1 . $Cambridge: exim/doc/doc-src/spec.src,v 1.6 2005/01/27 15:00:38 ph10 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
480 The following are the two main Exim mailing lists:
483 $it{exim-users@@exim.org} $t general discussion list
484 $it{exim-announce@@exim.org} $t moderated, low volume announcements list
486 You can subscribe to these lists, change your existing subscriptions, and view
487 or search the archives via the
489 [(A HREF="http://www.exim.org/maillist.html")]
495 link on the Exim home page. The $it{exim-users} mailing list is also forwarded
496 to \?http://www.egroups.com/list/exim-users?\, an archiving system with
497 searching capabilities.
499 .section Exim training
500 .index training courses
501 From time to time (approximately annually at the time of writing),
502 lecture-based training courses are run by the author of Exim in Cambridge, UK.
503 Details can be found on the web site
505 [(A HREF="http://www-tus.csx.cam.ac.uk/courses/exim/")]
507 \?http://www-tus@.csx@.cam@.ac.uk/courses/exim/?\.
514 .index reporting bugs
515 Reports of obvious bugs should be emailed to \*bugs@@exim.org*\. However, if
516 you are unsure whether some behaviour is a bug or not, the best thing to do is
517 to post a message to the $it{exim-users} mailing list and have it discussed.
521 .section Where to find the Exim distribution
522 .rset SECTavail "~~chapter.~~section"
524 .index distribution||ftp site
525 The master ftp site for the Exim distribution is
530 \?ftp://ftp.csx.cam.ac.uk/pub/software/email/exim?\
537 \?ftp://ftp.exim.org/pub/exim?\
539 The file references that follow are relative to the \(exim)\ directories at
542 There are now quite a number of independent mirror sites around the world.
543 Those that I know about are listed in the file called \(Mirrors)\.
545 Within the \(exim)\ directory there are subdirectories called \(exim3)\ (for
546 previous Exim 3 distributions), \(exim4)\ (for the latest Exim 4
547 distributions), and \(Testing)\ for testing versions. In the \(exim4)\
548 subdirectory, the current release can always be found in files called
550 \(exim-$it{n.nn}.tar.gz)\
551 \(exim-$it{n.nn}.tar.bz2)\
553 where $it{n.nn} is the highest such version number in the directory. The two
554 files contain identical data; the only difference is the type of compression.
555 The \(.bz2)\ file is usually a lot smaller than the \(.gz)\ file.
556 .index distribution||signing details
557 .index distribution||public key
558 .index public key for signed distribution
559 The distributions are currently signed with Philip Hazel's GPG key. The
560 corresponding public key is available from a number of keyservers, and there is
561 also a copy in the file \(Public-Key)\. The signatures for the tar bundles are
564 \(exim-$it{n.nn}.tar.gz.sig)\
565 \(exim-$it{n.nn}.tar.bz2.sig)\
567 For each released version, the log of changes is made separately available in a
568 separate file in the directory \(ChangeLogs)\ so that it is possible to
569 find out what has changed without having to download the entire distribution.
571 .index documentation||available formats
572 The main distribution contains ASCII versions of this specification and other
573 documentation; other formats of the documents are available in separate files
574 inside the \(exim4)\ directory of the FTP site:
576 \(exim-html-$it{n.nn}.tar.gz)\
577 \(exim-pdf-$it{n.nn}.tar.gz)\
578 \(exim-postscript-$it{n.nn}.tar.gz)\
579 \(exim-texinfo-$it{n.nn}.tar.gz)\
581 These tar files contain only the \(doc)\ directory, not the complete
582 distribution, and are also available in \(.bz2)\ as well as \(.gz)\ forms.
585 The FAQ is available for downloading in two different formats in these files:
588 \(exim4/FAQ.html.tar.gz)\
590 The first of these is a single ASCII file that can be searched with a text
591 editor. The second is a directory of HTML files, normally accessed by starting
592 at \(index.html)\. The HTML version of the FAQ (which is also included in the
593 HTML documentation tarbundle) includes a keyword-in-context index, which is
594 often the most convenient way of finding your way around.
598 A wish list is maintained, containing ideas for new features that have been
599 submitted. From time to time the file is exported to the ftp site into the file
600 \(exim4/WishList)\. Items are removed from the list if they get implemented.
603 .section Contributed material
604 .index contributed material
605 At the ftp site, there is a directory called \(Contrib)\ that contains
606 miscellaneous files contributed to the Exim community by Exim users. There is
607 also a collection of contributed configuration examples in
608 \(exim4/config.samples.tar.gz)\. These samples are referenced from the FAQ.
612 .index limitations of Exim
614 Exim is designed for use as an Internet MTA, and therefore handles addresses
615 in RFC 2822 domain format only.
616 .index bang paths||not handled by Exim
617 It cannot handle UUCP `bang paths', though simple two-component bang paths can
618 be converted by a straightforward rewriting configuration. This restriction
619 does not prevent Exim from being interfaced to UUCP as a transport mechanism,
620 provided that domain addresses are used.
622 .index domainless addresses
623 .index address||without domain
624 Exim insists that every address it handles has a domain attached. For incoming
625 local messages, domainless addresses are automatically qualified with a
626 configured domain value. Configuration options specify from which remote
627 systems unqualified addresses are acceptable. These are then qualified on
630 .index transport||external
631 .index external transports
632 The only external transport currently implemented is an SMTP transport over a
633 TCP/IP network (using sockets, including support for IPv6). However, a pipe
634 transport is available, and there are facilities for writing messages to files
635 and pipes, optionally in \*batched SMTP*\ format; these facilities can be used
636 to send messages to some other transport mechanism such as UUCP, provided it
637 can handle domain-style addresses. Batched SMTP input is also catered for.
639 Exim is not designed for storing mail for dial-in hosts. When the volumes of
640 such mail are large, it is better to get the messages `delivered' into files
641 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
645 Although Exim does have basic facilities for scanning incoming messages, these
646 are not comprehensive enough to do full virus or spam scanning. Such operations
647 are best carried out using additional specialized software packages. If you
648 compile Exim with the content-scanning extension, straightforward interfaces to
649 a number of common scanners are provided.
655 .section Run time configuration
656 Exim's run time configuration is held in a single text file that is divided
657 into a number of sections. The entries in this file consist of keywords and
658 values, in the style of Smail 3 configuration files. A default configuration
659 file which is suitable for simple online installations is provided in the
660 distribution, and is described in chapter ~~CHAPdefconfil below.
663 .section Calling interface
664 .index Sendmail compatibility||command line interface
665 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
666 can be a straight replacement for \(/usr/lib/sendmail)\ or
667 \(/usr/sbin/sendmail)\ when sending mail, but you do not need to know anything
668 about Sendmail in order to run Exim. For actions other than sending messages,
669 Sendmail-compatible options also exist, but those that produce output (for
670 example, \-bp-\, which lists the messages on the queue) do so in Exim's own
671 format. There are also some additional options that are compatible with Smail
672 3, and some further options that are new to Exim. Chapter ~~CHAPcommandline
673 documents all Exim's command line options. This information is automatically
674 made into the man page that forms part of the Exim distribution.
676 Control of messages on the queue can be done via certain privileged command
677 line options. There is also an optional monitor program called \*eximon*\, which
678 displays current information in an X window, and which contains a menu
679 interface to Exim's command line administration options.
683 .index terminology definitions
684 .index body of message||definition of
685 The \*body*\ of a message is the actual data that the sender wants to transmit.
686 It is the last part of a message, and is separated from the \*header*\ (see
687 below) by a blank line.
689 .index bounce message||definition of
690 When a message cannot be delivered, it is normally returned to the sender in a
691 delivery failure message or a `non-delivery report' (NDR). The term \*bounce*\
692 is commonly used for this action, and the error reports are often called
693 \*bounce messages*\. This is a convenient shorthand for `delivery failure error
694 report'. Such messages have an empty sender address in the message's
695 \*envelope*\ (see below) to ensure that they cannot themselves give rise to
696 further bounce messages.
698 The term \*default*\ appears frequently in this manual. It is used to qualify a
699 value which is used in the absence of any setting in the configuration. It may
700 also qualify an action which is taken unless a configuration setting specifies
703 The term \*defer*\ is used when the delivery of a message to a specific
704 destination cannot immediately take place for some reason (a remote host may be
705 down, or a user's local mailbox may be full). Such deliveries are \*deferred*\
708 The word \*domain*\ is sometimes used to mean all but the first component of a
709 host's name. It is $it{not} used in that sense here, where it normally
710 refers to the part of an email address following the @@ sign.
712 .index envelope, definition of
713 .index sender||definition of
714 A message in transit has an associated \*envelope*\, as well as a header and a
715 body. The envelope contains a sender address (to which bounce messages should
716 be delivered), and any number of recipient addresses. References to the
717 sender or the recipients of a message usually mean the addresses in the
718 envelope. An MTA uses these addresses for delivery, and for returning bounce
719 messages, not the addresses that appear in the header lines.
721 .index message||header, definition of
722 .index header section||definition of
723 The \*header*\ of a message is the first part of a message's text, consisting
724 of a number of lines, each of which has a name such as ::From::, ::To::,
725 ::Subject::, etc. Long header lines can be split over several text lines by
726 indenting the continuations. The header is separated from the body by a blank
729 .index local part||definition of
730 .index domain||definition of
731 The term \*local part*\, which is taken from RFC 2822, is used to refer to that
732 part of an email address that precedes the @@ sign. The part that follows the
733 @@ sign is called the \*domain*\ or \*mail domain*\.
735 .index local delivery||definition of
736 .index remote delivery, definition of
737 The terms \*local delivery*\ and \*remote delivery*\ are used to distinguish
738 delivery to a file or a pipe on the local host from delivery by SMTP over
739 TCP/IP to a remote host.
741 .index return path||definition of
742 \*Return path*\ is another name that is used for the sender address in a
745 .index queue||definition of
746 The term \*queue*\ is used to refer to the set of messages awaiting delivery,
747 because this term is in widespread use in the context of MTAs. However, in
748 Exim's case the reality is more like a pool than a queue, because there is
749 normally no ordering of waiting messages.
751 .index queue runner||definition of
752 The term \*queue runner*\ is used to describe a process that scans the queue
753 and attempts to deliver those messages whose retry times have come. This term
754 is used by other MTAs, and also relates to the command \runq\, but in Exim
755 the waiting messages are normally processed in an unpredictable order.
757 .index spool directory||definition of
758 The term \*spool directory*\ is used for a directory in which Exim keeps the
759 messages on its queue -- that is, those that it is in the process of
760 delivering. This should not be confused with the directory in which local
761 mailboxes are stored, which is called a `spool directory' by some people. In
762 the Exim documentation, `spool' is always used in the first sense.
770 . ============================================================================
771 .chapter Incorporated code
772 .set runningfoot "incorporated code"
773 .index incorporated code
774 .index regular expressions||library
776 A number of pieces of external code are included in the Exim distribution.
778 Regular expressions are supported in the main Exim program and in the Exim
779 monitor using the freely-distributable PCRE library, copyright (c) University
780 of Cambridge. The source is distributed in the directory \(src/pcre)\. However,
781 this is a cut-down version of PCRE. If you want to use the PCRE library in
782 other programs, you should obtain and install the full version from
783 \?ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre?\.
787 .index cdb||acknowledgement
788 Support for the cdb (Constant DataBase) lookup method is provided by code
789 contributed by Nigel Metheringham of (at the time he contributed it) Planet
790 Online Ltd. which contains the following statements:
797 Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd
799 This program is free software; you can redistribute it and/or modify it under
800 the terms of the GNU General Public License as published by the Free Software
801 Foundation; either version 2 of the License, or (at your option) any later
804 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
805 the spec and sample code for cdb can be obtained from
806 \?http://www.pobox.com/@~djb/cdb.html?\. This implementation borrows some code
807 from Dan Bernstein's implementation (which has no license restrictions applied
812 The implementation is completely contained within the code of Exim.
813 It does not link against an external cdb library.
816 .index SPA authentication
818 .index Microsoft Secure Password Authentication
819 Client support for Microsoft's \*Secure Password Authentication*\ is provided
820 by code contributed by Marc Prud'hommeaux. Server support was contributed by
821 Tom Kistner. This includes code taken from the Samba project, which is released
827 .index \*pwcheck*\ daemon
828 .index \*pwauthd*\ daemon
829 Support for calling the Cyrus \*pwcheck*\ and \*saslauthd*\ daemons is provided
830 by code taken from the Cyrus-SASL library and adapted by Alexander S.
831 Sabourenkov. The permission notice appears below, in accordance with the
832 conditions expressed therein.
840 Copyright (c) 2001 Carnegie Mellon University. All rights reserved.
842 Redistribution and use in source and binary forms, with or without
843 modification, are permitted provided that the following conditions
847 .cancelflag $npbracket
848 .flag $npbracket "" "."
851 Redistributions of source code must retain the above copyright
852 notice, this list of conditions and the following disclaimer.
854 Redistributions in binary form must reproduce the above copyright
855 notice, this list of conditions and the following disclaimer in
856 the documentation and/or other materials provided with the
859 The name `Carnegie Mellon University' must not be used to
860 endorse or promote products derived from this software without
861 prior written permission. For permission or any other legal
862 details, please contact
864 Office of Technology Transfer
865 Carnegie Mellon University
867 Pittsburgh, PA 15213-3890
868 (412) 268-4387, fax: (412) 268-7395
869 tech-transfer@@andrew.cmu.edu
872 Redistributions of any form whatsoever must retain the following
876 .indent ~~sys.indent + 3em
878 $it{This product includes software developed by Computing Services
879 at Carnegie Mellon University (\?http://www.cmu.edu/computing/?\).}
884 .cancelflag $npbracket
885 .flag $npbracket "(" ")"
888 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
889 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
890 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
891 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
892 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
893 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
894 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
904 The Exim Monitor program, which is an X-Window application, includes
905 modified versions of the Athena StripChart and TextPop widgets.
906 This code is copyright by DEC and MIT, and their permission notice appears
907 below, in accordance with the conditions expressed therein.
915 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
916 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
918 $c All Rights Reserved
920 Permission to use, copy, modify, and distribute this software and its
921 documentation for any purpose and without fee is hereby granted,
922 provided that the above copyright notice appear in all copies and that
923 both that copyright notice and this permission notice appear in
924 supporting documentation, and that the names of Digital or MIT not be
925 used in advertising or publicity pertaining to distribution of the
926 software without specific, written prior permission.
928 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
929 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
930 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
931 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
932 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
933 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
941 Many people have contributed code fragments, some large, some small, that were
942 not covered by any specific licence requirements. It is assumed that the
943 contributors are happy to see their code incoporated into Exim under the GPL.
