1 . $Cambridge: exim/doc/doc-src/spec.src,v 1.9 2008/01/16 09:51:00 tom Exp $
4 .set previousversion "4.40"
5 .set versionmonth "February"
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
24 .bindfont 51 "atl/Times-Bold" 9
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
142 .set confsection "~~1"
159 .macro conf "option" "type" "default" "6"
161 .if ~~sys.leftonpage < ~~4ld
164 .testunderscore "~~1"
170 .if "~~confsection" == ""
173 .set inssect "$rm{Use:} $it{~~confsection}###"
176 \**~~1**\ $c ~~inssect$rm{Type:} $it{~~2} $e $rm{Default:} $it{~~3}
182 .set displayindent 2em
184 .index @$1, @$2, etc. $it{see numerical variables}
185 .index address||rewriting $it{see rewriting}
186 .index CR character $it{see carriage return}
187 .index CRL $it{see certificate revocation list}
188 .index delivery||failure report $it{see bounce message}
189 .index dialup $it{see intermittently connected hosts}
190 .index exiscan $it{see content scanning}
191 .index failover $it{see fallback}
192 .index fallover $it{see fallback}
193 .index filter||Sieve $it{see Sieve filter}
194 .index ident $it{see RFC 1413}
195 .index LF character $it{see linefeed}
196 .index maximum $it{see limit}
197 .index NUL $it{see binary zero}
198 .index passwd file $it{see \(/etc/passwd)\}
199 .index process id $it{see pid}
200 .index RBL $it{see DNS list}
201 .index redirection $it{see address redirection}
202 .index return path||$it{see also envelope sender}
203 .index scanning $it{see content scanning}
204 .index SSL $it{see TLS}
205 .index string||expansion $it{see expansion}
206 .index top bit $it{see 8-bit characters}
207 .index variables $it{see expansion, variables}
208 .index zero, binary $it{see binary zero}
210 . This is used for the printed index. See setting above for
211 . the HTML index value.
213 .set ACL "access control lists (ACLs)"
215 . ======================================================
222 $chead{University of Cambridge Computing Service}
224 $chead{Specification of the Exim Mail Transfer Agent}
229 .space ~~sys.leftonpage - 15*~~sys.linedepth
231 University Computing Service
238 $it{phone:} $t +44 1223 334600
239 $it{fax:} $t +44 1223 334679
240 $it{email:} $t ph10 $it{at} cus.cam.ac.uk
242 Edition for Exim ~~version, ~~versionmonth ~~versionyear
247 $c$rm{Copyright (c) University of Cambridge ~~versionyear}
258 . Blank verso for title page
263 . Set up for actual text pages
265 . The first one to prevent a warning from sgfr
266 . set runningfoot "~~chapter"
272 .if "~~runningfoot" == ""
275 .set rhs "~~runningfoot (~~chapter)"
277 .set lhs "Exim ~~version"
278 .linelength ~~newlinelength
279 $it{~~lhs}$c[~~sys.pagenumber]$e$it{~~rhs}
290 . ============================================================================
291 .chapter Introduction
292 .set runningfoot "introduction"
295 $c$bi{If I have seen further it is by standing on the shoulders of giants.}##(Isaac Newton)
297 $c"If I have seen further it is by standing on the shoulders of giants."
301 \*If I have seen further it is by standing on the shoulders of giants.*\
306 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
307 Unix-like operating systems. It was designed on the assumption that it would be
308 run on hosts that are permanently connected to the Internet. However, it can be
309 used on intermittently connected hosts with suitable configuration adjustments.
311 Configuration files currently exist for the following operating systems: AIX,
312 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, FreeBSD, GNU/Hurd, GNU/Linux,
313 HI-OSF (Hitachi), HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD, QNX, SCO, SCO
314 SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4, Tru64-Unix (formerly
315 Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware. Some of these operating
316 systems are no longer current and cannot easily be tested, so the configuration
317 files may no longer work in practice.
319 There are also configuration files for compiling Exim in the Cygwin environment
320 that can be installed on systems running Windows. However, this document does
321 not contain any information about running Exim in the Cygwin environment.
323 The terms and conditions for the use and distribution of Exim are contained in
324 the file \(NOTICE)\. Exim is distributed under the terms of the GNU General
325 Public Licence, a copy of which may be found in the file \(LICENCE)\.
327 The use, supply or promotion of Exim for the purpose of sending bulk,
328 unsolicited electronic mail is incompatible with the basic aims of the program,
329 which revolve around the free provision of a service that enhances the quality
330 of personal communications. The author of Exim regards indiscriminate
331 mass-mailing as an antisocial, irresponsible abuse of the Internet.
333 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
334 experience of running and working on the Smail 3 code, I could never have
335 contemplated starting to write a new MTA. Many of the ideas and user interfaces
336 were originally taken from Smail 3, though the actual code of Exim is entirely
337 new, and has developed far beyond the initial concept.
339 Many people, both in Cambridge and around the world, have contributed to the
340 development and the testing of Exim, and to porting it to various operating
341 systems. I am grateful to them all. The distribution now contains a file called
342 \(ACKNOWLEDGMENTS)\, in which I have started recording the names of
346 .section Exim documentation
349 This edition of the Exim specification applies to version ~~version of Exim.
350 Substantive changes from the ~~previousversion edition are marked by bars in
351 the right-hand margin in the PostScript, PDF, and plain text versions of the
352 document, and by green text in the HTML version, as shown by this paragraph.
353 Changes are not marked in the Texinfo version, because Texinfo doesn't support
354 change bars. Minor corrections and rewordings are not marked.
357 This document is very much a reference manual; it is not a tutorial. The reader
358 is expected to have some familiarity with the SMTP mail transfer protocol and
359 with general Unix system administration. Although there are some discussions
360 and examples in places, the information is mostly organized in a way that makes
361 it easy to look up, rather than in a natural order for sequential reading.
362 Furthermore, the manual aims to cover every aspect of Exim in detail, including
363 a number of rarely-used, special-purpose features that are unlikely to be of
366 .index books about Exim
367 An `easier' discussion of Exim which provides more in-depth explanatory,
368 introductory, and tutorial material can be found in a book entitled
370 [(A HREF="http://www.uit.co.uk/exim-book/")]
371 $it{The Exim SMTP Mail Server},
373 published by UIT Cambridge.
375 $it{The Exim SMTP Mail Server}, published by UIT Cambridge
376 (\?http://www.uit.co.uk/exim-book/?\).
379 This book also contains a chapter that gives a general introduction to SMTP and
380 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
381 with the latest release of Exim. (Note that the earlier book about Exim,
382 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
384 .index \(doc/NewStuff)\
385 .index \(doc/ChangeLog)\
387 As the program develops, there may be features in newer versions that have not
388 yet made it into this document, which is updated only when the most significant
389 digit of the fractional part of the version number changes. Specifications of
390 new features that are not yet in this manual are placed in the file
391 \(doc/NewStuff)\ in the Exim distribution.
394 Some features may be classified as `experimental'. These may change
395 incompatibly while they are developing, or even be withdrawn. For this reason,
396 they are not documented in this manual. Information about experimental features
397 can be found in the file \(doc/experimental.txt)\.
400 All changes to the program (whether new features, bug fixes, or other kinds of
401 change) are noted briefly in the file called \(doc/ChangeLog)\.
403 .index \(doc/spec.txt)\
404 This specification itself is available as an ASCII file in \(doc/spec.txt)\ so
405 that it can easily be searched with a text editor. Other files in the \(doc)\
409 \(OptionLists.txt)\ $t $rm{list of all options in alphabetical order}
410 \(dbm.discuss.txt)\ $t $rm{discussion about DBM libraries}
411 \(exim.8)\ $t $rm{a man page of Exim's command line options}
414 \(experimental.txt)\ $t $rm{documentation of experimental features}
417 \(filter.txt)\ $t $rm{specification of the filter language}
418 \(pcrepattern.txt)\ $t $rm{specification of PCRE regular expressions}
419 \(pcretest.txt)\ $t $rm{specification of the PCRE testing program}
420 \(Exim3.upgrade)\ $t $rm{upgrade notes from release 2 to release 3}
421 \(Exim4.upgrade)\ $t $rm{upgrade notes from release 3 to release 4}
423 The main specification and the specification of the filtering language are also
424 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
425 ~~SECTavail below tells you how to get hold of these.
428 .section FTP and web sites
432 The primary distribution site for Exim is currently the University of
433 Cambridge's FTP site, whose contents are described in \*Where to find the Exim
434 distribution*\ below. In addition, there is a
436 [(A HREF="http://www.exim.org/")]
444 [(A HREF="ftp://ftp.exim.org/")]
450 at \exim.org\. These are now also hosted at the University of Cambridge.
451 The \exim.org\ site was previously hosted for a number of years by Energis
452 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
454 As well as Exim distribution tar files, the Exim web site contains a number of
455 differently formatted versions of the documentation, including the
458 [(A HREF="FAQ.html")]
464 in both text and HTML formats. The HTML version comes with a keyword-in-context
465 index. A recent addition to the online information is the
468 [(A HREF="http://www.exim.org/eximwiki/")]
472 Exim wiki (\?http://www.exim.org/eximwiki/?\).
474 We hope that this will make it easier for Exim users to contribute examples,
475 tips, and know-how for the benefit of others.
478 .section Mailing lists
479 .index mailing lists||for Exim users
481 The following are the three main Exim mailing lists:
484 $it{exim-users@@exim.org} $t general discussion list
485 $it{exim-dev@@exim.org} $t discussion of bugs, enhancements, etc.
486 $it{exim-announce@@exim.org} $t moderated, low volume announcements list
489 You can subscribe to these lists, change your existing subscriptions, and view
490 or search the archives via the
492 [(A HREF="http://www.exim.org/maillist.html")]
498 link on the Exim home page. The $it{exim-users} mailing list is also forwarded
499 to \?http://www.egroups.com/list/exim-users?\, an archiving system with
500 searching capabilities.
502 .section Exim training
503 .index training courses
504 From time to time (approximately annually at the time of writing),
505 lecture-based training courses are run by the author of Exim in Cambridge, UK.
506 Details can be found on the web site
508 [(A HREF="http://www-tus.csx.cam.ac.uk/courses/exim/")]
510 \?http://www-tus@.csx@.cam@.ac.uk/courses/exim/?\.
517 .index reporting bugs
518 Reports of obvious bugs should be emailed to \*bugs@@exim.org*\. However, if
519 you are unsure whether some behaviour is a bug or not, the best thing to do is
520 to post a message to the $it{exim-users} mailing list and have it discussed.
524 .section Where to find the Exim distribution
525 .rset SECTavail "~~chapter.~~section"
527 .index distribution||ftp site
528 The master ftp site for the Exim distribution is
533 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim?\
540 \?ftp://ftp.exim.org/pub/exim?\
542 The file references that follow are relative to the \(exim)\ directories at
545 There are now quite a number of independent mirror sites around the world.
546 Those that I know about are listed in the file called \(Mirrors)\.
548 Within the \(exim)\ directory there are subdirectories called \(exim3)\ (for
549 previous Exim 3 distributions), \(exim4)\ (for the latest Exim 4
550 distributions), and \(Testing)\ for testing versions. In the \(exim4)\
551 subdirectory, the current release can always be found in files called
553 \(exim-$it{n.nn}.tar.gz)\
554 \(exim-$it{n.nn}.tar.bz2)\
556 where $it{n.nn} is the highest such version number in the directory. The two
557 files contain identical data; the only difference is the type of compression.
558 The \(.bz2)\ file is usually a lot smaller than the \(.gz)\ file.
559 .index distribution||signing details
560 .index distribution||public key
561 .index public key for signed distribution
562 The distributions are currently signed with Philip Hazel's GPG key. The
563 corresponding public key is available from a number of keyservers, and there is
564 also a copy in the file \(Public-Key)\. The signatures for the tar bundles are
567 \(exim-$it{n.nn}.tar.gz.sig)\
568 \(exim-$it{n.nn}.tar.bz2.sig)\
570 For each released version, the log of changes is made separately available in a
571 separate file in the directory \(ChangeLogs)\ so that it is possible to
572 find out what has changed without having to download the entire distribution.
574 .index documentation||available formats
575 The main distribution contains ASCII versions of this specification and other
576 documentation; other formats of the documents are available in separate files
577 inside the \(exim4)\ directory of the FTP site:
579 \(exim-html-$it{n.nn}.tar.gz)\
580 \(exim-pdf-$it{n.nn}.tar.gz)\
581 \(exim-postscript-$it{n.nn}.tar.gz)\
582 \(exim-texinfo-$it{n.nn}.tar.gz)\
584 These tar files contain only the \(doc)\ directory, not the complete
585 distribution, and are also available in \(.bz2)\ as well as \(.gz)\ forms.
588 The FAQ is available for downloading in two different formats in these files:
591 \(exim4/FAQ.html.tar.gz)\
593 The first of these is a single ASCII file that can be searched with a text
594 editor. The second is a directory of HTML files, normally accessed by starting
595 at \(index.html)\. The HTML version of the FAQ (which is also included in the
596 HTML documentation tarbundle) includes a keyword-in-context index, which is
597 often the most convenient way of finding your way around.
601 A wish list is maintained, containing ideas for new features that have been
602 submitted. From time to time the file is exported to the ftp site into the file
603 \(exim4/WishList)\. Items are removed from the list if they get implemented.
606 .section Contributed material
607 .index contributed material
608 At the ftp site, there is a directory called \(Contrib)\ that contains
609 miscellaneous files contributed to the Exim community by Exim users. There is
610 also a collection of contributed configuration examples in
611 \(exim4/config.samples.tar.gz)\. These samples are referenced from the FAQ.
615 .index limitations of Exim
617 Exim is designed for use as an Internet MTA, and therefore handles addresses
618 in RFC 2822 domain format only.
619 .index bang paths||not handled by Exim
620 It cannot handle UUCP `bang paths', though simple two-component bang paths can
621 be converted by a straightforward rewriting configuration. This restriction
622 does not prevent Exim from being interfaced to UUCP as a transport mechanism,
623 provided that domain addresses are used.
625 .index domainless addresses
626 .index address||without domain
627 Exim insists that every address it handles has a domain attached. For incoming
628 local messages, domainless addresses are automatically qualified with a
629 configured domain value. Configuration options specify from which remote
630 systems unqualified addresses are acceptable. These are then qualified on
633 .index transport||external
634 .index external transports
635 The only external transport currently implemented is an SMTP transport over a
636 TCP/IP network (using sockets, including support for IPv6). However, a pipe
637 transport is available, and there are facilities for writing messages to files
638 and pipes, optionally in \*batched SMTP*\ format; these facilities can be used
639 to send messages to some other transport mechanism such as UUCP, provided it
640 can handle domain-style addresses. Batched SMTP input is also catered for.
642 Exim is not designed for storing mail for dial-in hosts. When the volumes of
643 such mail are large, it is better to get the messages `delivered' into files
644 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
648 Although Exim does have basic facilities for scanning incoming messages, these
649 are not comprehensive enough to do full virus or spam scanning. Such operations
650 are best carried out using additional specialized software packages. If you
651 compile Exim with the content-scanning extension, straightforward interfaces to
652 a number of common scanners are provided.
658 .section Run time configuration
659 Exim's run time configuration is held in a single text file that is divided
660 into a number of sections. The entries in this file consist of keywords and
661 values, in the style of Smail 3 configuration files. A default configuration
662 file which is suitable for simple online installations is provided in the
663 distribution, and is described in chapter ~~CHAPdefconfil below.
666 .section Calling interface
667 .index Sendmail compatibility||command line interface
668 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
669 can be a straight replacement for \(/usr/lib/sendmail)\ or
670 \(/usr/sbin/sendmail)\ when sending mail, but you do not need to know anything
671 about Sendmail in order to run Exim. For actions other than sending messages,
672 Sendmail-compatible options also exist, but those that produce output (for
673 example, \-bp-\, which lists the messages on the queue) do so in Exim's own
674 format. There are also some additional options that are compatible with Smail
675 3, and some further options that are new to Exim. Chapter ~~CHAPcommandline
676 documents all Exim's command line options. This information is automatically
677 made into the man page that forms part of the Exim distribution.
679 Control of messages on the queue can be done via certain privileged command
680 line options. There is also an optional monitor program called \*eximon*\, which
681 displays current information in an X window, and which contains a menu
682 interface to Exim's command line administration options.
686 .index terminology definitions
687 .index body of message||definition of
688 The \*body*\ of a message is the actual data that the sender wants to transmit.
689 It is the last part of a message, and is separated from the \*header*\ (see
690 below) by a blank line.
692 .index bounce message||definition of
693 When a message cannot be delivered, it is normally returned to the sender in a
694 delivery failure message or a `non-delivery report' (NDR). The term \*bounce*\
695 is commonly used for this action, and the error reports are often called
696 \*bounce messages*\. This is a convenient shorthand for `delivery failure error
697 report'. Such messages have an empty sender address in the message's
698 \*envelope*\ (see below) to ensure that they cannot themselves give rise to
699 further bounce messages.
701 The term \*default*\ appears frequently in this manual. It is used to qualify a
702 value which is used in the absence of any setting in the configuration. It may
703 also qualify an action which is taken unless a configuration setting specifies
706 The term \*defer*\ is used when the delivery of a message to a specific
707 destination cannot immediately take place for some reason (a remote host may be
708 down, or a user's local mailbox may be full). Such deliveries are \*deferred*\
711 The word \*domain*\ is sometimes used to mean all but the first component of a
712 host's name. It is $it{not} used in that sense here, where it normally
713 refers to the part of an email address following the @@ sign.
715 .index envelope, definition of
716 .index sender||definition of
717 A message in transit has an associated \*envelope*\, as well as a header and a
718 body. The envelope contains a sender address (to which bounce messages should
719 be delivered), and any number of recipient addresses. References to the
720 sender or the recipients of a message usually mean the addresses in the
721 envelope. An MTA uses these addresses for delivery, and for returning bounce
722 messages, not the addresses that appear in the header lines.
724 .index message||header, definition of
725 .index header section||definition of
726 The \*header*\ of a message is the first part of a message's text, consisting
727 of a number of lines, each of which has a name such as ::From::, ::To::,
728 ::Subject::, etc. Long header lines can be split over several text lines by
729 indenting the continuations. The header is separated from the body by a blank
732 .index local part||definition of
733 .index domain||definition of
734 The term \*local part*\, which is taken from RFC 2822, is used to refer to that
735 part of an email address that precedes the @@ sign. The part that follows the
736 @@ sign is called the \*domain*\ or \*mail domain*\.
738 .index local delivery||definition of
739 .index remote delivery, definition of
740 The terms \*local delivery*\ and \*remote delivery*\ are used to distinguish
741 delivery to a file or a pipe on the local host from delivery by SMTP over
742 TCP/IP to a remote host.
744 .index return path||definition of
745 \*Return path*\ is another name that is used for the sender address in a
748 .index queue||definition of
749 The term \*queue*\ is used to refer to the set of messages awaiting delivery,
750 because this term is in widespread use in the context of MTAs. However, in
751 Exim's case the reality is more like a pool than a queue, because there is
752 normally no ordering of waiting messages.
754 .index queue runner||definition of
755 The term \*queue runner*\ is used to describe a process that scans the queue
756 and attempts to deliver those messages whose retry times have come. This term
757 is used by other MTAs, and also relates to the command \runq\, but in Exim
758 the waiting messages are normally processed in an unpredictable order.
760 .index spool directory||definition of
761 The term \*spool directory*\ is used for a directory in which Exim keeps the
762 messages on its queue -- that is, those that it is in the process of
763 delivering. This should not be confused with the directory in which local
764 mailboxes are stored, which is called a `spool directory' by some people. In
765 the Exim documentation, `spool' is always used in the first sense.
773 . ============================================================================
774 .chapter Incorporated code
775 .set runningfoot "incorporated code"
776 .index incorporated code
777 .index regular expressions||library
779 A number of pieces of external code are included in the Exim distribution.
781 Regular expressions are supported in the main Exim program and in the Exim
782 monitor using the freely-distributable PCRE library, copyright (c) University
783 of Cambridge. The source is distributed in the directory \(src/pcre)\. However,
784 this is a cut-down version of PCRE. If you want to use the PCRE library in
785 other programs, you should obtain and install the full version from
786 \?ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre?\.
790 .index cdb||acknowledgement
791 Support for the cdb (Constant DataBase) lookup method is provided by code
792 contributed by Nigel Metheringham of (at the time he contributed it) Planet
793 Online Ltd. which contains the following statements:
800 Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd
802 This program is free software; you can redistribute it and/or modify it under
803 the terms of the GNU General Public License as published by the Free Software
804 Foundation; either version 2 of the License, or (at your option) any later
807 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
808 the spec and sample code for cdb can be obtained from
809 \?http://www.pobox.com/@~djb/cdb.html?\. This implementation borrows some code
810 from Dan Bernstein's implementation (which has no license restrictions applied
815 The implementation is completely contained within the code of Exim.
816 It does not link against an external cdb library.
819 .index SPA authentication
821 .index Microsoft Secure Password Authentication
822 Client support for Microsoft's \*Secure Password Authentication*\ is provided
823 by code contributed by Marc Prud'hommeaux. Server support was contributed by
824 Tom Kistner. This includes code taken from the Samba project, which is released
830 .index \*pwcheck*\ daemon
831 .index \*pwauthd*\ daemon
832 Support for calling the Cyrus \*pwcheck*\ and \*saslauthd*\ daemons is provided
833 by code taken from the Cyrus-SASL library and adapted by Alexander S.
834 Sabourenkov. The permission notice appears below, in accordance with the
835 conditions expressed therein.
843 Copyright (c) 2001 Carnegie Mellon University. All rights reserved.
845 Redistribution and use in source and binary forms, with or without
846 modification, are permitted provided that the following conditions
850 .cancelflag $npbracket
851 .flag $npbracket "" "."
854 Redistributions of source code must retain the above copyright
855 notice, this list of conditions and the following disclaimer.
857 Redistributions in binary form must reproduce the above copyright
858 notice, this list of conditions and the following disclaimer in
859 the documentation and/or other materials provided with the
862 The name `Carnegie Mellon University' must not be used to
863 endorse or promote products derived from this software without
864 prior written permission. For permission or any other legal
865 details, please contact
867 Office of Technology Transfer
868 Carnegie Mellon University
870 Pittsburgh, PA 15213-3890
871 (412) 268-4387, fax: (412) 268-7395
872 tech-transfer@@andrew.cmu.edu
875 Redistributions of any form whatsoever must retain the following
879 .indent ~~sys.indent + 3em
881 $it{This product includes software developed by Computing Services
882 at Carnegie Mellon University (\?http://www.cmu.edu/computing/?\).}
887 .cancelflag $npbracket
888 .flag $npbracket "(" ")"
891 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
892 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
893 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
894 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
895 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
896 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
897 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
907 The Exim Monitor program, which is an X-Window application, includes
908 modified versions of the Athena StripChart and TextPop widgets.
909 This code is copyright by DEC and MIT, and their permission notice appears
910 below, in accordance with the conditions expressed therein.
918 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
919 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
921 $c All Rights Reserved
923 Permission to use, copy, modify, and distribute this software and its
924 documentation for any purpose and without fee is hereby granted,
925 provided that the above copyright notice appear in all copies and that
926 both that copyright notice and this permission notice appear in
927 supporting documentation, and that the names of Digital or MIT not be
928 used in advertising or publicity pertaining to distribution of the
929 software without specific, written prior permission.
931 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
932 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
933 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
934 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
935 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
936 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
944 Many people have contributed code fragments, some large, some small, that were
945 not covered by any specific licence requirements. It is assumed that the
946 contributors are happy to see their code incoporated into Exim under the GPL.
956 . ============================================================================
957 .chapter How Exim receives and delivers mail
958 .set runningfoot "receiving & delivering mail"
960 .section Overall philosophy
961 .index design philosophy
962 Exim is designed to work efficiently on systems that are permanently connected
963 to the Internet and are handling a general mix of mail. In such circumstances,
964 most messages can be delivered immediately. Consequently, Exim does not
965 maintain independent queues of messages for specific domains or hosts, though
966 it does try to send several messages in a single SMTP connection after a host
967 has been down, and it also maintains per-host retry information.
970 .section Policy control
971 .index policy control||overview
972 Policy controls are now an important feature of MTAs that are connected to the
973 Internet. Perhaps their most important job is to stop MTAs being abused as
974 `open relays' by misguided individuals who send out vast amounts of unsolicited
975 junk, and want to disguise its source. Exim provides flexible facilities for
976 specifying policy controls on incoming mail:
978 .index ~~ACL||introduction
979 Exim 4 (unlike previous versions of Exim) implements policy controls on
980 incoming mail by means of \*Access Control Lists*\ (ACLs). Each list is a
981 series of statements that may either grant or deny access. ACLs can be used at
982 several places in the SMTP dialogue while receiving a message from a remote
983 host. However, the most common places are after each \\RCPT\\ command, and at
984 the very end of the message. The sysadmin can specify conditions for accepting
985 or rejecting individual recipients or the entire message, respectively, at
986 these two points (see chapter ~~CHAPACL). Denial of access results in an SMTP
989 An ACL is also available for locally generated, non-SMTP messages. In this
990 case, the only available actions are to accept or deny the entire message.
993 When Exim is compiled with the content-scanning extension, facilities are
994 provided in the ACL mechanism for passing the message to external virus and/or
995 spam scanning software. The result of such a scan is passed back to the ACL,
996 which can then use it to decide what to do with the message.
999 When a message has been received, either from a remote host or from the local
1000 host, but before the final acknowledgement has been sent, a locally supplied C
1001 function called \*local@_scan()*\ can be run to inspect the message and decide
1002 whether to accept it or not (see chapter ~~CHAPlocalscan). If the message is
1003 accepted, the list of recipients can be modified by the function.
1006 Using the \*local@_scan()*\ mechanism is another way of calling external
1007 scanner software. The \SA-Exim\ add-on package works this way. It does not
1008 require Exim to be compiled with the content-scanning extension.
1011 After a message has been accepted, a further checking mechanism is available in
1012 the form of the $it{system filter} (see chapter ~~CHAPsystemfilter). This runs
1013 at the start of every delivery process.
1016 .section User filters
1017 .index filter||introduction
1019 In a conventional Exim configuration, users are able to run private filters by
1020 setting up appropriate \(.forward)\ files in their home directories. See
1021 chapter ~~CHAPredirect (about the \%redirect%\ router) for the configuration
1022 needed to support this, and the separate document entitled
1024 [(A HREF="filter_toc.html")]
1026 \*Exim's interfaces to mail filtering*\
1030 for user details. Two different kinds of filtering are available:
1032 Sieve filters are written in the standard filtering language that is defined by
1035 Exim filters are written in a syntax that is unique to Exim, but which is more
1036 powerful than Sieve, which it pre-dates.
1038 User filters are run as part of the routing process, described below.
1041 .section Message identification
1042 .rset SECTmessiden "~~chapter.~~section"
1043 .index message||ids, details of format
1044 .index format||of message id
1045 .index id of message
1050 Every message handled by Exim is given a \*message id*\ which is sixteen
1051 characters long. It is divided into three parts, separated by hyphens, for
1052 example \"16VDhn-0001bo-D3"\. Each part is a sequence of letters and digits,
1053 normally encoding numbers in base 62. However, in the Darwin operating
1054 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
1055 (avoiding the use of lower case letters) is used instead, because the message
1056 id is used to construct file names, and the names of files in those systems are
1059 .index pid (process id)||re-use of
1060 The detail of the contents of the message id have changed as Exim has evolved.
1061 Earlier versions relied on the operating system not re-using a process id (pid)
1062 within one second. On modern operating systems, this assumption can no longer
1063 be made, so the algorithm had to be changed. To retain backward compatibility,
1064 the format of the message id was retained, which is why the following rules are
1067 The first six characters of the message id are the time at which the message
1068 started to be received, to a granularity of one second. That is, this field
1069 contains the number of seconds since the start of the epoch (the normal Unix
1070 way of representing the date and time of day).
1072 After the first hyphen, the next six characters are the id of the process that
1073 received the message.
1075 There are two different possibilities for the final two characters:
1077 .index \localhost@_number\
1078 If \localhost@_number\ is not set, this value is the fractional part of the
1079 time of reception, normally in units of 1/2000 of a second, but for systems
1080 that must use base 36 instead of base 62 (because of case-insensitive file
1081 systems), the units are 1/1000 of a second.
1083 If \localhost@_number\ is set, it is multiplied by 200 (100) and added to
1084 the fractional part of the time, which in this case is in units of 1/200
1085 (1/100) of a second.
1088 After a message has been received, Exim waits for the clock to tick at the
1089 appropriate resolution before proceeding, so that if another message is
1090 received by the same process, or by another process with the same (re-used)
1091 pid, it is guaranteed that the time will be different. In most cases, the clock
1092 will already have ticked while the message was being received.
1094 .section Receiving mail
1095 .index receiving mail
1096 .index message||reception
1097 The only way Exim can receive mail from a remote host is using SMTP over
1098 TCP/IP, in which case the sender and recipient addresses are tranferred using
1099 SMTP commands. However, from a locally running process (such as a user's MUA),
1100 there are several possibilities:
1102 If the process runs Exim with the \-bm-\ option, the message is read
1103 non-interactively (usually via a pipe), with the recipients taken from the
1104 command line, or from the body of the message if \-t-\ is also used.
1106 If the process runs Exim with the \-bS-\ option, the message is also read
1107 non-interactively, but in this case the recipients are listed at the start of
1108 the message in a series of SMTP \\RCPT\\ commands, terminated by a \\DATA\\
1109 command. This is so-called `batch SMTP' format,
1110 but it isn't really SMTP. The SMTP commands are just another way of passing
1111 envelope addresses in a non-interactive submission.
1113 If the process runs Exim with the \-bs-\ option, the message is read
1114 interactively, using the SMTP protocol. A two-way pipe is normally used for
1115 passing data between the local process and the Exim process.
1116 This is `real' SMTP and is handled in the same way as SMTP over TCP/IP. For
1117 example, the ACLs for SMTP commands are used for this form of submission.
1119 A local process may also make a TCP/IP call to the host's loopback address
1120 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1121 does not treat the loopback address specially. It treats all such connections
1122 in the same way as connections from other hosts.
1125 .index message||sender, constructed by Exim
1126 .index sender||constructed by Exim
1127 In the three cases that do not involve TCP/IP, the sender address is
1128 constructed from the login name of the user that called Exim and a default
1129 qualification domain (which can be set by the \qualify@_domain\ configuration
1130 option). For local or batch SMTP, a sender address that is passed using the
1131 SMTP \\MAIL\\ command is ignored. However, the system administrator may allow
1132 certain users (`trusted users') to specify a different sender address
1133 unconditionally, or all users to specify certain forms of different sender
1134 address. The \-f-\ option or the SMTP \\MAIL\\ command is used to specify these
1135 different addresses. See section ~~SECTtrustedadmin for details of trusted
1136 users, and the \untrusted@_set@_sender\ option for a way of allowing untrusted
1137 users to change sender addresses.
1139 Messages received by either of the non-interactive mechanisms are subject to
1140 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1141 (either over TCP/IP, or interacting with a local process) can be checked by a
1142 number of ACLs that operate at different times during the SMTP session. Either
1143 individual recipients, or the entire message, can be rejected if local policy
1144 requirements are not met. The \*local@_scan()*\ function (see chapter
1145 ~~CHAPlocalscan) is run for all incoming messages.
1147 Exim can be configured not to start a delivery process when a message is
1148 received; this can be unconditional, or depend on the number of incoming SMTP
1149 connections or the system load. In these situations, new messages wait on the
1150 queue until a queue runner process picks them up. However, in standard
1151 configurations under normal conditions, delivery is started as soon as a
1152 message is received.
1157 .section Handling an incoming message
1158 .index spool directory||files that hold a message
1159 .index file||how a message is held
1160 When Exim accepts a message, it writes two files in its spool directory. The
1161 first contains the envelope information, the current status of the message,
1162 and the header lines, and the second contains the body of the message. The
1163 names of the two spool files consist of the message id, followed by $tt{-H} for
1164 the file containing the envelope and header, and $tt{-D} for the data file.
1166 .index spool directory||\(input)\ sub-directory
1167 By default all these message files are held in a single directory called
1168 \(input)\ inside the general Exim spool directory. Some operating systems do
1169 not perform very well if the number of files in a directory gets very large; to
1170 improve performance in such cases, the \split@_spool@_directory\ option can be
1171 used. This causes Exim to split up the input files into 62 sub-directories
1172 whose names are single letters or digits.
1174 The envelope information consists of the address of the message's sender and
1175 the addresses of the recipients. This information is entirely separate from
1176 any addresses contained in the header lines. The status of the message includes
1177 a list of recipients who have already received the message. The format of the
1178 first spool file is described in chapter ~~CHAPspool.
1180 .index rewriting||addresses
1181 Address rewriting that is specified in the rewrite section of the configuration
1182 (see chapter ~~CHAPrewrite) is done once and for all on incoming addresses,
1183 both in the header lines and the envelope, at the time the message is accepted.
1184 If during the course of delivery additional addresses are generated (for
1185 example, via aliasing), these new addresses are rewritten as soon as they are
1186 generated. At the time a message is actually delivered (transported) further
1187 rewriting can take place; because this is a transport option, it can be
1188 different for different forms of delivery. It is also possible to specify the
1189 addition or removal of certain header lines at the time the message is
1190 delivered (see chapters ~~CHAProutergeneric and ~~CHAPtransportgeneric).
1193 .section Life of a message
1194 .index message||life of
1195 .index message||frozen
1196 A message remains in the spool directory until it is completely delivered to
1197 its recipients or to an error address, or until it is deleted by an
1198 administrator or by the user who originally created it. In cases when delivery
1199 cannot proceed -- for example, when a message can neither be delivered to its
1200 recipients nor returned to its sender, the message is marked `frozen' on the
1201 spool, and no more deliveries are attempted.
1203 .index frozen messages||thawing
1204 .index message||thawing frozen
1205 An administrator can `thaw' such messages when the problem has been corrected,
1206 and can also freeze individual messages by hand if necessary. In addition, an
1207 administrator can force a delivery error, causing a bounce message to be sent.
1210 There is an option called \auto@_thaw\, which can be used to cause Exim to
1211 retry frozen messages after a certain time. When this is set, no message will
1212 remain on the queue for ever, because the delivery timeout will eventually be
1213 reached. Delivery failure reports (bounce messages) that reach this timeout are
1215 .index \timeout@_frozen@_after\
1216 There is also an option called \timeout@_frozen@_after\, which discards frozen
1217 messages after a certain time.
1219 .index message||log file for
1220 .index log||file for each message
1221 While Exim is working on a message, it writes information about each delivery
1222 attempt to the main log file. This includes successful, unsuccessful, and
1223 delayed deliveries for each recipient (see chapter ~~CHAPlog). The log lines
1224 are also written to a separate $it{message log} file for each message. These
1225 logs are solely for the benefit of the administrator, and are normally deleted
1226 along with the spool files when processing of a message is complete.
1227 The use of individual message logs can be disabled by setting
1228 \no@_message@_logs\; this might give an improvement in performance on very
1232 .index file||journal
1233 All the information Exim itself needs to set up a delivery is kept in the first
1234 spool file, along with the header lines. When a successful delivery occurs, the
1235 address is immediately written at the end of a journal file, whose name is the
1236 message id followed by $tt{-J}. At the end of a delivery run, if there are some
1237 addresses left to be tried again later, the first spool file (the $tt{-H} file)
1238 is updated to indicate which these are, and the journal file is then deleted.
1239 Updating the spool file is done by writing a new file and renaming it, to
1240 minimize the possibility of data loss.
1242 Should the system or the program crash after a successful delivery but before
1243 the spool file has been updated, the journal is left lying around. The next
1244 time Exim attempts to deliver the message, it reads the journal file and
1245 updates the spool file before proceeding. This minimizes the chances of double
1246 deliveries caused by crashes.
1249 .section Processing an address for delivery
1250 .rset SECTprocaddress "~~chapter.~~section"
1251 .index drivers||definition of
1252 .index router||definition of
1253 .index transport||definition of
1254 The main delivery processing elements of Exim are called $it{routers} and
1255 $it{transports}, and collectively these are known as $it{drivers}. Code for a
1256 number of them is provided in the source distribution, and compile-time options
1257 specify which ones are included in the binary. Run time options specify which
1258 ones are actually used for delivering messages.
1260 .index drivers||instance definition
1261 Each driver that is specified in the run time configuration is an \*instance*\
1262 of that particular driver type. Multiple instances are allowed; for example,
1263 you can set up several different \%smtp%\ transports, each with different
1264 option values that might specify different ports or different timeouts. Each
1265 instance has its own identifying name. In what follows we will normally use the
1266 instance name when discussing one particular instance (that is, one specific
1267 configuration of the driver), and the generic driver name when discussing
1268 the driver's features in general.
1270 A $it{router} is a driver that operates on an address, either determining how
1271 its delivery should happen, by routing it to a specific transport, or
1272 converting the address into one or more new addresses (for example, via an
1273 alias file). A router may also explicitly choose to fail an address, causing it
1276 A $it{transport} is a driver that transmits a copy of the message from Exim's
1277 spool to some destination. There are two kinds of transport: for a $it{local}
1278 transport, the destination is a file or a pipe on the local host, whereas for a
1279 $it{remote} transport the destination is some other host. A message is passed
1280 to a specific transport as a result of successful routing. If a message has
1281 several recipients, it may be passed to a number of different transports.
1283 .index preconditions||definition of
1284 An address is processed by passing it to each configured router instance in
1285 turn, subject to certain preconditions, until a router accepts the address or
1286 specifies that it should be bounced. We will describe this process in more
1287 detail shortly. As a simple example, the diagram below illustrates how each
1288 recipient address in a message is processed in a small configuration of three
1289 routers that are configured in various ways.
1292 .figure "Routing an address" rm
1294 .call aspic -sgcal -nv
1295 centre ~~sys.linelength;
1298 ibox depth 14 "address";
1301 A: box width 100 "first router" "conditions ok?";
1303 C: box width 100 "run" "first router";
1305 D: ibox depth 20 "address bounces";
1307 arc clockwise from right of C "accept";
1309 ibox "queue for" "transport";
1311 arrow down from A align bottom of D plus (0,-20) "no"(-6,20)/r;
1312 E: box width 100 "second router" "conditions ok?";
1314 F: box width 100 "run" "second router";
1315 line right 100 "redirect";
1316 line up align middle of B;
1317 arrow left to middle of B "new addresses";
1319 line down 20 from bottom left of F plus (30,0);
1320 arrow left align centre of E "decline";
1322 line down 20 from bottom right of F plus (-30,0);
1324 ibox width 64 "address" "bounces";
1326 arrow down 64 from E "no"(-6,20)/r;
1327 G: box width 100 "third router" "conditions ok?";
1329 H: box width 100 "run" "third router";
1330 arc clockwise from right of H "accept";
1332 ibox "queue for" "transport";
1334 line down 20 from bottom of H;
1335 arrow left align centre of G "decline";
1336 arrow down 64 from G "no"(-6,20)/r;
1338 ibox "no more routers" "address bounces";
1346 |<------------- new addresses -----------------------------
1348 ----------------- ----------------- |
1349 | first router |----- yes ----->| run |--- accept |
1350 | conditions ok?| | first router | | |
1351 ----------------- ----------------- | |
1353 no | fail | queue for |
1358 ----------------- ----------------- |
1359 | second router |----- yes ----->| run |----redirect ----
1360 | conditions ok?| | second router |
1361 ----------------- -----------------
1364 |<-------- decline ----------- --- fail ---> address
1367 ----------------- -----------------
1368 | third router |----- yes ----->| run |--- accept
1369 | conditions ok?| | third router | |
1370 ----------------- ----------------- |
1373 |<-------- decline --------------- transport
1380 [(img src="routing.gif" alt="Routing an address")][(br)]
1382 To make this a more concrete example, we'll describe it in terms of some actual
1383 routers, but remember, this is only an example. You can configure Exim's
1384 routers in many different ways, and there may be any number of routers in a
1387 The first router that is specified in a configuration is often one that handles
1388 addresses in domains that are not recognized specially by the local host. These
1389 are typically addresses for arbitrary domains on the Internet. A precondition
1390 is set up which looks for the special domains known to the host (for example,
1391 its own domain name), and the router is run for addresses that do $it{not}
1392 match. Typically, this is a router that looks up domains in the DNS in order to
1393 find the hosts to which this address routes. If it succeeds, the address is
1394 queued for a suitable SMTP transport; if it does not succeed, the router is
1395 configured to fail the address.
1397 The example pictured could be a configuration of this type. The second and
1398 third routers can only be run for addresses for which the preconditions for
1399 the first router are not met. If one of these preconditions checks the
1400 domain, the second and third routers are run only for domains that are somehow
1401 special to the local host.
1403 The second router does redirection -- also known as aliasing and forwarding.
1404 When it generates one or more new addresses from the original, each of them is
1405 routed independently from the start. Otherwise, the router may cause an address
1406 to fail, or it may simply decline to handle the address, in which case the
1407 address is passed to the next router.
1409 The final router in many configurations is one that checks to see if the
1410 address belongs to a local mailbox. The precondition may involve a check to
1411 see if the local part is the name of a login account, or it may look up the
1412 local part in a file or a database. If its preconditions are not met, or if
1413 the router declines, we have reached the end of the routers. When this happens,
1414 the address is bounced.
1417 .section Processing an address for verification
1418 .index router||for verification
1419 .index verifying||address, overview
1420 As well as being used to decide how to deliver to an address, Exim's routers
1421 are also used for \*address verification*\. Verification can be requested as
1422 one of the checks to be performed in an ACL for incoming messages, on both
1423 sender and recipient addresses, and it can be tested using the \-bv-\ and
1424 \-bvs-\ command line options.
1426 When an address is being verified, the routers are run in `verify mode'. This
1427 does not affect the way the routers work, but it is a state that can be
1428 detected. By this means, a router can be skipped or made to behave differently
1429 when verifying. A common example is a configuration in which the first router
1430 sends all messages to a message-scanning program, unless they have been
1431 previously scanned. Thus, the first router accepts all addresses without any
1432 checking, making it useless for verifying. Normally, the \no@_verify\ option
1433 would be set for such a router, causing it to be skipped in verify mode.
1437 .section Running an individual router
1438 .rset SECTrunindrou "~~chapter.~~section"
1439 .index router||running details
1440 .index preconditions||checking
1441 .index router||result of running
1442 As explained in the example above, a number of preconditions are checked before
1443 running a router. If any are not met, the router is skipped, and the address is
1444 passed to the next router. When all the preconditions on a router $it{are} met,
1445 the router is run. What happens next depends on the outcome, which is one of
1448 \*accept*\: The router accepts the address, and either queues it for a
1449 transport, or generates one or more `child' addresses. Processing the original
1451 .index \unseen\ option
1452 unless the \unseen\ option is set on the router. This option
1453 can be used to set up multiple deliveries with different routing (for example,
1454 for keeping archive copies of messages). When \unseen\ is set, the address is
1455 passed to the next router. Normally, however, an \*accept*\ return marks the
1458 .index case of local parts
1459 .index address||duplicate, discarding
1460 If child addresses are generated, Exim checks to see whether they are
1461 duplicates of any existing recipient addresses. During this check, local parts
1462 are treated as case-sensitive. Duplicate addresses are discarded. Each of the
1463 remaining child addresses is then processed independently, starting with the
1464 first router by default. It is possible to change this by setting the
1465 \redirect@_router\ option to specify which router to start at for child
1466 addresses. Unlike \pass@_router\ (see below) the router specified by
1467 \redirect@_router\ may be anywhere in the router configuration.
1469 \*pass*\: The router recognizes the address, but cannot handle it itself. It
1470 requests that the address be passed to another router. By default the address
1471 is passed to the next router, but this can be changed by setting the
1472 \pass@_router\ option. However, (unlike \redirect@_router\) the named router
1473 must be below the current router (to avoid loops).
1475 \*decline*\: The router declines to accept the address because it does not
1476 recognize it at all. By default, the address is passed to the next router, but
1477 this can be prevented by setting the \no@_more\ option. When \no@_more\ is set,
1478 all the remaining routers are skipped.
1480 \*fail*\: The router determines that the address should fail, and queues it for
1481 the generation of a bounce message. There is no further processing of the
1482 original address unless \unseen\ is set on the router.
1484 \*defer*\: The router cannot handle the address at the present time. (A database
1485 may be offline, or a DNS lookup may have timed out.) No further processing of
1486 the address happens in this delivery attempt. It is tried again next time the
1487 message is considered for delivery.
1489 \*error*\: There is some error in the router (for example, a syntax error in
1490 its configuration). The action is as for defer.
1492 If an address reaches the end of the routers without having been accepted by
1493 any of them, it is bounced as unrouteable.
1494 The default error message in this situation is `unrouteable address', but you
1495 can set your own message by making use of the \cannot@_route@_message\ option.
1496 This can be set for any router; the value from the last router that `saw'
1497 the address is used.
1499 Sometimes while routing you want to fail a delivery when some conditions are
1500 met but others are not, instead of passing the address on for further routing.
1501 You can do this by having a second router that explicitly fails the delivery
1502 when the relevant conditions are met. The \%redirect%\ router has a `fail'
1503 facility for this purpose.
1507 .section Router preconditions
1508 .rset SECTrouprecon "~~chapter.~~section"
1509 .index router||preconditions, order of processing
1510 .index preconditions||order of processing
1511 The preconditions that are tested for each router are listed below, in the
1512 order in which they are tested. The individual configuration options are
1513 described in more detail in chapter ~~CHAProutergeneric.
1515 The \local@_part@_prefix\ and \local@_part@_suffix\ options can specify that
1516 the local parts handled by the router may or must have certain prefixes and/or
1517 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1518 skipped. These conditions are tested first. When an affix is present, it is
1519 removed from the local part before further processing, including the evaluation
1520 of any other conditions.
1522 Routers can be designated for use only when not verifying an address, that is,
1523 only when routing it for delivery (or testing its delivery routing). If the
1524 \verify\ option is set false, the router is skipped when Exim is verifying an
1526 Setting the \verify\ option actually sets two options, \verify@_sender\ and
1527 \verify@_recipient\, which independently control the use of the router for
1528 sender and recipient verification. You can set these options directly if
1529 you want a router to be used for only one type of verification.
1531 If the \address@_test\ option is set false, the router is skipped when Exim is
1532 run with the \-bt-\ option to test an address routing. This can be helpful when
1533 the first router sends all new messages to a scanner of some sort; it makes it
1534 possible to use \-bt-\ to test subsequent delivery routing without having to
1535 simulate the effect of the scanner.
1537 Routers can be designated for use only when verifying an address, as
1538 opposed to routing it for delivery. The \verify@_only\ option controls this.
1540 Certain routers can be explicitly skipped when running the routers to check an
1541 address given in the SMTP \\EXPN\\ command (see the \expn\ option).
1543 If the \domains\ option is set, the domain of the address must be in the set of
1544 domains that it defines.
1546 If the \local@_parts\ option is set, the local part of the address must be in
1547 the set of local parts that it defines. If \local@_part@_prefix\ or
1548 \local@_part@_suffix\ is in use, the prefix or suffix is removed from the local
1549 part before this check. If you want to do precondition tests on local parts
1550 that include affixes, you can do so by using a \condition\ option (see below)
1551 that uses the variables \$local@_part$\, \$local@_part@_prefix$\, and
1552 \$local@_part@_suffix$\ as necessary.
1554 If the \check@_local@_user\ option is set, the local part must be the name of
1555 an account on the local host.
1556 If this check succeeds, the uid and gid of the local user are placed in
1557 \$local@_user@_uid$\ and \$local@_user@_gid$\; these values can be used in the
1558 remaining preconditions.
1560 If the \router@_home@_directory\ option is set, it is expanded at this point,
1561 because it overrides the value of \$home$\. If this expansion were left till
1562 later, the value of \$home$\ as set by \check@_local@_user\ would be used in
1563 subsequent tests. Having two different values of \$home$\ in the same router
1564 could lead to confusion.
1566 If the \senders\ option is set, the envelope sender address must be in the set
1567 of addresses that it defines.
1569 If the \require@_files\ option is set, the existence or non-existence of
1570 specified files is tested.
1572 .index customizing||precondition
1573 If the \condition\ option is set, it is evaluated and tested. This option uses
1574 an expanded string to allow you to set up your own custom preconditions.
1575 Expanded strings are described in chapter ~~CHAPexpand.
1578 Note that \require@_files\ comes near the end of the list, so you cannot use it
1579 to check for the existence of a file in which to lookup up a domain, local
1580 part, or sender. However, as these options are all expanded, you can use the
1581 \exists\ expansion condition to make such tests within each condition. The
1582 \require@_files\ option is intended for checking files that the router may be
1583 going to use internally, or which are needed by a specific transport (for
1584 example, \(.procmailrc)\).
1587 .section Delivery in detail
1588 .index delivery||in detail
1589 When a message is to be delivered, the sequence of events is as follows:
1591 If a system-wide filter file is specified, the message is passed to it. The
1592 filter may add recipients to the message, replace the recipients, discard the
1593 message, cause a new message to be generated, or cause the message delivery to
1594 fail. The format of the system filter file is the same as for Exim user filter
1595 files, described in the separate document entitled
1597 [(A HREF="filter.html")]
1599 \*Exim's interfaces to mail filtering*\.
1603 .index Sieve filter||not available for system filter
1604 (\**Note**\: Sieve cannot be used for system filter files.)
1605 Some additional features are available in system filters -- see chapter
1606 ~~CHAPsystemfilter for details. Note that a message is passed to the system
1607 filter only once per delivery attempt, however many recipients it has. However,
1608 if there are several delivery attempts because one or more addresses could not
1609 be immediately delivered, the system filter is run each time. The filter
1610 condition \first@_delivery\ can be used to detect the first run of the system
1613 Each recipient address is offered to each configured router in turn, subject to
1614 its preconditions, until one is able to handle it. If no router can handle
1615 the address, that is, if they all decline, the address is failed. Because
1616 routers can be targeted at particular domains, several locally handled domains
1617 can be processed entirely independently of each other.
1619 .index routing||loops in
1620 .index loop||while routing
1621 A router that accepts an address may set up a local or a remote transport for
1622 it. However, the transport is not run at this time. Instead, the address is
1623 placed on a list for the particular transport, to be run later. Alternatively,
1624 the router may generate one or more new addresses (typically from alias,
1625 forward, or filter files). New addresses are fed back into this process from
1626 the top, but in order to avoid loops, a router ignores any address which has an
1627 identically-named ancestor that was processed by itself.
1629 When all the routing has been done, addresses that have been successfully
1630 handled are passed to their assigned transports. When local transports are
1631 doing real local deliveries, they handle only one address at a time, but if a
1632 local transport is being used as a pseudo-remote transport (for example, to
1633 collect batched SMTP messages for transmission by some other means) multiple
1634 addresses can be handled. Remote transports can always handle more than one
1635 address at a time, but can be configured not to do so, or to restrict multiple
1636 addresses to the same domain.
1638 Each local delivery to a file or a pipe runs in a separate process under a
1639 non-privileged uid, and these deliveries are run one at a time. Remote
1640 deliveries also run in separate processes, normally under a uid that is private
1641 to Exim (`the Exim user'), but in this case, several remote deliveries can be
1642 run in parallel. The maximum number of simultaneous remote deliveries for any
1643 one message is set by the \remote@_max@_parallel\ option.
1644 The order in which deliveries are done is not defined, except that all local
1645 deliveries happen before any remote deliveries.
1648 When it encounters a local delivery during a queue run, Exim checks its retry
1649 database to see if there has been a previous temporary delivery failure for the
1650 address before running the local transport. If there was a previous failure,
1651 Exim does not attempt a new delivery until the retry time for the address is
1652 reached. However, this happens only for delivery attempts that are part of a
1653 queue run. Local deliveries are always attempted when delivery immediately
1654 follows message reception, even if retry times are set for them. This makes for
1655 better behaviour if one particular message is causing problems (for example,
1656 causing quota overflow, or provoking an error in a filter file).
1658 .index delivery||retry in remote transports
1659 Remote transports do their own retry handling, since an address may be
1660 deliverable to one of a number of hosts, each of which may have a different
1661 retry time. If there have been previous temporary failures and no host has
1662 reached its retry time, no delivery is attempted, whether in a queue run or
1663 not. See chapter ~~CHAPretry for details of retry strategies.
1665 If there were any permanent errors, a bounce message is returned to an
1666 appropriate address (the sender in the common case), with details of the error
1667 for each failing address. Exim can be configured to send copies of bounce
1668 messages to other addresses.
1670 .index delivery||deferral
1671 If one or more addresses suffered a temporary failure, the message is left on
1672 the queue, to be tried again later. Delivery of these addresses is said to be
1675 When all the recipient addresses have either been delivered or bounced,
1676 handling of the message is complete. The spool files and message log are
1677 deleted, though the message log can optionally be preserved if required.
1681 .section Retry mechanism
1682 .index delivery||retry mechanism
1683 .index retry||description of mechanism
1685 Exim's mechanism for retrying messages that fail to get delivered at the first
1686 attempt is the queue runner process. You must either run an Exim daemon that
1687 uses the \-q-\ option with a time interval to start queue runners at regular
1688 intervals, or use some other means (such as \*cron*\) to start them. If you do
1689 not arrange for queue runners to be run, messages that fail temporarily at the
1690 first attempt will remain on your queue for ever. A queue runner process works
1691 it way through the queue, one message at a time, trying each delivery that has
1692 passed its retry time.
1693 You can run several queue runners at once.
1695 Exim uses a set of configured rules to determine when next to retry the failing
1696 address (see chapter ~~CHAPretry). These rules also specify when Exim should
1697 give up trying to deliver to the address, at which point it generates a bounce
1698 message. If no retry rules are set for a particular host, address, and error
1699 combination, no retries are attempted, and temporary errors are treated as
1703 .section Temporary delivery failure
1704 .index delivery||temporary failure
1705 There are many reasons why a message may not be immediately deliverable to a
1706 particular address. Failure to connect to a remote machine (because it, or the
1707 connection to it, is down) is one of the most common. Temporary failures may be
1708 detected during routing as well as during the transport stage of delivery.
1709 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1710 is on a file system where the user is over quota. Exim can be configured to
1711 impose its own quotas on local mailboxes; where system quotas are set they will
1714 If a host is unreachable for a period of time, a number of messages may be
1715 waiting for it by the time it recovers, and sending them in a single SMTP
1716 connection is clearly beneficial. Whenever a delivery to a remote host is
1718 .index hints database
1719 Exim makes a note in its hints database, and whenever a successful
1720 SMTP delivery has happened, it looks to see if any other messages are waiting
1721 for the same host. If any are found, they are sent over the same SMTP
1722 connection, subject to a configuration limit as to the maximum number in any
1727 .section Permanent delivery failure
1728 .index delivery||permanent failure
1729 .index bounce message||when generated
1730 When a message cannot be delivered to some or all of its intended recipients, a
1731 bounce message is generated. Temporary delivery failures turn into permanent
1732 errors when their timeout expires. All the addresses that fail in a given
1733 delivery attempt are listed in a single message. If the original message has
1734 many recipients, it is possible for some addresses to fail in one delivery
1735 attempt and others to fail subsequently, giving rise to more than one bounce
1736 message. The wording of bounce messages can be customized by the administrator.
1737 See chapter ~~CHAPemsgcust for details.
1739 .index ::X-Failed-Recipients:: header line
1740 Bounce messages contain an ::X-Failed-Recipients:: header line that lists the
1741 failed addresses, for the benefit of programs that try to analyse such messages
1744 .index bounce message||recipient of
1745 A bounce message is normally sent to the sender of the original message, as
1746 obtained from the message's envelope. For incoming SMTP messages, this is the
1747 address given in the \\MAIL\\ command. However, when an address is
1748 expanded via a forward or alias file, an alternative address can be specified
1749 for delivery failures of the generated addresses. For a mailing list expansion
1750 (see section ~~SECTmailinglists) it is common to direct bounce messages to the
1751 manager of the list.
1755 .section Failures to deliver bounce messages
1756 .index bounce message||failure to deliver
1757 If a bounce message (either locally generated or received from a remote host)
1758 itself suffers a permanent delivery failure, the message is left on the queue,
1759 but it is frozen, awaiting the attention of an administrator. There are options
1760 which can be used to make Exim discard such failed messages, or to keep them
1761 for only a short time (see \timeout@_frozen@_after\ and
1762 \ignore@_bounce@_errors@_after\).
1770 . ============================================================================
1771 .chapter Building and installing Exim
1772 .set runningfoot "building/installing"
1774 .index building Exim
1776 Exim is distributed as a gzipped or bzipped tar file which, when upacked,
1777 creates a directory with the name of the current release (for example,
1778 \(exim-~~version)\) into which the following files are placed:
1780 .if !~~sys.fancy && ~~sgcal
1785 \(ACKNOWLEDGMENTS)\ $t contains some acknowledgments
1787 \(CHANGES)\ $t contains a reference to where changes are documented
1788 \(LICENCE)\ $t the GNU General Public Licence
1789 \(Makefile)\ $t top-level make file
1790 \(NOTICE)\ $t conditions for the use of Exim
1791 \(README)\ $t list of files, directories and simple build instructions
1793 Other files whose names begin with \(README)\ may also be present. The
1794 following subdirectories are created:
1796 .if !~~sys.fancy && ~~sgcal
1801 \(Local)\ $t an empty directory for local configuration files
1802 \(OS)\ $t OS-specific files
1803 \(doc)\ $t documentation files
1804 \(exim@_monitor)\$t source files for the Exim monitor
1805 \(scripts)\ $t scripts used in the build process
1806 \(src)\ $t remaining source files
1807 \(util)\ $t independent utilities
1809 The main utility programs are contained in the \(src)\ directory, and are built
1810 with the Exim binary. The \(util)\ directory contains a few optional scripts
1811 that may be useful to some sites.
1813 .section Multiple machine architectures and operating systems
1814 .index building Exim||multiple OS/architectures
1815 The building process for Exim is arranged to make it easy to build binaries for
1816 a number of different architectures and operating systems from the same set of
1817 source files. Compilation does not take place in the \(src)\ directory. Instead,
1818 a \*build directory*\ is created for each architecture and operating system.
1819 .index symbolic link||to build directory
1820 Symbolic links to the sources are installed in this directory, which is where
1821 the actual building takes place.
1823 In most cases, Exim can discover the machine architecture and operating system
1824 for itself, but the defaults can be overridden if necessary.
1826 .section DBM libraries
1827 .rset SECTdb "~~chapter.~~section"
1828 .index DBM||libraries, discussion of
1829 .index hints database||DBM files used for
1830 Even if you do not use any DBM files in your configuration, Exim still needs a
1831 DBM library in order to operate, because it uses indexed files for its hints
1832 databases. Unfortunately, there are a number of DBM libraries in existence, and
1833 different operating systems often have different ones installed.
1835 .index Solaris||DBM library for
1836 .index IRIX, DBM library for
1837 .index BSD, DBM library for
1838 .index Linux, DBM library for
1839 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1840 Linux distribution, the DBM configuration should happen automatically, and you
1841 may be able to ignore this section. Otherwise, you may have to learn more than
1842 you would like about DBM libraries from what follows.
1844 .index \*ndbm*\ DBM library
1845 Licensed versions of Unix normally contain a library of DBM functions operating
1846 via the \*ndbm*\ interface, and this is what Exim expects by default. Free
1847 versions of Unix seem to vary in what they contain as standard. In particular,
1848 some early versions of Linux have no default DBM library, and different
1849 distributors have chosen to bundle different libraries with their packaged
1850 versions. However, the more recent releases seem to have standardised on the
1851 Berkeley DB library.
1853 Different DBM libraries have different conventions for naming the files they
1854 use. When a program opens a file called \(dbmfile)\, there are four
1857 A traditional \*ndbm*\ implementation, such as that supplied as part of
1858 Solaris, operates on two files called \(dbmfile.dir)\ and \(dbmfile.pag)\.
1860 .index \*gdbm*\ DBM library
1861 The GNU library, \*gdbm*\, operates on a single file. If used via its \*ndbm*\
1862 compatibility interface it makes two different hard links to it with names
1863 \(dbmfile.dir)\ and \(dbmfile.pag)\, but if used via its native interface, the
1864 file name is used unmodified.
1866 .index Berkeley DB library
1867 The Berkeley DB package, if called via its \*ndbm*\ compatibility interface,
1868 operates on a single file called \(dbmfile.db)\, but otherwise looks to the
1869 programmer exactly the same as the traditional \*ndbm*\ implementation.
1871 If the Berkeley package is used in its native mode, it operates on a single
1872 file called \(dbmfile)\; the programmer's interface is somewhat different to
1873 the traditional \*ndbm*\ interface.
1875 To complicate things further, there are several very different versions of the
1876 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1877 2.$it{x} and 3.$it{x} were current for a while, but the latest versions are now
1878 numbered 4.$it{x}. Maintenance of some of the earlier releases has ceased. All
1879 versions of Berkeley DB can be obtained from
1881 \?http://www.sleepycat.com/?\
1884 .index \*tdb*\ DBM library
1885 Yet another DBM library, called \*tdb*\, has become available from
1887 \?http://download.sourceforge.net/tdb?\
1889 It has its own interface, and also operates on a single file.
1892 .index DBM||libraries, configuration for building
1893 Exim and its utilities can be compiled to use any of these interfaces. In order
1894 to use any version of the Berkeley DB package in native mode, you must set
1895 \\USE@_DB\\ in an appropriate configuration file (typically
1896 \(Local/Makefile)\). For example:
1900 Similarly, for gdbm you set \\USE@_GDBM\\, and for tdb you set \\USE@_TDB\\. An
1901 error is diagnosed if you set more than one of these.
1903 At the lowest level, the build-time configuration sets none of these options,
1904 thereby assuming an interface of type (1). However, some operating system
1905 configuration files (for example, those for the BSD operating systems and
1906 Linux) assume type (4) by setting \\USE@_DB\\ as their default, and the
1907 configuration files for Cygwin set \\USE@_GDBM\\. Anything you set in
1908 \(Local/Makefile)\, however, overrides these system defaults.
1910 As well as setting \\USE@_DB\\, \\USE@_GDBM\\, or \\USE@_TDB\\, it may also be
1911 necessary to set \\DBMLIB\\, to cause inclusion of the appropriate library, as
1912 in one of these lines:
1917 Settings like that will work if the DBM library is installed in the standard
1918 place. Sometimes it is not, and the library's header file may also not be in
1919 the default path. You may need to set \\INCLUDE\\ to specify where the header
1920 file is, and to specify the path to the library more fully in \\DBMLIB\\, as in
1923 INCLUDE=-I/usr/local/include/db-4.1
1924 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1927 There is further detailed discussion about the various DBM libraries in the
1928 file \(doc/dbm.discuss.txt)\ in the Exim distribution.
1931 .section Pre-building configuration
1932 .index building Exim||pre-building configuration
1933 .index configuration for building Exim
1934 .index \(Local/Makefile)\
1935 .index \(src/EDITME)\
1936 Before building Exim, a local configuration file that specifies options
1937 independent of any operating system has to be created with the name
1938 \(Local/Makefile)\. A template for this file is supplied as the file
1939 \(src/EDITME)\, and it contains full descriptions of all the option settings
1940 therein. These descriptions are therefore not repeated here. If you are
1941 building Exim for the first time, the simplest thing to do is to copy
1942 \(src/EDITME)\ to \(Local/Makefile)\, then read it and edit it appropriately.
1944 There are three settings that you must supply, because Exim will not build
1945 without them. They are the location of the run time configuration file
1946 (\\CONFIGURE@_FILE\\), the directory in which Exim binaries will be installed
1947 (\\BIN@_DIRECTORY\\), and the identity of the Exim user (\\EXIM@_USER\\ and
1948 maybe \\EXIM@_GROUP\\ as well). The value of \\CONFIGURE@_FILE\\ can in fact be
1949 a colon-separated list of file names; Exim uses the first of them that exists.
1951 There are a few other parameters that can be specified either at build time or
1952 at run time, to enable the same binary to be used on a number of different
1953 machines. However, if the locations of Exim's spool directory and log file
1954 directory (if not within the spool directory) are fixed, it is recommended that
1955 you specify them in \(Local/Makefile)\ instead of at run time, so that errors
1956 detected early in Exim's execution (such as a malformed configuration file) can
1959 .index content scanning||specifying at build time
1961 Exim's interfaces for calling virus and spam scanning sofware directly from
1962 access control lists are not compiled by default. If you want to include these
1963 facilities, you need to set
1965 WITH_CONTENT_SCAN=yes
1967 in your \(Local/Makefile)\. For details of the facilities themselves, see
1968 chapter ~~CHAPexiscan.
1971 .index \(Local/eximon.conf)\
1972 .index \(exim@_monitor/EDITME)\
1973 If you are going to build the Exim monitor, a similar configuration process is
1974 required. The file \(exim@_monitor/EDITME)\ must be edited appropriately for
1975 your installation and saved under the name \(Local/eximon.conf)\. If you are
1976 happy with the default settings described in \(exim@_monitor/EDITME)\,
1977 \(Local/eximon.conf)\ can be empty, but it must exist.
1979 This is all the configuration that is needed in straightforward cases for known
1980 operating systems. However, the building process is set up so that it is easy
1981 to override options that are set by default or by operating-system-specific
1982 configuration files, for example to change the name of the C compiler, which
1983 defaults to \gcc\. See section ~~SECToverride below for details of how to do
1987 .section Support for iconv()
1988 .index \*iconv()*\ support
1989 The contents of header lines in messages may be encoded according to the rules
1990 described RFC 2047. This makes it possible to transmit characters that are not
1991 in the ASCII character set, and to label them as being in a particular
1992 character set. When Exim is inspecting header lines by means of the \@$h@_\
1993 mechanism, it decodes them, and translates them into a specified character set
1994 (default ISO-8859-1). The translation is possible only if the operating system
1995 supports the \*iconv()*\ function.
1997 However, some of the operating systems that supply \*iconv()*\ do not support
1998 very many conversions. The GNU \libiconv\ library (available from
1999 \?http:/@/www.gnu.org/software/libiconv/?\) can be installed on such systems to
2000 remedy this deficiency, as well as on systems that do not supply \*iconv()*\ at
2001 all. After installing \libiconv\, you should add
2005 to your \(Local/Makefile)\ and rebuild Exim.
2008 .section Including TLS/SSL encryption support
2009 .rset SECTinctlsssl "~~chapter.~~section"
2010 .index TLS||including support for TLS
2011 .index encryption||including support for
2012 .index \\SUPPORT@_TLS\\
2013 .index OpenSSL||building Exim with
2014 .index GnuTLS||building Exim with
2015 Exim can be built to support encrypted SMTP connections, using the \\STARTTLS\\
2016 command as per RFC 2487. It can also support legacy clients that expect to
2017 start a TLS session immediately on connection to a non-standard port (see the
2018 \tls@_on@_connect@_ports\ runtime option and the \-tls-on-connect-\ command
2021 If you want to build Exim with TLS support, you must first install either the
2022 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
2025 If OpenSSL is installed, you should set
2028 TLS_LIBS=-lssl -lcrypto
2030 in \(Local/Makefile)\. You may also need to specify the locations of the
2031 OpenSSL library and include files. For example:
2034 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
2035 TLS_INCLUDE=-I/usr/local/openssl/include/
2038 If GnuTLS is installed, you should set
2039 .index \\USE@_GNUTLS\\
2043 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
2045 in \(Local/Makefile)\, and again you may need to specify the locations of the
2046 library and include files. For example:
2050 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
2051 TLS_INCLUDE=-I/usr/gnu/include
2053 You do not need to set \\TLS@_INCLUDE\\ if the relevant directory is already
2054 specified in \\INCLUDE\\. Details of how to configure Exim to make use of TLS
2055 are given in chapter ~~CHAPTLS.
2059 .section Use of tcpwrappers
2060 .index tcpwrappers, building Exim to support
2061 .index \\USE@_TCP@_WRAPPERS\\
2062 Exim can be linked with the \*tcpwrappers*\ library in order to check incoming
2063 SMTP calls using the \*tcpwrappers*\ control files. This may be a convenient
2064 alternative to Exim's own checking facilities for installations that are
2065 already making use of \*tcpwrappers*\ for other purposes. To do this, you should
2066 set \\USE@_TCP@_WRAPPERS\\ in \(Local/Makefile)\, arrange for the file
2067 \(tcpd.h)\ to be available at compile time, and also ensure that the library
2068 \(libwrap.a)\ is available at link time, typically by including \-lwrap-\ in
2069 \\EXTRALIBS@_EXIM\\. For example, if \*tcpwrappers*\ is installed in
2070 \(/usr/local)\, you might have
2072 USE@_TCP@_WRAPPERS=yes
2073 CFLAGS=-O -I/usr/local/include
2075 EXTRALIBS@_EXIM=-L/usr/local/lib -lwrap
2077 in \(Local/Makefile)\. The name to use in the \*tcpwrappers*\ control files is
2078 `exim'. For example, the line
2080 exim : LOCAL 192.168.1. .friendly.domain.example
2082 in your \(/etc/hosts.allow)\ file allows connections from the local host, from
2083 the subnet 192.168.1.0/24, and from all hosts in \*friendly.domain.example*\.
2084 All other connections are denied. Consult the \*tcpwrappers*\ documentation for
2088 .section Including support for IPv6
2089 .index IPv6||including support for
2090 Exim contains code for use on systems that have IPv6 support. Setting
2091 \\HAVE@_IPV6=YES\\ in \(Local/Makefile)\ causes the IPv6 code to be included;
2092 it may also be necessary to set \\IPV6@_INCLUDE\\ and \\IPV6@_LIBS\\ on systems
2093 where the IPv6 support is not fully integrated into the normal include and
2097 Two different types of DNS record for handling IPv6 addresses have been
2098 defined. AAAA records (analagous to A records for IPv4) are in use, and are
2099 currently seen as the mainstream. Another record type called A6 was proposed
2100 as better than AAAA because it had more flexibility. However, it was felt to
2101 be over-complex, and its status was reduced to `experimental'. It is not known
2102 if anyone is actually using A6 records. Exim has support for A6 records, but
2103 this is included only if you set \\SUPPORT@_A6=YES\\ in \(Local/Makefile)\. The
2104 support has not been tested for some time.
2107 .section The building process
2108 .index build directory
2109 Once \(Local/Makefile)\ (and \(Local/eximon.conf)\, if required) have been
2110 created, run \*make*\ at the top level. It determines the architecture and
2111 operating system types, and creates a build directory if one does not exist.
2112 For example, on a Sun system running Solaris 8, the directory
2113 \(build-SunOS5-5.8-sparc)\ is created.
2114 .index symbolic link||to source files
2115 Symbolic links to relevant source files are installed in the build directory.
2117 \**Warning**\: The \-j-\ (parallel) flag must not be used with \*make*\; the
2118 building process fails if it is set.
2120 If this is the first time \*make*\ has been run, it calls a script that builds
2121 a make file inside the build directory, using the configuration files from the
2122 \(Local)\ directory. The new make file is then passed to another instance of
2123 \*make*\. This does the real work, building a number of utility scripts, and
2124 then compiling and linking the binaries for the Exim monitor (if configured), a
2125 number of utility programs, and finally Exim itself. The command \*make
2126 makefile*\ can be used to force a rebuild of the make file in the build
2127 directory, should this ever be necessary.
2129 If you have problems building Exim, check for any comments there may be in the
2130 \(README)\ file concerning your operating system, and also take a look at the
2132 [(A HREF="FAQ.html")]
2138 where some common problems are covered.
2142 .section Overriding build-time options for Exim
2143 .index build-time options, overriding
2144 .rset SECToverride "~~chapter.~~section"
2145 The main make file that is created at the beginning of the building process
2146 consists of the concatenation of a number of files which set configuration
2147 values, followed by a fixed set of \*make*\ instructions. If a value is set
2148 more than once, the last setting overrides any previous ones. This provides a
2149 convenient way of overriding defaults. The files that are concatenated are, in
2152 \(OS/Makefile-Default)\
2153 \(OS/Makefile-)\<<ostype>>
2155 \(Local/Makefile-)\<<ostype>>
2156 \(Local/Makefile-)\<<archtype>>
2157 \(Local/Makefile-)\<<ostype>>-<<archtype>>
2158 \(OS/Makefile-Base)\
2160 .index \(Local/Makefile)\
2161 where <<ostype>> is the operating system type and <<archtype>> is the
2162 .index building Exim||operating system type
2163 .index building Exim||architecture type
2164 architecture type. \(Local/Makefile)\ is required to exist, and the building
2165 process fails if it is absent. The other three \(Local)\ files are optional,
2166 and are often not needed.
2168 The values used for <<ostype>> and <<archtype>> are obtained from scripts
2169 called \(scripts/os-type)\ and \(scripts/arch-type)\ respectively. If either of
2170 the environment variables \\EXIM@_OSTYPE\\ or \\EXIM@_ARCHTYPE\\ is set, their
2171 values are used, thereby providing a means of forcing particular settings.
2172 Otherwise, the scripts try to get values from the \uname\ command. If this
2173 fails, the shell variables \\OSTYPE\\ and \\ARCHTYPE\\ are inspected. A number
2174 of $it{ad hoc} transformations are then applied, to produce the standard names
2175 that Exim expects. You can run these scripts directly from the shell in order
2176 to find out what values are being used on your system.
2179 \(OS/Makefile-Default)\ contains comments about the variables that are set
2180 therein. Some (but not all) are mentioned below. If there is something that
2181 needs changing, review the contents of this file and the contents of the make
2182 file for your operating system (\(OS/Makefile-<<ostype>>)\) to see what the
2186 .index building Exim||overriding default settings
2187 If you need to change any of the values that are set in \(OS/Makefile-Default)\
2188 or in \(OS/Makefile-<<ostype>>)\, or to add any new definitions, you do not
2189 need to change the original files. Instead, you should make the changes by
2190 putting the new values in an appropriate \(Local)\ file. For example,
2191 .index Tru64-Unix build-time settings
2192 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2193 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2194 compiler is called \*cc*\ rather than \*gcc*\. Also, the compiler must be
2195 called with the option \-std1-\, to make it recognize some of the features of
2196 Standard C that Exim uses. (Most other compilers recognize Standard C by
2197 default.) To do this, you should create a file called \(Local/Makefile-OSF1)\
2198 containing the lines
2203 If you are compiling for just one operating system, it may be easier to put
2204 these lines directly into \(Local/Makefile)\.
2206 Keeping all your local configuration settings separate from the distributed
2207 files makes it easy to transfer them to new versions of Exim simply by copying
2208 the contents of the \(Local)\ directory.
2211 .index NIS lookup type||including support for
2212 .index NIS@+ lookup type||including support for
2213 .index LDAP||including support for
2214 .index lookup||inclusion in binary
2215 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2216 lookup, but not all systems have these components installed, so the default is
2217 not to include the relevant code in the binary. All the different kinds of file
2218 and database lookup that Exim supports are implemented as separate code modules
2219 which are included only if the relevant compile-time options are set. In the
2220 case of LDAP, NIS, and NIS+, the settings for \(Local/Makefile)\ are:
2226 and similar settings apply to the other lookup types. They are all listed in
2227 \(src/EDITME)\. In most cases the relevant include files and interface
2228 libraries need to be installed before compiling Exim.
2229 .index cdb||including support for
2230 However, in the case of cdb, which is included in the binary only if
2234 is set, the code is entirely contained within Exim, and no external include
2235 files or libraries are required. When a lookup type is not included in the
2236 binary, attempts to configure Exim to use it cause run time configuration
2239 .index Perl||including support for
2240 Exim can be linked with an embedded Perl interpreter, allowing Perl
2241 subroutines to be called during string expansion. To enable this facility,
2245 must be defined in \(Local/Makefile)\. Details of this facility are given in
2248 .index X11 libraries, location of
2249 The location of the X11 libraries is something that varies a lot between
2250 operating systems, and of course there are different versions of X11 to cope
2251 with. Exim itself makes no use of X11, but if you are compiling the Exim
2252 monitor, the X11 libraries must be available.
2253 The following three variables are set in \(OS/Makefile-Default)\:
2256 XINCLUDE=-I$(X11)/include
2257 XLFLAGS=-L$(X11)/lib
2259 These are overridden in some of the operating-system configuration files. For
2260 example, in \(OS/Makefile-SunOS5)\ there is
2263 XINCLUDE=-I$(X11)/include
2264 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2266 If you need to override the default setting for your operating system, place a
2267 definition of all three of these variables into your
2268 \(Local/Makefile-<<ostype>>)\ file.
2270 .index \\EXTRALIBS\\
2271 If you need to add any extra libraries to the link steps, these can be put in a
2272 variable called \\EXTRALIBS\\, which appears in all the link commands, but by
2273 default is not defined. In contrast, \\EXTRALIBS@_EXIM\\ is used only on the
2274 command for linking the main Exim binary, and not for any associated utilities.
2275 .index DBM||libraries, configuration for building
2276 There is also \\DBMLIB\\, which appears in the link commands for binaries that
2277 use DBM functions (see also section ~~SECTdb). Finally, there is
2278 \\EXTRALIBS@_EXIMON\\, which appears only in the link step for the Exim monitor
2279 binary, and which can be used, for example, to include additional X11
2282 .index configuration file||editing
2283 The make file copes with rebuilding Exim correctly if any of the configuration
2284 files are edited. However, if an optional configuration file is deleted, it is
2285 necessary to touch the associated non-optional file (that is, \(Local/Makefile)\
2286 or \(Local/eximon.conf)\) before rebuilding.
2288 .section OS-specific header files
2290 .index building Exim||OS-specific C header files
2291 The \(OS)\ directory contains a number of files with names of the form
2292 \(os.h-<<ostype>>)\. These are system-specific C header files that should not
2293 normally need to be changed. There is a list of macro settings that are
2294 recognized in the file \(OS/os.configuring)\, which should be consulted if you
2295 are porting Exim to a new operating system.
2298 .section Overriding build-time options for the monitor
2299 .index building Eximon||overriding default options
2300 A similar process is used for overriding things when building the Exim monitor,
2301 where the files that are involved are
2303 \(OS/eximon.conf-Default)\
2304 \(OS/eximon.conf-)\<<ostype>>
2305 \(Local/eximon.conf)\
2306 \(Local/eximon.conf-)\<<ostype>>
2307 \(Local/eximon.conf-)\<<archtype>>
2308 \(Local/eximon.conf-)\<<ostype>>-<<archtype>>
2310 .index \(Local/eximon.conf)\
2311 As with Exim itself, the final three files need not exist, and in this case the
2312 \(OS/eximon.conf-<<ostype>>)\ file is also optional. The default values in
2313 \(OS/eximon.conf-Default)\ can be overridden dynamically by setting environment
2314 variables of the same name, preceded by \\EXIMON@_\\. For example, setting
2315 \\EXIMON@_LOG@_DEPTH\\ in the environment overrides the value of
2316 \\LOG@_DEPTH\\ at run time.
2320 .section Installing Exim binaries and scripts
2321 .index installing Exim
2322 .index \\BIN@_DIRECTORY\\
2323 The command \*make install*\ runs the \*exim@_install*\ script with no
2324 arguments. The script copies binaries and utility scripts into the directory
2325 whose name is specified by the \\BIN@_DIRECTORY\\ setting in
2328 Exim's run time configuration file is named by the \\CONFIGURE@_FILE\\ setting
2329 .index \\CONFIGURE@_FILE\\
2330 in \(Local/Makefile)\. If this names a single file, and the file does not
2331 exist, the default configuration file \(src/configure.default)\ is copied there
2332 by the installation script. If a run time configuration file already exists, it
2333 is left alone. If \\CONFIGURE@_FILE\\ is a colon-separated list, naming several
2334 alternative files, no default is installed.
2336 .index system aliases file
2337 .index \(/etc/aliases)\
2338 One change is made to the default configuration file when it is installed: the
2339 default configuration contains a router that references a system aliases file.
2340 The path to this file is set to the value specified by
2341 \\SYSTEM@_ALIASES@_FILE\\ in \(Local/Makefile)\ (\(/etc/aliases)\ by default).
2342 If the system aliases file does not exist, the installation script creates it,
2343 and outputs a comment to the user.
2345 The created file contains no aliases, but it does contain comments about the
2346 aliases a site should normally have. Mail aliases have traditionally been
2347 kept in \(/etc/aliases)\. However, some operating systems are now using
2348 \(/etc/mail/aliases)\. You should check if yours is one of these, and change
2349 Exim's configuration if necessary.
2351 The default configuration uses the local host's name as the only local domain,
2352 and is set up to do local deliveries into the shared directory \(/var/mail)\,
2353 running as the local user. System aliases and \(.forward)\ files in users' home
2354 directories are supported, but no NIS or NIS+ support is configured. Domains
2355 other than the name of the local host are routed using the DNS, with delivery
2358 The install script copies files only if they are newer than the files they are
2359 going to replace. The Exim binary is required to be owned by root and have the
2361 .index setuid||installing Exim with
2362 for normal configurations. Therefore, you must run \*make install*\ as root so
2363 that it can set up the Exim binary in this way. However, in some special
2364 situations (for example, if a host is doing no local deliveries) it may be
2365 possible to run Exim without making the binary setuid root (see chapter
2366 ~~CHAPsecurity for details).
2368 It is possible to install Exim for special purposes (such as building a binary
2369 distribution) in a private part of the file system. You can do this by a
2372 make DESTDIR=/some/directory/ install
2374 This has the effect of pre-pending the specified directory to all the file
2375 paths, except the name of the system aliases file that appears in the default
2376 configuration. (If a default alias file is created, its name \*is*\ modified.)
2377 For backwards compatibility, \\ROOT\\ is used if \\DESTDIR\\ is not set,
2378 but this usage is deprecated.
2380 .index installing Exim||what is not installed
2381 Running \*make install*\ does not copy the Exim 4 conversion script
2382 \*convert4r4*\, or the \*pcretest*\ test program. You will probably run the
2383 first of these only once (if you are upgrading from Exim 3), and the second
2384 isn't really part of Exim. None of the documentation files in the \(doc)\
2385 directory are copied, except for the info files when you have set
2386 \\INFO@_DIRECTORY\\, as described in section ~~SECTinsinfdoc below.
2388 For the utility programs, old versions are renamed by adding the suffix \(.O)\
2389 to their names. The Exim binary itself, however, is handled differently. It is
2390 installed under a name that includes the version number and the compile number,
2391 for example \(exim-~~version-1)\. The script then arranges for a symbolic link
2392 called \(exim)\ to point to the binary. If you are updating a previous version
2393 of Exim, the script takes care to ensure that the name \(exim)\ is never absent
2394 from the directory (as seen by other processes).
2396 .index installing Exim||testing the script
2397 If you want to see what the \*make install*\ will do before running it for
2398 real, you can pass the \-n-\ option to the installation script by this command:
2400 make INSTALL_ARG=-n install
2402 The contents of the variable \\INSTALL@_ARG\\ are passed to the installation
2403 script. You do not need to be root to run this test. Alternatively, you can run
2404 the installation script directly, but this must be from within the build
2405 directory. For example, from the top-level Exim directory you could use this
2408 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim@_install -n)
2411 .index installing Exim||install script options
2412 There are two other options that can be supplied to the installation script.
2414 \-no@_chown-\ bypasses the call to change the owner of the installed binary
2415 to root, and the call to make it a setuid binary.
2417 \-no@_symlink-\ bypasses the setting up of the symbolic link \(exim)\ to the
2420 \\INSTALL@_ARG\\ can be used to pass these options to the script. For example:
2422 make INSTALL_ARG=-no_symlink install
2425 The installation script can also be given arguments specifying which files are
2426 to be copied. For example, to install just the Exim binary, and nothing else,
2427 without creating the symbolic link, you could use:
2429 make INSTALL_ARG='-no_symlink exim' install
2433 .section Installing info documentation
2434 .rset SECTinsinfdoc "~~chapter.~~section"
2435 .index installing Exim||\*info*\ documentation
2436 Not all systems use the GNU \*info*\ system for documentation, and for this
2437 reason, the Texinfo source of Exim's documentation is not included in the main
2438 distribution. Instead it is available separately from the ftp site (see section
2441 If you have defined \\INFO@_DIRECTORY\\ in \(Local/Makefile)\ and the Texinfo
2442 source of the documentation is found in the source tree, running \*make
2443 install*\ automatically builds the info files and installs them.
2446 .section Setting up the spool directory
2447 .index spool directory||creating
2448 When it starts up, Exim tries to create its spool directory if it does not
2449 exist. The Exim uid and gid are used for the owner and group of the spool
2450 directory. Sub-directories are automatically created in the spool directory as
2456 .index testing||installation
2457 Having installed Exim, you can check that the run time configuration file is
2458 syntactically valid by running the following command, which assumes that the
2459 Exim binary directory is within your \\PATH\\ environment variable:
2463 If there are any errors in the configuration file, Exim outputs error messages.
2464 Otherwise it outputs the version number and build date,
2465 the DBM library that is being used, and information about which drivers and
2466 other optional code modules are included in the binary.
2467 Some simple routing tests can be done by using the address testing option. For
2470 exim -bt <<local username>>
2472 should verify that it recognizes a local mailbox, and
2474 exim -bt <<remote address>>
2476 a remote one. Then try getting it to deliver mail, both locally and remotely.
2477 This can be done by passing messages directly to Exim, without going through a
2478 user agent. For example:
2480 exim -v postmaster@@your.domain.example
2481 From: user@@your.domain.example
2482 To: postmaster@@your.domain.example
2483 Subject: Testing Exim
2485 This is a test message.
2488 The \-v-\ option causes Exim to output some verification of what it is doing.
2489 In this case you should see copies of three log lines, one for the message's
2490 arrival, one for its delivery, and one containing `Completed'.
2492 .index delivery||problems with
2493 If you encounter problems, look at Exim's log files (\*mainlog*\ and
2494 \*paniclog*\) to see if there is any relevant information there. Another source
2495 of information is running Exim with debugging turned on, by specifying the
2496 \-d-\ option. If a message is stuck on Exim's spool, you can force a delivery
2497 with debugging turned on by a command of the form
2499 exim -d -M <<message-id>>
2501 You must be root or an `admin user' in order to do this. The \-d-\ option
2502 produces rather a lot of output, but you can cut this down to specific areas.
2503 For example, if you use \-d-all+route-\ only the debugging information relevant
2504 to routing is included. (See the \-d-\ option in chapter ~~CHAPcommandline for
2509 One specific problem that has shown up on some sites is the inability to do
2510 local deliveries into a shared mailbox directory, because it does not have the
2511 `sticky bit' set on it. By default, Exim tries to create a lock file before
2512 writing to a mailbox file, and if it cannot create the lock file, the delivery
2513 is deferred. You can get round this either by setting the `sticky bit' on the
2514 directory, or by setting a specific group for local deliveries and allowing
2515 that group to create files in the directory (see the comments above the
2516 \%local@_delivery%\ transport in the default configuration file). Another
2517 approach is to configure Exim not to use lock files, but just to rely on
2518 \*fcntl()*\ locking instead. However, you should do this only if all user
2519 agents also use \*fcntl()*\ locking. For further discussion of locking issues,
2520 see chapter ~~CHAPappendfile.
2522 One thing that cannot be tested on a system that is already running an MTA is
2523 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2524 \-oX-\ option can be used to run an Exim daemon that listens on some other
2525 port, or \*inetd*\ can be used to do this. The \-bh-\ option and the
2526 \*exim@_checkaccess*\ utility can be used to check out policy controls on
2529 Testing a new version on a system that is already running Exim can most easily
2530 be done by building a binary with a different \\CONFIGURE@_FILE\\ setting. From
2531 within the run time configuration, all other file and directory names
2532 that Exim uses can be altered, in order to keep it entirely clear of the
2535 .section Replacing another MTA with Exim
2536 .index replacing another MTA
2537 Building and installing Exim for the first time does not of itself put it in
2538 general use. The name by which the system's MTA is called by mail user agents
2539 is either \(/usr/sbin/sendmail)\, or \(/usr/lib/sendmail)\ (depending on the
2540 operating system), and it is necessary to make this name point to the \*exim*\
2541 binary in order to get the user agents to pass messages to Exim. This is
2542 normally done by renaming any existing file and making \(/usr/sbin/sendmail)\
2543 or \(/usr/lib/sendmail)\
2544 .index symbolic link||to \*exim*\ binary
2545 a symbolic link to the \*exim*\ binary. It is a good idea to remove any setuid
2546 privilege and executable status from the old MTA. It is then necessary to stop
2547 and restart the mailer daemon, if one is running.
2549 .index FreeBSD, MTA indirection
2550 .index \(/etc/mail/mailer.conf)\
2551 Some operating systems have introduced alternative ways of switching MTAs. For
2552 example, if you are running FreeBSD, you need to edit the file
2553 \(/etc/mail/mailer.conf)\ instead of setting up a symbolic link as just
2554 described. A typical example of the contents of this file for running Exim is
2557 sendmail /usr/exim/bin/exim
2558 send-mail /usr/exim/bin/exim
2559 mailq /usr/exim/bin/exim -bp
2560 newaliases /usr/bin/true
2563 Once you have set up the symbolic link, or edited \(/etc/mail/mailer.conf)\,
2564 your Exim installation is `live'. Check it by sending a message from your
2565 favourite user agent.
2567 You should consider what to tell your users about the change of MTA. Exim may
2568 have different capabilities to what was previously running, and there are
2569 various operational differences such as the text of messages produced by
2570 command line options and in bounce messages. If you allow your users to make
2571 use of Exim's filtering capabilities, you should make the document entitled
2573 [(A HREF="filter.html")]
2575 \*Exim's interface to mail filtering*\
2582 .section Upgrading Exim
2583 .index upgrading Exim
2584 If you are already running Exim on your host, building and installing a new
2585 version automatically makes it available to MUAs, or any other programs that
2586 call the MTA directly. However, if you are running an Exim daemon, you do need
2587 to send it a HUP signal, to make it re-exec itself, and thereby pick up the new
2588 binary. You do not need to stop processing mail in order to install a new
2592 .section Stopping the Exim daemon on Solaris
2593 .index Solaris||stopping Exim on
2594 The standard command for stopping the mailer daemon on Solaris is
2596 /etc/init.d/sendmail stop
2598 If \(/usr/lib/sendmail)\ has been turned into a symbolic link, this script
2599 fails to stop Exim because it uses the command \*ps -e*\ and greps the output
2600 for the text `sendmail'; this is not present because the actual program name
2601 (that is, `exim') is given by the \*ps*\ command with these options. A solution
2602 is to replace the line that finds the process id with something like
2604 pid=`cat /var/spool/exim/exim-daemon.pid`
2606 to obtain the daemon's pid directly from the file that Exim saves it in.
2608 Note, however, that stopping the daemon does not `stop Exim'. Messages can
2609 still be received from local processes, and if automatic delivery is configured
2610 (the normal case), deliveries will still occur.
2617 . ============================================================================
2618 .chapter The Exim command line
2619 .set runningfoot "command line"
2620 .rset CHAPcommandline ~~chapter
2621 .index command line||options
2622 .index options||command line
2624 Exim's command line takes the standard Unix form of a sequence of options,
2625 each starting with a hyphen character, followed by a number of arguments. The
2626 options are compatible with the main options of Sendmail, and there are also
2627 some additional options, some of which are compatible with Smail 3. Certain
2628 combinations of options do not make sense, and provoke an error if used.
2629 The form of the arguments depends on which options are set.
2631 .section Setting options by program name
2633 If Exim is called under the name \*mailq*\, it behaves as if the option \-bp-\
2634 were present before any other options.
2635 The \-bp-\ option requests a listing of the contents of the mail queue on the
2637 This feature is for compatibility with some systems that contain a command of
2638 that name in one of the standard libraries, symbolically linked to
2639 \(/usr/sbin/sendmail)\ or \(/usr/lib/sendmail)\.
2642 If Exim is called under the name \*rsmtp*\ it behaves as if the option \-bS-\
2643 were present before any other options, for compatibility with Smail. The \-bS-\
2644 option is used for reading in a number of messages in batched SMTP format.
2647 If Exim is called under the name \*rmail*\ it behaves as if the \-i-\ and
2648 \-oee-\ options were present before any other options, for compatibility with
2649 Smail. The name \*rmail*\ is used as an interface by some UUCP systems.
2653 If Exim is called under the name \*runq*\ it behaves as if the option \-q-\ were
2654 present before any other options, for compatibility with Smail. The \-q-\
2655 option causes a single queue runner process to be started.
2657 .index \*newaliases*\
2658 .index alias file||building
2659 .index Sendmail compatibility||calling Exim as \*newaliases*\
2660 If Exim is called under the name \*newaliases*\ it behaves as if the option
2661 \-bi-\ were present before any other options, for compatibility with Sendmail.
2662 This option is used for rebuilding Sendmail's alias file. Exim does not have
2663 the concept of a single alias file, but can be configured to run a given
2664 command if called with the \-bi-\ option.
2666 .section Trusted and admin users
2667 .rset SECTtrustedadmin "~~chapter.~~section"
2668 Some Exim options are available only to \*trusted users*\ and others are
2669 available only to \*admin users*\. In the description below, the phrases `Exim
2670 user' and `Exim group' mean the user and group defined by \\EXIM@_USER\\ and
2671 \\EXIM@_GROUP\\ in \(Local/Makefile)\ or set by the \exim@_user\ and
2672 \exim@_group\ options. These do not necessarily have to use the name `exim'.
2675 .index trusted user||definition of
2676 .index user||trusted, definition of
2677 The trusted users are root, the Exim user, any user listed in the
2678 \trusted@_users\ configuration option, and any user whose current group or any
2679 supplementary group is one of those listed in the \trusted@_groups\
2680 configuration option. Note that the Exim group is not automatically trusted.
2683 .index envelope sender
2684 Trusted users are always permitted to use the \-f-\ option or a leading `From '
2685 line to specify the envelope sender of a message that is passed to Exim through
2686 the local interface (see the \-bm-\ and \-f-\ options below). See the
2687 \untrusted@_set@_sender\ option for a way of permitting non-trusted users to
2688 set envelope senders.
2689 .index ::From:: header line
2690 .index ::Sender:: header line
2691 For a trusted user, there is never any check on the contents of the ::From::
2692 header line, and a ::Sender:: line is never added. Furthermore, any existing
2693 ::Sender:: line in incoming local (non-TCP/IP) messages is not removed.
2695 Trusted users may also specify a host name, host address, interface address,
2696 protocol name, ident value, and authentication data when submitting a message
2697 locally. Thus, they are able to insert messages into Exim's queue locally that
2698 have the characteristics of messages received from a remote host. Untrusted
2699 users may in some circumstances use \-f-\, but can never set the other values
2700 that are available to trusted users.
2702 .index user||admin, definition of
2703 .index admin user||definition of
2704 The admin users are root, the Exim user, and any user that is a member of the
2705 Exim group or of any group listed in the \admin@_groups\ configuration option.
2706 The current group does not have to be one of these groups.
2708 Admin users are permitted to list the queue, and to carry out certain
2709 operations on messages, for example, to force delivery failures. It is also
2710 necessary to be an admin user in order to see the full information provided by
2711 the Exim monitor, and full debugging output.
2713 By default, the use of the \-M-\, \-q-\, \-R-\, and \-S-\ options to cause Exim
2714 to attempt delivery of messages on its queue is restricted to admin users.
2715 However, this restriction can be relaxed by setting the \prod@_requires@_admin\
2716 option false (that is, specifying \no@_prod@_requires@_admin\).
2718 Similarly, the use of the \-bp-\ option to list all the messages in the queue
2719 is restricted to admin users unless \queue@_list@_requires@_admin\ is set
2723 \**Warning**\: If you configure your system so that admin users are able to
2724 edit Exim's configuration file, you are giving those users an easy way of
2725 getting root. There is further discussion of this issue at the start of chapter
2730 .section Command line options
2731 The command options are described in alphabetical order below.
2736 .index options||command line, terminating
2737 This is a pseudo-option whose only purpose is to terminate the options and
2738 therefore to cause subsequent command line items to be treated as arguments
2739 rather than options, even if they begin with hyphens.
2742 This option causes Exim to output a few sentences stating what it is.
2743 The same output is generated if the Exim binary is called with no options and
2747 .index 8-bit characters
2748 .index Sendmail compatibility||8-bit characters
2749 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2750 clean; it ignores this option.
2754 .index SMTP listener
2756 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2757 the \-bd-\ option is combined with the \-q-\<<time>> option, to specify that
2758 the daemon should also initiate periodic queue runs.
2760 The \-bd-\ option can be used only by an admin user. If either of the \-d-\
2761 (debugging) or \-v-\ (verifying) options are set, the daemon does not
2762 disconnect from the controlling terminal. When running this way, it can be
2763 stopped by pressing ctrl-C.
2765 By default, Exim listens for incoming connections to the standard SMTP port on
2766 all the host's running interfaces. However, it is possible to listen on other
2767 ports, on multiple ports, and only on specific interfaces. Chapter
2768 ~~CHAPinterfaces contains a description of the options that control this.
2770 .index daemon||process id (pid)
2771 .index pid (process id)||of daemon
2772 When a listening daemon is started without the use of \-oX-\ (that is, without
2773 overriding the normal configuration), it writes its process id to a file called
2774 \(exim-daemon.pid)\ in Exim's spool directory. This location can be overridden
2775 by setting \\PID@_FILE@_PATH\\ in \(Local/Makefile)\. The file is written while
2776 Exim is still running as root.
2778 When \-oX-\ is used on the command line to start a listening daemon, the
2779 process id is not written to the normal pid file path. However, \-oP-\ can be
2780 used to specify a path on the command line if a pid file is required.
2783 The \\SIGHUP\\ signal can be used to cause the daemon to re-exec itself. This
2784 should be done whenever Exim's configuration file, or any file that is
2785 incorporated into it by means of the \.include\ facility, is changed, and also
2786 whenever a new version of Exim is installed. It is not necessary to do this
2787 when other files that are referenced from the configuration (for example, alias
2788 files) are changed, because these are reread each time they are used.
2791 This option has the same effect as \-bd-\ except that it never disconnects from
2792 the controlling terminal, even when no debugging is specified.
2795 .index testing||string expansion
2796 .index expansion||testing
2797 Run Exim in expansion testing mode. Exim discards its root privilege, to
2798 prevent ordinary users from using this mode to read otherwise inaccessible
2799 files. If no arguments are given, Exim runs interactively, prompting for lines
2802 If Exim was built with \\USE@_READLINE\\=yes in \(Local/Makefile)\, it tries
2803 to load the \libreadline\ library dynamically whenever the \-be-\ option is
2804 used without command line arguments. If successful, it uses the \*readline()*\
2805 function, which provides extensive line-editing facilities, for reading the
2806 test data. A line history is supported.
2809 Long expansion expressions can be split over several lines by using backslash
2810 continuations. As in Exim's run time configuration, whitespace at the start of
2811 continuation lines is ignored. Each argument or data line is passed through the
2812 string expansion mechanism, and the result is output. Variable values from the
2813 configuration file (for example, \$qualify@_domain$\) are available, but no
2814 message-specific values (such as \$domain$\) are set, because no message is
2817 .option bF #<<filename>>
2818 .index system filter||testing
2819 .index testing||system filter
2820 This option is the same as \-bf-\ except that it assumes that the filter being
2821 tested is a system filter. The additional commands that are available only in
2822 system filters are recognized.
2824 .option bf #<<filename>>
2825 .index filter||testing
2826 .index testing||filter file
2827 .index forward file||testing
2828 .index testing||forward file
2829 .index Sieve filter||testing
2830 This option runs Exim in user filter testing mode; the file is the filter file
2831 to be tested, and a test message must be supplied on the standard input. If
2832 there are no message-dependent tests in the filter, an empty file can be
2835 If you want to test a system filter file, use \-bF-\ instead of \-bf-\. You can
2836 use both \-bF-\ and \-bf-\ on the same command, in order to
2837 test a system filter and a user filter in the same run. For example:
2839 exim -bF /system/filter -bf /user/filter </test/message
2841 This is helpful when the system filter adds header lines or sets filter
2842 variables that are used by the user filter.
2845 If the test filter file does not begin with one of the special lines
2850 it is taken to be a normal \(.forward)\ file, and is tested for validity under
2851 that interpretation. See sections ~~SECTitenonfilred to ~~SECTspecitredli for a
2852 description of the possible contents of non-filter redirection lists.
2854 The result of an Exim command that uses \-bf-\, provided no errors are
2855 detected, is a list of the actions that Exim would try to take if presented
2856 with the message for real. More details of filter testing are given in the
2857 separate document entitled \*Exim's interfaces to mail filtering*\.
2860 .index envelope sender
2861 .index \-f-\ option||for filter testing
2862 When testing a filter file, the envelope sender can be set by the \-f-\ option,
2863 or by a `From ' line at the start of the test message. Various parameters that
2864 would normally be taken from the envelope recipient address of the message can
2865 be set by means of additional command line options (see the next four options).
2868 .option bfd #<<domain>>
2869 This sets the domain of the recipient address when a filter file is being
2870 tested by means of the \-bf-\ option. The default is the value of
2871 \$qualify@_domain$\.
2873 .option bfl #<<local part>>
2874 This sets the local part of the recipient address when a filter file is being
2875 tested by means of the \-bf-\ option. The default is the username of the
2876 process that calls Exim. A local part should be specified with any prefix or
2877 suffix stripped, because that is how it appears to the filter when a message is
2878 actually being delivered.
2880 .option bfp #<<prefix>>
2881 This sets the prefix of the local part of the recipient address when a filter
2882 file is being tested by means of the \-bf-\ option. The default is an empty
2885 .option bfp #<<suffix>>
2886 This sets the suffix of the local part of the recipient address when a filter
2887 file is being tested by means of the \-bf-\ option. The default is an empty
2892 .option bh #<<IP address>>
2893 .index testing||incoming SMTP
2894 .index SMTP||testing incoming
2895 .index testing||relay control
2896 .index relaying||testing configuration
2897 .index policy control||testing
2898 .index debugging||\-bh-\ option
2899 This option runs a fake SMTP session as if from the given IP address, using the
2900 standard input and output. The IP address may include a port number at the end,
2901 after a full stop. For example:
2903 exim -bh 10.9.8.7.1234
2904 exim -bh fe80::a00:20ff:fe86:a061.5678
2907 When an IPv6 address is given, it is converted into canonical form. In the case
2908 of the second example above, the value of \$sender@_host@_address$\ after
2909 conversion to the canonical form is \"fe80:0000:0000:0a00:20ff:fe86:a061.5678"\.
2912 Comments as to what is going on are written to the standard error file. These
2913 include lines beginning with `LOG' for anything that would have been logged.
2914 This facility is provided for testing configuration options for incoming
2915 messages, to make sure they implement the required policy. For example, you can
2916 test your relay controls using \-bh-\.
2919 \**Warning 1**\: You cannot test features of the configuration that rely on
2920 ident (RFC 1413) callouts. These cannot be done when testing using
2921 \-bh-\ because there is no incoming SMTP connection.
2923 \**Warning 2**\: Address verification callouts (see section ~~SECTcallver) are
2924 also skipped when testing using \-bh-\. If you want these callouts to occur,
2925 use \-bhc-\ instead.
2927 Messages supplied during the testing session are discarded, and nothing is
2928 written to any of the real log files. There may be pauses when DNS (and other)
2929 lookups are taking place, and of course these may time out. The \-oMi-\ option
2930 can be used to specify a specific IP interface and port if this is important.
2932 The \*exim@_checkaccess*\ utility is a `packaged' version of \-bh-\ whose
2933 output just states whether a given recipient address from a given host is
2934 acceptable or not. See section ~~SECTcheckaccess.
2936 .option bhc #<<IP address>>
2937 This option operates in the same way as \-bh-\, except that address
2938 verification callouts are performed if required. This includes consulting and
2939 updating the callout cache database.
2942 .index alias file||building
2943 .index building alias file
2944 .index Sendmail compatibility||\-bi-\ option
2945 Sendmail interprets the \-bi-\ option as a request to rebuild its alias file.
2946 Exim does not have the concept of a single alias file, and so it cannot mimic
2947 this behaviour. However, calls to \(/usr/lib/sendmail)\ with the \-bi-\ option
2948 tend to appear in various scripts such as NIS make files, so the option must be
2951 If \-bi-\ is encountered, the command specified by the \bi@_command\
2952 configuration option is run, under the uid and gid of the caller of Exim. If
2953 the \-oA-\ option is used, its value is passed to the command as an argument.
2954 The command set by \bi@_command\ may not contain arguments. The command can use
2955 the \*exim@_dbmbuild*\ utility, or some other means, to rebuild alias files if
2956 this is required. If the \bi@_command\ option is not set, calling Exim with
2960 .index local message reception
2961 This option runs an Exim receiving process that accepts an incoming,
2962 locally-generated message on the current input. The recipients are given as the
2963 command arguments (except when \-t-\ is also present -- see below). Each
2964 argument can be a comma-separated list of RFC 2822 addresses. This is the
2965 default option for selecting the overall action of an Exim call; it is assumed
2966 if no other conflicting option is present.
2968 If any addresses in the message are unqualified (have no domain), they are
2969 qualified by the values of the \qualify@_domain\ or \qualify@_recipient\
2970 options, as appropriate. The \-bnq-\ option (see below) provides a way of
2971 suppressing this for special cases.
2973 Policy checks on the contents of local messages can be enforced by means of the
2974 non-SMTP ACL. See chapter ~~CHAPACL for details.
2975 .index return code||for \-bm-\
2976 The return code is zero if the message is successfully accepted. Otherwise, the
2977 action is controlled by the \-oe$it{x}-\ option setting -- see below.
2979 .index message||format
2980 .index format||message
2982 .index UUCP||`From' line
2983 .index Sendmail compatibility||`From' line
2984 The format of the message must be as defined in RFC 2822, except that, for
2985 compatibility with Sendmail and Smail, a line in one of the forms
2987 From sender Fri Jan 5 12:55 GMT 1997
2988 From sender Fri, 5 Jan 97 12:55:01
2990 (with the weekday optional, and possibly with additional text after the date)
2991 is permitted to appear at the start of the message. There appears to be no
2992 authoritative specification of the format of this line. Exim recognizes it by
2993 matching against the regular expression defined by the \uucp@_from@_pattern\
2994 option, which can be changed if necessary.
2995 .index \-f-\ option||overriding `From' line
2996 The specified sender is treated as if it were given as the argument to the
2997 \-f-\ option, but if a \-f-\ option is also present, its argument is used in
2998 preference to the address taken from the message. The caller of Exim must be a
2999 trusted user for the sender of a message to be set in this way.
3002 .index address||qualification, suppressing
3003 By default, Exim automatically qualifies unqualified addresses (those
3004 without domains) that appear in messages that are submitted locally (that
3005 is, not over TCP/IP). This qualification applies both to addresses in
3006 envelopes, and addresses in header lines. Sender addresses are qualified using
3007 \qualify@_domain\, and recipient addresses using \qualify@_recipient\ (which
3008 defaults to the value of \qualify@_domain\).
3010 Sometimes, qualification is not wanted. For example, if \-bS-\ (batch SMTP) is
3011 being used to re-submit messages that originally came from remote hosts after
3012 content scanning, you probably do not want to qualify unqualified addresses in
3013 header lines. (Such lines will be present only if you have not enabled a header
3014 syntax check in the appropriate ACL.)
3016 The \-bnq-\ option suppresses all qualification of unqualified addresses in
3017 messages that originate on the local host. When this is used, unqualified
3018 addresses in the envelope provoke errors (causing message rejection) and
3019 unqualified addresses in header lines are left alone.
3023 .index configuration options, extracting
3024 .index options||configuration, extracting
3025 If this option is given with no arguments, it causes the values of all Exim's
3026 main configuration options to be written to the standard output. The values
3027 of one or more specific options can be requested by giving their names as
3028 arguments, for example:
3030 exim -bP qualify@_domain hold@_domains
3032 However, any option setting that is preceded by the word `hide' in the
3033 configuration file is not shown in full, except to an admin user. For other
3034 users, the output is as in this example:
3036 mysql_servers = <value not displayable>
3038 If \configure@_file\ is given as an argument, the name of the run time
3039 configuration file is output.
3040 If a list of configuration files was supplied, the value that is output here
3041 is the name of the file that was actually used.
3043 .index daemon||process id (pid)
3044 .index pid (process id)||of daemon
3045 If \log__file__path\ or \pid@_file@_path\ are given, the names of the
3046 directories where log files and daemon pid files are written are output,
3047 respectively. If these values are unset, log files are written in a
3048 sub-directory of the spool directory called \log\, and the pid file is written
3049 directly into the spool directory.
3051 If \-bP-\ is followed by a name preceded by \"+"\, for example,
3053 exim -bP +local_domains
3055 it searches for a matching named list of any type (domain, host, address, or
3056 local part) and outputs what it finds.
3058 .index options||router, extracting
3059 .index options||transport, extracting
3060 If one of the words \router\, \transport\, or \authenticator\ is given,
3061 followed by the name of an appropriate driver instance, the option settings for
3062 that driver are output. For example:
3064 exim -bP transport local@_delivery
3066 The generic driver options are output first, followed by the driver's private
3067 options. A list of the names of drivers of a particular type can be obtained by
3068 using one of the words \router@_list\, \transport@_list\, or
3069 \authenticator@_list\, and a complete list of all drivers with their option
3070 settings can be obtained by using \routers\, \transports\, or \authenticators\.
3074 .index queue||listing messages on
3075 .index listing||messages on the queue
3076 This option requests a listing of the contents of the mail queue on the
3077 standard output. If the \-bp-\ option is followed by a list of message ids,
3078 just those messages are listed. By default, this option can be used only by an
3079 admin user. However, the \queue__list__requires__admin\ option can be set false
3080 to allow any user to see the queue.
3082 Each message on the queue is displayed as in the following example:
3084 25m 2.9K 0t5C6f-0000c8-00 <alice@@wonderland.fict.example>
3085 red.king@@looking-glass.fict.example
3088 .index message||size in queue listing
3089 .index size||of message
3090 The first line contains the length of time the message has been on the queue
3091 (in this case 25 minutes), the size of the message (2.9K), the unique local
3092 identifier for the message, and the message sender, as contained in the
3093 envelope. For bounce messages, the sender address is empty, and appears as
3094 `<>'. If the message was submitted locally by an untrusted user who overrode
3095 the default sender address, the user's login name is shown in parentheses
3096 before the sender address.
3097 .index frozen messages||in queue listing
3098 If the message is frozen (attempts to deliver it are suspended) then the text
3099 `$*$$*$$*$ frozen $*$$*$$*$' is displayed at the end of this line.
3101 The recipients of the message (taken from the envelope, not the headers) are
3102 displayed on subsequent lines. Those addresses to which the message has already
3103 been delivered are marked with the letter D. If an original address gets
3104 expanded into several addresses via an alias or forward file, the original is
3105 displayed with a D only when deliveries for all of its child addresses are
3110 This option operates like \-bp-\, but in addition it shows delivered addresses
3111 that were generated from the original top level address(es) in each message by
3112 alias or forwarding operations. These addresses are flagged with `+D' instead
3117 .index queue||count of messages on
3118 This option counts the number of messages on the queue, and writes the total
3119 to the standard output. It is restricted to admin users, unless
3120 \queue__list__requires__admin\ is set false.
3124 This option operates like \-bp-\, but the output is not sorted into
3125 chronological order of message arrival. This can speed it up when there are
3126 lots of messages on the queue, and is particularly useful if the output is
3127 going to be post-processed in a way that doesn't need the sorting.
3130 This option is a combination of \-bpr-\ and \-bpa-\.
3133 This option is a combination of \-bpr-\ and \-bpu-\.
3137 This option operates like \-bp-\ but shows only undelivered top-level addresses
3138 for each message displayed. Addresses generated by aliasing or forwarding are
3139 not shown, unless the message was deferred after processing by a router with
3140 the \one@_time\ option set.
3144 .index testing||retry configuration
3145 .index retry||configuration testing
3146 This option is for testing retry rules, and it must be followed by up to three
3147 arguments. It causes Exim to look for a retry rule that matches the values
3148 and to write it to the standard output. For example:
3150 exim -brt bach.comp.mus.example
3151 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3153 See chapter ~~CHAPretry for a description of Exim's retry rules. The first
3154 argument, which is required, can be a complete address in the form
3155 \*local@_part@@domain*\, or it can be just a domain name. The second argument is
3156 an optional second domain name; if no retry rule is found for the first
3157 argument, the second is tried. This ties in with Exim's behaviour when looking
3158 for retry rules for remote hosts -- if no rule is found that matches the host,
3159 one that matches the mail domain is sought. The final argument is the name of a
3160 specific delivery error, as used in setting up retry rules, for example
3164 .index testing||rewriting
3165 .index rewriting||testing
3166 This option is for testing address rewriting rules, and it must be followed by
3167 a single argument, consisting of either a local part without a domain, or a
3168 complete address with a fully qualified domain. Exim outputs how this address
3169 would be rewritten for each possible place it might appear. See chapter
3170 ~~CHAPrewrite for further details.
3173 .index SMTP||batched incoming
3174 .index batched SMTP input
3175 This option is used for batched SMTP input, which is an alternative interface
3176 for non-interactive local message submission. A number of messages can be
3177 submitted in a single run. However, despite its name, this is not really SMTP
3178 input. Exim reads each message's envelope from SMTP commands on the standard
3179 input, but generates no responses. If the caller is trusted, or
3180 \untrusted@_set@_sender\ is set, the senders in the SMTP \\MAIL\\ commands are
3181 believed; otherwise the sender is always the caller of Exim.
3183 The message itself is read from the standard input, in SMTP format (leading
3184 dots doubled), terminated by a line containing just a single dot. An error is
3185 provoked if the terminating dot is missing. A further message may then follow.
3187 As for other local message submissions, the contents of incoming batch SMTP
3188 messages can be checked using the non-SMTP ACL (see chapter ~~CHAPACL).
3189 Unqualified addresses are automatically qualified using \qualify@_domain\ and
3190 \qualify@_recipient\, as appropriate, unless the \-bnq-\ option is used.
3192 Some other SMTP commands are recognized in the input. \\HELO\\ and \\EHLO\\ act
3193 as \\RSET\\; \\VRFY\\, \\EXPN\\, \\ETRN\\, and \\HELP\\ act as \\NOOP\\;
3194 \\QUIT\\ quits, ignoring the rest of the standard input.
3196 If any error is encountered, reports are written to the standard output and
3197 error streams, and Exim gives up immediately.
3198 .index return code||for \-bS-\
3199 The return code is 0 if no error was detected; it is 1 if one or more messages
3200 were accepted before the error was detected; otherwise it is 2.
3202 More details of input using batched SMTP are given in section
3203 ~~SECTincomingbatchedSMTP.
3206 .index SMTP||local input
3207 .index local SMTP input
3208 This option causes Exim to accept one or more messages by reading SMTP commands
3209 on the standard input, and producing SMTP replies on the standard output. SMTP
3210 policy controls, as defined in ACLs (see chapter ~~CHAPACL) are applied.
3212 Some user agents use this interface as a way of passing locally-generated
3213 messages to the MTA.
3214 .index sender||source of
3215 In this usage, if the caller of Exim is trusted, or \untrusted@_set@_sender\ is
3216 set, the senders of messages are taken from the SMTP \\MAIL\\ commands.
3217 Otherwise the content of these commands is ignored and the sender is set up as
3218 the calling user. Unqualified addresses are automatically qualified using
3219 \qualify@_domain\ and \qualify@_recipient\, as appropriate, unless the \-bnq-\
3223 The \-bs-\ option is also used to run Exim from \*inetd*\, as an alternative to
3224 using a listening daemon. Exim can distinguish the two cases by checking
3225 whether the standard input is a TCP/IP socket. When Exim is called from
3226 \*inetd*\, the source of the mail is assumed to be remote, and the comments
3227 above concerning senders and qualification do not apply. In this situation,
3228 Exim behaves in exactly the same way as it does when receiving a message via
3229 the listening daemon.
3232 .index testing||addresses
3233 .index address||testing
3234 This option runs Exim in address testing mode, in which each argument is taken
3235 as an address to be tested for deliverability. The results are written to the
3236 standard output. If a test fails, and the caller is not an admin user, no
3237 details of the failure are output, because these might contain sensitive
3238 information such as usernames and passwords for database lookups.
3240 If no arguments are given, Exim runs in an interactive manner, prompting with a
3241 right angle bracket for addresses to be tested.
3243 Unlike the \-be-\ test option, you cannot arrange for Exim to use the
3244 \*readline()*\ function, because it is running as \*root*\ and there are
3248 Each address is handled as if it were the recipient address of a message
3249 (compare the \-bv-\ option). It is passed to the routers and the result is
3250 written to the standard output. However, any router that has
3251 \no@_address@_test\ set is bypassed. This can make \-bt-\ easier to use for
3252 genuine routing tests if your first router passes everything to a scanner
3255 .index return code||for \-bt-\
3256 The return code is 2 if any address failed outright; it is 1 if no address
3257 failed outright but at least one could not be resolved for some reason. Return
3258 code 0 is given only when all addresses succeed.
3260 \**Warning**\: \-bt-\ can only do relatively simple testing. If any of the
3261 routers in the configuration makes any tests on the sender address of a
3263 .index \-f-\ option||for address testing
3264 you can use the \-f-\ option to set an appropriate sender when running
3265 \-bt-\ tests. Without it, the sender is assumed to be the calling user at the
3266 default qualifying domain. However, if you have set up (for example) routers
3267 whose behaviour depends on the contents of an incoming message, you cannot test
3268 those conditions using \-bt-\. The \-N-\ option provides a possible way of
3272 .index version number of Exim, verifying
3273 This option causes Exim to write the current version number, compilation
3274 number, and compilation date of the \*exim*\ binary to the standard output.
3275 It also lists the DBM library this is being used, the optional modules (such as
3276 specific lookup types), the drivers that are included in the binary, and the
3277 name of the run time configuration file that is in use.
3280 As part of its operation, \-bV-\ causes Exim to read and syntax check its
3281 configuration file. However, this is a static check only. It cannot check
3282 values that are to be expanded. For example, although a misspelt ACL verb is
3283 detected, an error in the verb's arguments is not. You cannot rely on \-bV-\
3284 alone to discover (for example) all the typos in the configuration; some
3285 realistic testing is needed. The \-bh-\ and \-N-\ options provide more dynamic
3291 .index verifying||address, using \-bv-\
3292 .index address||verification
3293 This option runs Exim in address verification mode, in which each argument is
3294 taken as an address to be verified. During normal operation, verification
3295 happens mostly as a consequence processing a \verify\ condition in an ACL (see
3296 chapter ~~CHAPACL). If you want to test an entire ACL, see the \-bh-\ option.
3298 If verification fails, and the caller is not an admin user, no details of the
3299 failure are output, because these might contain sensitive information such as
3300 usernames and passwords for database lookups.
3302 If no arguments are given, Exim runs in an interactive manner, prompting with a
3303 right angle bracket for addresses to be verified.
3305 Unlike the \-be-\ test option, you cannot arrange for Exim to use the
3306 \*readline()*\ function, because it is running as \*exim*\ and there are
3310 Verification differs from address testing (the \-bt-\ option) in that routers
3311 that have \no@_verify\ set are skipped, and if the address is accepted by a
3312 router that has \fail@_verify\ set, verification fails. The address is verified
3313 as a recipient if \-bv-\ is used; to test verification for a sender address,
3314 \-bvs-\ should be used.
3316 If the \-v-\ option is not set, the output consists of a single line for each
3317 address, stating whether it was verified or not, and giving a reason in the
3318 latter case. Otherwise, more details are given of how the address has been
3319 handled, and in the case of address redirection, all the generated addresses
3320 are also considered. Without \-v-\, generating more than one address by
3321 redirection causes verification to end sucessfully.
3323 .index return code||for \-bv-\
3324 The return code is 2 if any address failed outright; it is 1 if no address
3325 failed outright but at least one could not be resolved for some reason. Return
3326 code 0 is given only when all addresses succeed.
3328 If any of the routers in the configuration makes any tests on the sender
3329 address of a message, you should use the \-f-\ option to set an appropriate
3330 sender when running \-bv-\ tests. Without it, the sender is assumed to be the
3331 calling user at the default qualifying domain.
3334 This option acts like \-bv-\, but verifies the address as a sender rather
3335 than a recipient address. This affects any rewriting and qualification that
3338 .option C #<<filelist>>
3339 .index configuration file||alternate
3340 .index \\CONFIGURE@_FILE\\
3341 .index alternate configuration file
3342 This option causes Exim to find the run time configuration file from the given
3343 list instead of from the list specified by the \\CONFIGURE@_FILE\\
3344 compile-time setting. Usually, the list will consist of just a single file
3345 name, but it can be a colon-separated list of names. In this case, the first
3346 file that exists is used. Failure to open an existing file stops Exim from
3347 proceeding any further along the list, and an error is generated.
3349 When this option is used by a caller other than root or the Exim user, and the
3350 list is different from the compiled-in list, Exim gives up its root privilege
3351 immediately, and runs with the real and effective uid and gid set to those of
3352 the caller. However, if \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined in
3353 \(Local/Makefile)\, root privilege is retained for \-C-\ only if the caller of
3356 That is, the Exim user is no longer privileged in this regard. This build-time
3357 option is not set by default in the Exim source distribution tarbundle.
3358 However, if you are using a `packaged' version of Exim (source or binary), the
3359 packagers might have enabled it.
3362 Setting \\ALT@_CONFIG@_ROOT@_ONLY\\ locks out the possibility of testing a
3363 configuration using \-C-\ right through message reception and delivery, even if
3364 the caller is root. The reception works, but by that time, Exim is running as
3365 the Exim user, so when it re-execs to regain privilege for the delivery, the
3366 use of \-C-\ causes privilege to be lost. However, root can test reception and
3367 delivery using two separate commands (one to put a message on the queue, using
3368 \-odq-\, and another to do the delivery, using \-M-\).
3370 If \\ALT@_CONFIG@_PREFIX\\ is defined \(in Local/Makefile)\, it specifies a
3371 prefix string with which any file named in a \-C-\ command line option
3372 must start. In addition, the file name must not contain the sequence \"/../"\.
3373 However, if the value of the \-C-\ option is identical to the value of
3374 \\CONFIGURE@_FILE\\ in \(Local/Makefile)\, Exim ignores \-C-\ and proceeds as
3375 usual. There is no default setting for \\ALT@_CONFIG@_PREFIX\\; when it is
3376 unset, any file name can be used with \-C-\.
3378 \\ALT@_CONFIG@_PREFIX\\ can be used to confine alternative configuration files
3379 to a directory to which only root has access. This prevents someone who has
3380 broken into the Exim account from running a privileged Exim with an arbitrary
3383 The \-C-\ facility is useful for ensuring that configuration files are
3384 syntactically correct, but cannot be used for test deliveries, unless the
3385 caller is privileged, or unless it is an exotic configuration that does not
3386 require privilege. No check is made on the owner or group of the files
3387 specified by this option.
3389 .option D <<macro>>=<<value>>
3390 .index macro||setting on command line
3391 This option can be used to override macro definitions in the configuration file
3392 (see section ~~SECTmacrodefs). However, like \-C-\, if it is used by an
3393 unprivileged caller, it causes Exim to give up its root privilege.
3394 If \\DISABLE@_D@_OPTION\\ is defined in \(Local/Makefile)\, the use of \-D-\ is
3395 completely disabled, and its use causes an immediate error exit.
3397 The entire option (including equals sign if present) must all be within one
3398 command line item. \-D-\ can be used to set the value of a macro to the empty
3399 string, in which case the equals sign is optional. These two commands are
3405 To include spaces in a macro definition item, quotes must be used. If you use
3406 quotes, spaces are permitted around the macro name and the equals sign. For
3409 exim '-D ABC = something' ...
3411 \-D-\ may be repeated up to 10 times on a command line.
3413 .option d <<debug options>>
3414 .index debugging||list of selectors
3415 .index debugging||\-d-\ option
3416 This option causes debugging information to be written to the standard
3417 error stream. It is restricted to admin users because debugging output may show
3418 database queries that contain password information. Also, the details of users'
3419 filter files should be protected. When \-d-\ is used, \-v-\ is assumed. If
3420 \-d-\ is given on its own, a lot of standard debugging data is output. This can
3421 be reduced, or increased to include some more rarely needed information, by
3422 following \-d-\ with a string made up of names preceded by plus or minus
3423 characters. These add or remove sets of debugging data, respectively. For
3424 example, \-d+filter-\ adds filter debugging, whereas \-d-all+filter-\ selects
3425 only filter debugging. The available debugging categories are:
3429 . The odd formatting of the lines below is deliberate. It does not affect the
3430 . SGCAL output, but by putting in the space it keeps things aligned in the man
3431 . page that is automatically generated from this text.
3433 acl $t $rm{ACL interpretation}
3434 auth $t $rm{authenticators}
3435 deliver $t $rm{general delivery logic}
3436 dns $t $rm{DNS lookups (see also resolver)}
3437 dnsbl $t $rm{DNS black list (aka RBL) code}
3438 exec $t $rm{arguments for \execv@(@)\ calls}
3439 expand $t $rm{detailed debugging for string expansions}
3440 filter $t $rm{filter handling}
3441 hints@_lookup $t $rm{hints data lookups}
3442 host@_lookup $t $rm{all types of name-to-IP address handling}
3443 ident $t $rm{ident lookup}
3444 interface $t $rm{lists of local interfaces}
3445 lists $t $rm{matching things in lists}
3446 load $t $rm{system load checks}
3447 local@_scan $t $rm{can be used by \*local@_scan()*\ (see chapter ~~CHAPlocalscan)}
3448 lookup $t $rm{general lookup code and all lookups}
3449 memory $t $rm{memory handling}
3450 pid $t $rm{add pid to debug output lines}
3451 process@_info $t $rm{setting info for the process log}
3452 queue@_run $t $rm{queue runs}
3453 receive $t $rm{general message reception logic}
3454 resolver $t $rm{turn on the DNS resolver's debugging output}
3455 retry $t $rm{retry handling}
3456 rewrite $t $rm{address rewriting}
3457 route $t $rm{address routing}
3458 timestamp $t $rm{add timestamp to debug output lines}
3459 tls $t $rm{TLS logic}
3460 transport $t $rm{transports}
3461 uid $t $rm{changes of uid/gid and looking up uid/gid}
3462 verify $t $rm{address verification logic}
3464 all $t $rm{all of the above, and also \-v-\}
3466 .index resolver, debugging output
3467 .index DNS||resolver, debugging output
3468 The \"resolver"\ option produces output only if the DNS resolver was compiled
3469 with \\DEBUG\\ enabled. This is not the case in some operating systems. Also,
3470 unfortunately, debugging output from the DNS resolver is written to stdout
3473 The default (\-d-\ with no argument) omits \"expand"\, \"filter"\,
3474 \"interface"\, \"load"\, \"memory"\, \"pid"\, \"resolver"\, and \"timestamp"\.
3475 However, the \"pid"\ selector is forced when debugging is turned on for a
3476 daemon, which then passes it on to any re-executed Exims. Exim also
3477 automatically adds the pid to debug lines when several remote deliveries are
3480 The \"timestamp"\ selector causes the current time to be inserted at the start
3481 of all debug output lines. This can be useful when trying to track down delays
3484 If the \debug@_print\ option is set in any driver, it produces output whenever
3485 any debugging is selected, or if \-v-\ is used.
3488 .option dd <<debug options>>
3489 This option behaves exactly like \-d-\ except when used on a command that
3490 starts a daemon process. In that case, debugging is turned off for the
3491 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3492 behaviour of the daemon without creating as much output as full debugging does.
3496 This is an obsolete option that is now a no-op. It used to affect the way Exim
3497 handled CR and LF characters in incoming messages. What happens now is
3498 described in section ~~SECTlineendings.
3502 .index bounce message||generating
3503 This option specifies that an incoming message is a locally-generated delivery
3504 failure report. It is used internally by Exim when handling delivery failures
3505 and is not intended for external use. Its only effect is to stop Exim
3506 generating certain messages to the postmaster, as otherwise message cascades
3507 could occur in some situations. As part of the same option, a message id may
3508 follow the characters \-E-\. If it does, the log entry for the receipt of the
3509 new message contains the id, following `R=', as a cross-reference.
3512 There are a number of Sendmail options starting with \-oe-\ which seem to be
3513 called by various programs without the leading \o\ in the option. For example,
3514 the \vacation\ program uses \-eq-\. Exim treats all options of the form
3515 \-e$it{x}-\ as synonymous with the corresponding \-oe$it{x}-\ options.
3517 .option F #<<string>>
3519 .index name||of sender
3520 This option sets the sender's full name for use when a locally-generated
3521 message is being accepted. In the absence of this option, the user's \*gecos*\
3522 entry from the password data is used. As users are generally permitted to alter
3523 their \*gecos*\ entries, no security considerations are involved. White space
3524 between \-F-\ and the <<string>> is optional.
3526 .option f #<<address>>
3527 .index sender||address
3528 .index address||sender
3530 .index envelope sender
3531 .index user||trusted
3532 This option sets the address of the envelope sender of a locally-generated
3533 message (also known as the return path). The option can normally be used only
3534 by a trusted user, but \untrusted@_set@_sender\ can be set to allow untrusted
3537 Processes running as root or the Exim user are always trusted. Other
3538 trusted users are defined by the \trusted@_users\ or \trusted@_groups\ options.
3540 In the absence of \-f-\, or if the caller is not trusted, the sender of a local
3541 message is set to the caller's login name at the default qualify domain.
3543 There is one exception to the restriction on the use of \-f-\: an empty sender
3544 can be specified by any user, trusted or not,
3546 to create a message that can never provoke a bounce. An empty sender can be
3547 specified either as an empty string, or as a pair of angle brackets with
3548 nothing between them, as in these examples of shell commands:
3550 exim -f '<>' user@domain
3551 exim -f "" user@domain
3553 In addition, the use of \-f-\ is not restricted when testing a filter file with
3554 \-bf-\ or when testing or verifying addresses using the \-bt-\ or \-bv-\
3557 Allowing untrusted users to change the sender address does not of itself make
3558 it possible to send anonymous mail. Exim still checks that the ::From:: header
3559 refers to the local user, and if it does not, it adds a ::Sender:: header,
3560 though this can be overridden by setting \no@_local@_from@_check\.
3563 White space between \-f-\ and the <<address>> is optional
3564 (that is, they can be given as two arguments or one combined argument).
3565 The sender of a locally-generated message can also be set (when permitted) by
3566 an initial `From ' line in the message -- see the description of \-bm-\ above
3567 -- but if \-f-\ is also present, it overrides `From'.
3570 .index Sendmail compatibility||\-G-\ option ignored
3571 This is a Sendmail option which is ignored by Exim.
3573 .option h #<<number>>
3574 .index Sendmail compatibility||\-h-\ option ignored
3575 This option is accepted for compatibility with Sendmail, but has no effect. (In
3576 Sendmail it overrides the `hop count' obtained by counting ::Received::
3580 .index Solaris||\*mail*\ command
3581 .index dot||in incoming, non-SMTP message
3582 This option, which has the same effect as \-oi-\, specifies that a dot on a
3583 line by itself should not terminate an incoming, non-SMTP message. I can find
3584 no documentation for this option in Solaris 2.4 Sendmail, but the \*mailx*\
3585 command in Solaris 2.4 uses it. See also \-ti-\.
3587 .option M #<<message id>>#<<message id>> ...
3588 .index forcing delivery
3589 .index delivery||forcing attempt
3590 .index frozen messages||forcing delivery
3591 This option requests Exim to run a delivery attempt on each message in turn. If
3592 any of the messages are frozen, they are automatically thawed before the
3593 delivery attempt. The settings of \queue@_domains\, \queue@_smtp@_domains\, and
3594 \hold@_domains\ are ignored.
3595 .index hints database||overriding retry hints
3596 Retry hints for any of the addresses are
3597 overridden -- Exim tries to deliver even if the normal retry time has not yet
3598 been reached. This option requires the caller to be an admin user. However,
3599 there is an option called \prod@_requires@_admin\ which can be set false to
3600 relax this restriction (and also the same requirement for the \-q-\, \-R-\, and
3604 .option Mar #<<message id>>#<<address>>#<<address>> ...
3605 .index message||adding recipients
3606 .index recipient||adding
3607 This option requests Exim to add the addresses to the list of recipients of the
3608 message (`ar' for `add recipients'). The first argument must be a message id,
3609 and the remaining ones must be email addresses. However, if the message is
3610 active (in the middle of a delivery attempt), it is not altered. This option
3611 can be used only by an admin user.
3613 .index SMTP||passed connection
3614 .index SMTP||multiple deliveries
3615 .index multiple SMTP deliveries
3616 .option MC #<<transport>>#<<hostname>>#<<sequence number>>#<<message id>>
3617 This option is not intended for use by external callers. It is used internally
3618 by Exim to invoke another instance of itself to deliver a waiting message using
3619 an existing SMTP connection, which is passed as the standard input. Details are
3620 given in chapter ~~CHAPSMTP. This must be the final option, and the caller must
3621 be root or the Exim user in order to use it.
3624 This option is not intended for use by external callers. It is used internally
3625 by Exim in conjunction with the \-MC-\ option. It signifies that the connection
3626 to the remote host has been authenticated.
3629 This option is not intended for use by external callers. It is used internally
3630 by Exim in conjunction with the \-MC-\ option. It signifies that the server to
3631 which Exim is connected supports pipelining.
3633 .option MCQ #<<process id>> <<pipe fd>>
3634 This option is not intended for use by external callers. It is used internally
3635 by Exim in conjunction with the \-MC-\ option when the original delivery was
3636 started by a queue runner. It passes on the process id of the queue runner,
3637 together with the file descriptor number of an open pipe. Closure of the pipe
3638 signals the final completion of the sequence of processes that are passing
3639 messages through the same SMTP connection.
3642 This option is not intended for use by external callers. It is used internally
3643 by Exim in conjunction with the \-MC-\ option, and passes on the fact that the
3644 SMTP \\SIZE\\ option should be used on messages delivered down the existing
3648 This option is not intended for use by external callers. It is used internally
3649 by Exim in conjunction with the \-MC-\ option, and passes on the fact that the
3650 host to which Exim is connected supports TLS encryption.
3652 .option Mc #<<message id>>#<<message id>> ...
3653 .index hints database||not overridden by \-Mc-\
3654 .index delivery||manually started, not forced
3655 This option requests Exim to run a delivery attempt on each message in turn,
3656 but unlike the \-M-\ option, it does check for retry hints, and respects any
3657 that are found. This option is not very useful to external callers. It is
3658 provided mainly for internal use by Exim when it needs to re-invoke itself in
3659 order to regain root privilege for a delivery (see chapter ~~CHAPsecurity).
3660 However, \-Mc-\ can be useful when testing, in order to run a delivery that
3661 respects retry times and other options such as \hold@_domains\ that are
3662 overridden when \-M-\ is used. Such a delivery does not count as a queue run.
3663 If you want to run a specific delivery as if in a queue run, you should use
3664 \-q-\ with a message id argument. A distinction between queue run deliveries
3665 and other deliveries is made in one or two places.
3667 .option Mes #<<message id>>#<<address>>
3668 .index message||changing sender
3669 .index sender||changing
3670 This option requests Exim to change the sender address in the message to the
3671 given address, which must be a fully qualified address or `<>' (`es' for `edit
3672 sender'). There must be exactly two arguments. The first argument must be a
3673 message id, and the second one an email address. However, if the message is
3674 active (in the middle of a delivery attempt), its status is not altered. This
3675 option can be used only by an admin user.
3677 .option Mf #<<message id>>#<<message id>> ...
3678 .index freezing messages
3679 .index message||manually freezing
3680 This option requests Exim to mark each listed message as `frozen'. This
3681 prevents any delivery attempts taking place until the message is `thawed',
3682 either manually or as a result of the \auto@_thaw\ configuration option.
3683 However, if any of the messages are active (in the middle of a delivery
3684 attempt), their status is not altered. This option can be used only by an admin
3687 .option Mg #<<message id>>#<<message id>> ...
3688 .index giving up on messages
3689 .index message||abandoning delivery attempts
3690 .index delivery||abandoning further attempts
3691 This option requests Exim to give up trying to deliver the listed messages,
3692 including any that are frozen. However, if any of the messages are active,
3693 their status is not altered.
3694 For non-bounce messages, a delivery error message is sent to the sender,
3695 containing the text `cancelled by administrator'. Bounce messages are just
3697 This option can be used only by an admin user.
3699 .option Mmad #<<message id>>#<<message id>> ...
3700 .index delivery||cancelling all
3701 This option requests Exim to mark all the recipient addresses in the messages
3702 as already delivered (`mad' for `mark all delivered'). However, if any message
3703 is active (in the middle of a delivery attempt), its status is not altered.
3704 This option can be used only by an admin user.
3706 .option Mmd #<<message id>>#<<address>>#<<address>> ...
3707 .index delivery||cancelling by address
3708 .index recipient||removing
3709 .index removing recipients
3710 This option requests Exim to mark the given addresses as already delivered
3711 (`md' for `mark delivered'). The first argument must be a message id, and the
3712 remaining ones must be email addresses. These are matched to recipient
3713 addresses in the message in a case-sensitive manner. If the message is active
3714 (in the middle of a delivery attempt), its status is not altered. This option
3715 can be used only by an admin user.
3717 .option Mrm #<<message id>>#<<message id>> ...
3718 .index removing messages
3719 .index abandoning mail
3720 .index message||manually discarding
3721 This option requests Exim to remove the given messages from the queue. No
3722 bounce messages are sent; each message is simply forgotten. However, if any of
3723 the messages are active, their status is not altered. This option can be used
3724 only by an admin user or by the user who originally caused the message to be
3725 placed on the queue.
3727 .option Mt #<<message id>>#<<message id>> ...
3728 .index thawing messages
3729 .index unfreezing messages
3730 .index frozen messages||thawing
3731 .index message||thawing frozen
3732 This option requests Exim to `thaw' any of the listed messages that are
3733 `frozen', so that delivery attempts can resume. However, if any of the messages
3734 are active, their status is not altered. This option can be used only by an
3737 .option Mvb #<<message id>>
3738 .index listing||message body
3739 .index message||listing body of
3740 This option causes the contents of the message body (-D) spool file to be
3741 written to the standard output. This option can be used only by an admin user.
3743 .option Mvh #<<message id>>
3744 .index listing||message headers
3745 .index header lines||listing
3746 .index message||listing header lines
3747 This option causes the contents of the message headers (-H) spool file to be
3748 written to the standard output. This option can be used only by an admin user.
3750 .option Mvl #<<message id>>
3751 .index listing||message log
3752 .index message||listing message log
3753 This option causes the contents of the message log spool file to be written to
3754 the standard output. This option can be used only by an admin user.
3757 This is apparently a synonym for \-om-\ that is accepted by Sendmail, so Exim
3758 treats it that way too.
3761 .index debugging||\-N-\ option
3762 .index debugging||suppressing delivery
3763 This is a debugging option that inhibits delivery of a message at the transport
3764 level. It implies \-v-\. Exim goes through many of the motions of delivery --
3765 it just doesn't actually transport the message, but instead behaves as if it
3766 had successfully done so. However, it does not make any updates to the retry
3767 database, and the log entries for deliveries are flagged with `$*$>' rather
3770 Because \-N-\ discards any message to which it applies, only root or the Exim
3771 user are allowed to use it with \-bd-\, \-q-\, \-R-\ or \-M-\. In other words,
3772 an ordinary user can use it only when supplying an incoming message to which it
3773 will apply. Although transportation never fails when \-N-\ is set, an address
3774 may be deferred because of a configuration problem on a transport, or a routing
3775 problem. Once \-N-\ has been used for a delivery attempt, it sticks to the
3776 message, and applies to any subsequent delivery attempts that may happen for
3780 .index Sendmail compatibility||\-n-\ option ignored
3781 This option is interpreted by Sendmail to mean `no aliasing'. It is ignored by
3785 This option is interpreted by Sendmail to mean `set option`. It is ignored by
3788 .option oA #<<file name>>
3789 .index Sendmail compatibility||\-oA-\ option
3790 This option is used by Sendmail in conjunction with \-bi-\ to specify an
3791 alternative alias file name. Exim handles \-bi-\ differently; see the
3794 .index SMTP||passed connection
3796 .index SMTP||multiple deliveries
3797 .index multiple SMTP deliveries
3798 This is a debugging option which limits the maximum number of messages that can
3799 be delivered down one SMTP connection, overriding the value set in any \%smtp%\
3800 transport. If <<n>> is omitted, the limit is set to 1.
3803 .index background delivery
3804 .index delivery||in the background
3805 This option applies to all modes in which Exim accepts incoming messages,
3806 including the listening daemon. It requests `background' delivery of such
3807 messages, which means that the accepting process automatically starts a
3808 delivery process for each message received, but does not wait for the delivery
3809 processes to finish.
3811 When all the messages have been received, the reception process exits, leaving
3812 the delivery processes to finish in their own time. The standard output and
3813 error streams are closed at the start of each delivery process.
3815 This is the default action if none of the \-od-\ options are present.
3817 If one of the queueing options in the configuration file
3818 (\queue@_only\ or \queue@_only@_file\, for example) is in effect, \-odb-\
3819 overrides it if \queue@_only@_override\ is set true, which is the default
3820 setting. If \queue@_only@_override\ is set false, \-odb-\ has no effect.
3823 .index foreground delivery
3824 .index delivery||in the foreground
3825 This option requests `foreground' (synchronous) delivery when Exim has accepted
3826 a locally-generated message. (For the daemon it is exactly the same as
3827 \-odb-\.) A delivery process is automatically started to deliver the
3828 message, and Exim waits for it to complete before proceeding.
3830 The original Exim reception process does not finish until the delivery
3831 process for the final message has ended. The standard error stream is left open
3834 However, like \-odb-\, this option has no effect if \queue@_only@_override\ is
3835 false and one of the queueing options in the configuration file is in effect.
3838 If there is a temporary delivery error during foreground delivery, the message
3839 is left on the queue for later delivery, and the original reception process
3840 exists. See chapter ~~CHAPnonqueueing for a way of setting up a restricted
3841 configuration that never queues messages.
3845 This option is synonymous with \-odf-\. It is provided for compatibility with
3849 .index non-immediate delivery
3850 .index delivery||suppressing immediate
3851 .index queueing incoming messages
3852 This option applies to all modes in which Exim accepts incoming messages,
3853 including the listening daemon. It specifies that the accepting process should
3854 not automatically start a delivery process for each message received. Messages
3855 are placed on the queue, and remain there until a subsequent queue runner
3856 process encounters them.
3857 There are several configuration options (such as \queue@_only\) that can be
3858 used to queue incoming messages under certain conditions. This option overrides
3859 all of them and also \-odqs-\. It always forces queueing.
3862 .index SMTP||delaying delivery
3863 This option is a hybrid between \-odb-\/\-odi-\ and \-odq-\.
3864 However, like \-odb-\ and \-odi-\, this option has no effect if
3865 \queue@_only@_override\ is false and one of the queueing options in the
3866 configuration file is in effect.
3868 When \-odqs-\ does operate, a delivery process is started for each incoming
3869 message, in the background by default, but in the foreground if \-odi-\ is also
3871 The recipient addresses are routed, and local deliveries are done in the normal
3872 way. However, if any SMTP deliveries are required, they are not done at this
3873 time, so the message remains on the queue until a subsequent queue runner
3874 process encounters it. Because routing was done, Exim knows which messages are
3875 waiting for which hosts, and so a number of messages for the same host can be
3876 sent in a single SMTP connection. The \queue@_smtp@_domains\ configuration
3877 option has the same effect for specific domains. See also the \-qq-\ option.
3880 .index error||reporting
3881 If an error is detected while a non-SMTP message is being received (for
3882 example, a malformed address), the error is reported to the sender in a mail
3884 .index return code||for \-oee-\
3885 Provided this error message is successfully sent, the Exim receiving process
3886 exits with a return code of zero. If not, the return code is 2 if the problem
3887 is that the original message has no recipients, or 1 any other error. This is
3888 the default \-oe$it{x}-\ option if Exim is called as \*rmail*\.
3891 .index error||reporting
3892 .index return code||for \-oem-\
3893 This is the same as \-oee-\, except that Exim always exits with a non-zero
3894 return code, whether or not the error message was successfully sent.
3895 This is the default \-oe$it{x}-\ option, unless Exim is called as \*rmail*\.
3898 .index error||reporting
3899 If an error is detected while a non-SMTP message is being received, the
3900 error is reported by writing a message to the standard error file (stderr).
3901 .index return code||for \-oep-\
3902 The return code is 1 for all errors.
3905 .index error||reporting
3906 This option is supported for compatibility with Sendmail, but has the same
3910 .index error||reporting
3911 This option is supported for compatibility with Sendmail, but has the same
3915 .index dot||in incoming, non-SMTP message
3916 This option, which has the same effect as \-i-\, specifies that a dot on a line
3917 by itself should not terminate an incoming, non-SMTP message.
3918 Otherwise, a single dot does terminate, though Exim does no special processing
3919 for other lines that start with a dot.
3920 This option is set by default if Exim is called as \*rmail*\. See also \-ti-\.
3923 This option is treated as synonymous with \-oi-\.
3925 .option oMa #<<host address>>
3926 .index sender||host address, specifying for local message
3927 A number of options starting with \-oM-\ can be used to set values associated
3928 with remote hosts on locally-submitted messages (that is, messages not received
3929 over TCP/IP). These options can be used by any caller in conjunction with the
3932 \-bf-\, \-bF-\, \-bt-\, or \-bv-\ testing options. In other circumstances, they
3933 are ignored unless the caller is trusted.
3935 The \-oMa-\ option sets the sender host address. This may include a port number
3936 at the end, after a full stop (period). For example:
3938 exim -bs -oMa 10.9.8.7.1234
3940 An alternative syntax is to enclose the IP address in square brackets, followed
3941 by a colon and the port number:
3943 exim -bs -oMa [10.9.8.7]:1234
3945 The IP address is placed in the \$sender@_host@_address$\ variable, and the
3946 port, if present, in \$sender@_host@_port$\.
3948 .option oMaa #<<name>>
3949 .index authentication||name, specifying for local message
3950 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMaa-\
3951 option sets the value of \$sender@_host@_authenticated$\ (the authenticator
3952 name). See chapter ~~CHAPSMTPAUTH for a discussion of SMTP authentication.
3954 .option oMai #<<string>>
3955 .index authentication||id, specifying for local message
3956 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMai-\
3958 value of \$authenticated@_id$\ (the id that was authenticated).
3959 This overrides the default value (the caller's login id) for messages from
3960 local sources. See chapter ~~CHAPSMTPAUTH for a discussion of authenticated
3963 .option oMas #<<address>>
3964 .index authentication||sender, specifying for local message
3965 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMas-\
3966 option sets the authenticated sender value
3967 in \$authenticated@_sender$\.
3968 It overrides the sender address that is created from the caller's login id for
3969 messages from local sources. See chapter ~~CHAPSMTPAUTH for a discussion of
3970 authenticated senders.
3972 .option oMi #<<interface address>>
3973 .index interface||address, specifying for local message
3974 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMi-\
3975 option sets the IP interface address value. A port number may be included,
3976 using the same syntax as for \-oMa-\.
3977 The interface address is placed in \$interface@_address$\ and the port number,
3978 if present, in \$interface@_port$\.
3980 .option oMr #<<protocol name>>
3981 .index protocol||incoming, specifying for local message
3982 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMr-\
3983 option sets the received protocol value that is stored in
3984 \$received@_protocol$\. However, this applies only when \-bs-\ is not used. For
3985 interactive SMTP input (\-bs-\), the protocol is always
3987 `local-' followed by one of the standard SMTP protocol names (see the
3988 description of \$received@_protocol$\ in section ~~SECTexpvar).
3990 For \-bS-\ (batch SMTP) however, the protocol can be set by \-oMr-\.
3992 .option oMs #<<host name>>
3993 .index sender||host name, specifying for local message
3994 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMs-\
3995 option sets the sender host name
3996 in \$sender@_host@_name$\. When this option is present, Exim does not attempt
3997 to look up a host name from an IP address; it uses the name it is given.
3999 .option oMt #<<ident string>>
4000 .index sender||ident string, specifying for local message
4001 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMt-\
4002 option sets the sender ident value
4003 in \$sender@_ident$\.
4004 The default setting for local callers is the login id of the calling process.
4007 .index Sendmail compatibility||\-om-\ option ignored
4008 In Sendmail, this option means `me too', indicating that the sender of a
4009 message should receive a copy of the message if the sender appears in an alias
4010 expansion. Exim always does this, so the option does nothing.
4013 .index Sendmail compatibility||\-oo-\ option ignored
4014 This option is ignored. In Sendmail it specifies `old style headers', whatever
4017 .option oP #<<path>>
4018 .index pid (process id)||of daemon
4019 .index daemon||process id (pid)
4020 This option is useful only in conjunction with \-bd-\ or \-q-\ with a time
4021 value. The option specifies the file to which the process id of the daemon is
4022 written. When \-oX-\ is used with \-bd-\, or when \-q-\ with a time is used
4023 without \-bd-\, this is the only way of causing Exim to write a pid file,
4024 because in those cases, the normal pid file is not used.
4026 .option or #<<time>>
4027 .index timeout||for non-SMTP input
4028 This option sets a timeout value for incoming non-SMTP messages. If it is not
4029 set, Exim will wait forever for the standard input. The value can also be set
4030 by the \receive@_timeout\ option. The format used for specifying times is
4031 described in section ~~SECTtimeformat.
4033 .option os #<<time>>
4034 .index timeout||for SMTP input
4035 .index SMTP||timeout, input
4036 This option sets a timeout value for incoming SMTP messages. The timeout
4037 applies to each SMTP command and block of data. The value can also be set by
4038 the \smtp@_receive@_timeout\ option; it defaults to 5 minutes. The format used
4039 for specifying times is described in section ~~SECTtimeformat.
4042 This option has exactly the same effect as \-v-\.
4044 .option oX #<<number or string>>
4045 .index TCP/IP||setting listening ports
4046 .index TCP/IP||setting listening interfaces
4047 .index port||receiving TCP/IP
4048 This option is relevant only when the \-bd-\ (start listening daemon) option is
4049 also given. It controls which ports and interfaces the daemon uses. Details of
4050 the syntax, and how it interacts with configuration file options, are given in
4051 chapter ~~CHAPinterfaces. When \-oX-\ is used to start a daemon, no pid file is
4052 written unless \-oP-\ is also present to specify a pid file name.
4055 .index Perl||starting the interpreter
4056 This option applies when an embedded Perl interpreter is linked with Exim (see
4057 chapter ~~CHAPperl). It overrides the setting of the \perl@_at@_start\ option,
4058 forcing the starting of the interpreter to be delayed until it is needed.
4061 .index Perl||starting the interpreter
4062 This option applies when an embedded Perl interpreter is linked with Exim (see
4063 chapter ~~CHAPperl). It overrides the setting of the \perl@_at@_start\ option,
4064 forcing the starting of the interpreter to occur as soon as Exim is started.
4066 .option p<<rval>>:<<sval>>
4067 For compatibility with Sendmail, this option
4070 -oMr <<rval>> -oMs <<sval>>
4072 It sets the incoming protocol and host name (for trusted callers). The
4073 host name and its colon can be omitted when only the protocol is to be set.
4074 Note the Exim already has two private options, \-pd-\ and \-ps-\, that refer to
4075 embedded Perl. It is therefore impossible to set a protocol value of \"p"\ or
4076 \"s"\ using this option (but that does not seem a real limitation).
4079 .index queue runner||starting manually
4080 This option is normally restricted to admin users. However, there is a
4081 configuration option called \prod@_requires@_admin\ which can be set false to
4082 relax this restriction (and also the same requirement for the \-M-\, \-R-\, and
4085 .index queue runner||description of operation
4086 The \-q-\ option starts one queue runner process. This scans the queue of
4087 waiting messages, and runs a delivery process for each one in turn. It waits
4088 for each delivery process to finish before starting the next one. A delivery
4089 process may not actually do any deliveries if the retry times for the addresses
4090 have not been reached. Use \-qf-\ (see below) if you want to override this.
4091 .index SMTP||passed connection
4092 .index SMTP||multiple deliveries
4093 .index multiple SMTP deliveries
4094 If the delivery process spawns other processes to deliver other messages down
4095 passed SMTP connections, the queue runner waits for these to finish before
4098 When all the queued messages have been considered, the original queue runner
4099 process terminates. In other words, a single pass is made over the waiting
4100 mail, one message at a time. Use \-q-\ with a time (see below) if you want this
4101 to be repeated periodically.
4103 Exim processes the waiting messages in an unpredictable order. It isn't very
4104 random, but it is likely to be different each time, which is all that matters.
