &<<CHAPinterfaces>>& contains a full description of this option and the related
13803 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
13804 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
13805 &%local_interfaces%& is
13807 local_interfaces = 0.0.0.0
13809 when Exim is built without IPv6 support; otherwise it is
13811 local_interfaces = <; ::0 ; 0.0.0.0
13814 .option local_scan_timeout main time 5m
13815 .cindex "timeout" "for &[local_scan()]& function"
13816 .cindex "&[local_scan()]& function" "timeout"
13817 This timeout applies to the &[local_scan()]& function (see chapter
13818 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
13819 the incoming message is rejected with a temporary error if it is an SMTP
13820 message. For a non-SMTP message, the message is dropped and Exim ends with a
13821 non-zero code. The incident is logged on the main and reject logs.
13825 .option local_sender_retain main boolean false
13826 .cindex "&'Sender:'& header line" "retaining from local submission"
13827 When a message is submitted locally (that is, not over a TCP/IP connection) by
13828 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
13829 do not want this to happen, you must set &%local_sender_retain%&, and you must
13830 also set &%local_from_check%& to be false (Exim will complain if you do not).
13831 See also the ACL modifier &`control = suppress_local_fixups`&. Section
13832 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
13837 .option localhost_number main string&!! unset
13838 .cindex "host" "locally unique number for"
13839 .cindex "message ids" "with multiple hosts"
13840 .vindex "&$localhost_number$&"
13841 Exim's message ids are normally unique only within the local host. If
13842 uniqueness among a set of hosts is required, each host must set a different
13843 value for the &%localhost_number%& option. The string is expanded immediately
13844 after reading the configuration file (so that a number can be computed from the
13845 host name, for example) and the result of the expansion must be a number in the
13846 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
13847 systems). This is available in subsequent string expansions via the variable
13848 &$localhost_number$&. When &%localhost_number is set%&, the final two
13849 characters of the message id, instead of just being a fractional part of the
13850 time, are computed from the time and the local host number as described in
13851 section &<<SECTmessiden>>&.
13855 .option log_file_path main "string list&!!" "set at compile time"
13856 .cindex "log" "file path for"
13857 This option sets the path which is used to determine the names of Exim's log
13858 files, or indicates that logging is to be to syslog, or both. It is expanded
13859 when Exim is entered, so it can, for example, contain a reference to the host
13860 name. If no specific path is set for the log files at compile or run time, they
13861 are written in a sub-directory called &_log_& in Exim's spool directory.
13862 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
13863 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
13864 used. If this string is fixed at your installation (contains no expansion
13865 variables) it is recommended that you do not set this option in the
13866 configuration file, but instead supply the path using LOG_FILE_PATH in
13867 &_Local/Makefile_& so that it is available to Exim for logging errors detected
13868 early on &-- in particular, failure to read the configuration file.
13871 .option log_selector main string unset
13872 .cindex "log" "selectors"
13873 This option can be used to reduce or increase the number of things that Exim
13874 writes to its log files. Its argument is made up of names preceded by plus or
13875 minus characters. For example:
13877 log_selector = +arguments -retry_defer
13879 A list of possible names and what they control is given in the chapter on
13880 logging, in section &<<SECTlogselector>>&.
13883 .option log_timezone main boolean false
13884 .cindex "log" "timezone for entries"
13885 .vindex "&$tod_log$&"
13886 .vindex "&$tod_zone$&"
13887 By default, the timestamps on log lines are in local time without the
13888 timezone. This means that if your timezone changes twice a year, the timestamps
13889 in log lines are ambiguous for an hour when the clocks go back. One way of
13890 avoiding this problem is to set the timezone to UTC. An alternative is to set
13891 &%log_timezone%& true. This turns on the addition of the timezone offset to
13892 timestamps in log lines. Turning on this option can add quite a lot to the size
13893 of log files because each line is extended by 6 characters. Note that the
13894 &$tod_log$& variable contains the log timestamp without the zone, but there is
13895 another variable called &$tod_zone$& that contains just the timezone offset.
13898 .option lookup_open_max main integer 25
13899 .cindex "too many open files"
13900 .cindex "open files, too many"
13901 .cindex "file" "too many open"
13902 .cindex "lookup" "maximum open files"
13903 .cindex "limit" "open files for lookups"
13904 This option limits the number of simultaneously open files for single-key
13905 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
13906 Exim normally keeps these files open during routing, because often the same
13907 file is required several times. If the limit is reached, Exim closes the least
13908 recently used file. Note that if you are using the &'ndbm'& library, it
13909 actually opens two files for each logical DBM database, though it still counts
13910 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
13911 open files"& errors with NDBM, you need to reduce the value of
13912 &%lookup_open_max%&.
13915 .option max_username_length main integer 0
13916 .cindex "length of login name"
13917 .cindex "user name" "maximum length"
13918 .cindex "limit" "user name length"
13919 Some operating systems are broken in that they truncate long arguments to
13920 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
13921 this option is set greater than zero, any attempt to call &[getpwnam()]& with
13922 an argument that is longer behaves as if &[getpwnam()]& failed.
13925 .option message_body_newlines main bool false
13926 .cindex "message body" "newlines in variables"
13927 .cindex "newline" "in message body variables"
13928 .vindex "&$message_body$&"
13929 .vindex "&$message_body_end$&"
13930 By default, newlines in the message body are replaced by spaces when setting
13931 the &$message_body$& and &$message_body_end$& expansion variables. If this
13932 option is set true, this no longer happens.
13935 .option message_body_visible main integer 500
13936 .cindex "body of message" "visible size"
13937 .cindex "message body" "visible size"
13938 .vindex "&$message_body$&"
13939 .vindex "&$message_body_end$&"
13940 This option specifies how much of a message's body is to be included in the
13941 &$message_body$& and &$message_body_end$& expansion variables.
13944 .option message_id_header_domain main string&!! unset
13945 .cindex "&'Message-ID:'& header line"
13946 If this option is set, the string is expanded and used as the right hand side
13947 (domain) of the &'Message-ID:'& header that Exim creates if a
13948 locally-originated incoming message does not have one. &"Locally-originated"&
13949 means &"not received over TCP/IP."&
13950 Otherwise, the primary host name is used.
13951 Only letters, digits, dot and hyphen are accepted; any other characters are
13952 replaced by hyphens. If the expansion is forced to fail, or if the result is an
13953 empty string, the option is ignored.
13956 .option message_id_header_text main string&!! unset
13957 If this variable is set, the string is expanded and used to augment the text of
13958 the &'Message-id:'& header that Exim creates if a locally-originated incoming
13959 message does not have one. The text of this header is required by RFC 2822 to
13960 take the form of an address. By default, Exim uses its internal message id as
13961 the local part, and the primary host name as the domain. If this option is set,
13962 it is expanded, and provided the expansion is not forced to fail, and does not
13963 yield an empty string, the result is inserted into the header immediately
13964 before the @, separated from the internal message id by a dot. Any characters
13965 that are illegal in an address are automatically converted into hyphens. This
13966 means that variables such as &$tod_log$& can be used, because the spaces and
13967 colons will become hyphens.
13970 .option message_logs main boolean true
13971 .cindex "message logs" "disabling"
13972 .cindex "log" "message log; disabling"
13973 If this option is turned off, per-message log files are not created in the
13974 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
13975 Exim, by reducing the number of files involved in handling a message from a
13976 minimum of four (header spool file, body spool file, delivery journal, and
13977 per-message log) to three. The other major I/O activity is Exim's main log,
13978 which is not affected by this option.
13981 .option message_size_limit main string&!! 50M
13982 .cindex "message" "size limit"
13983 .cindex "limit" "message size"
13984 .cindex "size" "of message, limit"
13985 This option limits the maximum size of message that Exim will process. The
13986 value is expanded for each incoming connection so, for example, it can be made
13987 to depend on the IP address of the remote host for messages arriving via
13988 TCP/IP. After expansion, the value must be a sequence of decimal digits,
13989 optionally followed by K or M.
13991 &*Note*&: This limit cannot be made to depend on a message's sender or any
13992 other properties of an individual message, because it has to be advertised in
13993 the server's response to EHLO. String expansion failure causes a temporary
13994 error. A value of zero means no limit, but its use is not recommended. See also
13995 &%bounce_return_size_limit%&.
13997 Incoming SMTP messages are failed with a 552 error if the limit is
13998 exceeded; locally-generated messages either get a stderr message or a delivery
13999 failure message to the sender, depending on the &%-oe%& setting. Rejection of
14000 an oversized message is logged in both the main and the reject logs. See also
14001 the generic transport option &%message_size_limit%&, which limits the size of
14002 message that an individual transport can process.
14004 If you use a virus-scanner and set this option to to a value larger than the
14005 maximum size that your virus-scanner is configured to support, you may get
14006 failures triggered by large mails. The right size to configure for the
14007 virus-scanner depends upon what data is passed and the options in use but it's
14008 probably safest to just set it to a little larger than this value. Eg, with a
14009 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
14010 some problems may result.
14013 .option move_frozen_messages main boolean false
14014 .cindex "frozen messages" "moving"
14015 This option, which is available only if Exim has been built with the setting
14017 SUPPORT_MOVE_FROZEN_MESSAGES=yes
14019 in &_Local/Makefile_&, causes frozen messages and their message logs to be
14020 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
14021 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
14022 standard utilities for handling such moved messages, and they do not show up in
14023 lists generated by &%-bp%& or by the Exim monitor.
14026 .option mua_wrapper main boolean false
14027 Setting this option true causes Exim to run in a very restrictive mode in which
14028 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
14029 contains a full description of this facility.
14033 .option mysql_servers main "string list" unset
14034 .cindex "MySQL" "server list"
14035 This option provides a list of MySQL servers and associated connection data, to
14036 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
14037 option is available only if Exim has been built with MySQL support.
14040 .option never_users main "string list&!!" unset
14041 This option is expanded just once, at the start of Exim's processing. Local
14042 message deliveries are normally run in processes that are setuid to the
14043 recipient, and remote deliveries are normally run under Exim's own uid and gid.
14044 It is usually desirable to prevent any deliveries from running as root, as a
14047 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
14048 list of users that must not be used for local deliveries. This list is fixed in
14049 the binary and cannot be overridden by the configuration file. By default, it
14050 contains just the single user name &"root"&. The &%never_users%& runtime option
14051 can be used to add more users to the fixed list.
14053 If a message is to be delivered as one of the users on the fixed list or the
14054 &%never_users%& list, an error occurs, and delivery is deferred. A common
14057 never_users = root:daemon:bin
14059 Including root is redundant if it is also on the fixed list, but it does no
14060 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
14064 .option openssl_options main "string list" +dont_insert_empty_fragments
14065 .cindex "OpenSSL "compatibility options"
14066 This option allows an administrator to adjust the SSL options applied
14067 by OpenSSL to connections. It is given as a space-separated list of items,
14068 each one to be +added or -subtracted from the current value. The default
14069 value is one option which happens to have been set historically. You can
14070 remove all options with:
14072 openssl_options = -all
14074 This option is only available if Exim is built against OpenSSL. The values
14075 available for this option vary according to the age of your OpenSSL install.
14076 The &"all"& value controls a subset of flags which are available, typically
14077 the bug workaround options. The &'SSL_CTX_set_options'& man page will
14078 list the values known on your system and Exim should support all the
14079 &"bug workaround"& options and many of the &"modifying"& options. The Exim
14080 names lose the leading &"SSL_OP_"& and are lower-cased.
14082 Note that adjusting the options can have severe impact upon the security of
14083 SSL as used by Exim. It is possible to disable safety checks and shoot
14084 yourself in the foot in various unpleasant ways. This option should not be
14085 adjusted lightly. An unrecognised item will be detected at by invoking Exim
14086 with the &%-bV%& flag.
14090 openssl_options = -all +microsoft_big_sslv3_buffer
14094 .option oracle_servers main "string list" unset
14095 .cindex "Oracle" "server list"
14096 This option provides a list of Oracle servers and associated connection data,
14097 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
14098 The option is available only if Exim has been built with Oracle support.
14101 .option percent_hack_domains main "domain list&!!" unset
14102 .cindex "&""percent hack""&"
14103 .cindex "source routing" "in email address"
14104 .cindex "address" "source-routed"
14105 The &"percent hack"& is the convention whereby a local part containing a
14106 percent sign is re-interpreted as a new email address, with the percent
14107 replaced by @. This is sometimes called &"source routing"&, though that term is
14108 also applied to RFC 2822 addresses that begin with an @ character. If this
14109 option is set, Exim implements the percent facility for those domains listed,
14110 but no others. This happens before an incoming SMTP address is tested against
14113 &*Warning*&: The &"percent hack"& has often been abused by people who are
14114 trying to get round relaying restrictions. For this reason, it is best avoided
14115 if at all possible. Unfortunately, a number of less security-conscious MTAs
14116 implement it unconditionally. If you are running Exim on a gateway host, and
14117 routing mail through to internal MTAs without processing the local parts, it is
14118 a good idea to reject recipient addresses with percent characters in their
14119 local parts. Exim's default configuration does this.
14122 .option perl_at_start main boolean false
14123 This option is available only when Exim is built with an embedded Perl
14124 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14127 .option perl_startup main string unset
14128 This option is available only when Exim is built with an embedded Perl
14129 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14132 .option pgsql_servers main "string list" unset
14133 .cindex "PostgreSQL lookup type" "server list"
14134 This option provides a list of PostgreSQL servers and associated connection
14135 data, to be used in conjunction with &(pgsql)& lookups (see section
14136 &<<SECID72>>&). The option is available only if Exim has been built with
14137 PostgreSQL support.
14140 .option pid_file_path main string&!! "set at compile time"
14141 .cindex "daemon" "pid file path"
14142 .cindex "pid file, path for"
14143 This option sets the name of the file to which the Exim daemon writes its
14144 process id. The string is expanded, so it can contain, for example, references
14147 pid_file_path = /var/log/$primary_hostname/exim.pid
14149 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
14151 The value set by the option can be overridden by the &%-oP%& command line
14152 option. A pid file is not written if a &"non-standard"& daemon is run by means
14153 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
14156 .option pipelining_advertise_hosts main "host list&!!" *
14157 .cindex "PIPELINING" "suppressing advertising"
14158 This option can be used to suppress the advertisement of the SMTP
14159 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
14160 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
14161 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
14162 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
14163 that clients will use it; &"out of order"& commands that are &"expected"& do
14164 not count as protocol errors (see &%smtp_max_synprot_errors%&).
14167 .option preserve_message_logs main boolean false
14168 .cindex "message logs" "preserving"
14169 If this option is set, message log files are not deleted when messages are
14170 completed. Instead, they are moved to a sub-directory of the spool directory
14171 called &_msglog.OLD_&, where they remain available for statistical or debugging
14172 purposes. This is a dangerous option to set on systems with any appreciable
14173 volume of mail. Use with care!
14176 .option primary_hostname main string "see below"
14177 .cindex "name" "of local host"
14178 .cindex "host" "name of local"
14179 .cindex "local host" "name of"
14180 .vindex "&$primary_hostname$&"
14181 This specifies the name of the current host. It is used in the default EHLO or
14182 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
14183 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
14184 The value is also used by default in some SMTP response messages from an Exim
14185 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
14187 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
14188 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
14189 contains only one component, Exim passes it to &[gethostbyname()]& (or
14190 &[getipnodebyname()]& when available) in order to obtain the fully qualified
14191 version. The variable &$primary_hostname$& contains the host name, whether set
14192 explicitly by this option, or defaulted.
14195 .option print_topbitchars main boolean false
14196 .cindex "printing characters"
14197 .cindex "8-bit characters"
14198 By default, Exim considers only those characters whose codes lie in the range
14199 32&--126 to be printing characters. In a number of circumstances (for example,
14200 when writing log entries) non-printing characters are converted into escape
14201 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
14202 is set, code values of 128 and above are also considered to be printing
14205 This option also affects the header syntax checks performed by the
14206 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
14207 the user's full name when constructing From: and Sender: addresses (as
14208 described in section &<<SECTconstr>>&). Setting this option can cause
14209 Exim to generate eight bit message headers that do not conform to the
14213 .option process_log_path main string unset
14214 .cindex "process log path"
14215 .cindex "log" "process log"
14216 .cindex "&'exiwhat'&"
14217 This option sets the name of the file to which an Exim process writes its
14218 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
14219 utility script. If this option is unset, the file called &_exim-process.info_&
14220 in Exim's spool directory is used. The ability to specify the name explicitly
14221 can be useful in environments where two different Exims are running, using
14222 different spool directories.
14225 .option prod_requires_admin main boolean true
14229 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
14230 admin user unless &%prod_requires_admin%& is set false. See also
14231 &%queue_list_requires_admin%&.
14234 .option qualify_domain main string "see below"
14235 .cindex "domain" "for qualifying addresses"
14236 .cindex "address" "qualification"
14237 This option specifies the domain name that is added to any envelope sender
14238 addresses that do not have a domain qualification. It also applies to
14239 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
14240 are accepted by default only for locally-generated messages. Qualification is
14241 also applied to addresses in header lines such as &'From:'& and &'To:'& for
14242 locally-generated messages, unless the &%-bnq%& command line option is used.
14244 Messages from external sources must always contain fully qualified addresses,
14245 unless the sending host matches &%sender_unqualified_hosts%& or
14246 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
14247 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
14248 necessary. Internally, Exim always works with fully qualified envelope
14249 addresses. If &%qualify_domain%& is not set, it defaults to the
14250 &%primary_hostname%& value.
14253 .option qualify_recipient main string "see below"
14254 This option allows you to specify a different domain for qualifying recipient
14255 addresses to the one that is used for senders. See &%qualify_domain%& above.
14259 .option queue_domains main "domain list&!!" unset
14260 .cindex "domain" "specifying non-immediate delivery"
14261 .cindex "queueing incoming messages"
14262 .cindex "message" "queueing certain domains"
14263 This option lists domains for which immediate delivery is not required.
14264 A delivery process is started whenever a message is received, but only those
14265 domains that do not match are processed. All other deliveries wait until the
14266 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
14269 .option queue_list_requires_admin main boolean true
14271 The &%-bp%& command-line option, which lists the messages that are on the
14272 queue, requires the caller to be an admin user unless
14273 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
14276 .option queue_only main boolean false
14277 .cindex "queueing incoming messages"
14278 .cindex "message" "queueing unconditionally"
14279 If &%queue_only%& is set, a delivery process is not automatically started
14280 whenever a message is received. Instead, the message waits on the queue for the
14281 next queue run. Even if &%queue_only%& is false, incoming messages may not get
14282 delivered immediately when certain conditions (such as heavy load) occur.
14284 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
14285 and &%-odi%& command line options override &%queue_only%& unless
14286 &%queue_only_override%& is set false. See also &%queue_only_file%&,
14287 &%queue_only_load%&, and &%smtp_accept_queue%&.
14290 .option queue_only_file main string unset
14291 .cindex "queueing incoming messages"
14292 .cindex "message" "queueing by file existence"
14293 This option can be set to a colon-separated list of absolute path names, each
14294 one optionally preceded by &"smtp"&. When Exim is receiving a message,
14295 it tests for the existence of each listed path using a call to &[stat()]&. For
14296 each path that exists, the corresponding queueing option is set.
14297 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
14298 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
14300 queue_only_file = smtp/some/file
14302 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
14303 &_/some/file_& exists.
14306 .option queue_only_load main fixed-point unset
14307 .cindex "load average"
14308 .cindex "queueing incoming messages"
14309 .cindex "message" "queueing by load"
14310 If the system load average is higher than this value, incoming messages from
14311 all sources are queued, and no automatic deliveries are started. If this
14312 happens during local or remote SMTP input, all subsequent messages received on
14313 the same SMTP connection are queued by default, whatever happens to the load in
14314 the meantime, but this can be changed by setting &%queue_only_load_latch%&
14317 Deliveries will subsequently be performed by queue runner processes. This
14318 option has no effect on ancient operating systems on which Exim cannot
14319 determine the load average. See also &%deliver_queue_load_max%& and
14320 &%smtp_load_reserve%&.
14323 .option queue_only_load_latch main boolean true
14324 .cindex "load average" "re-evaluating per message"
14325 When this option is true (the default), once one message has been queued
14326 because the load average is higher than the value set by &%queue_only_load%&,
14327 all subsequent messages received on the same SMTP connection are also queued.
14328 This is a deliberate choice; even though the load average may fall below the
14329 threshold, it doesn't seem right to deliver later messages on the same
14330 connection when not delivering earlier ones. However, there are special
14331 circumstances such as very long-lived connections from scanning appliances
14332 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
14333 should be set false. This causes the value of the load average to be
14334 re-evaluated for each message.
14337 .option queue_only_override main boolean true
14338 .cindex "queueing incoming messages"
14339 When this option is true, the &%-od%&&'x'& command line options override the
14340 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
14341 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
14342 to override; they are accepted, but ignored.
14345 .option queue_run_in_order main boolean false
14346 .cindex "queue runner" "processing messages in order"
14347 If this option is set, queue runs happen in order of message arrival instead of
14348 in an arbitrary order. For this to happen, a complete list of the entire queue
14349 must be set up before the deliveries start. When the queue is all held in a
14350 single directory (the default), a single list is created for both the ordered
14351 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
14352 single list is not created when &%queue_run_in_order%& is false. In this case,
14353 the sub-directories are processed one at a time (in a random order), and this
14354 avoids setting up one huge list for the whole queue. Thus, setting
14355 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
14356 when the queue is large, because of the extra work in setting up the single,
14357 large list. In most situations, &%queue_run_in_order%& should not be set.
14361 .option queue_run_max main integer 5
14362 .cindex "queue runner" "maximum number of"
14363 This controls the maximum number of queue runner processes that an Exim daemon
14364 can run simultaneously. This does not mean that it starts them all at once,
14365 but rather that if the maximum number are still running when the time comes to
14366 start another one, it refrains from starting another one. This can happen with
14367 very large queues and/or very sluggish deliveries. This option does not,
14368 however, interlock with other processes, so additional queue runners can be
14369 started by other means, or by killing and restarting the daemon.
14371 Setting this option to zero does not suppress queue runs; rather, it disables
14372 the limit, allowing any number of simultaneous queue runner processes to be
14373 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
14374 the daemon's command line.
14376 .option queue_smtp_domains main "domain list&!!" unset
14377 .cindex "queueing incoming messages"
14378 .cindex "message" "queueing remote deliveries"
14379 When this option is set, a delivery process is started whenever a message is
14380 received, routing is performed, and local deliveries take place.
14381 However, if any SMTP deliveries are required for domains that match
14382 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
14383 message waits on the queue for the next queue run. Since routing of the message
14384 has taken place, Exim knows to which remote hosts it must be delivered, and so
14385 when the queue run happens, multiple messages for the same host are delivered
14386 over a single SMTP connection. The &%-odqs%& command line option causes all
14387 SMTP deliveries to be queued in this way, and is equivalent to setting
14388 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
14392 .option receive_timeout main time 0s
14393 .cindex "timeout" "for non-SMTP input"
14394 This option sets the timeout for accepting a non-SMTP message, that is, the
14395 maximum time that Exim waits when reading a message on the standard input. If
14396 the value is zero, it will wait for ever. This setting is overridden by the
14397 &%-or%& command line option. The timeout for incoming SMTP messages is
14398 controlled by &%smtp_receive_timeout%&.
14400 .option received_header_text main string&!! "see below"
14401 .cindex "customizing" "&'Received:'& header"
14402 .cindex "&'Received:'& header line" "customizing"
14403 This string defines the contents of the &'Received:'& message header that is
14404 added to each message, except for the timestamp, which is automatically added
14405 on at the end (preceded by a semicolon). The string is expanded each time it is
14406 used. If the expansion yields an empty string, no &'Received:'& header line is
14407 added to the message. Otherwise, the string should start with the text
14408 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
14409 header lines. The default setting is:
14412 received_header_text = Received: \
14413 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
14414 {${if def:sender_ident \
14415 {from ${quote_local_part:$sender_ident} }}\
14416 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
14417 by $primary_hostname \
14418 ${if def:received_protocol {with $received_protocol}} \
14419 ${if def:tls_cipher {($tls_cipher)\n\t}}\
14420 (Exim $version_number)\n\t\
14421 ${if def:sender_address \
14422 {(envelope-from <$sender_address>)\n\t}}\
14423 id $message_exim_id\
14424 ${if def:received_for {\n\tfor $received_for}}
14427 The reference to the TLS cipher is omitted when Exim is built without TLS
14428 support. The use of conditional expansions ensures that this works for both
14429 locally generated messages and messages received from remote hosts, giving
14430 header lines such as the following:
14432 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
14433 by marley.carol.example with esmtp (Exim 4.00)
14434 (envelope-from <bob@carol.example>)
14435 id 16IOWa-00019l-00
14436 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
14437 Received: by scrooge.carol.example with local (Exim 4.00)
14438 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
14440 Until the body of the message has been received, the timestamp is the time when
14441 the message started to be received. Once the body has arrived, and all policy
14442 checks have taken place, the timestamp is updated to the time at which the
14443 message was accepted.
14446 .option received_headers_max main integer 30
14447 .cindex "loop" "prevention"
14448 .cindex "mail loop prevention"
14449 .cindex "&'Received:'& header line" "counting"
14450 When a message is to be delivered, the number of &'Received:'& headers is
14451 counted, and if it is greater than this parameter, a mail loop is assumed to
14452 have occurred, the delivery is abandoned, and an error message is generated.
14453 This applies to both local and remote deliveries.
14456 .option recipient_unqualified_hosts main "host list&!!" unset
14457 .cindex "unqualified addresses"
14458 .cindex "host" "unqualified addresses from"
14459 This option lists those hosts from which Exim is prepared to accept unqualified
14460 recipient addresses in message envelopes. The addresses are made fully
14461 qualified by the addition of the &%qualify_recipient%& value. This option also
14462 affects message header lines. Exim does not reject unqualified recipient
14463 addresses in headers, but it qualifies them only if the message came from a
14464 host that matches &%recipient_unqualified_hosts%&,
14465 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
14466 option was not set.
14469 .option recipients_max main integer 0
14470 .cindex "limit" "number of recipients"
14471 .cindex "recipient" "maximum number"
14472 If this option is set greater than zero, it specifies the maximum number of
14473 original recipients for any message. Additional recipients that are generated
14474 by aliasing or forwarding do not count. SMTP messages get a 452 response for
14475 all recipients over the limit; earlier recipients are delivered as normal.
14476 Non-SMTP messages with too many recipients are failed, and no deliveries are
14479 .cindex "RCPT" "maximum number of incoming"
14480 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
14481 RCPT commands in a single message.
14484 .option recipients_max_reject main boolean false
14485 If this option is set true, Exim rejects SMTP messages containing too many
14486 recipients by giving 552 errors to the surplus RCPT commands, and a 554
14487 error to the eventual DATA command. Otherwise (the default) it gives a 452
14488 error to the surplus RCPT commands and accepts the message on behalf of the
14489 initial set of recipients. The remote server should then re-send the message
14490 for the remaining recipients at a later time.
14493 .option remote_max_parallel main integer 2
14494 .cindex "delivery" "parallelism for remote"
14495 This option controls parallel delivery of one message to a number of remote
14496 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
14497 does all the remote deliveries for a message one by one. Otherwise, if a single
14498 message has to be delivered to more than one remote host, or if several copies
14499 have to be sent to the same remote host, up to &%remote_max_parallel%&
14500 deliveries are done simultaneously. If more than &%remote_max_parallel%&
14501 deliveries are required, the maximum number of processes are started, and as
14502 each one finishes, another is begun. The order of starting processes is the
14503 same as if sequential delivery were being done, and can be controlled by the
14504 &%remote_sort_domains%& option. If parallel delivery takes place while running
14505 with debugging turned on, the debugging output from each delivery process is
14506 tagged with its process id.
14508 This option controls only the maximum number of parallel deliveries for one
14509 message in one Exim delivery process. Because Exim has no central queue
14510 manager, there is no way of controlling the total number of simultaneous
14511 deliveries if the configuration allows a delivery attempt as soon as a message
14514 .cindex "number of deliveries"
14515 .cindex "delivery" "maximum number of"
14516 If you want to control the total number of deliveries on the system, you
14517 need to set the &%queue_only%& option. This ensures that all incoming messages
14518 are added to the queue without starting a delivery process. Then set up an Exim
14519 daemon to start queue runner processes at appropriate intervals (probably
14520 fairly often, for example, every minute), and limit the total number of queue
14521 runners by setting the &%queue_run_max%& parameter. Because each queue runner
14522 delivers only one message at a time, the maximum number of deliveries that can
14523 then take place at once is &%queue_run_max%& multiplied by
14524 &%remote_max_parallel%&.
14526 If it is purely remote deliveries you want to control, use
14527 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
14528 doing the SMTP routing before queueing, so that several messages for the same
14529 host will eventually get delivered down the same connection.
14532 .option remote_sort_domains main "domain list&!!" unset
14533 .cindex "sorting remote deliveries"
14534 .cindex "delivery" "sorting remote"
14535 When there are a number of remote deliveries for a message, they are sorted by
14536 domain into the order given by this list. For example,
14538 remote_sort_domains = *.cam.ac.uk:*.uk
14540 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
14541 then to those in the &%uk%& domain, then to any others.
14544 .option retry_data_expire main time 7d
14545 .cindex "hints database" "data expiry"
14546 This option sets a &"use before"& time on retry information in Exim's hints
14547 database. Any older retry data is ignored. This means that, for example, once a
14548 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
14552 .option retry_interval_max main time 24h
14553 .cindex "retry" "limit on interval"
14554 .cindex "limit" "on retry interval"
14555 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
14556 intervals between delivery attempts for messages that cannot be delivered
14557 straight away. This option sets an overall limit to the length of time between
14558 retries. It cannot be set greater than 24 hours; any attempt to do so forces
14562 .option return_path_remove main boolean true
14563 .cindex "&'Return-path:'& header line" "removing"
14564 RFC 2821, section 4.4, states that an SMTP server must insert a
14565 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
14566 The &'Return-path:'& header preserves the sender address as received in the
14567 MAIL command. This description implies that this header should not be present
14568 in an incoming message. If &%return_path_remove%& is true, any existing
14569 &'Return-path:'& headers are removed from messages at the time they are
14570 received. Exim's transports have options for adding &'Return-path:'& headers at
14571 the time of delivery. They are normally used only for final local deliveries.
14574 .option return_size_limit main integer 100K
14575 This option is an obsolete synonym for &%bounce_return_size_limit%&.
14578 .option rfc1413_hosts main "host list&!!" *
14580 .cindex "host" "for RFC 1413 calls"
14581 RFC 1413 identification calls are made to any client host which matches an item
14584 .option rfc1413_query_timeout main time 5s
14585 .cindex "RFC 1413" "query timeout"
14586 .cindex "timeout" "for RFC 1413 call"
14587 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
14588 no RFC 1413 calls are ever made.
14591 .option sender_unqualified_hosts main "host list&!!" unset
14592 .cindex "unqualified addresses"
14593 .cindex "host" "unqualified addresses from"
14594 This option lists those hosts from which Exim is prepared to accept unqualified
14595 sender addresses. The addresses are made fully qualified by the addition of
14596 &%qualify_domain%&. This option also affects message header lines. Exim does
14597 not reject unqualified addresses in headers that contain sender addresses, but
14598 it qualifies them only if the message came from a host that matches
14599 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
14600 using TCP/IP), and the &%-bnq%& option was not set.
14603 .option smtp_accept_keepalive main boolean true
14604 .cindex "keepalive" "on incoming connection"
14605 This option controls the setting of the SO_KEEPALIVE option on incoming
14606 TCP/IP socket connections. When set, it causes the kernel to probe idle
14607 connections periodically, by sending packets with &"old"& sequence numbers. The
14608 other end of the connection should send an acknowledgment if the connection is
14609 still okay or a reset if the connection has been aborted. The reason for doing
14610 this is that it has the beneficial effect of freeing up certain types of
14611 connection that can get stuck when the remote host is disconnected without
14612 tidying up the TCP/IP call properly. The keepalive mechanism takes several
14613 hours to detect unreachable hosts.
14617 .option smtp_accept_max main integer 20
14618 .cindex "limit" "incoming SMTP connections"
14619 .cindex "SMTP" "incoming connection count"
14621 This option specifies the maximum number of simultaneous incoming SMTP calls
14622 that Exim will accept. It applies only to the listening daemon; there is no
14623 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
14624 value is set to zero, no limit is applied. However, it is required to be
14625 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
14626 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
14628 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
14629 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
14630 that limit has not been reached for the client host, &%smtp_accept_reserve%&
14631 and &%smtp_load_reserve%& are then checked before accepting the connection.
14634 .option smtp_accept_max_nonmail main integer 10
14635 .cindex "limit" "non-mail SMTP commands"
14636 .cindex "SMTP" "limiting non-mail commands"
14637 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
14638 the connection if there are too many. This option defines &"too many"&. The
14639 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
14640 client looping sending EHLO, for example. The check is applied only if the
14641 client host matches &%smtp_accept_max_nonmail_hosts%&.
14643 When a new message is expected, one occurrence of RSET is not counted. This
14644 allows a client to send one RSET between messages (this is not necessary,
14645 but some clients do it). Exim also allows one uncounted occurrence of HELO
14646 or EHLO, and one occurrence of STARTTLS between messages. After
14647 starting up a TLS session, another EHLO is expected, and so it too is not
14648 counted. The first occurrence of AUTH in a connection, or immediately
14649 following STARTTLS is not counted. Otherwise, all commands other than
14650 MAIL, RCPT, DATA, and QUIT are counted.
14653 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
14654 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
14655 check by setting this option. The default value makes it apply to all hosts. By
14656 changing the value, you can exclude any badly-behaved hosts that you have to
14660 . Allow this long option name to split; give it unsplit as a fifth argument
14661 . for the automatic .oindex that is generated by .option.
14663 .option "smtp_accept_max_per_ &~&~connection" main integer 1000 &&&
14664 smtp_accept_max_per_connection
14665 .cindex "SMTP" "limiting incoming message count"
14666 .cindex "limit" "messages per SMTP connection"
14667 The value of this option limits the number of MAIL commands that Exim is
14668 prepared to accept over a single SMTP connection, whether or not each command
14669 results in the transfer of a message. After the limit is reached, a 421
14670 response is given to subsequent MAIL commands. This limit is a safety
14671 precaution against a client that goes mad (incidents of this type have been
14675 .option smtp_accept_max_per_host main string&!! unset
14676 .cindex "limit" "SMTP connections from one host"
14677 .cindex "host" "limiting SMTP connections from"
14678 This option restricts the number of simultaneous IP connections from a single
14679 host (strictly, from a single IP address) to the Exim daemon. The option is
14680 expanded, to enable different limits to be applied to different hosts by
14681 reference to &$sender_host_address$&. Once the limit is reached, additional
14682 connection attempts from the same host are rejected with error code 421. This
14683 is entirely independent of &%smtp_accept_reserve%&. The option's default value
14684 of zero imposes no limit. If this option is set greater than zero, it is
14685 required that &%smtp_accept_max%& be non-zero.
14687 &*Warning*&: When setting this option you should not use any expansion
14688 constructions that take an appreciable amount of time. The expansion and test
14689 happen in the main daemon loop, in order to reject additional connections
14690 without forking additional processes (otherwise a denial-of-service attack
14691 could cause a vast number or processes to be created). While the daemon is
14692 doing this processing, it cannot accept any other incoming connections.
14696 .option smtp_accept_queue main integer 0
14697 .cindex "SMTP" "incoming connection count"
14698 .cindex "queueing incoming messages"
14699 .cindex "message" "queueing by SMTP connection count"
14700 If the number of simultaneous incoming SMTP connections being handled via the
14701 listening daemon exceeds this value, messages received by SMTP are just placed
14702 on the queue; no delivery processes are started automatically. The count is
14703 fixed at the start of an SMTP connection. It cannot be updated in the
14704 subprocess that receives messages, and so the queueing or not queueing applies
14705 to all messages received in the same connection.
14707 A value of zero implies no limit, and clearly any non-zero value is useful only
14708 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
14709 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
14710 various &%-od%&&'x'& command line options.
14713 . Allow this long option name to split; give it unsplit as a fifth argument
14714 . for the automatic .oindex that is generated by .option.
14716 .option "smtp_accept_queue_per_ &~&~connection" main integer 10 &&&
14717 smtp_accept_queue_per_connection
14718 .cindex "queueing incoming messages"
14719 .cindex "message" "queueing by message count"
14720 This option limits the number of delivery processes that Exim starts
14721 automatically when receiving messages via SMTP, whether via the daemon or by
14722 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
14723 and the number of messages received in a single SMTP session exceeds this
14724 number, subsequent messages are placed on the queue, but no delivery processes
14725 are started. This helps to limit the number of Exim processes when a server
14726 restarts after downtime and there is a lot of mail waiting for it on other
14727 systems. On large systems, the default should probably be increased, and on
14728 dial-in client systems it should probably be set to zero (that is, disabled).
14731 .option smtp_accept_reserve main integer 0
14732 .cindex "SMTP" "incoming call count"
14733 .cindex "host" "reserved"
14734 When &%smtp_accept_max%& is set greater than zero, this option specifies a
14735 number of SMTP connections that are reserved for connections from the hosts
14736 that are specified in &%smtp_reserve_hosts%&. The value set in
14737 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
14738 restricted to this number of connections; the option specifies a minimum number
14739 of connection slots for them, not a maximum. It is a guarantee that this group
14740 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
14741 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
14744 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
14745 set to 5, once there are 45 active connections (from any hosts), new
14746 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
14747 provided the other criteria for acceptance are met.
14750 .option smtp_active_hostname main string&!! unset
14751 .cindex "host" "name in SMTP responses"
14752 .cindex "SMTP" "host name in responses"
14753 .vindex "&$primary_hostname$&"
14754 This option is provided for multi-homed servers that want to masquerade as
14755 several different hosts. At the start of an incoming SMTP connection, its value
14756 is expanded and used instead of the value of &$primary_hostname$& in SMTP
14757 responses. For example, it is used as domain name in the response to an
14758 incoming HELO or EHLO command.
14760 .vindex "&$smtp_active_hostname$&"
14761 The active hostname is placed in the &$smtp_active_hostname$& variable, which
14762 is saved with any messages that are received. It is therefore available for use
14763 in routers and transports when the message is later delivered.
14765 If this option is unset, or if its expansion is forced to fail, or if the
14766 expansion results in an empty string, the value of &$primary_hostname$& is
14767 used. Other expansion failures cause a message to be written to the main and
14768 panic logs, and the SMTP command receives a temporary error. Typically, the
14769 value of &%smtp_active_hostname%& depends on the incoming interface address.
14772 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
14773 {cox.mydomain}{box.mydomain}}
14776 Although &$smtp_active_hostname$& is primarily concerned with incoming
14777 messages, it is also used as the default for HELO commands in callout
14778 verification if there is no remote transport from which to obtain a
14779 &%helo_data%& value.
14781 .option smtp_banner main string&!! "see below"
14782 .cindex "SMTP" "welcome banner"
14783 .cindex "banner for SMTP"
14784 .cindex "welcome banner for SMTP"
14785 .cindex "customizing" "SMTP banner"
14786 This string, which is expanded every time it is used, is output as the initial
14787 positive response to an SMTP connection. The default setting is:
14789 smtp_banner = $smtp_active_hostname ESMTP Exim \
14790 $version_number $tod_full
14792 Failure to expand the string causes a panic error. If you want to create a
14793 multiline response to the initial SMTP connection, use &"\n"& in the string at
14794 appropriate points, but not at the end. Note that the 220 code is not included
14795 in this string. Exim adds it automatically (several times in the case of a
14796 multiline response).
14799 .option smtp_check_spool_space main boolean true
14800 .cindex "checking disk space"
14801 .cindex "disk space, checking"
14802 .cindex "spool directory" "checking space"
14803 When this option is set, if an incoming SMTP session encounters the SIZE
14804 option on a MAIL command, it checks that there is enough space in the
14805 spool directory's partition to accept a message of that size, while still
14806 leaving free the amount specified by &%check_spool_space%& (even if that value
14807 is zero). If there isn't enough space, a temporary error code is returned.
14810 .option smtp_connect_backlog main integer 20
14811 .cindex "connection backlog"
14812 .cindex "SMTP" "connection backlog"
14813 .cindex "backlog of connections"
14814 This option specifies a maximum number of waiting SMTP connections. Exim passes
14815 this value to the TCP/IP system when it sets up its listener. Once this number
14816 of connections are waiting for the daemon's attention, subsequent connection
14817 attempts are refused at the TCP/IP level. At least, that is what the manuals
14818 say; in some circumstances such connection attempts have been observed to time
14819 out instead. For large systems it is probably a good idea to increase the
14820 value (to 50, say). It also gives some protection against denial-of-service
14821 attacks by SYN flooding.
14824 .option smtp_enforce_sync main boolean true
14825 .cindex "SMTP" "synchronization checking"
14826 .cindex "synchronization checking in SMTP"
14827 The SMTP protocol specification requires the client to wait for a response from
14828 the server at certain points in the dialogue. Without PIPELINING these
14829 synchronization points are after every command; with PIPELINING they are
14830 fewer, but they still exist.
14832 Some spamming sites send out a complete set of SMTP commands without waiting
14833 for any response. Exim protects against this by rejecting a message if the
14834 client has sent further input when it should not have. The error response &"554
14835 SMTP synchronization error"& is sent, and the connection is dropped. Testing
14836 for this error cannot be perfect because of transmission delays (unexpected
14837 input may be on its way but not yet received when Exim checks). However, it
14838 does detect many instances.
14840 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
14841 If you want to disable the check selectively (for example, only for certain
14842 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
14843 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
14847 .option smtp_etrn_command main string&!! unset
14848 .cindex "ETRN" "command to be run"
14849 .vindex "&$domain$&"
14850 If this option is set, the given command is run whenever an SMTP ETRN
14851 command is received from a host that is permitted to issue such commands (see
14852 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
14853 are independently expanded. The expansion variable &$domain$& is set to the
14854 argument of the ETRN command, and no syntax checking is done on it. For
14857 smtp_etrn_command = /etc/etrn_command $domain \
14858 $sender_host_address
14860 A new process is created to run the command, but Exim does not wait for it to
14861 complete. Consequently, its status cannot be checked. If the command cannot be
14862 run, a line is written to the panic log, but the ETRN caller still receives
14863 a 250 success response. Exim is normally running under its own uid when
14864 receiving SMTP, so it is not possible for it to change the uid before running
14868 .option smtp_etrn_serialize main boolean true
14869 .cindex "ETRN" "serializing"
14870 When this option is set, it prevents the simultaneous execution of more than
14871 one identical command as a result of ETRN in an SMTP connection. See
14872 section &<<SECTETRN>>& for details.
14875 .option smtp_load_reserve main fixed-point unset
14876 .cindex "load average"
14877 If the system load average ever gets higher than this, incoming SMTP calls are
14878 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
14879 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
14880 the load is over the limit. The option has no effect on ancient operating
14881 systems on which Exim cannot determine the load average. See also
14882 &%deliver_queue_load_max%& and &%queue_only_load%&.
14886 .option smtp_max_synprot_errors main integer 3
14887 .cindex "SMTP" "limiting syntax and protocol errors"
14888 .cindex "limit" "SMTP syntax and protocol errors"
14889 Exim rejects SMTP commands that contain syntax or protocol errors. In
14890 particular, a syntactically invalid email address, as in this command:
14892 RCPT TO:<abc xyz@a.b.c>
14894 causes immediate rejection of the command, before any other tests are done.
14895 (The ACL cannot be run if there is no valid address to set up for it.) An
14896 example of a protocol error is receiving RCPT before MAIL. If there are
14897 too many syntax or protocol errors in one SMTP session, the connection is
14898 dropped. The limit is set by this option.
14900 .cindex "PIPELINING" "expected errors"
14901 When the PIPELINING extension to SMTP is in use, some protocol errors are
14902 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
14903 Exim assumes that PIPELINING will be used if it advertises it (see
14904 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
14905 not count towards the limit.
14909 .option smtp_max_unknown_commands main integer 3
14910 .cindex "SMTP" "limiting unknown commands"
14911 .cindex "limit" "unknown SMTP commands"
14912 If there are too many unrecognized commands in an incoming SMTP session, an
14913 Exim server drops the connection. This is a defence against some kinds of abuse
14916 into making connections to SMTP ports; in these circumstances, a number of
14917 non-SMTP command lines are sent first.
14921 .option smtp_ratelimit_hosts main "host list&!!" unset
14922 .cindex "SMTP" "rate limiting"
14923 .cindex "limit" "rate of message arrival"
14924 .cindex "RCPT" "rate limiting"
14925 Some sites find it helpful to be able to limit the rate at which certain hosts
14926 can send them messages, and the rate at which an individual message can specify
14929 Exim has two rate-limiting facilities. This section describes the older
14930 facility, which can limit rates within a single connection. The newer
14931 &%ratelimit%& ACL condition can limit rates across all connections. See section
14932 &<<SECTratelimiting>>& for details of the newer facility.
14934 When a host matches &%smtp_ratelimit_hosts%&, the values of
14935 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
14936 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
14937 respectively. Each option, if set, must contain a set of four comma-separated
14941 A threshold, before which there is no rate limiting.
14943 An initial time delay. Unlike other times in Exim, numbers with decimal
14944 fractional parts are allowed here.
14946 A factor by which to increase the delay each time.
14948 A maximum value for the delay. This should normally be less than 5 minutes,
14949 because after that time, the client is liable to timeout the SMTP command.
14952 For example, these settings have been used successfully at the site which
14953 first suggested this feature, for controlling mail from their customers:
14955 smtp_ratelimit_mail = 2,0.5s,1.05,4m
14956 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
14958 The first setting specifies delays that are applied to MAIL commands after
14959 two have been received over a single connection. The initial delay is 0.5
14960 seconds, increasing by a factor of 1.05 each time. The second setting applies
14961 delays to RCPT commands when more than four occur in a single message.
14964 .option smtp_ratelimit_mail main string unset
14965 See &%smtp_ratelimit_hosts%& above.
14968 .option smtp_ratelimit_rcpt main string unset
14969 See &%smtp_ratelimit_hosts%& above.
14972 .option smtp_receive_timeout main time 5m
14973 .cindex "timeout" "for SMTP input"
14974 .cindex "SMTP" "input timeout"
14975 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
14976 input, including batch SMTP. If a line of input (either an SMTP command or a
14977 data line) is not received within this time, the SMTP connection is dropped and
14978 the message is abandoned.
14979 A line is written to the log containing one of the following messages:
14981 SMTP command timeout on connection from...
14982 SMTP data timeout on connection from...
14984 The former means that Exim was expecting to read an SMTP command; the latter
14985 means that it was in the DATA phase, reading the contents of a message.
14989 The value set by this option can be overridden by the
14990 &%-os%& command-line option. A setting of zero time disables the timeout, but
14991 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
14992 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
14993 timeout is controlled by &%receive_timeout%& and &%-or%&.
14996 .option smtp_reserve_hosts main "host list&!!" unset
14997 This option defines hosts for which SMTP connections are reserved; see
14998 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
15001 .option smtp_return_error_details main boolean false
15002 .cindex "SMTP" "details policy failures"
15003 .cindex "policy control" "rejection, returning details"
15004 In the default state, Exim uses bland messages such as
15005 &"Administrative prohibition"& when it rejects SMTP commands for policy
15006 reasons. Many sysadmins like this because it gives away little information
15007 to spammers. However, some other sysadmins who are applying strict checking
15008 policies want to give out much fuller information about failures. Setting
15009 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
15010 example, instead of &"Administrative prohibition"&, it might give:
15012 550-Rejected after DATA: '>' missing at end of address:
15013 550 failing address in "From" header is: <user@dom.ain
15016 .option spamd_address main string "see below"
15017 This option is available when Exim is compiled with the content-scanning
15018 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
15019 The default value is
15023 See section &<<SECTscanspamass>>& for more details.
15027 .option split_spool_directory main boolean false
15028 .cindex "multiple spool directories"
15029 .cindex "spool directory" "split"
15030 .cindex "directories, multiple"
15031 If this option is set, it causes Exim to split its input directory into 62
15032 subdirectories, each with a single alphanumeric character as its name. The
15033 sixth character of the message id is used to allocate messages to
15034 subdirectories; this is the least significant base-62 digit of the time of
15035 arrival of the message.
15037 Splitting up the spool in this way may provide better performance on systems
15038 where there are long mail queues, by reducing the number of files in any one
15039 directory. The msglog directory is also split up in a similar way to the input
15040 directory; however, if &%preserve_message_logs%& is set, all old msglog files
15041 are still placed in the single directory &_msglog.OLD_&.
15043 It is not necessary to take any special action for existing messages when
15044 changing &%split_spool_directory%&. Exim notices messages that are in the
15045 &"wrong"& place, and continues to process them. If the option is turned off
15046 after a period of being on, the subdirectories will eventually empty and be
15047 automatically deleted.
15049 When &%split_spool_directory%& is set, the behaviour of queue runner processes
15050 changes. Instead of creating a list of all messages in the queue, and then
15051 trying to deliver each one in turn, it constructs a list of those in one
15052 sub-directory and tries to deliver them, before moving on to the next
15053 sub-directory. The sub-directories are processed in a random order. This
15054 spreads out the scanning of the input directories, and uses less memory. It is
15055 particularly beneficial when there are lots of messages on the queue. However,
15056 if &%queue_run_in_order%& is set, none of this new processing happens. The
15057 entire queue has to be scanned and sorted before any deliveries can start.
15060 .option spool_directory main string&!! "set at compile time"
15061 .cindex "spool directory" "path to"
15062 This defines the directory in which Exim keeps its spool, that is, the messages
15063 it is waiting to deliver. The default value is taken from the compile-time
15064 configuration setting, if there is one. If not, this option must be set. The
15065 string is expanded, so it can contain, for example, a reference to
15066 &$primary_hostname$&.
15068 If the spool directory name is fixed on your installation, it is recommended
15069 that you set it at build time rather than from this option, particularly if the
15070 log files are being written to the spool directory (see &%log_file_path%&).
15071 Otherwise log files cannot be used for errors that are detected early on, such
15072 as failures in the configuration file.
15074 By using this option to override the compiled-in path, it is possible to run
15075 tests of Exim without using the standard spool.
15077 .option sqlite_lock_timeout main time 5s
15078 .cindex "sqlite lookup type" "lock timeout"
15079 This option controls the timeout that the &(sqlite)& lookup uses when trying to
15080 access an SQLite database. See section &<<SECTsqlite>>& for more details.
15082 .option strict_acl_vars main boolean false
15083 .cindex "&ACL;" "variables, handling unset"
15084 This option controls what happens if a syntactically valid but undefined ACL
15085 variable is referenced. If it is false (the default), an empty string
15086 is substituted; if it is true, an error is generated. See section
15087 &<<SECTaclvariables>>& for details of ACL variables.
15089 .option strip_excess_angle_brackets main boolean false
15090 .cindex "angle brackets, excess"
15091 If this option is set, redundant pairs of angle brackets round &"route-addr"&
15092 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
15093 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
15094 passed on to another MTA, the excess angle brackets are not passed on. If this
15095 option is not set, multiple pairs of angle brackets cause a syntax error.
15098 .option strip_trailing_dot main boolean false
15099 .cindex "trailing dot on domain"
15100 .cindex "dot" "trailing on domain"
15101 If this option is set, a trailing dot at the end of a domain in an address is
15102 ignored. If this is in the envelope and the message is passed on to another
15103 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
15104 domain causes a syntax error.
15105 However, addresses in header lines are checked only when an ACL requests header
15109 .option syslog_duplication main boolean true
15110 .cindex "syslog" "duplicate log lines; suppressing"
15111 When Exim is logging to syslog, it writes the log lines for its three
15112 separate logs at different syslog priorities so that they can in principle
15113 be separated on the logging hosts. Some installations do not require this
15114 separation, and in those cases, the duplication of certain log lines is a
15115 nuisance. If &%syslog_duplication%& is set false, only one copy of any
15116 particular log line is written to syslog. For lines that normally go to
15117 both the main log and the reject log, the reject log version (possibly
15118 containing message header lines) is written, at LOG_NOTICE priority.
15119 Lines that normally go to both the main and the panic log are written at
15120 the LOG_ALERT priority.
15123 .option syslog_facility main string unset
15124 .cindex "syslog" "facility; setting"
15125 This option sets the syslog &"facility"& name, used when Exim is logging to
15126 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
15127 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
15128 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
15129 details of Exim's logging.
15133 .option syslog_processname main string &`exim`&
15134 .cindex "syslog" "process name; setting"
15135 This option sets the syslog &"ident"& name, used when Exim is logging to
15136 syslog. The value must be no longer than 32 characters. See chapter
15137 &<<CHAPlog>>& for details of Exim's logging.
15141 .option syslog_timestamp main boolean true
15142 .cindex "syslog" "timestamps"
15143 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
15144 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
15145 details of Exim's logging.
15148 .option system_filter main string&!! unset
15149 .cindex "filter" "system filter"
15150 .cindex "system filter" "specifying"
15151 .cindex "Sieve filter" "not available for system filter"
15152 This option specifies an Exim filter file that is applied to all messages at
15153 the start of each delivery attempt, before any routing is done. System filters
15154 must be Exim filters; they cannot be Sieve filters. If the system filter
15155 generates any deliveries to files or pipes, or any new mail messages, the
15156 appropriate &%system_filter_..._transport%& option(s) must be set, to define
15157 which transports are to be used. Details of this facility are given in chapter
15158 &<<CHAPsystemfilter>>&.
15161 .option system_filter_directory_transport main string&!! unset
15162 .vindex "&$address_file$&"
15163 This sets the name of the transport driver that is to be used when the
15164 &%save%& command in a system message filter specifies a path ending in &"/"&,
15165 implying delivery of each message into a separate file in some directory.
15166 During the delivery, the variable &$address_file$& contains the path name.
15169 .option system_filter_file_transport main string&!! unset
15170 .cindex "file" "transport for system filter"
15171 This sets the name of the transport driver that is to be used when the &%save%&
15172 command in a system message filter specifies a path not ending in &"/"&. During
15173 the delivery, the variable &$address_file$& contains the path name.
15175 .option system_filter_group main string unset
15176 .cindex "gid (group id)" "system filter"
15177 This option is used only when &%system_filter_user%& is also set. It sets the
15178 gid under which the system filter is run, overriding any gid that is associated
15179 with the user. The value may be numerical or symbolic.
15181 .option system_filter_pipe_transport main string&!! unset
15182 .cindex "&(pipe)& transport" "for system filter"
15183 .vindex "&$address_pipe$&"
15184 This specifies the transport driver that is to be used when a &%pipe%& command
15185 is used in a system filter. During the delivery, the variable &$address_pipe$&
15186 contains the pipe command.
15189 .option system_filter_reply_transport main string&!! unset
15190 .cindex "&(autoreply)& transport" "for system filter"
15191 This specifies the transport driver that is to be used when a &%mail%& command
15192 is used in a system filter.
15194 .option system_filter_user main string unset
15195 .cindex "uid (user id)" "system filter"
15196 If this option is not set, the system filter is run in the main Exim delivery
15197 process, as root. When the option is set, the system filter runs in a separate
15198 process, as the given user. Unless the string consists entirely of digits, it
15199 is looked up in the password data. Failure to find the named user causes a
15200 configuration error. The gid is either taken from the password data, or
15201 specified by &%system_filter_group%&. When the uid is specified numerically,
15202 &%system_filter_group%& is required to be set.
15204 If the system filter generates any pipe, file, or reply deliveries, the uid
15205 under which the filter is run is used when transporting them, unless a
15206 transport option overrides. Normally you should set &%system_filter_user%& if
15207 your system filter generates these kinds of delivery.
15210 .option tcp_nodelay main boolean true
15211 .cindex "daemon" "TCP_NODELAY on sockets"
15212 .cindex "Nagle algorithm"
15213 .cindex "TCP_NODELAY on listening sockets"
15214 If this option is set false, it stops the Exim daemon setting the
15215 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
15216 turns off the &"Nagle algorithm"&, which is a way of improving network
15217 performance in interactive (character-by-character) situations. Turning it off
15218 should improve Exim's performance a bit, so that is what happens by default.
15219 However, it appears that some broken clients cannot cope, and time out. Hence
15220 this option. It affects only those sockets that are set up for listening by the
15221 daemon. Sockets created by the smtp transport for delivering mail always set
15225 .option timeout_frozen_after main time 0s
15226 .cindex "frozen messages" "timing out"
15227 .cindex "timeout" "frozen messages"
15228 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
15229 message of any kind that has been on the queue for longer than the given time
15230 is automatically cancelled at the next queue run. If the frozen message is a
15231 bounce message, it is just discarded; otherwise, a bounce is sent to the
15232 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
15233 If you want to timeout frozen bounce messages earlier than other kinds of
15234 frozen message, see &%ignore_bounce_errors_after%&.
15236 &*Note:*& the default value of zero means no timeouts; with this setting,
15237 frozen messages remain on the queue forever (except for any frozen bounce
15238 messages that are released by &%ignore_bounce_errors_after%&).
15241 .option timezone main string unset
15242 .cindex "timezone, setting"
15243 The value of &%timezone%& is used to set the environment variable TZ while
15244 running Exim (if it is different on entry). This ensures that all timestamps
15245 created by Exim are in the required timezone. If you want all your timestamps
15246 to be in UTC (aka GMT) you should set
15250 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
15251 or, if that is not set, from the value of the TZ environment variable when Exim
15252 is built. If &%timezone%& is set to the empty string, either at build or run
15253 time, any existing TZ variable is removed from the environment when Exim
15254 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
15255 unfortunately not all, operating systems.
15258 .option tls_advertise_hosts main "host list&!!" unset
15259 .cindex "TLS" "advertising"
15260 .cindex "encryption" "on SMTP connection"
15261 .cindex "SMTP" "encrypted connection"
15262 When Exim is built with support for TLS encrypted connections, the availability
15263 of the STARTTLS command to set up an encrypted session is advertised in
15264 response to EHLO only to those client hosts that match this option. See
15265 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
15268 .option tls_certificate main string&!! unset
15269 .cindex "TLS" "server certificate; location of"
15270 .cindex "certificate" "server, location of"
15271 The value of this option is expanded, and must then be the absolute path to a
15272 file which contains the server's certificates. The server's private key is also
15273 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
15274 &<<CHAPTLS>>& for further details.
15276 &*Note*&: The certificates defined by this option are used only when Exim is
15277 receiving incoming messages as a server. If you want to supply certificates for
15278 use when sending messages as a client, you must set the &%tls_certificate%&
15279 option in the relevant &(smtp)& transport.
15282 .option tls_crl main string&!! unset
15283 .cindex "TLS" "server certificate revocation list"
15284 .cindex "certificate" "revocation list for server"
15285 This option specifies a certificate revocation list. The expanded value must
15286 be the name of a file that contains a CRL in PEM format.
15289 .option tls_dhparam main string&!! unset
15290 .cindex "TLS" "D-H parameters for server"
15291 The value of this option is expanded, and must then be the absolute path to
15292 a file which contains the server's DH parameter values.
15293 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
15294 ignored. See section &<<SECTopenvsgnu>>& for further details.
15297 .option tls_on_connect_ports main "string list" unset
15298 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
15299 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
15300 set up without waiting for the client to issue a STARTTLS command. For
15301 further details, see section &<<SECTsupobssmt>>&.
15305 .option tls_privatekey main string&!! unset
15306 .cindex "TLS" "server private key; location of"
15307 The value of this option is expanded, and must then be the absolute path to a
15308 file which contains the server's private key. If this option is unset, or if
15309 the expansion is forced to fail, or the result is an empty string, the private
15310 key is assumed to be in the same file as the server's certificates. See chapter
15311 &<<CHAPTLS>>& for further details.
15314 .option tls_remember_esmtp main boolean false
15315 .cindex "TLS" "esmtp state; remembering"
15316 .cindex "TLS" "broken clients"
15317 If this option is set true, Exim violates the RFCs by remembering that it is in
15318 &"esmtp"& state after successfully negotiating a TLS session. This provides
15319 support for broken clients that fail to send a new EHLO after starting a
15323 .option tls_require_ciphers main string&!! unset
15324 .cindex "TLS" "requiring specific ciphers"
15325 .cindex "cipher" "requiring specific"
15326 This option controls which ciphers can be used for incoming TLS connections.
15327 The &(smtp)& transport has an option of the same name for controlling outgoing
15328 connections. This option is expanded for each connection, so can be varied for
15329 different clients if required. The value of this option must be a list of
15330 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
15331 in somewhat different ways. If GnuTLS is being used, the client controls the
15332 preference order of the available ciphers. Details are given in sections
15333 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
15336 .option tls_try_verify_hosts main "host list&!!" unset
15337 .cindex "TLS" "client certificate verification"
15338 .cindex "certificate" "verification of client"
15339 See &%tls_verify_hosts%& below.
15342 .option tls_verify_certificates main string&!! unset
15343 .cindex "TLS" "client certificate verification"
15344 .cindex "certificate" "verification of client"
15345 The value of this option is expanded, and must then be the absolute path to
15346 a file containing permitted certificates for clients that
15347 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
15348 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
15349 directory containing certificate files. This does not work with GnuTLS; the
15350 option must be set to the name of a single file if you are using GnuTLS.
15353 .option tls_verify_hosts main "host list&!!" unset
15354 .cindex "TLS" "client certificate verification"
15355 .cindex "certificate" "verification of client"
15356 This option, along with &%tls_try_verify_hosts%&, controls the checking of
15357 certificates from clients. The expected certificates are defined by
15358 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
15359 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
15360 &%tls_verify_certificates%& is not set.
15362 Any client that matches &%tls_verify_hosts%& is constrained by
15363 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
15364 present one of the listed certificates. If it does not, the connection is
15365 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
15366 the host to use TLS. It can still send SMTP commands through unencrypted
15367 connections. Forcing a client to use TLS has to be done separately using an
15368 ACL to reject inappropriate commands when the connection is not encrypted.
15370 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
15371 matches this option (but not &%tls_verify_hosts%&), Exim requests a
15372 certificate and checks it against &%tls_verify_certificates%&, but does not
15373 abort the connection if there is no certificate or if it does not match. This
15374 state can be detected in an ACL, which makes it possible to implement policies
15375 such as &"accept for relay only if a verified certificate has been received,
15376 but accept for local delivery if encrypted, even without a verified
15379 Client hosts that match neither of these lists are not asked to present
15383 .option trusted_groups main "string list&!!" unset
15384 .cindex "trusted groups"
15385 .cindex "groups" "trusted"
15386 This option is expanded just once, at the start of Exim's processing. If this
15387 option is set, any process that is running in one of the listed groups, or
15388 which has one of them as a supplementary group, is trusted. The groups can be
15389 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
15390 details of what trusted callers are permitted to do. If neither
15391 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
15394 .option trusted_users main "string list&!!" unset
15395 .cindex "trusted users"
15396 .cindex "user" "trusted"
15397 This option is expanded just once, at the start of Exim's processing. If this
15398 option is set, any process that is running as one of the listed users is
15399 trusted. The users can be specified numerically or by name. See section
15400 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
15401 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
15402 Exim user are trusted.
15404 .option unknown_login main string&!! unset
15405 .cindex "uid (user id)" "unknown caller"
15406 .vindex "&$caller_uid$&"
15407 This is a specialized feature for use in unusual configurations. By default, if
15408 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
15409 gives up. The &%unknown_login%& option can be used to set a login name to be
15410 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
15411 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
15412 is used for the user's real name (gecos field), unless this has been set by the
15415 .option unknown_username main string unset
15416 See &%unknown_login%&.
15418 .option untrusted_set_sender main "address list&!!" unset
15419 .cindex "trusted users"
15420 .cindex "sender" "setting by untrusted user"
15421 .cindex "untrusted user setting sender"
15422 .cindex "user" "untrusted setting sender"
15423 .cindex "envelope sender"
15424 When an untrusted user submits a message to Exim using the standard input, Exim
15425 normally creates an envelope sender address from the user's login and the
15426 default qualification domain. Data from the &%-f%& option (for setting envelope
15427 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
15428 is used) is ignored.
15430 However, untrusted users are permitted to set an empty envelope sender address,
15431 to declare that a message should never generate any bounces. For example:
15433 exim -f '<>' user@domain.example
15435 .vindex "&$sender_ident$&"
15436 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
15437 other envelope sender addresses in a controlled way. When it is set, untrusted
15438 users are allowed to set envelope sender addresses that match any of the
15439 patterns in the list. Like all address lists, the string is expanded. The
15440 identity of the user is in &$sender_ident$&, so you can, for example, restrict
15441 users to setting senders that start with their login ids
15442 followed by a hyphen
15443 by a setting like this:
15445 untrusted_set_sender = ^$sender_ident-
15447 If you want to allow untrusted users to set envelope sender addresses without
15448 restriction, you can use
15450 untrusted_set_sender = *
15452 The &%untrusted_set_sender%& option applies to all forms of local input, but
15453 only to the setting of the envelope sender. It does not permit untrusted users
15454 to use the other options which trusted user can use to override message
15455 parameters. Furthermore, it does not stop Exim from removing an existing
15456 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
15457 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
15458 overriding these actions. The handling of the &'Sender:'& header is also
15459 described in section &<<SECTthesenhea>>&.
15461 The log line for a message's arrival shows the envelope sender following
15462 &"<="&. For local messages, the user's login always follows, after &"U="&. In
15463 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
15464 envelope sender address, the user's login is shown in parentheses after the
15468 .option uucp_from_pattern main string "see below"
15469 .cindex "&""From""& line"
15470 .cindex "UUCP" "&""From""& line"
15471 Some applications that pass messages to an MTA via a command line interface use
15472 an initial line starting with &"From&~"& to pass the envelope sender. In
15473 particular, this is used by UUCP software. Exim recognizes such a line by means
15474 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
15475 matches, the sender address is constructed by expanding the contents of
15476 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
15477 default pattern recognizes lines in the following two forms:
15479 From ph10 Fri Jan 5 12:35 GMT 1996
15480 From ph10 Fri, 7 Jan 97 14:00:00 GMT
15482 The pattern can be seen by running
15484 exim -bP uucp_from_pattern
15486 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
15487 year in the second case. The first word after &"From&~"& is matched in the
15488 regular expression by a parenthesized subpattern. The default value for
15489 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
15490 (&"ph10"& in the example above) as the message's sender. See also
15491 &%ignore_fromline_hosts%&.
15494 .option uucp_from_sender main string&!! &`$1`&
15495 See &%uucp_from_pattern%& above.
15498 .option warn_message_file main string unset
15499 .cindex "warning of delay" "customizing the message"
15500 .cindex "customizing" "warning message"
15501 This option defines a template file containing paragraphs of text to be used
15502 for constructing the warning message which is sent by Exim when a message has
15503 been on the queue for a specified amount of time, as specified by
15504 &%delay_warning%&. Details of the file's contents are given in chapter
15505 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
15508 .option write_rejectlog main boolean true
15509 .cindex "reject log" "disabling"
15510 If this option is set false, Exim no longer writes anything to the reject log.
15511 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
15512 .ecindex IIDconfima
15513 .ecindex IIDmaiconf
15518 . ////////////////////////////////////////////////////////////////////////////
15519 . ////////////////////////////////////////////////////////////////////////////
15521 .chapter "Generic options for routers" "CHAProutergeneric"
15522 .scindex IIDgenoprou1 "options" "generic; for routers"
15523 .scindex IIDgenoprou2 "generic options" "router"
15524 This chapter describes the generic options that apply to all routers.
15525 Those that are preconditions are marked with ‡ in the &"use"& field.
15527 For a general description of how a router operates, see sections
15528 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
15529 which the preconditions are tested. The order of expansion of the options that
15530 provide data for a transport is: &%errors_to%&, &%headers_add%&,
15531 &%headers_remove%&, &%transport%&.
15535 .option address_data routers string&!! unset
15536 .cindex "router" "data attached to address"
15537 The string is expanded just before the router is run, that is, after all the
15538 precondition tests have succeeded. If the expansion is forced to fail, the
15539 router declines, the value of &%address_data%& remains unchanged, and the
15540 &%more%& option controls what happens next. Other expansion failures cause
15541 delivery of the address to be deferred.
15543 .vindex "&$address_data$&"
15544 When the expansion succeeds, the value is retained with the address, and can be
15545 accessed using the variable &$address_data$& in the current router, subsequent
15546 routers, and the eventual transport.
15548 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
15549 that runs a user's filter file, the contents of &$address_data$& are accessible
15550 in the filter. This is not normally a problem, because such data is usually
15551 either not confidential or it &"belongs"& to the current user, but if you do
15552 put confidential data into &$address_data$& you need to remember this point.
15554 Even if the router declines or passes, the value of &$address_data$& remains
15555 with the address, though it can be changed by another &%address_data%& setting
15556 on a subsequent router. If a router generates child addresses, the value of
15557 &$address_data$& propagates to them. This also applies to the special kind of
15558 &"child"& that is generated by a router with the &%unseen%& option.
15560 The idea of &%address_data%& is that you can use it to look up a lot of data
15561 for the address once, and then pick out parts of the data later. For example,
15562 you could use a single LDAP lookup to return a string of the form
15564 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
15566 In the transport you could pick out the mailbox by a setting such as
15568 file = ${extract{mailbox}{$address_data}}
15570 This makes the configuration file less messy, and also reduces the number of
15571 lookups (though Exim does cache lookups).
15573 .vindex "&$sender_address_data$&"
15574 .vindex "&$address_data$&"
15575 The &%address_data%& facility is also useful as a means of passing information
15576 from one router to another, and from a router to a transport. In addition, if
15577 &$address_data$& is set by a router when verifying a recipient address from an
15578 ACL, it remains available for use in the rest of the ACL statement. After
15579 verifying a sender, the value is transferred to &$sender_address_data$&.
15583 .option address_test routers&!? boolean true
15585 .cindex "router" "skipping when address testing"
15586 If this option is set false, the router is skipped when routing is being tested
15587 by means of the &%-bt%& command line option. This can be a convenience when
15588 your first router sends messages to an external scanner, because it saves you
15589 having to set the &"already scanned"& indicator when testing real address
15594 .option cannot_route_message routers string&!! unset
15595 .cindex "router" "customizing &""cannot route""& message"
15596 .cindex "customizing" "&""cannot route""& message"
15597 This option specifies a text message that is used when an address cannot be
15598 routed because Exim has run out of routers. The default message is
15599 &"Unrouteable address"&. This option is useful only on routers that have
15600 &%more%& set false, or on the very last router in a configuration, because the
15601 value that is used is taken from the last router that is considered. This
15602 includes a router that is skipped because its preconditions are not met, as
15603 well as a router that declines. For example, using the default configuration,
15606 cannot_route_message = Remote domain not found in DNS
15608 on the first router, which is a &(dnslookup)& router with &%more%& set false,
15611 cannot_route_message = Unknown local user
15613 on the final router that checks for local users. If string expansion fails for
15614 this option, the default message is used. Unless the expansion failure was
15615 explicitly forced, a message about the failure is written to the main and panic
15616 logs, in addition to the normal message about the routing failure.
15619 .option caseful_local_part routers boolean false
15620 .cindex "case of local parts"
15621 .cindex "router" "case of local parts"
15622 By default, routers handle the local parts of addresses in a case-insensitive
15623 manner, though the actual case is preserved for transmission with the message.
15624 If you want the case of letters to be significant in a router, you must set
15625 this option true. For individual router options that contain address or local
15626 part lists (for example, &%local_parts%&), case-sensitive matching can be
15627 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
15630 .vindex "&$local_part$&"
15631 .vindex "&$original_local_part$&"
15632 .vindex "&$parent_local_part$&"
15633 The value of the &$local_part$& variable is forced to lower case while a
15634 router is running unless &%caseful_local_part%& is set. When a router assigns
15635 an address to a transport, the value of &$local_part$& when the transport runs
15636 is the same as it was in the router. Similarly, when a router generates child
15637 addresses by aliasing or forwarding, the values of &$original_local_part$&
15638 and &$parent_local_part$& are those that were used by the redirecting router.
15640 This option applies to the processing of an address by a router. When a
15641 recipient address is being processed in an ACL, there is a separate &%control%&
15642 modifier that can be used to specify case-sensitive processing within the ACL
15643 (see section &<<SECTcontrols>>&).
15647 .option check_local_user routers&!? boolean false
15648 .cindex "local user, checking in router"
15649 .cindex "router" "checking for local user"
15650 .cindex "&_/etc/passwd_&"
15652 When this option is true, Exim checks that the local part of the recipient
15653 address (with affixes removed if relevant) is the name of an account on the
15654 local system. The check is done by calling the &[getpwnam()]& function rather
15655 than trying to read &_/etc/passwd_& directly. This means that other methods of
15656 holding password data (such as NIS) are supported. If the local part is a local
15657 user, &$home$& is set from the password data, and can be tested in other
15658 preconditions that are evaluated after this one (the order of evaluation is
15659 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
15660 overridden by &%router_home_directory%&. If the local part is not a local user,
15661 the router is skipped.
15663 If you want to check that the local part is either the name of a local user
15664 or matches something else, you cannot combine &%check_local_user%& with a
15665 setting of &%local_parts%&, because that specifies the logical &'and'& of the
15666 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
15667 setting to achieve this. For example:
15669 local_parts = passwd;$local_part : lsearch;/etc/other/users
15671 Note, however, that the side effects of &%check_local_user%& (such as setting
15672 up a home directory) do not occur when a &(passwd)& lookup is used in a
15673 &%local_parts%& (or any other) precondition.
15677 .option condition routers&!? string&!! unset
15678 .cindex "router" "customized precondition"
15679 This option specifies a general precondition test that has to succeed for the
15680 router to be called. The &%condition%& option is the last precondition to be
15681 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
15682 result is a forced failure, or an empty string, or one of the strings &"0"& or
15683 &"no"& or &"false"& (checked without regard to the case of the letters), the
15684 router is skipped, and the address is offered to the next one.
15686 If the result is any other value, the router is run (as this is the last
15687 precondition to be evaluated, all the other preconditions must be true).
15689 This option is unique in that multiple &%condition%& options may be present.
15690 All &%condition%& options must succeed.
15692 The &%condition%& option provides a means of applying custom conditions to the
15693 running of routers. Note that in the case of a simple conditional expansion,
15694 the default expansion values are exactly what is wanted. For example:
15696 condition = ${if >{$message_age}{600}}
15698 Because of the default behaviour of the string expansion, this is equivalent to
15700 condition = ${if >{$message_age}{600}{true}{}}
15702 A multiple condition example, which succeeds:
15704 condition = ${if >{$message_age}{600}}
15705 condition = ${if !eq{${lc:$local_part}}{postmaster}}
15708 If the expansion fails (other than forced failure) delivery is deferred. Some
15709 of the other precondition options are common special cases that could in fact
15710 be specified using &%condition%&.
15714 .option debug_print routers string&!! unset
15715 .cindex "testing" "variables in drivers"
15716 If this option is set and debugging is enabled (see the &%-d%& command line
15717 option), the string is expanded and included in the debugging output.
15718 If expansion of the string fails, the error message is written to the debugging
15719 output, and Exim carries on processing.
15720 This option is provided to help with checking out the values of variables and
15721 so on when debugging router configurations. For example, if a &%condition%&
15722 option appears not to be working, &%debug_print%& can be used to output the
15723 variables it references. The output happens after checks for &%domains%&,
15724 &%local_parts%&, and &%check_local_user%& but before any other preconditions
15725 are tested. A newline is added to the text if it does not end with one.
15729 .option disable_logging routers boolean false
15730 If this option is set true, nothing is logged for any routing errors
15731 or for any deliveries caused by this router. You should not set this option
15732 unless you really, really know what you are doing. See also the generic
15733 transport option of the same name.
15736 .option domains routers&!? "domain list&!!" unset
15737 .cindex "router" "restricting to specific domains"
15738 .vindex "&$domain_data$&"
15739 If this option is set, the router is skipped unless the current domain matches
15740 the list. If the match is achieved by means of a file lookup, the data that the
15741 lookup returned for the domain is placed in &$domain_data$& for use in string
15742 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
15743 a list of the order in which preconditions are evaluated.
15747 .option driver routers string unset
15748 This option must always be set. It specifies which of the available routers is
15753 .option errors_to routers string&!! unset
15754 .cindex "envelope sender"
15755 .cindex "router" "changing address for errors"
15756 If a router successfully handles an address, it may assign the address to a
15757 transport for delivery or it may generate child addresses. In both cases, if
15758 there is a delivery problem during later processing, the resulting bounce
15759 message is sent to the address that results from expanding this string,
15760 provided that the address verifies successfully. The &%errors_to%& option is
15761 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
15763 The &%errors_to%& setting associated with an address can be overridden if it
15764 subsequently passes through other routers that have their own &%errors_to%&
15765 settings, or if the message is delivered by a transport with a &%return_path%&
15768 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
15769 the expansion fails to verify, the errors address associated with the incoming
15770 address is used. At top level, this is the envelope sender. A non-forced
15771 expansion failure causes delivery to be deferred.
15773 If an address for which &%errors_to%& has been set ends up being delivered over
15774 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
15775 any bounces that are generated by other MTAs on the delivery route are also
15776 sent there. You can set &%errors_to%& to the empty string by either of these
15782 An expansion item that yields an empty string has the same effect. If you do
15783 this, a locally detected delivery error for addresses processed by this router
15784 no longer gives rise to a bounce message; the error is discarded. If the
15785 address is delivered to a remote host, the return path is set to &`<>`&, unless
15786 overridden by the &%return_path%& option on the transport.
15788 .vindex "&$address_data$&"
15789 If for some reason you want to discard local errors, but use a non-empty
15790 MAIL command for remote delivery, you can preserve the original return
15791 path in &$address_data$& in the router, and reinstate it in the transport by
15792 setting &%return_path%&.
15794 The most common use of &%errors_to%& is to direct mailing list bounces to the
15795 manager of the list, as described in section &<<SECTmailinglists>>&, or to
15796 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
15800 .option expn routers&!? boolean true
15801 .cindex "address" "testing"
15802 .cindex "testing" "addresses"
15803 .cindex "EXPN" "router skipping"
15804 .cindex "router" "skipping for EXPN"
15805 If this option is turned off, the router is skipped when testing an address
15806 as a result of processing an SMTP EXPN command. You might, for example,
15807 want to turn it off on a router for users' &_.forward_& files, while leaving it
15808 on for the system alias file.
15809 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15812 The use of the SMTP EXPN command is controlled by an ACL (see chapter
15813 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
15814 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
15818 .option fail_verify routers boolean false
15819 .cindex "router" "forcing verification failure"
15820 Setting this option has the effect of setting both &%fail_verify_sender%& and
15821 &%fail_verify_recipient%& to the same value.
15825 .option fail_verify_recipient routers boolean false
15826 If this option is true and an address is accepted by this router when
15827 verifying a recipient, verification fails.
15831 .option fail_verify_sender routers boolean false
15832 If this option is true and an address is accepted by this router when
15833 verifying a sender, verification fails.
15837 .option fallback_hosts routers "string list" unset
15838 .cindex "router" "fallback hosts"
15839 .cindex "fallback" "hosts specified on router"
15840 String expansion is not applied to this option. The argument must be a
15841 colon-separated list of host names or IP addresses. The list separator can be
15842 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
15843 each name or address. In fact, the format of each item is exactly the same as
15844 defined for the list of hosts in a &(manualroute)& router (see section
15845 &<<SECTformatonehostitem>>&).
15847 If a router queues an address for a remote transport, this host list is
15848 associated with the address, and used instead of the transport's fallback host
15849 list. If &%hosts_randomize%& is set on the transport, the order of the list is
15850 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
15851 transport for further details.
15854 .option group routers string&!! "see below"
15855 .cindex "gid (group id)" "local delivery"
15856 .cindex "local transports" "uid and gid"
15857 .cindex "transport" "local"
15858 .cindex "router" "setting group"
15859 When a router queues an address for a transport, and the transport does not
15860 specify a group, the group given here is used when running the delivery
15862 The group may be specified numerically or by name. If expansion fails, the
15863 error is logged and delivery is deferred.
15864 The default is unset, unless &%check_local_user%& is set, when the default
15865 is taken from the password information. See also &%initgroups%& and &%user%&
15866 and the discussion in chapter &<<CHAPenvironment>>&.
15870 .option headers_add routers string&!! unset
15871 .cindex "header lines" "adding"
15872 .cindex "router" "adding header lines"
15873 This option specifies a string of text that is expanded at routing time, and
15874 associated with any addresses that are accepted by the router. However, this
15875 option has no effect when an address is just being verified. The way in which
15876 the text is used to add header lines at transport time is described in section
15877 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
15878 message is in the process of being transported. This means that references to
15879 header lines in string expansions in the transport's configuration do not
15880 &"see"& the added header lines.
15882 The &%headers_add%& option is expanded after &%errors_to%&, but before
15883 &%headers_remove%& and &%transport%&. If the expanded string is empty, or if
15884 the expansion is forced to fail, the option has no effect. Other expansion
15885 failures are treated as configuration errors.
15887 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
15888 router that has the &%one_time%& option set.
15890 .cindex "duplicate addresses"
15891 .oindex "&%unseen%&"
15892 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15893 additions are deleted when the address is passed on to subsequent routers.
15894 For a &%redirect%& router, if a generated address is the same as the incoming
15895 address, this can lead to duplicate addresses with different header
15896 modifications. Exim does not do duplicate deliveries (except, in certain
15897 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
15898 which of the duplicates is discarded, so this ambiguous situation should be
15899 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
15903 .option headers_remove routers string&!! unset
15904 .cindex "header lines" "removing"
15905 .cindex "router" "removing header lines"
15906 This option specifies a string of text that is expanded at routing time, and
15907 associated with any addresses that are accepted by the router. However, this
15908 option has no effect when an address is just being verified. The way in which
15909 the text is used to remove header lines at transport time is described in
15910 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
15911 the message is in the process of being transported. This means that references
15912 to header lines in string expansions in the transport's configuration still
15913 &"see"& the original header lines.
15915 The &%headers_remove%& option is expanded after &%errors_to%& and
15916 &%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
15917 the option has no effect. Other expansion failures are treated as configuration
15920 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
15921 router that has the &%one_time%& option set.
15923 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15924 removal requests are deleted when the address is passed on to subsequent
15925 routers, and this can lead to problems with duplicates -- see the similar
15926 warning for &%headers_add%& above.
15929 .option ignore_target_hosts routers "host list&!!" unset
15930 .cindex "IP address" "discarding"
15931 .cindex "router" "discarding IP addresses"
15932 Although this option is a host list, it should normally contain IP address
15933 entries rather than names. If any host that is looked up by the router has an
15934 IP address that matches an item in this list, Exim behaves as if that IP
15935 address did not exist. This option allows you to cope with rogue DNS entries
15938 remote.domain.example. A 127.0.0.1
15942 ignore_target_hosts = 127.0.0.1
15944 on the relevant router. If all the hosts found by a &(dnslookup)& router are
15945 discarded in this way, the router declines. In a conventional configuration, an
15946 attempt to mail to such a domain would normally provoke the &"unrouteable
15947 domain"& error, and an attempt to verify an address in the domain would fail.
15948 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
15949 router declines if presented with one of the listed addresses.
15951 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
15952 means of the first or the second of the following settings, respectively:
15954 ignore_target_hosts = 0.0.0.0/0
15955 ignore_target_hosts = <; 0::0/0
15957 The pattern in the first line matches all IPv4 addresses, whereas the pattern
15958 in the second line matches all IPv6 addresses.
15960 This option may also be useful for ignoring link-local and site-local IPv6
15961 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
15962 is expanded before use as a list, it is possible to make it dependent on the
15963 domain that is being routed.
15965 .vindex "&$host_address$&"
15966 During its expansion, &$host_address$& is set to the IP address that is being
15969 .option initgroups routers boolean false
15970 .cindex "additional groups"
15971 .cindex "groups" "additional"
15972 .cindex "local transports" "uid and gid"
15973 .cindex "transport" "local"
15974 If the router queues an address for a transport, and this option is true, and
15975 the uid supplied by the router is not overridden by the transport, the
15976 &[initgroups()]& function is called when running the transport to ensure that
15977 any additional groups associated with the uid are set up. See also &%group%&
15978 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
15982 .option local_part_prefix routers&!? "string list" unset
15983 .cindex "router" "prefix for local part"
15984 .cindex "prefix" "for local part, used in router"
15985 If this option is set, the router is skipped unless the local part starts with
15986 one of the given strings, or &%local_part_prefix_optional%& is true. See
15987 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
15990 The list is scanned from left to right, and the first prefix that matches is
15991 used. A limited form of wildcard is available; if the prefix begins with an
15992 asterisk, it matches the longest possible sequence of arbitrary characters at
15993 the start of the local part. An asterisk should therefore always be followed by
15994 some character that does not occur in normal local parts.
15995 .cindex "multiple mailboxes"
15996 .cindex "mailbox" "multiple"
15997 Wildcarding can be used to set up multiple user mailboxes, as described in
15998 section &<<SECTmulbox>>&.
16000 .vindex "&$local_part$&"
16001 .vindex "&$local_part_prefix$&"
16002 During the testing of the &%local_parts%& option, and while the router is
16003 running, the prefix is removed from the local part, and is available in the
16004 expansion variable &$local_part_prefix$&. When a message is being delivered, if
16005 the router accepts the address, this remains true during subsequent delivery by
16006 a transport. In particular, the local part that is transmitted in the RCPT
16007 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
16008 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
16009 the relevant transport.
16011 When an address is being verified, &%local_part_prefix%& affects only the
16012 behaviour of the router. If the callout feature of verification is in use, this
16013 means that the full address, including the prefix, will be used during the
16016 The prefix facility is commonly used to handle local parts of the form
16017 &%owner-something%&. Another common use is to support local parts of the form
16018 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
16019 to tell a user their forwarding is broken &-- by placing a router like this one
16020 immediately before the router that handles &_.forward_& files:
16024 local_part_prefix = real-
16026 transport = local_delivery
16028 For security, it would probably be a good idea to restrict the use of this
16029 router to locally-generated messages, using a condition such as this:
16031 condition = ${if match {$sender_host_address}\
16032 {\N^(|127\.0\.0\.1)$\N}}
16035 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
16036 both conditions must be met if not optional. Care must be taken if wildcards
16037 are used in both a prefix and a suffix on the same router. Different
16038 separator characters must be used to avoid ambiguity.
16041 .option local_part_prefix_optional routers boolean false
16042 See &%local_part_prefix%& above.
16046 .option local_part_suffix routers&!? "string list" unset
16047 .cindex "router" "suffix for local part"
16048 .cindex "suffix for local part" "used in router"
16049 This option operates in the same way as &%local_part_prefix%&, except that the
16050 local part must end (rather than start) with the given string, the
16051 &%local_part_suffix_optional%& option determines whether the suffix is
16052 mandatory, and the wildcard * character, if present, must be the last
16053 character of the suffix. This option facility is commonly used to handle local
16054 parts of the form &%something-request%& and multiple user mailboxes of the form
16058 .option local_part_suffix_optional routers boolean false
16059 See &%local_part_suffix%& above.
16063 .option local_parts routers&!? "local part list&!!" unset
16064 .cindex "router" "restricting to specific local parts"
16065 .cindex "local part" "checking in router"
16066 The router is run only if the local part of the address matches the list.
16067 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16069 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
16070 string is expanded, it is possible to make it depend on the domain, for
16073 local_parts = dbm;/usr/local/specials/$domain
16075 .vindex "&$local_part_data$&"
16076 If the match is achieved by a lookup, the data that the lookup returned
16077 for the local part is placed in the variable &$local_part_data$& for use in
16078 expansions of the router's private options. You might use this option, for
16079 example, if you have a large number of local virtual domains, and you want to
16080 send all postmaster mail to the same place without having to set up an alias in
16081 each virtual domain:
16085 local_parts = postmaster
16086 data = postmaster@real.domain.example
16090 .option log_as_local routers boolean "see below"
16091 .cindex "log" "delivery line"
16092 .cindex "delivery" "log line format"
16093 Exim has two logging styles for delivery, the idea being to make local
16094 deliveries stand out more visibly from remote ones. In the &"local"& style, the
16095 recipient address is given just as the local part, without a domain. The use of
16096 this style is controlled by this option. It defaults to true for the &(accept)&
16097 router, and false for all the others. This option applies only when a
16098 router assigns an address to a transport. It has no effect on routers that
16099 redirect addresses.
16103 .option more routers boolean&!! true
16104 The result of string expansion for this option must be a valid boolean value,
16105 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
16106 result causes an error, and delivery is deferred. If the expansion is forced to
16107 fail, the default value for the option (true) is used. Other failures cause
16108 delivery to be deferred.
16110 If this option is set false, and the router declines to handle the address, no
16111 further routers are tried, routing fails, and the address is bounced.
16113 However, if the router explicitly passes an address to the following router by
16114 means of the setting
16118 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
16119 does not affect the behaviour if one of the precondition tests fails. In that
16120 case, the address is always passed to the next router.
16122 Note that &%address_data%& is not considered to be a precondition. If its
16123 expansion is forced to fail, the router declines, and the value of &%more%&
16124 controls what happens next.
16127 .option pass_on_timeout routers boolean false
16128 .cindex "timeout" "of router"
16129 .cindex "router" "timeout"
16130 If a router times out during a host lookup, it normally causes deferral of the
16131 address. If &%pass_on_timeout%& is set, the address is passed on to the next
16132 router, overriding &%no_more%&. This may be helpful for systems that are
16133 intermittently connected to the Internet, or those that want to pass to a smart
16134 host any messages that cannot immediately be delivered.
16136 There are occasional other temporary errors that can occur while doing DNS
16137 lookups. They are treated in the same way as a timeout, and this option
16138 applies to all of them.
16142 .option pass_router routers string unset
16143 .cindex "router" "go to after &""pass""&"
16144 Routers that recognize the generic &%self%& option (&(dnslookup)&,
16145 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
16146 routing to continue, and overriding a false setting of &%more%&. When one of
16147 these routers returns &"pass"&, the address is normally handed on to the next
16148 router in sequence. This can be changed by setting &%pass_router%& to the name
16149 of another router. However (unlike &%redirect_router%&) the named router must
16150 be below the current router, to avoid loops. Note that this option applies only
16151 to the special case of &"pass"&. It does not apply when a router returns
16152 &"decline"& because it cannot handle an address.
16156 .option redirect_router routers string unset
16157 .cindex "router" "start at after redirection"
16158 Sometimes an administrator knows that it is pointless to reprocess addresses
16159 generated from alias or forward files with the same router again. For
16160 example, if an alias file translates real names into login ids there is no
16161 point searching the alias file a second time, especially if it is a large file.
16163 The &%redirect_router%& option can be set to the name of any router instance.
16164 It causes the routing of any generated addresses to start at the named router
16165 instead of at the first router. This option has no effect if the router in
16166 which it is set does not generate new addresses.
16170 .option require_files routers&!? "string list&!!" unset
16171 .cindex "file" "requiring for router"
16172 .cindex "router" "requiring file existence"
16173 This option provides a general mechanism for predicating the running of a
16174 router on the existence or non-existence of certain files or directories.
16175 Before running a router, as one of its precondition tests, Exim works its way
16176 through the &%require_files%& list, expanding each item separately.
16178 Because the list is split before expansion, any colons in expansion items must
16179 be doubled, or the facility for using a different list separator must be used.
16180 If any expansion is forced to fail, the item is ignored. Other expansion
16181 failures cause routing of the address to be deferred.
16183 If any expanded string is empty, it is ignored. Otherwise, except as described
16184 below, each string must be a fully qualified file path, optionally preceded by
16185 &"!"&. The paths are passed to the &[stat()]& function to test for the
16186 existence of the files or directories. The router is skipped if any paths not
16187 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
16190 If &[stat()]& cannot determine whether a file exists or not, delivery of
16191 the message is deferred. This can happen when NFS-mounted filesystems are
16194 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
16195 options, so you cannot use it to check for the existence of a file in which to
16196 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
16197 full list of the order in which preconditions are evaluated.) However, as
16198 these options are all expanded, you can use the &%exists%& expansion condition
16199 to make such tests. The &%require_files%& option is intended for checking files
16200 that the router may be going to use internally, or which are needed by a
16201 transport (for example &_.procmailrc_&).
16203 During delivery, the &[stat()]& function is run as root, but there is a
16204 facility for some checking of the accessibility of a file by another user.
16205 This is not a proper permissions check, but just a &"rough"& check that
16206 operates as follows:
16208 If an item in a &%require_files%& list does not contain any forward slash
16209 characters, it is taken to be the user (and optional group, separated by a
16210 comma) to be checked for subsequent files in the list. If no group is specified
16211 but the user is specified symbolically, the gid associated with the uid is
16214 require_files = mail:/some/file
16215 require_files = $local_part:$home/.procmailrc
16217 If a user or group name in a &%require_files%& list does not exist, the
16218 &%require_files%& condition fails.
16220 Exim performs the check by scanning along the components of the file path, and
16221 checking the access for the given uid and gid. It checks for &"x"& access on
16222 directories, and &"r"& access on the final file. Note that this means that file
16223 access control lists, if the operating system has them, are ignored.
16225 &*Warning 1*&: When the router is being run to verify addresses for an
16226 incoming SMTP message, Exim is not running as root, but under its own uid. This
16227 may affect the result of a &%require_files%& check. In particular, &[stat()]&
16228 may yield the error EACCES (&"Permission denied"&). This means that the Exim
16229 user is not permitted to read one of the directories on the file's path.
16231 &*Warning 2*&: Even when Exim is running as root while delivering a message,
16232 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
16233 without root access. In this case, if a check for access by a particular user
16234 is requested, Exim creates a subprocess that runs as that user, and tries the
16235 check again in that process.
16237 The default action for handling an unresolved EACCES is to consider it to
16238 be caused by a configuration error, and routing is deferred because the
16239 existence or non-existence of the file cannot be determined. However, in some
16240 circumstances it may be desirable to treat this condition as if the file did
16241 not exist. If the file name (or the exclamation mark that precedes the file
16242 name for non-existence) is preceded by a plus sign, the EACCES error is treated
16243 as if the file did not exist. For example:
16245 require_files = +/some/file
16247 If the router is not an essential part of verification (for example, it
16248 handles users' &_.forward_& files), another solution is to set the &%verify%&
16249 option false so that the router is skipped when verifying.
16253 .option retry_use_local_part routers boolean "see below"
16254 .cindex "hints database" "retry keys"
16255 .cindex "local part" "in retry keys"
16256 When a delivery suffers a temporary routing failure, a retry record is created
16257 in Exim's hints database. For addresses whose routing depends only on the
16258 domain, the key for the retry record should not involve the local part, but for
16259 other addresses, both the domain and the local part should be included.
16260 Usually, remote routing is of the former kind, and local routing is of the
16263 This option controls whether the local part is used to form the key for retry
16264 hints for addresses that suffer temporary errors while being handled by this
16265 router. The default value is true for any router that has &%check_local_user%&
16266 set, and false otherwise. Note that this option does not apply to hints keys
16267 for transport delays; they are controlled by a generic transport option of the
16270 The setting of &%retry_use_local_part%& applies only to the router on which it
16271 appears. If the router generates child addresses, they are routed
16272 independently; this setting does not become attached to them.
16276 .option router_home_directory routers string&!! unset
16277 .cindex "router" "home directory for"
16278 .cindex "home directory" "for router"
16280 This option sets a home directory for use while the router is running. (Compare
16281 &%transport_home_directory%&, which sets a home directory for later
16282 transporting.) In particular, if used on a &(redirect)& router, this option
16283 sets a value for &$home$& while a filter is running. The value is expanded;
16284 forced expansion failure causes the option to be ignored &-- other failures
16285 cause the router to defer.