953 . ============================================================================
954 .chapter How Exim receives and delivers mail
955 .set runningfoot "receiving & delivering mail"
957 .section Overall philosophy
958 .index design philosophy
959 Exim is designed to work efficiently on systems that are permanently connected
960 to the Internet and are handling a general mix of mail. In such circumstances,
961 most messages can be delivered immediately. Consequently, Exim does not
962 maintain independent queues of messages for specific domains or hosts, though
963 it does try to send several messages in a single SMTP connection after a host
964 has been down, and it also maintains per-host retry information.
967 .section Policy control
968 .index policy control||overview
969 Policy controls are now an important feature of MTAs that are connected to the
970 Internet. Perhaps their most important job is to stop MTAs being abused as
971 `open relays' by misguided individuals who send out vast amounts of unsolicited
972 junk, and want to disguise its source. Exim provides flexible facilities for
973 specifying policy controls on incoming mail:
975 .index ~~ACL||introduction
976 Exim 4 (unlike previous versions of Exim) implements policy controls on
977 incoming mail by means of \*Access Control Lists*\ (ACLs). Each list is a
978 series of statements that may either grant or deny access. ACLs can be used at
979 several places in the SMTP dialogue while receiving a message from a remote
980 host. However, the most common places are after each \\RCPT\\ command, and at
981 the very end of the message. The sysadmin can specify conditions for accepting
982 or rejecting individual recipients or the entire message, respectively, at
983 these two points (see chapter ~~CHAPACL). Denial of access results in an SMTP
986 An ACL is also available for locally generated, non-SMTP messages. In this
987 case, the only available actions are to accept or deny the entire message.
990 When Exim is compiled with the content-scanning extension, facilities are
991 provided in the ACL mechanism for passing the message to external virus and/or
992 spam scanning software. The result of such a scan is passed back to the ACL,
993 which can then use it to decide what to do with the message.
996 When a message has been received, either from a remote host or from the local
997 host, but before the final acknowledgement has been sent, a locally supplied C
998 function called \*local@_scan()*\ can be run to inspect the message and decide
999 whether to accept it or not (see chapter ~~CHAPlocalscan). If the message is
1000 accepted, the list of recipients can be modified by the function.
1003 Using the \*local@_scan()*\ mechanism is another way of calling external
1004 scanner software. The \SA-Exim\ add-on package works this way. It does not
1005 require Exim to be compiled with the content-scanning extension.
1008 After a message has been accepted, a further checking mechanism is available in
1009 the form of the $it{system filter} (see chapter ~~CHAPsystemfilter). This runs
1010 at the start of every delivery process.
1013 .section User filters
1014 .index filter||introduction
1016 In a conventional Exim configuration, users are able to run private filters by
1017 setting up appropriate \(.forward)\ files in their home directories. See
1018 chapter ~~CHAPredirect (about the \%redirect%\ router) for the configuration
1019 needed to support this, and the separate document entitled
1021 [(A HREF="filter_toc.html")]
1023 \*Exim's interfaces to mail filtering*\
1027 for user details. Two different kinds of filtering are available:
1029 Sieve filters are written in the standard filtering language that is defined by
1032 Exim filters are written in a syntax that is unique to Exim, but which is more
1033 powerful than Sieve, which it pre-dates.
1035 User filters are run as part of the routing process, described below.
1038 .section Message identification
1039 .rset SECTmessiden "~~chapter.~~section"
1040 .index message||ids, details of format
1041 .index format||of message id
1042 .index id of message
1047 Every message handled by Exim is given a \*message id*\ which is sixteen
1048 characters long. It is divided into three parts, separated by hyphens, for
1049 example \"16VDhn-0001bo-D3"\. Each part is a sequence of letters and digits,
1050 normally encoding numbers in base 62. However, in the Darwin operating
1051 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
1052 (avoiding the use of lower case letters) is used instead, because the message
1053 id is used to construct file names, and the names of files in those systems are
1056 .index pid (process id)||re-use of
1057 The detail of the contents of the message id have changed as Exim has evolved.
1058 Earlier versions relied on the operating system not re-using a process id (pid)
1059 within one second. On modern operating systems, this assumption can no longer
1060 be made, so the algorithm had to be changed. To retain backward compatibility,
1061 the format of the message id was retained, which is why the following rules are
1064 The first six characters of the message id are the time at which the message
1065 started to be received, to a granularity of one second. That is, this field
1066 contains the number of seconds since the start of the epoch (the normal Unix
1067 way of representing the date and time of day).
1069 After the first hyphen, the next six characters are the id of the process that
1070 received the message.
1072 There are two different possibilities for the final two characters:
1074 .index \localhost@_number\
1075 If \localhost@_number\ is not set, this value is the fractional part of the
1076 time of reception, normally in units of 1/2000 of a second, but for systems
1077 that must use base 36 instead of base 62 (because of case-insensitive file
1078 systems), the units are 1/1000 of a second.
1080 If \localhost@_number\ is set, it is multiplied by 200 (100) and added to
1081 the fractional part of the time, which in this case is in units of 1/200
1082 (1/100) of a second.
1085 After a message has been received, Exim waits for the clock to tick at the
1086 appropriate resolution before proceeding, so that if another message is
1087 received by the same process, or by another process with the same (re-used)
1088 pid, it is guaranteed that the time will be different. In most cases, the clock
1089 will already have ticked while the message was being received.
1091 .section Receiving mail
1092 .index receiving mail
1093 .index message||reception
1094 The only way Exim can receive mail from a remote host is using SMTP over
1095 TCP/IP, in which case the sender and recipient addresses are tranferred using
1096 SMTP commands. However, from a locally running process (such as a user's MUA),
1097 there are several possibilities:
1099 If the process runs Exim with the \-bm-\ option, the message is read
1100 non-interactively (usually via a pipe), with the recipients taken from the
1101 command line, or from the body of the message if \-t-\ is also used.
1103 If the process runs Exim with the \-bS-\ option, the message is also read
1104 non-interactively, but in this case the recipients are listed at the start of
1105 the message in a series of SMTP \\RCPT\\ commands, terminated by a \\DATA\\
1106 command. This is so-called `batch SMTP' format,
1107 but it isn't really SMTP. The SMTP commands are just another way of passing
1108 envelope addresses in a non-interactive submission.
1110 If the process runs Exim with the \-bs-\ option, the message is read
1111 interactively, using the SMTP protocol. A two-way pipe is normally used for
1112 passing data between the local process and the Exim process.
1113 This is `real' SMTP and is handled in the same way as SMTP over TCP/IP. For
1114 example, the ACLs for SMTP commands are used for this form of submission.
1116 A local process may also make a TCP/IP call to the host's loopback address
1117 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1118 does not treat the loopback address specially. It treats all such connections
1119 in the same way as connections from other hosts.
1122 .index message||sender, constructed by Exim
1123 .index sender||constructed by Exim
1124 In the three cases that do not involve TCP/IP, the sender address is
1125 constructed from the login name of the user that called Exim and a default
1126 qualification domain (which can be set by the \qualify@_domain\ configuration
1127 option). For local or batch SMTP, a sender address that is passed using the
1128 SMTP \\MAIL\\ command is ignored. However, the system administrator may allow
1129 certain users (`trusted users') to specify a different sender address
1130 unconditionally, or all users to specify certain forms of different sender
1131 address. The \-f-\ option or the SMTP \\MAIL\\ command is used to specify these
1132 different addresses. See section ~~SECTtrustedadmin for details of trusted
1133 users, and the \untrusted@_set@_sender\ option for a way of allowing untrusted
1134 users to change sender addresses.
1136 Messages received by either of the non-interactive mechanisms are subject to
1137 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1138 (either over TCP/IP, or interacting with a local process) can be checked by a
1139 number of ACLs that operate at different times during the SMTP session. Either
1140 individual recipients, or the entire message, can be rejected if local policy
1141 requirements are not met. The \*local@_scan()*\ function (see chapter
1142 ~~CHAPlocalscan) is run for all incoming messages.
1144 Exim can be configured not to start a delivery process when a message is
1145 received; this can be unconditional, or depend on the number of incoming SMTP
1146 connections or the system load. In these situations, new messages wait on the
1147 queue until a queue runner process picks them up. However, in standard
1148 configurations under normal conditions, delivery is started as soon as a
1149 message is received.
1154 .section Handling an incoming message
1155 .index spool directory||files that hold a message
1156 .index file||how a message is held
1157 When Exim accepts a message, it writes two files in its spool directory. The
1158 first contains the envelope information, the current status of the message,
1159 and the header lines, and the second contains the body of the message. The
1160 names of the two spool files consist of the message id, followed by $tt{-H} for
1161 the file containing the envelope and header, and $tt{-D} for the data file.
1163 .index spool directory||\(input)\ sub-directory
1164 By default all these message files are held in a single directory called
1165 \(input)\ inside the general Exim spool directory. Some operating systems do
1166 not perform very well if the number of files in a directory gets very large; to
1167 improve performance in such cases, the \split@_spool@_directory\ option can be
1168 used. This causes Exim to split up the input files into 62 sub-directories
1169 whose names are single letters or digits.
1171 The envelope information consists of the address of the message's sender and
1172 the addresses of the recipients. This information is entirely separate from
1173 any addresses contained in the header lines. The status of the message includes
1174 a list of recipients who have already received the message. The format of the
1175 first spool file is described in chapter ~~CHAPspool.
1177 .index rewriting||addresses
1178 Address rewriting that is specified in the rewrite section of the configuration
1179 (see chapter ~~CHAPrewrite) is done once and for all on incoming addresses,
1180 both in the header lines and the envelope, at the time the message is accepted.
1181 If during the course of delivery additional addresses are generated (for
1182 example, via aliasing), these new addresses are rewritten as soon as they are
1183 generated. At the time a message is actually delivered (transported) further
1184 rewriting can take place; because this is a transport option, it can be
1185 different for different forms of delivery. It is also possible to specify the
1186 addition or removal of certain header lines at the time the message is
1187 delivered (see chapters ~~CHAProutergeneric and ~~CHAPtransportgeneric).
1190 .section Life of a message
1191 .index message||life of
1192 .index message||frozen
1193 A message remains in the spool directory until it is completely delivered to
1194 its recipients or to an error address, or until it is deleted by an
1195 administrator or by the user who originally created it. In cases when delivery
1196 cannot proceed -- for example, when a message can neither be delivered to its
1197 recipients nor returned to its sender, the message is marked `frozen' on the
1198 spool, and no more deliveries are attempted.
1200 .index frozen messages||thawing
1201 .index message||thawing frozen
1202 An administrator can `thaw' such messages when the problem has been corrected,
1203 and can also freeze individual messages by hand if necessary. In addition, an
1204 administrator can force a delivery error, causing a bounce message to be sent.
1207 There is an option called \auto@_thaw\, which can be used to cause Exim to
1208 retry frozen messages after a certain time. When this is set, no message will
1209 remain on the queue for ever, because the delivery timeout will eventually be
1210 reached. Delivery failure reports (bounce messages) that reach this timeout are
1212 .index \timeout@_frozen@_after\
1213 There is also an option called \timeout@_frozen@_after\, which discards frozen
1214 messages after a certain time.
1216 .index message||log file for
1217 .index log||file for each message
1218 While Exim is working on a message, it writes information about each delivery
1219 attempt to the main log file. This includes successful, unsuccessful, and
1220 delayed deliveries for each recipient (see chapter ~~CHAPlog). The log lines
1221 are also written to a separate $it{message log} file for each message. These
1222 logs are solely for the benefit of the administrator, and are normally deleted
1223 along with the spool files when processing of a message is complete.
1224 The use of individual message logs can be disabled by setting
1225 \no@_message@_logs\; this might give an improvement in performance on very
1229 .index file||journal
1230 All the information Exim itself needs to set up a delivery is kept in the first
1231 spool file, along with the header lines. When a successful delivery occurs, the
1232 address is immediately written at the end of a journal file, whose name is the
1233 message id followed by $tt{-J}. At the end of a delivery run, if there are some
1234 addresses left to be tried again later, the first spool file (the $tt{-H} file)
1235 is updated to indicate which these are, and the journal file is then deleted.
1236 Updating the spool file is done by writing a new file and renaming it, to
1237 minimize the possibility of data loss.
1239 Should the system or the program crash after a successful delivery but before
1240 the spool file has been updated, the journal is left lying around. The next
1241 time Exim attempts to deliver the message, it reads the journal file and
1242 updates the spool file before proceeding. This minimizes the chances of double
1243 deliveries caused by crashes.
1246 .section Processing an address for delivery
1247 .rset SECTprocaddress "~~chapter.~~section"
1248 .index drivers||definition of
1249 .index router||definition of
1250 .index transport||definition of
1251 The main delivery processing elements of Exim are called $it{routers} and
1252 $it{transports}, and collectively these are known as $it{drivers}. Code for a
1253 number of them is provided in the source distribution, and compile-time options
1254 specify which ones are included in the binary. Run time options specify which
1255 ones are actually used for delivering messages.
1257 .index drivers||instance definition
1258 Each driver that is specified in the run time configuration is an \*instance*\
1259 of that particular driver type. Multiple instances are allowed; for example,
1260 you can set up several different \%smtp%\ transports, each with different
1261 option values that might specify different ports or different timeouts. Each
1262 instance has its own identifying name. In what follows we will normally use the
1263 instance name when discussing one particular instance (that is, one specific
1264 configuration of the driver), and the generic driver name when discussing
1265 the driver's features in general.
1267 A $it{router} is a driver that operates on an address, either determining how
1268 its delivery should happen, by routing it to a specific transport, or
1269 converting the address into one or more new addresses (for example, via an
1270 alias file). A router may also explicitly choose to fail an address, causing it
1273 A $it{transport} is a driver that transmits a copy of the message from Exim's
1274 spool to some destination. There are two kinds of transport: for a $it{local}
1275 transport, the destination is a file or a pipe on the local host, whereas for a
1276 $it{remote} transport the destination is some other host. A message is passed
1277 to a specific transport as a result of successful routing. If a message has
1278 several recipients, it may be passed to a number of different transports.
1280 .index preconditions||definition of
1281 An address is processed by passing it to each configured router instance in
1282 turn, subject to certain preconditions, until a router accepts the address or
1283 specifies that it should be bounced. We will describe this process in more
1284 detail shortly. As a simple example, the diagram below illustrates how each
1285 recipient address in a message is processed in a small configuration of three
1286 routers that are configured in various ways.
