1 . $Cambridge: exim/doc/doc-src/spec.src,v 1.3 2005/01/14 16:18:57 tom Exp $
4 .set previousversion "4.40"
5 .set versionmonth "January"
6 .set versionyear "2005"
9 . The last of those is to make ACL index entries easier to type. It is put
10 . up here so that it gets picked up by the HTML converter, which otherwise
11 . skips to the first chapter. A longer version is set below for use in the
20 .linelength ~~sys.linelength + 0.2in
21 .set newlinelength ~~sys.linelength
22 .emphasis ~~sys.linelength + 0.1in
23 .pagedepth ~~sys.pagedepth - 0.2in
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25 .bindfont 52 "atl/Times-Roman" 9
26 .bindfont 53 "atl/Times-Roman" 7
27 .bindfont 54 "atl/Courier" 9
28 .bindfont 55 "atl/Courier-Bold" ~~maintypesize
29 .bindfont 56 "atl/Times-Italic" 7
30 .bindfont 57 "atl/Times-Bold" 7
31 .bindfont 58 "atl/Symbol" 7
35 . Used for the "small print" incorporated code stuff. Only rm, it, bf, sp are
36 . actually used at present.
37 . rm it sl bf bi ss tt sp sc
38 .fontgroup 9 = 53 56 0 57 0 0 0 58 0
43 .fontgroup 9 = 0 0 0 0 0 0 0 0 0
49 .flag $smc{ "$push$g0$f54"
50 .flag $sm{ "$push$g0$f53"
51 .flag $smi{ "$push$g0$f56"
52 .flag $as{ "$push$g0$f52"
53 .flag $ab{ "$push$g0$f51"
54 .flag $cb{ "$push$g0$f55"
63 .macro isunderscore "string"
65 .set length length "~~1"
69 .macro undrec "offset"
73 .set sub "~~string"(1,~~1)
83 .macro testunderscore "string"
112 .macro option "option" ""
114 .index \-~~1-\ option
131 .macro item "item" "6"
133 .if ~~sys.leftonpage < ~~2ld
158 .macro conf "option" "type" "default" "6"
160 .if ~~sys.leftonpage < ~~4ld
163 .testunderscore "~~1"
170 \**~~1**\ $c $rm{Type:} $it{~~2} $e $rm{Default:} $it{~~3}
176 .set displayindent 2em
178 .index @$1, @$2, etc. $it{see numerical variables}
179 .index address||rewriting $it{see rewriting}
180 .index CR character $it{see carriage return}
181 .index CRL $it{see certificate revocation list}
182 .index delivery||failure report $it{see bounce message}
183 .index dialup $it{see intermittently connected hosts}
184 .index exiscan $it{see content scanning}
185 .index failover $it{see fallback}
186 .index fallover $it{see fallback}
187 .index filter||Sieve $it{see Sieve filter}
188 .index ident $it{see RFC 1413}
189 .index LF character $it{see linefeed}
190 .index maximum $it{see limit}
191 .index NUL $it{see binary zero}
192 .index process id $it{see pid}
193 .index RBL $it{see DNS list}
194 .index redirection $it{see address redirection}
195 .index return path||$it{see also envelope sender}
196 .index scanning $it{see content scanning}
197 .index SSL $it{see TLS}
198 .index string||expansion $it{see expansion}
199 .index top bit $it{see 8-bit characters}
200 .index variables $it{see expansion, variables}
201 .index zero, binary $it{see binary zero}
203 . This is used for the printed index. See setting above for
204 . the HTML index value.
206 .set ACL "access control lists (ACLs)"
208 . ======================================================
215 $chead{University of Cambridge Computing Service}
217 $chead{Specification of the Exim Mail Transfer Agent}
222 .space ~~sys.leftonpage - 15*~~sys.linedepth
224 University Computing Service
231 $it{phone:} $t +44 1223 334600
232 $it{fax:} $t +44 1223 334679
233 $it{email:} $t ph10 $it{at} cus.cam.ac.uk
235 Edition for Exim ~~version, ~~versionmonth ~~versionyear
240 $c$rm{Copyright (c) University of Cambridge ~~versionyear}
251 . Blank verso for title page
256 . Set up for actual text pages
258 . The first one to prevent a warning from sgfr
259 . set runningfoot "~~chapter"
265 .if "~~runningfoot" == ""
268 .set rhs "~~runningfoot (~~chapter)"
270 .set lhs "Exim ~~version"
271 .linelength ~~newlinelength
272 $it{~~lhs}$c[~~sys.pagenumber]$e$it{~~rhs}
283 . ============================================================================
284 .chapter Introduction
285 .set runningfoot "introduction"
288 $c$bi{If I have seen further it is by standing on the shoulders of giants.}##(Isaac Newton)
290 $c"If I have seen further it is by standing on the shoulders of giants."
294 \*If I have seen further it is by standing on the shoulders of giants.*\
299 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
300 Unix-like operating systems. It was designed on the assumption that it would be
301 run on hosts that are permanently connected to the Internet. However, it can be
302 used on intermittently connected hosts with suitable configuration adjustments.
304 Configuration files currently exist for the following operating systems: AIX,
305 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, FreeBSD, GNU/Hurd, GNU/Linux,
306 HI-OSF (Hitachi), HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD, QNX, SCO, SCO
307 SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4, Tru64-Unix (formerly
308 Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware. Some of these operating
309 systems are no longer current and cannot easily be tested, so the configuration
310 files may no longer work in practice.
312 There are also configuration files for compiling Exim in the Cygwin environment
313 that can be installed on systems running Windows. However, this document does
314 not contain any information about running Exim in the Cygwin environment.
316 The terms and conditions for the use and distribution of Exim are contained in
317 the file \(NOTICE)\. Exim is distributed under the terms of the GNU General
318 Public Licence, a copy of which may be found in the file \(LICENCE)\.
320 The use, supply or promotion of Exim for the purpose of sending bulk,
321 unsolicited electronic mail is incompatible with the basic aims of the program,
322 which revolve around the free provision of a service that enhances the quality
323 of personal communications. The author of Exim regards indiscriminate
324 mass-mailing as an antisocial, irresponsible abuse of the Internet.
326 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
327 experience of running and working on the Smail 3 code, I could never have
328 contemplated starting to write a new MTA. Many of the ideas and user interfaces
329 were originally taken from Smail 3, though the actual code of Exim is entirely
330 new, and has developed far beyond the initial concept.
332 Many people, both in Cambridge and around the world, have contributed to the
333 development and the testing of Exim, and to porting it to various operating
334 systems. I am grateful to them all. The distribution now contains a file called
335 \(ACKNOWLEDGMENTS)\, in which I have started recording the names of
338 .section Exim documentation
340 This edition of the Exim specification applies to version ~~version of Exim.
341 Substantive changes from the ~~previousversion edition are marked by bars in
342 the right-hand margin in the PostScript, PDF, and plain text versions of the
343 document, and by green text in the HTML version, as shown by this paragraph.
344 Changes are not marked in the Texinfo version, because Texinfo doesn't support
345 change bars. Minor corrections and rewordings are not marked.
347 This document is very much a reference manual; it is not a tutorial. The reader
348 is expected to have some familiarity with the SMTP mail transfer protocol and
349 with general Unix system administration. Although there are some discussions
350 and examples in places, the information is mostly organized in a way that makes
351 it easy to look up, rather than in a natural order for sequential reading.
352 Furthermore, the manual aims to cover every aspect of Exim in detail, including
353 a number of rarely-used, special-purpose features that are unlikely to be of
356 .index books about Exim
357 An `easier' discussion of Exim which provides more in-depth explanatory,
358 introductory, and tutorial material can be found in a book entitled
360 [(A HREF="http://www.uit.co.uk/exim-book/")]
361 $it{The Exim SMTP Mail Server},
363 published by UIT Cambridge.
365 $it{The Exim SMTP Mail Server}, published by UIT Cambridge
366 (\?http://www.uit.co.uk/exim-book/?\).
369 This book also contains a chapter that gives a general introduction to SMTP and
370 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
371 with the latest release of Exim. (Note that the earlier book about Exim,
372 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
374 .index \(doc/NewStuff)\
375 .index \(doc/ChangeLog)\
377 As the program develops, there may be features in newer versions that have not
378 yet made it into this document, which is updated only when the most significant
379 digit of the fractional part of the version number changes. However,
380 specifications of new features that are not yet in this manual are placed in
381 the file \(doc/NewStuff)\ in the Exim distribution. All changes to the program
382 (whether new features, bug fixes, or other kinds of change) are noted briefly
383 in the file called \(doc/ChangeLog)\.
385 .index \(doc/spec.txt)\
386 This specification itself is available as an ASCII file in \(doc/spec.txt)\ so
387 that it can easily be searched with a text editor. Other files in the \(doc)\
391 \(OptionLists.txt)\ $t $rm{list of all options in alphabetical order}
392 \(dbm.discuss.txt)\ $t $rm{discussion about DBM libraries}
393 \(exim.8)\ $t $rm{a man page of Exim's command line options}
394 \(filter.txt)\ $t $rm{specification of the filter language}
395 \(pcrepattern.txt)\ $t $rm{specification of PCRE regular expressions}
396 \(pcretest.txt)\ $t $rm{specification of the PCRE testing program}
397 \(Exim3.upgrade)\ $t $rm{upgrade notes from release 2 to release 3}
398 \(Exim4.upgrade)\ $t $rm{upgrade notes from release 3 to release 4}
400 The main specification and the specification of the filtering language are also
401 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
402 ~~SECTavail below tells you how to get hold of these.
405 .section FTP and web sites, and mailing list
408 The primary distribution site for Exim is an FTP site, whose contents are
409 described in \*Where to find the Exim distribution*\ below. In addition,
410 there is a web site at \?http://www.exim.org?\ by courtesy of Energis Squared,
411 formerly Planet Online Ltd, who are situated in the UK. The site is mirrored in
412 a number of other countries; links to the mirrors are listed on the home page.
413 The web site contains the Exim distribution, and you can also find the
414 documentation and the
417 [(A HREF="FAQ.html")]
423 online there, as well as other relevant material.
425 .index mailing lists||for Exim users
426 Energis Squared also provide resources for the following mailing lists:
429 $it{exim-users@@exim.org} $t general discussion list
430 $it{exim-announce@@exim.org} $t moderated, low volume announcements list
432 You can subscribe to these lists, change your existing subscriptions, and view
433 or search the archives via the
435 [(A HREF="http://www.exim.org/maillist.html")]
441 link on the Exim home page. The $it{exim-users} mailing list is also forwarded
442 to \?http://www.egroups.com/list/exim-users?\, an archiving system with
443 searching capabilities.
445 .section Exim training
446 .index training courses
447 From time to time (approximately annually at the time of writing),
448 lecture-based training courses are run by the author of Exim in Cambridge, UK.
449 Details can be found on the web site
451 [(A HREF="http://www-tus.csx.cam.ac.uk/courses/exim/")]
453 \?http://www-tus@.csx@.cam@.ac.uk/courses/exim/?\.
460 .index reporting bugs
461 Reports of obvious bugs should be emailed to \*bugs@@exim.org*\. However, if
462 you are unsure whether some behaviour is a bug or not, the best thing to do is
463 to post a message to the $it{exim-users} mailing list and have it discussed.
466 .section Where to find the Exim distribution
467 .rset SECTavail "~~chapter.~~section"
469 .index distribution||ftp site
470 The master ftp site for the Exim distribution is
475 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim?\
477 Within that directory there are subdirectories called \(exim3)\ (for previous
478 Exim 3 distributions), \(exim4)\ (for the latest Exim 4 distributions), and
479 \(Testing)\ for occasional testing versions. Those mirror sites that I know
480 about are listed in the file
485 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/Mirrors?\
487 In the \(exim4)\ subdirectory, the current release can always be found in
490 \(exim-$it{n.nn}.tar.gz)\
491 \(exim-$it{n.nn}.tar.bz2)\
493 where $it{n.nn} is the highest such version number in the directory. The two
494 files contain identical data; the only difference is the type of compression.
495 The \(.bz2)\ file is usually a lot smaller than the \(.gz)\ file.
496 .index distribution||signing details
497 .index distribution||public key
498 .index public key for signed distribution
499 The distributions are signed with Philip Hazel's GPG key.
500 The corresponding public key is available from a number of keyservers, and
501 there is also a copy in the file:
506 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/Public-Key?\
508 The signatures for the tar bundles are in:
510 \(exim-$it{n.nn}.tar.gz.sig)\
511 \(exim-$it{n.nn}.tar.bz2.sig)\
514 When there is only a small amount of change from one release to the next, a
515 patch file may be provided, with a final component name of the form
517 \(exim-patch-$it{n.nn}-$it{m.mm}.gz)\
519 For each released version, the log of changes is made separately available in
522 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/ChangeLogs?\
524 so that it is possible to find out what has changed without having to download
525 the entire distribution.
527 .index documentation||available formats
528 The main distribution contains ASCII versions of this specification and other
529 documentation; other formats of the documents are available in separate files
530 inside the \(exim4)\ directory of the FTP site:
532 \(exim-html-$it{n.nn}.tar.gz)\
533 \(exim-pdf-$it{n.nn}.tar.gz)\
534 \(exim-postscript-$it{n.nn}.tar.gz)\
535 \(exim-texinfo-$it{n.nn}.tar.gz)\
537 These tar files contain only the \(doc)\ directory, not the complete
538 distribution, and are also available in \(.bz2)\ as well as \(.gz)\ forms.
541 The FAQ is available for downloading in two different formats from
546 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/exim4/FAQ.txt.gz?\
547 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/exim4/FAQ.html.tar.gz?\
549 The first of these is a single ASCII file that can be searched with a text
550 editor. The second is a directory of HTML files, normally accessed by starting
551 at \(index.html)\. The HTML version of the FAQ (which is also included in the
552 HTML documentation tarbundle) includes a keyword-in-context index, which is
553 often the most convenient way of finding your way around.
557 A wish list is maintained, containing ideas for new features that have been
558 submitted. From time to time the file is exported to the ftp site:
560 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/exim4/WishList?\
562 Items are removed from the list if they get implemented.
565 .section Contributed material
566 .index contributed material
567 At the ftp site, there is a directory called
572 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/exim4/Contrib/?\
574 which contains miscellaneous files contributed to the Exim community by Exim
575 users. There is also a collection of contributed configuration examples in
580 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/exim4/config.samples.tar.gz?\
582 These samples are referenced from the FAQ.
586 .index limitations of Exim
588 Exim is designed for use as an Internet MTA, and therefore handles addresses
589 in RFC 2822 domain format only.
590 .index bang paths||not handled by Exim
591 It cannot handle UUCP `bang paths', though simple two-component bang paths can
592 be converted by a straightforward rewriting configuration. This restriction
593 does not prevent Exim from being interfaced to UUCP as a transport mechanism,
594 provided that domain addresses are used.
596 .index domainless addresses
597 .index address||without domain
598 Exim insists that every address it handles has a domain attached. For incoming
599 local messages, domainless addresses are automatically qualified with a
600 configured domain value. Configuration options specify from which remote
601 systems unqualified addresses are acceptable. These are then qualified on
604 .index transport||external
605 .index external transports
606 The only external transport currently implemented is an SMTP transport over a
607 TCP/IP network (using sockets, including support for IPv6). However, a pipe
608 transport is available, and there are facilities for writing messages to files
609 and pipes, optionally in \*batched SMTP*\ format; these facilities can be used
610 to send messages to some other transport mechanism such as UUCP, provided it
611 can handle domain-style addresses. Batched SMTP input is also catered for.
613 Exim is not designed for storing mail for dial-in hosts. When the volumes of
614 such mail are large, it is better to get the messages `delivered' into files
615 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
618 Although Exim does have some facilities for scanning incoming messages, these
619 are not comprehensive enough to do full virus or spam scanning. Such operations
620 are best carried out using additional specialized software packages.
625 .section Run time configuration
626 Exim's run time configuration is held in a single text file that is divided
627 into a number of sections. The entries in this file consist of keywords and
628 values, in the style of Smail 3 configuration files. A default configuration
629 file which is suitable for simple online installations is provided in the
630 distribution, and is described in chapter ~~CHAPdefconfil below.
633 .section Calling interface
634 .index Sendmail compatibility||command line interface
635 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
636 can be a straight replacement for \(/usr/lib/sendmail)\ or
637 \(/usr/sbin/sendmail)\ when sending mail, but you do not need to know anything
638 about Sendmail in order to run Exim. For actions other than sending messages,
639 Sendmail-compatible options also exist, but those that produce output (for
640 example, \-bp-\, which lists the messages on the queue) do so in Exim's own
641 format. There are also some additional options that are compatible with Smail
642 3, and some further options that are new to Exim. Chapter ~~CHAPcommandline
643 documents all Exim's command line options. This information is automatically
644 made into the man page that forms part of the Exim distribution.
646 Control of messages on the queue can be done via certain privileged command
647 line options. There is also an optional monitor program called \*eximon*\, which
648 displays current information in an X window, and which contains a menu
649 interface to Exim's command line administration options.
653 .index terminology definitions
654 .index body of message||definition of
655 The \*body*\ of a message is the actual data that the sender wants to transmit.
656 It is the last part of a message, and is separated from the \*header*\ (see
657 below) by a blank line.
659 .index bounce message||definition of
660 When a message cannot be delivered, it is normally returned to the sender in a
661 delivery failure message. The term \*bounce*\ is commonly used for this action,
662 and the error reports are often called \*bounce messages*\. This is a
663 convenient shorthand for `delivery failure error report'. Such messages have an
664 empty sender address in the message's \*envelope*\ (see below) to ensure that
665 they cannot themselves give rise to further bounce messages.
667 The term \*default*\ appears frequently in this manual. It is used to qualify a
668 value which is used in the absence of any setting in the configuration. It may
669 also qualify an action which is taken unless a configuration setting specifies
672 The term \*defer*\ is used when the delivery of a message to a specific
673 destination cannot immediately take place for some reason (a remote host may be
674 down, or a user's local mailbox may be full). Such deliveries are \*deferred*\
677 The word \*domain*\ is sometimes used to mean all but the first component of a
678 host's name. It is $it{not} used in that sense here, where it normally
679 refers to the part of an email address following the @@ sign.
681 .index envelope, definition of
682 .index sender||definition of
683 A message in transit has an associated \*envelope*\, as well as a header and a
684 body. The envelope contains a sender address (to which bounce messages should
685 be delivered), and any number of recipient addresses. References to the
686 sender or the recipients of a message usually mean the addresses in the
687 envelope. An MTA uses these addresses for delivery, and for returning bounce
688 messages, not the addresses that appear in the header lines.
690 .index message||header, definition of
691 .index header section||definition of
692 The \*header*\ of a message is the first part of a message's text, consisting
693 of a number of lines, each of which has a name such as ::From::, ::To::,
694 ::Subject::, etc. Long header lines can be split over several text lines by
695 indenting the continuations. The header is separated from the body by a blank
698 .index local part||definition of
699 .index domain||definition of
700 The term \*local part*\, which is taken from RFC 2822, is used to refer to that
701 part of an email address that precedes the @@ sign. The part that follows the
702 @@ sign is called the \*domain*\ or \*mail domain*\.
704 .index local delivery||definition of
705 .index remote delivery, definition of
706 The terms \*local delivery*\ and \*remote delivery*\ are used to distinguish
707 delivery to a file or a pipe on the local host from delivery by SMTP over
708 TCP/IP to a remote host.
710 .index return path||definition of
711 \*Return path*\ is another name that is used for the sender address in a
714 .index queue||definition of
715 The term \*queue*\ is used to refer to the set of messages awaiting delivery,
716 because this term is in widespread use in the context of MTAs. However, in
717 Exim's case the reality is more like a pool than a queue, because there is
718 normally no ordering of waiting messages.
720 .index queue runner||definition of
721 The term \*queue runner*\ is used to describe a process that scans the queue
722 and attempts to deliver those messages whose retry times have come. This term
723 is used by other MTAs, and also relates to the command \runq\, but in Exim
724 the waiting messages are normally processed in an unpredictable order.
726 .index spool directory||definition of
727 The term \*spool directory*\ is used for a directory in which Exim keeps the
728 messages on its queue -- that is, those that it is in the process of
729 delivering. This should not be confused with the directory in which local
730 mailboxes are stored, which is called a `spool directory' by some people. In
731 the Exim documentation, `spool' is always used in the first sense.
739 . ============================================================================
740 .chapter Incorporated code
741 .set runningfoot "incorporated code"
742 .index incorporated code
743 .index regular expressions||library
745 A number of pieces of external code are included in the Exim distribution.
747 Regular expressions are supported in the main Exim program and in the Exim
748 monitor using the freely-distributable PCRE library, copyright (c) 2003
749 University of Cambridge. The source is distributed in the directory
750 \(src/pcre)\. However, this is a cut-down version of PCRE. If you want to use
751 the PCRE library in other programs, you should obtain and install the full
752 version from \?ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre?\.
756 .index cdb||acknowledgement
757 Support for the cdb (Constant DataBase) lookup method is provided by code
758 contributed by Nigel Metheringham of Planet Online Ltd. which contains the
759 following statements:
766 Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd
768 This program is free software; you can redistribute it and/or modify it under
769 the terms of the GNU General Public License as published by the Free Software
770 Foundation; either version 2 of the License, or (at your option) any later
773 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
774 the spec and sample code for cdb can be obtained from
775 \?http://www.pobox.com/@~djb/cdb.html?\. This implementation borrows some code
776 from Dan Bernstein's implementation (which has no license restrictions applied
781 The implementation is completely contained within the code of Exim.
782 It does not link against an external cdb library.
785 .index SPA authentication
787 .index Microsoft Secure Password Authentication
788 Client support for Microsoft's \*Secure Password Authentication*\ is provided
789 by code contributed by Marc Prud'hommeaux. Server support was contributed by
790 Tom Kistner. This includes code taken from the Samba project, which is released
796 .index \*pwcheck*\ daemon
797 .index \*pwauthd*\ daemon
798 Support for calling the Cyrus \*pwcheck*\ and \*saslauthd*\ daemons is provided
799 by code taken from the Cyrus-SASL library and adapted by Alexander S.
800 Sabourenkov. The permission notice appears below, in accordance with the
801 conditions expressed therein.
809 Copyright (c) 2001 Carnegie Mellon University. All rights reserved.
811 Redistribution and use in source and binary forms, with or without
812 modification, are permitted provided that the following conditions
816 .cancelflag $npbracket
817 .flag $npbracket "" "."
820 Redistributions of source code must retain the above copyright
821 notice, this list of conditions and the following disclaimer.
823 Redistributions in binary form must reproduce the above copyright
824 notice, this list of conditions and the following disclaimer in
825 the documentation and/or other materials provided with the
828 The name `Carnegie Mellon University' must not be used to
829 endorse or promote products derived from this software without
830 prior written permission. For permission or any other legal
831 details, please contact
833 Office of Technology Transfer
834 Carnegie Mellon University
836 Pittsburgh, PA 15213-3890
837 (412) 268-4387, fax: (412) 268-7395
838 tech-transfer@@andrew.cmu.edu
841 Redistributions of any form whatsoever must retain the following
845 .indent ~~sys.indent + 3em
847 $it{This product includes software developed by Computing Services
848 at Carnegie Mellon University (\?http://www.cmu.edu/computing/?\).}
853 .cancelflag $npbracket
854 .flag $npbracket "(" ")"
857 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
858 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
859 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
860 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
861 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
862 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
863 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
873 The Exim Monitor program, which is an X-Window application, includes
874 modified versions of the Athena StripChart and TextPop widgets.
875 This code is copyright by DEC and MIT, and their permission notice appears
876 below, in accordance with the conditions expressed therein.
884 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
885 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
887 $c All Rights Reserved
889 Permission to use, copy, modify, and distribute this software and its
890 documentation for any purpose and without fee is hereby granted,
891 provided that the above copyright notice appear in all copies and that
892 both that copyright notice and this permission notice appear in
893 supporting documentation, and that the names of Digital or MIT not be
894 used in advertising or publicity pertaining to distribution of the
895 software without specific, written prior permission.
897 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
898 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
899 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
900 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
901 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
902 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
915 . ============================================================================
916 .chapter How Exim receives and delivers mail
917 .set runningfoot "receiving & delivering mail"
919 .section Overall philosophy
920 .index design philosophy
921 Exim is designed to work efficiently on systems that are permanently connected
922 to the Internet and are handling a general mix of mail. In such circumstances,
923 most messages can be delivered immediately. Consequently, Exim does not
924 maintain independent queues of messages for specific domains or hosts, though
925 it does try to send several messages in a single SMTP connection after a host
926 has been down, and it also maintains per-host retry information.
929 .section Policy control
930 .index policy control||overview
931 Policy controls are now an important feature of MTAs that are connected to the
932 Internet. Perhaps their most important job is to stop MTAs being abused as
933 `open relays' by misguided individuals who send out vast amounts of unsolicited
934 junk, and want to disguise its source. Exim provides flexible facilities for
935 specifying policy controls on incoming mail:
937 .index ~~ACL||introduction
938 Exim 4 (unlike previous versions of Exim) implements policy controls on
939 incoming SMTP mail by means of \*Access Control Lists*\ (ACLs). Each list is a
940 series of statements that may either grant or deny access. ACLs can be used at
941 several places in the SMTP dialogue while receiving a message. However, the
942 most common places are after each \\RCPT\\ command, and at the very end of the
943 message. The sysadmin can specify conditions for accepting or rejecting
944 individual recipients or the entire message, respectively, at these two points
945 (see chapter ~~CHAPACL). Denial of access results in an SMTP error code.
947 An ACL is also available for locally generated, non-SMTP messages. In this
948 case, the only available actions are to accept or deny the entire message.
950 When a message has been received, either from a remote host or from the local
951 host, but before the final acknowledgement has been sent, a locally supplied C
952 function called \*local@_scan()*\ can be run to inspect the message and decide
953 whether to accept it or not (see chapter ~~CHAPlocalscan). If the message is
954 accepted, the list of recipients can be modified by the function.
956 After a message has been accepted, a further checking mechanism is available in
957 the form of the $it{system filter} (see chapter ~~CHAPsystemfilter). This runs
958 at the start of every delivery process.
961 .section User filters
962 .index filter||introduction
964 In a conventional Exim configuration, users are able to run private filters by
965 setting up appropriate \(.forward)\ files in their home directories. See
966 chapter ~~CHAPredirect (about the \%redirect%\ router) for the configuration
967 needed to support this, and the separate document entitled
969 [(A HREF="filter_toc.html")]
971 \*Exim's interfaces to mail filtering*\
975 for user details. Two different kinds of filtering are available:
977 Sieve filters are written in the standard filtering language that is defined by
980 Exim filters are written in a syntax that is unique to Exim, but which is more
981 powerful than Sieve, which it pre-dates.
983 User filters are run as part of the routing process, described below.
986 .section Message identification
987 .rset SECTmessiden "~~chapter.~~section"
988 .index message||ids, details of format
989 .index format||of message id
995 Every message handled by Exim is given a \*message id*\ which is sixteen
996 characters long. It is divided into three parts, separated by hyphens, for
997 example \"16VDhn-0001bo-D3"\. Each part is a sequence of letters and digits,
998 normally encoding numbers in base 62. However, in the Darwin operating
999 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
1000 (avoiding the use of lower case letters) is used instead, because the message
1001 id is used to construct file names, and the names of files in those systems are
1004 .index pid (process id)||re-use of
1005 The detail of the contents of the message id have changed as Exim has evolved.
1006 Earlier versions relied on the operating system not re-using a process id (pid)
1007 within one second. On modern operating systems, this assumption can no longer
1008 be made, so the algorithm had to be changed. To retain backward compatibility,
1009 the format of the message id was retained, which is why the following rules are
1012 The first six characters of the message id are the time at which the message
1013 started to be received, to a granularity of one second. That is, this field
1014 contains the number of seconds since the start of the epoch (the normal Unix
1015 way of representing the date and time of day).
1017 After the first hyphen, the next six characters are the id of the process that
1018 received the message.
1020 There are two different possibilities for the final two characters:
1022 .index \localhost@_number\
1023 If \localhost@_number\ is not set, this value is the fractional part of the
1024 time of reception, normally in units of 1/2000 of a second, but for systems
1025 that must use base 36 instead of base 62 (because of case-insensitive file
1026 systems), the units are 1/1000 of a second.
1028 If \localhost@_number\ is set, it is multiplied by 200 (100) and added to
1029 the fractional part of the time, which in this case is in units of 1/200
1030 (1/100) of a second.
1033 After a message has been received, Exim waits for the clock to tick at the
1034 appropriate resolution before proceeding, so that if another message is
1035 received by the same process, or by another process with the same (re-used)
1036 pid, it is guaranteed that the time will be different. In most cases, the clock
1037 will already have ticked while the message was being received.
1039 .section Receiving mail
1040 .index receiving mail
1041 .index message||reception
1042 The only way Exim can receive mail from a remote host is using SMTP over
1043 TCP/IP, in which case the sender and recipient addresses are tranferred using
1044 SMTP commands. However, from a locally running process (such as a user's MUA),
1045 there are several possibilities:
1047 If the process runs Exim with the \-bm-\ option, the message is read
1048 non-interactively (usually via a pipe), with the recipients taken from the
1049 command line, or from the body of the message if \-t-\ is also used.
1051 If the process runs Exim with the \-bS-\ option, the message is also read
1052 non-interactively, but in this case the recipients are listed at the start of
1053 the message in a series of SMTP \\RCPT\\ commands, terminated by a \\DATA\\
1054 command. This is so-called `batch SMTP' format,
1055 but it isn't really SMTP. The SMTP commands are just another way of passing
1056 envelope addresses in a non-interactive submission.
1058 If the process runs Exim with the \-bs-\ option, the message is read
1059 interactively, using the SMTP protocol. A two-way pipe is normally used for
1060 passing data between the local process and the Exim process.
1061 This is `real' SMTP and is handled in the same way as SMTP over TCP/IP. For
1062 example, the ACLs for SMTP commands are used for this form of submission.
1064 A local process may also make a TCP/IP call to the host's loopback address
1065 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1066 does not treat the loopback address specially. It treats all such connections
1067 in the same way as connections from other hosts.
1070 .index message||sender, constructed by Exim
1071 .index sender||constructed by Exim
1072 In the three cases that do not involve TCP/IP, the sender address is
1073 constructed from the login name of the user that called Exim and a default
1074 qualification domain (which can be set by the \qualify@_domain\ configuration
1075 option). For local or batch SMTP, a sender address that is passed using the
1076 SMTP \\MAIL\\ command is ignored. However, the system administrator may allow
1077 certain users (`trusted users') to specify a different sender address
1078 unconditionally, or all users to specify certain forms of different sender
1079 address. The \-f-\ option or the SMTP \\MAIL\\ command is used to specify these
1080 different addresses. See section ~~SECTtrustedadmin for details of trusted
1081 users, and the \untrusted@_set@_sender\ option for a way of allowing untrusted
1082 users to change sender addresses.
1084 Messages received by either of the non-interactive mechanisms are subject to
1085 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1086 (either over TCP/IP, or interacting with a local process) can be checked by a
1087 number of ACLs that operate at different times during the SMTP session. Either
1088 individual recipients, or the entire message, can be rejected if local policy
1089 requirements are not met. The \*local@_scan()*\ function (see chapter
1090 ~~CHAPlocalscan) is run for all incoming messages.
1092 Exim can be configured not to start a delivery process when a message is
1093 received; this can be unconditional, or depend on the number of incoming SMTP
1094 connections or the system load. In these situations, new messages wait on the
1095 queue until a queue runner process picks them up. However, in standard
1096 configurations under normal conditions, delivery is started as soon as a
1097 message is received.
1102 .section Handling an incoming message
1103 .index spool directory||files that hold a message
1104 .index file||how a message is held
1105 When Exim accepts a message, it writes two files in its spool directory. The
1106 first contains the envelope information, the current status of the message,
1107 and the header lines, and the second contains the body of the message. The
1108 names of the two spool files consist of the message id, followed by $tt{-H} for
1109 the file containing the envelope and header, and $tt{-D} for the data file.
1111 .index spool directory||\(input)\ sub-directory
1112 By default all these message files are held in a single directory called
1113 \(input)\ inside the general Exim spool directory. Some operating systems do
1114 not perform very well if the number of files in a directory gets very large; to
1115 improve performance in such cases, the \split@_spool@_directory\ option can be
1116 used. This causes Exim to split up the input files into 62 sub-directories
1117 whose names are single letters or digits.
1119 The envelope information consists of the address of the message's sender and
1120 the addresses of the recipients. This information is entirely separate from
1121 any addresses contained in the header lines. The status of the message includes
1122 a list of recipients who have already received the message. The format of the
1123 first spool file is described in chapter ~~CHAPspool.
1125 .index rewriting||addresses
1126 Address rewriting that is specified in the rewrite section of the configuration
1127 (see chapter ~~CHAPrewrite) is done once and for all on incoming addresses,
1128 both in the header lines and the envelope, at the time the message is accepted.
1129 If during the course of delivery additional addresses are generated (for
1130 example, via aliasing), these new addresses are rewritten as soon as they are
1131 generated. At the time a message is actually delivered (transported) further
1132 rewriting can take place; because this is a transport option, it can be
1133 different for different forms of delivery. It is also possible to specify the
1134 addition or removal of certain header lines at the time the message is
1135 delivered (see chapters ~~CHAProutergeneric and ~~CHAPtransportgeneric).
1138 .section Life of a message
1139 .index message||life of
1140 .index message||frozen
1141 A message remains in the spool directory until it is completely delivered to
1142 its recipients or to an error address, or until it is deleted by an
1143 administrator or by the user who originally created it. In cases when delivery
1144 cannot proceed -- for example, when a message can neither be delivered to its
1145 recipients nor returned to its sender, the message is marked `frozen' on the
1146 spool, and no more deliveries are attempted.
1148 .index frozen messages||thawing
1149 .index message||thawing frozen
1150 An administrator can `thaw' such messages when the problem has been corrected,
1151 and can also freeze individual messages by hand if necessary. In addition, an
1152 administrator can force a delivery error, causing a bounce message to be sent.
1155 There is an option called \auto@_thaw\, which can be used to cause Exim to
1156 retry frozen messages after a certain time. When this is set, no message will
1157 remain on the queue for ever, because the delivery timeout will eventually be
1158 reached. Delivery failure reports (bounce messages) that reach this timeout are
1160 .index \timeout@_frozen@_after\
1161 There is also an option called \timeout@_frozen@_after\, which discards frozen
1162 messages after a certain time.
1164 .index message||log file for
1165 .index log||file for each message
1166 While Exim is working on a message, it writes information about each delivery
1167 attempt to the main log file. This includes successful, unsuccessful, and
1168 delayed deliveries for each recipient (see chapter ~~CHAPlog). The log lines
1169 are also written to a separate $it{message log} file for each message. These
1170 logs are solely for the benefit of the administrator, and are normally deleted
1171 along with the spool files when processing of a message is complete.
1172 The use of individual message logs can be disabled by setting
1173 \no@_message@_logs\; this might give an improvement in performance on very
1177 .index file||journal
1178 All the information Exim itself needs to set up a delivery is kept in the first
1179 spool file, along with the header lines. When a successful delivery occurs, the
1180 address is immediately written at the end of a journal file, whose name is the
1181 message id followed by $tt{-J}. At the end of a delivery run, if there are some
1182 addresses left to be tried again later, the first spool file (the $tt{-H} file)
1183 is updated to indicate which these are, and the journal file is then deleted.
1184 Updating the spool file is done by writing a new file and renaming it, to
1185 minimize the possibility of data loss.
1187 Should the system or the program crash after a successful delivery but before
1188 the spool file has been updated, the journal is left lying around. The next
1189 time Exim attempts to deliver the message, it reads the journal file and
1190 updates the spool file before proceeding. This minimizes the chances of double
1191 deliveries caused by crashes.
1194 .section Processing an address for delivery
1195 .rset SECTprocaddress "~~chapter.~~section"
1196 .index drivers||definition of
1197 .index router||definition of
1198 .index transport||definition of
1199 The main delivery processing elements of Exim are called $it{routers} and
1200 $it{transports}, and collectively these are known as $it{drivers}. Code for a
1201 number of them is provided in the source distribution, and compile-time options
1202 specify which ones are included in the binary. Run time options specify which
1203 ones are actually used for delivering messages.
1205 .index drivers||instance definition
1206 Each driver that is specified in the run time configuration is an \*instance*\
1207 of that particular driver type. Multiple instances are allowed; for example,
1208 you can set up several different \%smtp%\ transports, each with different
1209 option values that might specify different ports or different timeouts. Each
1210 instance has its own identifying name. In what follows we will normally use the
1211 instance name when discussing one particular instance (that is, one specific
1212 configuration of the driver), and the generic driver name when discussing
1213 the driver's features in general.
1215 A $it{router} is a driver that operates on an address, either determining how
1216 its delivery should happen, by routing it to a specific transport, or
1217 converting the address into one or more new addresses (for example, via an
1218 alias file). A router may also explicitly choose to fail an address, causing it
1221 A $it{transport} is a driver that transmits a copy of the message from Exim's
1222 spool to some destination. There are two kinds of transport: for a $it{local}
1223 transport, the destination is a file or a pipe on the local host, whereas for a
1224 $it{remote} transport the destination is some other host. A message is passed
1225 to a specific transport as a result of successful routing. If a message has
1226 several recipients, it may be passed to a number of different transports.
1228 .index preconditions||definition of
1229 An address is processed by passing it to each configured router instance in
1230 turn, subject to certain preconditions, until a router accepts the address or
1231 specifies that it should be bounced. We will describe this process in more
1232 detail shortly. As a simple example, the diagram below illustrates how each
1233 recipient address in a message is processed in a small configuration of three
1234 routers that are configured in various ways.
1237 .figure "Routing an address" rm
1239 .call aspic -sgcal -nv
1240 centre ~~sys.linelength;
1243 ibox depth 14 "address";
1246 A: box width 100 "first router" "conditions ok?";
1248 C: box width 100 "run" "first router";
1250 D: ibox depth 20 "address bounces";
1252 arc clockwise from right of C "accept";
1254 ibox "queue for" "transport";
1256 arrow down from A align bottom of D plus (0,-20) "no"(-6,20)/r;
1257 E: box width 100 "second router" "conditions ok?";
1259 F: box width 100 "run" "second router";
1260 line right 100 "redirect";
1261 line up align middle of B;
1262 arrow left to middle of B "new addresses";
1264 line down 20 from bottom left of F plus (30,0);
1265 arrow left align centre of E "decline";
1267 line down 20 from bottom right of F plus (-30,0);
1269 ibox width 64 "address" "bounces";
1271 arrow down 64 from E "no"(-6,20)/r;
1272 G: box width 100 "third router" "conditions ok?";
1274 H: box width 100 "run" "third router";
1275 arc clockwise from right of H "accept";
1277 ibox "queue for" "transport";
1279 line down 20 from bottom of H;
1280 arrow left align centre of G "decline";
1281 arrow down 64 from G "no"(-6,20)/r;
1283 ibox "no more routers" "address bounces";
1291 |<------------- new addresses -----------------------------
1293 ----------------- ----------------- |
1294 | first router |----- yes ----->| run |--- accept |
1295 | conditions ok?| | first router | | |
1296 ----------------- ----------------- | |
1298 no | fail | queue for |
1303 ----------------- ----------------- |
1304 | second router |----- yes ----->| run |----redirect ----
1305 | conditions ok?| | second router |
1306 ----------------- -----------------
1309 |<-------- decline ----------- --- fail ---> address
1312 ----------------- -----------------
1313 | third router |----- yes ----->| run |--- accept
1314 | conditions ok?| | third router | |
1315 ----------------- ----------------- |
1318 |<-------- decline --------------- transport
1325 [(img src="routing.gif" alt="Routing an address")][(br)]
1327 To make this a more concrete example, we'll describe it in terms of some actual
1328 routers, but remember, this is only an example. You can configure Exim's
1329 routers in many different ways, and there may be any number of routers in a
1332 The first router that is specified in a configuration is often one that handles
1333 addresses in domains that are not recognized specially by the local host. These
1334 are typically addresses for arbitrary domains on the Internet. A precondition
1335 is set up which looks for the special domains known to the host (for example,
1336 its own domain name), and the router is run for addresses that do $it{not}
1337 match. Typically, this is a router that looks up domains in the DNS in order to
1338 find the hosts to which this address routes. If it succeeds, the address is
1339 queued for a suitable SMTP transport; if it does not succeed, the router is
1340 configured to fail the address.
1342 The example pictured could be a configuration of this type. The second and
1343 third routers can only be run for addresses for which the preconditions for
1344 the first router are not met. If one of these preconditions checks the
1345 domain, the second and third routers are run only for domains that are somehow
1346 special to the local host.
1348 The second router does redirection -- also known as aliasing and forwarding.
1349 When it generates one or more new addresses from the original, each of them is
1350 routed independently from the start. Otherwise, the router may cause an address
1351 to fail, or it may simply decline to handle the address, in which case the
1352 address is passed to the next router.
1354 The final router in many configurations is one that checks to see if the
1355 address belongs to a local mailbox. The precondition may involve a check to
1356 see if the local part is the name of a login account, or it may look up the
1357 local part in a file or a database. If its preconditions are not met, or if
1358 the router declines, we have reached the end of the routers. When this happens,
1359 the address is bounced.
1362 .section Processing an address for verification
1363 .index router||for verification
1364 .index verifying||address, overview
1365 As well as being used to decide how to deliver to an address, Exim's routers
1366 are also used for \*address verification*\. Verification can be requested as
1367 one of the checks to be performed in an ACL for incoming messages, on both
1368 sender and recipient addresses, and it can be tested using the \-bv-\ and
1369 \-bvs-\ command line options.
1371 When an address is being verified, the routers are run in `verify mode'. This
1372 does not affect the way the routers work, but it is a state that can be
1373 detected. By this means, a router can be skipped or made to behave differently
1374 when verifying. A common example is a configuration in which the first router
1375 sends all messages to a message-scanning program, unless they have been
1376 previously scanned. Thus, the first router accepts all addresses without any
1377 checking, making it useless for verifying. Normally, the \no@_verify\ option
1378 would be set for such a router, causing it to be skipped in verify mode.
1382 .section Running an individual router
1383 .rset SECTrunindrou "~~chapter.~~section"
1384 .index router||running details
1385 .index preconditions||checking
1386 .index router||result of running
1387 As explained in the example above, a number of preconditions are checked before
1388 running a router. If any are not met, the router is skipped, and the address is
1389 passed to the next router. When all the preconditions on a router $it{are} met,
1390 the router is run. What happens next depends on the outcome, which is one of
1393 \*accept*\: The router accepts the address, and either queues it for a
1394 transport, or generates one or more `child' addresses. Processing the original
1396 .index \unseen\ option
1397 unless the \unseen\ option is set on the router. This option
1398 can be used to set up multiple deliveries with different routing (for example,
1399 for keeping archive copies of messages). When \unseen\ is set, the address is
1400 passed to the next router. Normally, however, an \*accept*\ return marks the
1403 .index case of local parts
1404 .index address||duplicate, discarding
1405 If child addresses are generated, Exim checks to see whether they are
1406 duplicates of any existing recipient addresses. During this check, local parts
1407 are treated as case-sensitive. Duplicate addresses are discarded. Each of the
1408 remaining child addresses is then processed independently, starting with the
1409 first router by default. It is possible to change this by setting the
1410 \redirect@_router\ option to specify which router to start at for child
1411 addresses. Unlike \pass@_router\ (see below) the router specified by
1412 \redirect@_router\ may be anywhere in the router configuration.
1414 \*pass*\: The router recognizes the address, but cannot handle it itself. It
1415 requests that the address be passed to another router. By default the address
1416 is passed to the next router, but this can be changed by setting the
1417 \pass@_router\ option. However, (unlike \redirect@_router\) the named router
1418 must be below the current router (to avoid loops).
1420 \*decline*\: The router declines to accept the address because it does not
1421 recognize it at all. By default, the address is passed to the next router, but
1422 this can be prevented by setting the \no@_more\ option. When \no@_more\ is set,
1423 all the remaining routers are skipped.
1425 \*fail*\: The router determines that the address should fail, and queues it for
1426 the generation of a bounce message. There is no further processing of the
1427 original address unless \unseen\ is set on the router.
1429 \*defer*\: The router cannot handle the address at the present time. (A database
1430 may be offline, or a DNS lookup may have timed out.) No further processing of
1431 the address happens in this delivery attempt. It is tried again next time the
1432 message is considered for delivery.
1434 \*error*\: There is some error in the router (for example, a syntax error in
1435 its configuration). The action is as for defer.
1437 If an address reaches the end of the routers without having been accepted by
1438 any of them, it is bounced as unrouteable.
1439 The default error message in this situation is `unrouteable address', but you
1440 can set your own message by making use of the \cannot@_route@_message\ option.
1441 This can be set for any router; the value from the last router that `saw'
1442 the address is used.
1444 Sometimes while routing you want to fail a delivery when some conditions are
1445 met but others are not, instead of passing the address on for further routing.
1446 You can do this by having a second router that explicitly fails the delivery
1447 when the relevant conditions are met. The \%redirect%\ router has a `fail'
1448 facility for this purpose.
1452 .section Router preconditions
1453 .rset SECTrouprecon "~~chapter.~~section"
1454 .index router||preconditions, order of processing
1455 .index preconditions||order of processing
1456 The preconditions that are tested for each router are listed below, in the
1457 order in which they are tested. The individual configuration options are
1458 described in more detail in chapter ~~CHAProutergeneric.
1460 The \local@_part@_prefix\ and \local@_part@_suffix\ options can specify that
1461 the local parts handled by the router may or must have certain prefixes and/or
1462 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1463 skipped. These conditions are tested first. When an affix is present, it is
1464 removed from the local part before further processing, including the evaluation
1465 of any other conditions.
1467 Routers can be designated for use only when not verifying an address, that is,
1468 only when routing it for delivery (or testing its delivery routing). If the
1469 \verify\ option is set false, the router is skipped when Exim is verifying an
1471 Setting the \verify\ option actually sets two options, \verify@_sender\ and
1472 \verify@_recipient\, which independently control the use of the router for
1473 sender and recipient verification. You can set these options directly if
1474 you want a router to be used for only one type of verification.
1476 If the \address@_test\ option is set false, the router is skipped when Exim is
1477 run with the \-bt-\ option to test an address routing. This can be helpful when
1478 the first router sends all new messages to a scanner of some sort; it makes it
1479 possible to use \-bt-\ to test subsequent delivery routing without having to
1480 simulate the effect of the scanner.
1482 Routers can be designated for use only when verifying an address, as
1483 opposed to routing it for delivery. The \verify@_only\ option controls this.
1485 Certain routers can be explicitly skipped when running the routers to check an
1486 address given in the SMTP \\EXPN\\ command (see the \expn\ option).
1488 If the \domains\ option is set, the domain of the address must be in the set of
1489 domains that it defines.
1491 If the \local@_parts\ option is set, the local part of the address must be in
1492 the set of local parts that it defines. If \local@_part@_prefix\ or
1493 \local@_part@_suffix\ is in use, the prefix or suffix is removed from the local
1494 part before this check. If you want to do precondition tests on local parts
1495 that include affixes, you can do so by using a \condition\ option (see below)
1496 that uses the variables \$local@_part$\, \$local@_part@_prefix$\, and
1497 \$local@_part@_suffix$\ as necessary.
1499 If the \check@_local@_user\ option is set, the local part must be the name of
1500 an account on the local host.
1501 If this check succeeds, the uid and gid of the local user are placed in
1502 \$local@_user@_uid$\ and \$local@_user@_gid$\; these values can be used in the
1503 remaining preconditions.
1505 If the \router@_home@_directory\ option is set, it is expanded at this point,
1506 because it overrides the value of \$home$\. If this expansion were left till
1507 later, the value of \$home$\ as set by \check@_local@_user\ would be used in
1508 subsequent tests. Having two different values of \$home$\ in the same router
1509 could lead to confusion.
1511 If the \senders\ option is set, the envelope sender address must be in the set
1512 of addresses that it defines.
1514 If the \require@_files\ option is set, the existence or non-existence of
1515 specified files is tested.
1517 .index customizing||precondition
1518 If the \condition\ option is set, it is evaluated and tested. This option uses
1519 an expanded string to allow you to set up your own custom preconditions.
1520 Expanded strings are described in chapter ~~CHAPexpand.
1523 Note that \require@_files\ comes near the end of the list, so you cannot use it
1524 to check for the existence of a file in which to lookup up a domain, local
1525 part, or sender. However, as these options are all expanded, you can use the
1526 \exists\ expansion condition to make such tests within each condition. The
1527 \require@_files\ option is intended for checking files that the router may be
1528 going to use internally, or which are needed by a specific transport (for
1529 example, \(.procmailrc)\).
1532 .section Delivery in detail
1533 .index delivery||in detail
1534 When a message is to be delivered, the sequence of events is as follows:
1536 If a system-wide filter file is specified, the message is passed to it. The
1537 filter may add recipients to the message, replace the recipients, discard the
1538 message, cause a new message to be generated, or cause the message delivery to
1539 fail. The format of the system filter file is the same as for Exim user filter
1540 files, described in the separate document entitled
1542 [(A HREF="filter.html")]
1544 \*Exim's interfaces to mail filtering*\.
1548 .index Sieve filter||not available for system filter
1549 (\**Note**\: Sieve cannot be used for system filter files.)
1550 Some additional features are available in system filters -- see chapter
1551 ~~CHAPsystemfilter for details. Note that a message is passed to the system
1552 filter only once per delivery attempt, however many recipients it has. However,
1553 if there are several delivery attempts because one or more addresses could not
1554 be immediately delivered, the system filter is run each time. The filter
1555 condition \first@_delivery\ can be used to detect the first run of the system
1558 Each recipient address is offered to each configured router in turn, subject to
1559 its preconditions, until one is able to handle it. If no router can handle
1560 the address, that is, if they all decline, the address is failed. Because
1561 routers can be targeted at particular domains, several locally handled domains
1562 can be processed entirely independently of each other.
1564 .index routing||loops in
1565 .index loop||while routing
1566 A router that accepts an address may set up a local or a remote transport for
1567 it. However, the transport is not run at this time. Instead, the address is
1568 placed on a list for the particular transport, to be run later. Alternatively,
1569 the router may generate one or more new addresses (typically from alias,
1570 forward, or filter files). New addresses are fed back into this process from
1571 the top, but in order to avoid loops, a router ignores any address which has an
1572 identically-named ancestor that was processed by itself.
1574 When all the routing has been done, addresses that have been successfully
1575 handled are passed to their assigned transports. When local transports are
1576 doing real local deliveries, they handle only one address at a time, but if a
1577 local transport is being used as a pseudo-remote transport (for example, to
1578 collect batched SMTP messages for transmission by some other means) multiple
1579 addresses can be handled. Remote transports can always handle more than one
1580 address at a time, but can be configured not to do so, or to restrict multiple
1581 addresses to the same domain.
1583 Each local delivery to a file or a pipe runs in a separate process under a
1584 non-privileged uid, and these deliveries are run one at a time. Remote
1585 deliveries also run in separate processes, normally under a uid that is private
1586 to Exim (`the Exim user'), but in this case, several remote deliveries can be
1587 run in parallel. The maximum number of simultaneous remote deliveries for any
1588 one message is set by the \remote@_max@_parallel\ option.
1589 The order in which deliveries are done is not defined, except that all local
1590 deliveries happen before any remote deliveries.
1593 When it encounters a local delivery during a queue run, Exim checks its retry
1594 database to see if there has been a previous temporary delivery failure for the
1595 address before running the local transport. If there was a previous failure,
1596 Exim does not attempt a new delivery until the retry time for the address is
1597 reached. However, this happens only for delivery attempts that are part of a
1598 queue run. Local deliveries are always attempted when delivery immediately
1599 follows message reception, even if retry times are set for them. This makes for
1600 better behaviour if one particular message is causing problems (for example,
1601 causing quota overflow, or provoking an error in a filter file).
1603 .index delivery||retry in remote transports
1604 Remote transports do their own retry handling, since an address may be
1605 deliverable to one of a number of hosts, each of which may have a different
1606 retry time. If there have been previous temporary failures and no host has
1607 reached its retry time, no delivery is attempted, whether in a queue run or
1608 not. See chapter ~~CHAPretry for details of retry strategies.
1610 If there were any permanent errors, a bounce message is returned to an
1611 appropriate address (the sender in the common case), with details of the error
1612 for each failing address. Exim can be configured to send copies of bounce
1613 messages to other addresses.
1615 .index delivery||deferral
1616 If one or more addresses suffered a temporary failure, the message is left on
1617 the queue, to be tried again later. Delivery of these addresses is said to be
1620 When all the recipient addresses have either been delivered or bounced,
1621 handling of the message is complete. The spool files and message log are
1622 deleted, though the message log can optionally be preserved if required.
1626 .section Retry mechanism
1627 .index delivery||retry mechanism
1628 .index retry||description of mechanism
1630 Exim's mechanism for retrying messages that fail to get delivered at the first
1631 attempt is the queue runner process. You must either run an Exim daemon that
1632 uses the \-q-\ option with a time interval to start queue runners at regular
1633 intervals, or use some other means (such as \*cron*\) to start them. If you do
1634 not arrange for queue runners to be run, messages that fail temporarily at the
1635 first attempt will remain on your queue for ever. A queue runner process works
1636 it way through the queue, one message at a time, trying each delivery that has
1637 passed its retry time.
1638 You can run several queue runners at once.
1640 Exim uses a set of configured rules to determine when next to retry the failing
1641 address (see chapter ~~CHAPretry). These rules also specify when Exim should
1642 give up trying to deliver to the address, at which point it generates a bounce
1643 message. If no retry rules are set for a particular host, address, and error
1644 combination, no retries are attempted, and temporary errors are treated as
1648 .section Temporary delivery failure
1649 .index delivery||temporary failure
1650 There are many reasons why a message may not be immediately deliverable to a
1651 particular address. Failure to connect to a remote machine (because it, or the
1652 connection to it, is down) is one of the most common. Temporary failures may be
1653 detected during routing as well as during the transport stage of delivery.
1654 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1655 is on a file system where the user is over quota. Exim can be configured to
1656 impose its own quotas on local mailboxes; where system quotas are set they will
1659 If a host is unreachable for a period of time, a number of messages may be
1660 waiting for it by the time it recovers, and sending them in a single SMTP
1661 connection is clearly beneficial. Whenever a delivery to a remote host is
1663 .index hints database
1664 Exim makes a note in its hints database, and whenever a successful
1665 SMTP delivery has happened, it looks to see if any other messages are waiting
1666 for the same host. If any are found, they are sent over the same SMTP
1667 connection, subject to a configuration limit as to the maximum number in any
1672 .section Permanent delivery failure
1673 .index delivery||permanent failure
1674 .index bounce message||when generated
1675 When a message cannot be delivered to some or all of its intended recipients, a
1676 bounce message is generated. Temporary delivery failures turn into permanent
1677 errors when their timeout expires. All the addresses that fail in a given
1678 delivery attempt are listed in a single message. If the original message has
1679 many recipients, it is possible for some addresses to fail in one delivery
1680 attempt and others to fail subsequently, giving rise to more than one bounce
1681 message. The wording of bounce messages can be customized by the administrator.
1682 See chapter ~~CHAPemsgcust for details.
1684 .index ::X-Failed-Recipients:: header line
1685 Bounce messages contain an ::X-Failed-Recipients:: header line that lists the
1686 failed addresses, for the benefit of programs that try to analyse such messages
1689 .index bounce message||recipient of
1690 A bounce message is normally sent to the sender of the original message, as
1691 obtained from the message's envelope. For incoming SMTP messages, this is the
1692 address given in the \\MAIL\\ command. However, when an address is
1693 expanded via a forward or alias file, an alternative address can be specified
1694 for delivery failures of the generated addresses. For a mailing list expansion
1695 (see section ~~SECTmailinglists) it is common to direct bounce messages to the
1696 manager of the list.
1700 .section Failures to deliver bounce messages
1701 .index bounce message||failure to deliver
1702 If a bounce message (either locally generated or received from a remote host)
1703 itself suffers a permanent delivery failure, the message is left on the queue,
1704 but it is frozen, awaiting the attention of an administrator. There are options
1705 which can be used to make Exim discard such failed messages, or to keep them
1706 for only a short time (see \timeout@_frozen@_after\ and
1707 \ignore@_bounce@_errors@_after\).
1715 . ============================================================================
1716 .chapter Building and installing Exim
1717 .set runningfoot "building/installing"
1719 .index building Exim
1721 Exim is distributed as a gzipped or bzipped tar file which, when upacked,
1722 creates a directory with the name of the current release (for example,
1723 \(exim-~~version)\) into which the following files are placed:
1725 .if !~~sys.fancy && ~~sgcal
1730 \(ACKNOWLEDGMENTS)\ $t contains some acknowledgments
1732 \(CHANGES)\ $t contains a reference to where changes are documented
1733 \(LICENCE)\ $t the GNU General Public Licence
1734 \(Makefile)\ $t top-level make file
1735 \(NOTICE)\ $t conditions for the use of Exim
1736 \(README)\ $t list of files, directories and simple build instructions
1738 Other files whose names begin with \(README)\ may also be present. The
1739 following subdirectories are created:
1741 .if !~~sys.fancy && ~~sgcal
1746 \(Local)\ $t an empty directory for local configuration files
1747 \(OS)\ $t OS-specific files
1748 \(doc)\ $t documentation files
1749 \(exim@_monitor)\$t source files for the Exim monitor
1750 \(scripts)\ $t scripts used in the build process
1751 \(src)\ $t remaining source files
1752 \(util)\ $t independent utilities
1754 The main utility programs are contained in the \(src)\ directory, and are built
1755 with the Exim binary. The \(util)\ directory contains a few optional scripts
1756 that may be useful to some sites.
1758 .section Multiple machine architectures and operating systems
1759 .index building Exim||multiple OS/architectures
1760 The building process for Exim is arranged to make it easy to build binaries for
1761 a number of different architectures and operating systems from the same set of
1762 source files. Compilation does not take place in the \(src)\ directory. Instead,
1763 a \*build directory*\ is created for each architecture and operating system.
1764 .index symbolic link||to build directory
1765 Symbolic links to the sources are installed in this directory, which is where
1766 the actual building takes place.
1768 In most cases, Exim can discover the machine architecture and operating system
1769 for itself, but the defaults can be overridden if necessary.
1771 .section DBM libraries
1772 .rset SECTdb "~~chapter.~~section"
1773 .index DBM||libraries, discussion of
1774 .index hints database||DBM files used for
1775 Even if you do not use any DBM files in your configuration, Exim still needs a
1776 DBM library in order to operate, because it uses indexed files for its hints
1777 databases. Unfortunately, there are a number of DBM libraries in existence, and
1778 different operating systems often have different ones installed.
1780 .index Solaris||DBM library for
1781 .index IRIX, DBM library for
1782 .index BSD, DBM library for
1783 .index Linux, DBM library for
1784 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1785 Linux distribution, the DBM configuration should happen automatically, and you
1786 may be able to ignore this section. Otherwise, you may have to learn more than
1787 you would like about DBM libraries from what follows.
1789 .index \*ndbm*\ DBM library
1790 Licensed versions of Unix normally contain a library of DBM functions operating
1791 via the \*ndbm*\ interface, and this is what Exim expects by default. Free
1792 versions of Unix seem to vary in what they contain as standard. In particular,
1793 some early versions of Linux have no default DBM library, and different
1794 distributors have chosen to bundle different libraries with their packaged
1795 versions. However, the more recent releases seem to have standardised on the
1796 Berkeley DB library.
1798 Different DBM libraries have different conventions for naming the files they
1799 use. When a program opens a file called \(dbmfile)\, there are four
1802 A traditional \*ndbm*\ implementation, such as that supplied as part of
1803 Solaris, operates on two files called \(dbmfile.dir)\ and \(dbmfile.pag)\.
1805 .index \*gdbm*\ DBM library
1806 The GNU library, \*gdbm*\, operates on a single file. If used via its \*ndbm*\
1807 compatibility interface it makes two different hard links to it with names
1808 \(dbmfile.dir)\ and \(dbmfile.pag)\, but if used via its native interface, the
1809 file name is used unmodified.
1811 .index Berkeley DB library
1812 The Berkeley DB package, if called via its \*ndbm*\ compatibility interface,
1813 operates on a single file called \(dbmfile.db)\, but otherwise looks to the
1814 programmer exactly the same as the traditional \*ndbm*\ implementation.
1816 If the Berkeley package is used in its native mode, it operates on a single
1817 file called \(dbmfile)\; the programmer's interface is somewhat different to
1818 the traditional \*ndbm*\ interface.
1820 To complicate things further, there are several very different versions of the
1821 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1822 2.$it{x} and 3.$it{x} were current for a while, but the latest versions are now
1823 numbered 4.$it{x}. Maintenance of some of the earlier releases has ceased. All
1824 versions of Berkeley DB can be obtained from
1826 \?http://www.sleepycat.com/?\
1829 .index \*tdb*\ DBM library
1830 Yet another DBM library, called \*tdb*\, has become available from
1832 \?http://download.sourceforge.net/tdb?\
1834 It has its own interface, and also operates on a single file.
1837 .index DBM||libraries, configuration for building
1838 Exim and its utilities can be compiled to use any of these interfaces. In order
1839 to use any version of the Berkeley DB package in native mode, you must set
1840 \\USE@_DB\\ in an appropriate configuration file (typically
1841 \(Local/Makefile)\). For example:
1845 Similarly, for gdbm you set \\USE@_GDBM\\, and for tdb you set \\USE@_TDB\\. An
1846 error is diagnosed if you set more than one of these.
1848 At the lowest level, the build-time configuration sets none of these options,
1849 thereby assuming an interface of type (1). However, some operating system
1850 configuration files (for example, those for the BSD operating systems and
1851 Linux) assume type (4) by setting \\USE@_DB\\ as their default, and the
1852 configuration files for Cygwin set \\USE@_GDBM\\. Anything you set in
1853 \(Local/Makefile)\, however, overrides these system defaults.
1855 As well as setting \\USE@_DB\\, \\USE@_GDBM\\, or \\USE@_TDB\\, it may also be
1856 necessary to set \\DBMLIB\\, to cause inclusion of the appropriate library, as
1857 in one of these lines:
1862 Settings like that will work if the DBM library is installed in the standard
1863 place. Sometimes it is not, and the library's header file may also not be in
1864 the default path. You may need to set \\INCLUDE\\ to specify where the header
1865 file is, and to specify the path to the library more fully in \\DBMLIB\\, as in
1868 INCLUDE=-I/usr/local/include/db-4.1
1869 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1872 There is further detailed discussion about the various DBM libraries in the
1873 file \(doc/dbm.discuss.txt)\ in the Exim distribution.
1876 .section Pre-building configuration
1877 .index building Exim||pre-building configuration
1878 .index configuration for building Exim
1879 .index \(Local/Makefile)\
1880 .index \(src/EDITME)\
1881 Before building Exim, a local configuration file that specifies options
1882 independent of any operating system has to be created with the name
1883 \(Local/Makefile)\. A template for this file is supplied as the file
1884 \(src/EDITME)\, and it contains full descriptions of all the option settings
1885 therein. These descriptions are therefore not repeated here. If you are
1886 building Exim for the first time, the simplest thing to do is to copy
1887 \(src/EDITME)\ to \(Local/Makefile)\, then read it and edit it appropriately.
1889 There are three settings that you must supply, because Exim will not build
1890 without them. They are the location of the run time configuration file
1891 (\\CONFIGURE@_FILE\\), the directory in which Exim binaries will be installed
1892 (\\BIN@_DIRECTORY\\), and the identity of the Exim user (\\EXIM@_USER\\ and
1893 maybe \\EXIM@_GROUP\\ as well). The value of \\CONFIGURE@_FILE\\ can in fact be
1894 a colon-separated list of file names; Exim uses the first of them that exists.
1896 There are a few other parameters that can be specified either at build time or
1897 at run time, to enable the same binary to be used on a number of different
1898 machines. However, if the locations of Exim's spool directory and log file
1899 directory (if not within the spool directory) are fixed, it is recommended that
1900 you specify them in \(Local/Makefile)\ instead of at run time, so that errors
1901 detected early in Exim's execution (such as a malformed configuration file) can
1904 .index \(Local/eximon.conf)\
1905 .index \(exim@_monitor/EDITME)\
1906 If you are going to build the Exim monitor, a similar configuration process is
1907 required. The file \(exim@_monitor/EDITME)\ must be edited appropriately for
1908 your installation and saved under the name \(Local/eximon.conf)\. If you are
1909 happy with the default settings described in \(exim@_monitor/EDITME)\,
1910 \(Local/eximon.conf)\ can be empty, but it must exist.
1912 This is all the configuration that is needed in straightforward cases for known
1913 operating systems. However, the building process is set up so that it is easy
1914 to override options that are set by default or by operating-system-specific
1915 configuration files, for example to change the name of the C compiler, which
1916 defaults to \gcc\. See section ~~SECToverride below for details of how to do
1920 .section Support for iconv()
1921 .index \*iconv()*\ support
1922 The contents of header lines in messages may be encoded according to the rules
1923 described RFC 2047. This makes it possible to transmit characters that are not
1924 in the ASCII character set, and to label them as being in a particular
1925 character set. When Exim is inspecting header lines by means of the \@$h@_\
1926 mechanism, it decodes them, and translates them into a specified character set
1927 (default ISO-8859-1). The translation is possible only if the operating system
1928 supports the \*iconv()*\ function.
1930 However, some of the operating systems that supply \*iconv()*\ do not support
1931 very many conversions. The GNU \libiconv\ library (available from
1932 \?http:/@/www.gnu.org/software/libiconv/?\) can be installed on such systems to
1933 remedy this deficiency, as well as on systems that do not supply \*iconv()*\ at
1934 all. After installing \libiconv\, you should add
1938 to your \(Local/Makefile)\ and rebuild Exim.
1941 .section Including TLS/SSL encryption support
1942 .rset SECTinctlsssl "~~chapter.~~section"
1943 .index TLS||including support for TLS
1944 .index encryption||including support for
1945 .index \\SUPPORT@_TLS\\
1946 .index OpenSSL||building Exim with
1947 .index GnuTLS||building Exim with
1948 Exim can be built to support encrypted SMTP connections, using the \\STARTTLS\\
1949 command as per RFC 2487. It can also support legacy clients that expect to
1950 start a TLS session immediately on connection to a non-standard port (see the
1951 \-tls-on-connect-\ command line option).
1953 If you want to build Exim with TLS support, you must first install either the
1954 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1957 If OpenSSL is installed, you should set
1960 TLS_LIBS=-lssl -lcrypto
1962 in \(Local/Makefile)\. You may also need to specify the locations of the
1963 OpenSSL library and include files. For example:
1966 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1967 TLS_INCLUDE=-I/usr/local/openssl/include/
1970 If GnuTLS is installed, you should set
1971 .index \\USE@_GNUTLS\\
1975 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1977 in \(Local/Makefile)\, and again you may need to specify the locations of the
1978 library and include files. For example:
1982 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1983 TLS_INCLUDE=-I/usr/gnu/include
1985 You do not need to set \\TLS@_INCLUDE\\ if the relevant directory is already
1986 specified in \\INCLUDE\\. Details of how to configure Exim to make use of TLS
1987 are given in chapter ~~CHAPTLS.
1991 .section Use of tcpwrappers
1992 .index tcpwrappers, building Exim to support
1993 .index \\USE@_TCP@_WRAPPERS\\
1994 Exim can be linked with the \*tcpwrappers*\ library in order to check incoming
1995 SMTP calls using the \*tcpwrappers*\ control files. This may be a convenient
1996 alternative to Exim's own checking facilities for installations that are
1997 already making use of \*tcpwrappers*\ for other purposes. To do this, you should
1998 set \\USE@_TCP@_WRAPPERS\\ in \(Local/Makefile)\, arrange for the file
1999 \(tcpd.h)\ to be available at compile time, and also ensure that the library
2000 \(libwrap.a)\ is available at link time, typically by including \-lwrap-\ in
2001 \\EXTRALIBS@_EXIM\\. For example, if \*tcpwrappers*\ is installed in
2002 \(/usr/local)\, you might have
2004 USE@_TCP@_WRAPPERS=yes
2005 CFLAGS=-O -I/usr/local/include
2007 EXTRALIBS@_EXIM=-L/usr/local/lib -lwrap
2009 in \(Local/Makefile)\. The name to use in the \*tcpwrappers*\ control files is
2010 `exim'. For example, the line
2012 exim : LOCAL 192.168.1. .friendly.domain.example
2014 in your \(/etc/hosts.allow)\ file allows connections from the local host, from
2015 the subnet 192.168.1.0/24, and from all hosts in \*friendly.domain.example*\.
2016 All other connections are denied. Consult the \*tcpwrappers*\ documentation for
2020 .section Including support for IPv6
2021 .index IPv6||including support for
2022 Exim contains code for use on systems that have IPv6 support. Setting
2023 \\HAVE@_IPV6=YES\\ in \(Local/Makefile)\ causes the IPv6 code to be included;
2024 it may also be necessary to set \\IPV6@_INCLUDE\\ and \\IPV6@_LIBS\\ on systems
2025 where the IPv6 support is not fully integrated into the normal include and
2028 IPv6 is still changing rapidly. Two different types of DNS record for handling
2029 IPv6 addresses have been defined. AAAA records are already in use, and are
2030 currently seen as the `mainstream', but another record type called A6 is being
2031 argued about. Its status is currently `experimental'. Exim has support for A6
2032 records, but this is included only if you set \\SUPPORT@_A6=YES\\ in
2036 .section The building process
2037 .index build directory
2038 Once \(Local/Makefile)\ (and \(Local/eximon.conf)\, if required) have been
2039 created, run \*make*\ at the top level. It determines the architecture and
2040 operating system types, and creates a build directory if one does not exist.
2041 For example, on a Sun system running Solaris 8, the directory
2042 \(build-SunOS5-5.8-sparc)\ is created.
2043 .index symbolic link||to source files
2044 Symbolic links to relevant source files are installed in the build directory.
2046 \**Warning**\: The \-j-\ (parallel) flag must not be used with \*make*\; the
2047 building process fails if it is set.
2049 If this is the first time \*make*\ has been run, it calls a script that builds
2050 a make file inside the build directory, using the configuration files from the
2051 \(Local)\ directory. The new make file is then passed to another instance of
2052 \*make*\. This does the real work, building a number of utility scripts, and
2053 then compiling and linking the binaries for the Exim monitor (if configured), a
2054 number of utility programs, and finally Exim itself. The command \*make
2055 makefile*\ can be used to force a rebuild of the make file in the build
2056 directory, should this ever be necessary.
2058 If you have problems building Exim, check for any comments there may be in the
2059 \(README)\ file concerning your operating system, and also take a look at the
2061 [(A HREF="FAQ.html")]
2067 where some common problems are covered.
2071 .section Overriding build-time options for Exim
2072 .index build-time options, overriding
2073 .rset SECToverride "~~chapter.~~section"
2074 The main make file that is created at the beginning of the building process
2075 consists of the concatenation of a number of files which set configuration
2076 values, followed by a fixed set of \*make*\ instructions. If a value is set
2077 more than once, the last setting overrides any previous ones. This provides a
2078 convenient way of overriding defaults. The files that are concatenated are, in
2081 \(OS/Makefile-Default)\
2082 \(OS/Makefile-)\<<ostype>>
2084 \(Local/Makefile-)\<<ostype>>
2085 \(Local/Makefile-)\<<archtype>>
2086 \(Local/Makefile-)\<<ostype>>-<<archtype>>
2087 \(OS/Makefile-Base)\
2089 .index \(Local/Makefile)\
2090 where <<ostype>> is the operating system type and <<archtype>> is the
2091 .index building Exim||operating system type
2092 .index building Exim||architecture type
2093 architecture type. \(Local/Makefile)\ is required to exist, and the building
2094 process fails if it is absent. The other three \(Local)\ files are optional,
2095 and are often not needed.
2097 The values used for <<ostype>> and <<archtype>> are obtained from scripts
2098 called \(scripts/os-type)\ and \(scripts/arch-type)\ respectively. If either of
2099 the environment variables \\EXIM@_OSTYPE\\ or \\EXIM@_ARCHTYPE\\ is set, their
2100 values are used, thereby providing a means of forcing particular settings.
2101 Otherwise, the scripts try to get values from the \uname\ command. If this
2102 fails, the shell variables \\OSTYPE\\ and \\ARCHTYPE\\ are inspected. A number
2103 of $it{ad hoc} transformations are then applied, to produce the standard names
2104 that Exim expects. You can run these scripts directly from the shell in order
2105 to find out what values are being used on your system.
2108 \(OS/Makefile-Default)\ contains comments about the variables that are set
2109 therein. Some (but not all) are mentioned below. If there is something that
2110 needs changing, review the contents of this file and the contents of the make
2111 file for your operating system (\(OS/Makefile-<<ostype>>)\) to see what the
2115 .index building Exim||overriding default settings
2116 If you need to change any of the values that are set in \(OS/Makefile-Default)\
2117 or in \(OS/Makefile-<<ostype>>)\, or to add any new definitions, you do not
2118 need to change the original files. Instead, you should make the changes by
2119 putting the new values in an appropriate \(Local)\ file. For example,
2120 .index Tru64-Unix build-time settings
2121 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2122 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2123 compiler is called \*cc*\ rather than \*gcc*\. Also, the compiler must be
2124 called with the option \-std1-\, to make it recognize some of the features of
2125 Standard C that Exim uses. (Most other compilers recognize Standard C by
2126 default.) To do this, you should create a file called \(Local/Makefile-OSF1)\
2127 containing the lines
2132 If you are compiling for just one operating system, it may be easier to put
2133 these lines directly into \(Local/Makefile)\.
2135 Keeping all your local configuration settings separate from the distributed
2136 files makes it easy to transfer them to new versions of Exim simply by copying
2137 the contents of the \(Local)\ directory.
2140 .index NIS lookup type||including support for
2141 .index NIS@+ lookup type||including support for
2142 .index LDAP||including support for
2143 .index lookup||inclusion in binary
2144 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2145 lookup, but not all systems have these components installed, so the default is
2146 not to include the relevant code in the binary. All the different kinds of file
2147 and database lookup that Exim supports are implemented as separate code modules
2148 which are included only if the relevant compile-time options are set. In the
2149 case of LDAP, NIS, and NIS+, the settings for \(Local/Makefile)\ are:
2155 and similar settings apply to the other lookup types. They are all listed in
2156 \(src/EDITME)\. In most cases the relevant include files and interface
2157 libraries need to be installed before compiling Exim.
2158 .index cdb||including support for
2159 However, in the case of cdb, which is included in the binary only if
2163 is set, the code is entirely contained within Exim, and no external include
2164 files or libraries are required. When a lookup type is not included in the
2165 binary, attempts to configure Exim to use it cause run time configuration
2168 .index Perl||including support for
2169 Exim can be linked with an embedded Perl interpreter, allowing Perl
2170 subroutines to be called during string expansion. To enable this facility,
2174 must be defined in \(Local/Makefile)\. Details of this facility are given in
2177 .index X11 libraries, location of
2178 The location of the X11 libraries is something that varies a lot between
2179 operating systems, and of course there are different versions of X11 to cope
2180 with. Exim itself makes no use of X11, but if you are compiling the Exim
2181 monitor, the X11 libraries must be available.
2182 The following three variables are set in \(OS/Makefile-Default)\:
2185 XINCLUDE=-I$(X11)/include
2186 XLFLAGS=-L$(X11)/lib
2188 These are overridden in some of the operating-system configuration files. For
2189 example, in \(OS/Makefile-SunOS5)\ there is
2192 XINCLUDE=-I$(X11)/include
2193 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2195 If you need to override the default setting for your operating system, place a
2196 definition of all three of these variables into your
2197 \(Local/Makefile-<<ostype>>)\ file.
2199 .index \\EXTRALIBS\\
2200 If you need to add any extra libraries to the link steps, these can be put in a
2201 variable called \\EXTRALIBS\\, which appears in all the link commands, but by
2202 default is not defined. In contrast, \\EXTRALIBS@_EXIM\\ is used only on the
2203 command for linking the main Exim binary, and not for any associated utilities.
2204 .index DBM||libraries, configuration for building
2205 There is also \\DBMLIB\\, which appears in the link commands for binaries that
2206 use DBM functions (see also section ~~SECTdb). Finally, there is
2207 \\EXTRALIBS@_EXIMON\\, which appears only in the link step for the Exim monitor
2208 binary, and which can be used, for example, to include additional X11
2211 .index configuration file||editing
2212 The make file copes with rebuilding Exim correctly if any of the configuration
2213 files are edited. However, if an optional configuration file is deleted, it is
2214 necessary to touch the associated non-optional file (that is, \(Local/Makefile)\
2215 or \(Local/eximon.conf)\) before rebuilding.
2217 .section OS-specific header files
2219 .index building Exim||OS-specific C header files
2220 The \(OS)\ directory contains a number of files with names of the form
2221 \(os.h-<<ostype>>)\. These are system-specific C header files that should not
2222 normally need to be changed. There is a list of macro settings that are
2223 recognized in the file \(OS/os.configuring)\, which should be consulted if you
2224 are porting Exim to a new operating system.
2227 .section Overriding build-time options for the monitor
2228 .index building Eximon||overriding default options
2229 A similar process is used for overriding things when building the Exim monitor,
2230 where the files that are involved are
2232 \(OS/eximon.conf-Default)\
2233 \(OS/eximon.conf-)\<<ostype>>
2234 \(Local/eximon.conf)\
2235 \(Local/eximon.conf-)\<<ostype>>
2236 \(Local/eximon.conf-)\<<archtype>>
2237 \(Local/eximon.conf-)\<<ostype>>-<<archtype>>
2239 .index \(Local/eximon.conf)\
2240 As with Exim itself, the final three files need not exist, and in this case the
2241 \(OS/eximon.conf-<<ostype>>)\ file is also optional. The default values in
2242 \(OS/eximon.conf-Default)\ can be overridden dynamically by setting environment
2243 variables of the same name, preceded by \\EXIMON@_\\. For example, setting
2244 \\EXIMON@_LOG@_DEPTH\\ in the environment overrides the value of
2245 \\LOG@_DEPTH\\ at run time.
2249 .section Installing Exim binaries and scripts
2250 .index installing Exim
2251 .index \\BIN@_DIRECTORY\\
2252 The command \*make install*\ runs the \*exim@_install*\ script with no
2253 arguments. The script copies binaries and utility scripts into the directory
2254 whose name is specified by the \\BIN@_DIRECTORY\\ setting in
2257 Exim's run time configuration file is named by the \\CONFIGURE@_FILE\\ setting
2258 .index \\CONFIGURE@_FILE\\
2259 in \(Local/Makefile)\. If this names a single file, and the file does not
2260 exist, the default configuration file \(src/configure.default)\ is copied there
2261 by the installation script. If a run time configuration file already exists, it
2262 is left alone. If \\CONFIGURE@_FILE\\ is a colon-separated list, naming several
2263 alternative files, no default is installed.
2265 .index system aliases file
2266 .index \(/etc/aliases)\
2267 One change is made to the default configuration file when it is installed: the
2268 default configuration contains a router that references a system aliases file.
2269 The path to this file is set to the value specified by
2270 \\SYSTEM@_ALIASES@_FILE\\ in \(Local/Makefile)\ (\(/etc/aliases)\ by default).
2271 If the system aliases file does not exist, the installation script creates it,
2272 and outputs a comment to the user.
2274 The created file contains no aliases, but it does contain comments about the
2275 aliases a site should normally have. Mail aliases have traditionally been
2276 kept in \(/etc/aliases)\. However, some operating systems are now using
2277 \(/etc/mail/aliases)\. You should check if yours is one of these, and change
2278 Exim's configuration if necessary.
2280 The default configuration uses the local host's name as the only local domain,
2281 and is set up to do local deliveries into the shared directory \(/var/mail)\,
2282 running as the local user. System aliases and \(.forward)\ files in users' home
2283 directories are supported, but no NIS or NIS+ support is configured. Domains
2284 other than the name of the local host are routed using the DNS, with delivery
2287 The install script copies files only if they are newer than the files they are
2288 going to replace. The Exim binary is required to be owned by root and have the
2290 .index setuid||installing Exim with
2291 for normal configurations. Therefore, you must run \*make install*\ as root so
2292 that it can set up the Exim binary in this way. However, in some special
2293 situations (for example, if a host is doing no local deliveries) it may be
2294 possible to run Exim without making the binary setuid root (see chapter
2295 ~~CHAPsecurity for details).
2297 It is possible to install Exim for special purposes (such as building a binary
2298 distribution) in a private part of the file system. You can do this by a
2301 make DESTDIR=/some/directory/ install
2303 This has the effect of pre-pending the specified directory to all the file
2304 paths, except the name of the system aliases file that appears in the default
2305 configuration. (If a default alias file is created, its name \*is*\ modified.)
2306 For backwards compatibility, \\ROOT\\ is used if \\DESTDIR\\ is not set,
2307 but this usage is deprecated.
2309 .index installing Exim||what is not installed
2310 Running \*make install*\ does not copy the Exim 4 conversion script
2311 \*convert4r4*\, or the \*pcretest*\ test program. You will probably run the
2312 first of these only once (if you are upgrading from Exim 3), and the second
2313 isn't really part of Exim. None of the documentation files in the \(doc)\
2314 directory are copied, except for the info files when you have set
2315 \\INFO@_DIRECTORY\\, as described in section ~~SECTinsinfdoc below.
2317 For the utility programs, old versions are renamed by adding the suffix \(.O)\
2318 to their names. The Exim binary itself, however, is handled differently. It is
2319 installed under a name that includes the version number and the compile number,
2320 for example \(exim-~~version-1)\. The script then arranges for a symbolic link
2321 called \(exim)\ to point to the binary. If you are updating a previous version
2322 of Exim, the script takes care to ensure that the name \(exim)\ is never absent
2323 from the directory (as seen by other processes).
2325 .index installing Exim||testing the script
2326 If you want to see what the \*make install*\ will do before running it for
2327 real, you can pass the \-n-\ option to the installation script by this command:
2329 make INSTALL_ARG=-n install
2331 The contents of the variable \\INSTALL@_ARG\\ are passed to the installation
2332 script. You do not need to be root to run this test. Alternatively, you can run
2333 the installation script directly, but this must be from within the build
2334 directory. For example, from the top-level Exim directory you could use this
2337 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim@_install -n)
2340 .index installing Exim||install script options
2341 There are two other options that can be supplied to the installation script.
2343 \-no@_chown-\ bypasses the call to change the owner of the installed binary
2344 to root, and the call to make it a setuid binary.
2346 \-no@_symlink-\ bypasses the setting up of the symbolic link \(exim)\ to the
2349 \\INSTALL@_ARG\\ can be used to pass these options to the script. For example:
2351 make INSTALL_ARG=-no_symlink install
2354 The installation script can also be given arguments specifying which files are
2355 to be copied. For example, to install just the Exim binary, and nothing else,
2356 without creating the symbolic link, you could use:
2358 make INSTALL_ARG='-no_symlink exim' install
2362 .section Installing info documentation
2363 .rset SECTinsinfdoc "~~chapter.~~section"
2364 .index installing Exim||\*info*\ documentation
2365 Not all systems use the GNU \*info*\ system for documentation, and for this
2366 reason, the Texinfo source of Exim's documentation is not included in the main
2367 distribution. Instead it is available separately from the ftp site (see section
2370 If you have defined \\INFO@_DIRECTORY\\ in \(Local/Makefile)\ and the Texinfo
2371 source of the documentation is found in the source tree, running \*make
2372 install*\ automatically builds the info files and installs them.
2375 .section Setting up the spool directory
2376 .index spool directory||creating
2377 When it starts up, Exim tries to create its spool directory if it does not
2378 exist. The Exim uid and gid are used for the owner and group of the spool
2379 directory. Sub-directories are automatically created in the spool directory as
2385 .index testing||installation
2386 Having installed Exim, you can check that the run time configuration file is
2387 syntactically valid by running the following command, which assumes that the
2388 Exim binary directory is within your \\PATH\\ environment variable:
2392 If there are any errors in the configuration file, Exim outputs error messages.
2393 Otherwise it outputs the version number and build date,
2394 the DBM library that is being used, and information about which drivers and
2395 other optional code modules are included in the binary.
2396 Some simple routing tests can be done by using the address testing option. For
2399 exim -bt <<local username>>
2401 should verify that it recognizes a local mailbox, and
2403 exim -bt <<remote address>>
2405 a remote one. Then try getting it to deliver mail, both locally and remotely.
2406 This can be done by passing messages directly to Exim, without going through a
2407 user agent. For example:
2409 exim -v postmaster@@your.domain.example
2410 From: user@@your.domain.example
2411 To: postmaster@@your.domain.example
2412 Subject: Testing Exim
2414 This is a test message.
2417 The \-v-\ option causes Exim to output some verification of what it is doing.
2418 In this case you should see copies of three log lines, one for the message's
2419 arrival, one for its delivery, and one containing `Completed'.
2421 .index delivery||problems with
2422 If you encounter problems, look at Exim's log files (\*mainlog*\ and
2423 \*paniclog*\) to see if there is any relevant information there. Another source
2424 of information is running Exim with debugging turned on, by specifying the
2425 \-d-\ option. If a message is stuck on Exim's spool, you can force a delivery
2426 with debugging turned on by a command of the form
2428 exim -d -M <<message-id>>
2430 You must be root or an `admin user' in order to do this. The \-d-\ option
2431 produces rather a lot of output, but you can cut this down to specific areas.
2432 For example, if you use \-d-all+route-\ only the debugging information relevant
2433 to routing is included. (See the \-d-\ option in chapter ~~CHAPcommandline for
2438 One specific problem that has shown up on some sites is the inability to do
2439 local deliveries into a shared mailbox directory, because it does not have the
2440 `sticky bit' set on it. By default, Exim tries to create a lock file before
2441 writing to a mailbox file, and if it cannot create the lock file, the delivery
2442 is deferred. You can get round this either by setting the `sticky bit' on the
2443 directory, or by setting a specific group for local deliveries and allowing
2444 that group to create files in the directory (see the comments above the
2445 \%local@_delivery%\ transport in the default configuration file). Another
2446 approach is to configure Exim not to use lock files, but just to rely on
2447 \*fcntl()*\ locking instead. However, you should do this only if all user
2448 agents also use \*fcntl()*\ locking. For further discussion of locking issues,
2449 see chapter ~~CHAPappendfile.
2451 One thing that cannot be tested on a system that is already running an MTA is
2452 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2453 \-oX-\ option can be used to run an Exim daemon that listens on some other
2454 port, or \*inetd*\ can be used to do this. The \-bh-\ option and the
2455 \*exim@_checkaccess*\ utility can be used to check out policy controls on
2458 Testing a new version on a system that is already running Exim can most easily
2459 be done by building a binary with a different \\CONFIGURE@_FILE\\ setting. From
2460 within the run time configuration, all other file and directory names
2461 that Exim uses can be altered, in order to keep it entirely clear of the
2464 .section Replacing another MTA with Exim
2465 .index replacing another MTA
2466 Building and installing Exim for the first time does not of itself put it in
2467 general use. The name by which the system's MTA is called by mail user agents
2468 is either \(/usr/sbin/sendmail)\, or \(/usr/lib/sendmail)\ (depending on the
2469 operating system), and it is necessary to make this name point to the \*exim*\
2470 binary in order to get the user agents to pass messages to Exim. This is
2471 normally done by renaming any existing file and making \(/usr/sbin/sendmail)\
2472 or \(/usr/lib/sendmail)\
2473 .index symbolic link||to \*exim*\ binary
2474 a symbolic link to the \*exim*\ binary. It is a good idea to remove any setuid
2475 privilege and executable status from the old MTA. It is then necessary to stop
2476 and restart the mailer daemon, if one is running.
2478 .index FreeBSD, MTA indirection
2479 .index \(/etc/mail/mailer.conf)\
2480 Some operating systems have introduced alternative ways of switching MTAs. For
2481 example, if you are running FreeBSD, you need to edit the file
2482 \(/etc/mail/mailer.conf)\ instead of setting up a symbolic link as just
2483 described. A typical example of the contents of this file for running Exim is
2486 sendmail /usr/exim/bin/exim
2487 send-mail /usr/exim/bin/exim
2488 mailq /usr/exim/bin/exim -bp
2489 newaliases /usr/bin/true
2492 Once you have set up the symbolic link, or edited \(/etc/mail/mailer.conf)\,
2493 your Exim installation is `live'. Check it by sending a message from your
2494 favourite user agent.
2496 You should consider what to tell your users about the change of MTA. Exim may
2497 have different capabilities to what was previously running, and there are
2498 various operational differences such as the text of messages produced by
2499 command line options and in bounce messages. If you allow your users to make
2500 use of Exim's filtering capabilities, you should make the document entitled
2502 [(A HREF="filter.html")]
2504 \*Exim's interface to mail filtering*\
2511 .section Upgrading Exim
2512 .index upgrading Exim
2513 If you are already running Exim on your host, building and installing a new
2514 version automatically makes it available to MUAs, or any other programs that
2515 call the MTA directly. However, if you are running an Exim daemon, you do need
2516 to send it a HUP signal, to make it re-exec itself, and thereby pick up the new
2517 binary. You do not need to stop processing mail in order to install a new
2521 .section Stopping the Exim daemon on Solaris
2522 .index Solaris||stopping Exim on
2523 The standard command for stopping the mailer daemon on Solaris is
2525 /etc/init.d/sendmail stop
2527 If \(/usr/lib/sendmail)\ has been turned into a symbolic link, this script
2528 fails to stop Exim because it uses the command \*ps -e*\ and greps the output
2529 for the text `sendmail'; this is not present because the actual program name
2530 (that is, `exim') is given by the \*ps*\ command with these options. A solution
2531 is to replace the line that finds the process id with something like
2533 pid=`cat /var/spool/exim/exim-daemon.pid`
2535 to obtain the daemon's pid directly from the file that Exim saves it in.
2537 Note, however, that stopping the daemon does not `stop Exim'. Messages can
2538 still be received from local processes, and if automatic delivery is configured
2539 (the normal case), deliveries will still occur.
2546 . ============================================================================
2547 .chapter The Exim command line
2548 .set runningfoot "command line"
2549 .rset CHAPcommandline ~~chapter
2550 .index command line||options
2551 .index options||command line
2553 Exim's command line takes the standard Unix form of a sequence of options,
2554 each starting with a hyphen character, followed by a number of arguments. The
2555 options are compatible with the main options of Sendmail, and there are also
2556 some additional options, some of which are compatible with Smail 3. Certain
2557 combinations of options do not make sense, and provoke an error if used.
2558 The form of the arguments depends on which options are set.
2560 .section Setting options by program name
2562 If Exim is called under the name \*mailq*\, it behaves as if the option \-bp-\
2563 were present before any other options.
2564 The \-bp-\ option requests a listing of the contents of the mail queue on the
2566 This feature is for compatibility with some systems that contain a command of
2567 that name in one of the standard libraries, symbolically linked to
2568 \(/usr/sbin/sendmail)\ or \(/usr/lib/sendmail)\.
2571 If Exim is called under the name \*rsmtp*\ it behaves as if the option \-bS-\
2572 were present before any other options, for compatibility with Smail. The \-bS-\
2573 option is used for reading in a number of messages in batched SMTP format.
2576 If Exim is called under the name \*rmail*\ it behaves as if the \-i-\ and
2577 \-oee-\ options were present before any other options, for compatibility with
2578 Smail. The name \*rmail*\ is used as an interface by some UUCP systems.
2582 If Exim is called under the name \*runq*\ it behaves as if the option \-q-\ were
2583 present before any other options, for compatibility with Smail. The \-q-\
2584 option causes a single queue runner process to be started.
2586 .index \*newaliases*\
2587 .index alias file||building
2588 .index Sendmail compatibility||calling Exim as \*newaliases*\
2589 If Exim is called under the name \*newaliases*\ it behaves as if the option
2590 \-bi-\ were present before any other options, for compatibility with Sendmail.
2591 This option is used for rebuilding Sendmail's alias file. Exim does not have
2592 the concept of a single alias file, but can be configured to run a given
2593 command if called with the \-bi-\ option.
2595 .section Trusted and admin users
2596 .rset SECTtrustedadmin "~~chapter.~~section"
2597 Some Exim options are available only to \*trusted users*\ and others are
2598 available only to \*admin users*\. In the description below, the phrases `Exim
2599 user' and `Exim group' mean the user and group defined by \\EXIM@_USER\\ and
2600 \\EXIM@_GROUP\\ in \(Local/Makefile)\ or set by the \exim@_user\ and
2601 \exim@_group\ options. These do not necessarily have to use the name `exim'.
2604 .index trusted user||definition of
2605 .index user||trusted, definition of
2606 The trusted users are root, the Exim user, any user listed in the
2607 \trusted@_users\ configuration option, and any user whose current group or any
2608 supplementary group is one of those listed in the \trusted@_groups\
2609 configuration option. Note that the Exim group is not automatically trusted.
2612 .index envelope sender
2613 Trusted users are always permitted to use the \-f-\ option or a leading `From '
2614 line to specify the envelope sender of a message that is passed to Exim through
2615 the local interface (see the \-bm-\ and \-f-\ options below). See the
2616 \untrusted@_set@_sender\ option for a way of permitting non-trusted users to
2617 set envelope senders.
2618 .index ::From:: header line
2619 .index ::Sender:: header line
2620 For a trusted user, there is never any check on the contents of the ::From::
2621 header line, and a ::Sender:: line is never added. Furthermore, any existing
2622 ::Sender:: line in incoming local (non-TCP/IP) messages is not removed.
2624 Trusted users may also specify a host name, host address, interface address,
2625 protocol name, ident value, and authentication data when submitting a message
2626 locally. Thus, they are able to insert messages into Exim's queue locally that
2627 have the characteristics of messages received from a remote host. Untrusted
2628 users may in some circumstances use \-f-\, but can never set the other values
2629 that are available to trusted users.
2631 .index user||admin, definition of
2632 .index admin user||definition of
2633 The admin users are root, the Exim user, and any user that is a member of the
2634 Exim group or of any group listed in the \admin@_groups\ configuration option.
2635 The current group does not have to be one of these groups.
2637 Admin users are permitted to list the queue, and to carry out certain
2638 operations on messages, for example, to force delivery failures. It is also
2639 necessary to be an admin user in order to see the full information provided by
2640 the Exim monitor, and full debugging output.
2642 By default, the use of the \-M-\, \-q-\, \-R-\, and \-S-\ options to cause Exim
2643 to attempt delivery of messages on its queue is restricted to admin users.
2644 However, this restriction can be relaxed by setting the \prod@_requires@_admin\
2645 option false (that is, specifying \no@_prod@_requires@_admin\).
2647 Similarly, the use of the \-bp-\ option to list all the messages in the queue
2648 is restricted to admin users unless \queue@_list@_requires@_admin\ is set
2652 \**Warning**\: If you configure your system so that admin users are able to
2653 edit Exim's configuration file, you are giving those users an easy way of
2654 getting root. There is further discussion of this issue at the start of chapter
2659 .section Command line options
2660 The command options are described in alphabetical order below.
2665 .index options||command line, terminating
2666 This is a pseudo-option whose only purpose is to terminate the options and
2667 therefore to cause subsequent command line items to be treated as arguments
2668 rather than options, even if they begin with hyphens.
2671 This option causes Exim to output a few sentences stating what it is.
2672 The same output is generated if the Exim binary is called with no options and
2676 .index 8-bit characters
2677 .index Sendmail compatibility||8-bit characters
2678 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2679 clean; it ignores this option.
2683 .index SMTP listener
2685 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2686 the \-bd-\ option is combined with the \-q-\<<time>> option, to specify that
2687 the daemon should also initiate periodic queue runs.
2689 The \-bd-\ option can be used only by an admin user. If either of the \-d-\
2690 (debugging) or \-v-\ (verifying) options are set, the daemon does not
2691 disconnect from the controlling terminal. When running this way, it can be
2692 stopped by pressing ctrl-C.
2694 By default, Exim listens for incoming connections to the standard SMTP port on
2695 all the host's running interfaces. However, it is possible to listen on other
2696 ports, on multiple ports, and only on specific interfaces. Chapter
2697 ~~CHAPinterfaces contains a description of the options that control this.
2699 .index daemon||process id (pid)
2700 .index pid (process id)||of daemon
2701 When a listening daemon is started without the use of \-oX-\ (that is, without
2702 overriding the normal configuration), it writes its process id to a file called
2703 \(exim-daemon.pid)\ in Exim's spool directory. This location can be overridden
2704 by setting \\PID@_FILE@_PATH\\ in \(Local/Makefile)\. The file is written while
2705 Exim is still running as root.
2707 When \-oX-\ is used on the command line to start a listening daemon, the
2708 process id is not written to the normal pid file path. However, \-oP-\ can be
2709 used to specify a path on the command line if a pid file is required.
2712 The \\SIGHUP\\ signal can be used to cause the daemon to re-exec itself. This
2713 should be done whenever Exim's configuration file, or any file that is
2714 incorporated into it by means of the \.include\ facility, is changed, and also
2715 whenever a new version of Exim is installed. It is not necessary to do this
2716 when other files that are referenced from the configuration (for example, alias
2717 files) are changed, because these are reread each time they are used.
2720 This option has the same effect as \-bd-\ except that it never disconnects from
2721 the controlling terminal, even when no debugging is specified.
2724 .index testing||string expansion
2725 .index expansion||testing
2726 Run Exim in expansion testing mode. Exim discards its root privilege, to
2727 prevent ordinary users from using this mode to read otherwise inaccessible
2728 files. If no arguments are given, Exim runs interactively, prompting for lines
2729 of data. Long expressions can be split over several lines by using backslash
2731 As in Exim's run time configuration, whitespace at the start of continuation
2734 Each argument or data line is passed through the string expansion mechanism,
2735 and the result is output. Variable values from the configuration file (for
2736 example, \$qualify@_domain$\) are available, but no message-specific values
2737 (such as \$domain$\) are set, because no message is being processed.
2739 .option bF #<<filename>>
2740 .index system filter||testing
2741 .index testing||system filter
2742 This option is the same as \-bf-\ except that it assumes that the filter being
2743 tested is a system filter. The additional commands that are available only in
2744 system filters are recognized.
2746 .option bf #<<filename>>
2747 .index filter||testing
2748 .index testing||filter file
2749 .index forward file||testing
2750 .index testing||forward file
2751 .index Sieve filter||testing
2752 This option runs Exim in filter testing mode; the file is the filter file to be
2753 tested, and a test message must be supplied on the standard input. If there are
2754 no message-dependent tests in the filter, an empty file can be supplied. If a
2755 system filter file is being tested, \-bF-\ should be used instead of \-bf-\. If
2756 the test file does not begin with
2757 one of the special lines
2762 it is taken to be a normal \(.forward)\ file, and is tested for validity under
2763 that interpretation. See sections ~~SECTitenonfilred to ~~SECTspecitredli for a
2764 description of the possible contents of non-filter redirection lists.
2766 The result of an Exim command that uses \-bf-\, provided no errors are
2767 detected, is a list of the actions that Exim would try to take if presented
2768 with the message for real. More details of filter testing are given in the
2769 separate document entitled \*Exim's interfaces to mail filtering*\.
2772 .index envelope sender
2773 .index \-f-\ option||for filter testing
2774 When testing a filter file, the envelope sender can be set by the \-f-\ option,
2775 or by a `From ' line at the start of the test message. Various parameters that
2776 would normally be taken from the envelope recipient address of the message can
2777 be set by means of additional command line options. These are:
2784 . The odd alignment here gets it lined up in the man page.
2785 \-bfd-\ $t <<domain>> $t $rm{default is the qualify domain}
2786 \-bfl-\ $t <<local@_part>> $t $rm{default is the logged in user}
2787 \-bfp-\ $t <<local@_part@_prefix>> $t $rm{default is null}
2788 \-bfs-\ $t <<local@_part@_suffix>> $t $rm{default is null}
2790 The local part should always be set to the incoming address with any prefix or
2791 suffix stripped, because that is how it appears to the filter when a message is
2792 actually being delivered.
2794 .option bh #<<IP address>>
2795 .index testing||incoming SMTP
2796 .index SMTP||testing incoming
2797 .index testing||relay control
2798 .index relaying||testing configuration
2799 .index policy control||testing
2800 .index 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 Comments as to what is going on are written to the standard error file. These
2809 include lines beginning with `LOG' for anything that would have been logged.
2810 This facility is provided for testing configuration options for incoming
2811 messages, to make sure they implement the required policy. For example, you can
2812 test your relay controls using \-bh-\.
2815 \**Warning 1**\: You cannot test features of the configuration that rely on
2816 ident (RFC 1413) callouts. These cannot be done when testing using
2817 \-bh-\ because there is no incoming SMTP connection.
2819 \**Warning 2**\: Address verification callouts (see section ~~SECTcallver) are
2820 also skipped when testing using \-bh-\. If you want these callouts to occur,
2821 use \-bhc-\ instead.
2823 Messages supplied during the testing session are discarded, and nothing is
2824 written to any of the real log files. There may be pauses when DNS (and other)
2825 lookups are taking place, and of course these may time out. The \-oMi-\ option
2826 can be used to specify a specific IP interface and port if this is important.
2828 The \*exim@_checkaccess*\ utility is a `packaged' version of \-bh-\ whose
2829 output just states whether a given recipient address from a given host is
2830 acceptable or not. See section ~~SECTcheckaccess.
2832 .option bhc #<<IP address>>
2833 This option operates in the same way as \-bh-\, except that address
2834 verification callouts are performed if required. This includes consulting and
2835 updating the callout cache database.
2838 .index alias file||building
2839 .index building alias file
2840 .index Sendmail compatibility||\-bi-\ option
2841 Sendmail interprets the \-bi-\ option as a request to rebuild its alias file.
2842 Exim does not have the concept of a single alias file, and so it cannot mimic
2843 this behaviour. However, calls to \(/usr/lib/sendmail)\ with the \-bi-\ option
2844 tend to appear in various scripts such as NIS make files, so the option must be
2847 If \-bi-\ is encountered, the command specified by the \bi@_command\
2848 configuration option is run, under the uid and gid of the caller of Exim. If
2849 the \-oA-\ option is used, its value is passed to the command as an argument.
2850 The command set by \bi@_command\ may not contain arguments. The command can use
2851 the \*exim@_dbmbuild*\ utility, or some other means, to rebuild alias files if
2852 this is required. If the \bi@_command\ option is not set, calling Exim with
2856 .index local message reception
2857 This option runs an Exim receiving process that accepts an incoming,
2858 locally-generated message on the current input. The recipients are given as the
2859 command arguments (except when \-t-\ is also present -- see below). Each
2860 argument can be a comma-separated list of RFC 2822 addresses. This is the
2861 default option for selecting the overall action of an Exim call; it is assumed
2862 if no other conflicting option is present.
2864 If any addresses in the message are unqualified (have no domain), they are
2865 qualified by the values of the \qualify@_domain\ or \qualify@_recipient\
2866 options, as appropriate. The \-bnq-\ option (see below) provides a way of
2867 suppressing this for special cases.
2869 Policy checks on the contents of local messages can be enforced by means of the
2870 non-SMTP ACL. See chapter ~~CHAPACL for details.
2871 .index return code||for \-bm-\
2872 The return code is zero if the message is successfully accepted. Otherwise, the
2873 action is controlled by the \-oe$it{x}-\ option setting -- see below.
2875 .index message||format
2876 .index format||message
2878 .index UUCP||`From' line
2879 .index Sendmail compatibility||`From' line
2880 The format of the message must be as defined in RFC 2822, except that, for
2881 compatibility with Sendmail and Smail, a line in one of the forms
2883 From sender Fri Jan 5 12:55 GMT 1997
2884 From sender Fri, 5 Jan 97 12:55:01
2886 (with the weekday optional, and possibly with additional text after the date)
2887 is permitted to appear at the start of the message. There appears to be no
2888 authoritative specification of the format of this line. Exim recognizes it by
2889 matching against the regular expression defined by the \uucp@_from@_pattern\
2890 option, which can be changed if necessary.
2891 .index \-f-\ option||overriding `From' line
2892 The specified sender is treated as if it were given as the argument to the
2893 \-f-\ option, but if a \-f-\ option is also present, its argument is used in
2894 preference to the address taken from the message. The caller of Exim must be a
2895 trusted user for the sender of a message to be set in this way.
2898 .index address||qualification, suppressing
2899 By default, Exim automatically qualifies unqualified addresses (those
2900 without domains) that appear in messages that are submitted locally (that
2901 is, not over TCP/IP). This qualification applies both to addresses in
2902 envelopes, and addresses in header lines. Sender addresses are qualified using
2903 \qualify@_domain\, and recipient addresses using \qualify@_recipient\ (which
2904 defaults to the value of \qualify@_domain\).
2906 Sometimes, qualification is not wanted. For example, if \-bS-\ (batch SMTP) is
2907 being used to re-submit messages that originally came from remote hosts after
2908 content scanning, you probably do not want to qualify unqualified addresses in
2909 header lines. (Such lines will be present only if you have not enabled a header
2910 syntax check in the appropriate ACL.)
2912 The \-bnq-\ option suppresses all qualification of unqualified addresses in
2913 messages that originate on the local host. When this is used, unqualified
2914 addresses in the envelope provoke errors (causing message rejection) and
2915 unqualified addresses in header lines are left alone.
2919 .index configuration options, extracting
2920 .index options||configuration, extracting
2921 If this option is given with no arguments, it causes the values of all Exim's
2922 main configuration options to be written to the standard output. The values
2923 of one or more specific options can be requested by giving their names as
2924 arguments, for example:
2926 exim -bP qualify@_domain hold@_domains
2928 However, any option setting that is preceded by the word `hide' in the
2929 configuration file is not shown in full, except to an admin user. For other
2930 users, the output is as in this example:
2932 mysql_servers = <value not displayable>
2934 If \configure@_file\ is given as an argument, the name of the run time
2935 configuration file is output.
2936 If a list of configuration files was supplied, the value that is output here
2937 is the name of the file that was actually used.
2939 .index daemon||process id (pid)
2940 .index pid (process id)||of daemon
2941 If \log__file__path\ or \pid@_file@_path\ are given, the names of the
2942 directories where log files and daemon pid files are written are output,
2943 respectively. If these values are unset, log files are written in a
2944 sub-directory of the spool directory called \log\, and the pid file is written
2945 directly into the spool directory.
2947 If \-bP-\ is followed by a name preceded by \"+"\, for example,
2949 exim -bP +local_domains
2951 it searches for a matching named list of any type (domain, host, address, or
2952 local part) and outputs what it finds.
2954 .index options||router, extracting
2955 .index options||transport, extracting
2956 If one of the words \router\, \transport\, or \authenticator\ is given,
2957 followed by the name of an appropriate driver instance, the option settings for
2958 that driver are output. For example:
2960 exim -bP transport local@_delivery
2962 The generic driver options are output first, followed by the driver's private
2963 options. A list of the names of drivers of a particular type can be obtained by
2964 using one of the words \router@_list\, \transport@_list\, or
2965 \authenticator@_list\, and a complete list of all drivers with their option
2966 settings can be obtained by using \routers\, \transports\, or \authenticators\.
2970 .index queue||listing messages on
2971 .index listing||messages on the queue
2972 This option requests a listing of the contents of the mail queue on the
2973 standard output. If the \-bp-\ option is followed by a list of message ids,
2974 just those messages are listed. By default, this option can be used only by an
2975 admin user. However, the \queue__list__requires__admin\ option can be set false
2976 to allow any user to see the queue.
2978 Each message on the queue is displayed as in the following example:
2980 25m 2.9K 0t5C6f-0000c8-00 <alice@@wonderland.fict.example>
2981 red.king@@looking-glass.fict.example
2984 .index message||size in queue listing
2985 .index size||of message
2986 The first line contains the length of time the message has been on the queue
2987 (in this case 25 minutes), the size of the message (2.9K), the unique local
2988 identifier for the message, and the message sender, as contained in the
2989 envelope. For bounce messages, the sender address is empty, and appears as
2990 `<>'. If the message was submitted locally by an untrusted user who overrode
2991 the default sender address, the user's login name is shown in parentheses
2992 before the sender address.
2993 .index frozen messages||in queue listing
2994 If the message is frozen (attempts to deliver it are suspended) then the text
2995 `$*$$*$$*$ frozen $*$$*$$*$' is displayed at the end of this line.
2997 The recipients of the message (taken from the envelope, not the headers) are
2998 displayed on subsequent lines. Those addresses to which the message has already
2999 been delivered are marked with the letter D. If an original address gets
3000 expanded into several addresses via an alias or forward file, the original is
3001 displayed with a D only when deliveries for all of its child addresses are
3006 This option operates like \-bp-\, but in addition it shows delivered addresses
3007 that were generated from the original top level address(es) in each message by
3008 alias or forwarding operations. These addresses are flagged with `+D' instead
3013 .index queue||count of messages on
3014 This option counts the number of messages on the queue, and writes the total
3015 to the standard output. It is restricted to admin users, unless
3016 \queue__list__requires__admin\ is set false.
3020 This option operates like \-bp-\, but the output is not sorted into
3021 chronological order of message arrival. This can speed it up when there are
3022 lots of messages on the queue, and is particularly useful if the output is
3023 going to be post-processed in a way that doesn't need the sorting.
3026 This option is a combination of \-bpr-\ and \-bpa-\.
3029 This option is a combination of \-bpr-\ and \-bpu-\.
3033 This option operates like \-bp-\ but shows only undelivered top-level addresses
3034 for each message displayed. Addresses generated by aliasing or forwarding are
3035 not shown, unless the message was deferred after processing by a router with
3036 the \one@_time\ option set.
3040 .index testing||retry configuration
3041 .index retry||configuration testing
3042 This option is for testing retry rules, and it must be followed by up to three
3043 arguments. It causes Exim to look for a retry rule that matches the values
3044 and to write it to the standard output. For example:
3046 exim -brt bach.comp.mus.example
3047 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3049 See chapter ~~CHAPretry for a description of Exim's retry rules. The first
3050 argument, which is required, can be a complete address in the form
3051 \*local@_part@@domain*\, or it can be just a domain name. The second argument is
3052 an optional second domain name; if no retry rule is found for the first
3053 argument, the second is tried. This ties in with Exim's behaviour when looking
3054 for retry rules for remote hosts -- if no rule is found that matches the host,
3055 one that matches the mail domain is sought. The final argument is the name of a
3056 specific delivery error, as used in setting up retry rules, for example
3060 .index testing||rewriting
3061 .index rewriting||testing
3062 This option is for testing address rewriting rules, and it must be followed by
3063 a single argument, consisting of either a local part without a domain, or a
3064 complete address with a fully qualified domain. Exim outputs how this address
3065 would be rewritten for each possible place it might appear. See chapter
3066 ~~CHAPrewrite for further details.
3069 .index SMTP||batched incoming
3070 .index batched SMTP input
3071 This option is used for batched SMTP input, which is an alternative interface
3072 for non-interactive local message submission. A number of messages can be
3073 submitted in a single run. However, despite its name, this is not really SMTP
3074 input. Exim reads each message's envelope from SMTP commands on the standard
3075 input, but generates no responses. If the caller is trusted, or
3076 \untrusted@_set@_sender\ is set, the senders in the SMTP \\MAIL\\ commands are
3077 believed; otherwise the sender is always the caller of Exim.
3079 The message itself is read from the standard input, in SMTP format (leading
3080 dots doubled), terminated by a line containing just a single dot. An error is
3081 provoked if the terminating dot is missing. A further message may then follow.
3083 As for other local message submissions, the contents of incoming batch SMTP
3084 messages can be checked using the non-SMTP ACL (see chapter ~~CHAPACL).
3085 Unqualified addresses are automatically qualified using \qualify@_domain\ and
3086 \qualify@_recipient\, as appropriate, unless the \-bnq-\ option is used.
3088 Some other SMTP commands are recognized in the input. \\HELO\\ and \\EHLO\\ act
3089 as \\RSET\\; \\VRFY\\, \\EXPN\\, \\ETRN\\, and \\HELP\\ act as \\NOOP\\;
3090 \\QUIT\\ quits, ignoring the rest of the standard input.
3092 If any error is encountered, reports are written to the standard output and
3093 error streams, and Exim gives up immediately.
3094 .index return code||for \-bS-\
3095 The return code is 0 if no error was detected; it is 1 if one or more messages
3096 were accepted before the error was detected; otherwise it is 2.
3098 More details of input using batched SMTP are given in section
3099 ~~SECTincomingbatchedSMTP.
3102 .index SMTP||local input
3103 .index local SMTP input
3104 This option causes Exim to accept one or more messages by reading SMTP commands
3105 on the standard input, and producing SMTP replies on the standard output. SMTP
3106 policy controls, as defined in ACLs (see chapter ~~CHAPACL) are applied.
3108 Some user agents use this interface as a way of passing locally-generated
3109 messages to the MTA.
3110 .index sender||source of
3111 In this usage, if the caller of Exim is trusted, or \untrusted@_set@_sender\ is
3112 set, the senders of messages are taken from the SMTP \\MAIL\\ commands.
3113 Otherwise the content of these commands is ignored and the sender is set up as
3114 the calling user. Unqualified addresses are automatically qualified using
3115 \qualify@_domain\ and \qualify@_recipient\, as appropriate, unless the \-bnq-\
3119 The \-bs-\ option is also used to run Exim from \*inetd*\, as an alternative to
3120 using a listening daemon. Exim can distinguish the two cases by checking
3121 whether the standard input is a TCP/IP socket. When Exim is called from
3122 \*inetd*\, the source of the mail is assumed to be remote, and the comments
3123 above concerning senders and qualification do not apply. In this situation,
3124 Exim behaves in exactly the same way as it does when receiving a message via
3125 the listening daemon.
3128 .index testing||addresses
3129 .index address||testing
3130 This option runs Exim in address testing mode, in which each argument is taken
3131 as an address to be tested for deliverability. The results are written to the
3133 If a test fails, and the caller is not an admin user, no details of the
3134 failure are output, because these might contain sensitive information such as
3135 usernames and passwords for database lookups.
3137 If no arguments are given, Exim runs in an interactive manner, prompting with a
3138 right angle bracket for addresses to be tested. Each address is handled as if
3139 it were the recipient address of a message (compare the \-bv-\ option). It is
3140 passed to the routers and the result is written to the standard output.
3141 However, any router that has \no@_address@_test\ set is bypassed. This can
3142 make \-bt-\ easier to use for genuine routing tests if your first router passes
3143 everything to a scanner program.
3145 .index return code||for \-bt-\
3146 The return code is 2 if any address failed outright; it is 1 if no address
3147 failed outright but at least one could not be resolved for some reason. Return
3148 code 0 is given only when all addresses succeed.
3150 \**Warning**\: \-bt-\ can only do relatively simple testing. If any of the
3151 routers in the configuration makes any tests on the sender address of a
3153 .index \-f-\ option||for address testing
3154 you can use the \-f-\ option to set an appropriate sender when running
3155 \-bt-\ tests. Without it, the sender is assumed to be the calling user at the
3156 default qualifying domain. However, if you have set up (for example) routers
3157 whose behaviour depends on the contents of an incoming message, you cannot test
3158 those conditions using \-bt-\. The \-N-\ option provides a possible way of
3162 .index version number of Exim, verifying
3163 This option causes Exim to write the current version number, compilation
3164 number, and compilation date of the \*exim*\ binary to the standard output.
3165 It also lists the DBM library this is being used, the optional modules (such as
3166 specific lookup types), the drivers that are included in the binary, and the
3167 name of the run time configuration file that is in use.
3170 .index verifying||address, using \-bv-\
3171 .index address||verification
3172 This option runs Exim in address verification mode, in which each argument is
3173 taken as an address to be verified. During normal operation, verification
3174 happens mostly as a consequence processing a \verify\ condition in an ACL (see
3175 chapter ~~CHAPACL). If you want to test an entire ACL, see the \-bh-\ option.
3177 If verification fails, and the caller is not an admin user, no details of the
3178 failure are output, because these might contain sensitive information such as
3179 usernames and passwords for database lookups.
3181 If no arguments are given, Exim runs in an interactive manner, prompting with a
3182 right angle bracket for addresses to be verified. Verification differs from
3183 address testing (the \-bt-\ option) in that routers that have \no@_verify\ set
3184 are skipped, and if the address is accepted by a router that has \fail@_verify\
3185 set, verification fails. The address is verified as a recipient if \-bv-\ is
3186 used; to test verification for a sender address, \-bvs-\ should be used.
3188 If the \-v-\ option is not set, the output consists of a single line for each
3189 address, stating whether it was verified or not, and giving a reason in the
3190 latter case. Otherwise, more details are given of how the address has been
3191 handled, and in the case of address redirection, all the generated addresses
3192 are also considered. Without \-v-\, generating more than one address by
3193 redirection causes verification to end sucessfully.
3195 .index return code||for \-bv-\
3196 The return code is 2 if any address failed outright; it is 1 if no address
3197 failed outright but at least one could not be resolved for some reason. Return
3198 code 0 is given only when all addresses succeed.
3200 If any of the routers in the configuration makes any tests on the sender
3201 address of a message, you should use the \-f-\ option to set an appropriate
3202 sender when running \-bv-\ tests. Without it, the sender is assumed to be the
3203 calling user at the default qualifying domain.
3206 This option acts like \-bv-\, but verifies the address as a sender rather
3207 than a recipient address. This affects any rewriting and qualification that
3210 .option C #<<filelist>>
3211 .index configuration file||alternate
3212 .index \\CONFIGURE@_FILE\\
3213 .index alternate configuration file
3214 This option causes Exim to find the run time configuration file from the given
3215 list instead of from the list specified by the \\CONFIGURE@_FILE\\
3216 compile-time setting. Usually, the list will consist of just a single file
3217 name, but it can be a colon-separated list of names. In this case, the first
3218 file that exists is used. Failure to open an existing file stops Exim from
3219 proceeding any further along the list, and an error is generated.
3221 When this option is used by a caller other than root or the Exim user,
3222 and the list is different from the compiled-in list, Exim gives up
3223 its root privilege immediately, and runs with the real and effective uid and
3224 gid set to those of the caller.
3225 However, if \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined in \(Local/Makefile)\, root
3226 privilege is retained for \-C-\ only if the caller of Exim is root.
3227 This option is not set by default.
3229 Setting \\ALT@_CONFIG@_ROOT@_ONLY\\ locks out the possibility of testing a
3230 configuration using \-C-\ right through message reception and delivery, even if
3231 the caller is root. The reception works, but by that time, Exim is running as
3232 the Exim user, so when it re-execs to regain privilege for the delivery, the
3233 use of \-C-\ causes privilege to be lost. However, root can test reception and
3234 delivery using two separate commands (one to put a message on the queue, using
3235 \-odq-\, and another to do the delivery, using \-M-\).
3237 If \\ALT@_CONFIG@_PREFIX\\ is defined \(in Local/Makefile)\, it specifies a
3238 prefix string with which any file named in a \-C-\ command line option
3239 must start. In addition, the file name must not contain the sequence \"/../"\.
3240 However, if the value of the \-C-\ option is identical to the value of
3241 \\CONFIGURE@_FILE\\ in \(Local/Makefile)\, Exim ignores \-C-\ and proceeds as
3242 usual. There is no default setting for \\ALT@_CONFIG@_PREFIX\\; when it is
3243 unset, any file name can be used with \-C-\.
3245 \\ALT@_CONFIG@_PREFIX\\ can be used to confine alternative configuration files
3246 to a directory to which only root has access. This prevents someone who has
3247 broken into the Exim account from running a privileged Exim with an arbitrary
3250 The \-C-\ facility is useful for ensuring that configuration files are
3251 syntactically correct, but cannot be used for test deliveries, unless the
3252 caller is privileged, or unless it is an exotic configuration that does not
3253 require privilege. No check is made on the owner or group of the files
3254 specified by this option.
3256 .option D <<macro>>=<<value>>
3257 .index macro||setting on command line
3258 This option can be used to override macro definitions in the configuration file
3259 (see section ~~SECTmacrodefs). However, like \-C-\, if it is used by an
3260 unprivileged caller, it causes Exim to give up its root privilege.
3261 If \\DISABLE@_D@_OPTION\\ is defined in \(Local/Makefile)\, the use of \-D-\ is
3262 completely disabled, and its use causes an immediate error exit.
3264 The entire option (including equals sign if present) must all be within one
3265 command line item. \-D-\ can be used to set the value of a macro to the empty
3266 string, in which case the equals sign is optional. These two commands are
3272 To include spaces in a macro definition item, quotes must be used. If you use
3273 quotes, spaces are permitted around the macro name and the equals sign. For
3276 exim '-D ABC = something' ...
3278 \-D-\ may be repeated up to 10 times on a command line.
3280 .option d <<debug options>>
3281 .index debugging||list of selectors
3282 .index debugging||\-d-\ option
3283 This option causes debugging information to be written to the standard
3284 error stream. It is restricted to admin users because debugging output may show
3285 database queries that contain password information. Also, the details of users'
3286 filter files should be protected. When \-d-\ is used, \-v-\ is assumed. If
3287 \-d-\ is given on its own, a lot of standard debugging data is output. This can
3288 be reduced, or increased to include some more rarely needed information, by
3289 following \-d-\ with a string made up of names preceded by plus or minus
3290 characters. These add or remove sets of debugging data, respectively. For
3291 example, \-d+filter-\ adds filter debugging, whereas \-d-all+filter-\ selects
3292 only filter debugging. The available debugging categories are:
3296 . The odd formatting of the lines below is deliberate. It does not affect the
3297 . SGCAL output, but by putting in the space it keeps things aligned in the man
3298 . page that is automatically generated from this text.
3300 acl $t $rm{ACL interpretation}
3301 auth $t $rm{authenticators}
3302 deliver $t $rm{general delivery logic}
3303 dns $t $rm{DNS lookups (see also resolver)}
3304 dnsbl $t $rm{DNS black list (aka RBL) code}
3305 exec $t $rm{arguments for \execv@(@)\ calls}
3306 expand $t $rm{detailed debugging for string expansions}
3307 filter $t $rm{filter handling}
3308 hints@_lookup $t $rm{hints data lookups}
3309 host@_lookup $t $rm{all types of name-to-IP address handling}
3310 ident $t $rm{ident lookup}
3311 interface $t $rm{lists of local interfaces}
3312 lists $t $rm{matching things in lists}
3313 load $t $rm{system load checks}
3314 local@_scan $t $rm{can be used by \*local@_scan()*\ (see chapter ~~CHAPlocalscan)}
3315 lookup $t $rm{general lookup code and all lookups}
3316 memory $t $rm{memory handling}
3317 pid $t $rm{add pid to debug output lines}
3318 process@_info $t $rm{setting info for the process log}
3319 queue@_run $t $rm{queue runs}
3320 receive $t $rm{general message reception logic}
3321 resolver $t $rm{turn on the DNS resolver's debugging output}
3322 retry $t $rm{retry handling}
3323 rewrite $t $rm{address rewriting}
3324 route $t $rm{address routing}
3325 timestamp $t $rm{add timestamp to debug output lines}
3326 tls $t $rm{TLS logic}
3327 transport $t $rm{transports}
3328 uid $t $rm{changes of uid/gid and looking up uid/gid}
3329 verify $t $rm{address verification logic}
3331 all $t $rm{all of the above, and also \-v-\}
3333 .index resolver, debugging output
3334 .index DNS||resolver, debugging output
3335 The \"resolver"\ option produces output only if the DNS resolver was compiled
3336 with \\DEBUG\\ enabled. This is not the case in some operating systems. Also,
3337 unfortunately, debugging output from the DNS resolver is written to stdout
3340 The default (\-d-\ with no argument) omits \"expand"\, \"filter"\,
3341 \"interface"\, \"load"\, \"memory"\, \"pid"\, \"resolver"\, and \"timestamp"\.
3342 However, the \"pid"\ selector is forced when debugging is turned on for a
3343 daemon, which then passes it on to any re-executed Exims. Exim also
3344 automatically adds the pid to debug lines when several remote deliveries are
3347 The \"timestamp"\ selector causes the current time to be inserted at the start
3348 of all debug output lines. This can be useful when trying to track down delays
3351 If the \debug@_print\ option is set in any driver, it produces output whenever
3352 any debugging is selected, or if \-v-\ is used.
3355 This is an obsolete option that is now a no-op. It used to affect the way Exim
3356 handled CR and LF characters in incoming messages. What happens now is
3357 described in section ~~SECTlineendings.
3361 .index bounce message||generating
3362 This option specifies that an incoming message is a locally-generated delivery
3363 failure report. It is used internally by Exim when handling delivery failures
3364 and is not intended for external use. Its only effect is to stop Exim
3365 generating certain messages to the postmaster, as otherwise message cascades
3366 could occur in some situations. As part of the same option, a message id may
3367 follow the characters \-E-\. If it does, the log entry for the receipt of the
3368 new message contains the id, following `R=', as a cross-reference.
3371 There are a number of Sendmail options starting with \-oe-\ which seem to be
3372 called by various programs without the leading \o\ in the option. For example,
3373 the \vacation\ program uses \-eq-\. Exim treats all options of the form
3374 \-e$it{x}-\ as synonymous with the corresponding \-oe$it{x}-\ options.
3376 .option F #<<string>>
3378 .index name||of sender
3379 This option sets the sender's full name for use when a locally-generated
3380 message is being accepted. In the absence of this option, the user's \*gecos*\
3381 entry from the password data is used. As users are generally permitted to alter
3382 their \*gecos*\ entries, no security considerations are involved. White space
3383 between \-F-\ and the <<string>> is optional.
3385 .option f #<<address>>
3386 .index sender||address
3387 .index address||sender
3389 .index envelope sender
3390 .index user||trusted
3391 This option sets the address of the envelope sender of a locally-generated
3392 message (also known as the return path). The option can normally be used only
3393 by a trusted user, but \untrusted@_set@_sender\ can be set to allow untrusted
3394 users to use it. In the absence of \-f-\, or if the caller is not allowed to
3395 use it, the sender of a local message is set to the caller's login name at the
3396 default qualify domain.
3398 There is one exception to the restriction on the use of \-f-\: an empty sender
3399 can be specified by any user, to create a message that can never provoke a
3400 bounce. An empty sender can be specified either as an empty string, or as a
3401 pair of angle brackets with nothing between them, as in these examples of shell
3404 exim -f '<>' user@domain
3405 exim -f "" user@domain
3407 In addition, the use of \-f-\ is not restricted when testing a filter file with
3408 \-bf-\ or when testing or verifying addresses using the \-bt-\ or \-bv-\
3411 Allowing untrusted users to change the sender address does not of itself make
3412 it possible to send anonymous mail. Exim still checks that the ::From:: header
3413 refers to the local user, and if it does not, it adds a ::Sender:: header,
3414 though this can be overridden by setting \no@_local@_from@_check\.
3417 White space between \-f-\ and the <<address>> is optional
3418 (that is, they can be given as two arguments or one combined argument).
3419 The sender of a locally-generated message can also be set (when permitted) by
3420 an initial `From ' line in the message -- see the description of \-bm-\ above
3421 -- but if \-f-\ is also present, it overrides `From'.
3424 .index Sendmail compatibility||\-G-\ option ignored
3425 This is a Sendmail option which is ignored by Exim.
3427 .option h #<<number>>
3428 .index Sendmail compatibility||\-h-\ option ignored
3429 This option is accepted for compatibility with Sendmail, but has no effect. (In
3430 Sendmail it overrides the `hop count' obtained by counting ::Received::
3434 .index Solaris||\*mail*\ command
3435 .index dot||in incoming, non-SMTP message
3436 This option, which has the same effect as \-oi-\, specifies that a dot on a
3437 line by itself should not terminate an incoming, non-SMTP message. I can find
3438 no documentation for this option in Solaris 2.4 Sendmail, but the \*mailx*\
3439 command in Solaris 2.4 uses it. See also \-ti-\.
3441 .option M #<<message id>>#<<message id>> ...
3442 .index forcing delivery
3443 .index delivery||forcing attempt
3444 .index frozen messages||forcing delivery
3445 This option requests Exim to run a delivery attempt on each message in turn. If
3446 any of the messages are frozen, they are automatically thawed before the
3447 delivery attempt. The settings of \queue@_domains\, \queue@_smtp@_domains\, and
3448 \hold@_domains\ are ignored.
3449 .index hints database||overriding retry hints
3450 Retry hints for any of the addresses are
3451 overridden -- Exim tries to deliver even if the normal retry time has not yet
3452 been reached. This option requires the caller to be an admin user. However,
3453 there is an option called \prod@_requires@_admin\ which can be set false to
3454 relax this restriction (and also the same requirement for the \-q-\, \-R-\, and
3458 .option Mar #<<message id>>#<<address>>#<<address>> ...
3459 .index message||adding recipients
3460 .index recipient||adding
3461 This option requests Exim to add the addresses to the list of recipients of the
3462 message (`ar' for `add recipients'). The first argument must be a message id,
3463 and the remaining ones must be email addresses. However, if the message is
3464 active (in the middle of a delivery attempt), it is not altered. This option
3465 can be used only by an admin user.
3467 .index SMTP||passed connection
3468 .index SMTP||multiple deliveries
3469 .index multiple SMTP deliveries
3470 .option MC #<<transport>>#<<hostname>>#<<sequence number>>#<<message id>>
3471 This option is not intended for use by external callers. It is used internally
3472 by Exim to invoke another instance of itself to deliver a waiting message using
3473 an existing SMTP connection, which is passed as the standard input. Details are
3474 given in chapter ~~CHAPSMTP. This must be the final option, and the caller must
3475 be root or the Exim user in order to use it.
3478 This option is not intended for use by external callers. It is used internally
3479 by Exim in conjunction with the \-MC-\ option. It signifies that the connection
3480 to the remote host has been authenticated.
3483 This option is not intended for use by external callers. It is used internally
3484 by Exim in conjunction with the \-MC-\ option. It signifies that the server to
3485 which Exim is connected supports pipelining.
3487 .option MCQ #<<process id>> <<pipe fd>>
3488 This option is not intended for use by external callers. It is used internally
3489 by Exim in conjunction with the \-MC-\ option when the original delivery was
3490 started by a queue runner. It passes on the process id of the queue runner,
3491 together with the file descriptor number of an open pipe. Closure of the pipe
3492 signals the final completion of the sequence of processes that are passing
3493 messages through the same SMTP connection.
3496 This option is not intended for use by external callers. It is used internally
3497 by Exim in conjunction with the \-MC-\ option, and passes on the fact that the
3498 SMTP \\SIZE\\ option should be used on messages delivered down the existing
3502 This option is not intended for use by external callers. It is used internally
3503 by Exim in conjunction with the \-MC-\ option, and passes on the fact that the
3504 host to which Exim is connected supports TLS encryption.
3506 .option Mc #<<message id>>#<<message id>> ...
3507 .index hints database||not overridden by \-Mc-\
3508 .index delivery||manually started, not forced
3509 This option requests Exim to run a delivery attempt on each message in turn,
3510 but unlike the \-M-\ option, it does check for retry hints, and respects any
3511 that are found. This option is not very useful to external callers. It is
3512 provided mainly for internal use by Exim when it needs to re-invoke itself in
3513 order to regain root privilege for a delivery (see chapter ~~CHAPsecurity).
3514 However, \-Mc-\ can be useful when testing, in order to run a delivery that
3515 respects retry times and other options such as \hold@_domains\ that are
3516 overridden when \-M-\ is used. Such a delivery does not count as a queue run.
3517 If you want to run a specific delivery as if in a queue run, you should use
3518 \-q-\ with a message id argument. A distinction between queue run deliveries
3519 and other deliveries is made in one or two places.
3521 .option Mes #<<message id>>#<<address>>
3522 .index message||changing sender
3523 .index sender||changing
3524 This option requests Exim to change the sender address in the message to the
3525 given address, which must be a fully qualified address or `<>' (`es' for `edit
3526 sender'). There must be exactly two arguments. The first argument must be a
3527 message id, and the second one an email address. However, if the message is
3528 active (in the middle of a delivery attempt), its status is not altered. This
3529 option can be used only by an admin user.
3531 .option Mf #<<message id>>#<<message id>> ...
3532 .index freezing messages
3533 .index message||manually freezing
3534 This option requests Exim to mark each listed message as `frozen'. This
3535 prevents any delivery attempts taking place until the message is `thawed',
3536 either manually or as a result of the \auto@_thaw\ configuration option.
3537 However, if any of the messages are active (in the middle of a delivery
3538 attempt), their status is not altered. This option can be used only by an admin
3541 .option Mg #<<message id>>#<<message id>> ...
3542 .index giving up on messages
3543 .index message||abandoning delivery attempts
3544 .index delivery||abandoning further attempts
3545 This option requests Exim to give up trying to deliver the listed messages,
3546 including any that are frozen. However, if any of the messages are active,
3547 their status is not altered.
3548 For non-bounce messages, a delivery error message is sent to the sender,
3549 containing the text `cancelled by administrator'. Bounce messages are just
3551 This option can be used only by an admin user.
3553 .option Mmad #<<message id>>#<<message id>> ...
3554 .index delivery||cancelling all
3555 This option requests Exim to mark all the recipient addresses in the messages
3556 as already delivered (`mad' for `mark all delivered'). However, if any message
3557 is active (in the middle of a delivery attempt), its status is not altered.
3558 This option can be used only by an admin user.
3560 .option Mmd #<<message id>>#<<address>>#<<address>> ...
3561 .index delivery||cancelling by address
3562 .index recipient||removing
3563 .index removing recipients
3564 This option requests Exim to mark the given addresses as already delivered
3565 (`md' for `mark delivered'). The first argument must be a message id, and the
3566 remaining ones must be email addresses. These are matched to recipient
3567 addresses in the message in a case-sensitive manner. If the message is active
3568 (in the middle of a delivery attempt), its status is not altered. This option
3569 can be used only by an admin user.
3571 .option Mrm #<<message id>>#<<message id>> ...
3572 .index removing messages
3573 .index abandoning mail
3574 .index message||manually discarding
3575 This option requests Exim to remove the given messages from the queue. No
3576 bounce messages are sent; each message is simply forgotten. However, if any of
3577 the messages are active, their status is not altered. This option can be used
3578 only by an admin user or by the user who originally caused the message to be
3579 placed on the queue.
3581 .option Mt #<<message id>>#<<message id>> ...
3582 .index thawing messages
3583 .index unfreezing messages
3584 .index frozen messages||thawing
3585 .index message||thawing frozen
3586 This option requests Exim to `thaw' any of the listed messages that are
3587 `frozen', so that delivery attempts can resume. However, if any of the messages
3588 are active, their status is not altered. This option can be used only by an
3591 .option Mvb #<<message id>>
3592 .index listing||message body
3593 .index message||listing body of
3594 This option causes the contents of the message body (-D) spool file to be
3595 written to the standard output. This option can be used only by an admin user.
3597 .option Mvh #<<message id>>
3598 .index listing||message headers
3599 .index header lines||listing
3600 .index message||listing header lines
3601 This option causes the contents of the message headers (-H) spool file to be
3602 written to the standard output. This option can be used only by an admin user.
3604 .option Mvl #<<message id>>
3605 .index listing||message log
3606 .index message||listing message log
3607 This option causes the contents of the message log spool file to be written to
3608 the standard output. This option can be used only by an admin user.
3611 This is apparently a synonym for \-om-\ that is accepted by Sendmail, so Exim
3612 treats it that way too.
3615 .index debugging||\-N-\ option
3616 .index debugging||suppressing delivery
3617 This is a debugging option that inhibits delivery of a message at the transport
3618 level. It implies \-v-\. Exim goes through many of the motions of delivery --
3619 it just doesn't actually transport the message, but instead behaves as if it
3620 had successfully done so. However, it does not make any updates to the retry
3621 database, and the log entries for deliveries are flagged with `$*$>' rather
3624 Because \-N-\ discards any message to which it applies, only root or the Exim
3625 user are allowed to use it with \-bd-\, \-q-\, \-R-\ or \-M-\. In other words,
3626 an ordinary user can use it only when supplying an incoming message to which it
3627 will apply. Although transportation never fails when \-N-\ is set, an address
3628 may be deferred because of a configuration problem on a transport, or a routing
3629 problem. Once \-N-\ has been used for a delivery attempt, it sticks to the
3630 message, and applies to any subsequent delivery attempts that may happen for
3634 .index Sendmail compatibility||\-n-\ option ignored
3635 This option is interpreted by Sendmail to mean `no aliasing'. It is ignored by
3639 This option is interpreted by Sendmail to mean `set option`. It is ignored by
3642 .option oA #<<file name>>
3643 .index Sendmail compatibility||\-oA-\ option
3644 This option is used by Sendmail in conjunction with \-bi-\ to specify an
3645 alternative alias file name. Exim handles \-bi-\ differently; see the
3648 .index SMTP||passed connection
3650 .index SMTP||multiple deliveries
3651 .index multiple SMTP deliveries
3652 This is a debugging option which limits the maximum number of messages that can
3653 be delivered down one SMTP connection, overriding the value set in any \%smtp%\
3654 transport. If <<n>> is omitted, the limit is set to 1.
3657 .index background delivery
3658 .index delivery||in the background
3659 This option applies to all modes in which Exim accepts incoming messages,
3660 including the listening daemon. It requests `background' delivery of such
3661 messages, which means that the accepting process automatically starts delivery
3662 process for each message received, but does not wait for the delivery process
3663 to complete. This is the default action if none of the \-od-\ options are
3666 If one of the queueing options in the configuration file
3667 (\queue@_only\ or \queue@_only@_file\, for example) is in effect, \-odb-\
3668 overrides it if \queue@_only@_override\ is set true, which is the default
3669 setting. If \queue@_only@_override\ is set false, \-odb-\ has no effect.
3672 .index foreground delivery
3673 .index delivery||in the foreground
3674 This option requests `foreground' (synchronous) delivery when Exim has accepted
3675 a locally-generated message. (For the daemon it is exactly the same as
3676 \-odb-\.) A delivery process is automatically started to deliver the
3677 message, and Exim waits for it to complete before proceeding.
3678 However, like \-odb-\, this option has no effect if \queue@_only@_override\ is
3679 false and one of the queueing options in the configuration file is in effect.
3682 This option is synonymous with \-odf-\. It is provided for compatibility with
3686 .index non-immediate delivery
3687 .index delivery||suppressing immediate
3688 .index queueing incoming messages
3689 This option applies to all modes in which Exim accepts incoming messages,
3690 including the listening daemon. It specifies that the accepting process should
3691 not automatically start a delivery process for each message received. Messages
3692 are placed on the queue, and remain there until a subsequent queue runner
3693 process encounters them.
3694 There are several configuration options (such as \queue@_only\) that can be
3695 used to queue incoming messages under certain conditions. This option overrides
3696 all of them and also \-odqs-\. It always forces queueing.
3699 .index SMTP||delaying delivery
3700 This option is a hybrid between \-odb-\/\-odi-\ and \-odq-\.
3701 However, like \-odb-\ and \-odi-\, this option has no effect if
3702 \queue@_only@_override\ is false and one of the queueing options in the
3703 configuration file is in effect.
3705 When \-odqs-\ does operate, a delivery process is started for each incoming
3706 message, in the background by default, but in the foreground if \-odi-\ is also
3708 The recipient addresses are routed, and local deliveries are done in the normal
3709 way. However, if any SMTP deliveries are required, they are not done at this
3710 time, so the message remains on the queue until a subsequent queue runner
3711 process encounters it. Because routing was done, Exim knows which messages are
3712 waiting for which hosts, and so a number of messages for the same host can be
3713 sent in a single SMTP connection. The \queue@_smtp@_domains\ configuration
3714 option has the same effect for specific domains. See also the \-qq-\ option.
3717 .index error||reporting
3718 If an error is detected while a non-SMTP message is being received (for
3719 example, a malformed address), the error is reported to the sender in a mail
3721 .index return code||for \-oee-\
3722 Provided this error message is successfully sent, the Exim receiving process
3723 exits with a return code of zero. If not, the return code is 2 if the problem
3724 is that the original message has no recipients, or 1 any other error. This is
3725 the default \-oe$it{x}-\ option if Exim is called as \*rmail*\.
3728 .index error||reporting
3729 .index return code||for \-oem-\
3730 This is the same as \-oee-\, except that Exim always exits with a non-zero
3731 return code, whether or not the error message was successfully sent.
3732 This is the default \-oe$it{x}-\ option, unless Exim is called as \*rmail*\.
3735 .index error||reporting
3736 If an error is detected while a non-SMTP message is being received, the
3737 error is reported by writing a message to the standard error file (stderr).
3738 .index return code||for \-oep-\
3739 The return code is 1 for all errors.
3742 .index error||reporting
3743 This option is supported for compatibility with Sendmail, but has the same
3747 .index error||reporting
3748 This option is supported for compatibility with Sendmail, but has the same
3752 .index dot||in incoming, non-SMTP message
3753 This option, which has the same effect as \-i-\, specifies that a dot on a line
3754 by itself should not terminate an incoming, non-SMTP message.
3755 Otherwise, a single dot does terminate, though Exim does no special processing
3756 for other lines that start with a dot.
3757 This option is set by default if Exim is called as \*rmail*\. See also \-ti-\.
3760 This option is treated as synonymous with \-oi-\.
3762 .option oMa #<<host address>>
3763 .index sender||host address, specifying for local message
3764 A number of options starting with \-oM-\ can be used to set values associated
3765 with remote hosts on locally-submitted messages (that is, messages not received
3766 over TCP/IP). These options can be used by any caller in conjunction with the
3769 \-bf-\, \-bF-\, \-bt-\, or \-bv-\ testing options. In other circumstances, they
3770 are ignored unless the caller is trusted.
3772 The \-oMa-\ option sets the sender host address. This may include a port number
3773 at the end, after a full stop (period). For example:
3775 exim -bs -oMa 10.9.8.7.1234
3777 An alternative syntax is to enclose the IP address in square brackets, followed
3778 by a colon and the port number:
3780 exim -bs -oMa [10.9.8.7]:1234
3782 The IP address is placed in the \$sender@_host@_address$\ variable, and the
3783 port, if present, in \$sender@_host@_port$\.
3785 .option oMaa #<<name>>
3786 .index authentication||name, specifying for local message
3787 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMaa-\
3788 option sets the value of \$sender@_host@_authenticated$\ (the authenticator
3789 name). See chapter ~~CHAPSMTPAUTH for a discussion of SMTP authentication.
3791 .option oMai #<<string>>
3792 .index authentication||id, specifying for local message
3793 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMai-\
3795 value of \$authenticated@_id$\ (the id that was authenticated).
3796 This overrides the default value (the caller's login id) for messages from
3797 local sources. See chapter ~~CHAPSMTPAUTH for a discussion of authenticated
3800 .option oMas #<<address>>
3801 .index authentication||sender, specifying for local message
3802 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMas-\
3803 option sets the authenticated sender value
3804 in \$authenticated@_sender$\.
3805 It overrides the sender address that is created from the caller's login id for
3806 messages from local sources. See chapter ~~CHAPSMTPAUTH for a discussion of
3807 authenticated senders.
3809 .option oMi #<<interface address>>
3810 .index interface||address, specifying for local message
3811 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMi-\
3812 option sets the IP interface address value. A port number may be included,
3813 using the same syntax as for \-oMa-\.
3814 The interface address is placed in \$interface@_address$\ and the port number,
3815 if present, in \$interface@_port$\.
3817 .option oMr #<<protocol name>>
3818 .index protocol||incoming, specifying for local message
3819 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMr-\
3820 option sets the received protocol value
3821 in \$received@_protocol$\.
3822 However, this applies only when \-bs-\ is not used. For interactive SMTP input,
3823 the protocol is determined by whether \\EHLO\\ or \\HELO\\ is used, and is
3824 always either `local-esmtp' or `local-smtp'. For \-bS-\ (batch SMTP) however,
3825 the protocol can be set by \-oMr-\.
3827 .option oMs #<<host name>>
3828 .index sender||host name, specifying for local message
3829 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMs-\
3830 option sets the sender host name
3831 in \$sender@_host@_name$\. When this option is present, Exim does not attempt
3832 to look up a host name from an IP address; it uses the name it is given.
3834 .option oMt #<<ident string>>
3835 .index sender||ident string, specifying for local message
3836 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMt-\
3837 option sets the sender ident value
3838 in \$sender@_ident$\.
3839 The default setting for local callers is the login id of the calling process.
3842 .index Sendmail compatibility||\-om-\ option ignored
3843 In Sendmail, this option means `me too', indicating that the sender of a
3844 message should receive a copy of the message if the sender appears in an alias
3845 expansion. Exim always does this, so the option does nothing.
3848 .index Sendmail compatibility||\-oo-\ option ignored
3849 This option is ignored. In Sendmail it specifies `old style headers', whatever
3852 .option oP #<<path>>
3853 .index pid (process id)||of daemon
3854 .index daemon||process id (pid)
3855 This option is useful only in conjunction with \-bd-\ or \-q-\ with a time
3856 value. The option specifies the file to which the process id of the daemon is
3857 written. When \-oX-\ is used with \-bd-\, or when \-q-\ with a time is used
3858 without \-bd-\, this is the only way of causing Exim to write a pid file,
3859 because in those cases, the normal pid file is not used.