4105 If one particular message screws up a remote MTA, other messages to the same
4106 MTA have a chance of getting through if they get tried first.
4108 It is possible to cause the messages to be processed in lexical message id
4109 order, which is essentially the order in which they arrived, by setting the
4110 \queue@_run@_in@_order\ option, but this is not recommended for normal use.
4112 .option q <<qflags>>
4113 The \-q-\ option may be followed by one or more flag letters that change its
4114 behaviour. They are all optional, but if more than one is present, they must
4115 appear in the correct order. Each flag is described in a separate item below.
4118 .index queue||double scanning
4119 .index queue||routing
4120 .index routing||whole queue before delivery
4121 An option starting with \-qq-\ requests a two-stage queue run. In the first
4122 stage, the queue is scanned as if the \queue@_smtp@_domains\ option matched
4123 every domain. Addresses are routed, local deliveries happen, but no remote
4125 .index hints database||remembering routing
4126 The hints database that remembers which messages are
4127 waiting for specific hosts is updated, as if delivery to those hosts had been
4128 deferred. After this is complete, a second, normal queue scan happens, with
4129 routing and delivery taking place as normal. Messages that are routed to the
4130 same host should mostly be delivered down a single SMTP
4131 .index SMTP||passed connection
4132 .index SMTP||multiple deliveries
4133 .index multiple SMTP deliveries
4134 connection because of the hints that were set up during the first queue scan.
4135 This option may be useful for hosts that are connected to the Internet
4139 .index queue||initial delivery
4140 If the \*i*\ flag is present, the queue runner runs delivery processes only for
4141 those messages that haven't previously been tried. (\*i*\ stands for `initial
4142 delivery'.) This can be helpful if you are putting messages on the queue using
4143 \-odq-\ and want a queue runner just to process the new messages.
4146 .index queue||forcing delivery
4147 .index delivery||forcing in queue run
4148 If one \*f*\ flag is present, a delivery attempt is forced for each non-frozen
4149 message, whereas without \f\ only those non-frozen addresses that have passed
4150 their retry times are tried.
4152 .option q[q][i]ff...
4153 .index frozen messages||forcing delivery
4154 If \*ff*\ is present, a delivery attempt is forced for every message, whether
4157 .option q[q][i][f[f]]l
4158 .index queue||local deliveries only
4159 The \*l*\ (the letter `ell') flag specifies that only local deliveries are to be
4160 done. If a message requires any remote deliveries, it remains on the queue for
4163 .option q <<qflags>>#<<start id>>#<<end id>>
4164 .index queue||delivering specific messages
4165 When scanning the queue, Exim can be made to skip over messages whose ids are
4166 lexically less than a given value by following the \-q-\ option with a starting
4167 message id. For example:
4169 exim -q 0t5C6f-0000c8-00
4171 Messages that arrived earlier than \"0t5C6f-0000c8-00"\ are not inspected. If a
4172 second message id is given, messages whose ids are lexically greater than it
4173 are also skipped. If the same id is given twice, for example,
4175 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4177 just one delivery process is started, for that message. This differs from \-M-\
4178 in that retry data is respected, and it also differs from \-Mc-\ in that it
4179 counts as a delivery from a queue run. Note that the selection mechanism does
4180 not affect the order in which the messages are scanned. There are also other
4181 ways of selecting specific sets of messages for delivery in a queue run -- see
4184 .option q <<qflags>><<time>>
4185 .index queue runner||starting periodically
4186 .index periodic queue running
4187 When a time value is present, the \-q-\ option causes Exim to run as a daemon,
4188 starting a queue runner process at intervals specified by the given time value
4189 (whose format is described in section ~~SECTtimeformat). This form of the \-q-\
4190 option is commonly combined with the \-bd-\ option, in which case a single
4191 daemon process handles both functions. A common way of starting up a combined
4192 daemon at system boot time is to use a command such as
4194 /usr/exim/bin/exim -bd -q30m
4196 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4197 process every 30 minutes.
4199 When a daemon is started by \-q-\ with a time value, but without \-bd-\, no pid
4200 file is written unless one is explicitly requested by the \-oP-\ option.
4202 .option qR <<rsflags>>#<<string>>
4203 This option is synonymous with \-R-\. It is provided for Sendmail
4206 .option qS <<rsflags>>#<<string>>
4207 This option is synonymous with \-S-\.
4209 .option R <<rsflags>>#<<string>>
4210 .index queue runner||for specific recipients
4211 .index delivery||to given domain
4212 .index domain||delivery to
4213 The <<rsflags>> may be empty, in which case the white space before the string
4214 is optional, unless the string is \*f*\, \*ff*\, \*r*\, \*rf*\, or \*rff*\,
4215 which are the possible values for <<rsflags>>. White space is required if
4216 <<rsflags>> is not empty.
4218 This option is similar to \-q-\ with no time value, that is, it causes Exim to
4219 perform a single queue run, except that, when scanning the messages on the
4220 queue, Exim processes only those that have at least one undelivered recipient
4221 address containing the given string, which is checked in a case-independent
4222 way. If the <<rsflags>> start with \*r*\, <<string>> is interpreted as a regular
4223 expression; otherwise it is a literal string.
4225 Once a message is selected, all its addresses are processed. For the first
4226 selected message, Exim overrides any retry information and forces a delivery
4227 attempt for each undelivered address. This means that if delivery of any
4228 address in the first message is successful, any existing retry information is
4229 deleted, and so delivery attempts for that address in subsequently selected
4230 messages (which are processed without forcing) will run. However, if delivery
4231 of any address does not succeed, the retry information is updated, and in
4232 subsequently selected messages, the failing address will be skipped.
4234 If the <<rsflags>> contain \*f*\ or \*ff*\, the delivery forcing applies to all
4235 selected messages, not just the first;
4236 .index frozen messages||forcing delivery
4237 frozen messages are included when \*ff*\ is present.
4239 The \-R-\ option makes it straightforward to initiate delivery of all messages
4240 to a given domain after a host has been down for some time. When the SMTP
4241 command \\ETRN\\ is accepted by its ACL (see chapter ~~CHAPACL), its default
4242 effect is to run Exim with the \-R-\ option, but it can be configured to run an
4243 arbitrary command instead.
4246 This is a documented (for Sendmail) obsolete alternative name for \-f-\.
4248 .index delivery||from given sender
4249 .option S <<rsflags>>#<<string>>
4250 .index queue runner||for specific senders
4251 This option acts like \-R-\ except that it checks the string against each
4252 message's sender instead of against the recipients. If \-R-\ is also set, both
4253 conditions must be met for a message to be selected. If either of the options
4254 has \*f*\ or \*ff*\ in its flags, the associated action is taken.
4256 .option Tqt#<<times>>
4257 This an option that is exclusively for use by the Exim testing suite.
4258 It is not recognized when Exim is run normally. It allows for the setting up
4259 of explicit `queue times' so that various warning/retry features can be
4263 .index recipient||extracting from header lines
4264 .index ::Bcc:: header line
4265 .index ::Cc:: header line
4266 .index ::To:: header line
4267 When Exim is receiving a locally-generated, non-SMTP message on its standard
4268 input, the \-t-\ option causes the recipients of the message to be obtained
4269 from the ::To::, ::Cc::, and ::Bcc:: header lines in the message instead of from
4270 the command arguments. The addresses are extracted before any rewriting takes
4273 .index Sendmail compatibility||\-t-\ option
4274 If the command has any arguments, they specify addresses to which the message
4275 is $it{not} to be delivered. That is, the argument addresses are removed from
4276 the recipients list obtained from the headers. This is compatible with Smail 3
4277 and in accordance with the documented behaviour of several versions of
4278 Sendmail, as described in man pages on a number of operating systems (e.g.
4279 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail $it{add}
4280 argument addresses to those obtained from the headers, and the O'Reilly
4281 Sendmail book documents it that way. Exim can be made to add argument addresses
4282 instead of subtracting them by setting the option
4283 \extract__addresses__remove__arguments\ false.
4285 If a ::Bcc:: header line is present, it is removed from the message unless
4286 there is no ::To:: or ::Cc::, in which case a ::Bcc:: line with no data is
4287 created. This is necessary for conformity with the original RFC 822 standard;
4288 the requirement has been removed in RFC 2822, but that is still very new.
4290 .index \Resent@-\ header lines||with \-t-\
4291 If there are any \Resent@-\ header lines in the message, Exim extracts
4292 recipients from all ::Resent-To::, ::Resent-Cc::, and ::Resent-Bcc:: header
4293 lines instead of from ::To::, ::Cc::, and ::Bcc::. This is for compatibility
4294 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4295 \-t-\ was used in conjunction with \Resent@-\ header lines.)
4297 RFC 2822 talks about different sets of \Resent@-\ header lines (for when a
4298 message is resent several times). The RFC also specifies that they should be
4299 added at the front of the message, and separated by ::Received:: lines. It is
4300 not at all clear how \-t-\ should operate in the present of multiple sets,
4301 nor indeed exactly what constitutes a `set'.
4302 In practice, it seems that MUAs do not follow the RFC. The \Resent@-\ lines are
4303 often added at the end of the header, and if a message is resent more than
4304 once, it is common for the original set of \Resent@-\ headers to be renamed as
4305 \X-Resent@-\ when a new set is added. This removes any possible ambiguity.
4308 This option is exactly equivalent to \-t-\ \-i-\. It is provided for
4309 compatibility with Sendmail.
4311 .option tls-on-connect
4312 .index TLS||use without STARTTLS
4313 .index TLS||automatic start
4314 This option is available when Exim is compiled with TLS support.
4316 It forces all incoming SMTP connections to behave as if the incoming port is
4317 listed in the \tls@_on@_connect@_ports\ option. See section ~~SECTsupobssmt and
4318 chapter ~~CHAPTLS for further details.
4322 .index Sendmail compatibility||\-U-\ option ignored
4323 Sendmail uses this option for `initial message submission', and its
4324 documentation states that in future releases, it may complain about
4325 syntactically invalid messages rather than fixing them when this flag is not
4326 set. Exim ignores this option.
4329 This option causes Exim to write information to the standard error stream,
4330 describing what it is doing. In particular, it shows the log lines for
4331 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4332 dialogue is shown. Some of the log lines shown may not actually be written to
4333 the log if the setting of \log@_selector\ discards them. Any relevant selectors
4334 are shown with each log line. If none are shown, the logging is unconditional.
4337 AIX uses \-x-\ for a private purpose (`mail from a local mail program has
4338 National Language Support extended characters in the body of the mail item').
4339 It sets \-x-\ when calling the MTA from its \mail\ command. Exim ignores this
4350 . ============================================================================
4351 .chapter The Exim run time configuration file
4352 .set runningfoot "configuration file"
4353 .rset CHAPconf ~~chapter
4355 .index run time configuration
4356 .index configuration file||general description
4357 .index \\CONFIGURE@_FILE\\
4358 .index configuration file||errors in
4359 .index error||in configuration file
4360 .index return code||for bad configuration
4361 Exim uses a single run time configuration file that is read whenever an Exim
4362 binary is executed. Note that in normal operation, this happens frequently,
4363 because Exim is designed to operate in a distributed manner, without central
4367 If a syntax error is detected while reading the configuration file, Exim
4368 writes a message on the standard error, and exits with a non-zero return code.
4369 The message is also written to the panic log. \**Note**\: only simple syntax
4370 errors can be detected at this time. The values of any expanded options are
4371 not checked until the expansion happens, even when the expansion does not
4372 actually alter the string.
4376 The name of the configuration file is compiled into the binary for security
4377 reasons, and is specified by the \\CONFIGURE@_FILE\\ compilation option. In
4378 most configurations, this specifies a single file. However, it is permitted to
4379 give a colon-separated list of file names, in which case Exim uses the first
4380 existing file in the list.
4382 .index \\EXIM@_USER\\
4383 .index \\EXIM@_GROUP\\
4384 .index \\CONFIGURE@_OWNER\\
4385 .index \\CONFIGURE@_GROUP\\
4386 .index configuration file||ownership
4387 .index ownership||configuration file
4388 The run time configuration file must be owned by root or by the user that is
4389 specified at compile time by the \\EXIM@_USER\\ option, or by the user that is
4390 specified at compile time by the \\CONFIGURE@_OWNER\\ option (if set). The
4391 configuration file must not be world-writeable or group-writeable, unless its
4392 group is the one specified at compile time by the \\EXIM@_GROUP\\ option
4394 or by the \\CONFIGURE@_GROUP\\ option.
4397 \**Warning**\: In a conventional configuration, where the Exim binary is setuid
4398 to root, anybody who is able to edit the run time configuration file has an
4399 easy way to run commands as root. If you make your mail administrators members
4400 of the Exim group, but do not trust them with root, make sure that the run time
4401 configuration is not group writeable.
4403 A default configuration file, which will work correctly in simple situations,
4404 is provided in the file \(src/configure.default)\. If \\CONFIGURE@_FILE\\
4405 defines just one file name, the installation process copies the default
4406 configuration to a new file of that name if it did not previously exist. If
4407 \\CONFIGURE@_FILE\\ is a list, no default is automatically installed. Chapter
4408 ~~CHAPdefconfil is a `walk-through' discussion of the default configuration.
4411 .section Using a different configuration file
4412 .index configuration file||alternate
4413 A one-off alternate configuration can be specified by the \-C-\ command line
4414 option, which may specify a single file or a list of files. However, when \-C-\
4415 is used, Exim gives up its root privilege, unless called by root or the Exim
4416 user (or unless the argument for \-C-\ is identical to the built-in value from
4417 \\CONFIGURE@_FILE\\). \-C-\ is useful mainly for checking the syntax of
4418 configuration files before installing them. No owner or group checks are done
4419 on a configuration file specified by \-C-\.
4421 The privileged use of \-C-\ by the Exim user can be locked out by setting
4422 \\ALT@_CONFIG@_ROOT@_ONLY\\ in \(Local/Makefile)\ when building Exim. However,
4423 if you do this, you also lock out the possibility of testing a
4424 configuration using \-C-\ right through message reception and delivery, even if
4425 the caller is root. The reception works, but by that time, Exim is running as
4426 the Exim user, so when it re-execs to regain privilege for the delivery, the
4427 use of \-C-\ causes privilege to be lost. However, root can test reception and
4428 delivery using two separate commands (one to put a message on the queue, using
4429 \-odq-\, and another to do the delivery, using \-M-\).
4431 If \\ALT@_CONFIG@_PREFIX\\ is defined \(in Local/Makefile)\, it specifies a
4432 prefix string with which any file named in a \-C-\ command line option must
4433 start. In addition, the file name must not contain the sequence \"/../"\. There
4434 is no default setting for \\ALT@_CONFIG@_PREFIX\\; when it is unset, any file
4435 name can be used with \-C-\.
4437 One-off changes to a configuration can be specified by the \-D-\ command line
4438 option, which defines and overrides values for macros used inside the
4439 configuration file. However, like \-C-\, the use of this option by a
4440 non-privileged user causes Exim to discard its root privilege.
4441 If \\DISABLE@_D@_OPTION\\ is defined in \(Local/Makefile)\, the use of \-D-\ is
4442 completely disabled, and its use causes an immediate error exit.
4444 Some sites may wish to use the same Exim binary on different machines that
4445 share a file system, but to use different configuration files on each machine.
4446 If \\CONFIGURE@_FILE@_USE@_NODE\\ is defined in \(Local/Makefile)\, Exim first
4447 looks for a file whose name is the configuration file name followed by a dot
4448 and the machine's node name, as obtained from the \*uname()*\ function. If this
4449 file does not exist, the standard name is tried. This processing occurs for
4450 each file name in the list given by \\CONFIGURE@_FILE\\ or \-C-\.
4452 In some esoteric situations different versions of Exim may be run under
4453 different effective uids and the \\CONFIGURE@_FILE@_USE@_EUID\\ is defined to
4454 help with this. See the comments in \(src/EDITME)\ for details.
4457 .section Configuration file format
4458 .rset SECTconffilfor "~~chapter.~~section"
4459 .index configuration file||format of
4460 .index format||configuration file
4461 Exim's configuration file is divided into a number of different parts. General
4462 option settings must always appear at the start of the file. The other parts
4463 are all optional, and may appear in any order. Each part other than the first
4464 is introduced by the word `begin' followed by the name of the part. The
4468 \*ACL*\: Access control lists for controlling incoming SMTP mail.
4470 .index \\AUTH\\||configuration
4471 \*authenticators*\: Configuration settings for the authenticator drivers. These
4472 are concerned with the SMTP \\AUTH\\ command (see chapter ~~CHAPSMTPAUTH).
4474 \*routers*\: Configuration settings for the router drivers. Routers process
4475 addresses and determine how the message is to be delivered.
4477 \*transports*\: Configuration settings for the transport drivers. Transports
4478 define mechanisms for copying messages to destinations.
4480 \*retry*\: Retry rules, for use when a message cannot be immediately delivered.
4482 \*rewrite*\: Global address rewriting rules, for use when a message arrives and
4483 when new addresses are generated during delivery.
4485 \*local@_scan*\: Private options for the \*local@_scan()*\ function. If you
4486 want to use this feature, you must set
4488 LOCAL_SCAN_HAS_OPTIONS=yes
4490 in \(Local/Makefile)\ before building Exim. Full details of the
4491 \*local@_scan()*\ facility are given in chapter ~~CHAPlocalscan.
4493 .index configuration file||leading whitespace in
4494 .index configuration file||trailing whitespace in
4495 .index whitespace||in configuration file
4497 Leading and trailing whitespace in configuration lines is always ignored.
4499 Blank lines in the file, and lines starting with a @# character (ignoring
4500 leading white space) are treated as comments and are ignored. \**Note**\: a
4501 @# character other than at the beginning of a line is not treated specially,
4502 and does not introduce a comment.
4504 Any non-comment line can be continued by ending it with a backslash.
4506 Note that the general rule for whitespace means that trailing white space after
4507 the backslash is ignored, and leading white space at the start of continuation
4508 lines is also ignored.
4510 Comment lines beginning with @# (but not empty lines) may appear in the middle
4511 of a sequence of continuation lines.
4513 A convenient way to create a configuration file is to start from the
4514 default, which is supplied in \(src/configure.default)\, and add, delete, or
4515 change settings as required.
4517 The ACLs, retry rules, and rewriting rules have their own syntax which is
4518 described in chapters ~~CHAPACL, ~~CHAPretry, and ~~CHAPrewrite, respectively.
4519 The other parts of the configuration file have some syntactic items in common,
4520 and these are described below, from section ~~SECTcos onwards. Before that, the
4521 inclusion, macro, and conditional facilities are described.
4524 .section File inclusions in the configuration file
4525 .index inclusions in configuration file
4526 .index configuration file||including other files
4527 .index .include in configuration file
4528 .index .include@_if@_exists in configuration file
4529 You can include other files inside Exim's run time configuration file by
4532 @.include <<file name>>
4536 @.include@_if@_exists <<file name>>
4538 on a line by itself. Double quotes round the file name are optional. If you use
4539 the first form, a configuration error occurs if the file does not exist; the
4540 second form does nothing for non-existent files.
4542 Includes may be nested to any depth, but remember that Exim reads its
4543 configuration file often, so it is a good idea to keep them to a minimum.
4544 If you change the contents of an included file, you must HUP the daemon,
4545 because an included file is read only when the configuration itself is read.
4547 The processing of inclusions happens early, at a physical line level, so, like
4548 comment lines, an inclusion can be used in the middle of an option setting,
4551 hosts_lookup = a.b.c \
4554 Include processing happens
4556 macro processing (see below). Its effect is to process the lines of the file as
4557 if they occurred inline where the inclusion appears.
4560 .section Macros in the configuration file
4561 .rset SECTmacrodefs "~~chapter.~~section"
4562 .index macro||description of
4563 .index configuration file||macros
4564 If a line in the main part of the configuration (that is, before the first
4565 `begin' line) begins with an upper case letter, it is taken as a macro
4566 definition, and must be of the form
4568 <<name>> = <<rest of line>>
4570 The name must consist of letters, digits, and underscores, and need not all be
4571 in upper case, though that is recommended. The rest of the line, including any
4572 continuations, is the replacement text, and has leading and trailing white
4573 space removed. Quotes are not removed. The replacement text can never end with
4574 a backslash character, but this doesn't seem to be a serious limitation.
4576 Once a macro is defined, all subsequent lines in the file (and any included
4577 files) are scanned for the macro name; if there are several macros, the line is
4578 scanned for each in turn, in the order in which they are defined. The
4579 replacement text is not re-scanned for the current macro, though it is scanned
4580 for subsequently defined macros. For this reason, a macro name may not contain
4581 the name of a previously defined macro as a substring. You could, for example,
4584 ABCD_XYZ = <<something>>
4585 ABCD = <<something else>>
4587 but putting the definitions in the opposite order would provoke a configuration
4590 Macro expansion is applied to individual lines from the file, before checking
4591 for line continuation or file inclusion (see below). If a line consists solely
4592 of a macro name, and the expansion of the macro is empty, the line is ignored.
4593 A macro at the start of a line may turn the line into a comment line or a
4596 As an example of macro usage, consider a configuration where aliases are looked
4597 up in a MySQL database. It helps to keep the file less cluttered if long
4598 strings such as SQL statements are defined separately as macros, for example:
4600 ALIAS_QUERY = select mailbox from user where \
4601 login=${quote_mysql:$local_part};
4603 This can then be used in a \%redirect%\ router setting like this:
4605 data = ${lookup mysql{ALIAS_QUERY}}
4607 In earlier versions of Exim macros were sometimes used for domain, host, or
4608 address lists. In Exim 4 these are handled better by named lists -- see section
4611 Macros in the configuration file can be overridden by the \-D-\ command line
4612 option, but Exim gives up its root privilege when \-D-\ is used, unless called
4613 by root or the Exim user.
4616 .section Conditional skips in the configuration file
4617 .index configuration file||conditional skips
4619 You can use the directives \".ifdef"\, \".ifndef"\, \".elifdef"\,
4620 \".elifndef"\, \".else"\, and \".endif"\ to dynamically include or exclude
4621 portions of the configuration file. The processing happens whenever the file is
4622 read (that is, when an Exim binary starts to run).
4624 The implementation is very simple. Instances of the first four directives must
4625 be followed by text that includes the names of one or macros. The condition
4626 that is tested is whether or not any macro substitution has taken place in the
4630 message@_size@_limit = 50M
4632 message@_size@_limit = 100M
4635 sets a message size limit of 50M if the macro \"AAA"\ is defined, and 100M
4636 otherwise. If there is more than one macro named on the line, the condition
4637 is true if any of them are defined. That is, it is an `or' condition. To
4638 obtain an `and' condition, you need to use nested \".ifdef"\s.
4640 Although you can use a macro expansion to generate one of these directives,
4641 it is not very useful, because the condition `there was a macro substitution
4642 in this line' will always be true.
4644 Text following \".else"\ and \".endif"\ is ignored, and can be used as comment
4645 to clarify complicated nestings.
4648 .section Common option syntax
4649 .rset SECTcos "~~chapter.~~section"
4650 .index common option syntax
4651 .index syntax of common options
4652 .index configuration file||common option syntax
4653 For the main set of options, driver options, and \*local@_scan()*\ options,
4654 each setting is on a line by itself, and starts with a name consisting of
4655 lower-case letters and underscores. Many options require a data value, and in
4656 these cases the name must be followed by an equals sign (with optional white
4657 space) and then the value. For example:
4659 qualify_domain = mydomain.example.com
4661 Some option settings may contain sensitive data, for example, passwords for
4662 accessing databases. To stop non-admin users from using the \-bP-\ command line
4663 option to read these values, you can precede the option settings with the word
4664 `hide'. For example:
4666 hide mysql_servers = localhost/users/admin/secret-password
4668 For non-admin users, such options are displayed like this:
4670 mysql_servers = <value not displayable>
4672 If `hide' is used on a driver option, it hides the value of that option on all
4673 instances of the same driver.
4675 The following sections describe the syntax used for the different data types
4676 that are found in option settings.
4678 .section Boolean options
4679 .index format||boolean
4680 .index boolean configuration values
4681 Options whose type is given as boolean are on/off switches. There are two
4682 different ways of specifying such options: with and without a data value. If
4683 the option name is specified on its own without data, the switch is turned on;
4684 if it is preceded by `no@_' or `not@_' the switch is turned off. However,
4685 boolean options may optionally be followed by an equals sign and one of the
4686 words `true', `false', `yes', or `no', as an alternative syntax. For example,
4687 the following two settings have exactly the same effect:
4692 The following two lines also have the same (opposite) effect:
4697 You can use whichever syntax you prefer.
4701 .section Integer values
4702 .index integer configuration values
4703 .index format||integer
4704 If an integer data item starts with the characters `0x', the remainder of it
4705 is interpreted as a hexadecimal number. Otherwise, it is treated as octal if it
4706 starts with the digit 0, and decimal if not. If an integer value is followed by
4707 the letter K, it is multiplied by 1024; if it is followed by the letter M, it
4708 is multiplied by 1024x1024.
4710 When the values of integer option settings are output, values which are an
4711 exact multiple of 1024 or 1024x1024 are
4712 sometimes, but not always,
4713 printed using the letters K and M. The printing style is independent of the
4714 actual input format that was used.
4716 .section Octal integer values
4717 .index integer format
4718 .index format||octal integer
4719 The value of an option specified as an octal integer is always interpreted in
4720 octal, whether or not it starts with the digit zero. Such options are always
4724 .section Fixed point number values
4725 .index fixed point configuration values
4726 .index format||fixed point
4727 A fixed point number consists of a decimal integer, optionally followed by a
4728 decimal point and up to three further digits.
4731 .section Time interval values
4732 .index time interval||specifying in configuration
4733 .index format||time interval
4734 .rset SECTtimeformat "~~chapter.~~section"
4735 A time interval is specified as a sequence of numbers, each followed by one of
4736 the following letters, with no intervening white space:
4745 For example, `3h50m' specifies 3 hours and 50 minutes. The values of time
4746 intervals are output in the same format.
4747 Exim does not restrict the values; it is perfectly acceptable, for example, to
4748 specify `90m' instead of `1h30m'.
4751 .section String values
4752 .index string||format of configuration values
4753 .index format||string
4754 .rset SECTstrings "~~chapter.~~section"
4755 If a string data item does not start with a double-quote character, it is taken
4756 as consisting of the remainder of the line plus any continuation lines,
4757 starting at the first character after any leading white space, with trailing
4758 white space characters removed, and with no interpretation of the characters in
4759 the string. Because Exim removes comment lines (those beginning with @#) at an
4760 early stage, they can appear in the middle of a multi-line string. The
4761 following settings are therefore equivalent:
4763 trusted_users = uucp:mail
4765 trusted_users = uucp:\
4766 # This comment line is ignored
4769 .index string||quoted
4770 .index escape characters in quoted strings
4771 If a string does start with a double-quote, it must end with a closing
4772 double-quote, and any backslash characters other than those used for line
4773 continuation are interpreted as escape characters, as follows:
4776 @\@\ $t $rm{single backslash}
4778 @\r $t $rm{carriage return}
4780 @\<<octal digits>> $t $rm{up to 3 octal digits specify one character}
4781 @\x<<hex digits>> $t $rm{up to 2 hexadecimal digits specify one character}
4783 If a backslash is followed by some other character, including a double-quote
4784 character, that character replaces the pair.
4786 Quoting is necessary only if you want to make use of the backslash escapes to
4787 insert special characters, or if you need to specify a value with leading or
4788 trailing spaces. These cases are rare, so quoting is almost never needed in
4789 current versions of Exim. In versions of Exim before 3.14, quoting was required
4790 in order to continue lines, so you may come across older configuration files
4791 and examples that apparently quote unnecessarily.
4793 .section Expanded strings
4794 .index string||expansion, definition of
4795 .index expansion||definition of
4796 Some strings in the configuration file are subjected to \*string expansion*\,
4797 by which means various parts of the string may be changed according to the
4798 circumstances (see chapter ~~CHAPexpand). The input syntax for such strings is
4799 as just described; in particular, the handling of backslashes in quoted strings
4800 is done as part of the input process, before expansion takes place. However,
4801 backslash is also an escape character for the expander, so any backslashes that
4802 are required for that reason must be doubled if they are within a quoted
4803 configuration string.
4805 .section User and group names
4806 .index user name||format of
4807 .index format||user name
4808 .index group||name format
4809 .index format||group name
4810 User and group names are specified as strings, using the syntax described
4811 above, but the strings are interpreted specially. A user or group name must
4812 either consist entirely of digits, or be a name that can be looked up using the
4813 \*getpwnam()*\ or \*getgrnam()*\ function, as appropriate.
4815 .section List construction
4816 .index list||syntax of in configuration
4817 .index format||list item in configuration
4818 .index string list, definition
4819 .rset SECTlistconstruct "~~chapter.~~section"
4820 The data for some configuration options is a list of items, with colon as the
4821 default separator. Many of these options are shown with type `string list' in
4822 the descriptions later in this document. Others are listed as `domain list',
4823 `host list', `address list', or `local part list'. Syntactically, they are all
4824 the same; however, those other than `string list' are subject to particular
4825 kinds of interpretation, as described in chapter ~~CHAPdomhosaddlists.
4827 In all these cases, the entire list is treated as a single string as far as the
4828 input syntax is concerned. The \trusted@_users\ setting in section
4829 ~~SECTstrings above is an example. If a colon is actually needed in an item in
4830 a list, it must be entered as two colons. Leading and trailing white space on
4831 each item in a list is ignored. This makes it possible to include items that
4832 start with a colon, and in particular, certain forms of IPv6 address. For
4835 local_interfaces = 127.0.0.1 : ::::1
4837 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address
4839 .index list||separator, changing
4840 .index IPv6||addresses in lists
4841 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
4842 introduced to allow the separator character to be changed. If a list begins
4843 with a left angle bracket, followed by any punctuation character, that
4844 character is used instead of colon as the list separator. For example, the list
4845 above can be rewritten to use a semicolon separator like this:
4847 local_interfaces = <; 127.0.0.1 ; ::1
4849 This facility applies to all lists, with the exception of the list in
4850 \log@_file@_path\. It is recommended that the use of non-colon separators be
4851 confined to circumstances where they really are needed.
4855 .section Empty items in lists
4856 .rset SECTempitelis "~~chapter.~~section"
4857 .index list||empty item in
4858 An empty item at the end of a list is always ignored. In other words, trailing
4859 separator characters are ignored. Thus, the list in
4861 senders = user@domain :
4863 contains only a single item. If you want to include an empty string as one item
4864 in a list, it must not be the last item. For example, this list contains three
4865 items, the second of which is empty:
4867 senders = user1@domain : : user2@domain
4869 \**Note**\: there must be whitespace between the two colons, as otherwise they
4870 are interpreted as representing a single colon data character (and the list
4871 would then contain just one item). If you want to specify a list that contains
4872 just one, empty item, you can do it as in this example:
4876 In this case, the first item is empty, and the second is discarded because it
4877 is at the end of the list.
4881 .section Format of driver configurations
4882 .rset SECTfordricon "~~chapter.~~section"
4883 .index drivers||configuration format
4884 There are separate parts in the configuration for defining routers, transports,
4885 and authenticators. In each part, you are defining a number of driver
4886 instances, each with its own set of options. Each driver instance is defined by
4887 a sequence of lines like this:
4894 In the following example, the instance name is \%localuser%\, and it is
4895 followed by three options settings:
4900 transport = local_delivery
4902 For each driver instance, you specify which Exim code module it uses -- by the
4903 setting of the \driver\ option -- and (optionally) some configuration settings.
4904 For example, in the case of transports, if you want a transport to deliver with
4905 SMTP you would use the \%smtp%\ driver; if you want to deliver to a local file
4906 you would use the \%appendfile%\ driver. Each of the drivers is described in
4907 detail in its own separate chapter later in this manual.
4909 You can have several routers, transports, or authenticators that are based on
4910 the same underlying driver (each must have a different name).
4912 The order in which routers are defined is important, because addresses are
4913 passed to individual routers one by one, in order. The order in which
4914 transports are defined does not matter at all. The order in which
4915 authenticators are defined is used only when Exim, as a client, is searching
4916 them to find one that matches an authentication mechanism offered by the
4919 .index generic options
4920 .index options||generic, definition of
4921 Within a driver instance definition, there are two kinds of option:
4922 $it{generic} and $it{private}. The generic options are those that apply to all
4923 drivers of the same type (that is, all routers, all transports or all
4925 The \driver\ option is a generic option that must appear in every definition.
4926 .index private options
4927 The private options are special for each driver, and none need appear, because
4928 they all have default values.
4930 The options may appear in any order, except that the \driver\ option must
4931 precede any private options, since these depend on the particular driver. For
4932 this reason, it is recommended that \driver\ always be the first option.
4934 Driver instance names, which are used for reference in log entries and
4935 elsewhere, can be any sequence of letters, digits, and underscores (starting
4936 with a letter) and must be unique among drivers of the same type. A router and
4937 a transport (for example) can each have the same name, but no two router
4938 instances can have the same name. The name of a driver instance should not be
4939 confused with the name of the underlying driver module. For example, the
4940 configuration lines:
4945 create an instance of the \%smtp%\ transport driver whose name is
4946 \%remote@_smtp%\. The same driver code can be used more than once, with
4947 different instance names and different option settings each time. A second
4948 instance of the \%smtp%\ transport, with different options, might be defined
4954 command_timeout = 10s
4956 The names \%remote@_smtp%\ and \%special@_smtp%\ would be used to reference
4957 these transport instances from routers, and these names would appear in log
4960 Comment lines may be present in the middle of driver specifications. The full
4961 list of option settings for any particular driver instance, including all the
4962 defaulted values, can be extracted by making use of the \-bP-\ command line
4974 . ============================================================================
4975 .chapter The default configuration file
4976 .set runningfoot "default configuration"
4977 .rset CHAPdefconfil "~~chapter"
4978 .index configuration file||default, `walk through'
4979 .index default||configuration file `walk through'
4980 The default configuration file supplied with Exim as \(src/configure.default)\
4981 is sufficient for a host with simple mail requirements. As an introduction to
4982 the way Exim is configured, this chapter `walks through' the default
4983 configuration, giving brief explanations of the settings. Detailed descriptions
4984 of the options are given in subsequent chapters. The default configuration file
4985 itself contains extensive comments about ways you might want to modify the
4986 initial settings. However, note that there are many options that are not
4987 mentioned at all in the default configuration.
4990 .section Main configuration settings
4991 The main (global) configuration option settings must always come first in the
4992 file. The first thing you'll see in the file, after some initial comments, is
4995 # primary_hostname =
4997 This is a commented-out setting of the \primary@_hostname\ option. Exim needs
4998 to know the official, fully qualified name of your host, and this is where you
4999 can specify it. However, in most cases you do not need to set this option. When
5000 it is unset, Exim uses the \*uname()*\ system function to obtain the host name.
5002 The first three non-comment configuration lines are as follows:
5004 domainlist local_domains = @
5005 domainlist relay_to_domains =
5006 hostlist relay_from_hosts = 127.0.0.1
5008 These are not, in fact, option settings. They are definitions of two named
5009 domain lists and one named host list. Exim allows you to give names to lists of
5010 domains, hosts, and email addresses, in order to make it easier to manage the
5011 configuration file (see section ~~SECTnamedlists).
5013 The first line defines a domain list called \*local@_domains*\; this is used
5014 later in the configuration to identify domains that are to be delivered
5016 .index @@ in a domain list
5017 There is just one item in this list, the string `@@'. This is a special form of
5018 entry which means `the name of the local host'. Thus, if the local host is
5019 called \*a.host.example*\, mail to \*any.user@@a.host.example*\ is expected to
5020 be delivered locally. Because the local host's name is referenced indirectly,
5021 the same configuration file can be used on different hosts.
5023 The second line defines a domain list called \*relay@_to@_domains*\, but the
5024 list itself is empty. Later in the configuration we will come to the part that
5025 controls mail relaying through the local host; it allows relaying to any
5026 domains in this list. By default, therefore, no relaying on the basis of a mail
5027 domain is permitted.
5029 The third line defines a host list called \*relay@_from@_hosts*\. This list is
5030 used later in the configuration to permit relaying from any host or IP address
5031 that matches the list. The default contains just the IP address of the IPv4
5032 loopback interface, which means that processes on the local host are able to
5033 submit mail for relaying by sending it over TCP/IP to that interface. No other
5034 hosts are permitted to submit messages for relaying.
5036 Just to be sure there's no misunderstanding: at this point in the configuration
5037 we aren't actually setting up any controls. We are just defining some domains
5038 and hosts that will be used in the controls that are specified later.
5040 The next configuration line is a genuine option setting:
5042 acl_smtp_rcpt = acl_check_rcpt
5044 This option specifies an \*Access Control List*\ (ACL) which is to be used
5045 during an incoming SMTP session for every recipient of a message (every
5046 \\RCPT\\ command). The name of the list is \*acl@_check@_rcpt*\, and we will
5047 come to its definition below, in the ACL section of the configuration. ACLs
5048 control which recipients are accepted for an incoming message -- if a
5049 configuration does not provide an ACL to check recipients, no SMTP mail can be
5052 Two commented-out options settings are next:
5055 # qualify_recipient =
5057 The first of these specifies a domain that Exim uses when it constructs a
5058 complete email address from a local login name. This is often needed when Exim
5059 receives a message from a local process. If you do not set \qualify@_domain\,
5060 the value of \primary@_hostname\ is used. If you set both of these options, you
5061 can have different qualification domains for sender and recipient addresses. If
5062 you set only the first one, its value is used in both cases.
5064 .index domain literal||recognizing format
5065 The following line must be uncommented if you want Exim to recognize
5066 addresses of the form \*user@@[10.11.12.13]*\ that is, with a `domain literal'
5067 (an IP address) instead of a named domain.
5069 # allow_domain_literals
5071 The RFCs still require this form, but many people think that in the modern
5072 Internet it makes little sense to permit mail to be sent to specific hosts by
5073 quoting their IP addresses. This ancient format has been used by people who
5074 try to abuse hosts by using them for unwanted relaying. However, some
5075 people believe there are circumstances (for example, messages addressed to
5076 \*postmaster*\) where domain literals are still useful.
5078 The next configuration line is a kind of trigger guard:
5082 It specifies that no delivery must ever be run as the root user. The normal
5083 convention is to set up \*root*\ as an alias for the system administrator. This
5084 setting is a guard against slips in the configuration.
5085 The list of users specified by \never@_users\ is not, however, the complete
5086 list; the build-time configuration in \(Local/Makefile)\ has an option called
5087 \\FIXED@_NEVER@_USERS\\ specifying a list that cannot be overridden. The
5088 contents of \never@_users\ are added to this list. By default
5089 \\FIXED@_NEVER@_USERS\\ also specifies root.
5091 When a remote host connects to Exim in order to send mail, the only information
5092 Exim has about the host's identity is its IP address. The next configuration
5097 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5098 in order to get a host name. This improves the quality of the logging
5099 information, but if you feel it is too expensive, you can remove it entirely,
5100 or restrict the lookup to hosts on `nearby' networks.
5101 Note that it is not always possible to find a host name from an IP address,
5102 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5105 The next two lines are concerned with \*ident*\ callbacks, as defined by RFC
5106 1413 (hence their names):
5109 rfc1413_query_timeout = 30s
5111 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5112 You can limit the hosts to which these calls are made, or change the timeout
5113 that is used. If you set the timeout to zero, all ident calls are disabled.
5114 Although they are cheap and can provide useful information for tracing problem
5115 messages, some hosts and firewalls have problems with ident calls. This can
5116 result in a timeout instead of an immediate refused connection, leading to
5117 delays on starting up an incoming SMTP session.
5119 When Exim receives messages over SMTP connections, it expects all addresses to
5120 be fully qualified with a domain, as required by the SMTP definition. However,
5121 if you are running a server to which simple clients submit messages, you may
5122 find that they send unqualified addresses. The two commented-out options:
5124 # sender_unqualified_hosts =
5125 # recipient_unqualified_hosts =
5127 show how you can specify hosts that are permitted to send unqualified sender
5128 and recipient addresses, respectively.
5130 The \percent@_hack@_domains\ option is also commented out:
5132 # percent_hack_domains =
5134 It provides a list of domains for which the `percent hack' is to operate. This
5135 is an almost obsolete form of explicit email routing. If you do not know
5136 anything about it, you can safely ignore this topic.
5138 The last two settings in the main part of the default configuration are
5139 concerned with messages that have been `frozen' on Exim's queue. When a message
5140 is frozen, Exim no longer continues to try to deliver it. Freezing occurs when
5141 a bounce message encounters a permanent failure because the sender address of
5142 the original message that caused the bounce is invalid, so the bounce cannot be
5143 delivered. This is probably the most common case, but there are also other
5144 conditions that cause freezing, and frozen messages are not always bounce
5147 ignore_bounce_errors_after = 2d
5148 timeout_frozen_after = 7d
5150 The first of these options specifies that failing bounce messages are to be
5151 discarded after 2 days on the queue. The second specifies that any frozen
5152 message (whether a bounce message or not) is to be timed out (and discarded)
5153 after a week. In this configuration, the first setting ensures that no failing
5154 bounce message ever lasts a week.
5157 .section ACL configuration
5158 .index default||ACLs
5159 .index ~~ACL||default configuration
5160 In the default configuration, the ACL section follows the main configuration.
5161 It starts with the line
5165 and it contains the definition of one ACL called \*acl@_check@_rcpt*\ that was
5166 referenced in the setting of \acl@_smtp@_rcpt\ above.
5167 .index \\RCPT\\||ACL for
5168 This ACL is used for every \\RCPT\\ command in an incoming SMTP message. Each
5169 \\RCPT\\ command specifies one of the message's recipients. The ACL statements
5170 are considered in order, until the recipient address is either accepted or
5171 rejected. The \\RCPT\\ command is then accepted or rejected, according to the
5172 result of the ACL processing.
5176 This line, consisting of a name terminated by a colon, marks the start of the
5181 This ACL statement accepts the recipient if the sending host matches the list.
5182 But what does that strange list mean? It doesn't actually contain any host
5183 names or IP addresses. The presence of the colon puts an empty item in the
5184 list; Exim matches this only if the incoming message didn't come from a remote
5185 host. The colon is important. Without it, the list itself is empty, and can
5186 never match anything.
5188 What this statement is doing is to accept unconditionally all recipients in
5189 messages that are submitted by SMTP from local processes using the standard
5190 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5193 deny domains = +local_domains
5194 local_parts = ^[.] : ^.*[@%!/|]
5196 deny domains = !+local_domains
5197 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5199 These statements are concerned with local parts that contain any of the
5200 characters `@@', `%', `!', `/', `|', or dots in unusual places. Although these
5201 characters are entirely legal in local parts (in the case of `@@' and leading
5202 dots, only if correctly quoted), they do not commonly occur in Internet mail
5205 The first three have in the past been associated with explicitly routed
5206 addresses (percent is still sometimes used -- see the \percent@_hack@_domains\
5207 option). Addresses containing these characters are regularly tried by spammers
5208 in an attempt to bypass relaying restrictions, and also by open relay testing
5209 programs. Unless you really need them it is safest to reject these characters
5210 at this early stage. This configuration is heavy-handed in rejecting these
5211 characters for all messages it accepts from remote hosts. This is a deliberate
5212 policy of being as safe as possible.
5214 The first rule above is stricter, and is applied to messages that are addressed
5215 to one of the local domains handled by this host. This is implemented by the
5216 first condition, which restricts it to domains that are listed in the
5217 \*local@_domains*\ domain list. The `+' character is used to indicate a
5218 reference to a named list. In this configuration, there is just one domain in
5219 \*local@_domains*\, but in general there may be many.
5221 The second condition on the first statement uses two regular expressions to
5222 block local parts that begin with a dot or contain `@@', `%', `!', `/', or `|'.
5223 If you have local accounts that include these characters, you will have to
5226 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5227 allows them because they have been encountered in practice. (Consider local
5228 parts constructed as `first-initial.second-initial.family-name' when applied to
5229 someone like the author of Exim, who has no second initial.) However, a local
5230 part starting with a dot or containing `/../' can cause trouble if it is used
5231 as part of a file name (for example, for a mailing list). This is also true for
5232 local parts that contain slashes. A pipe symbol can also be troublesome if the
5233 local part is incorporated unthinkingly into a shell command line.
5235 The second rule above applies to all other domains, and is less strict. This
5236 allows your own users to send outgoing messages to sites that use slashes
5237 and vertical bars in their local parts. It blocks local parts that begin
5238 with a dot, slash, or vertical bar, but allows these characters within the
5239 local part. However, the sequence `/../' is barred. The use of `@@', `%', and
5240 `!' is blocked, as before. The motivation here is to prevent your users (or
5241 your users' viruses) from mounting certain kinds of attack on remote sites.
5244 accept local_parts = postmaster
5245 domains = +local_domains
5247 This statement, which has two conditions, accepts an incoming address if the
5248 local part is \*postmaster*\ and the domain is one of those listed in the
5249 \*local@_domains*\ domain list. The `+' character is used to indicate a
5250 reference to a named list. In this configuration, there is just one domain in
5251 \*local@_domains*\, but in general there may be many.
5253 The presence of this statement means that mail to postmaster is never blocked
5254 by any of the subsequent tests. This can be helpful while sorting out problems
5255 in cases where the subsequent tests are incorrectly denying access.
5257 require verify = sender
5259 This statement requires the sender address to be verified before any subsequent
5260 ACL statement can be used. If verification fails, the incoming recipient
5261 address is refused. Verification consists of trying to route the address, to
5264 message could be delivered to it. In the case of remote addresses, basic
5265 verification checks only the domain, but \*callouts*\ can be used for more
5266 verification if required. Section ~~SECTaddressverification discusses the
5267 details of address verification.
5270 # deny message = rejected because $sender_host_address is \
5271 # in a black list at $dnslist_domain\n\
5273 # dnslists = black.list.example
5275 # warn message = X-Warning: $sender_host_address is \
5276 # in a black list at $dnslist_domain
5277 # log_message = found in $dnslist_domain
5278 # dnslists = black.list.example
5280 These commented-out lines are examples of how you could configure Exim to check
5281 sending hosts against a DNS black list. The first statement rejects messages
5282 from blacklisted hosts, whereas the second merely inserts a warning header
5286 accept domains = +local_domains
5288 message = unknown user
5291 This statement accepts the incoming recipient address if its domain is one of
5292 the local domains, but only if the address can be verified. Verification of
5293 local addresses normally checks both the local part and the domain. The
5294 \endpass\ line needs some explanation: if the condition above \endpass\ fails,
5295 that is, if the address is not in a local domain, control is passed to the next
5296 ACL statement. However, if the condition below \endpass\ fails, that is, if a
5297 recipient in a local domain cannot be verified, access is denied and the
5298 recipient is rejected.
5299 .index customizing||ACL failure message
5300 The \message\ modifier provides a customized error message for the failure.
5302 accept domains = +relay_to_domains
5304 message = unrouteable address
5307 This statement accepts the incoming recipient address if its domain is one of
5308 the domains for which this host is a relay, but again, only if the address can
5311 accept hosts = +relay_from_hosts
5313 Control reaches this statement only if the recipient's domain is neither a
5314 local domain, nor a relay domain. The statement accepts the address if the
5315 message is coming from one of the hosts that are defined as being allowed to
5316 relay through this host. Recipient verification is omitted here, because in
5317 many cases the clients are dumb MUAs that do not cope well with SMTP error
5318 responses. If you are actually relaying out from MTAs, you should probably add
5319 recipient verification here.
5321 accept authenticated = *
5323 Control reaches here for attempts to relay to arbitrary domains from arbitrary
5324 hosts. The statement accepts the address only if the client host has
5325 authenticated itself. The default configuration does not define any
5326 authenticators, which means that no client can in fact authenticate. You will
5327 need to add authenticator definitions if you want to make use of this ACL
5330 deny message = relay not permitted
5332 The final statement denies access, giving a specific error message. Reaching
5333 the end of the ACL also causes access to be denied, but with the generic
5334 message `administrative prohibition'.
5337 .section Router configuration
5338 .index default||routers
5339 .index routers||default
5340 The router configuration comes next in the default configuration, introduced
5345 Routers are the modules in Exim that make decisions about where to send
5346 messages. An address is passed to each router in turn, until it is either
5347 accepted, or failed. This means that the order in which you define the routers
5348 matters. Each router is fully described in its own chapter later in this
5349 manual. Here we give only brief overviews.
5351 .index domain literal||default router
5354 # driver = ipliteral
5355 # domains = !+local_domains
5356 # transport = remote_smtp
5358 This router is commented out because the majority of sites do not want to
5359 support domain literal addresses (those of the form \*user@@[10.9.8.7]*\). If
5360 you uncomment this router, you also need to uncomment the setting of
5361 \allow@_domain@_literals\ in the main part of the configuration.
5366 domains = ! +local_domains
5367 transport = remote_smtp
5369 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5373 The first uncommented router handles addresses that do not involve any local
5374 domains. This is specified by the line
5376 domains = ! +local_domains
5378 The \domains\ option lists the domains to which this router applies, but the
5379 exclamation mark is a negation sign, so the router is used only for domains
5380 that are not in the domain list called \*local@_domains*\ (which was defined at
5381 the start of the configuration). The plus sign before \*local@_domains*\
5382 indicates that it is referring to a named list. Addresses in other domains are
5383 passed on to the following routers.
5385 The name of the router driver is \%dnslookup%\,
5386 and is specified by the \driver\ option. Do not be confused by the fact that
5387 the name of this router instance is the same as the name of the driver. The
5388 instance name is arbitrary, but the name set in the \driver\ option must be one
5389 of the driver modules that is in the Exim binary.
5391 The \%dnslookup%\ router routes addresses by looking up their domains in the
5392 DNS in order to obtain a list of hosts to which the address is routed. If the
5393 router succeeds, the address is queued for the \%remote@_smtp%\ transport, as
5394 specified by the \transport\ option. If the router does not find the domain in
5395 the DNS, no further routers are tried because of the \no@_more\ setting, so the
5396 address fails and is bounced.
5398 The \ignore@_target@_hosts\ option specifies a list of IP addresses that are to
5399 be entirely ignored. This option is present because a number of cases have been
5400 encountered where MX records in the DNS point to host names
5401 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5402 Completely ignoring these IP addresses causes Exim to fail to route the
5403 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5404 continue to try to deliver the message periodically until the address timed
5411 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5413 file_transport = address_file
5414 pipe_transport = address_pipe
5416 Control reaches this and subsequent routers only for addresses in the local
5417 domains. This router checks to see whether the local part is defined as an
5418 alias in the \(/etc/aliases)\ file, and if so, redirects it according to the
5419 data that it looks up from that file. If no data is found for the local part,
5420 the value of the \data\ option is empty, causing the address to be passed to
5423 \(/etc/aliases)\ is a conventional name for the system aliases file that is
5424 often used. That is why it is referenced by from the default configuration
5425 file. However, you can change this by setting \\SYSTEM@_ALIASES@_FILE\\ in
5426 \(Local/Makefile)\ before building Exim.
5432 file = $home/.forward
5437 file_transport = address_file
5438 pipe_transport = address_pipe
5439 reply_transport = address_reply
5441 This is the most complicated router in the default configuration. It is another
5442 redirection router, but this time it is looking for forwarding data set up by
5443 individual users. The \check@_local@_user\ setting means that the first thing it
5444 does is to check that the local part of the address is the login name of a
5445 local user. If it is not, the router is skipped. When a local user is found,
5446 the file called \(.forward)\ in the user's home directory is consulted. If it
5447 does not exist, or is empty, the router declines. Otherwise, the contents of
5448 \(.forward)\ are interpreted as redirection data (see chapter ~~CHAPredirect
5451 .index Sieve filter||enabling in default router
5452 Traditional \(.forward)\ files contain just a list of addresses, pipes, or
5453 files. Exim supports this by default. However, if \allow@_filter\ is set (it is
5454 commented out by default), the contents of the file are interpreted as a set of
5455 Exim or Sieve filtering instructions, provided the file begins with `@#Exim
5456 filter' or `@#Sieve filter', respectively. User filtering is discussed in the
5457 separate document entitled \*Exim's interfaces to mail filtering*\.
5459 The \no@_verify\ and \no@_expn\ options mean that this router is skipped when
5460 verifying addresses, or when running as a consequence of an SMTP \\EXPN\\
5462 There are two reasons for doing this:
5464 Whether or not a local user has a \(.forward)\ file is not really relevant when
5465 checking an address for validity; it makes sense not to waste resources doing
5468 More importantly, when Exim is verifying addresses or handling an \\EXPN\\
5469 command during an SMTP session, it is running as the Exim user, not as root.
5470 The group is the Exim group, and no additional groups are set up.
5471 It may therefore not be possible for Exim to read users' \(.forward)\ files at
5475 The setting of \check@_ancestor\ prevents the router from generating a new
5476 address that is the same as any previous address that was redirected. (This
5477 works round a problem concerning a bad interaction between aliasing and
5478 forwarding -- see section ~~SECTredlocmai).
5480 The final three option settings specify the transports that are to be used when
5481 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5482 auto-reply, respectively. For example, if a \(.forward)\ file contains
5484 a.nother@elsewhere.example, /home/spqr/archive
5486 the delivery to \(/home/spqr/archive)\ is done by running the \address@_file\
5492 transport = local_delivery
5494 The final router sets up delivery into local mailboxes, provided that the local
5495 part is the name of a local login, by accepting the address and queuing it for
5496 the \%local@_delivery%\ transport. Otherwise, we have reached the end of the
5497 routers, so the address is bounced.
5500 .section Transport configuration
5501 .index default||transports
5502 .index transports||default
5503 Transports define mechanisms for actually delivering messages. They operate
5504 only when referenced from routers, so the order in which they are defined does
5505 not matter. The transports section of the configuration starts with
5509 One remote transport and four local transports are defined.
5514 This transport is used for delivering messages over SMTP connections. All its
5515 options are defaulted. The list of remote hosts comes from the router.
5519 file = /var/mail/$local_part
5526 This \%appendfile%\ transport is used for local delivery to user mailboxes in
5527 traditional BSD mailbox format. By default it runs under the uid and gid of the
5528 local user, which requires the sticky bit to be set on the \(/var/mail)\
5529 directory. Some systems use the alternative approach of running mail deliveries
5530 under a particular group instead of using the sticky bit. The commented options
5531 show how this can be done.
5533 Exim adds three headers to the message as it delivers it: ::Delivery-date::,
5534 ::Envelope-to:: and ::Return-path::. This action is requested by the three
5535 similarly-named options above.
5541 This transport is used for handling deliveries to pipes that are generated by
5542 redirection (aliasing or users' \(.forward)\ files). The \return@_output\
5543 option specifies that any output generated by the pipe is to be returned to the
5552 This transport is used for handling deliveries to files that are generated by
5553 redirection. The name of the file is not specified in this instance of
5554 \%appendfile%\, because it comes from the \%redirect%\ router.
5559 This transport is used for handling automatic replies generated by users'
5563 .section Default retry rule
5564 .index retry||default rule
5565 .index default||retry rule
5566 The retry section of the configuration file contains rules which affect the way
5567 Exim retries deliveries that cannot be completed at the first attempt. It is
5568 introduced by the line
5572 In the default configuration, there is just one rule, which applies to all
5575 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5577 This causes any temporarily failing address to be retried every 15 minutes for
5578 2 hours, then at intervals starting at one hour and increasing by a factor of
5579 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5580 is not delivered after 4 days of failure, it is bounced.
5583 .section Rewriting configuration
5584 The rewriting section of the configuration, introduced by
5588 contains rules for rewriting addresses in messages as they arrive. There are no
5589 rewriting rules in the default configuration file.
5592 .section Authenticators configuration
5593 .index \\AUTH\\||configuration
5594 The authenticators section of the configuration, introduced by
5596 begin authenticators
5598 defines mechanisms for the use of the SMTP \\AUTH\\ command. No authenticators
5599 are specified in the default configuration file.
5607 . ============================================================================
5608 .chapter Regular expressions
5609 .set runningfoot "regular expressions"
5610 .rset CHAPregexp ~~chapter
5612 .index regular expressions||library
5614 Exim supports the use of regular expressions in many of its options. It
5615 uses the PCRE regular expression library; this provides regular expression
5616 matching that is compatible with Perl 5. The syntax and semantics of
5617 regular expressions is discussed in many Perl reference books, and also in
5620 [(A HREF="http://www.oreilly.com/catalog/regex/")]
5622 $it{Mastering Regular Expressions}
5626 (O'Reilly, ISBN 0-596-00289-0).
5628 The documentation for the syntax and semantics of the regular expressions that
5629 are supported by PCRE is included in plain text in the file
5630 \(doc/pcrepattern.txt)\ in the Exim distribution, and also in the HTML
5631 tarbundle of Exim documentation, and as an appendix to the
5633 [(A HREF="http://www.uit.co.uk/exim-book/")]
5639 It describes in detail the features of the regular expressions that PCRE
5640 supports, so no further description is included here. The PCRE functions are
5641 called from Exim using the default option settings (that is, with no PCRE
5642 options set), except that the \\PCRE@_CASELESS\\ option is set when the
5643 matching is required to be case-insensitive.
5645 In most cases, when a regular expression is required in an Exim configuration,
5646 it has to start with a circumflex, in order to distinguish it from plain text
5647 or an `ends with' wildcard. In this example of a configuration setting, the
5648 second item in the colon-separated list is a regular expression.
5650 domains = a.b.c : ^\\d{3} : *.y.z : ...
5652 The doubling of the backslash is required because of string expansion that
5653 precedes interpretation -- see section ~~SECTlittext for more discussion of
5654 this issue, and a way of avoiding the need for doubling backslashes. The
5655 regular expression that is eventually used in this example contains just one
5656 backslash. The circumflex is included in the regular expression, and has the
5657 normal effect of `anchoring' it to the start of the string that is being
5660 There are, however, two cases where a circumflex is not required for the
5661 recognition of a regular expression: these are the \match\ condition in a
5662 string expansion, and the \matches\ condition in an Exim filter file. In these
5663 cases, the relevant string is always treated as a regular expression; if it
5664 does not start with a circumflex, the expression is not anchored, and can match
5665 anywhere in the subject string.
5667 In all cases, if you want a regular expression to match at the end of a string,
5668 you must code the @$ metacharacter to indicate this. For example:
5670 domains = ^\\d{3}\\.example
5672 matches the domain \*123.example*\, but it also matches \*123.example.com*\.
5675 domains = ^\\d{3}\\.example\$
5677 if you want \*example*\ to be the top-level domain. (The backslash before the
5678 @$ is another artefact of string expansion.)
5681 .section Testing regular expressions
5682 .index testing||regular expressions
5683 .index regular expressions||testing
5685 A program called \*pcretest*\ forms part of the PCRE distribution and is built
5686 with PCRE during the process of building Exim. It is primarily intended for
5687 testing PCRE itself, but it can also be used for experimenting with regular
5688 expressions. After building Exim, the binary can be found in the build
5689 directory (it is not installed anywhere automatically). There is documentation
5690 of various options in \(doc/pcretest.txt)\, but for simple testing, none are
5691 needed. This is the output of a sample run of \*pcretest*\:
5693 re> $cb{/^([^@@]+)@@.+@\.(ac|edu)@\.(?!kr)[a-z]@{2@}@$/}
5694 data> $cb{x@@y.ac.uk}
5698 data> $cb{x@@y.ac.kr}
5700 data> $cb{x@@y.edu.com}
5702 data> $cb{x@@y.edu.co}
5708 Input typed by the user is shown in bold face.
5710 After the `re>' prompt, a regular expression enclosed in delimiters is
5711 expected. If this compiles without error, `data>' prompts are given for strings
5712 against which the expression is matched. An empty data line causes a new
5713 regular expression to be read. If the match is successful, the captured
5714 substring values (that is, what would be in the variables \$0$\, \$1$\, \$2$\,
5715 etc.) are shown. The above example tests for an email address whose domain ends
5716 with either `ac' or `edu' followed by a two-character top-level domain that is
5717 not `kr'. The local part is captured in \$1$\ and the `ac' or `edu' in \$2$\.
5728 . ============================================================================
5729 .chapter File and database lookups
5730 .set runningfoot "file/database lookups"
5731 .rset CHAPfdlookup "~~chapter"
5733 .index database lookups
5734 .index lookup||description of
5735 Exim can be configured to look up data in files or databases as it processes
5736 messages. Two different kinds of syntax are used:
5738 A string that is to be expanded may contain explicit lookup requests. These
5739 cause parts of the string to be replaced by data that is obtained from the
5742 Lists of domains, hosts, and email addresses can contain lookup requests as a
5743 way of avoiding excessively long linear lists. In this case, the data that is
5744 returned by the lookup is often (but not always) discarded; whether the lookup
5745 succeeds or fails is what really counts. These kinds of list are described in
5746 chapter ~~CHAPdomhosaddlists.
5748 It is easy to confuse the two different kinds of lookup, especially as the
5749 lists that may contain the second kind are always expanded before being
5750 processed as lists. Therefore, they may also contain lookups of the first kind.
5751 Be careful to distinguish between the following two examples:
5753 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
5754 domains = lsearch;/some/file
5756 The first uses a string expansion, the result of which must be a domain list.
5757 String expansions are described in detail in chapter ~~CHAPexpand. The
5758 expansion takes place first, and the file that is searched could contain lines
5761 192.168.3.4: domain1 : domain2 : ...
5762 192.168.1.9: domain3 : domain4 : ...
5764 Thus, the result of the expansion is a list of domains (and possibly other
5765 types of item that are allowed in domain lists).
5767 In the second case, the lookup is a single item in a domain list. It causes
5768 Exim to use a lookup to see if the domain that is being processed can be found
5769 in the file. The file could contains lines like this:
5774 Any data that follows the keys is not relevant when checking that the domain
5775 matches the list item.
5777 It is possible to use both kinds of lookup at once. Consider a file containing
5780 192.168.5.6: lsearch;/another/file
5782 If the value of \$sender@_host@_address$\ is 192.168.5.6, expansion of the
5783 first \domains\ setting above generates the second setting, which therefore
5784 causes a second lookup to occur.
5786 The rest of this chapter describes the different lookup types that are
5787 available. Any of them can be used in either of the circumstances described
5788 above. The syntax requirements for the two cases are described in chapters
5789 ~~CHAPexpand and ~~CHAPdomhosaddlists, respectively.
5791 .section Lookup types
5792 .index lookup||types of
5793 .index single-key lookup||definition of
5794 Two different styles of data lookup are implemented:
5796 The \*single-key*\ style requires the specification of a file in which to look,
5797 and a single key to search for.
5799 The key must be a non-empty string for the lookup to succeed.
5801 The lookup type determines how the file is searched.
5803 .index query-style lookup||definition of
5804 The \*query*\ style accepts a generalized database query.
5805 No particular key value is assumed by Exim for query-style lookups. You can
5806 use whichever Exim variable(s) you need to construct the database query.
5808 The code for each lookup type is in a separate source file that is included in
5809 the binary of Exim only if the corresponding compile-time option is set. The
5810 default settings in \(src/EDITME)\ are:
5815 which means that only linear searching and DBM lookups are included by default.
5816 For some types of lookup (e.g. SQL databases), you need to install appropriate
5817 libraries and header files before building Exim.
5821 .section Single-key lookup types
5822 .rset SECTsinglekeylookups "~~chapter.~~section"
5823 .index lookup||single-key types
5824 .index single-key lookup||list of types
5825 The following single-key lookup types are implemented:
5827 .index cdb||description of
5829 .index binary zero||in lookup key
5830 \%cdb%\: The given file is searched as a Constant DataBase file, using the key
5831 string without a terminating binary zero. The cdb format is designed for
5832 indexed files that are read frequently and never updated, except by total
5833 re-creation. As such, it is particulary suitable for large files containing
5834 aliases or other indexed data referenced by an MTA. Information about cdb can
5835 be found in several places:
5837 \?http://www.pobox.com/@~djb/cdb.html?\
5838 \?ftp://ftp.corpit.ru/pub/tinycdb/?\
5839 \?http://packages.debian.org/stable/utils/freecdb.html?\
5841 A cdb distribution is not needed in order to build Exim with cdb support,
5842 because the code for reading cdb files is included directly in Exim itself.
5843 However, no means of building or testing cdb files is provided with Exim, so
5844 you need to obtain a cdb distribution in order to do this.
5846 .index DBM||lookup type
5848 .index binary zero||in lookup key
5849 \%dbm%\: Calls to DBM library functions are used to extract data from the given
5850 DBM file by looking up the record with the given key. A terminating binary
5851 zero is included in the key that is passed to the DBM library. See section
5852 ~~SECTdb for a discussion of DBM libraries.
5853 .index Berkeley DB library||file format
5854 For all versions of Berkeley DB, Exim uses the \\DB@_HASH\\ style of database
5855 when building DBM files using the \exim@_dbmbuild\ utility. However, when using
5856 Berkeley DB versions 3 or 4, it opens existing databases for reading with the
5857 \\DB@_UNKNOWN\\ option. This enables it to handle any of the types of database
5858 that the library supports, and can be useful for accessing DBM files created by
5859 other applications. (For earlier DB versions, \\DB@_HASH\\ is always used.)
5862 .index lookup||dbmnz
5863 .index lookup||dbm, terminating zero
5864 .index binary zero||in lookup key
5866 .index \(/etc/userdbshadow.dat)\
5867 .index dmbnz lookup type
5868 \%dbmnz%\: This is the same as \%dbm%\, except that a terminating binary zero
5869 is not included in the key that is passed to the DBM library. You may need this
5870 if you want to look up data in files that are created by or shared with some
5871 other application that does not use terminating zeros. For example, you need to
5872 use \%dbmnz%\ rather than \%dbm%\ if you want to authenticate incoming SMTP
5873 calls using the passwords from Courier's \(/etc/userdbshadow.dat)\ file. Exim's
5874 utility program for creating DBM files (\*exim@_dbmbuild*\) includes the zeros
5875 by default, but has an option to omit them (see section ~~SECTdbmbuild).
5877 .index lookup||dsearch
5878 .index dsearch lookup type
5879 \%dsearch%\: The given file must be a directory; this is searched for a file
5880 whose name is the key. The key may not contain any forward slash characters.
5881 The result of a successful lookup is the name of the file. An example of how
5882 this lookup can be used to support virtual domains is given in section
5883 ~~SECTvirtualdomains.
5885 .index lookup||iplsearch
5886 .index iplsearch lookup type
5887 \%iplsearch%\: The given file is a text file containing keys and data. A key is
5888 terminated by a colon or white space or the end of the line. The keys in the
5889 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
5890 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
5891 being interpreted as a key terminator. For example:
5893 1.2.3.4: data for 1.2.3.4
5894 192.168.0.0/16 data for 192.168.0.0/16
5895 "abcd::cdab": data for abcd::cdab
5896 "abcd:abcd::/32" data for abcd:abcd::/32
5898 The key for an \%iplsearch%\ lookup must be an IP address (without a mask). The
5899 file is searched linearly, using the CIDR masks where present, until a matching
5900 key is found. The first key that matches is used; there is no attempt to find a
5901 `best' match. Apart from the way the keys are matched, the processing for
5902 \%iplsearch%\ is the same as for \%lsearch%\.
5904 \**Warning 1**\: Unlike most other single-key lookup types, a file of data for
5905 \%iplsearch%\ can \*not*\ be turned into a DBM or cdb file, because those
5906 lookup types support only literal keys.
5908 \**Warning 2**\: In a host list, you must always use \%net-iplsearch%\ so that
5909 the implicit key is the host's IP address rather than its name (see section
5910 ~~SECThoslispatsikey).
5913 .index linear search
5914 .index lookup||lsearch
5915 .index lsearch lookup type
5916 \%lsearch%\: The given file is a text file that is searched linearly for a
5917 line beginning with the search key, terminated by a colon or white space or the
5918 end of the line. The first occurrence that is found in the file is used. White
5919 space between the key and the colon is permitted. The remainder of the line,
5920 with leading and trailing white space removed, is the data. This can be
5921 continued onto subsequent lines by starting them with any amount of white
5922 space, but only a single space character is included in the data at such a
5923 junction. If the data begins with a colon, the key must be terminated by a
5928 Empty lines and lines beginning with @# are ignored, even if they occur in the
5929 middle of an item. This is the traditional textual format of alias files. Note
5930 that the keys in an \%lsearch%\ file are literal strings. There is no
5931 wildcarding of any kind.
5933 .index lookup||lsearch, colons in keys
5934 .index whitespace||in lsearch key
5935 In most \%lsearch%\ files, keys are not required to contain colons or @#
5936 characters, or whitespace. However, if you need this feature, it is available.
5937 If a key begins with a doublequote character, it is terminated only by a
5938 matching quote (or end of line), and the normal escaping rules apply to its
5939 contents (see section ~~SECTstrings). An optional colon is permitted after
5940 quoted keys (exactly as for unquoted keys). There is no special handling of
5941 quotes for the data part of an \%lsearch%\ line.
5943 .index NIS lookup type
5945 .index binary zero||in lookup key
5946 \%nis%\: The given file is the name of a NIS map, and a NIS lookup is done with
5947 the given key, without a terminating binary zero. There is a variant called
5948 \%nis0%\ which does include the terminating binary zero in the key. This is
5949 reportedly needed for Sun-style alias files. Exim does not recognize NIS
5950 aliases; the full map names must be used.
5952 .index wildlsearch lookup type
5953 .index lookup||wildlsearch
5954 .index nwildlsearch lookup type
5955 .index lookup||nwildlsearch
5956 \%wildlsearch%\ or \%nwildlsearch%\: These search a file linearly, like
5957 \%lsearch%\, but instead of being interpreted as a literal string, each key may
5958 be wildcarded. The difference between these two lookup types is that for
5959 \%wildlsearch%\, each key in the file is string-expanded before being used,
5960 whereas for \%nwildlsearch%\, no expansion takes place.
5962 Like \%lsearch%\, the testing is done case-insensitively. The following forms
5963 of wildcard are recognized:
5965 The string may begin with an asterisk to mean `ends with'. For example:
5967 *.a.b.c data for anything.a.b.c
5968 *fish data for anythingfish
5971 The string may begin with a circumflex to indicate a regular expression. For
5972 example, for \%wildlsearch%\:
5974 ^\N\d+\.a\.b\N data for <digits>.a.b
5976 Note the use of \"@\N"\ to disable expansion of the contents of the regular
5977 expression. If you are using \%nwildlsearch%\, where the keys are not
5978 string-expanded, the equivalent entry is:
5980 ^\d+\.a\.b data for <digits>.a.b
5983 If the regular expression contains white space or colon characters, you must
5984 either quote it (see \%lsearch%\ above), or represent these characters in other
5985 ways. For example, \"@\s"\ can be used for white space and \"@\x3A"\ for a
5986 colon. This may be easier than quoting, because if you quote, you have to
5987 escape all the backslashes inside the quotes.
5989 Although I cannot see it being of much use, the general matching function
5990 that is used to implement
5992 means that the string may begin with a lookup name terminated by a semicolon,
5993 and followed by lookup data. For example:
5995 cdb;/some/file data for keys that match the file
5997 The data that is obtained from the nested lookup is discarded.
5999 Keys that do not match any of these patterns are interpreted literally. The
6000 continuation rules for the data are the same as for \%lsearch%\, and keys may
6001 be followed by optional colons.
6003 \**Warning**\: Unlike most other single-key lookup types, a file of data for
6004 \%(n)wildlsearch%\ can \*not*\ be turned into a DBM or cdb file, because those
6005 lookup types support only literal keys.
6008 .section Query-style lookup types
6009 .index lookup||query-style types
6010 .index query-style lookup||list of types
6011 The supported query-style lookup types are listed below. Further details about
6012 many of them are given in later sections.
6014 .index DNS||as a lookup type
6016 \%dnsdb%\: This does a DNS search for
6018 one or more records whose domain names are given in the supplied query. The
6019 resulting data is the contents of the records.
6021 See section ~~SECTdnsdb.
6023 .index Interbase lookup type
6024 .index lookup||Interbase
6025 \%ibase%\: This does a lookup in an Interbase database.
6027 .index LDAP||lookup type
6029 \%ldap%\: This does an LDAP lookup using a query in the form of a URL, and
6030 returns attributes from a single entry. There is a variant called \%ldapm%\
6031 that permits values from multiple entries to be returned. A third variant
6032 called \%ldapdn%\ returns the Distinguished Name of a single entry instead of
6033 any attribute values. See section ~~SECTldap.
6035 .index MySQL||lookup type
6036 .index lookup||MySQL
6037 \%mysql%\: The format of the query is an SQL statement that is passed to a MySQL
6038 database. See section ~~SECTsql.
6040 .index NIS@+ lookup type
6042 \%nisplus%\: This does a NIS+ lookup using a query that can specify the name of
6043 the field to be returned. See section ~~SECTnisplus.
6045 .index Oracle||lookup type
6046 .index lookup||Oracle
6047 \%oracle%\: The format of the query is an SQL statement that is passed to an
6048 Oracle database. See section ~~SECTsql.
6050 .index lookup||passwd
6051 .index passwd lookup type
6052 .index \(/etc/passwd)\
6053 \%passwd%\ is a query-style lookup with queries that are just user names. The
6054 lookup calls \*getpwnam()*\ to interrogate the system password data, and on
6055 success, the result string is the same as you would get from an \%lsearch%\
6056 lookup on a traditional \(/etc/passwd file)\, though with \"*"\ for the
6057 password value. For example:
6059 *:42:42:King Rat:/home/kr:/bin/bash
6062 .index PostgreSQL lookup type
6063 .index lookup||PostgreSQL
6064 \%pgsql%\: The format of the query is an SQL statement that is passed to a
6065 PostgreSQL database. See section ~~SECTsql.
6067 \%testdb%\: This is a lookup type that is used for testing Exim. It is
6068 not likely to be useful in normal operation.
6070 .index whoson lookup type
6071 .index lookup||whoson
6072 \%whoson%\: \*Whoson*\ (\?http://whoson.sourceforge.net?\) is a proposed
6073 Internet protocol that allows Internet server programs to check whether a
6074 particular (dynamically allocated) IP address is currently allocated to a known
6075 (trusted) user and, optionally, to obtain the identity of the said user. In
6076 Exim, this can be used to implement `POP before SMTP' checking using ACL
6079 require condition = \
6080 ${lookup whoson {$sender_host_address}{yes}{no}}
6082 The query consists of a single IP address. The value returned is the name of
6083 the authenticated user.
6086 .section Temporary errors in lookups
6087 .index lookup||temporary error in
6088 Lookup functions can return temporary error codes if the lookup cannot be
6089 completed. For example, a NIS or LDAP database might be unavailable. For this
6090 reason, it is not advisable to use a lookup that might do this for critical
6091 options such as a list of local domains.
6093 When a lookup cannot be completed in a router or transport, delivery
6094 of the message (to the relevant address) is deferred, as for any other
6095 temporary error. In other circumstances Exim may assume the lookup has failed,
6096 or may give up altogether.
6099 .section Default values in single-key lookups
6100 .rset SECTdefaultvaluelookups "~~chapter.~~section"
6101 .index wildcard lookups
6102 .index lookup||default values
6103 .index lookup||wildcard
6104 .index lookup||$*$ added to type
6105 .index default||in single-key lookups
6106 In this context, a `default value' is a value specified by the administrator
6107 that is to be used if a lookup fails.
6109 If `$*$' is added to a single-key lookup type (for example, \lsearch$*$\) and
6110 the initial lookup fails, the key `$*$' is looked up in the file to provide
6111 a default value. See also the section on partial matching below.
6113 .index @*@@ with single-key lookup
6114 .index lookup||$*$@@ added to type
6115 .index alias file||per-domain default
6116 Alternatively, if `$*$@@' is added to a single-key lookup type (for example
6117 \dbm$*$@@\) then, if the initial lookup fails and the key contains an @@
6118 character, a second lookup is done with everything before the last @@ replaced
6119 by $*$. This makes it possible to provide per-domain defaults in alias files
6120 that include the domains in the keys. If the second lookup fails (or doesn't
6121 take place because there is no @@ in the key), `$*$' is looked up.
6122 For example, a \%redirect%\ router might contain:
6124 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mixed-aliases}}
6126 Suppose the address that is being processed is \*jane@@eyre.example*\. Exim
6127 looks up these keys, in this order:
6133 The data is taken from whichever key it finds first. \**Note**\: in an
6134 \%lsearch%\ file, this does not mean the first of these keys in the file. A
6135 complete scan is done for each key, and only if it is not found at all does
6136 Exim move on to try the next key.
6139 .section Partial matching in single-key lookups
6140 .rset SECTpartiallookup "~~chapter.~~section"
6141 .index partial matching
6142 .index wildcard lookups
6143 .index lookup||partial matching
6144 .index lookup||wildcard
6145 .index asterisk||in search type
6146 The normal operation of a single-key lookup is to search the file for an exact
6147 match with the given key. However, in a number of situations where domains are
6148 being looked up, it is useful to be able to do partial matching. In this case,
6149 information in the file that has a key starting with `$*$.' is matched by any
6150 domain that ends with the components that follow the full stop. For example, if
6151 a key in a DBM file is
6153 *.dates.fict.example
6155 then when partial matching is enabled this is matched by (amongst others)
6156 \*2001.dates.fict.example*\ and \*1984.dates.fict.example*\. It is also matched
6157 by \*dates.fict.example*\, if that does not appear as a separate key in the
6160 \**Note**\: Partial matching is not available for query-style lookups. It is
6161 also not available for any lookup items in address lists (see section
6164 Partial matching is implemented by doing a series of separate lookups using
6165 keys constructed by modifying the original subject key. This means that it can
6166 be used with any of the single-key lookup types, provided that
6167 partial matching keys
6168 beginning with a special prefix (default `$*$.') are included in the data file.
6169 Keys in the file that do not begin with the prefix are matched only by
6170 unmodified subject keys when partial matching is in use.
6172 Partial matching is requested by adding the string `partial-' to the front of
6173 the name of a single-key lookup type, for example, \partial-dbm\. When this is
6174 done, the subject key is first looked up unmodified; if that fails, `$*$.'
6175 is added at the start of the subject key, and it is looked up again. If that
6176 fails, further lookups are tried with dot-separated components removed
6177 from the start of the subject key, one-by-one, and `$*$.' added on the front of
6180 A minimum number of two non-$*$ components are required. This can be adjusted
6181 by including a number before the hyphen in the search type. For example,
6182 \partial3-lsearch\ specifies a minimum of three non-$*$ components in the
6183 modified keys. Omitting the number is equivalent to `partial2-'. If the subject
6184 key is \*2250.dates.fict.example*\ then the following keys are looked up when
6185 the minimum number of non-$*$ components is two:
6187 2250.dates.fict.example
6188 *.2250.dates.fict.example
6189 *.dates.fict.example
6192 As soon as one key in the sequence is successfully looked up, the lookup
6195 .index lookup||partial matching, changing prefix
6196 .index prefix||for partial matching
6197 The use of `$*$.' as the partial matching prefix is a default that can be
6198 changed. The motivation for this feature is to allow Exim to operate with file
6199 formats that are used by other MTAs. A different prefix can be supplied in
6200 parentheses instead of the hyphen after `partial'. For example:
6202 domains = partial(.)lsearch;/some/file
6204 In this example, if the domain is \*a.b.c*\, the sequence of lookups is
6205 \"a.b.c"\, \".a.b.c"\, and \".b.c"\ (the default minimum of 2 non-wild
6206 components is unchanged). The prefix may consist of any punctuation characters
6207 other than a closing parenthesis. It may be empty, for example:
6209 domains = partial1()cdb;/some/file
6211 For this example, if the domain is \*a.b.c*\, the sequence of lookups is
6212 \"a.b.c"\, \"b.c"\, and \"c"\.
6214 If `partial0' is specified, what happens at the end (when the lookup with just
6215 one non-wild component has failed, and the original key is shortened right down
6216 to the null string) depends on the prefix:
6218 If the prefix has zero length, the whole lookup fails.
6220 If the prefix has length 1, a lookup for just the prefix is done. For
6221 example, the final lookup for `partial0(.)' is for \"."\ alone.
6223 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6224 remainder is looked up. With the default prefix, therefore, the final lookup is
6225 for `$*$' on its own.
6227 Otherwise, the whole prefix is looked up.
6230 If the search type ends in `$*$' or `$*$@@' (see section
6231 ~~SECTdefaultvaluelookups above), the search for an ultimate default that this
6232 implies happens after all partial lookups have failed. If `partial0' is
6233 specified, adding `$*$' to the search type has no effect with the default
6234 prefix, because the `$*$' key is already included in the sequence of partial
6235 lookups. However, there might be a use for lookup types such as
6236 `partial0(.)lsearch$*$'.
6238 The use of `$*$' in lookup partial matching differs from its use as a wildcard
6239 in domain lists and the like. Partial matching works only in terms of
6240 dot-separated components; a key such as \"*fict.example"\
6241 in a database file is useless, because the asterisk in a partial matching
6242 subject key is always followed by a dot.
6246 .section Lookup caching
6247 .index lookup||caching
6248 .index caching||lookup data
6250 Exim caches all lookup results in order to avoid needless repetition of
6251 lookups. However, because (apart from the daemon) Exim operates as a collection
6252 of independent, short-lived processes, this caching applies only within a
6253 single Exim process. There is no inter-process caching facility.
6255 For single-key lookups, Exim keeps the relevant files open in case there is
6256 another lookup that needs them. In some types of configuration this can lead to
6257 many files being kept open for messages with many recipients. To avoid hitting
6258 the operating system limit on the number of simultaneously open files, Exim
6259 closes the least recently used file when it needs to open more files than its
6260 own internal limit, which can be changed via the \lookup@_open@_max\ option.
6262 The single-key lookup files are closed and the lookup caches are flushed at
6263 strategic points during delivery -- for example, after all routing is complete.
6267 .section Quoting lookup data
6268 .index lookup||quoting
6269 .index quoting||in lookups
6270 When data from an incoming message is included in a query-style lookup, there
6271 is the possibility of special characters in the data messing up the syntax of
6272 the query. For example, a NIS+ query that contains
6276 will be broken if the local part happens to contain a closing square bracket.
6277 For NIS+, data can be enclosed in double quotes like this:
6279 [name="$local_part"]
6281 but this still leaves the problem of a double quote in the data. The rule for
6282 NIS+ is that double quotes must be doubled. Other lookup types have different
6283 rules, and to cope with the differing requirements, an expansion operator
6284 of the following form is provided:
6286 @$@{quote@_<<lookup-type>>:<<string>>@}
6288 For example, the safest way to write the NIS+ query is
6290 [name="${quote_nisplus:$local_part}"]
6292 See chapter ~~CHAPexpand for full coverage of string expansions. The quote
6293 operator can be used for all lookup types, but has no effect for single-key
6294 lookups, since no quoting is ever needed in their key strings.
6298 .section More about dnsdb
6299 .rset SECTdnsdb "~~chapter.~~section"
6301 .index lookup||dnsdb
6302 .index DNS||as a lookup type
6303 The \%dnsdb%\ lookup type uses the DNS as its database. A simple query consists
6304 of a record type and a domain name, separated by an equals sign. For example,
6305 an expansion string could contain:
6307 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6309 The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and,
6310 when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6311 configured). If no type is given, TXT is assumed. When the type is PTR,
6313 the data can be an IP address, written as normal; inversion and the addition of
6314 \in-addr.arpa\ or \ip6.arpa\ happens automatically. For example:
6316 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6318 If the data for a PTR record is not a syntactically valid IP address, it is not
6319 altered and nothing is added.
6321 For any record type, if multiple records are found (or, for A6 lookups, if a
6322 single record leads to multiple addresses), the data is returned as a
6323 concatenation, with newline as the default separator. The order, of course,
6324 depends on the DNS resolver. You can specify a different separator character
6325 between multiple records by putting a right angle-bracket followed immediately
6326 by the new separator at the start of the query. For example:
6328 ${lookup dnsdb{>: a=host1.example}}
6330 It is permitted to specify a space as the separator character. Further
6331 whitespace is ignored.
6333 .index SRV record||in \%dnsdb%\ lookup
6334 For SRV records, the priority, weight, port, and host name are returned for
6335 each record, separated by spaces.
6337 .index MX record||in \%dnsdb%\ lookup
6338 For MX records, both the preference value and the host name are returned for
6339 each record, separated by a space. However, if you want only host names, you
6340 can use the pseudo-type MXH:
6342 ${lookup dnsdb{mxh=a.b.example}}
6344 In this case, the preference values are omitted.
6346 .index name server||for enclosing domain
6347 Another pseudo-type is ZNS (for `zone NS'). It performs a lookup for NS
6348 records on the given domain, but if none are found, it removes the first
6349 component of the domain name, and tries again. This process continues until NS
6350 records are found or there are no more components left (or there is a DNS
6351 error). In other words, it may return the name servers for a top-level domain,
6352 but it never returns the root name servers. If there are no NS records for the
6353 top-level domain, the lookup fails. Consider these examples:
6355 ${lookup dnsdb{zns=xxx.quercite.com}}
6356 ${lookup dnsdb{zns=xxx.edu}}
6358 Assuming that in each case there are no NS records for the full domain name,
6359 the first returns the name servers for \quercite.com\, and the second returns
6360 the name servers for \edu\.
6362 You should be careful about how you use this lookup because, unless the
6363 top-level domain does not exist, the lookup always returns some host names. The
6364 sort of use to which this might be put is for seeing if the name servers for a
6365 given domain are on a blacklist. You can probably assume that the name servers
6366 for the high-level domains such as \com\ or \co.uk\ are not going to be on such
6372 .section Multiple dnsdb lookups
6373 In the previous section, \%dnsdb%\ lookups for a single domain are described.
6374 However, you can specify a list of domains or IP addresses in a single
6375 \%dnsdb%\ lookup. The list is specified in the normal Exim way, with colon as
6376 the default separator, but with the ability to change this. For example:
6378 ${lookup dnsdb{one.domain.com:two.domain.com}}
6379 ${lookup dnsdb{a=one.host.com:two.host.com}}
6380 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6382 In order to retain backwards compatibility, there is one special case: if
6383 the lookup type is PTR and no change of separator is specified, Exim looks
6384 to see if the rest of the string is precisely one IPv6 address. In this
6385 case, it does not treat it as a list.
6387 The data from each lookup is concatenated, with newline separators by default,
6388 in the same way that multiple DNS records for a single item are handled. A
6389 different separator can be specified, as described above.
6391 The \%dnsdb%\ lookup fails only if all the DNS lookups fail. If there is a
6392 temporary DNS error for any of them, the behaviour is controlled by
6393 an optional keyword followed by a comma that may appear before the record
6394 type. The possible keywords are `defer@_strict', `defer@_never', and
6395 `defer@_lax'. With `strict' behaviour, any temporary DNS error causes the
6396 whole lookup to defer. With `never' behaviour, a temporary DNS error is
6397 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6398 With `lax' behaviour, all the queries are attempted, but a temporary DNS
6399 error causes the whole lookup to defer only if none of the other lookups
6400 succeed. The default is `lax', so the following lookups are equivalent:
6402 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6403 ${lookup dnsdb{a=one.host.com:two.host.com}}
6405 Thus, in the default case, as long as at least one of the DNS lookups
6406 yields some data, the lookup succeeds.
6410 .section More about LDAP
6411 .rset SECTldap "~~chapter.~~section"
6414 .index Solaris||LDAP
6415 The original LDAP implementation came from the University of Michigan; this has
6416 become `Open LDAP', and there are now two different releases. Another
6417 implementation comes from Netscape, and Solaris 7 and subsequent releases
6418 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6419 the lookup function level, their error handling is different. For this reason
6420 it is necessary to set a compile-time variable when building Exim with LDAP, to
6421 indicate which LDAP library is in use. One of the following should appear in
6422 your \(Local/Makefile)\:
6424 LDAP_LIB_TYPE=UMICHIGAN
6425 LDAP_LIB_TYPE=OPENLDAP1
6426 LDAP_LIB_TYPE=OPENLDAP2
6427 LDAP_LIB_TYPE=NETSCAPE
6428 LDAP_LIB_TYPE=SOLARIS
6430 If \\LDAP@_LIB@_TYPE\\ is not set, Exim assumes \"OPENLDAP1"\, which has the
6431 same interface as the University of Michigan version.
6433 There are three LDAP lookup types in Exim. These behave slightly differently in
6434 the way they handle the results of a query:
6436 \%ldap%\ requires the result to contain just one entry; if there are more, it
6439 \%ldapdn%\ also requires the result to contain just one entry, but it is the
6440 Distinguished Name that is returned rather than any attribute values.
6442 \%ldapm%\ permits the result to contain more than one entry; the attributes from
6443 all of them are returned.
6446 For \%ldap%\ and \%ldapm%\, if a query finds only entries with no attributes,
6447 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6448 the data returned by a successful lookup is described in the next section.
6449 First we explain how LDAP queries are coded.
6451 .section Format of LDAP queries
6452 .rset SECTforldaque "~~chapter.~~section"
6453 .index LDAP||query format
6454 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6455 the configuration of a \%redirect%\ router one might have this setting:
6457 data = ${lookup ldap \
6458 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6459 c=UK?mailbox?base?}}
6461 .index LDAP||with TLS
6462 The URL may begin with \"ldap"\ or \"ldaps"\ if your LDAP library supports
6463 secure (encrypted) LDAP connections. The second of these ensures that an
6464 encrypted TLS connection is used.
6466 .section LDAP quoting
6467 .index LDAP||quoting
6468 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6469 and the second because the LDAP query is represented as a URL. Furthermore,
6470 within an LDAP query, two different kinds of quoting are required. For this
6471 reason, there are two different LDAP-specific quoting operators.
6473 The \quote@_ldap\ operator is designed for use on strings that are part of
6474 filter specifications. Conceptually, it first does the following conversions on
6482 in accordance with RFC 2254. The resulting string is then quoted according
6483 to the rules for URLs, that is, all characters except
6487 are converted to their hex values, preceded by a percent sign. For example:
6489 ${quote_ldap: a(bc)*, a<yz>; }
6493 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6495 Removing the URL quoting, this is (with a leading and a trailing space):
6497 a\28bc\29\2A, a<yz>;
6500 The \quote@_ldap@_dn\ operator is designed for use on strings that are part of
6501 base DN specifications in queries. Conceptually, it first converts the string
6502 by inserting a backslash in front of any of the following characters:
6506 It also inserts a backslash before any leading spaces or @# characters, and
6507 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6508 is then quoted according to the rules for URLs. For example:
6510 ${quote_ldap_dn: a(bc)*, a<yz>; }
6514 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6516 Removing the URL quoting, this is (with a trailing space):
6518 \ a(bc)*\, a\<yz\>\;\
6520 There are some further comments about quoting in the section on LDAP
6521 authentication below.
6523 .section LDAP connections
6524 .index LDAP||connections
6525 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6526 is in use, via a Unix domain socket. The example given above does not specify
6527 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6530 ldap://<<hostname>>:<<port>>/...
6532 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6533 used. When no server is specified in a query, a list of default servers is
6534 taken from the \ldap@_default@_servers\ configuration option. This supplies a
6535 colon-separated list of servers which are tried in turn until one successfully
6536 handles a query, or there is a serious error. Successful handling either
6537 returns the requested data, or indicates that it does not exist. Serious errors
6538 are syntactical, or multiple values when only a single value is expected.
6539 Errors which cause the next server to be tried are connection failures, bind
6540 failures, and timeouts.
6542 For each server name in the list, a port number can be given. The standard way
6543 of specifing a host and port is to use a colon separator (RFC 1738). Because
6544 \ldap@_default@_servers\ is a colon-separated list, such colons have to be
6545 doubled. For example
6547 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6549 If \ldap@_default@_servers\ is unset, a URL with no server name is passed
6550 to the LDAP library with no server name, and the library's default (normally
6551 the local host) is used.
6553 If you are using the OpenLDAP library, you can connect to an LDAP server using
6554 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6555 \"ldapi"\ instead of \"ldap"\ in LDAP queries. What follows here applies only
6556 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6559 For this type of connection, instead of a host name for the server, a pathname
6560 for the socket is required, and the port number is not relevant. The pathname
6561 can be specified either as an item in \ldap@_default@_servers\, or inline in
6562 the query. In the former case, you can have settings such as
6564 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6566 When the pathname is given in the query, you have to escape the slashes as
6567 \"%2F"\ to fit in with the LDAP URL syntax. For example:
6569 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6571 When Exim processes an LDAP lookup and finds that the `hostname' is really
6572 a pathname, it uses the Unix domain socket code, even if the query actually
6573 specifies \"ldap"\ or \"ldaps"\. In particular, no encryption is used for a
6574 socket connection. This behaviour means that you can use a setting of
6575 \ldap@_default@_servers\ such as in the example above with traditional \"ldap"\
6576 or \"ldaps"\ queries, and it will work. First, Exim tries a connection via
6577 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6580 If an explicit \"ldapi"\ type is given in a query when a host name is
6581 specified, an error is diagnosed. However, if there are more items in
6582 \ldap@_default@_servers\, they are tried. In other words:
6584 Using a pathname with \"ldap"\ or \"ldaps"\ forces the use of the Unix domain
6587 Using \"ldapi"\ with a host name causes an error.
6590 Using \"ldapi"\ with no host or path in the query, and no setting of
6591 \ldap@_default@_servers\, does whatever the library does by default.
6594 .section LDAP authentication and control information
6595 .index LDAP||authentication
6596 The LDAP URL syntax provides no way of passing authentication and other control
6597 information to the server. To make this possible, the URL in an LDAP query may
6598 be preceded by any number of `<<name>>=<<value>>' settings, separated by
6599 spaces. If a value contains spaces it must be enclosed in double quotes, and
6600 when double quotes are used, backslash is interpreted in the usual way inside
6601 them. The following names are recognized:
6603 DEREFERENCE $rm{set the dereferencing parameter}
6606 NETTIME $rm{set a timeout for a network operation}
6609 USER $rm{set the DN, for authenticating the LDAP bind}
6610 PASS $rm{set the password, likewise}
6611 SIZE $rm{set the limit for the number of entries returned}
6612 TIME $rm{set the maximum waiting time for a query}
6614 The value of the \\DEREFERENCE\\ parameter must be one of the words `never',
6615 `searching', `finding', or `always'.
6618 The name \\CONNECT\\ is an obsolete name for \\NETTIME\\, retained for
6619 backwards compatibility. This timeout (specified as a number of seconds) is
6620 enforced from the client end for operations that can be carried out over a
6621 network. Specifically, it applies to network connections and calls to the
6622 \*ldap@_result()*\ function. If the value is greater than zero, it is used if
6623 \\LDAP@_OPT@_NETWORK@_TIMEOUT\\ is defined in the LDAP headers (OpenLDAP), or
6624 if \\LDAP@_X@_OPT@_CONNECT@_TIMEOUT\\ is defined in the LDAP headers (Netscape
6625 SDK 4.1). A value of zero forces an explicit setting of `no timeout' for
6626 Netscape SDK; for OpenLDAP no action is taken.
6628 The \\TIME\\ parameter (also a number of seconds) is passed to the server to
6629 set a server-side limit on the time taken to complete a search.
6632 Here is an example of an LDAP query in an Exim lookup that uses some of these
6633 values. This is a single line, folded for ease of reading:
6637 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6638 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6641 The encoding of spaces as %20 is a URL thing which should not be done for any
6642 of the auxiliary data. Exim configuration settings that include lookups which
6643 contain password information should be preceded by `hide' to prevent non-admin
6644 users from using the \-bP-\ option to see their values.
6646 The auxiliary data items may be given in any order. The default is no
6647 connection timeout (the system timeout is used), no user or password, no limit
6648 on the number of entries returned, and no time limit on queries.
6650 When a DN is quoted in the \\USER=\\ setting for LDAP authentication, Exim
6651 removes any URL quoting that it may contain before passing it LDAP. Apparently
6652 some libraries do this for themselves, but some do not. Removing the URL
6653 quoting has two advantages:
6655 It makes it possible to use the same \quote@_ldap@_dn\ expansion for \\USER=\\
6656 DNs as with DNs inside actual queries.
6658 It permits spaces inside \\USER=\\ DNs.
6660 For example, a setting such as
6662 USER=cn=${quote_ldap_dn:$1}
6664 should work even if \$1$\ contains spaces.
6666 Expanded data for the \\PASS=\\ value should be quoted using the \quote\
6667 expansion operator, rather than the LDAP quote operators. The only reason this
6668 field needs quoting is to ensure that it conforms to the Exim syntax, which
6669 does not allow unquoted spaces. For example:
6674 The LDAP authentication mechanism can be used to check passwords as part of
6675 SMTP authentication. See the \ldapauth\ expansion string condition in chapter
6679 .section Format of data returned by LDAP
6680 .index LDAP||returned data formats
6681 The \%ldapdn%\ lookup type returns the Distinguished Name from a single entry as
6682 a sequence of values, for example
6684 cn=manager, o=University of Cambridge, c=UK
6687 The \%ldap%\ lookup type generates an error if more than one entry matches the
6688 search filter, whereas \%ldapm%\ permits this case, and inserts a newline in
6689 the result between the data from different entries. It is possible for multiple
6690 values to be returned for both \%ldap%\ and \%ldapm%\, but in the former case
6691 you know that whatever values are returned all came from a single entry in the
6694 In the common case where you specify a single attribute in your LDAP query, the
6695 result is not quoted, and does not contain the attribute name. If the attribute
6696 has multiple values, they are separated by commas.
6698 If you specify multiple attributes, the result contains space-separated, quoted
6699 strings, each preceded by the attribute name and an equals sign. Within the
6700 quotes, the quote character, backslash, and newline are escaped with
6701 backslashes, and commas are used to separate multiple values for the attribute.
6702 Apart from the escaping, the string within quotes takes the same form as the
6703 output when a single attribute is requested. Specifying no attributes is the
6704 same as specifying all of an entry's attributes.
6706 Here are some examples of the output format. The first line of each pair is an
6707 LDAP query, and the second is the data that is returned. The attribute called
6708 \attr1\ has two values, whereas \attr2\ has only one value:
6710 ldap:///o=base?attr1?sub?(uid=fred)
6713 ldap:///o=base?attr2?sub?(uid=fred)
6716 ldap:///o=base?attr1,attr2?sub?(uid=fred)
6717 attr1="value1.1, value1.2" attr2="value two"
6719 ldap:///o=base??sub?(uid=fred)
6720 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
6722 The \extract\ operator in string expansions can be used to pick out individual
6723 fields from data that consists of $it{key}=$it{value} pairs. You can make use
6724 of Exim's \-be-\ option to run expansion tests and thereby check the results of
6729 .section More about NIS+
6730 .rset SECTnisplus "~~chapter.~~section"
6731 .index NIS@+ lookup type
6733 NIS+ queries consist of a NIS+ \*indexed name*\ followed by an optional colon
6734 and field name. If this is given, the result of a successful query is the
6735 contents of the named field; otherwise the result consists of a concatenation
6736 of \*field-name=field-value*\ pairs, separated by spaces. Empty values and
6737 values containing spaces are quoted. For example, the query
6739 [name=mg1456],passwd.org_dir
6741 might return the string
6743 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
6744 home=/home/mg1456 shell=/bin/bash shadow=""
6746 (split over two lines here to fit on the page), whereas
6748 [name=mg1456],passwd.org_dir:gcos
6754 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
6755 for the given indexed key. The effect of the \quote@_nisplus\ expansion
6756 operator is to double any quote characters within the text.
6759 .section More about MySQL, PostgreSQL, Oracle, and Interbase
6760 .rset SECTsql "~~chapter.~~section"
6761 .index MySQL||lookup type
6762 .index PostgreSQL lookup type
6763 .index lookup||MySQL
6764 .index lookup||PostgreSQL
6765 .index Oracle||lookup type
6766 .index lookup||Oracle
6767 .index Interbase lookup type
6768 .index lookup||Interbase
6769 If any MySQL, PostgreSQL, Oracle, or Interbase lookups are used, the
6770 \mysql@_servers\, \pgsql@_servers\, \oracle@_servers\, or \ibase@_servers\
6771 option (as appropriate) must be set to a colon-separated list of server
6772 information. Each item in the list is a slash-separated list of four items:
6773 host name, database name, user name, and password. In the case of Oracle, the
6774 host name field is used for the `service name', and the database name field is
6775 not used and should be empty. For example:
6777 hide oracle_servers = oracle.plc.example//ph10/abcdwxyz
6779 Because password data is sensitive, you should always precede the setting with
6780 `hide', to prevent non-admin users from obtaining the setting via the \-bP-\
6781 option. Here is an example where two MySQL servers are listed:
6783 hide mysql_servers = localhost/users/root/secret:\
6784 otherhost/users/root/othersecret
6786 For MySQL and PostgreSQL, a host may be specified as <<name>>:<<port>> but
6787 because this is a colon-separated list, the colon has to be doubled.
6789 For each query, these parameter groups are tried in order until a connection
6790 and a query succeeds. Queries for these databases are SQL statements, so an
6794 ${lookup mysql{select mailbox from users where id='ph10'}{$value}fail}
6796 If the result of the query contains more than one field, the data for
6797 each field in the row is returned, preceded by its name, so the result
6801 ${lookup pgsql{select home,name from users where id='ph10'}{$value}}
6805 home=/home/ph10 name="Philip Hazel"
6807 Values containing spaces and empty values are double quoted, with embedded
6808 quotes escaped by a backslash.
6810 If the result of the query contains just one field, the value is passed back
6811 verbatim, without a field name, for example:
6815 If the result of the query yields more than one row, it is all concatenated,
6816 with a newline between the data for each row.
6818 The \quote@_mysql\, \quote@_pgsql\, and \quote@_oracle\ expansion operators
6819 convert newline, tab, carriage return, and backspace to @\n, @\t, @\r, and @\b
6820 respectively, and the characters single-quote, double-quote, and backslash
6821 itself are escaped with backslashes. The \quote@_pgsql\ expansion operator, in
6822 addition, escapes the percent and underscore characters. This cannot be done
6823 for MySQL because these escapes are not recognized in contexts where these
6824 characters are not special.
6827 .section Special MySQL features
6828 For MySQL, an empty host name or the use of `localhost' in \mysql@_servers\
6829 causes a connection to the server on the local host by means of a Unix domain
6830 socket. An alternate socket can be specified in parentheses. The full syntax of
6831 each item in \mysql@_servers\ is:
6833 <<hostname>>@:@:<<port>>(<<socket name>>)/<<database>>/<<user>>/<<password>>
6835 Any of the three sub-parts of the first field can be omitted. For normal use on
6836 the local host it can be left blank or set to just `localhost'.
6838 No database need be supplied -- but if it is absent here, it must be given in
6841 If a MySQL query is issued that does not request any data (an insert, update,
6842 or delete command), the result of the lookup is the number of rows affected.
6844 \**Warning**\: this can be misleading. If an update does not actually change
6845 anything (for example, setting a field to the value it already has), the result
6846 is zero because no rows are affected.
6850 .section Special PostgreSQL features
6851 PostgreSQL lookups can also use Unix domain socket connections to the database.
6852 This is usually faster and costs less CPU time than a TCP/IP connection.
6853 However it can be used only if the mail server runs on the same machine as the
6854 database server. A configuration line for PostgreSQL via Unix domain sockets
6857 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
6859 In other words, instead of supplying a host name, a path to the socket is
6860 given. The path name is enclosed in parentheses so that its slashes aren't
6861 visually confused with the delimiters for the other server parameters.
6863 If a PostgreSQL query is issued that does not request any data (an insert,
6864 update, or delete command), the result of the lookup is the number of rows
6874 . ============================================================================
6875 .chapter Domain, host, address, and local part lists
6876 .set runningfoot "domain, host, and address lists"
6877 .rset CHAPdomhosaddlists "~~chapter"
6878 .index list||of domains, hosts, etc.
6879 A number of Exim configuration options contain lists of domains, hosts,
6880 email addresses, or local parts. For example, the \hold@_domains\ option
6881 contains a list of domains whose delivery is currently suspended. These lists
6882 are also used as data in ACL statements (see chapter ~~CHAPACL).
6884 Each item in one of these lists is a pattern to be matched against a domain,
6885 host, email address, or local part, respectively. In the sections below, the
6886 different types of pattern for each case are described, but first we cover some
6887 general facilities that apply to all four kinds of list.
6890 .section Expansion of lists
6891 .index expansion||of lists
6893 Each list is expanded as a single string before it is used. The result of
6894 expansion must be a list, possibly containing empty items, which is split up
6895 into separate items for matching. By default, colon is the separator character,
6896 but this can be varied if necessary. See sections ~~SECTlistconstruct and
6897 ~~SECTempitelis for details of the list syntax; the second of these discusses
6898 the way you specify empty list items.
6901 If the string expansion is forced to fail, Exim behaves as if the item it is
6902 testing (domain, host, address, or local part) is not in the list. Other
6903 expansion failures cause temporary errors.
6905 If an item in a list is a regular expression, backslashes, dollars and possibly
6906 other special characters in the expression must be protected against
6907 misinterpretation by the string expander. The easiest way to do this is to use
6908 the \"@\N"\ expansion feature to indicate that the contents of the regular
6909 expression should not be expanded. For example, in an ACL you might have:
6911 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N :
6912 ${lookup{$domain}lsearch{/badsenders/bydomain}}
6914 The first item is a regular expression that is protected from expansion by
6915 \"@\N"\, whereas the second uses the expansion to obtain a list of unwanted
6916 senders based on the receiving domain.
6920 .section Negated items in lists
6921 .index list||negation
6922 .index negation in lists
6923 Items in a list may be positive or negative. Negative items are indicated by a
6924 leading exclamation mark, which may be followed by optional white space. A list
6925 defines a set of items (domains, etc). When Exim processes one of these lists,
6926 it is trying to find out whether a domain, host, address, or local part
6927 (respectively) is in the set that is defined by the list. It works like this:
6929 The list is scanned from left to right. If a positive item is matched, the
6930 subject that is being checked is in the set; if a negative item is matched, the
6931 subject is not in the set. If the end of the list is reached without the
6932 subject having matched any of the patterns, it is in the set if the last item
6933 was a negative one, but not if it was a positive one. For example, the list in
6935 domainlist relay_domains = !a.b.c : *.b.c
6937 matches any domain ending in \*.b.c*\ except for \*a.b.c*\. Domains that match
6938 neither \*a.b.c*\ nor \*@*.b.c*\ do not match, because the last item in the
6939 list is positive. However, if the setting were
6941 domainlist relay_domains = !a.b.c
6943 then all domains other than \*a.b.c*\ would match because the last item in the
6944 list is negative. In other words, a list that ends with a negative item behaves
6945 as if it had an extra item \":*"\ on the end.
6947 Another way of thinking about positive and negative items in lists is to read
6948 the connector as `or' after a positive item and as `and' after a negative
6952 .section File names in lists
6953 .rset SECTfilnamlis "~~chapter.~~section"
6954 .index list||file name in
6955 If an item in a domain, host, address, or local part list is an absolute file
6956 name (beginning with a slash character), each line of the file is read and
6957 processed as if it were an independent item in the list, except that further
6958 file names are not allowed,
6959 and no expansion of the data from the file takes place.
6960 Empty lines in the file are ignored, and the file may also contain comment
6963 For domain and host lists, if a @# character appears anywhere in a line of the
6964 file, it and all following characters are ignored.
6966 Because local parts may legitimately contain @# characters, a comment in an
6967 address list or local part list file is recognized only if @# is preceded by
6968 white space or the start of the line. For example:
6970 not#comment@x.y.z # but this is a comment
6973 Putting a file name in a list has the same effect as inserting each line of the
6974 file as an item in the list (blank lines and comments excepted). However, there
6975 is one important difference: the file is read each time the list is processed,
6976 so if its contents vary over time, Exim's behaviour changes.
6978 If a file name is preceded by an exclamation mark, the sense of any match
6979 within the file is inverted. For example, if
6981 hold_domains = !/etc/nohold-domains
6983 and the file contains the lines
6988 then \*a.b.c*\ is in the set of domains defined by \hold@_domains\, whereas any
6989 domain matching \"*.b.c"\ is not.
6992 .section An lsearch file is not an out-of-line list
6993 As will be described in the sections that follow, lookups can be used in lists
6994 to provide indexed methods of checking list membership. There has been some
6995 confusion about the way \%lsearch%\ lookups work in lists. Because
6996 an \%lsearch%\ file contains plain text and is scanned sequentially, it is
6997 sometimes thought that it is allowed to contain wild cards and other kinds of
6998 non-constant pattern. This is not the case. The keys in an \%lsearch%\ file are
6999 always fixed strings, just as for any other single-key lookup type.
7001 If you want to use a file to contain wild-card patterns that form part of a
7002 list, just give the file name on its own, without a search type, as described
7003 in the previous section.
7007 .section Named lists
7008 .rset SECTnamedlists "~~chapter.~~section"
7011 A list of domains, hosts, email addresses, or local parts can be given a name
7012 which is then used to refer to the list elsewhere in the configuration. This is
7013 particularly convenient if the same list is required in several different
7014 places. It also allows lists to be given meaningful names, which can improve
7015 the readability of the configuration. For example, it is conventional to define
7016 a domain list called \*local@_domains*\ for all the domains that are handled
7017 locally on a host, using a configuration line such as
7019 domainlist local_domains = localhost:my.dom.example
7021 Named lists are referenced by giving their name preceded by a plus sign, so,
7022 for example, a router that is intended to handle local domains would be
7023 configured with the line
7025 domains = +local_domains
7027 The first router in a configuration is often one that handles all domains
7028 except the local ones, using a configuration with a negated item like this:
7032 domains = ! +local_domains
7033 transport = remote_smtp
7036 The four kinds of named list are created by configuration lines starting with
7037 the words \domainlist\, \hostlist\, \addresslist\, or \localpartlist\,
7038 respectively. Then there follows the name that you are defining, followed by an
7039 equals sign and the list itself. For example:
7041 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7042 addresslist bad_senders = cdb;/etc/badsenders
7044 A named list may refer to other named lists:
7046 domainlist dom1 = first.example : second.example
7047 domainlist dom2 = +dom1 : third.example
7048 domainlist dom3 = fourth.example : +dom2 : fifth.example
7051 \**Warning**\: If the last item in a referenced list is a negative one, the
7052 effect may not be what you intended, because the negation does not propagate
7053 out to the higher level. For example, consider:
7055 domainlist dom1 = !a.b
7056 domainlist dom2 = +dom1 : *.b
7058 The second list specifies `either in the \dom1\ list or \*@*.b*\'. The first
7059 list specifies just `not \*a.b*\', so the domain \*x.y*\ matches it. That means
7060 it matches the second list as well. The effect is not the same as
7062 domainlist dom2 = !a.b : *.b
7064 where \*x.y*\ does not match. It's best to avoid negation altogether in
7065 referenced lists if you can.
7067 Named lists may have a performance advantage. When Exim is routing an
7068 address or checking an incoming message, it caches the result of tests on named
7069 lists. So, if you have a setting such as
7071 domains = +local_domains
7073 on several of your routers
7074 or in several ACL statements,
7075 the actual test is done only for the first one. However, the caching works only
7076 if there are no expansions within the list itself or any sublists that it
7077 references. In other words, caching happens only for lists that are known to be
7078 the same each time they are referenced.
7080 By default, there may be up to 16 named lists of each type. This limit can be
7081 extended by changing a compile-time variable. The use of domain and host lists
7082 is recommended for concepts such as local domains, relay domains, and relay
7083 hosts. The default configuration is set up like this.
7086 .section Named lists compared with macros
7087 .index list||named compared with macro
7088 .index macro||compared with named list
7089 At first sight, named lists might seem to be no different from macros in the
7090 configuration file. However, macros are just textual substitutions. If you
7093 ALIST = host1 : host2
7094 auth_advertise_hosts = !ALIST
7096 it probably won't do what you want, because that is exactly the same as
7098 auth_advertise_hosts = !host1 : host2
7100 Notice that the second host name is not negated. However, if you use a host
7103 hostlist alist = host1 : host2
7104 auth_advertise_hosts = ! +alist
7106 the negation applies to the whole list, and so that is equivalent to
7108 auth_advertise_hosts = !host1 : !host2
7112 .section Named list caching
7113 .index list||caching of named
7114 .index caching||named lists
7115 While processing a message, Exim caches the result of checking a named list if
7116 it is sure that the list is the same each time. In practice, this means that
7117 the cache operates only if the list contains no @$ characters, which guarantees
7118 that it will not change when it is expanded. Sometimes, however, you may have
7119 an expanded list that you know will be the same each time within a given
7120 message. For example:
7122 domainlist special_domains = \
7123 ${lookup{$sender_host_address}cdb{/some/file}}
7125 This provides a list of domains that depends only on the sending host's IP
7126 address. If this domain list is referenced a number of times (for example,
7127 in several ACL lines, or in several routers) the result of the check is not
7128 cached by default, because Exim does not know that it is going to be the
7129 same list each time.
7131 By appending \"@_cache"\ to \"domainlist"\ you can tell Exim to go ahead and
7132 cache the result anyway. For example:
7134 domainlist_cache special_domains = ${lookup{...
7136 If you do this, you should be absolutely sure that caching is going to do
7137 the right thing in all cases. When in doubt, leave it out.
7140 .section Domain lists
7141 .rset SECTdomainlist "~~chapter.~~section"
7142 .index domain list||patterns for
7143 .index list||domain list
7144 Domain lists contain patterns that are to be matched against a mail domain.
7145 The following types of item may appear in domain lists:
7147 .index primary host name
7148 .index host||name, matched in domain list
7149 .index \primary@_hostname\
7150 .index domain list||matching primary host name
7151 .index @@ in a domain list
7152 If a pattern consists of a single @@ character, it matches the local host name,
7153 as set by the \primary@_hostname\ option (or defaulted). This makes it possible
7154 to use the same configuration file on several different hosts that differ only
7157 .index @@[] in a domain list
7158 .index domain list||matching local IP interfaces
7159 .index domain literal
7160 If a pattern consists of the string \"@@[]"\ it matches any local IP interface
7161 address, enclosed in square brackets, as in an email address that contains a
7163 In today's Internet, the use of domain literals is controversial.
7166 .index @@mx@_primary
7167 .index @@mx@_secondary
7168 .index domain list||matching MX pointers to local host
7169 If a pattern consists of the string \"@@mx@_any"\ it matches any domain that
7170 has an MX record pointing to the local host or to any host that is listed in
7171 .index \hosts@_treat@_as@_local\
7172 \hosts@_treat@_as@_local\. The items \"@@mx@_primary"\ and \"@@mx@_secondary"\
7173 are similar, except that the first matches only when a primary MX target is the
7174 local host, and the second only when no primary MX target is the local host,
7175 but a secondary MX target is. `Primary' means an MX record with the lowest
7176 preference value -- there may of course be more than one of them.
7178 The MX lookup that takes place when matching a pattern of this type is
7179 performed with the resolver options for widening names turned off. Thus, for
7180 example, a single-component domain will \*not*\ be expanded by adding the
7181 resolver's default domain. See the \qualify@_single\ and \search@_parents\
7182 options of the \%dnslookup%\ router for a discussion of domain widening.
7184 Sometimes you may want to ignore certain IP addresses when using one of these
7185 patterns. You can specify this by following the pattern with \"/ignore=<<ip
7186 list>>"\, where <<ip list>> is a list of IP addresses. These addresses are
7187 ignored when processing the pattern (compare the \ignore@_target@_hosts\ option
7188 on a router). For example:
7190 domains = @mx_any/ignore=127.0.0.1
7192 This example matches any domain that has an MX record pointing to one of
7193 the local host's IP addresses other than 127.0.0.1.
7195 The list of IP addresses is in fact processed by the same code that processes
7196 host lists, so it may contain CIDR-coded network specifications and it may also
7197 contain negative items.
7199 Because the list of IP addresses is a sublist within a domain list, you have to
7200 be careful about delimiters if there is more than one address. Like any other
7201 list, the default delimiter can be changed. Thus, you might have:
7203 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7204 an.other.domain : ...
7206 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7207 involved, it is easiest to change the delimiter for the main list as well:
7209 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7210 an.other.domain ? ...
7214 .index asterisk||in domain list
7215 .index domain list||asterisk in
7216 .index domain list||matching `ends with'
7217 If a pattern starts with an asterisk, the remaining characters of the pattern
7218 are compared with the terminating characters of the domain. The use of `$*$' in
7219 domain lists differs from its use in partial matching lookups. In a domain
7220 list, the character following the asterisk need not be a dot, whereas partial
7221 matching works only in terms of dot-separated components. For example, a domain
7222 list item such as \"*key.ex"\ matches \*donkey.ex*\ as well as
7225 .index regular expressions||in domain list
7226 .index domain list||matching regular expression
7227 If a pattern starts with a circumflex character, it is treated as a regular
7228 expression, and matched against the domain using a regular expression matching
7229 function. The circumflex is treated as part of the regular expression.
7230 References to descriptions of the syntax of regular expressions are given in
7231 chapter ~~CHAPregexp.
7233 \**Warning**\: Because domain lists are expanded before being processed, you
7234 must escape any backslash and dollar characters in the regular expression, or
7235 use the special \"@\N"\ sequence (see chapter ~~CHAPexpand) to specify that it
7236 is not to be expanded (unless you really do want to build a regular expression
7237 by expansion, of course).
7239 .index lookup||in domain list
7240 .index domain list||matching by lookup
7241 If a pattern starts with the name of a single-key lookup type followed by a
7242 semicolon (for example, `dbm;' or `lsearch;'), the remainder of the pattern
7243 must be a file name in a suitable format for the lookup type. For example, for
7244 `cdb;' it must be an absolute path:
7246 domains = cdb;/etc/mail/local_domains.cdb
7248 The appropriate type of lookup is done on the file using the domain name as the
7249 key. In most cases, the data that is looked up is not used; Exim is interested
7250 only in whether or not the key is present in the file. However, when a lookup
7251 is used for the \domains\ option on a router
7252 or a \domains\ condition in an ACL statement, the data is preserved in the
7253 \$domain@_data$\ variable and can be referred to in other router options or
7254 other statements in the same ACL.
7256 Any of the single-key lookup type names may be preceded by `partial<<n>>-',
7257 where the <<n>> is optional, for example,
7259 domains = partial-dbm;/partial/domains
7261 This causes partial matching logic to be invoked; a description of how this
7262 works is given in section ~~SECTpartiallookup.
7264 .index asterisk||in lookup type
7265 Any of the single-key lookup types may be followed by an asterisk. This causes
7266 a default lookup for a key consisting of a single asterisk to be done if the
7267 original lookup fails. This is not a useful feature when using a domain list to
7268 select particular domains (because any domain would match), but it might have
7269 value if the result of the lookup is being used via the \$domain@_data$\
7272 If the pattern starts with the name of a query-style lookup type followed by a
7273 semicolon (for example, `nisplus;' or `ldap;'), the remainder of the pattern
7274 must be an appropriate query for the lookup type, as described in chapter
7275 ~~CHAPfdlookup. For example:
7277 hold_domains = mysql;select domain from holdlist \
7278 where domain = '$domain';
7280 In most cases, the data that is looked up is not used (so for an SQL query, for
7281 example, it doesn't matter what field you select). Exim is interested only in
7282 whether or not the query succeeds. However, when a lookup is used for the
7283 \domains\ option on a router, the data is preserved in the \$domain@_data$\
7284 variable and can be referred to in other options.
7286 .index domain list||matching literal domain name
7287 If none of the above cases apply, a caseless textual comparison is made between
7288 the pattern and the domain.
7291 Here is an example that uses several different kinds of pattern:
7293 domainlist funny_domains = \
7296 *.foundation.fict.example : \
7297 \N^[1-2]\d{3}\.fict\.example$\N : \
7298 partial-dbm;/opt/data/penguin/book : \
7299 nis;domains.byname : \
7300 nisplus;[name=$domain,status=local],domains.org_dir
7302 There are obvious processing trade-offs among the various matching modes. Using
7303 an asterisk is faster than a regular expression, and listing a few names
7304 explicitly probably is too. The use of a file or database lookup is expensive,
7305 but may be the only option if hundreds of names are required. Because the
7306 patterns are tested in order, it makes sense to put the most commonly matched
7311 .rset SECThostlist "~~chapter.~~section"
7312 .index host list||patterns in
7313 .index list||host list
7314 Host lists are used to control what remote hosts are allowed to do. For
7315 example, some hosts may be allowed to use the local host as a relay, and some
7316 may be permitted to use the SMTP \\ETRN\\ command. Hosts can be identified in
7317 two different ways, by name or by IP address. In a host list, some types of
7318 pattern are matched to a host name, and some are matched to an IP address.
7319 You need to be particularly careful with this when single-key lookups are
7320 involved, to ensure that the right value is being used as the key.
7322 .section Special host list patterns
7323 .index empty item in hosts list
7324 .index host list||empty string in
7325 If a host list item is the empty string, it matches only when no remote host is
7326 involved. This is the case when a message is being received from a local
7327 process using SMTP on the standard input, that is, when a TCP/IP connection is
7330 .index asterisk||in host list
7331 The special pattern `$*$' in a host list matches any host or no host. Neither
7332 the IP address nor the name is actually inspected.
7335 .section Host list patterns that match by IP address
7336 .rset SECThoslispatip "~~chapter.~~section"
7337 .index host list||matching IP addresses
7338 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7339 the incoming address actually appears in the IPv6 host as
7340 `@:@:$tt{ffff}:<<v4address>>'. When such an address is tested against a host
7341 list, it is converted into a traditional IPv4 address first. (Not all operating
7342 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7345 The following types of pattern in a host list check the remote host by
7346 inspecting its IP address:
7348 If the pattern is a plain domain name (not a regular expression, not starting
7349 with $*$, not a lookup of any kind), Exim calls the operating system function
7350 to find the associated IP address(es). Exim uses the newer
7351 \*getipnodebyname()*\ function when available, otherwise \*gethostbyname()*\.
7352 This typically causes a forward DNS lookup of the name. The result is compared
7353 with the IP address of the subject host.
7355 If there is a temporary problem (such as a DNS timeout) with the host name
7356 lookup, a temporary error occurs. For example, if the list is being used in an
7357 ACL condition, the ACL gives a `defer' response, usually leading to a temporary
7358 SMTP error code. If no IP address can be found for the host name, what happens
7359 is described in section ~~SECTbehipnot below.
7362 .index @@ in a host list
7363 If the pattern is `@@', the primary host name is substituted and used as a
7364 domain name, as just described.
7366 If the pattern is an IP address, it is matched against the IP address of the
7367 subject host. IPv4 addresses are given in the normal `dotted-quad' notation.
7368 IPv6 addresses can be given in colon-separated format, but the colons have to
7369 be doubled so as not to be taken as item separators when the default list
7370 separator is used. IPv6 addresses are recognized even when Exim is compiled
7371 without IPv6 support. This means that if they appear in a host list on an
7372 IPv4-only host, Exim will not treat them as host names. They are just addresses
7373 that can never match a client host.
7375 .index @@[] in a host list
7376 If the pattern is `@@[]', it matches the IP address of any IP interface on
7377 the local host. For example, if the local host is an IPv4 host with one
7378 interface address 10.45.23.56, these two ACL statements have the same effect:
7380 accept hosts = 127.0.0.1 : 10.45.23.56
7384 If the pattern is an IP address followed by a slash and a mask length (for
7385 example 10.11.42.0/24), it is matched against the IP address of the subject
7386 host under the given mask.
7387 This allows, an entire network of hosts to be included (or excluded) by a
7389 .index CIDR notation
7390 The mask uses CIDR notation; it specifies the number of address bits that must
7391 match, starting from the most significant end of the address.
7393 \**Note**\: the mask is \*not*\ a count of addresses, nor is it the high number
7394 of a range of addresses. It is the number of bits in the network portion of the
7395 address. The above example specifies a 24-bit netmask, so it matches all 256
7396 addresses in the 10.11.42.0 network. An item such as
7400 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7401 32 for an IPv4 address is the same as no mask at all; just a single address
7404 Here is another example which shows an IPv4 and an IPv6 network:
7406 recipient_unqualified_hosts = 192.168.0.0/16: \
7407 3ffe::ffff::836f::::/48
7409 The doubling of list separator characters applies only when these items
7410 appear inline in a host list. It is not required when indirecting via a file.
7413 recipient_unqualified_hosts = /opt/exim/unqualnets
7415 could make use of a file containing
7420 to have exactly the same effect as the previous example. When listing IPv6
7421 addresses inline, it is usually more convenient to use the facility for
7422 changing separator characters. This list contains the same two networks:
7424 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7427 The separator is changed to semicolon by the leading `<;' at the start of the
7432 .section Host list patterns for single-key lookups by host address
7433 .rset SECThoslispatsikey "~~chapter.~~section"
7434 .index host list||lookup of IP address
7435 When a host is to be identified by a single-key lookup of its complete IP
7436 address, the pattern takes this form:
7438 net-<<single-key-search-type>>;<<search-data>>
7442 hosts_lookup = net-cdb;/hosts-by-ip.db
7444 The text form of the IP address of the subject host is used as the lookup key.
7445 IPv6 addresses are converted to an unabbreviated form, using lower case
7446 letters, with dots as separators because colon is the key terminator in
7447 \%lsearch%\ files. [Colons can in fact be used in keys in \%lsearch%\ files by
7448 quoting the keys, but this is a facility that was added later.] The data
7449 returned by the lookup is not used.
7451 .index IP address||masking
7452 .index host list||masked IP address
7453 Single-key lookups can also be performed using masked IP addresses, using
7454 patterns of this form:
7456 net<<number>>-<<single-key-search-type>>;<<search-data>>
7460 net24-dbm;/networks.db
7462 The IP address of the subject host is masked using <<number>> as the mask
7463 length. A textual string is constructed from the masked value, followed by the
7464 mask, and this is used as the lookup key. For example, if the host's IP address
7465 is 192.168.34.6, the key that is looked up for the above example is
7466 `192.168.34.0/24'. IPv6 addresses are converted to a text value using lower
7467 case letters and dots as separators instead of the more usual colon, because
7468 colon is the key terminator in \%lsearch%\ files. Full, unabbreviated IPv6
7469 addresses are always used.
7471 \**Warning**\: Specifing \net32@-\ (for an IPv4 address) or \net128@-\ (for an
7472 IPv6 address) is not the same as specifing just \net@-\ without a number. In
7473 the former case the key strings include the mask value, whereas in the latter
7474 case the IP address is used on its own.
7477 .section Host list patterns that match by host name
7478 .rset SECThoslispatnam "~~chapter.~~section"
7479 .index host||lookup failures
7480 .index unknown host name
7481 .index host list||matching host name
7482 There are several types of pattern that require Exim to know the name of the
7483 remote host. These are either wildcard patterns or lookups by name. (If a
7484 complete hostname is given without any wildcarding, it is used to find an IP
7485 address to match against, as described in the section ~~SECThoslispatip above.)
7487 If the remote host name is not already known when Exim encounters one of these
7488 patterns, it has to be found from the IP address.
7489 Although many sites on the Internet are conscientious about maintaining reverse
7490 DNS data for their hosts, there are also many that do not do this.
7491 Consequently, a name cannot always be found, and this may lead to unwanted
7492 effects. Take care when configuring host lists with wildcarded name patterns.
7493 Consider what will happen if a name cannot be found.
7495 Because of the problems of determining host names from IP addresses, matching
7496 against host names is not as common as matching against IP addresses.
7498 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7499 if no name is found in the DNS, the system function (\*gethostbyaddr()*\ or
7500 \*getipnodebyaddr()*\ if available) is tried. The order in which these lookups
7501 are done can be changed by setting the \host@_lookup@_order\ option.
7503 There are some options that control what happens if a host name cannot be
7504 found. These are described in section ~~SECTbehipnot below.
7507 .index host||alias for
7508 .index alias for host
7509 As a result of aliasing, hosts may have more than one name. When processing any
7510 of the following types of pattern, all the host's names are checked:
7512 .index asterisk||in host list
7513 If a pattern starts with `$*$' the remainder of the item must match the end of
7514 the host name. For example, \"*.b.c"\ matches all hosts whose names end in
7515 \*.b.c*\. This special simple form is provided because this is a very common
7516 requirement. Other kinds of wildcarding require the use of a regular
7519 .index regular expressions||in host list
7520 .index host list||regular expression in
7521 If the item starts with `@^' it is taken to be a regular expression which is
7522 matched against the host name. For example,
7526 is a regular expression that matches either of the two hosts \*a.c.d*\ or
7527 \*b.c.d*\. When a regular expression is used in a host list, you must take care
7528 that backslash and dollar characters are not misinterpreted as part of the
7529 string expansion. The simplest way to do this is to use \"@\N"\ to mark that
7530 part of the string as non-expandable. For example:
7532 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
7534 \**Warning**\: If you want to match a complete host name, you must include the
7535 \"@$"\ terminating metacharacter in the regular expression, as in the above
7536 example. Without it, a match at the start of the host name is all that is
7541 .section Behaviour when an IP address or name cannot be found
7542 .rset SECTbehipnot "~~chapter.~~section"
7543 .index host||lookup failures
7544 While processing a host list, Exim may need to look up an IP address from a
7545 name (see section ~~SECThoslispatip), or it may need to look up a host name
7546 from an IP address (see section ~~SECThoslispatnam). In either case, the
7547 behaviour when it fails to find the information it is seeking is the same.
7549 .index \"+include@_unknown"\
7550 .index \"+ignore@_unknown"\
7551 By default, Exim behaves as if the host does not match the list. This may not
7552 always be what you want to happen. To change Exim's behaviour, the special
7553 items \"+include@_unknown"\ or \"+ignore@_unknown"\ may appear in the list (at
7554 top level -- they are not recognized in an indirected file).
7556 If any item that follows \"+include@_unknown"\ requires information that
7557 cannot found, Exim behaves as if the host does match the list. For example,
7559 host_reject_connection = +include_unknown:*.enemy.ex
7561 rejects connections from any host whose name matches \"*.enemy.ex"\, and also
7562 any hosts whose name it cannot find.
7564 If any item that follows \"+ignore@_unknown"\ requires information that cannot
7565 be found, Exim ignores that item and proceeds to the rest of the list. For
7568 accept hosts = +ignore_unknown : friend.example : \
7571 accepts from any host whose name is \*friend.example*\ and from 192.168.4.5,
7572 whether or not its host name can be found. Without \"+ignore@_unknown"\, if no
7573 name can be found for 192.168.4.5, it is rejected.
7575 Both \"+include@_unknown"\ and \"+ignore@_unknown"\ may appear in the same
7576 list. The effect of each one lasts until the next, or until the end of the
7579 \**Note**\: This section applies to permanent lookup failures. It does \*not*\
7580 apply to temporary DNS errors. They always cause a defer action.
7583 .section Host list patterns for single-key lookups by host name
7584 .rset SECThoslispatnamsk "~~chapter.~~section"
7585 .index host||lookup failures
7586 .index unknown host name
7587 .index host list||matching host name
7588 If a pattern is of the form
7590 <<single-key-search-type>>;<<search-data>>
7594 dbm;/host/accept/list
7596 a single-key lookup is performend, using the host name as its key. If the
7597 lookup succeeds, the host matches the item. The actual data that is looked up
7600 \**Reminder**\: With this kind of pattern, you must have host $it{names} as
7601 keys in the file, not IP addresses. If you want to do lookups based on IP
7602 addresses, you must precede the search type with `net-' (see section
7603 ~~SECThoslispatsikey). There is, however, no reason why you could not use two
7604 items in the same list, one doing an address lookup and one doing a name
7605 lookup, both using the same file.
7608 .section Host list patterns for query-style lookups
7609 If a pattern is of the form
7611 <<query-style-search-type>>;<<query>>
7613 the query is obeyed, and if it succeeds, the host matches the item. The actual
7614 data that is looked up is not used. The variables \$sender@_host@_address$\ and
7615 \$sender@_host@_name$\ can be used in the query. For example:
7617 hosts_lookup = pgsql;\
7618 select ip from hostlist where ip='$sender_host_address'
7620 The value of \$sender@_host@_address$\ for an IPv6 address contains colons. You
7621 can use the \sg\ expansion item to change this if you need to. If you want to
7622 use masked IP addresses in database queries, you can use the \mask\ expansion
7625 If the query contains a reference to \$sender@_host@_name$\, Exim automatically
7626 looks up the host name if has not already done so. (See section
7627 ~~SECThoslispatnam for comments on finding host names.)
7629 Historical note: prior to release 4.30, Exim would always attempt to find a
7630 host name before running the query, unless the search type was preceded by
7631 \"net-"\. This is no longer the case. For backwards compatibility, \"net-"\ is
7632 still recognized for query-style lookups, but its presence or absence has no
7633 effect. (Of course, for single-key lookups, \"net-"\ $it{is} important.
7634 See section ~~SECThoslispatsikey.)
7637 .section Mixing wildcarded host names and addresses in host lists
7638 .rset SECTmixwilhos "~~chapter.~~section"
7639 .index host list||mixing names and addresses in
7640 If you have name lookups or wildcarded host names and IP addresses in the same
7641 host list, you should normally put the IP addresses first. For example, in an
7644 accept hosts = 10.9.8.7 : *.friend.example
7646 The reason for this lies in the left-to-right way that Exim processes lists.
7647 It can test IP addresses without doing any DNS lookups, but when it reaches an
7648 item that requires a host name, it fails if it cannot find a host name to
7649 compare with the pattern. If the above list is given in the opposite order, the
7650 \accept\ statement fails for a host whose name cannot be found, even if its
7651 IP address is 10.9.8.7.
7653 If you really do want to do the name check first, and still recognize the IP
7654 address, you can rewrite the ACL like this:
7656 accept hosts = *.friend.example
7657 accept hosts = 10.9.8.7
7659 If the first \accept\ fails, Exim goes on to try the second one. See chapter
7660 ~~CHAPACL for details of ACLs.
7665 .section Address lists
7666 .index list||address list
7667 .index address list||empty item
7668 .index address list||patterns
7669 .rset SECTaddresslist "~~chapter.~~section"
7670 Address lists contain patterns that are matched against mail addresses. There
7671 is one special case to be considered: the sender address of a bounce message is
7672 always empty. You can test for this by providing an empty item in an address
7673 list. For example, you can set up a router to process bounce messages by
7674 using this option setting:
7678 The presence of the colon creates an empty item. If you do not provide any
7679 data, the list is empty and matches nothing. The empty sender can also be
7680 detected by a regular expression that matches an empty string,
7682 and by a query-style lookup that succeeds when \$sender@_address$\ is empty.
7684 The following kinds of address list pattern can match any address, including
7685 the empty address that is characteristic of bounce message senders:
7689 As explained above, if a pattern item is empty, it matches the empty address
7693 .index regular expressions||in address list
7694 .index address list||regular expression in
7695 If (after expansion) a pattern starts with `@^', a regular expression match is
7696 done against the complete address, with the pattern as the regular expression.
7697 You must take care that backslash and dollar characters are not misinterpreted
7698 as part of the string expansion. The simplest way to do this is to use \"@\N"\
7699 to mark that part of the string as non-expandable. For example:
7701 deny senders = \N^\d{8}.+@spamhaus.example$\N : ...
7703 The \"@\N"\ sequences are removed by the expansion, so the item does start
7704 with `@^' by the time it is being interpreted as an address pattern.
7706 .index address list||lookup for complete address
7707 Complete addresses can be looked up by using a pattern that starts with a
7708 lookup type terminated by a semicolon, followed by the data for the lookup. For
7711 deny senders = cdb;/etc/blocked.senders : \
7712 mysql;select address from blocked where \
7713 address='${quote_mysql:$sender_address}'
7716 Both query-style and single-key lookup types can be used. For a single-key
7717 lookup type, Exim uses the complete address as the key. However, empty keys are
7718 not supported for single-key lookups, so a match against the empty address
7719 always fails. This restriction does not apply to query-style lookups.
7722 Partial matching for single-key lookups (section ~~SECTpartiallookup) cannot be
7723 used, and is ignored if specified, with an entry being written to the panic
7725 .index @*@@ with single-key lookup
7726 However, you can configure lookup defaults, as described in section
7727 ~~SECTdefaultvaluelookups, but this is useful only for the `$*$@@' type of
7728 default. For example, with this lookup:
7730 accept senders = lsearch*@;/some/file
7732 the file could contains lines like this:
7734 user1@domain1.example
7737 and for the sender address \*nimrod@@jaeger.example*\, the sequence of keys
7740 nimrod@jaeger.example
7744 \**Warning 1**\: Do not include a line keyed by `$*$' in the file, because that
7745 would mean that every address matches, thus rendering the test useless.
7747 \**Warning 2**\: Do not confuse these two kinds of item:
7749 deny recipients = dbm*@;/some/file
7750 deny recipients = *@dbm;/some/file
7752 The first does a whole address lookup, with defaulting, as just described,
7753 because it starts with a lookup type. The second matches the local part and
7754 domain independently, as described in a bullet point below.
7759 The following kinds of address list pattern can match only non-empty addresses.
7760 If the subject address is empty, a match against any of these pattern types
7765 .index @@@@ with single-key lookup
7766 .index address list||@@@@ lookup type
7767 .index address list||split local part and domain
7768 If a pattern starts with `@@@@' followed by a single-key lookup item
7769 (for example, \"@@@@lsearch;/some/file"\), the address that is being checked is
7770 split into a local part and a domain. The domain is looked up in the file. If
7771 it is not found, there is no match. If it is found, the data that is looked up
7772 from the file is treated as a colon-separated list of local part patterns, each
7773 of which is matched against the subject local part in turn.
7775 .index asterisk||in address list
7776 The lookup may be a partial one, and/or one involving a search for a default
7777 keyed by `$*$' (see section ~~SECTdefaultvaluelookups). The local part patterns
7778 that are looked up can be regular expressions or begin with `$*$', or even be
7779 further lookups. They may also be independently negated. For example, with
7781 deny senders = @@dbm;/etc/reject-by-domain
7783 the data from which the DBM file is built could contain lines like
7785 baddomain.com: !postmaster : *
7787 to reject all senders except \postmaster\ from that domain.
7788 .index local part||starting with !
7789 If a local part that actually begins with an exclamation mark is required, it
7790 has to be specified using a regular expression. In \%lsearch%\ files, an entry
7791 may be split over several lines by indenting the second and subsequent lines,
7792 but the separating colon must still be included at line breaks. White space
7793 surrounding the colons is ignored. For example:
7795 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
7798 As in all colon-separated lists in Exim, a colon can be included in an item by
7801 If the last item in the list starts with a right angle-bracket, the remainder
7802 of the item is taken as a new key to look up in order to obtain a continuation
7803 list of local parts. The new key can be any sequence of characters. Thus one
7804 might have entries like
7806 aol.com: spammer1 : spammer 2 : >*
7807 xyz.com: spammer3 : >*
7810 in a file that was searched with \@@@@dbm$*$\, to specify a match for 8-digit
7811 local parts for all domains, in addition to the specific local parts listed for
7812 each domain. Of course, using this feature costs another lookup each time a
7813 chain is followed, but the effort needed to maintain the data is reduced.
7814 .index loop||in lookups
7815 It is possible to construct loops using this facility, and in order to catch
7816 them, the chains may be no more than fifty items long.
7818 The @@@@<<lookup>> style of item can also be used with a query-style
7819 lookup, but in this case, the chaining facility is not available. The lookup
7820 can only return a single list of local parts.
7822 If a pattern contains an @@ character, but is not a regular expression and does
7823 not begin with a lookup type as described above, the local part of the subject
7824 address is compared with the local part of the pattern, which may start with an
7825 asterisk. If the local parts match, the domain is checked in exactly the same
7826 way as for a pattern in a domain list. For example, the domain can be
7827 wildcarded, refer to a named list, or be a lookup:
7829 deny senders = *@*.spamming.site:\
7830 *@+hostile_domains:\
7831 bozo@partial-lsearch;/list/of/dodgy/sites:\
7833 *@dbm;/bad/domains.db
7835 .index local part||starting with !
7836 .index address list||local part starting with !
7837 If a local part that begins with an exclamation mark is required, it has to be
7838 specified using a regular expression, because otherwise the exclamation mark is
7839 treated as a sign of negation.
7841 If a pattern is not one of the above syntax forms, that is, if a
7845 pattern that is not a regular expression or a lookup does not contain an @@
7846 character, it is matched against the domain part of the subject address. The
7847 only two formats that are recognized this way are a literal domain, or a domain
7848 pattern that starts with $*$. In both these cases, the effect is the same as if
7849 \"*@@"\ preceded the pattern.
7852 \**Warning**\: there is an important difference between the address list items
7853 in these two examples:
7856 senders = *@+my_list
7858 In the first one, \"my@_list"\ is a named address list, whereas in the second
7859 example it is a named domain list.
7863 .section Case of letters in address lists
7864 .rset SECTcasletadd "~~chapter.~~section"
7865 .index case of local parts
7866 .index address list||case forcing
7867 .index case forcing in address lists
7868 Domains in email addresses are always handled caselessly, but for local parts
7869 case may be significant on some systems (see \caseful@_local@_part\ for how
7870 Exim deals with this when routing addresses). However, RFC 2505 ($it{Anti-Spam
7871 Recommendations for SMTP MTAs}) suggests that matching of addresses to blocking
7872 lists should be done in a case-independent manner. Since most address lists in
7873 Exim are used for this kind of control, Exim attempts to do this by default.
7875 The domain portion of an address is always lowercased before matching it to an
7876 address list. The local part is lowercased by default, and any string
7877 comparisons that take place are done caselessly. This means that the data in
7878 the address list itself, in files included as plain file names, and in any file
7879 that is looked up using the `@@@@' mechanism, can be in any case. However, the
7880 keys in files that are looked up by a search type other than \%lsearch%\ (which
7881 works caselessly) must be in lower case, because these lookups are not
7885 To allow for the possibility of caseful address list matching, if an item in
7886 an address list is the string `+caseful', the original case of the local
7887 part is restored for any comparisons that follow, and string comparisons are no
7888 longer case-independent. This does not affect the domain, which remains in
7889 lower case. However, although independent matches on the domain alone are still
7890 performed caselessly, regular expressions that match against an entire address
7891 become case-sensitive after `+caseful' has been seen.
7894 .section Local part lists
7895 .rset SECTlocparlis "~~chapter.~~section"
7896 .index list||local part list
7897 .index local part||list
7898 Case-sensitivity in local part lists is handled in the same way as for address
7899 lists, as just described. The `+caseful' item can be used if required. In a
7900 setting of the \local@_parts\ option in a router with \caseful@_local@_part\
7901 set false, the subject is lowercased and the matching is initially
7902 case-insensitive. In this case, `+caseful' will restore case-sensitive matching
7903 in the local part list, but not elsewhere in the router. If
7904 \caseful@_local@_part\ is set true in a router, matching in the \local@_parts\
7905 option is case-sensitive from the start.
7907 If a local part list is indirected to a file (see section ~~SECTfilnamlis),
7908 comments are handled in the same way as address lists -- they are recognized
7909 only if the @# is preceded by white space or the start of the line.
7910 Otherwise, local part lists are matched in the same way as domain lists, except
7911 that the special items that refer to the local host (\"@@"\, \"@@[]"\,
7912 \"@@mx@_any"\, \"@@mx@_primary"\, and \"@@mx@_secondary"\) are not recognized.
7913 Refer to section ~~SECTdomainlist for details of the other available item
7922 . ============================================================================
7923 .chapter String expansions
7924 .set runningfoot "string expansions"
7925 .rset CHAPexpand ~~chapter
7926 .index expansion||of strings
7927 Many strings in Exim's run time configuration are expanded before use. Some of
7928 them are expanded every time they are used; others are expanded only once.
7930 When a string is being expanded it is copied verbatim from left to right except
7931 when a dollar or backslash character is encountered. A dollar specifies the
7932 start of a portion of the string which is interpreted and replaced as described
7933 below in section ~~SECTexpansionitems onwards. Backslash is used as an escape
7934 character, as described in the following section.
7937 .section Literal text in expanded strings
7938 .rset SECTlittext "~~chapter.~~section"
7939 .index expansion||including literal text
7940 An uninterpreted dollar can be included in an expanded string by putting a
7941 backslash in front of it. A backslash can be used to prevent any special
7942 character being treated specially in an expansion, including itself. If the
7943 string appears in quotes in the configuration file, two backslashes are
7944 required because the quotes themselves cause interpretation of backslashes when
7945 the string is read in (see section ~~SECTstrings).
7947 .index expansion||non-expandable substrings
7948 A portion of the string can specified as non-expandable by placing it between
7949 two occurrences of \"@\N"\. This is particularly useful for protecting regular
7950 expressions, which often contain backslashes and dollar signs. For example:
7952 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
7954 On encountering the first \"@\N"\, the expander copies subsequent characters
7955 without interpretation until it reaches the next \"@\N"\ or the end of the
7959 .section Character escape sequences in expanded strings
7960 .index expansion||escape sequences
7961 A backslash followed by one of the letters `n', `r', or `t' in an expanded
7962 string is recognized as an escape sequence for the character newline, carriage
7963 return, or tab, respectively. A backslash followed by up to three octal digits
7964 is recognized as an octal encoding for a single character, and a backslash
7965 followed by `x' and up to two hexadecimal digits is a hexadecimal encoding.
7967 These escape sequences are also recognized in quoted strings when they are read
7968 in. Their interpretation in expansions as well is useful for unquoted strings,
7969 and for other cases such as looked-up strings that are then expanded.
7971 .section Testing string expansions
7972 .index expansion||testing
7973 .index testing||string expansion
7974 .index \-be-\ option
7975 Many expansions can be tested by calling Exim with the \-be-\ option. This takes
7976 the command arguments, or lines from the standard input if there are no
7977 arguments, runs them through the string expansion code, and writes the results
7978 to the standard output. Variables based on configuration values are set up, but
7979 since no message is being processed, variables such as \$local@_part$\ have no
7980 value. Nevertheless the \-be-\ option can be useful for checking out file and
7981 database lookups, and the use of expansion operators such as \sg\, \substr\ and
7984 Exim gives up its root privilege when it is called with the \-be-\ option, and
7985 instead runs under the uid and gid it was called with, to prevent users from
7986 using \-be-\ for reading files to which they do not have access.
7990 .section Forced expansion failure
7991 .rset SECTforexpfai "~~chapter.~~section"
7992 .index expansion||forced failure
7993 A number of expansions that are described in the following section have
7994 alternative `true' and `false' substrings, enclosed in curly brackets. Which
7995 one is used depends on some condition that is evaluated as part of the
7996 expansion. If, instead of a `false' substring, the word `fail' is used (not in
7997 curly brackets), the entire string expansion fails in a way that can be
7998 detected by the code that requested the expansion. This is called `forced
7999 expansion failure', and its consequences depend on the circumstances. In some
8000 cases it is no different from any other expansion failure, but in others a
8001 different action may be taken. Such variations are mentioned in the
8002 documentation of the option that is being expanded.
8006 .section Expansion items
8007 .rset SECTexpansionitems "~~chapter.~~section"
8008 The following items are recognized in expanded strings. White space may be used
8009 between sub-items that are keywords or substrings enclosed in braces inside an
8010 outer set of braces, to improve readability. \**Warning**\: Within braces,
8011 white space is significant.
8015 .item "@$<<variable name>>#$rm{or}#@$@{<<variable name>>@}"
8016 .index expansion||variables
8017 Substitute the contents of the named variable, for example
8022 The second form can be used to separate the name from subsequent alphanumeric
8023 characters. This form (using curly brackets) is available only for variables;
8024 it does $it{not} apply to message headers. The names of the variables are given
8025 in section ~~SECTexpvar below. If the name of a non-existent variable is given,
8026 the expansion fails.
8028 .item "@$@{<<op>>:<<string>>@}"
8029 .index expansion||operators
8030 The string is first itself expanded, and then the operation specified by <<op>>
8031 is applied to it. For example,
8035 The string starts with the first character after the colon, which may be
8036 leading white space. A list of operators is given in section ~~SECTexpop below.
8037 The operator notation is used for simple expansion items that have just one
8038 argument, because it reduces the number of braces and therefore makes the
8039 string easier to understand.
8041 .item "@$@{extract@{<<key>>@}@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8042 .index expansion||extracting substrings by key
8043 The key and <<string1>> are first expanded separately.
8044 Leading and trailing whitespace is removed from the key (but not from any of
8046 The key must not consist entirely of digits. The expanded <<string1>> must be
8049 <<key1>> = <<value1>> <<key2>> = <<value2>> ...
8051 where the equals signs and spaces (but not both) are optional. If any of the
8052 values contain white space, they must be enclosed in double quotes, and any
8053 values that are enclosed in double quotes are subject to escape processing as
8054 described in section ~~SECTstrings. The expanded <<string1>> is searched for
8055 the value that corresponds to the key. The search is case-insensitive. If the
8056 key is found, <<string2>> is expanded, and replaces the whole item; otherwise
8057 <<string3>> is used. During the expansion of <<string2>> the variable \$value$\
8058 contains the value that has been extracted. Afterwards, it is restored to any
8059 previous value it might have had.
8061 If @{<<string3>>@} is omitted, the item is replaced by an empty string if the
8062 key is not found. If @{<<string2>>@} is also omitted, the value that was
8063 extracted is used. Thus, for example, these two expansions are identical, and
8066 @$@{extract@{gid@}{uid=1984 gid=2001@}@}
8067 @$@{extract@{gid@}{uid=1984 gid=2001@}@{@$value@}@}
8069 Instead of @{<<string3>>@} the word `fail' (not in curly brackets) can appear,
8072 @$@{extract@{Z@}@{A=... B=...@}@{@$value@} fail @}
8074 This forces an expansion failure (see section ~~SECTforexpfai); @{<<string2>>@}
8075 must be present for `fail' to be recognized.
8078 .item "@$@{extract@{<<number>>@}@{<<separators>>@}@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8079 .index expansion||extracting substrings by number
8080 The <<number>> argument must consist entirely of decimal digits,
8081 apart from leading and trailing whitespace, which is ignored.
8082 This is what distinguishes this form of \extract\ from the previous kind. It
8083 behaves in the same way, except that, instead of extracting a named field, it
8084 extracts from <<string1>> the field whose number is given as the first
8085 argument. You can use \$value$\ in <<string2>> or \"fail"\ instead of
8086 <<string3>> as before.
8088 The fields in the string are separated by any one of the characters in the
8089 separator string. These may include space or tab characters.
8090 The first field is numbered one. If the number is negative, the fields are
8091 counted from the end of the string, with the rightmost one numbered -1. If the
8092 number given is zero, the entire string is returned. If the modulus of the
8093 number is greater than the number of fields in the string, the result is the
8094 expansion of <<string3>>, or the empty string if <<string3>> is not provided.
8097 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8101 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8103 yields `99'. Two successive separators mean that the field between them is
8104 empty (for example, the fifth field above).
8107 .item "@$@{hash@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8108 .index hash function||textual
8109 .index expansion||textual hash
8110 This is a textual hashing function, and was the first to be implemented in
8111 early versions of Exim. In current releases, there are other hashing functions
8112 (numeric, MD5, and SHA-1), which are described below.
8114 The first two strings, after expansion, must be numbers. Call them <<m>> and
8115 <<n>>. If you are using fixed values for these numbers, that is, if <<string1>>
8116 and <<string2>> do not change when they are expanded, you can use the
8117 simpler operator notation that avoids some of the braces:
8119 @$@{hash@_<<n>>@_<<m>>:<<string>>@}
8121 The second number is optional (in both notations).
8123 If <<n>> is greater than or equal to the length of the string, the expansion
8124 item returns the string. Otherwise it computes a new string of length <<n>> by
8125 applying a hashing function to the string. The new string consists of
8126 characters taken from the first <<m>> characters of the string
8128 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8130 If <<m>> is not present the value 26 is used, so that only lower case
8131 letters appear. For example:
8133 @$@{hash@{3@}@{monty@}@} $rm{yields} \"jmg"\
8134 @$@{hash@{5@}@{monty@}@} $rm{yields} \"monty"\
8135 @$@{hash@{4@}@{62@}@{monty python@}@} $rm{yields} \"fbWx"\
8139 .item "@$header@_<<header name>>:#$rm{or}#@$h@_<<header name>>:"
8140 .item "@$bheader@_<<header name>>:#$rm{or}#@$bh@_<<header name>>:"
8141 .item "@$rheader@_<<header name>>:#$rm{or}#@$rh@_<<header name>>:"
8142 .index expansion||header insertion
8144 .index \$bheader@_$\
8145 .index \$rheader@_$\
8146 .index header lines||in expansion strings
8147 .index header lines||character sets
8148 .index header lines||decoding
8149 Substitute the contents of the named message header line, for example
8153 The newline that terminates a header line is not included in the expansion, but
8154 internal newlines (caused by splitting the header line over several physical
8155 lines) may be present.
8157 The difference between \rheader\, \bheader\, and \header\ is in the way the
8158 data in the header line is interpreted.
8160 .index whitespace||in header lines
8161 \rheader\ gives the original `raw' content of the header line, with no
8162 processing at all, and without the removal of leading and trailing whitespace.