1289 .figure "Routing an address" rm
1291 .call aspic -sgcal -nv
1292 centre ~~sys.linelength;
1295 ibox depth 14 "address";
1298 A: box width 100 "first router" "conditions ok?";
1300 C: box width 100 "run" "first router";
1302 D: ibox depth 20 "address bounces";
1304 arc clockwise from right of C "accept";
1306 ibox "queue for" "transport";
1308 arrow down from A align bottom of D plus (0,-20) "no"(-6,20)/r;
1309 E: box width 100 "second router" "conditions ok?";
1311 F: box width 100 "run" "second router";
1312 line right 100 "redirect";
1313 line up align middle of B;
1314 arrow left to middle of B "new addresses";
1316 line down 20 from bottom left of F plus (30,0);
1317 arrow left align centre of E "decline";
1319 line down 20 from bottom right of F plus (-30,0);
1321 ibox width 64 "address" "bounces";
1323 arrow down 64 from E "no"(-6,20)/r;
1324 G: box width 100 "third router" "conditions ok?";
1326 H: box width 100 "run" "third router";
1327 arc clockwise from right of H "accept";
1329 ibox "queue for" "transport";
1331 line down 20 from bottom of H;
1332 arrow left align centre of G "decline";
1333 arrow down 64 from G "no"(-6,20)/r;
1335 ibox "no more routers" "address bounces";
1343 |<------------- new addresses -----------------------------
1345 ----------------- ----------------- |
1346 | first router |----- yes ----->| run |--- accept |
1347 | conditions ok?| | first router | | |
1348 ----------------- ----------------- | |
1350 no | fail | queue for |
1355 ----------------- ----------------- |
1356 | second router |----- yes ----->| run |----redirect ----
1357 | conditions ok?| | second router |
1358 ----------------- -----------------
1361 |<-------- decline ----------- --- fail ---> address
1364 ----------------- -----------------
1365 | third router |----- yes ----->| run |--- accept
1366 | conditions ok?| | third router | |
1367 ----------------- ----------------- |
1370 |<-------- decline --------------- transport
1377 [(img src="routing.gif" alt="Routing an address")][(br)]
1379 To make this a more concrete example, we'll describe it in terms of some actual
1380 routers, but remember, this is only an example. You can configure Exim's
1381 routers in many different ways, and there may be any number of routers in a
1384 The first router that is specified in a configuration is often one that handles
1385 addresses in domains that are not recognized specially by the local host. These
1386 are typically addresses for arbitrary domains on the Internet. A precondition
1387 is set up which looks for the special domains known to the host (for example,
1388 its own domain name), and the router is run for addresses that do $it{not}
1389 match. Typically, this is a router that looks up domains in the DNS in order to
1390 find the hosts to which this address routes. If it succeeds, the address is
1391 queued for a suitable SMTP transport; if it does not succeed, the router is
1392 configured to fail the address.
1394 The example pictured could be a configuration of this type. The second and
1395 third routers can only be run for addresses for which the preconditions for
1396 the first router are not met. If one of these preconditions checks the
1397 domain, the second and third routers are run only for domains that are somehow
1398 special to the local host.
1400 The second router does redirection -- also known as aliasing and forwarding.
1401 When it generates one or more new addresses from the original, each of them is
1402 routed independently from the start. Otherwise, the router may cause an address
1403 to fail, or it may simply decline to handle the address, in which case the
1404 address is passed to the next router.
1406 The final router in many configurations is one that checks to see if the
1407 address belongs to a local mailbox. The precondition may involve a check to
1408 see if the local part is the name of a login account, or it may look up the
1409 local part in a file or a database. If its preconditions are not met, or if
1410 the router declines, we have reached the end of the routers. When this happens,
1411 the address is bounced.
1414 .section Processing an address for verification
1415 .index router||for verification
1416 .index verifying||address, overview
1417 As well as being used to decide how to deliver to an address, Exim's routers
1418 are also used for \*address verification*\. Verification can be requested as
1419 one of the checks to be performed in an ACL for incoming messages, on both
1420 sender and recipient addresses, and it can be tested using the \-bv-\ and
1421 \-bvs-\ command line options.
1423 When an address is being verified, the routers are run in `verify mode'. This
1424 does not affect the way the routers work, but it is a state that can be
1425 detected. By this means, a router can be skipped or made to behave differently
1426 when verifying. A common example is a configuration in which the first router
1427 sends all messages to a message-scanning program, unless they have been
1428 previously scanned. Thus, the first router accepts all addresses without any
1429 checking, making it useless for verifying. Normally, the \no@_verify\ option
1430 would be set for such a router, causing it to be skipped in verify mode.
1434 .section Running an individual router
1435 .rset SECTrunindrou "~~chapter.~~section"
1436 .index router||running details
1437 .index preconditions||checking
1438 .index router||result of running
1439 As explained in the example above, a number of preconditions are checked before
1440 running a router. If any are not met, the router is skipped, and the address is
1441 passed to the next router. When all the preconditions on a router $it{are} met,
1442 the router is run. What happens next depends on the outcome, which is one of
1445 \*accept*\: The router accepts the address, and either queues it for a
1446 transport, or generates one or more `child' addresses. Processing the original
1448 .index \unseen\ option
1449 unless the \unseen\ option is set on the router. This option
1450 can be used to set up multiple deliveries with different routing (for example,
1451 for keeping archive copies of messages). When \unseen\ is set, the address is
1452 passed to the next router. Normally, however, an \*accept*\ return marks the
1455 .index case of local parts
1456 .index address||duplicate, discarding
1457 If child addresses are generated, Exim checks to see whether they are
1458 duplicates of any existing recipient addresses. During this check, local parts
1459 are treated as case-sensitive. Duplicate addresses are discarded. Each of the
1460 remaining child addresses is then processed independently, starting with the
1461 first router by default. It is possible to change this by setting the
1462 \redirect@_router\ option to specify which router to start at for child
1463 addresses. Unlike \pass@_router\ (see below) the router specified by
1464 \redirect@_router\ may be anywhere in the router configuration.
1466 \*pass*\: The router recognizes the address, but cannot handle it itself. It
1467 requests that the address be passed to another router. By default the address
1468 is passed to the next router, but this can be changed by setting the
1469 \pass@_router\ option. However, (unlike \redirect@_router\) the named router
1470 must be below the current router (to avoid loops).
1472 \*decline*\: The router declines to accept the address because it does not
1473 recognize it at all. By default, the address is passed to the next router, but
1474 this can be prevented by setting the \no@_more\ option. When \no@_more\ is set,
1475 all the remaining routers are skipped.
1477 \*fail*\: The router determines that the address should fail, and queues it for
1478 the generation of a bounce message. There is no further processing of the
1479 original address unless \unseen\ is set on the router.
1481 \*defer*\: The router cannot handle the address at the present time. (A database
1482 may be offline, or a DNS lookup may have timed out.) No further processing of
1483 the address happens in this delivery attempt. It is tried again next time the
1484 message is considered for delivery.
1486 \*error*\: There is some error in the router (for example, a syntax error in
1487 its configuration). The action is as for defer.
1489 If an address reaches the end of the routers without having been accepted by
1490 any of them, it is bounced as unrouteable.
1491 The default error message in this situation is `unrouteable address', but you
1492 can set your own message by making use of the \cannot@_route@_message\ option.
1493 This can be set for any router; the value from the last router that `saw'
1494 the address is used.
1496 Sometimes while routing you want to fail a delivery when some conditions are
1497 met but others are not, instead of passing the address on for further routing.
1498 You can do this by having a second router that explicitly fails the delivery
1499 when the relevant conditions are met. The \%redirect%\ router has a `fail'
1500 facility for this purpose.
1504 .section Router preconditions
1505 .rset SECTrouprecon "~~chapter.~~section"
1506 .index router||preconditions, order of processing
1507 .index preconditions||order of processing
1508 The preconditions that are tested for each router are listed below, in the
1509 order in which they are tested. The individual configuration options are
1510 described in more detail in chapter ~~CHAProutergeneric.
1512 The \local@_part@_prefix\ and \local@_part@_suffix\ options can specify that
1513 the local parts handled by the router may or must have certain prefixes and/or
1514 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1515 skipped. These conditions are tested first. When an affix is present, it is
1516 removed from the local part before further processing, including the evaluation
1517 of any other conditions.
1519 Routers can be designated for use only when not verifying an address, that is,
1520 only when routing it for delivery (or testing its delivery routing). If the
1521 \verify\ option is set false, the router is skipped when Exim is verifying an
1523 Setting the \verify\ option actually sets two options, \verify@_sender\ and
1524 \verify@_recipient\, which independently control the use of the router for
1525 sender and recipient verification. You can set these options directly if
1526 you want a router to be used for only one type of verification.
1528 If the \address@_test\ option is set false, the router is skipped when Exim is
1529 run with the \-bt-\ option to test an address routing. This can be helpful when
1530 the first router sends all new messages to a scanner of some sort; it makes it
1531 possible to use \-bt-\ to test subsequent delivery routing without having to
1532 simulate the effect of the scanner.
1534 Routers can be designated for use only when verifying an address, as
1535 opposed to routing it for delivery. The \verify@_only\ option controls this.
1537 Certain routers can be explicitly skipped when running the routers to check an
1538 address given in the SMTP \\EXPN\\ command (see the \expn\ option).
1540 If the \domains\ option is set, the domain of the address must be in the set of
1541 domains that it defines.
1543 If the \local@_parts\ option is set, the local part of the address must be in
1544 the set of local parts that it defines. If \local@_part@_prefix\ or
1545 \local@_part@_suffix\ is in use, the prefix or suffix is removed from the local
1546 part before this check. If you want to do precondition tests on local parts
1547 that include affixes, you can do so by using a \condition\ option (see below)
1548 that uses the variables \$local@_part$\, \$local@_part@_prefix$\, and
1549 \$local@_part@_suffix$\ as necessary.
1551 If the \check@_local@_user\ option is set, the local part must be the name of
1552 an account on the local host.
1553 If this check succeeds, the uid and gid of the local user are placed in
1554 \$local@_user@_uid$\ and \$local@_user@_gid$\; these values can be used in the
1555 remaining preconditions.
1557 If the \router@_home@_directory\ option is set, it is expanded at this point,
1558 because it overrides the value of \$home$\. If this expansion were left till
1559 later, the value of \$home$\ as set by \check@_local@_user\ would be used in
1560 subsequent tests. Having two different values of \$home$\ in the same router
1561 could lead to confusion.
1563 If the \senders\ option is set, the envelope sender address must be in the set
1564 of addresses that it defines.
1566 If the \require@_files\ option is set, the existence or non-existence of
1567 specified files is tested.
1569 .index customizing||precondition
1570 If the \condition\ option is set, it is evaluated and tested. This option uses
1571 an expanded string to allow you to set up your own custom preconditions.
1572 Expanded strings are described in chapter ~~CHAPexpand.
1575 Note that \require@_files\ comes near the end of the list, so you cannot use it
1576 to check for the existence of a file in which to lookup up a domain, local
1577 part, or sender. However, as these options are all expanded, you can use the
1578 \exists\ expansion condition to make such tests within each condition. The
1579 \require@_files\ option is intended for checking files that the router may be
1580 going to use internally, or which are needed by a specific transport (for
1581 example, \(.procmailrc)\).
1584 .section Delivery in detail
1585 .index delivery||in detail
1586 When a message is to be delivered, the sequence of events is as follows:
1588 If a system-wide filter file is specified, the message is passed to it. The
1589 filter may add recipients to the message, replace the recipients, discard the
1590 message, cause a new message to be generated, or cause the message delivery to
1591 fail. The format of the system filter file is the same as for Exim user filter
1592 files, described in the separate document entitled
1594 [(A HREF="filter.html")]
1596 \*Exim's interfaces to mail filtering*\.
1600 .index Sieve filter||not available for system filter
1601 (\**Note**\: Sieve cannot be used for system filter files.)
1602 Some additional features are available in system filters -- see chapter
1603 ~~CHAPsystemfilter for details. Note that a message is passed to the system
1604 filter only once per delivery attempt, however many recipients it has. However,
1605 if there are several delivery attempts because one or more addresses could not
1606 be immediately delivered, the system filter is run each time. The filter
1607 condition \first@_delivery\ can be used to detect the first run of the system
1610 Each recipient address is offered to each configured router in turn, subject to
1611 its preconditions, until one is able to handle it. If no router can handle
1612 the address, that is, if they all decline, the address is failed. Because
1613 routers can be targeted at particular domains, several locally handled domains
1614 can be processed entirely independently of each other.
1616 .index routing||loops in
1617 .index loop||while routing
1618 A router that accepts an address may set up a local or a remote transport for
1619 it. However, the transport is not run at this time. Instead, the address is
1620 placed on a list for the particular transport, to be run later. Alternatively,
1621 the router may generate one or more new addresses (typically from alias,
1622 forward, or filter files). New addresses are fed back into this process from
1623 the top, but in order to avoid loops, a router ignores any address which has an
1624 identically-named ancestor that was processed by itself.
1626 When all the routing has been done, addresses that have been successfully
1627 handled are passed to their assigned transports. When local transports are
1628 doing real local deliveries, they handle only one address at a time, but if a
1629 local transport is being used as a pseudo-remote transport (for example, to
1630 collect batched SMTP messages for transmission by some other means) multiple
1631 addresses can be handled. Remote transports can always handle more than one
1632 address at a time, but can be configured not to do so, or to restrict multiple
1633 addresses to the same domain.
1635 Each local delivery to a file or a pipe runs in a separate process under a
1636 non-privileged uid, and these deliveries are run one at a time. Remote
1637 deliveries also run in separate processes, normally under a uid that is private
1638 to Exim (`the Exim user'), but in this case, several remote deliveries can be
1639 run in parallel. The maximum number of simultaneous remote deliveries for any
1640 one message is set by the \remote@_max@_parallel\ option.
1641 The order in which deliveries are done is not defined, except that all local
1642 deliveries happen before any remote deliveries.
1645 When it encounters a local delivery during a queue run, Exim checks its retry
1646 database to see if there has been a previous temporary delivery failure for the
1647 address before running the local transport. If there was a previous failure,
1648 Exim does not attempt a new delivery until the retry time for the address is
1649 reached. However, this happens only for delivery attempts that are part of a
1650 queue run. Local deliveries are always attempted when delivery immediately
1651 follows message reception, even if retry times are set for them. This makes for
1652 better behaviour if one particular message is causing problems (for example,
1653 causing quota overflow, or provoking an error in a filter file).
1655 .index delivery||retry in remote transports
1656 Remote transports do their own retry handling, since an address may be
1657 deliverable to one of a number of hosts, each of which may have a different
1658 retry time. If there have been previous temporary failures and no host has
1659 reached its retry time, no delivery is attempted, whether in a queue run or
1660 not. See chapter ~~CHAPretry for details of retry strategies.
1662 If there were any permanent errors, a bounce message is returned to an
1663 appropriate address (the sender in the common case), with details of the error
1664 for each failing address. Exim can be configured to send copies of bounce
1665 messages to other addresses.