3861 .option or #<<time>>
3862 .index timeout||for non-SMTP input
3863 This option sets a timeout value for incoming non-SMTP messages. If it is not
3864 set, Exim will wait forever for the standard input. The value can also be set
3865 by the \receive@_timeout\ option. The format used for specifying times is
3866 described in section ~~SECTtimeformat.
3868 .option os #<<time>>
3869 .index timeout||for SMTP input
3870 .index SMTP||timeout, input
3871 This option sets a timeout value for incoming SMTP messages. The timeout
3872 applies to each SMTP command and block of data. The value can also be set by
3873 the \smtp@_receive@_timeout\ option; it defaults to 5 minutes. The format used
3874 for specifying times is described in section ~~SECTtimeformat.
3877 This option has exactly the same effect as \-v-\.
3879 .option oX #<<number or string>>
3880 .index TCP/IP||setting listening ports
3881 .index TCP/IP||setting listening interfaces
3882 .index port||receiving TCP/IP
3883 This option is relevant only when the \-bd-\ (start listening daemon) option is
3884 also given. It controls which ports and interfaces the daemon uses. Details of
3885 the syntax, and how it interacts with configuration file options, are given in
3886 chapter ~~CHAPinterfaces. When \-oX-\ is used to start a daemon, no pid file is
3887 written unless \-oP-\ is also present to specify a pid file name.
3890 .index Perl||starting the interpreter
3891 This option applies when an embedded Perl interpreter is linked with Exim (see
3892 chapter ~~CHAPperl). It overrides the setting of the \perl@_at@_start\ option,
3893 forcing the starting of the interpreter to be delayed until it is needed.
3896 .index Perl||starting the interpreter
3897 This option applies when an embedded Perl interpreter is linked with Exim (see
3898 chapter ~~CHAPperl). It overrides the setting of the \perl@_at@_start\ option,
3899 forcing the starting of the interpreter to occur as soon as Exim is started.
3901 .option p<<rval>>:<<sval>>
3902 For compatibility with Sendmail, this option
3905 -oMr <<rval>> -oMs <<sval>>
3907 It sets the incoming protocol and host name (for trusted callers). The
3908 host name and its colon can be omitted when only the protocol is to be set.
3909 Note the Exim already has two private options, \-pd-\ and \-ps-\, that refer to
3910 embedded Perl. It is therefore impossible to set a protocol value of \"p"\ or
3911 \"s"\ using this option (but that does not seem a real limitation).
3914 .index queue runner||starting manually
3915 This option is normally restricted to admin users. However, there is a
3916 configuration option called \prod@_requires@_admin\ which can be set false to
3917 relax this restriction (and also the same requirement for the \-M-\, \-R-\, and
3920 .index queue runner||description of operation
3921 The \-q-\ option starts one queue runner process. This scans the queue of
3922 waiting messages, and runs a delivery process for each one in turn. It waits
3923 for each delivery process to finish before starting the next one. A delivery
3924 process may not actually do any deliveries if the retry times for the addresses
3925 have not been reached. Use \-qf-\ (see below) if you want to override this.
3926 .index SMTP||passed connection
3927 .index SMTP||multiple deliveries
3928 .index multiple SMTP deliveries
3929 If the delivery process spawns other processes to deliver other messages down
3930 passed SMTP connections, the queue runner waits for these to finish before
3933 When all the queued messages have been considered, the original queue runner
3934 process terminates. In other words, a single pass is made over the waiting
3935 mail, one message at a time. Use \-q-\ with a time (see below) if you want this
3936 to be repeated periodically.
3938 Exim processes the waiting messages in an unpredictable order. It isn't very
3939 random, but it is likely to be different each time, which is all that matters.
3940 If one particular message screws up a remote MTA, other messages to the same
3941 MTA have a chance of getting through if they get tried first.
3943 It is possible to cause the messages to be processed in lexical message id
3944 order, which is essentially the order in which they arrived, by setting the
3945 \queue@_run@_in@_order\ option, but this is not recommended for normal use.
3947 .option q <<qflags>>
3948 The \-q-\ option may be followed by one or more flag letters that change its
3949 behaviour. They are all optional, but if more than one is present, they must
3950 appear in the correct order. Each flag is described in a separate item below.
3953 .index queue||double scanning
3954 .index queue||routing
3955 .index routing||whole queue before delivery
3956 An option starting with \-qq-\ requests a two-stage queue run. In the first
3957 stage, the queue is scanned as if the \queue@_smtp@_domains\ option matched
3958 every domain. Addresses are routed, local deliveries happen, but no remote
3960 .index hints database||remembering routing
3961 The hints database that remembers which messages are
3962 waiting for specific hosts is updated, as if delivery to those hosts had been
3963 deferred. After this is complete, a second, normal queue scan happens, with
3964 routing and delivery taking place as normal. Messages that are routed to the
3965 same host should mostly be delivered down a single SMTP
3966 .index SMTP||passed connection
3967 .index SMTP||multiple deliveries
3968 .index multiple SMTP deliveries
3969 connection because of the hints that were set up during the first queue scan.
3970 This option may be useful for hosts that are connected to the Internet
3974 .index queue||initial delivery
3975 If the \*i*\ flag is present, the queue runner runs delivery processes only for
3976 those messages that haven't previously been tried. (\*i*\ stands for `initial
3977 delivery'.) This can be helpful if you are putting messages on the queue using
3978 \-odq-\ and want a queue runner just to process the new messages.
3981 .index queue||forcing delivery
3982 .index delivery||forcing in queue run
3983 If one \*f*\ flag is present, a delivery attempt is forced for each non-frozen
3984 message, whereas without \f\ only those non-frozen addresses that have passed
3985 their retry times are tried.
3987 .option q[q][i]ff...
3988 .index frozen messages||forcing delivery
3989 If \*ff*\ is present, a delivery attempt is forced for every message, whether
3992 .option q[q][i][f[f]]l
3993 .index queue||local deliveries only
3994 The \*l*\ (the letter `ell') flag specifies that only local deliveries are to be
3995 done. If a message requires any remote deliveries, it remains on the queue for
3998 .option q <<qflags>>#<<start id>>#<<end id>>
3999 .index queue||delivering specific messages
4000 When scanning the queue, Exim can be made to skip over messages whose ids are
4001 lexically less than a given value by following the \-q-\ option with a starting
4002 message id. For example:
4004 exim -q 0t5C6f-0000c8-00
4006 Messages that arrived earlier than \"0t5C6f-0000c8-00"\ are not inspected. If a
4007 second message id is given, messages whose ids are lexically greater than it
4008 are also skipped. If the same id is given twice, for example,
4010 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4012 just one delivery process is started, for that message. This differs from \-M-\
4013 in that retry data is respected, and it also differs from \-Mc-\ in that it
4014 counts as a delivery from a queue run. Note that the selection mechanism does
4015 not affect the order in which the messages are scanned. There are also other
4016 ways of selecting specific sets of messages for delivery in a queue run -- see
4019 .option q <<qflags>><<time>>
4020 .index queue runner||starting periodically
4021 .index periodic queue running
4022 When a time value is present, the \-q-\ option causes Exim to run as a daemon,
4023 starting a queue runner process at intervals specified by the given time value
4024 (whose format is described in section ~~SECTtimeformat). This form of the \-q-\
4025 option is commonly combined with the \-bd-\ option, in which case a single
4026 daemon process handles both functions. A common way of starting up a combined
4027 daemon at system boot time is to use a command such as
4029 /usr/exim/bin/exim -bd -q30m
4031 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4032 process every 30 minutes.
4034 When a daemon is started by \-q-\ with a time value, but without \-bd-\, no pid
4035 file is written unless one is explicitly requested by the \-oP-\ option.
4037 .option qR <<rsflags>>#<<string>>
4038 This option is synonymous with \-R-\. It is provided for Sendmail
4041 .option qS <<rsflags>>#<<string>>
4042 This option is synonymous with \-S-\.
4044 .option R <<rsflags>>#<<string>>
4045 .index queue runner||for specific recipients
4046 .index delivery||to given domain
4047 .index domain||delivery to
4048 The <<rsflags>> may be empty, in which case the white space before the string
4049 is optional, unless the string is \*f*\, \*ff*\, \*r*\, \*rf*\, or \*rff*\,
4050 which are the possible values for <<rsflags>>. White space is required if
4051 <<rsflags>> is not empty.
4053 This option is similar to \-q-\ with no time value, that is, it causes Exim to
4054 perform a single queue run, except that, when scanning the messages on the
4055 queue, Exim processes only those that have at least one undelivered recipient
4056 address containing the given string, which is checked in a case-independent
4057 way. If the <<rsflags>> start with \*r*\, <<string>> is interpreted as a regular
4058 expression; otherwise it is a literal string.
4060 Once a message is selected, all its addresses are processed. For the first
4061 selected message, Exim overrides any retry information and forces a delivery
4062 attempt for each undelivered address. This means that if delivery of any
4063 address in the first message is successful, any existing retry information is
4064 deleted, and so delivery attempts for that address in subsequently selected
4065 messages (which are processed without forcing) will run. However, if delivery
4066 of any address does not succeed, the retry information is updated, and in
4067 subsequently selected messages, the failing address will be skipped.
4069 If the <<rsflags>> contain \*f*\ or \*ff*\, the delivery forcing applies to all
4070 selected messages, not just the first;
4071 .index frozen messages||forcing delivery
4072 frozen messages are included when \*ff*\ is present.
4074 The \-R-\ option makes it straightforward to initiate delivery of all messages
4075 to a given domain after a host has been down for some time. When the SMTP
4076 command \\ETRN\\ is accepted by its ACL (see chapter ~~CHAPACL), its default
4077 effect is to run Exim with the \-R-\ option, but it can be configured to run an
4078 arbitrary command instead.
4081 This is a documented (for Sendmail) obsolete alternative name for \-f-\.
4083 .index delivery||from given sender
4084 .option S <<rsflags>>#<<string>>
4085 .index queue runner||for specific senders
4086 This option acts like \-R-\ except that it checks the string against each
4087 message's sender instead of against the recipients. If \-R-\ is also set, both
4088 conditions must be met for a message to be selected. If either of the options
4089 has \*f*\ or \*ff*\ in its flags, the associated action is taken.
4091 .option Tqt#<<times>>
4092 This an option that is exclusively for use by the Exim testing suite.
4093 It is not recognized when Exim is run normally. It allows for the setting up
4094 of explicit `queue times' so that various warning/retry features can be
4098 .index recipient||extracting from header lines
4099 .index ::Bcc:: header line
4100 .index ::Cc:: header line
4101 .index ::To:: header line
4102 When Exim is receiving a locally-generated, non-SMTP message on its standard
4103 input, the \-t-\ option causes the recipients of the message to be obtained
4104 from the ::To::, ::Cc::, and ::Bcc:: header lines in the message instead of from
4105 the command arguments. The addresses are extracted before any rewriting takes
4108 .index Sendmail compatibility||\-t-\ option
4109 If the command has any arguments, they specify addresses to which the message
4110 is $it{not} to be delivered. That is, the argument addresses are removed from
4111 the recipients list obtained from the headers. This is compatible with Smail 3
4112 and in accordance with the documented behaviour of several versions of
4113 Sendmail, as described in man pages on a number of operating systems (e.g.
4114 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail $it{add}
4115 argument addresses to those obtained from the headers, and the O'Reilly
4116 Sendmail book documents it that way. Exim can be made to add argument addresses
4117 instead of subtracting them by setting the option
4118 \extract__addresses__remove__arguments\ false.
4120 If a ::Bcc:: header line is present, it is removed from the message unless
4121 there is no ::To:: or ::Cc::, in which case a ::Bcc:: line with no data is
4122 created. This is necessary for conformity with the original RFC 822 standard;
4123 the requirement has been removed in RFC 2822, but that is still very new.
4125 .index \Resent@-\ header lines||with \-t-\
4126 If there are any \Resent@-\ header lines in the message, Exim extracts
4127 recipients from all ::Resent-To::, ::Resent-Cc::, and ::Resent-Bcc:: header
4128 lines instead of from ::To::, ::Cc::, and ::Bcc::. This is for compatibility
4129 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4130 \-t-\ was used in conjunction with \Resent@-\ header lines.)
4132 RFC 2822 talks about different sets of \Resent@-\ header lines (for when a
4133 message is resent several times). The RFC also specifies that they should be
4134 added at the front of the message, and separated by ::Received:: lines. It is
4135 not at all clear how \-t-\ should operate in the present of multiple sets,
4136 nor indeed exactly what constitutes a `set'.
4137 In practice, it seems that MUAs do not follow the RFC. The \Resent@-\ lines are
4138 often added at the end of the header, and if a message is resent more than
4139 once, it is common for the original set of \Resent@-\ headers to be renamed as
4140 \X-Resent@-\ when a new set is added. This removes any possible ambiguity.
4143 This option is exactly equivalent to \-t-\ \-i-\. It is provided for
4144 compatibility with Sendmail.
4146 .option tls-on-connect
4147 .index TLS||use without STARTTLS
4148 .index TLS||automatic start
4149 This option is available when Exim is compiled with TLS support. It makes it
4150 possible to support legacy clients that do not support the \\STARTTLS\\
4151 command, but instead expect to start up a TLS session as soon as a connection
4152 to the server is established. These clients use a special port (usually called
4153 the `ssmtp' port) instead of the normal SMTP port 25. The \-tls-on-connect-\
4154 option can be used to run Exim in this way from \*inetd*\, and it can also be
4155 used to run a special daemon that operates in this manner (use \-oX-\ to
4156 specify the port). However, although it is possible to run one daemon that
4157 listens on several ports, it is not possible to have some of them operate one
4158 way and some the other. With only a few clients that need the legacy support, a
4159 convenient approach is to use a daemon for normal SMTP (with or without
4160 \\STARTTLS\\) and \*inetd*\ with \-tls-on-connect-\ for the legacy clients.
4163 .index Sendmail compatibility||\-U-\ option ignored
4164 Sendmail uses this option for `initial message submission', and its
4165 documentation states that in future releases, it may complain about
4166 syntactically invalid messages rather than fixing them when this flag is not
4167 set. Exim ignores this option.
4170 This option causes Exim to write information to the standard error stream,
4171 describing what it is doing. In particular, it shows the log lines for
4172 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4173 dialogue is shown. Some of the log lines shown may not actually be written to
4174 the log if the setting of \log@_selector\ discards them. Any relevant selectors
4175 are shown with each log line. If none are shown, the logging is unconditional.
4178 AIX uses \-x-\ for a private purpose (`mail from a local mail program has
4179 National Language Support extended characters in the body of the mail item').
4180 It sets \-x-\ when calling the MTA from its \mail\ command. Exim ignores this
4191 . ============================================================================
4192 .chapter The Exim run time configuration file
4193 .set runningfoot "configuration file"
4194 .rset CHAPconf ~~chapter
4196 .index run time configuration
4197 .index configuration file||general description
4198 .index \\CONFIGURE@_FILE\\
4199 Exim uses a single run time configuration file that is read whenever an Exim
4200 binary is executed. Note that in normal operation, this happens frequently,
4201 because Exim is designed to operate in a distributed manner, without central
4204 The name of the configuration file is compiled into the binary for security
4205 reasons, and is specified by the \\CONFIGURE@_FILE\\ compilation option. In
4206 most configurations, this specifies a single file. However, it is permitted to
4207 give a colon-separated list of file names, in which case Exim uses the first
4208 existing file in the list.
4210 .index \\EXIM@_USER\\
4211 .index \\EXIM@_GROUP\\
4212 .index configuration file||ownership
4213 .index ownership||configuration file
4214 The run time configuration file must be owned by root or by the user that
4215 is specified at compile time by the \\EXIM@_USER\\ option,
4216 or by the user that is specified at compile time by the \\CONFIGURE@_OWNER\\
4218 The configuration file must not be world-writeable or group-writeable, unless
4219 its group is the one specified at compile time by the \\EXIM@_GROUP\\ option.
4221 \**Warning**\: In a conventional configuration, where the Exim binary is setuid
4222 to root, anybody who is able to edit the run time configuration file has an
4223 easy way to run commands as root. If you make your mail administrators members
4224 of the Exim group, but do not trust them with root, make sure that the run time
4225 configuration is not group writeable.
4228 A default configuration file, which will work correctly in simple situations,
4229 is provided in the file \(src/configure.default)\.
4230 If \\CONFIGURE@_FILE\\ defines just one file name, the installation process
4231 copies the default configuration to a new file of that name if it did not
4232 previously exist. If \\CONFIGURE@_FILE\\ is a list, no default is automatically
4233 installed. Chapter ~~CHAPdefconfil is a `walk-through' discussion of the
4234 default configuration.
4236 .index configuration file||errors in
4237 .index error||in configuration file
4238 .index return code||for bad configuration
4239 If a syntax error is detected while reading the configuration file, Exim
4240 writes a message on the standard error, and exits with a non-zero return code.
4241 The message is also written to the panic log.
4244 .section Using a different configuration file
4245 .index configuration file||alternate
4246 A one-off alternate configuration can be specified by the \-C-\ command line
4247 option, which may specify a single file or a list of files. However, when \-C-\
4248 is used, Exim gives up its root privilege, unless called by root or the Exim
4249 user (or unless the argument for \-C-\ is identical to the built-in value from
4250 \\CONFIGURE@_FILE\\). \-C-\ is useful mainly for checking the syntax of
4251 configuration files before installing them. No owner or group checks are done
4252 on a configuration file specified by \-C-\.
4254 The privileged use of \-C-\ by the Exim user can be locked out by setting
4255 \\ALT@_CONFIG@_ROOT@_ONLY\\ in \(Local/Makefile)\ when building Exim. However,
4256 if you do this, you also lock out the possibility of testing a
4257 configuration using \-C-\ right through message reception and delivery, even if
4258 the caller is root. The reception works, but by that time, Exim is running as
4259 the Exim user, so when it re-execs to regain privilege for the delivery, the
4260 use of \-C-\ causes privilege to be lost. However, root can test reception and
4261 delivery using two separate commands (one to put a message on the queue, using
4262 \-odq-\, and another to do the delivery, using \-M-\).
4264 If \\ALT@_CONFIG@_PREFIX\\ is defined \(in Local/Makefile)\, it specifies a
4265 prefix string with which any file named in a \-C-\ command line option must
4266 start. In addition, the file name must not contain the sequence \"/../"\. There
4267 is no default setting for \\ALT@_CONFIG@_PREFIX\\; when it is unset, any file
4268 name can be used with \-C-\.
4270 One-off changes to a configuration can be specified by the \-D-\ command line
4271 option, which defines and overrides values for macros used inside the
4272 configuration file. However, like \-C-\, the use of this option by a
4273 non-privileged user causes Exim to discard its root privilege.
4274 If \\DISABLE@_D@_OPTION\\ is defined in \(Local/Makefile)\, the use of \-D-\ is
4275 completely disabled, and its use causes an immediate error exit.
4277 Some sites may wish to use the same Exim binary on different machines that
4278 share a file system, but to use different configuration files on each machine.
4279 If \\CONFIGURE@_FILE@_USE@_NODE\\ is defined in \(Local/Makefile)\, Exim first
4280 looks for a file whose name is the configuration file name followed by a dot
4281 and the machine's node name, as obtained from the \*uname()*\ function. If this
4282 file does not exist, the standard name is tried. This processing occurs for
4283 each file name in the list given by \\CONFIGURE@_FILE\\ or \-C-\.
4285 In some esoteric situations different versions of Exim may be run under
4286 different effective uids and the \\CONFIGURE@_FILE@_USE@_EUID\\ is defined to
4287 help with this. See the comments in \(src/EDITME)\ for details.
4290 .section Configuration file format
4291 .rset SECTconffilfor "~~chapter.~~section"
4292 .index configuration file||format of
4293 .index format||configuration file
4294 Exim's configuration file is divided into a number of different parts. General
4295 option settings must always appear at the start of the file. The other parts
4296 are all optional, and may appear in any order. Each part other than the first
4297 is introduced by the word `begin' followed by the name of the part. The
4301 \*ACL*\: Access control lists for controlling incoming SMTP mail.
4303 .index \\AUTH\\||configuration
4304 \*authenticators*\: Configuration settings for the authenticator drivers. These
4305 are concerned with the SMTP \\AUTH\\ command (see chapter ~~CHAPSMTPAUTH).
4307 \*routers*\: Configuration settings for the router drivers. Routers process
4308 addresses and determine how the message is to be delivered.
4310 \*transports*\: Configuration settings for the transport drivers. Transports
4311 define mechanisms for copying messages to destinations.
4313 \*retry*\: Retry rules, for use when a message cannot be immediately delivered.
4315 \*rewrite*\: Global address rewriting rules, for use when a message arrives and
4316 when new addresses are generated during delivery.
4318 \*local@_scan*\: Private options for the \*local@_scan()*\ function. If you
4319 want to use this feature, you must set
4321 LOCAL_SCAN_HAS_OPTIONS=yes
4323 in \(Local/Makefile)\ before building Exim. Full details of the
4324 \*local@_scan()*\ facility are given in chapter ~~CHAPlocalscan.
4326 Blank lines in the file, and lines starting with a @# character (ignoring
4327 leading white space) are treated as comments and are ignored. \**Note**\: a
4328 @# character other than at the beginning of a line is not treated specially,
4329 and does not introduce a comment.
4331 Any non-comment line can be continued by ending it with a backslash. Trailing
4332 white space after the backslash is ignored, and leading white space at the
4333 start of continuation lines is also ignored.
4334 Comment lines beginning with @# (but not empty lines) may appear in the middle
4335 of a sequence of continuation lines.
4337 A convenient way to create a configuration file is to start from the
4338 default, which is supplied in \(src/configure.default)\, and add, delete, or
4339 change settings as required.
4341 The ACLs, retry rules, and rewriting rules have their own syntax which is
4342 described in chapters ~~CHAPACL, ~~CHAPretry, and ~~CHAPrewrite, respectively.
4343 The other parts of the configuration file have some syntactic items in common,
4344 and these are described below, from section ~~SECTcos onwards. Before that, the
4345 inclusion, macro, and conditional facilities are described.
4348 .section File inclusions in the configuration file
4349 .index inclusions in configuration file
4350 .index configuration file||including other files
4351 .index .include in configuration file
4352 .index .include@_if@_exists in configuration file
4353 You can include other files inside Exim's run time configuration file by
4356 @.include <<file name>>
4360 @.include@_if@_exists <<file name>>
4362 on a line by itself. Double quotes round the file name are optional. If you use
4363 the first form, a configuration error occurs if the file does not exist; the
4364 second form does nothing for non-existent files.
4366 Includes may be nested to any depth, but remember that Exim reads its
4367 configuration file often, so it is a good idea to keep them to a minimum.
4368 If you change the contents of an included file, you must HUP the daemon,
4369 because an included file is read only when the configuration itself is read.
4371 The processing of inclusions happens early, at a physical line level, so, like
4372 comment lines, an inclusion can be used in the middle of an option setting,
4375 hosts_lookup = a.b.c \
4378 Include processing happens
4380 macro processing (see below). Its effect is to process the lines of the file as
4381 if they occurred inline where the inclusion appears.
4384 .section Macros in the configuration file
4385 .rset SECTmacrodefs "~~chapter.~~section"
4386 .index macro||description of
4387 .index configuration file||macros
4388 If a line in the main part of the configuration (that is, before the first
4389 `begin' line) begins with an upper case letter, it is taken as a macro
4390 definition, and must be of the form
4392 <<name>> = <<rest of line>>
4394 The name must consist of letters, digits, and underscores, and need not all be
4395 in upper case, though that is recommended. The rest of the line, including any
4396 continuations, is the replacement text, and has leading and trailing white
4397 space removed. Quotes are not removed. The replacement text can never end with
4398 a backslash character, but this doesn't seem to be a serious limitation.
4400 Once a macro is defined, all subsequent lines in the file (and any included
4401 files) are scanned for the macro name; if there are several macros, the line is
4402 scanned for each in turn, in the order in which they are defined. The
4403 replacement text is not re-scanned for the current macro, though it is scanned
4404 for subsequently defined macros. For this reason, a macro name may not contain
4405 the name of a previously defined macro as a substring. You could, for example,
4408 ABCD_XYZ = <<something>>
4409 ABCD = <<something else>>
4411 but putting the definitions in the opposite order would provoke a configuration
4414 Macro expansion is applied to individual lines from the file, before checking
4415 for line continuation or file inclusion (see below). If a line consists solely
4416 of a macro name, and the expansion of the macro is empty, the line is ignored.
4417 A macro at the start of a line may turn the line into a comment line or a
4420 As an example of macro usage, consider a configuration where aliases are looked
4421 up in a MySQL database. It helps to keep the file less cluttered if long
4422 strings such as SQL statements are defined separately as macros, for example:
4424 ALIAS_QUERY = select mailbox from user where \
4425 login=${quote_mysql:$local_part};
4427 This can then be used in a \%redirect%\ router setting like this:
4429 data = ${lookup mysql{ALIAS_QUERY}}
4431 In earlier versions of Exim macros were sometimes used for domain, host, or
4432 address lists. In Exim 4 these are handled better by named lists -- see section
4435 Macros in the configuration file can be overridden by the \-D-\ command line
4436 option, but Exim gives up its root privilege when \-D-\ is used, unless called
4437 by root or the Exim user.
4440 .section Conditional skips in the configuration file
4441 .index configuration file||conditional skips
4443 You can use the directives \".ifdef"\, \".ifndef"\, \".elifdef"\,
4444 \".elifndef"\, \".else"\, and \".endif"\ to dynamically include or exclude
4445 portions of the configuration file. The processing happens whenever the file is
4446 read (that is, when an Exim binary starts to run).
4448 The implementation is very simple. Instances of the first four directives must
4449 be followed by text that includes the names of one or macros. The condition
4450 that is tested is whether or not any macro substitution has taken place in the
4454 message@_size@_limit = 50M
4456 message@_size@_limit = 100M
4459 sets a message size limit of 50M if the macro \"AAA"\ is defined, and 100M
4460 otherwise. If there is more than one macro named on the line, the condition
4461 is true if any of them are defined. That is, it is an `or' condition. To
4462 obtain an `and' condition, you need to use nested \".ifdef"\s.
4464 Although you can use a macro expansion to generate one of these directives,
4465 it is not very useful, because the condition `there was a macro substitution
4466 in this line' will always be true.
4468 Text following \".else"\ and \".endif"\ is ignored, and can be used as comment
4469 to clarify complicated nestings.
4472 .section Common option syntax
4473 .rset SECTcos "~~chapter.~~section"
4474 .index common option syntax
4475 .index syntax of common options
4476 .index configuration file||common option syntax
4477 For the main set of options, driver options, and \*local@_scan()*\ options,
4478 each setting is on a line by itself, and starts with a name consisting of
4479 lower-case letters and underscores. Many options require a data value, and in
4480 these cases the name must be followed by an equals sign (with optional white
4481 space) and then the value. For example:
4483 qualify_domain = mydomain.example.com
4485 Some option settings may contain sensitive data, for example, passwords for
4486 accessing databases. To stop non-admin users from using the \-bP-\ command line
4487 option to read these values, you can precede the option settings with the word
4488 `hide'. For example:
4490 hide mysql_servers = localhost/users/admin/secret-password
4492 For non-admin users, such options are displayed like this:
4494 mysql_servers = <value not displayable>
4496 If `hide' is used on a driver option, it hides the value of that option on all
4497 instances of the same driver.
4499 The following sections describe the syntax used for the different data types
4500 that are found in option settings.
4502 .section Boolean options
4503 .index format||boolean
4504 .index boolean configuration values
4505 Options whose type is given as boolean are on/off switches. There are two
4506 different ways of specifying such options: with and without a data value. If
4507 the option name is specified on its own without data, the switch is turned on;
4508 if it is preceded by `no@_' or `not@_' the switch is turned off. However,
4509 boolean options may optionally be followed by an equals sign and one of the
4510 words `true', `false', `yes', or `no', as an alternative syntax. For example,
4511 the following two settings have exactly the same effect:
4516 The following two lines also have the same (opposite) effect:
4521 You can use whichever syntax you prefer.
4525 .section Integer values
4526 .index integer configuration values
4527 .index format||integer
4528 If an integer data item starts with the characters `0x', the remainder of it
4529 is interpreted as a hexadecimal number. Otherwise, it is treated as octal if it
4530 starts with the digit 0, and decimal if not. If an integer value is followed by
4531 the letter K, it is multiplied by 1024; if it is followed by the letter M, it
4532 is multiplied by 1024x1024.
4534 When the values of integer option settings are output, values which are an
4535 exact multiple of 1024 or 1024x1024 are
4536 sometimes, but not always,
4537 printed using the letters K and M. The printing style is independent of the
4538 actual input format that was used.
4540 .section Octal integer values
4541 .index integer format
4542 .index format||octal integer
4543 The value of an option specified as an octal integer is always interpreted in
4544 octal, whether or not it starts with the digit zero. Such options are always
4548 .section Fixed point number values
4549 .index fixed point configuration values
4550 .index format||fixed point
4551 A fixed point number consists of a decimal integer, optionally followed by a
4552 decimal point and up to three further digits.
4555 .section Time interval values
4556 .index time interval||specifying in configuration
4557 .index format||time interval
4558 .rset SECTtimeformat "~~chapter.~~section"
4559 A time interval is specified as a sequence of numbers, each followed by one of
4560 the following letters, with no intervening white space:
4569 For example, `3h50m' specifies 3 hours and 50 minutes. The values of time
4570 intervals are output in the same format.
4571 Exim does not restrict the values; it is perfectly acceptable, for example, to
4572 specify `90m' instead of `1h30m'.
4575 .section String values
4576 .index string||format of configuration values
4577 .index format||string
4578 .rset SECTstrings "~~chapter.~~section"
4579 If a string data item does not start with a double-quote character, it is taken
4580 as consisting of the remainder of the line plus any continuation lines,
4581 starting at the first character after any leading white space, with trailing
4582 white space characters removed, and with no interpretation of the characters in
4583 the string. Because Exim removes comment lines (those beginning with @#) at an
4584 early stage, they can appear in the middle of a multi-line string. The
4585 following settings are therefore equivalent:
4587 trusted_users = uucp:mail
4589 trusted_users = uucp:\
4590 # This comment line is ignored
4593 .index string||quoted
4594 .index escape characters in quoted strings
4595 If a string does start with a double-quote, it must end with a closing
4596 double-quote, and any backslash characters other than those used for line
4597 continuation are interpreted as escape characters, as follows:
4600 @\@\ $t $rm{single backslash}
4602 @\r $t $rm{carriage return}
4604 @\<<octal digits>> $t $rm{up to 3 octal digits specify one character}
4605 @\x<<hex digits>> $t $rm{up to 2 hexadecimal digits specify one character}
4607 If a backslash is followed by some other character, including a double-quote
4608 character, that character replaces the pair.
4610 Quoting is necessary only if you want to make use of the backslash escapes to
4611 insert special characters, or if you need to specify a value with leading or
4612 trailing spaces. These cases are rare, so quoting is almost never needed in
4613 current versions of Exim. In versions of Exim before 3.14, quoting was required
4614 in order to continue lines, so you may come across older configuration files
4615 and examples that apparently quote unnecessarily.
4617 .section Expanded strings
4618 .index string||expansion, definition of
4619 .index expansion||definition of
4620 Some strings in the configuration file are subjected to \*string expansion*\,
4621 by which means various parts of the string may be changed according to the
4622 circumstances (see chapter ~~CHAPexpand). The input syntax for such strings is
4623 as just described; in particular, the handling of backslashes in quoted strings
4624 is done as part of the input process, before expansion takes place. However,
4625 backslash is also an escape character for the expander, so any backslashes that
4626 are required for that reason must be doubled if they are within a quoted
4627 configuration string.
4629 .section User and group names
4630 .index user name||format of
4631 .index format||user name
4632 .index group||name format
4633 .index format||group name
4634 User and group names are specified as strings, using the syntax described
4635 above, but the strings are interpreted specially. A user or group name must
4636 either consist entirely of digits, or be a name that can be looked up using the
4637 \*getpwnam()*\ or \*getgrnam()*\ function, as appropriate.
4639 .section List construction
4640 .index list||syntax of in configuration
4641 .index format||list item in configuration
4642 .index string list, definition
4643 .rset SECTlistconstruct "~~chapter.~~section"
4644 The data for some configuration options is a colon-separated list of items.
4645 Many of these options are shown with type `string list' in the descriptions
4646 later in this document. Others are listed as `domain list', `host list',
4647 `address list', or `local part list'. Syntactically, they are all the same;
4648 however, those other than `string list' are subject to particular kinds of
4649 interpretation, as described in chapter ~~CHAPdomhosaddlists.
4651 In all these cases, the entire list is treated as a single string as far as the
4652 input syntax is concerned. The \trusted@_users\ setting in section
4653 ~~SECTstrings above is an example. If a colon is actually needed in an item in
4654 a list, it must be entered as two colons. Leading and trailing white space on
4655 each item in a list is ignored. This makes it possible to include items that
4656 start with a colon, and in particular, certain forms of IPv6 address. For
4659 local_interfaces = 127.0.0.1 : ::::1
4661 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address
4662 @:@:1. IPv6 addresses are going to become more and more common as the new
4663 protocol gets more widely deployed.
4664 .index list||separator, changing
4665 .index IPv6||addresses in lists
4666 Doubling their colons is an unwelcome chore, so a mechanism was introduced to
4667 allow the separator character to be changed. If a list begins with a left angle
4668 bracket, followed by any punctuation character, that character is used instead
4669 of colon as the list separator. For example, the list above can be rewritten to
4670 use a semicolon separator like this:
4672 local_interfaces = <; 127.0.0.1 ; ::1
4674 This facility applies to all lists, with the exception of the list in
4675 \log@_file@_path\. It is recommended that the use of non-colon separators be
4676 confined to circumstances where they really are needed.
4679 .section Format of driver configurations
4680 .rset SECTfordricon "~~chapter.~~section"
4681 .index drivers||configuration format
4682 There are separate parts in the configuration for defining routers, transports,
4683 and authenticators. In each part, you are defining a number of driver
4684 instances, each with its own set of options. Each driver instance is defined by
4685 a sequence of lines like this:
4692 In the following example, the instance name is \%localuser%\, and it is
4693 followed by three options settings:
4698 transport = local_delivery
4700 For each driver instance, you specify which Exim code module it uses -- by the
4701 setting of the \driver\ option -- and (optionally) some configuration settings.
4702 For example, in the case of transports, if you want a transport to deliver with
4703 SMTP you would use the \%smtp%\ driver; if you want to deliver to a local file
4704 you would use the \%appendfile%\ driver. Each of the drivers is described in
4705 detail in its own separate chapter later in this manual.
4707 You can have several routers, transports, or authenticators that are based on
4708 the same underlying driver (each must have a different name).
4710 The order in which routers are defined is important, because addresses are
4711 passed to individual routers one by one, in order. The order in which
4712 transports are defined does not matter at all. The order in which
4713 authenticators are defined is used only when Exim, as a client, is searching
4714 them to find one that matches an authentication mechanism offered by the
4717 .index generic options
4718 .index options||generic, definition of
4719 Within a driver instance definition, there are two kinds of option:
4720 $it{generic} and $it{private}. The generic options are those that apply to all
4721 drivers of the same type (that is, all routers, all transports or all
4723 The \driver\ option is a generic option that must appear in every definition.
4724 .index private options
4725 The private options are special for each driver, and none need appear, because
4726 they all have default values.
4728 The options may appear in any order, except that the \driver\ option must
4729 precede any private options, since these depend on the particular driver. For
4730 this reason, it is recommended that \driver\ always be the first option.
4732 Driver instance names, which are used for reference in log entries and
4733 elsewhere, can be any sequence of letters, digits, and underscores (starting
4734 with a letter) and must be unique among drivers of the same type. A router and
4735 a transport (for example) can each have the same name, but no two router
4736 instances can have the same name. The name of a driver instance should not be
4737 confused with the name of the underlying driver module. For example, the
4738 configuration lines:
4743 create an instance of the \%smtp%\ transport driver whose name is
4744 \%remote@_smtp%\. The same driver code can be used more than once, with
4745 different instance names and different option settings each time. A second
4746 instance of the \%smtp%\ transport, with different options, might be defined
4752 command_timeout = 10s
4754 The names \%remote@_smtp%\ and \%special@_smtp%\ would be used to reference
4755 these transport instances from routers, and these names would appear in log
4758 Comment lines may be present in the middle of driver specifications. The full
4759 list of option settings for any particular driver instance, including all the
4760 defaulted values, can be extracted by making use of the \-bP-\ command line
4772 . ============================================================================
4773 .chapter The default configuration file
4774 .set runningfoot "default configuration"
4775 .rset CHAPdefconfil "~~chapter"
4776 .index configuration file||default, `walk through'
4777 .index default||configuration file `walk through'
4778 The default configuration file supplied with Exim as \(src/configure.default)\
4779 is sufficient for a host with simple mail requirements. As an introduction to
4780 the way Exim is configured, this chapter `walks through' the default
4781 configuration, giving brief explanations of the settings. Detailed descriptions
4782 of the options are given in subsequent chapters. The default configuration file
4783 itself contains extensive comments about ways you might want to modify the
4784 initial settings. However, note that there are many options that are not
4785 mentioned at all in the default configuration.
4788 .section Main configuration settings
4789 The main (global) configuration option settings must always come first in the
4790 file. The first thing you'll see in the file, after some initial comments, is
4793 # primary_hostname =
4795 This is a commented-out setting of the \primary@_hostname\ option. Exim needs
4796 to know the official, fully qualified name of your host, and this is where you
4797 can specify it. However, in most cases you do not need to set this option. When
4798 it is unset, Exim uses the \*uname()*\ system function to obtain the host name.
4800 The first three non-comment configuration lines are as follows:
4802 domainlist local_domains = @
4803 domainlist relay_to_domains =
4804 hostlist relay_from_hosts = 127.0.0.1
4806 These are not, in fact, option settings. They are definitions of two named
4807 domain lists and one named host list. Exim allows you to give names to lists of
4808 domains, hosts, and email addresses, in order to make it easier to manage the
4809 configuration file (see section ~~SECTnamedlists).
4811 The first line defines a domain list called \*local@_domains*\; this is used
4812 later in the configuration to identify domains that are to be delivered
4814 .index @@ in a domain list
4815 There is just one item in this list, the string `@@'. This is a special form of
4816 entry which means `the name of the local host'. Thus, if the local host is
4817 called \*a.host.example*\, mail to \*any.user@@a.host.example*\ is expected to
4818 be delivered locally. Because the local host's name is referenced indirectly,
4819 the same configuration file can be used on different hosts.
4821 The second line defines a domain list called \*relay@_to@_domains*\, but the
4822 list itself is empty. Later in the configuration we will come to the part that
4823 controls mail relaying through the local host; it allows relaying to any
4824 domains in this list. By default, therefore, no relaying on the basis of a mail
4825 domain is permitted.
4827 The third line defines a host list called \*relay@_from@_hosts*\. This list is
4828 used later in the configuration to permit relaying from any host or IP address
4829 that matches the list. The default contains just the IP address of the IPv4
4830 loopback interface, which means that processes on the local host are able to
4831 submit mail for relaying by sending it over TCP/IP to that interface. No other
4832 hosts are permitted to submit messages for relaying.
4834 Just to be sure there's no misunderstanding: at this point in the configuration
4835 we aren't actually setting up any controls. We are just defining some domains
4836 and hosts that will be used in the controls that are specified later.
4838 The next configuration line is a genuine option setting:
4840 acl_smtp_rcpt = acl_check_rcpt
4842 This option specifies an \*Access Control List*\ (ACL) which is to be used
4843 during an incoming SMTP session for every recipient of a message (every
4844 \\RCPT\\ command). The name of the list is \*acl@_check@_rcpt*\, and we will
4845 come to its definition below, in the ACL section of the configuration. ACLs
4846 control which recipients are accepted for an incoming message -- if a
4847 configuration does not provide an ACL to check recipients, no SMTP mail can be
4850 Two commented-out options settings are next:
4853 # qualify_recipient =
4855 The first of these specifies a domain that Exim uses when it constructs a
4856 complete email address from a local login name. This is often needed when Exim
4857 receives a message from a local process. If you do not set \qualify@_domain\,
4858 the value of \primary@_hostname\ is used. If you set both of these options, you
4859 can have different qualification domains for sender and recipient addresses. If
4860 you set only the first one, its value is used in both cases.
4862 .index domain literal||recognizing format
4863 The following line must be uncommented if you want Exim to recognize
4864 addresses of the form \*user@@[10.11.12.13]*\ that is, with a `domain literal'
4865 (an IP address) instead of a named domain.
4867 # allow_domain_literals
4869 The RFCs still require this form, but many people think that in the modern
4870 Internet it makes little sense to permit mail to be sent to specific hosts by
4871 quoting their IP addresses. This ancient format has been used by people who
4872 try to abuse hosts by using them for unwanted relaying. However, some
4873 people believe there are circumstances (for example, messages addressed to
4874 \*postmaster*\) where domain literals are still useful.
4876 The next configuration line is a kind of trigger guard:
4880 It specifies that no delivery must ever be run as the root user. The normal
4881 convention is to set up \*root*\ as an alias for the system administrator. This
4882 setting is a guard against slips in the configuration.
4883 The list of users specified by \never@_users\ is not, however, the complete
4884 list; the build-time configuration in \(Local/Makefile)\ has an option called
4885 \\FIXED@_NEVER@_USERS\\ specifying a list that cannot be overridden. The
4886 contents of \never@_users\ are added to this list. By default
4887 \\FIXED@_NEVER@_USERS\\ also specifies root.
4889 When a remote host connects to Exim in order to send mail, the only information
4890 Exim has about the host's identity is its IP address. The next configuration
4895 specifies that Exim should do a reverse DNS lookup on all incoming connections,
4896 in order to get a host name. This improves the quality of the logging
4897 information, but if you feel it is too expensive, you can remove it entirely,
4898 or restrict the lookup to hosts on `nearby' networks.
4899 Note that it is not always possible to find a host name from an IP address,
4900 because not all DNS reverse zones are maintained, and sometimes DNS servers are
4903 The next two lines are concerned with \*ident*\ callbacks, as defined by RFC
4904 1413 (hence their names):
4907 rfc1413_query_timeout = 30s
4909 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
4910 You can limit the hosts to which these calls are made, or change the timeout
4911 that is used. If you set the timeout to zero, all ident calls are disabled.
4912 Although they are cheap and can provide useful information for tracing problem
4913 messages, some hosts and firewalls have problems with ident calls. This can
4914 result in a timeout instead of an immediate refused connection, leading to
4915 delays on starting up an incoming SMTP session.
4917 When Exim receives messages over SMTP connections, it expects all addresses to
4918 be fully qualified with a domain, as required by the SMTP definition. However,
4919 if you are running a server to which simple clients submit messages, you may
4920 find that they send unqualified addresses. The two commented-out options:
4922 # sender_unqualified_hosts =
4923 # recipient_unqualified_hosts =
4925 show how you can specify hosts that are permitted to send unqualified sender
4926 and recipient addresses, respectively.
4928 The \percent@_hack@_domains\ option is also commented out:
4930 # percent_hack_domains =
4932 It provides a list of domains for which the `percent hack' is to operate. This
4933 is an almost obsolete form of explicit email routing. If you do not know
4934 anything about it, you can safely ignore this topic.
4936 The last two settings in the main part of the default configuration are
4937 concerned with messages that have been `frozen' on Exim's queue. When a message
4938 is frozen, Exim no longer continues to try to deliver it. Freezing occurs when
4939 a bounce message encounters a permanent failure because the sender address of
4940 the original message that caused the bounce is invalid, so the bounce cannot be
4941 delivered. This is probably the most common case, but there are also other
4942 conditions that cause freezing, and frozen messages are not always bounce
4945 ignore_bounce_errors_after = 2d
4946 timeout_frozen_after = 7d
4948 The first of these options specifies that failing bounce messages are to be
4949 discarded after 2 days on the queue. The second specifies that any frozen
4950 message (whether a bounce message or not) is to be timed out (and discarded)
4951 after a week. In this configuration, the first setting ensures that no failing
4952 bounce message ever lasts a week.
4955 .section ACL configuration
4956 .index default||ACLs
4957 .index ~~ACL||default configuration
4958 In the default configuration, the ACL section follows the main configuration.
4959 It starts with the line
4963 and it contains the definition of one ACL called \*acl@_check@_rcpt*\ that was
4964 referenced in the setting of \acl@_smtp@_rcpt\ above.
4965 .index \\RCPT\\||ACL for
4966 This ACL is used for every \\RCPT\\ command in an incoming SMTP message. Each
4967 \\RCPT\\ command specifies one of the message's recipients. The ACL statements
4968 are considered in order, until the recipient address is either accepted or
4969 rejected. The \\RCPT\\ command is then accepted or rejected, according to the
4970 result of the ACL processing.
4974 This line, consisting of a name terminated by a colon, marks the start of the
4979 This ACL statement accepts the recipient if the sending host matches the list.
4980 But what does that strange list mean? It doesn't actually contain any host
4981 names or IP addresses. The presence of the colon puts an empty item in the
4982 list; Exim matches this only if the incoming message didn't come from a remote
4983 host. The colon is important. Without it, the list itself is empty, and can
4984 never match anything.
4986 What this statement is doing is to accept unconditionally all recipients in
4987 messages that are submitted by SMTP from local processes using the standard
4988 input and output (that is, not using TCP/IP). A number of MUAs operate in this
4991 deny domains = +local_domains
4992 local_parts = ^[.] : ^.*[@%!/|]
4994 deny domains = !+local_domains
4995 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
4997 These statements are concerned with local parts that contain any of the
4998 characters `@@', `%', `!', `/', `|', or dots in unusual places. Although these
4999 characters are entirely legal in local parts (in the case of `@@' and leading
5000 dots, only if correctly quoted), they do not commonly occur in Internet mail
5003 The first three have in the past been associated with explicitly routed
5004 addresses (percent is still sometimes used -- see the \percent@_hack@_domains\
5005 option). Addresses containing these characters are regularly tried by spammers
5006 in an attempt to bypass relaying restrictions, and also by open relay testing
5007 programs. Unless you really need them it is safest to reject these characters
5008 at this early stage. This configuration is heavy-handed in rejecting these
5009 characters for all messages it accepts from remote hosts. This is a deliberate
5010 policy of being as safe as possible.
5012 The first rule above is stricter, and is applied to messages that are addressed
5013 to one of the local domains handled by this host. This is implemented by the
5014 first condition, which restricts it to domains that are listed in the
5015 \*local@_domains*\ domain list. The `+' character is used to indicate a
5016 reference to a named list. In this configuration, there is just one domain in
5017 \*local@_domains*\, but in general there may be many.
5019 The second condition on the first statement uses two regular expressions to
5020 block local parts that begin with a dot or contain `@@', `%', `!', `/', or `|'.
5021 If you have local accounts that include these characters, you will have to
5024 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5025 allows them because they have been encountered in practice. (Consider local
5026 parts constructed as `first-initial.second-initial.family-name' when applied to
5027 someone like the author of Exim, who has no second initial.) However, a local
5028 part starting with a dot or containing `/../' can cause trouble if it is used
5029 as part of a file name (for example, for a mailing list). This is also true for
5030 local parts that contain slashes. A pipe symbol can also be troublesome if the
5031 local part is incorporated unthinkingly into a shell command line.
5033 The second rule above applies to all other domains, and is less strict. This
5034 allows your own users to send outgoing messages to sites that use slashes
5035 and vertical bars in their local parts. It blocks local parts that begin
5036 with a dot, slash, or vertical bar, but allows these characters within the
5037 local part. However, the sequence `/../' is barred. The use of `@@', `%', and
5038 `!' is blocked, as before. The motivation here is to prevent your users (or
5039 your users' viruses) from mounting certain kinds of attack on remote sites.
5042 accept local_parts = postmaster
5043 domains = +local_domains
5045 This statement, which has two conditions, accepts an incoming address if the
5046 local part is \*postmaster*\ and the domain is one of those listed in the
5047 \*local@_domains*\ domain list. The `+' character is used to indicate a
5048 reference to a named list. In this configuration, there is just one domain in
5049 \*local@_domains*\, but in general there may be many.
5051 The presence of this statement means that mail to postmaster is never blocked
5052 by any of the subsequent tests. This can be helpful while sorting out problems
5053 in cases where the subsequent tests are incorrectly denying access.
5055 require verify = sender
5057 This statement requires the sender address to be verified before any subsequent
5058 ACL statement can be used. If verification fails, the incoming recipient
5059 address is refused. Verification consists of trying to route the address, to
5062 message could be delivered to it. In the case of remote addresses, basic
5063 verification checks only the domain, but \*callouts*\ can be used for more
5064 verification if required. Section ~~SECTaddressverification discusses the
5065 details of address verification.
5068 # deny message = rejected because $sender_host_address is \
5069 # in a black list at $dnslist_domain\n\
5071 # dnslists = black.list.example
5073 # warn message = X-Warning: $sender_host_address is \
5074 # in a black list at $dnslist_domain
5075 # log_message = found in $dnslist_domain
5076 # dnslists = black.list.example
5078 These commented-out lines are examples of how you could configure Exim to check
5079 sending hosts against a DNS black list. The first statement rejects messages
5080 from blacklisted hosts, whereas the second merely inserts a warning header
5084 accept domains = +local_domains
5086 message = unknown user
5089 This statement accepts the incoming recipient address if its domain is one of
5090 the local domains, but only if the address can be verified. Verification of
5091 local addresses normally checks both the local part and the domain. The
5092 \endpass\ line needs some explanation: if the condition above \endpass\ fails,
5093 that is, if the address is not in a local domain, control is passed to the next
5094 ACL statement. However, if the condition below \endpass\ fails, that is, if a
5095 recipient in a local domain cannot be verified, access is denied and the
5096 recipient is rejected.
5097 .index customizing||ACL failure message
5098 The \message\ modifier provides a customized error message for the failure.
5100 accept domains = +relay_to_domains
5102 message = unrouteable address
5105 This statement accepts the incoming recipient address if its domain is one of
5106 the domains for which this host is a relay, but again, only if the address can
5109 accept hosts = +relay_from_hosts
5111 Control reaches this statement only if the recipient's domain is neither a
5112 local domain, nor a relay domain. The statement accepts the address if the
5113 message is coming from one of the hosts that are defined as being allowed to
5114 relay through this host. Recipient verification is omitted here, because in
5115 many cases the clients are dumb MUAs that do not cope well with SMTP error
5116 responses. If you are actually relaying out from MTAs, you should probably add
5117 recipient verification here.
5119 accept authenticated = *
5121 Control reaches here for attempts to relay to arbitrary domains from arbitrary
5122 hosts. The statement accepts the address only if the client host has
5123 authenticated itself. The default configuration does not define any
5124 authenticators, which means that no client can in fact authenticate. You will
5125 need to add authenticator definitions if you want to make use of this ACL
5128 deny message = relay not permitted
5130 The final statement denies access, giving a specific error message. Reaching
5131 the end of the ACL also causes access to be denied, but with the generic
5132 message `administrative prohibition'.
5135 .section Router configuration
5136 .index default||routers
5137 .index routers||default
5138 The router configuration comes next in the default configuration, introduced
5143 Routers are the modules in Exim that make decisions about where to send
5144 messages. An address is passed to each router in turn, until it is either
5145 accepted, or failed. This means that the order in which you define the routers
5146 matters. Each router is fully described in its own chapter later in this
5147 manual. Here we give only brief overviews.
5149 .index domain literal||default router
5152 # driver = ipliteral
5153 # domains = !+local_domains
5154 # transport = remote_smtp
5156 This router is commented out because the majority of sites do not want to
5157 support domain literal addresses (those of the form \*user@@[10.9.8.7]*\). If
5158 you uncomment this router, you also need to uncomment the setting of
5159 \allow@_domain@_literals\ in the main part of the configuration.
5164 domains = ! +local_domains
5165 transport = remote_smtp
5167 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5171 The first uncommented router handles addresses that do not involve any local
5172 domains. This is specified by the line
5174 domains = ! +local_domains
5176 The \domains\ option lists the domains to which this router applies, but the
5177 exclamation mark is a negation sign, so the router is used only for domains
5178 that are not in the domain list called \*local@_domains*\ (which was defined at
5179 the start of the configuration). The plus sign before \*local@_domains*\
5180 indicates that it is referring to a named list. Addresses in other domains are
5181 passed on to the following routers.
5183 The name of the router driver is \%dnslookup%\,
5184 and is specified by the \driver\ option. Do not be confused by the fact that
5185 the name of this router instance is the same as the name of the driver. The
5186 instance name is arbitrary, but the name set in the \driver\ option must be one
5187 of the driver modules that is in the Exim binary.
5189 The \%dnslookup%\ router routes addresses by looking up their domains in the
5190 DNS in order to obtain a list of hosts to which the address is routed. If the
5191 router succeeds, the address is queued for the \%remote@_smtp%\ transport, as
5192 specified by the \transport\ option. If the router does not find the domain in
5193 the DNS, no further routers are tried because of the \no@_more\ setting, so the
5194 address fails and is bounced.
5196 The \ignore@_target@_hosts\ option specifies a list of IP addresses that are to
5197 be entirely ignored. This option is present because a number of cases have been
5198 encountered where MX records in the DNS point to host names
5199 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5200 Completely ignoring these IP addresses causes Exim to fail to route the
5201 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5202 continue to try to deliver the message periodically until the address timed
5209 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5211 file_transport = address_file
5212 pipe_transport = address_pipe
5214 Control reaches this and subsequent routers only for addresses in the local
5215 domains. This router checks to see whether the local part is defined as an
5216 alias in the \(/etc/aliases)\ file, and if so, redirects it according to the
5217 data that it looks up from that file. If no data is found for the local part,
5218 the value of the \data\ option is empty, causing the address to be passed to
5221 \(/etc/aliases)\ is a conventional name for the system aliases file that is
5222 often used. That is why it is referenced by from the default configuration
5223 file. However, you can change this by setting \\SYSTEM@_ALIASES@_FILE\\ in
5224 \(Local/Makefile)\ before building Exim.
5230 file = $home/.forward
5235 file_transport = address_file
5236 pipe_transport = address_pipe
5237 reply_transport = address_reply
5239 This is the most complicated router in the default configuration. It is another
5240 redirection router, but this time it is looking for forwarding data set up by
5241 individual users. The \check@_local@_user\ setting means that the first thing it
5242 does is to check that the local part of the address is the login name of a
5243 local user. If it is not, the router is skipped. When a local user is found,
5244 the file called \(.forward)\ in the user's home directory is consulted. If it
5245 does not exist, or is empty, the router declines. Otherwise, the contents of
5246 \(.forward)\ are interpreted as redirection data (see chapter ~~CHAPredirect
5249 .index Sieve filter||enabling in default router
5250 Traditional \(.forward)\ files contain just a list of addresses, pipes, or
5251 files. Exim supports this by default. However, if \allow@_filter\ is set (it is
5252 commented out by default), the contents of the file are interpreted as a set of
5253 Exim or Sieve filtering instructions, provided the file begins with `@#Exim
5254 filter' or `@#Sieve filter', respectively. User filtering is discussed in the
5255 separate document entitled \*Exim's interfaces to mail filtering*\.
5257 The \no@_verify\ and \no@_expn\ options mean that this router is skipped when
5258 verifying addresses, or when running as a consequence of an SMTP \\EXPN\\
5260 There are two reasons for doing this:
5262 Whether or not a local user has a \(.forward)\ file is not really relevant when
5263 checking an address for validity; it makes sense not to waste resources doing
5266 More importantly, when Exim is verifying addresses or handling an \\EXPN\\
5267 command during an SMTP session, it is running as the Exim user, not as root.
5268 The group is the Exim group, and no additional groups are set up.
5269 It may therefore not be possible for Exim to read users' \(.forward)\ files at
5273 The setting of \check@_ancestor\ prevents the router from generating a new
5274 address that is the same as any previous address that was redirected. (This
5275 works round a problem concerning a bad interaction between aliasing and
5276 forwarding -- see section ~~SECTredlocmai).
5278 The final three option settings specify the transports that are to be used when
5279 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5280 auto-reply, respectively. For example, if a \(.forward)\ file contains
5282 a.nother@elsewhere.example, /home/spqr/archive
5284 the delivery to \(/home/spqr/archive)\ is done by running the \address@_file\
5290 transport = local_delivery
5292 The final router sets up delivery into local mailboxes, provided that the local
5293 part is the name of a local login, by accepting the address and queuing it for
5294 the \%local@_delivery%\ transport. Otherwise, we have reached the end of the
5295 routers, so the address is bounced.
5298 .section Transport configuration
5299 .index default||transports
5300 .index transports||default
5301 Transports define mechanisms for actually delivering messages. They operate
5302 only when referenced from routers, so the order in which they are defined does
5303 not matter. The transports section of the configuration starts with
5307 One remote transport and four local transports are defined.
5312 This transport is used for delivering messages over SMTP connections. All its
5313 options are defaulted. The list of remote hosts comes from the router.
5317 file = /var/mail/$local_part
5324 This \%appendfile%\ transport is used for local delivery to user mailboxes in
5325 traditional BSD mailbox format. By default it runs under the uid and gid of the
5326 local user, which requires the sticky bit to be set on the \(/var/mail)\
5327 directory. Some systems use the alternative approach of running mail deliveries
5328 under a particular group instead of using the sticky bit. The commented options
5329 show how this can be done.
5331 Exim adds three headers to the message as it delivers it: ::Delivery-date::,
5332 ::Envelope-to:: and ::Return-path::. This action is requested by the three
5333 similarly-named options above.
5339 This transport is used for handling deliveries to pipes that are generated by
5340 redirection (aliasing or users' \(.forward)\ files). The \return@_output\
5341 option specifies that any output generated by the pipe is to be returned to the
5350 This transport is used for handling deliveries to files that are generated by
5351 redirection. The name of the file is not specified in this instance of
5352 \%appendfile%\, because it comes from the \%redirect%\ router.
5357 This transport is used for handling automatic replies generated by users'
5361 .section Default retry rule
5362 .index retry||default rule
5363 .index default||retry rule
5364 The retry section of the configuration file contains rules which affect the way
5365 Exim retries deliveries that cannot be completed at the first attempt. It is
5366 introduced by the line
5370 In the default configuration, there is just one rule, which applies to all
5373 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5375 This causes any temporarily failing address to be retried every 15 minutes for
5376 2 hours, then at intervals starting at one hour and increasing by a factor of
5377 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5378 is not delivered after 4 days of failure, it is bounced.
5381 .section Rewriting configuration
5382 The rewriting section of the configuration, introduced by
5386 contains rules for rewriting addresses in messages as they arrive. There are no
5387 rewriting rules in the default configuration file.
5390 .section Authenticators configuration
5391 .index \\AUTH\\||configuration
5392 The authenticators section of the configuration, introduced by
5394 begin authenticators
5396 defines mechanisms for the use of the SMTP \\AUTH\\ command. No authenticators
5397 are specified in the default configuration file.
5405 . ============================================================================
5406 .chapter Regular expressions
5407 .set runningfoot "regular expressions"
5408 .rset CHAPregexp ~~chapter
5410 .index regular expressions||library
5412 Exim supports the use of regular expressions in many of its options. It
5413 uses the PCRE regular expression library; this provides regular expression
5414 matching that is compatible with Perl 5. The syntax and semantics of
5415 regular expressions is discussed in many Perl reference books, and also in
5418 [(A HREF="http://www.oreilly.com/catalog/regex/")]
5420 $it{Mastering Regular Expressions}
5424 (O'Reilly, ISBN 0-596-00289-0).
5426 The documentation for the syntax and semantics of the regular expressions that
5427 are supported by PCRE is included in plain text in the file
5428 \(doc/pcrepattern.txt)\ in the Exim distribution, and also in the HTML
5429 tarbundle of Exim documentation, and as an appendix to the
5431 [(A HREF="http://www.uit.co.uk/exim-book/")]
5437 It describes in detail the features of the regular expressions that PCRE
5438 supports, so no further description is included here. The PCRE functions are
5439 called from Exim using the default option settings (that is, with no PCRE
5440 options set), except that the \\PCRE@_CASELESS\\ option is set when the
5441 matching is required to be case-insensitive.
5443 In most cases, when a regular expression is required in an Exim configuration,
5444 it has to start with a circumflex, in order to distinguish it from plain text
5445 or an `ends with' wildcard. In this example of a configuration setting, the
5446 second item in the colon-separated list is a regular expression.
5448 domains = a.b.c : ^\\d{3} : *.y.z : ...
5450 The doubling of the backslash is required because of string expansion that
5451 precedes interpretation -- see section ~~SECTlittext for more discussion of
5452 this issue, and a way of avoiding the need for doubling backslashes. The
5453 regular expression that is eventually used in this example contains just one
5454 backslash. The circumflex is included in the regular expression, and has the
5455 normal effect of `anchoring' it to the start of the string that is being
5458 There are, however, two cases where a circumflex is not required for the
5459 recognition of a regular expression: these are the \match\ condition in a
5460 string expansion, and the \matches\ condition in an Exim filter file. In these
5461 cases, the relevant string is always treated as a regular expression; if it
5462 does not start with a circumflex, the expression is not anchored, and can match
5463 anywhere in the subject string.
5465 In all cases, if you want a regular expression to match at the end of a string,
5466 you must code the @$ metacharacter to indicate this. For example:
5468 domains = ^\\d{3}\\.example
5470 matches the domain \*123.example*\, but it also matches \*123.example.com*\.
5473 domains = ^\\d{3}\\.example\$
5475 if you want \*example*\ to be the top-level domain. (The backslash before the
5476 @$ is another artefact of string expansion.)
5479 .section Testing regular expressions
5480 .index testing||regular expressions
5481 .index regular expressions||testing
5483 A program called \*pcretest*\ forms part of the PCRE distribution and is built
5484 with PCRE during the process of building Exim. It is primarily intended for
5485 testing PCRE itself, but it can also be used for experimenting with regular
5486 expressions. After building Exim, the binary can be found in the build
5487 directory (it is not installed anywhere automatically). There is documentation
5488 of various options in \(doc/pcretest.txt)\, but for simple testing, none are
5489 needed. This is the output of a sample run of \*pcretest*\:
5491 re> $cb{/^([^@@]+)@@.+@\.(ac|edu)@\.(?!kr)[a-z]@{2@}@$/}
5492 data> $cb{x@@y.ac.uk}
5496 data> $cb{x@@y.ac.kr}
5498 data> $cb{x@@y.edu.com}
5500 data> $cb{x@@y.edu.co}
5506 Input typed by the user is shown in bold face.
5508 After the `re>' prompt, a regular expression enclosed in delimiters is
5509 expected. If this compiles without error, `data>' prompts are given for strings
5510 against which the expression is matched. An empty data line causes a new
5511 regular expression to be read. If the match is successful, the captured
5512 substring values (that is, what would be in the variables \$0$\, \$1$\, \$2$\,
5513 etc.) are shown. The above example tests for an email address whose domain ends
5514 with either `ac' or `edu' followed by a two-character top-level domain that is
5515 not `kr'. The local part is captured in \$1$\ and the `ac' or `edu' in \$2$\.
5526 . ============================================================================
5527 .chapter File and database lookups
5528 .set runningfoot "file/database lookups"
5529 .rset CHAPfdlookup "~~chapter"
5531 .index database lookups
5532 .index lookup||description of
5533 Exim can be configured to look up data in files or databases as it processes
5534 messages. Two different kinds of syntax are used:
5536 A string that is to be expanded may contain explicit lookup requests. These
5537 cause parts of the string to be replaced by data that is obtained from the
5540 Lists of domains, hosts, and email addresses can contain lookup requests as a
5541 way of avoiding excessively long linear lists. In this case, the data that is
5542 returned by the lookup is often (but not always) discarded; whether the lookup
5543 succeeds or fails is what really counts. These kinds of list are described in
5544 chapter ~~CHAPdomhosaddlists.
5546 It is easy to confuse the two different kinds of lookup, especially as the
5547 lists that may contain the second kind are always expanded before being
5548 processed as lists. Therefore, they may also contain lookups of the first kind.
5549 Be careful to distinguish between the following two examples:
5551 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
5552 domains = lsearch;/some/file
5554 The first uses a string expansion, the result of which must be a domain list.
5555 String expansions are described in detail in chapter ~~CHAPexpand. The
5556 expansion takes place first, and the file that is searched could contain lines
5559 192.168.3.4: domain1 : domain2 : ...
5560 192.168.1.9: domain3 : domain4 : ...
5562 Thus, the result of the expansion is a list of domains (and possibly other
5563 types of item that are allowed in domain lists).
5565 In the second case, the lookup is a single item in a domain list. It causes
5566 Exim to use a lookup to see if the domain that is being processed can be found
5567 in the file. The file could contains lines like this:
5572 Any data that follows the keys is not relevant when checking that the domain
5573 matches the list item.
5575 It is possible to use both kinds of lookup at once. Consider a file containing
5578 192.168.5.6: lsearch;/another/file
5580 If the value of \$sender@_host@_address$\ is 192.168.5.6, expansion of the
5581 first \domains\ setting above generates the second setting, which therefore
5582 causes a second lookup to occur.
5584 The rest of this chapter describes the different lookup types that are
5585 available. Any of them can be used in either of the circumstances described
5586 above. The syntax requirements for the two cases are described in chapters
5587 ~~CHAPexpand and ~~CHAPdomhosaddlists, respectively.
5589 .section Lookup types
5590 .index lookup||types of
5591 .index single-key lookup||definition of
5592 Two different styles of data lookup are implemented:
5594 The \*single-key*\ style requires the specification of a file in which to look,
5595 and a single key to search for. The lookup type determines how the file is
5598 .index query-style lookup||definition of
5599 The \*query*\ style accepts a generalized database query.
5600 No particular key value is assumed by Exim for query-style lookups. You can
5601 use whichever Exim variable(s) you need to construct the database query.
5603 The code for each lookup type is in a separate source file that is included in
5604 the binary of Exim only if the corresponding compile-time option is set. The
5605 default settings in \(src/EDITME)\ are:
5610 which means that only linear searching and DBM lookups are included by default.
5611 For some types of lookup (e.g. SQL databases), you need to install appropriate
5612 libraries and header files before building Exim.
5616 .section Single-key lookup types
5617 .rset SECTsinglekeylookups "~~chapter.~~section"
5618 .index lookup||single-key types
5619 .index single-key lookup||list of types
5620 The following single-key lookup types are implemented:
5622 .index cdb||description of
5624 .index binary zero||in lookup key
5625 \%cdb%\: The given file is searched as a Constant DataBase file, using the key
5626 string without a terminating binary zero. The cdb format is designed for
5627 indexed files that are read frequently and never updated, except by total
5628 re-creation. As such, it is particulary suitable for large files containing
5629 aliases or other indexed data referenced by an MTA. Information about cdb can
5630 be found in several places:
5632 \?http://www.pobox.com/@~djb/cdb.html?\
5633 \?ftp://ftp.corpit.ru/pub/tinycdb/?\
5634 \?http://packages.debian.org/stable/utils/freecdb.html?\
5636 A cdb distribution is not needed in order to build Exim with cdb support,
5637 because the code for reading cdb files is included directly in Exim itself.
5638 However, no means of building or testing cdb files is provided with Exim, so
5639 you need to obtain a cdb distribution in order to do this.
5641 .index DBM||lookup type
5643 .index binary zero||in lookup key
5644 \%dbm%\: Calls to DBM library functions are used to extract data from the given
5645 DBM file by looking up the record with the given key. A terminating binary
5646 zero is included in the key that is passed to the DBM library. See section
5647 ~~SECTdb for a discussion of DBM libraries.
5648 .index Berkeley DB library||file format
5649 For all versions of Berkeley DB, Exim uses the \\DB@_HASH\\ style of database
5650 when building DBM files using the \exim@_dbmbuild\ utility. However, when using
5651 Berkeley DB versions 3 or 4, it opens existing databases for reading with the
5652 \\DB@_UNKNOWN\\ option. This enables it to handle any of the types of database
5653 that the library supports, and can be useful for accessing DBM files created by
5654 other applications. (For earlier DB versions, \\DB@_HASH\\ is always used.)
5657 .index lookup||dbmnz
5658 .index lookup||dbm, terminating zero
5659 .index binary zero||in lookup key
5661 .index \(/etc/userdbshadow.dat)\
5662 .index dmbnz lookup type
5663 \%dbmnz%\: This is the same as \%dbm%\, except that a terminating binary zero
5664 is not included in the key that is passed to the DBM library. You may need this
5665 if you want to look up data in files that are created by or shared with some
5666 other application that does not use terminating zeros. For example, you need to
5667 use \%dbmnz%\ rather than \%dbm%\ if you want to authenticate incoming SMTP
5668 calls using the passwords from Courier's \(/etc/userdbshadow.dat)\ file. Exim's
5669 utility program for creating DBM files (\*exim@_dbmbuild*\) includes the zeros
5670 by default, but has an option to omit them (see section ~~SECTdbmbuild).
5672 .index lookup||dsearch
5673 .index dsearch lookup type
5674 \%dsearch%\: The given file must be a directory; this is searched for a file
5675 whose name is the key. The key may not contain any forward slash characters.
5676 The result of a successful lookup is the name of the file. An example of how
5677 this lookup can be used to support virtual domains is given in section
5678 ~~SECTvirtualdomains.
5680 .index lookup||iplsearch
5681 .index iplsearch lookup type
5682 \%iplsearch%\: The given file is a text file containing keys and data. A key is
5683 terminated by a colon or white space or the end of the line. The keys in the
5684 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
5685 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
5686 being interpreted as a key terminator. For example:
5688 1.2.3.4: data for 1.2.3.4
5689 192.168.0.0/16 data for 192.168.0.0/16
5690 "abcd::cdab": data for abcd::cdab
5691 "abcd:abcd::/32" data for abcd:abcd::/32
5693 The key for an \%iplsearch%\ lookup must be an IP address (without a mask). The
5694 file is searched linearly, using the CIDR masks where present, until a matching
5695 key is found. The first key that matches is used; there is no attempt to find a
5696 `best' match. Apart from the way the keys are matched, the processing for
5697 \%iplsearch%\ is the same as for \%lsearch%\.
5699 \**Warning 1**\: Unlike most other single-key lookup types, a file of data for
5700 \%iplsearch%\ can \*not*\ be turned into a DBM or cdb file, because those
5701 lookup types support only literal keys.
5703 \**Warning 2**\: In a host list, you must always use \%net-iplsearch%\ so that
5704 the implicit key is the host's IP address rather than its name (see section
5705 ~~SECThoslispatsikey).
5708 .index linear search
5709 .index lookup||lsearch
5710 .index lsearch lookup type
5711 \%lsearch%\: The given file is a text file that is searched linearly for a
5712 line beginning with the search key, terminated by a colon or white space or the
5713 end of the line. The first occurrence that is found in the file is used. White
5714 space between the key and the colon is permitted. The remainder of the line,
5715 with leading and trailing white space removed, is the data. This can be
5716 continued onto subsequent lines by starting them with any amount of white
5717 space, but only a single space character is included in the data at such a
5718 junction. If the data begins with a colon, the key must be terminated by a
5723 Empty lines and lines beginning with @# are ignored, even if they occur in the
5724 middle of an item. This is the traditional textual format of alias files. Note
5725 that the keys in an \%lsearch%\ file are literal strings. There is no
5726 wildcarding of any kind.
5728 .index lookup||lsearch, colons in keys
5729 In most \%lsearch%\ files, keys are not required to contain colons
5730 or @# characters, or
5731 whitespace. However, if you need this feature, it is available. If a key begins
5732 with a doublequote character, it is terminated only by a matching quote (or end
5733 of line), and the normal escaping rules apply to its contents (see section
5734 ~~SECTstrings). An optional colon is permitted after quoted keys (exactly as
5735 for unquoted keys). There is no special handling of quotes for the data part of
5736 an \%lsearch%\ line.
5738 .index NIS lookup type
5740 .index binary zero||in lookup key
5741 \%nis%\: The given file is the name of a NIS map, and a NIS lookup is done with
5742 the given key, without a terminating binary zero. There is a variant called
5743 \%nis0%\ which does include the terminating binary zero in the key. This is
5744 reportedly needed for Sun-style alias files. Exim does not recognize NIS
5745 aliases; the full map names must be used.
5747 .index wildlsearch lookup type
5748 .index lookup||wildlsearch
5749 .index nwildlsearch lookup type
5750 .index lookup||nwildlsearch
5751 \%wildlsearch%\ or \%nwildlsearch%\: These search a file linearly, like
5752 \%lsearch%\, but instead of being interpreted as a literal string, each key may
5753 be wildcarded. The difference between these two lookup types is that for
5754 \%wildlsearch%\, each key in the file is string-expanded before being used,
5755 whereas for \%nwildlsearch%\, no expansion takes place.
5757 Like \%lsearch%\, the testing is done case-insensitively. The following forms
5758 of wildcard are recognized:
5760 The string may begin with an asterisk to mean `begins with'. For example:
5762 *.a.b.c data for anything.a.b.c
5763 *fish data for anythingfish
5766 The string may begin with a circumflex to indicate a regular expression. For
5767 example, for \%wildlsearch%\:
5769 ^\N\d+\.a\.b\N data for <digits>.a.b
5771 Note the use of \"@\N"\ to disable expansion of the contents of the regular
5772 expression. If you are using \%nwildlsearch%\, where the keys are not
5773 string-expanded, the equivalent entry is:
5775 ^\d+\.a\.b data for <digits>.a.b
5778 If the regular expression contains white space or colon characters, you must
5779 either quote it (see \%lsearch%\ above), or represent these characters in other
5780 ways. For example, \"@\s"\ can be used for white space and \"@\x3A"\ for a
5781 colon. This may be easier than quoting, because if you quote, you have to
5782 escape all the backslashes inside the quotes.
5784 Although I cannot see it being of much use, the general matching function
5785 that is used to implement
5787 means that the string may begin with a lookup name terminated by a semicolon,
5788 and followed by lookup data. For example:
5790 cdb;/some/file data for keys that match the file
5792 The data that is obtained from the nested lookup is discarded.
5794 Keys that do not match any of these patterns are interpreted literally. The
5795 continuation rules for the data are the same as for \%lsearch%\, and keys may
5796 be followed by optional colons.
5798 \**Warning**\: Unlike most other single-key lookup types, a file of data for
5799 \%(n)wildlsearch%\ can \*not*\ be turned into a DBM or cdb file, because those
5800 lookup types support only literal keys.
5803 .section Query-style lookup types
5804 .index lookup||query-style types
5805 .index query-style lookup||list of types
5806 The supported query-style lookup types are listed below. Further details about
5807 many of them are given in later sections.
5809 .index DNS||as a lookup type
5811 \%dnsdb%\: This does a DNS search for a record whose domain name is the supplied
5812 query. The resulting data is the contents of the record. See section
5815 .index Interbase lookup type
5816 .index lookup||Interbase
5817 \%ibase%\: This does a lookup in an Interbase database.
5819 .index LDAP||lookup type
5821 \%ldap%\: This does an LDAP lookup using a query in the form of a URL, and
5822 returns attributes from a single entry. There is a variant called \%ldapm%\
5823 that permits values from multiple entries to be returned. A third variant
5824 called \%ldapdn%\ returns the Distinguished Name of a single entry instead of
5825 any attribute values. See section ~~SECTldap.
5827 .index MySQL||lookup type
5828 .index lookup||MySQL
5829 \%mysql%\: The format of the query is an SQL statement that is passed to a MySQL
5830 database. See section ~~SECTsql.
5832 .index NIS@+ lookup type
5834 \%nisplus%\: This does a NIS+ lookup using a query that can specify the name of
5835 the field to be returned. See section ~~SECTnisplus.
5837 .index Oracle||lookup type
5838 .index lookup||Oracle
5839 \%oracle%\: The format of the query is an SQL statement that is passed to an
5840 Oracle database. See section ~~SECTsql.
5842 .index lookup||passwd
5843 .index passwd lookup type
5844 \%passwd%\ is a query-style lookup with queries that are just user names. The
5845 lookup calls \*getpwnam()*\ to interrogate the system password data, and on
5846 success, the result string is the same as you would get from an \%lsearch%\
5847 lookup on a traditional \(/etc/passwd file)\, though with \"*"\ for the
5848 password value. For example:
5850 *:42:42:King Rat:/home/kr:/bin/bash
5853 .index PostgreSQL lookup type
5854 .index lookup||PostgreSQL
5855 \%pgsql%\: The format of the query is an SQL statement that is passed to a
5856 PostgreSQL database. See section ~~SECTsql.
5858 \%testdb%\: This is a lookup type that is used for testing Exim. It is
5859 not likely to be useful in normal operation.
5861 .index whoson lookup type
5862 .index lookup||whoson
5863 \%whoson%\: \*Whoson*\ (\?http://whoson.sourceforge.net?\) is a proposed
5864 Internet protocol that allows Internet server programs to check whether a
5865 particular (dynamically allocated) IP address is currently allocated to a known
5866 (trusted) user and, optionally, to obtain the identity of the said user. In
5867 Exim, this can be used to implement `POP before SMTP' checking using ACL
5870 require condition = \
5871 ${lookup whoson {$sender_host_address}{yes}{no}}
5873 The query consists of a single IP address. The value returned is the name of
5874 the authenticated user.
5877 .section Temporary errors in lookups
5878 .index lookup||temporary error in
5879 Lookup functions can return temporary error codes if the lookup cannot be
5880 completed. For example, a NIS or LDAP database might be unavailable. For this
5881 reason, it is not advisable to use a lookup that might do this for critical
5882 options such as a list of local domains.
5884 When a lookup cannot be completed in a router or transport, delivery
5885 of the message (to the relevant address) is deferred, as for any other
5886 temporary error. In other circumstances Exim may assume the lookup has failed,
5887 or may give up altogether.
5890 .section Default values in single-key lookups
5891 .rset SECTdefaultvaluelookups "~~chapter.~~section"
5892 .index wildcard lookups
5893 .index lookup||default values
5894 .index lookup||wildcard
5895 .index lookup||$*$ added to type
5896 .index default||in single-key lookups
5897 In this context, a `default value' is a value specified by the administrator
5898 that is to be used if a lookup fails.
5900 If `$*$' is added to a single-key lookup type (for example, \lsearch$*$\) and
5901 the initial lookup fails, the key `$*$' is looked up in the file to provide
5902 a default value. See also the section on partial matching below.
5904 .index @*@@ with single-key lookup
5905 .index lookup||$*$@@ added to type
5906 .index alias file||per-domain default
5907 Alternatively, if `$*$@@' is added to a single-key lookup type (for example
5908 \dbm$*$@@\) then, if the initial lookup fails and the key contains an @@
5909 character, a second lookup is done with everything before the last @@ replaced
5910 by $*$. This makes it possible to provide per-domain defaults in alias files
5911 that include the domains in the keys. If the second lookup fails (or doesn't
5912 take place because there is no @@ in the key), `$*$' is looked up.
5913 For example, a \%redirect%\ router might contain:
5915 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mixed-aliases}}
5917 Suppose the address that is being processed is \*jane@@eyre.example*\. Exim
5918 looks up these keys, in this order:
5924 The data is taken from whichever key it finds first. \**Note**\: in an
5925 \%lsearch%\ file, this does not mean the first of these keys in the file. A
5926 complete scan is done for each key, and only if it is not found at all does
5927 Exim move on to try the next key.
5930 .section Partial matching in single-key lookups
5931 .rset SECTpartiallookup "~~chapter.~~section"
5932 .index partial matching
5933 .index wildcard lookups
5934 .index lookup||partial matching
5935 .index lookup||wildcard
5936 .index asterisk||in search type
5937 The normal operation of a single-key lookup is to search the file for an exact
5938 match with the given key. However, in a number of situations where domains are
5939 being looked up, it is useful to be able to do partial matching. In this case,
5940 information in the file that has a key starting with `$*$.' is matched by any
5941 domain that ends with the components that follow the full stop. For example, if
5942 a key in a DBM file is
5944 *.dates.fict.example
5946 then when partial matching is enabled this is matched by (amongst others)
5947 \*2001.dates.fict.example*\ and \*1984.dates.fict.example*\. It is also matched
5948 by \*dates.fict.example*\, if that does not appear as a separate key in the
5951 \**Note**\: Partial matching is not available for query-style lookups. It is
5952 also not available for any lookup items in address lists (see section
5955 Partial matching is implemented by doing a series of separate lookups using
5956 keys constructed by modifying the original subject key. This means that it can
5957 be used with any of the single-key lookup types, provided that
5958 partial matching keys
5959 beginning with a special prefix (default `$*$.') are included in the data file.
5960 Keys in the file that do not begin with the prefix are matched only by
5961 unmodified subject keys when partial matching is in use.
5963 Partial matching is requested by adding the string `partial-' to the front of
5964 the name of a single-key lookup type, for example, \partial-dbm\. When this is
5965 done, the subject key is first looked up unmodified; if that fails, `$*$.'
5966 is added at the start of the subject key, and it is looked up again. If that
5967 fails, further lookups are tried with dot-separated components removed
5968 from the start of the subject key, one-by-one, and `$*$.' added on the front of
5971 A minimum number of two non-$*$ components are required. This can be adjusted
5972 by including a number before the hyphen in the search type. For example,
5973 \partial3-lsearch\ specifies a minimum of three non-$*$ components in the
5974 modified keys. Omitting the number is equivalent to `partial2-'. If the subject
5975 key is \*2250.dates.fict.example*\ then the following keys are looked up when
5976 the minimum number of non-$*$ components is two:
5978 2250.dates.fict.example
5979 *.2250.dates.fict.example
5980 *.dates.fict.example
5983 As soon as one key in the sequence is successfully looked up, the lookup
5986 .index lookup||partial matching, changing prefix
5987 .index prefix||for partial matching
5988 The use of `$*$.' as the partial matching prefix is a default that can be
5989 changed. The motivation for this feature is to allow Exim to operate with file
5990 formats that are used by other MTAs. A different prefix can be supplied in
5991 parentheses instead of the hyphen after `partial'. For example:
5993 domains = partial(.)lsearch;/some/file
5995 In this example, if the domain is \*a.b.c*\, the sequence of lookups is
5996 \"a.b.c"\, \".a.b.c"\, and \".b.c"\ (the default minimum of 2 non-wild
5997 components is unchanged). The prefix may consist of any punctuation characters
5998 other than a closing parenthesis. It may be empty, for example:
6000 domains = partial1()cdb;/some/file
6002 For this example, if the domain is \*a.b.c*\, the sequence of lookups is
6003 \"a.b.c"\, \"b.c"\, and \"c"\.
6005 If `partial0' is specified, what happens at the end (when the lookup with just
6006 one non-wild component has failed, and the original key is shortened right down
6007 to the null string) depends on the prefix:
6009 If the prefix has zero length, the whole lookup fails.
6011 If the prefix has length 1, a lookup for just the prefix is done. For
6012 example, the final lookup for `partial0(.)' is for \"."\ alone.
6014 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6015 remainder is looked up. With the default prefix, therefore, the final lookup is
6016 for `$*$' on its own.
6018 Otherwise, the whole prefix is looked up.
6021 If the search type ends in `$*$' or `$*$@@' (see section
6022 ~~SECTdefaultvaluelookups above), the search for an ultimate default that this
6023 implies happens after all partial lookups have failed. If `partial0' is
6024 specified, adding `$*$' to the search type has no effect with the default
6025 prefix, because the `$*$' key is already included in the sequence of partial
6026 lookups. However, there might be a use for lookup types such as
6027 `partial0(.)lsearch$*$'.
6029 The use of `$*$' in lookup partial matching differs from its use as a wildcard
6030 in domain lists and the like. Partial matching works only in terms of
6031 dot-separated components; a key such as \"*fict.example"\
6032 in a database file is useless, because the asterisk in a partial matching
6033 subject key is always followed by a dot.
6037 .section Lookup caching
6038 .index lookup||caching
6039 .index caching||lookup data
6041 caches the most recent lookup result on a per-file basis for single-key
6042 lookup types, and keeps the relevant files open. In some types of configuration
6043 this can lead to many files being kept open for messages with many recipients.
6044 To avoid hitting the operating system limit on the number of simultaneously
6045 open files, Exim closes the least recently used file when it needs to open more
6046 files than its own internal limit, which can be changed via the
6047 \lookup@_open@_max\ option.
6049 For query-style lookups, a single data cache per lookup type is kept. The files
6050 are closed and the caches flushed at strategic points during delivery -- for
6051 example, after all routing is complete.
6054 .section Quoting lookup data
6055 .index lookup||quoting
6056 .index quoting||in lookups
6057 When data from an incoming message is included in a query-style lookup, there
6058 is the possibility of special characters in the data messing up the syntax of
6059 the query. For example, a NIS+ query that contains
6063 will be broken if the local part happens to contain a closing square bracket.
6064 For NIS+, data can be enclosed in double quotes like this:
6066 [name="$local_part"]
6068 but this still leaves the problem of a double quote in the data. The rule for
6069 NIS+ is that double quotes must be doubled. Other lookup types have different
6070 rules, and to cope with the differing requirements, an expansion operator
6071 of the following form is provided:
6073 @$@{quote@_<<lookup-type>>:<<string>>@}
6075 For example, the safest way to write the NIS+ query is
6077 [name="${quote_nisplus:$local_part}"]
6079 See chapter ~~CHAPexpand for full coverage of string expansions. The quote
6080 operator can be used for all lookup types, but has no effect for single-key
6081 lookups, since no quoting is ever needed in their key strings.
6085 .section More about dnsdb
6086 .rset SECTdnsdb "~~chapter.~~section"
6088 .index lookup||dnsdb
6089 .index DNS||as a lookup type
6090 The \%dnsdb%\ lookup type uses the DNS as its database. A query consists of a
6091 record type and a domain name, separated by an equals sign. For example, an
6092 expansion string could contain:
6094 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6096 The supported record types are A, CNAME, MX, NS, PTR, SRV, and TXT,
6097 and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6098 configured). If no type is given, TXT is assumed. When the type is PTR, the
6099 address should be given as normal; it is converted to the necessary inverted
6100 format internally. For example:
6102 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6105 .index MX record||in \%dnsdb%\ lookup
6106 For MX records, both the preference value and the host name are returned,
6107 separated by a space.
6108 .index SRV record||in \%dnsdb%\ lookup
6109 For SRV records, the priority, weight, port, and host name are returned,
6110 separated by spaces. For any record type,
6111 if multiple records are found (or, for A6 lookups, if a single record leads to
6112 multiple addresses), the data is returned as a concatenation, separated by
6113 newlines. The order, of course, depends on the DNS resolver.
6118 .section More about LDAP
6119 .rset SECTldap "~~chapter.~~section"
6122 .index Solaris||LDAP
6123 The original LDAP implementation came from the University of Michigan; this has
6124 become `Open LDAP', and there are now two different releases. Another
6125 implementation comes from Netscape, and Solaris 7 and subsequent releases
6126 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6127 the lookup function level, their error handling is different. For this reason
6128 it is necessary to set a compile-time variable when building Exim with LDAP, to
6129 indicate which LDAP library is in use. One of the following should appear in
6130 your \(Local/Makefile)\:
6132 LDAP_LIB_TYPE=UMICHIGAN
6133 LDAP_LIB_TYPE=OPENLDAP1
6134 LDAP_LIB_TYPE=OPENLDAP2
6135 LDAP_LIB_TYPE=NETSCAPE
6136 LDAP_LIB_TYPE=SOLARIS
6138 If \\LDAP@_LIB@_TYPE\\ is not set, Exim assumes \"OPENLDAP1"\, which has the
6139 same interface as the University of Michigan version.
6141 There are three LDAP lookup types in Exim. These behave slightly differently in
6142 the way they handle the results of a query:
6144 \%ldap%\ requires the result to contain just one entry; if there are more, it
6147 \%ldapdn%\ also requires the result to contain just one entry, but it is the
6148 Distinguished Name that is returned rather than any attribute values.
6150 \%ldapm%\ permits the result to contain more than one entry; the attributes from
6151 all of them are returned.
6154 For \%ldap%\ and \%ldapm%\, if a query finds only entries with no attributes,
6155 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6156 the data returned by a successful lookup is described in the next section.
6157 First we explain how LDAP queries are coded.
6159 .section Format of LDAP queries
6160 .rset SECTforldaque "~~chapter.~~section"
6161 .index LDAP||query format
6162 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6163 the configuration of a \%redirect%\ router one might have this setting:
6165 data = ${lookup ldap \
6166 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6167 c=UK?mailbox?base?}}
6169 .index LDAP||with TLS
6170 The URL may begin with \"ldap"\ or \"ldaps"\ if your LDAP library supports
6171 secure (encrypted) LDAP connections. The second of these ensures that an
6172 encrypted TLS connection is used.
6174 .section LDAP quoting
6175 .index LDAP||quoting
6176 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6177 and the second because the LDAP query is represented as a URL. Furthermore,
6178 within an LDAP query, two different kinds of quoting are required. For this
6179 reason, there are two different LDAP-specific quoting operators.
6181 The \quote@_ldap\ operator is designed for use on strings that are part of
6182 filter specifications. Conceptually, it first does the following conversions on
6190 in accordance with RFC 2254. The resulting string is then quoted according
6191 to the rules for URLs, that is, all characters except
6195 are converted to their hex values, preceded by a percent sign. For example:
6197 ${quote_ldap: a(bc)*, a<yz>; }
6201 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6203 Removing the URL quoting, this is (with a leading and a trailing space):
6205 a\28bc\29\2A, a<yz>;
6208 The \quote@_ldap@_dn\ operator is designed for use on strings that are part of
6209 base DN specifications in queries. Conceptually, it first converts the string
6210 by inserting a backslash in front of any of the following characters:
6214 It also inserts a backslash before any leading spaces or @# characters, and
6215 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6216 is then quoted according to the rules for URLs. For example:
6218 ${quote_ldap_dn: a(bc)*, a<yz>; }
6222 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6224 Removing the URL quoting, this is (with a trailing space):
6226 \ a(bc)*\, a\<yz\>\;\
6228 There are some further comments about quoting in the section on LDAP
6229 authentication below.
6231 .section LDAP connections
6232 .index LDAP||connections
6233 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6234 is in use, via a Unix domain socket. The example given above does not specify
6235 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6238 ldap://<<hostname>>:<<port>>/...
6240 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6241 used. When no server is specified in a query, a list of default servers is
6242 taken from the \ldap@_default@_servers\ configuration option. This supplies a
6243 colon-separated list of servers which are tried in turn until one successfully
6244 handles a query, or there is a serious error. Successful handling either
6245 returns the requested data, or indicates that it does not exist. Serious errors
6246 are syntactical, or multiple values when only a single value is expected.
6247 Errors which cause the next server to be tried are connection failures, bind
6248 failures, and timeouts.
6250 For each server name in the list, a port number can be given. The standard way
6251 of specifing a host and port is to use a colon separator (RFC 1738). Because
6252 \ldap@_default@_servers\ is a colon-separated list, such colons have to be
6253 doubled. For example
6255 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6257 If \ldap@_default@_servers\ is unset, a URL with no server name is passed
6258 to the LDAP library with no server name, and the library's default (normally
6259 the local host) is used.
6261 If you are using the OpenLDAP library, you can connect to an LDAP server using
6262 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6263 \"ldapi"\ instead of \"ldap"\ in LDAP queries. What follows here applies only
6264 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6267 For this type of connection, instead of a host name for the server, a pathname
6268 for the socket is required, and the port number is not relevant. The pathname
6269 can be specified either as an item in \ldap@_default@_servers\, or inline in
6270 the query. In the former case, you can have settings such as
6272 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6274 When the pathname is given in the query, you have to escape the slashes as
6275 \"%2F"\ to fit in with the LDAP URL syntax. For example:
6277 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6279 When Exim processes an LDAP lookup and finds that the `hostname' is really
6280 a pathname, it uses the Unix domain socket code, even if the query actually
6281 specifies \"ldap"\ or \"ldaps"\. In particular, no encryption is used for a
6282 socket connection. This behaviour means that you can use a setting of
6283 \ldap@_default@_servers\ such as in the example above with traditional \"ldap"\
6284 or \"ldaps"\ queries, and it will work. First, Exim tries a connection via
6285 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6288 If an explicit \"ldapi"\ type is given in a query when a host name is
6289 specified, an error is diagnosed. However, if there are more items in
6290 \ldap@_default@_servers\, they are tried. In other words:
6292 Using a pathname with \"ldap"\ or \"ldaps"\ forces the use of the Unix domain
6295 Using \"ldapi"\ with a host name causes an error.
6298 Using \"ldapi"\ with no host or path in the query, and no setting of
6299 \ldap@_default@_servers\, does whatever the library does by default.
6302 .section LDAP authentication and control information
6303 .index LDAP||authentication
6304 The LDAP URL syntax provides no way of passing authentication and other control
6305 information to the server. To make this possible, the URL in an LDAP query may
6306 be preceded by any number of `<<name>>=<<value>>' settings, separated by
6307 spaces. If a value contains spaces it must be enclosed in double quotes, and
6308 when double quotes are used, backslash is interpreted in the usual way inside
6311 The following names are recognized:
6313 CONNECT $rm{set a connection timeout}
6315 DEREFERENCE $rm{set the dereferencing parameter}
6316 USER $rm{set the DN, for authenticating the LDAP bind}
6317 PASS $rm{set the password, likewise}
6318 SIZE $rm{set the limit for the number of entries returned}
6319 TIME $rm{set the maximum waiting time for a query}
6321 The value of the \\DEREFERENCE\\ parameter must be one of the words `never',
6322 `searching', `finding', or `always'.
6324 Here is an example of an LDAP query in an Exim lookup that uses some of these
6325 values. This is a single line, folded for ease of reading:
6329 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6330 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6333 The encoding of spaces as %20 is a URL thing which should not be done for any
6334 of the auxiliary data. Exim configuration settings that include lookups which
6335 contain password information should be preceded by `hide' to prevent non-admin
6336 users from using the \-bP-\ option to see their values.
6338 The auxiliary data items may be given in any order. The default is no
6339 connection timeout (the system timeout is used), no user or password, no limit
6340 on the number of entries returned, and no time limit on queries.
6342 The time limit for connection is given in seconds; zero means use the default.
6343 This facility is available in Netscape SDK 4.1; it may not be available in
6344 other LDAP implementations. Exim uses the given value if
6345 \\LDAP@_X@_OPT@_CONNECT@_TIMEOUT\\ is defined in the LDAP headers.
6347 When a DN is quoted in the \\USER=\\ setting for LDAP authentication, Exim
6348 removes any URL quoting that it may contain before passing it LDAP. Apparently
6349 some libraries do this for themselves, but some do not. Removing the URL
6350 quoting has two advantages:
6352 It makes it possible to use the same \quote@_ldap@_dn\ expansion for \\USER=\\
6353 DNs as with DNs inside actual queries.
6355 It permits spaces inside \\USER=\\ DNs.
6357 For example, a setting such as
6359 USER=cn=${quote_ldap_dn:$1}
6361 should work even if \$1$\ contains spaces.
6363 Expanded data for the \\PASS=\\ value should be quoted using the \quote\
6364 expansion operator, rather than the LDAP quote operators. The only reason this
6365 field needs quoting is to ensure that it conforms to the Exim syntax, which
6366 does not allow unquoted spaces. For example:
6371 The LDAP authentication mechanism can be used to check passwords as part of
6372 SMTP authentication. See the \ldapauth\ expansion string condition in chapter
6376 .section Format of data returned by LDAP
6377 .index LDAP||returned data formats
6378 The \%ldapdn%\ lookup type returns the Distinguished Name from a single entry as
6379 a sequence of values, for example
6381 cn=manager, o=University of Cambridge, c=UK
6384 The \%ldap%\ lookup type generates an error if more than one entry matches the
6385 search filter, whereas \%ldapm%\ permits this case, and inserts a newline in the
6386 result between the data from different entries. It is possible for multiple
6387 values to be returned for both \%ldap%\ and \%ldapm%\, but in the former case you
6388 know that whatever values are returned all came from a single entry in the
6391 In the common case where you specify a single attribute in your LDAP query, the
6392 result is not quoted, and does not contain the attribute name. If the attribute
6393 has multiple values, they are separated by commas.
6395 If you specify multiple attributes, the result contains space-separated, quoted
6396 strings, each preceded by the attribute name and an equals sign. Within the
6397 quotes, the quote character, backslash, and newline are escaped with
6398 backslashes, and commas are used to separate multiple values for the attribute.
6399 Apart from the escaping, the string within quotes takes the same form as the
6400 output when a single attribute is requested. Specifying no attributes is the
6401 same as specifying all of an entry's attributes.
6403 Here are some examples of the output format. The first line of each pair is an
6404 LDAP query, and the second is the data that is returned. The attribute called
6405 \attr1\ has two values, whereas \attr2\ has only one value:
6407 ldap:///o=base?attr1?sub?(uid=fred)
6410 ldap:///o=base?attr2?sub?(uid=fred)
6413 ldap:///o=base?attr1,attr2?sub?(uid=fred)
6414 attr1="value1.1, value1.2" attr2="value two"
6416 ldap:///o=base??sub?(uid=fred)
6417 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
6419 The \extract\ operator in string expansions can be used to pick out individual
6420 fields from data that consists of $it{key}=$it{value} pairs. You can make use
6421 of Exim's \-be-\ option to run expansion tests and thereby check the results of
6426 .section More about NIS+
6427 .rset SECTnisplus "~~chapter.~~section"
6428 .index NIS@+ lookup type
6430 NIS+ queries consist of a NIS+ \*indexed name*\ followed by an optional colon
6431 and field name. If this is given, the result of a successful query is the
6432 contents of the named field; otherwise the result consists of a concatenation
6433 of \*field-name=field-value*\ pairs, separated by spaces. Empty values and
6434 values containing spaces are quoted. For example, the query
6436 [name=mg1456],passwd.org_dir
6438 might return the string
6440 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
6441 home=/home/mg1456 shell=/bin/bash shadow=""
6443 (split over two lines here to fit on the page), whereas
6445 [name=mg1456],passwd.org_dir:gcos
6451 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
6452 for the given indexed key. The effect of the \quote@_nisplus\ expansion
6453 operator is to double any quote characters within the text.
6456 .section More about MySQL, PostgreSQL, Oracle, and Interbase
6457 .rset SECTsql "~~chapter.~~section"
6458 .index MySQL||lookup type
6459 .index PostgreSQL lookup type
6460 .index lookup||MySQL
6461 .index lookup||PostgreSQL
6462 .index Oracle||lookup type
6463 .index lookup||Oracle
6464 .index Interbase lookup type
6465 .index lookup||Interbase
6466 If any MySQL, PostgreSQL, Oracle, or Interbase lookups are used, the
6467 \mysql@_servers\, \pgsql@_servers\, \oracle@_servers\, or \ibase@_servers\
6468 option (as appropriate) must be set to a colon-separated list of server
6469 information. Each item in the list is a slash-separated list of four items:
6470 host name, database name, user name, and password. In the case of Oracle, the
6471 host name field is used for the `service name', and the database name field is
6472 not used and should be empty. For example:
6474 hide oracle_servers = oracle.plc.example//ph10/abcdwxyz
6476 Because password data is sensitive, you should always precede the setting with
6477 `hide', to prevent non-admin users from obtaining the setting via the \-bP-\
6478 option. Here is an example where two MySQL servers are listed:
6480 hide mysql_servers = localhost/users/root/secret:\
6481 otherhost/users/root/othersecret
6483 For MySQL and PostgreSQL, a host may be specified as <<name>>:<<port>> but
6484 because this is a colon-separated list, the colon has to be doubled.
6486 For each query, these parameter groups are tried in order until a connection
6487 and a query succeeds. Queries for these databases are SQL statements, so an
6491 ${lookup mysql{select mailbox from users where id='ph10'}{$value}fail}
6493 If the result of the query contains more than one field, the data for
6494 each field in the row is returned, preceded by its name, so the result
6498 ${lookup pgsql{select home,name from users where id='ph10'}{$value}}
6502 home=/home/ph10 name="Philip Hazel"
6504 Values containing spaces and empty values are double quoted, with embedded
6505 quotes escaped by a backslash.
6507 If the result of the query contains just one field, the value is passed back
6508 verbatim, without a field name, for example:
6512 If the result of the query yields more than one row, it is all concatenated,
6513 with a newline between the data for each row.
6515 The \quote@_mysql\, \quote@_pgsql\, and \quote@_oracle\ expansion operators
6516 convert newline, tab, carriage return, and backspace to @\n, @\t, @\r, and @\b
6517 respectively, and the characters single-quote, double-quote, and backslash
6518 itself are escaped with backslashes. The \quote@_pgsql\ expansion operator, in
6519 addition, escapes the percent and underscore characters. This cannot be done
6520 for MySQL because these escapes are not recognized in contexts where these
6521 characters are not special.
6524 .section Special MySQL features
6525 For MySQL, an empty host name or the use of `localhost' in \mysql@_servers\
6526 causes a connection to the server on the local host by means of a Unix domain
6527 socket. An alternate socket can be specified in parentheses. The full syntax of
6528 each item in \mysql@_servers\ is:
6530 <<hostname>>@:@:<<port>>(<<socket name>>)/<<database>>/<<user>>/<<password>>
6532 Any of the three sub-parts of the first field can be omitted. For normal use on
6533 the local host it can be left blank or set to just `localhost'.
6535 No database need be supplied -- but if it is absent here, it must be given in
6538 If a MySQL query is issued that does not request any data (an insert, update,
6539 or delete command), the result of the lookup is the number of rows affected.
6543 .section Special PostgreSQL features
6544 PostgreSQL lookups can also use Unix domain socket connections to the database.
6545 This is usually faster and costs less CPU time than a TCP/IP connection.
6546 However it can be used only if the mail server runs on the same machine as the
6547 database server. A configuration line for PostgreSQL via Unix domain sockets
6550 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
6552 In other words, instead of supplying a host name, a path to the socket is
6553 given. The path name is enclosed in parentheses so that its slashes aren't
6554 visually confused with the delimiters for the other server parameters.
6556 If a PostgreSQL query is issued that does not request any data (an insert,
6557 update, or delete command), the result of the lookup is the number of rows
6567 . ============================================================================
6568 .chapter Domain, host, address, and local part lists
6569 .set runningfoot "domain, host, and address lists"
6570 .rset CHAPdomhosaddlists "~~chapter"
6571 .index list||of domains, hosts, etc.
6572 A number of Exim configuration options contain lists of domains, hosts,
6573 email addresses, or local parts. For example, the \hold@_domains\ option
6574 contains a list of domains whose delivery is currently suspended. These lists
6575 are also used as data in ACL statements (see chapter ~~CHAPACL).
6577 Each item in one of these lists is a pattern to be matched against a domain,
6578 host, email address, or local part, respectively. In the sections below, the
6579 different types of pattern for each case are described, but first we cover some
6580 general facilities that apply to all four kinds of list.
6583 .section Expansion of lists
6584 .index expansion||of lists
6585 Each list is expanded as a single string before it is used. If the expansion is
6586 forced to fail, Exim behaves as if the item it is testing (domain, host,
6587 address, or local part) is not in the list. Other expansion failures cause
6590 If an item in a list is a regular expression, backslashes, dollars and possibly
6591 other special characters in the expression must be protected against
6592 misinterpretation by the string expander. The easiest way to do this is to use
6593 the \"@\N"\ expansion feature to indicate that the contents of the regular
6594 expression should not be expanded. For example, in an ACL you might have:
6596 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N :
6597 ${lookup{$domain}lsearch{/badsenders/bydomain}}
6599 The first item is a regular expression that is protected from expansion by
6600 \"@\N"\, whereas the second uses the expansion to obtain a list of unwanted
6601 senders based on the receiving domain.
6603 After expansion, the list is split up into separate items for matching.
6604 Normally, colon is used as the separator character, but this can be varied if
6605 necessary, as described in section ~~SECTlistconstruct.
6608 .section Negated items in lists
6609 .index list||negation
6610 .index negation in lists
6611 Items in a list may be positive or negative. Negative items are indicated by a
6612 leading exclamation mark, which may be followed by optional white space. A list
6613 defines a set of items (domains, etc). When Exim processes one of these lists,
6614 it is trying to find out whether a domain, host, address, or local part
6615 (respectively) is in the set that is defined by the list. It works like this:
6617 The list is scanned from left to right. If a positive item is matched, the
6618 subject that is being checked is in the set; if a negative item is matched, the
6619 subject is not in the set. If the end of the list is reached without the
6620 subject having matched any of the patterns, it is in the set if the last item
6621 was a negative one, but not if it was a positive one. For example, the list in
6623 domainlist relay_domains = !a.b.c : *.b.c
6625 matches any domain ending in \*.b.c*\ except for \*a.b.c*\. Domains that match
6626 neither \*a.b.c*\ nor \*@*.b.c*\ do not match, because the last item in the
6627 list is positive. However, if the setting were
6629 domainlist relay_domains = !a.b.c
6631 then all domains other than \*a.b.c*\ would match because the last item in the
6632 list is negative. In other words, a list that ends with a negative item behaves
6633 as if it had an extra item \":*"\ on the end.
6635 Another way of thinking about positive and negative items in lists is to read
6636 the connector as `or' after a positive item and as `and' after a negative
6640 .section File names in lists
6641 .rset SECTfilnamlis "~~chapter.~~section"
6642 .index list||file name in
6643 If an item in a domain, host, address, or local part list is an absolute file
6644 name (beginning with a slash character), each line of the file is read and
6645 processed as if it were an independent item in the list, except that further
6646 file names are not allowed,
6647 and no expansion of the data from the file takes place.
6648 Empty lines in the file are ignored, and the file may also contain comment
6651 For domain and host lists, if a @# character appears anywhere in a line of the
6652 file, it and all following characters are ignored.
6654 Because local parts may legitimately contain @# characters, a comment in an
6655 address list or local part list file is recognized only if @# is preceded by
6656 white space or the start of the line. For example:
6658 not#comment@x.y.z # but this is a comment
6661 Putting a file name in a list has the same effect as inserting each line of the
6662 file as an item in the list (blank lines and comments excepted). However, there
6663 is one important difference: the file is read each time the list is processed,
6664 so if its contents vary over time, Exim's behaviour changes.
6666 If a file name is preceded by an exclamation mark, the sense of any match
6667 within the file is inverted. For example, if
6669 hold_domains = !/etc/nohold-domains
6671 and the file contains the lines
6676 then \*a.b.c*\ is in the set of domains defined by \hold@_domains\, whereas any
6677 domain matching \"*.b.c"\ is not.
6680 .section An lsearch file is not an out-of-line list
6681 As will be described in the sections that follow, lookups can be used in lists
6682 to provide indexed methods of checking list membership. There has been some
6683 confusion about the way \%lsearch%\ lookups work in lists. Because
6684 an \%lsearch%\ file contains plain text and is scanned sequentially, it is
6685 sometimes thought that it is allowed to contain wild cards and other kinds of
6686 non-constant pattern. This is not the case. The keys in an \%lsearch%\ file are
6687 always fixed strings, just as for any other single-key lookup type.
6689 If you want to use a file to contain wild-card patterns that form part of a
6690 list, just give the file name on its own, without a search type, as described
6691 in the previous section.
6695 .section Named lists
6696 .rset SECTnamedlists "~~chapter.~~section"
6699 A list of domains, hosts, email addresses, or local parts can be given a name
6700 which is then used to refer to the list elsewhere in the configuration. This is
6701 particularly convenient if the same list is required in several different
6702 places. It also allows lists to be given meaningful names, which can improve
6703 the readability of the configuration. For example, it is conventional to define
6704 a domain list called \*local@_domains*\ for all the domains that are handled
6705 locally on a host, using a configuration line such as
6707 domainlist local_domains = localhost:my.dom.example
6709 Named lists are referenced by giving their name preceded by a plus sign, so,
6710 for example, a router that is intended to handle local domains would be
6711 configured with the line
6713 domains = +local_domains
6715 The first router in a configuration is often one that handles all domains
6716 except the local ones, using a configuration with a negated item like this:
6720 domains = ! +local_domains
6721 transport = remote_smtp
6724 The four kinds of named list are created by configuration lines starting with
6725 the words \domainlist\, \hostlist\, \addresslist\, or \localpartlist\,
6726 respectively. Then there follows the name that you are defining, followed by an
6727 equals sign and the list itself. For example:
6729 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
6730 addresslist bad_senders = cdb;/etc/badsenders
6732 A named list may refer to other named lists:
6734 domainlist dom1 = first.example : second.example
6735 domainlist dom2 = +dom1 : third.example
6736 domainlist dom3 = fourth.example : +dom2 : fifth.example
6739 \**Warning**\: If the last item in a referenced list is a negative one, the
6740 effect may not be what you intended, because the negation does not propagate
6741 out to the higher level. For example, consider:
6743 domainlist dom1 = !a.b
6744 domainlist dom2 = +dom1 : *.b
6746 The second list specifies `either in the \dom1\ list or \*@*.b*\'. The first
6747 list specifies just `not \*a.b*\', so the domain \*x.y*\ matches it. That means
6748 it matches the second list as well. The effect is not the same as
6750 domainlist dom2 = !a.b : *.b
6752 where \*x.y*\ does not match. It's best to avoid negation altogether in
6753 referenced lists if you can.
6755 Named lists may have a performance advantage. When Exim is routing an
6756 address or checking an incoming message, it caches the result of tests on named
6757 lists. So, if you have a setting such as
6759 domains = +local_domains
6761 on several of your routers
6762 or in several ACL statements,
6763 the actual test is done only for the first one. However, the caching works only
6764 if there are no expansions within the list itself or any sublists that it
6765 references. In other words, caching happens only for lists that are known to be
6766 the same each time they are referenced.
6768 By default, there may be up to 16 named lists of each type. This limit can be
6769 extended by changing a compile-time variable. The use of domain and host lists
6770 is recommended for concepts such as local domains, relay domains, and relay
6771 hosts. The default configuration is set up like this.
6774 .section Named lists compared with macros
6775 .index list||named compared with macro
6776 .index macro||compared with named list
6777 At first sight, named lists might seem to be no different from macros in the
6778 configuration file. However, macros are just textual substitutions. If you
6781 ALIST = host1 : host2
6782 auth_advertise_hosts = !ALIST
6784 it probably won't do what you want, because that is exactly the same as
6786 auth_advertise_hosts = !host1 : host2
6788 Notice that the second host name is not negated. However, if you use a host
6791 hostlist alist = host1 : host2
6792 auth_advertise_hosts = ! +alist
6794 the negation applies to the whole list, and so that is equivalent to
6796 auth_advertise_hosts = !host1 : !host2
6800 .section Named list caching
6801 .index list||caching of named
6802 .index caching||named lists
6803 While processing a message, Exim caches the result of checking a named list if
6804 it is sure that the list is the same each time. In practice, this means that
6805 the cache operates only if the list contains no @$ characters, which guarantees
6806 that it will not change when it is expanded. Sometimes, however, you may have
6807 an expanded list that you know will be the same each time within a given
6808 message. For example:
6810 domainlist special_domains = \
6811 ${lookup{$sender_host_address}cdb{/some/file}}
6813 This provides a list of domains that depends only on the sending host's IP
6814 address. If this domain list is referenced a number of times (for example,
6815 in several ACL lines, or in several routers) the result of the check is not
6816 cached by default, because Exim does not know that it is going to be the
6817 same list each time.
6819 By appending \"@_cache"\ to \"domainlist"\ you can tell Exim to go ahead and
6820 cache the result anyway. For example:
6822 domainlist_cache special_domains = ${lookup{...
6824 If you do this, you should be absolutely sure that caching is going to do
6825 the right thing in all cases. When in doubt, leave it out.
6828 .section Domain lists
6829 .rset SECTdomainlist "~~chapter.~~section"
6830 .index domain list||patterns for
6831 .index list||domain list
6832 Domain lists contain patterns that are to be matched against a mail domain.
6833 The following types of item may appear in domain lists:
6835 .index primary host name
6836 .index host||name, matched in domain list
6837 .index \primary@_hostname\
6838 .index domain list||matching primary host name
6839 .index @@ in a domain list
6840 If a pattern consists of a single @@ character, it matches the local host name,
6841 as set by the \primary@_hostname\ option (or defaulted). This makes it possible
6842 to use the same configuration file on several different hosts that differ only
6845 .index @@[] in a domain list
6846 .index domain list||matching local IP interfaces
6847 .index domain literal
6848 If a pattern consists of the string \"@@[]"\ it matches any local IP interface
6849 address, enclosed in square brackets, as in an email address that contains a
6851 In today's Internet, the use of domain literals is controversial.
6854 .index @@mx@_primary
6855 .index @@mx@_secondary
6856 .index domain list||matching MX pointers to local host
6857 If a pattern consists of the string \"@@mx@_any"\ it matches any domain that
6858 has an MX record pointing to the local host or to any host that is listed in
6859 .index \hosts@_treat@_as@_local\
6860 \hosts@_treat@_as@_local\. The items \"@@mx@_primary"\ and \"@@mx@_secondary"\
6861 are similar, except that the first matches only when a primary MX target is the
6862 local host, and the second only when no primary MX target is the local host,
6863 but a secondary MX target is. `Primary' means an MX record with the lowest
6864 preference value -- there may of course be more than one of them.
6866 The MX lookup that takes place when matching a pattern of this type is
6867 performed with the resolver options for widening names turned off. Thus, for
6868 example, a single-component domain will \*not*\ be expanded by adding the
6869 resolver's default domain. See the \qualify@_single\ and \search@_parents\
6870 options of the \%dnslookup%\ router for a discussion of domain widening.
6872 Sometimes you may want to ignore certain IP addresses when using one of these
6873 patterns. You can specify this by following the pattern with \"/ignore=<<ip
6874 list>>"\, where <<ip list>> is a list of IP addresses. These addresses are
6875 ignored when processing the pattern (compare the \ignore@_target@_hosts\ option
6876 on a router). For example:
6878 domains = @mx_any/ignore=127.0.0.1
6880 This example matches any domain that has an MX record pointing to one of
6881 the local host's IP addresses other than 127.0.0.1.
6883 The list of IP addresses is in fact processed by the same code that processes
6884 host lists, so it may contain CIDR-coded network specifications and it may also
6885 contain negative items.
6887 Because the list of IP addresses is a sublist within a domain list, you have to
6888 be careful about delimiters if there is more than one address. Like any other
6889 list, the default delimiter can be changed. Thus, you might have:
6891 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
6892 an.other.domain : ...
6894 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
6895 involved, it is easiest to change the delimiter for the main list as well:
6897 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
6898 an.other.domain ? ...
6902 .index asterisk||in domain list
6903 .index domain list||asterisk in
6904 .index domain list||matching `ends with'
6905 If a pattern starts with an asterisk, the remaining characters of the pattern
6906 are compared with the terminating characters of the domain. The use of `$*$' in
6907 domain lists differs from its use in partial matching lookups. In a domain
6908 list, the character following the asterisk need not be a dot, whereas partial
6909 matching works only in terms of dot-separated components. For example, a domain
6910 list item such as \"*key.ex"\ matches \*donkey.ex*\ as well as
6913 .index regular expressions||in domain list
6914 .index domain list||matching regular expression
6915 If a pattern starts with a circumflex character, it is treated as a regular
6916 expression, and matched against the domain using a regular expression matching
6917 function. The circumflex is treated as part of the regular expression.
6918 References to descriptions of the syntax of regular expressions are given in
6919 chapter ~~CHAPregexp.
6921 \**Warning**\: Because domain lists are expanded before being processed, you
6922 must escape any backslash and dollar characters in the regular expression, or
6923 use the special \"@\N"\ sequence (see chapter ~~CHAPexpand) to specify that it
6924 is not to be expanded (unless you really do want to build a regular expression
6925 by expansion, of course).
6927 .index lookup||in domain list
6928 .index domain list||matching by lookup
6929 If a pattern starts with the name of a single-key lookup type followed by a
6930 semicolon (for example, `dbm;' or `lsearch;'), the remainder of the pattern
6931 must be a file name in a suitable format for the lookup type. For example, for
6932 `cdb;' it must be an absolute path:
6934 domains = cdb;/etc/mail/local_domains.cdb
6936 The appropriate type of lookup is done on the file using the domain name as the
6937 key. In most cases, the data that is looked up is not used; Exim is interested
6938 only in whether or not the key is present in the file. However, when a lookup
6939 is used for the \domains\ option on a router
6940 or a \domains\ condition in an ACL statement, the data is preserved in the
6941 \$domain@_data$\ variable and can be referred to in other router options or
6942 other statements in the same ACL.
6944 Any of the single-key lookup type names may be preceded by `partial<<n>>-',
6945 where the <<n>> is optional, for example,
6947 domains = partial-dbm;/partial/domains
6949 This causes partial matching logic to be invoked; a description of how this
6950 works is given in section ~~SECTpartiallookup.
6952 .index asterisk||in lookup type
6953 Any of the single-key lookup types may be followed by an asterisk. This causes
6954 a default lookup for a key consisting of a single asterisk to be done if the
6955 original lookup fails. This is not a useful feature when using a domain list to
6956 select particular domains (because any domain would match), but it might have
6957 value if the result of the lookup is being used via the \$domain@_data$\
6960 If the pattern starts with the name of a query-style lookup type followed by a
6961 semicolon (for example, `nisplus;' or `ldap;'), the remainder of the pattern
6962 must be an appropriate query for the lookup type, as described in chapter
6963 ~~CHAPfdlookup. For example:
6965 hold_domains = mysql;select domain from holdlist \
6966 where domain = '$domain';
6968 In most cases, the data that is looked up is not used (so for an SQL query, for
6969 example, it doesn't matter what field you select). Exim is interested only in
6970 whether or not the query succeeds. However, when a lookup is used for the
6971 \domains\ option on a router, the data is preserved in the \$domain@_data$\
6972 variable and can be referred to in other options.
6974 .index domain list||matching literal domain name
6975 If none of the above cases apply, a caseless textual comparison is made between
6976 the pattern and the domain.
6979 Here is an example that uses several different kinds of pattern:
6981 domainlist funny_domains = \
6984 *.foundation.fict.example : \
6985 \N^[1-2]\d{3}\.fict\.example$\N : \
6986 partial-dbm;/opt/data/penguin/book : \
6987 nis;domains.byname : \
6988 nisplus;[name=$domain,status=local],domains.org_dir
6990 There are obvious processing trade-offs among the various matching modes. Using
6991 an asterisk is faster than a regular expression, and listing a few names
6992 explicitly probably is too. The use of a file or database lookup is expensive,
6993 but may be the only option if hundreds of names are required. Because the
6994 patterns are tested in order, it makes sense to put the most commonly matched
6999 .rset SECThostlist "~~chapter.~~section"
7000 .index host list||patterns in
7001 .index list||host list
7002 Host lists are used to control what remote hosts are allowed to do. For
7003 example, some hosts may be allowed to use the local host as a relay, and some
7004 may be permitted to use the SMTP \\ETRN\\ command. Hosts can be identified in
7005 two different ways, by name or by IP address. In a host list, some types of
7006 pattern are matched to a host name, and some are matched to an IP address.
7007 You need to be particularly careful with this when single-key lookups are
7008 involved, to ensure that the right value is being used as the key.
7010 .section Special host list patterns
7011 .index empty item in hosts list
7012 .index host list||empty string in
7013 If a host list item is the empty string, it matches only when no remote host is
7014 involved. This is the case when a message is being received from a local
7015 process using SMTP on the standard input, that is, when a TCP/IP connection is
7018 .index asterisk||in host list
7019 The special pattern `$*$' in a host list matches any host or no host. Neither
7020 the IP address nor the name is actually inspected.
7023 .section Host list patterns that match by IP address
7024 .rset SECThoslispatip "~~chapter.~~section"
7025 .index host list||matching IP addresses
7026 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7027 the incoming address actually appears in the IPv6 host as
7028 `@:@:$tt{ffff}:<<v4address>>'. When such an address is tested against a host
7029 list, it is converted into a traditional IPv4 address first. (Not all operating
7030 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7033 The following types of pattern in a host list check the remote host by
7034 inspecting its IP address:
7036 If the pattern is a plain domain name (not a regular expression, not starting
7037 with $*$, not a lookup of any kind), Exim calls the operating system function
7038 to find the associated IP address(es). Exim uses the newer
7039 \*getipnodebyname()*\ function when available, otherwise \*gethostbyname()*\.
7040 This typically causes a forward DNS lookup of the name. The result is compared
7041 with the IP address of the subject host.
7043 If there is a temporary problem (such as a DNS timeout) with the host name
7044 lookup, a temporary error occurs. For example, if the list is being used in an
7045 ACL condition, the ACL gives a `defer' response, usually leading to a temporary
7046 SMTP error code. If no IP address can be found for the host name, what happens
7047 is described in section ~~SECTbehipnot below.
7050 .index @@ in a host list
7051 If the pattern is `@@', the primary host name is substituted and used as a
7052 domain name, as just described.
7054 If the pattern is an IP address, it is matched against the IP address of the
7055 subject host. IPv4 addresses are given in the normal `dotted-quad' notation.
7056 IPv6 addresses can be given in colon-separated format, but the colons have to
7057 be doubled so as not to be taken as item separators when the default list
7058 separator is used. IPv6 addresses are recognized even when Exim is compiled
7059 without IPv6 support. This means that if they appear in a host list on an
7060 IPv4-only host, Exim will not treat them as host names. They are just addresses
7061 that can never match a client host.
7063 .index @@[] in a host list
7064 If the pattern is `@@[]', it matches the IP address of any IP interface on
7065 the local host. For example, if the local host is an IPv4 host with one
7066 interface address 10.45.23.56, these two ACL statements have the same effect:
7068 accept hosts = 127.0.0.1 : 10.45.23.56
7072 If the pattern is an IP address followed by a slash and a mask length (for
7073 example 10.11.42.0/24), it is matched against the IP address of the subject
7074 host under the given mask.
7075 This allows, an entire network of hosts to be included (or excluded) by a
7077 .index CIDR notation
7078 The mask uses CIDR notation; it specifies the number of address bits that must
7079 match, starting from the most significant end of the address.
7081 \**Note**\: the mask is \*not*\ a count of addresses, nor is it the high number
7082 of a range of addresses. It is the number of bits in the network portion of the
7083 address. The above example specifies a 24-bit netmask, so it matches all 256
7084 addresses in the 10.11.42.0 network. An item such as
7088 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7089 32 for an IPv4 address is the same as no mask at all; just a single address
7092 Here is another example which shows an IPv4 and an IPv6 network:
7094 recipient_unqualified_hosts = 192.168.0.0/16: \
7095 3ffe::ffff::836f::::/48
7097 The doubling of list separator characters applies only when these items
7098 appear inline in a host list. It is not required when indirecting via a file.
7101 recipient_unqualified_hosts = /opt/exim/unqualnets
7103 could make use of a file containing
7108 to have exactly the same effect as the previous example. When listing IPv6
7109 addresses inline, it is usually more convenient to use the facility for
7110 changing separator characters. This list contains the same two networks:
7112 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7115 The separator is changed to semicolon by the leading `<;' at the start of the
7120 .section Host list patterns for single-key lookups by host address
7121 .rset SECThoslispatsikey "~~chapter.~~section"
7122 .index host list||lookup of IP address
7123 When a host is to be identified by a single-key lookup of its complete IP
7124 address, the pattern takes this form:
7126 net-<<single-key-search-type>>;<<search-data>>
7130 hosts_lookup = net-cdb;/hosts-by-ip.db
7132 The text form of the IP address of the subject host is used as the lookup key.
7133 IPv6 addresses are converted to an unabbreviated form, using lower case
7134 letters, with dots as separators because colon is the key terminator in
7135 \%lsearch%\ files. [Colons can in fact be used in keys in \%lsearch%\ files by
7136 quoting the keys, but this is a facility that was added later.] The data
7137 returned by the lookup is not used.
7139 .index IP address||masking
7140 .index host list||masked IP address
7141 Single-key lookups can also be performed using masked IP addresses, using
7142 patterns of this form:
7144 net<<number>>-<<single-key-search-type>>;<<search-data>>
7148 net24-dbm;/networks.db
7150 The IP address of the subject host is masked using <<number>> as the mask
7151 length. A textual string is constructed from the masked value, followed by the
7152 mask, and this is used as the lookup key. For example, if the host's IP address
7153 is 192.168.34.6, the key that is looked up for the above example is
7154 `192.168.34.0/24'. IPv6 addresses are converted to a text value using lower
7155 case letters and dots as separators instead of the more usual colon, because
7156 colon is the key terminator in \%lsearch%\ files. Full, unabbreviated IPv6
7157 addresses are always used.
7159 \**Warning**\: Specifing \net32@-\ (for an IPv4 address) or \net128@-\ (for an
7160 IPv6 address) is not the same as specifing just \net@-\ without a number. In
7161 the former case the key strings include the mask value, whereas in the latter
7162 case the IP address is used on its own.
7165 .section Host list patterns that match by host name
7166 .rset SECThoslispatnam "~~chapter.~~section"
7167 .index host||lookup failures
7168 .index unknown host name
7169 .index host list||matching host name
7170 There are several types of pattern that require Exim to know the name of the
7171 remote host. These are either wildcard patterns or lookups by name. (If a
7172 complete hostname is given without any wildcarding, it is used to find an IP
7173 address to match against, as described in the section ~~SECThoslispatip above.)
7175 If the remote host name is not already known when Exim encounters one of these
7176 patterns, it has to be found from the IP address.
7177 Although many sites on the Internet are conscientious about maintaining reverse
7178 DNS data for their hosts, there are also many that do not do this.
7179 Consequently, a name cannot always be found, and this may lead to unwanted
7180 effects. Take care when configuring host lists with wildcarded name patterns.
7181 Consider what will happen if a name cannot be found.
7183 Because of the problems of determining host names from IP addresses, matching
7184 against host names is not as common as matching against IP addresses.
7186 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7187 if no name is found in the DNS, the system function (\*gethostbyaddr()*\ or
7188 \*getipnodebyaddr()*\ if available) is tried. The order in which these lookups
7189 are done can be changed by setting the \host@_lookup@_order\ option.
7191 There are some options that control what happens if a host name cannot be
7192 found. These are described in section ~~SECTbehipnot below.
7195 .index host||alias for
7196 .index alias for host
7197 As a result of aliasing, hosts may have more than one name. When processing any
7198 of the following types of pattern, all the host's names are checked:
7200 .index asterisk||in host list
7201 If a pattern starts with `$*$' the remainder of the item must match the end of
7202 the host name. For example, \"*.b.c"\ matches all hosts whose names end in
7203 \*.b.c*\. This special simple form is provided because this is a very common
7204 requirement. Other kinds of wildcarding require the use of a regular
7207 .index regular expressions||in host list
7208 .index host list||regular expression in
7209 If the item starts with `@^' it is taken to be a regular expression which is
7210 matched against the host name. For example,
7214 is a regular expression that matches either of the two hosts \*a.c.d*\ or
7215 \*b.c.d*\. When a regular expression is used in a host list, you must take care
7216 that backslash and dollar characters are not misinterpreted as part of the
7217 string expansion. The simplest way to do this is to use \"@\N"\ to mark that
7218 part of the string as non-expandable. For example:
7220 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
7222 \**Warning**\: If you want to match a complete host name, you must include the
7223 \"@$"\ terminating metacharacter in the regular expression, as in the above
7224 example. Without it, a match at the start of the host name is all that is
7229 .section Behaviour when an IP address or name cannot be found
7230 .rset SECTbehipnot "~~chapter.~~section"
7231 .index host||lookup failures
7232 While processing a host list, Exim may need to look up an IP address from a
7233 name (see section ~~SECThoslispatip), or it may need to look up a host name
7234 from an IP address (see section ~~SECThoslispatnam). In either case, the
7235 behaviour when it fails to find the information it is seeking is the same.
7237 .index \"+include@_unknown"\
7238 .index \"+ignore@_unknown"\
7239 By default, Exim behaves as if the host does not match the list. This may not
7240 always be what you want to happen. To change Exim's behaviour, the special
7241 items \"+include@_unknown"\ or \"+ignore@_unknown"\ may appear in the list (at
7242 top level -- they are not recognized in an indirected file).
7244 If any item that follows \"+include@_unknown"\ requires information that
7245 cannot found, Exim behaves as if the host does match the list. For example,
7247 host_reject_connection = +include_unknown:*.enemy.ex
7249 rejects connections from any host whose name matches \"*.enemy.ex"\, and also
7250 any hosts whose name it cannot find.
7252 If any item that follows \"+ignore@_unknown"\ requires information that cannot
7253 be found, Exim ignores that item and proceeds to the rest of the list. For
7256 accept hosts = +ignore_unknown : friend.example : \
7259 accepts from any host whose name is \*friend.example*\ and from 192.168.4.5,
7260 whether or not its host name can be found. Without \"+ignore@_unknown"\, if no
7261 name can be found for 192.168.4.5, it is rejected.
7263 Both \"+include@_unknown"\ and \"+ignore@_unknown"\ may appear in the same
7264 list. The effect of each one lasts until the next, or until the end of the
7267 \**Note**\: This section applies to permanent lookup failures. It does \*not*\
7268 apply to temporary DNS errors. They always cause a defer action.
7271 .section Host list patterns for single-key lookups by host name
7272 .rset SECThoslispatnamsk "~~chapter.~~section"
7273 .index host||lookup failures
7274 .index unknown host name
7275 .index host list||matching host name
7276 If a pattern is of the form
7278 <<single-key-search-type>>;<<search-data>>
7282 dbm;/host/accept/list
7284 a single-key lookup is performend, using the host name as its key. If the
7285 lookup succeeds, the host matches the item. The actual data that is looked up
7288 \**Reminder**\: With this kind of pattern, you must have host $it{names} as
7289 keys in the file, not IP addresses. If you want to do lookups based on IP
7290 addresses, you must precede the search type with `net-' (see section
7291 ~~SECThoslispatsikey). There is, however, no reason why you could not use two
7292 items in the same list, one doing an address lookup and one doing a name
7293 lookup, both using the same file.
7296 .section Host list patterns for query-style lookups
7297 If a pattern is of the form
7299 <<query-style-search-type>>;<<query>>
7301 the query is obeyed, and if it succeeds, the host matches the item. The actual
7302 data that is looked up is not used. The variables \$sender@_host@_address$\ and
7303 \$sender@_host@_name$\ can be used in the query. For example:
7305 hosts_lookup = pgsql;\
7306 select ip from hostlist where ip='$sender_host_address'
7308 The value of \$sender@_host@_address$\ for an IPv6 address uses colon
7309 separators. You can use the \sg\ expansion item to change this if you need to.
7310 If you want to use masked IP addresses in database queries, you can use the
7311 \mask\ expansion operator.
7313 If the query contains a reference to \$sender@_host@_name$\, Exim automatically
7314 looks up the host name if has not already done so. (See section
7315 ~~SECThoslispatnam for comments on finding host names.)
7317 Historical note: prior to release 4.30, Exim would always attempt to find a
7318 host name before running the query, unless the search type was preceded by
7319 \"net-"\. This is no longer the case. For backwards compatibility, \"net-"\ is
7320 still recognized for query-style lookups, but its presence or absence has no
7321 effect. (Of course, for single-key lookups, \"net-"\ $it{is} important.)
7324 .section Mixing wildcarded host names and addresses in host lists
7325 .rset SECTmixwilhos "~~chapter.~~section"
7326 .index host list||mixing names and addresses in
7327 If you have name lookups or wildcarded host names and IP addresses in the same
7328 host list, you should normally put the IP addresses first. For example, in an
7331 accept hosts = 10.9.8.7 : *.friend.example
7333 The reason for this lies in the left-to-right way that Exim processes lists.
7334 It can test IP addresses without doing any DNS lookups, but when it reaches an
7335 item that requires a host name, it fails if it cannot find a host name to
7336 compare with the pattern. If the above list is given in the opposite order, the
7337 \accept\ statement fails for a host whose name cannot be found, even if its
7338 IP address is 10.9.8.7.
7340 If you really do want to do the name check first, and still recognize the IP
7341 address, you can rewrite the ACL like this:
7343 accept hosts = *.friend.example
7344 accept hosts = 10.9.8.7
7346 If the first \accept\ fails, Exim goes on to try the second one. See chapter
7347 ~~CHAPACL for details of ACLs.
7352 .section Address lists
7353 .index list||address list
7354 .index address list||empty item
7355 .index address list||patterns
7356 .rset SECTaddresslist "~~chapter.~~section"
7357 Address lists contain patterns that are matched against mail addresses. There
7358 is one special case to be considered: the sender address of a bounce message is
7359 always empty. You can test for this by providing an empty item in an address
7360 list. For example, you can set up a router to process bounce messages by
7361 using this option setting:
7365 The presence of the colon creates an empty item. If you do not provide any
7366 data, the list is empty and matches nothing. The empty sender can also be
7367 detected by a regular expression that matches an empty string.
7369 The following kinds of pattern are supported in address lists:
7371 .index regular expressions||in address list
7372 .index address list||regular expression in
7373 If (after expansion) a pattern starts with `@^', a regular expression match is
7374 done against the complete address, with the pattern as the regular expression.
7375 You must take care that backslash and dollar characters are not misinterpreted
7376 as part of the string expansion. The simplest way to do this is to use \"@\N"\
7377 to mark that part of the string as non-expandable. For example:
7379 deny senders = \N^\d{8}.+@spamhaus.example$\N : ...
7381 The \"@\N"\ sequences are removed by the expansion, so the item does start
7382 with `@^' by the time it is being interpreted as an address pattern.
7384 .index @@@@ with single-key lookup
7385 .index address list||@@@@ lookup type
7386 .index address list||split local part and domain
7387 If a pattern starts with `@@@@' followed by a single-key lookup item
7388 (for example, \"@@@@lsearch;/some/file"\), the address that is being checked is
7389 split into a local part and a domain. The domain is looked up in the file. If
7390 it is not found, there is no match. If it is found, the data that is looked up
7391 from the file is treated as a colon-separated list of local part patterns, each
7392 of which is matched against the subject local part in turn.
7394 .index asterisk||in address list
7395 The lookup may be a partial one, and/or one involving a search for a default
7396 keyed by `$*$' (see section ~~SECTdefaultvaluelookups). The local part patterns
7397 that are looked up can be regular expressions or begin with `$*$', or even be
7398 further lookups. They may also be independently negated. For example, with
7400 deny senders = @@dbm;/etc/reject-by-domain
7402 the data from which the DBM file is built could contain lines like
7404 baddomain.com: !postmaster : *
7406 to reject all senders except \postmaster\ from that domain.
7407 .index local part||starting with !
7408 If a local part that actually begins with an exclamation mark is required, it
7409 has to be specified using a regular expression. In \%lsearch%\ files, an entry
7410 may be split over several lines by indenting the second and subsequent lines,
7411 but the separating colon must still be included at line breaks. White space
7412 surrounding the colons is ignored. For example:
7414 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
7417 As in all colon-separated lists in Exim, a colon can be included in an item by
7420 If the last item in the list starts with a right angle-bracket, the remainder
7421 of the item is taken as a new key to look up in order to obtain a continuation
7422 list of local parts. The new key can be any sequence of characters. Thus one
7423 might have entries like
7425 aol.com: spammer1 : spammer 2 : >*
7426 xyz.com: spammer3 : >*
7429 in a file that was searched with \@@@@dbm$*$\, to specify a match for 8-digit
7430 local parts for all domains, in addition to the specific local parts listed for
7431 each domain. Of course, using this feature costs another lookup each time a
7432 chain is followed, but the effort needed to maintain the data is reduced.
7433 .index loop||in lookups
7434 It is possible to construct loops using this facility, and in order to catch
7435 them, the chains may be no more than fifty items long.
7437 The @@@@<<lookup>> style of item can also be used with a query-style
7438 lookup, but in this case, the chaining facility is not available. The lookup
7439 can only return a single list of local parts.
7441 .index address list||lookup for complete address
7442 Complete addresses can be looked up by using a pattern that
7443 starts with a lookup type terminated by a semicolon, follwed by the data for
7447 deny senders = cdb;/etc/blocked.senders : \
7448 mysql;select address from blocked where \
7449 address='${quote_mysql:$sender_address}'
7451 For a single-key lookup type, Exim uses the complete address as the key.
7452 Partial matching (section ~~SECTpartiallookup) cannot be used, and is ignored
7453 if specified, with an entry being written to the panic log.
7455 .index @*@@ with single-key lookup
7456 You can configure lookup defaults, as described in section
7457 ~~SECTdefaultvaluelookups, but this is useful only for the `$*$@@' type of
7458 default. For example, with this lookup:
7460 accept senders = lsearch*@;/some/file
7462 the file could contains lines like this:
7464 user1@domain1.example
7467 and for the sender address \*nimrod@@jaeger.example*\, the sequence of keys
7470 nimrod@jaeger.example
7474 \**Warning 1**\: Do not include a line keyed by `$*$' in the file, because that
7475 would mean that every address matches, thus rendering the test useless.
7477 \**Warning 2**\: Do not confuse these two kinds of item:
7479 deny recipients = dbm*@;/some/file
7480 deny recipients = *@dbm;/some/file
7482 The first does a whole address lookup, with defaulting, as just described,
7483 because it starts with a lookup type. The second matches the local part and
7484 domain independently, as described in the next paragraph.
7486 If a pattern contains an @@ character, but is not a regular expression
7487 and does not begin with a lookup type
7488 as described above, the local part of the subject address is compared with the
7489 local part of the pattern, which may start with an asterisk. If the local parts
7490 match, the domain is checked in exactly the same way as for a pattern in a
7491 domain list. For example, the domain can be wildcarded, refer to a named list,
7494 deny senders = *@*.spamming.site:\
7495 *@+hostile_domains:\
7496 bozo@partial-lsearch;/list/of/dodgy/sites:\
7498 *@dbm;/bad/domains.db
7500 .index local part||starting with !
7501 .index address list||local part starting with !
7502 If a local part that begins with an exclamation mark is required, it has to be
7503 specified using a regular expression, because otherwise the exclamation mark is
7504 treated as a sign of negation.
7506 If a pattern is not one of the above syntax forms, that is, if a pattern which
7507 is not a regular expression or a lookup does not contain an @@ character, it is
7508 matched against the domain part of the subject address. The only two formats
7509 that are recognized this way are a literal domain, or a domain pattern that
7510 starts with $*$. In both these cases, the effect is the same as if \"*@@"\
7511 preceded the pattern.
7514 \**Warning**\: there is an important difference between the address list items
7515 in these two examples:
7518 senders = *@+my_list
7520 In the first one, \"my@_list"\ is a named address list, whereas in the second
7521 example it is a named domain list.
7525 .section Case of letters in address lists
7526 .rset SECTcasletadd "~~chapter.~~section"
7527 .index case of local parts
7528 .index address list||case forcing
7529 .index case forcing in address lists
7530 Domains in email addresses are always handled caselessly, but for local parts
7531 case may be significant on some systems (see \caseful@_local@_part\ for how
7532 Exim deals with this when routing addresses). However, RFC 2505 ($it{Anti-Spam
7533 Recommendations for SMTP MTAs}) suggests that matching of addresses to blocking
7534 lists should be done in a case-independent manner. Since most address lists in
7535 Exim are used for this kind of control, Exim attempts to do this by default.
7537 The domain portion of an address is always lowercased before matching it to an
7538 address list. The local part is lowercased by default, and any string
7539 comparisons that take place are done caselessly. This means that the data in
7540 the address list itself, in files included as plain file names, and in any file
7541 that is looked up using the `@@@@' mechanism, can be in any case. However, the
7542 keys in files that are looked up by a search type other than \%lsearch%\ (which
7543 works caselessly) must be in lower case, because these lookups are not
7547 To allow for the possibility of caseful address list matching, if an item in
7548 an address list is the string `+caseful', the original case of the local
7549 part is restored for any comparisons that follow, and string comparisons are no
7550 longer case-independent. This does not affect the domain, which remains in
7551 lower case. However, although independent matches on the domain alone are still
7552 performed caselessly, regular expressions that match against an entire address
7553 become case-sensitive after `+caseful' has been seen.
7556 .section Local part lists
7557 .rset SECTlocparlis "~~chapter.~~section"
7558 .index list||local part list
7559 .index local part||list
7560 Case-sensitivity in local part lists is handled in the same way as for address
7561 lists, as just described. The `+caseful' item can be used if required. In a
7562 setting of the \local@_parts\ option in a router with \caseful@_local@_part\
7563 set false, the subject is lowercased and the matching is initially
7564 case-insensitive. In this case, `+caseful' will restore case-sensitive matching
7565 in the local part list, but not elsewhere in the router. If
7566 \caseful@_local@_part\ is set true in a router, matching in the \local@_parts\
7567 option is case-sensitive from the start.
7569 If a local part list is indirected to a file (see section ~~SECTfilnamlis),
7570 comments are handled in the same way as address lists -- they are recognized
7571 only if the @# is preceded by white space or the start of the line.
7572 Otherwise, local part lists are matched in the same way as domain lists, except
7573 that the special items that refer to the local host (\"@@"\, \"@@[]"\,
7574 \"@@mx@_any"\, \"@@mx@_primary"\, and \"@@mx@_secondary"\) are not recognized.
7575 Refer to section ~~SECTdomainlist for details of the other available item
7584 . ============================================================================
7585 .chapter String expansions
7586 .set runningfoot "string expansions"
7587 .rset CHAPexpand ~~chapter
7588 .index expansion||of strings
7589 Many strings in Exim's run time configuration are expanded before use. Some of
7590 them are expanded every time they are used; others are expanded only once.
7592 When a string is being expanded it is copied verbatim from left to right except
7593 when a dollar or backslash character is encountered. A dollar specifies the
7594 start of a portion of the string which is interpreted and replaced as described
7595 below in section ~~SECTexpansionitems onwards. Backslash is used as an escape
7596 character, as described in the following section.
7599 .section Literal text in expanded strings
7600 .rset SECTlittext "~~chapter.~~section"
7601 .index expansion||including literal text
7602 An uninterpreted dollar can be included in an expanded string by putting a
7603 backslash in front of it. A backslash can be used to prevent any special
7604 character being treated specially in an expansion, including itself. If the
7605 string appears in quotes in the configuration file, two backslashes are
7606 required because the quotes themselves cause interpretation of backslashes when
7607 the string is read in (see section ~~SECTstrings).
7609 .index expansion||non-expandable substrings
7610 A portion of the string can specified as non-expandable by placing it between
7611 two occurrences of \"@\N"\. This is particularly useful for protecting regular
7612 expressions, which often contain backslashes and dollar signs. For example:
7614 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
7616 On encountering the first \"@\N"\, the expander copies subsequent characters
7617 without interpretation until it reaches the next \"@\N"\ or the end of the
7621 .section Character escape sequences in expanded strings
7622 .index expansion||escape sequences
7623 A backslash followed by one of the letters `n', `r', or `t' in an expanded
7624 string is recognized as an escape sequence for the character newline, carriage
7625 return, or tab, respectively. A backslash followed by up to three octal digits
7626 is recognized as an octal encoding for a single character, and a backslash
7627 followed by `x' and up to two hexadecimal digits is a hexadecimal encoding.
7629 These escape sequences are also recognized in quoted strings when they are read
7630 in. Their interpretation in expansions as well is useful for unquoted strings,
7631 and for other cases such as looked-up strings that are then expanded.
7633 .section Testing string expansions
7634 .index expansion||testing
7635 .index testing||string expansion
7636 .index \-be-\ option
7637 Many expansions can be tested by calling Exim with the \-be-\ option. This takes
7638 the command arguments, or lines from the standard input if there are no
7639 arguments, runs them through the string expansion code, and writes the results
7640 to the standard output. Variables based on configuration values are set up, but
7641 since no message is being processed, variables such as \$local@_part$\ have no
7642 value. Nevertheless the \-be-\ option can be useful for checking out file and
7643 database lookups, and the use of expansion operators such as \sg\, \substr\ and
7646 Exim gives up its root privilege when it is called with the \-be-\ option, and
7647 instead runs under the uid and gid it was called with, to prevent users from
7648 using \-be-\ for reading files to which they do not have access.
7651 .section Expansion items
7652 .rset SECTexpansionitems "~~chapter.~~section"
7653 The following items are recognized in expanded strings. White space may be used
7654 between sub-items that are keywords or substrings enclosed in braces inside an
7655 outer set of braces, to improve readability. \**Warning**\: Within braces,
7656 white space is significant.
7660 .item "@$<<variable name>>#$rm{or}#@$@{<<variable name>>@}"
7661 .index expansion||variables
7662 Substitute the contents of the named variable, for example
7667 The second form can be used to separate the name from subsequent alphanumeric
7668 characters. This form (using curly brackets) is available only for variables;
7669 it does $it{not} apply to message headers. The names of the variables are given
7670 in section ~~SECTexpvar below. If the name of a non-existent variable is given,
7671 the expansion fails.
7673 .item "@$@{<<op>>:<<string>>@}"
7674 .index expansion||operators
7675 The string is first itself expanded, and then the operation specified by <<op>>
7676 is applied to it. For example,
7680 The string starts with the first character after the colon, which may be
7681 leading white space. A list of operators is given in section ~~SECTexpop below.
7682 The operator notation is used for simple expansion items that have just one
7683 argument, because it reduces the number of braces and therefore makes the
7684 string easier to understand.