16287 Expansion of &%router_home_directory%& happens immediately after the
16288 &%check_local_user%& test (if configured), before any further expansions take
16290 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16292 While the router is running, &%router_home_directory%& overrides the value of
16293 &$home$& that came from &%check_local_user%&.
16295 When a router accepts an address and assigns it to a local transport (including
16296 the cases when a &(redirect)& router generates a pipe, file, or autoreply
16297 delivery), the home directory setting for the transport is taken from the first
16298 of these values that is set:
16301 The &%home_directory%& option on the transport;
16303 The &%transport_home_directory%& option on the router;
16305 The password data if &%check_local_user%& is set on the router;
16307 The &%router_home_directory%& option on the router.
16310 In other words, &%router_home_directory%& overrides the password data for the
16311 router, but not for the transport.
16315 .option self routers string freeze
16316 .cindex "MX record" "pointing to local host"
16317 .cindex "local host" "MX pointing to"
16318 This option applies to those routers that use a recipient address to find a
16319 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
16320 and &(manualroute)& routers.
16321 Certain configurations of the &(queryprogram)& router can also specify a list
16323 Usually such routers are configured to send the message to a remote host via an
16324 &(smtp)& transport. The &%self%& option specifies what happens when the first
16325 host on the list turns out to be the local host.
16326 The way in which Exim checks for the local host is described in section
16327 &<<SECTreclocipadd>>&.
16329 Normally this situation indicates either an error in Exim's configuration (for
16330 example, the router should be configured not to process this domain), or an
16331 error in the DNS (for example, the MX should not point to this host). For this
16332 reason, the default action is to log the incident, defer the address, and
16333 freeze the message. The following alternatives are provided for use in special
16338 Delivery of the message is tried again later, but the message is not frozen.
16340 .vitem "&%reroute%&: <&'domain'&>"
16341 The domain is changed to the given domain, and the address is passed back to
16342 be reprocessed by the routers. No rewriting of headers takes place. This
16343 behaviour is essentially a redirection.
16345 .vitem "&%reroute: rewrite:%& <&'domain'&>"
16346 The domain is changed to the given domain, and the address is passed back to be
16347 reprocessed by the routers. Any headers that contain the original domain are
16352 .vindex "&$self_hostname$&"
16353 The router passes the address to the next router, or to the router named in the
16354 &%pass_router%& option if it is set. This overrides &%no_more%&. During
16355 subsequent routing and delivery, the variable &$self_hostname$& contains the
16356 name of the local host that the router encountered. This can be used to
16357 distinguish between different cases for hosts with multiple names. The
16363 ensures that only those addresses that routed to the local host are passed on.
16364 Without &%no_more%&, addresses that were declined for other reasons would also
16365 be passed to the next router.
16368 Delivery fails and an error report is generated.
16371 .cindex "local host" "sending to"
16372 The anomaly is ignored and the address is queued for the transport. This
16373 setting should be used with extreme caution. For an &(smtp)& transport, it
16374 makes sense only in cases where the program that is listening on the SMTP port
16375 is not this version of Exim. That is, it must be some other MTA, or Exim with a
16376 different configuration file that handles the domain in another way.
16381 .option senders routers&!? "address list&!!" unset
16382 .cindex "router" "checking senders"
16383 If this option is set, the router is skipped unless the message's sender
16384 address matches something on the list.
16385 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16388 There are issues concerning verification when the running of routers is
16389 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
16390 setting, it sets the sender to the null string. When using the &%-bt%& option
16391 to check a configuration file, it is necessary also to use the &%-f%& option to
16392 set an appropriate sender. For incoming mail, the sender is unset when
16393 verifying the sender, but is available when verifying any recipients. If the
16394 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
16398 .option translate_ip_address routers string&!! unset
16399 .cindex "IP address" "translating"
16400 .cindex "packet radio"
16401 .cindex "router" "IP address translation"
16402 There exist some rare networking situations (for example, packet radio) where
16403 it is helpful to be able to translate IP addresses generated by normal routing
16404 mechanisms into other IP addresses, thus performing a kind of manual IP
16405 routing. This should be done only if the normal IP routing of the TCP/IP stack
16406 is inadequate or broken. Because this is an extremely uncommon requirement, the
16407 code to support this option is not included in the Exim binary unless
16408 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
16410 .vindex "&$host_address$&"
16411 The &%translate_ip_address%& string is expanded for every IP address generated
16412 by the router, with the generated address set in &$host_address$&. If the
16413 expansion is forced to fail, no action is taken.
16414 For any other expansion error, delivery of the message is deferred.
16415 If the result of the expansion is an IP address, that replaces the original
16416 address; otherwise the result is assumed to be a host name &-- this is looked
16417 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
16418 produce one or more replacement IP addresses. For example, to subvert all IP
16419 addresses in some specific networks, this could be added to a router:
16421 translate_ip_address = \
16422 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
16425 The file would contain lines like
16427 10.2.3.128/26 some.host
16428 10.8.4.34/26 10.44.8.15
16430 You should not make use of this facility unless you really understand what you
16435 .option transport routers string&!! unset
16436 This option specifies the transport to be used when a router accepts an address
16437 and sets it up for delivery. A transport is never needed if a router is used
16438 only for verification. The value of the option is expanded at routing time,
16439 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
16440 and result must be the name of one of the configured transports. If it is not,
16441 delivery is deferred.
16443 The &%transport%& option is not used by the &(redirect)& router, but it does
16444 have some private options that set up transports for pipe and file deliveries
16445 (see chapter &<<CHAPredirect>>&).
16449 .option transport_current_directory routers string&!! unset
16450 .cindex "current directory for local transport"
16451 This option associates a current directory with any address that is routed
16452 to a local transport. This can happen either because a transport is
16453 explicitly configured for the router, or because it generates a delivery to a
16454 file or a pipe. During the delivery process (that is, at transport time), this
16455 option string is expanded and is set as the current directory, unless
16456 overridden by a setting on the transport.
16457 If the expansion fails for any reason, including forced failure, an error is
16458 logged, and delivery is deferred.
16459 See chapter &<<CHAPenvironment>>& for details of the local delivery
16465 .option transport_home_directory routers string&!! "see below"
16466 .cindex "home directory" "for local transport"
16467 This option associates a home directory with any address that is routed to a
16468 local transport. This can happen either because a transport is explicitly
16469 configured for the router, or because it generates a delivery to a file or a
16470 pipe. During the delivery process (that is, at transport time), the option
16471 string is expanded and is set as the home directory, unless overridden by a
16472 setting of &%home_directory%& on the transport.
16473 If the expansion fails for any reason, including forced failure, an error is
16474 logged, and delivery is deferred.
16476 If the transport does not specify a home directory, and
16477 &%transport_home_directory%& is not set for the router, the home directory for
16478 the transport is taken from the password data if &%check_local_user%& is set for
16479 the router. Otherwise it is taken from &%router_home_directory%& if that option
16480 is set; if not, no home directory is set for the transport.
16482 See chapter &<<CHAPenvironment>>& for further details of the local delivery
16488 .option unseen routers boolean&!! false
16489 .cindex "router" "carrying on after success"
16490 The result of string expansion for this option must be a valid boolean value,
16491 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
16492 result causes an error, and delivery is deferred. If the expansion is forced to
16493 fail, the default value for the option (false) is used. Other failures cause
16494 delivery to be deferred.
16496 When this option is set true, routing does not cease if the router accepts the
16497 address. Instead, a copy of the incoming address is passed to the next router,
16498 overriding a false setting of &%more%&. There is little point in setting
16499 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
16500 the value of &%unseen%& contains expansion items (and therefore, presumably, is
16501 sometimes true and sometimes false).
16503 .cindex "copy of message (&%unseen%& option)"
16504 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
16505 qualifier in filter files. It can be used to cause copies of messages to be
16506 delivered to some other destination, while also carrying out a normal delivery.
16507 In effect, the current address is made into a &"parent"& that has two children
16508 &-- one that is delivered as specified by this router, and a clone that goes on
16509 to be routed further. For this reason, &%unseen%& may not be combined with the
16510 &%one_time%& option in a &(redirect)& router.
16512 &*Warning*&: Header lines added to the address (or specified for removal) by
16513 this router or by previous routers affect the &"unseen"& copy of the message
16514 only. The clone that continues to be processed by further routers starts with
16515 no added headers and none specified for removal. For a &%redirect%& router, if
16516 a generated address is the same as the incoming address, this can lead to
16517 duplicate addresses with different header modifications. Exim does not do
16518 duplicate deliveries (except, in certain circumstances, to pipes -- see section
16519 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
16520 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
16521 &%redirect%& router may be of help.
16523 Unlike the handling of header modifications, any data that was set by the
16524 &%address_data%& option in the current or previous routers &'is'& passed on to
16525 subsequent routers.
16528 .option user routers string&!! "see below"
16529 .cindex "uid (user id)" "local delivery"
16530 .cindex "local transports" "uid and gid"
16531 .cindex "transport" "local"
16532 .cindex "router" "user for filter processing"
16533 .cindex "filter" "user for processing"
16534 When a router queues an address for a transport, and the transport does not
16535 specify a user, the user given here is used when running the delivery process.
16536 The user may be specified numerically or by name. If expansion fails, the
16537 error is logged and delivery is deferred.
16538 This user is also used by the &(redirect)& router when running a filter file.
16539 The default is unset, except when &%check_local_user%& is set. In this case,
16540 the default is taken from the password information. If the user is specified as
16541 a name, and &%group%& is not set, the group associated with the user is used.
16542 See also &%initgroups%& and &%group%& and the discussion in chapter
16543 &<<CHAPenvironment>>&.
16547 .option verify routers&!? boolean true
16548 Setting this option has the effect of setting &%verify_sender%& and
16549 &%verify_recipient%& to the same value.
16552 .option verify_only routers&!? boolean false
16553 .cindex "EXPN" "with &%verify_only%&"
16555 .cindex "router" "used only when verifying"
16556 If this option is set, the router is used only when verifying an address or
16557 testing with the &%-bv%& option, not when actually doing a delivery, testing
16558 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
16559 restricted to verifying only senders or recipients by means of
16560 &%verify_sender%& and &%verify_recipient%&.
16562 &*Warning*&: When the router is being run to verify addresses for an incoming
16563 SMTP message, Exim is not running as root, but under its own uid. If the router
16564 accesses any files, you need to make sure that they are accessible to the Exim
16568 .option verify_recipient routers&!? boolean true
16569 If this option is false, the router is skipped when verifying recipient
16571 or testing recipient verification using &%-bv%&.
16572 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16576 .option verify_sender routers&!? boolean true
16577 If this option is false, the router is skipped when verifying sender addresses
16578 or testing sender verification using &%-bvs%&.
16579 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16581 .ecindex IIDgenoprou1
16582 .ecindex IIDgenoprou2
16589 . ////////////////////////////////////////////////////////////////////////////
16590 . ////////////////////////////////////////////////////////////////////////////
16592 .chapter "The accept router" "CHID4"
16593 .cindex "&(accept)& router"
16594 .cindex "routers" "&(accept)&"
16595 The &(accept)& router has no private options of its own. Unless it is being
16596 used purely for verification (see &%verify_only%&) a transport is required to
16597 be defined by the generic &%transport%& option. If the preconditions that are
16598 specified by generic options are met, the router accepts the address and queues
16599 it for the given transport. The most common use of this router is for setting
16600 up deliveries to local mailboxes. For example:
16604 domains = mydomain.example
16606 transport = local_delivery
16608 The &%domains%& condition in this example checks the domain of the address, and
16609 &%check_local_user%& checks that the local part is the login of a local user.
16610 When both preconditions are met, the &(accept)& router runs, and queues the
16611 address for the &(local_delivery)& transport.
16618 . ////////////////////////////////////////////////////////////////////////////
16619 . ////////////////////////////////////////////////////////////////////////////
16621 .chapter "The dnslookup router" "CHAPdnslookup"
16622 .scindex IIDdnsrou1 "&(dnslookup)& router"
16623 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
16624 The &(dnslookup)& router looks up the hosts that handle mail for the
16625 recipient's domain in the DNS. A transport must always be set for this router,
16626 unless &%verify_only%& is set.
16628 If SRV support is configured (see &%check_srv%& below), Exim first searches for
16629 SRV records. If none are found, or if SRV support is not configured,
16630 MX records are looked up. If no MX records exist, address records are sought.
16631 However, &%mx_domains%& can be set to disable the direct use of address
16634 MX records of equal priority are sorted by Exim into a random order. Exim then
16635 looks for address records for the host names obtained from MX or SRV records.
16636 When a host has more than one IP address, they are sorted into a random order,
16637 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
16638 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
16639 generic option, the router declines.
16641 Unless they have the highest priority (lowest MX value), MX records that point
16642 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
16643 are discarded, together with any other MX records of equal or lower priority.
16645 .cindex "MX record" "pointing to local host"
16646 .cindex "local host" "MX pointing to"
16647 .oindex "&%self%&" "in &(dnslookup)& router"
16648 If the host pointed to by the highest priority MX record, or looked up as an
16649 address record, is the local host, or matches &%hosts_treat_as_local%&, what
16650 happens is controlled by the generic &%self%& option.
16653 .section "Problems with DNS lookups" "SECTprowitdnsloo"
16654 There have been problems with DNS servers when SRV records are looked up.
16655 Some mis-behaving servers return a DNS error or timeout when a non-existent
16656 SRV record is sought. Similar problems have in the past been reported for
16657 MX records. The global &%dns_again_means_nonexist%& option can help with this
16658 problem, but it is heavy-handed because it is a global option.
16660 For this reason, there are two options, &%srv_fail_domains%& and
16661 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
16662 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
16663 an attempt to look up an SRV or MX record causes one of these results, and the
16664 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
16665 such record"&. In the case of an SRV lookup, this means that the router
16666 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
16667 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
16668 case routing fails.
16673 .section "Private options for dnslookup" "SECID118"
16674 .cindex "options" "&(dnslookup)& router"
16675 The private options for the &(dnslookup)& router are as follows:
16677 .option check_secondary_mx dnslookup boolean false
16678 .cindex "MX record" "checking for secondary"
16679 If this option is set, the router declines unless the local host is found in
16680 (and removed from) the list of hosts obtained by MX lookup. This can be used to
16681 process domains for which the local host is a secondary mail exchanger
16682 differently to other domains. The way in which Exim decides whether a host is
16683 the local host is described in section &<<SECTreclocipadd>>&.
16686 .option check_srv dnslookup string&!! unset
16687 .cindex "SRV record" "enabling use of"
16688 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
16689 addition to MX and address records. The support is disabled by default. To
16690 enable SRV support, set the &%check_srv%& option to the name of the service
16691 required. For example,
16695 looks for SRV records that refer to the normal smtp service. The option is
16696 expanded, so the service name can vary from message to message or address
16697 to address. This might be helpful if SRV records are being used for a
16698 submission service. If the expansion is forced to fail, the &%check_srv%&
16699 option is ignored, and the router proceeds to look for MX records in the
16702 When the expansion succeeds, the router searches first for SRV records for
16703 the given service (it assumes TCP protocol). A single SRV record with a
16704 host name that consists of just a single dot indicates &"no such service for
16705 this domain"&; if this is encountered, the router declines. If other kinds of
16706 SRV record are found, they are used to construct a host list for delivery
16707 according to the rules of RFC 2782. MX records are not sought in this case.
16709 When no SRV records are found, MX records (and address records) are sought in
16710 the traditional way. In other words, SRV records take precedence over MX
16711 records, just as MX records take precedence over address records. Note that
16712 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
16713 defined it. It is apparently believed that MX records are sufficient for email
16714 and that SRV records should not be used for this purpose. However, SRV records
16715 have an additional &"weight"& feature which some people might find useful when
16716 trying to split an SMTP load between hosts of different power.
16718 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
16719 when there is a DNS lookup error.
16723 .option mx_domains dnslookup "domain list&!!" unset
16724 .cindex "MX record" "required to exist"
16725 .cindex "SRV record" "required to exist"
16726 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
16727 record in order to be recognized. (The name of this option could be improved.)
16728 For example, if all the mail hosts in &'fict.example'& are known to have MX
16729 records, except for those in &'discworld.fict.example'&, you could use this
16732 mx_domains = ! *.discworld.fict.example : *.fict.example
16734 This specifies that messages addressed to a domain that matches the list but
16735 has no MX record should be bounced immediately instead of being routed using
16736 the address record.
16739 .option mx_fail_domains dnslookup "domain list&!!" unset
16740 If the DNS lookup for MX records for one of the domains in this list causes a
16741 DNS lookup error, Exim behaves as if no MX records were found. See section
16742 &<<SECTprowitdnsloo>>& for more discussion.
16747 .option qualify_single dnslookup boolean true
16748 .cindex "DNS" "resolver options"
16749 .cindex "DNS" "qualifying single-component names"
16750 When this option is true, the resolver option RES_DEFNAMES is set for DNS
16751 lookups. Typically, but not standardly, this causes the resolver to qualify
16752 single-component names with the default domain. For example, on a machine
16753 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
16754 &'thesaurus.ref.example'& inside the resolver. For details of what your
16755 resolver actually does, consult your man pages for &'resolver'& and
16760 .option rewrite_headers dnslookup boolean true
16761 .cindex "rewriting" "header lines"
16762 .cindex "header lines" "rewriting"
16763 If the domain name in the address that is being processed is not fully
16764 qualified, it may be expanded to its full form by a DNS lookup. For example, if
16765 an address is specified as &'dormouse@teaparty'&, the domain might be
16766 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
16767 occur as a result of setting the &%widen_domains%& option. If
16768 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
16769 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
16770 header lines of the message are rewritten with the full domain name.
16772 This option should be turned off only when it is known that no message is
16773 ever going to be sent outside an environment where the abbreviation makes
16776 When an MX record is looked up in the DNS and matches a wildcard record, name
16777 servers normally return a record containing the name that has been looked up,
16778 making it impossible to detect whether a wildcard was present or not. However,
16779 some name servers have recently been seen to return the wildcard entry. If the
16780 name returned by a DNS lookup begins with an asterisk, it is not used for
16784 .option same_domain_copy_routing dnslookup boolean false
16785 .cindex "address" "copying routing"
16786 Addresses with the same domain are normally routed by the &(dnslookup)& router
16787 to the same list of hosts. However, this cannot be presumed, because the router
16788 options and preconditions may refer to the local part of the address. By
16789 default, therefore, Exim routes each address in a message independently. DNS
16790 servers run caches, so repeated DNS lookups are not normally expensive, and in
16791 any case, personal messages rarely have more than a few recipients.
16793 If you are running mailing lists with large numbers of subscribers at the same
16794 domain, and you are using a &(dnslookup)& router which is independent of the
16795 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
16796 lookups for identical domains in one message. In this case, when &(dnslookup)&
16797 routes an address to a remote transport, any other unrouted addresses in the
16798 message that have the same domain are automatically given the same routing
16799 without processing them independently,
16800 provided the following conditions are met:
16803 No router that processed the address specified &%headers_add%& or
16804 &%headers_remove%&.
16806 The router did not change the address in any way, for example, by &"widening"&
16813 .option search_parents dnslookup boolean false
16814 .cindex "DNS" "resolver options"
16815 When this option is true, the resolver option RES_DNSRCH is set for DNS
16816 lookups. This is different from the &%qualify_single%& option in that it
16817 applies to domains containing dots. Typically, but not standardly, it causes
16818 the resolver to search for the name in the current domain and in parent
16819 domains. For example, on a machine in the &'fict.example'& domain, if looking
16820 up &'teaparty.wonderland'& failed, the resolver would try
16821 &'teaparty.wonderland.fict.example'&. For details of what your resolver
16822 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
16824 Setting this option true can cause problems in domains that have a wildcard MX
16825 record, because any domain that does not have its own MX record matches the
16830 .option srv_fail_domains dnslookup "domain list&!!" unset
16831 If the DNS lookup for SRV records for one of the domains in this list causes a
16832 DNS lookup error, Exim behaves as if no SRV records were found. See section
16833 &<<SECTprowitdnsloo>>& for more discussion.
16838 .option widen_domains dnslookup "string list" unset
16839 .cindex "domain" "partial; widening"
16840 If a DNS lookup fails and this option is set, each of its strings in turn is
16841 added onto the end of the domain, and the lookup is tried again. For example,
16844 widen_domains = fict.example:ref.example
16846 is set and a lookup of &'klingon.dictionary'& fails,
16847 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
16848 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
16849 and &%search_parents%& options can cause some widening to be undertaken inside
16850 the DNS resolver. &%widen_domains%& is not applied to sender addresses
16851 when verifying, unless &%rewrite_headers%& is false (not the default).
16854 .section "Effect of qualify_single and search_parents" "SECID119"
16855 When a domain from an envelope recipient is changed by the resolver as a result
16856 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
16857 corresponding address in the message's header lines unless &%rewrite_headers%&
16858 is set false. Exim then re-routes the address, using the full domain.
16860 These two options affect only the DNS lookup that takes place inside the router
16861 for the domain of the address that is being routed. They do not affect lookups
16862 such as that implied by
16866 that may happen while processing a router precondition before the router is
16867 entered. No widening ever takes place for these lookups.
16868 .ecindex IIDdnsrou1
16869 .ecindex IIDdnsrou2
16879 . ////////////////////////////////////////////////////////////////////////////
16880 . ////////////////////////////////////////////////////////////////////////////
16882 .chapter "The ipliteral router" "CHID5"
16883 .cindex "&(ipliteral)& router"
16884 .cindex "domain literal" "routing"
16885 .cindex "routers" "&(ipliteral)&"
16886 This router has no private options. Unless it is being used purely for
16887 verification (see &%verify_only%&) a transport is required to be defined by the
16888 generic &%transport%& option. The router accepts the address if its domain part
16889 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
16890 router handles the address
16894 by setting up delivery to the host with that IP address. IPv4 domain literals
16895 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
16896 are similar, but the address is preceded by &`ipv6:`&. For example:
16898 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
16900 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
16901 grounds that sooner or later somebody will try it.
16903 .oindex "&%self%&" "in &(ipliteral)& router"
16904 If the IP address matches something in &%ignore_target_hosts%&, the router
16905 declines. If an IP literal turns out to refer to the local host, the generic
16906 &%self%& option determines what happens.
16908 The RFCs require support for domain literals; however, their use is
16909 controversial in today's Internet. If you want to use this router, you must
16910 also set the main configuration option &%allow_domain_literals%&. Otherwise,
16911 Exim will not recognize the domain literal syntax in addresses.
16915 . ////////////////////////////////////////////////////////////////////////////
16916 . ////////////////////////////////////////////////////////////////////////////
16918 .chapter "The iplookup router" "CHID6"
16919 .cindex "&(iplookup)& router"
16920 .cindex "routers" "&(iplookup)&"
16921 The &(iplookup)& router was written to fulfil a specific requirement in
16922 Cambridge University (which in fact no longer exists). For this reason, it is
16923 not included in the binary of Exim by default. If you want to include it, you
16926 ROUTER_IPLOOKUP=yes
16928 in your &_Local/Makefile_& configuration file.
16930 The &(iplookup)& router routes an address by sending it over a TCP or UDP
16931 connection to one or more specific hosts. The host can then return the same or
16932 a different address &-- in effect rewriting the recipient address in the
16933 message's envelope. The new address is then passed on to subsequent routers. If
16934 this process fails, the address can be passed on to other routers, or delivery
16935 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
16936 must not be specified for it.
16938 .cindex "options" "&(iplookup)& router"
16939 .option hosts iplookup string unset
16940 This option must be supplied. Its value is a colon-separated list of host
16941 names. The hosts are looked up using &[gethostbyname()]&
16942 (or &[getipnodebyname()]& when available)
16943 and are tried in order until one responds to the query. If none respond, what
16944 happens is controlled by &%optional%&.
16947 .option optional iplookup boolean false
16948 If &%optional%& is true, if no response is obtained from any host, the address
16949 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
16950 delivery to the address is deferred.
16953 .option port iplookup integer 0
16954 .cindex "port" "&(iplookup)& router"
16955 This option must be supplied. It specifies the port number for the TCP or UDP
16959 .option protocol iplookup string udp
16960 This option can be set to &"udp"& or &"tcp"& to specify which of the two
16961 protocols is to be used.
16964 .option query iplookup string&!! "see below"
16965 This defines the content of the query that is sent to the remote hosts. The
16968 $local_part@$domain $local_part@$domain
16970 The repetition serves as a way of checking that a response is to the correct
16971 query in the default case (see &%response_pattern%& below).
16974 .option reroute iplookup string&!! unset
16975 If this option is not set, the rerouted address is precisely the byte string
16976 returned by the remote host, up to the first white space, if any. If set, the
16977 string is expanded to form the rerouted address. It can include parts matched
16978 in the response by &%response_pattern%& by means of numeric variables such as
16979 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
16980 whether or not a pattern is in use. In all cases, the rerouted address must end
16981 up in the form &'local_part@domain'&.
16984 .option response_pattern iplookup string unset
16985 This option can be set to a regular expression that is applied to the string
16986 returned from the remote host. If the pattern does not match the response, the
16987 router declines. If &%response_pattern%& is not set, no checking of the
16988 response is done, unless the query was defaulted, in which case there is a
16989 check that the text returned after the first white space is the original
16990 address. This checks that the answer that has been received is in response to
16991 the correct question. For example, if the response is just a new domain, the
16992 following could be used:
16994 response_pattern = ^([^@]+)$
16995 reroute = $local_part@$1
16998 .option timeout iplookup time 5s
16999 This specifies the amount of time to wait for a response from the remote
17000 machine. The same timeout is used for the &[connect()]& function for a TCP
17001 call. It does not apply to UDP.
17006 . ////////////////////////////////////////////////////////////////////////////
17007 . ////////////////////////////////////////////////////////////////////////////
17009 .chapter "The manualroute router" "CHID7"
17010 .scindex IIDmanrou1 "&(manualroute)& router"
17011 .scindex IIDmanrou2 "routers" "&(manualroute)&"
17012 .cindex "domain" "manually routing"
17013 The &(manualroute)& router is so-called because it provides a way of manually
17014 routing an address according to its domain. It is mainly used when you want to
17015 route addresses to remote hosts according to your own rules, bypassing the
17016 normal DNS routing that looks up MX records. However, &(manualroute)& can also
17017 route to local transports, a facility that may be useful if you want to save
17018 messages for dial-in hosts in local files.
17020 The &(manualroute)& router compares a list of domain patterns with the domain
17021 it is trying to route. If there is no match, the router declines. Each pattern
17022 has associated with it a list of hosts and some other optional data, which may
17023 include a transport. The combination of a pattern and its data is called a
17024 &"routing rule"&. For patterns that do not have an associated transport, the
17025 generic &%transport%& option must specify a transport, unless the router is
17026 being used purely for verification (see &%verify_only%&).
17029 In the case of verification, matching the domain pattern is sufficient for the
17030 router to accept the address. When actually routing an address for delivery,
17031 an address that matches a domain pattern is queued for the associated
17032 transport. If the transport is not a local one, a host list must be associated
17033 with the pattern; IP addresses are looked up for the hosts, and these are
17034 passed to the transport along with the mail address. For local transports, a
17035 host list is optional. If it is present, it is passed in &$host$& as a single
17038 The list of routing rules can be provided as an inline string in
17039 &%route_list%&, or the data can be obtained by looking up the domain in a file
17040 or database by setting &%route_data%&. Only one of these settings may appear in
17041 any one instance of &(manualroute)&. The format of routing rules is described
17042 below, following the list of private options.
17045 .section "Private options for manualroute" "SECTprioptman"
17047 .cindex "options" "&(manualroute)& router"
17048 The private options for the &(manualroute)& router are as follows:
17050 .option host_all_ignored manualroute string defer
17051 See &%host_find_failed%&.
17053 .option host_find_failed manualroute string freeze
17054 This option controls what happens when &(manualroute)& tries to find an IP
17055 address for a host, and the host does not exist. The option can be set to one
17056 of the following values:
17065 The default (&"freeze"&) assumes that this state is a serious configuration
17066 error. The difference between &"pass"& and &"decline"& is that the former
17067 forces the address to be passed to the next router (or the router defined by
17070 overriding &%no_more%&, whereas the latter passes the address to the next
17071 router only if &%more%& is true.
17073 The value &"ignore"& causes Exim to completely ignore a host whose IP address
17074 cannot be found. If all the hosts in the list are ignored, the behaviour is
17075 controlled by the &%host_all_ignored%& option. This takes the same values
17076 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
17078 The &%host_find_failed%& option applies only to a definite &"does not exist"&
17079 state; if a host lookup gets a temporary error, delivery is deferred unless the
17080 generic &%pass_on_timeout%& option is set.
17083 .option hosts_randomize manualroute boolean false
17084 .cindex "randomized host list"
17085 .cindex "host" "list of; randomized"
17086 If this option is set, the order of the items in a host list in a routing rule
17087 is randomized each time the list is used, unless an option in the routing rule
17088 overrides (see below). Randomizing the order of a host list can be used to do
17089 crude load sharing. However, if more than one mail address is routed by the
17090 same router to the same host list, the host lists are considered to be the same
17091 (even though they may be randomized into different orders) for the purpose of
17092 deciding whether to batch the deliveries into a single SMTP transaction.
17094 When &%hosts_randomize%& is true, a host list may be split
17095 into groups whose order is separately randomized. This makes it possible to
17096 set up MX-like behaviour. The boundaries between groups are indicated by an
17097 item that is just &`+`& in the host list. For example:
17099 route_list = * host1:host2:host3:+:host4:host5
17101 The order of the first three hosts and the order of the last two hosts is
17102 randomized for each use, but the first three always end up before the last two.
17103 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
17104 randomized host list is passed to an &(smtp)& transport that also has
17105 &%hosts_randomize set%&, the list is not re-randomized.
17108 .option route_data manualroute string&!! unset
17109 If this option is set, it must expand to yield the data part of a routing rule.
17110 Typically, the expansion string includes a lookup based on the domain. For
17113 route_data = ${lookup{$domain}dbm{/etc/routes}}
17115 If the expansion is forced to fail, or the result is an empty string, the
17116 router declines. Other kinds of expansion failure cause delivery to be
17120 .option route_list manualroute "string list" unset
17121 This string is a list of routing rules, in the form defined below. Note that,
17122 unlike most string lists, the items are separated by semicolons. This is so
17123 that they may contain colon-separated host lists.
17126 .option same_domain_copy_routing manualroute boolean false
17127 .cindex "address" "copying routing"
17128 Addresses with the same domain are normally routed by the &(manualroute)&
17129 router to the same list of hosts. However, this cannot be presumed, because the
17130 router options and preconditions may refer to the local part of the address. By
17131 default, therefore, Exim routes each address in a message independently. DNS
17132 servers run caches, so repeated DNS lookups are not normally expensive, and in
17133 any case, personal messages rarely have more than a few recipients.
17135 If you are running mailing lists with large numbers of subscribers at the same
17136 domain, and you are using a &(manualroute)& router which is independent of the
17137 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
17138 lookups for identical domains in one message. In this case, when
17139 &(manualroute)& routes an address to a remote transport, any other unrouted
17140 addresses in the message that have the same domain are automatically given the
17141 same routing without processing them independently. However, this is only done
17142 if &%headers_add%& and &%headers_remove%& are unset.
17147 .section "Routing rules in route_list" "SECID120"
17148 The value of &%route_list%& is a string consisting of a sequence of routing
17149 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
17150 entered as two semicolons. Alternatively, the list separator can be changed as
17151 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
17152 Empty rules are ignored. The format of each rule is
17154 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
17156 The following example contains two rules, each with a simple domain pattern and
17160 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
17161 thes.ref.example mail-3.ref.example:mail-4.ref.example
17163 The three parts of a rule are separated by white space. The pattern and the
17164 list of hosts can be enclosed in quotes if necessary, and if they are, the
17165 usual quoting rules apply. Each rule in a &%route_list%& must start with a
17166 single domain pattern, which is the only mandatory item in the rule. The
17167 pattern is in the same format as one item in a domain list (see section
17168 &<<SECTdomainlist>>&),
17169 except that it may not be the name of an interpolated file.
17170 That is, it may be wildcarded, or a regular expression, or a file or database
17171 lookup (with semicolons doubled, because of the use of semicolon as a separator
17172 in a &%route_list%&).
17174 The rules in &%route_list%& are searched in order until one of the patterns
17175 matches the domain that is being routed. The list of hosts and then options are
17176 then used as described below. If there is no match, the router declines. When
17177 &%route_list%& is set, &%route_data%& must not be set.
17181 .section "Routing rules in route_data" "SECID121"
17182 The use of &%route_list%& is convenient when there are only a small number of
17183 routing rules. For larger numbers, it is easier to use a file or database to
17184 hold the routing information, and use the &%route_data%& option instead.
17185 The value of &%route_data%& is a list of hosts, followed by (optional) options.
17186 Most commonly, &%route_data%& is set as a string that contains an
17187 expansion lookup. For example, suppose we place two routing rules in a file
17190 dict.ref.example: mail-1.ref.example:mail-2.ref.example
17191 thes.ref.example: mail-3.ref.example:mail-4.ref.example
17193 This data can be accessed by setting
17195 route_data = ${lookup{$domain}lsearch{/the/file/name}}
17197 Failure of the lookup results in an empty string, causing the router to
17198 decline. However, you do not have to use a lookup in &%route_data%&. The only
17199 requirement is that the result of expanding the string is a list of hosts,
17200 possibly followed by options, separated by white space. The list of hosts must
17201 be enclosed in quotes if it contains white space.
17206 .section "Format of the list of hosts" "SECID122"
17207 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
17208 always separately expanded before use. If the expansion fails, the router
17209 declines. The result of the expansion must be a colon-separated list of names
17210 and/or IP addresses, optionally also including ports. The format of each item
17211 in the list is described in the next section. The list separator can be changed
17212 as described in section &<<SECTlistconstruct>>&.
17214 If the list of hosts was obtained from a &%route_list%& item, the following
17215 variables are set during its expansion:
17218 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
17219 If the domain was matched against a regular expression, the numeric variables
17220 &$1$&, &$2$&, etc. may be set. For example:
17222 route_list = ^domain(\d+) host-$1.text.example
17225 &$0$& is always set to the entire domain.
17227 &$1$& is also set when partial matching is done in a file lookup.
17230 .vindex "&$value$&"
17231 If the pattern that matched the domain was a lookup item, the data that was
17232 looked up is available in the expansion variable &$value$&. For example:
17234 route_list = lsearch;;/some/file.routes $value
17238 Note the doubling of the semicolon in the pattern that is necessary because
17239 semicolon is the default route list separator.
17243 .section "Format of one host item" "SECTformatonehostitem"
17244 Each item in the list of hosts is either a host name or an IP address,
17245 optionally with an attached port number. When no port is given, an IP address
17246 is not enclosed in brackets. When a port is specified, it overrides the port
17247 specification on the transport. The port is separated from the name or address
17248 by a colon. This leads to some complications:
17251 Because colon is the default separator for the list of hosts, either
17252 the colon that specifies a port must be doubled, or the list separator must
17253 be changed. The following two examples have the same effect:
17255 route_list = * "host1.tld::1225 : host2.tld::1226"
17256 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
17259 When IPv6 addresses are involved, it gets worse, because they contain
17260 colons of their own. To make this case easier, it is permitted to
17261 enclose an IP address (either v4 or v6) in square brackets if a port
17262 number follows. For example:
17264 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
17268 .section "How the list of hosts is used" "SECThostshowused"
17269 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
17270 the hosts is tried, in the order specified, when carrying out the SMTP
17271 delivery. However, the order can be changed by setting the &%hosts_randomize%&
17272 option, either on the router (see section &<<SECTprioptman>>& above), or on the
17275 Hosts may be listed by name or by IP address. An unadorned name in the list of
17276 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
17277 interpreted as an indirection to a sublist of hosts obtained by looking up MX
17278 records in the DNS. For example:
17280 route_list = * x.y.z:p.q.r/MX:e.f.g
17282 If this feature is used with a port specifier, the port must come last. For
17285 route_list = * dom1.tld/mx::1225
17287 If the &%hosts_randomize%& option is set, the order of the items in the list is
17288 randomized before any lookups are done. Exim then scans the list; for any name
17289 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
17290 be an interface on the local host and the item is not the first in the list,
17291 Exim discards it and any subsequent items. If it is the first item, what
17292 happens is controlled by the
17293 .oindex "&%self%&" "in &(manualroute)& router"
17294 &%self%& option of the router.
17296 A name on the list that is followed by &`/MX`& is replaced with the list of
17297 hosts obtained by looking up MX records for the name. This is always a DNS
17298 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
17299 below) are not relevant here. The order of these hosts is determined by the
17300 preference values in the MX records, according to the usual rules. Because
17301 randomizing happens before the MX lookup, it does not affect the order that is
17302 defined by MX preferences.
17304 If the local host is present in the sublist obtained from MX records, but is
17305 not the most preferred host in that list, it and any equally or less
17306 preferred hosts are removed before the sublist is inserted into the main list.
17308 If the local host is the most preferred host in the MX list, what happens
17309 depends on where in the original list of hosts the &`/MX`& item appears. If it
17310 is not the first item (that is, there are previous hosts in the main list),
17311 Exim discards this name and any subsequent items in the main list.
17313 If the MX item is first in the list of hosts, and the local host is the
17314 most preferred host, what happens is controlled by the &%self%& option of the
17317 DNS failures when lookup up the MX records are treated in the same way as DNS
17318 failures when looking up IP addresses: &%pass_on_timeout%& and
17319 &%host_find_failed%& are used when relevant.
17321 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
17322 whether obtained from an MX lookup or not.
17326 .section "How the options are used" "SECThowoptused"
17327 The options are a sequence of words; in practice no more than three are ever
17328 present. One of the words can be the name of a transport; this overrides the
17329 &%transport%& option on the router for this particular routing rule only. The
17330 other words (if present) control randomization of the list of hosts on a
17331 per-rule basis, and how the IP addresses of the hosts are to be found when
17332 routing to a remote transport. These options are as follows:
17335 &%randomize%&: randomize the order of the hosts in this list, overriding the
17336 setting of &%hosts_randomize%& for this routing rule only.
17338 &%no_randomize%&: do not randomize the order of the hosts in this list,
17339 overriding the setting of &%hosts_randomize%& for this routing rule only.
17341 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
17342 find IP addresses. This function may ultimately cause a DNS lookup, but it may
17343 also look in &_/etc/hosts_& or other sources of information.
17345 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
17346 no address records are found. If there is a temporary DNS error (such as a
17347 timeout), delivery is deferred.
17352 route_list = domain1 host1:host2:host3 randomize bydns;\
17353 domain2 host4:host5
17355 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
17356 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
17357 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
17358 or &[gethostbyname()]&, and the result of the lookup is the result of that
17361 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
17362 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
17363 instead of TRY_AGAIN. That is why the default action is to try a DNS
17364 lookup first. Only if that gives a definite &"no such host"& is the local
17369 If no IP address for a host can be found, what happens is controlled by the
17370 &%host_find_failed%& option.
17373 When an address is routed to a local transport, IP addresses are not looked up.
17374 The host list is passed to the transport in the &$host$& variable.
17378 .section "Manualroute examples" "SECID123"
17379 In some of the examples that follow, the presence of the &%remote_smtp%&
17380 transport, as defined in the default configuration file, is assumed:
17383 .cindex "smart host" "example router"
17384 The &(manualroute)& router can be used to forward all external mail to a
17385 &'smart host'&. If you have set up, in the main part of the configuration, a
17386 named domain list that contains your local domains, for example:
17388 domainlist local_domains = my.domain.example
17390 You can arrange for all other domains to be routed to a smart host by making
17391 your first router something like this:
17394 driver = manualroute
17395 domains = !+local_domains
17396 transport = remote_smtp
17397 route_list = * smarthost.ref.example
17399 This causes all non-local addresses to be sent to the single host
17400 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
17401 they are tried in order
17402 (but you can use &%hosts_randomize%& to vary the order each time).
17403 Another way of configuring the same thing is this:
17406 driver = manualroute
17407 transport = remote_smtp
17408 route_list = !+local_domains smarthost.ref.example
17410 There is no difference in behaviour between these two routers as they stand.
17411 However, they behave differently if &%no_more%& is added to them. In the first
17412 example, the router is skipped if the domain does not match the &%domains%&
17413 precondition; the following router is always tried. If the router runs, it
17414 always matches the domain and so can never decline. Therefore, &%no_more%&
17415 would have no effect. In the second case, the router is never skipped; it
17416 always runs. However, if it doesn't match the domain, it declines. In this case
17417 &%no_more%& would prevent subsequent routers from running.
17420 .cindex "mail hub example"
17421 A &'mail hub'& is a host which receives mail for a number of domains via MX
17422 records in the DNS and delivers it via its own private routing mechanism. Often
17423 the final destinations are behind a firewall, with the mail hub being the one
17424 machine that can connect to machines both inside and outside the firewall. The
17425 &(manualroute)& router is usually used on a mail hub to route incoming messages
17426 to the correct hosts. For a small number of domains, the routing can be inline,
17427 using the &%route_list%& option, but for a larger number a file or database
17428 lookup is easier to manage.
17430 If the domain names are in fact the names of the machines to which the mail is
17431 to be sent by the mail hub, the configuration can be quite simple. For
17435 driver = manualroute
17436 transport = remote_smtp
17437 route_list = *.rhodes.tvs.example $domain
17439 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
17440 whose names are the same as the mail domains. A similar approach can be taken
17441 if the host name can be obtained from the domain name by a string manipulation
17442 that the expansion facilities can handle. Otherwise, a lookup based on the
17443 domain can be used to find the host:
17446 driver = manualroute
17447 transport = remote_smtp
17448 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
17450 The result of the lookup must be the name or IP address of the host (or
17451 hosts) to which the address is to be routed. If the lookup fails, the route
17452 data is empty, causing the router to decline. The address then passes to the
17456 .cindex "batched SMTP output example"
17457 .cindex "SMTP" "batched outgoing; example"
17458 You can use &(manualroute)& to deliver messages to pipes or files in batched
17459 SMTP format for onward transportation by some other means. This is one way of
17460 storing mail for a dial-up host when it is not connected. The route list entry
17461 can be as simple as a single domain name in a configuration like this:
17464 driver = manualroute
17465 transport = batchsmtp_appendfile
17466 route_list = saved.domain.example
17468 though often a pattern is used to pick up more than one domain. If there are
17469 several domains or groups of domains with different transport requirements,
17470 different transports can be listed in the routing information:
17473 driver = manualroute
17475 *.saved.domain1.example $domain batch_appendfile; \
17476 *.saved.domain2.example \
17477 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
17480 .vindex "&$domain$&"
17482 The first of these just passes the domain in the &$host$& variable, which
17483 doesn't achieve much (since it is also in &$domain$&), but the second does a
17484 file lookup to find a value to pass, causing the router to decline to handle
17485 the address if the lookup fails.
17488 .cindex "UUCP" "example of router for"
17489 Routing mail directly to UUCP software is a specific case of the use of
17490 &(manualroute)& in a gateway to another mail environment. This is an example of
17491 one way it can be done:
17497 command = /usr/local/bin/uux -r - \
17498 ${substr_-5:$host}!rmail ${local_part}
17499 return_fail_output = true
17504 driver = manualroute
17506 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
17508 The file &_/usr/local/exim/uucphosts_& contains entries like
17510 darksite.ethereal.example: darksite.UUCP
17512 It can be set up more simply without adding and removing &".UUCP"& but this way
17513 makes clear the distinction between the domain name
17514 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
17516 .ecindex IIDmanrou1
17517 .ecindex IIDmanrou2
17526 . ////////////////////////////////////////////////////////////////////////////
17527 . ////////////////////////////////////////////////////////////////////////////
17529 .chapter "The queryprogram router" "CHAPdriverlast"
17530 .scindex IIDquerou1 "&(queryprogram)& router"
17531 .scindex IIDquerou2 "routers" "&(queryprogram)&"
17532 .cindex "routing" "by external program"
17533 The &(queryprogram)& router routes an address by running an external command
17534 and acting on its output. This is an expensive way to route, and is intended
17535 mainly for use in lightly-loaded systems, or for performing experiments.
17536 However, if it is possible to use the precondition options (&%domains%&,
17537 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
17538 be used in special cases, even on a busy host. There are the following private
17540 .cindex "options" "&(queryprogram)& router"
17542 .option command queryprogram string&!! unset
17543 This option must be set. It specifies the command that is to be run. The
17544 command is split up into a command name and arguments, and then each is
17545 expanded separately (exactly as for a &(pipe)& transport, described in chapter
17546 &<<CHAPpipetransport>>&).
17549 .option command_group queryprogram string unset
17550 .cindex "gid (group id)" "in &(queryprogram)& router"
17551 This option specifies a gid to be set when running the command while routing an
17552 address for deliver. It must be set if &%command_user%& specifies a numerical
17553 uid. If it begins with a digit, it is interpreted as the numerical value of the
17554 gid. Otherwise it is looked up using &[getgrnam()]&.
17557 .option command_user queryprogram string unset
17558 .cindex "uid (user id)" "for &(queryprogram)&"
17559 This option must be set. It specifies the uid which is set when running the
17560 command while routing an address for delivery. If the value begins with a digit,
17561 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
17562 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
17563 not set, a value for the gid also.
17565 &*Warning:*& Changing uid and gid is possible only when Exim is running as
17566 root, which it does during a normal delivery in a conventional configuration.
17567 However, when an address is being verified during message reception, Exim is
17568 usually running as the Exim user, not as root. If the &(queryprogram)& router
17569 is called from a non-root process, Exim cannot change uid or gid before running
17570 the command. In this circumstance the command runs under the current uid and
17574 .option current_directory queryprogram string /
17575 This option specifies an absolute path which is made the current directory
17576 before running the command.
17579 .option timeout queryprogram time 1h
17580 If the command does not complete within the timeout period, its process group
17581 is killed and the message is frozen. A value of zero time specifies no
17585 The standard output of the command is connected to a pipe, which is read when
17586 the command terminates. It should consist of a single line of output,
17587 containing up to five fields, separated by white space. The maximum length of
17588 the line is 1023 characters. Longer lines are silently truncated. The first
17589 field is one of the following words (case-insensitive):
17592 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
17595 &'Decline'&: the router declines; pass the address to the next router, unless
17596 &%no_more%& is set.
17598 &'Fail'&: routing failed; do not pass the address to any more routers. Any
17599 subsequent text on the line is an error message. If the router is run as part
17600 of address verification during an incoming SMTP message, the message is
17601 included in the SMTP response.
17603 &'Defer'&: routing could not be completed at this time; try again later. Any
17604 subsequent text on the line is an error message which is logged. It is not
17605 included in any SMTP response.
17607 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
17609 &'Pass'&: pass the address to the next router (or the router specified by
17610 &%pass_router%&), overriding &%no_more%&.
17612 &'Redirect'&: the message is redirected. The remainder of the line is a list of
17613 new addresses, which are routed independently, starting with the first router,
17614 or the router specified by &%redirect_router%&, if set.
17617 When the first word is &'accept'&, the remainder of the line consists of a
17618 number of keyed data values, as follows (split into two lines here, to fit on
17621 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
17622 LOOKUP=byname|bydns DATA=<text>
17624 The data items can be given in any order, and all are optional. If no transport
17625 is included, the transport specified by the generic &%transport%& option is
17626 used. The list of hosts and the lookup type are needed only if the transport is
17627 an &(smtp)& transport that does not itself supply a list of hosts.
17629 The format of the list of hosts is the same as for the &(manualroute)& router.
17630 As well as host names and IP addresses with optional port numbers, as described
17631 in section &<<SECTformatonehostitem>>&, it may contain names followed by
17632 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
17633 (see section &<<SECThostshowused>>&).
17635 If the lookup type is not specified, Exim behaves as follows when trying to
17636 find an IP address for each host: First, a DNS lookup is done. If this yields
17637 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
17638 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
17639 result of the lookup is the result of that call.
17641 .vindex "&$address_data$&"
17642 If the DATA field is set, its value is placed in the &$address_data$&
17643 variable. For example, this return line
17645 accept hosts=x1.y.example:x2.y.example data="rule1"
17647 routes the address to the default transport, passing a list of two hosts. When
17648 the transport runs, the string &"rule1"& is in &$address_data$&.
17649 .ecindex IIDquerou1
17650 .ecindex IIDquerou2
17655 . ////////////////////////////////////////////////////////////////////////////
17656 . ////////////////////////////////////////////////////////////////////////////
17658 .chapter "The redirect router" "CHAPredirect"
17659 .scindex IIDredrou1 "&(redirect)& router"
17660 .scindex IIDredrou2 "routers" "&(redirect)&"
17661 .cindex "alias file" "in a &(redirect)& router"
17662 .cindex "address redirection" "&(redirect)& router"
17663 The &(redirect)& router handles several kinds of address redirection. Its most
17664 common uses are for resolving local part aliases from a central alias file
17665 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
17666 files, but it has many other potential uses. The incoming address can be
17667 redirected in several different ways:
17670 It can be replaced by one or more new addresses which are themselves routed
17673 It can be routed to be delivered to a given file or directory.
17675 It can be routed to be delivered to a specified pipe command.
17677 It can cause an automatic reply to be generated.
17679 It can be forced to fail, optionally with a custom error message.
17681 It can be temporarily deferred, optionally with a custom message.
17683 It can be discarded.
17686 The generic &%transport%& option must not be set for &(redirect)& routers.
17687 However, there are some private options which define transports for delivery to
17688 files and pipes, and for generating autoreplies. See the &%file_transport%&,
17689 &%pipe_transport%& and &%reply_transport%& descriptions below.
17693 .section "Redirection data" "SECID124"
17694 The router operates by interpreting a text string which it obtains either by
17695 expanding the contents of the &%data%& option, or by reading the entire
17696 contents of a file whose name is given in the &%file%& option. These two
17697 options are mutually exclusive. The first is commonly used for handling system
17698 aliases, in a configuration like this:
17702 data = ${lookup{$local_part}lsearch{/etc/aliases}}
17704 If the lookup fails, the expanded string in this example is empty. When the
17705 expansion of &%data%& results in an empty string, the router declines. A forced
17706 expansion failure also causes the router to decline; other expansion failures
17707 cause delivery to be deferred.
17709 A configuration using &%file%& is commonly used for handling users'
17710 &_.forward_& files, like this:
17715 file = $home/.forward
17718 If the file does not exist, or causes no action to be taken (for example, it is
17719 empty or consists only of comments), the router declines. &*Warning*&: This
17720 is not the case when the file contains syntactically valid items that happen to
17721 yield empty addresses, for example, items containing only RFC 2822 address
17726 .section "Forward files and address verification" "SECID125"
17727 .cindex "address redirection" "while verifying"
17728 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
17729 &_.forward_& files, as in the example above. There are two reasons for this:
17732 When Exim is receiving an incoming SMTP message from a remote host, it is
17733 running under the Exim uid, not as root. Exim is unable to change uid to read
17734 the file as the user, and it may not be able to read it as the Exim user. So in
17735 practice the router may not be able to operate.
17737 However, even when the router can operate, the existence of a &_.forward_& file
17738 is unimportant when verifying an address. What should be checked is whether the
17739 local part is a valid user name or not. Cutting out the redirection processing
17740 saves some resources.
17748 .section "Interpreting redirection data" "SECID126"
17749 .cindex "Sieve filter" "specifying in redirection data"
17750 .cindex "filter" "specifying in redirection data"
17751 The contents of the data string, whether obtained from &%data%& or &%file%&,
17752 can be interpreted in two different ways:
17755 If the &%allow_filter%& option is set true, and the data begins with the text
17756 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
17757 &'filtering'& instructions in the form of an Exim or Sieve filter file,
17758 respectively. Details of the syntax and semantics of filter files are described
17759 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
17760 document is intended for use by end users.
17762 Otherwise, the data must be a comma-separated list of redirection items, as
17763 described in the next section.
17766 When a message is redirected to a file (a &"mail folder"&), the file name given
17767 in a non-filter redirection list must always be an absolute path. A filter may
17768 generate a relative path &-- how this is handled depends on the transport's
17769 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
17770 for the &(appendfile)& transport.
17774 .section "Items in a non-filter redirection list" "SECTitenonfilred"
17775 .cindex "address redirection" "non-filter list items"
17776 When the redirection data is not an Exim or Sieve filter, for example, if it
17777 comes from a conventional alias or forward file, it consists of a list of
17778 addresses, file names, pipe commands, or certain special items (see section
17779 &<<SECTspecitredli>>& below). The special items can be individually enabled or
17780 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
17781 depending on their default values. The items in the list are separated by
17782 commas or newlines.
17783 If a comma is required in an item, the entire item must be enclosed in double
17786 Lines starting with a # character are comments, and are ignored, and # may
17787 also appear following a comma, in which case everything between the # and the
17788 next newline character is ignored.
17790 If an item is entirely enclosed in double quotes, these are removed. Otherwise
17791 double quotes are retained because some forms of mail address require their use
17792 (but never to enclose the entire address). In the following description,
17793 &"item"& refers to what remains after any surrounding double quotes have been
17796 .vindex "&$local_part$&"
17797 &*Warning*&: If you use an Exim expansion to construct a redirection address,
17798 and the expansion contains a reference to &$local_part$&, you should make use
17799 of the &%quote_local_part%& expansion operator, in case the local part contains
17800 special characters. For example, to redirect all mail for the domain
17801 &'obsolete.example'&, retaining the existing local part, you could use this
17804 data = ${quote_local_part:$local_part}@newdomain.example
17808 .section "Redirecting to a local mailbox" "SECTredlocmai"
17809 .cindex "routing" "loops in"
17810 .cindex "loop" "while routing, avoidance of"
17811 .cindex "address redirection" "to local mailbox"
17812 A redirection item may safely be the same as the address currently under
17813 consideration. This does not cause a routing loop, because a router is
17814 automatically skipped if any ancestor of the address that is being processed
17815 is the same as the current address and was processed by the current router.
17816 Such an address is therefore passed to the following routers, so it is handled
17817 as if there were no redirection. When making this loop-avoidance test, the
17818 complete local part, including any prefix or suffix, is used.
17820 .cindex "address redirection" "local part without domain"
17821 Specifying the same local part without a domain is a common usage in personal
17822 filter files when the user wants to have messages delivered to the local
17823 mailbox and also forwarded elsewhere. For example, the user whose login is
17824 &'cleo'& might have a &_.forward_& file containing this:
17826 cleo, cleopatra@egypt.example
17828 .cindex "backslash in alias file"
17829 .cindex "alias file" "backslash in"
17830 For compatibility with other MTAs, such unqualified local parts may be
17831 preceded by &"\"&, but this is not a requirement for loop prevention. However,
17832 it does make a difference if more than one domain is being handled
17835 If an item begins with &"\"& and the rest of the item parses as a valid RFC
17836 2822 address that does not include a domain, the item is qualified using the
17837 domain of the incoming address. In the absence of a leading &"\"&, unqualified
17838 addresses are qualified using the value in &%qualify_recipient%&, but you can
17839 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
17841 Care must be taken if there are alias names for local users.
17842 Consider an MTA handling a single local domain where the system alias file
17847 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
17848 messages in the local mailbox, and also forward copies elsewhere. He creates
17851 Sam.Reman, spqr@reme.elsewhere.example
17853 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
17854 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
17855 second time round, because it has previously routed it,
17856 and the following routers presumably cannot handle the alias. The forward file
17857 should really contain
17859 spqr, spqr@reme.elsewhere.example
17861 but because this is such a common error, the &%check_ancestor%& option (see
17862 below) exists to provide a way to get round it. This is normally set on a
17863 &(redirect)& router that is handling users' &_.forward_& files.
17867 .section "Special items in redirection lists" "SECTspecitredli"
17868 In addition to addresses, the following types of item may appear in redirection
17869 lists (that is, in non-filter redirection data):
17872 .cindex "pipe" "in redirection list"
17873 .cindex "address redirection" "to pipe"
17874 An item is treated as a pipe command if it begins with &"|"& and does not parse
17875 as a valid RFC 2822 address that includes a domain. A transport for running the
17876 command must be specified by the &%pipe_transport%& option.
17877 Normally, either the router or the transport specifies a user and a group under
17878 which to run the delivery. The default is to use the Exim user and group.
17880 Single or double quotes can be used for enclosing the individual arguments of
17881 the pipe command; no interpretation of escapes is done for single quotes. If
17882 the command contains a comma character, it is necessary to put the whole item
17883 in double quotes, for example:
17885 "|/some/command ready,steady,go"
17887 since items in redirection lists are terminated by commas. Do not, however,
17888 quote just the command. An item such as
17890 |"/some/command ready,steady,go"
17892 is interpreted as a pipe with a rather strange command name, and no arguments.
17895 .cindex "file" "in redirection list"
17896 .cindex "address redirection" "to file"
17897 An item is interpreted as a path name if it begins with &"/"& and does not
17898 parse as a valid RFC 2822 address that includes a domain. For example,
17900 /home/world/minbari
17902 is treated as a file name, but
17904 /s=molari/o=babylon/@x400gate.way
17906 is treated as an address. For a file name, a transport must be specified using
17907 the &%file_transport%& option. However, if the generated path name ends with a
17908 forward slash character, it is interpreted as a directory name rather than a
17909 file name, and &%directory_transport%& is used instead.
17911 Normally, either the router or the transport specifies a user and a group under
17912 which to run the delivery. The default is to use the Exim user and group.
17914 .cindex "&_/dev/null_&"
17915 However, if a redirection item is the path &_/dev/null_&, delivery to it is
17916 bypassed at a high level, and the log entry shows &"**bypassed**"&
17917 instead of a transport name. In this case the user and group are not used.
17920 .cindex "included address list"
17921 .cindex "address redirection" "included external list"
17922 If an item is of the form
17924 :include:<path name>
17926 a list of further items is taken from the given file and included at that
17927 point. &*Note*&: Such a file can not be a filter file; it is just an
17928 out-of-line addition to the list. The items in the included list are separated
17929 by commas or newlines and are not subject to expansion. If this is the first
17930 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
17931 the alias name. This example is incorrect:
17933 list1 :include:/opt/lists/list1
17935 It must be given as
17937 list1: :include:/opt/lists/list1
17940 .cindex "address redirection" "to black hole"
17941 Sometimes you want to throw away mail to a particular local part. Making the
17942 &%data%& option expand to an empty string does not work, because that causes
17943 the router to decline. Instead, the alias item
17944 .cindex "black hole"
17945 .cindex "abandoning mail"
17946 &':blackhole:'& can be used. It does what its name implies. No delivery is
17947 done, and no error message is generated. This has the same effect as specifing
17948 &_/dev/null_& as a destination, but it can be independently disabled.
17950 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
17951 delivery is done for the original local part, even if other redirection items
17952 are present. If you are generating a multi-item list (for example, by reading a
17953 database) and need the ability to provide a no-op item, you must use
17957 .cindex "delivery" "forcing failure"
17958 .cindex "delivery" "forcing deferral"
17959 .cindex "failing delivery" "forcing"
17960 .cindex "deferred delivery, forcing"
17961 .cindex "customizing" "failure message"
17962 An attempt to deliver a particular address can be deferred or forced to fail by
17963 redirection items of the form
17968 respectively. When a redirection list contains such an item, it applies
17969 to the entire redirection; any other items in the list are ignored. Any
17970 text following &':fail:'& or &':defer:'& is placed in the error text
17971 associated with the failure. For example, an alias file might contain:
17973 X.Employee: :fail: Gone away, no forwarding address
17975 In the case of an address that is being verified from an ACL or as the subject
17977 .cindex "VRFY" "error text, display of"
17978 VRFY command, the text is included in the SMTP error response by
17980 .cindex "EXPN" "error text, display of"
17981 The text is not included in the response to an EXPN command. In non-SMTP cases
17982 the text is included in the error message that Exim generates.
17984 .cindex "SMTP" "error codes"
17985 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
17986 &':fail:'&. However, if the message starts with three digits followed by a
17987 space, optionally followed by an extended code of the form &'n.n.n'&, also
17988 followed by a space, and the very first digit is the same as the default error
17989 code, the code from the message is used instead. If the very first digit is
17990 incorrect, a panic error is logged, and the default code is used. You can
17991 suppress the use of the supplied code in a redirect router by setting the
17992 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
17995 .vindex "&$acl_verify_message$&"
17996 In an ACL, an explicitly provided message overrides the default, but the
17997 default message is available in the variable &$acl_verify_message$& and can
17998 therefore be included in a custom message if this is desired.
18000 Normally the error text is the rest of the redirection list &-- a comma does
18001 not terminate it &-- but a newline does act as a terminator. Newlines are not
18002 normally present in alias expansions. In &(lsearch)& lookups they are removed
18003 as part of the continuation process, but they may exist in other kinds of
18004 lookup and in &':include:'& files.
18006 During routing for message delivery (as opposed to verification), a redirection
18007 containing &':fail:'& causes an immediate failure of the incoming address,
18008 whereas &':defer:'& causes the message to remain on the queue so that a
18009 subsequent delivery attempt can happen at a later time. If an address is
18010 deferred for too long, it will ultimately fail, because the normal retry
18014 .cindex "alias file" "exception to default"
18015 Sometimes it is useful to use a single-key search type with a default (see
18016 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
18017 for exceptions to the default. These can be handled by aliasing them to
18018 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
18019 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
18020 results in an empty redirection list has the same effect.
18024 .section "Duplicate addresses" "SECTdupaddr"
18025 .cindex "duplicate addresses"
18026 .cindex "address duplicate, discarding"
18027 .cindex "pipe" "duplicated"
18028 Exim removes duplicate addresses from the list to which it is delivering, so as
18029 to deliver just one copy to each address. This does not apply to deliveries
18030 routed to pipes by different immediate parent addresses, but an indirect
18031 aliasing scheme of the type
18033 pipe: |/some/command $local_part
18037 does not work with a message that is addressed to both local parts, because
18038 when the second is aliased to the intermediate local part &"pipe"& it gets
18039 discarded as being the same as a previously handled address. However, a scheme
18042 localpart1: |/some/command $local_part
18043 localpart2: |/some/command $local_part
18045 does result in two different pipe deliveries, because the immediate parents of
18046 the pipes are distinct.
18050 .section "Repeated redirection expansion" "SECID128"
18051 .cindex "repeated redirection expansion"
18052 .cindex "address redirection" "repeated for each delivery attempt"
18053 When a message cannot be delivered to all of its recipients immediately,
18054 leading to two or more delivery attempts, redirection expansion is carried out
18055 afresh each time for those addresses whose children were not all previously
18056 delivered. If redirection is being used as a mailing list, this can lead to new
18057 members of the list receiving copies of old messages. The &%one_time%& option
18058 can be used to avoid this.
18061 .section "Errors in redirection lists" "SECID129"
18062 .cindex "address redirection" "errors"
18063 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
18064 error is skipped, and an entry is written to the main log. This may be useful
18065 for mailing lists that are automatically managed. Otherwise, if an error is
18066 detected while generating the list of new addresses, the original address is
18067 deferred. See also &%syntax_errors_to%&.
18071 .section "Private options for the redirect router" "SECID130"
18073 .cindex "options" "&(redirect)& router"
18074 The private options for the &(redirect)& router are as follows:
18077 .option allow_defer redirect boolean false
18078 Setting this option allows the use of &':defer:'& in non-filter redirection
18079 data, or the &%defer%& command in an Exim filter file.
18082 .option allow_fail redirect boolean false
18083 .cindex "failing delivery" "from filter"
18084 If this option is true, the &':fail:'& item can be used in a redirection list,
18085 and the &%fail%& command may be used in an Exim filter file.
18088 .option allow_filter redirect boolean false
18089 .cindex "filter" "enabling use of"
18090 .cindex "Sieve filter" "enabling use of"
18091 Setting this option allows Exim to interpret redirection data that starts with
18092 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
18093 are some features of Exim filter files that some administrators may wish to
18094 lock out; see the &%forbid_filter_%&&'xxx'& options below.
18096 It is also possible to lock out Exim filters or Sieve filters while allowing
18097 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
18100 The filter is run using the uid and gid set by the generic &%user%& and
18101 &%group%& options. These take their defaults from the password data if
18102 &%check_local_user%& is set, so in the normal case of users' personal filter
18103 files, the filter is run as the relevant user. When &%allow_filter%& is set
18104 true, Exim insists that either &%check_local_user%& or &%user%& is set.
18108 .option allow_freeze redirect boolean false
18109 .cindex "freezing messages" "allowing in filter"
18110 Setting this option allows the use of the &%freeze%& command in an Exim filter.
18111 This command is more normally encountered in system filters, and is disabled by
18112 default for redirection filters because it isn't something you usually want to
18113 let ordinary users do.
18117 .option check_ancestor redirect boolean false
18118 This option is concerned with handling generated addresses that are the same
18119 as some address in the list of redirection ancestors of the current address.
18120 Although it is turned off by default in the code, it is set in the default
18121 configuration file for handling users' &_.forward_& files. It is recommended
18122 for this use of the &(redirect)& router.
18124 When &%check_ancestor%& is set, if a generated address (including the domain)
18125 is the same as any ancestor of the current address, it is replaced by a copy of
18126 the current address. This helps in the case where local part A is aliased to B,
18127 and B has a &_.forward_& file pointing back to A. For example, within a single
18128 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
18129 &_&~jb/.forward_& contains:
18131 \Joe.Bloggs, <other item(s)>
18133 Without the &%check_ancestor%& setting, either local part (&"jb"& or
18134 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
18135 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
18136 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
18137 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
18138 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
18139 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
18140 original address. See also the &%repeat_use%& option below.
18143 .option check_group redirect boolean "see below"
18144 When the &%file%& option is used, the group owner of the file is checked only
18145 when this option is set. The permitted groups are those listed in the
18146 &%owngroups%& option, together with the user's default group if
18147 &%check_local_user%& is set. If the file has the wrong group, routing is
18148 deferred. The default setting for this option is true if &%check_local_user%&
18149 is set and the &%modemask%& option permits the group write bit, or if the
18150 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
18154 .option check_owner redirect boolean "see below"
18155 When the &%file%& option is used, the owner of the file is checked only when
18156 this option is set. If &%check_local_user%& is set, the local user is
18157 permitted; otherwise the owner must be one of those listed in the &%owners%&
18158 option. The default value for this option is true if &%check_local_user%& or
18159 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
18162 .option data redirect string&!! unset
18163 This option is mutually exclusive with &%file%&. One or other of them must be
18164 set, but not both. The contents of &%data%& are expanded, and then used as the
18165 list of forwarding items, or as a set of filtering instructions. If the
18166 expansion is forced to fail, or the result is an empty string or a string that
18167 has no effect (consists entirely of comments), the router declines.
18169 When filtering instructions are used, the string must begin with &"#Exim
18170 filter"&, and all comments in the string, including this initial one, must be
18171 terminated with newline characters. For example:
18173 data = #Exim filter\n\
18174 if $h_to: contains Exim then save $home/mail/exim endif
18176 If you are reading the data from a database where newlines cannot be included,
18177 you can use the &${sg}$& expansion item to turn the escape string of your
18178 choice into a newline.
18181 .option directory_transport redirect string&!! unset
18182 A &(redirect)& router sets up a direct delivery to a directory when a path name
18183 ending with a slash is specified as a new &"address"&. The transport used is
18184 specified by this option, which, after expansion, must be the name of a
18185 configured transport. This should normally be an &(appendfile)& transport.
18188 .option file redirect string&!! unset
18189 This option specifies the name of a file that contains the redirection data. It
18190 is mutually exclusive with the &%data%& option. The string is expanded before
18191 use; if the expansion is forced to fail, the router declines. Other expansion
18192 failures cause delivery to be deferred. The result of a successful expansion
18193 must be an absolute path. The entire file is read and used as the redirection
18194 data. If the data is an empty string or a string that has no effect (consists
18195 entirely of comments), the router declines.
18197 .cindex "NFS" "checking for file existence"
18198 If the attempt to open the file fails with a &"does not exist"& error, Exim
18199 runs a check on the containing directory,
18200 unless &%ignore_enotdir%& is true (see below).
18201 If the directory does not appear to exist, delivery is deferred. This can
18202 happen when users' &_.forward_& files are in NFS-mounted directories, and there
18203 is a mount problem. If the containing directory does exist, but the file does
18204 not, the router declines.
18207 .option file_transport redirect string&!! unset
18208 .vindex "&$address_file$&"
18209 A &(redirect)& router sets up a direct delivery to a file when a path name not
18210 ending in a slash is specified as a new &"address"&. The transport used is
18211 specified by this option, which, after expansion, must be the name of a
18212 configured transport. This should normally be an &(appendfile)& transport. When
18213 it is running, the file name is in &$address_file$&.
18216 .option filter_prepend_home redirect boolean true
18217 When this option is true, if a &(save)& command in an Exim filter specifies a
18218 relative path, and &$home$& is defined, it is automatically prepended to the
18219 relative path. If this option is set false, this action does not happen. The
18220 relative path is then passed to the transport unmodified.
18223 .option forbid_blackhole redirect boolean false
18224 If this option is true, the &':blackhole:'& item may not appear in a
18228 .option forbid_exim_filter redirect boolean false
18229 If this option is set true, only Sieve filters are permitted when
18230 &%allow_filter%& is true.
18235 .option forbid_file redirect boolean false
18236 .cindex "delivery" "to file; forbidding"
18237 .cindex "Sieve filter" "forbidding delivery to a file"
18238 .cindex "Sieve filter" "&""keep""& facility; disabling"
18239 If this option is true, this router may not generate a new address that
18240 specifies delivery to a local file or directory, either from a filter or from a
18241 conventional forward file. This option is forced to be true if &%one_time%& is
18242 set. It applies to Sieve filters as well as to Exim filters, but if true, it
18243 locks out the Sieve's &"keep"& facility.
18246 .option forbid_filter_dlfunc redirect boolean false
18247 .cindex "filter" "locking out certain features"
18248 If this option is true, string expansions in Exim filters are not allowed to
18249 make use of the &%dlfunc%& expansion facility to run dynamically loaded
18252 .option forbid_filter_existstest redirect boolean false
18253 .cindex "expansion" "statting a file"
18254 If this option is true, string expansions in Exim filters are not allowed to
18255 make use of the &%exists%& condition or the &%stat%& expansion item.
18257 .option forbid_filter_logwrite redirect boolean false
18258 If this option is true, use of the logging facility in Exim filters is not
18259 permitted. Logging is in any case available only if the filter is being run
18260 under some unprivileged uid (which is normally the case for ordinary users'
18261 &_.forward_& files).
18264 .option forbid_filter_lookup redirect boolean false
18265 If this option is true, string expansions in Exim filter files are not allowed
18266 to make use of &%lookup%& items.
18269 .option forbid_filter_perl redirect boolean false
18270 This option has an effect only if Exim is built with embedded Perl support. If
18271 it is true, string expansions in Exim filter files are not allowed to make use
18272 of the embedded Perl support.
18275 .option forbid_filter_readfile redirect boolean false
18276 If this option is true, string expansions in Exim filter files are not allowed
18277 to make use of &%readfile%& items.
18280 .option forbid_filter_readsocket redirect boolean false
18281 If this option is true, string expansions in Exim filter files are not allowed
18282 to make use of &%readsocket%& items.
18285 .option forbid_filter_reply redirect boolean false
18286 If this option is true, this router may not generate an automatic reply
18287 message. Automatic replies can be generated only from Exim or Sieve filter
18288 files, not from traditional forward files. This option is forced to be true if
18289 &%one_time%& is set.
18292 .option forbid_filter_run redirect boolean false
18293 If this option is true, string expansions in Exim filter files are not allowed
18294 to make use of &%run%& items.
18297 .option forbid_include redirect boolean false
18298 If this option is true, items of the form
18300 :include:<path name>
18302 are not permitted in non-filter redirection lists.
18305 .option forbid_pipe redirect boolean false
18306 .cindex "delivery" "to pipe; forbidding"
18307 If this option is true, this router may not generate a new address which
18308 specifies delivery to a pipe, either from an Exim filter or from a conventional
18309 forward file. This option is forced to be true if &%one_time%& is set.
18312 .option forbid_sieve_filter redirect boolean false
18313 If this option is set true, only Exim filters are permitted when
18314 &%allow_filter%& is true.
18317 .cindex "SMTP" "error codes"
18318 .option forbid_smtp_code redirect boolean false
18319 If this option is set true, any SMTP error codes that are present at the start
18320 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
18321 the default codes (451 and 550, respectively) are always used.
18326 .option hide_child_in_errmsg redirect boolean false
18327 .cindex "bounce message" "redirection details; suppressing"
18328 If this option is true, it prevents Exim from quoting a child address if it
18329 generates a bounce or delay message for it. Instead it says &"an address
18330 generated from <&'the top level address'&>"&. Of course, this applies only to
18331 bounces generated locally. If a message is forwarded to another host, &'its'&
18332 bounce may well quote the generated address.
18335 .option ignore_eacces redirect boolean false
18337 If this option is set and an attempt to open a redirection file yields the
18338 EACCES error (permission denied), the &(redirect)& router behaves as if the
18339 file did not exist.
18342 .option ignore_enotdir redirect boolean false
18344 If this option is set and an attempt to open a redirection file yields the
18345 ENOTDIR error (something on the path is not a directory), the &(redirect)&
18346 router behaves as if the file did not exist.
18348 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
18349 router that has the &%file%& option set discovers that the file does not exist
18350 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
18351 against unmounted NFS directories. If the parent can not be statted, delivery
18352 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
18353 is set, because that option tells Exim to ignore &"something on the path is not
18354 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
18355 that some operating systems give ENOENT where others give ENOTDIR.
18359 .option include_directory redirect string unset
18360 If this option is set, the path names of any &':include:'& items in a
18361 redirection list must start with this directory.
18364 .option modemask redirect "octal integer" 022
18365 This specifies mode bits which must not be set for a file specified by the
18366 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
18369 .option one_time redirect boolean false
18370 .cindex "one-time aliasing/forwarding expansion"
18371 .cindex "alias file" "one-time expansion"
18372 .cindex "forward file" "one-time expansion"
18373 .cindex "mailing lists" "one-time expansion"
18374 .cindex "address redirection" "one-time expansion"
18375 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
18376 files each time it tries to deliver a message causes a problem when one or more
18377 of the generated addresses fails be delivered at the first attempt. The problem
18378 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
18379 but of what happens when the redirection list changes during the time that the
18380 message is on Exim's queue. This is particularly true in the case of mailing
18381 lists, where new subscribers might receive copies of messages that were posted
18382 before they subscribed.
18384 If &%one_time%& is set and any addresses generated by the router fail to
18385 deliver at the first attempt, the failing addresses are added to the message as
18386 &"top level"& addresses, and the parent address that generated them is marked
18387 &"delivered"&. Thus, redirection does not happen again at the next delivery
18390 &*Warning 1*&: Any header line addition or removal that is specified by this
18391 router would be lost if delivery did not succeed at the first attempt. For this
18392 reason, the &%headers_add%& and &%headers_remove%& generic options are not
18393 permitted when &%one_time%& is set.
18395 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
18396 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
18397 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
18399 &*Warning 3*&: The &%unseen%& generic router option may not be set with
18402 The original top-level address is remembered with each of the generated
18403 addresses, and is output in any log messages. However, any intermediate parent
18404 addresses are not recorded. This makes a difference to the log only if
18405 &%all_parents%& log selector is set. It is expected that &%one_time%& will
18406 typically be used for mailing lists, where there is normally just one level of
18410 .option owners redirect "string list" unset
18411 .cindex "ownership" "alias file"
18412 .cindex "ownership" "forward file"
18413 .cindex "alias file" "ownership"
18414 .cindex "forward file" "ownership"
18415 This specifies a list of permitted owners for the file specified by &%file%&.
18416 This list is in addition to the local user when &%check_local_user%& is set.
18417 See &%check_owner%& above.
18420 .option owngroups redirect "string list" unset
18421 This specifies a list of permitted groups for the file specified by &%file%&.
18422 The list is in addition to the local user's primary group when
18423 &%check_local_user%& is set. See &%check_group%& above.
18426 .option pipe_transport redirect string&!! unset
18427 .vindex "&$address_pipe$&"
18428 A &(redirect)& router sets up a direct delivery to a pipe when a string
18429 starting with a vertical bar character is specified as a new &"address"&. The
18430 transport used is specified by this option, which, after expansion, must be the
18431 name of a configured transport. This should normally be a &(pipe)& transport.
18432 When the transport is run, the pipe command is in &$address_pipe$&.
18435 .option qualify_domain redirect string&!! unset
18436 .vindex "&$qualify_recipient$&"
18437 If this option is set, and an unqualified address (one without a domain) is
18438 generated, and that address would normally be qualified by the global setting
18439 in &%qualify_recipient%&, it is instead qualified with the domain specified by
18440 expanding this string. If the expansion fails, the router declines. If you want
18441 to revert to the default, you can have the expansion generate
18442 &$qualify_recipient$&.
18444 This option applies to all unqualified addresses generated by Exim filters,
18445 but for traditional &_.forward_& files, it applies only to addresses that are
18446 not preceded by a backslash. Sieve filters cannot generate unqualified
18449 .option qualify_preserve_domain redirect boolean false
18450 .cindex "domain" "in redirection; preserving"
18451 .cindex "preserving domain in redirection"
18452 .cindex "address redirection" "domain; preserving"
18453 If this option is set, the router's local &%qualify_domain%& option must not be
18454 set (a configuration error occurs if it is). If an unqualified address (one
18455 without a domain) is generated, it is qualified with the domain of the parent
18456 address (the immediately preceding ancestor) instead of the global
18457 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
18458 this applies whether or not the address is preceded by a backslash.
18461 .option repeat_use redirect boolean true
18462 If this option is set false, the router is skipped for a child address that has
18463 any ancestor that was routed by this router. This test happens before any of
18464 the other preconditions are tested. Exim's default anti-looping rules skip
18465 only when the ancestor is the same as the current address. See also
18466 &%check_ancestor%& above and the generic &%redirect_router%& option.
18469 .option reply_transport redirect string&!! unset
18470 A &(redirect)& router sets up an automatic reply when a &%mail%& or
18471 &%vacation%& command is used in a filter file. The transport used is specified
18472 by this option, which, after expansion, must be the name of a configured
18473 transport. This should normally be an &(autoreply)& transport. Other transports
18474 are unlikely to do anything sensible or useful.
18477 .option rewrite redirect boolean true
18478 .cindex "address redirection" "disabling rewriting"
18479 If this option is set false, addresses generated by the router are not
18480 subject to address rewriting. Otherwise, they are treated like new addresses
18481 and are rewritten according to the global rewriting rules.
18484 .option sieve_subaddress redirect string&!! unset
18485 The value of this option is passed to a Sieve filter to specify the
18486 :subaddress part of an address.
18488 .option sieve_useraddress redirect string&!! unset
18489 The value of this option is passed to a Sieve filter to specify the :user part
18490 of an address. However, if it is unset, the entire original local part
18491 (including any prefix or suffix) is used for :user.
18494 .option sieve_vacation_directory redirect string&!! unset
18495 .cindex "Sieve filter" "vacation directory"
18496 To enable the &"vacation"& extension for Sieve filters, you must set
18497 &%sieve_vacation_directory%& to the directory where vacation databases are held
18498 (do not put anything else in that directory), and ensure that the
18499 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
18500 needs their own directory; Exim will create it if necessary.
18504 .option skip_syntax_errors redirect boolean false
18505 .cindex "forward file" "broken"
18506 .cindex "address redirection" "broken files"
18507 .cindex "alias file" "broken"
18508 .cindex "broken alias or forward files"
18509 .cindex "ignoring faulty addresses"
18510 .cindex "skipping faulty addresses"
18511 .cindex "error" "skipping bad syntax"
18512 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
18513 non-filter redirection data are skipped, and each failing address is logged. If
18514 &%syntax_errors_to%& is set, a message is sent to the address it defines,
18515 giving details of the failures. If &%syntax_errors_text%& is set, its contents
18516 are expanded and placed at the head of the error message generated by
18517 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
18518 be the same address as the generic &%errors_to%& option. The
18519 &%skip_syntax_errors%& option is often used when handling mailing lists.
18521 If all the addresses in a redirection list are skipped because of syntax
18522 errors, the router declines to handle the original address, and it is passed to
18523 the following routers.
18525 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
18526 error in the filter causes filtering to be abandoned without any action being
18527 taken. The incident is logged, and the router declines to handle the address,
18528 so it is passed to the following routers.
18530 .cindex "Sieve filter" "syntax errors in"
18531 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
18532 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
18533 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
18535 &%skip_syntax_errors%& can be used to specify that errors in users' forward
18536 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
18537 option, used with an address that does not get redirected, can be used to
18538 notify users of these errors, by means of a router like this:
18544 file = $home/.forward
18545 file_transport = address_file
18546 pipe_transport = address_pipe
18547 reply_transport = address_reply
18550 syntax_errors_to = real-$local_part@$domain
18551 syntax_errors_text = \
18552 This is an automatically generated message. An error has\n\
18553 been found in your .forward file. Details of the error are\n\
18554 reported below. While this error persists, you will receive\n\
18555 a copy of this message for every message that is addressed\n\
18556 to you. If your .forward file is a filter file, or if it is\n\
18557 a non-filter file containing no valid forwarding addresses,\n\
18558 a copy of each incoming message will be put in your normal\n\
18559 mailbox. If a non-filter file contains at least one valid\n\
18560 forwarding address, forwarding to the valid addresses will\n\
18561 happen, and those will be the only deliveries that occur.
18563 You also need a router to ensure that local addresses that are prefixed by
18564 &`real-`& are recognized, but not forwarded or filtered. For example, you could
18565 put this immediately before the &(userforward)& router:
18570 local_part_prefix = real-
18571 transport = local_delivery
18573 For security, it would probably be a good idea to restrict the use of this
18574 router to locally-generated messages, using a condition such as this:
18576 condition = ${if match {$sender_host_address}\
18577 {\N^(|127\.0\.0\.1)$\N}}
18581 .option syntax_errors_text redirect string&!! unset
18582 See &%skip_syntax_errors%& above.
18585 .option syntax_errors_to redirect string unset
18586 See &%skip_syntax_errors%& above.
18587 .ecindex IIDredrou1
18588 .ecindex IIDredrou2
18595 . ////////////////////////////////////////////////////////////////////////////
18596 . ////////////////////////////////////////////////////////////////////////////
18598 .chapter "Environment for running local transports" "CHAPenvironment" &&&
18599 "Environment for local transports"
18600 .scindex IIDenvlotra1 "local transports" "environment for"
18601 .scindex IIDenvlotra2 "environment for local transports"
18602 .scindex IIDenvlotra3 "transport" "local; environment for"
18603 Local transports handle deliveries to files and pipes. (The &(autoreply)&
18604 transport can be thought of as similar to a pipe.) Exim always runs transports
18605 in subprocesses, under specified uids and gids. Typical deliveries to local
18606 mailboxes run under the uid and gid of the local user.
18608 Exim also sets a specific current directory while running the transport; for
18609 some transports a home directory setting is also relevant. The &(pipe)&
18610 transport is the only one that sets up environment variables; see section
18611 &<<SECTpipeenv>>& for details.
18613 The values used for the uid, gid, and the directories may come from several
18614 different places. In many cases, the router that handles the address associates
18615 settings with that address as a result of its &%check_local_user%&, &%group%&,
18616 or &%user%& options. However, values may also be given in the transport's own
18617 configuration, and these override anything that comes from the router.
18621 .section "Concurrent deliveries" "SECID131"
18622 .cindex "concurrent deliveries"
18623 .cindex "simultaneous deliveries"
18624 If two different messages for the same local recipient arrive more or less
18625 simultaneously, the two delivery processes are likely to run concurrently. When
18626 the &(appendfile)& transport is used to write to a file, Exim applies locking
18627 rules to stop concurrent processes from writing to the same file at the same
18630 However, when you use a &(pipe)& transport, it is up to you to arrange any
18631 locking that is needed. Here is a silly example:
18635 command = /bin/sh -c 'cat >>/some/file'
18637 This is supposed to write the message at the end of the file. However, if two
18638 messages arrive at the same time, the file will be scrambled. You can use the
18639 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
18640 file using the same algorithm that Exim itself uses.
18645 .section "Uids and gids" "SECTenvuidgid"
18646 .cindex "local transports" "uid and gid"
18647 .cindex "transport" "local; uid and gid"
18648 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
18649 overrides any group that the router set in the address, even if &%user%& is not
18650 set for the transport. This makes it possible, for example, to run local mail
18651 delivery under the uid of the recipient (set by the router), but in a special
18652 group (set by the transport). For example:
18655 # User/group are set by check_local_user in this router
18659 transport = group_delivery
18662 # This transport overrides the group
18664 driver = appendfile
18665 file = /var/spool/mail/$local_part
18668 If &%user%& is set for a transport, its value overrides what is set in the
18669 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
18670 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
18673 .oindex "&%initgroups%&"
18674 When the uid is taken from the transport's configuration, the &[initgroups()]&
18675 function is called for the groups associated with that uid if the
18676 &%initgroups%& option is set for the transport. When the uid is not specified
18677 by the transport, but is associated with the address by a router, the option
18678 for calling &[initgroups()]& is taken from the router configuration.
18680 .cindex "&(pipe)& transport" "uid for"
18681 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
18682 is set and &%user%& is not set, the uid of the process that called Exim to
18683 receive the message is used, and if &%group%& is not set, the corresponding
18684 original gid is also used.
18686 This is the detailed preference order for obtaining a gid; the first of the
18687 following that is set is used:
18690 A &%group%& setting of the transport;
18692 A &%group%& setting of the router;
18694 A gid associated with a user setting of the router, either as a result of
18695 &%check_local_user%& or an explicit non-numeric &%user%& setting;
18697 The group associated with a non-numeric &%user%& setting of the transport;
18699 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
18700 the uid is the creator's uid;
18702 The Exim gid if the Exim uid is being used as a default.
18705 If, for example, the user is specified numerically on the router and there are
18706 no group settings, no gid is available. In this situation, an error occurs.
18707 This is different for the uid, for which there always is an ultimate default.
18708 The first of the following that is set is used:
18711 A &%user%& setting of the transport;
18713 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
18715 A &%user%& setting of the router;
18717 A &%check_local_user%& setting of the router;
18722 Of course, an error will still occur if the uid that is chosen is on the
18723 &%never_users%& list.
18729 .section "Current and home directories" "SECID132"
18730 .cindex "current directory for local transport"
18731 .cindex "home directory" "for local transport"
18732 .cindex "transport" "local; home directory for"
18733 .cindex "transport" "local; current directory for"
18734 Routers may set current and home directories for local transports by means of
18735 the &%transport_current_directory%& and &%transport_home_directory%& options.
18736 However, if the transport's &%current_directory%& or &%home_directory%& options
18737 are set, they override the router's values. In detail, the home directory
18738 for a local transport is taken from the first of these values that is set:
18741 The &%home_directory%& option on the transport;
18743 The &%transport_home_directory%& option on the router;
18745 The password data if &%check_local_user%& is set on the router;
18747 The &%router_home_directory%& option on the router.
18750 The current directory is taken from the first of these values that is set:
18753 The &%current_directory%& option on the transport;
18755 The &%transport_current_directory%& option on the router.
18759 If neither the router nor the transport sets a current directory, Exim uses the
18760 value of the home directory, if it is set. Otherwise it sets the current
18761 directory to &_/_& before running a local transport.
18765 .section "Expansion variables derived from the address" "SECID133"
18766 .vindex "&$domain$&"
18767 .vindex "&$local_part$&"
18768 .vindex "&$original_domain$&"
18769 Normally a local delivery is handling a single address, and in that case the
18770 variables such as &$domain$& and &$local_part$& are set during local
18771 deliveries. However, in some circumstances more than one address may be handled
18772 at once (for example, while writing batch SMTP for onward transmission by some
18773 other means). In this case, the variables associated with the local part are
18774 never set, &$domain$& is set only if all the addresses have the same domain,
18775 and &$original_domain$& is never set.
18776 .ecindex IIDenvlotra1
18777 .ecindex IIDenvlotra2
18778 .ecindex IIDenvlotra3
18786 . ////////////////////////////////////////////////////////////////////////////
18787 . ////////////////////////////////////////////////////////////////////////////
18789 .chapter "Generic options for transports" "CHAPtransportgeneric"
18790 .scindex IIDgenoptra1 "generic options" "transport"
18791 .scindex IIDgenoptra2 "options" "generic; for transports"
18792 .scindex IIDgenoptra3 "transport" "generic options for"
18793 The following generic options apply to all transports:
18796 .option body_only transports boolean false
18797 .cindex "transport" "body only"
18798 .cindex "message" "transporting body only"
18799 .cindex "body of message" "transporting"
18800 If this option is set, the message's headers are not transported. It is
18801 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
18802 or &(pipe)& transports, the settings of &%message_prefix%& and
18803 &%message_suffix%& should be checked, because this option does not
18804 automatically suppress them.
18807 .option current_directory transports string&!! unset
18808 .cindex "transport" "current directory for"
18809 This specifies the current directory that is to be set while running the
18810 transport, overriding any value that may have been set by the router.
18811 If the expansion fails for any reason, including forced failure, an error is
18812 logged, and delivery is deferred.
18815 .option disable_logging transports boolean false
18816 If this option is set true, nothing is logged for any
18817 deliveries by the transport or for any
18818 transport errors. You should not set this option unless you really, really know
18819 what you are doing.
18822 .option debug_print transports string&!! unset
18823 .cindex "testing" "variables in drivers"
18824 If this option is set and debugging is enabled (see the &%-d%& command line
18825 option), the string is expanded and included in the debugging output when the
18827 If expansion of the string fails, the error message is written to the debugging
18828 output, and Exim carries on processing.
18829 This facility is provided to help with checking out the values of variables and
18830 so on when debugging driver configurations. For example, if a &%headers_add%&
18831 option is not working properly, &%debug_print%& could be used to output the
18832 variables it references. A newline is added to the text if it does not end with
18836 .option delivery_date_add transports boolean false
18837 .cindex "&'Delivery-date:'& header line"
18838 If this option is true, a &'Delivery-date:'& header is added to the message.
18839 This gives the actual time the delivery was made. As this is not a standard
18840 header, Exim has a configuration option (&%delivery_date_remove%&) which
18841 requests its removal from incoming messages, so that delivered messages can
18842 safely be resent to other recipients.
18845 .option driver transports string unset
18846 This specifies which of the available transport drivers is to be used.
18847 There is no default, and this option must be set for every transport.
18850 .option envelope_to_add transports boolean false
18851 .cindex "&'Envelope-to:'& header line"
18852 If this option is true, an &'Envelope-to:'& header is added to the message.
18853 This gives the original address(es) in the incoming envelope that caused this
18854 delivery to happen. More than one address may be present if the transport is
18855 configured to handle several addresses at once, or if more than one original
18856 address was redirected to the same final address. As this is not a standard
18857 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
18858 its removal from incoming messages, so that delivered messages can safely be
18859 resent to other recipients.
18862 .option group transports string&!! "Exim group"
18863 .cindex "transport" "group; specifying"
18864 This option specifies a gid for running the transport process, overriding any
18865 value that the router supplies, and also overriding any value associated with
18866 &%user%& (see below).
18869 .option headers_add transports string&!! unset
18870 .cindex "header lines" "adding in transport"
18871 .cindex "transport" "header lines; adding"
18872 This option specifies a string of text that is expanded and added to the header
18873 portion of a message as it is transported, as described in section
18874 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
18875 routers. If the result of the expansion is an empty string, or if the expansion
18876 is forced to fail, no action is taken. Other expansion failures are treated as
18877 errors and cause the delivery to be deferred.
18881 .option headers_only transports boolean false
18882 .cindex "transport" "header lines only"
18883 .cindex "message" "transporting headers only"
18884 .cindex "header lines" "transporting"
18885 If this option is set, the message's body is not transported. It is mutually
18886 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
18887 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
18888 checked, since this option does not automatically suppress them.
18891 .option headers_remove transports string&!! unset
18892 .cindex "header lines" "removing"
18893 .cindex "transport" "header lines; removing"
18894 This option specifies a string that is expanded into a list of header names;
18895 these headers are omitted from the message as it is transported, as described
18896 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
18897 routers. If the result of the expansion is an empty string, or if the expansion
18898 is forced to fail, no action is taken. Other expansion failures are treated as
18899 errors and cause the delivery to be deferred.
18903 .option headers_rewrite transports string unset
18904 .cindex "transport" "header lines; rewriting"
18905 .cindex "rewriting" "at transport time"
18906 This option allows addresses in header lines to be rewritten at transport time,
18907 that is, as the message is being copied to its destination. The contents of the
18908 option are a colon-separated list of rewriting rules. Each rule is in exactly
18909 the same form as one of the general rewriting rules that are applied when a
18910 message is received. These are described in chapter &<<CHAPrewrite>>&. For
18913 headers_rewrite = a@b c@d f : \
18916 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
18917 &'w@z'& in all address-bearing header lines. The rules are applied to the
18918 header lines just before they are written out at transport time, so they affect
18919 only those copies of the message that pass through the transport. However, only
18920 the message's original header lines, and any that were added by a system
18921 filter, are rewritten. If a router or transport adds header lines, they are not
18922 affected by this option. These rewriting rules are &'not'& applied to the
18923 envelope. You can change the return path using &%return_path%&, but you cannot
18924 change envelope recipients at this time.
18927 .option home_directory transports string&!! unset
18928 .cindex "transport" "home directory for"
18930 This option specifies a home directory setting for a local transport,
18931 overriding any value that may be set by the router. The home directory is
18932 placed in &$home$& while expanding the transport's private options. It is also
18933 used as the current directory if no current directory is set by the
18934 &%current_directory%& option on the transport or the
18935 &%transport_current_directory%& option on the router. If the expansion fails
18936 for any reason, including forced failure, an error is logged, and delivery is
18940 .option initgroups transports boolean false
18941 .cindex "additional groups"
18942 .cindex "groups" "additional"
18943 .cindex "transport" "group; additional"
18944 If this option is true and the uid for the delivery process is provided by the
18945 transport, the &[initgroups()]& function is called when running the transport
18946 to ensure that any additional groups associated with the uid are set up.
18949 .option message_size_limit transports string&!! 0
18950 .cindex "limit" "message size per transport"
18951 .cindex "size" "of message, limit"
18952 .cindex "transport" "message size; limiting"
18953 This option controls the size of messages passed through the transport. It is
18954 expanded before use; the result of the expansion must be a sequence of decimal
18955 digits, optionally followed by K or M. If the expansion fails for any reason,
18956 including forced failure, or if the result is not of the required form,
18957 delivery is deferred. If the value is greater than zero and the size of a
18958 message exceeds this limit, the address is failed. If there is any chance that
18959 the resulting bounce message could be routed to the same transport, you should
18960 ensure that &%return_size_limit%& is less than the transport's
18961 &%message_size_limit%&, as otherwise the bounce message will fail to get
18966 .option rcpt_include_affixes transports boolean false
18967 .cindex "prefix" "for local part, including in envelope"
18968 .cindex "suffix for local part" "including in envelope"
18969 .cindex "local part" "prefix"
18970 .cindex "local part" "suffix"
18971 When this option is false (the default), and an address that has had any
18972 affixes (prefixes or suffixes) removed from the local part is delivered by any
18973 form of SMTP or LMTP, the affixes are not included. For example, if a router
18976 local_part_prefix = *-
18978 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
18981 RCPT TO:<xyz@some.domain>
18983 This is also the case when an ACL-time callout is being used to verify a
18984 recipient address. However, if &%rcpt_include_affixes%& is set true, the
18985 whole local part is included in the RCPT command. This option applies to BSMTP
18986 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
18987 &(lmtp)& and &(smtp)& transports.