1667 .index delivery||deferral
1668 If one or more addresses suffered a temporary failure, the message is left on
1669 the queue, to be tried again later. Delivery of these addresses is said to be
1672 When all the recipient addresses have either been delivered or bounced,
1673 handling of the message is complete. The spool files and message log are
1674 deleted, though the message log can optionally be preserved if required.
1678 .section Retry mechanism
1679 .index delivery||retry mechanism
1680 .index retry||description of mechanism
1682 Exim's mechanism for retrying messages that fail to get delivered at the first
1683 attempt is the queue runner process. You must either run an Exim daemon that
1684 uses the \-q-\ option with a time interval to start queue runners at regular
1685 intervals, or use some other means (such as \*cron*\) to start them. If you do
1686 not arrange for queue runners to be run, messages that fail temporarily at the
1687 first attempt will remain on your queue for ever. A queue runner process works
1688 it way through the queue, one message at a time, trying each delivery that has
1689 passed its retry time.
1690 You can run several queue runners at once.
1692 Exim uses a set of configured rules to determine when next to retry the failing
1693 address (see chapter ~~CHAPretry). These rules also specify when Exim should
1694 give up trying to deliver to the address, at which point it generates a bounce
1695 message. If no retry rules are set for a particular host, address, and error
1696 combination, no retries are attempted, and temporary errors are treated as
1700 .section Temporary delivery failure
1701 .index delivery||temporary failure
1702 There are many reasons why a message may not be immediately deliverable to a
1703 particular address. Failure to connect to a remote machine (because it, or the
1704 connection to it, is down) is one of the most common. Temporary failures may be
1705 detected during routing as well as during the transport stage of delivery.
1706 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1707 is on a file system where the user is over quota. Exim can be configured to
1708 impose its own quotas on local mailboxes; where system quotas are set they will
1711 If a host is unreachable for a period of time, a number of messages may be
1712 waiting for it by the time it recovers, and sending them in a single SMTP
1713 connection is clearly beneficial. Whenever a delivery to a remote host is
1715 .index hints database
1716 Exim makes a note in its hints database, and whenever a successful
1717 SMTP delivery has happened, it looks to see if any other messages are waiting
1718 for the same host. If any are found, they are sent over the same SMTP
1719 connection, subject to a configuration limit as to the maximum number in any
1724 .section Permanent delivery failure
1725 .index delivery||permanent failure
1726 .index bounce message||when generated
1727 When a message cannot be delivered to some or all of its intended recipients, a
1728 bounce message is generated. Temporary delivery failures turn into permanent
1729 errors when their timeout expires. All the addresses that fail in a given
1730 delivery attempt are listed in a single message. If the original message has
1731 many recipients, it is possible for some addresses to fail in one delivery
1732 attempt and others to fail subsequently, giving rise to more than one bounce
1733 message. The wording of bounce messages can be customized by the administrator.
1734 See chapter ~~CHAPemsgcust for details.
1736 .index ::X-Failed-Recipients:: header line
1737 Bounce messages contain an ::X-Failed-Recipients:: header line that lists the
1738 failed addresses, for the benefit of programs that try to analyse such messages
1741 .index bounce message||recipient of
1742 A bounce message is normally sent to the sender of the original message, as
1743 obtained from the message's envelope. For incoming SMTP messages, this is the
1744 address given in the \\MAIL\\ command. However, when an address is
1745 expanded via a forward or alias file, an alternative address can be specified
1746 for delivery failures of the generated addresses. For a mailing list expansion
1747 (see section ~~SECTmailinglists) it is common to direct bounce messages to the
1748 manager of the list.
1752 .section Failures to deliver bounce messages
1753 .index bounce message||failure to deliver
1754 If a bounce message (either locally generated or received from a remote host)
1755 itself suffers a permanent delivery failure, the message is left on the queue,
1756 but it is frozen, awaiting the attention of an administrator. There are options
1757 which can be used to make Exim discard such failed messages, or to keep them
1758 for only a short time (see \timeout@_frozen@_after\ and
1759 \ignore@_bounce@_errors@_after\).
1767 . ============================================================================
1768 .chapter Building and installing Exim
1769 .set runningfoot "building/installing"
1771 .index building Exim
1773 Exim is distributed as a gzipped or bzipped tar file which, when upacked,
1774 creates a directory with the name of the current release (for example,
1775 \(exim-~~version)\) into which the following files are placed:
1777 .if !~~sys.fancy && ~~sgcal
1782 \(ACKNOWLEDGMENTS)\ $t contains some acknowledgments
1784 \(CHANGES)\ $t contains a reference to where changes are documented
1785 \(LICENCE)\ $t the GNU General Public Licence
1786 \(Makefile)\ $t top-level make file
1787 \(NOTICE)\ $t conditions for the use of Exim
1788 \(README)\ $t list of files, directories and simple build instructions
1790 Other files whose names begin with \(README)\ may also be present. The
1791 following subdirectories are created:
1793 .if !~~sys.fancy && ~~sgcal
1798 \(Local)\ $t an empty directory for local configuration files
1799 \(OS)\ $t OS-specific files
1800 \(doc)\ $t documentation files
1801 \(exim@_monitor)\$t source files for the Exim monitor
1802 \(scripts)\ $t scripts used in the build process
1803 \(src)\ $t remaining source files
1804 \(util)\ $t independent utilities
1806 The main utility programs are contained in the \(src)\ directory, and are built
1807 with the Exim binary. The \(util)\ directory contains a few optional scripts
1808 that may be useful to some sites.
1810 .section Multiple machine architectures and operating systems
1811 .index building Exim||multiple OS/architectures
1812 The building process for Exim is arranged to make it easy to build binaries for
1813 a number of different architectures and operating systems from the same set of
1814 source files. Compilation does not take place in the \(src)\ directory. Instead,
1815 a \*build directory*\ is created for each architecture and operating system.
1816 .index symbolic link||to build directory
1817 Symbolic links to the sources are installed in this directory, which is where
1818 the actual building takes place.
1820 In most cases, Exim can discover the machine architecture and operating system
1821 for itself, but the defaults can be overridden if necessary.
1823 .section DBM libraries
1824 .rset SECTdb "~~chapter.~~section"
1825 .index DBM||libraries, discussion of
1826 .index hints database||DBM files used for
1827 Even if you do not use any DBM files in your configuration, Exim still needs a
1828 DBM library in order to operate, because it uses indexed files for its hints
1829 databases. Unfortunately, there are a number of DBM libraries in existence, and
1830 different operating systems often have different ones installed.
1832 .index Solaris||DBM library for
1833 .index IRIX, DBM library for
1834 .index BSD, DBM library for
1835 .index Linux, DBM library for
1836 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1837 Linux distribution, the DBM configuration should happen automatically, and you
1838 may be able to ignore this section. Otherwise, you may have to learn more than
1839 you would like about DBM libraries from what follows.
1841 .index \*ndbm*\ DBM library
1842 Licensed versions of Unix normally contain a library of DBM functions operating
1843 via the \*ndbm*\ interface, and this is what Exim expects by default. Free
1844 versions of Unix seem to vary in what they contain as standard. In particular,
1845 some early versions of Linux have no default DBM library, and different
1846 distributors have chosen to bundle different libraries with their packaged
1847 versions. However, the more recent releases seem to have standardised on the
1848 Berkeley DB library.
1850 Different DBM libraries have different conventions for naming the files they
1851 use. When a program opens a file called \(dbmfile)\, there are four
1854 A traditional \*ndbm*\ implementation, such as that supplied as part of
1855 Solaris, operates on two files called \(dbmfile.dir)\ and \(dbmfile.pag)\.
1857 .index \*gdbm*\ DBM library
1858 The GNU library, \*gdbm*\, operates on a single file. If used via its \*ndbm*\
1859 compatibility interface it makes two different hard links to it with names
1860 \(dbmfile.dir)\ and \(dbmfile.pag)\, but if used via its native interface, the
1861 file name is used unmodified.
1863 .index Berkeley DB library
1864 The Berkeley DB package, if called via its \*ndbm*\ compatibility interface,
1865 operates on a single file called \(dbmfile.db)\, but otherwise looks to the
1866 programmer exactly the same as the traditional \*ndbm*\ implementation.
1868 If the Berkeley package is used in its native mode, it operates on a single
1869 file called \(dbmfile)\; the programmer's interface is somewhat different to
1870 the traditional \*ndbm*\ interface.
1872 To complicate things further, there are several very different versions of the
1873 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1874 2.$it{x} and 3.$it{x} were current for a while, but the latest versions are now
1875 numbered 4.$it{x}. Maintenance of some of the earlier releases has ceased. All
1876 versions of Berkeley DB can be obtained from
1878 \?http://www.sleepycat.com/?\
1881 .index \*tdb*\ DBM library
1882 Yet another DBM library, called \*tdb*\, has become available from
1884 \?http://download.sourceforge.net/tdb?\
1886 It has its own interface, and also operates on a single file.
1889 .index DBM||libraries, configuration for building
1890 Exim and its utilities can be compiled to use any of these interfaces. In order
1891 to use any version of the Berkeley DB package in native mode, you must set
1892 \\USE@_DB\\ in an appropriate configuration file (typically
1893 \(Local/Makefile)\). For example:
1897 Similarly, for gdbm you set \\USE@_GDBM\\, and for tdb you set \\USE@_TDB\\. An
1898 error is diagnosed if you set more than one of these.
1900 At the lowest level, the build-time configuration sets none of these options,
1901 thereby assuming an interface of type (1). However, some operating system
1902 configuration files (for example, those for the BSD operating systems and
1903 Linux) assume type (4) by setting \\USE@_DB\\ as their default, and the
1904 configuration files for Cygwin set \\USE@_GDBM\\. Anything you set in
1905 \(Local/Makefile)\, however, overrides these system defaults.
1907 As well as setting \\USE@_DB\\, \\USE@_GDBM\\, or \\USE@_TDB\\, it may also be
1908 necessary to set \\DBMLIB\\, to cause inclusion of the appropriate library, as
1909 in one of these lines:
1914 Settings like that will work if the DBM library is installed in the standard
1915 place. Sometimes it is not, and the library's header file may also not be in
1916 the default path. You may need to set \\INCLUDE\\ to specify where the header
1917 file is, and to specify the path to the library more fully in \\DBMLIB\\, as in
1920 INCLUDE=-I/usr/local/include/db-4.1
1921 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1924 There is further detailed discussion about the various DBM libraries in the
1925 file \(doc/dbm.discuss.txt)\ in the Exim distribution.
1928 .section Pre-building configuration
1929 .index building Exim||pre-building configuration
1930 .index configuration for building Exim
1931 .index \(Local/Makefile)\
1932 .index \(src/EDITME)\
1933 Before building Exim, a local configuration file that specifies options
1934 independent of any operating system has to be created with the name
1935 \(Local/Makefile)\. A template for this file is supplied as the file
1936 \(src/EDITME)\, and it contains full descriptions of all the option settings
1937 therein. These descriptions are therefore not repeated here. If you are
1938 building Exim for the first time, the simplest thing to do is to copy
1939 \(src/EDITME)\ to \(Local/Makefile)\, then read it and edit it appropriately.
1941 There are three settings that you must supply, because Exim will not build
1942 without them. They are the location of the run time configuration file
1943 (\\CONFIGURE@_FILE\\), the directory in which Exim binaries will be installed
1944 (\\BIN@_DIRECTORY\\), and the identity of the Exim user (\\EXIM@_USER\\ and
1945 maybe \\EXIM@_GROUP\\ as well). The value of \\CONFIGURE@_FILE\\ can in fact be
1946 a colon-separated list of file names; Exim uses the first of them that exists.
1948 There are a few other parameters that can be specified either at build time or
1949 at run time, to enable the same binary to be used on a number of different
1950 machines. However, if the locations of Exim's spool directory and log file
1951 directory (if not within the spool directory) are fixed, it is recommended that
1952 you specify them in \(Local/Makefile)\ instead of at run time, so that errors
1953 detected early in Exim's execution (such as a malformed configuration file) can
1956 .index content scanning||specifying at build time
1958 Exim's interfaces for calling virus and spam scanning sofware directly from
1959 access control lists are not compiled by default. If you want to include these
1960 facilities, you need to set
1962 WITH_CONTENT_SCAN=yes
1964 in your \(Local/Makefile)\. For details of the facilities themselves, see
1965 chapter ~~CHAPexiscan.
1968 .index \(Local/eximon.conf)\
1969 .index \(exim@_monitor/EDITME)\
1970 If you are going to build the Exim monitor, a similar configuration process is
1971 required. The file \(exim@_monitor/EDITME)\ must be edited appropriately for
1972 your installation and saved under the name \(Local/eximon.conf)\. If you are
1973 happy with the default settings described in \(exim@_monitor/EDITME)\,
1974 \(Local/eximon.conf)\ can be empty, but it must exist.
1976 This is all the configuration that is needed in straightforward cases for known
1977 operating systems. However, the building process is set up so that it is easy
1978 to override options that are set by default or by operating-system-specific
1979 configuration files, for example to change the name of the C compiler, which
1980 defaults to \gcc\. See section ~~SECToverride below for details of how to do
1984 .section Support for iconv()
1985 .index \*iconv()*\ support
1986 The contents of header lines in messages may be encoded according to the rules
1987 described RFC 2047. This makes it possible to transmit characters that are not
1988 in the ASCII character set, and to label them as being in a particular
1989 character set. When Exim is inspecting header lines by means of the \@$h@_\
1990 mechanism, it decodes them, and translates them into a specified character set
1991 (default ISO-8859-1). The translation is possible only if the operating system
1992 supports the \*iconv()*\ function.
1994 However, some of the operating systems that supply \*iconv()*\ do not support
1995 very many conversions. The GNU \libiconv\ library (available from
1996 \?http:/@/www.gnu.org/software/libiconv/?\) can be installed on such systems to
1997 remedy this deficiency, as well as on systems that do not supply \*iconv()*\ at
1998 all. After installing \libiconv\, you should add
2002 to your \(Local/Makefile)\ and rebuild Exim.