7686 .item "@$@{extract@{<<key>>@}@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
7687 .index expansion||extracting substrings by key
7688 The key and <<string1>> are first expanded separately.
7689 Leading and trailing whitespace is removed from the key (but not from any of
7691 The key must not consist entirely of digits. The expanded <<string1>> must be
7694 <<key1>> = <<value1>> <<key2>> = <<value2>> ...
7696 where the equals signs and spaces (but not both) are optional. If any of the
7697 values contain white space, they must be enclosed in double quotes, and any
7698 values that are enclosed in double quotes are subject to escape processing as
7699 described in section ~~SECTstrings. The expanded <<string1>> is searched for
7700 the value that corresponds to the key. The search is case-insensitive. If the
7701 key is found, <<string2>> is expanded, and replaces the whole item; otherwise
7702 <<string3>> is used. During the expansion of <<string2>> the variable \$value$\
7703 contains the value that has been extracted. Afterwards, it is restored to any
7704 previous value it might have had.
7706 If @{<<string3>>@} is omitted, the item is replaced by an empty string if the
7707 key is not found. If @{<<string2>>@} is also omitted, the value that was
7708 extracted is used. Thus, for example, these two expansions are identical, and
7711 @$@{extract@{gid@}{uid=1984 gid=2001@}@}
7712 @$@{extract@{gid@}{uid=1984 gid=2001@}@{@$value@}@}
7714 Instead of @{<<string3>>@} the word `fail' (not in curly brackets) can appear,
7717 @$@{extract@{Z@}@{A=... B=...@}@{@$value@} fail @}
7719 @{<<string2>>@} must be present for `fail' to be recognized. When this syntax
7720 is used, if the extraction fails, the entire string expansion fails in a way
7721 that can be detected by the code in Exim which requested the expansion. This is
7722 called `forced expansion failure', and its consequences depend on the
7723 circumstances. In some cases it is no different from any other expansion
7724 failure, but in others a different action may be taken. Such variations are
7725 mentioned in the documentation of the option which is expanded.
7728 .item "@$@{extract@{<<number>>@}@{<<separators>>@}@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
7729 .index expansion||extracting substrings by number
7730 The <<number>> argument must consist entirely of decimal digits,
7731 apart from leading and trailing whitespace, which is ignored.
7732 This is what distinguishes this form of \extract\ from the previous kind. It
7733 behaves in the same way, except that, instead of extracting a named field, it
7734 extracts from <<string1>> the field whose number is given as the first
7735 argument. You can use \$value$\ in <<string2>> or \"fail"\ instead of
7736 <<string3>> as before.
7738 The fields in the string are separated by any one of the characters in the
7739 separator string. These may include space or tab characters.
7740 The first field is numbered one. If the number is negative, the fields are
7741 counted from the end of the string, with the rightmost one numbered -1. If the
7742 number given is zero, the entire string is returned. If the modulus of the
7743 number is greater than the number of fields in the string, the result is the
7744 expansion of <<string3>>, or the empty string if <<string3>> is not provided.
7747 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
7751 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
7753 yields `99'. Two successive separators mean that the field between them is
7754 empty (for example, the fifth field above).
7757 .item "@$@{hash@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
7758 .index hash function||textual
7759 .index expansion||textual hash
7760 This is a textual hashing function, and was the first to be implemented in
7761 early versions of Exim. In current releases, there are other hashing functions
7762 (numeric, MD5, and SHA-1), which are described below.
7764 The first two strings, after expansion, must be numbers. Call them <<m>> and
7765 <<n>>. If you are using fixed values for these numbers, that is, if <<string1>>
7766 and <<string2>> do not change when they are expanded, you can use the
7767 simpler operator notation that avoids some of the braces:
7769 @$@{hash@_<<n>>@_<<m>>:<<string>>@}
7771 The second number is optional (in both notations).
7773 If <<n>> is greater than or equal to the length of the string, the expansion
7774 item returns the string. Otherwise it computes a new string of length <<n>> by
7775 applying a hashing function to the string. The new string consists of
7776 characters taken from the first <<m>> characters of the string
7778 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
7780 If <<m>> is not present the value 26 is used, so that only lower case
7781 letters appear. For example:
7783 @$@{hash@{3@}@{monty@}@} $rm{yields} \"jmg"\
7784 @$@{hash@{5@}@{monty@}@} $rm{yields} \"monty"\
7785 @$@{hash@{4@}@{62@}@{monty python@}@} $rm{yields} \"fbWx"\
7789 .item "@$header@_<<header name>>:#$rm{or}#@$h@_<<header name>>:"
7790 .item "@$bheader@_<<header name>>:#$rm{or}#@$bh@_<<header name>>:"
7791 .item "@$rheader@_<<header name>>:#$rm{or}#@$rh@_<<header name>>:"
7792 .index expansion||header insertion
7794 .index \$bheader@_$\
7795 .index \$rheader@_$\
7796 .index header lines||in expansion strings
7797 .index header lines||character sets
7798 .index header lines||decoding
7799 Substitute the contents of the named message header line, for example
7803 The newline that terminates a header line is not included in the expansion, but
7804 internal newlines (caused by splitting the header line over several physical
7805 lines) may be present.
7807 The difference between \rheader\, \bheader\, and \header\ is in the way the
7808 data in the header line is interpreted.
7810 \rheader\ gives the original `raw' content of the header line, with no
7811 processing at all, and without the removal of leading and trailing whitespace.
7813 .index base64 encoding||in header lines
7814 \bheader\ removes leading and trailing whitespace, and then decodes base64 or
7815 quoted-printable MIME `words' within the header text, but does no character
7816 set translation. If decoding of what looks superficially like a MIME `word'
7817 fails, the raw string is returned.
7818 .index binary zero||in header line
7819 If decoding produces a binary zero character, it is replaced by a question mark
7820 -- this is what Exim does for binary zeros that are actually received in header
7823 \header\ tries to translate the string as decoded by \bheader\ to a standard
7824 character set. This is an attempt to produce the same string as would be
7825 displayed on a user's MUA. If translation fails, the \bheader\ string is
7826 returned. Translation is attempted only on operating systems that support the
7827 \*iconv()*\ function. This is indicated by the compile-time macro
7828 \\HAVE@_ICONV\\ in a system Makefile or in \(Local/Makefile)\.
7831 In a filter file, the target character set for \header\ can be specified by a
7832 command of the following form:
7834 headers charset "UTF-8"
7836 This command affects all references to \$h@_$\ (or \$header@_$\) expansions in
7837 subsequently obeyed filter commands. In the absence of this command, the target
7838 character set in a filter is taken from the setting of the \headers@_charset\
7839 option in the runtime configuration. The value of this option defaults to the
7840 value of \\HEADERS@_CHARSET\\ in \(Local/Makefile)\. The ultimate default is
7843 Header names follow the syntax of RFC 2822, which states that they may contain
7844 any printing characters except space and colon. Consequently, curly brackets
7845 $it{do not} terminate header names, and should not be used to enclose them as
7846 if they were variables. Attempting to do so causes a syntax error.
7848 Only header lines that are common to all copies of a message are visible to
7849 this mechanism. These are the original header lines that are received with the
7850 message, and any that are added by
7851 an ACL \warn\ statement or by
7852 a system filter. Header lines that are added to a particular copy of a message
7853 by a router or transport are not accessible.
7855 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
7856 before the \\DATA\\ ACL, because the header structure is not set up until the
7857 message is received. Header lines that are added by \warn\ statements in a
7858 \\RCPT\\ ACL (for example) are saved until the message's incoming header lines
7859 are available, at which point they are added. When a \\DATA\\ ACL is running,
7860 however, header lines added by earlier ACLs are visible.
7862 Upper case and lower case letters are synonymous in header names. If the
7863 following character is white space, the terminating colon may be omitted, but
7864 this is not recommended, because you may then forget it when it is needed. When
7865 white space terminates the header name, it is included in the expanded string.
7866 If the message does not contain the given header, the expansion item is
7867 replaced by an empty string. (See the \def\ condition in section ~~SECTexpcond
7868 for a means of testing for the existence of a header.)
7870 If there is more than one header with the same name, they are all concatenated
7871 to form the substitution string, up to a maximum length of 64K. A newline
7872 character is inserted between each line.
7873 For the \header\ expansion, for those headers that contain lists of addresses,
7874 a comma is also inserted at the junctions between lines. This does not happen
7875 for the \rheader\ expansion.
7879 .item "@$@{hmac@{<<hashname>>@}@{<<secret>>@}@{<<string>>@}@}"
7880 .index expansion||hmac hashing
7881 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
7882 shared secret and some text into a message authentication code, as specified in
7884 This differs from \"@$@{md5:secret@_text...@}"\ or
7885 \"@$@{sha1:secret@_text...@}"\ in that the hmac step adds a signature to the
7886 cryptographic hash, allowing for authentication that is not possible with MD5
7888 The hash name must expand to either \"md5"\ or \"sha1"\ at present. For
7891 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
7893 For the hostname \*mail.example.com*\ and time 2002-10-17 11:30:59, this
7896 dd97e3ba5d1a61b5006108f8c8252953
7898 As an example of how this might be used, you might put in the main part of
7899 an Exim configuration:
7901 SPAMSCAN_SECRET=cohgheeLei2thahw
7903 In a router or a transport you could then have:
7906 X-Spam-Scanned: ${primary_hostname} ${message_id} \
7907 ${hmac{md5}{SPAMSCAN_SECRET}\
7908 {${primary_hostname},${message_id},$h_message-id:}}
7910 Then given a message, you can check where it was scanned by looking at the
7911 ::X-Spam-Scanned:: header line. If you know the secret, you can check that this
7912 header line is authentic by recomputing the authentication code from the host
7913 name, message ID and the ::Message-id:: header line. This can be done using
7914 Exim's \-be-\ option, or by other means, for example by using the
7915 \*hmac@_md5@_hex()*\ function in Perl.
7919 .item "@${if <<condition>> @{<<string1>>@}@{<<string2>>@}@}"
7920 .index expansion||conditional
7921 If <<condition>> is true, <<string1>> is expanded and replaces the whole item;
7922 otherwise <<string2>> is used. For example,
7924 ${if eq {$local_part}{postmaster} {yes}{no} }
7926 The second string need not be present; if it is not and the condition is not
7927 true, the item is replaced with nothing. Alternatively, the word `fail' may be
7928 present instead of the second string (without any curly brackets). In this
7929 case, the expansion is forced to fail if the condition is not true. The
7930 available conditions are described in section ~~SECTexpcond below.
7933 .item "@$@{length@{<<string1>>@}@{<<string2>>@}@}"
7934 .index expansion||string truncation
7935 The \length\ item is used to extract the initial portion of a string. Both
7936 strings are expanded, and the first one must yield a number, <<n>>, say. If you
7937 are using a fixed value for the number, that is, if <<string1>> does not change
7938 when expanded, you can use the simpler operator notation that avoids some of
7941 @$@{length@_<<n>>:<<string>>@}
7943 The result of this item is either the first <<n>> characters or the whole
7944 of <<string2>>, whichever is the shorter. Do not confuse \length\ with
7945 \strlen\, which gives the length of a string.
7948 .item "@${lookup@{<<key>>@} <<search type>> @{<<file>>@} @{<<string1>>@} @{<<string2>>@}@}"
7949 .item "@${lookup <<search type>> @{<<query>>@} @{<<string1>>@} @{<<string2>>@}@}"
7950 .index expansion||lookup in
7952 .index lookup||in expanded string
7953 These items specify data lookups in files and databases, as discussed in
7954 chapter ~~CHAPfdlookup. The first form is used for single-key lookups, and the
7955 second is used for query-style lookups. The <<key>>, <<file>>, and <<query>>
7956 strings are expanded before use.
7958 If there is any white space in a lookup item which is part of a filter command,
7959 a retry or rewrite rule, a routing rule for the \%manualroute%\ router, or any
7960 other place where white space is significant, the lookup item must be enclosed
7961 in double quotes. The use of data lookups in users' filter files may be locked
7962 out by the system administrator.
7965 If the lookup succeeds, <<string1>> is expanded and replaces the entire item.
7966 During its expansion, the variable \$value$\ contains the data returned by the
7967 lookup. Afterwards it reverts to the value it had previously (at the outer
7968 level it is empty). If the lookup fails, <<string2>> is expanded and replaces
7969 the entire item. If @{<<string2>>@} is omitted, the replacement is null on
7970 failure. Alternatively, <<string2>> can itself be a nested lookup, thus
7971 providing a mechanism for looking up a default value when the original lookup
7974 If a nested lookup is used as part of <<string1>>, \$value$\ contains the data
7975 for the outer lookup while the parameters of the second lookup are expanded,
7976 and also while <<string2>> of the second lookup is expanded, should the second
7979 Instead of @{<<string2>>@} the word `fail' can appear, and in this case, if the
7980 lookup fails, the entire expansion is forced to fail. If both @{<<string1>>@}
7981 and @{<<string2>>@} are omitted, the result is the looked up value in the case
7982 of a successful lookup, and nothing in the case of failure.
7984 For single-key lookups, the string `partial' is permitted to precede the
7985 search type in order to do partial matching, and $*$ or $*$@@ may follow a
7986 search type to request default lookups if the key does not match (see sections
7987 ~~SECTdefaultvaluelookups and ~~SECTpartiallookup for details).
7989 .index numerical variables (\$1$\, \$2$\, etc)||in lookup expansion
7990 If a partial search is used, the variables \$1$\ and \$2$\ contain the wild
7991 and non-wild parts of the key during the expansion of the replacement text.
7992 They return to their previous values at the end of the lookup item.
7994 This example looks up the postmaster alias in the conventional alias file:
7996 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
7998 This example uses NIS+ to look up the full name of the user corresponding to
7999 the local part of an address, forcing the expansion to fail if it is not found:
8001 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8006 .item "@$@{nhash@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8007 .index expansion||numeric hash
8008 .index hash function||numeric
8009 The three strings are expanded; the first two must yield numbers. Call them
8010 <<n>> and <<m>>. If you are using fixed values for these numbers, that is, if
8011 <<string1>> and <<string2>> do not change when they are expanded, you can use
8012 the simpler operator notation that avoids some of the braces:
8014 @$@{nhash@_<<n>>@_<<m>>:<<string>>@}
8016 The second number is optional (in both notations). If there is only one number,
8017 the result is a number in the range 0--<<n>>-1. Otherwise, the string is
8018 processed by a div/mod hash function that returns two numbers, separated by a
8019 slash, in the ranges 0 to <<n>>-1 and 0 to <<m>>-1, respectively. For example,
8021 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8023 returns the string `6/33'.
8027 .item "@$@{perl@{<<subroutine>>@}@{<<arg>>@}@{<<arg>>@}...@}"
8028 .index Perl||use in expanded string
8029 .index expansion||calling Perl from
8030 This item is available only if Exim has been built to include an embedded Perl
8031 interpreter. The subroutine name and the arguments are first separately
8032 expanded, and then the Perl subroutine is called with those arguments. No
8033 additional arguments need be given; the maximum number permitted, including the
8034 name of the subroutine, is nine.
8036 The return value of the subroutine is inserted into the expanded string, unless
8037 the return value is \undef\. In that case, the expansion fails in the same way
8038 as an explicit `fail' on a lookup item.
8039 The return value is a scalar. Whatever you return is evaluated in a scalar
8040 context. For example, if you return the name of a Perl vector, the
8041 return value is the size of the vector, not its contents.
8043 If the subroutine exits by calling Perl's \die\ function, the expansion fails
8044 with the error message that was passed to \die\. More details of the embedded
8045 Perl facility are given in chapter ~~CHAPperl.
8047 The \%redirect%\ router has an option called \forbid@_filter@_perl\ which locks
8048 out the use of this expansion item in filter files.
8051 .item "@$@{readfile@{<<file name>>@}@{<<eol string>>@}@}"
8052 .index expansion||inserting an entire file
8053 .index file||inserting into expansion
8054 The file name and end-of-line string are first expanded separately. The file is
8055 then read, and its contents replace the entire item. All newline characters in
8056 the file are replaced by the end-of-line string if it is present. Otherwise,
8057 newlines are left in the string.
8058 String expansion is not applied to the contents of the file. If you want this,
8059 you must wrap the item in an \expand\ operator. If the file cannot be read, the
8060 string expansion fails.
8062 The \%redirect%\ router has an option called \forbid@_filter@_readfile\ which
8063 locks out the use of this expansion item in filter files.
8067 .item "@$@{readsocket@{<<name>>@}@{<<request>>@}@{<<timeout>>@}@{<<eol string>>@}@{<<fail string>>@}@}"
8068 .index expansion||inserting from a socket
8069 .index socket, use of in expansion
8070 This item inserts data that is read from a Unix domain socket into the expanded
8071 string. The minimal way of using it uses just two arguments:
8073 ${readsocket{/socket/name}{request string}}
8075 Exim connects to the socket, writes the request string (unless it is an
8076 empty string) and reads from the socket until an end-of-file is read. A timeout
8077 of 5 seconds is applied. Additional, optional arguments extend what can be
8078 done. Firstly, you can vary the timeout. For example:
8080 ${readsocket{/socket/name}{request-string}{3s}}
8082 A fourth argument allows you to change any newlines that are in the data
8083 that is read, in the same way as for \readfile\ (see above). This example turns
8086 ${readsocket{/socket/name}{request-string}{3s}{ }}
8088 As with all expansions, the substrings are expanded before the processing
8089 happens. Errors in these sub-expansions cause the expansion to fail. In
8090 addition, the following errors can occur:
8092 Failure to create a socket file descriptor;
8094 Failure to connect the socket;
8096 Failure to write the request-string;
8098 Timeout on reading from the socket.
8100 By default, any of these errors causes the expansion to fail. However, if
8101 you supply a fifth substring, it is expanded and used when any of the above
8102 errors occurs. For example:
8104 ${readsocket{/socket/name}{request-string}{3s}{\n}\
8107 You can test for the existence of the socket by wrapping this expansion in
8108 \"@$@{if exists"\, but there is a race condition between that test and the
8109 actual opening of the socket, so it is safer to use the fifth argument if you
8110 want to be absolutely sure of avoiding an expansion error for a non-existent
8113 The \%redirect%\ router has an option called \forbid@_filter@_readsocket\ which
8114 locks out the use of this expansion item in filter files.
8116 .item "@$rheader@_<<header name>>:#$rm{or}#@$rh@_<<header name>>:"
8117 This item inserts `raw' header lines. It is described with the \header\
8118 expansion item above.
8122 .item "@$@{run@{<<command>> <<args>>@}@{<<string1>>@}@{<<string2>>@}@}"
8123 .index expansion||running a command
8124 The command and its arguments are first expanded separately, and then the
8125 command is run in a separate process, but under the same uid and gid. As in
8126 other command executions from Exim, a shell is not used by default. If you want
8127 a shell, you must explicitly code it.
8128 .index return code||from \run\ expansion
8129 If the command succeeds (gives a zero return code) <<string1>> is expanded and
8130 replaces the entire item; during this expansion, the standard output from the
8131 command is in the variable \$value$\. If the command fails, <<string2>>, if
8132 present, is expanded. If it is absent, the result is empty. Alternatively,
8133 <<string2>> can be the word `fail' (not in braces) to force expansion failure
8134 if the command does not succeed. If both strings are omitted, the result is the
8135 standard output on success, and nothing on failure.
8137 The return code from the command is put in the variable \$runrc$\, and this
8138 remains set afterwards, so in a filter file you can do things like this:
8140 if "${run{x y z}{}}$runrc" is 1 then ...
8141 elif $runrc is 2 then ...
8145 If execution of the command fails (for example, the command does not exist),
8146 the return code is 127 -- the same code that shells use for non-existent
8149 \**Warning**\: In a router or transport, you cannot assume the order in which
8150 option values are expanded, except for those pre-conditions whose order of
8151 testing is documented. Therefore, you cannot reliably expect to set \$runrc$\
8152 by the expansion of one option, and use it in another.
8154 The \%redirect%\ router has an option called \forbid@_filter@_run\ which locks
8155 out the use of this expansion item in filter files.
8158 .item "@$@{sg@{<<subject>>@}@{<<regex>>@}@{<<replacement>>@}@}"
8159 .index expansion||string substitution
8160 This item works like Perl's substitution operator (s) with the global (/g)
8161 option; hence its name. However, unlike the Perl equivalent, Exim does not
8162 modify the subject string; instead it returns the modified string for insertion
8163 into the overall expansion. The item takes three arguments: the subject string,
8164 a regular expression, and a substitution string. For example
8166 ${sg{abcdefabcdef}{abc}{xyz}}
8168 yields `xyzdefxyzdef'. Because all three arguments are expanded before use, if
8169 any @$ or @\ characters are required in the regular expression or in the
8170 substitution string, they have to be escaped. For example
8172 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
8174 yields `defabc', and
8176 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
8178 yields `K1=A K4=D K3=C'.
8179 Note the use of \"@\N"\ to protect the contents of the regular expression from
8184 .item "@$@{substr@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8186 .index substring extraction
8187 .index expansion||substring extraction
8188 The three strings are expanded; the first two must yield numbers. Call them
8189 <<n>> and <<m>>. If you are using fixed values for these numbers, that is, if
8190 <<string1>> and <<string2>> do not change when they are expanded, you can use
8191 the simpler operator notation that avoids some of the braces:
8193 @$@{substr@_<<n>>@_<<m>>:<<string>>@}
8195 The second number is optional (in both notations).
8197 The \substr\ item can be used to extract more general substrings than \length\.
8198 The first number, <<n>>, is a starting offset, and <<m>> is the length
8199 required. For example
8201 ${substr{3}{2}{$local_part}}
8203 If the starting offset is greater than the string length the result is the null
8204 string; if the length plus starting offset is greater than the string length,
8205 the result is the right-hand part of the string, starting from the given
8206 offset. The first character in the string has offset zero.
8208 The \substr\ expansion item can take negative offset values to count
8209 from the right-hand end of its operand. The last character is offset -1, the
8210 second-last is offset -2, and so on. Thus, for example,
8212 ${substr{-5}{2}{1234567}}
8214 yields `34'. If the absolute value of a negative offset is greater than the
8215 length of the string, the substring starts at the beginning of the string, and
8216 the length is reduced by the amount of overshoot. Thus, for example,
8218 ${substr{-5}{2}{12}}
8220 yields an empty string, but
8222 ${substr{-3}{2}{12}}
8226 If the second number is omitted from \substr\, the remainder of the string is
8227 taken if the offset was positive. If it was negative, all characters in the
8228 string preceding the offset point are taken. For example, an offset of -1 and
8229 no length yields all but the last character of the string.
8233 .item "@$@{tr@{<<subject>>@}@{<<characters>>@}@{<<replacements>>@}@}"
8234 .index expansion||character translation
8235 This item does single-character translation on its subject string. The second
8236 argument is a list of characters to be translated in the subject string. Each
8237 matching character is replaced by the corresponding character from the
8238 replacement list. For example
8240 ${tr{abcdea}{ac}{13}}
8242 yields `1b3de1'. If there are duplicates in the second character string, the
8243 last occurrence is used. If the third string is shorter than the second, its
8244 last character is replicated. However, if it is empty, no translation takes
8250 .section Expansion operators
8251 .rset SECTexpop "~~chapter.~~section"
8252 .index expansion||operators
8253 For expansion items that perform transformations on a single argument string,
8254 the `operator' notation is used because it is simpler and uses fewer braces.
8255 The substring is first expanded before the operation is applied to it. The
8256 following operations can be performed:
8260 .item "@$@{address:<<string>>@}"
8261 .index expansion||RFC 2822 address handling
8262 The string is interpreted as an RFC 2822 address, as it might appear in a
8263 header line, and the effective address is extracted from it. If the string does
8264 not parse successfully, the result is empty.
8267 .item "@$@{base62:<<digits>>@}"
8269 .index expansion||conversion to base 62
8270 The string must consist entirely of decimal digits. The number is converted to
8271 base 62 (sic) and output as a string of six characters, including leading
8272 zeros. \**Note**\: Just to be absolutely clear: this is \*not*\ base64
8275 .item "@$@{base62d:<<base-62 digits>>@}"
8277 .index expansion||conversion to base 62
8278 The string must consist entirely of base-62 digits. The number is converted to
8279 decimal and output as a string.
8282 .item "@$@{domain:<<string>>@}"
8283 .index domain||extraction
8284 .index expansion||domain extraction
8285 The string is interpreted as an RFC 2822 address and the domain is extracted
8286 from it. If the string does not parse successfully, the result is empty.
8289 .item "@$@{escape:<<string>>@}"
8290 .index expansion||escaping non-printing characters
8291 If the string contains any non-printing characters, they are converted to
8292 escape sequences starting with a backslash. Whether characters with the most
8293 significant bit set (so-called `8-bit characters') count as printing or not is
8294 controlled by the \print@_topbitchars\ option.
8297 .item "@$@{eval:<<string>>@}"
8298 .item "@$@{eval10:<<string>>@}"
8299 .index expansion||expression evaluation
8300 .index expansion||arithmetic expression
8301 These items supports simple arithmetic in expansion strings. The string (after
8302 expansion) must be a conventional arithmetic expression, but it is limited to
8303 the four basic operators (plus, minus, times, divide) and parentheses. All
8304 operations are carried out using integer arithmetic. Plus and minus have a
8305 lower priority than times and divide; operators with the same priority are
8306 evaluated from left to right.
8308 For \eval\, numbers may be decimal, octal (starting with `0') or hexadecimal
8309 (starting with `0x'). For \eval10\, all numbers are taken as decimal, even if
8310 they start with a leading zero. This can be useful when processing numbers
8311 extracted from dates or times, which often do have leading zeros.
8313 A number may be followed by `K' or `M' to multiply it by 1024 or 1024$*$1024,
8314 respectively. Negative numbers are supported. The result of the computation is
8315 a decimal representation of the answer (without `K' or `M'). For example:
8317 @$@{eval:1+1@} $rm{yields} 2
8318 @$@{eval:1+2*3@} $rm{yields} 7
8319 @$@{eval:(1+2)*3@} $rm{yields} 9
8321 As a more realistic example, in an ACL you might have
8323 deny message = Too many bad recipients
8326 {>{$rcpt_count}{10}} \
8329 {$recipients_count} \
8330 {${eval:$rcpt_count/2}} \
8334 The condition is true if there have been more than 10 \\RCPT\\ commands and
8335 fewer than half of them have resulted in a valid recipient.
8338 .item "@$@{expand:<<string>>@}"
8339 .index expansion||re-expansion of substring
8340 The \expand\ operator causes a string to be expanded for a second time. For
8343 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
8345 first looks up a string in a file while expanding the operand for \expand\, and
8346 then re-expands what it has found.
8349 .item "@$@{from@_utf8:<<string>>@}"
8351 .index UTF-8||conversion from
8352 .index expansion||UTF-8 conversion
8353 The world is slowly moving towards Unicode, although there are no standards for
8354 email yet. However, other applications (including some databases) are starting
8355 to store data in Unicode, using UTF-8 encoding. This operator converts from a
8356 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
8357 converted to underscores. The input must be a valid UTF-8 string. If it is not,
8358 the result is an undefined sequence of bytes.
8360 Unicode code points with values less than 256 are compatible with ASCII and
8361 ISO-8859-1 (also known as Latin-1).
8362 For example, character 169 is the copyright symbol in both cases, though the
8363 way it is encoded is different. In UTF-8, more than one byte is needed for
8364 characters with code values greater than 127, whereas ISO-8859-1 is a
8365 single-byte encoding (but thereby limited to 256 characters). This makes
8366 translation from UTF-8 to ISO-8859-1 straightforward.
8369 .item "@$@{hash@_<<n>>@_<<m>>:<<string>>@}"
8370 .index hash function||textual
8371 .index expansion||textual hash
8372 The \hash\ operator is a simpler interface to the hashing function that can be
8373 used when the two parameters are fixed numbers (as opposed to strings that
8374 change when expanded). The effect is the same as
8376 @$@{hash@{<<n>>@}@{<<m>>@}@{<<string>>@}@}
8378 See the description of the general \hash\ item above for details. The
8379 abbreviation \h\ can be used when \hash\ is used as an operator.
8383 .item "@$@{hex2b64:<<hexstring>>@}"
8384 .index base64 encoding||conversion from hex
8385 .index expansion||hex to base64
8386 This operator converts a hex string into one that is base64 encoded. This can
8387 be useful for processing the output of the MD5 and SHA-1 hashing functions.
8390 .item "@$@{lc:<<string>>@}"
8391 .index case forcing in strings
8392 .index string||case forcing
8394 .index expansion||case forcing
8395 This forces the letters in the string into lower-case, for example:
8401 .item "@$@{length@_<<number>>:<<string>>@}"
8402 .index expansion||string truncation
8403 The \length\ operator is a simpler interface to the \length\ function that can
8404 be used when the parameter is a fixed number (as opposed to a string that
8405 changes when expanded). The effect is the same as
8407 @$@{length@{<<number>>@}@{<<string>>@}@}
8409 See the description of the general \length\ item above for details. Note that
8410 \length\ is not the same as \strlen\. The abbreviation \l\ can be used when
8411 \length\ is used as an operator.
8414 .item "@$@{local@_part:<<string>>@}"
8415 .index expansion||local part extraction
8416 The string is interpreted as an RFC 2822 address and the local part is
8417 extracted from it. If the string does not parse successfully, the result is
8421 .item "@$@{mask:<<IP address>>/<<bit count>>@}"
8422 .index masked IP address
8423 .index IP address||masking
8424 .index CIDR notation
8425 .index expansion||IP address masking
8426 If the form of the string to be operated on is not an IP address followed by a
8427 slash and an integer (that is, a network address in CIDR notation), the
8428 expansion fails. Otherwise, this operator converts the IP address to binary,
8429 masks off the least significant bits according to the bit count, and converts
8430 the result back to text, with mask appended. For example,
8432 ${mask:10.111.131.206/28}
8434 returns the string `10.111.131.192/28'. Since this operation is expected to be
8435 mostly used for looking up masked addresses in files, the result for an IPv6
8436 address uses dots to separate components instead of colons, because colon
8437 terminates a key string in lsearch files. So, for example,
8439 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
8443 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
8445 Letters in IPv6 addresses are always output in lower case.
8448 .item "@$@{md5:<<string>>@}"
8450 .index expansion||MD5 hash
8451 The \md5\ operator computes the MD5 hash value of the string, and returns it as
8452 a 32-digit hexadecimal number,
8453 in which any letters are in lower case.
8456 .item "@$@{nhash@_<<n>>@_<<m>>:<<string>>@}"
8457 .index expansion||numeric hash
8458 .index hash function||numeric
8459 The \nhash\ operator is a simpler interface to the numeric hashing function
8460 that can be used when the two parameters are fixed numbers (as opposed to
8461 strings that change when expanded). The effect is the same as
8463 @$@{nhash@{<<n>>@}@{<<m>>@}@{<<string>>@}@}
8465 See the description of the general \nhash\ item above for details.
8468 .item "@$@{quote:<<string>>@}"
8469 .index quoting||in string expansions
8470 .index expansion||quoting
8471 The \quote\ operator puts its argument into double quotes if it
8472 is an empty string or
8473 contains anything other than letters, digits, underscores, dots, and hyphens.
8474 Any occurrences of double quotes and backslashes are escaped with a backslash.
8475 Newlines and carriage returns are converted to \"@\n"\ and \"@\r"\,
8476 respectively For example,
8484 The place where this is useful is when the argument is a substitution from a
8485 variable or a message header.
8487 .item "@$@{quote@_local@_part:<<string>>@}"
8488 This operator is like \quote\, except that it quotes the string only if
8489 required to do so by the rules of RFC 2822 for quoting local parts. For
8490 example, a plus sign would not cause quoting (but it would for \quote\).
8491 If you are creating a new email address from the contents of \$local@_part$\
8492 (or any other unknown data), you should always use this operator.
8495 .item "@$@{quote@_<<lookup-type>>:<<string>>@}"
8496 .index quoting||lookup-specific
8497 This operator applies lookup-specific quoting rules to the string. Each
8498 query-style lookup type has its own quoting rules which are described with
8499 the lookups in chapter ~~CHAPfdlookup. For example,
8501 ${quote_ldap:two * two}
8507 For single-key lookup types, no quoting is ever necessary and this operator
8508 yields an unchanged string.
8511 .item "@$@{rxquote:<<string>>@}"
8512 .index quoting||in regular expressions
8513 .index regular expressions||quoting
8514 The \rxquote\ operator inserts a backslash before any non-alphanumeric
8515 characters in its argument. This is useful when substituting the values of
8516 variables or headers inside regular expressions.
8519 .item "@$@{rfc2047:<<string>>@}"
8520 .index expansion||RFC 2047
8521 This operator encodes text according to the rules of RFC 2047. This is an
8522 encoding that is used in header lines to encode non-ASCII characters. It is
8523 assumed that the input string is in the encoding specified by the
8524 \headers@_charset\ option, which defaults to ISO-8859-1.
8525 If the string contains only characters in the range 33--126, and no instances
8528 ? = ( ) < > @ , ; : \ " . [ ] _
8530 it is not modified. Otherwise, the result is the RFC 2047 encoding, as a single
8534 .item "@$@{sha1:<<string>>@}"
8536 .index expansion||SHA-1 hashing
8537 The \sha1\ operator computes the SHA-1 hash value of the string, and returns it
8538 as a 40-digit hexadecimal number, in which any letters are in upper case.
8541 .item "@$@{stat:<<string>>@}"
8542 .index expansion||statting a file
8543 .index file||extracting characteristics
8544 The string, after expansion, must be a file path. A call to the \*stat()*\
8545 function is made for this path. If \*stat()*\ fails, an error occurs and the
8546 expansion fails. If it succeeds, the data from the stat replaces the item, as a
8547 series of <<name>>=<<value>> pairs, where the values are all numerical,
8548 except for the value of `smode'. The names are: `mode' (giving the mode as a
8549 4-digit octal number), `smode' (giving the mode in symbolic format as a
8550 10-character string, as for the \*ls*\ command), `inode', `device', `links',
8551 `uid', `gid', `size', `atime', `mtime', and `ctime'. You can extract individual
8552 fields using the \extract\ expansion item. \**Warning**\: The file size may be
8553 incorrect on 32-bit systems for files larger than 2GB.
8556 .item "@$@{strlen:<<string>>@}"
8557 .index expansion||string length
8558 .index string||length in expansion
8559 The item is replace by the length of the expanded string, expressed as a
8560 decimal number. \**Note**\: Do not confuse \strlen\ with \length\.
8563 .item "@$@{substr@_<<start>>@_<<length>>:<<string>>@}"
8565 .index substring extraction
8566 .index expansion||substring expansion
8567 The \substr\ operator is a simpler interface to the \substr\ function that can
8568 be used when the two parameters are fixed numbers (as opposed to strings that
8569 change when expanded). The effect is the same as
8571 @$@{substr@{<<start>>@}@{<<length>>@}@{<<string>>@}@}
8573 See the description of the general \substr\ item above for details. The
8574 abbreviation \s\ can be used when \substr\ is used as an operator.
8576 .item "@$@{time@_interval:<<string>>@}"
8577 .index \time@_interval\
8578 .index time interval||formatting
8579 The argument (after sub-expansion) must be a sequence of decimal digits that
8580 represents an interval of time as a number of seconds. It is converted into a
8581 number of larger units and output in Exim's normal time format, for example,
8584 .item "@$@{uc:<<string>>@}"
8585 .index case forcing in strings
8586 .index string||case forcing
8588 .index expansion||case forcing
8589 This forces the letters in the string into upper-case.
8595 .section Expansion conditions
8596 .rset SECTexpcond "~~chapter.~~section"
8597 .index expansion||conditions
8598 The following conditions are available for testing by the \@$@{if\ construct
8599 while expanding strings:
8603 .item "!<<condition>>"
8604 .index expansion||negating a condition
8605 Preceding any condition with an exclamation mark negates the result of the
8608 .item "<<symbolic operator>> @{<<string1>>@}@{<<string2>>@}"
8609 .index numeric comparison
8610 .index expansion||numeric comparison
8611 There are a number of symbolic operators for doing numeric comparisons. They
8618 >= $t $rm{greater or equal}
8620 <= $t $rm{less or equal}
8624 ${if >{$message_size}{10M} ...
8626 Note that the general negation operator provides for inequality testing. The
8627 two strings must take the form of optionally signed decimal integers,
8628 optionally followed by one of the letters `K' or `M' (in either upper or lower
8629 case), signifying multiplication by 1024 or 1024$*$1024, respectively.
8631 .item "crypteq @{<<string1>>@}@{<<string2>>@}"
8632 .index expansion||encrypted comparison
8633 .index encrypted strings, comparing
8634 This condition is included in the Exim binary if it is built to support any
8635 authentication mechanisms (see chapter ~~CHAPSMTPAUTH). Otherwise, it is
8636 necessary to define \\SUPPORT@_CRYPTEQ\\ in \(Local/Makefile)\ to get \crypteq\
8637 included in the binary.
8639 The \crypteq\ condition has two arguments. The first is encrypted and compared
8640 against the second, which is already encrypted. The second string may be in the
8641 LDAP form for storing encrypted strings, which starts with the encryption type
8642 in curly brackets, followed by the data. If the second string does not begin
8643 with `{' it is assumed to be encrypted with \*crypt()*\
8644 or \*crypt16()*\ (see below),
8645 since such strings cannot begin with `{'. Typically this will be a field from a
8648 An example of an encrypted string in LDAP form is:
8650 {md5}CY9rzUYh03PK3k6DJie09g==
8652 If such a string appears directly in an expansion, the curly brackets have to
8653 be quoted, because they are part of the expansion syntax. For example:
8655 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
8657 The following encryption types
8658 (whose names are matched case-independently)
8662 .index base64 encoding||in encrypted password
8663 \@{md5@}\ computes the MD5 digest of the first string, and expresses this as
8664 printable characters to compare with the remainder of the second string. If the
8665 length of the comparison string is 24, Exim assumes that it is base64 encoded
8666 (as in the above example). If the length is 32, Exim assumes that it is a
8667 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
8671 \@{sha1@}\ computes the SHA-1 digest of the first string, and expresses this as
8672 printable characters to compare with the remainder of the second string. If the
8673 length of the comparison string is 28, Exim assumes that it is base64 encoded.
8674 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
8675 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
8678 \@{crypt@}\ calls the \*crypt()*\ function, which uses only the first eight
8679 characters of the password.
8681 .index \*crypt16()*\
8682 \@{crypt16@}\ calls the \*crypt16()*\ function (also known as \*bigcrypt()*\),
8683 which uses up to 16 characters of the password.
8685 Exim has its own version of \*crypt16()*\ (which is just a double call to
8686 \*crypt()*\). For operating systems that have their own version, setting
8687 \\HAVE@_CRYPT16\\ in \(Local/Makefile)\ when building Exim causes it to use the
8688 operating system version instead of its own. This option is set by default in
8689 the OS-dependent \(Makefile)\ for those operating systems that are known to
8690 support \*crypt16()*\.
8692 If you do not put any curly bracket encryption type in a \crypteq\ comparison,
8693 the default is either \"@{crypt@}"\ or \"@{crypt16@}"\, as determined by the
8694 setting of \\DEFAULT@_CRYPT\\ in \(Local/Makefile)\. The default default is
8695 \"@{crypt@}"\. Whatever the default, you can always use either function by
8696 specifying it explicitly in curly brackets.
8698 Note that if a password is no longer than 8 characters, the results of
8699 encrypting it with \*crypt()*\ and \*crypt16()*\ are identical. That means that
8700 \*crypt16()*\ is backwards compatible, as long as nobody feeds it a password
8701 longer than 8 characters.
8704 .item "def:<<variable name>>"
8705 .index expansion||checking for empty variable
8706 The \def\ condition must be followed by the name of one of the expansion
8707 variables defined in section ~~SECTexpvar. The condition is true if the named
8708 expansion variable does not contain the empty string, for example
8710 ${if def:sender_ident {from $sender_ident}}
8712 Note that the variable name is given without a leading \@$\ character. If the
8713 variable does not exist, the expansion fails.
8715 .item "def:header@_<<header name>>:##or##def:h@_<<header name>>:"
8716 .index expansion||checking header line existence
8717 This condition is true if a message is being processed and the named header
8718 exists in the message. For example,
8720 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
8722 Note that no \@$\ appears before \header@_\ or \h@_\ in the condition,
8723 and that header names must be terminated by colons if white space does not
8726 .item "eq @{<<string1>>@}@{<<string2>>@}"
8727 .item "eqi @{<<string1>>@}@{<<string2>>@}"
8728 .index string||comparison
8729 .index expansion||string comparison
8730 The two substrings are first expanded. The condition is true if the two
8731 resulting strings are identical: for \eq\ the comparison includes the case of
8732 letters, whereas for \eqi\ the comparison is case-independent.
8734 .item "exists @{<<file name>>@}"
8735 .index expansion||file existence test
8736 .index file||existence test
8737 The substring is first expanded and then interpreted as an absolute path. The
8738 condition is true if the named file (or directory) exists. The existence test
8739 is done by calling the \*stat()*\ function. The use of the \exists\ test in
8740 users' filter files may be locked out by the system administrator.
8742 .item "first@_delivery"
8743 .index delivery||first
8744 .index first delivery
8745 .index expansion||first delivery test
8746 This condition, which has no data, is true during a message's first delivery
8747 attempt. It is false during any subsequent delivery attempts.
8749 .item "ge @{<<string1>>@}@{<<string2>>@}"
8750 .item "gei @{<<string1>>@}@{<<string2>>@}"
8751 .index string||comparison
8752 .index expansion||string comparison
8753 The two substrings are first expanded. The condition is true if the first
8754 string is lexically greater than or equal to the second string: for \ge\ the
8755 comparison includes the case of letters, whereas for \gei\ the comparison is
8758 .item "gt @{<<string1>>@}@{<<string2>>@}"
8759 .item "gti @{<<string1>>@}@{<<string2>>@}"
8760 .index string||comparison
8761 .index expansion||string comparison
8762 The two substrings are first expanded. The condition is true if the first
8763 string is lexically greater than the second string: for \gt\ the comparison
8764 includes the case of letters, whereas for \gti\ the comparison is
8767 .item "isip @{<<string>>@}" 8
8768 .item "isip4 @{<<string>>@}"
8769 .item "isip6 @{<<string>>@}"
8770 .index IP address||testing string format
8771 .index string||testing for IP address
8772 The substring is first expanded, and then tested to see if it has the form of
8773 an IP address. Both IPv4 and IPv6 addresses are valid for \isip\, whereas
8774 \isip4\ and \isip6\ test just for IPv4 or IPv6 addresses, respectively. For
8775 example, you could use
8777 ${if isip4{$sender_host_address}...
8779 to test which version of IP an incoming SMTP connection is using.
8782 .item "ldapauth @{<<ldap query>>@}"
8783 .index LDAP||use for authentication
8784 .index expansion||LDAP authentication test
8785 This condition supports user authentication using LDAP. See section ~~SECTldap
8786 for details of how to use LDAP in lookups and the syntax of queries. For this
8787 use, the query must contain a user name and password. The query itself is not
8788 used, and can be empty. The condition is true if
8789 the password is not empty, and the user name and password are accepted by the
8790 LDAP server. An empty password is rejected without calling LDAP because LDAP
8791 binds with an empty password are considered anonymous regardless of
8792 the username, and will succeed in most configurations.
8793 See chapter ~~CHAPSMTPAUTH for details of SMTP authentication, and chapter
8794 ~~CHAPplaintext for an example of how this can be used.
8797 .item "le @{<<string1>>@}@{<<string2>>@}"
8798 .item "lei @{<<string1>>@}@{<<string2>>@}"
8799 .index string||comparison
8800 .index expansion||string comparison
8801 The two substrings are first expanded. The condition is true if the first
8802 string is lexically less than or equal to the second string: for \le\ the
8803 comparison includes the case of letters, whereas for \lei\ the comparison is
8806 .item "lt @{<<string1>>@}@{<<string2>>@}"
8807 .item "lti @{<<string1>>@}@{<<string2>>@}"
8808 .index string||comparison
8809 .index expansion||string comparison
8810 The two substrings are first expanded. The condition is true if the first
8811 string is lexically less than the second string: for \lt\ the comparison
8812 includes the case of letters, whereas for \lti\ the comparison is
8816 .item "match @{<<string1>>@}@{<<string2>>@}"
8817 .index expansion||regular expression comparison
8818 .index regular expressions||match in expanded string
8819 The two substrings are first expanded. The second is then treated as a regular
8820 expression and applied to the first. Because of the pre-expansion, if the
8821 regular expression contains dollar, or backslash characters, they must be
8822 escaped. Care must also be taken if the regular expression contains braces
8823 (curly brackets). A closing brace must be escaped so that it is not taken as a
8824 premature termination of <<string2>>. The easiest approach is to use the
8825 \"@\N"\ feature to disable expansion of the regular expression.
8828 ${if match {$local_part}{\N^\d{3}\N} ...
8830 If the whole expansion string is in double quotes, further escaping of
8831 backslashes is also required.
8833 The condition is true if the regular expression match succeeds.
8834 The regular expression is not required to begin with a circumflex
8835 metacharacter, but if there is no circumflex, the expression is not anchored,
8836 and it may match anywhere in the subject, not just at the start. If you want
8837 the pattern to match at the end of the subject, you must include the \"@$"\
8838 metacharacter at an appropriate point.
8840 .index numerical variables (\$1$\, \$2$\, etc)||in \if\ expansion
8841 At the start of an \if\ expansion the values of the numeric variable
8842 substitutions \$1$\ etc. are remembered. Obeying a \match\ condition that
8843 succeeds causes them to be reset to the substrings of that condition and they
8844 will have these values during the expansion of the success string. At the end
8845 of the \if\ expansion, the previous values are restored. After testing a
8846 combination of conditions using \or\, the subsequent values of the numeric
8847 variables are those of the condition that succeeded.
8849 .item "match@_domain @{<<string1>>@}@{<<string2>>@}"
8850 .item "match@_address @{<<string1>>@}@{<<string2>>@}"
8851 .item "match@_local@_part @{<<string1>>@}@{<<string2>>@}"
8852 .index domain list||in expansion condition
8853 .index address list||in expansion condition
8854 .index local part list||in expansion condition
8855 These conditions make it possible to test domain, address, and local
8856 part lists within expansions. Each condition requires two arguments: an item
8857 and a list to match. A trivial example is:
8859 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
8861 In each case, the second argument may contain any of the allowable items for a
8862 list of the appropriate type. Also, because the second argument (after
8863 expansion) is a standard form of list, it is possible to refer to a named list.
8864 Thus, you can use conditions like this:
8866 ${if match_domain{$domain}{+local_domains}{...
8869 For address lists, the matching starts off caselessly, but the \"+caseful"\
8870 item can be used, as in all address lists, to cause subsequent items to
8871 have their local parts matched casefully. Domains are always matched
8874 \**Note**\: Host lists are \*not*\ supported in this way. This is because
8875 hosts have two identities: a name and an IP address, and it is not clear
8876 how to specify cleanly how such a test would work. At least, I haven't come
8877 up with anything yet.
8879 .item "pam {<<string1>>:<<string2>>:...@}"
8880 .index PAM authentication
8881 .index \\AUTH\\||with PAM
8882 .index Solaris||PAM support
8883 .index expansion||PAM authentication test
8884 \*Pluggable Authentication Modules*\
8885 (\?http://www.kernel.org/pub/linux/libs/pam/?\)
8886 are a facility which is available in the latest releases of Solaris and in some
8887 GNU/Linux distributions. The Exim support, which is intended for use in
8888 conjunction with the SMTP \\AUTH\\ command, is available only if Exim is
8893 in \(Local/Makefile)\. You probably need to add \-lpam-\ to \\EXTRALIBS\\, and
8894 in some releases of GNU/Linux \-ldl-\ is also needed.
8896 The argument string is first expanded, and the result must be a colon-separated
8898 Leading and trailing whitespace is ignored.
8899 The PAM module is initialized with the service name `exim' and the user name
8900 taken from the first item in the colon-separated data string (<<string1>>). The
8901 remaining items in the data string are passed over in response to requests from
8902 the authentication function. In the simple case there will only be one request,
8903 for a password, so the data consists of just two strings.
8905 There can be problems if any of the strings are permitted to contain colon
8906 characters. In the usual way, these have to be doubled to avoid being taken as
8907 separators. If the data is being inserted from a variable, the \sg\ expansion
8908 item can be used to double any existing colons. For example, the configuration
8909 of a LOGIN authenticator might contain this setting:
8911 server_condition = ${if pam{$1:${sg{$2}{:}{::}}}{yes}{no}}
8913 For a PLAIN authenticator you could use:
8915 server_condition = ${if pam{$2:${sg{$3}{:}{::}}}{yes}{no}}
8917 In some operating systems, PAM authentication can be done only from a process
8918 running as root. Since Exim is running as the Exim user when receiving
8919 messages, this means that PAM cannot be used directly in those systems.
8920 A patched version of the \*pam@_unix*\ module that comes with the
8921 Linux PAM package is available from \?http:@/@/www.e-admin.de/pam@_exim/?\.
8922 The patched module allows one special uid/gid combination, in addition to root,
8923 to authenticate. If you build the patched module to allow the Exim user and
8924 group, PAM can then be used from an Exim authenticator.
8927 .item "pwcheck {<<string1>>:<<string2>>@}"
8928 .index \*pwcheck*\ daemon
8930 .index expansion||\*pwcheck*\ authentication test
8931 This condition supports user authentication using the Cyrus \*pwcheck*\ daemon.
8932 This is one way of making it possible for passwords to be checked by a process
8933 that is not running as root.
8934 \**Note:**\ The use of \*pwcheck*\ is now deprecated. Its replacement is
8935 \*saslauthd*\ (see below).
8937 The pwcheck support is not included in Exim by default. You need to specify
8938 the location of the pwcheck daemon's socket in \(Local/Makefile)\ before
8939 building Exim. For example:
8941 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
8943 You do not need to install the full Cyrus software suite in order to use
8944 the pwcheck daemon. You can compile and install just the daemon alone
8945 from the Cyrus SASL library. Ensure that \*exim*\ is the only user that has
8946 access to the \(/var/pwcheck)\ directory.
8948 The \pwcheck\ condition takes one argument, which must be the user name and
8949 password, separated by a colon. For example, in a LOGIN authenticator
8950 configuration, you might have this:
8952 server_condition = ${if pwcheck{$1:$2}{1}{0}}
8955 .item "queue@_running"
8956 .index queue runner||detecting when delivering from
8957 .index expansion||queue runner test
8958 This condition, which has no data, is true during delivery attempts that are
8959 initiated by queue runner processes, and false otherwise.
8962 .item "radius {<<authentication string>>@}"
8964 .index expansion||Radius authentication
8965 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
8966 set \\RADIUS@_CONFIG@_FILE\\ in \(Local/Makefile)\ to specify the location of
8967 the Radius client configuration file in order to build Exim with Radius
8969 You may also have to supply a suitable setting in \\EXTRALIBS\\ so that the
8970 Radius library can be found when Exim is linked.
8971 The string specified by \\RADIUS@_CONFIG@_FILE\\ is expanded and passed to the
8972 Radius client library, which calls the Radius server. The condition is true if
8973 the authentication is successful. For example
8975 server@_condition = @$@{if radius@{<<arguments>>@}@{yes@}@{no@}@}
8980 .item "saslauthd @{@{<<user>>@}@{<<password>>@}@{<<service>>@}@{<<realm>>@}@}"
8981 .index \*saslauthd*\ daemon
8983 .index expansion||\*saslauthd*\ authentication test
8984 This condition supports user authentication using the Cyrus \*saslauthd*\
8985 daemon. This replaces the older \*pwcheck*\ daemon, which is now deprecated.
8986 Using this daemon is one way of making it possible for passwords to be checked
8987 by a process that is not running as root.
8989 The saslauthd support is not included in Exim by default. You need to specify
8990 the location of the saslauthd daemon's socket in \(Local/Makefile)\ before
8991 building Exim. For example:
8993 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
8995 You do not need to install the full Cyrus software suite in order to use
8996 the saslauthd daemon. You can compile and install just the daemon alone
8997 from the Cyrus SASL library.
8999 Up to four arguments can be supplied to the \saslauthd\ condition, but only two
9000 are mandatory. For example:
9002 server_condition = ${if saslauthd{{$1}{$2}}{1}{0}}
9004 The service and the realm are optional (which is why the arguments are enclosed
9005 in their own set of braces). For details of the meaning of the service and
9006 realm, and how to run the daemon, consult the Cyrus documentation.
9012 .section Combining expansion conditions
9013 .index expansion||combining conditions
9014 Several conditions can be tested at once by combining them using the \and\ and
9015 \or\ combination conditions. Note that \and\ and \or\ are complete conditions
9016 on their own, and precede their lists of sub-conditions. Each sub-condition
9017 must be enclosed in braces within the overall braces that contain the list. No
9018 repetition of \if\ is used.
9022 .item "or @{@{<<cond1>>@}@{<<cond2>>@}...@}"
9023 .index `or' expansion condition
9024 .index expansion||`or' of conditions
9025 The sub-conditions are evaluated from left to right. The condition is true if
9026 any one of the sub-conditions is true.
9029 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
9031 When a true sub-condition is found, the following ones are parsed but not
9032 evaluated. If there are several `match' sub-conditions the values of the
9033 numeric variables afterwards are taken from the first one that succeeds.
9035 .item "and @{@{<<cond1>>@}@{<<cond2>>@}...@}"
9036 .index `and' expansion condition
9037 .index expansion||`and' of conditions
9038 The sub-conditions are evaluated from left to right. The condition is true if
9039 all of the sub-conditions are true. If there are several `match'
9040 sub-conditions, the values of the numeric variables afterwards are taken from
9041 the last one. When a false sub-condition is found, the following ones are
9042 parsed but not evaluated.
9048 .section Expansion variables
9049 .rset SECTexpvar "~~chapter.~~section"
9050 .index expansion||variables, list of
9052 The variables that are available for use in expansion strings are:
9057 .index numerical variables (\$1$\, \$2$\, etc)
9058 \$0$\, \$1$\, etc: When a \match\ expansion condition succeeds, these
9059 variables contain the captured substrings identified by the regular expression
9060 during subsequent processing of the success string of the containing \if\
9061 expansion item. They may also be set externally by some other matching process
9062 which precedes the expansion of the string. For example, the commands available
9063 in Exim filter files include an \if\ command with its own regular expression
9067 \$acl@_c0$\ -- \$acl@_c9$\: Values can be placed in these variables by the
9068 \set\ modifier in an ACL. The values persist throughout the lifetime of an SMTP
9069 connection. They can be used to pass information between ACLs and different
9070 invocations of the same ACL.
9071 When a message is received, the values of these variables are saved with the
9072 message, and can be accessed by filters, routers, and transports during
9073 subsequent delivery.
9076 \$acl@_m0$\ -- \$acl@_m9$\: Values can be placed in these variables by the
9077 \set\ modifier in an ACL. They retain their values while a message is being
9078 received, but are reset afterwards. They are also reset by \\MAIL\\, \\RSET\\,
9079 \\EHLO\\, \\HELO\\, and after starting a TLS session.
9080 When a message is received, the values of these variables are saved with the
9081 message, and can be accessed by filters, routers, and transports during
9082 subsequent delivery.
9086 \$acl@_verify@_message$\: During the expansion of the \message\ and
9087 \log@_message\ modifiers in an ACL statement after an address verification has
9088 failed, this variable contains the original failure message that will be
9089 overridden by the expanded string.
9092 \$address@_data$\: This variable is set by means of the \address@_data\
9093 option in routers. The value then remains with the address while it is
9094 processed by subsequent routers and eventually a transport. If the transport is
9095 handling multiple addresses, the value from the first address is used. See
9096 chapter ~~CHAProutergeneric for more details.
9097 \**Note**\: the contents of \$address@_data$\ are visible in user filter files.
9099 If \$address@_data$\ is set when the routers are called to verify an address
9100 from an ACL, the final value remains available in subsequent conditions in the
9101 ACL statement. If routing the address caused it to be redirected to a single
9102 address, the child address is also routed as part of the verification, and in
9103 this case the final value of \$address@_data$\ is from the child's routing.
9106 \$address@_file$\: When, as a result of aliasing, forwarding, or filtering, a
9107 message is directed to a specific file, this variable holds the name of the
9108 file when the transport is running. At other times, the variable is empty. For
9109 example, using the default configuration, if user \r2d2\ has a \(.forward)\
9114 then when the \%address@_file%\ transport is running, \$address@_file$\
9115 contains `/home/r2d2/savemail'.
9116 .index Sieve filter||value of \$address@_file$\
9117 For Sieve filters, the value may be `inbox' or a relative folder name. It is
9118 then up to the transport configuration to generate an appropriate absolute path
9119 to the relevant file.
9123 \$address@_pipe$\: When, as a result of aliasing or forwarding, a message is
9124 directed to a pipe, this variable holds the pipe command when the transport is
9127 .index authentication||id
9129 \$authenticated@_id$\: When a server successfully authenticates a client it may
9130 be configured to preserve some of the authentication information in the
9131 variable \$authenticated@_id$\ (see chapter ~~CHAPSMTPAUTH). For example, a
9132 user/password authenticator configuration might preserve the user name for use
9133 in the routers. When a message is submitted locally (that is, not over a TCP
9134 connection), the value of \$authenticated@_id$\ is the login name of the
9137 .index sender||authenticated
9138 .index authentication||sender
9139 .index \\AUTH\\||on \\MAIL\\ command
9141 \$authenticated@_sender$\:
9142 When acting as a server, Exim takes note of the \\AUTH=\\ parameter on an
9143 incoming SMTP \\MAIL\\ command
9144 if it believes the sender is sufficiently trusted, as described in section
9145 ~~SECTauthparamail. Unless the data is the string `@<@>', it is set as the
9146 authenticated sender of the message, and the value is available during delivery
9147 in the \$authenticated@_sender$\ variable. If the sender is not trusted, Exim
9148 accepts the syntax of \\AUTH=\\, but ignores the data.
9150 When a message is submitted locally (that is, not over a TCP connection), the
9151 value of \$authenticated@_sender$\ is an address constructed from the login
9152 name of the calling process and \$qualify@_domain$\.
9155 .index authentication||failure
9157 \$authentication@_failed$\:
9158 This variable is set to `1' in an Exim server if a client issues an \\AUTH\\
9159 command that does not succeed. Otherwise it is set to `0'. This makes it
9160 possible to distinguish between `did not try to authenticate'
9161 (\$sender@_host@_authenticated$\ is empty and \$authentication__failed$\ is set
9162 to `0') and `tried to authenticate but failed' (\$sender@_host@_authenticated$\
9163 is empty and \$authentication@_failed$\ is set to `1'). Failure includes any
9164 negative response to an \\AUTH\\ command, including (for example) an attempt to
9165 use an undefined mechanism.
9168 .index message||body, line count
9169 .index body of message||line count
9171 \$body@_linecount$\:
9172 When a message is being received or delivered, this variable contains the
9173 number of lines in the message's body.
9175 .index message||body, binary zero count
9176 .index body of message||binary zero count
9177 .index binary zero||in message body
9179 \$body@_zerocount$\:
9180 When a message is being received or delivered, this variable contains the
9181 number of binary zero bytes in the message's body.
9184 \$bounce@_recipient$\:
9185 This is set to the recipient address of a bounce message while Exim is creating
9186 it. It is useful if a customized bounce message text file is in use (see
9187 chapter ~~CHAPemsgcust).
9190 \$bounce@_return@_size@_limit$\: This contains the value set in the
9191 \bounce@_return@_size@_limit\ option, rounded up to a multiple of 1000. It is
9192 useful when a customized error message text file is in use (see chapter
9195 .index gid (group id)||caller
9197 \$caller@_gid$\: The
9199 group id under which the process that called Exim was
9200 running. This is not the same as the group id of the originator of a message
9201 (see \$originator@_gid$\). If Exim re-execs itself, this variable in the new
9202 incarnation normally contains the Exim gid.
9204 .index uid (user id)||caller
9206 \$caller@_uid$\: The
9208 user id under which the process that called Exim was
9209 running. This is not the same as the user id of the originator of a message
9210 (see \$originator@_uid$\). If Exim re-execs itself, this variable in the new
9211 incarnation normally contains the Exim uid.
9214 \$compile@_date$\: The date on which the Exim binary was compiled.
9217 \$compile@_number$\: The building process for Exim keeps a count of the number
9218 of times it has been compiled. This serves to distinguish different
9219 compilations of the same version of the program.
9221 .index black list (DNS)
9223 \$dnslist@_domain$\: When a client host is found to be on a DNS (black) list,
9224 the list's domain name is put into this variable so that it can be included in
9225 the rejection message.
9228 \$dnslist@_text$\: When a client host is found to be on a DNS (black) list, the
9229 contents of any associated TXT record are placed in this variable.
9232 \$dnslist@_value$\: When a client host is found to be on a DNS (black) list,
9233 the IP address from the resource record is placed in this variable.
9234 If there are multiple records, all the addresses are included, comma-space
9238 \$domain$\: When an address is being routed, or delivered on its own, this
9239 variable contains the domain. Global address rewriting happens when a message
9240 is received, so the value of \$domain$\ during routing and delivery is the
9241 value after rewriting. \$domain$\ is set during user filtering, but not during
9242 system filtering, because a message may have many recipients and the system
9243 filter is called just once.
9245 When more than one address is being delivered at once (for example, several
9246 \\RCPT\\ commands in one SMTP delivery), \$domain$\ is set only if they all
9247 have the same domain. Transports can be restricted to handling only one domain
9248 at a time if the value of \$domain$\ is required at transport time -- this is
9249 the default for local transports. For further details of the environment in
9250 which local transports are run, see chapter ~~CHAPenvironment.
9252 .index \delay@_warning@_condition\
9253 At the end of a delivery, if all deferred addresses have the same domain, it is
9254 set in \$domain$\ during the expansion of \delay@_warning@_condition\.
9256 The \$domain$\ variable is also used in some other circumstances:
9258 When an ACL is running for a \\RCPT\\ command, \$domain$\ contains the domain
9259 of the recipient address.
9260 \**Note:**\ the domain of the sender address is in \$sender@_address@_domain$\
9261 at \\MAIL\\ time and at \\RCPT\\ time. \$domain$\ is not set for the \\MAIL\\
9264 When a rewrite item is being processed (see chapter ~~CHAPrewrite), \$domain$\
9265 contains the domain portion of the address that is being rewritten; it can be
9266 used in the expansion of the replacement address, for example, to rewrite
9267 domains by file lookup.
9269 With one important exception, whenever a domain list is being scanned,
9270 \$domain$\ contains the subject domain. \**Exception**\: When a domain list in
9271 a \sender@_domains\ condition in an ACL is being processed, the subject domain
9272 is in \$sender@_address@_domain$\ and not in \$domain$\. It works this way so
9273 that, in a \\RCPT\\ ACL, the sender domain list can be dependent on the
9274 recipient domain (which is what is in \$domain$\ at this time).
9276 .index \\ETRN\\||value of \$domain$\
9277 .index \smtp@_etrn@_command\
9278 When the \smtp@_etrn@_command\ option is being expanded, \$domain$\ contains
9279 the complete argument of the \\ETRN\\ command (see section ~~SECTETRN).
9283 \$domain@_data$\: When the \domains\ option on a router matches a domain by
9284 means of a lookup, the data read by the lookup is available during the running
9285 of the router as \$domain@_data$\. In addition, if the driver routes the
9286 address to a transport, the value is available in that transport. If the
9287 transport is handling multiple addresses, the value from the first address is
9290 \$domain@_data$\ is also set when the \domains\ condition in an ACL matches a
9291 domain by means of a lookup. The data read by the lookup is available during
9292 the rest of the ACL statement. In all other situations, this variable expands
9296 \$exim@_gid$\: This variable contains the numerical value of the Exim group id.
9299 \$exim@_path$\: This variable contains the path to the Exim binary.
9302 \$exim@_uid$\: This variable contains the numerical value of the Exim user id.
9305 \$header@_<<name>>$\: This is not strictly an expansion variable. It is
9306 expansion syntax for inserting the message header line with the given name.
9307 Note that the name must be terminated by colon or white space, because it may
9308 contain a wide variety of characters.
9309 Note also that braces must \*not*\ be used.
9313 When the \check@_local@_user\ option is set for a router, the user's home
9314 directory is placed in \$home$\ when the check succeeds. In particular, this
9315 means it is set during the running of users' filter files. A router may also
9316 explicitly set a home directory for use by a transport; this can be overridden
9317 by a setting on the transport itself.
9319 When running a filter test via the \-bf-\ option, \$home$\ is set to the value
9320 of the environment variable \\HOME\\.
9324 When the \%smtp%\ transport is expanding its options for encryption using TLS,
9325 \$host$\ contains the name of the host to which it is connected. Likewise, when
9326 used in the client part of an authenticator configuration (see chapter
9327 ~~CHAPSMTPAUTH), \$host$\ contains the name of the server to which the client
9329 .index transport||filter
9330 .index filter||transport filter
9331 When used in a transport filter (see chapter ~~CHAPtransportgeneric) \$host$\
9332 refers to the host involved in the current connection. When a local transport
9333 is run as a result of a router that sets up a host list, \$host$\ contains the
9334 name of the first host.
9338 This variable is set to the remote host's IP address whenever \$host$\ is set
9339 for a remote connection.
9343 If a \hosts\ condition in an ACL is satisfied by means of a lookup, the result
9344 of the lookup is made available in the \$host@_data$\ variable. This
9345 allows you, for example, to do things like this:
9347 deny hosts = net-lsearch;/some/file
9348 message = $host_data
9351 .index host||name lookup, failure of
9353 \$host@_lookup@_failed$\:
9354 This variable contains `1' if the message came from a remote host and there was
9355 an attempt to look up the host's name from its IP address, but the attempt
9356 failed. Otherwise the value of the variable is `0'.
9357 Exim checks that a forward lookup of at least one of the names it receives from
9358 a reverse lookup yields the original IP address. If this is not the case, Exim
9359 does not accept the looked up name(s), and \$host@_lookup@_failed$\ is set to
9360 `1'. Thus, being able to find a name from an IP address (for example, the
9361 existence of a PTR record in the DNS) is not sufficient on its own for the
9362 success of a host name lookup.
9366 The only time this variable is set is while expanding the \directory@_file\
9367 option in the \%appendfile%\ transport. The variable contains the inode number
9368 of the temporary file which is about to be renamed. It can be used to construct
9369 a unique name for the file.
9372 \$interface@_address$\:
9373 When a message is received over a TCP/IP connection, this variable contains the
9374 address of the local IP interface. See also the \-oMi-\ command line option.
9375 This variable can be used in ACLs and also, for example, to make the file name
9376 for a TLS certificate depend on which interface is being used.
9379 \$interface@_port$\:
9380 When a message is received over a TCP/IP connection, this variable contains the
9381 local port number. See also the \-oMi-\ command line option.
9382 This variable can be used in ACLs and also, for example, to make the file name
9383 for a TLS certificate depend on which port is being used.
9387 This variable, which is available only when Exim is compiled with LDAP support,
9388 contains the DN from the last entry in the most recently successful LDAP
9394 This variable contains the system load average, multiplied by 1000 to that it
9395 is an integer. For example, if the load average is 0.21, the value of the
9396 variable is 210. The value is recomputed every time the variable is referenced.
9399 \$local@_part$\: When an address is being routed, or delivered on its own, this
9400 variable contains the local part. When a number of addresses are being
9401 delivered together (for example, multiple \\RCPT\\ commands in an SMTP
9402 session), \$local@_part$\ is not set.
9404 Global address rewriting happens when a message is received, so the value of
9405 \$local@_part$\ during routing and delivery is the value after rewriting.
9406 \$local@_part$\ is set during user filtering, but not during system filtering,
9407 because a message may have many recipients and the system filter is called just
9410 If a local part prefix or suffix has been recognized, it is not included in the
9411 value of \$local@_part$\ during routing and subsequent delivery. The values of
9412 any prefix or suffix are in \$local@_part@_prefix$\ and
9413 \$local@_part@_suffix$\, respectively.
9415 When a message is being delivered to a file, pipe, or autoreply transport as a
9416 result of aliasing or forwarding, \$local@_part$\ is set to the local part of
9417 the parent address, not to the file name or command (see \$address@_file$\ and
9420 When an ACL is running for a \\RCPT\\ command, \$local@_part$\ contains the
9421 local part of the recipient address.
9423 When a rewrite item is being processed (see chapter ~~CHAPrewrite),
9424 \$local@_part$\ contains the local part of the address that is being rewritten;
9425 it can be used in the expansion of the replacement address, for example.
9427 In all cases, all quoting is removed from the local part. For example, for both
9430 "abc:xyz"@test.example
9431 abc\:xyz@test.example
9433 the value of \$local@_part$\ is
9437 If you use \$local@_part$\ to create another address, you should always wrap it
9438 inside a quoting operator. For example, in a \%redirect%\ router you could have:
9440 data = ${quote_local_part:$local_part}@new.domain.example
9442 \**Note**\: The value of \$local@_part$\ is normally lower cased. If you want
9443 to process local parts in a case-dependent manner in a router, you can set the
9444 \caseful@_local@_part\ option (see chapter ~~CHAProutergeneric).
9447 \$local@_part@_data$\:
9448 When the \local@_parts\ option on a router matches a local part by means of a
9449 lookup, the data read by the lookup is available during the running of the
9450 router as \$local@_part@_data$\. In addition, if the driver routes the address
9451 to a transport, the value is available in that transport. If the transport is
9452 handling multiple addresses, the value from the first address is used.
9454 \$local@_part@_data$\ is also set when the \local@_parts\ condition in an ACL
9455 matches a local part by means of a lookup. The data read by the lookup is
9456 available during the rest of the ACL statement. In all other situations, this
9457 variable expands to nothing.
9460 \$local@_part@_prefix$\: When an address is being routed or delivered, and a
9461 specific prefix for the local part was recognized, it is available in this
9462 variable, having been removed from \$local@_part$\.
9465 \$local@_part@_suffix$\: When an address is being routed or delivered, and a
9466 specific suffix for the local part was recognized, it is available in this
9467 variable, having been removed from \$local@_part$\.
9470 \$local@_scan@_data$\: This variable contains the text returned by the
9471 \*local@_scan()*\ function when a message is received. See chapter
9472 ~~CHAPlocalscan for more details.
9475 \$local@_user@_gid$\: See \$local@_user@_uid$\.
9478 \$local@_user@_uid$\: This variable and \$local@_user@_gid$\ are set to
9479 the uid and gid after the \check__local__user\ router precondition succeeds.
9480 This means that their values are available for the remaining preconditions
9481 (\senders\, \require@_files\, and \condition\), for the \address@_data\
9482 expansion, and for any router-specific expansions. At all other times, the
9483 values in these variables are \"(uid@_t)(-1)"\ and \"(gid@_t)(-1)"\,
9488 \$localhost@_number$\: This contains the expanded value of the
9489 \localhost@_number\ option. The expansion happens after the main options have
9493 \$mailstore@_basename$\: This variable is set only when doing deliveries in
9494 `mailstore' format in the \%appendfile%\ transport. During the expansion of the
9495 \mailstore@_prefix\, \mailstore@_suffix\, \message__prefix\, and
9496 \message@_suffix\ options, it contains the basename of the files that are being
9497 written, that is, the name without the `.tmp', `.env', or `.msg' suffix. At all
9498 other times, this variable is empty.
9500 .index message||age of
9502 \$message@_age$\: This variable is set at the start of a delivery attempt to
9503 contain the number of seconds since the message was received. It does not
9504 change during a single delivery attempt.
9506 .index body of message||expansion variable
9507 .index message||body, in expansion
9508 .index binary zero||in message body
9510 \$message@_body$\: This variable contains the initial portion of a message's
9511 body while it is being delivered, and is intended mainly for use in filter
9512 files. The maximum number of characters of the body that are put into the
9513 variable is set by the \message@_body@_visible\ configuration option; the
9514 default is 500. Newlines are converted into spaces to make it easier to search
9515 for phrases that might be split over a line break.
9516 Binary zeros are also converted into spaces.
9518 .index body of message||expansion variable
9519 .index message||body, in expansion
9521 \$message@_body@_end$\: This variable contains the final portion of a message's
9522 body while it is being delivered. The format and maximum size are as for
9525 .index body of message||size
9526 .index message||body, size
9528 \$message@_body@_size$\: When a message is being processed, this variable
9529 contains the size of the body in bytes. The count starts from the character
9530 after the blank line that separates the body from the header. Newlines are
9531 included in the count. See also \$message@_size$\ and \$body@_linecount$\.
9534 \$message@_headers$\:
9535 This variable contains a concatenation of all the header lines when a message
9536 is being processed, except for lines added by routers or transports. The header
9537 lines are separated by newline characters.
9541 When a message is being received or delivered, this variable contains the
9542 unique message id that is used by Exim to identify the message.
9543 An id is not created for a message until after its header has been
9544 successfully received.
9545 \**Note**\: This is \*not*\ the contents of the ::Message-ID:: header line; it
9546 is the local id that Exim assigns to the message, for example:
9547 \"1BXTIK-0001yO-VA"\.
9549 .index size||of message
9550 .index message||size
9553 When a message is being processed, this variable contains its size in bytes. In
9554 most cases, the size includes those headers that were received with the
9555 message, but not those (such as ::Envelope-to::) that are added to individual
9556 deliveries as they are written. However, there is one special case: during the
9557 expansion of the \maildir@_tag\ option in the \%appendfile%\ transport while
9558 doing a delivery in maildir format, the value of \$message@_size$\ is the
9559 precise size of the file that has been written. See also
9560 \$message@_body@_size$\ and \$body@_linecount$\.
9562 .index \\RCPT\\||value of \$message@_size$\
9563 While running an ACL at the time of an SMTP \\RCPT\\ command, \$message@_size$\
9564 contains the size supplied on the \\MAIL\\ command, or
9566 if no size was given. The value may not, of course, be truthful.
9569 \$n0$\ -- \$n9$\: These variables are counters that can be incremented by means
9570 of the \add\ command in filter files.
9573 \$original@_domain$\: When a top-level address is being processed for delivery,
9574 this contains the same value as \$domain$\. However, if a `child' address (for
9575 example, generated by an alias, forward, or filter file) is being processed,
9576 this variable contains the domain of the original address. This differs from
9577 \$parent@_domain$\ only when there is more than one level of aliasing or
9578 forwarding. When more than one address is being delivered in a single transport
9579 run, \$original@_domain$\ is not set.
9581 If new an address is created by means of a \deliver\ command in a system
9582 filter, it is set up with an artificial `parent' address. This has the local
9583 part \*system-filter*\ and the default qualify domain.
9586 \$original@_local@_part$\: When a top-level address is being processed for
9587 delivery, this contains the same value as \$local@_part$\, unless a prefix or
9588 suffix was removed from the local part, in which case \$original@_local@_part$\
9589 contains the full local part. When a `child' address (for example, generated by
9590 an alias, forward, or filter file) is being processed, this variable contains
9591 the full local part of the original address. If the router that did the
9592 redirection processed the local part case-insensitively, the value in
9593 \$original@_local@_part$\ is in lower case. This variable differs from
9594 \$parent@_local@_part$\ only when there is more than one level of aliasing or
9595 forwarding. When more than one address is being delivered in a single transport
9596 run, \$original@_local@_part$\ is not set.
9598 If new an address is created by means of a \deliver\ command in a system
9599 filter, it is set up with an artificial `parent' address. This has the local
9600 part \*system-filter*\ and the default qualify domain.
9603 .index gid (group id)||of originating user
9606 \$originator@_gid$\: The value of \$caller@_gid$\ that was set when the message
9607 was received. For messages received via the command line, this is the gid of
9608 the sending user. For messages received by SMTP over TCP/IP, this is normally
9609 the gid of the Exim user.
9611 .index uid (user id)||of originating user
9614 \$originator@_uid$\: The value of \$caller@_uid$\ that was set when the message
9615 was received. For messages received via the command line, this is the uid of
9616 the sending user. For messages received by SMTP over TCP/IP, this is normally
9617 the uid of the Exim user.
9620 \$parent@_domain$\: This variable is similar to \$original@_domain$\ (see
9621 above), except that it refers to the immediately preceding parent address.
9624 \$parent@_local@_part$\: This variable is similar to \$original@_local@_part$\
9625 (see above), except that it refers to the immediately preceding parent address.
9627 .index pid (process id)||of current process
9629 \$pid$\: This variable contains the current process id.
9631 .index filter||transport filter
9632 .index transport||filter
9634 \$pipe@_addresses$\: This is not an expansion variable, but is mentioned here
9635 because the string `@$pipe@_addresses' is handled specially in the command
9636 specification for the \%pipe%\ transport (chapter ~~CHAPpipetransport) and in
9637 transport filters (described under \transport@_filter\ in chapter
9638 ~~CHAPtransportgeneric). It cannot be used in general expansion strings, and
9639 provokes an `unknown variable' error if encountered.
9642 \$primary@_hostname$\: The value set in the configuration file, or read by the
9643 \*uname()*\ function. If \*uname()*\ returns a single-component name, Exim
9644 calls \*gethostbyname()*\ (or \*getipnodebyname()*\ where available) in an
9645 attempt to acquire a fully qualified host name.
9646 See also \$smtp@_active@_hostname$\.
9649 \$qualify@_domain$\: The value set for this option in the configuration file.
9652 \$qualify@_recipient$\: The value set for this option in the configuration file,
9653 or if not set, the value of \$qualify@_domain$\.
9656 \$rcpt@_count$\: When a message is being received by SMTP, this variable
9657 contains the number of \\RCPT\\ commands received for the current message. If
9658 this variable is used in a \\RCPT\\ ACL, its value includes the current
9662 \$rcpt@_defer@_count$\: When a message is being received by SMTP, this variable
9663 contains the number of \\RCPT\\ commands in the current message that have
9664 previously been rejected with a temporary (4\*xx*\) response.
9667 \$rcpt@_fail@_count$\: When a message is being received by SMTP, this variable
9668 contains the number of \\RCPT\\ commands in the current message that have
9669 previously been rejected with a permanent (5\*xx*\) response.
9672 \$received@_count$\: This variable contains the number of ::Received:: header
9673 lines in the message, including the one added by Exim (so its value is always
9674 greater than zero). It is available in the \\DATA\\ ACL, the non-SMTP ACL, and
9675 while routing and delivering.
9678 \$received@_for$\: If there is only a single recipient address in an incoming
9679 message, this variable contains that address when the ::Received:: header line
9681 The value is copied after recipient rewriting has happened, but before the
9682 \*local@_scan()*\ function is run.
9685 \$received@_protocol$\: When a message is being processed, this variable
9686 contains the name of the protocol by which it was received. See also the
9690 \$recipient@_data$\: This variable is set after an indexing lookup success in
9691 an ACL \recipients\ condition. It contains the data from the lookup, and the
9692 value remains set until the next \recipients\ test. Thus, you can do things
9695 require recipients = cdb*@@;/some/file
9696 deny \*some further test involving*\ @$recipient@_data
9698 \**Warning**\: This variable is set only when a lookup is used as an indexing
9699 method in the address list, using the semicolon syntax as in the example above.
9700 The variable is not set for a lookup that is used as part of the string
9701 expansion that all such lists undergo before being interpreted.
9704 \$recipients$\: This variable contains a list of envelope recipients for a
9705 message. A comma and a space separate the addresses in the replacement text.
9706 However, the variable is not generally available, to prevent exposure of Bcc
9707 recipients in unprivileged users' filter files. You can use \$recipients$\ only
9709 In a system filter file.
9711 In the \\DATA\\ or non-SMTP ACL, that is, in the final ACL for accepting a
9716 \$recipients@_count$\: When a message is being processed, this variable
9717 contains the number of envelope recipients that came with the message.
9718 Duplicates are not excluded from the count. While a message is being received
9719 over SMTP, the number increases for each accepted recipient. It can be
9720 referenced in an ACL.
9723 \$reply@_address$\: When a message is being processed, this variable contains
9724 the contents of the ::Reply-To:: header line if one exists
9725 and it is not empty,
9726 or otherwise the contents of the ::From:: header line.
9729 \$return@_path$\: When a message is being delivered, this variable contains the
9730 return path -- the sender field that will be sent as part of the envelope. It
9731 is not enclosed in @<@> characters.
9732 At the start of routing an address,
9733 \$return@_path$\ has the same value as \$sender@_address$\, but if, for
9734 example, an incoming message to a mailing list has been expanded by a router
9735 which specifies a different address for bounce messages, \$return@_path$\
9736 subsequently contains the new bounce address, whereas \$sender@_address$\
9737 always contains the original sender address that was received with the message.
9738 In other words, \$sender@_address$\ contains the incoming envelope sender, and
9739 \$return@_path$\ contains the outgoing envelope sender.
9742 \$return@_size@_limit$\: This is an obsolete name for
9743 \$bounce@_return@_size@_limit$\.
9745 .index return code||from \run\ expansion
9747 \$runrc$\: This variable contains the return code from a command that is run by
9748 the \@$@{run...@}\ expansion item.
9749 \**Warning**\: In a router or transport, you cannot assume the order in which
9750 option values are expanded, except for those pre-conditions whose order of
9751 testing is documented. Therefore, you cannot reliably expect to set \$runrc$\
9752 by the expansion of one option, and use it in another.
9755 \$self@_hostname$\: When an address is routed to a supposedly remote host that
9756 turns out to be the local host, what happens is controlled by the
9757 .index \self\ option||value of host name
9758 \self\ generic router option. One of its values causes the address to be passed
9759 to another router. When this happens, \$self@_hostname$\ is set to the name of
9760 the local host that the original router encountered. In other circumstances its
9764 \$sender@_address$\: When a message is being processed, this variable contains
9765 the sender's address that was received in the message's envelope. For bounce
9766 messages, the value of this variable is the empty string.
9767 See also \$return@_path$\.
9770 \$sender@_address@_domain$\: The domain portion of \$sender@_address$\.
9773 \$sender@_address@_local@_part$\: The local part portion of \$sender@_address$\.
9776 \$sender@_data$\: This variable is set after a lookup success in an ACL
9777 \senders\ condition or in a router \senders\ option. It contains the data from
9778 the lookup, and the value remains set until the next \senders\ test. Thus, you
9779 can do things like this:
9781 require senders = cdb*@@;/some/file
9782 deny \*some further test involving*\ @$sender@_data
9784 \**Warning**\: This variable is set only when a lookup is used as an indexing
9785 method in the address list, using the semicolon syntax as in the example above.
9786 The variable is not set for a lookup that is used as part of the string
9787 expansion that all such lists undergo before being interpreted.
9790 \$sender@_fullhost$\: When a message is received from a remote host, this
9791 variable contains the host name and IP address in a single string. It ends
9792 with the IP address in square brackets, followed by a colon and a port number
9793 if the logging of ports is enabled. The format of the rest of the string
9794 depends on whether the host issued a \\HELO\\ or \\EHLO\\ SMTP command, and
9795 whether the host name was verified by looking up its IP address. (Looking up
9796 the IP address can be forced by the \host@_lookup\ option, independent of
9797 verification.) A plain host name at the start of the string is a verified host
9798 name; if this is not present, verification either failed or was not requested.
9799 A host name in parentheses is the argument of a \\HELO\\ or \\EHLO\\ command.
9800 This is omitted if it is identical to the verified host name or to the host's
9801 IP address in square brackets.
9804 \$sender@_helo@_name$\: When a message is received from a remote host that has
9805 issued a \\HELO\\ or \\EHLO\\ command, the argument of that command is placed
9806 in this variable. It is also set if \\HELO\\ or \\EHLO\\ is used when a message
9807 is received using SMTP locally via the \-bs-\ or \-bS-\ options.
9810 \$sender@_host@_address$\: When a message is received from a remote host, this
9811 variable contains that host's IP address. For locally submitted messages, it is
9815 \$sender@_host@_authenticated$\: This variable contains the name (not the
9816 public name) of the authenticator driver which successfully authenticated the
9817 client from which the message was received. It is empty if there was no
9818 successful authentication.
9821 \$sender@_host@_name$\: When a message is received from a remote host, this
9822 variable contains the host's name as obtained by looking up its IP address.
9823 For messages received by other means, this variable is empty.
9825 If the host name has not previously been looked up, a reference to
9826 \$sender@_host@_name$\ triggers a lookup (for messages from remote hosts).
9827 A looked up name is accepted only if it leads back to the original IP address
9828 via a forward lookup. If either the reverse or the forward lookup fails, or if
9829 the forward lookup does not yield the original IP address,
9830 \$sender@_host@_name$\ remains empty, and \$host@_lookup@_failed$\ is set to
9833 Exim does not automatically look up every calling host's name. If you want
9834 maximum efficiency, you should arrange your configuration so that it avoids
9835 these lookups altogether. The lookup happens only if one or more of the
9838 A string containing \$sender@_host@_name$\ is expanded.
9840 The calling host matches the list in \host@_lookup\. In the default
9841 configuration, this option is set to $*$, so it must be changed if lookups are
9842 to be avoided. (In the code, the default for \host@_lookup\ is unset.)
9844 Exim needs the host name in order to test an item in a host list. The items
9845 that require this are described in sections ~~SECThoslispatnam and
9846 ~~SECThoslispatnamsk.
9848 The calling host matches \helo@_try@_verify@_hosts\ or \helo@_verify@_hosts\.
9849 In this case, the host name is required to compare with the name quoted in any
9850 \\EHLO\\ or \\HELO\\ commands that the client issues.
9852 The remote host issues a \\EHLO\\ or \\HELO\\ command that quotes one of the
9853 domains in \helo@_lookup@_domains\. The default value of this option is
9855 helo_lookup_domains = @ : @[]
9857 which causes a lookup if a remote host (incorrectly) gives the server's name or
9858 IP address in an \\EHLO\\ or \\HELO\\ command.
9862 \$sender@_host@_port$\: When a message is received from a remote host, this
9863 variable contains the port number that was used on the remote host.
9866 \$sender@_ident$\: When a message is received from a remote host, this variable
9867 contains the identification received in response to an RFC 1413 request. When a
9868 message has been received locally, this variable contains the login name of the
9869 user that called Exim.
9872 \$sender@_rcvhost$\: This is provided specifically for use in ::Received::
9873 headers. It starts with either the verified host name (as obtained from a
9874 .index DNS||reverse lookup
9875 .index reverse DNS lookup
9876 reverse DNS lookup) or, if there is no verified host name, the IP address in
9877 square brackets. After that there may be text in parentheses. When the first
9878 item is a verified host name, the first thing in the parentheses is the IP
9879 address in square brackets, followed by a colon and a port number if port
9880 logging is enabled. When the first item is an IP address, the port is recorded
9881 as `port=$it{xxxx}' inside the parentheses.
9883 There may also be items of the form `helo=$it{xxxx}' if \\HELO\\ or \\EHLO\\
9884 was used and its argument was not identical to the real host name or IP
9885 address, and `ident=$it{xxxx}' if an RFC 1413 ident string is available. If all
9886 three items are present in the parentheses, a newline and tab are inserted into
9887 the string, to improve the formatting of the ::Received:: header.
9889 .index \\AUTH\\||argument
9890 .index \\EXPN\\||argument
9891 .index \\ETRN\\||argument
9892 .index \\VRFY\\||argument
9894 \$smtp@_command@_argument$\: While an ACL is running to check an \\AUTH\\,
9895 \\EHLO\\, \\EXPN\\, \\ETRN\\, \\HELO\\, or \\VRFY\\ command, this variable
9896 contains the argument for the SMTP command.
9899 \$sn0$\ -- \$sn9$\: These variables are copies of the values of the \$n0$\
9900 -- \$n9$\ accumulators that were current at the end of the system filter file.
9901 This allows a system filter file to set values that can be tested in users'
9902 filter files. For example, a system filter could set a value indicating how
9903 likely it is that a message is junk mail.
9906 \$spool@_directory$\: The name of Exim's spool directory.
9909 \$thisaddress$\: This variable is set only during the processing of the
9910 \foranyaddress\ command in a filter file. Its use is explained in the
9911 description of that command.
9914 \$tls@_certificate@_verified$\:
9915 This variable is set to `1' if a TLS certificate was verified when the message
9916 was received, and `0' otherwise.
9919 \$tls@_cipher$\: When a message is received from a remote host over an
9920 encrypted SMTP connection, this variable is set to the cipher suite that was
9921 negotiated, for example DES-CBC3-SHA.
9922 In other circumstances, in particular, for message received over unencrypted
9923 connections, the variable is empty.
9924 See chapter ~~CHAPTLS for details of TLS support.
9927 \$tls@_peerdn$\: When a message is received from a remote host over an
9928 encrypted SMTP connection,
9929 and Exim is configured to request a certificate from the client,
9930 the value of the Distinguished Name of the certificate is made available in the
9931 \$tls@_peerdn$\ during subsequent processing.
9934 \$tod@_bsdinbox$\: The time of day and date, in the format required for
9935 BSD-style mailbox files, for example: Thu Oct 17 17:14:09 1995.
9938 \$tod@_epoch$\: The time and date as a number of seconds since the start of the
9942 \$tod@_full$\: A full version of the time and date, for example: Wed, 16 Oct
9943 1995 09:51:40 +0100. The timezone is always given as a numerical offset from
9944 UTC, with positive values used for timezones that are ahead (east) of UTC, and
9945 negative values for those that are behind (west).
9948 \$tod@_log$\: The time and date in the format used for writing Exim's log
9949 files, for example: 1995-10-12 15:32:29,
9950 but without a timezone.
9954 This variable contains the date in the format yyyymmdd. This is the format that
9955 is used for datestamping log files when \log@_file@_path\ contains the \"%D"\
9959 \$tod@_zone$\: This variable contains the numerical value of the local
9960 timezone, for example: -0500.
9964 This variable contains the UTC date and time in `Zulu' format, as specified by
9965 ISO 8601, for example: 20030221154023Z.
9969 \$value$\: This variable contains the result of an expansion lookup, extraction
9970 operation, or external command, as described above.
9973 \$version@_number$\: The version number of Exim.
9976 \$warn@_message@_delay$\: This variable is set only during the creation of a
9977 message warning about a delivery delay. Details of its use are explained in
9978 section ~~SECTcustwarn.
9981 \$warn@_message@_recipients$\: This variable is set only during the creation of
9982 a message warning about a delivery delay. Details of its use are explained in
9983 section ~~SECTcustwarn.
9990 . ============================================================================
9991 .chapter Embedded Perl
9992 .set runningfoot "embedded Perl"
9993 .rset CHAPperl "~~chapter"
9994 .index Perl||calling from Exim
9996 Exim can be built to include an embedded Perl interpreter. When this is done,
9997 Perl subroutines can be called as part of the string expansion process. To make
9998 use of the Perl support, you need version 5.004 or later of Perl installed on
9999 your system. To include the embedded interpreter in the Exim binary, include
10004 in your \(Local/Makefile)\ and then build Exim in the normal way.
10006 Access to Perl subroutines is via a global configuration option called
10007 .index \perl@_startup\
10008 \perl@_startup\ and an expansion string operator \@$@{perl ...@}\. If there is
10009 no \perl@_startup\ option in the Exim configuration file then no Perl
10010 interpreter is started and there is almost no overhead for Exim (since none of
10011 the Perl library will be paged in unless used). If there is a \perl@_startup\
10012 option then the associated value is taken to be Perl code which is executed in
10013 a newly created Perl interpreter.
10015 The value of \perl@_startup\ is not expanded in the Exim sense, so you do not
10016 need backslashes before any characters to escape special meanings. The option
10017 should usually be something like
10019 perl_startup = do '/etc/exim.pl'
10021 where \(/etc/exim.pl)\ is Perl code which defines any subroutines you want to
10022 use from Exim. Exim can be configured either to start up a Perl interpreter as
10023 soon as it is entered, or to wait until the first time it is needed. Starting
10024 the interpreter at the beginning ensures that it is done while Exim still has
10025 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
10026 fact used in a particular run. Also, note that this does not mean that Exim is
10027 necessarily running as root when Perl is called at a later time. By default,
10028 the interpreter is started only when it is needed, but this can be changed in
10031 .index \perl@_at@_start\
10032 Setting \perl@_at@_start\ (a boolean option) in the configuration requests
10033 a startup when Exim is entered.
10035 The command line option \-ps-\ also requests a startup when Exim is entered,
10036 overriding the setting of \perl@_at@_start\.
10038 There is also a command line option \-pd-\ (for delay) which suppresses the
10039 initial startup, even if \perl@_at@_start\ is set.
10041 When the configuration file includes a \perl@_startup\ option you can make use
10042 of the string expansion item to call the Perl subroutines that are defined
10043 by the \perl@_startup\ code. The operator is used in any of the following
10047 ${perl{foo}{argument}}
10048 ${perl{foo}{argument1}{argument2} ... }
10050 which calls the subroutine \foo\ with the given arguments. A maximum of eight
10051 arguments may be passed. Passing more than this results in an expansion failure
10052 with an error message of the form
10054 Too many arguments passed to Perl subroutine "foo" (max is 8)
10056 The return value of the Perl subroutine is evaluated in a scalar context before
10057 it is passed back to Exim to be inserted into the expanded string. If the
10058 return value is \*undef*\, the expansion fails in the same way as an explicit
10059 `fail' on an \@$@{if ...@}\ or \@$@{lookup...@}\ item.
10060 If the subroutine aborts by obeying Perl's \die\ function, the expansion fails
10061 with the error message that was passed to \die\.
10063 Within any Perl code called from Exim, the function \*Exim@:@:expand@_string*\
10064 is available to call back into Exim's string expansion function. For example,
10067 my $lp = Exim::expand_string('$local_part');
10069 makes the current Exim \$local@_part$\ available in the Perl variable \$lp$\.
10070 Note those are single quotes and not double quotes to protect against
10071 \$local@_part$\ being interpolated as a Perl variable.
10073 If the string expansion is forced to fail by a `fail' item, the result of
10074 \*Exim@:@:expand@_string*\ is \undef\. If there is a syntax error in the
10075 expansion string, the Perl call from the original expansion string fails with
10076 an appropriate error message, in the same way as if \die\ were used.
10078 .index debugging||from embedded Perl
10079 .index log||writing from embedded Perl
10080 Two other Exim functions are available for use from within Perl code.
10081 \*Exim@:@:debug@_write(<<string>>)*\ writes the string to the standard error
10082 stream if Exim's debugging is enabled. If you want a newline at the end, you
10083 must supply it. \*Exim@:@:log@_write(<<string>>)*\ writes the string to Exim's
10084 main log, adding a leading timestamp. In this case, you should not supply a
10085 terminating newline.
10093 . ============================================================================
10094 .chapter Starting the daemon and the use of network interfaces
10095 .set runningfoot "starting the daemon"
10096 .rset CHAPinterfaces "~~chapter"
10097 .index daemon||starting
10098 .index interface||listening
10099 .index network interface
10100 .index interface||network
10101 .index IP address||for listening
10102 .index daemon||listening IP addresses
10103 .index TCP/IP||setting listening interfaces
10104 .index TCP/IP||setting listening ports
10106 A host that is connected to a TCP/IP network may have one or more physical
10107 hardware network interfaces. Each of these interfaces may be configured as one
10108 or more `logical' interfaces, which are the entities that a program actually
10109 works with. Each of these logical interfaces is associated with an IP address.
10110 In addition, TCP/IP software supports `loopback' interfaces (127.0.0.1 in IPv4
10111 and @:@:1 in IPv6), which do not use any physical hardware. Exim requires
10112 knowledge about the host's interfaces for use in three different circumstances:
10114 When a listening daemon is started, Exim needs to know which interfaces
10115 and ports to listen on.
10117 When Exim is routing an address, it needs to know which IP addresses
10118 are associated with local interfaces. This is required for the correct
10119 processing of MX lists by removing the local host and others with the
10120 same or higher priority values. Also, Exim needs to detect cases
10121 when an address is routed to an IP address that in fact belongs to the
10122 local host. Unless the \self\ router option or the \allow@_localhost\
10123 option of the smtp transport is set (as appropriate), this is treated
10124 as an error situation.
10126 When Exim connects to a remote host, it may need to know which interface to use
10127 for the outgoing connection.
10130 Exim's default behaviour is likely to be appropriate in the vast majority
10131 of cases. If your host has only one interface, and you want all its IP
10132 addresses to be treated in the same way, and you are using only the
10133 standard SMTP port, you should not need to take any special action. The
10134 rest of this chapter does not apply to you.
10136 In a more complicated situation you may want to listen only on certain
10137 interfaces, or on different ports, and for this reason there are a number of
10138 options that can be used to influence Exim's behaviour. The rest of this
10139 chapter describes how they operate.
10141 When a message is received over TCP/IP, the interface and port that were
10142 actually used are set in \$interface@_address$\ and \$interface@_port$\.
10145 .section Starting a listening daemon
10146 When a listening daemon is started (by means of the \-bd-\ command line
10147 option), the interfaces and ports on which it listens are controlled by the
10150 \daemon@_smtp@_ports\ contains a list of default ports. (For backward
10151 compatibility, this option can also be specified in the singular.)
10153 \local@_interfaces\ contains list of interface IP addresses on which to
10154 listen. Each item may optionally also specify a port.
10156 The default list separator in both cases is a colon, but this can be changed as
10157 described in section ~~SECTlistconstruct. When IPv6 addresses are involved, it
10158 is usually best to change the separator to avoid having to double all the
10159 colons. For example:
10161 local_interfaces = <; 127.0.0.1 ; \
10164 3ffe:ffff:836f::fe86:a061
10166 There are two different formats for specifying a port along with an IP address
10167 in \local@_interfaces\:
10169 The port is added onto the address with a dot separator. For example, to listen
10170 on port 1234 on two different IP addresses:
10172 local_interfaces = <; 192.168.23.65.1234 ; \
10173 3ffe:ffff:836f::fe86:a061.1234
10176 The IP address is enclosed in square brackets, and the port is added
10177 with a colon separator, for example:
10179 local_interfaces = <; [192.168.23.65]:1234 ; \
10180 [3ffe:ffff:836f::fe86:a061]:1234
10183 When a port is not specified, the value of \daemon@_smtp@_ports\ is used. The
10184 default setting contains just one port:
10186 daemon_smtp_ports = smtp
10188 If more than one port is listed, each interface that does not have its own port
10189 specified listens on all of them. Ports that are listed in
10190 \daemon@_smtp@_ports\ can be identified either by name (defined in
10191 \(/etc/services)\) or by number. However, when ports are given with individual
10192 IP addresses in \local@_interfaces\, only numbers (not names) can be used.
10195 .section Special IP listening addresses
10196 The addresses 0.0.0.0 and @:@:0 are treated specially. They are interpreted
10197 as `all IPv4 interfaces' and `all IPv6 interfaces', respectively. In each
10198 case, Exim tells the TCP/IP stack to `listen on all IPv\*x*\ interfaces'
10199 instead of setting up separate listening sockets for each interface. The
10200 default value of \local@_interfaces\ is
10202 local_interfaces = 0.0.0.0
10204 when Exim is built without IPv6 support; otherwise it is:
10206 local_interfaces = <; ::0 ; 0.0.0.0
10208 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
10211 .section Overriding local@_interfaces and daemon@_smtp@_ports
10212 The \-oX-\ command line option can be used to override the values of
10213 \daemon@_smtp@_ports\ and/or \local@_interfaces\ for a particular daemon
10214 instance. Another way of doing this would be to use macros and the \-D-\
10215 option. However, \-oX-\ can be used by any admin user, whereas modification of
10216 the runtime configuration by \-D-\ is allowed only when the caller is root or
10219 The value of \-oX-\ is a list of items. The default colon separator can be
10220 changed in the usual way if required. If there are any items that do not
10221 contain dots or colons (that is, are not IP addresses), the value of
10222 \daemon@_smtp@_ports\ is replaced by the list of those items. If there are any
10223 items that do contain dots or colons, the value of \local@_interfaces\ is
10224 replaced by those items. Thus, for example,
10228 overrides \daemon@_smtp@_ports\, but leaves \local@_interfaces\ unchanged,
10231 -oX 192.168.34.5.1125
10233 overrides \local@_interfaces\, leaving \daemon@_smtp@_ports\ unchanged.
10234 (However, since \local@_interfaces\ now contains no items without ports, the
10235 value of \daemon@_smtp@_ports\ is no longer relevant in this example.)
10238 .section IPv6 address scopes
10239 IPv6 addresses have `scopes', and a host with multiple hardware interfaces
10240 can, in principle, have the same link-local IPv6 address on different
10241 interfaces. Thus, additional information is needed, over and above the IP
10242 address, to distinguish individual interfaces. A convention of using a
10243 percent sign followed by something (often the interface name) has been
10244 adopted in some cases, leading to addresses like this:
10246 3ffe:2101:12:1:a00:20ff:fe86:a061%eth0
10248 To accommodate this usage, a percent sign followed by an arbitrary string is
10249 allowed at the end of an IPv6 address. By default, Exim calls \*getaddrinfo()*\
10250 to convert a textual IPv6 address for actual use. This function recognizes the
10251 percent convention in operating systems that support it, and it processes the
10252 address appropriately. Unfortunately, some older libraries have problems with
10253 \*getaddrinfo()*\. If
10255 IPV6_USE_INET_PTON=yes
10257 is set in \(Local/Makefile)\ (or an OS-dependent Makefile) when Exim is built,
10258 Exim uses \*inet@_pton()*\ to convert a textual IPv6 address for actual use,
10259 instead of \*getaddrinfo()*\. (Before version 4.14, it always used this
10260 function.) Of course, this means that the additional functionality of
10261 \*getaddrinfo()*\ -- recognizing scoped addresses -- is lost.
10264 .section Examples of starting a listening daemon
10265 The default case in an IPv6 environment is
10267 daemon_smtp_port = smtp
10268 local_interfaces = <; ::0 ; 0.0.0.0
10270 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
10271 Either one or two sockets may be used, depending on the characteristics of
10272 the TCP/IP stack. (This is complicated and messy; for more information,
10273 read the comments in the \(daemon.c)\ source file.)
10275 To specify listening on ports 25 and 26 on all interfaces:
10277 daemon_smtp_ports = 25 : 26
10279 (leaving \local@_interfaces\ at the default setting) or, more explicitly:
10281 local_interfaces = <; ::0.25 ; ::0.26 \
10282 0.0.0.0.25 ; 0.0.0.0.26
10284 To listen on the default port on all IPv4 interfaces, and on port 26 on the
10285 IPv4 loopback address only:
10287 local_interfaces = 0.0.0.0 : 127.0.0.1.26
10289 To specify listening on the default port on specific interfaces only:
10291 local_interfaces = 192.168.34.67 : 192.168.34.67
10293 \**Note**\: such a setting excludes listening on the loopback interfaces.
10296 .section Recognising the local host
10297 .rset SECTreclocipadd "~~chapter.~~section"
10298 The \local@_interfaces\ option is also used when Exim needs to determine
10299 whether or not an IP address refers to the local host. That is, the IP
10300 addresses of all the interfaces on which a daemon is listening are always
10303 For this usage, port numbers in \local@_interfaces\ are ignored. If either of
10304 the items 0.0.0.0 or @:@:0 are encountered, Exim gets a complete list of
10305 available interfaces from the operating system, and extracts the relevant
10306 (that is, IPv4 or IPv6) addresses to use for checking.
10308 Some systems set up large numbers of virtual interfaces in order to provide
10309 many virtual web servers. In this situation, you may want to listen for
10310 email on only a few of the available interfaces, but nevertheless treat all
10311 interfaces as local when routing. You can do this by setting
10312 \extra@_local@_interfaces\ to a list of IP addresses, possibly including the
10313 `all' wildcard values. These addresses are recognized as local, but are not
10314 used for listening. Consider this example:
10316 local_interfaces = <; 127.0.0.1 ; ::1 ; \
10318 3ffe:2101:12:1:a00:20ff:fe86:a061
10320 extra_local_interfaces = <; ::0 ; 0.0.0.0
10322 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
10323 address, but all available interface addresses are treated as local when
10326 In some environments the local host name may be in an MX list, but with an IP
10327 address that is not assigned to any local interface. In other cases it may be
10328 desirable to treat other host names as if they referred to the local host. Both
10329 these cases can be handled by setting the \hosts@_treat@_as@_local\ option.
10330 This contains host names rather than IP addresses. When a host is referenced
10331 during routing, either via an MX record or directly, it is treated as the local
10332 host if its name matches \hosts@_treat@_as@_local\, or if any of its IP
10333 addresses match \local@_interfaces\ or \extra@_local@_interfaces\.
10336 .section Delivering to a remote host
10337 Delivery to a remote host is handled by the smtp transport. By default, it
10338 allows the system's TCP/IP functions to choose which interface to use (if
10339 there is more than one) when connecting to a remote host. However, the
10340 \interface\ option can be set to specify which interface is used. See the
10341 description of the smtp transport in chapter ~~CHAPsmtptrans for more details.
10351 . ============================================================================
10352 .chapter Main configuration
10353 .set runningfoot "main configuration"
10354 .rset CHAPmainconfig "~~chapter"
10355 .index configuration file||main section
10356 .index main configuration
10357 The first part of the run time configuration file contains three types of item:
10359 Macro definitions: These lines start with an upper case letter. See section
10360 ~~SECTmacrodefs for details of macro processing.
10362 Named list definitions: These lines start with one of the words `domainlist',
10363 `hostlist', `addresslist', or `localpartlist'. Their use is described in
10364 section ~~SECTnamedlists.
10366 Main configuration settings: Each setting occupies one line of the file
10367 (with possible continuations). If any setting is preceded by the word
10368 `hide', the \-bP-\ command line option displays its value to admin users only.
10369 See section ~~SECTcos for a description of the syntax of these option settings.
10371 This chapter specifies all the main configuration options, along with their
10372 types and default values. For ease of finding a particular option, they appear
10373 in alphabetical order in section ~~SECTalomo below. However, because there are
10374 now so many options, they are first listed briefly in functional groups, as an
10375 aid to finding the name of the option you are looking for.
10376 Some options are listed in more than one group.
10378 .set savedisplayflowcheck ~~displayflowcheck
10379 .set displayflowcheck 0
10381 .section Miscellaneous
10384 \bi@_command\ $t$rm{to run for \-bi-\ command line option}
10385 \keep@_malformed\ $t$rm{for broken files -- should not happen}
10386 \localhost@_number\ $t$rm{for unique message ids in clusters}
10387 \message@_body@_visible\ $t$rm{how much to show in \$message@_body$\}
10388 \print@_topbitchars\ $t$rm{top-bit characters are printing}
10389 \timezone\ $t$rm{force time zone}
10392 .section Exim parameters
10395 \exim@_group\ $t$rm{override compiled-in value}
10396 \exim@_path\ $t$rm{override compiled-in value}
10397 \exim@_user\ $t$rm{override compiled-in value}
10398 \primary@_hostname\ $t$rm{default from \*uname()*\}
10399 \split@_spool@_directory\ $t$rm{use multiple directories}
10400 \spool@_directory\ $t$rm{override compiled-in value}
10403 .section Privilege controls
10406 \admin@_groups\ $t$rm{groups that are Exim admin users}
10407 \deliver@_drop@_privilege\ $t$rm{drop root for delivery processes}
10408 \local@_from@_check\ $t$rm{insert ::Sender:: if necessary}
10409 \local@_from@_prefix\ $t$rm{for testing ::From:: for local sender}
10410 \local@_from@_suffix\ $t$rm{for testing ::From:: for local sender}
10411 \local@_sender@_retain\ $t$rm{keep ::Sender:: from untrusted user}
10412 \never@_users\ $t$rm{do not run deliveries as these}
10413 \prod@_requires@_admin\ $t$rm{forced delivery requires admin user}
10414 \queue@_list@_requires@_admin\ $t$rm{queue listing requires admin user}
10415 \trusted@_groups\ $t$rm{groups that are trusted}
10416 \trusted@_users\ $t$rm{users that are trusted}
10422 \log@_file@_path\ $t$rm{override compiled-in value}
10423 \log@_selector\ $t$rm{set/unset optional logging}
10424 \log@_timezone\ $t$rm{add timezone to log lines}
10425 \message@_logs\ $t$rm{create per-message logs}
10426 \preserve@_message@_logs\ $t$rm{after message completion}
10427 \process@_log@_path\ $t$rm{for SIGUSR1 and \*exiwhat*\}
10428 \syslog@_duplication\ $t$rm{controls duplicate log lines on syslog }
10429 \syslog@_facility\ $t$rm{set syslog `facility' field}
10430 \syslog@_processname\ $t$rm{set syslog `ident' field}
10431 \syslog@_timestamp\ $t$rm{timestamp syslog lines}
10433 \write@_rejectlog\ $t$rm{control use of message log}
10437 .section Frozen messages
10440 \auto@_thaw\ $t$rm{sets time for retrying frozen messages}
10441 \freeze@_tell\ $t$rm{send message when freezing}
10442 \move@_frozen@_messages\ $t$rm{to another directory}
10443 \timeout@_frozen@_after\ $t$rm{keep frozen messages only so long}
10446 .section Data lookups
10449 \ldap@_default@_servers\ $t$rm{used if no server in query}
10450 \ldap@_version\ $t$rm{set protocol version}
10451 \lookup@_open@_max\ $t$rm{lookup files held open}
10452 \mysql@_servers\ $t$rm{as it says}
10453 \oracle@_servers\ $t$rm{as it says}
10454 \pgsql@_servers\ $t$rm{as it says}
10457 .section Message ids
10460 \message@_id@_header@_domain\ $t$rm{used to build ::Message-ID:: header}
10461 \message@_id@_header@_text\ $t$rm{ditto}
10464 .section Embedded Perl Startup
10467 \perl@_at@_start\ $t$rm{always start the interpreter}
10468 \perl@_startup\ $t$rm{code to obey when starting Perl}
10474 \daemon@_smtp@_ports\ $t$rm{default ports}
10475 \extra@_local@_interfaces\ $t$rm{not necessarily listened on}
10476 \local@_interfaces\ $t$rm{on which to listen, with optional ports}
10477 \pid@_file@_path\ $t$rm{override compiled-in value}
10478 \queue@_run@_max\ $t$rm{maximum simultaneous queue runners}
10481 .section Resource control
10484 \check@_log@_inodes\ $t$rm{before accepting a message}
10485 \check@_log@_space\ $t$rm{before accepting a message}
10486 \check@_spool@_inodes\ $t$rm{before accepting a message}
10487 \check@_spool@_space\ $t$rm{before accepting a message}
10488 \deliver@_queue@_load@_max\ $t$rm{no queue deliveries if load high}
10489 \queue@_only@_load\ $t$rm{queue incoming if load high}
10490 \queue@_run@_max\ $t$rm{maximum simultaneous queue runners}
10491 \remote@_max@_parallel\ $t$rm{parallel SMTP delivery per message}
10492 \smtp@_accept@_max\ $t$rm{simultaneous incoming connections}
10493 \smtp@_accept@_max@_nommail\ $t$rm{non-mail commands}
10494 \smtp@_accept@_max@_nonmail@_hosts\ $t$rm{hosts to which the limit applies}
10495 \smtp@_accept@_max@_per@_connection\ $t$rm{messages per connection}
10496 \smtp@_accept@_max@_per@_host\ $t$rm{connections from one host}
10497 \smtp@_accept@_queue\ $t$rm{queue mail if more connections}
10498 \smtp@_accept@_queue@_per@_connection\ $t$rm{queue if more messages per connection}
10499 \smtp@_accept@_reserve\ $t$rm{only reserve hosts if more connections}
10500 \smtp@_check@_spool@_space\ $t$rm{from \\SIZE\\ on \\MAIL\\ command}
10501 \smtp@_connect@_backlog\ $t$rm{passed to TCP/IP stack}
10502 \smtp@_load@_reserve\ $t$rm{SMTP from reserved hosts if load high}
10503 \smtp@_reserve@_hosts\ $t$rm{these are the reserve hosts}
10506 .section Policy controls
10509 \acl@_not@_smtp\ $t$rm{set ACL for non-SMTP messages}
10510 \acl@_smtp@_auth\ $t$rm{set ACL for \\AUTH\\}
10511 \acl@_smtp@_connect\ $t$rm{set ACL for connection}
10512 \acl@_smtp@_data\ $t$rm{set ACL for \\DATA\\}
10513 \acl@_smtp@_etrn\ $t$rm{set ACL for \\ETRN\\}
10514 \acl@_smtp@_expn\ $t$rm{set ACL for \\EXPN\\}
10515 \acl@_smtp@_helo\ $t$rm{set ACL for \\EHLO\\ or \\HELO\\}
10516 \acl@_smtp@_mail\ $t$rm{set ACL for \\MAIL\\}
10517 \acl@_smtp@_mailauth\ $t$rm{set ACL for \\AUTH\\ on \\MAIL\\ command}
10518 \acl@_smtp@_rcpt\ $t$rm{set ACL for \\RCPT\\}
10519 \acl@_smtp@_starttls\ $t$rm{set ACL for \\STARTTLS\\}
10520 \acl@_smtp@_vrfy\ $t$rm{set ACL for \\VRFY\\}
10521 \header@_maxsize\ $t$rm{total size of message header}
10522 \header@_line@_maxsize\ $t$rm{individual header line limit}
10523 \helo@_accept@_junk@_hosts\ $t$rm{allow syntactic junk from these hosts}
10524 \helo@_allow@_chars\ $t$rm{allow illegal chars in \\HELO\\ names}
10525 \helo@_lookup@_domains\ $t$rm{lookup hostname for these \\HELO\\ names}
10526 \helo@_try@_verify@_hosts\ $t$rm{\\HELO\\ soft-checked for these hosts}
10527 \helo@_verify@_hosts\ $t$rm{\\HELO\\ hard-checked for these hosts}
10528 \host@_lookup\ $t$rm{host name looked up for these hosts}
10529 \host@_lookup@_order\ $t$rm{order of DNS and local name lookups}
10530 \host@_reject@_connection\ $t$rm{reject connection from these hosts}
10531 \hosts@_treat@_as@_local\ $t$rm{useful in some cluster configurations}
10532 \local@_scan@_timeout\ $t$rm{timeout for \*local@_scan()*\}
10533 \message@_size@_limit\ $t$rm{for all messages}
10534 \percent@_hack@_domains\ $t$rm{recognize %-hack for these domains}
10537 .section Callout cache
10540 \callout@_domain@_negative@_expire\ $t$rm{timeout for negative domain cache item}
10541 \callout@_domain@_positive@_expire\ $t$rm{timeout for positive domain cache item}
10542 \callout@_negative@_expire\ $t$rm{timeout for negative address cache item}
10543 \callout@_positive@_expire\ $t$rm{timeout for positive address cache item}
10544 \callout@_random@_local@_part\ $t$rm{string to use for `random' testing}
10550 \tls@_advertise@_hosts\ $t$rm{advertise TLS to these hosts}
10551 \tls@_certificate\ $t$rm{location of server certificate}
10553 \tls@_crl\ $t$rm{certificate revocation list}
10555 \tls@_dhparam\ $t$rm{DH parameters for server}
10556 \tls@_privatekey\ $t$rm{location of server private key}
10557 \tls@_remember@_esmtp\ $t$rm{don't reset after starting TLS}
10559 \tls@_require@_ciphers\ $t$rm{specify acceptable cipers}
10561 \tls@_try@_verify@_hosts\ $t$rm{try to verify client certificate}
10562 \tls@_verify@_certificates\ $t$rm{expected client certificates}
10563 \tls@_verify@_hosts\ $t$rm{insist on client certificate verify}
10566 .section Local user handling
10569 \finduser@_retries\ $t$rm{useful in NIS environments}
10570 \gecos@_name\ $t$rm{used when creating ::Sender::}
10571 \gecos@_pattern\ $t$rm{ditto}
10572 \max@_username@_length\ $t$rm{for systems that truncate}
10573 \unknown@_login\ $t$rm{used when no login name found}
10574 \unknown@_username\ $t$rm{ditto}
10575 \uucp@_from@_pattern\ $t$rm{for recognizing `From ' lines}
10576 \uucp@_from@_sender\ $t$rm{ditto}
10579 .section All incoming messages (SMTP and non-SMTP)
10582 \header@_maxsize\ $t$rm{total size of message header}
10583 \header@_line@_maxsize\ $t$rm{individual header line limit}
10584 \message@_size@_limit\ $t$rm{applies to all messages}
10585 \percent@_hack@_domains\ $t$rm{recognize %-hack for these domains}
10586 \received@_header@_text\ $t$rm{expanded to make ::Received::}
10587 \received@_headers@_max\ $t$rm{for mail loop detection}
10588 \recipients@_max\ $t$rm{limit per message}
10589 \recipients@_max@_reject\ $t$rm{permanently reject excess}
10593 .section Non-SMTP incoming messages
10596 \receive@_timeout\ $t$rm{for non-SMTP messages}
10601 .section Incoming SMTP messages
10602 See also the \*Policy controls*\ section above.
10605 \host@_lookup\ $t$rm{host name looked up for these hosts}
10606 \host@_lookup@_order\ $t$rm{order of DNS and local name lookups}
10607 \recipient@_unqualified@_hosts\ $t$rm{may send unqualified recipients}
10608 \rfc1413@_hosts\ $t$rm{make ident calls to these hosts}
10609 \rfc1413@_query@_timeout\ $t$rm{zero disables ident calls}
10610 \sender@_unqualified@_hosts\ $t$rm{may send unqualified senders}
10611 \smtp@_accept@_keepalive\ $t$rm{some TCP/IP magic}
10612 \smtp@_accept@_max\ $t$rm{simultaneous incoming connections}
10613 \smtp@_accept@_max@_nommail\ $t$rm{non-mail commands}
10614 \smtp@_accept@_max@_nonmail@_hosts\ $t$rm{hosts to which the limit applies}
10615 \smtp@_accept@_max@_per@_connection\ $t$rm{messages per connection}
10616 \smtp@_accept@_max@_per@_host\ $t$rm{connections from one host}
10617 \smtp@_accept@_queue\ $t$rm{queue mail if more connections}
10618 \smtp@_accept@_queue@_per@_connection\ $t$rm{queue if more messages per connection}
10619 \smtp@_accept@_reserve\ $t$rm{only reserve hosts if more connections}
10621 \smtp@_active@_hostname\ $t$rm{host name to use in messages}
10623 \smtp@_banner\ $t$rm{text for welcome banner}
10624 \smtp@_check@_spool@_space\ $t$rm{from \\SIZE\\ on \\MAIL\\ command}
10625 \smtp@_connect@_backlog\ $t$rm{passed to TCP/IP stack}
10626 \smtp@_enforce@_sync\ $t$rm{of SMTP command/responses}
10627 \smtp@_etrn@_command\ $t$rm{what to run for \\ETRN\\}
10628 \smtp@_etrn@_serialize\ $t$rm{only one at once}
10629 \smtp@_load@_reserve\ $t$rm{only reserve hosts if this load}
10630 \smtp@_max@_unknown@_commands\ $t$rm{before dropping connection}
10631 \smtp@_ratelimit@_hosts\ $t$rm{apply ratelimiting to these hosts}
10632 \smtp@_ratelimit@_mail\ $t$rm{ratelimit for \\MAIL\\ commands}
10633 \smtp@_ratelimit@_rcpt\ $t$rm{ratelimit for \\RCPT\\ commands}
10634 \smtp@_receive@_timeout\ $t$rm{per command or data line}
10635 \smtp@_reserve@_hosts\ $t$rm{these are the reserve hosts}
10636 \smtp@_return@_error@_details\ $t$rm{give detail on rejections}
10639 .section SMTP extensions
10642 \accept@_8bitmime\ $t$rm{advertise \\8BITMIME\\}
10643 \auth@_advertise@_hosts\ $t$rm{advertise \\AUTH\\ to these hosts}
10644 \ignore@_fromline@_hosts\ $t$rm{allow `From ' from these hosts}
10645 \ignore@_fromline@_local\ $t$rm{allow `From ' from local SMTP}
10646 \pipelining@_advertise@_hosts\ $t$rm{advertise pipelining to these hosts}
10647 \tls@_advertise@_hosts\ $t$rm{advertise TLS to these hosts}
10650 .section Processing messages
10653 \allow@_domain@_literals\ $t$rm{recognize domain literal syntax}
10654 \allow@_mx@_to@_ip\ $t$rm{allow MX to point to IP address}
10655 \allow@_utf8@_domains\ $t$rm{in addresses}
10656 \delivery@_date@_remove\ $t$rm{from incoming messages}
10657 \envelope@_to@_remote\ $t$rm{from incoming messages}
10658 \extract@_addresses@_remove@_arguments\ $t$rm{affects \-t-\ processing}
10659 \headers@_charset\ $t$rm{default for translations}
10660 \qualify@_domain\ $t$rm{default for senders}
10661 \qualify@_recipient\ $t$rm{default for recipients}
10662 \return@_path@_remove\ $t$rm{from incoming messages}
10663 \strip@_excess@_angle@_brackets\ $t$rm{in addresses}
10664 \strip@_trailing@_dot\ $t$rm{at end of addresses}
10665 \untrusted@_set@_sender\ $t$rm{untrusted can set envelope sender}
10668 .section System filter
10671 \system@_filter\ $t$rm{locate system filter}
10672 \system@_filter@_directory@_transport\ $t$rm{transport for delivery to a directory}
10673 \system@_filter@_file@_transport\ $t$rm{transport for delivery to a file}
10674 \system@_filter@_group\ $t$rm{group for filter running}
10675 \system@_filter@_pipe@_transport\ $t$rm{transport for delivery to a pipe}
10676 \system@_filter@_reply@_transport\ $t$rm{transport for autoreply delivery}
10677 \system@_filter@_user\ $t$rm{user for filter running}
10680 .section Routing and delivery
10683 \dns@_again@_means@_nonexist\ $t$rm{for broken domains}
10684 \dns@_check@_names@_pattern\ $t$rm{pre-DNS syntax check}
10685 \dns@_ipv4@_lookup\ $t$rm{only v4 lookup for these domains}
10686 \dns@_retrans\ $t$rm{parameter for resolver}
10687 \dns@_retry\ $t$rm{parameter for resolver}
10688 \hold@_domains\ $t$rm{hold delivery for these domains}
10689 \local@_interfaces\ $t$rm{for routing checks}
10690 \queue@_domains\ $t$rm{no immediate delivery for these}
10691 \queue@_only\ $t$rm{no immediate delivery at all}
10692 \queue@_only@_file\ $t$rm{no immediate deliveryif file exists}
10693 \queue@_only@_load\ $t$rm{no immediate delivery if load is high}
10694 \queue@_only@_override\ $t$rm{allow command line to override}
10695 \queue@_run@_in@_order\ $t$rm{order of arrival}
10696 \queue@_run@_max\ $t$rm{of simultaneous queue runners}
10697 \queue@_smtp@_domains\ $t$rm{no immediate SMTP delivery for these}
10698 \remote@_max@_parallel\ $t$rm{parallel SMTP delivery per message}
10699 \remote@_sort@_domains\ $t$rm{order of remote deliveries}
10700 \retry@_data@_expire\ $t$rm{timeout for retry data}
10701 \retry@_interval@_max\ $t$rm{safety net for retry rules}
10704 .section Bounce and warning messages
10707 \bounce@_message@_file\ $t$rm{content of bounce}
10708 \bounce@_message@_text\ $t$rm{content of bounce}
10709 \bounce@_return@_body\ $t$rm{include body if returning message}
10710 \bounce@_return@_message\ $t$rm{include original message in bounce}
10711 \bounce@_return@_size@_limit\ $t$rm{limit on returned message}
10712 \bounce@_sender@_authentication\ $t$rm{send authenticated sender with bounce}
10713 \errors@_copy\ $t$rm{copy bounce messages}
10714 \errors@_reply@_to\ $t$rm{::Reply-to:: in bounces}
10715 \delay@_warning\ $t$rm{time schedule}
10716 \delay@_warning@_condition\ $t$rm{condition for warning messages}
10717 \ignore@_bounce@_errors@_after\ $t$rm{discard undeliverable bounces}
10718 \warn@_message@_file\ $t$rm{content of warning message}
10721 .set displayflowcheck ~~savedisplayflowcheck
10723 .section Alphabetical list of main options
10724 .rset SECTalomo "~~chapter.~~section"
10726 Those options that undergo string expansion before use are marked with $**$.
10731 .index \\8BITMIME\\
10732 .index 8-bit characters
10733 .conf accept@_8bitmime boolean false
10734 This option causes Exim to send \\8BITMIME\\ in its response to an SMTP
10735 \\EHLO\\ command, and to accept the \\BODY=\\ parameter on \\MAIL\\ commands.
10736 However, though Exim is 8-bit clean, it is not a protocol converter, and it
10737 takes no steps to do anything special with messages received by this route.
10738 Consequently, this option is turned off by default.
10740 .index ~~ACL||for non-SMTP messages
10741 .index non-SMTP messages, ACL for
10742 .conf acl@_not@_smtp string$**$ unset
10743 This option defines the ACL that is run when a non-SMTP message is on the point
10744 of being accepted. See chapter ~~CHAPACL for further details.
10746 .index ~~ACL||on SMTP connection
10747 .conf acl@_smtp@_connect string$**$ unset
10748 This option defines the ACL that is run when an SMTP connection is received.
10749 See chapter ~~CHAPACL for further details.
10751 .index ~~ACL||setting up for SMTP commands
10752 .index \\AUTH\\||ACL for
10753 .conf acl@_smtp@_auth string$**$ unset
10754 This option defines the ACL that is run when an SMTP \\AUTH\\ command is
10755 received. See chapter ~~CHAPACL for further details.
10757 .index \\DATA\\, ACL for
10758 .conf acl@_smtp@_data string$**$ unset
10759 This option defines the ACL that is run after an SMTP \\DATA\\ command has been
10760 processed and the message itself has been received, but before the final
10761 acknowledgement is sent. See chapter ~~CHAPACL for further details.
10763 .index \\ETRN\\||ACL for
10764 .conf acl@_smtp@_etrn string$**$ unset
10765 This option defines the ACL that is run when an SMTP \\ETRN\\ command is
10766 received. See chapter ~~CHAPACL for further details.
10768 .index \\EXPN\\||ACL for
10769 .conf acl@_smtp@_expn string$**$ unset
10770 This option defines the ACL that is run when an SMTP \\EXPN\\ command is
10771 received. See chapter ~~CHAPACL for further details.
10773 .index \\EHLO\\||ACL for
10774 .index \\HELO\\||ACL for
10775 .conf acl@_smtp@_helo string$**$ unset
10776 This option defines the ACL that is run when an SMTP \\EHLO\\ or \\HELO\\
10777 command is received. See chapter ~~CHAPACL for further details.
10779 .index \\MAIL\\||ACL for
10780 .conf acl@_smtp@_mail string$**$ unset
10781 This option defines the ACL that is run when an SMTP \\MAIL\\ command is
10782 received. See chapter ~~CHAPACL for further details.
10784 .index \\AUTH\\||on \\MAIL\\ command
10785 .conf acl@_smtp@_mailauth string$**$ unset
10786 This option defines the ACL that is run when there is an \\AUTH\\ parameter on
10787 a \\MAIL\\ command. See chapter ~~CHAPACL for details of ACLs, and chapter
10788 ~~CHAPSMTPAUTH for details of authentication.
10790 .index \\RCPT\\||ACL for
10791 .conf acl@_smtp@_rcpt string$**$ unset
10792 This option defines the ACL that is run when an SMTP \\RCPT\\ command is
10793 received. See chapter ~~CHAPACL for further details.
10795 .index \\STARTTLS\\, ACL for
10796 .conf acl@_smtp@_starttls string$**$ unset
10797 This option defines the ACL that is run when an SMTP \\STARTTLS\\ command is
10798 received. See chapter ~~CHAPACL for further details.
10800 .index \\VRFY\\||ACL for
10801 .conf acl@_smtp@_vrfy string$**$ unset
10802 This option defines the ACL that is run when an SMTP \\VRFY\\ command is
10803 received. See chapter ~~CHAPACL for further details.
10805 .conf admin@_groups "string list" unset
10807 If the current group or any of the supplementary groups of the caller is in
10808 this colon-separated list, the caller has admin privileges. If all your system
10809 programmers are in a specific group, for example, you can give them all Exim
10810 admin privileges by putting that group in \admin@_groups\. However, this does
10811 not permit them to read Exim's spool files (whose group owner is the Exim gid).
10812 To permit this, you have to add individuals to the Exim group.
10814 .conf allow@_domain@_literals boolean false
10815 .index domain literal
10816 If this option is set, the RFC 2822 domain literal format is permitted in
10817 email addresses. The option is not set by default, because the domain literal
10818 format is not normally required these days, and few people know about it. It
10819 has, however, been exploited by mail abusers.
10821 Unfortunately, it seems that some DNS black list maintainers are using this
10822 format to report black listing to postmasters. If you want to accept messages
10823 addressed to your hosts by IP address, you need to set
10824 \allow@_domain@_literals\ true, and also to add \"@@[]"\ to the list of local
10825 domains (defined in the named domain list \local@_domains\ in the default
10826 configuration). This `magic string' matches the domain literal form of all the
10827 local host's IP addresses.
10829 .conf allow@_mx@_to@_ip boolean false
10830 .index MX record||pointing to IP address
10831 It appears that more and more DNS zone administrators are breaking the rules
10832 and putting domain names that look like IP addresses on the right hand side of
10833 MX records. Exim follows the rules and rejects this, giving an error message
10834 that explains the mis-configuration. However, some other MTAs support this
10835 practice, so to avoid `Why can't Exim do this?' complaints, \allow@_mx@_to@_ip\
10836 exists, in order to enable this heinous activity. It is not recommended, except
10837 when you have no other choice.
10839 .index domain||UTF-8 characters in
10840 .index UTF-8||in domain name
10841 .conf allow@_utf8@_domains boolean false
10842 Lots of discussion is going on about internationalized domain names. One
10843 camp is strongly in favour of just using UTF-8 characters, and it seems
10844 that at least two other MTAs permit this. This option allows Exim users to
10845 experiment if they wish.
10847 If it is set true, Exim's domain parsing function allows valid
10848 UTF-8 multicharacters to appear in domain name components, in addition to
10849 letters, digits, and hyphens. However, just setting this option is not
10850 enough; if you want to look up these domain names in the DNS, you must also
10851 adjust the value of \dns@_check@_names@_pattern\ to match the extended form. A
10852 suitable setting is:
10854 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
10855 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
10857 Alternatively, you can just disable this feature by setting
10859 dns_check_names_pattern =
10861 That is, set the option to an empty string so that no check is done.
10863 .conf auth@_advertise@_hosts "host list$**$" $*$
10864 .index authentication||advertising
10865 .index \\AUTH\\||advertising
10866 If any server authentication mechanisms are configured, Exim advertises them in
10867 response to an \\EHLO\\ command only if the calling host matches this list.
10868 Otherwise, Exim does not advertise \\AUTH\\.
10869 Exim does not accept \\AUTH\\ commands from clients to which it has not
10870 advertised the availability of \\AUTH\\. The advertising of individual
10871 authentication mechanisms can be controlled by the use of the
10872 \server@_advertise@_condition\ generic authenticator option on the individual
10873 authenticators. See chapter ~~CHAPSMTPAUTH for further details.
10875 Certain mail clients (for example, Netscape) require the user to provide a name
10876 and password for authentication if \\AUTH\\ is advertised, even though it may
10877 not be needed (the host may accept messages from hosts on its local LAN without
10878 authentication, for example). The \auth@_advertise@_hosts\ option can be used
10879 to make these clients more friendly by excluding them from the set of hosts to
10880 which Exim advertises \\AUTH\\.
10882 .index \\AUTH\\||advertising when encrypted
10883 If you want to advertise the availability of \\AUTH\\ only when the connection
10884 is encrypted using TLS, you can make use of the fact that the value of this
10885 option is expanded, with a setting like this:
10887 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
10889 If \$tls@_cipher$\ is empty, the session is not encrypted, and the result of
10890 the expansion is empty, thus matching no hosts. Otherwise, the result of the
10891 expansion is $*$, which matches all hosts.
10893 .conf auto@_thaw time 0s
10894 .index thawing messages
10895 .index unfreezing messages
10896 If this option is set to a time greater than zero, a queue runner will try a
10897 new delivery attempt on any frozen message if this much time has passed since
10898 it was frozen. This may result in the message being re-frozen if nothing has
10899 changed since the last attempt. It is a way of saying `keep on trying, even
10900 though there are big problems'. See also \timeout@_frozen@_after\ and
10901 \ignore@_bounce@_errors@_after\.
10903 .conf bi@_command string unset
10904 .index \-bi-\ option
10905 This option supplies the name of a command that is run when Exim is called with
10906 the \-bi-\ option (see chapter ~~CHAPcommandline). The string value is just the
10907 command name, it is not a complete command line. If an argument is required, it
10908 must come from the \-oA-\ command line option.
10910 .conf bounce@_message@_file string unset
10911 .index bounce message||customizing
10912 .index customizing||bounce message
10913 This option defines a template file containing paragraphs of text to be used
10914 for constructing bounce messages. Details of the file's contents are given in
10915 chapter ~~CHAPemsgcust. See also \warn@_message@_file\.
10917 .conf bounce@_message@_text string unset
10918 When this option is set, its contents are included in the default bounce
10919 message immediately after `This message was created automatically by mail
10920 delivery software.' It is not used if \bounce@_message@_file\ is set.
10922 .index bounce message||including body
10923 .conf bounce@_return@_body boolean true
10924 This option controls whether the body of an incoming message is included in a
10925 bounce message when \bounce@_return@_message\ is true. If it is not set, only
10926 the message header is included.
10928 .index bounce message||including original
10929 .conf bounce@_return@_message boolean true
10930 If this option is set false, the original message is not included in bounce
10931 messages generated by Exim. See also \bounce@_return@_size@_limit\.
10933 .conf bounce@_return@_size@_limit integer 100K
10934 .index size||of bounce, limit
10935 .index bounce message||size limit
10936 .index limit||bounce message size
10937 This option sets a limit in bytes on the size of messages that are returned to
10938 senders as part of bounce messages when \bounce@_return@_message\ is true. The
10939 limit should be less than the value of the global \message@_size@_limit\ and of
10940 any \message@_size@_limit\ settings on transports, to allow for the bounce text
10941 that Exim generates. If this option is set to zero there is no limit.
10943 When the body of any message that is to be included in a bounce message is
10944 greater than the limit, it is truncated, and a comment pointing this out is
10945 added at the top. The actual cutoff may be greater than the value given, owing
10946 to the use of buffering for transferring the message in chunks (typically 8K in
10947 size). The idea is to save bandwidth on those undeliverable 15-megabyte
10950 .index bounce message||sender authentication
10951 .index authentication||bounce message
10952 .index \\AUTH\\||on bounce message
10953 .conf bounce@_sender@_authentication string unset
10954 This option provides an authenticated sender address that is sent with any
10955 bounce messages generated by Exim that are sent over an authenticated SMTP
10956 connection. A typical setting might be:
10958 bounce_sender_authentication = mailer-daemon@my.domain.example
10960 which would cause bounce messages to be sent using the SMTP command:
10962 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
10964 The value of \bounce@_sender@_authentication\ must always be a complete email
10967 .index caching||callout, timeouts
10968 .index callout||caching timeouts
10969 .conf callout@_domain@_negative@_expire time 3h
10970 This option specifies the expiry time for negative callout cache data for a
10971 domain. See section ~~SECTcallver for details of callout verification, and
10972 section ~~SECTcallvercache for details of the caching.
10974 .conf callout@_domain@_positive@_expire time 7d
10975 This option specifies the expiry time for positive callout cache data for a
10976 domain. See section ~~SECTcallver for details of callout verification, and
10977 section ~~SECTcallvercache for details of the caching.
10979 .conf callout@_negative@_expire time 2h
10980 This option specifies the expiry time for negative callout cache data for an
10981 address. See section ~~SECTcallver for details of callout verification, and
10982 section ~~SECTcallvercache for details of the caching.
10984 .conf callout@_positive@_expire time 24h
10985 This option specifies the expiry time for positive callout cache data for an
10986 address. See section ~~SECTcallver for details of callout verification, and
10987 section ~~SECTcallvercache for details of the caching.
10989 .conf callout@_random@_local@_part string$**$ "see below"
10990 This option defines the `random' local part that can be used as part of callout
10991 verification. The default value is
10993 $primary_host_name-$tod_epoch-testing
10995 See section ~~CALLaddparcall for details of how this value is used.
10997 .conf check@_log@_inodes integer 0
10998 See \check@_spool@_space\ below.
11000 .conf check@_log@_space integer 0
11001 See \check@_spool@_space\ below.
11003 .conf check@_spool@_inodes integer 0
11004 See \check@_spool@_space\ below.
11006 .conf check@_spool@_space integer 0
11007 .index checking disk space
11008 .index disk space, checking
11009 .index spool directory||checking space
11010 The four \check@_...\ options allow for checking of disk resources before a
11011 message is accepted. \check@_spool@_space\ and \check@_spool@_inodes\ check the
11012 spool partition if either value is greater than zero, for example:
11014 check_spool_space = 10M
11015 check_spool_inodes = 100
11017 The spool partition is the one which contains the directory defined by
11018 \\SPOOL@_DIRECTORY\\ in \(Local/Makefile)\. It is used for holding messages in
11021 \check@_log@_space\ and \check@_log@_inodes\ check the partition in which log
11022 files are written if either is greater than zero. These should be set only if
11023 \log@_file@_path\ and \spool@_directory\ refer to different partitions.
11025 If there is less space or fewer inodes than requested, Exim refuses to accept
11026 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
11027 error response to the \\MAIL\\ command. If ESMTP is in use and there was a
11028 \\SIZE\\ parameter on the \\MAIL\\ command, its value is added to the
11029 \check@_spool@_space\ value, and the check is performed even if
11030 \check@_spool@_space\ is zero, unless \no@_smtp@_check@_spool@_space\ is set.
11032 The values for \check@_spool@_space\ and \check@_log@_space\ are held as a
11033 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
11035 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
11036 failure a message is written to stderr and Exim exits with a non-zero code, as
11037 it obviously cannot send an error message of any kind.
11039 .index port||for daemon
11040 .index TCP/IP||setting listening ports
11041 .conf daemon@_smtp@_ports string "$tt{smtp}"
11042 This option specifies one or more default SMTP ports on which the Exim daemon
11043 listens. See chapter ~~CHAPinterfaces for details of how it is used. For
11044 backward compatibility, \daemon@_smtp@_port\ (singular) is a synonym.
11046 .conf delay@_warning "time list" 24h
11047 .index warning of delay
11048 .index delay warning, specifying
11049 When a message is delayed, Exim sends a warning message to the sender at
11050 intervals specified by this option. If it is set to a zero, no warnings are
11051 sent. The data is a colon-separated list of times after which to send warning
11052 messages. Up to 10 times may be given. If a message has been on the queue for
11053 longer than the last time, the last interval between the times is used to
11054 compute subsequent warning times. For example, with
11056 delay_warning = 4h:8h:24h
11058 the first message is sent after 4 hours, the second after 8 hours, and
11059 the third one after 24 hours. After that, messages are sent every 16 hours,
11060 because that is the interval between the last two times on the list. If you set
11061 just one time, it specifies the repeat interval. For example, with:
11065 messages are repeated every six hours. To stop warnings after a given time, set
11066 a very large time at the end of the list. For example:
11068 delay_warning = 2h:12h:99d
11071 .conf delay@_warning@_condition string$**$ "see below"
11072 The string is expanded at the time a warning message might be sent. If all the
11073 deferred addresses have the same domain, it is set in \$domain$\ during the
11074 expansion. Otherwise \$domain$\ is empty. If the result of the expansion is a
11075 forced failure, an empty string, or a string matching any of `0', `no' or
11076 `false' (the comparison being done caselessly) then the warning message is not
11077 sent. The default is
11079 delay_warning_condition = \
11080 ${if match{$h_precedence:}{(?i)bulk|list|junk}{no}{yes}}
11082 which suppresses the sending of warnings about messages that have `bulk',
11083 `list' or `junk' in a ::Precedence:: header.
11085 .index unprivileged delivery
11086 .index delivery||unprivileged
11087 .conf deliver@_drop@_privilege boolean false
11088 If this option is set true, Exim drops its root privilege at the start of a
11089 delivery process, and runs as the Exim user throughout. This severely restricts
11090 the kinds of local delivery that are possible, but is viable in certain types
11091 of configuration. There is a discussion about the use of root privilege in
11092 chapter ~~CHAPsecurity.
11094 .index load average
11095 .index queue runner||abandoning
11096 .conf deliver@_queue@_load@_max fixed-point unset
11097 When this option is set, a queue run is abandoned if the system load average
11098 becomes greater than the value of the option. The option has no effect on
11099 ancient operating systems on which Exim cannot determine the load average.
11100 See also \queue@_only@_load\ and \smtp@_load@_reserve\.
11102 .conf delivery@_date@_remove boolean true
11103 .index ::Delivery-date:: header line
11104 Exim's transports have an option for adding a ::Delivery-date:: header to a
11105 message when it is delivered -- in exactly the same way as ::Return-path:: is
11106 handled. ::Delivery-date:: records the actual time of delivery. Such headers
11107 should not be present in incoming messages, and this option causes them to be
11108 removed at the time the message is received, to avoid any problems that might
11109 occur when a delivered message is subsequently sent on to some other recipient.
11111 .index DNS||`try again' response, overriding
11112 .conf dns@_again@_means@_nonexist "domain list$**$" unset
11113 DNS lookups give a `try again' response for the DNS errors `non-authoritative
11114 host not found' and `\\SERVERFAIL\\'. This can cause Exim to keep trying to
11115 deliver a message, or to give repeated temporary errors to incoming mail.
11116 Sometimes the effect is caused by a badly set up name server and may persist
11117 for a long time. If a domain which exhibits this problem matches anything in
11118 \dns__again__means__nonexist\, it is treated as if it did not exist. This
11119 option should be used with care.
11120 You can make it apply to reverse lookups by a setting such as this:
11122 dns_again_means_nonexist = *.in-addr.arpa
11125 .index DNS||pre-check of name syntax
11126 .conf dns@_check@_names@_pattern string "see below"
11127 When this option is set to a non-empty string, it causes Exim to check domain
11128 names for illegal characters before handing them to the DNS resolver, because
11129 some resolvers give temporary errors for malformed names. If a domain name
11130 contains any illegal characters, a `not found' result is forced, and the
11131 resolver is not called. The check is done by matching the domain name against a
11132 regular expression, which is the value of this option. The default pattern is
11134 dns_check_names_pattern = \
11135 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9-]*[^\W_])?)+$
11137 which permits only letters, digits, and hyphens in components, but they may not
11138 start or end with a hyphen.
11139 If you set \allow@_utf8@_domains\, you must modify this pattern, or set the
11140 option to an empty string.
11142 .conf dns@_ipv4@_lookup "domain list$**$" unset
11143 .index IPv6||DNS lookup for AAAA records
11144 .index DNS||IPv6 lookup for AAAA records
11145 When Exim is compiled with IPv6 support, it looks for IPv6 address records
11146 (AAAA and, if configured, A6) as well as IPv4 address records when trying to
11147 find IP addresses for hosts, unless the host's domain matches this list.
11149 This is a fudge to help with name servers that give big delays or otherwise do
11150 not work for the new IPv6 record types. If Exim is handed an IPv6 address
11151 record as a result of an MX lookup, it always recognizes it, and may as a
11152 result make an outgoing IPv6 connection. All this option does is to make Exim
11153 look only for IPv4-style A records when it needs to find an IP address for a
11154 host name. In due course, when the world's name servers have all been upgraded,
11155 there should be no need for this option.
11157 .conf dns@_retrans time 0s
11158 .index DNS||resolver options
11159 The options \dns@_retrans\ and \dns@_retry\ can be used to set the
11160 retransmission and retry parameters for DNS lookups. Values of zero (the
11161 defaults) leave the system default settings unchanged. The first value is the
11162 time between retries, and the second is the number of retries. It isn't
11163 totally clear exactly how these settings affect the total time a DNS lookup may
11164 take. I haven't found any documentation about timeouts on DNS lookups; these
11165 parameter values are available in the external resolver interface structure,
11166 but nowhere does it seem to describe how they are used or what you might want
11169 .conf dns@_retry integer 0
11170 See \dns@_retrans\ above.
11172 .conf drop@_cr boolean false
11173 This is an obsolete option that is now a no-op. It used to affect the way Exim
11174 handled CR and LF characters in incoming messages. What happens now is
11175 described in section ~~SECTlineendings.
11177 .conf envelope@_to@_remove boolean true
11178 .index ::Envelope-to:: header line
11179 Exim's transports have an option for adding an ::Envelope-to:: header to a
11180 message when it is delivered -- in exactly the same way as ::Return-path:: is
11181 handled. ::Envelope-to:: records the original recipient address from the
11182 messages's envelope that caused the delivery to happen. Such headers should not
11183 be present in incoming messages, and this option causes them to be removed at
11184 the time the message is received, to avoid any problems that might occur when a
11185 delivered message is subsequently sent on to some other recipient.
11187 .conf errors@_copy "string list$**$" unset
11188 .index bounce message||copy to other address
11189 .index copy of bounce message
11190 Setting this option causes Exim to send bcc copies of bounce messages that it
11191 generates to other addresses. \**Note**\: this does not apply to bounce messages
11192 coming from elsewhere. The value of the option is a colon-separated list of
11193 items. Each item consists of a pattern, terminated by white space, followed by
11194 a comma-separated list of email addresses. If a pattern contains spaces, it
11195 must be enclosed in double quotes.