8164 .index base64 encoding||in header lines
8165 \bheader\ removes leading and trailing whitespace, and then decodes base64 or
8166 quoted-printable MIME `words' within the header text, but does no character
8167 set translation. If decoding of what looks superficially like a MIME `word'
8168 fails, the raw string is returned.
8169 .index binary zero||in header line
8170 If decoding produces a binary zero character, it is replaced by a question mark
8171 -- this is what Exim does for binary zeros that are actually received in header
8174 \header\ tries to translate the string as decoded by \bheader\ to a standard
8175 character set. This is an attempt to produce the same string as would be
8176 displayed on a user's MUA. If translation fails, the \bheader\ string is
8177 returned. Translation is attempted only on operating systems that support the
8178 \*iconv()*\ function. This is indicated by the compile-time macro
8179 \\HAVE@_ICONV\\ in a system Makefile or in \(Local/Makefile)\.
8182 In a filter file, the target character set for \header\ can be specified by a
8183 command of the following form:
8185 headers charset "UTF-8"
8187 This command affects all references to \$h@_$\ (or \$header@_$\) expansions in
8188 subsequently obeyed filter commands. In the absence of this command, the target
8189 character set in a filter is taken from the setting of the \headers@_charset\
8190 option in the runtime configuration. The value of this option defaults to the
8191 value of \\HEADERS@_CHARSET\\ in \(Local/Makefile)\. The ultimate default is
8194 Header names follow the syntax of RFC 2822, which states that they may contain
8195 any printing characters except space and colon. Consequently, curly brackets
8196 $it{do not} terminate header names, and should not be used to enclose them as
8197 if they were variables. Attempting to do so causes a syntax error.
8199 Only header lines that are common to all copies of a message are visible to
8200 this mechanism. These are the original header lines that are received with the
8201 message, and any that are added by
8202 an ACL \warn\ statement or by
8203 a system filter. Header lines that are added to a particular copy of a message
8204 by a router or transport are not accessible.
8206 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8207 before the \\DATA\\ ACL, because the header structure is not set up until the
8208 message is received. Header lines that are added by \warn\ statements in a
8209 \\RCPT\\ ACL (for example) are saved until the message's incoming header lines
8210 are available, at which point they are added. When a \\DATA\\ ACL is running,
8211 however, header lines added by earlier ACLs are visible.
8213 Upper case and lower case letters are synonymous in header names. If the
8214 following character is white space, the terminating colon may be omitted, but
8215 this is not recommended, because you may then forget it when it is needed. When
8216 white space terminates the header name, it is included in the expanded string.
8217 If the message does not contain the given header, the expansion item is
8218 replaced by an empty string. (See the \def\ condition in section ~~SECTexpcond
8219 for a means of testing for the existence of a header.)
8221 If there is more than one header with the same name, they are all concatenated
8222 to form the substitution string, up to a maximum length of 64K. A newline
8223 character is inserted between each line.
8224 For the \header\ expansion, for those headers that contain lists of addresses,
8225 a comma is also inserted at the junctions between lines. This does not happen
8226 for the \rheader\ expansion.
8230 .item "@$@{hmac@{<<hashname>>@}@{<<secret>>@}@{<<string>>@}@}"
8231 .index expansion||hmac hashing
8232 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
8233 shared secret and some text into a message authentication code, as specified in
8235 This differs from \"@$@{md5:secret@_text...@}"\ or
8236 \"@$@{sha1:secret@_text...@}"\ in that the hmac step adds a signature to the
8237 cryptographic hash, allowing for authentication that is not possible with MD5
8239 The hash name must expand to either \"md5"\ or \"sha1"\ at present. For
8242 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
8244 For the hostname \*mail.example.com*\ and time 2002-10-17 11:30:59, this
8247 dd97e3ba5d1a61b5006108f8c8252953
8249 As an example of how this might be used, you might put in the main part of
8250 an Exim configuration:
8252 SPAMSCAN_SECRET=cohgheeLei2thahw
8254 In a router or a transport you could then have:
8257 X-Spam-Scanned: ${primary_hostname} ${message_id} \
8258 ${hmac{md5}{SPAMSCAN_SECRET}\
8259 {${primary_hostname},${message_id},$h_message-id:}}
8261 Then given a message, you can check where it was scanned by looking at the
8262 ::X-Spam-Scanned:: header line. If you know the secret, you can check that this
8263 header line is authentic by recomputing the authentication code from the host
8264 name, message ID and the ::Message-id:: header line. This can be done using
8265 Exim's \-be-\ option, or by other means, for example by using the
8266 \*hmac@_md5@_hex()*\ function in Perl.
8269 .item "@${if <<condition>> @{<<string1>>@}@{<<string2>>@}@}"
8270 .index expansion||conditional
8271 If <<condition>> is true, <<string1>> is expanded and replaces the whole item;
8272 otherwise <<string2>> is used. The available conditions are described in
8273 section ~~SECTexpcond below. For example:
8275 ${if eq {$local_part}{postmaster} {yes}{no} }
8277 The second string need not be present; if it is not and the condition is not
8278 true, the item is replaced with nothing. Alternatively, the word `fail' may be
8279 present instead of the second string (without any curly brackets). In this
8280 case, the expansion is forced to fail if the condition is not true (see section
8284 If both strings are omitted, the result is the string \"true"\ if the condition
8285 is true, and the empty string if the condition is false. This makes it less
8286 cumbersome to write custom ACL and router conditions. For example, instead of
8288 condition = ${if >{$acl_m4}{3}{true}{false}}
8292 condition = ${if >{$acl_m4}{3}}
8297 .item "@$@{length@{<<string1>>@}@{<<string2>>@}@}"
8298 .index expansion||string truncation
8299 The \length\ item is used to extract the initial portion of a string. Both
8300 strings are expanded, and the first one must yield a number, <<n>>, say. If you
8301 are using a fixed value for the number, that is, if <<string1>> does not change
8302 when expanded, you can use the simpler operator notation that avoids some of
8305 @$@{length@_<<n>>:<<string>>@}
8307 The result of this item is either the first <<n>> characters or the whole
8308 of <<string2>>, whichever is the shorter. Do not confuse \length\ with
8309 \strlen\, which gives the length of a string.
8312 .item "@${lookup@{<<key>>@} <<search type>> @{<<file>>@} @{<<string1>>@} @{<<string2>>@}@}"
8313 .item "@${lookup <<search type>> @{<<query>>@} @{<<string1>>@} @{<<string2>>@}@}"
8314 .index expansion||lookup in
8316 .index lookup||in expanded string
8317 These items specify data lookups in files and databases, as discussed in
8318 chapter ~~CHAPfdlookup. The first form is used for single-key lookups, and the
8319 second is used for query-style lookups. The <<key>>, <<file>>, and <<query>>
8320 strings are expanded before use.
8322 If there is any white space in a lookup item which is part of a filter command,
8323 a retry or rewrite rule, a routing rule for the \%manualroute%\ router, or any
8324 other place where white space is significant, the lookup item must be enclosed
8325 in double quotes. The use of data lookups in users' filter files may be locked
8326 out by the system administrator.
8329 If the lookup succeeds, <<string1>> is expanded and replaces the entire item.
8330 During its expansion, the variable \$value$\ contains the data returned by the
8331 lookup. Afterwards it reverts to the value it had previously (at the outer
8332 level it is empty). If the lookup fails, <<string2>> is expanded and replaces
8333 the entire item. If @{<<string2>>@} is omitted, the replacement is the empty
8334 string on failure. If <<string2>> is provided, it can itself be a nested
8335 lookup, thus providing a mechanism for looking up a default value when the
8336 original lookup fails.
8338 If a nested lookup is used as part of <<string1>>, \$value$\ contains the data
8339 for the outer lookup while the parameters of the second lookup are expanded,
8340 and also while <<string2>> of the second lookup is expanded, should the second
8343 Instead of @{<<string2>>@} the word `fail' can appear, and in this case, if the
8344 lookup fails, the entire expansion is forced to fail (see section
8345 ~~SECTforexpfai). If both @{<<string1>>@} and @{<<string2>>@} are omitted, the
8346 result is the looked up value in the case of a successful lookup, and nothing
8347 in the case of failure.
8349 For single-key lookups, the string `partial' is permitted to precede the
8350 search type in order to do partial matching, and $*$ or $*$@@ may follow a
8351 search type to request default lookups if the key does not match (see sections
8352 ~~SECTdefaultvaluelookups and ~~SECTpartiallookup for details).
8354 .index numerical variables (\$1$\, \$2$\, etc)||in lookup expansion
8355 If a partial search is used, the variables \$1$\ and \$2$\ contain the wild
8356 and non-wild parts of the key during the expansion of the replacement text.
8357 They return to their previous values at the end of the lookup item.
8359 This example looks up the postmaster alias in the conventional alias file:
8361 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
8363 This example uses NIS+ to look up the full name of the user corresponding to
8364 the local part of an address, forcing the expansion to fail if it is not found:
8366 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8371 .item "@$@{nhash@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8372 .index expansion||numeric hash
8373 .index hash function||numeric
8374 The three strings are expanded; the first two must yield numbers. Call them
8375 <<n>> and <<m>>. If you are using fixed values for these numbers, that is, if
8376 <<string1>> and <<string2>> do not change when they are expanded, you can use
8377 the simpler operator notation that avoids some of the braces:
8379 @$@{nhash@_<<n>>@_<<m>>:<<string>>@}
8381 The second number is optional (in both notations). If there is only one number,
8382 the result is a number in the range 0--<<n>>-1. Otherwise, the string is
8383 processed by a div/mod hash function that returns two numbers, separated by a
8384 slash, in the ranges 0 to <<n>>-1 and 0 to <<m>>-1, respectively. For example,
8386 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8388 returns the string `6/33'.
8392 .item "@$@{perl@{<<subroutine>>@}@{<<arg>>@}@{<<arg>>@}...@}"
8393 .index Perl||use in expanded string
8394 .index expansion||calling Perl from
8395 This item is available only if Exim has been built to include an embedded Perl
8396 interpreter. The subroutine name and the arguments are first separately
8397 expanded, and then the Perl subroutine is called with those arguments. No
8398 additional arguments need be given; the maximum number permitted, including the
8399 name of the subroutine, is nine.
8401 The return value of the subroutine is inserted into the expanded string, unless
8402 the return value is \undef\. In that case, the expansion fails in the same way
8403 as an explicit `fail' on a lookup item.
8404 The return value is a scalar. Whatever you return is evaluated in a scalar
8405 context. For example, if you return the name of a Perl vector, the
8406 return value is the size of the vector, not its contents.
8408 If the subroutine exits by calling Perl's \die\ function, the expansion fails
8409 with the error message that was passed to \die\. More details of the embedded
8410 Perl facility are given in chapter ~~CHAPperl.
8412 The \%redirect%\ router has an option called \forbid@_filter@_perl\ which locks
8413 out the use of this expansion item in filter files.
8416 .item "@$@{readfile@{<<file name>>@}@{<<eol string>>@}@}"
8417 .index expansion||inserting an entire file
8418 .index file||inserting into expansion
8419 The file name and end-of-line string are first expanded separately. The file is
8420 then read, and its contents replace the entire item. All newline characters in
8421 the file are replaced by the end-of-line string if it is present. Otherwise,
8422 newlines are left in the string.
8423 String expansion is not applied to the contents of the file. If you want this,
8424 you must wrap the item in an \expand\ operator. If the file cannot be read, the
8425 string expansion fails.
8427 The \%redirect%\ router has an option called \forbid@_filter@_readfile\ which
8428 locks out the use of this expansion item in filter files.
8432 .item "@$@{readsocket@{<<name>>@}@{<<request>>@}@{<<timeout>>@}@{<<eol string>>@}@{<<fail string>>@}@}"
8433 .index expansion||inserting from a socket
8434 .index socket, use of in expansion
8435 This item inserts data that is read from a Unix domain socket into the expanded
8436 string. The minimal way of using it uses just two arguments:
8438 ${readsocket{/socket/name}{request string}}
8440 Exim connects to the socket, writes the request string (unless it is an
8441 empty string) and reads from the socket until an end-of-file is read. A timeout
8442 of 5 seconds is applied. Additional, optional arguments extend what can be
8443 done. Firstly, you can vary the timeout. For example:
8445 ${readsocket{/socket/name}{request-string}{3s}}
8447 A fourth argument allows you to change any newlines that are in the data
8448 that is read, in the same way as for \readfile\ (see above). This example turns
8451 ${readsocket{/socket/name}{request-string}{3s}{ }}
8453 As with all expansions, the substrings are expanded before the processing
8454 happens. Errors in these sub-expansions cause the expansion to fail. In
8455 addition, the following errors can occur:
8457 Failure to create a socket file descriptor;
8459 Failure to connect the socket;
8461 Failure to write the request-string;
8463 Timeout on reading from the socket.
8465 By default, any of these errors causes the expansion to fail. However, if
8466 you supply a fifth substring, it is expanded and used when any of the above
8467 errors occurs. For example:
8469 ${readsocket{/socket/name}{request-string}{3s}{\n}\
8472 You can test for the existence of the socket by wrapping this expansion in
8473 \"@$@{if exists"\, but there is a race condition between that test and the
8474 actual opening of the socket, so it is safer to use the fifth argument if you
8475 want to be absolutely sure of avoiding an expansion error for a non-existent
8478 The \%redirect%\ router has an option called \forbid@_filter@_readsocket\ which
8479 locks out the use of this expansion item in filter files.
8481 .item "@$rheader@_<<header name>>:#$rm{or}#@$rh@_<<header name>>:"
8482 This item inserts `raw' header lines. It is described with the \header\
8483 expansion item above.
8487 .item "@$@{run@{<<command>> <<args>>@}@{<<string1>>@}@{<<string2>>@}@}"
8488 .index expansion||running a command
8489 The command and its arguments are first expanded separately, and then the
8490 command is run in a separate process, but under the same uid and gid. As in
8491 other command executions from Exim, a shell is not used by default. If you want
8492 a shell, you must explicitly code it.
8493 .index return code||from \run\ expansion
8494 If the command succeeds (gives a zero return code) <<string1>> is expanded and
8495 replaces the entire item; during this expansion, the standard output from the
8496 command is in the variable \$value$\. If the command fails, <<string2>>, if
8497 present, is expanded. If it is absent, the result is empty. Alternatively,
8498 <<string2>> can be the word `fail' (not in braces) to force expansion failure
8499 if the command does not succeed. If both strings are omitted, the result is the
8500 standard output on success, and nothing on failure.
8502 The return code from the command is put in the variable \$runrc$\, and this
8503 remains set afterwards, so in a filter file you can do things like this:
8505 if "${run{x y z}{}}$runrc" is 1 then ...
8506 elif $runrc is 2 then ...
8510 If execution of the command fails (for example, the command does not exist),
8511 the return code is 127 -- the same code that shells use for non-existent
8514 \**Warning**\: In a router or transport, you cannot assume the order in which
8515 option values are expanded, except for those pre-conditions whose order of
8516 testing is documented. Therefore, you cannot reliably expect to set \$runrc$\
8517 by the expansion of one option, and use it in another.
8519 The \%redirect%\ router has an option called \forbid@_filter@_run\ which locks
8520 out the use of this expansion item in filter files.
8523 .item "@$@{sg@{<<subject>>@}@{<<regex>>@}@{<<replacement>>@}@}"
8524 .index expansion||string substitution
8525 This item works like Perl's substitution operator (s) with the global (/g)
8526 option; hence its name. However, unlike the Perl equivalent, Exim does not
8527 modify the subject string; instead it returns the modified string for insertion
8528 into the overall expansion. The item takes three arguments: the subject string,
8529 a regular expression, and a substitution string. For example
8531 ${sg{abcdefabcdef}{abc}{xyz}}
8533 yields `xyzdefxyzdef'. Because all three arguments are expanded before use, if
8534 any @$ or @\ characters are required in the regular expression or in the
8535 substitution string, they have to be escaped. For example
8537 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
8539 yields `defabc', and
8541 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
8543 yields `K1=A K4=D K3=C'.
8544 Note the use of \"@\N"\ to protect the contents of the regular expression from
8549 .item "@$@{substr@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8551 .index substring extraction
8552 .index expansion||substring extraction
8553 The three strings are expanded; the first two must yield numbers. Call them
8554 <<n>> and <<m>>. If you are using fixed values for these numbers, that is, if
8555 <<string1>> and <<string2>> do not change when they are expanded, you can use
8556 the simpler operator notation that avoids some of the braces:
8558 @$@{substr@_<<n>>@_<<m>>:<<string>>@}
8560 The second number is optional (in both notations).
8562 If it is absent in the simpler format, the preceding underscore must also be
8566 The \substr\ item can be used to extract more general substrings than \length\.
8567 The first number, <<n>>, is a starting offset, and <<m>> is the length
8568 required. For example
8570 ${substr{3}{2}{$local_part}}
8572 If the starting offset is greater than the string length the result is the null
8573 string; if the length plus starting offset is greater than the string length,
8574 the result is the right-hand part of the string, starting from the given
8575 offset. The first character in the string has offset zero.
8577 The \substr\ expansion item can take negative offset values to count
8578 from the right-hand end of its operand. The last character is offset -1, the
8579 second-last is offset -2, and so on. Thus, for example,
8581 ${substr{-5}{2}{1234567}}
8583 yields `34'. If the absolute value of a negative offset is greater than the
8584 length of the string, the substring starts at the beginning of the string, and
8585 the length is reduced by the amount of overshoot. Thus, for example,
8587 ${substr{-5}{2}{12}}
8589 yields an empty string, but
8591 ${substr{-3}{2}{12}}
8595 When the second number is omitted from \substr\, the remainder of the string is
8596 taken if the offset is positive. If it is negative, all characters in the
8597 string preceding the offset point are taken. For example, an offset of -1 and
8598 no length, as in these semantically identical examples:
8601 ${substr{-1}{abcde}}
8603 yields all but the last character of the string, that is, `abcd'.
8607 .item "@$@{tr@{<<subject>>@}@{<<characters>>@}@{<<replacements>>@}@}"
8608 .index expansion||character translation
8609 This item does single-character translation on its subject string. The second
8610 argument is a list of characters to be translated in the subject string. Each
8611 matching character is replaced by the corresponding character from the
8612 replacement list. For example
8614 ${tr{abcdea}{ac}{13}}
8616 yields `1b3de1'. If there are duplicates in the second character string, the
8617 last occurrence is used. If the third string is shorter than the second, its
8618 last character is replicated. However, if it is empty, no translation takes
8624 .section Expansion operators
8625 .rset SECTexpop "~~chapter.~~section"
8626 .index expansion||operators
8627 For expansion items that perform transformations on a single argument string,
8628 the `operator' notation is used because it is simpler and uses fewer braces.
8629 The substring is first expanded before the operation is applied to it. The
8630 following operations can be performed:
8634 .item "@$@{address:<<string>>@}"
8635 .index expansion||RFC 2822 address handling
8636 The string is interpreted as an RFC 2822 address, as it might appear in a
8637 header line, and the effective address is extracted from it. If the string does
8638 not parse successfully, the result is empty.
8641 .item "@$@{base62:<<digits>>@}"
8643 .index expansion||conversion to base 62
8644 The string must consist entirely of decimal digits. The number is converted to
8645 base 62 (sic) and output as a string of six characters, including leading
8646 zeros. \**Note**\: Just to be absolutely clear: this is \*not*\ base64
8649 .item "@$@{base62d:<<base-62 digits>>@}"
8651 .index expansion||conversion to base 62
8652 The string must consist entirely of base-62 digits. The number is converted to
8653 decimal and output as a string.
8656 .item "@$@{domain:<<string>>@}"
8657 .index domain||extraction
8658 .index expansion||domain extraction
8659 The string is interpreted as an RFC 2822 address and the domain is extracted
8660 from it. If the string does not parse successfully, the result is empty.
8663 .item "@$@{escape:<<string>>@}"
8664 .index expansion||escaping non-printing characters
8665 If the string contains any non-printing characters, they are converted to
8666 escape sequences starting with a backslash. Whether characters with the most
8667 significant bit set (so-called `8-bit characters') count as printing or not is
8668 controlled by the \print@_topbitchars\ option.
8671 .item "@$@{eval:<<string>>@}"
8672 .item "@$@{eval10:<<string>>@}"
8673 .index expansion||expression evaluation
8674 .index expansion||arithmetic expression
8675 These items supports simple arithmetic in expansion strings. The string (after
8676 expansion) must be a conventional arithmetic expression, but it is limited to
8677 the four basic operators (plus, minus, times, divide) and parentheses. All
8678 operations are carried out using integer arithmetic. Plus and minus have a
8679 lower priority than times and divide; operators with the same priority are
8680 evaluated from left to right.
8682 For \eval\, numbers may be decimal, octal (starting with `0') or hexadecimal
8683 (starting with `0x'). For \eval10\, all numbers are taken as decimal, even if
8684 they start with a leading zero. This can be useful when processing numbers
8685 extracted from dates or times, which often do have leading zeros.
8687 A number may be followed by `K' or `M' to multiply it by 1024 or 1024$*$1024,
8688 respectively. Negative numbers are supported. The result of the computation is
8689 a decimal representation of the answer (without `K' or `M'). For example:
8691 @$@{eval:1+1@} $rm{yields} 2
8692 @$@{eval:1+2*3@} $rm{yields} 7
8693 @$@{eval:(1+2)*3@} $rm{yields} 9
8695 As a more realistic example, in an ACL you might have
8697 deny message = Too many bad recipients
8700 {>{$rcpt_count}{10}} \
8703 {$recipients_count} \
8704 {${eval:$rcpt_count/2}} \
8708 The condition is true if there have been more than 10 \\RCPT\\ commands and
8709 fewer than half of them have resulted in a valid recipient.
8712 .item "@$@{expand:<<string>>@}"
8713 .index expansion||re-expansion of substring
8714 The \expand\ operator causes a string to be expanded for a second time. For
8717 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
8719 first looks up a string in a file while expanding the operand for \expand\, and
8720 then re-expands what it has found.
8723 .item "@$@{from@_utf8:<<string>>@}"
8725 .index UTF-8||conversion from
8726 .index expansion||UTF-8 conversion
8727 The world is slowly moving towards Unicode, although there are no standards for
8728 email yet. However, other applications (including some databases) are starting
8729 to store data in Unicode, using UTF-8 encoding. This operator converts from a
8730 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
8731 converted to underscores. The input must be a valid UTF-8 string. If it is not,
8732 the result is an undefined sequence of bytes.
8734 Unicode code points with values less than 256 are compatible with ASCII and
8735 ISO-8859-1 (also known as Latin-1).
8736 For example, character 169 is the copyright symbol in both cases, though the
8737 way it is encoded is different. In UTF-8, more than one byte is needed for
8738 characters with code values greater than 127, whereas ISO-8859-1 is a
8739 single-byte encoding (but thereby limited to 256 characters). This makes
8740 translation from UTF-8 to ISO-8859-1 straightforward.
8743 .item "@$@{hash@_<<n>>@_<<m>>:<<string>>@}"
8744 .index hash function||textual
8745 .index expansion||textual hash
8746 The \hash\ operator is a simpler interface to the hashing function that can be
8747 used when the two parameters are fixed numbers (as opposed to strings that
8748 change when expanded). The effect is the same as
8750 @$@{hash@{<<n>>@}@{<<m>>@}@{<<string>>@}@}
8752 See the description of the general \hash\ item above for details. The
8753 abbreviation \h\ can be used when \hash\ is used as an operator.
8757 .item "@$@{hex2b64:<<hexstring>>@}"
8758 .index base64 encoding||conversion from hex
8759 .index expansion||hex to base64
8760 This operator converts a hex string into one that is base64 encoded. This can
8761 be useful for processing the output of the MD5 and SHA-1 hashing functions.
8764 .item "@$@{lc:<<string>>@}"
8765 .index case forcing in strings
8766 .index string||case forcing
8768 .index expansion||case forcing
8769 This forces the letters in the string into lower-case, for example:
8775 .item "@$@{length@_<<number>>:<<string>>@}"
8776 .index expansion||string truncation
8777 The \length\ operator is a simpler interface to the \length\ function that can
8778 be used when the parameter is a fixed number (as opposed to a string that
8779 changes when expanded). The effect is the same as
8781 @$@{length@{<<number>>@}@{<<string>>@}@}
8783 See the description of the general \length\ item above for details. Note that
8784 \length\ is not the same as \strlen\. The abbreviation \l\ can be used when
8785 \length\ is used as an operator.
8788 .item "@$@{local@_part:<<string>>@}"
8789 .index expansion||local part extraction
8790 The string is interpreted as an RFC 2822 address and the local part is
8791 extracted from it. If the string does not parse successfully, the result is
8795 .item "@$@{mask:<<IP address>>/<<bit count>>@}"
8796 .index masked IP address
8797 .index IP address||masking
8798 .index CIDR notation
8799 .index expansion||IP address masking
8800 If the form of the string to be operated on is not an IP address followed by a
8801 slash and an integer (that is, a network address in CIDR notation), the
8802 expansion fails. Otherwise, this operator converts the IP address to binary,
8803 masks off the least significant bits according to the bit count, and converts
8804 the result back to text, with mask appended. For example,
8806 ${mask:10.111.131.206/28}
8808 returns the string `10.111.131.192/28'. Since this operation is expected to be
8809 mostly used for looking up masked addresses in files, the result for an IPv6
8810 address uses dots to separate components instead of colons, because colon
8811 terminates a key string in lsearch files. So, for example,
8813 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
8817 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
8819 Letters in IPv6 addresses are always output in lower case.
8822 .item "@$@{md5:<<string>>@}"
8824 .index expansion||MD5 hash
8825 The \md5\ operator computes the MD5 hash value of the string, and returns it as
8826 a 32-digit hexadecimal number,
8827 in which any letters are in lower case.
8830 .item "@$@{nhash@_<<n>>@_<<m>>:<<string>>@}"
8831 .index expansion||numeric hash
8832 .index hash function||numeric
8833 The \nhash\ operator is a simpler interface to the numeric hashing function
8834 that can be used when the two parameters are fixed numbers (as opposed to
8835 strings that change when expanded). The effect is the same as
8837 @$@{nhash@{<<n>>@}@{<<m>>@}@{<<string>>@}@}
8839 See the description of the general \nhash\ item above for details.
8842 .item "@$@{quote:<<string>>@}"
8843 .index quoting||in string expansions
8844 .index expansion||quoting
8845 The \quote\ operator puts its argument into double quotes if it
8846 is an empty string or
8847 contains anything other than letters, digits, underscores, dots, and hyphens.
8848 Any occurrences of double quotes and backslashes are escaped with a backslash.
8849 Newlines and carriage returns are converted to \"@\n"\ and \"@\r"\,
8850 respectively For example,
8858 The place where this is useful is when the argument is a substitution from a
8859 variable or a message header.
8861 .item "@$@{quote@_local@_part:<<string>>@}"
8862 This operator is like \quote\, except that it quotes the string only if
8863 required to do so by the rules of RFC 2822 for quoting local parts. For
8864 example, a plus sign would not cause quoting (but it would for \quote\).
8865 If you are creating a new email address from the contents of \$local@_part$\
8866 (or any other unknown data), you should always use this operator.
8869 .item "@$@{quote@_<<lookup-type>>:<<string>>@}"
8870 .index quoting||lookup-specific
8871 This operator applies lookup-specific quoting rules to the string. Each
8872 query-style lookup type has its own quoting rules which are described with
8873 the lookups in chapter ~~CHAPfdlookup. For example,
8875 ${quote_ldap:two * two}
8881 For single-key lookup types, no quoting is ever necessary and this operator
8882 yields an unchanged string.
8885 .item "@$@{rxquote:<<string>>@}"
8886 .index quoting||in regular expressions
8887 .index regular expressions||quoting
8888 The \rxquote\ operator inserts a backslash before any non-alphanumeric
8889 characters in its argument. This is useful when substituting the values of
8890 variables or headers inside regular expressions.
8893 .item "@$@{rfc2047:<<string>>@}"
8894 .index expansion||RFC 2047
8895 This operator encodes text according to the rules of RFC 2047. This is an
8896 encoding that is used in header lines to encode non-ASCII characters. It is
8897 assumed that the input string is in the encoding specified by the
8898 \headers@_charset\ option, which defaults to ISO-8859-1. If the string contains
8899 only characters in the range 33--126, and no instances of the characters
8901 ? = ( ) < > @ , ; : \ " . [ ] _
8903 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
8906 using as many `coded words' as necessary to encode all the characters.
8910 .item "@$@{sha1:<<string>>@}"
8912 .index expansion||SHA-1 hashing
8913 The \sha1\ operator computes the SHA-1 hash value of the string, and returns it
8914 as a 40-digit hexadecimal number, in which any letters are in upper case.
8917 .item "@$@{stat:<<string>>@}"
8918 .index expansion||statting a file
8919 .index file||extracting characteristics
8920 The string, after expansion, must be a file path. A call to the \*stat()*\
8921 function is made for this path. If \*stat()*\ fails, an error occurs and the
8922 expansion fails. If it succeeds, the data from the stat replaces the item, as a
8923 series of <<name>>=<<value>> pairs, where the values are all numerical,
8924 except for the value of `smode'. The names are: `mode' (giving the mode as a
8925 4-digit octal number), `smode' (giving the mode in symbolic format as a
8926 10-character string, as for the \*ls*\ command), `inode', `device', `links',
8927 `uid', `gid', `size', `atime', `mtime', and `ctime'. You can extract individual
8928 fields using the \extract\ expansion item. \**Warning**\: The file size may be
8929 incorrect on 32-bit systems for files larger than 2GB.
8933 .item "@$@{str2b64:<<string>>@}"
8934 .index expansion||base64 encoding
8935 .index base64 encoding||in string expansion
8936 This operator converts a string into one that is base64 encoded.
8940 .item "@$@{strlen:<<string>>@}"
8941 .index expansion||string length
8942 .index string||length in expansion
8943 The item is replace by the length of the expanded string, expressed as a
8944 decimal number. \**Note**\: Do not confuse \strlen\ with \length\.
8947 .item "@$@{substr@_<<start>>@_<<length>>:<<string>>@}"
8949 .index substring extraction
8950 .index expansion||substring expansion
8951 The \substr\ operator is a simpler interface to the \substr\ function that can
8952 be used when the two parameters are fixed numbers (as opposed to strings that
8953 change when expanded). The effect is the same as
8955 @$@{substr@{<<start>>@}@{<<length>>@}@{<<string>>@}@}
8957 See the description of the general \substr\ item above for details. The
8958 abbreviation \s\ can be used when \substr\ is used as an operator.
8960 .item "@$@{time@_interval:<<string>>@}"
8961 .index \time@_interval\
8962 .index time interval||formatting
8963 The argument (after sub-expansion) must be a sequence of decimal digits that
8964 represents an interval of time as a number of seconds. It is converted into a
8965 number of larger units and output in Exim's normal time format, for example,
8968 .item "@$@{uc:<<string>>@}"
8969 .index case forcing in strings
8970 .index string||case forcing
8972 .index expansion||case forcing
8973 This forces the letters in the string into upper-case.
8979 .section Expansion conditions
8980 .rset SECTexpcond "~~chapter.~~section"
8981 .index expansion||conditions
8982 The following conditions are available for testing by the \@$@{if\ construct
8983 while expanding strings:
8987 .item "!<<condition>>"
8988 .index expansion||negating a condition
8989 Preceding any condition with an exclamation mark negates the result of the
8992 .item "<<symbolic operator>> @{<<string1>>@}@{<<string2>>@}"
8993 .index numeric comparison
8994 .index expansion||numeric comparison
8995 There are a number of symbolic operators for doing numeric comparisons. They
9002 >= $t $rm{greater or equal}
9004 <= $t $rm{less or equal}
9008 ${if >{$message_size}{10M} ...
9010 Note that the general negation operator provides for inequality testing. The
9011 two strings must take the form of optionally signed decimal integers,
9012 optionally followed by one of the letters `K' or `M' (in either upper or lower
9013 case), signifying multiplication by 1024 or 1024$*$1024, respectively.
9015 .item "crypteq @{<<string1>>@}@{<<string2>>@}"
9016 .index expansion||encrypted comparison
9017 .index encrypted strings, comparing
9018 This condition is included in the Exim binary if it is built to support any
9019 authentication mechanisms (see chapter ~~CHAPSMTPAUTH). Otherwise, it is
9020 necessary to define \\SUPPORT@_CRYPTEQ\\ in \(Local/Makefile)\ to get \crypteq\
9021 included in the binary.
9023 The \crypteq\ condition has two arguments. The first is encrypted and compared
9024 against the second, which is already encrypted. The second string may be in the
9025 LDAP form for storing encrypted strings, which starts with the encryption type
9026 in curly brackets, followed by the data. If the second string does not begin
9027 with `{' it is assumed to be encrypted with \*crypt()*\
9028 or \*crypt16()*\ (see below),
9029 since such strings cannot begin with `{'. Typically this will be a field from a
9032 An example of an encrypted string in LDAP form is:
9034 {md5}CY9rzUYh03PK3k6DJie09g==
9036 If such a string appears directly in an expansion, the curly brackets have to
9037 be quoted, because they are part of the expansion syntax. For example:
9039 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
9041 The following encryption types
9042 (whose names are matched case-independently)
9046 .index base64 encoding||in encrypted password
9047 \@{md5@}\ computes the MD5 digest of the first string, and expresses this as
9048 printable characters to compare with the remainder of the second string. If the
9049 length of the comparison string is 24, Exim assumes that it is base64 encoded
9050 (as in the above example). If the length is 32, Exim assumes that it is a
9051 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
9055 \@{sha1@}\ computes the SHA-1 digest of the first string, and expresses this as
9056 printable characters to compare with the remainder of the second string. If the
9057 length of the comparison string is 28, Exim assumes that it is base64 encoded.
9058 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
9059 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
9062 \@{crypt@}\ calls the \*crypt()*\ function,
9064 which traditionally used to use only the first eight characters of the
9065 password. However, in modern operating systems this is no longer true, and in
9066 many cases the entire password is used, whatever its length.
9069 .index \*crypt16()*\
9070 \@{crypt16@}\ calls the \*crypt16()*\ function (also known as \*bigcrypt()*\),
9073 was orginally created to use up to 16 characters of the password. Again, in
9074 modern operating systems, more characters may be used.
9077 Exim has its own version of \*crypt16()*\ (which is just a double call to
9078 \*crypt()*\). For operating systems that have their own version, setting
9079 \\HAVE@_CRYPT16\\ in \(Local/Makefile)\ when building Exim causes it to use the
9080 operating system version instead of its own. This option is set by default in
9081 the OS-dependent \(Makefile)\ for those operating systems that are known to
9082 support \*crypt16()*\.
9084 If you do not put any curly bracket encryption type in a \crypteq\ comparison,
9085 the default is either \"@{crypt@}"\ or \"@{crypt16@}"\, as determined by the
9086 setting of \\DEFAULT@_CRYPT\\ in \(Local/Makefile)\. The default default is
9087 \"@{crypt@}"\. Whatever the default, you can always use either function by
9088 specifying it explicitly in curly brackets.
9090 Note that if a password is no longer than 8 characters, the results of
9091 encrypting it with \*crypt()*\ and \*crypt16()*\ are identical. That means that
9092 \*crypt16()*\ is backwards compatible, as long as nobody feeds it a password
9093 longer than 8 characters.
9096 .item "def:<<variable name>>"
9097 .index expansion||checking for empty variable
9098 The \def\ condition must be followed by the name of one of the expansion
9099 variables defined in section ~~SECTexpvar. The condition is true if the named
9100 expansion variable does not contain the empty string, for example
9102 ${if def:sender_ident {from $sender_ident}}
9104 Note that the variable name is given without a leading \@$\ character. If the
9105 variable does not exist, the expansion fails.
9107 .item "def:header@_<<header name>>:##or##def:h@_<<header name>>:"
9108 .index expansion||checking header line existence
9109 This condition is true if a message is being processed and the named header
9110 exists in the message. For example,
9112 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
9114 Note that no \@$\ appears before \header@_\ or \h@_\ in the condition,
9115 and that header names must be terminated by colons if white space does not
9118 .item "eq @{<<string1>>@}@{<<string2>>@}"
9119 .item "eqi @{<<string1>>@}@{<<string2>>@}"
9120 .index string||comparison
9121 .index expansion||string comparison
9122 The two substrings are first expanded. The condition is true if the two
9123 resulting strings are identical: for \eq\ the comparison includes the case of
9124 letters, whereas for \eqi\ the comparison is case-independent.
9126 .item "exists @{<<file name>>@}"
9127 .index expansion||file existence test
9128 .index file||existence test
9129 The substring is first expanded and then interpreted as an absolute path. The
9130 condition is true if the named file (or directory) exists. The existence test
9131 is done by calling the \*stat()*\ function. The use of the \exists\ test in
9132 users' filter files may be locked out by the system administrator.
9134 .item "first@_delivery"
9135 .index delivery||first
9136 .index first delivery
9137 .index expansion||first delivery test
9138 This condition, which has no data, is true during a message's first delivery
9139 attempt. It is false during any subsequent delivery attempts.
9141 .item "ge @{<<string1>>@}@{<<string2>>@}"
9142 .item "gei @{<<string1>>@}@{<<string2>>@}"
9143 .index string||comparison
9144 .index expansion||string comparison
9145 The two substrings are first expanded. The condition is true if the first
9146 string is lexically greater than or equal to the second string: for \ge\ the
9147 comparison includes the case of letters, whereas for \gei\ the comparison is
9150 .item "gt @{<<string1>>@}@{<<string2>>@}"
9151 .item "gti @{<<string1>>@}@{<<string2>>@}"
9152 .index string||comparison
9153 .index expansion||string comparison
9154 The two substrings are first expanded. The condition is true if the first
9155 string is lexically greater than the second string: for \gt\ the comparison
9156 includes the case of letters, whereas for \gti\ the comparison is
9159 .item "isip @{<<string>>@}" 8
9160 .item "isip4 @{<<string>>@}"
9161 .item "isip6 @{<<string>>@}"
9162 .index IP address||testing string format
9163 .index string||testing for IP address
9164 The substring is first expanded, and then tested to see if it has the form of
9165 an IP address. Both IPv4 and IPv6 addresses are valid for \isip\, whereas
9166 \isip4\ and \isip6\ test just for IPv4 or IPv6 addresses, respectively. For
9167 example, you could use
9169 ${if isip4{$sender_host_address}...
9171 to test which version of IP an incoming SMTP connection is using.
9174 .item "ldapauth @{<<ldap query>>@}"
9175 .index LDAP||use for authentication
9176 .index expansion||LDAP authentication test
9177 This condition supports user authentication using LDAP. See section ~~SECTldap
9178 for details of how to use LDAP in lookups and the syntax of queries. For this
9179 use, the query must contain a user name and password. The query itself is not
9180 used, and can be empty. The condition is true if
9181 the password is not empty, and the user name and password are accepted by the
9182 LDAP server. An empty password is rejected without calling LDAP because LDAP
9183 binds with an empty password are considered anonymous regardless of
9184 the username, and will succeed in most configurations.
9185 See chapter ~~CHAPSMTPAUTH for details of SMTP authentication, and chapter
9186 ~~CHAPplaintext for an example of how this can be used.
9189 .item "le @{<<string1>>@}@{<<string2>>@}"
9190 .item "lei @{<<string1>>@}@{<<string2>>@}"
9191 .index string||comparison
9192 .index expansion||string comparison
9193 The two substrings are first expanded. The condition is true if the first
9194 string is lexically less than or equal to the second string: for \le\ the
9195 comparison includes the case of letters, whereas for \lei\ the comparison is
9198 .item "lt @{<<string1>>@}@{<<string2>>@}"
9199 .item "lti @{<<string1>>@}@{<<string2>>@}"
9200 .index string||comparison
9201 .index expansion||string comparison
9202 The two substrings are first expanded. The condition is true if the first
9203 string is lexically less than the second string: for \lt\ the comparison
9204 includes the case of letters, whereas for \lti\ the comparison is
9208 .item "match @{<<string1>>@}@{<<string2>>@}"
9209 .index expansion||regular expression comparison
9210 .index regular expressions||match in expanded string
9211 The two substrings are first expanded. The second is then treated as a regular
9212 expression and applied to the first. Because of the pre-expansion, if the
9213 regular expression contains dollar, or backslash characters, they must be
9214 escaped. Care must also be taken if the regular expression contains braces
9215 (curly brackets). A closing brace must be escaped so that it is not taken as a
9216 premature termination of <<string2>>. The easiest approach is to use the
9217 \"@\N"\ feature to disable expansion of the regular expression.
9220 ${if match {$local_part}{\N^\d{3}\N} ...
9222 If the whole expansion string is in double quotes, further escaping of
9223 backslashes is also required.
9225 The condition is true if the regular expression match succeeds.
9226 The regular expression is not required to begin with a circumflex
9227 metacharacter, but if there is no circumflex, the expression is not anchored,
9228 and it may match anywhere in the subject, not just at the start. If you want
9229 the pattern to match at the end of the subject, you must include the \"@$"\
9230 metacharacter at an appropriate point.
9232 .index numerical variables (\$1$\, \$2$\, etc)||in \if\ expansion
9233 At the start of an \if\ expansion the values of the numeric variable
9234 substitutions \$1$\ etc. are remembered. Obeying a \match\ condition that
9235 succeeds causes them to be reset to the substrings of that condition and they
9236 will have these values during the expansion of the success string. At the end
9237 of the \if\ expansion, the previous values are restored. After testing a
9238 combination of conditions using \or\, the subsequent values of the numeric
9239 variables are those of the condition that succeeded.
9241 .item "match@_domain @{<<string1>>@}@{<<string2>>@}"
9242 .item "match@_address @{<<string1>>@}@{<<string2>>@}"
9243 .item "match@_local@_part @{<<string1>>@}@{<<string2>>@}"
9244 .index domain list||in expansion condition
9245 .index address list||in expansion condition
9246 .index local part list||in expansion condition
9247 These conditions make it possible to test domain, address, and local
9248 part lists within expansions. Each condition requires two arguments: an item
9249 and a list to match. A trivial example is:
9251 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
9253 In each case, the second argument may contain any of the allowable items for a
9254 list of the appropriate type. Also, because the second argument (after
9255 expansion) is a standard form of list, it is possible to refer to a named list.
9256 Thus, you can use conditions like this:
9258 ${if match_domain{$domain}{+local_domains}{...
9261 For address lists, the matching starts off caselessly, but the \"+caseful"\
9262 item can be used, as in all address lists, to cause subsequent items to
9263 have their local parts matched casefully. Domains are always matched
9266 \**Note**\: Host lists are \*not*\ supported in this way. This is because
9267 hosts have two identities: a name and an IP address, and it is not clear
9268 how to specify cleanly how such a test would work. At least, I haven't come
9269 up with anything yet.
9271 .item "pam {<<string1>>:<<string2>>:...@}"
9272 .index PAM authentication
9273 .index \\AUTH\\||with PAM
9274 .index Solaris||PAM support
9275 .index expansion||PAM authentication test
9276 \*Pluggable Authentication Modules*\
9277 (\?http://www.kernel.org/pub/linux/libs/pam/?\)
9278 are a facility which is available in the latest releases of Solaris and in some
9279 GNU/Linux distributions. The Exim support, which is intended for use in
9280 conjunction with the SMTP \\AUTH\\ command, is available only if Exim is
9285 in \(Local/Makefile)\. You probably need to add \-lpam-\ to \\EXTRALIBS\\, and
9286 in some releases of GNU/Linux \-ldl-\ is also needed.
9288 The argument string is first expanded, and the result must be a colon-separated
9290 Leading and trailing whitespace is ignored.
9291 The PAM module is initialized with the service name `exim' and the user name
9292 taken from the first item in the colon-separated data string (<<string1>>). The
9293 remaining items in the data string are passed over in response to requests from
9294 the authentication function. In the simple case there will only be one request,
9295 for a password, so the data consists of just two strings.
9297 There can be problems if any of the strings are permitted to contain colon
9298 characters. In the usual way, these have to be doubled to avoid being taken as
9299 separators. If the data is being inserted from a variable, the \sg\ expansion
9300 item can be used to double any existing colons. For example, the configuration
9301 of a LOGIN authenticator might contain this setting:
9303 server_condition = ${if pam{$1:${sg{$2}{:}{::}}}{yes}{no}}
9305 For a PLAIN authenticator you could use:
9307 server_condition = ${if pam{$2:${sg{$3}{:}{::}}}{yes}{no}}
9309 In some operating systems, PAM authentication can be done only from a process
9310 running as root. Since Exim is running as the Exim user when receiving
9311 messages, this means that PAM cannot be used directly in those systems.
9312 A patched version of the \*pam@_unix*\ module that comes with the
9313 Linux PAM package is available from \?http:@/@/www.e-admin.de/pam@_exim/?\.
9314 The patched module allows one special uid/gid combination, in addition to root,
9315 to authenticate. If you build the patched module to allow the Exim user and
9316 group, PAM can then be used from an Exim authenticator.
9319 .item "pwcheck {<<string1>>:<<string2>>@}"
9320 .index \*pwcheck*\ daemon
9322 .index expansion||\*pwcheck*\ authentication test
9323 This condition supports user authentication using the Cyrus \*pwcheck*\ daemon.
9324 This is one way of making it possible for passwords to be checked by a process
9325 that is not running as root.
9326 \**Note:**\ The use of \*pwcheck*\ is now deprecated. Its replacement is
9327 \*saslauthd*\ (see below).
9329 The pwcheck support is not included in Exim by default. You need to specify
9330 the location of the pwcheck daemon's socket in \(Local/Makefile)\ before
9331 building Exim. For example:
9333 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
9335 You do not need to install the full Cyrus software suite in order to use
9336 the pwcheck daemon. You can compile and install just the daemon alone
9337 from the Cyrus SASL library. Ensure that \*exim*\ is the only user that has
9338 access to the \(/var/pwcheck)\ directory.
9340 The \pwcheck\ condition takes one argument, which must be the user name and
9341 password, separated by a colon. For example, in a LOGIN authenticator
9342 configuration, you might have this:
9344 server_condition = ${if pwcheck{$1:$2}{1}{0}}
9347 .item "queue@_running"
9348 .index queue runner||detecting when delivering from
9349 .index expansion||queue runner test
9350 This condition, which has no data, is true during delivery attempts that are
9351 initiated by queue runner processes, and false otherwise.
9354 .item "radius {<<authentication string>>@}"
9356 .index expansion||Radius authentication
9357 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
9358 set \\RADIUS@_CONFIG@_FILE\\ in \(Local/Makefile)\ to specify the location of
9359 the Radius client configuration file in order to build Exim with Radius
9362 With just that one setting, Exim expects to be linked with the \radiusclient\
9363 library. You can also link Exim with the \libradius\ library that comes with
9364 FreeBSD. To do this, set
9366 RADIUS_LIB_TYPE=RADLIB
9368 in \(Local/Makefile)\, in addition to setting \\RADIUS@_CONFIGURE@_FILE\\.
9370 You may also have to supply a suitable setting in \\EXTRALIBS\\ so that the
9371 Radius library can be found when Exim is linked.
9373 The string specified by \\RADIUS@_CONFIG@_FILE\\ is expanded and passed to the
9374 Radius client library, which calls the Radius server. The condition is true if
9375 the authentication is successful. For example
9377 server@_condition = @$@{if radius@{<<arguments>>@}@{yes@}@{no@}@}
9382 .item "saslauthd @{@{<<user>>@}@{<<password>>@}@{<<service>>@}@{<<realm>>@}@}"
9383 .index \*saslauthd*\ daemon
9385 .index expansion||\*saslauthd*\ authentication test
9386 This condition supports user authentication using the Cyrus \*saslauthd*\
9387 daemon. This replaces the older \*pwcheck*\ daemon, which is now deprecated.
9388 Using this daemon is one way of making it possible for passwords to be checked
9389 by a process that is not running as root.
9391 The saslauthd support is not included in Exim by default. You need to specify
9392 the location of the saslauthd daemon's socket in \(Local/Makefile)\ before
9393 building Exim. For example:
9395 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
9397 You do not need to install the full Cyrus software suite in order to use
9398 the saslauthd daemon. You can compile and install just the daemon alone
9399 from the Cyrus SASL library.
9401 Up to four arguments can be supplied to the \saslauthd\ condition, but only two
9402 are mandatory. For example:
9404 server_condition = ${if saslauthd{{$1}{$2}}{1}{0}}
9406 The service and the realm are optional (which is why the arguments are enclosed
9407 in their own set of braces). For details of the meaning of the service and
9408 realm, and how to run the daemon, consult the Cyrus documentation.
9414 .section Combining expansion conditions
9415 .index expansion||combining conditions
9416 Several conditions can be tested at once by combining them using the \and\ and
9417 \or\ combination conditions. Note that \and\ and \or\ are complete conditions
9418 on their own, and precede their lists of sub-conditions. Each sub-condition
9419 must be enclosed in braces within the overall braces that contain the list. No
9420 repetition of \if\ is used.
9424 .item "or @{@{<<cond1>>@}@{<<cond2>>@}...@}"
9425 .index `or' expansion condition
9426 .index expansion||`or' of conditions
9427 The sub-conditions are evaluated from left to right. The condition is true if
9428 any one of the sub-conditions is true.
9431 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
9433 When a true sub-condition is found, the following ones are parsed but not
9434 evaluated. If there are several `match' sub-conditions the values of the
9435 numeric variables afterwards are taken from the first one that succeeds.
9437 .item "and @{@{<<cond1>>@}@{<<cond2>>@}...@}"
9438 .index `and' expansion condition
9439 .index expansion||`and' of conditions
9440 The sub-conditions are evaluated from left to right. The condition is true if
9441 all of the sub-conditions are true. If there are several `match'
9442 sub-conditions, the values of the numeric variables afterwards are taken from
9443 the last one. When a false sub-condition is found, the following ones are
9444 parsed but not evaluated.
9450 .section Expansion variables
9451 .rset SECTexpvar "~~chapter.~~section"
9452 .index expansion||variables, list of
9455 This section contains an alphabetical list of all the expansion variables. Some
9456 of them are available only when Exim is compiled with specific options such as
9457 support for TLS or the content scanning extension.
9462 .index numerical variables (\$1$\, \$2$\, etc)
9464 \$0$\, \$1$\, etc: When a \match\ expansion condition succeeds, these
9465 variables contain the captured substrings identified by the regular expression
9466 during subsequent processing of the success string of the containing \if\
9467 expansion item. They may also be set externally by some other matching process
9468 which precedes the expansion of the string. For example, the commands available
9469 in Exim filter files include an \if\ command with its own regular expression
9473 \$acl@_c0$\ -- \$acl@_c9$\: Values can be placed in these variables by the
9474 \set\ modifier in an ACL. The values persist throughout the lifetime of an SMTP
9475 connection. They can be used to pass information between ACLs and different
9476 invocations of the same ACL.
9477 When a message is received, the values of these variables are saved with the
9478 message, and can be accessed by filters, routers, and transports during
9479 subsequent delivery.
9482 \$acl@_m0$\ -- \$acl@_m9$\: Values can be placed in these variables by the
9483 \set\ modifier in an ACL. They retain their values while a message is being
9484 received, but are reset afterwards. They are also reset by \\MAIL\\, \\RSET\\,
9485 \\EHLO\\, \\HELO\\, and after starting a TLS session.
9486 When a message is received, the values of these variables are saved with the
9487 message, and can be accessed by filters, routers, and transports during
9488 subsequent delivery.
9492 \$acl@_verify@_message$\: During the expansion of the \message\ and
9493 \log@_message\ modifiers in an ACL statement after an address verification has
9494 failed, this variable contains the original failure message that will be
9495 overridden by the expanded string.
9498 \$address@_data$\: This variable is set by means of the \address@_data\
9499 option in routers. The value then remains with the address while it is
9500 processed by subsequent routers and eventually a transport. If the transport is
9501 handling multiple addresses, the value from the first address is used. See
9502 chapter ~~CHAProutergeneric for more details. \**Note**\: the contents of
9503 \$address@_data$\ are visible in user filter files.
9506 If \$address@_data$\ is set when the routers are called from an ACL to verify
9507 a recipient address, the final value is still in the variable for subsequent
9508 conditions and modifiers of the ACL statement. If routing the address caused it
9509 to be redirected to just one address, the child address is also routed as part
9510 of the verification, and in this case the final value of \$address@_data$\ is
9511 from the child's routing.
9513 If \$address@_data$\ is set when the routers are called from an ACL to verify a
9514 sender address, the final value is also preserved, but this time in
9515 \$sender@_address@_data$\, to distinguish it from data from a recipient
9518 In both cases (recipient and sender verification), the value does not persist
9519 after the end of the current ACL statement. If you want to preserve
9520 these values for longer, you can save them in ACL variables.
9524 \$address@_file$\: When, as a result of aliasing, forwarding, or filtering, a
9525 message is directed to a specific file, this variable holds the name of the
9526 file when the transport is running. At other times, the variable is empty. For
9527 example, using the default configuration, if user \r2d2\ has a \(.forward)\
9532 then when the \%address@_file%\ transport is running, \$address@_file$\
9533 contains `/home/r2d2/savemail'.
9534 .index Sieve filter||value of \$address@_file$\
9535 For Sieve filters, the value may be `inbox' or a relative folder name. It is
9536 then up to the transport configuration to generate an appropriate absolute path
9537 to the relevant file.
9541 \$address@_pipe$\: When, as a result of aliasing or forwarding, a message is
9542 directed to a pipe, this variable holds the pipe command when the transport is
9545 .index authentication||id
9547 \$authenticated@_id$\: When a server successfully authenticates a client it may
9548 be configured to preserve some of the authentication information in the
9549 variable \$authenticated@_id$\ (see chapter ~~CHAPSMTPAUTH). For example, a
9550 user/password authenticator configuration might preserve the user name for use
9551 in the routers. When a message is submitted locally (that is, not over a TCP
9552 connection), the value of \$authenticated@_id$\ is the login name of the
9555 .index sender||authenticated
9556 .index authentication||sender
9557 .index \\AUTH\\||on \\MAIL\\ command
9559 \$authenticated@_sender$\:
9560 When acting as a server, Exim takes note of the \\AUTH=\\ parameter on an
9561 incoming SMTP \\MAIL\\ command
9562 if it believes the sender is sufficiently trusted, as described in section
9563 ~~SECTauthparamail. Unless the data is the string `@<@>', it is set as the
9564 authenticated sender of the message, and the value is available during delivery
9565 in the \$authenticated@_sender$\ variable. If the sender is not trusted, Exim
9566 accepts the syntax of \\AUTH=\\, but ignores the data.
9568 When a message is submitted locally (that is, not over a TCP connection), the
9569 value of \$authenticated@_sender$\ is an address constructed from the login
9570 name of the calling process and \$qualify@_domain$\.
9573 .index authentication||failure
9575 \$authentication@_failed$\:
9576 This variable is set to `1' in an Exim server if a client issues an \\AUTH\\
9577 command that does not succeed. Otherwise it is set to `0'. This makes it
9578 possible to distinguish between `did not try to authenticate'
9579 (\$sender@_host@_authenticated$\ is empty and \$authentication__failed$\ is set
9580 to `0') and `tried to authenticate but failed' (\$sender@_host@_authenticated$\
9581 is empty and \$authentication@_failed$\ is set to `1'). Failure includes any
9582 negative response to an \\AUTH\\ command, including (for example) an attempt to
9583 use an undefined mechanism.
9586 .index message||body, line count
9587 .index body of message||line count
9589 \$body@_linecount$\:
9590 When a message is being received or delivered, this variable contains the
9591 number of lines in the message's body.
9593 .index message||body, binary zero count
9594 .index body of message||binary zero count
9595 .index binary zero||in message body
9597 \$body@_zerocount$\:
9598 When a message is being received or delivered, this variable contains the
9599 number of binary zero bytes in the message's body.
9602 \$bounce@_recipient$\:
9603 This is set to the recipient address of a bounce message while Exim is creating
9604 it. It is useful if a customized bounce message text file is in use (see
9605 chapter ~~CHAPemsgcust).
9608 \$bounce@_return@_size@_limit$\: This contains the value set in the
9609 \bounce@_return@_size@_limit\ option, rounded up to a multiple of 1000. It is
9610 useful when a customized error message text file is in use (see chapter
9613 .index gid (group id)||caller
9615 \$caller@_gid$\: The
9617 group id under which the process that called Exim was
9618 running. This is not the same as the group id of the originator of a message
9619 (see \$originator@_gid$\). If Exim re-execs itself, this variable in the new
9620 incarnation normally contains the Exim gid.
9622 .index uid (user id)||caller
9624 \$caller@_uid$\: The
9626 user id under which the process that called Exim was
9627 running. This is not the same as the user id of the originator of a message
9628 (see \$originator@_uid$\). If Exim re-execs itself, this variable in the new
9629 incarnation normally contains the Exim uid.
9632 \$compile@_date$\: The date on which the Exim binary was compiled.
9635 \$compile@_number$\: The building process for Exim keeps a count of the number
9636 of times it has been compiled. This serves to distinguish different
9637 compilations of the same version of the program.
9641 \$demime@_errorlevel$\: This variable is available when Exim is compiled with
9642 the content-scanning extension and the obsolete \demime\ condition. For
9643 details, see section ~~SECTdemimecond.
9646 \$demime@_reason$\: This variable is available when Exim is compiled with the
9647 content-scanning extension and the obsolete \demime\ condition. For details,
9648 see section ~~SECTdemimecond.
9651 .index black list (DNS)
9653 \$dnslist@_domain$\: When a client host is found to be on a DNS (black) list,
9654 the list's domain name is put into this variable so that it can be included in
9655 the rejection message.
9658 \$dnslist@_text$\: When a client host is found to be on a DNS (black) list, the
9659 contents of any associated TXT record are placed in this variable.
9662 \$dnslist@_value$\: When a client host is found to be on a DNS (black) list,
9663 the IP address from the resource record is placed in this variable.
9664 If there are multiple records, all the addresses are included, comma-space
9668 \$domain$\: When an address is being routed, or delivered on its own, this
9669 variable contains the domain. Global address rewriting happens when a message
9670 is received, so the value of \$domain$\ during routing and delivery is the
9671 value after rewriting. \$domain$\ is set during user filtering, but not during
9672 system filtering, because a message may have many recipients and the system
9673 filter is called just once.
9675 When more than one address is being delivered at once (for example, several
9676 \\RCPT\\ commands in one SMTP delivery), \$domain$\ is set only if they all
9677 have the same domain. Transports can be restricted to handling only one domain
9678 at a time if the value of \$domain$\ is required at transport time -- this is
9679 the default for local transports. For further details of the environment in
9680 which local transports are run, see chapter ~~CHAPenvironment.
9682 .index \delay@_warning@_condition\
9683 At the end of a delivery, if all deferred addresses have the same domain, it is
9684 set in \$domain$\ during the expansion of \delay@_warning@_condition\.
9686 The \$domain$\ variable is also used in some other circumstances:
9688 When an ACL is running for a \\RCPT\\ command, \$domain$\ contains the domain
9689 of the recipient address.
9690 \**Note:**\ the domain of the sender address is in \$sender@_address@_domain$\
9691 at \\MAIL\\ time and at \\RCPT\\ time. \$domain$\ is not set for the \\MAIL\\
9694 When a rewrite item is being processed (see chapter ~~CHAPrewrite), \$domain$\
9695 contains the domain portion of the address that is being rewritten; it can be
9696 used in the expansion of the replacement address, for example, to rewrite
9697 domains by file lookup.
9699 With one important exception, whenever a domain list is being scanned,
9700 \$domain$\ contains the subject domain. \**Exception**\: When a domain list in
9701 a \sender@_domains\ condition in an ACL is being processed, the subject domain
9702 is in \$sender@_address@_domain$\ and not in \$domain$\. It works this way so
9703 that, in a \\RCPT\\ ACL, the sender domain list can be dependent on the
9704 recipient domain (which is what is in \$domain$\ at this time).
9706 .index \\ETRN\\||value of \$domain$\
9707 .index \smtp@_etrn@_command\
9708 When the \smtp@_etrn@_command\ option is being expanded, \$domain$\ contains
9709 the complete argument of the \\ETRN\\ command (see section ~~SECTETRN).
9713 \$domain@_data$\: When the \domains\ option on a router matches a domain by
9714 means of a lookup, the data read by the lookup is available during the running
9715 of the router as \$domain@_data$\. In addition, if the driver routes the
9716 address to a transport, the value is available in that transport. If the
9717 transport is handling multiple addresses, the value from the first address is
9720 \$domain@_data$\ is also set when the \domains\ condition in an ACL matches a
9721 domain by means of a lookup. The data read by the lookup is available during
9722 the rest of the ACL statement. In all other situations, this variable expands
9726 \$exim@_gid$\: This variable contains the numerical value of the Exim group id.
9729 \$exim@_path$\: This variable contains the path to the Exim binary.
9732 \$exim@_uid$\: This variable contains the numerical value of the Exim user id.
9736 \$found@_extension$\: This variable is available when Exim is compiled with the
9737 content-scanning extension and the obsolete \demime\ condition. For details,
9738 see section ~~SECTdemimecond.
9742 \$header@_<<name>>$\: This is not strictly an expansion variable. It is
9743 expansion syntax for inserting the message header line with the given name.
9744 Note that the name must be terminated by colon or white space, because it may
9745 contain a wide variety of characters.
9746 Note also that braces must \*not*\ be used.
9750 When the \check@_local@_user\ option is set for a router, the user's home
9751 directory is placed in \$home$\ when the check succeeds. In particular, this
9752 means it is set during the running of users' filter files. A router may also
9753 explicitly set a home directory for use by a transport; this can be overridden
9754 by a setting on the transport itself.
9756 When running a filter test via the \-bf-\ option, \$home$\ is set to the value
9757 of the environment variable \\HOME\\.
9761 When the \%smtp%\ transport is expanding its options for encryption using TLS,
9762 \$host$\ contains the name of the host to which it is connected. Likewise, when
9763 used in the client part of an authenticator configuration (see chapter
9764 ~~CHAPSMTPAUTH), \$host$\ contains the name of the server to which the client
9766 .index transport||filter
9767 .index filter||transport filter
9768 When used in a transport filter (see chapter ~~CHAPtransportgeneric) \$host$\
9769 refers to the host involved in the current connection. When a local transport
9770 is run as a result of a router that sets up a host list, \$host$\ contains the
9771 name of the first host.
9775 This variable is set to the remote host's IP address whenever \$host$\ is set
9776 for a remote connection.
9778 It is also set to the IP address that is being checked when the
9779 \ignore@_target@_hosts\ option is being processed.
9784 If a \hosts\ condition in an ACL is satisfied by means of a lookup, the result
9785 of the lookup is made available in the \$host@_data$\ variable. This
9786 allows you, for example, to do things like this:
9788 deny hosts = net-lsearch;/some/file
9789 message = $host_data
9793 .index host||name lookup, failure of
9795 \$host@_lookup@_deferred$\:
9796 This variable normally contains `0', as does \$host@_lookup@_failed$\. When a
9797 message comes from a remote host and there is an attempt to look up the host's
9798 name from its IP address, and the attempt is not successful, one of these
9799 variables is set to `1'.
9801 If the lookup receives a definite negative response (for example, a DNS lookup
9802 succeeded, but no records were found), \$host@_lookup@_failed$\ is set to `1'.
9804 If there is any kind of problem during the lookup, such that Exim cannot
9805 tell whether or not the host name is defined (for example, a timeout for a DNS
9806 lookup), \$host@_lookup@_deferred$\ is set to `1'.
9808 Looking up a host's name from its IP address consists of more than just a
9809 single reverse lookup. Exim checks that a forward lookup of at least one of the
9810 names it receives from a reverse lookup yields the original IP address. If this
9811 is not the case, Exim does not accept the looked up name(s), and
9812 \$host@_lookup@_failed$\ is set to `1'. Thus, being able to find a name from an
9813 IP address (for example, the existence of a PTR record in the DNS) is not
9814 sufficient on its own for the success of a host name lookup. If the reverse
9815 lookup succeeds, but there is a lookup problem such as a timeout when checking
9816 the result, the name is not accepted, and \$host@_lookup@_deferred$\ is set to
9817 `1'. See also \$sender@_host@_name$\.
9820 \$host@_lookup@_failed$\: See \$host@_lookup@_deferred$\.
9825 The only time this variable is set is while expanding the \directory@_file\
9826 option in the \%appendfile%\ transport. The variable contains the inode number
9827 of the temporary file which is about to be renamed. It can be used to construct
9828 a unique name for the file.
9831 \$interface@_address$\:
9832 When a message is received over a TCP/IP connection, this variable contains the
9833 address of the local IP interface. See also the \-oMi-\ command line option.
9834 This variable can be used in ACLs and also, for example, to make the file name
9835 for a TLS certificate depend on which interface is being used.
9838 \$interface@_port$\:
9839 When a message is received over a TCP/IP connection, this variable contains the
9840 local port number. See also the \-oMi-\ command line option.
9841 This variable can be used in ACLs and also, for example, to make the file name
9842 for a TLS certificate depend on which port is being used.
9846 This variable, which is available only when Exim is compiled with LDAP support,
9847 contains the DN from the last entry in the most recently successful LDAP
9852 This variable contains the system load average, multiplied by 1000 to that it
9853 is an integer. For example, if the load average is 0.21, the value of the
9854 variable is 210. The value is recomputed every time the variable is referenced.
9857 \$local@_part$\: When an address is being routed, or delivered on its own, this
9858 variable contains the local part. When a number of addresses are being
9859 delivered together (for example, multiple \\RCPT\\ commands in an SMTP
9860 session), \$local@_part$\ is not set.
9862 Global address rewriting happens when a message is received, so the value of
9863 \$local@_part$\ during routing and delivery is the value after rewriting.
9864 \$local@_part$\ is set during user filtering, but not during system filtering,
9865 because a message may have many recipients and the system filter is called just
9868 If a local part prefix or suffix has been recognized, it is not included in the
9869 value of \$local@_part$\ during routing and subsequent delivery. The values of
9870 any prefix or suffix are in \$local@_part@_prefix$\ and
9871 \$local@_part@_suffix$\, respectively.
9873 When a message is being delivered to a file, pipe, or autoreply transport as a
9874 result of aliasing or forwarding, \$local@_part$\ is set to the local part of
9875 the parent address, not to the file name or command (see \$address@_file$\ and
9878 When an ACL is running for a \\RCPT\\ command, \$local@_part$\ contains the
9879 local part of the recipient address.
9881 When a rewrite item is being processed (see chapter ~~CHAPrewrite),
9882 \$local@_part$\ contains the local part of the address that is being rewritten;
9883 it can be used in the expansion of the replacement address, for example.
9885 In all cases, all quoting is removed from the local part. For example, for both
9888 "abc:xyz"@test.example
9889 abc\:xyz@test.example
9891 the value of \$local@_part$\ is
9895 If you use \$local@_part$\ to create another address, you should always wrap it
9896 inside a quoting operator. For example, in a \%redirect%\ router you could have:
9898 data = ${quote_local_part:$local_part}@new.domain.example
9900 \**Note**\: The value of \$local@_part$\ is normally lower cased. If you want
9901 to process local parts in a case-dependent manner in a router, you can set the
9902 \caseful@_local@_part\ option (see chapter ~~CHAProutergeneric).
9905 \$local@_part@_data$\:
9906 When the \local@_parts\ option on a router matches a local part by means of a
9907 lookup, the data read by the lookup is available during the running of the
9908 router as \$local@_part@_data$\. In addition, if the driver routes the address
9909 to a transport, the value is available in that transport. If the transport is
9910 handling multiple addresses, the value from the first address is used.
9912 \$local@_part@_data$\ is also set when the \local@_parts\ condition in an ACL
9913 matches a local part by means of a lookup. The data read by the lookup is
9914 available during the rest of the ACL statement. In all other situations, this
9915 variable expands to nothing.
9918 \$local@_part@_prefix$\: When an address is being routed or delivered, and a
9919 specific prefix for the local part was recognized, it is available in this
9920 variable, having been removed from \$local@_part$\.
9923 \$local@_part@_suffix$\: When an address is being routed or delivered, and a
9924 specific suffix for the local part was recognized, it is available in this
9925 variable, having been removed from \$local@_part$\.
9928 \$local@_scan@_data$\: This variable contains the text returned by the
9929 \*local@_scan()*\ function when a message is received. See chapter
9930 ~~CHAPlocalscan for more details.
9933 \$local@_user@_gid$\: See \$local@_user@_uid$\.
9936 \$local@_user@_uid$\: This variable and \$local@_user@_gid$\ are set to
9937 the uid and gid after the \check__local__user\ router precondition succeeds.
9938 This means that their values are available for the remaining preconditions
9939 (\senders\, \require@_files\, and \condition\), for the \address@_data\
9940 expansion, and for any router-specific expansions. At all other times, the
9941 values in these variables are \"(uid@_t)(-1)"\ and \"(gid@_t)(-1)"\,
9945 \$localhost@_number$\: This contains the expanded value of the
9946 \localhost@_number\ option. The expansion happens after the main options have
9951 \$log@_inodes$\: The number of free inodes in the disk partition where Exim's
9952 log files are being written. The value is recalculated whenever the variable is
9953 referenced. If the relevant file system does not have the concept of inodes,
9954 the value of is -1. See also the \check@_log@_inodes\ option.
9957 \$log@_space$\: The amount of free space (as a number of kilobytes) in the disk
9958 partition where Exim's log files are being written. The value is recalculated
9959 whenever the variable is referenced. If the operating system does not have the
9960 ability to find the amount of free space (only true for experimental systems),
9961 the space value is -1. See also the \check@_log@_space\ option.
9965 \$mailstore@_basename$\: This variable is set only when doing deliveries in
9966 `mailstore' format in the \%appendfile%\ transport. During the expansion of the
9967 \mailstore@_prefix\, \mailstore@_suffix\, \message__prefix\, and
9968 \message@_suffix\ options, it contains the basename of the files that are being
9969 written, that is, the name without the `.tmp', `.env', or `.msg' suffix. At all
9970 other times, this variable is empty.
9974 \$malware@_name$\: This variable is available when Exim is compiled with the
9975 content-scanning extension. It is set to the name of the virus that was found
9976 when the ACL \malware\ condition is true (see section ~~SECTscanvirus).
9979 .index message||age of
9981 \$message@_age$\: This variable is set at the start of a delivery attempt to
9982 contain the number of seconds since the message was received. It does not
9983 change during a single delivery attempt.
9985 .index body of message||expansion variable
9986 .index message||body, in expansion
9987 .index binary zero||in message body
9989 \$message@_body$\: This variable contains the initial portion of a message's
9990 body while it is being delivered, and is intended mainly for use in filter
9991 files. The maximum number of characters of the body that are put into the
9992 variable is set by the \message@_body@_visible\ configuration option; the
9993 default is 500. Newlines are converted into spaces to make it easier to search
9994 for phrases that might be split over a line break.
9995 Binary zeros are also converted into spaces.
9997 .index body of message||expansion variable
9998 .index message||body, in expansion
10000 \$message@_body@_end$\: This variable contains the final portion of a message's
10001 body while it is being delivered. The format and maximum size are as for
10004 .index body of message||size
10005 .index message||body, size
10007 \$message@_body@_size$\: When a message is being delivered, this variable
10008 contains the size of the body in bytes. The count starts from the character
10009 after the blank line that separates the body from the header. Newlines are
10010 included in the count. See also \$message@_size$\, \$body@_linecount$\, and
10011 \$body@_zerocount$\.
10014 \$message@_headers$\:
10015 This variable contains a concatenation of all the header lines when a message
10016 is being processed, except for lines added by routers or transports. The header
10017 lines are separated by newline characters.
10021 When a message is being received or delivered, this variable contains the
10022 unique message id that is used by Exim to identify the message.
10023 An id is not created for a message until after its header has been
10024 successfully received.
10025 \**Note**\: This is \*not*\ the contents of the ::Message-ID:: header line; it
10026 is the local id that Exim assigns to the message, for example:
10027 \"1BXTIK-0001yO-VA"\.
10029 .index size||of message
10030 .index message||size
10033 When a message is being processed, this variable contains its size in bytes. In
10034 most cases, the size includes those headers that were received with the
10035 message, but not those (such as ::Envelope-to::) that are added to individual
10036 deliveries as they are written. However, there is one special case: during the
10037 expansion of the \maildir@_tag\ option in the \%appendfile%\ transport while
10038 doing a delivery in maildir format, the value of \$message@_size$\ is the
10039 precise size of the file that has been written. See also
10040 \$message@_body@_size$\, \$body@_linecount$\, and \$body@_zerocount$\.
10042 .index \\RCPT\\||value of \$message@_size$\
10043 While running an ACL at the time of an SMTP \\RCPT\\ command, \$message@_size$\
10044 contains the size supplied on the \\MAIL\\ command, or
10046 if no size was given. The value may not, of course, be truthful.
10050 \$mime@_$\\*xxx*\: A number of variables whose names start with \$mime$\ are
10051 available when Exim is compiled with the content-scanning extension. For
10052 details, see section ~~SECTscanmimepart.
10056 \$n0$\ -- \$n9$\: These variables are counters that can be incremented by means
10057 of the \add\ command in filter files.
10060 \$original@_domain$\: When a top-level address is being processed for delivery,
10061 this contains the same value as \$domain$\. However, if a `child' address (for
10062 example, generated by an alias, forward, or filter file) is being processed,
10063 this variable contains the domain of the original address. This differs from
10064 \$parent@_domain$\ only when there is more than one level of aliasing or
10065 forwarding. When more than one address is being delivered in a single transport
10066 run, \$original@_domain$\ is not set.
10068 If new an address is created by means of a \deliver\ command in a system
10069 filter, it is set up with an artificial `parent' address. This has the local
10070 part \*system-filter*\ and the default qualify domain.
10073 \$original@_local@_part$\: When a top-level address is being processed for
10074 delivery, this contains the same value as \$local@_part$\, unless a prefix or
10075 suffix was removed from the local part, because \$original@_local@_part$\
10076 always contains the full local part. When a `child' address (for example,
10077 generated by an alias, forward, or filter file) is being processed, this
10078 variable contains the full local part of the original address.
10080 If the router that did the redirection processed the local part
10081 case-insensitively, the value in \$original@_local@_part$\ is in lower case.
10082 This variable differs from \$parent@_local@_part$\ only when there is more than
10083 one level of aliasing or forwarding. When more than one address is being
10084 delivered in a single transport run, \$original@_local@_part$\ is not set.
10086 If new an address is created by means of a \deliver\ command in a system
10087 filter, it is set up with an artificial `parent' address. This has the local
10088 part \*system-filter*\ and the default qualify domain.
10091 .index gid (group id)||of originating user
10094 \$originator@_gid$\: The value of \$caller@_gid$\ that was set when the message
10095 was received. For messages received via the command line, this is the gid of
10096 the sending user. For messages received by SMTP over TCP/IP, this is normally
10097 the gid of the Exim user.
10099 .index uid (user id)||of originating user
10102 \$originator@_uid$\: The value of \$caller@_uid$\ that was set when the message
10103 was received. For messages received via the command line, this is the uid of
10104 the sending user. For messages received by SMTP over TCP/IP, this is normally
10105 the uid of the Exim user.
10108 \$parent@_domain$\: This variable is similar to \$original@_domain$\ (see
10109 above), except that it refers to the immediately preceding parent address.
10112 \$parent@_local@_part$\: This variable is similar to \$original@_local@_part$\
10113 (see above), except that it refers to the immediately preceding parent address.
10115 .index pid (process id)||of current process
10117 \$pid$\: This variable contains the current process id.
10119 .index filter||transport filter
10120 .index transport||filter
10122 \$pipe@_addresses$\: This is not an expansion variable, but is mentioned here
10123 because the string `@$pipe@_addresses' is handled specially in the command
10124 specification for the \%pipe%\ transport (chapter ~~CHAPpipetransport) and in
10125 transport filters (described under \transport@_filter\ in chapter
10126 ~~CHAPtransportgeneric). It cannot be used in general expansion strings, and
10127 provokes an `unknown variable' error if encountered.
10130 \$primary@_hostname$\: The value set in the configuration file, or read by the
10131 \*uname()*\ function. If \*uname()*\ returns a single-component name, Exim
10132 calls \*gethostbyname()*\ (or \*getipnodebyname()*\ where available) in an
10133 attempt to acquire a fully qualified host name.
10134 See also \$smtp@_active@_hostname$\.
10137 \$qualify@_domain$\: The value set for this option in the configuration file.
10140 \$qualify@_recipient$\: The value set for this option in the configuration file,
10141 or if not set, the value of \$qualify@_domain$\.
10144 \$rcpt@_count$\: When a message is being received by SMTP, this variable
10145 contains the number of \\RCPT\\ commands received for the current message. If
10146 this variable is used in a \\RCPT\\ ACL, its value includes the current
10150 \$rcpt@_defer@_count$\: When a message is being received by SMTP, this variable
10151 contains the number of \\RCPT\\ commands in the current message that have
10152 previously been rejected with a temporary (4\*xx*\) response.
10155 \$rcpt@_fail@_count$\: When a message is being received by SMTP, this variable
10156 contains the number of \\RCPT\\ commands in the current message that have
10157 previously been rejected with a permanent (5\*xx*\) response.
10160 \$received@_count$\: This variable contains the number of ::Received:: header
10161 lines in the message, including the one added by Exim (so its value is always
10162 greater than zero). It is available in the \\DATA\\ ACL, the non-SMTP ACL, and
10163 while routing and delivering.
10166 \$received@_for$\: If there is only a single recipient address in an incoming
10167 message, this variable contains that address when the ::Received:: header line
10169 The value is copied after recipient rewriting has happened, but before the
10170 \*local@_scan()*\ function is run.
10173 \$received@_protocol$\: When a message is being processed, this variable
10174 contains the name of the protocol by which it was received.
10176 Most of the names used by Exim are defined by RFCs 821, 2821, and 3848. They
10177 start with `smtp' (the client used \\HELO\\) or `esmtp' (the client used
10178 \\EHLO\\). This can be followed by `s' for secure (encrypted) and/or `a' for
10179 authenticated. Thus, for example, if the protocol is set to `esmtpsa', the
10180 message was received over an encrypted SMTP connection and the client was
10181 successfully authenticated.
10183 Exim uses the protocol name `smtps' for the case when encryption is
10184 automatically set up on connection without the use of \\STARTTLS\\ (see
10185 \tls@_on@_connect@_ports\), and the client uses \\HELO\\ to initiate the
10186 encrypted SMTP session. The name `smtps' is also used for the rare situation
10187 where the client initially uses \\EHLO\\, sets up an encrypted connection using
10188 \\STARTTLS\\, and then uses \\HELO\\ afterwards.
10190 The \-oMr-\ option provides a way of specifying a custom protocol name for
10191 messages that are injected locally by trusted callers. This is commonly used to
10192 identify messages that are being re-injected after some kind of scanning.
10196 \$recipient@_data$\: This variable is set after an indexing lookup success in
10197 an ACL \recipients\ condition. It contains the data from the lookup, and the
10198 value remains set until the next \recipients\ test. Thus, you can do things
10201 require recipients = cdb*@@;/some/file
10202 deny \*some further test involving*\ @$recipient@_data
10204 \**Warning**\: This variable is set only when a lookup is used as an indexing
10205 method in the address list, using the semicolon syntax as in the example above.
10206 The variable is not set for a lookup that is used as part of the string
10207 expansion that all such lists undergo before being interpreted.
10211 \$recipient@_verify@_failure$\: In an ACL, when a recipient verification fails,
10212 this variable contains information about the failure. It is set to one of the
10215 `qualify': The address was unqualified (no domain), and the message
10216 was neither local nor came from an exempted host.
10218 `route': Routing failed.
10220 `mail': Routing succeeded, and a callout was attempted; rejection occurred at
10221 or before the \\MAIL\\ command (that is, on initial connection, \\HELO\\, or
10224 `recipient': The \\RCPT\\ command in a callout was rejected.
10226 `postmaster': The postmaster check in a callout was rejected.
10228 The main use of this variable is expected to be to distinguish between
10229 rejections of \\MAIL\\ and rejections of \\RCPT\\.
10233 \$recipients$\: This variable contains a list of envelope recipients for a
10234 message. A comma and a space separate the addresses in the replacement text.
10235 However, the variable is not generally available, to prevent exposure of Bcc
10236 recipients in unprivileged users' filter files. You can use \$recipients$\ only
10237 in these two cases:
10239 In a system filter file.
10242 In the ACLs associated with the \\DATA\\ command, that is, the ACLs defined by
10243 \acl@_smtp@_predata\ and \acl@_smtp@_data\.
10248 \$recipients@_count$\: When a message is being processed, this variable
10249 contains the number of envelope recipients that came with the message.
10250 Duplicates are not excluded from the count. While a message is being received
10251 over SMTP, the number increases for each accepted recipient. It can be
10252 referenced in an ACL.
10255 \$reply@_address$\: When a message is being processed, this variable contains
10256 the contents of the ::Reply-To:: header line if one exists
10257 and it is not empty,
10258 or otherwise the contents of the ::From:: header line.
10261 \$return@_path$\: When a message is being delivered, this variable contains the
10262 return path -- the sender field that will be sent as part of the envelope. It
10263 is not enclosed in @<@> characters.
10264 At the start of routing an address,
10265 \$return@_path$\ has the same value as \$sender@_address$\, but if, for
10266 example, an incoming message to a mailing list has been expanded by a router
10267 which specifies a different address for bounce messages, \$return@_path$\
10268 subsequently contains the new bounce address, whereas \$sender@_address$\
10269 always contains the original sender address that was received with the message.
10270 In other words, \$sender@_address$\ contains the incoming envelope sender, and
10271 \$return@_path$\ contains the outgoing envelope sender.
10274 \$return@_size@_limit$\: This is an obsolete name for
10275 \$bounce@_return@_size@_limit$\.
10277 .index return code||from \run\ expansion
10279 \$runrc$\: This variable contains the return code from a command that is run by
10280 the \@$@{run...@}\ expansion item.
10281 \**Warning**\: In a router or transport, you cannot assume the order in which
10282 option values are expanded, except for those pre-conditions whose order of
10283 testing is documented. Therefore, you cannot reliably expect to set \$runrc$\
10284 by the expansion of one option, and use it in another.
10287 \$self@_hostname$\: When an address is routed to a supposedly remote host that
10288 turns out to be the local host, what happens is controlled by the
10289 .index \self\ option||value of host name
10290 \self\ generic router option. One of its values causes the address to be passed
10291 to another router. When this happens, \$self@_hostname$\ is set to the name of
10292 the local host that the original router encountered. In other circumstances its
10296 \$sender@_address$\: When a message is being processed, this variable contains
10297 the sender's address that was received in the message's envelope. For bounce
10298 messages, the value of this variable is the empty string.
10299 See also \$return@_path$\.
10303 \$sender@_address@_data$\: If \$address@_data$\ is set when the routers are
10304 called from an ACL to verify a sender address, the final value is preserved in
10305 \$sender@_address@_data$\, to distinguish it from data from a recipient
10306 address. The value does not persist after the end of the current ACL statement.
10307 If you want to preserve it for longer, you can save it in an ACL variable.
10311 \$sender@_address@_domain$\: The domain portion of \$sender@_address$\.
10314 \$sender@_address@_local@_part$\: The local part portion of \$sender@_address$\.
10317 \$sender@_data$\: This variable is set after a lookup success in an ACL
10318 \senders\ condition or in a router \senders\ option. It contains the data from
10319 the lookup, and the value remains set until the next \senders\ test. Thus, you
10320 can do things like this:
10322 require senders = cdb*@@;/some/file
10323 deny \*some further test involving*\ @$sender@_data
10325 \**Warning**\: This variable is set only when a lookup is used as an indexing
10326 method in the address list, using the semicolon syntax as in the example above.
10327 The variable is not set for a lookup that is used as part of the string
10328 expansion that all such lists undergo before being interpreted.
10331 \$sender@_fullhost$\: When a message is received from a remote host, this
10332 variable contains the host name and IP address in a single string. It ends
10333 with the IP address in square brackets, followed by a colon and a port number
10334 if the logging of ports is enabled. The format of the rest of the string
10335 depends on whether the host issued a \\HELO\\ or \\EHLO\\ SMTP command, and
10336 whether the host name was verified by looking up its IP address. (Looking up
10337 the IP address can be forced by the \host@_lookup\ option, independent of
10338 verification.) A plain host name at the start of the string is a verified host
10339 name; if this is not present, verification either failed or was not requested.
10340 A host name in parentheses is the argument of a \\HELO\\ or \\EHLO\\ command.
10341 This is omitted if it is identical to the verified host name or to the host's
10342 IP address in square brackets.
10345 \$sender@_helo@_name$\: When a message is received from a remote host that has
10346 issued a \\HELO\\ or \\EHLO\\ command, the argument of that command is placed
10347 in this variable. It is also set if \\HELO\\ or \\EHLO\\ is used when a message
10348 is received using SMTP locally via the \-bs-\ or \-bS-\ options.
10351 \$sender@_host@_address$\: When a message is received from a remote host, this
10352 variable contains that host's IP address. For locally submitted messages, it is
10356 \$sender@_host@_authenticated$\: This variable contains the name (not the
10357 public name) of the authenticator driver which successfully authenticated the
10358 client from which the message was received. It is empty if there was no
10359 successful authentication.
10362 \$sender@_host@_name$\: When a message is received from a remote host, this
10363 variable contains the host's name as obtained by looking up its IP address.
10364 For messages received by other means, this variable is empty.
10366 If the host name has not previously been looked up, a reference to
10367 \$sender@_host@_name$\ triggers a lookup (for messages from remote hosts).
10368 A looked up name is accepted only if it leads back to the original IP address
10369 via a forward lookup. If either the reverse or the forward lookup fails
10373 or if the forward lookup does not yield the original IP address,
10374 \$sender@_host@_name$\ remains empty, and \$host@_lookup@_failed$\ is set to
10377 However, if either of the lookups cannot be completed (for example, there is a
10378 DNS timeout), \$host@_lookup@_deferred$\ is set to `1', and
10379 \$host@_lookup@_failed$\ remains set to `0'.
10381 Once \$host@_lookup@_failed$\ is set to `1', Exim does not try to look up the
10382 host name again if there is a subsequent reference to \$sender@_host@_name$\
10383 in the same Exim process, but it does try again if \$sender@_host@_deferred$\
10387 Exim does not automatically look up every calling host's name. If you want
10388 maximum efficiency, you should arrange your configuration so that it avoids
10389 these lookups altogether. The lookup happens only if one or more of the
10390 following are true:
10392 A string containing \$sender@_host@_name$\ is expanded.
10394 The calling host matches the list in \host@_lookup\. In the default
10395 configuration, this option is set to $*$, so it must be changed if lookups are
10396 to be avoided. (In the code, the default for \host@_lookup\ is unset.)
10398 Exim needs the host name in order to test an item in a host list. The items
10399 that require this are described in sections ~~SECThoslispatnam and
10400 ~~SECThoslispatnamsk.
10402 The calling host matches \helo@_try@_verify@_hosts\ or \helo@_verify@_hosts\.
10403 In this case, the host name is required to compare with the name quoted in any
10404 \\EHLO\\ or \\HELO\\ commands that the client issues.
10406 The remote host issues a \\EHLO\\ or \\HELO\\ command that quotes one of the
10407 domains in \helo@_lookup@_domains\. The default value of this option is
10409 helo_lookup_domains = @ : @[]
10411 which causes a lookup if a remote host (incorrectly) gives the server's name or
10412 IP address in an \\EHLO\\ or \\HELO\\ command.
10416 \$sender@_host@_port$\: When a message is received from a remote host, this
10417 variable contains the port number that was used on the remote host.
10420 \$sender@_ident$\: When a message is received from a remote host, this variable
10421 contains the identification received in response to an RFC 1413 request. When a
10422 message has been received locally, this variable contains the login name of the
10423 user that called Exim.
10426 \$sender@_rcvhost$\: This is provided specifically for use in ::Received::
10427 headers. It starts with either the verified host name (as obtained from a
10428 .index DNS||reverse lookup
10429 .index reverse DNS lookup
10430 reverse DNS lookup) or, if there is no verified host name, the IP address in
10431 square brackets. After that there may be text in parentheses. When the first
10432 item is a verified host name, the first thing in the parentheses is the IP
10433 address in square brackets, followed by a colon and a port number if port
10434 logging is enabled. When the first item is an IP address, the port is recorded
10435 as `port=$it{xxxx}' inside the parentheses.
10437 There may also be items of the form `helo=$it{xxxx}' if \\HELO\\ or \\EHLO\\
10438 was used and its argument was not identical to the real host name or IP
10439 address, and `ident=$it{xxxx}' if an RFC 1413 ident string is available. If all
10440 three items are present in the parentheses, a newline and tab are inserted into
10441 the string, to improve the formatting of the ::Received:: header.
10445 \$sender@_verify@_failure$\: In an ACL, when a sender verification fails, this
10446 variable contains information about the failure. The details are the same as
10447 for \$recipient@_verify@_failure$\.
10450 \$smtp@_active@_hostname$\: During an SMTP session, this variable contains the
10451 value of the active host name, as specified by the \smtp@_active@_hostname\
10452 option. The value of \$smtp@_active@_hostname$\ is saved with any message that
10453 is received, so its value can be consulted during routing and delivery.
10456 .index \\AUTH\\||argument
10457 .index \\EXPN\\||argument
10458 .index \\ETRN\\||argument
10459 .index \\VRFY\\||argument
10461 \$smtp@_command@_argument$\: While an ACL is running to check an \\AUTH\\,
10462 \\EHLO\\, \\EXPN\\, \\ETRN\\, \\HELO\\, or \\VRFY\\ command, this variable
10463 contains the argument for the SMTP command.
10466 \$sn0$\ -- \$sn9$\: These variables are copies of the values of the \$n0$\
10467 -- \$n9$\ accumulators that were current at the end of the system filter file.
10468 This allows a system filter file to set values that can be tested in users'
10469 filter files. For example, a system filter could set a value indicating how
10470 likely it is that a message is junk mail.
10474 \$spam@_$\\*xxx*\: A number of variables whose names start with \$spam$\ are
10475 available when Exim is compiled with the content-scanning extension. For
10476 details, see section ~~SECTscanspamass.
10480 \$spool@_directory$\: The name of Exim's spool directory.
10484 \$spool@_inodes$\: The number of free inodes in the disk partition where Exim's
10485 spool files are being written. The value is recalculated whenever the variable
10486 is referenced. If the relevant file system does not have the concept of inodes,
10487 the value of is -1.
10488 See also the \check@_spool@_inodes\ option.
10491 \$spool@_space$\: The amount of free space (as a number of kilobytes) in the
10492 disk partition where Exim's spool files are being written. The value is
10493 recalculated whenever the variable is referenced. If the operating system does
10494 not have the ability to find the amount of free space (only true for
10495 experimental systems), the space value is -1. For example, to check in an ACL
10496 that there is at least 50 megabytes free on the spool, you could write:
10498 condition = ${if > {$spool_space}{50000}}
10500 See also the \check@_spool@_space\ option.
10504 \$thisaddress$\: This variable is set only during the processing of the
10505 \foranyaddress\ command in a filter file. Its use is explained in the
10506 description of that command.
10509 \$tls@_certificate@_verified$\:
10510 This variable is set to `1' if a TLS certificate was verified when the message
10511 was received, and `0' otherwise.
10514 \$tls@_cipher$\: When a message is received from a remote host over an
10515 encrypted SMTP connection, this variable is set to the cipher suite that was
10516 negotiated, for example DES-CBC3-SHA.
10517 In other circumstances, in particular, for message received over unencrypted
10518 connections, the variable is empty.
10519 See chapter ~~CHAPTLS for details of TLS support.
10522 \$tls@_peerdn$\: When a message is received from a remote host over an
10523 encrypted SMTP connection,
10524 and Exim is configured to request a certificate from the client,
10525 the value of the Distinguished Name of the certificate is made available in the
10526 \$tls@_peerdn$\ during subsequent processing.
10529 \$tod@_bsdinbox$\: The time of day and date, in the format required for
10530 BSD-style mailbox files, for example: Thu Oct 17 17:14:09 1995.
10533 \$tod@_epoch$\: The time and date as a number of seconds since the start of the
10537 \$tod@_full$\: A full version of the time and date, for example: Wed, 16 Oct
10538 1995 09:51:40 +0100. The timezone is always given as a numerical offset from
10539 UTC, with positive values used for timezones that are ahead (east) of UTC, and
10540 negative values for those that are behind (west).
10543 \$tod@_log$\: The time and date in the format used for writing Exim's log
10544 files, for example: 1995-10-12 15:32:29,
10545 but without a timezone.
10549 This variable contains the date in the format yyyymmdd. This is the format that
10550 is used for datestamping log files when \log@_file@_path\ contains the \"%D"\
10554 \$tod@_zone$\: This variable contains the numerical value of the local
10555 timezone, for example: -0500.
10559 This variable contains the UTC date and time in `Zulu' format, as specified by
10560 ISO 8601, for example: 20030221154023Z.
10564 \$value$\: This variable contains the result of an expansion lookup, extraction
10565 operation, or external command, as described above.
10568 \$version@_number$\: The version number of Exim.
10571 \$warn@_message@_delay$\: This variable is set only during the creation of a
10572 message warning about a delivery delay. Details of its use are explained in
10573 section ~~SECTcustwarn.
10576 \$warn@_message@_recipients$\: This variable is set only during the creation of
10577 a message warning about a delivery delay. Details of its use are explained in
10578 section ~~SECTcustwarn.
10585 . ============================================================================
10586 .chapter Embedded Perl
10587 .set runningfoot "embedded Perl"
10588 .rset CHAPperl "~~chapter"
10589 .index Perl||calling from Exim
10591 Exim can be built to include an embedded Perl interpreter. When this is done,
10592 Perl subroutines can be called as part of the string expansion process. To make
10593 use of the Perl support, you need version 5.004 or later of Perl installed on
10594 your system. To include the embedded interpreter in the Exim binary, include
10599 in your \(Local/Makefile)\ and then build Exim in the normal way.
10601 .section Setting up so Perl can be used
10602 Access to Perl subroutines is via a global configuration option called
10603 .index \perl@_startup\
10604 \perl@_startup\ and an expansion string operator \@$@{perl ...@}\. If there is
10605 no \perl@_startup\ option in the Exim configuration file then no Perl
10606 interpreter is started and there is almost no overhead for Exim (since none of
10607 the Perl library will be paged in unless used). If there is a \perl@_startup\
10608 option then the associated value is taken to be Perl code which is executed in
10609 a newly created Perl interpreter.
10611 The value of \perl@_startup\ is not expanded in the Exim sense, so you do not
10612 need backslashes before any characters to escape special meanings. The option
10613 should usually be something like
10615 perl_startup = do '/etc/exim.pl'
10617 where \(/etc/exim.pl)\ is Perl code which defines any subroutines you want to
10618 use from Exim. Exim can be configured either to start up a Perl interpreter as
10619 soon as it is entered, or to wait until the first time it is needed. Starting
10620 the interpreter at the beginning ensures that it is done while Exim still has
10621 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
10622 fact used in a particular run. Also, note that this does not mean that Exim is
10623 necessarily running as root when Perl is called at a later time. By default,
10624 the interpreter is started only when it is needed, but this can be changed in
10627 .index \perl@_at@_start\
10628 Setting \perl@_at@_start\ (a boolean option) in the configuration requests
10629 a startup when Exim is entered.
10631 The command line option \-ps-\ also requests a startup when Exim is entered,
10632 overriding the setting of \perl@_at@_start\.
10634 There is also a command line option \-pd-\ (for delay) which suppresses the
10635 initial startup, even if \perl@_at@_start\ is set.
10637 .section Calling Perl subroutines
10638 When the configuration file includes a \perl@_startup\ option you can make use
10639 of the string expansion item to call the Perl subroutines that are defined
10640 by the \perl@_startup\ code. The operator is used in any of the following
10644 ${perl{foo}{argument}}
10645 ${perl{foo}{argument1}{argument2} ... }
10647 which calls the subroutine \foo\ with the given arguments. A maximum of eight
10648 arguments may be passed. Passing more than this results in an expansion failure
10649 with an error message of the form
10651 Too many arguments passed to Perl subroutine "foo" (max is 8)
10653 The return value of the Perl subroutine is evaluated in a scalar context before
10654 it is passed back to Exim to be inserted into the expanded string. If the
10655 return value is \*undef*\, the expansion is forced to fail in the same way as
10656 an explicit `fail' on an \@$@{if ...@}\ or \@$@{lookup...@}\ item. If the
10657 subroutine aborts by obeying Perl's \die\ function, the expansion fails with
10658 the error message that was passed to \die\.
10660 .section Calling Exim functions from Perl
10661 Within any Perl code called from Exim, the function \*Exim@:@:expand@_string*\
10662 is available to call back into Exim's string expansion function. For example,
10665 my $lp = Exim::expand_string('$local_part');
10667 makes the current Exim \$local@_part$\ available in the Perl variable \$lp$\.
10668 Note those are single quotes and not double quotes to protect against
10669 \$local@_part$\ being interpolated as a Perl variable.
10671 If the string expansion is forced to fail by a `fail' item, the result of
10672 \*Exim@:@:expand@_string*\ is \undef\. If there is a syntax error in the
10673 expansion string, the Perl call from the original expansion string fails with
10674 an appropriate error message, in the same way as if \die\ were used.
10676 .index debugging||from embedded Perl
10677 .index log||writing from embedded Perl
10678 Two other Exim functions are available for use from within Perl code.
10679 \*Exim@:@:debug@_write(<<string>>)*\ writes the string to the standard error
10680 stream if Exim's debugging is enabled. If you want a newline at the end, you
10681 must supply it. \*Exim@:@:log@_write(<<string>>)*\ writes the string to Exim's
10682 main log, adding a leading timestamp. In this case, you should not supply a
10683 terminating newline.
10686 .section Use of standard output and error by Perl
10687 .index Perl||standard output and error
10688 You should not write to the standard error or output streams from within your
10689 Perl code, as it is not defined how these are set up. In versions of Exim
10690 before 4.50, it is possible for the standard output or error to refer to the
10691 SMTP connection during message reception via the daemon. Writing to this stream
10692 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
10693 error streams are connected to \(/dev/null)\ in the daemon. The chaos is
10694 avoided, but the output is lost.
10696 .index Perl||\warn\, use of
10697 The Perl \warn\ statement writes to the standard error stream by default. Calls
10698 to \warn\ may be embedded in Perl modules that you use, but over which you have
10699 no control. When Exim starts up the Perl interpreter, it arranges for output
10700 from the \warn\ statement to be written to the Exim main log. You can change
10701 this by including appropriate Perl magic somewhere in your Perl code. For
10702 example, to discard \warn\ output completely, you need this:
10704 $SIG{__WARN__} = sub { };
10706 Whenever a \warn\ is obeyed, the anonymous subroutine is called. In this
10707 example, the code for the subroutine is empty, so it does nothing, but you can
10708 include any Perl code that you like. The text of the \warn\ message is passed
10709 as the first subroutine argument.
10717 . ============================================================================
10718 .chapter Starting the daemon and the use of network interfaces
10719 .set runningfoot "starting the daemon"
10720 .rset CHAPinterfaces "~~chapter"
10721 .index daemon||starting
10722 .index interface||listening
10723 .index network interface
10724 .index interface||network
10725 .index IP address||for listening
10726 .index daemon||listening IP addresses
10727 .index TCP/IP||setting listening interfaces
10728 .index TCP/IP||setting listening ports
10730 A host that is connected to a TCP/IP network may have one or more physical
10731 hardware network interfaces. Each of these interfaces may be configured as one
10732 or more `logical' interfaces, which are the entities that a program actually
10733 works with. Each of these logical interfaces is associated with an IP address.
10734 In addition, TCP/IP software supports `loopback' interfaces (127.0.0.1 in IPv4
10735 and @:@:1 in IPv6), which do not use any physical hardware. Exim requires
10736 knowledge about the host's interfaces for use in three different circumstances:
10738 When a listening daemon is started, Exim needs to know which interfaces
10739 and ports to listen on.
10741 When Exim is routing an address, it needs to know which IP addresses
10742 are associated with local interfaces. This is required for the correct
10743 processing of MX lists by removing the local host and others with the
10744 same or higher priority values. Also, Exim needs to detect cases
10745 when an address is routed to an IP address that in fact belongs to the
10746 local host. Unless the \self\ router option or the \allow@_localhost\
10747 option of the smtp transport is set (as appropriate), this is treated
10748 as an error situation.
10750 When Exim connects to a remote host, it may need to know which interface to use
10751 for the outgoing connection.
10754 Exim's default behaviour is likely to be appropriate in the vast majority
10755 of cases. If your host has only one interface, and you want all its IP
10756 addresses to be treated in the same way, and you are using only the
10757 standard SMTP port, you should not need to take any special action. The
10758 rest of this chapter does not apply to you.
10760 In a more complicated situation you may want to listen only on certain
10761 interfaces, or on different ports, and for this reason there are a number of
10762 options that can be used to influence Exim's behaviour. The rest of this
10763 chapter describes how they operate.
10765 When a message is received over TCP/IP, the interface and port that were
10766 actually used are set in \$interface@_address$\ and \$interface@_port$\.
10769 .section Starting a listening daemon
10770 When a listening daemon is started (by means of the \-bd-\ command line
10771 option), the interfaces and ports on which it listens are controlled by the
10774 \daemon@_smtp@_ports\ contains a list of default ports. (For backward
10775 compatibility, this option can also be specified in the singular.)
10777 \local@_interfaces\ contains list of interface IP addresses on which to
10778 listen. Each item may optionally also specify a port.
10780 The default list separator in both cases is a colon, but this can be changed as
10781 described in section ~~SECTlistconstruct. When IPv6 addresses are involved, it
10782 is usually best to change the separator to avoid having to double all the
10783 colons. For example:
10785 local_interfaces = <; 127.0.0.1 ; \
10788 3ffe:ffff:836f::fe86:a061
10790 There are two different formats for specifying a port along with an IP address
10791 in \local@_interfaces\:
10793 The port is added onto the address with a dot separator. For example, to listen
10794 on port 1234 on two different IP addresses:
10796 local_interfaces = <; 192.168.23.65.1234 ; \
10797 3ffe:ffff:836f::fe86:a061.1234
10800 The IP address is enclosed in square brackets, and the port is added
10801 with a colon separator, for example:
10803 local_interfaces = <; [192.168.23.65]:1234 ; \
10804 [3ffe:ffff:836f::fe86:a061]:1234
10807 When a port is not specified, the value of \daemon@_smtp@_ports\ is used. The
10808 default setting contains just one port:
10810 daemon_smtp_ports = smtp
10812 If more than one port is listed, each interface that does not have its own port
10813 specified listens on all of them. Ports that are listed in
10814 \daemon@_smtp@_ports\ can be identified either by name (defined in
10815 \(/etc/services)\) or by number. However, when ports are given with individual
10816 IP addresses in \local@_interfaces\, only numbers (not names) can be used.
10819 .section Special IP listening addresses
10820 The addresses 0.0.0.0 and @:@:0 are treated specially. They are interpreted
10821 as `all IPv4 interfaces' and `all IPv6 interfaces', respectively. In each
10822 case, Exim tells the TCP/IP stack to `listen on all IPv\*x*\ interfaces'
10823 instead of setting up separate listening sockets for each interface. The
10824 default value of \local@_interfaces\ is
10826 local_interfaces = 0.0.0.0
10828 when Exim is built without IPv6 support; otherwise it is:
10830 local_interfaces = <; ::0 ; 0.0.0.0
10832 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
10835 .section Overriding local@_interfaces and daemon@_smtp@_ports
10836 The \-oX-\ command line option can be used to override the values of
10837 \daemon@_smtp@_ports\ and/or \local@_interfaces\ for a particular daemon
10838 instance. Another way of doing this would be to use macros and the \-D-\
10839 option. However, \-oX-\ can be used by any admin user, whereas modification of
10840 the runtime configuration by \-D-\ is allowed only when the caller is root or
10843 The value of \-oX-\ is a list of items. The default colon separator can be
10844 changed in the usual way if required. If there are any items that do not
10845 contain dots or colons (that is, are not IP addresses), the value of
10846 \daemon@_smtp@_ports\ is replaced by the list of those items. If there are any
10847 items that do contain dots or colons, the value of \local@_interfaces\ is
10848 replaced by those items. Thus, for example,
10852 overrides \daemon@_smtp@_ports\, but leaves \local@_interfaces\ unchanged,
10855 -oX 192.168.34.5.1125
10857 overrides \local@_interfaces\, leaving \daemon@_smtp@_ports\ unchanged.
10858 (However, since \local@_interfaces\ now contains no items without ports, the
10859 value of \daemon@_smtp@_ports\ is no longer relevant in this example.)
10863 .section Support for the obsolete SSMTP (or SMTPS) protocol
10864 .rset SECTsupobssmt "~~chapter.~~section"
10865 .index ssmtp protocol
10866 .index smtps protocol
10867 .index SMTP||ssmtp protocol
10868 .index SMTP||smtps protocol
10869 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
10870 before the \\STARTTLS\\ command was standardized for SMTP. Some legacy clients
10871 still use this protocol. If the \tls@_on@_connect@_ports\ option is set to a
10872 list of port numbers, connections to those ports must use SSMTP. The most
10873 common use of this option is expected to be
10875 tls_on_connect_ports = 465
10877 because 465 is the usual port number used by the legacy clients. There is also
10878 a command line option \-tls-on-connect-\, which forces all ports to behave in
10879 this way when a daemon is started.
10881 \**Warning**\: Setting \tls@_on@_connect@_ports\ does not of itself cause the
10882 daemon to listen on those ports. You must still specify them in
10883 \daemon@_smtp@_ports\, \local@_interfaces\, or the \-oX-\ option. (This is
10884 because \tls@_on@_connect@_ports\ applies to \inetd\ connections as well as to
10885 connections via the daemon.)
10889 .section IPv6 address scopes
10890 IPv6 addresses have `scopes', and a host with multiple hardware interfaces
10891 can, in principle, have the same link-local IPv6 address on different
10892 interfaces. Thus, additional information is needed, over and above the IP
10893 address, to distinguish individual interfaces. A convention of using a
10894 percent sign followed by something (often the interface name) has been
10895 adopted in some cases, leading to addresses like this:
10897 fe80::202:b3ff:fe03:45c1%eth0
10899 To accommodate this usage, a percent sign followed by an arbitrary string is
10900 allowed at the end of an IPv6 address. By default, Exim calls \*getaddrinfo()*\
10901 to convert a textual IPv6 address for actual use. This function recognizes the
10902 percent convention in operating systems that support it, and it processes the
10903 address appropriately. Unfortunately, some older libraries have problems with
10904 \*getaddrinfo()*\. If
10906 IPV6_USE_INET_PTON=yes
10908 is set in \(Local/Makefile)\ (or an OS-dependent Makefile) when Exim is built,
10909 Exim uses \*inet@_pton()*\ to convert a textual IPv6 address for actual use,
10910 instead of \*getaddrinfo()*\. (Before version 4.14, it always used this
10911 function.) Of course, this means that the additional functionality of
10912 \*getaddrinfo()*\ -- recognizing scoped addresses -- is lost.
10915 .section Examples of starting a listening daemon
10916 The default case in an IPv6 environment is
10918 daemon_smtp_ports = smtp
10919 local_interfaces = <; ::0 ; 0.0.0.0
10921 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
10922 Either one or two sockets may be used, depending on the characteristics of
10923 the TCP/IP stack. (This is complicated and messy; for more information,
10924 read the comments in the \(daemon.c)\ source file.)
10926 To specify listening on ports 25 and 26 on all interfaces:
10928 daemon_smtp_ports = 25 : 26
10930 (leaving \local@_interfaces\ at the default setting) or, more explicitly:
10932 local_interfaces = <; ::0.25 ; ::0.26 \
10933 0.0.0.0.25 ; 0.0.0.0.26
10935 To listen on the default port on all IPv4 interfaces, and on port 26 on the
10936 IPv4 loopback address only:
10938 local_interfaces = 0.0.0.0 : 127.0.0.1.26
10940 To specify listening on the default port on specific interfaces only:
10942 local_interfaces = 192.168.34.67 : 192.168.34.67
10944 \**Warning**\: such a setting excludes listening on the loopback interfaces.
10947 .section Recognising the local host
10948 .rset SECTreclocipadd "~~chapter.~~section"
10949 The \local@_interfaces\ option is also used when Exim needs to determine
10950 whether or not an IP address refers to the local host. That is, the IP
10951 addresses of all the interfaces on which a daemon is listening are always
10954 For this usage, port numbers in \local@_interfaces\ are ignored. If either of
10955 the items 0.0.0.0 or @:@:0 are encountered, Exim gets a complete list of
10956 available interfaces from the operating system, and extracts the relevant
10957 (that is, IPv4 or IPv6) addresses to use for checking.
10959 Some systems set up large numbers of virtual interfaces in order to provide
10960 many virtual web servers. In this situation, you may want to listen for
10961 email on only a few of the available interfaces, but nevertheless treat all
10962 interfaces as local when routing. You can do this by setting
10963 \extra@_local@_interfaces\ to a list of IP addresses, possibly including the
10964 `all' wildcard values. These addresses are recognized as local, but are not
10965 used for listening. Consider this example:
10967 local_interfaces = <; 127.0.0.1 ; ::1 ; \
10969 3ffe:2101:12:1:a00:20ff:fe86:a061
10971 extra_local_interfaces = <; ::0 ; 0.0.0.0
10973 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
10974 address, but all available interface addresses are treated as local when
10977 In some environments the local host name may be in an MX list, but with an IP
10978 address that is not assigned to any local interface. In other cases it may be
10979 desirable to treat other host names as if they referred to the local host. Both
10980 these cases can be handled by setting the \hosts@_treat@_as@_local\ option.
10981 This contains host names rather than IP addresses. When a host is referenced
10982 during routing, either via an MX record or directly, it is treated as the local
10983 host if its name matches \hosts@_treat@_as@_local\, or if any of its IP
10984 addresses match \local@_interfaces\ or \extra@_local@_interfaces\.
10987 .section Delivering to a remote host
10988 Delivery to a remote host is handled by the smtp transport. By default, it
10989 allows the system's TCP/IP functions to choose which interface to use (if
10990 there is more than one) when connecting to a remote host. However, the
10991 \interface\ option can be set to specify which interface is used. See the
10992 description of the smtp transport in chapter ~~CHAPsmtptrans for more details.
11001 . ============================================================================
11002 .chapter Main configuration
11003 .set runningfoot "main configuration"
11004 .rset CHAPmainconfig "~~chapter"
11005 .index configuration file||main section
11006 .index main configuration
11007 The first part of the run time configuration file contains three types of item:
11009 Macro definitions: These lines start with an upper case letter. See section
11010 ~~SECTmacrodefs for details of macro processing.
11012 Named list definitions: These lines start with one of the words `domainlist',
11013 `hostlist', `addresslist', or `localpartlist'. Their use is described in
11014 section ~~SECTnamedlists.
11016 Main configuration settings: Each setting occupies one line of the file
11017 (with possible continuations). If any setting is preceded by the word
11018 `hide', the \-bP-\ command line option displays its value to admin users only.
11019 See section ~~SECTcos for a description of the syntax of these option settings.
11021 This chapter specifies all the main configuration options, along with their
11022 types and default values. For ease of finding a particular option, they appear
11023 in alphabetical order in section ~~SECTalomo below. However, because there are
11024 now so many options, they are first listed briefly in functional groups, as an
11025 aid to finding the name of the option you are looking for. Some options are
11026 listed in more than one group.
11028 .set savedisplayflowcheck ~~displayflowcheck
11029 .set displayflowcheck 0
11031 .section Miscellaneous
11034 \bi@_command\ $t$rm{to run for \-bi-\ command line option}
11035 \keep@_malformed\ $t$rm{for broken files -- should not happen}
11036 \localhost@_number\ $t$rm{for unique message ids in clusters}
11037 \message@_body@_visible\ $t$rm{how much to show in \$message@_body$\}
11040 \mua@_wrapper\ $t$rm{run in `MUA wrapper' mode}
11043 \print@_topbitchars\ $t$rm{top-bit characters are printing}
11044 \timezone\ $t$rm{force time zone}
11047 .section Exim parameters
11050 \exim@_group\ $t$rm{override compiled-in value}
11051 \exim@_path\ $t$rm{override compiled-in value}
11052 \exim@_user\ $t$rm{override compiled-in value}
11053 \primary@_hostname\ $t$rm{default from \*uname()*\}
11054 \split@_spool@_directory\ $t$rm{use multiple directories}
11055 \spool@_directory\ $t$rm{override compiled-in value}
11058 .section Privilege controls
11061 \admin@_groups\ $t$rm{groups that are Exim admin users}
11062 \deliver@_drop@_privilege\ $t$rm{drop root for delivery processes}
11063 \local@_from@_check\ $t$rm{insert ::Sender:: if necessary}
11064 \local@_from@_prefix\ $t$rm{for testing ::From:: for local sender}
11065 \local@_from@_suffix\ $t$rm{for testing ::From:: for local sender}
11066 \local@_sender@_retain\ $t$rm{keep ::Sender:: from untrusted user}
11067 \never@_users\ $t$rm{do not run deliveries as these}
11068 \prod@_requires@_admin\ $t$rm{forced delivery requires admin user}
11069 \queue@_list@_requires@_admin\ $t$rm{queue listing requires admin user}
11070 \trusted@_groups\ $t$rm{groups that are trusted}
11071 \trusted@_users\ $t$rm{users that are trusted}
11078 \hosts@_connection@_nolog\ $t$rm{exemption from connect logging}
11081 \log@_file@_path\ $t$rm{override compiled-in value}
11082 \log@_selector\ $t$rm{set/unset optional logging}
11083 \log@_timezone\ $t$rm{add timezone to log lines}
11084 \message@_logs\ $t$rm{create per-message logs}
11085 \preserve@_message@_logs\ $t$rm{after message completion}
11086 \process@_log@_path\ $t$rm{for SIGUSR1 and \*exiwhat*\}
11087 \syslog@_duplication\ $t$rm{controls duplicate log lines on syslog }
11088 \syslog@_facility\ $t$rm{set syslog `facility' field}
11089 \syslog@_processname\ $t$rm{set syslog `ident' field}
11090 \syslog@_timestamp\ $t$rm{timestamp syslog lines}
11092 \write@_rejectlog\ $t$rm{control use of message log}
11096 .section Frozen messages
11099 \auto@_thaw\ $t$rm{sets time for retrying frozen messages}
11100 \freeze@_tell\ $t$rm{send message when freezing}
11101 \move@_frozen@_messages\ $t$rm{to another directory}
11102 \timeout@_frozen@_after\ $t$rm{keep frozen messages only so long}
11105 .section Data lookups
11108 \ldap@_default@_servers\ $t$rm{used if no server in query}
11109 \ldap@_version\ $t$rm{set protocol version}
11110 \lookup@_open@_max\ $t$rm{lookup files held open}
11111 \mysql@_servers\ $t$rm{as it says}
11112 \oracle@_servers\ $t$rm{as it says}
11113 \pgsql@_servers\ $t$rm{as it says}
11116 .section Message ids
11119 \message@_id@_header@_domain\ $t$rm{used to build ::Message-ID:: header}
11120 \message@_id@_header@_text\ $t$rm{ditto}
11123 .section Embedded Perl Startup
11126 \perl@_at@_start\ $t$rm{always start the interpreter}
11127 \perl@_startup\ $t$rm{code to obey when starting Perl}
11133 \daemon@_smtp@_ports\ $t$rm{default ports}
11134 \extra@_local@_interfaces\ $t$rm{not necessarily listened on}
11135 \local@_interfaces\ $t$rm{on which to listen, with optional ports}
11136 \pid@_file@_path\ $t$rm{override compiled-in value}
11137 \queue@_run@_max\ $t$rm{maximum simultaneous queue runners}
11140 .section Resource control
11143 \check@_log@_inodes\ $t$rm{before accepting a message}
11144 \check@_log@_space\ $t$rm{before accepting a message}
11145 \check@_spool@_inodes\ $t$rm{before accepting a message}
11146 \check@_spool@_space\ $t$rm{before accepting a message}
11147 \deliver@_queue@_load@_max\ $t$rm{no queue deliveries if load high}
11148 \queue@_only@_load\ $t$rm{queue incoming if load high}
11149 \queue@_run@_max\ $t$rm{maximum simultaneous queue runners}
11150 \remote@_max@_parallel\ $t$rm{parallel SMTP delivery per message}
11151 \smtp@_accept@_max\ $t$rm{simultaneous incoming connections}
11152 \smtp@_accept@_max@_nommail\ $t$rm{non-mail commands}
11153 \smtp@_accept@_max@_nonmail@_hosts\ $t$rm{hosts to which the limit applies}
11154 \smtp@_accept@_max@_per@_connection\ $t$rm{messages per connection}
11155 \smtp@_accept@_max@_per@_host\ $t$rm{connections from one host}
11156 \smtp@_accept@_queue\ $t$rm{queue mail if more connections}
11157 \smtp@_accept@_queue@_per@_connection\ $t$rm{queue if more messages per connection}
11158 \smtp@_accept@_reserve\ $t$rm{only reserve hosts if more connections}
11159 \smtp@_check@_spool@_space\ $t$rm{from \\SIZE\\ on \\MAIL\\ command}
11160 \smtp@_connect@_backlog\ $t$rm{passed to TCP/IP stack}
11161 \smtp@_load@_reserve\ $t$rm{SMTP from reserved hosts if load high}
11162 \smtp@_reserve@_hosts\ $t$rm{these are the reserve hosts}
11165 .section Policy controls
11168 \acl@_not@_smtp\ $t$rm{set ACL for non-SMTP messages}
11169 \acl@_smtp@_auth\ $t$rm{set ACL for \\AUTH\\}
11170 \acl@_smtp@_connect\ $t$rm{set ACL for connection}
11171 \acl@_smtp@_data\ $t$rm{set ACL for \\DATA\\}
11172 \acl@_smtp@_etrn\ $t$rm{set ACL for \\ETRN\\}
11173 \acl@_smtp@_expn\ $t$rm{set ACL for \\EXPN\\}
11174 \acl@_smtp@_helo\ $t$rm{set ACL for \\EHLO\\ or \\HELO\\}
11175 \acl@_smtp@_mail\ $t$rm{set ACL for \\MAIL\\}
11176 \acl@_smtp@_mailauth\ $t$rm{set ACL for \\AUTH\\ on \\MAIL\\ command}
11179 \acl@_smtp@_mime\ $t$rm{set ACL for MIME parts}
11180 \acl@_smtp@_predata\ $t$rm{set ACL for start of data}
11181 \acl@_smtp@_quit\ $t$rm{set ACL for \\QUIT\\}
11184 \acl@_smtp@_rcpt\ $t$rm{set ACL for \\RCPT\\}
11185 \acl@_smtp@_starttls\ $t$rm{set ACL for \\STARTTLS\\}
11186 \acl@_smtp@_vrfy\ $t$rm{set ACL for \\VRFY\\}
11189 \av@_scanner\ $t$rm{specify virus scanner}
11192 \header@_maxsize\ $t$rm{total size of message header}
11193 \header@_line@_maxsize\ $t$rm{individual header line limit}
11194 \helo@_accept@_junk@_hosts\ $t$rm{allow syntactic junk from these hosts}
11195 \helo@_allow@_chars\ $t$rm{allow illegal chars in \\HELO\\ names}
11196 \helo@_lookup@_domains\ $t$rm{lookup hostname for these \\HELO\\ names}
11197 \helo@_try@_verify@_hosts\ $t$rm{\\HELO\\ soft-checked for these hosts}
11198 \helo@_verify@_hosts\ $t$rm{\\HELO\\ hard-checked for these hosts}
11199 \host@_lookup\ $t$rm{host name looked up for these hosts}
11200 \host@_lookup@_order\ $t$rm{order of DNS and local name lookups}
11201 \host@_reject@_connection\ $t$rm{reject connection from these hosts}
11202 \hosts@_treat@_as@_local\ $t$rm{useful in some cluster configurations}
11203 \local@_scan@_timeout\ $t$rm{timeout for \*local@_scan()*\}
11204 \message@_size@_limit\ $t$rm{for all messages}
11205 \percent@_hack@_domains\ $t$rm{recognize %-hack for these domains}
11208 \spamd@_address\ $t$rm{set interface to SpamAssassin}
11213 .section Callout cache
11216 \callout@_domain@_negative@_expire\ $t$rm{timeout for negative domain cache item}
11217 \callout@_domain@_positive@_expire\ $t$rm{timeout for positive domain cache item}
11218 \callout@_negative@_expire\ $t$rm{timeout for negative address cache item}
11219 \callout@_positive@_expire\ $t$rm{timeout for positive address cache item}
11220 \callout@_random@_local@_part\ $t$rm{string to use for `random' testing}
11226 \tls@_advertise@_hosts\ $t$rm{advertise TLS to these hosts}
11227 \tls@_certificate\ $t$rm{location of server certificate}
11228 \tls@_crl\ $t$rm{certificate revocation list}
11229 \tls@_dhparam\ $t$rm{DH parameters for server}
11232 \tls@_on@_connect@_ports\ $t$rm{specify SSMTP (SMTPS) ports}
11235 \tls@_privatekey\ $t$rm{location of server private key}
11236 \tls@_remember@_esmtp\ $t$rm{don't reset after starting TLS}
11237 \tls@_require@_ciphers\ $t$rm{specify acceptable cipers}
11238 \tls@_try@_verify@_hosts\ $t$rm{try to verify client certificate}
11239 \tls@_verify@_certificates\ $t$rm{expected client certificates}
11240 \tls@_verify@_hosts\ $t$rm{insist on client certificate verify}
11243 .section Local user handling
11246 \finduser@_retries\ $t$rm{useful in NIS environments}
11247 \gecos@_name\ $t$rm{used when creating ::Sender::}
11248 \gecos@_pattern\ $t$rm{ditto}
11249 \max@_username@_length\ $t$rm{for systems that truncate}
11250 \unknown@_login\ $t$rm{used when no login name found}
11251 \unknown@_username\ $t$rm{ditto}
11252 \uucp@_from@_pattern\ $t$rm{for recognizing `From ' lines}
11253 \uucp@_from@_sender\ $t$rm{ditto}
11256 .section All incoming messages (SMTP and non-SMTP)
11259 \header@_maxsize\ $t$rm{total size of message header}
11260 \header@_line@_maxsize\ $t$rm{individual header line limit}
11261 \message@_size@_limit\ $t$rm{applies to all messages}
11262 \percent@_hack@_domains\ $t$rm{recognize %-hack for these domains}
11263 \received@_header@_text\ $t$rm{expanded to make ::Received::}
11264 \received@_headers@_max\ $t$rm{for mail loop detection}
11265 \recipients@_max\ $t$rm{limit per message}
11266 \recipients@_max@_reject\ $t$rm{permanently reject excess}
11270 .section Non-SMTP incoming messages
11273 \receive@_timeout\ $t$rm{for non-SMTP messages}
11278 .section Incoming SMTP messages
11279 See also the \*Policy controls*\ section above.
11282 \host@_lookup\ $t$rm{host name looked up for these hosts}
11283 \host@_lookup@_order\ $t$rm{order of DNS and local name lookups}
11284 \recipient@_unqualified@_hosts\ $t$rm{may send unqualified recipients}
11285 \rfc1413@_hosts\ $t$rm{make ident calls to these hosts}
11286 \rfc1413@_query@_timeout\ $t$rm{zero disables ident calls}
11287 \sender@_unqualified@_hosts\ $t$rm{may send unqualified senders}
11288 \smtp@_accept@_keepalive\ $t$rm{some TCP/IP magic}
11289 \smtp@_accept@_max\ $t$rm{simultaneous incoming connections}
11290 \smtp@_accept@_max@_nommail\ $t$rm{non-mail commands}
11291 \smtp@_accept@_max@_nonmail@_hosts\ $t$rm{hosts to which the limit applies}
11292 \smtp@_accept@_max@_per@_connection\ $t$rm{messages per connection}
11293 \smtp@_accept@_max@_per@_host\ $t$rm{connections from one host}
11294 \smtp@_accept@_queue\ $t$rm{queue mail if more connections}
11295 \smtp@_accept@_queue@_per@_connection\ $t$rm{queue if more messages per connection}
11296 \smtp@_accept@_reserve\ $t$rm{only reserve hosts if more connections}
11298 \smtp@_active@_hostname\ $t$rm{host name to use in messages}
11300 \smtp@_banner\ $t$rm{text for welcome banner}
11301 \smtp@_check@_spool@_space\ $t$rm{from \\SIZE\\ on \\MAIL\\ command}
11302 \smtp@_connect@_backlog\ $t$rm{passed to TCP/IP stack}
11303 \smtp@_enforce@_sync\ $t$rm{of SMTP command/responses}
11304 \smtp@_etrn@_command\ $t$rm{what to run for \\ETRN\\}
11305 \smtp@_etrn@_serialize\ $t$rm{only one at once}
11306 \smtp@_load@_reserve\ $t$rm{only reserve hosts if this load}
11307 \smtp@_max@_unknown@_commands\ $t$rm{before dropping connection}
11308 \smtp@_ratelimit@_hosts\ $t$rm{apply ratelimiting to these hosts}
11309 \smtp@_ratelimit@_mail\ $t$rm{ratelimit for \\MAIL\\ commands}
11310 \smtp@_ratelimit@_rcpt\ $t$rm{ratelimit for \\RCPT\\ commands}
11311 \smtp@_receive@_timeout\ $t$rm{per command or data line}
11312 \smtp@_reserve@_hosts\ $t$rm{these are the reserve hosts}
11313 \smtp@_return@_error@_details\ $t$rm{give detail on rejections}
11316 .section SMTP extensions
11319 \accept@_8bitmime\ $t$rm{advertise \\8BITMIME\\}
11320 \auth@_advertise@_hosts\ $t$rm{advertise \\AUTH\\ to these hosts}
11321 \ignore@_fromline@_hosts\ $t$rm{allow `From ' from these hosts}
11322 \ignore@_fromline@_local\ $t$rm{allow `From ' from local SMTP}
11323 \pipelining@_advertise@_hosts\ $t$rm{advertise pipelining to these hosts}
11324 \tls@_advertise@_hosts\ $t$rm{advertise TLS to these hosts}
11327 .section Processing messages
11330 \allow@_domain@_literals\ $t$rm{recognize domain literal syntax}
11331 \allow@_mx@_to@_ip\ $t$rm{allow MX to point to IP address}
11332 \allow@_utf8@_domains\ $t$rm{in addresses}
11333 \delivery@_date@_remove\ $t$rm{from incoming messages}
11334 \envelope@_to@_remote\ $t$rm{from incoming messages}
11335 \extract@_addresses@_remove@_arguments\ $t$rm{affects \-t-\ processing}
11336 \headers@_charset\ $t$rm{default for translations}
11337 \qualify@_domain\ $t$rm{default for senders}
11338 \qualify@_recipient\ $t$rm{default for recipients}
11339 \return@_path@_remove\ $t$rm{from incoming messages}
11340 \strip@_excess@_angle@_brackets\ $t$rm{in addresses}
11341 \strip@_trailing@_dot\ $t$rm{at end of addresses}
11342 \untrusted@_set@_sender\ $t$rm{untrusted can set envelope sender}
11345 .section System filter
11348 \system@_filter\ $t$rm{locate system filter}
11349 \system@_filter@_directory@_transport\ $t$rm{transport for delivery to a directory}
11350 \system@_filter@_file@_transport\ $t$rm{transport for delivery to a file}
11351 \system@_filter@_group\ $t$rm{group for filter running}
11352 \system@_filter@_pipe@_transport\ $t$rm{transport for delivery to a pipe}
11353 \system@_filter@_reply@_transport\ $t$rm{transport for autoreply delivery}
11354 \system@_filter@_user\ $t$rm{user for filter running}
11357 .section Routing and delivery
11360 \dns@_again@_means@_nonexist\ $t$rm{for broken domains}
11361 \dns@_check@_names@_pattern\ $t$rm{pre-DNS syntax check}
11362 \dns@_ipv4@_lookup\ $t$rm{only v4 lookup for these domains}
11363 \dns@_retrans\ $t$rm{parameter for resolver}
11364 \dns@_retry\ $t$rm{parameter for resolver}
11365 \hold@_domains\ $t$rm{hold delivery for these domains}
11366 \local@_interfaces\ $t$rm{for routing checks}
11367 \queue@_domains\ $t$rm{no immediate delivery for these}
11368 \queue@_only\ $t$rm{no immediate delivery at all}
11369 \queue@_only@_file\ $t$rm{no immediate deliveryif file exists}
11370 \queue@_only@_load\ $t$rm{no immediate delivery if load is high}
11371 \queue@_only@_override\ $t$rm{allow command line to override}
11372 \queue@_run@_in@_order\ $t$rm{order of arrival}
11373 \queue@_run@_max\ $t$rm{of simultaneous queue runners}
11374 \queue@_smtp@_domains\ $t$rm{no immediate SMTP delivery for these}
11375 \remote@_max@_parallel\ $t$rm{parallel SMTP delivery per message}
11376 \remote@_sort@_domains\ $t$rm{order of remote deliveries}
11377 \retry@_data@_expire\ $t$rm{timeout for retry data}
11378 \retry@_interval@_max\ $t$rm{safety net for retry rules}
11381 .section Bounce and warning messages
11384 \bounce@_message@_file\ $t$rm{content of bounce}
11385 \bounce@_message@_text\ $t$rm{content of bounce}
11386 \bounce@_return@_body\ $t$rm{include body if returning message}
11387 \bounce@_return@_message\ $t$rm{include original message in bounce}
11388 \bounce@_return@_size@_limit\ $t$rm{limit on returned message}
11389 \bounce@_sender@_authentication\ $t$rm{send authenticated sender with bounce}
11390 \errors@_copy\ $t$rm{copy bounce messages}
11391 \errors@_reply@_to\ $t$rm{::Reply-to:: in bounces}
11392 \delay@_warning\ $t$rm{time schedule}
11393 \delay@_warning@_condition\ $t$rm{condition for warning messages}
11394 \ignore@_bounce@_errors@_after\ $t$rm{discard undeliverable bounces}
11395 \warn@_message@_file\ $t$rm{content of warning message}
11398 .set displayflowcheck ~~savedisplayflowcheck
11400 .section Alphabetical list of main options
11401 .rset SECTalomo "~~chapter.~~section"
11403 Those options that undergo string expansion before use are marked with $**$.
11408 .index \\8BITMIME\\
11409 .index 8-bit characters
11410 .conf accept@_8bitmime boolean false
11411 This option causes Exim to send \\8BITMIME\\ in its response to an SMTP
11412 \\EHLO\\ command, and to accept the \\BODY=\\ parameter on \\MAIL\\ commands.
11413 However, though Exim is 8-bit clean, it is not a protocol converter, and it
11414 takes no steps to do anything special with messages received by this route.
11415 Consequently, this option is turned off by default.
11417 .index ~~ACL||for non-SMTP messages
11418 .index non-SMTP messages, ACL for
11419 .conf acl@_not@_smtp string$**$ unset
11420 This option defines the ACL that is run when a non-SMTP message is on the point
11421 of being accepted. See chapter ~~CHAPACL for further details.
11423 .index ~~ACL||setting up for SMTP commands
11424 .index \\AUTH\\||ACL for
11425 .conf acl@_smtp@_auth string$**$ unset
11426 This option defines the ACL that is run when an SMTP \\AUTH\\ command is
11427 received. See chapter ~~CHAPACL for further details.
11429 .index ~~ACL||on SMTP connection
11430 .conf acl@_smtp@_connect string$**$ unset
11431 This option defines the ACL that is run when an SMTP connection is received.
11432 See chapter ~~CHAPACL for further details.
11434 .index \\DATA\\, ACL for
11435 .conf acl@_smtp@_data string$**$ unset
11436 This option defines the ACL that is run after an SMTP \\DATA\\ command has been
11437 processed and the message itself has been received, but before the final
11438 acknowledgement is sent. See chapter ~~CHAPACL for further details.
11440 .index \\ETRN\\||ACL for
11441 .conf acl@_smtp@_etrn string$**$ unset
11442 This option defines the ACL that is run when an SMTP \\ETRN\\ command is
11443 received. See chapter ~~CHAPACL for further details.
11445 .index \\EXPN\\||ACL for
11446 .conf acl@_smtp@_expn string$**$ unset
11447 This option defines the ACL that is run when an SMTP \\EXPN\\ command is
11448 received. See chapter ~~CHAPACL for further details.
11450 .index \\EHLO\\||ACL for
11451 .index \\HELO\\||ACL for
11452 .conf acl@_smtp@_helo string$**$ unset
11453 This option defines the ACL that is run when an SMTP \\EHLO\\ or \\HELO\\
11454 command is received. See chapter ~~CHAPACL for further details.
11456 .index \\MAIL\\||ACL for
11457 .conf acl@_smtp@_mail string$**$ unset
11458 This option defines the ACL that is run when an SMTP \\MAIL\\ command is
11459 received. See chapter ~~CHAPACL for further details.
11461 .index \\AUTH\\||on \\MAIL\\ command
11462 .conf acl@_smtp@_mailauth string$**$ unset
11463 This option defines the ACL that is run when there is an \\AUTH\\ parameter on
11464 a \\MAIL\\ command. See chapter ~~CHAPACL for details of ACLs, and chapter
11465 ~~CHAPSMTPAUTH for details of authentication.
11468 .index MIME content scanning||ACL for
11469 .conf acl@_smtp@_mime string$**$ unset
11470 This option is available when Exim is built with the content-scanning
11471 extension. It defines the ACL that is run for each MIME part in a message. See
11472 section ~~SECTscanmimepart for details.
11474 .conf acl@_smtp@_predata string$**$ unset
11475 This option defines the ACL that is run when an SMTP \\DATA\\ command is
11476 received, before the message itself is received. See chapter ~~CHAPACL for
11479 .index \\QUIT\\||ACL for
11480 .conf acl@_smtp@_quit string$**$ unset
11481 This option defines the ACL that is run when an SMTP \\QUIT\\ command is
11482 received. See chapter ~~CHAPACL for further details.
11485 .index \\RCPT\\||ACL for
11486 .conf acl@_smtp@_rcpt string$**$ unset
11487 This option defines the ACL that is run when an SMTP \\RCPT\\ command is
11488 received. See chapter ~~CHAPACL for further details.
11490 .index \\STARTTLS\\, ACL for
11491 .conf acl@_smtp@_starttls string$**$ unset
11492 This option defines the ACL that is run when an SMTP \\STARTTLS\\ command is
11493 received. See chapter ~~CHAPACL for further details.
11495 .index \\VRFY\\||ACL for
11496 .conf acl@_smtp@_vrfy string$**$ unset
11497 This option defines the ACL that is run when an SMTP \\VRFY\\ command is
11498 received. See chapter ~~CHAPACL for further details.
11500 .conf admin@_groups "string list" unset
11502 If the current group or any of the supplementary groups of the caller is in
11503 this colon-separated list, the caller has admin privileges. If all your system
11504 programmers are in a specific group, for example, you can give them all Exim
11505 admin privileges by putting that group in \admin@_groups\. However, this does
11506 not permit them to read Exim's spool files (whose group owner is the Exim gid).
11507 To permit this, you have to add individuals to the Exim group.
11509 .conf allow@_domain@_literals boolean false
11510 .index domain literal
11511 If this option is set, the RFC 2822 domain literal format is permitted in
11512 email addresses. The option is not set by default, because the domain literal
11513 format is not normally required these days, and few people know about it. It
11514 has, however, been exploited by mail abusers.
11516 Unfortunately, it seems that some DNS black list maintainers are using this
11517 format to report black listing to postmasters. If you want to accept messages
11518 addressed to your hosts by IP address, you need to set
11519 \allow@_domain@_literals\ true, and also to add \"@@[]"\ to the list of local
11520 domains (defined in the named domain list \local@_domains\ in the default
11521 configuration). This `magic string' matches the domain literal form of all the
11522 local host's IP addresses.
11524 .conf allow@_mx@_to@_ip boolean false
11525 .index MX record||pointing to IP address
11526 It appears that more and more DNS zone administrators are breaking the rules
11527 and putting domain names that look like IP addresses on the right hand side of
11528 MX records. Exim follows the rules and rejects this, giving an error message
11529 that explains the mis-configuration. However, some other MTAs support this
11530 practice, so to avoid `Why can't Exim do this?' complaints, \allow@_mx@_to@_ip\
11531 exists, in order to enable this heinous activity. It is not recommended, except
11532 when you have no other choice.
11534 .index domain||UTF-8 characters in
11535 .index UTF-8||in domain name
11536 .conf allow@_utf8@_domains boolean false
11537 Lots of discussion is going on about internationalized domain names. One
11538 camp is strongly in favour of just using UTF-8 characters, and it seems
11539 that at least two other MTAs permit this. This option allows Exim users to
11540 experiment if they wish.
11542 If it is set true, Exim's domain parsing function allows valid
11543 UTF-8 multicharacters to appear in domain name components, in addition to
11544 letters, digits, and hyphens. However, just setting this option is not
11545 enough; if you want to look up these domain names in the DNS, you must also
11546 adjust the value of \dns@_check@_names@_pattern\ to match the extended form. A
11547 suitable setting is:
11549 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
11550 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
11552 Alternatively, you can just disable this feature by setting
11554 dns_check_names_pattern =
11556 That is, set the option to an empty string so that no check is done.
11558 .conf auth@_advertise@_hosts "host list$**$" $*$
11559 .index authentication||advertising
11560 .index \\AUTH\\||advertising
11561 If any server authentication mechanisms are configured, Exim advertises them in
11562 response to an \\EHLO\\ command only if the calling host matches this list.
11563 Otherwise, Exim does not advertise \\AUTH\\.
11564 Exim does not accept \\AUTH\\ commands from clients to which it has not
11565 advertised the availability of \\AUTH\\. The advertising of individual
11566 authentication mechanisms can be controlled by the use of the
11567 \server@_advertise@_condition\ generic authenticator option on the individual
11568 authenticators. See chapter ~~CHAPSMTPAUTH for further details.
11570 Certain mail clients (for example, Netscape) require the user to provide a name
11571 and password for authentication if \\AUTH\\ is advertised, even though it may
11572 not be needed (the host may accept messages from hosts on its local LAN without
11573 authentication, for example). The \auth@_advertise@_hosts\ option can be used
11574 to make these clients more friendly by excluding them from the set of hosts to
11575 which Exim advertises \\AUTH\\.
11577 .index \\AUTH\\||advertising when encrypted
11578 If you want to advertise the availability of \\AUTH\\ only when the connection
11579 is encrypted using TLS, you can make use of the fact that the value of this
11580 option is expanded, with a setting like this:
11582 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
11584 If \$tls@_cipher$\ is empty, the session is not encrypted, and the result of
11585 the expansion is empty, thus matching no hosts. Otherwise, the result of the
11586 expansion is $*$, which matches all hosts.
11588 .conf auto@_thaw time 0s
11589 .index thawing messages
11590 .index unfreezing messages
11591 If this option is set to a time greater than zero, a queue runner will try a
11592 new delivery attempt on any frozen message if this much time has passed since
11593 it was frozen. This may result in the message being re-frozen if nothing has
11594 changed since the last attempt. It is a way of saying `keep on trying, even
11595 though there are big problems'. See also \timeout@_frozen@_after\ and
11596 \ignore@_bounce@_errors@_after\.
11599 .conf av@_scanner string "see below"
11600 This option is available if Exim is built with the content-scanning extension.
11601 It specifies which anti-virus scanner to use. The default value is:
11603 sophie:/var/run/sophie
11605 If the value of \av@_scanner\ starts with dollar character, it is expanded
11606 before use. See section ~~SECTscanvirus for further details.
11609 .conf bi@_command string unset
11610 .index \-bi-\ option
11611 This option supplies the name of a command that is run when Exim is called with
11612 the \-bi-\ option (see chapter ~~CHAPcommandline). The string value is just the
11613 command name, it is not a complete command line. If an argument is required, it
11614 must come from the \-oA-\ command line option.
11616 .conf bounce@_message@_file string unset
11617 .index bounce message||customizing
11618 .index customizing||bounce message
11619 This option defines a template file containing paragraphs of text to be used
11620 for constructing bounce messages. Details of the file's contents are given in
11621 chapter ~~CHAPemsgcust. See also \warn@_message@_file\.
11623 .conf bounce@_message@_text string unset
11624 When this option is set, its contents are included in the default bounce
11625 message immediately after `This message was created automatically by mail
11626 delivery software.' It is not used if \bounce@_message@_file\ is set.
11628 .index bounce message||including body
11629 .conf bounce@_return@_body boolean true
11630 This option controls whether the body of an incoming message is included in a
11631 bounce message when \bounce@_return@_message\ is true. If it is not set, only
11632 the message header is included.
11634 .index bounce message||including original
11635 .conf bounce@_return@_message boolean true
11636 If this option is set false, the original message is not included in bounce
11637 messages generated by Exim. See also \bounce@_return@_size@_limit\.
11639 .conf bounce@_return@_size@_limit integer 100K
11640 .index size||of bounce, limit
11641 .index bounce message||size limit
11642 .index limit||bounce message size
11643 This option sets a limit in bytes on the size of messages that are returned to
11644 senders as part of bounce messages when \bounce@_return@_message\ is true. The
11645 limit should be less than the value of the global \message@_size@_limit\ and of
11646 any \message@_size@_limit\ settings on transports, to allow for the bounce text
11647 that Exim generates. If this option is set to zero there is no limit.
11649 When the body of any message that is to be included in a bounce message is
11650 greater than the limit, it is truncated, and a comment pointing this out is
11651 added at the top. The actual cutoff may be greater than the value given, owing
11652 to the use of buffering for transferring the message in chunks (typically 8K in
11653 size). The idea is to save bandwidth on those undeliverable 15-megabyte
11656 .index bounce message||sender authentication
11657 .index authentication||bounce message
11658 .index \\AUTH\\||on bounce message
11659 .conf bounce@_sender@_authentication string unset
11660 This option provides an authenticated sender address that is sent with any
11661 bounce messages generated by Exim that are sent over an authenticated SMTP
11662 connection. A typical setting might be:
11664 bounce_sender_authentication = mailer-daemon@my.domain.example
11666 which would cause bounce messages to be sent using the SMTP command:
11668 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
11670 The value of \bounce@_sender@_authentication\ must always be a complete email
11673 .index caching||callout, timeouts
11674 .index callout||caching timeouts
11675 .conf callout@_domain@_negative@_expire time 3h
11676 This option specifies the expiry time for negative callout cache data for a
11677 domain. See section ~~SECTcallver for details of callout verification, and
11678 section ~~SECTcallvercache for details of the caching.
11680 .conf callout@_domain@_positive@_expire time 7d
11681 This option specifies the expiry time for positive callout cache data for a
11682 domain. See section ~~SECTcallver for details of callout verification, and
11683 section ~~SECTcallvercache for details of the caching.
11685 .conf callout@_negative@_expire time 2h
11686 This option specifies the expiry time for negative callout cache data for an
11687 address. See section ~~SECTcallver for details of callout verification, and
11688 section ~~SECTcallvercache for details of the caching.
11690 .conf callout@_positive@_expire time 24h
11691 This option specifies the expiry time for positive callout cache data for an
11692 address. See section ~~SECTcallver for details of callout verification, and
11693 section ~~SECTcallvercache for details of the caching.
11695 .conf callout@_random@_local@_part string$**$ "see below"
11696 This option defines the `random' local part that can be used as part of callout
11697 verification. The default value is
11699 $primary_host_name-$tod_epoch-testing
11701 See section ~~CALLaddparcall for details of how this value is used.
11703 .conf check@_log@_inodes integer 0
11704 See \check@_spool@_space\ below.
11706 .conf check@_log@_space integer 0
11707 See \check@_spool@_space\ below.
11709 .conf check@_spool@_inodes integer 0
11710 See \check@_spool@_space\ below.
11712 .conf check@_spool@_space integer 0
11713 .index checking disk space
11714 .index disk space, checking
11715 .index spool directory||checking space
11716 The four \check@_...\ options allow for checking of disk resources before a
11717 message is accepted.
11719 When any of these options are set, they apply to all incoming messages. If you
11720 want to apply different checks to different kinds of message, you can do so
11721 by testing the the variables \$log@_inodes$\, \$log@_space$\,
11722 \$spool@_inodes$\, and \$spool@_space$\ in an ACL with appropriate additional
11726 \check@_spool@_space\ and \check@_spool@_inodes\ check the spool partition if
11727 either value is greater than zero, for example:
11729 check_spool_space = 10M
11730 check_spool_inodes = 100
11732 The spool partition is the one that contains the directory defined by
11733 \\SPOOL@_DIRECTORY\\ in \(Local/Makefile)\. It is used for holding messages in
11736 \check@_log@_space\ and \check@_log@_inodes\ check the partition in which log
11737 files are written if either is greater than zero. These should be set only if
11738 \log@_file@_path\ and \spool@_directory\ refer to different partitions.
11740 If there is less space or fewer inodes than requested, Exim refuses to accept
11741 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
11742 error response to the \\MAIL\\ command. If ESMTP is in use and there was a
11743 \\SIZE\\ parameter on the \\MAIL\\ command, its value is added to the
11744 \check@_spool@_space\ value, and the check is performed even if
11745 \check@_spool@_space\ is zero, unless \no@_smtp@_check@_spool@_space\ is set.
11747 The values for \check@_spool@_space\ and \check@_log@_space\ are held as a
11748 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
11750 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
11751 failure a message is written to stderr and Exim exits with a non-zero code, as
11752 it obviously cannot send an error message of any kind.
11754 .index port||for daemon
11755 .index TCP/IP||setting listening ports
11756 .conf daemon@_smtp@_ports string "$tt{smtp}"
11757 This option specifies one or more default SMTP ports on which the Exim daemon
11758 listens. See chapter ~~CHAPinterfaces for details of how it is used. For
11759 backward compatibility, \daemon@_smtp@_port\ (singular) is a synonym.
11761 .conf delay@_warning "time list" 24h
11762 .index warning of delay
11763 .index delay warning, specifying
11764 When a message is delayed, Exim sends a warning message to the sender at
11765 intervals specified by this option. The data is a colon-separated list of times
11766 after which to send warning messages.
11768 If the value of the option is an empty string or a zero time, no warnings are
11771 Up to 10 times may be given. If a message has been on the queue for longer than
11772 the last time, the last interval between the times is used to compute
11773 subsequent warning times. For example, with
11775 delay_warning = 4h:8h:24h
11777 the first message is sent after 4 hours, the second after 8 hours, and
11778 the third one after 24 hours. After that, messages are sent every 16 hours,
11779 because that is the interval between the last two times on the list. If you set
11780 just one time, it specifies the repeat interval. For example, with:
11784 messages are repeated every six hours. To stop warnings after a given time, set
11785 a very large time at the end of the list. For example:
11787 delay_warning = 2h:12h:99d
11790 .conf delay@_warning@_condition string$**$ "see below"
11791 The string is expanded at the time a warning message might be sent. If all the
11792 deferred addresses have the same domain, it is set in \$domain$\ during the
11793 expansion. Otherwise \$domain$\ is empty. If the result of the expansion is a
11794 forced failure, an empty string, or a string matching any of `0', `no' or
11795 `false' (the comparison being done caselessly) then the warning message is not
11796 sent. The default is
11798 delay_warning_condition = \
11799 ${if match{$h_precedence:}{(?i)bulk|list|junk}{no}{yes}}
11801 which suppresses the sending of warnings about messages that have `bulk',
11802 `list' or `junk' in a ::Precedence:: header.
11804 .index unprivileged delivery
11805 .index delivery||unprivileged
11806 .conf deliver@_drop@_privilege boolean false
11807 If this option is set true, Exim drops its root privilege at the start of a
11808 delivery process, and runs as the Exim user throughout. This severely restricts
11809 the kinds of local delivery that are possible, but is viable in certain types
11810 of configuration. There is a discussion about the use of root privilege in
11811 chapter ~~CHAPsecurity.
11813 .index load average
11814 .index queue runner||abandoning
11815 .conf deliver@_queue@_load@_max fixed-point unset
11816 When this option is set, a queue run is abandoned if the system load average
11817 becomes greater than the value of the option. The option has no effect on
11818 ancient operating systems on which Exim cannot determine the load average.
11819 See also \queue@_only@_load\ and \smtp@_load@_reserve\.
11821 .conf delivery@_date@_remove boolean true
11822 .index ::Delivery-date:: header line
11823 Exim's transports have an option for adding a ::Delivery-date:: header to a
11824 message when it is delivered -- in exactly the same way as ::Return-path:: is
11825 handled. ::Delivery-date:: records the actual time of delivery. Such headers
11826 should not be present in incoming messages, and this option causes them to be
11827 removed at the time the message is received, to avoid any problems that might
11828 occur when a delivered message is subsequently sent on to some other recipient.
11830 .index DNS||`try again' response, overriding
11831 .conf dns@_again@_means@_nonexist "domain list$**$" unset
11832 DNS lookups give a `try again' response for the DNS errors `non-authoritative
11833 host not found' and `\\SERVERFAIL\\'. This can cause Exim to keep trying to
11834 deliver a message, or to give repeated temporary errors to incoming mail.
11835 Sometimes the effect is caused by a badly set up name server and may persist
11836 for a long time. If a domain which exhibits this problem matches anything in
11837 \dns__again__means__nonexist\, it is treated as if it did not exist. This
11838 option should be used with care.
11839 You can make it apply to reverse lookups by a setting such as this:
11841 dns_again_means_nonexist = *.in-addr.arpa
11844 This option applies to all DNS lookups that Exim does. The \%dnslookup%\ router
11845 has some options of its own for controlling what happens when lookups for MX or
11846 SRV records give temporary errors. These more specific options are applied
11847 after the global option.
11850 .index DNS||pre-check of name syntax
11851 .conf dns@_check@_names@_pattern string "see below"
11852 When this option is set to a non-empty string, it causes Exim to check domain
11853 names for illegal characters before handing them to the DNS resolver, because
11854 some resolvers give temporary errors for malformed names. If a domain name
11855 contains any illegal characters, a `not found' result is forced, and the
11856 resolver is not called. The check is done by matching the domain name against a
11857 regular expression, which is the value of this option. The default pattern is
11859 dns_check_names_pattern = \
11860 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9-]*[^\W_])?)+$
11862 which permits only letters, digits, and hyphens in components, but they may not
11863 start or end with a hyphen.
11864 If you set \allow@_utf8@_domains\, you must modify this pattern, or set the
11865 option to an empty string.
11867 .conf dns@_ipv4@_lookup "domain list$**$" unset
11868 .index IPv6||DNS lookup for AAAA records
11869 .index DNS||IPv6 lookup for AAAA records
11870 When Exim is compiled with IPv6 support, it looks for IPv6 address records
11871 (AAAA and, if configured, A6) as well as IPv4 address records when trying to
11872 find IP addresses for hosts, unless the host's domain matches this list.
11874 This is a fudge to help with name servers that give big delays or otherwise do
11875 not work for the new IPv6 record types. If Exim is handed an IPv6 address
11876 record as a result of an MX lookup, it always recognizes it, and may as a
11877 result make an outgoing IPv6 connection. All this option does is to make Exim
11878 look only for IPv4-style A records when it needs to find an IP address for a
11879 host name. In due course, when the world's name servers have all been upgraded,
11880 there should be no need for this option.
11882 .conf dns@_retrans time 0s
11883 .index DNS||resolver options
11884 The options \dns@_retrans\ and \dns@_retry\ can be used to set the
11885 retransmission and retry parameters for DNS lookups. Values of zero (the
11886 defaults) leave the system default settings unchanged. The first value is the
11887 time between retries, and the second is the number of retries. It isn't
11888 totally clear exactly how these settings affect the total time a DNS lookup may
11889 take. I haven't found any documentation about timeouts on DNS lookups; these
11890 parameter values are available in the external resolver interface structure,
11891 but nowhere does it seem to describe how they are used or what you might want
11894 .conf dns@_retry integer 0
11895 See \dns@_retrans\ above.
11897 .conf drop@_cr boolean false
11898 This is an obsolete option that is now a no-op. It used to affect the way Exim
11899 handled CR and LF characters in incoming messages. What happens now is
11900 described in section ~~SECTlineendings.
11902 .conf envelope@_to@_remove boolean true
11903 .index ::Envelope-to:: header line
11904 Exim's transports have an option for adding an ::Envelope-to:: header to a
11905 message when it is delivered -- in exactly the same way as ::Return-path:: is
11906 handled. ::Envelope-to:: records the original recipient address from the
11907 messages's envelope that caused the delivery to happen. Such headers should not
11908 be present in incoming messages, and this option causes them to be removed at
11909 the time the message is received, to avoid any problems that might occur when a
11910 delivered message is subsequently sent on to some other recipient.