2005 .section Including TLS/SSL encryption support
2006 .rset SECTinctlsssl "~~chapter.~~section"
2007 .index TLS||including support for TLS
2008 .index encryption||including support for
2009 .index \\SUPPORT@_TLS\\
2010 .index OpenSSL||building Exim with
2011 .index GnuTLS||building Exim with
2012 Exim can be built to support encrypted SMTP connections, using the \\STARTTLS\\
2013 command as per RFC 2487. It can also support legacy clients that expect to
2014 start a TLS session immediately on connection to a non-standard port (see the
2015 \tls@_on@_connect@_ports\ runtime option and the \-tls-on-connect-\ command
2018 If you want to build Exim with TLS support, you must first install either the
2019 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
2022 If OpenSSL is installed, you should set
2025 TLS_LIBS=-lssl -lcrypto
2027 in \(Local/Makefile)\. You may also need to specify the locations of the
2028 OpenSSL library and include files. For example:
2031 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
2032 TLS_INCLUDE=-I/usr/local/openssl/include/
2035 If GnuTLS is installed, you should set
2036 .index \\USE@_GNUTLS\\
2040 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
2042 in \(Local/Makefile)\, and again you may need to specify the locations of the
2043 library and include files. For example:
2047 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
2048 TLS_INCLUDE=-I/usr/gnu/include
2050 You do not need to set \\TLS@_INCLUDE\\ if the relevant directory is already
2051 specified in \\INCLUDE\\. Details of how to configure Exim to make use of TLS
2052 are given in chapter ~~CHAPTLS.
2056 .section Use of tcpwrappers
2057 .index tcpwrappers, building Exim to support
2058 .index \\USE@_TCP@_WRAPPERS\\
2059 Exim can be linked with the \*tcpwrappers*\ library in order to check incoming
2060 SMTP calls using the \*tcpwrappers*\ control files. This may be a convenient
2061 alternative to Exim's own checking facilities for installations that are
2062 already making use of \*tcpwrappers*\ for other purposes. To do this, you should
2063 set \\USE@_TCP@_WRAPPERS\\ in \(Local/Makefile)\, arrange for the file
2064 \(tcpd.h)\ to be available at compile time, and also ensure that the library
2065 \(libwrap.a)\ is available at link time, typically by including \-lwrap-\ in
2066 \\EXTRALIBS@_EXIM\\. For example, if \*tcpwrappers*\ is installed in
2067 \(/usr/local)\, you might have
2069 USE@_TCP@_WRAPPERS=yes
2070 CFLAGS=-O -I/usr/local/include
2072 EXTRALIBS@_EXIM=-L/usr/local/lib -lwrap
2074 in \(Local/Makefile)\. The name to use in the \*tcpwrappers*\ control files is
2075 `exim'. For example, the line
2077 exim : LOCAL 192.168.1. .friendly.domain.example
2079 in your \(/etc/hosts.allow)\ file allows connections from the local host, from
2080 the subnet 192.168.1.0/24, and from all hosts in \*friendly.domain.example*\.
2081 All other connections are denied. Consult the \*tcpwrappers*\ documentation for
2085 .section Including support for IPv6
2086 .index IPv6||including support for
2087 Exim contains code for use on systems that have IPv6 support. Setting
2088 \\HAVE@_IPV6=YES\\ in \(Local/Makefile)\ causes the IPv6 code to be included;
2089 it may also be necessary to set \\IPV6@_INCLUDE\\ and \\IPV6@_LIBS\\ on systems
2090 where the IPv6 support is not fully integrated into the normal include and
2094 Two different types of DNS record for handling IPv6 addresses have been
2095 defined. AAAA records (analagous to A records for IPv4) are in use, and are
2096 currently seen as the mainstream. Another record type called A6 was proposed
2097 as better than AAAA because it had more flexibility. However, it was felt to
2098 be over-complex, and its status was reduced to `experimental'. It is not known
2099 if anyone is actually using A6 records. Exim has support for A6 records, but
2100 this is included only if you set \\SUPPORT@_A6=YES\\ in \(Local/Makefile)\. The
2101 support has not been tested for some time.
2104 .section The building process
2105 .index build directory
2106 Once \(Local/Makefile)\ (and \(Local/eximon.conf)\, if required) have been
2107 created, run \*make*\ at the top level. It determines the architecture and
2108 operating system types, and creates a build directory if one does not exist.
2109 For example, on a Sun system running Solaris 8, the directory
2110 \(build-SunOS5-5.8-sparc)\ is created.
2111 .index symbolic link||to source files
2112 Symbolic links to relevant source files are installed in the build directory.
2114 \**Warning**\: The \-j-\ (parallel) flag must not be used with \*make*\; the
2115 building process fails if it is set.
2117 If this is the first time \*make*\ has been run, it calls a script that builds
2118 a make file inside the build directory, using the configuration files from the
2119 \(Local)\ directory. The new make file is then passed to another instance of
2120 \*make*\. This does the real work, building a number of utility scripts, and
2121 then compiling and linking the binaries for the Exim monitor (if configured), a
2122 number of utility programs, and finally Exim itself. The command \*make
2123 makefile*\ can be used to force a rebuild of the make file in the build
2124 directory, should this ever be necessary.
2126 If you have problems building Exim, check for any comments there may be in the
2127 \(README)\ file concerning your operating system, and also take a look at the
2129 [(A HREF="FAQ.html")]
2135 where some common problems are covered.
2139 .section Overriding build-time options for Exim
2140 .index build-time options, overriding
2141 .rset SECToverride "~~chapter.~~section"
2142 The main make file that is created at the beginning of the building process
2143 consists of the concatenation of a number of files which set configuration
2144 values, followed by a fixed set of \*make*\ instructions. If a value is set
2145 more than once, the last setting overrides any previous ones. This provides a
2146 convenient way of overriding defaults. The files that are concatenated are, in
2149 \(OS/Makefile-Default)\
2150 \(OS/Makefile-)\<<ostype>>
2152 \(Local/Makefile-)\<<ostype>>
2153 \(Local/Makefile-)\<<archtype>>
2154 \(Local/Makefile-)\<<ostype>>-<<archtype>>
2155 \(OS/Makefile-Base)\
2157 .index \(Local/Makefile)\
2158 where <<ostype>> is the operating system type and <<archtype>> is the
2159 .index building Exim||operating system type
2160 .index building Exim||architecture type
2161 architecture type. \(Local/Makefile)\ is required to exist, and the building
2162 process fails if it is absent. The other three \(Local)\ files are optional,
2163 and are often not needed.
2165 The values used for <<ostype>> and <<archtype>> are obtained from scripts
2166 called \(scripts/os-type)\ and \(scripts/arch-type)\ respectively. If either of
2167 the environment variables \\EXIM@_OSTYPE\\ or \\EXIM@_ARCHTYPE\\ is set, their
2168 values are used, thereby providing a means of forcing particular settings.
2169 Otherwise, the scripts try to get values from the \uname\ command. If this
2170 fails, the shell variables \\OSTYPE\\ and \\ARCHTYPE\\ are inspected. A number
2171 of $it{ad hoc} transformations are then applied, to produce the standard names
2172 that Exim expects. You can run these scripts directly from the shell in order
2173 to find out what values are being used on your system.
2176 \(OS/Makefile-Default)\ contains comments about the variables that are set
2177 therein. Some (but not all) are mentioned below. If there is something that
2178 needs changing, review the contents of this file and the contents of the make
2179 file for your operating system (\(OS/Makefile-<<ostype>>)\) to see what the
2183 .index building Exim||overriding default settings
2184 If you need to change any of the values that are set in \(OS/Makefile-Default)\
2185 or in \(OS/Makefile-<<ostype>>)\, or to add any new definitions, you do not
2186 need to change the original files. Instead, you should make the changes by
2187 putting the new values in an appropriate \(Local)\ file. For example,
2188 .index Tru64-Unix build-time settings
2189 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2190 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2191 compiler is called \*cc*\ rather than \*gcc*\. Also, the compiler must be
2192 called with the option \-std1-\, to make it recognize some of the features of
2193 Standard C that Exim uses. (Most other compilers recognize Standard C by
2194 default.) To do this, you should create a file called \(Local/Makefile-OSF1)\
2195 containing the lines
2200 If you are compiling for just one operating system, it may be easier to put
2201 these lines directly into \(Local/Makefile)\.
2203 Keeping all your local configuration settings separate from the distributed
2204 files makes it easy to transfer them to new versions of Exim simply by copying
2205 the contents of the \(Local)\ directory.
2208 .index NIS lookup type||including support for
2209 .index NIS@+ lookup type||including support for
2210 .index LDAP||including support for
2211 .index lookup||inclusion in binary
2212 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2213 lookup, but not all systems have these components installed, so the default is
2214 not to include the relevant code in the binary. All the different kinds of file
2215 and database lookup that Exim supports are implemented as separate code modules
2216 which are included only if the relevant compile-time options are set. In the
2217 case of LDAP, NIS, and NIS+, the settings for \(Local/Makefile)\ are:
2223 and similar settings apply to the other lookup types. They are all listed in
2224 \(src/EDITME)\. In most cases the relevant include files and interface
2225 libraries need to be installed before compiling Exim.
2226 .index cdb||including support for
2227 However, in the case of cdb, which is included in the binary only if
2231 is set, the code is entirely contained within Exim, and no external include
2232 files or libraries are required. When a lookup type is not included in the
2233 binary, attempts to configure Exim to use it cause run time configuration
2236 .index Perl||including support for
2237 Exim can be linked with an embedded Perl interpreter, allowing Perl
2238 subroutines to be called during string expansion. To enable this facility,
2242 must be defined in \(Local/Makefile)\. Details of this facility are given in
2245 .index X11 libraries, location of
2246 The location of the X11 libraries is something that varies a lot between
2247 operating systems, and of course there are different versions of X11 to cope
2248 with. Exim itself makes no use of X11, but if you are compiling the Exim
2249 monitor, the X11 libraries must be available.
2250 The following three variables are set in \(OS/Makefile-Default)\:
2253 XINCLUDE=-I$(X11)/include
2254 XLFLAGS=-L$(X11)/lib
2256 These are overridden in some of the operating-system configuration files. For
2257 example, in \(OS/Makefile-SunOS5)\ there is
2260 XINCLUDE=-I$(X11)/include
2261 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2263 If you need to override the default setting for your operating system, place a
2264 definition of all three of these variables into your
2265 \(Local/Makefile-<<ostype>>)\ file.
2267 .index \\EXTRALIBS\\
2268 If you need to add any extra libraries to the link steps, these can be put in a
2269 variable called \\EXTRALIBS\\, which appears in all the link commands, but by
2270 default is not defined. In contrast, \\EXTRALIBS@_EXIM\\ is used only on the
2271 command for linking the main Exim binary, and not for any associated utilities.
2272 .index DBM||libraries, configuration for building
2273 There is also \\DBMLIB\\, which appears in the link commands for binaries that
2274 use DBM functions (see also section ~~SECTdb). Finally, there is
2275 \\EXTRALIBS@_EXIMON\\, which appears only in the link step for the Exim monitor
2276 binary, and which can be used, for example, to include additional X11
2279 .index configuration file||editing
2280 The make file copes with rebuilding Exim correctly if any of the configuration
2281 files are edited. However, if an optional configuration file is deleted, it is
2282 necessary to touch the associated non-optional file (that is, \(Local/Makefile)\
2283 or \(Local/eximon.conf)\) before rebuilding.
2285 .section OS-specific header files
2287 .index building Exim||OS-specific C header files
2288 The \(OS)\ directory contains a number of files with names of the form
2289 \(os.h-<<ostype>>)\. These are system-specific C header files that should not
2290 normally need to be changed. There is a list of macro settings that are
2291 recognized in the file \(OS/os.configuring)\, which should be consulted if you
2292 are porting Exim to a new operating system.
2295 .section Overriding build-time options for the monitor
2296 .index building Eximon||overriding default options
2297 A similar process is used for overriding things when building the Exim monitor,
2298 where the files that are involved are
2300 \(OS/eximon.conf-Default)\
2301 \(OS/eximon.conf-)\<<ostype>>
2302 \(Local/eximon.conf)\
2303 \(Local/eximon.conf-)\<<ostype>>
2304 \(Local/eximon.conf-)\<<archtype>>
2305 \(Local/eximon.conf-)\<<ostype>>-<<archtype>>
2307 .index \(Local/eximon.conf)\
2308 As with Exim itself, the final three files need not exist, and in this case the
2309 \(OS/eximon.conf-<<ostype>>)\ file is also optional. The default values in
2310 \(OS/eximon.conf-Default)\ can be overridden dynamically by setting environment
2311 variables of the same name, preceded by \\EXIMON@_\\. For example, setting
2312 \\EXIMON@_LOG@_DEPTH\\ in the environment overrides the value of
2313 \\LOG@_DEPTH\\ at run time.
2317 .section Installing Exim binaries and scripts
2318 .index installing Exim
2319 .index \\BIN@_DIRECTORY\\
2320 The command \*make install*\ runs the \*exim@_install*\ script with no
2321 arguments. The script copies binaries and utility scripts into the directory
2322 whose name is specified by the \\BIN@_DIRECTORY\\ setting in
2325 Exim's run time configuration file is named by the \\CONFIGURE@_FILE\\ setting
2326 .index \\CONFIGURE@_FILE\\
2327 in \(Local/Makefile)\. If this names a single file, and the file does not
2328 exist, the default configuration file \(src/configure.default)\ is copied there
2329 by the installation script. If a run time configuration file already exists, it
2330 is left alone. If \\CONFIGURE@_FILE\\ is a colon-separated list, naming several
2331 alternative files, no default is installed.
2333 .index system aliases file
2334 .index \(/etc/aliases)\
2335 One change is made to the default configuration file when it is installed: the
2336 default configuration contains a router that references a system aliases file.
2337 The path to this file is set to the value specified by
2338 \\SYSTEM@_ALIASES@_FILE\\ in \(Local/Makefile)\ (\(/etc/aliases)\ by default).
2339 If the system aliases file does not exist, the installation script creates it,
2340 and outputs a comment to the user.
2342 The created file contains no aliases, but it does contain comments about the
2343 aliases a site should normally have. Mail aliases have traditionally been
2344 kept in \(/etc/aliases)\. However, some operating systems are now using
2345 \(/etc/mail/aliases)\. You should check if yours is one of these, and change
2346 Exim's configuration if necessary.
2348 The default configuration uses the local host's name as the only local domain,
2349 and is set up to do local deliveries into the shared directory \(/var/mail)\,
2350 running as the local user. System aliases and \(.forward)\ files in users' home
2351 directories are supported, but no NIS or NIS+ support is configured. Domains
2352 other than the name of the local host are routed using the DNS, with delivery
2355 The install script copies files only if they are newer than the files they are
2356 going to replace. The Exim binary is required to be owned by root and have the
2358 .index setuid||installing Exim with
2359 for normal configurations. Therefore, you must run \*make install*\ as root so
2360 that it can set up the Exim binary in this way. However, in some special
2361 situations (for example, if a host is doing no local deliveries) it may be
2362 possible to run Exim without making the binary setuid root (see chapter
2363 ~~CHAPsecurity for details).