18990 .option retry_use_local_part transports boolean "see below"
18991 .cindex "hints database" "retry keys"
18992 When a delivery suffers a temporary failure, a retry record is created
18993 in Exim's hints database. For remote deliveries, the key for the retry record
18994 is based on the name and/or IP address of the failing remote host. For local
18995 deliveries, the key is normally the entire address, including both the local
18996 part and the domain. This is suitable for most common cases of local delivery
18997 temporary failure &-- for example, exceeding a mailbox quota should delay only
18998 deliveries to that mailbox, not to the whole domain.
19000 However, in some special cases you may want to treat a temporary local delivery
19001 as a failure associated with the domain, and not with a particular local part.
19002 (For example, if you are storing all mail for some domain in files.) You can do
19003 this by setting &%retry_use_local_part%& false.
19005 For all the local transports, its default value is true. For remote transports,
19006 the default value is false for tidiness, but changing the value has no effect
19007 on a remote transport in the current implementation.
19010 .option return_path transports string&!! unset
19011 .cindex "envelope sender"
19012 .cindex "transport" "return path; changing"
19013 .cindex "return path" "changing in transport"
19014 If this option is set, the string is expanded at transport time and replaces
19015 the existing return path (envelope sender) value in the copy of the message
19016 that is being delivered. An empty return path is permitted. This feature is
19017 designed for remote deliveries, where the value of this option is used in the
19018 SMTP MAIL command. If you set &%return_path%& for a local transport, the
19019 only effect is to change the address that is placed in the &'Return-path:'&
19020 header line, if one is added to the message (see the next option).
19022 &*Note:*& A changed return path is not logged unless you add
19023 &%return_path_on_delivery%& to the log selector.
19025 .vindex "&$return_path$&"
19026 The expansion can refer to the existing value via &$return_path$&. This is
19027 either the message's envelope sender, or an address set by the
19028 &%errors_to%& option on a router. If the expansion is forced to fail, no
19029 replacement occurs; if it fails for another reason, delivery is deferred. This
19030 option can be used to support VERP (Variable Envelope Return Paths) &-- see
19031 section &<<SECTverp>>&.
19033 &*Note*&: If a delivery error is detected locally, including the case when a
19034 remote server rejects a message at SMTP time, the bounce message is not sent to
19035 the value of this option. It is sent to the previously set errors address.
19036 This defaults to the incoming sender address, but can be changed by setting
19037 &%errors_to%& in a router.
19041 .option return_path_add transports boolean false
19042 .cindex "&'Return-path:'& header line"
19043 If this option is true, a &'Return-path:'& header is added to the message.
19044 Although the return path is normally available in the prefix line of BSD
19045 mailboxes, this is commonly not displayed by MUAs, and so the user does not
19046 have easy access to it.
19048 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
19049 the delivery SMTP server makes the final delivery"&. This implies that this
19050 header should not be present in incoming messages. Exim has a configuration
19051 option, &%return_path_remove%&, which requests removal of this header from
19052 incoming messages, so that delivered messages can safely be resent to other
19056 .option shadow_condition transports string&!! unset
19057 See &%shadow_transport%& below.
19060 .option shadow_transport transports string unset
19061 .cindex "shadow transport"
19062 .cindex "transport" "shadow"
19063 A local transport may set the &%shadow_transport%& option to the name of
19064 another local transport. Shadow remote transports are not supported.
19066 Whenever a delivery to the main transport succeeds, and either
19067 &%shadow_condition%& is unset, or its expansion does not result in the empty
19068 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
19069 passed to the shadow transport, with the same delivery address or addresses. If
19070 expansion fails, no action is taken except that non-forced expansion failures
19071 cause a log line to be written.
19073 The result of the shadow transport is discarded and does not affect the
19074 subsequent processing of the message. Only a single level of shadowing is
19075 provided; the &%shadow_transport%& option is ignored on any transport when it
19076 is running as a shadow. Options concerned with output from pipes are also
19077 ignored. The log line for the successful delivery has an item added on the end,
19080 ST=<shadow transport name>
19082 If the shadow transport did not succeed, the error message is put in
19083 parentheses afterwards. Shadow transports can be used for a number of different
19084 purposes, including keeping more detailed log information than Exim normally
19085 provides, and implementing automatic acknowledgment policies based on message
19086 headers that some sites insist on.
19089 .option transport_filter transports string&!! unset
19090 .cindex "transport" "filter"
19091 .cindex "filter" "transport filter"
19092 This option sets up a filtering (in the Unix shell sense) process for messages
19093 at transport time. It should not be confused with mail filtering as set up by
19094 individual users or via a system filter.
19096 When the message is about to be written out, the command specified by
19097 &%transport_filter%& is started up in a separate, parallel process, and
19098 the entire message, including the header lines, is passed to it on its standard
19099 input (this in fact is done from a third process, to avoid deadlock). The
19100 command must be specified as an absolute path.
19102 The lines of the message that are written to the transport filter are
19103 terminated by newline (&"\n"&). The message is passed to the filter before any
19104 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
19105 lines beginning with a dot, and also before any processing implied by the
19106 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
19107 &(pipe)& transports.
19109 The standard error for the filter process is set to the same destination as its
19110 standard output; this is read and written to the message's ultimate
19111 destination. The process that writes the message to the filter, the
19112 filter itself, and the original process that reads the result and delivers it
19113 are all run in parallel, like a shell pipeline.
19115 The filter can perform any transformations it likes, but of course should take
19116 care not to break RFC 2822 syntax. Exim does not check the result, except to
19117 test for a final newline when SMTP is in use. All messages transmitted over
19118 SMTP must end with a newline, so Exim supplies one if it is missing.
19120 .cindex "content scanning" "per user"
19121 A transport filter can be used to provide content-scanning on a per-user basis
19122 at delivery time if the only required effect of the scan is to modify the
19123 message. For example, a content scan could insert a new header line containing
19124 a spam score. This could be interpreted by a filter in the user's MUA. It is
19125 not possible to discard a message at this stage.
19127 .cindex "SMTP" "SIZE"
19128 A problem might arise if the filter increases the size of a message that is
19129 being sent down an SMTP connection. If the receiving SMTP server has indicated
19130 support for the SIZE parameter, Exim will have sent the size of the message
19131 at the start of the SMTP session. If what is actually sent is substantially
19132 more, the server might reject the message. This can be worked round by setting
19133 the &%size_addition%& option on the &(smtp)& transport, either to allow for
19134 additions to the message, or to disable the use of SIZE altogether.
19136 .vindex "&$pipe_addresses$&"
19137 The value of the &%transport_filter%& option is the command string for starting
19138 the filter, which is run directly from Exim, not under a shell. The string is
19139 parsed by Exim in the same way as a command string for the &(pipe)& transport:
19140 Exim breaks it up into arguments and then expands each argument separately (see
19141 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
19142 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
19143 of arguments, one for each address that applies to this delivery. (This isn't
19144 an ideal name for this feature here, but as it was already implemented for the
19145 &(pipe)& transport, it seemed sensible not to change it.)
19148 .vindex "&$host_address$&"
19149 The expansion variables &$host$& and &$host_address$& are available when the
19150 transport is a remote one. They contain the name and IP address of the host to
19151 which the message is being sent. For example:
19153 transport_filter = /some/directory/transport-filter.pl \
19154 $host $host_address $sender_address $pipe_addresses
19157 Two problems arise if you want to use more complicated expansion items to
19158 generate transport filter commands, both of which due to the fact that the
19159 command is split up &'before'& expansion.
19161 If an expansion item contains white space, you must quote it, so that it is all
19162 part of the same command item. If the entire option setting is one such
19163 expansion item, you have to take care what kind of quoting you use. For
19166 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
19168 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
19169 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
19170 stripped by Exim when it read the option's value. When the value is used, if
19171 the single quotes were missing, the line would be split into two items,
19172 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
19173 Exim tried to expand the first one.
19175 Except for the special case of &$pipe_addresses$& that is mentioned above, an
19176 expansion cannot generate multiple arguments, or a command name followed by
19177 arguments. Consider this example:
19179 transport_filter = ${lookup{$host}lsearch{/a/file}\
19180 {$value}{/bin/cat}}
19182 The result of the lookup is interpreted as the name of the command, even
19183 if it contains white space. The simplest way round this is to use a shell:
19185 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
19186 {$value}{/bin/cat}}
19190 The filter process is run under the same uid and gid as the normal delivery.
19191 For remote deliveries this is the Exim uid/gid by default. The command should
19192 normally yield a zero return code. Transport filters are not supposed to fail.
19193 A non-zero code is taken to mean that the transport filter encountered some
19194 serious problem. Delivery of the message is deferred; the message remains on
19195 the queue and is tried again later. It is not possible to cause a message to be
19196 bounced from a transport filter.
19198 If a transport filter is set on an autoreply transport, the original message is
19199 passed through the filter as it is being copied into the newly generated
19200 message, which happens if the &%return_message%& option is set.
19203 .option transport_filter_timeout transports time 5m
19204 .cindex "transport" "filter, timeout"
19205 When Exim is reading the output of a transport filter, it a applies a timeout
19206 that can be set by this option. Exceeding the timeout is normally treated as a
19207 temporary delivery failure. However, if a transport filter is used with a
19208 &(pipe)& transport, a timeout in the transport filter is treated in the same
19209 way as a timeout in the pipe command itself. By default, a timeout is a hard
19210 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
19211 becomes a temporary error.
19214 .option user transports string&!! "Exim user"
19215 .cindex "uid (user id)" "local delivery"
19216 .cindex "transport" "user, specifying"
19217 This option specifies the user under whose uid the delivery process is to be
19218 run, overriding any uid that may have been set by the router. If the user is
19219 given as a name, the uid is looked up from the password data, and the
19220 associated group is taken as the value of the gid to be used if the &%group%&
19223 For deliveries that use local transports, a user and group are normally
19224 specified explicitly or implicitly (for example, as a result of
19225 &%check_local_user%&) by the router or transport.
19227 .cindex "hints database" "access by remote transport"
19228 For remote transports, you should leave this option unset unless you really are
19229 sure you know what you are doing. When a remote transport is running, it needs
19230 to be able to access Exim's hints databases, because each host may have its own
19232 .ecindex IIDgenoptra1
19233 .ecindex IIDgenoptra2
19234 .ecindex IIDgenoptra3
19241 . ////////////////////////////////////////////////////////////////////////////
19242 . ////////////////////////////////////////////////////////////////////////////
19244 .chapter "Address batching in local transports" "CHAPbatching" &&&
19246 .cindex "transport" "local; address batching in"
19247 The only remote transport (&(smtp)&) is normally configured to handle more than
19248 one address at a time, so that when several addresses are routed to the same
19249 remote host, just one copy of the message is sent. Local transports, however,
19250 normally handle one address at a time. That is, a separate instance of the
19251 transport is run for each address that is routed to the transport. A separate
19252 copy of the message is delivered each time.
19254 .cindex "batched local delivery"
19255 .oindex "&%batch_max%&"
19256 .oindex "&%batch_id%&"
19257 In special cases, it may be desirable to handle several addresses at once in a
19258 local transport, for example:
19261 In an &(appendfile)& transport, when storing messages in files for later
19262 delivery by some other means, a single copy of the message with multiple
19263 recipients saves space.
19265 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
19266 a single copy saves time, and is the normal way LMTP is expected to work.
19268 In a &(pipe)& transport, when passing the message
19269 to a scanner program or
19270 to some other delivery mechanism such as UUCP, multiple recipients may be
19274 These three local transports all have the same options for controlling multiple
19275 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
19276 repeating the information for each transport, these options are described here.
19278 The &%batch_max%& option specifies the maximum number of addresses that can be
19279 delivered together in a single run of the transport. Its default value is one
19280 (no batching). When more than one address is routed to a transport that has a
19281 &%batch_max%& value greater than one, the addresses are delivered in a batch
19282 (that is, in a single run of the transport with multiple recipients), subject
19283 to certain conditions:
19286 .vindex "&$local_part$&"
19287 If any of the transport's options contain a reference to &$local_part$&, no
19288 batching is possible.
19290 .vindex "&$domain$&"
19291 If any of the transport's options contain a reference to &$domain$&, only
19292 addresses with the same domain are batched.
19294 .cindex "customizing" "batching condition"
19295 If &%batch_id%& is set, it is expanded for each address, and only those
19296 addresses with the same expanded value are batched. This allows you to specify
19297 customized batching conditions. Failure of the expansion for any reason,
19298 including forced failure, disables batching, but it does not stop the delivery
19301 Batched addresses must also have the same errors address (where to send
19302 delivery errors), the same header additions and removals, the same user and
19303 group for the transport, and if a host list is present, the first host must
19307 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
19308 both when the file or pipe command is specified in the transport, and when it
19309 is specified by a &(redirect)& router, but all the batched addresses must of
19310 course be routed to the same file or pipe command. These two transports have an
19311 option called &%use_bsmtp%&, which causes them to deliver the message in
19312 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
19313 &%check_string%& and &%escape_string%& options are forced to the values
19316 escape_string = ".."
19318 when batched SMTP is in use. A full description of the batch SMTP mechanism is
19319 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
19320 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
19322 .cindex "&'Envelope-to:'& header line"
19323 If the generic &%envelope_to_add%& option is set for a batching transport, the
19324 &'Envelope-to:'& header that is added to the message contains all the addresses
19325 that are being processed together. If you are using a batching &(appendfile)&
19326 transport without &%use_bsmtp%&, the only way to preserve the recipient
19327 addresses is to set the &%envelope_to_add%& option.
19329 .cindex "&(pipe)& transport" "with multiple addresses"
19330 .vindex "&$pipe_addresses$&"
19331 If you are using a &(pipe)& transport without BSMTP, and setting the
19332 transport's &%command%& option, you can include &$pipe_addresses$& as part of
19333 the command. This is not a true variable; it is a bit of magic that causes each
19334 of the recipient addresses to be inserted into the command as a separate
19335 argument. This provides a way of accessing all the addresses that are being
19336 delivered in the batch. &*Note:*& This is not possible for pipe commands that
19337 are specified by a &(redirect)& router.
19342 . ////////////////////////////////////////////////////////////////////////////
19343 . ////////////////////////////////////////////////////////////////////////////
19345 .chapter "The appendfile transport" "CHAPappendfile"
19346 .scindex IIDapptra1 "&(appendfile)& transport"
19347 .scindex IIDapptra2 "transports" "&(appendfile)&"
19348 .cindex "directory creation"
19349 .cindex "creating directories"
19350 The &(appendfile)& transport delivers a message by appending it to an existing
19351 file, or by creating an entirely new file in a specified directory. Single
19352 files to which messages are appended can be in the traditional Unix mailbox
19353 format, or optionally in the MBX format supported by the Pine MUA and
19354 University of Washington IMAP daemon, &'inter alia'&. When each message is
19355 being delivered as a separate file, &"maildir"& format can optionally be used
19356 to give added protection against failures that happen part-way through the
19357 delivery. A third form of separate-file delivery known as &"mailstore"& is also
19358 supported. For all file formats, Exim attempts to create as many levels of
19359 directory as necessary, provided that &%create_directory%& is set.
19361 The code for the optional formats is not included in the Exim binary by
19362 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
19363 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
19366 .cindex "quota" "system"
19367 Exim recognizes system quota errors, and generates an appropriate message. Exim
19368 also supports its own quota control within the transport, for use when the
19369 system facility is unavailable or cannot be used for some reason.
19371 If there is an error while appending to a file (for example, quota exceeded or
19372 partition filled), Exim attempts to reset the file's length and last
19373 modification time back to what they were before. If there is an error while
19374 creating an entirely new file, the new file is removed.
19376 Before appending to a file, a number of security checks are made, and the
19377 file is locked. A detailed description is given below, after the list of
19380 The &(appendfile)& transport is most commonly used for local deliveries to
19381 users' mailboxes. However, it can also be used as a pseudo-remote transport for
19382 putting messages into files for remote delivery by some means other than Exim.
19383 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
19388 .section "The file and directory options" "SECTfildiropt"
19389 The &%file%& option specifies a single file, to which the message is appended;
19390 the &%directory%& option specifies a directory, in which a new file containing
19391 the message is created. Only one of these two options can be set, and for
19392 normal deliveries to mailboxes, one of them &'must'& be set.
19394 .vindex "&$address_file$&"
19395 .vindex "&$local_part$&"
19396 However, &(appendfile)& is also used for delivering messages to files or
19397 directories whose names (or parts of names) are obtained from alias,
19398 forwarding, or filtering operations (for example, a &%save%& command in a
19399 user's Exim filter). When such a transport is running, &$local_part$& contains
19400 the local part that was aliased or forwarded, and &$address_file$& contains the
19401 name (or partial name) of the file or directory generated by the redirection
19402 operation. There are two cases:
19405 If neither &%file%& nor &%directory%& is set, the redirection operation
19406 must specify an absolute path (one that begins with &`/`&). This is the most
19407 common case when users with local accounts use filtering to sort mail into
19408 different folders. See for example, the &(address_file)& transport in the
19409 default configuration. If the path ends with a slash, it is assumed to be the
19410 name of a directory. A delivery to a directory can also be forced by setting
19411 &%maildir_format%& or &%mailstore_format%&.
19413 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
19414 used to determine the file or directory name for the delivery. Normally, the
19415 contents of &$address_file$& are used in some way in the string expansion.
19419 .cindex "Sieve filter" "configuring &(appendfile)&"
19420 .cindex "Sieve filter" "relative mailbox path handling"
19421 As an example of the second case, consider an environment where users do not
19422 have home directories. They may be permitted to use Exim filter commands of the
19427 or Sieve filter commands of the form:
19429 require "fileinto";
19430 fileinto "folder23";
19432 In this situation, the expansion of &%file%& or &%directory%& in the transport
19433 must transform the relative path into an appropriate absolute file name. In the
19434 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
19435 is used as a result of a &"keep"& action in the filter. This example shows one
19436 way of handling this requirement:
19438 file = ${if eq{$address_file}{inbox} \
19439 {/var/mail/$local_part} \
19440 {${if eq{${substr_0_1:$address_file}}{/} \
19442 {$home/mail/$address_file} \
19446 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
19447 location, absolute paths are used without change, and other folders are in the
19448 &_mail_& directory within the home directory.
19450 &*Note 1*&: While processing an Exim filter, a relative path such as
19451 &_folder23_& is turned into an absolute path if a home directory is known to
19452 the router. In particular, this is the case if &%check_local_user%& is set. If
19453 you want to prevent this happening at routing time, you can set
19454 &%router_home_directory%& empty. This forces the router to pass the relative
19455 path to the transport.
19457 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
19458 the &%file%& or &%directory%& option is still used if it is set.
19463 .section "Private options for appendfile" "SECID134"
19464 .cindex "options" "&(appendfile)& transport"
19468 .option allow_fifo appendfile boolean false
19469 .cindex "fifo (named pipe)"
19470 .cindex "named pipe (fifo)"
19471 .cindex "pipe" "named (fifo)"
19472 Setting this option permits delivery to named pipes (FIFOs) as well as to
19473 regular files. If no process is reading the named pipe at delivery time, the
19474 delivery is deferred.
19477 .option allow_symlink appendfile boolean false
19478 .cindex "symbolic link" "to mailbox"
19479 .cindex "mailbox" "symbolic link"
19480 By default, &(appendfile)& will not deliver if the path name for the file is
19481 that of a symbolic link. Setting this option relaxes that constraint, but there
19482 are security issues involved in the use of symbolic links. Be sure you know
19483 what you are doing if you set this. Details of exactly what this option affects
19484 are included in the discussion which follows this list of options.
19487 .option batch_id appendfile string&!! unset
19488 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19489 However, batching is automatically disabled for &(appendfile)& deliveries that
19490 happen as a result of forwarding or aliasing or other redirection directly to a
19494 .option batch_max appendfile integer 1
19495 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19498 .option check_group appendfile boolean false
19499 When this option is set, the group owner of the file defined by the &%file%&
19500 option is checked to see that it is the same as the group under which the
19501 delivery process is running. The default setting is false because the default
19502 file mode is 0600, which means that the group is irrelevant.
19505 .option check_owner appendfile boolean true
19506 When this option is set, the owner of the file defined by the &%file%& option
19507 is checked to ensure that it is the same as the user under which the delivery
19508 process is running.
19511 .option check_string appendfile string "see below"
19512 .cindex "&""From""& line"
19513 As &(appendfile)& writes the message, the start of each line is tested for
19514 matching &%check_string%&, and if it does, the initial matching characters are
19515 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
19516 a literal string, not a regular expression, and the case of any letters it
19517 contains is significant.
19519 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
19520 are forced to &"."& and &".."& respectively, and any settings in the
19521 configuration are ignored. Otherwise, they default to &"From&~"& and
19522 &">From&~"& when the &%file%& option is set, and unset when any of the
19523 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
19525 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
19526 suitable for traditional &"BSD"& mailboxes, where a line beginning with
19527 &"From&~"& indicates the start of a new message. All four options need changing
19528 if another format is used. For example, to deliver to mailboxes in MMDF format:
19529 .cindex "MMDF format mailbox"
19530 .cindex "mailbox" "MMDF format"
19532 check_string = "\1\1\1\1\n"
19533 escape_string = "\1\1\1\1 \n"
19534 message_prefix = "\1\1\1\1\n"
19535 message_suffix = "\1\1\1\1\n"
19537 .option create_directory appendfile boolean true
19538 .cindex "directory creation"
19539 When this option is true, Exim attempts to create any missing superior
19540 directories for the file that it is about to write. A created directory's mode
19541 is given by the &%directory_mode%& option.
19543 The group ownership of a newly created directory is highly dependent on the
19544 operating system (and possibly the file system) that is being used. For
19545 example, in Solaris, if the parent directory has the setgid bit set, its group
19546 is propagated to the child; if not, the currently set group is used. However,
19547 in FreeBSD, the parent's group is always used.
19551 .option create_file appendfile string anywhere
19552 This option constrains the location of files and directories that are created
19553 by this transport. It applies to files defined by the &%file%& option and
19554 directories defined by the &%directory%& option. In the case of maildir
19555 delivery, it applies to the top level directory, not the maildir directories
19558 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
19559 &"belowhome"&. In the second and third cases, a home directory must have been
19560 set for the transport. This option is not useful when an explicit file name is
19561 given for normal mailbox deliveries. It is intended for the case when file
19562 names are generated from users' &_.forward_& files. These are usually handled
19563 by an &(appendfile)& transport called &%address_file%&. See also
19564 &%file_must_exist%&.
19567 .option directory appendfile string&!! unset
19568 This option is mutually exclusive with the &%file%& option, but one of &%file%&
19569 or &%directory%& must be set, unless the delivery is the direct result of a
19570 redirection (see section &<<SECTfildiropt>>&).
19572 When &%directory%& is set, the string is expanded, and the message is delivered
19573 into a new file or files in or below the given directory, instead of being
19574 appended to a single mailbox file. A number of different formats are provided
19575 (see &%maildir_format%& and &%mailstore_format%&), and see section
19576 &<<SECTopdir>>& for further details of this form of delivery.
19579 .option directory_file appendfile string&!! "see below"
19581 .vindex "&$inode$&"
19582 When &%directory%& is set, but neither &%maildir_format%& nor
19583 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
19584 whose name is obtained by expanding this string. The default value is:
19586 q${base62:$tod_epoch}-$inode
19588 This generates a unique name from the current time, in base 62 form, and the
19589 inode of the file. The variable &$inode$& is available only when expanding this
19593 .option directory_mode appendfile "octal integer" 0700
19594 If &(appendfile)& creates any directories as a result of the
19595 &%create_directory%& option, their mode is specified by this option.
19598 .option escape_string appendfile string "see description"
19599 See &%check_string%& above.
19602 .option file appendfile string&!! unset
19603 This option is mutually exclusive with the &%directory%& option, but one of
19604 &%file%& or &%directory%& must be set, unless the delivery is the direct result
19605 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
19606 specifies a single file, to which the message is appended. One or more of
19607 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
19610 .cindex "NFS" "lock file"
19611 .cindex "locking files"
19612 .cindex "lock files"
19613 If you are using more than one host to deliver over NFS into the same
19614 mailboxes, you should always use lock files.
19616 The string value is expanded for each delivery, and must yield an absolute
19617 path. The most common settings of this option are variations on one of these
19620 file = /var/spool/mail/$local_part
19621 file = /home/$local_part/inbox
19624 .cindex "&""sticky""& bit"
19625 In the first example, all deliveries are done into the same directory. If Exim
19626 is configured to use lock files (see &%use_lockfile%& below) it must be able to
19627 create a file in the directory, so the &"sticky"& bit must be turned on for
19628 deliveries to be possible, or alternatively the &%group%& option can be used to
19629 run the delivery under a group id which has write access to the directory.
19633 .option file_format appendfile string unset
19634 .cindex "file" "mailbox; checking existing format"
19635 This option requests the transport to check the format of an existing file
19636 before adding to it. The check consists of matching a specific string at the
19637 start of the file. The value of the option consists of an even number of
19638 colon-separated strings. The first of each pair is the test string, and the
19639 second is the name of a transport. If the transport associated with a matched
19640 string is not the current transport, control is passed over to the other
19641 transport. For example, suppose the standard &(local_delivery)& transport has
19644 file_format = "From : local_delivery :\
19645 \1\1\1\1\n : local_mmdf_delivery"
19647 Mailboxes that begin with &"From"& are still handled by this transport, but if
19648 a mailbox begins with four binary ones followed by a newline, control is passed
19649 to a transport called &%local_mmdf_delivery%&, which presumably is configured
19650 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
19651 is assumed to match the current transport. If the start of a mailbox doesn't
19652 match any string, or if the transport named for a given string is not defined,
19653 delivery is deferred.
19656 .option file_must_exist appendfile boolean false
19657 If this option is true, the file specified by the &%file%& option must exist.
19658 A temporary error occurs if it does not, causing delivery to be deferred.
19659 If this option is false, the file is created if it does not exist.
19662 .option lock_fcntl_timeout appendfile time 0s
19663 .cindex "timeout" "mailbox locking"
19664 .cindex "mailbox" "locking, blocking and non-blocking"
19665 .cindex "locking files"
19666 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
19667 when locking an open mailbox file. If the call fails, the delivery process
19668 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
19669 Non-blocking calls are used so that the file is not kept open during the wait
19670 for the lock; the reason for this is to make it as safe as possible for
19671 deliveries over NFS in the case when processes might be accessing an NFS
19672 mailbox without using a lock file. This should not be done, but
19673 misunderstandings and hence misconfigurations are not unknown.
19675 On a busy system, however, the performance of a non-blocking lock approach is
19676 not as good as using a blocking lock with a timeout. In this case, the waiting
19677 is done inside the system call, and Exim's delivery process acquires the lock
19678 and can proceed as soon as the previous lock holder releases it.
19680 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
19681 timeout, are used. There may still be some retrying: the maximum number of
19684 (lock_retries * lock_interval) / lock_fcntl_timeout
19686 rounded up to the next whole number. In other words, the total time during
19687 which &(appendfile)& is trying to get a lock is roughly the same, unless
19688 &%lock_fcntl_timeout%& is set very large.
19690 You should consider setting this option if you are getting a lot of delayed
19691 local deliveries because of errors of the form
19693 failed to lock mailbox /some/file (fcntl)
19696 .option lock_flock_timeout appendfile time 0s
19697 This timeout applies to file locking when using &[flock()]& (see
19698 &%use_flock%&); the timeout operates in a similar manner to
19699 &%lock_fcntl_timeout%&.
19702 .option lock_interval appendfile time 3s
19703 This specifies the time to wait between attempts to lock the file. See below
19704 for details of locking.
19707 .option lock_retries appendfile integer 10
19708 This specifies the maximum number of attempts to lock the file. A value of zero
19709 is treated as 1. See below for details of locking.
19712 .option lockfile_mode appendfile "octal integer" 0600
19713 This specifies the mode of the created lock file, when a lock file is being
19714 used (see &%use_lockfile%& and &%use_mbx_lock%&).
19717 .option lockfile_timeout appendfile time 30m
19718 .cindex "timeout" "mailbox locking"
19719 When a lock file is being used (see &%use_lockfile%&), if a lock file already
19720 exists and is older than this value, it is assumed to have been left behind by
19721 accident, and Exim attempts to remove it.
19724 .option mailbox_filecount appendfile string&!! unset
19725 .cindex "mailbox" "specifying size of"
19726 .cindex "size" "of mailbox"
19727 If this option is set, it is expanded, and the result is taken as the current
19728 number of files in the mailbox. It must be a decimal number, optionally
19729 followed by K or M. This provides a way of obtaining this information from an
19730 external source that maintains the data.
19733 .option mailbox_size appendfile string&!! unset
19734 .cindex "mailbox" "specifying size of"
19735 .cindex "size" "of mailbox"
19736 If this option is set, it is expanded, and the result is taken as the current
19737 size the mailbox. It must be a decimal number, optionally followed by K or M.
19738 This provides a way of obtaining this information from an external source that
19739 maintains the data. This is likely to be helpful for maildir deliveries where
19740 it is computationally expensive to compute the size of a mailbox.
19744 .option maildir_format appendfile boolean false
19745 .cindex "maildir format" "specifying"
19746 If this option is set with the &%directory%& option, the delivery is into a new
19747 file, in the &"maildir"& format that is used by other mail software. When the
19748 transport is activated directly from a &(redirect)& router (for example, the
19749 &(address_file)& transport in the default configuration), setting
19750 &%maildir_format%& causes the path received from the router to be treated as a
19751 directory, whether or not it ends with &`/`&. This option is available only if
19752 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
19753 &<<SECTmaildirdelivery>>& below for further details.
19756 .option maildir_quota_directory_regex appendfile string "See below"
19757 .cindex "maildir format" "quota; directories included in"
19758 .cindex "quota" "maildir; directories included in"
19759 This option is relevant only when &%maildir_use_size_file%& is set. It defines
19760 a regular expression for specifying directories, relative to the quota
19761 directory (see &%quota_directory%&), that should be included in the quota
19762 calculation. The default value is:
19764 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
19766 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
19767 (directories whose names begin with a dot). If you want to exclude the
19769 folder from the count (as some sites do), you need to change this setting to
19771 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
19773 This uses a negative lookahead in the regular expression to exclude the
19774 directory whose name is &_.Trash_&. When a directory is excluded from quota
19775 calculations, quota processing is bypassed for any messages that are delivered
19776 directly into that directory.
19779 .option maildir_retries appendfile integer 10
19780 This option specifies the number of times to retry when writing a file in
19781 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
19784 .option maildir_tag appendfile string&!! unset
19785 This option applies only to deliveries in maildir format, and is described in
19786 section &<<SECTmaildirdelivery>>& below.
19789 .option maildir_use_size_file appendfile boolean false
19790 .cindex "maildir format" "&_maildirsize_& file"
19791 Setting this option true enables support for &_maildirsize_& files. Exim
19792 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
19793 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
19794 value is zero. See &%maildir_quota_directory_regex%& above and section
19795 &<<SECTmaildirdelivery>>& below for further details.
19797 .option maildirfolder_create_regex appendfile string unset
19798 .cindex "maildir format" "&_maildirfolder_& file"
19799 .cindex "&_maildirfolder_&, creating"
19800 The value of this option is a regular expression. If it is unset, it has no
19801 effect. Otherwise, before a maildir delivery takes place, the pattern is
19802 matched against the name of the maildir directory, that is, the directory
19803 containing the &_new_& and &_tmp_& subdirectories that will be used for the
19804 delivery. If there is a match, Exim checks for the existence of a file called
19805 &_maildirfolder_& in the directory, and creates it if it does not exist.
19806 See section &<<SECTmaildirdelivery>>& for more details.
19809 .option mailstore_format appendfile boolean false
19810 .cindex "mailstore format" "specifying"
19811 If this option is set with the &%directory%& option, the delivery is into two
19812 new files in &"mailstore"& format. The option is available only if
19813 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
19814 below for further details.
19817 .option mailstore_prefix appendfile string&!! unset
19818 This option applies only to deliveries in mailstore format, and is described in
19819 section &<<SECTopdir>>& below.
19822 .option mailstore_suffix appendfile string&!! unset
19823 This option applies only to deliveries in mailstore format, and is described in
19824 section &<<SECTopdir>>& below.
19827 .option mbx_format appendfile boolean false
19828 .cindex "locking files"
19829 .cindex "file" "locking"
19830 .cindex "file" "MBX format"
19831 .cindex "MBX format, specifying"
19832 This option is available only if Exim has been compiled with SUPPORT_MBX
19833 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
19834 the message is appended to the mailbox file in MBX format instead of
19835 traditional Unix format. This format is supported by Pine4 and its associated
19836 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
19838 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
19839 automatically changed by the use of &%mbx_format%&. They should normally be set
19840 empty when using MBX format, so this option almost always appears in this
19847 If none of the locking options are mentioned in the configuration,
19848 &%use_mbx_lock%& is assumed and the other locking options default to false. It
19849 is possible to specify the other kinds of locking with &%mbx_format%&, but
19850 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
19851 interworks with &'c-client'&, providing for shared access to the mailbox. It
19852 should not be used if any program that does not use this form of locking is
19853 going to access the mailbox, nor should it be used if the mailbox file is NFS
19854 mounted, because it works only when the mailbox is accessed from a single host.
19856 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
19857 the standard version of &'c-client'&, because as long as it has a mailbox open
19858 (this means for the whole of a Pine or IMAP session), Exim will not be able to
19859 append messages to it.
19862 .option message_prefix appendfile string&!! "see below"
19863 .cindex "&""From""& line"
19864 The string specified here is expanded and output at the start of every message.
19865 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
19866 in which case it is:
19868 message_prefix = "From ${if def:return_path{$return_path}\
19869 {MAILER-DAEMON}} $tod_bsdinbox\n"
19871 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
19872 &`\n`& to &`\r\n`& in &%message_prefix%&.
19874 .option message_suffix appendfile string&!! "see below"
19875 The string specified here is expanded and output at the end of every message.
19876 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
19877 in which case it is a single newline character. The suffix can be suppressed by
19882 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
19883 &`\n`& to &`\r\n`& in &%message_suffix%&.
19885 .option mode appendfile "octal integer" 0600
19886 If the output file is created, it is given this mode. If it already exists and
19887 has wider permissions, they are reduced to this mode. If it has narrower
19888 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
19889 if the delivery is the result of a &%save%& command in a filter file specifying
19890 a particular mode, the mode of the output file is always forced to take that
19891 value, and this option is ignored.
19894 .option mode_fail_narrower appendfile boolean true
19895 This option applies in the case when an existing mailbox file has a narrower
19896 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
19897 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
19898 continues with the delivery attempt, using the existing mode of the file.
19901 .option notify_comsat appendfile boolean false
19902 If this option is true, the &'comsat'& daemon is notified after every
19903 successful delivery to a user mailbox. This is the daemon that notifies logged
19904 on users about incoming mail.
19907 .option quota appendfile string&!! unset
19908 .cindex "quota" "imposed by Exim"
19909 This option imposes a limit on the size of the file to which Exim is appending,
19910 or to the total space used in the directory tree when the &%directory%& option
19911 is set. In the latter case, computation of the space used is expensive, because
19912 all the files in the directory (and any sub-directories) have to be
19913 individually inspected and their sizes summed. (See &%quota_size_regex%& and
19914 &%maildir_use_size_file%& for ways to avoid this in environments where users
19915 have no shell access to their mailboxes).
19917 As there is no interlock against two simultaneous deliveries into a
19918 multi-file mailbox, it is possible for the quota to be overrun in this case.
19919 For single-file mailboxes, of course, an interlock is a necessity.
19921 A file's size is taken as its &'used'& value. Because of blocking effects, this
19922 may be a lot less than the actual amount of disk space allocated to the file.
19923 If the sizes of a number of files are being added up, the rounding effect can
19924 become quite noticeable, especially on systems that have large block sizes.
19925 Nevertheless, it seems best to stick to the &'used'& figure, because this is
19926 the obvious value which users understand most easily.
19928 The value of the option is expanded, and must then be a numerical value
19929 (decimal point allowed), optionally followed by one of the letters K, M, or G,
19930 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
19931 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
19934 &*Note*&: A value of zero is interpreted as &"no quota"&.
19936 The expansion happens while Exim is running as root, before it changes uid for
19937 the delivery. This means that files that are inaccessible to the end user can
19938 be used to hold quota values that are looked up in the expansion. When delivery
19939 fails because this quota is exceeded, the handling of the error is as for
19940 system quota failures.
19942 By default, Exim's quota checking mimics system quotas, and restricts the
19943 mailbox to the specified maximum size, though the value is not accurate to the
19944 last byte, owing to separator lines and additional headers that may get added
19945 during message delivery. When a mailbox is nearly full, large messages may get
19946 refused even though small ones are accepted, because the size of the current
19947 message is added to the quota when the check is made. This behaviour can be
19948 changed by setting &%quota_is_inclusive%& false. When this is done, the check
19949 for exceeding the quota does not include the current message. Thus, deliveries
19950 continue until the quota has been exceeded; thereafter, no further messages are
19951 delivered. See also &%quota_warn_threshold%&.
19954 .option quota_directory appendfile string&!! unset
19955 This option defines the directory to check for quota purposes when delivering
19956 into individual files. The default is the delivery directory, or, if a file
19957 called &_maildirfolder_& exists in a maildir directory, the parent of the
19958 delivery directory.
19961 .option quota_filecount appendfile string&!! 0
19962 This option applies when the &%directory%& option is set. It limits the total
19963 number of files in the directory (compare the inode limit in system quotas). It
19964 can only be used if &%quota%& is also set. The value is expanded; an expansion
19965 failure causes delivery to be deferred. A value of zero is interpreted as
19969 .option quota_is_inclusive appendfile boolean true
19970 See &%quota%& above.
19973 .option quota_size_regex appendfile string unset
19974 This option applies when one of the delivery modes that writes a separate file
19975 for each message is being used. When Exim wants to find the size of one of
19976 these files in order to test the quota, it first checks &%quota_size_regex%&.
19977 If this is set to a regular expression that matches the file name, and it
19978 captures one string, that string is interpreted as a representation of the
19979 file's size. The value of &%quota_size_regex%& is not expanded.
19981 This feature is useful only when users have no shell access to their mailboxes
19982 &-- otherwise they could defeat the quota simply by renaming the files. This
19983 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
19984 the file length to the file name. For example:
19986 maildir_tag = ,S=$message_size
19987 quota_size_regex = ,S=(\d+)
19989 An alternative to &$message_size$& is &$message_linecount$&, which contains the
19990 number of lines in the message.
19992 The regular expression should not assume that the length is at the end of the
19993 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
19994 sometimes add other information onto the ends of message file names.
19998 .option quota_warn_message appendfile string&!! "see below"
19999 See below for the use of this option. If it is not set when
20000 &%quota_warn_threshold%& is set, it defaults to
20002 quota_warn_message = "\
20003 To: $local_part@$domain\n\
20004 Subject: Your mailbox\n\n\
20005 This message is automatically created \
20006 by mail delivery software.\n\n\
20007 The size of your mailbox has exceeded \
20008 a warning threshold that is\n\
20009 set by the system administrator.\n"
20013 .option quota_warn_threshold appendfile string&!! 0
20014 .cindex "quota" "warning threshold"
20015 .cindex "mailbox" "size warning"
20016 .cindex "size" "of mailbox"
20017 This option is expanded in the same way as &%quota%& (see above). If the
20018 resulting value is greater than zero, and delivery of the message causes the
20019 size of the file or total space in the directory tree to cross the given
20020 threshold, a warning message is sent. If &%quota%& is also set, the threshold
20021 may be specified as a percentage of it by following the value with a percent
20025 quota_warn_threshold = 75%
20027 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
20028 percent sign is ignored.
20030 The warning message itself is specified by the &%quota_warn_message%& option,
20031 and it must start with a &'To:'& header line containing the recipient(s) of the
20032 warning message. These do not necessarily have to include the recipient(s) of
20033 the original message. A &'Subject:'& line should also normally be supplied. You
20034 can include any other header lines that you want. If you do not include a
20035 &'From:'& line, the default is:
20037 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
20039 .oindex &%errors_reply_to%&
20040 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
20043 The &%quota%& option does not have to be set in order to use this option; they
20044 are independent of one another except when the threshold is specified as a
20048 .option use_bsmtp appendfile boolean false
20049 .cindex "envelope sender"
20050 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
20051 format, with the envelope sender and recipient(s) included as SMTP commands. If
20052 you want to include a leading HELO command with such messages, you can do
20053 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
20054 for details of batch SMTP.
20057 .option use_crlf appendfile boolean false
20058 .cindex "carriage return"
20060 This option causes lines to be terminated with the two-character CRLF sequence
20061 (carriage return, linefeed) instead of just a linefeed character. In the case
20062 of batched SMTP, the byte sequence written to the file is then an exact image
20063 of what would be sent down a real SMTP connection.
20065 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
20066 (which are used to supply the traditional &"From&~"& and blank line separators
20067 in Berkeley-style mailboxes) are written verbatim, so must contain their own
20068 carriage return characters if these are needed. In cases where these options
20069 have non-empty defaults, the values end with a single linefeed, so they must be
20070 changed to end with &`\r\n`& if &%use_crlf%& is set.
20073 .option use_fcntl_lock appendfile boolean "see below"
20074 This option controls the use of the &[fcntl()]& function to lock a file for
20075 exclusive use when a message is being appended. It is set by default unless
20076 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
20077 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
20078 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
20081 .option use_flock_lock appendfile boolean false
20082 This option is provided to support the use of &[flock()]& for file locking, for
20083 the few situations where it is needed. Most modern operating systems support
20084 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
20085 each other. Exim uses &[fcntl()]& locking by default.
20087 This option is required only if you are using an operating system where
20088 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
20089 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
20090 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
20092 .cindex "Solaris" "&[flock()]& support"
20093 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
20094 have it (and some, I think, provide a not quite right version built on top of
20095 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
20096 the ability to use it, and any attempt to do so will cause a configuration
20099 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
20100 is just being mapped onto &[fcntl()]& by the OS).
20103 .option use_lockfile appendfile boolean "see below"
20104 If this option is turned off, Exim does not attempt to create a lock file when
20105 appending to a mailbox file. In this situation, the only locking is by
20106 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
20107 sure that every MUA that is ever going to look at your users' mailboxes uses
20108 &[fcntl()]& rather than a lock file, and even then only when you are not
20109 delivering over NFS from more than one host.
20111 .cindex "NFS" "lock file"
20112 In order to append to an NFS file safely from more than one host, it is
20113 necessary to take out a lock &'before'& opening the file, and the lock file
20114 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
20117 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
20118 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
20119 except when &%mbx_format%& is set.
20122 .option use_mbx_lock appendfile boolean "see below"
20123 This option is available only if Exim has been compiled with SUPPORT_MBX
20124 set in &_Local/Makefile_&. Setting the option specifies that special MBX
20125 locking rules be used. It is set by default if &%mbx_format%& is set and none
20126 of the locking options are mentioned in the configuration. The locking rules
20127 are the same as are used by the &'c-client'& library that underlies Pine and
20128 the IMAP4 and POP daemons that come with it (see the discussion below). The
20129 rules allow for shared access to the mailbox. However, this kind of locking
20130 does not work when the mailbox is NFS mounted.
20132 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
20133 &%use_flock_lock%& to control what kind of locking is used in implementing the
20134 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
20135 without &%use_fcntl_lock%& or &%use_flock_lock%&.
20140 .section "Operational details for appending" "SECTopappend"
20141 .cindex "appending to a file"
20142 .cindex "file" "appending"
20143 Before appending to a file, the following preparations are made:
20146 If the name of the file is &_/dev/null_&, no action is taken, and a success
20150 .cindex "directory creation"
20151 If any directories on the file's path are missing, Exim creates them if the
20152 &%create_directory%& option is set. A created directory's mode is given by the
20153 &%directory_mode%& option.
20156 If &%file_format%& is set, the format of an existing file is checked. If this
20157 indicates that a different transport should be used, control is passed to that
20161 .cindex "file" "locking"
20162 .cindex "locking files"
20163 .cindex "NFS" "lock file"
20164 If &%use_lockfile%& is set, a lock file is built in a way that will work
20165 reliably over NFS, as follows:
20168 Create a &"hitching post"& file whose name is that of the lock file with the
20169 current time, primary host name, and process id added, by opening for writing
20170 as a new file. If this fails with an access error, delivery is deferred.
20172 Close the hitching post file, and hard link it to the lock file name.
20174 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
20175 Unlink the hitching post name.
20177 Otherwise, use &[stat()]& to get information about the hitching post file, and
20178 then unlink hitching post name. If the number of links is exactly two, creation
20179 of the lock file succeeded but something (for example, an NFS server crash and
20180 restart) caused this fact not to be communicated to the &[link()]& call.
20182 If creation of the lock file failed, wait for &%lock_interval%& and try again,
20183 up to &%lock_retries%& times. However, since any program that writes to a
20184 mailbox should complete its task very quickly, it is reasonable to time out old
20185 lock files that are normally the result of user agent and system crashes. If an
20186 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
20187 it before trying again.
20191 A call is made to &[lstat()]& to discover whether the main file exists, and if
20192 so, what its characteristics are. If &[lstat()]& fails for any reason other
20193 than non-existence, delivery is deferred.
20196 .cindex "symbolic link" "to mailbox"
20197 .cindex "mailbox" "symbolic link"
20198 If the file does exist and is a symbolic link, delivery is deferred, unless the
20199 &%allow_symlink%& option is set, in which case the ownership of the link is
20200 checked, and then &[stat()]& is called to find out about the real file, which
20201 is then subjected to the checks below. The check on the top-level link
20202 ownership prevents one user creating a link for another's mailbox in a sticky
20203 directory, though allowing symbolic links in this case is definitely not a good
20204 idea. If there is a chain of symbolic links, the intermediate ones are not
20208 If the file already exists but is not a regular file, or if the file's owner
20209 and group (if the group is being checked &-- see &%check_group%& above) are
20210 different from the user and group under which the delivery is running,
20211 delivery is deferred.
20214 If the file's permissions are more generous than specified, they are reduced.
20215 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
20216 is set false, in which case the delivery is tried using the existing
20220 The file's inode number is saved, and the file is then opened for appending.
20221 If this fails because the file has vanished, &(appendfile)& behaves as if it
20222 hadn't existed (see below). For any other failures, delivery is deferred.
20225 If the file is opened successfully, check that the inode number hasn't
20226 changed, that it is still a regular file, and that the owner and permissions
20227 have not changed. If anything is wrong, defer delivery and freeze the message.
20230 If the file did not exist originally, defer delivery if the &%file_must_exist%&
20231 option is set. Otherwise, check that the file is being created in a permitted
20232 directory if the &%create_file%& option is set (deferring on failure), and then
20233 open for writing as a new file, with the O_EXCL and O_CREAT options,
20234 except when dealing with a symbolic link (the &%allow_symlink%& option must be
20235 set). In this case, which can happen if the link points to a non-existent file,
20236 the file is opened for writing using O_CREAT but not O_EXCL, because
20237 that prevents link following.
20240 .cindex "loop" "while file testing"
20241 If opening fails because the file exists, obey the tests given above for
20242 existing files. However, to avoid looping in a situation where the file is
20243 being continuously created and destroyed, the exists/not-exists loop is broken
20244 after 10 repetitions, and the message is then frozen.
20247 If opening fails with any other error, defer delivery.
20250 .cindex "file" "locking"
20251 .cindex "locking files"
20252 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
20253 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
20254 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
20255 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
20256 file, and an exclusive lock on the file whose name is
20258 /tmp/.<device-number>.<inode-number>
20260 using the device and inode numbers of the open mailbox file, in accordance with
20261 the MBX locking rules. This file is created with a mode that is specified by
20262 the &%lockfile_mode%& option.
20264 If Exim fails to lock the file, there are two possible courses of action,
20265 depending on the value of the locking timeout. This is obtained from
20266 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
20268 If the timeout value is zero, the file is closed, Exim waits for
20269 &%lock_interval%&, and then goes back and re-opens the file as above and tries
20270 to lock it again. This happens up to &%lock_retries%& times, after which the
20271 delivery is deferred.
20273 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
20274 &[flock()]& are used (with the given timeout), so there has already been some
20275 waiting involved by the time locking fails. Nevertheless, Exim does not give up
20276 immediately. It retries up to
20278 (lock_retries * lock_interval) / <timeout>
20280 times (rounded up).
20283 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
20284 and/or &[flock()]& locks) and then deletes the lock file if one was created.
20287 .section "Operational details for delivery to a new file" "SECTopdir"
20288 .cindex "delivery" "to single file"
20289 .cindex "&""From""& line"
20290 When the &%directory%& option is set instead of &%file%&, each message is
20291 delivered into a newly-created file or set of files. When &(appendfile)& is
20292 activated directly from a &(redirect)& router, neither &%file%& nor
20293 &%directory%& is normally set, because the path for delivery is supplied by the
20294 router. (See for example, the &(address_file)& transport in the default
20295 configuration.) In this case, delivery is to a new file if either the path name
20296 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
20298 No locking is required while writing the message to a new file, so the various
20299 locking options of the transport are ignored. The &"From"& line that by default
20300 separates messages in a single file is not normally needed, nor is the escaping
20301 of message lines that start with &"From"&, and there is no need to ensure a
20302 newline at the end of each message. Consequently, the default values for
20303 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
20304 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
20306 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
20307 the files in the delivery directory by default. However, you can specify a
20308 different directory by setting &%quota_directory%&. Also, for maildir
20309 deliveries (see below) the &_maildirfolder_& convention is honoured.
20312 .cindex "maildir format"
20313 .cindex "mailstore format"
20314 There are three different ways in which delivery to individual files can be
20315 done, controlled by the settings of the &%maildir_format%& and
20316 &%mailstore_format%& options. Note that code to support maildir or mailstore
20317 formats is not included in the binary unless SUPPORT_MAILDIR or
20318 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
20320 .cindex "directory creation"
20321 In all three cases an attempt is made to create the directory and any necessary
20322 sub-directories if they do not exist, provided that the &%create_directory%&
20323 option is set (the default). The location of a created directory can be
20324 constrained by setting &%create_file%&. A created directory's mode is given by
20325 the &%directory_mode%& option. If creation fails, or if the
20326 &%create_directory%& option is not set when creation is required, delivery is
20331 .section "Maildir delivery" "SECTmaildirdelivery"
20332 .cindex "maildir format" "description of"
20333 If the &%maildir_format%& option is true, Exim delivers each message by writing
20334 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
20335 directory that is defined by the &%directory%& option (the &"delivery
20336 directory"&). If the delivery is successful, the file is renamed into the
20337 &_new_& subdirectory.
20339 In the file name, <&'stime'&> is the current time of day in seconds, and
20340 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
20341 Exim checks that the time-of-day clock has moved on by at least one microsecond
20342 before terminating the delivery process. This guarantees uniqueness for the
20343 file name. However, as a precaution, Exim calls &[stat()]& for the file before
20344 opening it. If any response other than ENOENT (does not exist) is given,
20345 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
20347 Before Exim carries out a maildir delivery, it ensures that subdirectories
20348 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
20349 do not exist, Exim tries to create them and any superior directories in their
20350 path, subject to the &%create_directory%& and &%create_file%& options. If the
20351 &%maildirfolder_create_regex%& option is set, and the regular expression it
20352 contains matches the delivery directory, Exim also ensures that a file called
20353 &_maildirfolder_& exists in the delivery directory. If a missing directory or
20354 &_maildirfolder_& file cannot be created, delivery is deferred.
20356 These features make it possible to use Exim to create all the necessary files
20357 and directories in a maildir mailbox, including subdirectories for maildir++
20358 folders. Consider this example:
20360 maildir_format = true
20361 directory = /var/mail/$local_part\
20362 ${if eq{$local_part_suffix}{}{}\
20363 {/.${substr_1:$local_part_suffix}}}
20364 maildirfolder_create_regex = /\.[^/]+$
20366 If &$local_part_suffix$& is empty (there was no suffix for the local part),
20367 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
20368 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
20369 not match this name, so Exim will not look for or create the file
20370 &_/var/mail/pimbo/maildirfolder_&, though it will create
20371 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
20373 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
20374 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
20375 does match &%maildirfolder_create_regex%&. In this case, Exim will create
20376 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
20377 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
20379 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
20380 not inadvertently match the toplevel maildir directory, because a
20381 &_maildirfolder_& file at top level would completely break quota calculations.
20383 .cindex "quota" "in maildir delivery"
20384 .cindex "maildir++"
20385 If Exim is required to check a &%quota%& setting before a maildir delivery, and
20386 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
20387 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
20388 Exim assumes the directory is a maildir++ folder directory, which is one level
20389 down from the user's top level mailbox directory. This causes it to start at
20390 the parent directory instead of the current directory when calculating the
20391 amount of space used.
20393 One problem with delivering into a multi-file mailbox is that it is
20394 computationally expensive to compute the size of the mailbox for quota
20395 checking. Various approaches have been taken to reduce the amount of work
20396 needed. The next two sections describe two of them. A third alternative is to
20397 use some external process for maintaining the size data, and use the expansion
20398 of the &%mailbox_size%& option as a way of importing it into Exim.
20403 .section "Using tags to record message sizes" "SECID135"
20404 If &%maildir_tag%& is set, the string is expanded for each delivery.
20405 When the maildir file is renamed into the &_new_& sub-directory, the
20406 tag is added to its name. However, if adding the tag takes the length of the
20407 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
20408 the tag is dropped and the maildir file is created with no tag.
20410 .vindex "&$message_size$&"
20411 Tags can be used to encode the size of files in their names; see
20412 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
20413 happens after the message has been written. The value of the &$message_size$&
20414 variable is set to the number of bytes actually written. If the expansion is
20415 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
20416 be deferred. The expanded tag may contain any printing characters except &"/"&.
20417 Non-printing characters in the string are ignored; if the resulting string is
20418 empty, it is ignored. If it starts with an alphanumeric character, a leading
20423 .section "Using a maildirsize file" "SECID136"
20424 .cindex "quota" "in maildir delivery"
20425 .cindex "maildir format" "&_maildirsize_& file"
20426 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
20427 storing quota and message size information in a file called &_maildirsize_&
20428 within the toplevel maildir directory. If this file does not exist, Exim
20429 creates it, setting the quota from the &%quota%& option of the transport. If
20430 the maildir directory itself does not exist, it is created before any attempt
20431 to write a &_maildirsize_& file.
20433 The &_maildirsize_& file is used to hold information about the sizes of
20434 messages in the maildir, thus speeding up quota calculations. The quota value
20435 in the file is just a cache; if the quota is changed in the transport, the new
20436 value overrides the cached value when the next message is delivered. The cache
20437 is maintained for the benefit of other programs that access the maildir and
20438 need to know the quota.
20440 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
20441 file is maintained (with a zero quota setting), but no quota is imposed.
20443 A regular expression is available for controlling which directories in the
20444 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
20445 See the description of the &%maildir_quota_directory_regex%& option above for
20449 .section "Mailstore delivery" "SECID137"
20450 .cindex "mailstore format" "description of"
20451 If the &%mailstore_format%& option is true, each message is written as two
20452 files in the given directory. A unique base name is constructed from the
20453 message id and the current delivery process, and the files that are written use
20454 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
20455 contains the message's envelope, and the &_.msg_& file contains the message
20456 itself. The base name is placed in the variable &$mailstore_basename$&.
20458 During delivery, the envelope is first written to a file with the suffix
20459 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
20460 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
20461 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
20462 file before accessing either of them. An alternative approach is to wait for
20463 the absence of a &_.tmp_& file.
20465 The envelope file starts with any text defined by the &%mailstore_prefix%&
20466 option, expanded and terminated by a newline if there isn't one. Then follows
20467 the sender address on one line, then all the recipient addresses, one per line.
20468 There can be more than one recipient only if the &%batch_max%& option is set
20469 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
20470 appended to the file, followed by a newline if it does not end with one.
20472 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
20473 failure, it is ignored. Other expansion errors are treated as serious
20474 configuration errors, and delivery is deferred. The variable
20475 &$mailstore_basename$& is available for use during these expansions.
20478 .section "Non-special new file delivery" "SECID138"
20479 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
20480 file is created directly in the named directory. For example, when delivering
20481 messages into files in batched SMTP format for later delivery to some host (see
20482 section &<<SECTbatchSMTP>>&), a setting such as
20484 directory = /var/bsmtp/$host
20486 might be used. A message is written to a file with a temporary name, which is
20487 then renamed when the delivery is complete. The final name is obtained by
20488 expanding the contents of the &%directory_file%& option.
20489 .ecindex IIDapptra1
20490 .ecindex IIDapptra2
20497 . ////////////////////////////////////////////////////////////////////////////
20498 . ////////////////////////////////////////////////////////////////////////////
20500 .chapter "The autoreply transport" "CHID8"
20501 .scindex IIDauttra1 "transports" "&(autoreply)&"
20502 .scindex IIDauttra2 "&(autoreply)& transport"
20503 The &(autoreply)& transport is not a true transport in that it does not cause
20504 the message to be transmitted. Instead, it generates a new mail message as an
20505 automatic reply to the incoming message. &'References:'& and
20506 &'Auto-Submitted:'& header lines are included. These are constructed according
20507 to the rules in RFCs 2822 and 3834, respectively.
20509 If the router that passes the message to this transport does not have the
20510 &%unseen%& option set, the original message (for the current recipient) is not
20511 delivered anywhere. However, when the &%unseen%& option is set on the router
20512 that passes the message to this transport, routing of the address continues, so
20513 another router can set up a normal message delivery.
20516 The &(autoreply)& transport is usually run as the result of mail filtering, a
20517 &"vacation"& message being the standard example. However, it can also be run
20518 directly from a router like any other transport. To reduce the possibility of
20519 message cascades, messages created by the &(autoreply)& transport always have
20520 empty envelope sender addresses, like bounce messages.
20522 The parameters of the message to be sent can be specified in the configuration
20523 by options described below. However, these are used only when the address
20524 passed to the transport does not contain its own reply information. When the
20525 transport is run as a consequence of a
20527 or &%vacation%& command in a filter file, the parameters of the message are
20528 supplied by the filter, and passed with the address. The transport's options
20529 that define the message are then ignored (so they are not usually set in this
20530 case). The message is specified entirely by the filter or by the transport; it
20531 is never built from a mixture of options. However, the &%file_optional%&,
20532 &%mode%&, and &%return_message%& options apply in all cases.
20534 &(Autoreply)& is implemented as a local transport. When used as a result of a
20535 command in a user's filter file, &(autoreply)& normally runs under the uid and
20536 gid of the user, and with appropriate current and home directories (see chapter
20537 &<<CHAPenvironment>>&).
20539 There is a subtle difference between routing a message to a &(pipe)& transport
20540 that generates some text to be returned to the sender, and routing it to an
20541 &(autoreply)& transport. This difference is noticeable only if more than one
20542 address from the same message is so handled. In the case of a pipe, the
20543 separate outputs from the different addresses are gathered up and returned to
20544 the sender in a single message, whereas if &(autoreply)& is used, a separate
20545 message is generated for each address that is passed to it.
20547 Non-printing characters are not permitted in the header lines generated for the
20548 message that &(autoreply)& creates, with the exception of newlines that are
20549 immediately followed by white space. If any non-printing characters are found,
20550 the transport defers.
20551 Whether characters with the top bit set count as printing characters or not is
20552 controlled by the &%print_topbitchars%& global option.
20554 If any of the generic options for manipulating headers (for example,
20555 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
20556 of the original message that is included in the generated message when
20557 &%return_message%& is set. They do not apply to the generated message itself.
20559 .vindex "&$sender_address$&"
20560 If the &(autoreply)& transport receives return code 2 from Exim when it submits
20561 the message, indicating that there were no recipients, it does not treat this
20562 as an error. This means that autoreplies sent to &$sender_address$& when this
20563 is empty (because the incoming message is a bounce message) do not cause
20564 problems. They are just discarded.
20568 .section "Private options for autoreply" "SECID139"
20569 .cindex "options" "&(autoreply)& transport"
20571 .option bcc autoreply string&!! unset
20572 This specifies the addresses that are to receive &"blind carbon copies"& of the
20573 message when the message is specified by the transport.
20576 .option cc autoreply string&!! unset
20577 This specifies recipients of the message and the contents of the &'Cc:'& header
20578 when the message is specified by the transport.
20581 .option file autoreply string&!! unset
20582 The contents of the file are sent as the body of the message when the message
20583 is specified by the transport. If both &%file%& and &%text%& are set, the text
20584 string comes first.
20587 .option file_expand autoreply boolean false
20588 If this is set, the contents of the file named by the &%file%& option are
20589 subjected to string expansion as they are added to the message.
20592 .option file_optional autoreply boolean false
20593 If this option is true, no error is generated if the file named by the &%file%&
20594 option or passed with the address does not exist or cannot be read.
20597 .option from autoreply string&!! unset
20598 This specifies the contents of the &'From:'& header when the message is
20599 specified by the transport.
20602 .option headers autoreply string&!! unset
20603 This specifies additional RFC 2822 headers that are to be added to the message
20604 when the message is specified by the transport. Several can be given by using
20605 &"\n"& to separate them. There is no check on the format.
20608 .option log autoreply string&!! unset
20609 This option names a file in which a record of every message sent is logged when
20610 the message is specified by the transport.
20613 .option mode autoreply "octal integer" 0600
20614 If either the log file or the &"once"& file has to be created, this mode is
20618 .option never_mail autoreply "address list&!!" unset
20619 If any run of the transport creates a message with a recipient that matches any
20620 item in the list, that recipient is quietly discarded. If all recipients are
20621 discarded, no message is created. This applies both when the recipients are
20622 generated by a filter and when they are specified in the transport.
20626 .option once autoreply string&!! unset
20627 This option names a file or DBM database in which a record of each &'To:'&
20628 recipient is kept when the message is specified by the transport. &*Note*&:
20629 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
20631 If &%once%& is unset, or is set to an empty string, the message is always sent.
20632 By default, if &%once%& is set to a non-empty file name, the message
20633 is not sent if a potential recipient is already listed in the database.
20634 However, if the &%once_repeat%& option specifies a time greater than zero, the
20635 message is sent if that much time has elapsed since a message was last sent to
20636 this recipient. A setting of zero time for &%once_repeat%& (the default)
20637 prevents a message from being sent a second time &-- in this case, zero means
20640 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
20641 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
20642 greater than zero, it changes the way Exim implements the &%once%& option.
20643 Instead of using a DBM file to record every recipient it sends to, it uses a
20644 regular file, whose size will never get larger than the given value.
20646 In the file, Exim keeps a linear list of recipient addresses and the times at
20647 which they were sent messages. If the file is full when a new address needs to
20648 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
20649 means that a given recipient may receive multiple messages, but at
20650 unpredictable intervals that depend on the rate of turnover of addresses in the
20651 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
20654 .option once_file_size autoreply integer 0
20655 See &%once%& above.
20658 .option once_repeat autoreply time&!! 0s
20659 See &%once%& above.
20660 After expansion, the value of this option must be a valid time value.
20663 .option reply_to autoreply string&!! unset
20664 This specifies the contents of the &'Reply-To:'& header when the message is
20665 specified by the transport.
20668 .option return_message autoreply boolean false
20669 If this is set, a copy of the original message is returned with the new
20670 message, subject to the maximum size set in the &%return_size_limit%& global
20671 configuration option.
20674 .option subject autoreply string&!! unset
20675 This specifies the contents of the &'Subject:'& header when the message is
20676 specified by the transport. It is tempting to quote the original subject in
20677 automatic responses. For example:
20679 subject = Re: $h_subject:
20681 There is a danger in doing this, however. It may allow a third party to
20682 subscribe your users to an opt-in mailing list, provided that the list accepts
20683 bounce messages as subscription confirmations. Well-managed lists require a
20684 non-bounce message to confirm a subscription, so the danger is relatively
20689 .option text autoreply string&!! unset
20690 This specifies a single string to be used as the body of the message when the
20691 message is specified by the transport. If both &%text%& and &%file%& are set,
20692 the text comes first.
20695 .option to autoreply string&!! unset
20696 This specifies recipients of the message and the contents of the &'To:'& header
20697 when the message is specified by the transport.
20698 .ecindex IIDauttra1
20699 .ecindex IIDauttra2
20704 . ////////////////////////////////////////////////////////////////////////////
20705 . ////////////////////////////////////////////////////////////////////////////
20707 .chapter "The lmtp transport" "CHAPLMTP"
20708 .cindex "transports" "&(lmtp)&"
20709 .cindex "&(lmtp)& transport"
20710 .cindex "LMTP" "over a pipe"
20711 .cindex "LMTP" "over a socket"
20712 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
20714 or by interacting with a Unix domain socket.
20715 This transport is something of a cross between the &(pipe)& and &(smtp)&
20716 transports. Exim also has support for using LMTP over TCP/IP; this is
20717 implemented as an option for the &(smtp)& transport. Because LMTP is expected
20718 to be of minority interest, the default build-time configure in &_src/EDITME_&
20719 has it commented out. You need to ensure that
20723 .cindex "options" "&(lmtp)& transport"
20724 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
20725 included in the Exim binary. The private options of the &(lmtp)& transport are
20728 .option batch_id lmtp string&!! unset
20729 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20732 .option batch_max lmtp integer 1
20733 This limits the number of addresses that can be handled in a single delivery.
20734 Most LMTP servers can handle several addresses at once, so it is normally a
20735 good idea to increase this value. See the description of local delivery
20736 batching in chapter &<<CHAPbatching>>&.
20739 .option command lmtp string&!! unset
20740 This option must be set if &%socket%& is not set. The string is a command which
20741 is run in a separate process. It is split up into a command name and list of
20742 arguments, each of which is separately expanded (so expansion cannot change the
20743 number of arguments). The command is run directly, not via a shell. The message
20744 is passed to the new process using the standard input and output to operate the
20747 .option ignore_quota lmtp boolean false
20748 .cindex "LMTP" "ignoring quota errors"
20749 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
20750 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
20751 in its response to the LHLO command.
20753 .option socket lmtp string&!! unset
20754 This option must be set if &%command%& is not set. The result of expansion must
20755 be the name of a Unix domain socket. The transport connects to the socket and
20756 delivers the message to it using the LMTP protocol.
20759 .option timeout lmtp time 5m
20760 The transport is aborted if the created process or Unix domain socket does not
20761 respond to LMTP commands or message input within this timeout. Delivery
20762 is deferred, and will be tried again later. Here is an example of a typical
20767 command = /some/local/lmtp/delivery/program
20771 This delivers up to 20 addresses at a time, in a mixture of domains if
20772 necessary, running as the user &'exim'&.
20776 . ////////////////////////////////////////////////////////////////////////////
20777 . ////////////////////////////////////////////////////////////////////////////
20779 .chapter "The pipe transport" "CHAPpipetransport"
20780 .scindex IIDpiptra1 "transports" "&(pipe)&"
20781 .scindex IIDpiptra2 "&(pipe)& transport"
20782 The &(pipe)& transport is used to deliver messages via a pipe to a command
20783 running in another process. One example is the use of &(pipe)& as a
20784 pseudo-remote transport for passing messages to some other delivery mechanism
20785 (such as UUCP). Another is the use by individual users to automatically process
20786 their incoming messages. The &(pipe)& transport can be used in one of the
20790 .vindex "&$local_part$&"
20791 A router routes one address to a transport in the normal way, and the
20792 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
20793 contains the local part of the address (as usual), and the command that is run
20794 is specified by the &%command%& option on the transport.
20796 .vindex "&$pipe_addresses$&"
20797 If the &%batch_max%& option is set greater than 1 (the default is 1), the
20798 transport can handle more than one address in a single run. In this case, when
20799 more than one address is routed to the transport, &$local_part$& is not set
20800 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
20801 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
20802 that are routed to the transport.
20804 .vindex "&$address_pipe$&"
20805 A router redirects an address directly to a pipe command (for example, from an
20806 alias or forward file). In this case, &$address_pipe$& contains the text of the
20807 pipe command, and the &%command%& option on the transport is ignored. If only
20808 one address is being transported (&%batch_max%& is not greater than one, or
20809 only one address was redirected to this pipe command), &$local_part$& contains
20810 the local part that was redirected.
20814 The &(pipe)& transport is a non-interactive delivery method. Exim can also
20815 deliver messages over pipes using the LMTP interactive protocol. This is
20816 implemented by the &(lmtp)& transport.
20818 In the case when &(pipe)& is run as a consequence of an entry in a local user's
20819 &_.forward_& file, the command runs under the uid and gid of that user. In
20820 other cases, the uid and gid have to be specified explicitly, either on the
20821 transport or on the router that handles the address. Current and &"home"&
20822 directories are also controllable. See chapter &<<CHAPenvironment>>& for
20823 details of the local delivery environment and chapter &<<CHAPbatching>>&
20824 for a discussion of local delivery batching.
20827 .section "Concurrent delivery" "SECID140"
20828 If two messages arrive at almost the same time, and both are routed to a pipe
20829 delivery, the two pipe transports may be run concurrently. You must ensure that
20830 any pipe commands you set up are robust against this happening. If the commands
20831 write to a file, the &%exim_lock%& utility might be of use.
20836 .section "Returned status and data" "SECID141"
20837 .cindex "&(pipe)& transport" "returned data"
20838 If the command exits with a non-zero return code, the delivery is deemed to
20839 have failed, unless either the &%ignore_status%& option is set (in which case
20840 the return code is treated as zero), or the return code is one of those listed
20841 in the &%temp_errors%& option, which are interpreted as meaning &"try again
20842 later"&. In this case, delivery is deferred. Details of a permanent failure are
20843 logged, but are not included in the bounce message, which merely contains
20844 &"local delivery failed"&.
20846 If the return code is greater than 128 and the command being run is a shell
20847 script, it normally means that the script was terminated by a signal whose
20848 value is the return code minus 128.
20850 If Exim is unable to run the command (that is, if &[execve()]& fails), the
20851 return code is set to 127. This is the value that a shell returns if it is
20852 asked to run a non-existent command. The wording for the log line suggests that
20853 a non-existent command may be the problem.
20855 The &%return_output%& option can affect the result of a pipe delivery. If it is
20856 set and the command produces any output on its standard output or standard
20857 error streams, the command is considered to have failed, even if it gave a zero
20858 return code or if &%ignore_status%& is set. The output from the command is
20859 included as part of the bounce message. The &%return_fail_output%& option is
20860 similar, except that output is returned only when the command exits with a
20861 failure return code, that is, a value other than zero or a code that matches
20866 .section "How the command is run" "SECThowcommandrun"
20867 .cindex "&(pipe)& transport" "path for command"
20868 The command line is (by default) broken down into a command name and arguments
20869 by the &(pipe)& transport itself. The &%allow_commands%& and
20870 &%restrict_to_path%& options can be used to restrict the commands that may be
20873 .cindex "quoting" "in pipe command"
20874 Unquoted arguments are delimited by white space. If an argument appears in
20875 double quotes, backslash is interpreted as an escape character in the usual
20876 way. If an argument appears in single quotes, no escaping is done.
20878 String expansion is applied to the command line except when it comes from a
20879 traditional &_.forward_& file (commands from a filter file are expanded). The
20880 expansion is applied to each argument in turn rather than to the whole line.
20881 For this reason, any string expansion item that contains white space must be
20882 quoted so as to be contained within a single argument. A setting such as
20884 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
20886 will not work, because the expansion item gets split between several
20887 arguments. You have to write
20889 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
20891 to ensure that it is all in one argument. The expansion is done in this way,
20892 argument by argument, so that the number of arguments cannot be changed as a
20893 result of expansion, and quotes or backslashes in inserted variables do not
20894 interact with external quoting. However, this leads to problems if you want to
20895 generate multiple arguments (or the command name plus arguments) from a single
20896 expansion. In this situation, the simplest solution is to use a shell. For
20899 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
20902 .cindex "transport" "filter"
20903 .cindex "filter" "transport filter"
20904 .vindex "&$pipe_addresses$&"
20905 Special handling takes place when an argument consists of precisely the text
20906 &`$pipe_addresses`&. This is not a general expansion variable; the only
20907 place this string is recognized is when it appears as an argument for a pipe or
20908 transport filter command. It causes each address that is being handled to be
20909 inserted in the argument list at that point &'as a separate argument'&. This
20910 avoids any problems with spaces or shell metacharacters, and is of use when a
20911 &(pipe)& transport is handling groups of addresses in a batch.
20913 After splitting up into arguments and expansion, the resulting command is run
20914 in a subprocess directly from the transport, &'not'& under a shell. The
20915 message that is being delivered is supplied on the standard input, and the
20916 standard output and standard error are both connected to a single pipe that is
20917 read by Exim. The &%max_output%& option controls how much output the command
20918 may produce, and the &%return_output%& and &%return_fail_output%& options
20919 control what is done with it.
20921 Not running the command under a shell (by default) lessens the security risks
20922 in cases when a command from a user's filter file is built out of data that was
20923 taken from an incoming message. If a shell is required, it can of course be
20924 explicitly specified as the command to be run. However, there are circumstances
20925 where existing commands (for example, in &_.forward_& files) expect to be run
20926 under a shell and cannot easily be modified. To allow for these cases, there is
20927 an option called &%use_shell%&, which changes the way the &(pipe)& transport
20928 works. Instead of breaking up the command line as just described, it expands it
20929 as a single string and passes the result to &_/bin/sh_&. The
20930 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
20931 with &%use_shell%&, and the whole mechanism is inherently less secure.
20935 .section "Environment variables" "SECTpipeenv"
20936 .cindex "&(pipe)& transport" "environment for command"
20937 .cindex "environment for pipe transport"
20938 The environment variables listed below are set up when the command is invoked.
20939 This list is a compromise for maximum compatibility with other MTAs. Note that
20940 the &%environment%& option can be used to add additional variables to this
20943 &`DOMAIN `& the domain of the address
20944 &`HOME `& the home directory, if set
20945 &`HOST `& the host name when called from a router (see below)
20946 &`LOCAL_PART `& see below
20947 &`LOCAL_PART_PREFIX `& see below
20948 &`LOCAL_PART_SUFFIX `& see below
20949 &`LOGNAME `& see below
20950 &`MESSAGE_ID `& Exim's local ID for the message
20951 &`PATH `& as specified by the &%path%& option below
20952 &`QUALIFY_DOMAIN `& the sender qualification domain
20953 &`RECIPIENT `& the complete recipient address
20954 &`SENDER `& the sender of the message (empty if a bounce)
20955 &`SHELL `& &`/bin/sh`&
20956 &`TZ `& the value of the &%timezone%& option, if set
20957 &`USER `& see below
20959 When a &(pipe)& transport is called directly from (for example) an &(accept)&
20960 router, LOCAL_PART is set to the local part of the address. When it is
20961 called as a result of a forward or alias expansion, LOCAL_PART is set to
20962 the local part of the address that was expanded. In both cases, any affixes are
20963 removed from the local part, and made available in LOCAL_PART_PREFIX and
20964 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
20965 same value as LOCAL_PART for compatibility with other MTAs.
20968 HOST is set only when a &(pipe)& transport is called from a router that
20969 associates hosts with an address, typically when using &(pipe)& as a
20970 pseudo-remote transport. HOST is set to the first host name specified by
20974 If the transport's generic &%home_directory%& option is set, its value is used
20975 for the HOME environment variable. Otherwise, a home directory may be set
20976 by the router's &%transport_home_directory%& option, which defaults to the
20977 user's home directory if &%check_local_user%& is set.
20980 .section "Private options for pipe" "SECID142"
20981 .cindex "options" "&(pipe)& transport"
20985 .option allow_commands pipe "string list&!!" unset
20986 .cindex "&(pipe)& transport" "permitted commands"
20987 The string is expanded, and is then interpreted as a colon-separated list of
20988 permitted commands. If &%restrict_to_path%& is not set, the only commands
20989 permitted are those in the &%allow_commands%& list. They need not be absolute
20990 paths; the &%path%& option is still used for relative paths. If
20991 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
20992 in the &%allow_commands%& list, or a name without any slashes that is found on
20993 the path. In other words, if neither &%allow_commands%& nor
20994 &%restrict_to_path%& is set, there is no restriction on the command, but
20995 otherwise only commands that are permitted by one or the other are allowed. For
20998 allow_commands = /usr/bin/vacation
21000 and &%restrict_to_path%& is not set, the only permitted command is
21001 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
21002 &%use_shell%& is set.
21005 .option batch_id pipe string&!! unset
21006 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21009 .option batch_max pipe integer 1
21010 This limits the number of addresses that can be handled in a single delivery.
21011 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21014 .option check_string pipe string unset
21015 As &(pipe)& writes the message, the start of each line is tested for matching
21016 &%check_string%&, and if it does, the initial matching characters are replaced
21017 by the contents of &%escape_string%&, provided both are set. The value of
21018 &%check_string%& is a literal string, not a regular expression, and the case of
21019 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
21020 of &%check_string%& and &%escape_string%& are forced to values that implement
21021 the SMTP escaping protocol. Any settings made in the configuration file are
21025 .option command pipe string&!! unset
21026 This option need not be set when &(pipe)& is being used to deliver to pipes
21027 obtained directly from address redirections. In other cases, the option must be
21028 set, to provide a command to be run. It need not yield an absolute path (see
21029 the &%path%& option below). The command is split up into separate arguments by
21030 Exim, and each argument is separately expanded, as described in section
21031 &<<SECThowcommandrun>>& above.
21034 .option environment pipe string&!! unset
21035 .cindex "&(pipe)& transport" "environment for command"
21036 .cindex "environment for &(pipe)& transport"
21037 This option is used to add additional variables to the environment in which the
21038 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
21039 a string which is expanded, and then interpreted as a colon-separated list of
21040 environment settings of the form <&'name'&>=<&'value'&>.
21043 .option escape_string pipe string unset
21044 See &%check_string%& above.
21047 .option freeze_exec_fail pipe boolean false
21048 .cindex "exec failure"
21049 .cindex "failure of exec"
21050 .cindex "&(pipe)& transport" "failure of exec"
21051 Failure to exec the command in a pipe transport is by default treated like
21052 any other failure while running the command. However, if &%freeze_exec_fail%&
21053 is set, failure to exec is treated specially, and causes the message to be
21054 frozen, whatever the setting of &%ignore_status%&.
21057 .option ignore_status pipe boolean false
21058 If this option is true, the status returned by the subprocess that is set up to
21059 run the command is ignored, and Exim behaves as if zero had been returned.
21060 Otherwise, a non-zero status or termination by signal causes an error return
21061 from the transport unless the status value is one of those listed in
21062 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
21064 &*Note*&: This option does not apply to timeouts, which do not return a status.
21065 See the &%timeout_defer%& option for how timeouts are handled.
21067 .option log_defer_output pipe boolean false
21068 .cindex "&(pipe)& transport" "logging output"
21069 If this option is set, and the status returned by the command is
21070 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
21071 and any output was produced, the first line of it is written to the main log.
21074 .option log_fail_output pipe boolean false
21075 If this option is set, and the command returns any output, and also ends with a
21076 return code that is neither zero nor one of the return codes listed in
21077 &%temp_errors%& (that is, the delivery failed), the first line of output is
21078 written to the main log. This option and &%log_output%& are mutually exclusive.
21079 Only one of them may be set.
21083 .option log_output pipe boolean false
21084 If this option is set and the command returns any output, the first line of
21085 output is written to the main log, whatever the return code. This option and
21086 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
21090 .option max_output pipe integer 20K
21091 This specifies the maximum amount of output that the command may produce on its
21092 standard output and standard error file combined. If the limit is exceeded, the
21093 process running the command is killed. This is intended as a safety measure to
21094 catch runaway processes. The limit is applied independently of the settings of
21095 the options that control what is done with such output (for example,
21096 &%return_output%&). Because of buffering effects, the amount of output may
21097 exceed the limit by a small amount before Exim notices.
21100 .option message_prefix pipe string&!! "see below"
21101 The string specified here is expanded and output at the start of every message.
21102 The default is unset if &%use_bsmtp%& is set. Otherwise it is
21105 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
21109 .cindex "&%tmail%&"
21110 .cindex "&""From""& line"
21111 This is required by the commonly used &_/usr/bin/vacation_& program.
21112 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
21113 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
21118 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21119 &`\n`& to &`\r\n`& in &%message_prefix%&.
21122 .option message_suffix pipe string&!! "see below"
21123 The string specified here is expanded and output at the end of every message.
21124 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
21125 The suffix can be suppressed by setting
21129 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21130 &`\n`& to &`\r\n`& in &%message_suffix%&.
21133 .option path pipe string "see below"
21134 This option specifies the string that is set up in the PATH environment
21135 variable of the subprocess. The default is:
21139 If the &%command%& option does not yield an absolute path name, the command is
21140 sought in the PATH directories, in the usual way. &*Warning*&: This does not
21141 apply to a command specified as a transport filter.
21144 .option permit_coredump pipe boolean false
21145 Normally Exim inhibits core-dumps during delivery. If you have a need to get
21146 a core-dump of a pipe command, enable this command. This enables core-dumps
21147 during delivery and affects both the Exim binary and the pipe command run.
21148 It is recommended that this option remain off unless and until you have a need
21149 for it and that this only be enabled when needed, as the risk of excessive
21150 resource consumption can be quite high. Note also that Exim is typically
21151 installed as a setuid binary and most operating systems will inhibit coredumps
21152 of these by default, so further OS-specific action may be required.
21155 .option pipe_as_creator pipe boolean false
21156 .cindex "uid (user id)" "local delivery"
21157 If the generic &%user%& option is not set and this option is true, the delivery
21158 process is run under the uid that was in force when Exim was originally called
21159 to accept the message. If the group id is not otherwise set (via the generic
21160 &%group%& option), the gid that was in force when Exim was originally called to
21161 accept the message is used.
21164 .option restrict_to_path pipe boolean false
21165 When this option is set, any command name not listed in &%allow_commands%& must
21166 contain no slashes. The command is searched for only in the directories listed
21167 in the &%path%& option. This option is intended for use in the case when a pipe
21168 command has been generated from a user's &_.forward_& file. This is usually
21169 handled by a &(pipe)& transport called &%address_pipe%&.
21172 .option return_fail_output pipe boolean false
21173 If this option is true, and the command produced any output and ended with a
21174 return code other than zero or one of the codes listed in &%temp_errors%& (that
21175 is, the delivery failed), the output is returned in the bounce message.
21176 However, if the message has a null sender (that is, it is itself a bounce
21177 message), output from the command is discarded. This option and
21178 &%return_output%& are mutually exclusive. Only one of them may be set.
21182 .option return_output pipe boolean false
21183 If this option is true, and the command produced any output, the delivery is
21184 deemed to have failed whatever the return code from the command, and the output
21185 is returned in the bounce message. Otherwise, the output is just discarded.
21186 However, if the message has a null sender (that is, it is a bounce message),
21187 output from the command is always discarded, whatever the setting of this
21188 option. This option and &%return_fail_output%& are mutually exclusive. Only one
21189 of them may be set.
21193 .option temp_errors pipe "string list" "see below"
21194 .cindex "&(pipe)& transport" "temporary failure"
21195 This option contains either a colon-separated list of numbers, or a single
21196 asterisk. If &%ignore_status%& is false
21197 and &%return_output%& is not set,
21198 and the command exits with a non-zero return code, the failure is treated as
21199 temporary and the delivery is deferred if the return code matches one of the
21200 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
21201 codes are treated as permanent errors. The default setting contains the codes
21202 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
21203 compiled on a system that does not define these macros, it assumes values of 75
21204 and 73, respectively.
21207 .option timeout pipe time 1h
21208 If the command fails to complete within this time, it is killed. This normally
21209 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
21210 specifies no timeout. In order to ensure that any subprocesses created by the
21211 command are also killed, Exim makes the initial process a process group leader,
21212 and kills the whole process group on a timeout. However, this can be defeated
21213 if one of the processes starts a new process group.
21215 .option timeout_defer pipe boolean false
21216 A timeout in a &(pipe)& transport, either in the command that the transport
21217 runs, or in a transport filter that is associated with it, is by default
21218 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
21219 is set true, both kinds of timeout become temporary errors, causing the
21220 delivery to be deferred.
21222 .option umask pipe "octal integer" 022
21223 This specifies the umask setting for the subprocess that runs the command.
21226 .option use_bsmtp pipe boolean false
21227 .cindex "envelope sender"
21228 If this option is set true, the &(pipe)& transport writes messages in &"batch
21229 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
21230 commands. If you want to include a leading HELO command with such messages,
21231 you can do so by setting the &%message_prefix%& option. See section
21232 &<<SECTbatchSMTP>>& for details of batch SMTP.
21234 .option use_classresources pipe boolean false
21235 .cindex "class resources (BSD)"
21236 This option is available only when Exim is running on FreeBSD, NetBSD, or
21237 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
21238 resource limits when a &(pipe)& transport is run to perform a delivery. The
21239 limits for the uid under which the pipe is to run are obtained from the login
21243 .option use_crlf pipe boolean false
21244 .cindex "carriage return"
21246 This option causes lines to be terminated with the two-character CRLF sequence
21247 (carriage return, linefeed) instead of just a linefeed character. In the case
21248 of batched SMTP, the byte sequence written to the pipe is then an exact image
21249 of what would be sent down a real SMTP connection.
21251 The contents of the &%message_prefix%& and &%message_suffix%& options are
21252 written verbatim, so must contain their own carriage return characters if these
21253 are needed. When &%use_bsmtp%& is not set, the default values for both
21254 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
21255 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
21258 .option use_shell pipe boolean false
21259 .vindex "&$pipe_addresses$&"
21260 If this option is set, it causes the command to be passed to &_/bin/sh_&
21261 instead of being run directly from the transport, as described in section
21262 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
21263 where the command is expected to be run under a shell and cannot easily be
21264 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
21265 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
21266 command is expanded as a single string, and handed to &_/bin/sh_& as data for
21271 .section "Using an external local delivery agent" "SECID143"
21272 .cindex "local delivery" "using an external agent"
21273 .cindex "&'procmail'&"
21274 .cindex "external local delivery"
21275 .cindex "delivery" "&'procmail'&"
21276 .cindex "delivery" "by external agent"
21277 The &(pipe)& transport can be used to pass all messages that require local
21278 delivery to a separate local delivery agent such as &%procmail%&. When doing
21279 this, care must be taken to ensure that the pipe is run under an appropriate
21280 uid and gid. In some configurations one wants this to be a uid that is trusted
21281 by the delivery agent to supply the correct sender of the message. It may be
21282 necessary to recompile or reconfigure the delivery agent so that it trusts an
21283 appropriate user. The following is an example transport and router
21284 configuration for &%procmail%&:
21289 command = /usr/local/bin/procmail -d $local_part
21293 check_string = "From "
21294 escape_string = ">From "
21303 transport = procmail_pipe
21305 In this example, the pipe is run as the local user, but with the group set to
21306 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
21307 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
21308 user to supply a correct sender address. If you do not specify either a
21309 &%group%& or a &%user%& option, the pipe command is run as the local user. The
21310 home directory is the user's home directory by default.
21312 &*Note*&: The command that the pipe transport runs does &'not'& begin with
21316 as shown in some &%procmail%& documentation, because Exim does not by default
21317 use a shell to run pipe commands.
21320 The next example shows a transport and a router for a system where local
21321 deliveries are handled by the Cyrus IMAP server.
21324 local_delivery_cyrus:
21326 command = /usr/cyrus/bin/deliver \
21327 -m ${substr_1:$local_part_suffix} -- $local_part
21339 local_part_suffix = .*
21340 transport = local_delivery_cyrus
21342 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
21343 &%return_output%& to cause any text written by Cyrus to be returned to the
21345 .ecindex IIDpiptra1
21346 .ecindex IIDpiptra2
21349 . ////////////////////////////////////////////////////////////////////////////
21350 . ////////////////////////////////////////////////////////////////////////////
21352 .chapter "The smtp transport" "CHAPsmtptrans"
21353 .scindex IIDsmttra1 "transports" "&(smtp)&"
21354 .scindex IIDsmttra2 "&(smtp)& transport"
21355 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
21356 or LMTP protocol. The list of hosts to try can either be taken from the address
21357 that is being processed (having been set up by the router), or specified
21358 explicitly for the transport. Timeout and retry processing (see chapter
21359 &<<CHAPretry>>&) is applied to each IP address independently.
21362 .section "Multiple messages on a single connection" "SECID144"
21363 The sending of multiple messages over a single TCP/IP connection can arise in
21367 If a message contains more than &%max_rcpt%& (see below) addresses that are
21368 routed to the same host, more than one copy of the message has to be sent to
21369 that host. In this situation, multiple copies may be sent in a single run of
21370 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
21371 does when it has too many addresses to send in one message also depends on the
21372 value of the global &%remote_max_parallel%& option. Details are given in
21373 section &<<SECToutSMTPTCP>>&.)
21375 .cindex "hints database" "remembering routing"
21376 When a message has been successfully delivered over a TCP/IP connection, Exim
21377 looks in its hints database to see if there are any other messages awaiting a
21378 connection to the same host. If there are, a new delivery process is started
21379 for one of them, and the current TCP/IP connection is passed on to it. The new
21380 process may in turn send multiple copies and possibly create yet another
21385 For each copy sent over the same TCP/IP connection, a sequence counter is
21386 incremented, and if it ever gets to the value of &%connection_max_messages%&,
21387 no further messages are sent over that connection.
21391 .section "Use of the $host and $host_address variables" "SECID145"
21393 .vindex "&$host_address$&"
21394 At the start of a run of the &(smtp)& transport, the values of &$host$& and
21395 &$host_address$& are the name and IP address of the first host on the host list
21396 passed by the router. However, when the transport is about to connect to a
21397 specific host, and while it is connected to that host, &$host$& and
21398 &$host_address$& are set to the values for that host. These are the values
21399 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
21400 &%serialize_hosts%&, and the various TLS options are expanded.
21403 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
21404 .vindex &$tls_cipher$&
21405 .vindex &$tls_peerdn$&
21406 At the start of a run of the &(smtp)& transport, the values of &$tls_cipher$&
21407 and &$tls_peerdn$& are the values that were set when the message was received.
21408 These are the values that are used for options that are expanded before any
21409 SMTP connections are made. Just before each connection is made, these two
21410 variables are emptied. If TLS is subsequently started, they are set to the
21411 appropriate values for the outgoing connection, and these are the values that
21412 are in force when any authenticators are run and when the
21413 &%authenticated_sender%& option is expanded.
21416 .section "Private options for smtp" "SECID146"
21417 .cindex "options" "&(smtp)& transport"
21418 The private options of the &(smtp)& transport are as follows:
21421 .option address_retry_include_sender smtp boolean true
21422 .cindex "4&'xx'& responses" "retrying after"
21423 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
21424 is the combination of sender and recipient that is delayed in subsequent queue
21425 runs until the retry time is reached. You can delay the recipient without
21426 reference to the sender (which is what earlier versions of Exim did), by
21427 setting &%address_retry_include_sender%& false. However, this can lead to
21428 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
21430 .option allow_localhost smtp boolean false
21431 .cindex "local host" "sending to"
21432 .cindex "fallback" "hosts specified on transport"
21433 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
21434 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
21435 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
21436 the delivery anyway. This should be used only in special cases when the
21437 configuration ensures that no looping will result (for example, a differently
21438 configured Exim is listening on the port to which the message is sent).
21441 .option authenticated_sender smtp string&!! unset
21443 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
21444 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
21445 overriding any existing authenticated sender value. If the string expansion is
21446 forced to fail, the option is ignored. Other expansion failures cause delivery
21447 to be deferred. If the result of expansion is an empty string, that is also
21450 The expansion happens after the outgoing connection has been made and TLS
21451 started, if required. This means that the &$host$&, &$host_address$&,
21452 &$tls_cipher$&, and &$tls_peerdn$& variables are set according to the
21453 particular connection.
21455 If the SMTP session is not authenticated, the expansion of
21456 &%authenticated_sender%& still happens (and can cause the delivery to be
21457 deferred if it fails), but no AUTH= item is added to MAIL commands
21458 unless &%authenticated_sender_force%& is true.
21460 This option allows you to use the &(smtp)& transport in LMTP mode to
21461 deliver mail to Cyrus IMAP and provide the proper local part as the
21462 &"authenticated sender"&, via a setting such as:
21464 authenticated_sender = $local_part
21466 This removes the need for IMAP subfolders to be assigned special ACLs to
21467 allow direct delivery to those subfolders.
21469 Because of expected uses such as that just described for Cyrus (when no
21470 domain is involved), there is no checking on the syntax of the provided
21474 .option authenticated_sender_force smtp boolean false
21475 If this option is set true, the &%authenticated_sender%& option's value
21476 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
21477 authenticated as a client.
21480 .option command_timeout smtp time 5m
21481 This sets a timeout for receiving a response to an SMTP command that has been
21482 sent out. It is also used when waiting for the initial banner line from the
21483 remote host. Its value must not be zero.
21486 .option connect_timeout smtp time 5m
21487 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
21488 to a remote host. A setting of zero allows the system timeout (typically
21489 several minutes) to act. To have any effect, the value of this option must be
21490 less than the system timeout. However, it has been observed that on some
21491 systems there is no system timeout, which is why the default value for this
21492 option is 5 minutes, a value recommended by RFC 1123.
21495 .option connection_max_messages smtp integer 500
21496 .cindex "SMTP" "passed connection"
21497 .cindex "SMTP" "multiple deliveries"
21498 .cindex "multiple SMTP deliveries"
21499 This controls the maximum number of separate message deliveries that are sent
21500 over a single TCP/IP connection. If the value is zero, there is no limit.
21501 For testing purposes, this value can be overridden by the &%-oB%& command line
21505 .option data_timeout smtp time 5m
21506 This sets a timeout for the transmission of each block in the data portion of
21507 the message. As a result, the overall timeout for a message depends on the size
21508 of the message. Its value must not be zero. See also &%final_timeout%&.
21511 .option delay_after_cutoff smtp boolean true
21512 This option controls what happens when all remote IP addresses for a given
21513 domain have been inaccessible for so long that they have passed their retry
21516 In the default state, if the next retry time has not been reached for any of
21517 them, the address is bounced without trying any deliveries. In other words,
21518 Exim delays retrying an IP address after the final cutoff time until a new
21519 retry time is reached, and can therefore bounce an address without ever trying
21520 a delivery, when machines have been down for a long time. Some people are
21521 unhappy at this prospect, so...
21523 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
21524 addresses are past their final cutoff time, Exim tries to deliver to those
21525 IP addresses that have not been tried since the message arrived. If there are
21526 none, of if they all fail, the address is bounced. In other words, it does not
21527 delay when a new message arrives, but immediately tries those expired IP
21528 addresses that haven't been tried since the message arrived. If there is a
21529 continuous stream of messages for the dead hosts, unsetting
21530 &%delay_after_cutoff%& means that there will be many more attempts to deliver
21534 .option dns_qualify_single smtp boolean true
21535 If the &%hosts%& or &%fallback_hosts%& option is being used,
21536 and the &%gethostbyname%& option is false,
21537 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
21538 in chapter &<<CHAPdnslookup>>& for more details.
21541 .option dns_search_parents smtp boolean false
21542 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
21543 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
21544 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
21549 .option fallback_hosts smtp "string list" unset
21550 .cindex "fallback" "hosts specified on transport"
21551 String expansion is not applied to this option. The argument must be a
21552 colon-separated list of host names or IP addresses, optionally also including
21553 port numbers, though the separator can be changed, as described in section
21554 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
21555 item in a &%route_list%& setting for the &(manualroute)& router, as described
21556 in section &<<SECTformatonehostitem>>&.
21558 Fallback hosts can also be specified on routers, which associate them with the
21559 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
21560 &%fallback_hosts%& specified on the transport is used only if the address does
21561 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
21562 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
21563 However, &%hosts_randomize%& does apply to fallback host lists.
21565 If Exim is unable to deliver to any of the hosts for a particular address, and
21566 the errors are not permanent rejections, the address is put on a separate
21567 transport queue with its host list replaced by the fallback hosts, unless the
21568 address was routed via MX records and the current host was in the original MX
21569 list. In that situation, the fallback host list is not used.