11912 .conf errors@_copy "string list$**$" unset
11913 .index bounce message||copy to other address
11914 .index copy of bounce message
11915 Setting this option causes Exim to send bcc copies of bounce messages that it
11916 generates to other addresses. \**Note**\: this does not apply to bounce messages
11917 coming from elsewhere. The value of the option is a colon-separated list of
11918 items. Each item consists of a pattern, terminated by white space, followed by
11919 a comma-separated list of email addresses. If a pattern contains spaces, it
11920 must be enclosed in double quotes.
11922 Each pattern is processed in the same way as a single item in an address list
11923 (see section ~~SECTaddresslist). When a pattern matches the recipient of the
11924 bounce message, the message is copied to the addresses on the list. The items
11925 are scanned in order, and once a matching one is found, no further items are
11926 examined. For example:
11928 errors_copy = spqr@mydomain postmaster@mydomain.example :\
11929 rqps@mydomain hostmaster@mydomain.example,\
11930 postmaster@mydomain.example
11932 The address list is expanded before use. The expansion variables
11933 \$local@_part$\ and \$domain$\ are set from the original recipient of the error
11934 message, and if there was any wildcard matching in the pattern, the expansion
11935 .index numerical variables (\$1$\, \$2$\, etc)||in \errors@_copy\
11936 variables \$0$\, \$1$\, etc. are set in the normal way.
11938 .conf errors@_reply@_to string unset
11939 .index bounce message||::Reply-to:: in
11940 Exim's bounce and delivery warning messages contain the header line
11942 From: Mail Delivery System @<Mailer-Daemon@@<<qualify-domain>>@>
11944 where <<qualify-domain>> is the value of the \qualify@_domain\ option.
11945 Experience shows that people reply to bounce messages. If the
11946 \errors@_reply@_to\ option is set, a ::Reply-To:: header is added to bounce and
11947 warning messages. For example:
11949 errors_reply_to = postmaster@my.domain.example
11951 The value of the option is not expanded. It must specify a valid RFC 2822
11954 .conf exim@_group string "compile-time configured"
11955 .index gid (group id)||Exim's own
11957 This option changes the gid under which Exim runs when it gives up root
11958 privilege. The default value is compiled into the binary. The value of this
11959 option is used only when \exim@_user\ is also set. Unless it consists entirely
11960 of digits, the string is looked up using \*getgrnam()*\, and failure causes a
11961 configuration error. See chapter ~~CHAPsecurity for a discussion of security
11964 .conf exim@_path string "see below"
11965 .index Exim binary, path name
11966 This option specifies the path name of the Exim binary, which is used when Exim
11967 needs to re-exec itself. The default is set up to point to the file \*exim*\ in
11968 the directory configured at compile time by the \\BIN@_DIRECTORY\\ setting. It
11969 is necessary to change \exim@_path\ if, exceptionally, Exim is run from some
11971 \**Warning**\: Do not use a macro to define the value of this option, because
11972 you will break those Exim utilities that scan the configuration file to find
11973 where the binary is. (They then use the \-bP-\ option to extract option
11974 settings such as the value of \spool@_directory\.)
11976 .conf exim@_user string "compile-time configured"
11977 .index uid (user id)||Exim's own
11979 This option changes the uid under which Exim runs when it gives up root
11980 privilege. The default value is compiled into the binary. Ownership of the run
11981 time configuration file and the use of the \-C-\ and \-D-\ command line options
11982 is checked against the values in the binary, not what is set here.
11984 Unless it consists entirely of digits, the string is looked up using
11985 \*getpwnam()*\, and failure causes a configuration error. If \exim@_group\ is
11986 not also supplied, the gid is taken from the result of \*getpwnam()*\ if it is
11987 used. See chapter ~~CHAPsecurity for a discussion of security issues.
11989 .conf extra@_local@_interfaces "string list" unset
11991 This option defines network interfaces that are to be considered local when
11992 routing, but which are not used for listening by the daemon. See section
11993 ~~SECTreclocipadd for details.
11995 .conf extract@_addresses@_remove@_arguments boolean true
11996 .index \-t-\ option
11997 .index command line||addresses with \-t-\
11998 .index Sendmail compatibility||\-t-\ option
11999 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
12000 are present on the command line when the \-t-\ option is used to build an
12001 envelope from a message's ::To::, ::Cc:: and ::Bcc:: headers, the command line
12002 addresses are removed from the recipients list. This is also how Smail behaves.
12003 However, other Sendmail documentation (the O'Reilly book) states that command
12004 line addresses are added to those obtained from the header lines. When
12005 \extract__addresses__remove__arguments\ is true (the default), Exim subtracts
12006 argument headers. If it is set false, Exim adds rather than removes argument
12009 .conf finduser@_retries integer 0
12010 .index NIS, looking up users, retrying
12011 On systems running NIS or other schemes in which user and group information is
12012 distributed from a remote system, there can be times when \*getpwnam()*\ and
12013 related functions fail, even when given valid data, because things time out.
12014 Unfortunately these failures cannot be distinguished from genuine `not found'
12015 errors. If \finduser@_retries\ is set greater than zero, Exim will try that
12016 many extra times to find a user or a group, waiting for one second between
12019 .index \(/etc/passwd)\, multiple reading of
12021 You should not set this option greater than zero if your user information is in
12022 a traditional \(/etc/passwd)\ file, because it will cause Exim needlessly to
12023 search the file multiple times for non-existent users, and also cause delay.
12026 .conf freeze@_tell "string list, comma separated" unset
12027 .index freezing messages||sending a message when freezing
12028 On encountering certain errors, or when configured to do so in a system filter,
12030 Exim freezes a message. This means that no further delivery attempts take place
12031 until an administrator (or the \auto@_thaw\ feature) thaws the message. If
12032 \freeze@_tell\ is set, Exim generates a warning message whenever it freezes
12033 something, unless the message it is freezing is a
12035 bounce message. (Without this exception there is the possibility of looping.)
12036 The warning message is sent to the addresses supplied as the comma-separated
12037 value of this option. If several of the message's addresses cause freezing,
12038 only a single message is sent.
12039 If the freezing was automatic, the reason(s) for freezing can be found in the
12040 message log. If you configure freezing in a filter or ACL, you must arrange for
12041 any logging that you require.
12043 .conf gecos@_name string$**$ unset
12045 .index `gecos' field, parsing
12046 Some operating systems, notably HP-UX, use the `gecos' field in the system
12047 password file to hold other information in addition to users' real names. Exim
12048 looks up this field for use when it is creating ::Sender:: or ::From:: headers.
12049 If either \gecos@_pattern\ or \gecos@_name\ are unset, the contents of the
12050 field are used unchanged, except that, if an ampersand is encountered, it is
12051 replaced by the user's login name with the first character forced to
12052 upper case, since this is a convention that is observed on many systems.
12054 When these options are set, \gecos@_pattern\ is treated as a regular expression
12055 that is to be applied to the field (again with & replaced by the login name),
12056 and if it matches, \gecos@_name\ is expanded and used as the user's name.
12057 .index numerical variables (\$1$\, \$2$\, etc)||in \gecos@_name\
12058 Numeric variables such as \$1$\, \$2$\, etc. can be used in the expansion to
12059 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
12060 name terminates at the first comma, the following can be used:
12062 gecos_pattern = ([^,]*)
12066 .conf gecos@_pattern string unset
12067 See \gecos@_name\ above.
12069 .conf headers@_charset string "see below"
12070 This option sets a default character set for translating from encoded MIME
12071 `words' in header lines, when referenced by an \$h@_xxx$\ expansion item. The
12072 default is the value of \\HEADERS@_CHARSET\\ in \(Local/Makefile)\. The
12073 ultimate default is ISO-8859-1. For more details see the description of header
12074 insertions in section ~~SECTexpansionitems.
12077 .conf header@_maxsize integer "see below"
12078 .index header section||maximum size of
12079 .index limit||size of message header section
12080 This option controls the overall maximum size of a message's header
12081 section. The default is the value of \\HEADER@_MAXSIZE\\ in
12082 \(Local/Makefile)\; the default for that is 1M. Messages with larger header
12083 sections are rejected.
12085 .conf header@_line@_maxsize integer 0
12086 .index header lines||maximum size of
12087 .index limit||size of one header line
12088 This option limits the length of any individual header line in a message, after
12089 all the continuations have been joined together. Messages with individual
12090 header lines that are longer than the limit are rejected. The default value of
12091 zero means `no limit'.
12095 .conf helo@_accept@_junk@_hosts "host list$**$" unset
12096 .index \\HELO\\||accepting junk data
12097 .index \\EHLO\\||accepting junk data
12098 Exim checks the syntax of \\HELO\\ and \\EHLO\\ commands for incoming SMTP
12099 mail, and gives an error response for invalid data. Unfortunately, there are
12100 some SMTP clients that send syntactic junk. They can be accommodated by setting
12101 this option. Note that this is a syntax check only. See \helo@_verify@_hosts\
12102 if you want to do semantic checking.
12103 See also \helo@_allow@_chars\ for a way of extending the permitted character
12106 .conf helo@_allow@_chars string unset
12107 .index \\HELO\\||underscores in
12108 .index \\EHLO\\||underscores in
12109 .index underscore in \\EHLO\\/\\HELO\\
12110 This option can be set to a string of rogue characters that are permitted in
12111 all \\EHLO\\ and \\HELO\\ names in addition to the standard letters, digits,
12112 hyphens, and dots. If you really must allow underscores, you can set
12114 helo_allow_chars = _
12116 Note that the value is one string, not a list.
12118 .conf helo@_lookup@_domains "domain list$**$" "$tt{@@:@@[]}"
12119 .index \\HELO\\||forcing reverse lookup
12120 .index \\EHLO\\||forcing reverse lookup
12121 If the domain given by a client in a \\HELO\\ or \\EHLO\\ command matches this
12122 list, a reverse lookup is done in order to establish the host's true name. The
12123 default forces a lookup if the client host gives the server's name or any of
12124 its IP addresses (in brackets), something that broken clients have been seen to
12127 .conf helo@_try@_verify@_hosts "host list$**$" unset
12128 .index \\HELO\\||verifying, optional
12129 .index \\EHLO\\||verifying, optional
12130 The RFCs mandate that a server must not reject a message because it doesn't
12131 like the \\HELO\\ or \\EHLO\\ command. By default, Exim just checks the syntax
12132 of these commands (see \helo__accept__junk__hosts\ and \helo@_allow@_chars\
12133 above). However, some sites like to be stricter. If the calling host matches
12134 \helo@_try@_verify@_hosts\, Exim checks that the host name given in the \\HELO\\
12135 or \\EHLO\\ command either:
12137 is an IP literal matching the calling address of the host (the RFCs
12138 specifically allow this), or
12140 .index DNS||reverse lookup
12141 .index reverse DNS lookup
12142 matches the host name that Exim obtains by doing a reverse lookup of the
12143 calling host address, or
12145 when looked up using \*gethostbyname()*\ (or \*getipnodebyname()*\ when
12146 available) yields the calling host address.
12148 However, the \\EHLO\\ or \\HELO\\ command is not rejected if any of the checks
12149 fail. Processing continues, but the result of the check is remembered, and can
12150 be detected later in an ACL by the \"verify = helo"\ condition. If you want
12151 verification failure to cause rejection of \\EHLO\\ or \\HELO\\, use
12152 \helo@_verify@_hosts\ instead.
12155 .conf helo@_verify@_hosts "host list$**$" unset
12156 .index \\HELO\\||verifying, mandatory
12157 .index \\EHLO\\||verifying, mandatory
12158 For hosts that match this option, Exim checks the host name given in the
12159 \\HELO\\ or \\EHLO\\ in the same way as for \helo@_try@_verify@_hosts\. If the
12160 check fails, the \\HELO\\ or \\EHLO\\ command is rejected with a 550 error, and
12161 entries are written to the main and reject logs. If a \\MAIL\\ command is
12162 received before \\EHLO\\ or \\HELO\\, it is rejected with a
12166 .conf hold@_domains "domain list$**$" unset
12167 .index domain||delaying delivery
12168 .index delivery||delaying certain domains
12169 This option allows mail for particular domains to be held on the queue
12170 manually. The option is overridden if a message delivery is forced with the
12171 \-M-\, \-qf-\, \-Rf-\ or \-Sf-\ options, and also while testing or verifying
12172 addresses using \-bt-\ or \-bv-\. Otherwise, if a domain matches an item in
12173 \hold@_domains\, no routing or delivery for that address is done, and it is
12174 deferred every time the message is looked at.
12176 This option is intended as a temporary operational measure for delaying the
12177 delivery of mail while some problem is being sorted out, or some new
12178 configuration tested. If you just want to delay the processing of some
12179 domains until a queue run occurs, you should use \queue@_domains\ or
12180 \queue@_smtp@_domains\, not \hold@_domains\.
12182 A setting of \hold@_domains\ does not override Exim's code for removing
12183 messages from the queue if they have been there longer than the longest retry
12184 time in any retry rule. If you want to hold messages for longer than the normal
12185 retry times, insert a dummy retry rule with a long retry time.
12187 .conf host@_lookup "host list$**$" unset
12188 .index host||name lookup, forcing
12189 Exim does not look up the name of a calling host from its IP address unless it
12190 is required to compare against some host list, or the host matches
12191 \helo@_try@_verify@_hosts\ or \helo@_verify@_hosts\, or the host matches this
12192 option (which normally contains IP addresses rather than host names). The
12193 default configuration file contains
12197 which causes a lookup to happen for all hosts. If the expense of these lookups
12198 is felt to be too great, the setting can be changed or removed.
12200 After a successful reverse lookup, Exim does a forward lookup on the name it
12201 has obtained, to verify that it yields the IP address that it started with. If
12202 this check fails, Exim behaves as if the name lookup failed.
12204 After any kind of failure, the host name (in \$sender@_host@_name$\) remains
12205 unset, and \$host@_lookup@_failed$\ is set to the string `1'. See also
12206 \dns@_again@_means@_nonexist\, \helo__lookup__domains\, and \"verify =
12207 reverse@_host@_lookup"\ in ACLs.
12209 .conf host@_lookup@_order "string list" $tt{bydns:byaddr}
12210 This option specifies the order of different lookup methods when Exim is trying
12211 to find a host name from an IP address. The default is to do a DNS lookup
12212 first, and then to try a local lookup (using \*gethostbyaddr()*\ or equivalent)
12213 if that fails. You can change the order of these lookups, or omit one entirely,
12216 \**Warning**\: the `byaddr' method does not always yield aliases when there are
12217 multiple PTR records in the DNS and the IP address is not listed in
12218 \(/etc/hosts)\. Different operating systems give different results in this
12219 case. That is why the default tries a DNS lookup first.
12222 .conf host@_reject@_connection "host list$**$" unset
12223 .index host||rejecting connections from
12224 If this option is set, incoming SMTP calls from the hosts listed are rejected
12225 as soon as the connection is made.
12226 This option is obsolete, and retained only for backward compatibility, because
12227 nowadays the ACL specified by \acl@_smtp@_connect\ can also reject incoming
12228 connections immediately.
12230 The ability to give an immediate rejection (either by this option or using an
12231 ACL) is provided for use in unusual cases. Many hosts will just try again,
12232 sometimes without much delay. Normally, it is better to use an ACL to reject
12233 incoming messages at a later stage, such as after \\RCPT\\ commands. See
12237 .conf hosts@_connection@_nolog "host list$**$" unset
12238 .index host||not logging connections from
12239 This option defines a list of hosts for which connection logging does not
12240 happen, even though the \smtp@_connection\ log selector is set. For example,
12241 you might want not to log SMTP connections from local processes, or from
12242 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
12243 the daemon; you should therefore strive to restrict its value to a short inline
12244 list of IP addresses and networks. To disable logging SMTP connections from
12245 local processes, you must create a host list with an empty item. For example:
12247 hosts_connection_nolog = :
12249 If the \smtp@_connection\ log selector is not set, this option has no effect.
12252 .conf hosts@_treat@_as@_local "domain list$**$" unset
12253 .index local host||domains treated as
12254 .index host||treated as local
12255 If this option is set, any host names that match the domain list are treated as
12256 if they were the local host when Exim is scanning host lists obtained from MX
12258 or other sources. Note that the value of this option is a domain list, not a
12259 host list, because it is always used to check host names, not IP addresses.
12261 This option also applies when Exim is matching the special items
12262 \"@@mx@_any"\, \"@@mx@_primary"\, and \"@@mx@_secondary"\ in a domain list (see
12263 section ~~SECTdomainlist), and when checking the \hosts\ option in the \%smtp%\
12264 transport for the local host (see the \allow@_localhost\ option in that
12266 See also \local@_interfaces\, \extra@_local@_interfaces\, and chapter
12267 ~~CHAPinterfaces, which contains a discussion about local network interfaces
12268 and recognising the local host.
12270 .conf ignore@_bounce@_errors@_after time 10w
12271 .index bounce message||discarding
12272 .index discarding bounce message
12273 This option affects the processing of bounce messages that cannot be delivered,
12274 that is, those that suffer a permanent delivery failure. (Bounce messages that
12275 suffer temporary delivery failures are of course retried in the usual way.)
12277 After a permanent delivery failure, bounce messages are frozen,
12278 because there is no sender to whom they can be returned. When a frozen bounce
12279 message has been on the queue for more than the given time, it is unfrozen at
12280 the next queue run, and a further delivery is attempted. If delivery fails
12281 again, the bounce message is discarded. This makes it possible to keep failed
12282 bounce messages around for a shorter time than the normal maximum retry time
12283 for frozen messages. For example,
12285 ignore_bounce_errors_after = 12h
12287 retries failed bounce message deliveries after 12 hours, discarding any further
12288 failures. If the value of this option is set to a zero time period, bounce
12289 failures are discarded immediately. Setting a very long time (as in the default
12290 value) has the effect of disabling this option. For ways of automatically
12291 dealing with other kinds of frozen message, see \auto@_thaw\ and
12292 \timeout@_frozen@_after\.
12294 .conf ignore@_fromline@_hosts "host list$**$" unset
12296 .index UUCP||`From' line
12297 Some broken SMTP clients insist on sending a UUCP-like `From' line before the
12298 headers of a message. By default this is treated as the start of the message's
12299 body, which means that any following headers are not recognized as such. Exim
12300 can be made to ignore it by setting \ignore@_fromline@_hosts\ to match those
12301 hosts that insist on sending it. If the sender is actually a local process
12302 rather than a remote host, and is using \-bs-\ to inject the messages,
12303 \ignore__fromline__local\ must be set to achieve this effect.
12305 .conf ignore@_fromline@_local boolean false
12306 See \ignore@_fromline@_hosts\ above.
12308 .conf keep@_malformed time 4d
12309 This option specifies the length of time to keep messages whose spool files
12310 have been corrupted in some way. This should, of course, never happen. At the
12311 next attempt to deliver such a message, it gets removed. The incident is
12314 .conf ldap@_default@_servers "string list" unset
12315 .index LDAP||default servers
12316 This option provides a list of LDAP servers which are tried in turn when an
12317 LDAP query does not contain a server. See section ~~SECTforldaque for details
12318 of LDAP queries. This option is available only when Exim has been built with
12321 .conf ldap@_version integer unset
12322 .index LDAP||protocol version, forcing
12323 This option can be used to force Exim to set a specific protocol version for
12324 LDAP. If it option is unset, it is shown by the \-bP-\ command line option as
12325 -1. When this is the case, the default is 3 if \\LDAP@_VERSION3\\ is defined in
12326 the LDAP headers; otherwise it is 2. This option is available only when Exim
12327 has been built with LDAP support.
12330 .conf local@_from@_check boolean true
12331 .index ::Sender:: header line||disabling addition of
12332 .index ::From:: header line||disabling checking of
12333 When a message is submitted locally (that is, not over a TCP/IP connection) by
12334 an untrusted user, Exim removes any existing ::Sender:: header line, and checks
12335 that the ::From:: header line matches
12337 the login of the calling user and the domain specified by \qualify@_domain\.
12339 \**Note**\: An unqualified address (no domain) in the ::From:: header in a
12340 locally submitted message is automatically qualified by Exim, unless the
12341 \-bnq-\ command line option is used.
12344 You can use \local@_from@_prefix\ and \local@_from@_suffix\ to permit affixes
12345 on the local part. If the ::From:: header line does not match, Exim adds a
12346 ::Sender:: header with an address constructed from the calling user's login and
12347 the default qualify domain.
12349 If \local@_from@_check\ is set false, the ::From:: header check is disabled,
12350 and no ::Sender:: header is ever added. If, in addition, you want to retain
12351 ::Sender:: header lines supplied by untrusted users, you must also set
12352 \local@_sender@_retain\ to be true.
12354 .index envelope sender
12355 These options affect only the header lines in the message. The envelope sender
12356 is still forced to be the login id at the qualify domain unless
12357 \untrusted@_set@_sender\ permits the user to supply an envelope sender.
12360 For messages received over TCP/IP, an ACL can specify `submission mode' to
12361 request similar header line checking. See section ~~SECTthesenhea, which has
12362 more details about ::Sender:: processing.
12366 .conf local@_from@_prefix string unset
12367 When Exim checks the ::From:: header line of locally submitted messages for
12368 matching the login id (see \local@_from@_check\ above), it can be configured to
12369 ignore certain prefixes and suffixes in the local part of the address. This is
12370 done by setting \local@_from@_prefix\ and/or \local@_from@_suffix\ to
12371 appropriate lists, in the same form as the \local@_part@_prefix\ and
12372 \local@_part@_suffix\ router options (see chapter ~~CHAProutergeneric). For
12375 local_from_prefix = *-
12377 is set, a ::From:: line containing
12379 From: anything-user@your.domain.example
12381 will not cause a ::Sender:: header to be added if \*user@@your.domain.example*\
12382 matches the actual sender address that is constructed from the login name and
12385 .conf local@_from@_suffix string unset
12386 See \local@_from@_prefix\ above.
12388 .conf local@_interfaces "string list" "see below"
12389 This option controls which network interfaces are used by the daemon for
12390 listening; they are also used to identify the local host when routing. Chapter
12391 ~~CHAPinterfaces contains a full description of this option and the related
12394 \daemon@_smtp@_ports\, \extra@_local@_interfaces\, \hosts@_treat@_as@_local\,
12395 and \tls@_on@_connect@_ports\.
12397 The default value for \local@_interfaces\ is
12399 local_interfaces = 0.0.0.0
12401 when Exim is built without IPv6 support; otherwise it is
12403 local_interfaces = <; ::0 ; 0.0.0.0
12406 .conf local@_scan@_timeout time 5m
12407 .index timeout||for \*local@_scan()*\ function
12408 .index \*local@_scan()*\ function||timeout
12409 This timeout applies to the \*local@_scan()*\ function (see chapter
12410 ~~CHAPlocalscan). Zero means `no timeout'. If the timeout is exceeded, the
12411 incoming message is rejected with a temporary error if it is an SMTP message.
12412 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
12413 code. The incident is logged on the main and reject logs.
12416 .conf local@_sender@_retain boolean false
12417 .index ::Sender:: header line||retaining from local submission
12418 When a message is submitted locally (that is, not over a TCP/IP connection) by
12419 an untrusted user, Exim removes any existing ::Sender:: header line. If you
12420 do not want this to happen, you must set \local@_sender@_retain\, and you must
12421 also set \local@_from@_check\ to be false (Exim will complain if you do not).
12422 Section ~~SECTthesenhea has more details about ::Sender:: processing.
12426 .conf localhost@_number string$**$ unset
12427 .index host||locally unique number for
12428 .index message||ids, with multiple hosts
12429 Exim's message ids are normally unique only within the local host. If
12430 uniqueness among a set of hosts is required, each host must set a different
12431 value for the \localhost@_number\ option. The string is expanded immediately
12432 after reading the configuration file (so that a number can be computed from the
12433 host name, for example) and the result of the expansion must be a number in the
12434 range 0--16 (or 0--10 on operating systems with case-insensitive file systems).
12435 This is available in subsequent string expansions via the variable
12436 \$localhost@_number$\. When \localhost@_number is set\, the final two
12437 characters of the message id, instead of just being a fractional part of the
12438 time, are computed from the time and the local host number as described in
12439 section ~~SECTmessiden.
12442 .conf log@_file@_path "string list$**$" "set at compile time"
12443 .index log||file path for
12444 This option sets the path which is used to determine the names of Exim's log
12445 files, or indicates that logging is to be to syslog, or both. It is expanded
12446 when Exim is entered, so it can, for example, contain a reference to the host
12447 name. If no specific path is set for the log files at compile or run time, they
12448 are written in a sub-directory called \(log)\ in Exim's spool directory.
12449 Chapter ~~CHAPlog contains further details about Exim's logging, and section
12450 ~~SECTwhelogwri describes how the contents of \log@_file@_path\ are used. If
12451 this string is fixed at your installation (contains no expansion variables) it
12452 is recommended that you do not set this option in the configuration file, but
12453 instead supply the path using \\LOG@_FILE@_PATH\\ in \(Local/Makefile)\ so that
12454 it is available to Exim for logging errors detected early on -- in particular,
12455 failure to read the configuration file.
12457 .conf log@_selector string unset
12458 .index log||selectors
12459 This option can be used to reduce or increase the number of things that Exim
12460 writes to its log files. Its argument is made up of names preceded by plus or
12461 minus characters. For example:
12463 log_selector = +arguments -retry_defer
12465 A list of possible names and what they control is given in the chapter on
12466 logging, in section ~~SECTlogselector.
12468 .conf log@_timezone boolean false
12469 .index log||timezone for entries
12470 By default, the timestamps on log lines are in local time without the
12471 timezone. This means that if your timezone changes twice a year, the timestamps
12472 in log lines are ambiguous for an hour when the clocks go back. One way of
12473 avoiding this problem is to set the timezone to UTC. An alternative is to set
12474 \log@_timezone\ true. This turns on the addition of the timezone offset to
12475 timestamps in log lines. Turning on this option can add quite a lot to the size
12476 of log files because each line is extended by 6 characters. Note that the
12477 \$tod@_log$\ variable contains the log timestamp without the zone, but there is
12478 another variable called \$tod@_zone$\ that contains just the timezone offset.
12480 .conf lookup@_open@_max integer 25
12481 .index too many open files
12482 .index open files, too many
12483 .index file||too many open
12484 .index lookup||maximum open files
12485 .index limit||open files for lookups
12486 This option limits the number of simultaneously open files for single-key
12487 lookups that use regular files (that is, \%lsearch%\, \%dbm%\, and \%cdb%\). Exim
12488 normally keeps these files open during routing, because often the same file is
12489 required several times. If the limit is reached, Exim closes the least recently
12490 used file. Note that if you are using the \*ndbm*\ library, it actually opens
12491 two files for each logical DBM database, though it still counts as one for the
12492 purposes of \lookup@_open@_max\. If you are getting `too many open files'
12493 errors with NDBM, you need to reduce the value of \lookup@_open@_max\.
12495 .conf max@_username@_length integer 0
12496 .index length of login name
12497 .index user name||maximum length
12498 .index limit||user name length
12499 Some operating systems are broken in that they truncate long arguments to
12500 \*getpwnam()*\ to eight characters, instead of returning `no such user'. If
12501 this option is set greater than zero, any attempt to call \*getpwnam()*\ with
12502 an argument that is longer behaves as if \*getpwnam()*\ failed.
12505 .conf message@_body@_visible integer 500
12506 .index body of message||visible size
12507 .index message||body, visible size
12508 This option specifies how much of a message's body is to be included in the
12509 \$message@_body$\ and \$message@_body@_end$\ expansion variables.
12511 .conf message@_id@_header@_domain string$**$ unset
12512 .index ::Message-ID:: header line
12513 If this option is set, the string is expanded and used as the right hand side
12514 (domain) of the ::Message-ID:: header that Exim creates if a
12515 locally-originated incoming message does not have one. `Locally-originated'
12516 means `not received over TCP/IP.'
12517 Otherwise, the primary host name is used.
12518 Only letters, digits, dot and hyphen are accepted; any other characters are
12519 replaced by hyphens. If the expansion is forced to fail, or if the result is an
12520 empty string, the option is ignored.
12522 .conf message@_id@_header@_text string$**$ unset
12523 If this variable is set, the string is expanded and used to augment the text of
12524 the ::Message-id:: header that Exim creates if a
12526 incoming message does not have one. The text of this header is required by RFC
12527 2822 to take the form of an address. By default, Exim uses its internal message
12528 id as the local part, and the primary host name as the domain. If this option
12529 is set, it is expanded, and provided the expansion is not forced to fail, and
12530 does not yield an empty string, the result is inserted into the header
12531 immediately before the @@, separated from the internal message id by a dot. Any
12532 characters that are illegal in an address are automatically converted into
12533 hyphens. This means that variables such as \$tod@_log$\ can be used, because
12534 the spaces and colons will become hyphens.
12536 .conf message@_logs boolean true
12537 .index message||log, disabling
12538 .index log||message log, disabling
12539 If this option is turned off, per-message log files are not created in the
12540 \(msglog)\ spool sub-directory. This reduces the amount of disk I/O required by
12541 Exim, by reducing the number of files involved in handling a message from a
12542 minimum of four (header spool file, body spool file, delivery journal, and
12543 per-message log) to three. The other major I/O activity is Exim's main log,
12544 which is not affected by this option.
12546 .conf message@_size@_limit string$**$ 50M
12547 .index message||size limit
12548 .index limit||message size
12549 .index size||of message, limit
12550 This option limits the maximum size of message that Exim will process. The
12551 value is expanded for each incoming
12552 connection so, for example, it can be made to depend on the IP address of the
12553 remote host for messages arriving via TCP/IP. \**Note**\: This limit cannot be
12554 made to depend on a message's sender or any other properties of an individual
12555 message, because it has to be advertised in the server's response to \\EHLO\\.
12556 String expansion failure causes a temporary error. A value of zero means no
12557 limit, but its use is not recommended. See also \bounce@_return@_size@_limit\.
12559 Incoming SMTP messages are failed with a 552 error if the limit is
12560 exceeded; locally-generated messages either get a stderr message or a delivery
12561 failure message to the sender, depending on the \-oe-\ setting. Rejection of an
12562 oversized message is logged in both the main and the reject logs. See also the
12563 generic transport option \message@_size@_limit\, which limits the size of
12564 message that an individual transport can process.
12566 .conf move@_frozen@_messages boolean false
12567 .index frozen messages||moving
12568 This option, which is available only if Exim has been built with the setting
12570 SUPPORT_MOVE_FROZEN_MESSAGES=yes
12572 in \(Local/Makefile)\, causes frozen messages and their message logs to be
12573 moved from the \(input)\ and \(msglog)\ directories on the spool to \(Finput)\
12574 and \(Fmsglog)\, respectively. There is currently no support in Exim or the
12575 standard utilities for handling such moved messages, and they do not show up in
12576 lists generated by \-bp-\ or by the Exim monitor.
12579 .conf mua@_wrapper boolean false
12580 Setting this option true causes Exim to run in a very restrictive mode in which
12581 it passes messages synchronously to a smart host. Chapter ~~CHAPnonqueueing
12582 contains a full description of this facility.
12585 .conf mysql@_servers "string list" unset
12586 .index MySQL||server list
12587 This option provides a list of MySQL servers and associated connection data, to
12588 be used in conjunction with \%mysql%\ lookups (see section ~~SECTsql). The
12589 option is available only if Exim has been built with MySQL support.
12591 .conf never@_users "string list" unset
12592 Local message deliveries are normally run in processes that are setuid to the
12593 recipient, and remote deliveries are normally run under Exim's own uid and gid.
12594 It is usually desirable to prevent any deliveries from running as root, as a
12597 When Exim is built, an option called \\FIXED@_NEVER@_USERS\\ can be set to a
12598 list of users that must not be used for local deliveries. This list is fixed in
12599 the binary and cannot be overridden by the configuration file. By default, it
12600 contains just the single user name `root'. The \never@_users\ runtime option
12601 can be used to add more users to the fixed list.
12603 If a message is to be delivered as one of the users on the fixed list or the
12604 \never@_users\ list, an error occurs, and delivery is deferred. A common
12607 never@_users = root:daemon:bin
12609 Including root is redundant if it is also on the fixed list, but it does no
12611 This option overrides the \pipe@_as@_creator\ option of the \%pipe%\ transport
12614 .conf oracle@_servers "string list" unset
12615 .index Oracle||server list
12616 This option provides a list of Oracle servers and associated connection data,
12617 to be used in conjunction with \%oracle%\ lookups (see section ~~SECTsql). The
12618 option is available only if Exim has been built with Oracle support.
12620 .conf percent@_hack@_domains "domain list$**$" unset
12621 .index `percent hack'
12622 .index source routing||in email address
12623 .index address||source-routed
12624 The `percent hack' is the convention whereby a local part containing a percent
12625 sign is re-interpreted as a new email address, with the percent replaced by @@.
12626 This is sometimes called `source routing', though that term is also applied to
12627 RFC 2822 addresses that begin with an @@ character. If this option is set, Exim
12628 implements the percent facility for those domains listed, but no others. This
12629 happens before an incoming SMTP address is tested against an ACL.
12631 \**Warning**\: The `percent hack' has often been abused by people who are
12632 trying to get round relaying restrictions. For this reason, it is best avoided
12633 if at all possible. Unfortunately, a number of less security-conscious MTAs
12634 implement it unconditionally. If you are running Exim on a gateway host, and
12635 routing mail through to internal MTAs without processing the local parts, it is
12636 a good idea to reject recipient addresses with percent characters in their
12637 local parts. Exim's default configuration does this.
12639 .conf perl@_at@_start boolean false
12640 This option is available only when Exim is built with an embedded Perl
12641 interpreter. See chapter ~~CHAPperl for details of its use.
12643 .conf perl@_startup string unset
12644 This option is available only when Exim is built with an embedded Perl
12645 interpreter. See chapter ~~CHAPperl for details of its use.
12647 .conf pgsql@_servers "string list" unset
12648 .index PostgreSQL lookup type||server list
12649 This option provides a list of PostgreSQL servers and associated connection
12650 data, to be used in conjunction with \%pgsql%\ lookups (see section ~~SECTsql).
12651 The option is available only if Exim has been built with PostgreSQL support.
12653 .conf pid@_file@_path string$**$ "set at compile time"
12654 .index daemon||pid file path
12655 .index pid file, path for
12656 This option sets the name of the file to which the Exim daemon writes its
12657 process id. The string is expanded, so it can contain, for example, references
12660 pid_file_path = /var/log/$primary_hostname/exim.pid
12662 If no path is set, the pid is written to the file \(exim-daemon.pid)\ in Exim's
12664 The value set by the option can be overridden by the \-oP-\ command line
12665 option. A pid file is not written if a `non-standard' daemon is run by means of
12666 the \-oX-\ option, unless a path is explicitly supplied by \-oP-\.
12668 .conf pipelining@_advertise@_hosts "host list$**$" $*$
12669 .index \\PIPELINING\\||advertising, suppressing
12670 This option can be used to suppress the advertisement of the SMTP
12671 \\PIPELINING\\ extension to specific hosts. When \\PIPELINING\\ is not
12672 advertised and \smtp@_enforce@_sync\ is true, an Exim server enforces strict
12673 synchronization for each SMTP command and response.
12674 When \\PIPELINING\\ is advertised, Exim assumes that clients will use it; `out
12675 of order' commands that are `expected' do not count as protocol errors (see
12676 \smtp@_max@_synprot@_errors\).
12678 .conf preserve@_message@_logs boolean false
12679 .index message logs, preserving
12680 If this option is set, message log files are not deleted when messages are
12681 completed. Instead, they are moved to a sub-directory of the spool directory
12682 called \(msglog.OLD)\, where they remain available for statistical or debugging
12683 purposes. This is a dangerous option to set on systems with any appreciable
12684 volume of mail. Use with care!
12686 .conf primary@_hostname string "see below"
12687 .index name||of local host
12688 .index host||name of local
12689 .index local host||name of
12690 This specifies the name of the current host. It is used in the default \\EHLO\\
12691 or \\HELO\\ command for outgoing SMTP messages (changeable via the \helo@_data\
12692 option in the \%smtp%\ transport),
12693 and as the default for \qualify@_domain\. If it is not set, Exim calls
12694 \*uname()*\ to find it. If this fails, Exim panics and dies. If the name
12695 returned by \*uname()*\ contains only one component, Exim passes it to
12696 \*gethostbyname()*\ (or \*getipnodebyname()*\ when available) in order to
12697 obtain the fully qualified version.
12699 The value of \$primary@_hostname$\ is also used by default in some SMTP
12700 response messages from an Exim server. This can be changed dynamically by
12701 setting \smtp@_active@_hostname\.
12703 .conf print@_topbitchars boolean false
12704 .index printing characters
12705 .index 8-bit characters
12706 By default, Exim considers only those characters whose codes lie in the range
12707 32--126 to be printing characters. In a number of circumstances (for example,
12708 when writing log entries) non-printing characters are converted into escape
12709 sequences, primarily to avoid messing up the layout. If \print@_topbitchars\ is
12710 set, code values of 128 and above are also considered to be printing
12713 .conf process@_log@_path string unset
12714 .index process log path
12715 .index log||process log
12717 This option sets the name of the file to which an Exim process writes its
12718 `process log' when sent a USR1 signal. This is used by the \*exiwhat*\ utility
12719 script. If this option is unset, the file called \(exim-process.info)\ in
12720 Exim's spool directory is used. The ability to specify the name explicitly can
12721 be useful in environments where two different Exims are running, using
12722 different spool directories.
12724 .conf prod@_requires@_admin boolean true
12725 .index \-M-\ option
12726 .index \-R-\ option
12727 .index \-q-\ option
12728 The \-M-\, \-R-\, and \-q-\ command-line options require the caller to be an
12729 admin user unless \prod@_requires@_admin\ is set false. See also
12730 \queue@_list@_requires@_admin\.
12732 .conf qualify@_domain string "see below"
12733 .index domain||for qualifying addresses
12734 .index address||qualification
12735 This option specifies the domain name that is added to any envelope sender
12736 addresses that do not have a domain qualification. It also applies to
12737 recipient addresses if \qualify@_recipient\ is not set.
12739 Unqualified addresses are accepted by default only for locally-generated
12742 Qualification is also applied to addresses in header lines such as ::From:: and
12743 ::To:: for locally-generated messages, unless the \-bnq-\ command line option
12747 Messages from external sources must always contain fully qualified addresses,
12748 unless the sending host matches \sender@_unqualified@_hosts\ or
12749 \recipient@_unqualified@_hosts\ (as appropriate), in which case incoming
12750 addresses are qualified with \qualify@_domain\ or \qualify@_recipient\ as
12751 necessary. Internally, Exim always works with fully qualified envelope
12752 addresses. If \qualify@_domain\ is not set, it defaults to the
12753 \primary@_hostname\ value.
12755 .conf qualify@_recipient string "see below"
12757 This option allows you to specify a different domain for qualifying recipient
12758 addresses to the one that is used for senders. See \qualify@_domain\ above.
12761 .conf queue@_domains "domain list$**$" unset
12762 .index domain||specifying non-immediate delivery
12763 .index queueing incoming messages
12764 .index message||queueing certain domains
12765 This option lists domains for which immediate delivery is not required.
12766 A delivery process is started whenever a message is received, but only those
12767 domains that do not match are processed. All other deliveries wait until the
12768 next queue run. See also \hold@_domains\ and \queue@_smtp@_domains\.
12770 .conf queue@_list@_requires@_admin boolean true
12771 .index \-bp-\ option
12772 The \-bp-\ command-line option, which lists the messages that are on the queue,
12773 requires the caller to be an admin user unless \queue__list__requires__admin\
12774 is set false. See also \prod@_requires@_admin\.
12776 .conf queue@_only boolean false
12777 .index queueing incoming messages
12778 .index message||queueing unconditionally
12779 If \queue@_only\ is set, a delivery process is not automatically started
12780 whenever a message is received. Instead, the message waits on the queue for the
12781 next queue run. Even if \queue@_only\ is false, incoming messages may not get
12782 delivered immediately when certain conditions (such as heavy load) occur.
12784 The \-odq-\ command line has the same effect as \queue@_only\. The \-odb-\ and
12785 \-odi-\ command line options override \queue@_only\ unless
12786 \queue@_only@_override\ is set false. See also \queue@_only@_file\,
12787 \queue@_only@_load\, and \smtp@_accept@_queue\.
12789 .conf queue@_only@_file string unset
12790 .index queueing incoming messages
12791 .index message||queueing by file existence
12792 This option can be set to a colon-separated list of absolute path names, each
12793 one optionally preceded by `smtp'. When Exim is receiving a message,
12794 it tests for the existence of each listed path using a call to \*stat()*\. For
12795 each path that exists, the corresponding queuing option is set.
12796 For paths with no prefix, \queue@_only\ is set; for paths prefixed by `smtp',
12797 \queue@_smtp@_domains\ is set to match all domains. So, for example,
12799 queue_only_file = smtp/some/file
12801 causes Exim to behave as if \queue@_smtp@_domains\ were set to `$*$' whenever
12802 \(/some/file)\ exists.
12804 .conf queue@_only@_load fixed-point unset
12805 .index load average
12806 .index queueing incoming messages
12807 .index message||queueing by load
12808 If the system load average is higher than this value, incoming messages from
12809 all sources are queued, and no automatic deliveries are started. If this
12810 happens during local or remote SMTP input, all subsequent messages on the same
12811 connection are queued. Deliveries will subsequently be performed by queue
12812 runner processes. This option has no effect on ancient operating systems on
12813 which Exim cannot determine the load average. See also
12814 \deliver@_queue@_load@_max\ and \smtp@_load@_reserve\.
12816 .conf queue@_only@_override boolean true
12817 .index queueing incoming messages
12818 When this option is true, the \-od\*x*\-\ command line options override the
12819 setting of \queue@_only\ or \queue@_only@_file\ in the configuration file. If
12820 \queue@_only@_override\ is set false, the \-od\*x*\-\ options cannot be used to
12821 override; they are accepted, but ignored.
12823 .conf queue@_run@_in@_order boolean false
12824 .index queue runner||processing messages in order
12825 If this option is set, queue runs happen in order of message arrival instead of
12826 in an arbitrary order. For this to happen, a complete list of the entire queue
12827 must be set up before the deliveries start. When the queue is all held in a
12828 single directory (the default),
12830 a single list is created for both the ordered and the non-ordered cases.
12831 However, if \split@_spool@_directory\ is set, a single list is not created when
12832 \queue@_run@_in@_order\ is false. In this case, the sub-directories are
12833 processed one at a time (in a random order), and this avoids setting up one
12834 huge list for the whole queue. Thus, setting \queue@_run@_in@_order\ with
12835 \split@_spool@_directory\ may degrade performance when the queue is large,
12836 because of the extra work in setting up the single, large list. In most
12837 situations, \queue@_run@_in@_order\ should not be set.
12840 .conf queue@_run@_max integer 5
12841 .index queue runner||maximum number of
12842 This controls the maximum number of queue runner processes that an Exim daemon
12843 can run simultaneously. This does not mean that it starts them all at once,
12844 but rather that if the maximum number are still running when the time comes to
12845 start another one, it refrains from starting another one. This can happen with
12846 very large queues and/or very sluggish deliveries. This option does not,
12847 however, interlock with other processes, so additional queue runners can be
12848 started by other means, or by killing and restarting the daemon.
12850 .conf queue@_smtp@_domains "domain list$**$" unset
12851 .index queueing incoming messages
12852 .index message||queueing remote deliveries
12853 When this option is set, a delivery process is started whenever a message is
12854 received, routing is performed, and local deliveries take place.
12855 However, if any SMTP deliveries are required for domains that match
12856 \queue@_smtp@_domains\, they are not immediately delivered, but instead the
12857 message waits on the queue for the next queue run. Since routing of the message
12858 has taken place, Exim knows to which remote hosts it must be delivered, and so
12859 when the queue run happens, multiple messages for the same host are delivered
12860 over a single SMTP connection. The \-odqs-\ command line option causes all SMTP
12861 deliveries to be queued in this way, and is equivalent to setting
12862 \queue@_smtp@_domains\ to `$*$'. See also \hold@_domains\ and \queue@_domains\.
12864 .conf receive@_timeout time 0s
12865 .index timeout||for non-SMTP input
12866 This option sets the timeout for accepting a non-SMTP message, that is, the
12867 maximum time that Exim waits when reading a message on the standard input. If
12868 the value is zero, it will wait for ever. This setting is overridden by the
12869 \-or-\ command line option. The timeout for incoming SMTP messages is
12870 controlled by \smtp@_receive@_timeout\.
12872 .index customizing|| ::Received:: header
12873 .index ::Received:: header line||customizing
12874 .conf received@_header@_text string$**$ "see below"
12875 This string defines the contents of the ::Received:: message header that is
12876 added to each message, except for the timestamp, which is automatically added
12877 on at the end (preceded by a semicolon). The string is expanded each time it is
12878 used. If the expansion yields an empty string, no ::Received:: header line is
12879 added to the message. Otherwise, the string should start with the text
12880 `Received:' and conform to the RFC 2822 specification for ::Received:: header
12881 lines. The default setting is:
12883 received_header_text = Received: \
12884 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
12885 {${if def:sender_ident {from $sender_ident }}\
12886 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
12887 by $primary_hostname \
12888 ${if def:received_protocol {with $received_protocol}} \
12889 ${if def:tls_cipher {($tls_cipher)\n\t}}\
12890 (Exim $version_number)\n\t\
12892 ${if def:received_for {\n\tfor $received_for}}
12894 Note the use of quotes, to allow the sequences \"@\n"\ and \"@\t"\ to be used
12895 for newlines and tabs, respectively. The reference to the TLS cipher is omitted
12896 when Exim is built without TLS support. The use of conditional expansions
12897 ensures that this works for both locally generated messages and messages
12898 received from remote hosts, giving header lines such as the following:
12900 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
12901 by marley.carol.example with esmtp (Exim 4.00)
12902 id 16IOWa-00019l-00
12903 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
12904 Received: by scrooge.carol.example with local (Exim 4.00)
12905 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
12907 Until the body of the message has been received, the timestamp is the time when
12908 the message started to be received. Once the body has arrived, and all policy
12909 checks have taken place, the timestamp is updated to the time at which the
12910 message was accepted.
12912 .conf received@_headers@_max integer 30
12913 .index loop||prevention
12914 .index mail loop prevention
12915 .index ::Received:: header line||counting
12916 When a message is to be delivered, the number of ::Received:: headers is
12917 counted, and if it is greater than this parameter, a mail loop is assumed to
12918 have occurred, the delivery is abandoned, and an error message is generated.
12919 This applies to both local and remote deliveries.
12921 .conf recipient@_unqualified@_hosts "host list$**$" unset
12922 .index unqualified addresses
12923 .index host||unqualified addresses from
12924 This option lists those hosts from which Exim is prepared to accept unqualified
12925 recipient addresses in message envelopes. The addresses are made fully
12926 qualified by the addition of the \qualify@_recipient\ value. This option also
12927 affects message header lines. Exim does not reject unqualified recipient
12928 addresses in headers, but it qualifies them only if the message came from a
12929 host that matches \recipient@_unqualified@_hosts\,
12930 or if the message was submitted locally (not using TCP/IP), and the \-bnq-\
12931 option was not set.
12933 .conf recipients@_max integer 0
12934 .index limit||number of recipients
12935 .index recipient||maximum number
12936 If this option is set greater than zero, it specifies the maximum number of
12937 original recipients for any message. Additional recipients that are generated
12938 by aliasing or forwarding do not count. SMTP messages get a 452 response for
12939 all recipients over the limit; earlier recipients are delivered as normal.
12940 Non-SMTP messages with too many recipients are failed, and no deliveries are
12942 .index \\RCPT\\||maximum number of incoming
12943 Note that the RFCs specify that an SMTP server should accept at least 100
12944 \\RCPT\\ commands in a single message.
12946 .conf recipients@_max@_reject boolean false
12947 If this option is set true, Exim rejects SMTP messages containing too many
12948 recipients by giving 552 errors to the surplus \\RCPT\\ commands, and a 554
12949 error to the eventual \\DATA\\ command. Otherwise (the default) it gives a 452
12950 error to the surplus \\RCPT\\ commands and accepts the message on behalf of the
12951 initial set of recipients. The remote server should then re-send the message
12952 for the remaining recipients at a later time.
12954 .conf remote@_max@_parallel integer 2
12955 .index delivery||parallelism for remote
12956 This option controls parallel delivery of one message to a number of remote
12957 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
12958 does all the remote deliveries for a message one by one. Otherwise, if a single
12959 message has to be delivered to more than one remote host, or if several copies
12960 have to be sent to the same remote host, up to \remote@_max@_parallel\
12961 deliveries are done simultaneously. If more than \remote@_max@_parallel\
12962 deliveries are required, the maximum number of processes are started, and as
12963 each one finishes, another is begun. The order of starting processes is the
12964 same as if sequential delivery were being done, and can be controlled by the
12965 \remote@_sort@_domains\ option. If parallel delivery takes place while running
12966 with debugging turned on, the debugging output from each delivery process is
12967 tagged with its process id.
12969 This option controls only the maximum number of parallel deliveries for one
12970 message in one Exim delivery process. Because Exim has no central queue
12971 manager, there is no way of controlling the total number of simultaneous
12972 deliveries if the configuration allows a delivery attempt as soon as a message
12974 .index number of deliveries
12975 .index delivery||maximum number of
12976 If you want to control the total number of deliveries on the system, you
12977 need to set the \queue@_only\ option. This ensures that all incoming messages
12978 are added to the queue without starting a delivery process. Then set up an Exim
12979 daemon to start queue runner processes at appropriate intervals (probably
12980 fairly often, for example, every minute), and limit the total number of queue
12981 runners by setting the \queue__run__max\ parameter. Because each queue runner
12982 delivers only one message at a time, the maximum number of deliveries that can
12983 then take place at once is \queue@_run@_max\ multiplied by
12984 \remote@_max@_parallel\.
12986 If it is purely remote deliveries you want to control, use
12987 \queue@_smtp@_domains\ instead of \queue@_only\. This has the added benefit of
12988 doing the SMTP routing before queuing, so that several messages for the same
12989 host will eventually get delivered down the same connection.
12991 .conf remote@_sort@_domains "domain list$**$" unset
12992 .index sorting remote deliveries
12993 .index delivery||sorting remote
12994 When there are a number of remote deliveries for a message, they are sorted by
12995 domain into the order given by this list. For example,
12997 remote_sort_domains = *.cam.ac.uk:*.uk
12999 would attempt to deliver to all addresses in the \*cam.ac.uk*\ domain first, then
13000 to those in the \uk\ domain, then to any others.
13002 .conf retry@_data@_expire time 7d
13003 .index hints database||data expiry
13004 This option sets a `use before' time on retry information in Exim's hints
13005 database. Any older retry data is ignored. This means that, for example, once a
13006 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
13009 .conf retry@_interval@_max time 24h
13010 .index retry||limit on interval
13011 .index limit||on retry interval
13012 Chapter ~~CHAPretry describes Exim's mechanisms for controlling the intervals
13013 between delivery attempts for messages that cannot be delivered straight away.
13014 This option sets an overall limit to the length of time between retries.
13016 .conf return@_path@_remove boolean true
13017 .index ::Return-path:: header line||removing
13018 RFC 2821, section 4.4, states that an SMTP server must insert a ::Return-path::
13019 header line into a message when it makes a `final delivery'. The ::Return-path::
13020 header preserves the sender address as received in the \\MAIL\\ command. This
13021 description implies that this header should not be present in an incoming
13022 message. If \return@_path@_remove\ is true, any existing ::Return-path::
13023 headers are removed from messages at the time they are received. Exim's
13024 transports have options for adding ::Return-path:: headers at the time of
13025 delivery. They are normally used only for final local deliveries.
13027 .conf return@_size@_limit integer 100K
13028 This option is an obsolete synonym for \bounce@_return@_size@_limit\.
13030 .conf rfc1413@_hosts "host list$**$" $*$
13032 .index host||for RFC 1413 calls
13033 RFC 1413 identification calls are made to any client host which matches an item
13036 .conf rfc1413@_query@_timeout time 30s
13037 .index RFC 1413||query timeout
13038 .index timeout||for RFC 1413 call
13039 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
13040 no RFC 1413 calls are ever made.
13042 .conf sender@_unqualified@_hosts "host list$**$" unset
13043 .index unqualified addresses
13044 .index host||unqualified addresses from
13045 This option lists those hosts from which Exim is prepared to accept unqualified
13046 sender addresses. The addresses are made fully qualified by the addition of
13047 \qualify@_domain\. This option also affects message header lines. Exim does not
13048 reject unqualified addresses in headers that contain sender addresses, but it
13049 qualifies them only if the message came from a host that matches
13050 \sender@_unqualified@_hosts\,
13051 or if the message was submitted locally (not using TCP/IP), and the \-bnq-\
13052 option was not set.
13054 .conf smtp@_accept@_keepalive boolean true
13055 .index keepalive||on incoming connection
13056 This option controls the setting of the \\SO@_KEEPALIVE\\ option on incoming
13057 TCP/IP socket connections. When set, it causes the kernel to probe idle
13058 connections periodically, by sending packets with `old' sequence numbers. The
13059 other end of the connection should send an acknowledgement if the connection is
13060 still okay or a reset if the connection has been aborted. The reason for doing
13061 this is that it has the beneficial effect of freeing up certain types of
13062 connection that can get stuck when the remote host is disconnected without
13063 tidying up the TCP/IP call properly. The keepalive mechanism takes several
13064 hours to detect unreachable hosts.
13067 .conf smtp@_accept@_max integer 20
13068 .index limit||incoming SMTP connections
13069 .index SMTP||incoming connection count
13071 This option specifies the maximum number of simultaneous incoming SMTP calls
13072 that Exim will accept. It applies only to the listening daemon; there is no
13073 control (in Exim) when incoming SMTP is being handled by \*inetd*\. If the value
13074 is set to zero, no limit is applied. However, it is required to be non-zero if
13075 either \smtp@_accept@_max@_per@_host\ or \smtp@_accept@_queue\ is set. See also
13076 \smtp@_accept@_reserve\.
13079 .conf smtp@_accept@_max@_nonmail integer 10
13080 .index limit||non-mail SMTP commands
13081 .index SMTP||limiting non-mail commands
13082 Exim counts the number of `non-mail' commands in an SMTP session, and drops the
13083 connection if there are too many. This option defines `too many'. The check
13084 catches some denial-of-service attacks, repeated failing \\AUTH\\s, or a mad
13085 client looping sending \\EHLO\\, for example. The check is applied only if the
13086 client host matches \smtp@_accept@_max@_nonmail@_hosts\.
13088 When a new message is expected, one occurrence of \\RSET\\ is not counted. This
13089 allows a client to send one \\RSET\\ between messages (this is not necessary,
13090 but some clients do it). Exim also allows one uncounted occurence of \\HELO\\
13091 or \\EHLO\\, and one occurrence of \\STARTTLS\\ between messages. After
13092 starting up a TLS session, another \\EHLO\\ is expected, and so it too is not
13093 counted. The first occurrence of \\AUTH\\ in a connection, or immediately
13094 following \\STARTTLS\\ is not counted. Otherwise, all commands other than
13095 \\MAIL\\, \\RCPT\\, \\DATA\\, and \\QUIT\\ are counted.
13097 .conf smtp@_accept@_max@_nonmail@_hosts "host list$**$" $*$
13098 You can control which hosts are subject to the \smtp@_accept@_max@_nonmail\
13099 check by setting this option. The default value makes it apply to all hosts. By
13100 changing the value, you can exclude any badly-behaved hosts that you have to
13104 .conf smtp@_accept@_max@_per@_connection integer 1000
13105 .index SMTP||incoming message count, limiting
13106 .index limit||messages per SMTP connection
13107 The value of this option limits the number of \\MAIL\\ commands that Exim is
13108 prepared to accept over a single SMTP connection, whether or not each command
13109 results in the transfer of a message. After the limit is reached, a 421
13110 response is given to subsequent \\MAIL\\ commands. This limit is a safety
13111 precaution against a client that goes mad (incidents of this type have been
13114 .conf smtp@_accept@_max@_per@_host string$**$ unset
13115 .index limit||SMTP connections from one host
13116 .index host||limiting SMTP connections from
13117 This option restricts the number of simultaneous IP connections from a single
13118 host (strictly, from a single IP address) to the Exim daemon. The option is
13119 expanded, to enable different limits to be applied to different hosts by
13120 reference to \$sender@_host@_address$\. Once the limit is reached, additional
13121 connection attempts from the same host are rejected with error code 421. The
13122 default value of zero imposes no limit. If this option is set, it is required
13123 that \smtp@_accept@_max\ be non-zero.
13125 \**Warning**\: When setting this option you should not use any expansion
13126 constructions that take an appreciable amount of time. The expansion and test
13127 happen in the main daemon loop, in order to reject additional connections
13128 without forking additional processes (otherwise a denial-of-service attack
13129 could cause a vast number or processes to be created). While the daemon is
13130 doing this processing, it cannot accept any other incoming connections.
13133 .conf smtp@_accept@_queue integer 0
13134 .index SMTP||incoming connection count
13135 .index queueing incoming messages
13136 .index message||queueing by SMTP connection count
13137 If the number of simultaneous incoming SMTP calls handled via the listening
13138 daemon exceeds this value, messages received by SMTP are just placed on the
13139 queue; no delivery processes are started automatically. A value of zero implies
13140 no limit, and clearly any non-zero value is useful only if it is less than the
13141 \smtp@_accept@_max\ value (unless that is zero). See also \queue@_only\,
13142 \queue@_only@_load\, \queue@_smtp@_domains\, and the various \-od-\ command
13145 .conf smtp@_accept@_queue@_per@_connection integer 10
13146 .index queueing incoming messages
13147 .index message||queueing by message count
13148 This option limits the number of delivery processes that Exim starts
13149 automatically when receiving messages via SMTP, whether via the daemon or by
13150 the use of \-bs-\ or \-bS-\. If the value of the option is greater than zero,
13151 and the number of messages received in a single SMTP session exceeds this
13152 number, subsequent messages are placed on the queue, but no delivery processes
13153 are started. This helps to limit the number of Exim processes when a server
13154 restarts after downtime and there is a lot of mail waiting for it on other
13155 systems. On large systems, the default should probably be increased, and on
13156 dial-in client systems it should probably be set to zero (that is, disabled).
13158 .conf smtp@_accept@_reserve integer 0
13159 .index SMTP||incoming call count
13160 .index host||reserved
13161 When \smtp@_accept@_max\ is set greater than zero, this option specifies a
13162 number of SMTP connections that are reserved for connections from the hosts
13163 that are specified in \smtp@_reserve@_hosts\. The value set in
13164 \smtp@_accept@_max\ includes this reserve pool. The specified hosts are not
13165 restricted to this number of connections; the option specifies a minimum number
13166 of connection slots for them, not a maximum. It is a guarantee that that group
13167 of hosts can always get at least \smtp@_accept@_reserve\ connections.
13169 For example, if \smtp@_accept@_max\ is set to 50 and \smtp@_accept@_reserve\ is
13170 set to 5, once there are 45 active connections (from any hosts), new
13171 connections are accepted only from hosts listed in \smtp@_reserve@_hosts\.
13172 See also \smtp@_accept@_max@_per@_host\.
13174 .conf smtp@_active@_hostname string$**$ unset
13175 .index host||name in SMTP responses
13176 .index SMTP||host name in responses
13177 This option is provided for multi-homed servers that want to masquerade as
13178 several different hosts. At the start of an SMTP connection, its value is
13179 expanded and used instead of the value of \$primary@_hostname$\ in SMTP
13180 responses. For example, it is used as domain name in the response to an
13181 incoming \\HELO\\ or \\EHLO\\ command.
13183 It is also used in \\HELO\\ commands for callout verification.
13184 The active hostname is placed in the \$smtp__active__hostname$\ variable, which
13185 is saved with any messages that are received. It is therefore available for use
13186 in routers and transports when the message is later delivered.
13189 If this option is unset, or if its expansion is forced to fail, or if the
13190 expansion results in an empty string, the value of \$primary@_hostname$\ is
13191 used. Other expansion failures cause a message to be written to the main and
13192 panic logs, and the SMTP command receives a temporary error. Typically, the
13193 value of \smtp@_active@_hostname\ depends on the incoming interface address.
13196 smtp_active_hostname = ${if eq{$interface_address}{10.0.0.1}\
13197 {cox.mydomain}{box.mydomain}}
13200 .conf smtp@_banner string$**$ "see below"
13201 .index SMTP||welcome banner
13202 .index banner for SMTP
13203 .index welcome banner for SMTP
13204 .index customizing||SMTP banner
13205 This string, which is expanded every time it is used, is output as the initial
13206 positive response to an SMTP connection. The default setting is:
13209 smtp_banner = $smtp_active_hostname ESMTP Exim \
13210 $version_number $tod_full
13213 Failure to expand the string causes a panic error. If you want to create a
13214 multiline response to the initial SMTP connection, use `@\n' in the string at
13215 appropriate points, but not at the end. Note that the 220 code is not included
13216 in this string. Exim adds it automatically (several times in the case of a
13217 multiline response).
13219 .conf smtp@_check@_spool@_space boolean true
13220 .index checking disk space
13221 .index disk space, checking
13222 .index spool directory||checking space
13223 When this option is set, if an incoming SMTP session encounters the \\SIZE\\
13224 option on a \\MAIL\\ command, it checks that there is enough space in the
13225 spool directory's partition to accept a message of that size, while still
13226 leaving free the amount specified by \check@_spool@_space\ (even if that value
13227 is zero). If there isn't enough space, a temporary error code is returned.
13229 .conf smtp@_connect@_backlog integer 20
13230 .index connection backlog
13231 .index SMTP||connection backlog
13232 .index backlog of connections
13233 This option specifies a maximum number of waiting SMTP connections. Exim passes
13234 this value to the TCP/IP system when it sets up its listener. Once this number
13235 of connections are waiting for the daemon's attention, subsequent connection
13236 attempts are refused at the TCP/IP level. At least, that is what the manuals
13237 say; in some circumstances such connection attempts have been observed to time
13238 out instead. For large systems it is probably a good idea to increase the
13239 value (to 50, say). It also gives some protection against denial-of-service
13240 attacks by SYN flooding.
13242 .conf smtp@_enforce@_sync boolean true
13243 .index SMTP||synchronization checking
13244 .index synchronization checking in SMTP
13245 The SMTP protocol specification requires the client to wait for a response from
13246 the server at certain points in the dialogue. Without \\PIPELINING\\ these
13247 synchronization points are after every command; with \\PIPELINING\\ they are
13248 fewer, but they still exist.
13250 Some spamming sites send out a complete set of SMTP commands without waiting
13251 for any response. Exim protects against this by rejecting a message if the
13252 client has sent further input when it should not have. The error response `554
13253 SMTP synchronization error' is sent, and the connection is dropped. Testing for
13254 this error cannot be perfect because of transmission delays (unexpected input
13255 may be on its way but not yet received when Exim checks). However, it does
13256 detect many instances.
13259 The check can be globally disabled by setting \smtp@_enforce@_sync\ false.
13260 If you want to disable the check selectively (for example, only for certain
13261 hosts), you can do so by an appropriate use of a \control\ modifier in an ACL
13262 (see section ~~SECTcontrols). See also \pipelining@_advertise@_hosts\.
13265 .conf smtp@_etrn@_command string$**$ unset
13266 .index \\ETRN\\||command to be run
13267 If this option is set, the given command is run whenever an SMTP \\ETRN\\
13268 command is received from a host that is permitted to issue such commands (see
13269 chapter ~~CHAPACL). The string is split up into separate arguments which are
13270 independently expanded. The expansion variable \$domain$\ is set to the
13271 argument of the \\ETRN\\ command, and no syntax checking is done on it. For
13274 smtp_etrn_command = /etc/etrn_command $domain $sender_host_address
13276 A new process is created to run the command, but Exim does not wait for it to
13277 complete. Consequently, its status cannot be checked. If the command cannot be
13278 run, a line is written to the panic log, but the \\ETRN\\ caller still receives
13279 a 250 success response. Exim is normally running under its own uid when
13280 receiving SMTP, so it is not possible for it to change the uid before running
13283 .conf smtp@_etrn@_serialize boolean true
13284 .index \\ETRN\\||serializing
13285 When this option is set, it prevents the simultaneous execution of more than
13286 one identical command as a result of \\ETRN\\ in an SMTP connection. See
13287 section ~~SECTETRN for details.
13289 .conf smtp@_load@_reserve fixed-point unset
13290 .index load average
13291 If the system load average ever gets higher than this, incoming SMTP calls are
13292 accepted only from those hosts that match an entry in \smtp@_reserve@_hosts\.
13293 If \smtp@_reserve@_hosts\ is not set, no incoming SMTP calls are accepted when
13294 the load is over the limit. The option has no effect on ancient operating
13295 systems on which Exim cannot determine the load average. See also
13296 \deliver@_queue@_load@_max\ and \queue@_only@_load\.
13299 .conf smtp@_max@_synprot@_errors integer 3
13300 .index SMTP||limiting syntax and protocol errors
13301 .index limit||SMTP syntax and protocol errors
13302 Exim rejects SMTP commands that contain syntax or protocol errors. In
13303 particular, a syntactically invalid email address, as in this command:
13305 RCPT TO:<abc xyz@a.b.c>
13307 causes immediate rejection of the command, before any other tests are done.
13308 (The ACL cannot be run if there is no valid address to set up for it.) An
13309 example of a protocol error is receiving \\RCPT\\ before \\MAIL\\. If there are
13310 too many syntax or protocol errors in one SMTP session, the connection is
13311 dropped. The limit is set by this option.
13313 .index \\PIPELINING\\||expected errors
13314 When the \\PIPELINING\\ extension to SMTP is in use, some protocol errors are
13315 `expected', for instance, a \\RCPT\\ command after a rejected \\MAIL\\ command.
13316 Exim assumes that \\PIPELINING\\ will be used if it advertises it (see
13317 \pipelining@_advertise@_hosts\), and in this situation, `expected' errors do
13318 not count towards the limit.
13321 .conf smtp@_max@_unknown@_commands integer 3
13322 .index SMTP||limiting unknown commands
13323 .index limit||unknown SMTP commands
13324 If there are too many unrecognized commands in an incoming SMTP session, an
13325 Exim server drops the connection. This is a defence against some kinds of abuse
13328 into making connections to SMTP ports; in these circumstances, a number of
13329 non-SMTP command lines are sent first.
13332 .conf smtp@_ratelimit@_hosts "host list$**$" unset
13333 .index SMTP||rate limiting
13334 .index limit||rate of message arrival
13335 .index \\RCPT\\||rate limiting
13336 Some sites find it helpful to be able to limit the rate at which certain hosts
13337 can send them messages, and the rate at which an individual message can specify
13338 recipients. When a host matches \smtp@_ratelimit@_hosts\, the values of
13339 \smtp@_ratelimit@_mail\ and \smtp@_ratelimit@_rcpt\ are used to control the
13340 rate of acceptance of \\MAIL\\ and \\RCPT\\ commands in a single SMTP session,
13341 respectively. Each option, if set, must contain a set of four comma-separated
13344 A threshold, before which there is no rate limiting.
13346 An initial time delay. Unlike other times in Exim, numbers with decimal
13347 fractional parts are allowed here.
13349 A factor by which to increase the delay each time.
13351 A maximum value for the delay. This should normally be less than 5 minutes,
13352 because after that time, the client is liable to timeout the SMTP command.
13354 For example, these settings have been used successfully at the site which
13355 first suggested this feature, for controlling mail from their customers:
13357 smtp_ratelimit_mail = 2,0.5s,1.05,4m
13358 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
13360 The first setting specifies delays that are applied to \\MAIL\\ commands after
13361 two have been received over a single connection. The initial delay is 0.5
13362 seconds, increasing by a factor of 1.05 each time. The second setting applies
13363 delays to \\RCPT\\ commands when more than four occur in a single message.
13365 It is also possible to configure delays explicitly in ACLs. See section
13366 ~~SECTACLmodi for details.
13369 .conf smtp@_ratelimit@_mail string unset
13370 See \smtp@_ratelimit@_hosts\ above.
13372 .conf smtp@_ratelimit@_rcpt string unset
13373 See \smtp@_ratelimit@_hosts\ above.
13375 .conf smtp@_receive@_timeout time 5m
13376 .index timeout||for SMTP input
13377 .index SMTP||timeout, input
13378 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
13379 input, including batch SMTP. If a line of input (either an SMTP command or a
13380 data line) is not received within this time, the SMTP connection is dropped and
13381 the message is abandoned.
13382 A line is written to the log containing one of the following messages:
13384 SMTP command timeout on connection from...
13385 SMTP data timeout on connection from...
13387 The former means that Exim was expecting to read an SMTP command; the latter
13388 means that it was in the \\DATA\\ phase, reading the contents of a message.
13391 .index \-os-\ option
13392 The value set by this option can be overridden by the
13393 \-os-\ command-line option. A setting of zero time disables the timeout, but
13394 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
13395 of local input using \-bs-\ or \-bS-\.) For non-SMTP input, the reception
13396 timeout is controlled by \receive@_timeout\ and \-or-\.
13398 .conf smtp@_reserve@_hosts "host list$**$" unset
13399 This option defines hosts for which SMTP connections are reserved; see
13400 \smtp@_accept@_reserve\ and \smtp@_load@_reserve\ above.
13402 .conf smtp@_return@_error@_details boolean false
13403 .index SMTP||details policy failures
13404 .index policy control||rejection, returning details
13405 In the default state, Exim uses bland messages such as
13406 `Administrative prohibition' when it rejects SMTP commands for policy
13407 reasons. Many sysadmins like this because it gives away little information
13408 to spammers. However, some other syadmins who are applying strict checking
13409 policies want to give out much fuller information about failures. Setting
13410 \smtp@_return@_error@_details\ true causes Exim to be more forthcoming. For
13411 example, instead of `Administrative prohibition', it might give:
13413 550-Rejected after DATA: '>' missing at end of address:
13414 550 failing address in "From" header is: <user@dom.ain
13418 .conf spamd@_address string "$tt{127.0.0.1 783}"
13419 This option is available when Exim is compiled with the content-scanning
13420 extension. It specifies how Exim connects to SpamAssassin's \spamd\ daemon. See
13421 section ~~SECTscanspamass for more details.
13424 .conf split@_spool@_directory boolean false
13425 .index multiple spool directories
13426 .index spool directory||split
13427 .index directories, multiple
13428 If this option is set, it causes Exim to split its input directory into 62
13429 subdirectories, each with a single alphanumeric character as its name. The
13430 sixth character of the message id is used to allocate messages to
13431 subdirectories; this is the least significant base-62 digit of the time of
13432 arrival of the message.
13434 Splitting up the spool in this way may provide better performance on systems
13435 where there are long mail queues, by reducing the number of files in any one
13436 directory. The msglog directory is also split up in a similar way to the input
13437 directory; however, if \preserve@_message@_logs\ is set, all old msglog files
13438 are still placed in the single directory \(msglog.OLD)\.
13440 It is not necessary to take any special action for existing messages when
13441 changing \split@_spool@_directory\. Exim notices messages that are in the
13442 `wrong' place, and continues to process them. If the option is turned off after
13443 a period of being on, the subdirectories will eventually empty and be
13444 automatically deleted.
13446 When \split@_spool@_directory\ is set, the behaviour of queue runner processes
13447 changes. Instead of creating a list of all messages in the queue, and then
13448 trying to deliver each one in turn, it constructs a list of those in one
13449 sub-directory and tries to deliver them, before moving on to the next
13450 sub-directory. The sub-directories are processed in a random order. This
13451 spreads out the scanning of the input directories, and uses less memory. It is
13452 particularly beneficial when there are lots of messages on the queue. However,
13453 if \queue@_run@_in@_order\ is set, none of this new processing happens. The
13454 entire queue has to be scanned and sorted before any deliveries can start.
13456 .conf spool@_directory string$**$ "set at compile time"
13457 .index spool directory||path to
13458 This defines the directory in which Exim keeps its spool, that is, the messages
13459 it is waiting to deliver. The default value is taken from the compile-time
13460 configuration setting, if there is one. If not, this option must be set. The
13461 string is expanded, so it can contain, for example, a reference to
13462 \$primary@_hostname$\.
13464 If the spool directory name is fixed on your installation, it is recommended
13465 that you set it at build time rather than from this option, particularly if the
13466 log files are being written to the spool directory (see \log@_file@_path\).
13467 Otherwise log files cannot be used for errors that are detected early on, such
13468 as failures in the configuration file.
13470 By using this option to override the compiled-in path, it is possible to run
13471 tests of Exim without using the standard spool.
13473 .conf strip@_excess@_angle@_brackets boolean false
13474 .index angle brackets, excess
13475 If this option is set, redundant pairs of angle brackets round `route-addr'
13476 items in addresses are stripped. For example, \*@<@<xxx@@a.b.c.d@>@>*\ is treated
13477 as \*@<xxx@@a.b.c.d@>*\. If this is in the envelope and the message is passed on
13478 to another MTA, the excess angle brackets are not passed on. If this option is
13479 not set, multiple pairs of angle brackets cause a syntax error.
13481 .conf strip@_trailing@_dot boolean false
13482 .index trailing dot on domain
13483 .index dot||trailing on domain
13484 If this option is set, a trailing dot at the end of a domain in an address is
13485 ignored. If this is in the envelope and the message is passed on to another
13486 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
13487 domain causes a syntax error.
13488 However, addresses in header lines are checked only when an ACL requests header
13491 .conf syslog@_duplication boolean true
13492 .index syslog||duplicate log lines, suppressing
13493 When Exim is logging to syslog, it writes the log lines for its three
13494 separate logs at different syslog priorities so that they can in principle
13495 be separated on the logging hosts. Some installations do not require this
13496 separation, and in those cases, the duplication of certain log lines is a
13497 nuisance. If \syslog@_duplication\ is set false, only one copy of any
13498 particular log line is written to syslog. For lines that normally go to
13499 both the main log and the reject log, the reject log version (possibly
13500 containing message header lines) is written, at \\LOG@_NOTICE\\ priority.
13501 Lines that normally go to both the main and the panic log are written at
13502 the \\LOG@_ALERT\\ priority.
13504 .conf syslog@_facility string unset
13505 .index syslog||facility, setting
13506 This option sets the syslog `facility' name, used when Exim is logging to
13507 syslog. The value must be one of the strings `mail', `user', `news', `uucp',
13508 `daemon', or `local\*x*\' where \*x*\ is a digit between 0 and 7. If this
13509 option is unset, `mail' is used. See chapter ~~CHAPlog for details of Exim's
13513 .conf syslog@_processname string "$tt{exim}"
13514 .index syslog||process name, setting
13515 This option sets the syslog `ident' name, used when Exim is logging to syslog.
13516 The value must be no longer than 32 characters. See chapter ~~CHAPlog for
13517 details of Exim's logging.
13520 .conf syslog@_timestamp boolean true
13521 .index syslog||timestamps
13522 If \syslog@_timestamp\ is set false, the timestamps on Exim's log lines are
13523 omitted when these lines are sent to syslog. See chapter ~~CHAPlog for
13524 details of Exim's logging.
13526 .conf system@_filter string$**$ unset
13527 .index filter||system filter
13528 .index system filter||specifying
13529 .index Sieve filter||not available for system filter
13530 This option specifies an Exim filter file that is applied to all messages at
13531 the start of each delivery attempt, before any routing is done. System filters
13532 must be Exim filters; they cannot be Sieve filters. If the system filter
13533 generates any deliveries to files or pipes, or any new mail messages, the
13534 appropriate \system@_filter@_...@_transport\ option(s) must be set, to define
13535 which transports are to be used. Details of this facility are given in chapter
13536 ~~CHAPsystemfilter.
13538 .conf system@_filter@_directory@_transport string$**$ unset
13539 This sets the name of the transport driver that is to be used when the
13540 \save\ command in a system message filter specifies a path ending in `/',
13541 implying delivery of each message into a separate file in some directory.
13542 During the delivery, the variable \$address@_file$\ contains the path name.
13544 .conf system@_filter@_file@_transport string$**$ unset
13545 .index file||transport for system filter
13546 This sets the name of the transport driver that is to be used when the \save\
13547 command in a system message filter specifies a path not ending in `/'. During
13548 the delivery, the variable \$address@_file$\ contains the path name.
13550 .index gid (group id)||system filter
13551 .conf system@_filter@_group string unset
13552 This option is used only when \system@_filter@_user\ is also set. It sets the
13553 gid under which the system filter is run, overriding any gid that is associated
13554 with the user. The value may be numerical or symbolic.
13556 .conf system@_filter@_pipe@_transport string$**$ unset 7
13557 .index \%pipe%\ transport||for system filter
13558 This specifies the transport driver that is to be used when a \pipe\ command is
13559 used in a system filter. During the delivery, the variable \$address@_pipe$\
13560 contains the pipe command.
13562 .conf system@_filter@_reply@_transport string$**$ unset
13563 .index \%autoreply%\ transport||for system filter
13564 This specifies the transport driver that is to be used when a \mail\ command is
13565 used in a system filter.
13567 .index uid (user id)||system filter
13568 .conf system@_filter@_user string unset
13569 If this option is not set, the system filter is run in the main Exim delivery
13570 process, as root. When the option is set, the system filter runs in a separate
13571 process, as the given user. Unless the string consists entirely of digits, it
13572 is looked up in the password data. Failure to find the named user causes a
13573 configuration error. The gid is either taken from the password data, or
13574 specified by \system@_filter@_group\. When the uid is specified numerically,
13575 \system@_filter@_group\ is required to be set.
13577 If the system filter generates any pipe, file, or reply deliveries, the uid
13578 under which the filter is run is used when transporting them, unless a
13579 transport option overrides.
13580 Normally you should set \system@_filter@_user\ if your system filter generates
13581 these kinds of delivery.
13583 .conf tcp@_nodelay boolean true
13584 .index daemon||\\TCP@_NODELAY\\ on sockets
13585 .index Nagle algorithm
13586 .index \\TCP@_NODELAY\\ on listening sockets
13587 If this option is set false, it stops the Exim daemon setting the
13588 \\TCP@_NODELAY\\ option on its listening sockets. Setting \\TCP@_NODELAY\\
13589 turns off the `Nagle algorithm', which is a way of improving network
13590 performance in interactive (character-by-character) situations. Turning it off
13591 should improve Exim's performance a bit, so that is what happens by default.
13592 However, it appears that some broken clients cannot cope, and time out. Hence
13593 this option. It affects only those sockets that are set up for listening by the
13594 daemon. Sockets created by the smtp transport for delivering mail always set
13597 .conf timeout@_frozen@_after time 0s
13598 .index frozen messages||timing out
13599 .index timeout||frozen messages
13600 If \timeout@_frozen@_after\ is set to a time greater than zero, a frozen
13601 message of any kind that has been on the queue for longer than the given
13602 time is automatically cancelled at the next queue run. If it is a bounce
13603 message, it is just discarded; otherwise, a bounce is sent to the sender, in a
13604 similar manner to cancellation by the \-Mg-\ command line option. If you want
13605 to timeout frozen bounce messages earlier than other kinds of frozen message,
13606 see \ignore@_bounce@_errors@_after\.
13608 .conf timezone string unset
13609 .index timezone, setting
13610 The value of \timezone\ is used to set the environment variable \\TZ\\ while
13611 running Exim (if it is different on entry). This ensures that all timestamps
13612 created by Exim are in the required timezone. If you want all your timestamps
13613 to be in UTC (aka GMT) you should set
13617 The default value is taken from \\TIMEZONE@_DEFAULT\\ in \(Local/Makefile)\,
13618 or, if that is not set, from the value of the TZ environment variable when Exim
13619 is built. If \timezone\ is set to the empty string, either at build or run
13620 time, any existing \\TZ\\ variable is removed from the environment when Exim
13621 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
13622 unfortunately not all, operating systems.
13624 .conf tls@_advertise@_hosts "host list$**$" unset
13625 .index TLS||advertising
13626 .index encryption||on SMTP connection
13627 .index SMTP||encrypted connection
13628 When Exim is built with support for TLS encrypted connections, the availability
13629 of the \\STARTTLS\\ command to set up an encrypted session is advertised in
13630 response to \\EHLO\\ only to those client hosts that match this option. See
13631 chapter ~~CHAPTLS for details of Exim's support for TLS.
13633 .conf tls@_certificate string$**$ unset
13634 .index TLS||server certificate, location of
13635 .index certificate||for server, location of
13636 The value of this option is expanded, and must then be the absolute path to a
13637 file which contains the server's certificates. The server's private key is also
13638 assumed to be in this file if \tls@_privatekey\ is unset. See chapter ~~CHAPTLS
13639 for further details.
13641 \**Note**\: The certificates defined by this option are used only when Exim is
13642 receiving incoming messages as a server. If you want to supply certificates for
13643 use when sending messages as a client, you must set the \tls@_certificate\
13644 option in the relevant \%smtp%\ transport.
13646 .conf tls@_crl string$**$ unset
13647 .index TLS||server certificate revocation list
13648 .index certificate||revocation list for server
13649 This option specifies a certificate revocation list. The expanded value must
13650 be the name of a file that contains a CRL in PEM format.
13652 .conf tls@_dhparam string$**$ unset
13653 .index TLS||D-H parameters for server
13654 The value of this option is expanded, and must then be the absolute path to
13655 a file which contains the server's DH parameter values.
13656 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
13657 ignored. See section ~~SECTopenvsgnu for further details.
13660 .conf tls@_on@_connect@_ports "string list" unset
13661 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
13662 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
13663 set up without waiting for the client to issue a \\STARTTLS\\ command. For
13664 further details, see section ~~SECTsupobssmt.
13667 .conf tls@_privatekey string$**$ unset
13668 .index TLS||server private key, location of
13669 The value of this option is expanded, and must then be the absolute path to a
13670 file which contains the server's private key. If this option is unset, the
13671 private key is assumed to be in the same file as the server's certificates. See
13672 chapter ~~CHAPTLS for further details.
13674 .conf tls@_remember@_esmtp boolean false
13675 .index TLS||esmtp state, remembering
13676 .index TLS||broken clients
13677 If this option is set true, Exim violates the RFCs by remembering that it is in
13678 `esmtp' state after successfully negotiating a TLS session. This provides
13679 support for broken clients that fail to send a new \\EHLO\\ after starting a
13682 .conf tls@_require@_ciphers string$**$ unset
13683 .index TLS||requiring specific ciphers
13684 .index cipher||requiring specific
13685 This option controls which ciphers can be used for incoming TLS connections.
13686 The \%smtp%\ transport has an option of the same name for controlling outgoing
13687 connections. This option is expanded for each connection, so can be varied for
13688 different clients if required. The value of this option must be a list of
13689 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
13690 in somewhat different ways.
13692 If GnuTLS is being used, the client controls the preference order of the
13695 Details are given in sections ~~SECTreqciphssl and ~~SECTreqciphgnu.
13697 .conf tls@_try@_verify@_hosts "host list$**$" unset
13698 .index TLS||client certificate verification
13699 .index certificate||verification of client
13700 See \tls@_verify@_hosts\ below.
13702 .conf tls@_verify@_certificates string$**$ unset
13703 .index TLS||client certificate verification
13704 .index certificate||verification of client
13705 The value of this option is expanded, and must then be the absolute path to
13706 a file containing permitted certificates for clients that
13707 match \tls@_verify@_hosts\ or \tls@_try@_verify@_hosts\. Alternatively, if you
13708 are using OpenSSL, you can set \tls@_verify@_certificates\ to the name of a
13709 directory containing certificate files. This does not work with GnuTLS; the
13710 option must be set to the name of a single file if you are using GnuTLS.
13712 .conf tls@_verify@_hosts "host list$**$" unset
13713 .index TLS||client certificate verification
13714 .index certificate||verification of client
13715 This option, along with \tls@_try@_verify@_hosts\, controls the checking of
13716 certificates from clients.
13717 The expected certificates are defined by \tls@_verify@_certificates\, which
13718 must be set. A configuration error occurs if either \tls@_verify@_hosts\ or
13719 \tls@_try@_verify@_hosts\ is set and \tls@_verify@_certificates\ is not set.
13721 Any client that matches \tls@_verify@_hosts\ is constrained by
13722 \tls@_verify@_certificates\. The client must present one of the listed
13723 certificates. If it does not, the connection is aborted.
13725 A weaker form of checking is provided by \tls@_try@_verify@_hosts\. If a client
13726 matches this option (but not \tls@_verify@_hosts\), Exim requests a
13727 certificate and checks it against \tls@_verify@_certificates\, but does not
13728 abort the connection if there is no certificate or if it does not match. This
13729 state can be detected in an ACL, which makes it possible to implement policies
13730 such as `accept for relay only if a verified certificate has been received, but
13731 accept for local delivery if encrypted, even without a verified certificate'.
13733 Client hosts that match neither of these lists are not asked to present
13736 .conf trusted@_groups "string list" unset
13737 .index trusted group
13738 .index group||trusted
13739 If this option is set, any process that is running in one of the listed groups,
13740 or which has one of them as a supplementary group, is trusted.
13741 The groups can be specified numerically or by name.
13742 See section ~~SECTtrustedadmin for details of what trusted callers are
13743 permitted to do. If neither \trusted@_groups\ nor \trusted@_users\ is set, only
13744 root and the Exim user are trusted.
13746 .conf trusted@_users "string list" unset
13747 .index trusted user
13748 .index user||trusted
13749 If this option is set, any process that is running as one of the listed users
13751 The users can be specified numerically or by name.
13752 See section ~~SECTtrustedadmin for details of what trusted callers are
13753 permitted to do. If neither \trusted@_groups\ nor \trusted@_users\ is set, only
13754 root and the Exim user are trusted.
13756 .index uid (user id)||unknown caller
13757 .conf unknown@_login string$**$ unset
13758 This is a specialized feature for use in unusual configurations. By default, if
13759 the uid of the caller of Exim cannot be looked up using \*getpwuid()*\, Exim
13760 gives up. The \unknown@_login\ option can be used to set a login name to be
13761 used in this circumstance. It is expanded, so values like \user@$caller@_uid\
13762 can be set. When \unknown@_login\ is used, the value of \unknown@_username\ is
13763 used for the user's real name (gecos field), unless this has been set by the
13766 .conf unknown@_username string unset
13767 See \unknown@_login\.
13769 .conf untrusted@_set@_sender "address list$**$" unset
13770 .index trusted user
13771 .index sender||setting by untrusted user
13772 .index untrusted user, setting sender
13773 .index user||untrusted setting sender
13774 .index envelope sender
13775 When an untrusted user submits a message to Exim using the standard input, Exim
13776 normally creates an envelope sender address from the user's login and the
13777 default qualification domain. Data from the \-f-\ option (for setting envelope
13778 senders on non-SMTP messages) or the SMTP \\MAIL\\ command (if \-bs-\ or \-bS-\
13779 is used) is ignored.
13781 However, untrusted users are permitted to set an empty envelope sender address,
13782 to declare that a message should never generate any bounces. For example:
13784 exim -f '<>' user@domain.example
13786 The \untrusted@_set@_sender\ option allows you to permit untrusted users to set
13787 other envelope sender addresses in a controlled way. When it is set, untrusted
13788 users are allowed to set envelope sender addresses that match any of the
13789 patterns in the list. Like all address lists, the string is expanded. The
13790 identity of the user is in \$sender@_ident$\, so you can, for example, restrict
13791 users to setting senders that start with their login ids
13792 followed by a hyphen
13793 by a setting like this:
13795 untrusted_set_sender = ^$sender_ident-
13797 If you want to allow untrusted users to set envelope sender addresses without
13798 restriction, you can use
13800 untrusted_set_sender = *
13802 The \untrusted@_set@_sender\ option applies to all forms of local input, but
13803 only to the setting of the envelope sender. It does not permit untrusted users
13804 to use the other options which trusted user can use to override message
13805 parameters. Furthermore, it does not stop Exim from removing an existing
13806 ::Sender:: header in the message, or from adding a ::Sender:: header if
13807 necessary. See \local__sender__retain\ and \local@_from@_check\ for ways of
13808 overriding these actions. The handling of the ::Sender:: header is also
13809 described in section ~~SECTthesenhea.
13811 The log line for a message's arrival shows the envelope sender following `<='.
13812 For local messages, the user's login always follows, after `U='. In \-bp-\
13813 displays, and in the Exim monitor, if an untrusted user sets an envelope sender
13814 address, the user's login is shown in parentheses after the sender address.
13816 .conf uucp@_from@_pattern string "see below"
13818 .index UUCP||`From' line
13819 Some applications that pass messages to an MTA via a command line interface use
13820 an initial line starting with `From' to pass the envelope sender. In
13821 particular, this is used by UUCP software. Exim recognizes such a line by means
13822 of a regular expression that is set in \uucp@_from@_pattern\. When the pattern
13823 matches, the sender address is constructed by expanding the contents of
13824 \uucp@_from@_sender\, provided that the caller of Exim is a trusted user. The
13825 default pattern recognizes lines in the following two forms:
13827 From ph10 Fri Jan 5 12:35 GMT 1996
13828 From ph10 Fri, 7 Jan 97 14:00:00 GMT
13830 The pattern can be seen by running
13832 exim -bP uucp_from_pattern
13834 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
13835 year in the second case. The first word after `From' is matched in the regular
13836 expression by a parenthesized subpattern. The default value for
13837 \uucp@_from@_sender\ is `$1', which therefore just uses this first word (`ph10'
13838 in the example above) as the message's sender. See also
13839 \ignore@_fromline@_hosts\.
13841 .conf uucp@_from@_sender string$**$ "$tt{@$1}"
13842 See \uucp@_from@_pattern\ above.
13844 .conf warn@_message@_file string unset
13845 .index warning of delay||customizing the message
13846 .index customizing||warning message
13847 This option defines a template file containing paragraphs of text to be used
13848 for constructing the warning message which is sent by Exim when a message has
13849 been on the queue for a specified amount of time, as specified by
13850 \delay@_warning\. Details of the file's contents are given in chapter
13851 ~~CHAPemsgcust. See also \bounce@_message@_file\.
13853 .conf write@_rejectlog boolean true
13854 .index reject log||disabling
13855 If this option is set false, Exim no longer writes anything to the reject log.
13856 See chapter ~~CHAPlog for details of what Exim writes to its logs.
13866 . ============================================================================
13867 .chapter Generic options for routers
13868 .rset CHAProutergeneric "~~chapter"
13869 .set runningfoot "generic router options"
13870 .index options||generic, for routers
13871 .index generic options||router
13873 This chapter describes the generic options that apply to all routers,
13874 identifying those that are preconditions. For a general description of how a
13875 router operates, see sections ~~SECTrunindrou and ~~SECTrouprecon. The latter
13876 specifies the order in which the preconditions are tested. The order of
13877 expansion of the options that provide data for a transport is: \errors@_to\,
13878 \headers@_add\, \headers@_remove\, \transport\.
13882 .conf address@_data string$**$ unset
13883 .index router||data attached to address
13884 The string is expanded just before the router is run, that is, after all the
13885 precondition tests have succeeded. If the expansion is forced to fail, the
13886 router declines. Other expansion failures cause delivery of the address to be
13889 When the expansion succeeds, the value is retained with the address, and can be
13890 accessed using the variable \$address@_data$\ in the current router, subsequent
13891 routers, and the eventual transport.
13893 \**Warning**\: if the current or any subsequent router is a \%redirect%\ router
13894 that runs a user's filter file, the contents of \$address@_data$\ are
13895 accessible in the filter. This is not normally a problem, because such data is
13896 usually either not confidential or it `belongs' to the current user, but if you
13897 do put confidential data into \$address@_data$\ you need to remember this
13900 Even if the router declines or passes, the value of \$address@_data$\ remains
13901 with the address, though it can be changed by another \address@_data\ setting
13902 on a subsequent router. If a router generates child addresses, the value of
13903 \$address@_data$\ propagates to them. This also applies to the special kind of
13904 `child' that is generated by a router with the \unseen\ option.
13906 The idea of \address@_data\ is that you can use it to look up a lot of data for
13907 the address once, and then pick out parts of the data later. For example, you
13908 could use a single LDAP lookup to return a string of the form
13910 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
13912 In the transport you could pick out the mailbox by a setting such as
13914 file = ${extract{mailbox}{$address_data}}
13916 This makes the configuration file less messy, and also reduces the number of
13917 lookups (though Exim does cache lookups).
13919 The \address@_data\ facility is also useful as a means of passing information
13920 from one router to another, and from a router to a transport. In addition, if
13922 \$address@_data$\ is set by a router when verifying a recipient address from an
13923 ACL, it remains available for use in the rest of the ACL statement. After
13924 verifying a sender, the value is transferred to \$sender@_address@_data$\.
13928 .conf address@_test "boolean (precondition)" true
13929 .index \-bt-\ option
13930 .index router||skipping when address testing
13931 If this option is set false, the router is skipped when routing is being tested
13932 by means of the \-bt-\ command line option. This can be a convenience when your
13933 first router sends messages to an external scanner, because it saves you
13934 having to set the `already scanned' indicator when testing real address
13938 .conf cannot@_route@_message string$**$ unset
13939 .index router||customizing `cannot route' message
13940 .index customizing||`cannot route' message
13941 This option specifies a text message that is used when an address cannot be
13942 routed because Exim has run out of routers. The default message is `Unrouteable
13943 address'. This option is useful only on routers that have \more\ set false, or
13944 on the very last router in a configuration, because the value that is used is
13945 taken from the last router that inspects an address. For example, using the
13946 default configuration, you could put:
13948 cannot_route_message = Remote domain not found in DNS
13950 on the first (\%dnslookup%\) router, and
13952 cannot_route_message = Unknown local user
13954 on the final router that checks for local users. If string expansion fails, the
13955 default message is used.
13956 Unless the expansion failure was explicitly forced, a message about the failure
13957 is written to the main and panic logs, in addition to the normal message about
13958 the routing failure.
13960 .conf caseful@_local@_part boolean false
13961 .index case of local parts
13962 .index router||case of local parts
13963 By default, routers handle the local parts of addresses in a case-insensitive
13964 manner, though the actual case is preserved for transmission with the message.
13965 If you want the case of letters to be significant in a router, you must set
13966 this option true. For individual router options that contain address or local
13967 part lists (for example, \local@_parts\), case-sensitive matching can be turned
13968 on by `+caseful' as a list item. See section ~~SECTcasletadd for more details.
13971 The value of the \$local@_part$\ variable is forced to lower case while a
13972 router is running unless \caseful@_local@_part\ is set. When a router assigns
13973 an address to a transport, the value of \$local@_part$\ when the transport runs
13974 is the same as it was in the router. Similarly, when a router generates child
13975 addresses by aliasing or forwarding, the values of \$original@_local@_part$\
13976 and \$parent@_local@_part$\ are those that were used by the redirecting router.
13978 This option applies to the processing of an address by a router. When a
13979 recipient address is being processed in an ACL, there is a separate \control\
13980 modifier that can be used to specify case-sensitive processing within the ACL
13981 (see section ~~SECTcontrols).
13984 .conf check@_local@_user "boolean (precondition)" false
13985 .index local user, checking in router
13986 .index router||checking for local user
13987 .index \(/etc/passwd)\
13988 When this option is true, Exim checks that the local part of the recipient
13989 address (with affixes removed if relevant) is the name of an account on the
13990 local system. The check is done by calling the \*getpwnam()*\ function rather
13991 than trying to read \(/etc/passwd)\ directly. This means that other methods of
13992 holding password data (such as NIS) are supported. If the local part is a local
13993 user, \$home$\ is set from the password data, and can be tested in other
13994 preconditions that are evaluated after this one (the order of evaluation is
13995 given in section ~~SECTrouprecon). However, the value of \$home$\ can be
13996 overridden by \router@_home@_directory\. If the local part is not a local user,
13997 the router is skipped.
13999 If you want to check that the local part is either the name of a local user
14000 or matches something else, you cannot combine \check@_local@_user\ with a
14001 setting of \local@_parts\, because that specifies the logical \*and*\ of the
14002 two conditions. However, you can use a \%passwd%\ lookup in a \local@_parts\
14003 setting to achieve this. For example:
14005 local_parts = passwd;$local_part : lsearch;/etc/other/users
14007 Note, however, that the side effects of \check@_local@_user\ (such as setting
14008 up a home directory) do not occur when a \%passwd%\ lookup is used in a
14009 \local@_parts\ (or any other) precondition.
14012 .conf condition "string$**$ (precondition)" unset
14013 .index router||customized precondition
14014 This option specifies a general precondition test that has to succeed for the
14015 router to be called. The \condition\ option is the last precondition to be
14016 evaluated (see section ~~SECTrouprecon). The string is expanded, and if the
14017 result is a forced failure, or an empty string, or one of the strings `0' or
14018 `no' or `false' (checked without regard to the case of the letters), the router
14019 is skipped, and the address is offered to the next one.
14021 If the result is any other value, the router is run (as this is the last
14022 precondition to be evaluated, all the other preconditions must be true).
14024 The \condition\ option provides a means of applying custom conditions to the
14025 running of routers. Note that in the case of a simple conditional expansion,
14026 the default expansion values are exactly what is wanted. For example:
14028 condition = ${if >{$message_age}{600}}
14030 Because of the default behaviour of the string expansion, this is equivalent to
14032 condition = ${if >{$message_age}{600}{true}{}}
14036 If the expansion fails (other than forced failure) delivery is deferred. Some
14037 of the other precondition options are common special cases that could in fact
14038 be specified using \condition\.
14041 .conf debug@_print string$**$ unset
14042 .index testing||variables in drivers
14043 If this option is set and debugging is enabled (see the \-d-\ command line
14044 option), the string is expanded and included in the debugging output.
14045 If expansion of the string fails, the error message is written to the debugging
14046 output, and Exim carries on processing.
14047 This option is provided to help with checking out the values of variables and
14048 so on when debugging router configurations. For example, if a \condition\
14049 option appears not to be working, \debug@_print\ can be used to output the
14050 variables it references. The output happens after checks for \domains\,
14051 \local@_parts\, and \check@_local@_user\ but before any other preconditions are
14052 tested. A newline is added to the text if it does not end with one.
14055 .conf disable@_logging boolean false
14056 If this option is set true, nothing is logged for any routing errors
14057 or for any deliveries caused by this router. You should not set this option
14058 unless you really, really know what you are doing. See also the generic
14059 transport option of the same name.
14061 .conf domains "domain list$**$ (precondition)" unset
14062 .index router||restricting to specific domains
14063 If this option is set, the router is skipped unless the current domain matches
14064 the list. If the match is achieved by means of a file lookup, the data that the
14065 lookup returned for the domain is placed in \$domain@_data$\ for use in string
14066 expansions of the driver's private options.
14067 See section ~~SECTrouprecon for a list of the order in which preconditions
14071 .conf driver string unset
14072 This option must always be set. It specifies which of the available routers is
14076 .conf errors@_to string$**$ unset
14077 .index envelope sender
14078 .index router||changing address for errors
14079 If a router successfully handles an address, it may queue the address for
14080 delivery or it may generate child addresses. In both cases, if there is a
14081 delivery problem during later processing, the resulting bounce message is sent
14082 to the address that results from expanding this string, provided that the
14083 address verifies successfully.
14084 \errors@_to\ is expanded before \headers@_add\, \headers@_remove\, and
14087 If the option is unset, or the expansion is forced to fail, or the result of
14088 the expansion fails to verify, the errors address associated with the incoming
14089 address is used. At top level, this is the envelope sender. A non-forced
14090 expansion failure causes delivery to be deferred.
14092 If an address for which \errors@_to\ has been set ends up being delivered over
14093 SMTP, the envelope sender for that delivery is the \errors@_to\ value, so that
14094 any bounces that are generated by other MTAs on the delivery route are also
14095 sent there. The most common use of \errors@_to\ is probably to direct mailing
14096 list bounces to the manager of the list, as described in section
14097 ~~SECTmailinglists.
14099 The \errors@_to\ setting associated with an address can be overridden if it
14100 subsequently passes through other routers that have their own \errors@_to\
14102 or if it is delivered by a transport with a \return@_path\ setting.
14104 You can set \errors@_to\ to the empty string by either of these settings:
14109 An expansion item that yields an empty string has the same effect. If you do
14110 this, a locally detected delivery error for addresses processed by this router
14111 no longer gives rise to a bounce message; the error is discarded. If the
14112 address is delivered to a remote host, the return path is set to \"<>"\, unless
14113 overridden by the \return@_path\ option on the transport.
14115 If for some reason you want to discard local errors, but use a non-empty
14116 \\MAIL\\ command for remote delivery, you can preserve the original return
14117 path in \$address@_data$\ in the router, and reinstate it in the transport by
14118 setting \return@_path\.
14121 .conf expn "boolean (precondition)" true
14122 .index address||testing
14123 .index testing||addresses
14124 .index \\EXPN\\||router skipping
14125 .index router||skipping for \\EXPN\\
14126 If this option is turned off, the router is skipped when testing an address
14127 as a result of processing an SMTP \\EXPN\\ command. You might, for example,
14128 want to turn it off on a router for users' \(.forward)\ files, while leaving it
14129 on for the system alias file.
14130 See section ~~SECTrouprecon for a list of the order in which preconditions
14133 The use of the SMTP \\EXPN\\ command is controlled by an ACL (see chapter
14134 ~~CHAPACL). When Exim is running an \\EXPN\\ command, it is similar to testing
14135 an address with \-bt-\. Compare \\VRFY\\, whose counterpart is \-bv-\.
14138 .conf fail@_verify boolean false
14139 .index router||forcing verification failure
14140 Setting this option has the effect of setting both \fail@_verify@_sender\ and
14141 \fail@_verify@_recipient\ to the same value.
14144 .conf fail@_verify@_recipient boolean false
14145 If this option is true and an address is accepted by this router when
14146 verifying a recipient, verification fails.
14149 .conf fail@_verify@_sender boolean false
14150 If this option is true and an address is accepted by this router when
14151 verifying a sender, verification fails.
14154 .conf fallback@_hosts "string list" unset
14155 .index router||fallback hosts
14156 .index fallback||hosts specified on router
14157 String expansion is not applied to this option. The argument must be a
14158 colon-separated list of host names or IP addresses. If a router queues an
14159 address for a remote transport, this host list is associated with the address,
14160 and used instead of the transport's fallback host list. If \hosts@_randomize\
14161 is set on the transport, the order of the list is randomized for each use. See
14162 the \fallback@_hosts\ option of the \%smtp%\ transport for further details.
14164 .conf group string$**$ "see below"
14165 .index gid (group id)||local delivery
14166 .index local transports||uid and gid
14167 .index transport||local
14168 .index router||setting group
14169 When a router queues an address for a transport, and the transport does not
14170 specify a group, the group given here is used when running the delivery
14172 The group may be specified numerically or by name. If expansion fails, the
14173 error is logged and delivery is deferred.
14174 The default is unset, unless \check@_local@_user\ is set, when the default
14175 is taken from the password information. See also \initgroups\ and \user\ and
14176 the discussion in chapter ~~CHAPenvironment.
14179 .conf headers@_add string$**$ unset
14180 .index header lines||adding
14181 .index router||adding header lines
14183 This option specifies a string of text that is expanded at routing time, and
14184 associated with any addresses that are accepted by the router. However, this
14185 option has no effect when an address is just being verified. The way in which
14186 the text is used to add header lines at transport time is described in section
14187 ~~SECTheadersaddrem.
14189 The \headers@_add\ option is expanded after \errors@_to\, but before
14190 \headers@_remove\ and \transport\. If the expanded string is empty, or if the
14191 expansion is forced to fail, the option has no effect. Other expansion failures
14192 are treated as configuration errors.
14194 \**Warning**\: The \headers@_add\ option cannot be used for a \%redirect%\
14195 router that has the \one@_time\ option set.
14199 .conf headers@_remove string$**$ unset
14200 .index header lines||removing
14201 .index router||removing header lines
14203 This option specifies a string of text that is expanded at routing time, and
14204 associated with any addresses that are accepted by the router. However, this
14205 option has no effect when an address is just being verified. The way in which
14206 the text is used to remove header lines at transport time is described in
14207 section ~~SECTheadersaddrem.
14209 The \headers@_remove\ option is expanded after \errors@_to\ and \headers@_add\,
14210 but before \transport\. If the expansion is forced to fail, the option has no
14211 effect. Other expansion failures are treated as configuration errors.
14213 \**Warning**\: The \headers@_remove\ option cannot be used for a \%redirect%\
14214 router that has the \one@_time\ option set.
14218 .conf ignore@_target@_hosts "host list$**$" unset
14219 .index IP address||discarding
14220 .index router||discarding IP addresses
14221 Although this option is a host list, it should normally contain IP address
14222 entries rather than names. If any host that is looked up by the router has an
14223 IP address that matches an item in this list, Exim behaves as if that IP
14224 address did not exist. This option allows you to cope with rogue DNS entries
14227 remote.domain.example. A 127.0.0.1
14231 ignore_target_hosts = 127.0.0.1
14233 on the relevant router. If all the hosts found by a \%dnslookup%\ router are
14234 discarded in this way, the router declines. In a conventional configuration, an
14235 attempt to mail to such a domain would normally provoke the `unrouteable
14236 domain' error, and an attempt to verify an address in the domain would fail.
14238 Similarly, if \ignore@_target@_hosts\ is set on an \%ipliteral%\ router, the
14239 router declines if presented with one of the listed addresses.
14241 This option may also be useful for ignoring link-local and site-local IPv6
14242 addresses. Because, like all host lists, the value of \ignore@_target@_hosts\
14243 is expanded before use as a list, it is possible to make it dependent on the
14244 domain that is being routed.
14246 During its expansion, \$host@_address$\ is set to the IP address that is being
14252 .index additional groups
14253 .index groups, additional
14254 .index local transports||uid and gid
14255 .index transport||local
14256 .conf initgroups boolean false
14257 If the router queues an address for a transport, and this option is true, and
14258 the uid supplied by the router is not overridden by the transport, the
14259 \*initgroups()*\ function is called when running the transport to ensure that
14260 any additional groups associated with the uid are set up. See also \group\ and
14261 \user\ and the discussion in chapter ~~CHAPenvironment.
14264 .conf local@_part@_prefix "string list (precondition)" unset
14265 .index router||prefix for local part
14266 .index prefix||for local part, used in router
14267 If this option is set, the router is skipped unless the local part
14268 starts with one of the given strings, or \local@_part@_prefix@_optional\ is
14270 See section ~~SECTrouprecon for a list of the order in which preconditions
14273 The list is scanned from left to right, and the first prefix that matches is
14274 used. A limited form of wildcard is available; if the prefix begins with an
14275 asterisk, it matches the longest possible sequence of arbitrary characters at
14276 the start of the local part. An asterisk should therefore always be followed by
14277 some character that does not occur in normal local parts.
14278 .index multiple mailboxes
14279 .index mailbox||multiple
14280 Wildcarding can be used to set up multiple user mailboxes, as described in
14281 section ~~SECTmulbox.
14283 During the testing of the \local@_parts\ option, and while the router is
14284 running, the prefix is removed from the local part, and is available in the
14285 expansion variable \$local@_part@_prefix$\. If the router accepts the address,
14286 this remains true during subsequent delivery.
14287 In particular, the local part that is transmitted in the \\RCPT\\ command
14288 for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default. This
14289 behaviour can be overridden by setting \rcpt@_include@_affixes\ true on the
14290 relevant transport.
14292 The prefix facility is commonly used to handle local parts of the form
14293 \owner-something\. Another common use is to support local parts of the form
14294 \real-username\ to bypass a user's \(.forward)\ file -- helpful when trying to
14295 tell a user their forwarding is broken -- by placing a router like this one
14296 immediately before the router that handles \(.forward)\ files:
14300 local_part_prefix = real-
14302 transport = local_delivery
14304 If both \local@_part@_prefix\ and \local@_part@_suffix\ are set for a router,
14305 both conditions must be met if not optional. Care must be taken if wildcards
14306 are used in both a prefix and a suffix on the same router. Different
14307 separator characters must be used to avoid ambiguity.
14309 .conf local@_part@_prefix@_optional boolean false
14310 See \local@_part@_prefix\ above.
14313 .conf local@_part@_suffix "string list (precondition)" unset
14314 .index router||suffix for local part
14315 .index suffix for local part, used in router
14316 This option operates in the same way as \local@_part@_prefix\, except that the
14317 local part must end (rather than start) with the given string, the
14318 \local@_part@_suffix@_optional\ option determines whether the suffix is
14319 mandatory, and the wildcard $*$ character, if present, must be the last
14320 character of the suffix. This option facility is commonly used to handle local
14321 parts of the form \something-request\ and multiple user mailboxes of the form
14324 .conf local@_part@_suffix@_optional boolean false
14325 See \local@_part@_suffix\ above.
14328 .conf local@_parts "local part list$**$ (precondition)" unset
14329 .index router||restricting to specific local parts
14330 .index local part||checking in router
14331 The router is run only if the local part of the address matches the list.
14332 See section ~~SECTrouprecon for a list of the order in which preconditions
14334 section ~~SECTlocparlis for a discussion of local part lists. Because the
14335 string is expanded, it is possible to make it depend on the domain, for
14338 local_parts = dbm;/usr/local/specials/$domain
14340 If the match is achieved by a lookup, the data that the lookup returned
14341 for the local part is placed in the variable \$local@_part@_data$\ for use in
14342 expansions of the router's private options. You might use this option, for
14343 example, if you have a large number of local virtual domains, and you want to
14344 send all postmaster mail to the same place without having to set up an alias in
14345 each virtual domain:
14349 local_parts = postmaster
14350 data = postmaster@real.domain.example
14354 .conf log@_as@_local boolean "see below"
14355 .index log||delivery line
14356 .index delivery||log line format
14357 Exim has two logging styles for delivery, the idea being to make local
14358 deliveries stand out more visibly from remote ones. In the `local' style, the
14359 recipient address is given just as the local part, without a domain. The use of
14360 this style is controlled by this option. It defaults to true for the \%accept%\
14361 router, and false for all the others.
14364 .conf more boolean$**$ true
14365 The result of string expansion for this option must be a valid boolean value,
14366 that is, one of the strings `yes', `no', `true', or `false'. Any other result
14367 causes an error, and delivery is deferred. If the expansion is forced to fail,
14368 the default value for the option (true) is used. Other failures cause delivery
14371 If this option is set false, and the router is run, but declines to handle the
14372 address, no further routers are tried, routing fails, and the address is
14374 .index \self\ option
14375 However, if the router explicitly passes an address to the following router by
14376 means of the setting
14380 or otherwise, the setting of \more\ is ignored. Also, the setting of \more\
14381 does not affect the behaviour if one of the precondition tests fails. In that
14382 case, the address is always passed to the next router.
14385 .conf pass@_on@_timeout boolean false
14386 .index timeout||of router
14387 .index router||timeout
14388 If a router times out during a host lookup, it normally causes deferral of the
14389 address. If \pass@_on@_timeout\ is set, the address is passed on to the next
14390 router, overriding \no@_more\. This may be helpful for systems that are
14391 intermittently connected to the Internet, or those that want to pass to a smart
14392 host any messages that cannot immediately be delivered.
14394 There are occasional other temporary errors that can occur while doing DNS
14395 lookups. They are treated in the same way as a timeout, and this option
14396 applies to all of them.
14399 .conf pass@_router string unset
14400 .index router||go to after `pass'
14401 When a router returns `pass', the address is normally handed on to the next
14402 router in sequence. This can be changed by setting \pass@_router\ to the name
14403 of another router. However (unlike \redirect@_router\) the named router must be
14404 below the current router, to avoid loops. Note that this option applies only to
14405 the special case of `pass'. It does not apply when a router returns `decline'.
14408 .conf redirect@_router string unset
14409 .index router||start at after redirection
14410 Sometimes an administrator knows that it is pointless to reprocess addresses
14411 generated from alias or forward files with the same router again. For
14412 example, if an alias file translates real names into login ids there is no
14413 point searching the alias file a second time, especially if it is a large file.
14415 The \redirect@_router\ option can be set to the name of any router instance. It
14416 causes the routing of any generated addresses to start at the named router
14417 instead of at the first router. This option has no effect if the router in
14418 which it is set does not generate new addresses.
14421 .conf require@_files "string list$**$ (precondition)" unset
14422 .index file||requiring for router
14423 .index router||requiring file existence
14424 This option provides a general mechanism for predicating the running of a
14425 router on the existence or non-existence of certain files or directories.
14426 Before running a router, as one of its precondition tests, Exim works its way
14427 through the \require@_files\ list, expanding each item separately.
14429 Because the list is split before expansion, any colons in expansion items must
14430 be doubled, or the facility for using a different list separator must be used.
14431 If any expansion is forced to fail, the item is ignored. Other expansion
14432 failures cause routing of the address to be deferred.
14434 If any expanded string is empty, it is ignored. Otherwise, except as described
14435 below, each string must be a fully qualified file path, optionally preceded by
14436 `!'. The paths are passed to the \*stat()*\ function to test for the existence
14437 of the files or directories. The router is skipped if any paths not preceded by
14438 `!' do not exist, or if any paths preceded by `!' do exist.
14441 If \*stat()*\ cannot determine whether a file exists or not, delivery of
14442 the message is deferred. This can happen when NFS-mounted filesystems are
14445 This option is checked after the \domains\, \local@_parts\, and \senders\
14446 options, so you cannot use it to check for the existence of a file in which to
14447 look up a domain, local part, or sender. (See section ~~SECTrouprecon for a
14448 full list of the order in which preconditions are evaluated.) However, as
14449 these options are all expanded, you can use the \exists\ expansion condition to
14450 make such tests. The \require@_files\ option is intended for checking files
14451 that the router may be going to use internally, or which are needed by a
14452 transport (for example \(.procmailrc)\).
14454 During delivery, the \*stat()*\ function is run as root, but there is a
14455 facility for some checking of the accessibility of a file by another user.
14456 This is not a proper permissions check, but just a `rough' check that
14457 operates as follows:
14459 If an item in a \require@_files\ list does not contain any forward slash
14460 characters, it is taken to be the user (and optional group, separated by a
14461 comma) to be checked for subsequent files in the list. If no group is specified
14462 but the user is specified symbolically, the gid associated with the uid is
14465 require_files = mail:/some/file
14466 require_files = $local_part:$home/.procmailrc
14468 If a user or group name in a \require@_files\ list does not exist, the
14469 \require@_files\ condition fails.
14471 Exim performs the check by scanning along the components of the file path, and
14472 checking the access for the given uid and gid. It checks for `x' access on
14473 directories, and `r' access on the final file. Note that this means that file
14474 access control lists, if the operating system has them, are ignored.
14476 \**Warning 1**\: When the router is being run to verify addresses for an
14477 incoming SMTP message, Exim is not running as root, but under its own uid. This
14478 may affect the result of a \require@_files\ check. In particular, \*stat()*\
14479 may yield the error \\EACCES\\ (`Permission denied'). This means that the Exim
14480 user is not permitted to read one of the directories on the file's path.
14482 \**Warning 2**\: Even when Exim is running as root while delivering a message,
14483 \*stat()*\ can yield \\EACCES\\ for a file in an NFS directory that is mounted
14484 without root access.
14486 In this case, if a check for access by a particular user is requested, Exim
14487 creates a subprocess that runs as that user, and tries the check again in that
14490 The default action for handling an unresolved \\EACCES\\ is to consider it to
14491 be caused by a configuration error,
14493 and routing is deferred because the existence or non-existence of the file
14494 cannot be determined. However, in some circumstances it may be desirable to
14495 treat this condition as if the file did not exist. If the file name (or the
14496 exclamation mark that precedes the file name for non-existence) is preceded by
14497 a plus sign, the \\EACCES\\ error is treated as if the file did not exist. For
14500 require_files = +/some/file
14502 If the router is not an essential part of verification (for example, it
14503 handles users' \(.forward)\ files), another solution is to set the \verify\
14504 option false so that the router is skipped when verifying.
14507 .conf retry@_use@_local@_part boolean "see below"
14508 .index hints database||retry keys
14509 .index local part||in retry keys
14510 When a delivery suffers a temporary routing failure, a retry record is created
14511 in Exim's hints database. For addresses whose routing depends only on the
14512 domain, the key for the retry record should not involve the local part, but for
14513 other addresses, both the domain and the local part should be included.
14514 Usually, remote routing is of the former kind, and local routing is of the
14517 This option controls whether the local part is used to form the key for retry
14518 hints for addresses that suffer temporary errors while being handled by this
14519 router. The default value is true for any router that has \check@_local@_user\
14520 set, and false otherwise. Note that this option does not apply to hints keys
14521 for transport delays; they are controlled by a generic transport option of the
14524 The setting of \retry@_use@_local@_part\ applies only to the router on which it
14525 appears. If the router generates child addresses, they are routed
14526 independently; this setting does not become attached to them.
14529 .conf router@_home@_directory string$**$ unset
14530 .index router||home directory for
14531 .index home directory||for router
14532 This option sets a home directory for use while the router is running. (Compare
14533 \transport__home@_directory\, which sets a home directory for later
14534 transporting.) In particular, if used on a \%redirect%\ router, this option
14535 sets a value for \$home$\ while a filter is running. The value is expanded;
14536 forced expansion failure causes the option to be ignored -- other failures
14537 cause the router to defer.
14539 Expansion of \router@_home@_directory\ happens immediately after the
14540 \check@_local@_user\ test (if configured), before any further expansions take
14542 (See section ~~SECTrouprecon for a list of the order in which preconditions
14544 While the router is running, \router__home@_directory\ overrides the value of
14545 \$home$\ that came from \check@_local@_user\.
14547 When a router accepts an address and routes it to a transport (including the
14548 cases when a redirect router generates a pipe, file, or autoreply delivery),
14549 the home directory setting for the transport is taken from the first of these
14550 values that is set:
14552 The \home@_directory\ option on the transport;
14554 The \transport@_home@_directory\ option on the router;
14556 The password data if \check@_local@_user\ is set on the router;
14558 The \router@_home@_directory\ option on the router.
14560 In other words, \router@_home@_directory\ overrides the password data for the
14561 router, but not for the transport.
14564 .conf self string "freeze"
14565 .index MX record||pointing to local host
14566 .index local host||MX pointing to
14567 This option applies to those routers that use a recipient address to find a
14568 list of remote hosts. Currently, these are the \%dnslookup%\, \%ipliteral%\,
14569 and \%manualroute%\ routers.
14570 Certain configurations of the \%queryprogram%\ router can also specify a list
14572 Usually such routers are configured to send the message to a remote host via an
14573 \%smtp%\ transport. The \self\ option specifies what happens when the first
14574 host on the list turns out to be the local host.
14575 The way in which Exim checks for the local host is described in section
14578 Normally this situation indicates either an error in Exim's configuration (for
14579 example, the router should be configured not to process this domain), or an
14580 error in the DNS (for example, the MX should not point to this host). For this
14581 reason, the default action is to log the incident, defer the address, and
14582 freeze the message. The following alternatives are provided for use in special
14587 Delivery of the message is tried again later, but the message is not frozen.
14589 \reroute: <<domain>>\
14591 The domain is changed to the given domain, and the address is passed back to
14592 be reprocessed by the routers. No rewriting of headers takes place. This
14593 behaviour is essentially a redirection.
14595 \reroute: rewrite: <<domain>>\
14597 The domain is changed to the given domain, and the address is passed back to be
14598 reprocessed by the routers. Any headers that contain the original domain are
14603 The router passes the address to the next router, or to the router named in the
14604 \pass@_router\ option if it is set.
14605 .index \more\ option
14606 This overrides \no@_more\.
14608 During subsequent routing and delivery, the variable
14609 \$self@_hostname$\ contains the name of the local host that the router
14610 encountered. This can be used to distinguish between different cases for hosts
14611 with multiple names. The combination
14616 ensures that only those addresses that routed to the local host are passed on.
14617 Without \no@_more\, addresses that were declined for other reasons would also
14618 be passed to the next router.
14622 Delivery fails and an error report is generated.
14626 .index local host||sending to
14627 The anomaly is ignored and the address is queued for the transport. This
14628 setting should be used with extreme caution. For an \%smtp%\ transport, it makes
14629 sense only in cases where the program that is listening on the SMTP port is not
14630 this version of Exim. That is, it must be some other MTA, or Exim with a
14631 different configuration file that handles the domain in another way.
14634 .conf senders "address list$**$ (precondition)" unset
14635 .index router||checking senders
14636 If this option is set, the router is skipped unless the message's sender
14637 address matches something on the list.
14638 See section ~~SECTrouprecon for a list of the order in which preconditions
14641 There are issues concerning verification when the running of routers is
14642 dependent on the sender. When Exim is verifying the address in an \errors@_to\
14643 setting, it sets the sender to the null string. When using the \-bt-\ option to
14644 check a configuration file, it is necessary also to use the \-f-\ option to set
14645 an appropriate sender. For incoming mail, the sender is unset when verifying
14646 the sender, but is available when verifying any recipients. If the SMTP
14647 \\VRFY\\ command is enabled, it must be used after \\MAIL\\ if the sender
14650 .conf translate@_ip@_address string$**$ unset
14651 .index IP address||translating
14652 .index packet radio
14653 .index router||IP address translation
14654 There exist some rare networking situations (for example, packet radio) where
14655 it is helpful to be able to translate IP addresses generated by normal routing
14656 mechanisms into other IP addresses, thus performing a kind of manual IP
14657 routing. This should be done only if the normal IP routing of the TCP/IP stack
14658 is inadequate or broken. Because this is an extremely uncommon requirement, the
14659 code to support this option is not included in the Exim binary unless
14660 \\SUPPORT__TRANSLATE__IP__ADDRESS\\=yes is set in \(Local/Makefile)\.
14662 The \translate@_ip@_address\ string is expanded for every IP address generated
14663 by the router, with the generated address set in \$host@_address$\. If the
14664 expansion is forced to fail, no action is taken.
14665 For any other expansion error, delivery of the message is deferred.
14666 If the result of the expansion is an IP address, that replaces the original
14667 address; otherwise the result is assumed to be a host name -- this is looked up
14668 using \*gethostbyname()*\ (or \*getipnodebyname()*\ when available) to produce
14669 one or more replacement IP addresses. For example, to subvert all IP addresses
14670 in some specific networks, this could be added to a router:
14672 $smc{translate@_ip@_address = @\
14673 @$@{lookup@{@$@{mask:@$host@_address/26@}@}lsearch@{/some/file@}@{@$value@}fail@}}
14675 The file would contain lines like
14677 10.2.3.128/26 some.host
14678 10.8.4.34/26 10.44.8.15
14680 You should not make use of this facility unless you really understand what you
14684 .conf transport string$**$ unset
14685 This option specifies the transport to be used when a router accepts an address
14686 and sets it up for delivery. A transport is never needed if a router is used
14687 only for verification. The value of the option is expanded at routing time,
14688 after the expansion of \errors@_to\, \headers@_add\, and \headers@_remove\, and
14689 result must be the name of one of the configured transports. If it is not,
14690 delivery is deferred.
14692 The \transport\ option is not used by the \%redirect%\ router, but it does have
14693 some private options that set up transports for pipe and file deliveries (see
14694 chapter ~~CHAPredirect).
14697 .conf transport@_current@_directory string$**$ unset
14698 .index current directory for local transport
14699 This option associates a current directory with any address that is routed
14700 to a local transport. This can happen either because a transport is
14701 explicitly configured for the router, or because it generates a delivery to a
14702 file or a pipe. During the delivery process (that is, at transport time), this
14703 option string is expanded and is set as the current directory, unless
14704 overridden by a setting on the transport.
14705 If the expansion fails for any reason, including forced failure, an error is
14706 logged, and delivery is deferred.
14707 See chapter ~~CHAPenvironment for details of the local delivery environment.
14711 .conf transport@_home@_directory string$**$ "see below"
14712 .index home directory||for local transport
14713 This option associates a home directory with any address that is routed to a
14714 local transport. This can happen either because a transport is explicitly
14715 configured for the router, or because it generates a delivery to a file or a
14716 pipe. During the delivery process (that is, at transport time), the option
14717 string is expanded and is set as the home directory, unless overridden by a
14718 setting of \home@_directory\ on the transport.
14719 If the expansion fails for any reason, including forced failure, an error is
14720 logged, and delivery is deferred.
14722 If the transport does not specify a home directory, and
14723 \transport@_home@_directory\ is not set for the router, the home directory for
14724 the tranport is taken from the password data if \check@_local@_user\ is set for
14725 the router. Otherwise it is taken from \router@_home@_directory\ if that option
14726 is set; if not, no home directory is set for the transport.
14728 See chapter ~~CHAPenvironment for further details of the local delivery
14733 .conf unseen boolean$**$ false
14734 .index router||carrying on after success
14735 The result of string expansion for this option must be a valid boolean value,
14736 that is, one of the strings `yes', `no', `true', or `false'. Any other result
14737 causes an error, and delivery is deferred. If the expansion is forced to fail,
14738 the default value for the option (false) is used. Other failures cause delivery
14741 When this option is set true, routing does not cease if the router accepts the
14742 address. Instead, a copy of the incoming address is passed to the next router,
14743 overriding a false setting of \more\. There is little point in setting \more\
14744 false if \unseen\ is always true, but it may be useful in cases when the value
14745 of \unseen\ contains expansion items (and therefore, presumably, is sometimes
14746 true and sometimes false).
14748 The \unseen\ option can be used to cause
14749 .index copy of message (\unseen\ option)
14750 copies of messages to be delivered to some other destination, while also
14751 carrying out a normal delivery. In effect, the current address is made into a
14752 `parent' that has two children -- one that is delivered as specified by this
14753 router, and a clone that goes on to be routed further.
14755 Header lines added to the address (or specified for removal) by this router or
14756 by previous routers affect the `unseen' copy of the message only. The clone
14757 that continues to be processed by further routers starts with no added headers
14758 and none specified for removal.
14760 However, any data that was set by the \address@_data\ option in the current or
14761 previous routers is passed on. Setting this option has a similar effect to the
14762 \unseen\ command qualifier in filter files.
14765 .conf user string$**$ "see below"
14766 .index uid (user id)||local delivery
14767 .index local transports||uid and gid
14768 .index transport||local
14769 .index router||user for filter processing
14770 .index filter||user for processing
14771 When a router queues an address for a transport, and the transport does not
14772 specify a user, the user given here is used when running the delivery process.
14773 The user may be specified numerically or by name. If expansion fails, the
14774 error is logged and delivery is deferred.
14775 This user is also used by the \%redirect%\ router when running a filter file.
14776 The default is unset, except when \check@_local@_user\ is set. In this case,
14777 the default is taken from the password information. If the user is specified as
14778 a name, and \group\ is not set, the group associated with the user is used. See
14779 also \initgroups\ and \group\ and the discussion in chapter ~~CHAPenvironment.
14782 .conf verify "boolean (precondition)" true
14783 Setting this option has the effect of setting \verify@_sender\ and
14784 \verify@_recipient\ to the same value.
14786 .conf verify@_only "boolean (precondition)" false
14787 .index \\EXPN\\||with \verify@_only\
14788 .index \-bv-\ option
14789 .index router||used only when verifying
14790 If this option is set, the router is used only when verifying an address or
14791 testing with the \-bv-\ option, not when actually doing a delivery, testing
14792 with the \-bt-\ option, or running the SMTP \\EXPN\\ command. It can be further
14793 restricted to verifying only senders or recipients by means of \verify@_sender\
14794 and \verify@_recipient\.
14796 \**Warning**\: When the router is being run to verify addresses for an incoming
14797 SMTP message, Exim is not running as root, but under its own uid. If the router
14798 accesses any files, you need to make sure that they are accessible to the Exim
14801 .conf verify@_recipient "boolean (precondition)" true
14802 If this option is false, the router is skipped when verifying recipient
14804 or testing recipient verification using \-bv-\.
14805 See section ~~SECTrouprecon for a list of the order in which preconditions
14808 .conf verify@_sender "boolean (precondition)" true
14809 If this option is false, the router is skipped when verifying sender addresses
14810 or testing sender verification using \-bvs-\.
14811 See section ~~SECTrouprecon for a list of the order in which preconditions
14824 . ============================================================================
14825 .chapter The accept router
14826 .set runningfoot "accept router"
14827 .index \%accept%\ router
14828 .index routers||\%accept%\
14829 The \%accept%\ router has no private options of its own. Unless it is being used
14830 purely for verification (see \verify@_only\) a transport is required to be
14831 defined by the generic \transport\ option. If the preconditions that are
14832 specified by generic options are met, the router accepts the address and queues
14833 it for the given transport. The most common use of this router is for setting
14834 up deliveries to local mailboxes. For example:
14838 domains = mydomain.example
14840 transport = local_delivery
14842 The \domains\ condition in this example checks the domain of the address, and
14843 \check@_local@_user\ checks that the local part is the login of a local user.
14844 When both preconditions are met, the \%accept%\ router runs, and queues the
14845 address for the \%local@_delivery%\ transport.
14856 . ============================================================================
14857 .chapter The dnslookup router
14858 .rset CHAPdnslookup "~~chapter"
14859 .set runningfoot "dnslookup router"
14860 .index \%dnslookup%\ router
14861 .index routers||\%dnslookup%\
14862 The \%dnslookup%\ router looks up the hosts that handle mail for the
14863 recipient's domain in the DNS. A transport must always be set for this router,
14864 unless \verify@_only\ is set.
14866 If SRV support is configured (see \check@_srv\ below), Exim first searches for
14867 SRV records. If none are found, or if SRV support is not configured,
14868 MX records are looked up. If no MX records exist, address records are sought.
14869 However, \mx@_domains\ can be set to disable the direct use of address records.
14871 MX records of equal priority are sorted by Exim into a random order. Exim then
14872 looks for address records for the host names obtained from MX or SRV records.
14873 When a host has more than one IP address, they are sorted into a random order,
14874 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
14875 IP addresses found are discarded by a setting of the \ignore@_target@_hosts\
14876 generic option, the router declines.
14878 Unless they have the highest priority (lowest MX value), MX records that point
14879 to the local host, or to any host name that matches \hosts__treat__as__local\,
14880 are discarded, together with any other MX records of equal or lower priority.
14882 .index MX record||pointing to local host
14883 .index local host||MX pointing to
14884 .index \self\ option||in \%dnslookup%\ router
14885 If the host pointed to by the highest priority MX record, or looked up as an
14886 address record, is the local host, or matches \hosts__treat__as__local\, what
14887 happens is controlled by the generic \self\ option.
14890 .section Problems with DNS lookups
14891 .rset SECTprowitdnsloo "~~chapter.~~section"
14892 There have been problems with DNS servers when SRV records are looked up.
14893 Some mis-behaving servers return a DNS error or timeout when a non-existent
14894 SRV record is sought. Similar problems have in the past been reported for
14895 MX records. The global \dns@_again@_means@_nonexist\ option can help with this
14896 problem, but it is heavy-handed because it is a global option.
14898 For this reason, there are two options, \srv@_fail@_domains\ and
14899 \mx@_fail@_domains\, that control what happens when a DNS lookup in a
14900 \%dnslookup%\ router results in a DNS failure or a `try again' response. If an
14901 attempt to look up an SRV or MX record causes one of these results, and the
14902 domain matches the relevant list, Exim behaves as if the DNS had responded `no
14903 such record'. In the case of an SRV lookup, this means that the router proceeds
14904 to look for MX records; in the case of an MX lookup, it proceeds to look for A
14905 or AAAA records, unless the domain matches \mx@_domains\, in which case routing
14910 .section Private options for dnslookup
14911 The private options for the \%dnslookup%\ router are as follows:
14914 .startconf dnslookup
14916 .index options||\%dnslookup%\ router
14917 .conf check@_secondary@_mx boolean false
14918 .index MX record||checking for secondary
14919 If this option is set, the router declines unless the local host is found in
14920 (and removed from) the list of hosts obtained by MX lookup. This can be used to
14921 process domains for which the local host is a secondary mail exchanger
14922 differently to other domains. The way in which Exim decides whether a host is
14923 the local host is described in section ~~SECTreclocipadd.
14925 .conf check@_srv string$**$ unset
14926 .index SRV record||enabling use of
14927 The \%dnslookup%\ router supports the use of SRV records (see RFC 2782) in
14928 addition to MX and address records. The support is disabled by default. To
14929 enable SRV support, set the \check@_srv\ option to the name of the service
14930 required. For example,
14934 looks for SRV records that refer to the normal smtp service. The option is
14935 expanded, so the service name can vary from message to message or address
14936 to address. This might be helpful if SRV records are being used for a
14937 submission service. If the expansion is forced to fail, the \check@_srv\
14938 option is ignored, and the router proceeds to look for MX records in the
14941 When the expansion succeeds, the router searches first for SRV records for
14942 the given service (it assumes TCP protocol). A single SRV record with a
14943 host name that consists of just a single dot indicates `no such service for
14944 this domain'; if this is encountered, the router declines. If other kinds of
14945 SRV record are found, they are used to construct a host list for delivery
14946 according to the rules of RFC 2782. MX records are not sought in this case.
14948 When no SRV records are found, MX records (and address records) are sought in
14949 the traditional way. In other words, SRV records take precedence over MX
14950 records, just as MX records take precedence over address records. Note that
14951 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
14952 defined it. It is apparently believed that MX records are sufficient for email
14953 and that SRV records should not be used for this purpose. However, SRV records
14954 have an additional `weight' feature which some people might find useful when
14955 trying to split an SMTP load between hosts of different power.
14958 See section ~~SECTprowitdnsloo above for a discussion of Exim's behaviour when
14959 there is a DNS lookup error.
14962 .conf mx@_domains "domain list$**$" unset
14963 .index MX record||required to exist
14964 .index SRV record||required to exist
14965 A domain that matches \mx@_domains\ is required to have either an MX or an SRV
14966 record in order to be recognised. (The name of this option could be improved.)
14967 For example, if all the mail hosts in \*fict.example*\ are known to have MX
14968 records, except for those in \*discworld.fict.example*\, you could use this
14971 mx_domains = ! *.discworld.fict.example : *.fict.example
14973 This specifies that messages addressed to a domain that matches the list but
14974 has no MX record should be bounced immediately instead of being routed using
14975 the address record.
14978 .conf mx@_fail@_domains "domain list$**$" unset
14979 If the DNS lookup for MX records for one of the domains in this list causes a
14980 DNS lookup error, Exim behaves as if no MX records were found. See section
14981 ~~SECTprowitdnsloo for more discussion.
14985 .conf qualify@_single boolean true
14986 .index DNS||resolver options
14987 .index DNS||qualifying single-component names
14988 When this option is true, the resolver option \\RES@_DEFNAMES\\ is set for DNS
14989 lookups. Typically, but not standardly, this causes the resolver to qualify
14990 single-component names with the default domain. For example, on a machine
14991 called \*dictionary.ref.example*\, the domain \*thesaurus*\ would be changed to
14992 \*thesaurus.ref.example*\ inside the resolver. For details of what your resolver
14993 actually does, consult your man pages for \*resolver*\ and \*resolv.conf*\.
14996 .conf rewrite@_headers boolean true
14997 .index rewriting||header lines
14998 .index header lines||rewriting
14999 If the domain name in the address that is being processed is not fully
15000 qualified, it may be expanded to its full form by a DNS lookup. For example, if
15001 an address is specified as \*dormouse@@teaparty*\, the domain might be
15002 expanded to \*teaparty.wonderland.fict.example*\. Domain expansion can also
15003 occur as a result of setting the \widen@_domains\ option. If \rewrite@_headers\
15004 is true, all occurrences of the abbreviated domain name in any ::Bcc::, ::Cc::,
15005 ::From::, ::Reply-to::, ::Sender::, and ::To:: header lines of the message are
15006 rewritten with the full domain name.
15008 This option should be turned off only when it is known that no message is
15009 ever going to be sent outside an environment where the abbreviation makes
15012 When an MX record is looked up in the DNS and matches a wildcard record, name
15013 servers normally return a record containing the name that has been looked up,
15014 making it impossible to detect whether a wildcard was present or not. However,
15015 some name servers have recently been seen to return the wildcard entry. If the
15016 name returned by a DNS lookup begins with an asterisk, it is not used for
15019 .conf same@_domain@_copy@_routing boolean false
15020 .index address||copying routing
15021 Addresses with the same domain are normally routed by the \%dnslookup%\ router
15022 to the same list of hosts. However, this cannot be presumed, because the router
15023 options and preconditions may refer to the local part of the address. By
15024 default, therefore, Exim routes each address in a message independently. DNS
15025 servers run caches, so repeated DNS lookups are not normally expensive, and in
15026 any case, personal messages rarely have more than a few recipients.
15028 If you are running mailing lists with large numbers of subscribers at the same
15029 domain, and you are using a \%dnslookup%\ router which is independent of the
15030 local part, you can set \same__domain__copy@_routing\ to bypass repeated DNS
15031 lookups for identical domains in one message. In this case, when \%dnslookup%\
15032 routes an address to a remote transport, any other unrouted addresses in the
15033 message that have the same domain are automatically given the same routing
15034 without processing them independently,
15035 provided the following conditions are met:
15037 No router that processed the address specified \headers@_add\ or
15040 The router did not change the address in any way, for example, by `widening'
15045 .conf search@_parents boolean false
15046 .index DNS||resolver options
15047 When this option is true, the resolver option \\RES@_DNSRCH\\ is set for DNS
15048 lookups. This is different from the \qualify@_single\ option in that it applies
15049 to domains containing dots. Typically, but not standardly, it causes the
15050 resolver to search for the name in the current domain and in parent domains.
15051 For example, on a machine in the \*fict.example*\ domain, if looking up
15052 \*teaparty.wonderland*\ failed, the resolver would try
15053 \*teaparty.wonderland.fict.example*\. For details of what your resolver
15054 actually does, consult your man pages for \*resolver*\ and \*resolv.conf*\.
15056 Setting this option true can cause problems in domains that have a wildcard MX
15057 record, because any domain that does not have its own MX record matches the
15062 .conf srv@_fail@_domains "domain list$**$" unset
15063 If the DNS lookup for SRV records for one of the domains in this list causes a
15064 DNS lookup error, Exim behaves as if no SRV records were found. See section
15065 ~~SECTprowitdnsloo for more discussion.
15069 .conf widen@_domains "string list" unset
15070 .index domain||partial, widening
15071 If a DNS lookup fails and this option is set, each of its strings in turn is
15072 added onto the end of the domain, and the lookup is tried again. For example,
15075 widen_domains = fict.example:ref.example
15077 is set and a lookup of \*klingon.dictionary*\ fails,
15078 \*klingon.dictionary.fict.example*\ is looked up, and if this fails,
15079 \*klingon.dictionary.ref.example*\ is tried. Note that the \qualify@_single\
15080 and \search@_parents\ options can cause some widening to be undertaken inside
15085 .section Effect of qualify@_single and search@_parents
15086 When a domain from an envelope recipient is changed by the resolver as a result
15087 of the \qualify@_single\ or \search@_parents\ options, Exim rewrites the
15088 corresponding address in the message's header lines unless \rewrite@_headers\
15089 is set false. Exim then re-routes the address, using the full domain.
15091 These two options affect only the DNS lookup that takes place inside the router
15092 for the domain of the address that is being routed. They do not affect lookups
15093 such as that implied by
15097 that may happen while processing a router precondition before the router is
15098 entered. No widening ever takes place for these lookups.
15112 . ============================================================================
15113 .chapter The ipliteral router
15114 .set runningfoot "ipliteral router"
15115 .index \%ipliteral%\ router
15116 .index domain literal||routing
15117 .index routers||\%ipliteral%\
15118 This router has no private options. Unless it is being used purely for
15119 verification (see \verify@_only\) a transport is required to be defined by the
15120 generic \transport\ option. The router accepts the address if its domain part
15121 takes the form of an RFC 2822 domain literal, that is, an IP address enclosed
15122 in square brackets. For example, this router handles the address
15126 by setting up delivery to the host with that IP address.
15128 If the IP address matches something in \ignore@_target@_hosts\, the router
15130 .index \self\ option||in \%ipliteral%\ router
15131 If an IP literal turns out to refer to the local host, the generic \self\
15132 option determines what happens.
15134 The RFCs require support for domain literals; however, their use is
15135 controversial in today's Internet. If you want to use this router, you must
15136 also set the main configuration option \allow@_domain@_literals\. Otherwise,
15137 Exim will not recognize the domain literal syntax in addresses.
15145 . ============================================================================
15146 .chapter The iplookup router
15147 .set runningfoot "iplookup router"
15148 .index \%iplookup%\ router
15149 .index routers||\%iplookup%\
15150 The \%iplookup%\ router was written to fulfil a specific requirement in
15151 Cambridge University (which in fact no longer exists). For this reason, it is
15152 not included in the binary of Exim by default. If you want to include it, you
15155 ROUTER_IPLOOKUP=yes
15157 in your \(Local/Makefile)\ configuration file.
15159 The \%iplookup%\ router routes an address by sending it over a TCP or UDP
15160 connection to one or more specific hosts. The host can then return the same or
15161 a different address -- in effect rewriting the recipient address in the
15162 message's envelope. The new address is then passed on to subsequent routers.
15165 If this process fails, the address can be passed on to
15166 other routers, or delivery can be deferred.
15168 Background, for those that are interested: We have an Oracle database of all
15169 Cambridge users, and one of the items of data it maintains for each user is
15170 where to send mail addressed to \*user@@cam.ac.uk*\. The MX records for
15171 \*cam.ac.uk*\ point to a central machine that has a large alias list that is
15172 abstracted from the database. Mail from outside is switched by this system, and
15173 originally internal mail was also done this way. However, this resulted in a
15174 fair number of messages travelling from some of our larger systems to the
15175 switch and back again. The Oracle machine now runs a UDP service that can be
15176 called by the \%iplookup%\ router in Exim to find out where \*user@@cam.ac.uk*\
15177 addresses really have to go; this saves passing through the central switch, and
15178 in many cases saves doing any remote delivery at all.
15180 Since \%iplookup%\ is just a rewriting router, a transport must not be
15183 .startconf iplookup
15184 .index options||\%iplookup%\ router
15186 .conf hosts string unset
15187 This option must be supplied. Its value is a colon-separated list of host
15188 names. The hosts are looked up using \*gethostbyname()*\
15189 (or \*getipnodebyname()*\ when available)
15190 and are tried in order until one responds to the query. If none respond, what
15191 happens is controlled by \optional\.
15193 .conf optional boolean false
15194 If \optional\ is true, if no response is obtained from any host, the address is
15195 passed to the next router, overriding \no@_more\. If \optional\ is false,
15196 delivery to the address is deferred.
15198 .conf port integer 0
15199 .index port||\%iplookup%\ router
15200 This option must be supplied. It specifies the port number for the TCP or UDP
15203 .conf protocol string "udp"
15204 This option can be set to `udp' or `tcp' to specify which of the two protocols
15207 .conf query string$**$ "$tt{@$local@_part@@@$domain @$local@_part@@@$domain}"
15208 This defines the content of the query that is sent to the remote hosts. The
15209 repetition serves as a way of checking that a response is to the correct query
15210 in the default case (see \response@_pattern\ below).
15212 .conf reroute string$**$ unset
15213 If this option is not set, the rerouted address is precisely the byte string
15214 returned by the remote host, up to the first white space, if any. If set, the
15215 string is expanded to form the rerouted address. It can include parts matched
15216 in the response by \response@_pattern\ by means of numeric variables such as
15217 \$1$\, \$2$\, etc. The variable \$0$\ refers to the entire input string,
15218 whether or not a pattern is in use. In all cases, the rerouted address must end
15219 up in the form \*local@_part@@domain*\.
15221 .conf response@_pattern string unset
15222 This option can be set to a regular expression that is applied to the string
15223 returned from the remote host. If the pattern does not match the response, the
15224 router declines. If \response@_pattern\ is not set, no checking of the response
15225 is done, unless the query was defaulted, in which case there is a check that
15226 the text returned after the first white space is the original address. This
15227 checks that the answer that has been received is in response to the correct
15228 question. For example, if the response is just a new domain, the following
15231 response_pattern = ^([^@]+)$
15232 reroute = $local_part@$1
15235 .conf timeout time 5s
15236 This specifies the amount of time to wait for a response from the remote
15237 machine. The same timeout is used for the \*connect()*\ function for a TCP
15238 call. It does not apply to UDP.
15249 . ============================================================================
15250 .chapter The manualroute router
15251 .set runningfoot "manualroute router"
15252 .index \%manualroute%\ router
15253 .index routers||\%manualroute%\
15254 .index domain||manually routing
15255 The \%manualroute%\ router is so-called because it provides a way of manually
15256 routing an address according to its domain. It is mainly used when you want to
15257 route addresses to remote hosts according to your own rules, bypassing the
15258 normal DNS routing that looks up MX records. However, \%manualroute%\ can also
15259 route to local transports, a facility that may be useful if you want to save
15260 messages for dial-in hosts in local files.
15262 The \%manualroute%\ router compares a list of domain patterns with the domain it
15263 is trying to route. If there is no match, the router declines. Each pattern has
15264 associated with it a list of hosts and some other optional data, which may
15265 include a transport. The combination of a pattern and its data is called a
15266 `routing rule'. For patterns that do not have an associated transport, the
15267 generic \transport\ option must specify a transport, unless the router is being
15268 used purely for verification (see \verify@_only\).
15270 In the case of verification, matching the domain pattern is sufficient for the
15271 router to accept the address. When actually routing an address for delivery,
15272 an address that matches a domain pattern is queued for the associated
15273 transport. If the transport is not a local one, a host list must be associated
15274 with the pattern; IP addresses are looked up for the hosts, and these are
15275 passed to the transport along with the mail address. For local transports, a
15276 host list is optional. If it is present, it is passed in \$host$\ as a single
15279 The list of routing rules can be provided as an inline string in \route@_list\,
15280 or the data can be obtained by looking up the domain in a file or database by
15281 setting \route@_data\. Only one of these settings may appear in any one
15282 instance of \%manualroute%\. The format of routing rules is described below,
15283 following the list of private options.
15285 .section Private options for manualroute
15286 .rset SECTprioptman "~~chapter.~~section"
15288 The private options for the \%manualroute%\ router are as follows:
15290 .startconf manualroute
15291 .index options||\%manualroute%\ router
15293 .conf host@_find@_failed string "freeze"
15294 This option controls what happens when \%manualroute%\ tries to find an IP
15295 address for a host, and the host does not exist. The option can be set to one
15304 The default assumes that this state is a serious configuration error. The
15305 difference between `pass' and `decline' is that the former forces the address
15306 to be passed to the next router (or the router defined by \pass@_router\),
15307 .index \more\ option
15308 overriding \no@_more\, whereas the latter passes the address to the next router
15309 only if \more\ is true.
15311 This option applies only to a definite `does not exist' state; if a host lookup
15312 gets a temporary error, delivery is deferred unless the generic
15313 \pass@_on@_timeout\ option is set.
15315 .conf hosts@_randomize boolean false
15316 .index randomized host list
15317 .index host||list of, randomized
15318 If this option is set, the order of the items in a host list in a routing rule
15319 is randomized each time the list is used, unless an option in the routing rule
15320 overrides (see below). Randomizing the order of a host list can be used to do
15321 crude load sharing. However, if more than one mail address is routed by the
15322 same router to the same host list, the host lists are considered to be the same
15323 (even though they may be randomized into different orders) for the purpose of
15324 deciding whether to batch the deliveries into a single SMTP transaction.
15326 When \hosts@_randomize\ is true, a host list may be split
15327 into groups whose order is separately randomized. This makes it possible to
15328 set up MX-like behaviour. The boundaries between groups are indicated by an
15329 item that is just \"+"\ in the host list. For example:
15331 route_list = * host1:host2:host3:+:host4:host5
15333 The order of the first three hosts and the order of the last two hosts is
15334 randomized for each use, but the first three always end up before the last two.
15335 If \hosts@_randomize\ is not set, a \"+"\ item in the list is ignored. If a
15336 randomized host list is passed to an \%smtp%\ transport that also has
15337 \hosts@_randomize set\, the list is not re-randomized.
15339 .conf route@_data string$**$ unset
15340 If this option is set, it must expand to yield the data part of a routing rule.
15341 Typically, the expansion string includes a lookup based on the domain. For
15344 route_data = ${lookup{$domain}dbm{/etc/routes}}
15346 If the expansion is forced to fail, or the result is an empty string, the
15347 router declines. Other kinds of expansion failure cause delivery to be
15350 .conf route@_list "string list, semicolon-separated" unset
15351 This string is a list of routing rules, in the form defined below. Note that,
15352 unlike most string lists, the items are separated by semicolons. This is so
15353 that they may contain colon-separated host lists.
15355 .conf same@_domain@_copy@_routing boolean false
15356 .index address||copying routing
15357 Addresses with the same domain are normally routed by the \%manualroute%\ router
15358 to the same list of hosts. However, this cannot be presumed, because the router
15359 options and preconditions may refer to the local part of the address. By
15360 default, therefore, Exim routes each address in a message independently. DNS
15361 servers run caches, so repeated DNS lookups are not normally expensive, and in
15362 any case, personal messages rarely have more than a few recipients.
15364 If you are running mailing lists with large numbers of subscribers at the same
15365 domain, and you are using a \%manualroute%\ router which is independent of the
15366 local part, you can set \same@_domain@_copy@_routing\ to bypass repeated DNS
15367 lookups for identical domains in one message. In this case, when \%manualroute%\
15368 routes an address to a remote transport, any other unrouted addresses in the
15369 message that have the same domain are automatically given the same routing
15370 without processing them independently. However, this is only done if
15371 \headers@_add\ and \headers@_remove\ are unset.
15376 .section Routing rules in route@_list
15377 The value of \route@_list\ is a string consisting of a sequence of routing
15378 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
15379 entered as two semicolons. Empty rules are ignored. The format of each rule is
15381 <<domain pattern>> <<list of hosts>> <<options>>
15383 The following example contains two rules, each with a simple domain pattern and
15387 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
15388 thes.ref.example mail-3.ref.example:mail-4.ref.example
15390 The three parts of a rule are separated by white space. The pattern and the
15391 list of hosts can be enclosed in quotes if necessary, and if they are, the
15392 usual quoting rules apply. Each rule in a \route@_list\ must start with a
15393 single domain pattern, which is the only mandatory item in the rule. The
15394 pattern is in the same format as one item in a domain list (see section
15396 except that it may not be the name of an interpolated file.
15397 That is, it may be wildcarded, or a regular expression, or a file or database
15398 lookup (with semicolons doubled, because of the use of semicolon as a separator
15399 in a \route@_list\).
15401 The rules in \route@_list\ are searched in order until one of the patterns
15402 matches the domain that is being routed. The list of hosts and then options are
15403 then used as described below. If there is no match, the router declines. When
15404 \route@_list\ is set, \route@_data\ must not be set.
15407 .section Routing rules in route@_data
15408 The use of \route@_list\ is convenient when there are only a small number of
15409 routing rules. For larger numbers, it is easier to use a file or database to
15410 hold the routing information, and use the \route@_data\ option instead.
15411 The value of \route@_data\ is a list of hosts, followed by (optional) options.
15412 Most commonly, \route@_data\ is set as a string that contains an
15413 expansion lookup. For example, suppose we place two routing rules in a file
15416 dict.ref.example: mail-1.ref.example:mail-2.ref.example
15417 thes.ref.example: mail-3.ref.example:mail-4.ref.example
15419 This data can be accessed by setting
15421 route_data = ${lookup{$domain}lsearch{/the/file/name}}
15423 Failure of the lookup results in an empty string, causing the router to
15424 decline. However, you do not have to use a lookup in \route@_data\. The only
15425 requirement is that the result of expanding the string is a list of hosts,
15426 possibly followed by options, separated by white space. The list of hosts must
15427 be enclosed in quotes if it contains white space.
15431 .section Format of the list of hosts
15432 A list of hosts, whether obtained via \route@_data\ or \route@_list\, is always
15433 separately expanded before use. If the expansion fails, the router declines.
15434 The result of the expansion must be a colon-separated list of names and/or
15435 IP addresses. IP addresses are not enclosed in brackets.
15437 If the list of hosts was obtained from a \route@_list\ item, the following
15438 variables are set during its expansion:
15439 .index numerical variables (\$1$\, \$2$\, etc)||in \%manualroute%\ router
15441 If the domain was matched against a regular expression, the numeric variables
15442 \$1$\, \$2$\, etc. may be set.
15444 \$0$\ is always set to the entire domain.
15446 \$1$\ is also set when partial matching is done in a file lookup.
15449 If the pattern that matched the domain was a lookup item, the data that was
15450 looked up is available in the expansion variable \$value$\.