2365 It is possible to install Exim for special purposes (such as building a binary
2366 distribution) in a private part of the file system. You can do this by a
2369 make DESTDIR=/some/directory/ install
2371 This has the effect of pre-pending the specified directory to all the file
2372 paths, except the name of the system aliases file that appears in the default
2373 configuration. (If a default alias file is created, its name \*is*\ modified.)
2374 For backwards compatibility, \\ROOT\\ is used if \\DESTDIR\\ is not set,
2375 but this usage is deprecated.
2377 .index installing Exim||what is not installed
2378 Running \*make install*\ does not copy the Exim 4 conversion script
2379 \*convert4r4*\, or the \*pcretest*\ test program. You will probably run the
2380 first of these only once (if you are upgrading from Exim 3), and the second
2381 isn't really part of Exim. None of the documentation files in the \(doc)\
2382 directory are copied, except for the info files when you have set
2383 \\INFO@_DIRECTORY\\, as described in section ~~SECTinsinfdoc below.
2385 For the utility programs, old versions are renamed by adding the suffix \(.O)\
2386 to their names. The Exim binary itself, however, is handled differently. It is
2387 installed under a name that includes the version number and the compile number,
2388 for example \(exim-~~version-1)\. The script then arranges for a symbolic link
2389 called \(exim)\ to point to the binary. If you are updating a previous version
2390 of Exim, the script takes care to ensure that the name \(exim)\ is never absent
2391 from the directory (as seen by other processes).
2393 .index installing Exim||testing the script
2394 If you want to see what the \*make install*\ will do before running it for
2395 real, you can pass the \-n-\ option to the installation script by this command:
2397 make INSTALL_ARG=-n install
2399 The contents of the variable \\INSTALL@_ARG\\ are passed to the installation
2400 script. You do not need to be root to run this test. Alternatively, you can run
2401 the installation script directly, but this must be from within the build
2402 directory. For example, from the top-level Exim directory you could use this
2405 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim@_install -n)
2408 .index installing Exim||install script options
2409 There are two other options that can be supplied to the installation script.
2411 \-no@_chown-\ bypasses the call to change the owner of the installed binary
2412 to root, and the call to make it a setuid binary.
2414 \-no@_symlink-\ bypasses the setting up of the symbolic link \(exim)\ to the
2417 \\INSTALL@_ARG\\ can be used to pass these options to the script. For example:
2419 make INSTALL_ARG=-no_symlink install
2422 The installation script can also be given arguments specifying which files are
2423 to be copied. For example, to install just the Exim binary, and nothing else,
2424 without creating the symbolic link, you could use:
2426 make INSTALL_ARG='-no_symlink exim' install
2430 .section Installing info documentation
2431 .rset SECTinsinfdoc "~~chapter.~~section"
2432 .index installing Exim||\*info*\ documentation
2433 Not all systems use the GNU \*info*\ system for documentation, and for this
2434 reason, the Texinfo source of Exim's documentation is not included in the main
2435 distribution. Instead it is available separately from the ftp site (see section
2438 If you have defined \\INFO@_DIRECTORY\\ in \(Local/Makefile)\ and the Texinfo
2439 source of the documentation is found in the source tree, running \*make
2440 install*\ automatically builds the info files and installs them.
2443 .section Setting up the spool directory
2444 .index spool directory||creating
2445 When it starts up, Exim tries to create its spool directory if it does not
2446 exist. The Exim uid and gid are used for the owner and group of the spool
2447 directory. Sub-directories are automatically created in the spool directory as
2453 .index testing||installation
2454 Having installed Exim, you can check that the run time configuration file is
2455 syntactically valid by running the following command, which assumes that the
2456 Exim binary directory is within your \\PATH\\ environment variable:
2460 If there are any errors in the configuration file, Exim outputs error messages.
2461 Otherwise it outputs the version number and build date,
2462 the DBM library that is being used, and information about which drivers and
2463 other optional code modules are included in the binary.
2464 Some simple routing tests can be done by using the address testing option. For
2467 exim -bt <<local username>>
2469 should verify that it recognizes a local mailbox, and
2471 exim -bt <<remote address>>
2473 a remote one. Then try getting it to deliver mail, both locally and remotely.
2474 This can be done by passing messages directly to Exim, without going through a
2475 user agent. For example:
2477 exim -v postmaster@@your.domain.example
2478 From: user@@your.domain.example
2479 To: postmaster@@your.domain.example
2480 Subject: Testing Exim
2482 This is a test message.
2485 The \-v-\ option causes Exim to output some verification of what it is doing.
2486 In this case you should see copies of three log lines, one for the message's
2487 arrival, one for its delivery, and one containing `Completed'.
2489 .index delivery||problems with
2490 If you encounter problems, look at Exim's log files (\*mainlog*\ and
2491 \*paniclog*\) to see if there is any relevant information there. Another source
2492 of information is running Exim with debugging turned on, by specifying the
2493 \-d-\ option. If a message is stuck on Exim's spool, you can force a delivery
2494 with debugging turned on by a command of the form
2496 exim -d -M <<message-id>>
2498 You must be root or an `admin user' in order to do this. The \-d-\ option
2499 produces rather a lot of output, but you can cut this down to specific areas.
2500 For example, if you use \-d-all+route-\ only the debugging information relevant
2501 to routing is included. (See the \-d-\ option in chapter ~~CHAPcommandline for
2506 One specific problem that has shown up on some sites is the inability to do
2507 local deliveries into a shared mailbox directory, because it does not have the
2508 `sticky bit' set on it. By default, Exim tries to create a lock file before
2509 writing to a mailbox file, and if it cannot create the lock file, the delivery
2510 is deferred. You can get round this either by setting the `sticky bit' on the
2511 directory, or by setting a specific group for local deliveries and allowing
2512 that group to create files in the directory (see the comments above the
2513 \%local@_delivery%\ transport in the default configuration file). Another
2514 approach is to configure Exim not to use lock files, but just to rely on
2515 \*fcntl()*\ locking instead. However, you should do this only if all user
2516 agents also use \*fcntl()*\ locking. For further discussion of locking issues,
2517 see chapter ~~CHAPappendfile.
2519 One thing that cannot be tested on a system that is already running an MTA is
2520 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2521 \-oX-\ option can be used to run an Exim daemon that listens on some other
2522 port, or \*inetd*\ can be used to do this. The \-bh-\ option and the
2523 \*exim@_checkaccess*\ utility can be used to check out policy controls on
2526 Testing a new version on a system that is already running Exim can most easily
2527 be done by building a binary with a different \\CONFIGURE@_FILE\\ setting. From
2528 within the run time configuration, all other file and directory names
2529 that Exim uses can be altered, in order to keep it entirely clear of the
2532 .section Replacing another MTA with Exim
2533 .index replacing another MTA
2534 Building and installing Exim for the first time does not of itself put it in
2535 general use. The name by which the system's MTA is called by mail user agents
2536 is either \(/usr/sbin/sendmail)\, or \(/usr/lib/sendmail)\ (depending on the
2537 operating system), and it is necessary to make this name point to the \*exim*\
2538 binary in order to get the user agents to pass messages to Exim. This is
2539 normally done by renaming any existing file and making \(/usr/sbin/sendmail)\
2540 or \(/usr/lib/sendmail)\
2541 .index symbolic link||to \*exim*\ binary
2542 a symbolic link to the \*exim*\ binary. It is a good idea to remove any setuid
2543 privilege and executable status from the old MTA. It is then necessary to stop
2544 and restart the mailer daemon, if one is running.
2546 .index FreeBSD, MTA indirection
2547 .index \(/etc/mail/mailer.conf)\
2548 Some operating systems have introduced alternative ways of switching MTAs. For
2549 example, if you are running FreeBSD, you need to edit the file
2550 \(/etc/mail/mailer.conf)\ instead of setting up a symbolic link as just
2551 described. A typical example of the contents of this file for running Exim is
2554 sendmail /usr/exim/bin/exim
2555 send-mail /usr/exim/bin/exim
2556 mailq /usr/exim/bin/exim -bp
2557 newaliases /usr/bin/true
2560 Once you have set up the symbolic link, or edited \(/etc/mail/mailer.conf)\,
2561 your Exim installation is `live'. Check it by sending a message from your
2562 favourite user agent.
2564 You should consider what to tell your users about the change of MTA. Exim may
2565 have different capabilities to what was previously running, and there are
2566 various operational differences such as the text of messages produced by
2567 command line options and in bounce messages. If you allow your users to make
2568 use of Exim's filtering capabilities, you should make the document entitled
2570 [(A HREF="filter.html")]
2572 \*Exim's interface to mail filtering*\
2579 .section Upgrading Exim
2580 .index upgrading Exim
2581 If you are already running Exim on your host, building and installing a new
2582 version automatically makes it available to MUAs, or any other programs that
2583 call the MTA directly. However, if you are running an Exim daemon, you do need
2584 to send it a HUP signal, to make it re-exec itself, and thereby pick up the new
2585 binary. You do not need to stop processing mail in order to install a new
2589 .section Stopping the Exim daemon on Solaris
2590 .index Solaris||stopping Exim on
2591 The standard command for stopping the mailer daemon on Solaris is
2593 /etc/init.d/sendmail stop
2595 If \(/usr/lib/sendmail)\ has been turned into a symbolic link, this script
2596 fails to stop Exim because it uses the command \*ps -e*\ and greps the output
2597 for the text `sendmail'; this is not present because the actual program name
2598 (that is, `exim') is given by the \*ps*\ command with these options. A solution
2599 is to replace the line that finds the process id with something like
2601 pid=`cat /var/spool/exim/exim-daemon.pid`
2603 to obtain the daemon's pid directly from the file that Exim saves it in.
2605 Note, however, that stopping the daemon does not `stop Exim'. Messages can
2606 still be received from local processes, and if automatic delivery is configured
2607 (the normal case), deliveries will still occur.
2614 . ============================================================================
2615 .chapter The Exim command line
2616 .set runningfoot "command line"
2617 .rset CHAPcommandline ~~chapter
2618 .index command line||options
2619 .index options||command line
2621 Exim's command line takes the standard Unix form of a sequence of options,
2622 each starting with a hyphen character, followed by a number of arguments. The
2623 options are compatible with the main options of Sendmail, and there are also
2624 some additional options, some of which are compatible with Smail 3. Certain
2625 combinations of options do not make sense, and provoke an error if used.
2626 The form of the arguments depends on which options are set.
2628 .section Setting options by program name
2630 If Exim is called under the name \*mailq*\, it behaves as if the option \-bp-\
2631 were present before any other options.
2632 The \-bp-\ option requests a listing of the contents of the mail queue on the
2634 This feature is for compatibility with some systems that contain a command of
2635 that name in one of the standard libraries, symbolically linked to
2636 \(/usr/sbin/sendmail)\ or \(/usr/lib/sendmail)\.
2639 If Exim is called under the name \*rsmtp*\ it behaves as if the option \-bS-\
2640 were present before any other options, for compatibility with Smail. The \-bS-\
2641 option is used for reading in a number of messages in batched SMTP format.
2644 If Exim is called under the name \*rmail*\ it behaves as if the \-i-\ and
2645 \-oee-\ options were present before any other options, for compatibility with
2646 Smail. The name \*rmail*\ is used as an interface by some UUCP systems.
2650 If Exim is called under the name \*runq*\ it behaves as if the option \-q-\ were
2651 present before any other options, for compatibility with Smail. The \-q-\
2652 option causes a single queue runner process to be started.
2654 .index \*newaliases*\
2655 .index alias file||building
2656 .index Sendmail compatibility||calling Exim as \*newaliases*\
2657 If Exim is called under the name \*newaliases*\ it behaves as if the option
2658 \-bi-\ were present before any other options, for compatibility with Sendmail.
2659 This option is used for rebuilding Sendmail's alias file. Exim does not have
2660 the concept of a single alias file, but can be configured to run a given
2661 command if called with the \-bi-\ option.
2663 .section Trusted and admin users
2664 .rset SECTtrustedadmin "~~chapter.~~section"
2665 Some Exim options are available only to \*trusted users*\ and others are
2666 available only to \*admin users*\. In the description below, the phrases `Exim
2667 user' and `Exim group' mean the user and group defined by \\EXIM@_USER\\ and
2668 \\EXIM@_GROUP\\ in \(Local/Makefile)\ or set by the \exim@_user\ and
2669 \exim@_group\ options. These do not necessarily have to use the name `exim'.
2672 .index trusted user||definition of
2673 .index user||trusted, definition of
2674 The trusted users are root, the Exim user, any user listed in the
2675 \trusted@_users\ configuration option, and any user whose current group or any
2676 supplementary group is one of those listed in the \trusted@_groups\
2677 configuration option. Note that the Exim group is not automatically trusted.
2680 .index envelope sender
2681 Trusted users are always permitted to use the \-f-\ option or a leading `From '
2682 line to specify the envelope sender of a message that is passed to Exim through
2683 the local interface (see the \-bm-\ and \-f-\ options below). See the
2684 \untrusted@_set@_sender\ option for a way of permitting non-trusted users to
2685 set envelope senders.
2686 .index ::From:: header line
2687 .index ::Sender:: header line
2688 For a trusted user, there is never any check on the contents of the ::From::
2689 header line, and a ::Sender:: line is never added. Furthermore, any existing
2690 ::Sender:: line in incoming local (non-TCP/IP) messages is not removed.
2692 Trusted users may also specify a host name, host address, interface address,
2693 protocol name, ident value, and authentication data when submitting a message
2694 locally. Thus, they are able to insert messages into Exim's queue locally that
2695 have the characteristics of messages received from a remote host. Untrusted
2696 users may in some circumstances use \-f-\, but can never set the other values
2697 that are available to trusted users.
2699 .index user||admin, definition of
2700 .index admin user||definition of
2701 The admin users are root, the Exim user, and any user that is a member of the
2702 Exim group or of any group listed in the \admin@_groups\ configuration option.
2703 The current group does not have to be one of these groups.
2705 Admin users are permitted to list the queue, and to carry out certain
2706 operations on messages, for example, to force delivery failures. It is also
2707 necessary to be an admin user in order to see the full information provided by
2708 the Exim monitor, and full debugging output.
2710 By default, the use of the \-M-\, \-q-\, \-R-\, and \-S-\ options to cause Exim
2711 to attempt delivery of messages on its queue is restricted to admin users.
2712 However, this restriction can be relaxed by setting the \prod@_requires@_admin\
2713 option false (that is, specifying \no@_prod@_requires@_admin\).
2715 Similarly, the use of the \-bp-\ option to list all the messages in the queue
2716 is restricted to admin users unless \queue@_list@_requires@_admin\ is set
2720 \**Warning**\: If you configure your system so that admin users are able to
2721 edit Exim's configuration file, you are giving those users an easy way of
2722 getting root. There is further discussion of this issue at the start of chapter
2727 .section Command line options
2728 The command options are described in alphabetical order below.
2733 .index options||command line, terminating
2734 This is a pseudo-option whose only purpose is to terminate the options and
2735 therefore to cause subsequent command line items to be treated as arguments
2736 rather than options, even if they begin with hyphens.