11197 Each pattern is processed in the same way as a single item in an address list
11198 (see section ~~SECTaddresslist). When a pattern matches the recipient of the
11199 bounce message, the message is copied to the addresses on the list. The items
11200 are scanned in order, and once a matching one is found, no further items are
11201 examined. For example:
11203 errors_copy = spqr@mydomain postmaster@mydomain.example :\
11204 rqps@mydomain hostmaster@mydomain.example,\
11205 postmaster@mydomain.example
11207 The address list is expanded before use. The expansion variables
11208 \$local@_part$\ and \$domain$\ are set from the original recipient of the error
11209 message, and if there was any wildcard matching in the pattern, the expansion
11210 .index numerical variables (\$1$\, \$2$\, etc)||in \errors@_copy\
11211 variables \$0$\, \$1$\, etc. are set in the normal way.
11213 .conf errors@_reply@_to string unset
11214 .index bounce message||::Reply-to:: in
11215 Exim's bounce and delivery warning messages contain the header line
11217 From: Mail Delivery System @<Mailer-Daemon@@<<qualify-domain>>@>
11219 where <<qualify-domain>> is the value of the \qualify@_domain\ option.
11220 Experience shows that people reply to bounce messages. If the
11221 \errors@_reply@_to\ option is set, a ::Reply-To:: header is added to bounce and
11222 warning messages. For example:
11224 errors_reply_to = postmaster@my.domain.example
11226 The value of the option is not expanded. It must specify a valid RFC 2822
11229 .conf exim@_group string "compile-time configured"
11230 .index gid (group id)||Exim's own
11232 This option changes the gid under which Exim runs when it gives up root
11233 privilege. The default value is compiled into the binary. The value of this
11234 option is used only when \exim@_user\ is also set. Unless it consists entirely
11235 of digits, the string is looked up using \*getgrnam()*\, and failure causes a
11236 configuration error. See chapter ~~CHAPsecurity for a discussion of security
11239 .conf exim@_path string "see below"
11240 .index Exim binary, path name
11241 This option specifies the path name of the Exim binary, which is used when Exim
11242 needs to re-exec itself. The default is set up to point to the file \*exim*\ in
11243 the directory configured at compile time by the \\BIN@_DIRECTORY\\ setting. It
11244 is necessary to change \exim@_path\ if, exceptionally, Exim is run from some
11246 \**Warning**\: Do not use a macro to define the value of this option, because
11247 you will break those Exim utilities that scan the configuration file to find
11248 where the binary is. (They then use the \-bP-\ option to extract option
11249 settings such as the value of \spool@_directory\.)
11251 .conf exim@_user string "compile-time configured"
11252 .index uid (user id)||Exim's own
11254 This option changes the uid under which Exim runs when it gives up root
11255 privilege. The default value is compiled into the binary. Ownership of the run
11256 time configuration file and the use of the \-C-\ and \-D-\ command line options
11257 is checked against the values in the binary, not what is set here.
11259 Unless it consists entirely of digits, the string is looked up using
11260 \*getpwnam()*\, and failure causes a configuration error. If \exim@_group\ is
11261 not also supplied, the gid is taken from the result of \*getpwnam()*\ if it is
11262 used. See chapter ~~CHAPsecurity for a discussion of security issues.
11264 .conf extra@_local@_interfaces "string list" unset
11266 This option defines network interfaces that are to be considered local when
11267 routing, but which are not used for listening by the daemon. See section
11268 ~~SECTreclocipadd for details.
11270 .conf extract@_addresses@_remove@_arguments boolean true
11271 .index \-t-\ option
11272 .index command line||addresses with \-t-\
11273 .index Sendmail compatibility||\-t-\ option
11274 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
11275 are present on the command line when the \-t-\ option is used to build an
11276 envelope from a message's ::To::, ::Cc:: and ::Bcc:: headers, the command line
11277 addresses are removed from the recipients list. This is also how Smail behaves.
11278 However, other Sendmail documentation (the O'Reilly book) states that command
11279 line addresses are added to those obtained from the header lines. When
11280 \extract@_addresses@_remove@_arguments\ is true (the default), Exim subtracts
11281 argument headers. If it is set false, Exim adds rather than removes argument
11284 .conf finduser@_retries integer 0
11285 .index NIS, looking up users, retrying
11286 On systems running NIS or other schemes in which user and group information is
11287 distributed from a remote system, there can be times when \*getpwnam()*\ and
11288 related functions fail, even when given valid data, because things time out.
11289 Unfortunately these failures cannot be distinguished from genuine `not found'
11290 errors. If \finduser@_retries\ is set greater than zero, Exim will try that
11291 many extra times to find a user or a group, waiting for one second between
11294 .conf freeze@_tell "string list, comma separated" unset
11295 .index freezing messages||sending a message when freezing
11296 On encountering certain errors, or when configured to do so in a system filter,
11298 Exim freezes a message. This means that no further delivery attempts take place
11299 until an administrator (or the \auto@_thaw\ feature) thaws the message. If
11300 \freeze@_tell\ is set, Exim generates a warning message whenever it freezes
11301 something, unless the message it is freezing is a
11303 bounce message. (Without this exception there is the possibility of looping.)
11304 The warning message is sent to the addresses supplied as the comma-separated
11305 value of this option. If several of the message's addresses cause freezing,
11306 only a single message is sent.
11307 If the freezing was automatic, the reason(s) for freezing can be found in the
11308 message log. If you configure freezing in a filter or ACL, you must arrange for
11309 any logging that you require.
11311 .conf gecos@_name string$**$ unset
11313 .index `gecos' field, parsing
11314 Some operating systems, notably HP-UX, use the `gecos' field in the system
11315 password file to hold other information in addition to users' real names. Exim
11316 looks up this field for use when it is creating ::Sender:: or ::From:: headers.
11317 If either \gecos@_pattern\ or \gecos@_name\ are unset, the contents of the
11318 field are used unchanged, except that, if an ampersand is encountered, it is
11319 replaced by the user's login name with the first character forced to
11320 upper case, since this is a convention that is observed on many systems.
11322 When these options are set, \gecos@_pattern\ is treated as a regular expression
11323 that is to be applied to the field (again with & replaced by the login name),
11324 and if it matches, \gecos@_name\ is expanded and used as the user's name.
11325 .index numerical variables (\$1$\, \$2$\, etc)||in \gecos@_name\
11326 Numeric variables such as \$1$\, \$2$\, etc. can be used in the expansion to
11327 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
11328 name terminates at the first comma, the following can be used:
11330 gecos_pattern = ([^,]*)
11334 .conf gecos@_pattern string unset
11335 See \gecos@_name\ above.
11337 .conf headers@_charset string "see below"
11338 This option sets a default character set for translating from encoded MIME
11339 `words' in header lines, when referenced by an \$h@_xxx$\ expansion item. The
11340 default is the value of \\HEADERS@_CHARSET\\ in \(Local/Makefile)\. The
11341 ultimate default is ISO-8859-1. For more details see the description of header
11342 insertions in section ~~SECTexpansionitems.
11345 .conf header@_maxsize integer "see below"
11346 .index header section||maximum size of
11347 .index limit||size of message header section
11348 This option controls the overall maximum size of a message's header
11349 section. The default is the value of \\HEADER@_MAXSIZE\\ in
11350 \(Local/Makefile)\; the default for that is 1M. Messages with larger header
11351 sections are rejected.
11353 .conf header@_line@_maxsize integer 0
11354 .index header lines||maximum size of
11355 .index limit||size of one header line
11356 This option limits the length of any individual header line in a message, after
11357 all the continuations have been joined together. Messages with individual
11358 header lines that are longer than the limit are rejected. The default value of
11359 zero means `no limit'.
11363 .conf helo@_accept@_junk@_hosts "host list$**$" unset
11364 .index \\HELO\\||accepting junk data
11365 .index \\EHLO\\||accepting junk data
11366 Exim checks the syntax of \\HELO\\ and \\EHLO\\ commands for incoming SMTP
11367 mail, and gives an error response for invalid data. Unfortunately, there are
11368 some SMTP clients that send syntactic junk. They can be accommodated by setting
11369 this option. Note that this is a syntax check only. See \helo@_verify@_hosts\
11370 if you want to do semantic checking.
11371 See also \helo@_allow@_chars\ for a way of extending the permitted character
11374 .conf helo@_allow@_chars string unset
11375 .index \\HELO\\||underscores in
11376 .index \\EHLO\\||underscores in
11377 .index underscore in \\EHLO\\/\\HELO\\
11378 This option can be set to a string of rogue characters that are permitted in
11379 all \\EHLO\\ and \\HELO\\ names in addition to the standard letters, digits,
11380 hyphens, and dots. If you really must allow underscores, you can set
11382 helo_allow_chars = _
11384 Note that the value is one string, not a list.
11386 .conf helo@_lookup@_domains "domain list$**$" "$tt{@@:@@[]}"
11387 .index \\HELO\\||forcing reverse lookup
11388 .index \\EHLO\\||forcing reverse lookup
11389 If the domain given by a client in a \\HELO\\ or \\EHLO\\ command matches this
11390 list, a reverse lookup is done in order to establish the host's true name. The
11391 default forces a lookup if the client host gives the server's name or any of
11392 its IP addresses (in brackets), something that broken clients have been seen to
11395 .conf helo@_try@_verify@_hosts "host list$**$" unset
11396 .index \\HELO\\||verifying, optional
11397 .index \\EHLO\\||verifying, optional
11398 The RFCs mandate that a server must not reject a message because it doesn't
11399 like the \\HELO\\ or \\EHLO\\ command. By default, Exim just checks the syntax
11400 of these commands (see \helo__accept__junk__hosts\ and \helo@_allow@_chars\
11401 above). However, some sites like to be stricter. If the calling host matches
11402 \helo@_try@_verify@_hosts\, Exim checks that the host name given in the \\HELO\\
11403 or \\EHLO\\ command either:
11405 is an IP literal matching the calling address of the host (the RFCs
11406 specifically allow this), or
11408 .index DNS||reverse lookup
11409 .index reverse DNS lookup
11410 matches the host name that Exim obtains by doing a reverse lookup of the
11411 calling host address, or
11413 when looked up using \*gethostbyname()*\ (or \*getipnodebyname()*\ when
11414 available) yields the calling host address.
11416 However, the \\EHLO\\ or \\HELO\\ command is not rejected if any of the checks
11417 fail. Processing continues, but the result of the check is remembered, and can
11418 be detected later in an ACL by the \"verify = helo"\ condition. If you want
11419 verification failure to cause rejection of \\EHLO\\ or \\HELO\\, use
11420 \helo@_verify@_hosts\ instead.
11423 .conf helo@_verify@_hosts "host list$**$" unset
11424 .index \\HELO\\||verifying, mandatory
11425 .index \\EHLO\\||verifying, mandatory
11426 For hosts that match this option, Exim checks the host name given in the
11427 \\HELO\\ or \\EHLO\\ in the same way as for \helo@_try@_verify@_hosts\. If the
11428 check fails, the \\HELO\\ or \\EHLO\\ command is rejected with a 550 error, and
11429 entries are written to the main and reject logs. If a \\MAIL\\ command is
11430 received before \\EHLO\\ or \\HELO\\, it is rejected with a
11434 .conf hold@_domains "domain list$**$" unset
11435 .index domain||delaying delivery
11436 .index delivery||delaying certain domains
11437 This option allows mail for particular domains to be held on the queue
11438 manually. The option is overridden if a message delivery is forced with the
11439 \-M-\, \-qf-\, \-Rf-\ or \-Sf-\ options, and also while testing or verifying
11440 addresses using \-bt-\ or \-bv-\. Otherwise, if a domain matches an item in
11441 \hold@_domains\, no routing or delivery for that address is done, and it is
11442 deferred every time the message is looked at.
11444 This option is intended as a temporary operational measure for delaying the
11445 delivery of mail while some problem is being sorted out, or some new
11446 configuration tested. If you just want to delay the processing of some
11447 domains until a queue run occurs, you should use \queue@_domains\ or
11448 \queue@_smtp@_domains\, not \hold@_domains\.
11450 A setting of \hold@_domains\ does not override Exim's code for removing
11451 messages from the queue if they have been there longer than the longest retry
11452 time in any retry rule. If you want to hold messages for longer than the normal
11453 retry times, insert a dummy retry rule with a long retry time.
11455 .conf host@_lookup "host list$**$" unset
11456 .index host||name lookup, forcing
11457 Exim does not look up the name of a calling host from its IP address unless it
11458 is required to compare against some host list, or the host matches
11459 \helo@_try@_verify@_hosts\ or \helo@_verify@_hosts\, or the host matches this
11460 option (which normally contains IP addresses rather than host names). The
11461 default configuration file contains
11465 which causes a lookup to happen for all hosts. If the expense of these lookups
11466 is felt to be too great, the setting can be changed or removed.
11468 After a successful reverse lookup, Exim does a forward lookup on the name it
11469 has obtained, to verify that it yields the IP address that it started with. If
11470 this check fails, Exim behaves as if the name lookup failed.
11472 After any kind of failure, the host name (in \$sender@_host@_name$\) remains
11473 unset, and \$host@_lookup@_failed$\ is set to the string `1'. See also
11474 \dns@_again@_means@_nonexist\, \helo__lookup__domains\, and \"verify =
11475 reverse@_host@_lookup"\ in ACLs.
11477 .conf host@_lookup@_order "string list" $tt{bydns:byaddr}
11478 This option specifies the order of different lookup methods when Exim is trying
11479 to find a host name from an IP address. The default is to do a DNS lookup
11480 first, and then to try a local lookup (using \*gethostbyaddr()*\ or equivalent)
11481 if that fails. You can change the order of these lookups, or omit one entirely,
11484 \**Warning**\: the `byaddr' method does not always yield aliases when there are
11485 multiple PTR records in the DNS and the IP address is not listed in
11486 \(/etc/hosts)\. Different operating systems give different results in this
11487 case. That is why the default tries a DNS lookup first.
11490 .conf host@_reject@_connection "host list$**$" unset
11491 .index host||rejecting connections from
11492 If this option is set, incoming SMTP calls from the hosts listed are rejected
11493 as soon as the connection is made.
11494 This option is obsolete, and retained only for backward compatibility, because
11495 nowadays the ACL specified by \acl@_smtp@_connect\ can also reject incoming
11496 connections immediately.
11498 The ability to give an immediate rejection (either by this option or using an
11499 ACL) is provided for use in unusual cases. Many hosts will just try again,
11500 sometimes without much delay. Normally, it is better to use an ACL to reject
11501 incoming messages at a later stage, such as after \\RCPT\\ commands. See
11504 .conf hosts@_treat@_as@_local "domain list$**$" unset
11505 .index local host||domains treated as
11506 .index host||treated as local
11507 If this option is set, any host names that match the domain list are treated as
11508 if they were the local host when Exim is scanning host lists obtained from MX
11510 or other sources. Note that the value of this option is a domain list, not a
11511 host list, because it is always used to check host names, not IP addresses.
11513 This option also applies when Exim is matching the special items
11514 \"@@mx@_any"\, \"@@mx@_primary"\, and \"@@mx@_secondary"\ in a domain list (see
11515 section ~~SECTdomainlist), and when checking the \hosts\ option in the \%smtp%\
11516 transport for the local host (see the \allow@_localhost\ option in that
11518 See also \local@_interfaces\, \extra@_local@_interfaces\, and chapter
11519 ~~CHAPinterfaces, which contains a discussion about local network interfaces
11520 and recognising the local host.
11522 .conf ignore@_bounce@_errors@_after time 10w
11523 .index bounce message||discarding
11524 .index discarding bounce message
11525 This option affects the processing of bounce messages that cannot be delivered,
11526 that is, those that suffer a permanent delivery failure. (Bounce messages that
11527 suffer temporary delivery failures are of course retried in the usual way.)
11529 After a permanent delivery failure, bounce messages are frozen,
11530 because there is no sender to whom they can be returned. When a frozen bounce
11531 message has been on the queue for more than the given time, it is unfrozen at
11532 the next queue run, and a further delivery is attempted. If delivery fails
11533 again, the bounce message is discarded. This makes it possible to keep failed
11534 bounce messages around for a shorter time than the normal maximum retry time
11535 for frozen messages. For example,
11537 ignore_bounce_errors_after = 12h
11539 retries failed bounce message deliveries after 12 hours, discarding any further
11540 failures. If the value of this option is set to a zero time period, bounce
11541 failures are discarded immediately. Setting a very long time (as in the default
11542 value) has the effect of disabling this option. For ways of automatically
11543 dealing with other kinds of frozen message, see \auto@_thaw\ and
11544 \timeout@_frozen@_after\.
11546 .conf ignore@_fromline@_hosts "host list$**$" unset
11548 .index UUCP||`From' line
11549 Some broken SMTP clients insist on sending a UUCP-like `From' line before the
11550 headers of a message. By default this is treated as the start of the message's
11551 body, which means that any following headers are not recognized as such. Exim
11552 can be made to ignore it by setting \ignore@_fromline@_hosts\ to match those
11553 hosts that insist on sending it. If the sender is actually a local process
11554 rather than a remote host, and is using \-bs-\ to inject the messages,
11555 \ignore__fromline__local\ must be set to achieve this effect.
11557 .conf ignore@_fromline@_local boolean false
11558 See \ignore@_fromline@_hosts\ above.
11560 .conf keep@_malformed time 4d
11561 This option specifies the length of time to keep messages whose spool files
11562 have been corrupted in some way. This should, of course, never happen. At the
11563 next attempt to deliver such a message, it gets removed. The incident is
11566 .conf ldap@_default@_servers "string list" unset
11567 .index LDAP||default servers
11568 This option provides a list of LDAP servers which are tried in turn when an
11569 LDAP query does not contain a server. See section ~~SECTforldaque for details
11570 of LDAP queries. This option is available only when Exim has been built with
11573 .conf ldap@_version integer unset
11574 .index LDAP||protocol version, forcing
11575 This option can be used to force Exim to set a specific protocol version for
11576 LDAP. If it option is unset, it is shown by the \-bP-\ command line option as
11577 -1. When this is the case, the default is 3 if \\LDAP@_VERSION3\\ is defined in
11578 the LDAP headers; otherwise it is 2. This option is available only when Exim
11579 has been built with LDAP support.
11582 .conf local@_from@_check boolean true
11583 .index ::Sender:: header line||disabling addition of
11584 .index ::From:: header line||disabling checking of
11585 When a message is submitted locally (that is, not over a TCP/IP connection) by
11586 an untrusted user, Exim removes any existing ::Sender:: header line, and checks
11587 that the ::From:: header line matches the login of the calling user. You can
11588 use \local@_from@_prefix\ and \local@_from@_suffix\ to permit affixes on the
11589 local part. If the ::From:: header line does not match, Exim adds a ::Sender::
11590 header with an address constructed from the calling user's login and the
11591 default qualify domain.
11593 If \local@_from@_check\ is set false, the ::From:: header check is disabled,
11594 and no ::Sender:: header is ever added. If, in addition, you want to retain
11595 ::Sender:: header lines supplied by untrusted users, you must also set
11596 \local@_sender@_retain\ to be true.
11598 .index envelope sender
11599 These options affect only the header lines in the message. The envelope sender
11600 is still forced to be the login id at the qualify domain unless
11601 \untrusted@_set@_sender\ permits the user to supply an envelope sender.
11602 Section ~~SECTthesenhea has more details about ::Sender:: processing.
11605 .conf local@_from@_prefix string unset
11606 When Exim checks the ::From:: header line of locally submitted messages for
11607 matching the login id (see \local@_from@_check\ above), it can be configured to
11608 ignore certain prefixes and suffixes in the local part of the address. This is
11609 done by setting \local@_from@_prefix\ and/or \local@_from@_suffix\ to
11610 appropriate lists, in the same form as the \local@_part@_prefix\ and
11611 \local@_part@_suffix\ router options (see chapter ~~CHAProutergeneric). For
11614 local_from_prefix = *-
11616 is set, a ::From:: line containing
11618 From: anything-user@your.domain.example
11620 will not cause a ::Sender:: header to be added if \*user@@your.domain.example*\
11621 matches the actual sender address that is constructed from the login name and
11624 .conf local@_from@_suffix string unset
11625 See \local@_from@_prefix\ above.
11627 .conf local@_interfaces "string list" "see below"
11628 This option controls which network interfaces are used by the daemon for
11629 listening; they are also used to identify the local host when routing. Chapter
11630 ~~CHAPinterfaces contains a full description of this option and the related
11631 options \extra@_local@_interfaces\ and \hosts@_treat@_as@_local\. The default
11632 value for \local@_interfaces\ is
11634 local_interfaces = 0.0.0.0
11636 when Exim is built without IPv6 support; otherwise it is
11638 local_interfaces = <; ::0 ; 0.0.0.0
11641 .conf local@_scan@_timeout time 5m
11642 .index timeout||for \*local@_scan()*\ function
11643 .index \*local@_scan()*\ function||timeout
11644 This timeout applies to the \*local@_scan()*\ function (see chapter
11645 ~~CHAPlocalscan). Zero means `no timeout'. If the timeout is exceeded, the
11646 incoming message is rejected with a temporary error if it is an SMTP message.
11647 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
11648 code. The incident is logged on the main and reject logs.
11651 .conf local@_sender@_retain boolean false
11652 .index ::Sender:: header line||retaining from local submission
11653 When a message is submitted locally (that is, not over a TCP/IP connection) by
11654 an untrusted user, Exim removes any existing ::Sender:: header line. If you
11655 do not want this to happen, you must set \local@_sender@_retain\, and you must
11656 also set \local@_from@_check\ to be false (Exim will complain if you do not).
11657 Section ~~SECTthesenhea has more details about ::Sender:: processing.
11661 .conf localhost@_number string$**$ unset
11662 .index host||locally unique number for
11663 .index message||ids, with multiple hosts
11664 Exim's message ids are normally unique only within the local host. If
11665 uniqueness among a set of hosts is required, each host must set a different
11666 value for the \localhost@_number\ option. The string is expanded immediately
11667 after reading the configuration file (so that a number can be computed from the
11668 host name, for example) and the result of the expansion must be a number in the
11669 range 0--16 (or 0--10 on operating systems with case-insensitive file systems).
11670 This is available in subsequent string expansions via the variable
11671 \$localhost@_number$\. When \localhost@_number is set\, the final two
11672 characters of the message id, instead of just being a fractional part of the
11673 time, are computed from the time and the local host number as described in
11674 section ~~SECTmessiden.
11677 .conf log@_file@_path "string list$**$" "set at compile time"
11678 .index log||file path for
11679 This option sets the path which is used to determine the names of Exim's log
11680 files, or indicates that logging is to be to syslog, or both. It is expanded
11681 when Exim is entered, so it can, for example, contain a reference to the host
11682 name. If no specific path is set for the log files at compile or run time, they
11683 are written in a sub-directory called \(log)\ in Exim's spool directory.
11684 Chapter ~~CHAPlog contains further details about Exim's logging, and section
11685 ~~SECTwhelogwri describes how the contents of \log@_file@_path\ are used. If
11686 this string is fixed at your installation (contains no expansion variables) it
11687 is recommended that you do not set this option in the configuration file, but
11688 instead supply the path using \\LOG@_FILE@_PATH\\ in \(Local/Makefile)\ so that
11689 it is available to Exim for logging errors detected early on -- in particular,
11690 failure to read the configuration file.
11692 .conf log@_selector string unset
11693 .index log||selectors
11694 This option can be used to reduce or increase the number of things that Exim
11695 writes to its log files. Its argument is made up of names preceded by plus or
11696 minus characters. For example:
11698 log_selector = +arguments -retry_defer
11700 A list of possible names and what they control is given in the chapter on
11701 logging, in section ~~SECTlogselector.
11703 .conf log@_timezone boolean false
11704 .index log||timezone for entries
11705 By default, the timestamps on log lines are in local time without the
11706 timezone. This means that if your timezone changes twice a year, the timestamps
11707 in log lines are ambiguous for an hour when the clocks go back. One way of
11708 avoiding this problem is to set the timezone to UTC. An alternative is to set
11709 \log@_timezone\ true. This turns on the addition of the timezone offset to
11710 timestamps in log lines. Turning on this option can add quite a lot to the size
11711 of log files because each line is extended by 6 characters. Note that the
11712 \$tod@_log$\ variable contains the log timestamp without the zone, but there is
11713 another variable called \$tod@_zone$\ that contains just the timezone offset.
11715 .conf lookup@_open@_max integer 25
11716 .index too many open files
11717 .index open files, too many
11718 .index file||too many open
11719 .index lookup||maximum open files
11720 .index limit||open files for lookups
11721 This option limits the number of simultaneously open files for single-key
11722 lookups that use regular files (that is, \%lsearch%\, \%dbm%\, and \%cdb%\). Exim
11723 normally keeps these files open during routing, because often the same file is
11724 required several times. If the limit is reached, Exim closes the least recently
11725 used file. Note that if you are using the \*ndbm*\ library, it actually opens
11726 two files for each logical DBM database, though it still counts as one for the
11727 purposes of \lookup@_open@_max\. If you are getting `too many open files'
11728 errors with NDBM, you need to reduce the value of \lookup@_open@_max\.
11730 .conf max@_username@_length integer 0
11731 .index length of login name
11732 .index user name||maximum length
11733 .index limit||user name length
11734 Some operating systems are broken in that they truncate long arguments to
11735 \*getpwnam()*\ to eight characters, instead of returning `no such user'. If
11736 this option is set greater than zero, any attempt to call \*getpwnam()*\ with
11737 an argument that is longer behaves as if \*getpwnam()*\ failed.
11740 .conf message@_body@_visible integer 500
11741 .index body of message||visible size
11742 .index message||body, visible size
11743 This option specifies how much of a message's body is to be included in the
11744 \$message@_body$\ and \$message@_body@_end$\ expansion variables.
11746 .conf message@_id@_header@_domain string$**$ unset
11747 .index ::Message-ID:: header line
11748 If this option is set, the string is expanded and used as the right hand side
11749 (domain) of the ::Message-ID:: header that Exim creates if a
11750 locally-originated incoming message does not have one. `Locally-originated'
11751 means `not received over TCP/IP.'
11752 Otherwise, the primary host name is used.
11753 Only letters, digits, dot and hyphen are accepted; any other characters are
11754 replaced by hyphens. If the expansion is forced to fail, or if the result is an
11755 empty string, the option is ignored.
11757 .conf message@_id@_header@_text string$**$ unset
11758 If this variable is set, the string is expanded and used to augment the text of
11759 the ::Message-id:: header that Exim creates if a
11761 incoming message does not have one. The text of this header is required by RFC
11762 2822 to take the form of an address. By default, Exim uses its internal message
11763 id as the local part, and the primary host name as the domain. If this option
11764 is set, it is expanded, and provided the expansion is not forced to fail, and
11765 does not yield an empty string, the result is inserted into the header
11766 immediately before the @@, separated from the internal message id by a dot. Any
11767 characters that are illegal in an address are automatically converted into
11768 hyphens. This means that variables such as \$tod@_log$\ can be used, because
11769 the spaces and colons will become hyphens.
11771 .conf message@_logs boolean true
11772 .index message||log, disabling
11773 .index log||message log, disabling
11774 If this option is turned off, per-message log files are not created in the
11775 \(msglog)\ spool sub-directory. This reduces the amount of disk I/O required by
11776 Exim, by reducing the number of files involved in handling a message from a
11777 minimum of four (header spool file, body spool file, delivery journal, and
11778 per-message log) to three. The other major I/O activity is Exim's main log,
11779 which is not affected by this option.
11781 .conf message@_size@_limit string$**$ 50M
11782 .index message||size limit
11783 .index limit||message size
11784 .index size||of message, limit
11785 This option limits the maximum size of message that Exim will process. The
11786 value is expanded for each incoming
11787 connection so, for example, it can be made to depend on the IP address of the
11788 remote host for messages arriving via TCP/IP. \**Note**\: This limit cannot be
11789 made to depend on a message's sender or any other properties of an individual
11790 message, because it has to be advertised in the server's response to \\EHLO\\.
11791 String expansion failure causes a temporary error. A value of zero means no
11792 limit, but its use is not recommended. See also \bounce@_return@_size@_limit\.
11794 Incoming SMTP messages are failed with a 552 error if the limit is
11795 exceeded; locally-generated messages either get a stderr message or a delivery
11796 failure message to the sender, depending on the \-oe-\ setting. Rejection of an
11797 oversized message is logged in both the main and the reject logs. See also the
11798 generic transport option \message@_size@_limit\, which limits the size of
11799 message that an individual transport can process.
11801 .conf move@_frozen@_messages boolean false
11802 .index frozen messages||moving
11803 This option, which is available only if Exim has been built with the setting
11805 SUPPORT_MOVE_FROZEN_MESSAGES=yes
11807 in \(Local/Makefile)\, causes frozen messages and their message logs to be
11808 moved from the \(input)\ and \(msglog)\ directories on the spool to \(Finput)\
11809 and \(Fmsglog)\, respectively. There is currently no support in Exim or the
11810 standard utilities for handling such moved messages, and they do not show up in
11811 lists generated by \-bp-\ or by the Exim monitor.
11813 .conf mysql@_servers "string list" unset
11814 .index MySQL||server list
11815 This option provides a list of MySQL servers and associated connection data, to
11816 be used in conjunction with \%mysql%\ lookups (see section ~~SECTsql). The
11817 option is available only if Exim has been built with MySQL support.
11819 .conf never@_users "string list" unset
11820 Local message deliveries are normally run in processes that are setuid to the
11821 recipient, and remote deliveries are normally run under Exim's own uid and gid.
11822 It is usually desirable to prevent any deliveries from running as root, as a
11825 When Exim is built, an option called \\FIXED@_NEVER@_USERS\\ can be set to a
11826 list of users that must not be used for local deliveries. This list is fixed in
11827 the binary and cannot be overridden by the configuration file. By default, it
11828 contains just the single user name `root'. The \never@_users\ runtime option
11829 can be used to add more users to the fixed list.
11831 If a message is to be delivered as one of the users on the fixed list or the
11832 \never@_users\ list, an error occurs, and delivery is deferred. A common
11835 never@_users = root:daemon:bin
11837 Including root is redundant if it is also on the fixed list, but it does no
11839 This option overrides the \pipe@_as@_creator\ option of the \%pipe%\ transport
11842 .conf oracle@_servers "string list" unset
11843 .index Oracle||server list
11844 This option provides a list of Oracle servers and associated connection data,
11845 to be used in conjunction with \%oracle%\ lookups (see section ~~SECTsql). The
11846 option is available only if Exim has been built with Oracle support.
11848 .conf percent@_hack@_domains "domain list$**$" unset
11849 .index `percent hack'
11850 .index source routing||in email address
11851 .index address||source-routed
11852 The `percent hack' is the convention whereby a local part containing a percent
11853 sign is re-interpreted as a new email address, with the percent replaced by @@.
11854 This is sometimes called `source routing', though that term is also applied to
11855 RFC 2822 addresses that begin with an @@ character. If this option is set, Exim
11856 implements the percent facility for those domains listed, but no others. This
11857 happens before an incoming SMTP address is tested against an ACL.
11859 \**Warning**\: The `percent hack' has often been abused by people who are
11860 trying to get round relaying restrictions. For this reason, it is best avoided
11861 if at all possible. Unfortunately, a number of less security-conscious MTAs
11862 implement it unconditionally. If you are running Exim on a gateway host, and
11863 routing mail through to internal MTAs without processing the local parts, it is
11864 a good idea to reject recipient addresses with percent characters in their
11865 local parts. Exim's default configuration does this.
11867 .conf perl@_at@_start boolean false
11868 This option is available only when Exim is built with an embedded Perl
11869 interpreter. See chapter ~~CHAPperl for details of its use.
11871 .conf perl@_startup string unset
11872 This option is available only when Exim is built with an embedded Perl
11873 interpreter. See chapter ~~CHAPperl for details of its use.
11875 .conf pgsql@_servers "string list" unset
11876 .index PostgreSQL lookup type||server list
11877 This option provides a list of PostgreSQL servers and associated connection
11878 data, to be used in conjunction with \%pgsql%\ lookups (see section ~~SECTsql).
11879 The option is available only if Exim has been built with PostgreSQL support.
11881 .conf pid@_file@_path string$**$ "set at compile time"
11882 .index daemon||pid file path
11883 .index pid file, path for
11884 This option sets the name of the file to which the Exim daemon writes its
11885 process id. The string is expanded, so it can contain, for example, references
11888 pid_file_path = /var/log/$primary_hostname/exim.pid
11890 If no path is set, the pid is written to the file \(exim-daemon.pid)\ in Exim's
11892 The value set by the option can be overridden by the \-oP-\ command line
11893 option. A pid file is not written if a `non-standard' daemon is run by means of
11894 the \-oX-\ option, unless a path is explicitly supplied by \-oP-\.
11896 .conf pipelining@_advertise@_hosts "host list$**$" $*$
11897 .index \\PIPELINING\\||advertising, suppressing
11898 This option can be used to suppress the advertisement of the SMTP
11899 \\PIPELINING\\ extension to specific hosts. When \\PIPELINING\\ is not
11900 advertised and \smtp@_enforce@_sync\ is true, an Exim server enforces strict
11901 synchronization for each SMTP command and response.
11902 When \\PIPELINING\\ is advertised, Exim assumes that clients will use it; `out
11903 of order' commands that are `expected' do not count as protocol errors (see
11904 \smtp@_max@_synprot@_errors\).
11906 .conf preserve@_message@_logs boolean false
11907 .index message logs, preserving
11908 If this option is set, message log files are not deleted when messages are
11909 completed. Instead, they are moved to a sub-directory of the spool directory
11910 called \(msglog.OLD)\, where they remain available for statistical or debugging
11911 purposes. This is a dangerous option to set on systems with any appreciable
11912 volume of mail. Use with care!
11914 .conf primary@_hostname string "see below"
11915 .index name||of local host
11916 .index host||name of local
11917 .index local host||name of
11918 This specifies the name of the current host. It is used in the default \\EHLO\\
11919 or \\HELO\\ command for outgoing SMTP messages (changeable via the \helo@_data\
11920 option in the \%smtp%\ transport),
11921 and as the default for \qualify@_domain\. If it is not set, Exim calls
11922 \*uname()*\ to find it. If this fails, Exim panics and dies. If the name
11923 returned by \*uname()*\ contains only one component, Exim passes it to
11924 \*gethostbyname()*\ (or \*getipnodebyname()*\ when available) in order to
11925 obtain the fully qualified version.
11927 The value of \$primary@_hostname$\ is also used by default in some SMTP
11928 response messages from an Exim server. This can be changed dynamically by
11929 setting \smtp@_active@_hostname\.
11931 .conf print@_topbitchars boolean false
11932 .index printing characters
11933 .index 8-bit characters
11934 By default, Exim considers only those characters whose codes lie in the range
11935 32--126 to be printing characters. In a number of circumstances (for example,
11936 when writing log entries) non-printing characters are converted into escape
11937 sequences, primarily to avoid messing up the layout. If \print@_topbitchars\ is
11938 set, code values of 128 and above are also considered to be printing
11941 .conf process@_log@_path string unset
11942 .index process log path
11943 .index log||process log
11945 This option sets the name of the file to which an Exim process writes its
11946 `process log' when sent a USR1 signal. This is used by the \*exiwhat*\ utility
11947 script. If this option is unset, the file called \(exim-process.info)\ in
11948 Exim's spool directory is used. The ability to specify the name explicitly can
11949 be useful in environments where two different Exims are running, using
11950 different spool directories.
11952 .conf prod@_requires@_admin boolean true
11953 .index \-M-\ option
11954 .index \-R-\ option
11955 .index \-q-\ option
11956 The \-M-\, \-R-\, and \-q-\ command-line options require the caller to be an
11957 admin user unless \prod@_requires@_admin\ is set false. See also
11958 \queue@_list@_requires@_admin\.
11960 .conf qualify@_domain string "see below"
11961 .index domain||for qualifying addresses
11962 .index address||qualification
11963 This option specifies the domain name that is added to any sender addresses
11964 that do not have a domain qualification. It also applies to recipient addresses
11965 if \qualify@_recipient\ is not set. Such addresses are accepted by default only
11966 for locally-generated messages. Messages from external sources must always
11967 contain fully qualified addresses, unless the sending host matches
11968 \sender@_unqualified@_hosts\ or \recipient@_unqualified@_hosts\ (as
11969 appropriate), in which case incoming addresses are qualified with
11970 \qualify@_domain\ or \qualify@_recipient\ as necessary. Internally, Exim always
11971 works with fully qualified addresses.
11972 If \qualify@_domain\ is not set, it defaults to the \primary@_hostname\ value.
11974 .conf qualify@_recipient string "see below"
11975 This specifies the domain name that is added to any recipient addresses that do
11976 not have a domain qualification. Such addresses are accepted by default only
11977 for locally-generated messages. Messages from external sources must always
11978 contain fully qualified recipient addresses, unless the sending host matches
11979 \recipient@_unqualified@_hosts\,
11980 in which case incoming recipient addresses are qualified with
11981 \qualify@_recipient\.
11982 If \qualify@_recipient\ is not set, it defaults to the \qualify@_domain\ value.
11984 .conf queue@_domains "domain list$**$" unset
11985 .index domain||specifying non-immediate delivery
11986 .index queueing incoming messages
11987 .index message||queueing certain domains
11988 This option lists domains for which immediate delivery is not required.
11989 A delivery process is started whenever a message is received, but only those
11990 domains that do not match are processed. All other deliveries wait until the
11991 next queue run. See also \hold@_domains\ and \queue@_smtp@_domains\.
11993 .conf queue@_list@_requires@_admin boolean true
11994 .index \-bp-\ option
11995 The \-bp-\ command-line option, which lists the messages that are on the queue,
11996 requires the caller to be an admin user unless \queue__list__requires__admin\
11997 is set false. See also \prod@_requires@_admin\.
11999 .conf queue@_only boolean false
12000 .index queueing incoming messages
12001 .index message||queueing unconditionally
12002 If \queue@_only\ is set, a delivery process is not automatically started
12003 whenever a message is received. Instead, the message waits on the queue for the
12004 next queue run. Even if \queue@_only\ is false, incoming messages may not get
12005 delivered immediately when certain conditions (such as heavy load) occur.
12007 The \-odq-\ command line has the same effect as \queue@_only\. The \-odb-\ and
12008 \-odi-\ command line options override \queue@_only\ unless
12009 \queue@_only@_override\ is set false. See also \queue@_only@_file\,
12010 \queue@_only@_load\, and \smtp@_accept@_queue\.
12012 .conf queue@_only@_file string unset
12013 .index queueing incoming messages
12014 .index message||queueing by file existence
12015 This option can be set to a colon-separated list of absolute path names, each
12016 one optionally preceded by `smtp'. When Exim is receiving a message,
12017 it tests for the existence of each listed path using a call to \*stat()*\. For
12018 each path that exists, the corresponding queuing option is set.
12019 For paths with no prefix, \queue@_only\ is set; for paths prefixed by `smtp',
12020 \queue@_smtp@_domains\ is set to match all domains. So, for example,
12022 queue_only_file = smtp/some/file
12024 causes Exim to behave as if \queue@_smtp@_domains\ were set to `$*$' whenever
12025 \(/some/file)\ exists.
12027 .conf queue@_only@_load fixed-point unset
12028 .index load average
12029 .index queueing incoming messages
12030 .index message||queueing by load
12031 If the system load average is higher than this value, incoming messages from
12032 all sources are queued, and no automatic deliveries are started. If this
12033 happens during local or remote SMTP input, all subsequent messages on the same
12034 connection are queued. Deliveries will subsequently be performed by queue
12035 runner processes. This option has no effect on ancient operating systems on
12036 which Exim cannot determine the load average. See also
12037 \deliver@_queue@_load@_max\ and \smtp@_load@_reserve\.
12039 .conf queue@_only@_override boolean true
12040 .index queueing incoming messages
12041 When this option is true, the \-od\*x*\-\ command line options override the
12042 setting of \queue@_only\ or \queue@_only@_file\ in the configuration file. If
12043 \queue@_only@_override\ is set false, the \-od\*x*\-\ options cannot be used to
12044 override; they are accepted, but ignored.
12046 .conf queue@_run@_in@_order boolean false
12047 .index queue runner||processing messages in order
12048 If this option is set, queue runs happen in order of message arrival instead of
12049 in an arbitrary order. For this to happen, a complete list of the entire queue
12050 must be set up before the deliveries start. When the queue is all in a single
12051 directory (the default), this happens anyway, but if \split@_spool@_directory\
12052 is set it does not -- for delivery in random order, the sub-directories are
12053 processed one at a time (in random order), to avoid setting up one huge list.
12054 Thus, setting \queue@_run@_in@_order\ with \split@_spool@_directory\ may
12055 degrade performance when the queue is large. In most situations,
12056 \queue@_run@_in@_order\ should not be set.
12058 .conf queue@_run@_max integer 5
12059 .index queue runner||maximum number of
12060 This controls the maximum number of queue runner processes that an Exim daemon
12061 can run simultaneously. This does not mean that it starts them all at once,
12062 but rather that if the maximum number are still running when the time comes to
12063 start another one, it refrains from starting another one. This can happen with
12064 very large queues and/or very sluggish deliveries. This option does not,
12065 however, interlock with other processes, so additional queue runners can be
12066 started by other means, or by killing and restarting the daemon.
12068 .conf queue@_smtp@_domains "domain list$**$" unset
12069 .index queueing incoming messages
12070 .index message||queueing remote deliveries
12071 When this option is set, a delivery process is started whenever a message is
12072 received, routing is performed, and local deliveries take place.
12073 However, if any SMTP deliveries are required for domains that match
12074 \queue@_smtp@_domains\, they are not immediately delivered, but instead the
12075 message waits on the queue for the next queue run. Since routing of the message
12076 has taken place, Exim knows to which remote hosts it must be delivered, and so
12077 when the queue run happens, multiple messages for the same host are delivered
12078 over a single SMTP connection. The \-odqs-\ command line option causes all SMTP
12079 deliveries to be queued in this way, and is equivalent to setting
12080 \queue@_smtp@_domains\ to `$*$'. See also \hold@_domains\ and \queue@_domains\.
12082 .conf receive@_timeout time 0s
12083 .index timeout||for non-SMTP input
12084 This option sets the timeout for accepting a non-SMTP message, that is, the
12085 maximum time that Exim waits when reading a message on the standard input. If
12086 the value is zero, it will wait for ever. This setting is overridden by the
12087 \-or-\ command line option. The timeout for incoming SMTP messages is
12088 controlled by \smtp@_receive@_timeout\.
12090 .index customizing|| ::Received:: header
12091 .index ::Received:: header line||customizing
12092 .conf received@_header@_text string$**$ "see below"
12093 This string defines the contents of the ::Received:: message header that is
12094 added to each message, except for the timestamp, which is automatically added
12095 on at the end (preceded by a semicolon). The string is expanded each time it is
12096 used. If the expansion yields an empty string, no ::Received:: header line is
12097 added to the message. Otherwise, the string should start with the text
12098 `Received:' and conform to the RFC 2822 specification for ::Received:: header
12099 lines. The default setting is:
12101 received_header_text = Received: \
12102 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
12103 {${if def:sender_ident {from $sender_ident }}\
12104 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
12105 by $primary_hostname \
12106 ${if def:received_protocol {with $received_protocol}} \
12107 ${if def:tls_cipher {($tls_cipher)\n\t}}\
12108 (Exim $version_number)\n\t\
12110 ${if def:received_for {\n\tfor $received_for}}
12112 Note the use of quotes, to allow the sequences \"@\n"\ and \"@\t"\ to be used
12113 for newlines and tabs, respectively. The reference to the TLS cipher is omitted
12114 when Exim is built without TLS support. The use of conditional expansions
12115 ensures that this works for both locally generated messages and messages
12116 received from remote hosts, giving header lines such as the following:
12118 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
12119 by marley.carol.example with esmtp (Exim 4.00)
12120 id 16IOWa-00019l-00
12121 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
12122 Received: by scrooge.carol.example with local (Exim 4.00)
12123 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
12125 Until the body of the message has been received, the timestamp is the time when
12126 the message started to be received. Once the body has arrived, and all policy
12127 checks have taken place, the timestamp is updated to the time at which the
12128 message was accepted.
12130 .conf received@_headers@_max integer 30
12131 .index loop||prevention
12132 .index mail loop prevention
12133 .index ::Received:: header line||counting
12134 When a message is to be delivered, the number of ::Received:: headers is
12135 counted, and if it is greater than this parameter, a mail loop is assumed to
12136 have occurred, the delivery is abandoned, and an error message is generated.
12137 This applies to both local and remote deliveries.
12139 .conf recipient@_unqualified@_hosts "host list$**$" unset
12140 .index unqualified addresses
12141 .index host||unqualified addresses from
12142 This option lists those hosts from which Exim is prepared to accept unqualified
12143 recipient addresses in message envelopes. The addresses are made fully
12144 qualified by the addition of the \qualify@_recipient\ value. This option also
12145 affects message header lines. Exim does not reject unqualified recipient
12146 addresses in headers, but it qualifies them only if the message came from a
12147 host that matches \recipient@_unqualified@_hosts\,
12148 or if the message was submitted locally (not using TCP/IP), and the \-bnq-\
12149 option was not set.
12151 .conf recipients@_max integer 0
12152 .index limit||number of recipients
12153 .index recipient||maximum number
12154 If this option is set greater than zero, it specifies the maximum number of
12155 original recipients for any message. Additional recipients that are generated
12156 by aliasing or forwarding do not count. SMTP messages get a 452 response for
12157 all recipients over the limit; earlier recipients are delivered as normal.
12158 Non-SMTP messages with too many recipients are failed, and no deliveries are
12160 .index \\RCPT\\||maximum number of incoming
12161 Note that the RFCs specify that an SMTP server should accept at least 100
12162 \\RCPT\\ commands in a single message.
12164 .conf recipients@_max@_reject boolean false
12165 If this option is set true, Exim rejects SMTP messages containing too many
12166 recipients by giving 552 errors to the surplus \\RCPT\\ commands, and a 554
12167 error to the eventual \\DATA\\ command. Otherwise (the default) it gives a 452
12168 error to the surplus \\RCPT\\ commands and accepts the message on behalf of the
12169 initial set of recipients. The remote server should then re-send the message
12170 for the remaining recipients at a later time.
12172 .conf remote@_max@_parallel integer 2
12173 .index delivery||parallelism for remote
12174 This option controls parallel delivery of one message to a number of remote
12175 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
12176 does all the remote deliveries for a message one by one. Otherwise, if a single
12177 message has to be delivered to more than one remote host, or if several copies
12178 have to be sent to the same remote host, up to \remote@_max@_parallel\
12179 deliveries are done simultaneously. If more than \remote@_max@_parallel\
12180 deliveries are required, the maximum number of processes are started, and as
12181 each one finishes, another is begun. The order of starting processes is the
12182 same as if sequential delivery were being done, and can be controlled by the
12183 \remote@_sort@_domains\ option. If parallel delivery takes place while running
12184 with debugging turned on, the debugging output from each delivery process is
12185 tagged with its process id.
12187 This option controls only the maximum number of parallel deliveries for one
12188 message in one Exim delivery process. Because Exim has no central queue
12189 manager, there is no way of controlling the total number of simultaneous
12190 deliveries if the configuration allows a delivery attempt as soon as a message
12192 .index number of deliveries
12193 .index delivery||maximum number of
12194 If you want to control the total number of deliveries on the system, you
12195 need to set the \queue@_only\ option. This ensures that all incoming messages
12196 are added to the queue without starting a delivery process. Then set up an Exim
12197 daemon to start queue runner processes at appropriate intervals (probably
12198 fairly often, for example, every minute), and limit the total number of queue
12199 runners by setting the \queue__run__max\ parameter. Because each queue runner
12200 delivers only one message at a time, the maximum number of deliveries that can
12201 then take place at once is \queue@_run@_max\ multiplied by
12202 \remote@_max@_parallel\.
12204 If it is purely remote deliveries you want to control, use \queue@_smtp\
12205 instead of \queue@_only\. This has the added benefit of doing the SMTP routing
12206 before queuing, so that several messages for the same host will eventually get
12207 delivered down the same connection.
12209 .conf remote@_sort@_domains "domain list$**$" unset
12210 .index sorting remote deliveries
12211 .index delivery||sorting remote
12212 When there are a number of remote deliveries for a message, they are sorted by
12213 domain into the order given by this list. For example,
12215 remote_sort_domains = *.cam.ac.uk:*.uk
12217 would attempt to deliver to all addresses in the \*cam.ac.uk*\ domain first, then
12218 to those in the \uk\ domain, then to any others.
12220 .conf retry@_data@_expire time 7d
12221 .index hints database||data expiry
12222 This option sets a `use before' time on retry information in Exim's hints
12223 database. Any older retry data is ignored. This means that, for example, once a
12224 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
12227 .conf retry@_interval@_max time 24h
12228 .index retry||limit on interval
12229 .index limit||on retry interval
12230 Chapter ~~CHAPretry describes Exim's mechanisms for controlling the intervals
12231 between delivery attempts for messages that cannot be delivered straight away.
12232 This option sets an overall limit to the length of time between retries.
12234 .conf return@_path@_remove boolean true
12235 .index ::Return-path:: header line||removing
12236 RFC 2821, section 4.4, states that an SMTP server must insert a ::Return-path::
12237 header line into a message when it makes a `final delivery'. The ::Return-path::
12238 header preserves the sender address as received in the \\MAIL\\ command. This
12239 description implies that this header should not be present in an incoming
12240 message. If \return@_path@_remove\ is true, any existing ::Return-path::
12241 headers are removed from messages at the time they are received. Exim's
12242 transports have options for adding ::Return-path:: headers at the time of
12243 delivery. They are normally used only for final local deliveries.
12245 .conf return@_size@_limit integer 100K
12246 This option is an obsolete synonym for \bounce@_return@_size@_limit\.
12248 .conf rfc1413@_hosts "host list$**$" $*$
12250 .index host||for RFC 1413 calls
12251 RFC 1413 identification calls are made to any client host which matches an item
12254 .conf rfc1413@_query@_timeout time 30s
12255 .index RFC 1413||query timeout
12256 .index timeout||for RFC 1413 call
12257 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
12258 no RFC 1413 calls are ever made.
12260 .conf sender@_unqualified@_hosts "host list$**$" unset
12261 .index unqualified addresses
12262 .index host||unqualified addresses from
12263 This option lists those hosts from which Exim is prepared to accept unqualified
12264 sender addresses. The addresses are made fully qualified by the addition of
12265 \qualify@_domain\. This option also affects message header lines. Exim does not
12266 reject unqualified addresses in headers that contain sender addresses, but it
12267 qualifies them only if the message came from a host that matches
12268 \sender@_unqualified@_hosts\,
12269 or if the message was submitted locally (not using TCP/IP), and the \-bnq-\
12270 option was not set.
12272 .conf smtp@_accept@_keepalive boolean true
12273 .index keepalive||on incoming connection
12274 This option controls the setting of the \\SO@_KEEPALIVE\\ option on incoming
12275 TCP/IP socket connections. When set, it causes the kernel to probe idle
12276 connections periodically, by sending packets with `old' sequence numbers. The
12277 other end of the connection should send an acknowledgement if the connection is
12278 still okay or a reset if the connection has been aborted. The reason for doing
12279 this is that it has the beneficial effect of freeing up certain types of
12280 connection that can get stuck when the remote host is disconnected without
12281 tidying up the TCP/IP call properly. The keepalive mechanism takes several
12282 hours to detect unreachable hosts.
12285 .conf smtp@_accept@_max integer 20
12286 .index limit||incoming SMTP connections
12287 .index SMTP||incoming connection count
12289 This option specifies the maximum number of simultaneous incoming SMTP calls
12290 that Exim will accept. It applies only to the listening daemon; there is no
12291 control (in Exim) when incoming SMTP is being handled by \*inetd*\. If the value
12292 is set to zero, no limit is applied. However, it is required to be non-zero if
12293 either \smtp@_accept@_max@_per@_host\ or \smtp@_accept@_queue\ is set. See also
12294 \smtp@_accept@_reserve\.
12297 .conf smtp@_accept@_max@_nonmail integer 10
12298 .index limit||non-mail SMTP commands
12299 .index SMTP||limiting non-mail commands
12300 Exim counts the number of `non-mail' commands in an SMTP session, and drops the
12301 connection if there are too many. This option defines `too many'. The check
12302 catches some denial-of-service attacks, repeated failing \\AUTH\\s, or a mad
12303 client looping sending \\EHLO\\, for example. The check is applied only if the
12304 client host matches \smtp@_accept@_max@_nonmail@_hosts\.
12306 When a new message is expected, one occurrence of \\RSET\\ is not counted. This
12307 allows a client to send one \\RSET\\ between messages (this is not necessary,
12308 but some clients do it). Exim also allows one uncounted occurence of \\HELO\\
12309 or \\EHLO\\, and one occurrence of \\STARTTLS\\ between messages. After
12310 starting up a TLS session, another \\EHLO\\ is expected, and so it too is not
12311 counted. The first occurrence of \\AUTH\\ in a connection, or immediately
12312 following \\STARTTLS\\ is not counted. Otherwise, all commands other than
12313 \\MAIL\\, \\RCPT\\, \\DATA\\, and \\QUIT\\ are counted.
12315 .conf smtp@_accept@_max@_nonmail@_hosts "host list$**$" $*$
12316 You can control which hosts are subject to the \smtp@_accept@_max@_nonmail\
12317 check by setting this option. The default value makes it apply to all hosts. By
12318 changing the value, you can exclude any badly-behaved hosts that you have to
12322 .conf smtp@_accept@_max@_per@_connection integer 1000
12323 .index SMTP||incoming message count, limiting
12324 .index limit||messages per SMTP connection
12325 The value of this option limits the number of \\MAIL\\ commands that Exim is
12326 prepared to accept over a single SMTP connection, whether or not each command
12327 results in the transfer of a message. After the limit is reached, a 421
12328 response is given to subsequent \\MAIL\\ commands. This limit is a safety
12329 precaution against a client that goes mad (incidents of this type have been
12332 .conf smtp@_accept@_max@_per@_host string$**$ unset
12333 .index limit||SMTP connections from one host
12334 .index host||limiting SMTP connections from
12335 This option restricts the number of simultaneous IP connections from a single
12336 host (strictly, from a single IP address) to the Exim daemon. The option is
12337 expanded, to enable different limits to be applied to different hosts by
12338 reference to \$sender@_host@_address$\. Once the limit is reached, additional
12339 connection attempts from the same host are rejected with error code 421. The
12340 default value of zero imposes no limit. If this option is set, it is required
12341 that \smtp@_accept@_max\ be non-zero.
12343 \**Warning**\: When setting this option you should not use any expansion
12344 constructions that take an appreciable amount of time. The expansion and test
12345 happen in the main daemon loop, in order to reject additional connections
12346 without forking additional processes (otherwise a denial-of-service attack
12347 could cause a vast number or processes to be created). While the daemon is
12348 doing this processing, it cannot accept any other incoming connections.
12351 .conf smtp@_accept@_queue integer 0
12352 .index SMTP||incoming connection count
12353 .index queueing incoming messages
12354 .index message||queueing by SMTP connection count
12355 If the number of simultaneous incoming SMTP calls handled via the listening
12356 daemon exceeds this value, messages received by SMTP are just placed on the
12357 queue; no delivery processes are started automatically. A value of zero implies
12358 no limit, and clearly any non-zero value is useful only if it is less than the
12359 \smtp@_accept@_max\ value (unless that is zero). See also \queue@_only\,
12360 \queue@_only@_load\, \queue@_smtp@_domains\, and the various \-od-\ command
12363 .conf smtp@_accept@_queue@_per@_connection integer 10
12364 .index queueing incoming messages
12365 .index message||queueing by message count
12366 This option limits the number of delivery processes that Exim starts
12367 automatically when receiving messages via SMTP, whether via the daemon or by
12368 the use of \-bs-\ or \-bS-\. If the value of the option is greater than zero,
12369 and the number of messages received in a single SMTP session exceeds this
12370 number, subsequent messages are placed on the queue, but no delivery processes
12371 are started. This helps to limit the number of Exim processes when a server
12372 restarts after downtime and there is a lot of mail waiting for it on other
12373 systems. On large systems, the default should probably be increased, and on
12374 dial-in client systems it should probably be set to zero (that is, disabled).
12376 .conf smtp@_accept@_reserve integer 0
12377 .index SMTP||incoming call count
12378 .index host||reserved
12379 When \smtp@_accept@_max\ is set greater than zero, this option specifies a
12380 number of SMTP connections that are reserved for connections from the hosts
12381 that are specified in \smtp@_reserve@_hosts\. The value set in
12382 \smtp@_accept@_max\ includes this reserve pool. The specified hosts are not
12383 restricted to this number of connections; the option specifies a minimum number
12384 of connection slots for them, not a maximum. It is a guarantee that that group
12385 of hosts can always get at least \smtp@_accept@_reserve\ connections.
12387 For example, if \smtp@_accept@_max\ is set to 50 and \smtp@_accept@_reserve\ is
12388 set to 5, once there are 45 active connections (from any hosts), new
12389 connections are accepted only from hosts listed in \smtp@_reserve@_hosts\.
12390 See also \smtp@_accept@_max@_per@_host\.
12392 .conf smtp@_active@_hostname string$**$ unset
12393 .index host||name in SMTP responses
12394 .index SMTP||host name in responses
12395 This option is provided for multi-homed servers that want to masquerade as
12396 several different hosts. At the start of an SMTP connection, its value is
12397 expanded and used instead of the value of \$primary@_hostname$\ in SMTP
12398 responses. For example, it is used as domain name in the response to an
12399 incoming \\HELO\\ or \\EHLO\\ command. If this option is unset, or if its
12400 expansion is forced to fail, or if the expansion results in an empty string,
12401 the value of \$primary@_hostname$\ is used. Other expansion failures cause a
12402 message to be written to the main and panic logs, and the SMTP command receives
12403 a temporary error. Typically, the value of \smtp@_active@_hostname\ depends on
12404 the incoming interface address. For example:
12406 smtp_active_hostname = ${if eq{$interface_address}{10.0.0.1}\
12407 {cox.mydomain}{box.mydomain}}
12409 If you set \smtp@_active@_hostname\, you probably also want to set
12410 \smtp@_banner\, since its default value references \$primary@_hostname$\.
12412 .conf smtp@_banner string$**$ "see below"
12413 .index SMTP||welcome banner
12414 .index banner for SMTP
12415 .index welcome banner for SMTP
12416 .index customizing||SMTP banner
12417 This string, which is expanded every time it is used, is output as the initial
12418 positive response to an SMTP connection. The default setting is:
12420 smtp_banner = $primary_hostname ESMTP Exim $version_number \
12423 Failure to expand the string causes a panic error. If you want to create a
12424 multiline response to the initial SMTP connection, use `@\n' in the string at
12425 appropriate points, but not at the end. Note that the 220 code is not included
12426 in this string. Exim adds it automatically (several times in the case of a
12427 multiline response).
12429 .conf smtp@_check@_spool@_space boolean true
12430 .index checking disk space
12431 .index disk space, checking
12432 .index spool directory||checking space
12433 When this option is set, if an incoming SMTP session encounters the \\SIZE\\
12434 option on a \\MAIL\\ command, it checks that there is enough space in the
12435 spool directory's partition to accept a message of that size, while still
12436 leaving free the amount specified by \check@_spool@_space\ (even if that value
12437 is zero). If there isn't enough space, a temporary error code is returned.
12439 .conf smtp@_connect@_backlog integer 20
12440 .index connection backlog
12441 .index SMTP||connection backlog
12442 .index backlog of connections
12443 This option specifies a maximum number of waiting SMTP connections. Exim passes
12444 this value to the TCP/IP system when it sets up its listener. Once this number
12445 of connections are waiting for the daemon's attention, subsequent connection
12446 attempts are refused at the TCP/IP level. At least, that is what the manuals
12447 say; in some circumstances such connection attempts have been observed to time
12448 out instead. For large systems it is probably a good idea to increase the
12449 value (to 50, say). It also gives some protection against denial-of-service
12450 attacks by SYN flooding.
12452 .conf smtp@_enforce@_sync boolean true
12453 .index SMTP||synchronization checking
12454 .index synchronization checking in SMTP
12455 The SMTP protocol specification requires the client to wait for a response from
12456 the server at certain points in the dialogue. Without \\PIPELINING\\ these
12457 synchronization points are after every command; with \\PIPELINING\\ they are
12458 fewer, but they still exist. Some spamming sites send out a complete set of
12459 SMTP commands without waiting for any response. Exim protects against this by
12460 rejecting a message if the client has sent further input when it should not
12461 have. The error response `554 SMTP synchronization error' is sent, and the
12462 connection is dropped. Testing for this error cannot be perfect because of
12463 transmission delays (unexpected input may be on its way but not yet received
12464 when Exim checks). However, it does detect many instances. The check can be
12465 disabled by setting \smtp@_enforce@_sync\ false.
12466 See also \pipelining@_advertise@_hosts\.
12468 .conf smtp@_etrn@_command string$**$ unset
12469 .index \\ETRN\\||command to be run
12470 If this option is set, the given command is run whenever an SMTP \\ETRN\\
12471 command is received from a host that is permitted to issue such commands (see
12472 chapter ~~CHAPACL). The string is split up into separate arguments which are
12473 independently expanded. The expansion variable \$domain$\ is set to the
12474 argument of the \\ETRN\\ command, and no syntax checking is done on it. For
12477 smtp_etrn_command = /etc/etrn_command $domain $sender_host_address
12479 A new process is created to run the command, but Exim does not wait for it to
12480 complete. Consequently, its status cannot be checked. If the command cannot be
12481 run, a line is written to the panic log, but the \\ETRN\\ caller still receives
12482 a 250 success response. Exim is normally running under its own uid when
12483 receiving SMTP, so it is not possible for it to change the uid before running
12486 .conf smtp@_etrn@_serialize boolean true
12487 .index \\ETRN\\||serializing
12488 When this option is set, it prevents the simultaneous execution of more than
12489 one identical command as a result of \\ETRN\\ in an SMTP connection. See
12490 section ~~SECTETRN for details.
12492 .conf smtp@_load@_reserve fixed-point unset
12493 .index load average
12494 If the system load average ever gets higher than this, incoming SMTP calls are
12495 accepted only from those hosts that match an entry in \smtp@_reserve@_hosts\.
12496 If \smtp@_reserve@_hosts\ is not set, no incoming SMTP calls are accepted when
12497 the load is over the limit. The option has no effect on ancient operating
12498 systems on which Exim cannot determine the load average. See also
12499 \deliver@_queue@_load@_max\ and \queue@_only@_load\.
12502 .conf smtp@_max@_synprot@_errors integer 3
12503 .index SMTP||limiting syntax and protocol errors
12504 .index limit||SMTP syntax and protocol errors
12505 Exim rejects SMTP commands that contain syntax or protocol errors. In
12506 particular, a syntactically invalid email address, as in this command:
12508 RCPT TO:<abc xyz@a.b.c>
12510 causes immediate rejection of the command, before any other tests are done.
12511 (The ACL cannot be run if there is no valid address to set up for it.) An
12512 example of a protocol error is receiving \\RCPT\\ before \\MAIL\\. If there are
12513 too many syntax or protocol errors in one SMTP session, the connection is
12514 dropped. The limit is set by this option.
12516 .index \\PIPELINING\\||expected errors
12517 When the \\PIPELINING\\ extension to SMTP is in use, some protocol errors are
12518 `expected', for instance, a \\RCPT\\ command after a rejected \\MAIL\\ command.
12519 Exim assumes that \\PIPELINING\\ will be used if it advertises it (see
12520 \pipelining@_advertise@_hosts\), and in this situation, `expected' errors do
12521 not count towards the limit.
12524 .conf smtp@_max@_unknown@_commands integer 3
12525 .index SMTP||limiting unknown commands
12526 .index limit||unknown SMTP commands
12527 If there are too many unrecognized commands in an incoming SMTP session, an
12528 Exim server drops the connection. This is a defence against some kinds of abuse
12531 into making connections to SMTP ports; in these circumstances, a number of
12532 non-SMTP command lines are sent first.
12535 .conf smtp@_ratelimit@_hosts "host list$**$" unset
12536 .index SMTP||rate limiting
12537 .index limit||rate of message arrival
12538 .index \\RCPT\\||rate limiting
12539 Some sites find it helpful to be able to limit the rate at which certain hosts
12540 can send them messages, and the rate at which an individual message can specify
12541 recipients. When a host matches \smtp@_ratelimit@_hosts\, the values of
12542 \smtp@_ratelimit@_mail\ and \smtp@_ratelimit@_rcpt\ are used to control the
12543 rate of acceptance of \\MAIL\\ and \\RCPT\\ commands in a single SMTP session,
12544 respectively. Each option, if set, must contain a set of four comma-separated
12547 A threshold, before which there is no rate limiting.
12549 An initial time delay. Unlike other times in Exim, numbers with decimal
12550 fractional parts are allowed here.
12552 A factor by which to increase the delay each time.
12554 A maximum value for the delay. This should normally be less than 5 minutes,
12555 because after that time, the client is liable to timeout the SMTP command.
12557 For example, these settings have been used successfully at the site which
12558 first suggested this feature, for controlling mail from their customers:
12560 smtp_ratelimit_mail = 2,0.5s,1.05,4m
12561 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
12563 The first setting specifies delays that are applied to \\MAIL\\ commands after
12564 two have been received over a single connection. The initial delay is 0.5
12565 seconds, increasing by a factor of 1.05 each time. The second setting applies
12566 delays to \\RCPT\\ commands when more than four occur in a single message.
12568 It is also possible to configure delays explicitly in ACLs. See section
12569 ~~SECTACLmodi for details.
12572 .conf smtp@_ratelimit@_mail string unset
12573 See \smtp@_ratelimit@_hosts\ above.
12575 .conf smtp@_ratelimit@_rcpt string unset
12576 See \smtp@_ratelimit@_hosts\ above.
12578 .conf smtp@_receive@_timeout time 5m
12579 .index timeout||for SMTP input
12580 .index SMTP||timeout, input
12581 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
12582 input, including batch SMTP. If a line of input (either an SMTP command or a
12583 data line) is not received within this time, the SMTP connection is dropped and
12584 the message is abandoned.
12585 A line is written to the log containing one of the following messages:
12587 SMTP command timeout on connection from...
12588 SMTP data timeout on connection from...
12590 The former means that Exim was expecting to read an SMTP command; the latter
12591 means that it was in the \\DATA\\ phase, reading the contents of a message.
12594 .index \-os-\ option
12595 The value set by this option can be overridden by the
12596 \-os-\ command-line option. A setting of zero time disables the timeout, but
12597 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
12598 of local input using \-bs-\ or \-bS-\.) For non-SMTP input, the reception
12599 timeout is controlled by \receive@_timeout\ and \-or-\.
12601 .conf smtp@_reserve@_hosts "host list$**$" unset
12602 This option defines hosts for which SMTP connections are reserved; see
12603 \smtp@_accept@_reserve\ and \smtp@_load@_reserve\ above.
12605 .conf smtp@_return@_error@_details boolean false
12606 .index SMTP||details policy failures
12607 .index policy control||rejection, returning details
12608 In the default state, Exim uses bland messages such as
12609 `Administrative prohibition' when it rejects SMTP commands for policy
12610 reasons. Many sysadmins like this because it gives away little information
12611 to spammers. However, some other syadmins who are applying strict checking
12612 policies want to give out much fuller information about failures. Setting
12613 \smtp@_return@_error@_details\ true causes Exim to be more forthcoming. For
12614 example, instead of `Administrative prohibition', it might give:
12616 550-Rejected after DATA: '>' missing at end of address:
12617 550 failing address in "From" header is: <user@dom.ain
12620 .conf split@_spool@_directory boolean false
12621 .index multiple spool directories
12622 .index spool directory||split
12623 .index directories, multiple
12624 If this option is set, it causes Exim to split its input directory into 62
12625 subdirectories, each with a single alphanumeric character as its name. The
12626 sixth character of the message id is used to allocate messages to
12627 subdirectories; this is the least significant base-62 digit of the time of
12628 arrival of the message.
12630 Splitting up the spool in this way may provide better performance on systems
12631 where there are long mail queues, by reducing the number of files in any one
12632 directory. The msglog directory is also split up in a similar way to the input
12633 directory; however, if \preserve@_message@_logs\ is set, all old msglog files
12634 are still placed in the single directory \(msglog.OLD)\.
12636 It is not necessary to take any special action for existing messages when
12637 changing \split@_spool@_directory\. Exim notices messages that are in the
12638 `wrong' place, and continues to process them. If the option is turned off after
12639 a period of being on, the subdirectories will eventually empty and be
12640 automatically deleted.
12642 When \split@_spool@_directory\ is set, the behaviour of queue runner processes
12643 changes. Instead of creating a list of all messages in the queue, and then
12644 trying to deliver each one in turn, it constructs a list of those in one
12645 sub-directory and tries to deliver them, before moving on to the next
12646 sub-directory. The sub-directories are processed in a random order. This
12647 spreads out the scanning of the input directories, and uses less memory. It is
12648 particularly beneficial when there are lots of messages on the queue. However,
12649 if \queue@_run@_in@_order\ is set, none of this new processing happens. The
12650 entire queue has to be scanned and sorted before any deliveries can start.
12652 .conf spool@_directory string$**$ "set at compile time"
12653 .index spool directory||path to
12654 This defines the directory in which Exim keeps its spool, that is, the messages
12655 it is waiting to deliver. The default value is taken from the compile-time
12656 configuration setting, if there is one. If not, this option must be set. The
12657 string is expanded, so it can contain, for example, a reference to
12658 \$primary@_hostname$\.
12660 If the spool directory name is fixed on your installation, it is recommended
12661 that you set it at build time rather than from this option, particularly if the
12662 log files are being written to the spool directory (see \log@_file@_path\).
12663 Otherwise log files cannot be used for errors that are detected early on, such
12664 as failures in the configuration file.
12666 By using this option to override the compiled-in path, it is possible to run
12667 tests of Exim without using the standard spool.
12669 .conf strip@_excess@_angle@_brackets boolean false
12670 .index angle brackets, excess
12671 If this option is set, redundant pairs of angle brackets round `route-addr'
12672 items in addresses are stripped. For example, \*@<@<xxx@@a.b.c.d@>@>*\ is treated
12673 as \*@<xxx@@a.b.c.d@>*\. If this is in the envelope and the message is passed on
12674 to another MTA, the excess angle brackets are not passed on. If this option is
12675 not set, multiple pairs of angle brackets cause a syntax error.
12677 .conf strip@_trailing@_dot boolean false
12678 .index trailing dot on domain
12679 .index dot||trailing on domain
12680 If this option is set, a trailing dot at the end of a domain in an address is
12681 ignored. If this is in the envelope and the message is passed on to another
12682 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
12683 domain causes a syntax error.
12684 However, addresses in header lines are checked only when an ACL requests header
12687 .conf syslog@_duplication boolean true
12688 .index syslog||duplicate log lines, suppressing
12689 When Exim is logging to syslog, it writes the log lines for its three
12690 separate logs at different syslog priorities so that they can in principle
12691 be separated on the logging hosts. Some installations do not require this
12692 separation, and in those cases, the duplication of certain log lines is a
12693 nuisance. If \syslog@_duplication\ is set false, only one copy of any
12694 particular log line is written to syslog. For lines that normally go to
12695 both the main log and the reject log, the reject log version (possibly
12696 containing message header lines) is written, at \\LOG@_NOTICE\\ priority.
12697 Lines that normally go to both the main and the panic log are written at
12698 the \\LOG@_ALERT\\ priority.
12700 .conf syslog@_facility string unset
12701 .index syslog||facility, setting
12702 This option sets the syslog `facility' name, used when Exim is logging to
12703 syslog. The value must be one of the strings `mail', `user', `news', `uucp',
12704 `daemon', or `local\*x*\' where \*x*\ is a digit between 0 and 7. If this
12705 option is unset, `mail' is used. See chapter ~~CHAPlog for details of Exim's
12709 .conf syslog@_processname string "$tt{exim}"
12710 .index syslog||process name, setting
12711 This option sets the syslog `ident' name, used when Exim is logging to syslog.
12712 The value must be no longer than 32 characters. See chapter ~~CHAPlog for
12713 details of Exim's logging.
12716 .conf syslog@_timestamp boolean true
12717 .index syslog||timestamps
12718 If \syslog@_timestamp\ is set false, the timestamps on Exim's log lines are
12719 omitted when these lines are sent to syslog. See chapter ~~CHAPlog for
12720 details of Exim's logging.
12722 .conf system@_filter string$**$ unset
12723 .index filter||system filter
12724 .index system filter||specifying
12725 .index Sieve filter||not available for system filter
12726 This option specifies an Exim filter file that is applied to all messages at
12727 the start of each delivery attempt, before any routing is done. System filters
12728 must be Exim filters; they cannot be Sieve filters. If the system filter
12729 generates any deliveries to files or pipes, or any new mail messages, the
12730 appropriate \system@_filter@_...@_transport\ option(s) must be set, to define
12731 which transports are to be used. Details of this facility are given in chapter
12732 ~~CHAPsystemfilter.
12734 .conf system@_filter@_directory@_transport string$**$ unset
12735 This sets the name of the transport driver that is to be used when the
12736 \save\ command in a system message filter specifies a path ending in `/',
12737 implying delivery of each message into a separate file in some directory.
12738 During the delivery, the variable \$address@_file$\ contains the path name.
12740 .conf system@_filter@_file@_transport string$**$ unset
12741 .index file||transport for system filter
12742 This sets the name of the transport driver that is to be used when the \save\
12743 command in a system message filter specifies a path not ending in `/'. During
12744 the delivery, the variable \$address@_file$\ contains the path name.
12746 .index gid (group id)||system filter
12747 .conf system@_filter@_group string unset
12748 This option is used only when \system@_filter@_user\ is also set. It sets the
12749 gid under which the system filter is run, overriding any gid that is associated
12750 with the user. The value may be numerical or symbolic.
12752 .conf system@_filter@_pipe@_transport string$**$ unset 7
12753 .index \%pipe%\ transport||for system filter
12754 This specifies the transport driver that is to be used when a \pipe\ command is
12755 used in a system filter. During the delivery, the variable \$address@_pipe$\
12756 contains the pipe command.
12758 .conf system@_filter@_reply@_transport string$**$ unset
12759 .index \%autoreply%\ transport||for system filter
12760 This specifies the transport driver that is to be used when a \mail\ command is
12761 used in a system filter.
12763 .index uid (user id)||system filter
12764 .conf system@_filter@_user string unset
12765 If this option is not set, the system filter is run in the main Exim delivery
12766 process, as root. When the option is set, the system filter runs in a separate
12767 process, as the given user. Unless the string consists entirely of digits, it
12768 is looked up in the password data. Failure to find the named user causes a
12769 configuration error. The gid is either taken from the password data, or
12770 specified by \system@_filter@_group\. When the uid is specified numerically,
12771 \system@_filter@_group\ is required to be set.
12773 If the system filter generates any pipe, file, or reply deliveries, the uid
12774 under which the filter is run is used when transporting them, unless a
12775 transport option overrides.
12776 Normally you should set \system@_filter@_user\ if your system filter generates
12777 these kinds of delivery.
12779 .conf tcp@_nodelay boolean true
12780 .index daemon||\\TCP@_NODELAY\\ on sockets
12781 .index Nagle algorithm
12782 .index \\TCP@_NODELAY\\ on listening sockets
12783 If this option is set false, it stops the Exim daemon setting the
12784 \\TCP@_NODELAY\\ option on its listening sockets. Setting \\TCP@_NODELAY\\
12785 turns off the `Nagle algorithm', which is a way of improving network
12786 performance in interactive (character-by-character) situations. Turning it off
12787 should improve Exim's performance a bit, so that is what happens by default.
12788 However, it appears that some broken clients cannot cope, and time out. Hence
12789 this option. It affects only those sockets that are set up for listening by the
12790 daemon. Sockets created by the smtp transport for delivering mail always set
12793 .conf timeout@_frozen@_after time 0s
12794 .index frozen messages||timing out
12795 .index timeout||frozen messages
12796 If \timeout@_frozen@_after\ is set to a time greater than zero, a frozen
12797 message of any kind that has been on the queue for longer than the given
12798 time is automatically cancelled at the next queue run. If it is a bounce
12799 message, it is just discarded; otherwise, a bounce is sent to the sender, in a
12800 similar manner to cancellation by the \-Mg-\ command line option. If you want
12801 to timeout frozen bounce messages earlier than other kinds of frozen message,
12802 see \ignore@_bounce@_errors@_after\.
12804 .conf timezone string unset
12805 .index timezone, setting
12806 The value of \timezone\ is used to set the environment variable \\TZ\\ while
12807 running Exim (if it is different on entry). This ensures that all timestamps
12808 created by Exim are in the required timezone. If you want all your timestamps
12809 to be in UTC (aka GMT) you should set
12813 The default value is taken from \\TIMEZONE@_DEFAULT\\ in \(Local/Makefile)\,
12814 or, if that is not set, from the value of the TZ environment variable when Exim
12815 is built. If \timezone\ is set to the empty string, either at build or run
12816 time, any existing \\TZ\\ variable is removed from the environment when Exim
12817 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
12818 unfortunately not all, operating systems.
12820 .conf tls@_advertise@_hosts "host list$**$" unset
12821 .index TLS||advertising
12822 .index encryption||on SMTP connection
12823 .index SMTP||encrypted connection
12824 When Exim is built with support for TLS encrypted connections, the availability
12825 of the \\STARTTLS\\ command to set up an encrypted session is advertised in
12826 response to \\EHLO\\ only to those client hosts that match this option. See
12827 chapter ~~CHAPTLS for details of Exim's support for TLS.
12829 .conf tls@_certificate string$**$ unset
12830 .index TLS||server certificate, location of
12831 .index certificate||for server, location of
12832 The value of this option is expanded, and must then be the absolute path to a
12833 file which contains the server's certificates. The server's private key is also
12834 assumed to be in this file if \tls@_privatekey\ is unset. See chapter ~~CHAPTLS
12835 for further details.
12837 \**Note**\: The certificates defined by this option are used only when Exim is
12838 receiving incoming messages as a server. If you want to supply certificates for
12839 use when sending messages as a client, you must set the \tls@_certificate\
12840 option in the relevant \%smtp%\ transport.
12842 .conf tls@_crl string$**$ unset
12843 .index TLS||server certificate revocation list
12844 .index certificate||revocation list for server
12845 This option specifies a certificate revocation list. The expanded value must
12846 be the name of a file that contains a CRL in PEM format.
12848 .conf tls@_dhparam string$**$ unset
12849 .index TLS||D-H parameters for server
12850 The value of this option is expanded, and must then be the absolute path to
12851 a file which contains the server's DH parameter values.
12852 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
12853 ignored. See section ~~SECTopenvsgnu for further details.
12855 .conf tls@_privatekey string$**$ unset
12856 .index TLS||server private key, location of
12857 The value of this option is expanded, and must then be the absolute path to
12858 a file which contains the server's private key.
12859 If this option is unset, the private key is assumed to be in the same file as
12860 the server's certificates. See chapter ~~CHAPTLS for further details.
12862 .conf tls@_remember@_esmtp boolean false
12863 .index TLS||esmtp state, remembering
12864 .index TLS||broken clients
12865 If this option is set true, Exim violates the RFCs by remembering that it is in
12866 `esmtp' state after successfully negotiating a TLS session. This provides
12867 support for broken clients that fail to send a new \\EHLO\\ after starting a
12870 .conf tls@_require@_ciphers string$**$ unset
12871 .index TLS||requiring specific ciphers
12872 .index cipher||requiring specific
12873 This option controls which ciphers can be used for incoming TLS connections.
12874 (The \%smtp%\ transport has an option of the same name for controlling outgoing
12875 connections.) This option is expanded for each connection, so can be varied for
12876 different clients if required. The value of this option must be a list of
12877 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
12878 in somewhat different ways. Details are given in section ~~SECTreqciphsslgnu.
12880 .conf tls@_try@_verify@_hosts "host list$**$" unset
12881 .index TLS||client certificate verification
12882 .index certificate||verification of client
12883 See \tls@_verify@_hosts\ below.
12885 .conf tls@_verify@_certificates string$**$ unset
12886 .index TLS||client certificate verification
12887 .index certificate||verification of client
12888 The value of this option is expanded, and must then be the absolute path to
12889 a file containing permitted certificates for clients that
12890 match \tls@_verify@_hosts\ or \tls@_try@_verify@_hosts\. Alternatively, if you
12891 are using OpenSSL, you can set \tls@_verify@_certificates\ to the name of a
12892 directory containing certificate files. This does not work with GnuTLS; the
12893 option must be set to the name of a single file if you are using GnuTLS.
12895 .conf tls@_verify@_hosts "host list$**$" unset
12896 .index TLS||client certificate verification
12897 .index certificate||verification of client
12898 This option, along with \tls@_try@_verify@_hosts\, controls the checking of
12899 certificates from clients.
12900 The expected certificates are defined by \tls@_verify@_certificates\, which
12901 must be set. A configuration error occurs if either \tls@_verify@_hosts\ or
12902 \tls@_try@_verify@_hosts\ is set and \tls@_verify@_certificates\ is not set.
12904 Any client that matches \tls@_verify@_hosts\ is constrained by
12905 \tls@_verify@_certificates\. The client must present one of the listed
12906 certificates. If it does not, the connection is aborted.
12908 A weaker form of checking is provided by \tls@_try@_verify@_hosts\. If a client
12909 matches this option (but not \tls@_verify@_hosts\), Exim requests a
12910 certificate and checks it against \tls@_verify@_certificates\, but does not
12911 abort the connection if there is no certificate or if it does not match. This
12912 state can be detected in an ACL, which makes it possible to implement policies
12913 such as `accept for relay only if a verified certificate has been received, but
12914 accept for local delivery if encrypted, even without a verified certificate'.
12916 Client hosts that match neither of these lists are not asked to present
12919 .conf trusted@_groups "string list" unset
12920 .index trusted group
12921 .index group||trusted
12922 If this option is set, any process that is running in one of the listed groups,
12923 or which has one of them as a supplementary group, is trusted.
12924 The groups can be specified numerically or by name.
12925 See section ~~SECTtrustedadmin for details of what trusted callers are
12926 permitted to do. If neither \trusted@_groups\ nor \trusted@_users\ is set, only
12927 root and the Exim user are trusted.
12929 .conf trusted@_users "string list" unset
12930 .index trusted user
12931 .index user||trusted
12932 If this option is set, any process that is running as one of the listed users
12934 The users can be specified numerically or by name.
12935 See section ~~SECTtrustedadmin for details of what trusted callers are
12936 permitted to do. If neither \trusted@_groups\ nor \trusted@_users\ is set, only
12937 root and the Exim user are trusted.
12939 .index uid (user id)||unknown caller
12940 .conf unknown@_login string$**$ unset
12941 This is a specialized feature for use in unusual configurations. By default, if
12942 the uid of the caller of Exim cannot be looked up using \*getpwuid()*\, Exim
12943 gives up. The \unknown@_login\ option can be used to set a login name to be
12944 used in this circumstance. It is expanded, so values like \user@$caller@_uid\
12945 can be set. When \unknown@_login\ is used, the value of \unknown@_username\ is
12946 used for the user's real name (gecos field), unless this has been set by the
12949 .conf unknown@_username string unset
12950 See \unknown@_login\.
12952 .conf untrusted@_set@_sender "address list$**$" unset
12953 .index trusted user
12954 .index sender||setting by untrusted user
12955 .index untrusted user, setting sender
12956 .index user||untrusted setting sender
12957 .index envelope sender
12958 When an untrusted user submits a message to Exim using the standard input, Exim
12959 normally creates an envelope sender address from the user's login and the
12960 default qualification domain. Data from the \-f-\ option (for setting envelope
12961 senders on non-SMTP messages) or the SMTP \\MAIL\\ command (if \-bs-\ or \-bS-\
12962 is used) is ignored.
12964 However, untrusted users are permitted to set an empty envelope sender address,
12965 to declare that a message should never generate any bounces. For example:
12967 exim -f '<>' user@domain.example
12969 The \untrusted@_set@_sender\ option allows you to permit untrusted users to set
12970 other envelope sender addresses in a controlled way. When it is set, untrusted
12971 users are allowed to set envelope sender addresses that match any of the
12972 patterns in the list. Like all address lists, the string is expanded. The
12973 identity of the user is in \$sender@_ident$\, so you can, for example, restrict
12974 users to setting senders that start with their login ids
12975 followed by a hyphen
12976 by a setting like this:
12978 untrusted_set_sender = ^$sender_ident-
12980 If you want to allow untrusted users to set envelope sender addresses without
12981 restriction, you can use
12983 untrusted_set_sender = *
12985 The \untrusted@_set@_sender\ option applies to all forms of local input, but
12986 only to the setting of the envelope sender. It does not permit untrusted users
12987 to use the other options which trusted user can use to override message
12988 parameters. Furthermore, it does not stop Exim from removing an existing
12989 ::Sender:: header in the message, or from adding a ::Sender:: header if
12990 necessary. See \local__sender__retain\ and \local@_from@_check\ for ways of
12991 overriding these actions. The handling of the ::Sender:: header is also
12992 described in section ~~SECTthesenhea.
12994 The log line for a message's arrival shows the envelope sender following `<='.
12995 For local messages, the user's login always follows, after `U='. In \-bp-\
12996 displays, and in the Exim monitor, if an untrusted user sets an envelope sender
12997 address, the user's login is shown in parentheses after the sender address.
12999 .conf uucp@_from@_pattern string "see below"
13001 .index UUCP||`From' line
13002 Some applications that pass messages to an MTA via a command line interface use
13003 an initial line starting with `From' to pass the envelope sender. In
13004 particular, this is used by UUCP software. Exim recognizes such a line by means
13005 of a regular expression that is set in \uucp@_from@_pattern\. When the pattern
13006 matches, the sender address is constructed by expanding the contents of
13007 \uucp@_from@_sender\, provided that the caller of Exim is a trusted user. The
13008 default pattern recognizes lines in the following two forms:
13010 From ph10 Fri Jan 5 12:35 GMT 1996
13011 From ph10 Fri, 7 Jan 97 14:00:00 GMT
13013 The pattern can be seen by running
13015 exim -bP uucp_from_pattern
13017 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
13018 year in the second case. The first word after `From' is matched in the regular
13019 expression by a parenthesized subpattern. The default value for
13020 \uucp@_from@_sender\ is `$1', which therefore just uses this first word (`ph10'
13021 in the example above) as the message's sender. See also
13022 \ignore@_fromline@_hosts\.
13024 .conf uucp@_from@_sender string$**$ "$tt{@$1}"
13025 See \uucp@_from@_pattern\ above.
13027 .conf warn@_message@_file string unset
13028 .index warning of delay||customizing the message
13029 .index customizing||warning message
13030 This option defines a template file containing paragraphs of text to be used
13031 for constructing the warning message which is sent by Exim when a message has
13032 been on the queue for a specified amount of time, as specified by
13033 \delay@_warning\. Details of the file's contents are given in chapter
13034 ~~CHAPemsgcust. See also \bounce@_message@_file\.
13036 .conf write@_rejectlog boolean true
13037 .index reject log||disabling
13038 If this option is set false, Exim no longer writes anything to the reject log.
13039 See chapter ~~CHAPlog for details of what Exim writes to its logs.
13049 . ============================================================================
13050 .chapter Generic options for routers
13051 .rset CHAProutergeneric "~~chapter"
13052 .set runningfoot "generic router options"
13053 .index options||generic, for routers
13054 .index generic options||router
13056 This chapter describes the generic options that apply to all routers,
13057 identifying those that are preconditions. For a general description of how a
13058 router operates, see sections ~~SECTrunindrou and ~~SECTrouprecon. The second
13059 of these sections specifies the order in which the preconditions are tested.
13060 The order of expansion of the options that provide data for a transport is:
13061 \errors@_to\, \headers@_add\, \headers@_remove\, \transport\.
13065 .conf address@_data string$**$ unset
13066 .index router||data attached to address
13067 The string is expanded just before the router is run, that is, after all the
13068 precondition tests have succeeded. If the expansion is forced to fail, the
13069 router declines. Other expansion failures cause delivery of the address to be
13072 When the expansion succeeds, the value is retained with the address, and can be
13073 accessed using the variable \$address@_data$\ in the current router, subsequent
13074 routers, and the eventual transport.
13076 \**Warning**\: if the current or any subsequent router is a \%redirect%\ router
13077 that runs a user's filter file, the contents of \$address@_data$\ are
13078 accessible in the filter. This is not normally a problem, because such data is
13079 usually either not confidential or it `belongs' to the current user, but if you
13080 do put confidential data into \$address@_data$\ you need to remember this
13083 Even if the router declines or passes, the value of \$address@_data$\ remains
13084 with the address, though it can be changed by another \address@_data\ setting
13085 on a subsequent router. If a router generates child addresses, the value of
13086 \$address@_data$\ propagates to them. This also applies to the special kind of
13087 `child' that is generated by a router with the \unseen\ option.
13089 The idea of \address@_data\ is that you can use it to look up a lot of data for
13090 the address once, and then pick out parts of the data later. For example, you
13091 could use a single LDAP lookup to return a string of the form
13093 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
13095 In the transport you could pick out the mailbox by a setting such as
13097 file = ${extract{mailbox}{$address_data}}
13099 This makes the configuration file less messy, and also reduces the number of
13100 lookups. (Exim does cache the most recent lookup, but there may be several
13101 addresses in a message which cause lookups to occur.)
13103 The \address@_data\ facility is also useful as a means of passing information
13104 from one router to another,
13105 and from a router to a transport. In addition, if \address@_data\ is set by a
13106 router when verifying an address from an ACL, its value is available for use in
13107 the rest of the ACL statement.
13110 .conf address@_test "boolean (precondition)" true
13111 .index \-bt-\ option
13112 .index router||skipping when address testing
13113 If this option is set false, the router is skipped when routing is being tested
13114 by means of the \-bt-\ command line option. This can be a convenience when your
13115 first router sends messages to an external scanner, because it saves you
13116 having to set the `already scanned' indicator when testing real address
13120 .conf cannot@_route@_message string$**$ unset
13121 .index router||customizing `cannot route' message
13122 .index customizing||`cannot route' message
13123 This option specifies a text message that is used when an address cannot be
13124 routed because Exim has run out of routers. The default message is `Unrouteable
13125 address'. This option is useful only on routers that have \more\ set false, or
13126 on the very last router in a configuration, because the value that is used is
13127 taken from the last router that inspects an address. For example, using the
13128 default configuration, you could put:
13130 cannot_route_message = Remote domain not found in DNS
13132 on the first (\%dnslookup%\) router, and
13134 cannot_route_message = Unknown local user
13136 on the final router that checks for local users. If string expansion fails, the
13137 default message is used.
13138 Unless the expansion failure was explicitly forced, a message about the failure
13139 is written to the main and panic logs, in addition to the normal message about
13140 the routing failure.
13142 .conf caseful@_local@_part boolean false
13143 .index case of local parts
13144 .index router||case of local parts
13145 By default, routers handle the local parts of addresses in a case-insensitive
13146 manner, though the actual case is preserved for transmission with the message.
13147 If you want the case of letters to be significant in a router, you must set
13148 this option true. For individual router options that contain address or local
13149 part lists (for example, \local@_parts\), case-sensitive matching can be turned
13150 on by `+caseful' as a list item. See section ~~SECTcasletadd for more details.
13153 .conf check@_local@_user "boolean (precondition)" false
13154 .index local user, checking in router
13155 .index router||checking for local user
13156 When this option is true, Exim checks that the local part of the recipient
13157 address (with affixes removed if relevant) is the name of an account on the
13158 local system. The check is done by calling the \*getpwnam()*\ function rather
13159 than trying to read \(/etc/passwd)\ directly. This means that other methods of
13160 holding password data (such as NIS) are supported. If the local part is a local
13161 user, \$home$\ is set from the password data, and can be tested in other
13162 preconditions that are evaluated after this one
13163 (the order of evaluation is given in section ~~SECTrouprecon). However, the
13164 value of \$home$\ can be overridden by \router@_home@_directory\.
13165 If the local part is not a local user, the router is skipped.
13167 If you want to check that the local part is either the name of a local user
13168 or matches something else, you cannot combine \check@_local@_user\ with a
13169 setting of \local@_parts\, because that specifies the logical \*and*\ of the
13170 two conditions. However, you can use a \%passwd%\ lookup in a \local@_parts\
13171 setting to achieve this. For example:
13173 local_parts = passwd;$local_part : lsearch;/etc/other/users
13175 Note, however, that the side effects of \check@_local@_user\ (such as setting
13176 up a home directory) do not occur when a \%passwd%\ lookup is used in a
13177 \local@_parts\ (or any other) precondition.
13179 .conf condition "string$**$ (precondition)" unset
13180 .index router||customized precondition
13181 This option specifies a general precondition test that has to succeed for the
13182 router to be called. The string is expanded, and if the result is a forced
13183 failure or an empty string or one of the strings `0' or `no' or `false'
13184 (checked without regard to the case of the letters), the router is skipped, and
13185 the address is offered to the next one. This provides a means of applying
13186 special-purpose conditions to the running of routers.
13188 If the expansion fails (other than forced failure) delivery is deferred. Some
13189 of the other options below are common special cases that could in fact be
13190 specified using \condition\.
13191 Note that \condition\ is the last precondition to be evaluated (see
13192 section ~~SECTrouprecon).
13195 .conf debug@_print string$**$ unset
13196 .index testing||variables in drivers
13197 If this option is set and debugging is enabled (see the \-d-\ command line
13198 option), the string is expanded and included in the debugging output.
13199 If expansion of the string fails, the error message is written to the debugging
13200 output, and Exim carries on processing.
13201 This option is provided to help with checking out the values of variables and
13202 so on when debugging router configurations. For example, if a \condition\
13203 option appears not to be working, \debug@_print\ can be used to output the
13204 variables it references. The output happens after checks for \domains\,
13205 \local@_parts\, and \check@_local@_user\ but before any other preconditions are
13206 tested. A newline is added to the text if it does not end with one.
13209 .conf disable@_logging boolean false
13210 If this option is set true, nothing is logged for any routing errors
13211 or for any deliveries caused by this router. You should not set this option
13212 unless you really, really know what you are doing. See also the generic
13213 transport option of the same name.
13215 .conf domains "domain list$**$ (precondition)" unset
13216 .index router||restricting to specific domains
13217 If this option is set, the router is skipped unless the current domain matches
13218 the list. If the match is achieved by means of a file lookup, the data that the
13219 lookup returned for the domain is placed in \$domain@_data$\ for use in string
13220 expansions of the driver's private options.
13221 See section ~~SECTrouprecon for a list of the order in which preconditions
13225 .conf driver string unset
13226 This option must always be set. It specifies which of the available routers is
13230 .conf errors@_to string$**$ unset
13231 .index envelope sender
13232 .index router||changing address for errors
13233 If a router successfully handles an address, it may queue the address for
13234 delivery or it may generate child addresses. In both cases, if there is a
13235 delivery problem during later processing, the resulting bounce message is sent
13236 to the address that results from expanding this string, provided that the
13237 address verifies successfully.
13238 \errors@_to\ is expanded before \headers@_add\, \headers@_remove\, and
13241 If the option is unset, or the expansion is forced to fail, or the result of
13242 the expansion fails to verify, the errors address associated with the incoming
13243 address is used. At top level, this is the envelope sender. A non-forced
13244 expansion failure causes delivery to be deferred.
13246 If an address for which \errors@_to\ has been set ends up being delivered over
13247 SMTP, the envelope sender for that delivery is the \errors@_to\ value, so that
13248 any bounces that are generated by other MTAs on the delivery route are also
13249 sent there. The most common use of \errors@_to\ is probably to direct mailing
13250 list bounces to the manager of the list, as described in section
13251 ~~SECTmailinglists.
13253 The \errors@_to\ setting associated with an address can be overridden if it
13254 subsequently passes through other routers that have their own \errors@_to\
13256 or if it is delivered by a transport with a \return@_path\ setting.
13258 You can set \errors@_to\ to the empty string by either of these settings:
13263 An expansion item that yields an empty string has the same effect. If you do
13264 this, a locally detected delivery error for addresses processed by this router
13265 no longer gives rise to a bounce message; the error is discarded. If the
13266 address is delivered to a remote host, the return path is set to \"<>"\, unless
13267 overridden by the \return@_path\ option on the transport.
13269 If for some reason you want to discard local errors, but use a non-empty
13270 \\MAIL\\ command for remote delivery, you can preserve the original return
13271 path in \$address@_data$\ in the router, and reinstate it in the transport by
13272 setting \return@_path\.
13275 .conf expn "boolean (precondition)" true
13276 .index address||testing
13277 .index testing||addresses
13278 .index \\EXPN\\||router skipping
13279 .index router||skipping for \\EXPN\\
13280 If this option is turned off, the router is skipped when testing an address
13281 as a result of processing an SMTP \\EXPN\\ command. You might, for example,
13282 want to turn it off on a router for users' \(.forward)\ files, while leaving it
13283 on for the system alias file.
13284 See section ~~SECTrouprecon for a list of the order in which preconditions
13287 The use of the SMTP \\EXPN\\ command is controlled by an ACL (see chapter
13288 ~~CHAPACL). When Exim is running an \\EXPN\\ command, it is similar to testing
13289 an address with \-bt-\. Compare \\VRFY\\, whose counterpart is \-bv-\.
13292 .conf fail@_verify boolean false
13293 .index router||forcing verification failure
13294 Setting this option has the effect of setting both \fail@_verify@_sender\ and
13295 \fail@_verify@_recipient\ to the same value.
13298 .conf fail@_verify@_recipient boolean false
13299 If this option is true and an address is accepted by this router when
13300 verifying a recipient, verification fails.
13303 .conf fail@_verify@_sender boolean false
13304 If this option is true and an address is accepted by this router when
13305 verifying a sender, verification fails.
13308 .conf fallback@_hosts "string list" unset
13309 .index router||fallback hosts
13310 .index fallback||hosts specified on router
13311 String expansion is not applied to this option. The argument must be a
13312 colon-separated list of host names or IP addresses. If a router queues an
13313 address for a remote transport, this host list is associated with the address,
13314 and used instead of the transport's fallback host list. If \hosts@_randomize\
13315 is set on the transport, the order of the list is randomized for each use. See
13316 the \fallback@_hosts\ option of the \%smtp%\ transport for further details.
13318 .conf group string$**$ "see below"
13319 .index gid (group id)||local delivery
13320 .index local transports||uid and gid
13321 .index transport||local
13322 .index router||setting group
13323 When a router queues an address for a transport, and the transport does not
13324 specify a group, the group given here is used when running the delivery
13326 The group may be specified numerically or by name. If expansion fails, the
13327 error is logged and delivery is deferred.
13328 The default is unset, unless \check@_local@_user\ is set, when the default
13329 is taken from the password information. See also \initgroups\ and \user\ and
13330 the discussion in chapter ~~CHAPenvironment.
13333 .conf headers@_add string$**$ unset
13334 .index header lines||adding
13335 .index router||adding header lines
13336 This option specifies a string of text that is expanded at routing time, and
13337 associated with any addresses that are processed by the router
13338 when delivering a message. This option has no effect when an address is just
13341 The \headers@_add\ option is expanded after \errors@_to\, but before
13342 \headers@_remove\ and \transport\.
13343 If the expanded string is empty, or if the expansion is forced to fail, the
13344 option has no effect. Other expansion failures are treated as configuration
13345 errors. The expanded string must be in the form of one or more RFC 2822 header
13346 lines, separated by newlines (coded as `@\n'). For example:
13348 headers_add = X-added-header: added by $primary_hostname\n\
13349 X-added-second: another added header line
13351 Exim does not check the syntax of these added header lines. If an address
13352 passes through several routers as a result of aliasing or forwarding
13353 operations, any \headers@_add\ or \headers@_remove\ specifications are
13354 cumulative. This does not apply for multiple routers that result from the use
13357 At transport time, all the original headers listed in \headers__remove\ are
13358 removed. If there are multiple instances of any listed header, they are all
13360 Then the new headers specified by \headers@_add\ are added, in the order in
13361 which they were attached to the address. Finally, any additional headers
13362 specified by the transport are added. It is not possible to remove headers
13363 added to an address by \headers@_add\.
13365 Because the addition does not happen until transport time, header lines that
13366 are added by \headers@_add\ are not accessible by means of the \$header@_xxx$\
13367 expansion syntax. Conversely, header lines that are removed by
13368 \headers@_remove\ remain visible.
13370 Addresses with different \headers@_add\ or \headers@_remove\ settings cannot be
13371 delivered together in a batch. The \headers@_add\ option cannot be used for a
13372 \%redirect%\ router that has the \one@_time\ option set.
13375 .conf headers@_remove string$**$ unset
13376 .index header lines||removing
13377 .index router||removing header lines
13378 The string is expanded at routing time and is then associated with any
13379 addresses that are processed by the router when delivering a message. This
13380 option has no effect when an address is being verified. The \headers@_remove\
13381 option is expanded after \errors@_to\ and \headers@_add\, but before
13382 \transport\. If the expansion is forced to fail, the option has no effect.
13383 Other expansion failures are treated as configuration errors.
13385 After expansion, the string must consist of a colon-separated list of header
13386 names. This is confusing, because header names themselves are often terminated
13387 by colons. In this case, the colons are the list separators, not part of the
13391 headers_remove = return-receipt-to:acknowledge-to
13393 The list is used at transport time as described under \headers@_add\ above. The
13394 \headers@_remove\ option cannot be used for a \%redirect%\ router that has the
13395 \one@_time\ option set.
13397 .conf ignore@_target@_hosts "host list$**$" unset
13398 .index IP address||discarding
13399 .index router||discarding IP addresses
13400 Although this option is a host list, it should normally contain IP address
13401 entries rather than names. If any host that is looked up by the router has an
13402 IP address that matches an item in this list, Exim behaves as if that IP
13403 address did not exist. This option allows you to cope with rogue DNS entries
13406 remote.domain.example. A 127.0.0.1
13410 ignore_target_hosts = 127.0.0.1
13412 on the relevant router.
13413 If all the hosts found by a \%dnslookup%\ router are discarded in this way, the
13414 router declines. In a conventional configuration, an attempt to mail to such a
13415 domain would then normally provoke the `unrouteable domain' error, and an
13416 attempt to verify an address in the domain would fail.
13418 Similarly, if \ignore@_target@_hosts\ is set on an \%ipliteral%\ router, the
13419 router declines if presented with one of the listed addresses.
13421 This option may also be useful for ignoring link-local and site-local IPv6
13422 addresses. Because, like all host lists, the value of \ignore@_target@_hosts\
13423 is expanded before use as a list, it is possible to make it dependent on the
13424 domain that is being routed.
13428 .index additional groups
13429 .index groups, additional
13430 .index local transports||uid and gid
13431 .index transport||local
13432 .conf initgroups boolean false
13433 If the router queues an address for a transport, and this option is true, and
13434 the uid supplied by the router is not overridden by the transport, the
13435 \*initgroups()*\ function is called when running the transport to ensure that
13436 any additional groups associated with the uid are set up. See also \group\ and
13437 \user\ and the discussion in chapter ~~CHAPenvironment.
13440 .conf local@_part@_prefix "string list (precondition)" unset
13441 .index router||prefix for local part
13442 .index prefix||for local part, used in router
13443 If this option is set, the router is skipped unless the local part
13444 starts with one of the given strings, or \local@_part@_prefix@_optional\ is
13446 See section ~~SECTrouprecon for a list of the order in which preconditions
13449 The list is scanned from left to right, and the first prefix that matches is
13450 used. A limited form of wildcard is available; if the prefix begins with an
13451 asterisk, it matches the longest possible sequence of arbitrary characters at
13452 the start of the local part. An asterisk should therefore always be followed by
13453 some character that does not occur in normal local parts.
13454 .index multiple mailboxes
13455 .index mailbox||multiple
13456 Wildcarding can be used to set up multiple user mailboxes, as described in
13457 section ~~SECTmulbox.
13459 During the testing of the \local@_parts\ option, and while the router is
13460 running, the prefix is removed from the local part, and is available in the
13461 expansion variable \$local@_part@_prefix$\. If the router accepts the address,
13462 this remains true during subsequent delivery.
13463 In particular, the local part that is transmitted in the \\RCPT\\ command
13464 for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default. This
13465 behaviour can be overridden by setting \rcpt@_include@_affixes\ true on the
13466 relevant transport.
13468 The prefix facility is commonly used to handle local parts of the form
13469 \owner-something\. Another common use is to support local parts of the form
13470 \real-username\ to bypass a user's \(.forward)\ file -- helpful when trying to
13471 tell a user their forwarding is broken -- by placing a router like this one
13472 immediately before the router that handles \(.forward)\ files:
13476 local_part_prefix = real-
13478 transport = local_delivery
13480 If both \local@_part@_prefix\ and \local@_part@_suffix\ are set for a router,
13481 both conditions must be met if not optional. Care must be taken if wildcards
13482 are used in both a prefix and a suffix on the same router. Different
13483 separator characters must be used to avoid ambiguity.
13485 .conf local@_part@_prefix@_optional boolean false
13486 See \local@_part@_prefix\ above.
13489 .conf local@_part@_suffix "string list (precondition)" unset
13490 .index router||suffix for local part
13491 .index suffix for local part, used in router
13492 This option operates in the same way as \local@_part@_prefix\, except that the
13493 local part must end (rather than start) with the given string, the
13494 \local@_part@_suffix@_optional\ option determines whether the suffix is
13495 mandatory, and the wildcard $*$ character, if present, must be the last
13496 character of the suffix. This option facility is commonly used to handle local
13497 parts of the form \something-request\ and multiple user mailboxes of the form
13500 .conf local@_part@_suffix@_optional boolean false
13501 See \local@_part@_suffix\ above.
13504 .conf local@_parts "local part list$**$ (precondition)" unset
13505 .index router||restricting to specific local parts
13506 .index local part||checking in router
13507 The router is run only if the local part of the address matches the list.
13508 See section ~~SECTrouprecon for a list of the order in which preconditions
13510 section ~~SECTlocparlis for a discussion of local part lists. Because the
13511 string is expanded, it is possible to make it depend on the domain, for
13514 local_parts = dbm;/usr/local/specials/$domain
13516 If the match is achieved by a lookup, the data that the lookup returned
13517 for the local part is placed in the variable \$local@_part@_data$\ for use in
13518 expansions of the router's private options. You might use this option, for
13519 example, if you have a large number of local virtual domains, and you want to
13520 send all postmaster mail to the same place without having to set up an alias in
13521 each virtual domain:
13525 local_parts = postmaster
13526 data = postmaster@real.domain.example
13530 .conf log@_as@_local boolean "see below"
13531 .index log||delivery line
13532 .index delivery||log line format
13533 Exim has two logging styles for delivery, the idea being to make local
13534 deliveries stand out more visibly from remote ones. In the `local' style, the
13535 recipient address is given just as the local part, without a domain. The use of
13536 this style is controlled by this option. It defaults to true for the \%accept%\
13537 router, and false for all the others.
13540 .conf more boolean$**$ true
13541 The result of string expansion for this option must be a valid boolean value,
13542 that is, one of the strings `yes', `no', `true', or `false'. Any other result
13543 causes an error, and delivery is deferred. If the expansion is forced to fail,
13544 the default value for the option (true) is used. Other failures cause delivery
13547 If this option is set false, and the router is run, but declines to handle the
13548 address, no further routers are tried, routing fails, and the address is
13550 .index \self\ option
13551 However, if the router explicitly passes an address to the following router by
13552 means of the setting
13556 or otherwise, the setting of \more\ is ignored. Also, the setting of \more\
13557 does not affect the behaviour if one of the precondition tests fails. In that
13558 case, the address is always passed to the next router.
13561 .conf pass@_on@_timeout boolean false
13562 .index timeout||of router
13563 .index router||timeout
13564 If a router times out during a host lookup, it normally causes deferral of the
13565 address. If \pass@_on@_timeout\ is set, the address is passed on to the next
13566 router, overriding \no@_more\. This may be helpful for systems that are
13567 intermittently connected to the Internet, or those that want to pass to a smart
13568 host any messages that cannot immediately be delivered.
13570 There are occasional other temporary errors that can occur while doing DNS
13571 lookups. They are treated in the same way as a timeout, and this option
13572 applies to all of them.
13575 .conf pass@_router string unset
13576 .index router||go to after `pass'
13577 When a router returns `pass', the address is normally handed on to the next
13578 router in sequence. This can be changed by setting \pass@_router\ to the name
13579 of another router. However (unlike \redirect@_router\) the named router must be
13580 below the current router, to avoid loops. Note that this option applies only to
13581 the special case of `pass'. It does not apply when a router returns `decline'.
13584 .conf redirect@_router string unset
13585 .index router||start at after redirection
13586 Sometimes an administrator knows that it is pointless to reprocess addresses
13587 generated from alias or forward files with the same router again. For
13588 example, if an alias file translates real names into login ids there is no
13589 point searching the alias file a second time, especially if it is a large file.
13591 The \redirect@_router\ option can be set to the name of any router instance. It
13592 causes the routing of any generated addresses to start at the named router
13593 instead of at the first router. This option has no effect if the router in
13594 which it is set does not generate new addresses.
13597 .conf require@_files "string list$**$ (precondition)" unset
13598 .index file||requiring for router
13599 .index router||requiring file existence
13600 This option provides a general mechanism for predicating the running of a
13601 router on the existence or non-existence of certain files or directories.
13602 Before running a router, as one of its precondition tests, Exim works its way
13603 through the \require@_files\ list, expanding each item separately.
13605 Because the list is split before expansion, any colons in expansion items must
13606 be doubled, or the facility for using a different list separator must be used.
13607 If any expansion is forced to fail, the item is ignored. Other expansion
13608 failures cause routing of the address to be deferred.
13610 If any expanded string is empty, it is ignored. Otherwise, except as described
13611 below, each string must be a fully qualified file path, optionally preceded by
13612 `!'. The paths are passed to the \*stat()*\ function to test for the existence
13613 of the files or directories. The router is skipped if any paths not preceded by
13614 `!' do not exist, or if any paths preceded by `!' do exist.
13617 If \*stat()*\ cannot determine whether a file exists or not, delivery of
13618 the message is deferred. This can happen when NFS-mounted filesystems are
13621 This option is checked after the \domains\, \local@_parts\, and \senders\
13622 options, so you cannot use it to check for the existence of a file in which to
13623 look up a domain, local part, or sender. (See section ~~SECTrouprecon for a
13624 full list of the order in which preconditions are evaluated.) However, as
13625 these options are all expanded, you can use the \exists\ expansion condition to
13626 make such tests. The \require@_files\ option is intended for checking files
13627 that the router may be going to use internally, or which are needed by a
13628 transport (for example \(.procmailrc)\).
13630 During delivery, the \*stat()*\ function is run as root, but there is a
13631 facility for some checking of the accessibility of a file by another user.
13632 This is not a proper permissions check, but just a `rough' check that
13633 operates as follows:
13635 If an item in a \require@_files\ list does not contain any forward slash
13636 characters, it is taken to be the user (and optional group, separated by a
13637 comma) to be checked for subsequent files in the list. If no group is specified
13638 but the user is specified symbolically, the gid associated with the uid is
13641 require_files = mail:/some/file
13642 require_files = $local_part:$home/.procmailrc
13644 If a user or group name in a \require@_files\ list does not exist, the
13645 \require@_files\ condition fails.
13647 Exim performs the check by scanning along the components of the file path, and
13648 checking the access for the given uid and gid. It checks for `x' access on
13649 directories, and `r' access on the final file. Note that this means that file
13650 access control lists, if the operating system has them, are ignored.
13652 \**Warning 1**\: When the router is being run to verify addresses for an
13653 incoming SMTP message, Exim is not running as root, but under its own uid. This
13654 may affect the result of a \require@_files\ check. In particular, \*stat()*\
13655 may yield the error \\EACCES\\ (`Permission denied'). This means that the Exim
13656 user is not permitted to read one of the directories on the file's path.
13658 \**Warning 2**\: Even when Exim is running as root while delivering a message,
13659 \*stat()*\ can yield \\EACCES\\ for a file on an NFS directory that is mounted
13660 without root access.
13663 the default action is to consider this a configuration error, and routing is
13664 deferred because the existence or non-existence of the file cannot be
13665 determined. However, in some circumstances it may be desirable to treat this
13666 condition as if the file did not exist. If the file name (or the exclamation
13667 mark that precedes the file name for non-existence) is preceded by a plus sign,
13668 the \\EACCES\\ error is treated as if the file did not exist. For example:
13670 require_files = +/some/file
13672 If the router is not an essential part of verification (for example, it
13673 handles users' \(.forward)\ files), another solution is to set the \verify\
13674 option false so that the router is skipped when verifying.
13677 .conf retry@_use@_local@_part boolean "see below"
13678 .index hints database||retry keys
13679 .index local part||in retry keys
13680 When a delivery suffers a temporary routing failure, a retry record is created
13681 in Exim's hints database. For addresses whose routing depends only on the
13682 domain, the key for the retry record should not involve the local part, but for
13683 other addresses, both the domain and the local part should be included.
13684 Usually, remote routing is of the former kind, and local routing is of the
13687 This option controls whether the local part is used to form the key for retry
13688 hints for addresses that suffer temporary errors while being handled by this
13689 router. The default value is true for any router that has \check@_local@_user\
13690 set, and false otherwise. Note that this option does not apply to hints keys
13691 for transport delays; they are controlled by a generic transport option of the
13694 The setting of \retry@_use@_local@_part\ applies only to the router on which it
13695 appears. If the router generates child addresses, they are routed
13696 independently; this setting does not become attached to them.
13699 .conf router@_home@_directory string$**$ unset
13700 .index router||home directory for
13701 .index home directory||for router
13702 This option sets a home directory for use while the router is running. (Compare
13703 \transport__home@_directory\, which sets a home directory for later
13704 transporting.) In particular, if used on a \%redirect%\ router, this option
13705 sets a value for \$home$\ while a filter is running. The value is expanded;
13706 forced expansion failure causes the option to be ignored -- other failures
13707 cause the router to defer.
13709 Expansion of \router@_home@_directory\ happens immediately after the
13710 \check@_local@_user\ test (if configured), before any further expansions take
13712 (See section ~~SECTrouprecon for a list of the order in which preconditions
13714 While the router is running, \router__home@_directory\ overrides the value of
13715 \$home$\ that came from \check@_local@_user\.
13717 When a router accepts an address and routes it to a transport (including the
13718 cases when a redirect router generates a pipe, file, or autoreply delivery),
13719 the home directory setting for the transport is taken from the first of these
13720 values that is set:
13722 The \home@_directory\ option on the transport;
13724 The \transport@_home@_directory\ option on the router;
13726 The password data if \check@_local@_user\ is set on the router;
13728 The \router@_home@_directory\ option on the router.
13730 In other words, \router@_home@_directory\ overrides the password data for the
13731 router, but not for the transport.
13734 .conf self string "freeze"
13735 .index MX record||pointing to local host
13736 .index local host||MX pointing to
13737 This option applies to those routers that use a recipient address to find a
13738 list of remote hosts. Currently, these are the \%dnslookup%\, \%ipliteral%\,
13739 and \%manualroute%\ routers.
13740 Certain configurations of the \%queryprogram%\ router can also specify a list
13742 Usually such routers are configured to send the message to a remote host via an
13743 \%smtp%\ transport. The \self\ option specifies what happens when the first
13744 host on the list turns out to be the local host.
13745 The way in which Exim checks for the local host is described in section
13748 Normally this situation indicates either an error in Exim's configuration (for
13749 example, the router should be configured not to process this domain), or an
13750 error in the DNS (for example, the MX should not point to this host). For this
13751 reason, the default action is to log the incident, defer the address, and
13752 freeze the message. The following alternatives are provided for use in special
13757 Delivery of the message is tried again later, but the message is not frozen.
13759 \reroute: <<domain>>\
13761 The domain is changed to the given domain, and the address is passed back to
13762 be reprocessed by the routers. No rewriting of headers takes place. This
13763 behaviour is essentially a redirection.
13765 \reroute: rewrite: <<domain>>\
13767 The domain is changed to the given domain, and the address is passed back to be
13768 reprocessed by the routers. Any headers that contain the original domain are
13773 The router passes the address to the next router, or to the router named in the
13774 \pass@_router\ option if it is set.
13775 .index \more\ option
13776 This overrides \no@_more\.
13778 During subsequent routing and delivery, the variable
13779 \$self@_hostname$\ contains the name of the local host that the router
13780 encountered. This can be used to distinguish between different cases for hosts
13781 with multiple names. The combination
13786 ensures that only those addresses that routed to the local host are passed on.
13787 Without \no@_more\, addresses that were declined for other reasons would also
13788 be passed to the next router.
13792 Delivery fails and an error report is generated.
13796 .index local host||sending to
13797 The anomaly is ignored and the address is queued for the transport. This
13798 setting should be used with extreme caution. For an \%smtp%\ transport, it makes
13799 sense only in cases where the program that is listening on the SMTP port is not
13800 this version of Exim. That is, it must be some other MTA, or Exim with a
13801 different configuration file that handles the domain in another way.
13804 .conf senders "address list$**$ (precondition)" unset
13805 .index router||checking senders
13806 If this option is set, the router is skipped unless the message's sender
13807 address matches something on the list.
13808 See section ~~SECTrouprecon for a list of the order in which preconditions
13811 There are issues concerning verification when the running of routers is
13812 dependent on the sender. When Exim is verifying the address in an \errors@_to\
13813 setting, it sets the sender to the null string. When using the \-bt-\ option to
13814 check a configuration file, it is necessary also to use the \-f-\ option to set
13815 an appropriate sender. For incoming mail, the sender is unset when verifying
13816 the sender, but is available when verifying any recipients. If the SMTP
13817 \\VRFY\\ command is enabled, it must be used after \\MAIL\\ if the sender
13820 .conf translate@_ip@_address string$**$ unset
13821 .index IP address||translating
13822 .index packet radio
13823 .index router||IP address translation
13824 There exist some rare networking situations (for example, packet radio) where
13825 it is helpful to be able to translate IP addresses generated by normal routing
13826 mechanisms into other IP addresses, thus performing a kind of manual IP
13827 routing. This should be done only if the normal IP routing of the TCP/IP stack
13828 is inadequate or broken. Because this is an extremely uncommon requirement, the
13829 code to support this option is not included in the Exim binary unless
13830 \\SUPPORT__TRANSLATE__IP__ADDRESS\\=yes is set in \(Local/Makefile)\.
13832 The \translate@_ip@_address\ string is expanded for every IP address generated
13833 by the router, with the generated address set in \$host@_address$\. If the
13834 expansion is forced to fail, no action is taken.
13835 For any other expansion error, delivery of the message is deferred.
13836 If the result of the expansion is an IP address, that replaces the original
13837 address; otherwise the result is assumed to be a host name -- this is looked up
13838 using \*gethostbyname()*\ (or \*getipnodebyname()*\ when available) to produce
13839 one or more replacement IP addresses. For example, to subvert all IP addresses
13840 in some specific networks, this could be added to a router:
13842 $smc{translate@_ip@_address = @\
13843 @$@{lookup@{@$@{mask:@$host@_address/26@}@}lsearch@{/some/file@}@{@$value@}fail@}}
13845 The file would contain lines like
13847 10.2.3.128/26 some.host
13848 10.8.4.34/26 10.44.8.15
13850 You should not make use of this facility unless you really understand what you
13854 .conf transport string$**$ unset
13855 This option specifies the transport to be used when a router accepts an address
13856 and sets it up for delivery. A transport is never needed if a router is used
13857 only for verification. The value of the option is expanded at routing time,
13858 after the expansion of \errors@_to\,
13859 \headers@_add\, and \headers@_remove\,
13860 and result must be the name of one of the configured transports. If it is
13861 not, delivery is deferred.
13863 The \transport\ option is not used by the \%redirect%\ router, but it does have
13864 some private options that set up transports for pipe and file deliveries (see
13865 chapter ~~CHAPredirect).
13868 .conf transport@_current@_directory string$**$ unset
13869 .index current directory for local transport
13870 This option associates a current directory with any address that is routed
13871 to a local transport. This can happen either because a transport is
13872 explicitly configured for the router, or because it generates a delivery to a
13873 file or a pipe. During the delivery process (that is, at transport time), this
13874 option string is expanded and is set as the current directory, unless
13875 overridden by a setting on the transport.
13876 If the expansion fails for any reason, including forced failure, an error is
13877 logged, and delivery is deferred.
13878 See chapter ~~CHAPenvironment for details of the local delivery environment.
13882 .conf transport@_home@_directory string$**$ "see below"
13883 .index home directory||for local transport
13884 This option associates a home directory with any address that is routed to a
13885 local transport. This can happen either because a transport is explicitly
13886 configured for the router, or because it generates a delivery to a file or a
13887 pipe. During the delivery process (that is, at transport time), the option
13888 string is expanded and is set as the home directory, unless overridden by a
13889 setting of \home@_directory\ on the transport.
13890 If the expansion fails for any reason, including forced failure, an error is
13891 logged, and delivery is deferred.
13893 If the transport does not specify a home directory, and
13894 \transport@_home@_directory\ is not set for the router, the home directory for
13895 the tranport is taken from the password data if \check@_local@_user\ is set for
13896 the router. Otherwise it is taken from \router@_home@_directory\ if that option
13897 is set; if not, no home directory is set for the transport.
13899 See chapter ~~CHAPenvironment for further details of the local delivery
13904 .conf unseen boolean$**$ false
13905 .index router||carrying on after success
13906 The result of string expansion for this option must be a valid boolean value,
13907 that is, one of the strings `yes', `no', `true', or `false'. Any other result
13908 causes an error, and delivery is deferred. If the expansion is forced to fail,
13909 the default value for the option (false) is used. Other failures cause delivery
13912 When this option is set true, routing does not cease if the router accepts the
13913 address. Instead, a copy of the incoming address is passed to the next router,
13914 overriding a false setting of \more\. There is little point in setting \more\
13915 false if \unseen\ is always true, but it may be useful in cases when the value
13916 of \unseen\ contains expansion items (and therefore, presumably, is sometimes
13917 true and sometimes false).
13919 The \unseen\ option can be used to cause
13920 .index copy of message (\unseen\ option)
13921 copies of messages to be delivered to some other destination, while also
13922 carrying out a normal delivery. In effect, the current address is made into a
13923 `parent' that has two children -- one that is delivered as specified by this
13924 router, and a clone that goes on to be routed further.
13926 Header lines added to the address (or specified for removal) by this router or
13927 by previous routers affect the `unseen' copy of the message only. The clone
13928 that continues to be processed by further routers starts with no added headers
13929 and none specified for removal.
13931 However, any data that was set by the \address@_data\ option in the current or
13932 previous routers is passed on. Setting this option has a similar effect to the
13933 \unseen\ command qualifier in filter files.
13936 .conf user string$**$ "see below"
13937 .index uid (user id)||local delivery
13938 .index local transports||uid and gid
13939 .index transport||local
13940 .index router||user for filter processing
13941 .index filter||user for processing
13942 When a router queues an address for a transport, and the transport does not
13943 specify a user, the user given here is used when running the delivery process.
13944 The user may be specified numerically or by name. If expansion fails, the
13945 error is logged and delivery is deferred.
13946 This user is also used by the \%redirect%\ router when running a filter file.
13947 The default is unset, except when \check@_local@_user\ is set. In this case,
13948 the default is taken from the password information. If the user is specified as
13949 a name, and \group\ is not set, the group associated with the user is used. See
13950 also \initgroups\ and \group\ and the discussion in chapter ~~CHAPenvironment.
13953 .conf verify "boolean (precondition)" true
13954 Setting this option has the effect of setting \verify@_sender\ and
13955 \verify@_recipient\ to the same value.
13957 .conf verify@_only "boolean (precondition)" false
13958 .index \\EXPN\\||with \verify@_only\
13959 .index \-bv-\ option
13960 .index router||used only when verifying
13961 If this option is set, the router is used only when verifying an address or
13962 testing with the \-bv-\ option, not when actually doing a delivery, testing
13963 with the \-bt-\ option, or running the SMTP \\EXPN\\ command. It can be further
13964 restricted to verifying only senders or recipients by means of \verify@_sender\
13965 and \verify@_recipient\.
13967 \**Warning**\: When the router is being run to verify addresses for an incoming
13968 SMTP message, Exim is not running as root, but under its own uid. If the router
13969 accesses any files, you need to make sure that they are accessible to the Exim
13972 .conf verify@_recipient "boolean (precondition)" true
13973 If this option is false, the router is skipped when verifying recipient
13975 or testing recipient verification using \-bv-\.
13976 See section ~~SECTrouprecon for a list of the order in which preconditions
13979 .conf verify@_sender "boolean (precondition)" true
13980 If this option is false, the router is skipped when verifying sender addresses
13981 or testing sender verification using \-bvs-\.
13982 See section ~~SECTrouprecon for a list of the order in which preconditions
13995 . ============================================================================
13996 .chapter The accept router
13997 .set runningfoot "accept router"
13998 .index \%accept%\ router
13999 .index routers||\%accept%\
14000 The \%accept%\ router has no private options of its own. Unless it is being used
14001 purely for verification (see \verify@_only\) a transport is required to be
14002 defined by the generic \transport\ option. If the preconditions that are
14003 specified by generic options are met, the router accepts the address and queues
14004 it for the given transport. The most common use of this router is for setting
14005 up deliveries to local mailboxes. For example:
14009 domains = mydomain.example
14011 transport = local_delivery
14013 The \domains\ condition in this example checks the domain of the address, and
14014 \check@_local@_user\ checks that the local part is the login of a local user.
14015 When both preconditions are met, the \%accept%\ router runs, and queues the
14016 address for the \%local@_delivery%\ transport.
14027 . ============================================================================
14028 .chapter The dnslookup router
14029 .rset CHAPdnslookup "~~chapter"
14030 .set runningfoot "dnslookup router"
14031 .index \%dnslookup%\ router
14032 .index routers||\%dnslookup%\
14033 The \%dnslookup%\ router looks up the hosts that handle mail for the given
14034 domain in the DNS. A transport must always be set for this router, unless
14035 \verify@_only\ is set.
14037 If SRV support is configured (see \check@_srv\ below), Exim first searches for
14038 SRV records. If none are found, or if SRV support is not configured,
14039 MX records are looked up. If no MX records exist, address records are sought.
14040 However, \mx@_domains\ can be set to disable the direct use of address records.
14042 MX records of equal priority are sorted by Exim into a random order. Exim then
14043 looks for address records for the host names obtained from MX or SRV records.
14044 When a host has more than one IP address, they are sorted into a random order,
14045 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
14046 IP addresses found are discarded by a setting of the \ignore@_target@_hosts\
14047 generic option, the router declines.
14049 Unless they have the highest priority (lowest MX value), MX records that point
14050 to the local host, or to any host name that matches \hosts__treat__as__local\,
14051 are discarded, together with any other MX records of equal or lower priority.
14053 .index MX record||pointing to local host
14054 .index local host||MX pointing to
14055 .index \self\ option||in \%dnslookup%\ router
14056 If the host pointed to by the highest priority MX record, or looked up as an
14057 address record, is the local host, or matches \hosts__treat__as__local\, what
14058 happens is controlled by the generic \self\ option.
14060 There are a number of private options that can be used to vary the way the DNS
14065 .index options||\%dnslookup%\ router
14066 .conf check@_secondary@_mx boolean false
14067 .index MX record||checking for secondary
14068 If this option is set, the router declines unless the local host is found in
14069 (and removed from) the list of hosts obtained by MX lookup. This can be used to
14070 process domains for which the local host is a secondary mail exchanger
14071 differently to other domains. The way in which Exim decides whether a host is
14072 the local host is described in section ~~SECTreclocipadd.
14074 .conf check@_srv string$**$ unset
14075 .index SRV record||enabling use of
14076 The dnslookup router supports the use of SRV records (see RFC 2782) in
14077 addition to MX and address records. The support is disabled by default. To
14078 enable SRV support, set the \check@_srv\ option to the name of the service
14079 required. For example,
14083 looks for SRV records that refer to the normal smtp service. The option is
14084 expanded, so the service name can vary from message to message or address
14085 to address. This might be helpful if SRV records are being used for a
14086 submission service. If the expansion is forced to fail, the \check@_srv\
14087 option is ignored, and the router proceeds to look for MX records in the
14090 When the expansion succeeds, the router searches first for SRV records for
14091 the given service (it assumes TCP protocol). A single SRV record with the
14092 host name \"."\ indicates `no such service for this domain'; if this is
14093 encountered, the router declines. If other kinds of SRV record are found,
14094 they are used to construct a host list for delivery according to the rules
14095 of RFC 2782. MX records are not sought in this case.
14097 However, when no SRV records are found, MX records (and address records)
14098 are sought in the traditional way. In other words, SRV records take
14099 precedence over MX records, just as MX records take precedence over address
14100 records. Note that this behaviour is not sanctioned by RFC 2782, though a
14101 previous draft RFC defined it. It is apparently believed that MX records
14102 are sufficient for email and that SRV records should not be used for this
14103 purpose. However, SRV records have an additional `weight' feature which
14104 some people might find useful when trying to split an SMTP load between
14105 hosts of different power.
14107 .conf mx@_domains "domain list$**$" unset
14108 .index MX record||required to exist
14109 .index SRV record||required to exist
14110 A domain that matches \mx@_domains\ is required to have either an MX or an SRV
14111 record in order to be recognised. (The name of this option could be improved.)
14112 For example, if all the mail hosts in \*fict.example*\ are known to have MX
14113 records, except for those in \*discworld.fict.example*\, you could use this
14116 mx_domains = ! *.discworld.fict.example : *.fict.example
14118 This specifies that messages addressed to a domain that matches the list but
14119 has no MX record should be bounced immediately instead of being routed using
14120 the address record.
14122 .conf qualify@_single boolean true
14123 .index DNS||resolver options
14124 .index DNS||qualifying single-component names
14125 When this option is true, the resolver option \\RES@_DEFNAMES\\ is set for DNS
14126 lookups. Typically, but not standardly, this causes the resolver to qualify
14127 single-component names with the default domain. For example, on a machine
14128 called \*dictionary.ref.example*\, the domain \*thesaurus*\ would be changed to
14129 \*thesaurus.ref.example*\ inside the resolver. For details of what your resolver
14130 actually does, consult your man pages for \*resolver*\ and \*resolv.conf*\.
14133 .conf rewrite@_headers boolean true
14134 .index rewriting||header lines
14135 .index header lines||rewriting
14136 If the domain name in the address that is being processed is not fully
14137 qualified, it may be expanded to its full form by a DNS lookup. For example, if
14138 an address is specified as \*dormouse@@teaparty*\, the domain might be
14139 expanded to \*teaparty.wonderland.fict.example*\. Domain expansion can also
14140 occur as a result of setting the \widen@_domains\ option. If \rewrite@_headers\
14141 is true, all occurrences of the abbreviated domain name in any ::Bcc::, ::Cc::,
14142 ::From::, ::Reply-to::, ::Sender::, and ::To:: header lines of the message are
14143 rewritten with the full domain name.
14145 This option should be turned off only when it is known that no message is
14146 ever going to be sent outside an environment where the abbreviation makes
14149 When an MX record is looked up in the DNS and matches a wildcard record, name
14150 servers normally return a record containing the name that has been looked up,
14151 making it impossible to detect whether a wildcard was present or not. However,
14152 some name servers have recently been seen to return the wildcard entry. If the
14153 name returned by a DNS lookup begins with an asterisk, it is not used for
14156 .conf same@_domain@_copy@_routing boolean false
14157 .index address||copying routing
14158 Addresses with the same domain are normally routed by the \%dnslookup%\ router
14159 to the same list of hosts. However, this cannot be presumed, because the router
14160 options and preconditions may refer to the local part of the address. By
14161 default, therefore, Exim routes each address in a message independently. DNS
14162 servers run caches, so repeated DNS lookups are not normally expensive, and in
14163 any case, personal messages rarely have more than a few recipients.
14165 If you are running mailing lists with large numbers of subscribers at the same
14166 domain, and you are using a \%dnslookup%\ router which is independent of the
14167 local part, you can set \same__domain__copy@_routing\ to bypass repeated DNS
14168 lookups for identical domains in one message. In this case, when \%dnslookup%\
14169 routes an address to a remote transport, any other unrouted addresses in the
14170 message that have the same domain are automatically given the same routing
14171 without processing them independently,
14172 provided the following conditions are met:
14174 No router that processed the address specified \headers@_add\ or
14177 The router did not change the address in any way, for example, by `widening'
14182 .conf search@_parents boolean false
14183 .index DNS||resolver options
14184 When this option is true, the resolver option \\RES@_DNSRCH\\ is set for DNS
14185 lookups. This is different from the \qualify@_single\ option in that it applies
14186 to domains containing dots. Typically, but not standardly, it causes the
14187 resolver to search for the name in the current domain and in parent domains.
14188 For example, on a machine in the \*fict.example*\ domain, if looking up
14189 \*teaparty.wonderland*\ failed, the resolver would try
14190 \*teaparty.wonderland.fict.example*\. For details of what your resolver
14191 actually does, consult your man pages for \*resolver*\ and \*resolv.conf*\.
14193 Setting this option true can cause problems in domains that have a wildcard MX
14194 record, because any domain that does not have its own MX record matches the
14197 .conf widen@_domains "string list" unset
14198 .index domain||partial, widening
14199 If a DNS lookup fails and this option is set, each of its strings in turn is
14200 added onto the end of the domain, and the lookup is tried again. For example,
14203 widen_domains = fict.example:ref.example
14205 is set and a lookup of \*klingon.dictionary*\ fails,
14206 \*klingon.dictionary.fict.example*\ is looked up, and if this fails,
14207 \*klingon.dictionary.ref.example*\ is tried. Note that the \qualify@_single\
14208 and \search@_parents\ options can cause some widening to be undertaken inside
14213 .section Effect of qualify@_single and search@_parents
14214 When a domain from an envelope recipient is changed by the resolver as a result
14215 of the \qualify@_single\ or \search@_parents\ options, Exim rewrites the
14216 corresponding address in the message's header lines unless \rewrite@_headers\
14217 is set false. Exim then re-routes the address, using the full domain.
14219 These two options affect only the DNS lookup that takes place inside the router
14220 for the domain of the address that is being routed. They do not affect lookups
14221 such as that implied by
14225 that may happen while processing a router precondition before the router is
14226 entered. No widening ever takes place for these lookups.
14240 . ============================================================================
14241 .chapter The ipliteral router
14242 .set runningfoot "ipliteral router"
14243 .index \%ipliteral%\ router
14244 .index domain literal||routing
14245 .index routers||\%ipliteral%\
14246 This router has no private options. Unless it is being used purely for
14247 verification (see \verify@_only\) a transport is required to be defined by the
14248 generic \transport\ option. The router accepts the address if its domain part
14249 takes the form of an RFC 2822 domain literal, that is, an IP address enclosed
14250 in square brackets. For example, this router handles the address
14254 by setting up delivery to the host with that IP address.
14256 If the IP address matches something in \ignore@_target@_hosts\, the router
14258 .index \self\ option||in \%ipliteral%\ router
14259 If an IP literal turns out to refer to the local host, the generic \self\
14260 option determines what happens.
14262 The RFCs require support for domain literals; however, their use is
14263 controversial in today's Internet. If you want to use this router, you must
14264 also set the main configuration option \allow@_domain@_literals\. Otherwise,
14265 Exim will not recognize the domain literal syntax in addresses.
14273 . ============================================================================
14274 .chapter The iplookup router
14275 .set runningfoot "iplookup router"
14276 .index \%iplookup%\ router
14277 .index routers||\%iplookup%\
14278 The \%iplookup%\ router was written to fulfil a specific requirement in
14279 Cambridge University. For this reason, it is not included in the binary of Exim
14280 by default. If you want to include it, you must set
14282 ROUTER_IPLOOKUP=yes
14284 in your \(Local/Makefile)\ configuration file.
14286 The \%iplookup%\ router routes an address by sending it over a TCP or UDP
14287 connection to one or more specific hosts. The host can then return the same or
14288 a different address -- in effect rewriting the recipient address in the
14289 message's envelope. The new address is then passed on to subsequent routers.
14292 If this process fails, the address can be passed on to
14293 other routers, or delivery can be deferred.
14295 Background, for those that are interested: We have an Oracle database of all
14296 Cambridge users, and one of the items of data it maintains for each user is
14297 where to send mail addressed to \*user@@cam.ac.uk*\. The MX records for
14298 \*cam.ac.uk*\ point to a central machine that has a large alias list that is
14299 abstracted from the database. Mail from outside is switched by this system, and
14300 originally internal mail was also done this way. However, this resulted in a
14301 fair number of messages travelling from some of our larger systems to the
14302 switch and back again. The Oracle machine now runs a UDP service that can be
14303 called by the \%iplookup%\ router in Exim to find out where \*user@@cam.ac.uk*\
14304 addresses really have to go; this saves passing through the central switch, and
14305 in many cases saves doing any remote delivery at all.
14307 Since \%iplookup%\ is just a rewriting router, a transport must not be
14311 .index options||\%iplookup%\ router
14313 .conf hosts string unset
14314 This option must be supplied. Its value is a colon-separated list of host
14315 names. The hosts are looked up using \*gethostbyname()*\
14316 (or \*getipnodebyname()*\ when available)
14317 and are tried in order until one responds to the query. If none respond, what
14318 happens is controlled by \optional\.
14320 .conf optional boolean false
14321 If \optional\ is true, if no response is obtained from any host, the address is
14322 passed to the next router, overriding \no@_more\. If \optional\ is false,
14323 delivery to the address is deferred.
14325 .conf port integer 0
14326 .index port||\%iplookup%\ router
14327 This option must be supplied. It specifies the port number for the TCP or UDP
14330 .conf protocol string "udp"
14331 This option can be set to `udp' or `tcp' to specify which of the two protocols
14334 .conf query string$**$ "$tt{@$local@_part@@@$domain @$local@_part@@@$domain}"
14335 This defines the content of the query that is sent to the remote hosts. The
14336 repetition serves as a way of checking that a response is to the correct query
14337 in the default case (see \response@_pattern\ below).
14339 .conf reroute string$**$ unset
14340 If this option is not set, the rerouted address is precisely the byte string
14341 returned by the remote host, up to the first white space, if any. If set, the
14342 string is expanded to form the rerouted address. It can include parts matched
14343 in the response by \response@_pattern\ by means of numeric variables such as
14344 \$1$\, \$2$\, etc. The variable \$0$\ refers to the entire input string,
14345 whether or not a pattern is in use. In all cases, the rerouted address must end
14346 up in the form \*local@_part@@domain*\.
14348 .conf response@_pattern string unset
14349 This option can be set to a regular expression that is applied to the string
14350 returned from the remote host. If the pattern does not match the response, the
14351 router declines. If \response@_pattern\ is not set, no checking of the response
14352 is done, unless the query was defaulted, in which case there is a check that
14353 the text returned after the first white space is the original address. This
14354 checks that the answer that has been received is in response to the correct
14355 question. For example, if the response is just a new domain, the following
14358 response_pattern = ^([^@]+)$
14359 reroute = $local_part@$1
14362 .conf timeout time 5s
14363 This specifies the amount of time to wait for a response from the remote
14364 machine. The same timeout is used for the \*connect()*\ function for a TCP
14365 call. It does not apply to UDP.
14376 . ============================================================================
14377 .chapter The manualroute router
14378 .set runningfoot "manualroute router"
14379 .index \%manualroute%\ router
14380 .index routers||\%manualroute%\
14381 .index domain||manually routing
14382 The \%manualroute%\ router is so-called because it provides a way of manually
14383 routing an address according to its domain. It is mainly used when you want to
14384 route addresses to remote hosts according to your own rules, bypassing the
14385 normal DNS routing that looks up MX records. However, \%manualroute%\ can also
14386 route to local transports, a facility that may be useful if you want to save
14387 messages for dial-in hosts in local files.
14389 The \%manualroute%\ router compares a list of domain patterns with the domain it
14390 is trying to route. If there is no match, the router declines. Each pattern has
14391 associated with it a list of hosts and some other optional data, which may
14392 include a transport. The combination of a pattern and its data is called a
14393 `routing rule'. For patterns that do not have an associated transport, the
14394 generic \transport\ option must specify a transport, unless the router is being
14395 used purely for verification (see \verify@_only\).
14397 In the case of verification, matching the domain pattern is sufficient for the
14398 router to accept the address. When actually routing an address for delivery,
14399 an address that matches a domain pattern is queued for the associated
14400 transport. If the transport is not a local one, a host list must be associated
14401 with the pattern; IP addresses are looked up for the hosts, and these are
14402 passed to the transport along with the mail address. For local transports, a
14403 host list is optional. If it is present, it is passed in \$host$\ as a single
14406 The list of routing rules can be provided as an inline string in \route@_list\,
14407 or the data can be obtained by looking up the domain in a file or database by
14408 setting \route@_data\. Only one of these settings may appear in any one
14409 instance of \%manualroute%\. The format of routing rules is described below,
14410 following the list of private options.
14412 .section Private options for manualroute
14413 .rset SECTprioptman "~~chapter.~~section"
14415 The private options for the \%manualroute%\ router are as follows:
14418 .index options||\%manualroute%\ router
14420 .conf host@_find@_failed string "freeze"
14421 This option controls what happens when \%manualroute%\ tries to find an IP
14422 address for a host, and the host does not exist. The option can be set to one
14431 The default assumes that this state is a serious configuration error. The
14432 difference between `pass' and `decline' is that the former forces the address
14433 to be passed to the next router (or the router defined by \pass@_router\),
14434 .index \more\ option
14435 overriding \no@_more\, whereas the latter passes the address to the next router
14436 only if \more\ is true.
14438 This option applies only to a definite `does not exist' state; if a host lookup
14439 gets a temporary error, delivery is deferred unless the generic
14440 \pass@_on@_timeout\ option is set.
14442 .conf hosts@_randomize boolean false
14443 .index randomized host list
14444 .index host||list of, randomized
14445 If this option is set, the order of the items in a host list in a routing rule
14446 is randomized each time the list is used, unless an option in the routing rule
14447 overrides (see below). Randomizing the order of a host list can be used to do
14448 crude load sharing. However, if more than one mail address is routed by the
14449 same router to the same host list, the host lists are considered to be the same
14450 (even though they may be randomized into different orders) for the purpose of
14451 deciding whether to batch the deliveries into a single SMTP transaction.
14453 When \hosts@_randomize\ is true, a host list may be split
14454 into groups whose order is separately randomized. This makes it possible to
14455 set up MX-like behaviour. The boundaries between groups are indicated by an
14456 item that is just \"+"\ in the host list. For example:
14458 route_list = * host1:host2:host3:+:host4:host5
14460 The order of the first three hosts and the order of the last two hosts is
14461 randomized for each use, but the first three always end up before the last two.
14462 If \hosts@_randomize\ is not set, a \"+"\ item in the list is ignored. If a
14463 randomized host list is passed to an \%smtp%\ transport that also has
14464 \hosts@_randomize set\, the list is not re-randomized.
14466 .conf route@_data string$**$ unset
14467 If this option is set, it must expand to yield the data part of a routing rule.
14468 Typically, the expansion string includes a lookup based on the domain. For
14471 route_data = ${lookup{$domain}dbm{/etc/routes}}
14473 If the expansion is forced to fail, or the result is an empty string, the
14474 router declines. Other kinds of expansion failure cause delivery to be
14477 .conf route@_list "string list, semicolon-separated" unset
14478 This string is a list of routing rules, in the form defined below. Note that,
14479 unlike most string lists, the items are separated by semicolons. This is so
14480 that they may contain colon-separated host lists.
14482 .conf same@_domain@_copy@_routing boolean false
14483 .index address||copying routing
14484 Addresses with the same domain are normally routed by the \%manualroute%\ router
14485 to the same list of hosts. However, this cannot be presumed, because the router
14486 options and preconditions may refer to the local part of the address. By
14487 default, therefore, Exim routes each address in a message independently. DNS
14488 servers run caches, so repeated DNS lookups are not normally expensive, and in
14489 any case, personal messages rarely have more than a few recipients.
14491 If you are running mailing lists with large numbers of subscribers at the same
14492 domain, and you are using a \%manualroute%\ router which is independent of the
14493 local part, you can set \same@_domain@_copy@_routing\ to bypass repeated DNS
14494 lookups for identical domains in one message. In this case, when \%manualroute%\
14495 routes an address to a remote transport, any other unrouted addresses in the
14496 message that have the same domain are automatically given the same routing
14497 without processing them independently. However, this is only done if
14498 \headers@_add\ and \headers@_remove\ are unset.
14503 .section Routing rules in route@_list
14504 The value of \route@_list\ is a string consisting of a sequence of routing
14505 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
14506 entered as two semicolons. Empty rules are ignored. The format of each rule is
14508 <<domain pattern>> <<list of hosts>> <<options>>
14510 The following example contains two rules, each with a simple domain pattern and
14514 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
14515 thes.ref.example mail-3.ref.example:mail-4.ref.example
14517 The three parts of a rule are separated by white space. The pattern and the
14518 list of hosts can be enclosed in quotes if necessary, and if they are, the
14519 usual quoting rules apply. Each rule in a \route@_list\ must start with a
14520 single domain pattern, which is the only mandatory item in the rule. The
14521 pattern is in the same format as one item in a domain list (see section
14523 except that it may not be the name of an interpolated file.