15454 .section How the list of hosts is used
15455 When an address is routed to an \%smtp%\ transport by \%manualroute%\, each of
15456 the hosts is tried, in the order specified, when carrying out the SMTP
15457 delivery. However, the order can be changed by setting the \hosts@_randomize\
15458 option, either on the router (see section ~~SECTprioptman above), or on the
15461 Hosts may be listed by name or by IP address. An unadorned name in the list of
15462 hosts is interpreted as a host name. A name that is followed by \"/MX"\ is
15463 interpreted as an indirection to a sublist of hosts obtained by looking up MX
15464 records in the DNS. For example:
15466 route_list = * x.y.z:p.q.r/MX:e.f.g
15468 If the \hosts@_randomize\ option is set, the order of the items in the list is
15469 randomized before any lookups are done. Exim then scans the list; for any name
15470 that is not followed by \"/MX"\ it looks up an IP address. If this turns out to
15471 be an interface on the local host and the item is not the first in the list,
15472 Exim discards it and any subsequent items. If it is the first item, what
15473 happens is controlled by the
15474 .index \self\ option||in \%manualroute%\ router
15475 \self\ option of the router.
15477 A name on the list that is followed by \"/MX"\ is replaced with the list of
15478 hosts obtained by looking up MX records for the name. This is always a DNS
15479 lookup; the \bydns\ and \byname\ options (see section ~~SECThowoptused below)
15480 are not relevant here. The order of these hosts is determined by the preference
15481 values in the MX records, according to the usual rules. Because randomizing
15482 happens before the MX lookup, it does not affect the order that is defined by
15485 If the local host is present in the sublist obtained from MX records, but is
15486 not the most preferred host in that list, it and any equally or less
15487 preferred hosts are removed before the sublist is inserted into the main list.
15489 If the local host is the most preferred host in the MX list, what happens
15490 depends on where in the original list of hosts the \"/MX"\ item appears. If it
15491 is not the first item (that is, there are previous hosts in the main list),
15492 Exim discards this name and any subsequent items in the main list.
15494 If the MX item is first in the list of hosts, and the local host is the
15495 most preferred host, what happens is controlled by the \self\ option of the
15498 DNS failures when lookup up the MX records are treated in the same way as DNS
15499 failures when looking up IP addresses: \pass@_on@_timeout\ and
15500 \host@_find@_failed\ are used when relevant.
15502 The generic \ignore@_target@_hosts\ option applies to all hosts in the list,
15503 whether obtained from an MX lookup or not.
15506 .section How the options are used
15507 .rset SECThowoptused "~~chapter.~~section"
15508 The options are a sequence of words; in practice no more than three are ever
15509 present. One of the words can be the name of a transport; this overrides the
15510 \transport\ option on the router for this particular routing rule only. The
15511 other words (if present) control randomization of the list of hosts on a
15512 per-rule basis, and how the IP addresses of the hosts are to be found when
15513 routing to a remote transport. These options are as follows:
15515 \randomize\: randomize the order of the hosts in this list, overriding the
15516 setting of \hosts@_randomize\ for this routing rule only.
15518 \no@_randomize\: do not randomize the order of the hosts in this list,
15519 overriding the setting of \hosts@_randomize\ for this routing rule only.
15521 \byname\: use \*getipnodebyname()*\ (\*gethostbyname()*\ on older systems) to
15522 find IP addresses. This function may ultimately cause a DNS lookup, but it may
15523 also look in \(/etc/hosts)\ or other sources of information.
15525 \bydns\: look up address records for the hosts directly in the DNS; fail if
15526 no address records are found. If there is a temporary DNS error (such as a
15527 timeout), delivery is deferred.
15531 route_list = domain1 host1:host2:host3 randomize bydns;\
15532 domain2 host4:host5
15534 If neither \byname\ nor \bydns\ is given, Exim behaves as follows: First, a DNS
15535 lookup is done. If this yields anything other than \\HOST@_NOT@_FOUND\\, that
15536 result is used. Otherwise, Exim goes on to try a call to \*getipnodebyname()*\
15537 or \*gethostbyname()*\, and the result of the lookup is the result of that
15540 \**Warning**\: It has been discovered that on some systems, if a DNS lookup
15541 called via \*getipnodebyname()*\ times out, \\HOST@_NOT@_FOUND\\ is returned
15542 instead of \\TRY@_AGAIN\\. That is why the default action is to try a DNS
15543 lookup first. Only if that gives a definite `no such host' is the local
15548 If no IP address for a host can be found, what happens is controlled by the
15549 \host@_find@_failed\ option.
15551 When an address is routed to a local transport, IP addresses are not looked up.
15552 The host list is passed to the transport in the \$host$\ variable.
15555 .section Manualroute examples
15556 In some of the examples that follow, the presence of the \remote@_smtp\
15557 transport, as defined in the default configuration file, is assumed:
15560 .index smart host||example router
15561 The \%manualroute%\ router can be used to forward all external mail to a
15562 \*smart host*\. If you have set up, in the main part of the configuration, a
15563 named domain list that contains your local domains, for example,
15565 domainlist local_domains = my.domain.example
15567 you can arrange for all other domains to be routed to a smart host by making
15568 your first router something like this:
15571 driver = manualroute
15572 domains = !+local_domains
15573 transport = remote_smtp
15574 route_list = * smarthost.ref.example
15576 This causes all non-local addresses to be sent to the single host
15577 \*smarthost.ref.example*\. If a colon-separated list of smart hosts is given,
15578 they are tried in order
15579 (but you can use \hosts@_randomize\ to vary the order each time).
15580 Another way of configuring the same thing is this:
15583 driver = manualroute
15584 transport = remote_smtp
15585 route_list = !+local_domains smarthost.ref.example
15587 There is no difference in behaviour between these two routers as they stand.
15588 However, they behave differently if \no@_more\ is added to them. In the first
15589 example, the router is skipped if the domain does not match the \domains\
15590 precondition; the following router is always tried. If the router runs, it
15591 always matches the domain and so can never decline. Therefore, \no@_more\ would
15592 have no effect. In the second case, the router is never skipped; it always
15593 runs. However, if it doesn't match the domain, it declines. In this case
15594 \no@_more\ would prevent subsequent routers from running.
15597 .index mail hub example
15598 A \*mail hub*\ is a host which receives mail for a number of domains via MX
15599 records in the DNS and delivers it via its own private routing mechanism. Often
15600 the final destinations are behind a firewall, with the mail hub being the one
15601 machine that can connect to machines both inside and outside the firewall. The
15602 \%manualroute%\ router is usually used on a mail hub to route incoming messages
15603 to the correct hosts. For a small number of domains, the routing can be inline,
15604 using the \route@_list\ option, but for a larger number a file or database
15605 lookup is easier to manage.
15607 If the domain names are in fact the names of the machines to which the mail is
15608 to be sent by the mail hub, the configuration can be quite simple. For
15612 driver = manualroute
15613 transport = remote_smtp
15614 route_list = *.rhodes.tvs.example $domain
15616 This configuration routes domains that match \"*.rhodes.tvs.example"\ to hosts
15617 whose names are the same as the mail domains. A similar approach can be taken
15618 if the host name can be obtained from the domain name by a string manipulation
15619 that the expansion facilities can handle. Otherwise, a lookup based on the
15620 domain can be used to find the host:
15623 driver = manualroute
15624 transport = remote_smtp
15625 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
15627 The result of the lookup must be the name or IP address of the host (or
15628 hosts) to which the address is to be routed. If the lookup fails, the route
15629 data is empty, causing the router to decline. The address then passes to the
15633 .index batched SMTP output example
15634 .index SMTP||batched outgoing, example
15635 You can use \%manualroute%\ to deliver messages to pipes or files in batched
15636 SMTP format for onward transportation by some other means. This is one way of
15637 storing mail for a dial-up host when it is not connected. The route list entry
15638 can be as simple as a single domain name in a configuration like this:
15641 driver = manualroute
15642 transport = batchsmtp_appendfile
15643 route_list = saved.domain.example
15645 though often a pattern is used to pick up more than one domain. If there are
15646 several domains or groups of domains with different transport requirements,
15647 different transports can be listed in the routing information:
15650 driver = manualroute
15652 *.saved.domain1.example $domain batch_appendfile; \
15653 *.saved.domain2.example \
15654 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
15657 The first of these just passes the domain in the \$host$\ variable, which
15658 doesn't achieve much (since it is also in \$domain$\), but the second does a
15659 file lookup to find a value to pass, causing the router to decline to handle
15660 the address if the lookup fails.
15662 .index UUCP||example of router for
15663 Routing mail directly to UUCP software is a specific case of the use of
15664 \%manualroute%\ in a gateway to another mail environment. This is an example of
15665 one way it can be done:
15671 command = /usr/local/bin/uux -r - \
15672 ${substr_-5:$host}!rmail ${local_part}
15673 return_fail_output = true
15679 driver = manualroute
15681 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
15683 The file \(/usr/local/exim/uucphosts)\ contains entries like
15685 darksite.ethereal.example: darksite.UUCP
15687 It can be set up more simply without adding and removing `.UUCP' but this way
15688 makes clear the distinction between the domain name
15689 \*darksite.ethereal.example*\ and the UUCP host name \*darksite*\.
15701 . ============================================================================
15702 .chapter The queryprogram router
15703 .set runningfoot "queryprogram router"
15704 .rset CHAPdriverlast "~~chapter"
15705 .index \%queryprogram%\ router
15706 .index routers||\%queryprogram%\
15707 .index routing||by external program
15708 The \%queryprogram%\ router routes an address by running an external command and
15709 acting on its output. This is an expensive way to route, and is intended mainly
15710 for use in lightly-loaded systems, or for performing experiments. However, if
15711 it is possible to use the precondition options (\domains\, \local@_parts\,
15712 etc) to skip this router for most addresses, it could sensibly be used in
15713 special cases, even on a busy host. There are the following private options:
15715 .startconf queryprogram
15716 .index options||\%queryprogram%\ router
15717 .conf command string$**$ unset
15718 This option must be set. It specifies the command that is to be run. The
15719 command is split up into a command name and arguments, and then each is
15720 expanded separately (exactly as for a \%pipe%\ transport, described in chapter
15721 ~~CHAPpipetransport).
15723 .conf command@_group string unset
15724 .index gid (group id)||in \%queryprogram%\ router
15725 This option specifies a gid to be set when running the command. It must be set
15726 if \command@_user\ specifies a numerical uid. If it begins with a digit, it is
15727 interpreted as the numerical value of the gid. Otherwise it is looked up using
15730 .conf command@_user string unset
15731 .index uid (user id)||for \%queryprogram%\
15732 This option must be set. It specifies the uid which is set when running the
15733 command. If it begins with a digit it is interpreted as the numerical value of
15734 the uid. Otherwise, it is looked up using \*getpwnam()*\ to obtain a value for
15735 the uid and, if \command@_group\ is not set, a value for the gid also.
15737 .conf current@_directory string /
15738 This option specifies an absolute path which is made the current directory
15739 before running the command.
15741 .conf timeout time 1h
15742 If the command does not complete within the timeout period, its process group
15743 is killed and the message is frozen. A value of zero time specifies no
15748 The standard output of the command is connected to a pipe, which is read when
15749 the command terminates. It should consist of a single line of output,
15750 containing up to five fields, separated by white space.
15752 The maximum length of the line is 1023 characters. Longer lines are silently
15755 The first field is one of the following words (case-insensitive):
15757 \*Accept*\: routing succeeded; the remaining fields specify what to do (see
15760 \*Decline*\: the router declines; pass the address to the next router, unless
15763 \*Fail*\: routing failed; do not pass the address to any more routers. Any
15764 subsequent text on the line is an error message. If the router is run as part
15765 of address verification during an incoming SMTP message, the message is
15766 included in the SMTP response.
15768 \*Defer*\: routing could not be completed at this time; try again later. Any
15769 subsequent text on the line is an error message which is logged. It is not
15770 included in any SMTP response.
15772 \*Freeze*\: the same as \*defer*\, except that the message is frozen.
15774 \*Pass*\: pass the address to the next router (or the router specified by
15775 \pass@_router\), overriding \no@_more\.
15777 \*Redirect*\: the message is redirected. The remainder of the line is a list of
15778 new addresses, which are routed independently, starting with the first router,
15779 or the router specified by \redirect@_router\, if set.
15781 When the first word is \*accept*\, the remainder of the line consists of a
15782 number of keyed data values, as follows (split into two lines here, to fit on
15785 ACCEPT TRANSPORT=<<transport>> HOSTS=<<list of hosts>>
15786 LOOKUP=byname|bydns DATA=<<text>>
15788 The data items can be given in any order, and all are optional. If no transport
15789 is included, the transport specified by the generic \transport\ option is used.
15790 The list of hosts and the lookup type are needed only if the transport is an
15791 \%smtp%\ transport that does not itself supply a list of hosts.
15793 The format of the list of hosts is the same as for the \%manualroute%\ router.
15794 As well as host names and IP addresses, it may contain names followed by
15795 \"/MX"\ to specify sublists of hosts that are obtained by looking up MX
15798 If the lookup type is not specified, Exim behaves as follows when trying to
15799 find an IP address for each host: First, a DNS lookup is done. If this yields
15800 anything other than \\HOST@_NOT@_FOUND\\, that result is used. Otherwise, Exim
15801 goes on to try a call to \*getipnodebyname()*\ or \*gethostbyname()*\, and the
15802 result of the lookup is the result of that call.
15804 If the DATA field is set, its value is placed in the \$address@_data$\
15805 variable. For example, this return line
15807 accept hosts=x1.y.example:x2.y.example data="rule1"
15809 routes the address to the default transport, passing a list of two hosts. When
15810 the transport runs, the string `rule1' is in \$address@_data$\.
15818 . ============================================================================
15819 .chapter The redirect router
15820 .set runningfoot "redirect router"
15821 .rset CHAPredirect "~~chapter"
15822 .index \%redirect%\ router
15823 .index routers||\%redirect%\
15824 .index alias file||in a \%redirect%\ router
15825 .index address redirection||\%redirect%\ router
15826 The \%redirect%\ router handles several kinds of address redirection. Its most
15827 common uses are for resolving local part aliases from a central alias file
15828 (usually called \(/etc/aliases)\) and for handling users' personal \(.forward)\
15829 files, but it has many other potential uses. The incoming address can be
15830 redirected in several different ways:
15832 It can be replaced by one or more new addresses which are themselves routed
15835 It can be routed to be delivered to a given file or directory.
15837 It can be routed to be delivered to a specified pipe command.
15839 It can cause an automatic reply to be generated.
15841 It can be forced to fail, with a custom error message.
15843 It can be temporarily deferred.
15845 It can be discarded.
15847 The generic \transport\ option must not be set for \%redirect%\ routers.
15848 However, there are some private options which define transports for delivery to
15849 files and pipes, and for generating autoreplies. See the \file@_transport\,
15850 \pipe@_transport\ and \reply@_transport\ descriptions below.
15853 .section Redirection data
15854 The router operates by interpreting a text string which it obtains either by
15855 expanding the contents of the \data\ option, or by reading the entire contents
15856 of a file whose name is given in the \file\ option. These two options are
15857 mutually exclusive. The first is commonly used for handling system aliases, in
15858 a configuration like this:
15862 data = ${lookup{$local_part}lsearch{/etc/aliases}}
15864 If the lookup fails, the expanded string in this example is empty. When the
15865 expansion of \data\ results in an empty string, the router declines. A forced
15866 expansion failure also causes the router to decline; other expansion failures
15867 cause delivery to be deferred.
15869 A configuration using \file\ is commonly used for handling users' \(.forward)\
15875 file = $home/.forward
15878 If the file does not exist, or causes no action to be taken (for example, it is
15879 empty or consists only of comments), the router declines. \**Warning**\: This
15880 is not the case when the file contains syntactically valid items that happen to
15881 yield empty addresses, for example, items containing only RFC 2822 address
15885 .section Forward files and address verification
15886 .index address redirection||while verifying
15887 It is usual to set \no@_verify\ on \%redirect%\ routers which handle users'
15888 \(.forward)\ files, as in the example above. There are two reasons for this:
15890 When Exim is receiving an incoming SMTP message from a remote host, it is
15891 running under the Exim uid, not as root.
15892 No additional groups are set up, even if the Exim uid is a member of other
15893 groups (that is, the \*initgroups()*\ function is not run).
15894 Exim is unable to change uid to read the file as the user, and it may not be
15895 able to read it as the Exim user. So in practice the router may not be able to
15898 However, even when the router can operate, the existence of a \(.forward)\ file
15899 is unimportant when verifying an address. What should be checked is whether the
15900 local part is a valid user name or not. Cutting out the redirection processing
15901 saves some resources.
15907 .section Interpreting redirection data
15908 .index Sieve filter||specifying in redirection data
15909 .index filter||specifying in redirection data
15910 The contents of the data string, whether obtained from \data\ or \file\, can be
15911 interpreted in two different ways:
15913 If the \allow@_filter\ option is set true, and the data begins with the text
15914 `@#Exim filter' or `@#Sieve filter', it is interpreted as a list of
15915 \*filtering*\ instructions in the form of an Exim or Sieve filter file,
15916 respectively. Details of the syntax and semantics of filter files are described
15917 in a separate document entitled \*Exim's interfaces to mail filtering*\; this
15918 document is intended for use by end users.
15920 Otherwise, the data must be a comma-separated list of redirection items, as
15921 described in the next section.
15923 When a message is redirected to a file (a `mail folder'), the file name given
15924 in a non-filter redirection list must always be an absolute path. A filter may
15925 generate a relative path -- how this is handled depends on the transport's
15926 configuration. See section ~~SECTfildiropt for a discussion of this issue for
15927 the \%appendfile%\ transport.
15930 .section Items in a non-filter redirection list
15931 .rset SECTitenonfilred "~~chapter.~~section"
15932 .index address redirection||non-filter list items
15933 When the redirection data is not an Exim or Sieve filter, for example, if it
15934 comes from a conventional alias or forward file, it consists of a list of
15935 addresses, file names, pipe commands, or certain special items (see section
15936 ~~SECTspecitredli below). The special items can be individually enabled or
15937 disabled by means of options whose names begin with \allow@_\ or \forbid@_\,
15938 depending on their default values. The items in the list are separated by
15939 commas or newlines.
15940 If a comma is required in an item, the entire item must be enclosed in double
15943 Lines starting with a @# character are comments, and are ignored, and @# may
15944 also appear following a comma, in which case everything between the @# and the
15945 next newline character is ignored.
15947 If an item is entirely enclosed in double quotes, these are removed. Otherwise
15948 double quotes are retained because some forms of mail address require their use
15949 (but never to enclose the entire address). In the following description, `item'
15950 refers to what remains after any surrounding double quotes have been removed.
15952 \**Warning**\: If you use an Exim expansion to construct a redirection address,
15953 and the expansion contains a reference to \$local@_part$\, you should make use
15954 of the \quote\ expansion operator, in case the local part contains special
15955 characters. For example, to redirect all mail for the domain
15956 \*obsolete.example*\, retaining the existing local part, you could use this
15959 data = ${quote:$local_part}@newdomain.example
15963 .section Redirecting to a local mailbox
15964 .rset SECTredlocmai "~~chapter.~~section"
15965 .index routing||loops in
15966 .index loop||while routing, avoidance of
15967 .index address redirection||to local mailbox
15968 A redirection item may safely be the same as the address currently under
15969 consideration. This does not cause a routing loop, because a router is
15970 automatically skipped if any ancestor of the address that is being processed
15971 is the same as the current address and was processed by the current router.
15972 Such an address is therefore passed to the following routers, so it is handled
15973 as if there were no redirection. When making this loop-avoidance test, the
15974 complete local part, including any prefix or suffix, is used.
15976 .index address redirection||local part without domain
15977 Specifying the same local part without a domain is a common usage in personal
15978 filter files when the user wants to have messages delivered to the local
15979 mailbox and also forwarded elsewhere. For example, the user whose login is
15980 \*cleo*\ might have a \(.forward)\ file containing this:
15982 cleo, cleopatra@egypt.example
15984 .index backslash in alias file
15985 .index alias file||backslash in
15986 For compatibility with other MTAs, such unqualified local parts may be
15987 preceeded by `@\', but this is not a requirement for loop prevention. However,
15988 it does make a difference if more than one domain is being handled
15991 If an item begins with `@\' and the rest of the item parses as a valid RFC 2822
15992 address that does not include a domain, the item is qualified using the domain
15993 of the incoming address. In the absence of a leading `@\', unqualified
15994 addresses are qualified using the value in \qualify@_recipient\, but you can
15995 force the incoming domain to be used by setting \qualify__preserve@_domain\.
15997 Care must be taken if there are alias names for local users.
15998 Consider an MTA handling a single local domain where the system alias file
16003 Now suppose that Sam (whose login id is \*spqr*\) wants to save copies of
16004 messages in the local mailbox, and also forward copies elsewhere. He creates
16007 Sam.Reman, spqr@reme.elsewhere.example
16009 With these settings, an incoming message addressed to \*Sam.Reman*\ fails. The
16010 \%redirect%\ router for system aliases does not process \*Sam.Reman*\ the
16011 second time round, because it has previously routed it,
16012 and the following routers presumably cannot handle the alias. The forward file
16013 should really contain
16015 spqr, spqr@reme.elsewhere.example
16017 but because this is such a common error, the \check@_ancestor\ option (see
16018 below) exists to provide a way to get round it. This is normally set on a
16019 \%redirect%\ router that is handling users' \(.forward)\ files.
16022 .section Special items in redirection lists
16023 .rset SECTspecitredli "~~chapter.~~section"
16024 In addition to addresses, the following types of item may appear in redirection
16025 lists (that is, in non-filter redirection data):
16028 .index pipe||in redirection list
16029 .index address redirection||to pipe
16030 An item is treated as a pipe command if it begins with `|' and does not parse
16031 as a valid RFC 2822 address that includes a domain. A transport for running the
16032 command must be specified by the \pipe@_transport\ option.
16033 Normally, either the router or the transport specifies a user and a group under
16034 which to run the delivery. The default is to use the Exim user and group.
16036 Single or double quotes can be used for enclosing the individual arguments of
16037 the pipe command; no interpretation of escapes is done for single quotes. If
16038 the command contains a comma character, it is necessary to put the whole item
16039 in double quotes, for example:
16041 "|/some/command ready,steady,go"
16043 since items in redirection lists are terminated by commas. Do not, however,
16044 quote just the command. An item such as
16046 |"/some/command ready,steady,go"
16048 is interpreted as a pipe with a rather strange command name, and no arguments.
16050 .index file||in redirection list
16051 .index address redirection||to file
16052 An item is interpreted as a path name if it begins with `/' and does not parse
16053 as a valid RFC 2822 address that includes a domain. For example,
16055 /home/world/minbari
16057 is treated as a file name, but
16059 /s=molari/o=babylon/@x400gate.way
16061 is treated as an address. For a file name, a transport must be specified using
16062 the \file@_transport\ option. However, if the generated path name ends with a
16063 forward slash character, it is interpreted as a directory name rather than a
16064 file name, and \directory@_transport\ is used instead.
16066 Normally, either the router or the transport specifies a user and a group under
16067 which to run the delivery. The default is to use the Exim user and group.
16068 .index \(/dev/null)\
16069 However, if a redirection item is the path \(/dev/null)\, delivery to it is
16070 bypassed at a high level, and the log entry shows `$*$$*$bypassed$*$$*$'
16071 instead of a transport name. In this case the user and group are not used.
16073 .index included address list
16074 .index address redirection||included external list
16075 If an item is of the form
16077 :include:<<path name>>
16079 a list of further items is taken from the given file and included at that
16081 \**Note**\: such a file can not be a filter file; it is just an out-of-line
16082 addition to the list.
16083 The items in the included list are separated by commas or newlines and are not
16084 subject to expansion. If this is the first item in an alias list in an
16085 \%lsearch%\ file, a colon must be used to terminate the alias name. This
16086 example is incorrect:
16088 list1 :include:/opt/lists/list1
16090 It must be given as
16092 list1: :include:/opt/lists/list1
16095 .index address redirection||to black hole
16096 Sometimes you want to throw away mail to a particular local part. Making the
16097 \data\ option expand to an empty string does not work, because that causes the
16098 router to decline. Instead, the alias item
16100 .index abandoning mail
16104 can be used. It does what its name implies. No delivery is done, and no error
16105 message is generated. This has the same effect as specifing \(/dev/null)\, but
16106 can be independently disabled.
16108 \**Warning**\: If \":blackhole:"\ appears anywhere in a redirection list, no
16109 delivery is done for the original local part, even if other redirection items
16110 are present. If you are generating a multi-item list (for example, by reading a
16111 database) and need the ability to provide a no-op item, you must use
16115 .index delivery||forcing failure
16116 .index delivery||forcing deferral
16117 .index failing delivery||forcing
16118 .index deferred delivery, forcing
16119 .index customizing||failure message
16120 An attempt to deliver a particular address can be deferred or forced to fail by
16121 redirection items of the form
16127 respectively. When a redirection list contains such an item, it applies to the
16128 entire redirection; any other items in the list are ignored (:::blackhole:: is
16129 different). Any text following :::fail:: or :::defer:: is placed in the error
16130 text associated with the failure. For example, an alias file might contain:
16132 X.Employee: :fail: Gone away, no forwarding address
16134 In the case of an address that is being verified from an ACL or as the subject
16136 .index \\VRFY\\||error text, display of
16137 \\VRFY\\ command, the text is included in the SMTP error response by
16140 .index \\EXPN\\||error text, display of
16141 The text is not included in the response to an \\EXPN\\ command.
16144 In an ACL, an explicitly provided message overrides the default, but the
16145 default message is available in the variable \$acl@_verify@_message$\ and can
16146 therefore be included in a custom message if this is desired. Exim sends a 451
16147 SMTP code for a :::defer::, and 550 for :::fail::. In non-SMTP cases the text
16148 is included in the error message that Exim generates.
16152 Normally the error text is the rest of the redirection list -- a comma does not
16153 terminate it -- but a newline does act as a terminator. Newlines are not
16154 normally present in alias expansions. In \%lsearch%\ lookups they are removed as
16155 part of the continuation process, but they may exist in other kinds of lookup
16156 and in :::include:: files.
16158 During routing for message delivery (as opposed to verification), a redirection
16159 containing :::fail:: causes an immediate failure of the incoming address,
16160 whereas :::defer:: causes the message to remain on the queue so that a
16161 subsequent delivery attempt can happen at a later time. If an address is
16162 deferred for too long, it will ultimately fail, because the normal retry
16165 .index alias file||exception to default
16166 Sometimes it is useful to use a single-key search type with a default (see
16167 chapter ~~CHAPfdlookup) to look up aliases. However, there may be a need for
16168 exceptions to the default. These can be handled by aliasing them to
16172 This differs from :::fail:: in that it causes the \%redirect%\ router to decline,
16173 whereas :::fail:: forces routing to fail. A lookup which results in an empty
16174 redirection list has the same effect.
16177 .section Duplicate addresses
16178 .index duplicate addresses
16179 .index address||duplicate, discarding
16180 .index pipe||duplicated
16181 Exim removes duplicate addresses from the list to which it is delivering, so as
16182 to deliver just one copy to each address. This does not apply to deliveries
16183 routed to pipes by different immediate parent addresses, but an indirect
16184 aliasing scheme of the type
16186 pipe: |/some/command $local_part
16190 does not work with a message that is addressed to both local parts, because
16191 when the second is aliased to the intermediate local part `pipe' it gets
16192 discarded as being the same as a previously handled address. However, a scheme
16195 localpart1: |/some/command $local_part
16196 localpart2: |/some/command $local_part
16198 does result in two different pipe deliveries, because the immediate parents of
16199 the pipes are distinct.
16202 .section Repeated redirection expansion
16203 .index repeated redirection expansion
16204 .index address redirection||repeated for each delivery attempt
16205 When a message cannot be delivered to all of its recipients immediately,
16206 leading to two or more delivery attempts, redirection expansion is carried out
16207 afresh each time for those addresses whose children were not all previously
16208 delivered. If redirection is being used as a mailing list, this can lead to new
16209 members of the list receiving copies of old messages. The \one@_time\ option
16210 can be used to avoid this.
16212 .section Errors in redirection lists
16213 .index address redirection||errors
16214 If \skip@_syntax@_errors\ is set, a malformed address that causes a parsing
16215 error is skipped, and an entry is written to the main log. This may be useful
16216 for mailing lists that are automatically managed. Otherwise, if an error is
16217 detected while generating the list of new addresses, the original address is
16218 deferred. See also \syntax@_errors@_to\.
16221 .section Private options for the redirect router
16223 The private options for the \%redirect%\ router are as follows:
16225 .startconf redirect
16226 .index options||\%redirect%\ router
16228 .conf allow@_defer boolean false
16229 Setting this option allows the use of :::defer:: in non-filter redirection
16231 or the \defer\ command in an Exim filter file.
16233 .conf allow@_fail boolean false
16234 .index failing delivery||from filter
16235 If this option is true, the :::fail:: item can be used in a redirection list,
16236 and the \fail\ command may be used in a filter file.
16238 .conf allow@_filter boolean false
16239 .index filter||enabling use of
16240 .index Sieve filter||enabling use of
16241 Setting this option allows Exim to interpret redirection data that starts with
16242 `@#Exim filter' or `@#Sieve filter' as a set of filtering instructions. There
16243 are some features of Exim filter files that some administrators may wish to
16244 lock out; see the \forbid@_filter@_xxx\ options below.
16246 It is also possible to lock out Exim filters or Sieve filters while allowing
16247 the other type; see \forbid@_exim@_filter\ and \forbid@_sieve@_filter\.
16250 The filter is run using the uid and gid set by the generic \user\ and \group\
16251 options. These take their defaults from the password data if
16252 \check@_local@_user\ is set, so in the normal case of users' personal filter
16253 files, the filter is run as the relevant user. When \allow@_filter\ is set
16254 true, Exim insists that either \check@_local@_user\ or \user\ is set.
16257 .conf allow@_freeze boolean false
16258 .index freezing messages||allowing in filter
16259 Setting this option allows the use of the \freeze\ command in an Exim filter.
16260 This command is more normally encountered in system filters, and is disabled by
16261 default for redirection filters because it isn't something you usually want to
16262 let ordinary users do.
16265 .conf check@_ancestor boolean false
16266 This option is concerned with handling generated addresses that are the same
16267 as some address in the list of redirection ancestors of the current address.
16268 Although it is turned off by default in the code, it is set in the default
16269 configuration file for handling users' \(.forward)\ files. It is recommended
16270 for this use of the \%redirect%\ router.
16272 When \check@_ancestor\ is set, if a generated address (including the domain) is
16273 the same as any ancestor of the current address, it is replaced by a copy of
16274 the current address. This helps in the case where local part A is aliased to B,
16275 and B has a \(.forward)\ file pointing back to A. For example, within a single
16276 domain, the local part `Joe.Bloggs' is aliased to `jb' and \(@~jb/.forward)\
16279 @\Joe.Bloggs, <<other item(s)>>
16281 Without the \check@_ancestor\ setting, either local part (`jb' or `joe.bloggs')
16282 gets processed once by each router and so ends up as it was originally. If `jb'
16283 is the real mailbox name, mail to `jb' gets delivered (having been turned into
16284 `joe.bloggs' by the \(.forward)\ file and back to `jb' by the alias), but mail
16285 to `joe.bloggs' fails. Setting \check@_ancestor\ on the \%redirect%\ router that
16286 handles the \(.forward)\ file prevents it from turning `jb' back into
16287 `joe.bloggs' when that was the original address. See also the \repeat@_use\
16290 .conf check@_group boolean "see below"
16291 When the \file\ option is used, the group owner of the file is checked only
16292 when this option is set. The permitted groups are those listed in the
16293 \owngroups\ option, together with the user's default group if
16294 \check@_local@_user\ is set. If the file has the wrong group, routing is
16295 deferred. The default setting for this option is true if \check@_local@_user\
16296 is set and the \modemask\ option permits the group write bit, or if the
16297 \owngroups\ option is set. Otherwise it is false, and no group check occurs.
16300 .conf check@_owner boolean "see below"
16301 When the \file\ option is used, the owner of the file is checked only when this
16302 option is set. If \check@_local@_user\ is set, the local user is permitted;
16303 otherwise the owner must be one of those listed in the \owners\ option. The
16304 default value for this option is true if \check@_local@_user\ or \owners\ is
16305 set. Otherwise the default is false, and no owner check occurs.
16307 .conf data string$**$ unset
16308 This option is mutually exclusive with \file\. One or other of them must be
16309 set, but not both. The contents of \data\ are expanded, and then used as the
16310 list of forwarding items, or as a set of filtering instructions. If the
16311 expansion is forced to fail, or the result is an empty string or a string that
16312 has no effect (consists entirely of comments), the router declines.
16314 When filtering instructions are used, the string must begin with `@#Exim
16315 filter', and all comments in the string, including this initial one, must be
16316 terminated with newline characters. For example:
16318 data = #Exim filter\n\
16319 if $h_to: contains Exim then save $home/mail/exim endif
16321 If you are reading the data from a database where newlines cannot be included,
16322 you can use the \$@{sg@}$\ expansion item to turn the escape string of your
16323 choice into a newline.
16325 .conf directory@_transport string$**$ unset
16326 A \%redirect%\ router sets up a direct delivery to a directory when a path name
16327 ending with a slash is specified as a new `address'. The transport used is
16328 specified by this option, which, after expansion, must be the name of a
16329 configured transport. This should normally be an \%appendfile%\ transport.
16331 .conf file string$**$ unset
16332 This option specifies the name of a file that contains the redirection data. It
16333 is mutually exclusive with the \data\ option. The string is expanded before
16334 use; if the expansion is forced to fail, the router declines. Other expansion
16335 failures cause delivery to be deferred. The result of a successful expansion
16336 must be an absolute path. The entire file is read and used as the redirection
16337 data. If the data is an empty string or a string that has no effect (consists
16338 entirely of comments), the router declines.
16340 .index NFS||checking for file existence
16341 If the attempt to open the file fails with a `does not exist' error, Exim
16342 runs a check on the containing directory,
16343 unless \ignore@_enotdir\ is true (see below).
16344 If the directory does not appear to exist, delivery is deferred. This can
16345 happen when users' \(.forward)\ files are in NFS-mounted directories, and there
16346 is a mount problem. If the containing directory does exist, but the file does
16347 not, the router declines.
16349 .conf file@_transport string$**$ unset
16350 A \%redirect%\ router sets up a direct delivery to a file when a path name not
16351 ending in a slash is specified as a new `address'. The transport used is
16352 specified by this option, which, after expansion, must be the name of a
16353 configured transport.
16354 This should normally be an \%appendfile%\ transport.
16355 When it is running, the file name is in \$address@_file$\.
16357 .conf forbid@_blackhole boolean false
16358 If this option is true, the :::blackhole:: item may not appear in a redirection
16362 .conf forbid@_exim@_filter boolean false
16363 If this option is set true, only Sieve filters are permitted when
16364 \allow@_filter\ is true.
16368 .conf forbid@_file boolean false
16369 .index delivery||to file, forbidding
16370 .index Sieve filter||forbidding delivery to a file
16371 .index Sieve filter||`keep' facility, disabling
16372 If this option is true, this router may not generate a new address that
16373 specifies delivery to a local file or directory, either from a filter or from a
16374 conventional forward file. This option is forced to be true if \one@_time\ is
16375 set. It applies to Sieve filters as well as to Exim filters, but if true, it
16376 locks out the Sieve's `keep' facility.
16378 .conf forbid@_filter@_existstest boolean false
16379 .index filter||locking out certain features
16380 If this option is true, string expansions in Exim filters are not allowed to
16381 make use of the \exists\ condition.
16383 .conf forbid@_filter@_logwrite boolean false
16384 If this option is true, use of the logging facility in Exim filters is not
16385 permitted. Logging is in any case available only if the filter is being run
16386 under some unprivileged uid (which is normally the case for ordinary users'
16387 \(.forward)\ files).
16389 .conf forbid@_filter@_lookup boolean false
16390 If this option is true, string expansions in Exim filter files are not allowed
16391 to make use of \lookup\ items.
16393 .conf forbid@_filter@_perl boolean false
16394 This option is available only if Exim is built with embedded Perl support. If
16395 it is true, string expansions in Exim filter files are not allowed to make use
16396 of the embedded Perl support.
16398 .conf forbid@_filter@_readfile boolean false
16399 If this option is true, string expansions in Exim filter files are not allowed
16400 to make use of \readfile\ items.
16402 .conf forbid@_filter@_readsocket boolean false
16403 If this option is true, string expansions in Exim filter files are not allowed
16404 to make use of \readsocket\ items.
16406 .conf forbid@_filter@_reply boolean false
16407 If this option is true, this router may not generate an automatic reply
16408 message. Automatic replies can be generated only from Exim
16410 or Sieve filter files, not from traditional forward files.
16412 This option is forced to be true if \one@_time\ is set.
16414 .conf forbid@_filter@_run boolean false
16415 If this option is true, string expansions in Exim filter files are not allowed
16416 to make use of \run\ items.
16418 .conf forbid@_include boolean false
16419 If this option is true, items of the form
16421 :include:<<path name>>
16423 are not permitted in non-filter redirection lists.
16425 .conf forbid@_pipe boolean false
16426 .index delivery||to pipe, forbidding
16427 If this option is true, this router may not generate a new address which
16428 specifies delivery to a pipe, either from an Exim filter or from a conventional
16429 forward file. This option is forced to be true if \one@_time\ is set.
16432 .conf forbid@_sieve@_filter boolean false
16433 If this option is set true, only Exim filters are permitted when
16434 \allow@_filter\ is true.
16438 .conf hide@_child@_in@_errmsg boolean false
16439 .index bounce message||redirection details, suppressing
16440 If this option is true, it prevents Exim from quoting a child address if it
16441 generates a bounce or delay message for it. Instead it says `an address
16442 generated from <<the top level address>>'. Of course, this applies only to
16443 bounces generated locally. If a message is forwarded to another host, $it{its}
16444 bounce may well quote the generated address.
16446 .conf ignore@_eacces boolean false
16448 If this option is set and an attempt to open a redirection file yields the
16449 \\EACCES\\ error (permission denied), the \%redirect%\ router behaves as if the
16450 file did not exist.
16452 .conf ignore@_enotdir boolean false
16454 If this option is set and an attempt to open a redirection file yields the
16455 \\ENOTDIR\\ error (something on the path is not a directory), the \%redirect%\
16456 router behaves as if the file did not exist.
16458 Setting \ignore@_enotdir\ has another effect as well: When a \%redirect%\
16459 router that has the \file\ option set discovers that the file does not exist
16460 (the \\ENOENT\\ error), it tries to \*stat()*\ the parent directory, as a check
16461 against unmounted NFS directories. If the parent can not be statted, delivery
16462 is deferred. However, it seems wrong to do this check when \ignore@_enotdir\ is
16463 set, because that option tells Exim to ignore `something on the path is not a
16464 directory' (the \\ENOTDIR\\ error). This is a confusing area, because it seems
16465 that some operating systems give \\ENOENT\\ where others give \\ENOTDIR\\.
16468 .conf include@_directory string unset
16469 If this option is set, the path names of any :::include:: items in a redirection
16470 list must start with this directory.
16472 .conf modemask "octal integer" 022
16473 This specifies mode bits which must not be set for a file specified by the
16474 \file\ option. If any of the forbidden bits are set, delivery is deferred.
16476 .conf one@_time boolean false
16477 .index one-time aliasing/forwarding expansion
16478 .index alias file||one-time expansion
16479 .index forward file||one-time expansion
16480 .index mailing lists||one-time expansion
16481 .index address redirection||one-time expansion
16482 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
16483 files each time it tries to deliver a message causes a problem
16484 when one or more of the generated addresses fails be delivered at the first
16485 attempt. The problem is not one of duplicate delivery -- Exim is clever enough
16486 to handle that -- but of what happens when the redirection list changes during
16487 the time that the message is on Exim's queue. This is particularly true in the
16488 case of mailing lists, where new subscribers might receive copies of messages
16489 that were posted before they subscribed.
16491 If \one@_time\ is set and any addresses generated by the router fail to
16492 deliver at the first attempt, the failing addresses are added to the message as
16493 `top level' addresses, and the parent address that generated them is marked
16494 `delivered'. Thus, redirection does not happen again at the next
16497 \**Warning 1**\: This means that any header line addition or removal that is
16498 specified by this router would be lost if delivery did not succeed at the
16499 first attempt. For this reason, the \headers@_add\ and \headers@_remove\
16500 generic options are not permitted when \one@_time\ is set.
16502 \**Warning 2**\: To ensure that the router generates only addresses (as opposed
16503 to pipe or file deliveries or auto-replies) \forbid@_file\, \forbid@_pipe\,
16504 and \forbid@_filter@_reply\ are forced to be true when \one@_time\ is set.
16506 The original top-level address is remembered with each of the generated
16507 addresses, and is output in any log messages. However, any intermediate parent
16508 addresses are not recorded. This makes a difference to the log only if
16509 \all__parents\ log selector is set. It is expected that \one@_time\ will
16510 typically be used for mailing lists, where there is normally just one level of
16513 .conf owners "string list" unset
16514 .index ownership||alias file
16515 .index ownership||forward file
16516 .index alias file||ownership
16517 .index forward file||ownership
16518 This specifies a list of permitted owners for the file specified by \file\.
16519 This list is in addition to the local user when \check@_local@_user\ is set.
16520 See \check@_owner\ above.
16522 .conf owngroups "string list" unset
16523 This specifies a list of permitted groups for the file specified by \file\. The
16524 list is in addition to the local user's primary group when \check@_local@_user\
16525 is set. See \check@_group\ above.
16527 .conf pipe@_transport string$**$ unset
16528 A \%redirect%\ router sets up a direct delivery to a pipe when a string starting
16529 with a vertical bar character is specified as a new `address'. The transport
16530 used is specified by this option, which, after expansion, must be the name of a
16531 configured transport.
16532 This should normally be a \%pipe%\ transport.
16533 When the transport is run, the pipe command is in \$address@_pipe$\.
16535 .conf qualify@_domain string$**$ unset
16536 If this option is set and an unqualified address (one without a domain) is
16537 generated, it is qualified with the domain specified by expanding this string,
16538 instead of the global setting in \qualify@_recipient\. If the expansion fails,
16539 the router declines. If you want to revert to the default, you can have the
16540 expansion generate \$qualify@_recipient$\.
16542 .conf qualify@_preserve@_domain boolean false
16543 .index domain||in redirection, preserving
16544 .index preserving domain in redirection
16545 .index address redirection||domain, preserving
16546 If this is set and an unqualified address (one without a domain) is generated,
16547 it is qualified with the domain of the
16548 parent address (the immediately preceding ancestor) instead of the local
16549 \qualify@_domain\ or global \qualify@_recipient\ value.
16551 .conf repeat@_use boolean true
16552 If this option is set false, the router is skipped for a child address that has
16553 any ancestor that was routed by this router. This test happens before any of
16554 the other preconditions are tested. Exim's default anti-looping rules skip
16555 only when the ancestor is the same as the current address. See also
16556 \check@_ancestor\ above and the generic \redirect@_router\ option.
16558 .conf reply@_transport string$**$ unset
16559 A \%redirect%\ router sets up an automatic reply when a \mail\ or \vacation\
16560 command is used in a filter file. The transport used is specified by this
16561 option, which, after expansion, must be the name of a configured transport.
16562 This should normally be an \%autoreply%\ transport. Other transports are
16563 unlikely to do anything sensible or useful.
16565 .conf rewrite boolean true
16566 .index address redirection||disabling rewriting
16567 If this option is set false, addresses generated by the router are not
16568 subject to address rewriting. Otherwise, they are treated like new addresses
16569 and are rewritten according to the global rewriting rules.
16573 .conf sieve@_vacation@_directory string$**$ unset
16574 .index Sieve filter||vacation directory
16575 To enable the `vacation' extension for Sieve filters, you must set
16576 \sieve@_vacation@_directory\ to the directory where vacation databases are held
16577 (do not put anything else in that directory), and ensure that the
16578 \reply@_transport\ option refers to an \%autoreply%\ transport.
16582 .conf skip@_syntax@_errors boolean false
16583 .index forward file||broken
16584 .index address redirection||broken files
16585 .index alias file||broken
16586 .index broken alias or forward files
16587 .index ignoring faulty addresses
16588 .index skipping faulty addresses
16589 .index error||skipping bad syntax
16590 If \skip@_syntax@_errors\ is set, syntactically malformed addresses in
16591 non-filter redirection data are skipped, and each failing address is logged. If
16592 \syntax@_errors@_to\ is set, a message is sent to the address it defines,
16593 giving details of the failures. If \syntax@_errors@_text\ is set, its contents
16594 are expanded and placed at the head of the error message generated by
16595 \syntax@_errors@_to\. Usually it is appropriate to set \syntax@_errors@_to\ to
16596 be the same address as the generic \errors@_to\ option. The
16597 \skip@_syntax@_errors\ option is often used when handling mailing lists.
16599 If all the addresses in a redirection list are skipped because of syntax
16600 errors, the router declines to handle the original address, and it is passed to
16601 the following routers.
16603 If \skip@_syntax@_errors\ is set when an Exim filter is interpreted, any syntax
16604 error in the filter causes filtering to be abandoned without any action being
16605 taken. The incident is logged, and the router declines to handle the address,
16606 so it is passed to the following routers.
16608 .index Sieve filter||syntax errors in
16610 Syntax errors in a Sieve filter file cause the `keep' action to
16611 occur. This action is specified by RFC 3028.
16613 The values of \skip@_syntax@_errors\, \syntax@_errors@_to\, and
16614 \syntax@_errors@_text\ are not used.
16616 \skip@_syntax@_errors\ can be used to specify that errors in users' forward
16617 lists or filter files should not prevent delivery. The \syntax@_errors@_to\
16618 option, used with an address that does not get redirected, can be used to
16619 notify users of these errors, by means of a router like this:
16625 file = $home/.forward
16626 file_transport = address_file
16627 pipe_transport = address_pipe
16628 reply_transport = address_reply
16631 syntax_errors_to = real-$local_part@$domain
16632 syntax_errors_text = \
16633 This is an automatically generated message. An error has\n\
16634 been found in your .forward file. Details of the error are\n\
16635 reported below. While this error persists, you will receive\n\
16636 a copy of this message for every message that is addressed\n\
16637 to you. If your .forward file is a filter file, or if it is\n\
16638 a non-filter file containing no valid forwarding addresses,\n\
16639 a copy of each incoming message will be put in your normal\n\
16640 mailbox. If a non-filter file contains at least one valid\n\
16641 forwarding address, forwarding to the valid addresses will\n\
16642 happen, and those will be the only deliveries that occur.
16644 You also need a router to ensure that local addresses that are prefixed by
16645 \"real-"\ are recognized, but not forwarded or filtered. For example, you could
16646 put this immediately before the \%userforward%\ router:
16651 local_part_prefix = real-
16652 transport = local_delivery
16655 .conf syntax@_errors@_text string$**$ unset
16656 See \skip@_syntax@_errors\ above.
16658 .conf syntax@_errors@_to string unset
16659 See \skip@_syntax@_errors\ above.
16670 . ============================================================================
16671 .chapter Environment for running local transports
16672 .rset CHAPenvironment "~~chapter"
16673 .set runningfoot "local transport environment"
16674 .index local transports||environment for
16675 .index environment for local transports
16676 .index transport||local, environment for
16677 Local transports handle deliveries to files and pipes. (The \%autoreply%\
16678 transport can be thought of as similar to a pipe.) Exim always runs transports
16679 in subprocesses, under specified uids and gids. Typical deliveries to local
16680 mailboxes run under the uid and gid of the local user.
16682 Exim also sets a specific current directory while running the transport; for
16683 some transports a home directory setting is also relevant. The \%pipe%\
16684 transport is the only one that sets up environment variables; see section
16685 ~~SECTpipeenv for details.
16687 The values used for the uid, gid, and the directories may come from several
16688 different places. In many cases, the router that handles the address associates
16689 settings with that address as a result of its \check@_local@_user\, \group\, or
16690 \user\ options. However, values may also be given in the transport's own
16691 configuration, and these override anything that comes from the router.
16695 .section Concurrent deliveries
16696 .index concurrent deliveries
16697 .index simultaneous deliveries
16698 If two different messages for the same local recpient arrive more or less
16699 simultaneously, the two delivery processes are likely to run concurrently. When
16700 the \%appendfile%\ transport is used to write to a file, Exim applies locking
16701 rules to stop concurrent processes from writing to the same file at the same
16704 However, when you use a \%pipe%\ transport, it is up to you to arrange any
16705 locking that is needed. Here is a silly example:
16709 command = /bin/sh -c 'cat >>/some/file'
16711 This is supposed to write the message at the end of the file. However, if two
16712 messages arrive at the same time, the file will be scrambled. You can use the
16713 \exim@_lock\ utility program (see section ~~SECTmailboxmaint) to lock a file
16714 using the same algorithm that Exim itself uses.
16718 .section Uids and gids
16719 .rset SECTenvuidgid "~~chapter.~~section"
16720 .index local transports||uid and gid
16721 .index transport||local, uid and gid
16722 All transports have the options \group\ and \user\. If \group\ is set, it
16723 overrides any group that the router set in the address, even if \user\ is not
16724 set for the transport. This makes it possible, for example, to run local mail
16725 delivery under the uid of the recipient (set by the router), but in a special
16726 group (set by the transport). For example:
16729 # User/group are set by check_local_user in this router
16733 transport = group_delivery
16736 # This transport overrides the group
16738 driver = appendfile
16739 file = /var/spool/mail/$local_part
16742 If \user\ is set for a transport, its value overrides what is set in the
16743 address. If \user\ is non-numeric and \group\ is not set, the gid associated
16744 with the user is used. If \user\ is numeric, \group\ must be set.
16746 .index \initgroups\ option
16747 When the uid is taken from the transport's configuration, the \*initgroups()*\
16748 function is called for the groups associated with that uid if the \initgroups\
16749 option is set for the transport. When the uid is not specified by the
16750 transport, but is associated with the address by a router, the option for
16751 calling \*initgroups()*\ is taken from the router configuration.
16753 .index \%pipe%\ transport||uid for
16754 The \%pipe%\ transport contains the special option \pipe@_as@_creator\. If this
16755 is set and \user\ is not set, the uid of the process that called Exim to
16756 receive the message is used, and if \group\ is not set, the corresponding
16757 original gid is also used.
16760 .section Current and home directories
16761 .index current directory for local transport
16762 .index home directory||for local transport
16763 .index transport||local, home directory for
16764 .index transport||local, current directory for
16765 Routers may set current and home directories for local transports by means of
16766 the \transport__current@_directory\ and \transport@_home@_directory\ options.
16767 However, if the transport's \current__directory\ or \home@_directory\ options
16768 are set, they override the router's values. In detail, the home directory
16769 for a local transport is taken from the first of these values that is set:
16771 The \home@_directory\ option on the transport;
16773 The \transport@_home@_directory\ option on the router;
16775 The password data if \check@_local@_user\ is set on the router;
16777 The \router@_home@_directory\ option on the router.
16779 The current directory is taken from the first of these values that is set:
16781 The \current@_directory\ option on the transport;
16783 The \transport@_current@_directory\ option on the router.
16786 If neither the router nor the transport sets a current directory, Exim uses the
16787 value of the home directory, if it is set. Otherwise it sets the current
16788 directory to \(/)\ before running a local transport.
16791 .section Expansion variables derived from the address
16792 Normally a local delivery is handling a single address, and in that case the
16793 variables such as \$domain$\ and \$local@_part$\ are set during local
16794 deliveries. However, in some circumstances more than one address may be handled
16795 at once (for example, while writing batch SMTP for onward transmission by some
16796 other means). In this case, the variables associated with the local part are
16797 never set, \$domain$\ is set only if all the addresses have the same
16798 domain, and \$original@_domain$\ is never set.
16809 . ============================================================================
16810 .chapter Generic options for transports
16811 .rset CHAPtransportgeneric "~~chapter"
16812 .set runningfoot "generic transport options"
16814 .index generic options||transport
16815 .index options||generic, for transports
16816 .index transport||generic options for
16817 The following generic options apply to all transports:
16819 .startconf transports
16820 .conf body@_only boolean false
16821 .index transport||body only
16822 .index message||transporting body only
16823 .index body of message||transporting
16824 If this option is set, the message's headers are not transported. It is
16825 mutually exclusive with \headers@_only\. If it is used with the \%appendfile%\ or
16826 \%pipe%\ transports, the settings of \message@_prefix\ and \message@_suffix\
16827 should be checked, because this option does not automatically suppress them.
16829 .conf current@_directory string$**$ unset
16830 .index transport||current directory for
16831 This specifies the current directory that is to be set while running the
16832 transport, overriding any value that may have been set by the router.
16833 If the expansion fails for any reason, including forced failure, an error is
16834 logged, and delivery is deferred.
16836 .conf disable@_logging boolean false
16837 If this option is set true, nothing is logged for any
16838 deliveries by the transport or for any
16839 transport errors. You should not set this option unless you really, really know
16840 what you are doing.
16842 .conf debug@_print string$**$ unset
16843 .index testing||variables in drivers
16844 If this option is set and debugging is enabled (see the \-d-\ command line
16845 option), the string is expanded and included in the debugging output when the
16847 If expansion of the string fails, the error message is written to the debugging
16848 output, and Exim carries on processing.
16849 This facility is provided to help with checking out the values of variables and
16850 so on when debugging driver configurations. For example, if a \headers@_add\
16851 option is not working properly, \debug@_print\ could be used to output the
16852 variables it references. A newline is added to the text if it does not end with
16855 .conf delivery@_date@_add boolean false
16856 .index ::Delivery-date:: header line
16857 If this option is true, a ::Delivery-date:: header is added to the message. This
16858 gives the actual time the delivery was made. As this is not a standard header,
16859 Exim has a configuration option (\delivery@_date@_remove\) which requests its
16860 removal from incoming messages, so that delivered messages can safely be resent
16861 to other recipients.
16863 .conf driver string unset
16864 This specifies which of the available transport drivers is to be used.
16865 There is no default, and this option must be set for every transport.
16867 .conf envelope@_to@_add boolean false
16868 .index ::Envelope-to:: header line
16869 If this option is true, an ::Envelope-to:: header is added to the message. This
16870 gives the original address(es) in the incoming envelope that caused this
16871 delivery to happen. More than one address may be present if the transport is
16872 configured to handle several addresses at once, or if more than one original
16873 address was redirected to the same final address. As this is not a standard
16874 header, Exim has a configuration option (\envelope@_to@_remove\) which requests
16875 its removal from incoming messages, so that delivered messages can safely be
16876 resent to other recipients.
16878 .conf group string$**$ "Exim group"
16879 .index transport||group, specifying
16880 This option specifies a gid for running the transport process, overriding any
16881 value that the router supplies, and also overriding any value associated with
16882 \user\ (see below).
16884 .conf headers@_add string$**$ unset
16885 .index header lines||adding in transport
16886 .index transport||header lines, adding
16888 This option specifies a string of text that is expanded and added to the header
16889 portion of a message as it is transported, as described in section
16890 ~~SECTheadersaddrem. Additional header lines can also be specified by routers.
16891 If the result of the expansion is an empty string, or if the expansion is
16892 forced to fail, no action is taken. Other expansion failures are treated as
16893 errors and cause the delivery to be deferred.
16896 .conf headers@_only boolean false
16897 .index transport||header lines only
16898 .index message||transporting headers only
16899 .index header lines||transporting
16900 If this option is set, the message's body is not transported. It is mutually
16901 exclusive with \body@_only\. If it is used with the \%appendfile%\ or \%pipe%\
16902 transports, the settings of \message@_prefix\ and \message__suffix\ should be
16903 checked, since this option does not automatically suppress them.
16905 .conf headers@_remove string$**$ unset
16906 .index header lines||removing
16907 .index transport||header lines, removing
16909 This option specifies a string that is expanded into a list of header names;
16910 these headers are omitted from the message as it is transported, as described
16911 in section ~~SECTheadersaddrem. Header removal can also be specified by
16912 routers. If the result of the expansion is an empty string, or if the expansion
16913 is forced to fail, no action is taken. Other expansion failures are treated as
16914 errors and cause the delivery to be deferred.
16917 .conf headers@_rewrite string unset
16918 .index transport||header lines, rewriting
16919 .index rewriting||at transport time
16920 This option allows addresses in header lines to be rewritten at transport time,
16921 that is, as the message is being copied to its destination. The contents of the
16922 option are a colon-separated list of rewriting rules. Each rule is in exactly
16923 the same form as one of the general rewriting rules that are applied when a
16924 message is received. These are described in chapter ~~CHAPrewrite. For example,
16926 headers_rewrite = a@b c@d f : \
16929 changes \a@@b\ into \c@@d\ in ::From:: header lines, and \x@@y\ into \w@@z\ in
16930 all address-bearing header lines. The rules are applied to the header lines
16931 just before they are written out at transport time, so they affect only those
16932 copies of the message that pass through the transport. However, only the
16933 message's original header lines, and any that were added by a system filter,
16934 are rewritten. If a router or transport adds header lines, they are
16935 not affected by this option. These rewriting rules are $it{not} applied to the
16936 envelope. You can change the return path using \return@_path\, but you cannot
16937 change envelope recipients at this time.
16939 .conf home@_directory string$**$ unset
16940 .index transport||home directory for
16941 This option specifies a home directory setting for the transport, overriding
16942 any value that may be set by the router. The home directory is placed in
16943 \$home$\ while expanding the transport's private options. It is also used as
16944 the current directory if no current directory is set by the
16945 \current__directory\ option on the transport or the
16946 \transport__current__directory\ option on the router.
16947 If the expansion fails for any reason, including forced failure, an error is
16948 logged, and delivery is deferred.
16951 .index additional groups
16952 .index groups, additional
16953 .index transport||group, additional
16954 .conf initgroups boolean false
16955 If this option is true and the uid for the delivery process is provided by the
16956 transport, the \*initgroups()*\ function is called when running the transport
16957 to ensure that any additional groups associated with the uid are set up.
16959 .conf message@_size@_limit string$**$ 0
16960 .index limit||message size per transport
16961 .index size||of message, limit
16962 .index transport||message size, limiting
16963 This option controls the size of messages passed through the transport. It is
16964 expanded before use; the result of the expansion must be a sequence of digits,
16965 optionally followed by K or M.
16966 If the expansion fails for any reason, including forced failure, or if the
16967 result is not of the required form, delivery is deferred.
16968 If the value is greater than zero and the size of a message exceeds this
16969 limit, the address is failed. If there is any chance that the resulting bounce
16970 message could be routed to the same transport, you should ensure that
16971 \return@_size@_limit\ is less than the transport's \message@_size@_limit\, as
16972 otherwise the bounce message will fail to get delivered.
16975 .conf rcpt@_include@_affixes boolean false
16976 .index prefix||for local part, including in envelope
16977 .index suffix||for local part, including in envelope
16978 .index local part||prefix
16979 .index local part||suffix
16980 When this option is false (the default), and an address that has had any
16981 affixes (prefixes or suffixes) removed from the local part is delivered by any
16982 form of SMTP or LMTP, the affixes are not included. For example, if a router
16985 local_part_prefix = *-
16987 routes the address \*abc-xyz@@some.domain*\ to an SMTP transport, the envelope
16990 RCPT TO:<xyz@some.domain>
16992 If \rcpt@_include@_affixes\ is set true, the whole local part is included in
16993 the \\RCPT\\ command. This option applies to BSMTP deliveries by the
16994 \%appendfile%\ and \%pipe%\ transports as well as to the \%lmtp%\ and \%smtp%\
16997 .conf retry@_use@_local@_part boolean "see below"
16998 .index hints database||retry keys
16999 When a delivery suffers a temporary failure, a retry record is created
17000 in Exim's hints database. For remote deliveries, the key for the retry record
17001 is based on the name and/or IP address of the failing remote host. For local
17002 deliveries, the key is normally the entire address, including both the local
17003 part and the domain. This is suitable for most common cases of local delivery
17004 temporary failure -- for example, exceeding a mailbox quota should delay only
17005 deliveries to that mailbox, not to the whole domain.
17007 However, in some special cases you may want to treat a temporary local delivery
17008 as a failure associated with the domain, and not with a particular local part.
17009 (For example, if you are storing all mail for some domain in files.) You can do
17010 this by setting \retry@_use@_local@_part\ false.
17012 For all the local transports, its default value is true. For remote transports,
17013 the default value is false for tidiness, but changing the value has no effect
17014 on a remote transport in the current implementation.
17016 .conf return@_path string$**$ unset
17017 .index envelope sender
17018 .index transport||return path, changing
17019 .index return path||changing in transport
17020 If this option is set, the string is expanded at transport time and replaces
17021 the existing return path (envelope sender) value in the copy of the message
17022 that is being delivered. An empty return path is permitted. This feature is
17023 designed for remote deliveries, where the value of this option is used in the
17024 SMTP \\MAIL\\ command. If you set \return@_path\ for a local transport, the
17025 only effect is to change the address that is placed in the ::Return-path::
17026 header line, if one is added to the message (see the next option).
17028 The expansion can refer to the existing value via \$return@_path$\. This is
17029 either the message's envelope sender, or an address set by the
17030 \errors@_to\ option on a router. If the expansion is forced to fail, no
17031 replacement occurs; if it fails for another reason, delivery is deferred. This
17032 option can be used to support VERP (Variable Envelope Return Paths) -- see
17033 chapter ~~CHAPSMTP.
17035 \**Note**\: If a delivery error is detected locally,
17036 including the case when a remote server rejects a message at SMTP time,
17037 the bounce message is not sent to the value of this option, but to the
17038 previously set errors address (which defaults to the incoming sender address).
17041 .conf return@_path@_add boolean false
17042 .index ::Return-path:: header line
17043 If this option is true, a ::Return-path:: header is added to the message.
17044 Although the return path is normally available in the prefix line of BSD
17045 mailboxes, this is commonly not displayed by MUAs, and so the user does not
17046 have easy access to it.
17048 RFC 2821 states that the ::Return-path:: header is added to a message `when the
17049 delivery SMTP server makes the final delivery'. This implies that this header
17050 should not be present in incoming messages. Exim has a configuration option,
17051 \return@_path@_remove\, which requests removal of this header from incoming
17052 messages, so that delivered messages can safely be resent to other recipients.
17054 .conf shadow@_condition string$**$ unset
17055 See \shadow@_transport\ below.
17057 .conf shadow@_transport string unset
17058 .index shadow transport
17059 .index transport||shadow
17060 A local transport may set the \shadow@_transport\ option to the name of another
17061 local transport. Shadow remote transports are not supported.
17063 Whenever a delivery to the main transport succeeds, and either
17064 \shadow@_condition\ is unset, or its expansion does not result in the empty
17065 string or one of the strings `0' or `no' or `false', the message is also passed
17066 to the shadow transport, with the same delivery address or addresses.
17067 If expansion fails, no action is taken except that non-forced expansion
17068 failures cause a log line to be written.
17070 The result of the shadow transport is discarded and does not affect the
17071 subsequent processing of the message. Only a single level of shadowing is
17072 provided; the \shadow@_transport\ option is ignored on any transport when it is
17073 running as a shadow. Options concerned with output from pipes are also ignored.
17075 The log line for the successful delivery has an item added on the end, of the
17078 ST=<<shadow transport name>>
17080 If the shadow transport did not succeed, the error message is put in
17081 parentheses afterwards.
17083 Shadow transports can be used for a number of different purposes, including
17084 keeping more detailed log information than Exim normally provides, and
17085 implementing automatic acknowledgement policies based on message headers that
17086 some sites insist on.
17088 .conf transport@_filter string$**$ unset
17089 .index transport||filter
17090 .index filter||transport filter
17091 This option sets up a filtering (in the Unix shell sense) process for messages
17092 at transport time. It should not be confused with mail filtering as set up by
17093 individual users or via a system filter.
17095 When the message is about to be written out, the command specified by
17096 \transport@_filter\ is started up in a separate process, and the entire
17097 message, including the header lines, is passed to it on its standard input
17098 (this in fact is done from a third process, to avoid deadlock).
17099 The command must be specified as an absolute path.
17102 The lines of the message that are written to the transport filter are
17103 terminated by newline (`@\n').
17105 The message is passed to the filter before any SMTP-specific processing, such
17106 as turning `@\n' into `@\r@\n' and escaping lines beginning with a dot, and
17107 also before any processing implied by the settings of \check@_string\ and
17108 \escape@_string\ in the \%appendfile%\ or \%pipe%\ transports.
17111 The standard error for the filter process is set to the same destination as its
17112 standard output; this is read and written to the message's ultimate
17115 The filter can perform any transformations it likes, but of course should take
17116 care not to break RFC 2822 syntax. A demonstration Perl script is provided in
17117 \(util/transport-filter.pl)\; this makes a few arbitrary modifications just to
17118 show the possibilities. Exim does not check the result, except to test for a
17119 final newline when SMTP is in use. All messages transmitted over SMTP must end
17120 with a newline, so Exim supplies one if it is missing.
17122 .index SMTP||\\SIZE\\
17123 A problem might arise if the filter increases the size of a message that is
17124 being sent down an SMTP connection. If the receiving SMTP server has indicated
17125 support for the \\SIZE\\ parameter, Exim will have sent the size of the message
17126 at the start of the SMTP session. If what is actually sent is substantially
17127 more, the server might reject the message. This can be worked round by setting
17128 the \size@_addition\ option on the \%smtp%\ transport, either to allow for
17129 additions to the message, or to disable the use of \\SIZE\\ altogether.
17131 The value of the \transport@_filter\ option is the command string for starting
17132 the filter, which is run directly from Exim, not under a shell. The string is
17133 parsed by Exim in the same way as a command string for the \%pipe%\ transport:
17134 Exim breaks it up into arguments and then expands each argument separately. The
17135 special argument \$pipe@_addresses$\ is replaced by a number of arguments, one
17136 for each address that applies to this delivery. (This isn't an ideal name for
17137 this feature here, but as it was already implemented for the \%pipe%\
17138 transport, it seemed sensible not to change it.)
17141 .index \$host@_address$\
17142 The expansion variables \$host$\ and \$host@_address$\ are available when the
17143 transport is a remote one. They contain the name and IP address of the host to
17144 which the message is being sent. For example:
17146 transport_filter = /some/directory/transport-filter.pl \
17147 $host $host_address $sender_address $pipe_addresses
17149 The filter process is run under the same uid and gid as the normal delivery.
17150 For remote deliveries this is the Exim uid/gid by default.
17152 The command should normally yield a zero return code. A non-zero code is taken
17153 to mean that the transport filter failed in some way. Delivery of the message
17154 is deferred. It is not possible to cause a message to be bounced from a
17158 If a transport filter is set on an autoreply transport, the original message is
17159 passed through the filter as it is being copied into the newly generated
17160 message, which happens if the \return@_message\ option is set.
17162 .conf transport@_filter@_timeout time 5m
17163 .index transport||filter, timeout
17164 When Exim is reading the output of a transport filter, it a applies a timeout
17165 that can be set by this option. Exceeding the timeout is treated as a
17166 temporary delivery failure.
17169 .conf user string$**$ "Exim user"
17170 .index uid (user id)||local delivery
17171 .index transport||user, specifying
17172 This option specifies the user under whose uid the delivery process is to be
17173 run, overriding any uid that may have been set by the router. If the user is
17174 given as a name, the uid is looked up from the password data, and the
17175 associated group is taken as the value of the gid to be used if the \group\
17178 For deliveries that use local transports, a user and group are normally
17179 specified explicitly or implicitly (for example, as a result of
17180 \check@_local@_user\) by the router or transport.
17182 .index hints database||access by remote transport
17183 For remote transports, you should leave this option unset unless you really are
17184 sure you know what you are doing. When a remote transport is running, it needs
17185 to be able to access Exim's hints databases, because each host may have its own
17197 . ============================================================================
17198 .chapter Address batching in local transports
17199 .set runningfoot "address batching"
17200 .rset CHAPbatching ~~chapter
17201 .index transport||local, address batching in
17202 The only remote transport (\%smtp%\) is normally configured to handle more than
17203 one address at a time, so that when several addresses are routed to the same
17204 remote host, just one copy of the message is sent. Local transports, however,
17205 normally handle one address at a time. That is, a separate instance of the
17206 transport is run for each address that is routed to the transport. A separate
17207 copy of the message is delivered each time.
17209 .index batched local delivery
17210 .index \batch@_max\
17212 In special cases, it may be desirable to handle several addresses at once in a
17213 local transport, for example:
17215 In an \%appendfile%\ transport, when storing messages in files for later
17216 delivery by some other means, a single copy of the message with multiple
17217 recipients saves space.
17219 In an \%lmtp%\ transport, when delivering over `local SMTP' to some process,
17220 a single copy saves time, and is the normal way LMTP is expected to work.
17222 In a \%pipe%\ transport, when passing the message
17223 to a scanner program or
17224 to some other delivery mechanism such as UUCP, multiple recipients may be
17227 The three local transports (\%appendfile%\, \%lmtp%\, and \%pipe%\) all have
17228 the same options for controlling multiple (`batched') deliveries, namely
17229 \batch@_max\ and \batch@_id\. To save repeating the information for each
17230 transport, these options are described here.
17232 The \batch@_max\ option specifies the maximum number of addresses that can be
17233 delivered together in a single run of the transport. Its default value is one.
17234 When more than one address is routed to a transport that has a \batch@_max\
17235 value greater than one, the addresses are delivered in a batch (that is, in a
17236 single run of the transport), subject to certain conditions:
17238 If any of the transport's options contain a reference to \$local@_part$\, no
17239 batching is possible.
17241 If any of the transport's options contain a reference to \$domain$\, only
17242 addresses with the same domain are batched.
17244 .index customizing||batching condition
17245 If \batch@_id\ is set, it is expanded for each address, and only those
17246 addresses with the same expanded value are batched. This allows you to specify
17247 customized batching conditions.
17248 Failure of the expansion for any reason, including forced failure, disables
17249 batching, but it does not stop the delivery from taking place.
17251 Batched addresses must also have the same errors address (where to send
17252 delivery errors), the same header additions and removals, the same user and
17253 group for the transport, and if a host list is present, the first host must
17256 .index ::Envelope-to:: header line
17257 If the generic \envelope@_to@_add\ option is set for the transport, the
17258 ::Envelope-to:: header that is added to the message contains all the addresses
17259 that are batched together.
17261 The \%appendfile%\ and \%pipe%\ transports have an option called \use@_bsmtp\,
17262 which causes them to deliver the message in `batched SMTP' format, with the
17263 envelope represented as SMTP commands. The \check@_string\ and \escape@_string\
17264 options are forced to the values
17267 escape_string = ".."
17269 when batched SMTP is in use. A full description of the batch SMTP mechanism is
17270 given in section ~~SECTbatchSMTP. The \%lmtp%\ transport does not have a
17271 \use@_bsmtp\ option, because it always delivers using the SMTP protocol.
17273 .index \%pipe%\ transport||with multiple addresses
17274 If you are not using BSMTP, but are using a \%pipe%\ transport, you can include
17275 \$pipe@_addresses$\ as part of the command. This is not a true variable; it is
17276 a bit of magic that causes each of the recipient addresses to be inserted into
17277 the command as a separate argument. This provides a way of accessing all the
17278 addresses that are being delivered in the batch.
17280 If you are using a batching \%appendfile%\ transport without \use@_bsmtp\, the
17281 only way to preserve the recipient addresses is to set the \envelope@_to@_add\
17282 option. This causes an ::Envelope-to:: header line to be added to the message,
17283 containing all the recipients.
17290 . ============================================================================
17291 .chapter The appendfile transport
17292 .set runningfoot "appendfile transport"
17293 .rset CHAPappendfile ~~chapter
17294 .index \%appendfile%\ transport
17295 .index transports||\%appendfile%\
17296 .index directory creation
17297 .index creating directories
17298 The \%appendfile%\ transport delivers a message by appending it to an existing
17299 file, or by creating an entirely new file in a specified directory. Single
17300 files to which messages are appended can be in the traditional Unix mailbox
17301 format, or optionally in the MBX format supported by the Pine MUA and
17302 University of Washington IMAP daemon, $it{inter alia}. When each message is
17303 being delivered as a separate file, `maildir' format can optionally be used to
17304 give added protection against failures that happen part-way through the
17305 delivery. A third form of separate-file delivery known as `mailstore' is also
17306 supported. For all file formats, Exim attempts to create as many levels of
17307 directory as necessary, provided that \create@_directory\ is set.
17309 The code for the optional formats is not included in the Exim binary by
17310 default. It is necessary to set \\SUPPORT@_MBX\\, \\SUPPORT@_MAILDIR\\ and/or
17311 \\SUPPORT@_MAILSTORE\\ in \(Local/Makefile)\ to have the appropriate code
17314 .index quota||system
17315 Exim recognises system quota errors, and generates an appropriate message. Exim
17316 also supports its own quota control within the transport, for use when the
17317 system facility is unavailable or cannot be used for some reason.
17319 If there is an error while appending to a file (for example, quota exceeded or
17320 partition filled), Exim attempts to reset the file's length and last
17321 modification time back to what they were before. If there is an error while
17322 creating an entirely new file, the new file is removed.
17324 Before appending to a file, a number of security checks are made, and the
17325 file is locked. A detailed description is given below, after the list of
17328 \%appendfile%\ is most commonly used for local deliveries to users' mailboxes.
17329 However, it can also be used as a pseudo-remote transport for putting messages
17330 into files for remote delivery by some means other than Exim. `Batch SMTP'
17331 format is often used in this case (see the \use@_bsmtp\ option).
17334 .section The file and directory options
17335 .rset SECTfildiropt "~~chapter.~~section"
17336 The \file\ option specifies a single file, to which the message is appended;
17337 the \directory\ option specifies a directory, in which a new file containing
17338 the message is created. Only one of these two options can be set, and for
17339 normal deliveries to mailboxes, one of them \*must*\ be set.
17341 However, \%appendfile%\ is also used for delivering messages to files or
17342 directories whose names (or parts of names) are obtained from alias,
17343 forwarding, or filtering operations (for example, a \save\ command in a user's
17344 Exim filter). When such a transport is running, \$local@_part$\ contains the
17345 local part that was aliased or forwarded, and \$address@_file$\ contains the
17346 name (or partial name) of the file or directory generated by the redirection
17347 operation. There are two cases:
17349 If neither \file\ nor \directory\ is set, the redirection operation
17350 must specify an absolute path (one that begins with \"/"\). This is the most
17351 common case when users with local accounts use filtering to sort mail into
17352 different folders. See for example, the \%address@_file%\ transport in the
17353 default configuration. If the path ends with a slash, it is assumed to be the
17354 name of a directory. A delivery to a directory can also be forced by setting
17355 \maildir@_format\ or \mailstore@_format\.
17357 If \file\ or \directory\ is set for a delivery from a redirection, it is used
17358 to determine the file or directory name for the delivery. Normally, the
17359 contents of \$address@_file$\ are used in some way in the string expansion.
17362 .index Sieve filter||configuring \%appendfile%\
17363 .index Sieve filter||relative mailbox path handling
17364 As an example of the second case, consider an environment where users do not
17365 have home directories. They may be permitted to use Exim filter commands of the
17370 or Sieve filter commands of the form:
17372 require "fileinto";
17373 fileinto "folder23";
17375 In this situation, the expansion of \file\ or \directory\ in the transport must
17376 transform the relative path into an appropriate absolute file name. In the case
17377 of Sieve filters, the name \*inbox*\ must be handled. It is the name that is
17378 used as a result of a `keep' action in the filter. This example shows one way
17379 of handling this requirement:
17381 file = ${if eq{$address_file}{inbox} \
17382 {/var/mail/$local_part} \
17383 {${if eq{${substr_0_1:$address_file}}{/} \
17385 {$home/mail/$address_file} \
17389 With this setting of \file\, \*inbox*\ refers to the standard mailbox location,
17390 absolute paths are used without change, and other folders are in the \(mail)\
17391 directory within the home directory.
17393 \**Note 1**\: While processing an Exim filter, a relative path such as
17394 \(folder23)\ is turned into an absolute path if a home directory is known to
17395 the router. In particular, this is the case if \check@_local@_user\ is set. If
17396 you want to prevent this happening at routing time, you can set
17397 \router@_home@_directory\ empty. This forces the router to pass the relative
17398 path to the transport.
17400 \**Note 2**\: An absolute path in \$address@_file$\ is not treated specially;
17401 the \file\ or \directory\ option is still used if it is set.
17405 .section Private options for appendfile
17406 .index options||\%appendfile%\ transport
17408 .startconf appendfile
17410 .conf allow@_fifo boolean false
17411 .index fifo (named pipe)
17412 .index named pipe (fifo)
17413 .index pipe||named (fifo)
17414 Setting this option permits delivery to named pipes (FIFOs) as well as to
17415 regular files. If no process is reading the named pipe at delivery time, the
17416 delivery is deferred.
17418 .conf allow@_symlink boolean false
17419 .index symbolic link||to mailbox
17420 .index mailbox||symbolic link
17421 By default, \%appendfile%\ will not deliver if the path name for the file is
17422 that of a symbolic link. Setting this option relaxes that constraint, but there
17423 are security issues involved in the use of symbolic links. Be sure you know
17424 what you are doing if you set this. Details of exactly what this option affects
17425 are included in the discussion which follows this list of options.
17427 .conf batch@_id string$**$ unset
17428 See the description of local delivery batching in chapter ~~CHAPbatching.
17429 However, batching is automatically disabled for \%appendfile%\ deliveries that
17430 happen as a result of forwarding or aliasing or other redirection directly to a
17433 .conf batch@_max integer 1
17434 See the description of local delivery batching in chapter ~~CHAPbatching.
17436 .conf check@_group boolean false
17437 When this option is set, the group owner of the file defined by the \file\
17438 option is checked to see that it is the same as the group under which the
17439 delivery process is running. The default setting is false because the default
17440 file mode is 0600, which means that the group is irrelevant.
17442 .conf check@_owner boolean true
17443 When this option is set, the owner of the file defined by the \file\ option is
17444 checked to ensure that it is the same as the user under which the delivery
17445 process is running.
17447 .conf check@_string string "see below"
17449 As \%appendfile%\ writes the message, the start of each line is tested for
17450 matching \check@_string\, and if it does, the initial matching characters are
17451 replaced by the contents of \escape@_string\. The value of \check@_string\ is a
17452 literal string, not a regular expression, and the case of any letters it
17453 contains is significant.
17455 If \use@_bsmtp\ is set the values of \check@_string\ and \escape@_string\ are
17456 forced to `.' and `..' respectively, and any settings in the configuration are
17457 ignored. Otherwise, they default to `From ' and `>From ' when the \file\ option
17458 is set, and unset when
17459 any of the \directory\, \maildir\, or \mailstore\ options are set.
17461 The default settings, along with \message@_prefix\ and \message@_suffix\, are
17462 suitable for traditional `BSD' mailboxes, where a line beginning with `From '
17463 indicates the start of a new message. All four options need changing if another
17464 format is used. For example, to deliver to mailboxes in MMDF format:
17465 .index MMDF format mailbox
17466 .index mailbox||MMDF format
17468 check_string = "\1\1\1\1\n"
17469 escape_string = "\1\1\1\1 \n"
17470 message_prefix = "\1\1\1\1\n"
17471 message_suffix = "\1\1\1\1\n"
17474 .index directory creation
17475 .conf create@_directory boolean true
17476 When this option is true, Exim attempts to create any missing superior
17477 directories for the file that it is about to write. A created directory's mode
17478 is given by the \directory@_mode\ option.
17480 The group ownership of a newly created directory is highly dependent on the
17481 operating system (and possibly the file system) that is being used. For
17482 example, in Solaris, if the parent directory has the setgid bit set, its group
17483 is propagated to the child; if not, the currently set group is used. However,
17484 in FreeBSD, the parent's group is always used.
17487 .conf create@_file string "anywhere"
17488 This option constrains the location of files and directories that are created
17489 by this transport. It applies to files defined by the \file\ option and
17490 directories defined by the \directory\ option. In the case of maildir delivery,
17491 it applies to the top level directory, not the maildir directories beneath.
17493 The option must be set to one of the words `anywhere', `inhome', or
17494 `belowhome'. In the second and third cases, a home directory must have been set
17495 for the transport. This option is not useful when an explicit file name is
17496 given for normal mailbox deliveries. It is intended for the case when file
17497 names are generated from users' \(.forward)\ files. These are usually handled
17498 by an \%appendfile%\ transport called \address@_file\. See also
17499 \file@_must@_exist\.
17501 .conf directory string$**$ unset
17502 This option is mutually exclusive with the \file\ option, but one of \file\ or
17503 \directory\ must be set, unless the delivery is the direct result of a
17504 redirection (see section ~~SECTfildiropt).
17506 When \directory\ is set, the string is expanded, and the message is delivered
17507 into a new file or files in or below the given directory, instead of being
17508 appended to a single mailbox file. A number of different formats are provided
17509 (see \maildir@_format\ and \mailstore@_format\), and see section ~~SECTopdir
17510 for further details of this form of delivery.
17512 .conf directory@_file string$**$ "$tt{q@$@{base62:@$tod@_epoch@}-@$inode}"
17514 When \directory\ is set, but neither \maildir@_format\ nor \mailstore@_format\
17515 is set, \%appendfile%\ delivers each message into a file whose name is obtained
17516 by expanding this string. The default value generates a unique name from the
17517 current time, in base 62 form, and the inode of the file. The variable
17518 \$inode$\ is available only when expanding this option.
17520 .conf directory@_mode "octal integer" 0700
17521 If \%appendfile%\ creates any directories as a result of the \create@_directory\
17522 option, their mode is specified by this option.
17524 .conf escape@_string string "see description"
17525 See \check@_string\ above.
17527 .conf file string$**$ unset
17528 This option is mutually exclusive with the \directory\ option, but one of
17529 \file\ or \directory\ must be set, unless the delivery is the direct result of
17530 a redirection (see section ~~SECTfildiropt). The \file\ option specifies a
17531 single file, to which the message is appended. One or more of
17532 \use@_fcntl@_lock\, \use@_flock@_lock\, or \use@_lockfile\ must be set with
17534 .index NFS||lock file
17535 .index locking files
17537 If you are using more than one host to deliver over NFS into the same
17538 mailboxes, you should always use lock files.
17540 The string value is expanded for each delivery, and must yield an absolute
17541 path. The most common settings of this option are variations on one of these
17544 file = /var/spool/mail/$local_part
17545 file = /home/$local_part/inbox
17548 .index `sticky' bit
17549 In the first example, all deliveries are done into the same directory. If Exim
17550 is configured to use lock files (see \use@_lockfile\ below) it must be able to
17551 create a file in the directory, so the `sticky' bit must be turned on for
17552 deliveries to be possible, or alternatively the \group\ option can be used to
17553 run the delivery under a group id which has write access to the directory.
17556 .conf file@_format string unset
17557 .index file||mailbox, checking existing format
17558 This option requests the transport to check the format of an existing file
17559 before adding to it. The check consists of matching a specific string at the
17560 start of the file. The value of the option consists of an even number of
17561 colon-separated strings. The first of each pair is the test string, and the
17562 second is the name of a transport. If the transport associated with a matched
17563 string is not the current transport, control is passed over to the other
17564 transport. For example, suppose the standard \%local@_delivery%\ transport has
17567 file_format = "From : local_delivery :\
17568 \1\1\1\1\n : local_mmdf_delivery"
17570 Mailboxes that begin with `From' are still handled by this transport, but if a
17571 mailbox begins with four binary ones followed by a newline, control is passed
17572 to a transport called \local__mmdf__delivery\, which presumably is configured
17573 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
17574 is assumed to match the current transport. If the start of a mailbox doesn't
17575 match any string, or if the transport named for a given string is not defined,
17576 delivery is deferred.
17578 .conf file@_must@_exist boolean false
17579 If this option is true, the file specified by the \file\ option must exist, and
17580 an error occurs if it does not. Otherwise, it is created if it does not exist.
17582 .conf lock@_fcntl@_timeout time 0s
17583 .index timeout||mailbox locking
17584 .index mailbox locking||blocking and non-blocking
17585 .index locking files
17586 By default, the \%appendfile%\ transport uses non-blocking calls to \*fcntl()*\
17587 when locking an open mailbox file. If the call fails, the delivery process
17588 sleeps for \lock@_interval\ and tries again, up to \lock@_retries\ times.
17589 Non-blocking calls are used so that the file is not kept open during the wait
17590 for the lock; the reason for this is to make it as safe as possible for
17591 deliveries over NFS in the case when processes might be accessing an NFS
17592 mailbox without using a lock file. This should not be done, but
17593 misunderstandings and hence misconfigurations are not unknown.
17595 On a busy system, however, the performance of a non-blocking lock approach is
17596 not as good as using a blocking lock with a timeout. In this case, the waiting
17597 is done inside the system call, and Exim's delivery process acquires the lock
17598 and can proceed as soon as the previous lock holder releases it.
17600 If \lock@_fcntl@_timeout\ is set to a non-zero time, blocking locks, with that
17601 timeout, are used. There may still be some retrying: the maximum number of
17604 (lock_retries * lock_interval) / lock_fcntl_timeout
17606 rounded up to the next whole number. In other words, the total time during
17607 which \%appendfile%\ is trying to get a lock is roughly the same, unless
17608 \lock@_fcntl@_timeout\ is set very large.
17610 You should consider setting this option if you are getting a lot of delayed
17611 local deliveries because of errors of the form
17613 failed to lock mailbox /some/file (fcntl)
17616 .conf lock@_flock@_timeout time 0s
17617 This timeout applies to file locking when using \*flock()*\ (see \use@_flock\);
17618 the timeout operates in a similar manner to \lock@_fcntl@_timeout\.
17620 .conf lock@_interval time 3s
17621 This specifies the time to wait between attempts to lock the file. See below
17622 for details of locking.
17624 .conf lock@_retries integer 10
17625 This specifies the maximum number of attempts to lock the file. A value of zero
17626 is treated as 1. See below for details of locking.
17628 .conf lockfile@_mode "octal integer" 0600
17629 This specifies the mode of the created lock file, when a lock file is being
17630 used (see \use@_lockfile\).
17632 .conf lockfile@_timeout time 30m
17633 .index timeout||mailbox locking
17634 When a lock file is being used (see \use@_lockfile\), if a lock file already
17635 exists and is older than this value, it is assumed to have been left behind by
17636 accident, and Exim attempts to remove it.
17639 .conf mailbox@_filecount string$**$ unset
17640 .index mailbox||specifying size of
17641 .index size||of mailbox
17642 If this option is set, it is expanded, and the result is taken as the current
17643 number of files in the mailbox. It must be a decimal number, optionally
17644 followed by K or M. This provides a way of obtaining this information from an
17645 external source that maintains the data.
17647 .conf mailbox@_size string$**$ unset
17648 .index mailbox||specifying size of
17649 .index size||of mailbox
17650 If this option is set, it is expanded, and the result is taken as the current
17651 size the mailbox. It must be a decimal number, optionally followed by K or M.
17652 This provides a way of obtaining this information from an external source that
17653 maintains the data. This is likely to be helpful for maildir deliveries where
17654 it is computationally expensive to compute the size of a mailbox.
17657 .conf maildir@_format boolean false
17658 .index maildir format||specifying
17659 If this option is set with the \directory\ option, the delivery is into a new
17660 file, in the `maildir' format that is used by other mail software. When the
17661 transport is activated directly from a \%redirect%\ router (for example, the
17662 \%address@_file%\ transport in the default configuration), setting
17663 \maildir@_format\ causes the path received from the router to be treated as a
17664 directory, whether or not it ends with \"/"\. This option is available only if
17665 \\SUPPORT@_MAILDIR\\ is present in \(Local/Makefile)\. See section
17666 ~~SECTmaildirdelivery below for further details.
17668 .conf maildir@_quota@_directory@_regex string "See below"
17669 .index maildir format||quota, directories included in
17670 .index quota||maildir, directories included in
17671 This option is relevant only when \maildir@_use@_size@_file\ is set. It defines
17672 a regular expression for specifying directories that should be included in the
17673 quota calculation. The default value is
17675 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
17677 which includes the \(cur)\ and \(new)\ directories, and any maildir++ folders
17678 (directories whose names begin with a dot). If you want to exclude the
17680 folder from the count (as some sites do), you need to change this setting to
17682 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
17684 This uses a negative lookahead in the regular expression to exclude the
17685 directory whose name is \(.Trash)\.
17687 .conf maildir@_retries integer 10
17688 This option specifies the number of times to retry when writing a file in
17689 `maildir' format. See section ~~SECTmaildirdelivery below.
17691 .conf maildir@_tag string$**$ unset
17692 This option applies only to deliveries in maildir format, and is described in
17693 section ~~SECTmaildirdelivery below.
17695 .conf maildir@_use@_size@_file boolean false
17696 .index maildir format||\(maildirsize)\ file
17697 Setting this option true enables support for \(maildirsize)\ files. Exim
17698 creates a \(maildirsize)\ file in a maildir if one does not exist, taking the
17699 quota from the \quota\ option of the transport. If \quota\ is unset, the value
17700 is zero. See section ~~SECTmaildirdelivery below for further details.
17702 .conf mailstore@_format boolean false
17703 .index mailstore format||specifying
17704 If this option is set with the \directory\ option, the delivery is into two new
17705 files in `mailstore' format. The option is available only if
17706 \\SUPPORT@_MAILSTORE\\ is present in \(Local/Makefile)\. See section
17707 ~~SECTopdir below for further details.
17709 .conf mailstore@_prefix string$**$ unset
17710 This option applies only to deliveries in mailstore format, and is described in
17711 section ~~SECTopdir below.
17713 .conf mailstore@_suffix string$**$ unset
17714 This option applies only to deliveries in mailstore format, and is described in
17715 section ~~SECTopdir below.
17717 .conf mbx@_format boolean false
17718 .index locking files
17719 .index file||locking
17720 .index file||MBX format
17721 .index MBX format, specifying
17722 This option is available only if Exim has been compiled with \\SUPPORT@_MBX\\
17723 set in \(Local/Makefile)\. If \mbx@_format\ is set with the \file\ option,
17724 the message is appended to the mailbox file in MBX format instead of
17725 traditional Unix format. This format is supported by Pine4 and its associated
17726 IMAP and POP daemons, by means of the \*c-client*\ library that they all use.
17728 \**Note**\: The \message@_prefix\ and \message@_suffix\ options are not
17729 automatically changed by the use of \mbx@_format\. They should normally be set
17730 empty when using MBX format, so this option almost always appears in this
17738 If none of the locking options are mentioned in the configuration,
17739 \use@_mbx@_lock\ is assumed and the other locking options default to false. It
17740 is possible to specify the other kinds of locking with \mbx@_format\, but
17741 \use@_fcntl@_lock\ and \use@_mbx@_lock\ are mutually exclusive. MBX locking
17742 interworks with \*c-client*\, providing for shared access to the mailbox. It
17743 should not be used if any program that does not use this form of locking is
17744 going to access the mailbox, nor should it be used if the mailbox file is NFS
17745 mounted, because it works only when the mailbox is accessed from a single host.
17747 If you set \use@_fcntl@_lock\ with an MBX-format mailbox, you cannot use
17748 the standard version of \*c-client*\, because as long as it has a mailbox open
17749 (this means for the whole of a Pine or IMAP session), Exim will not be able to
17750 append messages to it.
17752 .conf message@_prefix string$**$ "see below"
17754 The string specified here is expanded and output at the start of every message.
17755 The default is unset unless \file\ is specified and \use@_bsmtp\ is not set, in
17758 message_prefix = "From ${if def:return_path{$return_path}\
17759 {MAILER-DAEMON}} $tod_bsdinbox\n"
17762 .conf message@_suffix string$**$ "see below"
17763 The string specified here is expanded and output at the end of every message.
17764 The default is unset unless \file\ is specified and \use@_bsmtp\ is not set, in
17765 which case it is a single newline character. The suffix can be suppressed by
17771 .conf mode "octal integer" 0600
17772 If the output file is created, it is given this mode. If it already exists and
17773 has wider permissions, they are reduced to this mode. If it has narrower
17774 permissions, an error occurs unless \mode__fail__narrower\ is false. However,
17775 if the delivery is the result of a \save\ command in a filter file specifing a
17776 particular mode, the mode of the output file is always forced to take that
17777 value, and this option is ignored.
17779 .conf mode@_fail@_narrower boolean true
17780 This option applies in the case when an existing mailbox file has a narrower
17781 mode than that specified by the \mode\ option. If \mode@_fail@_narrower\ is
17782 true, the delivery is deferred (`mailbox has the wrong mode'); otherwise Exim
17783 continues with the delivery attempt, using the existing mode of the file.
17785 .conf notify@_comsat boolean false
17786 If this option is true, the \*comsat*\ daemon is notified after every successful
17787 delivery to a user mailbox. This is the daemon that notifies logged on users
17788 about incoming mail.
17790 .conf quota string$**$ unset
17791 .index quota||imposed by Exim
17792 This option imposes a limit on the size of the file to which Exim is appending,
17793 or to the total space used in the directory tree when the \directory\ option is
17794 set. In the latter case, computation of the space used is expensive, because
17795 all the files in the directory (and any sub-directories) have to be
17796 individually inspected and their sizes summed.
17797 (See \quota@_size@_regex\ and \maildir@_use@_size@_file\ for ways to avoid this
17798 in environments where users have no shell access to their mailboxes).
17800 As there is no interlock against two simultaneous deliveries into a
17801 multi-file mailbox, it is possible for the quota to be overrun in this case.
17802 For single-file mailboxes, of course, an interlock is a necessity.
17804 A file's size is taken as its \*used*\ value. Because of blocking effects, this
17805 may be a lot less than the actual amount of disk space allocated to the file.
17806 If the sizes of a number of files are being added up, the rounding effect can
17807 become quite noticeable, especially on systems that have large block sizes.
17808 Nevertheless, it seems best to stick to the \*used*\ figure, because this is
17809 the obvious value which users understand most easily.
17811 The value of the option is expanded, and must then be a numerical value
17812 (decimal point allowed), optionally followed by one of the letters K or M. The
17813 expansion happens while Exim is running as root, before it changes uid for the
17814 delivery. This means that files which are inaccessible to the end user can be
17815 used to hold quota values that are looked up in the expansion. When delivery
17816 fails because this quota is exceeded, the handling of the error is as for
17817 system quota failures.
17819 \**Note**\: A value of zero is interpreted as `no quota'.
17821 By default, Exim's quota checking mimics system quotas, and restricts the
17822 mailbox to the specified maximum size, though the value is not accurate to the
17823 last byte, owing to separator lines and additional headers that may get added
17824 during message delivery. When a mailbox is nearly full, large messages may get
17825 refused even though small ones are accepted, because the size of the current
17826 message is added to the quota when the check is made. This behaviour can be
17827 changed by setting \quota@_is@_inclusive\ false. When this is done, the check
17828 for exceeding the quota does not include the current message. Thus, deliveries
17829 continue until the quota has been exceeded; thereafter, no further messages are
17830 delivered. See also \quota@_warn@_threshold\.
17832 .conf quota@_directory string$**$ unset
17833 This option defines the directory to check for quota purposes when delivering
17834 into individual files. The default is the delivery directory, or, if a file
17835 called \(maildirfolder)\ exists in a maildir directory, the parent of the
17836 delivery directory.
17838 .conf quota@_filecount string$**$ 0
17839 This option applies when the \directory\ option is set. It limits the total
17840 number of files in the directory (compare the inode limit in system quotas). It
17841 can only be used if \quota\ is also set. The value is expanded; an expansion
17842 failure causes delivery to be deferred.
17844 .conf quota@_is@_inclusive boolean true
17847 .conf quota@_size@_regex string unset
17848 This option applies when one of the delivery modes that writes a separate file
17849 for each message is being used. When Exim wants to find the size of one of
17850 these files in order to test the quota, it first checks \quota@_size@_regex\.
17851 If this is set to a regular expression that matches the file name, and it
17852 captures one string, that string is interpreted as a representation of the
17853 file's size. The value of \quota@_size@_regex\ is not expanded.
17855 This feature is useful only when users have no shell access to their mailboxes
17856 -- otherwise they could defeat the quota simply by renaming the files. This
17857 facility can be used with maildir deliveries, by setting \maildir@_tag\ to add
17858 the file length to the file name. For example:
17860 maildir_tag = ,S=$message_size
17861 quota_size_regex = ,S=(\d+)
17863 The regular expression should not assume that the length is at the end of the
17864 file name (even though \maildir@_tag\ puts it there) because maildir MUAs
17865 sometimes add other information onto the ends of message file names.
17867 .conf quota@_warn@_message string$**$ "see below"
17868 See below for the use of this option. If it is not set when
17869 \quota@_warn@_threshold\ is set, it defaults to
17871 quota_warn_message = "\
17872 To: $local_part@$domain\n\
17873 Subject: Your mailbox\n\n\
17874 This message is automatically created \
17875 by mail delivery software.\n\n\
17876 The size of your mailbox has exceeded \
17877 a warning threshold that is\n\
17878 set by the system administrator.\n"
17881 .conf quota@_warn@_threshold string$**$ 0
17882 .index quota||warning threshold
17883 .index mailbox||size warning
17884 .index size||of mailbox
17885 This option is expanded in the same way as \quota\ (see above). If the
17886 resulting value is greater than zero, and delivery of the message causes the
17887 size of the file or total space in the directory tree to cross the given
17888 threshold, a warning message is sent. If \quota\ is also set, the threshold may
17889 be specified as a percentage of it by following the value with a percent sign.
17893 quota_warn_threshold = 75%
17895 If \quota\ is not set, a setting of \quota@_warn@_threshold\ that ends with a
17896 percent sign is ignored.
17898 The warning message itself is specified by the \quota@_warn@_message\ option,
17899 and it must start with a ::To:: header line containing the recipient(s). A
17900 ::Subject:: line should also normally be supplied. The \quota\ option does not
17901 have to be set in order to use this option; they are independent of one
17902 another except when the threshold is specified as a percentage.
17904 .conf use@_bsmtp boolean false
17905 .index envelope sender
17906 If this option is set true, \%appendfile%\ writes messages in `batch SMTP'
17907 format, with the envelope sender and recipient(s) included as SMTP commands. If
17908 you want to include a leading \\HELO\\ command with such messages, you can do
17909 so by setting the \message@_prefix\ option. See section ~~SECTbatchSMTP for
17910 details of batch SMTP.
17912 .conf use@_crlf boolean false
17913 .index carriage return
17915 This option causes lines to be terminated with the two-character CRLF sequence
17916 (carriage return, linefeed) instead of just a linefeed character. In the case
17917 of batched SMTP, the byte sequence written to the file is then an exact image
17918 of what would be sent down a real SMTP connection.
17920 The contents of the \message@_prefix\ and \message@_suffix\ options are written
17921 verbatim, so must contain their own carriage return characters if these are
17922 needed. In cases where these options have non-empty defaults, the values end
17923 with a single linefeed, so they
17925 be changed to end with \"@\r@\n"\ if \use@_crlf\ is set.
17927 .conf use@_fcntl@_lock boolean "see below"
17928 This option controls the use of the \*fcntl()*\ function to lock a file for
17929 exclusive use when a message is being appended. It is set by default unless
17930 \use@_flock@_lock\ is set. Otherwise, it should be turned off only if you know
17931 that all your MUAs use lock file locking. When both \use@_fcntl@_lock\ and
17932 \use@_flock@_lock\ are unset, \use@_lockfile\ must be set.
17934 .conf use@_flock@_lock boolean false
17935 This option is provided to support the use of \*flock()*\ for file locking, for
17936 the few situations where it is needed. Most modern operating systems support
17937 \*fcntl()*\ and \*lockf()*\ locking, and these two functions interwork with
17938 each other. Exim uses \*fcntl()*\ locking by default.
17940 This option is required only if you are using an operating system where
17941 \*flock()*\ is used by programs that access mailboxes (typically MUAs), and
17942 where \*flock()*\ does not correctly interwork with \*fcntl()*\. You can use
17943 both \*fcntl()*\ and \*flock()*\ locking simultaneously if you want.
17945 .index Solaris||\*flock()*\ support
17946 Not all operating systems provide \*flock()*\. Some versions of Solaris do not
17947 have it (and some, I think, provide a not quite right version built on top of
17948 \*lockf()*\). If the OS does not have \*flock()*\, Exim will be built without
17949 the ability to use it, and any attempt to do so will cause a configuration
17952 \**Warning**\: \*flock()*\ locks do not work on NFS files (unless \*flock()*\
17953 is just being mapped onto \*fcntl()*\ by the OS).
17955 .conf use@_lockfile boolean "see below"
17956 If this option is turned off, Exim does not attempt to create a lock file when
17957 appending to a mailbox file. In this situation, the only locking is by
17958 \*fcntl()*\. You should only turn \use@_lockfile\ off if you are absolutely
17959 sure that every MUA that is ever going to look at your users' mailboxes uses
17960 \*fcntl()*\ rather than a lock file, and even then only when you are not
17961 delivering over NFS from more than one host.
17963 .index NFS||lock file
17964 In order to append to an NFS file safely from more than one host, it is
17965 necessary to take out a lock $it{before} opening the file, and the lock file
17966 achieves this. Otherwise, even with \*fcntl()*\ locking, there is a risk of
17969 The \use@_lockfile\ option is set by default unless \use@_mbx@_lock\ is set. It
17970 is not possible to turn both \use@_lockfile\ and \use@_fcntl@_lock\ off, except
17971 when \mbx@_format\ is set.
17973 .conf use@_mbx@_lock boolean "see below"
17974 This option is available only if Exim has been compiled with \\SUPPORT@_MBX\\
17975 set in \(Local/Makefile)\. Setting the option specifies that special MBX
17976 locking rules be used. It is set by default if \mbx@_format\ is set and none of
17977 the locking options are mentioned in the configuration. The locking rules are
17978 the same as are used by the \*c-client*\ library that underlies Pine and the
17979 IMAP4 and POP daemons that come with it (see the discussion below). The rules
17980 allow for shared access to the mailbox. However, this kind of locking does not
17981 work when the mailbox is NFS mounted.
17983 You can set \use@_mbx@_lock\ with either (or both) of \use@_fcntl@_lock\ and
17984 \use@_flock@_lock\ to control what kind of locking is used in implementing the
17985 MBX locking rules. The default is to use \*fcntl()*\ if \use@_mbx@_lock\ is set
17986 without \use@_fcntl@_lock\ or \use@_flock@_lock\.
17990 .section Operational details for appending
17991 .rset SECTopappend "~~chapter.~~section"
17992 .index appending to a file
17993 .index file||appending
17994 Before appending to a file, the following preparations are made:
17996 If the name of the file is \(/dev/null)\, no action is taken, and a success
17999 .index directory creation
18000 If any directories on the file's path are missing, Exim creates them if the
18001 \create@_directory\ option is set. A created directory's mode is given by the
18002 \directory@_mode\ option.
18004 If \file@_format\ is set, the format of an existing file is checked. If this
18005 indicates that a different transport should be used, control is passed to that
18008 .index file||locking
18009 .index locking files
18010 .index NFS||lock file
18011 If \use@_lockfile\ is set, a lock file is built in a way that will work
18012 reliably over NFS, as follows:
18014 Create a `hitching post' file whose name is that of the lock file with the
18015 current time, primary host name, and process id added, by opening for writing
18016 as a new file. If this fails with an access error, delivery is deferred.
18018 Close the hitching post file, and hard link it to the lock file name.
18020 If the call to \*link()*\ succeeds, creation of the lock file has succeeded.
18021 Unlink the hitching post name.
18023 Otherwise, use \*stat()*\ to get information about the hitching post file, and
18024 then unlink hitching post name. If the number of links is exactly two, creation
18025 of the lock file succeeded but something (for example, an NFS server crash and
18026 restart) caused this fact not to be communicated to the \*link()*\ call.
18028 If creation of the lock file failed, wait for \lock@_interval\ and try again,
18029 up to \lock@_retries\ times. However, since any program that writes to a
18030 mailbox should complete its task very quickly, it is reasonable to time out old
18031 lock files that are normally the result of user agent and system crashes. If an
18032 existing lock file is older than \lockfile@_timeout\ Exim attempts to unlink it
18033 before trying again.
18036 A call is made to \*lstat()*\ to discover whether the main file exists, and if
18037 so, what its characteristics are. If \*lstat()*\ fails for any reason other
18038 than non-existence, delivery is deferred.
18040 .index symbolic link||to mailbox
18041 .index mailbox||symbolic link
18042 If the file does exist and is a symbolic link, delivery is deferred, unless the
18043 \allow@_symlink\ option is set, in which case the ownership of the link is
18044 checked, and then \*stat()*\ is called to find out about the real file, which
18045 is then subjected to the checks below. The check on the top-level link
18046 ownership prevents one user creating a link for another's mailbox in a sticky
18047 directory, though allowing symbolic links in this case is definitely not a good
18048 idea. If there is a chain of symbolic links, the intermediate ones are not
18051 If the file already exists but is not a regular file, or if the file's owner
18052 and group (if the group is being checked -- see \check@_group\ above) are
18053 different from the user and group under which the delivery is running,
18054 delivery is deferred.
18056 If the file's permissions are more generous than specified, they are reduced.
18057 If they are insufficient, delivery is deferred, unless \mode@_fail@_narrower\
18058 is set false, in which case the delivery is tried using the existing
18061 The file's inode number is saved, and the file is then opened for appending. If
18062 this fails because the file has vanished, \%appendfile%\ behaves as if it hadn't
18063 existed (see below). For any other failures, delivery is deferred.
18065 If the file is opened successfully, check that the inode number hasn't
18066 changed, that it is still a regular file, and that the owner and permissions
18067 have not changed. If anything is wrong, defer delivery and freeze the message.
18069 If the file did not exist originally, defer delivery if the \file@_must@_exist\
18070 option is set. Otherwise, check that the file is being created in a permitted
18071 directory if the \create@_file\ option is set (deferring on failure), and then
18072 open for writing as a new file, with the \\O@_EXCL\\ and \\O@_CREAT\\ options,
18073 except when dealing with a symbolic link (the \allow@_symlink\ option must be
18074 set). In this case, which can happen if the link points to a non-existent file,
18075 the file is opened for writing using \\O@_CREAT\\ but not \\O@_EXCL\\, because
18076 that prevents link following.
18078 .index loop||while file testing
18079 If opening fails because the file exists, obey the tests given above for
18080 existing files. However, to avoid looping in a situation where the file is
18081 being continuously created and destroyed, the exists/not-exists loop is broken
18082 after 10 repetitions, and the message is then frozen.
18084 If opening fails with any other error, defer delivery.
18086 .index file||locking
18087 .index locking files
18088 Once the file is open, unless both \use@_fcntl@_lock\ and \use@_flock@_lock\
18089 are false, it is locked using \*fcntl()*\ or \*flock()*\ or both. If
18090 \use@_mbx@_lock\ is false, an exclusive lock is requested in each case.
18091 However, if \use@_mbx@_lock\ is true,
18092 Exim takes out a shared lock on the open file,
18093 and an exclusive lock on the file whose name is
18095 /tmp/.<<device-number>>.<<inode-number>>
18097 using the device and inode numbers of the open mailbox file, in accordance with
18098 the MBX locking rules.
18100 If Exim fails to lock the file, there are two possible courses of action,
18101 depending on the value of the locking timeout. This is obtained from
18102 \lock@_fcntl@_timeout\ or \lock@_flock@_timeout\, as appropriate.
18104 If the timeout value is zero, the file is closed, Exim waits for
18105 \lock@_interval\, and then goes back and re-opens the file as above and tries
18106 to lock it again. This happens up to \lock@_retries\ times, after which the
18107 delivery is deferred.
18109 If the timeout has a value greater than zero, blocking calls to \*fcntl()*\ or
18110 \*flock()*\ are used (with the given timeout), so there has already been some
18111 waiting involved by the time locking fails. Nevertheless, Exim does not give up
18112 immediately. It retries up to
18114 (lock@_retries * lock@_interval) / <<timeout>>
18116 times (rounded up).
18119 At the end of delivery, Exim closes the file (which releases the \*fcntl()*\
18120 and/or \*flock()*\ locks) and then deletes the lock file if one was created.
18122 .section Operational details for delivery to a new file
18123 .rset SECTopdir "~~chapter.~~section"
18124 .index delivery||to single file
18126 When the \directory\ option is set instead of \file\, each message is delivered
18127 into a newly-created file or set of files. When \%appendfile%\ is activated
18128 directly from a \%redirect%\ router, neither \file\ nor \directory\ is normally
18129 set, because the path for delivery is supplied by the router. (See for example,
18130 the \%address@_file%\ transport in the default configuration.) In this case,
18131 delivery is to a new file if either the path name ends in \"/"\, or the
18132 \maildir@_format\ or \mailstore@_format\ option is set.
18134 No locking is required while writing the message to a new file, so the various
18135 locking options of the transport are ignored. The `From' line that by default
18136 separates messages in a single file is not normally needed, nor is the escaping
18137 of message lines that start with `From', and there is no need to ensure a
18138 newline at the end of each message. Consequently, the default values for
18139 \check@_string\, \message@_prefix\, and \message@_suffix\ are all unset when
18140 any of \directory\, \maildir@_format\, or \mailstore@_format\ is set.
18142 If Exim is required to check a \quota\ setting, it adds up the sizes of all the
18143 files in the delivery directory by default. However, you can specify a
18144 different directory by setting \quota@_directory\. Also, for maildir deliveries
18145 (see below) the \(maildirfolder)\ convention is honoured.
18148 .index maildir format
18149 .index mailstore format
18150 There are three different ways in which delivery to individual files can be
18151 done, controlled by the settings of the \maildir@_format\ and
18152 \mailstore@_format\ options. Note that code to support maildir or mailstore
18153 formats is not included in the binary unless \\SUPPORT@_MAILDIR\\ or
18154 \\SUPPORT@_MAILSTORE\\, respectively, is set in \(Local/Makefile)\.
18156 .index directory creation
18157 In all three cases an attempt is made to create the directory and any necessary
18158 sub-directories if they do not exist, provided that the \create@_directory\
18159 option is set (the default). The location of a created directory can be
18160 constrained by setting \create@_file\. A created directory's mode is given by
18161 the \directory@_mode\ option. If creation fails, or if the \create@_directory\
18162 option is not set when creation is required, delivery is deferred.
18165 .section Maildir delivery
18166 .rset SECTmaildirdelivery "~~chapter.~~section"
18167 .index maildir format||description of
18168 If the \maildir@_format\ option is true, Exim delivers each message by writing
18169 it to a file whose name is \(tmp/<<stime>>.H<<mtime>>P<<pid>>.<<host>>)\ in the
18170 given directory. If the delivery is successful, the file is renamed into the
18171 \(new)\ subdirectory.
18173 In the file name, <<stime>> is the current time of day in seconds, and
18174 <<mtime>> is the microsecond fraction of the time. After a maildir delivery,
18175 Exim checks that the time-of-day clock has moved on by at least one microsecond
18176 before terminating the delivery process. This guarantees uniqueness for the
18177 file name. However, as a precaution, Exim calls \*stat()*\ for the file before
18178 opening it. If any response other than \\ENOENT\\ (does not exist) is given,
18179 Exim waits 2 seconds and tries again, up to \maildir@_retries\ times.
18181 .index quota||in maildir delivery
18183 If Exim is required to check a \quota\ setting before a maildir delivery, and
18184 \quota@_directory\ is not set, it looks for a file called \(maildirfolder)\ in
18185 the maildir directory (alongside \(new)\, \(cur)\, \(tmp)\). If this exists,
18186 Exim assumes the directory is a maildir++ folder directory, which is one level
18187 down from the user's top level mailbox directory. This causes it to start at
18188 the parent directory instead of the current directory when calculating the
18189 amount of space used.
18192 One problem with delivering into a multi-file mailbox is that it is
18193 computationally expensive to compute the size of the mailbox for quota
18194 checking. Various approaches have been taken to reduce the amount of work
18195 needed. The next two sections describe two of them. A third alternative is to
18196 use some external process for maintaining the size data, and use the expansion
18197 of the \mailbox@_size\ option as a way of importing it into Exim.
18201 .section Using tags to record message sizes
18202 If \maildir@_tag\ is set, the string is expanded for each delivery.
18203 When the maildir file is renamed into the \(new)\ sub-directory, the
18204 tag is added to its name. However, if adding the tag takes the length of the
18205 name to the point where the test \*stat()*\ call fails with \\ENAMETOOLONG\\,
18206 the tag is dropped and the maildir file is created with no tag.
18208 Tags can be used to encode the size of files in their names; see
18209 \quota@_size@_regex\ above for an example. The expansion of \maildir@_tag\
18210 happens after the message has been written. The value of the \$message@_size$\
18211 variable is set to the number of bytes actually written. If the expansion is
18212 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
18213 be deferred. The expanded tag may contain any printing characters except `/'.
18214 Non-printing characters in the string are ignored; if the resulting string is
18215 empty, it is ignored. If it starts with an alphanumeric character, a leading
18219 .section Using a maildirsize file
18220 .index quota||in maildir delivery
18221 .index maildir format||\(maildirsize)\ file
18222 If \maildir@_use@_size@_file\ is true, Exim implements the maildir++ rules for
18223 storing quota and message size information in a file called \(maildirsize)\
18224 within the maildir directory. If this file does not exist, Exim creates it,
18225 setting the quota from the \quota\ option of the transport. If the maildir
18226 directory itself does not exist, it is created before any attempt to write a
18227 \(maildirsize)\ file.
18229 The \(maildirsize)\ file is used to hold information about the sizes of
18230 messages in the maildir, thus speeding up quota calculations. The quota value
18231 in the file is just a cache; if the quota is changed in the transport, the new
18232 value overrides the cached value when the next message is delivered. The cache
18233 is maintained for the benefit of other programs that access the maildir and
18234 need to know the quota.
18236 If the \quota\ option in the transport is unset or zero, the \(maildirsize)\
18237 file is maintained (with a zero quota setting), but no quota is imposed.
18239 A regular expression is available for controlling which directories in the
18240 maildir participate in quota calculations. See the description of the
18241 \maildir@_quota@_directory@_regex\ option above for details.
18244 .section Mailstore delivery
18245 .index mailstore format||description of
18246 If the \mailstore@_format\ option is true, each message is written as two files
18247 in the given directory. A unique base name is constructed from the message id
18248 and the current delivery process, and the files that are written use this base
18249 name plus the suffixes \(.env)\ and \(.msg)\. The \(.env)\ file contains the
18250 message's envelope, and the \(.msg)\ file contains the message itself.
18252 During delivery, the envelope is first written to a file with the suffix
18253 \(.tmp)\. The \(.msg)\ file is then written, and when it is complete, the
18254 \(.tmp)\ file is renamed as the \(.env)\ file. Programs that access messages in
18255 mailstore format should wait for the presence of both a \(.msg)\ and a \(.env)\
18256 file before accessing either of them. An alternative approach is to wait for
18257 the absence of a \(.tmp)\ file.
18259 The envelope file starts with any text defined by the \mailstore@_prefix\
18260 option, expanded and terminated by a newline if there isn't one. Then follows
18261 the sender address on one line, then all the recipient addresses, one per line.
18262 There can be more than one recipient only if the \batch@_max\ option is set
18263 greater than one. Finally, \mailstore@_suffix\ is expanded and the result
18264 appended to the file, followed by a newline if it does not end with one.
18266 If expansion of \mailstore@_prefix\ or \mailstore@_suffix\ ends with a forced
18267 failure, it is ignored. Other expansion errors are treated as serious
18268 configuration errors, and delivery is deferred.
18271 .section Non-special new file delivery
18272 If neither \maildir@_format\ nor \mailstore@_format\ is set, a single new file
18273 is created directly in the named directory. For example, when delivering
18274 messages into files in batched SMTP format for later delivery to some host (see
18275 section ~~SECTbatchSMTP), a setting such as
18277 directory = /var/bsmtp/$host
18279 might be used. A message is written to a file with a temporary name, which is
18280 then renamed when the delivery is complete. The final name is obtained by
18281 expanding the contents of the \directory@_file\ option.
18291 . ============================================================================
18292 .chapter The autoreply transport
18293 .set runningfoot "autoreply transport"
18294 .index transports||\%autoreply%\
18295 .index \%autoreply%\ transport
18296 The \%autoreply%\ transport is not a true transport in that it does not cause
18297 the message to be transmitted. Instead, it generates a new mail message.
18299 If the router that passes the message to this transport does not have the
18300 \unseen\ option set, the original message (for the current recipient) is not
18301 delivered anywhere. However, when the \unseen\ option is set on the router that
18302 passes the message to this transport, routing of the address continues, so
18303 another router can set up a normal message delivery.
18306 The \%autoreply%\ transport is usually run as the result of mail filtering, a
18307 `vacation' message being the standard example. However, it can also be run
18308 directly from a router like any other transport. To reduce the possibility of
18309 message cascades, messages created by the \%autoreply%\ transport always have
18310 empty envelope sender addresses, like bounce messages.
18312 The parameters of the message to be sent can be specified in the configuration
18313 by options described below. However, these are used only when the address
18314 passed to the transport does not contain its own reply information. When the
18315 transport is run as a consequence of a
18317 or \vacation\ command in a filter file, the parameters of the message are
18318 supplied by the filter, and passed with the address. The transport's options
18319 that define the message are then ignored (so they are not usually set in this
18320 case). The message is specified entirely by the filter or by the transport; it
18321 is never built from a mixture of options. However, the \file@_optional\,
18322 \mode\, and \return@_message\ options apply in all cases.
18324 \%Autoreply%\ is implemented as a local transport. When used as a result of a
18325 command in a user's filter file, \%autoreply%\ normally runs under the uid and
18326 gid of the user, and with appropriate current and home directories (see chapter
18327 ~~CHAPenvironment).
18329 There is a subtle difference between routing a message to a \%pipe%\ transport
18330 that generates some text to be returned to the sender, and routing it to an
18331 \%autoreply%\ transport. This difference is noticeable only if more than one
18332 address from the same message is so handled. In the case of a pipe, the
18333 separate outputs from the different addresses are gathered up and returned to
18334 the sender in a single message, whereas if \%autoreply%\ is used, a separate
18335 message is generated for each address that is passed to it.
18337 Non-printing characters are not permitted in the header lines generated for the
18338 message that \%autoreply%\ creates, with the exception of newlines that are
18339 immediately followed by whitespace. If any non-printing characters are found,
18340 the transport defers.
18341 Whether characters with the top bit set count as printing characters or not is
18342 controlled by the \print@_topbitchars\ global option.
18344 If any of the generic options for manipulating headers (for example,
18345 \headers@_add\) are set on an \%autoreply%\ transport, they apply to the copy of
18346 the original message that is included in the generated message when
18347 \return@_message\ is set. They do not apply to the generated message itself.
18349 If the \%autoreply%\ transport receives return code 2 from Exim when it submits
18350 the message, indicating that there were no recipients, it does not treat this
18351 as an error. This means that autoreplies sent to \$sender@_address$\ when this
18352 is empty (because the incoming message is a bounce message) do not cause
18353 problems. They are just discarded.
18356 .section Private options for autoreply
18358 .startconf autoreply
18359 .index options||\%autoreply%\ transport
18360 .conf bcc string$**$ unset
18361 This specifies the addresses that are to receive `blind carbon copies' of the
18362 message when the message is specified by the transport.
18364 .conf cc string$**$ unset
18365 This specifies recipients of the message and the contents of the ::Cc:: header
18366 when the message is specified by the transport.
18368 .conf file string$**$ unset
18369 The contents of the file are sent as the body of the message when the message
18370 is specified by the transport. If both \file\ and \text\ are set, the text
18371 string comes first.
18373 .conf file@_expand boolean false
18374 If this is set, the contents of the file named by the \file\ option are
18375 subjected to string expansion as they are added to the message.
18377 .conf file@_optional boolean false
18378 If this option is true, no error is generated if the file named by the \file\
18379 option or passed with the address does not exist or cannot be read.
18381 .conf from string$**$ unset
18382 This specifies the contents of the ::From:: header when the message is specified
18385 .conf headers string$**$ unset
18386 This specifies additional RFC 2822 headers that are to be added to the message when
18387 the message is specified by the transport. Several can be given by using `@\n'
18388 to separate them. There is no check on the format.
18390 .conf log string$**$ unset
18391 This option names a file in which a record of every message sent is logged when
18392 the message is specified by the transport.
18394 .conf mode "octal integer" 0600
18395 If either the log file or the `once' file has to be created, this mode is used.
18398 .conf never@_mail "address list$**$" unset
18399 If any run of the transport creates a message with a recipient that matches any
18400 item in the list, that recipient is quietly discarded. If all recipients are
18401 discarded, no message is created.
18404 .conf once string$**$ unset
18405 This option names a file or DBM database in which a record of each
18406 ::To:: recipient is kept when the message is specified by the transport.
18407 \**Note**\: This does not apply to ::Cc:: or ::Bcc:: recipients.
18408 If \once@_file@_size\ is not set, a DBM database is used, and it is allowed to
18409 grow as large as necessary. If a potential recipient is already in the
18410 database, no message is sent by default. However, if \once@_repeat\ specifies a
18411 time greater than zero, the message is sent if that much time has elapsed since
18412 a message was last sent to this recipient. If \once\ is unset, the message is
18415 If \once@_file@_size\ is set greater than zero, it changes the way Exim
18416 implements the \once\ option. Instead of using a DBM file to record every
18417 recipient it sends to, it uses a regular file, whose size will never get larger
18418 than the given value. In the file, it keeps a linear list of recipient
18419 addresses and times at which they were sent messages. If the file is full when
18420 a new address needs to be added, the oldest address is dropped. If
18421 \once@_repeat\ is not set, this means that a given recipient may receive
18422 multiple messages, but at unpredictable intervals that depend on the rate of
18423 turnover of addresses in the file. If \once@_repeat\ is set, it specifies a
18424 maximum time between repeats.
18426 .conf once@_file@_size integer 0
18429 .conf once@_repeat time$**$ 0s
18431 After expansion, the value of this option must be a valid time value.
18433 .conf reply@_to string$**$ unset
18434 This specifies the contents of the ::Reply-To:: header when the message is
18435 specified by the transport.
18437 .conf return@_message boolean false
18438 If this is set, a copy of the original message is returned with the new
18439 message, subject to the maximum size set in the \return@_size@_limit\ global
18440 configuration option.
18442 .conf subject string$**$ unset
18443 This specifies the contents of the ::Subject:: header when the message is
18444 specified by the transport.
18446 It is tempting to quote the original subject in automatic responses. For
18449 subject = Re: $h_subject:
18451 There is a danger in doing this, however. It may allow a third party to
18452 subscribe your users to an opt-in mailing list, provided that the list accepts
18453 bounce messages as subscription confirmations. Well-managed lists require a
18454 non-bounce message to confirm a subscription, so the danger is relatively
18458 .conf text string$**$ unset
18459 This specifies a single string to be used as the body of the message when the
18460 message is specified by the transport. If both \text\ and \file\ are set, the
18463 .conf to string$**$ unset
18464 This specifies recipients of the message and the contents of the ::To:: header
18465 when the message is specified by the transport.
18475 . ============================================================================
18476 .chapter The lmtp transport
18477 .set runningfoot "lmtp transport"
18478 .index transports||\%lmtp%\
18479 .index \%lmtp%\ transport
18480 .index LMTP||over a pipe
18481 .index LMTP||over a socket
18482 .rset CHAPLMTP "~~chapter"
18483 The \%lmtp%\ transport runs the LMTP protocol (RFC 2033) over a pipe to a
18485 or by interacting with a Unix domain socket.
18486 This transport is something of a cross between the \%pipe%\ and \%smtp%\
18487 transports. Exim also has support for using LMTP over TCP/IP; this is
18488 implemented as an option for the \%smtp%\ transport. Because LMTP is expected
18489 to be of minority interest, the default build-time configure in \(src/EDITME)\
18490 has it commented out. You need to ensure that
18494 is present in your \(Local/Makefile)\ in order to have the \%lmtp%\ transport
18495 included in the Exim binary.
18497 The private options of the \%lmtp%\ transport are as follows:
18500 .index options||\%lmtp%\ transport
18502 .conf batch@_id string$**$ unset
18503 See the description of local delivery batching in chapter ~~CHAPbatching.
18505 .conf batch@_max integer 1
18506 This limits the number of addresses that can be handled in a single delivery.
18507 Most LMTP servers can handle several addresses at once, so it is normally a
18508 good idea to increase this value. See the description of local delivery
18509 batching in chapter ~~CHAPbatching.
18511 .conf command string$**$ unset
18512 This option must be set if \socket\ is not set.
18513 The string is a command which is run in a separate process. It is split up into
18514 a command name and list of arguments, each of which is separately expanded (so
18515 expansion cannot change the number of arguments). The command is run directly,
18516 not via a shell. The message is passed to the new process using the standard
18517 input and output to operate the LMTP protocol.
18519 .conf socket string$**$ unset
18520 This option must be set if \command\ is not set. The result of expansion must
18521 be the name of a Unix domain socket. The transport connects to the socket and
18522 delivers the message to it using the LMTP protocol.
18524 .conf timeout time 5m
18525 The transport is aborted if the created process
18526 or Unix domain socket
18527 does not respond to LMTP commands or message input within this timeout.
18531 Here is an example of a typical LMTP transport:
18535 command = /some/local/lmtp/delivery/program
18539 This delivers up to 20 addresses at a time, in a mixture of domains if
18540 necessary, running as the user \*exim*\.
18548 . ============================================================================
18549 .chapter The pipe transport
18550 .rset CHAPpipetransport "~~chapter"
18551 .set runningfoot "pipe transport"
18552 .index transports||\%pipe%\
18553 .index \%pipe%\ transport
18554 The \%pipe%\ transport is used to deliver messages via a pipe to a command
18555 running in another process.
18558 use of \%pipe%\ as a pseudo-remote transport for passing messages to some other
18559 delivery mechanism (such as UUCP). Another is the use by individual users to
18560 automatically process their incoming messages. The \%pipe%\ transport can be
18561 used in one of the following ways:
18564 A router routes one address to a transport in the normal way, and the transport
18565 is configured as a \%pipe%\ transport. In this case, \$local@_part$\ contains
18566 the local part of the address (as usual), and the command that is run is
18567 specified by the \command\ option on the transport.
18570 If the \batch@_max\ option is set greater than 1 (the default), the transport
18571 can be called upon to handle more than one address in a single run. In this
18572 case, \$local@_part$\ is not set (because it is not unique). However, the
18573 pseudo-variable \$pipe@_addresses$\ (described in section ~~SECThowcommandrun
18574 below) contains all the addresses that are being handled.
18577 A router redirects an address directly to a pipe command (for example, from an
18578 alias or forward file). In this case, \$local@_part$\ contains the local part
18579 that was redirected, and \$address@_pipe$\ contains the text of the pipe
18580 command itself. The \command\ option on the transport is ignored.
18583 The \%pipe%\ transport is a non-interactive delivery method. Exim can also
18584 deliver messages over pipes using the LMTP interactive protocol. This is
18585 implemented by the \%lmtp%\ transport.
18587 In the case when \%pipe%\ is run as a consequence of an entry in a local user's
18588 \(.forward)\ file, the command runs under the uid and gid of that user. In
18589 other cases, the uid and gid have to be specified explicitly, either on the
18590 transport or on the router that handles the address. Current and `home'
18591 directories are also controllable. See chapter ~~CHAPenvironment for details of
18592 the local delivery environment.
18596 .section Concurrent delivery
18597 If two messages arrive at almost the same time, and both are routed to a pipe
18598 delivery, the two pipe transports may be run concurrently. You must ensure that
18599 any pipe commands you set up are robust against this happening. If the commands
18600 write to a file, the \exim@_lock\ utility might be of use.
18604 .section Returned status and data
18605 .index \%pipe%\ transport||returned data
18606 If the command exits with a non-zero return code, the delivery is deemed to
18607 have failed, unless either the \ignore@_status\ option is set (in which case
18608 the return code is treated as zero), or the return code is one of those listed
18609 in the \temp@_errors\ option, which are interpreted as meaning `try again
18610 later'. In this case, delivery is deferred. Details of a permanent failure are
18611 logged, but are not included in the bounce message, which merely contains
18612 `local delivery failed'.
18614 If the return code is greater than 128 and the command being run is a shell
18615 script, it normally means that the script was terminated by a signal whose
18616 value is the return code minus 128.
18618 If Exim is unable to run the command (that is, if \*execve()*\ fails), the
18619 return code is set to 127. This is the value that a shell returns if it is
18620 asked to run a non-existent command. The wording for the log line suggests that
18621 a non-existent command may be the problem.
18623 The \return@_output\ option can affect the result of a pipe delivery. If it is
18624 set and the command produces any output on its standard output or standard
18625 error streams, the command is considered to have failed, even if it gave a zero
18626 return code or if \ignore@_status\ is set. The output from the command is
18627 included as part of the bounce message. The \return@_fail@_output\ option is
18628 similar, except that output is returned only when the command exits with a
18629 failure return code, that is, a value other than zero or a code that matches
18633 .section How the command is run
18634 .rset SECThowcommandrun "~~chapter.~~section"
18635 .index \%pipe%\ transport||path for command
18636 The command line is (by default) broken down into a command name and arguments
18637 by the \%pipe%\ transport itself. The \allow@_commands\ and \restrict@_to@_path\
18638 options can be used to restrict the commands that may be run.
18639 .index quoting||in pipe command
18640 Unquoted arguments are delimited by white space. If an argument appears in
18641 double quotes, backslash is interpreted as an escape character in the usual
18642 way. If an argument appears in single quotes, no escaping is done.
18644 String expansion is applied to the command line except when it comes from a
18645 traditional \(.forward)\ file (commands from a filter file are expanded). The
18646 expansion is applied to each argument in turn rather than to the whole line.
18647 For this reason, any string expansion item that contains white space must be
18648 quoted so as to be contained within a single argument. A setting such as
18650 command = /some/path ${if eq{$local_part}{postmaster}{xxx}{yyy}}
18652 will not work, because the expansion item gets split between several
18653 arguments. You have to write
18655 command = /some/path "${if eq{$local_part}{postmaster}{xxx}{yyy}}"
18657 to ensure that it is all in one argument. The expansion is done in this way,
18658 argument by argument, so that the number of arguments cannot be changed as a
18659 result of expansion, and quotes or backslashes in inserted variables do not
18660 interact with external quoting.
18662 .index transport||filter
18663 .index filter||transport filter
18664 Special handling takes place when an argument consists of precisely the text
18665 `$tt{@$pipe@_addresses}'. This is not a general expansion variable; the only
18666 place this string is recognized is when it appears as an argument for a pipe or
18667 transport filter command. It causes each address that is being handled to be
18668 inserted in the argument list at that point $it{as a separate argument}. This
18669 avoids any problems with spaces or shell metacharacters, and is of use when a
18670 \%pipe%\ transport is handling groups of addresses in a batch.
18672 After splitting up into arguments and expansion, the resulting command is run
18673 in a subprocess directly from the transport, $it{not} under a shell. The
18674 message that is being delivered is supplied on the standard input, and the
18675 standard output and standard error are both connected to a single pipe that is
18676 read by Exim. The \max@_output\ option controls how much output the command may
18677 produce, and the \return@_output\ and \return@_fail@_output\ options control
18678 what is done with it.
18680 Not running the command under a shell (by default) lessens the security risks
18681 in cases when a command from a user's filter file is built out of data that was
18682 taken from an incoming message. If a shell is required, it can of course be
18683 explicitly specified as the command to be run. However, there are circumstances
18684 where existing commands (for example, in \(.forward)\ files) expect to be run
18685 under a shell and cannot easily be modified. To allow for these cases, there is
18686 an option called \use@_shell\, which changes the way the \%pipe%\ transport
18687 works. Instead of breaking up the command line as just described, it expands it
18688 as a single string and passes the result to \(/bin/sh)\. The
18689 \restrict@_to@_path\ option and the \$pipe@_addresses$\ facility cannot be used
18690 with \use@_shell\, and the whole mechanism is inherently less secure.
18693 .section Environment variables
18694 .rset SECTpipeenv "~~chapter.~~section"
18695 .index \%pipe%\ transport||environment for command
18696 .index environment for pipe transport
18697 The environment variables listed below are set up when the command is invoked.
18698 This list is a compromise for maximum compatibility with other MTAs. Note that
18699 the \environment\ option can be used to add additional variables to this
18703 DOMAIN $t $rm{the domain of the address}
18704 HOME $t $rm{the home directory, if set}
18705 HOST $t $rm{the host name when called from a router (see below)}
18706 LOCAL@_PART $t $rm{see below}
18707 LOCAL@_PART@_PREFIX $t $rm{see below}
18708 LOCAL@_PART@_SUFFIX $t $rm{see below}
18709 LOGNAME $t $rm{see below}
18710 MESSAGE@_ID $t $rm{the message's id}
18711 PATH $t $rm{as specified by the \path\ option below}
18712 QUALIFY@_DOMAIN $t $rm{the sender qualification domain}
18713 RECIPIENT $t $rm{the complete recipient address}
18714 SENDER $t $rm{the sender of the message (empty if a bounce)}
18715 SHELL $t `$tt{/bin/sh}'
18716 TZ $t $rm{the value of the \timezone\ option, if set}
18717 USER $t $rm{see below}
18720 When a \%pipe%\ transport is called directly from (for example) an \%accept%\
18721 router, \\LOCAL@_PART\\ is set to the local part of the address. When it is
18722 called as a result of a forward or alias expansion, \\LOCAL@_PART\\ is set to
18723 the local part of the address that was expanded. In both cases, any affixes are
18724 removed from the local part, and made available in \\LOCAL@_PART@_PREFIX\\ and
18725 \\LOCAL@_PART@_SUFFIX\\, respectively. \\LOGNAME\\ and \\USER\\ are set to the
18726 same value as \\LOCAL@_PART\\ for compatibility with other MTAs.
18729 \\HOST\\ is set only when a \%pipe%\ transport is called from a router that
18730 associates hosts with an address, typically when using \%pipe%\ as a
18731 pseudo-remote transport. \\HOST\\ is set to the first host name specified by
18735 If the transport's generic \home@_directory\ option is set, its value is used
18736 for the \\HOME\\ environment variable. Otherwise, a home directory may be set
18737 by the router's \transport@_home@_directory\ option, which defaults to the
18738 user's home directory if \check@_local@_user\ is set.
18740 .section Private options for pipe
18741 .index options||\%pipe%\ transport
18745 .conf allow@_commands "string list$**$" unset
18746 .index \%pipe%\ transport||permitted commands
18747 The string is expanded, and is then interpreted as a colon-separated list of
18748 permitted commands. If \restrict@_to@_path\ is not set, the only commands
18749 permitted are those in the \allow@_commands\ list. They need not be absolute
18750 paths; the \path\ option is still used for relative paths. If
18751 \restrict@_to@_path\ is set with \allow@_commands\, the command must either be
18752 in the \allow@_commands\ list, or a name without any slashes that is found on
18753 the path. In other words, if neither \allow@_commands\ nor \restrict@_to@_path\
18754 is set, there is no restriction on the command, but otherwise only commands
18755 that are permitted by one or the other are allowed. For example, if
18757 allow_commands = /usr/bin/vacation
18759 and \restrict@_to@_path\ is not set, the only permitted command is
18760 \(/usr/bin/vacation)\. The \allow@_commands\ option may not be set if
18761 \use@_shell\ is set.
18763 .conf batch@_id string$**$ unset
18764 See the description of local delivery batching in chapter ~~CHAPbatching.
18766 .conf batch@_max integer 1
18767 This limits the number of addresses that can be handled in a single delivery.
18768 See the description of local delivery batching in chapter ~~CHAPbatching.
18770 .conf check@_string string unset
18771 As \%pipe%\ writes the message, the start of each line is tested for matching
18772 \check@_string\, and if it does, the initial matching characters are replaced
18773 by the contents of \escape@_string\, provided both are set. The value of
18774 \check@_string\ is a literal string, not a regular expression, and the case of
18775 any letters it contains is significant. When \use@_bsmtp\ is set, the contents
18776 of \check@_string\ and \escape@_string\ are forced to values that implement the
18777 SMTP escaping protocol. Any settings made in the configuration file are
18780 .conf command string$**$ unset
18781 This option need not be set when \%pipe%\ is being used to deliver to pipes
18782 obtained directly from address redirections. In other cases, the option must be
18783 set, to provide a command to be run. It need not yield an absolute path (see
18784 the \path\ option below). The command is split up into separate arguments by
18785 Exim, and each argument is separately expanded, as described in section
18786 ~~SECThowcommandrun above.
18788 .conf environment string$**$ unset
18789 .index \%pipe%\ transport||environment for command
18790 .index environment for \%pipe%\ transport
18791 This option is used to add additional variables to the environment in which the
18792 command runs (see section ~~SECTpipeenv for the default list). Its value is a
18793 string which is expanded, and then interpreted as a colon-separated list of
18794 environment settings of the form `<<name>>=<<value>>'.
18796 .conf escape@_string string unset
18797 See \check@_string\ above.
18799 .conf freeze@_exec@_fail boolean false
18800 .index exec failure
18801 .index failure of exec
18802 .index \%pipe%\ transport||failure of exec
18803 Failure to exec the command in a pipe transport is by default treated like
18804 any other failure while running the command. However, if \freeze@_exec@_fail\
18805 is set, failure to exec is treated specially, and causes the message to be
18806 frozen, whatever the setting of \ignore@_status\.
18808 .conf ignore@_status boolean false
18809 If this option is true, the status returned by the subprocess that is set up to
18810 run the command is ignored, and Exim behaves as if zero had been returned.
18811 Otherwise, a non-zero status
18812 or termination by signal
18813 causes an error return from the transport unless the status value is one of
18814 those listed in \temp@_errors\; these cause the delivery to be deferred and
18817 .conf log@_defer@_output boolean false
18818 .index \%pipe%\ transport||logging output
18819 If this option is set, and the status returned by the command is
18820 one of the codes listed in \temp@_errors\ (that is, delivery was deferred),
18821 and any output was produced, the first line of it is written to the main log.
18823 .conf log@_fail@_output boolean false
18824 If this option is set, and the command returns any output, and also ends with a
18825 return code that is neither zero nor one of the return codes listed in
18826 \temp@_errors\ (that is, the delivery failed), the first line of output is
18827 written to the main log.
18829 This option and \log@_output\ are mutually exclusive. Only one of them may be
18833 .conf log@_output boolean false
18834 If this option is set and the command returns any output, the first line of
18835 output is written to the main log, whatever the return code.
18837 This option and \log@_fail@_output\ are mutually exclusive. Only one of them
18841 .conf max@_output integer 20K
18842 This specifies the maximum amount of output that the command may produce on its
18843 standard output and standard error file combined. If the limit is exceeded, the
18844 process running the command is killed. This is intended as a safety measure to
18845 catch runaway processes. The limit is applied independently of the settings of
18846 the options that control what is done with such output (for example,
18847 \return@_output\). Because of buffering effects, the amount of output may
18848 exceed the limit by a small amount before Exim notices.
18850 .conf message@_prefix string$**$ "see below"
18851 The string specified here is expanded and output at the start of every message.
18852 The default is unset if \use@_bsmtp\ is set. Otherwise it is
18855 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
18861 This is required by the commonly used \(/usr/bin/vacation)\ program.
18862 However, it must $it{not} be present if delivery is to the Cyrus IMAP server,
18863 or to the \tmail\ local delivery agent. The prefix can be suppressed by setting
18868 .conf message@_suffix string$**$ "see below"
18869 The string specified here is expanded and output at the end of every message.
18870 The default is unset if \use@_bsmtp\ is set. Otherwise it is a single newline.
18871 The suffix can be suppressed by setting
18876 .conf path string $tt{/usr/bin}
18877 This option specifies the string that is set up in the \\PATH\\ environment
18878 variable of the subprocess. If the \command\ option does not yield an absolute
18879 path name, the command is sought in the \\PATH\\ directories, in the usual way.
18880 \**Warning**\: This does not apply to a command specified as a transport
18883 .conf pipe@_as@_creator boolean false
18884 .index uid (user id)||local delivery
18885 If the generic \user\ option is not set and this option is true, the delivery
18886 process is run under the uid that was in force when Exim was originally called
18887 to accept the message. If the group id is not otherwise set (via the generic
18888 \group\ option), the gid that was in force when Exim was originally called to
18889 accept the message is used.
18891 .conf restrict@_to@_path boolean false
18892 When this option is set, any command name not listed in \allow@_commands\ must
18893 contain no slashes. The command is searched for only in the directories listed
18894 in the \path\ option. This option is intended for use in the case when a pipe
18895 command has been generated from a user's \(.forward)\ file. This is usually
18896 handled by a \%pipe%\ transport called \address@_pipe\.
18898 .conf return@_fail@_output boolean false
18899 If this option is true, and the command produced any output and ended with a
18900 return code other than zero or one of the codes listed in \temp@_errors\ (that
18901 is, the delivery failed), the output is returned in the bounce message.
18902 However, if the message has a null sender (that is, it is itself a bounce
18903 message), output from the command is discarded.
18905 This option and \return@_output\ are mutually exclusive. Only one of them may
18909 .conf return@_output boolean false
18910 If this option is true, and the command produced any output, the delivery is
18911 deemed to have failed whatever the return code from the command, and the output
18912 is returned in the bounce message. Otherwise, the output is just discarded.
18913 However, if the message has a null sender (that is, it is a bounce message),
18914 output from the command is always discarded, whatever the setting of this
18917 This option and \return@_fail@_output\ are mutually exclusive. Only one of them
18921 .conf temp@_errors "string list" "see below"
18922 .index \%pipe%\ transport||temporary failure
18923 This option contains either a colon-separated list of numbers, or a single
18924 asterisk. If \ignore@_status\ is false
18925 and \return@_output\ is not set,
18926 and the command exits with a non-zero return code, the failure is treated as
18927 temporary and the delivery is deferred if the return code matches one of the
18928 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
18929 codes are treated as permanent errors. The default setting contains the codes
18930 defined by \\EX@_TEMPFAIL\\ and \\EX@_CANTCREAT\\ in \(sysexits.h)\. If Exim is
18931 compiled on a system that does not define these macros, it assumes values of 75
18932 and 73, respectively.
18934 .conf timeout time 1h
18935 If the command fails to complete within this time, it is killed. This normally
18936 causes the delivery to fail. A zero time interval specifies no timeout. In
18937 order to ensure that any subprocesses created by the command are also killed,
18938 Exim makes the initial process a process group leader, and kills the whole
18939 process group on a timeout. However, this can be defeated if one of the
18940 processes starts a new process group.
18942 .conf umask "octal integer" 022
18943 This specifies the umask setting for the subprocess that runs the command.
18945 .conf use@_bsmtp boolean false
18946 .index envelope sender
18947 If this option is set true, the \%pipe%\ transport writes messages in `batch
18948 SMTP' format, with the envelope sender and recipient(s) included as SMTP
18949 commands. If you want to include a leading \\HELO\\ command with such messages,
18950 you can do so by setting the \message@_prefix\ option. See section
18951 ~~SECTbatchSMTP for details of batch SMTP.
18953 .conf use@_crlf boolean false
18954 .index carriage return
18956 This option causes lines to be terminated with the two-character CRLF sequence
18957 (carriage return, linefeed) instead of just a linefeed character. In the case
18958 of batched SMTP, the byte sequence written to the pipe is then an exact image
18959 of what would be sent down a real SMTP connection.
18961 The contents of the \message@_prefix\ and \message@_suffix\ options are written
18962 verbatim, so must contain their own carriage return characters if these are
18963 needed. Since the default values for both \message@_prefix\ and
18964 \message@_suffix\ end with a single linefeed, their values
18966 be changed to end with \"@\r@\n"\ if \use@_crlf\ is set.
18968 .conf use@_shell boolean false
18969 If this option is set, it causes the command to be passed to \(/bin/sh)\
18970 instead of being run directly from the transport, as described in section
18971 ~~SECThowcommandrun. This is less secure, but is needed in some situations
18972 where the command is expected to be run under a shell and cannot easily be
18973 modified. The \allow@_commands\ and \restrict@_to@_path\ options, and the
18974 `$tt{@$pipe@_addresses}' facility are incompatible with \use@_shell\. The
18975 command is expanded as a single string, and handed to \(/bin/sh)\ as data for
18980 .section Using an external local delivery agent
18981 .index local delivery||using an external agent
18982 .index \*procmail*\
18983 .index external local delivery
18984 .index delivery||\*procmail*\
18985 .index delivery||by external agent
18986 The \%pipe%\ transport can be used to pass all messages that require local
18987 delivery to a separate local delivery agent such as \procmail\. When doing
18988 this, care must be taken to ensure that the pipe is run under an appropriate
18989 uid and gid. In some configurations one wants this to be a uid that is trusted
18990 by the delivery agent to supply the correct sender of the message. It may be
18991 necessary to recompile or reconfigure the delivery agent so that it trusts an
18992 appropriate user. The following is an example transport and router
18993 configuration for \procmail\:
18998 command = /usr/local/bin/procmail -d $local_part
19002 check_string = "From "
19003 escape_string = ">From "
19012 transport = procmail_pipe
19015 In this example, the pipe is run as the local user, but with the group set to
19016 \*mail*\. An alternative is to run the pipe as a specific user such as \*mail*\
19017 or \*exim*\, but in this case you must arrange for \procmail\ to trust that
19018 user to supply a correct sender address. If you do not specify either a \group\
19019 or a \user\ option, the pipe command is run as the local user. The home
19020 directory is the user's home directory by default.
19022 Note that the command that the pipe transport runs does $it{not} begin with
19026 as shown in the \procmail\ documentation, because Exim does not by default use
19027 a shell to run pipe commands.
19030 The next example shows a transport and a router for a system where local
19031 deliveries are handled by the Cyrus IMAP server.
19034 local_delivery_cyrus:
19036 command = /usr/cyrus/bin/deliver \
19037 -m ${substr_1:$local_part_suffix} -- $local_part
19050 local_part_suffix = .*
19051 transport = local_delivery_cyrus
19053 Note the unsetting of \message@_prefix\ and \message@_suffix\, and the use of
19054 \return@_output\ to cause any text written by Cyrus to be returned to the
19062 . ============================================================================
19063 .chapter The smtp transport
19064 .rset CHAPsmtptrans "~~chapter"
19065 .set runningfoot "smtp transport"
19066 .index transports||\%smtp%\
19067 .index \%smtp%\ transport
19068 The \%smtp%\ transport delivers messages over TCP/IP connections using the SMTP
19069 or LMTP protocol. The list of hosts to try can either be taken from the address
19070 that is being processed (having been set up by the router), or specified
19071 explicitly for the transport. Timeout and retry processing (see chapter
19072 ~~CHAPretry) is applied to each IP address independently.
19074 .section Multiple messages on a single connection
19075 The sending of multiple messages over a single TCP/IP connection can arise in
19078 If a message contains more than \max@_rcpt\ (see below) addresses that are
19079 routed to the same host, more than one copy of the message has to be sent to
19080 that host. In this situation, multiple copies may be sent in a single run of
19081 the \%smtp%\ transport over a single TCP/IP connection. (What Exim actually does
19082 when it has too many addresses to send in one message also depends on the value
19083 of the global \remote@_max@_parallel\ option. Details are given in section
19086 .index hints database||remembering routing
19087 When a message has been successfully delivered over a TCP/IP connection, Exim
19088 looks in its hints database to see if there are any other messages awaiting a
19089 connection to the same host. If there are, a new delivery process is started
19090 for one of them, and the current TCP/IP connection is passed on to it. The new
19091 process may in turn send multiple copies and possibly create yet another
19095 For each copy sent over the same TCP/IP connection, a sequence counter is
19096 incremented, and if it ever gets to the value of \connection@_max@_messages\,
19097 no further messages are sent over that connection.
19100 .section Use of the @$host variable
19102 .index \$host@_address$\
19103 At the start of a run of the \%smtp%\ transport, the values of \$host$\ and
19104 \$host@_address$\ are the name and IP address of the first host on the host list
19105 passed by the router. However, when the transport is about to connect to a
19106 specific host, and while it is connected to that host, \$host$\ and
19107 \$host@_address$\ are set to the values for that host. These are the values
19108 that are in force when the \helo@_data\, \hosts@_try@_auth\, \interface\,
19109 \serialize@_hosts\, and the various TLS options are expanded.
19112 .section Private options for smtp
19113 The private options of the \%smtp%\ transport are as follows:
19115 .index options||\%smtp%\ transport
19117 .conf allow@_localhost boolean false
19118 .index local host||sending to
19119 .index fallback||hosts specified on transport
19120 When a host specified in \hosts\ or \fallback@_hosts\ (see below) turns out to
19121 be the local host, or is listed in \hosts@_treat@_as@_local\, delivery is
19122 deferred by default. However, if \allow@_localhost\ is set, Exim goes on to do
19123 the delivery anyway. This should be used only in special cases when the
19124 configuration ensures that no looping will result (for example, a differently
19125 configured Exim is listening on the port to which the message is sent).
19127 .conf authenticated@_sender string$**$ unset
19129 When Exim has authenticated as a client, this option sets a value for the
19130 \\AUTH=\\ item on outgoing \\MAIL\\ commands, overriding any existing
19131 authenticated sender value. If the string expansion is forced to fail, the
19132 option is ignored. Other expansion failures cause delivery to be deferred. If
19133 the result of expansion is an empty string, that is also ignored.
19135 If the SMTP session is not authenticated, the expansion of
19136 \authenticated@_sender\ still happens (and can cause the delivery to be
19137 deferred if it fails), but no \\AUTH=\\ item is added to \\MAIL\\ commands.
19139 This option allows you to use the \%smtp%\ transport in LMTP mode to
19140 deliver mail to Cyrus IMAP and provide the proper local part as the
19141 `authenticated sender', via a setting such as:
19143 authenticated_sender = $local_part
19145 This removes the need for IMAP subfolders to be assigned special ACLs to
19146 allow direct delivery to those subfolders.
19148 Because of expected uses such as that just described for Cyrus (when no
19149 domain is involved), there is no checking on the syntax of the provided
19152 .conf command@_timeout time 5m
19153 This sets a timeout for receiving a response to an SMTP command that has been
19154 sent out. It is also used when waiting for the initial banner line from the
19155 remote host. Its value must not be zero.
19157 .conf connect@_timeout time 5m
19158 This sets a timeout for the \*connect()*\ function, which sets up a TCP/IP call
19159 to a remote host. A setting of zero allows the system timeout (typically
19160 several minutes) to act. To have any effect, the value of this option must be
19161 less than the system timeout. However, it has been observed that on some
19162 systems there is no system timeout, which is why the default value for this
19163 option is 5 minutes, a value recommended by RFC 1123.
19165 .index SMTP||passed connection
19166 .index SMTP||multiple deliveries
19167 .index multiple SMTP deliveries
19168 .conf connection@_max@_messages integer 500
19169 This controls the maximum number of separate message deliveries that are sent
19170 over a single TCP/IP connection. If the value is zero, there is no limit.
19171 For testing purposes, this value can be overridden by the \-oB-\ command line
19174 .conf data@_timeout time 5m
19175 This sets a timeout for the transmission of each block in the data portion of
19176 the message. As a result, the overall timeout for a message depends on the size
19177 of the message. Its value must not be zero. See also \final@_timeout\.
19179 .conf delay@_after@_cutoff boolean true
19180 This option controls what happens when all remote IP addresses for a given
19181 domain have been inaccessible for so long that they have passed their retry
19184 In the default state, if the next retry time has not been reached for any of
19185 them, the address is bounced without trying any deliveries. In other words,
19186 Exim delays retrying an IP address after the final cutoff time until a new
19187 retry time is reached, and can therefore bounce an address without ever trying
19188 a delivery, when machines have been down for a long time. Some people are
19189 unhappy at this prospect, so...
19191 If \delay@_after@_cutoff\ is set false, Exim behaves differently. If all IP
19192 addresses are past their final cutoff time, Exim tries to deliver to those
19193 IP addresses that have not been tried since the message arrived. If there are
19194 none, of if they all fail, the address is bounced. In other words, it does not
19195 delay when a new message arrives, but immediately tries those expired IP
19196 addresses that haven't been tried since the message arrived. If there is a
19197 continuous stream of messages for the dead hosts, unsetting
19198 \delay@_after@_cutoff\ means that there will be many more attempts to deliver
19201 .conf dns@_qualify@_single boolean true
19202 If the \hosts\ or \fallback@_hosts\ option is being used,
19203 and the \gethostbyname\ option is false,
19204 the \\RES@_DEFNAMES\\ resolver option is set. See the \qualify@_single\ option
19205 in chapter ~~CHAPdnslookup for more details.
19207 .conf dns@_search@_parents boolean false
19208 .index \search@_parents\
19209 If the \hosts\ or \fallback@_hosts\ option is being used, and the
19210 \gethostbyname\ option is false, the \\RES@_DNSRCH\\ resolver option is set.
19211 See the \search@_parents\ option in chapter ~~CHAPdnslookup for more details.
19214 .conf fallback@_hosts "string list" unset
19215 .index fallback||hosts specified on transport
19216 String expansion is not applied to this option. The argument must be a
19217 colon-separated list of host names or IP addresses. Fallback hosts can also be
19218 specified on routers, which associate them with the addresses they process. As
19219 for the \hosts\ option without \hosts@_override\, \fallback@_hosts\ specified
19220 on the transport is used only if the address does not have its own associated
19221 fallback host list. Unlike \hosts\, a setting of \fallback@_hosts\ on an
19222 address is not overridden by \hosts@_override\. However, \hosts@_randomize\
19223 does apply to fallback host lists.