2739 This option causes Exim to output a few sentences stating what it is.
2740 The same output is generated if the Exim binary is called with no options and
2744 .index 8-bit characters
2745 .index Sendmail compatibility||8-bit characters
2746 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2747 clean; it ignores this option.
2751 .index SMTP listener
2753 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2754 the \-bd-\ option is combined with the \-q-\<<time>> option, to specify that
2755 the daemon should also initiate periodic queue runs.
2757 The \-bd-\ option can be used only by an admin user. If either of the \-d-\
2758 (debugging) or \-v-\ (verifying) options are set, the daemon does not
2759 disconnect from the controlling terminal. When running this way, it can be
2760 stopped by pressing ctrl-C.
2762 By default, Exim listens for incoming connections to the standard SMTP port on
2763 all the host's running interfaces. However, it is possible to listen on other
2764 ports, on multiple ports, and only on specific interfaces. Chapter
2765 ~~CHAPinterfaces contains a description of the options that control this.
2767 .index daemon||process id (pid)
2768 .index pid (process id)||of daemon
2769 When a listening daemon is started without the use of \-oX-\ (that is, without
2770 overriding the normal configuration), it writes its process id to a file called
2771 \(exim-daemon.pid)\ in Exim's spool directory. This location can be overridden
2772 by setting \\PID@_FILE@_PATH\\ in \(Local/Makefile)\. The file is written while
2773 Exim is still running as root.
2775 When \-oX-\ is used on the command line to start a listening daemon, the
2776 process id is not written to the normal pid file path. However, \-oP-\ can be
2777 used to specify a path on the command line if a pid file is required.
2780 The \\SIGHUP\\ signal can be used to cause the daemon to re-exec itself. This
2781 should be done whenever Exim's configuration file, or any file that is
2782 incorporated into it by means of the \.include\ facility, is changed, and also
2783 whenever a new version of Exim is installed. It is not necessary to do this
2784 when other files that are referenced from the configuration (for example, alias
2785 files) are changed, because these are reread each time they are used.
2788 This option has the same effect as \-bd-\ except that it never disconnects from
2789 the controlling terminal, even when no debugging is specified.
2792 .index testing||string expansion
2793 .index expansion||testing
2794 Run Exim in expansion testing mode. Exim discards its root privilege, to
2795 prevent ordinary users from using this mode to read otherwise inaccessible
2796 files. If no arguments are given, Exim runs interactively, prompting for lines
2799 If Exim was built with \\USE@_READLINE\\=yes in \(Local/Makefile)\, it tries
2800 to load the \libreadline\ library dynamically whenever the \-be-\ option is
2801 used without command line arguments. If successful, it uses the \*readline()*\
2802 function, which provides extensive line-editing facilities, for reading the
2803 test data. A line history is supported.
2806 Long expansion expressions can be split over several lines by using backslash
2807 continuations. As in Exim's run time configuration, whitespace at the start of
2808 continuation lines is ignored. Each argument or data line is passed through the
2809 string expansion mechanism, and the result is output. Variable values from the
2810 configuration file (for example, \$qualify@_domain$\) are available, but no
2811 message-specific values (such as \$domain$\) are set, because no message is
2814 .option bF #<<filename>>
2815 .index system filter||testing
2816 .index testing||system filter
2817 This option is the same as \-bf-\ except that it assumes that the filter being
2818 tested is a system filter. The additional commands that are available only in
2819 system filters are recognized.
2821 .option bf #<<filename>>
2822 .index filter||testing
2823 .index testing||filter file
2824 .index forward file||testing
2825 .index testing||forward file
2826 .index Sieve filter||testing
2827 This option runs Exim in user filter testing mode; the file is the filter file
2828 to be tested, and a test message must be supplied on the standard input. If
2829 there are no message-dependent tests in the filter, an empty file can be
2832 If you want to test a system filter file, use \-bF-\ instead of \-bf-\. You can
2833 use both \-bF-\ and \-bf-\ on the same command, in order to
2834 test a system filter and a user filter in the same run. For example:
2836 exim -bF /system/filter -bf /user/filter </test/message
2838 This is helpful when the system filter adds header lines or sets filter
2839 variables that are used by the user filter.
2842 If the test filter file does not begin with one of the special lines
2847 it is taken to be a normal \(.forward)\ file, and is tested for validity under
2848 that interpretation. See sections ~~SECTitenonfilred to ~~SECTspecitredli for a
2849 description of the possible contents of non-filter redirection lists.
2851 The result of an Exim command that uses \-bf-\, provided no errors are
2852 detected, is a list of the actions that Exim would try to take if presented
2853 with the message for real. More details of filter testing are given in the
2854 separate document entitled \*Exim's interfaces to mail filtering*\.
2857 .index envelope sender
2858 .index \-f-\ option||for filter testing
2859 When testing a filter file, the envelope sender can be set by the \-f-\ option,
2860 or by a `From ' line at the start of the test message. Various parameters that
2861 would normally be taken from the envelope recipient address of the message can
2862 be set by means of additional command line options (see the next four options).
2865 .option bfd #<<domain>>
2866 This sets the domain of the recipient address when a filter file is being
2867 tested by means of the \-bf-\ option. The default is the value of
2868 \$qualify@_domain$\.
2870 .option bfl #<<local part>>
2871 This sets the local part of the recipient address when a filter file is being
2872 tested by means of the \-bf-\ option. The default is the username of the
2873 process that calls Exim. A local part should be specified with any prefix or
2874 suffix stripped, because that is how it appears to the filter when a message is
2875 actually being delivered.
2877 .option bfp #<<prefix>>
2878 This sets the prefix of the local part of the recipient address when a filter
2879 file is being tested by means of the \-bf-\ option. The default is an empty
2882 .option bfp #<<suffix>>
2883 This sets the suffix of the local part of the recipient address when a filter
2884 file is being tested by means of the \-bf-\ option. The default is an empty
2889 .option bh #<<IP address>>
2890 .index testing||incoming SMTP
2891 .index SMTP||testing incoming
2892 .index testing||relay control
2893 .index relaying||testing configuration
2894 .index policy control||testing
2895 .index debugging||\-bh-\ option
2896 This option runs a fake SMTP session as if from the given IP address, using the
2897 standard input and output. The IP address may include a port number at the end,
2898 after a full stop. For example:
2900 exim -bh 10.9.8.7.1234
2901 exim -bh fe80::a00:20ff:fe86:a061.5678
2904 When an IPv6 address is given, it is converted into canonical form. In the case
2905 of the second example above, the value of \$sender@_host@_address$\ after
2906 conversion to the canonical form is \"fe80:0000:0000:0a00:20ff:fe86:a061.5678"\.
2909 Comments as to what is going on are written to the standard error file. These
2910 include lines beginning with `LOG' for anything that would have been logged.
2911 This facility is provided for testing configuration options for incoming
2912 messages, to make sure they implement the required policy. For example, you can
2913 test your relay controls using \-bh-\.
2916 \**Warning 1**\: You cannot test features of the configuration that rely on
2917 ident (RFC 1413) callouts. These cannot be done when testing using
2918 \-bh-\ because there is no incoming SMTP connection.
2920 \**Warning 2**\: Address verification callouts (see section ~~SECTcallver) are
2921 also skipped when testing using \-bh-\. If you want these callouts to occur,
2922 use \-bhc-\ instead.
2924 Messages supplied during the testing session are discarded, and nothing is
2925 written to any of the real log files. There may be pauses when DNS (and other)
2926 lookups are taking place, and of course these may time out. The \-oMi-\ option
2927 can be used to specify a specific IP interface and port if this is important.
2929 The \*exim@_checkaccess*\ utility is a `packaged' version of \-bh-\ whose
2930 output just states whether a given recipient address from a given host is
2931 acceptable or not. See section ~~SECTcheckaccess.
2933 .option bhc #<<IP address>>
2934 This option operates in the same way as \-bh-\, except that address
2935 verification callouts are performed if required. This includes consulting and
2936 updating the callout cache database.
2939 .index alias file||building
2940 .index building alias file
2941 .index Sendmail compatibility||\-bi-\ option
2942 Sendmail interprets the \-bi-\ option as a request to rebuild its alias file.
2943 Exim does not have the concept of a single alias file, and so it cannot mimic
2944 this behaviour. However, calls to \(/usr/lib/sendmail)\ with the \-bi-\ option
2945 tend to appear in various scripts such as NIS make files, so the option must be
2948 If \-bi-\ is encountered, the command specified by the \bi@_command\
2949 configuration option is run, under the uid and gid of the caller of Exim. If
2950 the \-oA-\ option is used, its value is passed to the command as an argument.
2951 The command set by \bi@_command\ may not contain arguments. The command can use
2952 the \*exim@_dbmbuild*\ utility, or some other means, to rebuild alias files if
2953 this is required. If the \bi@_command\ option is not set, calling Exim with
2957 .index local message reception
2958 This option runs an Exim receiving process that accepts an incoming,
2959 locally-generated message on the current input. The recipients are given as the
2960 command arguments (except when \-t-\ is also present -- see below). Each
2961 argument can be a comma-separated list of RFC 2822 addresses. This is the
2962 default option for selecting the overall action of an Exim call; it is assumed
2963 if no other conflicting option is present.
2965 If any addresses in the message are unqualified (have no domain), they are
2966 qualified by the values of the \qualify@_domain\ or \qualify@_recipient\
2967 options, as appropriate. The \-bnq-\ option (see below) provides a way of
2968 suppressing this for special cases.
2970 Policy checks on the contents of local messages can be enforced by means of the
2971 non-SMTP ACL. See chapter ~~CHAPACL for details.
2972 .index return code||for \-bm-\
2973 The return code is zero if the message is successfully accepted. Otherwise, the
2974 action is controlled by the \-oe$it{x}-\ option setting -- see below.
2976 .index message||format
2977 .index format||message
2979 .index UUCP||`From' line
2980 .index Sendmail compatibility||`From' line
2981 The format of the message must be as defined in RFC 2822, except that, for
2982 compatibility with Sendmail and Smail, a line in one of the forms
2984 From sender Fri Jan 5 12:55 GMT 1997
2985 From sender Fri, 5 Jan 97 12:55:01
2987 (with the weekday optional, and possibly with additional text after the date)
2988 is permitted to appear at the start of the message. There appears to be no
2989 authoritative specification of the format of this line. Exim recognizes it by
2990 matching against the regular expression defined by the \uucp@_from@_pattern\
2991 option, which can be changed if necessary.
2992 .index \-f-\ option||overriding `From' line
2993 The specified sender is treated as if it were given as the argument to the
2994 \-f-\ option, but if a \-f-\ option is also present, its argument is used in
2995 preference to the address taken from the message. The caller of Exim must be a
2996 trusted user for the sender of a message to be set in this way.
2999 .index address||qualification, suppressing
3000 By default, Exim automatically qualifies unqualified addresses (those
3001 without domains) that appear in messages that are submitted locally (that
3002 is, not over TCP/IP). This qualification applies both to addresses in
3003 envelopes, and addresses in header lines. Sender addresses are qualified using
3004 \qualify@_domain\, and recipient addresses using \qualify@_recipient\ (which
3005 defaults to the value of \qualify@_domain\).
3007 Sometimes, qualification is not wanted. For example, if \-bS-\ (batch SMTP) is
3008 being used to re-submit messages that originally came from remote hosts after
3009 content scanning, you probably do not want to qualify unqualified addresses in
3010 header lines. (Such lines will be present only if you have not enabled a header
3011 syntax check in the appropriate ACL.)
3013 The \-bnq-\ option suppresses all qualification of unqualified addresses in
3014 messages that originate on the local host. When this is used, unqualified
3015 addresses in the envelope provoke errors (causing message rejection) and
3016 unqualified addresses in header lines are left alone.
3020 .index configuration options, extracting
3021 .index options||configuration, extracting
3022 If this option is given with no arguments, it causes the values of all Exim's
3023 main configuration options to be written to the standard output. The values
3024 of one or more specific options can be requested by giving their names as
3025 arguments, for example:
3027 exim -bP qualify@_domain hold@_domains
3029 However, any option setting that is preceded by the word `hide' in the
3030 configuration file is not shown in full, except to an admin user. For other
3031 users, the output is as in this example:
3033 mysql_servers = <value not displayable>
3035 If \configure@_file\ is given as an argument, the name of the run time
3036 configuration file is output.
3037 If a list of configuration files was supplied, the value that is output here
3038 is the name of the file that was actually used.
3040 .index daemon||process id (pid)
3041 .index pid (process id)||of daemon
3042 If \log__file__path\ or \pid@_file@_path\ are given, the names of the
3043 directories where log files and daemon pid files are written are output,
3044 respectively. If these values are unset, log files are written in a
3045 sub-directory of the spool directory called \log\, and the pid file is written
3046 directly into the spool directory.
3048 If \-bP-\ is followed by a name preceded by \"+"\, for example,
3050 exim -bP +local_domains
3052 it searches for a matching named list of any type (domain, host, address, or
3053 local part) and outputs what it finds.
3055 .index options||router, extracting
3056 .index options||transport, extracting
3057 If one of the words \router\, \transport\, or \authenticator\ is given,
3058 followed by the name of an appropriate driver instance, the option settings for
3059 that driver are output. For example:
3061 exim -bP transport local@_delivery
3063 The generic driver options are output first, followed by the driver's private
3064 options. A list of the names of drivers of a particular type can be obtained by
3065 using one of the words \router@_list\, \transport@_list\, or
3066 \authenticator@_list\, and a complete list of all drivers with their option
3067 settings can be obtained by using \routers\, \transports\, or \authenticators\.
3071 .index queue||listing messages on
3072 .index listing||messages on the queue
3073 This option requests a listing of the contents of the mail queue on the
3074 standard output. If the \-bp-\ option is followed by a list of message ids,
3075 just those messages are listed. By default, this option can be used only by an
3076 admin user. However, the \queue__list__requires__admin\ option can be set false
3077 to allow any user to see the queue.
3079 Each message on the queue is displayed as in the following example:
3081 25m 2.9K 0t5C6f-0000c8-00 <alice@@wonderland.fict.example>
3082 red.king@@looking-glass.fict.example
3085 .index message||size in queue listing
3086 .index size||of message
3087 The first line contains the length of time the message has been on the queue
3088 (in this case 25 minutes), the size of the message (2.9K), the unique local
3089 identifier for the message, and the message sender, as contained in the
3090 envelope. For bounce messages, the sender address is empty, and appears as
3091 `<>'. If the message was submitted locally by an untrusted user who overrode
3092 the default sender address, the user's login name is shown in parentheses
3093 before the sender address.