21571 Once normal deliveries are complete, the fallback queue is delivered by
21572 re-running the same transports with the new host lists. If several failing
21573 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
21574 copy of the message is sent.
21576 The resolution of the host names on the fallback list is controlled by the
21577 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
21578 both to cases when the host list comes with the address and when it is taken
21579 from &%hosts%&. This option provides a &"use a smart host only if delivery
21583 .option final_timeout smtp time 10m
21584 This is the timeout that applies while waiting for the response to the final
21585 line containing just &"."& that terminates a message. Its value must not be
21588 .option gethostbyname smtp boolean false
21589 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
21590 being used, names are looked up using &[gethostbyname()]&
21591 (or &[getipnodebyname()]& when available)
21592 instead of using the DNS. Of course, that function may in fact use the DNS, but
21593 it may also consult other sources of information such as &_/etc/hosts_&.
21595 .option gnutls_require_kx smtp string unset
21596 This option controls the key exchange mechanisms when GnuTLS is used in an Exim
21597 client. For details, see section &<<SECTreqciphgnu>>&.
21599 .option gnutls_require_mac smtp string unset
21600 This option controls the MAC algorithms when GnuTLS is used in an Exim
21601 client. For details, see section &<<SECTreqciphgnu>>&.
21603 .option gnutls_require_protocols smtp string unset
21604 This option controls the protocols when GnuTLS is used in an Exim
21605 client. For details, see section &<<SECTreqciphgnu>>&.
21607 .option gnutls_compat_mode smtp boolean unset
21608 This option controls whether GnuTLS is used in compatibility mode in an Exim
21609 server. This reduces security slightly, but improves interworking with older
21610 implementations of TLS.
21612 .option helo_data smtp string&!! "see below"
21613 .cindex "HELO" "argument, setting"
21614 .cindex "EHLO" "argument, setting"
21615 .cindex "LHLO argument setting"
21616 The value of this option is expanded after a connection to a another host has
21617 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
21618 command that starts the outgoing SMTP or LMTP session. The default value of the
21623 During the expansion, the variables &$host$& and &$host_address$& are set to
21624 the identity of the remote host, and the variables &$sending_ip_address$& and
21625 &$sending_port$& are set to the local IP address and port number that are being
21626 used. These variables can be used to generate different values for different
21627 servers or different local IP addresses. For example, if you want the string
21628 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
21629 interface address, you could use this:
21631 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
21632 {$primary_hostname}}
21634 The use of &%helo_data%& applies both to sending messages and when doing
21637 .option hosts smtp "string list&!!" unset
21638 Hosts are associated with an address by a router such as &(dnslookup)&, which
21639 finds the hosts by looking up the address domain in the DNS, or by
21640 &(manualroute)&, which has lists of hosts in its configuration. However,
21641 email addresses can be passed to the &(smtp)& transport by any router, and not
21642 all of them can provide an associated list of hosts.
21644 The &%hosts%& option specifies a list of hosts to be used if the address being
21645 processed does not have any hosts associated with it. The hosts specified by
21646 &%hosts%& are also used, whether or not the address has its own hosts, if
21647 &%hosts_override%& is set.
21649 The string is first expanded, before being interpreted as a colon-separated
21650 list of host names or IP addresses, possibly including port numbers. The
21651 separator may be changed to something other than colon, as described in section
21652 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
21653 item in a &%route_list%& setting for the &(manualroute)& router, as described
21654 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
21655 of the &(manualroute)& router is not available here.
21657 If the expansion fails, delivery is deferred. Unless the failure was caused by
21658 the inability to complete a lookup, the error is logged to the panic log as
21659 well as the main log. Host names are looked up either by searching directly for
21660 address records in the DNS or by calling &[gethostbyname()]& (or
21661 &[getipnodebyname()]& when available), depending on the setting of the
21662 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
21663 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
21666 During delivery, the hosts are tried in order, subject to their retry status,
21667 unless &%hosts_randomize%& is set.
21670 .option hosts_avoid_esmtp smtp "host list&!!" unset
21671 .cindex "ESMTP, avoiding use of"
21672 .cindex "HELO" "forcing use of"
21673 .cindex "EHLO" "avoiding use of"
21674 .cindex "PIPELINING" "avoiding the use of"
21675 This option is for use with broken hosts that announce ESMTP facilities (for
21676 example, PIPELINING) and then fail to implement them properly. When a host
21677 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
21678 start of the SMTP session. This means that it cannot use any of the ESMTP
21679 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
21682 .option hosts_avoid_pipelining smtp "host list&!!" unset
21683 .cindex "PIPELINING" "avoiding the use of"
21684 Exim will not use the SMTP PIPELINING extension when delivering to any host
21685 that matches this list, even if the server host advertises PIPELINING support.
21688 .option hosts_avoid_tls smtp "host list&!!" unset
21689 .cindex "TLS" "avoiding for certain hosts"
21690 Exim will not try to start a TLS session when delivering to any host that
21691 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
21694 .option hosts_max_try smtp integer 5
21695 .cindex "host" "maximum number to try"
21696 .cindex "limit" "number of hosts tried"
21697 .cindex "limit" "number of MX tried"
21698 .cindex "MX record" "maximum tried"
21699 This option limits the number of IP addresses that are tried for any one
21700 delivery in cases where there are temporary delivery errors. Section
21701 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
21704 .option hosts_max_try_hardlimit smtp integer 50
21705 This is an additional check on the maximum number of IP addresses that Exim
21706 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
21711 .option hosts_nopass_tls smtp "host list&!!" unset
21712 .cindex "TLS" "passing connection"
21713 .cindex "multiple SMTP deliveries"
21714 .cindex "TLS" "multiple message deliveries"
21715 For any host that matches this list, a connection on which a TLS session has
21716 been started will not be passed to a new delivery process for sending another
21717 message on the same connection. See section &<<SECTmulmessam>>& for an
21718 explanation of when this might be needed.
21721 .option hosts_override smtp boolean false
21722 If this option is set and the &%hosts%& option is also set, any hosts that are
21723 attached to the address are ignored, and instead the hosts specified by the
21724 &%hosts%& option are always used. This option does not apply to
21725 &%fallback_hosts%&.
21728 .option hosts_randomize smtp boolean false
21729 .cindex "randomized host list"
21730 .cindex "host" "list of; randomized"
21731 .cindex "fallback" "randomized hosts"
21732 If this option is set, and either the list of hosts is taken from the
21733 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
21734 were not obtained from MX records (this includes fallback hosts from the
21735 router), and were not randomized by the router, the order of trying the hosts
21736 is randomized each time the transport runs. Randomizing the order of a host
21737 list can be used to do crude load sharing.
21739 When &%hosts_randomize%& is true, a host list may be split into groups whose
21740 order is separately randomized. This makes it possible to set up MX-like
21741 behaviour. The boundaries between groups are indicated by an item that is just
21742 &`+`& in the host list. For example:
21744 hosts = host1:host2:host3:+:host4:host5
21746 The order of the first three hosts and the order of the last two hosts is
21747 randomized for each use, but the first three always end up before the last two.
21748 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
21750 .option hosts_require_auth smtp "host list&!!" unset
21751 .cindex "authentication" "required by client"
21752 This option provides a list of servers for which authentication must succeed
21753 before Exim will try to transfer a message. If authentication fails for
21754 servers which are not in this list, Exim tries to send unauthenticated. If
21755 authentication fails for one of these servers, delivery is deferred. This
21756 temporary error is detectable in the retry rules, so it can be turned into a
21757 hard failure if required. See also &%hosts_try_auth%&, and chapter
21758 &<<CHAPSMTPAUTH>>& for details of authentication.
21761 .option hosts_require_tls smtp "host list&!!" unset
21762 .cindex "TLS" "requiring for certain servers"
21763 Exim will insist on using a TLS session when delivering to any host that
21764 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
21765 &*Note*&: This option affects outgoing mail only. To insist on TLS for
21766 incoming messages, use an appropriate ACL.
21768 .option hosts_try_auth smtp "host list&!!" unset
21769 .cindex "authentication" "optional in client"
21770 This option provides a list of servers to which, provided they announce
21771 authentication support, Exim will attempt to authenticate as a client when it
21772 connects. If authentication fails, Exim will try to transfer the message
21773 unauthenticated. See also &%hosts_require_auth%&, and chapter
21774 &<<CHAPSMTPAUTH>>& for details of authentication.
21776 .option interface smtp "string list&!!" unset
21777 .cindex "bind IP address"
21778 .cindex "IP address" "binding"
21780 .vindex "&$host_address$&"
21781 This option specifies which interface to bind to when making an outgoing SMTP
21782 call. The value is an IP address, not an interface name such as
21783 &`eth0`&. Do not confuse this with the interface address that was used when a
21784 message was received, which is in &$received_ip_address$&, formerly known as
21785 &$interface_address$&. The name was changed to minimize confusion with the
21786 outgoing interface address. There is no variable that contains an outgoing
21787 interface address because, unless it is set by this option, its value is
21790 During the expansion of the &%interface%& option the variables &$host$& and
21791 &$host_address$& refer to the host to which a connection is about to be made
21792 during the expansion of the string. Forced expansion failure, or an empty
21793 string result causes the option to be ignored. Otherwise, after expansion, the
21794 string must be a list of IP addresses, colon-separated by default, but the
21795 separator can be changed in the usual way. For example:
21797 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
21799 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
21800 connection. If none of them are the correct type, the option is ignored. If
21801 &%interface%& is not set, or is ignored, the system's IP functions choose which
21802 interface to use if the host has more than one.
21805 .option keepalive smtp boolean true
21806 .cindex "keepalive" "on outgoing connection"
21807 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
21808 connections. When set, it causes the kernel to probe idle connections
21809 periodically, by sending packets with &"old"& sequence numbers. The other end
21810 of the connection should send a acknowledgment if the connection is still okay
21811 or a reset if the connection has been aborted. The reason for doing this is
21812 that it has the beneficial effect of freeing up certain types of connection
21813 that can get stuck when the remote host is disconnected without tidying up the
21814 TCP/IP call properly. The keepalive mechanism takes several hours to detect
21818 .option lmtp_ignore_quota smtp boolean false
21819 .cindex "LMTP" "ignoring quota errors"
21820 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
21821 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
21822 has advertised support for IGNOREQUOTA in its response to the LHLO command.
21824 .option max_rcpt smtp integer 100
21825 .cindex "RCPT" "maximum number of outgoing"
21826 This option limits the number of RCPT commands that are sent in a single
21827 SMTP message transaction. Each set of addresses is treated independently, and
21828 so can cause parallel connections to the same host if &%remote_max_parallel%&
21832 .option multi_domain smtp boolean true
21833 .vindex "&$domain$&"
21834 When this option is set, the &(smtp)& transport can handle a number of
21835 addresses containing a mixture of different domains provided they all resolve
21836 to the same list of hosts. Turning the option off restricts the transport to
21837 handling only one domain at a time. This is useful if you want to use
21838 &$domain$& in an expansion for the transport, because it is set only when there
21839 is a single domain involved in a remote delivery.
21842 .option port smtp string&!! "see below"
21843 .cindex "port" "sending TCP/IP"
21844 .cindex "TCP/IP" "setting outgoing port"
21845 This option specifies the TCP/IP port on the server to which Exim connects.
21846 &*Note:*& Do not confuse this with the port that was used when a message was
21847 received, which is in &$received_port$&, formerly known as &$interface_port$&.
21848 The name was changed to minimize confusion with the outgoing port. There is no
21849 variable that contains an outgoing port.
21851 If the value of this option begins with a digit it is taken as a port number;
21852 otherwise it is looked up using &[getservbyname()]&. The default value is
21853 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
21854 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
21859 .option protocol smtp string smtp
21860 .cindex "LMTP" "over TCP/IP"
21861 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
21862 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
21863 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
21864 deliveries into closed message stores. Exim also has support for running LMTP
21865 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
21868 .option retry_include_ip_address smtp boolean true
21869 Exim normally includes both the host name and the IP address in the key it
21870 constructs for indexing retry data after a temporary delivery failure. This
21871 means that when one of several IP addresses for a host is failing, it gets
21872 tried periodically (controlled by the retry rules), but use of the other IP
21873 addresses is not affected.
21875 However, in some dialup environments hosts are assigned a different IP address
21876 each time they connect. In this situation the use of the IP address as part of
21877 the retry key leads to undesirable behaviour. Setting this option false causes
21878 Exim to use only the host name. This should normally be done on a separate
21879 instance of the &(smtp)& transport, set up specially to handle the dialup
21883 .option serialize_hosts smtp "host list&!!" unset
21884 .cindex "serializing connections"
21885 .cindex "host" "serializing connections"
21886 Because Exim operates in a distributed manner, if several messages for the same
21887 host arrive at around the same time, more than one simultaneous connection to
21888 the remote host can occur. This is not usually a problem except when there is a
21889 slow link between the hosts. In that situation it may be helpful to restrict
21890 Exim to one connection at a time. This can be done by setting
21891 &%serialize_hosts%& to match the relevant hosts.
21893 .cindex "hints database" "serializing deliveries to a host"
21894 Exim implements serialization by means of a hints database in which a record is
21895 written whenever a process connects to one of the restricted hosts. The record
21896 is deleted when the connection is completed. Obviously there is scope for
21897 records to get left lying around if there is a system or program crash. To
21898 guard against this, Exim ignores any records that are more than six hours old.
21900 If you set up this kind of serialization, you should also arrange to delete the
21901 relevant hints database whenever your system reboots. The names of the files
21902 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21903 may be one or two files, depending on the type of DBM in use. The same files
21904 are used for ETRN serialization.
21907 .option size_addition smtp integer 1024
21908 .cindex "SMTP" "SIZE"
21909 .cindex "message" "size issue for transport filter"
21910 .cindex "size" "of message"
21911 .cindex "transport" "filter"
21912 .cindex "filter" "transport filter"
21913 If a remote SMTP server indicates that it supports the SIZE option of the
21914 MAIL command, Exim uses this to pass over the message size at the start of
21915 an SMTP transaction. It adds the value of &%size_addition%& to the value it
21916 sends, to allow for headers and other text that may be added during delivery by
21917 configuration options or in a transport filter. It may be necessary to increase
21918 this if a lot of text is added to messages.
21920 Alternatively, if the value of &%size_addition%& is set negative, it disables
21921 the use of the SIZE option altogether.
21924 .option tls_certificate smtp string&!! unset
21925 .cindex "TLS" "client certificate, location of"
21926 .cindex "certificate" "client, location of"
21928 .vindex "&$host_address$&"
21929 The value of this option must be the absolute path to a file which contains the
21930 client's certificate, for possible use when sending a message over an encrypted
21931 connection. The values of &$host$& and &$host_address$& are set to the name and
21932 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
21935 &*Note*&: This option must be set if you want Exim to be able to use a TLS
21936 certificate when sending messages as a client. The global option of the same
21937 name specifies the certificate for Exim as a server; it is not automatically
21938 assumed that the same certificate should be used when Exim is operating as a
21942 .option tls_crl smtp string&!! unset
21943 .cindex "TLS" "client certificate revocation list"
21944 .cindex "certificate" "revocation list for client"
21945 This option specifies a certificate revocation list. The expanded value must
21946 be the name of a file that contains a CRL in PEM format.
21949 .option tls_privatekey smtp string&!! unset
21950 .cindex "TLS" "client private key, location of"
21952 .vindex "&$host_address$&"
21953 The value of this option must be the absolute path to a file which contains the
21954 client's private key. This is used when sending a message over an encrypted
21955 connection using a client certificate. The values of &$host$& and
21956 &$host_address$& are set to the name and address of the server during the
21957 expansion. If this option is unset, or the expansion is forced to fail, or the
21958 result is an empty string, the private key is assumed to be in the same file as
21959 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
21962 .option tls_require_ciphers smtp string&!! unset
21963 .cindex "TLS" "requiring specific ciphers"
21964 .cindex "cipher" "requiring specific"
21966 .vindex "&$host_address$&"
21967 The value of this option must be a list of permitted cipher suites, for use
21968 when setting up an outgoing encrypted connection. (There is a global option of
21969 the same name for controlling incoming connections.) The values of &$host$& and
21970 &$host_address$& are set to the name and address of the server during the
21971 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
21972 is used in different ways by OpenSSL and GnuTLS (see sections
21973 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
21974 ciphers is a preference order.
21978 .option tls_tempfail_tryclear smtp boolean true
21979 .cindex "4&'xx'& responses" "to STARTTLS"
21980 When the server host is not in &%hosts_require_tls%&, and there is a problem in
21981 setting up a TLS session, this option determines whether or not Exim should try
21982 to deliver the message unencrypted. If it is set false, delivery to the
21983 current host is deferred; if there are other hosts, they are tried. If this
21984 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
21985 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
21986 TLS negotiation fails, Exim closes the current connection (because it is in an
21987 unknown state), opens a new one to the same host, and then tries the delivery
21991 .option tls_verify_certificates smtp string&!! unset
21992 .cindex "TLS" "server certificate verification"
21993 .cindex "certificate" "verification of server"
21995 .vindex "&$host_address$&"
21996 The value of this option must be the absolute path to a file containing
21997 permitted server certificates, for use when setting up an encrypted connection.
21998 Alternatively, if you are using OpenSSL, you can set
21999 &%tls_verify_certificates%& to the name of a directory containing certificate
22000 files. This does not work with GnuTLS; the option must be set to the name of a
22001 single file if you are using GnuTLS. The values of &$host$& and
22002 &$host_address$& are set to the name and address of the server during the
22003 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
22008 .section "How the limits for the number of hosts to try are used" &&&
22010 .cindex "host" "maximum number to try"
22011 .cindex "limit" "hosts; maximum number tried"
22012 There are two options that are concerned with the number of hosts that are
22013 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
22014 &%hosts_max_try_hardlimit%&.
22017 The &%hosts_max_try%& option limits the number of hosts that are tried
22018 for a single delivery. However, despite the term &"host"& in its name, the
22019 option actually applies to each IP address independently. In other words, a
22020 multihomed host is treated as several independent hosts, just as it is for
22023 Many of the larger ISPs have multiple MX records which often point to
22024 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
22025 created as a result of routing one of these domains.
22027 Trying every single IP address on such a long list does not seem sensible; if
22028 several at the top of the list fail, it is reasonable to assume there is some
22029 problem that is likely to affect all of them. Roughly speaking, the value of
22030 &%hosts_max_try%& is the maximum number that are tried before deferring the
22031 delivery. However, the logic cannot be quite that simple.
22033 Firstly, IP addresses that are skipped because their retry times have not
22034 arrived do not count, and in addition, addresses that are past their retry
22035 limits are also not counted, even when they are tried. This means that when
22036 some IP addresses are past their retry limits, more than the value of
22037 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
22038 that all IP addresses are considered before timing out an email address (but
22039 see below for an exception).
22041 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
22042 list to see if there is a subsequent host with a different (higher valued) MX.
22043 If there is, that host is considered next, and the current IP address is used
22044 but not counted. This behaviour helps in the case of a domain with a retry rule
22045 that hardly ever delays any hosts, as is now explained:
22047 Consider the case of a long list of hosts with one MX value, and a few with a
22048 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
22049 hosts at the top of the list are tried at first. With the default retry rule,
22050 which specifies increasing retry times, the higher MX hosts are eventually
22051 tried when those at the top of the list are skipped because they have not
22052 reached their retry times.
22054 However, it is common practice to put a fixed short retry time on domains for
22055 large ISPs, on the grounds that their servers are rarely down for very long.
22056 Unfortunately, these are exactly the domains that tend to resolve to long lists
22057 of hosts. The short retry time means that the lowest MX hosts are tried every
22058 time. The attempts may be in a different order because of random sorting, but
22059 without the special MX check, the higher MX hosts would never be tried until
22060 all the lower MX hosts had timed out (which might be several days), because
22061 there are always some lower MX hosts that have reached their retry times. With
22062 the special check, Exim considers at least one IP address from each MX value at
22063 every delivery attempt, even if the &%hosts_max_try%& limit has already been
22066 The above logic means that &%hosts_max_try%& is not a hard limit, and in
22067 particular, Exim normally eventually tries all the IP addresses before timing
22068 out an email address. When &%hosts_max_try%& was implemented, this seemed a
22069 reasonable thing to do. Recently, however, some lunatic DNS configurations have
22070 been set up with hundreds of IP addresses for some domains. It can
22071 take a very long time indeed for an address to time out in these cases.
22073 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
22074 Exim never tries more than this number of IP addresses; if it hits this limit
22075 and they are all timed out, the email address is bounced, even though not all
22076 possible IP addresses have been tried.
22077 .ecindex IIDsmttra1
22078 .ecindex IIDsmttra2
22084 . ////////////////////////////////////////////////////////////////////////////
22085 . ////////////////////////////////////////////////////////////////////////////
22087 .chapter "Address rewriting" "CHAPrewrite"
22088 .scindex IIDaddrew "rewriting" "addresses"
22089 There are some circumstances in which Exim automatically rewrites domains in
22090 addresses. The two most common are when an address is given without a domain
22091 (referred to as an &"unqualified address"&) or when an address contains an
22092 abbreviated domain that is expanded by DNS lookup.
22094 Unqualified envelope addresses are accepted only for locally submitted
22095 messages, or for messages that are received from hosts matching
22096 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
22097 appropriate. Unqualified addresses in header lines are qualified if they are in
22098 locally submitted messages, or messages from hosts that are permitted to send
22099 unqualified envelope addresses. Otherwise, unqualified addresses in header
22100 lines are neither qualified nor rewritten.
22102 One situation in which Exim does &'not'& automatically rewrite a domain is
22103 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
22104 such a domain should be rewritten using the &"canonical"& name, and some MTAs
22105 do this. The new RFCs do not contain this suggestion.
22108 .section "Explicitly configured address rewriting" "SECID147"
22109 This chapter describes the rewriting rules that can be used in the
22110 main rewrite section of the configuration file, and also in the generic
22111 &%headers_rewrite%& option that can be set on any transport.
22113 Some people believe that configured address rewriting is a Mortal Sin.
22114 Others believe that life is not possible without it. Exim provides the
22115 facility; you do not have to use it.
22117 The main rewriting rules that appear in the &"rewrite"& section of the
22118 configuration file are applied to addresses in incoming messages, both envelope
22119 addresses and addresses in header lines. Each rule specifies the types of
22120 address to which it applies.
22122 Whether or not addresses in header lines are rewritten depends on the origin of
22123 the headers and the type of rewriting. Global rewriting, that is, rewriting
22124 rules from the rewrite section of the configuration file, is applied only to
22125 those headers that were received with the message. Header lines that are added
22126 by ACLs or by a system filter or by individual routers or transports (which
22127 are specific to individual recipient addresses) are not rewritten by the global
22130 Rewriting at transport time, by means of the &%headers_rewrite%& option,
22131 applies all headers except those added by routers and transports. That is, as
22132 well as the headers that were received with the message, it also applies to
22133 headers that were added by an ACL or a system filter.
22136 In general, rewriting addresses from your own system or domain has some
22137 legitimacy. Rewriting other addresses should be done only with great care and
22138 in special circumstances. The author of Exim believes that rewriting should be
22139 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
22140 Although it can sometimes be used as a routing tool, this is very strongly
22143 There are two commonly encountered circumstances where rewriting is used, as
22144 illustrated by these examples:
22147 The company whose domain is &'hitch.fict.example'& has a number of hosts that
22148 exchange mail with each other behind a firewall, but there is only a single
22149 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
22150 &'hitch.fict.example'& when sending mail off-site.
22152 A host rewrites the local parts of its own users so that, for example,
22153 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
22158 .section "When does rewriting happen?" "SECID148"
22159 .cindex "rewriting" "timing of"
22160 .cindex "&ACL;" "rewriting addresses in"
22161 Configured address rewriting can take place at several different stages of a
22162 message's processing.
22164 .vindex "&$sender_address$&"
22165 At the start of an ACL for MAIL, the sender address may have been rewritten
22166 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
22167 ordinary rewrite rules have yet been applied. If, however, the sender address
22168 is verified in the ACL, it is rewritten before verification, and remains
22169 rewritten thereafter. The subsequent value of &$sender_address$& is the
22170 rewritten address. This also applies if sender verification happens in a
22171 RCPT ACL. Otherwise, when the sender address is not verified, it is
22172 rewritten as soon as a message's header lines have been received.
22174 .vindex "&$domain$&"
22175 .vindex "&$local_part$&"
22176 Similarly, at the start of an ACL for RCPT, the current recipient's address
22177 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
22178 rewrite rules have yet been applied to it. However, the behaviour is different
22179 from the sender address when a recipient is verified. The address is rewritten
22180 for the verification, but the rewriting is not remembered at this stage. The
22181 value of &$local_part$& and &$domain$& after verification are always the same
22182 as they were before (that is, they contain the unrewritten &-- except for
22183 SMTP-time rewriting &-- address).
22185 As soon as a message's header lines have been received, all the envelope
22186 recipient addresses are permanently rewritten, and rewriting is also applied to
22187 the addresses in the header lines (if configured). This happens before adding
22188 any header lines that were specified in MAIL or RCPT ACLs, and
22189 .cindex "&[local_scan()]& function" "address rewriting; timing of"
22190 before the DATA ACL and &[local_scan()]& functions are run.
22192 When an address is being routed, either for delivery or for verification,
22193 rewriting is applied immediately to child addresses that are generated by
22194 redirection, unless &%no_rewrite%& is set on the router.
22196 .cindex "envelope sender" "rewriting at transport time"
22197 .cindex "rewriting" "at transport time"
22198 .cindex "header lines" "rewriting at transport time"
22199 At transport time, additional rewriting of addresses in header lines can be
22200 specified by setting the generic &%headers_rewrite%& option on a transport.
22201 This option contains rules that are identical in form to those in the rewrite
22202 section of the configuration file. They are applied to the original message
22203 header lines and any that were added by ACLs or a system filter. They are not
22204 applied to header lines that are added by routers or the transport.
22206 The outgoing envelope sender can be rewritten by means of the &%return_path%&
22207 transport option. However, it is not possible to rewrite envelope recipients at
22213 .section "Testing the rewriting rules that apply on input" "SECID149"
22214 .cindex "rewriting" "testing"
22215 .cindex "testing" "rewriting"
22216 Exim's input rewriting configuration appears in a part of the run time
22217 configuration file headed by &"begin rewrite"&. It can be tested by the
22218 &%-brw%& command line option. This takes an address (which can be a full RFC
22219 2822 address) as its argument. The output is a list of how the address would be
22220 transformed by the rewriting rules for each of the different places it might
22221 appear in an incoming message, that is, for each different header and for the
22222 envelope sender and recipient fields. For example,
22224 exim -brw ph10@exim.workshop.example
22226 might produce the output
22228 sender: Philip.Hazel@exim.workshop.example
22229 from: Philip.Hazel@exim.workshop.example
22230 to: ph10@exim.workshop.example
22231 cc: ph10@exim.workshop.example
22232 bcc: ph10@exim.workshop.example
22233 reply-to: Philip.Hazel@exim.workshop.example
22234 env-from: Philip.Hazel@exim.workshop.example
22235 env-to: ph10@exim.workshop.example
22237 which shows that rewriting has been set up for that address when used in any of
22238 the source fields, but not when it appears as a recipient address. At the
22239 present time, there is no equivalent way of testing rewriting rules that are
22240 set for a particular transport.
22243 .section "Rewriting rules" "SECID150"
22244 .cindex "rewriting" "rules"
22245 The rewrite section of the configuration file consists of lines of rewriting
22248 <&'source pattern'&> <&'replacement'&> <&'flags'&>
22250 Rewriting rules that are specified for the &%headers_rewrite%& generic
22251 transport option are given as a colon-separated list. Each item in the list
22252 takes the same form as a line in the main rewriting configuration (except that
22253 any colons must be doubled, of course).
22255 The formats of source patterns and replacement strings are described below.
22256 Each is terminated by white space, unless enclosed in double quotes, in which
22257 case normal quoting conventions apply inside the quotes. The flags are single
22258 characters which may appear in any order. Spaces and tabs between them are
22261 For each address that could potentially be rewritten, the rules are scanned in
22262 order, and replacements for the address from earlier rules can themselves be
22263 replaced by later rules (but see the &"q"& and &"R"& flags).
22265 The order in which addresses are rewritten is undefined, may change between
22266 releases, and must not be relied on, with one exception: when a message is
22267 received, the envelope sender is always rewritten first, before any header
22268 lines are rewritten. For example, the replacement string for a rewrite of an
22269 address in &'To:'& must not assume that the message's address in &'From:'& has
22270 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
22271 that the envelope sender has already been rewritten.
22273 .vindex "&$domain$&"
22274 .vindex "&$local_part$&"
22275 The variables &$local_part$& and &$domain$& can be used in the replacement
22276 string to refer to the address that is being rewritten. Note that lookup-driven
22277 rewriting can be done by a rule of the form
22281 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
22282 refer to the address that is being rewritten.
22285 .section "Rewriting patterns" "SECID151"
22286 .cindex "rewriting" "patterns"
22287 .cindex "address list" "in a rewriting pattern"
22288 The source pattern in a rewriting rule is any item which may appear in an
22289 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
22290 single-item address list, which means that it is expanded before being tested
22291 against the address. As always, if you use a regular expression as a pattern,
22292 you must take care to escape dollar and backslash characters, or use the &`\N`&
22293 facility to suppress string expansion within the regular expression.
22295 Domains in patterns should be given in lower case. Local parts in patterns are
22296 case-sensitive. If you want to do case-insensitive matching of local parts, you
22297 can use a regular expression that starts with &`^(?i)`&.
22299 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
22300 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
22301 depending on the type of match which occurred. These can be used in the
22302 replacement string to insert portions of the incoming address. &$0$& always
22303 refers to the complete incoming address. When a regular expression is used, the
22304 numerical variables are set from its capturing subexpressions. For other types
22305 of pattern they are set as follows:
22308 If a local part or domain starts with an asterisk, the numerical variables
22309 refer to the character strings matched by asterisks, with &$1$& associated with
22310 the first asterisk, and &$2$& with the second, if present. For example, if the
22313 *queen@*.fict.example
22315 is matched against the address &'hearts-queen@wonderland.fict.example'& then
22317 $0 = hearts-queen@wonderland.fict.example
22321 Note that if the local part does not start with an asterisk, but the domain
22322 does, it is &$1$& that contains the wild part of the domain.
22325 If the domain part of the pattern is a partial lookup, the wild and fixed parts
22326 of the domain are placed in the next available numerical variables. Suppose,
22327 for example, that the address &'foo@bar.baz.example'& is processed by a
22328 rewriting rule of the form
22330 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
22332 and the key in the file that matches the domain is &`*.baz.example`&. Then
22338 If the address &'foo@baz.example'& is looked up, this matches the same
22339 wildcard file entry, and in this case &$2$& is set to the empty string, but
22340 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
22341 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
22342 whole domain. For non-partial domain lookups, no numerical variables are set.
22346 .section "Rewriting replacements" "SECID152"
22347 .cindex "rewriting" "replacements"
22348 If the replacement string for a rule is a single asterisk, addresses that
22349 match the pattern and the flags are &'not'& rewritten, and no subsequent
22350 rewriting rules are scanned. For example,
22352 hatta@lookingglass.fict.example * f
22354 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
22357 .vindex "&$domain$&"
22358 .vindex "&$local_part$&"
22359 If the replacement string is not a single asterisk, it is expanded, and must
22360 yield a fully qualified address. Within the expansion, the variables
22361 &$local_part$& and &$domain$& refer to the address that is being rewritten.
22362 Any letters they contain retain their original case &-- they are not lower
22363 cased. The numerical variables are set up according to the type of pattern that
22364 matched the address, as described above. If the expansion is forced to fail by
22365 the presence of &"fail"& in a conditional or lookup item, rewriting by the
22366 current rule is abandoned, but subsequent rules may take effect. Any other
22367 expansion failure causes the entire rewriting operation to be abandoned, and an
22368 entry written to the panic log.
22372 .section "Rewriting flags" "SECID153"
22373 There are three different kinds of flag that may appear on rewriting rules:
22376 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
22379 A flag that specifies rewriting at SMTP time: S.
22381 Flags that control the rewriting process: Q, q, R, w.
22384 For rules that are part of the &%headers_rewrite%& generic transport option,
22385 E, F, T, and S are not permitted.
22389 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
22391 .cindex "rewriting" "flags"
22392 If none of the following flag letters, nor the &"S"& flag (see section
22393 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
22394 and to both the sender and recipient fields of the envelope, whereas a
22395 transport-time rewriting rule just applies to all headers. Otherwise, the
22396 rewriting rule is skipped unless the relevant addresses are being processed.
22398 &`E`& rewrite all envelope fields
22399 &`F`& rewrite the envelope From field
22400 &`T`& rewrite the envelope To field
22401 &`b`& rewrite the &'Bcc:'& header
22402 &`c`& rewrite the &'Cc:'& header
22403 &`f`& rewrite the &'From:'& header
22404 &`h`& rewrite all headers
22405 &`r`& rewrite the &'Reply-To:'& header
22406 &`s`& rewrite the &'Sender:'& header
22407 &`t`& rewrite the &'To:'& header
22409 "All headers" means all of the headers listed above that can be selected
22410 individually, plus their &'Resent-'& versions. It does not include
22411 other headers such as &'Subject:'& etc.
22413 You should be particularly careful about rewriting &'Sender:'& headers, and
22414 restrict this to special known cases in your own domains.
22417 .section "The SMTP-time rewriting flag" "SECTrewriteS"
22418 .cindex "SMTP" "rewriting malformed addresses"
22419 .cindex "RCPT" "rewriting argument of"
22420 .cindex "MAIL" "rewriting argument of"
22421 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
22422 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
22423 before any other processing; even before syntax checking. The pattern is
22424 required to be a regular expression, and it is matched against the whole of the
22425 data for the command, including any surrounding angle brackets.
22427 .vindex "&$domain$&"
22428 .vindex "&$local_part$&"
22429 This form of rewrite rule allows for the handling of addresses that are not
22430 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
22431 input). Because the input is not required to be a syntactically valid address,
22432 the variables &$local_part$& and &$domain$& are not available during the
22433 expansion of the replacement string. The result of rewriting replaces the
22434 original address in the MAIL or RCPT command.
22437 .section "Flags controlling the rewriting process" "SECID155"
22438 There are four flags which control the way the rewriting process works. These
22439 take effect only when a rule is invoked, that is, when the address is of the
22440 correct type (matches the flags) and matches the pattern:
22443 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
22444 unqualified local part. It is qualified with &%qualify_recipient%&. In the
22445 absence of &"Q"& the rewritten address must always include a domain.
22447 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
22448 even if no rewriting actually takes place because of a &"fail"& in the
22449 expansion. The &"q"& flag is not effective if the address is of the wrong type
22450 (does not match the flags) or does not match the pattern.
22452 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
22453 address, up to ten times. It can be combined with the &"q"& flag, to stop
22454 rewriting once it fails to match (after at least one successful rewrite).
22456 .cindex "rewriting" "whole addresses"
22457 When an address in a header is rewritten, the rewriting normally applies only
22458 to the working part of the address, with any comments and RFC 2822 &"phrase"&
22459 left unchanged. For example, rewriting might change
22461 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
22465 From: Ford Prefect <prefectf@hitch.fict.example>
22468 Sometimes there is a need to replace the whole address item, and this can be
22469 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
22470 causes an address in a header line to be rewritten, the entire address is
22471 replaced, not just the working part. The replacement must be a complete RFC
22472 2822 address, including the angle brackets if necessary. If text outside angle
22473 brackets contains a character whose value is greater than 126 or less than 32
22474 (except for tab), the text is encoded according to RFC 2047. The character set
22475 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
22477 When the &"w"& flag is set on a rule that causes an envelope address to be
22478 rewritten, all but the working part of the replacement address is discarded.
22482 .section "Rewriting examples" "SECID156"
22483 Here is an example of the two common rewriting paradigms:
22485 *@*.hitch.fict.example $1@hitch.fict.example
22486 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
22487 {$value}fail}@hitch.fict.example bctfrF
22489 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
22490 the string expansion to fail if the lookup does not succeed. In this context it
22491 has the effect of leaving the original address unchanged, but Exim goes on to
22492 consider subsequent rewriting rules, if any, because the &"q"& flag is not
22493 present in that rule. An alternative to &"fail"& would be to supply &$1$&
22494 explicitly, which would cause the rewritten address to be the same as before,
22495 at the cost of a small bit of processing. Not supplying either of these is an
22496 error, since the rewritten address would then contain no local part.
22498 The first example above replaces the domain with a superior, more general
22499 domain. This may not be desirable for certain local parts. If the rule
22501 root@*.hitch.fict.example *
22503 were inserted before the first rule, rewriting would be suppressed for the
22504 local part &'root'& at any domain ending in &'hitch.fict.example'&.
22506 Rewriting can be made conditional on a number of tests, by making use of
22507 &${if$& in the expansion item. For example, to apply a rewriting rule only to
22508 messages that originate outside the local host:
22510 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
22511 {$1@hitch.fict.example}fail}"
22513 The replacement string is quoted in this example because it contains white
22516 .cindex "rewriting" "bang paths"
22517 .cindex "bang paths" "rewriting"
22518 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
22519 an address it treats it as an unqualified local part which it qualifies with
22520 the local qualification domain (if the source of the message is local or if the
22521 remote host is permitted to send unqualified addresses). Rewriting can
22522 sometimes be used to handle simple bang paths with a fixed number of
22523 components. For example, the rule
22525 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
22527 rewrites a two-component bang path &'host.name!user'& as the domain address
22528 &'user@host.name'&. However, there is a security implication in using this as
22529 a global rewriting rule for envelope addresses. It can provide a backdoor
22530 method for using your system as a relay, because the incoming addresses appear
22531 to be local. If the bang path addresses are received via SMTP, it is safer to
22532 use the &"S"& flag to rewrite them as they are received, so that relay checking
22533 can be done on the rewritten addresses.
22540 . ////////////////////////////////////////////////////////////////////////////
22541 . ////////////////////////////////////////////////////////////////////////////
22543 .chapter "Retry configuration" "CHAPretry"
22544 .scindex IIDretconf1 "retry" "configuration, description of"
22545 .scindex IIDregconf2 "configuration file" "retry section"
22546 The &"retry"& section of the runtime configuration file contains a list of
22547 retry rules that control how often Exim tries to deliver messages that cannot
22548 be delivered at the first attempt. If there are no retry rules (the section is
22549 empty or not present), there are no retries. In this situation, temporary
22550 errors are treated as permanent. The default configuration contains a single,
22551 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
22552 line option can be used to test which retry rule will be used for a given
22553 address, domain and error.
22555 The most common cause of retries is temporary failure to deliver to a remote
22556 host because the host is down, or inaccessible because of a network problem.
22557 Exim's retry processing in this case is applied on a per-host (strictly, per IP
22558 address) basis, not on a per-message basis. Thus, if one message has recently
22559 been delayed, delivery of a new message to the same host is not immediately
22560 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
22561 log selector is set, the message
22562 .cindex "retry" "time not reached"
22563 &"retry time not reached"& is written to the main log whenever a delivery is
22564 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
22565 the handling of errors during remote deliveries.
22567 Retry processing applies to routing as well as to delivering, except as covered
22568 in the next paragraph. The retry rules do not distinguish between these
22569 actions. It is not possible, for example, to specify different behaviour for
22570 failures to route the domain &'snark.fict.example'& and failures to deliver to
22571 the host &'snark.fict.example'&. I didn't think anyone would ever need this
22572 added complication, so did not implement it. However, although they share the
22573 same retry rule, the actual retry times for routing and transporting a given
22574 domain are maintained independently.
22576 When a delivery is not part of a queue run (typically an immediate delivery on
22577 receipt of a message), the routers are always run, and local deliveries are
22578 always attempted, even if retry times are set for them. This makes for better
22579 behaviour if one particular message is causing problems (for example, causing
22580 quota overflow, or provoking an error in a filter file). If such a delivery
22581 suffers a temporary failure, the retry data is updated as normal, and
22582 subsequent delivery attempts from queue runs occur only when the retry time for
22583 the local address is reached.
22585 .section "Changing retry rules" "SECID157"
22586 If you change the retry rules in your configuration, you should consider
22587 whether or not to delete the retry data that is stored in Exim's spool area in
22588 files with names like &_db/retry_&. Deleting any of Exim's hints files is
22589 always safe; that is why they are called &"hints"&.
22591 The hints retry data contains suggested retry times based on the previous
22592 rules. In the case of a long-running problem with a remote host, it might
22593 record the fact that the host has timed out. If your new rules increase the
22594 timeout time for such a host, you should definitely remove the old retry data
22595 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
22596 messages that it should now be retaining.
22600 .section "Format of retry rules" "SECID158"
22601 .cindex "retry" "rules"
22602 Each retry rule occupies one line and consists of three or four parts,
22603 separated by white space: a pattern, an error name, an optional list of sender
22604 addresses, and a list of retry parameters. The pattern and sender lists must be
22605 enclosed in double quotes if they contain white space. The rules are searched
22606 in order until one is found where the pattern, error name, and sender list (if
22607 present) match the failing host or address, the error that occurred, and the
22608 message's sender, respectively.
22611 The pattern is any single item that may appear in an address list (see section
22612 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
22613 which means that it is expanded before being tested against the address that
22614 has been delayed. A negated address list item is permitted. Address
22615 list processing treats a plain domain name as if it were preceded by &"*@"&,
22616 which makes it possible for many retry rules to start with just a domain. For
22619 lookingglass.fict.example * F,24h,30m;
22621 provides a rule for any address in the &'lookingglass.fict.example'& domain,
22624 alice@lookingglass.fict.example * F,24h,30m;
22626 applies only to temporary failures involving the local part &%alice%&.
22627 In practice, almost all rules start with a domain name pattern without a local
22630 .cindex "regular expressions" "in retry rules"
22631 &*Warning*&: If you use a regular expression in a routing rule pattern, it
22632 must match a complete address, not just a domain, because that is how regular
22633 expressions work in address lists.
22635 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
22636 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
22640 .section "Choosing which retry rule to use for address errors" "SECID159"
22641 When Exim is looking for a retry rule after a routing attempt has failed (for
22642 example, after a DNS timeout), each line in the retry configuration is tested
22643 against the complete address only if &%retry_use_local_part%& is set for the
22644 router. Otherwise, only the domain is used, except when matching against a
22645 regular expression, when the local part of the address is replaced with &"*"&.
22646 A domain on its own can match a domain pattern, or a pattern that starts with
22647 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
22648 &%check_local_user%& is true, and false for other routers.
22650 Similarly, when Exim is looking for a retry rule after a local delivery has
22651 failed (for example, after a mailbox full error), each line in the retry
22652 configuration is tested against the complete address only if
22653 &%retry_use_local_part%& is set for the transport (it defaults true for all
22656 .cindex "4&'xx'& responses" "retry rules for"
22657 However, when Exim is looking for a retry rule after a remote delivery attempt
22658 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
22659 whole address is always used as the key when searching the retry rules. The
22660 rule that is found is used to create a retry time for the combination of the
22661 failing address and the message's sender. It is the combination of sender and
22662 recipient that is delayed in subsequent queue runs until its retry time is
22663 reached. You can delay the recipient without regard to the sender by setting
22664 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
22665 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
22670 .section "Choosing which retry rule to use for host and message errors" &&&
22672 For a temporary error that is not related to an individual address (for
22673 example, a connection timeout), each line in the retry configuration is checked
22674 twice. First, the name of the remote host is used as a domain name (preceded by
22675 &"*@"& when matching a regular expression). If this does not match the line,
22676 the domain from the email address is tried in a similar fashion. For example,
22677 suppose the MX records for &'a.b.c.example'& are
22679 a.b.c.example MX 5 x.y.z.example
22683 and the retry rules are
22685 p.q.r.example * F,24h,30m;
22686 a.b.c.example * F,4d,45m;
22688 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
22689 first rule matches neither the host nor the domain, so Exim looks at the second
22690 rule. This does not match the host, but it does match the domain, so it is used
22691 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
22692 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
22693 first retry rule is used, because it matches the host.
22695 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
22696 first rule to determine retry times, but for all the other hosts for the domain
22697 &'a.b.c.example'&, the second rule is used. The second rule is also used if
22698 routing to &'a.b.c.example'& suffers a temporary failure.
22700 &*Note*&: The host name is used when matching the patterns, not its IP address.
22701 However, if a message is routed directly to an IP address without the use of a
22702 host name, for example, if a &(manualroute)& router contains a setting such as:
22704 route_list = *.a.example 192.168.34.23
22706 then the &"host name"& that is used when searching for a retry rule is the
22707 textual form of the IP address.
22709 .section "Retry rules for specific errors" "SECID161"
22710 .cindex "retry" "specific errors; specifying"
22711 The second field in a retry rule is the name of a particular error, or an
22712 asterisk, which matches any error. The errors that can be tested for are:
22715 .vitem &%auth_failed%&
22716 Authentication failed when trying to send to a host in the
22717 &%hosts_require_auth%& list in an &(smtp)& transport.
22719 .vitem &%data_4xx%&
22720 A 4&'xx'& error was received for an outgoing DATA command, either immediately
22721 after the command, or after sending the message's data.
22723 .vitem &%mail_4xx%&
22724 A 4&'xx'& error was received for an outgoing MAIL command.
22726 .vitem &%rcpt_4xx%&
22727 A 4&'xx'& error was received for an outgoing RCPT command.
22730 For the three 4&'xx'& errors, either the first or both of the x's can be given
22731 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
22732 recognize 452 errors given to RCPT commands for addresses in a certain domain,
22733 and have retries every ten minutes with a one-hour timeout, you could set up a
22734 retry rule of this form:
22736 the.domain.name rcpt_452 F,1h,10m
22738 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
22739 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
22742 .vitem &%lost_connection%&
22743 A server unexpectedly closed the SMTP connection. There may, of course,
22744 legitimate reasons for this (host died, network died), but if it repeats a lot
22745 for the same host, it indicates something odd.
22747 .vitem &%refused_MX%&
22748 A connection to a host obtained from an MX record was refused.
22750 .vitem &%refused_A%&
22751 A connection to a host not obtained from an MX record was refused.
22754 A connection was refused.
22756 .vitem &%timeout_connect_MX%&
22757 A connection attempt to a host obtained from an MX record timed out.
22759 .vitem &%timeout_connect_A%&
22760 A connection attempt to a host not obtained from an MX record timed out.
22762 .vitem &%timeout_connect%&
22763 A connection attempt timed out.
22765 .vitem &%timeout_MX%&
22766 There was a timeout while connecting or during an SMTP session with a host
22767 obtained from an MX record.
22769 .vitem &%timeout_A%&
22770 There was a timeout while connecting or during an SMTP session with a host not
22771 obtained from an MX record.
22774 There was a timeout while connecting or during an SMTP session.
22776 .vitem &%tls_required%&
22777 The server was required to use TLS (it matched &%hosts_require_tls%& in the
22778 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
22779 to STARTTLS, or there was a problem setting up the TLS connection.
22782 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
22785 .vitem &%quota_%&<&'time'&>
22786 .cindex "quota" "error testing in retry rule"
22787 .cindex "retry" "quota error testing"
22788 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
22789 transport, and the mailbox has not been accessed for <&'time'&>. For example,
22790 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
22794 .cindex "mailbox" "time of last read"
22795 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
22796 timeouts when the mailbox is full and is not being read by its owner. Ideally,
22797 it should be based on the last time that the user accessed the mailbox.
22798 However, it is not always possible to determine this. Exim uses the following
22802 If the mailbox is a single file, the time of last access (the &"atime"&) is
22803 used. As no new messages are being delivered (because the mailbox is over
22804 quota), Exim does not access the file, so this is the time of last user access.
22806 .cindex "maildir format" "time of last read"
22807 For a maildir delivery, the time of last modification of the &_new_&
22808 subdirectory is used. As the mailbox is over quota, no new files are created in
22809 the &_new_& subdirectory, because no new messages are being delivered. Any
22810 change to the &_new_& subdirectory is therefore assumed to be the result of an
22811 MUA moving a new message to the &_cur_& directory when it is first read. The
22812 time that is used is therefore the last time that the user read a new message.
22814 For other kinds of multi-file mailbox, the time of last access cannot be
22815 obtained, so a retry rule that uses this type of error field is never matched.
22818 The quota errors apply both to system-enforced quotas and to Exim's own quota
22819 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
22820 when a local delivery is deferred because a partition is full (the ENOSPC
22825 .section "Retry rules for specified senders" "SECID162"
22826 .cindex "retry" "rules; sender-specific"
22827 You can specify retry rules that apply only when the failing message has a
22828 specific sender. In particular, this can be used to define retry rules that
22829 apply only to bounce messages. The third item in a retry rule can be of this
22832 &`senders=`&<&'address list'&>
22834 The retry timings themselves are then the fourth item. For example:
22836 * rcpt_4xx senders=: F,1h,30m
22838 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
22839 host. If the address list contains white space, it must be enclosed in quotes.
22842 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
22844 &*Warning*&: This facility can be unhelpful if it is used for host errors
22845 (which do not depend on the recipient). The reason is that the sender is used
22846 only to match the retry rule. Once the rule has been found for a host error,
22847 its contents are used to set a retry time for the host, and this will apply to
22848 all messages, not just those with specific senders.
22850 When testing retry rules using &%-brt%&, you can supply a sender using the
22851 &%-f%& command line option, like this:
22853 exim -f "" -brt user@dom.ain
22855 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
22856 list is never matched.
22862 .section "Retry parameters" "SECID163"
22863 .cindex "retry" "parameters in rules"
22864 The third (or fourth, if a senders list is present) field in a retry rule is a
22865 sequence of retry parameter sets, separated by semicolons. Each set consists of
22867 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
22869 The letter identifies the algorithm for computing a new retry time; the cutoff
22870 time is the time beyond which this algorithm no longer applies, and the
22871 arguments vary the algorithm's action. The cutoff time is measured from the
22872 time that the first failure for the domain (combined with the local part if
22873 relevant) was detected, not from the time the message was received.
22875 .cindex "retry" "algorithms"
22876 .cindex "retry" "fixed intervals"
22877 .cindex "retry" "increasing intervals"
22878 .cindex "retry" "random intervals"
22879 The available algorithms are:
22882 &'F'&: retry at fixed intervals. There is a single time parameter specifying
22885 &'G'&: retry at geometrically increasing intervals. The first argument
22886 specifies a starting value for the interval, and the second a multiplier, which
22887 is used to increase the size of the interval at each retry.
22889 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
22890 retry, the previous interval is multiplied by the factor in order to get a
22891 maximum for the next interval. The minimum interval is the first argument of
22892 the parameter, and an actual interval is chosen randomly between them. Such a
22893 rule has been found to be helpful in cluster configurations when all the
22894 members of the cluster restart at once, and may therefore synchronize their
22895 queue processing times.
22898 When computing the next retry time, the algorithm definitions are scanned in
22899 order until one whose cutoff time has not yet passed is reached. This is then
22900 used to compute a new retry time that is later than the current time. In the
22901 case of fixed interval retries, this simply means adding the interval to the
22902 current time. For geometrically increasing intervals, retry intervals are
22903 computed from the rule's parameters until one that is greater than the previous
22904 interval is found. The main configuration variable
22905 .cindex "limit" "retry interval"
22906 .cindex "retry" "interval, maximum"
22907 .oindex "&%retry_interval_max%&"
22908 &%retry_interval_max%& limits the maximum interval between retries. It
22909 cannot be set greater than &`24h`&, which is its default value.
22911 A single remote domain may have a number of hosts associated with it, and each
22912 host may have more than one IP address. Retry algorithms are selected on the
22913 basis of the domain name, but are applied to each IP address independently. If,
22914 for example, a host has two IP addresses and one is unusable, Exim will
22915 generate retry times for it and will not try to use it until its next retry
22916 time comes. Thus the good IP address is likely to be tried first most of the
22919 .cindex "hints database" "use for retrying"
22920 Retry times are hints rather than promises. Exim does not make any attempt to
22921 run deliveries exactly at the computed times. Instead, a queue runner process
22922 starts delivery processes for delayed messages periodically, and these attempt
22923 new deliveries only for those addresses that have passed their next retry time.
22924 If a new message arrives for a deferred address, an immediate delivery attempt
22925 occurs only if the address has passed its retry time. In the absence of new
22926 messages, the minimum time between retries is the interval between queue runner
22927 processes. There is not much point in setting retry times of five minutes if
22928 your queue runners happen only once an hour, unless there are a significant
22929 number of incoming messages (which might be the case on a system that is
22930 sending everything to a smart host, for example).
22932 The data in the retry hints database can be inspected by using the
22933 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
22934 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
22935 &'exinext'& utility script can be used to find out what the next retry times
22936 are for the hosts associated with a particular mail domain, and also for local
22937 deliveries that have been deferred.
22940 .section "Retry rule examples" "SECID164"
22941 Here are some example retry rules:
22943 alice@wonderland.fict.example quota_5d F,7d,3h
22944 wonderland.fict.example quota_5d
22945 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
22946 lookingglass.fict.example * F,24h,30m;
22947 * refused_A F,2h,20m;
22948 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
22950 The first rule sets up special handling for mail to
22951 &'alice@wonderland.fict.example'& when there is an over-quota error and the
22952 mailbox has not been read for at least 5 days. Retries continue every three
22953 hours for 7 days. The second rule handles over-quota errors for all other local
22954 parts at &'wonderland.fict.example'&; the absence of a local part has the same
22955 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
22956 fail are bounced immediately if the mailbox has not been read for at least 5
22959 The third rule handles all other errors at &'wonderland.fict.example'&; retries
22960 happen every 15 minutes for an hour, then with geometrically increasing
22961 intervals until two days have passed since a delivery first failed. After the
22962 first hour there is a delay of one hour, then two hours, then four hours, and
22963 so on (this is a rather extreme example).
22965 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
22966 They happen every 30 minutes for 24 hours only. The remaining two rules handle
22967 all other domains, with special action for connection refusal from hosts that
22968 were not obtained from an MX record.
22970 The final rule in a retry configuration should always have asterisks in the
22971 first two fields so as to provide a general catch-all for any addresses that do
22972 not have their own special handling. This example tries every 15 minutes for 2
22973 hours, then with intervals starting at one hour and increasing by a factor of
22974 1.5 up to 16 hours, then every 8 hours up to 5 days.
22978 .section "Timeout of retry data" "SECID165"
22979 .cindex "timeout" "of retry data"
22980 .oindex "&%retry_data_expire%&"
22981 .cindex "hints database" "data expiry"
22982 .cindex "retry" "timeout of data"
22983 Exim timestamps the data that it writes to its retry hints database. When it
22984 consults the data during a delivery it ignores any that is older than the value
22985 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
22986 been tried for 7 days, Exim will try to deliver to it immediately a message
22987 arrives, and if that fails, it will calculate a retry time as if it were
22988 failing for the first time.
22990 This improves the behaviour for messages routed to rarely-used hosts such as MX
22991 backups. If such a host was down at one time, and happens to be down again when
22992 Exim tries a month later, using the old retry data would imply that it had been
22993 down all the time, which is not a justified assumption.
22995 If a host really is permanently dead, this behaviour causes a burst of retries
22996 every now and again, but only if messages routed to it are rare. If there is a
22997 message at least once every 7 days the retry data never expires.
23002 .section "Long-term failures" "SECID166"
23003 .cindex "delivery failure, long-term"
23004 .cindex "retry" "after long-term failure"
23005 Special processing happens when an email address has been failing for so long
23006 that the cutoff time for the last algorithm is reached. For example, using the
23007 default retry rule:
23009 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
23011 the cutoff time is four days. Reaching the retry cutoff is independent of how
23012 long any specific message has been failing; it is the length of continuous
23013 failure for the recipient address that counts.
23015 When the cutoff time is reached for a local delivery, or for all the IP
23016 addresses associated with a remote delivery, a subsequent delivery failure
23017 causes Exim to give up on the address, and a bounce message is generated.
23018 In order to cater for new messages that use the failing address, a next retry
23019 time is still computed from the final algorithm, and is used as follows:
23021 For local deliveries, one delivery attempt is always made for any subsequent
23022 messages. If this delivery fails, the address fails immediately. The
23023 post-cutoff retry time is not used.
23025 If the delivery is remote, there are two possibilities, controlled by the
23026 .oindex "&%delay_after_cutoff%&"
23027 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
23028 default. Until the post-cutoff retry time for one of the IP addresses is
23029 reached, the failing email address is bounced immediately, without a delivery
23030 attempt taking place. After that time, one new delivery attempt is made to
23031 those IP addresses that are past their retry times, and if that still fails,
23032 the address is bounced and new retry times are computed.
23034 In other words, when all the hosts for a given email address have been failing
23035 for a long time, Exim bounces rather then defers until one of the hosts' retry
23036 times is reached. Then it tries once, and bounces if that attempt fails. This
23037 behaviour ensures that few resources are wasted in repeatedly trying to deliver
23038 to a broken destination, but if the host does recover, Exim will eventually
23041 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23042 addresses are past their final cutoff time, Exim tries to deliver to those IP
23043 addresses that have not been tried since the message arrived. If there are
23044 no suitable IP addresses, or if they all fail, the address is bounced. In other
23045 words, it does not delay when a new message arrives, but tries the expired
23046 addresses immediately, unless they have been tried since the message arrived.
23047 If there is a continuous stream of messages for the failing domains, setting
23048 &%delay_after_cutoff%& false means that there will be many more attempts to
23049 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
23052 .section "Deliveries that work intermittently" "SECID167"
23053 .cindex "retry" "intermittently working deliveries"
23054 Some additional logic is needed to cope with cases where a host is
23055 intermittently available, or when a message has some attribute that prevents
23056 its delivery when others to the same address get through. In this situation,
23057 because some messages are successfully delivered, the &"retry clock"& for the
23058 host or address keeps getting reset by the successful deliveries, and so
23059 failing messages remain on the queue for ever because the cutoff time is never
23062 Two exceptional actions are applied to prevent this happening. The first
23063 applies to errors that are related to a message rather than a remote host.
23064 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
23065 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
23066 commands, and quota failures. For this type of error, if a message's arrival
23067 time is earlier than the &"first failed"& time for the error, the earlier time
23068 is used when scanning the retry rules to decide when to try next and when to
23069 time out the address.
23071 The exceptional second action applies in all cases. If a message has been on
23072 the queue for longer than the cutoff time of any applicable retry rule for a
23073 given address, a delivery is attempted for that address, even if it is not yet
23074 time, and if this delivery fails, the address is timed out. A new retry time is
23075 not computed in this case, so that other messages for the same address are
23076 considered immediately.
23077 .ecindex IIDretconf1
23078 .ecindex IIDregconf2
23085 . ////////////////////////////////////////////////////////////////////////////
23086 . ////////////////////////////////////////////////////////////////////////////
23088 .chapter "SMTP authentication" "CHAPSMTPAUTH"
23089 .scindex IIDauthconf1 "SMTP" "authentication configuration"
23090 .scindex IIDauthconf2 "authentication"
23091 The &"authenticators"& section of Exim's run time configuration is concerned
23092 with SMTP authentication. This facility is an extension to the SMTP protocol,
23093 described in RFC 2554, which allows a client SMTP host to authenticate itself
23094 to a server. This is a common way for a server to recognize clients that are
23095 permitted to use it as a relay. SMTP authentication is not of relevance to the
23096 transfer of mail between servers that have no managerial connection with each
23099 .cindex "AUTH" "description of"
23100 Very briefly, the way SMTP authentication works is as follows:
23103 The server advertises a number of authentication &'mechanisms'& in response to
23104 the client's EHLO command.
23106 The client issues an AUTH command, naming a specific mechanism. The command
23107 may, optionally, contain some authentication data.
23109 The server may issue one or more &'challenges'&, to which the client must send
23110 appropriate responses. In simple authentication mechanisms, the challenges are
23111 just prompts for user names and passwords. The server does not have to issue
23112 any challenges &-- in some mechanisms the relevant data may all be transmitted
23113 with the AUTH command.
23115 The server either accepts or denies authentication.
23117 If authentication succeeds, the client may optionally make use of the AUTH
23118 option on the MAIL command to pass an authenticated sender in subsequent
23119 mail transactions. Authentication lasts for the remainder of the SMTP
23122 If authentication fails, the client may give up, or it may try a different
23123 authentication mechanism, or it may try transferring mail over the
23124 unauthenticated connection.
23127 If you are setting up a client, and want to know which authentication
23128 mechanisms the server supports, you can use Telnet to connect to port 25 (the
23129 SMTP port) on the server, and issue an EHLO command. The response to this
23130 includes the list of supported mechanisms. For example:
23132 &`$ `&&*&`telnet server.example 25`&*&
23133 &`Trying 192.168.34.25...`&
23134 &`Connected to server.example.`&
23135 &`Escape character is '^]'.`&
23136 &`220 server.example ESMTP Exim 4.20 ...`&
23137 &*&`ehlo client.example`&*&
23138 &`250-server.example Hello client.example [10.8.4.5]`&
23139 &`250-SIZE 52428800`&
23144 The second-last line of this example output shows that the server supports
23145 authentication using the PLAIN mechanism. In Exim, the different authentication
23146 mechanisms are configured by specifying &'authenticator'& drivers. Like the
23147 routers and transports, which authenticators are included in the binary is
23148 controlled by build-time definitions. The following are currently available,
23149 included by setting
23152 AUTH_CYRUS_SASL=yes
23156 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
23157 authentication mechanism (RFC 2195), and the second provides an interface to
23158 the Cyrus SASL authentication library. The third can be configured to support
23159 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
23160 not formally documented, but used by several MUAs. The fourth authenticator
23161 supports Microsoft's &'Secure Password Authentication'& mechanism.
23163 The authenticators are configured using the same syntax as other drivers (see
23164 section &<<SECTfordricon>>&). If no authenticators are required, no
23165 authentication section need be present in the configuration file. Each
23166 authenticator can in principle have both server and client functions. When Exim
23167 is receiving SMTP mail, it is acting as a server; when it is sending out
23168 messages over SMTP, it is acting as a client. Authenticator configuration
23169 options are provided for use in both these circumstances.
23171 To make it clear which options apply to which situation, the prefixes
23172 &%server_%& and &%client_%& are used on option names that are specific to
23173 either the server or the client function, respectively. Server and client
23174 functions are disabled if none of their options are set. If an authenticator is
23175 to be used for both server and client functions, a single definition, using
23176 both sets of options, is required. For example:
23180 public_name = CRAM-MD5
23181 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
23183 client_secret = secret2
23185 The &%server_%& option is used when Exim is acting as a server, and the
23186 &%client_%& options when it is acting as a client.
23188 Descriptions of the individual authenticators are given in subsequent chapters.
23189 The remainder of this chapter covers the generic options for the
23190 authenticators, followed by general discussion of the way authentication works
23195 .section "Generic options for authenticators" "SECID168"
23196 .cindex "authentication" "generic options"
23197 .cindex "options" "generic; for authenticators"
23199 .option client_condition authenticators string&!! unset
23200 When Exim is authenticating as a client, it skips any authenticator whose
23201 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
23202 used, for example, to skip plain text authenticators when the connection is not
23203 encrypted by a setting such as:
23205 client_condition = ${if !eq{$tls_cipher}{}}
23207 (Older documentation incorrectly states that &$tls_cipher$& contains the cipher
23208 used for incoming messages. In fact, during SMTP delivery, it contains the
23209 cipher used for the delivery.)
23212 .option driver authenticators string unset
23213 This option must always be set. It specifies which of the available
23214 authenticators is to be used.
23217 .option public_name authenticators string unset
23218 This option specifies the name of the authentication mechanism that the driver
23219 implements, and by which it is known to the outside world. These names should
23220 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
23221 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
23222 defaults to the driver's instance name.
23225 .option server_advertise_condition authenticators string&!! unset
23226 When a server is about to advertise an authentication mechanism, the condition
23227 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
23228 mechanism is not advertised.
23229 If the expansion fails, the mechanism is not advertised. If the failure was not
23230 forced, and was not caused by a lookup defer, the incident is logged.
23231 See section &<<SECTauthexiser>>& below for further discussion.
23234 .option server_condition authenticators string&!! unset
23235 This option must be set for a &%plaintext%& server authenticator, where it
23236 is used directly to control authentication. See section &<<SECTplainserver>>&
23239 For the other authenticators, &%server_condition%& can be used as an additional
23240 authentication or authorization mechanism that is applied after the other
23241 authenticator conditions succeed. If it is set, it is expanded when the
23242 authenticator would otherwise return a success code. If the expansion is forced
23243 to fail, authentication fails. Any other expansion failure causes a temporary
23244 error code to be returned. If the result of a successful expansion is an empty
23245 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23246 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
23247 other result, a temporary error code is returned, with the expanded string as
23251 .option server_debug_print authenticators string&!! unset
23252 If this option is set and authentication debugging is enabled (see the &%-d%&
23253 command line option), the string is expanded and included in the debugging
23254 output when the authenticator is run as a server. This can help with checking
23255 out the values of variables.
23256 If expansion of the string fails, the error message is written to the debugging
23257 output, and Exim carries on processing.
23260 .option server_set_id authenticators string&!! unset
23261 .vindex "&$authenticated_id$&"
23262 When an Exim server successfully authenticates a client, this string is
23263 expanded using data from the authentication, and preserved for any incoming
23264 messages in the variable &$authenticated_id$&. It is also included in the log
23265 lines for incoming messages. For example, a user/password authenticator
23266 configuration might preserve the user name that was used to authenticate, and
23267 refer to it subsequently during delivery of the message.
23268 If expansion fails, the option is ignored.
23271 .option server_mail_auth_condition authenticators string&!! unset
23272 This option allows a server to discard authenticated sender addresses supplied
23273 as part of MAIL commands in SMTP connections that are authenticated by the
23274 driver on which &%server_mail_auth_condition%& is set. The option is not used
23275 as part of the authentication process; instead its (unexpanded) value is
23276 remembered for later use.
23277 How it is used is described in the following section.
23283 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
23284 .cindex "authentication" "sender; authenticated"
23285 .cindex "AUTH" "on MAIL command"
23286 When a client supplied an AUTH= item on a MAIL command, Exim applies
23287 the following checks before accepting it as the authenticated sender of the
23291 If the connection is not using extended SMTP (that is, HELO was used rather
23292 than EHLO), the use of AUTH= is a syntax error.
23294 If the value of the AUTH= parameter is &"<>"&, it is ignored.
23296 .vindex "&$authenticated_sender$&"
23297 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
23298 running, the value of &$authenticated_sender$& is set to the value obtained
23299 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
23300 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
23301 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
23302 given for the MAIL command.
23304 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
23305 is accepted and placed in &$authenticated_sender$& only if the client has
23308 If the AUTH= value was accepted by either of the two previous rules, and
23309 the client has authenticated, and the authenticator has a setting for the
23310 &%server_mail_auth_condition%&, the condition is checked at this point. The
23311 valued that was saved from the authenticator is expanded. If the expansion
23312 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
23313 &$authenticated_sender$& is deleted. If the expansion yields any other value,
23314 the value of &$authenticated_sender$& is retained and passed on with the
23319 When &$authenticated_sender$& is set for a message, it is passed on to other
23320 hosts to which Exim authenticates as a client. Do not confuse this value with
23321 &$authenticated_id$&, which is a string obtained from the authentication
23322 process, and which is not usually a complete email address.
23324 .vindex "&$sender_address$&"
23325 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
23326 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
23327 therefore make use of &$authenticated_sender$&. The converse is not true: the
23328 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
23333 .section "Authentication on an Exim server" "SECTauthexiser"
23334 .cindex "authentication" "on an Exim server"
23335 When Exim receives an EHLO command, it advertises the public names of those
23336 authenticators that are configured as servers, subject to the following
23340 The client host must match &%auth_advertise_hosts%& (default *).
23342 It the &%server_advertise_condition%& option is set, its expansion must not
23343 yield the empty string, &"0"&, &"no"&, or &"false"&.
23346 The order in which the authenticators are defined controls the order in which
23347 the mechanisms are advertised.
23349 Some mail clients (for example, some versions of Netscape) require the user to
23350 provide a name and password for authentication whenever AUTH is advertised,
23351 even though authentication may not in fact be needed (for example, Exim may be
23352 set up to allow unconditional relaying from the client by an IP address check).
23353 You can make such clients more friendly by not advertising AUTH to them.
23354 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
23355 that runs for RCPT) to relay without authentication, you should set
23357 auth_advertise_hosts = ! 10.9.8.0/24
23359 so that no authentication mechanisms are advertised to them.
23361 The &%server_advertise_condition%& controls the advertisement of individual
23362 authentication mechanisms. For example, it can be used to restrict the
23363 advertisement of a particular mechanism to encrypted connections, by a setting
23366 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
23368 .vindex "&$tls_cipher$&"
23369 If the session is encrypted, &$tls_cipher$& is not empty, and so the expansion
23370 yields &"yes"&, which allows the advertisement to happen.
23372 When an Exim server receives an AUTH command from a client, it rejects it
23373 immediately if AUTH was not advertised in response to an earlier EHLO
23374 command. This is the case if
23377 The client host does not match &%auth_advertise_hosts%&; or
23379 No authenticators are configured with server options; or
23381 Expansion of &%server_advertise_condition%& blocked the advertising of all the
23382 server authenticators.
23386 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
23387 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
23388 AUTH is accepted from any client host.
23390 If AUTH is not rejected by the ACL, Exim searches its configuration for a
23391 server authentication mechanism that was advertised in response to EHLO and
23392 that matches the one named in the AUTH command. If it finds one, it runs
23393 the appropriate authentication protocol, and authentication either succeeds or
23394 fails. If there is no matching advertised mechanism, the AUTH command is
23395 rejected with a 504 error.
23397 .vindex "&$received_protocol$&"
23398 .vindex "&$sender_host_authenticated$&"
23399 When a message is received from an authenticated host, the value of
23400 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
23401 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
23402 public name) of the authenticator driver that successfully authenticated the
23403 client from which the message was received. This variable is empty if there was
23404 no successful authentication.
23409 .section "Testing server authentication" "SECID169"
23410 .cindex "authentication" "testing a server"
23411 .cindex "AUTH" "testing a server"
23412 .cindex "base64 encoding" "creating authentication test data"
23413 Exim's &%-bh%& option can be useful for testing server authentication
23414 configurations. The data for the AUTH command has to be sent using base64
23415 encoding. A quick way to produce such data for testing is the following Perl
23419 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
23421 .cindex "binary zero" "in authentication data"
23422 This interprets its argument as a Perl string, and then encodes it. The
23423 interpretation as a Perl string allows binary zeros, which are required for
23424 some kinds of authentication, to be included in the data. For example, a
23425 command line to run this script on such data might be
23427 encode '\0user\0password'
23429 Note the use of single quotes to prevent the shell interpreting the
23430 backslashes, so that they can be interpreted by Perl to specify characters
23431 whose code value is zero.
23433 &*Warning 1*&: If either of the user or password strings starts with an octal
23434 digit, you must use three zeros instead of one after the leading backslash. If
23435 you do not, the octal digit that starts your string will be incorrectly
23436 interpreted as part of the code for the first character.
23438 &*Warning 2*&: If there are characters in the strings that Perl interprets
23439 specially, you must use a Perl escape to prevent them being misinterpreted. For
23440 example, a command such as
23442 encode '\0user@domain.com\0pas$$word'
23444 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
23446 If you have the &%mimencode%& command installed, another way to do produce
23447 base64-encoded strings is to run the command
23449 echo -e -n `\0user\0password' | mimencode
23451 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
23452 in the argument, and the &%-n%& option specifies no newline at the end of its
23453 output. However, not all versions of &%echo%& recognize these options, so you
23454 should check your version before relying on this suggestion.
23458 .section "Authentication by an Exim client" "SECID170"
23459 .cindex "authentication" "on an Exim client"
23460 The &(smtp)& transport has two options called &%hosts_require_auth%& and
23461 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
23462 announces support for authentication, and the host matches an entry in either
23463 of these options, Exim (as a client) tries to authenticate as follows:
23466 For each authenticator that is configured as a client, in the order in which
23467 they are defined in the configuration, it searches the authentication
23468 mechanisms announced by the server for one whose name matches the public name
23469 of the authenticator.
23472 .vindex "&$host_address$&"
23473 When it finds one that matches, it runs the authenticator's client code. The
23474 variables &$host$& and &$host_address$& are available for any string expansions
23475 that the client might do. They are set to the server's name and IP address. If
23476 any expansion is forced to fail, the authentication attempt is abandoned, and
23477 Exim moves on to the next authenticator. Otherwise an expansion failure causes
23478 delivery to be deferred.
23480 If the result of the authentication attempt is a temporary error or a timeout,
23481 Exim abandons trying to send the message to the host for the moment. It will
23482 try again later. If there are any backup hosts available, they are tried in the
23485 If the response to authentication is a permanent error (5&'xx'& code), Exim
23486 carries on searching the list of authenticators and tries another one if
23487 possible. If all authentication attempts give permanent errors, or if there are
23488 no attempts because no mechanisms match (or option expansions force failure),
23489 what happens depends on whether the host matches &%hosts_require_auth%& or
23490 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
23491 delivery is deferred. The error can be detected in the retry rules, and thereby
23492 turned into a permanent error if you wish. In the second case, Exim tries to
23493 deliver the message unauthenticated.
23496 .cindex "AUTH" "on MAIL command"
23497 When Exim has authenticated itself to a remote server, it adds the AUTH
23498 parameter to the MAIL commands it sends, if it has an authenticated sender for
23499 the message. If the message came from a remote host, the authenticated sender
23500 is the one that was receiving on an incoming MAIL command, provided that the
23501 incoming connection was authenticated and the &%server_mail_auth%& condition
23502 allowed the authenticated sender to be retained. If a local process calls Exim
23503 to send a message, the sender address that is built from the login name and
23504 &%qualify_domain%& is treated as authenticated. However, if the
23505 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
23506 the authenticated sender that was received with the message.
23507 .ecindex IIDauthconf1
23508 .ecindex IIDauthconf2
23515 . ////////////////////////////////////////////////////////////////////////////
23516 . ////////////////////////////////////////////////////////////////////////////
23518 .chapter "The plaintext authenticator" "CHAPplaintext"
23519 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
23520 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
23521 The &(plaintext)& authenticator can be configured to support the PLAIN and
23522 LOGIN authentication mechanisms, both of which transfer authentication data as
23523 plain (unencrypted) text (though base64 encoded). The use of plain text is a
23524 security risk; you are strongly advised to insist on the use of SMTP encryption
23525 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
23526 use unencrypted plain text, you should not use the same passwords for SMTP
23527 connections as you do for login accounts.
23529 .section "Plaintext options" "SECID171"
23530 .cindex "options" "&(plaintext)& authenticator (server)"
23531 When configured as a server, &(plaintext)& uses the following options:
23533 .option server_condition authenticators string&!! unset
23534 This is actually a global authentication option, but it must be set in order to
23535 configure the &(plaintext)& driver as a server. Its use is described below.
23537 .option server_prompts plaintext string&!! unset
23538 The contents of this option, after expansion, must be a colon-separated list of
23539 prompt strings. If expansion fails, a temporary authentication rejection is
23542 .section "Using plaintext in a server" "SECTplainserver"
23543 .cindex "AUTH" "in &(plaintext)& authenticator"
23544 .cindex "binary zero" "in &(plaintext)& authenticator"
23545 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
23546 "in &(plaintext)& authenticator"
23547 .vindex "&$auth1$&, &$auth2$&, etc"
23548 .cindex "base64 encoding" "in &(plaintext)& authenticator"
23550 When running as a server, &(plaintext)& performs the authentication test by
23551 expanding a string. The data sent by the client with the AUTH command, or in
23552 response to subsequent prompts, is base64 encoded, and so may contain any byte
23553 values when decoded. If any data is supplied with the command, it is treated as
23554 a list of strings, separated by NULs (binary zeros), the first three of which
23555 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
23556 (neither LOGIN nor PLAIN uses more than three strings).
23558 For compatibility with previous releases of Exim, the values are also placed in
23559 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
23560 variables for this purpose is now deprecated, as it can lead to confusion in
23561 string expansions that also use them for other things.
23563 If there are more strings in &%server_prompts%& than the number of strings
23564 supplied with the AUTH command, the remaining prompts are used to obtain more
23565 data. Each response from the client may be a list of NUL-separated strings.
23567 .vindex "&$authenticated_id$&"
23568 Once a sufficient number of data strings have been received,
23569 &%server_condition%& is expanded. If the expansion is forced to fail,
23570 authentication fails. Any other expansion failure causes a temporary error code
23571 to be returned. If the result of a successful expansion is an empty string,
23572 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23573 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
23574 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
23575 For any other result, a temporary error code is returned, with the expanded
23576 string as the error text.
23578 &*Warning*&: If you use a lookup in the expansion to find the user's
23579 password, be sure to make the authentication fail if the user is unknown.
23580 There are good and bad examples at the end of the next section.
23584 .section "The PLAIN authentication mechanism" "SECID172"
23585 .cindex "PLAIN authentication mechanism"
23586 .cindex "authentication" "PLAIN mechanism"
23587 .cindex "binary zero" "in &(plaintext)& authenticator"
23588 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
23589 sent as one item of data (that is, one combined string containing two NUL
23590 separators). The data is sent either as part of the AUTH command, or
23591 subsequently in response to an empty prompt from the server.
23593 The second and third strings are a user name and a corresponding password.
23594 Using a single fixed user name and password as an example, this could be
23595 configured as follows:
23599 public_name = PLAIN
23601 server_condition = \
23602 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
23603 server_set_id = $auth2
23605 Note that the default result strings from &%if%& (&"true"& or an empty string)
23606 are exactly what we want here, so they need not be specified. Obviously, if the
23607 password contains expansion-significant characters such as dollar, backslash,
23608 or closing brace, they have to be escaped.
23610 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
23611 the end of a string list are ignored). If all the data comes as part of the
23612 AUTH command, as is commonly the case, the prompt is not used. This
23613 authenticator is advertised in the response to EHLO as
23617 and a client host can authenticate itself by sending the command
23619 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
23621 As this contains three strings (more than the number of prompts), no further
23622 data is required from the client. Alternatively, the client may just send
23626 to initiate authentication, in which case the server replies with an empty
23627 prompt. The client must respond with the combined data string.
23629 The data string is base64 encoded, as required by the RFC. This example,
23630 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
23631 represents a zero byte. This is split up into three strings, the first of which
23632 is empty. The &%server_condition%& option in the authenticator checks that the
23633 second two are &`username`& and &`mysecret`& respectively.
23635 Having just one fixed user name and password, as in this example, is not very
23636 realistic, though for a small organization with only a handful of
23637 authenticating clients it could make sense.
23639 A more sophisticated instance of this authenticator could use the user name in
23640 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
23641 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
23642 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
23643 This is an incorrect example:
23645 server_condition = \
23646 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
23648 The expansion uses the user name (&$auth2$&) as the key to look up a password,
23649 which it then compares to the supplied password (&$auth3$&). Why is this example
23650 incorrect? It works fine for existing users, but consider what happens if a
23651 non-existent user name is given. The lookup fails, but as no success/failure
23652 strings are given for the lookup, it yields an empty string. Thus, to defeat
23653 the authentication, all a client has to do is to supply a non-existent user
23654 name and an empty password. The correct way of writing this test is:
23656 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
23657 {${if eq{$value}{$auth3}}} {false}}
23659 In this case, if the lookup succeeds, the result is checked; if the lookup
23660 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
23661 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
23662 always fails if its second argument is empty. However, the second way of
23663 writing the test makes the logic clearer.
23666 .section "The LOGIN authentication mechanism" "SECID173"
23667 .cindex "LOGIN authentication mechanism"
23668 .cindex "authentication" "LOGIN mechanism"
23669 The LOGIN authentication mechanism is not documented in any RFC, but is in use
23670 in a number of programs. No data is sent with the AUTH command. Instead, a
23671 user name and password are supplied separately, in response to prompts. The
23672 plaintext authenticator can be configured to support this as in this example:
23676 public_name = LOGIN
23677 server_prompts = User Name : Password
23678 server_condition = \
23679 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
23680 server_set_id = $auth1
23682 Because of the way plaintext operates, this authenticator accepts data supplied
23683 with the AUTH command (in contravention of the specification of LOGIN), but
23684 if the client does not supply it (as is the case for LOGIN clients), the prompt
23685 strings are used to obtain two data items.
23687 Some clients are very particular about the precise text of the prompts. For
23688 example, Outlook Express is reported to recognize only &"Username:"& and
23689 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
23690 strings. It uses the &%ldapauth%& expansion condition to check the user
23691 name and password by binding to an LDAP server:
23695 public_name = LOGIN
23696 server_prompts = Username:: : Password::
23697 server_condition = ${if and{{
23699 ldapauth{user="cn=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
23700 pass=${quote:$auth2} \
23701 ldap://ldap.example.org/} }} }
23702 server_set_id = uid=$auth1,ou=people,o=example.org
23704 We have to check that the username is not empty before using it, because LDAP
23705 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
23706 operator to correctly quote the DN for authentication. However, the basic
23707 &%quote%& operator, rather than any of the LDAP quoting operators, is the
23708 correct one to use for the password, because quoting is needed only to make
23709 the password conform to the Exim syntax. At the LDAP level, the password is an
23710 uninterpreted string.
23713 .section "Support for different kinds of authentication" "SECID174"
23714 A number of string expansion features are provided for the purpose of
23715 interfacing to different ways of user authentication. These include checking
23716 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
23717 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
23723 .section "Using plaintext in a client" "SECID175"
23724 .cindex "options" "&(plaintext)& authenticator (client)"
23725 The &(plaintext)& authenticator has two client options:
23727 .option client_ignore_invalid_base64 plaintext boolean false
23728 If the client receives a server prompt that is not a valid base64 string,
23729 authentication is abandoned by default. However, if this option is set true,
23730 the error in the challenge is ignored and the client sends the response as
23733 .option client_send plaintext string&!! unset
23734 The string is a colon-separated list of authentication data strings. Each
23735 string is independently expanded before being sent to the server. The first
23736 string is sent with the AUTH command; any more strings are sent in response
23737 to prompts from the server. Before each string is expanded, the value of the
23738 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
23739 with &$auth1$& for the first prompt. Up to three prompts are stored in this
23740 way. Thus, the prompt that is received in response to sending the first string
23741 (with the AUTH command) can be used in the expansion of the second string, and
23742 so on. If an invalid base64 string is received when
23743 &%client_ignore_invalid_base64%& is set, an empty string is put in the
23744 &$auth$&<&'n'&> variable.
23746 &*Note*&: You cannot use expansion to create multiple strings, because
23747 splitting takes priority and happens first.
23749 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
23750 the data, further processing is applied to each string before it is sent. If
23751 there are any single circumflex characters in the string, they are converted to
23752 NULs. Should an actual circumflex be required as data, it must be doubled in
23755 This is an example of a client configuration that implements the PLAIN
23756 authentication mechanism with a fixed user name and password:
23760 public_name = PLAIN
23761 client_send = ^username^mysecret
23763 The lack of colons means that the entire text is sent with the AUTH
23764 command, with the circumflex characters converted to NULs. A similar example
23765 that uses the LOGIN mechanism is:
23769 public_name = LOGIN
23770 client_send = : username : mysecret
23772 The initial colon means that the first string is empty, so no data is sent with
23773 the AUTH command itself. The remaining strings are sent in response to
23775 .ecindex IIDplaiauth1
23776 .ecindex IIDplaiauth2
23781 . ////////////////////////////////////////////////////////////////////////////
23782 . ////////////////////////////////////////////////////////////////////////////
23784 .chapter "The cram_md5 authenticator" "CHID9"
23785 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
23786 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
23787 .cindex "CRAM-MD5 authentication mechanism"
23788 .cindex "authentication" "CRAM-MD5 mechanism"
23789 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
23790 sends a challenge string to the client, and the response consists of a user
23791 name and the CRAM-MD5 digest of the challenge string combined with a secret
23792 string (password) which is known to both server and client. Thus, the secret
23793 is not sent over the network as plain text, which makes this authenticator more
23794 secure than &(plaintext)&. However, the downside is that the secret has to be
23795 available in plain text at either end.
23798 .section "Using cram_md5 as a server" "SECID176"
23799 .cindex "options" "&(cram_md5)& authenticator (server)"
23800 This authenticator has one server option, which must be set to configure the
23801 authenticator as a server:
23803 .option server_secret cram_md5 string&!! unset
23804 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
23805 When the server receives the client's response, the user name is placed in
23806 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
23807 obtain the password for that user. The server then computes the CRAM-MD5 digest
23808 that the client should have sent, and checks that it received the correct
23809 string. If the expansion of &%server_secret%& is forced to fail, authentication
23810 fails. If the expansion fails for some other reason, a temporary error code is
23811 returned to the client.
23813 For compatibility with previous releases of Exim, the user name is also placed
23814 in &$1$&. However, the use of this variables for this purpose is now
23815 deprecated, as it can lead to confusion in string expansions that also use
23816 numeric variables for other things.
23818 For example, the following authenticator checks that the user name given by the
23819 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
23820 user name, authentication fails.
23824 public_name = CRAM-MD5
23825 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
23826 server_set_id = $auth1
23828 .vindex "&$authenticated_id$&"
23829 If authentication succeeds, the setting of &%server_set_id%& preserves the user
23830 name in &$authenticated_id$&. A more typical configuration might look up the
23831 secret string in a file, using the user name as the key. For example:
23835 public_name = CRAM-MD5
23836 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
23838 server_set_id = $auth1
23840 Note that this expansion explicitly forces failure if the lookup fails
23841 because &$auth1$& contains an unknown user name.
23844 .section "Using cram_md5 as a client" "SECID177"
23845 .cindex "options" "&(cram_md5)& authenticator (client)"
23846 When used as a client, the &(cram_md5)& authenticator has two options:
23850 .option client_name cram_md5 string&!! "the primary host name"
23851 This string is expanded, and the result used as the user name data when
23852 computing the response to the server's challenge.
23855 .option client_secret cram_md5 string&!! unset
23856 This option must be set for the authenticator to work as a client. Its value is
23857 expanded and the result used as the secret string when computing the response.
23861 .vindex "&$host_address$&"
23862 Different user names and secrets can be used for different servers by referring
23863 to &$host$& or &$host_address$& in the options. Forced failure of either
23864 expansion string is treated as an indication that this authenticator is not
23865 prepared to handle this case. Exim moves on to the next configured client
23866 authenticator. Any other expansion failure causes Exim to give up trying to
23867 send the message to the current server.
23869 A simple example configuration of a &(cram_md5)& authenticator, using fixed
23874 public_name = CRAM-MD5
23876 client_secret = secret
23878 .ecindex IIDcramauth1
23879 .ecindex IIDcramauth2
23883 . ////////////////////////////////////////////////////////////////////////////
23884 . ////////////////////////////////////////////////////////////////////////////
23886 .chapter "The cyrus_sasl authenticator" "CHID10"
23887 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
23888 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
23889 .cindex "Cyrus" "SASL library"
23891 The code for this authenticator was provided by Matthew Byng-Maddick of A L
23892 Digital Ltd (&url(http://www.aldigital.co.uk)).
23894 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
23895 library implementation of the RFC 2222 (&"Simple Authentication and Security
23896 Layer"&). This library supports a number of authentication mechanisms,
23897 including PLAIN and LOGIN, but also several others that Exim does not support
23898 directly. In particular, there is support for Kerberos authentication.
23900 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
23901 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
23902 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
23903 name of the driver to determine which mechanism to support.
23905 Where access to some kind of secret file is required, for example in GSSAPI
23906 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
23907 user, and that the Cyrus SASL library has no way of escalating privileges
23908 by default. You may also find you need to set environment variables,
23909 depending on the driver you are using.
23911 The application name provided by Exim is &"exim"&, so various SASL options may
23912 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
23913 Kerberos, note that because of limitations in the GSSAPI interface,
23914 changing the server keytab might need to be communicated down to the Kerberos
23915 layer independently. The mechanism for doing so is dependent upon the Kerberos
23916 implementation. For example, for Heimdal, the environment variable KRB5_KTNAME
23917 may be set to point to an alternative keytab file. Exim will pass this
23918 variable through from its own inherited environment when started as root or the
23919 Exim user. The keytab file needs to be readable by the Exim user.
23922 .section "Using cyrus_sasl as a server" "SECID178"
23923 The &(cyrus_sasl)& authenticator has four private options. It puts the username
23924 (on a successful authentication) into &$auth1$&. For compatibility with
23925 previous releases of Exim, the username is also placed in &$1$&. However, the
23926 use of this variable for this purpose is now deprecated, as it can lead to
23927 confusion in string expansions that also use numeric variables for other
23931 .option server_hostname cyrus_sasl string&!! "see below"
23932 This option selects the hostname that is used when communicating with the
23933 library. The default value is &`$primary_hostname`&. It is up to the underlying
23934 SASL plug-in what it does with this data.
23937 .option server_mech cyrus_sasl string "see below"
23938 This option selects the authentication mechanism this driver should use. The
23939 default is the value of the generic &%public_name%& option. This option allows
23940 you to use a different underlying mechanism from the advertised name. For
23944 driver = cyrus_sasl
23945 public_name = X-ANYTHING
23946 server_mech = CRAM-MD5
23947 server_set_id = $auth1
23950 .option server_realm cyrus_sasl string unset
23951 This specifies the SASL realm that the server claims to be in.
23954 .option server_service cyrus_sasl string &`smtp`&
23955 This is the SASL service that the server claims to implement.
23958 For straightforward cases, you do not need to set any of the authenticator's
23959 private options. All you need to do is to specify an appropriate mechanism as
23960 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
23961 PLAIN, you could have two authenticators as follows:
23964 driver = cyrus_sasl
23965 public_name = CRAM-MD5
23966 server_set_id = $auth1
23969 driver = cyrus_sasl
23970 public_name = PLAIN
23971 server_set_id = $auth2
23973 Cyrus SASL does implement the LOGIN authentication method, even though it is
23974 not a standard method. It is disabled by default in the source distribution,
23975 but it is present in many binary distributions.
23976 .ecindex IIDcyrauth1
23977 .ecindex IIDcyrauth2
23982 . ////////////////////////////////////////////////////////////////////////////
23983 . ////////////////////////////////////////////////////////////////////////////
23984 .chapter "The dovecot authenticator" "CHAPdovecot"
23985 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
23986 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
23987 This authenticator is an interface to the authentication facility of the
23988 Dovecot POP/IMAP server, which can support a number of authentication methods.
23989 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
23990 to use the same mechanisms for SMTP authentication. This is a server
23991 authenticator only. There is only one option:
23993 .option server_socket dovecot string unset
23995 This option must specify the socket that is the interface to Dovecot
23996 authentication. The &%public_name%& option must specify an authentication
23997 mechanism that Dovecot is configured to support. You can have several
23998 authenticators for different mechanisms. For example:
24002 public_name = PLAIN
24003 server_socket = /var/run/dovecot/auth-client
24004 server_set_id = $auth2
24009 server_socket = /var/run/dovecot/auth-client
24010 server_set_id = $auth1
24012 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
24013 &$received_ip_address$& (that is, the connection is local), the &"secured"&
24014 option is passed in the Dovecot authentication command. If, for a TLS
24015 connection, a client certificate has been verified, the &"valid-client-cert"&
24016 option is passed. When authentication succeeds, the identity of the user
24017 who authenticated is placed in &$auth1$&.
24018 .ecindex IIDdcotauth1
24019 .ecindex IIDdcotauth2
24022 . ////////////////////////////////////////////////////////////////////////////
24023 . ////////////////////////////////////////////////////////////////////////////
24025 .chapter "The spa authenticator" "CHAPspa"
24026 .scindex IIDspaauth1 "&(spa)& authenticator"
24027 .scindex IIDspaauth2 "authenticators" "&(spa)&"
24028 .cindex "authentication" "Microsoft Secure Password"
24029 .cindex "authentication" "NTLM"
24030 .cindex "Microsoft Secure Password Authentication"
24031 .cindex "NTLM authentication"
24032 The &(spa)& authenticator provides client support for Microsoft's &'Secure
24033 Password Authentication'& mechanism,
24034 which is also sometimes known as NTLM (NT LanMan). The code for client side of
24035 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
24036 taken from the Samba project (&url(http://www.samba.org)). The code for the
24037 server side was subsequently contributed by Tom Kistner. The mechanism works as
24041 After the AUTH command has been accepted, the client sends an SPA
24042 authentication request based on the user name and optional domain.
24044 The server sends back a challenge.
24046 The client builds a challenge response which makes use of the user's password
24047 and sends it to the server, which then accepts or rejects it.
24050 Encryption is used to protect the password in transit.
24054 .section "Using spa as a server" "SECID179"
24055 .cindex "options" "&(spa)& authenticator (server)"
24056 The &(spa)& authenticator has just one server option:
24058 .option server_password spa string&!! unset
24059 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
24060 This option is expanded, and the result must be the cleartext password for the
24061 authenticating user, whose name is at this point in &$auth1$&. For
24062 compatibility with previous releases of Exim, the user name is also placed in
24063 &$1$&. However, the use of this variable for this purpose is now deprecated, as
24064 it can lead to confusion in string expansions that also use numeric variables
24065 for other things. For example:
24070 server_password = \
24071 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
24073 If the expansion is forced to fail, authentication fails. Any other expansion
24074 failure causes a temporary error code to be returned.
24080 .section "Using spa as a client" "SECID180"
24081 .cindex "options" "&(spa)& authenticator (client)"
24082 The &(spa)& authenticator has the following client options:
24086 .option client_domain spa string&!! unset
24087 This option specifies an optional domain for the authentication.
24090 .option client_password spa string&!! unset
24091 This option specifies the user's password, and must be set.
24094 .option client_username spa string&!! unset
24095 This option specifies the user name, and must be set. Here is an example of a
24096 configuration of this authenticator for use with the mail servers at
24102 client_username = msn/msn_username
24103 client_password = msn_plaintext_password
24104 client_domain = DOMAIN_OR_UNSET
24106 .ecindex IIDspaauth1
24107 .ecindex IIDspaauth2
24113 . ////////////////////////////////////////////////////////////////////////////
24114 . ////////////////////////////////////////////////////////////////////////////
24116 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
24117 "Encrypted SMTP connections"
24118 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
24119 .scindex IIDencsmtp2 "SMTP" "encryption"
24120 .cindex "TLS" "on SMTP connection"
24123 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
24124 Sockets Layer), is implemented by making use of the OpenSSL library or the
24125 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
24126 cryptographic code in the Exim distribution itself for implementing TLS. In
24127 order to use this feature you must install OpenSSL or GnuTLS, and then build a
24128 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
24129 You also need to understand the basic concepts of encryption at a managerial
24130 level, and in particular, the way that public keys, private keys, and
24131 certificates are used.
24133 RFC 3207 defines how SMTP connections can make use of encryption. Once a
24134 connection is established, the client issues a STARTTLS command. If the
24135 server accepts this, the client and the server negotiate an encryption
24136 mechanism. If the negotiation succeeds, the data that subsequently passes
24137 between them is encrypted.
24139 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
24140 and if so, what cipher suite is in use, whether the client supplied a
24141 certificate, and whether or not that certificate was verified. This makes it
24142 possible for an Exim server to deny or accept certain commands based on the
24145 &*Warning*&: Certain types of firewall and certain anti-virus products can
24146 disrupt TLS connections. You need to turn off SMTP scanning for these products
24147 in order to get TLS to work.
24151 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
24153 .cindex "ssmtp protocol"
24154 .cindex "smtps protocol"
24155 .cindex "SMTP" "ssmtp protocol"
24156 .cindex "SMTP" "smtps protocol"
24157 Early implementations of encrypted SMTP used a different TCP port from normal
24158 SMTP, and expected an encryption negotiation to start immediately, instead of
24159 waiting for a STARTTLS command from the client using the standard SMTP
24160 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
24161 allocated for this purpose.