14524 That is, it may be wildcarded, or a regular expression, or a file or database
14525 lookup (with semicolons doubled, because of the use of semicolon as a separator
14526 in a \route@_list\).
14528 The rules in \route@_list\ are searched in order until one of the patterns
14529 matches the domain that is being routed. The list of hosts and then options are
14530 then used as described below. If there is no match, the router declines. When
14531 \route@_list\ is set, \route@_data\ must not be set.
14534 .section Routing rules in route@_data
14535 The use of \route@_list\ is convenient when there are only a small number of
14536 routing rules. For larger numbers, it is easier to use a file or database to
14537 hold the routing information, and use the \route@_data\ option instead.
14538 The value of \route@_data\ is a list of hosts, followed by (optional) options.
14539 Most commonly, \route@_data\ is set as a string that contains an
14540 expansion lookup. For example, suppose we place two routing rules in a file
14543 dict.ref.example: mail-1.ref.example:mail-2.ref.example
14544 thes.ref.example: mail-3.ref.example:mail-4.ref.example
14546 This data can be accessed by setting
14548 route_data = ${lookup{$domain}lsearch{/the/file/name}}
14550 Failure of the lookup results in an empty string, causing the router to
14551 decline. However, you do not have to use a lookup in \route@_data\. The only
14552 requirement is that the result of expanding the string is a list of hosts,
14553 possibly followed by options, separated by white space. The list of hosts must
14554 be enclosed in quotes if it contains white space.
14558 .section Format of the list of hosts
14559 A list of hosts, whether obtained via \route@_data\ or \route@_list\, is always
14560 separately expanded before use. If the expansion fails, the router declines.
14561 The result of the expansion must be a colon-separated list of names and/or
14562 IP addresses. IP addresses are not enclosed in brackets.
14564 If the list of hosts was obtained from a \route@_list\ item, the following
14565 variables are set during its expansion:
14566 .index numerical variables (\$1$\, \$2$\, etc)||in \%manualroute%\ router
14568 If the domain was matched against a regular expression, the numeric variables
14569 \$1$\, \$2$\, etc. may be set.
14571 \$0$\ is always set to the entire domain.
14573 \$1$\ is also set when partial matching is done in a file lookup.
14576 If the pattern that matched the domain was a lookup item, the data that was
14577 looked up is available in the expansion variable \$value$\.
14581 .section How the list of hosts is used
14582 When an address is routed to an \%smtp%\ transport by \%manualroute%\, each of
14583 the hosts is tried, in the order specified, when carrying out the SMTP
14584 delivery. However, the order can be changed by setting the \hosts@_randomize\
14585 option, either on the router (see section ~~SECTprioptman above), or on the
14588 Hosts may be listed by name or by IP address. An unadorned name in the list of
14589 hosts is interpreted as a host name. A name that is followed by \"/MX"\ is
14590 interpreted as an indirection to a sublist of hosts obtained by looking up MX
14591 records in the DNS. For example:
14593 route_list = * x.y.z:p.q.r/MX:e.f.g
14595 If the \hosts@_randomize\ option is set, the order of the items in the list is
14596 randomized before any lookups are done. Exim then scans the list; for any name
14597 that is not followed by \"/MX"\ it looks up an IP address. If this turns out to
14598 be an interface on the local host and the item is not the first in the list,
14599 Exim discards it and any subsequent items. If it is the first item, what
14600 happens is controlled by the
14601 .index \self\ option||in \%manualroute%\ router
14602 \self\ option of the router.
14604 A name on the list that is followed by \"/MX"\ is replaced with the list of
14605 hosts obtained by looking up MX records for the name. This is always a DNS
14606 lookup; the \bydns\ and \byname\ options (see section ~~SECThowoptused below)
14607 are not relevant here. The order of these hosts is determined by the preference
14608 values in the MX records, according to the usual rules. Because randomizing
14609 happens before the MX lookup, it does not affect the order that is defined by
14612 If the local host is present in the sublist obtained from MX records, but is
14613 not the most preferred host in that list, it and any equally or less
14614 preferred hosts are removed before the sublist is inserted into the main list.
14616 If the local host is the most preferred host in the MX list, what happens
14617 depends on where in the original list of hosts the \"/MX"\ item appears. If it
14618 is not the first item (that is, there are previous hosts in the main list),
14619 Exim discards this name and any subsequent items in the main list.
14621 If the MX item is first in the list of hosts, and the local host is the
14622 most preferred host, what happens is controlled by the \self\ option of the
14625 DNS failures when lookup up the MX records are treated in the same way as DNS
14626 failures when looking up IP addresses: \pass@_on@_timeout\ and
14627 \host@_find@_failed\ are used when relevant.
14629 The generic \ignore@_target@_hosts\ option applies to all hosts in the list,
14630 whether obtained from an MX lookup or not.
14633 .section How the options are used
14634 .rset SECThowoptused "~~chapter.~~section"
14635 The options are a sequence of words; in practice no more than three are ever
14636 present. One of the words can be the name of a transport; this overrides the
14637 \transport\ option on the router for this particular routing rule only. The
14638 other words (if present) control randomization of the list of hosts on a
14639 per-rule basis, and how the IP addresses of the hosts are to be found when
14640 routing to a remote transport. These options are as follows:
14642 \randomize\: randomize the order of the hosts in this list, overriding the
14643 setting of \hosts@_randomize\ for this routing rule only.
14645 \no@_randomize\: do not randomize the order of the hosts in this list,
14646 overriding the setting of \hosts@_randomize\ for this routing rule only.
14648 \byname\: use \*getipnodebyname()*\ (\*gethostbyname()*\ on older systems) to
14649 find IP addresses. This function may ultimately cause a DNS lookup, but it may
14650 also look in \(/etc/hosts)\ or other sources of information.
14652 \bydns\: look up address records for the hosts directly in the DNS; fail if
14653 no address records are found. If there is a temporary DNS error (such as a
14654 timeout), delivery is deferred.
14658 route_list = domain1 host1:host2:host3 randomize bydns;\
14659 domain2 host4:host5
14661 If neither \byname\ nor \bydns\ is given, Exim behaves as follows: First, a DNS
14662 lookup is done. If this yields anything other than \\HOST@_NOT@_FOUND\\, that
14663 result is used. Otherwise, Exim goes on to try a call to \*getipnodebyname()*\
14664 or \*gethostbyname()*\, and the result of the lookup is the result of that
14667 \**Warning**\: It has been discovered that on some systems, if a DNS lookup
14668 called via \*getipnodebyname()*\ times out, \\HOST@_NOT@_FOUND\\ is returned
14669 instead of \\TRY@_AGAIN\\. That is why the default action is to try a DNS
14670 lookup first. Only if that gives a definite `no such host' is the local
14675 If no IP address for a host can be found, what happens is controlled by the
14676 \host@_find@_failed\ option.
14678 When an address is routed to a local transport, IP addresses are not looked up.
14679 The host list is passed to the transport in the \$host$\ variable.
14682 .section Manualroute examples
14683 In some of the examples that follow, the presence of the \remote@_smtp\
14684 transport, as defined in the default configuration file, is assumed:
14687 .index smart host||example router
14688 The \%manualroute%\ router can be used to forward all external mail to a
14689 \*smart host*\. If you have set up, in the main part of the configuration, a
14690 named domain list that contains your local domains, for example,
14692 domainlist local_domains = my.domain.example
14694 you can arrange for all other domains to be routed to a smart host by making
14695 your first router something like this:
14698 driver = manualroute
14699 domains = !+local_domains
14700 transport = remote_smtp
14701 route_list = * smarthost.ref.example
14703 This causes all non-local addresses to be sent to the single host
14704 \*smarthost.ref.example*\. If a colon-separated list of smart hosts is given,
14705 they are tried in order
14706 (but you can use \hosts@_randomize\ to vary the order each time).
14707 Another way of configuring the same thing is this:
14710 driver = manualroute
14711 transport = remote_smtp
14712 route_list = !+local_domains smarthost.ref.example
14714 There is no difference in behaviour between these two routers as they stand.
14715 However, they behave differently if \no@_more\ is added to them. In the first
14716 example, the router is skipped if the domain does not match the \domains\
14717 precondition; the following router is always tried. If the router runs, it
14718 always matches the domain and so can never decline. Therefore, \no@_more\ would
14719 have no effect. In the second case, the router is never skipped; it always
14720 runs. However, if it doesn't match the domain, it declines. In this case
14721 \no@_more\ would prevent subsequent routers from running.
14724 .index mail hub example
14725 A \*mail hub*\ is a host which receives mail for a number of domains via MX
14726 records in the DNS and delivers it via its own private routing mechanism. Often
14727 the final destinations are behind a firewall, with the mail hub being the one
14728 machine that can connect to machines both inside and outside the firewall. The
14729 \%manualroute%\ router is usually used on a mail hub to route incoming messages
14730 to the correct hosts. For a small number of domains, the routing can be inline,
14731 using the \route@_list\ option, but for a larger number a file or database
14732 lookup is easier to manage.
14734 If the domain names are in fact the names of the machines to which the mail is
14735 to be sent by the mail hub, the configuration can be quite simple. For
14739 driver = manualroute
14740 transport = remote_smtp
14741 route_list = *.rhodes.tvs.example $domain
14743 This configuration routes domains that match \"*.rhodes.tvs.example"\ to hosts
14744 whose names are the same as the mail domains. A similar approach can be taken
14745 if the host name can be obtained from the domain name by a string manipulation
14746 that the expansion facilities can handle. Otherwise, a lookup based on the
14747 domain can be used to find the host:
14750 driver = manualroute
14751 transport = remote_smtp
14752 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
14754 The result of the lookup must be the name or IP address of the host (or
14755 hosts) to which the address is to be routed. If the lookup fails, the route
14756 data is empty, causing the router to decline. The address then passes to the
14760 .index batched SMTP output example
14761 .index SMTP||batched outgoing, example
14762 You can use \%manualroute%\ to deliver messages to pipes or files in batched
14763 SMTP format for onward transportation by some other means. This is one way of
14764 storing mail for a dial-up host when it is not connected. The route list entry
14765 can be as simple as a single domain name in a configuration like this:
14768 driver = manualroute
14769 transport = batchsmtp_appendfile
14770 route_list = saved.domain.example
14772 though often a pattern is used to pick up more than one domain. If there are
14773 several domains or groups of domains with different transport requirements,
14774 different transports can be listed in the routing information:
14777 driver = manualroute
14779 *.saved.domain1.example $domain batch_appendfile; \
14780 *.saved.domain2.example \
14781 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
14784 The first of these just passes the domain in the \$host$\ variable, which
14785 doesn't achieve much (since it is also in \$domain$\), but the second does a
14786 file lookup to find a value to pass, causing the router to decline to handle
14787 the address if the lookup fails.
14789 .index UUCP||example of router for
14790 Routing mail directly to UUCP software is a specific case of the use of
14791 \%manualroute%\ in a gateway to another mail environment. This is an example of
14792 one way it can be done:
14798 command = /usr/local/bin/uux -r - \
14799 ${substr_-5:$host}!rmail ${local_part}
14800 return_fail_output = true
14806 driver = manualroute
14808 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
14810 The file \(/usr/local/exim/uucphosts)\ contains entries like
14812 darksite.ethereal.example: darksite.UUCP
14814 It can be set up more simply without adding and removing `.UUCP' but this way
14815 makes clear the distinction between the domain name
14816 \*darksite.ethereal.example*\ and the UUCP host name \*darksite*\.
14828 . ============================================================================
14829 .chapter The queryprogram router
14830 .set runningfoot "queryprogram router"
14831 .rset CHAPdriverlast "~~chapter"
14832 .index \%queryprogram%\ router
14833 .index routers||\%queryprogram%\
14834 .index routing||by external program
14835 The \%queryprogram%\ router routes an address by running an external command and
14836 acting on its output. This is an expensive way to route, and is intended mainly
14837 for use in lightly-loaded systems, or for performing experiments. However, if
14838 it is possible to use the precondition options (\domains\, \local@_parts\,
14839 etc) to skip this router for most addresses, it could sensibly be used in
14840 special cases, even on a busy host. There are the following private options:
14843 .index options||\%queryprogram%\ router
14844 .conf command string$**$ unset
14845 This option must be set. It specifies the command that is to be run. The
14846 command is split up into a command name and arguments, and then each is
14847 expanded separately (exactly as for a \%pipe%\ transport, described in chapter
14848 ~~CHAPpipetransport).
14850 .conf command@_group string unset
14851 .index gid (group id)||in \%queryprogram%\ router
14852 This option specifies a gid to be set when running the command. It must be set
14853 if \command@_user\ specifies a numerical uid. If it begins with a digit, it is
14854 interpreted as the numerical value of the gid. Otherwise it is looked up using
14857 .conf command@_user string unset
14858 .index uid (user id)||for \%queryprogram%\
14859 This option must be set. It specifies the uid which is set when running the
14860 command. If it begins with a digit it is interpreted as the numerical value of
14861 the uid. Otherwise, it is looked up using \*getpwnam()*\ to obtain a value for
14862 the uid and, if \command@_group\ is not set, a value for the gid also.
14864 .conf current@_directory string /
14865 This option specifies an absolute path which is made the current directory
14866 before running the command.
14868 .conf timeout time 1h
14869 If the command does not complete within the timeout period, its process group
14870 is killed and the message is frozen. A value of zero time specifies no
14875 The standard output of the command is connected to a pipe, which is read when
14876 the command terminates. It should consist of a single line of output,
14877 containing up to five fields, separated by white space. The first field is one
14878 of the following words (case-insensitive):
14880 \*Accept*\: routing succeeded; the remaining fields specify what to do (see
14883 \*Decline*\: the router declines; pass the address to the next router, unless
14886 \*Fail*\: routing failed; do not pass the address to any more routers. Any
14887 subsequent text on the line is an error message. If the router is run as part
14888 of address verification during an incoming SMTP message, the message is
14889 included in the SMTP response.
14891 \*Defer*\: routing could not be completed at this time; try again later. Any
14892 subsequent text on the line is an error message which is logged. It is not
14893 included in any SMTP response.
14895 \*Freeze*\: the same as \*defer*\, except that the message is frozen.
14897 \*Pass*\: pass the address to the next router (or the router specified by
14898 \pass@_router\), overriding \no@_more\.
14900 \*Redirect*\: the message is redirected. The remainder of the line is a list of
14901 new addresses, which are routed independently, starting with the first router,
14902 or the router specified by \redirect@_router\, if set.
14904 When the first word is \*accept*\, the remainder of the line consists of a
14905 number of keyed data values, as follows (split into two lines here, to fit on
14908 ACCEPT TRANSPORT=<<transport>> HOSTS=<<list of hosts>>
14909 LOOKUP=byname|bydns DATA=<<text>>
14911 The data items can be given in any order, and all are optional. If no transport
14912 is included, the transport specified by the generic \transport\ option is used.
14913 The list of hosts and the lookup type are needed only if the transport is an
14914 \%smtp%\ transport that does not itself supply a list of hosts.
14916 The format of the list of hosts is the same as for the \%manualroute%\ router.
14917 As well as host names and IP addresses, it may contain names followed by
14918 \"/MX"\ to specify sublists of hosts that are obtained by looking up MX
14921 If the lookup type is not specified, Exim behaves as follows when trying to
14922 find an IP address for each host: First, a DNS lookup is done. If this yields
14923 anything other than \\HOST@_NOT@_FOUND\\, that result is used. Otherwise, Exim
14924 goes on to try a call to \*getipnodebyname()*\ or \*gethostbyname()*\, and the
14925 result of the lookup is the result of that call.
14927 If the DATA field is set, its value is placed in the \$address@_data$\
14928 variable. For example, this return line
14930 accept hosts=x1.y.example:x2.y.example data="rule1"
14932 routes the address to the default transport, with a host list containing two
14933 hosts. When the transport runs, the string `rule1' is in \$address@_data$\.
14941 . ============================================================================
14942 .chapter The redirect router
14943 .set runningfoot "redirect router"
14944 .rset CHAPredirect "~~chapter"
14945 .index \%redirect%\ router
14946 .index routers||\%redirect%\
14947 .index alias file||in a \%redirect%\ router
14948 .index address redirection||\%redirect%\ router
14949 The \%redirect%\ router handles several kinds of address redirection. Its most
14950 common uses are for resolving local part aliases from a central alias file
14951 (usually called \(/etc/aliases)\) and for handling users' personal \(.forward)\
14952 files, but it has many other potential uses. The incoming address can be
14953 redirected in several different ways:
14955 It can be replaced by one or more new addresses which are themselves routed
14958 It can be routed to be delivered to a given file or directory.
14960 It can be routed to be delivered to a specified pipe command.
14962 It can cause an automatic reply to be generated.
14964 It can be forced to fail, with a custom error message.
14966 It can be temporarily deferred.
14968 It can be discarded.
14970 The generic \transport\ option must not be set for \%redirect%\ routers.
14971 However, there are some private options which define transports for delivery to
14972 files and pipes, and for generating autoreplies. See the \file@_transport\,
14973 \pipe@_transport\ and \reply@_transport\ descriptions below.
14976 .section Redirection data
14977 The router operates by interpreting a text string which it obtains either by
14978 expanding the contents of the \data\ option, or by reading the entire contents
14979 of a file whose name is given in the \file\ option. These two options are
14980 mutually exclusive. The first is commonly used for handling system aliases, in
14981 a configuration like this:
14985 data = ${lookup{$local_part}lsearch{/etc/aliases}}
14987 If the lookup fails, the expanded string in this example is empty. When the
14988 expansion of \data\ results in an empty string, the router declines. A forced
14989 expansion failure also causes the router to decline; other expansion failures
14990 cause delivery to be deferred.
14992 A configuration using \file\ is commonly used for handling users' \(.forward)\
14998 file = $home/.forward
15001 If the file does not exist, or causes no action to be taken (for example, it is
15002 empty or consists only of comments), the router declines. \**Warning**\: This
15003 is not the case when the file contains syntactically valid items that happen to
15004 yield empty addresses, for example, items containing only RFC 2822 address
15008 .section Forward files and address verification
15009 .index address redirection||while verifying
15010 It is usual to set \no@_verify\ on \%redirect%\ routers which handle users'
15011 \(.forward)\ files, as in the example above. There are two reasons for this:
15013 When Exim is receiving an incoming SMTP message from a remote host, it is
15014 running under the Exim uid, not as root.
15015 No additional groups are set up, even if the Exim uid is a member of other
15016 groups (that is, the \*initgroups()*\ function is not run).
15017 Exim is unable to change uid to read the file as the user, and it may not be
15018 able to read it as the Exim user. So in practice the router may not be able to
15021 However, even when the router can operate, the existence of a \(.forward)\ file
15022 is unimportant when verifying an address. What should be checked is whether the
15023 local part is a valid user name or not. Cutting out the redirection processing
15024 saves some resources.
15030 .section Interpreting redirection data
15031 .index Sieve filter||specifying in redirection data
15032 .index filter||specifying in redirection data
15033 The contents of the data string, whether obtained from \data\ or \file\, can be
15034 interpreted in two different ways:
15036 If the \allow@_filter\ option is set true, and the data begins with the text
15037 `@#Exim filter' or `@#Sieve filter', it is interpreted as a list of
15038 \*filtering*\ instructions in the form of an Exim or Sieve filter file,
15039 respectively. Details of the syntax and semantics of filter files are described
15040 in a separate document entitled \*Exim's interfaces to mail filtering*\; this
15041 document is intended for use by end users.
15043 Otherwise, the data must be a comma-separated list of redirection items, as
15044 described in the next section.
15046 When a message is redirected to a file (a `mail folder'), the file name given
15047 in a non-filter redirection list must always be an absolute path. A filter may
15048 generate a relative path -- how this is handled depends on the transport's
15049 configuration. See section ~~SECTfildiropt for a discussion of this issue for
15050 the \%appendfile%\ transport.
15053 .section Items in a non-filter redirection list
15054 .rset SECTitenonfilred "~~chapter.~~section"
15055 .index address redirection||non-filter list items
15056 When the redirection data is not an Exim or Sieve filter, for example, if it
15057 comes from a conventional alias or forward file, it consists of a list of
15058 addresses, file names, pipe commands, or certain special items (see section
15059 ~~SECTspecitredli below). The special items can be individually enabled or
15060 disabled by means of options whose names begin with \allow@_\ or \forbid@_\,
15061 depending on their default values. The items in the list are separated by
15062 commas or newlines.
15063 If a comma is required in an item, the entire item must be enclosed in double
15066 Lines starting with a @# character are comments, and are ignored, and @# may
15067 also appear following a comma, in which case everything between the @# and the
15068 next newline character is ignored.
15070 If an item is entirely enclosed in double quotes, these are removed. Otherwise
15071 double quotes are retained because some forms of mail address require their use
15072 (but never to enclose the entire address). In the following description, `item'
15073 refers to what remains after any surrounding double quotes have been removed.
15075 \**Warning**\: If you use an Exim expansion to construct a redirection address,
15076 and the expansion contains a reference to \$local@_part$\, you should make use
15077 of the \quote\ expansion operator, in case the local part contains special
15078 characters. For example, to redirect all mail for the domain
15079 \*obsolete.example*\, retaining the existing local part, you could use this
15082 data = ${quote:$local_part}@newdomain.example
15086 .section Redirecting to a local mailbox
15087 .rset SECTredlocmai "~~chapter.~~section"
15088 .index routing||loops in
15089 .index loop||while routing, avoidance of
15090 .index address redirection||to local mailbox
15091 A redirection item may safely be the same as the address currently under
15092 consideration. This does not cause a routing loop, because a router is
15093 automatically skipped if any ancestor of the address that is being processed
15094 is the same as the current address and was processed by the current router.
15095 Such an address is therefore passed to the following routers, so it is handled
15096 as if there were no redirection. When making this loop-avoidance test, the
15097 complete local part, including any prefix or suffix, is used.
15099 .index address redirection||local part without domain
15100 Specifying the same local part without a domain is a common usage in personal
15101 filter files when the user wants to have messages delivered to the local
15102 mailbox and also forwarded elsewhere. For example, the user whose login is
15103 \*cleo*\ might have a \(.forward)\ file containing this:
15105 cleo, cleopatra@egypt.example
15107 .index backslash in alias file
15108 .index alias file||backslash in
15109 For compatibility with other MTAs, such unqualified local parts may be
15110 preceeded by `@\', but this is not a requirement for loop prevention. However,
15111 it does make a difference if more than one domain is being handled
15114 If an item begins with `@\' and the rest of the item parses as a valid RFC 2822
15115 address that does not include a domain, the item is qualified using the domain
15116 of the incoming address. In the absence of a leading `@\', unqualified
15117 addresses are qualified using the value in \qualify@_recipient\, but you can
15118 force the incoming domain to be used by setting \qualify__preserve@_domain\.
15120 Care must be taken if there are alias names for local users.
15121 Consider an MTA handling a single local domain where the system alias file
15126 Now suppose that Sam (whose login id is \*spqr*\) wants to save copies of
15127 messages in the local mailbox, and also forward copies elsewhere. He creates
15130 Sam.Reman, spqr@reme.elsewhere.example
15132 With these settings, an incoming message addressed to \*Sam.Reman*\ fails. The
15133 \%redirect%\ router for system aliases does not process \*Sam.Reman*\ the
15134 second time round, because it has previously routed it,
15135 and the following routers presumably cannot handle the alias. The forward file
15136 should really contain
15138 spqr, spqr@reme.elsewhere.example
15140 but because this is such a common error, the \check@_ancestor\ option (see
15141 below) exists to provide a way to get round it. This is normally set on a
15142 \%redirect%\ router that is handling users' \(.forward)\ files.
15145 .section Special items in redirection lists
15146 .rset SECTspecitredli "~~chapter.~~section"
15147 In addition to addresses, the following types of item may appear in redirection
15148 lists (that is, in non-filter redirection data):
15151 .index pipe||in redirection list
15152 .index address redirection||to pipe
15153 An item is treated as a pipe command if it begins with `|' and does not parse
15154 as a valid RFC 2822 address that includes a domain. A transport for running the
15155 command must be specified by the \pipe@_transport\ option.
15156 Normally, either the router or the transport specifies a user and a group under
15157 which to run the delivery. The default is to use the Exim user and group.
15159 Single or double quotes can be used for enclosing the individual arguments of
15160 the pipe command; no interpretation of escapes is done for single quotes. If
15161 the command contains a comma character, it is necessary to put the whole item
15162 in double quotes, for example:
15164 "|/some/command ready,steady,go"
15166 since items in redirection lists are terminated by commas. Do not, however,
15167 quote just the command. An item such as
15169 |"/some/command ready,steady,go"
15171 is interpreted as a pipe with a rather strange command name, and no arguments.
15173 .index file||in redirection list
15174 .index address redirection||to file
15175 An item is interpreted as a path name if it begins with `/' and does not parse
15176 as a valid RFC 2822 address that includes a domain. For example,
15178 /home/world/minbari
15180 is treated as a file name, but
15182 /s=molari/o=babylon/@x400gate.way
15184 is treated as an address. For a file name, a transport must be specified using
15185 the \file@_transport\ option. However, if the generated path name ends with a
15186 forward slash character, it is interpreted as a directory name rather than a
15187 file name, and \directory@_transport\ is used instead.
15189 Normally, either the router or the transport specifies a user and a group under
15190 which to run the delivery. The default is to use the Exim user and group.
15191 .index \(/dev/null)\
15192 However, if a redirection item is the path \(/dev/null)\, delivery to it is
15193 bypassed at a high level, and the log entry shows `$*$$*$bypassed$*$$*$'
15194 instead of a transport name. In this case the user and group are not used.
15196 .index included address list
15197 .index address redirection||included external list
15198 If an item is of the form
15200 :include:<<path name>>
15202 a list of further items is taken from the given file and included at that
15204 \**Note**\: such a file can not be a filter file; it is just an out-of-line
15205 addition to the list.
15206 The items in the included list are separated by commas or newlines and are not
15207 subject to expansion. If this is the first item in an alias list in an
15208 \%lsearch%\ file, a colon must be used to terminate the alias name. This
15209 example is incorrect:
15211 list1 :include:/opt/lists/list1
15213 It must be given as
15215 list1: :include:/opt/lists/list1
15218 .index address redirection||to black hole
15219 Sometimes you want to throw away mail to a particular local part. Making the
15220 \data\ option expand to an empty string does not work, because that causes the
15221 router to decline. Instead, the alias item
15223 .index abandoning mail
15227 can be used. It does what its name implies. No delivery is done, and no error
15228 message is generated. This has the same effect as specifing \(/dev/null)\, but
15229 can be independently disabled.
15231 \**Warning**\: If \":blackhole:"\ appears anywhere in a redirection list, no
15232 delivery is done for the original local part, even if other redirection items
15233 are present. If you are generating a multi-item list (for example, by reading a
15234 database) and need the ability to provide a no-op item, you must use
15238 .index delivery||forcing failure
15239 .index delivery||forcing deferral
15240 .index failing delivery||forcing
15241 .index deferred delivery, forcing
15242 .index customizing||failure message
15243 An attempt to deliver a particular address can be deferred or forced to fail by
15244 redirection items of the form
15250 respectively. When a redirection list contains such an item, it applies to the
15251 entire redirection; any other items in the list are ignored (:::blackhole:: is
15252 different). Any text following :::fail:: or :::defer:: is placed in the error
15253 text associated with the failure. For example, an alias file might contain:
15255 X.Employee: :fail: Gone away, no forwarding address
15257 In the case of an address that is being verified from an ACL or as the subject
15258 of a \\VRFY\\ command, the text is included in the SMTP error response by
15259 default. In an ACL, an explicitly provided message overrides the default, but
15260 the default message is available in the variable \$acl@_verify@_message$\ and
15261 can therefore be included in a custom message if this is desired. Exim sends a
15262 451 SMTP code for a :::defer::, and 550 for :::fail::. In non-SMTP cases the
15263 text is included in the error message that Exim generates.
15267 Normally the error text is the rest of the redirection list -- a comma does not
15268 terminate it -- but a newline does act as a terminator. Newlines are not
15269 normally present in alias expansions. In \%lsearch%\ lookups they are removed as
15270 part of the continuation process, but they may exist in other kinds of lookup
15271 and in :::include:: files.
15273 During routing for message delivery (as opposed to verification), a redirection
15274 containing :::fail:: causes an immediate failure of the incoming address,
15275 whereas :::defer:: causes the message to remain on the queue so that a
15276 subsequent delivery attempt can happen at a later time. If an address is
15277 deferred for too long, it will ultimately fail, because the normal retry
15280 .index alias file||exception to default
15281 Sometimes it is useful to use a single-key search type with a default (see
15282 chapter ~~CHAPfdlookup) to look up aliases. However, there may be a need for
15283 exceptions to the default. These can be handled by aliasing them to
15287 This differs from :::fail:: in that it causes the \%redirect%\ router to decline,
15288 whereas :::fail:: forces routing to fail. A lookup which results in an empty
15289 redirection list has the same effect.
15292 .section Duplicate addresses
15293 .index duplicate addresses
15294 .index address||duplicate, discarding
15295 .index pipe||duplicated
15296 Exim removes duplicate addresses from the list to which it is delivering, so as
15297 to deliver just one copy to each address. This does not apply to deliveries
15298 routed to pipes by different immediate parent addresses, but an indirect
15299 aliasing scheme of the type
15301 pipe: |/some/command $local_part
15305 does not work with a message that is addressed to both local parts, because
15306 when the second is aliased to the intermediate local part `pipe' it gets
15307 discarded as being the same as a previously handled address. However, a scheme
15310 localpart1: |/some/command $local_part
15311 localpart2: |/some/command $local_part
15313 does result in two different pipe deliveries, because the immediate parents of
15314 the pipes are distinct.
15317 .section Repeated redirection expansion
15318 .index repeated redirection expansion
15319 .index address redirection||repeated for each delivery attempt
15320 When a message cannot be delivered to all of its recipients immediately,
15321 leading to two or more delivery attempts, redirection expansion is carried out
15322 afresh each time for those addresses whose children were not all previously
15323 delivered. If redirection is being used as a mailing list, this can lead to new
15324 members of the list receiving copies of old messages. The \one@_time\ option
15325 can be used to avoid this.
15327 .section Errors in redirection lists
15328 .index address redirection||errors
15329 If \skip@_syntax@_errors\ is set, a malformed address that causes a parsing
15330 error is skipped, and an entry is written to the main log. This may be useful
15331 for mailing lists that are automatically managed. Otherwise, if an error is
15332 detected while generating the list of new addresses, the original address is
15333 deferred. See also \syntax@_errors@_to\.
15336 .section Private options for the redirect router
15338 The private options for the \%redirect%\ router are as follows:
15341 .index options||\%redirect%\ router
15343 .conf allow@_defer boolean false
15344 Setting this option allows the use of :::defer:: in non-filter redirection
15346 or the \defer\ command in an Exim filter file.
15348 .conf allow@_fail boolean false
15349 .index failing delivery||from filter
15350 If this option is true, the :::fail:: item can be used in a redirection list,
15351 and the \fail\ command may be used in a filter file.
15353 .conf allow@_filter boolean false
15354 .index filter||enabling use of
15355 .index Sieve filter||enabling use of
15356 Setting this option allows Exim to interpret redirection data that starts with
15357 `@#Exim filter' or `@#Sieve filter' as a set of filtering instructions. There
15358 are some features of Exim filter files that some administrators may wish to
15359 lock out; see the \forbid@_filter@_xxx\ options below. The filter is run using
15360 the uid and gid set by the generic \user\ and \group\ options. These take their
15361 defaults from the password data if \check@_local@_user\ is set, so in the
15362 normal case of users' personal filter files, the filter is run as the relevant
15363 user. When \allow@_filter\ is set true, Exim insists that either
15364 \check@_local@_user\ or \user\ is set.
15367 .conf allow@_freeze boolean false
15368 .index freezing messages||allowing in filter
15369 Setting this option allows the use of the \freeze\ command in an Exim filter.
15370 This command is more normally encountered in system filters, and is disabled by
15371 default for redirection filters because it isn't something you usually want to
15372 let ordinary users do.
15375 .conf check@_ancestor boolean false
15376 This option is concerned with handling generated addresses that are the same
15377 as some address in the list of redirection ancestors of the current address.
15378 Although it is turned off by default in the code, it is set in the default
15379 configuration file for handling users' \(.forward)\ files. It is recommended
15380 for this use of the \%redirect%\ router.
15382 When \check@_ancestor\ is set, if a generated address (including the domain) is
15383 the same as any ancestor of the current address, it is replaced by a copy of
15384 the current address. This helps in the case where local part A is aliased to B,
15385 and B has a \(.forward)\ file pointing back to A. For example, within a single
15386 domain, the local part `Joe.Bloggs' is aliased to `jb' and \(@~jb/.forward)\
15389 @\Joe.Bloggs, <<other item(s)>>
15391 Without the \check@_ancestor\ setting, either local part (`jb' or `joe.bloggs')
15392 gets processed once by each router and so ends up as it was originally. If `jb'
15393 is the real mailbox name, mail to `jb' gets delivered (having been turned into
15394 `joe.bloggs' by the \(.forward)\ file and back to `jb' by the alias), but mail
15395 to `joe.bloggs' fails. Setting \check@_ancestor\ on the \%redirect%\ router that
15396 handles the \(.forward)\ file prevents it from turning `jb' back into
15397 `joe.bloggs' when that was the original address. See also the \repeat@_use\
15400 .conf check@_group boolean "see below"
15401 When the \file\ option is used, the group owner of the file is checked only
15402 when this option is set. The permitted groups are those listed in the
15403 \owngroups\ option, together with the user's default group if
15404 \check@_local@_user\ is set. If the file has the wrong group, routing is
15405 deferred. The default setting for this option is true if \check@_local@_user\
15406 is set and the \modemask\ option permits the group write bit, or if the
15407 \owngroups\ option is set. Otherwise it is false, and no group check occurs.
15410 .conf check@_owner boolean "see below"
15411 When the \file\ option is used, the owner of the file is checked only when this
15412 option is set. If \check@_local@_user\ is set, the local user is permitted;
15413 otherwise the owner must be one of those listed in the \owners\ option. The
15414 default value for this option is true if \check@_local@_user\ or \owners\ is
15415 set. Otherwise the default is false, and no owner check occurs.
15417 .conf data string$**$ unset
15418 This option is mutually exclusive with \file\. One or other of them must be
15419 set, but not both. The contents of \data\ are expanded, and then used as the
15420 list of forwarding items, or as a set of filtering instructions. If the
15421 expansion is forced to fail, or the result is an empty string or a string that
15422 has no effect (consists entirely of comments), the router declines.
15424 When filtering instructions are used, the string must begin with `@#Exim
15425 filter', and all comments in the string, including this initial one, must be
15426 terminated with newline characters. For example:
15428 data = #Exim filter\n\
15429 if $h_to: contains Exim then save $home/mail/exim endif
15431 If you are reading the data from a database where newlines cannot be included,
15432 you can use the \$@{sg@}$\ expansion item to turn the escape string of your
15433 choice into a newline.
15435 .conf directory@_transport string$**$ unset
15436 A \%redirect%\ router sets up a direct delivery to a directory when a path name
15437 ending with a slash is specified as a new `address'. The transport used is
15438 specified by this option, which, after expansion, must be the name of a
15439 configured transport. This should normally be an \%appendfile%\ transport.
15441 .conf file string$**$ unset
15442 This option specifies the name of a file that contains the redirection data. It
15443 is mutually exclusive with the \data\ option. The string is expanded before
15444 use; if the expansion is forced to fail, the router declines. Other expansion
15445 failures cause delivery to be deferred. The result of a successful expansion
15446 must be an absolute path. The entire file is read and used as the redirection
15447 data. If the data is an empty string or a string that has no effect (consists
15448 entirely of comments), the router declines.
15450 .index NFS||checking for file existence
15451 If the attempt to open the file fails with a `does not exist' error, Exim
15452 runs a check on the containing directory,
15453 unless \ignore@_enotdir\ is true (see below).
15454 If the directory does not appear to exist, delivery is deferred. This can
15455 happen when users' \(.forward)\ files are in NFS-mounted directories, and there
15456 is a mount problem. If the containing directory does exist, but the file does
15457 not, the router declines.
15459 .conf file@_transport string$**$ unset
15460 A \%redirect%\ router sets up a direct delivery to a file when a path name not
15461 ending in a slash is specified as a new `address'. The transport used is
15462 specified by this option, which, after expansion, must be the name of a
15463 configured transport.
15464 This should normally be an \%appendfile%\ transport.
15465 When it is running, the file name is in \$address@_file$\.
15467 .conf forbid@_blackhole boolean false
15468 If this option is true, the :::blackhole:: item may not appear in a redirection
15471 .conf forbid@_file boolean false
15472 .index delivery||to file, forbidding
15473 .index Sieve filter||forbidding delivery to a file
15474 .index Sieve filter||`keep' facility, disabling
15475 If this option is true, this router may not generate a new address that
15476 specifies delivery to a local file or directory, either from a filter or from a
15477 conventional forward file. This option is forced to be true if \one@_time\ is
15478 set. It applies to Sieve filters as well as to Exim filters, but if true, it
15479 locks out the Sieve's `keep' facility.
15481 .conf forbid@_filter@_existstest boolean false
15482 .index filter||locking out certain features
15483 If this option is true, string expansions in Exim filters are not allowed to
15484 make use of the \exists\ condition.
15486 .conf forbid@_filter@_logwrite boolean false
15487 If this option is true, use of the logging facility in Exim filters is not
15488 permitted. Logging is in any case available only if the filter is being run
15489 under some unprivileged uid (which is normally the case for ordinary users'
15490 \(.forward)\ files).
15492 .conf forbid@_filter@_lookup boolean false
15493 If this option is true, string expansions in Exim filter files are not allowed
15494 to make use of \lookup\ items.
15496 .conf forbid@_filter@_perl boolean false
15497 This option is available only if Exim is built with embedded Perl support. If
15498 it is true, string expansions in Exim filter files are not allowed to make use
15499 of the embedded Perl support.
15501 .conf forbid@_filter@_readfile boolean false
15502 If this option is true, string expansions in Exim filter files are not allowed
15503 to make use of \readfile\ items.
15505 .conf forbid@_filter@_readsocket boolean false
15506 If this option is true, string expansions in Exim filter files are not allowed
15507 to make use of \readsocket\ items.
15509 .conf forbid@_filter@_reply boolean false
15510 If this option is true, this router may not generate an automatic reply
15511 message. Automatic replies can be generated only from Exim filter files, not
15512 from traditional forward files or Sieve filters. This option is forced to be
15513 true if \one@_time\ is set.
15515 .conf forbid@_filter@_run boolean false
15516 If this option is true, string expansions in Exim filter files are not allowed
15517 to make use of \run\ items.
15519 .conf forbid@_include boolean false
15520 If this option is true, items of the form
15522 :include:<<path name>>
15524 are not permitted in non-filter redirection lists.
15526 .conf forbid@_pipe boolean false
15527 .index delivery||to pipe, forbidding
15528 If this option is true, this router may not generate a new address which
15529 specifies delivery to a pipe, either from an Exim filter or from a conventional
15530 forward file. This option is forced to be true if \one@_time\ is set.
15532 .conf hide@_child@_in@_errmsg boolean false
15533 .index bounce message||redirection details, suppressing
15534 If this option is true, it prevents Exim from quoting a child address if it
15535 generates a bounce or delay message for it. Instead it says `an address
15536 generated from <<the top level address>>'. Of course, this applies only to
15537 bounces generated locally. If a message is forwarded to another host, $it{its}
15538 bounce may well quote the generated address.
15540 .conf ignore@_eacces boolean false
15542 If this option is set and an attempt to open a redirection file yields the
15543 \\EACCES\\ error (permission denied), the \%redirect%\ router behaves as if the
15544 file did not exist.
15546 .conf ignore@_enotdir boolean false
15548 If this option is set and an attempt to open a redirection file yields the
15549 \\ENOTDIR\\ error (something on the path is not a directory), the \%redirect%\
15550 router behaves as if the file did not exist.
15552 Setting \ignore@_enotdir\ has another effect as well: When a \%redirect%\
15553 router that has the \file\ option set discovers that the file does not exist
15554 (the \\ENOENT\\ error), it tries to \*stat()*\ the parent directory, as a check
15555 against unmounted NFS directories. If the parent can not be statted, delivery
15556 is deferred. However, it seems wrong to do this check when \ignore@_enotdir\ is
15557 set, because that option tells Exim to ignore `something on the path is not a
15558 directory' (the \\ENOTDIR\\ error). This is a confusing area, because it seems
15559 that some operating systems give \\ENOENT\\ where others give \\ENOTDIR\\.
15562 .conf include@_directory string unset
15563 If this option is set, the path names of any :::include:: items in a redirection
15564 list must start with this directory.
15566 .conf modemask "octal integer" 022
15567 This specifies mode bits which must not be set for a file specified by the
15568 \file\ option. If any of the forbidden bits are set, delivery is deferred.
15570 .conf one@_time boolean false
15571 .index one-time aliasing/forwarding expansion
15572 .index alias file||one-time expansion
15573 .index forward file||one-time expansion
15574 .index mailing lists||one-time expansion
15575 .index address redirection||one-time expansion
15576 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
15577 files each time it tries to deliver a message causes a problem
15578 when one or more of the generated addresses fails be delivered at the first
15579 attempt. The problem is not one of duplicate delivery -- Exim is clever enough
15580 to handle that -- but of what happens when the redirection list changes during
15581 the time that the message is on Exim's queue. This is particularly true in the
15582 case of mailing lists, where new subscribers might receive copies of messages
15583 that were posted before they subscribed.
15585 If \one@_time\ is set and any addresses generated by the router fail to
15586 deliver at the first attempt, the failing addresses are added to the message as
15587 `top level' addresses, and the parent address that generated them is marked
15588 `delivered'. Thus, redirection does not happen again at the next
15591 \**Warning 1**\: This means that any header line addition or removal that is
15592 specified by this router would be lost if delivery did not succeed at the
15593 first attempt. For this reason, the \headers@_add\ and \headers@_remove\
15594 generic options are not permitted when \one@_time\ is set.
15596 \**Warning 2**\: To ensure that the router generates only addresses (as opposed
15597 to pipe or file deliveries or auto-replies) \forbid@_file\, \forbid@_pipe\,
15598 and \forbid@_filter@_reply\ are forced to be true when \one@_time\ is set.
15600 The original top-level address is remembered with each of the generated
15601 addresses, and is output in any log messages. However, any intermediate parent
15602 addresses are not recorded. This makes a difference to the log only if
15603 \all__parents\ log selector is set. It is expected that \one@_time\ will
15604 typically be used for mailing lists, where there is normally just one level of
15607 .conf owners "string list" unset
15608 .index ownership||alias file
15609 .index ownership||forward file
15610 .index alias file||ownership
15611 .index forward file||ownership
15612 This specifies a list of permitted owners for the file specified by \file\.
15613 This list is in addition to the local user when \check@_local@_user\ is set.
15614 See \check@_owner\ above.
15616 .conf owngroups "string list" unset
15617 This specifies a list of permitted groups for the file specified by \file\. The
15618 list is in addition to the local user's primary group when \check@_local@_user\
15619 is set. See \check@_group\ above.
15621 .conf qualify@_domain string$**$ unset
15622 If this option is set and an unqualified address (one without a domain) is
15623 generated, it is qualified with the domain specified by expanding this string,
15624 instead of the global setting in \qualify@_recipient\. If the expansion fails,
15625 the router declines. If you want to revert to the default, you can have the
15626 expansion generate \$qualify@_recipient$\.
15628 .conf pipe@_transport string$**$ unset
15629 A \%redirect%\ router sets up a direct delivery to a pipe when a string starting
15630 with a vertical bar character is specified as a new `address'. The transport
15631 used is specified by this option, which, after expansion, must be the name of a
15632 configured transport.
15633 This should normally be a \%pipe%\ transport.
15634 When the transport is run, the pipe command is in \$address@_pipe$\.
15636 .conf qualify@_preserve@_domain boolean false
15637 .index domain||in redirection, preserving
15638 .index preserving domain in redirection
15639 .index address redirection||domain, preserving
15640 If this is set and an unqualified address (one without a domain) is generated,
15641 it is qualified with the domain of the
15642 parent address (the immediately preceding ancestor) instead of the local
15643 \qualify@_domain\ or global \qualify@_recipient\ value.
15645 .conf repeat@_use boolean true
15646 If this option is set false, the router is skipped for a child address that has
15647 any ancestor that was routed by this router. This test happens before any of
15648 the other preconditions are tested. Exim's default anti-looping rules skip
15649 only when the ancestor is the same as the current address. See also
15650 \check@_ancestor\ above and the generic \redirect@_router\ option.
15652 .conf reply@_transport string$**$ unset
15653 A \%redirect%\ router sets up an automatic reply when a \mail\ or \vacation\
15654 command is used in a filter file. The transport used is specified by this
15655 option, which, after expansion, must be the name of a configured transport.
15656 This should normally be an \%autoreply%\ transport. Other transports are
15657 unlikely to do anything sensible or useful.
15659 .conf rewrite boolean true
15660 .index address redirection||disabling rewriting
15661 If this option is set false, addresses generated by the router are not
15662 subject to address rewriting. Otherwise, they are treated like new addresses
15663 and are rewritten according to the global rewriting rules.
15665 .conf skip@_syntax@_errors boolean false
15666 .index forward file||broken
15667 .index address redirection||broken files
15668 .index alias file||broken
15669 .index broken alias or forward files
15670 .index ignoring faulty addresses
15671 .index skipping faulty addresses
15672 .index error||skipping bad syntax
15673 If \skip@_syntax@_errors\ is set, syntactically malformed addresses in
15674 non-filter redirection data are skipped, and each failing address is logged. If
15675 \syntax@_errors@_to\ is set, a message is sent to the address it defines,
15676 giving details of the failures. If \syntax@_errors@_text\ is set, its contents
15677 are expanded and placed at the head of the error message generated by
15678 \syntax@_errors@_to\. Usually it is appropriate to set \syntax@_errors@_to\ to
15679 be the same address as the generic \errors@_to\ option. The
15680 \skip@_syntax@_errors\ option is often used when handling mailing lists.
15682 If all the addresses in a redirection list are skipped because of syntax
15683 errors, the router declines to handle the original address, and it is passed to
15684 the following routers.
15686 If \skip@_syntax@_errors\ is set when an Exim filter is interpreted, any syntax
15687 error in the filter causes filtering to be abandoned without any action being
15688 taken. The incident is logged, and the router declines to handle the address,
15689 so it is passed to the following routers.
15691 .index Sieve filter||syntax errors in
15692 Currently, any syntax errors in a Sieve filter file cause the `keep' action to
15693 occur. The values of \skip@_syntax@_errors\, \syntax@_errors@_to\, and
15694 \syntax@_errors@_text\ are not used.
15696 \skip@_syntax@_errors\ can be used to specify that errors in users' forward
15697 lists or filter files should not prevent delivery. The \syntax@_errors@_to\
15698 option, used with an address that does not get redirected, can be used to
15699 notify users of these errors, by means of a router like this:
15705 file = $home/.forward
15706 file_transport = address_file
15707 pipe_transport = address_pipe
15708 reply_transport = address_reply
15711 syntax_errors_to = real-$local_part@$domain
15712 syntax_errors_text = \
15713 This is an automatically generated message. An error has\n\
15714 been found in your .forward file. Details of the error are\n\
15715 reported below. While this error persists, you will receive\n\
15716 a copy of this message for every message that is addressed\n\
15717 to you. If your .forward file is a filter file, or if it is\n\
15718 a non-filter file containing no valid forwarding addresses,\n\
15719 a copy of each incoming message will be put in your normal\n\
15720 mailbox. If a non-filter file contains at least one valid\n\
15721 forwarding address, forwarding to the valid addresses will\n\
15722 happen, and those will be the only deliveries that occur.
15724 You also need a router to ensure that local addresses that are prefixed by
15725 \"real-"\ are recognized, but not forwarded or filtered. For example, you could
15726 put this immediately before the \%userforward%\ router:
15731 local_part_prefix = real-
15732 transport = local_delivery
15735 .conf syntax@_errors@_text string$**$ unset
15736 See \skip@_syntax@_errors\ above.
15738 .conf syntax@_errors@_to string unset
15739 See \skip@_syntax@_errors\ above.
15750 . ============================================================================
15751 .chapter Environment for running local transports
15752 .rset CHAPenvironment "~~chapter"
15753 .set runningfoot "local transport environment"
15754 .index local transports||environment for
15755 .index environment for local transports
15756 .index transport||local, environment for
15757 Local transports handle deliveries to files and pipes. (The \%autoreply%\
15758 transport can be thought of as similar to a pipe.) Exim always runs transports
15759 in subprocesses, under specified uids and gids. Typical deliveries to local
15760 mailboxes run under the uid and gid of the local user.
15762 Exim also sets a specific current directory while running the transport; for
15763 some transports a home directory setting is also relevant. The \%pipe%\
15764 transport is the only one which sets up environment variables; see section
15765 ~~SECTpipeenv for details.
15767 The values used for the uid, gid, and the directories may come from several
15768 different places. In many cases, the router that handles the address associates
15769 settings with that address as a result of its \check@_local@_user\, \group\, or
15770 \user\ options. However, values may also be given in the transport's own
15771 configuration, and these override anything that comes from the router.
15773 .section Uids and gids
15774 .rset SECTenvuidgid "~~chapter.~~section"
15775 .index local transports||uid and gid
15776 .index transport||local, uid and gid
15777 All transports have the options \group\ and \user\. If \group\ is set, it
15778 overrides any group that the router set in the address, even if \user\ is not
15779 set for the transport. This makes it possible, for example, to run local mail
15780 delivery under the uid of the recipient (set by the router), but in a special
15781 group (set by the transport). For example:
15784 # User/group are set by check_local_user in this router
15788 transport = group_delivery
15791 # This transport overrides the group
15793 driver = appendfile
15794 file = /var/spool/mail/$local_part
15797 If \user\ is set for a transport, its value overrides what is set in the
15798 address. If \user\ is non-numeric and \group\ is not set, the gid associated
15799 with the user is used. If \user\ is numeric, \group\ must be set.
15801 .index \initgroups\ option
15802 When the uid is taken from the transport's configuration, the \*initgroups()*\
15803 function is called for the groups associated with that uid if the \initgroups\
15804 option is set for the transport. When the uid is not specified by the
15805 transport, but is associated with the address by a router, the option for
15806 calling \*initgroups()*\ is taken from the router configuration.
15808 .index \%pipe%\ transport||uid for
15809 The \%pipe%\ transport contains the special option \pipe@_as@_creator\. If this
15810 is set and \user\ is not set, the uid of the process that called Exim to
15811 receive the message is used, and if \group\ is not set, the corresponding
15812 original gid is also used.
15815 .section Current and home directories
15816 .index current directory for local transport
15817 .index home directory||for local transport
15818 .index transport||local, home directory for
15819 .index transport||local, current directory for
15820 Routers may set current and home directories for local transports by means of
15821 the \transport__current@_directory\ and \transport@_home@_directory\ options.
15822 However, if the transport's \current__directory\ or \home@_directory\ options
15823 are set, they override the router's values. In detail, the home directory
15824 for a local transport is taken from the first of these values that is set:
15826 The \home@_directory\ option on the transport;
15828 The \transport@_home@_directory\ option on the router;
15830 The password data if \check@_local@_user\ is set on the router;
15832 The \router@_home@_directory\ option on the router.
15834 The current directory is taken from the first of these values that is set:
15836 The \current@_directory\ option on the transport;
15838 The \transport@_current@_directory\ option on the router.
15841 If neither the router nor the transport sets a current directory, Exim uses the
15842 value of the home directory, if it is set. Otherwise it sets the current
15843 directory to \(/)\ before running a local transport.
15846 .section Expansion variables derived from the address
15847 Normally a local delivery is handling a single address, and in that case the
15848 variables such as \$domain$\ and \$local@_part$\ are set during local
15849 deliveries. However, in some circumstances more than one address may be handled
15850 at once (for example, while writing batch SMTP for onward transmission by some
15851 other means). In this case, the variables associated with the local part are
15852 never set, \$domain$\ is set only if all the addresses have the same
15853 domain, and \$original@_domain$\ is never set.
15864 . ============================================================================
15865 .chapter Generic options for transports
15866 .rset CHAPtransportgeneric "~~chapter"
15867 .set runningfoot "generic transport options"
15869 .index generic options||transport
15870 .index options||generic, for transports
15871 .index transport||generic options for
15872 The following generic options apply to all transports:
15875 .conf body@_only boolean false
15876 .index transport||body only
15877 .index message||transporting body only
15878 .index body of message||transporting
15879 If this option is set, the message's headers are not transported. It is
15880 mutually exclusive with \headers@_only\. If it is used with the \%appendfile%\ or
15881 \%pipe%\ transports, the settings of \message@_prefix\ and \message@_suffix\
15882 should be checked, because this option does not automatically suppress them.
15884 .conf current@_directory string$**$ unset
15885 .index transport||current directory for
15886 This specifies the current directory that is to be set while running the
15887 transport, overriding any value that may have been set by the router.
15888 If the expansion fails for any reason, including forced failure, an error is
15889 logged, and delivery is deferred.
15891 .conf disable@_logging boolean false
15892 If this option is set true, nothing is logged for any
15893 deliveries by the transport or for any
15894 transport errors. You should not set this option unless you really, really know
15895 what you are doing.
15897 .conf debug@_print string$**$ unset
15898 .index testing||variables in drivers
15899 If this option is set and debugging is enabled (see the \-d-\ command line
15900 option), the string is expanded and included in the debugging output when the
15902 If expansion of the string fails, the error message is written to the debugging
15903 output, and Exim carries on processing.
15904 This facility is provided to help with checking out the values of variables and
15905 so on when debugging driver configurations. For example, if a \headers@_add\
15906 option is not working properly, \debug@_print\ could be used to output the
15907 variables it references. A newline is added to the text if it does not end with
15910 .conf delivery@_date@_add boolean false
15911 .index ::Delivery-date:: header line
15912 If this option is true, a ::Delivery-date:: header is added to the message. This
15913 gives the actual time the delivery was made. As this is not a standard header,
15914 Exim has a configuration option (\delivery@_date@_remove\) which requests its
15915 removal from incoming messages, so that delivered messages can safely be resent
15916 to other recipients.
15918 .conf driver string unset
15919 This specifies which of the available transport drivers is to be used.
15920 There is no default, and this option must be set for every transport.
15922 .conf envelope@_to@_add boolean false
15923 .index ::Envelope-to:: header line
15924 If this option is true, an ::Envelope-to:: header is added to the message. This
15925 gives the original address(es) in the incoming envelope that caused this
15926 delivery to happen. More than one address may be present if the transport is
15927 configured to handle several addresses at once, or if more than one original
15928 address was redirected to the same final address. As this is not a standard
15929 header, Exim has a configuration option (\envelope@_to@_remove\) which requests
15930 its removal from incoming messages, so that delivered messages can safely be
15931 resent to other recipients.
15933 .conf group string$**$ "Exim group"
15934 .index transport||group, specifying
15935 This option specifies a gid for running the transport process, overriding any
15936 value that the router supplies, and also overriding any value associated with
15937 \user\ (see below).
15939 .conf headers@_add string$**$ unset
15940 .index header lines||adding in transport
15941 .index transport||header lines, adding
15942 This option specifies a string of text which is expanded and added to the
15943 header portion of a message as it is transported. If the result of the
15944 expansion is an empty string, or if the expansion is forced to fail, no action
15945 is taken. Other expansion failures are treated as errors and cause the delivery
15946 to be deferred. The expanded string should be in the form of one or more RFC
15947 2822 header lines, separated by newlines (coded as `@\n'), for example:
15949 headers_add = X-added: this is a header added at $tod_log\n\
15950 X-added: this is another
15952 Exim does not check the syntax of these added header lines. They are added at
15953 the end of the existing header lines. If you include a blank line within the
15954 string, you can subvert this facility into adding text at the start of the
15955 message's body. This is not recommended. Additional header lines can also be
15956 specified by routers. See chapter ~~CHAProutergeneric and section
15957 ~~SECTheadersaddrem.
15959 .conf headers@_only boolean false
15960 .index transport||header lines only
15961 .index message||transporting headers only
15962 .index header lines||transporting
15963 If this option is set, the message's body is not transported. It is mutually
15964 exclusive with \body@_only\. If it is used with the \%appendfile%\ or \%pipe%\
15965 transports, the settings of \message@_prefix\ and \message__suffix\ should be
15966 checked, since this option does not automatically suppress them.
15968 .conf headers@_remove string$**$ unset
15969 .index header lines||removing
15970 .index transport||header lines, removing
15971 This option is expanded; the result must consist of a colon-separated list of
15972 header names, not including the terminating colon, for example:
15974 headers_remove = return-receipt-to:acknowledge-to
15976 Any existing headers matching those names are not included in any message that
15977 is transmitted by the transport.
15978 If the result of the expansion is an empty string, or if the expansion is
15979 forced to fail, no action is taken. Other expansion failures are treated as
15980 errors and cause the delivery to be deferred.
15982 If there are multiple instances of a header, they are all removed. However,
15983 added headers may have these names. Thus it is possible to replace a header by
15984 specifying it in \headers@_remove\ and supplying the replacement in
15985 \headers@_add\. Headers to be removed can also be specified by routers. See
15986 chapter ~~CHAProutergeneric and section ~~SECTheadersaddrem.
15988 .conf headers@_rewrite string unset
15989 .index transport||header lines, rewriting
15990 .index rewriting||at transport time
15991 This option allows addresses in header lines to be rewritten at transport time,
15992 that is, as the message is being copied to its destination. The contents of the
15993 option are a colon-separated list of rewriting rules. Each rule is in exactly
15994 the same form as one of the general rewriting rules that are applied when a
15995 message is received. These are described in chapter ~~CHAPrewrite. For example,
15997 headers_rewrite = a@b c@d f : \
16000 changes \a@@b\ into \c@@d\ in ::From:: header lines, and \x@@y\ into \w@@z\ in
16001 all address-bearing header lines. The rules are applied to the header lines
16002 just before they are written out at transport time, so they affect only those
16003 copies of the message that pass through the transport. However, only the
16004 message's original header lines, and any that were added by a system filter,
16005 are rewritten. If a router or transport adds header lines, they are
16006 not affected by this option. These rewriting rules are $it{not} applied to the
16007 envelope. You can change the return path using \return@_path\, but you cannot
16008 change envelope recipients at this time.
16010 .conf home@_directory string$**$ unset
16011 .index transport||home directory for
16012 This option specifies a home directory setting for the transport, overriding
16013 any value that may be set by the router. The home directory is placed in
16014 \$home$\ while expanding the transport's private options. It is also used as
16015 the current directory if no current directory is set by the
16016 \current__directory\ option on the transport or the
16017 \transport__current__directory\ option on the router.
16018 If the expansion fails for any reason, including forced failure, an error is
16019 logged, and delivery is deferred.
16022 .index additional groups
16023 .index groups, additional
16024 .index transport||group, additional
16025 .conf initgroups boolean false
16026 If this option is true and the uid for the delivery process is provided by the
16027 transport, the \*initgroups()*\ function is called when running the transport
16028 to ensure that any additional groups associated with the uid are set up.
16030 .conf message@_size@_limit string$**$ 0
16031 .index limit||message size per transport
16032 .index size||of message, limit
16033 .index transport||message size, limiting
16034 This option controls the size of messages passed through the transport. It is
16035 expanded before use; the result of the expansion must be a sequence of digits,
16036 optionally followed by K or M.
16037 If the expansion fails for any reason, including forced failure, or if the
16038 result is not of the required form, delivery is deferred.
16039 If the value is greater than zero and the size of a message exceeds this
16040 limit, the address is failed. If there is any chance that the resulting bounce
16041 message could be routed to the same transport, you should ensure that
16042 \return@_size@_limit\ is less than the transport's \message@_size@_limit\, as
16043 otherwise the bounce message will fail to get delivered.
16046 .conf rcpt@_include@_affixes boolean false
16047 .index prefix||for local part, including in envelope
16048 .index suffix||for local part, including in envelope
16049 .index local part||prefix
16050 .index local part||suffix
16051 When this option is false (the default), and an address that has had any
16052 affixes (prefixes or suffixes) removed from the local part is delivered by any
16053 form of SMTP or LMTP, the affixes are not included. For example, if a router
16056 local_part_prefix = *-
16058 routes the address \*abc-xyz@@some.domain*\ to an SMTP transport, the envelope
16061 RCPT TO:<xyz@some.domain>
16063 If \rcpt@_include@_affixes\ is set true, the whole local part is included in
16064 the \\RCPT\\ command. This option applies to BSMTP deliveries by the
16065 \%appendfile%\ and \%pipe%\ transports as well as to the \%lmtp%\ and \%smtp%\
16068 .conf retry@_use@_local@_part boolean "see below"
16069 .index hints database||retry keys
16070 When a delivery suffers a temporary failure, a retry record is created
16071 in Exim's hints database. For remote deliveries, the key for the retry record
16072 is based on the name and/or IP address of the failing remote host. For local
16073 deliveries, the key is normally the entire address, including both the local
16074 part and the domain. This is suitable for most common cases of local delivery
16075 temporary failure -- for example, exceeding a mailbox quota should delay only
16076 deliveries to that mailbox, not to the whole domain.
16078 However, in some special cases you may want to treat a temporary local delivery
16079 as a failure associated with the domain, and not with a particular local part.
16080 (For example, if you are storing all mail for some domain in files.) You can do
16081 this by setting \retry@_use@_local@_part\ false.
16083 For all the local transports, its default value is true. For remote transports,
16084 the default value is false for tidiness, but changing the value has no effect
16085 on a remote transport in the current implementation.
16087 .conf return@_path string$**$ unset
16088 .index envelope sender
16089 .index transport||return path, changing
16090 .index return path||changing in transport
16091 If this option is set, the string is expanded at transport time and replaces
16092 the existing return path (envelope sender) value in the copy of the message
16093 that is being delivered. An empty return path is permitted. This feature is
16094 designed for remote deliveries, where the value of this option is used in the
16095 SMTP \\MAIL\\ command. If you set \return@_path\ for a local transport, the
16096 only effect is to change the address that is placed in the ::Return-path::
16097 header line, if one is added to the message (see the next option).
16099 The expansion can refer to the existing value via \$return@_path$\. This is
16100 either the message's envelope sender, or an address set by the
16101 \errors@_to\ option on a router. If the expansion is forced to fail, no
16102 replacement occurs; if it fails for another reason, delivery is deferred. This
16103 option can be used to support VERP (Variable Envelope Return Paths) -- see
16104 chapter ~~CHAPSMTP.
16106 \**Note**\: If a delivery error is detected locally,
16107 including the case when a remote server rejects a message at SMTP time,
16108 the bounce message is not sent to the value of this option, but to the
16109 previously set errors address (which defaults to the incoming sender address).
16112 .conf return@_path@_add boolean false
16113 .index ::Return-path:: header line
16114 If this option is true, a ::Return-path:: header is added to the message.
16115 Although the return path is normally available in the prefix line of BSD
16116 mailboxes, this is commonly not displayed by MUAs, and so the user does not
16117 have easy access to it.
16119 RFC 2821 states that the ::Return-path:: header is added to a message `when the
16120 delivery SMTP server makes the final delivery'. This implies that this header
16121 should not be present in incoming messages. Exim has a configuration option,
16122 \return@_path@_remove\, which requests removal of this header from incoming
16123 messages, so that delivered messages can safely be resent to other recipients.
16125 .conf shadow@_condition string$**$ unset
16126 See \shadow@_transport\ below.
16128 .conf shadow@_transport string unset
16129 .index shadow transport
16130 .index transport||shadow
16131 A local transport may set the \shadow@_transport\ option to the name of another
16132 local transport. Shadow remote transports are not supported.
16134 Whenever a delivery to the main transport succeeds, and either
16135 \shadow@_condition\ is unset, or its expansion does not result in the empty
16136 string or one of the strings `0' or `no' or `false', the message is also passed
16137 to the shadow transport, with the same delivery address or addresses.
16138 If expansion fails, no action is taken except that non-forced expansion
16139 failures cause a log line to be written.
16141 The result of the shadow transport is discarded and does not affect the
16142 subsequent processing of the message. Only a single level of shadowing is
16143 provided; the \shadow@_transport\ option is ignored on any transport when it is
16144 running as a shadow. Options concerned with output from pipes are also ignored.
16146 The log line for the successful delivery has an item added on the end, of the
16149 ST=<<shadow transport name>>
16151 If the shadow transport did not succeed, the error message is put in
16152 parentheses afterwards.
16154 Shadow transports can be used for a number of different purposes, including
16155 keeping more detailed log information than Exim normally provides, and
16156 implementing automatic acknowledgement policies based on message headers that
16157 some sites insist on.
16159 .conf transport@_filter string$**$ unset
16160 .index transport||filter
16161 .index filter||transport filter
16162 This option sets up a filtering (in the Unix shell sense) process for messages
16163 at transport time. It should not be confused with mail filtering as set up by
16164 individual users or via a system filter.
16166 When the message is about to be written out, the command specified by
16167 \transport@_filter\ is started up in a separate process, and the entire
16168 message, including the header lines, is passed to it on its standard input
16169 (this in fact is done from a third process, to avoid deadlock).
16170 The command must be specified as an absolute path.
16172 The message is passed to the filter before any SMTP-specific processing, such
16173 as turning `@\n' into `@\r@\n' and escaping lines beginning with a dot, and
16174 also before any processing implied by the settings of \check@_string\ and
16175 \escape@_string\ in the \%appendfile%\ or \%pipe%\ transports.
16177 The filter's standard output is read and written to the message's destination.
16178 The filter can perform any transformations it likes, but of course should take
16179 care not to break RFC 2822 syntax. A demonstration Perl script is provided in
16180 \(util/transport-filter.pl)\; this makes a few arbitrary modifications just to
16181 show the possibilities. Exim does not check the result, except to test for a
16182 final newline when SMTP is in use. All messages transmitted over SMTP must end
16183 with a newline, so Exim supplies one if it is missing.
16185 .index SMTP||\\SIZE\\
16186 A problem might arise if the filter increases the size of a message that is
16187 being sent down an SMTP connection. If the receiving SMTP server has indicated
16188 support for the \\SIZE\\ parameter, Exim will have sent the size of the message
16189 at the start of the SMTP session. If what is actually sent is substantially
16190 more, the server might reject the message. This can be worked round by setting
16191 the \size@_addition\ option on the \%smtp%\ transport, either to allow for
16192 additions to the message, or to disable the use of \\SIZE\\ altogether.
16194 The value of the option is the command string for starting up the filter, which
16195 is run directly from Exim, not under a shell. The string is parsed by Exim in
16196 the same way as a command string for the \%pipe%\ transport: Exim breaks it up
16197 into arguments and then expands each argument separately. The special argument
16198 \$pipe@_addresses$\ is replaced by a number of arguments, one for each address
16199 that applies to this delivery. (This isn't an ideal name for this feature here,
16200 but as it was already implemented for the \%pipe%\ transport, it seemed sensible
16204 .index \$host@_address$\
16205 The expansion variables \$host$\ and \$host@_address$\ are available when the
16206 transport is a remote one. They contain the name and IP address of the host to
16207 which the message is being sent. For example:
16209 transport_filter = /some/directory/transport-filter.pl \
16210 $host $host_address $sender_address $pipe_addresses
16212 The filter process is run under the same uid and gid as the normal delivery.
16213 For remote deliveries this is the Exim uid/gid by default.
16215 If a transport filter is set on an autoreply transport, the original message is
16216 passed through the filter as it is being copied into the newly generated
16217 message, which happens if the \return@_message\ option is set.
16219 .conf transport@_filter@_timeout time 5m
16220 .index transport||filter, timeout
16221 When Exim is reading the output of a transport filter, it a applies a timeout
16222 that can be set by this option. Exceeding the timeout is treated as a
16223 temporary delivery failure.
16226 .conf user string$**$ "Exim user"
16227 .index uid (user id)||local delivery
16228 .index transport||user, specifying
16229 This option specifies the user under whose uid the delivery process is to be
16230 run, overriding any uid that may have been set by the router. If the user is
16231 given as a name, the uid is looked up from the password data, and the
16232 associated group is taken as the value of the gid to be used if the \group\
16235 For deliveries that use local transports, a user and group are normally
16236 specified explicitly or implicitly (for example, as a result of
16237 \check@_local@_user\) by the router or transport.
16239 .index hints database||access by remote transport
16240 For remote transports, you should leave this option unset unless you really are
16241 sure you know what you are doing. When a remote transport is running, it needs
16242 to be able to access Exim's hints databases, because each host may have its own
16254 . ============================================================================
16255 .chapter Address batching in local transports
16256 .set runningfoot "address batching"
16257 .rset CHAPbatching ~~chapter
16258 .index transport||local, address batching in
16259 The only remote transport (\%smtp%\) is normally configured to handle more than
16260 one address at a time, so that when several addresses are routed to the same
16261 remote host, just one copy of the message is sent. Local transports, however,
16262 normally handle one address at a time. That is, a separate instance of the
16263 transport is run for each address that is routed to the transport. A separate
16264 copy of the message is delivered each time.
16266 .index batched local delivery
16267 .index \batch@_max\
16269 In special cases, it may be desirable to handle several addresses at once in a
16270 local transport, for example:
16272 In an \%appendfile%\ transport, when storing messages in files for later
16273 delivery by some other means, a single copy of the message with multiple
16274 recipients saves space.
16276 In an \%lmtp%\ transport, when delivering over `local SMTP' to some process,
16277 a single copy saves time, and is the normal way LMTP is expected to work.
16279 In a \%pipe%\ transport, when passing the message
16280 to a scanner program or
16281 to some other delivery mechanism such as UUCP, multiple recipients may be
16284 The three local transports (\%appendfile%\, \%lmtp%\, and \%pipe%\) all have
16285 the same options for controlling multiple (`batched') deliveries, namely
16286 \batch@_max\ and \batch@_id\. To save repeating the information for each
16287 transport, these options are described here.
16289 The \batch@_max\ option specifies the maximum number of addresses that can be
16290 delivered together in a single run of the transport. Its default value is one.
16291 When more than one address is routed to a transport that has a \batch@_max\
16292 value greater than one, the addresses are delivered in a batch (that is, in a
16293 single run of the transport), subject to certain conditions:
16295 If any of the transport's options contain a reference to \$local@_part$\, no
16296 batching is possible.
16298 If any of the transport's options contain a reference to \$domain$\, only
16299 addresses with the same domain are batched.
16301 .index customizing||batching condition
16302 If \batch@_id\ is set, it is expanded for each address, and only those
16303 addresses with the same expanded value are batched. This allows you to specify
16304 customized batching conditions.
16305 Failure of the expansion for any reason, including forced failure, disables
16306 batching, but it does not stop the delivery from taking place.
16308 Batched addresses must also have the same errors address (where to send
16309 delivery errors), the same header additions and removals, the same user and
16310 group for the transport, and if a host list is present, the first host must
16313 .index ::Envelope-to:: header line
16314 If the generic \envelope@_to@_add\ option is set for the transport, the
16315 ::Envelope-to:: header that is added to the message contains all the addresses
16316 that are batched together.
16318 The \%appendfile%\ and \%pipe%\ transports have an option called \use@_bsmtp\,
16319 which causes them to deliver the message in `batched SMTP' format, with the
16320 envelope represented as SMTP commands. The \check@_string\ and \escape@_string\
16321 options are forced to the values
16324 escape_string = ".."
16326 when batched SMTP is in use. A full description of the batch SMTP mechanism is
16327 given in section ~~SECTbatchSMTP. The \%lmtp%\ transport does not have a
16328 \use@_bsmtp\ option, because it always delivers using the SMTP protocol.
16330 .index \%pipe%\ transport||with multiple addresses
16331 If you are not using BSMTP, but are using a \%pipe%\ transport, you can include
16332 \$pipe@_addresses$\ as part of the command. This is not a true variable; it is
16333 a bit of magic that causes each of the recipient addresses to be inserted into
16334 the command as a separate argument. This provides a way of accessing all the
16335 addresses that are being delivered in the batch.
16337 If you are using a batching \%appendfile%\ transport without \use@_bsmtp\, the
16338 only way to preserve the recipient addresses is to set the \envelope@_to@_add\
16339 option. This causes an ::Envelope-to:: header line to be added to the message,
16340 containing all the recipients.
16347 . ============================================================================
16348 .chapter The appendfile transport
16349 .set runningfoot "appendfile transport"
16350 .rset CHAPappendfile ~~chapter
16351 .index \%appendfile%\ transport
16352 .index transports||\%appendfile%\
16353 .index directory creation
16354 .index creating directories
16355 The \%appendfile%\ transport delivers a message by appending it to an existing
16356 file, or by creating an entirely new file in a specified directory. Single
16357 files to which messages are appended can be in the traditional Unix mailbox
16358 format, or optionally in the MBX format supported by the Pine MUA and
16359 University of Washington IMAP daemon, $it{inter alia}. When each message is
16360 being delivered as a separate file, `maildir' format can optionally be used to
16361 give added protection against failures that happen part-way through the
16362 delivery. A third form of separate-file delivery known as `mailstore' is also
16363 supported. For all file formats, Exim attempts to create as many levels of
16364 directory as necessary, provided that \create@_directory\ is set.
16366 The code for the optional formats is not included in the Exim binary by
16367 default. It is necessary to set \\SUPPORT@_MBX\\, \\SUPPORT@_MAILDIR\\ and/or
16368 \\SUPPORT@_MAILSTORE\\ in \(Local/Makefile)\ to have the appropriate code
16371 .index quota||system
16372 Exim recognises system quota errors, and generates an appropriate message. Exim
16373 also supports its own quota control within the transport, for use when the
16374 system facility is unavailable or cannot be used for some reason.
16376 If there is an error while appending to a file (for example, quota exceeded or
16377 partition filled), Exim attempts to reset the file's length and last
16378 modification time back to what they were before. If there is an error while
16379 creating an entirely new file, the new file is removed.
16381 Before appending to a file, a number of security checks are made, and the
16382 file is locked. A detailed description is given below, after the list of
16385 \%appendfile%\ is most commonly used for local deliveries to users' mailboxes.
16386 However, it can also be used as a pseudo-remote transport for putting messages
16387 into files for remote delivery by some means other than Exim. `Batch SMTP'
16388 format is often used in this case (see the \use@_bsmtp\ option).
16391 .section The file and directory options
16392 .rset SECTfildiropt "~~chapter.~~section"
16393 The \file\ option specifies a single file, to which the message is appended;
16394 the \directory\ option specifies a directory, in which a new file containing
16395 the message is created. Only one of these two options can be set, and for
16396 normal deliveries to mailboxes, one of them \*must*\ be set.
16398 However, \%appendfile%\ is also used for delivering messages to files or
16399 directories whose names (or parts of names) are obtained from alias,
16400 forwarding, or filtering operations (for example, a \save\ command in a user's
16401 Exim filter). When such a transport is running, \$local@_part$\ contains the
16402 local part that was aliased or forwarded, and \$address@_file$\ contains the
16403 name (or partial name) of the file or directory generated by the redirection
16404 operation. There are two cases:
16406 If neither \file\ nor \directory\ is set, the redirection operation
16407 must specify an absolute path (one that begins with \"/"\). This is the most
16408 common case when users with local accounts use filtering to sort mail into
16409 different folders. See for example, the \%address@_file%\ transport in the
16410 default configuration. If the path ends with a slash, it is assumed to be the
16411 name of a directory. A delivery to a directory can also be forced by setting
16412 \maildir@_format\ or \mailstore@_format\.
16414 If \file\ or \directory\ is set for a delivery from a redirection, it is used
16415 to determine the file or directory name for the delivery. Normally, the
16416 contents of \$address@_file$\ are used in some way in the string expansion.
16419 .index Sieve filter||configuring \%appendfile%\
16420 .index Sieve filter||relative mailbox path handling
16421 As an example of the second case, consider an environment where users do not
16422 have home directories. They may be permitted to use Exim filter commands of the
16427 or Sieve filter commands of the form:
16429 require "fileinto";
16430 fileinto "folder23";
16432 In this situation, the expansion of \file\ or \directory\ in the transport must
16433 transform the relative path into an appropriate absolute file name. In the case
16434 of Sieve filters, the name \*inbox*\ must be handled. It is the name that is
16435 used as a result of a `keep' action in the filter. This example shows one way
16436 of handling this requirement:
16438 file = ${if eq{$address_file}{inbox} \
16439 {/var/mail/$local_part} \
16440 {${if eq{${substr_0_1:$address_file}}{/} \
16442 {$home/mail/$address_file} \
16446 With this setting of \file\, \*inbox*\ refers to the standard mailbox location,
16447 absolute paths are used without change, and other folders are in the \(mail)\
16448 directory within the home directory.
16450 \**Note 1**\: While processing an Exim filter, a relative path such as
16451 \(folder23)\ is turned into an absolute path if a home directory is known to
16452 the router. In particular, this is the case if \check@_local@_user\ is set. If
16453 you want to prevent this happening at routing time, you can set
16454 \router@_home@_directory\ empty. This forces the router to pass the relative
16455 path to the transport.
16457 \**Note 2**\: An absolute path in \$address@_file$\ is not treated specially;
16458 the \file\ or \directory\ option is still used if it is set.
16462 .section Private options for appendfile
16463 .index options||\%appendfile%\ transport
16467 .conf allow@_fifo boolean false
16468 .index fifo (named pipe)
16469 .index named pipe (fifo)
16470 .index pipe||named (fifo)
16471 Setting this option permits delivery to named pipes (FIFOs) as well as to
16472 regular files. If no process is reading the named pipe at delivery time, the
16473 delivery is deferred.
16475 .conf allow@_symlink boolean false
16476 .index symbolic link||to mailbox
16477 .index mailbox||symbolic link
16478 By default, \%appendfile%\ will not deliver if the path name for the file is
16479 that of a symbolic link. Setting this option relaxes that constraint, but there
16480 are security issues involved in the use of symbolic links. Be sure you know
16481 what you are doing if you set this. Details of exactly what this option affects
16482 are included in the discussion which follows this list of options.
16484 .conf batch@_id string$**$ unset
16485 See the description of local delivery batching in chapter ~~CHAPbatching.
16486 However, batching is automatically disabled for \%appendfile%\ deliveries that
16487 happen as a result of forwarding or aliasing or other redirection directly to a
16490 .conf batch@_max integer 1
16491 See the description of local delivery batching in chapter ~~CHAPbatching.
16493 .conf check@_group boolean false
16494 When this option is set, the group owner of the file defined by the \file\
16495 option is checked to see that it is the same as the group under which the
16496 delivery process is running. The default setting is false because the default
16497 file mode is 0600, which means that the group is irrelevant.
16499 .conf check@_owner boolean true
16500 When this option is set, the owner of the file defined by the \file\ option is
16501 checked to ensure that it is the same as the user under which the delivery
16502 process is running.
16504 .conf check@_string string "see below"
16506 As \%appendfile%\ writes the message, the start of each line is tested for
16507 matching \check@_string\, and if it does, the initial matching characters are
16508 replaced by the contents of \escape@_string\. The value of \check@_string\ is a
16509 literal string, not a regular expression, and the case of any letters it
16510 contains is significant.
16512 If \use@_bsmtp\ is set the values of \check@_string\ and \escape@_string\ are
16513 forced to `.' and `..' respectively, and any settings in the configuration are
16514 ignored. Otherwise, they default to `From ' and `>From ' when the \file\ option
16515 is set, and unset when
16516 any of the \directory\, \maildir\, or \mailstore\ options are set.
16518 The default settings, along with \message@_prefix\ and \message@_suffix\, are
16519 suitable for traditional `BSD' mailboxes, where a line beginning with `From '
16520 indicates the start of a new message. All four options need changing if another
16521 format is used. For example, to deliver to mailboxes in MMDF format:
16522 .index MMDF format mailbox
16523 .index mailbox||MMDF format
16525 check_string = "\1\1\1\1\n"
16526 escape_string = "\1\1\1\1 \n"
16527 message_prefix = "\1\1\1\1\n"
16528 message_suffix = "\1\1\1\1\n"
16531 .index directory creation
16532 .conf create@_directory boolean true
16533 When this option is true, Exim attempts to create any missing superior
16534 directories for the file that it is about to write. A created directory's mode
16535 is given by the \directory@_mode\ option.
16537 .conf create@_file string "anywhere"
16538 This option constrains the location of files and directories that are created
16539 by this transport. It applies to files defined by the \file\ option and
16540 directories defined by the \directory\ option. In the case of maildir delivery,
16541 it applies to the top level directory, not the maildir directories beneath.
16543 The option must be set to one of the words `anywhere', `inhome', or
16544 `belowhome'. In the second and third cases, a home directory must have been set
16545 for the transport. This option is not useful when an explicit file name is
16546 given for normal mailbox deliveries. It is intended for the case when file
16547 names are generated from users' \(.forward)\ files. These are usually handled
16548 by an \%appendfile%\ transport called \address@_file\. See also
16549 \file@_must@_exist\.
16551 .conf directory string$**$ unset
16552 This option is mutually exclusive with the \file\ option, but one of \file\ or
16553 \directory\ must be set, unless the delivery is the direct result of a
16554 redirection (see section ~~SECTfildiropt).
16556 When \directory\ is set, the string is expanded, and the message is delivered
16557 into a new file or files in or below the given directory, instead of being
16558 appended to a single mailbox file. A number of different formats are provided
16559 (see \maildir@_format\ and \mailstore@_format\), and see section ~~SECTopdir
16560 for further details of this form of delivery.
16562 .conf directory@_file string$**$ "$tt{q@$@{base62:@$tod@_epoch@}-@$inode}"
16564 When \directory\ is set, but neither \maildir@_format\ nor \mailstore@_format\
16565 is set, \%appendfile%\ delivers each message into a file whose name is obtained
16566 by expanding this string. The default value generates a unique name from the
16567 current time, in base 62 form, and the inode of the file. The variable
16568 \$inode$\ is available only when expanding this option.
16570 .conf directory@_mode "octal integer" 0700
16571 If \%appendfile%\ creates any directories as a result of the \create@_directory\
16572 option, their mode is specified by this option.
16574 .conf escape@_string string "see description"
16575 See \check@_string\ above.
16577 .conf file string$**$ unset
16578 This option is mutually exclusive with the \directory\ option, but one of
16579 \file\ or \directory\ must be set, unless the delivery is the direct result of
16580 a redirection (see section ~~SECTfildiropt). The \file\ option specifies a
16581 single file, to which the message is appended. One or more of
16582 \use@_fcntl@_lock\, \use@_flock@_lock\, or \use@_lockfile\ must be set with
16584 .index NFS||lock file
16585 .index locking files
16587 If you are using more than one host to deliver over NFS into the same
16588 mailboxes, you should always use lock files.
16590 The string value is expanded for each delivery, and must yield an absolute
16591 path. The most common settings of this option are variations on one of these
16594 file = /var/spool/mail/$local_part
16595 file = /home/$local_part/inbox
16598 .index `sticky' bit
16599 In the first example, all deliveries are done into the same directory. If Exim
16600 is configured to use lock files (see \use@_lockfile\ below) it must be able to
16601 create a file in the directory, so the `sticky' bit must be turned on for
16602 deliveries to be possible, or alternatively the \group\ option can be used to
16603 run the delivery under a group id which has write access to the directory.
16606 .conf file@_format string unset
16607 .index file||mailbox, checking existing format
16608 This option requests the transport to check the format of an existing file
16609 before adding to it. The check consists of matching a specific string at the
16610 start of the file. The value of the option consists of an even number of
16611 colon-separated strings. The first of each pair is the test string, and the
16612 second is the name of a transport. If the transport associated with a matched
16613 string is not the current transport, control is passed over to the other
16614 transport. For example, suppose the standard \%local@_delivery%\ transport has
16617 file_format = "From : local_delivery :\
16618 \1\1\1\1\n : local_mmdf_delivery"
16620 Mailboxes that begin with `From' are still handled by this transport, but if a
16621 mailbox begins with four binary ones followed by a newline, control is passed
16622 to a transport called \local__mmdf__delivery\, which presumably is configured
16623 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
16624 is assumed to match the current transport. If the start of a mailbox doesn't
16625 match any string, or if the transport named for a given string is not defined,
16626 delivery is deferred.
16628 .conf file@_must@_exist boolean false
16629 If this option is true, the file specified by the \file\ option must exist, and
16630 an error occurs if it does not. Otherwise, it is created if it does not exist.
16632 .conf lock@_fcntl@_timeout time 0s
16633 .index timeout||mailbox locking
16634 .index mailbox locking||blocking and non-blocking
16635 .index locking files
16636 By default, the \%appendfile%\ transport uses non-blocking calls to \*fcntl()*\
16637 when locking an open mailbox file. If the call fails, the delivery process
16638 sleeps for \lock@_interval\ and tries again, up to \lock@_retries\ times.
16639 Non-blocking calls are used so that the file is not kept open during the wait
16640 for the lock; the reason for this is to make it as safe as possible for
16641 deliveries over NFS in the case when processes might be accessing an NFS
16642 mailbox without using a lock file. This should not be done, but
16643 misunderstandings and hence misconfigurations are not unknown.
16645 On a busy system, however, the performance of a non-blocking lock approach is
16646 not as good as using a blocking lock with a timeout. In this case, the waiting
16647 is done inside the system call, and Exim's delivery process acquires the lock
16648 and can proceed as soon as the previous lock holder releases it.
16650 If \lock@_fcntl@_timeout\ is set to a non-zero time, blocking locks, with that
16651 timeout, are used. There may still be some retrying: the maximum number of
16654 (lock_retries * lock_interval) / lock_fcntl_timeout
16656 rounded up to the next whole number. In other words, the total time during
16657 which \%appendfile%\ is trying to get a lock is roughly the same, unless
16658 \lock@_fcntl@_timeout\ is set very large.
16660 You should consider setting this option if you are getting a lot of delayed
16661 local deliveries because of errors of the form
16663 failed to lock mailbox /some/file (fcntl)
16666 .conf lock@_flock@_timeout time 0s
16667 This timeout applies to file locking when using \*flock()*\ (see \use@_flock\);
16668 the timeout operates in a similar manner to \lock@_fcntl@_timeout\.
16670 .conf lock@_interval time 3s
16671 This specifies the time to wait between attempts to lock the file. See below
16672 for details of locking.
16674 .conf lock@_retries integer 10
16675 This specifies the maximum number of attempts to lock the file. A value of zero
16676 is treated as 1. See below for details of locking.
16678 .conf lockfile@_mode "octal integer" 0600
16679 This specifies the mode of the created lock file, when a lock file is being
16680 used (see \use@_lockfile\).
16682 .conf lockfile@_timeout time 30m
16683 .index timeout||mailbox locking
16684 When a lock file is being used (see \use@_lockfile\), if a lock file already
16685 exists and is older than this value, it is assumed to have been left behind by
16686 accident, and Exim attempts to remove it.
16688 .conf maildir@_format boolean false
16689 .index maildir format||specifying
16690 If this option is set with the \directory\ option, the delivery is into a new
16691 file, in the `maildir' format that is used by other mail software. When the
16692 transport is activated directly from a \%redirect%\ router (for example, the
16693 \%address@_file%\ transport in the default configuration), setting
16694 \maildir@_format\ causes the path received from the router to be treated as a
16695 directory, whether or not it ends with \"/"\. This option is available only if
16696 \\SUPPORT@_MAILDIR\\ is present in \(Local/Makefile)\. See section
16697 ~~SECTmaildirdelivery below for further details.
16699 .conf maildir@_quota@_directory@_regex string "See below"
16700 .index maildir format||quota, directories included in
16701 .index quota||maildir, directories included in
16702 This option is relevant only when \maildir@_use@_size@_file\ is set. It defines
16703 a regular expression for specifying directories that should be included in the
16704 quota calculation. The default value is
16706 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
16708 which includes the \(cur)\ and \(new)\ directories, and any maildir++ folders
16709 (directories whose names begin with a dot). If you want to exclude the
16711 folder from the count (as some sites do), you need to change this setting to
16713 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
16715 This uses a negative lookahead in the regular expression to exclude the
16716 directory whose name is \(.Trash)\.
16718 .conf maildir@_retries integer 10
16719 This option specifies the number of times to retry when writing a file in
16720 `maildir' format. See section ~~SECTmaildirdelivery below.
16722 .conf maildir@_tag string$**$ unset
16723 This option applies only to deliveries in maildir format, and is described in
16724 section ~~SECTmaildirdelivery below.
16726 .conf maildir@_use@_size@_file boolean false
16727 .index maildir format||\(maildirsize)\ file
16728 Setting this option true enables support for \(maildirsize)\ files. Exim
16729 creates a \(maildirsize)\ file in a maildir if one does not exist, taking the
16730 quota from the \quota\ option of the transport. If \quota\ is unset, the value
16731 is zero. See section ~~SECTmaildirdelivery below for further details.
16733 .conf mailstore@_format boolean false
16734 .index mailstore format||specifying
16735 If this option is set with the \directory\ option, the delivery is into two new
16736 files in `mailstore' format. The option is available only if
16737 \\SUPPORT@_MAILSTORE\\ is present in \(Local/Makefile)\. See section
16738 ~~SECTopdir below for further details.
16740 .conf mailstore@_prefix string$**$ unset
16741 This option applies only to deliveries in mailstore format, and is described in
16742 section ~~SECTopdir below.
16744 .conf mailstore@_suffix string$**$ unset
16745 This option applies only to deliveries in mailstore format, and is described in
16746 section ~~SECTopdir below.
16748 .conf mbx@_format boolean false
16749 .index locking files
16750 .index file||locking
16751 .index file||MBX format
16752 .index MBX format, specifying
16753 This option is available only if Exim has been compiled with \\SUPPORT@_MBX\\
16754 set in \(Local/Makefile)\. If \mbx@_format\ is set with the \file\ option,
16755 the message is appended to the mailbox file in MBX format instead of
16756 traditional Unix format. This format is supported by Pine4 and its associated
16757 IMAP and POP daemons, by means of the \*c-client*\ library that they all use.
16759 \**Note**\: The \message@_prefix\ and \message@_suffix\ options are not
16760 automatically changed by the use of \mbx@_format\. They should normally be set
16761 empty when using MBX format, so this option almost always appears in this
16769 If none of the locking options are mentioned in the configuration,
16770 \use@_mbx@_lock\ is assumed and the other locking options default to false. It
16771 is possible to specify the other kinds of locking with \mbx@_format\, but
16772 \use@_fcntl@_lock\ and \use@_mbx@_lock\ are mutually exclusive. MBX locking
16773 interworks with \*c-client*\, providing for shared access to the mailbox. It
16774 should not be used if any program that does not use this form of locking is
16775 going to access the mailbox, nor should it be used if the mailbox file is NFS
16776 mounted, because it works only when the mailbox is accessed from a single host.
16778 If you set \use@_fcntl@_lock\ with an MBX-format mailbox, you cannot use
16779 the standard version of \*c-client*\, because as long as it has a mailbox open
16780 (this means for the whole of a Pine or IMAP session), Exim will not be able to
16781 append messages to it.
16783 .conf message@_prefix string$**$ "see below"
16785 The string specified here is expanded and output at the start of every message.
16786 The default is unset unless \file\ is specified and \use@_bsmtp\ is not set, in
16789 message_prefix = "From ${if def:return_path{$return_path}\
16790 {MAILER-DAEMON}} $tod_bsdinbox\n"
16793 .conf message@_suffix string$**$ "see below"
16794 The string specified here is expanded and output at the end of every message.
16795 The default is unset unless \file\ is specified and \use@_bsmtp\ is not set, in
16796 which case it is a single newline character. The suffix can be suppressed by
16802 .conf mode "octal integer" 0600
16803 If the output file is created, it is given this mode. If it already exists and
16804 has wider permissions, they are reduced to this mode. If it has narrower
16805 permissions, an error occurs unless \mode__fail__narrower\ is false. However,
16806 if the delivery is the result of a \save\ command in a filter file specifing a
16807 particular mode, the mode of the output file is always forced to take that
16808 value, and this option is ignored.
16810 .conf mode@_fail@_narrower boolean true
16811 This option applies in the case when an existing mailbox file has a narrower
16812 mode than that specified by the \mode\ option. If \mode@_fail@_narrower\ is
16813 true, the delivery is deferred (`mailbox has the wrong mode'); otherwise Exim
16814 continues with the delivery attempt, using the existing mode of the file.
16816 .conf notify@_comsat boolean false
16817 If this option is true, the \*comsat*\ daemon is notified after every successful
16818 delivery to a user mailbox. This is the daemon that notifies logged on users
16819 about incoming mail.
16821 .conf quota string$**$ unset
16822 .index quota||imposed by Exim
16823 This option imposes a limit on the size of the file to which Exim is appending,
16824 or to the total space used in the directory tree when the \directory\ option is
16825 set. In the latter case, computation of the space used is expensive, because
16826 all the files in the directory (and any sub-directories) have to be
16827 individually inspected and their sizes summed.
16828 (See \quota@_size@_regex\ and \maildir@_use@_size@_file\ for ways to avoid this
16829 in environments where users have no shell access to their mailboxes).
16831 As there is no interlock against two simultaneous deliveries into a
16832 multi-file mailbox, it is possible for the quota to be overrun in this case.
16833 For single-file mailboxes, of course, an interlock is a necessity.
16835 A file's size is taken as its \*used*\ value. Because of blocking effects, this
16836 may be a lot less than the actual amount of disk space allocated to the file.
16837 If the sizes of a number of files are being added up, the rounding effect can
16838 become quite noticeable, especially on systems that have large block sizes.
16839 Nevertheless, it seems best to stick to the \*used*\ figure, because this is
16840 the obvious value which users understand most easily.
16842 The value of the option is expanded, and must then be a numerical value
16843 (decimal point allowed), optionally followed by one of the letters K or M. The
16844 expansion happens while Exim is running as root, before it changes uid for the
16845 delivery. This means that files which are inaccessible to the end user can be
16846 used to hold quota values that are looked up in the expansion. When delivery
16847 fails because this quota is exceeded, the handling of the error is as for
16848 system quota failures.
16850 \**Note**\: A value of zero is interpreted as `no quota'.
16852 By default, Exim's quota checking mimics system quotas, and restricts the
16853 mailbox to the specified maximum size, though the value is not accurate to the
16854 last byte, owing to separator lines and additional headers that may get added
16855 during message delivery. When a mailbox is nearly full, large messages may get
16856 refused even though small ones are accepted, because the size of the current
16857 message is added to the quota when the check is made. This behaviour can be
16858 changed by setting \quota@_is@_inclusive\ false. When this is done, the check
16859 for exceeding the quota does not include the current message. Thus, deliveries
16860 continue until the quota has been exceeded; thereafter, no further messages are
16861 delivered. See also \quota@_warn@_threshold\.
16863 .conf quota@_directory string$**$ unset
16864 This option defines the directory to check for quota purposes when delivering
16865 into individual files. The default is the delivery directory, or, if a file
16866 called \(maildirfolder)\ exists in a maildir directory, the parent of the
16867 delivery directory.
16869 .conf quota@_filecount string$**$ 0
16870 This option applies when the \directory\ option is set. It limits the total
16871 number of files in the directory (compare the inode limit in system quotas). It
16872 can only be used if \quota\ is also set. The value is expanded; an expansion
16873 failure causes delivery to be deferred.
16875 .conf quota@_is@_inclusive boolean true
16878 .conf quota@_size@_regex string unset
16879 This option applies when one of the delivery modes that writes a separate file
16880 for each message is being used. When Exim wants to find the size of one of
16881 these files in order to test the quota, it first checks \quota@_size@_regex\.
16882 If this is set to a regular expression that matches the file name, and it
16883 captures one string, that string is interpreted as a representation of the
16884 file's size. The value of \quota@_size@_regex\ is not expanded.
16886 This feature is useful only when users have no shell access to their mailboxes
16887 -- otherwise they could defeat the quota simply by renaming the files. This
16888 facility can be used with maildir deliveries, by setting \maildir@_tag\ to add
16889 the file length to the file name. For example:
16891 maildir_tag = ,S=$message_size
16892 quota_size_regex = ,S=(\d+)
16894 The regular expression should not assume that the length is at the end of the
16895 file name (even though \maildir@_tag\ puts it there) because maildir MUAs
16896 sometimes add other information onto the ends of message file names.
16898 .conf quota@_warn@_message string$**$ "see below"
16899 See below for the use of this option. If it is not set when
16900 \quota@_warn@_threshold\ is set, it defaults to
16902 quota_warn_message = "\
16903 To: $local_part@$domain\n\
16904 Subject: Your mailbox\n\n\
16905 This message is automatically created \
16906 by mail delivery software.\n\n\
16907 The size of your mailbox has exceeded \
16908 a warning threshold that is\n\
16909 set by the system administrator.\n"
16912 .conf quota@_warn@_threshold string$**$ 0
16913 .index quota||warning threshold
16914 .index mailbox||size warning
16915 .index size||of mailbox
16916 This option is expanded in the same way as \quota\ (see above). If the
16917 resulting value is greater than zero, and delivery of the message causes the
16918 size of the file or total space in the directory tree to cross the given
16919 threshold, a warning message is sent. If \quota\ is also set, the threshold may
16920 be specified as a percentage of it by following the value with a percent sign.
16924 quota_warn_threshold = 75%
16926 If \quota\ is not set, a setting of \quota@_warn@_threshold\ that ends with a
16927 percent sign is ignored.
16929 The warning message itself is specified by the \quota@_warn@_message\ option,
16930 and it must start with a ::To:: header line containing the recipient(s). A
16931 ::Subject:: line should also normally be supplied. The \quota\ option does not
16932 have to be set in order to use this option; they are independent of one
16933 another except when the threshold is specified as a percentage.
16935 .conf use@_bsmtp boolean false
16936 .index envelope sender
16937 If this option is set true, \%appendfile%\ writes messages in `batch SMTP'
16938 format, with the envelope sender and recipient(s) included as SMTP commands. If
16939 you want to include a leading \\HELO\\ command with such messages, you can do
16940 so by setting the \message@_prefix\ option. See section ~~SECTbatchSMTP for
16941 details of batch SMTP.
16943 .conf use@_crlf boolean false
16944 .index carriage return
16946 This option causes lines to be terminated with the two-character CRLF sequence
16947 (carriage return, linefeed) instead of just a linefeed character. In the case
16948 of batched SMTP, the byte sequence written to the file is then an exact image
16949 of what would be sent down a real SMTP connection.
16951 The contents of the \message@_prefix\ and \message@_suffix\ options are written
16952 verbatim, so must contain their own carriage return characters if these are
16953 needed. In cases where these options have non-empty defaults, the values end
16954 with a single linefeed, so they
16956 be changed to end with \"@\r@\n"\ if \use@_crlf\ is set.
16958 .conf use@_fcntl@_lock boolean "see below"
16959 This option controls the use of the \*fcntl()*\ function to lock a file for
16960 exclusive use when a message is being appended. It is set by default unless
16961 \use@_flock@_lock\ is set. Otherwise, it should be turned off only if you know
16962 that all your MUAs use lock file locking. When both \use@_fcntl@_lock\ and
16963 \use@_flock@_lock\ are unset, \use@_lockfile\ must be set.
16965 .conf use@_flock@_lock boolean false
16966 This option is provided to support the use of \*flock()*\ for file locking, for
16967 the few situations where it is needed. Most modern operating systems support
16968 \*fcntl()*\ and \*lockf()*\ locking, and these two functions interwork with
16969 each other. Exim uses \*fcntl()*\ locking by default.
16971 This option is required only if you are using an operating system where
16972 \*flock()*\ is used by programs that access mailboxes (typically MUAs), and
16973 where \*flock()*\ does not correctly interwork with \*fcntl()*\. You can use
16974 both \*fcntl()*\ and \*flock()*\ locking simultaneously if you want.
16976 .index Solaris||\*flock()*\ support
16977 Not all operating systems provide \*flock()*\. Some versions of Solaris do not
16978 have it (and some, I think, provide a not quite right version built on top of
16979 \*lockf()*\). If the OS does not have \*flock()*\, Exim will be built without
16980 the ability to use it, and any attempt to do so will cause a configuration
16983 \**Warning**\: \*flock()*\ locks do not work on NFS files (unless \*flock()*\
16984 is just being mapped onto \*fcntl()*\ by the OS).
16986 .conf use@_lockfile boolean "see below"
16987 If this option is turned off, Exim does not attempt to create a lock file when
16988 appending to a mailbox file. In this situation, the only locking is by
16989 \*fcntl()*\. You should only turn \use@_lockfile\ off if you are absolutely
16990 sure that every MUA that is ever going to look at your users' mailboxes uses
16991 \*fcntl()*\ rather than a lock file, and even then only when you are not
16992 delivering over NFS from more than one host.
16994 .index NFS||lock file
16995 In order to append to an NFS file safely from more than one host, it is
16996 necessary to take out a lock $it{before} opening the file, and the lock file
16997 achieves this. Otherwise, even with \*fcntl()*\ locking, there is a risk of
17000 The \use@_lockfile\ option is set by default unless \use@_mbx@_lock\ is set. It
17001 is not possible to turn both \use@_lockfile\ and \use@_fcntl@_lock\ off, except
17002 when \mbx@_format\ is set.
17004 .conf use@_mbx@_lock boolean "see below"
17005 This option is available only if Exim has been compiled with \\SUPPORT@_MBX\\
17006 set in \(Local/Makefile)\. Setting the option specifies that special MBX
17007 locking rules be used. It is set by default if \mbx@_format\ is set and none of
17008 the locking options are mentioned in the configuration. The locking rules are
17009 the same as are used by the \*c-client*\ library that underlies Pine and the
17010 IMAP4 and POP daemons that come with it (see the discussion below). The rules
17011 allow for shared access to the mailbox. However, this kind of locking does not
17012 work when the mailbox is NFS mounted.
17014 You can set \use@_mbx@_lock\ with either (or both) of \use@_fcntl@_lock\ and
17015 \use@_flock@_lock\ to control what kind of locking is used in implementing the
17016 MBX locking rules. The default is to use \*fcntl()*\ if \use@_mbx@_lock\ is set
17017 without \use@_fcntl@_lock\ or \use@_flock@_lock\.
17021 .section Operational details for appending
17022 .rset SECTopappend "~~chapter.~~section"
17023 .index appending to a file
17024 .index file||appending
17025 Before appending to a file, the following preparations are made:
17027 If the name of the file is \(/dev/null)\, no action is taken, and a success
17030 .index directory creation
17031 If any directories on the file's path are missing, Exim creates them if the
17032 \create@_directory\ option is set. A created directory's mode is given by the
17033 \directory@_mode\ option.
17035 If \file@_format\ is set, the format of an existing file is checked. If this
17036 indicates that a different transport should be used, control is passed to that
17039 .index file||locking
17040 .index locking files
17041 .index NFS||lock file
17042 If \use@_lockfile\ is set, a lock file is built in a way that will work
17043 reliably over NFS, as follows:
17045 Create a `hitching post' file whose name is that of the lock file with the
17046 current time, primary host name, and process id added, by opening for writing
17047 as a new file. If this fails with an access error, delivery is deferred.
17049 Close the hitching post file, and hard link it to the lock file name.
17051 If the call to \*link()*\ succeeds, creation of the lock file has succeeded.
17052 Unlink the hitching post name.
17054 Otherwise, use \*stat()*\ to get information about the hitching post file, and
17055 then unlink hitching post name. If the number of links is exactly two, creation
17056 of the lock file succeeded but something (for example, an NFS server crash and
17057 restart) caused this fact not to be communicated to the \*link()*\ call.
17059 If creation of the lock file failed, wait for \lock@_interval\ and try again,
17060 up to \lock@_retries\ times. However, since any program that writes to a
17061 mailbox should complete its task very quickly, it is reasonable to time out old
17062 lock files that are normally the result of user agent and system crashes. If an
17063 existing lock file is older than \lockfile@_timeout\ Exim attempts to unlink it
17064 before trying again.
17067 A call is made to \*lstat()*\ to discover whether the main file exists, and if
17068 so, what its characteristics are. If \*lstat()*\ fails for any reason other
17069 than non-existence, delivery is deferred.
17071 .index symbolic link||to mailbox
17072 .index mailbox||symbolic link
17073 If the file does exist and is a symbolic link, delivery is deferred, unless the
17074 \allow@_symlink\ option is set, in which case the ownership of the link is
17075 checked, and then \*stat()*\ is called to find out about the real file, which
17076 is then subjected to the checks below. The check on the top-level link
17077 ownership prevents one user creating a link for another's mailbox in a sticky
17078 directory, though allowing symbolic links in this case is definitely not a good
17079 idea. If there is a chain of symbolic links, the intermediate ones are not
17082 If the file already exists but is not a regular file, or if the file's owner
17083 and group (if the group is being checked -- see \check@_group\ above) are
17084 different from the user and group under which the delivery is running,
17085 delivery is deferred.
17087 If the file's permissions are more generous than specified, they are reduced.
17088 If they are insufficient, delivery is deferred, unless \mode@_fail@_narrower\
17089 is set false, in which case the delivery is tried using the existing
17092 The file's inode number is saved, and the file is then opened for appending. If
17093 this fails because the file has vanished, \%appendfile%\ behaves as if it hadn't
17094 existed (see below). For any other failures, delivery is deferred.
17096 If the file is opened successfully, check that the inode number hasn't
17097 changed, that it is still a regular file, and that the owner and permissions
17098 have not changed. If anything is wrong, defer delivery and freeze the message.
17100 If the file did not exist originally, defer delivery if the \file@_must@_exist\
17101 option is set. Otherwise, check that the file is being created in a permitted
17102 directory if the \create@_file\ option is set (deferring on failure), and then
17103 open for writing as a new file, with the \\O@_EXCL\\ and \\O@_CREAT\\ options,
17104 except when dealing with a symbolic link (the \allow@_symlink\ option must be
17105 set). In this case, which can happen if the link points to a non-existent file,
17106 the file is opened for writing using \\O@_CREAT\\ but not \\O@_EXCL\\, because
17107 that prevents link following.
17109 .index loop||while file testing
17110 If opening fails because the file exists, obey the tests given above for
17111 existing files. However, to avoid looping in a situation where the file is
17112 being continuously created and destroyed, the exists/not-exists loop is broken
17113 after 10 repetitions, and the message is then frozen.
17115 If opening fails with any other error, defer delivery.
17117 .index file||locking
17118 .index locking files
17119 Once the file is open, unless both \use@_fcntl@_lock\ and \use@_flock@_lock\
17120 are false, it is locked using \*fcntl()*\ or \*flock()*\ or both. If
17121 \use@_mbx@_lock\ is false, an exclusive lock is requested in each case.
17122 However, if \use@_mbx@_lock\ is true,
17123 Exim takes out a shared lock on the open file,
17124 and an exclusive lock on the file whose name is
17126 /tmp/.<<device-number>>.<<inode-number>>
17128 using the device and inode numbers of the open mailbox file, in accordance with
17129 the MBX locking rules.
17131 If Exim fails to lock the file, there are two possible courses of action,
17132 depending on the value of the locking timeout. This is obtained from
17133 \lock@_fcntl@_timeout\ or \lock@_flock@_timeout\, as appropriate.
17135 If the timeout value is zero, the file is closed, Exim waits for
17136 \lock@_interval\, and then goes back and re-opens the file as above and tries
17137 to lock it again. This happens up to \lock@_retries\ times, after which the
17138 delivery is deferred.
17140 If the timeout has a value greater than zero, blocking calls to \*fcntl()*\ or
17141 \*flock()*\ are used (with the given timeout), so there has already been some
17142 waiting involved by the time locking fails. Nevertheless, Exim does not give up
17143 immediately. It retries up to
17145 (lock@_retries * lock@_interval) / <<timeout>>
17147 times (rounded up).
17150 At the end of delivery, Exim closes the file (which releases the \*fcntl()*\
17151 and/or \*flock()*\ locks) and then deletes the lock file if one was created.
17153 .section Operational details for delivery to a new file
17154 .rset SECTopdir "~~chapter.~~section"
17155 .index delivery||to single file
17157 When the \directory\ option is set instead of \file\, each message is delivered
17158 into a newly-created file or set of files. When \%appendfile%\ is activated
17159 directly from a \%redirect%\ router, neither \file\ nor \directory\ is normally
17160 set, because the path for delivery is supplied by the router. (See for example,
17161 the \%address@_file%\ transport in the default configuration.) In this case,
17162 delivery is to a new file if either the path name ends in \"/"\, or the
17163 \maildir@_format\ or \mailstore@_format\ option is set.
17165 No locking is required while writing the message to a new file, so the various
17166 locking options of the transport are ignored. The `From' line that by default
17167 separates messages in a single file is not normally needed, nor is the escaping
17168 of message lines that start with `From', and there is no need to ensure a
17169 newline at the end of each message. Consequently, the default values for
17170 \check@_string\, \message@_prefix\, and \message@_suffix\ are all unset when
17171 any of \directory\, \maildir@_format\, or \mailstore@_format\ is set.
17173 If Exim is required to check a \quota\ setting, it adds up the sizes of all the
17174 files in the delivery directory by default. However, you can specify a
17175 different directory by setting \quota@_directory\. Also, for maildir deliveries
17176 (see below) the \(maildirfolder)\ convention is honoured.
17179 .index maildir format
17180 .index mailstore format
17181 There are three different ways in which delivery to individual files can be
17182 done, controlled by the settings of the \maildir@_format\ and
17183 \mailstore@_format\ options. Note that code to support maildir or mailstore
17184 formats is not included in the binary unless \\SUPPORT@_MAILDIR\\ or
17185 \\SUPPORT@_MAILSTORE\\, respectively, is set in \(Local/Makefile)\.
17187 .index directory creation
17188 In all three cases an attempt is made to create the directory and any necessary
17189 sub-directories if they do not exist, provided that the \create@_directory\
17190 option is set (the default). The location of a created directory can be
17191 constrained by setting \create@_file\. A created directory's mode is given by
17192 the \directory@_mode\ option. If creation fails, or if the \create@_directory\
17193 option is not set when creation is required, delivery is deferred.
17196 .section Maildir delivery
17197 .rset SECTmaildirdelivery "~~chapter.~~section"
17198 .index maildir format||description of
17199 If the \maildir@_format\ option is true, Exim delivers each message by writing
17200 it to a file whose name is \(tmp/<<stime>>.H<<mtime>>P<<pid>>.<<host>>)\ in the
17201 given directory. If the delivery is successful, the file is renamed into the
17202 \(new)\ subdirectory.
17204 In the file name, <<stime>> is the current time of day in seconds, and
17205 <<mtime>> is the microsecond fraction of the time. After a maildir delivery,
17206 Exim checks that the time-of-day clock has moved on by at least one microsecond
17207 before terminating the delivery process. This guarantees uniqueness for the
17208 file name. However, as a precaution, Exim calls \*stat()*\ for the file before
17209 opening it. If any response other than \\ENOENT\\ (does not exist) is given,
17210 Exim waits 2 seconds and tries again, up to \maildir@_retries\ times.
17212 .index quota||in maildir delivery
17214 If Exim is required to check a \quota\ setting before a maildir delivery, and
17215 \quota@_directory\ is not set, it looks for a file called \(maildirfolder)\ in
17216 the maildir directory (alongside \(new)\, \(cur)\, \(tmp)\). If this exists,
17217 Exim assumes the directory is a maildir++ folder directory, which is one level
17218 down from the user's top level mailbox directory. This causes it to start at
17219 the parent directory instead of the current directory when calculating the
17220 amount of space used.
17223 .section Using tags to record message sizes
17224 If \maildir@_tag\ is set, the string is expanded for each delivery.
17225 When the maildir file is renamed into the \(new)\ sub-directory, the
17226 tag is added to its name. However, if adding the tag takes the length of the
17227 name to the point where the test \*stat()*\ call fails with \\ENAMETOOLONG\\,
17228 the tag is dropped and the maildir file is created with no tag.
17230 Tags can be used to encode the size of files in their names; see
17231 \quota@_size@_regex\ above for an example. The expansion of \maildir@_tag\
17232 happens after the message has been written. The value of the \$message@_size$\
17233 variable is set to the number of bytes actually written. If the expansion is
17234 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
17235 be deferred. The expanded tag may contain any printing characters except `/'.
17236 Non-printing characters in the string are ignored; if the resulting string is
17237 empty, it is ignored. If it starts with an alphanumeric character, a leading
17241 .section Using a maildirsize file
17242 .index quota||in maildir delivery
17243 .index maildir format||\(maildirsize)\ file
17244 If \maildir@_use@_size@_file\ is true, Exim implements the maildir++ rules for
17245 storing quota and message size information in a file called \(maildirsize)\
17246 within the maildir directory. If this file does not exist, Exim creates it,
17247 setting the quota from the \quota\ option of the transport. If the maildir
17248 directory itself does not exist, it is created before any attempt to write a
17249 \(maildirsize)\ file.
17251 The \(maildirsize)\ file is used to hold information about the sizes of
17252 messages in the maildir, thus speeding up quota calculations. The quota value
17253 in the file is just a cache; if the quota is changed in the transport, the new
17254 value overrides the cached value when the next message is delivered. The cache
17255 is maintained for the benefit of other programs that access the maildir and
17256 need to know the quota.
17258 If the \quota\ option in the transport is unset or zero, the \(maildirsize)\
17259 file is maintained (with a zero quota setting), but no quota is imposed.
17261 A regular expression is available for controlling which directories in the
17262 maildir participate in quota calculations. See the description of the
17263 \maildir@_quota@_directory@_regex\ option above for details.
17266 .section Mailstore delivery
17267 .index mailstore format||description of
17268 If the \mailstore@_format\ option is true, each message is written as two files
17269 in the given directory. A unique base name is constructed from the message id
17270 and the current delivery process, and the files that are written use this base
17271 name plus the suffixes \(.env)\ and \(.msg)\. The \(.env)\ file contains the
17272 message's envelope, and the \(.msg)\ file contains the message itself.
17274 During delivery, the envelope is first written to a file with the suffix
17275 \(.tmp)\. The \(.msg)\ file is then written, and when it is complete, the
17276 \(.tmp)\ file is renamed as the \(.env)\ file. Programs that access messages in
17277 mailstore format should wait for the presence of both a \(.msg)\ and a \(.env)\
17278 file before accessing either of them. An alternative approach is to wait for
17279 the absence of a \(.tmp)\ file.
17281 The envelope file starts with any text defined by the \mailstore@_prefix\
17282 option, expanded and terminated by a newline if there isn't one. Then follows
17283 the sender address on one line, then all the recipient addresses, one per line.
17284 There can be more than one recipient only if the \batch@_max\ option is set
17285 greater than one. Finally, \mailstore@_suffix\ is expanded and the result
17286 appended to the file, followed by a newline if it does not end with one.
17288 If expansion of \mailstore@_prefix\ or \mailstore@_suffix\ ends with a forced
17289 failure, it is ignored. Other expansion errors are treated as serious
17290 configuration errors, and delivery is deferred.
17293 .section Non-special new file delivery
17294 If neither \maildir@_format\ nor \mailstore@_format\ is set, a single new file
17295 is created directly in the named directory. For example, when delivering
17296 messages into files in batched SMTP format for later delivery to some host (see
17297 section ~~SECTbatchSMTP), a setting such as
17299 directory = /var/bsmtp/$host
17301 might be used. A message is written to a file with a temporary name, which is
17302 then renamed when the delivery is complete. The final name is obtained by
17303 expanding the contents of the \directory@_file\ option.
17313 . ============================================================================
17314 .chapter The autoreply transport
17315 .set runningfoot "autoreply transport"
17316 .index transports||\%autoreply%\
17317 .index \%autoreply%\ transport
17318 The \%autoreply%\ transport is not a true transport in that it does not cause
17319 the message to be transmitted. Instead, it generates another mail message. It
17320 is usually run as the result of mail filtering, a `vacation' message being the
17321 standard example. However, it can also be run directly from a router like any
17322 other transport. To reduce the possibility of message cascades, messages
17323 created by the \%autoreply%\ transport always have empty envelope sender
17324 addresses, like bounce messages.
17326 The parameters of the message to be sent can be specified in the configuration
17327 by options described below. However, these are used only when the address
17328 passed to the transport does not contain its own reply information. When the
17329 transport is run as a consequence of a
17331 or \vacation\ command in a filter file, the parameters of the message are
17332 supplied by the filter, and passed with the address. The transport's options
17333 that define the message are then ignored (so they are not usually set in this
17334 case). The message is specified entirely by the filter or by the transport; it
17335 is never built from a mixture of options. However, the \file@_optional\,
17336 \mode\, and \return@_message\ options apply in all cases.
17338 \%Autoreply%\ is implemented as a local transport. When used as a result of a
17339 command in a user's filter file, \%autoreply%\ normally runs under the uid and
17340 gid of the user, and with appropriate current and home directories (see chapter
17341 ~~CHAPenvironment).
17343 There is a subtle difference between routing a message to a \%pipe%\ transport
17344 that generates some text to be returned to the sender, and routing it to an
17345 \%autoreply%\ transport. This difference is noticeable only if more than one
17346 address from the same message is so handled. In the case of a pipe, the
17347 separate outputs from the different addresses are gathered up and returned to
17348 the sender in a single message, whereas if \%autoreply%\ is used, a separate
17349 message is generated for each address that is passed to it.
17351 Non-printing characters are not permitted in the header lines generated for the
17352 message that \%autoreply%\ creates, with the exception of newlines that are
17353 immediately followed by whitespace. If any non-printing characters are found,
17354 the transport defers.
17355 Whether characters with the top bit set count as printing characters or not is
17356 controlled by the \print@_topbitchars\ global option.
17358 If any of the generic options for manipulating headers (for example,
17359 \headers@_add\) are set on an \%autoreply%\ transport, they apply to the copy of
17360 the original message that is included in the generated message when
17361 \return@_message\ is set. They do not apply to the generated message itself.
17363 If the \%autoreply%\ transport receives return code 2 from Exim when it submits
17364 the message, indicating that there were no recipients, it does not treat this
17365 as an error. This means that autoreplies sent to \$sender@_address$\ when this
17366 is empty (because the incoming message is a bounce message) do not cause
17367 problems. They are just discarded.
17370 .section Private options for autoreply
17373 .index options||\%autoreply%\ transport
17374 .conf bcc string$**$ unset
17375 This specifies the addresses that are to receive `blind carbon copies' of the
17376 message when the message is specified by the transport.
17378 .conf cc string$**$ unset
17379 This specifies recipients of the message and the contents of the ::Cc:: header
17380 when the message is specified by the transport.
17382 .conf file string$**$ unset
17383 The contents of the file are sent as the body of the message when the message
17384 is specified by the transport. If both \file\ and \text\ are set, the text
17385 string comes first.
17387 .conf file@_expand boolean false
17388 If this is set, the contents of the file named by the \file\ option are
17389 subjected to string expansion as they are added to the message.
17391 .conf file@_optional boolean false
17392 If this option is true, no error is generated if the file named by the \file\
17393 option or passed with the address does not exist or cannot be read.
17395 .conf from string$**$ unset
17396 This specifies the contents of the ::From:: header when the message is specified
17399 .conf headers string$**$ unset
17400 This specifies additional RFC 2822 headers that are to be added to the message when
17401 the message is specified by the transport. Several can be given by using `@\n'
17402 to separate them. There is no check on the format.
17404 .conf log string$**$ unset
17405 This option names a file in which a record of every message sent is logged when
17406 the message is specified by the transport.
17408 .conf mode "octal integer" 0600
17409 If either the log file or the `once' file has to be created, this mode is used.
17411 .conf once string$**$ unset
17412 This option names a file or DBM database in which a record of each
17413 ::To:: recipient is kept when the message is specified by the transport.
17414 \**Note**\: This does not apply to ::Cc:: or ::Bcc:: recipients.
17415 If \once@_file@_size\ is not set, a DBM database is used, and it is allowed to
17416 grow as large as necessary. If a potential recipient is already in the
17417 database, no message is sent by default. However, if \once@_repeat\ specifies a
17418 time greater than zero, the message is sent if that much time has elapsed since
17419 a message was last sent to this recipient. If \once\ is unset, the message is
17422 If \once@_file@_size\ is set greater than zero, it changes the way Exim
17423 implements the \once\ option. Instead of using a DBM file to record every
17424 recipient it sends to, it uses a regular file, whose size will never get larger
17425 than the given value. In the file, it keeps a linear list of recipient
17426 addresses and times at which they were sent messages. If the file is full when
17427 a new address needs to be added, the oldest address is dropped. If
17428 \once@_repeat\ is not set, this means that a given recipient may receive
17429 multiple messages, but at unpredictable intervals that depend on the rate of
17430 turnover of addresses in the file. If \once@_repeat\ is set, it specifies a
17431 maximum time between repeats.
17433 .conf once@_file@_size integer 0
17436 .conf once@_repeat time$**$ 0s
17438 After expansion, the value of this option must be a valid time value.
17440 .conf reply@_to string$**$ unset
17441 This specifies the contents of the ::Reply-To:: header when the message is
17442 specified by the transport.
17444 .conf return@_message boolean false
17445 If this is set, a copy of the original message is returned with the new
17446 message, subject to the maximum size set in the \return@_size@_limit\ global
17447 configuration option.
17449 .conf subject string$**$ unset
17450 This specifies the contents of the ::Subject:: header when the message is
17451 specified by the transport.
17453 .conf text string$**$ unset
17454 This specifies a single string to be used as the body of the message when the
17455 message is specified by the transport. If both \text\ and \file\ are set, the
17458 .conf to string$**$ unset
17459 This specifies recipients of the message and the contents of the ::To:: header
17460 when the message is specified by the transport.
17470 . ============================================================================
17471 .chapter The lmtp transport
17472 .set runningfoot "lmtp transport"
17473 .index transports||\%lmtp%\
17474 .index \%lmtp%\ transport
17475 .index LMTP||over a pipe
17476 .index LMTP||over a socket
17477 .rset CHAPLMTP "~~chapter"
17478 The \%lmtp%\ transport runs the LMTP protocol (RFC 2033) over a pipe to a
17480 or by interacting with a Unix domain socket.
17481 This transport is something of a cross between the \%pipe%\ and \%smtp%\
17482 transports. Exim also has support for using LMTP over TCP/IP; this is
17483 implemented as an option for the \%smtp%\ transport. Because LMTP is expected
17484 to be of minority interest, the default build-time configure in \(src/EDITME)\
17485 has it commented out. You need to ensure that
17489 is present in your \(Local/Makefile)\ in order to have the \%lmtp%\ transport
17490 included in the Exim binary.
17492 The private options of the \%lmtp%\ transport are as follows:
17495 .index options||\%lmtp%\ transport
17497 .conf batch@_id string$**$ unset
17498 See the description of local delivery batching in chapter ~~CHAPbatching.
17500 .conf batch@_max integer 1
17501 This limits the number of addresses that can be handled in a single delivery.
17502 Most LMTP servers can handle several addresses at once, so it is normally a
17503 good idea to increase this value. See the description of local delivery
17504 batching in chapter ~~CHAPbatching.
17506 .conf command string$**$ unset
17507 This option must be set if \socket\ is not set.
17508 The string is a command which is run in a separate process. It is split up into
17509 a command name and list of arguments, each of which is separately expanded (so
17510 expansion cannot change the number of arguments). The command is run directly,
17511 not via a shell. The message is passed to the new process using the standard
17512 input and output to operate the LMTP protocol.
17514 .conf socket string$**$ unset
17515 This option must be set if \command\ is not set. The result of expansion must
17516 be the name of a Unix domain socket. The transport connects to the socket and
17517 delivers the message to it using the LMTP protocol.
17519 .conf timeout time 5m
17520 The transport is aborted if the created process
17521 or Unix domain socket
17522 does not respond to LMTP commands or message input within this timeout.
17526 Here is an example of a typical LMTP transport:
17530 command = /some/local/lmtp/delivery/program
17534 This delivers up to 20 addresses at a time, in a mixture of domains if
17535 necessary, running as the user \*exim*\.
17543 . ============================================================================
17544 .chapter The pipe transport
17545 .rset CHAPpipetransport "~~chapter"
17546 .set runningfoot "pipe transport"
17547 .index transports||\%pipe%\
17548 .index \%pipe%\ transport
17549 The \%pipe%\ transport is used to deliver messages via a pipe to a command
17550 running in another process. This can happen in one of two ways:
17552 A router routes an address to a transport in the normal way, and the transport
17553 is configured as a \%pipe%\ transport. In this case, \$local@_part$\ contains
17554 the address (as usual), and the command which is run is specified by the
17555 \command\ option on the transport. An example of this is the use of \%pipe%\ as
17556 a pseudo-remote transport for passing messages to some other delivery mechanism
17559 A router redirects an address directly to a pipe command (for example, from an
17560 alias or forward file). In this case, \$local@_part$\ contains the local part
17561 that was redirected, and \$address@_pipe$\ contains the text of the pipe
17562 command itself. The \command\ option on the transport is ignored.
17565 The \%pipe%\ transport is a non-interactive delivery method. Exim can also
17566 deliver messages over pipes using the LMTP interactive protocol. This is
17567 implemented by the \%lmtp%\ transport.
17569 In the case when \%pipe%\ is run as a consequence of an entry in a local user's
17570 \(.forward)\ file, the command runs under the uid and gid of that user. In
17571 other cases, the uid and gid have to be specified explicitly, either on the
17572 transport or on the router that handles the address. Current and `home'
17573 directories are also controllable. See chapter ~~CHAPenvironment for details of
17574 the local delivery environment.
17576 .section Returned status and data
17577 .index \%pipe%\ transport||returned data
17578 If the command exits with a non-zero return code, the delivery is deemed to
17579 have failed, unless either the \ignore@_status\ option is set (in which case
17580 the return code is treated as zero), or the return code is one of those listed
17581 in the \temp@_errors\ option, which are interpreted as meaning `try again
17582 later'. In this case, delivery is deferred. Details of a permanent failure are
17583 logged, but are not included in the bounce message, which merely contains
17584 `local delivery failed'.
17586 If the return code is greater than 128 and the command being run is a shell
17587 script, it normally means that the script was terminated by a signal whose
17588 value is the return code minus 128.
17590 If Exim is unable to run the command (that is, if \*execve()*\ fails), the
17591 return code is set to 127. This is the value that a shell returns if it is
17592 asked to run a non-existent command. The wording for the log line suggests that
17593 a non-existent command may be the problem.
17595 The \return@_output\ option can affect the result of a pipe delivery. If it is
17596 set and the command produces any output on its standard output or standard
17597 error streams, the command is considered to have failed, even if it gave a zero
17598 return code or if \ignore@_status\ is set. The output from the command is
17599 included as part of the bounce message. The \return@_fail@_output\ option is
17600 similar, except that output is returned only when the command exits with a
17601 failure return code, that is, a value other than zero or a code that matches
17605 .section How the command is run
17606 .rset SECThowcommandrun "~~chapter.~~section"
17607 .index \%pipe%\ transport||path for command
17608 The command line is (by default) broken down into a command name and arguments
17609 by the \%pipe%\ transport itself. The \allow@_commands\ and \restrict@_to@_path\
17610 options can be used to restrict the commands that may be run.
17611 .index quoting||in pipe command
17612 Unquoted arguments are delimited by white space. If an argument appears in
17613 double quotes, backslash is interpreted as an escape character in the usual
17614 way. If an argument appears in single quotes, no escaping is done.
17616 String expansion is applied to the command line except when it comes from a
17617 traditional \(.forward)\ file (commands from a filter file are expanded). The
17618 expansion is applied to each argument in turn rather than to the whole line.
17619 For this reason, any string expansion item that contains white space must be
17620 quoted so as to be contained within a single argument. A setting such as
17622 command = /some/path ${if eq{$local_part}{postmaster}{xxx}{yyy}}
17624 will not work, because the expansion item gets split between several
17625 arguments. You have to write
17627 command = /some/path "${if eq{$local_part}{postmaster}{xxx}{yyy}}"
17629 to ensure that it is all in one argument. The expansion is done in this way,
17630 argument by argument, so that the number of arguments cannot be changed as a
17631 result of expansion, and quotes or backslashes in inserted variables do not
17632 interact with external quoting.
17634 .index transport||filter
17635 .index filter||transport filter
17636 Special handling takes place when an argument consists of precisely the text
17637 `$tt{@$pipe@_addresses}'. This is not a general expansion variable; the only
17638 place this string is recognized is when it appears as an argument for a pipe or
17639 transport filter command. It causes each address that is being handled to be
17640 inserted in the argument list at that point $it{as a separate argument}. This
17641 avoids any problems with spaces or shell metacharacters, and is of use when a
17642 \%pipe%\ transport is handling groups of addresses in a batch.
17644 After splitting up into arguments and expansion, the resulting command is run
17645 in a subprocess directly from the transport, $it{not} under a shell. The
17646 message that is being delivered is supplied on the standard input, and the
17647 standard output and standard error are both connected to a single pipe that is
17648 read by Exim. The \max@_output\ option controls how much output the command may
17649 produce, and the \return@_output\ and \return@_fail@_output\ options control
17650 what is done with it.
17652 Not running the command under a shell (by default) lessens the security risks
17653 in cases when a command from a user's filter file is built out of data that was
17654 taken from an incoming message. If a shell is required, it can of course be
17655 explicitly specified as the command to be run. However, there are circumstances
17656 where existing commands (for example, in \(.forward)\ files) expect to be run
17657 under a shell and cannot easily be modified. To allow for these cases, there is
17658 an option called \use@_shell\, which changes the way the \%pipe%\ transport
17659 works. Instead of breaking up the command line as just described, it expands it
17660 as a single string and passes the result to \(/bin/sh)\. The
17661 \restrict@_to@_path\ option and the \$pipe@_addresses$\ facility cannot be used
17662 with \use@_shell\, and the whole mechanism is inherently less secure.
17665 .section Environment variables
17666 .rset SECTpipeenv "~~chapter.~~section"
17667 .index \%pipe%\ transport||environment for command
17668 .index environment for pipe transport
17669 The environment variables listed below are set up when the command is invoked.
17670 This list is a compromise for maximum compatibility with other MTAs. Note that
17671 the \environment\ option can be used to add additional variables to this
17675 DOMAIN $t $rm{the domain of the address}
17676 HOME $t $rm{the home directory, if set}
17677 HOST $t $rm{the host name when called from a router (see below)}
17678 LOCAL@_PART $t $rm{see below}
17679 LOCAL@_PART@_PREFIX $t $rm{see below}
17680 LOCAL@_PART@_SUFFIX $t $rm{see below}
17681 LOGNAME $t $rm{see below}
17682 MESSAGE@_ID $t $rm{the message's id}
17683 PATH $t $rm{as specified by the \path\ option below}
17684 QUALIFY@_DOMAIN $t $rm{the sender qualification domain}
17685 RECIPIENT $t $rm{the complete recipient address}
17686 SENDER $t $rm{the sender of the message (empty if a bounce)}
17687 SHELL $t `$tt{/bin/sh}'
17688 TZ $t $rm{the value of the \timezone\ option, if set}
17689 USER $t $rm{see below}
17692 When a \%pipe%\ transport is called directly from (for example) an \%accept%\
17693 router, \\LOCAL@_PART\\ is set to the local part of the address. When it is
17694 called as a result of a forward or alias expansion, \\LOCAL@_PART\\ is set to
17695 the local part of the address that was expanded. In both cases, any affixes are
17696 removed from the local part, and made available in \\LOCAL@_PART@_PREFIX\\ and
17697 \\LOCAL@_PART@_SUFFIX\\, respectively. \\LOGNAME\\ and \\USER\\ are set to the
17698 same value as \\LOCAL@_PART\\ for compatibility with other MTAs.
17701 \\HOST\\ is set only when a \%pipe%\ transport is called from a router that
17702 associates hosts with an address, typically when using \%pipe%\ as a
17703 pseudo-remote transport. \\HOST\\ is set to the first host name specified by
17707 If the transport's generic \home@_directory\ option is set, its value is used
17708 for the \\HOME\\ environment variable. Otherwise, a home directory may be set
17709 by the router's \transport@_home@_directory\ option, which defaults to the
17710 user's home directory if \check@_local@_user\ is set.
17712 .section Private options for pipe
17713 .index options||\%pipe%\ transport
17716 .conf allow@_commands "string list$**$" unset
17717 .index \%pipe%\ transport||permitted commands
17718 The string is expanded, and is then interpreted as a colon-separated list of
17719 permitted commands. If \restrict@_to@_path\ is not set, the only commands
17720 permitted are those in the \allow@_commands\ list. They need not be absolute
17721 paths; the \path\ option is still used for relative paths. If
17722 \restrict@_to@_path\ is set with \allow@_commands\, the command must either be
17723 in the \allow@_commands\ list, or a name without any slashes that is found on
17724 the path. In other words, if neither \allow@_commands\ nor \restrict@_to@_path\
17725 is set, there is no restriction on the command, but otherwise only commands
17726 that are permitted by one or the other are allowed. For example, if
17728 allow_commands = /usr/bin/vacation
17730 and \restrict@_to@_path\ is not set, the only permitted command is
17731 \(/usr/bin/vacation)\. The \allow@_commands\ option may not be set if
17732 \use@_shell\ is set.
17734 .conf batch@_id string$**$ unset
17735 See the description of local delivery batching in chapter ~~CHAPbatching.
17737 .conf batch@_max integer 1
17738 This limits the number of addresses that can be handled in a single delivery.
17739 See the description of local delivery batching in chapter ~~CHAPbatching.
17741 .conf check@_string string unset
17742 As \%pipe%\ writes the message, the start of each line is tested for matching
17743 \check@_string\, and if it does, the initial matching characters are replaced
17744 by the contents of \escape@_string\, provided both are set. The value of
17745 \check@_string\ is a literal string, not a regular expression, and the case of
17746 any letters it contains is significant. When \use@_bsmtp\ is set, the contents
17747 of \check@_string\ and \escape@_string\ are forced to values that implement the
17748 SMTP escaping protocol. Any settings made in the configuration file are
17751 .conf command string$**$ unset
17752 This option need not be set when \%pipe%\ is being used to deliver to pipes
17753 obtained directly from address redirections. In other cases, the option must be
17754 set, to provide a command to be run. It need not yield an absolute path (see
17755 the \path\ option below). The command is split up into separate arguments by
17756 Exim, and each argument is separately expanded, as described in section
17757 ~~SECThowcommandrun above.
17759 .conf environment string$**$ unset
17760 .index \%pipe%\ transport||environment for command
17761 .index environment for \%pipe%\ transport
17762 This option is used to add additional variables to the environment in which the
17763 command runs (see section ~~SECTpipeenv for the default list). Its value is a
17764 string which is expanded, and then interpreted as a colon-separated list of
17765 environment settings of the form `<<name>>=<<value>>'.
17767 .conf escape@_string string unset
17768 See \check@_string\ above.
17770 .conf freeze@_exec@_fail boolean false
17771 .index exec failure
17772 .index failure of exec
17773 .index \%pipe%\ transport||failure of exec
17774 Failure to exec the command in a pipe transport is by default treated like
17775 any other failure while running the command. However, if \freeze@_exec@_fail\
17776 is set, failure to exec is treated specially, and causes the message to be
17777 frozen, whatever the setting of \ignore@_status\.
17779 .conf ignore@_status boolean false
17780 If this option is true, the status returned by the subprocess that is set up to
17781 run the command is ignored, and Exim behaves as if zero had been returned.
17782 Otherwise, a non-zero status
17783 or termination by signal
17784 causes an error return from the transport unless the status value is one of
17785 those listed in \temp@_errors\; these cause the delivery to be deferred and
17788 .conf log@_defer@_output boolean false
17789 .index \%pipe%\ transport||logging output
17790 If this option is set, and the status returned by the command is
17791 one of the codes listed in \temp@_errors\ (that is, delivery was deferred),
17792 and any output was produced, the first line of it is written to the main log.
17794 .conf log@_fail@_output boolean false
17795 If this option is set, and the command returns any output, and also ends with a
17796 return code that is neither zero nor one of the return codes listed in
17797 \temp@_errors\ (that is, the delivery failed), the first line of output is
17798 written to the main log.
17800 .conf log@_output boolean false
17801 If this option is set and the command returns any output, the first line of
17802 output is written to the main log, whatever the return code.
17804 .conf max@_output integer 20K
17805 This specifies the maximum amount of output that the command may produce on its
17806 standard output and standard error file combined. If the limit is exceeded, the
17807 process running the command is killed. This is intended as a safety measure to
17808 catch runaway processes. The limit is applied independently of the settings of
17809 the options that control what is done with such output (for example,
17810 \return@_output\). Because of buffering effects, the amount of output may
17811 exceed the limit by a small amount before Exim notices.
17813 .conf message@_prefix string$**$ "see below"
17814 The string specified here is expanded and output at the start of every message.
17815 The default is unset if \use@_bsmtp\ is set. Otherwise it is
17818 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
17824 This is required by the commonly used \(/usr/bin/vacation)\ program.
17825 However, it must $it{not} be present if delivery is to the Cyrus IMAP server,
17826 or to the \tmail\ local delivery agent. The prefix can be suppressed by setting
17831 .conf message@_suffix string$**$ "see below"
17832 The string specified here is expanded and output at the end of every message.
17833 The default is unset if \use@_bsmtp\ is set. Otherwise it is a single newline.
17834 The suffix can be suppressed by setting
17839 .conf path string $tt{/usr/bin}
17840 This option specifies the string that is set up in the \\PATH\\ environment
17841 variable of the subprocess. If the \command\ option does not yield an absolute
17842 path name, the command is sought in the \\PATH\\ directories, in the usual way.
17843 \**Warning**\: This does not apply to a command specified as a transport
17846 .conf pipe@_as@_creator boolean false
17847 .index uid (user id)||local delivery
17848 If the generic \user\ option is not set and this option is true, the delivery
17849 process is run under the uid that was in force when Exim was originally called
17850 to accept the message. If the group id is not otherwise set (via the generic
17851 \group\ option), the gid that was in force when Exim was originally called to
17852 accept the message is used.
17854 .conf restrict@_to@_path boolean false
17855 When this option is set, any command name not listed in \allow@_commands\ must
17856 contain no slashes. The command is searched for only in the directories listed
17857 in the \path\ option. This option is intended for use in the case when a pipe
17858 command has been generated from a user's \(.forward)\ file. This is usually
17859 handled by a \%pipe%\ transport called \address@_pipe\.
17861 .conf return@_fail@_output boolean false
17862 If this option is true, and the command produced any output and ended with a
17863 return code other than zero or one of the codes listed in \temp@_errors\ (that
17864 is, the delivery failed), the output is returned in the bounce message.
17865 However, if the message has a null sender (that is, it is itself a bounce
17866 message), output from the command is discarded.
17868 .conf return@_output boolean false
17869 If this option is true, and the command produced any output, the delivery is
17870 deemed to have failed whatever the return code from the command, and the output
17871 is returned in the bounce message. Otherwise, the output is just discarded.
17872 However, if the message has a null sender (that is, it is a bounce message),
17873 output from the command is always discarded, whatever the setting of this
17876 .conf temp@_errors "string list" "see below"
17877 .index \%pipe%\ transport||temporary failure
17878 This option contains either a colon-separated list of numbers, or a single
17879 asterisk. If \ignore@_status\ is false
17880 and \return@_output\ is not set,
17881 and the command exits with a non-zero return code, the failure is treated as
17882 temporary and the delivery is deferred if the return code matches one of the
17883 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
17884 codes are treated as permanent errors. The default setting contains the codes
17885 defined by \\EX@_TEMPFAIL\\ and \\EX@_CANTCREAT\\ in \(sysexits.h)\. If Exim is
17886 compiled on a system that does not define these macros, it assumes values of 75
17887 and 73, respectively.
17889 .conf timeout time 1h
17890 If the command fails to complete within this time, it is killed. This normally
17891 causes the delivery to fail. A zero time interval specifies no timeout. In
17892 order to ensure that any subprocesses created by the command are also killed,
17893 Exim makes the initial process a process group leader, and kills the whole
17894 process group on a timeout. However, this can be defeated if one of the
17895 processes starts a new process group.
17897 .conf umask "octal integer" 022
17898 This specifies the umask setting for the subprocess that runs the command.
17900 .conf use@_bsmtp boolean false
17901 .index envelope sender
17902 If this option is set true, the \%pipe%\ transport writes messages in `batch
17903 SMTP' format, with the envelope sender and recipient(s) included as SMTP
17904 commands. If you want to include a leading \\HELO\\ command with such messages,
17905 you can do so by setting the \message@_prefix\ option. See section
17906 ~~SECTbatchSMTP for details of batch SMTP.
17908 .conf use@_crlf boolean false
17909 .index carriage return
17911 This option causes lines to be terminated with the two-character CRLF sequence
17912 (carriage return, linefeed) instead of just a linefeed character. In the case
17913 of batched SMTP, the byte sequence written to the pipe is then an exact image
17914 of what would be sent down a real SMTP connection.
17916 The contents of the \message@_prefix\ and \message@_suffix\ options are written
17917 verbatim, so must contain their own carriage return characters if these are
17918 needed. Since the default values for both \message@_prefix\ and
17919 \message@_suffix\ end with a single linefeed, their values
17921 be changed to end with \"@\r@\n"\ if \use@_crlf\ is set.
17923 .conf use@_shell boolean false
17924 If this option is set, it causes the command to be passed to \(/bin/sh)\
17925 instead of being run directly from the transport, as described in section
17926 ~~SECThowcommandrun. This is less secure, but is needed in some situations
17927 where the command is expected to be run under a shell and cannot easily be
17928 modified. The \allow@_commands\ and \restrict@_to@_path\ options, and the
17929 `$tt{@$pipe@_addresses}' facility are incompatible with \use@_shell\. The
17930 command is expanded as a single string, and handed to \(/bin/sh)\ as data for
17935 .section Using an external local delivery agent
17936 .index local delivery||using an external agent
17937 .index \*procmail*\
17938 .index external local delivery
17939 .index delivery||\*procmail*\
17940 .index delivery||by external agent
17941 The \%pipe%\ transport can be used to pass all messages that require local
17942 delivery to a separate local delivery agent such as \procmail\. When doing
17943 this, care must be taken to ensure that the pipe is run under an appropriate
17944 uid and gid. In some configurations one wants this to be a uid that is trusted
17945 by the delivery agent to supply the correct sender of the message. It may be
17946 necessary to recompile or reconfigure the delivery agent so that it trusts an
17947 appropriate user. The following is an example transport and router
17948 configuration for \procmail\:
17953 command = /usr/local/bin/procmail -d $local_part
17957 check_string = "From "
17958 escape_string = ">From "
17967 transport = procmail_pipe
17970 In this example, the pipe is run as the local user, but with the group set to
17971 \*mail*\. An alternative is to run the pipe as a specific user such as \*mail*\
17972 or \*exim*\, but in this case you must arrange for \procmail\ to trust that
17973 user to supply a correct sender address. If you do not specify either a \group\
17974 or a \user\ option, the pipe command is run as the local user. The home
17975 directory is the user's home directory by default.
17977 Note that the command that the pipe transport runs does $it{not} begin with
17981 as shown in the \procmail\ documentation, because Exim does not by default use
17982 a shell to run pipe commands.
17985 The next example shows a transport and a router for a system where local
17986 deliveries are handled by the Cyrus IMAP server.
17989 local_delivery_cyrus:
17991 command = /usr/cyrus/bin/deliver \
17992 -m ${substr_1:$local_part_suffix} -- $local_part
18005 local_part_suffix = .*
18006 transport = local_delivery_cyrus
18008 Note the unsetting of \message@_prefix\ and \message@_suffix\, and the use of
18009 \return@_output\ to cause any text written by Cyrus to be returned to the
18017 . ============================================================================
18018 .chapter The smtp transport
18019 .rset CHAPsmtptrans "~~chapter"
18020 .set runningfoot "smtp transport"
18021 .index transports||\%smtp%\
18022 .index \%smtp%\ transport
18023 The \%smtp%\ transport delivers messages over TCP/IP connections using the SMTP
18024 or LMTP protocol. The list of hosts to try can either be taken from the address
18025 that is being processed (having been set up by the router), or specified
18026 explicitly for the transport. Timeout and retry processing (see chapter
18027 ~~CHAPretry) is applied to each IP address independently.
18029 .section Multiple messages on a single connection
18030 The sending of multiple messages over a single TCP/IP connection can arise in
18033 If a message contains more than \max@_rcpt\ (see below) addresses that are
18034 routed to the same host, more than one copy of the message has to be sent to
18035 that host. In this situation, multiple copies may be sent in a single run of
18036 the \%smtp%\ transport over a single TCP/IP connection. (What Exim actually does
18037 when it has too many addresses to send in one message also depends on the value
18038 of the global \remote@_max@_parallel\ option. Details are given in section
18041 .index hints database||remembering routing
18042 When a message has been successfully delivered over a TCP/IP connection, Exim
18043 looks in its hints database to see if there are any other messages awaiting a
18044 connection to the same host. If there are, a new delivery process is started
18045 for one of them, and the current TCP/IP connection is passed on to it. The new
18046 process may in turn send multiple copies and possibly create yet another
18050 For each copy sent over the same TCP/IP connection, a sequence counter is
18051 incremented, and if it ever gets to the value of \connection@_max@_messages\,
18052 no further messages are sent over that connection.