19225 If Exim is unable to deliver to any of the hosts for a particular address, and
19226 the errors are not permanent rejections, the address is put on a separate
19227 transport queue with its host list replaced by the fallback hosts, unless the
19228 address was routed via MX records and the current host was in the original MX
19229 list. In that situation, the fallback host list is not used.
19231 Once normal deliveries are complete, the fallback queue is delivered by
19232 re-running the same transports with the new host lists. If several failing
19233 addresses have the same fallback hosts (and \max@_rcpt\ permits it), a single
19234 copy of the message is sent.
19236 The resolution of the host names on the fallback list is controlled by the
19237 \gethostbyname\ option, as for the \hosts\ option. Fallback hosts apply
19238 both to cases when the host list comes with the address and when it is taken
19239 from \hosts\. This option provides a `use a smart host only if delivery fails'
19242 .conf final@_timeout time 10m
19243 This is the timeout that applies while waiting for the response to the final
19244 line containing just `.' that terminates a message. Its value must not be zero.
19246 .conf gethostbyname boolean false
19247 If this option is true when the \hosts\ and/or \fallback@_hosts\ options are
19248 being used, names are looked up using \*gethostbyname()*\
19249 (or \*getipnodebyname()*\ when available)
19250 instead of using the DNS. Of course, that function may in fact use the DNS, but
19251 it may also consult other sources of information such as \(/etc/hosts)\.
19253 .index \\HELO\\||argument, setting
19254 .index \\EHLO\\||argument, setting
19255 .conf helo@_data string$**$ $tt{@$primary@_hostname}
19256 The value of this option is expanded, and used as the argument for the \\EHLO\\
19257 or \\HELO\\ command that starts the outgoing SMTP session.
19259 .conf hosts "string list$**$" unset
19260 Hosts are associated with an address by a router such as \%dnslookup%\, which
19261 finds the hosts by looking up the address domain in the DNS. However, addresses
19262 can be passed to the \%smtp%\ transport by any router, and not all of them can
19263 provide an associated host list. The \hosts\ option specifies a list of hosts
19264 which are used if the address being processed does not have any hosts
19265 associated with it. The hosts specified by \hosts\ are also used, whether or
19266 not the address has its own hosts, if \hosts@_override\ is set.
19268 The string is first expanded, before being interpreted as a colon-separated
19269 list of host names or IP addresses. If the expansion fails, delivery is
19270 deferred. Unless the failure was caused by the inability to complete a lookup,
19271 the error is logged to the panic log as well as the main log. Host names are
19272 looked up either by searching directly for address records in the DNS or by
19273 calling \*gethostbyname()*\
19274 (or \*getipnodebyname()*\ when available),
19275 depending on the setting of the \gethostbyname\ option. When Exim is compiled
19276 with IPv6 support, if a host that is looked up in the DNS has both IPv4 and
19277 IPv6 addresses, both types of address are used.
19279 During delivery, the hosts are tried in order, subject to their retry status,
19280 unless \hosts@_randomize\ is set.
19282 .conf hosts@_avoid@_esmtp "host list$**$" unset
19283 .index ESMTP, avoiding use of
19284 .index \\HELO\\||forcing use of
19285 .index \\EHLO\\||avoiding use of
19286 .index \\PIPELINING\\||avoiding the use of
19287 This option is for use with broken hosts that announce ESMTP facilities (for
19288 example, \\PIPELINING\\) and then fail to implement them properly. When a host
19289 matches \hosts@_avoid@_esmtp\, Exim sends \\HELO\\ rather than \\EHLO\\ at the
19290 start of the SMTP session. This means that it cannot use any of the ESMTP
19291 facilities such as \\AUTH\\, \\PIPELINING\\, \\SIZE\\, and \\STARTTLS\\.
19293 .conf hosts@_avoid@_tls "host list$**$" unset
19294 .index TLS||avoiding for certain hosts
19295 Exim will not try to start a TLS session when delivering to any host that
19296 matches this list. See chapter ~~CHAPTLS for details of TLS.
19298 .conf hosts@_max@_try integer 5
19299 .index host||maximum number to try
19300 .index limit||number of hosts tried
19301 .index limit||number of MX tried
19302 .index MX record||maximum tried
19303 This option limits the number of IP addresses that are tried for any one
19304 delivery in cases where there are temporary delivery errors. Section
19305 ~~SECTvalhosmax describes in detail how the value of this option is used.
19308 .conf hosts@_max@_try@_hardlimit integer 50
19309 This is an additional check on the maximum number of IP addresses that Exim
19310 tries for any one delivery. Section ~~SECTvalhosmax describes its use and why
19314 .conf hosts@_nopass@_tls "host list$**$" unset
19315 .index TLS||passing connection
19316 .index multiple SMTP deliveries
19317 .index TLS||multiple message deliveries
19318 For any host that matches this list, a connection on which a TLS session has
19319 been started will not be passed to a new delivery process for sending another
19320 message on the same connection. See section ~~SECTmulmessam for an explanation
19321 of when this might be needed.
19323 .conf hosts@_override boolean false
19324 If this option is set and the \hosts\ option is also set, any hosts that are
19325 attached to the address are ignored, and instead the hosts specified by the
19326 \hosts\ option are always used. This option does not apply to
19329 .conf hosts@_randomize boolean false
19330 .index randomized host list
19331 .index host||list of, randomized
19332 .index fallback||randomized hosts
19333 If this option is set, and either the list of hosts is taken from the
19334 \hosts\ or the \fallback@_hosts\ option, or the hosts supplied by the router
19335 were not obtained from MX records (this includes fallback hosts from the
19336 router), and were not randomizied by the router, the order of trying the hosts
19337 is randomized each time the transport runs. Randomizing the order of a host
19338 list can be used to do crude load sharing.
19340 When \hosts@_randomize\ is true, a host list may be split into groups whose
19341 order is separately randomized. This makes it possible to set up MX-like
19342 behaviour. The boundaries between groups are indicated by an item that is just
19343 \"+"\ in the host list. For example:
19345 hosts = host1:host2:host3:+:host4:host5
19347 The order of the first three hosts and the order of the last two hosts is
19348 randomized for each use, but the first three always end up before the last two.
19349 If \hosts@_randomize\ is not set, a \"+"\ item in the list is ignored.
19351 .index authentication||required by client
19352 .conf hosts@_require@_auth "host list$**$" unset
19353 This option provides a list of servers for which authentication must succeed
19354 before Exim will try to transfer a message. If authentication fails for
19355 servers which are not in this list, Exim tries to send unauthenticated. If
19356 authentication fails for one of these servers, delivery is deferred. This
19357 temporary error is detectable in the retry rules, so it can be turned into a
19358 hard failure if required. See also \hosts@_try@_auth\, and chapter
19359 ~~CHAPSMTPAUTH for details of authentication.
19361 .conf hosts@_require@_tls "host list$**$" unset
19362 .index TLS||requiring for certain servers
19363 Exim will insist on using a TLS session when delivering to any host that
19364 matches this list. See chapter ~~CHAPTLS for details of TLS.
19365 \**Note**\: This option affects outgoing mail only. To insist on TLS for
19366 incoming messages, use an appropriate ACL.
19368 .index authentication||optional in client
19369 .conf hosts@_try@_auth "host list$**$" unset
19370 This option provides a list of servers to which, provided they announce
19371 authentication support, Exim will attempt to authenticate as a client when it
19372 connects. If authentication fails, Exim will try to transfer the message
19373 unauthenticated. See also \hosts@_require@_auth\, and chapter ~~CHAPSMTPAUTH
19374 for details of authentication.
19376 .index bind IP address
19377 .index IP address||binding
19378 .conf interface "string list$**$" unset
19379 This option specifies which interface to bind to when making an outgoing SMTP
19380 call. The variables \$host$\ and \$host@_address$\ refer to the host to which a
19381 connection is about to be made during the expansion of the string. Forced
19382 expansion failure, or an empty string result causes the option to be ignored.
19383 Otherwise, after expansion,
19384 the string must be a list of IP addresses, colon-separated by default, but the
19385 separator can be changed in the usual way.
19388 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
19390 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
19391 connection. If none of them are the correct type, the option is ignored. If
19392 \interface\ is not set, or is ignored, the system's IP functions choose which
19393 interface to use if the host has more than one.
19395 .conf keepalive boolean true
19396 .index keepalive||on outgoing connection
19397 This option controls the setting of \\SO@_KEEPALIVE\\ on outgoing TCP/IP socket
19398 connections. When set, it causes the kernel to probe idle connections
19399 periodically, by sending packets with `old' sequence numbers. The other end of
19400 the connection should send a acknowledgement if the connection is still okay or
19401 a reset if the connection has been aborted. The reason for doing this is that
19402 it has the beneficial effect of freeing up certain types of connection that can
19403 get stuck when the remote host is disconnected without tidying up the TCP/IP
19404 call properly. The keepalive mechanism takes several hours to detect
19407 .conf max@_rcpt integer 100
19408 .index \\RCPT\\||maximum number of outgoing
19409 This option limits the number of \\RCPT\\ commands that are sent in a single
19410 SMTP message transaction. Each set of addresses is treated independently, and
19411 so can cause parallel connections to the same host if \remote@_max@_parallel\
19414 .conf multi@_domain boolean true
19415 When this option is set, the \%smtp%\ transport can handle a number of addresses
19416 containing a mixture of different domains provided they all resolve to the same
19417 list of hosts. Turning the option off restricts the transport to handling only
19418 one domain at a time. This is useful if you want to use \$domain$\ in an
19419 expansion for the transport, because it is set only when there is a single
19420 domain involved in a remote delivery.
19422 .conf port string$**$ "see below"
19423 .index port||sending TCP/IP
19424 .index TCP/IP||setting outgoing port
19425 This option specifies the TCP/IP port on the server to which Exim connects. If
19426 it begins with a digit it is taken as a port number; otherwise it is looked up
19427 using \*getservbyname()*\. The default value is normally `smtp', but if
19428 \protocol\ is set to `lmtp', the default is `lmtp'.
19429 If the expansion fails, or if a port number cannot be found, delivery is
19433 .conf protocol string "smtp"
19434 .index LMTP||over TCP/IP
19435 If this option is set to `lmtp' instead of `smtp', the default value for the
19436 \port\ option changes to `lmtp', and the transport operates the LMTP protocol
19437 (RFC 2033) instead of SMTP. This protocol is sometimes used for local
19438 deliveries into closed message stores. Exim also has support for running LMTP
19439 over a pipe to a local process -- see chapter ~~CHAPLMTP.
19441 .conf retry@_include@_ip@_address boolean true
19442 Exim normally includes both the host name and the IP address in the key it
19443 constructs for indexing retry data after a temporary delivery failure. This
19444 means that when one of several IP addresses for a host is failing, it gets
19445 tried periodically (controlled by the retry rules), but use of the other IP
19446 addresses is not affected.
19448 However, in some dialup environments hosts are assigned a different IP address
19449 each time they connect. In this situation the use of the IP address as part of
19450 the retry key leads to undesirable behaviour. Setting this option false causes
19451 Exim to use only the host name. This should normally be done on a separate
19452 instance of the \%smtp%\ transport, set up specially to handle the dialup hosts.
19454 .conf serialize@_hosts "host list$**$" unset
19455 .index serializing connections
19456 .index host||serializing connections
19457 Because Exim operates in a distributed manner, if several messages for the same
19458 host arrive at around the same time, more than one simultaneous connection to
19459 the remote host can occur. This is not usually a problem except when there is a
19460 slow link between the hosts. In that situation it may be helpful to restrict
19461 Exim to one connection at a time. This can be done by setting
19462 \serialize@_hosts\ to match the relevant hosts.
19464 .index hints database||serializing deliveries to a host
19465 Exim implements serialization by means of a hints database in which a record is
19466 written whenever a process connects to one of the restricted hosts. The record
19467 is deleted when the connection is completed. Obviously there is scope for
19468 records to get left lying around if there is a system or program crash. To
19469 guard against this, Exim ignores any records that are more than six hours old.
19471 If you set up this kind of serialization, you should also arrange to delete the
19472 relevant hints database whenever your system reboots. The names of the files
19473 start with \(misc)\ and they are kept in the \(spool/db)\ directory. There
19474 may be one or two files, depending on the type of DBM in use. The same files
19475 are used for ETRN serialization.
19477 .conf size@_addition integer 1024
19478 .index SMTP||\\SIZE\\
19479 .index message||size issue for transport filter
19480 .index size||of message
19481 .index transport||filter
19482 .index filter||transport filter
19483 If a remote SMTP server indicates that it supports the \\SIZE\\ option of the
19484 \\MAIL\\ command, Exim uses this to pass over the message size at the start of
19485 an SMTP transaction. It adds the value of \size@_addition\ to the value it
19486 sends, to allow for headers and other text that may be added during delivery by
19487 configuration options or in a transport filter. It may be necessary to increase
19488 this if a lot of text is added to messages.
19490 Alternatively, if the value of \size@_addition\ is set negative, it disables
19491 the use of the \\SIZE\\ option altogether.
19493 .conf tls@_certificate string$**$ unset
19494 .index TLS||client certificate, location of
19495 .index certificate||for client, location of
19496 The value of this option must be the absolute path to a file which contains the
19497 client's certificate, for use when sending a message over an encrypted
19498 connection. The values of \$host$\ and \$host@_address$\ are set to the name
19499 and address of the server during the expansion. See chapter ~~CHAPTLS for
19502 \**Note**\: This option must be set if you want Exim to use TLS when sending
19503 messages as a client. The global option of the same name specifies the
19504 certificate for Exim as a server; it is not automatically assumed that the same
19505 certificate should be used when Exim is operating as a client.
19507 .conf tls@_crl string$**$ unset
19508 .index TLS||client certificate revocation list
19509 .index certificate||revocation list for client
19510 This option specifies a certificate revocation list. The expanded value must
19511 be the name of a file that contains a CRL in PEM format.
19513 .conf tls@_privatekey string$**$ unset
19514 .index TLS||client private key, location of
19515 The value of this option must be the absolute path to a file which contains the
19516 client's private key, for use when sending a message over an encrypted
19517 connection. The values of \$host$\ and \$host@_address$\ are set to the name
19518 and address of the server during the expansion.
19519 If this option is unset, the private key is assumed to be in the same file as
19521 See chapter ~~CHAPTLS for details of TLS.
19523 .conf tls@_require@_ciphers string$**$ unset
19524 .index TLS||requiring specific ciphers
19525 .index cipher||requiring specific
19526 The value of this option must be a list of permitted cipher suites, for use
19527 when setting up an outgoing encrypted connection. (There is a global option of
19528 the same name for controlling incoming connections.) The values of \$host$\ and
19529 \$host@_address$\ are set to the name and address of the server during the
19530 expansion. See chapter ~~CHAPTLS for details of TLS; note that this option is
19531 used in different ways by OpenSSL and GnuTLS (see sections ~~SECTreqciphssl and
19534 For GnuTLS, the order of the ciphers is a preference order.
19537 .conf tls@_tempfail@_tryclear boolean true
19538 When the server host is not in \hosts@_require@_tls\, and there is a problem in
19539 setting up a TLS session, this option determines whether or not Exim should try
19540 to deliver the message unencrypted. If it is set false, delivery to the
19541 current host is deferred; if there are other hosts, they are tried. If this
19542 option is set true, Exim attempts to deliver unencrypted after a 4\*xx*\
19543 response to \\STARTTLS\\. Also, if \\STARTTLS\\ is accepted, but the subsequent
19544 TLS negotiation fails, Exim closes the current connection (because it is in an
19545 unknown state), opens a new one to the same host, and then tries the delivery
19548 .conf tls@_verify@_certificates string$**$ unset
19549 .index TLS||server certificate verification
19550 .index certificate||verification of server
19551 The value of this option must be the absolute path to a file containing
19552 permitted server certificates, for use when setting up an encrypted connection.
19553 Alternatively, if you are using OpenSSL, you can set
19554 \tls@_verify@_certificates\ to the name of a directory containing certificate
19555 files. This does not work with GnuTLS; the option must be set to the name of a
19556 single file if you are using GnuTLS. The values of \$host$\ and
19557 \$host@_address$\ are set to the name and address of the server during the
19558 expansion of this option. See chapter ~~CHAPTLS for details of TLS.
19563 .section How the limits for the number of hosts to try are used
19564 .rset SECTvalhosmax "~~chapter.~~section"
19565 .index host||maximum number to try
19566 .index limit||hosts, maximum number tried
19568 There are two options that are concerned with the number of hosts that are
19569 tried when an SMTP delivery takes place. They are \hosts@_max@_try\ and
19570 \hosts@_max@_try@_hardlimit\.
19573 The \hosts@_max@_try\ option limits the number of hosts that are tried
19574 for a single delivery. However, despite the term `host' in its name, the option
19575 actually applies to each IP address independently. In other words, a multihomed
19576 host is treated as several independent hosts, just as it is for retrying.
19578 Many of the larger ISPs have multiple MX records which often point to
19579 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
19580 created as a result of routing one of these domains.
19582 Trying every single IP address on such a long list does not seem sensible; if
19583 several at the top of the list fail, it is reasonable to assume there is some
19584 problem that is likely to affect all of them. Roughly speaking, the value of
19585 \hosts@_max@_try\ is the maximum number that are tried before deferring the
19586 delivery. However, the logic cannot be quite that simple.
19588 Firstly, IP addresses that are skipped because their retry times have not
19589 arrived do not count, and in addition, addresses that are past their retry
19590 limits are also not counted, even when they are tried. This means that when
19591 some IP addresses are past their retry limits, more than the value of
19592 \hosts@_max@_retry\ may be tried. The reason for this behaviour is to ensure
19593 that all IP addresses are considered before timing out an email address (but
19594 see below for an exception).
19596 Secondly, when the \hosts@_max@_try\ limit is reached, Exim looks down the host
19597 list to see if there is a subsequent host with a different (higher valued) MX.
19598 If there is, that host is considered next, and the current IP address is used
19599 but not counted. This behaviour helps in the case of a domain with a retry rule
19600 that hardly ever delays any hosts, as is now explained:
19602 Consider the case of a long list of hosts with one MX value, and a few with a
19603 higher MX value. If \hosts@_max@_try\ is small (the default is 5) only a few
19604 hosts at the top of the list are tried at first. With the default retry rule,
19605 which specifies increasing retry times, the higher MX hosts are eventually
19606 tried when those at the top of the list are skipped because they have not
19607 reached their retry times.
19609 However, it is common practice to put a fixed short retry time on domains for
19610 large ISPs, on the grounds that their servers are rarely down for very long.
19611 Unfortunately, these are exactly the domains that tend to resolve to long lists
19612 of hosts. The short retry time means that the lowest MX hosts are tried every
19613 time. The attempts may be in a different order because of random sorting, but
19614 without the special MX check, the higher MX hosts would never be tried
19616 until all the lower MX hosts had timed out (which might be several days),
19617 because there are always some lower MX hosts that have reached their retry
19618 times. With the special check, Exim considers at least one IP address from each
19619 MX value at every delivery attempt, even if the \hosts@_max@_try\ limit has
19620 already been reached.
19622 The above logic means that \hosts@_max@_try\ is not a hard limit, and in
19623 particular, Exim normally eventually tries all the IP addresses before timing
19624 out an email address. When \hosts@_max@_try\ was implemented, this seemed a
19625 reasonable thing to do. Recently, however, some lunatic DNS configurations have
19626 been set up with hundreds of IP addresses for some domains. It can
19627 take a very long time indeed for an address to time out in these cases.
19629 The \hosts@_max@_try@_hardlimit\ option was added to help with this problem.
19630 Exim never tries more than this number of IP addresses; if it hits this limit
19631 and they are all timed out, the email address is bounced, even though not all
19632 possible IP addresses have been tried.
19642 . ============================================================================
19643 .chapter Address rewriting
19644 .set runningfoot "address rewriting"
19645 .rset CHAPrewrite ~~chapter
19646 .index rewriting||addresses
19647 There are some circumstances in which Exim automatically rewrites domains in
19648 addresses. The two most common are when an address is given without a domain
19649 (referred to as an `unqualified address') or when an address contains an
19650 abbreviated domain that is expanded by DNS lookup.
19652 Unqualified envelope addresses are accepted only for locally submitted
19653 messages, or messages from hosts that match \sender@_unqualified@_hosts\ or
19654 \recipient@_unqualified@_hosts\, respectively. Unqualified addresses in header
19655 lines are qualified if they are in locally submitted messages, or messages from
19656 hosts that are permitted to send unqualified envelope addresses. Otherwise,
19657 unqualified addresses in header lines are neither qualified nor rewritten.
19659 One situation in which Exim does $it{not} automatically rewrite a domain is
19660 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
19661 such a domain should be rewritten using the `canonical' name, and some MTAs do
19662 this. The new RFCs do not contain this suggestion.
19664 .section Explicitly configured address rewriting
19665 This chapter describes the rewriting rules that can be used in the
19666 main rewrite section of the configuration file, and also in the generic
19667 \headers@_rewrite\ option that can be set on any transport.
19669 Some people believe that configured address rewriting is a Mortal Sin.
19670 Others believe that life is not possible without it. Exim provides the
19671 facility; you do not have to use it.
19673 The main rewriting rules that appear in the `rewrite' section of the
19674 configuration file are applied to addresses in incoming messages, both envelope
19675 addresses and addresses in header lines. Each rule specifies the types of
19676 address to which it applies.
19678 Rewriting of addresses in header lines applies only to those headers that
19679 were received with the message, and, in the case of transport rewriting, those
19680 that were added by a system filter. That is, it applies only to those headers
19681 that are common to all copies of the message. Header lines that are added by
19682 individual routers or transports (and which are therefore specific to
19683 individual recipient addresses) are not rewritten.
19685 In general, rewriting addresses from your own system or domain has some
19686 legitimacy. Rewriting other addresses should be done only with great care and
19687 in special circumstances. The author of Exim believes that rewriting should be
19688 used sparingly, and mainly for `regularizing' addresses in your own domains.
19689 Although it can sometimes be used as a routing tool, this is very strongly
19692 There are two commonly encountered circumstances where rewriting is used, as
19693 illustrated by these examples:
19695 The company whose domain is \*hitch.fict.example*\ has a number of hosts that
19696 exchange mail with each other behind a firewall, but there is only a single
19697 gateway to the outer world. The gateway rewrites \*@*.hitch.fict.example*\ as
19698 \*hitch.fict.example*\ when sending mail off-site.
19700 A host rewrites the local parts of its own users so that, for example,
19701 \*fp42@@hitch.fict.example*\ becomes \*Ford.Prefect@@hitch.fict.example*\.
19704 .section When does rewriting happen?
19705 .index rewriting||timing of
19706 .index ~~ACL||rewriting addresses in
19707 Configured address rewriting can take place at several different stages of a
19708 message's processing.
19710 At the start of an ACL for \\MAIL\\, the sender address may have been rewritten
19711 by a special SMTP-time rewrite rule (see section ~~SECTrewriteS), but no
19712 ordinary rewrite rules have yet been applied. If, however, the sender address
19713 is verified in the ACL, it is rewritten before verification, and remains
19714 rewritten thereafter. The subsequent value of \$sender@_address$\ is the
19715 rewritten address. This also applies if sender verification happens in a
19716 \\RCPT\\ ACL. Otherwise, when the sender address is not verified, it is
19717 rewritten as soon as a message's header lines have been received.
19719 Similarly, at the start of an ACL for \\RCPT\\, the current recipient's address
19720 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
19721 rewrite rules have yet been applied to it. However, the behaviour is different
19722 from the sender address when a recipient is verified. The address is rewritten
19723 for the verification, but the rewriting is not remembered at this stage. The
19724 value of \$local@_part$\ and \$domain$\ after verification are always the same
19725 as they were before (that is, they contain the unrewritten -- except for
19726 SMTP-time rewriting -- address).
19728 Once a message's header lines have been received, all the envelope recipient
19729 addresses are permanently rewritten, and rewriting is also applied to the
19730 addresses in the header lines (if configured).
19731 .index \*local@_scan()*\ function||address rewriting, timing of
19732 Thus, all the rewriting is completed before the \\DATA\\ ACL and
19733 \*local@_scan()*\ functions are run.
19735 When an address is being routed, either for delivery or for verification,
19736 rewriting is applied immediately to child addresses that are generated by
19737 redirection, unless \no@_rewrite\ is set on the router.
19739 .index envelope sender, rewriting
19740 .index rewriting||at transport time
19741 At transport time, additional rewriting of addresses in header lines can be
19742 specified by setting the generic \headers@_rewrite\ option on a transport. This
19743 option contains rules that are identical in form to those in the rewrite
19744 section of the configuration file. In addition, the outgoing envelope sender
19745 can be rewritten by means of the \return@_path\ transport option. However, it
19746 is not possible to rewrite envelope recipients at transport time.
19750 .section Testing the rewriting rules that apply on input
19751 .index rewriting||testing
19752 .index testing||rewriting
19753 Exim's input rewriting configuration appears in a part of the run time
19754 configuration file headed by `begin rewrite'. It can be tested by the \-brw-\
19755 command line option. This takes an address (which can be a full RFC 2822
19756 address) as its argument. The output is a list of how the address would be
19757 transformed by the rewriting rules for each of the different places it might
19758 appear in an incoming message, that is, for each different header and for the
19759 envelope sender and recipient fields. For example,
19761 exim -brw ph10@exim.workshop.example
19763 might produce the output
19765 sender: Philip.Hazel@exim.workshop.example
19766 from: Philip.Hazel@exim.workshop.example
19767 to: ph10@exim.workshop.example
19768 cc: ph10@exim.workshop.example
19769 bcc: ph10@exim.workshop.example
19770 reply-to: Philip.Hazel@exim.workshop.example
19771 env-from: Philip.Hazel@exim.workshop.example
19772 env-to: ph10@exim.workshop.example
19774 which shows that rewriting has been set up for that address when used in any of
19775 the source fields, but not when it appears as a recipient address. At the
19776 present time, there is no equivalent way of testing rewriting rules that are
19777 set for a particular transport.
19779 .section Rewriting rules
19780 .index rewriting||rules
19781 The rewrite section of the configuration file consists of lines of rewriting
19784 <<source pattern>> <<replacement>> <<flags>>
19786 Rewriting rules that are specified for the \headers@_rewrite\ generic transport
19787 option are given as a colon-separated list. Each item in the list takes the
19788 same form as a line in the main rewriting configuration
19789 (except that any colons must be doubled, of course).
19791 The formats of source patterns and replacement strings are described below.
19792 Each is terminated by white space, unless enclosed in double quotes, in which
19793 case normal quoting conventions apply inside the quotes. The flags are single
19794 characters which may appear in any order. Spaces and tabs between them are
19797 For each address that could potentially be rewritten, the rules are scanned in
19798 order, and replacements for the address from earlier rules can themselves be
19799 replaced by later rules (but see the `q' and `R' flags).
19801 The order in which addresses are rewritten is undefined, may change between
19802 releases, and must not be relied on, with one exception: when a message is
19803 received, the envelope sender is always rewritten first, before any header
19804 lines are rewritten. For example, the replacement string for a rewrite of an
19805 address in ::To:: must not assume that the message's address in ::From:: has (or
19806 has not) already been rewritten. However, a rewrite of ::From:: may assume that
19807 the envelope sender has already been rewritten.
19809 The variables \$local@_part$\ and \$domain$\ can be used in the replacement
19810 string to refer to the address that is being rewritten. Note that lookup-driven
19811 rewriting can be done by a rule of the form
19815 where the lookup key uses \$1$\ and \$2$\ or \$local@_part$\ and \$domain$\ to
19816 refer to the address that is being rewritten.
19818 .section Rewriting patterns
19819 .index rewriting||patterns
19820 .index address list||in a rewriting pattern
19821 The source pattern in a rewriting rule is any item which may appear in an
19822 address list (see section ~~SECTaddresslist). It is in fact processed as a
19823 single-item address list, which means that it is expanded before being tested
19824 against the address.
19826 Domains in patterns should be given in lower case. Local parts in patterns are
19827 case-sensitive. If you want to do case-insensitive matching of local parts, you
19828 can use a regular expression that starts with \"^(?i)"\.
19830 .index numerical variables (\$1$\, \$2$\, etc)||in rewriting rules
19831 After matching, the numerical variables \$1$\, \$2$\, etc. may be set,
19832 depending on the type of match which occurred. These can be used in the
19833 replacement string to insert portions of the incoming address. \$0$\ always
19834 refers to the complete incoming address. When a regular expression is used, the
19835 numerical variables are set from its capturing subexpressions. For other types
19836 of pattern they are set as follows:
19839 If a local part or domain starts with an asterisk, the numerical variables
19840 refer to the character strings matched by asterisks, with \$1$\ associated with
19841 the first asterisk, and \$2$\ with the second, if present. For example, if the
19844 *queen@@*.fict.example
19846 is matched against the address \*hearts-queen@@wonderland.fict.example*\ then
19848 $0 = hearts-queen@wonderland.fict.example
19852 Note that if the local part does not start with an asterisk, but the domain
19853 does, it is \$1$\ that contains the wild part of the domain.
19855 If the domain part of the pattern is a partial lookup, the wild and fixed parts
19856 of the domain are placed in the next available numerical variables. Suppose,
19857 for example, that the address \*foo@@bar.baz.example*\ is processed by a
19858 rewriting rule of the form
19860 *@@partial-dbm;/some/dbm/file <<replacement string>>
19862 and the key in the file that matches the domain is \"*.baz.example"\. Then
19868 If the address \*foo@@baz.example*\ is looked up, this matches the same
19869 wildcard file entry, and in this case \$2$\ is set to the empty string, but
19870 \$3$\ is still set to \*baz.example*\. If a non-wild key is matched in a
19871 partial lookup, \$2$\ is again set to the empty string and \$3$\ is set to the
19872 whole domain. For non-partial domain lookups, no numerical variables are set.
19875 .section Rewriting replacements
19876 .index rewriting||replacements
19877 If the replacement string for a rule is a single asterisk, addresses that
19878 match the pattern and the flags are $it{not} rewritten, and no subsequent
19879 rewriting rules are scanned. For example,
19881 hatta@lookingglass.fict.example * f
19883 specifies that \*hatta@@lookingglass.fict.example*\ is never to be rewritten in
19886 If the replacement string is not a single asterisk, it is expanded, and must
19887 yield a fully qualified address. Within the expansion, the variables
19888 \$local@_part$\ and \$domain$\ refer to the address that is being rewritten.
19889 Any letters they contain retain their original case -- they are not lower
19890 cased. The numerical variables are set up according to the type of pattern that
19891 matched the address, as described above. If the expansion is forced to fail by
19892 the presence of `fail' in a conditional or lookup item, rewriting by the
19893 current rule is abandoned, but subsequent rules may take effect. Any other
19894 expansion failure causes the entire rewriting operation to be abandoned, and an
19895 entry written to the panic log.
19898 .section Rewriting flags
19899 There are three different kinds of flag that may appear on rewriting rules:
19901 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
19904 A flag that specifies rewriting at SMTP time: S.
19906 Flags that control the rewriting process: Q, q, R, w.
19908 For rules that are part of the \headers@_rewrite\ generic transport option,
19909 E, F, T, and S are not permitted.
19912 .section Flags specifying which headers and envelope addresses to rewrite
19913 .index rewriting||flags
19914 If none of the following flag letters, nor the `S' flag (see section
19915 ~~SECTrewriteS) are present, a main rewriting rule applies to all headers and
19916 to both the sender and recipient fields of the envelope, whereas a
19917 transport-time rewriting rule just applies to all headers. Otherwise, the
19918 rewriting rule is skipped unless the relevant addresses are being processed.
19920 E $rm{rewrite all envelope fields}
19921 F $rm{rewrite the envelope From field}
19922 T $rm{rewrite the envelope To field}
19923 b $rm{rewrite the ::Bcc:: header}
19924 c $rm{rewrite the ::Cc:: header}
19925 f $rm{rewrite the ::From:: header}
19926 h $rm{rewrite all headers}
19927 r $rm{rewrite the ::Reply-To:: header}
19928 s $rm{rewrite the ::Sender:: header}
19929 t $rm{rewrite the ::To:: header}
19931 You should be particularly careful about rewriting ::Sender:: headers, and
19932 restrict this to special known cases in your own domains.
19934 .section The SMTP-time rewriting flag
19935 .rset SECTrewriteS "~~chapter.~~section"
19936 .index SMTP||rewriting malformed addresses
19937 .index \\RCPT\\||rewriting argument of
19938 .index \\MAIL\\||rewriting argument of
19939 The rewrite flag `S' specifies a rewrite of incoming envelope addresses at SMTP
19940 time, as soon as an address is received in a \\MAIL\\ or \\RCPT\\ command, and
19941 before any other processing; even before syntax checking. The pattern is
19942 required to be a regular expression, and it is matched against the whole of the
19943 data for the command, including any surrounding angle brackets.
19945 This form of rewrite rule allows for the handling of addresses that are not
19946 compliant with RFCs 2821 and 2822 (for example, `bang paths' in batched SMTP
19947 input). Because the input is not required to be a syntactically valid address,
19948 the variables \$local@_part$\ and \$domain$\ are not available during the
19949 expansion of the replacement string. The result of rewriting replaces the
19950 original address in the \\MAIL\\ or \\RCPT\\ command.
19952 .section Flags controlling the rewriting process
19953 There are four flags which control the way the rewriting process works. These
19954 take effect only when a rule is invoked, that is, when the address is of the
19955 correct type (matches the flags) and matches the pattern:
19957 If the `Q' flag is set on a rule, the rewritten address is permitted to be an
19958 unqualified local part. It is qualified with \qualify@_recipient\. In the
19959 absence of `Q' the rewritten address must always include a domain.
19961 If the `q' flag is set on a rule, no further rewriting rules are considered,
19962 even if no rewriting actually takes place because of a `fail' in the expansion.
19963 The `q' flag is not effective if the address is of the wrong type (does not
19964 match the flags) or does not match the pattern.
19966 The `R' flag causes a successful rewriting rule to be re-applied to the new
19967 address, up to ten times. It can be combined with the `q' flag, to stop
19968 rewriting once it fails to match (after at least one successful rewrite).
19970 .index rewriting||whole addresses
19971 When an address in a header is rewritten, the rewriting normally applies only
19972 to the working part of the address, with any comments and RFC 2822 `phrase'
19973 left unchanged. For example, rewriting might change
19975 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
19979 From: Ford Prefect <prefectf@hitch.fict.example>
19981 Sometimes there is a need to replace the whole address item, and this can be
19982 done by adding the flag letter `w' to a rule. If this is set on a rule that
19983 causes an address in a header line to be rewritten, the entire address is
19984 replaced, not just the working part. The replacement must be a complete RFC
19985 2822 address, including the angle brackets if necessary. If text outside angle
19986 brackets contains a character whose value is greater than 126 or less than 32
19987 (except for tab), the text is encoded according to RFC 2047.
19988 The character set is taken from \headers@_charset\, which defaults to
19991 When the `w' flag is set on a rule that causes an envelope address to be
19992 rewritten, all but the working part of the replacement address is discarded.
19995 .section Rewriting examples
19996 Here is an example of the two common rewriting paradigms:
19998 *@*.hitch.fict.example $1@hitch.fict.example
19999 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
20000 {$value}fail}@hitch.fict.example bctfrF
20002 Note the use of `fail' in the lookup expansion in the second rule, forcing
20003 the string expansion to fail if the lookup does not succeed. In this context it
20004 has the effect of leaving the original address unchanged, but Exim goes on to
20005 consider subsequent rewriting rules, if any, because the `q' flag is not
20006 present in that rule. An alternative to `fail' would be to supply \$1$\
20007 explicitly, which would cause the rewritten address to be the same as before,
20008 at the cost of a small bit of processing. Not supplying either of these is an
20009 error, since the rewritten address would then contain no local part.
20011 The first example above replaces the domain with a superior, more general
20012 domain. This may not be desirable for certain local parts. If the rule
20014 root@*.hitch.fict.example *
20016 were inserted before the first rule, rewriting would be suppressed for the
20017 local part \*root*\ at any domain ending in \*hitch.fict.example*\.
20019 Rewriting can be made conditional on a number of tests, by making use of
20020 \${if$\ in the expansion item. For example, to apply a rewriting rule only to
20021 messages that originate outside the local host:
20023 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
20024 {$1@hitch.fict.example}fail}"
20026 The replacement string is quoted in this example because it contains white
20029 .index rewriting||bang paths
20030 .index bang paths||rewriting
20031 Exim does not handle addresses in the form of `bang paths'. If it sees such an
20032 address it treats it as an unqualified local part which it qualifies with the
20033 local qualification domain (if the source of the message is local or if the
20034 remote host is permitted to send unqualified addresses). Rewriting can
20035 sometimes be used to handle simple bang paths with a fixed number of
20036 components. For example, the rule
20038 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
20040 rewrites a two-component bang path \*host.name!user*\ as the domain address
20041 \*user@@host.name*\. However, there is a security implication in using this as
20042 a global rewriting rule for envelope addresses. It can provide a backdoor
20043 method for using your system as a relay, because the incoming addresses appear
20044 to be local. If the bang path addresses are received via SMTP, it is safer to
20045 use the `S' flag to rewrite them as they are received, so that relay checking
20046 can be done on the rewritten addresses.
20056 . ============================================================================
20057 .chapter Retry configuration
20058 .set runningfoot "retry configuration"
20059 .rset CHAPretry ~~chapter
20060 .index retry||configuration, description of
20061 .index configuration file||retry section
20062 The `retry' section of the run time configuration file contains a list of retry
20063 rules which control how often Exim tries to deliver messages that cannot be
20064 delivered at the first attempt. If there are no retry rules, temporary errors
20065 are treated as permanent. The \-brt-\ command line option can be used to test
20066 which retry rule will be used for a given address or domain.
20068 The most common cause of retries is temporary failure to deliver to a remote
20069 host because the host is down, or inaccessible because of a network problem.
20070 Exim's retry processing in this case is applied on a per-host (strictly, per IP
20071 address) basis, not on a per-message basis. Thus, if one message has recently
20072 been delayed, delivery of a new message to the same host is not immediately
20073 tried, but waits for the host's retry time to arrive. If the \retry@_defer\ log
20074 selector is set, the message
20075 .index retry||time not reached
20076 `retry time not reached' is written to the main log whenever a delivery is
20077 skipped for this reason. Section ~~SECToutSMTPerr contains more details of the
20078 handling of errors during remote deliveries.
20080 Retry processing applies to routing as well as to delivering, except as covered
20081 in the next paragraph. The retry rules do not distinguish between these
20082 actions. It is not possible, for example, to specify different behaviour for
20083 failures to route the domain \*snark.fict.example*\ and failures to deliver to
20084 the host \*snark.fict.example*\. I didn't think anyone would ever need this
20085 added complication, so did not implement it. However, although they share the
20086 same retry rule, the actual retry times for routing and transporting a given
20087 domain are maintained independently.
20089 When a delivery is not part of a queue run (typically an immediate delivery on
20090 receipt of a message), the routers are always run, and local deliveries are
20091 always attempted, even if retry times are set for them. This makes for better
20092 behaviour if one particular message is causing problems (for example, causing
20093 quota overflow, or provoking an error in a filter file). If such a delivery
20094 suffers a temporary failure, the retry data is updated as normal, and
20095 subsequent delivery attempts from queue runs occur only when the retry time for
20096 the local address is reached.
20099 .section Retry rules
20100 .index retry||rules
20102 Each retry rule occupies one line and consists of three or four parts,
20103 separated by white space: a pattern, an error name, an optional list of sender
20104 addresses, and a list of retry parameters. The pattern and sender lists must be
20105 enclosed in double quotes if they contain white space. The rules are searched in
20106 order until one is found where the pattern, error name, and sender list (if
20107 present) match the failing host or address, the error that occurred, and the
20108 message's sender, respectively.
20111 The pattern is any single item that may appear in an address list (see section
20112 ~~SECTaddresslist). It is in fact processed as a one-item address list, which
20113 means that it is expanded before being tested against the address that has
20114 been delayed. Address list processing treats a plain domain name as if it were
20115 preceded by `*@@', which makes it possible for many retry rules to start with
20116 just a domain. For example,
20118 lookingglass.fict.example * F,24h,30m;
20120 provides a rule for any address in the \*lookingglass.fict.example*\ domain,
20123 alice@lookingglass.fict.example * F,24h,30m;
20125 applies only to temporary failures involving the local part \alice\.
20126 In practice, almost all rules start with a domain name pattern without a local
20129 .index regular expressions||in retry rules
20130 \**Warning**\: If you use a regular expression in a routing rule pattern, it
20131 must match a complete address, not just a domain, because that is how regular
20132 expressions work in address lists.
20134 ^@\Nxyz@\d+@\.abc@\.example@$@\N * G,1h,10m,2 \Wrong\
20135 ^@\N[^@@]+@@xyz@\d+@\.abc@\.example@$@\N * G,1h,10m,2 \Right\
20139 .section Choosing which retry rule to use
20140 When Exim is looking for a retry rule after a routing attempt has failed (for
20141 example, after a DNS timeout), each line in the retry configuration is tested
20142 against the complete address only if \retry__use@_local@_part\ is set for the
20143 router. Otherwise, only the domain is used, except when matching against a
20144 regular expression, when the local part of the address is replaced with `*'. A
20145 domain on its own can match a domain pattern, or a pattern that starts with
20146 `*@@'. By default, \retry@_use@_local@_part\ is true for routers where
20147 \check@_local@_user\ is true, and false for other routers.
20149 Similarly, when Exim is looking for a retry rule after a local delivery has
20150 failed (for example, after a mailbox full error), each line in the retry
20151 configuration is tested against the complete address only if
20152 \retry@_use@_local@_part\ is set for the transport (it defaults true for all
20155 When Exim is looking for a retry rule after a remote delivery attempt has
20156 failed, what happens depends on the type of failure. After a 4\*xx*\ SMTP
20157 response for a recipient address, the whole address is used when searching the
20158 retry rules. The rule that is found is used to create a retry time for the
20161 For a temporary error that is not related to an individual address,
20162 (for example, a connection timeout), each line in the retry configuration is
20163 checked twice. First, the name of the remote host is used as a domain name
20164 (preceded by `*@@' when matching a regular expression). If this does not match
20165 the line, the domain from the email address is tried in a similar fashion. For
20166 example, suppose the MX records for \*a.b.c.example*\ are
20168 a.b.c.example MX 5 x.y.z.example
20172 and the retry rules are
20174 p.q.r.example * F,24h,30m;
20175 a.b.c.example * F,4d,45m;
20177 and a delivery to the host \*x.y.z.example*\ fails. The first rule matches
20178 neither the host nor the domain, so Exim looks at the second rule. This does
20179 not match the host, but it does match the domain, so it is used to calculate
20180 the retry time for the host \*x.y.z.example*\. Meanwhile, Exim tries to deliver
20181 to \*p.q.r.example*\. If this fails, the first retry rule is used, because it
20184 In other words, failures to deliver to host \*p.q.r.example*\ use the first
20185 rule to determine retry times, but for all the other hosts for the domain
20186 \*a.b.c.example*\, the second rule is used. The second rule is also used if
20187 routing to \*a.b.c.example*\ suffers a temporary failure.
20189 .section Retry rules for specific errors
20190 .index retry||specific errors, specifying
20191 The second field in a retry rule is the name of a particular error, or an
20192 asterisk, which matches any error. The errors that can be tested for are:
20198 \auth@_failed\: Authentication failed when trying to send to a host in the
20199 \hosts@_require@_auth\ list in an \%smtp%\ transport.
20202 \rcpt@_4xx\: A 4\*xx*\ error was received for an outgoing \\RCPT\\ command.
20203 Either the first or both of the x's can be given as specific digits, for
20204 example: \"rcpt@_45x"\ or \"rcpt@_436"\. For example, to recognize 452 errors
20205 given to \\RCPT\\ commands by a particular host, and have retries every ten
20206 minutes and a one-hour timeout, you could set up a retry rule of this form:
20208 the.host.name rcpt_452 F,1h,10m
20210 These errors apply to both outgoing SMTP (the \%smtp%\ transport) and outgoing
20211 LMTP (either the \%lmtp%\ transport, or the \%smtp%\ transport in LMTP mode).
20212 Note, however, that they apply only to responses to \\RCPT\\ commands.
20215 \refused@_MX\: A connection to a host obtained from an MX record was refused.
20218 \refused@_A\: A connection to a host not obtained from an MX record was
20222 \refused\: A connection was refused.
20225 \timeout@_connect@_MX\: A connection attempt to a host obtained from an MX
20229 \timeout@_connect@_A\: A connection attempt to a host not obtained from an MX
20233 \timeout@_connect\: A connection attempt timed out.
20236 \timeout@_MX\: There was a timeout while connecting or during an SMTP session
20237 with a host obtained from an MX record.
20240 \timeout@_A\: There was a timeout while connecting or during an SMTP session
20241 with a host not obtained from an MX record.
20244 \timeout\: There was a timeout while connecting or during an SMTP session.
20247 \quota\: A mailbox quota was exceeded in a local delivery by the
20248 \%appendfile%\ transport.
20250 .index quota||error testing in retry rule
20251 .index retry||quota error testing
20253 \quota@_\<<time>>: A mailbox quota was exceeded in a local delivery by
20254 the \%appendfile%\ transport, and the mailbox has not been accessed for
20255 <<time>>. For example, \*quota@_4d*\ applies to a quota error when the mailbox
20256 has not been accessed for four days.
20261 .index mailbox||time of last read
20262 The idea of \quota@_\<<time>> is to make it possible to have shorter timeouts
20263 when the mailbox is full and is not being read by its owner. Ideally, it should
20264 be based on the last time that the user accessed the mailbox. However, it is
20265 not always possible to determine this. Exim uses the following heuristic rules:
20267 If the mailbox is a single file, the time of last access (the `atime') is used.
20268 As no new messages are being delivered (because the mailbox is over quota),
20269 Exim does not access the file, so this is the time of last user access.
20271 .index maildir format||time of last read
20272 For a maildir delivery, the time of last modification of the \(new)\
20273 subdirectory is used. As the mailbox is over quota, no new files are created in
20274 the \(new)\ subdirectory, because no new messages are being delivered. Any
20275 change to the \(new)\ subdirectory is therefore assumed to be the result of an
20276 MUA moving a new message to the \(cur)\ directory when it is first read. The
20277 time that is used is therefore the last time that the user read a new message.
20279 For other kinds of multi-file mailbox, the time of last access cannot be
20280 obtained, so a retry rule that uses this type of error field is never matched.
20283 The quota errors apply both to system-enforced quotas and to Exim's own quota
20284 mechanism in the \%appendfile%\ transport. The \*quota*\ error also applies
20285 when a local delivery is deferred because a partition is full (the \\ENOSPC\\
20290 .section Retry rules for specified senders
20291 .index retry||rules, sender-specific
20292 You can specify retry rules that apply only when the failing message has a
20293 specific sender. In particular, this can be used to define retry rules that
20294 apply only to bounce messages. The third item in a retry rule can be of this
20297 senders=<<address list>>
20299 The retry timings themselves are then the fourth item. For example:
20301 * * senders=: F,1h,30m
20303 matches all temporary errors for bounce messages sent to any host. If the
20304 address list contains white space, it must be enclosed in quotes. For example:
20306 a.domain timeout senders="x@b.dom : y@c.dom" G,8h,10m,1.5
20308 When testing retry rules using \-brt-\, you can supply a sender using the \-f-\
20309 command line option, like this:
20311 exim -f "" -brt user@dom.ain
20313 If you do not set \-f-\ with \-brt-\, a retry rule that contains a senders list
20319 .section Retry parameters
20320 .index retry||parameters in rules
20323 (or fourth, if a senders list is present)
20325 field in a retry rule is a sequence of retry parameter sets, separated by
20326 semicolons. Each set consists of
20328 <<letter>>,<<cutoff time>>,<<arguments>>
20330 The letter identifies the algorithm for computing a new retry time; the cutoff
20331 time is the time beyond which this algorithm no longer applies, and the
20332 arguments vary the algorithm's action. The cutoff time is measured from the
20333 time that the first failure for the domain (combined with the local part if
20334 relevant) was detected, not from the time the message was received.
20335 .index retry||algorithms
20336 The available algorithms are:
20338 \*F*\: retry at fixed intervals. There is a single time parameter specifying
20341 \*G*\: retry at geometrically increasing intervals. The first argument
20342 specifies a starting value for the interval, and the second a multiplier, which
20343 is used to increase the size of the interval at each retry.
20345 When computing the next retry time, the algorithm definitions are scanned in
20346 order until one whose cutoff time has not yet passed is reached. This is then
20347 used to compute a new retry time that is later than the current time. In the
20348 case of fixed interval retries, this simply means adding the interval to the
20349 current time. For geometrically increasing intervals, retry intervals are
20350 computed from the rule's parameters until one that is greater than the previous
20351 interval is found. The main configuration variable
20352 .index limit||retry interval
20353 .index retry||interval, maximum
20354 .index \retry@_interval@_max\
20355 \retry@_interval@_max\ limits the maximum interval between retries.
20357 A single remote domain may have a number of hosts associated with it, and each
20358 host may have more than one IP address. Retry algorithms are selected on the
20359 basis of the domain name, but are applied to each IP address independently. If,
20360 for example, a host has two IP addresses and one is unusable, Exim will
20361 generate retry times for it and will not try to use it until its next retry
20362 time comes. Thus the good IP address is likely to be tried first most of the
20365 .index hints database||use for retrying
20366 Retry times are hints rather than promises. Exim does not make any attempt to
20367 run deliveries exactly at the computed times. Instead, a queue runner process
20368 starts delivery processes for delayed messages periodically, and these attempt
20369 new deliveries only for those addresses that have passed their next retry time.
20370 If a new message arrives for a deferred address, an immediate delivery attempt
20371 occurs only if the address has passed its retry time. In the absence of new
20372 messages, the minimum time between retries is the interval between queue runner
20373 processes. There is not much point in setting retry times of five minutes if
20374 your queue runners happen only once an hour, unless there are a significant
20375 number of incoming messages (which might be the case on a system that is
20376 sending everything to a smart host, for example).
20378 The data in the retry hints database can be inspected by using the
20379 \*exim@_dumpdb*\ or \*exim@_fixdb*\ utility programs (see chapter ~~CHAPutils). The
20380 latter utility can also be used to change the data. The \*exinext*\ utility
20381 script can be used to find out what the next retry times are for the hosts
20382 associated with a particular mail domain, and also for local deliveries that
20383 have been deferred.
20385 .section Retry rule examples
20386 Here are some example retry rules:
20388 alice@wonderland.fict.example quota_5d F,7d,3h
20389 wonderland.fict.example quota_5d
20390 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
20391 lookingglass.fict.example * F,24h,30m;
20392 * refused_A F,2h,20m;
20393 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
20395 The first rule sets up special handling for mail to
20396 \*alice@@wonderland.fict.example*\ when there is an over-quota error and the
20397 mailbox has not been read for at least 5 days. Retries continue every three
20398 hours for 7 days. The second rule handles over-quota errors for all other local
20399 parts at \*wonderland.fict.example*\; the absence of a local part has the same
20400 effect as supplying `$*$@@'. As no retry algorithms are supplied, messages that
20401 fail are bounced immediately if the mailbox has not been read for at least 5
20404 The third rule handles all other errors at \*wonderland.fict.example*\; retries
20405 happen every 15 minutes for an hour, then with geometrically increasing
20406 intervals until two days have passed since a delivery first failed. After the
20407 first hour there is a delay of one hour, then two hours, then four hours, and
20408 so on (this is a rather extreme example).
20410 The fourth rule controls retries for the domain \*lookingglass.fict.example*\.
20411 They happen every 30 minutes for 24 hours only. The remaining two rules handle
20412 all other domains, with special action for connection refusal from hosts that
20413 were not obtained from an MX record.
20415 The final rule in a retry configuration should always have asterisks in the
20416 first two fields so as to provide a general catch-all for any addresses that do
20417 not have their own special handling. This example tries every 15 minutes for 2
20418 hours, then with intervals starting at one hour and increasing by a factor of
20419 1.5 up to 16 hours, then every 8 hours up to 5 days.
20422 .section Timeout of retry data
20423 .index timeout||of retry data
20424 .index \retry@_data@_expire\
20425 .index hints database||data expiry
20426 .index retry||timeout of data
20427 Exim timestamps the data that it writes to its retry hints database. When it
20428 consults the data during a delivery it ignores any that is older than the value
20429 set in \retry@_data@_expire\ (default 7 days). If, for example, a host hasn't
20430 been tried for 7 days, Exim will try to deliver to it immediately a message
20431 arrives, and if that fails, it will calculate a retry time as if it were
20432 failing for the first time.
20434 This improves the behaviour for messages routed to rarely-used hosts such as MX
20435 backups. If such a host was down at one time, and happens to be down again when
20436 Exim tries a month later, using the old retry data would imply that it had been
20437 down all the time, which is not a justified assumption.
20439 If a host really is permanently dead, this behaviour causes a burst of retries
20440 every now and again, but only if messages routed to it are rare. It there is a
20441 message at least once every 7 days the retry data never expires.
20445 .section Long-term failures
20446 .index delivery||failure, long-term
20447 .index retry||after long-term failure
20448 Special processing happens when an email address has been failing for so long
20449 that the cutoff time for the last algorithm is reached. For example, using the
20450 default retry rule:
20452 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
20454 the cutoff time is four days. Reaching the retry cutoff is independent of how
20455 long any specific message has been failing; it is the length of continuous
20456 failure for the recipient address that counts.
20458 When the cutoff time is reached for a local delivery, or for all the IP
20459 addresses associated with a remote delivery, a subsequent delivery failure
20460 causes Exim to give up on the address, and a bounce message is generated.
20461 In order to cater for new messages that use the failing address, a next retry
20462 time is still computed from the final algorithm, and is used as follows:
20464 For local deliveries, one delivery attempt is always made for any subsequent
20465 messages. If this delivery fails, the address fails immediately. The
20466 post-cutoff retry time is not used.
20468 If the delivery is remote, there are two possibilities, controlled by the
20469 .index \delay@_after@_cutoff\
20470 \delay@_after@_cutoff\ option of the \%smtp%\ transport. The option is true by
20471 default and in that case:
20473 Until the post-cutoff retry time for one of the IP addresses is reached,
20474 the failing email address is bounced immediately, without a delivery attempt
20475 taking place. After that time, one new delivery attempt is made to those IP
20476 addresses that are past their retry times, and if that still fails, the address
20477 is bounced and new retry times are computed.
20480 In other words, when all the hosts for a given email address have been failing
20481 for a long time, Exim bounces rather then defers until one of the hosts' retry
20482 times is reached. Then it tries once, and bounces if that attempt fails. This
20483 behaviour ensures that few resources are wasted in repeatedly trying to deliver
20484 to a broken destination, but if the host does recover, Exim will eventually
20487 If \delay@_after@_cutoff\ is set false, Exim behaves differently. If all IP
20488 addresses are past their final cutoff time, Exim tries to deliver to those IP
20489 addresses that have not been tried since the message arrived. If there are
20490 no suitable IP addresses, or if they all fail, the address is bounced. In other
20491 words, it does not delay when a new message arrives, but tries the expired
20492 addresses immediately, unless they have been tried since the message arrived.
20493 If there is a continuous stream of messages for the failing domains, setting
20494 \delay@_after@_cutoff\ false means that there will be many more attempts to
20495 deliver to permanently failing IP addresses than when \delay@_after@_cutoff\ is
20498 .section Ultimate address timeout
20499 .index retry||ultimate address timeout
20500 An additional rule is needed to cope with cases where a host is intermittently
20501 available, or when a message has some attribute that prevents its delivery when
20502 others to the same address get through. In this situation, because some
20503 messages are successfully delivered, the `retry clock' for the address keeps
20504 getting restarted, and so a message could remain on the queue for ever. To
20505 prevent this, if a message has been on the queue for longer than the cutoff
20506 time of any applicable retry rule for a given address, a delivery is attempted
20507 for that address, even if it is not yet time, and if this delivery fails, the
20508 address is timed out. A new retry time is not computed in this case, so that
20509 other messages for the same address are considered immediately.
20519 . ============================================================================
20520 .chapter SMTP authentication
20521 .set runningfoot "SMTP authentication"
20522 .rset CHAPSMTPAUTH "~~chapter"
20523 .index SMTP||authentication configuration
20524 .index authentication
20525 The `authenticators' section of Exim's run time configuration is concerned with
20526 SMTP authentication. This facility is an extension to the SMTP protocol,
20527 described in RFC 2554, which allows a client SMTP host to authenticate itself
20528 to a server. This is a common way for a server to recognize clients that
20529 are permitted to use it as a relay. SMTP authentication is not of relevance to
20530 the transfer of mail between servers that have no managerial connection with
20533 .index \\AUTH\\||description of
20534 Very briefly, the way SMTP authentication works is as follows:
20536 The server advertises a number of authentication \*mechanisms*\ in response to
20537 the client's \\EHLO\\ command.
20539 The client issues an \\AUTH\\ command, naming a specific mechanism. The command
20540 may, optionally, contain some authentication data.
20542 The server may issue one or more \*challenges*\, to which the client must send
20543 appropriate responses. In simple authentication mechanisms, the challenges are
20544 just prompts for user names and passwords. The server does not have to issue
20545 any challenges -- in some mechanisms the relevant data may all be transmitted
20546 with the \\AUTH\\ command.
20548 The server either accepts or denies authentication.
20550 If authentication succeeds, the client may optionally make use of the \\AUTH\\
20551 option on the \\MAIL\\ command to pass an authenticated sender in subsequent
20552 mail transactions. Authentication lasts for the remainder of the SMTP
20555 If authentication fails, the client may give up, or it may try a different
20556 authentication mechanism, or it may try transferring mail over the
20557 unauthenticated connection.
20559 If you are setting up a client, and want to know which authentication
20560 mechanisms the server supports, you can use Telnet to connect to port 25 (the
20561 SMTP port) on the server, and issue an \\EHLO\\ command. The response to this
20562 includes the list of supported mechanisms. For example:
20564 @$ $cb{telnet server.example 25}
20565 Trying 192.168.34.25...
20566 Connected to server.example.
20567 Escape character is '@^]'.
20568 220 server.example ESMTP Exim 4.20 ...
20569 $cb{ehlo client.example}
20570 250-server.example Hello client.example [10.8.4.5]
20576 The second-last line of this example output shows that the server supports
20577 authentication using the PLAIN mechanism. In Exim, the different authentication
20578 mechanisms are configured by specifying \*authenticator*\ drivers. Like the
20579 routers and transports, which authenticators are included in the binary is
20580 controlled by build-time definitions. The following are currently available,
20581 included by setting
20587 in \(Local/Makefile)\, respectively. The first of these supports the CRAM-MD5
20588 authentication mechanism (RFC 2195), and the second can be configured to
20589 support the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism,
20590 which is not formally documented, but used by several MUAs. The third
20591 authenticator supports Microsoft's \*Secure Password Authentication*\
20594 The authenticators are configured using the same syntax as other drivers (see
20595 section ~~SECTfordricon). If no authenticators are required, no authentication
20596 section need be present in the configuration file. Each authenticator can in
20597 principle have both server and client functions. When Exim is receiving SMTP
20598 mail, it is acting as a server; when it is sending out messages over SMTP, it
20599 is acting as a client. Authenticator configuration options are provided for use
20600 in both these circumstances.
20602 To make it clear which options apply to which situation, the prefixes
20603 \server@_\ and \client@_\ are used on option names that are specific to either
20604 the server or the client function, respectively. Server and client functions
20605 are disabled if none of their options are set. If an authenticator is to be
20606 used for both server and client functions, a single definition, using both sets
20607 of options, is required. For example:
20611 public_name = CRAM-MD5
20612 server_secret = ${if eq{$1}{ph10}{secret1}fail}
20614 client_secret = secret2
20616 The \server@_\ option is used when Exim is acting as a server, and the
20617 \client@_\ options when it is acting as a client.
20619 Descriptions of the individual authenticators are given in subsequent chapters.
20620 The remainder of this chapter covers the generic options for the
20621 authenticators, followed by general discussion of the way authentication works
20625 .section Generic options for authenticators
20626 .index authentication||generic options
20628 .startconf authenticators
20629 .index options||generic, for authenticators
20631 .conf driver string unset
20632 This option must always be set. It specifies which of the available
20633 authenticators is to be used.
20635 .conf public@_name string unset
20636 This option specifies the name of the authentication mechanism that the driver
20637 implements, and by which it is known to the outside world. These names should
20638 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
20639 but Exim in fact matches them caselessly. If \public@_name\ is not set, it
20640 defaults to the driver's instance name.
20642 .conf server@_advertise@_condition string$**$ unset
20643 When a server is about to advertise an authentication mechanism, the condition
20644 is expanded. If it yields the empty string, `0', `no', or `false', the
20645 mechanism is not advertised.
20646 If the expansion fails, the mechanism is not advertised. If the failure was not
20647 forced, and was not caused by a lookup defer, the incident is logged.
20648 See section ~~SECTauthexiser below for further discussion.
20650 .conf server@_debug@_print string$**$ unset
20651 If this option is set and authentication debugging is enabled (see the \-d-\
20652 command line option), the string is expanded and included in the debugging
20653 output when the authenticator is run as a server. This can help with checking
20654 out the values of variables.
20655 If expansion of the string fails, the error message is written to the debugging
20656 output, and Exim carries on processing.
20658 .conf server@_set@_id string$**$ unset
20659 When an Exim server successfully authenticates a client, this string is
20660 expanded using data from the authentication, and preserved for any incoming
20661 messages in the variable \$authenticated@_id$\. It is also included in the log
20662 lines for incoming messages. For example, a user/password authenticator
20663 configuration might preserve the user name that was used to authenticate, and
20664 refer to it subsequently during delivery of the message.
20665 If expansion fails, the option is ignored.
20667 .conf server@_mail@_auth@_condition string$**$ unset
20668 This option allows a server to discard authenticated sender addresses supplied
20669 as part of \\MAIL\\ commands in SMTP connections that are authenticated by the
20670 driver on which \server__mail__auth@_condition\ is set. The option is not used
20671 as part of the authentication process; instead its (unexpanded) value is
20672 remembered for later use.
20673 How it is used is described in the following section.
20678 .section The AUTH parameter on MAIL commands
20679 .rset SECTauthparamail "~~chapter.~~section"
20680 .index authentication||sender, authenticated
20681 .index \\AUTH\\||on \\MAIL\\ command
20682 When a client supplied an \\AUTH=\\ item on a \\MAIL\\ command, Exim applies
20683 the following checks before accepting it as the authenticated sender of the
20686 If the connection is not using extended SMTP (that is, \\HELO\\ was used rather
20687 than \\EHLO\\), the use of \\AUTH=\\ is a syntax error.
20689 If the value of the \\AUTH=\\ parameter is `@<@>', it is ignored.
20691 If \acl@_smtp@_mailauth\ is defined, the ACL it specifies is run. While it is
20692 running, the value of \$authenticated@_sender$\ is set to the value obtained
20693 from the \\AUTH=\\ parameter. If the ACL does not yield `accept', the value of
20694 \$authenticated@_sender$\ is deleted. The \acl@_smtp@_mailauth\ ACL may not
20695 return `drop' or `discard'. If it defers, a temporary error code (451) is given
20696 for the \\MAIL\\ command.
20698 If \acl@_smtp@_mailauth\ is not defined, the value of the \\AUTH=\\ parameter
20699 is accepted and placed in \$authenticated@_sender$\ only if the client has
20702 If the \\AUTH=\\ value was accepted by either of the two previous rules, and
20703 the client has authenticated, and the authenticator has a setting for the
20704 \server@_mail@_auth@_condition\, the condition is checked at this point. The
20705 valued that was saved from the authenticator is expanded. If the expansion
20706 fails, or yields an empty string, `0', `no', or `false', the value of
20707 \$authenticated__sender$\ is deleted. If the expansion yields any other value,
20708 the value of \$authenticated@_sender$\ is retained and passed on with the
20712 When \$authenticated@_sender$\ is set for a message, it is passed on to other
20713 hosts to which Exim authenticates as a client. Do not confuse this value with
20714 \$authenticated@_id$\, which is a string obtained from the authentication
20715 process, and which is not usually a complete email address.
20717 Whenever an \\AUTH=\\ value is ignored, the incident is logged. The ACL for
20718 \\MAIL\\, if defined, is run after \\AUTH=\\ is accepted or ignored. It can
20719 therefore make use of \$authenticated@_sender$\. The converse is not true: the
20720 value of \$sender@_address$\ is not yet set up when the \acl@_smtp@_mailauth\
20724 .section Authentication on an Exim server
20725 .rset SECTauthexiser "~~chapter.~~section"
20726 .index authentication||on an Exim server
20727 When Exim receives an \\EHLO\\ command, it advertises the public names of those
20728 authenticators that are configured as servers, subject to the following
20731 The client host must match \auth@_advertise@_hosts\ (default $*$).
20733 It the \server@_advertise@_condition\ option is set, its expansion must not
20734 yield the empty string, `0', `no', or `false'.
20736 The order in which the authenticators are defined controls the order in which
20737 the mechanisms are advertised.
20739 Some mail clients (for example, some versions of Netscape) require the user to
20740 provide a name and password for authentication whenever \\AUTH\\ is advertised,
20741 even though authentication may not in fact be needed (for example, Exim may be
20742 set up to allow unconditional relaying from the client by an IP address check).
20743 You can make such clients more friendly by not advertising \\AUTH\\ to them.
20744 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
20745 that runs for \\RCPT\\) to relay without authentication, you should set
20747 auth_advertise_hosts = ! 10.9.8.0/24
20749 so that no authentication mechanisms are advertised to them.
20751 The \server@_advertise@_condition\ controls the advertisement of individual
20752 authentication mechanisms. For example, it can be used to restrict the
20753 advertisement of a patricular mechanism to encrypted connections, by a setting
20756 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
20758 If the session is encrypted, \$tls@_cipher$\ is not empty, and so the expansion
20759 yields `yes', which allows the advertisement to happen.
20761 When an Exim server receives an \\AUTH\\ command from a client, it rejects it
20762 immediately if \\AUTH\\ was not advertised in response to an earlier \\EHLO\\
20763 command. This is the case if
20765 The client host does not match \auth@_advertise@_hosts\; or
20767 No authenticators are configured with server options; or
20769 Expansion of \server@_advertise@_condition\ blocked the advertising of all the
20770 server authenticators.
20773 Otherwise, Exim runs the ACL specified by \acl@_smtp@_auth\ in order
20774 to decide whether to accept the command. If \acl@_smtp@_auth\ is not set,
20775 \\AUTH\\ is accepted from any client host.
20777 If \\AUTH\\ is not rejected by the ACL, Exim searches its configuration for a
20778 server authentication mechanism that was advertised in response to \\EHLO\\ and
20779 that matches the one named in the \\AUTH\\ command. If it finds one, it runs
20780 the appropriate authentication protocol, and authentication either succeeds or
20781 fails. If there is no matching advertised mechanism, the \\AUTH\\ command is
20782 rejected with a 504 error.
20784 When a message is received from an authenticated host, the value of
20785 \$received@_protocol$\ is set to
20789 instead of `esmtp', and \$sender@_host@_authenticated$\ contains the name (not
20790 the public name) of the authenticator driver that successfully authenticated
20791 the client from which the message was received. This variable is empty if there
20792 was no successful authentication.
20796 .section Testing server authentication
20797 .index authentication||testing a server
20798 .index \\AUTH\\||testing a server
20799 .index base64 encoding||creating authentication test data
20800 Exim's \-bh-\ option can be useful for testing server authentication
20801 configurations. The data for the \\AUTH\\ command has to be sent using base64
20802 encoding. A quick way to produce such data for testing is the following Perl
20806 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
20808 .index binary zero||in authentication data
20809 This interprets its argument as a Perl string, and then encodes it. The
20810 interpretation as a Perl string allows binary zeros, which are required for
20811 some kinds of authentication, to be included in the data. For example, a
20812 command line to run this script on such data might be
20814 encode '\0user\0password'
20816 Note the use of single quotes to prevent the shell interpreting the
20817 backslashes, so that they can be interpreted by Perl to specify characters
20818 whose code value is zero.
20820 \**Warning 1**\: If either of the user or password strings starts with an octal
20821 digit, you must use three zeros instead of one after the leading backslash. If
20822 you do not, the octal digit that starts your string will be incorrectly
20823 interpreted as part of the code for the first character.
20825 \**Warning 2**\: If there are characters in the strings that Perl interprets
20826 specially, you must use a Perl escape to prevent them being misinterpreted. For
20827 example, a command such as
20829 encode '\0user@domain.com\0pas$$word'
20831 gives an incorrect answer because of the unescaped `@@' and `@$' characters.
20833 If you have the \mimencode\ command installed, another way to do produce
20834 base64-encoded strings is to run the command
20836 echo -e -n `\0user\0password' | mimencode
20838 The \-e-\ option of \echo\ enables the interpretation of backslash escapes in
20839 the argument, and the \-n-\ option specifies no newline at the end of its
20840 output. However, not all versions of \echo\ recognize these options, so you
20841 should check your version before relying on this suggestion.
20844 .section Authentication by an Exim client
20845 .index authentication||on an Exim client
20846 The \%smtp%\ transport has two options called \hosts@_require@_auth\ and
20847 \hosts@_try@_auth\. When the \%smtp%\ transport connects to a server that
20848 announces support for authentication, and the host matches an entry in either
20849 of these options, Exim (as a client) tries to authenticate as follows:
20851 For each authenticator that is configured as a client, it searches the
20852 authentication mechanisms announced by the server for one whose name
20853 matches the public name of the authenticator.
20855 When it finds one that matches, it runs the authenticator's client code.
20856 The variables \$host$\ and \$host@_address$\ are available for any string
20857 expansions that the client might do. They are set to the server's name and
20858 IP address. If any expansion is forced to fail, the authentication attempt
20860 and Exim moves on to the next authenticator.
20861 Otherwise an expansion failure causes delivery to be
20864 If the result of the authentication attempt is a temporary error or a timeout,
20865 Exim abandons trying to send the message to the host for the moment. It will
20866 try again later. If there are any backup hosts available, they are tried in the
20869 If the response to authentication is a permanent error (5xx code), Exim carries
20870 on searching the list of authenticators and tries another one if possible. If
20871 all authentication attempts give permanent errors, or if there are no attempts
20872 because no mechanisms match
20873 (or option expansions force failure),
20874 what happens depends on whether the host matches \hosts@_require@_auth\ or
20875 \hosts@_try@_auth\. In the first case, a temporary error is generated, and
20876 delivery is deferred. The error can be detected in the retry rules, and thereby
20877 turned into a permanent error if you wish. In the second case, Exim tries to
20878 deliver the message unauthenticated.
20880 .index \\AUTH\\||on \\MAIL\\ command
20881 When Exim has authenticated itself to a remote server, it adds the \\AUTH\\
20882 parameter to the \\MAIL\\ commands it sends, if it has an authenticated sender
20884 If the message came from a remote host, the authenticated sender is the one
20885 that was receiving on an incoming \\MAIL\\ command, provided that the incoming
20886 connection was authenticated and the \server@_mail@_auth\ condition allowed the
20887 authenticated sender to be retained. If a local process calls Exim to send a
20888 message, the sender address that is built from the login name and
20889 \qualify@_domain\ is treated as authenticated. However, if the
20890 \authenticated@_sender\ option is set on the \%smtp%\ transport, it overrides
20891 the authenticated sender that was received with the message.
20902 . ============================================================================
20903 .chapter The plaintext authenticator
20904 .rset CHAPplaintext "~~chapter"
20905 .set runningfoot "plaintext authenticator"
20906 .index \%plaintext%\ authenticator
20907 .index authenticators||\%plaintext%\
20908 The \%plaintext%\ authenticator can be configured to support the PLAIN and
20909 LOGIN authentication mechanisms, both of which transfer authentication data as
20910 plain (unencrypted) text (though base64 encoded). The use of plain text is a
20911 security risk. If you use one of these mechanisms without also making use of
20912 SMTP encryption (see chapter ~~CHAPTLS) you should not use the same passwords
20913 for SMTP connections as you do for login accounts.
20915 .section Using plaintext in a server
20916 When running as a server, \%plaintext%\ performs the authentication test by
20917 expanding a string. It has the following options:
20919 .startconf plaintext
20920 .index options||\%plaintext%\ authenticator (server)
20922 .conf server@_prompts string$**$ unset
20923 The contents of this option, after expansion, must be a colon-separated list of
20924 prompt strings. If expansion fails, a temporary authentication rejection is
20927 .conf server@_condition string$**$ unset
20928 This option must be set in order to configure the driver as a server. Its use
20929 is described below.
20933 .index \\AUTH\\||in \%plaintext%\ authenticator
20934 .index binary zero||in \%plaintext%\ authenticator
20935 .index numerical variables (\$1$\, \$2$\, etc)||in \%plaintext%\ authenticator
20936 .index base64 encoding||in \%plaintext%\ authenticator
20937 The data sent by the client with the \\AUTH\\ command, or in response to
20938 subsequent prompts, is base64 encoded, and so may contain any byte values
20939 when decoded. If any data is supplied with the command, it is treated as a
20940 list of strings, separated by NULs (binary zeros), which are placed in the
20941 expansion variables \$1$\, \$2$\, etc. If there are more strings in
20942 \server@_prompts\ than the number of strings supplied with the \\AUTH\\
20943 command, the remaining prompts are used to obtain more data. Each response from
20944 the client may be a list of NUL-separated strings.
20946 Once a sufficient number of data strings have been received,
20947 \server@_condition\ is expanded.
20948 If the expansion is forced to fail, authentication fails. Any other expansion
20949 failure causes a temporary error code to be returned.
20950 If the result of a successful expansion is an empty string, `0', `no', or
20951 `false', authentication fails. If the result of the expansion is `1', `yes', or
20952 `true', authentication succeeds and the generic \server@_set@_id\ option is
20953 expanded and saved in \$authenticated@_id$\. For any other result, a temporary
20954 error code is returned, with the expanded string as the error text.
20956 \**Warning**\: If you use a lookup in the expansion to find the user's
20957 password, be sure to make the authentication fail if the user is unknown.
20958 There are good and bad examples at the end of the next section.
20961 .section The PLAIN authentication mechanism
20962 .index PLAIN authentication mechanism
20963 .index authentication||PLAIN mechanism
20964 .index binary zero||in \%plaintext%\ authenticator
20965 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
20966 sent as one item of data (that is, one combined string containing two NUL
20967 separators). The data is sent either as part of the \\AUTH\\ command, or
20968 subsequently in response to an empty prompt from the server.
20970 The second and third strings are a user name and a corresponding password.
20971 Using a single fixed user name and password as an example, this could be
20972 configured as follows:
20976 public_name = PLAIN
20978 server_condition = \
20979 ${if and {{eq{$2}{username}}{eq{$3}{mysecret}}}{yes}{no}}
20982 The \server@_prompts\ setting specifies a single, empty prompt (empty items at
20983 the end of a string list are ignored). If all the data comes as part of the
20984 \\AUTH\\ command, as is commonly the case, the prompt is not used. This
20985 authenticator is advertised in the response to \\EHLO\\ as
20989 and a client host can authenticate itself by sending the command
20991 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
20993 As this contains three strings (more than the number of prompts), no further
20994 data is required from the client. Alternatively, the client may just send
20998 to initiate authentication, in which case the server replies with an empty
20999 prompt. The client must respond with the combined data string.
21001 The data string is base64 encoded, as required by the RFC. This example,
21002 when decoded, is \"<<NUL>>username<<NUL>>mysecret"\, where <<NUL>> represents a
21003 zero byte. This is split up into three strings, the first of which is empty.
21004 The \server@_condition\ option in the authenticator checks that the second two
21005 are \"username"\ and \"mysecret"\ respectively.
21007 Having just one fixed user name and password, as in this example, is not very
21008 realistic, though for a small organization with only a handful of
21009 authenticating clients it could make sense.
21011 A more sophisticated instance of this authenticator could use the user name in
21012 \$2$\ to look up a password in a file or database, and maybe do an encrypted
21013 comparison (see \crypteq\ in chapter ~~CHAPexpand). Here is a example of this
21014 approach, where the passwords are looked up in a DBM file. \**Warning**\: This
21015 is an incorrect example:
21017 server_condition = \
21018 ${if eq{$3}{${lookup{$2}dbm{/etc/authpwd}}}{yes}{no}}
21020 The expansion uses the user name (\$2$\) as the key to look up a password,
21021 which it then compares to the supplied password (\$3$\). Why is this example
21022 incorrect? It works fine for existing users, but consider what happens if a
21023 non-existent user name is given. The lookup fails, but as no success/failure
21024 strings are given for the lookup, it yields an empty string. Thus, to defeat
21025 the authentication, all a client has to do is to supply a non-existent user
21026 name and an empty password. The correct way of writing this test is:
21028 server_condition = ${lookup{$2}dbm{/etc/authpwd}\
21029 {${if eq{$value}{$3}{yes}{no}}}{no}}
21031 In this case, if the lookup succeeds, the result is checked; if the lookup
21032 fails, authentication fails. If \crypteq\ is being used instead of \eq\, the
21033 first example is in fact safe, because \crypteq\ always fails if its second
21034 argument is empty. However, the second way of writing the test makes the logic
21038 .section The LOGIN authentication mechanism
21039 .index LOGIN authentication mechanism
21040 .index authentication||LOGIN mechanism
21041 The LOGIN authentication mechanism is not documented in any RFC, but is in use
21042 in a number of programs. No data is sent with the \\AUTH\\ command. Instead, a
21043 user name and password are supplied separately, in response to prompts. The
21044 plaintext authenticator can be configured to support this as in this example:
21048 public_name = LOGIN
21049 server_prompts = User Name : Password
21050 server_condition = \
21051 ${if and {{eq{$1}{username}}{eq{$2}{mysecret}}}{yes}{no}}
21054 Because of the way plaintext operates, this authenticator accepts data supplied
21055 with the \\AUTH\\ command (in contravention of the specification of LOGIN), but
21056 if the client does not supply it (as is the case for LOGIN clients), the prompt
21057 strings are used to obtain two data items.
21059 Some clients are very particular about the precise text of the prompts. For
21060 example, Outlook Express is reported to recognize only `Username:' and
21061 `Password:'. Here is an example of a LOGIN authenticator which uses those
21062 strings, and which uses the \ldapauth\ expansion condition to check the user
21063 name and password by binding to an LDAP server:
21067 public_name = LOGIN
21068 server_prompts = Username:: : Password::
21069 server_condition = ${if ldapauth \
21071 {user="cn=${quote_ldap_dn:$1},ou=people,o=example.org" \
21074 ldap://ldap.example.org/}{yes}{no}}
21075 server_set_id = uid=$1,ou=people,o=example.org
21077 Note the use of the \quote@_ldap@_dn\ operator to correctly quote the DN for
21078 authentication. However, the basic \quote\ operator, rather than any of the
21079 LDAP quoting operators, is the correct one to use for the password, because
21080 quoting is needed only to make the password conform to the Exim syntax. At the
21081 LDAP level, the password is an uninterpreted string.
21084 .section Support for different kinds of authentication
21085 A number of string expansion features are provided for the purpose of
21086 interfacing to different ways of user authentication. These include checking
21087 traditionally encrypted passwords from \(/etc/passwd)\ (or equivalent), PAM,
21088 Radius, \ldapauth\, and \*pwcheck*\. For details see section ~~SECTexpcond.
21092 .section Using plaintext in a client
21093 The \%plaintext%\ authenticator has just one client option:
21095 .startconf plaintext
21096 .index options||\%plaintext%\ authenticator (client)
21098 .conf client@_send string$**$ unset
21099 The string is a colon-separated list of authentication data strings. Each
21100 string is independently expanded before being sent to the server. The first
21101 string is sent with the \\AUTH\\ command; any more strings are sent in response
21102 to prompts from the server.
21104 \**Note**\: you cannot use expansion to create multiple strings, because
21105 splitting takes priority and happens first.
21107 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
21108 the data, further processing is applied to each string before it is sent. If
21109 there are any single circumflex characters in the string, they are converted to
21110 NULs. Should an actual circumflex be required as data, it must be doubled in
21115 This is an example of a client configuration that implements the PLAIN
21116 authentication mechanism with a fixed user name and password:
21120 public_name = PLAIN
21121 client_send = ^username^mysecret
21123 The lack of colons means that the entire text is sent with the \\AUTH\\
21124 command, with the circumflex characters converted to NULs. A similar example
21125 that uses the LOGIN mechanism is:
21129 public_name = LOGIN
21130 client_send = : username : mysecret
21132 The initial colon means that the first string is empty, so no data is sent with
21133 the \\AUTH\\ command itself. The remaining strings are sent in response to
21143 . ============================================================================
21144 .chapter The cram@_md5 authenticator
21145 .set runningfoot "cram@_md5 authenticator"
21146 .index \%cram@_md5%\ authenticator
21147 .index authenticators||\%cram@_md5%\
21148 .index CRAM-MD5 authentication mechanism
21149 .index authentication||CRAM-MD5 mechanism
21150 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
21151 sends a challenge string to the client, and the response consists of a user
21152 name and the CRAM-MD5 digest of the challenge string combined with a secret
21153 string (password) which is known to both server and client. Thus, the secret
21154 is not sent over the network as plain text, which makes this authenticator more
21155 secure than \%plaintext%\. However, the downside is that the secret has to be
21156 available in plain text at either end.
21158 .section Using cram@_md5 as a server
21159 This authenticator has one server option, which must be set to configure the
21160 authenticator as a server:
21162 .startconf cram@_md5
21163 .index options||\%cram@_md5%\ authenticator (server)
21165 .conf server@_secret string$**$ unset
21166 .index numerical variables (\$1$\, \$2$\, etc)||in \%cram@_md5%\ authenticator
21167 When the server receives the client's response, the user name is placed in
21168 the expansion variable \$1$\, and \server@_secret\ is expanded to obtain the
21169 password for that user. The server then computes the CRAM-MD5 digest that the
21170 client should have sent, and checks that it received the correct string. If the
21171 expansion of \server@_secret\ is forced to fail, authentication fails. If the
21172 expansion fails for some other reason, a temporary error code is returned to
21177 For example, the following authenticator checks that the user name given by the
21178 client is `ph10', and if so, uses `secret' as the password. For any other user
21179 name, authentication fails.
21183 public_name = CRAM-MD5
21184 server_secret = ${if eq{$1}{ph10}{secret}fail}
21187 If authentication succeeds, the setting of \server@_set@_id\ preserves the user
21188 name in \$authenticated@_id$\.
21189 A more tyical configuration might look up the secret string in a file, using
21190 the user name as the key. For example:
21194 public_name = CRAM-MD5
21195 server_secret = ${lookup{$1}lsearch{/etc/authpwd}{$value}fail}
21198 Note that this expansion explicitly forces failure if the lookup fails
21199 because \$1$\ contains an unknown user name.
21201 .section Using cram@_md5 as a client
21202 When used as a client, the \%cram@_md5%\ authenticator has two options:
21204 .startconf cram@_md5
21205 .index options||\%cram@_md5%\ authenticator (client)
21207 .conf client@_name string$**$ "the primary host name"
21208 This string is expanded, and the result used as the user name data when
21209 computing the response to the server's challenge.
21211 .conf client@_secret string$**$ unset
21212 This option must be set for the authenticator to work as a client. Its value is
21213 expanded and the result used as the secret string when computing the response.
21217 Different user names and secrets can be used for different servers by referring
21218 to \$host$\ or \$host@_address$\ in the options.
21220 Forced failure of either expansion string is treated as an indication that this
21221 authenticator is not prepared to handle this case. Exim moves on to the next
21222 configured client authenticator. Any other expansion failure causes Exim to
21223 give up trying to send the message to the current server.
21225 A simple example configuration of a \%cram@_md5%\ authenticator, using fixed
21230 public_name = CRAM-MD5
21232 client_secret = secret
21242 . ============================================================================
21243 .chapter The cyrus@_sasl authenticator
21244 .set runningfoot "cyrus@_sasl authenticator"
21245 .index \%cyrus@_sasl%\ authenticator
21246 .index authenticators||\%cyrus@_sasl%\
21247 .index Cyrus, SASL library
21249 The code for this authenticator was provided by Matthew Byng-Maddick of A L
21250 Digital Ltd (\?http://www.aldigital.co.uk?\).
21252 The \%cyrus@_sasl%\ authenticator provides server support for the Cyrus SASL
21253 library implementation of the RFC 2222 (`Simple Authentication and Security
21254 Layer'). This library supports a number of authentication mechanisms, including
21255 PLAIN and LOGIN, but also several others that Exim does not support directly.
21256 In particular, there is support for Kerberos authentication.
21258 The \%cyrus@_sasl%\ authenticator provides a gatewaying mechanism directly to
21259 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
21260 then so can the \%cyrus@_sasl%\ authenticator. By default it uses the public
21261 name of the driver to determine which mechanism to support.
21263 Where access to some kind of secret file is required, for example in GSSAPI
21264 or CRAM-MD5, it is worth noting that the authenticator runs as the \*exim*\
21265 user, and that the Cyrus SASL library has no way of escalating privileges
21266 by default. You may also find you need to set environment variables,
21267 depending on the driver you are using.
21269 .section Using cyrus@_sasl as a server
21270 The \%cyrus@_sasl%\ authenticator has four private options. It puts the
21271 username (on a successful authentication) into \$1$\.
21273 .startconf cyrus@_sasl
21274 .conf server@_hostname string$**$ $tt{$primary@_hostname}
21275 This option selects the hostname that is used when communicating with
21276 the library. It is up to the underlying SASL plug-in what it does with
21279 .conf server@_mech string $tt{public@_name}
21280 This option selects the authentication mechanism this driver should
21281 use. It allows you to use a different underlying mechanism from the
21282 advertised name. For example:
21285 driver = cyrus_sasl
21286 public_name = X-ANYTHING
21287 server_mech = CRAM-MD5
21291 .conf server@_realm string unset
21292 This specifies the SASL realm that the server claims to be in.
21294 .conf server@_service string $tt{smtp}
21295 This is the SASL service that the server claims to implement.
21299 For straightforward cases, you do not need to set any of the authenticator's
21300 private options. All you need to do is to specify an appropriate mechanism as
21301 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
21302 PLAIN, you could have two authenticators as follows:
21305 driver = cyrus_sasl
21306 public_name = CRAM-MD5
21310 driver = cyrus_sasl
21311 public_name = PLAIN
21315 Cyrus SASL does implement the LOGIN authentication method, even though it is
21316 not a standard method. It is disabled by default in the source distribution,
21317 but it is present in many binary distributions.
21327 . ============================================================================
21328 .chapter The spa authenticator
21329 .set runningfoot "spa authenticator"
21330 .index \%spa%\ authenticator
21331 .index authenticators||\%spa%\
21332 .index authentication||Microsoft Secure Password
21333 .index authentication||NTLM
21334 .index Microsoft Secure Password Authentication
21335 .index NTLM authentication
21336 The \%spa%\ authenticator provides client support for Microsoft's \*Secure
21337 Password Authentication*\ mechanism,
21338 which is also sometimes known as NTLM (NT LanMan). The code for client side of
21339 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
21340 taken from the Samba project (\?http://www.samba.org?\). The code for the
21341 server side was subsequently contributed by Tom Kistner.
21343 The mechanism works as follows:
21345 After the \\AUTH\\ command has been accepted, the client sends an SPA
21346 authentication request based on the user name and optional domain.
21348 The server sends back a challenge.
21350 The client builds a challenge response which makes use of the user's password
21351 and sends it to the server, which then accepts or rejects it.
21353 Encryption is used to protect the password in transit.
21356 .section Using spa as a server
21357 The \%spa%\ authenticator has just one server option:
21360 .index options||\%spa%\ authenticator (server)
21362 .conf server@_password string$**$ unset
21363 .index numerical variables (\$1$\, \$2$\, etc)||in \%spa%\ authenticator
21364 This option is expanded, and the result must be the cleartext password for the
21365 authenticating user, whose name is at this point in \$1$\. For example:
21370 server_password = ${lookup{$1}lsearch{/etc/exim/spa_clearpass}}
21372 If the expansion is forced to fail, authentication fails. Any other expansion
21373 failure causes a temporary error code to be returned.
21379 .section Using spa as a client
21380 The \%spa%\ authenticator has the following client options:
21383 .index options||\%spa%\ authenticator (client)
21385 .conf client@_domain string$**$ unset
21386 This option specifies an optional domain for the authentication.
21388 .conf client@_password string$**$ unset
21389 This option specifies the user's password, and must be set.
21391 .conf client@_username string$**$ unset
21392 This option specifies the user name, and must be set.
21396 Here is an example of a configuration of this authenticator for use with the
21397 mail servers at \*msn.com*\:
21402 client_username = msn/msn_username
21403 client_password = msn_plaintext_password
21404 client_domain = DOMAIN_OR_UNSET
21416 . ============================================================================
21417 .chapter Encrypted SMTP connections using TLS/SSL
21418 .set runningfoot "TLS encryption"
21419 .rset CHAPTLS "~~chapter"
21420 .index encryption||on SMTP connection
21421 .index SMTP||encryption
21422 .index TLS||on SMTP connection
21425 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
21426 Sockets Layer), is implemented by making use of the OpenSSL library or the
21427 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
21428 cryptographic code in the Exim distribution itself for implementing TLS. In
21429 order to use this feature you must install OpenSSL or GnuTLS, and then build a
21430 version of Exim that includes TLS support (see section ~~SECTinctlsssl). You
21431 also need to understand the basic concepts of encryption at a managerial level,
21432 and in particular, the way that public keys, private keys, and certificates are
21435 RFC 2487 defines how SMTP connections can make use of encryption. Once a
21436 connection is established, the client issues a \\STARTTLS\\ command. If the
21437 server accepts this, the client and the server negotiate an encryption
21438 mechanism. If the negotiation succeeds, the data that subsequently passes
21439 between them is encrypted.
21441 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
21442 and if so, what cipher suite is in use, whether the client supplied a
21443 certificate, and whether or not that certificate was verified. This makes it
21444 possible for an Exim server to deny or accept certain commands based on the
21447 \**Warning**\: certain types of firewall and certain anti-virus products can
21448 disrupt TLS connections. You need to turn off SMTP scanning for these products
21449 in order to get TLS to work.
21453 .section Support for the legacy `ssmtp' (aka `smtps') protocol
21454 .index ssmtp protocol
21455 .index smtps protocol
21456 .index SMTP||ssmtp protocol
21457 .index SMTP||smtps protocol
21458 Early implementations of encrypted SMTP used a different TCP port from normal
21459 SMTP, and expected an encryption negotiation to start immediately, instead of
21460 waiting for a \\STARTTLS\\ command from the client using the standard SMTP
21461 port. The protocol was called `ssmtp' or `smtps', and port 465 was allocated
21464 This approach was abandoned when encrypted SMTP was standardised, but there are
21465 still some legacy clients that use it. Exim supports these clients by means of
21466 the \tls@_on@_connect@_ports\ global option. Its value must be a list of port
21467 numbers; the most common use is expected to be:
21469 tls_on_connect_ports = 465
21471 The port numbers specified by this option apply to all SMTP connections, both
21472 via the daemon and via \*inetd*\. You still need to specify all the ports that
21473 the daemon uses (by setting \daemon@_smtp@_ports\ or \local@_interfaces\ or the
21474 \-oX-\ command line option) because \tls@_on@_connect@_ports\ does not add an
21475 extra port -- rather, it specifies different behaviour on a port that is
21478 There is also a \-tls-on-connect-\ command line option. This overrides
21479 \tls@_on@_connect@_ports\; it forces the legacy behaviour for all ports.
21485 .section OpenSSL vs GnuTLS
21486 .index TLS||OpenSSL \*vs*\ GnuTLS
21487 .rset SECTopenvsgnu "~~chapter.~~section"
21488 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
21489 followed later, when the first versions of GnuTLS were released. To build Exim
21490 to use GnuTLS, you need to set
21494 in Local/Makefile, in addition to
21498 You must also set \\TLS@_LIBS\\ and \\TLS@_INCLUDE\\ appropriately, so that the
21499 include files and libraries for GnuTLS can be found.
21501 There are some differences in usage when using GnuTLS instead of OpenSSL:
21503 The \tls@_verify@_certificates\ option must contain the name of a file, not the
21504 name of a directory (for OpenSSL it can be either).
21506 The \tls@_dhparam\ option is ignored, because early versions of GnuTLS had no
21507 facility for varying its Diffie-Hellman parameters. I understand that this has
21508 changed, but Exim has not been updated to provide this facility.
21510 GnuTLS uses RSA and D-H parameters that take a substantial amount of
21511 time to compute. It is unreasonable to re-compute them for every TLS
21512 session. Therefore, Exim keeps this data in a file in its spool
21513 directory, called \(gnutls-params)\. The file is owned by the Exim user and is
21514 readable only by its owner. Every Exim process that start up GnuTLS reads the
21515 RSA and D-H parameters from this file. If the file does not exist, the first
21516 Exim process that needs it computes the data and writes it to a temporary file
21517 which is renamed once it is complete. It does not matter if several Exim
21518 processes do this simultaneously (apart from wasting a few resources). Once a
21519 file is in place, new Exim processes immediately start using it.
21521 For maximum security, the parameters that are stored in this file should be
21522 recalculated periodically, the frequency depending on your paranoia level.
21523 Arranging this is easy; just delete the file when you want new values to be
21526 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
21527 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
21528 affects the value of the \$tls@_peerdn$\ variable.
21530 OpenSSL identifies cipher suites using hyphens as separators, for example:
21531 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA@_ARCFOUR@_SHA. What is
21532 more, OpenSSL complains if underscores are present in a cipher list. To make
21533 life simpler, Exim changes underscores to hyhens for OpenSSL and hyphens to
21534 underscores for GnuTLS when processing lists of cipher suites in the
21535 \tls@_require@_ciphers\ options (the global option and the \%smtp%\ transport
21538 The \tls@_require@_ciphers\ options operate differently, as described in the
21539 following sections.
21542 .section Requiring specific ciphers in OpenSSL
21543 .rset SECTreqciphssl "~~chapter.~~section"
21544 .index TLS||requiring specific ciphers (OpenSSL)
21545 .index \tls@_require@_ciphers\||OpenSSL
21546 There is a function in the OpenSSL library that can be passed a list of cipher
21547 suites before the cipher negotiation takes place. This specifies which ciphers
21548 are acceptable. The list is colon separated and may contain names like
21549 DES-CBC3-SHA. Exim passes the expanded value of \tls@_require@_ciphers\
21550 directly to this function call. The following quotation from the OpenSSL
21551 documentation specifies what forms of item are allowed in the cipher string:
21553 It can consist of a single cipher suite such as RC4-SHA.
21555 It can represent a list of cipher suites containing a certain algorithm,
21556 or cipher suites of a certain type. For example SHA1 represents all
21557 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
21560 Lists of cipher suites can be combined in a single cipher string using
21561 the + character. This is used as a logical and operation. For example
21562 SHA1+DES represents all cipher suites containing the SHA1 and the DES
21565 Each cipher string can be optionally preceded by the characters \"!"\, \"-"\ or
21568 If \"!"\ is used then the ciphers are permanently deleted from the list. The
21569 ciphers deleted can never reappear in the list even if they are explicitly
21572 If \"-"\ is used then the ciphers are deleted from the list, but some or all
21573 of the ciphers can be added again by later options.
21575 If \"+"\ is used then the ciphers are moved to the end of the list. This
21576 option doesn't add any new ciphers it just moves matching existing ones.
21578 If none of these characters is present then the string is just interpreted as a
21579 list of ciphers to be appended to the current preference list. If the list
21580 includes any ciphers already present they will be ignored: that is, they will
21581 not moved to the end of the list.
21586 .section Requiring specific ciphers in GnuTLS
21587 .rset SECTreqciphgnu "~~chapter.~~section"
21588 .index TLS||requiring specific ciphers (GnuTLS)
21589 .index \tls@_require@_ciphers\||GnuTLS
21590 The GnuTLS library does not have a combined function like OpenSSL. Instead,
21591 it allows the caller to specify separate lists of key-exchange methods,
21592 main cipher algorithms, and MAC algorithms. Unfortunately, these lists are
21593 numerical, and the library does not have a function for turning names into
21594 numbers. Consequently, the list of recognized names has to be built into
21597 At present, Exim permits only the list of main cipher algorithms to be
21598 changed. The \tls@_require@_ciphers\ option is in the same format as for
21599 OpenSSL. Exim searches each item for the name of available algorithm. For
21600 example, if the list contains RSA@_AES@_SHA then AES is recognized.
21602 The cipher algorithms list starts out with a default set of algorithms. If
21603 the first item in \tls@_require@_ciphers\ does \*not*\ start with an
21604 exclamation mark, all the default items are deleted. Thus, only those specified
21605 can be used. If the first item in \tls@_require@_ciphers\ \*does*\ start with
21606 an exclamation mark, the defaults are left on the list.
21608 Then, any item that starts with an exclamation mark causes the relevent
21609 algorithms to be removed from the list, and any item that does not start
21610 with an exclamation mark causes the relevant algorithms to be added to the
21613 tls_require_ciphers = !RSA_ARCFOUR_SHA
21615 allows all the defaults except those that use ARCFOUR, whereas
21617 tls_require_ciphers = AES : 3DES
21619 allows only cipher suites that use AES and 3DES. The currently recognized
21622 AES@_256, AES@_128, AES (both of the preceding), 3DES, and ARCFOUR@_128.
21623 Unrecognized algorithms are ignored. In a server, the order of the list is
21624 unimportant; the server will advertise the availability of all the relevant
21625 cipher suites. However, in a client, the order of the list specifies a
21626 preference order for the algorithms. The first one in the client's list that is
21627 also advertised by the server is tried first. The default order is as listed
21632 .section Configuring an Exim server to use TLS
21633 .index TLS||configuring an Exim server
21634 When Exim has been built with TLS support, it advertises the availability of
21635 the \\STARTTLS\\ command to client hosts that match \tls@_advertise@_hosts\,
21636 but not to any others. The default value of this option is unset, which means
21637 that \\STARTTLS\\ is not advertised at all. This default is chosen because you
21638 need to set some other options in order to make TLS avaliable, and also it is
21639 sensible for systems that want to use TLS only as a client.
21641 If a client issues a \\STARTTLS\\ command and there is some configuration
21642 problem in the server, the command is rejected with a 454 error. If the client
21643 persists in trying to issue SMTP commands, all except \\QUIT\\ are rejected
21646 554 Security failure
21648 If a \\STARTTLS\\ command is issued within an existing TLS session, it is
21649 rejected with a 554 error code.
21651 To enable TLS operations on a server, you must set \tls@_advertise@_hosts\ to
21652 match some hosts. You can, of course, set it to $*$ to match all hosts.
21653 However, this is not all you need to do. TLS sessions to a server won't work
21654 without some further configuration at the server end.
21656 It is rumoured that all existing clients that support TLS/SSL use RSA
21657 encryption. To make this work you need to set, in the server,
21659 tls_certificate = /some/file/name
21660 tls_privatekey = /some/file/name
21662 The first file contains the server's X509 certificate, and the second contains
21663 the private key that goes with it. These files need to be readable by the Exim
21664 user, and must always be given as full path names. They can be the same file if
21665 both the certificate and the key are contained within it. If \tls@_privatekey\
21666 is not set, this is assumed to be the case. The certificate file may also
21667 contain intermediate certificates that need to be sent to the client to enable
21668 it to authenticate the server's certificate.
21670 If you do not understand about certificates and keys, please try to find a
21671 source of this background information, which is not Exim-specific. (There are a
21672 few comments below in section ~~SECTcerandall.)
21674 \**Note**\: These options do not apply when Exim is operating as a client --
21675 they apply only in the case of a server. For a client, you must set the options
21676 of the same name in an \%smtp%\ transport.
21678 With just these options, Exim will work as a server with clients such as
21679 Netscape. It does not require the client to have a certificate (but see below
21680 for how to insist on this). There is one other option that may be needed in
21681 other situations. If
21683 tls_dhparam = /some/file/name
21685 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
21686 with the parameters contained in the file. This increases the set of cipher
21687 suites that the server supports. See the command
21691 for a way of generating this data.
21692 At present, \tls@_dhparam\ is used only when Exim is linked with OpenSSL. It is
21693 ignored if GnuTLS is being used.
21695 The strings supplied for these three options are expanded every time a client
21696 host connects. It is therefore possible to use different certificates and keys
21697 for different hosts, if you so wish, by making use of the client's IP address
21698 in \$sender@_host@_address$\ to control the expansion. If a string expansion is
21699 forced to fail, Exim behaves as if the option is not set.
21701 .index cipher||logging
21702 .index log||TLS cipher
21703 The variable \$tls@_cipher$\ is set to the cipher suite that was negotiated for
21704 an incoming TLS connection. It is included in the ::Received:: header of an
21705 incoming message (by default -- you can, of course, change this), and it is
21706 also included in the log line that records a message's arrival, keyed by `X=',
21707 unless the \tls@_cipher\ log selector is turned off.
21708 The \encrypted\ condition can be used to test for specific cipher suites in
21711 The ACLs that run for subsequent SMTP commands can check the name of the cipher
21712 suite and vary their actions accordingly. The cipher suite names are those used
21713 by OpenSSL. These may differ from the names used elsewhere. For example,
21714 OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts
21715 is known as TLS@_RSA@_WITH@_3DES@_EDE@_CBC@_SHA. Check the OpenSSL
21716 documentation for more details.
21719 .section Requesting and verifying client certificates
21720 .index certificate||verification of client
21721 .index TLS||client certificate verification
21722 If you want an Exim server to request a certificate when negotiating a TLS
21723 session with a client, you must set either \tls@_verify@_hosts\ or
21724 \tls@_try@_verify@_hosts\. You can, of course, set either of them to $*$ to
21725 apply to all TLS connections. For any host that matches one of these options,
21726 Exim requests a certificate as part of the setup of the TLS session. The
21727 contents of the certificate are verified by comparing it with a list of
21728 expected certificates. These must be available in a file or,
21729 for OpenSSL only (not GnuTLS), a directory, identified by
21730 \tls@_verify@_certificates\.
21732 A file can contain multiple certificates, concatenated end to end. If a
21735 each certificate must be in a separate file, with a name (or a symbolic link)
21736 of the form <<hash>>.0, where <<hash>> is a hash value constructed from the
21737 certificate. You can compute the relevant hash by running the command
21739 openssl x509 -hash -noout -in /cert/file
21741 where \(/cert/file)\ contains a single certificate.
21743 The difference between \tls@_verify@_hosts\ and \tls@_try@_verify@_hosts\ is
21744 what happens if the client does not supply a certificate, or if the certificate
21745 does not match any of the certificates in the collection named by
21746 \tls@_verify@_certificates\. If the client matches \tls@_verify@_hosts\, the
21747 attempt to set up a TLS session is aborted, and the incoming connection is
21748 dropped. If the client matches \tls@_try@_verify@_hosts\, the (encrypted) SMTP
21749 session continues. ACLs that run for subsequent SMTP commands can detect the
21750 fact that no certificate was verified, and vary their actions accordingly. For
21751 example, you can insist on a certificate before accepting a message for
21752 relaying, but not when the message is destined for local delivery.
21754 When a client supplies a certificate (whether it verifies or not), the value of
21755 the Distinguished Name of the certificate is made available in the variable
21756 \$tls@_peerdn$\ during subsequent processing of the message.
21757 .index log||distinguished name
21758 Because it is often a long text string, it is not included in the log line or
21759 ::Received:: header by default. You can arrange for it to be logged, keyed by
21760 `DN=', by setting the \tls@_peerdn\ log selector, and you can use
21761 \received@_header@_text\ to change the ::Received:: header. When no certificate
21762 is supplied, \$tls@_peerdn$\ is empty.
21764 .section Revoked certificates
21765 .index TLS||revoked certificates
21766 .index revocation list
21767 .index certificate||revocation list
21768 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
21769 certificates are revoked. If you have such a list, you can pass it to an Exim
21770 server using the global option called \tls@_crl\ and to an Exim client using an
21771 identically named option for the \%smtp%\ transport. In each case, the value of
21772 the option is expanded and must then be the name of a file that contains a CRL
21775 .section Configuring an Exim client to use TLS
21776 .index cipher||logging
21777 .index log||TLS cipher
21778 .index log||distinguished name
21779 .index TLS||configuring an Exim client
21780 The \tls@_cipher\ and \tls@_peerdn\ log selectors apply to outgoing SMTP
21781 deliveries as well as to incoming, the latter one causing logging of the
21782 server certificate's DN. The remaining client configuration for TLS is all
21783 within the \%smtp%\ transport.
21785 It is not necessary to set any options to have TLS work in the \%smtp%\
21786 transport. If Exim is built with TLS support, and TLS is advertised by a
21787 server, the \%smtp%\ transport always tries to start a TLS session. However,
21788 this can be prevented by setting \hosts@_avoid@_tls\ (an option of the
21789 transport) to a list of server hosts for which TLS should not be used.
21791 If you do not want Exim to attempt to send messages unencrypted when an attempt
21792 to set up an encrypted connection fails in any way, you can set
21793 \hosts@_require@_tls\ to a list of hosts for which encryption is mandatory. For
21794 those hosts, delivery is always deferred if an encrypted connection cannot be
21795 set up. If there are any other hosts for the address, they are tried in the
21798 When the server host is not in \hosts@_require@_tls\, Exim may try to deliver
21799 the message unencrypted. It always does this if the response to \\STARTTLS\\ is
21800 a 5\*xx*\ code. For a temporary error code, or for a failure to negotiate a TLS
21801 session after a success response code, what happens is controlled by the
21802 \tls@_tempfail@_tryclear\ option of the \%smtp%\ transport. If it is false,
21803 delivery to this host is deferred, and other hosts (if available) are tried. If
21804 it is true, Exim attempts to deliver unencrypted after a 4\*xx*\ response to
21805 \\STARTTLS\\, and if \\STARTTLS\\ is accepted, but the subsequent TLS
21806 negotiation fails, Exim closes the current connection (because it is in an
21807 unknown state), opens a new one to the same host, and then tries the delivery
21811 The \tls@_certificate\ and \tls@_privatekey\ options of the \%smtp%\ transport
21812 provide the client with a certificate, which is passed to the server if it
21813 requests it. If the server is Exim, it will request a certificate only if
21814 \tls@_verify@_hosts\ or \tls@_try@_verify@_hosts\ matches the client.
21815 \**Note**\: these options must be set in the \%smtp%\ transport for Exim to use
21816 TLS when it is operating as a client. Exim does not assume that a server
21817 certificate (set by the global options of the same name) should also be used
21818 when operating as a client.
21820 If \tls@_verify@_certificates\ is set, it must name a file or,
21821 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
21822 expected server certificates. The client verifies the server's certificate
21823 against this collection, taking into account any revoked certificates that are
21824 in the list defined by \tls@_crl\.
21827 \tls@_require@_ciphers\ is set on the \%smtp%\ transport, it must contain a
21828 list of permitted cipher suites. If either of these checks fails, delivery to
21829 the current host is abandoned, and the \%smtp%\ transport tries to deliver to
21830 alternative hosts, if any.
21832 All the TLS options in the \%smtp%\ transport are expanded before use, with
21833 \$host$\ and \$host@_address$\ containing the name and address of the server to
21834 which the client is connected. Forced failure of an expansion causes Exim to
21835 behave as if the relevant option were unset.
21838 .section Multiple messages on the same encrypted TCP/IP connection
21839 .rset SECTmulmessam "~~chapter.~~section"
21840 .index multiple SMTP deliveries with TLS
21841 .index TLS||multiple message deliveries
21842 Exim sends multiple messages down the same TCP/IP connection by starting up
21843 an entirely new delivery process for each message, passing the socket from
21844 one process to the next. This implementation does not fit well with the use
21845 of TLS, because there is quite a lot of state information associated with a TLS
21846 connection, not just a socket identification. Passing all the state information
21847 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
21848 session before passing the socket to a new process. The new process may then
21849 try to start a new TLS session, and if successful, may try to re-authenticate
21850 if \\AUTH\\ is in use, before sending the next message.
21852 The RFC is not clear as to whether or not an SMTP session continues in clear
21853 after TLS has been shut down, or whether TLS may be restarted again later, as
21854 just described. However, if the server is Exim, this shutdown and
21855 reinitialization works. It is not known which (if any) other servers operate
21856 successfully if the client closes a TLS session and continues with unencrypted
21857 SMTP, but there are certainly some that do not work. For such servers, Exim
21858 should not pass the socket to another process, because the failure of the
21859 subsequent attempt to use it would cause Exim to record a temporary host error,
21860 and delay other deliveries to that host.
21862 To test for this case, Exim sends an \\EHLO\\ command to the server after
21863 closing down the TLS session. If this fails in any way, the connection is
21864 closed instead of being passed to a new delivery process, but no retry
21865 information is recorded.
21867 There is also a manual override; you can set \hosts@_nopass@_tls\ on the
21868 \%smtp%\ transport to match those hosts for which Exim should not pass
21869 connections to new processes if TLS has been used.
21873 .section Certificates and all that
21874 .rset SECTcerandall "~~chapter.~~section"
21875 .index certificate||references to discussion
21876 In order to understand fully how TLS works, you need to know about
21877 certificates, certificate signing, and certificate authorities. This is not the
21878 place to give a tutorial, especially as I do not know very much about it
21879 myself. Some helpful introduction can be found in the FAQ for the SSL addition
21880 to Apache, currently at
21882 \?http://www.modssl.org/docs/2.7/ssl@_faq.html@#ToC24?\
21884 Other parts of the \*modssl*\ documentation are also helpful, and have
21885 links to further files.
21886 Eric Rescorla's book, \*SSL and TLS*\, published by Addison-Wesley (ISBN
21887 0-201-61598-3), contains both introductory and more in-depth descriptions.
21888 Some sample programs taken from the book are available from
21890 \?http://www.rtfm.com/openssl-examples/?\
21893 .section Certificate chains
21894 The file named by \tls@_certificate\ may contain more than one
21895 certificate. This is useful in the case where the certificate that is being
21896 sent is validated by an intermediate certificate which the other end does
21897 not have. Multiple certificates must be in the correct order in the file.
21898 First the host's certificate itself, then the first intermediate
21899 certificate to validate the issuer of the host certificate, then the next
21900 intermediate certificate to validate the issuer of the first intermediate
21901 certificate, and so on, until finally (optionally) the root certificate.
21902 The root certificate must already be trusted by the recipient for
21903 validation to succeed, of course, but if it's not preinstalled, sending the
21904 root certificate along with the rest makes it available for the user to
21905 install if the receiving end is a client MUA that can interact with a user.
21907 .section Self-signed certificates
21908 .index certificate||self-signed
21909 You can create a self-signed certificate using the \*req*\ command provided
21910 with OpenSSL, like this:
21912 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
21915 \(file1)\ and \(file2)\ can be the same file; the key and the certificate are
21916 delimited and so can be identified independently. The \-days-\ option
21917 specifies a period for which the certificate is valid. The \-nodes-\ option is
21918 important: if you do not set it, the key is encrypted with a passphrase
21919 that you are prompted for, and any use that is made of the key causes more
21920 prompting for the passphrase. This is not helpful if you are going to use
21921 this certificate and key in an MTA, where prompting is not possible.
21923 A self-signed certificate made in this way is sufficient for testing, and
21924 may be adequate for all your requirements if you are mainly interested in
21925 encrypting transfers, and not in secure identification.
21927 However, many clients require that the certificate presented by the server be a
21928 user (also called `leaf' or `site') certificate, and not a self-signed
21929 certificate. In this situation, the self-signed certificate described above
21930 must be installed on the client host as a trusted root \*certification
21931 authority*\ (CA), and the certificate used by Exim must be a user certificate
21932 signed with that self-signed certificate.
21934 For information on creating self-signed CA certificates and using them to sign
21935 user certificates, see the \*General implementation overview*\ chapter of the
21936 Open-source PKI book, available online at \?http://ospkibook.sourceforge.net/?\.
21944 . ============================================================================
21945 .chapter Access control lists
21946 .set runningfoot "ACL"
21947 .rset CHAPACL "~~chapter"
21948 .index ~~ACL||description
21949 .index control of incoming mail
21950 .index message||controlling incoming
21951 .index policy control||access control lists
21952 Access Control Lists (ACLs) are defined in a separate section of the run time
21953 configuration file, headed by `begin acl'. Each ACL definition starts with a
21954 name, terminated by a colon. Here is a complete ACL section that contains just
21955 one very small ACL:
21960 accept hosts = one.host.only
21962 You can have as many lists as you like in the ACL section, and the order in
21963 which they appear does not matter. The lists are self-terminating.
21965 The majority of ACLs are used to control Exim's behaviour when it receives
21966 certain SMTP commands. This applies both to incoming TCP/IP connections, and
21967 when a local process submits a message using SMTP by specifying the \-bs-\
21968 option. The most common use is for controlling which recipients are accepted
21969 in incoming messages. In addition, you can define an ACL that is used to check
21970 local non-SMTP messages. The default configuration file contains an example of
21971 a realistic ACL for checking \\RCPT\\ commands. This is discussed in chapter
21974 .section Testing ACLs
21975 The \-bh-\ command line option provides a way of testing your ACL configuration
21976 locally by running a fake SMTP session with which you interact. The host
21977 \*relay-test.mail-abuse.org*\ provides a service for checking your relaying
21978 configuration (see section ~~SECTcheralcon for more details).
21981 .section Specifying when ACLs are used
21982 .index ~~ACL||options for specifying
21983 In order to cause an ACL to be used, you have to name it in one of the relevant
21984 options in the main part of the configuration. These options are:
21985 .index \\AUTH\\||ACL for
21986 .index \\DATA\\, ACLs for
21987 .index \\ETRN\\||ACL for
21988 .index \\EXPN\\||ACL for
21989 .index \\HELO\\||ACL for
21990 .index \\EHLO\\||ACL for
21991 .index \\MAIL\\||ACL for
21992 .index \\QUIT\\, ACL for
21993 .index \\RCPT\\||ACL for
21994 .index \\STARTTLS\\, ACL for
21995 .index \\VRFY\\||ACL for
21996 .index SMTP||connection, ACL for
21997 .index non-smtp message, ACL for
22003 \acl@_not@_smtp\ $t $rm{ACL for non-SMTP messages}
22004 \acl@_smtp@_auth\ $t $rm{ACL for \\AUTH\\}
22005 \acl@_smtp@_connect\ $t $rm{ACL for start of SMTP connection}
22006 \acl@_smtp@_data\ $t $rm{ACL after \\DATA\\ is complete}
22007 \acl@_smtp@_etrn\ $t $rm{ACL for \\ETRN\\}
22008 \acl@_smtp@_expn\ $t $rm{ACL for \\EXPN\\}
22009 \acl@_smtp@_helo\ $t $rm{ACL for \\HELO\\ or \\EHLO\\}
22010 \acl@_smtp@_mail\ $t $rm{ACL for \\MAIL\\}
22011 \acl@_smtp@_mailauth\ $t $rm{ACL for the \\AUTH\\ parameter of \\MAIL\\}
22014 \acl@_smtp@_mime\ $t $rm{ACL for content-scanning MIME parts}
22015 \acl@_smtp@_predata\ $t $rm{ACL at start of \\DATA\\ command}
22016 \acl@_smtp@_quit\ $t $rm{ACL for \\QUIT\\}
22019 \acl@_smtp@_rcpt\ $t $rm{ACL for \\RCPT\\}
22020 \acl@_smtp@_starttls\ $t $rm{ACL for \\STARTTLS\\}
22021 \acl@_smtp@_vrfy\ $t $rm{ACL for \\VRFY\\}
22023 For example, if you set
22025 acl_smtp_rcpt = small_acl
22027 the little ACL defined above is used whenever Exim receives a \\RCPT\\ command
22028 in an SMTP dialogue. The majority of policy tests on incoming messages can be
22029 done when \\RCPT\\ commands arrive. A rejection of \\RCPT\\ should cause the
22030 sending MTA to give up on the recipient address contained in the \\RCPT\\
22031 command, whereas rejection at other times may cause the client MTA to keep on
22032 trying to deliver the message. It is therefore recommended that you do as much
22033 testing as possible at \\RCPT\\ time.
22035 .section The non-SMTP ACL
22036 .index non-smtp message, ACL for
22037 The non-SMTP ACL applies to all non-interactive incoming messages, that is, it
22038 applies to batch SMTP as well as to non-SMTP messages. (Batch SMTP is not
22039 really SMTP.) This ACL is run just before the \*local@_scan()*\ function. Any
22040 kind of rejection is treated as permanent, because there is no way of sending a
22041 temporary error for these kinds of message. Many of the ACL conditions (for
22042 example, host tests, and tests on the state of the SMTP connection such as
22043 encryption and authentication) are not relevant and are forbidden in this ACL.
22045 .section The connect ACL
22046 .index SMTP||connection, ACL for
22047 The ACL test specified by \acl@_smtp@_connect\ happens after the test specified
22048 by \host__reject__connection\ (which is now an anomaly) and any TCP Wrappers
22049 testing (if configured).
22052 .section The DATA ACLs
22053 .index \\DATA\\, ACLs for
22054 Two ACLs are associated with the \\DATA\\ command, because it is two-stage
22055 command, with two responses being sent to the client.
22056 When the \\DATA\\ command is received, the ACL defined by \acl@_smtp@_predata\
22057 is obeyed. This gives you control after all the \\RCPT\\ commands, but before
22058 the message itself is received. It offers the opportunity to give a negative
22059 response to the \\DATA\\ command before the data is transmitted. Header lines
22060 added by \\MAIL\\ or \\RCPT\\ ACLs are not visible at this time, but any that
22061 are defined here are visible when the \acl@_smtp@_data\ ACL is run.
22063 You cannot test the contents of the message, for example, to verify addresses
22064 in the headers, at \\RCPT\\ time or when the \\DATA\\ command is received. Such
22065 tests have to appear in the ACL that is run after the message itself has been
22066 received, before the final response to the \\DATA\\ command is sent. This is
22067 the ACL specified by \acl@_smtp@_data\, which is the second ACL that is
22068 associated with the \\DATA\\ command.
22070 For both of these ACLs, it is not possible to reject individual recipients. An
22071 error response rejects the entire message. Unfortunately, it is known that some
22072 MTAs do not treat hard (5$it{xx}) responses to the \\DATA\\ command (either
22073 before or after the data) correctly -- they keep the message on their queues
22074 and try again later, but that is their problem, though it does waste some of
22077 .section The MIME ACL
22078 The \acl@_smtp@_mime\ option is available only when Exim is compiled with the
22079 content-scanning extension. For details, see chapter ~~CHAPexiscan.
22081 .section The QUIT ACL
22082 .rset SECTQUITACL "~~chapter.~~section"
22083 .index \\QUIT\\, ACL for
22084 The ACL for the SMTP \\QUIT\\ command is anomalous, in that the
22085 outcome of the ACL does not affect the response code to \\QUIT\\,
22086 which is always 221. Thus, the ACL does not in fact control any access.
22087 For this reason, the only verbs that are permitted are \accept\ and \warn\.
22089 This ACL can be used for tasks such as custom logging at the end of an SMTP
22090 session. For example, you can use ACL variables in other ACLs to count
22091 messages, recipients, etc., and log the totals at \\QUIT\\ time using one or
22092 more \logwrite\ modifiers on a \warn\ verb.
22094 You do not need to have a final \accept\, but if you do, you can use a
22095 \message\ modifier to specify custom text that is sent as part of the 221
22096 response to \\QUIT\\.
22098 This ACL is run only for a `normal' \\QUIT\\. For certain kinds of disastrous
22099 failure (for example, failure to open a log file, or when Exim is bombing out
22100 because it has detected an unrecoverable error), all SMTP commands from the
22101 client are given temporary error responses until \\QUIT\\ is received or the
22102 connection is closed. In these special cases, the \\QUIT\\ ACL does not run.
22105 .section Finding an ACL to use
22106 .index ~~ACL||finding which to use
22107 The value of an \acl@_smtp@_$it{xxx}\ option is expanded before use, so you can
22108 use different ACLs in different circumstances. The resulting string does not
22109 have to be the name of an ACL in the configuration file; there are other
22110 possibilities. Having expanded the string, Exim searches for an ACL as follows:
22112 If the string begins with a slash, Exim uses it as a file name, and reads its
22113 contents as an ACL. The lines are processed in the same way as lines in the
22114 Exim configuration file. In particular, continuation lines are supported, blank
22115 lines are ignored, as are lines whose first non-whitespace character is `@#'.
22116 If the file does not exist or cannot be read, an error occurs (typically
22117 causing a temporary failure of whatever caused the ACL to be run). For example:
22119 acl_smtp_data = /etc/acls/\
22120 ${lookup{$sender_host_address}lsearch\
22121 {/etc/acllist}{$value}{default}}
22123 This looks up an ACL file to use on the basis of the host's IP address, falling
22124 back to a default if the lookup fails. If an ACL is successfully read from a
22125 file, it is retained in memory for the duration of the Exim process, so that it
22126 can be re-used without having to re-read the file.
22128 If the string does not start with a slash, and does not contain any spaces,
22129 Exim searches the ACL section of the configuration for an ACL whose name
22130 matches the string.
22132 If no named ACL is found, or if the string contains spaces, Exim parses
22133 the string as an inline ACL. This can save typing in cases where you just
22134 want to have something like
22136 acl_smtp_vrfy = accept
22138 in order to allow free use of the \\VRFY\\ command. Such a string may contain
22139 newlines; it is processed in the same way as an ACL that is read from a file.
22143 .section ACL return codes
22144 .index ~~ACL||return codes
22146 Except for the \\QUIT\\ ACL, which does not affect the SMTP return code (see
22147 section ~~SECTQUITACL above), the
22149 result of running an ACL is either `accept' or `deny', or, if some test
22150 cannot be completed (for example, if a database is down), `defer'. These
22151 results cause 2$it{xx}, 5$it{xx}, and 4$it{xx} return codes, respectively, to
22152 be used in the SMTP dialogue. A fourth return, `error', occurs when there is an
22153 error such as invalid syntax in the ACL. This also causes a 4$it{xx} return
22157 For the non-SMTP ACL, `defer' and `error' are treated in the same way as
22158 `deny', because there is no mechanism for passing temporary errors to the
22159 submitters of non-SMTP messages.
22162 ACLs that are relevant to message reception may also return `discard'. This
22163 has the effect of `accept', but causes either the entire message or an
22164 individual recipient address to be discarded. In other words, it is a
22165 blackholing facility. Use it with care.
22167 If the ACL for \\MAIL\\ returns `discard', all recipients are discarded, and no
22168 ACL is run for subsequent \\RCPT\\ commands. The effect of `discard' in a
22169 \\RCPT\\ ACL is to discard just the one recipient address. If there are no
22170 recipients left when the message's data is received, the \\DATA\\ ACL is not
22171 run. A `discard' return from the \\DATA\\ or the non-SMTP ACL discards all the
22172 remaining recipients.
22174 The `discard' return is not permitted for the \acl@_smtp@_predata\ ACL.
22177 .index \*local@_scan()*\ function||when all recipients discarded
22178 The \*local@_scan()*\ function is always run, even if there are no remaining
22179 recipients; it may create new recipients.
22182 .section Unset ACL options
22183 .index ~~ACL||unset options
22184 The default actions when any of the \acl@_$it{xxx}\ options are unset are not
22185 all the same. \**Note**\: These defaults apply only when the relevant ACL is
22186 not defined at all. For any defined ACL, the default action when control reaches
22187 the end of the ACL statements is `deny'.
22189 For \acl@_not@_smtp\, \acl@_smtp@_auth\, \acl@_smtp@_connect\,
22190 \acl@_smtp@_data\, \acl@_smtp@_helo\, \acl__smtp__mail\, \acl@_smtp@_mailauth\,
22192 \acl@_smtp@_mime\, \acl@_smtp@_predata\, \acl@_smtp@_quit\,
22194 and \acl__smtp__starttls\, the action when the ACL is not defined is `accept'.
22196 For the others (\acl@_smtp@_etrn\, \acl@_smtp@_expn\, \acl@_smtp@_rcpt\, and
22197 \acl@_smtp@_vrfy\), the action when the ACL is not defined is `deny'.
22198 This means that \acl@_smtp@_rcpt\ must be defined in order to receive any
22199 messages over an SMTP connection. For an example, see the ACL in the default
22200 configuration file.
22204 .section Data for message ACLs
22205 .index ~~ACL||data for message ACL
22207 When a \\MAIL\\ or \\RCPT\\ ACL, or either of the \\DATA\\ ACLs, is running,
22208 the variables that contain information about the host and the message's sender
22209 (for example, \$sender@_host@_address$\ and \$sender@_address$\) are set, and
22210 can be used in ACL statements. In the case of \\RCPT\\ (but not \\MAIL\\ or
22211 \\DATA\\), \$domain$\ and \$local@_part$\ are set from the argument address.
22213 When an ACL for the \\AUTH\\ parameter of \\MAIL\\ is running, the variables
22214 that contain information about the host are set, but \$sender@_address$\ is not
22215 yet set. Section ~~SECTauthparamail contains a discussion of this parameter and
22218 The \$message@_size$\ variable is set to the value of the \\SIZE\\ parameter on
22219 the \\MAIL\\ command at \\MAIL\\, \\RCPT\\ and pre-data time, or to -1 if
22220 that parameter is not given. The value is updated to the true message size by
22221 the time the final \\DATA\\ ACL is run (after the message data has been
22224 The \$rcpt@_count$\ variable increases by one for each \\RCPT\\ command
22225 received. The \$recipients@_count$\ variable increases by one each time a
22226 \\RCPT\\ command is accepted, so while an ACL for \\RCPT\\ is being processed,
22227 it contains the number of previously accepted recipients. At \\DATA\\ time (for
22228 both the \\DATA\\ ACLs), \$rcpt@_count$\ contains the total number of \\RCPT\\
22229 commands, and \$recipients@_count$\ contains the total number of accepted
22235 .section Data for non-message ACLs
22236 .rset SECTdatfornon "~~chapter.~~section"
22237 .index ~~ACL||data for non-message ACL
22239 When an ACL is being run for \\AUTH\\, \\EHLO\\, \\ETRN\\, \\EXPN\\, \\HELO\\,
22241 \\STARTTLS\\, or \\VRFY\\, the remainder of the SMTP command line is placed in
22242 \$smtp@_command@_argument$\. This can be tested using a \condition\ condition.
22243 For example, here is an ACL for use with \\AUTH\\, which insists that either
22244 the session is encrypted, or the CRAM-MD5 authentication method is used. In
22245 other words, it does not permit authentication methods that use cleartext
22246 passwords on unencrypted connections.
22249 accept encrypted = *
22252 accept condition = ${if eq{${uc:$smtp_command_argument}}\
22256 deny message = TLS encryption or CRAM-MD5 required
22258 (Another way of applying this restriction is to arrange for the authenticators
22259 that use cleartext passwords not to be advertised when the connection is not
22260 encrypted. You can use the generic \server@_advertise@_condition\ authenticator
22261 option to do this.)
22264 .section Format of an ACL
22265 .index ~~ACL||format of
22266 .index ~~ACL||verbs, definition of
22267 An individual ACL consists of a number of statements. Each statement starts
22268 with a verb, optionally followed by a number of conditions and `modifiers'.
22270 Modifiers can change the way the verb operates, define error and log messages,
22271 set variables, insert delays, and vary the processing of accepted messages.
22274 If all the conditions are met, the verb is obeyed. The same condition may be
22275 used (with different arguments) more than once in the same statement. This
22276 provides a means of specifying an `and' conjunction between conditions. For
22279 deny dnslists = list1.example
22280 dnslists = list2.example
22282 If there are no conditions, the verb is always obeyed.
22284 Exim stops evaluating the conditions and modifiers when it reaches a condition
22285 that fails. What happens then
22287 depends on the verb (and in one case, on a special modifier). Not all the
22288 conditions make sense at every testing point. For example, you cannot test a
22289 sender address in the ACL that is run for a \\VRFY\\ command.
22292 The ACL verbs are as follows:
22294 .index \accept\, ACL verb
22295 \accept\: If all the conditions are met, the ACL returns `accept'. If any of
22296 the conditions are not met, what happens depends on whether \endpass\ appears
22297 among the conditions (for syntax see below). If the failing condition is before
22298 \endpass\, control is passed to the next ACL statement; if it is after
22299 \endpass\, the ACL returns `deny'. Consider this statement, used to check a
22302 accept domains = +local_domains
22306 If the recipient domain does not match the \domains\ condition, control passes
22307 to the next statement. If it does match, the recipient is verified, and the
22308 command is accepted if verification succeeds. However, if verification fails,
22309 the ACL yields `deny', because the failing condition is after \endpass\.
22311 .index \defer\, ACL verb
22312 \defer\: If all the conditions are met, the ACL returns `defer' which, in an
22313 SMTP session, causes a 4\*xx*\ response to be given. For a non-SMTP ACL,
22314 \defer\ is the same as \deny\, because there is no way of sending a temporary
22315 error. For a \\RCPT\\ command, \defer\ is much the same as using a
22316 \%redirect%\ router and \":defer:"\ while verifying, but the \defer\ verb can
22317 be used in any ACL, and even for a recipient it might be a simpler approach.
22319 .index \deny\, ACL verb
22320 \deny\: If all the conditions are met, the ACL returns `deny'. If any of the
22321 conditions are not met, control is passed to the next ACL statement. For
22324 deny dnslists = blackholes.mail-abuse.org
22326 rejects commands from hosts that are on a DNS black list.
22328 .index \discard\, ACL verb
22329 \discard\: This verb behaves like \accept\, except that it returns `discard'
22330 from the ACL instead of `accept'. It is permitted only on ACLs that are
22331 concerned with receiving messages, and it causes recipients to be discarded.
22332 If the \log@_message\ modifier is set when \discard\ operates, its contents are
22333 added to the line that is automatically written to the log.
22335 If \discard\ is used in an ACL for \\RCPT\\, just the one recipient is
22336 discarded; if used for \\MAIL\\, \\DATA\\ or in the non-SMTP ACL, all the
22337 message's recipients are discarded. Recipients that are discarded before
22338 \\DATA\\ do not appear in the log line when the \log@_recipients\ log selector
22341 .index \drop\, ACL verb
22342 \drop\: This verb behaves like \deny\, except that an SMTP connection is
22343 forcibly closed after the 5\*xx*\ error message has been sent. For example:
22345 drop message = I don't take more than 20 RCPTs
22348 condition = ${if > {$rcpt_count}{20}}
22351 There is no difference between \deny\ and \drop\ for the connect-time ACL. The
22352 connection is always dropped after sending a 550 response.
22354 .index \require\, ACL verb
22355 \require\: If all the conditions are met, control is passed to the next ACL
22356 statement. If any of the conditions are not met, the ACL returns `deny'. For
22357 example, when checking a \\RCPT\\ command,
22359 require verify = sender
22361 passes control to subsequent statements only if the message's sender can be
22362 verified. Otherwise, it rejects the command.
22364 .index \warn\, ACL verb
22365 \warn\: If all the conditions are met, a header line is added to an incoming
22366 message and/or a line is written to Exim's main log. In all cases, control
22367 passes to the next ACL statement. The text of the added header line and the log
22368 line are specified by modifiers; if they are not present, a \warn\ verb just
22369 checks its conditions and obeys any `immediate' modifiers such as \set\ and
22372 There is more about adding header lines in section ~~SECTaddheadwarn.
22375 If any condition on a \warn\ statement cannot be completed (that is, there is
22376 some sort of defer), no header lines are added and the configured log line is
22377 not written. No further conditions or modifiers in the \warn\ statement are
22378 processed. The incident is logged, but the ACL continues to be processed, from
22379 the next statement onwards.
22381 If a \message\ modifier is present on a \warn\ verb in an ACL that is not
22382 testing an incoming message, it is ignored, and the incident is logged.
22384 A \warn\ statement may use the \log@_message\ modifier to cause a line to be
22385 written to the main log when the statement's conditions are true.
22386 If an identical log line is requested several times in the same message, only
22387 one copy is actually written to the log. If you want to force duplicates to be
22388 written, use the \logwrite\ modifier instead.
22390 When one of the \warn\ conditions is an address verification that fails, the
22391 text of the verification failure message is in \$acl@_verify@_message$\. If you
22392 want this logged, you must set it up explicitly. For example:
22394 warn !verify = sender
22395 log_message = sender verify failed: $acl_verify_message
22399 At the end of each ACL there is an implicit unconditional \deny\.
22401 As you can see from the examples above, the conditions and modifiers are
22402 written one to a line, with the first one on the same line as the verb, and
22403 subsequent ones on following lines. If you have a very long condition, you can
22404 continue it onto several physical lines by the usual backslash continuation
22405 mechanism. It is conventional to align the conditions vertically.
22408 .section ACL variables
22409 .rset SECTaclvariables "~~chapter.~~section"
22410 .index ~~ACL||variables
22411 There are some special variables that can be set during ACL processing. They
22412 can be used to pass information between different ACLs, different invocations
22413 of the same ACL in the same SMTP connection, and between ACLs and the routers,
22414 transports, and filters that are used to deliver a message. There are two sets
22415 of these variables:
22417 The values of \$acl@_c0$\ to \$acl@_c9$\ persist throughout an SMTP connection.
22418 They are never reset. Thus, a value that is set while receiving one message is
22419 still available when receiving the next message on the same SMTP connection.
22421 The values of \$acl@_m0$\ to \$acl@_m9$\ persist only while a message is being
22422 received. They are reset afterwards. They are also reset by \\MAIL\\, \\RSET\\,
22423 \\EHLO\\, \\HELO\\, and after starting up a TLS session.
22425 When a message is accepted, the current values of all the ACL variables are
22426 preserved with the message and are subsequently made available at delivery
22427 time. The ACL variables are set by modifier called \set\. For example:
22429 accept hosts = whatever
22430 set acl_m4 = some value
22432 \**Note**\: a leading dollar sign is not used when naming a variable that is to
22433 be set. If you want to set a variable without taking any action, you can use a
22434 \warn\ verb without any other modifiers or conditions.
22437 .section Condition and modifier processing
22438 .index ~~ACL||conditions, processing
22439 .index ~~ACL||modifiers, processing
22440 An exclamation mark preceding a condition negates its result. For example,
22442 deny domains = *.dom.example
22443 !verify = recipient
22445 causes the ACL to return `deny' if the recipient domain ends in
22446 \*dom.example*\ and the recipient address cannot be verified.
22448 The arguments of conditions and modifiers are expanded. A forced failure
22449 of an expansion causes a condition to be ignored, that is, it behaves as if the
22450 condition is true. Consider these two statements:
22452 accept senders = ${lookup{$host_name}lsearch\
22453 {/some/file}{$value}fail}
22454 accept senders = ${lookup{$host_name}lsearch\
22455 {/some/file}{$value}{}}
22457 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
22458 the returned list is searched, but if the lookup fails the behaviour is
22459 different in the two cases. The \fail\ in the first statement causes the
22460 condition to be ignored, leaving no further conditions. The \accept\ verb
22461 therefore succeeds. The second statement, however, generates an empty list when
22462 the lookup fails. No sender can match an empty list, so the condition fails,
22463 and therefore the \accept\ also fails.
22465 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
22466 specify actions that are taken as the conditions for a statement are checked;
22467 others specify text for messages that are used when access is denied or a
22468 warning is generated.
22470 The \control\ modifier affects the way an incoming message is handled.
22473 The positioning of the modifiers in an ACL statement important, because the
22474 processing of a verb ceases as soon as its outcome is known. Only those
22475 modifiers that have already been encountered will take effect. For example,
22476 consider this use of the \message\ modifier:
22478 require message = Can't verify sender
22480 message = Can't verify recipient
22482 message = This message cannot be used
22484 If sender verification fails, Exim knows that the result of the statement is
22485 `deny', so it goes no further. The first \message\ modifier has been seen, so
22486 its text is used as the error message. If sender verification succeeds, but
22487 recipient verification fails, the second message is used. If recipient
22488 verification succeeds, the third message becomes `current', but is never used
22489 because there are no more conditions to cause failure.
22491 For the \deny\ verb, on the other hand, it is always the last \message\
22492 modifier that is used, because all the conditions must be true for rejection to
22493 happen. Specifying more than one \message\ modifier does not make sense, and
22494 the message can even be specified after all the conditions. For example:
22497 !senders = *@my.domain.example
22498 message = Invalid sender from client host
22500 The `deny' result does not happen until the end of the statement is reached, by
22501 which time Exim has set up the message.
22504 .section ACL modifiers
22505 .rset SECTACLmodi "~~chapter.~~section"
22506 .index ~~ACL||modifiers, list of
22507 The ACL modifiers are as follows:
22511 .item "control = <<text>>"
22512 .index \control\, ACL modifier
22514 This modifier affects the subsequent processing of the SMTP connection or of an
22515 incoming message that is accepted. The effect of the first type of control
22516 lasts for the duration of the connection, whereas the effect of the second type
22517 lasts only until the current message has been received. The message-specific
22518 controls always apply to the whole message, not to individual recipients,
22519 even if the \control\ modifier appears in a \\RCPT\\ ACL.
22521 As there are now quite a few controls that can be applied, they are described
22522 separately in section ~~SECTcontrols.
22524 The \control\ modifier can be used in several different ways. For example:
22526 It can be at the end of an \accept\ statement:
22528 accept ...some conditions
22529 control = queue_only
22531 In this case, the control is applied when this statement yields `accept', in
22532 other words, when the conditions are all true.
22534 It can be in the middle of an \accept\ statement:
22536 accept ...some conditions...
22537 control = queue_only
22538 ...some more conditions...
22540 If the first set of conditions are true, the control is applied, even if the
22541 statement does not accept because one of the second set of conditions is false.
22542 In this case, some subsequent statement must yield `accept' for the control to
22545 It can be used with \warn\ to apply the control, leaving the
22546 decision about accepting or denying to a subsequent verb. For
22549 warn ...some conditions...
22553 This example of \warn\ does not contain \message\, \log@_message\, or
22554 \logwrite\, so it does not add anything to the message and does not write a log
22558 If you want to apply a control unconditionally, you can use it with a \require\
22561 require control = no_multiline_response
22566 .item "delay = <<time>>"
22567 .index \delay\, ACL modifier
22568 .index \-bh-\ option
22569 This modifier causes Exim to wait for the time interval before proceeding. The
22570 time is given in the usual Exim notation. This modifier may appear in any ACL.
22571 The delay happens as soon as the modifier is processed. However, when testing
22572 Exim using the \-bh-\ option, the delay is not actually imposed (an appropriate
22573 message is output instead).
22575 Like \control\, \delay\ can be used with \accept\ or
22576 \deny\, for example:
22578 deny ...some conditions...
22581 The delay happens if all the conditions are true, before the statement returns
22582 `deny'. Compare this with:
22585 ...some conditions...
22587 which waits for 30s before processing the conditions. The \delay\ modifier can
22588 also be used with \warn\ and together with \control\:
22590 warn ...some conditions...
22597 .index \endpass\, ACL modifier
22598 This modifier, which has no argument, is recognized only in \accept\
22599 statements. It marks the boundary between the conditions whose failure causes
22600 control to pass to the next statement, and the conditions whose failure causes
22601 the ACL to return `deny'. See the description of \accept\ above.
22603 .item "log@_message = <<text>>"
22604 .index \log@_message\, ACL modifier
22605 This modifier sets up a message that is used as part of the log message if the
22606 ACL denies access or a \warn\ statement's conditions are true. For example:
22608 require log_message = wrong cipher suite $tls_cipher
22609 encrypted = DES-CBC3-SHA
22611 \log@_message\ adds to any underlying error message that may exist because of
22612 the condition failure. For example, while verifying a recipient address, a
22613 :::fail:: redirection might have already set up a message. Although the message
22614 is usually defined before the conditions to which it applies, the expansion
22615 does not happen until Exim decides that access is to be denied. This means that
22616 any variables that are set by the condition are available for inclusion in the
22617 message. For example, the \$dnslist@_<<xxx>>$\ variables are set after a DNS
22618 black list lookup succeeds. If the expansion of \log@_message\ fails, or if the
22619 result is an empty string, the modifier is ignored.
22621 If you want to use a \warn\ statement to log the result of an address
22622 verification, you can use \$acl__verify__message$\ to include the verification
22625 If \log@_message\ is used with a \warn\ statement, `Warning:' is added to the
22626 start of the logged message. If the same warning log message is requested more
22627 than once while receiving a single email message, only one copy is actually
22628 logged. If you want to log multiple copies, use \logwrite\ instead of
22629 \log@_message\. In the absence of \log@_message\ and \logwrite\, nothing is
22630 logged for a succesful \warn\ statement.
22632 If \log@_message\ is not present and there is no underlying error message (for
22633 example, from the failure of address verification), but \message\ is present,
22634 the \message\ text is used for logging rejections. However, if any text for
22635 logging contains newlines, only the first line is logged. In the absence of
22636 both \log@_message\ and \message\, a default built-in message is used for
22637 logging rejections.
22639 .item "logwrite = <<text>>"
22640 .index \logwrite\, ACL modifier
22641 .index log||in ACL, immediate
22642 This modifier writes a message to a log file as soon as it is encountered when
22643 processing an ACL. (Compare \log@_message\, which, except in the case of
22644 \warn\, is used only if the ACL statement denies access.) The \logwrite\
22645 modifier can be used to log special incidents in ACLs. For example:
22647 accept <<some special conditions>>
22649 logwrite = froze message because ...
22651 By default, the message is written to the main log. However, it may begin
22652 with a colon, followed by a comma-separated list of log names, and then
22653 another colon, to specify exactly which logs are to be written. For
22656 logwrite = :main,reject: text for main and reject logs
22657 logwrite = :panic: text for panic log only
22660 .item "message = <<text>>"
22661 .index \message\, ACL modifier
22662 This modifier sets up a text string that is expanded and used as an error
22663 message if the current statement causes the ACL to deny access. The expansion
22664 happens at the time Exim decides that access is to be denied, not at the time
22665 it processes \message\. If the expansion fails, or generates an empty string,
22666 the modifier is ignored. For ACLs that are triggered by SMTP commands, the
22667 message is returned as part of the SMTP error response.
22669 The \message\ modifier is also used with the \warn\ verb to specify one or more
22670 header lines to be added to an incoming message when all the conditions are
22671 true. See section ~~SECTaddheadwarn for more details. If \message\ is used with
22672 \warn\ in an ACL that is not concerned with receiving a message, it has no
22675 The text is literal; any quotes are taken as literals, but because the string
22676 is expanded, backslash escapes are processed anyway. If the message contains
22677 newlines, this gives rise to a multi-line SMTP response. Like \log@_message\,
22678 the contents of \message\ are not expanded until after a condition has failed.
22680 If \message\ is used on a statement that verifies an address, the message
22681 specified overrides any message that is generated by the verification process.
22682 However, the original message is available in the variable
22683 \$acl@_verify@_message$\, so you can incorporate it into your message if you
22684 wish. In particular, if you want the text from \:fail:\ items in \%redirect%\
22685 routers to be passed back as part of the SMTP response, you should either not
22686 use a \message\ modifier, or make use of \$acl@_verify@_message$\.
22688 .item "set <<acl@_name>> = <<value>>"
22689 .index \set\, ACL modifier
22690 This modifier puts a value into one of the ACL variables (see section
22691 ~~SECTaclvariables).
22697 .section Use of the control modifier
22698 .rset SECTcontrols "~~chapter.~~section"
22699 .index \control\, ACL modifier
22700 The \control\ modifier supports the following settings:
22704 .item "control = caseful@_local@_part"
22705 .item "control = caselower@_local@_part"
22706 .index ~~ACL||case of local part in
22707 .index case of local parts
22708 These two controls are permitted only in the ACL specified by \acl@_smtp@_rcpt\
22709 (that is, during \\RCPT\\ processing). By default, the contents of
22710 \$local@_part$\ are lower cased before ACL processing. If
22711 `caseful@_local@_part' is specified, any uppercase letters in the original
22712 local part are restored in \$local@_part$\ for the rest of the ACL, or until a
22713 control that sets `caselower@_local@_part' is encountered.
22715 This control affects only the current recipient. Moreover, it applies only to
22716 local part handling that takes place directly in the ACL (for example, as a key
22717 in lookups). If a test to verify the recipient is obeyed, the case-related
22718 handling of the local part during the verification is controlled by the router
22719 configuration (see the \caseful@_local@_part\ generic router option).
22721 This facility could be used, for example, to add a spam score to local parts
22722 containing upper case letters. For example, using \$acl@_m4$\ to accumulate the
22725 warn control = caseful_local_part
22726 set acl_m4 = ${eval:\
22728 ${if match{$local_part}{[A-Z]}{1}{0}}\
22730 control = caselower_local_part
22732 Notice that we put back the lower cased version afterwards, assuming that
22733 is what is wanted for subsequent tests.
22735 .item "control = enforce@_sync"
22736 .item "control = no@_enforce@_sync"
22737 .index SMTP||synchronization checking
22738 .index synchronization checking in SMTP
22739 These controls make it possible to be selective about when SMTP synchronization
22740 is enforced. The global option \smtp@_enforce@_sync\ specifies the initial
22741 state of the switch (it is true by default). See the description of this option
22742 in chapter ~~CHAPmainconfig for details of SMTP synchronization checking.
22744 The effect of these two controls lasts for the remainder of the SMTP
22745 connection. They can appear in any ACL except the one for the non-SMTP
22746 messages. The most straightforward place to put them is in the ACL defined by
22747 \acl@_smtp@_connect\, which is run at the start of an incoming SMTP connection,
22748 before the first synchronization check. The expected use is to turn off the
22749 synchronization checks for badly-behaved hosts that you nevertheless need to
22752 .item "control = fakereject/<<message>>"
22753 .index fake rejection
22754 .index rejection, fake
22755 This control is permitted only for the \\MAIL\\, \\RCPT\\, and \\DATA\\ ACLs,
22756 in other words, only when an SMTP message is being received. If Exim accepts
22757 the message, instead the final 250 response, a 550 rejection message is sent.
22758 However, Exim proceeds to deliver the message as normal. The control applies
22759 only to the current message, not to any subsequent ones that may be received in
22760 the same SMTP connection.
22762 The text for the 550 response is taken from the \control\ modifier. If no
22763 message is supplied, the following is used:
22765 550-Your message has been rejected but is being
22766 550-kept for evaluation.
22767 550-If it was a legitimate message, it may still be
22768 550 delivered to the target recipient(s).
22770 This facilty should be used with extreme caution.
22773 .item "control = freeze"
22774 .index frozen messages||forcing in ACL
22775 This control is permitted only for the \\MAIL\\, \\RCPT\\, \\DATA\\, and
22776 non-SMTP ACLs, in other words, only when a message is being received. If the
22777 message is accepted, it is placed on Exim's queue and frozen. The control
22778 applies only to the current message, not to any subsequent ones that may be
22779 received in the same SMTP connection.
22782 .item "control = no@_mbox@_unspool"
22783 This control is available when Exim is compiled with the content scanning
22784 extension. Content scanning may require a copy of the current message, or parts
22785 of it, to be written in `mbox format' to a spool file, for passing to a virus
22786 or spam scanner. Normally, such copies are deleted when they are no longer
22787 needed. If this control is set, the copies are not deleted. The control
22788 applies only to the current message, not to any subsequent ones that may be
22789 received in the same SMTP connection. It is provided for debugging purposes and
22790 is unlikely to be useful in production.
22793 .item "control = no@_multiline@_response"
22794 .index multiline responses, suppressing
22795 This control is permitted for any ACL except the one for non-SMTP messages.
22796 It seems that there are broken clients in use that cannot handle multiline
22797 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
22799 If this control is set, multiline SMTP responses from ACL rejections are
22800 suppressed. One way of doing this would have been to put out these responses as
22801 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
22802 (`use multiline responses for more' it says -- ha!), and some of the responses
22803 might get close to that. So this facility, which is after all only a sop to
22804 broken clients, is implemented by doing two very easy things:
22806 Extra information that is normally output as part of a rejection caused by
22807 sender verification failure is omitted. Only the final line (typically `sender
22808 verification failed') is sent.
22810 If a \message\ modifier supplies a multiline response, only the first
22813 The setting of the switch can, of course, be made conditional on the
22814 calling host. Its effect lasts until the end of the SMTP connection.
22817 .item "control = queue@_only"
22818 .index \queue@_only\
22819 .index queueing incoming messages
22820 This control is permitted only for the \\MAIL\\, \\RCPT\\, \\DATA\\, and
22821 non-SMTP ACLs, in other words, only when a message is being received. If the
22822 message is accepted, it is placed on Exim's queue and left there for delivery
22823 by a subsequent queue runner. No immediate delivery process is started. In
22824 other words, it has the effect as the \queue@_only\ global option. However, the
22825 control applies only to the current message, not to any subsequent ones that
22826 may be received in the same SMTP connection.
22829 .item "control = submission/<<options>>"
22830 .index message||submission
22831 .index submission mode
22832 This control is permitted only for the \\MAIL\\, \\RCPT\\, and start of data
22833 ACLs (the latter is the one defined by \acl@_smtp@_predata\). Setting it tells
22834 Exim that the current message is a submission from a local MUA. In this case,
22835 Exim operates in `submission mode', and applies certain fixups to the message
22836 if necessary. For example, it add a ::Date:: header line if one is not present.
22837 This control is not permitted in the \acl@_smtp@_data\ ACL, because that is too
22838 late (the message has already been created).
22840 Chapter ~~CHAPmsgproc describes the processing that Exim applies to messages.
22841 Section ~~SECTsubmodnon covers the processing that happens in submission mode;
22842 the available options for this control are described there. The control applies
22843 only to the current message, not to any subsequent ones that may be received in
22844 the same SMTP connection.
22851 .section Adding header lines with the warn verb
22852 .rset SECTaddheadwarn "~~chapter.~~section"
22853 .index header lines||adding in an ACL
22854 .index header lines||position of added lines
22855 .index \warn\, ACL verb
22856 .index \message\, ACL modifier
22857 The \message\ modifier can be used on a \warn\ statement to add an extra header
22858 line to an incoming message, as in this example:
22860 warn message = X-blacklisted-at: $dnslist_domain
22861 dnslists = sbl.spamhaus.org : \
22862 dialup.mail-abuse.org
22864 If an identical header line is requested several times (provoked, for example,
22865 by multiple \\RCPT\\ commands), only one copy is actually added to the message.
22866 If the text of the \message\ modifier contains one or more newlines that are
22867 not followed by a space or a tab, it is assumed to contain multiple header
22868 lines. Each one is checked for valid syntax; \"X-ACL-Warn:"\ is added to the
22869 front of any line that is not a valid header line.
22871 By default, new lines are added at the end of the existing header lines.
22872 However, you can specify that any particular header line should be added right
22873 at the start (before all the ::Received:: lines), immediately after the first
22874 block of ::Received:: lines, or immediately before any line that is not a
22875 ::Received:: or ::Resent-something:: header.
22877 This is done by specifying `:at@_start:', `:after@_received:', or
22878 `:at@_start@_rfc:' (or, for completeness, `:at@_end:') before the text of the
22879 header line, respectively. (Header text cannot start with a colon, as there has
22880 to be a header name first.) For example:
22882 warn message = :after_received:X-My-Header: something or other...
22885 If more than one header is supplied in a single warn statement, each one is
22886 treated independently and can therefore be placed differently. If you add
22887 more than one line at the start, or after the Received: block, they will
22888 end up in reverse order.
22890 \**Warning**\: This facility currently applies only to header lines that are
22891 added in an ACL. It does NOT work for header lines that are added in a
22892 system filter or in a router or transport.
22894 .index header lines||added, visibility of
22895 Header lines that are added by an ACL at \\MAIL\\ or \\RCPT\\ time are not
22896 visible in string expansions in ACLs for subsequent \\RCPT\\ commands or in the
22897 \acl@_smtp@_predata\ ACL. However, they are visible in string expansions in the
22898 ACL that is run after \\DATA\\ is complete (the \acl@_smtp@_data\ ACL). This is
22899 also true for header lines that are added in the \acl@_smtp@_predata\ ACL.
22900 If a message is rejected after \\DATA\\, all added header lines are included in
22901 the entry that is written to the reject log.
22903 If you want to preserve data between \\MAIL\\, \\RCPT\\, and the
22904 \acl@_smtp@_predata\ ACLs, you can use ACL variables, as described in section
22905 ~~SECTaclvariables.
22910 .section ACL conditions
22911 .rset SECTaclconditions "~~chapter.~~section"
22912 .index ~~ACL||conditions, list of
22914 Some of conditions listed in this section are available only when Exim is
22915 compiled with the content-scanning extension. They are included here briefly
22916 for completeness. More detailed descriptions can be found in the discussion on
22917 content scanning in chapter ~~CHAPexiscan.