24163 This approach was abandoned when encrypted SMTP was standardized, but there are
24164 still some legacy clients that use it. Exim supports these clients by means of
24165 the &%tls_on_connect_ports%& global option. Its value must be a list of port
24166 numbers; the most common use is expected to be:
24168 tls_on_connect_ports = 465
24170 The port numbers specified by this option apply to all SMTP connections, both
24171 via the daemon and via &'inetd'&. You still need to specify all the ports that
24172 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
24173 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
24174 an extra port &-- rather, it specifies different behaviour on a port that is
24177 There is also a &%-tls-on-connect%& command line option. This overrides
24178 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
24185 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
24186 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
24187 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
24188 followed later, when the first versions of GnuTLS were released. To build Exim
24189 to use GnuTLS, you need to set
24193 in Local/Makefile, in addition to
24197 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
24198 include files and libraries for GnuTLS can be found.
24200 There are some differences in usage when using GnuTLS instead of OpenSSL:
24203 The &%tls_verify_certificates%& option must contain the name of a file, not the
24204 name of a directory (for OpenSSL it can be either).
24206 The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no
24207 facility for varying its Diffie-Hellman parameters. I understand that this has
24208 changed, but Exim has not been updated to provide this facility.
24210 .vindex "&$tls_peerdn$&"
24211 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
24212 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
24213 affects the value of the &$tls_peerdn$& variable.
24215 OpenSSL identifies cipher suites using hyphens as separators, for example:
24216 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA_ARCFOUR_SHA. What is
24217 more, OpenSSL complains if underscores are present in a cipher list. To make
24218 life simpler, Exim changes underscores to hyphens for OpenSSL and hyphens to
24219 underscores for GnuTLS when processing lists of cipher suites in the
24220 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
24223 The &%tls_require_ciphers%& options operate differently, as described in the
24224 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
24228 .section "GnuTLS parameter computation" "SECID181"
24229 GnuTLS uses D-H parameters that may take a substantial amount of time
24230 to compute. It is unreasonable to re-compute them for every TLS session.
24231 Therefore, Exim keeps this data in a file in its spool directory, called
24232 &_gnutls-params_&. The file is owned by the Exim user and is readable only by
24233 its owner. Every Exim process that start up GnuTLS reads the D-H
24234 parameters from this file. If the file does not exist, the first Exim process
24235 that needs it computes the data and writes it to a temporary file which is
24236 renamed once it is complete. It does not matter if several Exim processes do
24237 this simultaneously (apart from wasting a few resources). Once a file is in
24238 place, new Exim processes immediately start using it.
24240 For maximum security, the parameters that are stored in this file should be
24241 recalculated periodically, the frequency depending on your paranoia level.
24242 Arranging this is easy in principle; just delete the file when you want new
24243 values to be computed. However, there may be a problem. The calculation of new
24244 parameters needs random numbers, and these are obtained from &_/dev/random_&.
24245 If the system is not very active, &_/dev/random_& may delay returning data
24246 until enough randomness (entropy) is available. This may cause Exim to hang for
24247 a substantial amount of time, causing timeouts on incoming connections.
24249 The solution is to generate the parameters externally to Exim. They are stored
24250 in &_gnutls-params_& in PEM format, which means that they can be generated
24251 externally using the &(certtool)& command that is part of GnuTLS.
24253 To replace the parameters with new ones, instead of deleting the file
24254 and letting Exim re-create it, you can generate new parameters using
24255 &(certtool)& and, when this has been done, replace Exim's cache file by
24256 renaming. The relevant commands are something like this:
24260 # chown exim:exim new-params
24261 # chmod 0400 new-params
24262 # certtool --generate-privkey --bits 512 >new-params
24263 # echo "" >>new-params
24264 # certtool --generate-dh-params --bits 1024 >> new-params
24265 # mv new-params gnutls-params
24267 If Exim never has to generate the parameters itself, the possibility of
24268 stalling is removed.
24271 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
24272 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
24273 .oindex "&%tls_require_ciphers%&" "OpenSSL"
24274 There is a function in the OpenSSL library that can be passed a list of cipher
24275 suites before the cipher negotiation takes place. This specifies which ciphers
24276 are acceptable. The list is colon separated and may contain names like
24277 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
24278 directly to this function call. The following quotation from the OpenSSL
24279 documentation specifies what forms of item are allowed in the cipher string:
24282 It can consist of a single cipher suite such as RC4-SHA.
24284 It can represent a list of cipher suites containing a certain algorithm,
24285 or cipher suites of a certain type. For example SHA1 represents all
24286 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
24289 Lists of cipher suites can be combined in a single cipher string using
24290 the + character. This is used as a logical and operation. For example
24291 SHA1+DES represents all cipher suites containing the SHA1 and the DES
24295 Each cipher string can be optionally preceded by one of the characters &`!`&,
24298 If &`!`& is used, the ciphers are permanently deleted from the list. The
24299 ciphers deleted can never reappear in the list even if they are explicitly
24302 If &`-`& is used, the ciphers are deleted from the list, but some or all
24303 of the ciphers can be added again by later options.
24305 If &`+`& is used, the ciphers are moved to the end of the list. This
24306 option does not add any new ciphers; it just moves matching existing ones.
24309 If none of these characters is present, the string is interpreted as
24310 a list of ciphers to be appended to the current preference list. If the list
24311 includes any ciphers already present they will be ignored: that is, they will
24312 not be moved to the end of the list.
24317 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
24319 .cindex "GnuTLS" "specifying parameters for"
24320 .cindex "TLS" "specifying ciphers (GnuTLS)"
24321 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
24322 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
24323 .cindex "TLS" "specifying protocols (GnuTLS)"
24324 .oindex "&%tls_require_ciphers%&" "GnuTLS"
24325 The GnuTLS library allows the caller to specify separate lists of permitted key
24326 exchange methods, main cipher algorithms, MAC algorithms, and protocols.
24327 Unfortunately, these lists are numerical, and the library does not have a
24328 function for turning names into numbers. Consequently, lists of recognized
24329 names have to be built into the application. The permitted key exchange
24330 methods, ciphers, and MAC algorithms may be used in any combination to form a
24331 cipher suite. This is unlike OpenSSL, where complete cipher suite names are
24332 passed to its control function.
24334 For compatibility with OpenSSL, the &%tls_require_ciphers%& option can be set
24335 to complete cipher suite names such as RSA_ARCFOUR_SHA, but for GnuTLS this
24336 option controls only the cipher algorithms. Exim searches each item in the
24337 list for the name of an available algorithm. For example, if the list
24338 contains RSA_AES_SHA, then AES is recognized, and the behaviour is exactly
24339 the same as if just AES were given.
24341 .oindex "&%gnutls_require_kx%&"
24342 .oindex "&%gnutls_require_mac%&"
24343 .oindex "&%gnutls_require_protocols%&"
24344 There are additional options called &%gnutls_require_kx%&,
24345 &%gnutls_require_mac%&, and &%gnutls_require_protocols%& that can be used to
24346 restrict the key exchange methods, MAC algorithms, and protocols, respectively.
24347 These options are ignored if OpenSSL is in use.
24349 All four options are available as global options, controlling how Exim
24350 behaves as a server, and also as options of the &(smtp)& transport, controlling
24351 how Exim behaves as a client. All the values are string expanded. After
24352 expansion, the values must be colon-separated lists, though the separator
24353 can be changed in the usual way.
24355 Each of the four lists starts out with a default set of algorithms. If the
24356 first item in a list does &'not'& start with an exclamation mark, all the
24357 default items are deleted. In this case, only those that are explicitly
24358 specified can be used. If the first item in a list &'does'& start with an
24359 exclamation mark, the defaults are left on the list.
24361 Then, any item that starts with an exclamation mark causes the relevant
24362 entry to be removed from the list, and any item that does not start with an
24363 exclamation mark causes a new entry to be added to the list. Unrecognized
24364 items in the list are ignored. Thus:
24366 tls_require_ciphers = !ARCFOUR
24368 allows all the defaults except ARCFOUR, whereas
24370 tls_require_ciphers = AES : 3DES
24372 allows only cipher suites that use AES or 3DES.
24374 For &%tls_require_ciphers%& the recognized names are AES_256, AES_128, AES
24375 (both of the preceding), 3DES, ARCFOUR_128, ARCFOUR_40, and ARCFOUR (both of
24376 the preceding). The default list does not contain all of these; it just has
24377 AES_256, AES_128, 3DES, and ARCFOUR_128.
24379 For &%gnutls_require_kx%&, the recognized names are DHE_RSA, RSA (which
24380 includes DHE_RSA), DHE_DSS, and DHE (which includes both DHE_RSA and
24381 DHE_DSS). The default list contains RSA, DHE_DSS, DHE_RSA.
24383 For &%gnutls_require_mac%&, the recognized names are SHA (synonym SHA1), and
24384 MD5. The default list contains SHA, MD5.
24386 For &%gnutls_require_protocols%&, the recognized names are TLS1 and SSL3.
24387 The default list contains TLS1, SSL3.
24389 In a server, the order of items in these lists is unimportant. The server
24390 advertises the availability of all the relevant cipher suites. However, in a
24391 client, the order in the &%tls_require_ciphers%& list specifies a preference
24392 order for the cipher algorithms. The first one in the client's list that is
24393 also advertised by the server is tried first. The default order is as listed
24398 .section "Configuring an Exim server to use TLS" "SECID182"
24399 .cindex "TLS" "configuring an Exim server"
24400 When Exim has been built with TLS support, it advertises the availability of
24401 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
24402 but not to any others. The default value of this option is unset, which means
24403 that STARTTLS is not advertised at all. This default is chosen because you
24404 need to set some other options in order to make TLS available, and also it is
24405 sensible for systems that want to use TLS only as a client.
24407 If a client issues a STARTTLS command and there is some configuration
24408 problem in the server, the command is rejected with a 454 error. If the client
24409 persists in trying to issue SMTP commands, all except QUIT are rejected
24412 554 Security failure
24414 If a STARTTLS command is issued within an existing TLS session, it is
24415 rejected with a 554 error code.
24417 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
24418 match some hosts. You can, of course, set it to * to match all hosts.
24419 However, this is not all you need to do. TLS sessions to a server won't work
24420 without some further configuration at the server end.
24422 It is rumoured that all existing clients that support TLS/SSL use RSA
24423 encryption. To make this work you need to set, in the server,
24425 tls_certificate = /some/file/name
24426 tls_privatekey = /some/file/name
24428 These options are, in fact, expanded strings, so you can make them depend on
24429 the identity of the client that is connected if you wish. The first file
24430 contains the server's X509 certificate, and the second contains the private key
24431 that goes with it. These files need to be readable by the Exim user, and must
24432 always be given as full path names. They can be the same file if both the
24433 certificate and the key are contained within it. If &%tls_privatekey%& is not
24434 set, or if its expansion is forced to fail or results in an empty string, this
24435 is assumed to be the case. The certificate file may also contain intermediate
24436 certificates that need to be sent to the client to enable it to authenticate
24437 the server's certificate.
24439 If you do not understand about certificates and keys, please try to find a
24440 source of this background information, which is not Exim-specific. (There are a
24441 few comments below in section &<<SECTcerandall>>&.)
24443 &*Note*&: These options do not apply when Exim is operating as a client &--
24444 they apply only in the case of a server. If you need to use a certificate in an
24445 Exim client, you must set the options of the same names in an &(smtp)&
24448 With just these options, an Exim server will be able to use TLS. It does not
24449 require the client to have a certificate (but see below for how to insist on
24450 this). There is one other option that may be needed in other situations. If
24452 tls_dhparam = /some/file/name
24454 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
24455 with the parameters contained in the file. This increases the set of cipher
24456 suites that the server supports. See the command
24460 for a way of generating this data. At present, &%tls_dhparam%& is used only
24461 when Exim is linked with OpenSSL. It is ignored if GnuTLS is being used.
24463 The strings supplied for these three options are expanded every time a client
24464 host connects. It is therefore possible to use different certificates and keys
24465 for different hosts, if you so wish, by making use of the client's IP address
24466 in &$sender_host_address$& to control the expansion. If a string expansion is
24467 forced to fail, Exim behaves as if the option is not set.
24469 .cindex "cipher" "logging"
24470 .cindex "log" "TLS cipher"
24471 .vindex "&$tls_cipher$&"
24472 The variable &$tls_cipher$& is set to the cipher suite that was negotiated for
24473 an incoming TLS connection. It is included in the &'Received:'& header of an
24474 incoming message (by default &-- you can, of course, change this), and it is
24475 also included in the log line that records a message's arrival, keyed by
24476 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
24477 condition can be used to test for specific cipher suites in ACLs.
24478 (For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section
24481 Once TLS has been established, the ACLs that run for subsequent SMTP commands
24482 can check the name of the cipher suite and vary their actions accordingly. The
24483 cipher suite names vary, depending on which TLS library is being used. For
24484 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
24485 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
24486 documentation for more details.
24489 .section "Requesting and verifying client certificates" "SECID183"
24490 .cindex "certificate" "verification of client"
24491 .cindex "TLS" "client certificate verification"
24492 If you want an Exim server to request a certificate when negotiating a TLS
24493 session with a client, you must set either &%tls_verify_hosts%& or
24494 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
24495 apply to all TLS connections. For any host that matches one of these options,
24496 Exim requests a certificate as part of the setup of the TLS session. The
24497 contents of the certificate are verified by comparing it with a list of
24498 expected certificates. These must be available in a file or,
24499 for OpenSSL only (not GnuTLS), a directory, identified by
24500 &%tls_verify_certificates%&.
24502 A file can contain multiple certificates, concatenated end to end. If a
24505 each certificate must be in a separate file, with a name (or a symbolic link)
24506 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
24507 certificate. You can compute the relevant hash by running the command
24509 openssl x509 -hash -noout -in /cert/file
24511 where &_/cert/file_& contains a single certificate.
24513 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
24514 what happens if the client does not supply a certificate, or if the certificate
24515 does not match any of the certificates in the collection named by
24516 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
24517 attempt to set up a TLS session is aborted, and the incoming connection is
24518 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
24519 session continues. ACLs that run for subsequent SMTP commands can detect the
24520 fact that no certificate was verified, and vary their actions accordingly. For
24521 example, you can insist on a certificate before accepting a message for
24522 relaying, but not when the message is destined for local delivery.
24524 .vindex "&$tls_peerdn$&"
24525 When a client supplies a certificate (whether it verifies or not), the value of
24526 the Distinguished Name of the certificate is made available in the variable
24527 &$tls_peerdn$& during subsequent processing of the message.
24529 .cindex "log" "distinguished name"
24530 Because it is often a long text string, it is not included in the log line or
24531 &'Received:'& header by default. You can arrange for it to be logged, keyed by
24532 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
24533 &%received_header_text%& to change the &'Received:'& header. When no
24534 certificate is supplied, &$tls_peerdn$& is empty.
24537 .section "Revoked certificates" "SECID184"
24538 .cindex "TLS" "revoked certificates"
24539 .cindex "revocation list"
24540 .cindex "certificate" "revocation list"
24541 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
24542 certificates are revoked. If you have such a list, you can pass it to an Exim
24543 server using the global option called &%tls_crl%& and to an Exim client using
24544 an identically named option for the &(smtp)& transport. In each case, the value
24545 of the option is expanded and must then be the name of a file that contains a
24549 .section "Configuring an Exim client to use TLS" "SECID185"
24550 .cindex "cipher" "logging"
24551 .cindex "log" "TLS cipher"
24552 .cindex "log" "distinguished name"
24553 .cindex "TLS" "configuring an Exim client"
24554 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
24555 deliveries as well as to incoming, the latter one causing logging of the
24556 server certificate's DN. The remaining client configuration for TLS is all
24557 within the &(smtp)& transport.
24559 It is not necessary to set any options to have TLS work in the &(smtp)&
24560 transport. If Exim is built with TLS support, and TLS is advertised by a
24561 server, the &(smtp)& transport always tries to start a TLS session. However,
24562 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
24563 transport) to a list of server hosts for which TLS should not be used.
24565 If you do not want Exim to attempt to send messages unencrypted when an attempt
24566 to set up an encrypted connection fails in any way, you can set
24567 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
24568 those hosts, delivery is always deferred if an encrypted connection cannot be
24569 set up. If there are any other hosts for the address, they are tried in the
24572 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
24573 the message unencrypted. It always does this if the response to STARTTLS is
24574 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
24575 session after a success response code, what happens is controlled by the
24576 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
24577 delivery to this host is deferred, and other hosts (if available) are tried. If
24578 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
24579 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
24580 negotiation fails, Exim closes the current connection (because it is in an
24581 unknown state), opens a new one to the same host, and then tries the delivery
24584 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
24585 transport provide the client with a certificate, which is passed to the server
24586 if it requests it. If the server is Exim, it will request a certificate only if
24587 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
24589 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
24590 must name a file or,
24591 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
24592 expected server certificates. The client verifies the server's certificate
24593 against this collection, taking into account any revoked certificates that are
24594 in the list defined by &%tls_crl%&.
24597 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
24598 list of permitted cipher suites. If either of these checks fails, delivery to
24599 the current host is abandoned, and the &(smtp)& transport tries to deliver to
24600 alternative hosts, if any.
24603 These options must be set in the &(smtp)& transport for Exim to use TLS when it
24604 is operating as a client. Exim does not assume that a server certificate (set
24605 by the global options of the same name) should also be used when operating as a
24609 .vindex "&$host_address$&"
24610 All the TLS options in the &(smtp)& transport are expanded before use, with
24611 &$host$& and &$host_address$& containing the name and address of the server to
24612 which the client is connected. Forced failure of an expansion causes Exim to
24613 behave as if the relevant option were unset.
24615 .vindex &$tls_cipher$&
24616 .vindex &$tls_peerdn$&
24617 Before an SMTP connection is established, the &$tls_cipher$& and &$tls_peerdn$&
24618 variables are emptied. (Until the first connection, they contain the values
24619 that were set when the message was received.) If STARTTLS is subsequently
24620 successfully obeyed, these variables are set to the relevant values for the
24621 outgoing connection.
24625 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
24627 .cindex "multiple SMTP deliveries with TLS"
24628 .cindex "TLS" "multiple message deliveries"
24629 Exim sends multiple messages down the same TCP/IP connection by starting up
24630 an entirely new delivery process for each message, passing the socket from
24631 one process to the next. This implementation does not fit well with the use
24632 of TLS, because there is quite a lot of state information associated with a TLS
24633 connection, not just a socket identification. Passing all the state information
24634 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
24635 session before passing the socket to a new process. The new process may then
24636 try to start a new TLS session, and if successful, may try to re-authenticate
24637 if AUTH is in use, before sending the next message.
24639 The RFC is not clear as to whether or not an SMTP session continues in clear
24640 after TLS has been shut down, or whether TLS may be restarted again later, as
24641 just described. However, if the server is Exim, this shutdown and
24642 reinitialization works. It is not known which (if any) other servers operate
24643 successfully if the client closes a TLS session and continues with unencrypted
24644 SMTP, but there are certainly some that do not work. For such servers, Exim
24645 should not pass the socket to another process, because the failure of the
24646 subsequent attempt to use it would cause Exim to record a temporary host error,
24647 and delay other deliveries to that host.
24649 To test for this case, Exim sends an EHLO command to the server after
24650 closing down the TLS session. If this fails in any way, the connection is
24651 closed instead of being passed to a new delivery process, but no retry
24652 information is recorded.
24654 There is also a manual override; you can set &%hosts_nopass_tls%& on the
24655 &(smtp)& transport to match those hosts for which Exim should not pass
24656 connections to new processes if TLS has been used.
24661 .section "Certificates and all that" "SECTcerandall"
24662 .cindex "certificate" "references to discussion"
24663 In order to understand fully how TLS works, you need to know about
24664 certificates, certificate signing, and certificate authorities. This is not the
24665 place to give a tutorial, especially as I do not know very much about it
24666 myself. Some helpful introduction can be found in the FAQ for the SSL addition
24667 to Apache, currently at
24669 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
24671 Other parts of the &'modssl'& documentation are also helpful, and have
24672 links to further files.
24673 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
24674 0-201-61598-3), contains both introductory and more in-depth descriptions.
24675 Some sample programs taken from the book are available from
24677 &url(http://www.rtfm.com/openssl-examples/)
24681 .section "Certificate chains" "SECID186"
24682 The file named by &%tls_certificate%& may contain more than one
24683 certificate. This is useful in the case where the certificate that is being
24684 sent is validated by an intermediate certificate which the other end does
24685 not have. Multiple certificates must be in the correct order in the file.
24686 First the host's certificate itself, then the first intermediate
24687 certificate to validate the issuer of the host certificate, then the next
24688 intermediate certificate to validate the issuer of the first intermediate
24689 certificate, and so on, until finally (optionally) the root certificate.
24690 The root certificate must already be trusted by the recipient for
24691 validation to succeed, of course, but if it's not preinstalled, sending the
24692 root certificate along with the rest makes it available for the user to
24693 install if the receiving end is a client MUA that can interact with a user.
24696 .section "Self-signed certificates" "SECID187"
24697 .cindex "certificate" "self-signed"
24698 You can create a self-signed certificate using the &'req'& command provided
24699 with OpenSSL, like this:
24701 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
24704 &_file1_& and &_file2_& can be the same file; the key and the certificate are
24705 delimited and so can be identified independently. The &%-days%& option
24706 specifies a period for which the certificate is valid. The &%-nodes%& option is
24707 important: if you do not set it, the key is encrypted with a passphrase
24708 that you are prompted for, and any use that is made of the key causes more
24709 prompting for the passphrase. This is not helpful if you are going to use
24710 this certificate and key in an MTA, where prompting is not possible.
24712 A self-signed certificate made in this way is sufficient for testing, and
24713 may be adequate for all your requirements if you are mainly interested in
24714 encrypting transfers, and not in secure identification.
24716 However, many clients require that the certificate presented by the server be a
24717 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
24718 certificate. In this situation, the self-signed certificate described above
24719 must be installed on the client host as a trusted root &'certification
24720 authority'& (CA), and the certificate used by Exim must be a user certificate
24721 signed with that self-signed certificate.
24723 For information on creating self-signed CA certificates and using them to sign
24724 user certificates, see the &'General implementation overview'& chapter of the
24725 Open-source PKI book, available online at
24726 &url(http://ospkibook.sourceforge.net/).
24727 .ecindex IIDencsmtp1
24728 .ecindex IIDencsmtp2
24732 . ////////////////////////////////////////////////////////////////////////////
24733 . ////////////////////////////////////////////////////////////////////////////
24735 .chapter "Access control lists" "CHAPACL"
24736 .scindex IIDacl "&ACL;" "description"
24737 .cindex "control of incoming mail"
24738 .cindex "message" "controlling incoming"
24739 .cindex "policy control" "access control lists"
24740 Access Control Lists (ACLs) are defined in a separate section of the run time
24741 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
24742 name, terminated by a colon. Here is a complete ACL section that contains just
24743 one very small ACL:
24747 accept hosts = one.host.only
24749 You can have as many lists as you like in the ACL section, and the order in
24750 which they appear does not matter. The lists are self-terminating.
24752 The majority of ACLs are used to control Exim's behaviour when it receives
24753 certain SMTP commands. This applies both to incoming TCP/IP connections, and
24754 when a local process submits a message using SMTP by specifying the &%-bs%&
24755 option. The most common use is for controlling which recipients are accepted
24756 in incoming messages. In addition, you can define an ACL that is used to check
24757 local non-SMTP messages. The default configuration file contains an example of
24758 a realistic ACL for checking RCPT commands. This is discussed in chapter
24759 &<<CHAPdefconfil>>&.
24762 .section "Testing ACLs" "SECID188"
24763 The &%-bh%& command line option provides a way of testing your ACL
24764 configuration locally by running a fake SMTP session with which you interact.
24765 The host &'relay-test.mail-abuse.org'& provides a service for checking your
24766 relaying configuration (see section &<<SECTcheralcon>>& for more details).
24770 .section "Specifying when ACLs are used" "SECID189"
24771 .cindex "&ACL;" "options for specifying"
24772 In order to cause an ACL to be used, you have to name it in one of the relevant
24773 options in the main part of the configuration. These options are:
24774 .cindex "AUTH" "ACL for"
24775 .cindex "DATA" "ACLs for"
24776 .cindex "ETRN" "ACL for"
24777 .cindex "EXPN" "ACL for"
24778 .cindex "HELO" "ACL for"
24779 .cindex "EHLO" "ACL for"
24780 .cindex "MAIL" "ACL for"
24781 .cindex "QUIT, ACL for"
24782 .cindex "RCPT" "ACL for"
24783 .cindex "STARTTLS, ACL for"
24784 .cindex "VRFY" "ACL for"
24785 .cindex "SMTP" "connection, ACL for"
24786 .cindex "non-SMTP messages" "ACLs for"
24787 .cindex "MIME content scanning" "ACL for"
24790 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
24791 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
24792 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
24793 .irow &%acl_smtp_auth%& "ACL for AUTH"
24794 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
24795 .irow &%acl_smtp_data%& "ACL after DATA is complete"
24796 .irow &%acl_smtp_etrn%& "ACL for ETRN"
24797 .irow &%acl_smtp_expn%& "ACL for EXPN"
24798 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
24799 .irow &%acl_smtp_mail%& "ACL for MAIL"
24800 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
24801 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
24802 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
24803 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
24804 .irow &%acl_smtp_quit%& "ACL for QUIT"
24805 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
24806 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
24807 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
24810 For example, if you set
24812 acl_smtp_rcpt = small_acl
24814 the little ACL defined above is used whenever Exim receives a RCPT command
24815 in an SMTP dialogue. The majority of policy tests on incoming messages can be
24816 done when RCPT commands arrive. A rejection of RCPT should cause the
24817 sending MTA to give up on the recipient address contained in the RCPT
24818 command, whereas rejection at other times may cause the client MTA to keep on
24819 trying to deliver the message. It is therefore recommended that you do as much
24820 testing as possible at RCPT time.
24823 .section "The non-SMTP ACLs" "SECID190"
24824 .cindex "non-SMTP messages" "ACLs for"
24825 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
24826 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
24827 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
24828 the state of the SMTP connection such as encryption and authentication) are not
24829 relevant and are forbidden in these ACLs. However, the sender and recipients
24830 are known, so the &%senders%& and &%sender_domains%& conditions and the
24831 &$sender_address$& and &$recipients$& variables can be used. Variables such as
24832 &$authenticated_sender$& are also available. You can specify added header lines
24833 in any of these ACLs.
24835 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
24836 non-SMTP message, before any of the message has been read. (This is the
24837 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
24838 batched SMTP input, it runs after the DATA command has been reached. The
24839 result of this ACL is ignored; it cannot be used to reject a message. If you
24840 really need to, you could set a value in an ACL variable here and reject based
24841 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
24842 controls, and in particular, it can be used to set
24844 control = suppress_local_fixups
24846 This cannot be used in the other non-SMTP ACLs because by the time they are
24847 run, it is too late.
24849 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
24850 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
24852 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
24853 kind of rejection is treated as permanent, because there is no way of sending a
24854 temporary error for these kinds of message.
24857 .section "The SMTP connect ACL" "SECID191"
24858 .cindex "SMTP" "connection, ACL for"
24859 .oindex &%smtp_banner%&
24860 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
24861 session, after the test specified by &%host_reject_connection%& (which is now
24862 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
24863 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
24864 the message override the banner message that is otherwise specified by the
24865 &%smtp_banner%& option.
24868 .section "The EHLO/HELO ACL" "SECID192"
24869 .cindex "EHLO" "ACL for"
24870 .cindex "HELO" "ACL for"
24871 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
24872 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
24873 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
24874 Note that a client may issue more than one EHLO or HELO command in an SMTP
24875 session, and indeed is required to issue a new EHLO or HELO after successfully
24876 setting up encryption following a STARTTLS command.
24878 If the command is accepted by an &%accept%& verb that has a &%message%&
24879 modifier, the message may not contain more than one line (it will be truncated
24880 at the first newline and a panic logged if it does). Such a message cannot
24881 affect the EHLO options that are listed on the second and subsequent lines of
24885 .section "The DATA ACLs" "SECID193"
24886 .cindex "DATA" "ACLs for"
24887 Two ACLs are associated with the DATA command, because it is two-stage
24888 command, with two responses being sent to the client.
24889 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
24890 is obeyed. This gives you control after all the RCPT commands, but before
24891 the message itself is received. It offers the opportunity to give a negative
24892 response to the DATA command before the data is transmitted. Header lines
24893 added by MAIL or RCPT ACLs are not visible at this time, but any that
24894 are defined here are visible when the &%acl_smtp_data%& ACL is run.
24896 You cannot test the contents of the message, for example, to verify addresses
24897 in the headers, at RCPT time or when the DATA command is received. Such
24898 tests have to appear in the ACL that is run after the message itself has been
24899 received, before the final response to the DATA command is sent. This is
24900 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
24901 associated with the DATA command.
24903 For both of these ACLs, it is not possible to reject individual recipients. An
24904 error response rejects the entire message. Unfortunately, it is known that some
24905 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
24906 before or after the data) correctly &-- they keep the message on their queues
24907 and try again later, but that is their problem, though it does waste some of
24911 .section "The SMTP MIME ACL" "SECID194"
24912 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
24913 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
24916 .section "The QUIT ACL" "SECTQUITACL"
24917 .cindex "QUIT, ACL for"
24918 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
24919 does not affect the response code to QUIT, which is always 221. Thus, the ACL
24920 does not in fact control any access. For this reason, the only verbs that are
24921 permitted are &%accept%& and &%warn%&.
24923 This ACL can be used for tasks such as custom logging at the end of an SMTP
24924 session. For example, you can use ACL variables in other ACLs to count
24925 messages, recipients, etc., and log the totals at QUIT time using one or
24926 more &%logwrite%& modifiers on a &%warn%& verb.
24928 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
24929 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
24931 You do not need to have a final &%accept%&, but if you do, you can use a
24932 &%message%& modifier to specify custom text that is sent as part of the 221
24935 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
24936 failure (for example, failure to open a log file, or when Exim is bombing out
24937 because it has detected an unrecoverable error), all SMTP commands from the
24938 client are given temporary error responses until QUIT is received or the
24939 connection is closed. In these special cases, the QUIT ACL does not run.
24942 .section "The not-QUIT ACL" "SECTNOTQUITACL"
24943 .vindex &$acl_smtp_notquit$&
24944 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
24945 an SMTP session ends without sending QUIT. However, when Exim itself is is bad
24946 trouble, such as being unable to write to its log files, this ACL is not run,
24947 because it might try to do things (such as write to log files) that make the
24948 situation even worse.
24950 Like the QUIT ACL, this ACL is provided to make it possible to do customized
24951 logging or to gather statistics, and its outcome is ignored. The &%delay%&
24952 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
24955 .vindex &$smtp_notquit_reason$&
24956 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
24957 to a string that indicates the reason for the termination of the SMTP
24958 connection. The possible values are:
24960 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
24961 .irow &`bad-commands`& "Too many unknown or non-mail commands"
24962 .irow &`command-timeout`& "Timeout while reading SMTP commands"
24963 .irow &`connection-lost`& "The SMTP connection has been lost"
24964 .irow &`data-timeout`& "Timeout while reading message data"
24965 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
24966 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
24967 .irow &`signal-exit`& "SIGTERM or SIGINT"
24968 .irow &`synchronization-error`& "SMTP synchronization error"
24969 .irow &`tls-failed`& "TLS failed to start"
24971 In most cases when an SMTP connection is closed without having received QUIT,
24972 Exim sends an SMTP response message before actually closing the connection.
24973 With the exception of the &`acl-drop`& case, the default message can be
24974 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
24975 &%drop%& verb in another ACL, it is the message from the other ACL that is
24979 .section "Finding an ACL to use" "SECID195"
24980 .cindex "&ACL;" "finding which to use"
24981 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
24982 you can use different ACLs in different circumstances. For example,
24984 acl_smtp_rcpt = ${if ={25}{$interface_port} \
24985 {acl_check_rcpt} {acl_check_rcpt_submit} }
24987 In the default configuration file there are some example settings for
24988 providing an RFC 4409 message submission service on port 587 and a
24989 non-standard &"smtps"& service on port 465. You can use a string
24990 expansion like this to choose an ACL for MUAs on these ports which is
24991 more appropriate for this purpose than the default ACL on port 25.
24993 The expanded string does not have to be the name of an ACL in the
24994 configuration file; there are other possibilities. Having expanded the
24995 string, Exim searches for an ACL as follows:
24998 If the string begins with a slash, Exim uses it as a file name, and reads its
24999 contents as an ACL. The lines are processed in the same way as lines in the
25000 Exim configuration file. In particular, continuation lines are supported, blank
25001 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
25002 If the file does not exist or cannot be read, an error occurs (typically
25003 causing a temporary failure of whatever caused the ACL to be run). For example:
25005 acl_smtp_data = /etc/acls/\
25006 ${lookup{$sender_host_address}lsearch\
25007 {/etc/acllist}{$value}{default}}
25009 This looks up an ACL file to use on the basis of the host's IP address, falling
25010 back to a default if the lookup fails. If an ACL is successfully read from a
25011 file, it is retained in memory for the duration of the Exim process, so that it
25012 can be re-used without having to re-read the file.
25014 If the string does not start with a slash, and does not contain any spaces,
25015 Exim searches the ACL section of the configuration for an ACL whose name
25016 matches the string.
25018 If no named ACL is found, or if the string contains spaces, Exim parses
25019 the string as an inline ACL. This can save typing in cases where you just
25020 want to have something like
25022 acl_smtp_vrfy = accept
25024 in order to allow free use of the VRFY command. Such a string may contain
25025 newlines; it is processed in the same way as an ACL that is read from a file.
25031 .section "ACL return codes" "SECID196"
25032 .cindex "&ACL;" "return codes"
25033 Except for the QUIT ACL, which does not affect the SMTP return code (see
25034 section &<<SECTQUITACL>>& above), the result of running an ACL is either
25035 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
25036 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
25037 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
25038 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
25039 This also causes a 4&'xx'& return code.
25041 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
25042 &"deny"&, because there is no mechanism for passing temporary errors to the
25043 submitters of non-SMTP messages.
25046 ACLs that are relevant to message reception may also return &"discard"&. This
25047 has the effect of &"accept"&, but causes either the entire message or an
25048 individual recipient address to be discarded. In other words, it is a
25049 blackholing facility. Use it with care.
25051 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
25052 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
25053 RCPT ACL is to discard just the one recipient address. If there are no
25054 recipients left when the message's data is received, the DATA ACL is not
25055 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
25056 remaining recipients. The &"discard"& return is not permitted for the
25057 &%acl_smtp_predata%& ACL.
25060 .cindex "&[local_scan()]& function" "when all recipients discarded"
25061 The &[local_scan()]& function is always run, even if there are no remaining
25062 recipients; it may create new recipients.
25066 .section "Unset ACL options" "SECID197"
25067 .cindex "&ACL;" "unset options"
25068 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
25069 all the same. &*Note*&: These defaults apply only when the relevant ACL is
25070 not defined at all. For any defined ACL, the default action when control
25071 reaches the end of the ACL statements is &"deny"&.
25073 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
25074 these two are ACLs that are used only for their side effects. They cannot be
25075 used to accept or reject anything.
25077 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
25078 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
25079 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
25080 when the ACL is not defined is &"accept"&.
25082 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
25083 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
25084 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
25085 messages over an SMTP connection. For an example, see the ACL in the default
25086 configuration file.
25091 .section "Data for message ACLs" "SECID198"
25092 .cindex "&ACL;" "data for message ACL"
25094 .vindex &$local_part$&
25095 .vindex &$sender_address$&
25096 .vindex &$sender_host_address$&
25097 .vindex &$smtp_command$&
25098 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
25099 that contain information about the host and the message's sender (for example,
25100 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
25101 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
25102 &$local_part$& are set from the argument address. The entire SMTP command
25103 is available in &$smtp_command$&.
25105 When an ACL for the AUTH parameter of MAIL is running, the variables that
25106 contain information about the host are set, but &$sender_address$& is not yet
25107 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
25110 .vindex "&$message_size$&"
25111 The &$message_size$& variable is set to the value of the SIZE parameter on
25112 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
25113 that parameter is not given. The value is updated to the true message size by
25114 the time the final DATA ACL is run (after the message data has been
25117 .vindex "&$rcpt_count$&"
25118 .vindex "&$recipients_count$&"
25119 The &$rcpt_count$& variable increases by one for each RCPT command received.
25120 The &$recipients_count$& variable increases by one each time a RCPT command is
25121 accepted, so while an ACL for RCPT is being processed, it contains the number
25122 of previously accepted recipients. At DATA time (for both the DATA ACLs),
25123 &$rcpt_count$& contains the total number of RCPT commands, and
25124 &$recipients_count$& contains the total number of accepted recipients.
25130 .section "Data for non-message ACLs" "SECTdatfornon"
25131 .cindex "&ACL;" "data for non-message ACL"
25132 .vindex &$smtp_command_argument$&
25133 .vindex &$smtp_command$&
25134 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
25135 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
25136 and the entire SMTP command is available in &$smtp_command$&.
25137 These variables can be tested using a &%condition%& condition. For example,
25138 here is an ACL for use with AUTH, which insists that either the session is
25139 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
25140 does not permit authentication methods that use cleartext passwords on
25141 unencrypted connections.
25144 accept encrypted = *
25145 accept condition = ${if eq{${uc:$smtp_command_argument}}\
25147 deny message = TLS encryption or CRAM-MD5 required
25149 (Another way of applying this restriction is to arrange for the authenticators
25150 that use cleartext passwords not to be advertised when the connection is not
25151 encrypted. You can use the generic &%server_advertise_condition%& authenticator
25152 option to do this.)
25156 .section "Format of an ACL" "SECID199"
25157 .cindex "&ACL;" "format of"
25158 .cindex "&ACL;" "verbs, definition of"
25159 An individual ACL consists of a number of statements. Each statement starts
25160 with a verb, optionally followed by a number of conditions and &"modifiers"&.
25161 Modifiers can change the way the verb operates, define error and log messages,
25162 set variables, insert delays, and vary the processing of accepted messages.
25164 If all the conditions are met, the verb is obeyed. The same condition may be
25165 used (with different arguments) more than once in the same statement. This
25166 provides a means of specifying an &"and"& conjunction between conditions. For
25169 deny dnslists = list1.example
25170 dnslists = list2.example
25172 If there are no conditions, the verb is always obeyed. Exim stops evaluating
25173 the conditions and modifiers when it reaches a condition that fails. What
25174 happens then depends on the verb (and in one case, on a special modifier). Not
25175 all the conditions make sense at every testing point. For example, you cannot
25176 test a sender address in the ACL that is run for a VRFY command.
25179 .section "ACL verbs" "SECID200"
25180 The ACL verbs are as follows:
25183 .cindex "&%accept%& ACL verb"
25184 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
25185 of the conditions are not met, what happens depends on whether &%endpass%&
25186 appears among the conditions (for syntax see below). If the failing condition
25187 is before &%endpass%&, control is passed to the next ACL statement; if it is
25188 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
25189 check a RCPT command:
25191 accept domains = +local_domains
25195 If the recipient domain does not match the &%domains%& condition, control
25196 passes to the next statement. If it does match, the recipient is verified, and
25197 the command is accepted if verification succeeds. However, if verification
25198 fails, the ACL yields &"deny"&, because the failing condition is after
25201 The &%endpass%& feature has turned out to be confusing to many people, so its
25202 use is not recommended nowadays. It is always possible to rewrite an ACL so
25203 that &%endpass%& is not needed, and it is no longer used in the default
25206 .cindex "&%message%& ACL modifier" "with &%accept%&"
25207 If a &%message%& modifier appears on an &%accept%& statement, its action
25208 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
25209 (when an &%accept%& verb either accepts or passes control to the next
25210 statement), &%message%& can be used to vary the message that is sent when an
25211 SMTP command is accepted. For example, in a RCPT ACL you could have:
25213 &`accept `&<&'some conditions'&>
25214 &` message = OK, I will allow you through today`&
25216 You can specify an SMTP response code, optionally followed by an &"extended
25217 response code"& at the start of the message, but the first digit must be the
25218 same as would be sent by default, which is 2 for an &%accept%& verb.
25220 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
25221 an error message that is used when access is denied. This behaviour is retained
25222 for backward compatibility, but current &"best practice"& is to avoid the use
25227 .cindex "&%defer%& ACL verb"
25228 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
25229 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
25230 &%defer%& is the same as &%deny%&, because there is no way of sending a
25231 temporary error. For a RCPT command, &%defer%& is much the same as using a
25232 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
25233 be used in any ACL, and even for a recipient it might be a simpler approach.
25237 .cindex "&%deny%& ACL verb"
25238 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
25239 the conditions are not met, control is passed to the next ACL statement. For
25242 deny dnslists = blackholes.mail-abuse.org
25244 rejects commands from hosts that are on a DNS black list.
25248 .cindex "&%discard%& ACL verb"
25249 &%discard%&: This verb behaves like &%accept%&, except that it returns
25250 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
25251 that are concerned with receiving messages. When all the conditions are true,
25252 the sending entity receives a &"success"& response. However, &%discard%& causes
25253 recipients to be discarded. If it is used in an ACL for RCPT, just the one
25254 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
25255 message's recipients are discarded. Recipients that are discarded before DATA
25256 do not appear in the log line when the &%received_recipients%& log selector is set.
25258 If the &%log_message%& modifier is set when &%discard%& operates,
25259 its contents are added to the line that is automatically written to the log.
25260 The &%message%& modifier operates exactly as it does for &%accept%&.
25264 .cindex "&%drop%& ACL verb"
25265 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
25266 forcibly closed after the 5&'xx'& error message has been sent. For example:
25268 drop message = I don't take more than 20 RCPTs
25269 condition = ${if > {$rcpt_count}{20}}
25271 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
25272 The connection is always dropped after sending a 550 response.
25275 .cindex "&%require%& ACL verb"
25276 &%require%&: If all the conditions are met, control is passed to the next ACL
25277 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
25278 example, when checking a RCPT command,
25280 require message = Sender did not verify
25283 passes control to subsequent statements only if the message's sender can be
25284 verified. Otherwise, it rejects the command. Note the positioning of the
25285 &%message%& modifier, before the &%verify%& condition. The reason for this is
25286 discussed in section &<<SECTcondmodproc>>&.
25289 .cindex "&%warn%& ACL verb"
25290 &%warn%&: If all the conditions are true, a line specified by the
25291 &%log_message%& modifier is written to Exim's main log. Control always passes
25292 to the next ACL statement. If any condition is false, the log line is not
25293 written. If an identical log line is requested several times in the same
25294 message, only one copy is actually written to the log. If you want to force
25295 duplicates to be written, use the &%logwrite%& modifier instead.
25297 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
25298 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
25299 &%logwrite%&, and &%add_header%&) that appear before the first failing
25300 condition. There is more about adding header lines in section
25301 &<<SECTaddheadacl>>&.
25303 If any condition on a &%warn%& statement cannot be completed (that is, there is
25304 some sort of defer), the log line specified by &%log_message%& is not written.
25305 This does not include the case of a forced failure from a lookup, which
25306 is considered to be a successful completion. After a defer, no further
25307 conditions or modifiers in the &%warn%& statement are processed. The incident
25308 is logged, and the ACL continues to be processed, from the next statement
25312 .vindex "&$acl_verify_message$&"
25313 When one of the &%warn%& conditions is an address verification that fails, the
25314 text of the verification failure message is in &$acl_verify_message$&. If you
25315 want this logged, you must set it up explicitly. For example:
25317 warn !verify = sender
25318 log_message = sender verify failed: $acl_verify_message
25322 At the end of each ACL there is an implicit unconditional &%deny%&.
25324 As you can see from the examples above, the conditions and modifiers are
25325 written one to a line, with the first one on the same line as the verb, and
25326 subsequent ones on following lines. If you have a very long condition, you can
25327 continue it onto several physical lines by the usual backslash continuation
25328 mechanism. It is conventional to align the conditions vertically.
25332 .section "ACL variables" "SECTaclvariables"
25333 .cindex "&ACL;" "variables"
25334 There are some special variables that can be set during ACL processing. They
25335 can be used to pass information between different ACLs, different invocations
25336 of the same ACL in the same SMTP connection, and between ACLs and the routers,
25337 transports, and filters that are used to deliver a message. The names of these
25338 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
25339 an underscore, but the remainder of the name can be any sequence of
25340 alphanumeric characters and underscores that you choose. There is no limit on
25341 the number of ACL variables. The two sets act as follows:
25343 The values of those variables whose names begin with &$acl_c$& persist
25344 throughout an SMTP connection. They are never reset. Thus, a value that is set
25345 while receiving one message is still available when receiving the next message
25346 on the same SMTP connection.
25348 The values of those variables whose names begin with &$acl_m$& persist only
25349 while a message is being received. They are reset afterwards. They are also
25350 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
25353 When a message is accepted, the current values of all the ACL variables are
25354 preserved with the message and are subsequently made available at delivery
25355 time. The ACL variables are set by a modifier called &%set%&. For example:
25357 accept hosts = whatever
25358 set acl_m4 = some value
25359 accept authenticated = *
25360 set acl_c_auth = yes
25362 &*Note*&: A leading dollar sign is not used when naming a variable that is to
25363 be set. If you want to set a variable without taking any action, you can use a
25364 &%warn%& verb without any other modifiers or conditions.
25366 .oindex &%strict_acl_vars%&
25367 What happens if a syntactically valid but undefined ACL variable is
25368 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
25369 false (the default), an empty string is substituted; if it is true, an
25370 error is generated.
25372 Versions of Exim before 4.64 have a limited set of numbered variables, but
25373 their names are compatible, so there is no problem with upgrading.
25376 .section "Condition and modifier processing" "SECTcondmodproc"
25377 .cindex "&ACL;" "conditions; processing"
25378 .cindex "&ACL;" "modifiers; processing"
25379 An exclamation mark preceding a condition negates its result. For example:
25381 deny domains = *.dom.example
25382 !verify = recipient
25384 causes the ACL to return &"deny"& if the recipient domain ends in
25385 &'dom.example'& and the recipient address cannot be verified. Sometimes
25386 negation can be used on the right-hand side of a condition. For example, these
25387 two statements are equivalent:
25389 deny hosts = !192.168.3.4
25390 deny !hosts = 192.168.3.4
25392 However, for many conditions (&%verify%& being a good example), only left-hand
25393 side negation of the whole condition is possible.
25395 The arguments of conditions and modifiers are expanded. A forced failure
25396 of an expansion causes a condition to be ignored, that is, it behaves as if the
25397 condition is true. Consider these two statements:
25399 accept senders = ${lookup{$host_name}lsearch\
25400 {/some/file}{$value}fail}
25401 accept senders = ${lookup{$host_name}lsearch\
25402 {/some/file}{$value}{}}
25404 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
25405 the returned list is searched, but if the lookup fails the behaviour is
25406 different in the two cases. The &%fail%& in the first statement causes the
25407 condition to be ignored, leaving no further conditions. The &%accept%& verb
25408 therefore succeeds. The second statement, however, generates an empty list when
25409 the lookup fails. No sender can match an empty list, so the condition fails,
25410 and therefore the &%accept%& also fails.
25412 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
25413 specify actions that are taken as the conditions for a statement are checked;
25414 others specify text for messages that are used when access is denied or a
25415 warning is generated. The &%control%& modifier affects the way an incoming
25416 message is handled.
25418 The positioning of the modifiers in an ACL statement important, because the
25419 processing of a verb ceases as soon as its outcome is known. Only those
25420 modifiers that have already been encountered will take effect. For example,
25421 consider this use of the &%message%& modifier:
25423 require message = Can't verify sender
25425 message = Can't verify recipient
25427 message = This message cannot be used
25429 If sender verification fails, Exim knows that the result of the statement is
25430 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
25431 so its text is used as the error message. If sender verification succeeds, but
25432 recipient verification fails, the second message is used. If recipient
25433 verification succeeds, the third message becomes &"current"&, but is never used
25434 because there are no more conditions to cause failure.
25436 For the &%deny%& verb, on the other hand, it is always the last &%message%&
25437 modifier that is used, because all the conditions must be true for rejection to
25438 happen. Specifying more than one &%message%& modifier does not make sense, and
25439 the message can even be specified after all the conditions. For example:
25442 !senders = *@my.domain.example
25443 message = Invalid sender from client host
25445 The &"deny"& result does not happen until the end of the statement is reached,
25446 by which time Exim has set up the message.
25450 .section "ACL modifiers" "SECTACLmodi"
25451 .cindex "&ACL;" "modifiers; list of"
25452 The ACL modifiers are as follows:
25455 .vitem &*add_header*&&~=&~<&'text'&>
25456 This modifier specifies one or more header lines that are to be added to an
25457 incoming message, assuming, of course, that the message is ultimately
25458 accepted. For details, see section &<<SECTaddheadacl>>&.
25460 .vitem &*continue*&&~=&~<&'text'&>
25461 .cindex "&%continue%& ACL modifier"
25462 .cindex "database" "updating in ACL"
25463 This modifier does nothing of itself, and processing of the ACL always
25464 continues with the next condition or modifier. The value of &%continue%& is in
25465 the side effects of expanding its argument. Typically this could be used to
25466 update a database. It is really just a syntactic tidiness, to avoid having to
25467 write rather ugly lines like this:
25469 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
25471 Instead, all you need is
25473 &`continue = `&<&'some expansion'&>
25476 .vitem &*control*&&~=&~<&'text'&>
25477 .cindex "&%control%& ACL modifier"
25478 This modifier affects the subsequent processing of the SMTP connection or of an
25479 incoming message that is accepted. The effect of the first type of control
25480 lasts for the duration of the connection, whereas the effect of the second type
25481 lasts only until the current message has been received. The message-specific
25482 controls always apply to the whole message, not to individual recipients,
25483 even if the &%control%& modifier appears in a RCPT ACL.
25485 As there are now quite a few controls that can be applied, they are described
25486 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
25487 in several different ways. For example:
25489 . ==== As this is a nested list, any displays it contains must be indented
25490 . ==== as otherwise they are too far to the left. That comment applies only
25491 . ==== when xmlto and fop are used; formatting with sdop gets it right either
25495 It can be at the end of an &%accept%& statement:
25497 accept ...some conditions
25498 control = queue_only
25500 In this case, the control is applied when this statement yields &"accept"&, in
25501 other words, when the conditions are all true.
25504 It can be in the middle of an &%accept%& statement:
25506 accept ...some conditions...
25507 control = queue_only
25508 ...some more conditions...
25510 If the first set of conditions are true, the control is applied, even if the
25511 statement does not accept because one of the second set of conditions is false.
25512 In this case, some subsequent statement must yield &"accept"& for the control
25516 It can be used with &%warn%& to apply the control, leaving the
25517 decision about accepting or denying to a subsequent verb. For
25520 warn ...some conditions...
25524 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
25525 &%logwrite%&, so it does not add anything to the message and does not write a
25529 If you want to apply a control unconditionally, you can use it with a
25530 &%require%& verb. For example:
25532 require control = no_multiline_responses
25536 .vitem &*delay*&&~=&~<&'time'&>
25537 .cindex "&%delay%& ACL modifier"
25539 This modifier may appear in any ACL. It causes Exim to wait for the time
25540 interval before proceeding. However, when testing Exim using the &%-bh%&
25541 option, the delay is not actually imposed (an appropriate message is output
25542 instead). The time is given in the usual Exim notation, and the delay happens
25543 as soon as the modifier is processed. In an SMTP session, pending output is
25544 flushed before the delay is imposed.
25546 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
25549 deny ...some conditions...
25552 The delay happens if all the conditions are true, before the statement returns
25553 &"deny"&. Compare this with:
25556 ...some conditions...
25558 which waits for 30s before processing the conditions. The &%delay%& modifier
25559 can also be used with &%warn%& and together with &%control%&:
25561 warn ...some conditions...
25567 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
25568 responses to several commands are no longer buffered and sent in one packet (as
25569 they would normally be) because all output is flushed before imposing the
25570 delay. This optimization is disabled so that a number of small delays do not
25571 appear to the client as one large aggregated delay that might provoke an
25572 unwanted timeout. You can, however, disable output flushing for &%delay%& by
25573 using a &%control%& modifier to set &%no_delay_flush%&.
25577 .cindex "&%endpass%& ACL modifier"
25578 This modifier, which has no argument, is recognized only in &%accept%& and
25579 &%discard%& statements. It marks the boundary between the conditions whose
25580 failure causes control to pass to the next statement, and the conditions whose
25581 failure causes the ACL to return &"deny"&. This concept has proved to be
25582 confusing to some people, so the use of &%endpass%& is no longer recommended as
25583 &"best practice"&. See the description of &%accept%& above for more details.
25586 .vitem &*log_message*&&~=&~<&'text'&>
25587 .cindex "&%log_message%& ACL modifier"
25588 This modifier sets up a message that is used as part of the log message if the
25589 ACL denies access or a &%warn%& statement's conditions are true. For example:
25591 require log_message = wrong cipher suite $tls_cipher
25592 encrypted = DES-CBC3-SHA
25594 &%log_message%& is also used when recipients are discarded by &%discard%&. For
25597 &`discard `&<&'some conditions'&>
25598 &` log_message = Discarded $local_part@$domain because...`&
25600 When access is denied, &%log_message%& adds to any underlying error message
25601 that may exist because of a condition failure. For example, while verifying a
25602 recipient address, a &':fail:'& redirection might have already set up a
25605 The message may be defined before the conditions to which it applies, because
25606 the string expansion does not happen until Exim decides that access is to be
25607 denied. This means that any variables that are set by the condition are
25608 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
25609 variables are set after a DNS black list lookup succeeds. If the expansion of
25610 &%log_message%& fails, or if the result is an empty string, the modifier is
25613 .vindex "&$acl_verify_message$&"
25614 If you want to use a &%warn%& statement to log the result of an address
25615 verification, you can use &$acl_verify_message$& to include the verification
25618 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
25619 the start of the logged message. If the same warning log message is requested
25620 more than once while receiving a single email message, only one copy is
25621 actually logged. If you want to log multiple copies, use &%logwrite%& instead
25622 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
25623 is logged for a successful &%warn%& statement.
25625 If &%log_message%& is not present and there is no underlying error message (for
25626 example, from the failure of address verification), but &%message%& is present,
25627 the &%message%& text is used for logging rejections. However, if any text for
25628 logging contains newlines, only the first line is logged. In the absence of
25629 both &%log_message%& and &%message%&, a default built-in message is used for
25630 logging rejections.
25633 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
25634 .cindex "&%log_reject_target%& ACL modifier"
25635 .cindex "logging in ACL" "specifying which log"
25636 This modifier makes it possible to specify which logs are used for messages
25637 about ACL rejections. Its argument is a colon-separated list of words that can
25638 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
25639 may be empty, in which case a rejection is not logged at all. For example, this
25640 ACL fragment writes no logging information when access is denied:
25642 &`deny `&<&'some conditions'&>
25643 &` log_reject_target =`&
25645 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
25646 permanent and temporary rejections. Its effect lasts for the rest of the
25650 .vitem &*logwrite*&&~=&~<&'text'&>
25651 .cindex "&%logwrite%& ACL modifier"
25652 .cindex "logging in ACL" "immediate"
25653 This modifier writes a message to a log file as soon as it is encountered when
25654 processing an ACL. (Compare &%log_message%&, which, except in the case of
25655 &%warn%& and &%discard%&, is used only if the ACL statement denies
25656 access.) The &%logwrite%& modifier can be used to log special incidents in
25659 &`accept `&<&'some special conditions'&>
25660 &` control = freeze`&
25661 &` logwrite = froze message because ...`&
25663 By default, the message is written to the main log. However, it may begin
25664 with a colon, followed by a comma-separated list of log names, and then
25665 another colon, to specify exactly which logs are to be written. For
25668 logwrite = :main,reject: text for main and reject logs
25669 logwrite = :panic: text for panic log only
25673 .vitem &*message*&&~=&~<&'text'&>
25674 .cindex "&%message%& ACL modifier"
25675 This modifier sets up a text string that is expanded and used as a response
25676 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
25677 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
25678 there is some complication if &%endpass%& is involved; see the description of
25679 &%accept%& for details.)
25681 The expansion of the message happens at the time Exim decides that the ACL is
25682 to end, not at the time it processes &%message%&. If the expansion fails, or
25683 generates an empty string, the modifier is ignored. Here is an example where
25684 &%message%& must be specified first, because the ACL ends with a rejection if
25685 the &%hosts%& condition fails:
25687 require message = Host not recognized
25690 (Once a condition has failed, no further conditions or modifiers are
25693 .cindex "SMTP" "error codes"
25694 .oindex "&%smtp_banner%&
25695 For ACLs that are triggered by SMTP commands, the message is returned as part
25696 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
25697 is meaningful only for SMTP, as no message is returned when a non-SMTP message
25698 is accepted. In the case of the connect ACL, accepting with a message modifier
25699 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
25700 accept message may not contain more than one line (otherwise it will be
25701 truncated at the first newline and a panic logged), and it cannot affect the
25704 When SMTP is involved, the message may begin with an overriding response code,
25705 consisting of three digits optionally followed by an &"extended response code"&
25706 of the form &'n.n.n'&, each code being followed by a space. For example:
25708 deny message = 599 1.2.3 Host not welcome
25709 hosts = 192.168.34.0/24
25711 The first digit of the supplied response code must be the same as would be sent
25712 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
25713 access, but for the predata ACL, note that the default success code is 354, not
25716 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
25717 the message modifier cannot override the 221 response code.
25719 The text in a &%message%& modifier is literal; any quotes are taken as
25720 literals, but because the string is expanded, backslash escapes are processed
25721 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
25724 .vindex "&$acl_verify_message$&"
25725 If &%message%& is used on a statement that verifies an address, the message
25726 specified overrides any message that is generated by the verification process.
25727 However, the original message is available in the variable
25728 &$acl_verify_message$&, so you can incorporate it into your message if you
25729 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
25730 routers to be passed back as part of the SMTP response, you should either not
25731 use a &%message%& modifier, or make use of &$acl_verify_message$&.
25733 For compatibility with previous releases of Exim, a &%message%& modifier that
25734 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
25735 modifier, but this usage is now deprecated. However, &%message%& acts only when
25736 all the conditions are true, wherever it appears in an ACL command, whereas
25737 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
25738 &%warn%& in an ACL that is not concerned with receiving a message, it has no
25742 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
25743 .cindex "&%set%& ACL modifier"
25744 This modifier puts a value into one of the ACL variables (see section
25745 &<<SECTaclvariables>>&).
25752 .section "Use of the control modifier" "SECTcontrols"
25753 .cindex "&%control%& ACL modifier"
25754 The &%control%& modifier supports the following settings:
25757 .vitem &*control&~=&~allow_auth_unadvertised*&
25758 This modifier allows a client host to use the SMTP AUTH command even when it
25759 has not been advertised in response to EHLO. Furthermore, because there are
25760 apparently some really broken clients that do this, Exim will accept AUTH after
25761 HELO (rather than EHLO) when this control is set. It should be used only if you
25762 really need it, and you should limit its use to those broken clients that do
25763 not work without it. For example:
25765 warn hosts = 192.168.34.25
25766 control = allow_auth_unadvertised
25768 Normally, when an Exim server receives an AUTH command, it checks the name of
25769 the authentication mechanism that is given in the command to ensure that it
25770 matches an advertised mechanism. When this control is set, the check that a
25771 mechanism has been advertised is bypassed. Any configured mechanism can be used
25772 by the client. This control is permitted only in the connection and HELO ACLs.
25775 .vitem &*control&~=&~caseful_local_part*& &&&
25776 &*control&~=&~caselower_local_part*&
25777 .cindex "&ACL;" "case of local part in"
25778 .cindex "case of local parts"
25779 .vindex "&$local_part$&"
25780 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
25781 (that is, during RCPT processing). By default, the contents of &$local_part$&
25782 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
25783 any uppercase letters in the original local part are restored in &$local_part$&
25784 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
25787 These controls affect only the current recipient. Moreover, they apply only to
25788 local part handling that takes place directly in the ACL (for example, as a key
25789 in lookups). If a test to verify the recipient is obeyed, the case-related
25790 handling of the local part during the verification is controlled by the router
25791 configuration (see the &%caseful_local_part%& generic router option).
25793 This facility could be used, for example, to add a spam score to local parts
25794 containing upper case letters. For example, using &$acl_m4$& to accumulate the
25797 warn control = caseful_local_part
25798 set acl_m4 = ${eval:\
25800 ${if match{$local_part}{[A-Z]}{1}{0}}\
25802 control = caselower_local_part
25804 Notice that we put back the lower cased version afterwards, assuming that
25805 is what is wanted for subsequent tests.
25807 .vitem &*control&~=&~debug/*&<&'options'&>
25808 .cindex "&ACL;" "enabling debug logging"
25809 .cindex "debugging" "enabling from an ACL"
25810 This control turns on debug logging, almost as though Exim had been invoked
25811 with &`-d`&, with the output going to a new logfile, by default called
25812 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
25813 may access any variables already defined. The logging may be adjusted with
25814 the &'opts'& option, which takes the same values as the &`-d`& command-line
25815 option. Some examples (which depend on variables that don't exist in all
25819 control = debug/tag=.$sender_host_address
25820 control = debug/opts=+expand+acl
25821 control = debug/tag=.$message_exim_id/opts=+expand
25824 .vitem &*control&~=&~enforce_sync*& &&&
25825 &*control&~=&~no_enforce_sync*&
25826 .cindex "SMTP" "synchronization checking"
25827 .cindex "synchronization checking in SMTP"
25828 These controls make it possible to be selective about when SMTP synchronization
25829 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
25830 state of the switch (it is true by default). See the description of this option
25831 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
25833 The effect of these two controls lasts for the remainder of the SMTP
25834 connection. They can appear in any ACL except the one for the non-SMTP
25835 messages. The most straightforward place to put them is in the ACL defined by
25836 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
25837 before the first synchronization check. The expected use is to turn off the
25838 synchronization checks for badly-behaved hosts that you nevertheless need to
25842 .vitem &*control&~=&~fakedefer/*&<&'message'&>
25843 .cindex "fake defer"
25844 .cindex "defer, fake"
25845 This control works in exactly the same way as &%fakereject%& (described below)
25846 except that it causes an SMTP 450 response after the message data instead of a
25847 550 response. You must take care when using &%fakedefer%& because it causes the
25848 messages to be duplicated when the sender retries. Therefore, you should not
25849 use &%fakedefer%& if the message is to be delivered normally.
25851 .vitem &*control&~=&~fakereject/*&<&'message'&>
25852 .cindex "fake rejection"
25853 .cindex "rejection, fake"
25854 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
25855 words, only when an SMTP message is being received. If Exim accepts the
25856 message, instead the final 250 response, a 550 rejection message is sent.
25857 However, Exim proceeds to deliver the message as normal. The control applies
25858 only to the current message, not to any subsequent ones that may be received in
25859 the same SMTP connection.
25861 The text for the 550 response is taken from the &%control%& modifier. If no
25862 message is supplied, the following is used:
25864 550-Your message has been rejected but is being
25865 550-kept for evaluation.
25866 550-If it was a legitimate message, it may still be
25867 550 delivered to the target recipient(s).
25869 This facility should be used with extreme caution.
25871 .vitem &*control&~=&~freeze*&
25872 .cindex "frozen messages" "forcing in ACL"
25873 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
25874 other words, only when a message is being received. If the message is accepted,
25875 it is placed on Exim's queue and frozen. The control applies only to the
25876 current message, not to any subsequent ones that may be received in the same
25879 This modifier can optionally be followed by &`/no_tell`&. If the global option
25880 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
25881 is told about the freezing), provided all the &*control=freeze*& modifiers that
25882 are obeyed for the current message have the &`/no_tell`& option.
25884 .vitem &*control&~=&~no_delay_flush*&
25885 .cindex "SMTP" "output flushing, disabling for delay"
25886 Exim normally flushes SMTP output before implementing a delay in an ACL, to
25887 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
25888 use. This control, as long as it is encountered before the &%delay%& modifier,
25889 disables such output flushing.
25891 .vitem &*control&~=&~no_callout_flush*&
25892 .cindex "SMTP" "output flushing, disabling for callout"
25893 Exim normally flushes SMTP output before performing a callout in an ACL, to
25894 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
25895 use. This control, as long as it is encountered before the &%verify%& condition
25896 that causes the callout, disables such output flushing.
25898 .vitem &*control&~=&~no_mbox_unspool*&
25899 This control is available when Exim is compiled with the content scanning
25900 extension. Content scanning may require a copy of the current message, or parts
25901 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
25902 or spam scanner. Normally, such copies are deleted when they are no longer
25903 needed. If this control is set, the copies are not deleted. The control applies
25904 only to the current message, not to any subsequent ones that may be received in
25905 the same SMTP connection. It is provided for debugging purposes and is unlikely
25906 to be useful in production.
25908 .vitem &*control&~=&~no_multiline_responses*&
25909 .cindex "multiline responses, suppressing"
25910 This control is permitted for any ACL except the one for non-SMTP messages.
25911 It seems that there are broken clients in use that cannot handle multiline
25912 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
25914 If this control is set, multiline SMTP responses from ACL rejections are
25915 suppressed. One way of doing this would have been to put out these responses as
25916 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
25917 (&"use multiline responses for more"& it says &-- ha!), and some of the
25918 responses might get close to that. So this facility, which is after all only a
25919 sop to broken clients, is implemented by doing two very easy things:
25922 Extra information that is normally output as part of a rejection caused by
25923 sender verification failure is omitted. Only the final line (typically &"sender
25924 verification failed"&) is sent.
25926 If a &%message%& modifier supplies a multiline response, only the first
25930 The setting of the switch can, of course, be made conditional on the
25931 calling host. Its effect lasts until the end of the SMTP connection.
25933 .vitem &*control&~=&~no_pipelining*&
25934 .cindex "PIPELINING" "suppressing advertising"
25935 This control turns off the advertising of the PIPELINING extension to SMTP in
25936 the current session. To be useful, it must be obeyed before Exim sends its
25937 response to an EHLO command. Therefore, it should normally appear in an ACL
25938 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
25939 &%pipelining_advertise_hosts%&.
25941 .vitem &*control&~=&~queue_only*&
25942 .oindex "&%queue_only%&"
25943 .cindex "queueing incoming messages"
25944 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
25945 other words, only when a message is being received. If the message is accepted,
25946 it is placed on Exim's queue and left there for delivery by a subsequent queue
25947 runner. No immediate delivery process is started. In other words, it has the
25948 effect as the &%queue_only%& global option. However, the control applies only
25949 to the current message, not to any subsequent ones that may be received in the
25950 same SMTP connection.
25952 .vitem &*control&~=&~submission/*&<&'options'&>
25953 .cindex "message" "submission"
25954 .cindex "submission mode"
25955 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
25956 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
25957 the current message is a submission from a local MUA. In this case, Exim
25958 operates in &"submission mode"&, and applies certain fixups to the message if
25959 necessary. For example, it adds a &'Date:'& header line if one is not present.
25960 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
25961 late (the message has already been created).
25963 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
25964 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
25965 submission mode; the available options for this control are described there.
25966 The control applies only to the current message, not to any subsequent ones
25967 that may be received in the same SMTP connection.
25969 .vitem &*control&~=&~suppress_local_fixups*&
25970 .cindex "submission fixups, suppressing"
25971 This control applies to locally submitted (non TCP/IP) messages, and is the
25972 complement of &`control = submission`&. It disables the fixups that are
25973 normally applied to locally-submitted messages. Specifically:
25976 Any &'Sender:'& header line is left alone (in this respect, it is a
25977 dynamic version of &%local_sender_retain%&).
25979 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
25981 There is no check that &'From:'& corresponds to the actual sender.
25984 This control may be useful when a remotely-originated message is accepted,
25985 passed to some scanning program, and then re-submitted for delivery. It can be
25986 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
25987 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
25990 &*Note:*& This control applies only to the current message, not to any others
25991 that are being submitted at the same time using &%-bs%& or &%-bS%&.
25995 .section "Summary of message fixup control" "SECTsummesfix"
25996 All four possibilities for message fixups can be specified:
25999 Locally submitted, fixups applied: the default.
26001 Locally submitted, no fixups applied: use
26002 &`control = suppress_local_fixups`&.
26004 Remotely submitted, no fixups applied: the default.
26006 Remotely submitted, fixups applied: use &`control = submission`&.
26011 .section "Adding header lines in ACLs" "SECTaddheadacl"
26012 .cindex "header lines" "adding in an ACL"
26013 .cindex "header lines" "position of added lines"
26014 .cindex "&%message%& ACL modifier"
26015 The &%add_header%& modifier can be used to add one or more extra header lines
26016 to an incoming message, as in this example:
26018 warn dnslists = sbl.spamhaus.org : \
26019 dialup.mail-abuse.org
26020 add_header = X-blacklisted-at: $dnslist_domain
26022 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
26023 MIME, and non-SMTP ACLs (in other words, those that are concerned with
26024 receiving a message). The message must ultimately be accepted for
26025 &%add_header%& to have any significant effect. You can use &%add_header%& with
26026 any ACL verb, including &%deny%& (though this is potentially useful only in a
26029 If the data for the &%add_header%& modifier contains one or more newlines that
26030 are not followed by a space or a tab, it is assumed to contain multiple header
26031 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
26032 front of any line that is not a valid header line.
26034 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
26035 They are added to the message before processing the DATA and MIME ACLs.
26036 However, if an identical header line is requested more than once, only one copy
26037 is actually added to the message. Further header lines may be accumulated
26038 during the DATA and MIME ACLs, after which they are added to the message, again
26039 with duplicates suppressed. Thus, it is possible to add two identical header
26040 lines to an SMTP message, but only if one is added before DATA and one after.
26041 In the case of non-SMTP messages, new headers are accumulated during the
26042 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
26043 message is rejected after DATA or by the non-SMTP ACL, all added header lines
26044 are included in the entry that is written to the reject log.
26046 .cindex "header lines" "added; visibility of"
26047 Header lines are not visible in string expansions until they are added to the
26048 message. It follows that header lines defined in the MAIL, RCPT, and predata
26049 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
26050 header lines that are added by the DATA or MIME ACLs are not visible in those
26051 ACLs. Because of this restriction, you cannot use header lines as a way of
26052 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
26053 this, you can use ACL variables, as described in section
26054 &<<SECTaclvariables>>&.
26056 The &%add_header%& modifier acts immediately it is encountered during the
26057 processing of an ACL. Notice the difference between these two cases:
26059 &`accept add_header = ADDED: some text`&
26060 &` `&<&'some condition'&>
26062 &`accept `&<&'some condition'&>
26063 &` add_header = ADDED: some text`&
26065 In the first case, the header line is always added, whether or not the
26066 condition is true. In the second case, the header line is added only if the
26067 condition is true. Multiple occurrences of &%add_header%& may occur in the same
26068 ACL statement. All those that are encountered before a condition fails are
26071 .cindex "&%warn%& ACL verb"
26072 For compatibility with previous versions of Exim, a &%message%& modifier for a
26073 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
26074 effect only if all the conditions are true, even if it appears before some of
26075 them. Furthermore, only the last occurrence of &%message%& is honoured. This
26076 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
26077 are present on a &%warn%& verb, both are processed according to their
26080 By default, new header lines are added to a message at the end of the existing
26081 header lines. However, you can specify that any particular header line should
26082 be added right at the start (before all the &'Received:'& lines), immediately
26083 after the first block of &'Received:'& lines, or immediately before any line
26084 that is not a &'Received:'& or &'Resent-something:'& header.
26086 This is done by specifying &":at_start:"&, &":after_received:"&, or
26087 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
26088 header line, respectively. (Header text cannot start with a colon, as there has
26089 to be a header name first.) For example:
26091 warn add_header = \
26092 :after_received:X-My-Header: something or other...
26094 If more than one header line is supplied in a single &%add_header%& modifier,
26095 each one is treated independently and can therefore be placed differently. If
26096 you add more than one line at the start, or after the Received: block, they end
26097 up in reverse order.
26099 &*Warning*&: This facility currently applies only to header lines that are
26100 added in an ACL. It does NOT work for header lines that are added in a
26101 system filter or in a router or transport.
26106 .section "ACL conditions" "SECTaclconditions"
26107 .cindex "&ACL;" "conditions; list of"
26108 Some of conditions listed in this section are available only when Exim is
26109 compiled with the content-scanning extension. They are included here briefly
26110 for completeness. More detailed descriptions can be found in the discussion on
26111 content scanning in chapter &<<CHAPexiscan>>&.
26113 Not all conditions are relevant in all circumstances. For example, testing
26114 senders and recipients does not make sense in an ACL that is being run as the
26115 result of the arrival of an ETRN command, and checks on message headers can be
26116 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
26117 can use the same condition (with different parameters) more than once in the
26118 same ACL statement. This provides a way of specifying an &"and"& conjunction.
26119 The conditions are as follows:
26123 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
26124 .cindex "&ACL;" "nested"
26125 .cindex "&ACL;" "indirect"
26126 .cindex "&%acl%& ACL condition"
26127 The possible values of the argument are the same as for the
26128 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
26129 &"accept"& the condition is true; if it returns &"deny"& the condition is
26130 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
26131 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
26132 condition false. This means that further processing of the &%warn%& verb
26133 ceases, but processing of the ACL continues.
26135 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
26136 the connection is dropped. If it returns &"discard"&, the verb must be
26137 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
26138 conditions are tested.
26140 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
26141 loops. This condition allows you to use different ACLs in different
26142 circumstances. For example, different ACLs can be used to handle RCPT commands
26143 for different local users or different local domains.
26145 .vitem &*authenticated&~=&~*&<&'string&~list'&>
26146 .cindex "&%authenticated%& ACL condition"
26147 .cindex "authentication" "ACL checking"
26148 .cindex "&ACL;" "testing for authentication"
26149 If the SMTP connection is not authenticated, the condition is false. Otherwise,
26150 the name of the authenticator is tested against the list. To test for
26151 authentication by any authenticator, you can set
26156 .vitem &*condition&~=&~*&<&'string'&>
26157 .cindex "&%condition%& ACL condition"
26158 .cindex "customizing" "ACL condition"
26159 .cindex "&ACL;" "customized test"
26160 .cindex "&ACL;" "testing, customized"
26161 This feature allows you to make up custom conditions. If the result of
26162 expanding the string is an empty string, the number zero, or one of the strings
26163 &"no"& or &"false"&, the condition is false. If the result is any non-zero
26164 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
26165 any other value, some error is assumed to have occurred, and the ACL returns
26166 &"defer"&. However, if the expansion is forced to fail, the condition is
26167 ignored. The effect is to treat it as true, whether it is positive or
26170 .vitem &*decode&~=&~*&<&'location'&>
26171 .cindex "&%decode%& ACL condition"
26172 This condition is available only when Exim is compiled with the
26173 content-scanning extension, and it is allowed only in the ACL defined by
26174 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
26175 If all goes well, the condition is true. It is false only if there are
26176 problems such as a syntax error or a memory shortage. For more details, see
26177 chapter &<<CHAPexiscan>>&.
26179 .vitem &*demime&~=&~*&<&'extension&~list'&>
26180 .cindex "&%demime%& ACL condition"
26181 This condition is available only when Exim is compiled with the
26182 content-scanning extension. Its use is described in section
26183 &<<SECTdemimecond>>&.
26185 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
26186 .cindex "&%dnslists%& ACL condition"
26187 .cindex "DNS list" "in ACL"
26188 .cindex "black list (DNS)"
26189 .cindex "&ACL;" "testing a DNS list"
26190 This condition checks for entries in DNS black lists. These are also known as
26191 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
26192 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
26193 different variants of this condition to describe briefly here. See sections
26194 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
26196 .vitem &*domains&~=&~*&<&'domain&~list'&>
26197 .cindex "&%domains%& ACL condition"
26198 .cindex "domain" "ACL checking"
26199 .cindex "&ACL;" "testing a recipient domain"
26200 .vindex "&$domain_data$&"
26201 This condition is relevant only after a RCPT command. It checks that the domain
26202 of the recipient address is in the domain list. If percent-hack processing is
26203 enabled, it is done before this test is done. If the check succeeds with a
26204 lookup, the result of the lookup is placed in &$domain_data$& until the next
26207 &*Note carefully*& (because many people seem to fall foul of this): you cannot
26208 use &%domains%& in a DATA ACL.
26211 .vitem &*encrypted&~=&~*&<&'string&~list'&>
26212 .cindex "&%encrypted%& ACL condition"
26213 .cindex "encryption" "checking in an ACL"
26214 .cindex "&ACL;" "testing for encryption"
26215 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
26216 name of the cipher suite in use is tested against the list. To test for
26217 encryption without testing for any specific cipher suite(s), set
26223 .vitem &*hosts&~=&~*&<&'&~host&~list'&>
26224 .cindex "&%hosts%& ACL condition"
26225 .cindex "host" "ACL checking"
26226 .cindex "&ACL;" "testing the client host"
26227 This condition tests that the calling host matches the host list. If you have
26228 name lookups or wildcarded host names and IP addresses in the same host list,
26229 you should normally put the IP addresses first. For example, you could have:
26231 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
26233 The lookup in this example uses the host name for its key. This is implied by
26234 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
26235 and it wouldn't matter which way round you had these two items.)
26237 The reason for the problem with host names lies in the left-to-right way that
26238 Exim processes lists. It can test IP addresses without doing any DNS lookups,
26239 but when it reaches an item that requires a host name, it fails if it cannot
26240 find a host name to compare with the pattern. If the above list is given in the
26241 opposite order, the &%accept%& statement fails for a host whose name cannot be
26242 found, even if its IP address is 10.9.8.7.
26244 If you really do want to do the name check first, and still recognize the IP
26245 address even if the name lookup fails, you can rewrite the ACL like this:
26247 accept hosts = dbm;/etc/friendly/hosts
26248 accept hosts = 10.9.8.7
26250 The default action on failing to find the host name is to assume that the host
26251 is not in the list, so the first &%accept%& statement fails. The second
26252 statement can then check the IP address.
26254 .vindex "&$host_data$&"
26255 If a &%hosts%& condition is satisfied by means of a lookup, the result
26256 of the lookup is made available in the &$host_data$& variable. This
26257 allows you, for example, to set up a statement like this:
26259 deny hosts = net-lsearch;/some/file
26260 message = $host_data
26262 which gives a custom error message for each denied host.
26264 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
26265 .cindex "&%local_parts%& ACL condition"
26266 .cindex "local part" "ACL checking"
26267 .cindex "&ACL;" "testing a local part"
26268 .vindex "&$local_part_data$&"
26269 This condition is relevant only after a RCPT command. It checks that the local
26270 part of the recipient address is in the list. If percent-hack processing is
26271 enabled, it is done before this test. If the check succeeds with a lookup, the
26272 result of the lookup is placed in &$local_part_data$&, which remains set until
26273 the next &%local_parts%& test.
26275 .vitem &*malware&~=&~*&<&'option'&>
26276 .cindex "&%malware%& ACL condition"
26277 .cindex "&ACL;" "virus scanning"
26278 .cindex "&ACL;" "scanning for viruses"
26279 This condition is available only when Exim is compiled with the
26280 content-scanning extension. It causes the incoming message to be scanned for
26281 viruses. For details, see chapter &<<CHAPexiscan>>&.
26283 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
26284 .cindex "&%mime_regex%& ACL condition"
26285 .cindex "&ACL;" "testing by regex matching"
26286 This condition is available only when Exim is compiled with the
26287 content-scanning extension, and it is allowed only in the ACL defined by
26288 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
26289 with any of the regular expressions. For details, see chapter
26292 .vitem &*ratelimit&~=&~*&<&'parameters'&>
26293 .cindex "rate limiting"
26294 This condition can be used to limit the rate at which a user or host submits
26295 messages. Details are given in section &<<SECTratelimiting>>&.
26297 .vitem &*recipients&~=&~*&<&'address&~list'&>
26298 .cindex "&%recipients%& ACL condition"
26299 .cindex "recipient" "ACL checking"
26300 .cindex "&ACL;" "testing a recipient"
26301 This condition is relevant only after a RCPT command. It checks the entire
26302 recipient address against a list of recipients.
26304 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
26305 .cindex "&%regex%& ACL condition"
26306 .cindex "&ACL;" "testing by regex matching"
26307 This condition is available only when Exim is compiled with the
26308 content-scanning extension, and is available only in the DATA, MIME, and
26309 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
26310 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
26312 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
26313 .cindex "&%sender_domains%& ACL condition"
26314 .cindex "sender" "ACL checking"
26315 .cindex "&ACL;" "testing a sender domain"
26316 .vindex "&$domain$&"
26317 .vindex "&$sender_address_domain$&"
26318 This condition tests the domain of the sender of the message against the given
26319 domain list. &*Note*&: The domain of the sender address is in
26320 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
26321 of this condition. This is an exception to the general rule for testing domain
26322 lists. It is done this way so that, if this condition is used in an ACL for a
26323 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
26324 influence the sender checking.
26326 &*Warning*&: It is a bad idea to use this condition on its own as a control on
26327 relaying, because sender addresses are easily, and commonly, forged.
26329 .vitem &*senders&~=&~*&<&'address&~list'&>
26330 .cindex "&%senders%& ACL condition"
26331 .cindex "sender" "ACL checking"
26332 .cindex "&ACL;" "testing a sender"
26333 This condition tests the sender of the message against the given list. To test
26334 for a bounce message, which has an empty sender, set
26338 &*Warning*&: It is a bad idea to use this condition on its own as a control on
26339 relaying, because sender addresses are easily, and commonly, forged.
26341 .vitem &*spam&~=&~*&<&'username'&>
26342 .cindex "&%spam%& ACL condition"
26343 .cindex "&ACL;" "scanning for spam"
26344 This condition is available only when Exim is compiled with the
26345 content-scanning extension. It causes the incoming message to be scanned by
26346 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
26348 .vitem &*verify&~=&~certificate*&
26349 .cindex "&%verify%& ACL condition"
26350 .cindex "TLS" "client certificate verification"
26351 .cindex "certificate" "verification of client"
26352 .cindex "&ACL;" "certificate verification"
26353 .cindex "&ACL;" "testing a TLS certificate"
26354 This condition is true in an SMTP session if the session is encrypted, and a
26355 certificate was received from the client, and the certificate was verified. The
26356 server requests a certificate only if the client matches &%tls_verify_hosts%&
26357 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
26359 .vitem &*verify&~=&~csa*&
26360 .cindex "CSA verification"
26361 This condition checks whether the sending host (the client) is authorized to
26362 send email. Details of how this works are given in section
26363 &<<SECTverifyCSA>>&.
26365 .vitem &*verify&~=&~header_sender/*&<&'options'&>
26366 .cindex "&%verify%& ACL condition"
26367 .cindex "&ACL;" "verifying sender in the header"
26368 .cindex "header lines" "verifying the sender in"
26369 .cindex "sender" "verifying in header"
26370 .cindex "verifying" "sender in header"
26371 This condition is relevant only in an ACL that is run after a message has been
26372 received, that is, in an ACL specified by &%acl_smtp_data%& or
26373 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
26374 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
26375 is loosely thought of as a &"sender"& address (hence the name of the test).
26376 However, an address that appears in one of these headers need not be an address
26377 that accepts bounce messages; only sender addresses in envelopes are required
26378 to accept bounces. Therefore, if you use the callout option on this check, you
26379 might want to arrange for a non-empty address in the MAIL command.
26381 Details of address verification and the options are given later, starting at
26382 section &<<SECTaddressverification>>& (callouts are described in section
26383 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
26384 condition to restrict it to bounce messages only:
26387 message = A valid sender header is required for bounces
26388 !verify = header_sender
26391 .vitem &*verify&~=&~header_syntax*&
26392 .cindex "&%verify%& ACL condition"
26393 .cindex "&ACL;" "verifying header syntax"
26394 .cindex "header lines" "verifying syntax"
26395 .cindex "verifying" "header syntax"
26396 This condition is relevant only in an ACL that is run after a message has been
26397 received, that is, in an ACL specified by &%acl_smtp_data%& or
26398 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
26399 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
26400 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
26401 permitted only in locally generated messages and from hosts that match
26402 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26405 Note that this condition is a syntax check only. However, a common spamming
26406 ploy used to be to send syntactically invalid headers such as
26410 and this condition can be used to reject such messages, though they are not as
26411 common as they used to be.
26413 .vitem &*verify&~=&~helo*&
26414 .cindex "&%verify%& ACL condition"
26415 .cindex "&ACL;" "verifying HELO/EHLO"
26416 .cindex "HELO" "verifying"
26417 .cindex "EHLO" "verifying"
26418 .cindex "verifying" "EHLO"
26419 .cindex "verifying" "HELO"
26420 This condition is true if a HELO or EHLO command has been received from the
26421 client host, and its contents have been verified. If there has been no previous
26422 attempt to verify the HELO/EHLO contents, it is carried out when this
26423 condition is encountered. See the description of the &%helo_verify_hosts%& and
26424 &%helo_try_verify_hosts%& options for details of how to request verification
26425 independently of this condition.
26427 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
26428 option), this condition is always true.
26431 .vitem &*verify&~=&~not_blind*&
26432 .cindex "verifying" "not blind"
26433 .cindex "bcc recipients, verifying none"
26434 This condition checks that there are no blind (bcc) recipients in the message.
26435 Every envelope recipient must appear either in a &'To:'& header line or in a
26436 &'Cc:'& header line for this condition to be true. Local parts are checked
26437 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
26438 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
26439 used only in a DATA or non-SMTP ACL.
26441 There are, of course, many legitimate messages that make use of blind (bcc)
26442 recipients. This check should not be used on its own for blocking messages.
26445 .vitem &*verify&~=&~recipient/*&<&'options'&>
26446 .cindex "&%verify%& ACL condition"
26447 .cindex "&ACL;" "verifying recipient"
26448 .cindex "recipient" "verifying"
26449 .cindex "verifying" "recipient"
26450 .vindex "&$address_data$&"
26451 This condition is relevant only after a RCPT command. It verifies the current
26452 recipient. Details of address verification are given later, starting at section
26453 &<<SECTaddressverification>>&. After a recipient has been verified, the value
26454 of &$address_data$& is the last value that was set while routing the address.
26455 This applies even if the verification fails. When an address that is being
26456 verified is redirected to a single address, verification continues with the new
26457 address, and in that case, the subsequent value of &$address_data$& is the
26458 value for the child address.
26460 .vitem &*verify&~=&~reverse_host_lookup*&
26461 .cindex "&%verify%& ACL condition"
26462 .cindex "&ACL;" "verifying host reverse lookup"
26463 .cindex "host" "verifying reverse lookup"
26464 This condition ensures that a verified host name has been looked up from the IP
26465 address of the client host. (This may have happened already if the host name
26466 was needed for checking a host list, or if the host matched &%host_lookup%&.)
26467 Verification ensures that the host name obtained from a reverse DNS lookup, or
26468 one of its aliases, does, when it is itself looked up in the DNS, yield the
26469 original IP address.
26471 If this condition is used for a locally generated message (that is, when there
26472 is no client host involved), it always succeeds.
26474 .vitem &*verify&~=&~sender/*&<&'options'&>
26475 .cindex "&%verify%& ACL condition"
26476 .cindex "&ACL;" "verifying sender"
26477 .cindex "sender" "verifying"
26478 .cindex "verifying" "sender"
26479 This condition is relevant only after a MAIL or RCPT command, or after a
26480 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
26481 the message's sender is empty (that is, this is a bounce message), the
26482 condition is true. Otherwise, the sender address is verified.
26484 .vindex "&$address_data$&"
26485 .vindex "&$sender_address_data$&"
26486 If there is data in the &$address_data$& variable at the end of routing, its
26487 value is placed in &$sender_address_data$& at the end of verification. This
26488 value can be used in subsequent conditions and modifiers in the same ACL
26489 statement. It does not persist after the end of the current statement. If you
26490 want to preserve the value for longer, you can save it in an ACL variable.
26492 Details of verification are given later, starting at section
26493 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
26494 to avoid doing it more than once per message.
26496 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
26497 .cindex "&%verify%& ACL condition"
26498 This is a variation of the previous option, in which a modified address is
26499 verified as a sender.
26504 .section "Using DNS lists" "SECTmorednslists"
26505 .cindex "DNS list" "in ACL"
26506 .cindex "black list (DNS)"
26507 .cindex "&ACL;" "testing a DNS list"
26508 In its simplest form, the &%dnslists%& condition tests whether the calling host
26509 is on at least one of a number of DNS lists by looking up the inverted IP
26510 address in one or more DNS domains. (Note that DNS list domains are not mail
26511 domains, so the &`+`& syntax for named lists doesn't work - it is used for
26512 special options instead.) For example, if the calling host's IP
26513 address is 192.168.62.43, and the ACL statement is
26515 deny dnslists = blackholes.mail-abuse.org : \
26516 dialups.mail-abuse.org
26518 the following records are looked up:
26520 43.62.168.192.blackholes.mail-abuse.org
26521 43.62.168.192.dialups.mail-abuse.org
26523 As soon as Exim finds an existing DNS record, processing of the list stops.
26524 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
26525 to test that a host is on more than one list (an &"and"& conjunction), you can
26526 use two separate conditions:
26528 deny dnslists = blackholes.mail-abuse.org
26529 dnslists = dialups.mail-abuse.org
26531 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
26532 behaves as if the host does not match the list item, that is, as if the DNS
26533 record does not exist. If there are further items in the DNS list, they are
26536 This is usually the required action when &%dnslists%& is used with &%deny%&
26537 (which is the most common usage), because it prevents a DNS failure from
26538 blocking mail. However, you can change this behaviour by putting one of the
26539 following special items in the list:
26541 &`+include_unknown `& behave as if the item is on the list
26542 &`+exclude_unknown `& behave as if the item is not on the list (default)
26543 &`+defer_unknown `& give a temporary error
26545 .cindex "&`+include_unknown`&"
26546 .cindex "&`+exclude_unknown`&"
26547 .cindex "&`+defer_unknown`&"
26548 Each of these applies to any subsequent items on the list. For example:
26550 deny dnslists = +defer_unknown : foo.bar.example
26552 Testing the list of domains stops as soon as a match is found. If you want to
26553 warn for one list and block for another, you can use two different statements:
26555 deny dnslists = blackholes.mail-abuse.org
26556 warn message = X-Warn: sending host is on dialups list
26557 dnslists = dialups.mail-abuse.org
26559 DNS list lookups are cached by Exim for the duration of the SMTP session,
26560 so a lookup based on the IP address is done at most once for any incoming
26561 connection. Exim does not share information between multiple incoming
26562 connections (but your local name server cache should be active).
26566 .section "Specifying the IP address for a DNS list lookup" "SECID201"
26567 .cindex "DNS list" "keyed by explicit IP address"
26568 By default, the IP address that is used in a DNS list lookup is the IP address
26569 of the calling host. However, you can specify another IP address by listing it
26570 after the domain name, introduced by a slash. For example:
26572 deny dnslists = black.list.tld/192.168.1.2
26574 This feature is not very helpful with explicit IP addresses; it is intended for
26575 use with IP addresses that are looked up, for example, the IP addresses of the
26576 MX hosts or nameservers of an email sender address. For an example, see section
26577 &<<SECTmulkeyfor>>& below.
26582 .section "DNS lists keyed on domain names" "SECID202"
26583 .cindex "DNS list" "keyed by domain name"
26584 There are some lists that are keyed on domain names rather than inverted IP
26585 addresses (see for example the &'domain based zones'& link at
26586 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
26587 with these lists. You can change the name that is looked up in a DNS list by
26588 listing it after the domain name, introduced by a slash. For example,
26590 deny message = Sender's domain is listed at $dnslist_domain
26591 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
26593 This particular example is useful only in ACLs that are obeyed after the
26594 RCPT or DATA commands, when a sender address is available. If (for
26595 example) the message's sender is &'user@tld.example'& the name that is looked
26596 up by this example is
26598 tld.example.dsn.rfc-ignorant.org
26600 A single &%dnslists%& condition can contain entries for both names and IP
26601 addresses. For example:
26603 deny dnslists = sbl.spamhaus.org : \
26604 dsn.rfc-ignorant.org/$sender_address_domain
26606 The first item checks the sending host's IP address; the second checks a domain
26607 name. The whole condition is true if either of the DNS lookups succeeds.
26612 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
26613 .cindex "DNS list" "multiple keys for"
26614 The syntax described above for looking up explicitly-defined values (either
26615 names or IP addresses) in a DNS blacklist is a simplification. After the domain
26616 name for the DNS list, what follows the slash can in fact be a list of items.
26617 As with all lists in Exim, the default separator is a colon. However, because
26618 this is a sublist within the list of DNS blacklist domains, it is necessary
26619 either to double the separators like this:
26621 dnslists = black.list.tld/name.1::name.2
26623 or to change the separator character, like this:
26625 dnslists = black.list.tld/<;name.1;name.2
26627 If an item in the list is an IP address, it is inverted before the DNS
26628 blacklist domain is appended. If it is not an IP address, no inversion
26629 occurs. Consider this condition:
26631 dnslists = black.list.tld/<;192.168.1.2;a.domain
26633 The DNS lookups that occur are:
26635 2.1.168.192.black.list.tld
26636 a.domain.black.list.tld
26638 Once a DNS record has been found (that matches a specific IP return
26639 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
26640 are done. If there is a temporary DNS error, the rest of the sublist of domains
26641 or IP addresses is tried. A temporary error for the whole dnslists item occurs
26642 only if no other DNS lookup in this sublist succeeds. In other words, a
26643 successful lookup for any of the items in the sublist overrides a temporary
26644 error for a previous item.
26646 The ability to supply a list of items after the slash is in some sense just a
26647 syntactic convenience. These two examples have the same effect:
26649 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
26650 dnslists = black.list.tld/a.domain::b.domain
26652 However, when the data for the list is obtained from a lookup, the second form
26653 is usually much more convenient. Consider this example:
26655 deny message = The mail servers for the domain \
26656 $sender_address_domain \
26657 are listed at $dnslist_domain ($dnslist_value); \
26659 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
26660 ${lookup dnsdb {>|mxh=\
26661 $sender_address_domain} }} }
26663 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
26664 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
26665 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
26666 of expanding the condition might be something like this:
26668 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
26670 Thus, this example checks whether or not the IP addresses of the sender
26671 domain's mail servers are on the Spamhaus black list.
26673 The key that was used for a successful DNS list lookup is put into the variable
26674 &$dnslist_matched$& (see section &<<SECID204>>&).
26679 .section "Data returned by DNS lists" "SECID203"
26680 .cindex "DNS list" "data returned from"
26681 DNS lists are constructed using address records in the DNS. The original RBL
26682 just used the address 127.0.0.1 on the right hand side of each record, but the
26683 RBL+ list and some other lists use a number of values with different meanings.
26684 The values used on the RBL+ list are:
26688 127.1.0.3 DUL and RBL
26690 127.1.0.5 RSS and RBL
26691 127.1.0.6 RSS and DUL
26692 127.1.0.7 RSS and DUL and RBL
26694 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
26695 different values. Some DNS lists may return more than one address record;
26696 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
26699 .section "Variables set from DNS lists" "SECID204"
26700 .cindex "expansion" "variables, set from DNS list"
26701 .cindex "DNS list" "variables set from"
26702 .vindex "&$dnslist_domain$&"
26703 .vindex "&$dnslist_matched$&"
26704 .vindex "&$dnslist_text$&"
26705 .vindex "&$dnslist_value$&"
26706 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
26707 the name of the overall domain that matched (for example,
26708 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
26709 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
26710 the DNS record. When the key is an IP address, it is not reversed in
26711 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
26712 cases, for example:
26714 deny dnslists = spamhaus.example
26716 the key is also available in another variable (in this case,
26717 &$sender_host_address$&). In more complicated cases, however, this is not true.
26718 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
26719 might generate a dnslists lookup like this:
26721 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
26723 If this condition succeeds, the value in &$dnslist_matched$& might be
26724 &`192.168.6.7`& (for example).