18055 .section Use of the @$host variable
18057 .index \$host@_address$\
18058 At the start of a run of the \%smtp%\ transport, the values of \$host$\ and
18059 \$host@_address$\ are the name and IP address of the first host on the host list
18060 passed by the router. However, when the transport is about to connect to a
18061 specific host, and while it is connected to that host, \$host$\ and
18062 \$host@_address$\ are set to the values for that host. These are the values
18063 that are in force when the \helo@_data\, \hosts@_try@_auth\, \interface\,
18064 \serialize@_hosts\, and the various TLS options are expanded.
18067 .section Private options for smtp
18068 The private options of the \%smtp%\ transport are as follows:
18070 .index options||\%smtp%\ transport
18072 .conf allow@_localhost boolean false
18073 .index local host||sending to
18074 .index fallback||hosts specified on transport
18075 When a host specified in \hosts\ or \fallback@_hosts\ (see below) turns out to
18076 be the local host, or is listed in \hosts@_treat@_as@_local\, delivery is
18077 deferred by default. However, if \allow@_localhost\ is set, Exim goes on to do
18078 the delivery anyway. This should be used only in special cases when the
18079 configuration ensures that no looping will result (for example, a differently
18080 configured Exim is listening on the port to which the message is sent).
18082 .conf authenticated@_sender string$**$ unset
18084 When Exim has authenticated as a client, this option sets a value for the
18085 \\AUTH=\\ item on outgoing \\MAIL\\ commands, overriding any existing
18086 authenticated sender value. If the string expansion is forced to fail, the
18087 option is ignored. Other expansion failures cause delivery to be deferred. If
18088 the result of expansion is an empty string, that is also ignored.
18090 If the SMTP session is not authenticated, the expansion of
18091 \authenticated@_sender\ still happens (and can cause the delivery to be
18092 deferred if it fails), but no \\AUTH=\\ item is added to \\MAIL\\ commands.
18094 This option allows you to use the \%smtp%\ transport in LMTP mode to
18095 deliver mail to Cyrus IMAP and provide the proper local part as the
18096 `authenticated sender', via a setting such as:
18098 authenticated_sender = $local_part
18100 This removes the need for IMAP subfolders to be assigned special ACLs to
18101 allow direct delivery to those subfolders.
18103 Because of expected uses such as that just described for Cyrus (when no
18104 domain is involved), there is no checking on the syntax of the provided
18107 .conf command@_timeout time 5m
18108 This sets a timeout for receiving a response to an SMTP command that has been
18109 sent out. It is also used when waiting for the initial banner line from the
18110 remote host. Its value must not be zero.
18112 .conf connect@_timeout time 5m
18113 This sets a timeout for the \*connect()*\ function, which sets up a TCP/IP call
18114 to a remote host. A setting of zero allows the system timeout (typically
18115 several minutes) to act. To have any effect, the value of this option must be
18116 less than the system timeout. However, it has been observed that on some
18117 systems there is no system timeout, which is why the default value for this
18118 option is 5 minutes, a value recommended by RFC 1123.
18120 .index SMTP||passed connection
18121 .index SMTP||multiple deliveries
18122 .index multiple SMTP deliveries
18123 .conf connection@_max@_messages integer 500
18124 This controls the maximum number of separate message deliveries that are sent
18125 over a single TCP/IP connection. If the value is zero, there is no limit.
18126 For testing purposes, this value can be overridden by the \-oB-\ command line
18129 .conf data@_timeout time 5m
18130 This sets a timeout for the transmission of each block in the data portion of
18131 the message. As a result, the overall timeout for a message depends on the size
18132 of the message. Its value must not be zero. See also \final@_timeout\.
18134 .conf delay@_after@_cutoff boolean true
18135 This option controls what happens when all remote IP addresses for a given
18136 domain have been inaccessible for so long that they have passed their retry
18139 In the default state, if the next retry time has not been reached for any of
18140 them, the address is bounced without trying any deliveries. In other words,
18141 Exim delays retrying an IP address after the final cutoff time until a new
18142 retry time is reached, and can therefore bounce an address without ever trying
18143 a delivery, when machines have been down for a long time. Some people are
18144 unhappy at this prospect, so...
18146 If \delay@_after@_cutoff\ is set false, Exim behaves differently. If all IP
18147 addresses are past their final cutoff time, Exim tries to deliver to those
18148 IP addresses that have not been tried since the message arrived. If there are
18149 none, of if they all fail, the address is bounced. In other words, it does not
18150 delay when a new message arrives, but immediately tries those expired IP
18151 addresses that haven't been tried since the message arrived. If there is a
18152 continuous stream of messages for the dead hosts, unsetting
18153 \delay@_after@_cutoff\ means that there will be many more attempts to deliver
18156 .conf dns@_qualify@_single boolean true
18157 If the \hosts\ or \fallback@_hosts\ option is being used,
18158 and the \gethostbyname\ option is false,
18159 the \\RES@_DEFNAMES\\ resolver option is set. See the \qualify@_single\ option
18160 in chapter ~~CHAPdnslookup for more details.
18162 .conf dns@_search@_parents boolean false
18163 .index \search@_parents\
18164 If the \hosts\ or \fallback@_hosts\ option is being used, and the
18165 \gethostbyname\ option is false, the \\RES@_DNSRCH\\ resolver option is set.
18166 See the \search@_parents\ option in chapter ~~CHAPdnslookup for more details.
18169 .conf fallback@_hosts "string list" unset
18170 .index fallback||hosts specified on transport
18171 String expansion is not applied to this option. The argument must be a
18172 colon-separated list of host names or IP addresses. Fallback hosts can also be
18173 specified on routers, which associate them with the addresses they process. As
18174 for the \hosts\ option without \hosts@_override\, \fallback@_hosts\ specified
18175 on the transport is used only if the address does not have its own associated
18176 fallback host list. Unlike \hosts\, a setting of \fallback@_hosts\ on an
18177 address is not overridden by \hosts@_override\. However, \hosts@_randomize\
18178 does apply to fallback host lists.
18180 If Exim is unable to deliver to any of the hosts for a particular address, and
18181 the errors are not permanent rejections, the address is put on a separate
18182 transport queue with its host list replaced by the fallback hosts, unless the
18183 address was routed via MX records and the current host was in the original MX
18184 list. In that situation, the fallback host list is not used.
18186 Once normal deliveries are complete, the fallback queue is delivered by
18187 re-running the same transports with the new host lists. If several failing
18188 addresses have the same fallback hosts (and \max@_rcpt\ permits it), a single
18189 copy of the message is sent.
18191 The resolution of the host names on the fallback list is controlled by the
18192 \gethostbyname\ option, as for the \hosts\ option. Fallback hosts apply
18193 both to cases when the host list comes with the address and when it is taken
18194 from \hosts\. This option provides a `use a smart host only if delivery fails'
18197 .conf final@_timeout time 10m
18198 This is the timeout that applies while waiting for the response to the final
18199 line containing just `.' that terminates a message. Its value must not be zero.
18201 .conf gethostbyname boolean false
18202 If this option is true when the \hosts\ and/or \fallback@_hosts\ options are
18203 being used, names are looked up using \*gethostbyname()*\
18204 (or \*getipnodebyname()*\ when available)
18205 instead of using the DNS. Of course, that function may in fact use the DNS, but
18206 it may also consult other sources of information such as \(/etc/hosts)\.
18208 .index \\HELO\\||argument, setting
18209 .index \\EHLO\\||argument, setting
18210 .conf helo@_data string$**$ $tt{@$primary@_hostname}
18211 The value of this option is expanded, and used as the argument for the \\EHLO\\
18212 or \\HELO\\ command that starts the outgoing SMTP session.
18214 .conf hosts "string list$**$" unset
18215 Hosts are associated with an address by a router such as \%dnslookup%\, which
18216 finds the hosts by looking up the address domain in the DNS. However, addresses
18217 can be passed to the \%smtp%\ transport by any router, and not all of them can
18218 provide an associated host list. The \hosts\ option specifies a list of hosts
18219 which are used if the address being processed does not have any hosts
18220 associated with it. The hosts specified by \hosts\ are also used, whether or
18221 not the address has its own hosts, if \hosts@_override\ is set.
18223 The string is first expanded, before being interpreted as a colon-separated
18224 list of host names or IP addresses. If the expansion fails, delivery is
18225 deferred. Unless the failure was caused by the inability to complete a lookup,
18226 the error is logged to the panic log as well as the main log. Host names are
18227 looked up either by searching directly for address records in the DNS or by
18228 calling \*gethostbyname()*\
18229 (or \*getipnodebyname()*\ when available),
18230 depending on the setting of the \gethostbyname\ option. When Exim is compiled
18231 with IPv6 support, if a host that is looked up in the DNS has both IPv4 and
18232 IPv6 addresses, both types of address are used.
18234 During delivery, the hosts are tried in order, subject to their retry status,
18235 unless \hosts@_randomize\ is set.
18237 .conf hosts@_avoid@_esmtp "host list$**$" unset
18238 .index ESMTP, avoiding use of
18239 .index \\HELO\\||forcing use of
18240 .index \\EHLO\\||avoiding use of
18241 .index \\PIPELINING\\||avoiding the use of
18242 This option is for use with broken hosts that announce ESMTP facilities (for
18243 example, \\PIPELINING\\) and then fail to implement them properly. When a host
18244 matches \hosts@_avoid@_esmtp\, Exim sends \\HELO\\ rather than \\EHLO\\ at the
18245 start of the SMTP session. This means that it cannot use any of the ESMTP
18246 facilities such as \\AUTH\\, \\PIPELINING\\, \\SIZE\\, and \\STARTTLS\\.
18248 .conf hosts@_avoid@_tls "host list$**$" unset
18249 .index TLS||avoiding for certain hosts
18250 Exim will not try to start a TLS session when delivering to any host that
18251 matches this list. See chapter ~~CHAPTLS for details of TLS.
18253 .conf hosts@_max@_try integer 5
18254 .index host||maximum number to try
18255 .index limit||number of hosts tried
18256 .index limit||number of MX tried
18257 .index MX record||maximum tried
18258 This option limits the number of IP addresses that are tried for any one
18260 in cases where there are temporary delivery errors.
18261 Section ~~SECTvalhosmax describes in detail how the value of this option is
18264 .conf hosts@_nopass@_tls "host list$**$" unset
18265 .index TLS||passing connection
18266 .index multiple SMTP deliveries
18267 .index TLS||multiple message deliveries
18268 For any host that matches this list, a connection on which a TLS session has
18269 been started will not be passed to a new delivery process for sending another
18270 message on the same connection. See section ~~SECTmulmessam for an explanation
18271 of when this might be needed.
18273 .conf hosts@_override boolean false
18274 If this option is set and the \hosts\ option is also set, any hosts that are
18275 attached to the address are ignored, and instead the hosts specified by the
18276 \hosts\ option are always used. This option does not apply to
18279 .conf hosts@_randomize boolean false
18280 .index randomized host list
18281 .index host||list of, randomized
18282 .index fallback||randomized hosts
18283 If this option is set, and either the list of hosts is taken from the
18284 \hosts\ or the \fallback@_hosts\ option, or the hosts supplied by the router
18285 were not obtained from MX records (this includes fallback hosts from the
18286 router), and were not randomizied by the router, the order of trying the hosts
18287 is randomized each time the transport runs. Randomizing the order of a host
18288 list can be used to do crude load sharing.
18290 When \hosts@_randomize\ is true, a host list may be split into groups whose
18291 order is separately randomized. This makes it possible to set up MX-like
18292 behaviour. The boundaries between groups are indicated by an item that is just
18293 \"+"\ in the host list. For example:
18295 hosts = host1:host2:host3:+:host4:host5
18297 The order of the first three hosts and the order of the last two hosts is
18298 randomized for each use, but the first three always end up before the last two.
18299 If \hosts@_randomize\ is not set, a \"+"\ item in the list is ignored.
18301 .index authentication||required by client
18302 .conf hosts@_require@_auth "host list$**$" unset
18303 This option provides a list of servers for which authentication must succeed
18304 before Exim will try to transfer a message. If authentication fails for
18305 servers which are not in this list, Exim tries to send unauthenticated. If
18306 authentication fails for one of these servers, delivery is deferred. This
18307 temporary error is detectable in the retry rules, so it can be turned into a
18308 hard failure if required. See also \hosts@_try@_auth\, and chapter
18309 ~~CHAPSMTPAUTH for details of authentication.
18311 .conf hosts@_require@_tls "host list$**$" unset
18312 .index TLS||requiring for certain servers
18313 Exim will insist on using a TLS session when delivering to any host that
18314 matches this list. See chapter ~~CHAPTLS for details of TLS.
18315 \**Note**\: This option affects outgoing mail only. To insist on TLS for
18316 incoming messages, use an appropriate ACL.
18318 .index authentication||optional in client
18319 .conf hosts@_try@_auth "host list$**$" unset
18320 This option provides a list of servers to which, provided they announce
18321 authentication support, Exim will attempt to authenticate as a client when it
18322 connects. If authentication fails, Exim will try to transfer the message
18323 unauthenticated. See also \hosts@_require@_auth\, and chapter ~~CHAPSMTPAUTH
18324 for details of authentication.
18326 .index bind IP address
18327 .index IP address||binding
18328 .conf interface "string list$**$" unset
18329 This option specifies which interface to bind to when making an outgoing SMTP
18330 call. The variables \$host$\ and \$host@_address$\ refer to the host to which a
18331 connection is about to be made during the expansion of the string. Forced
18332 expansion failure, or an empty string result causes the option to be ignored.
18333 Otherwise, after expansion,
18334 the string must be a list of IP addresses, colon-separated by default, but the
18335 separator can be changed in the usual way.
18338 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
18340 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
18341 connection. If none of them are the correct type, the option is ignored. If
18342 \interface\ is not set, or is ignored, the system's IP functions choose which
18343 interface to use if the host has more than one.
18345 .conf keepalive boolean true
18346 .index keepalive||on outgoing connection
18347 This option controls the setting of \\SO@_KEEPALIVE\\ on outgoing TCP/IP socket
18348 connections. When set, it causes the kernel to probe idle connections
18349 periodically, by sending packets with `old' sequence numbers. The other end of
18350 the connection should send a acknowledgement if the connection is still okay or
18351 a reset if the connection has been aborted. The reason for doing this is that
18352 it has the beneficial effect of freeing up certain types of connection that can
18353 get stuck when the remote host is disconnected without tidying up the TCP/IP
18354 call properly. The keepalive mechanism takes several hours to detect
18357 .conf max@_rcpt integer 100
18358 .index \\RCPT\\||maximum number of outgoing
18359 This option limits the number of \\RCPT\\ commands that are sent in a single
18360 SMTP message transaction. Each set of addresses is treated independently, and
18361 so can cause parallel connections to the same host if \remote@_max@_parallel\
18364 .conf multi@_domain boolean true
18365 When this option is set, the \%smtp%\ transport can handle a number of addresses
18366 containing a mixture of different domains provided they all resolve to the same
18367 list of hosts. Turning the option off restricts the transport to handling only
18368 one domain at a time. This is useful if you want to use \$domain$\ in an
18369 expansion for the transport, because it is set only when there is a single
18370 domain involved in a remote delivery.
18372 .conf port string$**$ "see below"
18373 .index port||sending TCP/IP
18374 .index TCP/IP||setting outgoing port
18375 This option specifies the TCP/IP port on the server to which Exim connects. If
18376 it begins with a digit it is taken as a port number; otherwise it is looked up
18377 using \*getservbyname()*\. The default value is normally `smtp', but if
18378 \protocol\ is set to `lmtp', the default is `lmtp'.
18379 If the expansion fails, or if a port number cannot be found, delivery is
18383 .conf protocol string "smtp"
18384 .index LMTP||over TCP/IP
18385 If this option is set to `lmtp' instead of `smtp', the default value for the
18386 \port\ option changes to `lmtp', and the transport operates the LMTP protocol
18387 (RFC 2033) instead of SMTP. This protocol is sometimes used for local
18388 deliveries into closed message stores. Exim also has support for running LMTP
18389 over a pipe to a local process -- see chapter ~~CHAPLMTP.
18391 .conf retry@_include@_ip@_address boolean true
18392 Exim normally includes both the host name and the IP address in the key it
18393 constructs for indexing retry data after a temporary delivery failure. This
18394 means that when one of several IP addresses for a host is failing, it gets
18395 tried periodically (controlled by the retry rules), but use of the other IP
18396 addresses is not affected.
18398 However, in some dialup environments hosts are assigned a different IP address
18399 each time they connect. In this situation the use of the IP address as part of
18400 the retry key leads to undesirable behaviour. Setting this option false causes
18401 Exim to use only the host name. This should normally be done on a separate
18402 instance of the \%smtp%\ transport, set up specially to handle the dialup hosts.
18404 .conf serialize@_hosts "host list$**$" unset
18405 .index serializing connections
18406 .index host||serializing connections
18407 Because Exim operates in a distributed manner, if several messages for the same
18408 host arrive at around the same time, more than one simultaneous connection to
18409 the remote host can occur. This is not usually a problem except when there is a
18410 slow link between the hosts. In that situation it may be helpful to restrict
18411 Exim to one connection at a time. This can be done by setting
18412 \serialize@_hosts\ to match the relevant hosts.
18414 .index hints database||serializing deliveries to a host
18415 Exim implements serialization by means of a hints database in which a record is
18416 written whenever a process connects to one of the restricted hosts. The record
18417 is deleted when the connection is completed. Obviously there is scope for
18418 records to get left lying around if there is a system or program crash. To
18419 guard against this, Exim ignores any records that are more than six hours old.
18421 If you set up this kind of serialization, you should also arrange to delete the
18422 relevant hints database whenever your system reboots. The names of the files
18423 start with \(misc)\ and they are kept in the \(spool/db)\ directory. There
18424 may be one or two files, depending on the type of DBM in use. The same files
18425 are used for ETRN serialization.
18427 .conf size@_addition integer 1024
18428 .index SMTP||\\SIZE\\
18429 .index message||size issue for transport filter
18430 .index size||of message
18431 .index transport||filter
18432 .index filter||transport filter
18433 If a remote SMTP server indicates that it supports the \\SIZE\\ option of the
18434 \\MAIL\\ command, Exim uses this to pass over the message size at the start of
18435 an SMTP transaction. It adds the value of \size@_addition\ to the value it
18436 sends, to allow for headers and other text that may be added during delivery by
18437 configuration options or in a transport filter. It may be necessary to increase
18438 this if a lot of text is added to messages.
18440 Alternatively, if the value of \size@_addition\ is set negative, it disables
18441 the use of the \\SIZE\\ option altogether.
18443 .conf tls@_certificate string$**$ unset
18444 .index TLS||client certificate, location of
18445 .index certificate||for client, location of
18446 The value of this option must be the absolute path to a file which contains the
18447 client's certificate, for use when sending a message over an encrypted
18448 connection. The values of \$host$\ and \$host@_address$\ are set to the name
18449 and address of the server during the expansion. See chapter ~~CHAPTLS for
18452 \**Note**\: This option must be set if you want Exim to use TLS when sending
18453 messages as a client. The global option of the same name specifies the
18454 certificate for Exim as a server; it is not automatically assumed that the same
18455 certificate should be used when Exim is operating as a client.
18457 .conf tls@_crl string$**$ unset
18458 .index TLS||client certificate revocation list
18459 .index certificate||revocation list for client
18460 This option specifies a certificate revocation list. The expanded value must
18461 be the name of a file that contains a CRL in PEM format.
18463 .conf tls@_privatekey string$**$ unset
18464 .index TLS||client private key, location of
18465 The value of this option must be the absolute path to a file which contains the
18466 client's private key, for use when sending a message over an encrypted
18467 connection. The values of \$host$\ and \$host@_address$\ are set to the name
18468 and address of the server during the expansion.
18469 If this option is unset, the private key is assumed to be in the same file as
18471 See chapter ~~CHAPTLS for details of TLS.
18473 .conf tls@_require@_ciphers string$**$ unset
18474 .index TLS||requiring specific ciphers
18475 .index cipher||requiring specific
18476 The value of this option must be a list of permitted cipher suites, for use
18478 outgoing encrypted connection. (There is a global option of the same name for
18479 controlling incoming connections.)
18480 The values of \$host$\ and \$host@_address$\ are set to the name and address of
18481 the server during the expansion. See chapter ~~CHAPTLS for details of TLS; note
18482 that this option is used in different ways by OpenSSL and GnuTLS (see section
18483 ~~SECTreqciphsslgnu).
18485 .conf tls@_tempfail@_tryclear boolean true
18486 When the server host is not in \hosts@_require@_tls\, and there is a problem in
18487 setting up a TLS session, this option determines whether or not Exim should try
18488 to deliver the message unencrypted. If it is set false, delivery to the
18489 current host is deferred; if there are other hosts, they are tried. If this
18490 option is set true, Exim attempts to deliver unencrypted after a 4\*xx*\
18491 response to \\STARTTLS\\. Also, if \\STARTTLS\\ is accepted, but the subsequent
18492 TLS negotiation fails, Exim closes the current connection (because it is in an
18493 unknown state), opens a new one to the same host, and then tries the delivery
18496 .conf tls@_verify@_certificates string$**$ unset
18497 .index TLS||server certificate verification
18498 .index certificate||verification of server
18499 The value of this option must be the absolute path to a file containing
18500 permitted server certificates, for use when setting up an encrypted connection.
18501 Alternatively, if you are using OpenSSL, you can set
18502 \tls@_verify@_certificates\ to the name of a directory containing certificate
18503 files. This does not work with GnuTLS; the option must be set to the name of a
18504 single file if you are using GnuTLS. The values of \$host$\ and
18505 \$host@_address$\ are set to the name and address of the server during the
18506 expansion of this option. See chapter ~~CHAPTLS for details of TLS.
18511 .section How the value of hosts@_max@_try is used
18512 .rset SECTvalhosmax "~~chapter.~~section"
18513 .index host||maximum number to try
18514 .index limit||hosts, maximum number tried
18515 The \hosts@_max@_try\ option limits the number of hosts that are tried
18516 for a single delivery. However, despite the term `host' in its name, the option
18517 actually applies to each IP address independently. In other words, a multihomed
18518 host is treated as several independent hosts, just as it is for retrying.
18520 Many of the larger ISPs have multiple MX records which often point to
18521 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
18522 created as a result of routing one of these domains.
18524 Trying every single IP address on such a long list does not seem sensible; if
18525 several at the top of the list fail, it is reasonable to assume there is some
18526 problem that is likely to affect all of them. Roughly speaking, the value of
18527 \hosts@_max@_try\ is the maximum number that are tried before deferring the
18528 delivery. However, the logic cannot be quite that simple.
18530 Firstly, IP addresses that are skipped because their retry times have not
18531 arrived do not count, and in addition, addresses that are past their retry
18532 limits are also not counted, even when they are tried. This means that when
18533 some IP addresses are past their retry limits, more than the value of
18534 \hosts@_max@_retry\ may be tried. The reason for this behaviour is to ensure
18535 that all IP addresses are considered before timing out an email address.
18537 Secondly, when the \hosts@_max@_try\ limit is reached, Exim looks down the host
18538 list to see if there is a subsequent host with a different (higher valued) MX.
18539 If there is, that host is used next, and the current IP address is used but not
18540 counted. This behaviour helps in the case of a domain with a retry rule that
18541 hardly ever delays any hosts, as is now explained:
18543 Consider the case of a long list of hosts with one MX value, and a few with a
18544 higher MX value. If \hosts@_max@_try\ is small (the default is 5) only a few
18545 hosts at the top of the list are tried at first. With the default retry rule,
18546 which specifies increasing retry times, the higher MX hosts are eventually
18547 tried when those at the top of the list are skipped because they have not
18548 reached their retry times.
18550 However, it is common practice to put a fixed short retry time on domains for
18551 large ISPs, on the grounds that their servers are rarely down for very long.
18552 Unfortunately, these are exactly the domains that tend to resolve to long lists
18553 of hosts. The short retry time means that the lowest MX hosts are tried every
18554 time. The attempts may be in a different order because of random sorting, but
18555 without the special MX check mentioned about, the higher MX hosts would never
18556 be tried at all because the lower MX hosts are never all past their retry
18559 With the special check, Exim tries least one address from each MX value, even
18560 if the \hosts@_max@_try\ limit has already been reached.
18571 . ============================================================================
18572 .chapter Address rewriting
18573 .set runningfoot "address rewriting"
18574 .rset CHAPrewrite ~~chapter
18575 .index rewriting||addresses
18576 There are some circumstances in which Exim automatically rewrites domains in
18577 addresses. The two most common are when an address is given without a domain
18578 (referred to as an `unqualified address') or when an address contains an
18579 abbreviated domain that is expanded by DNS lookup.
18581 Unqualified envelope addresses are accepted only for locally submitted
18582 messages, or messages from hosts that match \sender@_unqualified@_hosts\ or
18583 \recipient@_unqualified@_hosts\, respectively. Unqualified addresses in header
18584 lines are qualified if they are in locally submitted messages, or messages from
18585 hosts that are permitted to send unqualified envelope addresses. Otherwise,
18586 unqualified addresses in header lines are neither qualified nor rewritten.
18588 One situation in which Exim does $it{not} automatically rewrite a domain is
18589 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
18590 such a domain should be rewritten using the `canonical' name, and some MTAs do
18591 this. The new RFCs do not contain this suggestion.
18593 .section Explicitly configured address rewriting
18594 This chapter describes the rewriting rules that can be used in the
18595 main rewrite section of the configuration file, and also in the generic
18596 \headers@_rewrite\ option that can be set on any transport.
18598 Some people believe that configured address rewriting is a Mortal Sin.
18599 Others believe that life is not possible without it. Exim provides the
18600 facility; you do not have to use it.
18602 The main rewriting rules that appear in the `rewrite' section of the
18603 configuration file are applied to addresses in incoming messages, both envelope
18604 addresses and addresses in header lines. Each rule specifies the types of
18605 address to which it applies.
18607 Rewriting of addresses in header lines applies only to those headers that
18608 were received with the message, and, in the case of transport rewriting, those
18609 that were added by a system filter. That is, it applies only to those headers
18610 that are common to all copies of the message. Header lines that are added by
18611 individual routers or transports (and which are therefore specific to
18612 individual recipient addresses) are not rewritten.
18614 In general, rewriting addresses from your own system or domain has some
18615 legitimacy. Rewriting other addresses should be done only with great care and
18616 in special circumstances. The author of Exim believes that rewriting should be
18617 used sparingly, and mainly for `regularizing' addresses in your own domains.
18618 Although it can sometimes be used as a routing tool, this is very strongly
18621 There are two commonly encountered circumstances where rewriting is used, as
18622 illustrated by these examples:
18624 The company whose domain is \*hitch.fict.example*\ has a number of hosts that
18625 exchange mail with each other behind a firewall, but there is only a single
18626 gateway to the outer world. The gateway rewrites \*@*.hitch.fict.example*\ as
18627 \*hitch.fict.example*\ when sending mail off-site.
18629 A host rewrites the local parts of its own users so that, for example,
18630 \*fp42@@hitch.fict.example*\ becomes \*Ford.Prefect@@hitch.fict.example*\.
18633 .section When does rewriting happen?
18634 .index rewriting||timing of
18635 .index ~~ACL||rewriting addresses in
18636 Configured address rewriting can take place at several different stages of a
18637 message's processing.
18639 At the start of an ACL for \\MAIL\\, the sender address may have been rewritten
18640 by a special SMTP-time rewrite rule (see section ~~SECTrewriteS), but no
18641 ordinary rewrite rules have yet been applied. If, however, the sender address
18642 is verified in the ACL, it is rewritten before verification, and remains
18643 rewritten thereafter. The subsequent value of \$sender@_address$\ is the
18644 rewritten address. This also applies if sender verification happens in a
18645 \\RCPT\\ ACL. Otherwise, when the sender address is not verified, it is
18646 rewritten as soon as a message's header lines have been received.
18648 Similarly, at the start of an ACL for \\RCPT\\, the current recipient's address
18649 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
18650 rewrite rules have yet been applied to it. However, the behaviour is different
18651 from the sender address when a recipient is verified. The address is rewritten
18652 for the verification, but the rewriting is not remembered at this stage. The
18653 value of \$local@_part$\ and \$domain$\ after verification are always the same
18654 as they were before (that is, they contain the unrewritten -- except for
18655 SMTP-time rewriting -- address).
18657 Once a message's header lines have been received, all the envelope recipient
18658 addresses are permanently rewritten, and rewriting is also applied to the
18659 addresses in the header lines (if configured).
18660 .index \*local@_scan()*\ function||address rewriting, timing of
18661 Thus, all the rewriting is completed before the \\DATA\\ ACL and
18662 \*local@_scan()*\ functions are run.
18664 When an address is being routed, either for delivery or for verification,
18665 rewriting is applied immediately to child addresses that are generated by
18666 redirection, unless \no@_rewrite\ is set on the router.
18668 .index envelope sender, rewriting
18669 .index rewriting||at transport time
18670 At transport time, additional rewriting of addresses in header lines can be
18671 specified by setting the generic \headers@_rewrite\ option on a transport. This
18672 option contains rules that are identical in form to those in the rewrite
18673 section of the configuration file. In addition, the outgoing envelope sender
18674 can be rewritten by means of the \return@_path\ transport option. However, it
18675 is not possible to rewrite envelope recipients at transport time.
18679 .section Testing the rewriting rules that apply on input
18680 .index rewriting||testing
18681 .index testing||rewriting
18682 Exim's input rewriting configuration appears in a part of the run time
18683 configuration file headed by `begin rewrite'. It can be tested by the \-brw-\
18684 command line option. This takes an address (which can be a full RFC 2822
18685 address) as its argument. The output is a list of how the address would be
18686 transformed by the rewriting rules for each of the different places it might
18687 appear in an incoming message, that is, for each different header and for the
18688 envelope sender and recipient fields. For example,
18690 exim -brw ph10@exim.workshop.example
18692 might produce the output
18694 sender: Philip.Hazel@exim.workshop.example
18695 from: Philip.Hazel@exim.workshop.example
18696 to: ph10@exim.workshop.example
18697 cc: ph10@exim.workshop.example
18698 bcc: ph10@exim.workshop.example
18699 reply-to: Philip.Hazel@exim.workshop.example
18700 env-from: Philip.Hazel@exim.workshop.example
18701 env-to: ph10@exim.workshop.example
18703 which shows that rewriting has been set up for that address when used in any of
18704 the source fields, but not when it appears as a recipient address. At the
18705 present time, there is no equivalent way of testing rewriting rules that are
18706 set for a particular transport.
18708 .section Rewriting rules
18709 .index rewriting||rules
18710 The rewrite section of the configuration file consists of lines of rewriting
18713 <<source pattern>> <<replacement>> <<flags>>
18715 Rewriting rules that are specified for the \headers@_rewrite\ generic transport
18716 option are given as a colon-separated list. Each item in the list takes the
18717 same form as a line in the main rewriting configuration
18718 (except that any colons must be doubled, of course).
18720 The formats of source patterns and replacement strings are described below.
18721 Each is terminated by white space, unless enclosed in double quotes, in which
18722 case normal quoting conventions apply inside the quotes. The flags are single
18723 characters which may appear in any order. Spaces and tabs between them are
18726 For each address that could potentially be rewritten, the rules are scanned in
18727 order, and replacements for the address from earlier rules can themselves be
18728 replaced by later rules (but see the `q' and `R' flags).
18730 The order in which addresses are rewritten is undefined, may change between
18731 releases, and must not be relied on, with one exception: when a message is
18732 received, the envelope sender is always rewritten first, before any header
18733 lines are rewritten. For example, the replacement string for a rewrite of an
18734 address in ::To:: must not assume that the message's address in ::From:: has (or
18735 has not) already been rewritten. However, a rewrite of ::From:: may assume that
18736 the envelope sender has already been rewritten.
18738 The variables \$local@_part$\ and \$domain$\ can be used in the replacement
18739 string to refer to the address that is being rewritten. Note that lookup-driven
18740 rewriting can be done by a rule of the form
18744 where the lookup key uses \$1$\ and \$2$\ or \$local@_part$\ and \$domain$\ to
18745 refer to the address that is being rewritten.
18747 .section Rewriting patterns
18748 .index rewriting||patterns
18749 .index address list||in a rewriting pattern
18750 The source pattern in a rewriting rule is any item which may appear in an
18751 address list (see section ~~SECTaddresslist). It is in fact processed as a
18752 single-item address list, which means that it is expanded before being tested
18753 against the address.
18755 Domains in patterns should be given in lower case. Local parts in patterns are
18756 case-sensitive. If you want to do case-insensitive matching of local parts, you
18757 can use a regular expression that starts with \"^(?i)"\.
18759 .index numerical variables (\$1$\, \$2$\, etc)||in rewriting rules
18760 After matching, the numerical variables \$1$\, \$2$\, etc. may be set,
18761 depending on the type of match which occurred. These can be used in the
18762 replacement string to insert portions of the incoming address. \$0$\ always
18763 refers to the complete incoming address. When a regular expression is used, the
18764 numerical variables are set from its capturing subexpressions. For other types
18765 of pattern they are set as follows:
18768 If a local part or domain starts with an asterisk, the numerical variables
18769 refer to the character strings matched by asterisks, with \$1$\ associated with
18770 the first asterisk, and \$2$\ with the second, if present. For example, if the
18773 *queen@@*.fict.example
18775 is matched against the address \*hearts-queen@@wonderland.fict.example*\ then
18777 $0 = hearts-queen@wonderland.fict.example
18781 Note that if the local part does not start with an asterisk, but the domain
18782 does, it is \$1$\ that contains the wild part of the domain.
18784 If the domain part of the pattern is a partial lookup, the wild and fixed parts
18785 of the domain are placed in the next available numerical variables. Suppose,
18786 for example, that the address \*foo@@bar.baz.example*\ is processed by a
18787 rewriting rule of the form
18789 *@@partial-dbm;/some/dbm/file <<replacement string>>
18791 and the key in the file that matches the domain is \"*.baz.example"\. Then
18797 If the address \*foo@@baz.example*\ is looked up, this matches the same
18798 wildcard file entry, and in this case \$2$\ is set to the empty string, but
18799 \$3$\ is still set to \*baz.example*\. If a non-wild key is matched in a
18800 partial lookup, \$2$\ is again set to the empty string and \$3$\ is set to the
18801 whole domain. For non-partial domain lookups, no numerical variables are set.
18804 .section Rewriting replacements
18805 .index rewriting||replacements
18806 If the replacement string for a rule is a single asterisk, addresses that
18807 match the pattern and the flags are $it{not} rewritten, and no subsequent
18808 rewriting rules are scanned. For example,
18810 hatta@lookingglass.fict.example * f
18812 specifies that \*hatta@@lookingglass.fict.example*\ is never to be rewritten in
18815 If the replacement string is not a single asterisk, it is expanded, and must
18816 yield a fully qualified address. Within the expansion, the variables
18817 \$local@_part$\ and \$domain$\ refer to the address that is being rewritten.
18818 Any letters they contain retain their original case -- they are not lower
18819 cased. The numerical variables are set up according to the type of pattern that
18820 matched the address, as described above. If the expansion is forced to fail by
18821 the presence of `fail' in a conditional or lookup item, rewriting by the
18822 current rule is abandoned, but subsequent rules may take effect. Any other
18823 expansion failure causes the entire rewriting operation to be abandoned, and an
18824 entry written to the panic log.
18827 .section Rewriting flags
18828 There are three different kinds of flag that may appear on rewriting rules:
18830 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
18833 A flag that specifies rewriting at SMTP time: S.
18835 Flags that control the rewriting process: Q, q, R, w.
18837 For rules that are part of the \headers@_rewrite\ generic transport option,
18838 E, F, T, and S are not permitted.
18841 .section Flags specifying which headers and envelope addresses to rewrite
18842 .index rewriting||flags
18843 If none of the following flag letters, nor the `S' flag (see section
18844 ~~SECTrewriteS) are present, a main rewriting rule applies to all headers and
18845 to both the sender and recipient fields of the envelope, whereas a
18846 transport-time rewriting rule just applies to all headers. Otherwise, the
18847 rewriting rule is skipped unless the relevant addresses are being processed.
18849 E $rm{rewrite all envelope fields}
18850 F $rm{rewrite the envelope From field}
18851 T $rm{rewrite the envelope To field}
18852 b $rm{rewrite the ::Bcc:: header}
18853 c $rm{rewrite the ::Cc:: header}
18854 f $rm{rewrite the ::From:: header}
18855 h $rm{rewrite all headers}
18856 r $rm{rewrite the ::Reply-To:: header}
18857 s $rm{rewrite the ::Sender:: header}
18858 t $rm{rewrite the ::To:: header}
18860 You should be particularly careful about rewriting ::Sender:: headers, and
18861 restrict this to special known cases in your own domains.
18863 .section The SMTP-time rewriting flag
18864 .rset SECTrewriteS "~~chapter.~~section"
18865 .index SMTP||rewriting malformed addresses
18866 .index \\RCPT\\||rewriting argument of
18867 .index \\MAIL\\||rewriting argument of
18868 The rewrite flag `S' specifies a rewrite of incoming envelope addresses at SMTP
18869 time, as soon as an address is received in a \\MAIL\\ or \\RCPT\\ command, and
18870 before any other processing; even before syntax checking. The pattern is
18871 required to be a regular expression, and it is matched against the whole of the
18872 data for the command, including any surrounding angle brackets.
18874 This form of rewrite rule allows for the handling of addresses that are not
18875 compliant with RFCs 2821 and 2822 (for example, `bang paths' in batched SMTP
18876 input). Because the input is not required to be a syntactically valid address,
18877 the variables \$local@_part$\ and \$domain$\ are not available during the
18878 expansion of the replacement string. The result of rewriting replaces the
18879 original address in the \\MAIL\\ or \\RCPT\\ command.
18881 .section Flags controlling the rewriting process
18882 There are four flags which control the way the rewriting process works. These
18883 take effect only when a rule is invoked, that is, when the address is of the
18884 correct type (matches the flags) and matches the pattern:
18886 If the `Q' flag is set on a rule, the rewritten address is permitted to be an
18887 unqualified local part. It is qualified with \qualify@_recipient\. In the
18888 absence of `Q' the rewritten address must always include a domain.
18890 If the `q' flag is set on a rule, no further rewriting rules are considered,
18891 even if no rewriting actually takes place because of a `fail' in the expansion.
18892 The `q' flag is not effective if the address is of the wrong type (does not
18893 match the flags) or does not match the pattern.
18895 The `R' flag causes a successful rewriting rule to be re-applied to the new
18896 address, up to ten times. It can be combined with the `q' flag, to stop
18897 rewriting once it fails to match (after at least one successful rewrite).
18899 .index rewriting||whole addresses
18900 When an address in a header is rewritten, the rewriting normally applies only
18901 to the working part of the address, with any comments and RFC 2822 `phrase'
18902 left unchanged. For example, rewriting might change
18904 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
18908 From: Ford Prefect <prefectf@hitch.fict.example>
18910 Sometimes there is a need to replace the whole address item, and this can be
18911 done by adding the flag letter `w' to a rule. If this is set on a rule that
18912 causes an address in a header line to be rewritten, the entire address is
18913 replaced, not just the working part. The replacement must be a complete RFC
18914 2822 address, including the angle brackets if necessary. If text outside angle
18915 brackets contains a character whose value is greater than 126 or less than 32
18916 (except for tab), the text is encoded according to RFC 2047.
18917 The character set is taken from \headers@_charset\, which defaults to
18920 When the `w' flag is set on a rule that causes an envelope address to be
18921 rewritten, all but the working part of the replacement address is discarded.
18924 .section Rewriting examples
18925 Here is an example of the two common rewriting paradigms:
18927 *@*.hitch.fict.example $1@hitch.fict.example
18928 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
18929 {$value}fail}@hitch.fict.example bctfrF
18931 Note the use of `fail' in the lookup expansion in the second rule, forcing
18932 the string expansion to fail if the lookup does not succeed. In this context it
18933 has the effect of leaving the original address unchanged, but Exim goes on to
18934 consider subsequent rewriting rules, if any, because the `q' flag is not
18935 present in that rule. An alternative to `fail' would be to supply \$1$\
18936 explicitly, which would cause the rewritten address to be the same as before,
18937 at the cost of a small bit of processing. Not supplying either of these is an
18938 error, since the rewritten address would then contain no local part.
18940 The first example above replaces the domain with a superior, more general
18941 domain. This may not be desirable for certain local parts. If the rule
18943 root@*.hitch.fict.example *
18945 were inserted before the first rule, rewriting would be suppressed for the
18946 local part \*root*\ at any domain ending in \*hitch.fict.example*\.
18948 Rewriting can be made conditional on a number of tests, by making use of
18949 \${if$\ in the expansion item. For example, to apply a rewriting rule only to
18950 messages that originate outside the local host:
18952 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
18953 {$1@hitch.fict.example}fail}"
18955 The replacement string is quoted in this example because it contains white
18958 .index rewriting||bang paths
18959 .index bang paths||rewriting
18960 Exim does not handle addresses in the form of `bang paths'. If it sees such an
18961 address it treats it as an unqualified local part which it qualifies with the
18962 local qualification domain (if the source of the message is local or if the
18963 remote host is permitted to send unqualified addresses). Rewriting can
18964 sometimes be used to handle simple bang paths with a fixed number of
18965 components. For example, the rule
18967 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
18969 rewrites a two-component bang path \*host.name!user*\ as the domain address
18970 \*user@@host.name*\. However, there is a security implication in using this as
18971 a global rewriting rule for envelope addresses. It can provide a backdoor
18972 method for using your system as a relay, because the incoming addresses appear
18973 to be local. If the bang path addresses are received via SMTP, it is safer to
18974 use the `S' flag to rewrite them as they are received, so that relay checking
18975 can be done on the rewritten addresses.
18985 . ============================================================================
18986 .chapter Retry configuration
18987 .set runningfoot "retry configuration"
18988 .rset CHAPretry ~~chapter
18989 .index retry||configuration, description of
18990 .index configuration file||retry section
18991 The `retry' section of the run time configuration file contains a list of retry
18992 rules which control how often Exim tries to deliver messages that cannot be
18993 delivered at the first attempt. If there are no retry rules, temporary errors
18994 are treated as permanent. The \-brt-\ command line option can be used to test
18995 which retry rule will be used for a given address or domain.
18997 The most common cause of retries is temporary failure to deliver to a remote
18998 host because the host is down, or inaccessible because of a network problem.
18999 Exim's retry processing in this case is applied on a per-host (strictly, per IP
19000 address) basis, not on a per-message basis. Thus, if one message has recently
19001 been delayed, delivery of a new message to the same host is not immediately
19002 tried, but waits for the host's retry time to arrive. If the \retry@_defer\ log
19003 selector is set, the message
19004 .index retry||time not reached
19005 `retry time not reached' is written to the main log whenever a delivery is
19006 skipped for this reason. Section ~~SECToutSMTPerr contains more details of the
19007 handling of errors during remote deliveries.
19009 Retry processing applies to routing as well as to delivering, except as covered
19010 in the next paragraph. The retry rules do not distinguish between these
19011 actions. It is not possible, for example, to specify different behaviour for
19012 failures to route the domain \*snark.fict.example*\ and failures to deliver to
19013 the host \*snark.fict.example*\. I didn't think anyone would ever need this
19014 added complication, so did not implement it. However, although they share the
19015 same retry rule, the actual retry times for routing and transporting a given
19016 domain are maintained independently.
19018 When a delivery is not part of a queue run (typically an immediate delivery on
19019 receipt of a message), the routers are always run, and local deliveries are
19020 always attempted, even if retry times are set for them. This makes for better
19021 behaviour if one particular message is causing problems (for example, causing
19022 quota overflow, or provoking an error in a filter file). If such a delivery
19023 suffers a temporary failure, the retry data is updated as normal, and
19024 subsequent delivery attempts from queue runs occur only when the retry time for
19025 the local address is reached.
19028 .section Retry rules
19029 .index retry||rules
19030 Each retry rule occupies one line and consists of three parts, separated by
19031 white space: a pattern, an error name, and a list of retry parameters. The
19032 pattern must be enclosed in double quotes if it contains white space. The rules
19033 are searched in order until one is found whose pattern matches the failing host
19036 The pattern is any single item that may appear in an address list (see section
19037 ~~SECTaddresslist). It is in fact processed as a one-item address list, which
19038 means that it is expanded before being tested against the address that has
19039 been delayed. Address list processing treats a plain domain name as if it were
19040 preceded by `*@@', which makes it possible for many retry rules to start with
19041 just a domain. For example,
19043 lookingglass.fict.example * F,24h,30m;
19045 provides a rule for any address in the \*lookingglass.fict.example*\ domain,
19048 alice@lookingglass.fict.example * F,24h,30m;
19050 applies only to temporary failures involving the local part \alice\.
19051 In practice, almost all rules start with a domain name pattern without a local
19054 .index regular expressions||in retry rules
19055 \**Warning**\: If you use a regular expression in a routing rule, it must match
19056 a complete address, not just a domain, because that is how regular expressions
19057 work in address lists.
19059 ^@\Nxyz@\d+@\.abc@\.example@$@\N * G,1h,10m,2 \Wrong\
19060 ^@\N[^@@]+@@xyz@\d+@\.abc@\.example@$@\N * G,1h,10m,2 \Right\
19064 .section Choosing which retry rule to use
19065 When Exim is looking for a retry rule after a routing attempt has failed (for
19066 example, after a DNS timeout), each line in the retry configuration is tested
19067 against the complete address only if \retry__use@_local@_part\ is set for the
19068 router. Otherwise, only the domain is used, except when matching against a
19069 regular expression, when the local part of the address is replaced with `*'. A
19070 domain on its own can match a domain pattern, or a pattern that starts with
19071 `*@@'. By default, \retry@_use@_local@_part\ is true for routers where
19072 \check@_local@_user\ is true, and false for other routers.
19074 Similarly, when Exim is looking for a retry rule after a local delivery has
19075 failed (for example, after a mailbox full error), each line in the retry
19076 configuration is tested against the complete address only if
19077 \retry@_use@_local@_part\ is set for the transport (it defaults true for all
19080 When Exim is looking for a retry rule after a remote delivery attempt has
19081 failed, what happens depends on the type of failure. After a 4\*xx*\ SMTP
19082 response for a recipient address, the whole address is used when searching the
19083 retry rules. The rule that is found is used to create a retry time for the
19086 For a temporary error that is not related to an individual address,
19087 (for example, a connection timeout), each line in the retry configuration is
19088 checked twice. First, the name of the remote host is used as a domain name
19089 (preceded by `*@@' when matching a regular expression). If this does not match
19090 the line, the domain from the email address is tried in a similar fashion. For
19091 example, suppose the MX records for \*a.b.c.example*\ are
19093 a.b.c.example MX 5 x.y.z.example
19097 and the retry rules are
19099 p.q.r.example * F,24h,30m;
19100 a.b.c.example * F,4d,45m;
19102 and a delivery to the host \*x.y.z.example*\ fails. The first rule matches
19103 neither the host nor the domain, so Exim looks at the second rule. This does
19104 not match the host, but it does match the domain, so it is used to calculate
19105 the retry time for the host \*x.y.z.example*\. Meanwhile, Exim tries to deliver
19106 to \*p.q.r.example*\. If this fails, the first retry rule is used, because it
19109 In other words, failures to deliver to host \*p.q.r.example*\ use the first
19110 rule to determine retry times, but for all the other hosts for the domain
19111 \*a.b.c.example*\, the second rule is used. The second rule is also used if
19112 routing to \*a.b.c.example*\ suffers a temporary failure.
19114 .section Retry rules for specific errors
19115 .index retry||specific errors, specifying
19116 The second field in a retry rule is the name of a particular error, or an
19117 asterisk, which matches any error. The errors that can be tested for are:
19119 \*auth@_failed*\: authentication failed when trying to send to a host in the
19120 \hosts@_require@_auth\ list in an \%smtp%\ transport
19122 \*refused@_MX*\: connection refused from a host obtained from an MX record
19124 \*refused@_A*\: connection refused from a host not obtained from an MX record
19126 \*refused*\: any connection refusal
19128 \*timeout@_connect@_MX*\: connection timeout from a host obtained from an MX
19131 \*timeout@_connect@_A*\: connection timeout from a host not obtained from an MX
19134 \*timeout@_connect*\: any connection timeout
19136 \*timeout@_MX*\: any timeout from a host obtained from an MX
19139 \*timeout@_A*\: any timeout from a host not obtained from an MX
19142 \*timeout*\: any timeout
19144 \*quota*\: quota exceeded in local delivery by \%appendfile%\
19146 .index quota||error testing in retry rule
19147 .index retry||quota error testing
19148 \*quota@_*\<<time>>: quota exceeded in local delivery, and the mailbox has not
19149 been read for <<time>>. For example, \*quota@_4d*\ applies to a quota error
19150 when the mailbox has not been read for four days.
19152 .index mailbox||time of last read
19153 \**Warning**\: It is not always possible to determine a `time of last read' for
19156 If the mailbox is a single file, the time of last access is used.
19158 .index maildir format||time of last read
19159 For a maildir delivery, the time of last modification of the \(new)\
19160 subdirectory is used. As the mailbox is over quota, no new files will be
19161 created in the \(new)\ subdirectory, so any change is assumed to be the result
19162 of an MUA moving a new message to the \(cur)\ directory when it is first read.
19164 For other kinds of multi-file delivery, the time of last read cannot be
19165 obtained, and so a retry rule that uses this type of error field is never
19169 The quota errors apply both to system-enforced quotas and to Exim's own quota
19170 mechanism in the \%appendfile%\ transport. The \*quota*\ error also applies
19171 when a local delivery is deferred because a partition is full (the \\ENOSPC\\
19175 .section Retry rule parameters
19176 .index retry||parameters in rules
19177 The third field in a retry rule is a sequence of retry parameter sets,
19178 separated by semicolons. Each set consists of
19180 <<letter>>,<<cutoff time>>,<<arguments>>
19182 The letter identifies the algorithm for computing a new retry time; the cutoff
19183 time is the time beyond which this algorithm no longer applies, and the
19184 arguments vary the algorithm's action. The cutoff time is measured from the
19185 time that the first failure for the domain (combined with the local part if
19186 relevant) was detected, not from the time the message was received.
19187 .index retry||algorithms
19188 The available algorithms are:
19190 \*F*\: retry at fixed intervals. There is a single time parameter specifying the
19193 \*G*\: retry at geometrically increasing intervals. The first argument specifies
19194 a starting value for the interval, and the second a multiplier, which is used
19195 to increase the size of the interval at each retry.
19197 When computing the next retry time, the algorithm definitions are scanned in
19198 order until one whose cutoff time has not yet passed is reached. This is then
19199 used to compute a new retry time that is later than the current time. In the
19200 case of fixed interval retries, this simply means adding the interval to the
19201 current time. For geometrically increasing intervals, retry intervals are
19202 computed from the rule's parameters until one that is greater than the previous
19203 interval is found. The main configuration variable
19204 .index limit||retry interval
19205 .index retry||interval, maximum
19206 .index \retry@_interval@_max\
19207 \retry@_interval@_max\ limits the maximum interval between retries.
19209 A single remote domain may have a number of hosts associated with it, and each
19210 host may have more than one IP address. Retry algorithms are selected on the
19211 basis of the domain name, but are applied to each IP address independently. If,
19212 for example, a host has two IP addresses and one is unusable, Exim will
19213 generate retry times for it and will not try to use it until its next retry
19214 time comes. Thus the good IP address is likely to be tried first most of the
19217 .index hints database||use for retrying
19218 Retry times are hints rather than promises. Exim does not make any attempt to
19219 run deliveries exactly at the computed times. Instead, a queue runner process
19220 starts delivery processes for delayed messages periodically, and these attempt
19221 new deliveries only for those addresses that have passed their next retry time.
19222 If a new message arrives for a deferred address, an immediate delivery attempt
19223 occurs only if the address has passed its retry time. In the absence of new
19224 messages, the minimum time between retries is the interval between queue runner
19225 processes. There is not much point in setting retry times of five minutes if
19226 your queue runners happen only once an hour, unless there are a significant
19227 number of incoming messages (which might be the case on a system that is
19228 sending everything to a smart host, for example).
19230 The data in the retry hints database can be inspected by using the
19231 \*exim@_dumpdb*\ or \*exim@_fixdb*\ utility programs (see chapter ~~CHAPutils). The
19232 latter utility can also be used to change the data. The \*exinext*\ utility
19233 script can be used to find out what the next retry times are for the hosts
19234 associated with a particular mail domain, and also for local deliveries that
19235 have been deferred.
19237 .section Retry rule examples
19238 Here are some example retry rules:
19240 alice@wonderland.fict.example quota_5d F,7d,3h
19241 wonderland.fict.example quota_5d
19242 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
19243 lookingglass.fict.example * F,24h,30m;
19244 * refused_A F,2h,20m;
19245 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
19247 The first rule sets up special handling for mail to
19248 \*alice@@wonderland.fict.example*\ when there is an over-quota error and the
19249 mailbox has not been read for at least 5 days. Retries continue every three
19250 hours for 7 days. The second rule handles over-quota errors for all other local
19251 parts at \*wonderland.fict.example*\; the absence of a local part has the same
19252 effect as supplying `$*$@@'. As no retry algorithms are supplied, messages that
19253 fail are bounced immediately if the mailbox has not been read for at least 5
19256 The third rule handles all other errors at \*wonderland.fict.example*\; retries
19257 happen every 15 minutes for an hour, then with geometrically increasing
19258 intervals until two days have passed since a delivery first failed. After the
19259 first hour there is a delay of one hour, then two hours, then four hours, and
19260 so on (this is a rather extreme example).
19262 The fourth rule controls retries for the domain \*lookingglass.fict.example*\.
19263 They happen every 30 minutes for 24 hours only. The remaining two rules handle
19264 all other domains, with special action for connection refusal from hosts that
19265 were not obtained from an MX record.
19267 The final rule in a retry configuration should always have asterisks in the
19268 first two fields so as to provide a general catch-all for any addresses that do
19269 not have their own special handling. This example tries every 15 minutes for 2
19270 hours, then with intervals starting at one hour and increasing by a factor of
19271 1.5 up to 16 hours, then every 8 hours up to 5 days.
19274 .section Timeout of retry data
19275 .index timeout||of retry data
19276 .index \retry@_data@_expire\
19277 .index hints database||data expiry
19278 .index retry||timeout of data
19279 Exim timestamps the data that it writes to its retry hints database. When it
19280 consults the data during a delivery it ignores any that is older than the value
19281 set in \retry@_data@_expire\ (default 7 days). If, for example, a host hasn't
19282 been tried for 7 days, Exim will try to deliver to it immediately a message
19283 arrives, and if that fails, it will calculate a retry time as if it were
19284 failing for the first time.
19286 This improves the behaviour for messages routed to rarely-used hosts such as MX
19287 backups. If such a host was down at one time, and happens to be down again when
19288 Exim tries a month later, using the old retry data would imply that it had been
19289 down all the time, which is not a justified assumption.
19291 If a host really is permanently dead, this behaviour causes a burst of retries
19292 every now and again, but only if messages routed to it are rare. It there is a
19293 message at least once every 7 days the retry data never expires.
19297 .section Long-term failures
19298 .index delivery||failure, long-term
19299 .index retry||after long-term failure
19300 Special processing happens when an email address has been failing for so long
19301 that the cutoff time for the last algorithm is reached. For example, using the
19302 default retry rule:
19304 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
19306 the cutoff time is four days. Reaching the retry cutoff is independent of how
19307 long any specific message has been failing; it is the length of continuous
19308 failure for the recipient address that counts.
19310 When the cutoff time is reached for a local delivery, or for all the IP
19311 addresses associated with a remote delivery, a subsequent delivery failure
19312 causes Exim to give up on the address, and a bounce message is generated.
19313 In order to cater for new messages that use the failing address, a next retry
19314 time is still computed from the final algorithm, and is used as follows:
19316 For local deliveries, one delivery attempt is always made for any subsequent
19317 messages. If this delivery fails, the address fails immediately. The
19318 post-cutoff retry time is not used.
19320 If the delivery is remote, there are two possibilities, controlled by the
19321 .index \delay@_after@_cutoff\
19322 \delay@_after@_cutoff\ option of the \%smtp%\ transport. The option is true by
19323 default and in that case:
19325 Until the post-cutoff retry time for one of the IP addresses is reached,
19326 the failing email address is bounced immediately, without a delivery attempt
19327 taking place. After that time, one new delivery attempt is made to those IP
19328 addresses that are past their retry times, and if that still fails, the address
19329 is bounced and new retry times are computed.
19332 In other words, when all the hosts for a given email address have been failing
19333 for a long time, Exim bounces rather then defers until one of the hosts' retry
19334 times is reached. Then it tries once, and bounces if that attempt fails. This
19335 behaviour ensures that few resources are wasted in repeatedly trying to deliver
19336 to a broken destination, but if the host does recover, Exim will eventually
19339 If \delay@_after@_cutoff\ is set false, Exim behaves differently. If all IP
19340 addresses are past their final cutoff time, Exim tries to deliver to those IP
19341 addresses that have not been tried since the message arrived. If there are
19342 no suitable IP addresses, or if they all fail, the address is bounced. In other
19343 words, it does not delay when a new message arrives, but tries the expired
19344 addresses immediately, unless they have been tried since the message arrived.
19345 If there is a continuous stream of messages for the failing domains, setting
19346 \delay@_after@_cutoff\ false means that there will be many more attempts to
19347 deliver to permanently failing IP addresses than when \delay@_after@_cutoff\ is
19350 .section Ultimate address timeout
19351 .index retry||ultimate address timeout
19352 An additional rule is needed to cope with cases where a host is intermittently
19353 available, or when a message has some attribute that prevents its delivery when
19354 others to the same address get through. In this situation, because some
19355 messages are successfully delivered, the `retry clock' for the address keeps
19356 getting restarted, and so a message could remain on the queue for ever. To
19357 prevent this, if a message has been on the queue for longer than the cutoff
19358 time of any applicable retry rule for a given address, a delivery is attempted
19359 for that address, even if it is not yet time, and if this delivery fails, the
19360 address is timed out. A new retry time is not computed in this case, so that
19361 other messages for the same address are considered immediately.
19371 . ============================================================================
19372 .chapter SMTP authentication
19373 .set runningfoot "SMTP authentication"
19374 .rset CHAPSMTPAUTH "~~chapter"
19375 .index SMTP||authentication configuration
19376 .index authentication
19377 The `authenticators' section of Exim's run time configuration is concerned with
19378 SMTP authentication. This facility is an extension to the SMTP protocol,
19379 described in RFC 2554, which allows a client SMTP host to authenticate itself
19380 to a server. This is a common way for a server to recognize clients that
19381 are permitted to use it as a relay. SMTP authentication is not of relevance to
19382 the transfer of mail between servers that have no managerial connection with
19385 .index \\AUTH\\||description of
19386 Very briefly, the way SMTP authentication works is as follows:
19388 The server advertises a number of authentication \*mechanisms*\ in response to
19389 the client's \\EHLO\\ command.
19391 The client issues an \\AUTH\\ command, naming a specific mechanism. The command
19392 may, optionally, contain some authentication data.
19394 The server may issue one or more \*challenges*\, to which the client must send
19395 appropriate responses. In simple authentication mechanisms, the challenges are
19396 just prompts for user names and passwords. The server does not have to issue
19397 any challenges -- in some mechanisms the relevant data may all be transmitted
19398 with the \\AUTH\\ command.
19400 The server either accepts or denies authentication.
19402 If authentication succeeds, the client may optionally make use of the \\AUTH\\
19403 option on the \\MAIL\\ command to pass an authenticated sender in subsequent
19404 mail transactions. Authentication lasts for the remainder of the SMTP
19407 If authentication fails, the client may give up, or it may try a different
19408 authentication mechanism, or it may try transferring mail over the
19409 unauthenticated connection.
19411 If you are setting up a client, and want to know which authentication
19412 mechanisms the server supports, you can use Telnet to connect to port 25 (the
19413 SMTP port) on the server, and issue an \\EHLO\\ command. The response to this
19414 includes the list of supported mechanisms. For example:
19416 @$ $cb{telnet server.example 25}
19417 Trying 192.168.34.25...
19418 Connected to server.example.
19419 Escape character is '@^]'.
19420 220 server.example ESMTP Exim 4.20 ...
19421 $cb{ehlo client.example}
19422 250-server.example Hello client.example [10.8.4.5]
19428 The second-last line of this example output shows that the server supports
19429 authentication using the PLAIN mechanism. In Exim, the different authentication
19430 mechanisms are configured by specifying \*authenticator*\ drivers. Like the
19431 routers and transports, which authenticators are included in the binary is
19432 controlled by build-time definitions. The following are currently available,
19433 included by setting
19439 in \(Local/Makefile)\, respectively. The first of these supports the CRAM-MD5
19440 authentication mechanism (RFC 2195), and the second can be configured to
19441 support the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism,
19442 which is not formally documented, but used by several MUAs. The third
19443 authenticator supports Microsoft's \*Secure Password Authentication*\
19446 The authenticators are configured using the same syntax as other drivers (see
19447 section ~~SECTfordricon). If no authenticators are required, no authentication
19448 section need be present in the configuration file. Each authenticator can in
19449 principle have both server and client functions. When Exim is receiving SMTP
19450 mail, it is acting as a server; when it is sending out messages over SMTP, it
19451 is acting as a client. Authenticator configuration options are provided for use
19452 in both these circumstances.
19454 To make it clear which options apply to which situation, the prefixes
19455 \server@_\ and \client@_\ are used on option names that are specific to either
19456 the server or the client function, respectively. Server and client functions
19457 are disabled if none of their options are set. If an authenticator is to be
19458 used for both server and client functions, a single definition, using both sets
19459 of options, is required. For example:
19463 public_name = CRAM-MD5
19464 server_secret = ${if eq{$1}{ph10}{secret1}fail}
19466 client_secret = secret2
19468 The \server@_\ option is used when Exim is acting as a server, and the
19469 \client@_\ options when it is acting as a client.
19471 Descriptions of the individual authenticators are given in subsequent chapters.
19472 The remainder of this chapter covers the generic options for the
19473 authenticators, followed by general discussion of the way authentication works
19477 .section Generic options for authenticators
19478 .index authentication||generic options
19481 .index options||generic, for authenticators
19483 .conf driver string unset
19484 This option must always be set. It specifies which of the available
19485 authenticators is to be used.
19487 .conf public@_name string unset
19488 This option specifies the name of the authentication mechanism that the driver
19489 implements, and by which it is known to the outside world. These names should
19490 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
19491 but Exim in fact matches them caselessly. If \public@_name\ is not set, it
19492 defaults to the driver's instance name.
19494 .conf server@_advertise@_condition string$**$ unset
19495 When a server is about to advertise an authentication mechanism, the condition
19496 is expanded. If it yields the empty string, `0', `no', or `false', the
19497 mechanism is not advertised.
19498 If the expansion fails, the mechanism is not advertised. If the failure was not
19499 forced, and was not caused by a lookup defer, the incident is logged.
19500 See section ~~SECTauthexiser below for further discussion.
19502 .conf server@_debug@_print string$**$ unset
19503 If this option is set and authentication debugging is enabled (see the \-d-\
19504 command line option), the string is expanded and included in the debugging
19505 output when the authenticator is run as a server. This can help with checking
19506 out the values of variables.
19507 If expansion of the string fails, the error message is written to the debugging
19508 output, and Exim carries on processing.
19510 .conf server@_set@_id string$**$ unset
19511 When an Exim server successfully authenticates a client, this string is
19512 expanded using data from the authentication, and preserved for any incoming
19513 messages in the variable \$authenticated@_id$\. It is also included in the log
19514 lines for incoming messages. For example, a user/password authenticator
19515 configuration might preserve the user name that was used to authenticate, and
19516 refer to it subsequently during delivery of the message.
19517 If expansion fails, the option is ignored.
19519 .conf server@_mail@_auth@_condition string$**$ unset
19520 This option allows a server to discard authenticated sender addresses supplied
19521 as part of \\MAIL\\ commands in SMTP connections that are authenticated by the
19522 driver on which \server__mail__auth@_condition\ is set. The option is not used
19523 as part of the authentication process; instead its (unexpanded) value is
19524 remembered for later use.
19525 How it is used is described in the following section.
19530 .section The AUTH parameter on MAIL commands
19531 .rset SECTauthparamail "~~chapter.~~section"
19532 .index authentication||sender, authenticated
19533 .index \\AUTH\\||on \\MAIL\\ command
19534 When a client supplied an \\AUTH=\\ item on a \\MAIL\\ command, Exim applies
19535 the following checks before accepting it as the authenticated sender of the
19538 If the connection is not using extended SMTP (that is, \\HELO\\ was used rather
19539 than \\EHLO\\), the use of \\AUTH=\\ is a syntax error.
19541 If the value of the \\AUTH=\\ parameter is `@<@>', it is ignored.
19543 If \acl@_smtp@_mailauth\ is defined, the ACL it specifies is run. While it is
19544 running, the value of \$authenticated@_sender$\ is set to the value obtained
19545 from the \\AUTH=\\ parameter. If the ACL does not yield `accept', the value of
19546 \$authenticated@_sender$\ is deleted. The \acl@_smtp@_mailauth\ ACL may not
19547 return `drop' or `discard'. If it defers, a temporary error code (451) is given
19548 for the \\MAIL\\ command.
19550 If \acl@_smtp@_mailauth\ is not defined, the value of the \\AUTH=\\ parameter
19551 is accepted and placed in \$authenticated@_sender$\ only if the client has
19554 If the \\AUTH=\\ value was accepted by either of the two previous rules, and
19555 the client has authenticated, and the authenticator has a setting for the
19556 \server@_mail@_auth@_condition\, the condition is checked at this point. The
19557 valued that was saved from the authenticator is expanded. If the expansion
19558 fails, or yields an empty string, `0', `no', or `false', the value of
19559 \$authenticated__sender$\ is deleted. If the expansion yields any other value,
19560 the value of \$authenticated@_sender$\ is retained and passed on with the
19564 When \$authenticated@_sender$\ is set for a message, it is passed on to other
19565 hosts to which Exim authenticates as a client. Do not confuse this value with
19566 \$authenticated@_id$\, which is a string obtained from the authentication
19567 process, and which is not usually a complete email address.
19569 Whenever an \\AUTH=\\ value is ignored, the incident is logged. The ACL for
19570 \\MAIL\\, if defined, is run after \\AUTH=\\ is accepted or ignored. It can
19571 therefore make use of \$authenticated@_sender$\. The converse is not true: the
19572 value of \$sender@_address$\ is not yet set up when the \acl@_smtp@_mailauth\
19576 .section Authentication on an Exim server
19577 .rset SECTauthexiser "~~chapter.~~section"
19578 .index authentication||on an Exim server
19579 When Exim receives an \\EHLO\\ command, it advertises the public names of those
19580 authenticators that are configured as servers, subject to the following
19583 The client host must match \auth@_advertise@_hosts\ (default $*$).
19585 It the \server@_advertise@_condition\ option is set, its expansion must not
19586 yield the empty string, `0', `no', or `false'.
19588 The order in which the authenticators are defined controls the order in which
19589 the mechanisms are advertised.
19591 Some mail clients (for example, some versions of Netscape) require the user to
19592 provide a name and password for authentication whenever \\AUTH\\ is advertised,
19593 even though authentication may not in fact be needed (for example, Exim may be
19594 set up to allow unconditional relaying from the client by an IP address check).
19595 You can make such clients more friendly by not advertising \\AUTH\\ to them.
19596 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
19597 that runs for \\RCPT\\) to relay without authentication, you should set
19599 auth_advertise_hosts = ! 10.9.8.0/24
19601 so that no authentication mechanisms are advertised to them.
19603 The \server@_advertise@_condition\ controls the advertisement of individual
19604 authentication mechanisms. For example, it can be used to restrict the
19605 advertisement of a patricular mechanism to encrypted connections, by a setting
19608 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
19610 If the session is encrypted, \$tls@_cipher$\ is not empty, and so the expansion
19611 yields `yes', which allows the advertisement to happen.
19613 When an Exim server receives an \\AUTH\\ command from a client, it rejects it
19614 immediately if \\AUTH\\ was not advertised in response to an earlier \\EHLO\\
19615 command. This is the case if
19617 The client host does not match \auth@_advertise@_hosts\; or
19619 No authenticators are configured with server options; or
19621 Expansion of \server@_advertise@_condition\ blocked the advertising of all the
19622 server authenticators.
19625 Otherwise, Exim runs the ACL specified by \acl@_smtp@_auth\ in order
19626 to decide whether to accept the command. If \acl@_smtp@_auth\ is not set,
19627 \\AUTH\\ is accepted from any client host.
19629 If \\AUTH\\ is not rejected by the ACL, Exim searches its configuration for a
19630 server authentication mechanism that was advertised in response to \\EHLO\\ and
19631 that matches the one named in the \\AUTH\\ command. If it finds one, it runs
19632 the appropriate authentication protocol, and authentication either succeeds or
19633 fails. If there is no matching advertised mechanism, the \\AUTH\\ command is
19634 rejected with a 504 error.
19636 When a message is received from an authenticated host, the value of
19637 \$received@_protocol$\ is set to `asmtp' instead of `esmtp', and
19638 \$sender@_host@_authenticated$\ contains the name (not the public name) of the
19639 authenticator driver that successfully authenticated the client from which the
19640 message was received. This variable is empty if there was no successful
19645 .section Testing server authentication
19646 .index authentication||testing a server
19647 .index \\AUTH\\||testing a server
19648 .index base64 encoding||creating authentication test data
19649 Exim's \-bh-\ option can be useful for testing server authentication
19650 configurations. The data for the \\AUTH\\ command has to be sent using base64
19651 encoding. A quick way to produce such data for testing is the following Perl
19655 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
19657 .index binary zero||in authentication data
19658 This interprets its argument as a Perl string, and then encodes it. The
19659 interpretation as a Perl string allows binary zeros, which are required for
19660 some kinds of authentication, to be included in the data. For example, a
19661 command line to run this script on such data might be
19663 encode '\0user\0password'
19665 Note the use of single quotes to prevent the shell interpreting the
19666 backslashes, so that they can be interpreted by Perl to specify characters
19667 whose code value is zero.
19669 \**Warning 1**\: If either of the user or password strings starts with an octal
19670 digit, you must use three zeros instead of one after the leading backslash. If
19671 you do not, the octal digit that starts your string will be incorrectly
19672 interpreted as part of the code for the first character.
19674 \**Warning 2**\: If there are characters in the strings that Perl interprets
19675 specially, you must use a Perl escape to prevent them being misinterpreted. For
19676 example, a command such as
19678 encode '\0user@domain.com\0pas$$word'
19680 gives an incorrect answer because of the unescaped `@@' and `@$' characters.
19682 If you have the \mimencode\ command installed, another way to do produce
19683 base64-encoded strings is to run the command
19685 echo -e -n `\0user\0password' | mimencode
19687 The \-e-\ option of \echo\ enables the interpretation of backslash escapes in
19688 the argument, and the \-n-\ option specifies no newline at the end of its
19689 output. However, not all versions of \echo\ recognize these options, so you
19690 should check your version before relying on this suggestion.
19693 .section Authentication by an Exim client
19694 .index authentication||on an Exim client
19695 The \%smtp%\ transport has two options called \hosts@_require@_auth\ and
19696 \hosts@_try@_auth\. When the \%smtp%\ transport connects to a server that
19697 announces support for authentication, and the host matches an entry in either
19698 of these options, Exim (as a client) tries to authenticate as follows:
19700 For each authenticator that is configured as a client, it searches the
19701 authentication mechanisms announced by the server for one whose name
19702 matches the public name of the authenticator.
19704 When it finds one that matches, it runs the authenticator's client code.
19705 The variables \$host$\ and \$host@_address$\ are available for any string
19706 expansions that the client might do. They are set to the server's name and
19707 IP address. If any expansion is forced to fail, the authentication attempt
19709 and Exim moves on to the next authenticator.
19710 Otherwise an expansion failure causes delivery to be
19713 If the result of the authentication attempt is a temporary error or a timeout,
19714 Exim abandons trying to send the message to the host for the moment. It will
19715 try again later. If there are any backup hosts available, they are tried in the
19718 If the response to authentication is a permanent error (5xx code), Exim carries
19719 on searching the list of authenticators and tries another one if possible. If
19720 all authentication attempts give permanent errors, or if there are no attempts
19721 because no mechanisms match
19722 (or option expansions force failure),
19723 what happens depends on whether the host matches \hosts@_require@_auth\ or
19724 \hosts@_try@_auth\. In the first case, a temporary error is generated, and
19725 delivery is deferred. The error can be detected in the retry rules, and thereby
19726 turned into a permanent error if you wish. In the second case, Exim tries to
19727 deliver the message unauthenticated.
19729 .index \\AUTH\\||on \\MAIL\\ command
19730 When Exim has authenticated itself to a remote server, it adds the \\AUTH\\
19731 parameter to the \\MAIL\\ commands it sends, if it has an authenticated sender
19733 If the message came from a remote host, the authenticated sender is the one
19734 that was receiving on an incoming \\MAIL\\ command, provided that the incoming
19735 connection was authenticated and the \server@_mail@_auth\ condition allowed the
19736 authenticated sender to be retained. If a local process calls Exim to send a
19737 message, the sender address that is built from the login name and
19738 \qualify@_domain\ is treated as authenticated. However, if the
19739 \authenticated@_sender\ option is set on the \%smtp%\ transport, it overrides
19740 the authenticated sender that was received with the message.
19751 . ============================================================================
19752 .chapter The plaintext authenticator
19753 .rset CHAPplaintext "~~chapter"
19754 .set runningfoot "plaintext authenticator"
19755 .index \%plaintext%\ authenticator
19756 .index authenticators||\%plaintext%\
19757 The \%plaintext%\ authenticator can be configured to support the PLAIN and
19758 LOGIN authentication mechanisms, both of which transfer authentication data as
19759 plain (unencrypted) text (though base64 encoded). The use of plain text is a
19760 security risk. If you use one of these mechanisms without also making use of
19761 SMTP encryption (see chapter ~~CHAPTLS) you should not use the same passwords
19762 for SMTP connections as you do for login accounts.
19764 .section Using plaintext in a server
19765 When running as a server, \%plaintext%\ performs the authentication test by
19766 expanding a string. It has the following options:
19769 .index options||\%plaintext%\ authenticator (server)
19771 .conf server@_prompts string$**$ unset
19772 The contents of this option, after expansion, must be a colon-separated list of
19773 prompt strings. If expansion fails, a temporary authentication rejection is
19776 .conf server@_condition string$**$ unset
19777 This option must be set in order to configure the driver as a server. Its use
19778 is described below.
19782 .index \\AUTH\\||in \%plaintext%\ authenticator
19783 .index binary zero||in \%plaintext%\ authenticator
19784 .index numerical variables (\$1$\, \$2$\, etc)||in \%plaintext%\ authenticator
19785 .index base64 encoding||in \%plaintext%\ authenticator
19786 The data sent by the client with the \\AUTH\\ command, or in response to
19787 subsequent prompts, is base64 encoded, and so may contain any byte values
19788 when decoded. If any data is supplied with the command, it is treated as a
19789 list of strings, separated by NULs (binary zeros), which are placed in the
19790 expansion variables \$1$\, \$2$\, etc. If there are more strings in
19791 \server@_prompts\ than the number of strings supplied with the \\AUTH\\
19792 command, the remaining prompts are used to obtain more data. Each response from
19793 the client may be a list of NUL-separated strings.
19795 Once a sufficient number of data strings have been received,
19796 \server@_condition\ is expanded.
19797 If the expansion is forced to fail, authentication fails. Any other expansion
19798 failure causes a temporary error code to be returned.
19799 If the result of a successful expansion is an empty string, `0', `no', or
19800 `false', authentication fails. If the result of the expansion is `1', `yes', or
19801 `true', authentication succeeds and the generic \server@_set@_id\ option is
19802 expanded and saved in \$authenticated@_id$\. For any other result, a temporary
19803 error code is returned, with the expanded string as the error text.
19805 \**Warning**\: If you use a lookup in the expansion to find the user's
19806 password, be sure to make the authentication fail if the user is unknown.
19807 There are good and bad examples at the end of the next section.
19810 .section The PLAIN authentication mechanism
19811 .index PLAIN authentication mechanism
19812 .index authentication||PLAIN mechanism
19813 .index binary zero||in \%plaintext%\ authenticator
19814 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
19815 sent as one item of data (that is, one combined string containing two NUL
19816 separators). The data is sent either as part of the \\AUTH\\ command, or
19817 subsequently in response to an empty prompt from the server.
19819 The second and third strings are a user name and a corresponding password.
19820 Using a single fixed user name and password as an example, this could be
19821 configured as follows:
19825 public_name = PLAIN
19827 server_condition = \
19828 ${if and {{eq{$2}{username}}{eq{$3}{mysecret}}}{yes}{no}}
19831 The \server@_prompts\ setting specifies a single, empty prompt (empty items at
19832 the end of a string list are ignored). If all the data comes as part of the
19833 \\AUTH\\ command, as is commonly the case, the prompt is not used. This
19834 authenticator is advertised in the response to \\EHLO\\ as
19838 and a client host can authenticate itself by sending the command
19840 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
19842 As this contains three strings (more than the number of prompts), no further
19843 data is required from the client. Alternatively, the client may just send
19847 to initiate authentication, in which case the server replies with an empty
19848 prompt. The client must respond with the combined data string.
19850 The data string is base64 encoded, as required by the RFC. This example,
19851 when decoded, is \"<<NUL>>username<<NUL>>mysecret"\, where <<NUL>> represents a
19852 zero byte. This is split up into three strings, the first of which is empty.
19853 The \server@_condition\ option in the authenticator checks that the second two
19854 are \"username"\ and \"mysecret"\ respectively.
19856 Having just one fixed user name and password, as in this example, is not very
19857 realistic, though for a small organization with only a handful of
19858 authenticating clients it could make sense.
19860 A more sophisticated instance of this authenticator could use the user name in
19861 \$2$\ to look up a password in a file or database, and maybe do an encrypted
19862 comparison (see \crypteq\ in chapter ~~CHAPexpand). Here is a example of this
19863 approach, where the passwords are looked up in a DBM file. \**Warning**\: This
19864 is an incorrect example:
19866 server_condition = \
19867 ${if eq{$3}{${lookup{$2}dbm{/etc/authpwd}}}{yes}{no}}
19869 The expansion uses the user name (\$2$\) as the key to look up a password,
19870 which it then compares to the supplied password (\$3$\). Why is this example
19871 incorrect? It works fine for existing users, but consider what happens if a
19872 non-existent user name is given. The lookup fails, but as no success/failure
19873 strings are given for the lookup, it yields an empty string. Thus, to defeat
19874 the authentication, all a client has to do is to supply a non-existent user
19875 name and an empty password. The correct way of writing this test is:
19877 server_condition = ${lookup{$2}dbm{/etc/authpwd}\
19878 {${if eq{$value}{$3}{yes}{no}}}{no}}
19880 In this case, if the lookup succeeds, the result is checked; if the lookup
19881 fails, authentication fails. If \crypteq\ is being used instead of \eq\, the
19882 first example is in fact safe, because \crypteq\ always fails if its second
19883 argument is empty. However, the second way of writing the test makes the logic
19887 .section The LOGIN authentication mechanism
19888 .index LOGIN authentication mechanism
19889 .index authentication||LOGIN mechanism
19890 The LOGIN authentication mechanism is not documented in any RFC, but is in use
19891 in a number of programs. No data is sent with the \\AUTH\\ command. Instead, a
19892 user name and password are supplied separately, in response to prompts. The
19893 plaintext authenticator can be configured to support this as in this example:
19897 public_name = LOGIN
19898 server_prompts = User Name : Password
19899 server_condition = \
19900 ${if and {{eq{$1}{username}}{eq{$2}{mysecret}}}{yes}{no}}
19903 Because of the way plaintext operates, this authenticator accepts data supplied
19904 with the \\AUTH\\ command (in contravention of the specification of LOGIN), but
19905 if the client does not supply it (as is the case for LOGIN clients), the prompt
19906 strings are used to obtain two data items.
19908 Some clients are very particular about the precise text of the prompts. For
19909 example, Outlook Express is reported to recognize only `Username:' and
19910 `Password:'. Here is an example of a LOGIN authenticator which uses those
19911 strings, and which uses the \ldapauth\ expansion condition to check the user
19912 name and password by binding to an LDAP server:
19916 public_name = LOGIN
19917 server_prompts = Username:: : Password::
19918 server_condition = ${if ldapauth \
19920 {user="cn=${quote_ldap_dn:$1},ou=people,o=example.org" \
19923 ldap://ldap.example.org/}{yes}{no}}
19924 server_set_id = uid=$1,ou=people,o=example.org
19926 Note the use of the \quote@_ldap@_dn\ operator to correctly quote the DN for
19927 authentication. However, the basic \quote\ operator, rather than any of the
19928 LDAP quoting operators, is the correct one to use for the password, because
19929 quoting is needed only to make the password conform to the Exim syntax. At the
19930 LDAP level, the password is an uninterpreted string.
19933 .section Support for different kinds of authentication
19934 A number of string expansion features are provided for the purpose of
19935 interfacing to different ways of user authentication. These include checking
19936 traditionally encrypted passwords from \(/etc/passwd)\ (or equivalent), PAM,
19937 Radius, \ldapauth\, and \*pwcheck*\. For details see section ~~SECTexpcond.
19941 .section Using plaintext in a client
19942 The \%plaintext%\ authenticator has just one client option:
19945 .index options||\%plaintext%\ authenticator (client)
19947 .conf client@_send string$**$ unset
19948 The string is a colon-separated list of authentication data strings. Each
19949 string is independently expanded before being sent to the server. The first
19950 string is sent with the \\AUTH\\ command; any more strings are sent in response
19951 to prompts from the server.
19953 \**Note**\: you cannot use expansion to create multiple strings, because
19954 splitting takes priority and happens first.
19956 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
19957 the data, further processing is applied to each string before it is sent. If
19958 there are any single circumflex characters in the string, they are converted to
19959 NULs. Should an actual circumflex be required as data, it must be doubled in
19964 This is an example of a client configuration that implements the PLAIN
19965 authentication mechanism with a fixed user name and password:
19969 public_name = PLAIN
19970 client_send = ^username^mysecret
19972 The lack of colons means that the entire text is sent with the \\AUTH\\
19973 command, with the circumflex characters converted to NULs. A similar example
19974 that uses the LOGIN mechanism is:
19978 public_name = LOGIN
19979 client_send = : username : mysecret
19981 The initial colon means that the first string is empty, so no data is sent with
19982 the \\AUTH\\ command itself. The remaining strings are sent in response to
19992 . ============================================================================
19993 .chapter The cram@_md5 authenticator
19994 .set runningfoot "cram@_md5 authenticator"
19995 .index \%cram@_md5%\ authenticator
19996 .index authenticators||\%cram@_md5%\
19997 .index CRAM-MD5 authentication mechanism
19998 .index authentication||CRAM-MD5 mechanism
19999 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
20000 sends a challenge string to the client, and the response consists of a user
20001 name and the CRAM-MD5 digest of the challenge string combined with a secret
20002 string (password) which is known to both server and client. Thus, the secret
20003 is not sent over the network as plain text, which makes this authenticator more
20004 secure than \%plaintext%\. However, the downside is that the secret has to be
20005 available in plain text at either end.
20007 .section Using cram@_md5 as a server
20008 This authenticator has one server option, which must be set to configure the
20009 authenticator as a server:
20012 .index options||\%cram@_md5%\ authenticator (server)
20014 .conf server@_secret string$**$ unset
20015 .index numerical variables (\$1$\, \$2$\, etc)||in \%cram@_md5%\ authenticator
20016 When the server receives the client's response, the user name is placed in
20017 the expansion variable \$1$\, and \server@_secret\ is expanded to obtain the
20018 password for that user. The server then computes the CRAM-MD5 digest that the
20019 client should have sent, and checks that it received the correct string. If the
20020 expansion of \server@_secret\ is forced to fail, authentication fails. If the
20021 expansion fails for some other reason, a temporary error code is returned to
20026 For example, the following authenticator checks that the user name given by the
20027 client is `ph10', and if so, uses `secret' as the password. For any other user
20028 name, authentication fails.
20032 public_name = CRAM-MD5
20033 server_secret = ${if eq{$1}{ph10}{secret}fail}
20036 If authentication succeeds, the setting of \server@_set@_id\ preserves the user
20037 name in \$authenticated@_id$\.
20038 A more tyical configuration might look up the secret string in a file, using
20039 the user name as the key. For example:
20043 public_name = CRAM-MD5
20044 server_secret = ${lookup{$1}lsearch{/etc/authpwd}{$value}fail}
20047 Note that this expansion explicitly forces failure if the lookup fails
20048 because \$1$\ contains an unknown user name.
20050 .section Using cram@_md5 as a client
20051 When used as a client, the \%cram@_md5%\ authenticator has two options:
20054 .index options||\%cram@_md5%\ authenticator (client)
20056 .conf client@_name string$**$ "the primary host name"
20057 This string is expanded, and the result used as the user name data when
20058 computing the response to the server's challenge.
20060 .conf client@_secret string$**$ unset
20061 This option must be set for the authenticator to work as a client. Its value is
20062 expanded and the result used as the secret string when computing the response.
20066 Different user names and secrets can be used for different servers by referring
20067 to \$host$\ or \$host@_address$\ in the options.
20069 Forced failure of either expansion string is treated as an indication that this
20070 authenticator is not prepared to handle this case. Exim moves on to the next
20071 configured client authenticator. Any other expansion failure causes Exim to
20072 give up trying to send the message to the current server.
20074 A simple example configuration of a \%cram@_md5%\ authenticator, using fixed
20079 public_name = CRAM-MD5
20081 client_secret = secret
20092 . ============================================================================
20093 .chapter The spa authenticator
20094 .set runningfoot "spa authenticator"
20095 .index \%spa%\ authenticator
20096 .index authenticators||\%spa%\
20097 .index authentication||Microsoft Secure Password
20098 .index authentication||NTLM
20099 .index Microsoft Secure Password Authentication
20100 .index NTLM authentication
20101 The \%spa%\ authenticator provides client support for Microsoft's \*Secure
20102 Password Authentication*\ mechanism,
20103 which is also sometimes known as NTLM (NT LanMan). The code for client side of
20104 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
20105 taken from the Samba project (\?http://www.samba.org?\). The code for the
20106 server side was subsequently contributed by Tom Kistner.
20108 The mechanism works as follows:
20110 After the \\AUTH\\ command has been accepted, the client sends an SPA
20111 authentication request based on the user name and optional domain.
20113 The server sends back a challenge.
20115 The client builds a challenge response which makes use of the user's password
20116 and sends it to the server, which then accepts or rejects it.
20118 Encryption is used to protect the password in transit.
20121 .section Using spa as a server
20122 The \%spa%\ authenticator has just one server option:
20125 .index options||\%spa%\ authenticator (server)
20127 .conf server@_password string$**$ unset
20128 .index numerical variables (\$1$\, \$2$\, etc)||in \%spa%\ authenticator
20129 This option is expanded, and the result must be the cleartext password for the
20130 authenticating user, whose name is at this point in \$1$\. For example:
20135 server_password = ${lookup{$1}lsearch{/etc/exim/spa_clearpass}}
20137 If the expansion is forced to fail, authentication fails. Any other expansion
20138 failure causes a temporary error code to be returned.
20144 .section Using spa as a client
20145 The \%spa%\ authenticator has the following client options:
20148 .index options||\%spa%\ authenticator (client)
20150 .conf client@_domain string$**$ unset
20151 This option specifies an optional domain for the authentication.
20153 .conf client@_password string$**$ unset
20154 This option specifies the user's password, and must be set.
20156 .conf client@_username string$**$ unset
20157 This option specifies the user name, and must be set.
20161 Here is an example of a configuration of this authenticator for use with the
20162 mail servers at \*msn.com*\:
20167 client_username = msn/msn_username
20168 client_password = msn_plaintext_password
20169 client_domain = DOMAIN_OR_UNSET
20181 . ============================================================================
20182 .chapter Encrypted SMTP connections using TLS/SSL
20183 .set runningfoot "TLS encryption"
20184 .rset CHAPTLS "~~chapter"
20185 .index encryption||on SMTP connection
20186 .index SMTP||encryption
20187 .index TLS||on SMTP connection
20190 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
20191 Sockets Layer), is implemented by making use of the OpenSSL library or the
20192 GnuTLS library (Exim requires GnuTLS release 1.0 or later).
20193 There is no cryptographic code in the Exim distribution itself for implementing
20194 TLS. In order to use this feature you must install OpenSSL or GnuTLS, and then
20195 build a version of Exim that includes TLS support (see section
20196 ~~SECTinctlsssl). You also need to understand the basic concepts of encryption
20197 at a managerial level, and in particular, the way that public keys, private
20198 keys, and certificates are used.
20200 RFC 2487 defines how SMTP connections can make use of encryption. Once a
20201 connection is established, the client issues a \\STARTTLS\\ command. If the
20202 server accepts this, the client and the server negotiate an encryption
20203 mechanism. If the negotiation succeeds, the data that subsequently passes
20204 between them is encrypted.
20206 Exim also has support for legacy clients that do not use the \\STARTTLS\\
20207 mechanism. Instead, they connect to a different port on the server (usually
20208 called the `ssmtp' port), and expect to negotiate a TLS session as soon as the
20209 connection to the server is established. The \-tls-on-connect-\ command line
20210 option can be used to run an Exim server in this way from \*inetd*\, and it can
20211 also be used to run a special daemon that operates in this manner (use \-oX-\
20212 to specify the port).
20214 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
20215 and if so, what cipher suite is in use, whether the client supplied a
20216 certificate, and whether or not that certificate was verified. This makes it
20217 possible for an Exim server to deny or accept certain commands based on the
20220 \**Warning**\: certain types of firewall and certain anti-virus products can
20221 disrupt TLS connections. You need to turn off SMTP scanning for these products
20222 in order to get TLS to work.
20225 .section OpenSSL vs GnuTLS
20226 .index TLS||OpenSSL \*vs*\ GnuTLS
20227 .rset SECTopenvsgnu "~~chapter.~~section"
20228 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
20229 followed later, when the first versions of GnuTLS were released. To build Exim
20230 to use GnuTLS, you need to set
20234 in Local/Makefile, in addition to
20238 You must also set \\TLS@_LIBS\\ and \\TLS@_INCLUDE\\ appropriately, so that the
20239 include files and libraries for GnuTLS can be found.
20241 There are some differences in usage when using GnuTLS instead of OpenSSL:
20243 The \tls@_verify@_certificates\ option must contain the name of a file, not the
20244 name of a directory (for OpenSSL it can be either).
20246 The \tls@_dhparam\ option is ignored, because early versions of GnuTLS had no
20247 facility for varying its Diffie-Hellman parameters. I understand that this has
20248 changed, but Exim has not been updated to provide this facility.
20250 GnuTLS uses RSA and D-H parameters that take a substantial amount of
20251 time to compute. It is unreasonable to re-compute them for every TLS
20252 session. Therefore, Exim keeps this data in a file in its spool
20253 directory, called \(gnutls-params)\. The file is owned by the Exim user and is
20254 readable only by its owner. Every Exim process that start up GnuTLS reads the
20255 RSA and D-H parameters from this file. If the file does not exist, the first
20256 Exim process that needs it computes the data and writes it to a temporary file
20257 which is renamed once it is complete. It does not matter if several Exim
20258 processes do this simultaneously (apart from wasting a few resources). Once a
20259 file is in place, new Exim processes immediately start using it.
20261 For maximum security, the parameters that are stored in this file should be
20262 recalculated periodically, the frequency depending on your paranoia level.
20263 Arranging this is easy; just delete the file when you want new values to be
20266 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
20267 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
20268 affects the value of the \$tls@_peerdn$\ variable.
20270 OpenSSL identifies cipher suites using hyphens as separators, for example:
20271 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA@_ARCFOUR@_SHA. What is
20272 more, OpenSSL complains if underscores are present in a cipher list. To make
20273 life simpler, Exim changes underscores to hyhens for OpenSSL and hyphens to
20274 underscores for GnuTLS when processing lists of cipher suites in the
20275 \tls@_require@_ciphers\ options (the global option and the \%smtp%\ transport
20278 The \tls@_require@_ciphers\ options operate differently, as described in the
20282 .section Requiring specific ciphers in OpenSSL and GnuTLS
20283 .rset SECTreqciphsslgnu "~~chapter.~~section"
20284 .index TLS||requiring specific ciphers
20285 .index \tls@_require@_ciphers\||OpenSSL \*vs*\ GnuTLS
20286 This section documents the different ways the \tls@_require@_ciphers\ options
20287 (the global option and the \%smtp%\ transport option) operate in OpenSSL and
20290 There is a function in the OpenSSL library that can be passed a list of
20291 cipher suites before the cipher negotiation takes place. This specifies which
20292 ciphers are acceptable. The list is colon separated and may contain names like
20293 DES-CBC3-SHA. Exim passes the expanded value of \tls@_require@_ciphers\
20294 directly to this function call. The following quotation from
20295 the OpenSSL documentation specifies what forms of item are allowed in the
20298 It can consist of a single cipher suite such as RC4-SHA.
20300 It can represent a list of cipher suites containing a certain algorithm,
20301 or cipher suites of a certain type. For example SHA1 represents all
20302 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
20305 Lists of cipher suites can be combined in a single cipher string using
20306 the + character. This is used as a logical and operation. For example
20307 SHA1+DES represents all cipher suites containing the SHA1 and the DES
20310 Each cipher string can be optionally preceded by the characters \"!"\, \"-"\ or
20313 If \"!"\ is used then the ciphers are permanently deleted from the list. The
20314 ciphers deleted can never reappear in the list even if they are explicitly
20317 If \"-"\ is used then the ciphers are deleted from the list, but some or all
20318 of the ciphers can be added again by later options.
20320 If \"+"\ is used then the ciphers are moved to the end of the list. This
20321 option doesn't add any new ciphers it just moves matching existing ones.
20323 If none of these characters is present then the string is just interpreted as a
20324 list of ciphers to be appended to the current preference list. If the list
20325 includes any ciphers already present they will be ignored: that is, they will
20326 not moved to the end of the list.
20330 The GnuTLS library does not have a combined function like OpenSSL. Instead,
20331 it allows the caller to specify separate lists of key-exchange methods,
20332 main cipher algorithms, and MAC algorithms. Unfortunately, these lists are
20333 numerical, and the library does not have a function for turning names into
20334 numbers. Consequently, the list of recognized names has to be built into
20337 At present, Exim permits only the list of main cipher algorithms to be
20338 changed. The \tls@_require@_ciphers\ option is in the same format as for
20339 OpenSSL. Exim searches each item for the name of available algorithm. For
20340 example, if the list contains RSA@_ARCFOUR@_SHA then ARCFOUR is recognized.
20342 The cipher algorithms list starts out with a default set of algorithms. If
20343 the first item in \tls@_require@_ciphers\ does \*not*\ start with an
20344 exclamation mark, all the default items are deleted. Thus, only those specified
20345 can be used. If the first item in \tls@_require@_ciphers\ \*does*\ start with
20346 an exclamation mark, the defaults are left on the list.
20348 Then, any item that starts with an exclamation mark causes the relevent
20349 algorithms to be removed from the list, and any item that does not start
20350 with an exclamation mark causes the relevant algorithms to be added to the
20353 tls_require_ciphers = !RSA_ARCFOUR_SHA
20355 allows all the defaults except those that use ARCFOUR, whereas
20357 tls_require_ciphers = AES : 3DES
20359 allows only cipher suites that use AES and 3DES. The currently recognized
20360 algorithms are: ARCFOUR@_128, ARCFOUR@_40, ARCFOUR (both of the preceding),
20361 AES@_256, AES@_128, AES (both of the preceding), and 3DES.
20363 Unrecognized algorithms are ignored. In a client, the order of the list
20364 specifies a preference order for the algorithms.
20367 .section Configuring an Exim server to use TLS
20368 .index TLS||configuring an Exim server
20369 When Exim has been built with TLS support, it advertises the availability of
20370 the \\STARTTLS\\ command to client hosts that match \tls@_advertise@_hosts\,
20371 but not to any others. The default value of this option is unset, which means
20372 that \\STARTTLS\\ is not advertised at all. This default is chosen because you
20373 need to set some other options in order to make TLS avaliable, and also it is
20374 sensible for systems that want to use TLS only as a client.
20376 If a client issues a \\STARTTLS\\ command and there is some configuration
20377 problem in the server, the command is rejected with a 454 error. If the client
20378 persists in trying to issue SMTP commands, all except \\QUIT\\ are rejected
20381 554 Security failure
20383 If a \\STARTTLS\\ command is issued within an existing TLS session, it is
20384 rejected with a 554 error code.
20386 To enable TLS operations on a server, you must set \tls@_advertise@_hosts\ to
20387 match some hosts. You can, of course, set it to $*$ to match all hosts.
20388 However, this is not all you need to do. TLS sessions to a server won't work
20389 without some further configuration at the server end.
20391 It is rumoured that all existing clients that support TLS/SSL use RSA
20392 encryption. To make this work you need to set, in the server,
20394 tls_certificate = /some/file/name
20395 tls_privatekey = /some/file/name
20397 The first file contains the server's X509 certificate, and the second contains
20398 the private key that goes with it. These files need to be readable by the Exim
20399 user, and must always be given as full path names. They can be the same file if
20400 both the certificate and the key are contained within it. If \tls@_privatekey\
20401 is not set, this is assumed to be the case. The certificate file may also
20402 contain intermediate certificates that need to be sent to the client to enable
20403 it to authenticate the server's certificate.
20405 If you do not understand about certificates and keys, please try to find a
20406 source of this background information, which is not Exim-specific. (There are a
20407 few comments below in section ~~SECTcerandall.)
20409 \**Note**\: These options do not apply when Exim is operating as a client --
20410 they apply only in the case of a server. For a client, you must set the options
20411 of the same name in an \%smtp%\ transport.
20413 With just these options, Exim will work as a server with clients such as
20414 Netscape. It does not require the client to have a certificate (but see below
20415 for how to insist on this). There is one other option that may be needed in
20416 other situations. If
20418 tls_dhparam = /some/file/name
20420 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
20421 with the parameters contained in the file. This increases the set of cipher
20422 suites that the server supports. See the command
20426 for a way of generating this data.
20427 At present, \tls@_dhparam\ is used only when Exim is linked with OpenSSL. It is
20428 ignored if GnuTLS is being used.
20430 The strings supplied for these three options are expanded every time a client
20431 host connects. It is therefore possible to use different certificates and keys
20432 for different hosts, if you so wish, by making use of the client's IP address
20433 in \$sender@_host@_address$\ to control the expansion. If a string expansion is
20434 forced to fail, Exim behaves as if the option is not set.
20436 .index cipher||logging
20437 .index log||TLS cipher
20438 The variable \$tls@_cipher$\ is set to the cipher suite that was negotiated for
20439 an incoming TLS connection. It is included in the ::Received:: header of an
20440 incoming message (by default -- you can, of course, change this), and it is
20441 also included in the log line that records a message's arrival, keyed by `X=',
20442 unless the \tls@_cipher\ log selector is turned off.
20443 The \encrypted\ condition can be used to test for specific cipher suites in
20446 The ACLs that run for subsequent SMTP commands can check the name of the cipher
20447 suite and vary their actions accordingly. The cipher suite names are those used
20448 by OpenSSL. These may differ from the names used elsewhere. For example,
20449 OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts
20450 is known as TLS@_RSA@_WITH@_3DES@_EDE@_CBC@_SHA. Check the OpenSSL
20451 documentation for more details.
20454 .section Requesting and verifying client certificates
20455 .index certificate||verification of client
20456 .index TLS||client certificate verification
20457 If you want an Exim server to request a certificate when negotiating a TLS
20458 session with a client, you must set either \tls@_verify@_hosts\ or
20459 \tls@_try@_verify@_hosts\. You can, of course, set either of them to $*$ to
20460 apply to all TLS connections. For any host that matches one of these options,
20461 Exim requests a certificate as part of the setup of the TLS session. The
20462 contents of the certificate are verified by comparing it with a list of
20463 expected certificates. These must be available in a file or,
20464 for OpenSSL only (not GnuTLS), a directory, identified by
20465 \tls@_verify@_certificates\.
20467 A file can contain multiple certificates, concatenated end to end. If a
20470 each certificate must be in a separate file, with a name (or a symbolic link)
20471 of the form <<hash>>.0, where <<hash>> is a hash value constructed from the
20472 certificate. You can compute the relevant hash by running the command
20474 openssl x509 -hash -noout -in /cert/file
20476 where \(/cert/file)\ contains a single certificate.
20478 The difference between \tls@_verify@_hosts\ and \tls@_try@_verify@_hosts\ is
20479 what happens if the client does not supply a certificate, or if the certificate
20480 does not match any of the certificates in the collection named by
20481 \tls@_verify@_certificates\. If the client matches \tls@_verify@_hosts\, the
20482 attempt to set up a TLS session is aborted, and the incoming connection is
20483 dropped. If the client matches \tls@_try@_verify@_hosts\, the (encrypted) SMTP
20484 session continues. ACLs that run for subsequent SMTP commands can detect the
20485 fact that no certificate was verified, and vary their actions accordingly. For
20486 example, you can insist on a certificate before accepting a message for
20487 relaying, but not when the message is destined for local delivery.
20489 When a client supplies a certificate (whether it verifies or not), the value of
20490 the Distinguished Name of the certificate is made available in the variable
20491 \$tls@_peerdn$\ during subsequent processing of the message.
20492 .index log||distinguished name
20493 Because it is often a long text string, it is not included in the log line or
20494 ::Received:: header by default. You can arrange for it to be logged, keyed by
20495 `DN=', by setting the \tls@_peerdn\ log selector, and you can use
20496 \received@_header@_text\ to change the ::Received:: header. When no certificate
20497 is supplied, \$tls@_peerdn$\ is empty.
20499 .section Revoked certificates
20500 .index TLS||revoked certificates
20501 .index revocation list
20502 .index certificate||revocation list
20503 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
20504 certificates are revoked. If you have such a list, you can pass it to an Exim
20505 server using the global option called \tls@_crl\ and to an Exim client using an
20506 identically named option for the \%smtp%\ transport. In each case, the value of
20507 the option is expanded and must then be the name of a file that contains a CRL
20510 .section Configuring an Exim client to use TLS
20511 .index cipher||logging
20512 .index log||TLS cipher
20513 .index log||distinguished name
20514 .index TLS||configuring an Exim client
20515 The \tls@_cipher\ and \tls@_peerdn\ log selectors apply to outgoing SMTP
20516 deliveries as well as to incoming, the latter one causing logging of the
20517 server certificate's DN. The remaining client configuration for TLS is all
20518 within the \%smtp%\ transport.
20520 It is not necessary to set any options to have TLS work in the \%smtp%\
20521 transport. If Exim is built with TLS support, and TLS is advertised by a
20522 server, the \%smtp%\ transport always tries to start a TLS session. However,
20523 this can be prevented by setting \hosts@_avoid@_tls\ (an option of the
20524 transport) to a list of server hosts for which TLS should not be used.
20526 If you do not want Exim to attempt to send messages unencrypted when an attempt
20527 to set up an encrypted connection fails in any way, you can set
20528 \hosts@_require@_tls\ to a list of hosts for which encryption is mandatory. For
20529 those hosts, delivery is always deferred if an encrypted connection cannot be
20530 set up. If there are any other hosts for the address, they are tried in the
20533 When the server host is not in \hosts@_require@_tls\, Exim may try to deliver
20534 the message unencrypted. It always does this if the response to \\STARTTLS\\ is
20535 a 5\*xx*\ code. For a temporary error code, or for a failure to negotiate a TLS
20536 session after a success response code, what happens is controlled by the
20537 \tls@_tempfail@_tryclear\ option of the \%smtp%\ transport. If it is false,
20538 delivery to this host is deferred, and other hosts (if available) are tried. If
20539 it is true, Exim attempts to deliver unencrypted after a 4\*xx*\ response to
20540 \\STARTTLS\\, and if \\STARTTLS\\ is accepted, but the subsequent TLS
20541 negotiation fails, Exim closes the current connection (because it is in an
20542 unknown state), opens a new one to the same host, and then tries the delivery
20546 The \tls@_certificate\ and \tls@_privatekey\ options of the \%smtp%\ transport
20547 provide the client with a certificate, which is passed to the server if it
20548 requests it. If the server is Exim, it will request a certificate only if
20549 \tls@_verify@_hosts\ or \tls@_try@_verify@_hosts\ matches the client.
20550 \**Note**\: these options must be set in the \%smtp%\ transport for Exim to use
20551 TLS when it is operating as a client. Exim does not assume that a server
20552 certificate (set by the global options of the same name) should also be used
20553 when operating as a client.
20555 If \tls@_verify@_certificates\ is set, it must name a file or,
20556 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
20557 expected server certificates. The client verifies the server's certificate
20558 against this collection, taking into account any revoked certificates that are
20559 in the list defined by \tls@_crl\.
20562 \tls@_require@_ciphers\ is set on the \%smtp%\ transport, it must contain a
20563 list of permitted cipher suites. If either of these checks fails, delivery to
20564 the current host is abandoned, and the \%smtp%\ transport tries to deliver to
20565 alternative hosts, if any.
20567 All the TLS options in the \%smtp%\ transport are expanded before use, with
20568 \$host$\ and \$host@_address$\ containing the name and address of the server to
20569 which the client is connected. Forced failure of an expansion causes Exim to
20570 behave as if the relevant option were unset.
20573 .section Multiple messages on the same encrypted TCP/IP connection
20574 .rset SECTmulmessam "~~chapter.~~section"
20575 .index multiple SMTP deliveries with TLS
20576 .index TLS||multiple message deliveries
20577 Exim sends multiple messages down the same TCP/IP connection by starting up
20578 an entirely new delivery process for each message, passing the socket from
20579 one process to the next. This implementation does not fit well with the use
20580 of TLS, because there is quite a lot of state information associated with a TLS
20581 connection, not just a socket identification. Passing all the state information
20582 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
20583 session before passing the socket to a new process. The new process may then
20584 try to start a new TLS session, and if successful, may try to re-authenticate
20585 if \\AUTH\\ is in use, before sending the next message.
20587 The RFC is not clear as to whether or not an SMTP session continues in clear
20588 after TLS has been shut down, or whether TLS may be restarted again later, as
20589 just described. However, if the server is Exim, this shutdown and
20590 reinitialization works. It is not known which (if any) other servers operate
20591 successfully if the client closes a TLS session and continues with unencrypted
20592 SMTP, but there are certainly some that do not work. For such servers, Exim
20593 should not pass the socket to another process, because the failure of the
20594 subsequent attempt to use it would cause Exim to record a temporary host error,
20595 and delay other deliveries to that host.
20597 To test for this case, Exim sends an \\EHLO\\ command to the server after
20598 closing down the TLS session. If this fails in any way, the connection is
20599 closed instead of being passed to a new delivery process, but no retry
20600 information is recorded.
20602 There is also a manual override; you can set \hosts@_nopass@_tls\ on the
20603 \%smtp%\ transport to match those hosts for which Exim should not pass
20604 connections to new processes if TLS has been used.
20608 .section Certificates and all that
20609 .rset SECTcerandall "~~chapter.~~section"
20610 .index certificate||references to discussion
20611 In order to understand fully how TLS works, you need to know about
20612 certificates, certificate signing, and certificate authorities. This is not the
20613 place to give a tutorial, especially as I do not know very much about it
20614 myself. Some helpful introduction can be found in the FAQ for the SSL addition
20615 to Apache, currently at
20617 \?http://www.modssl.org/docs/2.7/ssl@_faq.html@#ToC24?\
20619 Other parts of the \*modssl*\ documentation are also helpful, and have
20620 links to further files.
20621 Eric Rescorla's book, \*SSL and TLS*\, published by Addison-Wesley (ISBN
20622 0-201-61598-3), contains both introductory and more in-depth descriptions.
20623 Some sample programs taken from the book are available from
20625 \?http://www.rtfm.com/openssl-examples/?\
20628 .section Certificate chains
20629 The file named by \tls@_certificate\ may contain more than one
20630 certificate. This is useful in the case where the certificate that is being
20631 sent is validated by an intermediate certificate which the other end does
20632 not have. Multiple certificates must be in the correct order in the file.
20633 First the host's certificate itself, then the first intermediate
20634 certificate to validate the issuer of the host certificate, then the next
20635 intermediate certificate to validate the issuer of the first intermediate
20636 certificate, and so on, until finally (optionally) the root certificate.
20637 The root certificate must already be trusted by the recipient for
20638 validation to succeed, of course, but if it's not preinstalled, sending the
20639 root certificate along with the rest makes it available for the user to
20640 install if the receiving end is a client MUA that can interact with a user.
20642 .section Self-signed certificates
20643 .index certificate||self-signed
20644 You can create a self-signed certificate using the \*req*\ command provided
20645 with OpenSSL, like this:
20647 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
20650 \(file1)\ and \(file2)\ can be the same file; the key and the certificate are
20651 delimited and so can be identified independently. The \-days-\ option
20652 specifies a period for which the certificate is valid. The \-nodes-\ option is
20653 important: if you do not set it, the key is encrypted with a passphrase
20654 that you are prompted for, and any use that is made of the key causes more
20655 prompting for the passphrase. This is not helpful if you are going to use
20656 this certificate and key in an MTA, where prompting is not possible.
20658 A self-signed certificate made in this way is sufficient for testing, and
20659 may be adequate for all your requirements if you are mainly interested in
20660 encrypting transfers, and not in secure identification.
20662 However, many clients require that the certificate presented by the server be a
20663 user (also called `leaf' or `site') certificate, and not a self-signed
20664 certificate. In this situation, the self-signed certificate described above
20665 must be installed on the client host as a trusted root \*certification
20666 authority*\ (CA), and the certificate used by Exim must be a user certificate
20667 signed with that self-signed certificate.
20669 For information on creating self-signed CA certificates and using them to sign
20670 user certificates, see the \*General implementation overview*\ chapter of the
20671 Open-source PKI book, available online at \?http://ospkibook.sourceforge.net/?\.
20679 . ============================================================================
20680 .chapter Access control lists
20681 .set runningfoot "ACL"
20682 .rset CHAPACL "~~chapter"
20683 .index ~~ACL||description
20684 .index control of incoming mail
20685 .index message||controlling incoming
20686 .index policy control||access control lists
20687 Access Control Lists (ACLs) are defined in a separate section of the run time
20688 configuration file, headed by `begin acl'. Each ACL definition starts with a
20689 name, terminated by a colon. Here is a complete ACL section that contains just
20690 one very small ACL:
20695 accept hosts = one.host.only
20697 You can have as many lists as you like in the ACL section, and the order in
20698 which they appear does not matter. The lists are self-terminating.
20700 The majority of ACLs are used to control Exim's behaviour when it receives
20701 certain SMTP commands. This applies both to incoming TCP/IP connections, and
20702 when a local process submits a message using SMTP by specifying the \-bs-\
20703 option. The most common use is for controlling which recipients are accepted
20704 in incoming messages. In addition, you can define an ACL that is used to check
20705 local non-SMTP messages. The default configuration file contains an example of
20706 a realistic ACL for checking \\RCPT\\ commands. This is discussed in chapter
20709 .section Testing ACLs
20710 The \-bh-\ command line option provides a way of testing your ACL configuration
20711 locally by running a fake SMTP session with which you interact. The host
20712 \*relay-test.mail-abuse.org*\ provides a service for checking your relaying
20713 configuration (see section ~~SECTcheralcon for more details).
20716 .section Specifying when ACLs are used
20717 .index ~~ACL||options for specifying
20718 In order to cause an ACL to be used, you have to name it in one of the relevant
20719 options in the main part of the configuration. These options are:
20720 .index \\AUTH\\||ACL for
20721 .index \\DATA\\, ACLs for
20722 .index \\ETRN\\||ACL for
20723 .index \\EXPN\\||ACL for
20724 .index \\HELO\\||ACL for
20725 .index \\EHLO\\||ACL for
20726 .index \\MAIL\\||ACL for
20727 .index \\QUIT\\, ACL for
20728 .index \\RCPT\\||ACL for
20729 .index \\STARTTLS\\, ACL for
20730 .index \\VRFY\\||ACL for
20731 .index SMTP||connection, ACL for
20732 .index non-smtp message, ACL for
20738 \acl@_not@_smtp\ $t $rm{ACL for non-SMTP messages}
20739 \acl@_smtp@_auth\ $t $rm{ACL for \\AUTH\\}
20740 \acl@_smtp@_connect\ $t $rm{ACL for start of SMTP connection}
20741 \acl@_smtp@_data\ $t $rm{ACL after \\DATA\\ is complete}
20742 \acl@_smtp@_etrn\ $t $rm{ACL for \\ETRN\\}
20743 \acl@_smtp@_expn\ $t $rm{ACL for \\EXPN\\}
20744 \acl@_smtp@_helo\ $t $rm{ACL for \\HELO\\ or \\EHLO\\}
20745 \acl@_smtp@_mail\ $t $rm{ACL for \\MAIL\\}
20746 \acl@_smtp@_mailauth\ $t $rm{ACL for the \\AUTH\\ parameter of \\MAIL\\}
20749 \acl@_smtp@_mime\ $t $rm{ACL for content-scanning MIME parts}
20750 \acl@_smtp@_predata\ $t $rm{ACL at start of \\DATA\\ command}
20751 \acl@_smtp@_quit\ $t $rm{ACL for \\QUIT\\}
20754 \acl@_smtp@_rcpt\ $t $rm{ACL for \\RCPT\\}
20755 \acl@_smtp@_starttls\ $t $rm{ACL for \\STARTTLS\\}
20756 \acl@_smtp@_vrfy\ $t $rm{ACL for \\VRFY\\}
20758 For example, if you set
20760 acl_smtp_rcpt = small_acl
20762 the little ACL defined above is used whenever Exim receives a \\RCPT\\ command
20763 in an SMTP dialogue. The majority of policy tests on incoming messages can be
20764 done when \\RCPT\\ commands arrive. A rejection of \\RCPT\\ should cause the
20765 sending MTA to give up on the recipient address contained in the \\RCPT\\
20766 command, whereas rejection at other times may cause the client MTA to keep on
20767 trying to deliver the message. It is therefore recommended that you do as much
20768 testing as possible at \\RCPT\\ time.
20771 .section The MIME ACLs
20772 The \acl@_smtp@_mime\ option is available only when Exim is compiled with the
20773 content-scanning extension. For details, see chapter ~~CHAPexiscan.
20776 .section The DATA ACLs
20777 .index \\DATA\\, ACLs for
20778 Two ACLs are associated with the \\DATA\\ command. When the command is
20779 received, the ACL defined by \acl@_smtp@_predata\ is obeyed. This gives you
20780 control after all the \\RCPT\\ commands, but before the message itself
20781 is received. It offers the opportunity to give a negative response to the
20782 \\DATA\\ command itself. Header lines added by \\MAIL\\ or \\RCPT\\ ACLs are
20783 not visible at this time, but any that are defined here are visible when the
20784 \acl@_smtp@_data\ ACL is run.
20786 You cannot test the contents of the message, for example, to verify
20787 addresses in the headers, at \\RCPT\\ time or when the \\DATA\\ command is
20790 Such tests have to appear in the ACL that is run after the message has been
20791 received, before the final response to the \\DATA\\ command is sent. This is
20792 the ACL specified by \acl@_smtp@_data\. At this time, it is no longer possible
20793 to reject individual recipients. An error response rejects the entire message.
20794 Unfortunately, it is known that some MTAs do not treat hard (5$it{xx}) errors
20795 correctly at this point -- they keep the message on their queues and try again
20796 later, but that is their problem, though it does waste some of your resources.
20798 .section The connect ACL
20799 .index SMTP||connection, ACL for
20800 The ACL test specified by \acl@_smtp@_connect\ happens after the test specified
20801 by \host__reject__connection\ (which is now an anomaly) and any TCP Wrappers
20802 testing (if configured).
20805 .section The QUIT ACL
20806 .rset SECTQUITACL "~~chapter.~~section"
20807 .index \\QUIT\\, ACL for
20808 The ACL for the SMTP \\QUIT\\ command is anomalous, in that the
20809 outcome of the ACL does not affect the response code to \\QUIT\\,
20810 which is always 221. Thus, the ACL does not in fact control any access.
20811 For this reason, the only verbs that are permitted are \accept\ and \warn\.
20813 This ACL can be used for tasks such as custom logging at the end of an SMTP
20814 session. For example, you can use ACL variables in other ACLs to count
20815 messages, recipients, etc., and log the totals at \\QUIT\\ time using one or
20816 more \logwrite\ modifiers on a \warn\ verb.
20818 You do not need to have a final \accept\, but if you do, you can use a
20819 \message\ modifier to specify custom text that is sent as part of the 221
20820 response to \\QUIT\\.
20822 This ACL is run only for a `normal' \\QUIT\\. For certain kinds of disastrous
20823 failure (for example, failure to open a log file, or when Exim is bombing out
20824 because it has detected an unrecoverable error), all SMTP commands from the
20825 client are given temporary error responses until \\QUIT\\ is received or the
20826 connection is closed. In these special cases, the \\QUIT\\ ACL does not run.
20829 .section The non-SMTP ACL
20830 .index non-smtp message, ACL for
20831 The non-SMTP ACL applies to all non-interactive incoming messages, that is, it
20832 applies to batch SMTP as well as to non-SMTP messages. (Batch SMTP is not
20833 really SMTP.) This ACL is run just before the \*local@_scan()*\ function. Any
20834 kind of rejection is treated as permanent, because there is no way of sending a
20835 temporary error for these kinds of message. Many of the ACL conditions (for
20836 example, host tests, and tests on the state of the SMTP connection such as
20837 encryption and authentication) are not relevant and are forbidden in this ACL.
20840 .section Finding an ACL to use
20841 .index ~~ACL||finding which to use
20842 The value of an \acl@_smtp@_$it{xxx}\ option is expanded before use, so you can
20843 use different ACLs in different circumstances. The resulting string does not
20844 have to be the name of an ACL in the configuration file; there are other
20845 possibilities. Having expanded the string, Exim searches for an ACL as follows:
20847 If the string begins with a slash, Exim uses it as a file name, and reads its
20848 contents as an ACL. The lines are processed in the same way as lines in the
20849 Exim configuration file. In particular, continuation lines are supported, blank
20850 lines are ignored, as are lines whose first non-whitespace character is `@#'.
20851 If the file does not exist or cannot be read, an error occurs (typically
20852 causing a temporary failure of whatever caused the ACL to be run). For example:
20854 acl_smtp_data = /etc/acls/\
20855 ${lookup{$sender_host_address}lsearch\
20856 {/etc/acllist}{$value}{default}}
20858 This looks up an ACL file to use on the basis of the host's IP address, falling
20859 back to a default if the lookup fails. If an ACL is successfully read from a
20860 file, it is retained in memory for the duration of the Exim process, so that it
20861 can be re-used without having to re-read the file.
20863 If the string does not start with a slash, and does not contain any spaces,
20864 Exim searches the ACL section of the configuration for an ACL whose name
20865 matches the string.
20867 If no named ACL is found, or if the string contains spaces, Exim parses
20868 the string as an inline ACL. This can save typing in cases where you just
20869 want to have something like
20871 acl_smtp_vrfy = accept
20873 in order to allow free use of the \\VRFY\\ command. Such a string may contain
20874 newlines; it is processed in the same way as an ACL that is read from a file.
20878 .section ACL return codes
20879 .index ~~ACL||return codes
20881 Except for the \\QUIT\\ ACL, which does not affect the SMTP return code (see
20882 section ~~SECTQUITACL above), the
20884 result of running an ACL is either `accept' or `deny', or, if some test
20885 cannot be completed (for example, if a database is down), `defer'. These
20886 results cause 2$it{xx}, 5$it{xx}, and 4$it{xx} return codes, respectively, to
20887 be used in the SMTP dialogue. A fourth return, `error', occurs when there is an
20888 error such as invalid syntax in the ACL. This also causes a 4$it{xx} return
20892 For the non-SMTP ACL, `defer' and `error' are treated in the same way as
20893 `deny', because there is no mechanism for passing temporary errors to the
20894 submitters of non-SMTP messages.
20897 ACLs that are relevant to message reception may also return `discard'. This
20898 has the effect of `accept', but causes either the entire message or an
20899 individual recipient address to be discarded. In other words, it is a
20900 blackholing facility. Use it with care.
20902 If the ACL for \\MAIL\\ returns `discard', all recipients are discarded, and no
20903 ACL is run for subsequent \\RCPT\\ commands. The effect of `discard' in a
20904 \\RCPT\\ ACL is to discard just the one recipient address. If there are no
20905 recipients left when the message's data is received, the \\DATA\\ ACL is not
20906 run. A `discard' return from the \\DATA\\ or the non-SMTP ACL discards all the
20907 remaining recipients.
20909 The `discard' return is not permitted for the \acl@_smtp@_predata\ ACL.
20912 .index \*local@_scan()*\ function||when all recipients discarded
20913 The \*local@_scan()*\ function is always run, even if there are no remaining
20914 recipients; it may create new recipients.
20917 .section Unset ACL options
20918 .index ~~ACL||unset options
20919 The default actions when any of the \acl@_$it{xxx}\ options are unset are not
20920 all the same. \**Note**\: These defaults apply only when the relevant ACL is
20921 not defined at all. For any defined ACL, the default action when control reaches
20922 the end of the ACL statements is `deny'.
20924 For \acl@_not@_smtp\, \acl@_smtp@_auth\, \acl@_smtp@_connect\,
20925 \acl@_smtp@_data\, \acl@_smtp@_helo\, \acl__smtp__mail\, \acl@_smtp@_mailauth\,
20927 \acl@_smtp@_predata\, \acl@_smtp@_quit\,
20929 and \acl@_smtp@_starttls\, the action when the ACL is not defined is `accept'.
20931 For the others (\acl@_smtp@_etrn\, \acl@_smtp@_expn\, \acl@_smtp@_rcpt\, and
20932 \acl@_smtp@_vrfy\), the action when the ACL is not defined is `deny'.
20933 This means that \acl@_smtp@_rcpt\ must be defined in order to receive any
20934 messages over an SMTP connection. For an example, see the ACL in the default
20935 configuration file.
20939 .section Data for message ACLs
20940 .index ~~ACL||data for message ACL
20941 When an ACL for \\MAIL\\, \\RCPT\\, or \\DATA\\ is being run, the variables
20942 that contain information about the host and the message's sender (for example,
20943 \$sender@_host@_address$\ and \$sender@_address$\) are set, and can be used in
20944 ACL statements. In the case of \\RCPT\\ (but not \\MAIL\\ or \\DATA\\),
20945 \$domain$\ and \$local@_part$\ are set from the argument address.
20947 When an ACL for the \\AUTH\\ parameter of \\MAIL\\ is being run, the variables
20948 that contain information about the host are set, but \$sender@_address$\ is not
20951 Section ~~SECTauthparamail contains a discussion of this parameter and
20955 The \$message@_size$\ variable is set to the value of the \\SIZE\\ parameter on
20956 the \\MAIL\\ command at \\MAIL\\ and \\RCPT\\ time, or -1 if that parameter was
20957 not given. Its value is updated to the true message size by the time the ACL
20958 after \\DATA\\ is run.
20960 The \$rcpt@_count$\ variable increases by one for each \\RCPT\\ command
20961 received. The \$recipients@_count$\ variable increases by one each time a
20962 \\RCPT\\ command is accepted, so while an ACL for \\RCPT\\ is being processed,
20963 it contains the number of previously accepted recipients. At \\DATA\\ time,
20964 \$rcpt@_count$\ contains the total number of \\RCPT\\ commands, and
20965 \$recipients@_count$\ contains the total number of accepted recipients.
20969 .section Data for non-message ACLs
20970 .rset SECTdatfornon "~~chapter.~~section"
20971 .index ~~ACL||data for non-message ACL
20973 When an ACL is being run for \\AUTH\\, \\EHLO\\, \\ETRN\\, \\EXPN\\, \\HELO\\,
20975 \\STARTTLS\\, or \\VRFY\\, the remainder of the SMTP command line is placed in
20976 \$smtp@_command@_argument$\. This can be tested using a \condition\ condition.
20977 For example, here is an ACL for use with \\AUTH\\, which insists that either
20978 the session is encrypted, or the CRAM-MD5 authentication method is used. In
20979 other words, it does not permit authentication methods that use cleartext
20980 passwords on unencrypted connections.
20983 accept encrypted = *
20986 accept condition = ${if eq{${uc:$smtp_command_argument}}\
20990 deny message = TLS encryption or CRAM-MD5 required
20992 (Another way of applying this restriction is to arrange for the authenticators
20993 that use cleartext passwords not to be advertised when the connection is not
20994 encrypted. You can use the generic \server@_advertise@_condition\ authenticator
20995 option to do this.)
20998 .section Format of an ACL
20999 .index ~~ACL||format of
21000 .index ~~ACL||verbs, definition of
21001 An individual ACL consists of a number of statements. Each statement starts
21002 with a verb, optionally followed by a number of conditions and `modifiers'.
21004 Modifiers can change the way the verb operates, define error and log messages,
21005 set variables, insert delays, and vary the processing of accepted messages.
21008 If all the conditions are met, the verb is obeyed. The same condition may be
21009 used (with different arguments) more than once in the same statement. This
21010 provides a means of specifying an `and' conjunction between conditions. For
21013 deny dnslists = list1.example
21014 dnslists = list2.example
21016 If there are no conditions, the verb is always obeyed.
21018 Exim stops evaluating the conditions and modifiers when it reaches a condition
21019 that fails. What happens then
21021 depends on the verb (and in one case, on a special modifier). Not all the
21022 conditions make sense at every testing point. For example, you cannot test a
21023 sender address in the ACL that is run for a \\VRFY\\ command.
21026 The ACL verbs are as follows:
21028 \accept\: If all the conditions are met, the ACL returns `accept'. If any of
21029 the conditions are not met, what happens depends on whether \endpass\ appears
21030 among the conditions (for syntax see below). If the failing condition is before
21031 \endpass\, control is passed to the next ACL statement; if it is after
21032 \endpass\, the ACL returns `deny'. Consider this statement, used to check a
21035 accept domains = +local_domains
21039 If the recipient domain does not match the \domains\ condition, control passes
21040 to the next statement. If it does match, the recipient is verified, and the
21041 command is accepted if verification succeeds. However, if verification fails,
21042 the ACL yields `deny', because the failing condition is after \endpass\.
21044 \defer\: If all the conditions are met, the ACL returns `defer' which, in an
21045 SMTP session, causes a 4\*xx*\ response to be given. For a non-SMTP ACL,
21046 \defer\ is the same as \deny\, because there is no way of sending a temporary
21047 error. For a \\RCPT\\ command, \defer\ is much the same as using a
21048 \%redirect%\ router and \":defer:"\ while verifying, but the \defer\ verb can
21049 be used in any ACL, and even for a recipient it might be a simpler approach.
21051 \deny\: If all the conditions are met, the ACL returns `deny'. If any of the
21052 conditions are not met, control is passed to the next ACL statement. For
21055 deny dnslists = blackholes.mail-abuse.org
21057 rejects commands from hosts that are on a DNS black list.
21059 \discard\: This verb behaves like \accept\, except that it returns `discard'
21060 from the ACL instead of `accept'. It is permitted only on ACLs that are
21061 concerned with receiving messages, and it causes recipients to be discarded.
21062 If the \log@_message\ modifier is set when \discard\ operates, its contents are
21063 added to the line that is automatically written to the log.
21065 If \discard\ is used in an ACL for \\RCPT\\, just the one recipient is
21066 discarded; if used for \\MAIL\\, \\DATA\\ or in the non-SMTP ACL, all the
21067 message's recipients are discarded. Recipients that are discarded before
21068 \\DATA\\ do not appear in the log line when the \log@_recipients\ log selector
21071 \drop\: This verb behaves like \deny\, except that an SMTP connection is
21072 forcibly closed after the 5\*xx*\ error message has been sent. For example:
21074 drop message = I don't take more than 20 RCPTs
21077 condition = ${if > {$rcpt_count}{20}}
21080 There is no difference between \deny\ and \drop\ for the connect-time ACL. The
21081 connection is always dropped after sending a 550 response.
21083 \require\: If all the conditions are met, control is passed to the next ACL
21084 statement. If any of the conditions are not met, the ACL returns `deny'. For
21085 example, when checking a \\RCPT\\ command,
21087 require verify = sender
21089 passes control to subsequent statements only if the message's sender can be
21090 verified. Otherwise, it rejects the command.
21092 \warn\: If all the conditions are met, a header line is added to an incoming
21093 message and/or a line is written to Exim's main log. In all cases, control
21094 passes to the next ACL statement. The text of the added header line and the log
21095 line are specified by modifiers; if they are not present, a \warn\ verb just
21096 checks its conditions and obeys any `immediate' modifiers such as \set\ and
21099 There is more about adding header lines in section ~~SECTaddheadwarn.
21102 If any condition on a \warn\ statement cannot be completed (that is, there is
21103 some sort of defer), no header lines are added and the configured log line is
21104 not written. No further conditions or modifiers in the \warn\ statement are
21105 processed. The incident is logged, but the ACL continues to be processed, from
21106 the next statement onwards.
21108 If a \message\ modifier is present on a \warn\ verb in an ACL that is not
21109 testing an incoming message, it is ignored, and the incident is logged.
21111 A \warn\ statement may use the \log@_message\ modifier to cause a line to be
21112 written to the main log when the statement's conditions are true.
21113 If an identical log line is requested several times in the same message, only
21114 one copy is actually written to the log. If you want to force duplicates to be
21115 written, use the \logwrite\ modifier instead.
21117 When one of the \warn\ conditions is an address verification that fails, the
21118 text of the verification failure message is in \$acl@_verify@_message$\. If you
21119 want this logged, you must set it up explicitly. For example:
21121 warn !verify = sender
21122 log_message = sender verify failed: $acl_verify_message
21126 At the end of each ACL there is an implicit unconditional \deny\.
21128 As you can see from the examples above, the conditions and modifiers are
21129 written one to a line, with the first one on the same line as the verb, and
21130 subsequent ones on following lines. If you have a very long condition, you can
21131 continue it onto several physical lines by the usual backslash continuation
21132 mechanism. It is conventional to align the conditions vertically.
21135 .section ACL variables
21136 .rset SECTaclvariables "~~chapter.~~section"
21137 .index ~~ACL||variables
21138 There are some special variables that can be set during ACL processing. They
21139 can be used to pass information between different ACLs, different invocations
21140 of the same ACL in the same SMTP connection, and between ACLs and the routers,
21141 transports, and filters that are used to deliver a message. There are two sets
21142 of these variables:
21144 The values of \$acl@_c0$\ to \$acl@_c9$\ persist throughout an SMTP connection.
21145 They are never reset. Thus, a value that is set while receiving one message is
21146 still available when receiving the next message on the same SMTP connection.
21148 The values of \$acl@_m0$\ to \$acl@_m9$\ persist only while a message is being
21149 received. They are reset afterwards. They are also reset by \\MAIL\\, \\RSET\\,
21150 \\EHLO\\, \\HELO\\, and after starting up a TLS session.
21152 When a message is accepted, the current values of all the ACL variables are
21153 preserved with the message and are subsequently made available at delivery
21154 time. The ACL variables are set by modifier called \set\. For example:
21156 accept hosts = whatever
21157 set acl_m4 = some value
21159 \**Note**\: a leading dollar sign is not used when naming a variable that is to
21160 be set. If you want to set a variable without taking any action, you can use a
21161 \warn\ verb without any other modifiers or conditions.
21164 .section Condition and modifier processing
21165 .index ~~ACL||conditions, processing
21166 .index ~~ACL||modifiers, processing
21167 An exclamation mark preceding a condition negates its result. For example,
21169 deny domains = *.dom.example
21170 !verify = recipient
21172 causes the ACL to return `deny' if the recipient domain ends in
21173 \*dom.example*\ and the recipient address cannot be verified.
21175 The arguments of conditions and modifiers are expanded. A forced failure
21176 of an expansion causes a condition to be ignored, that is, it behaves as if the
21177 condition is true. Consider these two statements:
21179 accept senders = ${lookup{$host_name}lsearch\
21180 {/some/file}{$value}fail}
21181 accept senders = ${lookup{$host_name}lsearch\
21182 {/some/file}{$value}{}}
21184 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
21185 the returned list is searched, but if the lookup fails the behaviour is
21186 different in the two cases. The \fail\ in the first statement causes the
21187 condition to be ignored, leaving no further conditions. The \accept\ verb
21188 therefore succeeds. The second statement, however, generates an empty list when
21189 the lookup fails. No sender can match an empty list, so the condition fails,
21190 and therefore the \accept\ also fails.
21192 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
21193 specify actions that are taken as the conditions for a statement are checked;
21194 others specify text for messages that are used when access is denied or a
21195 warning is generated.
21197 The \control\ modifier affects the way an incoming message is handled.
21200 The positioning of the modifiers in an ACL statement important, because the
21201 processing of a verb ceases as soon as its outcome is known. Only those
21202 modifiers that have already been encountered will take effect. For example,
21203 consider this use of the \message\ modifier:
21205 require message = Can't verify sender
21207 message = Can't verify recipient
21209 message = This message cannot be used
21211 If sender verification fails, Exim knows that the result of the statement is
21212 `deny', so it goes no further. The first \message\ modifier has been seen, so
21213 its text is used as the error message. If sender verification succeeds, but
21214 recipient verification fails, the second message is used. If recipient
21215 verification succeeds, the third message becomes `current', but is never used
21216 because there are no more conditions to cause failure.
21218 For the \deny\ verb, on the other hand, it is always the last \message\
21219 modifier that is used, because all the conditions must be true for rejection to
21220 happen. Specifying more than one \message\ modifier does not make sense, and
21221 the message can even be specified after all the conditions. For example:
21224 !senders = *@my.domain.example
21225 message = Invalid sender from client host
21227 The `deny' result does not happen until the end of the statement is reached, by
21228 which time Exim has set up the message.
21231 .section ACL modifiers
21232 .rset SECTACLmodi "~~chapter.~~section"
21233 .index ~~ACL||modifiers, list of
21234 The ACL modifiers are as follows:
21238 .item "control = <<text>>"
21240 This modifier affects the subsequent processing of the SMTP connection or of an
21241 incoming message that is accepted. As there are now quite a few controls that
21242 can be applied, they are described separately in section ~~SECTcontrols below.
21245 Once one of these controls is set, it remains set for the message. For example,
21246 if \control\ is used in a \\RCPT\\ ACL, it applies to the whole message, not
21247 just the individual recipient. The \control\ modifier can be used in several
21248 different ways. For example:
21250 It can be at the end of an \accept\ statement:
21252 accept ...some conditions
21253 control = queue_only
21255 In this case, the control is applied when this statement yields `accept', in
21256 other words, when the conditions are all true.
21258 It can be in the middle of an \accept\ statement:
21260 accept ...some conditions...
21261 control = queue_only
21262 ...some more conditions...
21264 If the first set of conditions are true, the control is applied, even if the
21265 statement does not accept because one of the second set of conditions is false.
21266 In this case, some subsequent statement must yield `accept' for the control to
21269 It can be used with \warn\ to apply the control, leaving the
21270 decision about accepting or denying to a subsequent verb. For
21273 warn ...some conditions...
21277 This example of \warn\ does not contain \message\, \log@_message\, or
21278 \logwrite\, so it does not add anything to the message and does not write a log
21282 .item "delay = <<time>>"
21283 .index \-bh-\ option
21284 This modifier causes Exim to wait for the time interval before proceeding. The
21285 time is given in the usual Exim notation. This modifier may appear in any ACL.
21286 The delay happens as soon as the modifier is processed. However, when testing
21287 Exim using the \-bh-\ option, the delay is not actually imposed (an appropriate
21288 message is output instead).
21290 Like \control\, \delay\ can be used with \accept\ or
21291 \deny\, for example:
21293 deny ...some conditions...
21296 The delay happens if all the conditions are true, before the statement returns
21297 `deny'. Compare this with:
21300 ...some conditions...
21302 which waits for 30s before processing the conditions. The \delay\ modifier can
21303 also be used with \warn\ and together with \control\:
21305 warn ...some conditions...
21312 This modifier, which has no argument, is recognized only in \accept\
21313 statements. It marks the boundary between the conditions whose failure causes
21314 control to pass to the next statement, and the conditions whose failure causes
21315 the ACL to return `deny'. See the description of \accept\ above.
21317 .item "log@_message = <<text>>"
21318 This modifier sets up a message that is used as part of the log message if the
21319 ACL denies access or a \warn\ statement's conditions are true. For example:
21321 require log_message = wrong cipher suite $tls_cipher
21322 encrypted = DES-CBC3-SHA
21324 \log@_message\ adds to any underlying error message that may exist because of
21325 the condition failure. For example, while verifying a recipient address, a
21326 :::fail:: redirection might have already set up a message. Although the message
21327 is usually defined before the conditions to which it applies, the expansion
21328 does not happen until Exim decides that access is to be denied. This means that
21329 any variables that are set by the condition are available for inclusion in the
21330 message. For example, the \$dnslist@_<<xxx>>$\ variables are set after a DNS
21331 black list lookup succeeds. If the expansion of \log@_message\ fails, or if the
21332 result is an empty string, the modifier is ignored.
21334 If you want to use a \warn\ statement to log the result of an address
21335 verification, you can use \$acl__verify__message$\ to include the verification
21338 If \log@_message\ is used with a \warn\ statement, `Warning:' is added to the
21339 start of the logged message. If the same warning log message is requested more
21340 than once while receiving a single email message, only one copy is actually
21341 logged. If you want to log multiple copies, use \logwrite\ instead of
21342 \log@_message\. In the absence of \log@_message\ and \logwrite\, nothing is
21343 logged for a succesful \warn\ statement.
21345 If \log@_message\ is not present and there is no underlying error message (for
21346 example, from the failure of address verification), but \message\ is present,
21347 the \message\ text is used for logging rejections. However, if any text for
21348 logging contains newlines, only the first line is logged. In the absence of
21349 both \log@_message\ and \message\, a default built-in message is used for
21350 logging rejections.
21352 .item "logwrite = <<text>>"
21353 .index log||in ACL, immediate
21354 This modifier writes a message to a log file as soon as it is encountered when
21355 processing an ACL. (Compare \log@_message\, which, except in the case of
21356 \warn\, is used only if the ACL statement denies access.) The \logwrite\
21357 modifier can be used to log special incidents in ACLs. For example:
21359 accept <<some special conditions>>
21361 logwrite = froze message because ...
21363 By default, the message is written to the main log. However, it may begin
21364 with a colon, followed by a comma-separated list of log names, and then
21365 another colon, to specify exactly which logs are to be written. For
21368 logwrite = :main,reject: text for main and reject logs
21369 logwrite = :panic: text for panic log only
21372 .item "message = <<text>>"
21373 This modifier sets up a text string that is expanded and used as an error
21374 message if the current statement causes the ACL to deny access. The expansion
21375 happens at the time Exim decides that access is to be denied, not at the time
21376 it processes \message\. If the expansion fails, or generates an empty string,
21377 the modifier is ignored. For ACLs that are triggered by SMTP commands, the
21378 message is returned as part of the SMTP error response.
21380 The \message\ modifier is also used with the \warn\ verb to specify one or more
21381 header lines to be added to an incoming message when all the conditions are
21382 true. See section ~~SECTaddheadwarn for more details. If \message\ is used with
21383 \warn\ in an ACL that is not concerned with receiving a message, it has no
21386 The text is literal; any quotes are taken as literals, but because the string
21387 is expanded, backslash escapes are processed anyway. If the message contains
21388 newlines, this gives rise to a multi-line SMTP response. Like \log@_message\,
21389 the contents of \message\ are not expanded until after a condition has failed.
21391 If \message\ is used on a statement that verifies an address, the message
21392 specified overrides any message that is generated by the verification process.
21393 However, the original message is available in the variable
21394 \$acl@_verify@_message$\, so you can incorporate it into your message if you
21395 wish. In particular, if you want the text from \:fail:\ items in \%redirect%\
21396 routers to be passed back as part of the SMTP response, you should either not
21397 use a \message\ modifier, or make use of \$acl@_verify@_message$\.
21399 .item "set <<acl@_name>> = <<value>>"
21400 This modifier puts a value into one of the ACL variables (see section
21401 ~~SECTaclvariables).
21407 .section Use of the control modifier
21408 .rset SECTcontrols "~~chapter.~~section"
21409 .index \control\ modifier
21410 The \control\ modifier supports the following settings:
21414 .item "control = caseful@_local@_part"
21415 .item "control = caselower@_local@_part"
21416 .index ~~ACL||case of local part in
21417 .index case of local parts
21418 These two controls are permitted only in the ACL specified by \acl@_smtp@_rcpt\
21419 (that is, during \\RCPT\\ processing). By default, the contents of
21420 \$local@_part$\ are lower cased before ACL processing. If
21421 `caseful@_local@_part' is specified, any uppercase letters in the original
21422 local part are restored in \$local@_part$\ for the rest of the ACL, or until a
21423 control that sets `caselower@_local@_part' is encountered. However, this
21424 applies only to local part handling that takes place directly in the ACL (for
21425 example, as a key in lookups). If a test to verify the recipient is obeyed, the
21426 case-related handling of the local part during the verification is controlled
21427 by the router configuration (see the \caseful@_local@_part\ generic router
21430 This facility could be used, for example, to add a spam score to local parts
21431 containing upper case letters. For example, using \$acl@_m4$\ to accumulate the
21434 warn control = caseful_local_part
21435 set acl_m4 = ${eval:\
21437 ${if match{$local_part}{[A-Z]}{1}{0}}\
21439 control = caselower_local_part
21441 Notice that we put back the lower cased version afterwards, assuming that
21442 is what is wanted for subsequent tests.
21444 .item "control = enforce@_sync"
21445 .item "control = no@_enforce@_sync"
21446 .index SMTP||synchronization checking
21447 .index synchronization checking in SMTP
21448 These controls make it possible to be selective about when SMTP synchronization
21449 is enforced. The global option \smtp@_enforce@_sync\ specifies the initial
21450 state of the switch (it is true by default). See the description of this option
21451 in chapter ~~CHAPmainconfig for details of SMTP synchronization checking.
21453 These two controls can appear in any ACL except the one for the non-SMTP
21454 messages. The most straightforward place to put them is in the ACL defined by
21455 \acl@_smtp@_connect\, which is run at the start of an incoming SMTP connection,
21456 before the first synchronization check. The expected use is to turn off the
21457 synchronization checks for badly-behaved hosts that you nevertheless need to
21460 .item "control = fakereject/<<message>>"
21461 .index fake rejection
21462 .index rejection, fake
21463 This control is permitted only for the \\MAIL\\, \\RCPT\\, and \\DATA\\ ACLs,
21464 in other words, only when an SMTP message is being received. If Exim accepts
21465 the message, instead the final 250 response, a 550 rejection message is sent.
21466 However, Exim proceeds to deliver the message as normal.
21468 The text for the 550 response is taken from the \control\ modifier. If no
21469 message is supplied, the following is used:
21471 550-Your message has been rejected but is being
21472 550-kept for evaluation.
21473 550-If it was a legit message, it may still be
21474 550 delivered to the target recipient(s).
21476 This facilty should be used with extreme caution.
21479 .item "control = freeze"
21480 .index frozen messages||forcing in ACL
21481 This control is permitted only for the \\MAIL\\, \\RCPT\\, \\DATA\\, and
21482 non-SMTP ACLs, in other words, only when a message is being received. If the
21483 message is accepted, it is placed on Exim's queue and frozen.
21486 .item "control = no@_multiline@_response"
21487 .index multiline responses, suppressing
21488 This control is permitted for any ACL except the one for non-SMTP messages.
21489 It seems that there are broken clients in use that cannot handle multiline
21490 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
21492 If this control is set, multiline SMTP responses from ACL rejections are
21493 suppressed. One way of doing this would have been to put out these responses as
21494 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
21495 (`use multiline responses for more' it says -- ha!), and some of the responses
21496 might get close to that. So this facility, which is after all only a sop to
21497 broken clients, is implemented by doing two very easy things:
21499 Extra information that is normally output as part of a rejection
21500 caused by sender verification failure is omitted. Only the final line
21501 (typically `sender verification failed') is sent.
21503 If a \message\ modifier supplies a multiline response, only the first
21506 The setting of the switch can, of course, be made conditional on the
21510 .item "control = queue@_only"
21511 .index \queue@_only\
21512 .index queueing incoming messages
21513 This control is permitted only for the \\MAIL\\, \\RCPT\\, \\DATA\\, and
21514 non-SMTP ACLs, in other words, only when a message is being received. If the
21515 message is accepted, it is placed on Exim's queue and left there for delivery
21516 by a subsequent queue runner. No immediate delivery process is started. In
21517 other words, it has the effect of the \queue@_only\ global option for just the
21521 .item "control = submission/<<options>>"
21522 .index message||submission
21523 .index submission mode
21524 This control is permitted only for the \\MAIL\\, \\RCPT\\, and start of data
21525 ACLs (the latter is the one defined by \acl@_smtp@_predata\). Setting it tells
21526 Exim that the message is a submission from a local MUA. In this case, Exim
21527 operates in `submission mode', and applies certain fixups to the message if
21528 necessary. For example, it add a ::Date:: header line if one is not present.