22920 Not all conditions are relevant in all circumstances. For example, testing
22921 senders and recipients does not make sense in an ACL that is being run as the
22922 result of the arrival of an \\ETRN\\ command, and checks on message headers can
22923 be done only in the ACLs specified by \acl@_smtp@_data\ and \acl__not__smtp\.
22924 You can use the same condition (with different parameters) more than once in
22925 the same ACL statement. This provides a way of specifying an `and' conjunction.
22926 The conditions are as follows:
22930 .item "acl = <<name of acl or ACL string or file name >>"
22931 .index ~~ACL||nested
22932 .index ~~ACL||indirect
22933 .index \acl\, ACL condition
22934 The possible values of the argument are the same as for the
22935 \acl@_smtp@_$it{xxx}\ options. The named or inline ACL is run. If it returns
22936 `accept' the condition is true; if it returns `deny' the condition is false. If
22937 it returns `defer', the current ACL returns `defer'
22939 unless the condition is on a \warn\ verb. In that case, a `defer' return makes
22940 the condition false. This means that further processing of the \warn\ verb
22941 ceases, but processing of the ACL continues.
22944 If the nested \acl\ returns `drop' and the outer condition denies access,
22945 the connection is dropped. If it returns `discard', the verb must be \accept\
22946 or \discard\, and the action is taken immediately -- no further conditions are
22949 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
22950 loops. This condition allows you to use different ACLs in different
22951 circumstances. For example, different ACLs can be used to handle \\RCPT\\
22952 commands for different local users or different local domains.
22954 .item "authenticated = <<string list>>"
22955 .index \authenticated\, ACL condition
22956 .index authentication||ACL checking
22957 .index ~~ACL||testing for authentication
22958 If the SMTP connection is not authenticated, the condition is false. Otherwise,
22959 the name of the authenticator is tested against the list. To test for
22960 authentication by any authenticator, you can set
22965 .item "condition = <<string>>"
22966 .index \condition\, ACL condition
22967 .index customizing||ACL condition
22968 .index ~~ACL||customized test
22969 .index ~~ACL||testing, customized
22970 This feature allows you to make up custom conditions. If the result of
22971 expanding the string is an empty string, the number zero, or one of the strings
22972 `no' or `false', the condition is false. If the result is any non-zero number,
22973 or one of the strings `yes' or `true', the condition is true. For any other
22974 values, some error is assumed to have occured, and the ACL returns `defer'.
22978 .item "decode = <<location>>"
22979 .index \decode\, ACL condition
22980 This condition is available only when Exim is compiled with the
22981 content-scanning extension, and it is allowed only the the ACL defined by
22982 \acl@_smtp@_mime\. It causes the current MIME part to be decoded into a file.
22983 For details, see chapter ~~CHAPexiscan.
22987 .item "dnslists = <<list of domain names and other data>>"
22988 .index \dnslists\, ACL condition
22989 .index DNS list||in ACL
22990 .index black list (DNS)
22991 .index ~~ACL||testing a DNS list
22992 This condition checks for entries in DNS black lists. These are also known as
22993 `RBL lists', after the original Realtime Blackhole List, but note that the use
22994 of the lists at \*mail-abuse.org*\ now carries a charge.
22995 There are too many different variants of this condition to describe briefly
22996 here. See sections ~~SECTmorednslists--~~SECTmorednslistslast for details.
22998 .item "domains = <<domain list>>"
22999 .index \domains\, ACL condition
23000 .index domain||ACL checking
23001 .index ~~ACL||testing a recipient domain
23002 This condition is relevant only after a \\RCPT\\ command. It checks that the
23003 domain of the recipient address is in the domain list. If percent-hack
23004 processing is enabled, it is done before this test is done. If the check
23005 succeeds with a lookup, the result of the lookup is placed in \$domain@_data$\
23006 until the next \domains\ test.
23008 .item "encrypted = <<string list>>"
23009 .index \encrypted\, ACL condition
23010 .index encryption||checking in an ACL
23011 .index ~~ACL||testing for encryption
23012 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
23013 name of the cipher suite in use is tested against the list. To test for
23014 encryption without testing for any specific cipher suite(s), set
23019 .item "hosts = << host list>>"
23020 .index \hosts\, ACL condition
23021 .index host||ACL checking
23022 .index ~~ACL||testing the client host
23023 This condition tests that the calling host matches the host list. If you have
23024 name lookups or wildcarded host names and IP addresses in the same host list,
23025 you should normally put the IP addresses first. For example, you could have:
23027 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
23029 The reason for this lies in the left-to-right way that Exim processes lists.
23030 It can test IP addresses without doing any DNS lookups, but when it reaches an
23031 item that requires a host name, it fails if it cannot find a host name to
23032 compare with the pattern. If the above list is given in the opposite order, the
23033 \accept\ statement fails for a host whose name cannot be found, even if its
23034 IP address is 10.9.8.7.
23036 If you really do want to do the name check first, and still recognize the IP
23037 address even if the name lookup fails, you can rewrite the ACL like this:
23039 accept hosts = dbm;/etc/friendly/hosts
23040 accept hosts = 10.9.8.7
23042 The default action on failing to find the host name is to assume that the host
23043 is not in the list, so the first \accept\ statement fails. The second statement
23044 can then check the IP address.
23046 If a \hosts\ condition is satisfied by means of a lookup, the result
23047 of the lookup is made available in the \$host@_data$\ variable. This
23048 allows you, for example, to set up a statement like this:
23050 deny hosts = net-lsearch;/some/file
23051 message = $host_data
23053 which gives a custom error message for each denied host.
23055 .item "local@_parts = <<local part list>>"
23056 .index \local@_parts\, ACL condition
23057 .index local part||ACL checking
23058 .index ~~ACL||testing a local part
23059 This condition is relevant only after a \\RCPT\\ command. It checks that the
23060 local part of the recipient address is in the list. If percent-hack processing
23061 is enabled, it is done before this test. If the check succeeds with a lookup,
23062 the result of the lookup is placed in \$local@_part@_data$\ until the next
23063 \local@_parts\ test.
23067 .item "malware = <<option>>"
23068 .index \malware\, ACL condition
23069 .index ~~ACL||virus scanning
23070 .index ~~ACL||scanning for viruses
23071 This condition is available only when Exim is compiled with the
23072 content-scanning extension. It causes the incoming message to be scanned for
23073 viruses. For details, see chapter ~~CHAPexiscan.
23078 .item "mime@_regex = <<list of regular expressions>>"
23079 .index \mime@_regex\, ACL condition
23080 .index ~~ACL||testing by regex matching
23081 This condition is available only when Exim is compiled with the
23082 content-scanning extension, and it is allowed only the the ACL defined by
23083 \acl@_smtp@_mime\. It causes the current MIME part to be scanned for a match
23084 with any of the regular expressions. For details, see chapter ~~CHAPexiscan.
23088 .item "recipients = <<address list>>"
23089 .index \recipients\, ACL condition
23090 .index recipient||ACL checking
23091 .index ~~ACL||testing a recipient
23092 This condition is relevant only after a \\RCPT\\ command. It checks the entire
23093 recipient address against a list of recipients.
23097 .item "regex = <<list of regular expressions>>"
23098 .index \regex\, ACL condition
23099 .index ~~ACL||testing by regex matching
23100 This condition is available only when Exim is compiled with the
23101 content-scanning extension. It causes the incoming message to be scanned
23102 for a match with any of the regular expressions. For details, see chapter
23107 .item "sender@_domains = <<domain list>>"
23108 .index \sender@_domains\, ACL condition
23109 .index sender||ACL checking
23110 .index ~~ACL||testing a sender domain
23111 This condition tests the domain of the sender of the message against the given
23113 \**Note**\: the domain of the sender address is in
23114 \$sender@_address@_domain$\. It is \*not*\ put in \$domain$\ during the testing
23115 of this condition. This is an exception to the general rule for testing
23116 domain lists. It is done this way so that, if this condition is used in an
23117 ACL for a \\RCPT\\ command, the recipient's domain (which is in \$domain$\) can
23118 be used to influence the sender checking.
23120 .item "senders = <<address list>>"
23121 .index \senders\, ACL condition
23122 .index sender||ACL checking
23123 .index ~~ACL||testing a sender
23124 This condition tests the sender of the message against the given list. To test
23125 for a bounce message, which has an empty sender, set
23132 .item "spam = <<username>>"
23133 .index \spam\, ACL condition
23134 .index ~~ACL||scanning for spam
23135 This condition is available only when Exim is compiled with the
23136 content-scanning extension. It causes the incoming message to be scanned by
23137 SpamAssassin. For details, see chapter ~~CHAPexiscan.
23141 .item "verify = certificate"
23142 .index \verify\, ACL condition
23143 .index TLS||client certificate verification
23144 .index certificate||verification of client
23145 .index ~~ACL||certificate verification
23146 .index ~~ACL||testing a TLS certificate
23147 This condition is true in an SMTP session if the session is encrypted, and a
23148 certificate was received from the client, and the certificate was verified. The
23149 server requests a certificate only if the client matches \tls@_verify@_hosts\
23150 or \tls@_try@_verify@_hosts\ (see chapter ~~CHAPTLS).
23152 .item "verify = header@_sender/<<options>>"
23153 .index \verify\, ACL condition
23154 .index ~~ACL||verifying sender in the header
23155 .index header lines||verifying the sender in
23156 .index sender||verifying in header
23157 .index verifying||sender in header
23158 This condition is relevant only in an ACL that is run after a message has been
23159 received, that is, in an ACL specified by \acl@_smtp@_data\
23161 or \acl@_not@_smtp\. It checks that there is a verifiable address in at least
23162 one of the ::Sender::, ::Reply-To::, or ::From:: header lines. Such an address
23163 is loosely thought of as a `sender' address (hence the name of the test).
23164 However, an address that appears in one of these headers need not be an address
23165 that accepts bounce messages; only sender addresses in envelopes are required
23166 to accept bounces. Therefore, if you use the callout option on this check, you
23167 might want to arrange for a non-empty address in the \\MAIL\\ command.
23170 Details of address verification and the options are given later, starting at
23171 section ~~SECTaddressverification (callouts are described in section
23172 ~~SECTcallver). You can combine this condition with the \senders\ condition to
23173 restrict it to bounce messages only:
23176 message = A valid sender header is required for bounces
23177 !verify = header_sender
23180 .item "verify = header@_syntax"
23181 .index \verify\, ACL condition
23182 .index ~~ACL||verifying header syntax
23183 .index header lines||verifying syntax
23184 .index verifying||header syntax
23185 This condition is relevant only in an ACL that is run after a message has been
23186 received, that is, in an ACL specified by \acl@_smtp@_data\
23187 or \acl@_not@_smtp\.
23188 It checks the syntax of all header lines that can contain lists of addresses
23189 (::Sender::, ::From::, ::Reply-To::, ::To::, ::Cc::, and ::Bcc::).
23190 Unqualified addresses (local parts without domains) are permitted only in
23191 locally generated messages and from hosts that match
23192 \sender@_unqualified@_hosts\ or \recipient@_unqualified@_hosts\, as
23195 Note that this condition is a syntax check only. However, a common spamming
23196 ploy is to send syntactically invalid headers such as
23200 and this condition can be used to reject such messages.
23202 .item "verify = helo"
23203 .index \verify\, ACL condition
23204 .index ~~ACL||verifying HELO/EHLO
23205 .index \\HELO\\||verifying
23206 .index \\EHLO\\||verifying
23207 .index verifying||\\EHLO\\
23208 .index verifying||\\HELO\\
23209 This condition is true if a \\HELO\\ or \\EHLO\\ command has been received from
23210 the client host, and its contents have been verified. Verification of these
23211 commands does not happen by default. See the description of the
23212 \helo@_verify@_hosts\ and \helo@_try@_verify@_hosts\ options for details of how
23215 .item "verify = recipient/<<options>>"
23216 .index \verify\, ACL condition
23217 .index ~~ACL||verifying recipient
23218 .index recipient||verifying
23219 .index verifying||recipient
23220 This condition is relevant only after a \\RCPT\\ command. It verifies the
23221 current recipient. Details of address verification are given later, starting at
23222 section ~~SECTaddressverification. After a recipient has been verified, the
23223 value of \$address@_data$\ is the last value that was set while routing the
23224 address. This applies even if the verification fails. When an address that is
23225 being verified is redirected to a single address, verification continues with
23226 the new address, and in that case, the subsequent value of \$address@_data$\ is
23227 the value for the child address.
23230 .item "verify = reverse@_host@_lookup"
23231 .index \verify\, ACL condition
23232 .index ~~ACL||verifying host reverse lookup
23233 .index host||verifying reverse lookup
23234 This condition ensures that a verified host name has been looked up from the IP
23235 address of the client host. (This may have happened already if the host name
23236 was needed for checking a host list, or if the host matched \host@_lookup\.)
23237 Verification ensures that the host name obtained from a reverse DNS lookup, or
23238 one of its aliases, does, when it is itself looked up in the DNS, yield the
23239 original IP address.
23241 If this condition is used for a locally generated message (that is, when there
23242 is no client host involved), it always succeeds.
23245 .item "verify = sender/<<options>>"
23246 .index \verify\, ACL condition
23247 .index ~~ACL||verifying sender
23248 .index sender||verifying
23249 .index verifying||sender
23250 This condition is relevant only after a \\MAIL\\ or \\RCPT\\ command, or after
23251 a message has been received (the \acl@_smtp@_data\ or \acl@_not@_smtp\ ACLs).
23252 If the message's sender is empty (that is, this is a bounce message), the
23253 condition is true. Otherwise, the sender address is verified.
23255 If there is data in the \$address@_data$\ variable at the end of routing, its
23256 value is placed in \$sender__address__data$\ at the end of verification. This
23257 value can be used in subsequent conditions and modifiers in the same ACL
23258 statement. It does not persist after the end of the current statement. If you
23259 want to preserve the value for longer, you can save it in an ACL variable.
23261 Details of verification are given later, starting at section
23262 ~~SECTaddressverification. Exim caches the result of sender verification, to
23263 avoid doing it more than once per message.
23265 .item "verify = sender=<<address>>/<<options>>"
23266 .index \verify\, ACL condition
23267 This is a variation of the previous option, in which a modified address is
23268 verified as a sender.
23274 .section Using DNS lists
23275 .rset SECTmorednslists "~~chapter.~~section"
23276 .index DNS list||in ACL
23277 .index black list (DNS)
23278 .index ~~ACL||testing a DNS list
23279 In its simplest form, the \dnslists\ condition tests whether the calling host
23280 is on at least one of a number of DNS lists by looking up the inverted IP
23281 address in one or more DNS domains. For example, if the calling host's IP
23282 address is 192.168.62.43, and the ACL statement is
23284 deny dnslists = blackholes.mail-abuse.org : \
23285 dialups.mail-abuse.org
23287 the following records are looked up:
23289 43.62.168.192.blackholes.mail-abuse.org
23290 43.62.168.192.dialups.mail-abuse.org
23293 As soon as Exim finds an existing DNS record, processing of the list stops.
23294 Thus, multiple entries on the list provide an `or' conjunction. If you want to
23295 test that a host is on more than one list (an `and' conjunction), you can use
23296 two separate conditions:
23298 deny dnslists = blackholes.mail-abuse.org
23299 dnslists = dialups.mail-abuse.org
23302 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
23303 behaves as if the host
23305 does not match the list item, that is, as if the DNS record does not exist. If
23306 there are further items in the DNS list, they are processed.
23308 This is usually the required action when \dnslists\ is used with \deny\ (which
23309 is the most common usage), because it prevents a DNS failure from blocking
23310 mail. However, you can change this behaviour by putting one of the following
23311 special items in the list:
23312 .index \"+include@_unknown"\
23313 .index \"+exclude@_unknown"\
23314 .index \"+defer@_unknown"\
23316 +include@_unknown $rm{behave as if the item is on the list}
23317 +exclude@_unknown $rm{behave as if the item is not on the list (default)}
23318 +defer@_unknown $rm{give a temporary error}
23320 Each of these applies to any subsequent items on the list. For example:
23322 deny dnslists = +defer_unknown : foo.bar.example
23325 Testing the list of domains stops as soon as a match is found. If you want to
23326 warn for one list and block for another, you can use two different statements:
23328 deny dnslists = blackholes.mail-abuse.org
23329 warn message = X-Warn: sending host is on dialups list
23330 dnslists = dialups.mail-abuse.org
23333 DNS list lookups are cached by Exim for the duration of the SMTP session,
23334 so a lookup based on the IP address is done at most once for any incoming
23335 connection. Exim does not share information between multiple incoming
23336 connections (but your local name server cache should be active).
23340 .section Specifying the IP address for a DNS list lookup
23341 .index DNS list||keyed by explicit IP address
23342 By default, the IP address that is used in a DNS list lookup is the IP address
23343 of the calling host. However, you can specify another IP address by listing it
23344 after the domain name, introduced by a slash. For example:
23346 deny dnslists = black.list.tls/192.168.1.2
23348 This feature is not very helpful with explicit IP addresses; it is intended for
23349 use with IP addresses that are looked up, for example, the IP addresses of the
23350 MX hosts or nameservers of an email sender address. For an example, see section
23351 ~~SECTmulkeyfor below.
23355 .section DNS lists keyed on domain names
23356 .index DNS list||keyed by domain name
23357 There are some lists that are keyed on domain names rather than inverted IP
23358 addresses (see for example the \*domain based zones*\ link at
23359 \?http://www.rfc-ignorant.org/?\). No reversing of components is used with
23360 these lists. You can change the name that is looked up in a DNS list by listing
23361 it after the domain name, introduced by a slash. For example,
23363 deny message = Sender's domain is listed at $dnslist_domain
23364 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
23366 This particular example is useful only in ACLs that are obeyed after the
23367 \\RCPT\\ or \\DATA\\ commands, when a sender address is available. If (for
23368 example) the message's sender is \*user@@tld.example*\ the name that is looked
23369 up by this example is
23371 tld.example.dsn.rfc-ignorant.org
23374 A single \dnslists\ condition can contain entries for both names and IP
23375 addresses. For example:
23377 deny dnslists = sbl.spamhaus.org : \
23378 dsn.rfc-ignorant.org/$sender_address_domain
23380 The first item checks the sending host's IP address; the second checks a domain
23381 name. The whole condition is true if either of the DNS lookups succeeds.
23386 .section Multiple explicit keys for a DNS list
23387 .rset SECTmulkeyfor "~~chapter.~~section"
23388 .index DNS list||multiple keys for
23389 The syntax described above for looking up explicitly-defined values (either
23390 names or IP addresses) in a DNS blacklist is a simplification. After the domain
23391 name for the DNS list, what follows the slash can in fact be a list of items.
23392 As with all lists in Exim, the default separator is a colon. However, because
23393 this is a sublist within the list of DNS blacklist domains, it is necessary
23394 either to double the separators like this:
23396 dnslists = black.list.tld/name.1::name.2
23398 or to change the separator character, like this:
23400 dnslists = black.list.tld/<;name.1;name.2
23402 If an item in the list is an IP address, it is inverted before the DNS
23403 blacklist domain is appended. If it is not an IP address, no inversion
23404 occurs. Consider this condition:
23406 dnslists = black.list.tld/<;192.168.1.2;a.domain
23408 The DNS lookups that occur are:
23410 2.1.168.192.black.list.tld
23411 a.domain.black.list.tld
23413 Once a DNS record has been found (that matches a specific IP return
23414 address, if specified -- see section ~~SECTaddmatcon), no further lookups are
23415 done. If there is a temporary DNS error, the rest of the sublist of domains or
23416 IP addresses is tried. A temporary error for the whole dnslists item occurs
23417 only if no other DNS lookup in this sublist succeeds. In other words, a
23418 successful lookup for any of the items in the sublist overrides a temporary
23419 error for a previous item.
23421 The ability to supply a list of items after the slash is in some sense just a
23422 syntactic convenience. These two examples have the same effect:
23424 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
23425 dnslists = black.list.tld/a.domain::b.domain
23427 However, when the data for the list is obtained from a lookup, the second form
23428 is usually much more convenient. Consider this example:
23430 deny message = The mail servers for the domain \
23431 $sender_address_domain \
23432 are listed at $dnslist_domain ($dnslist_value); \
23434 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
23435 ${lookup dnsdb {>|mxh=\
23436 $sender_address_domain} }} }
23438 Note the use of \">|"\ in the dnsdb lookup to specify the separator for
23439 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
23440 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
23441 of expanding the condition might be something like this:
23443 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
23445 Thus, this example checks whether or not the IP addresses of the sender
23446 domain's mail servers are on the Spamhaus black list.
23451 .section Data returned by DNS lists
23452 .index DNS list||data returned from
23453 DNS lists are constructed using address records in the DNS. The original RBL
23454 just used the address 127.0.0.1 on the right hand side of each record, but the
23455 RBL+ list and some other lists use a number of values with different meanings.
23456 The values used on the RBL+ list are:
23461 127.1.0.3 $t DUL and RBL
23463 127.1.0.5 $t RSS and RBL
23464 127.1.0.6 $t RSS and DUL
23465 127.1.0.7 $t RSS and DUL and RBL
23467 Some DNS lists may return more than one address record.
23469 .section Variables set from DNS lists
23470 .index DNS list||variables set from
23471 When an entry is found in a DNS list, the variable \$dnslist@_domain$\
23472 contains the name of the domain that matched, \$dnslist@_value$\ contains the
23473 data from the entry, and \$dnslist@_text$\ contains the contents of any
23474 associated TXT record. If more than one address record is returned by the DNS
23475 lookup, all the IP addresses are included in \$dnslist@_value$\, separated by
23478 You can use these variables in \message\ or \log@_message\ modifiers --
23479 although these appear before the condition in the ACL, they are not expanded
23480 until after it has failed. For example:
23482 deny hosts = !+local_networks
23483 message = $sender_host_address is listed \
23485 dnslists = rbl-plus.mail-abuse.example
23489 .section Additional matching conditions for DNS lists
23490 .rset SECTaddmatcon "~~chapter.~~section"
23491 .index DNS list||matching specific returned data
23492 You can add an equals sign and an IP address after a \dnslists\ domain name in
23493 order to restrict its action to DNS records with a matching right hand side.
23496 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
23498 rejects only those hosts that yield 127.0.0.2. Without this additional data,
23499 any address record is considered to be a match. If more than one address record
23500 is found on the list, they are all checked for a matching right-hand side.
23502 More than one IP address may be given for checking, using a comma as a
23503 separator. These are alternatives -- if any one of them matches, the \dnslists\
23504 condition is true. For example:
23506 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
23509 If you want to specify a constraining address list and also specify names or IP
23510 addresses to be looked up, the constraining address list must be specified
23511 first. For example:
23513 deny dnslists = dsn.rfc-ignorant.org\
23514 =127.0.0.2/$sender_address_domain
23517 If the character `&' is used instead of `=', the comparison for each listed
23518 IP address is done by a bitwise `and' instead of by an equality test. In
23519 other words, the listed addresses are used as bit masks. The comparison is
23520 true if all the bits in the mask are present in the address that is being
23521 tested. For example:
23523 dnslists = a.b.c&0.0.0.3
23525 matches if the address is \*x.x.x.*\3, \*x.x.x.*\7, \*x.x.x.*\11, etc. If you
23526 want to test whether one bit or another bit is present (as opposed to both
23527 being present), you must use multiple values. For example:
23529 dnslists = a.b.c&0.0.0.1,0.0.0.2
23531 matches if the final component of the address is an odd number or two times
23535 .section Negated DNS matching conditions
23536 You can supply a negative list of IP addresses as part of a \dnslists\
23539 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
23541 means `deny if the host is in the black list at the domain \*a.b.c*\ and the IP
23542 address yielded by the list is either 127.0.0.2 or 127.0.0.3',
23544 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
23546 means `deny if the host is in the black list at the domain \*a.b.c*\ and the IP
23547 address yielded by the list is not 127.0.0.2 and not 127.0.0.3'. In other
23548 words, the result of the test is inverted if an exclamation mark appears before
23549 the `=' (or the `&') sign.
23551 \**Note**\: this kind of negation is not the same as negation in a domain,
23552 host, or address list (which is why the syntax is different).
23554 If you are using just one list, the negation syntax does not gain you much. The
23555 previous example is precisely equivalent to
23557 deny dnslists = a.b.c
23558 !dnslists = a.b.c=127.0.0.2,127.0.0.3
23560 However, if you are using multiple lists, the negation syntax is clearer.
23561 Consider this example:
23563 deny dnslists = sbl.spamhaus.org : \
23565 dnsbl.njabl.org!=127.0.0.3 : \
23568 Using only positive lists, this would have to be:
23570 deny dnslists = sbl.spamhaus.org : \
23572 deny dnslists = dnsbl.njabl.org
23573 !dnslists = dnsbl.njabl.org=127.0.0.3
23574 deny dnslists = relays.ordb.org
23576 which is less clear, and harder to maintain.
23580 .section DNS lists and IPv6
23581 .rset SECTmorednslistslast "~~chapter.~~section"
23582 .index IPv6||DNS black lists
23583 .index DNS list||IPv6 usage
23584 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
23585 nibble by nibble. For example, if the calling host's IP address is
23586 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
23588 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
23589 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
23591 (split over two lines here to fit on the page). Unfortunately, some of the DNS
23592 lists contain wildcard records, intended for IPv4, that interact badly with
23593 IPv6. For example, the DNS entry
23595 *.3.some.list.example. A 127.0.0.1
23597 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
23598 Unfortunately, it also matches the entire 3@:@:/4 IPv6 network.
23600 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
23601 \condition\ condition, as in this example:
23605 deny condition = ${if isip4{$sender_host_address}}
23608 dnslists = some.list.example
23612 .section Address verification
23613 .rset SECTaddressverification "~~chapter.~~section"
23614 .index verifying||address, options for
23615 .index policy control||address verification
23616 Several of the \verify\ conditions described in section ~~SECTaclconditions
23617 cause addresses to be verified. These conditions can be followed by options
23618 that modify the verification process. The options are separated from the
23619 keyword and from each other by slashes, and some of them contain parameters.
23622 verify = sender/callout
23623 verify = recipient/defer_ok/callout=10s,defer_ok
23626 The first stage of address verification, which always happens, is to run the
23627 address through the routers, in `verify mode'. Routers can detect the
23628 difference between verification and routing for delivery, and their actions can
23629 be varied by a number of generic options such as \verify\ and \verify@_only\
23630 (see chapter ~~CHAProutergeneric). If routing fails, verification fails.
23631 The available options are as follows:
23633 If the \callout\ option is specified, successful routing to one or more remote
23634 hosts is followed by a `callout' to those hosts as an additional check.
23635 Callouts and their sub-options are discussed in the next section.
23637 If there is a defer error while doing verification routing, the ACL
23638 normally returns `defer'. However, if you include \defer@_ok\ in the options,
23639 the condition is forced to be true instead. Note that this is a main
23640 verification option as well as a suboption for callouts.
23642 The \no@_details\ option is covered in section ~~SECTsenaddver, which discusses
23643 the reporting of sender address verification failures.
23646 .index verifying||address, differentiating failures
23647 After an address verification failure, \$sender@_verify@_failure$\ or
23648 \$recipient@_verify@_failure$\ (as appropriate) contains one of the following
23651 \qualify\: The address was unqualified (no domain), and the message
23652 was neither local nor came from an exempted host.
23654 \route\: Routing failed.
23656 \mail\: Routing succeeded, and a callout was attempted; rejection
23657 occurred at or before the \\MAIL\\ command (that is, on initial
23658 connection, \\HELO\\, or \\MAIL\\).
23660 \recipient\: The \\RCPT\\ command in a callout was rejected.
23662 \postmaster\: The postmaster check in a callout was rejected.
23665 The main use of these variables is expected to be to distinguish between
23666 rejections of \\MAIL\\ and rejections of \\RCPT\\ in callouts.
23671 .section Callout verification
23672 .rset SECTcallver "~~chapter.~~section"
23673 .index verifying||address, by callout
23674 .index callout||verification
23675 .index SMTP||callout verification
23676 For non-local addresses, routing verifies the domain, but is unable to do any
23677 checking of the local part. There are situations where some means of verifying
23678 the local part is desirable. One way this can be done is to make an SMTP
23679 \*callback*\ to the sending host (for a sender address) or a \*callforward*\ to
23680 a subsequent host (for a recipient address), to see if the host accepts the
23681 address. We use the term \*callout*\ to cover both cases. This facility should
23682 be used with care, because it can add a lot of resource usage to the cost of
23683 verifying an address. However, Exim does cache the results of callouts, which
23684 helps to reduce the cost. Details of caching are in the next section.
23686 Recipient callouts are usually used only between hosts that are controlled by
23687 the same administration. For example, a corporate gateway host could use
23688 callouts to check for valid recipients on an internal mailserver.
23689 A successful callout does not guarantee that a real delivery to the address
23690 would succeed; on the other hand, a failing callout does guarantee that
23691 a delivery would fail.
23693 If the \callout\ option is present on a condition that verifies an address, a
23694 second stage of verification occurs if the address is successfully routed to
23695 one or more remote hosts. The usual case is routing by a \%dnslookup%\ or a
23696 \%manualroute%\ router, where the router specifies the hosts. However, if a
23697 router that does not set up hosts routes to an \%smtp%\ transport with a
23698 \hosts\ setting, the transport's hosts are used. If an \%smtp%\ transport has
23699 \hosts@_override\ set, its hosts are always used, whether or not the router
23700 supplies a host list.
23702 The port that is used is taken from the transport, if it is specified and is a
23703 remote transport. (For routers that do verification only, no transport need be
23704 specified.) Otherwise, the default SMTP port is used. If a remote transport
23705 specifies an outgoing interface, this is used; otherwise the interface is not
23708 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
23709 test whether a bounce message could be delivered to the sender address. The
23710 following SMTP commands are sent:
23714 HELO <<smtp active host name>>
23718 RCPT TO:<<the address to be tested>>
23721 \\LHLO\\ is used instead of \\HELO\\ if the transport's \protocol\ option is
23724 A recipient callout check is similar. By default, it also uses an empty address
23725 for the sender. This default is chosen because most hosts do not make use of
23726 the sender address when verifying a recipient. Using the same address means
23727 that a single cache entry can be used for each recipient. Some sites, however,
23728 do make use of the sender address when verifying. These are catered for by the
23729 \use@_sender\ and \use@_postmaster\ options, described in the next section.
23731 If the response to the \\RCPT\\ command is a 2$it{xx} code, the verification
23732 succeeds. If it is 5$it{xx}, the verification fails. For any other condition,
23733 Exim tries the next host, if any. If there is a problem with all the remote
23734 hosts, the ACL yields `defer', unless the \defer@_ok\ parameter of the
23735 \callout\ option is given, in which case the condition is forced to succeed.
23740 .section Additional parameters for callouts
23741 .rset CALLaddparcall "~~chapter.~~section"
23742 .index callout||additional parameters for
23743 The \callout\ option can be followed by an equals sign and a number of optional
23744 parameters, separated by commas. For example:
23746 verify = recipient/callout=10s,defer_ok
23748 The old syntax, which had \callout@_defer@_ok\ and \check@_postmaster\ as
23749 separate verify options, is retained for backwards compatibility, but is now
23750 deprecated. The additional parameters for \callout\ are as follows:
23754 .item "<<a time interval>>"
23755 .index callout||timeout, specifying
23756 This specifies the timeout that applies for the callout attempt to each host.
23759 verify = sender/callout=5s
23761 The default is 30 seconds. The timeout is used for each response from the
23764 It is also used for the intial connection, unless overridden by the \connect\
23769 .item "connect = <<time interval>>"
23770 .index callout||connection timeout, specifying
23771 This parameter makes it possible to set a different (usually
23772 smaller) timeout for making the SMTP connection.
23775 verify = sender/callout=5s,connect=1s
23777 If not specified, this timeout defaults to the general timeout value.
23781 .index callout||defer, action on
23782 When this parameter is present, failure to contact any host, or any other kind
23783 of temporary error, is treated as success by the ACL. However, the cache is not
23784 updated in this circumstance.
23787 .item "mailfrom = <<email address>>"
23788 .index callout||sender when verifying header
23789 When verifying addresses in header lines using the \header@_sender\
23790 verification option, Exim behaves by default as if the addresses are envelope
23791 sender addresses from a message. Callout verification therefore tests to see
23792 whether a bounce message could be delivered, by using an empty address in the
23793 \\MAIL\\ command. However, it is arguable that these addresses might never be
23794 used as envelope senders, and could therefore justifiably reject bounce
23795 messages (empty senders). The \mailfrom\ callout parameter allows you to
23796 specify what address to use in the \\MAIL\\ command. For example:
23798 require verify = header_sender/callout=mailfrom=abcd@x.y.z
23800 This parameter is available only for the \header@_sender\ verification option.
23804 .item "maxwait = <<time interval>>"
23805 .index callout||overall timeout, specifying
23806 This parameter sets an overall timeout for performing a callout verification.
23809 verify = sender/callout=5s,maxwait=30s
23811 This timeout defaults to four times the callout timeout for individual SMTP
23812 commands. The overall timeout applies when there is more than one host that can
23813 be tried. The timeout is checked before trying the next host. This prevents
23814 very long delays if there are a large number of hosts and all are timing out
23815 (for example, when network connections are timing out).
23819 .index callout||cache, suppressing
23820 .index caching||callout, suppressing
23821 When this parameter is given, the callout cache is neither read nor updated.
23824 .index callout||postmaster, checking
23825 When this parameter is set, a sucessful callout check is followed by a similar
23826 check for the local part \*postmaster*\ at the same domain. If this address is
23827 rejected, the callout fails. The result of the postmaster check is recorded in
23828 a cache record; if it is a failure, this is used to fail subsequent callouts
23829 for the domain without a connection being made, until the cache record expires.
23832 .item "postmaster@_mailfrom = <<email address>>"
23833 The postmaster check uses an empty sender in the \\MAIL\\ command by default.
23834 You can use this parameter to do a postmaster check using a different address.
23837 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
23839 If both \postmaster\ and \postmaster@_mailfrom\ are present, the rightmost one
23840 overrides. The \postmaster\ parameter is equivalent to this example:
23842 require verify = sender/callout=postmaster_mailfrom=
23844 \**Warning**\: The caching arrangements for postmaster checking do not take
23845 account of the sender address. It is assumed that either the empty address or
23846 a fixed non-empty address will be used. All that Exim remembers is that the
23847 postmaster check for the domain succeeded or failed.
23851 .index callout||`random' check
23852 When this parameter is set, before doing the normal callout check, Exim does a
23853 check for a `random' local part at the same domain. The local part is not
23854 really random -- it is defined by the expansion of the option
23855 \callout@_random@_local@_part\, which defaults to
23857 $primary_host_name-$tod_epoch-testing
23859 The idea here is to try to determine whether the remote host accepts all local
23860 parts without checking. If it does, there is no point in doing callouts for
23861 specific local parts. If the `random' check succeeds, the result is saved in
23862 a cache record, and used to force the current and subsequent callout checks to
23863 succeed without a connection being made, until the cache record expires.
23865 .item "use@_postmaster"
23866 .index callout||sender for recipient check
23867 This parameter applies to recipient callouts only. For example:
23869 deny !verify = recipient/callout=use_postmaster
23871 It causes a non-empty postmaster address to be used in the \\MAIL\\ command
23872 when performing the callout. The local part of the address is \"postmaster"\
23873 and the domain is the contents of \$qualify@_domain$\.
23875 .item "use@_sender"
23876 This option applies to recipient callouts only. For example:
23878 require verify = recipient/callout=use_sender
23880 It causes the message's actual sender address to be used in the \\MAIL\\
23881 command when performing the callout, instead of an empty address. There is no
23882 need to use this option unless you know that the called hosts make use of the
23883 sender when checking recipients. If used indiscriminately, it reduces the
23884 usefulness of callout caching.
23889 If you use any of the parameters that set a non-empty sender for the \\MAIL\\
23890 command (\mailfrom\, \postmaster@_mailfrom\, \use@_postmaster\, or
23891 \use@_sender\), you should think about possible loops. Recipient checking is
23892 usually done between two hosts that are under the same management, and the host
23893 that receives the callouts is not normally configured to do callouts itself.
23894 Therefore, it is normally safe to use \use@_postmaster\ or \use@_sender\ in
23895 these circumstances.
23897 However, if you use a non-empty sender address for a callout to an arbitrary
23898 host, there is the likelihood that the remote host will itself initiate a
23899 callout check back to your host. As it is checking what appears to be a message
23900 sender, it is likely to use an empty address in \\MAIL\\, thus avoiding a
23901 callout loop. However, to be on the safe side it would be best to set up your
23902 own ACLs so that they do not do sender verification checks when the recipient
23903 is the address you use for header sender or postmaster callout checking.
23905 Another issue to think about when using non-empty senders for callouts is
23906 caching. When you set \mailfrom\ or \use@_sender\, the cache record is keyed by
23907 the sender/recipient combination; thus, for any given recipient, many more
23908 actual callouts are performed than when an empty sender or postmaster is used.
23913 .section Callout caching
23914 .rset SECTcallvercache "~~chapter.~~section"
23915 .index hints database||callout cache
23916 .index callout||caching
23917 .index caching||callout
23918 Exim caches the results of callouts in order to reduce the amount of resources
23919 used, unless you specify the \no@_cache\ parameter with the \callout\ option.
23920 A hints database called `callout' is used for the cache. Two different record
23921 types are used: one records the result of a callout check for a specific
23922 address, and the other records information that applies to the entire domain
23923 (for example, that it accepts the local part \*postmaster*\).
23925 When an original callout fails, a detailed SMTP error message is given about
23926 the failure. However, for subsequent failures use the cache data, this message
23929 The expiry times for negative and positive address cache records are
23930 independent, and can be set by the global options \callout@_negative@_expire\
23931 (default 2h) and \callout@_positive@_expire\ (default 24h), respectively.
23933 If a host gives a negative response to an SMTP connection, or rejects any
23934 commands up to and including
23938 (but not including the \\MAIL\\ command with a non-empty address),
23939 any callout attempt is bound to fail. Exim remembers such failures in a
23940 domain cache record, which it uses to fail callouts for the domain without
23941 making new connections, until the domain record times out. There are two
23942 separate expiry times for domain cache records:
23943 \callout@_domain@_negative@_expire\ (default 3h) and
23944 \callout__domain__positive@_expire\ (default 7d).
23946 Domain records expire when the negative expiry time is reached if callouts
23947 cannot be made for the domain, or if the postmaster check failed.
23948 Otherwise, they expire when the positive expiry time is reached. This
23949 ensures that, for example, a host that stops accepting `random' local parts
23950 will eventually be noticed.
23952 The callout caching mechanism is based on the domain of the address that is
23953 being tested. If the domain routes to several hosts, it is assumed that their
23954 behaviour will be the same.
23957 .section Sender address verification reporting
23958 .rset SECTsenaddver "~~chapter.~~section"
23959 .index verifying||suppressing error details
23960 When sender verification fails in an ACL, the details of the failure are
23961 given as additional output lines before the 550 response to the relevant
23962 SMTP command (\\RCPT\\ or \\DATA\\). For example, if sender callout is in use,
23965 MAIL FROM:<xyz@abc.example>
23967 RCPT TO:<pqr@def.example>
23968 550-Verification failed for <xyz@abc.example>
23969 550-Called: 192.168.34.43
23970 550-Sent: RCPT TO:<xyz@abc.example>
23971 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
23972 550 Sender verification failed
23974 If more than one \\RCPT\\ command fails in the same way, the details are given
23975 only for the first of them. However, some administrators do not want to send
23976 out this much information. You can suppress the details by adding
23977 `/no@_details' to the ACL statement that requests sender verification. For
23980 verify = sender/no_details
23984 .section Redirection while verifying
23985 .index verifying||redirection while
23986 .index address redirection||while verifying
23987 A dilemma arises when a local address is redirected by aliasing or forwarding
23988 during verification: should the generated addresses themselves be verified,
23989 or should the successful expansion of the original address be enough to verify
23990 it? Exim takes the following pragmatic approach:
23992 When an incoming address is redirected to just one child address, verification
23993 continues with the child address, and if that fails to verify, the original
23994 verification also fails.
23996 When an incoming address is redirected to more than one child address,
23997 verification does not continue. A success result is returned.
23999 This seems the most reasonable behaviour for the common use of aliasing as a
24000 way of redirecting different local parts to the same mailbox. It means, for
24001 example, that a pair of alias entries of the form
24004 aw123: :fail: Gone away, no forwarding address
24006 work as expected, with both local parts causing verification failure. When a
24007 redirection generates more than one address, the behaviour is more like a
24008 mailing list, where the existence of the alias itself is sufficient for
24009 verification to succeed.
24012 .section Using an ACL to control relaying
24013 .rset SECTrelaycontrol "~~chapter.~~section"
24014 .index ~~ACL||relay control
24015 .index relaying||control by ACL
24016 .index policy control||relay control
24017 An MTA is said to \*relay*\ a message if it receives it from some host and
24018 delivers it directly to another host as a result of a remote address contained
24019 within it. Redirecting a local address via an alias or forward file and then
24020 passing the message on to another host is not relaying,
24021 .index `percent hack'
24022 but a redirection as a result of the `percent hack' is.
24024 Two kinds of relaying exist, which are termed `incoming' and `outgoing'. A host
24025 which is acting as a gateway or an MX backup is concerned with incoming
24026 relaying from arbitrary hosts to a specific set of domains. On the other hand,
24027 a host which is acting as a smart host for a number of clients is concerned
24028 with outgoing relaying from those clients to the Internet at large. Often the
24029 same host is fulfilling both functions, as illustrated in the diagram below,
24030 but in principle these two kinds of relaying are entirely independent. What is
24031 not wanted is the transmission of mail from arbitrary remote hosts through your
24032 system to arbitrary domains.
24034 .figure "Controlled relaying" rm
24036 .call aspic -sgcal -nv
24037 centre ~~sys.linelength;
24043 A: box "Arbitrary" "remote hosts";
24045 D: box "Arbitrary" "domains";
24046 iline down 50 from bottom of C;
24047 H: box width 180 "Local host";
24050 SH: box "Specific" "hosts";
24051 SD: box join right to E "Specific" "domains";
24052 arcarrow clockwise from top of SH to bottom of D plus (-10,-4)
24053 via right of H plus (-20,0);
24054 arcarrow clockwise from bottom of A to top of SD plus (10,4)
24055 via left of H plus (20,0);
24057 ibox join left to right of H "$it{Outgoing}";
24059 ibox join right to left of H "$it{Incoming}";
24061 L: line dashed from right of A to top of H plus (-15,0);
24062 arc dashed to top of H plus (15,0);
24063 arrow dashed to left of D plus (-2,0);
24065 arrow dashed back up 72 right 32 from middle of L plus (8,0);
24066 text at end plus (0, 4) "$it{Not wanted}";
24071 -------------- -----------
24072 | Arbitrary | |Arbitrary|
24073 |remote hosts| | domains |
24074 -------------- -----------
24077 c ---v----------------^--- t
24080 i ---v----------------^--- i
24087 [(IMG SRC="relaying.gif" alt="Controlled relaying")][(br)]
24090 You can implement relay control by means of suitable statements in the ACL that
24091 runs for each \\RCPT\\ command. For convenience, it is often easiest to use
24092 Exim's named list facility to define the domains and hosts involved. For
24093 example, suppose you want to do the following:
24095 Deliver a number of domains to mailboxes on the local host (or process them
24096 locally in some other way). Let's say these are \*my.dom1.example*\ and
24097 \*my.dom2.example*\.
24099 Relay mail for a number of other domains for which you are the secondary MX.
24100 These might be \*friend1.example*\ and \*friend2.example*\.
24102 Relay mail from the hosts on your local LAN, to whatever domains are involved.
24103 Suppose your LAN is 192.168.45.0/24.
24105 In the main part of the configuration, you put the following definitions:
24107 domainlist local_domains = my.dom1.example : my.dom2.example
24108 domainlist relay_domains = friend1.example : friend2.example
24109 hostlist relay_hosts = 192.168.45.0/24
24111 Now you can use these definitions in the ACL that is run for every \\RCPT\\
24115 accept domains = +local_domains : +relay_domains
24116 accept hosts = +relay_hosts
24118 The first statement accepts any \\RCPT\\ command that contains an address in
24119 the local or relay domains. For any other domain, control passes to the second
24120 statement, which accepts the command only if it comes from one of the relay
24121 hosts. In practice, you will probably want to make your ACL more sophisticated
24122 than this, for example, by including sender and recipient verification. The
24123 default configuration includes a more comprehensive example, which is described
24124 in chapter ~~CHAPdefconfil.
24127 .section Checking a relay configuration
24128 .rset SECTcheralcon "~~chapter.~~section"
24129 .index relaying||checking control of
24130 You can check the relay characteristics of your configuration in the same way
24131 that you can test any ACL behaviour for an incoming SMTP connection, by using
24132 the \-bh-\ option to run a fake SMTP session with which you interact.
24134 For specifically testing for unwanted relaying, the host
24135 \*relay-test.mail-abuse.org*\ provides a useful service. If you telnet to this
24136 host from the host on which Exim is running, using the normal telnet port, you
24137 will see a normal telnet connection message and then quite a long delay. Be
24138 patient. The remote host is making an SMTP connection back to your host, and
24139 trying a number of common probes to test for open relay vulnerability. The
24140 results of the tests will eventually appear on your terminal.
24149 . ============================================================================
24150 .chapter Content scanning
24151 .set runningfoot "content scanning"
24152 .rset CHAPexiscan "~~chapter"
24153 .index content scanning
24155 The content-scanning extension of Exim, formerly known as `exiscan', was
24156 originally implemented as a patch by Tom Kistner. The code was integrated into
24157 the main source for Exim release 4.50, and Tom continues to maintain it. Most
24158 of the wording of this chapter is taken from Tom's specification.
24160 If you want to include the content-scanning features when you compile Exim, you
24161 need to arrange for \\WITH@_CONTENT@_SCAN\\ to be defined in your
24162 \(Local/Makefile)\. When you do that, the Exim binary is built with:
24164 An additional ACL (\acl@_smtp@_mime\) that is run for all MIME parts.
24166 Additional ACL conditions and modifiers: \decode\, \malware\, \mime@_regex\,
24167 \regex\, and \spam\. These can be used in the ACL that is run at the end of
24168 message reception (the \acl@_smtp@_data\ ACL).
24170 An additional control feature (`no@_mbox@_unspool') that saves spooled copies
24171 of messages, or parts of messages, for debugging purposes.
24173 Additional expansion variables that are set in the new ACL and by the new
24176 Two new main configuration options: \av@_scanner\ and \spamd@_address\.
24178 There is another content-scanning configuration option for \(Local/Makefile)\,
24179 called \\WITH@_OLD@_DEMIME\\. If this is set, the old, deprecated \demime\ ACL
24180 condition is compiled, in addition to all the other content-scanning features.
24182 Content-scanning is continually evolving, and new features are still being
24183 added. While such features are still unstable and liable to incompatible
24184 changes, they are made available in Exim by setting options whose names begin
24185 \\EXPERIMENTAL@_\\ in \(Local/Makefile)\. Such features are not documented in
24186 this manual. You can find out about them by reading the file called
24187 \(doc/experimental.txt)\.
24189 All the content-scanning facilites work on a MBOX copy of the message that is
24190 temporarily created in a file called:
24192 <<spool@_directory>>/scan/<<message@_id>>/<<message@_id>>.eml
24194 The \(.eml)\ extension is a friendly hint to virus scanners that they can
24195 expect an MBOX-like structure inside that file. The file is created when the
24196 first content scanning facility is called. Subsequent calls to content
24197 scanning conditions open the same file again. The directory is recursively
24198 removed when the \acl@_smtp@_data\ ACL has finished running, unless
24200 control = no_mbox_unspool
24202 has been encountered. When the MIME ACL decodes files, they are put into the
24203 same directory by default.
24206 .section Scanning for viruses
24207 .rset SECTscanvirus "~~chapter.~~section"
24208 .index virus scanning
24209 .index content scanning||for viruses
24210 .index content scanning||the \malware\ condition
24211 The \malware\ ACL condition lets you connect virus scanner software to Exim. It
24212 supports a `generic' interface to scanners called via the shell, and
24213 specialized interfaces for `daemon' type virus scanners, which are resident in
24214 memory and thus are much faster.
24216 .index \av@_scanner\
24217 You can set the \av@_scanner\ option in first part of the Exim configuration
24218 file to specify which scanner to use, together with any additional options that
24219 are needed. The basic syntax is as follows:
24221 av@_scanner = <<scanner-type>>:<<option1>>:<<option2>>:[...]
24223 If you do not set \av@_scanner\, it defaults to
24225 av_scanner = sophie:/var/run/sophie
24227 If the value of \av@_scanner\ starts with dollar character, it is expanded
24230 The following scanner types are supported in this release:
24232 .index virus scanners||Kaspersky
24233 \aveserver\: This is the scanner daemon of Kaspersky Version 5. You can get a
24234 trial version at \?http://www.kaspersky.com?\. This scanner type takes one
24235 option, which is the path to the daemon's UNIX socket. The default is shown in
24238 av_scanner = aveserver:/var/run/aveserver
24242 .index virus scanners||clamd
24243 \clamd\: This daemon-type scanner is GPL and free. You can get it at
24244 \?http://www.clamav.net/?\. Clamd does not seem to unpack MIME containers, so
24245 it is recommended to unpack MIME attachments in the MIME ACL. It takes one
24246 option: either the path and name of a UNIX socket file, or a hostname or IP
24247 number, and a port, separated by space, as in the second of these examples:
24249 av_scanner = clamd:/opt/clamd/socket
24250 av_scanner = clamd:192.168.2.100 1234
24252 If the option is unset, the default is \(/tmp/clamd)\. Thanks to David Saez for
24253 contributing the code for this scanner.
24256 .index virus scanners||command line interface
24257 \cmdline\: This is the keyword for the generic command line scanner interface.
24258 It can be used to attach virus scanners that are invoked from the shell. This
24259 scanner type takes 3 mandatory options:
24261 The full path and name of the scanner binary, with all command line options,
24262 and a placeholder (%s) for the directory to scan.
24264 A regular expression to match against the STDOUT and STDERR output of the virus
24265 scanner. If the expression matches, a virus was found. You must make absolutely
24266 sure that this expression matches on `virus found'. This is called the
24267 `trigger' expression.
24269 Another regular expression, containing exactly one pair of parentheses, to
24270 match the name of the virus found in the scanners output. This is called the
24273 For example, Sophos Sweep reports a virus on a line like this:
24275 Virus 'W32/Magistr-B' found in file ./those.bat
24277 For the trigger expression, we can just match the word `found'. For the name
24278 expression, we want to extract the W32/Magistr-B string, so we can match for
24279 the single quotes left and right of it. Altogether, this makes the
24280 configuration setting:
24282 av_scanner = cmdline:\
24283 /path/to/sweep -all -rec -archive %s:\
24288 .index virus scanners||DrWeb
24289 \drweb\: The DrWeb daemon scanner (\?http://www.sald.com/?\) interface
24290 takes one argument, either a full path to a UNIX socket, or an IP address and
24291 port separated by whitespace, as in these examples:
24293 av_scanner = drweb:/var/run/drwebd.sock
24294 av_scanner = drweb:192.168.2.20 31337
24296 If you omit the argument, the default path \(/usr/local/drweb/run/drwebd.sock)\
24297 is used. Thanks to Alex Miller for contributing the code for this scanner.
24300 .index virus scanners||F-Secure
24301 \fsecure\: The F-Secure daemon scanner (\?http://www.f-secure.com?\) takes one
24302 argument which is the path to a UNIX socket. For example:
24304 av_scanner = fsecure:/path/to/.fsav
24306 If no argument is given, the default is \(/var/run/.fsav)\. Thanks to Johan
24307 Thelmen for contributing the code for this scanner.
24310 .index virus scanners||Kaspersky
24311 \kavdaemon\: This is the scanner daemon of Kaspersky Version 4. This version of
24312 the Kaspersky scanner is outdated. Please upgrade (see \aveserver\ above). This
24313 scanner type takes one option, which is the path to the daemon's UNIX socket.
24316 av_scanner = kavdaemon:/opt/AVP/AvpCtl
24318 The default path is \(/var/run/AvpCtl)\.
24321 .index virus scanners||mksd
24322 \mksd\: This is a daemon type scanner that is aimed mainly at Polish users,
24323 though some parts of documentation are now available in English. You can get it
24324 at \?http://linux.mks.com.pl/?\. The only option for this scanner type is the
24325 maximum number of processes used simultaneously to scan the attachments,
24326 provided that the demime facility is employed and also provided that mksd has
24327 been run with at least the same number of child processes. For example:
24329 av_scanner = mksd:2
24331 You can safely omit this option (the default value is 1).
24334 .index virus scanners||Sophos and Sophie
24335 \sophie\: Sophie is a daemon that uses Sophos' \libsavi\ library to scan for
24336 viruses. You can get Sophie at \?http://www.vanja.com/tools/sophie/?\. The only
24337 option for this scanner type is the path to the UNIX socket that Sophie uses
24338 for client communication. For example:
24340 av_scanner = sophie:/tmp/sophie
24342 The default path is \(/var/run/sophie)\, so if you are using this, you can omit
24346 When \av@_scanner\ is correctly set, you can use the \malware\ condition in the
24347 \\DATA\\ ACL. The \av@_scanner\ option is expanded each time \malware\ is
24348 called. This makes it possible to use different scanners. See further below for
24349 an example. The \malware\ condition caches its results, so when you use it
24350 multiple times for the same message, the actual scanning process is only
24351 carried out once. However, using expandable items in \av@_scanner\ disables
24352 this caching, in which case each use of the \malware\ condition causes a new
24353 scan of the message.
24355 The \malware\ condition takes a right-hand argument that is expanded before
24356 use. It can then be one of
24358 `true', `*', or `1', in which case the message is scanned for viruses. The
24359 condition succeeds if a virus was found, and fail otherwise. This is the
24362 `false' or `0', in which case no scanning is done and the condition fails
24365 A regular expression, in which case the message is scanned for viruses. The
24366 condition succeeds if a virus is found and its name matches the regular
24367 expression. This allows you to take special actions on certain types of virus.
24369 You can append \"/defer@_ok"\ to the \malware\ condition to accept messages even
24370 if there is a problem with the virus scanner.
24372 .index \$malware@_name$\
24373 When a virus is found, the condition sets up an expansion variable called
24374 \$malware@_name$\ that contains the name of the virus. You can use it in a
24375 \message\ modifier that specifies the error returned to the sender, and/or in
24378 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
24379 use the \demime\ condition (see section ~~SECTdemimecond) before the \malware\
24382 Here is a very simple scanning example:
24384 deny message = This message contains malware ($malware_name)
24388 The next example accepts messages when there is a problem with the scanner:
24390 deny message = This message contains malware ($malware_name)
24392 malware = */defer_ok
24394 The next example shows how to use an ACL variable to scan with both sophie and
24395 aveserver. It assumes you have set:
24397 av_scanner = $acl_m0
24399 in the main Exim configuration.
24401 deny message = This message contains malware ($malware_name)
24402 set acl_m0 = sophie
24405 deny message = This message contains malware ($malware_name)
24406 set acl_m0 = aveserver
24411 .section Scanning with SpamAssassin
24412 .rset SECTscanspamass "~~chapter.~~section"
24413 .index content scanning||for spam
24414 .index spam scanning
24415 .index SpamAssassin, scanning with
24416 The \spam\ ACL condition calls SpamAssassin's \spamd\ daemon to get a spam
24417 score and a report for the message. You can get SpamAssassin at
24418 \?http://www.spamassassin.org?\, or, if you have a working Perl installation,
24419 you can use CPAN by running:
24421 perl -MCPAN -e 'install Mail::SpamAssassin'
24423 SpamAssassin has its own set of configuration files. Please review its
24424 documentation to see how you can tweak it. The default installation should work
24427 .index \spamd@_address\
24428 After having installed and configured SpamAssassin, start the \spamd\ daemon.
24429 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
24430 port for \spamd\, you must set the \spamd@_address\ option in the global part
24431 of the Exim configuration as follows (example):
24433 spamd_address = 192.168.99.45 387
24435 You do not need to set this option if you use the default. As of version 2.60,
24436 \spamd\ also supports communication over UNIX sockets. If you want to use
24437 these, supply \spamd@_address\ with an absolute file name instead of a
24440 spamd_address = /var/run/spamd_socket
24443 You can have multiple \spamd\ servers to improve scalability. These can reside
24444 on other hardware reachable over the network. To specify multiple \spamd\
24445 servers, put multiple address/port pairs in the \spamd@_address\ option,
24446 separated with colons:
24448 spamd_address = 192.168.2.10 783 : \
24449 192.168.2.11 783 : \
24452 Up to 32 \spamd\ servers are supported. The servers are
24453 queried in a random fashion. When a server fails to respond
24454 to the connection attempt, all other servers are tried
24455 until one succeeds. If no server responds, the \spam\
24458 \**Warning**\: It is not possible to use the UNIX socket connection method with
24459 multiple \spamd\ servers.
24461 The spamd_address variable is expanded before use if it starts with a dollar
24462 sign. In this case, the expansion may return a string that is used as the
24463 list so that multiple spamd servers can be the result of an expansion.
24465 Here is a simple example of the use of the \spam\ condition in a DATA ACL:
24467 deny message = This message was classified as SPAM
24470 The right-hand side of the \spam\ condition specifies the username that
24471 SpamAssassin should scan for. If you do not want to scan for a particular user,
24472 but rather use the SpamAssassin system-wide default profile, you can scan for
24473 an unknown user, or simply use `nobody'. However, you must put something on the
24476 The username allows you to use per-domain or per-user antispam profiles. The
24477 right-hand side is expanded before being used, so you can put lookups or
24478 conditions there. When the right-hand side evaluates to `0' or `false', no
24479 scanning is done and the condition fails immediately.
24481 The \spam\ condition returns true if the threshold specified in the user's
24482 SpamAssassin profile has been matched or exceeded. If you want to use the
24483 \spam\ condition for its side effects (see the variables below), you can make
24484 it always return `true' by appending \":true"\ to the username.
24486 .index spam scanning||returned variables
24487 When the \spam\ condition is run, it sets up the following expansion
24494 \$spam@_score$\: The spam score of the message, for example `3.4' or `30.5'.
24495 This is useful for inclusion in log or reject messages.
24498 \$spam@_score@_int$\: The spam score of the message, multiplied by ten, as an
24499 integer value. For example `34' or `305'. This is useful for numeric
24500 comparisons in conditions. This variable is special; it is saved with the
24501 message, and written to Exim's spool file. This means that it can be used
24502 during the whole life of the message on your Exim system, in particular, in
24503 routers or transports during the later delivery phase.
24506 \$spam@_bar$\: A string consisting of a number of `+' or `@-' characters,
24507 representing the integer part of the spam score value. A spam score of 4.4
24508 would have a \$spam@_bar$\ value of `++++'. This is useful for inclusion in
24509 warning headers, since MUAs can match on such strings.
24512 \$spam@_report$\: A multiline text table, containing the full SpamAssassin
24513 report for the message. Useful for inclusion in headers or reject messages.
24517 The \spam\ condition caches its results unless expansion in spamd_address was
24518 used. If you call it again with the same user name, it does not scan again,
24519 but rather returns the same values as before.
24521 The \spam\ condition returns DEFER if there is any error while running the
24522 message through SpamAssassin or if the expansion of spamd_address failed. If
24523 you want to treat DEFER as FAIL (to pass on to the next ACL statement block),
24524 append \"/defer_ok"\ to the right-hand side of the spam condition, like this:
24526 deny message = This message was classified as SPAM
24527 spam = joe/defer_ok
24529 This causes messages to be accepted even if there is a
24530 problem with \spamd\.
24532 Here is a longer, commented example of the use of the \spam\
24535 # put headers in all messages (no matter if spam or not)
24536 warn message = X-Spam-Score: $spam_score ($spam_bar)
24538 warn message = X-Spam-Report: $spam_report
24541 # add second subject line with *SPAM* marker when message
24542 # is over threshold
24543 warn message = Subject: *SPAM* $h_Subject:
24546 # reject spam at high scores (> 12)
24547 deny message = This message scored $spam_score spam points.
24549 condition = ${if >{$spam_score_int}{120}{1}{0}}
24554 .section Scanning MIME parts
24555 .rset SECTscanmimepart "~~chapter.~~section"
24556 .index content scanning||MIME parts
24557 .index MIME content scanning
24558 .index \acl@_smtp@_mime\
24559 The \acl@_smtp@_mime\ global option defines an ACL that is called once for each
24560 MIME part of a message, including multipart types, in the sequence of their
24561 position in the message.
24563 This ACL is called (possibly many times) just before the \acl@_smtp@_data\ ACL,
24564 but only if the message has a ::MIME-Version:: header. When a call to the MIME
24565 ACL does not yield `accept', ACL processing is aborted and the appropriate
24566 result code is sent to the remote client. The \acl@_smtp@_data\ ACL is not
24567 called in this circumstance.
24569 At the start of the MIME ACL, a number of variables are set from the header
24570 information for the relevant MIME part. These are described below. The contents
24571 of the MIME part are not by default decoded into a disk file except for MIME
24572 parts whose content-type is `message/rfc822'. If you want to decode a MIME part
24573 into a disk file, you can use the \decode\ modifier. The general syntax is:
24575 decode = [/<<path>>/]<<filename>>
24577 The right hand side is expanded before use. After expansion,
24580 `0' or `false', in which case no decoding is done.
24582 The string `default'. In that case, the file is put in the temporary `default'
24583 directory \(<<spool@_directory>>/scan/<<message@_id>>/)\ with a sequential file
24584 name consisting of the message id and a sequence number. The full path and name
24585 is available in \$mime@_decoded@_filename$\ after decoding.
24587 A full path name starting with a slash. If the full name is an existing
24588 directory, it is used as a replacement for the default directory. The filename
24589 is then sequentially assigned. If the path does not exist, it is used as
24590 the full path and file name.
24592 If the string does not start with a slash, it is used as the
24593 filename, and the default path is then used.
24595 You can easily decode a file with its original, proposed
24598 decode = $mime_filename
24600 However, you should keep in mind that \$mime@_filename$\ might contain
24601 anything. If you place files outside of the default path, they are not
24602 automatically unlinked.
24604 For RFC822 attachments (these are messages attached to messages, with a
24605 content-type of `message/rfc822'), the ACL is called again in the same manner
24606 as for the primary message, only that the \$mime@_is@_rfc822$\ expansion
24607 variable is set (see below). Attached messages are always decoded to disk
24608 before being checked, and the files are unlinked once the check is done.
24610 The MIME ACL supports the \regex\ and \mime@_regex\ conditions. These can be
24611 used to match regular expressions against raw and decoded MIME parts,
24612 respectively. They are described in section ~~SECTscanregex.
24614 .index MIME content scanning||returned variables
24615 The following list describes all expansion variables that are
24616 available in the MIME ACL:
24622 \$mime@_boundary$\:
24623 If the current part is a multipart (see \$mime@_is@_multipart$\) below, it
24624 should have a boundary string, which is stored in this variable. If the current
24625 part has no boundary parameter in the ::Content-Type:: header, this variable
24626 contains the empty string.
24630 This variable contains the character set identifier, if one was found in the
24631 ::Content-Type:: header. Examples for charset identifiers are:
24637 Please note that this value is not normalized, so you should do matches
24638 case-insensitively.
24641 \$mime@_content@_description$\:
24642 This variable contains the normalized content of the ::Content-Description::
24643 header. It can contain a human-readable description of the parts content. Some
24644 implementations repeat the filename for attachments here, but they are
24645 usually only used for display purposes.
24648 \$mime@_content@_disposition$\:
24649 This variable contains the normalized content of the ::Content-Disposition::
24650 header. You can expect strings like `attachment' or `inline' here.
24653 \$mime@_content@_id$\:
24654 This variable contains the normalized content of the ::Content-ID:: header.
24655 This is a unique ID that can be used to reference a part from another part.
24658 \$mime@_content@_size$\:
24659 This variable is set only after the \decode\ modifier (see above) has been
24660 successfully run. It contains the size of the decoded part in kilobytes. The
24661 size is always rounded up to full kilobytes, so only a completely empty part
24662 has a \$mime@_content@_size$\ of zero.
24665 \$mime@_content@_transfer@_encoding$\:
24666 This variable contains the normalized content of the
24667 ::Content-transfer-encoding:: header. This is a symbolic name for an encoding
24668 type. Typical values are `base64' and `quoted-printable'.
24671 \$mime@_content@_type$\: If the MIME part has a ::Content-Type:: header, this
24672 variable contains its value, lowercased, and without any options (like `name'
24673 or `charset'). Here are some examples of popular MIME types, as they may appear
24678 application/octet-stream
24682 If the MIME part has no ::Content-Type:: header, this variable contains the
24686 \$mime@_decoded@_filename$\:
24687 This variable is set only after the \decode\ modifier (see above) has been
24688 successfully run. It contains the full path and file name of the file
24689 containing the decoded data.
24692 \$mime@_filename$\: This is perhaps the most important of the MIME variables.
24693 It contains a proposed filename for an attachment, if one was found in either
24694 the ::Content-Type:: or ::Content-Disposition:: headers. The filename will be
24695 RFC2047 decoded, but no additional sanity checks are done. If no filename was
24696 found, this variable contains the empty string.
24699 \$mime@_is@_coverletter$\:
24700 This variable attempts to differentiate the `cover letter' of an e-mail from
24701 attached data. It can be used to clamp down on flashy or unneccessarily encoded
24702 content in the cover letter, while not restricting attachments at all.
24704 The variable contains 1 (true) for a MIME part believed to be part of the
24705 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
24708 The outermost MIME part of a message is always a cover letter.
24710 If a multipart/alternative or multipart/related MIME part is a cover letter, so
24711 are all MIME subparts within that multipart.
24713 If any other multipart is a cover letter, the first subpart is a cover letter,
24714 and the rest are attachments.
24716 All parts contained within an attachment multipart are attachments.
24719 As an example, the following will ban `HTML mail' (including that sent with
24720 alternative plain text), while allowing HTML files to be attached. HTML
24721 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
24723 deny message = HTML mail is not accepted here
24724 !condition = $mime_is_rfc822
24725 condition = $mime_is_coverletter
24726 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
24731 \$mime@_is@_multipart$\:
24732 This variable has the value 1 (true) when the current part has the main type
24733 `multipart', for example `multipart/alternative' or `multipart/mixed'. Since
24734 multipart entities only serve as containers for other parts, you may not want
24735 to carry out specific actions on them.
24738 \$mime@_is@_rfc822$\:
24739 This variable has the value 1 (true) if the current part is not a part of the
24740 checked message itself, but part of an attached message. Attached message
24741 decoding is fully recursive.
24744 \$mime@_part@_count$\:
24745 This variable is a counter that is raised for each processed MIME part. It
24746 starts at zero for the very first part (which is usually a multipart). The
24747 counter is per-message, so it is reset when processing RFC822 attachments (see
24748 \$mime@_is@_rfc822$\). The counter stays set after \acl@_smtp@_mime\ is
24749 complete, so you can use it in the DATA ACL to determine the number of MIME
24750 parts of a message. For non-MIME messages, this variable contains the value -1.
24755 .section Scanning with regular expressions
24756 .rset SECTscanregex "~~chapter.~~section"
24757 .index content scanning||with regular expressions
24758 .index regular expressions||content scanning with
24759 You can specify your own custom regular expression matches on the full body of
24760 the message, or on individual MIME parts.
24762 The \regex\ condition takes one or more regular expressions as arguments and
24763 matches them against the full message (when called in the DATA ACL) or a raw
24764 MIME part (when called in the MIME ACL). The \regex\ condition matches
24765 linewise, with a maximum line length of 32K characters. That means you cannot
24766 have multiline matches with the \regex\ condition.
24768 The \mime@_regex\ condition can be called only in the MIME ACL. It matches up
24769 to 32K of decoded content (the whole content at once, not linewise). If the
24770 part has not been decoded with the \decode\ modifier earlier in the ACL, it is
24771 decoded automatically when \mime@_regex\ is executed (using default path and
24772 filename values). If the decoded data is larger than 32K, only the first 32K
24773 characters are checked.
24775 The regular expressions are passed as a colon-separated list. To include a
24776 literal colon, you must double it. Since the whole right-hand side string is
24777 expanded before being used, you must also escape dollar signs and backslashes
24778 with more backslashes, or use the \"@\N"\ facility to disable expansion.
24779 Here is a simple example that contains two regular expressions:
24781 deny message = contains blacklisted regex ($regex_match_string)
24782 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
24784 The conditions returns true if any one of the regular expressions matches. The
24785 \$regex@_match@_string$\ expansion variable is then set up and contains the
24786 matching regular expression.
24788 \**Warning**\: With large messages, these conditions can be fairly
24793 .section The demime condition
24794 .rset SECTdemimecond "~~chapter.~~section"
24795 .index content scanning||MIME checking
24796 .index MIME content scanning
24797 The \demime\ ACL condition provides MIME unpacking, sanity checking and file
24798 extension blocking. It uses a simpler interface to MIME decoding than the MIME
24799 ACL functionality, but provides no additional facilities. Please note that this
24800 condition is deprecated and kept only for for backward compatibility. You must
24801 set the \\WITH@_OLD@_DEMIME\\ option in \(Local/Makefile)\ at build time to be
24802 able to use the \demime\ condition.
24804 The \demime\ condition unpacks MIME containers in the message. It detects
24805 errors in MIME containers and can match file extensions found in the message
24806 against a list. Using this facility produces files containing the unpacked MIME
24807 parts of the message in the temporary scan directory. If you do antivirus
24808 scanning, it is recommened that you use the \demime\ condition before the
24809 antivirus (\malware\) condition.
24811 On the right-hand side of the \demime\ condition you can pass a colon-separated
24812 list of file extensions that it should match against. For example:
24814 deny message = Found blacklisted file attachment
24815 demime = vbs:com:bat:pif:prf:lnk
24817 If one of the file extensions is found, the condition is true, otherwise it is
24818 false. If there is a temporary error while demimeing (for example, `disk
24819 full'), the condition defers, and the message is temporarily rejected (unless
24820 the condition is on a \warn\ verb).
24822 The right-hand side is expanded before being treated as a list, so you can have
24823 conditions and lookups there. If it expands to an empty string, `false', or
24824 zero (`0'), no demimeing is done and the condition is false.
24826 The \demime\ condition set the following variables:
24832 \$demime@_errorlevel$\: When an error is detected in a MIME container, this
24833 variable contains the severity of the error, as an integer number. The higher
24834 the value, the more severe the error. If this variable is unset or zero, no
24838 \$demime@_reason$\: When \$demime@_errorlevel$\ is greater than zero, this
24839 variable contains a human-readable text string describing the MIME error that
24843 \$found@_extension$\: When the \demime\ condition is true, this variable
24844 contains the file extension it found.
24848 Both \$demime@_errorlevel$\ and \$demime@_reason$\ are set by the first call of
24849 the \demime\ condition, and are not changed on subsequent calls.
24851 If you do not want to check for file extensions, but rather use the \demime\
24852 condition for unpacking or error checking purposes, pass `*' as the
24853 right-hand side value. Here is a more elaborate example of how to use this
24856 # Reject messages with serious MIME container errors
24857 deny message = Found MIME error ($demime_reason).
24859 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
24861 # Reject known virus spreading file extensions.
24862 # Accepting these is pretty much braindead.
24863 deny message = contains $found_extension file (blacklisted).
24864 demime = com:vbs:bat:pif:scr
24866 # Freeze .exe and .doc files. Postmaster can
24867 # examine them and eventually thaw them.
24868 deny log_message = Another $found_extension file.
24882 . ============================================================================
24883 .chapter Adding a local scan function to Exim
24884 .set runningfoot "local scan function"
24885 .rset CHAPlocalscan "~~chapter"
24886 .index \*local@_scan()*\ function||description of
24887 .index customizing||input scan using C function
24888 .index policy control||by local scan function
24890 In these days of email worms, viruses, and ever-increasing spam, some sites
24891 want to apply a lot of checking to messages before accepting them.
24893 The content scanning extension (chapter ~~CHAPexiscan) has facilities for
24894 passing messages to external virus and spam scanning software. You can also do
24896 a certain amount in Exim itself through string expansions and the \condition\
24897 condition in the ACL that runs after the SMTP \\DATA\\ command or the ACL for
24898 non-SMTP messages (see chapter ~~CHAPACL), but this has its limitations.
24900 To allow for further customization to a site's own requirements, there is the
24901 possibility of linking Exim with a private message scanning function, written
24902 in C. If you want to run code that is written in something other than C, you
24903 can of course use a little C stub to call it.
24905 The local scan function is run once for every incoming message, at the point
24906 when Exim is just about to accept the message.
24907 It can therefore be used to control non-SMTP messages from local processes as
24908 well as messages arriving via SMTP.
24910 Exim applies a timeout to calls of the local scan function, and there is an
24911 option called \local@_scan@_timeout\ for setting it. The default is 5 minutes.
24912 Zero means `no timeout'.
24913 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
24914 before calling the local scan function, so that the most common types of crash
24915 are caught. If the timeout is exceeded or one of those signals is caught, the
24916 incoming message is rejected with a temporary error if it is an SMTP message.
24917 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
24918 code. The incident is logged on the main and reject logs.
24921 .section Building Exim to use a local scan function
24922 .index \*local@_scan()*\ function||building Exim to use
24923 To make use of the local scan function feature, you must tell Exim where your
24924 function is before building Exim, by setting \\LOCAL@_SCAN@_SOURCE\\ in your
24925 \(Local/Makefile)\. A recommended place to put it is in the \(Local)\
24926 directory, so you might set
24928 LOCAL_SCAN_SOURCE=Local/local_scan.c
24930 for example. The function must be called \*local@_scan()*\. It is called by
24931 Exim after it has received a message, when the success return code is about to
24932 be sent. This is after all the ACLs have been run. The return code from your
24933 function controls whether the message is actually accepted or not. There is a
24934 commented template function (that just accepts the message) in the file
24935 \(src/local@_scan.c)\.
24937 If you want to make use of Exim's run time configuration file to set options
24938 for your \*local@_scan()*\ function, you must also set
24940 LOCAL_SCAN_HAS_OPTIONS=yes
24942 in \(Local/Makefile)\ (see section ~~SECTconoptloc below).
24946 .section API for local@_scan()
24947 .rset SECTapiforloc "~~chapter.~~section"
24948 .index \*local@_scan()*\ function||API description
24949 You must include this line near the start of your code:
24951 #include "local_scan.h"
24953 This header file defines a number of variables and other values, and the
24954 prototype for the function itself. Exim is coded to use unsigned char values
24955 almost exclusively, and one of the things this header defines is a shorthand
24956 for \"unsigned char"\ called \"uschar"\.
24957 It also contains the following macro definitions, to simplify casting character
24958 strings and pointers to character strings:
24960 #define CS (char *)
24961 #define CCS (const char *)
24962 #define CSS (char **)
24963 #define US (unsigned char *)
24964 #define CUS (const unsigned char *)
24965 #define USS (unsigned char **)
24968 The function prototype for \*local@_scan()*\ is:
24970 extern int local_scan(int fd, uschar **return_text);
24972 The arguments are as follows:
24974 \fd\ is a file descriptor for the file that contains the body of the message
24976 The file is open for reading and writing, but updating it is not recommended.
24977 \**Warning**\: You must \*not*\ close this file descriptor.
24979 The descriptor is positioned at character 19 of the file, which is the first
24980 character of the body itself, because the first 19 characters are the message
24981 id followed by \"-D"\ and a newline. If you rewind the file, you should use the
24982 macro \\SPOOL@_DATA@_START@_OFFSET\\ to reset to the start of the data, just in
24983 case this changes in some future version.
24986 \return@_text\ is an address which you can use to return a pointer to a text
24987 string at the end of the function. The value it points to on entry is NULL.
24989 The function must return an \int\ value which is one of the following macros:
24991 \"LOCAL@_SCAN@_ACCEPT"\
24993 The message is accepted. If you pass back a string of text, it is saved with
24994 the message, and made available in the variable \$local@_scan@_data$\. No
24995 newlines are permitted (if there are any, they are turned into spaces) and the
24996 maximum length of text is 1000 characters.
24998 \"LOCAL@_SCAN@_ACCEPT@_FREEZE"\
25000 This behaves as \\LOCAL@_SCAN@_ACCEPT\\, except that the accepted message is
25001 queued without immediate delivery, and is frozen.
25003 \"LOCAL@_SCAN@_ACCEPT@_QUEUE"\
25005 This behaves as \\LOCAL@_SCAN@_ACCEPT\\, except that the accepted message is
25006 queued without immediate delivery.
25008 \"LOCAL@_SCAN@_REJECT"\
25010 The message is rejected; the returned text is used as an error message which is
25011 passed back to the sender and which is also logged. Newlines are permitted --
25012 they cause a multiline response for SMTP rejections, but are converted to
25013 \"@\n"\ in log lines.
25014 If no message is given, `Administrative prohibition' is used.
25016 \"LOCAL@_SCAN@_TEMPREJECT"\
25018 The message is temporarily rejected; the returned text is used as an error
25019 message as for \\LOCAL@_SCAN@_REJECT\\. If no message is given, `Temporary
25020 local problem' is used.
25022 \"LOCAL@_SCAN@_REJECT@_NOLOGHDR"\
25024 This behaves as \\LOCAL@_SCAN@_REJECT\\, except that the header of the rejected
25025 message is not written to the reject log. It has the effect of unsetting the
25026 \rejected@_header\ log selector for just this rejection. If \rejected@_header\
25027 is already unset (see the discussion of the \log@_selection\ option in section
25028 ~~SECTlogselector), this code is the same as \\LOCAL@_SCAN@_REJECT\\.
25031 \"LOCAL@_SCAN@_TEMPREJECT@_NOLOGHDR"\
25033 This code is a variation of \\LOCAL@_SCAN@_TEMPREJECT\\ in the same way that
25034 \\LOCAL__SCAN__REJECT__NOLOGHDR\\ is a variation of \\LOCAL@_SCAN@_REJECT\\.
25037 If the message is not being received by interactive SMTP, rejections are
25038 reported by writing to \stderr\ or by sending an email, as configured by the
25039 \-oe-\ command line options.
25042 .section Configuration options for local@_scan()
25043 .rset SECTconoptloc "~~chapter.~~section"
25044 .index \*local@_scan()*\ function||configuration options
25045 It is possible to have option settings in the main configuration file
25046 that set values in static variables in the \*local@_scan()*\ module. If you
25047 want to do this, you must have the line
25049 LOCAL_SCAN_HAS_OPTIONS=yes
25051 in your \(Local/Makefile)\ when you build Exim. (This line is in
25052 \(OS/Makefile-Default)\, commented out). Then, in the \*local@_scan()*\ source
25053 file, you must define static variables to hold the option values, and a table to
25056 The table must be a vector called \local@_scan@_options\, of type
25057 \"optionlist"\. Each entry is a triplet, consisting of a name, an option type,
25058 and a pointer to the variable that holds the value. The entries must appear in
25059 alphabetical order. Following \local@_scan@_options\ you must also define a
25060 variable called \local@_scan@_options@_count\ that contains the number of
25061 entries in the table. Here is a short example, showing two kinds of option:
25063 static int my_integer_option = 42;
25064 static uschar *my_string_option = US"a default string";
25066 optionlist local_scan_options[] = {
25067 { "my_integer", opt_int, &my_integer_option },
25068 { "my_string", opt_stringptr, &my_string_option }
25070 int local_scan_options_count =
25071 sizeof(local_scan_options)/sizeof(optionlist);
25073 The values of the variables can now be changed from Exim's runtime
25074 configuration file by including a local scan section as in this example:
25078 my_string = some string of text...
25080 The available types of option data are as follows:
25085 This specifies a boolean (true/false) option. The address should point to
25086 a variable of type \"BOOL"\, which will be set to \\TRUE\\ or \\FALSE\\, which
25087 are macros that are defined as `1' and `0', respectively. If you want to detect
25088 whether such a variable has been set at all, you can initialize it to
25089 \\TRUE@_UNSET\\. (BOOL variables are integers underneath, so can hold more than
25093 This specifies a fixed point number, such as is used for load averages.
25094 The address should point to a variable of type \"int"\. The value is stored
25095 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
25098 This specifies an integer; the address should point to a variable of type
25099 \"int"\. The value may be specified in any of the integer formats accepted by
25103 This is the same as \opt@_int\, except that when such a value is output in a
25104 \-bP-\ listing, if it is an exact number of kilobytes or megabytes, it is
25105 printed with the suffix K or M.
25107 .item "opt@_octint"
25108 This also specifies an integer, but the value is always interpeted as an
25109 octal integer, whether or not it starts with the digit zero, and it is
25110 always output in octal.
25112 .item "opt@_stringptr"
25113 This specifies a string value; the address must be a pointer to a
25114 variable that points to a string (for example, of type \"uschar $*$"\).
25117 This specifies a time interval value. The address must point to a variable of
25118 type \"int"\. The value that is placed there is a number of seconds.
25122 If the \-bP-\ command line option is followed by \"local@_scan"\, Exim prints
25123 out the values of all the \*local@_scan()*\ options.
25126 .section Available Exim variables
25127 .index \*local@_scan()*\ function||available Exim variables
25128 The header \(local@_scan.h)\ gives you access to a number of C variables.
25129 These are the only ones that are guaranteed to be maintained from release to
25130 release. Note, however, that you can obtain the value of any Exim variable by
25131 calling \*expand@_string()*\. The exported variables are as follows:
25135 .item "unsigned int debug@_selector"
25136 This variable is set to zero when no debugging is taking place. Otherwise, it
25137 is a bitmap of debugging selectors. Two bits are identified for use in
25138 \*local@_scan()*\; they are defined as macros:
25140 The \"D@_v"\ bit is set when \-v-\ was present on the command line. This is a
25141 testing option that is not privileged -- any caller may set it. All the
25142 other selector bits can be set only by admin users.
25144 The \"D@_local@_scan"\ bit is provided for use by \*local@_scan()*\; it is set
25145 by the \"+local@_scan"\ debug selector. It is not included in the default set
25148 Thus, to write to the debugging output only when \"+local@_scan"\ has been
25149 selected, you should use code like this:
25151 if ((debug_selector & D_local_scan) != 0)
25152 debug_printf("xxx", ...);
25155 .item "uschar *expand@_string@_message"
25156 After a failing call to \*expand@_string()*\ (returned value NULL), the
25157 variable \expand__string__message\ contains the error message, zero-terminated.
25159 .item "header@_line *header@_list"
25160 A pointer to a chain of header lines. The \header@_line\ structure is discussed
25163 .item "header@_line *header@_last"
25164 A pointer to the last of the header lines.
25166 .item "uschar *headers@_charset"
25167 The value of the \headers@_charset\ configuration option.
25169 .item "BOOL host@_checking"
25170 This variable is TRUE during a host checking session that is initiated by the
25171 \-bh-\ command line option.
25173 .item "uschar *interface@_address"
25174 The IP address of the interface that received the message, as a string. This
25175 is NULL for locally submitted messages.
25177 .item "int interface@_port"
25178 The port on which this message was received.
25180 .item "uschar *message@_id"
25181 This variable contains the message id for the incoming message as a
25182 zero-terminated string.
25185 .item "uschar *received@_protocol"
25186 The name of the protocol by which the message was received.
25188 .item "int recipients@_count"
25189 The number of accepted recipients.
25191 .item "recipient@_item *recipients@_list"
25192 .index recipient||adding in local scan
25193 .index recipient||removing in local scan
25194 The list of accepted recipients, held in a vector of length
25195 \recipients@_count\. The \recipient@_item\ structure is discussed below. You
25196 can add additional recipients by calling \*receive@_add@_recipient()*\ (see
25197 below). You can delete recipients by removing them from the vector and adusting
25198 the value in \recipients@_count\. In particular, by setting \recipients@_count\
25199 to zero you remove all recipients. If you then return the value
25200 \"LOCAL@_SCAN@_ACCEPT"\, the message is accepted, but immediately blackholed.
25201 To replace the recipients, set \recipients@_count\ to zero and then call
25202 \*receive@_add@_recipient()*\ as often as needed.
25204 .item "uschar *sender@_address"
25205 The envelope sender address. For bounce messages this is the empty string.
25207 .item "uschar *sender@_host@_address"
25208 The IP address of the sending host, as a string. This is NULL for
25209 locally-submitted messages.
25211 .item "uschar *sender@_host@_authenticated"
25212 The name of the authentication mechanism that was used, or NULL if the message
25213 was not received over an authenticated SMTP connection.
25215 .item "uschar *sender@_host@_name"
25216 The name of the sending host, if known.
25218 .item "int sender@_host@_port"
25219 The port on the sending host.
25221 .item "BOOL smtp@_input"
25222 This variable is TRUE for all SMTP input, including BSMTP.
25224 .item "BOOL smtp@_batched@_input"
25225 This variable is TRUE for BSMTP input.
25227 .item "int store@_pool"
25228 The contents of this variable control which pool of memory is used for new
25229 requests. See section ~~SECTmemhanloc for details.
25234 .section Structure of header lines
25235 The \header@_line\ structure contains the members listed below.
25236 You can add additional header lines by calling the \*header@_add()*\ function
25237 (see below). You can cause header lines to be ignored (deleted) by setting
25242 .item "struct header@_line *next"
25243 A pointer to the next header line, or NULL for the last line.
25246 A code identifying certain headers that Exim recognizes. The codes are printing
25247 characters, and are documented in chapter ~~CHAPspool of this manual. Notice in
25248 particular that any header line whose type is $*$ is not transmitted with the
25249 message. This flagging is used for header lines that have been rewritten, or
25250 are to be removed (for example, ::Envelope-sender:: header lines.) Effectively,
25251 $*$ means `deleted'.
25254 The number of characters in the header line, including the terminating and any
25257 .item "uschar *text"
25258 A pointer to the text of the header. It always ends with a newline, followed by
25259 a zero byte. Internal newlines are preserved.
25265 .section Structure of recipient items
25266 The \recipient@_item\ structure contains these members:
25270 .item "uschar *address"
25271 This is a pointer to the recipient address as it was received.
25274 This is used in later Exim processing when top level addresses are created
25275 by the \one@_time\ option. It is not relevant at the time \*local@_scan()*\ is
25277 must always contain -1 at this stage.
25279 .item "uschar *errors@_to"
25280 If this value is not NULL, bounce messages caused by failing to deliver to the
25281 recipient are sent to the address it contains. In other words, it overrides the
25282 envelope sender for this one recipient. (Compare the \errors@_to\ generic
25284 If a \*local@_scan()*\ function sets an \errors@_to\ field to an unqualified
25285 address, Exim qualifies it using the domain from \qualify@_recipient\.
25286 When \*local@_scan()*\ is called, the \errors@_to\ field is NULL for all
25291 .section Available Exim functions
25292 .index \*local@_scan()*\ function||available Exim functions
25293 The header \(local@_scan.h)\ gives you access to a number of Exim functions.
25294 These are the only ones that are guaranteed to be maintained from release to
25299 .item "pid@_t child@_open(uschar **argv, uschar **envp, int newumask, int *infdptr, int *outfdptr, BOOL make@_leader)"
25300 This function creates a child process that runs the command specified by
25301 \argv\. The environment for the process is specified by \envp\, which can be
25302 NULL if no environment variables are to be passed. A new umask is supplied for
25303 the process in \newumask\.
25305 Pipes to the standard input and output of the new process are set up
25306 and returned to the caller via the \infdptr\ and \outfdptr\ arguments. The
25307 standard error is cloned to the standard output. If there are any file
25308 descriptors `in the way' in the new process, they are closed. If the final
25309 argument is TRUE, the new process is made into a process group leader.
25311 The function returns the pid of the new process, or -1 if things go wrong.
25314 .item "int child@_close(pid@_t pid, int timeout)"
25315 This function waits for a child process to terminate, or for a timeout (in
25316 seconds) to expire. A timeout value of zero means wait as long as it takes. The
25317 return value is as follows:
25321 The process terminated by a normal exit and the value is the process ending
25326 The process was terminated by a signal and the value is the negation of the
25331 The process timed out.
25335 The was some other error in wait(); \errno\ is still set.
25339 .item "pid@_t child@_open@_exim(int *fd)"
25340 This function provide you with a means of submitting a new message to
25341 Exim. (Of course, you can also call \(/usr/sbin/sendmail)\ yourself if you
25342 want, but this packages it all up for you.) The function creates a pipe,
25343 forks a subprocess that is running
25345 exim -t -oem -oi -f <>
25347 and returns to you (via the \"int *"\ argument) a file descriptor for the pipe
25348 that is connected to the standard input. The yield of the function is the PID
25349 of the subprocess. You can then write a message to the file descriptor, with
25350 recipients in ::To::, ::Cc::, and/or ::Bcc:: header lines.
25352 When you have finished, call \*child@_close()*\ to wait for the process to
25353 finish and to collect its ending status. A timeout value of zero is usually
25354 fine in this circumstance. Unless you have made a mistake with the recipient
25355 addresses, you should get a return code of zero.
25357 .item "void debug@_printf(char *, ...)"
25358 This is Exim's debugging function, with arguments as for \*(printf()*\. The
25359 output is written to the standard error stream. If no debugging is selected,
25360 calls to \*debug@_printf()*\ have no effect. Normally, you should make calls
25361 conditional on the \"local@_scan"\ debug selector by coding like this:
25363 if ((debug_selector & D_local_scan) != 0)
25364 debug_printf("xxx", ...);
25367 .item "uschar *expand@_string(uschar *string)"
25368 This is an interface to Exim's string expansion code. The return value is the
25369 expanded string, or NULL if there was an expansion failure.
25370 The C variable \expand@_string@_message\ contains an error message after an
25371 expansion failure. If expansion does not change the string, the return value is
25372 the pointer to the input string. Otherwise, the return value points to a new
25373 block of memory that was obtained by a call to \*store@_get()*\. See section
25374 ~~SECTmemhanloc below for a discussion of memory handling.
25376 .item "void header@_add(int type, char *format, ...)"
25378 This function allows you to an add additional header line at the end of the
25381 The first argument is the type, and should normally be a space character. The
25382 second argument is a format string and any number of substitution arguments as
25383 for \*sprintf()*\. You may include internal newlines if you want, and you must
25384 ensure that the string ends with a newline.
25387 .item "void header@_add@_at@_position(BOOL after, uschar *name, BOOL topnot, int type, char *$nh{format}, ...)"
25388 This function adds a new header line at a specified point in the header
25389 chain. The header itself is specified as for \*header@_add()*\.
25391 If \name\ is NULL, the new header is added at the end of the chain if \after\
25392 is true, or at the start if \after\ is false. If \name\ is not NULL, the header
25393 lines are searched for the first non-deleted header that matches the name. If
25394 one is found, the new header is added before it if \after\ is false. If \after\
25395 is true, the new header is added after the found header and any adjacent
25396 subsequent ones with the same name (even if marked `deleted'). If no matching
25397 non-deleted header is found, the \topnot\ option controls where the header is
25398 added. If it is true, addition is at the top; otherwise at the bottom. Thus, to
25399 add a header after all the ::Received:: headers, or at the top if there are no
25400 ::Received:: headers, you could use
25402 header_add_at_position(TRUE, US"Received", TRUE,
25403 ' ', "X-xxx: ...");
25405 Normally, there is always at least one non-deleted ::Received:: header, but
25406 there may not be if \received@_header@_text\ expands to an empty string.
25409 .item "void header@_remove(int occurrence, uschar *name)"
25410 This function removes header lines. If \occurrence\ is zero or negative, all
25411 occurrences of the header are removed. If occurrence is greater than zero, that
25412 particular instance of the header is removed. If no header(s) can be found that
25413 match the specification, the function does nothing.
25416 .item "BOOL header@_testname(header@_line *hdr, uschar *name, int length, BOOL notdel)"
25417 This function tests whether the given header has the given name. It is not just
25418 a string comparison, because whitespace is permitted between the name and the
25419 colon. If the \notdel\ argument is true, a false return is forced for all
25420 `deleted' headers; otherwise they are not treated specially. For example:
25422 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
25427 .item "uschar *lss@_b64encode(uschar *cleartext, int length)"
25428 .index base64 encoding||functions for \*local@_scan()*\ use
25429 This function base64-encodes a string, which is passed by address and length.
25430 The text may contain bytes of any value, including zero. The result is passed
25431 back in dynamic memory that is obtained by calling \*store@_get()*\. It is
25434 .item "int lss@_b64decode(uschar *codetext, uschar **cleartext)"
25435 This function decodes a base64-encoded string. Its arguments are a
25436 zero-terminated base64-encoded string and the address of a variable that is set
25437 to point to the result, which is in dynamic memory. The length of the
25438 decoded string is the yield of the function. If the input is invalid base64
25439 data, the yield is -1. A zero byte is added to the end of the output string to
25440 make it easy to interpret as a C string (assuming it contains no zeros of its
25441 own). The added zero byte is not included in the returned count.
25443 .item "int lss@_match@_domain(uschar *domain, uschar *list)"
25444 This function checks for a match in a domain list. Domains are always
25445 matched caselessly. The return value is one of the following:
25447 OK $rm{match succeeded}
25448 FAIL $rm{match failed}
25449 DEFER $rm{match deferred}
25451 DEFER is usually caused by some kind of lookup defer, such as the
25452 inability to contact a database.
25454 .item "int lss@_match@_local@_part(uschar *localpart, uschar *list, BOOL caseless)"
25455 This function checks for a match in a local part list. The third argument
25456 controls case-sensitivity. The return values are as for
25457 \*lss@_match@_domain()*\.
25459 .item "int lss@_match@_address(uschar *address, uschar *list, BOOL caseless)"
25460 This function checks for a match in an address list. The third argument
25461 controls the case-sensitivity of the local part match. The domain is always
25462 matched caselessly. The return values are as for \*lss@_match@_domain()*\.
25464 .item "int lss@_match@_host(uschar *host@_name, uschar *host@_address, uschar *list)"
25465 This function checks for a match in a host list. The most common usage is
25468 lss_match_host(sender_host_name, sender_host_address, ...)
25470 An empty address field matches an empty item in the host list. If the
25471 host name is NULL, the name corresponding to \$sender@_host@_address$\ is
25472 automatically looked up if a host name is required to match an item in the
25473 list. The return values are as for \*lss@_match@_domain()*\, but in addition,
25474 \*lss@_match@_host()*\ returns ERROR in the case when it had to look up a host
25475 name, but the lookup failed.
25477 .item "void log@_write(unsigned int selector, int which, char *format, ...)"
25478 This function writes to Exim's log files. The first argument should be zero (it
25479 is concerned with \log@_selector\). The second argument can be \"LOG@_MAIN"\ or
25481 \"LOG@_PANIC"\ or the inclusive `or' of any combination of them. It specifies
25482 to which log or logs the message is written.
25483 The remaining arguments are a format and relevant insertion arguments. The
25484 string should not contain any newlines, not even at the end.
25487 .item "void receive@_add@_recipient(uschar *address, int pno)"
25488 This function adds an additional recipient to the message. The first argument
25489 is the recipient address. If it is unqualified (has no domain), it is qualified
25490 with the \qualify@_recipient\ domain. The second argument must always be -1.
25492 This function does not allow you to specify a private \errors@_to\ address (as
25493 described with the structure of \recipient@_item\ above), because it pre-dates
25494 the addition of that field to the structure. However, it is easy to add such a
25495 value afterwards. For example:
25497 receive_add_recipient(US"monitor@mydom.example", -1);
25498 recipients_list[recipients_count-1].errors_to =
25499 US"postmaster@mydom.example";
25503 .item "BOOL receive@_remove@_recipient(uschar *recipient)"
25504 This is a convenience function to remove a named recipient from the
25505 list of recipients. It returns true if a recipient was removed, and
25506 false if no matching recipient could be found. The argument must be a
25507 complete email address.
25511 .item "uschar *rfc2047@_decode(uschar *string, BOOL lencheck, uschar *target, int zeroval, int *lenptr, uschar **error)"
25512 This function decodes strings that are encoded according to RFC 2047. Typically
25513 these are the contents of header lines. First, each encoded `word' is decoded
25514 from the Q or B encoding into a byte-string. Then, if provided with the name of
25515 a charset encoding, and if the \*iconv()*\ function is available, an attempt is
25516 made to translate the result to the named character set. If this fails, the
25517 binary string is returned with an error message.
25519 The first argument is the string to be decoded. If \lencheck\ is TRUE, the
25520 maximum MIME word length is enforced. The third argument is the target
25521 encoding, or NULL if no translation is wanted.
25523 .index binary zero||in RFC 2047 decoding
25524 If a binary zero is encountered in the decoded string, it is replaced by the
25525 contents of the \zeroval\ argument. For use with Exim headers, the value must
25526 not be 0 because header lines are handled as zero-terminated strings.
25528 The function returns the result of processing the string, zero-terminated; if
25529 \lenptr\ is not NULL, the length of the result is set in the variable to which
25530 it points. When \zeroval\ is 0, \lenptr\ should not be NULL.
25532 If an error is encountered, the function returns NULL and uses the \error\
25533 argument to return an error message. The variable pointed to by \error\ is set
25534 to NULL if there is no error; it may be set non-NULL even when the function
25535 returns a non-NULL value if decoding was successful, but there was a problem
25539 .item "int smtp@_fflush(void)"
25540 This function is used in conjunction with \*smtp@_printf()*\, as described
25543 .item "void smtp@_printf(char *, ...)"
25544 The arguments of this function are like \*printf()*\; it writes to the SMTP
25545 output stream. You should use this function only when there is an SMTP output
25546 stream, that is, when the incoming message is being received via interactive
25547 SMTP. This is the case when \smtp@_input\ is TRUE and \smtp@_batched@_input\ is
25548 FALSE. If you want to test for an incoming message from another host (as
25549 opposed to a local process that used the \-bs-\ command line option), you can
25550 test the value of \sender@_host@_address\, which is non-NULL when a remote host
25553 If an SMTP TLS connection is established, \*smtp@_printf()*\ uses the TLS
25554 output function, so it can be used for all forms of SMTP connection.
25556 Strings that are written by \*smtp@_printf()*\ from within \*local@_scan()*\
25557 must start with an appropriate response code: 550 if you are going to return
25558 \\LOCAL@_SCAN@_REJECT\\, 451 if you are going to return
25559 \\LOCAL@_SCAN@_TEMPREJECT\\, and 250 otherwise. Because you are writing the
25560 initial lines of a multi-line response, the code must be followed by a hyphen
25561 to indicate that the line is not the final response line. You must also ensure
25562 that the lines you write terminate with CRLF. For example:
25564 smtp_printf("550-this is some extra info\r\n");
25565 return LOCAL_SCAN_REJECT;
25567 Note that you can also create multi-line responses by including newlines in
25568 the data returned via the \return@_text\ argument. The added value of using
25569 \*smtp@_printf()*\ is that, for instance, you could introduce delays between
25570 multiple output lines.
25572 The \*smtp@_printf()*\ function does not return any error indication, because it
25573 does not automatically flush pending output, and therefore does not test
25574 the state of the stream. (In the main code of Exim, flushing and error
25575 detection is done when Exim is ready for the next SMTP input command.) If
25576 you want to flush the output and check for an error (for example, the
25577 dropping of a TCP/IP connection), you can call \*smtp@_fflush()*\, which has no
25578 arguments. It flushes the output stream, and returns a non-zero value if there
25581 .item "void *store@_get(int)"
25582 This function accesses Exim's internal store (memory) manager. It gets a new
25583 chunk of memory whose size is given by the argument. Exim bombs out if it ever
25584 runs out of memory. See the next section for a discussion of memory handling.
25586 .item "void *store@_get@_perm(int)"
25587 This function is like \*store@_get()*\, but it always gets memory from the
25588 permanent pool. See the next section for a discussion of memory handling.
25590 .item "uschar *string@_copy(uschar *string)"
25591 .item "uschar *string@_copyn(uschar *string, int length)" 0
25592 .item "uschar *string@_sprintf(char *format, ...)" 0
25593 These three functions create strings using Exim's dynamic memory facilities.
25594 The first makes a copy of an entire string. The second copies up to a maximum
25595 number of characters, indicated by the second argument. The third uses a format
25596 and insertion arguments to create a new string. In each case, the result is a
25597 pointer to a new string
25598 in the current memory pool. See the next section for more discussion.
25604 .section More about Exim's memory handling
25605 .rset SECTmemhanloc "~~chapter.~~section"
25606 .index \*local@_scan()*\ function||memory handling
25607 No function is provided for freeing memory, because that is never needed.
25608 The dynamic memory that Exim uses when receiving a message is automatically
25609 recycled if another message is received by the same process (this applies only
25610 to incoming SMTP connections -- other input methods can supply only one message
25611 at a time). After receiving the last message, a reception process terminates.
25613 Because it is recycled, the normal dynamic memory cannot be used for holding
25614 data that must be preserved over a number of incoming messages on the same SMTP
25615 connection. However, Exim in fact uses two pools of dynamic memory; the second
25616 one is not recycled, and can be used for this purpose.
25618 If you want to allocate memory that remains available for subsequent messages
25619 in the same SMTP connection, you should set
25621 store_pool = POOL_PERM
25623 before calling the function that does the allocation. There is no need to
25624 restore the value if you do not need to; however, if you do want to revert to
25625 the normal pool, you can either restore the previous value of \store@_pool\ or
25626 set it explicitly to \\POOL@_MAIN\\.
25628 The pool setting applies to all functions that get dynamic memory, including
25629 \*expand@_string()*\, \*store@_get()*\, and the \*string@_xxx()*\ functions.
25630 There is also a convenience function called \*store__get__perm()*\ that gets a
25631 block of memory from the permanent pool while preserving the value of
25642 . ============================================================================
25643 .chapter System-wide message filtering
25644 .set runningfoot "system filtering"
25645 .rset CHAPsystemfilter "~~chapter"
25646 .index filter||system filter
25647 .index filtering all mail
25648 .index system filter
25649 The previous chapters (on ACLs and the local scan function) describe checks
25650 that can be applied to messages before they are accepted by a host. There is
25651 also a mechanism for checking messages once they have been received, but before
25652 they are delivered. This is called the $it{system filter}.
25654 The system filter operates in a similar manner to users' filter files, but it
25655 is run just once per message (however many recipients the message has).
25656 It should not normally be used as a substitute for routing, because \deliver\
25657 commands in a system router provide new envelope recipient addresses.
25658 The system filter must be an Exim filter. It cannot be a Sieve filter.
25660 The system filter is run at the start of a delivery attempt, before any routing
25661 is done. If a message fails to be completely delivered at the first attempt,
25662 the system filter is run again at the start of every retry.
25663 If you want your filter to do something only once per message, you can make use
25664 of the \first@_delivery\ condition in an \if\ command in the filter to prevent
25665 it happening on retries.
25667 \**Warning**\: Because the system filter runs just once, variables that are
25668 specific to individual recipient addresses, such as \$local@_part$\ and
25669 \$domain$\, are not set, and the `personal' condition is not meaningful. If you
25670 want to run a centrally-specified filter for each recipient address
25671 independently, you can do so by setting up a suitable \%redirect%\ router, as
25672 described in section ~~SECTperaddfil below.
25674 .section Specifying a system filter
25675 .index uid (user id)||system filter
25676 .index gid (group id)||system filter
25677 The name of the file that contains the system filter must be specified by
25678 setting \system@_filter\. If you want the filter to run under a uid and gid
25679 other than root, you must also set \system@_filter@_user\ and
25680 \system@_filter@_group\ as appropriate. For example:
25682 system_filter = /etc/mail/exim.filter
25683 system_filter_user = exim
25685 If a system filter generates any deliveries directly to files or pipes (via the
25686 \save\ or \pipe\ commands), transports to handle these deliveries must be
25687 specified by setting \system@_filter@_file@_transport\ and
25688 \system@_filter@_pipe@_transport\, respectively. Similarly,
25689 \system@_filter@_reply@_transport\ must be set to handle any messages generated
25690 by the \reply\ command.
25692 .section Testing a system filter
25693 You can run simple tests of a system filter in the same way as for a user
25694 filter, but you should use \-bF-\ rather than \-bf-\, so that features that
25695 are permitted only in system filters are recognized.
25697 If you want to test the combined effect of a system filter and a user filter,
25698 you can use both \-bF-\ and \-bf-\ on the same command line.
25701 .section Contents of a system filter
25702 The language used to specify system filters is the same as for users' filter
25703 files. It is described in the separate end-user document \*Exim's interface to
25704 mail filtering*\. However, there are some additional features that are
25705 available only in system filters; these are described in subsequent sections.
25706 If they are encountered in a user's filter file or when testing with \-bf-\,
25709 .index frozen messages||manual thaw, testing in filter
25710 There are two special conditions which, though available in users' filter
25711 files, are designed for use in system filters. The condition \first@_delivery\
25712 is true only for the first attempt at delivering a message, and
25713 \manually@_thawed\ is true only if the message has been frozen, and
25714 subsequently thawed by an admin user. An explicit forced delivery counts as a
25715 manual thaw, but thawing as a result of the \auto__thaw\ setting does not.
25717 \**Warning**\: If a system filter uses the \first@_delivery\ condition to
25718 specify an `unseen' (non-significant) delivery, and that delivery does not
25719 succeed, it will not be tried again.
25720 If you want Exim to retry an unseen delivery until it succeeds, you should
25721 arrange to set it up every time the filter runs.
25723 When a system filter finishes running, the values of the variables \$n0$\ --
25724 \$n9$\ are copied into \$sn0$\ -- \$sn9$\ and are thereby made available to
25725 users' filter files. Thus a system filter can, for example, set up `scores' to
25726 which users' filter files can refer.
25729 .section Additional variable for system filters
25730 The expansion variable \$recipients$\, containing a list of all the recipients
25731 of the message (separated by commas and white space), is available in system
25732 filters. It is not available in users' filters for privacy reasons.
25735 .section Defer, freeze, and fail commands for system filters
25736 .index freezing messages
25737 .index message||freezing
25738 .index message||forced failure
25739 .index \fail\||in system filter
25740 .index \freeze\ in system filter
25741 .index \defer\ in system filter
25742 There are three extra commands (\defer\, \freeze\ and \fail\) which are always
25743 available in system filters, but are not normally enabled in users' filters.
25744 (See the \allow@_defer\,
25745 \allow@_freeze\ and \allow@_fail\ options for the \%redirect%\ router.) These
25746 commands can optionally be followed by the word \text\ and a string containing
25747 an error message, for example:
25749 fail text "this message looks like spam to me"
25751 The keyword \text\ is optional if the next character is a double quote.
25753 The \defer\ command defers delivery of the original recipients of the message.
25754 The \fail\ command causes all the original recipients to be failed, and a
25755 bounce message to be created. The \freeze\ command suspends all delivery
25756 attempts for the original recipients. In all cases, any new deliveries that are
25757 specified by the filter are attempted as normal after the filter has run.
25759 The \freeze\ command is ignored if the message has been manually unfrozen and
25760 not manually frozen since. This means that automatic freezing by a system
25761 filter can be used as a way of checking out suspicious messages. If a message
25762 is found to be all right, manually unfreezing it allows it to be delivered.
25764 .index log||\fail\ command log line
25765 .index \fail\||log line, reducing
25766 The text given with a fail command is used as part of the bounce message as
25767 well as being written to the log. If the message is quite long, this can fill
25768 up a lot of log space when such failures are common. To reduce the size of the
25769 log message, Exim interprets the text in a special way if it starts with the
25770 two characters \"@<@<"\ and contains \"@>@>"\ later. The text between these two
25771 strings is written to the log, and the rest of the text is used in the bounce
25772 message. For example:
25774 fail "<<filter test 1>>Your message is rejected \
25775 because it contains attachments that we are \
25776 not prepared to receive."
25779 .index loop||caused by \fail\
25780 Take great care with the \fail\ command when basing the decision to fail on the
25781 contents of the message, because the bounce message will of course include the
25782 contents of the original message and will therefore trigger the \fail\ command
25783 again (causing a mail loop) unless steps are taken to prevent this. Testing the
25784 \error@_message\ condition is one way to prevent this. You could use, for
25787 if $message_body contains "this is spam" and not error_message
25788 then fail text "spam is not wanted here" endif
25790 though of course that might let through unwanted bounce messages. The
25791 alternative is clever checking of the body and/or headers to detect bounces
25792 generated by the filter.
25794 The interpretation of a system filter file ceases after a
25796 \freeze\, or \fail\ command is obeyed. However, any deliveries that were set up
25797 earlier in the filter file are honoured, so you can use a sequence such as
25802 to send a specified message when the system filter is freezing (or deferring or
25803 failing) a message. The normal deliveries for the message do not, of course,
25807 .section Adding and removing headers in a system filter
25808 .rset SECTaddremheasys "~~chapter.~~section"
25809 .index header lines||adding, in system filter
25810 .index header lines||removing, in system filter
25811 .index filter||header lines, adding/removing
25812 Two filter commands that are available only in system filters are:
25814 headers add <<string>>
25815 headers remove <<string>>
25817 The argument for the \headers add\ is a string that is expanded and then added
25818 to the end of the message's headers. It is the responsibility of the filter
25819 maintainer to make sure it conforms to RFC 2822 syntax. Leading white space is
25820 ignored, and if the string is otherwise empty, or if the expansion is forced to
25821 fail, the command has no effect.
25823 You can use `@\n' within the string, followed by white space, to specify
25824 continued header lines. More than one header may be added in one command by
25825 including `@\n' within the string without any following white space. For
25828 headers add "X-header-1: ....\n \
25829 continuation of X-header-1 ...\n\
25832 Note that the header line continuation white space after the first newline must
25833 be placed before the backslash that continues the input string, because white
25834 space after input continuations is ignored.
25836 The argument for \headers remove\ is a colon-separated list of header names.
25837 This command applies only to those headers that are stored with the message;
25838 those that are added at delivery time (such as ::Envelope-To:: and
25839 ::Return-Path::) cannot be removed by this means. If there is more than one
25840 header with the same name, they are all removed.
25843 The \headers\ command in a system filter makes an immediate change to the set
25844 of header lines that was received with the message (with possible additions
25845 from ACL processing). Subsequent commands in the system filter operate on the
25846 modified set, which also forms the basis for subsequent message delivery.
25847 Unless further modified during routing or transporting, this set of headers is
25848 used for all recipients of the message.
25850 During routing and transporting, the variables that refer to the contents of
25851 header lines refer only to those lines that are in this set. Thus, header lines
25852 that are added by a system filter are visible to users' filter files and to all
25853 routers and transports. This contrasts with the manipulation of header lines by
25854 routers and transports, which is not immediate, but which instead is saved up
25855 until the message is actually being written (see section ~~SECTheadersaddrem).
25857 If the message is not delivered at the first attempt, header lines that were
25858 added by the system filter are stored with the message, and so are still
25859 present at the next delivery attempt. Header lines that were removed are still
25860 present, but marked `deleted' so that they are not transported with the
25861 message. For this reason, it is usual to make the \headers\ command conditional
25862 on \first@_delivery\ so that the set of header lines is not modified more than
25865 Because header modification in a system filter acts immediately, you have to
25866 use an indirect approach if you want to modify the contents of a header line.
25869 headers add "Old-Subject: $h_subject:"
25870 headers remove "Subject"
25871 headers add "Subject: new subject (was: $h_old-subject:)"
25872 headers remove "Old-Subject"
25878 .section Setting an errors address in a system filter
25879 .index envelope sender
25880 In a system filter, if a \deliver\ command is followed by
25882 errors@_to <<some address>>
25884 in order to change the envelope sender (and hence the error reporting) for that
25885 delivery, any address may be specified. (In a user filter, only the current
25886 user's address can be set.) For example, if some mail is being monitored, you
25889 unseen deliver monitor@spying.example errors_to root@local.example
25891 to take a copy which would not be sent back to the normal error reporting
25892 address if its delivery failed.
25895 .section Per-address filtering
25896 .rset SECTperaddfil "~~chapter.~~section"
25897 In contrast to the system filter, which is run just once per message for each
25898 delivery attempt, it is also possible to set up a system-wide filtering
25899 operation that runs once for each recipient address. In this case, variables
25900 such as \$local@_part$\ and \$domain$\ can be used, and indeed, the choice of
25901 filter file could be made dependent on them. This is an example of a router
25902 which implements such a filter:
25909 domains = +local_domains
25910 file = /central/filters/$local_part
25915 The filter is run in a separate process under its own uid. Therefore, either
25916 \check@_local@_user\ must be set (as above), in which case the filter is run as
25917 the local user, or the \user\ option must be used to specify which user to use.
25918 If both are set, \user\ overrides.
25920 Care should be taken to ensure that none of the commands in the filter file
25921 specify a significant delivery if the message is to go on to be delivered to
25922 its intended recipient. The router will not then claim to have dealt with the
25923 address, so it will be passed on to subsequent routers to be delivered in the
25935 . ============================================================================
25936 .chapter Message processing
25937 .set runningfoot "message processing"
25938 .rset CHAPmsgproc "~~chapter"
25939 .index message||general processing
25940 Exim performs various transformations on the sender and recipient addresses of
25941 all messages that it handles, and also on the messages' header lines. Some of
25942 these are optional and configurable, while others always take place. All of
25943 this processing, except rewriting as a result of routing, and the addition or
25944 removal of header lines while delivering, happens when a message is received,
25945 before it is placed on Exim's queue.
25947 Some of the automatic processing takes place by default only for
25948 `locally-originated' messages. This adjective is used to describe messages that
25949 are not received over TCP/IP, but instead are passed to an Exim process on its
25950 standard input. This includes the interactive `local SMTP' case that is set up
25951 by the \-bs-\ command line option.
25953 \**Note**\: messages received over TCP/IP on the loopback interface (127.0.0.1
25954 or @:@:1) are not considered to be locally-originated. Exim does not treat the
25955 loopback interface specially in any way.
25957 If you want the loopback interface to be treated specially, you must ensure
25958 that there are appropriate entries in your ACLs.
25962 .section Submission mode for non-local messages
25963 .rset SECTsubmodnon "~~chapter.~~section"
25964 .index message||submission
25965 .index submission mode
25967 Processing that happens automatically for locally-originated messages can also
25968 be requested for other messages. The term `submission mode' is used to describe
25969 this state. Submisssion mode is set by the modifier
25971 control = submission
25973 in a \\MAIL\\, \\RCPT\\, or pre-data ACL for an incoming SMTP message (see
25974 sections ~~SECTACLmodi and ~~SECTcontrols). This makes Exim treat the message
25975 as a local submission, and is normally used when the source of the message is
25976 known to be an MUA running on a client host (as opposed to an MTA). For
25977 example, to set submission mode for messages originating on the IPv4 loopback
25978 interface, you could include the following in the \\MAIL\\ ACL:
25980 warn hosts = 127.0.0.1
25981 control = submission
25983 There are some options that can be used when setting submission mode. A slash
25984 is used to separate options. For example:
25986 control = submission/sender_retain
25988 Specifying \sender@_retain\ has the effect of setting \local@_sender@_retain\
25989 true and \local@_from@_check\ false for the current incoming message. The first
25990 of these allows an existing ::Sender:: header in the message to remain, and the
25991 second suppresses the check to ensure that ::From:: matches the authenticated
25992 sender. With this setting, Exim still fixes up messages by adding ::Date:: and
25993 ::Message-ID:: header lines if they are missing, but makes no attempt to check
25994 sender authenticity in header lines.
25996 A submission mode setting may also specify a domain to be used when generating
25997 a ::From:: or ::Sender:: header. For example:
25999 control = submission/domain=some.domain
26001 The domain may be empty. How this value is used is described in sections
26002 ~~SECTthefrohea and ~~SECTthesenhea.
26007 .section Line endings
26008 .rset SECTlineendings "~~chapter.~~section"
26009 .index line endings
26010 .index carriage return
26012 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
26013 linefeed) is the line ending for messages transmitted over the Internet using
26014 SMTP over TCP/IP. However, within individual operating systems, different
26015 conventions are used. For example, Unix-like systems use just LF, but others
26016 use CRLF or just CR.
26018 Exim was designed for Unix-like systems, and internally, it stores messages
26019 using the system's convention of a single LF as a line terminator. When
26020 receiving a message, all line endings are translated to this standard format.
26021 Originally, it was thought that programs that passed messages directly to an
26022 MTA within an operating system would use that system's convention. Experience
26023 has shown that this is not the case; for example, there are Unix applications
26024 that use CRLF in this circumstance. For this reason, and for compatibility with
26025 other MTAs, the way Exim handles line endings for all messages is now as
26028 LF not preceded by CR is treated as a line ending.
26030 CR is treated as a line ending; if it is immediately followed by LF, the LF
26033 The sequence `CR, dot, CR' does not terminate an incoming SMTP message,
26034 nor a local message in the state where a line containing only a dot is a
26037 If a bare CR is encountered within a header line, an extra space is added after
26038 the line terminator so as not to end the header line. The reasoning behind this
26039 is that bare CRs in header lines are most likely either to be mistakes, or
26040 people trying to play silly games.
26042 If the first header line received in a message ends with CRLF, a subsequent
26043 bare LF in a header line is treated in the same way as a bare CR in a header
26049 .section Unqualified addresses
26050 .index unqualified addresses
26051 .index address||qualification
26052 By default, Exim expects every envelope address it receives from an external
26053 host to be fully qualified. Unqualified addresses cause negative responses to
26054 SMTP commands. However, because SMTP is used as a means of transporting
26055 messages from MUAs running on personal workstations, there is sometimes a
26056 requirement to accept unqualified addresses from specific hosts or IP networks.
26058 Exim has two options that separately control which hosts may send unqualified
26059 sender or receipient addresses in SMTP commands, namely
26060 \sender__unqualified__hosts\ and \recipient__unqualified__hosts\. In both
26061 cases, if an unqualified address is accepted, it is qualified by adding the
26062 value of \qualify__domain\ or \qualify__recipient\, as appropriate.
26063 .index \qualify@_domain\
26064 .index \qualify@_recipient\
26067 Unqualified addresses in header lines are automatically qualified for messages
26068 that are locally originated, unless the \-bnq-\ option is given on the command
26069 line. For messages received over SMTP, unqualified addresses in header lines
26070 are qualified only if unqualified addresses are permitted in SMTP commands. In
26071 other words, such qualification is also controlled by
26072 \sender__unqualified__hosts\ and \recipient__unqualified__hosts\,
26076 .section The UUCP From line
26078 .index UUCP||`From' line
26079 .index sender||address
26080 .index \uucp@_from@_pattern\
26081 .index \uucp@_from@_sender\
26082 .index envelope sender
26083 .index Sendmail compatibility||`From' line
26084 Messages that have come from UUCP (and some other applications) often begin
26085 with a line containing the envelope sender and a timestamp, following the word
26086 `From'. Examples of two common formats are:
26088 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
26089 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
26091 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
26092 Exim recognizes such lines at the start of messages that are submitted to it
26093 via the command line (that is, on the standard input). It does not recognize
26094 such lines in incoming SMTP messages, unless the sending host matches
26095 \ignore@_fromline@_hosts\ or the \-bs-\ option was used for a local message and
26096 \ignore@_fromline@_local\ is set. The recognition is controlled by a regular
26097 expression that is defined by the \uucp@_from@_pattern\ option, whose default
26098 value matches the two common cases shown above and puts the address that
26099 follows `From' into \$1$\.
26101 .index numerical variables (\$1$\, \$2$\, etc)||in `From ' line handling
26102 When the caller of Exim for a non-SMTP message that contains a `From' line is a
26103 trusted user, the message's sender address is constructed by expanding the
26104 contents of \uucp@_sender@_address\, whose default value is `@$1'. This is then
26105 parsed as an RFC 2822 address. If there is no domain, the local part is
26106 qualified with \qualify@_domain\ unless it is the empty string. However, if the
26107 command line \-f-\ option is used, it overrides the `From' line.
26109 If the caller of Exim is not trusted, the `From' line is recognized, but the
26110 sender address is not changed. This is also the case for incoming SMTP messages
26111 that are permitted to contain `From' lines.
26113 Only one `From' line is recognized. If there is more than one, the second is
26114 treated as a data line that starts the body of the message, as it is not valid
26115 as a header line. This also happens if a `From' line is present in an incoming
26116 SMTP message from a source that is not permitted to send them.
26119 .section Resent- header lines
26120 .index \Resent@-\ header lines
26121 RFC 2822 makes provision for sets of header lines starting with the string
26122 \"Resent-"\ to be added to a message when it is resent by the original
26123 recipient to somebody else. These headers are ::Resent-Date::, ::Resent-From::,
26124 ::Resent-Sender::, ::Resent-To::, ::Resent-Cc::, ::Resent-Bcc:: and
26125 ::Resent-Message-ID::. The RFC says:
26127 \*Resent fields are strictly informational. They MUST NOT be used in the normal
26128 processing of replies or other such automatic actions on messages.*\
26130 This leaves things a bit vague as far as other processing actions such as
26131 address rewriting are concerned. Exim treats \Resent@-\ header lines as
26134 A ::Resent-From:: line that just contains the login id of the submitting user
26135 is automatically rewritten in the same way as ::From:: (see below).
26137 If there's a rewriting rule for a particular header line, it is also applied to
26138 \Resent@-\ header lines of the same type. For example, a rule that rewrites
26139 ::From:: also rewrites ::Resent-From::.
26141 For local messages, if ::Sender:: is removed on input, ::Resent-Sender:: is also
26144 For a locally-submitted message,
26145 if there are any \Resent@-\ header lines but no ::Resent-Date::,
26146 ::Resent-From::, or ::Resent-Message-Id::, they are added as necessary. It is
26147 the contents of ::Resent-Message-Id:: (rather than ::Message-Id::) which are
26148 included in log lines in this case.
26150 The logic for adding ::Sender:: is duplicated for ::Resent-Sender:: when any
26151 \Resent@-\ header lines are present.
26155 .section The Auto-Submitted: header line
26156 Whenever Exim generates a bounce or a delay warning message, it includes the
26159 Auto-Submitted: auto-generated
26163 .section The Bcc: header line
26164 .index ::Bcc:: header line
26165 If Exim is called with the \-t-\ option, to take recipient addresses from a
26166 message's header, it removes any ::Bcc:: header line that may exist (after
26167 extracting its addresses). If \-t-\ is not present on the command line, any
26168 existing ::Bcc:: is not removed.
26170 .section The Date: header line
26171 .index ::Date:: header line
26172 If a locally-generated
26174 message has no ::Date:: header line, Exim adds one, using the current date and
26177 .section The Delivery-date: header line
26178 .index ::Delivery-date:: header line
26179 .index \delivery@_date@_remove\
26180 ::Delivery-date:: header lines are not part of the standard RFC 2822 header
26181 set. Exim can be configured to add them to the final delivery of messages. (See
26182 the generic \delivery@_date@_add\ transport option.) They should not be present
26183 in messages in transit. If the \delivery@_date@_remove\ configuration option is
26184 set (the default), Exim removes ::Delivery-date:: header lines from incoming
26187 .section The Envelope-to: header line
26188 .index ::Envelope-to:: header line
26189 .index \envelope@_to@_remove\
26190 ::Envelope-to:: header lines are not part of the standard RFC 2822 header set.
26191 Exim can be configured to add them to the final delivery of messages. (See the
26192 generic \envelope@_to@_add\ transport option.) They should not be present in
26193 messages in transit. If the \envelope@_to@_remove\ configuration option is set
26194 (the default), Exim removes ::Envelope-to:: header lines from incoming
26197 .section The From: header line
26198 .rset SECTthefrohea "~~chapter.~~section"
26199 .index ::From:: header line
26200 .index Sendmail compatibility||`From' line
26201 .index message||submission
26202 .index submission mode
26203 If a submission-mode message does not contain a ::From:: header line, Exim adds
26204 one if either of the following conditions is true:
26206 The envelope sender address is not empty (that is, this is not a bounce
26207 message). The added header line copies the envelope sender address.
26209 The SMTP session is authenticated and \$authenticated@_id$\ is not empty.
26212 If no domain is specified by the submission control, the local part is
26213 \$authenticated@_id$\ and the domain is \$qualify@_domain$\.
26215 If a non-empty domain is specified by the submission control, the local part is
26216 \$authenticated@_id$\, and the the domain is the specified domain.
26218 If an empty domain is specified by the submission control,
26219 \$authenticated@_id$\ is assumed to be the complete address.
26223 A non-empty envelope sender takes precedence.
26225 If a locally-generated incoming message does not contain a ::From:: header
26226 line, Exim adds one containing the sender's address. The calling user's login
26227 name and full name are used to construct the address, as described in section
26228 ~~SECTconstr. They are obtained from the password data by calling
26229 \*getpwuid()*\ (but see the \unknown@_login\ configuration option). The address
26230 is qualified with \qualify@_domain\.
26232 For compatibility with Sendmail, if an incoming, non-SMTP message has a
26233 ::From:: header line containing just the unqualified login name of the calling
26234 user, this is replaced by an address containing the user's login name and full
26235 name as described in section ~~SECTconstr.
26237 .section The Message-ID: header line
26238 .index ::Message-ID:: header line
26239 .index message||submission
26240 If a locally-generated or submission-mode incoming message does not contain a
26241 ::Message-ID:: or ::Resent-Message-ID:: header line, Exim adds one to the
26242 message. If there are any ::Resent-:: headers in the message, it creates
26243 ::Resent-Message-ID::. The id is constructed from Exim's internal message id,
26244 preceded by the letter E to ensure it starts with a letter, and followed by @@
26245 and the primary host name. Additional information can be included in this
26246 header line by setting the
26247 .index \message@_id@_header@_text\
26248 \message@_id@_header@_text\ and/or \message__id__header__domain\ options.
26251 .section The Received: header line
26252 .index ::Received:: header line
26253 A ::Received:: header line is added at the start of every message. The contents
26254 are defined by the \received@_header@_text\ configuration option, and Exim
26255 automatically adds a semicolon and a timestamp to the configured string.
26257 The ::Received:: header is generated as soon as the message's header lines have
26258 been received. At this stage, the timestamp in the ::Received:: header line is
26259 the time that the message started to be received. This is the value that is
26260 seen by the \\DATA\\ ACL and by the \*local@_scan()*\ function.
26262 Once a message is accepted, the timestamp in the ::Received:: header line is
26263 changed to the time of acceptance, which is (apart from a small delay while the
26264 -H spool file is written) the earliest time at which delivery could start.
26267 .section The Return-path: header line
26268 .index ::Return-path:: header line
26269 .index \return@_path@_remove\
26270 ::Return-path:: header lines are defined as something an MTA may insert when
26271 it does the final delivery of messages. (See the generic \return@_path@_add\
26272 transport option.) Therefore, they should not be present in messages in
26273 transit. If the \return@_path@_remove\ configuration option is set (the
26274 default), Exim removes ::Return-path:: header lines from incoming messages.
26277 .section The Sender: header line
26278 .rset SECTthesenhea "~~chapter.~~section"
26279 .index ::Sender:: header line
26280 .index message||submission
26281 For a locally-originated message from an untrusted user, Exim may remove an
26282 existing ::Sender:: header line, and it may add a new one. You can modify these
26283 actions by setting \local@_sender@_retain\ true or \local@_from@_check\ false.
26285 When a local message is received from an untrusted user and
26286 \local@_from@_check\ is true (the default), a check is made to see if the
26287 address given in the ::From:: header line is the correct (local) sender of the
26288 message. The address that is expected has the login name as the local part and
26289 the value of \qualify@_domain\ as the domain. Prefixes and suffixes for the
26290 local part can be permitted by setting \local@_from@_prefix\ and
26291 \local@_from@_suffix\ appropriately. If ::From:: does not contain the correct
26292 sender, a ::Sender:: line is added to the message.
26294 If you set \local@_from@_check\ false, this checking does not occur. However,
26295 the removal of an existing ::Sender:: line still happens, unless you also set
26296 \local@_sender@_retain\ to be true. It is not possible to set both of these
26297 options true at the same time.
26300 .index submission mode
26301 By default, no processing of ::Sender:: header lines is done for messages
26302 received over TCP/IP or for messages submitted by trusted users. However, when
26303 a message is received over TCP/IP in submission mode, and \sender@_retain\ is
26304 not specified on the submission control, the following processing takes place:
26306 First, any existing ::Sender:: lines are removed. Then, if the SMTP session is
26307 authenticated, and \$authenticated@_id$\ is not empty, a sender address is
26308 created as follows:
26310 If no domain is specified by the submission control, the local part is
26311 \$authenticated@_id$\ and the domain is \$qualify@_domain$\.
26313 If a non-empty domain is specified by the submission control, the local part is
26314 \$authenticated@_id$\, and the the domain is the specified domain.
26316 If an empty domain is specified by the submission control,
26317 \$authenticated@_id$\ is assumed to be the complete address.
26319 This address is compared with the address in the ::From:: header line. If they
26320 are different, a ::Sender:: header line containing the created address is
26321 added. Prefixes and suffixes for the local part in ::From:: can be permitted by
26322 setting \local@_from@_prefix\ and \local@_from@_suffix\ appropriately.
26326 .section Adding and removing header lines in routers and transports
26327 .index header lines||adding, in router or transport
26328 .index header lines||removing, in router or transport
26329 .rset SECTheadersaddrem "~~chapter.~~section"
26331 When a message is delivered, the addition and removal of header lines can be
26332 specified in a system filter, or on any of the routers and transports that
26333 process the message. Section ~~SECTaddremheasys contains details about
26334 modifying headers in a system filter.
26336 In contrast to what happens in a system filter, header modifications that are
26337 specified on routers and transports apply only to the particular recipient
26338 addresses that are being processed by those routers and transports. These
26339 changes do not actually take place until a copy of the message is being
26340 transported. Therefore, they do not affect the basic set of header lines, and
26341 they do not affect the values of the variables that refer to header lines.
26343 For both routers and transports, the result of expanding a \headers@_add\
26344 option must be in the form of one or more RFC 2822 header lines, separated by
26345 newlines (coded as `@\n'). For example:
26347 headers_add = X-added-header: added by $primary_hostname\n\
26348 X-added-second: another added header line
26350 Exim does not check the syntax of these added header lines.
26352 The result of expanding \headers@_remove\ must consist of a colon-separated
26353 list of header names. This is confusing, because header names themselves are
26354 often terminated by colons. In this case, the colons are the list separators,
26355 not part of the names. For example:
26357 headers_remove = return-receipt-to:acknowledge-to
26360 When \headers@_add\ or \headers@_remove\ is specified on a router, its value is
26361 expanded at routing time, and then associated with all addresses that are
26362 accepted by that router, and also with any new addresses that it generates. If
26363 an address passes through several routers as a result of aliasing or
26364 forwarding, the changes are cumulative.
26365 .index \unseen\ option
26366 However, this does not apply to multiple routers that result from the use of
26367 the \unseen\ option. Any header modifications that were specified by the
26368 `unseen' router or its predecessors apply only to the `unseen' delivery.
26370 Addresses that end up with different \headers@_add\ or \headers@_remove\
26371 settings cannot be delivered together in a batch, so a transport is always
26372 dealing with a set of addresses that have the same header-processing
26375 The transport starts by writing the original set of header lines that arrived
26376 with the message, possibly modified by the system filter. As it writes out
26377 these lines, it consults the list of header names that were attached to the
26378 recipient address(es) by \headers@_remove\ options in routers, and it also
26379 consults the transport's own \headers@_remove\ option. Header lines whose names
26380 are on either of these lists are not written out. If there are multiple
26381 instances of any listed header, they are all skipped.
26383 After the remaining original header lines have been written, new header
26384 lines that were specified by routers' \headers@_add\ options are written, in
26385 the order in which they were attached to the address. These are followed by any
26386 header lines specified by the transport's \headers@_add\ option.
26388 This way of handling header line modifications in routers and transports has
26389 the following consequences:
26391 The original set of header lines, possibly modified by the system filter,
26392 remains `visible', in the sense that the \$header@_$\\*xxx*\ variables refer to
26395 Header lines that are added by a router's
26396 \headers@_add\ option are not accessible by means of the \$header@_$\\*xxx*\
26397 expansion syntax in subsequent routers or the transport.
26399 Conversely, header lines that are specified for removal by \headers@_remove\ in
26400 a router remain visible to subsequent routers and the transport.
26402 Headers added to an address by \headers@_add\ in a router cannot be removed by
26403 a later router or by a transport.
26405 An added header can refer to the contents of an original header that is to be
26406 removed, even it has the same name as the added header. For example:
26408 headers_remove = subject
26409 headers_add = Subject: new subject (was: $h_subject:)
26413 \**Warning**\: The \headers@_add\ and \headers@_remove\ options cannot be used
26414 for a \%redirect%\ router that has the \one@_time\ option set.
26419 .section Constructed addresses
26420 .rset SECTconstr "~~chapter.~~section"
26421 .index address||constructed
26422 .index constructed address
26423 When Exim constructs a sender address for a locally-generated message, it uses
26426 <<user name>> <$$<<login>>@@<<qualify@_domain>>$$>
26430 Zaphod Beeblebrox <zaphod@end.univ.example>
26432 The user name is obtained from the \-F-\ command line option if set, or
26433 otherwise by looking up the calling user by \*getpwuid()*\ and extracting the
26434 `gecos' field from the password entry. If the `gecos' field contains an
26435 ampersand character, this is replaced by the login name with the first letter
26436 upper cased, as is conventional in a number of operating systems. See the
26437 \gecos@_name\ option for a way to tailor the handling of the `gecos' field. The
26438 \unknown@_username\ option can be used to specify user names in cases when
26439 there is no password file entry.
26441 In all cases, the user name is made to conform to RFC 2822 by quoting all or
26442 parts of it if necessary. In addition, if it contains any non-printing
26443 characters, it is encoded as described in RFC 2047, which defines a way of
26444 including non-ASCII characters in header lines.
26445 The value of the \headers@_charset\ option specifies the name of the encoding
26446 that is used (the characters are assumed to be in this encoding).
26447 The setting of \print@_topbitchars\ controls whether characters with the top
26448 bit set (that is, with codes greater than 127) count as printing characters or
26452 .section Case of local parts
26453 .index case of local parts
26454 .index local part||case of
26455 RFC 2822 states that the case of letters in the local parts of addresses cannot
26456 be assumed to be non-significant. Exim preserves the case of local parts of
26457 addresses, but by default it uses a lower-cased form when it is routing,
26458 because on most Unix systems, usernames are in lower case and case-insensitive
26459 routing is required. However, any particular router can be made to use the
26460 original case for local parts by setting the \caseful@_local@_part\ generic
26463 .index mixed-case login names
26464 If you must have mixed-case user names on your system, the best way to proceed,
26465 assuming you want case-independent handling of incoming email, is to set up
26466 your first router to convert incoming local parts in your domains to the
26467 correct case by means of a file lookup. For example:
26471 domains = +local_domains
26472 data = ${lookup{$local_part}cdb\
26473 {/etc/usercased.cdb}{$value}fail}\
26476 For this router, the local part is forced to lower case by the default action
26477 (\caseful@_local@_part\ is not set). The lower-cased local part is used to look
26478 up a new local part in the correct case. If you then set \caseful@_local@_part\
26479 on any subsequent routers which process your domains, they will operate on
26480 local parts with the correct case in a case-sensitive manner.
26483 .section Dots in local parts
26484 .index dot||in local part
26485 .index local part||dots in
26486 RFC 2822 forbids empty components in local parts. That is, an unquoted local
26487 part may not begin or end with a dot, nor have two consecutive dots in the
26488 middle. However, it seems that many MTAs do not enforce this, so Exim permits
26489 empty components for compatibility.
26492 .section Rewriting addresses
26493 .index rewriting||addresses
26494 Rewriting of sender and recipient addresses, and addresses in headers, can
26495 happen automatically, or as the result of configuration options, as described
26496 in chapter ~~CHAPrewrite. The headers that may be affected by this are ::Bcc::,
26497 ::Cc::, ::From::, ::Reply-To::, ::Sender::, and ::To::.
26499 Automatic rewriting includes qualification, as mentioned above. The other case
26500 in which it can happen is when an incomplete non-local domain is given. The
26501 routing process may cause this to be expanded into the full domain name. For
26502 example, a header such as
26506 might get rewritten as
26508 To: hare@teaparty.wonderland.fict.example
26510 Rewriting as a result of routing is the one kind of message processing that
26511 does not happen at input time, as it cannot be done until the address has
26514 Strictly, one should not do $it{any} deliveries of a message until all its
26515 addresses have been routed, in case any of the headers get changed as a
26516 result of routing. However, doing this in practice would hold up many
26517 deliveries for unreasonable amounts of time, just because one address could not
26518 immediately be routed. Exim therefore does not delay other deliveries when
26519 routing of one or more addresses is deferred.
26526 . ============================================================================
26527 .chapter SMTP processing
26528 .set runningfoot "smtp processing"
26529 .rset CHAPSMTP ~~chapter
26530 .index SMTP||processing details
26531 .index LMTP||processing details
26532 Exim supports a number of different ways of using the SMTP protocol, and its
26533 LMTP variant, which is an interactive protocol for transferring messages into a
26534 closed mail store application. This chapter contains details of how SMTP is
26535 processed. For incoming mail, the following are available:
26537 SMTP over TCP/IP (Exim daemon or \*inetd*\);
26539 SMTP over the standard input and output (the \-bs-\ option);
26541 Batched SMTP on the standard input (the \-bS-\ option).
26543 For mail delivery, the following are available:
26545 SMTP over TCP/IP (the \%smtp%\ transport);
26547 LMTP over TCP/IP (the \%smtp%\ transport with the \protocol\ option set to
26550 LMTP over a pipe to a process running in the local host (the \%lmtp%\
26553 Batched SMTP to a file or pipe (the \%appendfile%\ and \%pipe%\ transports with
26554 the \use@_bsmtp\ option set).
26556 \*Batched SMTP*\ is the name for a process in which batches of messages are
26557 stored in or read from files (or pipes), in a format in which SMTP commands are
26558 used to contain the envelope information.
26561 .section Outgoing SMTP and LMTP over TCP/IP
26562 .rset SECToutSMTPTCP "~~chapter.~~section"
26563 .index SMTP||outgoing over TCP/IP
26564 .index outgoing SMTP over TCP/IP
26565 .index LMTP||over TCP/IP
26566 .index outgoing LMTP over TCP/IP
26569 .index \\SIZE\\ option on \\MAIL\\ command
26570 Outgoing SMTP and LMTP over TCP/IP is implemented by the \%smtp%\ transport.
26571 The \protocol\ option selects which protocol is to be used, but the actual
26572 processing is the same in both cases.
26574 If, in response to its \\EHLO\\ command, Exim is told that the \\SIZE\\
26575 parameter is supported, it adds \\SIZE\\=<<n>> to each subsequent \\MAIL\\
26576 command. The value of <<n>> is the message size plus the value of the
26577 \size@_addition\ option (default 1024) to allow for additions to the message
26578 such as per-transport header lines, or changes made in a
26579 .index transport||filter
26580 .index filter||transport filter
26581 transport filter. If \size@_addition\ is set negative, the use of \\SIZE\\ is
26584 If the remote server advertises support for \\PIPELINING\\, Exim uses the
26585 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
26586 required for the transaction.
26588 If the remote server advertises support for the \\STARTTLS\\ command, and Exim
26589 was built to support TLS encryption, it tries to start a TLS session unless the
26590 server matches \hosts@_avoid@_tls\. See chapter ~~CHAPTLS for more details.
26592 If the remote server advertises support for the \\AUTH\\ command, Exim scans
26593 the authenticators configuration for any suitable client settings, as described
26594 in chapter ~~CHAPSMTPAUTH.
26596 .index carriage return
26598 Responses from the remote host are supposed to be terminated by CR followed by
26599 LF. However, there are known to be hosts that do not send CR characters, so in
26600 order to be able to interwork with such hosts, Exim treats LF on its own as a
26603 If a message contains a number of different addresses, all those with the same
26604 characteristics (for example, the same envelope sender) that resolve to the
26605 same set of hosts, in the same order, are sent in a single SMTP transaction,
26606 even if they are for different domains, unless there are more than the setting
26607 of the \max@_rcpts\ option in the \%smtp%\ transport allows, in which case they
26608 are split into groups containing no more than \max@_rcpts\ addresses each. If
26609 \remote@_max@_parallel\ is greater than one, such groups may be sent in
26610 parallel sessions. The order of hosts with identical MX values is not
26611 significant when checking whether addresses can be batched in this way.
26613 When the \%smtp%\ transport suffers a temporary failure that is not
26614 message-related, Exim updates its transport-specific database, which contains
26615 records indexed by host name that remember which messages are waiting for each
26616 particular host. It also updates the retry database with new retry times.
26617 .index hints database||retry keys
26618 Exim's retry hints are based on host name plus IP address, so if one address of
26619 a multi-homed host is broken, it will soon be skipped most of the time.
26620 See the next section for more detail about error handling.
26622 .index SMTP||passed connection
26623 .index SMTP||batching over TCP/IP
26624 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
26625 looks in the hints database for the transport to see if there are any queued
26626 messages waiting for the host to which it is connected. If it finds one, it
26627 creates a new Exim process using the \-MC-\ option (which can only be used by a
26628 process running as root or the Exim user) and passes the TCP/IP socket to it so
26629 that it can deliver another message using the same socket. The new process does
26630 only those deliveries that are routed to the connected host, and may in turn
26631 pass the socket on to a third process, and so on.
26633 The \connection@_max@_messages\ option of the \%smtp%\ transport can be used to
26634 limit the number of messages sent down a single TCP/IP connection.
26635 .index asterisk||after IP address
26636 The second and subsequent messages delivered down an existing connection are
26637 identified in the main log by the addition of an asterisk after the closing
26638 square bracket of the IP address.
26642 .section Errors in outgoing SMTP
26643 .rset SECToutSMTPerr "~~chapter.~~section"
26644 .index error||in outgoing SMTP
26645 .index SMTP||errors in outgoing
26647 Three different kinds of error are recognized for outgoing SMTP: host errors,
26648 message errors, and recipient errors.
26650 A host error is not associated with a particular message or with a
26651 particular recipient of a message. The host errors are:
26653 Connection refused or timed out,
26655 Any error response code on connection,
26657 Any error response code to \\EHLO\\ or \\HELO\\,
26659 Loss of connection at any time, except after `.',
26661 I/O errors at any time,
26663 Timeouts during the session, other than in response to \\MAIL\\, \\RCPT\\ or
26664 the `.' at the end of the data.
26666 For a host error, a permanent error response on connection, or in response to
26667 \\EHLO\\, causes all addresses routed to the host to be failed. Any other host
26668 error causes all addresses to be deferred, and retry data to be created for the
26669 host. It is not tried again, for any message, until its retry time arrives. If
26670 the current set of addresses are not all delivered in this run (to some
26671 alternative host), the message is added to the list of those waiting for this
26672 host, so if it is still undelivered when a subsequent successful delivery is
26673 made to the host, it will be sent down the same SMTP connection.
26675 .index message||error
26676 A message error is associated with a particular message when sent to a
26677 particular host, but not with a particular recipient of the message. The
26678 message errors are:
26680 Any error response code to \\MAIL\\, \\DATA\\, or the `.' that terminates
26683 Timeout after \\MAIL\\,
26686 or loss of connection after the `.' that terminates the data. A timeout after
26687 the \\DATA\\ command itself is treated as a host error, as is loss of
26688 connection at any other time.
26690 For a message error, a permanent error response (5$it{xx}) causes all addresses
26691 to be failed, and a delivery error report to be returned to the sender. A
26692 temporary error response (4$it{xx}), or one of the timeouts, causes all
26693 addresses to be deferred. Retry data is not created for the host, but instead,
26694 a retry record for the combination of host plus message id is created. The
26695 message is not added to the list of those waiting for this host. This ensures
26696 that the failing message will not be sent to this host again until the retry
26697 time arrives. However, other messages that are routed to the host are not
26698 affected, so if it is some property of the message that is causing the error,
26699 it will not stop the delivery of other mail.
26701 If the remote host specified support for the \\SIZE\\ parameter in its response
26702 to \\EHLO\\, Exim adds SIZE=$it{nnn} to the \\MAIL\\ command, so an
26703 over-large message will cause a message error because the error arrives as a
26704 response to \\MAIL\\.
26706 .index recipient||error
26707 A recipient error is associated with a particular recipient of a message. The
26708 recipient errors are:
26710 Any error response to \\RCPT\\,
26712 Timeout after \\RCPT\\.
26714 For a recipient error, a permanent error response (5$it{xx}) causes the
26715 recipient address to be failed, and a bounce message to be returned to the
26716 sender. A temporary error response (4$it{xx}) or a timeout causes the failing
26717 address to be deferred, and routing retry data to be created for it. This is
26718 used to delay processing of the address in subsequent queue runs, until its
26719 routing retry time arrives. This applies to all messages, but because it
26720 operates only in queue runs, one attempt will be made to deliver a new message
26721 to the failing address before the delay starts to operate. This ensures that,
26722 if the failure is really related to the message rather than the recipient
26723 (`message too big for this recipient' is a possible example), other messages
26724 have a chance of getting delivered. If a delivery to the address does succeed,
26725 the retry information gets cleared, so all stuck messages get tried again, and
26726 the retry clock is reset.
26728 The message is not added to the list of those waiting for this host. Use of the
26729 host for other messages is unaffected, and except in the case of a timeout,
26730 other recipients are processed independently, and may be successfully delivered
26731 in the current SMTP session. After a timeout it is of course impossible to
26732 proceed with the session, so all addresses get deferred. However, those other
26733 than the one that failed do not suffer any subsequent retry delays. Therefore,
26734 if one recipient is causing trouble, the others have a chance of getting
26735 through when a subsequent delivery attempt occurs before the failing
26736 recipient's retry time.
26739 In all cases, if there are other hosts (or IP addresses) available for the
26740 current set of addresses (for example, from multiple MX records), they are
26741 tried in this run for any undelivered addresses, subject of course to their
26742 own retry data. In other words, recipient error retry data does not take effect
26743 until the next delivery attempt.
26745 Some hosts have been observed to give temporary error responses to every
26746 \\MAIL\\ command at certain times (`insufficient space' has been seen). It
26747 would be nice if such circumstances could be recognized, and defer data for the
26748 host itself created, but this is not possible within the current Exim design.
26749 What actually happens is that retry data for every (host, message) combination
26752 The reason that timeouts after \\MAIL\\ and \\RCPT\\ are treated specially is
26753 that these can sometimes arise as a result of the remote host's verification
26754 procedures. Exim makes this assumption, and treats them as if a temporary error
26755 response had been received. A timeout after `.' is treated specially because it
26756 is known that some broken implementations fail to recognize the end of the
26757 message if the last character of the last line is a binary zero. Thus, it is
26758 helpful to treat this case as a message error.
26760 Timeouts at other times are treated as host errors, assuming a problem with the
26761 host, or the connection to it. If a timeout after \\MAIL\\, \\RCPT\\,
26762 or `.' is really a connection problem, the assumption is that at the next try
26763 the timeout is likely to occur at some other point in the dialogue, causing it
26764 then to be treated as a host error.
26766 There is experimental evidence that some MTAs drop the connection after the
26767 terminating `.' if they do not like the contents of the message for some
26768 reason, in contravention of the RFC, which indicates that a 5$it{xx} response
26769 should be given. That is why Exim treats this case as a message rather than a
26770 host error, in order not to delay other messages to the same host.
26775 .section Variable Envelope Return Paths (VERP)
26777 .index Variable Envelope Return Paths
26778 .index envelope sender
26779 Variable Envelope Return Paths -- see
26780 \?ftp://koobera.math.uic.edu/www/proto/verp.txt?\ -- can be supported in Exim
26781 by using the \return@_path\ generic transport option to rewrite the return path
26782 at transport time. For example, the following could be used on an \%smtp%\
26786 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
26787 {$1-request=$local_part%$domain@your.dom.example}fail}
26789 This has the effect of rewriting the return path (envelope sender) on all
26790 outgoing SMTP messages, if the local part of the original return path ends in
26791 `-request', and the domain is \*your.dom.example*\. The rewriting inserts the
26792 local part and domain of the recipient into the return path. Suppose, for
26793 example, that a message whose return path has been set to
26794 \*somelist-request@@your.dom.example*\ is sent to
26795 \*subscriber@@other.dom.example*\. In the transport, the return path is
26798 somelist-request=subscriber%other.dom.example@your.dom.example
26800 For this to work, you must arrange for outgoing messages that have `-request'
26801 in their return paths to have just a single recipient. This can be done by
26806 in the \%smtp%\ transport. Otherwise a single copy of a message might be
26807 addressed to several different recipients in the same domain, in which case
26808 \$local@_part$\ is not available (because it is not unique). Of course, if you
26809 do start sending out messages with this kind of return path, you must also
26810 configure Exim to accept the bounce messages that come back to those paths.
26811 Typically this would be done by setting an \local@_part@_suffix\ option for a
26814 The overhead incurred in using VERP depends very much on the size of the
26815 message, the number of recipient addresses that resolve to the same remote
26816 host, and the speed of the connection over which the message is being sent. If
26817 a lot of addresses resolve to the same host and the connection is slow, sending
26818 a separate copy of the message for each address may take substantially longer
26819 than sending a single copy with many recipients (for which VERP cannot be
26823 .section Incoming SMTP messages over TCP/IP
26824 .index SMTP||incoming over TCP/IP
26825 .index incoming SMTP over TCP/IP
26828 Incoming SMTP messages can be accepted in one of two ways: by running a
26829 listening daemon, or by using \*inetd*\. In the latter case, the entry in
26830 \(/etc/inetd.conf)\ should be like this:
26832 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
26834 Exim distinguishes between this case and the case of a locally running user
26835 agent using the \-bs-\ option by checking whether or not the standard input is
26836 a socket. When it is, either the port must be privileged (less than 1024), or
26837 the caller must be root or the Exim user. If any other user passes a socket
26838 with an unprivileged port number, Exim prints a message on the standard error
26839 stream and exits with an error code.
26841 By default, Exim does not make a log entry when a remote host connects or
26842 disconnects (either via the daemon or \*inetd*\), unless the disconnection is
26843 unexpected. It can be made to write such log entries by setting the
26844 \smtp@_connection\ log selector.
26846 .index carriage return
26848 Commands from the remote host are supposed to be terminated by CR followed by
26849 LF. However, there are known to be hosts that do not send CR characters. In
26850 order to be able to interwork with such hosts, Exim treats LF on its own as a
26852 Furthermore, because common code is used for receiving messages from all
26853 sources, a CR on its own is also interpreted as a line terminator. However, the
26854 sequence `CR, dot, CR' does not terminate incoming SMTP data.
26856 .index \\EHLO\\||invalid data
26857 .index \\HELO\\||invalid data
26858 One area that sometimes gives rise to problems concerns the \\EHLO\\ or
26859 \\HELO\\ commands. Some clients send syntactically invalid versions of these
26860 commands, which Exim rejects by default. (This is nothing to do with verifying
26861 the data that is sent, so \helo@_verify@_hosts\ is not relevant.) You can tell
26862 Exim not to apply a syntax check by setting \helo@_accept@_junk@_hosts\ to
26863 match the broken hosts that send invalid commands.
26865 .index \\SIZE\\ option on \\MAIL\\ command
26866 .index \\MAIL\\||\\SIZE\\ option
26867 The amount of disk space available is checked whenever \\SIZE\\ is received on
26868 a \\MAIL\\ command, independently of whether \message@_size@_limit\ or
26869 \check@_spool@_space\ is configured, unless \smtp__check__spool__space\ is set
26870 false. A temporary error is given if there is not enough space. If
26871 \check@_spool@_space\ is set, the check is for that amount of space plus the
26872 value given with \\SIZE\\, that is, it checks that the addition of the incoming
26873 message will not reduce the space below the threshold.
26875 When a message is successfully received, Exim includes the local message id in
26876 its response to the final `.' that terminates the data. If the remote host logs
26877 this text it can help with tracing what has happened to a message.
26879 The Exim daemon can limit the number of simultaneous incoming connections it is
26880 prepared to handle (see the \smtp@_accept@_max\ option). It can also limit the
26881 number of simultaneous incoming connections from a single remote host (see the
26882 \smtp@_accept@_max@_per@_host\ option). Additional connection attempts are
26883 rejected using the SMTP temporary error code 421.
26885 The Exim daemon does not rely on the \\SIGCHLD\\ signal to detect when a
26886 subprocess has finished, as this can get lost at busy times. Instead, it looks
26887 for completed subprocesses every time it wakes up. Provided there are other
26888 things happening (new incoming calls, starts of queue runs), completed
26889 processes will be noticed and tidied away. On very quiet systems you may
26890 sometimes see a `defunct' Exim process hanging about. This is not a problem; it
26891 will be noticed when the daemon next wakes up.