26726 If more than one address record is returned by the DNS lookup, all the IP
26727 addresses are included in &$dnslist_value$&, separated by commas and spaces.
26728 The variable &$dnslist_text$& contains the contents of any associated TXT
26729 record. For lists such as RBL+ the TXT record for a merged entry is often not
26730 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
26733 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
26734 &-- although these appear before the condition in the ACL, they are not
26735 expanded until after it has failed. For example:
26737 deny hosts = !+local_networks
26738 message = $sender_host_address is listed \
26740 dnslists = rbl-plus.mail-abuse.example
26745 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
26746 .cindex "DNS list" "matching specific returned data"
26747 You can add an equals sign and an IP address after a &%dnslists%& domain name
26748 in order to restrict its action to DNS records with a matching right hand side.
26751 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
26753 rejects only those hosts that yield 127.0.0.2. Without this additional data,
26754 any address record is considered to be a match. For the moment, we assume
26755 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
26756 describes how multiple records are handled.
26758 More than one IP address may be given for checking, using a comma as a
26759 separator. These are alternatives &-- if any one of them matches, the
26760 &%dnslists%& condition is true. For example:
26762 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
26764 If you want to specify a constraining address list and also specify names or IP
26765 addresses to be looked up, the constraining address list must be specified
26766 first. For example:
26768 deny dnslists = dsn.rfc-ignorant.org\
26769 =127.0.0.2/$sender_address_domain
26772 If the character &`&&`& is used instead of &`=`&, the comparison for each
26773 listed IP address is done by a bitwise &"and"& instead of by an equality test.
26774 In other words, the listed addresses are used as bit masks. The comparison is
26775 true if all the bits in the mask are present in the address that is being
26776 tested. For example:
26778 dnslists = a.b.c&0.0.0.3
26780 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
26781 want to test whether one bit or another bit is present (as opposed to both
26782 being present), you must use multiple values. For example:
26784 dnslists = a.b.c&0.0.0.1,0.0.0.2
26786 matches if the final component of the address is an odd number or two times
26791 .section "Negated DNS matching conditions" "SECID205"
26792 You can supply a negative list of IP addresses as part of a &%dnslists%&
26795 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
26797 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
26798 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
26800 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
26802 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
26803 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
26804 words, the result of the test is inverted if an exclamation mark appears before
26805 the &`=`& (or the &`&&`&) sign.
26807 &*Note*&: This kind of negation is not the same as negation in a domain,
26808 host, or address list (which is why the syntax is different).
26810 If you are using just one list, the negation syntax does not gain you much. The
26811 previous example is precisely equivalent to
26813 deny dnslists = a.b.c
26814 !dnslists = a.b.c=127.0.0.2,127.0.0.3
26816 However, if you are using multiple lists, the negation syntax is clearer.
26817 Consider this example:
26819 deny dnslists = sbl.spamhaus.org : \
26821 dnsbl.njabl.org!=127.0.0.3 : \
26824 Using only positive lists, this would have to be:
26826 deny dnslists = sbl.spamhaus.org : \
26828 deny dnslists = dnsbl.njabl.org
26829 !dnslists = dnsbl.njabl.org=127.0.0.3
26830 deny dnslists = relays.ordb.org
26832 which is less clear, and harder to maintain.
26837 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
26838 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
26839 thereby providing more than one IP address. When an item in a &%dnslists%& list
26840 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
26841 the match to specific results from the DNS lookup, there are two ways in which
26842 the checking can be handled. For example, consider the condition:
26844 dnslists = a.b.c=127.0.0.1
26846 What happens if the DNS lookup for the incoming IP address yields both
26847 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
26848 condition true because at least one given value was found, or is it false
26849 because at least one of the found values was not listed? And how does this
26850 affect negated conditions? Both possibilities are provided for with the help of
26851 additional separators &`==`& and &`=&&`&.
26854 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
26855 IP addresses matches one of the listed addresses. For the example above, the
26856 condition is true because 127.0.0.1 matches.
26858 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
26859 looked up IP addresses matches one of the listed addresses. If the condition is
26862 dnslists = a.b.c==127.0.0.1
26864 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26865 false because 127.0.0.2 is not listed. You would need to have:
26867 dnslists = a.b.c==127.0.0.1,127.0.0.2
26869 for the condition to be true.
26872 When &`!`& is used to negate IP address matching, it inverts the result, giving
26873 the precise opposite of the behaviour above. Thus:
26875 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
26876 addresses matches one of the listed addresses. Consider:
26878 dnslists = a.b.c!&0.0.0.1
26880 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26881 false because 127.0.0.1 matches.
26883 If &`!==`& or &`!=&&`& is used, the condition is true there is at least one
26884 looked up IP address that does not match. Consider:
26886 dnslists = a.b.c!=&0.0.0.1
26888 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26889 true, because 127.0.0.2 does not match. You would need to have:
26891 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
26893 for the condition to be false.
26895 When the DNS lookup yields only a single IP address, there is no difference
26896 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
26901 .section "Detailed information from merged DNS lists" "SECTmordetinf"
26902 .cindex "DNS list" "information from merged"
26903 When the facility for restricting the matching IP values in a DNS list is used,
26904 the text from the TXT record that is set in &$dnslist_text$& may not reflect
26905 the true reason for rejection. This happens when lists are merged and the IP
26906 address in the A record is used to distinguish them; unfortunately there is
26907 only one TXT record. One way round this is not to use merged lists, but that
26908 can be inefficient because it requires multiple DNS lookups where one would do
26909 in the vast majority of cases when the host of interest is not on any of the
26912 A less inefficient way of solving this problem is available. If
26913 two domain names, comma-separated, are given, the second is used first to
26914 do an initial check, making use of any IP value restrictions that are set.
26915 If there is a match, the first domain is used, without any IP value
26916 restrictions, to get the TXT record. As a byproduct of this, there is also
26917 a check that the IP being tested is indeed on the first list. The first
26918 domain is the one that is put in &$dnslist_domain$&. For example:
26921 rejected because $sender_host_address is blacklisted \
26922 at $dnslist_domain\n$dnslist_text
26924 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
26925 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
26927 For the first blacklist item, this starts by doing a lookup in
26928 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
26929 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
26930 value, and as long as something is found, it looks for the corresponding TXT
26931 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
26932 The second blacklist item is processed similarly.
26934 If you are interested in more than one merged list, the same list must be
26935 given several times, but because the results of the DNS lookups are cached,
26936 the DNS calls themselves are not repeated. For example:
26938 reject dnslists = \
26939 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
26940 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
26941 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
26942 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
26944 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
26945 values matches (or if no record is found), this is the only lookup that is
26946 done. Only if there is a match is one of the more specific lists consulted.
26950 .section "DNS lists and IPv6" "SECTmorednslistslast"
26951 .cindex "IPv6" "DNS black lists"
26952 .cindex "DNS list" "IPv6 usage"
26953 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
26954 nibble by nibble. For example, if the calling host's IP address is
26955 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
26957 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
26958 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
26960 (split over two lines here to fit on the page). Unfortunately, some of the DNS
26961 lists contain wildcard records, intended for IPv4, that interact badly with
26962 IPv6. For example, the DNS entry
26964 *.3.some.list.example. A 127.0.0.1
26966 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
26967 Unfortunately, it also matches the entire 3::/4 IPv6 network.
26969 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
26970 &%condition%& condition, as in this example:
26972 deny condition = ${if isip4{$sender_host_address}}
26973 dnslists = some.list.example
26976 .section "Rate limiting incoming messages" "SECTratelimiting"
26977 .cindex "rate limiting" "client sending"
26978 .cindex "limiting client sending rates"
26979 .oindex "&%smtp_ratelimit_*%&"
26980 The &%ratelimit%& ACL condition can be used to measure and control the rate at
26981 which clients can send email. This is more powerful than the
26982 &%smtp_ratelimit_*%& options, because those options control the rate of
26983 commands in a single SMTP session only, whereas the &%ratelimit%& condition
26984 works across all connections (concurrent and sequential) from the same client
26985 host. The syntax of the &%ratelimit%& condition is:
26987 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
26989 If the average client sending rate is less than &'m'& messages per time
26990 period &'p'& then the condition is false; otherwise it is true.
26992 As a side-effect, the &%ratelimit%& condition sets the expansion variable
26993 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
26994 configured value of &'m'&, and &$sender_rate_period$& to the configured value
26997 The parameter &'p'& is the smoothing time constant, in the form of an Exim
26998 time interval, for example, &`8h`& for eight hours. A larger time constant
26999 means that it takes Exim longer to forget a client's past behaviour. The
27000 parameter &'m'& is the maximum number of messages that a client is permitted to
27001 send in each time interval. It also specifies the number of messages permitted
27002 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
27003 constant, you can allow a client to send more messages in a burst without
27004 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
27005 both small, messages must be sent at an even rate.
27007 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
27008 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
27009 when deploying the &%ratelimit%& ACL condition. The script prints usage
27010 instructions when it is run with no arguments.
27012 The key is used to look up the data for calculating the client's average
27013 sending rate. This data is stored in Exim's spool directory, alongside the
27014 retry and other hints databases. The default key is &$sender_host_address$&,
27015 which means Exim computes the sending rate of each client host IP address.
27016 By changing the key you can change how Exim identifies clients for the purpose
27017 of ratelimiting. For example, to limit the sending rate of each authenticated
27018 user, independent of the computer they are sending from, set the key to
27019 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
27020 example, &$authenticated_id$& is only meaningful if the client has
27021 authenticated (which you can check with the &%authenticated%& ACL condition).
27023 The lookup key does not have to identify clients: If you want to limit the
27024 rate at which a recipient receives messages, you can use the key
27025 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
27028 Internally, Exim appends the smoothing constant &'p'& and the options onto the
27029 lookup key because they alter the meaning of the stored data. This is not true
27030 for the limit &'m'&, so you can alter the configured maximum rate and Exim will
27031 still remember clients' past behaviour, but if you alter the other ratelimit
27032 parameters Exim forgets past behaviour.
27034 Each &%ratelimit%& condition can have up to three options. One option
27035 specifies what Exim measures the rate of, and the second specifies how Exim
27036 handles excessively fast clients. The third option can be &`noupdate`&, to
27037 disable updating of the ratelimiting database (see section &<<rearatdat>>&).
27038 The options are separated by a slash, like the other parameters. They may
27039 appear in any order.
27041 .section "Ratelimit options for what is being measured" "ratoptmea"
27042 The &%per_conn%& option limits the client's connection rate.
27044 The &%per_mail%& option limits the client's rate of sending messages. This is
27045 the default if none of the &%per_*%& options is specified.
27047 The &%per_byte%& option limits the sender's email bandwidth. Note that it is
27048 best to use this option in the DATA ACL; if it is used in an earlier ACL it
27049 relies on the SIZE parameter specified by the client in its MAIL command,
27050 which may be inaccurate or completely missing. You can follow the limit &'m'&
27051 in the configuration with K, M, or G to specify limits in kilobytes,
27052 megabytes, or gigabytes, respectively.
27054 The &%per_rcpt%& option causes Exim to limit the rate at which
27055 recipients are accepted. To be effective, it would need to be used in
27056 either the &%acl_smtp_rcpt%& or the &%acl_not_smtp%& ACL. In the
27057 &%acl_smtp_rcpt%& ACL, the number of recipients is incremented by one.
27058 In the case of a locally submitted message in the &%acl_not_smtp%& ACL,
27059 the number of recipients is incremented by the &%$recipients_count%&
27060 for the entire message. Note that in either case the rate limiting
27061 engine will see a message with many recipients as a large high-speed
27064 The &%per_cmd%& option causes Exim to recompute the rate every time the
27065 condition is processed. This can be used to limit the SMTP command rate.
27066 This command is essentially an alias of &%per_rcpt%& to make it clear
27067 that the effect is to limit the rate at which individual commands,
27068 rather than recipients, are accepted.
27070 .section "Ratelimit options for handling fast clients" "ratophanfas"
27071 If a client's average rate is greater than the maximum, the rate limiting
27072 engine can react in two possible ways, depending on the presence of the
27073 &%strict%& or &%leaky%& options. This is independent of the other
27074 counter-measures (such as rejecting the message) that may be specified by the
27075 rest of the ACL. The default mode is leaky, which avoids a sender's
27076 over-aggressive retry rate preventing it from getting any email through.
27078 The &%strict%& option means that the client's recorded rate is always
27079 updated. The effect of this is that Exim measures the client's average rate
27080 of attempts to send email, which can be much higher than the maximum it is
27081 actually allowed. If the client is over the limit it may be subjected to
27082 counter-measures by the ACL until it slows down below the maximum rate. If
27083 the client stops attempting to send email for the time specified in the &'p'&
27084 parameter then its computed rate will decay exponentially to 37% of its peak
27085 value. You can work out the time (the number of smoothing periods) that a
27086 client is subjected to counter-measures after an over-limit burst with this
27089 ln(peakrate/maxrate)
27091 The &%leaky%& (default) option means that the client's recorded rate is not
27092 updated if it is above the limit. The effect of this is that Exim measures the
27093 client's average rate of successfully sent email, which cannot be greater than
27094 the maximum allowed. If the client is over the limit it may suffer some
27095 counter-measures (as specified in the ACL), but it will still be able to send
27096 email at the configured maximum rate, whatever the rate of its attempts. This
27097 is generally the better choice if you have clients that retry automatically.
27099 .section "Using rate limiting" "useratlim"
27100 Exim's other ACL facilities are used to define what counter-measures are taken
27101 when the rate limit is exceeded. This might be anything from logging a warning
27102 (for example, while measuring existing sending rates in order to define
27103 policy), through time delays to slow down fast senders, up to rejecting the
27104 message. For example:
27106 # Log all senders' rates
27107 warn ratelimit = 0 / 1h / strict
27108 log_message = Sender rate $sender_rate / $sender_rate_period
27110 # Slow down fast senders; note the need to truncate $sender_rate
27111 # at the decimal point.
27112 warn ratelimit = 100 / 1h / per_rcpt / strict
27113 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
27114 $sender_rate_limit }s
27116 # Keep authenticated users under control
27117 deny authenticated = *
27118 ratelimit = 100 / 1d / strict / $authenticated_id
27120 # System-wide rate limit
27121 defer message = Sorry, too busy. Try again later.
27122 ratelimit = 10 / 1s / $primary_hostname
27124 # Restrict incoming rate from each host, with a default
27125 # set using a macro and special cases looked up in a table.
27126 defer message = Sender rate exceeds $sender_rate_limit \
27127 messages per $sender_rate_period
27128 ratelimit = ${lookup {$sender_host_address} \
27129 cdb {DB/ratelimits.cdb} \
27130 {$value} {RATELIMIT} }
27132 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
27133 especially with the &%per_rcpt%& option, you may suffer from a performance
27134 bottleneck caused by locking on the ratelimit hints database. Apart from
27135 making your ACLs less complicated, you can reduce the problem by using a
27136 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
27137 this means that Exim will lose its hints data after a reboot (including retry
27138 hints, the callout cache, and ratelimit data).
27141 .section "Reading ratelimit data without updating" "rearatdat"
27142 .cindex "rate limitint" "reading data without updating"
27143 If the &%noupdate%& option is present on a &%ratelimit%& ACL condition, Exim
27144 computes the rate and checks the limit as normal, but it does not update the
27145 saved data. This means that, in relevant ACLs, it is possible to lookup the
27146 existence of a specified (or auto-generated) ratelimit key without incrementing
27147 the ratelimit counter for that key. In order for this to be useful, another ACL
27148 entry must set the rate for the same key (otherwise it will always be zero).
27152 deny ratelimit = 100 / 5m / strict / per_cmd / noupdate
27153 log_message = RATE: $sender_rate/$sender_rate_period \
27154 (max $sender_rate_limit)
27157 &'... some other logic and tests...'&
27161 warn ratelimit = 100 / 5m / strict / per_cmd
27162 condition = ${if le{$sender_rate}{$sender_rate_limit}}
27163 logwrite = RATE UPDATE: $sender_rate/$sender_rate_period \
27164 (max $sender_rate_limit)
27166 In this example, the rate is tested and used to deny access (when it is too
27167 high) in the connect ACL, but the actual computation of the remembered rate
27168 happens later, on a per-command basis, in another ACL.
27172 .section "Address verification" "SECTaddressverification"
27173 .cindex "verifying address" "options for"
27174 .cindex "policy control" "address verification"
27175 Several of the &%verify%& conditions described in section
27176 &<<SECTaclconditions>>& cause addresses to be verified. Section
27177 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
27178 The verification conditions can be followed by options that modify the
27179 verification process. The options are separated from the keyword and from each
27180 other by slashes, and some of them contain parameters. For example:
27182 verify = sender/callout
27183 verify = recipient/defer_ok/callout=10s,defer_ok
27185 The first stage of address verification, which always happens, is to run the
27186 address through the routers, in &"verify mode"&. Routers can detect the
27187 difference between verification and routing for delivery, and their actions can
27188 be varied by a number of generic options such as &%verify%& and &%verify_only%&
27189 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
27190 The available options are as follows:
27193 If the &%callout%& option is specified, successful routing to one or more
27194 remote hosts is followed by a &"callout"& to those hosts as an additional
27195 check. Callouts and their sub-options are discussed in the next section.
27197 If there is a defer error while doing verification routing, the ACL
27198 normally returns &"defer"&. However, if you include &%defer_ok%& in the
27199 options, the condition is forced to be true instead. Note that this is a main
27200 verification option as well as a suboption for callouts.
27202 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
27203 discusses the reporting of sender address verification failures.
27205 The &%success_on_redirect%& option causes verification always to succeed
27206 immediately after a successful redirection. By default, if a redirection
27207 generates just one address, that address is also verified. See further
27208 discussion in section &<<SECTredirwhilveri>>&.
27211 .cindex "verifying address" "differentiating failures"
27212 .vindex "&$recipient_verify_failure$&"
27213 .vindex "&$sender_verify_failure$&"
27214 .vindex "&$acl_verify_message$&"
27215 After an address verification failure, &$acl_verify_message$& contains the
27216 error message that is associated with the failure. It can be preserved by
27219 warn !verify = sender
27220 set acl_m0 = $acl_verify_message
27222 If you are writing your own custom rejection message or log message when
27223 denying access, you can use this variable to include information about the
27224 verification failure.
27226 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
27227 appropriate) contains one of the following words:
27230 &%qualify%&: The address was unqualified (no domain), and the message
27231 was neither local nor came from an exempted host.
27233 &%route%&: Routing failed.
27235 &%mail%&: Routing succeeded, and a callout was attempted; rejection
27236 occurred at or before the MAIL command (that is, on initial
27237 connection, HELO, or MAIL).
27239 &%recipient%&: The RCPT command in a callout was rejected.
27241 &%postmaster%&: The postmaster check in a callout was rejected.
27244 The main use of these variables is expected to be to distinguish between
27245 rejections of MAIL and rejections of RCPT in callouts.
27250 .section "Callout verification" "SECTcallver"
27251 .cindex "verifying address" "by callout"
27252 .cindex "callout" "verification"
27253 .cindex "SMTP" "callout verification"
27254 For non-local addresses, routing verifies the domain, but is unable to do any
27255 checking of the local part. There are situations where some means of verifying
27256 the local part is desirable. One way this can be done is to make an SMTP
27257 &'callback'& to a delivery host for the sender address or a &'callforward'& to
27258 a subsequent host for a recipient address, to see if the host accepts the
27259 address. We use the term &'callout'& to cover both cases. Note that for a
27260 sender address, the callback is not to the client host that is trying to
27261 deliver the message, but to one of the hosts that accepts incoming mail for the
27264 Exim does not do callouts by default. If you want them to happen, you must
27265 request them by setting appropriate options on the &%verify%& condition, as
27266 described below. This facility should be used with care, because it can add a
27267 lot of resource usage to the cost of verifying an address. However, Exim does
27268 cache the results of callouts, which helps to reduce the cost. Details of
27269 caching are in section &<<SECTcallvercache>>&.
27271 Recipient callouts are usually used only between hosts that are controlled by
27272 the same administration. For example, a corporate gateway host could use
27273 callouts to check for valid recipients on an internal mailserver. A successful
27274 callout does not guarantee that a real delivery to the address would succeed;
27275 on the other hand, a failing callout does guarantee that a delivery would fail.
27277 If the &%callout%& option is present on a condition that verifies an address, a
27278 second stage of verification occurs if the address is successfully routed to
27279 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
27280 &(manualroute)& router, where the router specifies the hosts. However, if a
27281 router that does not set up hosts routes to an &(smtp)& transport with a
27282 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
27283 &%hosts_override%& set, its hosts are always used, whether or not the router
27284 supplies a host list.
27286 The port that is used is taken from the transport, if it is specified and is a
27287 remote transport. (For routers that do verification only, no transport need be
27288 specified.) Otherwise, the default SMTP port is used. If a remote transport
27289 specifies an outgoing interface, this is used; otherwise the interface is not
27290 specified. Likewise, the text that is used for the HELO command is taken from
27291 the transport's &%helo_data%& option; if there is no transport, the value of
27292 &$smtp_active_hostname$& is used.
27294 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
27295 test whether a bounce message could be delivered to the sender address. The
27296 following SMTP commands are sent:
27298 &`HELO `&<&'local host name'&>
27300 &`RCPT TO:`&<&'the address to be tested'&>
27303 LHLO is used instead of HELO if the transport's &%protocol%& option is
27306 A recipient callout check is similar. By default, it also uses an empty address
27307 for the sender. This default is chosen because most hosts do not make use of
27308 the sender address when verifying a recipient. Using the same address means
27309 that a single cache entry can be used for each recipient. Some sites, however,
27310 do make use of the sender address when verifying. These are catered for by the
27311 &%use_sender%& and &%use_postmaster%& options, described in the next section.
27313 If the response to the RCPT command is a 2&'xx'& code, the verification
27314 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
27315 Exim tries the next host, if any. If there is a problem with all the remote
27316 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
27317 &%callout%& option is given, in which case the condition is forced to succeed.
27319 .cindex "SMTP" "output flushing, disabling for callout"
27320 A callout may take a little time. For this reason, Exim normally flushes SMTP
27321 output before performing a callout in an ACL, to avoid unexpected timeouts in
27322 clients when the SMTP PIPELINING extension is in use. The flushing can be
27323 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
27328 .section "Additional parameters for callouts" "CALLaddparcall"
27329 .cindex "callout" "additional parameters for"
27330 The &%callout%& option can be followed by an equals sign and a number of
27331 optional parameters, separated by commas. For example:
27333 verify = recipient/callout=10s,defer_ok
27335 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
27336 separate verify options, is retained for backwards compatibility, but is now
27337 deprecated. The additional parameters for &%callout%& are as follows:
27341 .vitem <&'a&~time&~interval'&>
27342 .cindex "callout" "timeout, specifying"
27343 This specifies the timeout that applies for the callout attempt to each host.
27346 verify = sender/callout=5s
27348 The default is 30 seconds. The timeout is used for each response from the
27349 remote host. It is also used for the initial connection, unless overridden by
27350 the &%connect%& parameter.
27353 .vitem &*connect&~=&~*&<&'time&~interval'&>
27354 .cindex "callout" "connection timeout, specifying"
27355 This parameter makes it possible to set a different (usually smaller) timeout
27356 for making the SMTP connection. For example:
27358 verify = sender/callout=5s,connect=1s
27360 If not specified, this timeout defaults to the general timeout value.
27362 .vitem &*defer_ok*&
27363 .cindex "callout" "defer, action on"
27364 When this parameter is present, failure to contact any host, or any other kind
27365 of temporary error, is treated as success by the ACL. However, the cache is not
27366 updated in this circumstance.
27368 .vitem &*fullpostmaster*&
27369 .cindex "callout" "full postmaster check"
27370 This operates like the &%postmaster%& option (see below), but if the check for
27371 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
27372 accordance with the specification in RFC 2821. The RFC states that the
27373 unqualified address &'postmaster'& should be accepted.
27376 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
27377 .cindex "callout" "sender when verifying header"
27378 When verifying addresses in header lines using the &%header_sender%&
27379 verification option, Exim behaves by default as if the addresses are envelope
27380 sender addresses from a message. Callout verification therefore tests to see
27381 whether a bounce message could be delivered, by using an empty address in the
27382 MAIL command. However, it is arguable that these addresses might never be used
27383 as envelope senders, and could therefore justifiably reject bounce messages
27384 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
27385 address to use in the MAIL command. For example:
27387 require verify = header_sender/callout=mailfrom=abcd@x.y.z
27389 This parameter is available only for the &%header_sender%& verification option.
27392 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
27393 .cindex "callout" "overall timeout, specifying"
27394 This parameter sets an overall timeout for performing a callout verification.
27397 verify = sender/callout=5s,maxwait=30s
27399 This timeout defaults to four times the callout timeout for individual SMTP
27400 commands. The overall timeout applies when there is more than one host that can
27401 be tried. The timeout is checked before trying the next host. This prevents
27402 very long delays if there are a large number of hosts and all are timing out
27403 (for example, when network connections are timing out).
27406 .vitem &*no_cache*&
27407 .cindex "callout" "cache, suppressing"
27408 .cindex "caching callout, suppressing"
27409 When this parameter is given, the callout cache is neither read nor updated.
27411 .vitem &*postmaster*&
27412 .cindex "callout" "postmaster; checking"
27413 When this parameter is set, a successful callout check is followed by a similar
27414 check for the local part &'postmaster'& at the same domain. If this address is
27415 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
27416 the postmaster check is recorded in a cache record; if it is a failure, this is
27417 used to fail subsequent callouts for the domain without a connection being
27418 made, until the cache record expires.
27420 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
27421 The postmaster check uses an empty sender in the MAIL command by default.
27422 You can use this parameter to do a postmaster check using a different address.
27425 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
27427 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
27428 one overrides. The &%postmaster%& parameter is equivalent to this example:
27430 require verify = sender/callout=postmaster_mailfrom=
27432 &*Warning*&: The caching arrangements for postmaster checking do not take
27433 account of the sender address. It is assumed that either the empty address or
27434 a fixed non-empty address will be used. All that Exim remembers is that the
27435 postmaster check for the domain succeeded or failed.
27439 .cindex "callout" "&""random""& check"
27440 When this parameter is set, before doing the normal callout check, Exim does a
27441 check for a &"random"& local part at the same domain. The local part is not
27442 really random &-- it is defined by the expansion of the option
27443 &%callout_random_local_part%&, which defaults to
27445 $primary_host_name-$tod_epoch-testing
27447 The idea here is to try to determine whether the remote host accepts all local
27448 parts without checking. If it does, there is no point in doing callouts for
27449 specific local parts. If the &"random"& check succeeds, the result is saved in
27450 a cache record, and used to force the current and subsequent callout checks to
27451 succeed without a connection being made, until the cache record expires.
27453 .vitem &*use_postmaster*&
27454 .cindex "callout" "sender for recipient check"
27455 This parameter applies to recipient callouts only. For example:
27457 deny !verify = recipient/callout=use_postmaster
27459 .vindex "&$qualify_domain$&"
27460 It causes a non-empty postmaster address to be used in the MAIL command when
27461 performing the callout for the recipient, and also for a &"random"& check if
27462 that is configured. The local part of the address is &`postmaster`& and the
27463 domain is the contents of &$qualify_domain$&.
27465 .vitem &*use_sender*&
27466 This option applies to recipient callouts only. For example:
27468 require verify = recipient/callout=use_sender
27470 It causes the message's actual sender address to be used in the MAIL
27471 command when performing the callout, instead of an empty address. There is no
27472 need to use this option unless you know that the called hosts make use of the
27473 sender when checking recipients. If used indiscriminately, it reduces the
27474 usefulness of callout caching.
27477 If you use any of the parameters that set a non-empty sender for the MAIL
27478 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
27479 &%use_sender%&), you should think about possible loops. Recipient checking is
27480 usually done between two hosts that are under the same management, and the host
27481 that receives the callouts is not normally configured to do callouts itself.
27482 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
27483 these circumstances.
27485 However, if you use a non-empty sender address for a callout to an arbitrary
27486 host, there is the likelihood that the remote host will itself initiate a
27487 callout check back to your host. As it is checking what appears to be a message
27488 sender, it is likely to use an empty address in MAIL, thus avoiding a
27489 callout loop. However, to be on the safe side it would be best to set up your
27490 own ACLs so that they do not do sender verification checks when the recipient
27491 is the address you use for header sender or postmaster callout checking.
27493 Another issue to think about when using non-empty senders for callouts is
27494 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
27495 by the sender/recipient combination; thus, for any given recipient, many more
27496 actual callouts are performed than when an empty sender or postmaster is used.
27501 .section "Callout caching" "SECTcallvercache"
27502 .cindex "hints database" "callout cache"
27503 .cindex "callout" "cache, description of"
27504 .cindex "caching" "callout"
27505 Exim caches the results of callouts in order to reduce the amount of resources
27506 used, unless you specify the &%no_cache%& parameter with the &%callout%&
27507 option. A hints database called &"callout"& is used for the cache. Two
27508 different record types are used: one records the result of a callout check for
27509 a specific address, and the other records information that applies to the
27510 entire domain (for example, that it accepts the local part &'postmaster'&).
27512 When an original callout fails, a detailed SMTP error message is given about
27513 the failure. However, for subsequent failures use the cache data, this message
27516 The expiry times for negative and positive address cache records are
27517 independent, and can be set by the global options &%callout_negative_expire%&
27518 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
27520 If a host gives a negative response to an SMTP connection, or rejects any
27521 commands up to and including
27525 (but not including the MAIL command with a non-empty address),
27526 any callout attempt is bound to fail. Exim remembers such failures in a
27527 domain cache record, which it uses to fail callouts for the domain without
27528 making new connections, until the domain record times out. There are two
27529 separate expiry times for domain cache records:
27530 &%callout_domain_negative_expire%& (default 3h) and
27531 &%callout_domain_positive_expire%& (default 7d).
27533 Domain records expire when the negative expiry time is reached if callouts
27534 cannot be made for the domain, or if the postmaster check failed.
27535 Otherwise, they expire when the positive expiry time is reached. This
27536 ensures that, for example, a host that stops accepting &"random"& local parts
27537 will eventually be noticed.
27539 The callout caching mechanism is based on the domain of the address that is
27540 being tested. If the domain routes to several hosts, it is assumed that their
27541 behaviour will be the same.
27545 .section "Sender address verification reporting" "SECTsenaddver"
27546 .cindex "verifying" "suppressing error details"
27547 See section &<<SECTaddressverification>>& for a general discussion of
27548 verification. When sender verification fails in an ACL, the details of the
27549 failure are given as additional output lines before the 550 response to the
27550 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
27553 MAIL FROM:<xyz@abc.example>
27555 RCPT TO:<pqr@def.example>
27556 550-Verification failed for <xyz@abc.example>
27557 550-Called: 192.168.34.43
27558 550-Sent: RCPT TO:<xyz@abc.example>
27559 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
27560 550 Sender verification failed
27562 If more than one RCPT command fails in the same way, the details are given
27563 only for the first of them. However, some administrators do not want to send
27564 out this much information. You can suppress the details by adding
27565 &`/no_details`& to the ACL statement that requests sender verification. For
27568 verify = sender/no_details
27571 .section "Redirection while verifying" "SECTredirwhilveri"
27572 .cindex "verifying" "redirection while"
27573 .cindex "address redirection" "while verifying"
27574 A dilemma arises when a local address is redirected by aliasing or forwarding
27575 during verification: should the generated addresses themselves be verified,
27576 or should the successful expansion of the original address be enough to verify
27577 it? By default, Exim takes the following pragmatic approach:
27580 When an incoming address is redirected to just one child address, verification
27581 continues with the child address, and if that fails to verify, the original
27582 verification also fails.
27584 When an incoming address is redirected to more than one child address,
27585 verification does not continue. A success result is returned.
27588 This seems the most reasonable behaviour for the common use of aliasing as a
27589 way of redirecting different local parts to the same mailbox. It means, for
27590 example, that a pair of alias entries of the form
27593 aw123: :fail: Gone away, no forwarding address
27595 work as expected, with both local parts causing verification failure. When a
27596 redirection generates more than one address, the behaviour is more like a
27597 mailing list, where the existence of the alias itself is sufficient for
27598 verification to succeed.
27600 It is possible, however, to change the default behaviour so that all successful
27601 redirections count as successful verifications, however many new addresses are
27602 generated. This is specified by the &%success_on_redirect%& verification
27603 option. For example:
27605 require verify = recipient/success_on_redirect/callout=10s
27607 In this example, verification succeeds if a router generates a new address, and
27608 the callout does not occur, because no address was routed to a remote host.
27610 When verification is being tested via the &%-bv%& option, the treatment of
27611 redirections is as just described, unless the &%-v%& or any debugging option is
27612 also specified. In that case, full verification is done for every generated
27613 address and a report is output for each of them.
27617 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
27618 .cindex "CSA" "verifying"
27619 Client SMTP Authorization is a system that allows a site to advertise
27620 which machines are and are not permitted to send email. This is done by placing
27621 special SRV records in the DNS; these are looked up using the client's HELO
27622 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
27623 Authorization checks in Exim are performed by the ACL condition:
27627 This fails if the client is not authorized. If there is a DNS problem, or if no
27628 valid CSA SRV record is found, or if the client is authorized, the condition
27629 succeeds. These three cases can be distinguished using the expansion variable
27630 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
27631 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
27632 be likely to cause problems for legitimate email.
27634 The error messages produced by the CSA code include slightly more
27635 detail. If &$csa_status$& is &"defer"&, this may be because of problems
27636 looking up the CSA SRV record, or problems looking up the CSA target
27637 address record. There are four reasons for &$csa_status$& being &"fail"&:
27640 The client's host name is explicitly not authorized.
27642 The client's IP address does not match any of the CSA target IP addresses.
27644 The client's host name is authorized but it has no valid target IP addresses
27645 (for example, the target's addresses are IPv6 and the client is using IPv4).
27647 The client's host name has no CSA SRV record but a parent domain has asserted
27648 that all subdomains must be explicitly authorized.
27651 The &%csa%& verification condition can take an argument which is the domain to
27652 use for the DNS query. The default is:
27654 verify = csa/$sender_helo_name
27656 This implementation includes an extension to CSA. If the query domain
27657 is an address literal such as [192.0.2.95], or if it is a bare IP
27658 address, Exim searches for CSA SRV records in the reverse DNS as if
27659 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
27662 verify = csa/$sender_host_address
27664 In fact, this is the check that Exim performs if the client does not say HELO.
27665 This extension can be turned off by setting the main configuration option
27666 &%dns_csa_use_reverse%& to be false.
27668 If a CSA SRV record is not found for the domain itself, a search
27669 is performed through its parent domains for a record which might be
27670 making assertions about subdomains. The maximum depth of this search is limited
27671 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
27672 default. Exim does not look for CSA SRV records in a top level domain, so the
27673 default settings handle HELO domains as long as seven
27674 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
27675 of legitimate HELO domains.
27677 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
27678 direct SRV lookups, this is not sufficient because of the extra parent domain
27679 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
27680 addresses into lookups in the reverse DNS space. The result of a successful
27683 ${lookup dnsdb {csa=$sender_helo_name}}
27685 has two space-separated fields: an authorization code and a target host name.
27686 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
27687 authorization required but absent, or &"?"& for unknown.
27692 .section "Bounce address tag validation" "SECTverifyPRVS"
27693 .cindex "BATV, verifying"
27694 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
27695 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
27696 Genuine incoming bounce messages should therefore always be addressed to
27697 recipients that have a valid tag. This scheme is a way of detecting unwanted
27698 bounce messages caused by sender address forgeries (often called &"collateral
27699 spam"&), because the recipients of such messages do not include valid tags.
27701 There are two expansion items to help with the implementation of the BATV
27702 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
27703 the original envelope sender address by using a simple key to add a hash of the
27704 address and some time-based randomizing information. The &%prvs%& expansion
27705 item creates a signed address, and the &%prvscheck%& expansion item checks one.
27706 The syntax of these expansion items is described in section
27707 &<<SECTexpansionitems>>&.
27709 As an example, suppose the secret per-address keys are stored in an MySQL
27710 database. A query to look up the key for an address could be defined as a macro
27713 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
27714 WHERE sender='${quote_mysql:$prvscheck_address}'\
27717 Suppose also that the senders who make use of BATV are defined by an address
27718 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
27721 # Bounces: drop unsigned addresses for BATV senders
27722 deny message = This address does not send an unsigned reverse path
27724 recipients = +batv_senders
27726 # Bounces: In case of prvs-signed address, check signature.
27727 deny message = Invalid reverse path signature.
27729 condition = ${prvscheck {$local_part@$domain}\
27730 {PRVSCHECK_SQL}{1}}
27731 !condition = $prvscheck_result
27733 The first statement rejects recipients for bounce messages that are addressed
27734 to plain BATV sender addresses, because it is known that BATV senders do not
27735 send out messages with plain sender addresses. The second statement rejects
27736 recipients that are prvs-signed, but with invalid signatures (either because
27737 the key is wrong, or the signature has timed out).
27739 A non-prvs-signed address is not rejected by the second statement, because the
27740 &%prvscheck%& expansion yields an empty string if its first argument is not a
27741 prvs-signed address, thus causing the &%condition%& condition to be false. If
27742 the first argument is a syntactically valid prvs-signed address, the yield is
27743 the third string (in this case &"1"&), whether or not the cryptographic and
27744 timeout checks succeed. The &$prvscheck_result$& variable contains the result
27745 of the checks (empty for failure, &"1"& for success).
27747 There is one more issue you must consider when implementing prvs-signing:
27748 you have to ensure that the routers accept prvs-signed addresses and
27749 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
27750 router to remove the signature with a configuration along these lines:
27754 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
27756 This works because, if the third argument of &%prvscheck%& is empty, the result
27757 of the expansion of a prvs-signed address is the decoded value of the original
27758 address. This router should probably be the first of your routers that handles
27761 To create BATV-signed addresses in the first place, a transport of this form
27764 external_smtp_batv:
27766 return_path = ${prvs {$return_path} \
27767 {${lookup mysql{SELECT \
27768 secret FROM batv_prvs WHERE \
27769 sender='${quote_mysql:$sender_address}'} \
27772 If no key can be found for the existing return path, no signing takes place.
27776 .section "Using an ACL to control relaying" "SECTrelaycontrol"
27777 .cindex "&ACL;" "relay control"
27778 .cindex "relaying" "control by ACL"
27779 .cindex "policy control" "relay control"
27780 An MTA is said to &'relay'& a message if it receives it from some host and
27781 delivers it directly to another host as a result of a remote address contained
27782 within it. Redirecting a local address via an alias or forward file and then
27783 passing the message on to another host is not relaying,
27784 .cindex "&""percent hack""&"
27785 but a redirection as a result of the &"percent hack"& is.
27787 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
27788 A host which is acting as a gateway or an MX backup is concerned with incoming
27789 relaying from arbitrary hosts to a specific set of domains. On the other hand,
27790 a host which is acting as a smart host for a number of clients is concerned
27791 with outgoing relaying from those clients to the Internet at large. Often the
27792 same host is fulfilling both functions,
27794 . as illustrated in the diagram below,
27796 but in principle these two kinds of relaying are entirely independent. What is
27797 not wanted is the transmission of mail from arbitrary remote hosts through your
27798 system to arbitrary domains.
27801 You can implement relay control by means of suitable statements in the ACL that
27802 runs for each RCPT command. For convenience, it is often easiest to use
27803 Exim's named list facility to define the domains and hosts involved. For
27804 example, suppose you want to do the following:
27807 Deliver a number of domains to mailboxes on the local host (or process them
27808 locally in some other way). Let's say these are &'my.dom1.example'& and
27809 &'my.dom2.example'&.
27811 Relay mail for a number of other domains for which you are the secondary MX.
27812 These might be &'friend1.example'& and &'friend2.example'&.
27814 Relay mail from the hosts on your local LAN, to whatever domains are involved.
27815 Suppose your LAN is 192.168.45.0/24.
27819 In the main part of the configuration, you put the following definitions:
27821 domainlist local_domains = my.dom1.example : my.dom2.example
27822 domainlist relay_domains = friend1.example : friend2.example
27823 hostlist relay_hosts = 192.168.45.0/24
27825 Now you can use these definitions in the ACL that is run for every RCPT
27829 accept domains = +local_domains : +relay_domains
27830 accept hosts = +relay_hosts
27832 The first statement accepts any RCPT command that contains an address in
27833 the local or relay domains. For any other domain, control passes to the second
27834 statement, which accepts the command only if it comes from one of the relay
27835 hosts. In practice, you will probably want to make your ACL more sophisticated
27836 than this, for example, by including sender and recipient verification. The
27837 default configuration includes a more comprehensive example, which is described
27838 in chapter &<<CHAPdefconfil>>&.
27842 .section "Checking a relay configuration" "SECTcheralcon"
27843 .cindex "relaying" "checking control of"
27844 You can check the relay characteristics of your configuration in the same way
27845 that you can test any ACL behaviour for an incoming SMTP connection, by using
27846 the &%-bh%& option to run a fake SMTP session with which you interact.
27848 For specifically testing for unwanted relaying, the host
27849 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
27850 host from the host on which Exim is running, using the normal telnet port, you
27851 will see a normal telnet connection message and then quite a long delay. Be
27852 patient. The remote host is making an SMTP connection back to your host, and
27853 trying a number of common probes to test for open relay vulnerability. The
27854 results of the tests will eventually appear on your terminal.
27859 . ////////////////////////////////////////////////////////////////////////////
27860 . ////////////////////////////////////////////////////////////////////////////
27862 .chapter "Content scanning at ACL time" "CHAPexiscan"
27863 .scindex IIDcosca "content scanning" "at ACL time"
27864 The extension of Exim to include content scanning at ACL time, formerly known
27865 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
27866 was integrated into the main source for Exim release 4.50, and Tom continues to
27867 maintain it. Most of the wording of this chapter is taken from Tom's
27870 It is also possible to scan the content of messages at other times. The
27871 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
27872 scanning after all the ACLs have run. A transport filter can be used to scan
27873 messages at delivery time (see the &%transport_filter%& option, described in
27874 chapter &<<CHAPtransportgeneric>>&).
27876 If you want to include the ACL-time content-scanning features when you compile
27877 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
27878 &_Local/Makefile_&. When you do that, the Exim binary is built with:
27881 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
27882 for all MIME parts for SMTP and non-SMTP messages, respectively.
27884 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
27885 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
27886 run at the end of message reception (the &%acl_smtp_data%& ACL).
27888 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
27889 of messages, or parts of messages, for debugging purposes.
27891 Additional expansion variables that are set in the new ACL and by the new
27894 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
27897 There is another content-scanning configuration option for &_Local/Makefile_&,
27898 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
27899 condition is compiled, in addition to all the other content-scanning features.
27901 Content-scanning is continually evolving, and new features are still being
27902 added. While such features are still unstable and liable to incompatible
27903 changes, they are made available in Exim by setting options whose names begin
27904 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
27905 this manual. You can find out about them by reading the file called
27906 &_doc/experimental.txt_&.
27908 All the content-scanning facilities work on a MBOX copy of the message that is
27909 temporarily created in a file called:
27911 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
27913 The &_.eml_& extension is a friendly hint to virus scanners that they can
27914 expect an MBOX-like structure inside that file. The file is created when the
27915 first content scanning facility is called. Subsequent calls to content
27916 scanning conditions open the same file again. The directory is recursively
27917 removed when the &%acl_smtp_data%& ACL has finished running, unless
27919 control = no_mbox_unspool
27921 has been encountered. When the MIME ACL decodes files, they are put into the
27922 same directory by default.
27926 .section "Scanning for viruses" "SECTscanvirus"
27927 .cindex "virus scanning"
27928 .cindex "content scanning" "for viruses"
27929 .cindex "content scanning" "the &%malware%& condition"
27930 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
27931 It supports a &"generic"& interface to scanners called via the shell, and
27932 specialized interfaces for &"daemon"& type virus scanners, which are resident
27933 in memory and thus are much faster.
27935 .oindex "&%av_scanner%&"
27936 You can set the &%av_scanner%& option in first part of the Exim configuration
27937 file to specify which scanner to use, together with any additional options that
27938 are needed. The basic syntax is as follows:
27940 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
27942 If you do not set &%av_scanner%&, it defaults to
27944 av_scanner = sophie:/var/run/sophie
27946 If the value of &%av_scanner%& starts with a dollar character, it is expanded
27947 before use. The following scanner types are supported in this release:
27950 .vitem &%aveserver%&
27951 .cindex "virus scanners" "Kaspersky"
27952 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
27953 at &url(http://www.kaspersky.com). This scanner type takes one option,
27954 which is the path to the daemon's UNIX socket. The default is shown in this
27957 av_scanner = aveserver:/var/run/aveserver
27961 .cindex "virus scanners" "clamd"
27962 This daemon-type scanner is GPL and free. You can get it at
27963 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
27964 unpack MIME containers, so it used to be recommended to unpack MIME attachments
27965 in the MIME ACL. This no longer believed to be necessary. One option is
27966 required: either the path and name of a UNIX socket file, or a hostname or IP
27967 number, and a port, separated by space, as in the second of these examples:
27969 av_scanner = clamd:/opt/clamd/socket
27970 av_scanner = clamd:192.0.2.3 1234
27971 av_scanner = clamd:192.0.2.3 1234:local
27973 If the value of av_scanner points to a UNIX socket file or contains the local
27974 keyword, then the ClamAV interface will pass a filename containing the data
27975 to be scanned, which will should normally result in less I/O happening and be
27976 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
27977 Exim does not assume that there is a common filesystem with the remote host.
27978 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
27979 you be running a version of ClamAV prior to 0.95.
27980 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
27981 contributing the code for this scanner.
27984 .cindex "virus scanners" "command line interface"
27985 This is the keyword for the generic command line scanner interface. It can be
27986 used to attach virus scanners that are invoked from the shell. This scanner
27987 type takes 3 mandatory options:
27990 The full path and name of the scanner binary, with all command line options,
27991 and a placeholder (&`%s`&) for the directory to scan.
27994 A regular expression to match against the STDOUT and STDERR output of the
27995 virus scanner. If the expression matches, a virus was found. You must make
27996 absolutely sure that this expression matches on &"virus found"&. This is called
27997 the &"trigger"& expression.
28000 Another regular expression, containing exactly one pair of parentheses, to
28001 match the name of the virus found in the scanners output. This is called the
28002 &"name"& expression.
28005 For example, Sophos Sweep reports a virus on a line like this:
28007 Virus 'W32/Magistr-B' found in file ./those.bat
28009 For the trigger expression, we can match the phrase &"found in file"&. For the
28010 name expression, we want to extract the W32/Magistr-B string, so we can match
28011 for the single quotes left and right of it. Altogether, this makes the
28012 configuration setting:
28014 av_scanner = cmdline:\
28015 /path/to/sweep -ss -all -rec -archive %s:\
28016 found in file:'(.+)'
28019 .cindex "virus scanners" "DrWeb"
28020 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
28021 argument, either a full path to a UNIX socket, or an IP address and port
28022 separated by white space, as in these examples:
28024 av_scanner = drweb:/var/run/drwebd.sock
28025 av_scanner = drweb:192.168.2.20 31337
28027 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
28028 is used. Thanks to Alex Miller for contributing the code for this scanner.
28031 .cindex "virus scanners" "F-Secure"
28032 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
28033 argument which is the path to a UNIX socket. For example:
28035 av_scanner = fsecure:/path/to/.fsav
28037 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
28038 Thelmen for contributing the code for this scanner.
28040 .vitem &%kavdaemon%&
28041 .cindex "virus scanners" "Kaspersky"
28042 This is the scanner daemon of Kaspersky Version 4. This version of the
28043 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
28044 scanner type takes one option, which is the path to the daemon's UNIX socket.
28047 av_scanner = kavdaemon:/opt/AVP/AvpCtl
28049 The default path is &_/var/run/AvpCtl_&.
28052 .cindex "virus scanners" "mksd"
28053 This is a daemon type scanner that is aimed mainly at Polish users, though some
28054 parts of documentation are now available in English. You can get it at
28055 &url(http://linux.mks.com.pl/). The only option for this scanner type is
28056 the maximum number of processes used simultaneously to scan the attachments,
28057 provided that the demime facility is employed and also provided that mksd has
28058 been run with at least the same number of child processes. For example:
28060 av_scanner = mksd:2
28062 You can safely omit this option (the default value is 1).
28065 .cindex "virus scanners" "Sophos and Sophie"
28066 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
28067 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
28068 for this scanner type is the path to the UNIX socket that Sophie uses for
28069 client communication. For example:
28071 av_scanner = sophie:/tmp/sophie
28073 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
28077 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
28078 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
28081 The &%av_scanner%& option is expanded each time &%malware%& is called. This
28082 makes it possible to use different scanners. See further below for an example.
28083 The &%malware%& condition caches its results, so when you use it multiple times
28084 for the same message, the actual scanning process is only carried out once.
28085 However, using expandable items in &%av_scanner%& disables this caching, in
28086 which case each use of the &%malware%& condition causes a new scan of the
28089 The &%malware%& condition takes a right-hand argument that is expanded before
28090 use. It can then be one of
28093 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
28094 The condition succeeds if a virus was found, and fail otherwise. This is the
28097 &"false"& or &"0"& or an empty string, in which case no scanning is done and
28098 the condition fails immediately.
28100 A regular expression, in which case the message is scanned for viruses. The
28101 condition succeeds if a virus is found and its name matches the regular
28102 expression. This allows you to take special actions on certain types of virus.
28105 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
28106 even if there is a problem with the virus scanner. Otherwise, such a problem
28107 causes the ACL to defer.
28109 .vindex "&$malware_name$&"
28110 When a virus is found, the condition sets up an expansion variable called
28111 &$malware_name$& that contains the name of the virus. You can use it in a
28112 &%message%& modifier that specifies the error returned to the sender, and/or in
28115 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
28116 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
28117 &%malware%& condition.
28119 Beware the interaction of Exim's &%message_size_limit%& with any size limits
28120 imposed by your anti-virus scanner.
28122 Here is a very simple scanning example:
28124 deny message = This message contains malware ($malware_name)
28128 The next example accepts messages when there is a problem with the scanner:
28130 deny message = This message contains malware ($malware_name)
28132 malware = */defer_ok
28134 The next example shows how to use an ACL variable to scan with both sophie and
28135 aveserver. It assumes you have set:
28137 av_scanner = $acl_m0
28139 in the main Exim configuration.
28141 deny message = This message contains malware ($malware_name)
28142 set acl_m0 = sophie
28145 deny message = This message contains malware ($malware_name)
28146 set acl_m0 = aveserver
28151 .section "Scanning with SpamAssassin" "SECTscanspamass"
28152 .cindex "content scanning" "for spam"
28153 .cindex "spam scanning"
28154 .cindex "SpamAssassin"
28155 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
28156 score and a report for the message. You can get SpamAssassin at
28157 &url(http://www.spamassassin.org), or, if you have a working Perl
28158 installation, you can use CPAN by running:
28160 perl -MCPAN -e 'install Mail::SpamAssassin'
28162 SpamAssassin has its own set of configuration files. Please review its
28163 documentation to see how you can tweak it. The default installation should work
28166 .oindex "&%spamd_address%&"
28167 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
28168 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
28169 port for &%spamd%&, you must set the &%spamd_address%& option in the global
28170 part of the Exim configuration as follows (example):
28172 spamd_address = 192.168.99.45 387
28174 You do not need to set this option if you use the default. As of version 2.60,
28175 &%spamd%& also supports communication over UNIX sockets. If you want to use
28176 these, supply &%spamd_address%& with an absolute file name instead of a
28179 spamd_address = /var/run/spamd_socket
28181 You can have multiple &%spamd%& servers to improve scalability. These can
28182 reside on other hardware reachable over the network. To specify multiple
28183 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
28184 option, separated with colons:
28186 spamd_address = 192.168.2.10 783 : \
28187 192.168.2.11 783 : \
28190 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
28191 fashion. When a server fails to respond to the connection attempt, all other
28192 servers are tried until one succeeds. If no server responds, the &%spam%&
28195 &*Warning*&: It is not possible to use the UNIX socket connection method with
28196 multiple &%spamd%& servers.
28198 The &%spamd_address%& variable is expanded before use if it starts with
28199 a dollar sign. In this case, the expansion may return a string that is
28200 used as the list so that multiple spamd servers can be the result of an
28203 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
28204 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
28206 deny message = This message was classified as SPAM
28209 The right-hand side of the &%spam%& condition specifies a name. This is
28210 relevant if you have set up multiple SpamAssassin profiles. If you do not want
28211 to scan using a specific profile, but rather use the SpamAssassin system-wide
28212 default profile, you can scan for an unknown name, or simply use &"nobody"&.
28213 However, you must put something on the right-hand side.
28215 The name allows you to use per-domain or per-user antispam profiles in
28216 principle, but this is not straightforward in practice, because a message may
28217 have multiple recipients, not necessarily all in the same domain. Because the
28218 &%spam%& condition has to be called from a DATA ACL in order to be able to
28219 read the contents of the message, the variables &$local_part$& and &$domain$&
28222 The right-hand side of the &%spam%& condition is expanded before being used, so
28223 you can put lookups or conditions there. When the right-hand side evaluates to
28224 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
28227 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
28228 large ones may cause significant performance degradation. As most spam messages
28229 are quite small, it is recommended that you do not scan the big ones. For
28232 deny message = This message was classified as SPAM
28233 condition = ${if < {$message_size}{10K}}
28237 The &%spam%& condition returns true if the threshold specified in the user's
28238 SpamAssassin profile has been matched or exceeded. If you want to use the
28239 &%spam%& condition for its side effects (see the variables below), you can make
28240 it always return &"true"& by appending &`:true`& to the username.
28242 .cindex "spam scanning" "returned variables"
28243 When the &%spam%& condition is run, it sets up a number of expansion
28244 variables. These variables are saved with the received message, thus they are
28245 available for use at delivery time.
28248 .vitem &$spam_score$&
28249 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
28250 for inclusion in log or reject messages.
28252 .vitem &$spam_score_int$&
28253 The spam score of the message, multiplied by ten, as an integer value. For
28254 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
28255 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
28256 The integer value is useful for numeric comparisons in conditions.
28259 .vitem &$spam_bar$&
28260 A string consisting of a number of &"+"& or &"-"& characters, representing the
28261 integer part of the spam score value. A spam score of 4.4 would have a
28262 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
28263 headers, since MUAs can match on such strings.
28265 .vitem &$spam_report$&
28266 A multiline text table, containing the full SpamAssassin report for the
28267 message. Useful for inclusion in headers or reject messages.
28270 The &%spam%& condition caches its results unless expansion in
28271 spamd_address was used. If you call it again with the same user name, it
28272 does not scan again, but rather returns the same values as before.
28274 The &%spam%& condition returns DEFER if there is any error while running
28275 the message through SpamAssassin or if the expansion of spamd_address
28276 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
28277 statement block), append &`/defer_ok`& to the right-hand side of the
28278 spam condition, like this:
28280 deny message = This message was classified as SPAM
28281 spam = joe/defer_ok
28283 This causes messages to be accepted even if there is a problem with &%spamd%&.
28285 Here is a longer, commented example of the use of the &%spam%&
28288 # put headers in all messages (no matter if spam or not)
28289 warn spam = nobody:true
28290 add_header = X-Spam-Score: $spam_score ($spam_bar)
28291 add_header = X-Spam-Report: $spam_report
28293 # add second subject line with *SPAM* marker when message
28294 # is over threshold
28296 add_header = Subject: *SPAM* $h_Subject:
28298 # reject spam at high scores (> 12)
28299 deny message = This message scored $spam_score spam points.
28301 condition = ${if >{$spam_score_int}{120}{1}{0}}
28306 .section "Scanning MIME parts" "SECTscanmimepart"
28307 .cindex "content scanning" "MIME parts"
28308 .cindex "MIME content scanning"
28309 .oindex "&%acl_smtp_mime%&"
28310 .oindex "&%acl_not_smtp_mime%&"
28311 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
28312 each MIME part of an SMTP message, including multipart types, in the sequence
28313 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
28314 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
28315 options may both refer to the same ACL if you want the same processing in both
28318 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
28319 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
28320 the case of a non-SMTP message. However, a MIME ACL is called only if the
28321 message contains a &'Content-Type:'& header line. When a call to a MIME
28322 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
28323 result code is sent to the client. In the case of an SMTP message, the
28324 &%acl_smtp_data%& ACL is not called when this happens.
28326 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
28327 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
28328 condition to match against the raw MIME part. You can also use the
28329 &%mime_regex%& condition to match against the decoded MIME part (see section
28330 &<<SECTscanregex>>&).
28332 At the start of a MIME ACL, a number of variables are set from the header
28333 information for the relevant MIME part. These are described below. The contents
28334 of the MIME part are not by default decoded into a disk file except for MIME
28335 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
28336 part into a disk file, you can use the &%decode%& condition. The general
28339 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
28341 The right hand side is expanded before use. After expansion,
28345 &"0"& or &"false"&, in which case no decoding is done.
28347 The string &"default"&. In that case, the file is put in the temporary
28348 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
28349 a sequential file name consisting of the message id and a sequence number. The
28350 full path and name is available in &$mime_decoded_filename$& after decoding.
28352 A full path name starting with a slash. If the full name is an existing
28353 directory, it is used as a replacement for the default directory. The filename
28354 is then sequentially assigned. If the path does not exist, it is used as
28355 the full path and file name.
28357 If the string does not start with a slash, it is used as the
28358 filename, and the default path is then used.
28360 The &%decode%& condition normally succeeds. It is only false for syntax
28361 errors or unusual circumstances such as memory shortages. You can easily decode
28362 a file with its original, proposed filename using
28364 decode = $mime_filename
28366 However, you should keep in mind that &$mime_filename$& might contain
28367 anything. If you place files outside of the default path, they are not
28368 automatically unlinked.
28370 For RFC822 attachments (these are messages attached to messages, with a
28371 content-type of &"message/rfc822"&), the ACL is called again in the same manner
28372 as for the primary message, only that the &$mime_is_rfc822$& expansion
28373 variable is set (see below). Attached messages are always decoded to disk
28374 before being checked, and the files are unlinked once the check is done.
28376 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
28377 used to match regular expressions against raw and decoded MIME parts,
28378 respectively. They are described in section &<<SECTscanregex>>&.
28380 .cindex "MIME content scanning" "returned variables"
28381 The following list describes all expansion variables that are
28382 available in the MIME ACL:
28385 .vitem &$mime_boundary$&
28386 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
28387 have a boundary string, which is stored in this variable. If the current part
28388 has no boundary parameter in the &'Content-Type:'& header, this variable
28389 contains the empty string.
28391 .vitem &$mime_charset$&
28392 This variable contains the character set identifier, if one was found in the
28393 &'Content-Type:'& header. Examples for charset identifiers are:
28399 Please note that this value is not normalized, so you should do matches
28400 case-insensitively.
28402 .vitem &$mime_content_description$&
28403 This variable contains the normalized content of the &'Content-Description:'&
28404 header. It can contain a human-readable description of the parts content. Some
28405 implementations repeat the filename for attachments here, but they are usually
28406 only used for display purposes.
28408 .vitem &$mime_content_disposition$&
28409 This variable contains the normalized content of the &'Content-Disposition:'&
28410 header. You can expect strings like &"attachment"& or &"inline"& here.
28412 .vitem &$mime_content_id$&
28413 This variable contains the normalized content of the &'Content-ID:'& header.
28414 This is a unique ID that can be used to reference a part from another part.
28416 .vitem &$mime_content_size$&
28417 This variable is set only after the &%decode%& modifier (see above) has been
28418 successfully run. It contains the size of the decoded part in kilobytes. The
28419 size is always rounded up to full kilobytes, so only a completely empty part
28420 has a &$mime_content_size$& of zero.
28422 .vitem &$mime_content_transfer_encoding$&
28423 This variable contains the normalized content of the
28424 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
28425 type. Typical values are &"base64"& and &"quoted-printable"&.
28427 .vitem &$mime_content_type$&
28428 If the MIME part has a &'Content-Type:'& header, this variable contains its
28429 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
28430 are some examples of popular MIME types, as they may appear in this variable:
28434 application/octet-stream
28438 If the MIME part has no &'Content-Type:'& header, this variable contains the
28441 .vitem &$mime_decoded_filename$&
28442 This variable is set only after the &%decode%& modifier (see above) has been
28443 successfully run. It contains the full path and file name of the file
28444 containing the decoded data.
28449 .vitem &$mime_filename$&
28450 This is perhaps the most important of the MIME variables. It contains a
28451 proposed filename for an attachment, if one was found in either the
28452 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
28453 RFC2047 decoded, but no additional sanity checks are done. If no filename was
28454 found, this variable contains the empty string.
28456 .vitem &$mime_is_coverletter$&
28457 This variable attempts to differentiate the &"cover letter"& of an e-mail from
28458 attached data. It can be used to clamp down on flashy or unnecessarily encoded
28459 content in the cover letter, while not restricting attachments at all.
28461 The variable contains 1 (true) for a MIME part believed to be part of the
28462 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
28466 The outermost MIME part of a message is always a cover letter.
28469 If a multipart/alternative or multipart/related MIME part is a cover letter,
28470 so are all MIME subparts within that multipart.
28473 If any other multipart is a cover letter, the first subpart is a cover letter,
28474 and the rest are attachments.
28477 All parts contained within an attachment multipart are attachments.
28480 As an example, the following will ban &"HTML mail"& (including that sent with
28481 alternative plain text), while allowing HTML files to be attached. HTML
28482 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
28484 deny message = HTML mail is not accepted here
28485 !condition = $mime_is_rfc822
28486 condition = $mime_is_coverletter
28487 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
28489 .vitem &$mime_is_multipart$&
28490 This variable has the value 1 (true) when the current part has the main type
28491 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
28492 Since multipart entities only serve as containers for other parts, you may not
28493 want to carry out specific actions on them.
28495 .vitem &$mime_is_rfc822$&
28496 This variable has the value 1 (true) if the current part is not a part of the
28497 checked message itself, but part of an attached message. Attached message
28498 decoding is fully recursive.
28500 .vitem &$mime_part_count$&
28501 This variable is a counter that is raised for each processed MIME part. It
28502 starts at zero for the very first part (which is usually a multipart). The
28503 counter is per-message, so it is reset when processing RFC822 attachments (see
28504 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
28505 complete, so you can use it in the DATA ACL to determine the number of MIME
28506 parts of a message. For non-MIME messages, this variable contains the value -1.
28511 .section "Scanning with regular expressions" "SECTscanregex"
28512 .cindex "content scanning" "with regular expressions"
28513 .cindex "regular expressions" "content scanning with"
28514 You can specify your own custom regular expression matches on the full body of
28515 the message, or on individual MIME parts.
28517 The &%regex%& condition takes one or more regular expressions as arguments and
28518 matches them against the full message (when called in the DATA ACL) or a raw
28519 MIME part (when called in the MIME ACL). The &%regex%& condition matches
28520 linewise, with a maximum line length of 32K characters. That means you cannot
28521 have multiline matches with the &%regex%& condition.
28523 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
28524 to 32K of decoded content (the whole content at once, not linewise). If the
28525 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
28526 is decoded automatically when &%mime_regex%& is executed (using default path
28527 and filename values). If the decoded data is larger than 32K, only the first
28528 32K characters are checked.
28530 The regular expressions are passed as a colon-separated list. To include a
28531 literal colon, you must double it. Since the whole right-hand side string is
28532 expanded before being used, you must also escape dollar signs and backslashes
28533 with more backslashes, or use the &`\N`& facility to disable expansion.
28534 Here is a simple example that contains two regular expressions:
28536 deny message = contains blacklisted regex ($regex_match_string)
28537 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
28539 The conditions returns true if any one of the regular expressions matches. The
28540 &$regex_match_string$& expansion variable is then set up and contains the
28541 matching regular expression.
28543 &*Warning*&: With large messages, these conditions can be fairly
28549 .section "The demime condition" "SECTdemimecond"
28550 .cindex "content scanning" "MIME checking"
28551 .cindex "MIME content scanning"
28552 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
28553 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
28554 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
28555 ACL functionality, but provides no additional facilities. Please note that this
28556 condition is deprecated and kept only for backward compatibility. You must set
28557 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
28558 use the &%demime%& condition.
28560 The &%demime%& condition unpacks MIME containers in the message. It detects
28561 errors in MIME containers and can match file extensions found in the message
28562 against a list. Using this facility produces files containing the unpacked MIME
28563 parts of the message in the temporary scan directory. If you do antivirus
28564 scanning, it is recommended that you use the &%demime%& condition before the
28565 antivirus (&%malware%&) condition.
28567 On the right-hand side of the &%demime%& condition you can pass a
28568 colon-separated list of file extensions that it should match against. For
28571 deny message = Found blacklisted file attachment
28572 demime = vbs:com:bat:pif:prf:lnk
28574 If one of the file extensions is found, the condition is true, otherwise it is
28575 false. If there is a temporary error while demimeing (for example, &"disk
28576 full"&), the condition defers, and the message is temporarily rejected (unless
28577 the condition is on a &%warn%& verb).
28579 The right-hand side is expanded before being treated as a list, so you can have
28580 conditions and lookups there. If it expands to an empty string, &"false"&, or
28581 zero (&"0"&), no demimeing is done and the condition is false.
28583 The &%demime%& condition set the following variables:
28586 .vitem &$demime_errorlevel$&
28587 .vindex "&$demime_errorlevel$&"
28588 When an error is detected in a MIME container, this variable contains the
28589 severity of the error, as an integer number. The higher the value, the more
28590 severe the error (the current maximum value is 3). If this variable is unset or
28591 zero, no error occurred.
28593 .vitem &$demime_reason$&
28594 .vindex "&$demime_reason$&"
28595 When &$demime_errorlevel$& is greater than zero, this variable contains a
28596 human-readable text string describing the MIME error that occurred.
28600 .vitem &$found_extension$&
28601 .vindex "&$found_extension$&"
28602 When the &%demime%& condition is true, this variable contains the file
28603 extension it found.
28606 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
28607 the &%demime%& condition, and are not changed on subsequent calls.
28609 If you do not want to check for file extensions, but rather use the &%demime%&
28610 condition for unpacking or error checking purposes, pass &"*"& as the
28611 right-hand side value. Here is a more elaborate example of how to use this
28614 # Reject messages with serious MIME container errors
28615 deny message = Found MIME error ($demime_reason).
28617 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
28619 # Reject known virus spreading file extensions.
28620 # Accepting these is pretty much braindead.
28621 deny message = contains $found_extension file (blacklisted).
28622 demime = com:vbs:bat:pif:scr
28624 # Freeze .exe and .doc files. Postmaster can
28625 # examine them and eventually thaw them.
28626 deny log_message = Another $found_extension file.
28635 . ////////////////////////////////////////////////////////////////////////////
28636 . ////////////////////////////////////////////////////////////////////////////
28638 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
28639 "Local scan function"
28640 .scindex IIDlosca "&[local_scan()]& function" "description of"
28641 .cindex "customizing" "input scan using C function"
28642 .cindex "policy control" "by local scan function"
28643 In these days of email worms, viruses, and ever-increasing spam, some sites
28644 want to apply a lot of checking to messages before accepting them.
28646 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
28647 passing messages to external virus and spam scanning software. You can also do
28648 a certain amount in Exim itself through string expansions and the &%condition%&
28649 condition in the ACL that runs after the SMTP DATA command or the ACL for
28650 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
28652 To allow for further customization to a site's own requirements, there is the
28653 possibility of linking Exim with a private message scanning function, written
28654 in C. If you want to run code that is written in something other than C, you
28655 can of course use a little C stub to call it.
28657 The local scan function is run once for every incoming message, at the point
28658 when Exim is just about to accept the message.
28659 It can therefore be used to control non-SMTP messages from local processes as
28660 well as messages arriving via SMTP.
28662 Exim applies a timeout to calls of the local scan function, and there is an
28663 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
28664 Zero means &"no timeout"&.
28665 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
28666 before calling the local scan function, so that the most common types of crash
28667 are caught. If the timeout is exceeded or one of those signals is caught, the
28668 incoming message is rejected with a temporary error if it is an SMTP message.
28669 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
28670 code. The incident is logged on the main and reject logs.
28674 .section "Building Exim to use a local scan function" "SECID207"
28675 .cindex "&[local_scan()]& function" "building Exim to use"
28676 To make use of the local scan function feature, you must tell Exim where your
28677 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
28678 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
28679 directory, so you might set
28681 LOCAL_SCAN_SOURCE=Local/local_scan.c
28683 for example. The function must be called &[local_scan()]&. It is called by
28684 Exim after it has received a message, when the success return code is about to
28685 be sent. This is after all the ACLs have been run. The return code from your
28686 function controls whether the message is actually accepted or not. There is a
28687 commented template function (that just accepts the message) in the file
28688 _src/local_scan.c_.
28690 If you want to make use of Exim's run time configuration file to set options
28691 for your &[local_scan()]& function, you must also set
28693 LOCAL_SCAN_HAS_OPTIONS=yes
28695 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
28700 .section "API for local_scan()" "SECTapiforloc"
28701 .cindex "&[local_scan()]& function" "API description"
28702 You must include this line near the start of your code:
28704 #include "local_scan.h"
28706 This header file defines a number of variables and other values, and the
28707 prototype for the function itself. Exim is coded to use unsigned char values
28708 almost exclusively, and one of the things this header defines is a shorthand
28709 for &`unsigned char`& called &`uschar`&.
28710 It also contains the following macro definitions, to simplify casting character
28711 strings and pointers to character strings:
28713 #define CS (char *)
28714 #define CCS (const char *)
28715 #define CSS (char **)
28716 #define US (unsigned char *)
28717 #define CUS (const unsigned char *)
28718 #define USS (unsigned char **)
28720 The function prototype for &[local_scan()]& is:
28722 extern int local_scan(int fd, uschar **return_text);
28724 The arguments are as follows:
28727 &%fd%& is a file descriptor for the file that contains the body of the message
28728 (the -D file). The file is open for reading and writing, but updating it is not
28729 recommended. &*Warning*&: You must &'not'& close this file descriptor.
28731 The descriptor is positioned at character 19 of the file, which is the first
28732 character of the body itself, because the first 19 characters are the message
28733 id followed by &`-D`& and a newline. If you rewind the file, you should use the
28734 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
28735 case this changes in some future version.
28737 &%return_text%& is an address which you can use to return a pointer to a text
28738 string at the end of the function. The value it points to on entry is NULL.
28741 The function must return an &%int%& value which is one of the following macros:
28744 .vitem &`LOCAL_SCAN_ACCEPT`&
28745 .vindex "&$local_scan_data$&"
28746 The message is accepted. If you pass back a string of text, it is saved with
28747 the message, and made available in the variable &$local_scan_data$&. No
28748 newlines are permitted (if there are any, they are turned into spaces) and the
28749 maximum length of text is 1000 characters.
28751 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
28752 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
28753 queued without immediate delivery, and is frozen.
28755 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
28756 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
28757 queued without immediate delivery.
28759 .vitem &`LOCAL_SCAN_REJECT`&
28760 The message is rejected; the returned text is used as an error message which is
28761 passed back to the sender and which is also logged. Newlines are permitted &--
28762 they cause a multiline response for SMTP rejections, but are converted to
28763 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
28766 .vitem &`LOCAL_SCAN_TEMPREJECT`&
28767 The message is temporarily rejected; the returned text is used as an error
28768 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
28771 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
28772 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
28773 message is not written to the reject log. It has the effect of unsetting the
28774 &%rejected_header%& log selector for just this rejection. If
28775 &%rejected_header%& is already unset (see the discussion of the
28776 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
28777 same as LOCAL_SCAN_REJECT.
28779 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
28780 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
28781 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
28784 If the message is not being received by interactive SMTP, rejections are
28785 reported by writing to &%stderr%& or by sending an email, as configured by the
28786 &%-oe%& command line options.
28790 .section "Configuration options for local_scan()" "SECTconoptloc"
28791 .cindex "&[local_scan()]& function" "configuration options"
28792 It is possible to have option settings in the main configuration file
28793 that set values in static variables in the &[local_scan()]& module. If you
28794 want to do this, you must have the line
28796 LOCAL_SCAN_HAS_OPTIONS=yes
28798 in your &_Local/Makefile_& when you build Exim. (This line is in
28799 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
28800 file, you must define static variables to hold the option values, and a table
28803 The table must be a vector called &%local_scan_options%&, of type
28804 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
28805 and a pointer to the variable that holds the value. The entries must appear in
28806 alphabetical order. Following &%local_scan_options%& you must also define a
28807 variable called &%local_scan_options_count%& that contains the number of
28808 entries in the table. Here is a short example, showing two kinds of option:
28810 static int my_integer_option = 42;
28811 static uschar *my_string_option = US"a default string";
28813 optionlist local_scan_options[] = {
28814 { "my_integer", opt_int, &my_integer_option },
28815 { "my_string", opt_stringptr, &my_string_option }
28818 int local_scan_options_count =
28819 sizeof(local_scan_options)/sizeof(optionlist);
28821 The values of the variables can now be changed from Exim's runtime
28822 configuration file by including a local scan section as in this example:
28826 my_string = some string of text...
28828 The available types of option data are as follows:
28831 .vitem &*opt_bool*&
28832 This specifies a boolean (true/false) option. The address should point to a
28833 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
28834 that are defined as &"1"& and &"0"&, respectively. If you want to detect
28835 whether such a variable has been set at all, you can initialize it to
28836 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
28839 .vitem &*opt_fixed*&
28840 This specifies a fixed point number, such as is used for load averages.
28841 The address should point to a variable of type &`int`&. The value is stored
28842 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
28845 This specifies an integer; the address should point to a variable of type
28846 &`int`&. The value may be specified in any of the integer formats accepted by
28849 .vitem &*opt_mkint*&
28850 This is the same as &%opt_int%&, except that when such a value is output in a
28851 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
28852 printed with the suffix K or M.
28854 .vitem &*opt_octint*&
28855 This also specifies an integer, but the value is always interpreted as an
28856 octal integer, whether or not it starts with the digit zero, and it is
28857 always output in octal.
28859 .vitem &*opt_stringptr*&
28860 This specifies a string value; the address must be a pointer to a
28861 variable that points to a string (for example, of type &`uschar *`&).
28863 .vitem &*opt_time*&
28864 This specifies a time interval value. The address must point to a variable of
28865 type &`int`&. The value that is placed there is a number of seconds.
28868 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
28869 out the values of all the &[local_scan()]& options.
28873 .section "Available Exim variables" "SECID208"
28874 .cindex "&[local_scan()]& function" "available Exim variables"
28875 The header &_local_scan.h_& gives you access to a number of C variables. These
28876 are the only ones that are guaranteed to be maintained from release to release.
28877 Note, however, that you can obtain the value of any Exim expansion variable,
28878 including &$recipients$&, by calling &'expand_string()'&. The exported
28879 C variables are as follows:
28882 .vitem &*int&~body_linecount*&
28883 This variable contains the number of lines in the message's body.
28885 .vitem &*int&~body_zerocount*&
28886 This variable contains the number of binary zero bytes in the message's body.
28888 .vitem &*unsigned&~int&~debug_selector*&
28889 This variable is set to zero when no debugging is taking place. Otherwise, it
28890 is a bitmap of debugging selectors. Two bits are identified for use in
28891 &[local_scan()]&; they are defined as macros:
28894 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
28895 testing option that is not privileged &-- any caller may set it. All the
28896 other selector bits can be set only by admin users.
28899 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
28900 by the &`+local_scan`& debug selector. It is not included in the default set
28904 Thus, to write to the debugging output only when &`+local_scan`& has been
28905 selected, you should use code like this:
28907 if ((debug_selector & D_local_scan) != 0)
28908 debug_printf("xxx", ...);
28910 .vitem &*uschar&~*expand_string_message*&
28911 After a failing call to &'expand_string()'& (returned value NULL), the
28912 variable &%expand_string_message%& contains the error message, zero-terminated.
28914 .vitem &*header_line&~*header_list*&
28915 A pointer to a chain of header lines. The &%header_line%& structure is
28918 .vitem &*header_line&~*header_last*&
28919 A pointer to the last of the header lines.
28921 .vitem &*uschar&~*headers_charset*&
28922 The value of the &%headers_charset%& configuration option.
28924 .vitem &*BOOL&~host_checking*&
28925 This variable is TRUE during a host checking session that is initiated by the
28926 &%-bh%& command line option.
28928 .vitem &*uschar&~*interface_address*&
28929 The IP address of the interface that received the message, as a string. This
28930 is NULL for locally submitted messages.
28932 .vitem &*int&~interface_port*&
28933 The port on which this message was received. When testing with the &%-bh%&
28934 command line option, the value of this variable is -1 unless a port has been
28935 specified via the &%-oMi%& option.
28937 .vitem &*uschar&~*message_id*&
28938 This variable contains Exim's message id for the incoming message (the value of
28939 &$message_exim_id$&) as a zero-terminated string.
28941 .vitem &*uschar&~*received_protocol*&
28942 The name of the protocol by which the message was received.
28944 .vitem &*int&~recipients_count*&
28945 The number of accepted recipients.
28947 .vitem &*recipient_item&~*recipients_list*&
28948 .cindex "recipient" "adding in local scan"
28949 .cindex "recipient" "removing in local scan"
28950 The list of accepted recipients, held in a vector of length
28951 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
28952 can add additional recipients by calling &'receive_add_recipient()'& (see
28953 below). You can delete recipients by removing them from the vector and
28954 adjusting the value in &%recipients_count%&. In particular, by setting
28955 &%recipients_count%& to zero you remove all recipients. If you then return the
28956 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
28957 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
28958 and then call &'receive_add_recipient()'& as often as needed.
28960 .vitem &*uschar&~*sender_address*&
28961 The envelope sender address. For bounce messages this is the empty string.
28963 .vitem &*uschar&~*sender_host_address*&
28964 The IP address of the sending host, as a string. This is NULL for
28965 locally-submitted messages.
28967 .vitem &*uschar&~*sender_host_authenticated*&
28968 The name of the authentication mechanism that was used, or NULL if the message
28969 was not received over an authenticated SMTP connection.
28971 .vitem &*uschar&~*sender_host_name*&
28972 The name of the sending host, if known.
28974 .vitem &*int&~sender_host_port*&
28975 The port on the sending host.
28977 .vitem &*BOOL&~smtp_input*&
28978 This variable is TRUE for all SMTP input, including BSMTP.
28980 .vitem &*BOOL&~smtp_batched_input*&
28981 This variable is TRUE for BSMTP input.
28983 .vitem &*int&~store_pool*&
28984 The contents of this variable control which pool of memory is used for new
28985 requests. See section &<<SECTmemhanloc>>& for details.
28989 .section "Structure of header lines" "SECID209"
28990 The &%header_line%& structure contains the members listed below.
28991 You can add additional header lines by calling the &'header_add()'& function
28992 (see below). You can cause header lines to be ignored (deleted) by setting
28997 .vitem &*struct&~header_line&~*next*&
28998 A pointer to the next header line, or NULL for the last line.
29000 .vitem &*int&~type*&
29001 A code identifying certain headers that Exim recognizes. The codes are printing
29002 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
29003 Notice in particular that any header line whose type is * is not transmitted
29004 with the message. This flagging is used for header lines that have been
29005 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
29006 lines.) Effectively, * means &"deleted"&.
29008 .vitem &*int&~slen*&
29009 The number of characters in the header line, including the terminating and any
29012 .vitem &*uschar&~*text*&
29013 A pointer to the text of the header. It always ends with a newline, followed by
29014 a zero byte. Internal newlines are preserved.
29019 .section "Structure of recipient items" "SECID210"
29020 The &%recipient_item%& structure contains these members:
29023 .vitem &*uschar&~*address*&
29024 This is a pointer to the recipient address as it was received.
29026 .vitem &*int&~pno*&
29027 This is used in later Exim processing when top level addresses are created by
29028 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
29029 and must always contain -1 at this stage.
29031 .vitem &*uschar&~*errors_to*&
29032 If this value is not NULL, bounce messages caused by failing to deliver to the
29033 recipient are sent to the address it contains. In other words, it overrides the
29034 envelope sender for this one recipient. (Compare the &%errors_to%& generic
29035 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
29036 an unqualified address, Exim qualifies it using the domain from
29037 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
29038 is NULL for all recipients.
29043 .section "Available Exim functions" "SECID211"
29044 .cindex "&[local_scan()]& function" "available Exim functions"
29045 The header &_local_scan.h_& gives you access to a number of Exim functions.
29046 These are the only ones that are guaranteed to be maintained from release to
29050 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
29051 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
29053 This function creates a child process that runs the command specified by
29054 &%argv%&. The environment for the process is specified by &%envp%&, which can
29055 be NULL if no environment variables are to be passed. A new umask is supplied
29056 for the process in &%newumask%&.
29058 Pipes to the standard input and output of the new process are set up
29059 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
29060 standard error is cloned to the standard output. If there are any file
29061 descriptors &"in the way"& in the new process, they are closed. If the final
29062 argument is TRUE, the new process is made into a process group leader.
29064 The function returns the pid of the new process, or -1 if things go wrong.
29066 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
29067 This function waits for a child process to terminate, or for a timeout (in
29068 seconds) to expire. A timeout value of zero means wait as long as it takes. The
29069 return value is as follows:
29074 The process terminated by a normal exit and the value is the process
29080 The process was terminated by a signal and the value is the negation of the
29086 The process timed out.
29090 The was some other error in wait(); &%errno%& is still set.
29093 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
29094 This function provide you with a means of submitting a new message to
29095 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
29096 want, but this packages it all up for you.) The function creates a pipe,
29097 forks a subprocess that is running
29099 exim -t -oem -oi -f <>
29101 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
29102 that is connected to the standard input. The yield of the function is the PID
29103 of the subprocess. You can then write a message to the file descriptor, with
29104 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
29106 When you have finished, call &'child_close()'& to wait for the process to
29107 finish and to collect its ending status. A timeout value of zero is usually
29108 fine in this circumstance. Unless you have made a mistake with the recipient
29109 addresses, you should get a return code of zero.
29112 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
29113 *sender_authentication)*&
29114 This function is a more sophisticated version of &'child_open()'&. The command
29117 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
29119 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
29122 .vitem &*void&~debug_printf(char&~*,&~...)*&
29123 This is Exim's debugging function, with arguments as for &'(printf()'&. The
29124 output is written to the standard error stream. If no debugging is selected,
29125 calls to &'debug_printf()'& have no effect. Normally, you should make calls
29126 conditional on the &`local_scan`& debug selector by coding like this:
29128 if ((debug_selector & D_local_scan) != 0)
29129 debug_printf("xxx", ...);
29132 .vitem &*uschar&~*expand_string(uschar&~*string)*&
29133 This is an interface to Exim's string expansion code. The return value is the
29134 expanded string, or NULL if there was an expansion failure.
29135 The C variable &%expand_string_message%& contains an error message after an
29136 expansion failure. If expansion does not change the string, the return value is
29137 the pointer to the input string. Otherwise, the return value points to a new
29138 block of memory that was obtained by a call to &'store_get()'&. See section
29139 &<<SECTmemhanloc>>& below for a discussion of memory handling.
29141 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
29142 This function allows you to an add additional header line at the end of the
29143 existing ones. The first argument is the type, and should normally be a space
29144 character. The second argument is a format string and any number of
29145 substitution arguments as for &[sprintf()]&. You may include internal newlines
29146 if you want, and you must ensure that the string ends with a newline.
29148 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
29149 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
29150 This function adds a new header line at a specified point in the header
29151 chain. The header itself is specified as for &'header_add()'&.
29153 If &%name%& is NULL, the new header is added at the end of the chain if
29154 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
29155 NULL, the header lines are searched for the first non-deleted header that
29156 matches the name. If one is found, the new header is added before it if
29157 &%after%& is false. If &%after%& is true, the new header is added after the
29158 found header and any adjacent subsequent ones with the same name (even if
29159 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
29160 option controls where the header is added. If it is true, addition is at the
29161 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
29162 headers, or at the top if there are no &'Received:'& headers, you could use
29164 header_add_at_position(TRUE, US"Received", TRUE,
29165 ' ', "X-xxx: ...");
29167 Normally, there is always at least one non-deleted &'Received:'& header, but
29168 there may not be if &%received_header_text%& expands to an empty string.
29171 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
29172 This function removes header lines. If &%occurrence%& is zero or negative, all
29173 occurrences of the header are removed. If occurrence is greater than zero, that
29174 particular instance of the header is removed. If no header(s) can be found that
29175 match the specification, the function does nothing.
29178 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
29179 int&~length,&~BOOL&~notdel)*&"
29180 This function tests whether the given header has the given name. It is not just
29181 a string comparison, because white space is permitted between the name and the
29182 colon. If the &%notdel%& argument is true, a false return is forced for all
29183 &"deleted"& headers; otherwise they are not treated specially. For example:
29185 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
29187 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
29188 .cindex "base64 encoding" "functions for &[local_scan()]& use"
29189 This function base64-encodes a string, which is passed by address and length.
29190 The text may contain bytes of any value, including zero. The result is passed
29191 back in dynamic memory that is obtained by calling &'store_get()'&. It is
29194 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
29195 This function decodes a base64-encoded string. Its arguments are a
29196 zero-terminated base64-encoded string and the address of a variable that is set
29197 to point to the result, which is in dynamic memory. The length of the decoded
29198 string is the yield of the function. If the input is invalid base64 data, the
29199 yield is -1. A zero byte is added to the end of the output string to make it
29200 easy to interpret as a C string (assuming it contains no zeros of its own). The
29201 added zero byte is not included in the returned count.
29203 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
29204 This function checks for a match in a domain list. Domains are always
29205 matched caselessly. The return value is one of the following:
29207 &`OK `& match succeeded
29208 &`FAIL `& match failed
29209 &`DEFER `& match deferred
29211 DEFER is usually caused by some kind of lookup defer, such as the
29212 inability to contact a database.
29214 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
29216 This function checks for a match in a local part list. The third argument
29217 controls case-sensitivity. The return values are as for
29218 &'lss_match_domain()'&.
29220 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
29222 This function checks for a match in an address list. The third argument
29223 controls the case-sensitivity of the local part match. The domain is always
29224 matched caselessly. The return values are as for &'lss_match_domain()'&.
29226 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
29228 This function checks for a match in a host list. The most common usage is
29231 lss_match_host(sender_host_name, sender_host_address, ...)
29233 .vindex "&$sender_host_address$&"
29234 An empty address field matches an empty item in the host list. If the host name
29235 is NULL, the name corresponding to &$sender_host_address$& is automatically
29236 looked up if a host name is required to match an item in the list. The return
29237 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
29238 returns ERROR in the case when it had to look up a host name, but the lookup
29241 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
29243 This function writes to Exim's log files. The first argument should be zero (it
29244 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
29245 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
29246 them. It specifies to which log or logs the message is written. The remaining
29247 arguments are a format and relevant insertion arguments. The string should not
29248 contain any newlines, not even at the end.
29251 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
29252 This function adds an additional recipient to the message. The first argument
29253 is the recipient address. If it is unqualified (has no domain), it is qualified
29254 with the &%qualify_recipient%& domain. The second argument must always be -1.
29256 This function does not allow you to specify a private &%errors_to%& address (as
29257 described with the structure of &%recipient_item%& above), because it pre-dates
29258 the addition of that field to the structure. However, it is easy to add such a
29259 value afterwards. For example:
29261 receive_add_recipient(US"monitor@mydom.example", -1);
29262 recipients_list[recipients_count-1].errors_to =
29263 US"postmaster@mydom.example";
29266 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
29267 This is a convenience function to remove a named recipient from the list of
29268 recipients. It returns true if a recipient was removed, and false if no
29269 matching recipient could be found. The argument must be a complete email
29276 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
29277 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
29278 This function decodes strings that are encoded according to RFC 2047. Typically
29279 these are the contents of header lines. First, each &"encoded word"& is decoded
29280 from the Q or B encoding into a byte-string. Then, if provided with the name of
29281 a charset encoding, and if the &[iconv()]& function is available, an attempt is
29282 made to translate the result to the named character set. If this fails, the
29283 binary string is returned with an error message.
29285 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
29286 maximum MIME word length is enforced. The third argument is the target
29287 encoding, or NULL if no translation is wanted.
29289 .cindex "binary zero" "in RFC 2047 decoding"
29290 .cindex "RFC 2047" "binary zero in"
29291 If a binary zero is encountered in the decoded string, it is replaced by the
29292 contents of the &%zeroval%& argument. For use with Exim headers, the value must
29293 not be 0 because header lines are handled as zero-terminated strings.
29295 The function returns the result of processing the string, zero-terminated; if
29296 &%lenptr%& is not NULL, the length of the result is set in the variable to
29297 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
29299 If an error is encountered, the function returns NULL and uses the &%error%&
29300 argument to return an error message. The variable pointed to by &%error%& is
29301 set to NULL if there is no error; it may be set non-NULL even when the function
29302 returns a non-NULL value if decoding was successful, but there was a problem
29306 .vitem &*int&~smtp_fflush(void)*&
29307 This function is used in conjunction with &'smtp_printf()'&, as described
29310 .vitem &*void&~smtp_printf(char&~*,&~...)*&
29311 The arguments of this function are like &[printf()]&; it writes to the SMTP
29312 output stream. You should use this function only when there is an SMTP output
29313 stream, that is, when the incoming message is being received via interactive
29314 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
29315 is FALSE. If you want to test for an incoming message from another host (as
29316 opposed to a local process that used the &%-bs%& command line option), you can
29317 test the value of &%sender_host_address%&, which is non-NULL when a remote host
29320 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
29321 output function, so it can be used for all forms of SMTP connection.
29323 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
29324 must start with an appropriate response code: 550 if you are going to return
29325 LOCAL_SCAN_REJECT, 451 if you are going to return
29326 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
29327 initial lines of a multi-line response, the code must be followed by a hyphen
29328 to indicate that the line is not the final response line. You must also ensure
29329 that the lines you write terminate with CRLF. For example:
29331 smtp_printf("550-this is some extra info\r\n");
29332 return LOCAL_SCAN_REJECT;
29334 Note that you can also create multi-line responses by including newlines in
29335 the data returned via the &%return_text%& argument. The added value of using
29336 &'smtp_printf()'& is that, for instance, you could introduce delays between
29337 multiple output lines.
29339 The &'smtp_printf()'& function does not return any error indication, because it
29340 does not automatically flush pending output, and therefore does not test
29341 the state of the stream. (In the main code of Exim, flushing and error
29342 detection is done when Exim is ready for the next SMTP input command.) If
29343 you want to flush the output and check for an error (for example, the
29344 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
29345 arguments. It flushes the output stream, and returns a non-zero value if there
29348 .vitem &*void&~*store_get(int)*&
29349 This function accesses Exim's internal store (memory) manager. It gets a new
29350 chunk of memory whose size is given by the argument. Exim bombs out if it ever
29351 runs out of memory. See the next section for a discussion of memory handling.
29353 .vitem &*void&~*store_get_perm(int)*&
29354 This function is like &'store_get()'&, but it always gets memory from the
29355 permanent pool. See the next section for a discussion of memory handling.
29357 .vitem &*uschar&~*string_copy(uschar&~*string)*&
29360 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
29363 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
29364 These three functions create strings using Exim's dynamic memory facilities.
29365 The first makes a copy of an entire string. The second copies up to a maximum
29366 number of characters, indicated by the second argument. The third uses a format
29367 and insertion arguments to create a new string. In each case, the result is a
29368 pointer to a new string in the current memory pool. See the next section for
29374 .section "More about Exim's memory handling" "SECTmemhanloc"
29375 .cindex "&[local_scan()]& function" "memory handling"
29376 No function is provided for freeing memory, because that is never needed.
29377 The dynamic memory that Exim uses when receiving a message is automatically
29378 recycled if another message is received by the same process (this applies only
29379 to incoming SMTP connections &-- other input methods can supply only one
29380 message at a time). After receiving the last message, a reception process
29383 Because it is recycled, the normal dynamic memory cannot be used for holding
29384 data that must be preserved over a number of incoming messages on the same SMTP
29385 connection. However, Exim in fact uses two pools of dynamic memory; the second
29386 one is not recycled, and can be used for this purpose.
29388 If you want to allocate memory that remains available for subsequent messages
29389 in the same SMTP connection, you should set
29391 store_pool = POOL_PERM
29393 before calling the function that does the allocation. There is no need to
29394 restore the value if you do not need to; however, if you do want to revert to
29395 the normal pool, you can either restore the previous value of &%store_pool%& or
29396 set it explicitly to POOL_MAIN.
29398 The pool setting applies to all functions that get dynamic memory, including
29399 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
29400 There is also a convenience function called &'store_get_perm()'& that gets a
29401 block of memory from the permanent pool while preserving the value of
29408 . ////////////////////////////////////////////////////////////////////////////
29409 . ////////////////////////////////////////////////////////////////////////////
29411 .chapter "System-wide message filtering" "CHAPsystemfilter"
29412 .scindex IIDsysfil1 "filter" "system filter"
29413 .scindex IIDsysfil2 "filtering all mail"
29414 .scindex IIDsysfil3 "system filter"
29415 The previous chapters (on ACLs and the local scan function) describe checks
29416 that can be applied to messages before they are accepted by a host. There is
29417 also a mechanism for checking messages once they have been received, but before
29418 they are delivered. This is called the &'system filter'&.
29420 The system filter operates in a similar manner to users' filter files, but it
29421 is run just once per message (however many recipients the message has).
29422 It should not normally be used as a substitute for routing, because &%deliver%&
29423 commands in a system router provide new envelope recipient addresses.
29424 The system filter must be an Exim filter. It cannot be a Sieve filter.
29426 The system filter is run at the start of a delivery attempt, before any routing
29427 is done. If a message fails to be completely delivered at the first attempt,
29428 the system filter is run again at the start of every retry.
29429 If you want your filter to do something only once per message, you can make use
29430 of the &%first_delivery%& condition in an &%if%& command in the filter to
29431 prevent it happening on retries.
29433 .vindex "&$domain$&"
29434 .vindex "&$local_part$&"
29435 &*Warning*&: Because the system filter runs just once, variables that are
29436 specific to individual recipient addresses, such as &$local_part$& and
29437 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
29438 you want to run a centrally-specified filter for each recipient address
29439 independently, you can do so by setting up a suitable &(redirect)& router, as
29440 described in section &<<SECTperaddfil>>& below.
29443 .section "Specifying a system filter" "SECID212"
29444 .cindex "uid (user id)" "system filter"
29445 .cindex "gid (group id)" "system filter"
29446 The name of the file that contains the system filter must be specified by
29447 setting &%system_filter%&. If you want the filter to run under a uid and gid
29448 other than root, you must also set &%system_filter_user%& and
29449 &%system_filter_group%& as appropriate. For example:
29451 system_filter = /etc/mail/exim.filter
29452 system_filter_user = exim
29454 If a system filter generates any deliveries directly to files or pipes (via the
29455 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
29456 specified by setting &%system_filter_file_transport%& and
29457 &%system_filter_pipe_transport%&, respectively. Similarly,
29458 &%system_filter_reply_transport%& must be set to handle any messages generated
29459 by the &%reply%& command.
29462 .section "Testing a system filter" "SECID213"
29463 You can run simple tests of a system filter in the same way as for a user
29464 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
29465 are permitted only in system filters are recognized.
29467 If you want to test the combined effect of a system filter and a user filter,
29468 you can use both &%-bF%& and &%-bf%& on the same command line.
29472 .section "Contents of a system filter" "SECID214"
29473 The language used to specify system filters is the same as for users' filter
29474 files. It is described in the separate end-user document &'Exim's interface to
29475 mail filtering'&. However, there are some additional features that are
29476 available only in system filters; these are described in subsequent sections.