21529 This control is not permitted in the \\DATA\\ ACL, because that is too late
21530 (the message has already been created).
21532 Chapter ~~CHAPmsgproc describes the processing that Exim applies to messages.
21533 Section ~~SECTsubmodnon covers the processing that happens in submission mode;
21534 the available options for this control are described there.
21541 .section Adding header lines with the warn verb
21542 .rset SECTaddheadwarn "~~chapter.~~section"
21543 .index header lines||adding in an ACL
21544 .index header lines||position of added lines
21545 The \message\ modifier can be used on a \warn\ statement to add an extra header
21546 line to an incoming message, as in this example:
21548 warn message = X-blacklisted-at: $dnslist_domain
21549 dnslists = sbl.spamhaus.org : \
21550 dialup.mail-abuse.org
21552 If an identical header line is requested several times (provoked, for example,
21553 by multiple \\RCPT\\ commands), only one copy is actually added to the message.
21554 If the text of the \message\ modifier contains one or more newlines that are
21555 not followed by a space or a tab, it is assumed to contain multiple header
21556 lines. Each one is checked for valid syntax; \"X-ACL-Warn:"\ is added to the
21557 front of any line that is not a valid header line.
21559 By default, new lines are added at the end of the existing header lines.
21560 However, you can specify that any particular header line should be added right
21561 at the start (before all the ::Received:: lines), immediately after the first
21562 block of ::Received:: lines, or immediately before any line that is not a
21563 ::Received:: or ::Resent-something:: header.
21565 This is done by specifying `:at@_start:', `:after@_received:', or
21566 `:at@_start@_rfc:' (or, for completeness, `:at@_end:') before the text of the
21567 header line, respectively. (Header text cannot start with a colon, as there has
21568 to be a header name first.) For example:
21570 warn message = :after_received:X-My-Header: something or other...
21573 If more than one header is supplied in a single warn statement, each one is
21574 treated independently and can therefore be placed differently. If you add
21575 more than one line at the start, or after the Received: block, they will
21576 end up in reverse order.
21578 \**Warning**\: This facility currently applies only to header lines that are
21579 added in an ACL. It does NOT work for header lines that are added in a
21580 system filter or in a router or transport.
21582 .index header lines||added, visibility of
21583 Header lines that are added by an ACL at \\MAIL\\ or \\RCPT\\ time are not
21584 visible in string expansions in ACLs for subsequent \\RCPT\\ commands or in the
21585 \acl@_smtp@_predata\ ACL. However, they are visible in string expansions in the
21586 ACL that is run after \\DATA\\ is complete (the \acl@_smtp@_data\ ACL). This is
21587 also true for header lines that are added in the \acl@_smtp@_predata\ ACL.
21588 If a message is rejected after \\DATA\\, all added header lines are included in
21589 the entry that is written to the reject log.
21591 If you want to preserve data between \\MAIL\\, \\RCPT\\, and the
21592 \acl@_smtp@_predata\ ACLs, you can use ACL variables, as described in section
21593 ~~SECTaclvariables.
21598 .section ACL conditions
21599 .rset SECTaclconditions "~~chapter.~~section"
21600 .index ~~ACL||conditions, list of
21602 Some of conditions listed in this section are available only when Exim is
21603 compiled with the content-scanning extension. They are included here briefly
21604 for completeness. More detailed descriptions can be found in the discussion on
21605 content scanning in chapter ~~CHAPexiscan.
21608 Not all conditions are relevant in all circumstances. For example, testing
21609 senders and recipients does not make sense in an ACL that is being run as the
21610 result of the arrival of an \\ETRN\\ command, and checks on message headers can
21611 be done only in the ACLs specified by \acl@_smtp@_data\ and \acl__not__smtp\.
21612 You can use the same condition (with different parameters) more than once in
21613 the same ACL statement. This provides a way of specifying an `and' conjunction.
21614 The conditions are as follows:
21618 .item "acl = <<name of acl or ACL string or file name >>"
21619 .index ~~ACL||nested
21620 .index ~~ACL||indirect
21621 The possible values of the argument are the same as for the
21622 \acl@_smtp@_$it{xxx}\ options. The named or inline ACL is run. If it returns
21623 `accept' the condition is true; if it returns `deny' the condition is false. If
21624 it returns `defer', the current ACL returns `defer'
21626 unless the condition is on a \warn\ verb. In that case, a `defer' return makes
21627 the condition false. This means that further processing of the \warn\ verb
21628 ceases, but processing of the ACL continues.
21631 If the nested \acl\ returns `drop' and the outer condition denies access,
21632 the connection is dropped. If it returns `discard', the verb must be \accept\
21633 or \discard\, and the action is taken immediately -- no further conditions are
21636 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
21637 loops. This condition allows you to use different ACLs in different
21638 circumstances. For example, different ACLs can be used to handle \\RCPT\\
21639 commands for different local users or different local domains.
21641 .item "authenticated = <<string list>>"
21642 .index authentication||ACL checking
21643 .index ~~ACL||testing for authentication
21644 If the SMTP connection is not authenticated, the condition is false. Otherwise,
21645 the name of the authenticator is tested against the list. To test for
21646 authentication by any authenticator, you can set
21651 .item "condition = <<string>>"
21652 .index customizing||ACL condition
21653 .index ~~ACL||customized test
21654 This feature allows you to make up custom conditions. If the result of
21655 expanding the string is an empty string, the number zero, or one of the strings
21656 `no' or `false', the condition is false. If the result is any non-zero number,
21657 or one of the strings `yes' or `true', the condition is true. For any other
21658 values, some error is assumed to have occured, and the ACL returns `defer'.
21662 .item "decode = <<location>>"
21663 This condition is available only when Exim is compiled with the
21664 content-scanning extension, and it is allowed only the the ACL defined by
21665 \acl@_smtp@_mime\. It causes the current MIME part to be decoded into a file.
21666 For details, see chapter ~~CHAPexiscan.
21670 .item "dnslists = <<list of domain names and other data>>"
21671 .index DNS list||in ACL
21672 .index black list (DNS)
21673 .index ~~ACL||testing a DNS list
21674 This condition checks for entries in DNS black lists. These are also known as
21675 `RBL lists', after the original Realtime Blackhole List, but note that the use
21676 of the lists at \*mail-abuse.org*\ now carries a charge.
21677 There are too many different variants of this condition to describe briefly
21678 here. See sections ~~SECTmorednslists--~~SECTmorednslistslast for details.
21680 .item "domains = <<domain list>>"
21681 .index domain||ACL checking
21682 .index ~~ACL||testing a recipient domain
21683 This condition is relevant only after a \\RCPT\\ command. It checks that the
21684 domain of the recipient address is in the domain list. If percent-hack
21685 processing is enabled, it is done before this test is done. If the check
21686 succeeds with a lookup, the result of the lookup is placed in \$domain@_data$\
21687 until the next \domains\ test.
21689 .item "encrypted = <<string list>>"
21690 .index encryption||checking in an ACL
21691 .index ~~ACL||testing for encryption
21692 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
21693 name of the cipher suite in use is tested against the list. To test for
21694 encryption without testing for any specific cipher suite(s), set
21699 .item "hosts = << host list>>"
21700 .index host||ACL checking
21701 .index ~~ACL||testing the client host
21702 This condition tests that the calling host matches the host list. If you have
21703 name lookups or wildcarded host names and IP addresses in the same host list,
21704 you should normally put the IP addresses first. For example, you could have:
21706 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
21708 The reason for this lies in the left-to-right way that Exim processes lists.
21709 It can test IP addresses without doing any DNS lookups, but when it reaches an
21710 item that requires a host name, it fails if it cannot find a host name to
21711 compare with the pattern. If the above list is given in the opposite order, the
21712 \accept\ statement fails for a host whose name cannot be found, even if its
21713 IP address is 10.9.8.7.
21715 If you really do want to do the name check first, and still recognize the IP
21716 address even if the name lookup fails, you can rewrite the ACL like this:
21718 accept hosts = dbm;/etc/friendly/hosts
21719 accept hosts = 10.9.8.7
21721 The default action on failing to find the host name is to assume that the host
21722 is not in the list, so the first \accept\ statement fails. The second statement
21723 can then check the IP address.
21725 If a \hosts\ condition is satisfied by means of a lookup, the result
21726 of the lookup is made available in the \$host@_data$\ variable. This
21727 allows you, for example, to set up a statement like this:
21729 deny hosts = net-lsearch;/some/file
21730 message = $host_data
21732 which gives a custom error message for each denied host.
21734 .item "local@_parts = <<local part list>>"
21735 .index local part||ACL checking
21736 .index ~~ACL||testing a local part
21737 This condition is relevant only after a \\RCPT\\ command. It checks that the
21738 local part of the recipient address is in the list. If percent-hack processing
21739 is enabled, it is done before this test. If the check succeeds with a lookup,
21740 the result of the lookup is placed in \$local@_part@_data$\ until the next
21741 \local@_parts\ test.
21745 .item "malware = <<option>>"
21746 This condition is available only when Exim is compiled with the
21747 content-scanning extension. It causes the incoming message to be scanned for
21748 viruses. For details, see chapter ~~CHAPexiscan.
21753 .item "mime@_regex = <<list of regular expressions>>"
21754 This condition is available only when Exim is compiled with the
21755 content-scanning extension, and it is allowed only the the ACL defined by
21756 \acl@_smtp@_mime\. It causes the current MIME part to be scanned for a match
21757 with any of the regular expressions. For details, see chapter ~~CHAPexiscan.
21761 .item "recipients = <<address list>>"
21762 .index recipient||ACL checking
21763 .index ~~ACL||testing a recipient
21764 This condition is relevant only after a \\RCPT\\ command. It checks the entire
21765 recipient address against a list of recipients.
21769 .item "regex = <<list of regular expressions>>"
21770 This condition is available only when Exim is compiled with the
21771 content-scanning extension. It causes the incoming message to be scanned
21772 for a match with any of the regular expressions. For details, see chapter
21777 .item "sender@_domains = <<domain list>>"
21778 .index sender||ACL checking
21779 .index ~~ACL||testing a sender domain
21780 This condition tests the domain of the sender of the message against the given
21782 \**Note**\: the domain of the sender address is in
21783 \$sender@_address@_domain$\. It is \*not*\ put in \$domain$\ during the testing
21784 of this condition. This is an exception to the general rule for testing
21785 domain lists. It is done this way so that, if this condition is used in an
21786 ACL for a \\RCPT\\ command, the recipient's domain (which is in \$domain$\) can
21787 be used to influence the sender checking.
21789 .item "senders = <<address list>>"
21790 .index sender||ACL checking
21791 .index ~~ACL||testing a sender
21792 This condition tests the sender of the message against the given list. To test
21793 for a bounce message, which has an empty sender, set
21800 .item "spam = <<username>>"
21801 This condition is available only when Exim is compiled with the
21802 content-scanning extension. It causes the incoming message to be scanned by
21803 SpamAssassin. For details, see chapter ~~CHAPexiscan.
21807 .item "verify = certificate"
21808 .index TLS||client certificate verification
21809 .index certificate||verification of client
21810 .index ~~ACL||certificate verification
21811 This condition is true in an SMTP session if the session is encrypted, and a
21812 certificate was received from the client, and the certificate was verified. The
21813 server requests a certificate only if the client matches \tls@_verify@_hosts\
21814 or \tls@_try@_verify@_hosts\ (see chapter ~~CHAPTLS).
21816 .item "verify = header@_sender/<<options>>"
21817 .index ~~ACL||verifying sender in the header
21818 .index header lines||verifying the sender in
21819 .index sender||verifying in header
21820 .index verifying||sender in header
21821 This condition is relevant only in an ACL that is run after a message has been
21822 received, that is, in an ACL specified by \acl@_smtp@_data\
21824 or \acl@_not@_smtp\. It checks that there is a verifiable address in at least
21825 one of the ::Sender::, ::Reply-To::, or ::From:: header lines. Such an address
21826 is loosely thought of as a `sender' address (hence the name of the test).
21827 However, an address that appears in one of these headers need not be an address
21828 that accepts bounce messages; only sender addresses in envelopes are required
21829 to accept bounces. Therefore, if you use the callout option on this check, you
21830 might want to arrange for a non-empty address in the \\MAIL\\ command.
21833 Details of address verification and the options are given later, starting at
21834 section ~~SECTaddressverification (callouts are described in section
21835 ~~SECTcallver). You can combine this condition with the \senders\ condition to
21836 restrict it to bounce messages only:
21839 message = A valid sender header is required for bounces
21840 !verify = header_sender
21843 .item "verify = header@_syntax"
21844 .index ~~ACL||verifying header syntax
21845 .index header lines||verifying syntax
21846 .index verifying||header syntax
21847 This condition is relevant only in an ACL that is run after a message has been
21848 received, that is, in an ACL specified by \acl@_smtp@_data\
21849 or \acl@_not@_smtp\.
21850 It checks the syntax of all header lines that can contain lists of addresses
21851 (::Sender::, ::From::, ::Reply-To::, ::To::, ::Cc::, and ::Bcc::).
21852 Unqualified addresses (local parts without domains) are permitted only in
21853 locally generated messages and from hosts that match
21854 \sender@_unqualified@_hosts\ or \recipient@_unqualified@_hosts\, as
21857 Note that this condition is a syntax check only. However, a common spamming
21858 ploy is to send syntactically invalid headers such as
21862 and this condition can be used to reject such messages.
21864 .item "verify = helo"
21865 .index ~~ACL||verifying HELO/EHLO
21866 .index \\HELO\\||verifying
21867 .index \\EHLO\\||verifying
21868 .index verifying||\\EHLO\\
21869 .index verifying||\\HELO\\
21870 This condition is true if a \\HELO\\ or \\EHLO\\ command has been received from
21871 the client host, and its contents have been verified. Verification of these
21872 commands does not happen by default. See the description of the
21873 \helo@_verify@_hosts\ and \helo@_try@_verify@_hosts\ options for details of how
21876 .item "verify = recipient/<<options>>"
21877 .index ~~ACL||verifying recipient
21878 .index recipient||verifying
21879 .index verifying||recipient
21880 This condition is relevant only after a \\RCPT\\ command. It verifies the
21881 current recipient. Details of address verification are given later, starting at
21882 section ~~SECTaddressverification. After a recipient has been verified, the
21883 value of \$address@_data$\ is the last value that was set while routing the
21884 address. This applies even if the verification fails. When an address that is
21885 being verified is redirected to a single address, verification continues with
21886 the new address, and in that case, the subsequent value of \$address@_data$\ is
21887 the value for the child address.
21890 .item "verify = reverse@_host@_lookup"
21891 .index ~~ACL||verifying host reverse lookup
21892 .index host||verifying reverse lookup
21893 This condition ensures that a verified host name has been looked up from the IP
21894 address of the client host. (This may have happened already if the host name
21895 was needed for checking a host list, or if the host matched \host@_lookup\.)
21896 Verification ensures that the host name obtained from a reverse DNS lookup, or
21897 one of its aliases, does, when it is itself looked up in the DNS, yield the
21898 original IP address.
21900 If this condition is used for a locally generated message (that is, when there
21901 is no client host involved), it always succeeds.
21904 .item "verify = sender/<<options>>"
21905 .index ~~ACL||verifying sender
21906 .index sender||verifying
21907 .index verifying||sender
21908 This condition is relevant only after a
21909 \\MAIL\\ or \\RCPT\\ command, or after a message has been received (the
21910 \acl@_smtp@_data\ or \acl@_not@_smtp\ ACLs).
21911 If the message's sender is empty (that is, this is a bounce message), the
21912 condition is true. Otherwise, the sender address is verified. Details of
21913 verification are given later, starting at section ~~SECTaddressverification.
21914 Exim caches the result of sender verification, to avoid doing it more than once
21917 .item "verify = sender=address/<<options>>"
21918 This is a variation of the previous option, in which a modified address is
21919 verified as a sender.
21925 .section Using DNS lists
21926 .rset SECTmorednslists "~~chapter.~~section"
21927 .index DNS list||in ACL
21928 .index black list (DNS)
21929 .index ~~ACL||testing a DNS list
21930 In its simplest form, the \dnslists\ condition tests whether the calling host
21931 is on at least one of a number of DNS lists by looking up the inverted IP
21932 address in one or more DNS domains. For example, if the calling host's IP
21933 address is 192.168.62.43, and the ACL statement is
21935 deny dnslists = blackholes.mail-abuse.org : \
21936 dialups.mail-abuse.org
21938 the following records are looked up:
21940 43.62.168.192.blackholes.mail-abuse.org
21941 43.62.168.192.dialups.mail-abuse.org
21944 As soon as Exim finds an existing DNS record, processing of the list stops.
21945 Thus, multiple entries on the list provide an `or' conjunction. If you want to
21946 test that a host is on more than one list (an `and' conjunction), you can use
21947 two separate conditions:
21949 deny dnslists = blackholes.mail-abuse.org
21950 dnslists = dialups.mail-abuse.org
21953 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
21954 behaves as if the host
21956 does not match the list item, that is, as if the DNS record does not exist. If
21957 there are further items in the DNS list, they are processed.
21959 This is usually the required action when \dnslists\ is used with \deny\ (which
21960 is the most common usage), because it prevents a DNS failure from blocking
21961 mail. However, you can change this behaviour by putting one of the following
21962 special items in the list:
21963 .index \"+include@_unknown"\
21964 .index \"+exclude@_unknown"\
21965 .index \"+defer@_unknown"\
21967 +include@_unknown $rm{behave as if the item is on the list}
21968 +exclude@_unknown $rm{behave as if the item is not on the list (default)}
21969 +defer@_unknown $rm{give a temporary error}
21971 Each of these applies to any subsequent items on the list. For example:
21973 deny dnslists = +defer_unknown : foo.bar.example
21976 Testing the list of domains stops as soon as a match is found. If you want to
21977 warn for one list and block for another, you can use two different statements:
21979 deny dnslists = blackholes.mail-abuse.org
21980 warn message = X-Warn: sending host is on dialups list
21981 dnslists = dialups.mail-abuse.org
21984 DNS list lookups are cached by Exim for the duration of the SMTP session,
21985 so a lookup based on the IP address is done at most once for any incoming
21986 connection. Exim does not share information between multiple incoming
21987 connections (but your local name server cache should be active).
21991 .section Specifying the IP address for a DNS list lookup
21992 .index DNS list||keyed by explicit IP address
21993 By default, the IP address that is used in a DNS list lookup is the IP address
21994 of the calling host. However, you can specify another IP address by listing it
21995 after the domain name, introduced by a slash. For example:
21997 deny dnslists = black.list.tls/192.168.1.2
21999 This feature is not very helpful with explicit IP addresses; it is intended for
22000 use with IP addresses that are looked up, for example, the IP addresses of the
22001 MX hosts or nameservers of an email sender address. For an example, see section
22002 ~~SECTmulkeyfor below.
22006 .section DNS lists keyed on domain names
22007 .index DNS list||keyed by domain name
22008 There are some lists that are keyed on domain names rather than inverted IP
22009 addresses (see for example the \*domain based zones*\ link at
22010 \?http://www.rfc-ignorant.org/?\). No reversing of components is used with
22011 these lists. You can change the name that is looked up in a DNS list by listing
22012 it after the domain name, introduced by a slash. For example,
22014 deny message = Sender's domain is listed at $dnslist_domain
22015 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
22017 This particular example is useful only in ACLs that are obeyed after the
22018 \\RCPT\\ or \\DATA\\ commands, when a sender address is available. If (for
22019 example) the message's sender is \*user@@tld.example*\ the name that is looked
22020 up by this example is
22022 tld.example.dsn.rfc-ignorant.org
22025 A single \dnslists\ condition can contain entries for both names and IP
22026 addresses. For example:
22028 deny dnslists = sbl.spamhaus.org : \
22029 dsn.rfc-ignorant.org/$sender_address_domain
22031 The first item checks the sending host's IP address; the second checks a domain
22032 name. The whole condition is true if either of the DNS lookups succeeds.
22037 .section Multiple explicit keys for a DNS list
22038 .rset SECTmulkeyfor "~~chapter.~~section"
22039 .index DNS list||multiple keys for
22040 The syntax described above for looking up explicitly-defined values (either
22041 names or IP addresses) in a DNS blacklist is a simplification. After the domain
22042 name for the DNS list, what follows the slash can in fact be a list of items.
22043 As with all lists in Exim, the default separator is a colon. However, because
22044 this is a sublist within the list of DNS blacklist domains, it is necessary
22045 either to double the separators like this:
22047 dnslists = black.list.tld/name.1::name.2
22049 or to change the separator character, like this:
22051 dnslists = black.list.tld/<;name.1;name.2
22053 If an item in the list is an IP address, it is inverted before the DNS
22054 blacklist domain is appended. If it is not an IP address, no inversion
22055 occurs. Consider this condition:
22057 dnslists = black.list.tld/<;192.168.1.2;a.domain
22059 The DNS lookups that occur are:
22061 2.1.168.192.black.list.tld
22062 a.domain.black.list.tld
22064 Once a DNS record has been found (that matches a specific IP return
22065 address, if specified -- see section ~~SECTaddmatcon), no further lookups are
22066 done. If there is a temporary DNS error, the rest of the sublist of domains or
22067 IP addresses is tried. A temporary error for the whole dnslists item occurs
22068 only if no other DNS lookup in this sublist succeeds. In other words, a
22069 successful lookup for any of the items in the sublist overrides a temporary
22070 error for a previous item.
22072 The ability to supply a list of items after the slash is in some sense just a
22073 syntactic convenience. These two examples have the same effect:
22075 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
22076 dnslists = black.list.tld/a.domain::b.domain
22078 However, when the data for the list is obtained from a lookup, the second form
22079 is usually much more convenient. Consider this example:
22081 deny message = The mail servers for the domain \
22082 $sender_address_domain \
22083 are listed at $dnslist_domain ($dnslist_value); \
22085 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
22086 ${lookup dnsdb {>|mxh=\
22087 $sender_address_domain} }} }
22089 Note the use of \">|"\ in the dnsdb lookup to specify the separator for
22090 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
22091 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
22092 of expanding the condition might be something like this:
22094 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
22096 Thus, this example checks whether or not the IP addresses of the sender
22097 domain's mail servers are on the Spamhaus black list.
22102 .section Data returned by DNS lists
22103 .index DNS list||data returned from
22104 DNS lists are constructed using address records in the DNS. The original RBL
22105 just used the address 127.0.0.1 on the right hand side of each record, but the
22106 RBL+ list and some other lists use a number of values with different meanings.
22107 The values used on the RBL+ list are:
22112 127.1.0.3 $t DUL and RBL
22114 127.1.0.5 $t RSS and RBL
22115 127.1.0.6 $t RSS and DUL
22116 127.1.0.7 $t RSS and DUL and RBL
22118 Some DNS lists may return more than one address record.
22120 .section Variables set from DNS lists
22121 .index DNS list||variables set from
22122 When an entry is found in a DNS list, the variable \$dnslist@_domain$\
22123 contains the name of the domain that matched, \$dnslist@_value$\ contains the
22124 data from the entry, and \$dnslist@_text$\ contains the contents of any
22125 associated TXT record. If more than one address record is returned by the DNS
22126 lookup, all the IP addresses are included in \$dnslist@_value$\, separated by
22129 You can use these variables in \message\ or \log@_message\ modifiers --
22130 although these appear before the condition in the ACL, they are not expanded
22131 until after it has failed. For example:
22133 deny hosts = !+local_networks
22134 message = $sender_host_address is listed \
22136 dnslists = rbl-plus.mail-abuse.example
22140 .section Additional matching conditions for DNS lists
22141 .rset SECTaddmatcon "~~chapter.~~section"
22142 .index DNS list||matching specific returned data
22143 You can add an equals sign and an IP address after a \dnslists\ domain name in
22144 order to restrict its action to DNS records with a matching right hand side.
22147 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
22149 rejects only those hosts that yield 127.0.0.2. Without this additional data,
22150 any address record is considered to be a match. If more than one address record
22151 is found on the list, they are all checked for a matching right-hand side.
22153 More than one IP address may be given for checking, using a comma as a
22154 separator. These are alternatives -- if any one of them matches, the \dnslists\
22155 condition is true. For example:
22157 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
22160 If you want to specify a constraining address list and also specify names or IP
22161 addresses to be looked up, the constraining address list must be specified
22162 first. For example:
22164 deny dnslists = dsn.rfc-ignorant.org\
22165 =127.0.0.2/$sender_address_domain
22168 If the character `&' is used instead of `=', the comparison for each listed
22169 IP address is done by a bitwise `and' instead of by an equality test. In
22170 other words, the listed addresses are used as bit masks. The comparison is
22171 true if all the bits in the mask are present in the address that is being
22172 tested. For example:
22174 dnslists = a.b.c&0.0.0.3
22176 matches if the address is \*x.x.x.*\3, \*x.x.x.*\7, \*x.x.x.*\11, etc. If you
22177 want to test whether one bit or another bit is present (as opposed to both
22178 being present), you must use multiple values. For example:
22180 dnslists = a.b.c&0.0.0.1,0.0.0.2
22182 matches if the final component of the address is an odd number or two times
22186 .section Negated DNS matching conditions
22187 You can supply a negative list of IP addresses as part of a \dnslists\
22190 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
22192 means `deny if the host is in the black list at the domain \*a.b.c*\ and the IP
22193 address yielded by the list is either 127.0.0.2 or 127.0.0.3',
22195 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
22197 means `deny if the host is in the black list at the domain \*a.b.c*\ and the IP
22198 address yielded by the list is not 127.0.0.2 and not 127.0.0.3'. In other
22199 words, the result of the test is inverted if an exclamation mark appears before
22200 the `=' (or the `&') sign.
22202 \**Note**\: this kind of negation is not the same as negation in a domain,
22203 host, or address list (which is why the syntax is different).
22205 If you are using just one list, the negation syntax does not gain you much. The
22206 previous example is precisely equivalent to
22208 deny dnslists = a.b.c
22209 !dnslists = a.b.c=127.0.0.2,127.0.0.3
22211 However, if you are using multiple lists, the negation syntax is clearer.
22212 Consider this example:
22214 deny dnslists = sbl.spamhaus.org : \
22216 dnsbl.njabl.org!=127.0.0.3 : \
22219 Using only positive lists, this would have to be:
22221 deny dnslists = sbl.spamhaus.org : \
22223 deny dnslists = dnsbl.njabl.org
22224 !dnslists = dnsbl.njabl.org=127.0.0.3
22225 deny dnslists = relays.ordb.org
22227 which is less clear, and harder to maintain.
22231 .section DNS lists and IPv6
22232 .rset SECTmorednslistslast "~~chapter.~~section"
22233 .index IPv6||DNS black lists
22234 .index DNS list||IPv6 usage
22235 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
22236 nibble by nibble. For example, if the calling host's IP address is
22237 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
22239 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
22240 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
22242 (split over two lines here to fit on the page). Unfortunately, some of the DNS
22243 lists contain wildcard records, intended for IPv4, that interact badly with
22244 IPv6. For example, the DNS entry
22246 *.3.some.list.example. A 127.0.0.1
22248 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
22249 Unfortunately, it also matches the entire 3@:@:/4 IPv6 network.
22251 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
22252 \condition\ condition, as in this example:
22256 deny condition = ${if isip4{$sender_host_address}}
22259 dnslists = some.list.example
22263 .section Address verification
22264 .rset SECTaddressverification "~~chapter.~~section"
22265 .index verifying||address, options for
22266 .index policy control||address verification
22267 Several of the \verify\ conditions described in section ~~SECTaclconditions
22268 cause addresses to be verified. These conditions can be followed by options
22269 that modify the verification process. The options are separated from the
22270 keyword and from each other by slashes, and some of them contain parameters.
22273 verify = sender/callout
22274 verify = recipient/defer_ok/callout=10s,defer_ok
22277 The first stage of address verification, which always happens, is to run the
22278 address through the routers, in `verify mode'. Routers can detect the
22279 difference between verification and routing for delivery, and their actions can
22280 be varied by a number of generic options such as \verify\ and \verify@_only\
22281 (see chapter ~~CHAProutergeneric). If routing fails, verification fails.
22282 The available options are as follows:
22284 If the \callout\ option is specified, successful routing to one or more remote
22285 hosts is followed by a `callout' to those hosts as an additional check.
22286 Callouts and their sub-options are discussed in the next section.
22288 If there is a defer error while doing verification routing, the ACL
22289 normally returns `defer'. However, if you include \defer@_ok\ in the options,
22290 the condition is forced to be true instead. Note that this is a main
22291 verification option as well as a suboption for callouts.
22293 The \no@_details\ option is covered in section ~~SECTsenaddver, which discusses
22294 the reporting of sender address verification failures.
22297 .index verifying||address, differentiating failures
22298 After an address verification failure, \$sender@_verify@_failure$\ or
22299 \$recipient@_verify@_failure$\ (as appropriate) contains one of the following
22302 \qualify\: The address was unqualified (no domain), and the message
22303 was neither local nor came from an exempted host.
22305 \route\: Routing failed.
22307 \mail\: Routing succeeded, and a callout was attempted; rejection
22308 occurred at or before the \\MAIL\\ command (that is, on initial
22309 connection, \\HELO\\, or \\MAIL\\).
22311 \recipient\: The \\RCPT\\ command in a callout was rejected.
22313 \postmaster\: The postmaster check in a callout was rejected.
22316 The main use of these variables is expected to be to distinguish between
22317 rejections of \\MAIL\\ and rejections of \\RCPT\\ in callouts.
22322 .section Callout verification
22323 .rset SECTcallver "~~chapter.~~section"
22324 .index verifying||address, by callout
22325 .index callout||verification
22326 .index SMTP||callout verification
22327 For non-local addresses, routing verifies the domain, but is unable to do any
22328 checking of the local part. There are situations where some means of verifying
22329 the local part is desirable. One way this can be done is to make an SMTP
22330 \*callback*\ to the sending host (for a sender address) or a \*callforward*\ to
22331 a subsequent host (for a recipient address), to see if the host accepts the
22332 address. We use the term \*callout*\ to cover both cases. This facility should
22333 be used with care, because it can add a lot of resource usage to the cost of
22334 verifying an address. However, Exim does cache the results of callouts, which
22335 helps to reduce the cost. Details of caching are in the next section.
22337 Recipient callouts are usually used only between hosts that are controlled by
22338 the same administration. For example, a corporate gateway host could use
22339 callouts to check for valid recipients on an internal mailserver.
22340 A successful callout does not guarantee that a real delivery to the address
22341 would succeed; on the other hand, a failing callout does guarantee that
22342 a delivery would fail.
22344 If the \callout\ option is present on a condition that verifies an address, a
22345 second stage of verification occurs if the address is successfully routed to
22346 one or more remote hosts. The usual case is routing by a \%dnslookup%\ or a
22347 \%manualroute%\ router, where the router specifies the hosts. However, if a
22348 router that does not set up hosts routes to an \%smtp%\ transport with a
22349 \hosts\ setting, the transport's hosts are used. If an \%smtp%\ transport has
22350 \hosts@_override\ set, its hosts are always used, whether or not the router
22351 supplies a host list.
22353 The port that is used is taken from the transport, if it is specified and is a
22354 remote transport. (For routers that do verification only, no transport need be
22355 specified.) Otherwise, the default SMTP port is used. If a remote transport
22356 specifies an outgoing interface, this is used; otherwise the interface is not
22359 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
22360 test whether a bounce message could be delivered to the sender address. The
22361 following SMTP commands are sent:
22365 HELO <<smtp active host name>>
22369 RCPT TO:<<the address to be tested>>
22372 \\LHLO\\ is used instead of \\HELO\\ if the transport's \protocol\ option is
22375 A recipient callout check is similar. By default, it also uses an empty address
22376 for the sender. This default is chosen because most hosts do not make use of
22377 the sender address when verifying a recipient. Using the same address means
22378 that a single cache entry can be used for each recipient. Some sites, however,
22379 do make use of the sender address when verifying. These are catered for by the
22380 \use@_sender\ and \use@_postmaster\ options, described in the next section.
22382 If the response to the \\RCPT\\ command is a 2$it{xx} code, the verification
22383 succeeds. If it is 5$it{xx}, the verification fails. For any other condition,
22384 Exim tries the next host, if any. If there is a problem with all the remote
22385 hosts, the ACL yields `defer', unless the \defer@_ok\ parameter of the
22386 \callout\ option is given, in which case the condition is forced to succeed.
22391 .section Additional parameters for callouts
22392 .rset CALLaddparcall "~~chapter.~~section"
22393 .index callout||additional parameters for
22394 The \callout\ option can be followed by an equals sign and a number of optional
22395 parameters, separated by commas. For example:
22397 verify = recipient/callout=10s,defer_ok
22399 The old syntax, which had \callout@_defer@_ok\ and \check@_postmaster\ as
22400 separate verify options, is retained for backwards compatibility, but is now
22401 deprecated. The additional parameters for \callout\ are as follows:
22405 .item "<<a time interval>>"
22406 .index callout||timeout, specifying
22407 This specifies the timeout that applies for the callout attempt to each host.
22410 verify = sender/callout=5s
22412 The default is 30 seconds. The timeout is used for each response from the
22415 It is also used for the intial connection, unless overridden by the \connect\
22420 .item "connect = <<time interval>>"
22421 .index callout||connection timeout, specifying
22422 This parameter makes it possible to set a different (usually
22423 smaller) timeout for making the SMTP connection.
22426 verify = sender/callout=5s,connect=1s
22428 If not specified, this timeout defaults to the general timeout value.
22432 .index callout||defer, action on
22433 When this parameter is present, failure to contact any host, or any other kind
22434 of temporary error, is treated as success by the ACL. However, the cache is not
22435 updated in this circumstance.
22438 .item "mailfrom = <<email address>>"
22439 .index callout||sender when verifying header
22440 When verifying addresses in header lines using the \header@_sender\
22441 verification option, Exim behaves by default as if the addresses are envelope
22442 sender addresses from a message. Callout verification therefore tests to see
22443 whether a bounce message could be delivered, by using an empty address in the
22444 \\MAIL\\ command. However, it is arguable that these addresses might never be
22445 used as envelope senders, and could therefore justifiably reject bounce
22446 messages (empty senders). The \mailfrom\ callout parameter allows you to
22447 specify what address to use in the \\MAIL\\ command. For example:
22449 require verify = header_sender/callout=mailfrom=abcd@x.y.z
22451 This parameter is available only for the \header@_sender\ verification option.
22455 .item "maxwait = <<time interval>>"
22456 .index callout||overall timeout, specifying
22457 This parameter sets an overall timeout for performing a callout verification.
22460 verify = sender/callout=5s,maxwait=30s
22462 This timeout defaults to four times the callout timeout for individual SMTP
22463 commands. The overall timeout applies when there is more than one host that can
22464 be tried. The timeout is checked before trying the next host. This prevents
22465 very long delays if there are a large number of hosts and all are timing out
22466 (for example, when network connections are timing out).
22470 .index callout||cache, suppressing
22471 .index caching||callout, suppressing
22472 When this parameter is given, the callout cache is neither read nor updated.
22475 .index callout||postmaster, checking
22476 When this parameter is set, a sucessful callout check is followed by a similar
22477 check for the local part \*postmaster*\ at the same domain. If this address is
22478 rejected, the callout fails. The result of the postmaster check is recorded in
22479 a cache record; if it is a failure, this is used to fail subsequent callouts
22480 for the domain without a connection being made, until the cache record expires.
22483 .item "postmaster@_mailfrom = <<email address>>"
22484 The postmaster check uses an empty sender in the \\MAIL\\ command by default.
22485 You can use this parameter to do a postmaster check using a different address.
22488 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
22490 If both \postmaster\ and \postmaster@_mailfrom\ are present, the rightmost one
22491 overrides. The \postmaster\ parameter is equivalent to this example:
22493 require verify = sender/callout=postmaster_mailfrom=
22495 \**Warning**\: The caching arrangements for postmaster checking do not take
22496 account of the sender address. It is assumed that either the empty address or
22497 a fixed non-empty address will be used. All that Exim remembers is that the
22498 postmaster check for the domain succeeded or failed.
22502 .index callout||`random' check
22503 When this parameter is set, before doing the normal callout check, Exim does a
22504 check for a `random' local part at the same domain. The local part is not
22505 really random -- it is defined by the expansion of the option
22506 \callout@_random@_local@_part\, which defaults to
22508 $primary_host_name-$tod_epoch-testing
22510 The idea here is to try to determine whether the remote host accepts all local
22511 parts without checking. If it does, there is no point in doing callouts for
22512 specific local parts. If the `random' check succeeds, the result is saved in
22513 a cache record, and used to force the current and subsequent callout checks to
22514 succeed without a connection being made, until the cache record expires.
22516 .item "use@_postmaster"
22517 .index callout||sender for recipient check
22518 This parameter applies to recipient callouts only. For example:
22520 deny !verify = recipient/callout=use_postmaster
22522 It causes a non-empty postmaster address to be used in the \\MAIL\\ command
22523 when performing the callout. The local part of the address is \"postmaster"\
22524 and the domain is the contents of \$qualify@_domain$\.
22526 .item "use@_sender"
22527 This option applies to recipient callouts only. For example:
22529 require verify = recipient/callout=use_sender
22531 It causes the message's actual sender address to be used in the \\MAIL\\
22532 command when performing the callout, instead of an empty address. There is no
22533 need to use this option unless you know that the called hosts make use of the
22534 sender when checking recipients. If used indiscriminately, it reduces the
22535 usefulness of callout caching.
22540 If you use any of the parameters that set a non-empty sender for the \\MAIL\\
22541 command (\mailfrom\, \postmaster@_mailfrom\, \use@_postmaster\, or
22542 \use@_sender\), you should think about possible loops. Recipient checking is
22543 usually done between two hosts that are under the same management, and the host
22544 that receives the callouts is not normally configured to do callouts itself.
22545 Therefore, it is normally safe to use \use@_postmaster\ or \use@_sender\ in
22546 these circumstances.
22548 However, if you use a non-empty sender address for a callout to an arbitrary
22549 host, there is the likelihood that the remote host will itself initiate a
22550 callout check back to your host. As it is checking what appears to be a message
22551 sender, it is likely to use an empty address in \\MAIL\\, thus avoiding a
22552 callout loop. However, to be on the safe side it would be best to set up your
22553 own ACLs so that they do not do sender verification checks when the recipient
22554 is the address you use for header sender or postmaster callout checking.
22556 Another issue to think about when using non-empty senders for callouts is
22557 caching. When you set \mailfrom\ or \use@_sender\, the cache record is keyed by
22558 the sender/recipient combination; thus, for any given recipient, many more
22559 actual callouts are performed than when an empty sender or postmaster is used.
22564 .section Callout caching
22565 .rset SECTcallvercache "~~chapter.~~section"
22566 .index hints database||callout cache
22567 .index callout||caching
22568 .index caching||callout
22569 Exim caches the results of callouts in order to reduce the amount of resources
22570 used, unless you specify the \no@_cache\ parameter with the \callout\ option.
22571 A hints database called `callout' is used for the cache. Two different record
22572 types are used: one records the result of a callout check for a specific
22573 address, and the other records information that applies to the entire domain
22574 (for example, that it accepts the local part \*postmaster*\).
22576 When an original callout fails, a detailed SMTP error message is given about
22577 the failure. However, for subsequent failures use the cache data, this message
22580 The expiry times for negative and positive address cache records are
22581 independent, and can be set by the global options \callout@_negative@_expire\
22582 (default 2h) and \callout@_positive@_expire\ (default 24h), respectively.
22584 If a host gives a negative response to an SMTP connection, or rejects any
22585 commands up to and including
22589 (but not including the \\MAIL\\ command with a non-empty address),
22590 any callout attempt is bound to fail. Exim remembers such failures in a
22591 domain cache record, which it uses to fail callouts for the domain without
22592 making new connections, until the domain record times out. There are two
22593 separate expiry times for domain cache records:
22594 \callout@_domain@_negative@_expire\ (default 3h) and
22595 \callout__domain__positive@_expire\ (default 7d).
22597 Domain records expire when the negative expiry time is reached if callouts
22598 cannot be made for the domain, or if the postmaster check failed.
22599 Otherwise, they expire when the positive expiry time is reached. This
22600 ensures that, for example, a host that stops accepting `random' local parts
22601 will eventually be noticed.
22603 The callout caching mechanism is based on the domain of the address that is
22604 being tested. If the domain routes to several hosts, it is assumed that their
22605 behaviour will be the same.
22608 .section Sender address verification reporting
22609 .rset SECTsenaddver "~~chapter.~~section"
22610 .index verifying||suppressing error details
22611 When sender verification fails in an ACL, the details of the failure are
22612 given as additional output lines before the 550 response to the relevant
22613 SMTP command (\\RCPT\\ or \\DATA\\). For example, if sender callout is in use,
22616 MAIL FROM:<xyz@abc.example>
22618 RCPT TO:<pqr@def.example>
22619 550-Verification failed for <xyz@abc.example>
22620 550-Called: 192.168.34.43
22621 550-Sent: RCPT TO:<xyz@abc.example>
22622 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
22623 550 Sender verification failed
22625 If more than one \\RCPT\\ command fails in the same way, the details are given
22626 only for the first of them. However, some administrators do not want to send
22627 out this much information. You can suppress the details by adding
22628 `/no@_details' to the ACL statement that requests sender verification. For
22631 verify = sender/no_details
22635 .section Redirection while verifying
22636 .index verifying||redirection while
22637 .index address redirection||while verifying
22638 A dilemma arises when a local address is redirected by aliasing or forwarding
22639 during verification: should the generated addresses themselves be verified,
22640 or should the successful expansion of the original address be enough to verify
22641 it? Exim takes the following pragmatic approach:
22643 When an incoming address is redirected to just one child address, verification
22644 continues with the child address, and if that fails to verify, the original
22645 verification also fails.
22647 When an incoming address is redirected to more than one child address,
22648 verification does not continue. A success result is returned.
22650 This seems the most reasonable behaviour for the common use of aliasing as a
22651 way of redirecting different local parts to the same mailbox. It means, for
22652 example, that a pair of alias entries of the form
22655 aw123: :fail: Gone away, no forwarding address
22657 work as expected, with both local parts causing verification failure. When a
22658 redirection generates more than one address, the behaviour is more like a
22659 mailing list, where the existence of the alias itself is sufficient for
22660 verification to succeed.
22663 .section Using an ACL to control relaying
22664 .rset SECTrelaycontrol "~~chapter.~~section"
22665 .index ~~ACL||relay control
22666 .index relaying||control by ACL
22667 .index policy control||relay control
22668 An MTA is said to \*relay*\ a message if it receives it from some host and
22669 delivers it directly to another host as a result of a remote address contained
22670 within it. Redirecting a local address via an alias or forward file and then
22671 passing the message on to another host is not relaying,
22672 .index `percent hack'
22673 but a redirection as a result of the `percent hack' is.
22675 Two kinds of relaying exist, which are termed `incoming' and `outgoing'. A host
22676 which is acting as a gateway or an MX backup is concerned with incoming
22677 relaying from arbitrary hosts to a specific set of domains. On the other hand,
22678 a host which is acting as a smart host for a number of clients is concerned
22679 with outgoing relaying from those clients to the Internet at large. Often the
22680 same host is fulfilling both functions, as illustrated in the diagram below,
22681 but in principle these two kinds of relaying are entirely independent. What is
22682 not wanted is the transmission of mail from arbitrary remote hosts through your
22683 system to arbitrary domains.
22685 .figure "Controlled relaying" rm
22687 .call aspic -sgcal -nv
22688 centre ~~sys.linelength;
22694 A: box "Arbitrary" "remote hosts";
22696 D: box "Arbitrary" "domains";
22697 iline down 50 from bottom of C;
22698 H: box width 180 "Local host";
22701 SH: box "Specific" "hosts";
22702 SD: box join right to E "Specific" "domains";
22703 arcarrow clockwise from top of SH to bottom of D plus (-10,-4)
22704 via right of H plus (-20,0);
22705 arcarrow clockwise from bottom of A to top of SD plus (10,4)
22706 via left of H plus (20,0);
22708 ibox join left to right of H "$it{Outgoing}";
22710 ibox join right to left of H "$it{Incoming}";
22712 L: line dashed from right of A to top of H plus (-15,0);
22713 arc dashed to top of H plus (15,0);
22714 arrow dashed to left of D plus (-2,0);
22716 arrow dashed back up 72 right 32 from middle of L plus (8,0);
22717 text at end plus (0, 4) "$it{Not wanted}";
22722 -------------- -----------
22723 | Arbitrary | |Arbitrary|
22724 |remote hosts| | domains |
22725 -------------- -----------
22728 c ---v----------------^--- t
22731 i ---v----------------^--- i
22738 [(IMG SRC="relaying.gif" alt="Controlled relaying")][(br)]
22741 You can implement relay control by means of suitable statements in the ACL that
22742 runs for each \\RCPT\\ command. For convenience, it is often easiest to use
22743 Exim's named list facility to define the domains and hosts involved. For
22744 example, suppose you want to do the following:
22746 Deliver a number of domains to mailboxes on the local host (or process them
22747 locally in some other way). Let's say these are \*my.dom1.example*\ and
22748 \*my.dom2.example*\.
22750 Relay mail for a number of other domains for which you are the secondary MX.
22751 These might be \*friend1.example*\ and \*friend2.example*\.
22753 Relay mail from the hosts on your local LAN, to whatever domains are involved.
22754 Suppose your LAN is 192.168.45.0/24.
22756 In the main part of the configuration, you put the following definitions:
22758 domainlist local_domains = my.dom1.example : my.dom2.example
22759 domainlist relay_domains = friend1.example : friend2.example
22760 hostlist relay_hosts = 192.168.45.0/24
22762 Now you can use these definitions in the ACL that is run for every \\RCPT\\
22766 accept domains = +local_domains : +relay_domains
22767 accept hosts = +relay_hosts
22769 The first statement accepts any \\RCPT\\ command that contains an address in
22770 the local or relay domains. For any other domain, control passes to the second
22771 statement, which accepts the command only if it comes from one of the relay
22772 hosts. In practice, you will probably want to make your ACL more sophisticated
22773 than this, for example, by including sender and recipient verification. The
22774 default configuration includes a more comprehensive example, which is described
22775 in chapter ~~CHAPdefconfil.
22778 .section Checking a relay configuration
22779 .rset SECTcheralcon "~~chapter.~~section"
22780 .index relaying||checking control of
22781 You can check the relay characteristics of your configuration in the same way
22782 that you can test any ACL behaviour for an incoming SMTP connection, by using
22783 the \-bh-\ option to run a fake SMTP session with which you interact.
22785 For specifically testing for unwanted relaying, the host
22786 \*relay-test.mail-abuse.org*\ provides a useful service. If you telnet to this
22787 host from the host on which Exim is running, using the normal telnet port, you
22788 will see a normal telnet connection message and then quite a long delay. Be
22789 patient. The remote host is making an SMTP connection back to your host, and
22790 trying a number of common probes to test for open relay vulnerability. The
22791 results of the tests will eventually appear on your terminal.
22800 . ============================================================================
22801 .chapter Content scanning using the `exiscan' features
22802 .set runningfoot "content scanning"
22803 .rset CHAPexiscan "~~chapter"
22804 .index content scanning
22806 The content-scanning extension of Exim, also known as `exiscan', was originally
22807 implemented as a patch by Tom Kistner. The code was integrated into the main
22808 source for Exim release 4.50, and Tom continues to maintain it. Most of the
22809 wording of this chapter is taken from Tom's exiscan specification.
22811 If you want to include the content-scanning features when you compile Exim, you
22812 need to arrange for \\WITH@_CONTENT@_SCAN\\ to be defined in your
22813 \(Local/Makefile)\. When you do that, the Exim binary is built with:
22815 An additional ACL (\acl@_smtp@_mime\) that is run for all MIME parts.
22817 Additional ACL conditions and modifiers: \decode\, \malware\, \mime@_regex\,
22818 \regex\, and \spam\. These can be used in the ACL that is run at the end of
22819 message reception (the \acl@_smtp@_data\ ACL).
22821 Additional expansion variables that are set in the new ACL and by the new
22824 Two new main configuration options: \av@_scanner\ and \spamd@_address\.
22826 There is another content-scanning configuration option for \(Local/Makefile)\,
22827 called \\WITH@_OLD@_DEMIME\\. If this is set, the old, deprecated \demime\ ACL
22828 condition is compiled, in addition to all the other content-scanning features.
22830 Content-scanning is continually evolving, and new features are still being
22831 added. While such features are still unstable and liable to incompatible
22832 changes, they are made available in Exim by setting options whose names begin
22833 \\EXPERIMENTAL@_\\ in \(Local/Makefile)\. Such features are not documented in
22834 this manual. You can find out about them by reading the file called
22835 \(doc/experimental.txt)\.
22837 All the content-scanning facilites work on a MBOX copy of the message that is
22838 temporarily created in a file called:
22840 <<spool@_directory>>/scan/<<message@_id>>/<<message@_id>>.eml
22842 The \(.eml)\ extension is a friendly hint to virus scanners that they can
22843 expect an MBOX-like structure inside that file. The file is created when the
22844 first content scanning facility is called. Subsequent calls to content
22845 scanning conditions open the same file again. The directory is recursively
22846 removed when the \acl@_smtp@_data\ ACL has finished running. When the MIME
22847 ACL decodes files, they are put into that same directory by default.
22850 .section Scanning for viruses
22851 .rset SECTscanvirus "~~chapter.~~section"
22852 .index virus scanning
22853 .index content scanning||for viruses
22854 .index content scanning||the \malware\ condition
22855 The \malware\ ACL condition lets you connect virus scanner software to Exim. It
22856 supports a `generic' interface to scanners called via the shell, and
22857 specialized interfaces for `daemon' type virus scanners, which are resident in
22858 memory and thus are much faster.
22860 .index \av@_scanner\
22861 You can set the \av@_scanner\ option in first part of the Exim configuration
22862 file to specify which scanner to use, together with any additional options that
22863 are needed. The basic syntax is as follows:
22865 av@_scanner = <<scanner-type>>:<<option1>>:<<option2>>:[...]
22867 If you do not set \av@_scanner\, it defaults to
22869 av_scanner = sophie:/var/run/sophie
22871 If the value of \av@_scanner\ starts with dollar character, it is expanded
22874 The following scanner types are supported in this release:
22876 .index virus scanners||Kaspersky
22877 \aveserver\: This is the scanner daemon of Kaspersky Version 5. You can get a
22878 trial version at \?http://www.kaspersky.com?\. This scanner type takes one
22879 option, which is the path to the daemon's UNIX socket. The default is shown in
22882 av_scanner = aveserver:/var/run/aveserver
22886 .index virus scanners||clamd
22887 \clamd\: This daemon-type scanner is GPL and free. You can get it at
22888 \?http://www.clamav.net/?\. Clamd does not seem to unpack MIME containers,
22889 so it is recommended to unpack MIME attachments in the MIME ACL. It takes one option:
22890 either the path and name of a UNIX socket file, or a hostname or IP number, and
22891 a port, separated by space, as in the second of these examples:
22893 av_scanner = clamd:/opt/clamd/socket
22894 av_scanner = clamd:192.168.2.100 1234
22896 If the option is unset, the default is \(/tmp/clamd)\.
22899 .index virus scanners||command line interface
22900 \cmdline\: This is the keyword for the generic command line scanner interface.
22901 It can be used to attach virus scanners that are invoked from the shell. This
22902 scanner type takes 3 mantadory options:
22904 The full path and name of the scanner binary, with all command line options,
22905 and a placeholder (%s) for the directory to scan.
22907 A regular expression to match against the STDOUT and STDERR output of the virus
22908 scanner. If the expression matches, a virus was found. You must make absolutely
22909 sure that this expression matches on `virus found'. This is called the
22910 `trigger' expression.
22912 Another regular expression, containing exactly one pair of parentheses, to match the
22913 name of the virus found in the scanners output. This is called the `name'
22916 For example, Sophos Sweep reports a virus on a line like this:
22918 Virus 'W32/Magistr-B' found in file ./those.bat
22920 For the trigger expression, we can just match the word `found'. For the name
22921 expression, we want to extract the W32/Magistr-B string, so we can match for
22922 the single quotes left and right of it. Altogether, this makes the
22923 configuration setting:
22925 av_scanner = cmdline:\
22926 /path/to/sweep -all -rec -archive %s:\
22931 .index virus scanners||DrWeb
22932 \drweb\: The DrWeb daemon scanner (\?http://www.sald.com/?\) interface
22933 takes one argument, either a full path to a UNIX socket, or an IP address and
22934 port separated by whitespace, as in these examples:
22936 av_scanner = drweb:/var/run/drwebd.sock
22937 av_scanner = drweb:192.168.2.20 31337
22939 If you omit the argument, the default path \(/usr/local/drweb/run/drwebd.sock)\
22940 is used. Thanks to Alex Miller for contributing the code for this scanner.
22943 .index virus scanners||F-Secure
22944 \fsecure\: The F-Secure daemon scanner (\?http://www.f-secure.com?\) takes one
22945 argument which is the path to a UNIX socket. For example:
22947 av_scanner = fsecure:/path/to/.fsav
22949 If no argument is given, the default is \(/var/run/.fsav)\. Thanks to Johan
22950 Thelmen for contributing the code for this scanner.
22953 .index virus scanners||Kaspersky
22954 \kavdaemon\: This is the scanner daemon of Kaspersky Version 4. This version of
22955 the Kaspersky scanner is outdated. Please upgrade (see \aveserver\ above). This
22956 scanner type takes one option, which is the path to the daemon's UNIX socket.
22959 av_scanner = kavdaemon:/opt/AVP/AvpCtl
22961 The default path is \(/var/run/AvpCtl)\.
22964 .index virus scanners||mksd
22965 \mksd\: This is a daemon type scanner that is aimed mainly at Polish users,
22966 though some parts of documentation are now available in English. You can get it
22967 at \?http://linux.mks.com.pl/?\. The only option for this scanner type is the
22968 maximum number of processes used simultaneously to scan the attachments,
22969 provided that the demime facility is employed and also provided that mksd has
22970 been run with at least the same number of child processes. For example:
22972 av_scanner = mksd:2
22974 You can safely omit this option (the default value is 1).
22977 .index virus scanners||Sophos and Sophie
22978 \sophie\: Sophie is a daemon that uses Sophos' \libsavi\ library to scan for
22979 viruses. You can get Sophie at \?http://www.vanja.com/tools/sophie/?\. The only
22980 option for this scanner type is the path to the UNIX socket that Sophie uses
22981 for client communication. For example:
22983 av_scanner = sophie:/tmp/sophie
22985 The default path is \(/var/run/sophie)\, so if you are using this, you can omit
22989 When \av@_scanner\ is correctly set, you can use the \malware\ condition in the
22992 The \malware\ condition caches its results, so when you use it multiple times
22993 for the same message, the actual scanning process is only carried out once.
22995 \av@_scanner\ is expanded each time \malware\ is called. This makes
22996 it possible to use different scanners. See further below for an example.
22997 However, using expandable items in \av@_scanner\ disables the result caching
22998 of the \malware\ condition.
23000 The condition takes a right-hand argument that is expanded before
23001 use. It can then be one of
23003 `true', `*', or `1', in which case the message is scanned for viruses. The
23004 condition succeeds if a virus was found, and fail otherwise. This is the
23007 `false' or `0', in which case no scanning is done and the condition fails
23010 A regular expression, in which case the message is scanned for viruses. The
23011 condition succeeds if a virus is found and its name matches the regular
23012 expression. This allows you to take special actions on certain types of virus.
23014 You can append \"/defer@_ok"\ to the \malware\ condition to accept messages even
23015 if there is a problem with the virus scanner.
23017 .index \$malware@_name$\
23018 When a virus is found, the condition sets up an expansion variable called
23019 \$malware@_name$\ that contains the name of the virus. You can use it in a
23020 \message\ modifier that specifies the error returned to the sender, and/or in
23023 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
23024 use the \demime\ condition (see section ~~SECTdemimecond) before the \malware\
23027 Here is a very simple scanning example:
23029 deny message = This message contains malware ($malware_name)
23033 The next example accepts messages when there is a problem with the scanner:
23035 deny message = This message contains malware ($malware_name)
23037 malware = */defer_ok
23039 The next example shows how to use an ACL variable to scan with both sophie and
23040 aveserver. It assumes you have set:
23042 av_scanner = $acl_m0
23044 in the main Exim configuration.
23046 deny message = This message contains malware ($malware_name)
23047 set acl_m0 = sophie
23050 deny message = This message contains malware ($malware_name)
23051 set acl_m0 = aveserver
23056 .section Scanning with SpamAssassin
23057 .rset SECTscanspamass "~~chapter.~~section"
23058 .index content scanning||for spam
23059 .index spam scanning
23060 .index SpamAssassin, scanning with
23061 The \spam\ ACL condition calls SpamAssassin's \spamd\ daemon to get a spam
23062 score and a report for the message. You can get SpamAssassin at
23063 \?http://www.spamassassin.org?\, or, if you have a working Perl installation,
23064 you can use CPAN by running:
23066 perl -MCPAN -e 'install Mail::SpamAssassin'
23068 SpamAssassin has its own set of configuration files. Please review its
23069 documentation to see how you can tweak it. The default installation should work
23072 .index \spamd@_address\
23073 After having installed and configured SpamAssassin, start the \spamd\ daemon.
23074 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
23075 port for \spamd\, you must set the \spamd@_address\ option in the global part
23076 of the Exim configuration as follows (example):
23078 spamd_address = 192.168.99.45 387
23080 You do not need to set this option if you use the default. As of version 2.60,
23081 \spamd\ also supports communication over UNIX sockets. If you want to use
23082 these, supply \spamd@_address\ with an absolute file name instead of a
23085 spamd_address = /var/run/spamd_socket
23088 You can have multiple \spamd\ servers to improve scalability. These can reside
23089 on other hardware reachable over the network. To specify multiple \spamd\
23090 servers, put multiple address/port pairs in the \spamd@_address\ option,
23091 separated with colons:
23093 spamd_address = 192.168.2.10 783 : \
23094 192.168.2.11 783 : \
23097 Up to 32 \spamd\ servers are supported. The servers are
23098 queried in a random fashion. When a server fails to respond
23099 to the connection attempt, all other servers are tried
23100 until one succeeds. If no server responds, the \spam\
23103 \**Warning**\: It is not possible to use the UNIX socket connection method with
23104 multiple \spamd\ servers.
23106 Here is a simple example of the use of the \spam\ condition in a DATA ACL:
23108 deny message = This message was classified as SPAM
23111 The right-hand side of the \spam\ condition specifies the username that
23112 SpamAssassin should scan for. If you do not want to scan for a particular user,
23113 but rather use the SpamAssassin system-wide default profile, you can scan for
23114 an unknown user, or simply use `nobody'. However, you must put something on the
23117 The username allows you to use per-domain or per-user antispam profiles. The
23118 right-hand side is expanded before being used, so you can put lookups or
23119 conditions there. When the right-hand side evaluates to `0' or `false', no
23120 scanning is done and the condition fails immediately.
23122 The \spam\ condition returns true if the threshold specified in the user's
23123 SpamAssassin profile has been matched or exceeded. If you want to use the
23124 \spam\ condition for its side effects (see the variables below), you can make
23125 it always return `true' by appending \":true"\ to the username.
23127 .index spam scanning||returned variables
23128 When the \spam\ condition is run, it sets up the following expansion
23135 \$spam@_score$\: The spam score of the message, for example `3.4' or `30.5'.
23136 This is useful for inclusion in log or reject messages.
23139 \$spam@_score@_int$\: The spam score of the message, multiplied by ten, as an
23140 integer value. For example `34' or `305'. This is useful for numeric
23141 comparisons in conditions. This variable is special; it is saved with the
23142 message, and written to Exim's spool file. This means that it can be used
23143 during the whole life of the message on your Exim system, in particualr, in
23144 routers or transports during the later delivery phase.
23147 \$spam@_bar$\: A string consisting of a number of `+' or `@-' characters,
23148 representing the integer part of the spam score value. A spam score of 4.4
23149 would have a \$spam@_bar$\ value of `++++'. This is useful for inclusion in
23150 warning headers, since MUAs can match on such strings.
23153 \$spam@_report$\: A multiline text table, containing the full SpamAssassin
23154 report for the message. Useful for inclusion in headers or reject messages.
23158 The \spam\ condition caches its results. If you call it again with the same user
23159 name, it does not scan again, but rather returns the same values as before.
23161 The \spam\ condition returns DEFER if there is any error while running the
23162 message through SpamAssassin. If you want to treat DEFER as FAIL (to pass on to
23163 the next ACL statement block), append \"/defer@_ok"\ to the right-hand side of
23164 the spam condition, like this:
23166 deny message = This message was classified as SPAM
23167 spam = joe/defer_ok
23169 This causes messages to be accepted even if there is a
23170 problem with \spamd\.
23172 Here is a longer, commented example of the use of the \spam\
23175 # put headers in all messages (no matter if spam or not)
23176 warn message = X-Spam-Score: $spam_score ($spam_bar)
23178 warn message = X-Spam-Report: $spam_report
23181 # add second subject line with *SPAM* marker when message
23182 # is over threshold
23183 warn message = Subject: *SPAM* $h_Subject:
23186 # reject spam at high scores (> 12)
23187 deny message = This message scored $spam_score spam points.
23189 condition = ${if >{$spam_score_int}{120}{1}{0}}
23194 .section Scanning MIME parts
23195 .rset SECTscanmimepart "~~chapter.~~section"
23196 .index content scanning||MIME parts
23197 .index MIME content scanning
23198 .index \acl@_smtp@_mime\
23199 The \acl@_smtp@_mime\ global option defines an ACL that is called once for each
23200 MIME part of a message, including multipart types, in the sequence of their
23201 position in the message.
23203 This ACL is called (possibly many times) just before the \acl@_smtp@_data\ ACL,
23204 but only if the message has a ::MIME-Version:: header. When a call to the MIME
23205 ACL does not yield `accept', ACL processing is aborted and the appropriate
23206 result code is sent to the remote client. The \acl@_smtp@_data\ ACL is not
23207 called in this circumstance.
23209 At the start of the MIME ACL, a number of variables are set from the header
23210 information for the relevant MIME part. These are described below. The contents
23211 of the MIME part are not by default decoded into a disk file except for MIME
23212 parts whose content-type is `message/rfc822'. If you want to decode a MIME part
23213 into a disk file, you can use the \decode\ modifier. The general syntax is:
23215 decode = [/<<path>>/]<<filename>>
23217 The right hand side is expanded before use. After expansion,
23220 `0' or `false', in which case no decoding is done.
23222 The string `default'. In that case, the file is put in the temporary `default'
23223 directory \(<<spool@_directory>>/scan/<<message@_id>>/)\ with a sequential file
23224 name consisting of the message id and a sequence number. The full path and name
23225 is available in \$mime@_decoded@_filename$\ after decoding.
23227 A full path name starting with a slash. If the full name is an existing
23228 directory, it is used as a replacement for the default directory. The filename
23229 is then sequentially assigned. If the path does not exist, it is used as
23230 the full path and file name.
23232 If the string does not start with a slash, it is used as the
23233 filename, and the default path is then used.
23235 You can easily decode a file with its original, proposed
23238 decode = $mime_filename
23240 However, you should keep in mind that \$mime@_filename$\ might contain
23241 anything. If you place files outside of the default path, they are not
23242 automatically unlinked.
23244 For RFC822 attachments (these are messages attached to messages, with a
23245 content-type of `message/rfc822'), the ACL is called again in the same manner
23246 as for the primary message, only that the \$mime@_is@_rfc822$\ expansion
23247 variable is set (see below). Attached messages are always decoded to disk
23248 before being checked, and the files are unlinked once the check is done.
23250 The MIME ACL supports the \regex\ and \mime@_regex\ conditions. These can be
23251 used to match regular expressions against raw and decoded MIME parts,
23252 respectively. They are described in section ~~SECTscanregex.
23254 .index MIME content scanning||returned variables
23255 The following list describes all expansion variables that are
23256 available in the MIME ACL:
23262 \$mime@_boundary$\:
23263 If the current part is a multipart (see \$mime@_is@_multipart$\) below, it
23264 should have a boundary string, which is stored in this variable. If the current
23265 part has no boundary parameter in the ::Content-Type:: header, this variable
23266 contains the empty string.
23270 This variable contains the character set identifier, if one was found in the
23271 ::Content-Type:: header. Examples for charset identifiers are:
23277 Please note that this value is not normalized, so you should do matches
23278 case-insensitively.
23281 \$mime@_content@_description$\:
23282 This variable contains the normalized content of the ::Content-Description::
23283 header. It can contain a human-readable description of the parts content. Some
23284 implementations repeat the filename for attachments here, but they are
23285 usually only used for display purposes.
23288 \$mime@_content@_disposition$\:
23289 This variable contains the normalized content of the ::Content-Disposition::
23290 header. You can expect strings like `attachment' or `inline' here.
23293 \$mime@_content@_id$\:
23294 This variable contains the normalized content of the ::Content-ID:: header.
23295 This is a unique ID that can be used to reference a part from another part.
23298 \$mime@_content@_size$\:
23299 This variable is set only after the \decode\ modifier (see above) has been
23300 successfully run. It contains the size of the decoded part in kilobytes. The
23301 size is always rounded up to full kilobytes, so only a completely empty part
23302 has a \$mime@_content@_size$\ of zero.
23305 \$mime@_content@_transfer@_encoding$\:
23306 This variable contains the normalized content of the
23307 ::Content-transfer-encoding:: header. This is a symbolic name for an encoding
23308 type. Typical values are `base64' and `quoted-printable'.
23311 \$mime@_content@_type$\: If the MIME part has a ::Content-Type:: header, this
23312 variable contains its value, lowercased, and without any options (like `name'
23313 or `charset'). Here are some examples of popular MIME types, as they may appear
23318 application/octet-stream
23322 If the MIME part has no ::Content-Type:: header, this variable contains the
23326 \$mime@_decoded@_filename$\:
23327 This variable is set only after the \decode\ modifier (see above) has been
23328 successfully run. It contains the full path and file name of the file
23329 containing the decoded data.
23332 \$mime@_filename$\: This is perhaps the most important of the MIME variables.
23333 It contains a proposed filename for an attachment, if one was found in either
23334 the ::Content-Type:: or ::Content-Disposition:: headers. The filename will be
23335 RFC2047 decoded, but no additional sanity checks are done. If no filename was
23336 found, this variable contains the empty string.
23339 \$mime@_is@_coverletter$\:
23340 This variable attempts to differentiate the `cover letter' of an e-mail from
23341 attached data. It can be used to clamp down on flashy or unneccessarily encoded
23342 content in the cover letter, while not restricting attachments at all.
23344 The variable contains 1 (true) for a MIME part believed to be part of the
23345 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
23348 The outermost MIME part of a message always a cover letter.
23350 If a multipart/alternative or multipart/related MIME part is a cover letter, so
23351 are all MIME subparts within that multipart.
23353 If any other multipart is a cover letter, the first subpart is a cover letter,
23354 and the rest are attachments.
23356 All parts contained within an attachment multipart are attachments.
23359 As an example, the following will ban `HTML mail' (including that sent with
23360 alternative plain text), while allowing HTML files to be attached. HTML
23361 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
23363 deny message = HTML mail is not accepted here
23364 !condition = $mime_is_rfc822
23365 condition = $mime_is_coverletter
23366 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
23371 \$mime@_is@_multipart$\:
23372 This variable has the value 1 (true) when the current part has the main type
23373 `multipart', for example `multipart/alternative' or `multipart/mixed'. Since
23374 multipart entities only serve as containers for other parts, you may not want
23375 to carry out specific actions on them.
23378 \$mime@_is@_rfc822$\:
23379 This variable has the value 1 (true) if the current part is not a part of the
23380 checked message itself, but part of an attached message. Attached message
23381 decoding is fully recursive.
23384 \$mime@_part@_count$\:
23385 This variable is a counter that is raised for each processed MIME part. It
23386 starts at zero for the very first part (which is usually a multipart). The
23387 counter is per-message, so it is reset when processing RFC822 attachments (see
23388 \$mime@_is@_rfc822$\). The counter stays set after \acl@_smtp@_mime\ is
23389 complete, so you can use it in the DATA ACL to determine the number of MIME
23390 parts of a message. For non-MIME messages, this variable contains the value -1.
23397 .section Scanning with regular expressions
23398 .rset SECTscanregex "~~chapter.~~section"
23399 .index content scanning||with regular expressions
23400 .index regular expressions||content scanning with
23401 You can specify your own custom regular expression matches on the full body of
23402 the message, or on individual MIME parts.
23404 The \regex\ condition takes one or more regular expressions as arguments and
23405 matches them against the full message (when called in the DATA ACL) or a raw
23406 MIME part (when called in the MIME ACL). The \regex\ condition matches
23407 linewise, with a maximum line length of 32K characters. That means you cannot
23408 have multiline matches with the \regex\ condition.
23410 The \mime@_regex\ condition can be called only in the MIME ACL. It matches up
23411 to 32K of decoded content (the whole content at once, not linewise). If the
23412 part has not been decoded with the \decode\ modifier earlier in the ACL, it is
23413 decoded automatically when \mime@_regex\ is executed (using default path and
23414 filename values). If the decoded data is larger than 32K, only the first 32K
23415 characters are checked.
23417 The regular expressions are passed as a colon-separated list. To include a
23418 literal colon, you must double it. Since the whole right-hand side string is
23419 expanded before being used, you must also escape dollar signs and backslashes
23420 with more backslashes, or use the \"@\N"\ facility to disable expansion.
23421 Here is a simple example that contains two regular expressions:
23423 deny message = contains blacklisted regex ($regex_match_string)
23424 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
23426 The conditions returns true if any one of the regular expressions matches. The
23427 \$regex@_match@_string$\ expansion variable is then set up and contains the
23428 matching regular expression.
23430 \**Warning**\: With large messages, these conditions can be fairly
23435 .section The demime condition
23436 .rset SECTdemimecond "~~chapter.~~section"
23437 .index content scanning||MIME checking
23438 .index MIME content scanning
23439 The \demime\ ACL condition provides MIME unpacking, sanity checking and file
23440 extension blocking. It uses a simpler interface to MIME decoding than the MIME
23441 ACL functionality, but provides no additional facilities. Please note that this
23442 condition is deprecated and kept only for for backward compatibility. You must
23443 set the WITH_OLD_DEMIME option in the Makefile at build time to be able to use
23444 the \demime\ condition.
23446 The \demime\ condition unpacks MIME containers in the message. It detects
23447 errors in MIME containers and can match file extensions found in the message
23448 against a list. Using this facility produces files containing the unpacked MIME
23449 parts of the message in the temporary scan directory. If you do antivirus
23450 scanning, it is recommened that you use the \demime\ condition before the
23451 antivirus (\malware\) condition.
23453 On the right-hand side of the \demime\ condition you can pass a colon-separated
23454 list of file extensions that it should match against. For example:
23456 deny message = Found blacklisted file attachment
23457 demime = vbs:com:bat:pif:prf:lnk
23459 If one of the file extensions is found, the condition is true, otherwise it is
23460 false. If there is a temporary error while demimeing (for example, `disk
23461 full'), the condition defers, and the message is temporarily rejected (unless
23462 the condition is on a \warn\ verb).
23464 The right-hand side is expanded before being treated as a list, so you can have
23465 conditions and lookups there. If it expands to an empty string, `false', or
23466 zero (`0'), no demimeing is done and the condition is false.
23468 The \demime\ condition set the following variables:
23474 \$demime@_errorlevel$\: When an error is detected in a MIME container, this
23475 variable contains the severity of the error, as an integer number. The higher
23476 the value, the more severe the error. If this variable is unset or zero, no
23480 \$demime@_reason$\: When \$demime@_errorlevel$\ is greater than zero, this
23481 variable contains a human-readable text string describing the MIME error that
23485 \$found@_extension$\: When the \demime\ condition is true, this variable
23486 contains the file extension it found.
23490 Both \$demime@_errorlevel$\ and \$demime@_reason$\ are set by the first call of
23491 the \demime\ condition, and are not changed on subsequent calls.
23493 If you do not want to check for file extensions, but rather use the \demime\
23494 condition for unpacking or error checking purposes, pass `*' as the
23495 right-hand side value. Here is a more elaborate example of how to use this
23498 # Reject messages with serious MIME container errors
23499 deny message = Found MIME error ($demime_reason).
23501 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
23503 # Reject known virus spreading file extensions.
23504 # Accepting these is pretty much braindead.
23505 deny message = contains $found_extension file (blacklisted).
23506 demime = com:vbs:bat:pif:scr
23508 # Freeze .exe and .doc files. Postmaster can
23509 # examine them and eventually thaw them.
23510 deny log_message = Another $found_extension file.
23524 . ============================================================================
23525 .chapter Adding a local scan function to Exim
23526 .set runningfoot "local scan function"
23527 .rset CHAPlocalscan "~~chapter"
23528 .index \*local@_scan()*\ function||description of
23529 .index customizing||input scan using C function
23530 .index policy control||by local scan function
23532 In these days of email worms, viruses, and ever-increasing spam, some sites
23533 want to apply a lot of checking to messages before accepting them. You can do a
23534 certain amount through string expansions and the \condition\ condition in the
23535 ACL that runs after the SMTP \\DATA\\ command or the ACL for non-SMTP messages
23536 (see chapter ~~CHAPACL), but this has its limitations.
23538 To allow for even more general checking that can be customized to a site's own
23539 requirements, there is the possibility of linking Exim with a private message
23540 scanning function, written in C. If you want to run code that is written in
23541 something other than C, you can of course use a little C stub to call it.
23543 The local scan function is run once for every incoming message, at the point
23544 when Exim is just about to accept the message.
23545 It can therefore be used to control non-SMTP messages from local processes as
23546 well as messages arriving via SMTP.
23548 Exim applies a timeout to calls of the local scan function, and there is an
23549 option called \local@_scan@_timeout\ for setting it. The default is 5 minutes.
23550 Zero means `no timeout'.
23551 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
23552 before calling the local scan function, so that the most common types of crash
23553 are caught. If the timeout is exceeded or one of those signals is caught, the
23554 incoming message is rejected with a temporary error if it is an SMTP message.
23555 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
23556 code. The incident is logged on the main and reject logs.
23559 .section Building Exim to use a local scan function
23560 .index \*local@_scan()*\ function||building Exim to use
23561 To make use of the local scan function feature, you must tell Exim where your
23562 function is before building Exim, by setting \\LOCAL@_SCAN@_SOURCE\\ in your
23563 \(Local/Makefile)\. A recommended place to put it is in the \(Local)\
23564 directory, so you might set
23566 LOCAL_SCAN_SOURCE=Local/local_scan.c
23568 for example. The function must be called \*local@_scan()*\. It is called by
23569 Exim after it has received a message, when the success return code is about to
23570 be sent. This is after all the ACLs have been run. The return code from your
23571 function controls whether the message is actually accepted or not. There is a
23572 commented template function (that just accepts the message) in the file
23573 \(src/local@_scan.c)\.
23575 If you want to make use of Exim's run time configuration file to set options
23576 for your \*local@_scan()*\ function, you must also set
23578 LOCAL_SCAN_HAS_OPTIONS=yes
23580 in \(Local/Makefile)\ (see section ~~SECTconoptloc below).
23584 .section API for local@_scan()
23585 .rset SECTapiforloc "~~chapter.~~section"
23586 .index \*local@_scan()*\ function||API description
23587 You must include this line near the start of your code:
23589 #include "local_scan.h"
23591 This header file defines a number of variables and other values, and the
23592 prototype for the function itself. Exim is coded to use unsigned char values
23593 almost exclusively, and one of the things this header defines is a shorthand
23594 for \"unsigned char"\ called \"uschar"\.
23595 It also contains the following macro definitions, to simplify casting character
23596 strings and pointers to character strings:
23598 #define CS (char *)
23599 #define CCS (const char *)
23600 #define CSS (char **)
23601 #define US (unsigned char *)
23602 #define CUS (const unsigned char *)
23603 #define USS (unsigned char **)
23606 The function prototype for \*local@_scan()*\ is:
23608 extern int local_scan(int fd, uschar **return_text);
23610 The arguments are as follows:
23612 \fd\ is a file descriptor for the file that contains the body of the message
23614 The file is open for reading and writing, but updating it is not recommended.
23615 \**Warning**\: You must \*not*\ close this file descriptor.
23617 The descriptor is positioned at character 19 of the file, which is the first
23618 character of the body itself, because the first 19 characters are the message
23619 id followed by \"-D"\ and a newline. If you rewind the file, you should use the
23620 macro \\SPOOL@_DATA@_START@_OFFSET\\ to reset to the start of the data, just in
23621 case this changes in some future version.
23624 \return@_text\ is an address which you can use to return a pointer to a text
23625 string at the end of the function. The value it points to on entry is NULL.
23627 The function must return an \int\ value which is one of the following macros:
23629 \"LOCAL@_SCAN@_ACCEPT"\
23631 The message is accepted. If you pass back a string of text, it is saved with
23632 the message, and made available in the variable \$local@_scan@_data$\. No
23633 newlines are permitted (if there are any, they are turned into spaces) and the
23634 maximum length of text is 1000 characters.
23636 \"LOCAL@_SCAN@_ACCEPT@_FREEZE"\
23638 This behaves as \\LOCAL@_SCAN@_ACCEPT\\, except that the accepted message is
23639 queued without immediate delivery, and is frozen.
23641 \"LOCAL@_SCAN@_ACCEPT@_QUEUE"\
23643 This behaves as \\LOCAL@_SCAN@_ACCEPT\\, except that the accepted message is
23644 queued without immediate delivery.
23646 \"LOCAL@_SCAN@_REJECT"\
23648 The message is rejected; the returned text is used as an error message which is
23649 passed back to the sender and which is also logged. Newlines are permitted --
23650 they cause a multiline response for SMTP rejections, but are converted to
23651 \"@\n"\ in log lines.
23652 If no message is given, `Administrative prohibition' is used.
23654 \"LOCAL@_SCAN@_TEMPREJECT"\
23656 The message is temporarily rejected; the returned text is used as an error
23657 message as for \\LOCAL@_SCAN@_REJECT\\. If no message is given, `Temporary
23658 local problem' is used.
23660 \"LOCAL@_SCAN@_REJECT@_NOLOGHDR"\
23662 This behaves as \\LOCAL@_SCAN@_REJECT\\, except that the header of the rejected
23663 message is not written to the reject log. It has the effect of unsetting the
23664 \rejected@_header\ log selector for just this rejection. If \rejected@_header\
23665 is already unset (see the discussion of the \log@_selection\ option in section
23666 ~~SECTlogselector), this code is the same as \\LOCAL@_SCAN@_REJECT\\.
23669 \"LOCAL@_SCAN@_TEMPREJECT@_NOLOGHDR"\
23671 This code is a variation of \\LOCAL@_SCAN@_TEMPREJECT\\ in the same way that
23672 \\LOCAL__SCAN__REJECT__NOLOGHDR\\ is a variation of \\LOCAL@_SCAN@_REJECT\\.
23675 If the message is not being received by interactive SMTP, rejections are
23676 reported by writing to \stderr\ or by sending an email, as configured by the
23677 \-oe-\ command line options.
23680 .section Configuration options for local@_scan()
23681 .rset SECTconoptloc "~~chapter.~~section"
23682 .index \*local@_scan()*\ function||configuration options
23683 It is possible to have option settings in the main configuration file
23684 that set values in static variables in the \*local@_scan()*\ module. If you
23685 want to do this, you must have the line
23687 LOCAL_SCAN_HAS_OPTIONS=yes
23689 in your \(Local/Makefile)\ when you build Exim. (This line is in
23690 \(OS/Makefile-Default)\, commented out). Then, in the \*local@_scan()*\ source
23691 file, you must define static variables to hold the option values, and a table to
23694 The table must be a vector called \local@_scan@_options\, of type
23695 \"optionlist"\. Each entry is a triplet, consisting of a name, an option type,
23696 and a pointer to the variable that holds the value. The entries must appear in
23697 alphabetical order. Following \local@_scan@_options\ you must also define a
23698 variable called \local@_scan@_options@_count\ that contains the number of
23699 entries in the table. Here is a short example, showing two kinds of option:
23701 static int my_integer_option = 42;
23702 static uschar *my_string_option = US"a default string";
23704 optionlist local_scan_options[] = {
23705 { "my_integer", opt_int, &my_integer_option },
23706 { "my_string", opt_stringptr, &my_string_option }
23708 int local_scan_options_count =
23709 sizeof(local_scan_options)/sizeof(optionlist);
23711 The values of the variables can now be changed from Exim's runtime
23712 configuration file by including a local scan section as in this example:
23716 my_string = some string of text...
23718 The available types of option data are as follows:
23723 This specifies a boolean (true/false) option. The address should point to
23724 a variable of type \"BOOL"\, which will be set to \\TRUE\\ or \\FALSE\\, which
23725 are macros that are defined as `1' and `0', respectively. If you want to detect
23726 whether such a variable has been set at all, you can initialize it to
23727 \\TRUE@_UNSET\\. (BOOL variables are integers underneath, so can hold more than
23731 This specifies a fixed point number, such as is used for load averages.
23732 The address should point to a variable of type \"int"\. The value is stored
23733 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
23736 This specifies an integer; the address should point to a variable of type
23737 \"int"\. The value may be specified in any of the integer formats accepted by
23741 This is the same as \opt@_int\, except that when such a value is output in a
23742 \-bP-\ listing, if it is an exact number of kilobytes or megabytes, it is
23743 printed with the suffix K or M.
23745 .item "opt@_octint"
23746 This also specifies an integer, but the value is always interpeted as an
23747 octal integer, whether or not it starts with the digit zero, and it is
23748 always output in octal.
23750 .item "opt@_stringptr"
23751 This specifies a string value; the address must be a pointer to a
23752 variable that points to a string (for example, of type \"uschar $*$"\).
23755 This specifies a time interval value. The address must point to a variable of
23756 type \"int"\. The value that is placed there is a number of seconds.
23760 If the \-bP-\ command line option is followed by \"local@_scan"\, Exim prints
23761 out the values of all the \*local@_scan()*\ options.
23764 .section Available Exim variables
23765 .index \*local@_scan()*\ function||available Exim variables
23766 The header \(local@_scan.h)\ gives you access to a number of C variables.
23767 These are the only ones that are guaranteed to be maintained from release to
23768 release. Note, however, that you can obtain the value of any Exim variable by
23769 calling \*expand@_string()*\. The exported variables are as follows:
23773 .item "unsigned int debug@_selector"
23774 This variable is set to zero when no debugging is taking place. Otherwise, it
23775 is a bitmap of debugging selectors. Two bits are identified for use in
23776 \*local@_scan()*\; they are defined as macros:
23778 The \"D@_v"\ bit is set when \-v-\ was present on the command line. This is a
23779 testing option that is not privileged -- any caller may set it. All the
23780 other selector bits can be set only by admin users.
23782 The \"D@_local@_scan"\ bit is provided for use by \*local@_scan()*\; it is set
23783 by the \"+local@_scan"\ debug selector. It is not included in the default set
23786 Thus, to write to the debugging output only when \"+local@_scan"\ has been
23787 selected, you should use code like this:
23789 if ((debug_selector & D_local_scan) != 0)
23790 debug_printf("xxx", ...);
23793 .item "uschar *expand@_string@_message"
23794 After a failing call to \*expand@_string()*\ (returned value NULL), the
23795 variable \expand__string__message\ contains the error message, zero-terminated.
23797 .item "header@_line *header@_list"
23798 A pointer to a chain of header lines. The \header@_line\ structure is discussed
23801 .item "header@_line *header@_last"
23802 A pointer to the last of the header lines.
23804 .item "uschar *headers@_charset"
23805 The value of the \headers@_charset\ configuration option.
23807 .item "BOOL host@_checking"
23808 This variable is TRUE during a host checking session that is initiated by the
23809 \-bh-\ command line option.
23811 .item "uschar *interface@_address"
23812 The IP address of the interface that received the message, as a string. This
23813 is NULL for locally submitted messages.
23815 .item "int interface@_port"
23816 The port on which this message was received.
23818 .item "uschar *message@_id"
23819 This variable contains the message id for the incoming message as a
23820 zero-terminated string.
23823 .item "uschar *received@_protocol"
23824 The name of the protocol by which the message was received.
23826 .item "int recipients@_count"
23827 The number of accepted recipients.
23829 .item "recipient@_item *recipients@_list"
23830 .index recipient||adding in local scan
23831 .index recipient||removing in local scan
23832 The list of accepted recipients, held in a vector of length
23833 \recipients@_count\. The \recipient@_item\ structure is discussed below. You
23834 can add additional recipients by calling \*receive@_add@_recipient()*\ (see
23835 below). You can delete recipients by removing them from the vector and adusting
23836 the value in \recipients@_count\. In particular, by setting \recipients@_count\
23837 to zero you remove all recipients. If you then return the value
23838 \"LOCAL@_SCAN@_ACCEPT"\, the message is accepted, but immediately blackholed.
23839 To replace the recipients, set \recipients@_count\ to zero and then call
23840 \*receive@_add@_recipient()*\ as often as needed.
23842 .item "uschar *sender@_address"
23843 The envelope sender address. For bounce messages this is the empty string.
23845 .item "uschar *sender@_host@_address"
23846 The IP address of the sending host, as a string. This is NULL for
23847 locally-submitted messages.
23849 .item "uschar *sender@_host@_authenticated"
23850 The name of the authentication mechanism that was used, or NULL if the message
23851 was not received over an authenticated SMTP connection.
23853 .item "uschar *sender@_host@_name"
23854 The name of the sending host, if known.
23856 .item "int sender@_host@_port"
23857 The port on the sending host.
23859 .item "BOOL smtp@_input"
23860 This variable is TRUE for all SMTP input, including BSMTP.
23862 .item "BOOL smtp@_batched@_input"
23863 This variable is TRUE for BSMTP input.
23865 .item "int store@_pool"
23866 The contents of this variable control which pool of memory is used for new
23867 requests. See section ~~SECTmemhanloc for details.
23872 .section Structure of header lines
23873 The \header@_line\ structure contains the members listed below.
23874 You can add additional header lines by calling the \*header@_add()*\ function
23875 (see below). You can cause header lines to be ignored (deleted) by setting
23880 .item "struct header@_line *next"
23881 A pointer to the next header line, or NULL for the last line.
23884 A code identifying certain headers that Exim recognizes. The codes are printing
23885 characters, and are documented in chapter ~~CHAPspool of this manual. Notice in
23886 particular that any header line whose type is $*$ is not transmitted with the
23887 message. This flagging is used for header lines that have been rewritten, or
23888 are to be removed (for example, ::Envelope-sender:: header lines.) Effectively,
23889 $*$ means `deleted'.
23892 The number of characters in the header line, including the terminating and any
23895 .item "uschar *text"
23896 A pointer to the text of the header. It always ends with a newline, followed by
23897 a zero byte. Internal newlines are preserved.
23903 .section Structure of recipient items
23904 The \recipient@_item\ structure contains these members:
23908 .item "uschar *address"
23909 This is a pointer to the recipient address as it was received.
23912 This is used in later Exim processing when top level addresses are created
23913 by the \one@_time\ option. It is not relevant at the time \*local@_scan()*\ is
23915 must always contain -1 at this stage.
23917 .item "uschar *errors@_to"
23918 If this value is not NULL, bounce messages caused by failing to deliver to the
23919 recipient are sent to the address it contains. In other words, it overrides the
23920 envelope sender for this one recipient. (Compare the \errors@_to\ generic
23922 If a \*local@_scan()*\ function sets an \errors@_to\ field to an unqualified
23923 address, Exim qualifies it using the domain from \qualify@_recipient\.
23924 When \*local@_scan()*\ is called, the \errors@_to\ field is NULL for all
23929 .section Available Exim functions
23930 .index \*local@_scan()*\ function||available Exim functions
23931 The header \(local@_scan.h)\ gives you access to a number of Exim functions.
23932 These are the only ones that are guaranteed to be maintained from release to
23937 .item "pid@_t child@_open(uschar **argv, uschar **envp, int newumask, int *infdptr, int *outfdptr, BOOL make@_leader)"
23938 This function creates a child process that runs the command specified by
23939 \argv\. The environment for the process is specified by \envp\, which can be
23940 NULL if no environment variables are to be passed. A new umask is supplied for
23941 the process in \newumask\.
23943 Pipes to the standard input and output of the new process are set up
23944 and returned to the caller via the \infdptr\ and \outfdptr\ arguments. The
23945 standard error is cloned to the standard output. If there are any file
23946 descriptors `in the way' in the new process, they are closed. If the final
23947 argument is TRUE, the new process is made into a process group leader.
23949 The function returns the pid of the new process, or -1 if things go wrong.
23952 .item "int child@_close(pid@_t pid, int timeout)"
23953 This function waits for a child process to terminate, or for a timeout (in
23954 seconds) to expire. A timeout value of zero means wait as long as it takes. The
23955 return value is as follows:
23959 The process terminated by a normal exit and the value is the process ending
23964 The process was terminated by a signal and the value is the negation of the
23969 The process timed out.
23973 The was some other error in wait(); \errno\ is still set.
23977 .item "pid@_t child@_open@_exim(int *fd)"
23978 This function provide you with a means of submitting a new message to
23979 Exim. (Of course, you can also call \(/usr/sbin/sendmail)\ yourself if you
23980 want, but this packages it all up for you.) The function creates a pipe,
23981 forks a subprocess that is running
23983 exim -t -oem -oi -f <>
23985 and returns to you (via the \"int *"\ argument) a file descriptor for the pipe
23986 that is connected to the standard input. The yield of the function is the PID
23987 of the subprocess. You can then write a message to the file descriptor, with
23988 recipients in ::To::, ::Cc::, and/or ::Bcc:: header lines.
23990 When you have finished, call \*child@_close()*\ to wait for the process to
23991 finish and to collect its ending status. A timeout value of zero is usually
23992 fine in this circumstance. Unless you have made a mistake with the recipient
23993 addresses, you should get a return code of zero.
23995 .item "void debug@_printf(char *, ...)"
23996 This is Exim's debugging function, with arguments as for \*(printf()*\. The
23997 output is written to the standard error stream. If no debugging is selected,
23998 calls to \*debug@_printf()*\ have no effect. Normally, you should make calls
23999 conditional on the \"local@_scan"\ debug selector by coding like this:
24001 if ((debug_selector & D_local_scan) != 0)
24002 debug_printf("xxx", ...);
24005 .item "uschar *expand@_string(uschar *string)"
24006 This is an interface to Exim's string expansion code. The return value is the
24007 expanded string, or NULL if there was an expansion failure.
24008 The C variable \expand@_string@_message\ contains an error message after an
24009 expansion failure. If expansion does not change the string, the return value is
24010 the pointer to the input string. Otherwise, the return value points to a new
24011 block of memory that was obtained by a call to \*store@_get()*\. See section
24012 ~~SECTmemhanloc below for a discussion of memory handling.
24014 .item "void header@_add(int type, char *format, ...)"
24015 This function allows you to add additional header lines. The first argument is
24016 the type, and should normally be a space character. The second argument is a
24017 format string and any number of substitution arguments as for \*sprintf()*\.
24018 You may include internal newlines if you want, and you must ensure that the
24019 string ends with a newline.
24021 .item "uschar *lss@_b64encode(uschar *cleartext, int length)"
24022 .index base64 encoding||functions for \*local@_scan()*\ use
24023 This function base64-encodes a string, which is passed by address and length.
24024 The text may contain bytes of any value, including zero. The result is passed
24025 back in dynamic memory that is obtained by calling \*store@_get()*\. It is
24028 .item "int lss@_b64decode(uschar *codetext, uschar **cleartext)"
24029 This function decodes a base64-encoded string. Its arguments are a
24030 zero-terminated base64-encoded string and the address of a variable that is set
24031 to point to the result, which is in dynamic memory. The length of the
24032 decoded string is the yield of the function. If the input is invalid base64
24033 data, the yield is -1. A zero byte is added to the end of the output string to
24034 make it easy to interpret as a C string (assuming it contains no zeros of its
24035 own). The added zero byte is not included in the returned count.
24037 .item "int lss@_match@_domain(uschar *domain, uschar *list)"
24038 This function checks for a match in a domain list. Domains are always
24039 matched caselessly. The return value is one of the following:
24041 OK $rm{match succeeded}
24042 FAIL $rm{match failed}
24043 DEFER $rm{match deferred}
24045 DEFER is usually caused by some kind of lookup defer, such as the
24046 inability to contact a database.
24048 .item "int lss@_match@_local@_part(uschar *localpart, uschar *list, BOOL caseless)"
24049 This function checks for a match in a local part list. The third argument
24050 controls case-sensitivity. The return values are as for
24051 \*lss@_match@_domain()*\.
24053 .item "int lss@_match@_address(uschar *address, uschar *list, BOOL caseless)"
24054 This function checks for a match in an address list. The third argument
24055 controls the case-sensitivity of the local part match. The domain is always
24056 matched caselessly. The return values are as for \*lss@_match@_domain()*\.
24058 .item "int lss@_match@_host(uschar *host@_name, uschar *host@_address, uschar *list)"
24059 This function checks for a match in a host list. The most common usage is
24062 lss_match_host(sender_host_name, sender_host_address, ...)
24064 An empty address field matches an empty item in the host list. If the
24065 host name is NULL, the name corresponding to \$sender@_host@_address$\ is
24066 automatically looked up if a host name is required to match an item in the
24067 list. The return values are as for \*lss@_match@_domain()*\, but in addition,
24068 \*lss@_match@_host()*\ returns ERROR in the case when it had to look up a host
24069 name, but the lookup failed.
24071 .item "void log@_write(unsigned int selector, int which, char *format, ...)"
24072 This function writes to Exim's log files. The first argument should be zero (it
24073 is concerned with \log@_selector\). The second argument can be \"LOG@_MAIN"\ or
24075 \"LOG@_PANIC"\ or the inclusive `or' of any combination of them. It specifies
24076 to which log or logs the message is written.
24077 The remaining arguments are a format and relevant insertion arguments. The
24078 string should not contain any newlines, not even at the end.
24081 .item "void receive@_add@_recipient(uschar *address, int pno)"
24082 This function adds an additional recipient to the message. The first argument
24083 is the recipient address. If it is unqualified (has no domain), it is qualified
24084 with the \qualify@_recipient\ domain. The second argument must always be -1.
24086 This function does not allow you to specify a private \errors@_to\ address (as
24087 described with the structure of \recipient@_item\ above), because it pre-dates
24088 the addition of that field to the structure. However, it is easy to add such a
24089 value afterwards. For example:
24091 receive_add_recipient(US"monitor@mydom.example", -1);
24092 recipients_list[recipients_count-1].errors_to =
24093 US"postmaster@mydom.example";
24096 .item "uschar *rfc2047@_decode(uschar *string, BOOL lencheck, uschar *target, int zeroval, int *lenptr, uschar **error)"
24097 This function decodes strings that are encoded according to RFC 2047. Typically
24098 these are the contents of header lines. First, each encoded `word' is decoded
24099 from the Q or B encoding into a byte-string. Then, if provided with the name of
24100 a charset encoding, and if the \*iconv()*\ function is available, an attempt is
24101 made to translate the result to the named character set. If this fails, the
24102 binary string is returned with an error message.
24104 The first argument is the string to be decoded. If \lencheck\ is TRUE, the
24105 maximum MIME word length is enforced. The third argument is the target
24106 encoding, or NULL if no translation is wanted.
24108 .index binary zero||in RFC 2047 decoding
24109 If a binary zero is encountered in the decoded string, it is replaced by the
24110 contents of the \zeroval\ argument. For use with Exim headers, the value must
24111 not be 0 because header lines are handled as zero-terminated strings.
24113 The function returns the result of processing the string, zero-terminated; if
24114 \lenptr\ is not NULL, the length of the result is set in the variable to which
24115 it points. When \zeroval\ is 0, \lenptr\ should not be NULL.
24117 If an error is encountered, the function returns NULL and uses the \error\
24118 argument to return an error message. The variable pointed to by \error\ is set
24119 to NULL if there is no error; it may be set non-NULL even when the function
24120 returns a non-NULL value if decoding was successful, but there was a problem
24124 .item "int smtp@_fflush(void)"
24125 This function is used in conjunction with \*smtp@_printf()*\, as described
24128 .item "void smtp@_printf(char *, ...)"
24129 The arguments of this function are like \*printf()*\; it writes to the SMTP
24130 output stream. You should use this function only when there is an SMTP output
24131 stream, that is, when the incoming message is being received via interactive
24132 SMTP. This is the case when \smtp@_input\ is TRUE and \smtp@_batched@_input\ is
24133 FALSE. If you want to test for an incoming message from another host (as
24134 opposed to a local process that used the \-bs-\ command line option), you can
24135 test the value of \sender@_host@_address\, which is non-NULL when a remote host
24138 If an SMTP TLS connection is established, \*smtp@_printf()*\ uses the TLS
24139 output function, so it can be used for all forms of SMTP connection.
24141 Strings that are written by \*smtp@_printf()*\ from within \*local@_scan()*\
24142 must start with an appropriate response code: 550 if you are going to return
24143 \\LOCAL@_SCAN@_REJECT\\, 451 if you are going to return
24144 \\LOCAL@_SCAN@_TEMPREJECT\\, and 250 otherwise. Because you are writing the
24145 initial lines of a multi-line response, the code must be followed by a hyphen
24146 to indicate that the line is not the final response line. You must also ensure
24147 that the lines you write terminate with CRLF. For example:
24149 smtp_printf("550-this is some extra info\r\n");
24150 return LOCAL_SCAN_REJECT;
24152 Note that you can also create multi-line responses by including newlines in
24153 the data returned via the \return@_text\ argument. The added value of using
24154 \*smtp@_printf()*\ is that, for instance, you could introduce delays between
24155 multiple output lines.
24157 The \*smtp@_printf()*\ function does not return any error indication, because it
24158 does not automatically flush pending output, and therefore does not test
24159 the state of the stream. (In the main code of Exim, flushing and error
24160 detection is done when Exim is ready for the next SMTP input command.) If
24161 you want to flush the output and check for an error (for example, the
24162 dropping of a TCP/IP connection), you can call \*smtp@_fflush()*\, which has no
24163 arguments. It flushes the output stream, and returns a non-zero value if there
24166 .item "void *store@_get(int)"
24167 This function accesses Exim's internal store (memory) manager. It gets a new
24168 chunk of memory whose size is given by the argument. Exim bombs out if it ever
24169 runs out of memory. See the next section for a discussion of memory handling.
24171 .item "void *store@_get@_perm(int)"
24172 This function is like \*store@_get()*\, but it always gets memory from the
24173 permanent pool. See the next section for a discussion of memory handling.
24175 .item "uschar *string@_copy(uschar *string)"
24176 .item "uschar *string@_copyn(uschar *string, int length)" 0
24177 .item "uschar *string@_sprintf(char *format, ...)" 0
24178 These three functions create strings using Exim's dynamic memory facilities.
24179 The first makes a copy of an entire string. The second copies up to a maximum
24180 number of characters, indicated by the second argument. The third uses a format
24181 and insertion arguments to create a new string. In each case, the result is a
24182 pointer to a new string
24183 in the current memory pool. See the next section for more discussion.
24189 .section More about Exim's memory handling
24190 .rset SECTmemhanloc "~~chapter.~~section"
24191 .index \*local@_scan()*\ function||memory handling
24192 No function is provided for freeing memory, because that is never needed.
24193 The dynamic memory that Exim uses when receiving a message is automatically
24194 recycled if another message is received by the same process (this applies only
24195 to incoming SMTP connections -- other input methods can supply only one message
24196 at a time). After receiving the last message, a reception process terminates.
24198 Because it is recycled, the normal dynamic memory cannot be used for holding
24199 data that must be preserved over a number of incoming messages on the same SMTP
24200 connection. However, Exim in fact uses two pools of dynamic memory; the second
24201 one is not recycled, and can be used for this purpose.
24203 If you want to allocate memory that remains available for subsequent messages
24204 in the same SMTP connection, you should set
24206 store_pool = POOL_PERM
24208 before calling the function that does the allocation. There is no need to
24209 restore the value if you do not need to; however, if you do want to revert to
24210 the normal pool, you can either restore the previous value of \store@_pool\ or
24211 set it explicitly to \\POOL@_MAIN\\.
24213 The pool setting applies to all functions that get dynamic memory, including
24214 \*expand@_string()*\, \*store@_get()*\, and the \*string@_xxx()*\ functions.
24215 There is also a convenience function called \*store@_get@_perm()*\ that gets a
24216 block of memory from the permanent pool while preserving the value of
24227 . ============================================================================
24228 .chapter System-wide message filtering
24229 .set runningfoot "system filtering"
24230 .rset CHAPsystemfilter "~~chapter"
24231 .index filter||system filter
24232 .index filtering all mail
24233 .index system filter
24234 The previous chapters (on ACLs and the local scan function) describe checks
24235 that can be applied to messages before they are accepted by a host. There is
24236 also a mechanism for checking messages once they have been received, but before
24237 they are delivered. This is called the $it{system filter}.
24239 The system filter operates in a similar manner to users' filter files, but it
24240 is run just once per message (however many recipients the message has).
24241 It should not normally be used as a substitute for routing, because \deliver\
24242 commands in a system router provide new envelope recipient addresses.
24243 The system filter must be an Exim filter. It cannot be a Sieve filter.
24245 The system filter is run at the start of a delivery attempt, before any routing
24246 is done. If a message fails to be completely delivered at the first attempt,
24247 the system filter is run again at the start of every retry.
24248 If you want your filter to do something only once per message, you can make use
24249 of the \first@_delivery\ condition in an \if\ command in the filter to prevent
24250 it happening on retries.
24252 \**Warning**\: Because the system filter runs just once, variables that are
24253 specific to individual recipient addresses, such as \$local@_part$\ and
24254 \$domain$\, are not set, and the `personal' condition is not meaningful. If you
24255 want to run a centrally-specified filter for each recipient address
24256 independently, you can do so by setting up a suitable \%redirect%\ router, as
24257 described in section ~~SECTperaddfil below.
24259 .section Specifying a system filter
24260 .index uid (user id)||system filter
24261 .index gid (group id)||system filter
24262 The name of the file that contains the system filter must be specified by
24263 setting \system@_filter\. If you want the filter to run under a uid and gid
24264 other than root, you must also set \system@_filter@_user\ and
24265 \system@_filter@_group\ as appropriate. For example:
24267 system_filter = /etc/mail/exim.filter
24268 system_filter_user = exim
24270 If a system filter generates any deliveries directly to files or pipes (via the
24271 \save\ or \pipe\ commands), transports to handle these deliveries must be
24272 specified by setting \system@_filter@_file@_transport\ and
24273 \system@_filter@_pipe@_transport\, respectively. Similarly,
24274 \system@_filter@_reply@_transport\ must be set to handle any messages generated
24275 by the \reply\ command.
24277 .section Testing a system filter
24278 You can run simple tests of a system filter in the same way as for a user
24279 filter, but you should use \-bF-\ rather than \-bf-\, so that features that
24280 are permitted only in system filters are recognized.
24282 .section Contents of a system filter
24283 The language used to specify system filters is the same as for users' filter
24284 files. It is described in the separate end-user document \*Exim's interface to
24285 mail filtering*\. However, there are some additional features that are
24286 available only in system filters; these are described in subsequent sections.
24287 If they are encountered in a user's filter file or when testing with \-bf-\,
24290 .index frozen messages||manual thaw, testing in filter
24291 There are two special conditions which, though available in users' filter
24292 files, are designed for use in system filters. The condition \first@_delivery\
24293 is true only for the first attempt at delivering a message, and
24294 \manually@_thawed\ is true only if the message has been frozen, and
24295 subsequently thawed by an admin user. An explicit forced delivery counts as a
24296 manual thaw, but thawing as a result of the \auto__thaw\ setting does not.
24298 \**Warning**\: If a system filter uses the \first@_delivery\ condition to
24299 specify an `unseen' (non-significant) delivery, and that delivery does not
24300 succeed, it will not be tried again.
24301 If you want Exim to retry an unseen delivery until it succeeds, you should
24302 arrange to set it up every time the filter runs.
24304 When a system filter finishes running, the values of the variables \$n0$\ --
24305 \$n9$\ are copied into \$sn0$\ -- \$sn9$\ and are thereby made available to
24306 users' filter files. Thus a system filter can, for example, set up `scores' to
24307 which users' filter files can refer.
24310 .section Additional variable for system filters
24311 The expansion variable \$recipients$\, containing a list of all the recipients
24312 of the message (separated by commas and white space), is available in system
24313 filters. It is not available in users' filters for privacy reasons.
24316 .section Defer, freeze, and fail commands for system filters
24317 .index freezing messages
24318 .index message||freezing
24319 .index message||forced failure
24320 .index \fail\||in system filter
24321 .index \freeze\ in system filter
24322 .index \defer\ in system filter
24323 There are three extra commands (\defer\, \freeze\ and \fail\) which are always
24324 available in system filters, but are not normally enabled in users' filters.
24325 (See the \allow@_defer\,
24326 \allow@_freeze\ and \allow@_fail\ options for the \%redirect%\ router.) These
24327 commands can optionally be followed by the word \text\ and a string containing
24328 an error message, for example:
24330 fail text "this message looks like spam to me"
24332 The keyword \text\ is optional if the next character is a double quote.
24334 The \defer\ command defers delivery of the original recipients of the message.
24335 The \fail\ command causes all the original recipients to be failed, and a
24336 bounce message to be created. The \freeze\ command suspends all delivery
24337 attempts for the original recipients. In all cases, any new deliveries that are
24338 specified by the filter are attempted as normal after the filter has run.
24340 The \freeze\ command is ignored if the message has been manually unfrozen and
24341 not manually frozen since. This means that automatic freezing by a system
24342 filter can be used as a way of checking out suspicious messages. If a message
24343 is found to be all right, manually unfreezing it allows it to be delivered.
24345 .index log||\fail\ command log line
24346 .index \fail\||log line, reducing
24347 The text given with a fail command is used as part of the bounce message as
24348 well as being written to the log. If the message is quite long, this can fill
24349 up a lot of log space when such failures are common. To reduce the size of the
24350 log message, Exim interprets the text in a special way if it starts with the
24351 two characters \"@<@<"\ and contains \"@>@>"\ later. The text between these two
24352 strings is written to the log, and the rest of the text is used in the bounce
24353 message. For example:
24355 fail "<<filter test 1>>Your message is rejected \
24356 because it contains attachments that we are \
24357 not prepared to receive."
24360 .index loop||caused by \fail\
24361 Take great care with the \fail\ command when basing the decision to fail on the
24362 contents of the message, because the bounce message will of course include the
24363 contents of the original message and will therefore trigger the \fail\ command
24364 again (causing a mail loop) unless steps are taken to prevent this. Testing the
24365 \error@_message\ condition is one way to prevent this. You could use, for
24368 if $message_body contains "this is spam" and not error_message
24369 then fail text "spam is not wanted here" endif
24371 though of course that might let through unwanted bounce messages. The
24372 alternative is clever checking of the body and/or headers to detect bounces
24373 generated by the filter.
24375 The interpretation of a system filter file ceases after a
24377 \freeze\, or \fail\ command is obeyed. However, any deliveries that were set up
24378 earlier in the filter file are honoured, so you can use a sequence such as
24383 to send a specified message when the system filter is freezing (or deferring or
24384 failing) a message. The normal deliveries for the message do not, of course,
24388 .section Adding and removing headers in a system filter
24389 .index header lines||adding in system filter
24390 .index header lines||removing in system filter
24391 .index filter||header lines, adding/removing
24392 Two filter commands that are available only in system filters are:
24394 headers add <<string>>
24395 headers remove <<string>>
24397 The argument for the \headers add\ is a string which is expanded and then added
24398 to the end of the message's headers. It is the responsibility of the filter
24399 maintainer to make sure it conforms to RFC 2822 syntax. Leading white space is
24400 ignored, and if the string is otherwise empty, or if the expansion is forced to
24401 fail, the command has no effect.
24403 If the message is not delivered at the first attempt, header lines that were
24404 added by the system filter are stored with the message, and so are still
24405 present at the next delivery attempt. For that reason, it is usual to make the
24406 \headers add\ command conditional on \first@_delivery\.
24408 You can use `@\n' within the string, followed by white space, to specify
24409 continued header lines. More than one header may be added in one command by
24410 including `@\n' within the string without any following white space. For
24413 headers add "X-header-1: ....\n \
24414 continuation of X-header-1 ...\n\
24417 Note that the header line continuation white space after the first newline must
24418 be placed before the backslash that continues the input string, because white
24419 space after input continuations is ignored.
24421 Header lines that are added by a system filter are visible to users' filter
24422 files and to all routers and transports.
24424 The argument for \headers remove\ is a colon-separated list of header names.
24425 This command applies only to those headers that are stored with the message;
24426 those that are added at delivery time (such as ::Envelope-To:: and
24427 ::Return-Path::) cannot be removed by this means.
24428 If there is more than one header with the same name, they are all removed.
24431 .section Setting an errors address in a system filter
24432 .index envelope sender
24433 In a system filter, if a \deliver\ command is followed by
24435 errors@_to <<some address>>
24437 in order to change the envelope sender (and hence the error reporting) for that
24438 delivery, any address may be specified. (In a user filter, only the current
24439 user's address can be set.) For example, if some mail is being monitored, you
24442 unseen deliver monitor@spying.example errors_to root@local.example
24444 to take a copy which would not be sent back to the normal error reporting
24445 address if its delivery failed.
24448 .section Per-address filtering
24449 .rset SECTperaddfil "~~chapter.~~section"
24450 In contrast to the system filter, which is run just once per message for each
24451 delivery attempt, it is also possible to set up a system-wide filtering
24452 operation that runs once for each recipient address. In this case, variables
24453 such as \$local@_part$\ and \$domain$\ can be used, and indeed, the choice of
24454 filter file could be made dependent on them. This is an example of a router
24455 which implements such a filter:
24462 domains = +local_domains
24463 file = /central/filters/$local_part
24468 The filter is run in a separate process under its own uid. Therefore, either
24469 \check@_local@_user\ must be set (as above), in which case the filter is run as
24470 the local user, or the \user\ option must be used to specify which user to use.
24471 If both are set, \user\ overrides.
24473 Care should be taken to ensure that none of the commands in the filter file
24474 specify a significant delivery if the message is to go on to be delivered to
24475 its intended recipient. The router will not then claim to have dealt with the
24476 address, so it will be passed on to subsequent routers to be delivered in the
24487 . ============================================================================
24488 .chapter Customizing bounce and warning messages
24489 .set runningfoot "customizing messages"
24490 .rset CHAPemsgcust "~~chapter"
24491 When a message fails to be delivered, or remains on the queue for more than a
24492 configured amount of time, Exim sends a message to the original sender, or
24493 to an alternative configured address. The text of these messages is built into
24494 the code of Exim, but it is possible to change it, either by adding a single
24495 string, or by replacing each of the paragraphs by text supplied in a file.
24497 The ::From:: and ::To:: header lines are automatically generated; you can cause
24498 a ::Reply-To:: line to be added by setting the \errors@_reply@_to\ option. Exim
24501 Auto-Submitted: auto-generated
24503 to all warning and bounce messages,
24505 .section Customizing bounce messages
24506 .index customizing||bounce message
24507 .index bounce message||customizing
24508 If \bounce@_message@_text\ is set, its contents are included in the default
24509 message immediately after `This message was created automatically by mail
24510 delivery software.' The string is not expanded. It is not used if
24511 \bounce@_message@_file\ is set.
24513 When \bounce@_message@_file\ is set, it must point to a template file for
24514 constructing error messages. The file consists of a series of text items,
24515 separated by lines consisting of exactly four asterisks. If the file cannot be
24516 opened, default text is used and a message is written to the main and panic
24517 logs. If any text item in the file is empty, default text is used for that
24520 Each item of text that is read from the file is expanded, and there are two
24521 expansion variables which can be of use here: \$bounce@_recipient$\ is set to
24522 the recipient of an error message while it is being created, and
24523 \$return@_size@_limit$\ contains the value of the \return@_size@_limit\ option,
24524 rounded to a whole number.
24526 The items must appear in the file in the following order:
24528 The first item is included in the headers, and should include at least a
24529 ::Subject:: header. Exim does not check the syntax of these headers.
24531 The second item forms the start of the error message. After it, Exim lists the
24532 failing addresses with their error messages.
24534 The third item is used to introduce any text from pipe transports that is to be
24535 returned to the sender. It is omitted if there is no such text.
24537 The fourth item is used to introduce the copy of the message that is returned
24538 as part of the error report.
24540 The fifth item is added after the fourth one if the returned message is
24541 truncated because it is bigger than \return@_size@_limit\.
24543 The sixth item is added after the copy of the original message.
24545 The default state (\bounce@_message@_file\ unset) is equivalent to the
24546 following file, in which the sixth item is empty. The ::Subject:: line has been
24547 split into two here in order to fit it on the page:
24558 Subject: Mail delivery failed
24559 ${if eq{$sender_address}{$bounce_recipient}{: returning message to sender}}
24561 This message was created automatically by mail delivery software.
24563 A message ${if eq{$sender_address}{$bounce_recipient}{that you sent }{sent by
24567 }}could not be delivered to all of its recipients.
24568 The following address(es) failed:
24570 The following text was generated during the delivery attempt(s):
24572 ------ This is a copy of the message, including all the headers. ------
24574 ------ The body of the message is $message_size characters long; only the first
24575 ------ $return_size_limit or so are included here.
24582 .section Customizing warning messages
24583 .rset SECTcustwarn "~~chapter.~~section"
24584 .index customizing||warning message
24585 .index warning of delay||customizing the message
24587 \warn@_message@_file\
24588 can be pointed at a template file for use when
24589 warnings about message delays are created. In this case there are only three
24592 The first item is included in the headers, and should include at least a
24593 ::Subject:: header. Exim does not check the syntax of these headers.
24595 The second item forms the start of the warning message. After it, Exim lists
24596 the delayed addresses.
24598 The third item then ends the message.
24600 The default state is equivalent to the following file, except that the line
24601 starting `A message' has been split here, in order to fit it on the page:
24613 Subject: Warning: message $message_id delayed $warn_message_delay
24615 This message was created automatically by mail delivery software.
24617 A message ${if eq{$sender_address}{$warn_message_recipients}
24618 {that you sent }{sent by
24622 }}has not been delivered to all of its recipients after
24623 more than $warn_message_delay on the queue on $primary_hostname.
24626 The message identifier is: $message_id
24627 The subject of the message is: $h_subject
24628 The date of the message is: $h_date
24630 The following address(es) have not yet been delivered:
24632 No action is required on your part. Delivery attempts will continue for
24633 some time, and this warning may be repeated at intervals if the message
24634 remains undelivered. Eventually the mail delivery software will give up,
24635 and when that happens, the message will be returned to you.
24640 except that in the default state the subject and date lines are omitted if no
24641 appropriate headers exist. During the expansion of this file,
24642 \$warn@_message@_delay$\
24643 is set to the delay time in one of the forms `<<n>> minutes'
24644 or `<<n>> hours', and
24645 \$warn@_message@_recipients$\
24646 contains a list of recipients for the warning message. There may be more than
24647 one if there are multiple addresses with different \errors@_to\ settings on the
24648 routers that handled them.
24656 . ============================================================================
24657 .chapter Some common configuration requirements
24658 .set runningfoot "common configuration requirements"
24659 .rset CHAPcomconreq "~~chapter"
24660 This chapter discusses some configuration requirements that seem to be fairly
24661 common. More examples and discussion can be found in the Exim book.
24664 .section Sending mail to a smart host
24665 .index smart host||example router
24666 If you want to send all mail for non-local domains to a `smart host', you
24667 should replace the default \%dnslookup%\ router with a router which does the
24668 routing explicitly:
24670 send_to_smart_host:
24671 driver = manualroute
24672 route_list = !+local_domains smart.host.name
24673 transport = remote_smtp
24675 You can use the smart host's IP address instead of the name if you wish.
24678 .section Using Exim to handle mailing lists
24679 .rset SECTmailinglists "~~chapter.~~section"
24680 .index mailing lists
24681 Exim can be used to run simple mailing lists, but for large and/or complicated
24682 requirements, the use of additional specialized mailing list software such as
24683 Majordomo or Mailman is recommended.
24685 The \%redirect%\ router can be used to handle mailing lists where each list
24686 is maintained in a separate file, which can therefore be managed by an
24687 independent manager. The \domains\ router option can be used to run these
24688 lists in a separate domain from normal mail. For example:
24692 domains = lists.example
24693 file = /usr/lists/$local_part
24696 errors_to = $local_part-request@lists.example
24699 This router is skipped for domains other than \*lists.example*\. For addresses
24700 in that domain, it looks for a file that matches the local part. If there is no
24701 such file, the router declines, but because \no@_more\ is set, no subsequent
24702 routers are tried, and so the whole delivery fails.
24704 The \forbid@_pipe\ and \forbid@_file\ options prevent a local part from being
24705 expanded into a file name or a pipe delivery, which is usually inappropriate in
24708 .index \errors@_to\
24709 The \errors@_to\ option specifies that any delivery errors caused by addresses
24710 taken from a mailing list are to be sent to the given address rather than the
24711 original sender of the message. However, before acting on this, Exim verifies
24712 the error address, and ignores it if verification fails.
24714 For example, using the configuration above, mail sent to
24715 \*dicts@@lists.example*\ is passed on to those addresses contained in
24716 \(/usr/lists/dicts)\, with error reports directed to
24717 \*dicts-request@@lists.example*\, provided that this address can be verified.
24718 There could be a file called \(/usr/lists/dicts-request)\ containing
24719 the address(es) of this particular list's manager(s), but other approaches,
24720 such as setting up an earlier router (possibly using the \local@_part@_prefix\
24721 or \local@_part@_suffix\ options) to handle addresses of the form \owner-xxx\
24722 or \xxx-request\, are also possible.
24725 .section Syntax errors in mailing lists
24726 .index mailing lists||syntax errors in
24727 If an entry in redirection data contains a syntax error, Exim normally defers
24728 delivery of the original address. That means that a syntax error in a mailing
24729 list holds up all deliveries to the list. This may not be appropriate when a
24730 list is being maintained automatically from data supplied by users, and the
24731 addresses are not rigorously checked.
24733 If the \skip@_syntax@_errors\ option is set, the \%redirect%\ router just skips
24734 entries that fail to parse, noting the incident in the log. If in addition
24735 \syntax@_errors@_to\ is set to a verifiable address, a message is sent to it
24736 whenever a broken address is skipped. It is usually appropriate to set
24737 \syntax@_errors@_to\ to the same address as \errors@_to\.
24740 .section Re-expansion of mailing lists
24741 .index mailing lists||re-expansion of
24742 Exim remembers every individual address to which a message has been delivered,
24743 in order to avoid duplication, but it normally stores only the original
24744 recipient addresses with a message. If all the deliveries to a mailing list
24745 cannot be done at the first attempt, the mailing list is re-expanded when the
24746 delivery is next tried. This means that alterations to the list are taken into
24747 account at each delivery attempt, so addresses that have been added to
24748 the list since the message arrived will therefore receive a copy of the
24749 message, even though it pre-dates their subscription.
24751 If this behaviour is felt to be undesirable, the \one@_time\ option can be set
24752 on the \%redirect%\ router. If this is done, any addresses generated by the
24753 router that fail to deliver at the first attempt are added to the message as
24754 `top level' addresses, and the parent address that generated them is marked
24755 `delivered'. Thus, expansion of the mailing list does not happen again at the
24756 subsequent delivery attempts. The disadvantage of this is that if any of the
24757 failing addresses are incorrect, correcting them in the file has no effect on
24758 pre-existing messages.
24760 The original top-level address is remembered with each of the generated
24761 addresses, and is output in any log messages. However, any intermediate parent
24762 addresses are not recorded. This makes a difference to the log only if the
24763 \all@_parents\ selector is set, but for mailing lists there is normally only
24764 one level of expansion anyway.
24767 .section Closed mailing lists
24768 .index mailing lists||closed
24769 The examples so far have assumed open mailing lists, to which anybody may
24770 send mail. It is also possible to set up closed lists, where mail is accepted
24771 from specified senders only. This is done by making use of the generic
24772 \senders\ option to restrict the router that handles the list.
24774 The following example uses the same file as a list of recipients and as a list
24775 of permitted senders. It requires three routers:
24779 domains = lists.example
24780 local_part_suffix = -request
24781 file = /usr/lists/$local_part$local_part_suffix
24786 domains = lists.example
24787 senders = ${if exists {/usr/lists/$local_part}\
24788 {lsearch;/usr/lists/$local_part}{*}}
24789 file = /usr/lists/$local_part
24792 errors_to = $local_part-request@lists.example
24797 domains = lists.example
24799 data = :fail: $local_part@lists.example is a closed mailing list
24801 All three routers have the same \domains\ setting, so for any other domains,
24802 they are all skipped. The first router runs only if the local part ends in
24803 \@-request\. It handles messages to the list manager(s) by means of an open
24806 The second router runs only if the \senders\ precondition is satisfied. It
24807 checks for the existence of a list that corresponds to the local part, and then
24808 checks that the sender is on the list by means of a linear search. It is
24809 necessary to check for the existence of the file before trying to search it,
24810 because otherwise Exim thinks there is a configuration error. If the file does
24811 not exist, the expansion of \senders\ is $*$, which matches all senders. This
24812 means that the router runs, but because there is no list, declines, and
24813 \no@_more\ ensures that no further routers are run. The address fails with an
24814 `unrouteable address' error.
24816 The third router runs only if the second router is skipped, which happens when
24817 a mailing list exists, but the sender is not on it. This router forcibly fails
24818 the address, giving a suitable error message.
24822 .section Virtual domains
24823 .rset SECTvirtualdomains "~~chapter.~~section"
24824 .index virtual domains
24825 .index domain||virtual
24826 The phrase \*virtual domain*\ is unfortunately used with two rather different
24829 A domain for which there are no real mailboxes; all valid local parts are
24830 aliases for other email addresses. Common examples are organizational
24831 top-level domains and `vanity' domains.
24833 One of a number of independent domains that are all handled by the same host,
24834 with mailboxes on that host, but where the mailbox owners do not necessarily
24835 have login accounts on that host.
24837 The first usage is probably more common, and does seem more `virtual' than the
24838 second. This kind of domain can be handled in Exim with a straightforward
24839 aliasing router. One approach is to create a separate alias file for each
24840 virtual domain. Exim can test for the existence of the alias file to determine
24841 whether the domain exists. The \%dsearch%\ lookup type is useful here, leading
24842 to a router of this form:
24846 domains = dsearch;/etc/mail/virtual
24847 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
24850 The \domains\ option specifies that the router is to be skipped, unless there
24851 is a file in the \(/etc/mail/virtual)\ directory whose name is the same as the
24852 domain that is being processed. When the router runs, it looks up the local
24853 part in the file to find a new address (or list of addresses). The \no@_more\
24854 setting ensures that if the lookup fails (leading to \data\ being an empty
24855 string), Exim gives up on the address without trying any subsequent routers.
24857 This one router can handle all the virtual domains because the alias file names
24858 follow a fixed pattern. Permissions can be arranged so that appropriate people
24859 can edit the different alias files. A successful aliasing operation results in
24860 a new envelope recipient address, which is then routed from scratch.
24862 The other kind of `virtual' domain can also be handled in a straightforward
24863 way. One approach is to create a file for each domain containing a list of
24864 valid local parts, and use it in a router like this:
24868 domains = dsearch;/etc/mail/domains
24869 local_parts = lsearch;/etc/mail/domains/$domain
24870 transport = my_mailboxes
24872 The address is accepted if there is a file for the domain, and the local part
24873 can be found in the file. The \domains\ option is used to check for the file's
24874 existence because \domains\ is tested before the \local@_parts\ option (see
24875 section ~~SECTrouprecon). You can't use \require@_files\, because that option
24876 is tested after \local@_parts\. The transport is as follows:
24879 driver = appendfile
24880 file = /var/mail/$domain/$local_part
24883 This uses a directory of mailboxes for each domain. The \user\ setting is
24884 required, to specify which uid is to be used for writing to the mailboxes.
24886 The configuration shown here is just one example of how you might support this
24887 requirement. There are many other ways this kind of configuration can be set
24888 up, for example, by using a database instead of separate files to hold all the
24889 information about the domains.
24892 .section Multiple user mailboxes
24893 .rset SECTmulbox "~~chapter.~~section"
24894 .index multiple mailboxes
24895 .index mailbox||multiple
24896 .index local part||prefix
24897 .index local part||suffix
24898 Heavy email users often want to operate with multiple mailboxes, into which
24899 incoming mail is automatically sorted. A popular way of handling this is to
24900 allow users to use multiple sender addresses, so that replies can easily be
24901 identified. Users are permitted to add prefixes or suffixes to their local
24902 parts for this purpose. The wildcard facility of the generic router options
24903 \local@_part@_prefix\ and \local@_part@_suffix\ can be used for this. For
24904 example, consider this router:
24909 file = $home/.forward
24910 local_part_suffix = -*
24911 local_part_suffix_optional
24914 It runs a user's \(.forward)\ file for all local parts of the form
24915 \*username-$*$*\. Within the filter file the user can distinguish different
24916 cases by testing the variable \$local@_part@_suffix$\. For example:
24918 if $local_part_suffix contains -special then
24919 save /home/$local_part/Mail/special
24922 If the filter file does not exist, or does not deal with such addresses, they
24923 fall through to subsequent routers, and, assuming no subsequent use of the
24924 \local@_part@_suffix\ option is made, they presumably fail. Thus, users have
24925 control over which suffixes are valid.
24927 Alternatively, a suffix can be used to trigger the use of a different
24928 \(.forward)\ file -- which is the way a similar facility is implemented in
24934 file = $home/.forward$local_part_suffix
24935 local_part_suffix = -*
24936 local_part_suffix_optional
24939 If there is no suffix, \(.forward)\ is used; if the suffix is \*-special*\, for
24940 example, \(.forward-special)\ is used. Once again, if the appropriate file
24941 does not exist, or does not deal with the address, it is passed on to
24942 subsequent routers, which could, if required, look for an unqualified
24943 \(.forward)\ file to use as a default.
24946 .section Simplified vacation processing
24947 .index vacation processing
24948 The traditional way of running the \*vacation*\ program is for a user to set up
24949 a pipe command in a \(.forward)\ file
24950 (see section ~~SECTspecitredli for syntax details).
24951 This is prone to error by inexperienced users. There are two features of Exim
24952 that can be used to make this process simpler for users:
24954 A local part prefix such as `vacation-' can be specified on a router which
24955 can cause the message to be delivered directly to the \*vacation*\ program, or
24956 alternatively can use Exim's \%autoreply%\ transport. The contents of a user's
24957 \(.forward)\ file are then much simpler. For example:
24959 spqr, vacation-spqr
24962 The \require@_files\ generic router option can be used to trigger a
24963 vacation delivery by checking for the existence of a certain file in the
24964 user's home directory. The \unseen\ generic option should also be used, to
24965 ensure that the original delivery also proceeds. In this case, all the user has
24966 to do is to create a file called, say, \(.vacation)\, containing a vacation
24969 Another advantage of both these methods is that they both work even when the
24970 use of arbitrary pipes by users is locked out.
24973 .section Taking copies of mail
24974 .index message||copying every
24975 Some installations have policies that require archive copies of all messages to
24976 be made. A single copy of each message can easily be taken by an appropriate
24977 command in a system filter, which could, for example, use a different file for
24978 each day's messages.
24980 There is also a shadow transport mechanism that can be used to take copies of
24981 messages that are successfully delivered by local transports, one copy per
24982 delivery. This could be used, $it{inter alia}, to implement automatic
24983 notification of delivery by sites that insist on doing such things.
24986 .section Intermittently connected hosts
24987 .index intermittently connected hosts
24988 It has become quite common (because it is cheaper) for hosts to connect to the
24989 Internet periodically rather than remain connected all the time. The normal
24990 arrangement is that mail for such hosts accumulates on a system that is
24991 permanently connected.
24993 Exim was designed for use on permanently connected hosts, and so it is not
24994 particularly well-suited to use in an intermittently connected environment.
24995 Nevertheless there are some features that can be used.
24997 .section Exim on the upstream server host
24998 It is tempting to arrange for incoming mail for the intermittently connected
24999 host to remain on Exim's queue until the client connects. However, this
25000 approach does not scale very well. Two different kinds of waiting message are
25001 being mixed up in the same queue -- those that cannot be delivered because of
25002 some temporary problem, and those that are waiting for their destination host
25003 to connect. This makes it hard to manage the queue, as well as wasting
25004 resources, because each queue runner scans the entire queue.
25006 A better approach is to separate off those messages that are waiting for an
25007 intermittently connected host. This can be done by delivering these messages
25008 into local files in batch SMTP, `mailstore', or other envelope-preserving
25009 format, from where they are transmitted by other software when their
25010 destination connects. This makes it easy to collect all the mail for one host
25011 in a single directory, and to apply local timeout rules on a per-message basis
25014 On a very small scale, leaving the mail on Exim's queue can be made to work. If
25015 you are doing this, you should configure Exim with a long retry period for the
25016 intermittent host. For example:
25018 cheshire.wonderland.fict.example * F,5d,24h
25020 This stops a lot of failed delivery attempts from occurring, but Exim remembers
25021 which messages it has queued up for that host. Once the intermittent host comes
25022 online, forcing delivery of one message (either by using the \-M-\ or \-R-\
25023 options, or by using the \\ETRN\\ SMTP command (see section ~~SECTETRN)
25024 causes all the queued up messages to be delivered, often down a single SMTP
25025 connection. While the host remains connected, any new messages get delivered
25028 If the connecting hosts do not have fixed IP addresses, that is, if a host is
25029 issued with a different IP address each time it connects, Exim's retry
25030 mechanisms on the holding host get confused, because the IP address is normally
25031 used as part of the key string for holding retry information. This can be
25032 avoided by unsetting \retry__include__ip__address\ on the \%smtp%\ transport.
25033 Since this has disadvantages for permanently connected hosts, it is best to
25034 arrange a separate transport for the intermittently connected ones.
25037 .section Exim on the intermittently connected client host
25038 The value of \smtp@_accept@_queue@_per@_connection\ should probably be
25039 increased, or even set to zero (that is, disabled) on the intermittently
25040 connected host, so that all incoming messages down a single connection get
25041 delivered immediately.
25043 .index SMTP||passed connection
25044 .index SMTP||multiple deliveries
25045 .index multiple SMTP deliveries
25046 Mail waiting to be sent from an intermittently connected host will probably
25047 not have been routed, because without a connection DNS lookups are not
25048 possible. This means that if a normal queue run is done at connection time,
25049 each message is likely to be sent in a separate SMTP session. This can be
25050 avoided by starting the queue run with a command line option beginning with
25051 \-qq-\ instead of \-q-\. In this case, the queue is scanned twice. In the first
25052 pass, routing is done but no deliveries take place. The second pass is a normal
25053 queue run; since all the messages have been previously routed, those destined
25054 for the same host are likely to get sent as multiple deliveries in a single
25065 . ============================================================================
25066 .chapter SMTP processing
25067 .set runningfoot "smtp processing"
25068 .rset CHAPSMTP ~~chapter
25069 .index SMTP||processing details
25070 .index LMTP||processing details
25071 Exim supports a number of different ways of using the SMTP protocol, and its
25072 LMTP variant, which is an interactive protocol for transferring messages into a
25073 closed mail store application. This chapter contains details of how SMTP is
25074 processed. For incoming mail, the following are available:
25076 SMTP over TCP/IP (Exim daemon or \*inetd*\);
25078 SMTP over the standard input and output (the \-bs-\ option);
25080 Batched SMTP on the standard input (the \-bS-\ option).
25082 For mail delivery, the following are available:
25084 SMTP over TCP/IP (the \%smtp%\ transport);
25086 LMTP over TCP/IP (the \%smtp%\ transport with the \protocol\ option set to
25089 LMTP over a pipe to a process running in the local host (the \%lmtp%\
25092 Batched SMTP to a file or pipe (the \%appendfile%\ and \%pipe%\ transports with
25093 the \use@_bsmtp\ option set).
25095 \*Batched SMTP*\ is the name for a process in which batches of messages are
25096 stored in or read from files (or pipes), in a format in which SMTP commands are
25097 used to contain the envelope information.
25100 .section Outgoing SMTP and LMTP over TCP/IP
25101 .rset SECToutSMTPTCP "~~chapter.~~section"
25102 .index SMTP||outgoing over TCP/IP
25103 .index outgoing SMTP over TCP/IP
25104 .index LMTP||over TCP/IP
25105 .index outgoing LMTP over TCP/IP
25108 .index \\SIZE\\ option on \\MAIL\\ command
25109 Outgoing SMTP and LMTP over TCP/IP is implemented by the \%smtp%\ transport.
25110 The \protocol\ option selects which protocol is to be used, but the actual
25111 processing is the same in both cases.
25113 If, in response to its \\EHLO\\ command, Exim is told that the \\SIZE\\
25114 parameter is supported, it adds \\SIZE\\=<<n>> to each subsequent \\MAIL\\
25115 command. The value of <<n>> is the message size plus the value of the
25116 \size@_addition\ option (default 1024) to allow for additions to the message
25117 such as per-transport header lines, or changes made in a
25118 .index transport||filter
25119 .index filter||transport filter
25120 transport filter. If \size@_addition\ is set negative, the use of \\SIZE\\ is
25123 If the remote server advertises support for \\PIPELINING\\, Exim uses the
25124 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
25125 required for the transaction.
25127 If the remote server advertises support for the \\STARTTLS\\ command, and Exim
25128 was built to support TLS encryption, it tries to start a TLS session unless the
25129 server matches \hosts@_avoid@_tls\. See chapter ~~CHAPTLS for more details.
25131 If the remote server advertises support for the \\AUTH\\ command, Exim scans
25132 the authenticators configuration for any suitable client settings, as described
25133 in chapter ~~CHAPSMTPAUTH.
25135 .index carriage return
25137 Responses from the remote host are supposed to be terminated by CR followed by
25138 LF. However, there are known to be hosts that do not send CR characters, so in
25139 order to be able to interwork with such hosts, Exim treats LF on its own as a
25142 If a message contains a number of different addresses, all those with the same
25143 characteristics (for example, the same envelope sender) that resolve to the
25144 same set of hosts, in the same order, are sent in a single SMTP transaction,
25145 even if they are for different domains, unless there are more than the setting
25146 of the \max@_rcpts\ option in the \%smtp%\ transport allows, in which case they
25147 are split into groups containing no more than \max@_rcpts\ addresses each. If
25148 \remote@_max@_parallel\ is greater than one, such groups may be sent in
25149 parallel sessions. The order of hosts with identical MX values is not
25150 significant when checking whether addresses can be batched in this way.
25152 When the \%smtp%\ transport suffers a temporary failure that is not
25153 message-related, Exim updates its transport-specific database, which contains
25154 records indexed by host name that remember which messages are waiting for each
25155 particular host. It also updates the retry database with new retry times.
25156 .index hints database||retry keys
25157 Exim's retry hints are based on host name plus IP address, so if one address of
25158 a multi-homed host is broken, it will soon be skipped most of the time.
25159 See the next section for more detail about error handling.
25161 .index SMTP||passed connection
25162 .index SMTP||batching over TCP/IP
25163 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
25164 looks in the hints database for the transport to see if there are any queued
25165 messages waiting for the host to which it is connected. If it finds one, it
25166 creates a new Exim process using the \-MC-\ option (which can only be used by a
25167 process running as root or the Exim user) and passes the TCP/IP socket to it so
25168 that it can deliver another message using the same socket. The new process does
25169 only those deliveries that are routed to the connected host, and may in turn
25170 pass the socket on to a third process, and so on.
25172 The \connection@_max@_messages\ option of the \%smtp%\ transport can be used to
25173 limit the number of messages sent down a single TCP/IP connection.
25174 .index asterisk||after IP address
25175 The second and subsequent messages delivered down an existing connection are
25176 identified in the main log by the addition of an asterisk after the closing
25177 square bracket of the IP address.
25181 .section Errors in outgoing SMTP
25182 .rset SECToutSMTPerr "~~chapter.~~section"
25183 .index error||in outgoing SMTP
25184 .index SMTP||errors in outgoing
25186 Three different kinds of error are recognized for outgoing SMTP: host errors,
25187 message errors, and recipient errors.
25189 A host error is not associated with a particular message or with a
25190 particular recipient of a message. The host errors are:
25192 Connection refused or timed out,
25194 Any error response code on connection,
25196 Any error response code to \\EHLO\\ or \\HELO\\,
25198 Loss of connection at any time, except after `.',
25200 I/O errors at any time,
25202 Timeouts during the session, other than in response to \\MAIL\\, \\RCPT\\ or
25203 the `.' at the end of the data.
25205 For a host error, a permanent error response on connection, or in response to
25206 \\EHLO\\, causes all addresses routed to the host to be failed. Any other host
25207 error causes all addresses to be deferred, and retry data to be created for the
25208 host. It is not tried again, for any message, until its retry time arrives. If
25209 the current set of addresses are not all delivered in this run (to some
25210 alternative host), the message is added to the list of those waiting for this
25211 host, so if it is still undelivered when a subsequent successful delivery is
25212 made to the host, it will be sent down the same SMTP connection.
25214 .index message||error
25215 A message error is associated with a particular message when sent to a
25216 particular host, but not with a particular recipient of the message. The
25217 message errors are:
25219 Any error response code to \\MAIL\\, \\DATA\\, or the `.' that terminates
25222 Timeout after \\MAIL\\,
25225 or loss of connection after the `.' that terminates the data. A timeout after
25226 the \\DATA\\ command itself is treated as a host error, as is loss of
25227 connection at any other time.
25229 For a message error, a permanent error response (5$it{xx}) causes all addresses
25230 to be failed, and a delivery error report to be returned to the sender. A
25231 temporary error response (4$it{xx}), or one of the timeouts, causes all
25232 addresses to be deferred. Retry data is not created for the host, but instead,
25233 a retry record for the combination of host plus message id is created. The
25234 message is not added to the list of those waiting for this host. This ensures
25235 that the failing message will not be sent to this host again until the retry
25236 time arrives. However, other messages that are routed to the host are not
25237 affected, so if it is some property of the message that is causing the error,
25238 it will not stop the delivery of other mail.
25240 If the remote host specified support for the \\SIZE\\ parameter in its response
25241 to \\EHLO\\, Exim adds SIZE=$it{nnn} to the \\MAIL\\ command, so an
25242 over-large message will cause a message error because the error arrives as a
25243 response to \\MAIL\\.
25245 .index recipient||error
25246 A recipient error is associated with a particular recipient of a message. The
25247 recipient errors are:
25249 Any error response to \\RCPT\\,
25251 Timeout after \\RCPT\\.
25253 For a recipient error, a permanent error response (5$it{xx}) causes the
25254 recipient address to be failed, and a bounce message to be returned to the
25255 sender. A temporary error response (4$it{xx}) or a timeout causes the failing
25256 address to be deferred, and routing retry data to be created for it. This is
25257 used to delay processing of the address in subsequent queue runs, until its
25258 routing retry time arrives. This applies to all messages, but because it
25259 operates only in queue runs, one attempt will be made to deliver a new message
25260 to the failing address before the delay starts to operate. This ensures that,
25261 if the failure is really related to the message rather than the recipient
25262 (`message too big for this recipient' is a possible example), other messages
25263 have a chance of getting delivered. If a delivery to the address does succeed,
25264 the retry information gets cleared, so all stuck messages get tried again, and
25265 the retry clock is reset.
25267 The message is not added to the list of those waiting for this host. Use of the
25268 host for other messages is unaffected, and except in the case of a timeout,
25269 other recipients are processed independently, and may be successfully delivered
25270 in the current SMTP session. After a timeout it is of course impossible to
25271 proceed with the session, so all addresses get deferred. However, those other
25272 than the one that failed do not suffer any subsequent retry delays. Therefore,
25273 if one recipient is causing trouble, the others have a chance of getting
25274 through when a subsequent delivery attempt occurs before the failing
25275 recipient's retry time.
25278 In all cases, if there are other hosts (or IP addresses) available for the
25279 current set of addresses (for example, from multiple MX records), they are
25280 tried in this run for any undelivered addresses, subject of course to their
25281 own retry data. In other words, recipient error retry data does not take effect
25282 until the next delivery attempt.
25284 Some hosts have been observed to give temporary error responses to every
25285 \\MAIL\\ command at certain times (`insufficient space' has been seen). It
25286 would be nice if such circumstances could be recognized, and defer data for the
25287 host itself created, but this is not possible within the current Exim design.
25288 What actually happens is that retry data for every (host, message) combination
25291 The reason that timeouts after \\MAIL\\ and \\RCPT\\ are treated specially is
25292 that these can sometimes arise as a result of the remote host's verification
25293 procedures. Exim makes this assumption, and treats them as if a temporary error
25294 response had been received. A timeout after `.' is treated specially because it
25295 is known that some broken implementations fail to recognize the end of the
25296 message if the last character of the last line is a binary zero. Thus, it is
25297 helpful to treat this case as a message error.
25299 Timeouts at other times are treated as host errors, assuming a problem with the
25300 host, or the connection to it. If a timeout after \\MAIL\\, \\RCPT\\,
25301 or `.' is really a connection problem, the assumption is that at the next try
25302 the timeout is likely to occur at some other point in the dialogue, causing it
25303 then to be treated as a host error.
25305 There is experimental evidence that some MTAs drop the connection after the
25306 terminating `.' if they do not like the contents of the message for some
25307 reason, in contravention of the RFC, which indicates that a 5$it{xx} response
25308 should be given. That is why Exim treats this case as a message rather than a
25309 host error, in order not to delay other messages to the same host.
25314 .section Variable Envelope Return Paths (VERP)
25316 .index Variable Envelope Return Paths
25317 .index envelope sender
25318 Variable Envelope Return Paths -- see
25319 \?ftp://koobera.math.uic.edu/www/proto/verp.txt?\ -- can be supported in Exim
25320 by using the \return@_path\ generic transport option to rewrite the return path
25321 at transport time. For example, the following could be used on an \%smtp%\
25325 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
25326 {$1-request=$local_part%$domain@your.dom.example}fail}
25328 This has the effect of rewriting the return path (envelope sender) on all
25329 outgoing SMTP messages, if the local part of the original return path ends in
25330 `-request', and the domain is \*your.dom.example*\. The rewriting inserts the
25331 local part and domain of the recipient into the return path. Suppose, for
25332 example, that a message whose return path has been set to
25333 \*somelist-request@@your.dom.example*\ is sent to
25334 \*subscriber@@other.dom.example*\. In the transport, the return path is
25337 somelist-request=subscriber%other.dom.example@your.dom.example
25339 For this to work, you must arrange for outgoing messages that have `-request'
25340 in their return paths to have just a single recipient. This can be done by
25345 in the \%smtp%\ transport. Otherwise a single copy of a message might be
25346 addressed to several different recipients in the same domain, in which case
25347 \$local@_part$\ is not available (because it is not unique). Of course, if you
25348 do start sending out messages with this kind of return path, you must also
25349 configure Exim to accept the bounce messages that come back to those paths.
25350 Typically this would be done by setting an \local@_part@_suffix\ option for a
25353 The overhead incurred in using VERP depends very much on the size of the
25354 message, the number of recipient addresses that resolve to the same remote
25355 host, and the speed of the connection over which the message is being sent. If
25356 a lot of addresses resolve to the same host and the connection is slow, sending
25357 a separate copy of the message for each address may take substantially longer
25358 than sending a single copy with many recipients (for which VERP cannot be
25362 .section Incoming SMTP messages over TCP/IP
25363 .index SMTP||incoming over TCP/IP
25364 .index incoming SMTP over TCP/IP
25367 Incoming SMTP messages can be accepted in one of two ways: by running a
25368 listening daemon, or by using \*inetd*\. In the latter case, the entry in
25369 \(/etc/inetd.conf)\ should be like this:
25371 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
25373 Exim distinguishes between this case and the case of a locally running user
25374 agent using the \-bs-\ option by checking whether or not the standard input is
25375 a socket. When it is, either the port must be privileged (less than 1024), or
25376 the caller must be root or the Exim user. If any other user passes a socket
25377 with an unprivileged port number, Exim prints a message on the standard error
25378 stream and exits with an error code.
25380 By default, Exim does not make a log entry when a remote host connects or
25381 disconnects (either via the daemon or \*inetd*\), unless the disconnection is
25382 unexpected. It can be made to write such log entries by setting the
25383 \smtp@_connection\ log selector.
25385 .index carriage return
25387 Commands from the remote host are supposed to be terminated by CR followed by
25388 LF. However, there are known to be hosts that do not send CR characters. In
25389 order to be able to interwork with such hosts, Exim treats LF on its own as a
25391 Furthermore, because common code is used for receiving messages from all
25392 sources, a CR on its own is also interpreted as a line terminator. However, the
25393 sequence `CR, dot, CR' does not terminate incoming SMTP data.