26893 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
26894 and can also be set up to reject SMTP calls from non-reserved hosts at times of
26895 high system load -- for details see the \smtp@_accept@_reserve\,
26896 \smtp@_load@_reserve\, and \smtp@_reserve@_hosts\ options. The load check
26897 applies in both the daemon and \*inetd*\ cases.
26899 Exim normally starts a delivery process for each message received, though this
26900 can be varied by means of the \-odq-\ command line option and the
26901 \queue@_only\, \queue@_only@_file\, and \queue@_only@_load\ options. The number
26902 of simultaneously running delivery processes started in this way from SMTP
26903 input can be limited by the \smtp__accept__queue\ and
26904 \smtp__accept__queue__per__connection\ options. When either limit is reached,
26905 subsequently received messages are just put on the input queue without starting
26906 a delivery process.
26908 The controls that involve counts of incoming SMTP calls (\smtp@_accept@_max\,
26909 \smtp@_accept@_queue\, \smtp__accept__reserve\) are not available when Exim is
26910 started up from the \*inetd*\ daemon, because in that case each connection is
26911 handled by an entirely independent Exim process. Control by load average is,
26912 however, available with \*inetd*\.
26914 Exim can be configured to verify addresses in incoming SMTP commands as they
26915 are received. See chapter ~~CHAPACL for details. It can also be configured to
26916 rewrite addresses at this time -- before any syntax checking is done. See
26917 section ~~SECTrewriteS.
26919 Exim can also be configured to limit the rate at which a client host submits
26920 \\MAIL\\ and \\RCPT\\ commands in a single SMTP session. See the
26921 \smtp@_ratelimit@_hosts\ option.
26924 .section Unrecognized SMTP commands
26925 .index SMTP||unrecognized commands
26926 If Exim receives more than \smtp@_max@_unknown@_commands\ unrecognized SMTP
26927 commands during a single SMTP connection, it drops the connection after sending
26928 the error response to the last command. The default value for
26929 \smtp@_max@_unknown@_commands\ is 3. This is a defence against some kinds of
26930 abuse that subvert web servers into making connections to SMTP ports; in these
26931 circumstances, a number of non-SMTP lines are sent first.
26933 .section Syntax and protocol errors in SMTP commands
26934 .index SMTP||syntax errors
26935 .index SMTP||protocol errors
26936 A syntax error is detected if an SMTP command is recognized, but there is
26937 something syntactically wrong with its data, for example, a malformed email
26938 address in a \\RCPT\\ command. Protocol errors include invalid command
26939 sequencing such as \\RCPT\\ before \\MAIL\\. If Exim receives more than
26940 \smtp@_max@_synprot@_errors\ such commands during a single SMTP connection, it
26941 drops the connection after sending the error response to the last command. The
26942 default value for \smtp__max__synprot__errors\ is 3. This is a defence against
26943 broken clients that loop sending bad commands (yes, it has been seen).
26946 .section Use of non-mail SMTP commands
26947 .index SMTP||non-mail commands
26948 The `non-mail' SMTP commands are those other than \\MAIL\\, \\RCPT\\, and
26949 \\DATA\\. Exim counts such commands, and drops the connection if there are too
26950 many of them in a single SMTP session. This action catches some
26951 denial-of-service attempts and things like repeated failing \\AUTH\\s, or a mad
26952 client looping sending \\EHLO\\. The global option \smtp@_accept@_max@_nonmail\
26953 defines what `too many' means. Its default value is 10.
26955 When a new message is expected, one occurrence of \\RSET\\ is not counted. This
26956 allows a client to send one \\RSET\\ between messages (this is not necessary,
26957 but some clients do it). Exim also allows one uncounted occurence of \\HELO\\
26958 or \\EHLO\\, and one occurrence of \\STARTTLS\\ between messages. After
26959 starting up a TLS session, another \\EHLO\\ is expected, and so it too is not
26962 The first occurrence of \\AUTH\\ in a connection, or immediately following
26963 \\STARTTLS\\ is also not counted. Otherwise, all commands other than \\MAIL\\,
26964 \\RCPT\\, \\DATA\\, and \\QUIT\\ are counted.
26966 You can control which hosts are subject to the limit set by
26967 \smtp@_accept@_max@_nonmail\ by setting
26968 \smtp@_accept@_max@_nonmail@_hosts\. The default value is \"$*$"\, which makes
26969 the limit apply to all hosts. This option means that you can exclude any
26970 specific badly-behaved hosts that you have to live with.
26974 .section The \\VRFY\\ and \\EXPN\\ commands
26975 When Exim receives a \\VRFY\\ or \\EXPN\\ command on a TCP/IP connection, it
26976 runs the ACL specified by \acl@_smtp@_vrfy\ or \acl@_smtp@_expn\ (as
26977 appropriate) in order to decide whether the command should be accepted or not.
26978 If no ACL is defined, the command is rejected.
26980 .index \\VRFY\\||processing
26981 When \\VRFY\\ is accepted, it runs exactly the same code as when Exim is
26982 called with the \-bv-\ option.
26983 .index \\EXPN\\||processing
26984 When \\EXPN\\ is accepted, a single-level expansion of the address is done.
26985 \\EXPN\\ is treated as an `address test' (similar to the \-bt-\ option) rather
26986 than a verification (the \-bv-\ option). If an unqualified local part is given
26987 as the argument to \\EXPN\\, it is qualified with \qualify@_domain\. Rejections
26988 of \\VRFY\\ and \\EXPN\\ commands are logged on the main and reject logs, and
26989 \\VRFY\\ verification failures are logged on the main log for consistency with
26993 .section The \\ETRN\\ command
26994 .rset SECTETRN "~~chapter.~~section"
26995 .index \\ETRN\\||processing
26996 RFC 1985 describes an SMTP command called \\ETRN\\ that is designed to
26997 overcome the security problems of the \\TURN\\ command (which has fallen into
26998 disuse). When Exim receives an \\ETRN\\ command on a TCP/IP connection, it runs
26999 the ACL specified by \acl@_smtp@_etrn\ in order to decide whether the command
27000 should be accepted or not. If no ACL is defined, the command is rejected.
27002 The \\ETRN\\ command is concerned with `releasing' messages that are awaiting
27003 delivery to certain hosts. As Exim does not organize its message queue by host,
27004 the only form of \\ETRN\\ that is supported by default is the one where the
27005 text starts with the `@#' prefix, in which case the remainder of the text is
27006 specific to the SMTP server. A valid \\ETRN\\ command causes a run of Exim with
27007 the \-R-\ option to happen, with the remainder of the \\ETRN\\ text as its
27008 argument. For example,
27016 which causes a delivery attempt on all messages with undelivered addresses
27017 containing the text `brigadoon'. When \smtp@_etrn@_serialize\ is set (the
27018 default), Exim prevents the simultaneous execution of more than one queue run
27019 for the same argument string as a result of an \\ETRN\\ command. This stops
27020 a misbehaving client from starting more than one queue runner at once.
27022 .index hints database||\\ETRN\\ serialization
27023 Exim implements the serialization by means of a hints database in which a
27024 record is written whenever a process is started by \\ETRN\\, and deleted when
27025 the process completes. However, Exim does not keep the SMTP session waiting for
27026 the \\ETRN\\ process to complete. Once \\ETRN\\ is accepted, the client is sent
27027 a `success' return code. Obviously there is scope for hints records to get left
27028 lying around if there is a system or program crash. To guard against this, Exim
27029 ignores any records that are more than six hours old.
27031 .index \smtp@_etrn@_command\
27032 For more control over what \\ETRN\\ does, the \smtp@_etrn@_command\ option can
27033 used. This specifies a command that is run whenever \\ETRN\\ is received,
27034 whatever the form of its argument. For
27037 smtp_etrn_command = /etc/etrn_command $domain $sender_host_address
27039 The string is split up into arguments which are independently expanded. The
27040 expansion variable \$domain$\ is set to the argument of the \\ETRN\\ command,
27041 and no syntax checking is done on the contents of this argument. Exim does not
27042 wait for the command to complete, so its status code is not checked. Exim runs
27043 under its own uid and gid when receiving incoming SMTP, so it is not possible
27044 for it to change them before running the command.
27047 .section Incoming local SMTP
27048 .index SMTP||local incoming
27049 Some user agents use SMTP to pass messages to their local MTA using the
27050 standard input and output, as opposed to passing the envelope on the command
27051 line and writing the message to the standard input. This is supported by the
27052 \-bs-\ option. This form of SMTP is handled in the same way as incoming
27053 messages over TCP/IP (including the use of ACLs), except that the envelope
27054 sender given in a \\MAIL\\ command is ignored unless the caller is trusted. In
27055 an ACL you can detect this form of SMTP input by testing for an empty host
27056 identification. It is common to have this as the first line in the ACL that
27057 runs for \\RCPT\\ commands:
27061 This accepts SMTP messages from local processes without doing any other tests.
27064 .section Outgoing batched SMTP
27065 .rset SECTbatchSMTP "~~chapter.~~section"
27066 .index SMTP||batched outgoing
27067 .index batched SMTP output
27068 Both the \%appendfile%\ and \%pipe%\ transports can be used for handling batched
27069 SMTP. Each has an option called \use@_bsmtp\ which causes messages to be output
27070 in BSMTP format. No SMTP responses are possible for this form of delivery. All
27071 it is doing is using SMTP commands as a way of transmitting the envelope along
27074 The message is written to the file or pipe preceded by the SMTP commands
27075 \\MAIL\\ and \\RCPT\\, and followed by a line containing a single dot. Lines in
27076 the message that start with a dot have an extra dot added. The SMTP command
27077 \\HELO\\ is not normally used. If it is required, the \message@_prefix\ option
27078 can be used to specify it.
27080 Because \%appendfile%\ and \%pipe%\ are both local transports, they accept only
27081 one recipient address at a time by default. However, you can arrange for them
27082 to handle several addresses at once by setting the \batch@_max\ option. When
27083 this is done for BSMTP, messages may contain multiple \\RCPT\\ commands. See
27084 chapter ~~CHAPbatching for more details.
27086 When one or more addresses are routed to a BSMTP transport by a router that
27087 sets up a host list, the name of the first host on the list is available to the
27088 transport in the variable \$host$\. Here is an example of such a transport and
27093 driver = manualroute
27094 transport = smtp_appendfile
27095 route_list = domain.example batch.host.example
27099 driver = appendfile
27100 directory = /var/bsmtp/$host
27105 This causes messages addressed to \*domain.example*\ to be written in BSMTP
27106 format to \(/var/bsmtp/batch.host.example)\, with only a single copy of each
27107 message (unless there are more than 1000 recipients).
27110 .section Incoming batched SMTP
27111 .rset SECTincomingbatchedSMTP "~~chapter.~~section"
27112 .index SMTP||batched incoming
27113 .index batched SMTP input
27114 The \-bS-\ command line option causes Exim to accept one or more messages by
27115 reading SMTP on the standard input, but to generate no responses. If the caller
27116 is trusted, the senders in the \\MAIL\\ commands are believed; otherwise the
27117 sender is always the caller of Exim. Unqualified senders and receivers are not
27118 rejected (there seems little point) but instead just get qualified. \\HELO\\
27119 and \\EHLO\\ act as \\RSET\\; \\VRFY\\, \\EXPN\\, \\ETRN\\ and \\HELP\\, act
27120 as \\NOOP\\; \\QUIT\\ quits.
27122 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
27123 In this respect it is like non-SMTP local input.
27125 If an error is detected while reading a message, including a missing `.' at
27126 the end, Exim gives up immediately. It writes details of the error to the
27127 standard output in a stylized way that the calling program should be able to
27128 make some use of automatically, for example:
27130 554 Unexpected end of file
27131 Transaction started in line 10
27132 Error detected in line 14
27134 It writes a more verbose version, for human consumption, to the standard error
27137 An error was detected while processing a file of BSMTP input.
27138 The error message was:
27140 501 '>' missing at end of address
27142 The SMTP transaction started in line 10.
27143 The error was detected in line 12.
27144 The SMTP command at fault was:
27146 rcpt to:<malformed@in.com.plete
27148 1 previous message was successfully processed.
27149 The rest of the batch was abandoned.
27151 The return code from Exim is zero only if there were no errors. It is 1 if some
27152 messages were accepted before an error was detected, and 2 if no messages were
27161 . ============================================================================
27162 .chapter Customizing bounce and warning messages
27163 .set runningfoot "customizing messages"
27164 .rset CHAPemsgcust "~~chapter"
27165 When a message fails to be delivered, or remains on the queue for more than a
27166 configured amount of time, Exim sends a message to the original sender, or
27167 to an alternative configured address. The text of these messages is built into
27168 the code of Exim, but it is possible to change it, either by adding a single
27169 string, or by replacing each of the paragraphs by text supplied in a file.
27171 The ::From:: and ::To:: header lines are automatically generated; you can cause
27172 a ::Reply-To:: line to be added by setting the \errors@_reply@_to\ option. Exim
27175 Auto-Submitted: auto-generated
27177 to all warning and bounce messages,
27179 .section Customizing bounce messages
27180 .index customizing||bounce message
27181 .index bounce message||customizing
27182 If \bounce@_message@_text\ is set, its contents are included in the default
27183 message immediately after `This message was created automatically by mail
27184 delivery software.' The string is not expanded. It is not used if
27185 \bounce@_message@_file\ is set.
27187 When \bounce@_message@_file\ is set, it must point to a template file for
27188 constructing error messages. The file consists of a series of text items,
27189 separated by lines consisting of exactly four asterisks. If the file cannot be
27190 opened, default text is used and a message is written to the main and panic
27191 logs. If any text item in the file is empty, default text is used for that
27194 Each item of text that is read from the file is expanded, and there are two
27195 expansion variables which can be of use here: \$bounce@_recipient$\ is set to
27196 the recipient of an error message while it is being created, and
27197 \$return@_size@_limit$\ contains the value of the \return@_size@_limit\ option,
27198 rounded to a whole number.
27200 The items must appear in the file in the following order:
27202 The first item is included in the headers, and should include at least a
27203 ::Subject:: header. Exim does not check the syntax of these headers.
27205 The second item forms the start of the error message. After it, Exim lists the
27206 failing addresses with their error messages.
27208 The third item is used to introduce any text from pipe transports that is to be
27209 returned to the sender. It is omitted if there is no such text.
27211 The fourth item is used to introduce the copy of the message that is returned
27212 as part of the error report.
27214 The fifth item is added after the fourth one if the returned message is
27215 truncated because it is bigger than \return@_size@_limit\.
27217 The sixth item is added after the copy of the original message.
27219 The default state (\bounce@_message@_file\ unset) is equivalent to the
27220 following file, in which the sixth item is empty. The ::Subject:: line has been
27221 split into two here in order to fit it on the page:
27232 Subject: Mail delivery failed
27233 ${if eq{$sender_address}{$bounce_recipient}{: returning message to sender}}
27235 This message was created automatically by mail delivery software.
27237 A message ${if eq{$sender_address}{$bounce_recipient}{that you sent }{sent by
27241 }}could not be delivered to all of its recipients.
27242 The following address(es) failed:
27244 The following text was generated during the delivery attempt(s):
27246 ------ This is a copy of the message, including all the headers. ------
27248 ------ The body of the message is $message_size characters long; only the first
27249 ------ $return_size_limit or so are included here.
27256 .section Customizing warning messages
27257 .rset SECTcustwarn "~~chapter.~~section"
27258 .index customizing||warning message
27259 .index warning of delay||customizing the message
27261 \warn@_message@_file\
27262 can be pointed at a template file for use when
27263 warnings about message delays are created. In this case there are only three
27266 The first item is included in the headers, and should include at least a
27267 ::Subject:: header. Exim does not check the syntax of these headers.
27269 The second item forms the start of the warning message. After it, Exim lists
27270 the delayed addresses.
27272 The third item then ends the message.
27274 The default state is equivalent to the following file, except that the line
27275 starting `A message' has been split here, in order to fit it on the page:
27287 Subject: Warning: message $message_id delayed $warn_message_delay
27289 This message was created automatically by mail delivery software.
27291 A message ${if eq{$sender_address}{$warn_message_recipients}
27292 {that you sent }{sent by
27296 }}has not been delivered to all of its recipients after
27297 more than $warn_message_delay on the queue on $primary_hostname.
27300 The message identifier is: $message_id
27301 The subject of the message is: $h_subject
27302 The date of the message is: $h_date
27304 The following address(es) have not yet been delivered:
27306 No action is required on your part. Delivery attempts will continue for
27307 some time, and this warning may be repeated at intervals if the message
27308 remains undelivered. Eventually the mail delivery software will give up,
27309 and when that happens, the message will be returned to you.
27314 except that in the default state the subject and date lines are omitted if no
27315 appropriate headers exist. During the expansion of this file,
27316 \$warn@_message@_delay$\
27317 is set to the delay time in one of the forms `<<n>> minutes'
27318 or `<<n>> hours', and
27319 \$warn@_message@_recipients$\
27320 contains a list of recipients for the warning message. There may be more than
27321 one if there are multiple addresses with different \errors@_to\ settings on the
27322 routers that handled them.
27330 . ============================================================================
27331 .chapter Some common configuration requirements
27332 .set runningfoot "common configuration requirements"
27333 .rset CHAPcomconreq "~~chapter"
27334 This chapter discusses some configuration requirements that seem to be fairly
27335 common. More examples and discussion can be found in the Exim book.
27338 .section Sending mail to a smart host
27339 .index smart host||example router
27340 If you want to send all mail for non-local domains to a `smart host', you
27341 should replace the default \%dnslookup%\ router with a router which does the
27342 routing explicitly:
27344 send_to_smart_host:
27345 driver = manualroute
27346 route_list = !+local_domains smart.host.name
27347 transport = remote_smtp
27349 You can use the smart host's IP address instead of the name if you wish.
27351 If you are using Exim only to submit messages to a smart host, and not for
27352 receiving incoming messages, you can arrange for it to do the submission
27353 synchronously by setting the \mua@_wrapper\ option (see chapter
27354 ~~CHAPnonqueueing).
27358 .section Using Exim to handle mailing lists
27359 .rset SECTmailinglists "~~chapter.~~section"
27360 .index mailing lists
27361 Exim can be used to run simple mailing lists, but for large and/or complicated
27362 requirements, the use of additional specialized mailing list software such as
27363 Majordomo or Mailman is recommended.
27365 The \%redirect%\ router can be used to handle mailing lists where each list
27366 is maintained in a separate file, which can therefore be managed by an
27367 independent manager. The \domains\ router option can be used to run these
27368 lists in a separate domain from normal mail. For example:
27372 domains = lists.example
27373 file = /usr/lists/$local_part
27376 errors_to = $local_part-request@lists.example
27379 This router is skipped for domains other than \*lists.example*\. For addresses
27380 in that domain, it looks for a file that matches the local part. If there is no
27381 such file, the router declines, but because \no@_more\ is set, no subsequent
27382 routers are tried, and so the whole delivery fails.
27384 The \forbid@_pipe\ and \forbid@_file\ options prevent a local part from being
27385 expanded into a file name or a pipe delivery, which is usually inappropriate in
27388 .index \errors@_to\
27389 The \errors@_to\ option specifies that any delivery errors caused by addresses
27390 taken from a mailing list are to be sent to the given address rather than the
27391 original sender of the message. However, before acting on this, Exim verifies
27392 the error address, and ignores it if verification fails.
27394 For example, using the configuration above, mail sent to
27395 \*dicts@@lists.example*\ is passed on to those addresses contained in
27396 \(/usr/lists/dicts)\, with error reports directed to
27397 \*dicts-request@@lists.example*\, provided that this address can be verified.
27398 There could be a file called \(/usr/lists/dicts-request)\ containing
27399 the address(es) of this particular list's manager(s), but other approaches,
27400 such as setting up an earlier router (possibly using the \local@_part@_prefix\
27401 or \local@_part@_suffix\ options) to handle addresses of the form \owner-xxx\
27402 or \xxx-request\, are also possible.
27405 .section Syntax errors in mailing lists
27406 .index mailing lists||syntax errors in
27407 If an entry in redirection data contains a syntax error, Exim normally defers
27408 delivery of the original address. That means that a syntax error in a mailing
27409 list holds up all deliveries to the list. This may not be appropriate when a
27410 list is being maintained automatically from data supplied by users, and the
27411 addresses are not rigorously checked.
27413 If the \skip@_syntax@_errors\ option is set, the \%redirect%\ router just skips
27414 entries that fail to parse, noting the incident in the log. If in addition
27415 \syntax@_errors@_to\ is set to a verifiable address, a message is sent to it
27416 whenever a broken address is skipped. It is usually appropriate to set
27417 \syntax@_errors@_to\ to the same address as \errors@_to\.
27420 .section Re-expansion of mailing lists
27421 .index mailing lists||re-expansion of
27422 Exim remembers every individual address to which a message has been delivered,
27423 in order to avoid duplication, but it normally stores only the original
27424 recipient addresses with a message. If all the deliveries to a mailing list
27425 cannot be done at the first attempt, the mailing list is re-expanded when the
27426 delivery is next tried. This means that alterations to the list are taken into
27427 account at each delivery attempt, so addresses that have been added to
27428 the list since the message arrived will therefore receive a copy of the
27429 message, even though it pre-dates their subscription.
27431 If this behaviour is felt to be undesirable, the \one@_time\ option can be set
27432 on the \%redirect%\ router. If this is done, any addresses generated by the
27433 router that fail to deliver at the first attempt are added to the message as
27434 `top level' addresses, and the parent address that generated them is marked
27435 `delivered'. Thus, expansion of the mailing list does not happen again at the
27436 subsequent delivery attempts. The disadvantage of this is that if any of the
27437 failing addresses are incorrect, correcting them in the file has no effect on
27438 pre-existing messages.
27440 The original top-level address is remembered with each of the generated
27441 addresses, and is output in any log messages. However, any intermediate parent
27442 addresses are not recorded. This makes a difference to the log only if the
27443 \all@_parents\ selector is set, but for mailing lists there is normally only
27444 one level of expansion anyway.
27447 .section Closed mailing lists
27448 .index mailing lists||closed
27449 The examples so far have assumed open mailing lists, to which anybody may
27450 send mail. It is also possible to set up closed lists, where mail is accepted
27451 from specified senders only. This is done by making use of the generic
27452 \senders\ option to restrict the router that handles the list.
27454 The following example uses the same file as a list of recipients and as a list
27455 of permitted senders. It requires three routers:
27459 domains = lists.example
27460 local_part_suffix = -request
27461 file = /usr/lists/$local_part$local_part_suffix
27466 domains = lists.example
27467 senders = ${if exists {/usr/lists/$local_part}\
27468 {lsearch;/usr/lists/$local_part}{*}}
27469 file = /usr/lists/$local_part
27472 errors_to = $local_part-request@lists.example
27477 domains = lists.example
27479 data = :fail: $local_part@lists.example is a closed mailing list
27481 All three routers have the same \domains\ setting, so for any other domains,
27482 they are all skipped. The first router runs only if the local part ends in
27483 \@-request\. It handles messages to the list manager(s) by means of an open
27486 The second router runs only if the \senders\ precondition is satisfied. It
27487 checks for the existence of a list that corresponds to the local part, and then
27488 checks that the sender is on the list by means of a linear search. It is
27489 necessary to check for the existence of the file before trying to search it,
27490 because otherwise Exim thinks there is a configuration error. If the file does
27491 not exist, the expansion of \senders\ is $*$, which matches all senders. This
27492 means that the router runs, but because there is no list, declines, and
27493 \no@_more\ ensures that no further routers are run. The address fails with an
27494 `unrouteable address' error.
27496 The third router runs only if the second router is skipped, which happens when
27497 a mailing list exists, but the sender is not on it. This router forcibly fails
27498 the address, giving a suitable error message.
27502 .section Virtual domains
27503 .rset SECTvirtualdomains "~~chapter.~~section"
27504 .index virtual domains
27505 .index domain||virtual
27506 The phrase \*virtual domain*\ is unfortunately used with two rather different
27509 A domain for which there are no real mailboxes; all valid local parts are
27510 aliases for other email addresses. Common examples are organizational
27511 top-level domains and `vanity' domains.
27513 One of a number of independent domains that are all handled by the same host,
27514 with mailboxes on that host, but where the mailbox owners do not necessarily
27515 have login accounts on that host.
27517 The first usage is probably more common, and does seem more `virtual' than the
27518 second. This kind of domain can be handled in Exim with a straightforward
27519 aliasing router. One approach is to create a separate alias file for each
27520 virtual domain. Exim can test for the existence of the alias file to determine
27521 whether the domain exists. The \%dsearch%\ lookup type is useful here, leading
27522 to a router of this form:
27526 domains = dsearch;/etc/mail/virtual
27527 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
27530 The \domains\ option specifies that the router is to be skipped, unless there
27531 is a file in the \(/etc/mail/virtual)\ directory whose name is the same as the
27532 domain that is being processed. When the router runs, it looks up the local
27533 part in the file to find a new address (or list of addresses). The \no@_more\
27534 setting ensures that if the lookup fails (leading to \data\ being an empty
27535 string), Exim gives up on the address without trying any subsequent routers.
27537 This one router can handle all the virtual domains because the alias file names
27538 follow a fixed pattern. Permissions can be arranged so that appropriate people
27539 can edit the different alias files. A successful aliasing operation results in
27540 a new envelope recipient address, which is then routed from scratch.
27542 The other kind of `virtual' domain can also be handled in a straightforward
27543 way. One approach is to create a file for each domain containing a list of
27544 valid local parts, and use it in a router like this:
27548 domains = dsearch;/etc/mail/domains
27549 local_parts = lsearch;/etc/mail/domains/$domain
27550 transport = my_mailboxes
27552 The address is accepted if there is a file for the domain, and the local part
27553 can be found in the file. The \domains\ option is used to check for the file's
27554 existence because \domains\ is tested before the \local@_parts\ option (see
27555 section ~~SECTrouprecon). You can't use \require@_files\, because that option
27556 is tested after \local@_parts\. The transport is as follows:
27559 driver = appendfile
27560 file = /var/mail/$domain/$local_part
27563 This uses a directory of mailboxes for each domain. The \user\ setting is
27564 required, to specify which uid is to be used for writing to the mailboxes.
27566 The configuration shown here is just one example of how you might support this
27567 requirement. There are many other ways this kind of configuration can be set
27568 up, for example, by using a database instead of separate files to hold all the
27569 information about the domains.
27572 .section Multiple user mailboxes
27573 .rset SECTmulbox "~~chapter.~~section"
27574 .index multiple mailboxes
27575 .index mailbox||multiple
27576 .index local part||prefix
27577 .index local part||suffix
27578 Heavy email users often want to operate with multiple mailboxes, into which
27579 incoming mail is automatically sorted. A popular way of handling this is to
27580 allow users to use multiple sender addresses, so that replies can easily be
27581 identified. Users are permitted to add prefixes or suffixes to their local
27582 parts for this purpose. The wildcard facility of the generic router options
27583 \local@_part@_prefix\ and \local@_part@_suffix\ can be used for this. For
27584 example, consider this router:
27589 file = $home/.forward
27590 local_part_suffix = -*
27591 local_part_suffix_optional
27594 It runs a user's \(.forward)\ file for all local parts of the form
27595 \*username-$*$*\. Within the filter file the user can distinguish different
27596 cases by testing the variable \$local@_part@_suffix$\. For example:
27598 if $local_part_suffix contains -special then
27599 save /home/$local_part/Mail/special
27602 If the filter file does not exist, or does not deal with such addresses, they
27603 fall through to subsequent routers, and, assuming no subsequent use of the
27604 \local@_part@_suffix\ option is made, they presumably fail. Thus, users have
27605 control over which suffixes are valid.
27607 Alternatively, a suffix can be used to trigger the use of a different
27608 \(.forward)\ file -- which is the way a similar facility is implemented in
27614 file = $home/.forward$local_part_suffix
27615 local_part_suffix = -*
27616 local_part_suffix_optional
27619 If there is no suffix, \(.forward)\ is used; if the suffix is \*-special*\, for
27620 example, \(.forward-special)\ is used. Once again, if the appropriate file
27621 does not exist, or does not deal with the address, it is passed on to
27622 subsequent routers, which could, if required, look for an unqualified
27623 \(.forward)\ file to use as a default.
27626 .section Simplified vacation processing
27627 .index vacation processing
27628 The traditional way of running the \*vacation*\ program is for a user to set up
27629 a pipe command in a \(.forward)\ file
27630 (see section ~~SECTspecitredli for syntax details).
27631 This is prone to error by inexperienced users. There are two features of Exim
27632 that can be used to make this process simpler for users:
27634 A local part prefix such as `vacation-' can be specified on a router which
27635 can cause the message to be delivered directly to the \*vacation*\ program, or
27636 alternatively can use Exim's \%autoreply%\ transport. The contents of a user's
27637 \(.forward)\ file are then much simpler. For example:
27639 spqr, vacation-spqr
27642 The \require@_files\ generic router option can be used to trigger a
27643 vacation delivery by checking for the existence of a certain file in the
27644 user's home directory. The \unseen\ generic option should also be used, to
27645 ensure that the original delivery also proceeds. In this case, all the user has
27646 to do is to create a file called, say, \(.vacation)\, containing a vacation
27649 Another advantage of both these methods is that they both work even when the
27650 use of arbitrary pipes by users is locked out.
27653 .section Taking copies of mail
27654 .index message||copying every
27655 Some installations have policies that require archive copies of all messages to
27656 be made. A single copy of each message can easily be taken by an appropriate
27657 command in a system filter, which could, for example, use a different file for
27658 each day's messages.
27660 There is also a shadow transport mechanism that can be used to take copies of
27661 messages that are successfully delivered by local transports, one copy per
27662 delivery. This could be used, $it{inter alia}, to implement automatic
27663 notification of delivery by sites that insist on doing such things.
27666 .section Intermittently connected hosts
27667 .index intermittently connected hosts
27668 It has become quite common (because it is cheaper) for hosts to connect to the
27669 Internet periodically rather than remain connected all the time. The normal
27670 arrangement is that mail for such hosts accumulates on a system that is
27671 permanently connected.
27673 Exim was designed for use on permanently connected hosts, and so it is not
27674 particularly well-suited to use in an intermittently connected environment.
27675 Nevertheless there are some features that can be used.
27677 .section Exim on the upstream server host
27678 It is tempting to arrange for incoming mail for the intermittently connected
27679 host to remain on Exim's queue until the client connects. However, this
27680 approach does not scale very well. Two different kinds of waiting message are
27681 being mixed up in the same queue -- those that cannot be delivered because of
27682 some temporary problem, and those that are waiting for their destination host
27683 to connect. This makes it hard to manage the queue, as well as wasting
27684 resources, because each queue runner scans the entire queue.
27686 A better approach is to separate off those messages that are waiting for an
27687 intermittently connected host. This can be done by delivering these messages
27688 into local files in batch SMTP, `mailstore', or other envelope-preserving
27689 format, from where they are transmitted by other software when their
27690 destination connects. This makes it easy to collect all the mail for one host
27691 in a single directory, and to apply local timeout rules on a per-message basis
27694 On a very small scale, leaving the mail on Exim's queue can be made to work. If
27695 you are doing this, you should configure Exim with a long retry period for the
27696 intermittent host. For example:
27698 cheshire.wonderland.fict.example * F,5d,24h
27700 This stops a lot of failed delivery attempts from occurring, but Exim remembers
27701 which messages it has queued up for that host. Once the intermittent host comes
27702 online, forcing delivery of one message (either by using the \-M-\ or \-R-\
27703 options, or by using the \\ETRN\\ SMTP command (see section ~~SECTETRN)
27704 causes all the queued up messages to be delivered, often down a single SMTP
27705 connection. While the host remains connected, any new messages get delivered
27708 If the connecting hosts do not have fixed IP addresses, that is, if a host is
27709 issued with a different IP address each time it connects, Exim's retry
27710 mechanisms on the holding host get confused, because the IP address is normally
27711 used as part of the key string for holding retry information. This can be
27712 avoided by unsetting \retry__include__ip__address\ on the \%smtp%\ transport.
27713 Since this has disadvantages for permanently connected hosts, it is best to
27714 arrange a separate transport for the intermittently connected ones.
27717 .section Exim on the intermittently connected client host
27718 The value of \smtp@_accept@_queue@_per@_connection\ should probably be
27719 increased, or even set to zero (that is, disabled) on the intermittently
27720 connected host, so that all incoming messages down a single connection get
27721 delivered immediately.
27723 .index SMTP||passed connection
27724 .index SMTP||multiple deliveries
27725 .index multiple SMTP deliveries
27726 Mail waiting to be sent from an intermittently connected host will probably
27727 not have been routed, because without a connection DNS lookups are not
27728 possible. This means that if a normal queue run is done at connection time,
27729 each message is likely to be sent in a separate SMTP session. This can be
27730 avoided by starting the queue run with a command line option beginning with
27731 \-qq-\ instead of \-q-\. In this case, the queue is scanned twice. In the first
27732 pass, routing is done but no deliveries take place. The second pass is a normal
27733 queue run; since all the messages have been previously routed, those destined
27734 for the same host are likely to get sent as multiple deliveries in a single
27743 . ============================================================================
27744 .chapter Using Exim as a non-queueing client
27745 .set runningfoot "non-queueing client"
27746 .rset CHAPnonqueueing "~~chapter"
27747 .index client, non-queueing
27748 .index smart host||queueing, suppressing
27750 On a personal computer, it is a common requirement for all
27751 email to be sent to a `smart host'. There are plenty of MUAs that can be
27752 configured to operate that way, for all the popular operating systems.
27753 However, there are some MUAs for Unix-like systems that cannot be so
27754 configured: they submit messages using the command line interface of
27755 \(/usr/sbin/sendmail)\. Furthermore, utility programs such as \*cron*\ submit
27758 If the personal computer runs continuously, there is no problem, because it can
27759 run a conventional MTA that handles delivery to the smart host, and deal with
27760 any delays via its queueing mechanism. However, if the computer does not run
27761 continuously or runs different operating systems at different times, queueing
27762 email is not desirable.
27764 There is therefore a requirement for something that can provide the
27765 \(/usr/sbin/sendmail)\ interface but deliver messages to a smart host without
27766 any queueing or retrying facilities. Furthermore, the delivery to the smart
27767 host should be synchronous, so that if it fails, the sending MUA is immediately
27768 informed. In other words, we want something that extends an MUA that submits
27769 to a local MTA via the command line so that it behaves like one that submits
27770 to a remote smart host using TCP/SMTP.
27772 There are a number of applications (for example, there is one called \*ssmtp*\)
27773 that do this job. However, people have found them to be lacking in various
27774 ways. For instance, you might want to allow aliasing and forwarding to be done
27775 before sending a message to the smart host.
27777 Exim already had the necessary infrastructure for doing this job. Just a few
27778 tweaks were needed to make it behave as required, though it is somewhat of an
27779 overkill to use a fully-featured MTA for this purpose.
27781 .index \mua@_wrapper\
27782 There is a Boolean global option called \mua@_wrapper\, defaulting false.
27783 Setting \mua@_wrapper\ true causes Exim to run in a special mode where it
27784 assumes that it is being used to `wrap' a command-line MUA in the manner
27785 just described. As well as setting \mua@_wrapper\, you also need to provide a
27786 compatible router and transport configuration. Typically there will be just one
27787 router and one transport, sending everything to a smart host.
27789 When run in MUA wrapping mode, the behaviour of Exim changes in the
27792 A daemon cannot be run, nor will Exim accept incoming messages from \*inetd*\.
27793 In other words, the only way to submit messages is via the command line.
27795 Each message is synchonously delivered as soon as it is received (\-odi-\ is
27796 assumed). All queueing options (\queue@_only\, \queue@_smtp@_domains\,
27797 \control\ in an ACL, etc.) are quietly ignored. The Exim reception process does
27798 not finish until the delivery attempt is complete. If the delivery is
27799 successful, a zero return code is given.
27801 Address redirection is permitted, but the final routing for all addresses must
27802 be to the same remote transport, and to the same list of hosts. Furthermore,
27803 the return address (envelope sender) must be the same for all recipients, as
27804 must any added or deleted header lines. In other words, it must be possible to
27805 deliver the message in a single SMTP transaction, however many recipients there
27808 If these conditions are not met, or if routing any address results in a failure
27809 or defer status, or if Exim is unable to deliver all the recipients
27810 successfully to one of the smart hosts, delivery of the entire message fails.
27812 Because no queueing is allowed, all failures are treated as permanent; there is
27813 no distinction between 4\*xx*\ and 5\*xx*\ SMTP response codes from the smart
27814 host. Furthermore, because only a single yes/no response can be given to the
27815 caller, it is not possible to deliver to some recipients and not others. If
27816 there is an error (temporary or permanent) for any recipient, all are failed.
27818 If more than one smart host is listed, Exim will try another host after a
27819 connection failure or a timeout, in the normal way. However, if this kind of
27820 failure happens for all the hosts, the delivery fails.
27822 When delivery fails, an error message is written to the standard error stream
27823 (as well as to Exim's log), and Exim exits to the caller with a return code
27824 value 1. The message is expunged from Exim's spool files. No bounce messages
27825 are ever generated.
27827 No retry data is maintained, and any retry rules are ignored.
27829 A number of Exim options are overridden: \deliver@_drop@_privilege\ is forced
27830 true, \max@_rcpt\ in the smtp transport is forced to `unlimited',
27831 \remote@_max@_parallel\ is forced to one, and fallback hosts are ignored.
27833 The overall effect is that Exim makes a single synchronous attempt to deliver
27834 the message, failing if there is any kind of problem. Because no local
27835 deliveries are done and no daemon can be run, Exim does not need root
27836 privilege. It should be possible to run it setuid to \*exim*\ instead of setuid
27837 to \*root*\. See section ~~SECTrunexiwitpri for a general discussion about the
27838 advantages and disadvantages of running without root privilege.
27847 . ============================================================================
27849 .set runningfoot "log files"
27850 .rset CHAPlog "~~chapter"
27851 .index log||types of
27852 .index log||general description
27853 Exim writes three different logs, referred to as the main log, the reject log,
27857 The main log records the arrival of each message and each delivery in a single
27858 line in each case. The format is as compact as possible, in an attempt to keep
27859 down the size of log files. Two-character flag sequences make it easy to pick
27860 out these lines. A number of other events are recorded in the main log. Some of
27861 them are optional, in which case the \log@_selector\ option controls whether
27862 they are included or not. A Perl script called \*eximstats*\, which does simple
27863 analysis of main log files, is provided in the Exim distribution (see section
27867 The reject log records information from messages that are rejected as a result
27868 of a configuration option (that is, for policy reasons).
27869 The first line of each rejection is a copy of the line that is also written to
27870 the main log. Then, if the message's header has been read at the time the log
27871 is written, its contents are written to this log. Only the original header
27872 lines are available; header lines added by ACLs are not logged. You can use the
27873 reject log to check that your policy controls are working correctly; on a busy
27874 host this may be easier than scanning the main log for rejection messages. You
27875 can suppress the writing of the reject log by setting \write@_rejectlog\ false.
27879 When certain serious errors occur, Exim writes entries to its panic log. If the
27880 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
27881 are usually written to the main log as well, but can get lost amid the mass of
27882 other entries. The panic log should be empty under normal circumstances. It is
27883 therefore a good idea to check it (or to have a \*cron*\ script check it)
27884 regularly, in order to become aware of any problems. When Exim cannot open its
27885 panic log, it tries as a last resort to write to the system log (syslog). This
27886 is opened with LOG@_PID+LOG@_CONS and the facility code of LOG@_MAIL. The
27887 message itself is written at priority LOG@_CRIT.
27889 Every log line starts with a timestamp, in the format shown in this example:
27891 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed by QUIT
27893 By default, the timestamps are in the local timezone. There are two
27894 ways of changing this:
27896 You can set the \timezone\ option to a different time zone; in particular, if
27901 the timestamps will be in UTC (aka GMT).
27903 If you set \log@_timezone\ true, the time zone is added to the timestamp, for
27906 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
27912 .section Where the logs are written
27913 .rset SECTwhelogwri "~~chapter.~~section"
27914 .index log||destination
27915 .index log||to file
27916 .index log||to syslog
27918 The logs may be written to local files, or to syslog, or both. However, it
27919 should be noted that many syslog implementations use UDP as a transport, and
27920 are therefore unreliable in the sense that messages are not guaranteed to
27921 arrive at the loghost, nor is the ordering of messages necessarily maintained.
27922 It has also been reported that on large log files (tens of megabytes) you may
27923 need to tweak syslog to prevent it syncing the file with each write -- on Linux
27924 this has been seen to make syslog take 90% plus of CPU time.
27926 The destination for Exim's logs is configured by setting \\LOG@_FILE@_PATH\\ in
27927 \(Local/Makefile)\ or by setting \log@_file@_path\ in the run time
27928 configuration. This latter string is expanded, so it can contain, for example,
27929 references to the host name:
27931 log_file_path = /var/log/$primary_hostname/exim_%slog
27933 It is generally advisable, however, to set the string in \(Local/Makefile)\
27934 rather than at run time, because then the setting is available right from the
27935 start of Exim's execution. Otherwise, if there's something it wants to log
27936 before it has read the configuration file (for example, an error in the
27937 configuration file) it will not use the path you want, and may not be able to
27940 The value of \\LOG@_FILE@_PATH\\ or \log@_file@_path\ is a colon-separated
27941 list, currently limited to at most two items. This is one option where the
27942 facility for changing a list separator may not be used. The list must always be
27943 colon-separated. If an item in the list is `syslog' then syslog is used;
27944 otherwise the item must either be an absolute path, containing \"%s"\ at the
27945 point where `main', `reject', or `panic' is to be inserted, or be empty,
27946 implying the use of a default path.
27948 When Exim encounters an empty item in the list, it searches the list defined by
27949 \\LOG@_FILE@_PATH\\, and uses the first item it finds that is neither empty nor
27950 `syslog'. This means that an empty item in \log@_file@_path\ can be used to
27951 mean `use the path specified at build time'. It no such item exists, log files
27952 are written in the \(log)\ subdirectory of the spool directory. This is
27953 equivalent to the setting:
27955 log_file_path = $spool_directory/log/%slog
27957 If you do not specify anything at build time or run time, that is where the
27960 A log file path may also contain \"%D"\ if datestamped log file names are in
27961 use -- see section ~~SECTdatlogfil below.
27963 Here are some examples of possible settings:
27966 LOG@_FILE@_PATH=syslog $t $rm{syslog only}
27967 LOG@_FILE@_PATH=:syslog $t $rm{syslog and default path}
27968 LOG@_FILE@_PATH=syslog : /usr/log/exim@_%s $t $rm{syslog and specified path}
27969 LOG@_FILE@_PATH=/usr/log/exim@_%s $t $rm{specified path only}
27971 If there are more than two paths in the list, the first is used and a panic
27975 .section Logging to local files that are periodically `cycled'
27976 .index log||cycling local files
27977 .index cycling logs
27978 .index \*exicyclog*\
27979 .index log||local files, writing to
27980 Some operating systems provide centralized and standardised methods for cycling
27981 log files. For those that do not, a utility script called \*exicyclog*\ is
27982 provided (see section ~~SECTcyclogfil). This renames and compresses the main
27983 and reject logs each time it is called. The maximum number of old logs to keep
27984 can be set. It is suggested this script is run as a daily \*cron*\ job.
27986 An Exim delivery process opens the main log when it first needs to write to it,
27987 and it keeps the file open in case subsequent entries are required -- for
27988 example, if a number of different deliveries are being done for the same
27989 message. However, remote SMTP deliveries can take a long time, and this means
27990 that the file may be kept open long after it is renamed if \*exicyclog*\ or
27991 something similar is being used to rename log files on a regular basis. To
27992 ensure that a switch of log files is noticed as soon as possible, Exim calls
27993 \*stat()*\ on the main log's name before reusing an open file, and if the file
27994 does not exist, or its inode has changed, the old file is closed and Exim
27995 tries to open the main log from scratch. Thus, an old log file may remain open
27996 for quite some time, but no Exim processes should write to it once it has been
28000 .section Datestamped log files
28001 .rset SECTdatlogfil "~~chapter.~~section"
28002 .index log||datestamped files
28003 Instead of cycling the main and reject log files by renaming them
28004 periodically, some sites like to use files whose names contain a datestamp,
28005 for example, \(mainlog-20031225)\. The datestamp is in the form \(yyyymmdd)\.
28006 Exim has support for this way of working. It is enabled by setting the
28007 \log@_file@_path\ option to a path that includes \"%D"\ at the point where the
28008 datestamp is required. For example:
28010 log_file_path = /var/spool/exim/log/%slog-%D
28011 log_file_path = /var/log/exim-%s-%D.log
28012 log_file_path = /var/spool/exim/log/%D-%slog
28014 As before, \"%s"\ is replaced by `main' or `reject'; the following are examples
28015 of names generated by the above examples:
28017 /var/spool/exim/log/mainlog-20021225
28018 /var/log/exim-reject-20021225.log
28019 /var/spool/exim/log/20021225-mainlog
28021 When this form of log file is specified, Exim automatically switches to new
28022 files at midnight. It does not make any attempt to compress old logs; you
28023 will need to write your own script if you require this. You should not
28024 run \*exicyclog*\ with this form of logging.
28026 The location of the panic log is also determined by \log@_file@_path\, but it
28027 is not datestamped, because rotation of the panic log does not make sense.
28028 When generating the name of the panic log, \"%D"\ is removed from the string.
28029 In addition, if it immediately follows a slash, a following non-alphanumeric
28030 character is removed; otherwise a preceding non-alphanumeric character is
28031 removed. Thus, the three examples above would give these panic log names:
28033 /var/spool/exim/log/paniclog
28034 /var/log/exim-panic.log
28035 /var/spool/exim/log/paniclog
28039 .section Logging to syslog
28040 .index log||syslog, writing to
28041 The use of syslog does not change what Exim logs or the format of its messages,
28042 except in one respect. If \syslog@_timestamp\ is set false, the timestamps on
28043 Exim's log lines are omitted when these lines are sent to syslog. Apart from
28044 that, the same strings are written to syslog as to log files. The syslog
28045 `facility' is set to \\LOG@_MAIL\\, and the program name to `exim'
28046 by default, but you can change these by setting the \syslog@_facility\ and
28047 \syslog@_processname\ options, respectively. If Exim was compiled with
28048 \\SYSLOG@_LOG@_PID\\ set in \(Local/Makefile)\ (this is the default in
28049 \(src/EDITME)\), then, on systems that permit it (all except ULTRIX), the
28050 \\LOG@_PID\\ flag is set so that the \*syslog()*\ call adds the pid as well as
28051 the time and host name to each line.
28052 The three log streams are mapped onto syslog priorities as follows:
28054 \*mainlog*\ is mapped to \\LOG@_INFO\\
28056 \*rejectlog*\ is mapped to \\LOG@_NOTICE\\
28058 \*paniclog*\ is mapped to \\LOG@_ALERT\\
28060 Many log lines are written to both \*mainlog*\ and \*rejectlog*\, and some are
28061 written to both \*mainlog*\ and \*paniclog*\, so there will be duplicates if
28062 these are routed by syslog to the same place. You can suppress this duplication
28063 by setting \syslog@_duplication\ false.
28065 Exim's log lines can sometimes be very long, and some of its \*rejectlog*\
28066 entries contain multiple lines when headers are included. To cope with both
28067 these cases, entries written to syslog are split into separate \*syslog()*\
28068 calls at each internal newline, and also after a maximum of
28069 870 data characters. (This allows for a total syslog line length of 1024, when
28070 additions such as timestamps are added.) If you are running a syslog
28071 replacement that can handle lines longer than the 1024 characters allowed by
28072 RFC 3164, you should set
28074 SYSLOG_LONG_LINES=yes
28076 in \(Local/Makefile)\ before building Exim. That stops Exim from splitting long
28077 lines, but it still splits at internal newlines in \*reject*\ log entries.
28079 To make it easy to re-assemble split lines later, each component of a split
28080 entry starts with a string of the form `[<<n>>/<<m>>]' or `[<<n>>@\<<m>>]'
28081 where <<n>> is the component number and <<m>> is the total number of components
28082 in the entry. The / delimiter is used when the line was split because it was
28083 too long; if it was split because of an internal newline, the @\ delimiter is
28084 used. For example, supposing the length limit to be 70 instead of 1000, the
28085 following would be the result of a typical rejection message to \*mainlog*\
28086 (LOG@_INFO), each line in addition being preceded by the time, host name, and
28087 pid as added by syslog:
28090 $smc{[1/3] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from [127.0.0.1] (ph10):
28091 [2/3] syntax error in 'From' header when scanning for sender: missing or ma
28092 [3/3] lformed local part in "<>" (envelope sender is <ph10@@cam.example>)}
28094 The same error might cause the following lines to be written to `rejectlog'
28098 $smc{[1/14] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from [127.0.0.1] (ph10):
28099 [2/14] syntax error in 'From' header when scanning for sender: missing or ma
28100 [3@\14] lformed local part in "@<@>" (envelope sender is <ph10@@cam.example>)
28101 [4@\14] Recipients: ph10@@some.domain.cam.example
28102 [5@\14] P Received: from [127.0.0.1] (ident=ph10)
28103 [6@\14] by xxxxx.cam.example with smtp (Exim 4.00)
28104 [7@\14] id 16RdAL-0006pc-00
28105 [8@\14] for ph10@@cam.example; Mon, 16 Sep 2002 16:09:43 +0100
28106 [9@\14] F From: @<@>
28107 [10@\14] Subject: this is a test header
28108 [11@\14] X-something: this is another header
28109 [12@\14] I Message-Id: <E16RdAL-0006pc-00@@xxxxx.cam.example>
28111 [14/14] Date: Mon, 16 Sep 2002 16:09:43 +0100}
28113 Log lines that are neither too long nor contain newlines are written to syslog
28114 without modification.
28116 If only syslog is being used, the Exim monitor is unable to provide a log tail
28117 display, unless syslog is routing \*mainlog*\ to a file on the local host and
28118 the environment variable \\EXIMON@_LOG@_FILE@_PATH\\ is set to tell the monitor
28122 .section Log line flags
28123 One line is written to the main log for each message received, and for each
28124 successful, unsuccessful, and delayed delivery. These lines can readily be
28125 picked out by the distinctive two-character flags that immediately follow the
28126 timestamp. The flags are:
28129 <= $t $rm{message arrival}
28130 => $t $rm{normal message delivery}
28131 -> $t $rm{additional address in same delivery}
28132 *> $t $rm{delivery suppressed by \-N-\}
28133 ** $t $rm{delivery failed; address bounced}
28134 == $t $rm{delivery deferred; temporary problem}
28138 .section Logging message reception
28139 .index log||reception line
28140 The format of the single-line entry in the main log that is written for every
28141 message received is shown in the basic example below, which is split over
28142 several lines in order to fit it on the page:
28145 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@@dwarf.fict.example
28146 H=mailer.fict.example [192.168.123.123] U=exim
28147 P=smtp S=5678 id=<<incoming message id>>
28149 The address immediately following `<=' is the envelope sender address. A bounce
28150 message is shown with the sender address `<>', and if it is locally generated,
28151 this is followed by an item of the form
28155 which is a reference to the message that caused the bounce to be sent.
28159 For messages from other hosts, the H and U fields identify the remote host and
28160 record the RFC 1413 identity of the user that sent the message, if one was
28161 received. The number given in square brackets is the IP address of the sending
28162 host. If there is a single, unparenthesized host name in the H field, as
28163 above, it has been verified to correspond to the IP address (see the
28164 \host@_lookup\ option). If the name is in parentheses, it was the name quoted
28165 by the remote host in the SMTP \\HELO\\ or \\EHLO\\ command, and has not been
28166 verified. If verification yields a different name to that given for \\HELO\\ or
28167 \\EHLO\\, the verified name appears first, followed by the \\HELO\\ or \\EHLO\\
28168 name in parentheses.
28170 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
28171 without brackets, in the \\HELO\\ or \\EHLO\\ command, leading to entries in
28172 the log containing text like these examples:
28174 H=(10.21.32.43) [192.168.8.34]
28175 H=([10.21.32.43]) [192.168.8.34]
28177 This can be confusing. Only the final address in square brackets can be relied
28180 For locally generated messages (that is, messages not received over TCP/IP),
28181 the H field is omitted, and the U field contains the login name of the caller
28184 .index authentication||logging
28185 .index \\AUTH\\||logging
28186 For all messages, the P field specifies the protocol used to receive the
28187 message. This is set to
28191 for messages received from hosts that have authenticated themselves using the
28192 SMTP \\AUTH\\ command. In this case there is an additional item A= followed by
28193 the name of the authenticator that was used. If an authenticated identification
28194 was set up by the authenticator's \server@_set@_id\ option, this is logged too,
28195 separated by a colon from the authenticator name.
28197 The id field records the existing message id, if present.
28198 .index size||of message
28199 The size of the received message is given by the S field. When the message is
28200 delivered, headers may get removed or added, so that the size of delivered
28201 copies of the message may not correspond with this value (and indeed may be
28202 different to each other).
28204 The \log@_selector\ option can be used to request the logging of additional
28205 data when a message is received. See section ~~SECTlogselector below.
28208 .section Logging deliveries
28209 .index log||delivery line
28210 The format of the single-line entry in the main log that is written for every
28211 delivery is shown in one of the examples below, for local and remote deliveries,
28212 respectively. Each example has been split into two lines in order to fit
28216 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv <marv@@hitch.fict.example>
28217 R=localuser T=local@_delivery
28218 2002-10-31 09:00:10 16ZCW1-0005MB-00 => monk@@holistic.fict.example
28219 R=dnslookup T=remote@_smtp H=holistic.fict.example [192.168.234.234]
28221 For ordinary local deliveries, the original address is given in angle brackets
28222 after the final delivery address, which might be a pipe or a file. If
28223 intermediate address(es) exist between the original and the final address, the
28224 last of these is given in parentheses after the final address. The R and T
28225 fields record the router and transport that were used to process the address.
28227 If a shadow transport was run after a successful local delivery, the log line
28228 for the successful delivery has an item added on the end, of the form
28230 ST=<<shadow transport name>>
28232 If the shadow transport did not succeed, the error message is put in
28233 parentheses afterwards.
28235 When more than one address is included in a single delivery (for example, two
28236 SMTP \\RCPT\\ commands in one transaction) the second and subsequent
28237 addresses are flagged with `$tt{@-@>}' instead of `$tt{@=@>}'. When two or more
28238 messages are delivered down a single SMTP connection, an asterisk follows the
28239 IP address in the log lines for the second and subsequent messages.
28241 The generation of a reply message by a filter file gets logged as a `delivery'
28242 to the addressee, preceded by `>'.
28244 The \log@_selector\ option can be used to request the logging of additional
28245 data when a message is delivered. See section ~~SECTlogselector below.
28248 .section Discarded deliveries
28249 .index discarded messages
28250 .index message||discarded
28251 .index delivery||discarded, logging
28252 When a message is discarded as a result of the command `seen finish' being
28253 obeyed in a filter file which generates no deliveries, a log entry of the form
28255 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
28256 <low.club@@bridge.example> R=userforward
28258 is written, to record why no deliveries are logged. When a message is discarded
28259 because it is aliased to `:blackhole:' the log line is like this:
28261 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
28262 <hole@nowhere.example> R=blackhole_router
28266 .section Deferred deliveries
28267 When a delivery is deferred, a line of the following form is logged:
28270 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@@endrest.example
28271 R=dnslookup T=smtp defer (146): Connection refused
28273 In the case of remote deliveries, the error is the one that was given for the
28274 last IP address that was tried. Details of individual SMTP failures are also
28275 written to the log, so the above line would be preceded by something like
28278 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
28279 mail1.endrest.example [192.168.239.239]: Connection refused
28281 When a deferred address is skipped because its retry time has not been reached,
28282 a message is written to the log, but this can be suppressed by setting an
28283 appropriate value in \log@_selector\.
28286 .section Delivery failures
28287 .index delivery||failure, logging
28288 If a delivery fails because an address cannot be routed, a line of the
28289 following form is logged:
28292 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
28293 <jim@trek99.example>: unknown mail domain
28295 If a delivery fails at transport time, the router and transport are shown, and
28296 the response from the remote host is included, as in this example:
28299 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example R=dnslookup
28301 T=remote_smtp: SMTP error from remote mailer after pipelined
28303 RCPT TO:<ace400@pb.example>: host pbmail3.py.example
28304 [192.168.63.111]: 553 5.3.0 <ace400@pb.example>...
28307 The word `pipelined' indicates that the SMTP \\PIPELINING\\ extension was being
28308 used. See \hosts@_avoid@_esmtp\ in the \%smtp%\ transport for a way of
28309 disabling \\PIPELINING\\.
28311 The log lines for all forms of delivery failure are flagged with \"**"\.
28314 .section Fake deliveries
28315 .index delivery||fake, logging
28316 If a delivery does not actually take place because the \-N-\ option has been
28317 used to suppress it, a normal delivery line is written to the log, except that
28318 `=>' is replaced by `$*$>'.
28321 .section Completion
28324 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
28326 is written to the main log when a message is about to be removed from the spool
28327 at the end of its processing.
28331 .section Summary of Fields in Log Lines
28332 .index log||summary of fields
28333 A summary of the field identifiers that are used in log lines is shown in
28334 the following table:
28337 A $t $rm{authenticator name (and optional id)}
28338 C $t $rm{SMTP confirmation on delivery}
28339 CV $t $rm{certificate verification status}
28340 DN $t $rm{distinguished name from peer certificate}
28343 DT $t $rm{on \"=>"\ lines: time taken for a delivery}
28346 F $t $rm{sender address (on delivery lines)}
28347 H $t $rm{host name and IP address}
28348 I $t $rm{local interface used}
28349 id $t $rm{message id for incoming message}
28350 P $t $rm{on \"<="\ lines: protocol used}
28353 $t $rm{on \"=>"\ and \"**"\ lines: return path}
28354 QT $t $rm{on \"=>"\ lines: time spent on queue so far}
28355 $t $rm{on `Completed' lines: time spent on queue}
28358 R $t $rm{on \"<="\ lines: reference for local bounce}
28361 $t $rm{on \"=>"\ \"**"\ and \"=="\ lines: router name}
28364 S $t $rm{size of message}
28365 ST $t $rm{shadow transport name}
28366 T $t $rm{on \"<="\ lines: message subject (topic)}
28369 $t $rm{on \"=>"\ \"**"\ and \"=="\ lines: transport name}
28372 U $t $rm{local user or RFC 1413 identity}
28373 X $t $rm{TLS cipher suite}
28377 .section Other log entries
28378 Various other types of log entry are written from time to time. Most should be
28379 self-explanatory. Among the more common are:
28381 .index retry||time not reached
28382 \*retry time not reached*\##An address previously suffered a temporary error
28383 during routing or local delivery, and the time to retry has not yet arrived.
28384 This message is not written to an individual message log file unless it happens
28385 during the first delivery attempt.
28387 \*retry time not reached for any host*\##An address previously suffered
28388 temporary errors during remote delivery, and the retry time has not yet arrived
28389 for any of the hosts to which it is routed.
28391 .index spool directory||file locked
28392 \*spool file locked*\##An attempt to deliver a message cannot proceed because
28393 some other Exim process is already working on the message. This can be quite
28394 common if queue running processes are started at frequent intervals. The
28395 \*exiwhat*\ utility script can be used to find out what Exim processes are
28398 .index error||ignored
28399 \*error ignored*\##There are several circumstances that give rise to this
28402 Exim failed to deliver a bounce message whose age was greater than
28403 \ignore__bounce__errors__after\. The bounce was discarded.
28405 A filter file set up a delivery using the `noerror' option, and the delivery
28406 failed. The delivery was discarded.
28408 A delivery set up by a router configured with
28412 failed. The delivery was discarded.
28418 .section Reducing or increasing what is logged
28419 .rset SECTlogselector "~~chapter.~~section"
28420 .index log||selectors
28421 By setting the \log@_selector\ global option, you can disable some of Exim's
28422 default logging, or you can request additional logging. The value of
28423 \log@_selector\ is made up of names preceded by plus or minus characters. For
28426 log_selector = +arguments -retry_defer
28428 The list of optional log items is in the following table, with the default
28429 selection marked by asterisks:
28432 address@_rewrite $t $rm{address rewriting}
28433 all@_parents $t $rm{all parents in => lines}
28434 arguments $t $rm{command line arguments}
28435 *connection@_reject $t $rm{connection rejections}
28436 *delay@_delivery $t $rm{immediate delivery delayed}
28437 deliver@_time $t $rm{time taken to perform delivery}
28438 delivery@_size $t $rm{add S=nnn to => lines}
28439 *dnslist@_defer $t $rm{defers of DNS list (aka RBL) lookups}
28440 *etrn $t $rm{ETRN commands}
28441 *host@_lookup@_failed $t $rm{as it says}
28442 ident@_timeout $t $rm{timeout for ident connection}
28443 incoming@_interface $t $rm{incoming interface on <= lines}
28444 incoming@_port $t $rm{incoming port on <= lines}
28445 *lost@_incoming@_connection $t $rm{as it says (includes timeouts)}
28446 outgoing@_port $t $rm{add remote port to => lines}
28447 *queue@_run $t $rm{start and end queue runs}
28450 queue@_time $t $rm{time on queue for one recipient}
28451 queue@_time@_overall $t $rm{time on queue for whole message}
28454 received@_recipients $t $rm{recipients on <= lines}
28455 received@_sender $t $rm{sender on <= lines}
28456 *rejected@_header $t $rm{header contents on reject log}
28457 *retry@_defer $t $rm{`retry time not reached'}
28458 return@_path@_on@_delivery $t $rm{put return path on => and ** lines}
28459 sender@_on@_delivery $t $rm{add sender to => lines}
28460 *size@_reject $t $rm{rejection because too big}
28461 *skip@_delivery $t $rm{delivery skipped in a queue run}
28462 smtp@_confirmation $t $rm{SMTP confirmation on => lines}
28463 smtp@_connection $t $rm{SMTP connections}
28464 smtp@_incomplete@_transaction $t $rm{incomplete SMTP transactions}
28465 smtp@_protocol@_error $t $rm{SMTP protocol errors}
28466 smtp@_syntax@_error $t $rm{SMTP syntax errors}
28467 subject $t $rm{contents of ::Subject:: on <= lines}
28468 tls@_certificate@_verified $t $rm{certificate verification status}
28469 *tls@_cipher $t $rm{TLS cipher suite on <= and => lines}
28470 tls@_peerdn $t $rm{TLS peer DN on <= and => lines}
28472 all $t $rm{all of the above}
28474 More details on each of these items follows:
28476 .index log||rewriting
28477 .index rewriting||logging
28478 \address@_rewrite\: This applies both to global rewrites and per-transport
28480 but not to rewrites in filters run as an unprivileged user (because such users
28481 cannot access the log).
28483 .index log||full parentage
28484 \all@_parents\: Normally only the original and final addresses are logged on
28485 delivery lines; with this selector, intermediate parents are given in
28486 parentheses between them.
28488 .index log||Exim arguments
28489 .index Exim arguments, logging
28490 \arguments\: This causes Exim to write the arguments with which it was called
28492 preceded by the current working directory.
28493 This is a debugging feature, added to make it easier to find out how certain
28494 MUAs call \(/usr/sbin/sendmail)\. The logging does not happen if Exim has given
28495 up root privilege because it was called with the \-C-\ or \-D-\ options.
28496 Arguments that are empty or that contain whitespace are quoted. Non-printing
28497 characters are shown as escape sequences.
28498 This facility cannot log unrecognized arguments, because the arguments are
28499 checked before the configuration file is read. The only way to log such cases
28500 is to interpose a script such as \(util/logargs.sh)\ between the caller and
28503 .index log||connection rejections
28504 \connection@_reject\: A log entry is written whenever an incoming SMTP
28505 connection is rejected, for whatever reason.
28507 .index log||delayed delivery
28508 .index delayed delivery, logging
28509 \delay@_delivery\: A log entry is written whenever a delivery process is not
28510 started for an incoming message because the load is too high or too many
28511 messages were received on one connection. Logging does not occur if no delivery
28512 process is started because \queue@_only\ is set or \-odq-\ was used.
28514 .index log||delivery duration
28515 \deliver@_time\: For each delivery, the amount of real time it has taken to
28516 perform the actual delivery is logged as DT=<<time>>, for example, \"DT=1s"\.
28518 .index log||message size on delivery
28519 .index size||of message
28520 \delivery@_size\: For each delivery, the size of message delivered is added to
28521 the `=>' line, tagged with S=.
28523 .index log||dnslist defer
28524 .index DNS list||logging defer
28525 .index black list (DNS)
28526 \dnslist@_defer\: A log entry is written if an attempt to look up a host in a
28527 DNS black list suffers a temporary error.
28529 .index log||ETRN commands
28530 .index \\ETRN\\||logging
28531 \etrn\: Every legal ETRN command that is received is logged, before the ACL is
28532 run to determine whether or not it is actually accepted. An invalid ETRN
28533 command, or one received within a message transaction is not logged by this
28534 selector (see \smtp@_syntax@_error\ and \smtp@_protocol@_error\).
28536 .index log||host lookup failure
28537 \host@_lookup@_failed\: When a lookup of a host's IP addresses fails to find
28538 any addresses, or when a lookup of an IP address fails to find a host name, a
28539 log line is written. This logging does not apply to direct DNS lookups when
28540 routing email addresses, but it does apply to `byname' lookups.
28542 .index log||ident timeout
28543 .index RFC 1413||logging timeout
28544 \ident@_timeout\: A log line is written whenever an attempt to connect to a
28545 client's ident port times out.
28547 .index log||incoming interface
28548 .index interface||logging
28549 \incoming@_interface\: The interface on which a message was received is added
28550 to the `<=' line as an IP address in square brackets, tagged by I= and followed
28551 by a colon and the port number.
28552 The local interface and port are also added to other SMTP log
28553 lines, for example `SMTP connection from', and to rejection lines.
28555 .index log||incoming remote port
28556 .index port||logging remote
28557 .index TCP/IP||logging incoming remote port
28558 \incoming@_port\: The remote port number from which a message was received is
28559 added to log entries and ::Received:: header lines, following the IP address in
28560 square brackets, and separated from it by a colon. This is implemented by
28561 changing the value that is put in the \$sender@_fullhost$\ and
28562 \$sender@_rcvhost$\ variables. Recording the remote port number has become more
28563 important with the widening use of NAT (see RFC 2505).
28565 .index log||dropped connection
28566 \lost@_incoming@_connection\: A log line is written when an incoming SMTP
28567 connection is unexpectedly dropped.
28569 .index log||outgoing remote port
28570 .index port||logging outgoint remote
28571 .index TCP/IP||logging ougtoing remote port
28572 \outgoing@_port\: The remote port number is added to delivery log lines (those
28573 containing => tags) following the IP address. This option is not included in
28574 the default setting, because for most ordinary configurations, the remote port
28575 number is always 25 (the SMTP port).
28577 .index log||queue run
28578 .index queue runner||logging
28579 \queue@_run\: The start and end of every queue run are logged.
28581 .index log||queue time
28582 \queue@_time\: The amount of time the message has been in the queue on the
28583 local host is logged as QT=<<time>>
28585 on delivery (\"=>"\) lines, for example, \"QT=3m45s"\. The clock starts when
28586 Exim starts to receive the message, so it includes reception time as well as
28587 the delivery time for the current address. This means that it may be longer
28588 than the difference between the arrival and delivery log line times, because
28589 the arrival log line is not written until the message has been successfully
28595 \queue@_time@_overall\: The amount of time the message has been in the queue on
28596 the local host is logged as QT=<<time>> on `Completed' lines, for
28597 example, \"QT=3m45s"\. The clock starts when Exim starts to receive the
28598 message, so it includes reception time as well as the total delivery time.
28601 .index log||recipients
28602 \received@_recipients\: The recipients of a message are listed in the main log
28603 as soon as the message is received. The list appears at the end of the log line
28604 that is written when a message is received, preceded by the word `for'. The
28605 addresses are listed after they have been qualified, but before any rewriting
28607 Recipients that were discarded by an ACL for \\MAIL\\ or \\RCPT\\ do not appear
28610 .index log||sender reception
28611 \received@_sender\: The unrewritten original sender of a message is added to
28612 the end of the log line that records the message's arrival, after the word
28613 `from' (before the recipients if \received@_recipients\ is also set).
28615 .index log||header lines for rejection
28616 \rejected@_header\: If a message's header has been received at the time a
28617 rejection is written to the reject log, the complete header is added to the
28618 log. Header logging can be turned off individually for messages that are
28619 rejected by the \*local@_scan()*\ function (see section ~~SECTapiforloc).
28621 .index log||retry defer
28622 \retry@_defer\: A log line is written if a delivery is deferred because a retry
28623 time has not yet been reached. However, this `retry time not reached' message
28624 is always omitted from individual message logs after the first delivery
28627 .index log||return path
28628 \return@_path@_on@_delivery\: The return path that is being transmitted with
28629 the message is included in delivery and bounce lines, using the tag P=.
28631 This is omitted if no delivery actually happens, for example, if routing fails,
28632 or if delivery is to \(/dev/null)\ or to \":blackhole:"\.
28635 .index log||sender on delivery
28636 \sender@_on@_delivery\: The message's sender address is added to every delivery
28637 and bounce line, tagged by F= (for `from').
28638 This is the original sender that was received with the message; it is not
28639 necessarily the same as the outgoing return path.
28641 .index log||size rejection
28642 \size@_reject\: A log line is written whenever a message is rejected because it
28645 .index log||frozen messages, skipped
28646 .index frozen messages||logging skipping
28647 \skip@_delivery\: A log line is written whenever a message is skipped during a
28648 queue run because it is frozen or because another process is already delivering
28651 .index `spool file is locked'
28652 The message that is written is `spool file is locked'.
28655 .index log||smtp confirmation
28656 .index SMTP||logging confirmation
28657 \smtp@_confirmation\: The response to the final `.' in the SMTP dialogue for
28658 outgoing messages is added to delivery log lines in the form `C="<<text>>"'. A
28659 number of MTAs (including Exim) return an identifying string in this response.
28661 .index log||SMTP connections
28662 .index SMTP||logging connections
28663 \smtp@_connection\: A log line is written whenever an SMTP connection is
28664 established or closed,
28666 unless the connection is from a host that matches \hosts@_connection@_nolog\.
28668 (In contrast, \lost__incoming__connection\ applies only when the closure is
28669 unexpected.) This applies to connections from local processes that use \-bs-\
28670 as well as to TCP/IP connections. If a connection is dropped in the middle of a
28671 message, a log line is always written, whether or not this selector is set, but
28672 otherwise nothing is written at the start and end of connections unless this
28673 selector is enabled.
28675 For TCP/IP connections to an Exim daemon, the current number of connections is
28676 included in the log message for each new connection, but note that the count is
28677 reset if the daemon is restarted.
28678 Also, because connections are closed (and the closure is logged) in
28679 subprocesses, the count may not include connections that have been closed but
28680 whose termination the daemon has not yet noticed. Thus, while it is possible to
28681 match up the opening and closing of connections in the log, the value of the
28682 logged counts may not be entirely accurate.
28684 .index log||SMTP transaction, incomplete
28685 .index SMTP||logging incomplete transactions
28686 \smtp@_incomplete@_transaction\: When a mail transaction is aborted by
28687 \\RSET\\, \\QUIT\\, loss of connection, or otherwise, the incident is logged,
28688 and the message sender plus any accepted recipients are included in the log
28689 line. This can provide evidence of dictionary attacks.
28691 .index log||SMTP protocol error
28692 .index SMTP||logging protocol error
28693 \smtp@_protocol@_error\: A log line is written for every SMTP protocol error
28695 Exim does not have perfect detection of all protocol errors because of
28696 transmission delays and the use of pipelining. If \\PIPELINING\\ has been
28697 advertised to a client, an Exim server assumes that the client will use it, and
28698 therefore it does not count `expected' errors (for example, \\RCPT\\ received
28699 after rejecting \\MAIL\\) as protocol errors.
28701 .index SMTP||logging syntax errors
28702 .index SMTP||syntax errors, logging
28703 .index SMTP||unknown command, logging
28704 .index log||unknown SMTP command
28705 .index log||SMTP syntax error
28706 \smtp@_syntax@_error\: A log line is written for every SMTP syntax error
28707 encountered. An unrecognized command is treated as a syntax error. For an
28708 external connection, the host identity is given; for an internal connection
28709 using \-bs-\ the sender identification (normally the calling user) is given.
28711 .index log||subject
28712 .index subject, logging
28713 \subject\: The subject of the message is added to the arrival log line,
28714 preceded by `T=' (T for `topic', since S is already used for `size').
28715 Any MIME `words' in the subject are decoded. The \print@_topbitchars\ option
28716 specifies whether characters with values greater than 127 should be logged
28717 unchanged, or whether they should be rendered as escape sequences.
28719 .index log||certificate verification
28720 \tls@_certificate@_verified\: An extra item is added to <= and => log lines
28721 when TLS is in use. The item is \"CV=yes"\ if the peer's certificate was
28722 verified, and \"CV=no"\ if not.
28724 .index log||TLS cipher
28725 .index TLS||logging cipher
28726 \tls@_cipher\: When a message is sent or received over an encrypted connection,
28727 the cipher suite used is added to the log line, preceded by X=.
28729 .index log||TLS peer DN
28730 .index TLS||logging peer DN
28731 \tls@_peerdn\: When a message is sent or received over an encrypted connection,
28732 and a certificate is supplied by the remote host, the peer DN is added to the
28733 log line, preceded by DN=.
28736 .section Message log
28737 .index message||log file for
28738 .index log||message log, description of
28739 In addition to the general log files, Exim writes a log file for each message
28740 that it handles. The names of these per-message logs are the message ids, and
28741 .index \(msglog)\ directory
28742 they are kept in the \(msglog)\ sub-directory of the spool directory. Each
28743 message log contains copies of the log lines that apply to the message. This
28744 makes it easier to inspect the status of an individual message without having
28745 to search the main log. A message log is deleted when processing of the message
28747 .index \preserve@_message@_logs\
28748 unless \preserve__message__logs\ is set, but this should be used only with
28749 great care because they can fill up your disk very quickly.
28751 On a heavily loaded system, it may be desirable to disable the use of
28752 per-message logs, in order to reduce disk I/O. This can be done by setting the
28753 \message@_logs\ option false.
28760 . ============================================================================
28761 .chapter Exim utilities
28762 .set runningfoot "utilities"
28763 .rset CHAPutils ~~chapter
28765 A number of utility scripts and programs are supplied with Exim and are
28766 described in this chapter. There is also the Exim Monitor, which is covered in
28767 the next chapter. The utilities described here are:
28769 . This duplication seems to be the only way to arrange that the cross-
28770 . references are omitted in the Texinfo version. They look horribly ugly.
28775 \*exiwhat*\ $t $rm{list what Exim processes are doing}
28777 \*exiqgrep*\ $t $rm{grep the queue}
28779 \*exiqsumm*\ $t $rm{summarize the queue}
28780 \*exigrep*\ $t $rm{search the main log}
28781 \*exipick*\ $t $rm{select messages on various criteria}
28782 \*exicyclog*\ $t $rm{cycle (rotate) log files}
28783 \*eximstats*\ $t $rm{extract statistics from the log}
28784 \*exim@_checkaccess*\ $t $rm{check address acceptance from given IP}
28785 \*exim@_dbmbuild*\ $t $rm{build a DBM file}
28786 \*exinext*\ $t $rm{extract retry information}
28787 \*exim@_dumpdb*\ $t $rm{dump a hints database}
28788 \*exim@_tidydb*\ $t $rm{clean up a hints database}
28789 \*exim@_fixdb*\ $t $rm{patch a hints database}
28790 \*exim@_lock*\ $t $rm{lock a mailbox file}
28797 ~~SECTfinoutwha \*exiwhat*\ $t $rm{list what Exim processes are doing}
28798 ~~SECTgreptheque \*exiqgrep*\ $t $rm{grep the queue}
28799 ~~SECTsumtheque \*exiqsumm*\ $t $rm{summarize the queue}
28800 ~~SECTextspeinf \*exigrep*\ $t $rm{search the main log}
28801 ~~SECTexipick \*exipick*\ $t $rm{select messages on various criteria}
28802 ~~SECTcyclogfil \*exicyclog*\ $t $rm{cycle (rotate) log files}
28803 ~~SECTmailstat \*eximstats*\ $t $rm{extract statistics from the log}
28804 ~~SECTcheckaccess \*exim@_checkaccess*\ $t $rm{check address acceptance from given IP}
28805 ~~SECTdbmbuild \*exim@_dbmbuild*\ $t $rm{build a DBM file}
28806 ~~SECTfinindret \*exinext*\ $t $rm{extract retry information}
28807 ~~SECThindatmai \*exim@_dumpdb*\ $t $rm{dump a hints database}
28808 ~~SECThindatmai \*exim@_tidydb*\ $t $rm{clean up a hints database}
28809 ~~SECThindatmai \*exim@_fixdb*\ $t $rm{patch a hints database}
28810 ~~SECTmailboxmaint \*exim@_lock*\ $t $rm{lock a mailbox file}
28814 .section Finding out what Exim processes are doing (exiwhat)
28815 .rset SECTfinoutwha "~~chapter.~~section"
28817 .index process, querying
28819 On operating systems that can restart a system call after receiving a signal
28820 (most modern OS), an Exim process responds to the \\SIGUSR1\\ signal by writing
28821 a line describing what it is doing to the file \(exim-process.info)\ in the
28822 Exim spool directory. The \*exiwhat*\ script sends the signal to all Exim
28823 processes it can find, having first emptied the file. It then waits for one
28824 second to allow the Exim processes to react before displaying the results. In
28825 order to run \*exiwhat*\ successfully you have to have sufficient privilege to
28826 send the signal to the Exim processes, so it is normally run as root.
28829 \**Warning**\: This is not an efficient process. It is intended for occasional
28830 use by system administrators. It is not sensible, for example, to set up a
28831 script that sends \\SIGUSR1\\ signals to Exim processes at short intervals.
28834 Unfortunately, the \*ps*\ command that \*exiwhat*\ uses to find Exim processes
28835 varies in different operating systems. Not only are different options used,
28836 but the format of the output is different. For this reason, there are some
28837 system configuration options that configure exactly how \*exiwhat*\ works. If it
28838 doesn't seem to be working for you, check the following compile-time options:
28840 EXIWHAT@_PS@_CMD $rm{the command for running \*ps*\}
28841 EXIWHAT@_PS@_ARG $rm{the argument for \*ps*\}
28842 EXIWHAT@_EGREP@_ARG $rm{the argument for \*egrep*\ to select from \*ps*\ output}
28843 EXIWHAT@_KILL@_ARG $rm{the argument for the \*kill*\ command}
28845 An example of typical output from \*exiwhat*\ is
28848 164 daemon: -q1h, listening on port 25
28849 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
28850 10492 delivering 0tAycK-0002ij-00 to mail.ref.example [10.19.42.42]
28851 (editor@@ref.example)
28852 10592 handling incoming call from [192.168.243.242]
28853 10628 accepting a local non-SMTP message
28855 The first number in the output line is the process number. The third line has
28856 been split here, in order to fit it on the page.
28859 .section Selective queue listing (exiqgrep)
28860 .rset SECTgreptheque "~~chapter.~~section"
28861 .index \*exiqgrep*\
28862 .index queue||grepping
28863 This utility is a Perl script contributed by Matt Hubbard. It runs
28867 to obtain a queue listing with undelivered recipients only, and then greps the
28868 output to select messages that match given criteria. The following selection
28869 options are available:
28873 .option f <<regex>>
28874 Match the sender address. The field that is tested is enclosed in angle
28875 brackets, so you can test for bounce messages with
28880 .option r <<regex>>
28881 Match a recipient address. The field that is tested is not enclosed in angle
28884 .option s <<regex>>
28885 Match against the size field.
28887 .option y <<seconds>>
28888 Match messages that are younger than the given time.
28890 .option o <<seconds>>
28891 Match messages that are older than the given time.
28894 Match only frozen messages.
28897 Match only non-frozen messages.
28901 The following options control the format of the output:
28906 Display only the count of matching messages.
28909 Long format -- display the full message information as output by Exim. This is
28913 Display message ids only.
28916 Brief format -- one line per message.
28919 Display messages in reverse order.
28923 There is one more option, \-h-\, which outputs a list of options.
28926 .section Summarising the queue (exiqsumm)
28927 .rset SECTsumtheque "~~chapter.~~section"
28928 .index \*exiqsumm*\
28929 .index queue||summary
28930 The \*exiqsumm*\ utility is a Perl script which reads the output of \*exim
28931 -bp*\ and produces a summary of the messages on the queue. Thus, you use it by
28932 running a command such as
28934 exim -bp | exiqsumm
28936 The output consists of one line for each domain that has messages waiting for
28937 it, as in the following example:
28939 3 2322 74m 66m msn.com.example
28941 Each line lists the number of
28942 pending deliveries for a domain, their total volume, and the length of time
28943 that the oldest and the newest messages have been waiting. Note that the number
28944 of pending deliveries is greater than the number of messages when messages
28945 have more than one recipient.
28947 A summary line is output at the end. By default the output is sorted on the
28948 domain name, but \*exiqsumm*\ has the options \-a-\ and \-c-\, which cause the
28949 output to be sorted by oldest message and by count of messages, respectively.
28951 The output of \*exim -bp*\ contains the original addresses in the message, so
28952 this also applies to the output from \*exiqsumm*\. No domains from addresses
28953 generated by aliasing or forwarding are included (unless the \one@_time\ option
28954 of the \%redirect%\ router has been used to convert them into `top level'
28959 .section Extracting specific information from the log (exigrep)
28960 .rset SECTextspeinf "~~chapter.~~section"
28962 .index log||extracts, grepping for
28963 The \*exigrep*\ utility is a Perl script that searches one or more main log
28964 files for entries that match a given pattern. When it finds a match, it
28965 extracts all the log entries for the relevant message, not just those that
28966 match the pattern. Thus, \*exigrep*\ can extract complete log entries for a
28967 given message, or all mail for a given user, or for a given host, for example.
28969 If a matching log line is not associated with a specific message, it is always
28970 included in \*exigrep*\'s output.
28973 exigrep [-l] [-t<n>] <pattern> [<log file>] ...
28975 The \-t-\ argument specifies a number of seconds. It adds an additional
28976 condition for message selection. Messages that are complete are shown only if
28977 they spent more than <<n>> seconds on the queue.
28979 The \-l-\ flag means `literal', that is, treat all characters in the
28980 pattern as standing for themselves. Otherwise the pattern must be a Perl
28981 regular expression. The pattern match is case-insensitive. If no file names are
28982 given on the command line, the standard input is read.
28984 If the location of a \*zcat*\ command is known from the definition of
28985 \\ZCAT@_COMMAND\\ in \(Local/Makefile)\, \*exigrep*\ automatically passes any
28986 file whose name ends in \\COMPRESS@_SUFFIX\\ through \*zcat*\ as it searches
28989 .section Selecting messages by various criteria (exipick)
28990 .rset SECTexipick "~~chapter.~~section"
28992 John Jetmore's \*exipick*\ utility is included in the Exim distribution. It
28993 lists messages from the queue according to a variety of criteria. For details,
29000 .section Cycling log files (exicyclog)
29001 .rset SECTcyclogfil "~~chapter.~~section"
29002 .index log||cycling local files
29003 .index cycling logs
29004 .index \*exicyclog*\
29005 The \*exicyclog*\ script can be used to cycle (rotate) \*mainlog*\ and
29006 \*rejectlog*\ files. This is not necessary if only syslog is being used, or if
29007 you are using log files with datestamps in their names (see section
29008 ~~SECTdatlogfil). Some operating systems have their own standard mechanisms for
29009 log cycling, and these can be used instead of \*exicyclog*\ if preferred.
29011 Each time \*exicyclog*\ is run the file names get `shuffled down' by one. If
29012 the main log file name is \(mainlog)\ (the default) then when \*exicyclog*\ is
29013 run \(mainlog)\ becomes \(mainlog.01)\, the previous \(mainlog.01)\ becomes
29014 \(mainlog.02)\ and so on, up to a limit which is set in the script, and which
29017 Log files whose numbers exceed the limit are discarded.
29019 Reject logs are handled similarly.
29022 If the limit is greater than 99, the script uses 3-digit numbers such as
29023 \(mainlog.001)\, \(mainlog.002)\, etc. If you change from a number less than 99
29024 to one that is greater, or \*vice versa*\, you will have to fix the names of
29025 any existing log files.
29028 If no \(mainlog)\ file exists, the script does nothing. Files that `drop off'
29029 the end are deleted. All files with numbers greater than 01 are compressed,
29030 using a compression command which is configured by the \\COMPRESS@_COMMAND\\
29031 setting in \(Local/Makefile)\. It is usual to run \*exicyclog*\ daily from a
29032 root \crontab\ entry of the form
29034 1 0 * * * su exim -c /usr/exim/bin/exicyclog
29036 assuming you have used the name `exim' for the Exim user. You can run
29037 \*exicyclog*\ as root if you wish, but there is no need.
29040 .section Mail statistics (eximstats)
29041 .rset SECTmailstat "~~chapter.~~section"
29043 .index \*eximstats*\
29044 A Perl script called \*eximstats*\ is provided for extracting statistical
29045 information from log files. The output is either plain text, or HTML.
29046 Exim log files are also suported by the \*Lire*\ system produced by the
29047 LogReport Foundation (\?http://www.logreport.org?\).
29049 The \*eximstats*\ script has been hacked about quite a bit over time. The
29050 latest version is the result of some extensive revision by Steve Campbell. A
29051 lot of information is given by default, but there are options for suppressing
29052 various parts of it. Following any options, the arguments to the script are a
29053 list of files, which should be main log files. For example:
29055 eximstats -nr /var/spool/exim/log/mainlog.01
29057 By default, \*eximstats*\ extracts information about the number and volume of
29058 messages received from or delivered to various hosts. The information is sorted
29059 both by message count and by volume, and the top fifty hosts in each category
29060 are listed on the standard output. Similar information, based on email
29061 addresses or domains instead of hosts can be requested by means of various
29062 options. For messages delivered and received locally, similar statistics are
29063 also produced per user.
29065 The output also includes total counts and statistics about delivery errors, and
29066 histograms showing the number of messages received and deliveries made in each
29067 hour of the day. A delivery with more than one address in its envelope (for
29068 example, an SMTP transaction with more than one \\RCPT\\ command) is counted
29069 as a single delivery by \*eximstats*\.
29071 Though normally more deliveries than receipts are reported (as messages may
29072 have multiple recipients), it is possible for \*eximstats*\ to report more
29073 messages received than delivered, even though the queue is empty at the start
29074 and end of the period in question. If an incoming message contains no valid
29075 recipients, no deliveries are recorded for it. A bounce message is handled as
29076 an entirely separate message.
29078 \*eximstats*\ always outputs a grand total summary giving the volume and number
29079 of messages received and deliveries made, and the number of hosts involved in
29080 each case. It also outputs the number of messages that were delayed (that is,
29081 not completely delivered at the first attempt), and the number that had at
29082 least one address that failed.
29084 The remainder of the output is in sections that can be independently disabled
29085 or modified by various options. It consists of a summary of deliveries by
29086 transport, histograms of messages received and delivered per time interval
29087 (default per hour), information about the time messages spent on the queue,
29088 a list of relayed messages, lists of the top fifty sending hosts, local
29089 senders, destination hosts, and destination local users by count and by volume,
29090 and a list of delivery errors that occurred.
29092 The relay information lists messages that were actually relayed, that is, they
29093 came from a remote host and were directly delivered to some other remote host,
29094 without being processed (for example, for aliasing or forwarding) locally.
29096 The options for \*eximstats*\ are as follows:
29099 .index \*eximstats*\||options
29101 The `league tables' are computed on the basis of the superior domains of the
29102 sending hosts instead of the sending and receiving hosts. This option may be
29103 combined with \-byhost-\ and/or \-byemail-\.
29106 This is a synonym for \-byemaildomain-\.
29109 The `league tables' are computed on the basis of complete email addresses,
29110 instead of sending and receiving hosts. This option may be combined with
29111 \-byhost-\ and/or \-bydomain-\.
29113 .option byemaildomain
29114 The `league tables' are computed on the basis of the sender's email domain
29115 instead of the sending and receiving hosts. This option may be combined with
29116 \-byhost-\, \-bydomain-\, or \-byemail-\.
29119 The `league tables' are computed on the basis of sending and receiving hosts.
29120 This is the default option. It may be combined with \-bydomain-\ and/or
29124 Cache results of \*timegm()*\ lookups. This results in a significant speedup
29125 when processing hundreds of thousands of messages, at a cost of increasing the
29126 memory utilisation.
29128 .option chartdir <<dir>>
29129 When \-charts-\ is specified, create the charts in the directory <<dir>>.
29131 .option chartrel <<dir>>
29132 When \-charts-\ is specified, this option specifies the relative directory for
29133 the \"img src="\ tags from where to include the charts.
29136 Create graphical charts to be displayed in HTML output. This requires the
29137 \"GD"\, \"GDTextUtil"\, and \"GDGraph"\ Perl modules, which can be obtained
29138 from \?http://www.cpan.org/modules/01modules.index.html?\.
29140 To install these, download and unpack them, then use the normal Perl
29141 installation procedure:
29150 This is a debug flag. It causes \*eximstats*\ to output the \*eval()*\'d parser
29151 to the standard output, which makes it easier to trap errors in the eval
29152 section. Remember to add one to the line numbers to allow for the title.
29156 Show help information about \*eximstats*\' options.
29159 This option controls the histograms of messages received and deliveries per
29160 time interval. By default the time interval is one hour. If \-h0-\ is given,
29161 the histograms are suppressed; otherwise the value of <<n>> gives the number of
29162 divisions per hour. Valid values are 0, 1, 2, 3, 5, 10, 15, 20, 30 or 60, so
29163 \-h2-\ sets an interval of 30 minutes, and the default is equivalent to \-h1-\.
29166 Output the results in HTML instead of plain text.
29169 This option causes \*eximstats*\ to merge old reports into a combined report.
29170 When this option is used, the input files must be outputs from previous calls
29171 to \*eximstats*\, not raw log files. For example, you could produce a set of
29172 daily reports and a weekly report by commands such as
29174 eximstats mainlog.sun > report.sun.txt
29175 eximstats mainlog.mon > report.mon.txt
29176 eximstats mainlog.tue > report.tue.txt
29177 eximstats mainlog.wed > report.wed.txt
29178 eximstats mainlog.thu > report.thu.txt
29179 eximstats mainlog.fri > report.fri.txt
29180 eximstats mainlog.sat > report.sat.txt
29181 eximstats -merge -html report.*.txt > weekly_report.html
29183 You can merge text or html reports and output the results as text or html. You
29184 can use all the normal \*eximstats*\ output options, but only data included in
29185 the original reports can be shown. When merging reports, some loss of accuracy
29186 may occur in the `league tables', towards the ends of the lists. The order of
29187 items in the `league tables' may vary when the data volumes round to the same
29191 Suppress the display of information about failed deliveries (errors).
29194 Suppress information about messages relayed through this host.
29196 .option nr /pattern/
29197 Suppress information about relayed messages that match the pattern, which is
29198 matched against a string of the following form (split over two lines here in
29199 order to fit it on the page):
29201 H=<host> [<ip address>] A=<sender address> =>
29202 H=<host> A=<recipient address>
29206 H=in.host [1.2.3.4] A=from@some.where.example =>
29207 H=out.host A=to@else.where.example
29209 The sending host name appears in parentheses if it has not been verified as
29210 matching the IP address. The mail addresses are taken from the envelope, not
29211 the headers. This option allows you to screen out hosts whom you are happy to
29212 have using your host as a relay.
29215 Suppress the statistics about delivery by transport.
29217 .option nt/<<pattern>>/
29218 Suppress the statistics about delivery by any transport whose name matches the
29219 pattern. If you are using one transport to send all messages to a scanning
29220 mechanism before doing the real delivery, this feature can be used to omit that
29221 transport from your normal statistics (on the grounds that it is of no
29225 .option "pattern" "#<<description>>#/<<pattern>>/"
29226 Count lines matching specified patterns and show them in
29227 the results. For example:
29229 -pattern 'Refused connections' '/refused connection/'
29231 This option can be specified multiple times.
29234 Suppress information about times messages spend on the queue.
29236 .option q <<n1>>...
29237 This option sets an alternative list of time intervals for the queueing
29238 information. The values are separated by commas and are in seconds, but can
29239 involve arithmetic multipliers, so for example you can set 3$*$60 to specify 3
29240 minutes. A setting such as
29244 causes \*eximstats*\ to give counts of messages that stayed on the queue for less
29245 than one minute, less than five minutes, less than ten minutes, and over ten
29249 Sets the `top' count to <<n>>. This controls the listings of the `top <<n>>'
29250 hosts and users by count and volume. The default is 50, and setting 0
29251 suppresses the output altogether.
29254 Omit local information from the `top' listings.
29256 .option t@_remote@_users
29257 Include remote users in the `top' listings.
29262 .section Checking access policy (exim@_checkaccess)
29263 .rset SECTcheckaccess "~~chapter.~~section"
29264 .index \*exim@_checkaccess*\
29265 .index policy control||checking access
29266 .index checking access
29267 The \-bh-\ command line argument allows you to run a fake SMTP session with
29268 debugging output, in order to check what Exim is doing when it is applying
29269 policy controls to incoming SMTP mail. However, not everybody is sufficiently
29270 familiar with the SMTP protocol to be able to make full use of \-bh-\, and
29271 sometimes you just want to answer the question \*Does this address have
29272 access?*\ without bothering with any further details.
29274 The \*exim@_checkaccess*\ utility is a `packaged' version of \-bh-\. It takes
29275 two arguments, an IP address and an email address:
29277 exim_checkaccess 10.9.8.7 A.User@a.domain.example
29279 The utility runs a call to Exim with the \-bh-\ option, to test whether the
29280 given email address would be accepted in a \\RCPT\\ command in a TCP/IP
29281 connection from the host with the given IP address. The output of the utility
29282 is either the word `accepted', or the SMTP error response, for example:
29285 550 Relay not permitted
29287 When running this test, the utility uses \"<>"\ as the envelope sender address
29288 for the \\MAIL\\ command, but you can change this by providing additional
29289 options. These are passed directly to the Exim command. For example, to specify
29290 that the test is to be run with the sender address \*himself@@there.example*\
29293 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
29294 -f himself@there.example
29296 Note that these additional Exim command line items must be given after the two
29297 mandatory arguments.
29299 Because the \exim@_checkaccess\ uses \-bh-\, it does not perform callouts while
29300 running its checks. You can run checks that include callouts by using \-bhc-\,
29301 but this is not yet available in a `packaged' form.
29304 .section Making DBM files (exim@_dbmbuild)
29305 .rset SECTdbmbuild "~~chapter.~~section"
29306 .index DBM||building dbm files
29307 .index building DBM files
29308 .index \*exim@_dbmbuild*\
29309 .index lower casing
29310 .index binary zero||in lookup key
29311 The \*exim@_dbmbuild*\ program reads an input file containing keys and data in
29312 the format used by the \%lsearch%\ lookup (see section ~~SECTsinglekeylookups).
29313 It writes a DBM file using the lower-cased alias names as keys and the
29314 remainder of the information as data. The lower-casing can be prevented by
29315 calling the program with the \-nolc-\ option.
29317 A terminating zero is included as part of the key string. This is expected by
29318 the \%dbm%\ lookup type. However, if the option \-nozero-\ is given,
29319 \*exim@_dbmbuild*\ creates files without terminating zeroes in either the key
29320 strings or the data strings. The \%dbmnz%\ lookup type can be used with such
29323 The program requires two arguments: the name of the input file (which can be a
29324 single hyphen to indicate the standard input), and the name of the output file.
29325 It creates the output under a temporary name, and then renames it if all went
29328 If the native DB interface is in use (\\USE@_DB\\ is set in a compile-time
29329 configuration file -- this is common in free versions of Unix) the two file
29330 names must be different, because in this mode the Berkeley DB functions create
29331 a single output file using exactly the name given. For example,
29333 exim_dbmbuild /etc/aliases /etc/aliases.db
29335 reads the system alias file and creates a DBM version of it in
29336 \(/etc/aliases.db)\.
29338 In systems that use the \*ndbm*\ routines (mostly proprietary versions of Unix),
29339 two files are used, with the suffixes \(.dir)\ and \(.pag)\. In this
29340 environment, the suffixes are added to the second argument of
29341 \*exim@_dbmbuild*\, so it can be the same as the first. This is also the case
29342 when the Berkeley functions are used in compatibility mode (though this is not
29343 recommended), because in that case it adds a \(.db)\ suffix to the file name.
29345 If a duplicate key is encountered, the program outputs a warning, and when it
29346 finishes, its return code is 1 rather than zero, unless the \-noduperr-\ option
29347 is used. By default, only the first of a set of duplicates is used -- this
29348 makes it compatible with \%lsearch%\ lookups. There is an option \-lastdup-\
29349 which causes it to use the data for the last duplicate instead. There is also
29350 an option \-nowarn-\, which stops it listing duplicate keys to \stderr\. For
29351 other errors, where it doesn't actually make a new file, the return code is 2.
29355 .section Finding individual retry times (exinext)
29356 .rset SECTfinindret "~~chapter.~~section"
29357 .index retry||times
29359 A utility called \*exinext*\ (mostly a Perl script) provides the ability to fish
29360 specific information out of the retry database. Given a mail domain (or a
29361 complete address), it looks up the hosts for that domain, and outputs any retry
29362 information for the hosts or for the domain. At present, the retry information
29363 is obtained by running \*exim@_dumpdb*\ (see below) and post-processing the
29364 output. For example:
29366 $ exinext piglet@milne.fict.example
29367 kanga.milne.fict.example:192.168.8.1 error 146: Connection refused
29368 first failed: 21-Feb-1996 14:57:34
29369 last tried: 21-Feb-1996 14:57:34
29370 next try at: 21-Feb-1996 15:02:34
29371 roo.milne.fict.example:192.168.8.3 error 146: Connection refused
29372 first failed: 20-Jan-1996 13:12:08
29373 last tried: 21-Feb-1996 11:42:03
29374 next try at: 21-Feb-1996 19:42:03
29375 past final cutoff time
29377 You can also give \*exinext*\ a local part, without a domain, and it
29378 will give any retry information for that local part in your default domain.
29379 A message id can be used to obtain retry information pertaining to a specific
29380 message. This exists only when an attempt to deliver a message to a remote host
29381 suffers a message-specific error (see section ~~SECToutSMTPerr). \*exinext*\ is
29382 not particularly efficient, but then it isn't expected to be run very often.
29384 The \*exinext*\ utility calls Exim to find out information such as the location
29385 of the spool directory. The utility has \-C-\ and \-D-\ options, which are
29386 passed on to the \*exim*\ commands. The first specifies an alternate Exim
29387 configuration file, and the second sets macros for use within the configuration
29388 file. These features are mainly to help in testing, but might also be useful in
29389 environments where more than one configuration file is in use.
29393 .section Hints database maintenance (exim@_dumpdb, exim@_fixdb, exim@_tidydb)
29394 .rset SECThindatmai "~~chapter.~~section"
29395 .index hints database||maintenance
29396 .index maintaining Exim's hints database
29397 Three utility programs are provided for maintaining the DBM files that Exim
29398 uses to contain its delivery hint information. Each program requires two
29399 arguments. The first specifies the name of Exim's spool directory, and the
29400 second is the name of the database it is to operate on. These are as
29403 \*retry*\: the database of retry information
29405 \*wait-*\<<transport name>>: databases of information about messages waiting
29408 \*callout*\: the callout cache
29410 \*misc*\: other hints data
29412 The \*misc*\ database is used for
29414 Serializing \\ETRN\\ runs (when \smtp@_etrn@_serialize\ is set)
29416 Serializing delivery to a specific host (when \serialize@_hosts\ is set in an
29417 \%smtp%\ transport)
29420 .section exim@_dumpdb
29421 .index \*exim@_dumpdb*\
29422 The entire contents of a database are written to the standard output by the
29423 \*exim@_dumpdb*\ program, which has no options or arguments other than the
29424 spool and database names. For example, to dump the retry database:
29426 exim_dumpdb /var/spool/exim retry
29428 Two lines of output are produced for each entry:
29430 T:mail.ref.example:192.168.242.242 146 77 Connection refused
29431 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
29433 The first item on the first line is the key of the record. It starts with one
29434 of the letters R, or T, depending on whether it refers to a routing or
29435 transport retry. For a local delivery, the next part is the local address; for
29436 a remote delivery it is the name of the remote host, followed by its failing IP
29437 address (unless \no@_retry@_include@_ip@_address\ is set on the \%smtp%\
29438 transport). If the remote port is not the standard one (port 25), it is added
29439 to the IP address. Then there follows an error code, an additional error code,
29440 and a textual description of the error.
29442 The three times on the second line are the time of first failure, the time of
29443 the last delivery attempt, and the computed time for the next attempt. The line
29444 ends with an asterisk if the cutoff time for the last retry rule has been
29447 Each output line from \*exim@_dumpdb*\ for the \*wait-*\$it{xxx} databases
29448 consists of a host name followed by a list of ids for messages that are or were
29449 waiting to be delivered to that host. If there are a very large number for any
29450 one host, continuation records, with a sequence number added to the host name,
29451 may be seen. The data in these records is often out of date, because a message
29452 may be routed to several alternative hosts, and Exim makes no effort to keep
29456 .section exim@_tidydb
29457 .index \*exim@_tidydb*\
29458 The \*exim@_tidydb*\ utility program is used to tidy up the contents of the
29459 hints databases. If run with no options, it removes all records from a database
29460 that are more than 30 days old. The cutoff date can be altered by means of the
29461 \-t-\ option, which must be followed by a time. For example, to remove all
29462 records older than a week from the retry database:
29464 exim_tidydb -t 7d /var/spool/exim retry
29466 Both the \*wait-*\$it{xxx} and \*retry*\ databases contain items that involve
29467 message ids. In the former these appear as data in records keyed by host --
29468 they were messages that were waiting for that host -- and in the latter they
29469 are the keys for retry information for messages that have suffered certain
29470 types of error. When \*exim@_tidydb*\ is run, a check is made to ensure that
29471 message ids in database records are those of messages that are still on the
29472 queue. Message ids for messages that no longer exist are removed from
29473 \*wait-*\$it{xxx} records, and if this leaves any records empty, they are
29474 deleted. For the \*retry*\ database, records whose keys are non-existent
29475 message ids are removed. The \*exim@_tidydb*\ utility outputs comments on the
29476 standard output whenever it removes information from the database.
29479 Certain records are automatically removed by Exim when they are no longer
29480 needed, but others are not. For example, if all the MX hosts for a domain are
29481 down, a retry record is created for each one. If the primary MX host comes back
29482 first, its record is removed when Exim successfully delivers to it, but the
29483 records for the others remain because Exim has not tried to use those hosts.
29485 It is important, therefore, to run \*exim@_tidydb*\ periodically on all the
29486 hints databases. You should do this at a quiet time of day, because it requires
29487 a database to be locked (and therefore inaccessible to Exim) while it does its
29488 work. Removing records from a DBM file does not normally make the file smaller,
29489 but all the common DBM libraries are able to re-use the space that is released.
29490 After an initial phase of increasing in size, the databases normally reach a
29491 point at which they no longer get any bigger, as long as they are regularly
29494 \**Warning**\: If you never run \*exim@_tidydb*\, the space used by the hints
29495 databases is likely to keep on increasing.
29499 .section exim@_fixdb
29500 .index \*exim@_fixdb*\
29501 The \*exim@_fixdb*\ program is a utility for interactively modifying databases.
29502 Its main use is for testing Exim, but it might also be occasionally useful for
29503 getting round problems in a live system. It has no options, and its interface
29504 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
29505 key of a database record can then be entered, and the data for that record is
29508 If `d' is typed at the next prompt, the entire record is deleted. For all
29509 except the \*retry*\ database, that is the only operation that can be carried
29510 out. For the \*retry*\ database, each field is output preceded by a number, and
29511 data for individual fields can be changed by typing the field number followed
29512 by new data, for example:
29516 resets the time of the next delivery attempt. Time values are given as a
29517 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
29518 used as optional separators.
29522 .section Mailbox maintenance (exim@_lock)
29523 .rset SECTmailboxmaint "~~chapter.~~section"
29524 .index mailbox||maintenance
29525 .index \*exim@_lock*\
29526 .index locking mailboxes
29527 The \*exim@_lock*\ utility locks a mailbox file using the same algorithm as
29528 Exim. For a discussion of locking issues, see section ~~SECTopappend.
29529 \*Exim@_lock*\ can be used to prevent any modification of a mailbox by Exim or
29530 a user agent while investigating a problem. The utility requires the name of
29531 the file as its first argument. If the locking is successful, the second
29532 argument is run as a command (using C's \*system()*\ function); if there is no
29533 second argument, the value of the SHELL environment variable is used; if this
29534 is unset or empty, \(/bin/sh)\ is run. When the command finishes, the mailbox
29535 is unlocked and the utility ends. The following options are available:
29540 Use \*fcntl()*\ locking on the open mailbox.
29543 Use \*flock()*\ locking on the open mailbox, provided the operating system
29547 This must be followed by a number, which is a number of seconds; it sets the
29548 interval to sleep between retries (default 3).
29551 Create a lock file before opening the mailbox.
29554 Lock the mailbox using MBX rules.
29557 Suppress verification output.
29560 This must be followed by a number; it sets the number of times to try to get
29561 the lock (default 10).
29563 .option restore@_time
29564 This option causes \exim@_lock\ to restore the modified and read times to the
29565 locked file before exiting. This allows you to access a locked mailbox (for
29566 example, to take a backup copy) without disturbing the times that the user
29570 This must be followed by a number, which is a number of seconds; it sets a
29571 timeout to be used with a blocking \*fcntl()*\ lock. If it is not set (the
29572 default), a non-blocking call is used.
29575 Generate verbose output.
29579 If none of \-fcntl-\,
29581 \-lockfile-\ or \-mbx-\ are given, the default is to create a lock file and
29582 also to use \*fcntl()*\ locking on the mailbox, which is the same as Exim's
29583 default. The use of
29585 or \-fcntl-\ requires that the file be writeable; the use of
29586 \-lockfile-\ requires that the directory containing the file be writeable.
29587 Locking by lock file does not last for ever; Exim assumes that a lock file is
29588 expired if it is more than 30 minutes old.
29590 The \-mbx-\ option can be used with either or both of \-fcntl-\ or \-flock-\.
29591 It assumes \-fcntl-\ by default.
29592 MBX locking causes a shared lock to be taken out on the open mailbox, and an
29593 exclusive lock on the file \(/tmp/.$it{n}.$it{m})\ where $it{n} and $it{m} are
29594 the device number and inode number of the mailbox file. When the locking is
29595 released, if an exclusive lock can be obtained for the mailbox, the file in
29596 \(/tmp)\ is deleted.
29598 The default output contains verification of the locking that takes place. The
29599 \-v-\ option causes some additional information to be given. The \-q-\ option
29600 suppresses all output except error messages.
29604 exim_lock /var/spool/mail/spqr
29606 runs an interactive shell while the file is locked, whereas
29608 exim@_lock -q /var/spool/mail/spqr @<@<End
29612 runs a specific non-interactive sequence of commands while the file is locked,
29613 suppressing all verification output. A single command can be run by a command
29616 exim_lock -q /var/spool/mail/spqr \
29617 "cp /var/spool/mail/spqr /some/where"
29619 Note that if a command is supplied, it must be entirely contained within the
29620 second argument -- hence the quotes.
29628 . ============================================================================
29629 .chapter The Exim monitor
29630 .set runningfoot "monitor"
29631 .rset CHAPeximon ~~chapter
29633 .index Exim monitor
29636 .index Local/eximon.conf
29637 .index \(exim@_monitor/EDITME)\
29638 The Exim monitor is an application which displays in an X window information
29639 about the state of Exim's queue and what Exim is doing. An admin user can
29640 perform certain operations on messages from this GUI interface; however all
29641 such facilities are also available from the command line, and indeed, the
29642 monitor itself makes use of the command line to perform any actions requested.
29645 .section Running the monitor
29646 The monitor is started by running the script called \*eximon*\. This is a shell
29647 script that sets up a number of environment variables, and then runs the
29648 binary called \(eximon.bin)\. The default appearance of the monitor window can
29649 be changed by editing the \(Local/eximon.conf)\ file created by editing
29650 \(exim@_monitor/EDITME)\. Comments in that file describe what the various
29651 parameters are for.
29653 The parameters that get built into the \*eximon*\ script can be overridden for a
29654 particular invocation by setting up environment variables of the same names,
29655 preceded by `$tt{EXIMON@_}'. For example, a shell command such as
29657 EXIMON_LOG_DEPTH=400 eximon
29659 (in a Bourne-compatible shell) runs \*eximon*\ with an overriding setting of the
29660 \\LOG@_DEPTH\\ parameter. If \\EXIMON@_LOG@_FILE@_PATH\\ is set in the
29661 environment, it overrides the Exim log file configuration. This makes it
29662 possible to have \*eximon*\ tailing log data that is written to syslog, provided
29663 that MAIL.INFO syslog messages are routed to a file on the local host.
29665 X resources can be used to change the appearance of the window in the normal
29666 way. For example, a resource setting of the form
29668 Eximon*background: gray94
29670 changes the colour of the background to light grey rather than white. The
29671 stripcharts are drawn with both the data lines and the reference lines in
29672 black. This means that the reference lines are not visible when on top of the
29673 data. However, their colour can be changed by setting a resource called
29674 `highlight' (an odd name, but that's what the Athena stripchart widget uses).
29675 For example, if your X server is running Unix, you could set up lighter
29676 reference lines in the stripcharts by obeying
29679 Eximon*highlight: gray
29684 In order to see the contents of messages on the queue, and to operate on them,
29685 \*eximon*\ must either be run as root or by an admin user.
29687 The monitor's window is divided into three parts. The first contains one or
29688 more stripcharts and two action buttons, the second contains a `tail' of the
29689 main log file, and the third is a display of the queue of messages awaiting
29690 delivery, with two more action buttons. The following sections describe these
29691 different parts of the display.
29695 .section The stripcharts
29697 The first stripchart is always a count of messages on the queue. Its name can
29698 be configured by setting \\QUEUE@_STRIPCHART@_NAME\\ in the
29699 \(Local/eximon.conf)\ file. The remaining stripcharts are defined in the
29700 configuration script by regular expression matches on log file entries, making
29701 it possible to display, for example, counts of messages delivered to certain
29702 hosts or using certain transports. The supplied defaults display counts of
29703 received and delivered messages, and of local and SMTP deliveries. The default
29704 period between stripchart updates is one minute; this can be adjusted by a
29705 parameter in the \(Local/eximon.conf)\ file.
29707 The stripchart displays rescale themselves automatically as the value they are
29708 displaying changes. There are always 10 horizontal lines in each chart; the
29709 title string indicates the value of each division when it is greater than one.
29710 For example, `x2' means that each division represents a value of 2.
29712 It is also possible to have a stripchart which shows the percentage fullness of
29713 a particular disk partition, which is useful when local deliveries are confined
29714 to a single partition.
29715 .index \statvfs\ function
29716 This relies on the availability of the \*statvfs()*\ function or equivalent in
29717 the operating system. Most, but not all versions of Unix that support Exim have
29718 this. For this particular stripchart, the top of the chart always represents
29719 100%, and the scale is given as `x10%'. This chart is configured by setting
29720 \\SIZE@_STRIPCHART\\ and (optionally) \\SIZE@_STRIPCHART@_NAME\\ in the
29721 \(Local/eximon.conf)\ file.
29725 .section Main action buttons
29726 .index size||of monitor window
29727 .index monitor window size
29729 Below the stripcharts there is an action button for quitting the monitor. Next
29730 to this is another button marked `Size'. They are placed here so that shrinking
29731 the window to its default minimum size leaves just the queue count stripchart
29732 and these two buttons visible. Pressing the `Size' button causes the window to
29733 expand to its maximum size, unless it is already at the maximum, in which case
29734 it is reduced to its minimum.
29736 When expanding to the maximum, if the window cannot be fully seen where it
29737 currently is, it is moved back to where it was the last time it was at full
29738 size. When it is expanding from its minimum size, the old position is
29739 remembered, and next time it is reduced to the minimum it is moved back there.
29741 The idea is that you can keep a reduced window just showing one or two
29742 stripcharts at a convenient place on your screen, easily expand it to show
29743 the full window when required, and just as easily put it back to what it was.
29744 The idea is copied from what the \*twm*\ window manager does for its
29745 \*f.fullzoom*\ action. The minimum size of the window can be changed by setting
29746 the \\MIN@_HEIGHT\\ and \\MIN@_WIDTH\\ values in \(Local/eximon.conf)\.
29748 Normally, the monitor starts up with the window at its full size, but it can be
29749 built so that it starts up with the window at its smallest size, by setting
29750 \\START@_SMALL\\=yes in \(Local/eximon.conf)\.
29753 .section The log display
29754 .index log||tail of, in monitor
29755 The second section of the window is an area in which a display of the tail of
29756 the main log is maintained.
29757 To save space on the screen, the timestamp on each log line is shortened by
29758 removing the date and, if \log@_timezone\ is set, the timezone.
29759 The log tail is not available when the only destination for logging data is
29760 syslog, unless the syslog lines are routed to a local file whose name is passed
29761 to \*eximon*\ via the \\EXIMON@_LOG@_FILE@_PATH\\ environment variable.
29763 The log sub-window has a scroll bar at its lefthand side which can be used to
29764 move back to look at earlier text, and the up and down arrow keys also have a
29765 scrolling effect. The amount of log that is kept depends on the setting of
29766 \\LOG@_BUFFER\\ in \(Local/eximon.conf)\, which specifies the amount of memory
29767 to use. When this is full, the earlier 50% of data is discarded -- this is much
29768 more efficient than throwing it away line by line. The sub-window also has a
29769 horizontal scroll bar for accessing the ends of long log lines. This is the
29770 only means of horizontal scrolling; the right and left arrow keys are not
29771 available. Text can be cut from this part of the window using the mouse in the
29772 normal way. The size of this subwindow is controlled by parameters in the
29773 configuration file \(Local/eximon.conf)\.
29775 Searches of the text in the log window can be carried out by means of the ^R
29776 and ^S keystrokes, which default to a reverse and a forward search,
29777 respectively. The search covers only the text that is displayed in the window.
29778 It cannot go further back up the log.
29780 The point from which the search starts is indicated by a caret marker. This is
29781 normally at the end of the text in the window, but can be positioned explicitly
29782 by pointing and clicking with the left mouse button, and is moved automatically
29783 by a successful search. If new text arrives in the window when it is scrolled
29784 back, the caret remains where it is, but if the window is not scrolled back,
29785 the caret is moved to the end of the new text.
29787 Pressing ^R or ^S pops up a window into which the search text can be typed.
29788 There are buttons for selecting forward or reverse searching, for carrying out
29789 the search, and for cancelling. If the `Search' button is pressed, the search
29790 happens and the window remains so that further searches can be done. If the
29791 `Return' key is pressed, a single search is done and the window is closed. If
29792 ^C is typed the search is cancelled.
29794 The searching facility is implemented using the facilities of the Athena text
29795 widget. By default this pops up a window containing both `search' and `replace'
29796 options. In order to suppress the unwanted `replace' portion for eximon, a
29797 modified version of the \TextPop\ widget is distributed with Exim. However, the
29798 linkers in BSDI and HP-UX seem unable to handle an externally provided version
29799 of \TextPop\ when the remaining parts of the text widget come from the standard
29800 libraries. The compile-time option \\EXIMON@_TEXTPOP\\ can be unset to cut out
29801 the modified \TextPop\, making it possible to build Eximon on these systems, at
29802 the expense of having unwanted items in the search popup window.
29805 .section The queue display
29806 .index queue||display in monitor
29807 The bottom section of the monitor window contains a list of all messages that
29808 are on the queue, which includes those currently being received or delivered,
29809 as well as those awaiting delivery. The size of this subwindow is controlled by
29810 parameters in the configuration file \(Local/eximon.conf)\, and the frequency
29811 at which it is updated is controlled by another parameter in the same file --
29812 the default is 5 minutes, since queue scans can be quite expensive. However,
29813 there is an `Update' action button just above the display which can be used to
29814 force an update of the queue display at any time.
29816 When a host is down for some time, a lot of pending mail can build up for it,
29817 and this can make it hard to deal with other messages on the queue. To help
29818 with this situation there is a button next to `Update' called `Hide'. If
29819 pressed, a dialogue box called `Hide addresses ending with' is put up. If you
29820 type anything in here and press `Return', the text is added to a chain of such
29821 texts, and if every undelivered address in a message matches at least one
29822 of the texts, the message is not displayed.
29824 If there is an address that does not match any of the texts, all the addresses
29825 are displayed as normal. The matching happens on the ends of addresses so, for
29826 example, \*cam.ac.uk*\ specifies all addresses in Cambridge, while
29827 \*xxx@@foo.com.example*\ specifies just one specific address. When any hiding
29828 has been set up, a button called `Unhide' is displayed. If pressed, it cancels
29829 all hiding. Also, to ensure that hidden messages do not get forgotten, a hide
29830 request is automatically cancelled after one hour.
29832 While the dialogue box is displayed, you can't press any buttons or do anything
29833 else to the monitor window. For this reason, if you want to cut text from the
29834 queue display to use in the dialogue box, you have to do the cutting before
29835 pressing the `Hide' button.
29837 The queue display contains, for each unhidden queued message, the length of
29838 time it has been on the queue, the size of the message, the message id, the
29839 message sender, and the first undelivered recipient, all on one line. If it is
29840 a bounce message, the sender is shown as `<>'. If there is more than one
29841 recipient to which the message has not yet been delivered, subsequent ones are
29842 listed on additional lines, up to a maximum configured number, following which
29843 an ellipsis is displayed. Recipients that have already received the message are
29845 .index frozen messages||display
29846 If a message is frozen, an asterisk is displayed at the left-hand side.
29848 The queue display has a vertical scroll bar, and can also be scrolled by means
29849 of the arrow keys. Text can be cut from it using the mouse in the normal way.
29850 The text searching facilities, as described above for the log window, are also
29851 available, but the caret is always moved to the end of the text when the queue
29852 display is updated.
29855 .section The queue menu
29856 .index queue||menu in monitor
29857 If the \shift\ key is held down and the left button is clicked when the mouse
29858 pointer is over the text for any message, an action menu pops up, and the first
29859 line of the queue display for the message is highlighted. This does not affect
29862 If you want to use some other event for popping up the menu, you can set the
29863 \\MENU@_EVENT\\ parameter in \(Local/eximon.conf)\ to change the default, or
29864 set \\EXIMON@_MENU@_EVENT\\ in the environment before starting the monitor. The
29865 value set in this parameter is a standard X event description. For example, to
29866 run eximon using \ctrl\ rather than \shift\ you could use
29868 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
29870 The title of the menu is the message id, and it contains entries which act as
29873 \*message log*\: The contents of the message log for the message are displayed in
29876 \*headers*\: Information from the spool file that contains the envelope
29877 information and headers is displayed in a new text window. See chapter
29878 ~~CHAPspool for a description of the format of spool files.
29880 \*body*\: The contents of the spool file containing the body of the message are
29881 displayed in a new text window. There is a default limit of 20,000 bytes to the
29882 amount of data displayed. This can be changed by setting the \\BODY@_MAX\\
29883 option at compile time, or the \\EXIMON@_BODY@_MAX\\ option at run time.
29885 \*deliver message*\: A call to Exim is made using the \-M-\ option to request
29886 delivery of the message. This causes an automatic thaw if the message is
29887 frozen. The \-v-\ option is also set, and the output from Exim is displayed in
29888 a new text window. The delivery is run in a separate process, to avoid holding
29889 up the monitor while the delivery proceeds.
29891 \*freeze message*\: A call to Exim is made using the \-Mf-\ option to request
29892 that the message be frozen.
29894 .index thawing messages
29895 .index unfreezing messages
29896 .index frozen messages||thawing
29897 \*thaw message*\: A call to Exim is made using the \-Mt-\ option to request that
29898 the message be thawed.
29900 .index delivery||forcing failure
29901 \*give up on msg*\: A call to Exim is made using the \-Mg-\ option to request
29902 that Exim gives up trying to deliver the message. A bounce message is generated
29903 for any remaining undelivered addresses.
29905 \*remove message*\: A call to Exim is made using the \-Mrm-\ option to request
29906 that the message be deleted from the system without generating a bounce
29909 \*add recipient*\: A dialog box is displayed into which a recipient address can
29910 be typed. If the address is not qualified and the \\QUALIFY@_DOMAIN\\ parameter
29911 is set in \(Local/eximon.conf)\, the address is qualified with that domain.
29912 Otherwise it must be entered as a fully qualified address. Pressing \\RETURN\\
29913 causes a call to Exim to be made using the \-Mar-\ option to request that an
29914 additional recipient be added to the message, unless the entry box is empty, in
29915 which case no action is taken.
29917 \*mark delivered*\: A dialog box is displayed into which a recipient address can
29918 be typed. If the address is not qualified and the \\QUALIFY@_DOMAIN\\ parameter
29919 is set in \(Local/eximon.conf)\, the address is qualified with that domain.
29920 Otherwise it must be entered as a fully qualified address. Pressing \\RETURN\\
29921 causes a call to Exim to be made using the \-Mmd-\ option to mark the given
29922 recipient address as already delivered, unless the entry box is empty, in which
29923 case no action is taken.
29925 \*mark all delivered*\: A call to Exim is made using the \-Mmad-\ option to mark
29926 all recipient addresses as already delivered.
29928 \*edit sender*\: A dialog box is displayed initialized with the current sender's
29929 address. Pressing \\RETURN\\ causes a call to Exim to be made using the \-Mes-\
29930 option to replace the sender address, unless the entry box is empty, in which
29931 case no action is taken. If you want to set an empty sender (as in bounce
29932 messages), you must specify it as `<>'. Otherwise, if the address is not
29933 qualified and the \\QUALIFY@_DOMAIN\\ parameter is set in
29934 \(Local/eximon.conf)\, the address is qualified with that domain.
29936 When a delivery is forced, a window showing the \-v-\ output is displayed. In
29937 other cases when a call to Exim is made, if there is any output from Exim (in
29938 particular, if the command fails) a window containing the command and the
29939 output is displayed. Otherwise, the results of the action are normally apparent
29940 from the log and queue displays. However, if you set \\ACTION@_OUTPUT\\=yes in
29941 \(Local/eximon.conf)\, a window showing the Exim command is always opened, even
29942 if no output is generated.
29944 The queue display is automatically updated for actions such as freezing and
29945 thawing, unless \\ACTION@_QUEUE@_UPDATE\\=no has been set in
29946 \(Local/eximon.conf)\. In this case the `Update' button has to be used to force
29947 an update of the display after one of these actions.
29949 In any text window that is displayed as result of a menu action, the normal
29950 cut-and-paste facility is available, and searching can be carried out using ^R
29951 and ^S, as described above for the log tail window.
29962 . ============================================================================
29963 .chapter Security considerations
29964 .set runningfoot "security"
29965 .rset CHAPsecurity ~~chapter
29967 This chapter discusses a number of issues concerned with security, some of
29968 which are also covered in other parts of this manual.
29970 For reasons that this author does not understand, some people have promoted
29971 Exim as a `particularly secure' mailer. Perhaps it is because of the existence
29972 of this chapter in the documentation. However, the intent of the chapter is
29973 simply to describe the way Exim works in relation to certain security concerns,
29974 not to make any specific claims about the effectiveness of its security as
29975 compared with other MTAs.
29977 What follows is a description of the way Exim is supposed to be. Best efforts
29978 have been made to try to ensure that the code agrees with the theory, but an
29979 absence of bugs can never be guaranteed. Any that are reported will get fixed
29980 as soon as possible.
29982 .section Building a more `hardened' Exim
29983 .index security||build-time features
29984 There are a number of build-time options that can be set in \(Local/Makefile)\
29985 to create Exim binaries that are `harder' to attack, in particular by a rogue
29986 Exim administrator who does not have the root password, or by someone who has
29987 penetrated the Exim (but not the root) account. These options are as follows:
29989 \\ALT@_CONFIG@_PREFIX\\ can be set to a string that is required to match the
29990 start of any file names used with the \-C-\ option. When it is set, these file
29991 names are also not allowed to contain the sequence `/../'. (However, if the
29992 value of the \-C-\ option is identical to the value of \\CONFIGURE@_FILE\\ in
29993 \(Local/Makefile)\, Exim ignores \-C-\ and proceeds as usual.) There is no
29994 default setting for \ALT@_CONFIG@_PREFIX\.
29996 If the permitted configuration files are confined to a directory to
29997 which only root has access, this guards against someone who has broken
29998 into the Exim account from running a privileged Exim with an arbitrary
29999 configuration file, and using it to break into other accounts.
30001 If \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined, root privilege is retained for \-C-\
30002 and \-D-\ only if the caller of Exim is root. Without it, the Exim user may
30003 also use \-C-\ and \-D-\ and retain privilege. Setting this option locks out
30004 the possibility of testing a configuration using \-C-\ right through message
30005 reception and delivery, even if the caller is root. The reception works, but by
30006 that time, Exim is running as the Exim user, so when it re-execs to regain
30007 privilege for the delivery, the use of \-C-\ causes privilege to be lost.
30008 However, root can test reception and delivery using two separate commands.
30009 \\ALT@_CONFIG@_ROOT@_ONLY\\ is not set by default.
30011 If \\DISABLE@_D@_OPTION\\ is defined, the use of the \-D-\ command line option
30014 \\FIXED@_NEVER@_USERS\\ can be set to a colon-separated list of users that are
30015 never to be used for any deliveries. This is like the \never@_users\ runtime
30016 option, but it cannot be overridden; the runtime option adds additional users
30017 to the list. The default setting is `root'; this prevents a non-root user who
30018 is permitted to modify the runtime file from using Exim as a way to get root.
30022 .section Root privilege
30024 .index root privilege
30025 The Exim binary is normally setuid to root, which means that it gains root
30026 privilege (runs as root) when it starts execution. In some special cases (for
30027 example, when the daemon is not in use and there are no local deliveries), it
30028 may be possible to run Exim setuid to some user other than root. This is
30029 discussed in the next section. However, in most installations, root privilege
30030 is required for two things:
30032 To set up a socket connected to the standard SMTP port (25) when initialising
30033 the listening daemon. If Exim is run from \*inetd*\, this privileged action is
30036 To be able to change uid and gid in order to read users' \(.forward)\ files and
30037 perform local deliveries as the receiving user or as specified in the
30040 It is not necessary to be root to do any of the other things Exim does, such as
30041 receiving messages and delivering them externally over SMTP, and it is
30042 obviously more secure if Exim does not run as root except when necessary.
30043 For this reason, a user and group for Exim to use must be defined in
30044 \(Local/Makefile)\. These are known as `the Exim user' and `the Exim group'.
30045 Their values can be changed by the run time configuration, though this is not
30046 recommended. Often a user called \*exim*\ is used, but some sites use \*mail*\
30047 or another user name altogether.
30049 Exim uses \*setuid()*\ whenever it gives up root privilege. This is a permanent
30050 abdication; the process cannot regain root afterwards. Prior to release 4.00,
30051 \*seteuid()*\ was used in some circumstances, but this is no longer the case.
30053 After a new Exim process has interpreted its command line options, it changes
30054 uid and gid in the following cases:
30056 .index \-C-\ option
30057 .index \-D-\ option
30058 If the \-C-\ option is used to specify an alternate configuration file, or if
30059 the \-D-\ option is used to define macro values for the configuration, and the
30060 calling process is not running as root or the Exim user, the uid and gid are
30061 changed to those of the calling process.
30062 However, if \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined in \(Local/Makefile)\, only
30063 root callers may use \-C-\ and \-D-\ without losing privilege, and if
30064 \\DISABLE@_D@_OPTION\\ is set, the \-D-\ option may not be used at all.
30066 .index \-be-\ option
30067 .index \-bf-\ option
30068 .index \-bF-\ option
30069 If the expansion test option (\-be-\) or one of the filter testing options
30070 (\-bf-\ or \-bF-\) are used, the uid and gid are changed to those of the
30073 If the process is not a daemon process or a queue runner process or a delivery
30074 process or a process for testing address routing (started with \-bt-\), the uid
30075 and gid are changed to the Exim user and group. This means that Exim always
30076 runs under its own uid and gid when receiving messages. This also applies when
30077 testing address verification
30078 .index \-bv-\ option
30079 .index \-bh-\ option
30080 (the \-bv-\ option) and testing incoming message policy controls (the \-bh-\
30083 For a daemon, queue runner, delivery, or address testing process, the uid
30084 remains as root at this stage, but the gid is changed to the Exim group.
30086 The processes that initially retain root privilege behave as follows:
30088 A daemon process changes the gid to the Exim group and the uid to the Exim user
30089 after setting up one or more listening sockets. The \*initgroups()*\ function
30090 is called, so that if the Exim user is in any additional groups, they will be
30091 used during message reception.
30093 A queue runner process retains root privilege throughout its execution. Its job
30094 is to fork a controlled sequence of delivery processes.
30096 A delivery process retains root privilege throughout most of its execution,
30097 but any actual deliveries (that is, the transports themselves) are run in
30098 subprocesses which always change to a non-root uid and gid. For local
30099 deliveries this is typically the uid and gid of the owner of the mailbox; for
30100 remote deliveries, the Exim uid and gid are used. Once all the delivery
30101 subprocesses have been run, a delivery process changes to the Exim uid and gid
30102 while doing post-delivery tidying up such as updating the retry database and
30103 generating bounce and warning messages.
30105 While the recipient addresses in a message are being routed, the delivery
30106 process runs as root. However, if a user's filter file has to be processed,
30107 this is done in a subprocess that runs under the individual user's uid and
30108 gid. A system filter is run as root unless \system@_filter@_user\ is set.
30110 A process that is testing addresses (the \-bt-\ option) runs as root so that
30111 the routing is done in the same environment as a message delivery.
30115 .section Running Exim without privilege
30116 .rset SECTrunexiwitpri "~~chapter.~~section"
30117 .index privilege, running without
30118 .index unprivileged running
30119 .index root privilege||running without
30120 Some installations like to run Exim in an unprivileged state for more of its
30121 operation, for added security. Support for this mode of operation is provided
30122 by the global option \deliver@_drop@_privilege\. When this is set, the uid and
30123 gid are changed to the Exim user and group at the start of a delivery process
30124 (and also queue runner and address testing processes). This means that address
30125 routing is no longer run as root, and the deliveries themselves cannot change
30128 Leaving the binary setuid to root, but setting \deliver@_drop@_privilege\ means
30129 that the daemon can still be started in the usual way, and it can respond
30130 correctly to SIGHUP because the re-invocation regains root privilege.
30132 An alternative approach is to make Exim setuid to the Exim user and also setgid
30134 If you do this, the daemon must be started from a root process. (Calling
30135 Exim from a root process makes it behave in the way it does when it is setuid
30136 root.) However, the daemon cannot restart itself after a SIGHUP signal because
30137 it cannot regain privilege.
30139 It is still useful to set \deliver@_drop@_privilege\ in this case, because it
30140 stops Exim from trying to re-invoke itself to do a delivery after a message has
30141 been received. Such a re-invocation is a waste of resources because it has no
30144 If restarting the daemon is not an issue (for example, if
30146 \mua@_wrapper\ is set, or
30148 \*inetd*\ is being used instead of a daemon), having the binary setuid to the
30149 Exim user seems a clean approach, but there is one complication:
30151 In this style of operation, Exim is running with the real uid and gid set to
30152 those of the calling process, and the effective uid/gid set to Exim's values.
30153 Ideally, any association with the calling process' uid/gid should be dropped,
30154 that is, the real uid/gid should be reset to the effective values so as to
30155 discard any privileges that the caller may have. While some operating systems
30156 have a function that permits this action for a non-root effective uid, quite a
30157 number of them do not. Because of this lack of standardization, Exim does not
30158 address this problem at this time.
30160 For this reason, the recommended approach for `mostly unprivileged' running is
30161 to keep the Exim binary setuid to root, and to set \deliver@_drop@_privilege\.
30162 This also has the advantage of allowing a daemon to be used in the most
30163 straightforward way.
30165 If you configure Exim not to run delivery processes as root, there are a
30166 number of restrictions on what you can do:
30168 You can deliver only as the Exim user/group. You should explicitly use the
30169 \user\ and \group\ options to override routers or local transports that
30170 normally deliver as the recipient. This makes sure that configurations that
30171 work in this mode function the same way in normal mode. Any implicit or
30172 explicit specification of another user causes an error.
30174 Use of \(.forward)\ files is severely restricted, such that it is usually
30175 not worthwhile to include them in the configuration.
30177 Users who wish to use \(.forward)\ would have to make their home directory and
30178 the file itself accessible to the Exim user. Pipe and append-to-file entries,
30179 and their equivalents in Exim filters, cannot be used. While they could be
30180 enabled in the Exim user's name, that would be insecure and not very useful.
30182 Unless the local user mailboxes are all owned by the Exim user (possible in
30183 some POP3 or IMAP-only environments):
30185 They must be owned by the Exim group and be writable by that group. This
30186 implies you must set \mode\ in the appendfile configuration, as well as the
30187 mode of the mailbox files themselves.
30189 You must set \no@_check@_owner\, since most or all of the files will not be
30190 owned by the Exim user.
30192 You must set \file@_must@_exist\, because Exim cannot set the owner correctly
30193 on a newly created mailbox when unprivileged. This also implies that new
30194 mailboxes need to be created manually.
30197 These restrictions severely restrict what can be done in local deliveries.
30198 However, there are no restrictions on remote deliveries. If you are running a
30199 gateway host that does no local deliveries, setting \deliver@_drop@_privilege\
30200 gives more security at essentially no cost.
30202 If you are using the \mua@_wrapper\ facility (see chapter ~~CHAPnonqueueing),
30203 \deliver@_drop@_privilege\ is forced to be true.
30207 .section Delivering to local files
30208 Full details of the checks applied by \%appendfile%\ before it writes to a file
30209 are given in chapter ~~CHAPappendfile.
30212 .section IPv4 source routing
30213 .index source routing||in IP packets
30214 .index IP source routing
30215 Many operating systems suppress IP source-routed packets in the kernel, but
30216 some cannot be made to do this, so Exim does its own check. It logs incoming
30217 IPv4 source-routed TCP calls, and then drops them. Things are all different in
30218 IPv6. No special checking is currently done.
30221 .section The VRFY, EXPN, and ETRN commands in SMTP
30222 Support for these SMTP commands is disabled by default. If required, they can
30223 be enabled by defining suitable ACLs.
30227 .section Privileged users
30228 .index trusted user
30230 .index privileged user
30231 .index user||trusted
30233 Exim recognises two sets of users with special privileges. Trusted users are
30234 able to submit new messages to Exim locally, but supply their own sender
30235 addresses and information about a sending host. For other users submitting
30236 local messages, Exim sets up the sender address from the uid, and doesn't
30237 permit a remote host to be specified.
30239 .index \-f-\ option
30240 However, an untrusted user is permitted to use the \-f-\ command line option in
30241 the special form \-f @<@>-\ to indicate that a delivery failure for the message
30242 should not cause an error report. This affects the message's envelope, but it
30243 does not affect the ::Sender:: header. Untrusted users may also be permitted to
30244 use specific forms of address with the \-f-\ option by setting the
30245 \untrusted@_set@_sender\ option.
30247 Trusted users are used to run processes that receive mail messages from some
30248 other mail domain and pass them on to Exim for delivery either locally, or over
30249 the Internet. Exim trusts a caller that is running as root, as the Exim user,
30250 as any user listed in the \trusted@_users\ configuration option, or under any
30251 group listed in the \trusted@_groups\ option.
30253 Admin users are permitted to do things to the messages on Exim's queue. They
30254 can freeze or thaw messages, cause them to be returned to their senders, remove
30255 them entirely, or modify them in various ways. In addition, admin users can run
30256 the Exim monitor and see all the information it is capable of providing, which
30257 includes the contents of files on the spool.
30259 .index \-M-\ option
30260 .index \-q-\ option
30261 By default, the use of the \-M-\ and \-q-\ options to cause Exim to attempt
30262 delivery of messages on its queue is restricted to admin users. This
30263 restriction can be relaxed by setting the \no@_prod@_requires@_admin\ option.
30264 Similarly, the use of \-bp-\ (and its variants) to list the contents of the
30265 queue is also restricted to admin users. This restriction can be relaxed by
30266 setting \no@_queue@_list@_requires@_admin\.
30268 Exim recognises an admin user if the calling process is running as root or as
30269 the Exim user or if any of the groups associated with the calling process is
30270 the Exim group. It is not necessary actually to be running under the Exim
30271 group. However, if admin users who are not root or the Exim user are to access
30272 the contents of files on the spool via the Exim monitor (which runs
30273 unprivileged), Exim must be built to allow group read access to its spool
30277 .section Spool files
30278 .index spool directory||files
30279 Exim's spool directory and everything it contains is owned by the Exim user and
30280 set to the Exim group. The mode for spool files is defined in the
30281 \(Local/Makefile)\ configuration file, and defaults to 0640. This means that
30282 any user who is a member of the Exim group can access these files.
30285 .section Use of argv[0]
30286 Exim examines the last component of \argv[0]\, and if it matches one of a set
30287 of specific strings, Exim assumes certain options. For example, calling Exim
30288 with the last component of \argv[0]\ set to `rsmtp' is exactly equivalent to
30289 calling it with the option \-bS-\. There are no security implications in this.
30292 .section Use of %f formatting
30293 The only use made of `%f' by Exim is in formatting load average values. These
30294 are actually stored in integer variables as 1000 times the load average.
30295 Consequently, their range is limited and so therefore is the length of the
30299 .section Embedded Exim path
30300 Exim uses its own path name, which is embedded in the code, only when it needs
30301 to re-exec in order to regain root privilege. Therefore, it is not root when it
30302 does so. If some bug allowed the path to get overwritten, it would lead to an
30303 arbitrary program's being run as exim, not as root.
30306 .section Use of sprintf()
30307 .index \*sprintf()*\
30308 A large number of occurrences of `sprintf' in the code are actually calls to
30309 \*string@_sprintf()*\, a function that returns the result in malloc'd store.
30310 The intermediate formatting is done into a large fixed buffer by a function
30311 that runs through the format string itself, and checks the length of each
30312 conversion before performing it, thus preventing buffer overruns.
30314 The remaining uses of \*sprintf()*\ happen in controlled circumstances where
30315 the output buffer is known to be sufficiently long to contain the converted
30319 .section Use of debug@_printf() and log@_write()
30320 Arbitrary strings are passed to both these functions, but they do their
30321 formatting by calling the function \*string@_vformat()*\, which runs through
30322 the format string itself, and checks the length of each conversion.
30325 .section Use of strcat() and strcpy()
30326 These are used only in cases where the output buffer is known to be large
30327 enough to hold the result.
30336 . ============================================================================
30337 .chapter Format of spool files
30338 .set runningfoot "spool file format"
30339 .rset CHAPspool ~~chapter
30340 .index format||spool files
30341 .index spool directory||format of files
30342 .index spool||files, format of
30343 .index spool||files, editing
30344 A message on Exim's queue consists of two files, whose names are the message id
30345 followed by -D and -H, respectively. The data portion of the message is kept in
30346 the -D file on its own. The message's envelope, status, and headers are all
30347 kept in the -H file, whose format is described in this chapter. Each of these
30348 two files contains the final component of its own name as its first line. This
30349 is insurance against disk crashes where the directory is lost but the files
30350 themselves are recoverable.
30352 Some people are tempted into editing -D files in order to modify messages. You
30353 need to be extremely careful if you do this; it is not recommended and you are
30354 on your own if you do it. Here are some of the pitfalls:
30356 You must use the \*exim@_lock*\ utility to ensure that Exim does not try to
30357 deliver the message while you are fiddling with it. The lock is implemented
30358 by opening the -D file and taking out a write lock on it. If you update the
30359 file in place, the lock will be retained. If you write a new file and rename
30360 it, the lock will be lost at the instant of rename.
30362 If you change the number of lines in the file, the value of
30363 \$body@_linecount$\, which is stored in the -H file, will be incorrect.
30365 If the message is in MIME format, you must take care not to break it.
30367 If the message is cryptographically signed, any change will invalidate the
30371 Files whose names end with -J may also be seen in the \(input)\ directory (or
30372 its subdirectories when \split@_spool@_directory\ is set). These are journal
30373 files, used to record addresses to which the message has been delivered during
30374 the course of a delivery run. At the end of the run, the -H file is updated,
30375 and the -J file is deleted.
30377 .section Format of the -H file
30378 .index uid (user id)||in spool file
30379 .index gid (group id)||in spool file
30380 The second line of the -H file contains the login name for the uid of the
30381 process that called Exim to read the message, followed by the numerical uid and
30382 gid. For a locally generated message, this is normally the user who sent the
30383 message. For a message received over TCP/IP, it is normally the Exim user.
30385 The third line of the file contains the address of the message's sender as
30386 transmitted in the envelope, contained in angle brackets. The sender address is
30387 empty for bounce messages. For incoming SMTP mail, the sender address is given
30388 in the \\MAIL\\ command. For locally generated mail, the sender address is
30389 created by Exim from the login name of the current user and the configured
30390 \qualify@_domain\. However, this can be overridden by the \-f-\ option or a
30391 leading `From' line if the caller is trusted, or if the supplied address is
30392 `@<@>' or an address that matches \untrusted@_set@_senders\.
30394 The fourth line contains two numbers. The first is the time that the message
30395 was received, in the conventional Unix form -- the number of seconds since the
30396 start of the epoch. The second number is a count of the number of messages
30397 warning of delayed delivery that have been sent to the sender.
30399 There follow a number of lines starting with a hyphen. These can appear in any
30400 order, and are omitted when not relevant:
30402 \-acl <<number>> <<length>>-\: A line of this form is present for every ACL
30403 variable that is not empty. The number identifies the variable; the
30404 \acl@_c\*x*\$$\ variables are numbered 0--9 and the \acl@_m\*x*\$$\ variables
30405 are numbered 10--19. The length is the length of the data string for the
30406 variable. The string itself starts at the beginning of the next line, and is
30407 followed by a newline character. It may contain internal newlines.
30410 \-active@_hostname <<hostname>>-\: This is present if, when the message was
30411 received over SMTP, the value of \$smtp@_active@_hostname$\ was different to
30412 the value of \$primary@_hostname$\.
30415 \-allow@_unqualified@_recipient-\: This is present if unqualified recipient
30416 addresses are permitted in header lines (to stop such addresses from being
30417 qualified if rewriting occurs at transport time). Local messages that were
30418 input using \-bnq-\ and remote messages from hosts that match
30419 \recipient@_unqualified@_hosts\ set this flag.
30421 \-allow@_unqualified@_sender-\: This is present if unqualified sender
30422 addresses are permitted in header lines (to stop such addresses from being
30423 qualified if rewriting occurs at transport time). Local messages that were
30424 input using \-bnq-\ and remote messages from hosts that match
30425 \sender@_unqualified@_hosts\ set this flag.
30427 \-auth@_id <<text>>-\: The id information for a message received on an
30428 authenticated SMTP connection -- the value of the \$authenticated@_id$\
30431 \-auth@_sender <<address>>-\: The address of an authenticated sender -- the
30432 value of the \$authenticated@_sender$\ variable.
30434 \-body@_linecount <<number>>-\: This records the number of lines in the body of
30435 the message, and is always present.
30438 \-body@_zerocount <<number>>-\: This records the number of binary zero bytes in
30439 the body of the message, and is present if the number is greater than zero.
30442 \-deliver@_firsttime-\: This is written when a new message is first added to
30443 the spool. When the spool file is updated after a deferral, it is omitted.
30445 .index frozen messages||spool data
30446 \-frozen <<time>>-\: The message is frozen, and the freezing happened at
30449 \-helo@_name <<text>>-\: This records the host name as specified by a remote
30450 host in a \\HELO\\ or \\EHLO\\ command.
30452 \-host@_address <<address>>.<<port>>-\: This records the IP address of the host
30453 from which the message was received and the remote port number that was used.
30454 It is omitted for locally generated messages.
30456 \-host@_auth <<text>>-\: If the message was received on an authenticated SMTP
30457 connection, this records the name of the authenticator -- the value of the
30458 \$sender@_host@_authenticated$\ variable.
30460 \-host@_lookup@_failed-\: This is present if an attempt to look up the sending
30461 host's name from its IP address failed. It corresponds to the
30462 \$host@_lookup@_failed$\ variable.
30464 .index DNS||reverse lookup
30465 .index reverse DNS lookup
30466 \-host@_name <<text>>-\: This records the name of the remote host from which
30467 the message was received, if the host name was looked up from the IP address
30468 when the message was being received. It is not present if no reverse lookup was
30471 \-ident <<text>>-\: For locally submitted messages, this records the login of
30472 the originating user, unless it was a trusted user and the \-oMt-\ option was
30473 used to specify an ident value. For messages received over TCP/IP, this records
30474 the ident string supplied by the remote host, if any.
30476 \-interface@_address <<address>>.<<port>>-\: This records the IP address of the
30477 local interface and the port number through which a message was received from a
30478 remote host. It is omitted for locally generated messages.
30480 \-local-\: The message is from a local sender.
30482 \-localerror-\: The message is a locally-generated bounce message.
30484 \-local@_scan <<string>>-\: This records the data string that was
30485 returned by the \*local@_scan()*\ function when the message was received -- the
30486 value of the \$local@_scan@_data$\ variable. It is omitted if no data was
30489 \-manual@_thaw-\: The message was frozen but has been thawed manually, that is,
30490 by an explicit Exim command rather than via the auto-thaw process.
30492 \-N-\: A testing delivery process was started using the \-N-\ option to
30493 suppress any actual deliveries, but delivery was deferred. At any further
30494 delivery attempts, \-N-\ is assumed.
30496 \-received@_protocol-\: This records the value of the \$received@_protocol$\
30497 variable, which contains the name of the protocol by which the message was
30500 \-sender@_set@_untrusted-\: The envelope sender of this message was set by an
30501 untrusted local caller (used to ensure that the caller is displayed in queue
30505 \-spam@_score@_int-\: If a message was scanned by SpamAssassin, this is
30506 present. It records the value of \$spam@_score@_int$\.
30509 \-tls@_certificate@_verified-\: A TLS certificate was received from the client
30510 that sent this message, and the certificate was verified by the server.
30512 \-tls@_cipher <<cipher name>>-\: When the message was received over an
30513 encrypted connection, this records the name of the cipher suite that was used.
30515 \-tls@_peerdn <<peer DN>>-\: When the message was received over an encrypted
30516 connection, and a certificate was received from the client, this records the
30517 Distinguished Name from that certificate.
30520 Following the options there is a list of those addresses to which the message
30521 is not to be delivered. This set of addresses is initialized from the command
30522 line when the \-t-\ option is used and \extract__addresses__remove__arguments\
30523 is set; otherwise it starts out empty. Whenever a successful delivery is made,
30524 the address is added to this set. The addresses are kept internally as a
30525 balanced binary tree, and it is a representation of that tree which is written
30526 to the spool file. If an address is expanded via an alias or forward file, the
30527 original address is added to the tree when deliveries to all its child
30528 addresses are complete.
30530 If the tree is empty, there is a single line in the spool file containing just
30531 the text `XX'. Otherwise, each line consists of two letters, which are either Y
30532 or N, followed by an address. The address is the value for the node of the
30533 tree, and the letters indicate whether the node has a left branch and/or a
30534 right branch attached to it, respectively. If branches exist, they immediately
30535 follow. Here is an example of a three-node tree:
30537 YY darcy@austen.fict.example
30538 NN alice@wonderland.fict.example
30539 NN editor@thesaurus.ref.example
30541 After the non-recipients tree, there is a list of the message's recipients.
30542 This is a simple list, preceded by a count. It includes all the original
30543 recipients of the message, including those to whom the message has already been
30544 delivered. In the simplest case, the list contains one address per line. For
30548 editor@thesaurus.ref.example
30549 darcy@austen.fict.example
30551 alice@wonderland.fict.example
30553 However, when a child address has been added to the top-level addresses as a
30554 result of the use of the \one@_time\ option on a \%redirect%\ router, each line
30555 is of the following form:
30557 <<top-level address>> <<errors@_to address>> <<length>>,<<parent number>>@#<<flag bits>>
30559 The 01 flag bit indicates the presence of the three other fields that follow
30560 the top-level address. Other bits may be used in future to support additional
30561 fields. The <<parent number>> is the offset in the recipients list of the
30562 original parent of the `one time' address. The first two fields are the
30563 envelope sender that is associated with this address and its length. If the
30564 length is zero, there is no special envelope sender (there are then two space
30565 characters in the line). A non-empty field can arise from a \%redirect%\ router
30566 that has an \errors@_to\ setting.
30569 A blank line separates the envelope and status information from the headers
30570 which follow. A header may occupy several lines of the file, and to save effort
30571 when reading it in, each header is preceded by a number and an identifying
30572 character. The number is the number of characters in the header, including any
30573 embedded newlines and the terminating newline. The character is one of the
30577 <<blank>> $t $rm{header in which Exim has no special interest}
30578 #B $t $rm{::Bcc:: header}
30579 #C $t $rm{::Cc:: header}
30580 #F $t $rm{::From:: header}
30581 #I $t $rm{::Message-id:: header}
30582 #P $t $rm{::Received:: header -- P for `postmark'}
30583 #R $t $rm{::Reply-To:: header}
30584 #S $t $rm{::Sender:: header}
30585 #T $t $rm{::To:: header}
30586 #* $t $rm{replaced or deleted header}
30588 Deleted or replaced (rewritten) headers remain in the spool file for debugging
30589 purposes. They are not transmitted when the message is delivered. Here is a
30590 typical set of headers:
30592 111P Received: by hobbit.fict.example with local (Exim 4.00)
30593 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
30594 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
30595 038* X-rewrote-sender: bb@hobbit.fict.example
30596 042* From: Bilbo Baggins <bb@hobbit.fict.example>
30597 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
30598 099* To: alice@wonderland.fict.example, rdo@foundation,
30599 darcy@austen.fict.example, editor@thesaurus.ref.example
30600 109T To: alice@wonderland.fict.example, rdo@foundation.fict.example,
30601 darcy@austen.fict.example, editor@thesaurus.ref.example
30602 038 Date: Fri, 11 May 2001 10:28:59 +0100
30604 The asterisked headers indicate that the envelope sender, ::From:: header, and
30605 ::To:: header have been rewritten, the last one because routing expanded the
30606 unqualified domain \*foundation*\.
30612 . ============================================================================
30613 .chapter Adding new drivers or lookup types
30614 .set runningfoot "adding drivers"
30615 .index adding drivers
30616 .index new drivers, adding
30617 .index drivers||adding new
30618 The following actions have to be taken in order to add a new router, transport,
30619 authenticator, or lookup type to Exim:
30621 Choose a name for the driver or lookup type that does not conflict with any
30622 existing name; I will use `newdriver' in what follows.
30624 Add to \(src/EDITME)\ the line
30626 <<type>>@_NEWDRIVER=yes
30628 where <<type>> is \\ROUTER\\, \\TRANSPORT\\, \\AUTH\\, or \\LOOKUP\\. If the
30629 code is not to be included in the binary by default, comment this line out. You
30630 should also add any relevant comments about the driver or lookup type.
30632 Add to \(src/config.h.defaults)\ the line
30634 @#define <<type>>@_NEWDRIVER
30637 Edit \(src/drtables.c)\, adding conditional code to pull in the private header
30638 and create a table entry as is done for all the other drivers and lookup types.
30640 Edit \(Makefile)\ in the appropriate sub-directory (\(src/routers)\,
30641 \(src/transports)\, \(src/auths)\, or \(src/lookups)\); add a line for the new
30642 driver or lookup type and add it to the definition of OBJ.
30644 Create \(newdriver.h)\ and \(newdriver.c)\ in the appropriate sub-directory of
30647 Edit \(scripts/MakeLinks)\ and add commands to link the \(.h)\ and \(.c)\ files
30648 as for other drivers and lookups.
30650 Then all you need to do is write the code! A good way to start is to make a
30651 proforma by copying an existing module of the same type, globally changing all
30652 occurrences of the name, and cutting out most of the code. Note that any
30653 options you create must be listed in alphabetical order, because the tables are
30654 searched using a binary chop procedure.
30656 There is a \(README)\ file in each of the sub-directories of \(src)\ describing
30657 the interface that is expected.
30663 . ============================================================================
30664 . Fudge for the index page number. We want it to be on a right-hand page.
30666 .set indexpage ~~sys.pagenumber + 1
30667 .if even ~~indexpage
30668 .set indexpage ~~indexpage + 1
30671 .%index Index$e~~indexpage--
30675 . End of Exim specification
git://git.exim.org / users / heiko / exim.git / blob