29477 If they are encountered in a user's filter file or when testing with &%-bf%&,
29480 .cindex "frozen messages" "manual thaw; testing in filter"
29481 There are two special conditions which, though available in users' filter
29482 files, are designed for use in system filters. The condition &%first_delivery%&
29483 is true only for the first attempt at delivering a message, and
29484 &%manually_thawed%& is true only if the message has been frozen, and
29485 subsequently thawed by an admin user. An explicit forced delivery counts as a
29486 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
29488 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
29489 specify an &"unseen"& (non-significant) delivery, and that delivery does not
29490 succeed, it will not be tried again.
29491 If you want Exim to retry an unseen delivery until it succeeds, you should
29492 arrange to set it up every time the filter runs.
29494 When a system filter finishes running, the values of the variables &$n0$& &--
29495 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
29496 users' filter files. Thus a system filter can, for example, set up &"scores"&
29497 to which users' filter files can refer.
29501 .section "Additional variable for system filters" "SECID215"
29502 .vindex "&$recipients$&"
29503 The expansion variable &$recipients$&, containing a list of all the recipients
29504 of the message (separated by commas and white space), is available in system
29505 filters. It is not available in users' filters for privacy reasons.
29509 .section "Defer, freeze, and fail commands for system filters" "SECID216"
29510 .cindex "freezing messages"
29511 .cindex "message" "freezing"
29512 .cindex "message" "forced failure"
29513 .cindex "&%fail%&" "in system filter"
29514 .cindex "&%freeze%& in system filter"
29515 .cindex "&%defer%& in system filter"
29516 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
29517 always available in system filters, but are not normally enabled in users'
29518 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
29519 for the &(redirect)& router.) These commands can optionally be followed by the
29520 word &%text%& and a string containing an error message, for example:
29522 fail text "this message looks like spam to me"
29524 The keyword &%text%& is optional if the next character is a double quote.
29526 The &%defer%& command defers delivery of the original recipients of the
29527 message. The &%fail%& command causes all the original recipients to be failed,
29528 and a bounce message to be created. The &%freeze%& command suspends all
29529 delivery attempts for the original recipients. In all cases, any new deliveries
29530 that are specified by the filter are attempted as normal after the filter has
29533 The &%freeze%& command is ignored if the message has been manually unfrozen and
29534 not manually frozen since. This means that automatic freezing by a system
29535 filter can be used as a way of checking out suspicious messages. If a message
29536 is found to be all right, manually unfreezing it allows it to be delivered.
29538 .cindex "log" "&%fail%& command log line"
29539 .cindex "&%fail%&" "log line; reducing"
29540 The text given with a fail command is used as part of the bounce message as
29541 well as being written to the log. If the message is quite long, this can fill
29542 up a lot of log space when such failures are common. To reduce the size of the
29543 log message, Exim interprets the text in a special way if it starts with the
29544 two characters &`<<`& and contains &`>>`& later. The text between these two
29545 strings is written to the log, and the rest of the text is used in the bounce
29546 message. For example:
29548 fail "<<filter test 1>>Your message is rejected \
29549 because it contains attachments that we are \
29550 not prepared to receive."
29553 .cindex "loop" "caused by &%fail%&"
29554 Take great care with the &%fail%& command when basing the decision to fail on
29555 the contents of the message, because the bounce message will of course include
29556 the contents of the original message and will therefore trigger the &%fail%&
29557 command again (causing a mail loop) unless steps are taken to prevent this.
29558 Testing the &%error_message%& condition is one way to prevent this. You could
29561 if $message_body contains "this is spam" and not error_message
29562 then fail text "spam is not wanted here" endif
29564 though of course that might let through unwanted bounce messages. The
29565 alternative is clever checking of the body and/or headers to detect bounces
29566 generated by the filter.
29568 The interpretation of a system filter file ceases after a
29570 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
29571 set up earlier in the filter file are honoured, so you can use a sequence such
29577 to send a specified message when the system filter is freezing (or deferring or
29578 failing) a message. The normal deliveries for the message do not, of course,
29583 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
29584 .cindex "header lines" "adding; in system filter"
29585 .cindex "header lines" "removing; in system filter"
29586 .cindex "filter" "header lines; adding/removing"
29587 Two filter commands that are available only in system filters are:
29589 headers add <string>
29590 headers remove <string>
29592 The argument for the &%headers add%& is a string that is expanded and then
29593 added to the end of the message's headers. It is the responsibility of the
29594 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
29595 space is ignored, and if the string is otherwise empty, or if the expansion is
29596 forced to fail, the command has no effect.
29598 You can use &"\n"& within the string, followed by white space, to specify
29599 continued header lines. More than one header may be added in one command by
29600 including &"\n"& within the string without any following white space. For
29603 headers add "X-header-1: ....\n \
29604 continuation of X-header-1 ...\n\
29607 Note that the header line continuation white space after the first newline must
29608 be placed before the backslash that continues the input string, because white
29609 space after input continuations is ignored.
29611 The argument for &%headers remove%& is a colon-separated list of header names.
29612 This command applies only to those headers that are stored with the message;
29613 those that are added at delivery time (such as &'Envelope-To:'& and
29614 &'Return-Path:'&) cannot be removed by this means. If there is more than one
29615 header with the same name, they are all removed.
29617 The &%headers%& command in a system filter makes an immediate change to the set
29618 of header lines that was received with the message (with possible additions
29619 from ACL processing). Subsequent commands in the system filter operate on the
29620 modified set, which also forms the basis for subsequent message delivery.
29621 Unless further modified during routing or transporting, this set of headers is
29622 used for all recipients of the message.
29624 During routing and transporting, the variables that refer to the contents of
29625 header lines refer only to those lines that are in this set. Thus, header lines
29626 that are added by a system filter are visible to users' filter files and to all
29627 routers and transports. This contrasts with the manipulation of header lines by
29628 routers and transports, which is not immediate, but which instead is saved up
29629 until the message is actually being written (see section
29630 &<<SECTheadersaddrem>>&).
29632 If the message is not delivered at the first attempt, header lines that were
29633 added by the system filter are stored with the message, and so are still
29634 present at the next delivery attempt. Header lines that were removed are still
29635 present, but marked &"deleted"& so that they are not transported with the
29636 message. For this reason, it is usual to make the &%headers%& command
29637 conditional on &%first_delivery%& so that the set of header lines is not
29638 modified more than once.
29640 Because header modification in a system filter acts immediately, you have to
29641 use an indirect approach if you want to modify the contents of a header line.
29644 headers add "Old-Subject: $h_subject:"
29645 headers remove "Subject"
29646 headers add "Subject: new subject (was: $h_old-subject:)"
29647 headers remove "Old-Subject"
29652 .section "Setting an errors address in a system filter" "SECID217"
29653 .cindex "envelope sender"
29654 In a system filter, if a &%deliver%& command is followed by
29656 errors_to <some address>
29658 in order to change the envelope sender (and hence the error reporting) for that
29659 delivery, any address may be specified. (In a user filter, only the current
29660 user's address can be set.) For example, if some mail is being monitored, you
29663 unseen deliver monitor@spying.example errors_to root@local.example
29665 to take a copy which would not be sent back to the normal error reporting
29666 address if its delivery failed.
29670 .section "Per-address filtering" "SECTperaddfil"
29671 .vindex "&$domain$&"
29672 .vindex "&$local_part$&"
29673 In contrast to the system filter, which is run just once per message for each
29674 delivery attempt, it is also possible to set up a system-wide filtering
29675 operation that runs once for each recipient address. In this case, variables
29676 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
29677 filter file could be made dependent on them. This is an example of a router
29678 which implements such a filter:
29683 domains = +local_domains
29684 file = /central/filters/$local_part
29689 The filter is run in a separate process under its own uid. Therefore, either
29690 &%check_local_user%& must be set (as above), in which case the filter is run as
29691 the local user, or the &%user%& option must be used to specify which user to
29692 use. If both are set, &%user%& overrides.
29694 Care should be taken to ensure that none of the commands in the filter file
29695 specify a significant delivery if the message is to go on to be delivered to
29696 its intended recipient. The router will not then claim to have dealt with the
29697 address, so it will be passed on to subsequent routers to be delivered in the
29699 .ecindex IIDsysfil1
29700 .ecindex IIDsysfil2
29701 .ecindex IIDsysfil3
29708 . ////////////////////////////////////////////////////////////////////////////
29709 . ////////////////////////////////////////////////////////////////////////////
29711 .chapter "Message processing" "CHAPmsgproc"
29712 .scindex IIDmesproc "message" "general processing"
29713 Exim performs various transformations on the sender and recipient addresses of
29714 all messages that it handles, and also on the messages' header lines. Some of
29715 these are optional and configurable, while others always take place. All of
29716 this processing, except rewriting as a result of routing, and the addition or
29717 removal of header lines while delivering, happens when a message is received,
29718 before it is placed on Exim's queue.
29720 Some of the automatic processing takes place by default only for
29721 &"locally-originated"& messages. This adjective is used to describe messages
29722 that are not received over TCP/IP, but instead are passed to an Exim process on
29723 its standard input. This includes the interactive &"local SMTP"& case that is
29724 set up by the &%-bs%& command line option.
29726 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
29727 or ::1) are not considered to be locally-originated. Exim does not treat the
29728 loopback interface specially in any way.
29730 If you want the loopback interface to be treated specially, you must ensure
29731 that there are appropriate entries in your ACLs.
29736 .section "Submission mode for non-local messages" "SECTsubmodnon"
29737 .cindex "message" "submission"
29738 .cindex "submission mode"
29739 Processing that happens automatically for locally-originated messages (unless
29740 &%suppress_local_fixups%& is set) can also be requested for messages that are
29741 received over TCP/IP. The term &"submission mode"& is used to describe this
29742 state. Submission mode is set by the modifier
29744 control = submission
29746 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
29747 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
29748 a local submission, and is normally used when the source of the message is
29749 known to be an MUA running on a client host (as opposed to an MTA). For
29750 example, to set submission mode for messages originating on the IPv4 loopback
29751 interface, you could include the following in the MAIL ACL:
29753 warn hosts = 127.0.0.1
29754 control = submission
29756 .cindex "&%sender_retain%& submission option"
29757 There are some options that can be used when setting submission mode. A slash
29758 is used to separate options. For example:
29760 control = submission/sender_retain
29762 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
29763 true and &%local_from_check%& false for the current incoming message. The first
29764 of these allows an existing &'Sender:'& header in the message to remain, and
29765 the second suppresses the check to ensure that &'From:'& matches the
29766 authenticated sender. With this setting, Exim still fixes up messages by adding
29767 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
29768 attempt to check sender authenticity in header lines.
29770 When &%sender_retain%& is not set, a submission mode setting may specify a
29771 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
29774 control = submission/domain=some.domain
29776 The domain may be empty. How this value is used is described in sections
29777 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
29778 that allows you to specify the user's full name for inclusion in a created
29779 &'Sender:'& or &'From:'& header line. For example:
29781 accept authenticated = *
29782 control = submission/domain=wonderland.example/\
29783 name=${lookup {$authenticated_id} \
29784 lsearch {/etc/exim/namelist}}
29786 Because the name may contain any characters, including slashes, the &%name%&
29787 option must be given last. The remainder of the string is used as the name. For
29788 the example above, if &_/etc/exim/namelist_& contains:
29790 bigegg: Humpty Dumpty
29792 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
29795 Sender: Humpty Dumpty <bigegg@wonderland.example>
29797 .cindex "return path" "in submission mode"
29798 By default, submission mode forces the return path to the same address as is
29799 used to create the &'Sender:'& header. However, if &%sender_retain%& is
29800 specified, the return path is also left unchanged.
29802 &*Note*&: The changes caused by submission mode take effect after the predata
29803 ACL. This means that any sender checks performed before the fix-ups use the
29804 untrusted sender address specified by the user, not the trusted sender address
29805 specified by submission mode. Although this might be slightly unexpected, it
29806 does mean that you can configure ACL checks to spot that a user is trying to
29807 spoof another's address.
29809 .section "Line endings" "SECTlineendings"
29810 .cindex "line endings"
29811 .cindex "carriage return"
29813 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
29814 linefeed) is the line ending for messages transmitted over the Internet using
29815 SMTP over TCP/IP. However, within individual operating systems, different
29816 conventions are used. For example, Unix-like systems use just LF, but others
29817 use CRLF or just CR.
29819 Exim was designed for Unix-like systems, and internally, it stores messages
29820 using the system's convention of a single LF as a line terminator. When
29821 receiving a message, all line endings are translated to this standard format.
29822 Originally, it was thought that programs that passed messages directly to an
29823 MTA within an operating system would use that system's convention. Experience
29824 has shown that this is not the case; for example, there are Unix applications
29825 that use CRLF in this circumstance. For this reason, and for compatibility with
29826 other MTAs, the way Exim handles line endings for all messages is now as
29830 LF not preceded by CR is treated as a line ending.
29832 CR is treated as a line ending; if it is immediately followed by LF, the LF
29835 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
29836 nor a local message in the state where a line containing only a dot is a
29839 If a bare CR is encountered within a header line, an extra space is added after
29840 the line terminator so as not to end the header line. The reasoning behind this
29841 is that bare CRs in header lines are most likely either to be mistakes, or
29842 people trying to play silly games.
29844 If the first header line received in a message ends with CRLF, a subsequent
29845 bare LF in a header line is treated in the same way as a bare CR in a header
29853 .section "Unqualified addresses" "SECID218"
29854 .cindex "unqualified addresses"
29855 .cindex "address" "qualification"
29856 By default, Exim expects every envelope address it receives from an external
29857 host to be fully qualified. Unqualified addresses cause negative responses to
29858 SMTP commands. However, because SMTP is used as a means of transporting
29859 messages from MUAs running on personal workstations, there is sometimes a
29860 requirement to accept unqualified addresses from specific hosts or IP networks.
29862 Exim has two options that separately control which hosts may send unqualified
29863 sender or recipient addresses in SMTP commands, namely
29864 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
29865 cases, if an unqualified address is accepted, it is qualified by adding the
29866 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
29868 .oindex "&%qualify_domain%&"
29869 .oindex "&%qualify_recipient%&"
29870 Unqualified addresses in header lines are automatically qualified for messages
29871 that are locally originated, unless the &%-bnq%& option is given on the command
29872 line. For messages received over SMTP, unqualified addresses in header lines
29873 are qualified only if unqualified addresses are permitted in SMTP commands. In
29874 other words, such qualification is also controlled by
29875 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
29880 .section "The UUCP From line" "SECID219"
29881 .cindex "&""From""& line"
29882 .cindex "UUCP" "&""From""& line"
29883 .cindex "sender" "address"
29884 .oindex "&%uucp_from_pattern%&"
29885 .oindex "&%uucp_from_sender%&"
29886 .cindex "envelope sender"
29887 .cindex "Sendmail compatibility" "&""From""& line"
29888 Messages that have come from UUCP (and some other applications) often begin
29889 with a line containing the envelope sender and a timestamp, following the word
29890 &"From"&. Examples of two common formats are:
29892 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
29893 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
29895 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
29896 Exim recognizes such lines at the start of messages that are submitted to it
29897 via the command line (that is, on the standard input). It does not recognize
29898 such lines in incoming SMTP messages, unless the sending host matches
29899 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
29900 and &%ignore_fromline_local%& is set. The recognition is controlled by a
29901 regular expression that is defined by the &%uucp_from_pattern%& option, whose
29902 default value matches the two common cases shown above and puts the address
29903 that follows &"From"& into &$1$&.
29905 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
29906 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
29907 a trusted user, the message's sender address is constructed by expanding the
29908 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
29909 then parsed as an RFC 2822 address. If there is no domain, the local part is
29910 qualified with &%qualify_domain%& unless it is the empty string. However, if
29911 the command line &%-f%& option is used, it overrides the &"From"& line.
29913 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
29914 sender address is not changed. This is also the case for incoming SMTP messages
29915 that are permitted to contain &"From"& lines.
29917 Only one &"From"& line is recognized. If there is more than one, the second is
29918 treated as a data line that starts the body of the message, as it is not valid
29919 as a header line. This also happens if a &"From"& line is present in an
29920 incoming SMTP message from a source that is not permitted to send them.
29924 .section "Resent- header lines" "SECID220"
29925 .cindex "&%Resent-%& header lines"
29926 RFC 2822 makes provision for sets of header lines starting with the string
29927 &`Resent-`& to be added to a message when it is resent by the original
29928 recipient to somebody else. These headers are &'Resent-Date:'&,
29929 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
29930 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
29933 &'Resent fields are strictly informational. They MUST NOT be used in the normal
29934 processing of replies or other such automatic actions on messages.'&
29937 This leaves things a bit vague as far as other processing actions such as
29938 address rewriting are concerned. Exim treats &%Resent-%& header lines as
29942 A &'Resent-From:'& line that just contains the login id of the submitting user
29943 is automatically rewritten in the same way as &'From:'& (see below).
29945 If there's a rewriting rule for a particular header line, it is also applied to
29946 &%Resent-%& header lines of the same type. For example, a rule that rewrites
29947 &'From:'& also rewrites &'Resent-From:'&.
29949 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
29952 For a locally-submitted message,
29953 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
29954 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
29955 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
29956 included in log lines in this case.
29958 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
29959 &%Resent-%& header lines are present.
29965 .section "The Auto-Submitted: header line" "SECID221"
29966 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
29967 includes the header line:
29969 Auto-Submitted: auto-replied
29972 .section "The Bcc: header line" "SECID222"
29973 .cindex "&'Bcc:'& header line"
29974 If Exim is called with the &%-t%& option, to take recipient addresses from a
29975 message's header, it removes any &'Bcc:'& header line that may exist (after
29976 extracting its addresses). If &%-t%& is not present on the command line, any
29977 existing &'Bcc:'& is not removed.
29980 .section "The Date: header line" "SECID223"
29981 .cindex "&'Date:'& header line"
29982 If a locally-generated or submission-mode message has no &'Date:'& header line,
29983 Exim adds one, using the current date and time, unless the
29984 &%suppress_local_fixups%& control has been specified.
29986 .section "The Delivery-date: header line" "SECID224"
29987 .cindex "&'Delivery-date:'& header line"
29988 .oindex "&%delivery_date_remove%&"
29989 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
29990 set. Exim can be configured to add them to the final delivery of messages. (See
29991 the generic &%delivery_date_add%& transport option.) They should not be present
29992 in messages in transit. If the &%delivery_date_remove%& configuration option is
29993 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
29997 .section "The Envelope-to: header line" "SECID225"
29998 .cindex "&'Envelope-to:'& header line"
29999 .oindex "&%envelope_to_remove%&"
30000 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
30001 Exim can be configured to add them to the final delivery of messages. (See the
30002 generic &%envelope_to_add%& transport option.) They should not be present in
30003 messages in transit. If the &%envelope_to_remove%& configuration option is set
30004 (the default), Exim removes &'Envelope-to:'& header lines from incoming
30008 .section "The From: header line" "SECTthefrohea"
30009 .cindex "&'From:'& header line"
30010 .cindex "Sendmail compatibility" "&""From""& line"
30011 .cindex "message" "submission"
30012 .cindex "submission mode"
30013 If a submission-mode message does not contain a &'From:'& header line, Exim
30014 adds one if either of the following conditions is true:
30017 The envelope sender address is not empty (that is, this is not a bounce
30018 message). The added header line copies the envelope sender address.
30020 .vindex "&$authenticated_id$&"
30021 The SMTP session is authenticated and &$authenticated_id$& is not empty.
30023 .vindex "&$qualify_domain$&"
30024 If no domain is specified by the submission control, the local part is
30025 &$authenticated_id$& and the domain is &$qualify_domain$&.
30027 If a non-empty domain is specified by the submission control, the local
30028 part is &$authenticated_id$&, and the domain is the specified domain.
30030 If an empty domain is specified by the submission control,
30031 &$authenticated_id$& is assumed to be the complete address.
30035 A non-empty envelope sender takes precedence.
30037 If a locally-generated incoming message does not contain a &'From:'& header
30038 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
30039 containing the sender's address. The calling user's login name and full name
30040 are used to construct the address, as described in section &<<SECTconstr>>&.
30041 They are obtained from the password data by calling &[getpwuid()]& (but see the
30042 &%unknown_login%& configuration option). The address is qualified with
30043 &%qualify_domain%&.
30045 For compatibility with Sendmail, if an incoming, non-SMTP message has a
30046 &'From:'& header line containing just the unqualified login name of the calling
30047 user, this is replaced by an address containing the user's login name and full
30048 name as described in section &<<SECTconstr>>&.
30051 .section "The Message-ID: header line" "SECID226"
30052 .cindex "&'Message-ID:'& header line"
30053 .cindex "message" "submission"
30054 .oindex "&%message_id_header_text%&"
30055 If a locally-generated or submission-mode incoming message does not contain a
30056 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
30057 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
30058 to the message. If there are any &'Resent-:'& headers in the message, it
30059 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
30060 message id, preceded by the letter E to ensure it starts with a letter, and
30061 followed by @ and the primary host name. Additional information can be included
30062 in this header line by setting the &%message_id_header_text%& and/or
30063 &%message_id_header_domain%& options.
30066 .section "The Received: header line" "SECID227"
30067 .cindex "&'Received:'& header line"
30068 A &'Received:'& header line is added at the start of every message. The
30069 contents are defined by the &%received_header_text%& configuration option, and
30070 Exim automatically adds a semicolon and a timestamp to the configured string.
30072 The &'Received:'& header is generated as soon as the message's header lines
30073 have been received. At this stage, the timestamp in the &'Received:'& header
30074 line is the time that the message started to be received. This is the value
30075 that is seen by the DATA ACL and by the &[local_scan()]& function.
30077 Once a message is accepted, the timestamp in the &'Received:'& header line is
30078 changed to the time of acceptance, which is (apart from a small delay while the
30079 -H spool file is written) the earliest time at which delivery could start.
30082 .section "The References: header line" "SECID228"
30083 .cindex "&'References:'& header line"
30084 Messages created by the &(autoreply)& transport include a &'References:'&
30085 header line. This is constructed according to the rules that are described in
30086 section 3.64 of RFC 2822 (which states that replies should contain such a
30087 header line), and section 3.14 of RFC 3834 (which states that automatic
30088 responses are not different in this respect). However, because some mail
30089 processing software does not cope well with very long header lines, no more
30090 than 12 message IDs are copied from the &'References:'& header line in the
30091 incoming message. If there are more than 12, the first one and then the final
30092 11 are copied, before adding the message ID of the incoming message.
30096 .section "The Return-path: header line" "SECID229"
30097 .cindex "&'Return-path:'& header line"
30098 .oindex "&%return_path_remove%&"
30099 &'Return-path:'& header lines are defined as something an MTA may insert when
30100 it does the final delivery of messages. (See the generic &%return_path_add%&
30101 transport option.) Therefore, they should not be present in messages in
30102 transit. If the &%return_path_remove%& configuration option is set (the
30103 default), Exim removes &'Return-path:'& header lines from incoming messages.
30107 .section "The Sender: header line" "SECTthesenhea"
30108 .cindex "&'Sender:'& header line"
30109 .cindex "message" "submission"
30110 For a locally-originated message from an untrusted user, Exim may remove an
30111 existing &'Sender:'& header line, and it may add a new one. You can modify
30112 these actions by setting the &%local_sender_retain%& option true, the
30113 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
30116 When a local message is received from an untrusted user and
30117 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
30118 control has not been set, a check is made to see if the address given in the
30119 &'From:'& header line is the correct (local) sender of the message. The address
30120 that is expected has the login name as the local part and the value of
30121 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
30122 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
30123 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
30124 line is added to the message.
30126 If you set &%local_from_check%& false, this checking does not occur. However,
30127 the removal of an existing &'Sender:'& line still happens, unless you also set
30128 &%local_sender_retain%& to be true. It is not possible to set both of these
30129 options true at the same time.
30131 .cindex "submission mode"
30132 By default, no processing of &'Sender:'& header lines is done for messages
30133 received over TCP/IP or for messages submitted by trusted users. However, when
30134 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
30135 not specified on the submission control, the following processing takes place:
30137 .vindex "&$authenticated_id$&"
30138 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
30139 authenticated, and &$authenticated_id$& is not empty, a sender address is
30140 created as follows:
30143 .vindex "&$qualify_domain$&"
30144 If no domain is specified by the submission control, the local part is
30145 &$authenticated_id$& and the domain is &$qualify_domain$&.
30147 If a non-empty domain is specified by the submission control, the local part
30148 is &$authenticated_id$&, and the domain is the specified domain.
30150 If an empty domain is specified by the submission control,
30151 &$authenticated_id$& is assumed to be the complete address.
30154 This address is compared with the address in the &'From:'& header line. If they
30155 are different, a &'Sender:'& header line containing the created address is
30156 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
30157 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
30159 .cindex "return path" "created from &'Sender:'&"
30160 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
30161 the message (the envelope sender address) is changed to be the same address,
30162 except in the case of submission mode when &%sender_retain%& is specified.
30166 .section "Adding and removing header lines in routers and transports" &&&
30167 "SECTheadersaddrem"
30168 .cindex "header lines" "adding; in router or transport"
30169 .cindex "header lines" "removing; in router or transport"
30170 When a message is delivered, the addition and removal of header lines can be
30171 specified in a system filter, or on any of the routers and transports that
30172 process the message. Section &<<SECTaddremheasys>>& contains details about
30173 modifying headers in a system filter. Header lines can also be added in an ACL
30174 as a message is received (see section &<<SECTaddheadacl>>&).
30176 In contrast to what happens in a system filter, header modifications that are
30177 specified on routers and transports apply only to the particular recipient
30178 addresses that are being processed by those routers and transports. These
30179 changes do not actually take place until a copy of the message is being
30180 transported. Therefore, they do not affect the basic set of header lines, and
30181 they do not affect the values of the variables that refer to header lines.
30183 &*Note*&: In particular, this means that any expansions in the configuration of
30184 the transport cannot refer to the modified header lines, because such
30185 expansions all occur before the message is actually transported.
30187 For both routers and transports, the result of expanding a &%headers_add%&
30188 option must be in the form of one or more RFC 2822 header lines, separated by
30189 newlines (coded as &"\n"&). For example:
30191 headers_add = X-added-header: added by $primary_hostname\n\
30192 X-added-second: another added header line
30194 Exim does not check the syntax of these added header lines.
30196 The result of expanding &%headers_remove%& must consist of a colon-separated
30197 list of header names. This is confusing, because header names themselves are
30198 often terminated by colons. In this case, the colons are the list separators,
30199 not part of the names. For example:
30201 headers_remove = return-receipt-to:acknowledge-to
30203 When &%headers_add%& or &%headers_remove%& is specified on a router, its value
30204 is expanded at routing time, and then associated with all addresses that are
30205 accepted by that router, and also with any new addresses that it generates. If
30206 an address passes through several routers as a result of aliasing or
30207 forwarding, the changes are cumulative.
30209 .oindex "&%unseen%&"
30210 However, this does not apply to multiple routers that result from the use of
30211 the &%unseen%& option. Any header modifications that were specified by the
30212 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
30214 Addresses that end up with different &%headers_add%& or &%headers_remove%&
30215 settings cannot be delivered together in a batch, so a transport is always
30216 dealing with a set of addresses that have the same header-processing
30219 The transport starts by writing the original set of header lines that arrived
30220 with the message, possibly modified by the system filter. As it writes out
30221 these lines, it consults the list of header names that were attached to the
30222 recipient address(es) by &%headers_remove%& options in routers, and it also
30223 consults the transport's own &%headers_remove%& option. Header lines whose
30224 names are on either of these lists are not written out. If there are multiple
30225 instances of any listed header, they are all skipped.
30227 After the remaining original header lines have been written, new header
30228 lines that were specified by routers' &%headers_add%& options are written, in
30229 the order in which they were attached to the address. These are followed by any
30230 header lines specified by the transport's &%headers_add%& option.
30232 This way of handling header line modifications in routers and transports has
30233 the following consequences:
30236 The original set of header lines, possibly modified by the system filter,
30237 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
30238 to it, at all times.
30240 Header lines that are added by a router's
30241 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
30242 expansion syntax in subsequent routers or the transport.
30244 Conversely, header lines that are specified for removal by &%headers_remove%&
30245 in a router remain visible to subsequent routers and the transport.
30247 Headers added to an address by &%headers_add%& in a router cannot be removed by
30248 a later router or by a transport.
30250 An added header can refer to the contents of an original header that is to be
30251 removed, even it has the same name as the added header. For example:
30253 headers_remove = subject
30254 headers_add = Subject: new subject (was: $h_subject:)
30258 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
30259 for a &(redirect)& router that has the &%one_time%& option set.
30265 .section "Constructed addresses" "SECTconstr"
30266 .cindex "address" "constructed"
30267 .cindex "constructed address"
30268 When Exim constructs a sender address for a locally-generated message, it uses
30271 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
30275 Zaphod Beeblebrox <zaphod@end.univ.example>
30277 The user name is obtained from the &%-F%& command line option if set, or
30278 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
30279 &"gecos"& field from the password entry. If the &"gecos"& field contains an
30280 ampersand character, this is replaced by the login name with the first letter
30281 upper cased, as is conventional in a number of operating systems. See the
30282 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
30283 The &%unknown_username%& option can be used to specify user names in cases when
30284 there is no password file entry.
30287 In all cases, the user name is made to conform to RFC 2822 by quoting all or
30288 parts of it if necessary. In addition, if it contains any non-printing
30289 characters, it is encoded as described in RFC 2047, which defines a way of
30290 including non-ASCII characters in header lines. The value of the
30291 &%headers_charset%& option specifies the name of the encoding that is used (the
30292 characters are assumed to be in this encoding). The setting of
30293 &%print_topbitchars%& controls whether characters with the top bit set (that
30294 is, with codes greater than 127) count as printing characters or not.
30298 .section "Case of local parts" "SECID230"
30299 .cindex "case of local parts"
30300 .cindex "local part" "case of"
30301 RFC 2822 states that the case of letters in the local parts of addresses cannot
30302 be assumed to be non-significant. Exim preserves the case of local parts of
30303 addresses, but by default it uses a lower-cased form when it is routing,
30304 because on most Unix systems, usernames are in lower case and case-insensitive
30305 routing is required. However, any particular router can be made to use the
30306 original case for local parts by setting the &%caseful_local_part%& generic
30309 .cindex "mixed-case login names"
30310 If you must have mixed-case user names on your system, the best way to proceed,
30311 assuming you want case-independent handling of incoming email, is to set up
30312 your first router to convert incoming local parts in your domains to the
30313 correct case by means of a file lookup. For example:
30317 domains = +local_domains
30318 data = ${lookup{$local_part}cdb\
30319 {/etc/usercased.cdb}{$value}fail}\
30322 For this router, the local part is forced to lower case by the default action
30323 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
30324 up a new local part in the correct case. If you then set &%caseful_local_part%&
30325 on any subsequent routers which process your domains, they will operate on
30326 local parts with the correct case in a case-sensitive manner.
30330 .section "Dots in local parts" "SECID231"
30331 .cindex "dot" "in local part"
30332 .cindex "local part" "dots in"
30333 RFC 2822 forbids empty components in local parts. That is, an unquoted local
30334 part may not begin or end with a dot, nor have two consecutive dots in the
30335 middle. However, it seems that many MTAs do not enforce this, so Exim permits
30336 empty components for compatibility.
30340 .section "Rewriting addresses" "SECID232"
30341 .cindex "rewriting" "addresses"
30342 Rewriting of sender and recipient addresses, and addresses in headers, can
30343 happen automatically, or as the result of configuration options, as described
30344 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
30345 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
30347 Automatic rewriting includes qualification, as mentioned above. The other case
30348 in which it can happen is when an incomplete non-local domain is given. The
30349 routing process may cause this to be expanded into the full domain name. For
30350 example, a header such as
30354 might get rewritten as
30356 To: hare@teaparty.wonderland.fict.example
30358 Rewriting as a result of routing is the one kind of message processing that
30359 does not happen at input time, as it cannot be done until the address has
30362 Strictly, one should not do &'any'& deliveries of a message until all its
30363 addresses have been routed, in case any of the headers get changed as a
30364 result of routing. However, doing this in practice would hold up many
30365 deliveries for unreasonable amounts of time, just because one address could not
30366 immediately be routed. Exim therefore does not delay other deliveries when
30367 routing of one or more addresses is deferred.
30368 .ecindex IIDmesproc
30372 . ////////////////////////////////////////////////////////////////////////////
30373 . ////////////////////////////////////////////////////////////////////////////
30375 .chapter "SMTP processing" "CHAPSMTP"
30376 .scindex IIDsmtpproc1 "SMTP" "processing details"
30377 .scindex IIDsmtpproc2 "LMTP" "processing details"
30378 Exim supports a number of different ways of using the SMTP protocol, and its
30379 LMTP variant, which is an interactive protocol for transferring messages into a
30380 closed mail store application. This chapter contains details of how SMTP is
30381 processed. For incoming mail, the following are available:
30384 SMTP over TCP/IP (Exim daemon or &'inetd'&);
30386 SMTP over the standard input and output (the &%-bs%& option);
30388 Batched SMTP on the standard input (the &%-bS%& option).
30391 For mail delivery, the following are available:
30394 SMTP over TCP/IP (the &(smtp)& transport);
30396 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
30399 LMTP over a pipe to a process running in the local host (the &(lmtp)&
30402 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
30403 the &%use_bsmtp%& option set).
30406 &'Batched SMTP'& is the name for a process in which batches of messages are
30407 stored in or read from files (or pipes), in a format in which SMTP commands are
30408 used to contain the envelope information.
30412 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
30413 .cindex "SMTP" "outgoing over TCP/IP"
30414 .cindex "outgoing SMTP over TCP/IP"
30415 .cindex "LMTP" "over TCP/IP"
30416 .cindex "outgoing LMTP over TCP/IP"
30419 .cindex "SIZE option on MAIL command"
30420 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
30421 The &%protocol%& option selects which protocol is to be used, but the actual
30422 processing is the same in both cases.
30424 If, in response to its EHLO command, Exim is told that the SIZE
30425 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
30426 command. The value of <&'n'&> is the message size plus the value of the
30427 &%size_addition%& option (default 1024) to allow for additions to the message
30428 such as per-transport header lines, or changes made in a
30429 .cindex "transport" "filter"
30430 .cindex "filter" "transport filter"
30431 transport filter. If &%size_addition%& is set negative, the use of SIZE is
30434 If the remote server advertises support for PIPELINING, Exim uses the
30435 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
30436 required for the transaction.
30438 If the remote server advertises support for the STARTTLS command, and Exim
30439 was built to support TLS encryption, it tries to start a TLS session unless the
30440 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
30442 If the remote server advertises support for the AUTH command, Exim scans
30443 the authenticators configuration for any suitable client settings, as described
30444 in chapter &<<CHAPSMTPAUTH>>&.
30446 .cindex "carriage return"
30448 Responses from the remote host are supposed to be terminated by CR followed by
30449 LF. However, there are known to be hosts that do not send CR characters, so in
30450 order to be able to interwork with such hosts, Exim treats LF on its own as a
30453 If a message contains a number of different addresses, all those with the same
30454 characteristics (for example, the same envelope sender) that resolve to the
30455 same set of hosts, in the same order, are sent in a single SMTP transaction,
30456 even if they are for different domains, unless there are more than the setting
30457 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
30458 they are split into groups containing no more than &%max_rcpt%&s addresses
30459 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
30460 in parallel sessions. The order of hosts with identical MX values is not
30461 significant when checking whether addresses can be batched in this way.
30463 When the &(smtp)& transport suffers a temporary failure that is not
30464 message-related, Exim updates its transport-specific database, which contains
30465 records indexed by host name that remember which messages are waiting for each
30466 particular host. It also updates the retry database with new retry times.
30468 .cindex "hints database" "retry keys"
30469 Exim's retry hints are based on host name plus IP address, so if one address of
30470 a multi-homed host is broken, it will soon be skipped most of the time.
30471 See the next section for more detail about error handling.
30473 .cindex "SMTP" "passed connection"
30474 .cindex "SMTP" "batching over TCP/IP"
30475 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
30476 looks in the hints database for the transport to see if there are any queued
30477 messages waiting for the host to which it is connected. If it finds one, it
30478 creates a new Exim process using the &%-MC%& option (which can only be used by
30479 a process running as root or the Exim user) and passes the TCP/IP socket to it
30480 so that it can deliver another message using the same socket. The new process
30481 does only those deliveries that are routed to the connected host, and may in
30482 turn pass the socket on to a third process, and so on.
30484 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
30485 limit the number of messages sent down a single TCP/IP connection.
30487 .cindex "asterisk" "after IP address"
30488 The second and subsequent messages delivered down an existing connection are
30489 identified in the main log by the addition of an asterisk after the closing
30490 square bracket of the IP address.
30495 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
30496 .cindex "error" "in outgoing SMTP"
30497 .cindex "SMTP" "errors in outgoing"
30498 .cindex "host" "error"
30499 Three different kinds of error are recognized for outgoing SMTP: host errors,
30500 message errors, and recipient errors.
30503 .vitem "&*Host errors*&"
30504 A host error is not associated with a particular message or with a
30505 particular recipient of a message. The host errors are:
30508 Connection refused or timed out,
30510 Any error response code on connection,
30512 Any error response code to EHLO or HELO,
30514 Loss of connection at any time, except after &"."&,
30516 I/O errors at any time,
30518 Timeouts during the session, other than in response to MAIL, RCPT or
30519 the &"."& at the end of the data.
30522 For a host error, a permanent error response on connection, or in response to
30523 EHLO, causes all addresses routed to the host to be failed. Any other host
30524 error causes all addresses to be deferred, and retry data to be created for the
30525 host. It is not tried again, for any message, until its retry time arrives. If
30526 the current set of addresses are not all delivered in this run (to some
30527 alternative host), the message is added to the list of those waiting for this
30528 host, so if it is still undelivered when a subsequent successful delivery is
30529 made to the host, it will be sent down the same SMTP connection.
30531 .vitem "&*Message errors*&"
30532 .cindex "message" "error"
30533 A message error is associated with a particular message when sent to a
30534 particular host, but not with a particular recipient of the message. The
30535 message errors are:
30538 Any error response code to MAIL, DATA, or the &"."& that terminates
30541 Timeout after MAIL,
30543 Timeout or loss of connection after the &"."& that terminates the data. A
30544 timeout after the DATA command itself is treated as a host error, as is loss of
30545 connection at any other time.
30548 For a message error, a permanent error response (5&'xx'&) causes all addresses
30549 to be failed, and a delivery error report to be returned to the sender. A
30550 temporary error response (4&'xx'&), or one of the timeouts, causes all
30551 addresses to be deferred. Retry data is not created for the host, but instead,
30552 a retry record for the combination of host plus message id is created. The
30553 message is not added to the list of those waiting for this host. This ensures
30554 that the failing message will not be sent to this host again until the retry
30555 time arrives. However, other messages that are routed to the host are not
30556 affected, so if it is some property of the message that is causing the error,
30557 it will not stop the delivery of other mail.
30559 If the remote host specified support for the SIZE parameter in its response
30560 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
30561 over-large message will cause a message error because the error arrives as a
30564 .vitem "&*Recipient errors*&"
30565 .cindex "recipient" "error"
30566 A recipient error is associated with a particular recipient of a message. The
30567 recipient errors are:
30570 Any error response to RCPT,
30572 Timeout after RCPT.
30575 For a recipient error, a permanent error response (5&'xx'&) causes the
30576 recipient address to be failed, and a bounce message to be returned to the
30577 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
30578 address to be deferred, and routing retry data to be created for it. This is
30579 used to delay processing of the address in subsequent queue runs, until its
30580 routing retry time arrives. This applies to all messages, but because it
30581 operates only in queue runs, one attempt will be made to deliver a new message
30582 to the failing address before the delay starts to operate. This ensures that,
30583 if the failure is really related to the message rather than the recipient
30584 (&"message too big for this recipient"& is a possible example), other messages
30585 have a chance of getting delivered. If a delivery to the address does succeed,
30586 the retry information gets cleared, so all stuck messages get tried again, and
30587 the retry clock is reset.
30589 The message is not added to the list of those waiting for this host. Use of the
30590 host for other messages is unaffected, and except in the case of a timeout,
30591 other recipients are processed independently, and may be successfully delivered
30592 in the current SMTP session. After a timeout it is of course impossible to
30593 proceed with the session, so all addresses get deferred. However, those other
30594 than the one that failed do not suffer any subsequent retry delays. Therefore,
30595 if one recipient is causing trouble, the others have a chance of getting
30596 through when a subsequent delivery attempt occurs before the failing
30597 recipient's retry time.
30600 In all cases, if there are other hosts (or IP addresses) available for the
30601 current set of addresses (for example, from multiple MX records), they are
30602 tried in this run for any undelivered addresses, subject of course to their
30603 own retry data. In other words, recipient error retry data does not take effect
30604 until the next delivery attempt.
30606 Some hosts have been observed to give temporary error responses to every
30607 MAIL command at certain times (&"insufficient space"& has been seen). It
30608 would be nice if such circumstances could be recognized, and defer data for the
30609 host itself created, but this is not possible within the current Exim design.
30610 What actually happens is that retry data for every (host, message) combination
30613 The reason that timeouts after MAIL and RCPT are treated specially is that
30614 these can sometimes arise as a result of the remote host's verification
30615 procedures. Exim makes this assumption, and treats them as if a temporary error
30616 response had been received. A timeout after &"."& is treated specially because
30617 it is known that some broken implementations fail to recognize the end of the
30618 message if the last character of the last line is a binary zero. Thus, it is
30619 helpful to treat this case as a message error.
30621 Timeouts at other times are treated as host errors, assuming a problem with the
30622 host, or the connection to it. If a timeout after MAIL, RCPT,
30623 or &"."& is really a connection problem, the assumption is that at the next try
30624 the timeout is likely to occur at some other point in the dialogue, causing it
30625 then to be treated as a host error.
30627 There is experimental evidence that some MTAs drop the connection after the
30628 terminating &"."& if they do not like the contents of the message for some
30629 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
30630 should be given. That is why Exim treats this case as a message rather than a
30631 host error, in order not to delay other messages to the same host.
30636 .section "Incoming SMTP messages over TCP/IP" "SECID233"
30637 .cindex "SMTP" "incoming over TCP/IP"
30638 .cindex "incoming SMTP over TCP/IP"
30641 Incoming SMTP messages can be accepted in one of two ways: by running a
30642 listening daemon, or by using &'inetd'&. In the latter case, the entry in
30643 &_/etc/inetd.conf_& should be like this:
30645 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
30647 Exim distinguishes between this case and the case of a locally running user
30648 agent using the &%-bs%& option by checking whether or not the standard input is
30649 a socket. When it is, either the port must be privileged (less than 1024), or
30650 the caller must be root or the Exim user. If any other user passes a socket
30651 with an unprivileged port number, Exim prints a message on the standard error
30652 stream and exits with an error code.
30654 By default, Exim does not make a log entry when a remote host connects or
30655 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
30656 unexpected. It can be made to write such log entries by setting the
30657 &%smtp_connection%& log selector.
30659 .cindex "carriage return"
30661 Commands from the remote host are supposed to be terminated by CR followed by
30662 LF. However, there are known to be hosts that do not send CR characters. In
30663 order to be able to interwork with such hosts, Exim treats LF on its own as a
30665 Furthermore, because common code is used for receiving messages from all
30666 sources, a CR on its own is also interpreted as a line terminator. However, the
30667 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
30669 .cindex "EHLO" "invalid data"
30670 .cindex "HELO" "invalid data"
30671 One area that sometimes gives rise to problems concerns the EHLO or
30672 HELO commands. Some clients send syntactically invalid versions of these
30673 commands, which Exim rejects by default. (This is nothing to do with verifying
30674 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
30675 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
30676 match the broken hosts that send invalid commands.
30678 .cindex "SIZE option on MAIL command"
30679 .cindex "MAIL" "SIZE option"
30680 The amount of disk space available is checked whenever SIZE is received on
30681 a MAIL command, independently of whether &%message_size_limit%& or
30682 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
30683 false. A temporary error is given if there is not enough space. If
30684 &%check_spool_space%& is set, the check is for that amount of space plus the
30685 value given with SIZE, that is, it checks that the addition of the incoming
30686 message will not reduce the space below the threshold.
30688 When a message is successfully received, Exim includes the local message id in
30689 its response to the final &"."& that terminates the data. If the remote host
30690 logs this text it can help with tracing what has happened to a message.
30692 The Exim daemon can limit the number of simultaneous incoming connections it is
30693 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
30694 number of simultaneous incoming connections from a single remote host (see the
30695 &%smtp_accept_max_per_host%& option). Additional connection attempts are
30696 rejected using the SMTP temporary error code 421.
30698 The Exim daemon does not rely on the SIGCHLD signal to detect when a
30699 subprocess has finished, as this can get lost at busy times. Instead, it looks
30700 for completed subprocesses every time it wakes up. Provided there are other
30701 things happening (new incoming calls, starts of queue runs), completed
30702 processes will be noticed and tidied away. On very quiet systems you may
30703 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
30704 it will be noticed when the daemon next wakes up.
30706 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
30707 and can also be set up to reject SMTP calls from non-reserved hosts at times of
30708 high system load &-- for details see the &%smtp_accept_reserve%&,
30709 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
30710 applies in both the daemon and &'inetd'& cases.
30712 Exim normally starts a delivery process for each message received, though this
30713 can be varied by means of the &%-odq%& command line option and the
30714 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
30715 number of simultaneously running delivery processes started in this way from
30716 SMTP input can be limited by the &%smtp_accept_queue%& and
30717 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
30718 subsequently received messages are just put on the input queue without starting
30719 a delivery process.
30721 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
30722 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
30723 started up from the &'inetd'& daemon, because in that case each connection is
30724 handled by an entirely independent Exim process. Control by load average is,
30725 however, available with &'inetd'&.
30727 Exim can be configured to verify addresses in incoming SMTP commands as they
30728 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
30729 to rewrite addresses at this time &-- before any syntax checking is done. See
30730 section &<<SECTrewriteS>>&.
30732 Exim can also be configured to limit the rate at which a client host submits
30733 MAIL and RCPT commands in a single SMTP session. See the
30734 &%smtp_ratelimit_hosts%& option.
30738 .section "Unrecognized SMTP commands" "SECID234"
30739 .cindex "SMTP" "unrecognized commands"
30740 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
30741 commands during a single SMTP connection, it drops the connection after sending
30742 the error response to the last command. The default value for
30743 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
30744 abuse that subvert web servers into making connections to SMTP ports; in these
30745 circumstances, a number of non-SMTP lines are sent first.
30748 .section "Syntax and protocol errors in SMTP commands" "SECID235"
30749 .cindex "SMTP" "syntax errors"
30750 .cindex "SMTP" "protocol errors"
30751 A syntax error is detected if an SMTP command is recognized, but there is
30752 something syntactically wrong with its data, for example, a malformed email
30753 address in a RCPT command. Protocol errors include invalid command
30754 sequencing such as RCPT before MAIL. If Exim receives more than
30755 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
30756 drops the connection after sending the error response to the last command. The
30757 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
30758 broken clients that loop sending bad commands (yes, it has been seen).
30762 .section "Use of non-mail SMTP commands" "SECID236"
30763 .cindex "SMTP" "non-mail commands"
30764 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
30765 DATA. Exim counts such commands, and drops the connection if there are too
30766 many of them in a single SMTP session. This action catches some
30767 denial-of-service attempts and things like repeated failing AUTHs, or a mad
30768 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
30769 defines what &"too many"& means. Its default value is 10.
30771 When a new message is expected, one occurrence of RSET is not counted. This
30772 allows a client to send one RSET between messages (this is not necessary,
30773 but some clients do it). Exim also allows one uncounted occurrence of HELO
30774 or EHLO, and one occurrence of STARTTLS between messages. After
30775 starting up a TLS session, another EHLO is expected, and so it too is not
30778 The first occurrence of AUTH in a connection, or immediately following
30779 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
30780 RCPT, DATA, and QUIT are counted.
30782 You can control which hosts are subject to the limit set by
30783 &%smtp_accept_max_nonmail%& by setting
30784 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
30785 the limit apply to all hosts. This option means that you can exclude any
30786 specific badly-behaved hosts that you have to live with.
30791 .section "The VRFY and EXPN commands" "SECID237"
30792 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
30793 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
30794 appropriate) in order to decide whether the command should be accepted or not.
30795 If no ACL is defined, the command is rejected.
30797 .cindex "VRFY" "processing"
30798 When VRFY is accepted, it runs exactly the same code as when Exim is
30799 called with the &%-bv%& option.
30801 .cindex "EXPN" "processing"
30802 When EXPN is accepted, a single-level expansion of the address is done.
30803 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
30804 than a verification (the &%-bv%& option). If an unqualified local part is given
30805 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
30806 of VRFY and EXPN commands are logged on the main and reject logs, and
30807 VRFY verification failures are logged on the main log for consistency with
30812 .section "The ETRN command" "SECTETRN"
30813 .cindex "ETRN" "processing"
30814 RFC 1985 describes an SMTP command called ETRN that is designed to
30815 overcome the security problems of the TURN command (which has fallen into
30816 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
30817 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
30818 should be accepted or not. If no ACL is defined, the command is rejected.
30820 The ETRN command is concerned with &"releasing"& messages that are awaiting
30821 delivery to certain hosts. As Exim does not organize its message queue by host,
30822 the only form of ETRN that is supported by default is the one where the
30823 text starts with the &"#"& prefix, in which case the remainder of the text is
30824 specific to the SMTP server. A valid ETRN command causes a run of Exim with
30825 the &%-R%& option to happen, with the remainder of the ETRN text as its
30826 argument. For example,
30834 which causes a delivery attempt on all messages with undelivered addresses
30835 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
30836 default), Exim prevents the simultaneous execution of more than one queue run
30837 for the same argument string as a result of an ETRN command. This stops
30838 a misbehaving client from starting more than one queue runner at once.
30840 .cindex "hints database" "ETRN serialization"
30841 Exim implements the serialization by means of a hints database in which a
30842 record is written whenever a process is started by ETRN, and deleted when
30843 the process completes. However, Exim does not keep the SMTP session waiting for
30844 the ETRN process to complete. Once ETRN is accepted, the client is sent
30845 a &"success"& return code. Obviously there is scope for hints records to get
30846 left lying around if there is a system or program crash. To guard against this,
30847 Exim ignores any records that are more than six hours old.
30849 .oindex "&%smtp_etrn_command%&"
30850 For more control over what ETRN does, the &%smtp_etrn_command%& option can
30851 used. This specifies a command that is run whenever ETRN is received,
30852 whatever the form of its argument. For
30855 smtp_etrn_command = /etc/etrn_command $domain \
30856 $sender_host_address
30858 .vindex "&$domain$&"
30859 The string is split up into arguments which are independently expanded. The
30860 expansion variable &$domain$& is set to the argument of the ETRN command,
30861 and no syntax checking is done on the contents of this argument. Exim does not
30862 wait for the command to complete, so its status code is not checked. Exim runs
30863 under its own uid and gid when receiving incoming SMTP, so it is not possible
30864 for it to change them before running the command.
30868 .section "Incoming local SMTP" "SECID238"
30869 .cindex "SMTP" "local incoming"
30870 Some user agents use SMTP to pass messages to their local MTA using the
30871 standard input and output, as opposed to passing the envelope on the command
30872 line and writing the message to the standard input. This is supported by the
30873 &%-bs%& option. This form of SMTP is handled in the same way as incoming
30874 messages over TCP/IP (including the use of ACLs), except that the envelope
30875 sender given in a MAIL command is ignored unless the caller is trusted. In
30876 an ACL you can detect this form of SMTP input by testing for an empty host
30877 identification. It is common to have this as the first line in the ACL that
30878 runs for RCPT commands:
30882 This accepts SMTP messages from local processes without doing any other tests.
30886 .section "Outgoing batched SMTP" "SECTbatchSMTP"
30887 .cindex "SMTP" "batched outgoing"
30888 .cindex "batched SMTP output"
30889 Both the &(appendfile)& and &(pipe)& transports can be used for handling
30890 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
30891 be output in BSMTP format. No SMTP responses are possible for this form of
30892 delivery. All it is doing is using SMTP commands as a way of transmitting the
30893 envelope along with the message.
30895 The message is written to the file or pipe preceded by the SMTP commands
30896 MAIL and RCPT, and followed by a line containing a single dot. Lines in
30897 the message that start with a dot have an extra dot added. The SMTP command
30898 HELO is not normally used. If it is required, the &%message_prefix%& option
30899 can be used to specify it.
30901 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
30902 one recipient address at a time by default. However, you can arrange for them
30903 to handle several addresses at once by setting the &%batch_max%& option. When
30904 this is done for BSMTP, messages may contain multiple RCPT commands. See
30905 chapter &<<CHAPbatching>>& for more details.
30908 When one or more addresses are routed to a BSMTP transport by a router that
30909 sets up a host list, the name of the first host on the list is available to the
30910 transport in the variable &$host$&. Here is an example of such a transport and
30915 driver = manualroute
30916 transport = smtp_appendfile
30917 route_list = domain.example batch.host.example
30921 driver = appendfile
30922 directory = /var/bsmtp/$host
30927 This causes messages addressed to &'domain.example'& to be written in BSMTP
30928 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
30929 message (unless there are more than 1000 recipients).
30933 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
30934 .cindex "SMTP" "batched incoming"
30935 .cindex "batched SMTP input"
30936 The &%-bS%& command line option causes Exim to accept one or more messages by
30937 reading SMTP on the standard input, but to generate no responses. If the caller
30938 is trusted, the senders in the MAIL commands are believed; otherwise the
30939 sender is always the caller of Exim. Unqualified senders and receivers are not
30940 rejected (there seems little point) but instead just get qualified. HELO
30941 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
30942 as NOOP; QUIT quits.
30944 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
30945 In this respect it is like non-SMTP local input.
30947 If an error is detected while reading a message, including a missing &"."& at
30948 the end, Exim gives up immediately. It writes details of the error to the
30949 standard output in a stylized way that the calling program should be able to
30950 make some use of automatically, for example:
30952 554 Unexpected end of file
30953 Transaction started in line 10
30954 Error detected in line 14
30956 It writes a more verbose version, for human consumption, to the standard error
30959 An error was detected while processing a file of BSMTP input.
30960 The error message was:
30962 501 '>' missing at end of address
30964 The SMTP transaction started in line 10.
30965 The error was detected in line 12.
30966 The SMTP command at fault was:
30968 rcpt to:<malformed@in.com.plete
30970 1 previous message was successfully processed.
30971 The rest of the batch was abandoned.
30973 The return code from Exim is zero only if there were no errors. It is 1 if some
30974 messages were accepted before an error was detected, and 2 if no messages were
30976 .ecindex IIDsmtpproc1
30977 .ecindex IIDsmtpproc2
30981 . ////////////////////////////////////////////////////////////////////////////
30982 . ////////////////////////////////////////////////////////////////////////////
30984 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
30985 "Customizing messages"
30986 When a message fails to be delivered, or remains on the queue for more than a
30987 configured amount of time, Exim sends a message to the original sender, or
30988 to an alternative configured address. The text of these messages is built into
30989 the code of Exim, but it is possible to change it, either by adding a single
30990 string, or by replacing each of the paragraphs by text supplied in a file.
30992 The &'From:'& and &'To:'& header lines are automatically generated; you can
30993 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
30994 option. Exim also adds the line
30996 Auto-Submitted: auto-generated
30998 to all warning and bounce messages,
31001 .section "Customizing bounce messages" "SECID239"
31002 .cindex "customizing" "bounce message"
31003 .cindex "bounce message" "customizing"
31004 If &%bounce_message_text%& is set, its contents are included in the default
31005 message immediately after &"This message was created automatically by mail
31006 delivery software."& The string is not expanded. It is not used if
31007 &%bounce_message_file%& is set.
31009 When &%bounce_message_file%& is set, it must point to a template file for
31010 constructing error messages. The file consists of a series of text items,
31011 separated by lines consisting of exactly four asterisks. If the file cannot be
31012 opened, default text is used and a message is written to the main and panic
31013 logs. If any text item in the file is empty, default text is used for that
31016 .vindex "&$bounce_recipient$&"
31017 .vindex "&$bounce_return_size_limit$&"
31018 Each item of text that is read from the file is expanded, and there are two
31019 expansion variables which can be of use here: &$bounce_recipient$& is set to
31020 the recipient of an error message while it is being created, and
31021 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
31022 option, rounded to a whole number.
31024 The items must appear in the file in the following order:
31027 The first item is included in the headers, and should include at least a
31028 &'Subject:'& header. Exim does not check the syntax of these headers.
31030 The second item forms the start of the error message. After it, Exim lists the
31031 failing addresses with their error messages.
31033 The third item is used to introduce any text from pipe transports that is to be
31034 returned to the sender. It is omitted if there is no such text.
31036 The fourth item is used to introduce the copy of the message that is returned
31037 as part of the error report.
31039 The fifth item is added after the fourth one if the returned message is
31040 truncated because it is bigger than &%return_size_limit%&.
31042 The sixth item is added after the copy of the original message.
31045 The default state (&%bounce_message_file%& unset) is equivalent to the
31046 following file, in which the sixth item is empty. The &'Subject:'& and some
31047 other lines have been split in order to fit them on the page:
31049 Subject: Mail delivery failed
31050 ${if eq{$sender_address}{$bounce_recipient}
31051 {: returning message to sender}}
31053 This message was created automatically by mail delivery software.
31055 A message ${if eq{$sender_address}{$bounce_recipient}
31056 {that you sent }{sent by
31060 }}could not be delivered to all of its recipients.
31061 This is a permanent error. The following address(es) failed:
31063 The following text was generated during the delivery attempt(s):
31065 ------ This is a copy of the message, including all the headers.
31068 ------ The body of the message is $message_size characters long;
31070 ------ $bounce_return_size_limit or so are included here.
31073 .section "Customizing warning messages" "SECTcustwarn"
31074 .cindex "customizing" "warning message"
31075 .cindex "warning of delay" "customizing the message"
31076 The option &%warn_message_file%& can be pointed at a template file for use when
31077 warnings about message delays are created. In this case there are only three
31081 The first item is included in the headers, and should include at least a
31082 &'Subject:'& header. Exim does not check the syntax of these headers.
31084 The second item forms the start of the warning message. After it, Exim lists
31085 the delayed addresses.
31087 The third item then ends the message.
31090 The default state is equivalent to the following file, except that some lines
31091 have been split here, in order to fit them on the page:
31093 Subject: Warning: message $message_exim_id delayed
31094 $warn_message_delay
31096 This message was created automatically by mail delivery software.
31098 A message ${if eq{$sender_address}{$warn_message_recipients}
31099 {that you sent }{sent by
31103 }}has not been delivered to all of its recipients after
31104 more than $warn_message_delay on the queue on $primary_hostname.
31106 The message identifier is: $message_exim_id
31107 The subject of the message is: $h_subject
31108 The date of the message is: $h_date
31110 The following address(es) have not yet been delivered:
31112 No action is required on your part. Delivery attempts will
31113 continue for some time, and this warning may be repeated at
31114 intervals if the message remains undelivered. Eventually the
31115 mail delivery software will give up, and when that happens,
31116 the message will be returned to you.
31118 .vindex "&$warn_message_delay$&"
31119 .vindex "&$warn_message_recipients$&"
31120 However, in the default state the subject and date lines are omitted if no
31121 appropriate headers exist. During the expansion of this file,
31122 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
31123 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
31124 of recipients for the warning message. There may be more than one if there are
31125 multiple addresses with different &%errors_to%& settings on the routers that
31131 . ////////////////////////////////////////////////////////////////////////////
31132 . ////////////////////////////////////////////////////////////////////////////
31134 .chapter "Some common configuration settings" "CHAPcomconreq"
31135 This chapter discusses some configuration settings that seem to be fairly
31136 common. More examples and discussion can be found in the Exim book.
31140 .section "Sending mail to a smart host" "SECID240"
31141 .cindex "smart host" "example router"
31142 If you want to send all mail for non-local domains to a &"smart host"&, you
31143 should replace the default &(dnslookup)& router with a router which does the
31144 routing explicitly:
31146 send_to_smart_host:
31147 driver = manualroute
31148 route_list = !+local_domains smart.host.name
31149 transport = remote_smtp
31151 You can use the smart host's IP address instead of the name if you wish.
31152 If you are using Exim only to submit messages to a smart host, and not for
31153 receiving incoming messages, you can arrange for it to do the submission
31154 synchronously by setting the &%mua_wrapper%& option (see chapter
31155 &<<CHAPnonqueueing>>&).
31160 .section "Using Exim to handle mailing lists" "SECTmailinglists"
31161 .cindex "mailing lists"
31162 Exim can be used to run simple mailing lists, but for large and/or complicated
31163 requirements, the use of additional specialized mailing list software such as
31164 Majordomo or Mailman is recommended.
31166 The &(redirect)& router can be used to handle mailing lists where each list
31167 is maintained in a separate file, which can therefore be managed by an
31168 independent manager. The &%domains%& router option can be used to run these
31169 lists in a separate domain from normal mail. For example:
31173 domains = lists.example
31174 file = /usr/lists/$local_part
31177 errors_to = $local_part-request@lists.example
31180 This router is skipped for domains other than &'lists.example'&. For addresses
31181 in that domain, it looks for a file that matches the local part. If there is no
31182 such file, the router declines, but because &%no_more%& is set, no subsequent
31183 routers are tried, and so the whole delivery fails.
31185 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
31186 expanded into a file name or a pipe delivery, which is usually inappropriate in
31189 .oindex "&%errors_to%&"
31190 The &%errors_to%& option specifies that any delivery errors caused by addresses
31191 taken from a mailing list are to be sent to the given address rather than the
31192 original sender of the message. However, before acting on this, Exim verifies
31193 the error address, and ignores it if verification fails.
31195 For example, using the configuration above, mail sent to
31196 &'dicts@lists.example'& is passed on to those addresses contained in
31197 &_/usr/lists/dicts_&, with error reports directed to
31198 &'dicts-request@lists.example'&, provided that this address can be verified.
31199 There could be a file called &_/usr/lists/dicts-request_& containing
31200 the address(es) of this particular list's manager(s), but other approaches,
31201 such as setting up an earlier router (possibly using the &%local_part_prefix%&
31202 or &%local_part_suffix%& options) to handle addresses of the form
31203 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
31207 .section "Syntax errors in mailing lists" "SECID241"
31208 .cindex "mailing lists" "syntax errors in"
31209 If an entry in redirection data contains a syntax error, Exim normally defers
31210 delivery of the original address. That means that a syntax error in a mailing
31211 list holds up all deliveries to the list. This may not be appropriate when a
31212 list is being maintained automatically from data supplied by users, and the
31213 addresses are not rigorously checked.
31215 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
31216 entries that fail to parse, noting the incident in the log. If in addition
31217 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
31218 whenever a broken address is skipped. It is usually appropriate to set
31219 &%syntax_errors_to%& to the same address as &%errors_to%&.
31223 .section "Re-expansion of mailing lists" "SECID242"
31224 .cindex "mailing lists" "re-expansion of"
31225 Exim remembers every individual address to which a message has been delivered,
31226 in order to avoid duplication, but it normally stores only the original
31227 recipient addresses with a message. If all the deliveries to a mailing list
31228 cannot be done at the first attempt, the mailing list is re-expanded when the
31229 delivery is next tried. This means that alterations to the list are taken into
31230 account at each delivery attempt, so addresses that have been added to
31231 the list since the message arrived will therefore receive a copy of the
31232 message, even though it pre-dates their subscription.
31234 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
31235 on the &(redirect)& router. If this is done, any addresses generated by the
31236 router that fail to deliver at the first attempt are added to the message as
31237 &"top level"& addresses, and the parent address that generated them is marked
31238 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
31239 subsequent delivery attempts. The disadvantage of this is that if any of the
31240 failing addresses are incorrect, correcting them in the file has no effect on
31241 pre-existing messages.
31243 The original top-level address is remembered with each of the generated
31244 addresses, and is output in any log messages. However, any intermediate parent
31245 addresses are not recorded. This makes a difference to the log only if the
31246 &%all_parents%& selector is set, but for mailing lists there is normally only
31247 one level of expansion anyway.
31251 .section "Closed mailing lists" "SECID243"
31252 .cindex "mailing lists" "closed"
31253 The examples so far have assumed open mailing lists, to which anybody may
31254 send mail. It is also possible to set up closed lists, where mail is accepted
31255 from specified senders only. This is done by making use of the generic
31256 &%senders%& option to restrict the router that handles the list.
31258 The following example uses the same file as a list of recipients and as a list
31259 of permitted senders. It requires three routers:
31263 domains = lists.example
31264 local_part_suffix = -request
31265 file = /usr/lists/$local_part$local_part_suffix
31270 domains = lists.example
31271 senders = ${if exists {/usr/lists/$local_part}\
31272 {lsearch;/usr/lists/$local_part}{*}}
31273 file = /usr/lists/$local_part
31276 errors_to = $local_part-request@lists.example
31281 domains = lists.example
31283 data = :fail: $local_part@lists.example is a closed mailing list
31285 All three routers have the same &%domains%& setting, so for any other domains,
31286 they are all skipped. The first router runs only if the local part ends in
31287 &%-request%&. It handles messages to the list manager(s) by means of an open
31290 The second router runs only if the &%senders%& precondition is satisfied. It
31291 checks for the existence of a list that corresponds to the local part, and then
31292 checks that the sender is on the list by means of a linear search. It is
31293 necessary to check for the existence of the file before trying to search it,
31294 because otherwise Exim thinks there is a configuration error. If the file does
31295 not exist, the expansion of &%senders%& is *, which matches all senders. This
31296 means that the router runs, but because there is no list, declines, and
31297 &%no_more%& ensures that no further routers are run. The address fails with an
31298 &"unrouteable address"& error.
31300 The third router runs only if the second router is skipped, which happens when
31301 a mailing list exists, but the sender is not on it. This router forcibly fails
31302 the address, giving a suitable error message.
31307 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
31309 .cindex "Variable Envelope Return Paths"
31310 .cindex "envelope sender"
31311 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
31312 are a way of helping mailing list administrators discover which subscription
31313 address is the cause of a particular delivery failure. The idea is to encode
31314 the original recipient address in the outgoing envelope sender address, so that
31315 if the message is forwarded by another host and then subsequently bounces, the
31316 original recipient can be extracted from the recipient address of the bounce.
31318 .oindex &%errors_to%&
31319 .oindex &%return_path%&
31320 Envelope sender addresses can be modified by Exim using two different
31321 facilities: the &%errors_to%& option on a router (as shown in previous mailing
31322 list examples), or the &%return_path%& option on a transport. The second of
31323 these is effective only if the message is successfully delivered to another
31324 host; it is not used for errors detected on the local host (see the description
31325 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
31326 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
31332 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
31333 {$1-request+$local_part=$domain@your.dom.example}fail}
31335 This has the effect of rewriting the return path (envelope sender) on outgoing
31336 SMTP messages, if the local part of the original return path ends in
31337 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
31338 local part and domain of the recipient into the return path. Suppose, for
31339 example, that a message whose return path has been set to
31340 &'somelist-request@your.dom.example'& is sent to
31341 &'subscriber@other.dom.example'&. In the transport, the return path is
31344 somelist-request+subscriber=other.dom.example@your.dom.example
31346 .vindex "&$local_part$&"
31347 For this to work, you must tell Exim to send multiple copies of messages that
31348 have more than one recipient, so that each copy has just one recipient. This is
31349 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
31350 might be sent to several different recipients in the same domain, in which case
31351 &$local_part$& is not available in the transport, because it is not unique.
31353 Unless your host is doing nothing but mailing list deliveries, you should
31354 probably use a separate transport for the VERP deliveries, so as not to use
31355 extra resources in making one-per-recipient copies for other deliveries. This
31356 can easily be done by expanding the &%transport%& option in the router:
31360 domains = ! +local_domains
31362 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
31363 {verp_smtp}{remote_smtp}}
31366 If you want to change the return path using &%errors_to%& in a router instead
31367 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
31368 routers that handle mailing list addresses. This will ensure that all delivery
31369 errors, including those detected on the local host, are sent to the VERP
31372 On a host that does no local deliveries and has no manual routing, only the
31373 &(dnslookup)& router needs to be changed. A special transport is not needed for
31374 SMTP deliveries. Every mailing list recipient has its own return path value,
31375 and so Exim must hand them to the transport one at a time. Here is an example
31376 of a &(dnslookup)& router that implements VERP:
31380 domains = ! +local_domains
31381 transport = remote_smtp
31383 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
31384 {$1-request+$local_part=$domain@your.dom.example}fail}
31387 Before you start sending out messages with VERPed return paths, you must also
31388 configure Exim to accept the bounce messages that come back to those paths.
31389 Typically this is done by setting a &%local_part_suffix%& option for a
31390 router, and using this to route the messages to wherever you want to handle
31393 The overhead incurred in using VERP depends very much on the size of the
31394 message, the number of recipient addresses that resolve to the same remote
31395 host, and the speed of the connection over which the message is being sent. If
31396 a lot of addresses resolve to the same host and the connection is slow, sending
31397 a separate copy of the message for each address may take substantially longer
31398 than sending a single copy with many recipients (for which VERP cannot be
31406 .section "Virtual domains" "SECTvirtualdomains"
31407 .cindex "virtual domains"
31408 .cindex "domain" "virtual"
31409 The phrase &'virtual domain'& is unfortunately used with two rather different
31413 A domain for which there are no real mailboxes; all valid local parts are
31414 aliases for other email addresses. Common examples are organizational
31415 top-level domains and &"vanity"& domains.
31417 One of a number of independent domains that are all handled by the same host,
31418 with mailboxes on that host, but where the mailbox owners do not necessarily
31419 have login accounts on that host.
31422 The first usage is probably more common, and does seem more &"virtual"& than
31423 the second. This kind of domain can be handled in Exim with a straightforward
31424 aliasing router. One approach is to create a separate alias file for each
31425 virtual domain. Exim can test for the existence of the alias file to determine
31426 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
31427 to a router of this form:
31431 domains = dsearch;/etc/mail/virtual
31432 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
31435 The &%domains%& option specifies that the router is to be skipped, unless there
31436 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
31437 domain that is being processed. When the router runs, it looks up the local
31438 part in the file to find a new address (or list of addresses). The &%no_more%&
31439 setting ensures that if the lookup fails (leading to &%data%& being an empty
31440 string), Exim gives up on the address without trying any subsequent routers.
31442 This one router can handle all the virtual domains because the alias file names
31443 follow a fixed pattern. Permissions can be arranged so that appropriate people
31444 can edit the different alias files. A successful aliasing operation results in
31445 a new envelope recipient address, which is then routed from scratch.
31447 The other kind of &"virtual"& domain can also be handled in a straightforward
31448 way. One approach is to create a file for each domain containing a list of
31449 valid local parts, and use it in a router like this:
31453 domains = dsearch;/etc/mail/domains
31454 local_parts = lsearch;/etc/mail/domains/$domain
31455 transport = my_mailboxes
31457 The address is accepted if there is a file for the domain, and the local part
31458 can be found in the file. The &%domains%& option is used to check for the
31459 file's existence because &%domains%& is tested before the &%local_parts%&
31460 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
31461 because that option is tested after &%local_parts%&. The transport is as
31465 driver = appendfile
31466 file = /var/mail/$domain/$local_part
31469 This uses a directory of mailboxes for each domain. The &%user%& setting is
31470 required, to specify which uid is to be used for writing to the mailboxes.
31472 The configuration shown here is just one example of how you might support this
31473 requirement. There are many other ways this kind of configuration can be set
31474 up, for example, by using a database instead of separate files to hold all the
31475 information about the domains.
31479 .section "Multiple user mailboxes" "SECTmulbox"
31480 .cindex "multiple mailboxes"
31481 .cindex "mailbox" "multiple"
31482 .cindex "local part" "prefix"
31483 .cindex "local part" "suffix"
31484 Heavy email users often want to operate with multiple mailboxes, into which
31485 incoming mail is automatically sorted. A popular way of handling this is to
31486 allow users to use multiple sender addresses, so that replies can easily be
31487 identified. Users are permitted to add prefixes or suffixes to their local
31488 parts for this purpose. The wildcard facility of the generic router options
31489 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
31490 example, consider this router:
31495 file = $home/.forward
31496 local_part_suffix = -*
31497 local_part_suffix_optional
31500 .vindex "&$local_part_suffix$&"
31501 It runs a user's &_.forward_& file for all local parts of the form
31502 &'username-*'&. Within the filter file the user can distinguish different
31503 cases by testing the variable &$local_part_suffix$&. For example:
31505 if $local_part_suffix contains -special then
31506 save /home/$local_part/Mail/special
31509 If the filter file does not exist, or does not deal with such addresses, they
31510 fall through to subsequent routers, and, assuming no subsequent use of the
31511 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
31512 control over which suffixes are valid.
31514 Alternatively, a suffix can be used to trigger the use of a different
31515 &_.forward_& file &-- which is the way a similar facility is implemented in
31521 file = $home/.forward$local_part_suffix
31522 local_part_suffix = -*
31523 local_part_suffix_optional
31526 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
31527 example, &_.forward-special_& is used. Once again, if the appropriate file
31528 does not exist, or does not deal with the address, it is passed on to
31529 subsequent routers, which could, if required, look for an unqualified
31530 &_.forward_& file to use as a default.
31534 .section "Simplified vacation processing" "SECID244"
31535 .cindex "vacation processing"
31536 The traditional way of running the &'vacation'& program is for a user to set up
31537 a pipe command in a &_.forward_& file
31538 (see section &<<SECTspecitredli>>& for syntax details).
31539 This is prone to error by inexperienced users. There are two features of Exim
31540 that can be used to make this process simpler for users:
31543 A local part prefix such as &"vacation-"& can be specified on a router which
31544 can cause the message to be delivered directly to the &'vacation'& program, or
31545 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
31546 &_.forward_& file are then much simpler. For example:
31548 spqr, vacation-spqr
31551 The &%require_files%& generic router option can be used to trigger a
31552 vacation delivery by checking for the existence of a certain file in the
31553 user's home directory. The &%unseen%& generic option should also be used, to
31554 ensure that the original delivery also proceeds. In this case, all the user has
31555 to do is to create a file called, say, &_.vacation_&, containing a vacation
31559 Another advantage of both these methods is that they both work even when the
31560 use of arbitrary pipes by users is locked out.
31564 .section "Taking copies of mail" "SECID245"
31565 .cindex "message" "copying every"
31566 Some installations have policies that require archive copies of all messages to
31567 be made. A single copy of each message can easily be taken by an appropriate
31568 command in a system filter, which could, for example, use a different file for
31569 each day's messages.
31571 There is also a shadow transport mechanism that can be used to take copies of
31572 messages that are successfully delivered by local transports, one copy per
31573 delivery. This could be used, &'inter alia'&, to implement automatic
31574 notification of delivery by sites that insist on doing such things.
31578 .section "Intermittently connected hosts" "SECID246"
31579 .cindex "intermittently connected hosts"
31580 It has become quite common (because it is cheaper) for hosts to connect to the
31581 Internet periodically rather than remain connected all the time. The normal
31582 arrangement is that mail for such hosts accumulates on a system that is
31583 permanently connected.
31585 Exim was designed for use on permanently connected hosts, and so it is not
31586 particularly well-suited to use in an intermittently connected environment.
31587 Nevertheless there are some features that can be used.
31590 .section "Exim on the upstream server host" "SECID247"
31591 It is tempting to arrange for incoming mail for the intermittently connected
31592 host to remain on Exim's queue until the client connects. However, this
31593 approach does not scale very well. Two different kinds of waiting message are
31594 being mixed up in the same queue &-- those that cannot be delivered because of
31595 some temporary problem, and those that are waiting for their destination host
31596 to connect. This makes it hard to manage the queue, as well as wasting
31597 resources, because each queue runner scans the entire queue.
31599 A better approach is to separate off those messages that are waiting for an
31600 intermittently connected host. This can be done by delivering these messages
31601 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
31602 format, from where they are transmitted by other software when their
31603 destination connects. This makes it easy to collect all the mail for one host
31604 in a single directory, and to apply local timeout rules on a per-message basis
31607 On a very small scale, leaving the mail on Exim's queue can be made to work. If
31608 you are doing this, you should configure Exim with a long retry period for the
31609 intermittent host. For example:
31611 cheshire.wonderland.fict.example * F,5d,24h
31613 This stops a lot of failed delivery attempts from occurring, but Exim remembers
31614 which messages it has queued up for that host. Once the intermittent host comes
31615 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
31616 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
31617 causes all the queued up messages to be delivered, often down a single SMTP
31618 connection. While the host remains connected, any new messages get delivered
31621 If the connecting hosts do not have fixed IP addresses, that is, if a host is
31622 issued with a different IP address each time it connects, Exim's retry
31623 mechanisms on the holding host get confused, because the IP address is normally
31624 used as part of the key string for holding retry information. This can be
31625 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
31626 Since this has disadvantages for permanently connected hosts, it is best to
31627 arrange a separate transport for the intermittently connected ones.
31631 .section "Exim on the intermittently connected client host" "SECID248"
31632 The value of &%smtp_accept_queue_per_connection%& should probably be
31633 increased, or even set to zero (that is, disabled) on the intermittently
31634 connected host, so that all incoming messages down a single connection get
31635 delivered immediately.
31637 .cindex "SMTP" "passed connection"
31638 .cindex "SMTP" "multiple deliveries"
31639 .cindex "multiple SMTP deliveries"
31640 Mail waiting to be sent from an intermittently connected host will probably
31641 not have been routed, because without a connection DNS lookups are not
31642 possible. This means that if a normal queue run is done at connection time,
31643 each message is likely to be sent in a separate SMTP session. This can be
31644 avoided by starting the queue run with a command line option beginning with
31645 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
31646 first pass, routing is done but no deliveries take place. The second pass is a
31647 normal queue run; since all the messages have been previously routed, those
31648 destined for the same host are likely to get sent as multiple deliveries in a
31649 single SMTP connection.
31653 . ////////////////////////////////////////////////////////////////////////////
31654 . ////////////////////////////////////////////////////////////////////////////
31656 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
31657 "Exim as a non-queueing client"
31658 .cindex "client, non-queueing"
31659 .cindex "smart host" "suppressing queueing"
31660 On a personal computer, it is a common requirement for all
31661 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
31662 configured to operate that way, for all the popular operating systems.
31663 However, there are some MUAs for Unix-like systems that cannot be so
31664 configured: they submit messages using the command line interface of
31665 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
31668 If the personal computer runs continuously, there is no problem, because it can
31669 run a conventional MTA that handles delivery to the smart host, and deal with
31670 any delays via its queueing mechanism. However, if the computer does not run
31671 continuously or runs different operating systems at different times, queueing
31672 email is not desirable.
31674 There is therefore a requirement for something that can provide the
31675 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
31676 any queueing or retrying facilities. Furthermore, the delivery to the smart
31677 host should be synchronous, so that if it fails, the sending MUA is immediately
31678 informed. In other words, we want something that extends an MUA that submits
31679 to a local MTA via the command line so that it behaves like one that submits
31680 to a remote smart host using TCP/SMTP.
31682 There are a number of applications (for example, there is one called &'ssmtp'&)
31683 that do this job. However, people have found them to be lacking in various
31684 ways. For instance, you might want to allow aliasing and forwarding to be done
31685 before sending a message to the smart host.
31687 Exim already had the necessary infrastructure for doing this job. Just a few
31688 tweaks were needed to make it behave as required, though it is somewhat of an
31689 overkill to use a fully-featured MTA for this purpose.
31691 .oindex "&%mua_wrapper%&"
31692 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
31693 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
31694 assumes that it is being used to &"wrap"& a command-line MUA in the manner
31695 just described. As well as setting &%mua_wrapper%&, you also need to provide a
31696 compatible router and transport configuration. Typically there will be just one
31697 router and one transport, sending everything to a smart host.
31699 When run in MUA wrapping mode, the behaviour of Exim changes in the
31703 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
31704 In other words, the only way to submit messages is via the command line.
31706 Each message is synchronously delivered as soon as it is received (&%-odi%& is
31707 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
31708 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
31709 does not finish until the delivery attempt is complete. If the delivery is
31710 successful, a zero return code is given.
31712 Address redirection is permitted, but the final routing for all addresses must
31713 be to the same remote transport, and to the same list of hosts. Furthermore,
31714 the return address (envelope sender) must be the same for all recipients, as
31715 must any added or deleted header lines. In other words, it must be possible to
31716 deliver the message in a single SMTP transaction, however many recipients there
31719 If these conditions are not met, or if routing any address results in a
31720 failure or defer status, or if Exim is unable to deliver all the recipients
31721 successfully to one of the smart hosts, delivery of the entire message fails.
31723 Because no queueing is allowed, all failures are treated as permanent; there
31724 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
31725 smart host. Furthermore, because only a single yes/no response can be given to
31726 the caller, it is not possible to deliver to some recipients and not others. If
31727 there is an error (temporary or permanent) for any recipient, all are failed.
31729 If more than one smart host is listed, Exim will try another host after a
31730 connection failure or a timeout, in the normal way. However, if this kind of
31731 failure happens for all the hosts, the delivery fails.
31733 When delivery fails, an error message is written to the standard error stream
31734 (as well as to Exim's log), and Exim exits to the caller with a return code
31735 value 1. The message is expunged from Exim's spool files. No bounce messages
31736 are ever generated.
31738 No retry data is maintained, and any retry rules are ignored.
31740 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
31741 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
31742 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
31745 The overall effect is that Exim makes a single synchronous attempt to deliver
31746 the message, failing if there is any kind of problem. Because no local
31747 deliveries are done and no daemon can be run, Exim does not need root
31748 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
31749 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
31750 the advantages and disadvantages of running without root privilege.
31755 . ////////////////////////////////////////////////////////////////////////////
31756 . ////////////////////////////////////////////////////////////////////////////
31758 .chapter "Log files" "CHAPlog"
31759 .scindex IIDloggen "log" "general description"
31760 .cindex "log" "types of"
31761 Exim writes three different logs, referred to as the main log, the reject log,
31766 The main log records the arrival of each message and each delivery in a single
31767 line in each case. The format is as compact as possible, in an attempt to keep
31768 down the size of log files. Two-character flag sequences make it easy to pick
31769 out these lines. A number of other events are recorded in the main log. Some of
31770 them are optional, in which case the &%log_selector%& option controls whether
31771 they are included or not. A Perl script called &'eximstats'&, which does simple
31772 analysis of main log files, is provided in the Exim distribution (see section
31773 &<<SECTmailstat>>&).
31775 .cindex "reject log"
31776 The reject log records information from messages that are rejected as a result
31777 of a configuration option (that is, for policy reasons).
31778 The first line of each rejection is a copy of the line that is also written to
31779 the main log. Then, if the message's header has been read at the time the log
31780 is written, its contents are written to this log. Only the original header
31781 lines are available; header lines added by ACLs are not logged. You can use the
31782 reject log to check that your policy controls are working correctly; on a busy
31783 host this may be easier than scanning the main log for rejection messages. You
31784 can suppress the writing of the reject log by setting &%write_rejectlog%&
31787 .cindex "panic log"
31788 .cindex "system log"
31789 When certain serious errors occur, Exim writes entries to its panic log. If the
31790 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
31791 are usually written to the main log as well, but can get lost amid the mass of
31792 other entries. The panic log should be empty under normal circumstances. It is
31793 therefore a good idea to check it (or to have a &'cron'& script check it)
31794 regularly, in order to become aware of any problems. When Exim cannot open its
31795 panic log, it tries as a last resort to write to the system log (syslog). This
31796 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
31797 message itself is written at priority LOG_CRIT.
31800 Every log line starts with a timestamp, in the format shown in the following
31801 example. Note that many of the examples shown in this chapter are line-wrapped.
31802 In the log file, this would be all on one line:
31804 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
31807 By default, the timestamps are in the local timezone. There are two
31808 ways of changing this:
31811 You can set the &%timezone%& option to a different time zone; in particular, if
31816 the timestamps will be in UTC (aka GMT).
31818 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
31821 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
31825 .cindex "log" "process ids in"
31826 .cindex "pid (process id)" "in log lines"
31827 Exim does not include its process id in log lines by default, but you can
31828 request that it does so by specifying the &`pid`& log selector (see section
31829 &<<SECTlogselector>>&). When this is set, the process id is output, in square
31830 brackets, immediately after the time and date.
31835 .section "Where the logs are written" "SECTwhelogwri"
31836 .cindex "log" "destination"
31837 .cindex "log" "to file"
31838 .cindex "log" "to syslog"
31840 The logs may be written to local files, or to syslog, or both. However, it
31841 should be noted that many syslog implementations use UDP as a transport, and
31842 are therefore unreliable in the sense that messages are not guaranteed to
31843 arrive at the loghost, nor is the ordering of messages necessarily maintained.
31844 It has also been reported that on large log files (tens of megabytes) you may
31845 need to tweak syslog to prevent it syncing the file with each write &-- on
31846 Linux this has been seen to make syslog take 90% plus of CPU time.
31848 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
31849 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
31850 configuration. This latter string is expanded, so it can contain, for example,
31851 references to the host name:
31853 log_file_path = /var/log/$primary_hostname/exim_%slog
31855 It is generally advisable, however, to set the string in &_Local/Makefile_&
31856 rather than at run time, because then the setting is available right from the
31857 start of Exim's execution. Otherwise, if there's something it wants to log
31858 before it has read the configuration file (for example, an error in the
31859 configuration file) it will not use the path you want, and may not be able to
31862 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
31863 list, currently limited to at most two items. This is one option where the
31864 facility for changing a list separator may not be used. The list must always be
31865 colon-separated. If an item in the list is &"syslog"& then syslog is used;
31866 otherwise the item must either be an absolute path, containing &`%s`& at the
31867 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
31868 implying the use of a default path.
31870 When Exim encounters an empty item in the list, it searches the list defined by
31871 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
31872 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
31873 mean &"use the path specified at build time"&. It no such item exists, log
31874 files are written in the &_log_& subdirectory of the spool directory. This is
31875 equivalent to the setting:
31877 log_file_path = $spool_directory/log/%slog
31879 If you do not specify anything at build time or run time, that is where the
31882 A log file path may also contain &`%D`& if datestamped log file names are in
31883 use &-- see section &<<SECTdatlogfil>>& below.
31885 Here are some examples of possible settings:
31887 &`LOG_FILE_PATH=syslog `& syslog only
31888 &`LOG_FILE_PATH=:syslog `& syslog and default path
31889 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
31890 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
31892 If there are more than two paths in the list, the first is used and a panic
31897 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
31898 .cindex "log" "cycling local files"
31899 .cindex "cycling logs"
31900 .cindex "&'exicyclog'&"
31901 .cindex "log" "local files; writing to"
31902 Some operating systems provide centralized and standardized methods for cycling
31903 log files. For those that do not, a utility script called &'exicyclog'& is
31904 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
31905 main and reject logs each time it is called. The maximum number of old logs to
31906 keep can be set. It is suggested this script is run as a daily &'cron'& job.
31908 An Exim delivery process opens the main log when it first needs to write to it,
31909 and it keeps the file open in case subsequent entries are required &-- for
31910 example, if a number of different deliveries are being done for the same
31911 message. However, remote SMTP deliveries can take a long time, and this means
31912 that the file may be kept open long after it is renamed if &'exicyclog'& or
31913 something similar is being used to rename log files on a regular basis. To
31914 ensure that a switch of log files is noticed as soon as possible, Exim calls
31915 &[stat()]& on the main log's name before reusing an open file, and if the file
31916 does not exist, or its inode has changed, the old file is closed and Exim
31917 tries to open the main log from scratch. Thus, an old log file may remain open
31918 for quite some time, but no Exim processes should write to it once it has been
31923 .section "Datestamped log files" "SECTdatlogfil"
31924 .cindex "log" "datestamped files"
31925 Instead of cycling the main and reject log files by renaming them
31926 periodically, some sites like to use files whose names contain a datestamp,
31927 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_&.
31928 Exim has support for this way of working. It is enabled by setting the
31929 &%log_file_path%& option to a path that includes &`%D`& at the point where the
31930 datestamp is required. For example:
31932 log_file_path = /var/spool/exim/log/%slog-%D
31933 log_file_path = /var/log/exim-%s-%D.log
31934 log_file_path = /var/spool/exim/log/%D-%slog
31936 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
31937 examples of names generated by the above examples:
31939 /var/spool/exim/log/mainlog-20021225
31940 /var/log/exim-reject-20021225.log
31941 /var/spool/exim/log/20021225-mainlog
31943 When this form of log file is specified, Exim automatically switches to new
31944 files at midnight. It does not make any attempt to compress old logs; you
31945 will need to write your own script if you require this. You should not
31946 run &'exicyclog'& with this form of logging.
31948 The location of the panic log is also determined by &%log_file_path%&, but it
31949 is not datestamped, because rotation of the panic log does not make sense.
31950 When generating the name of the panic log, &`%D`& is removed from the string.
31951 In addition, if it immediately follows a slash, a following non-alphanumeric
31952 character is removed; otherwise a preceding non-alphanumeric character is
31953 removed. Thus, the three examples above would give these panic log names:
31955 /var/spool/exim/log/paniclog
31956 /var/log/exim-panic.log
31957 /var/spool/exim/log/paniclog
31961 .section "Logging to syslog" "SECID249"
31962 .cindex "log" "syslog; writing to"
31963 The use of syslog does not change what Exim logs or the format of its messages,
31964 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
31965 Exim's log lines are omitted when these lines are sent to syslog. Apart from
31966 that, the same strings are written to syslog as to log files. The syslog
31967 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
31968 by default, but you can change these by setting the &%syslog_facility%& and
31969 &%syslog_processname%& options, respectively. If Exim was compiled with
31970 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
31971 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
31972 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
31973 the time and host name to each line.
31974 The three log streams are mapped onto syslog priorities as follows:
31977 &'mainlog'& is mapped to LOG_INFO
31979 &'rejectlog'& is mapped to LOG_NOTICE
31981 &'paniclog'& is mapped to LOG_ALERT
31984 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
31985 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
31986 these are routed by syslog to the same place. You can suppress this duplication
31987 by setting &%syslog_duplication%& false.
31989 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
31990 entries contain multiple lines when headers are included. To cope with both
31991 these cases, entries written to syslog are split into separate &[syslog()]&
31992 calls at each internal newline, and also after a maximum of
31993 870 data characters. (This allows for a total syslog line length of 1024, when
31994 additions such as timestamps are added.) If you are running a syslog
31995 replacement that can handle lines longer than the 1024 characters allowed by
31996 RFC 3164, you should set
31998 SYSLOG_LONG_LINES=yes
32000 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
32001 lines, but it still splits at internal newlines in &'reject'& log entries.
32003 To make it easy to re-assemble split lines later, each component of a split
32004 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
32005 where <&'n'&> is the component number and <&'m'&> is the total number of
32006 components in the entry. The / delimiter is used when the line was split
32007 because it was too long; if it was split because of an internal newline, the \
32008 delimiter is used. For example, supposing the length limit to be 50 instead of
32009 870, the following would be the result of a typical rejection message to
32010 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
32011 name, and pid as added by syslog:
32013 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
32014 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
32015 [3/5] when scanning for sender: missing or malformed lo
32016 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
32019 The same error might cause the following lines to be written to &"rejectlog"&
32022 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
32023 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
32024 [3/18] er when scanning for sender: missing or malformed
32025 [4/18] local part in "<>" (envelope sender is <ph10@cam
32027 [6\18] Recipients: ph10@some.domain.cam.example
32028 [7\18] P Received: from [127.0.0.1] (ident=ph10)
32029 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
32030 [9\18] id 16RdAL-0006pc-00
32031 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
32032 [11\18] 09:43 +0100
32034 [13\18] Subject: this is a test header
32035 [18\18] X-something: this is another header
32036 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
32039 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
32041 Log lines that are neither too long nor contain newlines are written to syslog
32042 without modification.
32044 If only syslog is being used, the Exim monitor is unable to provide a log tail
32045 display, unless syslog is routing &'mainlog'& to a file on the local host and
32046 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
32051 .section "Log line flags" "SECID250"
32052 One line is written to the main log for each message received, and for each
32053 successful, unsuccessful, and delayed delivery. These lines can readily be
32054 picked out by the distinctive two-character flags that immediately follow the
32055 timestamp. The flags are:
32057 &`<=`& message arrival
32058 &`=>`& normal message delivery
32059 &`->`& additional address in same delivery
32060 &`*>`& delivery suppressed by &%-N%&
32061 &`**`& delivery failed; address bounced
32062 &`==`& delivery deferred; temporary problem
32066 .section "Logging message reception" "SECID251"
32067 .cindex "log" "reception line"
32068 The format of the single-line entry in the main log that is written for every
32069 message received is shown in the basic example below, which is split over
32070 several lines in order to fit it on the page:
32072 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
32073 H=mailer.fict.example [192.168.123.123] U=exim
32074 P=smtp S=5678 id=<incoming message id>
32076 The address immediately following &"<="& is the envelope sender address. A
32077 bounce message is shown with the sender address &"<>"&, and if it is locally
32078 generated, this is followed by an item of the form
32082 which is a reference to the message that caused the bounce to be sent.
32086 For messages from other hosts, the H and U fields identify the remote host and
32087 record the RFC 1413 identity of the user that sent the message, if one was
32088 received. The number given in square brackets is the IP address of the sending
32089 host. If there is a single, unparenthesized host name in the H field, as
32090 above, it has been verified to correspond to the IP address (see the
32091 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
32092 by the remote host in the SMTP HELO or EHLO command, and has not been
32093 verified. If verification yields a different name to that given for HELO or
32094 EHLO, the verified name appears first, followed by the HELO or EHLO
32095 name in parentheses.
32097 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
32098 without brackets, in the HELO or EHLO command, leading to entries in
32099 the log containing text like these examples:
32101 H=(10.21.32.43) [192.168.8.34]
32102 H=([10.21.32.43]) [192.168.8.34]
32104 This can be confusing. Only the final address in square brackets can be relied
32107 For locally generated messages (that is, messages not received over TCP/IP),
32108 the H field is omitted, and the U field contains the login name of the caller
32111 .cindex "authentication" "logging"
32112 .cindex "AUTH" "logging"
32113 For all messages, the P field specifies the protocol used to receive the
32114 message. This is the value that is stored in &$received_protocol$&. In the case
32115 of incoming SMTP messages, the value indicates whether or not any SMTP
32116 extensions (ESMTP), encryption, or authentication were used. If the SMTP
32117 session was encrypted, there is an additional X field that records the cipher
32118 suite that was used.
32120 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
32121 hosts that have authenticated themselves using the SMTP AUTH command. The first
32122 value is used when the SMTP connection was encrypted (&"secure"&). In this case
32123 there is an additional item A= followed by the name of the authenticator that
32124 was used. If an authenticated identification was set up by the authenticator's
32125 &%server_set_id%& option, this is logged too, separated by a colon from the
32126 authenticator name.
32128 .cindex "size" "of message"
32129 The id field records the existing message id, if present. The size of the
32130 received message is given by the S field. When the message is delivered,
32131 headers may be removed or added, so that the size of delivered copies of the
32132 message may not correspond with this value (and indeed may be different to each
32135 The &%log_selector%& option can be used to request the logging of additional
32136 data when a message is received. See section &<<SECTlogselector>>& below.
32140 .section "Logging deliveries" "SECID252"
32141 .cindex "log" "delivery line"
32142 The format of the single-line entry in the main log that is written for every
32143 delivery is shown in one of the examples below, for local and remote
32144 deliveries, respectively. Each example has been split into two lines in order
32145 to fit it on the page:
32147 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
32148 <marv@hitch.fict.example> R=localuser T=local_delivery
32149 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
32150 monk@holistic.fict.example R=dnslookup T=remote_smtp
32151 H=holistic.fict.example [192.168.234.234]
32153 For ordinary local deliveries, the original address is given in angle brackets
32154 after the final delivery address, which might be a pipe or a file. If
32155 intermediate address(es) exist between the original and the final address, the
32156 last of these is given in parentheses after the final address. The R and T
32157 fields record the router and transport that were used to process the address.