25395 .index \\EHLO\\||invalid data
25396 .index \\HELO\\||invalid data
25397 One area that sometimes gives rise to problems concerns the \\EHLO\\ or
25398 \\HELO\\ commands. Some clients send syntactically invalid versions of these
25399 commands, which Exim rejects by default. (This is nothing to do with verifying
25400 the data that is sent, so \helo@_verify@_hosts\ is not relevant.) You can tell
25401 Exim not to apply a syntax check by setting \helo@_accept@_junk@_hosts\ to
25402 match the broken hosts that send invalid commands.
25404 .index \\SIZE\\ option on \\MAIL\\ command
25405 .index \\MAIL\\||\\SIZE\\ option
25406 The amount of disk space available is checked whenever \\SIZE\\ is received on
25407 a \\MAIL\\ command, independently of whether \message@_size@_limit\ or
25408 \check@_spool@_space\ is configured, unless \smtp__check__spool__space\ is set
25409 false. A temporary error is given if there is not enough space. If
25410 \check@_spool@_space\ is set, the check is for that amount of space plus the
25411 value given with \\SIZE\\, that is, it checks that the addition of the incoming
25412 message will not reduce the space below the threshold.
25414 When a message is successfully received, Exim includes the local message id in
25415 its response to the final `.' that terminates the data. If the remote host logs
25416 this text it can help with tracing what has happened to a message.
25418 The Exim daemon can limit the number of simultaneous incoming connections it is
25419 prepared to handle (see the \smtp@_accept@_max\ option). It can also limit the
25420 number of simultaneous incoming connections from a single remote host (see the
25421 \smtp@_accept@_max@_per@_host\ option). Additional connection attempts are
25422 rejected using the SMTP temporary error code 421.
25424 The Exim daemon does not rely on the \\SIGCHLD\\ signal to detect when a
25425 subprocess has finished, as this can get lost at busy times. Instead, it looks
25426 for completed subprocesses every time it wakes up. Provided there are other
25427 things happening (new incoming calls, starts of queue runs), completed
25428 processes will be noticed and tidied away. On very quiet systems you may
25429 sometimes see a `defunct' Exim process hanging about. This is not a problem; it
25430 will be noticed when the daemon next wakes up.
25432 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
25433 and can also be set up to reject SMTP calls from non-reserved hosts at times of
25434 high system load -- for details see the \smtp@_accept@_reserve\,
25435 \smtp@_load@_reserve\, and \smtp@_reserve@_hosts\ options. The load check
25436 applies in both the daemon and \*inetd*\ cases.
25438 Exim normally starts a delivery process for each message received, though this
25439 can be varied by means of the \-odq-\ command line option and the
25440 \queue@_only\, \queue@_only@_file\, and \queue@_only@_load\ options. The number
25441 of simultaneously running delivery processes started in this way from SMTP
25442 input can be limited by the \smtp__accept__queue\ and
25443 \smtp__accept__queue__per__connection\ options. When either limit is reached,
25444 subsequently received messages are just put on the input queue without starting
25445 a delivery process.
25447 The controls that involve counts of incoming SMTP calls (\smtp@_accept@_max\,
25448 \smtp@_accept@_queue\, \smtp__accept__reserve\) are not available when Exim is
25449 started up from the \*inetd*\ daemon, because in that case each connection is
25450 handled by an entirely independent Exim process. Control by load average is,
25451 however, available with \*inetd*\.
25453 Exim can be configured to verify addresses in incoming SMTP commands as they
25454 are received. See chapter ~~CHAPACL for details. It can also be configured to
25455 rewrite addresses at this time -- before any syntax checking is done. See
25456 section ~~SECTrewriteS.
25458 Exim can also be configured to limit the rate at which a client host submits
25459 \\MAIL\\ and \\RCPT\\ commands in a single SMTP session. See the
25460 \smtp@_ratelimit@_hosts\ option.
25463 .section Unrecognized SMTP commands
25464 .index SMTP||unrecognized commands
25465 If Exim receives more than \smtp@_max@_unknown@_commands\ unrecognized SMTP
25466 commands during a single SMTP connection, it drops the connection after sending
25467 the error response to the last command. The default value for
25468 \smtp@_max@_unknown@_commands\ is 3. This is a defence against some kinds of
25469 abuse that subvert web servers into making connections to SMTP ports; in these
25470 circumstances, a number of non-SMTP lines are sent first.
25472 .section Syntax and protocol errors in SMTP commands
25473 .index SMTP||syntax errors
25474 .index SMTP||protocol errors
25475 A syntax error is detected if an SMTP command is recognized, but there is
25476 something syntactically wrong with its data, for example, a malformed email
25477 address in a \\RCPT\\ command. Protocol errors include invalid command
25478 sequencing such as \\RCPT\\ before \\MAIL\\. If Exim receives more than
25479 \smtp@_max@_synprot@_errors\ such commands during a single SMTP connection, it
25480 drops the connection after sending the error response to the last command. The
25481 default value for \smtp__max__synprot__errors\ is 3. This is a defence against
25482 broken clients that loop sending bad commands (yes, it has been seen).
25485 .section Use of non-mail SMTP commands
25486 .index SMTP||non-mail commands
25487 The `non-mail' SMTP commands are those other than \\MAIL\\, \\RCPT\\, and
25488 \\DATA\\. Exim counts such commands, and drops the connection if there are too
25489 many of them in a single SMTP session. This action catches some
25490 denial-of-service attempts and things like repeated failing \\AUTH\\s, or a mad
25491 client looping sending \\EHLO\\. The global option \smtp@_accept@_max@_nonmail\
25492 defines what `too many' means. Its default value is 10.
25494 When a new message is expected, one occurrence of \\RSET\\ is not counted. This
25495 allows a client to send one \\RSET\\ between messages (this is not necessary,
25496 but some clients do it). Exim also allows one uncounted occurence of \\HELO\\
25497 or \\EHLO\\, and one occurrence of \\STARTTLS\\ between messages. After
25498 starting up a TLS session, another \\EHLO\\ is expected, and so it too is not
25501 The first occurrence of \\AUTH\\ in a connection, or immediately following
25502 \\STARTTLS\\ is also not counted. Otherwise, all commands other than \\MAIL\\,
25503 \\RCPT\\, \\DATA\\, and \\QUIT\\ are counted.
25505 You can control which hosts are subject to the limit set by
25506 \smtp@_accept@_max@_nonmail\ by setting
25507 \smtp@_accept@_max@_nonmail@_hosts\. The default value is \"$*$"\, which makes
25508 the limit apply to all hosts. This option means that you can exclude any
25509 specific badly-behaved hosts that you have to live with.
25513 .section The \\VRFY\\ and \\EXPN\\ commands
25514 When Exim receives a \\VRFY\\ or \\EXPN\\ command on a TCP/IP connection, it
25515 runs the ACL specified by \acl@_smtp@_vrfy\ or \acl@_smtp@_expn\ (as
25516 appropriate) in order to decide whether the command should be accepted or not.
25517 If no ACL is defined, the command is rejected.
25519 .index \\VRFY\\||processing
25520 When \\VRFY\\ is accepted, it runs exactly the same code as when Exim is
25521 called with the \-bv-\ option.
25522 .index \\EXPN\\||processing
25523 When \\EXPN\\ is accepted, a single-level expansion of the address is done.
25524 \\EXPN\\ is treated as an `address test' (similar to the \-bt-\ option) rather
25525 than a verification (the \-bv-\ option). If an unqualified local part is given
25526 as the argument to \\EXPN\\, it is qualified with \qualify@_domain\. Rejections
25527 of \\VRFY\\ and \\EXPN\\ commands are logged on the main and reject logs, and
25528 \\VRFY\\ verification failures are logged on the main log for consistency with
25532 .section The \\ETRN\\ command
25533 .rset SECTETRN "~~chapter.~~section"
25534 .index \\ETRN\\||processing
25535 RFC 1985 describes an SMTP command called \\ETRN\\ that is designed to
25536 overcome the security problems of the \\TURN\\ command (which has fallen into
25537 disuse). When Exim receives an \\ETRN\\ command on a TCP/IP connection, it runs
25538 the ACL specified by \acl@_smtp@_etrn\ in order to decide whether the command
25539 should be accepted or not. If no ACL is defined, the command is rejected.
25541 The \\ETRN\\ command is concerned with `releasing' messages that are awaiting
25542 delivery to certain hosts. As Exim does not organize its message queue by host,
25543 the only form of \\ETRN\\ that is supported by default is the one where the
25544 text starts with the `@#' prefix, in which case the remainder of the text is
25545 specific to the SMTP server. A valid \\ETRN\\ command causes a run of Exim with
25546 the \-R-\ option to happen, with the remainder of the \\ETRN\\ text as its
25547 argument. For example,
25555 which causes a delivery attempt on all messages with undelivered addresses
25556 containing the text `brigadoon'. When \smtp@_etrn@_serialize\ is set (the
25557 default), Exim prevents the simultaneous execution of more than one queue run
25558 for the same argument string as a result of an \\ETRN\\ command. This stops
25559 a misbehaving client from starting more than one queue runner at once.
25561 .index hints database||\\ETRN\\ serialization
25562 Exim implements the serialization by means of a hints database in which a
25563 record is written whenever a process is started by \\ETRN\\, and deleted when
25564 the process completes. However, Exim does not keep the SMTP session waiting for
25565 the \\ETRN\\ process to complete. Once \\ETRN\\ is accepted, the client is sent
25566 a `success' return code. Obviously there is scope for hints records to get left
25567 lying around if there is a system or program crash. To guard against this, Exim
25568 ignores any records that are more than six hours old.
25570 .index \smtp@_etrn@_command\
25571 For more control over what \\ETRN\\ does, the \smtp@_etrn@_command\ option can
25572 used. This specifies a command that is run whenever \\ETRN\\ is received,
25573 whatever the form of its argument. For
25576 smtp_etrn_command = /etc/etrn_command $domain $sender_host_address
25578 The string is split up into arguments which are independently expanded. The
25579 expansion variable \$domain$\ is set to the argument of the \\ETRN\\ command,
25580 and no syntax checking is done on the contents of this argument. Exim does not
25581 wait for the command to complete, so its status code is not checked. Exim runs
25582 under its own uid and gid when receiving incoming SMTP, so it is not possible
25583 for it to change them before running the command.
25586 .section Incoming local SMTP
25587 .index SMTP||local incoming
25588 Some user agents use SMTP to pass messages to their local MTA using the
25589 standard input and output, as opposed to passing the envelope on the command
25590 line and writing the message to the standard input. This is supported by the
25591 \-bs-\ option. This form of SMTP is handled in the same way as incoming
25592 messages over TCP/IP (including the use of ACLs), except that the envelope
25593 sender given in a \\MAIL\\ command is ignored unless the caller is trusted. In
25594 an ACL you can detect this form of SMTP input by testing for an empty host
25595 identification. It is common to have this as the first line in the ACL that
25596 runs for \\RCPT\\ commands:
25600 This accepts SMTP messages from local processes without doing any other tests.
25603 .section Outgoing batched SMTP
25604 .rset SECTbatchSMTP "~~chapter.~~section"
25605 .index SMTP||batched outgoing
25606 .index batched SMTP output
25607 Both the \%appendfile%\ and \%pipe%\ transports can be used for handling batched
25608 SMTP. Each has an option called \use@_bsmtp\ which causes messages to be output
25609 in BSMTP format. No SMTP responses are possible for this form of delivery. All
25610 it is doing is using SMTP commands as a way of transmitting the envelope along
25613 The message is written to the file or pipe preceded by the SMTP commands
25614 \\MAIL\\ and \\RCPT\\, and followed by a line containing a single dot. Lines in
25615 the message that start with a dot have an extra dot added. The SMTP command
25616 \\HELO\\ is not normally used. If it is required, the \message@_prefix\ option
25617 can be used to specify it.
25619 Because \%appendfile%\ and \%pipe%\ are both local transports, they accept only
25620 one recipient address at a time by default. However, you can arrange for them
25621 to handle several addresses at once by setting the \batch@_max\ option. When
25622 this is done for BSMTP, messages may contain multiple \\RCPT\\ commands. See
25623 chapter ~~CHAPbatching for more details.
25625 When one or more addresses are routed to a BSMTP transport by a router that
25626 sets up a host list, the name of the first host on the list is available to the
25627 transport in the variable \$host$\. Here is an example of such a transport and
25632 driver = manualroute
25633 transport = smtp_appendfile
25634 route_list = domain.example batch.host.example
25638 driver = appendfile
25639 directory = /var/bsmtp/$host
25644 This causes messages addressed to \*domain.example*\ to be written in BSMTP
25645 format to \(/var/bsmtp/batch.host.example)\, with only a single copy of each
25646 message (unless there are more than 1000 recipients).
25649 .section Incoming batched SMTP
25650 .rset SECTincomingbatchedSMTP "~~chapter.~~section"
25651 .index SMTP||batched incoming
25652 .index batched SMTP input
25653 The \-bS-\ command line option causes Exim to accept one or more messages by
25654 reading SMTP on the standard input, but to generate no responses. If the caller
25655 is trusted, the senders in the \\MAIL\\ commands are believed; otherwise the
25656 sender is always the caller of Exim. Unqualified senders and receivers are not
25657 rejected (there seems little point) but instead just get qualified. \\HELO\\
25658 and \\EHLO\\ act as \\RSET\\; \\VRFY\\, \\EXPN\\, \\ETRN\\ and \\HELP\\, act
25659 as \\NOOP\\; \\QUIT\\ quits.
25661 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
25662 In this respect it is like non-SMTP local input.
25664 If an error is detected while reading a message, including a missing `.' at
25665 the end, Exim gives up immediately. It writes details of the error to the
25666 standard output in a stylized way that the calling program should be able to
25667 make some use of automatically, for example:
25669 554 Unexpected end of file
25670 Transaction started in line 10
25671 Error detected in line 14
25673 It writes a more verbose version, for human consumption, to the standard error
25676 An error was detected while processing a file of BSMTP input.
25677 The error message was:
25679 501 '>' missing at end of address
25681 The SMTP transaction started in line 10.
25682 The error was detected in line 12.
25683 The SMTP command at fault was:
25685 rcpt to:<malformed@in.com.plete
25687 1 previous message was successfully processed.
25688 The rest of the batch was abandoned.
25690 The return code from Exim is zero only if there were no errors. It is 1 if some
25691 messages were accepted before an error was detected, and 2 if no messages were
25701 . ============================================================================
25702 .chapter Message processing
25703 .set runningfoot "message processing"
25704 .rset CHAPmsgproc "~~chapter"
25705 .index message||general processing
25706 Exim performs various transformations on the sender and recipient addresses of
25707 all messages that it handles, and also on the messages' header lines. Some of
25708 these are optional and configurable, while others always take place. All of
25709 this processing, except rewriting as a result of routing, and the addition or
25710 removal of header lines while delivering, happens when a message is received,
25711 before it is placed on Exim's queue.
25713 Some of the automatic processing takes place
25715 only for `locally-originated' messages. This adjective is used to describe
25716 messages that are not received over TCP/IP, but instead are passed to an Exim
25717 process on its standard input. This includes the interactive `local SMTP' case
25718 that is set up by the \-bs-\ command line option. \**Note**\: messages received
25719 over TCP/IP on the loopback interface (127.0.0.1 or @:@:1) are not considered
25720 to be locally-originated. Exim does not treat the loopback interface specially
25724 .section Submission mode for non-local messages
25725 .rset SECTsubmodnon "~~chapter.~~section"
25727 .index message||submission
25728 Processing that happens automatically for locally-originated messages can also
25729 be requested for other messages. This is done by obeying the modifier
25731 control = submission
25733 in one of the ACLs that are run for an incoming message (see section
25734 ~~SECTACLmodi). This makes Exim treat the message as a local submission, and is
25735 normally used when the source of the message is known to be an MUA running on a
25736 client host (as opposed to an MTA). In the descriptions below, the term
25737 `submission mode' is used to describe this state.
25739 When a ::From:: or ::Sender:: header is generated in submission mode, the value
25740 of \qualify@_domain\ is used by default. However, it is possible to specify
25741 another domain by a setting such as
25743 control = submission/domain=some.other.domain
25748 .section Line endings
25749 .rset SECTlineendings "~~chapter.~~section"
25750 .index line endings
25751 .index carriage return
25753 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
25754 linefeed) is the line ending for messages transmitted over the Internet using
25755 SMTP over TCP/IP. However, within individual operating systems, different
25756 conventions are used. For example, Unix-like systems use just LF, but others
25757 use CRLF or just CR.
25759 Exim was designed for Unix-like systems, and internally, it stores messages
25760 using the system's convention of a single LF as a line terminator. When
25761 receiving a message, all line endings are translated to this standard format.
25762 Originally, it was thought that programs that passed messages directly to an
25763 MTA within an operating system would use that system's convention. Experience
25764 has shown that this is not the case; for example, there are Unix applications
25765 that use CRLF in this circumstance. For this reason, and for compatibility with
25766 other MTAs, the way Exim handles line endings for all messages is now as
25769 LF not preceded by CR is treated as a line ending.
25771 CR is treated as a line ending; if it is immediately followed by LF, the LF
25774 The sequence `CR, dot, CR' does not terminate an incoming SMTP message,
25775 nor a local message in the state where a line containing only a dot is a
25778 If a bare CR is encountered within a header line, an extra space is added after
25779 the line terminator so as not to end the header line. The reasoning behind this
25780 is that bare CRs in header lines are most likely either to be mistakes, or
25781 people trying to play silly games.
25783 If the first header line received in a message ends with CRLF, a subsequent
25784 bare LF in a header line is treated in the same way as a bare CR in a header
25790 .section Unqualified addresses
25791 .index unqualified addresses
25792 .index address||qualification
25793 By default, Exim expects every address it receives from an external host to be
25794 fully qualified. Unqualified addresses cause negative responses to SMTP
25795 commands. However, because SMTP is used as a means of transporting messages
25796 from MUAs running on personal workstations, there is sometimes a requirement to
25797 accept unqualified addresses from specific hosts or IP networks.
25799 Exim has two options that separately control which hosts may send unqualified
25800 sender or receipient addresses in SMTP commands, namely
25801 \sender__unqualified__hosts\ and \recipient__unqualified__hosts\. In both
25802 cases, if an unqualified address is accepted, it is qualified by adding the
25803 value of \qualify__domain\ or \qualify__recipient\, as appropriate.
25804 .index \qualify@_domain\
25805 .index \qualify@_recipient\
25808 .section The UUCP From line
25810 .index UUCP||`From' line
25811 .index sender||address
25812 .index \uucp@_from@_pattern\
25813 .index \uucp@_from@_sender\
25814 .index envelope sender
25815 .index Sendmail compatibility||`From' line
25816 Messages that have come from UUCP (and some other applications) often begin
25817 with a line containing the envelope sender and a timestamp, following the word
25818 `From'. Examples of two common formats are:
25820 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
25821 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
25823 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
25824 Exim recognizes such lines at the start of messages that are submitted to it
25825 via the command line (that is, on the standard input). It does not recognize
25826 such lines in incoming SMTP messages, unless the sending host matches
25827 \ignore@_fromline@_hosts\ or the \-bs-\ option was used for a local message and
25828 \ignore@_fromline@_local\ is set. The recognition is controlled by a regular
25829 expression that is defined by the \uucp@_from@_pattern\ option, whose default
25830 value matches the two common cases shown above and puts the address that
25831 follows `From' into \$1$\.
25833 .index numerical variables (\$1$\, \$2$\, etc)||in `From ' line handling
25834 When the caller of Exim for a non-SMTP message that contains a `From' line is a
25835 trusted user, the message's sender address is constructed by expanding the
25836 contents of \uucp@_sender@_address\, whose default value is `@$1'. This is then
25837 parsed as an RFC 2822 address. If there is no domain, the local part is
25838 qualified with \qualify@_domain\ unless it is the empty string. However, if the
25839 command line \-f-\ option is used, it overrides the `From' line.
25841 If the caller of Exim is not trusted, the `From' line is recognized, but the
25842 sender address is not changed. This is also the case for incoming SMTP messages
25843 that are permitted to contain `From' lines.
25845 Only one `From' line is recognized. If there is more than one, the second is
25846 treated as a data line that starts the body of the message, as it is not valid
25847 as a header line. This also happens if a `From' line is present in an incoming
25848 SMTP message from a source that is not permitted to send them.
25851 .section Resent- header lines
25852 .index \Resent@-\ header lines
25853 RFC 2822 makes provision for sets of header lines starting with the string
25854 \"Resent-"\ to be added to a message when it is resent by the original
25855 recipient to somebody else. These headers are ::Resent-Date::, ::Resent-From::,
25856 ::Resent-Sender::, ::Resent-To::, ::Resent-Cc::, ::Resent-Bcc:: and
25857 ::Resent-Message-ID::. The RFC says:
25859 \*Resent fields are strictly informational. They MUST NOT be used in the normal
25860 processing of replies or other such automatic actions on messages.*\
25862 This leaves things a bit vague as far as other processing actions such as
25863 address rewriting are concerned. Exim treats \Resent@-\ header lines as
25866 A ::Resent-From:: line that just contains the login id of the submitting user
25867 is automatically rewritten in the same way as ::From:: (see below).
25869 If there's a rewriting rule for a particular header line, it is also applied to
25870 \Resent@-\ header lines of the same type. For example, a rule that rewrites
25871 ::From:: also rewrites ::Resent-From::.
25873 For local messages, if ::Sender:: is removed on input, ::Resent-Sender:: is also
25876 For a locally-submitted message,
25877 if there are any \Resent@-\ header lines but no ::Resent-Date::,
25878 ::Resent-From::, or ::Resent-Message-Id::, they are added as necessary. It is
25879 the contents of ::Resent-Message-Id:: (rather than ::Message-Id::) which are
25880 included in log lines in this case.
25882 The logic for adding ::Sender:: is duplicated for ::Resent-Sender:: when any
25883 \Resent@-\ header lines are present.
25887 .section The Auto-Submitted: header line
25888 Whenever Exim generates a bounce or a delay warning message, it includes the
25891 Auto-Submitted: auto-generated
25895 .section The Bcc: header line
25896 .index ::Bcc:: header line
25897 If Exim is called with the \-t-\ option, to take recipient addresses from a
25898 message's header, it removes any ::Bcc:: header line that may exist (after
25899 extracting its addresses). If \-t-\ is not present on the command line, any
25900 existing ::Bcc:: is not removed.
25902 .section The Date: header line
25903 .index ::Date:: header line
25904 If a locally-generated
25906 message has no ::Date:: header line, Exim adds one, using the current date and
25909 .section The Delivery-date: header line
25910 .index ::Delivery-date:: header line
25911 .index \delivery@_date@_remove\
25912 ::Delivery-date:: header lines are not part of the standard RFC 2822 header
25913 set. Exim can be configured to add them to the final delivery of messages. (See
25914 the generic \delivery@_date@_add\ transport option.) They should not be present
25915 in messages in transit. If the \delivery@_date@_remove\ configuration option is
25916 set (the default), Exim removes ::Delivery-date:: header lines from incoming
25919 .section The Envelope-to: header line
25920 .index ::Envelope-to:: header line
25921 .index \envelope@_to@_remove\
25922 ::Envelope-to:: header lines are not part of the standard RFC 2822 header set.
25923 Exim can be configured to add them to the final delivery of messages. (See the
25924 generic \envelope@_to@_add\ transport option.) They should not be present in
25925 messages in transit. If the \envelope@_to@_remove\ configuration option is set
25926 (the default), Exim removes ::Envelope-to:: header lines from incoming
25929 .section The From: header line
25930 .index ::From:: header line
25931 .index Sendmail compatibility||`From' line
25932 If a submission-mode message does not contain a ::From:: header line, Exim adds
25933 one if either of the following conditions is true:
25935 The envelope sender address is not empty (that is, this is not a bounce
25936 message); the added header line copies the envelope sender address.
25938 The SMTP session is authenticated and \$authenticated@_id$\ is not empty; the
25939 added header's local part is \$authenticated@_id$\ and the domain is
25940 the domain specified on the submission control, or \$qualify@_domain$\ if that
25943 A non-empty envelope sender takes precedence.
25945 If a locally-generated incoming message does not contain a ::From:: header
25946 line, Exim adds one containing the sender's address. The calling user's login
25947 name and full name are used to construct the address, as described in section
25948 ~~SECTconstr. They are obtained from the password data by calling
25949 \*getpwuid()*\ (but see the \unknown@_login\ configuration option). The address
25950 is qualified with \qualify@_domain\.
25952 For compatibility with Sendmail, if an incoming, non-SMTP message has a
25953 ::From:: header line containing just the unqualified login name of the calling
25954 user, this is replaced by an address containing the user's login name and full
25955 name as described in section ~~SECTconstr.
25957 .section The Message-ID: header line
25958 .index ::Message-ID:: header line
25959 If a locally-generated
25961 incoming message does not contain a ::Message-ID:: or ::Resent-Message-ID::
25962 header line, Exim adds one to the message. If there are any ::Resent-:: headers
25963 in the message, it creates ::Resent-Message-ID::. The id is constructed from
25964 Exim's internal message id, preceded by the letter E to ensure it starts with a
25965 letter, and followed by @@ and the primary host name. Additional information
25966 can be included in this header line by setting the
25967 .index \message@_id@_header@_text\
25968 \message@_id@_header@_text\ and/or \message__id__header__domain\ options.
25971 .section The Received: header line
25972 .index ::Received:: header line
25973 A ::Received:: header line is added at the start of every message. The contents
25974 are defined by the \received@_header@_text\ configuration option, and Exim
25975 automatically adds a semicolon and a timestamp to the configured string.
25977 The ::Received:: header is generated as soon as the message's header lines have
25978 been received. At this stage, the timestamp in the ::Received:: header line is
25979 the time that the message started to be received. This is the value that is
25980 seen by the \\DATA\\ ACL and by the \*local@_scan()*\ function.
25982 Once a message is accepted, the timestamp in the ::Received:: header line is
25983 changed to the time of acceptance, which is (apart from a small delay while the
25984 -H spool file is written) the earliest time at which delivery could start.
25987 .section The Return-path: header line
25988 .index ::Return-path:: header line
25989 .index \return@_path@_remove\
25990 ::Return-path:: header lines are defined as something an MTA may insert when
25991 it does the final delivery of messages. (See the generic \return@_path@_add\
25992 transport option.) Therefore, they should not be present in messages in
25993 transit. If the \return@_path@_remove\ configuration option is set (the
25994 default), Exim removes ::Return-path:: header lines from incoming messages.
25997 .section The Sender: header line
25998 .rset SECTthesenhea "~~chapter.~~section"
25999 .index ::Sender:: header line
26000 For a locally-originated message from an untrusted user, Exim may remove an
26001 existing ::Sender:: header line, and it may add a new one. You can modify these
26002 actions by setting \local@_sender@_retain\ true or \local@_from@_check\ false.
26004 When a local message is received from an untrusted user and
26005 \local@_from@_check\ is true (the default), a check is made to see if the
26006 address given in the ::From:: header line is the correct (local) sender of the
26007 message. The address that is expected has the login name as the local part and
26008 the value of \qualify@_domain\ as the domain. Prefixes and suffixes for the
26009 local part can be permitted by setting \local@_from@_prefix\ and
26010 \local@_from@_suffix\ appropriately. If ::From:: does not contain the correct
26011 sender, a ::Sender:: line is added to the message.
26013 If you set \local@_from@_check\ false, this checking does not occur. However,
26014 the removal of an existing ::Sender:: line still happens, unless you also set
26015 \local@_sender@_retain\ to be true. It is not possible to set both of these
26016 options true at the same time.
26018 By default, no processing of ::Sender:: header lines is done for messages
26019 received by TCP/IP or for messages submitted by trusted users. However, when a
26020 message is received over TCP/IP in submission mode, ::Sender:: header lines are
26021 always removed. If the SMTP session is authenticated, and \$authenticated@_id$\
26022 is not empty, a sender address is created with \$authenticated@_id$\ as the
26023 local part and either the domain specified in the submission control or, if
26024 that is not specified, \$qualify@_domain$\ as the domain. This is compared with
26025 the address in the ::From:: header line. If they are different, a ::Sender::
26026 header line is added. Prefixes and suffixes for the local part in ::From:: can
26027 be permitted by setting \local@_from@_prefix\ and \local@_from@_suffix\
26031 .section Adding and removing header lines
26032 .index header lines||adding
26033 .index header lines||removing
26034 .rset SECTheadersaddrem "~~chapter.~~section"
26035 When a message is delivered, the addition and removal of header lines can be
26036 specified on any of the routers and transports, and also in the system filter.
26037 Changes specified in the system filter affect all deliveries of a message.
26039 Header changes specified on a router affect all addresses handled by that
26040 router, and also any new addresses it generates. If an address passes through
26041 several routers, the changes are cumulative. When a message is processed by a
26042 transport, the message's original set of header lines is output, except for
26043 those named in any \headers@_remove\ options that the address has encountered
26044 as it was processed, and any in the transport's own \headers@_remove\ option.
26045 Then the new header lines from \headers@_add\ options are output.
26048 .section Constructed addresses
26049 .rset SECTconstr "~~chapter.~~section"
26050 .index address||constructed
26051 .index constructed address
26052 When Exim constructs a sender address for a locally-generated message, it uses
26055 <<user name>> <$$<<login>>@@<<qualify@_domain>>$$>
26059 Zaphod Beeblebrox <zaphod@end.univ.example>
26061 The user name is obtained from the \-F-\ command line option if set, or
26062 otherwise by looking up the calling user by \*getpwuid()*\ and extracting the
26063 `gecos' field from the password entry. If the `gecos' field contains an
26064 ampersand character, this is replaced by the login name with the first letter
26065 upper cased, as is conventional in a number of operating systems. See the
26066 \gecos@_name\ option for a way to tailor the handling of the `gecos' field. The
26067 \unknown@_username\ option can be used to specify user names in cases when
26068 there is no password file entry.
26070 In all cases, the user name is made to conform to RFC 2822 by quoting all or
26071 parts of it if necessary. In addition, if it contains any non-printing
26072 characters, it is encoded as described in RFC 2047, which defines a way of
26073 including non-ASCII characters in header lines.
26074 The value of the \headers@_charset\ option specifies the name of the encoding
26075 that is used (the characters are assumed to be in this encoding).
26076 The setting of \print@_topbitchars\ controls whether characters with the top
26077 bit set (that is, with codes greater than 127) count as printing characters or
26081 .section Case of local parts
26082 .index case of local parts
26083 .index local part||case of
26084 RFC 2822 states that the case of letters in the local parts of addresses cannot
26085 be assumed to be non-significant. Exim preserves the case of local parts of
26086 addresses, but by default it uses a lower-cased form when it is routing,
26087 because on most Unix systems, usernames are in lower case and case-insensitive
26088 routing is required. However, any particular router can be made to use the
26089 original case for local parts by setting the \caseful@_local@_part\ generic
26092 .index mixed-case login names
26093 If you must have mixed-case user names on your system, the best way to proceed,
26094 assuming you want case-independent handling of incoming email, is to set up
26095 your first router to convert incoming local parts in your domains to the
26096 correct case by means of a file lookup. For example:
26100 domains = +local_domains
26101 data = ${lookup{$local_part}cdb\
26102 {/etc/usercased.cdb}{$value}fail}\
26105 For this router, the local part is forced to lower case by the default action
26106 (\caseful@_local@_part\ is not set). The lower-cased local part is used to look
26107 up a new local part in the correct case. If you then set \caseful@_local@_part\
26108 on any subsequent routers which process your domains, they will operate on
26109 local parts with the correct case in a case-sensitive manner.
26112 .section Dots in local parts
26113 .index dot||in local part
26114 .index local part||dots in
26115 RFC 2822 forbids empty components in local parts. That is, an unquoted local
26116 part may not begin or end with a dot, nor have two consecutive dots in the
26117 middle. However, it seems that many MTAs do not enforce this, so Exim permits
26118 empty components for compatibility.
26121 .section Rewriting addresses
26122 .index rewriting||addresses
26123 Rewriting of sender and recipient addresses, and addresses in headers, can
26124 happen automatically, or as the result of configuration options, as described
26125 in chapter ~~CHAPrewrite. The headers that may be affected by this are ::Bcc::,
26126 ::Cc::, ::From::, ::Reply-To::, ::Sender::, and ::To::.
26128 Automatic rewriting includes qualification, as mentioned above. The other case
26129 in which it can happen is when an incomplete non-local domain is given. The
26130 routing process may cause this to be expanded into the full domain name. For
26131 example, a header such as
26135 might get rewritten as
26137 To: hare@teaparty.wonderland.fict.example
26139 Rewriting as a result of routing is the one kind of message processing that
26140 does not happen at input time, as it cannot be done until the address has
26143 Strictly, one should not do $it{any} deliveries of a message until all its
26144 addresses have been routed, in case any of the headers get changed as a
26145 result of routing. However, doing this in practice would hold up many
26146 deliveries for unreasonable amounts of time, just because one address could not
26147 immediately be routed. Exim therefore does not delay other deliveries when
26148 routing of one or more addresses is deferred.
26158 . ============================================================================
26160 .set runningfoot "log files"
26161 .rset CHAPlog "~~chapter"
26162 .index log||types of
26163 .index log||general description
26164 Exim writes three different logs, referred to as the main log, the reject log,
26168 The main log records the arrival of each message and each delivery in a single
26169 line in each case. The format is as compact as possible, in an attempt to keep
26170 down the size of log files. Two-character flag sequences make it easy to pick
26171 out these lines. A number of other events are recorded in the main log. Some of
26172 them are optional, in which case the \log@_selector\ option controls whether
26173 they are included or not. A Perl script called \*eximstats*\, which does simple
26174 analysis of main log files, is provided in the Exim distribution (see section
26178 The reject log records information from messages that are rejected as a result
26179 of a configuration option (that is, for policy reasons).
26180 The first line of each rejection is a copy of the line that is also written to
26181 the main log. Then, if the message's header has been read at the time the log
26182 is written, its contents are written to this log. Only the original header
26183 lines are available; header lines added by ACLs are not logged. You can use the
26184 reject log to check that your policy controls are working correctly; on a busy
26185 host this may be easier than scanning the main log for rejection messages. You
26186 can suppress the writing of the reject log by setting \write@_rejectlog\ false.
26190 When certain serious errors occur, Exim writes entries to its panic log. If the
26191 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
26192 are usually written to the main log as well, but can get lost amid the mass of
26193 other entries. The panic log should be empty under normal circumstances. It is
26194 therefore a good idea to check it (or to have a \*cron*\ script check it)
26195 regularly, in order to become aware of any problems. When Exim cannot open its
26196 panic log, it tries as a last resort to write to the system log (syslog). This
26197 is opened with LOG@_PID+LOG@_CONS and the facility code of LOG@_MAIL. The
26198 message itself is written at priority LOG@_CRIT.
26200 Every log line starts with a timestamp, in the format shown in this example:
26202 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed by QUIT
26204 By default, the timestamps are in the local timezone. There are two
26205 ways of changing this:
26207 You can set the \timezone\ option to a different time zone; in particular, if
26212 the timestamps will be in UTC (aka GMT).
26214 If you set \log@_timezone\ true, the time zone is added to the timestamp, for
26217 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
26223 .section Where the logs are written
26224 .rset SECTwhelogwri "~~chapter.~~section"
26225 .index log||destination
26226 .index log||to file
26227 .index log||to syslog
26229 The logs may be written to local files, or to syslog, or both. However, it
26230 should be noted that many syslog implementations use UDP as a transport, and
26231 are therefore unreliable in the sense that messages are not guaranteed to
26232 arrive at the loghost, nor is the ordering of messages necessarily maintained.
26233 It has also been reported that on large log files (tens of megabytes) you may
26234 need to tweak syslog to prevent it syncing the file with each write -- on Linux
26235 this has been seen to make syslog take 90% plus of CPU time.
26237 The destination for Exim's logs is configured by setting \\LOG@_FILE@_PATH\\ in
26238 \(Local/Makefile)\ or by setting \log@_file@_path\ in the run time
26239 configuration. This latter string is expanded, so it can contain, for example,
26240 references to the host name:
26242 log_file_path = /var/log/$primary_hostname/exim_%slog
26244 It is generally advisable, however, to set the string in \(Local/Makefile)\
26245 rather than at run time, because then the setting is available right from the
26246 start of Exim's execution. Otherwise, if there's something it wants to log
26247 before it has read the configuration file (for example, an error in the
26248 configuration file) it will not use the path you want, and may not be able to
26251 The value of \\LOG@_FILE@_PATH\\ or \log@_file@_path\ is a colon-separated
26252 list, currently limited to at most two items. This is one option where the
26253 facility for changing a list separator may not be used. The list must always be
26254 colon-separated. If an item in the list is `syslog' then syslog is used;
26255 otherwise the item must either be an absolute path, containing \"%s"\ at the
26256 point where `main', `reject', or `panic' is to be inserted, or be empty,
26257 implying the use of a default path.
26259 When Exim encounters an empty item in the list, it searches the list defined by
26260 \\LOG@_FILE@_PATH\\, and uses the first item it finds that is neither empty nor
26261 `syslog'. This means that an empty item in \log@_file@_path\ can be used to
26262 mean `use the path specified at build time'. It no such item exists, log files
26263 are written in the \(log)\ subdirectory of the spool directory. This is
26264 equivalent to the setting:
26266 log_file_path = $spool_directory/log/%slog
26268 If you do not specify anything at build time or run time, that is where the
26271 A log file path may also contain \"%D"\ if datestamped log file names are in
26272 use -- see section ~~SECTdatlogfil below.
26274 Here are some examples of possible settings:
26277 LOG@_FILE@_PATH=syslog $t $rm{syslog only}
26278 LOG@_FILE@_PATH=:syslog $t $rm{syslog and default path}
26279 LOG@_FILE@_PATH=syslog : /usr/log/exim@_%s $t $rm{syslog and specified path}
26280 LOG@_FILE@_PATH=/usr/log/exim@_%s $t $rm{specified path only}
26282 If there are more than two paths in the list, the first is used and a panic
26286 .section Logging to local files that are periodically `cycled'
26287 .index log||cycling local files
26288 .index cycling logs
26289 .index \*exicyclog*\
26290 .index log||local files, writing to
26291 Some operating systems provide centralized and standardised methods for cycling
26292 log files. For those that do not, a utility script called \*exicyclog*\ is
26293 provided (see section ~~SECTcyclogfil). This renames and compresses the main
26294 and reject logs each time it is called. The maximum number of old logs to keep
26295 can be set. It is suggested this script is run as a daily \*cron*\ job.
26297 An Exim delivery process opens the main log when it first needs to write to it,
26298 and it keeps the file open in case subsequent entries are required -- for
26299 example, if a number of different deliveries are being done for the same
26300 message. However, remote SMTP deliveries can take a long time, and this means
26301 that the file may be kept open long after it is renamed if \*exicyclog*\ or
26302 something similar is being used to rename log files on a regular basis. To
26303 ensure that a switch of log files is noticed as soon as possible, Exim calls
26304 \*stat()*\ on the main log's name before reusing an open file, and if the file
26305 does not exist, or its inode has changed, the old file is closed and Exim
26306 tries to open the main log from scratch. Thus, an old log file may remain open
26307 for quite some time, but no Exim processes should write to it once it has been
26311 .section Datestamped log files
26312 .rset SECTdatlogfil "~~chapter.~~section"
26313 .index log||datestamped files
26314 Instead of cycling the main and reject log files by renaming them
26315 periodically, some sites like to use files whose names contain a datestamp,
26316 for example, \(mainlog-20031225)\. The datestamp is in the form \(yyyymmdd)\.
26317 Exim has support for this way of working. It is enabled by setting the
26318 \log@_file@_path\ option to a path that includes \"%D"\ at the point where the
26319 datestamp is required. For example:
26321 log_file_path = /var/spool/exim/log/%slog-%D
26322 log_file_path = /var/log/exim-%s-%D.log
26323 log_file_path = /var/spool/exim/log/%D-%slog
26325 As before, \"%s"\ is replaced by `main' or `reject'; the following are examples
26326 of names generated by the above examples:
26328 /var/spool/exim/log/mainlog-20021225
26329 /var/log/exim-reject-20021225.log
26330 /var/spool/exim/log/20021225-mainlog
26332 When this form of log file is specified, Exim automatically switches to new
26333 files at midnight. It does not make any attempt to compress old logs; you
26334 will need to write your own script if you require this. You should not
26335 run \*exicyclog*\ with this form of logging.
26337 The location of the panic log is also determined by \log@_file@_path\, but it
26338 is not datestamped, because rotation of the panic log does not make sense.
26339 When generating the name of the panic log, \"%D"\ is removed from the string.
26340 In addition, if it immediately follows a slash, a following non-alphanumeric
26341 character is removed; otherwise a preceding non-alphanumeric character is
26342 removed. Thus, the three examples above would give these panic log names:
26344 /var/spool/exim/log/paniclog
26345 /var/log/exim-panic.log
26346 /var/spool/exim/log/paniclog
26350 .section Logging to syslog
26351 .index log||syslog, writing to
26352 The use of syslog does not change what Exim logs or the format of its messages,
26353 except in one respect. If \syslog@_timestamp\ is set false, the timestamps on
26354 Exim's log lines are omitted when these lines are sent to syslog. Apart from
26355 that, the same strings are written to syslog as to log files. The syslog
26356 `facility' is set to \\LOG@_MAIL\\, and the program name to `exim'
26357 by default, but you can change these by setting the \syslog@_facility\ and
26358 \syslog@_processname\ options, respectively. If Exim was compiled with
26359 \\SYSLOG@_LOG@_PID\\ set in \(Local/Makefile)\ (this is the default in
26360 \(src/EDITME)\), then, on systems that permit it (all except ULTRIX), the
26361 \\LOG@_PID\\ flag is set so that the \*syslog()*\ call adds the pid as well as
26362 the time and host name to each line.
26363 The three log streams are mapped onto syslog priorities as follows:
26365 \*mainlog*\ is mapped to \\LOG@_INFO\\
26367 \*rejectlog*\ is mapped to \\LOG@_NOTICE\\
26369 \*paniclog*\ is mapped to \\LOG@_ALERT\\
26371 Many log lines are written to both \*mainlog*\ and \*rejectlog*\, and some are
26372 written to both \*mainlog*\ and \*paniclog*\, so there will be duplicates if
26373 these are routed by syslog to the same place. You can suppress this duplication
26374 by setting \syslog@_duplication\ false.
26376 Exim's log lines can sometimes be very long, and some of its \*rejectlog*\
26377 entries contain multiple lines when headers are included. To cope with both
26378 these cases, entries written to syslog are split into separate \*syslog()*\
26379 calls at each internal newline, and also after a maximum of
26380 870 data characters. (This allows for a total syslog line length of 1024, when
26381 additions such as timestamps are added.) If you are running a syslog
26382 replacement that can handle lines longer than the 1024 characters allowed by
26383 RFC 3164, you should set
26385 SYSLOG_LONG_LINES=yes
26387 in \(Local/Makefile)\ before building Exim. That stops Exim from splitting long
26388 lines, but it still splits at internal newlines in \*reject*\ log entries.
26390 To make it easy to re-assemble split lines later, each component of a split
26391 entry starts with a string of the form `[<<n>>/<<m>>]' or `[<<n>>@\<<m>>]'
26392 where <<n>> is the component number and <<m>> is the total number of components
26393 in the entry. The / delimiter is used when the line was split because it was
26394 too long; if it was split because of an internal newline, the @\ delimiter is
26395 used. For example, supposing the length limit to be 70 instead of 1000, the
26396 following would be the result of a typical rejection message to \*mainlog*\
26397 (LOG@_INFO), each line in addition being preceded by the time, host name, and
26398 pid as added by syslog:
26401 $smc{[1/3] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from [127.0.0.1] (ph10):
26402 [2/3] syntax error in 'From' header when scanning for sender: missing or ma
26403 [3/3] lformed local part in "<>" (envelope sender is <ph10@@cam.example>)}
26405 The same error might cause the following lines to be written to `rejectlog'
26409 $smc{[1/14] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from [127.0.0.1] (ph10):
26410 [2/14] syntax error in 'From' header when scanning for sender: missing or ma
26411 [3@\14] lformed local part in "@<@>" (envelope sender is <ph10@@cam.example>)
26412 [4@\14] Recipients: ph10@@some.domain.cam.example
26413 [5@\14] P Received: from [127.0.0.1] (ident=ph10)
26414 [6@\14] by xxxxx.cam.example with smtp (Exim 4.00)
26415 [7@\14] id 16RdAL-0006pc-00
26416 [8@\14] for ph10@@cam.example; Mon, 16 Sep 2002 16:09:43 +0100
26417 [9@\14] F From: @<@>
26418 [10@\14] Subject: this is a test header
26419 [11@\14] X-something: this is another header
26420 [12@\14] I Message-Id: <E16RdAL-0006pc-00@@xxxxx.cam.example>
26422 [14/14] Date: Mon, 16 Sep 2002 16:09:43 +0100}
26424 Log lines that are neither too long nor contain newlines are written to syslog
26425 without modification.
26427 If only syslog is being used, the Exim monitor is unable to provide a log tail
26428 display, unless syslog is routing \*mainlog*\ to a file on the local host and
26429 the environment variable \\EXIMON@_LOG@_FILE@_PATH\\ is set to tell the monitor
26433 .section Log line flags
26434 One line is written to the main log for each message received, and for each
26435 successful, unsuccessful, and delayed delivery. These lines can readily be
26436 picked out by the distinctive two-character flags that immediately follow the
26437 timestamp. The flags are:
26440 <= $t $rm{message arrival}
26441 => $t $rm{normal message delivery}
26442 -> $t $rm{additional address in same delivery}
26443 *> $t $rm{delivery suppressed by \-N-\}
26444 ** $t $rm{delivery failed; address bounced}
26445 == $t $rm{delivery deferred; temporary problem}
26449 .section Logging message reception
26450 .index log||reception line
26451 The format of the single-line entry in the main log that is written for every
26452 message received is shown in the basic example below, which is split over
26453 several lines in order to fit it on the page:
26456 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@@dwarf.fict.example
26457 H=mailer.fict.example [192.168.123.123] U=exim
26458 P=smtp S=5678 id=<<incoming message id>>
26460 The address immediately following `<=' is the envelope sender address. A bounce
26461 message is shown with the sender address `<>', and if it is locally generated,
26462 this is followed by an item of the form
26466 which is a reference to the message that caused the bounce to be sent.
26470 For messages from other hosts, the H and U fields identify the remote host and
26471 record the RFC 1413 identity of the user that sent the message, if one was
26472 received. The number given in square brackets is the IP address of the sending
26473 host. If there is a single, unparenthesized host name in the H field, as
26474 above, it has been verified to correspond to the IP address (see the
26475 \host@_lookup\ option). If the name is in parentheses, it was the name quoted
26476 by the remote host in the SMTP \\HELO\\ or \\EHLO\\ command, and has not been
26477 verified. If verification yields a different name to that given for \\HELO\\ or
26478 \\EHLO\\, the verified name appears first, followed by the \\HELO\\ or \\EHLO\\
26479 name in parentheses.
26481 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
26482 without brackets, in the \\HELO\\ or \\EHLO\\ command, leading to entries in
26483 the log containing text like these examples:
26485 H=(10.21.32.43) [192.168.8.34]
26486 H=([10.21.32.43]) [192.168.8.34]
26488 This can be confusing. Only the final address in square brackets can be relied
26491 For locally generated messages (that is, messages not received over TCP/IP),
26492 the H field is omitted, and the U field contains the login name of the caller
26495 .index authentication||logging
26496 .index \\AUTH\\||logging
26497 For all messages, the P field specifies the protocol used to receive the
26498 message. This is set to `asmtp' for messages received from hosts which have
26499 authenticated themselves using the SMTP \\AUTH\\ command. In this case there is
26500 an additional item A= followed by the name of the authenticator that was used.
26501 If an authenticated identification was set up by the authenticator's
26502 \server@_set@_id\ option, this is logged too, separated by a colon from the
26503 authenticator name.
26505 The id field records the existing message id, if present.
26506 .index size||of message
26507 The size of the received message is given by the S field. When the message is
26508 delivered, headers may get removed or added, so that the size of delivered
26509 copies of the message may not correspond with this value (and indeed may be
26510 different to each other).
26512 The \log@_selector\ option can be used to request the logging of additional
26513 data when a message is received. See section ~~SECTlogselector below.
26516 .section Logging deliveries
26517 .index log||delivery line
26518 The format of the single-line entry in the main log that is written for every
26519 delivery is shown in one of the examples below, for local and remote deliveries,
26520 respectively. Each example has been split into two lines in order to fit
26524 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv <marv@@hitch.fict.example>
26525 R=localuser T=local@_delivery
26526 2002-10-31 09:00:10 16ZCW1-0005MB-00 => monk@@holistic.fict.example
26527 R=dnslookup T=remote@_smtp H=holistic.fict.example [192.168.234.234]
26529 For ordinary local deliveries, the original address is given in angle brackets
26530 after the final delivery address, which might be a pipe or a file. If
26531 intermediate address(es) exist between the original and the final address, the
26532 last of these is given in parentheses after the final address. The R and T
26533 fields record the router and transport that were used to process the address.
26535 If a shadow transport was run after a successful local delivery, the log line
26536 for the successful delivery has an item added on the end, of the form
26538 ST=<<shadow transport name>>
26540 If the shadow transport did not succeed, the error message is put in
26541 parentheses afterwards.
26543 When more than one address is included in a single delivery (for example, two
26544 SMTP \\RCPT\\ commands in one transaction) the second and subsequent
26545 addresses are flagged with `$tt{@-@>}' instead of `$tt{@=@>}'. When two or more
26546 messages are delivered down a single SMTP connection, an asterisk follows the
26547 IP address in the log lines for the second and subsequent messages.
26549 The generation of a reply message by a filter file gets logged as a `delivery'
26550 to the addressee, preceded by `>'.
26552 The \log@_selector\ option can be used to request the logging of additional
26553 data when a message is delivered. See section ~~SECTlogselector below.
26556 .section Discarded deliveries
26557 .index discarded messages
26558 .index message||discarded
26559 .index delivery||discarded, logging
26560 When a message is discarded as a result of the command `seen finish' being
26561 obeyed in a filter file which generates no deliveries, a log entry of the form
26563 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
26564 <low.club@@bridge.example> R=userforward
26566 is written, to record why no deliveries are logged. When a message is discarded
26567 because it is aliased to `:blackhole:' the log line is like this:
26569 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
26570 <hole@nowhere.example> R=blackhole_router
26574 .section Deferred deliveries
26575 When a delivery is deferred, a line of the following form is logged:
26578 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@@endrest.example
26579 R=dnslookup T=smtp defer (146): Connection refused
26581 In the case of remote deliveries, the error is the one that was given for the
26582 last IP address that was tried. Details of individual SMTP failures are also
26583 written to the log, so the above line would be preceded by something like
26586 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
26587 mail1.endrest.example [192.168.239.239]: Connection refused
26589 When a deferred address is skipped because its retry time has not been reached,
26590 a message is written to the log, but this can be suppressed by setting an
26591 appropriate value in \log@_selector\.
26594 .section Delivery failures
26595 .index delivery||failure, logging
26596 If a delivery fails because an address cannot be routed, a line of the
26597 following form is logged:
26600 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
26601 <jim@trek99.example>: unknown mail domain
26603 If a delivery fails at transport time, the router and transport are shown, and
26604 the response from the remote host is included, as in this example:
26607 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example R=dnslookup
26609 T=remote_smtp: SMTP error from remote mailer after pipelined
26611 RCPT TO:<ace400@pb.example>: host pbmail3.py.example
26612 [192.168.63.111]: 553 5.3.0 <ace400@pb.example>...
26615 The word `pipelined' indicates that the SMTP \\PIPELINING\\ extension was being
26616 used. See \hosts@_avoid@_esmtp\ in the \%smtp%\ transport for a way of
26617 disabling \\PIPELINING\\.
26619 The log lines for all forms of delivery failure are flagged with \"**"\.
26622 .section Fake deliveries
26623 .index delivery||fake, logging
26624 If a delivery does not actually take place because the \-N-\ option has been
26625 used to suppress it, a normal delivery line is written to the log, except that
26626 `=>' is replaced by `$*$>'.
26629 .section Completion
26632 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
26634 is written to the main log when a message is about to be removed from the spool
26635 at the end of its processing.
26639 .section Summary of Fields in Log Lines
26640 .index log||summary of fields
26641 A summary of the field identifiers that are used in log lines is shown in
26642 the following table:
26645 A $t $rm{authenticator name (and optional id)}
26646 C $t $rm{SMTP confirmation on delivery}
26648 CV $t $rm{certificate verification status}
26649 DN $t $rm{distinguished name from peer certificate}
26650 DT $t $rm{time taken for a delivery}
26652 F $t $rm{sender address (on delivery lines)}
26653 H $t $rm{host name and IP address}
26655 I $t $rm{local interface used}
26657 id $t $rm{message id for incoming message}
26658 P $t $rm{on \"<="\ lines: protocol used}
26660 $t $rm{on \"=>"\ lines: return path}
26661 QT $t $rm{time spent on queue}
26663 R $t $rm{on \"<="\ lines: reference for local bounce}
26664 $t $rm{on \"=>"\ lines: router name}
26665 S $t $rm{size of message}
26666 ST $t $rm{shadow transport name}
26667 T $t $rm{on \"<="\ lines: message subject (topic)}
26668 $t $rm{on \"=>"\ lines: transport name}
26669 U $t $rm{local user or RFC 1413 identity}
26670 X $t $rm{TLS cipher suite}
26674 .section Other log entries
26675 Various other types of log entry are written from time to time. Most should be
26676 self-explanatory. Among the more common are:
26678 .index retry||time not reached
26679 \*retry time not reached*\##An address previously suffered a temporary error
26680 during routing or local delivery, and the time to retry has not yet arrived.
26681 This message is not written to an individual message log file unless it happens
26682 during the first delivery attempt.
26684 \*retry time not reached for any host*\##An address previously suffered
26685 temporary errors during remote delivery, and the retry time has not yet arrived
26686 for any of the hosts to which it is routed.
26688 .index spool directory||file locked
26689 \*spool file locked*\##An attempt to deliver a message cannot proceed because
26690 some other Exim process is already working on the message. This can be quite
26691 common if queue running processes are started at frequent intervals. The
26692 \*exiwhat*\ utility script can be used to find out what Exim processes are
26695 .index error||ignored
26696 \*error ignored*\##There are several circumstances that give rise to this
26699 Exim failed to deliver a bounce message whose age was greater than
26700 \ignore__bounce__errors__after\. The bounce was discarded.
26702 A filter file set up a delivery using the `noerror' option, and the delivery
26703 failed. The delivery was discarded.
26705 A delivery set up by a router configured with
26709 failed. The delivery was discarded.
26715 .section Reducing or increasing what is logged
26716 .rset SECTlogselector "~~chapter.~~section"
26717 .index log||selectors
26718 By setting the \log@_selector\ global option, you can disable some of Exim's
26719 default logging, or you can request additional logging. The value of
26720 \log@_selector\ is made up of names preceded by plus or minus characters. For
26723 log_selector = +arguments -retry_defer
26725 The list of optional log items is in the following table, with the default
26726 selection marked by asterisks:
26729 address@_rewrite $t $rm{address rewriting}
26730 all@_parents $t $rm{all parents in => lines}
26731 arguments $t $rm{command line arguments}
26732 *connection@_reject $t $rm{connection rejections}
26733 *delay@_delivery $t $rm{immediate delivery delayed}
26735 deliver@_time $t $rm{time taken to perform delivery}
26737 delivery@_size $t $rm{add S=nnn to => lines}
26738 *dnslist@_defer $t $rm{defers of DNS list (aka RBL) lookups}
26739 *etrn $t $rm{ETRN commands}
26740 *host@_lookup@_failed $t $rm{as it says}
26742 ident@_timeout $t $rm{timeout for ident connection}
26744 incoming@_interface $t $rm{incoming interface on <= lines}
26745 incoming@_port $t $rm{incoming port on <= lines}
26746 *lost@_incoming@_connection $t $rm{as it says (includes timeouts)}
26748 outgoing@_port $t $rm{add remote port to => lines}
26750 *queue@_run $t $rm{start and end queue runs}
26752 queue@_time $t $rm{time on queue}
26754 received@_recipients $t $rm{recipients on <= lines}
26755 received@_sender $t $rm{sender on <= lines}
26756 *rejected@_header $t $rm{header contents on reject log}
26757 *retry@_defer $t $rm{`retry time not reached'}
26759 return@_path@_on@_delivery $t $rm{put return path on => and ** lines}
26761 sender@_on@_delivery $t $rm{add sender to => lines}
26762 *size@_reject $t $rm{rejection because too big}
26763 *skip@_delivery $t $rm{delivery skipped in a queue run}
26765 smtp@_confirmation $t $rm{SMTP confirmation on => lines}
26767 smtp@_connection $t $rm{SMTP connections}
26768 smtp@_incomplete@_transaction $t $rm{incomplete SMTP transactions}
26769 smtp@_protocol@_error $t $rm{SMTP protocol errors}
26770 smtp@_syntax@_error $t $rm{SMTP syntax errors}
26771 subject $t $rm{contents of ::Subject:: on <= lines}
26773 tls@_certificate@_verified $t $rm{certificate verification status}
26775 *tls@_cipher $t $rm{TLS cipher suite on <= and => lines}
26776 tls@_peerdn $t $rm{TLS peer DN on <= and => lines}
26778 all $t $rm{all of the above}
26780 More details on each of these items follows:
26782 .index log||rewriting
26783 .index rewriting||logging
26784 \address@_rewrite\: This applies both to global rewrites and per-transport
26786 but not to rewrites in filters run as an unprivileged user (because such users
26787 cannot access the log).
26789 .index log||full parentage
26790 \all@_parents\: Normally only the original and final addresses are logged on
26791 delivery lines; with this selector, intermediate parents are given in
26792 parentheses between them.
26794 .index log||Exim arguments
26795 .index Exim arguments, logging
26796 \arguments\: This causes Exim to write the arguments with which it was called
26798 preceded by the current working directory.
26799 This is a debugging feature, added to make it easier to find out how certain
26800 MUAs call \(/usr/sbin/sendmail)\. The logging does not happen if Exim has given
26801 up root privilege because it was called with the \-C-\ or \-D-\ options.
26802 Arguments that are empty or that contain whitespace are quoted. Non-printing
26803 characters are shown as escape sequences.
26804 This facility cannot log unrecognized arguments, because the arguments are
26805 checked before the configuration file is read. The only way to log such cases
26806 is to interpose a script such as \(util/logargs.sh)\ between the caller and
26809 .index log||connection rejections
26810 \connection@_reject\: A log entry is written whenever an incoming SMTP
26811 connection is rejected, for whatever reason.
26813 .index log||delayed delivery
26814 .index delayed delivery, logging
26815 \delay@_delivery\: A log entry is written whenever a delivery process is not
26816 started for an incoming message because the load is too high or too many
26817 messages were received on one connection. Logging does not occur if no delivery
26818 process is started because \queue@_only\ is set or \-odq-\ was used.
26820 .index log||delivery duration
26821 \deliver@_time\: For each delivery, the amount of real time it has taken to
26822 perform the actual delivery is logged as DT=<<time>>, for example, \"DT=1s"\.
26824 .index log||message size on delivery
26825 .index size||of message
26826 \delivery@_size\: For each delivery, the size of message delivered is added to
26827 the `=>' line, tagged with S=.
26829 .index log||dnslist defer
26830 .index DNS list||logging defer
26831 .index black list (DNS)
26832 \dnslist@_defer\: A log entry is written if an attempt to look up a host in a
26833 DNS black list suffers a temporary error.
26835 .index log||ETRN commands
26836 .index \\ETRN\\||logging
26837 \etrn\: Every legal ETRN command that is received is logged, before the ACL is
26838 run to determine whether or not it is actually accepted. An invalid ETRN
26839 command, or one received within a message transaction is not logged by this
26840 selector (see \smtp@_syntax@_error\ and \smtp@_protocol@_error\).
26842 .index log||host lookup failure
26843 \host@_lookup@_failed\: When a lookup of a host's IP addresses fails to find
26844 any addresses, or when a lookup of an IP address fails to find a host name, a
26845 log line is written. This logging does not apply to direct DNS lookups when
26846 routing email addresses, but it does apply to `byname' lookups.
26848 .index log||ident timeout
26849 .index RFC 1413||logging timeout
26850 \ident@_timeout\: A log line is written whenever an attempt to connect to a
26851 client's ident port times out.
26853 .index log||incoming interface
26854 .index interface||logging
26855 \incoming@_interface\: The interface on which a message was received is added
26856 to the `<=' line as an IP address in square brackets, tagged by I= and followed
26857 by a colon and the port number.
26858 The local interface and port are also added to other SMTP log
26859 lines, for example `SMTP connection from', and to rejection lines.
26861 .index log||incoming remote port
26862 .index port||logging remote
26863 .index TCP/IP||logging incoming remote port
26864 \incoming@_port\: The remote port number from which a message was received is
26865 added to log entries and ::Received:: header lines, following the IP address in
26866 square brackets, and separated from it by a colon. This is implemented by
26867 changing the value that is put in the \$sender@_fullhost$\ and
26868 \$sender@_rcvhost$\ variables. Recording the remote port number has become more
26869 important with the widening use of NAT (see RFC 2505).
26871 .index log||dropped connection
26872 \lost@_incoming@_connection\: A log line is written when an incoming SMTP
26873 connection is unexpectedly dropped.
26875 .index log||outgoing remote port
26876 .index port||logging outgoint remote
26877 .index TCP/IP||logging ougtoing remote port
26878 \outgoing@_port\: The remote port number is added to delivery log lines (those
26879 containing => tags) following the IP address. This option is not included in
26880 the default setting, because for most ordinary configurations, the remote port
26881 number is always 25 (the SMTP port).
26883 .index log||queue run
26884 .index queue runner||logging
26885 \queue@_run\: The start and end of every queue run are logged.
26887 .index log||queue time
26888 \queue@_time\: The amount of time the message has been in the queue on the
26889 local host is logged as QT=<<time>>, for example, \"QT=3m45s"\. The clock
26890 starts when Exim starts to receive the message, so it includes reception time
26891 as well as the delivery time of the current address.
26893 .index log||recipients
26894 \received@_recipients\: The recipients of a message are listed in the main log
26895 as soon as the message is received. The list appears at the end of the log line
26896 that is written when a message is received, preceded by the word `for'. The
26897 addresses are listed after they have been qualified, but before any rewriting
26899 Recipients that were discarded by an ACL for \\MAIL\\ or \\RCPT\\ do not appear
26902 .index log||sender reception
26903 \received@_sender\: The unrewritten original sender of a message is added to
26904 the end of the log line that records the message's arrival, after the word
26905 `from' (before the recipients if \received@_recipients\ is also set).
26907 .index log||header lines for rejection
26908 \rejected@_header\: If a message's header has been received at the time a
26909 rejection is written to the reject log, the complete header is added to the
26910 log. Header logging can be turned off individually for messages that are
26911 rejected by the \*local@_scan()*\ function (see section ~~SECTapiforloc).
26913 .index log||retry defer
26914 \retry@_defer\: A log line is written if a delivery is deferred because a retry
26915 time has not yet been reached. However, this `retry time not reached' message
26916 is always omitted from individual message logs after the first delivery
26919 .index log||return path
26920 \return@_path@_on@_delivery\: The return path that is being transmitted with
26921 the message is included in delivery and bounce lines, using the tag P=.
26923 .index log||sender on delivery
26924 \sender@_on@_delivery\: The message's sender address is added to every delivery
26925 and bounce line, tagged by F= (for `from').
26926 This is the original sender that was received with the message; it is not
26927 necessarily the same as the outgoing return path.
26929 .index log||size rejection
26930 \size@_reject\: A log line is written whenever a message is rejected because it
26933 .index log||frozen messages, skipped
26934 .index frozen messages||logging skipping
26935 \skip@_delivery\: A log line is written whenever a message is skipped during a
26936 queue run because it is frozen or because another process is already delivering
26939 .index log||smtp confirmation
26940 .index SMTP||logging confirmation
26941 \smtp@_confirmation\: The response to the final `.' in the SMTP dialogue for
26942 outgoing messages is added to delivery log lines in the form `C="<<text>>"'. A
26943 number of MTAs (including Exim) return an identifying string in this response.
26945 .index log||SMTP connections
26946 .index SMTP||logging connections
26947 \smtp@_connection\: A log line is written whenever an SMTP connection is
26948 established or closed. (By contrast, \lost@_incoming@_connection\ applies only
26949 when the closure is unexpected.) This applies to connections from local
26950 processes that use \-bs-\ as well as to TCP/IP connections. If a connection is
26951 dropped in the middle of a message, a log line is always written, whether this
26952 selector is set or not, but otherwise nothing is written at the start and end
26953 of connections unless this selector is enabled.
26955 For TCP/IP connections to an Exim daemon, the current number of connections is
26956 included in the log message for each new connection, but note that the count is
26957 reset if the daemon is restarted.
26958 Also, because connections are closed (and the closure is logged) in
26959 subprocesses, the count may not include connections that have been closed but
26960 whose termination the daemon has not yet noticed. Thus, while it is possible to
26961 match up the opening and closing of connections in the log, the value of the
26962 logged counts may not be entirely accurate.
26964 .index log||SMTP transaction, incomplete
26965 .index SMTP||logging incomplete transactions
26966 \smtp@_incomplete@_transaction\: When a mail transaction is aborted by
26967 \\RSET\\, \\QUIT\\, loss of connection, or otherwise, the incident is logged,
26968 and the message sender plus any accepted recipients are included in the log
26969 line. This can provide evidence of dictionary attacks.
26971 .index log||SMTP protocol error
26972 .index SMTP||logging protocol error
26973 \smtp@_protocol@_error\: A log line is written for every SMTP protocol error
26975 Exim does not have perfect detection of all protocol errors because of
26976 transmission delays and the use of pipelining. If \\PIPELINING\\ has been
26977 advertised to a client, an Exim server assumes that the client will use it, and
26978 therefore it does not count `expected' errors (for example, \\RCPT\\ received
26979 after rejecting \\MAIL\\) as protocol errors.
26981 .index SMTP||logging syntax errors
26982 .index SMTP||syntax errors, logging
26983 .index SMTP||unknown command, logging
26984 .index log||unknown SMTP command
26985 .index log||SMTP syntax error
26986 \smtp@_syntax@_error\: A log line is written for every SMTP syntax error
26987 encountered. An unrecognized command is treated as a syntax error. For an
26988 external connection, the host identity is given; for an internal connection
26989 using \-bs-\ the sender identification (normally the calling user) is given.
26991 .index log||subject
26992 .index subject, logging
26993 \subject\: The subject of the message is added to the arrival log line,
26994 preceded by `T=' (T for `topic', since S is already used for `size').
26995 Any MIME `words' in the subject are decoded. The \print@_topbitchars\ option
26996 specifies whether characters with values greater than 127 should be logged
26997 unchanged, or whether they should be rendered as escape sequences.
26999 .index log||certificate verification
27000 \tls@_certificate@_verified\: An extra item is added to <= and => log lines
27001 when TLS is in use. The item is \"CV=yes"\ if the peer's certificate was
27002 verified, and \"CV=no"\ if not.
27004 .index log||TLS cipher
27005 .index TLS||logging cipher
27006 \tls@_cipher\: When a message is sent or received over an encrypted connection,
27007 the cipher suite used is added to the log line, preceded by X=.
27009 .index log||TLS peer DN
27010 .index TLS||logging peer DN
27011 \tls@_peerdn\: When a message is sent or received over an encrypted connection,
27012 and a certificate is supplied by the remote host, the peer DN is added to the
27013 log line, preceded by DN=.
27016 .section Message log
27017 .index message||log file for
27018 .index log||message log, description of
27019 In addition to the general log files, Exim writes a log file for each message
27020 that it handles. The names of these per-message logs are the message ids, and
27021 .index \(msglog)\ directory
27022 they are kept in the \(msglog)\ sub-directory of the spool directory. Each
27023 message log contains copies of the log lines that apply to the message. This
27024 makes it easier to inspect the status of an individual message without having
27025 to search the main log. A message log is deleted when processing of the message
27027 .index \preserve@_message@_logs\
27028 unless \preserve__message__logs\ is set, but this should be used only with
27029 great care because they can fill up your disk very quickly.
27031 On a heavily loaded system, it may be desirable to disable the use of
27032 per-message logs, in order to reduce disk I/O. This can be done by setting the
27033 \message@_logs\ option false.
27040 . ============================================================================
27041 .chapter Exim utilities
27042 .set runningfoot "utilities"
27043 .rset CHAPutils ~~chapter
27045 A number of utility scripts and programs are supplied with Exim and are
27046 described in this chapter. There is also the Exim Monitor, which is covered in
27047 the next chapter. The utilities described here are:
27049 . This duplication seems to be the only way to arrange that the cross-
27050 . references are omitted in the Texinfo version. They look horribly ugly.
27055 \*exiwhat*\ $t $rm{list what Exim processes are doing}
27057 \*exiqgrep*\ $t $rm{grep the queue}
27059 \*exiqsumm*\ $t $rm{summarize the queue}
27060 \*exigrep*\ $t $rm{search the main log}
27061 \*exipick*\ $t $rm{select messages on various criteria}
27062 \*exicyclog*\ $t $rm{cycle (rotate) log files}
27063 \*eximstats*\ $t $rm{extract statistics from the log}
27064 \*exim@_checkaccess*\ $t $rm{check address acceptance from given IP}
27065 \*exim@_dbmbuild*\ $t $rm{build a DBM file}
27066 \*exinext*\ $t $rm{extract retry information}
27067 \*exim@_dumpdb*\ $t $rm{dump a hints database}
27068 \*exim@_tidydb*\ $t $rm{clean up a hints database}
27069 \*exim@_fixdb*\ $t $rm{patch a hints database}
27070 \*exim@_lock*\ $t $rm{lock a mailbox file}
27077 ~~SECTfinoutwha \*exiwhat*\ $t $rm{list what Exim processes are doing}
27079 ~~SECTgreptheque \*exiqgrep*\ $t $rm{grep the queue}
27081 ~~SECTsumtheque \*exiqsumm*\ $t $rm{summarize the queue}
27082 ~~SECTextspeinf \*exigrep*\ $t $rm{search the main log}
27084 ~~SECTexipick \*exipick*\ $t $rm{select messages on various criteria}
27086 ~~SECTcyclogfil \*exicyclog*\ $t $rm{cycle (rotate) log files}
27087 ~~SECTmailstat \*eximstats*\ $t $rm{extract statistics from the log}
27088 ~~SECTcheckaccess \*exim@_checkaccess*\ $t $rm{check address acceptance from given IP}
27089 ~~SECTdbmbuild \*exim@_dbmbuild*\ $t $rm{build a DBM file}
27090 ~~SECTfinindret \*exinext*\ $t $rm{extract retry information}
27091 ~~SECThindatmai \*exim@_dumpdb*\ $t $rm{dump a hints database}
27092 ~~SECThindatmai \*exim@_tidydb*\ $t $rm{clean up a hints database}
27093 ~~SECThindatmai \*exim@_fixdb*\ $t $rm{patch a hints database}
27094 ~~SECTmailboxmaint \*exim@_lock*\ $t $rm{lock a mailbox file}
27098 .section Finding out what Exim processes are doing (exiwhat)
27099 .rset SECTfinoutwha "~~chapter.~~section"
27101 .index process, querying
27103 On operating systems that can restart a system call after receiving a signal
27104 (most modern OS), an Exim process responds to the \\SIGUSR1\\ signal by writing
27105 a line describing what it is doing to the file \(exim-process.info)\ in the
27106 Exim spool directory. The \*exiwhat*\ script sends the signal to all Exim
27107 processes it can find, having first emptied the file. It then waits for one
27108 second to allow the Exim processes to react before displaying the results.
27109 In order to run \*exiwhat*\ successfully you have to have sufficient privilege to
27110 send the signal to the Exim processes, so it is normally run as root.
27112 Unfortunately, the \*ps*\ command which \*exiwhat*\ uses to find Exim processes
27113 varies in different operating systems. Not only are different options used,
27114 but the format of the output is different. For this reason, there are some
27115 system configuration options that configure exactly how \*exiwhat*\ works. If it
27116 doesn't seem to be working for you, check the following compile-time options:
27118 EXIWHAT@_PS@_CMD $rm{the command for running \*ps*\}
27119 EXIWHAT@_PS@_ARG $rm{the argument for \*ps*\}
27120 EXIWHAT@_EGREP@_ARG $rm{the argument for \*egrep*\ to select from \*ps*\ output}
27121 EXIWHAT@_KILL@_ARG $rm{the argument for the \*kill*\ command}
27123 An example of typical output from \*exiwhat*\ is
27126 164 daemon: -q1h, listening on port 25
27127 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
27128 10492 delivering 0tAycK-0002ij-00 to mail.ref.example [10.19.42.42]
27129 (editor@@ref.example)
27130 10592 handling incoming call from [192.168.243.242]
27131 10628 accepting a local non-SMTP message
27133 The first number in the output line is the process number. The third line has
27134 been split here, in order to fit it on the page.
27137 .section Selective queue listing (exiqgrep)
27138 .rset SECTgreptheque "~~chapter.~~section"
27139 .index \*exiqgrep*\
27140 .index queue||grepping
27141 This utility is a Perl script contributed by Matt Hubbard. It runs
27145 to obtain a queue listing with undelivered recipients only, and then greps the
27146 output to select messages that match given criteria. The following selection
27147 options are available:
27151 .option f <<regex>>
27152 Match the sender address. The field that is tested is enclosed in angle
27153 brackets, so you can test for bounce messages with
27158 .option r <<regex>>
27159 Match a recipient address. The field that is tested is not enclosed in angle
27162 .option s <<regex>>
27163 Match against the size field.
27165 .option y <<seconds>>
27166 Match messages that are younger than the given time.
27168 .option o <<seconds>>
27169 Match messages that are older than the given time.
27172 Match only frozen messages.
27175 Match only non-frozen messages.
27179 The following options control the format of the output:
27184 Display only the count of matching messages.
27187 Long format -- display the full message information as output by Exim. This is
27191 Display message ids only.
27194 Brief format -- one line per message.
27197 Display messages in reverse order.
27201 There is one more option, \-h-\, which outputs a list of options.
27204 .section Summarising the queue (exiqsumm)
27205 .rset SECTsumtheque "~~chapter.~~section"
27206 .index \*exiqsumm*\
27207 .index queue||summary
27208 The \*exiqsumm*\ utility is a Perl script which reads the output of \*exim
27209 -bp*\ and produces a summary of the messages on the queue. Thus, you use it by
27210 running a command such as
27212 exim -bp | exiqsumm
27214 The output consists of one line for each domain that has messages waiting for
27215 it, as in the following example:
27217 3 2322 74m 66m msn.com.example
27219 Each line lists the number of
27220 pending deliveries for a domain, their total volume, and the length of time
27221 that the oldest and the newest messages have been waiting. Note that the number
27222 of pending deliveries is greater than the number of messages when messages
27223 have more than one recipient.
27225 A summary line is output at the end. By default the output is sorted on the
27226 domain name, but \*exiqsumm*\ has the options \-a-\ and \-c-\, which cause the
27227 output to be sorted by oldest message and by count of messages, respectively.
27229 The output of \*exim -bp*\ contains the original addresses in the message, so
27230 this also applies to the output from \*exiqsumm*\. No domains from addresses
27231 generated by aliasing or forwarding are included (unless the \one@_time\ option
27232 of the \%redirect%\ router has been used to convert them into `top level'
27237 .section Extracting specific information from the log (exigrep)
27238 .rset SECTextspeinf "~~chapter.~~section"
27240 .index log||extracts, grepping for
27241 The \*exigrep*\ utility is a Perl script that searches one or more main log
27242 files for entries that match a given pattern. When it finds a match, it
27243 extracts all the log entries for the relevant message, not just those that
27244 match the pattern. Thus, \*exigrep*\ can extract complete log entries for a
27245 given message, or all mail for a given user, or for a given host, for example.
27247 If a matching log line is not associated with a specific message, it is always
27248 included in \*exigrep*\'s output.
27251 exigrep [-l] [-t<n>] <pattern> [<log file>] ...
27253 The \-t-\ argument specifies a number of seconds. It adds an additional
27254 condition for message selection. Messages that are complete are shown only if
27255 they spent more than <<n>> seconds on the queue.
27257 The \-l-\ flag means `literal', that is, treat all characters in the
27258 pattern as standing for themselves. Otherwise the pattern must be a Perl
27259 regular expression. The pattern match is case-insensitive. If no file names are
27260 given on the command line, the standard input is read.
27262 If the location of a \*zcat*\ command is known from the definition of
27263 \\ZCAT@_COMMAND\\ in \(Local/Makefile)\, \*exigrep*\ automatically passes any
27264 file whose name ends in \\COMPRESS@_SUFFIX\\ through \*zcat*\ as it searches
27267 .section Selecting messages by various criteria (exipick)
27268 .rset SECTexipick "~~chapter.~~section"
27270 John Jetmore's \*exipick*\ utility is included in the Exim distribution. It
27271 lists messages from the queue according to a variety of criteria. For details,
27278 .section Cycling log files (exicyclog)
27279 .rset SECTcyclogfil "~~chapter.~~section"
27280 .index log||cycling local files
27281 .index cycling logs
27282 .index \*exicyclog*\
27283 The \*exicyclog*\ script can be used to cycle (rotate) \*mainlog*\ and
27284 \*rejectlog*\ files. This is not necessary if only syslog is being used,
27285 or if you are using log files with datestamps in their names (see section
27287 Some operating systems have their own standard mechanisms for log cycling, and
27288 these can be used instead of \*exicyclog*\ if preferred.
27290 Each time \*exicyclog*\ is run the file names get `shuffled down' by one. If the
27291 main log file name is \(mainlog)\ (the default) then when \*exicyclog*\ is run
27292 \(mainlog)\ becomes \(mainlog.01)\, the previous \(mainlog.01)\ becomes
27293 \(mainlog.02)\ and so on, up to a limit which is set in the script, and which
27294 defaults to 10. Reject logs are handled similarly.
27296 If no \(mainlog)\ file exists, the script does nothing. Files that `drop off'
27297 the end are deleted. All files with numbers greater than 01 are compressed,
27298 using a compression command which is configured by the \\COMPRESS@_COMMAND\\
27299 setting in \(Local/Makefile)\. It is usual to run \*exicyclog*\ daily from a
27300 root \crontab\ entry of the form
27302 1 0 * * * su exim -c /usr/exim/bin/exicyclog
27304 assuming you have used the name `exim' for the Exim user. You can run
27305 \*exicyclog*\ as root if you wish, but there is no need.
27308 .section Mail statistics (eximstats)
27309 .rset SECTmailstat "~~chapter.~~section"
27311 .index \*eximstats*\
27312 A Perl script called \*eximstats*\ is provided for extracting statistical
27313 information from log files. The output is either plain text, or HTML.
27314 Exim log files are also suported by the \*Lire*\ system produced by the
27315 LogReport Foundation (\?http://www.logreport.org?\).
27317 The \*eximstats*\ script has been hacked about quite a bit over time. The
27318 latest version is the result of some extensive revision by Steve Campbell. A
27319 lot of information is given by default, but there are options for suppressing
27320 various parts of it. Following any options, the arguments to the script are a
27321 list of files, which should be main log files. For example:
27323 eximstats -nr /var/spool/exim/log/mainlog.01
27325 By default, \*eximstats*\ extracts information about the number and volume of
27326 messages received from or delivered to various hosts. The information is sorted
27327 both by message count and by volume, and the top fifty hosts in each category
27328 are listed on the standard output. Similar information, based on email
27329 addresses or domains instead of hosts can be requested by means of various
27330 options. For messages delivered and received locally, similar statistics are
27331 also produced per user.
27333 The output also includes total counts and statistics about delivery errors, and
27334 histograms showing the number of messages received and deliveries made in each
27335 hour of the day. A delivery with more than one address in its envelope (for
27336 example, an SMTP transaction with more than one \\RCPT\\ command) is counted
27337 as a single delivery by \*eximstats*\.
27339 Though normally more deliveries than receipts are reported (as messages may
27340 have multiple recipients), it is possible for \*eximstats*\ to report more
27341 messages received than delivered, even though the queue is empty at the start
27342 and end of the period in question. If an incoming message contains no valid
27343 recipients, no deliveries are recorded for it. A bounce message is handled as
27344 an entirely separate message.
27346 \*eximstats*\ always outputs a grand total summary giving the volume and number
27347 of messages received and deliveries made, and the number of hosts involved in
27348 each case. It also outputs the number of messages that were delayed (that is,
27349 not completely delivered at the first attempt), and the number that had at
27350 least one address that failed.
27352 The remainder of the output is in sections that can be independently disabled
27353 or modified by various options. It consists of a summary of deliveries by
27354 transport, histograms of messages received and delivered per time interval
27355 (default per hour), information about the time messages spent on the queue,
27356 a list of relayed messages, lists of the top fifty sending hosts, local
27357 senders, destination hosts, and destination local users by count and by volume,
27358 and a list of delivery errors that occurred.
27360 The relay information lists messages that were actually relayed, that is, they
27361 came from a remote host and were directly delivered to some other remote host,
27362 without being processed (for example, for aliasing or forwarding) locally.
27364 The options for \*eximstats*\ are as follows:
27367 .index \*eximstats*\||options
27369 The `league tables' are computed on the basis of the superior domains of the
27370 sending hosts instead of the sending and receiving hosts. This option may be
27371 combined with \-byhost-\ and/or \-byemail-\.
27374 This is a synonym for \-byemaildomain-\.
27377 The `league tables' are computed on the basis of complete email addresses,
27378 instead of sending and receiving hosts. This option may be combined with
27379 \-byhost-\ and/or \-bydomain-\.
27381 .option byemaildomain
27382 The `league tables' are computed on the basis of the sender's email domain
27383 instead of the sending and receiving hosts. This option may be combined with
27384 \-byhost-\, \-bydomain-\, or \-byemail-\.
27387 The `league tables' are computed on the basis of sending and receiving hosts.
27388 This is the default option. It may be combined with \-bydomain-\ and/or
27392 Cache results of \*timegm()*\ lookups. This results in a significant speedup
27393 when processing hundreds of thousands of messages, at a cost of increasing the
27394 memory utilisation.
27396 .option chartdir <<dir>>
27397 When \-charts-\ is specified, create the charts in the directory <<dir>>.
27399 .option chartrel <<dir>>
27400 When \-charts-\ is specified, this option specifies the relative directory for
27401 the \"img src="\ tags from where to include the charts.
27404 Create graphical charts to be displayed in HTML output. This requires the
27405 \"GD"\, \"GDTextUtil"\, and \"GDGraph"\ Perl modules, which can be obtained
27406 from \?http://www.cpan.org/modules/01modules.index.html?\.
27408 To install these, download and unpack them, then use the normal Perl
27409 installation procedure:
27418 This is a debug flag. It causes \*eximstats*\ to output the \*eval()*\'d parser
27419 to the standard output, which makes it easier to trap errors in the eval
27420 section. Remember to add one to the line numbers to allow for the title.
27424 Show help information about \*eximstats*\' options.
27427 This option controls the histograms of messages received and deliveries per
27428 time interval. By default the time interval is one hour. If \-h0-\ is given,
27429 the histograms are suppressed; otherwise the value of <<n>> gives the number of
27430 divisions per hour. Valid values are 0, 1, 2, 3, 5, 10, 15, 20, 30 or 60, so
27431 \-h2-\ sets an interval of 30 minutes, and the default is equivalent to \-h1-\.
27434 Output the results in HTML instead of plain text.
27437 This option causes \*eximstats*\ to merge old reports into a combined report.
27438 When this option is used, the input files must be outputs from previous calls
27439 to \*eximstats*\, not raw log files. For example, you could produce a set of
27440 daily reports and a weekly report by commands such as
27442 eximstats mainlog.sun > report.sun.txt
27443 eximstats mainlog.mon > report.mon.txt
27444 eximstats mainlog.tue > report.tue.txt
27445 eximstats mainlog.wed > report.wed.txt
27446 eximstats mainlog.thu > report.thu.txt
27447 eximstats mainlog.fri > report.fri.txt
27448 eximstats mainlog.sat > report.sat.txt
27449 eximstats -merge -html report.*.txt > weekly_report.html
27451 You can merge text or html reports and output the results as text or html. You
27452 can use all the normal \*eximstats*\ output options, but only data included in
27453 the original reports can be shown. When merging reports, some loss of accuracy
27454 may occur in the `league tables', towards the ends of the lists. The order of
27455 items in the `league tables' may vary when the data volumes round to the same
27459 Suppress the display of information about failed deliveries (errors).
27462 Suppress information about messages relayed through this host.
27464 .option nr /pattern/
27465 Suppress information about relayed messages that match the pattern, which is
27466 matched against a string of the following form (split over two lines here in
27467 order to fit it on the page):
27469 H=<host> [<ip address>] A=<sender address> =>
27470 H=<host> A=<recipient address>
27474 H=in.host [1.2.3.4] A=from@some.where.example =>
27475 H=out.host A=to@else.where.example
27477 The sending host name appears in parentheses if it has not been verified as
27478 matching the IP address. The mail addresses are taken from the envelope, not
27479 the headers. This option allows you to screen out hosts whom you are happy to
27480 have using your host as a relay.
27483 Suppress the statistics about delivery by transport.
27485 .option nt/<<pattern>>/
27486 Suppress the statistics about delivery by any transport whose name matches the
27487 pattern. If you are using one transport to send all messages to a scanning
27488 mechanism before doing the real delivery, this feature can be used to omit that
27489 transport from your normal statistics (on the grounds that it is of no
27493 .option "pattern" "#<<description>>#/<<pattern>>/"
27494 Count lines matching specified patterns and show them in
27495 the results. For example:
27497 -pattern 'Refused connections' '/refused connection/'
27499 This option can be specified multiple times.
27502 Suppress information about times messages spend on the queue.
27504 .option q <<n1>>...
27505 This option sets an alternative list of time intervals for the queueing
27506 information. The values are separated by commas and are in seconds, but can
27507 involve arithmetic multipliers, so for example you can set 3$*$60 to specify 3
27508 minutes. A setting such as
27512 causes \*eximstats*\ to give counts of messages that stayed on the queue for less
27513 than one minute, less than five minutes, less than ten minutes, and over ten
27517 Sets the `top' count to <<n>>. This controls the listings of the `top <<n>>'
27518 hosts and users by count and volume. The default is 50, and setting 0
27519 suppresses the output altogether.
27522 Omit local information from the `top' listings.
27524 .option t@_remote@_users
27525 Include remote users in the `top' listings.
27530 .section Checking access policy (exim@_checkaccess)
27531 .rset SECTcheckaccess "~~chapter.~~section"
27532 .index \*exim@_checkaccess*\
27533 .index policy control||checking access
27534 .index checking access
27535 The \-bh-\ command line argument allows you to run a fake SMTP session with
27536 debugging output, in order to check what Exim is doing when it is applying
27537 policy controls to incoming SMTP mail. However, not everybody is sufficiently
27538 familiar with the SMTP protocol to be able to make full use of \-bh-\, and
27539 sometimes you just want to answer the question \*Does this address have
27540 access?*\ without bothering with any further details.
27542 The \*exim@_checkaccess*\ utility is a `packaged' version of \-bh-\. It takes
27543 two arguments, an IP address and an email address:
27545 exim_checkaccess 10.9.8.7 A.User@a.domain.example
27547 The utility runs a call to Exim with the \-bh-\ option, to test whether the
27548 given email address would be accepted in a \\RCPT\\ command in a TCP/IP
27549 connection from the host with the given IP address. The output of the utility
27550 is either the word `accepted', or the SMTP error response, for example:
27553 550 Relay not permitted
27555 When running this test, the utility uses \"<>"\ as the envelope sender address
27556 for the \\MAIL\\ command, but you can change this by providing additional
27557 options. These are passed directly to the Exim command. For example, to specify
27558 that the test is to be run with the sender address \*himself@@there.example*\
27561 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
27562 -f himself@there.example
27564 Note that these additional Exim command line items must be given after the two
27565 mandatory arguments.
27567 Because the \exim@_checkaccess\ uses \-bh-\, it does not perform callouts while
27568 running its checks. You can run checks that include callouts by using \-bhc-\,
27569 but this is not yet available in a `packaged' form.
27572 .section Making DBM files (exim@_dbmbuild)
27573 .rset SECTdbmbuild "~~chapter.~~section"
27574 .index DBM||building dbm files
27575 .index building DBM files
27576 .index \*exim@_dbmbuild*\
27577 .index lower casing
27578 .index binary zero||in lookup key
27579 The \*exim@_dbmbuild*\ program reads an input file containing keys and data in
27580 the format used by the \%lsearch%\ lookup (see section ~~SECTsinglekeylookups).
27581 It writes a DBM file using the lower-cased alias names as keys and the
27582 remainder of the information as data. The lower-casing can be prevented by
27583 calling the program with the \-nolc-\ option.
27585 A terminating zero is included as part of the key string. This is expected by
27586 the \%dbm%\ lookup type. However, if the option \-nozero-\ is given,
27587 \*exim@_dbmbuild*\ creates files without terminating zeroes in either the key
27588 strings or the data strings. The \%dbmnz%\ lookup type can be used with such
27591 The program requires two arguments: the name of the input file (which can be a
27592 single hyphen to indicate the standard input), and the name of the output file.
27593 It creates the output under a temporary name, and then renames it if all went
27596 If the native DB interface is in use (\\USE@_DB\\ is set in a compile-time
27597 configuration file -- this is common in free versions of Unix) the two file
27598 names must be different, because in this mode the Berkeley DB functions create
27599 a single output file using exactly the name given. For example,
27601 exim_dbmbuild /etc/aliases /etc/aliases.db
27603 reads the system alias file and creates a DBM version of it in
27604 \(/etc/aliases.db)\.
27606 In systems that use the \*ndbm*\ routines (mostly proprietary versions of Unix),
27607 two files are used, with the suffixes \(.dir)\ and \(.pag)\. In this
27608 environment, the suffixes are added to the second argument of
27609 \*exim@_dbmbuild*\, so it can be the same as the first. This is also the case
27610 when the Berkeley functions are used in compatibility mode (though this is not
27611 recommended), because in that case it adds a \(.db)\ suffix to the file name.
27613 If a duplicate key is encountered, the program outputs a warning, and when it
27614 finishes, its return code is 1 rather than zero, unless the \-noduperr-\ option
27615 is used. By default, only the first of a set of duplicates is used -- this
27616 makes it compatible with \%lsearch%\ lookups. There is an option \-lastdup-\
27617 which causes it to use the data for the last duplicate instead. There is also
27618 an option \-nowarn-\, which stops it listing duplicate keys to \stderr\. For
27619 other errors, where it doesn't actually make a new file, the return code is 2.
27623 .section Finding individual retry times (exinext)
27624 .rset SECTfinindret "~~chapter.~~section"
27625 .index retry||times
27627 A utility called \*exinext*\ (mostly a Perl script) provides the ability to fish
27628 specific information out of the retry database. Given a mail domain (or a
27629 complete address), it looks up the hosts for that domain, and outputs any retry
27630 information for the hosts or for the domain. At present, the retry information
27631 is obtained by running \*exim@_dumpdb*\ (see below) and post-processing the
27632 output. For example:
27634 $ exinext piglet@milne.fict.example
27635 kanga.milne.fict.example:192.168.8.1 error 146: Connection refused
27636 first failed: 21-Feb-1996 14:57:34
27637 last tried: 21-Feb-1996 14:57:34
27638 next try at: 21-Feb-1996 15:02:34
27639 roo.milne.fict.example:192.168.8.3 error 146: Connection refused
27640 first failed: 20-Jan-1996 13:12:08
27641 last tried: 21-Feb-1996 11:42:03
27642 next try at: 21-Feb-1996 19:42:03
27643 past final cutoff time
27645 You can also give \*exinext*\ a local part, without a domain, and it
27646 will give any retry information for that local part in your default domain.
27647 A message id can be used to obtain retry information pertaining to a specific
27648 message. This exists only when an attempt to deliver a message to a remote host
27649 suffers a message-specific error (see section ~~SECToutSMTPerr). \*exinext*\ is
27650 not particularly efficient, but then it isn't expected to be run very often.
27652 The \*exinext*\ utility calls Exim to find out information such as the location
27653 of the spool directory. The utility has \-C-\ and \-D-\ options, which are
27654 passed on to the \*exim*\ commands. The first specifies an alternate Exim
27655 configuration file, and the second sets macros for use within the configuration
27656 file. These features are mainly to help in testing, but might also be useful in
27657 environments where more than one configuration file is in use.
27661 .section Hints database maintenance (exim@_dumpdb, exim@_fixdb, exim@_tidydb)
27662 .rset SECThindatmai "~~chapter.~~section"
27663 .index hints database||maintenance
27664 .index maintaining Exim's hints database
27665 Three utility programs are provided for maintaining the DBM files that Exim
27666 uses to contain its delivery hint information. Each program requires two
27667 arguments. The first specifies the name of Exim's spool directory, and the
27668 second is the name of the database it is to operate on. These are as
27671 \*retry*\: the database of retry information
27673 \*wait-*\<<transport name>>: databases of information about messages waiting
27676 \*callout*\: the callout cache
27678 \*misc*\: other hints data
27680 The \*misc*\ database is used for
27682 Serializing \\ETRN\\ runs (when \smtp@_etrn@_serialize\ is set)
27684 Serializing delivery to a specific host (when \serialize@_hosts\ is set in an
27685 \%smtp%\ transport)
27687 .index \*exim@_dumpdb*\
27688 The entire contents of a database are written to the standard output by the
27689 \*exim@_dumpdb*\ program, which has no options or arguments other than the
27690 spool and database names. For example, to dump the retry database:
27692 exim_dumpdb /var/spool/exim retry
27694 Two lines of output are produced for each entry:
27696 T:mail.ref.example:192.168.242.242 146 77 Connection refused
27697 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
27699 The first item on the first line is the key of the record. It starts with one
27700 of the letters R, or T, depending on whether it refers to a routing or
27701 transport retry. For a local delivery, the next part is the local address; for
27702 a remote delivery it is the name of the remote host, followed by its failing IP
27703 address (unless \no@_retry@_include@_ip@_address\ is set on the \%smtp%\
27705 If the remote port is not the standard one (port 25), it is added to the IP
27707 Then there follows an error code, an additional error code, and a
27708 textual description of the error.
27710 The three times on the second line are the time of first failure, the time of
27711 the last delivery attempt, and the computed time for the next attempt. The line
27712 ends with an asterisk if the cutoff time for the last retry rule has been
27715 Each output line from \*exim@_dumpdb*\ for the \*wait-*\$it{xxx} databases
27716 consists of a host name followed by a list of ids for messages that are or were
27717 waiting to be delivered to that host. If there are a very large number for any
27718 one host, continuation records, with a sequence number added to the host name,
27719 may be seen. The data in these records is often out of date, because a message
27720 may be routed to several alternative hosts, and Exim makes no effort to keep
27723 .index \*exim@_tidydb*\
27724 The \*exim@_tidydb*\ utility program is used to tidy up the contents of the
27725 hints databases. If run with no options, it removes all records from a database
27726 that are more than 30 days old. The cutoff date can be altered by means of the
27727 \-t-\ option, which must be followed by a time. For example, to remove all
27728 records older than a week from the retry database:
27730 exim_tidydb -t 7d /var/spool/exim retry
27732 Both the \*wait-*\$it{xxx} and \*retry*\ databases contain items that involve
27733 message ids. In the former these appear as data in records keyed by host --
27734 they were messages that were waiting for that host -- and in the latter they
27735 are the keys for retry information for messages that have suffered certain
27736 types of error. When \*exim@_tidydb*\ is run, a check is made to ensure that
27737 message ids in database records are those of messages that are still on the
27738 queue. Message ids for messages that no longer exist are removed from
27739 \*wait-*\$it{xxx} records, and if this leaves any records empty, they are
27740 deleted. For the \*retry*\ database, records whose keys are non-existent message
27741 ids are removed. The \*exim@_tidydb*\ utility outputs comments on the standard
27742 output whenever it removes information from the database.
27744 Removing records from a DBM file does not normally make the file smaller, but
27745 all the common DBM libraries are able to re-use the space that is released.
27746 It is therefore suggested that \*exim@_tidydb*\ be run periodically on all the
27747 hints databases, but at a quiet time of day, because it requires a database to
27748 be locked (and therefore inaccessible to Exim) while it does its work.
27750 .index \*exim@_fixdb*\
27751 The \*exim@_fixdb*\ program is a utility for interactively modifying databases.
27752 Its main use is for testing Exim, but it might also be occasionally useful for
27753 getting round problems in a live system. It has no options, and its interface
27754 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
27755 key of a database record can then be entered, and the data for that record is
27758 If `d' is typed at the next prompt, the entire record is deleted. For all
27759 except the \*retry*\ database, that is the only operation that can be carried
27760 out. For the \*retry*\ database, each field is output preceded by a number, and
27761 data for individual fields can be changed by typing the field number followed
27762 by new data, for example:
27766 resets the time of the next delivery attempt. Time values are given as a
27767 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
27768 used as optional separators.
27772 .section Mailbox maintenance (exim@_lock)
27773 .rset SECTmailboxmaint "~~chapter.~~section"
27774 .index mailbox||maintenance
27775 .index \*exim@_lock*\
27776 .index locking mailboxes
27777 The \*exim@_lock*\ utility locks a mailbox file using the same algorithm as
27778 Exim. For a discussion of locking issues, see section ~~SECTopappend.
27779 \*Exim@_lock*\ can be used to prevent any modification of a mailbox by Exim or
27780 a user agent while investigating a problem. The utility requires the name of
27781 the file as its first argument. If the locking is successful, the second
27782 argument is run as a command (using C's \*system()*\ function); if there is no
27783 second argument, the value of the SHELL environment variable is used; if this
27784 is unset or empty, \(/bin/sh)\ is run. When the command finishes, the mailbox
27785 is unlocked and the utility ends. The following options are available:
27790 Use \*fcntl()*\ locking on the open mailbox.
27793 Use \*flock()*\ locking on the open mailbox, provided the operating system
27797 This must be followed by a number, which is a number of seconds; it sets the
27798 interval to sleep between retries (default 3).
27801 Create a lock file before opening the mailbox.
27804 Lock the mailbox using MBX rules.
27807 Suppress verification output.
27810 This must be followed by a number; it sets the number of times to try to get
27811 the lock (default 10).
27813 .option restore@_time
27814 This option causes \exim@_lock\ to restore the modified and read times to the
27815 locked file before exiting. This allows you to access a locked mailbox (for
27816 example, to take a backup copy) without disturbing the times that the user
27820 This must be followed by a number, which is a number of seconds; it sets a
27821 timeout to be used with a blocking \*fcntl()*\ lock. If it is not set (the
27822 default), a non-blocking call is used.
27825 Generate verbose output.
27829 If none of \-fcntl-\,
27831 \-lockfile-\ or \-mbx-\ are given, the default is to create a lock file and
27832 also to use \*fcntl()*\ locking on the mailbox, which is the same as Exim's
27833 default. The use of
27835 or \-fcntl-\ requires that the file be writeable; the use of
27836 \-lockfile-\ requires that the directory containing the file be writeable.
27837 Locking by lock file does not last for ever; Exim assumes that a lock file is
27838 expired if it is more than 30 minutes old.
27840 The \-mbx-\ option can be used with either or both of \-fcntl-\ or \-flock-\.
27841 It assumes \-fcntl-\ by default.
27842 MBX locking causes a shared lock to be taken out on the open mailbox, and an
27843 exclusive lock on the file \(/tmp/.$it{n}.$it{m})\ where $it{n} and $it{m} are
27844 the device number and inode number of the mailbox file. When the locking is
27845 released, if an exclusive lock can be obtained for the mailbox, the file in
27846 \(/tmp)\ is deleted.
27848 The default output contains verification of the locking that takes place. The
27849 \-v-\ option causes some additional information to be given. The \-q-\ option
27850 suppresses all output except error messages.
27854 exim_lock /var/spool/mail/spqr
27856 runs an interactive shell while the file is locked, whereas
27858 exim@_lock -q /var/spool/mail/spqr @<@<End
27862 runs a specific non-interactive sequence of commands while the file is locked,
27863 suppressing all verification output. A single command can be run by a command
27866 exim_lock -q /var/spool/mail/spqr \
27867 "cp /var/spool/mail/spqr /some/where"
27869 Note that if a command is supplied, it must be entirely contained within the
27870 second argument -- hence the quotes.
27878 . ============================================================================
27879 .chapter The Exim monitor
27880 .set runningfoot "monitor"
27881 .rset CHAPeximon ~~chapter
27883 .index Exim monitor
27886 .index Local/eximon.conf
27887 .index \(exim@_monitor/EDITME)\
27888 The Exim monitor is an application which displays in an X window information
27889 about the state of Exim's queue and what Exim is doing. An admin user can
27890 perform certain operations on messages from this GUI interface; however all
27891 such facilities are also available from the command line, and indeed, the
27892 monitor itself makes use of the command line to perform any actions requested.
27895 .section Running the monitor
27896 The monitor is started by running the script called \*eximon*\. This is a shell
27897 script that sets up a number of environment variables, and then runs the
27898 binary called \(eximon.bin)\. The default appearance of the monitor window can
27899 be changed by editing the \(Local/eximon.conf)\ file created by editing
27900 \(exim@_monitor/EDITME)\. Comments in that file describe what the various
27901 parameters are for.
27903 The parameters that get built into the \*eximon*\ script can be overridden for a
27904 particular invocation by setting up environment variables of the same names,
27905 preceded by `$tt{EXIMON@_}'. For example, a shell command such as
27907 EXIMON_LOG_DEPTH=400 eximon
27909 (in a Bourne-compatible shell) runs \*eximon*\ with an overriding setting of the
27910 \\LOG@_DEPTH\\ parameter. If \\EXIMON@_LOG@_FILE@_PATH\\ is set in the
27911 environment, it overrides the Exim log file configuration. This makes it
27912 possible to have \*eximon*\ tailing log data that is written to syslog, provided
27913 that MAIL.INFO syslog messages are routed to a file on the local host.
27915 X resources can be used to change the appearance of the window in the normal
27916 way. For example, a resource setting of the form
27918 Eximon*background: gray94
27920 changes the colour of the background to light grey rather than white. The
27921 stripcharts are drawn with both the data lines and the reference lines in
27922 black. This means that the reference lines are not visible when on top of the
27923 data. However, their colour can be changed by setting a resource called
27924 `highlight' (an odd name, but that's what the Athena stripchart widget uses).
27925 For example, if your X server is running Unix, you could set up lighter
27926 reference lines in the stripcharts by obeying
27929 Eximon*highlight: gray
27934 In order to see the contents of messages on the queue, and to operate on them,
27935 \*eximon*\ must either be run as root or by an admin user.
27937 The monitor's window is divided into three parts. The first contains one or
27938 more stripcharts and two action buttons, the second contains a `tail' of the
27939 main log file, and the third is a display of the queue of messages awaiting
27940 delivery, with two more action buttons. The following sections describe these
27941 different parts of the display.
27945 .section The stripcharts
27947 The first stripchart is always a count of messages on the queue. Its name can
27948 be configured by setting \\QUEUE@_STRIPCHART@_NAME\\ in the
27949 \(Local/eximon.conf)\ file. The remaining stripcharts are defined in the
27950 configuration script by regular expression matches on log file entries, making
27951 it possible to display, for example, counts of messages delivered to certain
27952 hosts or using certain transports. The supplied defaults display counts of
27953 received and delivered messages, and of local and SMTP deliveries. The default
27954 period between stripchart updates is one minute; this can be adjusted by a
27955 parameter in the \(Local/eximon.conf)\ file.
27957 The stripchart displays rescale themselves automatically as the value they are
27958 displaying changes. There are always 10 horizontal lines in each chart; the
27959 title string indicates the value of each division when it is greater than one.
27960 For example, `x2' means that each division represents a value of 2.
27962 It is also possible to have a stripchart which shows the percentage fullness of
27963 a particular disk partition, which is useful when local deliveries are confined
27964 to a single partition.
27965 .index \statvfs\ function
27966 This relies on the availability of the \*statvfs()*\ function or equivalent in
27967 the operating system. Most, but not all versions of Unix that support Exim have
27968 this. For this particular stripchart, the top of the chart always represents
27969 100%, and the scale is given as `x10%'. This chart is configured by setting
27970 \\SIZE@_STRIPCHART\\ and (optionally) \\SIZE@_STRIPCHART@_NAME\\ in the
27971 \(Local/eximon.conf)\ file.
27975 .section Main action buttons
27976 .index size||of monitor window
27977 .index monitor window size
27979 Below the stripcharts there is an action button for quitting the monitor. Next
27980 to this is another button marked `Size'. They are placed here so that shrinking
27981 the window to its default minimum size leaves just the queue count stripchart
27982 and these two buttons visible. Pressing the `Size' button causes the window to
27983 expand to its maximum size, unless it is already at the maximum, in which case
27984 it is reduced to its minimum.
27986 When expanding to the maximum, if the window cannot be fully seen where it
27987 currently is, it is moved back to where it was the last time it was at full
27988 size. When it is expanding from its minimum size, the old position is
27989 remembered, and next time it is reduced to the minimum it is moved back there.
27991 The idea is that you can keep a reduced window just showing one or two
27992 stripcharts at a convenient place on your screen, easily expand it to show
27993 the full window when required, and just as easily put it back to what it was.
27994 The idea is copied from what the \*twm*\ window manager does for its
27995 \*f.fullzoom*\ action. The minimum size of the window can be changed by setting
27996 the \\MIN@_HEIGHT\\ and \\MIN@_WIDTH\\ values in \(Local/eximon.conf)\.
27998 Normally, the monitor starts up with the window at its full size, but it can be
27999 built so that it starts up with the window at its smallest size, by setting
28000 \\START@_SMALL\\=yes in \(Local/eximon.conf)\.
28003 .section The log display
28004 .index log||tail of, in monitor
28005 The second section of the window is an area in which a display of the tail of
28006 the main log is maintained.
28007 To save space on the screen, the timestamp on each log line is shortened by
28008 removing the date and, if \log@_timezone\ is set, the timezone.
28009 The log tail is not available when the only destination for logging data is
28010 syslog, unless the syslog lines are routed to a local file whose name is passed
28011 to \*eximon*\ via the \\EXIMON@_LOG@_FILE@_PATH\\ environment variable.
28013 The log sub-window has a scroll bar at its lefthand side which can be used to
28014 move back to look at earlier text, and the up and down arrow keys also have a
28015 scrolling effect. The amount of log that is kept depends on the setting of
28016 \\LOG@_BUFFER\\ in \(Local/eximon.conf)\, which specifies the amount of memory
28017 to use. When this is full, the earlier 50% of data is discarded -- this is much
28018 more efficient than throwing it away line by line. The sub-window also has a
28019 horizontal scroll bar for accessing the ends of long log lines. This is the
28020 only means of horizontal scrolling; the right and left arrow keys are not
28021 available. Text can be cut from this part of the window using the mouse in the
28022 normal way. The size of this subwindow is controlled by parameters in the
28023 configuration file \(Local/eximon.conf)\.
28025 Searches of the text in the log window can be carried out by means of the ^R
28026 and ^S keystrokes, which default to a reverse and a forward search,
28027 respectively. The search covers only the text that is displayed in the window.
28028 It cannot go further back up the log.
28030 The point from which the search starts is indicated by a caret marker. This is
28031 normally at the end of the text in the window, but can be positioned explicitly
28032 by pointing and clicking with the left mouse button, and is moved automatically
28033 by a successful search. If new text arrives in the window when it is scrolled
28034 back, the caret remains where it is, but if the window is not scrolled back,
28035 the caret is moved to the end of the new text.
28037 Pressing ^R or ^S pops up a window into which the search text can be typed.
28038 There are buttons for selecting forward or reverse searching, for carrying out
28039 the search, and for cancelling. If the `Search' button is pressed, the search
28040 happens and the window remains so that further searches can be done. If the
28041 `Return' key is pressed, a single search is done and the window is closed. If
28042 ^C is typed the search is cancelled.
28044 The searching facility is implemented using the facilities of the Athena text
28045 widget. By default this pops up a window containing both `search' and `replace'
28046 options. In order to suppress the unwanted `replace' portion for eximon, a
28047 modified version of the \TextPop\ widget is distributed with Exim. However, the
28048 linkers in BSDI and HP-UX seem unable to handle an externally provided version
28049 of \TextPop\ when the remaining parts of the text widget come from the standard
28050 libraries. The compile-time option \\EXIMON@_TEXTPOP\\ can be unset to cut out
28051 the modified \TextPop\, making it possible to build Eximon on these systems, at
28052 the expense of having unwanted items in the search popup window.
28055 .section The queue display
28056 .index queue||display in monitor
28057 The bottom section of the monitor window contains a list of all messages that
28058 are on the queue, which includes those currently being received or delivered,
28059 as well as those awaiting delivery. The size of this subwindow is controlled by
28060 parameters in the configuration file \(Local/eximon.conf)\, and the frequency
28061 at which it is updated is controlled by another parameter in the same file --
28062 the default is 5 minutes, since queue scans can be quite expensive. However,
28063 there is an `Update' action button just above the display which can be used to
28064 force an update of the queue display at any time.
28066 When a host is down for some time, a lot of pending mail can build up for it,
28067 and this can make it hard to deal with other messages on the queue. To help
28068 with this situation there is a button next to `Update' called `Hide'. If
28069 pressed, a dialogue box called `Hide addresses ending with' is put up. If you
28070 type anything in here and press `Return', the text is added to a chain of such
28071 texts, and if every undelivered address in a message matches at least one
28072 of the texts, the message is not displayed.
28074 If there is an address that does not match any of the texts, all the addresses
28075 are displayed as normal. The matching happens on the ends of addresses so, for
28076 example, \*cam.ac.uk*\ specifies all addresses in Cambridge, while
28077 \*xxx@@foo.com.example*\ specifies just one specific address. When any hiding
28078 has been set up, a button called `Unhide' is displayed. If pressed, it cancels
28079 all hiding. Also, to ensure that hidden messages do not get forgotten, a hide
28080 request is automatically cancelled after one hour.
28082 While the dialogue box is displayed, you can't press any buttons or do anything
28083 else to the monitor window. For this reason, if you want to cut text from the
28084 queue display to use in the dialogue box, you have to do the cutting before
28085 pressing the `Hide' button.
28087 The queue display contains, for each unhidden queued message, the length of
28088 time it has been on the queue, the size of the message, the message id, the
28089 message sender, and the first undelivered recipient, all on one line. If it is
28090 a bounce message, the sender is shown as `<>'. If there is more than one
28091 recipient to which the message has not yet been delivered, subsequent ones are
28092 listed on additional lines, up to a maximum configured number, following which
28093 an ellipsis is displayed. Recipients that have already received the message are
28095 .index frozen messages||display
28096 If a message is frozen, an asterisk is displayed at the left-hand side.
28098 The queue display has a vertical scroll bar, and can also be scrolled by means
28099 of the arrow keys. Text can be cut from it using the mouse in the normal way.
28100 The text searching facilities, as described above for the log window, are also
28101 available, but the caret is always moved to the end of the text when the queue
28102 display is updated.
28105 .section The queue menu
28106 .index queue||menu in monitor
28107 If the \shift\ key is held down and the left button is clicked when the mouse
28108 pointer is over the text for any message, an action menu pops up, and the first
28109 line of the queue display for the message is highlighted. This does not affect
28112 If you want to use some other event for popping up the menu, you can set the
28113 \\MENU@_EVENT\\ parameter in \(Local/eximon.conf)\ to change the default, or
28114 set \\EXIMON@_MENU@_EVENT\\ in the environment before starting the monitor. The
28115 value set in this parameter is a standard X event description. For example, to
28116 run eximon using \ctrl\ rather than \shift\ you could use
28118 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
28120 The title of the menu is the message id, and it contains entries which act as
28123 \*message log*\: The contents of the message log for the message are displayed in
28126 \*headers*\: Information from the spool file that contains the envelope
28127 information and headers is displayed in a new text window. See chapter
28128 ~~CHAPspool for a description of the format of spool files.
28130 \*body*\: The contents of the spool file containing the body of the message are
28131 displayed in a new text window. There is a default limit of 20,000 bytes to the
28132 amount of data displayed. This can be changed by setting the \\BODY@_MAX\\
28133 option at compile time, or the \\EXIMON@_BODY@_MAX\\ option at run time.
28135 \*deliver message*\: A call to Exim is made using the \-M-\ option to request
28136 delivery of the message. This causes an automatic thaw if the message is
28137 frozen. The \-v-\ option is also set, and the output from Exim is displayed in
28138 a new text window. The delivery is run in a separate process, to avoid holding
28139 up the monitor while the delivery proceeds.
28141 \*freeze message*\: A call to Exim is made using the \-Mf-\ option to request
28142 that the message be frozen.
28144 .index thawing messages
28145 .index unfreezing messages
28146 .index frozen messages||thawing
28147 \*thaw message*\: A call to Exim is made using the \-Mt-\ option to request that
28148 the message be thawed.
28150 .index delivery||forcing failure
28151 \*give up on msg*\: A call to Exim is made using the \-Mg-\ option to request
28152 that Exim gives up trying to deliver the message. A bounce message is generated
28153 for any remaining undelivered addresses.
28155 \*remove message*\: A call to Exim is made using the \-Mrm-\ option to request
28156 that the message be deleted from the system without generating a bounce
28159 \*add recipient*\: A dialog box is displayed into which a recipient address can
28160 be typed. If the address is not qualified and the \\QUALIFY@_DOMAIN\\ parameter
28161 is set in \(Local/eximon.conf)\, the address is qualified with that domain.
28162 Otherwise it must be entered as a fully qualified address. Pressing \\RETURN\\
28163 causes a call to Exim to be made using the \-Mar-\ option to request that an
28164 additional recipient be added to the message, unless the entry box is empty, in
28165 which case no action is taken.
28167 \*mark delivered*\: A dialog box is displayed into which a recipient address can
28168 be typed. If the address is not qualified and the \\QUALIFY@_DOMAIN\\ parameter
28169 is set in \(Local/eximon.conf)\, the address is qualified with that domain.
28170 Otherwise it must be entered as a fully qualified address. Pressing \\RETURN\\
28171 causes a call to Exim to be made using the \-Mmd-\ option to mark the given
28172 recipient address as already delivered, unless the entry box is empty, in which
28173 case no action is taken.
28175 \*mark all delivered*\: A call to Exim is made using the \-Mmad-\ option to mark
28176 all recipient addresses as already delivered.
28178 \*edit sender*\: A dialog box is displayed initialized with the current sender's
28179 address. Pressing \\RETURN\\ causes a call to Exim to be made using the \-Mes-\
28180 option to replace the sender address, unless the entry box is empty, in which
28181 case no action is taken. If you want to set an empty sender (as in bounce
28182 messages), you must specify it as `<>'. Otherwise, if the address is not
28183 qualified and the \\QUALIFY@_DOMAIN\\ parameter is set in
28184 \(Local/eximon.conf)\, the address is qualified with that domain.
28186 When a delivery is forced, a window showing the \-v-\ output is displayed. In
28187 other cases when a call to Exim is made, if there is any output from Exim (in
28188 particular, if the command fails) a window containing the command and the
28189 output is displayed. Otherwise, the results of the action are normally apparent
28190 from the log and queue displays. However, if you set \\ACTION@_OUTPUT\\=yes in
28191 \(Local/eximon.conf)\, a window showing the Exim command is always opened, even
28192 if no output is generated.
28194 The queue display is automatically updated for actions such as freezing and
28195 thawing, unless \\ACTION@_QUEUE@_UPDATE\\=no has been set in
28196 \(Local/eximon.conf)\. In this case the `Update' button has to be used to force
28197 an update of the display after one of these actions.
28199 In any text window that is displayed as result of a menu action, the normal
28200 cut-and-paste facility is available, and searching can be carried out using ^R
28201 and ^S, as described above for the log tail window.
28212 . ============================================================================
28213 .chapter Security considerations
28214 .set runningfoot "security"
28215 .rset CHAPsecurity ~~chapter
28217 This chapter discusses a number of issues concerned with security, some of
28218 which are also covered in other parts of this manual.
28220 For reasons that this author does not understand, some people have promoted
28221 Exim as a `particularly secure' mailer. Perhaps it is because of the existence
28222 of this chapter in the documentation. However, the intent of the chapter is
28223 simply to describe the way Exim works in relation to certain security concerns,
28224 not to make any specific claims about the effectiveness of its security as
28225 compared with other MTAs.
28227 What follows is a description of the way Exim is supposed to be. Best efforts
28228 have been made to try to ensure that the code agrees with the theory, but an
28229 absence of bugs can never be guaranteed. Any that are reported will get fixed
28230 as soon as possible.
28232 .section Building a more `hardened' Exim
28233 .index security||build-time features
28234 There are a number of build-time options that can be set in \(Local/Makefile)\
28235 to create Exim binaries that are `harder' to attack, in particular by a rogue
28236 Exim administrator who does not have the root password, or by someone who has
28237 penetrated the Exim (but not the root) account. These options are as follows:
28239 \\ALT@_CONFIG@_PREFIX\\ can be set to a string that is required to match the
28240 start of any file names used with the \-C-\ option. When it is set, these file
28241 names are also not allowed to contain the sequence `/../'. (However, if the
28242 value of the \-C-\ option is identical to the value of \\CONFIGURE@_FILE\\ in
28243 \(Local/Makefile)\, Exim ignores \-C-\ and proceeds as usual.) There is no
28244 default setting for \ALT@_CONFIG@_PREFIX\.
28246 If the permitted configuration files are confined to a directory to
28247 which only root has access, this guards against someone who has broken
28248 into the Exim account from running a privileged Exim with an arbitrary
28249 configuration file, and using it to break into other accounts.
28251 If \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined, root privilege is retained for \-C-\
28252 and \-D-\ only if the caller of Exim is root. Without it, the Exim user may
28253 also use \-C-\ and \-D-\ and retain privilege. Setting this option locks out
28254 the possibility of testing a configuration using \-C-\ right through message
28255 reception and delivery, even if the caller is root. The reception works, but by
28256 that time, Exim is running as the Exim user, so when it re-execs to regain
28257 privilege for the delivery, the use of \-C-\ causes privilege to be lost.
28258 However, root can test reception and delivery using two separate commands.
28259 \\ALT@_CONFIG@_ROOT@_ONLY\\ is not set by default.
28261 If \\DISABLE@_D@_OPTION\\ is defined, the use of the \-D-\ command line option
28264 \\FIXED@_NEVER@_USERS\\ can be set to a colon-separated list of users that are
28265 never to be used for any deliveries. This is like the \never@_users\ runtime
28266 option, but it cannot be overridden; the runtime option adds additional users
28267 to the list. The default setting is `root'; this prevents a non-root user who
28268 is permitted to modify the runtime file from using Exim as a way to get root.
28272 .section Root privilege
28274 .index root privilege
28275 The Exim binary is normally setuid to root, which means that it gains root
28276 privilege (runs as root) when it starts execution. In some special cases (for
28277 example, when the daemon is not in use and there are no local deliveries), it
28278 may be possible to run Exim setuid to some user other than root. This is
28279 discussed in the next section. However, in most installations, root privilege
28280 is required for two things:
28282 To set up a socket connected to the standard SMTP port (25) when initialising
28283 the listening daemon. If Exim is run from \*inetd*\, this privileged action is
28286 To be able to change uid and gid in order to read users' \(.forward)\ files and
28287 perform local deliveries as the receiving user or as specified in the
28290 It is not necessary to be root to do any of the other things Exim does, such as
28291 receiving messages and delivering them externally over SMTP, and it is
28292 obviously more secure if Exim does not run as root except when necessary.
28293 For this reason, a user and group for Exim to use must be defined in
28294 \(Local/Makefile)\. These are known as `the Exim user' and `the Exim group'.
28295 Their values can be changed by the run time configuration, though this is not
28296 recommended. Often a user called \*exim*\ is used, but some sites use \*mail*\
28297 or another user name altogether.
28299 Exim uses \*setuid()*\ whenever it gives up root privilege. This is a permanent
28300 abdication; the process cannot regain root afterwards. Prior to release 4.00,
28301 \*seteuid()*\ was used in some circumstances, but this is no longer the case.
28303 After a new Exim process has interpreted its command line options, it changes
28304 uid and gid in the following cases:
28306 .index \-C-\ option
28307 .index \-D-\ option
28308 If the \-C-\ option is used to specify an alternate configuration file, or if
28309 the \-D-\ option is used to define macro values for the configuration, and the
28310 calling process is not running as root or the Exim user, the uid and gid are
28311 changed to those of the calling process.
28312 However, if \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined in \(Local/Makefile)\, only
28313 root callers may use \-C-\ and \-D-\ without losing privilege, and if
28314 \\DISABLE@_D@_OPTION\\ is set, the \-D-\ option may not be used at all.
28316 .index \-be-\ option
28317 .index \-bf-\ option
28318 .index \-bF-\ option
28319 If the expansion test option (\-be-\) or one of the filter testing options
28320 (\-bf-\ or \-bF-\) are used, the uid and gid are changed to those of the
28323 If the process is not a daemon process or a queue runner process or a delivery
28324 process or a process for testing address routing (started with \-bt-\), the uid
28325 and gid are changed to the Exim user and group. This means that Exim always
28326 runs under its own uid and gid when receiving messages. This also applies when
28327 testing address verification
28328 .index \-bv-\ option
28329 .index \-bh-\ option
28330 (the \-bv-\ option) and testing incoming message policy controls (the \-bh-\
28333 For a daemon, queue runner, delivery, or address testing process, the uid
28334 remains as root at this stage, but the gid is changed to the Exim group.
28336 The processes that initially retain root privilege behave as follows:
28338 A daemon process changes the gid to the Exim group and the uid to the Exim user
28339 after setting up one or more listening sockets. The \*initgroups()*\ function
28340 is called, so that if the Exim user is in any additional groups, they will be
28341 used during message reception.
28343 A queue runner process retains root privilege throughout its execution. Its job
28344 is to fork a controlled sequence of delivery processes.
28346 A delivery process retains root privilege throughout most of its execution,
28347 but any actual deliveries (that is, the transports themselves) are run in
28348 subprocesses which always change to a non-root uid and gid. For local
28349 deliveries this is typically the uid and gid of the owner of the mailbox; for
28350 remote deliveries, the Exim uid and gid are used. Once all the delivery
28351 subprocesses have been run, a delivery process changes to the Exim uid and gid
28352 while doing post-delivery tidying up such as updating the retry database and
28353 generating bounce and warning messages.
28355 While the recipient addresses in a message are being routed, the delivery
28356 process runs as root. However, if a user's filter file has to be processed,
28357 this is done in a subprocess that runs under the individual user's uid and
28358 gid. A system filter is run as root unless \system@_filter@_user\ is set.
28360 A process that is testing addresses (the \-bt-\ option) runs as root so that
28361 the routing is done in the same environment as a message delivery.
28365 .section Running Exim without privilege
28366 .index privilege, running without
28367 .index unprivileged running
28368 .index root privilege||running without
28369 Some installations like to run Exim in an unprivileged state for more of its
28370 operation, for added security. Support for this mode of operation is provided
28371 by the global option \deliver@_drop@_privilege\. When this is set, the uid and
28372 gid are changed to the Exim user and group at the start of a delivery process
28373 (and also queue runner and address testing processes). This means that address
28374 routing is no longer run as root, and the deliveries themselves cannot change
28377 Leaving the binary setuid to root, but setting \deliver@_drop@_privilege\ means
28378 that the daemon can still be started in the usual way, and it can respond
28379 correctly to SIGHUP because the re-invocation regains root privilege.
28381 An alternative approach is to make Exim setuid to the Exim user and also setgid
28383 If you do this, the daemon must be started from a root process. (Calling
28384 Exim from a root process makes it behave in the way it does when it is setuid
28385 root.) However, the daemon cannot restart itself after a SIGHUP signal because
28386 it cannot regain privilege.
28388 It is still useful to set \deliver@_drop@_privilege\ in this case, because it
28389 stops Exim from trying to re-invoke itself to do a delivery after a message has
28390 been received. Such a re-invocation is a waste of resources because it has no
28393 If restarting the daemon is not an issue (for example, if \*inetd*\ is being
28394 used instead of a daemon), having the binary setuid to the Exim user seems a
28395 clean approach, but there is one complication:
28397 In this style of operation, Exim is running with the real uid and gid set to
28398 those of the calling process, and the effective uid/gid set to Exim's values.
28399 Ideally, any association with the calling process' uid/gid should be dropped,
28400 that is, the real uid/gid should be reset to the effective values so as to
28401 discard any privileges that the caller may have. While some operating systems
28402 have a function that permits this action for a non-root effective uid, quite a
28403 number of them do not. Because of this lack of standardization, Exim does not
28404 address this problem at this time.
28406 For this reason, the recommended approach for `mostly unprivileged' running is
28407 to keep the Exim binary setuid to root, and to set \deliver@_drop@_privilege\.
28408 This also has the advantage of allowing a daemon to be used in the most
28409 straightforward way.
28411 If you configure Exim not to run delivery processes as root, there are a
28412 number of restrictions on what you can do:
28414 You can deliver only as the Exim user/group. You should explicitly use the
28415 \user\ and \group\ options to override routers or local transports that
28416 normally deliver as the recipient. This makes sure that configurations that
28417 work in this mode function the same way in normal mode. Any implicit or
28418 explicit specification of another user causes an error.
28420 Use of \(.forward)\ files is severely restricted, such that it is usually
28421 not worthwhile to include them in the configuration.
28423 Users who wish to use \(.forward)\ would have to make their home directory and
28424 the file itself accessible to the Exim user. Pipe and append-to-file entries,
28425 and their equivalents in Exim filters, cannot be used. While they could be
28426 enabled in the Exim user's name, that would be insecure and not very useful.
28428 Unless the local user mailboxes are all owned by the Exim user (possible in
28429 some POP3 or IMAP-only environments):
28431 They must be owned by the Exim group and be writable by that group. This
28432 implies you must set \mode\ in the appendfile configuration, as well as the
28433 mode of the mailbox files themselves.
28435 You must set \no@_check@_owner\, since most or all of the files will not be
28436 owned by the Exim user.
28438 You must set \file@_must@_exist\, because Exim cannot set the owner correctly
28439 on a newly created mailbox when unprivileged. This also implies that new
28440 mailboxes need to be created manually.
28443 These restrictions severely restrict what can be done in local deliveries.
28444 However, there are no restrictions on remote deliveries. If you are running a
28445 gateway host that does no local deliveries, setting \deliver@_drop@_privilege\
28446 gives more security at essentially no cost.
28449 .section Delivering to local files
28450 Full details of the checks applied by \%appendfile%\ before it writes to a file
28451 are given in chapter ~~CHAPappendfile.
28454 .section IPv4 source routing
28455 .index source routing||in IP packets
28456 .index IP source routing
28457 Many operating systems suppress IP source-routed packets in the kernel, but
28458 some cannot be made to do this, so Exim does its own check. It logs incoming
28459 IPv4 source-routed TCP calls, and then drops them. Things are all different in
28460 IPv6. No special checking is currently done.
28463 .section The VRFY, EXPN, and ETRN commands in SMTP
28464 Support for these SMTP commands is disabled by default. If required, they can
28465 be enabled by defining suitable ACLs.
28469 .section Privileged users
28470 .index trusted user
28472 .index privileged user
28473 .index user||trusted
28475 Exim recognises two sets of users with special privileges. Trusted users are
28476 able to submit new messages to Exim locally, but supply their own sender
28477 addresses and information about a sending host. For other users submitting
28478 local messages, Exim sets up the sender address from the uid, and doesn't
28479 permit a remote host to be specified.
28481 .index \-f-\ option
28482 However, an untrusted user is permitted to use the \-f-\ command line option in
28483 the special form \-f @<@>-\ to indicate that a delivery failure for the message
28484 should not cause an error report. This affects the message's envelope, but it
28485 does not affect the ::Sender:: header. Untrusted users may also be permitted to
28486 use specific forms of address with the \-f-\ option by setting the
28487 \untrusted@_set@_sender\ option.
28489 Trusted users are used to run processes that receive mail messages from some
28490 other mail domain and pass them on to Exim for delivery either locally, or over
28491 the Internet. Exim trusts a caller that is running as root, as the Exim user,
28492 as any user listed in the \trusted@_users\ configuration option, or under any
28493 group listed in the \trusted@_groups\ option.
28495 Admin users are permitted to do things to the messages on Exim's queue. They
28496 can freeze or thaw messages, cause them to be returned to their senders, remove
28497 them entirely, or modify them in various ways. In addition, admin users can run
28498 the Exim monitor and see all the information it is capable of providing, which
28499 includes the contents of files on the spool.
28501 .index \-M-\ option
28502 .index \-q-\ option
28503 By default, the use of the \-M-\ and \-q-\ options to cause Exim to attempt
28504 delivery of messages on its queue is restricted to admin users. This
28505 restriction can be relaxed by setting the \no@_prod@_requires@_admin\ option.
28506 Similarly, the use of \-bp-\ (and its variants) to list the contents of the
28507 queue is also restricted to admin users. This restriction can be relaxed by
28508 setting \no@_queue@_list@_requires@_admin\.
28510 Exim recognises an admin user if the calling process is running as root or as
28511 the Exim user or if any of the groups associated with the calling process is
28512 the Exim group. It is not necessary actually to be running under the Exim
28513 group. However, if admin users who are not root or the Exim user are to access
28514 the contents of files on the spool via the Exim monitor (which runs
28515 unprivileged), Exim must be built to allow group read access to its spool
28519 .section Spool files
28520 .index spool directory||files
28521 Exim's spool directory and everything it contains is owned by the Exim user and
28522 set to the Exim group. The mode for spool files is defined in the
28523 \(Local/Makefile)\ configuration file, and defaults to 0640. This means that
28524 any user who is a member of the Exim group can access these files.
28527 .section Use of argv[0]
28528 Exim examines the last component of \argv[0]\, and if it matches one of a set
28529 of specific strings, Exim assumes certain options. For example, calling Exim
28530 with the last component of \argv[0]\ set to `rsmtp' is exactly equivalent to
28531 calling it with the option \-bS-\. There are no security implications in this.
28534 .section Use of %f formatting
28535 The only use made of `%f' by Exim is in formatting load average values. These
28536 are actually stored in integer variables as 1000 times the load average.
28537 Consequently, their range is limited and so therefore is the length of the
28541 .section Embedded Exim path
28542 Exim uses its own path name, which is embedded in the code, only when it needs
28543 to re-exec in order to regain root privilege. Therefore, it is not root when it
28544 does so. If some bug allowed the path to get overwritten, it would lead to an
28545 arbitrary program's being run as exim, not as root.
28548 .section Use of sprintf()
28549 .index \*sprintf()*\
28550 A large number of occurrences of `sprintf' in the code are actually calls to
28551 \*string@_sprintf()*\, a function that returns the result in malloc'd store.
28552 The intermediate formatting is done into a large fixed buffer by a function
28553 that runs through the format string itself, and checks the length of each
28554 conversion before performing it, thus preventing buffer overruns.
28556 The remaining uses of \*sprintf()*\ happen in controlled circumstances where
28557 the output buffer is known to be sufficiently long to contain the converted
28561 .section Use of debug@_printf() and log@_write()
28562 Arbitrary strings are passed to both these functions, but they do their
28563 formatting by calling the function \*string@_vformat()*\, which runs through
28564 the format string itself, and checks the length of each conversion.
28567 .section Use of strcat() and strcpy()
28568 These are used only in cases where the output buffer is known to be large
28569 enough to hold the result.
28578 . ============================================================================
28579 .chapter Format of spool files
28580 .set runningfoot "spool file format"
28581 .rset CHAPspool ~~chapter
28582 .index format||spool files
28583 .index spool directory||format of files
28584 .index spool||files, format of
28585 .index spool||files, editing
28586 A message on Exim's queue consists of two files, whose names are the message id
28587 followed by -D and -H, respectively. The data portion of the message is kept in
28588 the -D file on its own. The message's envelope, status, and headers are all
28589 kept in the -H file, whose format is described in this chapter. Each of these
28590 two files contains the final component of its own name as its first line. This
28591 is insurance against disk crashes where the directory is lost but the files
28592 themselves are recoverable.
28594 Some people are tempted into editing -D files in order to modify messages. You
28595 need to be extremely careful if you do this; it is not recommended and you are
28596 on your own if you do it. Here are some of the pitfalls:
28598 You must use the \*exim@_lock*\ utility to ensure that Exim does not try to
28599 deliver the message while you are fiddling with it. The lock is implemented
28600 by opening the -D file and taking out a write lock on it. If you update the
28601 file in place, the lock will be retained. If you write a new file and rename
28602 it, the lock will be lost at the instant of rename.
28604 If you change the number of lines in the file, the value of
28605 \$body@_linecount$\, which is stored in the -H file, will be incorrect.
28607 If the message is in MIME format, you must take care not to break it.
28609 If the message is cryptographically signed, any change will invalidate the
28613 Files whose names end with -J may also be seen in the \(input)\ directory (or
28614 its subdirectories when \split@_spool@_directory\ is set). These are journal
28615 files, used to record addresses to which the message has been delivered during
28616 the course of a delivery run. At the end of the run, the -H file is updated,
28617 and the -J file is deleted.
28619 .section Format of the -H file
28620 .index uid (user id)||in spool file
28621 .index gid (group id)||in spool file
28622 The second line of the -H file contains the login name for the uid of the
28623 process that called Exim to read the message, followed by the numerical uid and
28624 gid. For a locally generated message, this is normally the user who sent the
28625 message. For a message received over TCP/IP, it is normally the Exim user.
28627 The third line of the file contains the address of the message's sender as
28628 transmitted in the envelope, contained in angle brackets. The sender address is
28629 empty for bounce messages. For incoming SMTP mail, the sender address is given
28630 in the \\MAIL\\ command. For locally generated mail, the sender address is
28631 created by Exim from the login name of the current user and the configured
28632 \qualify@_domain\. However, this can be overridden by the \-f-\ option or a
28633 leading `From' line if the caller is trusted, or if the supplied address is
28634 `@<@>' or an address that matches \untrusted@_set@_senders\.
28636 The fourth line contains two numbers. The first is the time that the message
28637 was received, in the conventional Unix form -- the number of seconds since the
28638 start of the epoch. The second number is a count of the number of messages
28639 warning of delayed delivery that have been sent to the sender.
28641 There follow a number of lines starting with a hyphen. These can appear in any
28642 order, and are omitted when not relevant:
28644 \-acl <<number>> <<length>>-\: A line of this form is present for every ACL
28645 variable that is not empty. The number identifies the variable; the
28646 \acl@_c\*x*\$$\ variables are numbered 0--9 and the \acl@_m\*x*\$$\ variables
28647 are numbered 10--19. The length is the length of the data string for the
28648 variable. The string itself starts at the beginning of the next line, and is
28649 followed by a newline character. It may contain internal newlines.
28651 \-allow@_unqualified@_recipient-\: This is present if unqualified recipient
28652 addresses are permitted in header lines (to stop such addresses from being
28653 qualified if rewriting occurs at transport time). Local messages that were
28654 input using \-bnq-\ and remote messages from hosts that match
28655 \recipient@_unqualified@_hosts\ set this flag.
28657 \-allow@_unqualified@_sender-\: This is present if unqualified sender
28658 addresses are permitted in header lines (to stop such addresses from being
28659 qualified if rewriting occurs at transport time). Local messages that were
28660 input using \-bnq-\ and remote messages from hosts that match
28661 \sender@_unqualified@_hosts\ set this flag.
28663 \-auth@_id <<text>>-\: The id information for a message received on an
28664 authenticated SMTP connection -- the value of the \$authenticated@_id$\
28667 \-auth@_sender <<address>>-\: The address of an authenticated sender -- the
28668 value of the \$authenticated@_sender$\ variable.
28670 \-body@_linecount <<number>>-\: This records the number of lines in the body of
28671 the message, and is always present.
28673 \-deliver@_firsttime-\: This is written when a new message is first added to
28674 the spool. When the spool file is updated after a deferral, it is omitted.
28676 .index frozen messages||spool data
28677 \-frozen <<time>>-\: The message is frozen, and the freezing happened at
28680 \-helo@_name <<text>>-\: This records the host name as specified by a remote
28681 host in a \\HELO\\ or \\EHLO\\ command.
28683 \-host@_address <<address>>.<<port>>-\: This records the IP address of the host
28684 from which the message was received and the remote port number that was used.
28685 It is omitted for locally generated messages.
28687 \-host@_auth <<text>>-\: If the message was received on an authenticated SMTP
28688 connection, this records the name of the authenticator -- the value of the
28689 \$sender@_host@_authenticated$\ variable.
28691 \-host@_lookup@_failed-\: This is present if an attempt to look up the sending
28692 host's name from its IP address failed. It corresponds to the
28693 \$host@_lookup@_failed$\ variable.
28695 .index DNS||reverse lookup
28696 .index reverse DNS lookup
28697 \-host@_name <<text>>-\: This records the name of the remote host from which
28698 the message was received, if the host name was looked up from the IP address
28699 when the message was being received. It is not present if no reverse lookup was
28702 \-ident <<text>>-\: For locally submitted messages, this records the login of
28703 the originating user, unless it was a trusted user and the \-oMt-\ option was
28704 used to specify an ident value. For messages received over TCP/IP, this records
28705 the ident string supplied by the remote host, if any.
28707 \-interface@_address <<address>>.<<port>>-\: This records the IP address of the
28708 local interface and the port number through which a message was received from a
28709 remote host. It is omitted for locally generated messages.
28711 \-local-\: The message is from a local sender.
28713 \-localerror-\: The message is a locally-generated bounce message.
28715 \-local@_scan <<string>>-\: This records the data string that was
28716 returned by the \*local@_scan()*\ function when the message was received -- the
28717 value of the \$local@_scan@_data$\ variable. It is omitted if no data was
28720 \-manual@_thaw-\: The message was frozen but has been thawed manually, that is,
28721 by an explicit Exim command rather than via the auto-thaw process.
28723 \-N-\: A testing delivery process was started using the \-N-\ option to
28724 suppress any actual deliveries, but delivery was deferred. At any further
28725 delivery attempts, \-N-\ is assumed.
28727 \-received@_protocol-\: This records the value of the \$received@_protocol$\
28728 variable, which contains the name of the protocol by which the message was
28731 \-sender@_set@_untrusted-\: The envelope sender of this message was set by an
28732 untrusted local caller (used to ensure that the caller is displayed in queue
28735 \-tls@_certificate@_verified-\: A TLS certificate was received from the client
28736 that sent this message, and the certificate was verified by the server.
28738 \-tls@_cipher <<cipher name>>-\: When the message was received over an
28739 encrypted connection, this records the name of the cipher suite that was used.
28741 \-tls@_peerdn <<peer DN>>-\: When the message was received over an encrypted
28742 connection, and a certificate was received from the client, this records the
28743 Distinguished Name from that certificate.
28746 Following the options there is a list of those addresses to which the message
28747 is not to be delivered. This set of addresses is initialized from the command
28748 line when the \-t-\ option is used and \extract__addresses__remove__arguments\
28749 is set; otherwise it starts out empty. Whenever a successful delivery is made,
28750 the address is added to this set. The addresses are kept internally as a
28751 balanced binary tree, and it is a representation of that tree which is written
28752 to the spool file. If an address is expanded via an alias or forward file, the
28753 original address is added to the tree when deliveries to all its child
28754 addresses are complete.
28756 If the tree is empty, there is a single line in the spool file containing just
28757 the text `XX'. Otherwise, each line consists of two letters, which are either Y
28758 or N, followed by an address. The address is the value for the node of the
28759 tree, and the letters indicate whether the node has a left branch and/or a
28760 right branch attached to it, respectively. If branches exist, they immediately
28761 follow. Here is an example of a three-node tree:
28763 YY darcy@austen.fict.example
28764 NN alice@wonderland.fict.example
28765 NN editor@thesaurus.ref.example
28767 After the non-recipients tree, there is a list of the message's recipients.
28768 This is a simple list, preceded by a count. It includes all the original
28769 recipients of the message, including those to whom the message has already been
28770 delivered. In the simplest case, the list contains one address per line. For
28774 editor@thesaurus.ref.example
28775 darcy@austen.fict.example
28777 alice@wonderland.fict.example
28779 However, when a child address has been added to the top-level addresses as a
28780 result of the use of the \one@_time\ option on a \%redirect%\ router, each line
28781 is of the following form:
28783 <<top-level address>> <<errors@_to address>> <<length>>,<<parent number>>@#<<flag bits>>
28785 The 01 flag bit indicates the presence of the three other fields that follow
28786 the top-level address. Other bits may be used in future to support additional
28787 fields. The <<parent number>> is the offset in the recipients list of the
28788 original parent of the `one time' address. The first two fields are the
28789 envelope sender that is associated with this address and its length. If the
28790 length is zero, there is no special envelope sender (there are then two space
28791 characters in the line). A non-empty field can arise from a \%redirect%\ router
28792 that has an \errors@_to\ setting.
28795 A blank line separates the envelope and status information from the headers
28796 which follow. A header may occupy several lines of the file, and to save effort
28797 when reading it in, each header is preceded by a number and an identifying
28798 character. The number is the number of characters in the header, including any
28799 embedded newlines and the terminating newline. The character is one of the
28803 <<blank>> $t $rm{header in which Exim has no special interest}
28804 #B $t $rm{::Bcc:: header}
28805 #C $t $rm{::Cc:: header}
28806 #F $t $rm{::From:: header}
28807 #I $t $rm{::Message-id:: header}
28808 #P $t $rm{::Received:: header -- P for `postmark'}
28809 #R $t $rm{::Reply-To:: header}
28810 #S $t $rm{::Sender:: header}
28811 #T $t $rm{::To:: header}
28812 #* $t $rm{replaced or deleted header}
28814 Deleted or replaced (rewritten) headers remain in the spool file for debugging
28815 purposes. They are not transmitted when the message is delivered. Here is a
28816 typical set of headers:
28818 111P Received: by hobbit.fict.example with local (Exim 4.00)
28819 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
28820 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
28821 038* X-rewrote-sender: bb@hobbit.fict.example
28822 042* From: Bilbo Baggins <bb@hobbit.fict.example>
28823 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
28824 099* To: alice@wonderland.fict.example, rdo@foundation,
28825 darcy@austen.fict.example, editor@thesaurus.ref.example
28826 109T To: alice@wonderland.fict.example, rdo@foundation.fict.example,
28827 darcy@austen.fict.example, editor@thesaurus.ref.example
28828 038 Date: Fri, 11 May 2001 10:28:59 +0100
28830 The asterisked headers indicate that the envelope sender, ::From:: header, and
28831 ::To:: header have been rewritten, the last one because routing expanded the
28832 unqualified domain \*foundation*\.
28838 . ============================================================================
28839 .chapter Adding new drivers or lookup types
28840 .set runningfoot "adding drivers"
28841 .index adding drivers
28842 .index new drivers, adding
28843 .index drivers||adding new
28844 The following actions have to be taken in order to add a new router, transport,
28845 authenticator, or lookup type to Exim:
28847 Choose a name for the driver or lookup type that does not conflict with any
28848 existing name; I will use `newdriver' in what follows.
28850 Add to \(src/EDITME)\ the line
28852 <<type>>@_NEWDRIVER=yes
28854 where <<type>> is \\ROUTER\\, \\TRANSPORT\\, \\AUTH\\, or \\LOOKUP\\. If the
28855 code is not to be included in the binary by default, comment this line out. You
28856 should also add any relevant comments about the driver or lookup type.
28858 Add to \(src/config.h.defaults)\ the line
28860 @#define <<type>>@_NEWDRIVER
28863 Edit \(src/drtables.c)\, adding conditional code to pull in the private header
28864 and create a table entry as is done for all the other drivers and lookup types.
28866 Edit \(Makefile)\ in the appropriate sub-directory (\(src/routers)\,
28867 \(src/transports)\, \(src/auths)\, or \(src/lookups)\); add a line for the new
28868 driver or lookup type and add it to the definition of OBJ.
28870 Create \(newdriver.h)\ and \(newdriver.c)\ in the appropriate sub-directory of
28873 Edit \(scripts/MakeLinks)\ and add commands to link the \(.h)\ and \(.c)\ files
28874 as for other drivers and lookups.
28876 Then all you need to do is write the code! A good way to start is to make a
28877 proforma by copying an existing module of the same type, globally changing all
28878 occurrences of the name, and cutting out most of the code. Note that any
28879 options you create must be listed in alphabetical order, because the tables are
28880 searched using a binary chop procedure.
28882 There is a \(README)\ file in each of the sub-directories of \(src)\ describing
28883 the interface that is expected.
28889 . ============================================================================
28890 . Fudge for the index page number. We want it to be on a right-hand page.
28892 .set indexpage ~~sys.pagenumber + 1
28893 .if even ~~indexpage
28894 .set indexpage ~~indexpage + 1
28897 .%index Index$e~~indexpage--
28901 . End of Exim specification
git://git.exim.org / exim.git / blob