32159 If a shadow transport was run after a successful local delivery, the log line
32160 for the successful delivery has an item added on the end, of the form
32162 &`ST=<`&&'shadow transport name'&&`>`&
32164 If the shadow transport did not succeed, the error message is put in
32165 parentheses afterwards.
32167 .cindex "asterisk" "after IP address"
32168 When more than one address is included in a single delivery (for example, two
32169 SMTP RCPT commands in one transaction) the second and subsequent addresses are
32170 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
32171 down a single SMTP connection, an asterisk follows the IP address in the log
32172 lines for the second and subsequent messages.
32174 The generation of a reply message by a filter file gets logged as a
32175 &"delivery"& to the addressee, preceded by &">"&.
32177 The &%log_selector%& option can be used to request the logging of additional
32178 data when a message is delivered. See section &<<SECTlogselector>>& below.
32181 .section "Discarded deliveries" "SECID253"
32182 .cindex "discarded messages"
32183 .cindex "message" "discarded"
32184 .cindex "delivery" "discarded; logging"
32185 When a message is discarded as a result of the command &"seen finish"& being
32186 obeyed in a filter file which generates no deliveries, a log entry of the form
32188 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
32189 <low.club@bridge.example> R=userforward
32191 is written, to record why no deliveries are logged. When a message is discarded
32192 because it is aliased to &":blackhole:"& the log line is like this:
32194 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
32195 <hole@nowhere.example> R=blackhole_router
32199 .section "Deferred deliveries" "SECID254"
32200 When a delivery is deferred, a line of the following form is logged:
32202 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
32203 R=dnslookup T=smtp defer (146): Connection refused
32205 In the case of remote deliveries, the error is the one that was given for the
32206 last IP address that was tried. Details of individual SMTP failures are also
32207 written to the log, so the above line would be preceded by something like
32209 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
32210 mail1.endrest.example [192.168.239.239]: Connection refused
32212 When a deferred address is skipped because its retry time has not been reached,
32213 a message is written to the log, but this can be suppressed by setting an
32214 appropriate value in &%log_selector%&.
32218 .section "Delivery failures" "SECID255"
32219 .cindex "delivery" "failure; logging"
32220 If a delivery fails because an address cannot be routed, a line of the
32221 following form is logged:
32223 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
32224 <jim@trek99.example>: unknown mail domain
32226 If a delivery fails at transport time, the router and transport are shown, and
32227 the response from the remote host is included, as in this example:
32229 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
32230 R=dnslookup T=remote_smtp: SMTP error from remote mailer
32231 after pipelined RCPT TO:<ace400@pb.example>: host
32232 pbmail3.py.example [192.168.63.111]: 553 5.3.0
32233 <ace400@pb.example>...Addressee unknown
32235 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
32236 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
32237 disabling PIPELINING. The log lines for all forms of delivery failure are
32238 flagged with &`**`&.
32242 .section "Fake deliveries" "SECID256"
32243 .cindex "delivery" "fake; logging"
32244 If a delivery does not actually take place because the &%-N%& option has been
32245 used to suppress it, a normal delivery line is written to the log, except that
32246 &"=>"& is replaced by &"*>"&.
32250 .section "Completion" "SECID257"
32253 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
32255 is written to the main log when a message is about to be removed from the spool
32256 at the end of its processing.
32261 .section "Summary of Fields in Log Lines" "SECID258"
32262 .cindex "log" "summary of fields"
32263 A summary of the field identifiers that are used in log lines is shown in
32264 the following table:
32266 &`A `& authenticator name (and optional id)
32267 &`C `& SMTP confirmation on delivery
32268 &` `& command list for &"no mail in SMTP session"&
32269 &`CV `& certificate verification status
32270 &`D `& duration of &"no mail in SMTP session"&
32271 &`DN `& distinguished name from peer certificate
32272 &`DT `& on &`=>`& lines: time taken for a delivery
32273 &`F `& sender address (on delivery lines)
32274 &`H `& host name and IP address
32275 &`I `& local interface used
32276 &`id `& message id for incoming message
32277 &`P `& on &`<=`& lines: protocol used
32278 &` `& on &`=>`& and &`**`& lines: return path
32279 &`QT `& on &`=>`& lines: time spent on queue so far
32280 &` `& on &"Completed"& lines: time spent on queue
32281 &`R `& on &`<=`& lines: reference for local bounce
32282 &` `& on &`=>`& &`**`& and &`==`& lines: router name
32283 &`S `& size of message
32284 &`ST `& shadow transport name
32285 &`T `& on &`<=`& lines: message subject (topic)
32286 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
32287 &`U `& local user or RFC 1413 identity
32288 &`X `& TLS cipher suite
32292 .section "Other log entries" "SECID259"
32293 Various other types of log entry are written from time to time. Most should be
32294 self-explanatory. Among the more common are:
32297 .cindex "retry" "time not reached"
32298 &'retry time not reached'&&~&~An address previously suffered a temporary error
32299 during routing or local delivery, and the time to retry has not yet arrived.
32300 This message is not written to an individual message log file unless it happens
32301 during the first delivery attempt.
32303 &'retry time not reached for any host'&&~&~An address previously suffered
32304 temporary errors during remote delivery, and the retry time has not yet arrived
32305 for any of the hosts to which it is routed.
32307 .cindex "spool directory" "file locked"
32308 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
32309 some other Exim process is already working on the message. This can be quite
32310 common if queue running processes are started at frequent intervals. The
32311 &'exiwhat'& utility script can be used to find out what Exim processes are
32314 .cindex "error" "ignored"
32315 &'error ignored'&&~&~There are several circumstances that give rise to this
32318 Exim failed to deliver a bounce message whose age was greater than
32319 &%ignore_bounce_errors_after%&. The bounce was discarded.
32321 A filter file set up a delivery using the &"noerror"& option, and the delivery
32322 failed. The delivery was discarded.
32324 A delivery set up by a router configured with
32325 . ==== As this is a nested list, any displays it contains must be indented
32326 . ==== as otherwise they are too far to the left.
32330 failed. The delivery was discarded.
32338 .section "Reducing or increasing what is logged" "SECTlogselector"
32339 .cindex "log" "selectors"
32340 By setting the &%log_selector%& global option, you can disable some of Exim's
32341 default logging, or you can request additional logging. The value of
32342 &%log_selector%& is made up of names preceded by plus or minus characters. For
32345 log_selector = +arguments -retry_defer
32347 The list of optional log items is in the following table, with the default
32348 selection marked by asterisks:
32350 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
32351 &` address_rewrite `& address rewriting
32352 &` all_parents `& all parents in => lines
32353 &` arguments `& command line arguments
32354 &`*connection_reject `& connection rejections
32355 &`*delay_delivery `& immediate delivery delayed
32356 &` deliver_time `& time taken to perform delivery
32357 &` delivery_size `& add &`S=`&&'nnn'& to => lines
32358 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
32359 &`*etrn `& ETRN commands
32360 &`*host_lookup_failed `& as it says
32361 &` ident_timeout `& timeout for ident connection
32362 &` incoming_interface `& incoming interface on <= lines
32363 &` incoming_port `& incoming port on <= lines
32364 &`*lost_incoming_connection `& as it says (includes timeouts)
32365 &` outgoing_port `& add remote port to => lines
32366 &`*queue_run `& start and end queue runs
32367 &` queue_time `& time on queue for one recipient
32368 &` queue_time_overall `& time on queue for whole message
32369 &` pid `& Exim process id
32370 &` received_recipients `& recipients on <= lines
32371 &` received_sender `& sender on <= lines
32372 &`*rejected_header `& header contents on reject log
32373 &`*retry_defer `& &"retry time not reached"&
32374 &` return_path_on_delivery `& put return path on => and ** lines
32375 &` sender_on_delivery `& add sender to => lines
32376 &`*sender_verify_fail `& sender verification failures
32377 &`*size_reject `& rejection because too big
32378 &`*skip_delivery `& delivery skipped in a queue run
32379 &` smtp_confirmation `& SMTP confirmation on => lines
32380 &` smtp_connection `& SMTP connections
32381 &` smtp_incomplete_transaction`& incomplete SMTP transactions
32382 &` smtp_no_mail `& session with no MAIL commands
32383 &` smtp_protocol_error `& SMTP protocol errors
32384 &` smtp_syntax_error `& SMTP syntax errors
32385 &` subject `& contents of &'Subject:'& on <= lines
32386 &` tls_certificate_verified `& certificate verification status
32387 &`*tls_cipher `& TLS cipher suite on <= and => lines
32388 &` tls_peerdn `& TLS peer DN on <= and => lines
32389 &` unknown_in_list `& DNS lookup failed in list match
32391 &` all `& all of the above
32393 More details on each of these items follows:
32396 .cindex "&%warn%& ACL verb" "log when skipping"
32397 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
32398 its conditions cannot be evaluated, a log line to this effect is written if
32399 this log selector is set.
32401 .cindex "log" "rewriting"
32402 .cindex "rewriting" "logging"
32403 &%address_rewrite%&: This applies both to global rewrites and per-transport
32404 rewrites, but not to rewrites in filters run as an unprivileged user (because
32405 such users cannot access the log).
32407 .cindex "log" "full parentage"
32408 &%all_parents%&: Normally only the original and final addresses are logged on
32409 delivery lines; with this selector, intermediate parents are given in
32410 parentheses between them.
32412 .cindex "log" "Exim arguments"
32413 .cindex "Exim arguments, logging"
32414 &%arguments%&: This causes Exim to write the arguments with which it was called
32415 to the main log, preceded by the current working directory. This is a debugging
32416 feature, added to make it easier to find out how certain MUAs call
32417 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
32418 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
32419 that are empty or that contain white space are quoted. Non-printing characters
32420 are shown as escape sequences. This facility cannot log unrecognized arguments,
32421 because the arguments are checked before the configuration file is read. The
32422 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
32423 between the caller and Exim.
32425 .cindex "log" "connection rejections"
32426 &%connection_reject%&: A log entry is written whenever an incoming SMTP
32427 connection is rejected, for whatever reason.
32429 .cindex "log" "delayed delivery"
32430 .cindex "delayed delivery, logging"
32431 &%delay_delivery%&: A log entry is written whenever a delivery process is not
32432 started for an incoming message because the load is too high or too many
32433 messages were received on one connection. Logging does not occur if no delivery
32434 process is started because &%queue_only%& is set or &%-odq%& was used.
32436 .cindex "log" "delivery duration"
32437 &%deliver_time%&: For each delivery, the amount of real time it has taken to
32438 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
32440 .cindex "log" "message size on delivery"
32441 .cindex "size" "of message"
32442 &%delivery_size%&: For each delivery, the size of message delivered is added to
32443 the &"=>"& line, tagged with S=.
32445 .cindex "log" "dnslist defer"
32446 .cindex "DNS list" "logging defer"
32447 .cindex "black list (DNS)"
32448 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
32449 DNS black list suffers a temporary error.
32451 .cindex "log" "ETRN commands"
32452 .cindex "ETRN" "logging"
32453 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
32454 is run to determine whether or not it is actually accepted. An invalid ETRN
32455 command, or one received within a message transaction is not logged by this
32456 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
32458 .cindex "log" "host lookup failure"
32459 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
32460 any addresses, or when a lookup of an IP address fails to find a host name, a
32461 log line is written. This logging does not apply to direct DNS lookups when
32462 routing email addresses, but it does apply to &"byname"& lookups.
32464 .cindex "log" "ident timeout"
32465 .cindex "RFC 1413" "logging timeout"
32466 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
32467 client's ident port times out.
32469 .cindex "log" "incoming interface"
32470 .cindex "interface" "logging"
32471 &%incoming_interface%&: The interface on which a message was received is added
32472 to the &"<="& line as an IP address in square brackets, tagged by I= and
32473 followed by a colon and the port number. The local interface and port are also
32474 added to other SMTP log lines, for example &"SMTP connection from"&, and to
32477 .cindex "log" "incoming remote port"
32478 .cindex "port" "logging remote"
32479 .cindex "TCP/IP" "logging incoming remote port"
32480 .vindex "&$sender_fullhost$&"
32481 .vindex "&$sender_rcvhost$&"
32482 &%incoming_port%&: The remote port number from which a message was received is
32483 added to log entries and &'Received:'& header lines, following the IP address
32484 in square brackets, and separated from it by a colon. This is implemented by
32485 changing the value that is put in the &$sender_fullhost$& and
32486 &$sender_rcvhost$& variables. Recording the remote port number has become more
32487 important with the widening use of NAT (see RFC 2505).
32489 .cindex "log" "dropped connection"
32490 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
32491 connection is unexpectedly dropped.
32493 .cindex "log" "outgoing remote port"
32494 .cindex "port" "logging outgoint remote"
32495 .cindex "TCP/IP" "logging ougtoing remote port"
32496 &%outgoing_port%&: The remote port number is added to delivery log lines (those
32497 containing => tags) following the IP address. This option is not included in
32498 the default setting, because for most ordinary configurations, the remote port
32499 number is always 25 (the SMTP port).
32501 .cindex "log" "process ids in"
32502 .cindex "pid (process id)" "in log lines"
32503 &%pid%&: The current process id is added to every log line, in square brackets,
32504 immediately after the time and date.
32506 .cindex "log" "queue run"
32507 .cindex "queue runner" "logging"
32508 &%queue_run%&: The start and end of every queue run are logged.
32510 .cindex "log" "queue time"
32511 &%queue_time%&: The amount of time the message has been in the queue on the
32512 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
32513 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
32514 includes reception time as well as the delivery time for the current address.
32515 This means that it may be longer than the difference between the arrival and
32516 delivery log line times, because the arrival log line is not written until the
32517 message has been successfully received.
32519 &%queue_time_overall%&: The amount of time the message has been in the queue on
32520 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
32521 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
32522 message, so it includes reception time as well as the total delivery time.
32524 .cindex "log" "recipients"
32525 &%received_recipients%&: The recipients of a message are listed in the main log
32526 as soon as the message is received. The list appears at the end of the log line
32527 that is written when a message is received, preceded by the word &"for"&. The
32528 addresses are listed after they have been qualified, but before any rewriting
32530 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
32533 .cindex "log" "sender reception"
32534 &%received_sender%&: The unrewritten original sender of a message is added to
32535 the end of the log line that records the message's arrival, after the word
32536 &"from"& (before the recipients if &%received_recipients%& is also set).
32538 .cindex "log" "header lines for rejection"
32539 &%rejected_header%&: If a message's header has been received at the time a
32540 rejection is written to the reject log, the complete header is added to the
32541 log. Header logging can be turned off individually for messages that are
32542 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
32544 .cindex "log" "retry defer"
32545 &%retry_defer%&: A log line is written if a delivery is deferred because a
32546 retry time has not yet been reached. However, this &"retry time not reached"&
32547 message is always omitted from individual message logs after the first delivery
32550 .cindex "log" "return path"
32551 &%return_path_on_delivery%&: The return path that is being transmitted with
32552 the message is included in delivery and bounce lines, using the tag P=.
32553 This is omitted if no delivery actually happens, for example, if routing fails,
32554 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
32556 .cindex "log" "sender on delivery"
32557 &%sender_on_delivery%&: The message's sender address is added to every delivery
32558 and bounce line, tagged by F= (for &"from"&).
32559 This is the original sender that was received with the message; it is not
32560 necessarily the same as the outgoing return path.
32562 .cindex "log" "sender verify failure"
32563 &%sender_verify_fail%&: If this selector is unset, the separate log line that
32564 gives details of a sender verification failure is not written. Log lines for
32565 the rejection of SMTP commands contain just &"sender verify failed"&, so some
32568 .cindex "log" "size rejection"
32569 &%size_reject%&: A log line is written whenever a message is rejected because
32572 .cindex "log" "frozen messages; skipped"
32573 .cindex "frozen messages" "logging skipping"
32574 &%skip_delivery%&: A log line is written whenever a message is skipped during a
32575 queue run because it is frozen or because another process is already delivering
32577 .cindex "&""spool file is locked""&"
32578 The message that is written is &"spool file is locked"&.
32580 .cindex "log" "smtp confirmation"
32581 .cindex "SMTP" "logging confirmation"
32582 &%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for
32583 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
32584 A number of MTAs (including Exim) return an identifying string in this
32587 .cindex "log" "SMTP connections"
32588 .cindex "SMTP" "logging connections"
32589 &%smtp_connection%&: A log line is written whenever an SMTP connection is
32590 established or closed, unless the connection is from a host that matches
32591 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
32592 only when the closure is unexpected.) This applies to connections from local
32593 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
32594 dropped in the middle of a message, a log line is always written, whether or
32595 not this selector is set, but otherwise nothing is written at the start and end
32596 of connections unless this selector is enabled.
32598 For TCP/IP connections to an Exim daemon, the current number of connections is
32599 included in the log message for each new connection, but note that the count is
32600 reset if the daemon is restarted.
32601 Also, because connections are closed (and the closure is logged) in
32602 subprocesses, the count may not include connections that have been closed but
32603 whose termination the daemon has not yet noticed. Thus, while it is possible to
32604 match up the opening and closing of connections in the log, the value of the
32605 logged counts may not be entirely accurate.
32607 .cindex "log" "SMTP transaction; incomplete"
32608 .cindex "SMTP" "logging incomplete transactions"
32609 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
32610 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
32611 and the message sender plus any accepted recipients are included in the log
32612 line. This can provide evidence of dictionary attacks.
32614 .cindex "log" "non-MAIL SMTP sessions"
32615 .cindex "MAIL" "logging session without"
32616 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
32617 connection terminates without having issued a MAIL command. This includes both
32618 the case when the connection is dropped, and the case when QUIT is used. It
32619 does not include cases where the connection is rejected right at the start (by
32620 an ACL, or because there are too many connections, or whatever). These cases
32621 already have their own log lines.
32623 The log line that is written contains the identity of the client in the usual
32624 way, followed by D= and a time, which records the duration of the connection.
32625 If the connection was authenticated, this fact is logged exactly as it is for
32626 an incoming message, with an A= item. If the connection was encrypted, CV=,
32627 DN=, and X= items may appear as they do for an incoming message, controlled by
32628 the same logging options.
32630 Finally, if any SMTP commands were issued during the connection, a C= item
32631 is added to the line, listing the commands that were used. For example,
32635 shows that the client issued QUIT straight after EHLO. If there were fewer
32636 than 20 commands, they are all listed. If there were more than 20 commands,
32637 the last 20 are listed, preceded by &"..."&. However, with the default
32638 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
32639 have been aborted before 20 non-mail commands are processed.
32641 .cindex "log" "SMTP protocol error"
32642 .cindex "SMTP" "logging protocol error"
32643 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
32644 encountered. Exim does not have perfect detection of all protocol errors
32645 because of transmission delays and the use of pipelining. If PIPELINING has
32646 been advertised to a client, an Exim server assumes that the client will use
32647 it, and therefore it does not count &"expected"& errors (for example, RCPT
32648 received after rejecting MAIL) as protocol errors.
32650 .cindex "SMTP" "logging syntax errors"
32651 .cindex "SMTP" "syntax errors; logging"
32652 .cindex "SMTP" "unknown command; logging"
32653 .cindex "log" "unknown SMTP command"
32654 .cindex "log" "SMTP syntax error"
32655 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
32656 encountered. An unrecognized command is treated as a syntax error. For an
32657 external connection, the host identity is given; for an internal connection
32658 using &%-bs%& the sender identification (normally the calling user) is given.
32660 .cindex "log" "subject"
32661 .cindex "subject, logging"
32662 &%subject%&: The subject of the message is added to the arrival log line,
32663 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
32664 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
32665 specifies whether characters with values greater than 127 should be logged
32666 unchanged, or whether they should be rendered as escape sequences.
32668 .cindex "log" "certificate verification"
32669 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
32670 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
32671 verified, and &`CV=no`& if not.
32673 .cindex "log" "TLS cipher"
32674 .cindex "TLS" "logging cipher"
32675 &%tls_cipher%&: When a message is sent or received over an encrypted
32676 connection, the cipher suite used is added to the log line, preceded by X=.
32678 .cindex "log" "TLS peer DN"
32679 .cindex "TLS" "logging peer DN"
32680 &%tls_peerdn%&: When a message is sent or received over an encrypted
32681 connection, and a certificate is supplied by the remote host, the peer DN is
32682 added to the log line, preceded by DN=.
32684 .cindex "log" "DNS failure in list"
32685 &%unknown_in_list%&: This setting causes a log entry to be written when the
32686 result of a list match is failure because a DNS lookup failed.
32690 .section "Message log" "SECID260"
32691 .cindex "message" "log file for"
32692 .cindex "log" "message log; description of"
32693 .cindex "&_msglog_& directory"
32694 .oindex "&%preserve_message_logs%&"
32695 In addition to the general log files, Exim writes a log file for each message
32696 that it handles. The names of these per-message logs are the message ids, and
32697 they are kept in the &_msglog_& sub-directory of the spool directory. Each
32698 message log contains copies of the log lines that apply to the message. This
32699 makes it easier to inspect the status of an individual message without having
32700 to search the main log. A message log is deleted when processing of the message
32701 is complete, unless &%preserve_message_logs%& is set, but this should be used
32702 only with great care because they can fill up your disk very quickly.
32704 On a heavily loaded system, it may be desirable to disable the use of
32705 per-message logs, in order to reduce disk I/O. This can be done by setting the
32706 &%message_logs%& option false.
32712 . ////////////////////////////////////////////////////////////////////////////
32713 . ////////////////////////////////////////////////////////////////////////////
32715 .chapter "Exim utilities" "CHAPutils"
32716 .scindex IIDutils "utilities"
32717 A number of utility scripts and programs are supplied with Exim and are
32718 described in this chapter. There is also the Exim Monitor, which is covered in
32719 the next chapter. The utilities described here are:
32721 .itable none 0 0 3 7* left 15* left 40* left
32722 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
32723 "list what Exim processes are doing"
32724 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
32725 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
32726 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
32727 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
32729 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
32730 .irow &<<SECTmailstat>>& &'eximstats'& &&&
32731 "extract statistics from the log"
32732 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
32733 "check address acceptance from given IP"
32734 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
32735 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
32736 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
32737 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
32738 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
32739 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
32742 Another utility that might be of use to sites with many MTAs is Tom Kistner's
32743 &'exilog'&. It provides log visualizations across multiple Exim servers. See
32744 &url(http://duncanthrax.net/exilog/) for details.
32749 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
32750 .cindex "&'exiwhat'&"
32751 .cindex "process, querying"
32753 On operating systems that can restart a system call after receiving a signal
32754 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
32755 a line describing what it is doing to the file &_exim-process.info_& in the
32756 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
32757 processes it can find, having first emptied the file. It then waits for one
32758 second to allow the Exim processes to react before displaying the results. In
32759 order to run &'exiwhat'& successfully you have to have sufficient privilege to
32760 send the signal to the Exim processes, so it is normally run as root.
32762 &*Warning*&: This is not an efficient process. It is intended for occasional
32763 use by system administrators. It is not sensible, for example, to set up a
32764 script that sends SIGUSR1 signals to Exim processes at short intervals.
32767 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
32768 varies in different operating systems. Not only are different options used,
32769 but the format of the output is different. For this reason, there are some
32770 system configuration options that configure exactly how &'exiwhat'& works. If
32771 it doesn't seem to be working for you, check the following compile-time
32774 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
32775 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
32776 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
32777 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
32779 An example of typical output from &'exiwhat'& is
32781 164 daemon: -q1h, listening on port 25
32782 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
32783 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
32784 [10.19.42.42] (editor@ref.example)
32785 10592 handling incoming call from [192.168.243.242]
32786 10628 accepting a local non-SMTP message
32788 The first number in the output line is the process number. The third line has
32789 been split here, in order to fit it on the page.
32793 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
32794 .cindex "&'exiqgrep'&"
32795 .cindex "queue" "grepping"
32796 This utility is a Perl script contributed by Matt Hubbard. It runs
32800 to obtain a queue listing with undelivered recipients only, and then greps the
32801 output to select messages that match given criteria. The following selection
32802 options are available:
32805 .vitem &*-f*&&~<&'regex'&>
32806 Match the sender address. The field that is tested is enclosed in angle
32807 brackets, so you can test for bounce messages with
32811 .vitem &*-r*&&~<&'regex'&>
32812 Match a recipient address. The field that is tested is not enclosed in angle
32815 .vitem &*-s*&&~<&'regex'&>
32816 Match against the size field.
32818 .vitem &*-y*&&~<&'seconds'&>
32819 Match messages that are younger than the given time.
32821 .vitem &*-o*&&~<&'seconds'&>
32822 Match messages that are older than the given time.
32825 Match only frozen messages.
32828 Match only non-frozen messages.
32831 The following options control the format of the output:
32835 Display only the count of matching messages.
32838 Long format &-- display the full message information as output by Exim. This is
32842 Display message ids only.
32845 Brief format &-- one line per message.
32848 Display messages in reverse order.
32851 There is one more option, &%-h%&, which outputs a list of options.
32855 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
32856 .cindex "&'exiqsumm'&"
32857 .cindex "queue" "summary"
32858 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
32859 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
32860 running a command such as
32862 exim -bp | exiqsumm
32864 The output consists of one line for each domain that has messages waiting for
32865 it, as in the following example:
32867 3 2322 74m 66m msn.com.example
32869 Each line lists the number of pending deliveries for a domain, their total
32870 volume, and the length of time that the oldest and the newest messages have
32871 been waiting. Note that the number of pending deliveries is greater than the
32872 number of messages when messages have more than one recipient.
32874 A summary line is output at the end. By default the output is sorted on the
32875 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
32876 the output to be sorted by oldest message and by count of messages,
32877 respectively. There are also three options that split the messages for each
32878 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
32879 separates frozen messages, and &%-s%& separates messages according to their
32882 The output of &'exim -bp'& contains the original addresses in the message, so
32883 this also applies to the output from &'exiqsumm'&. No domains from addresses
32884 generated by aliasing or forwarding are included (unless the &%one_time%&
32885 option of the &(redirect)& router has been used to convert them into &"top
32886 level"& addresses).
32891 .section "Extracting specific information from the log (exigrep)" &&&
32893 .cindex "&'exigrep'&"
32894 .cindex "log" "extracts; grepping for"
32895 The &'exigrep'& utility is a Perl script that searches one or more main log
32896 files for entries that match a given pattern. When it finds a match, it
32897 extracts all the log entries for the relevant message, not just those that
32898 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
32899 given message, or all mail for a given user, or for a given host, for example.
32900 The input files can be in Exim log format or syslog format.
32901 If a matching log line is not associated with a specific message, it is
32902 included in &'exigrep'&'s output without any additional lines. The usage is:
32904 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
32906 If no log file names are given on the command line, the standard input is read.
32908 The &%-t%& argument specifies a number of seconds. It adds an additional
32909 condition for message selection. Messages that are complete are shown only if
32910 they spent more than <&'n'&> seconds on the queue.
32912 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
32913 makes it case-sensitive. This may give a performance improvement when searching
32914 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
32915 option; with &%-I%& they do not. In both cases it is possible to change the
32916 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
32918 The &%-l%& option means &"literal"&, that is, treat all characters in the
32919 pattern as standing for themselves. Otherwise the pattern must be a Perl
32920 regular expression.
32922 The &%-v%& option inverts the matching condition. That is, a line is selected
32923 if it does &'not'& match the pattern.
32925 If the location of a &'zcat'& command is known from the definition of
32926 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
32927 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
32930 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
32931 .cindex "&'exipick'&"
32932 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
32933 lists messages from the queue according to a variety of criteria. For details
32934 of &'exipick'&'s facilities, visit the web page at
32935 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
32936 the &%--help%& option.
32939 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
32940 .cindex "log" "cycling local files"
32941 .cindex "cycling logs"
32942 .cindex "&'exicyclog'&"
32943 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
32944 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
32945 you are using log files with datestamps in their names (see section
32946 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
32947 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
32948 There are two command line options for &'exicyclog'&:
32950 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
32951 default that is set when Exim is built. The default default is 10.
32953 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
32954 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
32955 overriding the script's default, which is to find the setting from Exim's
32959 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
32960 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
32961 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
32962 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
32963 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
32964 logs are handled similarly.
32966 If the limit is greater than 99, the script uses 3-digit numbers such as
32967 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
32968 to one that is greater, or &'vice versa'&, you will have to fix the names of
32969 any existing log files.
32971 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
32972 the end are deleted. All files with numbers greater than 01 are compressed,
32973 using a compression command which is configured by the COMPRESS_COMMAND
32974 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
32975 root &%crontab%& entry of the form
32977 1 0 * * * su exim -c /usr/exim/bin/exicyclog
32979 assuming you have used the name &"exim"& for the Exim user. You can run
32980 &'exicyclog'& as root if you wish, but there is no need.
32984 .section "Mail statistics (eximstats)" "SECTmailstat"
32985 .cindex "statistics"
32986 .cindex "&'eximstats'&"
32987 A Perl script called &'eximstats'& is provided for extracting statistical
32988 information from log files. The output is either plain text, or HTML.
32989 Exim log files are also supported by the &'Lire'& system produced by the
32990 LogReport Foundation &url(http://www.logreport.org).
32992 The &'eximstats'& script has been hacked about quite a bit over time. The
32993 latest version is the result of some extensive revision by Steve Campbell. A
32994 lot of information is given by default, but there are options for suppressing
32995 various parts of it. Following any options, the arguments to the script are a
32996 list of files, which should be main log files. For example:
32998 eximstats -nr /var/spool/exim/log/mainlog.01
33000 By default, &'eximstats'& extracts information about the number and volume of
33001 messages received from or delivered to various hosts. The information is sorted
33002 both by message count and by volume, and the top fifty hosts in each category
33003 are listed on the standard output. Similar information, based on email
33004 addresses or domains instead of hosts can be requested by means of various
33005 options. For messages delivered and received locally, similar statistics are
33006 also produced per user.
33008 The output also includes total counts and statistics about delivery errors, and
33009 histograms showing the number of messages received and deliveries made in each
33010 hour of the day. A delivery with more than one address in its envelope (for
33011 example, an SMTP transaction with more than one RCPT command) is counted
33012 as a single delivery by &'eximstats'&.
33014 Though normally more deliveries than receipts are reported (as messages may
33015 have multiple recipients), it is possible for &'eximstats'& to report more
33016 messages received than delivered, even though the queue is empty at the start
33017 and end of the period in question. If an incoming message contains no valid
33018 recipients, no deliveries are recorded for it. A bounce message is handled as
33019 an entirely separate message.
33021 &'eximstats'& always outputs a grand total summary giving the volume and number
33022 of messages received and deliveries made, and the number of hosts involved in
33023 each case. It also outputs the number of messages that were delayed (that is,
33024 not completely delivered at the first attempt), and the number that had at
33025 least one address that failed.
33027 The remainder of the output is in sections that can be independently disabled
33028 or modified by various options. It consists of a summary of deliveries by
33029 transport, histograms of messages received and delivered per time interval
33030 (default per hour), information about the time messages spent on the queue,
33031 a list of relayed messages, lists of the top fifty sending hosts, local
33032 senders, destination hosts, and destination local users by count and by volume,
33033 and a list of delivery errors that occurred.
33035 The relay information lists messages that were actually relayed, that is, they
33036 came from a remote host and were directly delivered to some other remote host,
33037 without being processed (for example, for aliasing or forwarding) locally.
33039 There are quite a few options for &'eximstats'& to control exactly what it
33040 outputs. These are documented in the Perl script itself, and can be extracted
33041 by running the command &(perldoc)& on the script. For example:
33043 perldoc /usr/exim/bin/eximstats
33046 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
33047 .cindex "&'exim_checkaccess'&"
33048 .cindex "policy control" "checking access"
33049 .cindex "checking access"
33050 The &%-bh%& command line argument allows you to run a fake SMTP session with
33051 debugging output, in order to check what Exim is doing when it is applying
33052 policy controls to incoming SMTP mail. However, not everybody is sufficiently
33053 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
33054 sometimes you just want to answer the question &"Does this address have
33055 access?"& without bothering with any further details.
33057 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
33058 two arguments, an IP address and an email address:
33060 exim_checkaccess 10.9.8.7 A.User@a.domain.example
33062 The utility runs a call to Exim with the &%-bh%& option, to test whether the
33063 given email address would be accepted in a RCPT command in a TCP/IP
33064 connection from the host with the given IP address. The output of the utility
33065 is either the word &"accepted"&, or the SMTP error response, for example:
33068 550 Relay not permitted
33070 When running this test, the utility uses &`<>`& as the envelope sender address
33071 for the MAIL command, but you can change this by providing additional
33072 options. These are passed directly to the Exim command. For example, to specify
33073 that the test is to be run with the sender address &'himself@there.example'&
33076 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
33077 -f himself@there.example
33079 Note that these additional Exim command line items must be given after the two
33080 mandatory arguments.
33082 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
33083 while running its checks. You can run checks that include callouts by using
33084 &%-bhc%&, but this is not yet available in a &"packaged"& form.
33088 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
33089 .cindex "DBM" "building dbm files"
33090 .cindex "building DBM files"
33091 .cindex "&'exim_dbmbuild'&"
33092 .cindex "lower casing"
33093 .cindex "binary zero" "in lookup key"
33094 The &'exim_dbmbuild'& program reads an input file containing keys and data in
33095 the format used by the &(lsearch)& lookup (see section
33096 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
33097 names as keys and the remainder of the information as data. The lower-casing
33098 can be prevented by calling the program with the &%-nolc%& option.
33100 A terminating zero is included as part of the key string. This is expected by
33101 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
33102 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
33103 strings or the data strings. The &(dbmnz)& lookup type can be used with such
33106 The program requires two arguments: the name of the input file (which can be a
33107 single hyphen to indicate the standard input), and the name of the output file.
33108 It creates the output under a temporary name, and then renames it if all went
33112 If the native DB interface is in use (USE_DB is set in a compile-time
33113 configuration file &-- this is common in free versions of Unix) the two file
33114 names must be different, because in this mode the Berkeley DB functions create
33115 a single output file using exactly the name given. For example,
33117 exim_dbmbuild /etc/aliases /etc/aliases.db
33119 reads the system alias file and creates a DBM version of it in
33120 &_/etc/aliases.db_&.
33122 In systems that use the &'ndbm'& routines (mostly proprietary versions of
33123 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
33124 environment, the suffixes are added to the second argument of
33125 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
33126 when the Berkeley functions are used in compatibility mode (though this is not
33127 recommended), because in that case it adds a &_.db_& suffix to the file name.
33129 If a duplicate key is encountered, the program outputs a warning, and when it
33130 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
33131 option is used. By default, only the first of a set of duplicates is used &--
33132 this makes it compatible with &(lsearch)& lookups. There is an option
33133 &%-lastdup%& which causes it to use the data for the last duplicate instead.
33134 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
33135 &%stderr%&. For other errors, where it doesn't actually make a new file, the
33141 .section "Finding individual retry times (exinext)" "SECTfinindret"
33142 .cindex "retry" "times"
33143 .cindex "&'exinext'&"
33144 A utility called &'exinext'& (mostly a Perl script) provides the ability to
33145 fish specific information out of the retry database. Given a mail domain (or a
33146 complete address), it looks up the hosts for that domain, and outputs any retry
33147 information for the hosts or for the domain. At present, the retry information
33148 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
33149 output. For example:
33151 $ exinext piglet@milne.fict.example
33152 kanga.milne.example:192.168.8.1 error 146: Connection refused
33153 first failed: 21-Feb-1996 14:57:34
33154 last tried: 21-Feb-1996 14:57:34
33155 next try at: 21-Feb-1996 15:02:34
33156 roo.milne.example:192.168.8.3 error 146: Connection refused
33157 first failed: 20-Jan-1996 13:12:08
33158 last tried: 21-Feb-1996 11:42:03
33159 next try at: 21-Feb-1996 19:42:03
33160 past final cutoff time
33162 You can also give &'exinext'& a local part, without a domain, and it
33163 will give any retry information for that local part in your default domain.
33164 A message id can be used to obtain retry information pertaining to a specific
33165 message. This exists only when an attempt to deliver a message to a remote host
33166 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
33167 &'exinext'& is not particularly efficient, but then it is not expected to be
33170 The &'exinext'& utility calls Exim to find out information such as the location
33171 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
33172 passed on to the &'exim'& commands. The first specifies an alternate Exim
33173 configuration file, and the second sets macros for use within the configuration
33174 file. These features are mainly to help in testing, but might also be useful in
33175 environments where more than one configuration file is in use.
33179 .section "Hints database maintenance" "SECThindatmai"
33180 .cindex "hints database" "maintenance"
33181 .cindex "maintaining Exim's hints database"
33182 Three utility programs are provided for maintaining the DBM files that Exim
33183 uses to contain its delivery hint information. Each program requires two
33184 arguments. The first specifies the name of Exim's spool directory, and the
33185 second is the name of the database it is to operate on. These are as follows:
33188 &'retry'&: the database of retry information
33190 &'wait-'&<&'transport name'&>: databases of information about messages waiting
33193 &'callout'&: the callout cache
33195 &'ratelimit'&: the data for implementing the ratelimit ACL condition
33197 &'misc'&: other hints data
33200 The &'misc'& database is used for
33203 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
33205 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
33206 &(smtp)& transport)
33211 .section "exim_dumpdb" "SECID261"
33212 .cindex "&'exim_dumpdb'&"
33213 The entire contents of a database are written to the standard output by the
33214 &'exim_dumpdb'& program, which has no options or arguments other than the
33215 spool and database names. For example, to dump the retry database:
33217 exim_dumpdb /var/spool/exim retry
33219 Two lines of output are produced for each entry:
33221 T:mail.ref.example:192.168.242.242 146 77 Connection refused
33222 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
33224 The first item on the first line is the key of the record. It starts with one
33225 of the letters R, or T, depending on whether it refers to a routing or
33226 transport retry. For a local delivery, the next part is the local address; for
33227 a remote delivery it is the name of the remote host, followed by its failing IP
33228 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
33229 transport). If the remote port is not the standard one (port 25), it is added
33230 to the IP address. Then there follows an error code, an additional error code,
33231 and a textual description of the error.
33233 The three times on the second line are the time of first failure, the time of
33234 the last delivery attempt, and the computed time for the next attempt. The line
33235 ends with an asterisk if the cutoff time for the last retry rule has been
33238 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
33239 consists of a host name followed by a list of ids for messages that are or were
33240 waiting to be delivered to that host. If there are a very large number for any
33241 one host, continuation records, with a sequence number added to the host name,
33242 may be seen. The data in these records is often out of date, because a message
33243 may be routed to several alternative hosts, and Exim makes no effort to keep
33248 .section "exim_tidydb" "SECID262"
33249 .cindex "&'exim_tidydb'&"
33250 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
33251 database. If run with no options, it removes all records that are more than 30
33252 days old. The age is calculated from the date and time that the record was last
33253 updated. Note that, in the case of the retry database, it is &'not'& the time
33254 since the first delivery failure. Information about a host that has been down
33255 for more than 30 days will remain in the database, provided that the record is
33256 updated sufficiently often.
33258 The cutoff date can be altered by means of the &%-t%& option, which must be
33259 followed by a time. For example, to remove all records older than a week from
33260 the retry database:
33262 exim_tidydb -t 7d /var/spool/exim retry
33264 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
33265 message ids. In the former these appear as data in records keyed by host &--
33266 they were messages that were waiting for that host &-- and in the latter they
33267 are the keys for retry information for messages that have suffered certain
33268 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
33269 message ids in database records are those of messages that are still on the
33270 queue. Message ids for messages that no longer exist are removed from
33271 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
33272 For the &'retry'& database, records whose keys are non-existent message ids are
33273 removed. The &'exim_tidydb'& utility outputs comments on the standard output
33274 whenever it removes information from the database.
33276 Certain records are automatically removed by Exim when they are no longer
33277 needed, but others are not. For example, if all the MX hosts for a domain are
33278 down, a retry record is created for each one. If the primary MX host comes back
33279 first, its record is removed when Exim successfully delivers to it, but the
33280 records for the others remain because Exim has not tried to use those hosts.
33282 It is important, therefore, to run &'exim_tidydb'& periodically on all the
33283 hints databases. You should do this at a quiet time of day, because it requires
33284 a database to be locked (and therefore inaccessible to Exim) while it does its
33285 work. Removing records from a DBM file does not normally make the file smaller,
33286 but all the common DBM libraries are able to re-use the space that is released.
33287 After an initial phase of increasing in size, the databases normally reach a
33288 point at which they no longer get any bigger, as long as they are regularly
33291 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
33292 databases is likely to keep on increasing.
33297 .section "exim_fixdb" "SECID263"
33298 .cindex "&'exim_fixdb'&"
33299 The &'exim_fixdb'& program is a utility for interactively modifying databases.
33300 Its main use is for testing Exim, but it might also be occasionally useful for
33301 getting round problems in a live system. It has no options, and its interface
33302 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
33303 key of a database record can then be entered, and the data for that record is
33306 If &"d"& is typed at the next prompt, the entire record is deleted. For all
33307 except the &'retry'& database, that is the only operation that can be carried
33308 out. For the &'retry'& database, each field is output preceded by a number, and
33309 data for individual fields can be changed by typing the field number followed
33310 by new data, for example:
33314 resets the time of the next delivery attempt. Time values are given as a
33315 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
33316 used as optional separators.
33321 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
33322 .cindex "mailbox" "maintenance"
33323 .cindex "&'exim_lock'&"
33324 .cindex "locking mailboxes"
33325 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
33326 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
33327 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
33328 a user agent while investigating a problem. The utility requires the name of
33329 the file as its first argument. If the locking is successful, the second
33330 argument is run as a command (using C's &[system()]& function); if there is no
33331 second argument, the value of the SHELL environment variable is used; if this
33332 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
33333 is unlocked and the utility ends. The following options are available:
33337 Use &[fcntl()]& locking on the open mailbox.
33340 Use &[flock()]& locking on the open mailbox, provided the operating system
33343 .vitem &%-interval%&
33344 This must be followed by a number, which is a number of seconds; it sets the
33345 interval to sleep between retries (default 3).
33347 .vitem &%-lockfile%&
33348 Create a lock file before opening the mailbox.
33351 Lock the mailbox using MBX rules.
33354 Suppress verification output.
33356 .vitem &%-retries%&
33357 This must be followed by a number; it sets the number of times to try to get
33358 the lock (default 10).
33360 .vitem &%-restore_time%&
33361 This option causes &%exim_lock%& to restore the modified and read times to the
33362 locked file before exiting. This allows you to access a locked mailbox (for
33363 example, to take a backup copy) without disturbing the times that the user
33366 .vitem &%-timeout%&
33367 This must be followed by a number, which is a number of seconds; it sets a
33368 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
33369 default), a non-blocking call is used.
33372 Generate verbose output.
33375 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
33376 default is to create a lock file and also to use &[fcntl()]& locking on the
33377 mailbox, which is the same as Exim's default. The use of &%-flock%& or
33378 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
33379 requires that the directory containing the file be writeable. Locking by lock
33380 file does not last for ever; Exim assumes that a lock file is expired if it is
33381 more than 30 minutes old.
33383 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
33384 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
33385 to be taken out on the open mailbox, and an exclusive lock on the file
33386 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
33387 number of the mailbox file. When the locking is released, if an exclusive lock
33388 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
33390 The default output contains verification of the locking that takes place. The
33391 &%-v%& option causes some additional information to be given. The &%-q%& option
33392 suppresses all output except error messages.
33396 exim_lock /var/spool/mail/spqr
33398 runs an interactive shell while the file is locked, whereas
33400 &`exim_lock -q /var/spool/mail/spqr <<End`&
33401 <&'some commands'&>
33404 runs a specific non-interactive sequence of commands while the file is locked,
33405 suppressing all verification output. A single command can be run by a command
33408 exim_lock -q /var/spool/mail/spqr \
33409 "cp /var/spool/mail/spqr /some/where"
33411 Note that if a command is supplied, it must be entirely contained within the
33412 second argument &-- hence the quotes.
33416 . ////////////////////////////////////////////////////////////////////////////
33417 . ////////////////////////////////////////////////////////////////////////////
33419 .chapter "The Exim monitor" "CHAPeximon"
33420 .scindex IIDeximon "Exim monitor" "description"
33421 .cindex "X-windows"
33422 .cindex "&'eximon'&"
33423 .cindex "Local/eximon.conf"
33424 .cindex "&_exim_monitor/EDITME_&"
33425 The Exim monitor is an application which displays in an X window information
33426 about the state of Exim's queue and what Exim is doing. An admin user can
33427 perform certain operations on messages from this GUI interface; however all
33428 such facilities are also available from the command line, and indeed, the
33429 monitor itself makes use of the command line to perform any actions requested.
33433 .section "Running the monitor" "SECID264"
33434 The monitor is started by running the script called &'eximon'&. This is a shell
33435 script that sets up a number of environment variables, and then runs the
33436 binary called &_eximon.bin_&. The default appearance of the monitor window can
33437 be changed by editing the &_Local/eximon.conf_& file created by editing
33438 &_exim_monitor/EDITME_&. Comments in that file describe what the various
33439 parameters are for.
33441 The parameters that get built into the &'eximon'& script can be overridden for
33442 a particular invocation by setting up environment variables of the same names,
33443 preceded by &`EXIMON_`&. For example, a shell command such as
33445 EXIMON_LOG_DEPTH=400 eximon
33447 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
33448 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
33449 overrides the Exim log file configuration. This makes it possible to have
33450 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
33451 syslog messages are routed to a file on the local host.
33453 X resources can be used to change the appearance of the window in the normal
33454 way. For example, a resource setting of the form
33456 Eximon*background: gray94
33458 changes the colour of the background to light grey rather than white. The
33459 stripcharts are drawn with both the data lines and the reference lines in
33460 black. This means that the reference lines are not visible when on top of the
33461 data. However, their colour can be changed by setting a resource called
33462 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
33463 For example, if your X server is running Unix, you could set up lighter
33464 reference lines in the stripcharts by obeying
33467 Eximon*highlight: gray
33470 .cindex "admin user"
33471 In order to see the contents of messages on the queue, and to operate on them,
33472 &'eximon'& must either be run as root or by an admin user.
33474 The monitor's window is divided into three parts. The first contains one or
33475 more stripcharts and two action buttons, the second contains a &"tail"& of the
33476 main log file, and the third is a display of the queue of messages awaiting
33477 delivery, with two more action buttons. The following sections describe these
33478 different parts of the display.
33483 .section "The stripcharts" "SECID265"
33484 .cindex "stripchart"
33485 The first stripchart is always a count of messages on the queue. Its name can
33486 be configured by setting QUEUE_STRIPCHART_NAME in the
33487 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
33488 configuration script by regular expression matches on log file entries, making
33489 it possible to display, for example, counts of messages delivered to certain
33490 hosts or using certain transports. The supplied defaults display counts of
33491 received and delivered messages, and of local and SMTP deliveries. The default
33492 period between stripchart updates is one minute; this can be adjusted by a
33493 parameter in the &_Local/eximon.conf_& file.
33495 The stripchart displays rescale themselves automatically as the value they are
33496 displaying changes. There are always 10 horizontal lines in each chart; the
33497 title string indicates the value of each division when it is greater than one.
33498 For example, &"x2"& means that each division represents a value of 2.
33500 It is also possible to have a stripchart which shows the percentage fullness of
33501 a particular disk partition, which is useful when local deliveries are confined
33502 to a single partition.
33504 .cindex "&%statvfs%& function"
33505 This relies on the availability of the &[statvfs()]& function or equivalent in
33506 the operating system. Most, but not all versions of Unix that support Exim have
33507 this. For this particular stripchart, the top of the chart always represents
33508 100%, and the scale is given as &"x10%"&. This chart is configured by setting
33509 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
33510 &_Local/eximon.conf_& file.
33515 .section "Main action buttons" "SECID266"
33516 .cindex "size" "of monitor window"
33517 .cindex "Exim monitor" "window size"
33518 .cindex "window size"
33519 Below the stripcharts there is an action button for quitting the monitor. Next
33520 to this is another button marked &"Size"&. They are placed here so that
33521 shrinking the window to its default minimum size leaves just the queue count
33522 stripchart and these two buttons visible. Pressing the &"Size"& button causes
33523 the window to expand to its maximum size, unless it is already at the maximum,
33524 in which case it is reduced to its minimum.
33526 When expanding to the maximum, if the window cannot be fully seen where it
33527 currently is, it is moved back to where it was the last time it was at full
33528 size. When it is expanding from its minimum size, the old position is
33529 remembered, and next time it is reduced to the minimum it is moved back there.
33531 The idea is that you can keep a reduced window just showing one or two
33532 stripcharts at a convenient place on your screen, easily expand it to show
33533 the full window when required, and just as easily put it back to what it was.
33534 The idea is copied from what the &'twm'& window manager does for its
33535 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
33536 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
33538 Normally, the monitor starts up with the window at its full size, but it can be
33539 built so that it starts up with the window at its smallest size, by setting
33540 START_SMALL=yes in &_Local/eximon.conf_&.
33544 .section "The log display" "SECID267"
33545 .cindex "log" "tail of; in monitor"
33546 The second section of the window is an area in which a display of the tail of
33547 the main log is maintained.
33548 To save space on the screen, the timestamp on each log line is shortened by
33549 removing the date and, if &%log_timezone%& is set, the timezone.
33550 The log tail is not available when the only destination for logging data is
33551 syslog, unless the syslog lines are routed to a local file whose name is passed
33552 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
33554 The log sub-window has a scroll bar at its lefthand side which can be used to
33555 move back to look at earlier text, and the up and down arrow keys also have a
33556 scrolling effect. The amount of log that is kept depends on the setting of
33557 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
33558 to use. When this is full, the earlier 50% of data is discarded &-- this is
33559 much more efficient than throwing it away line by line. The sub-window also has
33560 a horizontal scroll bar for accessing the ends of long log lines. This is the
33561 only means of horizontal scrolling; the right and left arrow keys are not
33562 available. Text can be cut from this part of the window using the mouse in the
33563 normal way. The size of this subwindow is controlled by parameters in the
33564 configuration file &_Local/eximon.conf_&.
33566 Searches of the text in the log window can be carried out by means of the ^R
33567 and ^S keystrokes, which default to a reverse and a forward search,
33568 respectively. The search covers only the text that is displayed in the window.
33569 It cannot go further back up the log.
33571 The point from which the search starts is indicated by a caret marker. This is
33572 normally at the end of the text in the window, but can be positioned explicitly
33573 by pointing and clicking with the left mouse button, and is moved automatically
33574 by a successful search. If new text arrives in the window when it is scrolled
33575 back, the caret remains where it is, but if the window is not scrolled back,
33576 the caret is moved to the end of the new text.
33578 Pressing ^R or ^S pops up a window into which the search text can be typed.
33579 There are buttons for selecting forward or reverse searching, for carrying out
33580 the search, and for cancelling. If the &"Search"& button is pressed, the search
33581 happens and the window remains so that further searches can be done. If the
33582 &"Return"& key is pressed, a single search is done and the window is closed. If
33583 ^C is typed the search is cancelled.
33585 The searching facility is implemented using the facilities of the Athena text
33586 widget. By default this pops up a window containing both &"search"& and
33587 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
33588 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
33589 However, the linkers in BSDI and HP-UX seem unable to handle an externally
33590 provided version of &%TextPop%& when the remaining parts of the text widget
33591 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
33592 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
33593 on these systems, at the expense of having unwanted items in the search popup
33598 .section "The queue display" "SECID268"
33599 .cindex "queue" "display in monitor"
33600 The bottom section of the monitor window contains a list of all messages that
33601 are on the queue, which includes those currently being received or delivered,
33602 as well as those awaiting delivery. The size of this subwindow is controlled by
33603 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
33604 at which it is updated is controlled by another parameter in the same file &--
33605 the default is 5 minutes, since queue scans can be quite expensive. However,
33606 there is an &"Update"& action button just above the display which can be used
33607 to force an update of the queue display at any time.
33609 When a host is down for some time, a lot of pending mail can build up for it,
33610 and this can make it hard to deal with other messages on the queue. To help
33611 with this situation there is a button next to &"Update"& called &"Hide"&. If
33612 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
33613 type anything in here and press &"Return"&, the text is added to a chain of
33614 such texts, and if every undelivered address in a message matches at least one
33615 of the texts, the message is not displayed.
33617 If there is an address that does not match any of the texts, all the addresses
33618 are displayed as normal. The matching happens on the ends of addresses so, for
33619 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
33620 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
33621 has been set up, a button called &"Unhide"& is displayed. If pressed, it
33622 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
33623 a hide request is automatically cancelled after one hour.
33625 While the dialogue box is displayed, you can't press any buttons or do anything
33626 else to the monitor window. For this reason, if you want to cut text from the
33627 queue display to use in the dialogue box, you have to do the cutting before
33628 pressing the &"Hide"& button.
33630 The queue display contains, for each unhidden queued message, the length of
33631 time it has been on the queue, the size of the message, the message id, the
33632 message sender, and the first undelivered recipient, all on one line. If it is
33633 a bounce message, the sender is shown as &"<>"&. If there is more than one
33634 recipient to which the message has not yet been delivered, subsequent ones are
33635 listed on additional lines, up to a maximum configured number, following which
33636 an ellipsis is displayed. Recipients that have already received the message are
33639 .cindex "frozen messages" "display"
33640 If a message is frozen, an asterisk is displayed at the left-hand side.
33642 The queue display has a vertical scroll bar, and can also be scrolled by means
33643 of the arrow keys. Text can be cut from it using the mouse in the normal way.
33644 The text searching facilities, as described above for the log window, are also
33645 available, but the caret is always moved to the end of the text when the queue
33646 display is updated.
33650 .section "The queue menu" "SECID269"
33651 .cindex "queue" "menu in monitor"
33652 If the &%shift%& key is held down and the left button is clicked when the mouse
33653 pointer is over the text for any message, an action menu pops up, and the first
33654 line of the queue display for the message is highlighted. This does not affect
33657 If you want to use some other event for popping up the menu, you can set the
33658 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
33659 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
33660 value set in this parameter is a standard X event description. For example, to
33661 run eximon using &%ctrl%& rather than &%shift%& you could use
33663 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
33665 The title of the menu is the message id, and it contains entries which act as
33669 &'message log'&: The contents of the message log for the message are displayed
33670 in a new text window.
33672 &'headers'&: Information from the spool file that contains the envelope
33673 information and headers is displayed in a new text window. See chapter
33674 &<<CHAPspool>>& for a description of the format of spool files.
33676 &'body'&: The contents of the spool file containing the body of the message are
33677 displayed in a new text window. There is a default limit of 20,000 bytes to the
33678 amount of data displayed. This can be changed by setting the BODY_MAX
33679 option at compile time, or the EXIMON_BODY_MAX option at run time.
33681 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
33682 delivery of the message. This causes an automatic thaw if the message is
33683 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
33684 a new text window. The delivery is run in a separate process, to avoid holding
33685 up the monitor while the delivery proceeds.
33687 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
33688 that the message be frozen.
33690 .cindex "thawing messages"
33691 .cindex "unfreezing messages"
33692 .cindex "frozen messages" "thawing"
33693 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
33694 that the message be thawed.
33696 .cindex "delivery" "forcing failure"
33697 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
33698 that Exim gives up trying to deliver the message. A bounce message is generated
33699 for any remaining undelivered addresses.
33701 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
33702 that the message be deleted from the system without generating a bounce
33705 &'add recipient'&: A dialog box is displayed into which a recipient address can
33706 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
33707 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
33708 Otherwise it must be entered as a fully qualified address. Pressing RETURN
33709 causes a call to Exim to be made using the &%-Mar%& option to request that an
33710 additional recipient be added to the message, unless the entry box is empty, in
33711 which case no action is taken.
33713 &'mark delivered'&: A dialog box is displayed into which a recipient address
33714 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
33715 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
33716 Otherwise it must be entered as a fully qualified address. Pressing RETURN
33717 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
33718 recipient address as already delivered, unless the entry box is empty, in which
33719 case no action is taken.
33721 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
33722 mark all recipient addresses as already delivered.
33724 &'edit sender'&: A dialog box is displayed initialized with the current
33725 sender's address. Pressing RETURN causes a call to Exim to be made using the
33726 &%-Mes%& option to replace the sender address, unless the entry box is empty,
33727 in which case no action is taken. If you want to set an empty sender (as in
33728 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
33729 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
33730 the address is qualified with that domain.
33733 When a delivery is forced, a window showing the &%-v%& output is displayed. In
33734 other cases when a call to Exim is made, if there is any output from Exim (in
33735 particular, if the command fails) a window containing the command and the
33736 output is displayed. Otherwise, the results of the action are normally apparent
33737 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
33738 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
33739 if no output is generated.
33741 The queue display is automatically updated for actions such as freezing and
33742 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
33743 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
33744 force an update of the display after one of these actions.
33746 In any text window that is displayed as result of a menu action, the normal
33747 cut-and-paste facility is available, and searching can be carried out using ^R
33748 and ^S, as described above for the log tail window.
33755 . ////////////////////////////////////////////////////////////////////////////
33756 . ////////////////////////////////////////////////////////////////////////////
33758 .chapter "Security considerations" "CHAPsecurity"
33759 .scindex IIDsecurcon "security" "discussion of"
33760 This chapter discusses a number of issues concerned with security, some of
33761 which are also covered in other parts of this manual.
33763 For reasons that this author does not understand, some people have promoted
33764 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
33765 existence of this chapter in the documentation. However, the intent of the
33766 chapter is simply to describe the way Exim works in relation to certain
33767 security concerns, not to make any specific claims about the effectiveness of
33768 its security as compared with other MTAs.
33770 What follows is a description of the way Exim is supposed to be. Best efforts
33771 have been made to try to ensure that the code agrees with the theory, but an
33772 absence of bugs can never be guaranteed. Any that are reported will get fixed
33773 as soon as possible.
33776 .section "Building a more &""hardened""& Exim" "SECID286"
33777 .cindex "security" "build-time features"
33778 There are a number of build-time options that can be set in &_Local/Makefile_&
33779 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
33780 Exim administrator who does not have the root password, or by someone who has
33781 penetrated the Exim (but not the root) account. These options are as follows:
33784 ALT_CONFIG_PREFIX can be set to a string that is required to match the
33785 start of any file names used with the &%-C%& option. When it is set, these file
33786 names are also not allowed to contain the sequence &"/../"&. (However, if the
33787 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
33788 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
33789 default setting for &%ALT_CONFIG_PREFIX%&.
33791 If the permitted configuration files are confined to a directory to
33792 which only root has access, this guards against someone who has broken
33793 into the Exim account from running a privileged Exim with an arbitrary
33794 configuration file, and using it to break into other accounts.
33796 If ALT_CONFIG_ROOT_ONLY is defined, root privilege is retained for &%-C%&
33797 and &%-D%& only if the caller of Exim is root. Without it, the Exim user may
33798 also use &%-C%& and &%-D%& and retain privilege. Setting this option locks out
33799 the possibility of testing a configuration using &%-C%& right through message
33800 reception and delivery, even if the caller is root. The reception works, but by
33801 that time, Exim is running as the Exim user, so when it re-execs to regain
33802 privilege for the delivery, the use of &%-C%& causes privilege to be lost.
33803 However, root can test reception and delivery using two separate commands.
33804 ALT_CONFIG_ROOT_ONLY is not set by default.
33806 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
33809 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
33810 never to be used for any deliveries. This is like the &%never_users%& runtime
33811 option, but it cannot be overridden; the runtime option adds additional users
33812 to the list. The default setting is &"root"&; this prevents a non-root user who
33813 is permitted to modify the runtime file from using Exim as a way to get root.
33819 .section "Root privilege" "SECID270"
33821 .cindex "root privilege"
33822 The Exim binary is normally setuid to root, which means that it gains root
33823 privilege (runs as root) when it starts execution. In some special cases (for
33824 example, when the daemon is not in use and there are no local deliveries), it
33825 may be possible to run Exim setuid to some user other than root. This is
33826 discussed in the next section. However, in most installations, root privilege
33827 is required for two things:
33830 To set up a socket connected to the standard SMTP port (25) when initialising
33831 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
33834 To be able to change uid and gid in order to read users' &_.forward_& files and
33835 perform local deliveries as the receiving user or as specified in the
33839 It is not necessary to be root to do any of the other things Exim does, such as
33840 receiving messages and delivering them externally over SMTP, and it is
33841 obviously more secure if Exim does not run as root except when necessary.
33842 For this reason, a user and group for Exim to use must be defined in
33843 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
33844 group"&. Their values can be changed by the run time configuration, though this
33845 is not recommended. Often a user called &'exim'& is used, but some sites use
33846 &'mail'& or another user name altogether.
33848 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
33849 abdication; the process cannot regain root afterwards. Prior to release 4.00,
33850 &[seteuid()]& was used in some circumstances, but this is no longer the case.
33852 After a new Exim process has interpreted its command line options, it changes
33853 uid and gid in the following cases:
33858 If the &%-C%& option is used to specify an alternate configuration file, or if
33859 the &%-D%& option is used to define macro values for the configuration, and the
33860 calling process is not running as root or the Exim user, the uid and gid are
33861 changed to those of the calling process.
33862 However, if ALT_CONFIG_ROOT_ONLY is defined in &_Local/Makefile_&, only
33863 root callers may use &%-C%& and &%-D%& without losing privilege, and if
33864 DISABLE_D_OPTION is set, the &%-D%& option may not be used at all.
33869 If the expansion test option (&%-be%&) or one of the filter testing options
33870 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
33873 If the process is not a daemon process or a queue runner process or a delivery
33874 process or a process for testing address routing (started with &%-bt%&), the
33875 uid and gid are changed to the Exim user and group. This means that Exim always
33876 runs under its own uid and gid when receiving messages. This also applies when
33877 testing address verification
33880 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
33883 For a daemon, queue runner, delivery, or address testing process, the uid
33884 remains as root at this stage, but the gid is changed to the Exim group.
33887 The processes that initially retain root privilege behave as follows:
33890 A daemon process changes the gid to the Exim group and the uid to the Exim
33891 user after setting up one or more listening sockets. The &[initgroups()]&
33892 function is called, so that if the Exim user is in any additional groups, they
33893 will be used during message reception.
33895 A queue runner process retains root privilege throughout its execution. Its
33896 job is to fork a controlled sequence of delivery processes.
33898 A delivery process retains root privilege throughout most of its execution,
33899 but any actual deliveries (that is, the transports themselves) are run in
33900 subprocesses which always change to a non-root uid and gid. For local
33901 deliveries this is typically the uid and gid of the owner of the mailbox; for
33902 remote deliveries, the Exim uid and gid are used. Once all the delivery
33903 subprocesses have been run, a delivery process changes to the Exim uid and gid
33904 while doing post-delivery tidying up such as updating the retry database and
33905 generating bounce and warning messages.
33907 While the recipient addresses in a message are being routed, the delivery
33908 process runs as root. However, if a user's filter file has to be processed,
33909 this is done in a subprocess that runs under the individual user's uid and
33910 gid. A system filter is run as root unless &%system_filter_user%& is set.
33912 A process that is testing addresses (the &%-bt%& option) runs as root so that
33913 the routing is done in the same environment as a message delivery.
33919 .section "Running Exim without privilege" "SECTrunexiwitpri"
33920 .cindex "privilege, running without"
33921 .cindex "unprivileged running"
33922 .cindex "root privilege" "running without"
33923 Some installations like to run Exim in an unprivileged state for more of its
33924 operation, for added security. Support for this mode of operation is provided
33925 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
33926 gid are changed to the Exim user and group at the start of a delivery process
33927 (and also queue runner and address testing processes). This means that address
33928 routing is no longer run as root, and the deliveries themselves cannot change
33932 .cindex "daemon" "restarting"
33933 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
33934 that the daemon can still be started in the usual way, and it can respond
33935 correctly to SIGHUP because the re-invocation regains root privilege.
33937 An alternative approach is to make Exim setuid to the Exim user and also setgid
33938 to the Exim group. If you do this, the daemon must be started from a root
33939 process. (Calling Exim from a root process makes it behave in the way it does
33940 when it is setuid root.) However, the daemon cannot restart itself after a
33941 SIGHUP signal because it cannot regain privilege.
33943 It is still useful to set &%deliver_drop_privilege%& in this case, because it
33944 stops Exim from trying to re-invoke itself to do a delivery after a message has
33945 been received. Such a re-invocation is a waste of resources because it has no
33948 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
33949 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
33950 to the Exim user seems a clean approach, but there is one complication:
33952 In this style of operation, Exim is running with the real uid and gid set to
33953 those of the calling process, and the effective uid/gid set to Exim's values.
33954 Ideally, any association with the calling process' uid/gid should be dropped,
33955 that is, the real uid/gid should be reset to the effective values so as to
33956 discard any privileges that the caller may have. While some operating systems
33957 have a function that permits this action for a non-root effective uid, quite a
33958 number of them do not. Because of this lack of standardization, Exim does not
33959 address this problem at this time.
33961 For this reason, the recommended approach for &"mostly unprivileged"& running
33962 is to keep the Exim binary setuid to root, and to set
33963 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
33964 be used in the most straightforward way.
33966 If you configure Exim not to run delivery processes as root, there are a
33967 number of restrictions on what you can do:
33970 You can deliver only as the Exim user/group. You should explicitly use the
33971 &%user%& and &%group%& options to override routers or local transports that
33972 normally deliver as the recipient. This makes sure that configurations that
33973 work in this mode function the same way in normal mode. Any implicit or
33974 explicit specification of another user causes an error.
33976 Use of &_.forward_& files is severely restricted, such that it is usually
33977 not worthwhile to include them in the configuration.
33979 Users who wish to use &_.forward_& would have to make their home directory and
33980 the file itself accessible to the Exim user. Pipe and append-to-file entries,
33981 and their equivalents in Exim filters, cannot be used. While they could be
33982 enabled in the Exim user's name, that would be insecure and not very useful.
33984 Unless the local user mailboxes are all owned by the Exim user (possible in
33985 some POP3 or IMAP-only environments):
33988 They must be owned by the Exim group and be writeable by that group. This
33989 implies you must set &%mode%& in the appendfile configuration, as well as the
33990 mode of the mailbox files themselves.
33992 You must set &%no_check_owner%&, since most or all of the files will not be
33993 owned by the Exim user.
33995 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
33996 on a newly created mailbox when unprivileged. This also implies that new
33997 mailboxes need to be created manually.
34002 These restrictions severely restrict what can be done in local deliveries.
34003 However, there are no restrictions on remote deliveries. If you are running a
34004 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
34005 gives more security at essentially no cost.
34007 If you are using the &%mua_wrapper%& facility (see chapter
34008 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
34013 .section "Delivering to local files" "SECID271"
34014 Full details of the checks applied by &(appendfile)& before it writes to a file
34015 are given in chapter &<<CHAPappendfile>>&.
34019 .section "IPv4 source routing" "SECID272"
34020 .cindex "source routing" "in IP packets"
34021 .cindex "IP source routing"
34022 Many operating systems suppress IP source-routed packets in the kernel, but
34023 some cannot be made to do this, so Exim does its own check. It logs incoming
34024 IPv4 source-routed TCP calls, and then drops them. Things are all different in
34025 IPv6. No special checking is currently done.
34029 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
34030 Support for these SMTP commands is disabled by default. If required, they can
34031 be enabled by defining suitable ACLs.
34036 .section "Privileged users" "SECID274"
34037 .cindex "trusted users"
34038 .cindex "admin user"
34039 .cindex "privileged user"
34040 .cindex "user" "trusted"
34041 .cindex "user" "admin"
34042 Exim recognizes two sets of users with special privileges. Trusted users are
34043 able to submit new messages to Exim locally, but supply their own sender
34044 addresses and information about a sending host. For other users submitting
34045 local messages, Exim sets up the sender address from the uid, and doesn't
34046 permit a remote host to be specified.
34049 However, an untrusted user is permitted to use the &%-f%& command line option
34050 in the special form &%-f <>%& to indicate that a delivery failure for the
34051 message should not cause an error report. This affects the message's envelope,
34052 but it does not affect the &'Sender:'& header. Untrusted users may also be
34053 permitted to use specific forms of address with the &%-f%& option by setting
34054 the &%untrusted_set_sender%& option.
34056 Trusted users are used to run processes that receive mail messages from some
34057 other mail domain and pass them on to Exim for delivery either locally, or over
34058 the Internet. Exim trusts a caller that is running as root, as the Exim user,
34059 as any user listed in the &%trusted_users%& configuration option, or under any
34060 group listed in the &%trusted_groups%& option.
34062 Admin users are permitted to do things to the messages on Exim's queue. They
34063 can freeze or thaw messages, cause them to be returned to their senders, remove
34064 them entirely, or modify them in various ways. In addition, admin users can run
34065 the Exim monitor and see all the information it is capable of providing, which
34066 includes the contents of files on the spool.
34070 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
34071 delivery of messages on its queue is restricted to admin users. This
34072 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
34073 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
34074 queue is also restricted to admin users. This restriction can be relaxed by
34075 setting &%no_queue_list_requires_admin%&.
34077 Exim recognizes an admin user if the calling process is running as root or as
34078 the Exim user or if any of the groups associated with the calling process is
34079 the Exim group. It is not necessary actually to be running under the Exim
34080 group. However, if admin users who are not root or the Exim user are to access
34081 the contents of files on the spool via the Exim monitor (which runs
34082 unprivileged), Exim must be built to allow group read access to its spool
34087 .section "Spool files" "SECID275"
34088 .cindex "spool directory" "files"
34089 Exim's spool directory and everything it contains is owned by the Exim user and
34090 set to the Exim group. The mode for spool files is defined in the
34091 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
34092 any user who is a member of the Exim group can access these files.
34096 .section "Use of argv[0]" "SECID276"
34097 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
34098 of specific strings, Exim assumes certain options. For example, calling Exim
34099 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
34100 to calling it with the option &%-bS%&. There are no security implications in
34105 .section "Use of %f formatting" "SECID277"
34106 The only use made of &"%f"& by Exim is in formatting load average values. These
34107 are actually stored in integer variables as 1000 times the load average.
34108 Consequently, their range is limited and so therefore is the length of the
34113 .section "Embedded Exim path" "SECID278"
34114 Exim uses its own path name, which is embedded in the code, only when it needs
34115 to re-exec in order to regain root privilege. Therefore, it is not root when it
34116 does so. If some bug allowed the path to get overwritten, it would lead to an
34117 arbitrary program's being run as exim, not as root.
34121 .section "Use of sprintf()" "SECID279"
34122 .cindex "&[sprintf()]&"
34123 A large number of occurrences of &"sprintf"& in the code are actually calls to
34124 &'string_sprintf()'&, a function that returns the result in malloc'd store.
34125 The intermediate formatting is done into a large fixed buffer by a function
34126 that runs through the format string itself, and checks the length of each
34127 conversion before performing it, thus preventing buffer overruns.
34129 The remaining uses of &[sprintf()]& happen in controlled circumstances where
34130 the output buffer is known to be sufficiently long to contain the converted
34135 .section "Use of debug_printf() and log_write()" "SECID280"
34136 Arbitrary strings are passed to both these functions, but they do their
34137 formatting by calling the function &'string_vformat()'&, which runs through
34138 the format string itself, and checks the length of each conversion.
34142 .section "Use of strcat() and strcpy()" "SECID281"
34143 These are used only in cases where the output buffer is known to be large
34144 enough to hold the result.
34145 .ecindex IIDsecurcon
34150 . ////////////////////////////////////////////////////////////////////////////
34151 . ////////////////////////////////////////////////////////////////////////////
34153 .chapter "Format of spool files" "CHAPspool"
34154 .scindex IIDforspo1 "format" "spool files"
34155 .scindex IIDforspo2 "spool directory" "format of files"
34156 .scindex IIDforspo3 "spool files" "format of"
34157 .cindex "spool files" "editing"
34158 A message on Exim's queue consists of two files, whose names are the message id
34159 followed by -D and -H, respectively. The data portion of the message is kept in
34160 the -D file on its own. The message's envelope, status, and headers are all
34161 kept in the -H file, whose format is described in this chapter. Each of these
34162 two files contains the final component of its own name as its first line. This
34163 is insurance against disk crashes where the directory is lost but the files
34164 themselves are recoverable.
34166 Some people are tempted into editing -D files in order to modify messages. You
34167 need to be extremely careful if you do this; it is not recommended and you are
34168 on your own if you do it. Here are some of the pitfalls:
34171 You must ensure that Exim does not try to deliver the message while you are
34172 fiddling with it. The safest way is to take out a write lock on the -D file,
34173 which is what Exim itself does, using &[fcntl()]&. If you update the file in
34174 place, the lock will be retained. If you write a new file and rename it, the
34175 lock will be lost at the instant of rename.
34177 .vindex "&$body_linecount$&"
34178 If you change the number of lines in the file, the value of
34179 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
34180 present, this value is not used by Exim, but there is no guarantee that this
34181 will always be the case.
34183 If the message is in MIME format, you must take care not to break it.
34185 If the message is cryptographically signed, any change will invalidate the
34188 All in all, modifying -D files is fraught with danger.
34190 Files whose names end with -J may also be seen in the &_input_& directory (or
34191 its subdirectories when &%split_spool_directory%& is set). These are journal
34192 files, used to record addresses to which the message has been delivered during
34193 the course of a delivery attempt. If there are still undelivered recipients at
34194 the end, the -H file is updated, and the -J file is deleted. If, however, there
34195 is some kind of crash (for example, a power outage) before this happens, the -J
34196 file remains in existence. When Exim next processes the message, it notices the
34197 -J file and uses it to update the -H file before starting the next delivery
34200 .section "Format of the -H file" "SECID282"
34201 .cindex "uid (user id)" "in spool file"
34202 .cindex "gid (group id)" "in spool file"
34203 The second line of the -H file contains the login name for the uid of the
34204 process that called Exim to read the message, followed by the numerical uid and
34205 gid. For a locally generated message, this is normally the user who sent the
34206 message. For a message received over TCP/IP via the daemon, it is
34207 normally the Exim user.
34209 The third line of the file contains the address of the message's sender as
34210 transmitted in the envelope, contained in angle brackets. The sender address is
34211 empty for bounce messages. For incoming SMTP mail, the sender address is given
34212 in the MAIL command. For locally generated mail, the sender address is
34213 created by Exim from the login name of the current user and the configured
34214 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
34215 leading &"From&~"& line if the caller is trusted, or if the supplied address is
34216 &"<>"& or an address that matches &%untrusted_set_senders%&.
34218 The fourth line contains two numbers. The first is the time that the message
34219 was received, in the conventional Unix form &-- the number of seconds since the
34220 start of the epoch. The second number is a count of the number of messages
34221 warning of delayed delivery that have been sent to the sender.
34223 There follow a number of lines starting with a hyphen. These can appear in any
34224 order, and are omitted when not relevant:
34227 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
34228 This item is obsolete, and is not generated from Exim release 4.61 onwards;
34229 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
34230 recognized, to provide backward compatibility. In the old format, a line of
34231 this form is present for every ACL variable that is not empty. The number
34232 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
34233 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
34234 the data string for the variable. The string itself starts at the beginning of
34235 the next line, and is followed by a newline character. It may contain internal
34238 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
34239 A line of this form is present for every ACL connection variable that is
34240 defined. Note that there is a space between &%-aclc%& and the rest of the name.
34241 The length is the length of the data string for the variable. The string itself
34242 starts at the beginning of the next line, and is followed by a newline
34243 character. It may contain internal newlines.
34245 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
34246 A line of this form is present for every ACL message variable that is defined.
34247 Note that there is a space between &%-aclm%& and the rest of the name. The
34248 length is the length of the data string for the variable. The string itself
34249 starts at the beginning of the next line, and is followed by a newline
34250 character. It may contain internal newlines.
34252 .vitem "&%-active_hostname%&&~<&'hostname'&>"
34253 This is present if, when the message was received over SMTP, the value of
34254 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
34256 .vitem &%-allow_unqualified_recipient%&
34257 This is present if unqualified recipient addresses are permitted in header
34258 lines (to stop such addresses from being qualified if rewriting occurs at
34259 transport time). Local messages that were input using &%-bnq%& and remote
34260 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
34262 .vitem &%-allow_unqualified_sender%&
34263 This is present if unqualified sender addresses are permitted in header lines
34264 (to stop such addresses from being qualified if rewriting occurs at transport
34265 time). Local messages that were input using &%-bnq%& and remote messages from
34266 hosts that match &%sender_unqualified_hosts%& set this flag.
34268 .vitem "&%-auth_id%&&~<&'text'&>"
34269 The id information for a message received on an authenticated SMTP connection
34270 &-- the value of the &$authenticated_id$& variable.
34272 .vitem "&%-auth_sender%&&~<&'address'&>"
34273 The address of an authenticated sender &-- the value of the
34274 &$authenticated_sender$& variable.
34276 .vitem "&%-body_linecount%&&~<&'number'&>"
34277 This records the number of lines in the body of the message, and is always
34280 .vitem "&%-body_zerocount%&&~<&'number'&>"
34281 This records the number of binary zero bytes in the body of the message, and is
34282 present if the number is greater than zero.
34284 .vitem &%-deliver_firsttime%&
34285 This is written when a new message is first added to the spool. When the spool
34286 file is updated after a deferral, it is omitted.
34288 .vitem "&%-frozen%&&~<&'time'&>"
34289 .cindex "frozen messages" "spool data"
34290 The message is frozen, and the freezing happened at <&'time'&>.
34292 .vitem "&%-helo_name%&&~<&'text'&>"
34293 This records the host name as specified by a remote host in a HELO or EHLO
34296 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
34297 This records the IP address of the host from which the message was received and
34298 the remote port number that was used. It is omitted for locally generated
34301 .vitem "&%-host_auth%&&~<&'text'&>"
34302 If the message was received on an authenticated SMTP connection, this records
34303 the name of the authenticator &-- the value of the
34304 &$sender_host_authenticated$& variable.
34306 .vitem &%-host_lookup_failed%&
34307 This is present if an attempt to look up the sending host's name from its IP
34308 address failed. It corresponds to the &$host_lookup_failed$& variable.
34310 .vitem "&%-host_name%&&~<&'text'&>"
34311 .cindex "reverse DNS lookup"
34312 .cindex "DNS" "reverse lookup"
34313 This records the name of the remote host from which the message was received,
34314 if the host name was looked up from the IP address when the message was being
34315 received. It is not present if no reverse lookup was done.
34317 .vitem "&%-ident%&&~<&'text'&>"
34318 For locally submitted messages, this records the login of the originating user,
34319 unless it was a trusted user and the &%-oMt%& option was used to specify an
34320 ident value. For messages received over TCP/IP, this records the ident string
34321 supplied by the remote host, if any.
34323 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
34324 This records the IP address of the local interface and the port number through
34325 which a message was received from a remote host. It is omitted for locally
34326 generated messages.
34329 The message is from a local sender.
34331 .vitem &%-localerror%&
34332 The message is a locally-generated bounce message.
34334 .vitem "&%-local_scan%&&~<&'string'&>"
34335 This records the data string that was returned by the &[local_scan()]& function
34336 when the message was received &-- the value of the &$local_scan_data$&
34337 variable. It is omitted if no data was returned.
34339 .vitem &%-manual_thaw%&
34340 The message was frozen but has been thawed manually, that is, by an explicit
34341 Exim command rather than via the auto-thaw process.
34344 A testing delivery process was started using the &%-N%& option to suppress any
34345 actual deliveries, but delivery was deferred. At any further delivery attempts,
34348 .vitem &%-received_protocol%&
34349 This records the value of the &$received_protocol$& variable, which contains
34350 the name of the protocol by which the message was received.
34352 .vitem &%-sender_set_untrusted%&
34353 The envelope sender of this message was set by an untrusted local caller (used
34354 to ensure that the caller is displayed in queue listings).
34356 .vitem "&%-spam_score_int%&&~<&'number'&>"
34357 If a message was scanned by SpamAssassin, this is present. It records the value
34358 of &$spam_score_int$&.
34360 .vitem &%-tls_certificate_verified%&
34361 A TLS certificate was received from the client that sent this message, and the
34362 certificate was verified by the server.
34364 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
34365 When the message was received over an encrypted connection, this records the
34366 name of the cipher suite that was used.
34368 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
34369 When the message was received over an encrypted connection, and a certificate
34370 was received from the client, this records the Distinguished Name from that
34374 Following the options there is a list of those addresses to which the message
34375 is not to be delivered. This set of addresses is initialized from the command
34376 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
34377 is set; otherwise it starts out empty. Whenever a successful delivery is made,
34378 the address is added to this set. The addresses are kept internally as a
34379 balanced binary tree, and it is a representation of that tree which is written
34380 to the spool file. If an address is expanded via an alias or forward file, the
34381 original address is added to the tree when deliveries to all its child
34382 addresses are complete.
34384 If the tree is empty, there is a single line in the spool file containing just
34385 the text &"XX"&. Otherwise, each line consists of two letters, which are either
34386 Y or N, followed by an address. The address is the value for the node of the
34387 tree, and the letters indicate whether the node has a left branch and/or a
34388 right branch attached to it, respectively. If branches exist, they immediately
34389 follow. Here is an example of a three-node tree:
34391 YY darcy@austen.fict.example
34392 NN alice@wonderland.fict.example
34393 NN editor@thesaurus.ref.example
34395 After the non-recipients tree, there is a list of the message's recipients.
34396 This is a simple list, preceded by a count. It includes all the original
34397 recipients of the message, including those to whom the message has already been
34398 delivered. In the simplest case, the list contains one address per line. For
34402 editor@thesaurus.ref.example
34403 darcy@austen.fict.example
34405 alice@wonderland.fict.example
34407 However, when a child address has been added to the top-level addresses as a
34408 result of the use of the &%one_time%& option on a &(redirect)& router, each
34409 line is of the following form:
34411 <&'top-level address'&> <&'errors_to address'&> &&&
34412 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
34414 The 01 flag bit indicates the presence of the three other fields that follow
34415 the top-level address. Other bits may be used in future to support additional
34416 fields. The <&'parent number'&> is the offset in the recipients list of the
34417 original parent of the &"one time"& address. The first two fields are the
34418 envelope sender that is associated with this address and its length. If the
34419 length is zero, there is no special envelope sender (there are then two space
34420 characters in the line). A non-empty field can arise from a &(redirect)& router
34421 that has an &%errors_to%& setting.
34424 A blank line separates the envelope and status information from the headers
34425 which follow. A header may occupy several lines of the file, and to save effort
34426 when reading it in, each header is preceded by a number and an identifying
34427 character. The number is the number of characters in the header, including any
34428 embedded newlines and the terminating newline. The character is one of the
34432 .row <&'blank'&> "header in which Exim has no special interest"
34433 .row &`B`& "&'Bcc:'& header"
34434 .row &`C`& "&'Cc:'& header"
34435 .row &`F`& "&'From:'& header"
34436 .row &`I`& "&'Message-id:'& header"
34437 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
34438 .row &`R`& "&'Reply-To:'& header"
34439 .row &`S`& "&'Sender:'& header"
34440 .row &`T`& "&'To:'& header"
34441 .row &`*`& "replaced or deleted header"
34444 Deleted or replaced (rewritten) headers remain in the spool file for debugging
34445 purposes. They are not transmitted when the message is delivered. Here is a
34446 typical set of headers:
34448 111P Received: by hobbit.fict.example with local (Exim 4.00)
34449 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
34450 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
34451 038* X-rewrote-sender: bb@hobbit.fict.example
34452 042* From: Bilbo Baggins <bb@hobbit.fict.example>
34453 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
34454 099* To: alice@wonderland.fict.example, rdo@foundation,
34455 darcy@austen.fict.example, editor@thesaurus.ref.example
34456 104T To: alice@wonderland.fict.example, rdo@foundation.example,
34457 darcy@austen.fict.example, editor@thesaurus.ref.example
34458 038 Date: Fri, 11 May 2001 10:28:59 +0100
34460 The asterisked headers indicate that the envelope sender, &'From:'& header, and
34461 &'To:'& header have been rewritten, the last one because routing expanded the
34462 unqualified domain &'foundation'&.
34463 .ecindex IIDforspo1
34464 .ecindex IIDforspo2
34465 .ecindex IIDforspo3
34467 . ////////////////////////////////////////////////////////////////////////////
34468 . ////////////////////////////////////////////////////////////////////////////
34470 .chapter "Support for DKIM (DomainKeys Identified Mail) - RFC4871" "CHID12" &&&
34474 Since version 4.70, DKIM support is compiled into Exim by default. It can be
34475 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
34477 Exim's DKIM implementation allows to
34479 Sign outgoing messages: This function is implemented in the SMTP transport.
34480 It can co-exist with all other Exim features, including transport filters.
34482 Verify signatures in incoming messages: This is implemented by an additional
34483 ACL (acl_smtp_dkim), which can be called several times per message, with
34484 different signature contexts.
34487 In typical Exim style, the verification implementation does not include any
34488 default "policy". Instead it enables you to build your own policy using
34489 Exim's standard controls.
34491 Please note that verification of DKIM signatures in incoming mail is turned
34492 on by default for logging purposes. For each signature in incoming email,
34493 exim will log a line displaying the most important signature details, and the
34494 signature status. Here is an example:
34496 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM: d=facebookmail.com s=q1-2009b c=relaxed/relaxed a=rsa-sha1 i=@facebookmail.com t=1252484542 [verification succeeded]
34498 You might want to turn off DKIM verification processing entirely for internal
34499 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
34500 control modifier. This should typically be done in the RCPT ACL, at points
34501 where you accept mail from relay sources (internal hosts or authenticated
34505 .section "Signing outgoing messages" "SECID513"
34506 .cindex "DKIM" "signing"
34508 Signing is implemented by setting private options on the SMTP transport.
34509 These options take (expandable) strings as arguments.
34511 .option dkim_domain smtp string&!! unset
34513 The domain you want to sign with. The result of this expanded
34514 option is put into the &%$dkim_domain%& expansion variable.
34516 .option dkim_selector smtp string&!! unset
34518 This sets the key selector string. You can use the &%$dkim_domain%& expansion
34519 variable to look up a matching selector. The result is put in the expansion
34520 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
34521 option along with &%$dkim_domain%&.
34523 .option dkim_private_key smtp string&!! unset
34525 This sets the private key to use. You can use the &%$dkim_domain%& and
34526 &%$dkim_selector%& expansion variables to determine the private key to use.
34527 The result can either
34529 be a valid RSA private key in ASCII armor, including line breaks.
34531 start with a slash, in which case it is treated as a file that contains
34534 be "0", "false" or the empty string, in which case the message will not
34535 be signed. This case will not result in an error, even if &%dkim_strict%&
34539 .option dkim_canon smtp string&!! unset
34541 This option sets the canonicalization method used when signing a message.
34542 The DKIM RFC currently supports two methods: "simple" and "relaxed".
34543 The option defaults to "relaxed" when unset. Note: the current implementation
34544 only supports using the same canonicalization method for both headers and body.
34546 .option dkim_strict smtp string&!! unset
34548 This option defines how Exim behaves when signing a message that
34549 should be signed fails for some reason. When the expansion evaluates to
34550 either "1" or "true", Exim will defer. Otherwise Exim will send the message
34551 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
34554 .option dkim_sign_headers smtp string&!! unset
34556 When set, this option must expand to (or be specified as) a colon-separated
34557 list of header names. Headers with these names will be included in the message
34558 signature. When unspecified, the header names recommended in RFC4871 will be
34562 .section "Verifying DKIM signatures in incoming mail" "SECID514"
34563 .cindex "DKIM" "verification"
34565 Verification of DKIM signatures in incoming email is implemented via the
34566 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
34567 syntactically(!) correct signature in the incoming message.
34569 To evaluate the signature in the ACL a large number of expansion variables
34570 containing the signature status and its details are set up during the
34571 runtime of the ACL.
34573 Calling the ACL only for existing signatures is not sufficient to build
34574 more advanced policies. For that reason, the global option
34575 &%dkim_verify_signers%&, and a global expansion variable
34576 &%$dkim_signers%& exist.
34578 The global option &%dkim_verify_signers%& can be set to a colon-separated
34579 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
34580 called. It is expanded when the message has been received. At this point,
34581 the expansion variable &%$dkim_signers%& already contains a colon-separated
34582 list of signer domains and identities for the message. When
34583 &%dkim_verify_signers%& is not specified in the main configuration,
34586 dkim_verify_signers = $dkim_signers
34588 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
34589 DKIM signature in the message. Current DKIM verifiers may want to explicitly
34590 call the ACL for known domains or identities. This would be achieved as follows:
34592 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
34594 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
34595 and "ebay.com", plus all domains and identities that have signatures in the message.
34596 You can also be more creative in constructing your policy. For example:
34598 dkim_verify_signers = $sender_address_domain:$dkim_signers
34601 If a domain or identity is listed several times in the (expanded) value of
34602 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
34605 Inside the &%acl_smtp_dkim%&, the following expansion variables are
34606 available (from most to least important):
34609 .vitem &%$dkim_cur_signer%&
34610 The signer that is being evaluated in this ACL run. This can be a domain or
34611 an identity. This is one of the list items from the expanded main option
34612 &%dkim_verify_signers%& (see above).
34613 .vitem &%$dkim_verify_status%&
34614 A string describing the general status of the signature. One of
34616 &%none%&: There is no signature in the message for the current domain or
34617 identity (as reflected by &%$dkim_cur_signer%&).
34619 &%invalid%&: The signature could not be verified due to a processing error.
34620 More detail is available in &%$dkim_verify_reason%&.
34622 &%fail%&: Verification of the signature failed. More detail is
34623 available in &%$dkim_verify_reason%&.
34625 &%pass%&: The signature passed verification. It is valid.
34627 .vitem &%$dkim_verify_reason%&
34628 A string giving a litte bit more detail when &%$dkim_verify_status%& is either
34629 "fail" or "invalid". One of
34631 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
34632 key for the domain could not be retrieved. This may be a temporary problem.
34634 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
34635 record for the domain is syntactically invalid.
34637 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
34638 body hash does not match the one specified in the signature header. This
34639 means that the message body was modified in transit.
34641 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
34642 could not be verified. This may mean that headers were modified,
34643 re-written or otherwise changed in a way which is incompatible with
34644 DKIM verification. It may of course also mean that the signature is forged.
34646 .vitem &%$dkim_domain%&
34647 The signing domain. IMPORTANT: This variable is only populated if there is
34648 an actual signature in the message for the current domain or identity (as
34649 reflected by &%$dkim_cur_signer%&).
34650 .vitem &%$dkim_identity%&
34651 The signing identity, if present. IMPORTANT: This variable is only populated
34652 if there is an actual signature in the message for the current domain or
34653 identity (as reflected by &%$dkim_cur_signer%&).
34654 .vitem &%$dkim_selector%&
34655 The key record selector string.
34656 .vitem &%$dkim_algo%&
34657 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
34658 .vitem &%$dkim_canon_body%&
34659 The body canonicalization method. One of 'relaxed' or 'simple'.
34660 .vitem &%dkim_canon_headers%&
34661 The header canonicalization method. One of 'relaxed' or 'simple'.
34662 .vitem &%$dkim_copiedheaders%&
34663 A transcript of headers and their values which are included in the signature
34664 (copied from the 'z=' tag of the signature).
34665 .vitem &%$dkim_bodylength%&
34666 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
34667 limit was set by the signer, "9999999999999" is returned. This makes sure
34668 that this variable always expands to an integer value.
34669 .vitem &%$dkim_created%&
34670 UNIX timestamp reflecting the date and time when the signature was created.
34671 When this was not specified by the signer, "0" is returned.
34672 .vitem &%$dkim_expires%&
34673 UNIX timestamp reflecting the date and time when the signer wants the
34674 signature to be treated as "expired". When this was not specified by the
34675 signer, "9999999999999" is returned. This makes it possible to do useful
34676 integer size comparisons against this value.
34677 .vitem &%$dkim_headernames%&
34678 A colon-separated list of names of headers included in the signature.
34679 .vitem &%$dkim_key_testing%&
34680 "1" if the key record has the "testing" flag set, "0" if not.
34681 .vitem &%$dkim_key_nosubdomaining%&
34682 "1" if the key record forbids subdomaining, "0" otherwise.
34683 .vitem &%$dkim_key_srvtype%&
34684 Service type (tag s=) from the key record. Defaults to "*" if not specified
34686 .vitem &%$dkim_key_granularity%&
34687 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
34689 .vitem &%$dkim_key_notes%&
34690 Notes from the key record (tag n=).
34693 In addition, two ACL conditions are provided:
34696 .vitem &%dkim_signers%&
34697 ACL condition that checks a colon-separated list of domains or identities
34698 for a match against the domain or identity that the ACL is currently verifying
34699 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
34700 verb to a group of domains or identities. For example:
34703 # Warn when message apparently from GMail has no signature at all
34704 warn log_message = GMail sender without DKIM signature
34705 sender_domains = gmail.com
34706 dkim_signers = gmail.com
34710 .vitem &%dkim_status%&
34711 ACL condition that checks a colon-separated list of possible DKIM verification
34712 results agains the actual result of verification. This is typically used
34713 to restrict an ACL verb to a list of verification outcomes, like:
34716 deny message = Message from Paypal with invalid or missing signature
34717 sender_domains = paypal.com:paypal.de
34718 dkim_signers = paypal.com:paypal.de
34719 dkim_status = none:invalid:fail
34722 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
34723 see the documentation of the &%$dkim_verify_status%& expansion variable above
34724 for more information of what they mean.
34727 . ////////////////////////////////////////////////////////////////////////////
34728 . ////////////////////////////////////////////////////////////////////////////
34730 .chapter "Adding new drivers or lookup types" "CHID13" &&&
34731 "Adding drivers or lookups"
34732 .cindex "adding drivers"
34733 .cindex "new drivers, adding"
34734 .cindex "drivers" "adding new"
34735 The following actions have to be taken in order to add a new router, transport,
34736 authenticator, or lookup type to Exim:
34739 Choose a name for the driver or lookup type that does not conflict with any
34740 existing name; I will use &"newdriver"& in what follows.
34742 Add to &_src/EDITME_& the line:
34744 <&'type'&>&`_NEWDRIVER=yes`&
34746 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
34747 code is not to be included in the binary by default, comment this line out. You
34748 should also add any relevant comments about the driver or lookup type.
34750 Add to &_src/config.h.defaults_& the line:
34752 #define <type>_NEWDRIVER
34755 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
34756 and create a table entry as is done for all the other drivers and lookup types.
34758 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
34759 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
34760 driver or lookup type and add it to the definition of OBJ.
34762 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
34765 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
34766 as for other drivers and lookups.
34769 Then all you need to do is write the code! A good way to start is to make a
34770 proforma by copying an existing module of the same type, globally changing all
34771 occurrences of the name, and cutting out most of the code. Note that any
34772 options you create must be listed in alphabetical order, because the tables are
34773 searched using a binary chop procedure.
34775 There is a &_README_& file in each of the sub-directories of &_src_& describing
34776 the interface that is expected.
34781 . ////////////////////////////////////////////////////////////////////////////
34782 . ////////////////////////////////////////////////////////////////////////////
34784 . /////////////////////////////////////////////////////////////////////////////
34785 . These lines are processing instructions for the Simple DocBook Processor that
34786 . Philip Hazel has developed as a less cumbersome way of making PostScript and
34787 . PDFs than using xmlto and fop. They will be ignored by all other XML
34789 . /////////////////////////////////////////////////////////////////////////////
34794 foot_right_recto="&chaptertitle;"
34795 foot_right_verso="&chaptertitle;"
34799 .makeindex "Options index" "option"
34800 .makeindex "Variables index" "variable"
34801 .makeindex "Concept index" "concept"
34804 . /////////////////////////////////////////////////////////////////////////////
34805 . /////////////////////////////////////////////////////////////////////////////