3094 .index frozen messages||in queue listing
3095 If the message is frozen (attempts to deliver it are suspended) then the text
3096 `$*$$*$$*$ frozen $*$$*$$*$' is displayed at the end of this line.
3098 The recipients of the message (taken from the envelope, not the headers) are
3099 displayed on subsequent lines. Those addresses to which the message has already
3100 been delivered are marked with the letter D. If an original address gets
3101 expanded into several addresses via an alias or forward file, the original is
3102 displayed with a D only when deliveries for all of its child addresses are
3107 This option operates like \-bp-\, but in addition it shows delivered addresses
3108 that were generated from the original top level address(es) in each message by
3109 alias or forwarding operations. These addresses are flagged with `+D' instead
3114 .index queue||count of messages on
3115 This option counts the number of messages on the queue, and writes the total
3116 to the standard output. It is restricted to admin users, unless
3117 \queue__list__requires__admin\ is set false.
3121 This option operates like \-bp-\, but the output is not sorted into
3122 chronological order of message arrival. This can speed it up when there are
3123 lots of messages on the queue, and is particularly useful if the output is
3124 going to be post-processed in a way that doesn't need the sorting.
3127 This option is a combination of \-bpr-\ and \-bpa-\.
3130 This option is a combination of \-bpr-\ and \-bpu-\.
3134 This option operates like \-bp-\ but shows only undelivered top-level addresses
3135 for each message displayed. Addresses generated by aliasing or forwarding are
3136 not shown, unless the message was deferred after processing by a router with
3137 the \one@_time\ option set.
3141 .index testing||retry configuration
3142 .index retry||configuration testing
3143 This option is for testing retry rules, and it must be followed by up to three
3144 arguments. It causes Exim to look for a retry rule that matches the values
3145 and to write it to the standard output. For example:
3147 exim -brt bach.comp.mus.example
3148 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3150 See chapter ~~CHAPretry for a description of Exim's retry rules. The first
3151 argument, which is required, can be a complete address in the form
3152 \*local@_part@@domain*\, or it can be just a domain name. The second argument is
3153 an optional second domain name; if no retry rule is found for the first
3154 argument, the second is tried. This ties in with Exim's behaviour when looking
3155 for retry rules for remote hosts -- if no rule is found that matches the host,
3156 one that matches the mail domain is sought. The final argument is the name of a
3157 specific delivery error, as used in setting up retry rules, for example
3161 .index testing||rewriting
3162 .index rewriting||testing
3163 This option is for testing address rewriting rules, and it must be followed by
3164 a single argument, consisting of either a local part without a domain, or a
3165 complete address with a fully qualified domain. Exim outputs how this address
3166 would be rewritten for each possible place it might appear. See chapter
3167 ~~CHAPrewrite for further details.
3170 .index SMTP||batched incoming
3171 .index batched SMTP input
3172 This option is used for batched SMTP input, which is an alternative interface
3173 for non-interactive local message submission. A number of messages can be
3174 submitted in a single run. However, despite its name, this is not really SMTP
3175 input. Exim reads each message's envelope from SMTP commands on the standard
3176 input, but generates no responses. If the caller is trusted, or
3177 \untrusted@_set@_sender\ is set, the senders in the SMTP \\MAIL\\ commands are
3178 believed; otherwise the sender is always the caller of Exim.
3180 The message itself is read from the standard input, in SMTP format (leading
3181 dots doubled), terminated by a line containing just a single dot. An error is
3182 provoked if the terminating dot is missing. A further message may then follow.
3184 As for other local message submissions, the contents of incoming batch SMTP
3185 messages can be checked using the non-SMTP ACL (see chapter ~~CHAPACL).
3186 Unqualified addresses are automatically qualified using \qualify@_domain\ and
3187 \qualify@_recipient\, as appropriate, unless the \-bnq-\ option is used.
3189 Some other SMTP commands are recognized in the input. \\HELO\\ and \\EHLO\\ act
3190 as \\RSET\\; \\VRFY\\, \\EXPN\\, \\ETRN\\, and \\HELP\\ act as \\NOOP\\;
3191 \\QUIT\\ quits, ignoring the rest of the standard input.
3193 If any error is encountered, reports are written to the standard output and
3194 error streams, and Exim gives up immediately.
3195 .index return code||for \-bS-\
3196 The return code is 0 if no error was detected; it is 1 if one or more messages
3197 were accepted before the error was detected; otherwise it is 2.
3199 More details of input using batched SMTP are given in section
3200 ~~SECTincomingbatchedSMTP.
3203 .index SMTP||local input
3204 .index local SMTP input
3205 This option causes Exim to accept one or more messages by reading SMTP commands
3206 on the standard input, and producing SMTP replies on the standard output. SMTP
3207 policy controls, as defined in ACLs (see chapter ~~CHAPACL) are applied.
3209 Some user agents use this interface as a way of passing locally-generated
3210 messages to the MTA.
3211 .index sender||source of
3212 In this usage, if the caller of Exim is trusted, or \untrusted@_set@_sender\ is
3213 set, the senders of messages are taken from the SMTP \\MAIL\\ commands.
3214 Otherwise the content of these commands is ignored and the sender is set up as
3215 the calling user. Unqualified addresses are automatically qualified using
3216 \qualify@_domain\ and \qualify@_recipient\, as appropriate, unless the \-bnq-\
3220 The \-bs-\ option is also used to run Exim from \*inetd*\, as an alternative to
3221 using a listening daemon. Exim can distinguish the two cases by checking
3222 whether the standard input is a TCP/IP socket. When Exim is called from
3223 \*inetd*\, the source of the mail is assumed to be remote, and the comments
3224 above concerning senders and qualification do not apply. In this situation,
3225 Exim behaves in exactly the same way as it does when receiving a message via
3226 the listening daemon.
3229 .index testing||addresses
3230 .index address||testing
3231 This option runs Exim in address testing mode, in which each argument is taken
3232 as an address to be tested for deliverability. The results are written to the
3233 standard output. If a test fails, and the caller is not an admin user, no
3234 details of the failure are output, because these might contain sensitive
3235 information such as usernames and passwords for database lookups.
3237 If no arguments are given, Exim runs in an interactive manner, prompting with a
3238 right angle bracket for addresses to be tested.
3240 Unlike the \-be-\ test option, you cannot arrange for Exim to use the
3241 \*readline()*\ function, because it is running as \*root*\ and there are
3245 Each address is handled as if it were the recipient address of a message
3246 (compare the \-bv-\ option). It is passed to the routers and the result is
3247 written to the standard output. However, any router that has
3248 \no@_address@_test\ set is bypassed. This can make \-bt-\ easier to use for
3249 genuine routing tests if your first router passes everything to a scanner
3252 .index return code||for \-bt-\
3253 The return code is 2 if any address failed outright; it is 1 if no address
3254 failed outright but at least one could not be resolved for some reason. Return
3255 code 0 is given only when all addresses succeed.
3257 \**Warning**\: \-bt-\ can only do relatively simple testing. If any of the
3258 routers in the configuration makes any tests on the sender address of a
3260 .index \-f-\ option||for address testing
3261 you can use the \-f-\ option to set an appropriate sender when running
3262 \-bt-\ tests. Without it, the sender is assumed to be the calling user at the
3263 default qualifying domain. However, if you have set up (for example) routers
3264 whose behaviour depends on the contents of an incoming message, you cannot test
3265 those conditions using \-bt-\. The \-N-\ option provides a possible way of
3269 .index version number of Exim, verifying
3270 This option causes Exim to write the current version number, compilation
3271 number, and compilation date of the \*exim*\ binary to the standard output.
3272 It also lists the DBM library this is being used, the optional modules (such as
3273 specific lookup types), the drivers that are included in the binary, and the
3274 name of the run time configuration file that is in use.
3277 As part of its operation, \-bV-\ causes Exim to read and syntax check its
3278 configuration file. However, this is a static check only. It cannot check
3279 values that to be expanded. You cannot rely on \-bV-\ alone to discover (for
3280 example) all the typos in the configuration; some realistic testing is needed.
3281 The \-bh-\ and \-N-\ options provide more dynamic testing facilities.
3286 .index verifying||address, using \-bv-\
3287 .index address||verification
3288 This option runs Exim in address verification mode, in which each argument is
3289 taken as an address to be verified. During normal operation, verification
3290 happens mostly as a consequence processing a \verify\ condition in an ACL (see
3291 chapter ~~CHAPACL). If you want to test an entire ACL, see the \-bh-\ option.
3293 If verification fails, and the caller is not an admin user, no details of the
3294 failure are output, because these might contain sensitive information such as
3295 usernames and passwords for database lookups.
3297 If no arguments are given, Exim runs in an interactive manner, prompting with a
3298 right angle bracket for addresses to be verified.
3300 Unlike the \-be-\ test option, you cannot arrange for Exim to use the
3301 \*readline()*\ function, because it is running as \*exim*\ and there are
3305 Verification differs from address testing (the \-bt-\ option) in that routers
3306 that have \no@_verify\ set are skipped, and if the address is accepted by a
3307 router that has \fail@_verify\ set, verification fails. The address is verified
3308 as a recipient if \-bv-\ is used; to test verification for a sender address,
3309 \-bvs-\ should be used.
3311 If the \-v-\ option is not set, the output consists of a single line for each
3312 address, stating whether it was verified or not, and giving a reason in the
3313 latter case. Otherwise, more details are given of how the address has been
3314 handled, and in the case of address redirection, all the generated addresses
3315 are also considered. Without \-v-\, generating more than one address by
3316 redirection causes verification to end sucessfully.
3318 .index return code||for \-bv-\
3319 The return code is 2 if any address failed outright; it is 1 if no address
3320 failed outright but at least one could not be resolved for some reason. Return
3321 code 0 is given only when all addresses succeed.
3323 If any of the routers in the configuration makes any tests on the sender
3324 address of a message, you should use the \-f-\ option to set an appropriate
3325 sender when running \-bv-\ tests. Without it, the sender is assumed to be the
3326 calling user at the default qualifying domain.
3329 This option acts like \-bv-\, but verifies the address as a sender rather
3330 than a recipient address. This affects any rewriting and qualification that
3333 .option C #<<filelist>>
3334 .index configuration file||alternate
3335 .index \\CONFIGURE@_FILE\\
3336 .index alternate configuration file
3337 This option causes Exim to find the run time configuration file from the given
3338 list instead of from the list specified by the \\CONFIGURE@_FILE\\
3339 compile-time setting. Usually, the list will consist of just a single file
3340 name, but it can be a colon-separated list of names. In this case, the first
3341 file that exists is used. Failure to open an existing file stops Exim from
3342 proceeding any further along the list, and an error is generated.
3344 When this option is used by a caller other than root or the Exim user, and the
3345 list is different from the compiled-in list, Exim gives up its root privilege
3346 immediately, and runs with the real and effective uid and gid set to those of
3347 the caller. However, if \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined in
3348 \(Local/Makefile)\, root privilege is retained for \-C-\ only if the caller of
3351 That is, the Exim user is no longer privileged in this regard. This build-time
3352 option is not set by default in the Exim source distribution tarbundle.
3353 However, if you are using a `packaged' version of Exim (source or binary), the
3354 packagers might have enabled it.
3357 Setting \\ALT@_CONFIG@_ROOT@_ONLY\\ locks out the possibility of testing a
3358 configuration using \-C-\ right through message reception and delivery, even if
3359 the caller is root. The reception works, but by that time, Exim is running as
3360 the Exim user, so when it re-execs to regain privilege for the delivery, the
3361 use of \-C-\ causes privilege to be lost. However, root can test reception and
3362 delivery using two separate commands (one to put a message on the queue, using
3363 \-odq-\, and another to do the delivery, using \-M-\).
3365 If \\ALT@_CONFIG@_PREFIX\\ is defined \(in Local/Makefile)\, it specifies a
3366 prefix string with which any file named in a \-C-\ command line option
3367 must start. In addition, the file name must not contain the sequence \"/../"\.
3368 However, if the value of the \-C-\ option is identical to the value of
3369 \\CONFIGURE@_FILE\\ in \(Local/Makefile)\, Exim ignores \-C-\ and proceeds as
3370 usual. There is no default setting for \\ALT@_CONFIG@_PREFIX\\; when it is
3371 unset, any file name can be used with \-C-\.
3373 \\ALT@_CONFIG@_PREFIX\\ can be used to confine alternative configuration files
3374 to a directory to which only root has access. This prevents someone who has
3375 broken into the Exim account from running a privileged Exim with an arbitrary
3378 The \-C-\ facility is useful for ensuring that configuration files are
3379 syntactically correct, but cannot be used for test deliveries, unless the
3380 caller is privileged, or unless it is an exotic configuration that does not
3381 require privilege. No check is made on the owner or group of the files
3382 specified by this option.
3384 .option D <<macro>>=<<value>>
3385 .index macro||setting on command line
3386 This option can be used to override macro definitions in the configuration file
3387 (see section ~~SECTmacrodefs). However, like \-C-\, if it is used by an
3388 unprivileged caller, it causes Exim to give up its root privilege.
3389 If \\DISABLE@_D@_OPTION\\ is defined in \(Local/Makefile)\, the use of \-D-\ is
3390 completely disabled, and its use causes an immediate error exit.
3392 The entire option (including equals sign if present) must all be within one
3393 command line item. \-D-\ can be used to set the value of a macro to the empty
3394 string, in which case the equals sign is optional. These two commands are
3400 To include spaces in a macro definition item, quotes must be used. If you use
3401 quotes, spaces are permitted around the macro name and the equals sign. For
3404 exim '-D ABC = something' ...
3406 \-D-\ may be repeated up to 10 times on a command line.
3408 .option d <<debug options>>
3409 .index debugging||list of selectors
3410 .index debugging||\-d-\ option
3411 This option causes debugging information to be written to the standard
3412 error stream. It is restricted to admin users because debugging output may show
3413 database queries that contain password information. Also, the details of users'
3414 filter files should be protected. When \-d-\ is used, \-v-\ is assumed. If
3415 \-d-\ is given on its own, a lot of standard debugging data is output. This can
3416 be reduced, or increased to include some more rarely needed information, by
3417 following \-d-\ with a string made up of names preceded by plus or minus
3418 characters. These add or remove sets of debugging data, respectively. For
3419 example, \-d+filter-\ adds filter debugging, whereas \-d-all+filter-\ selects
3420 only filter debugging. The available debugging categories are:
3424 . The odd formatting of the lines below is deliberate. It does not affect the
3425 . SGCAL output, but by putting in the space it keeps things aligned in the man
3426 . page that is automatically generated from this text.
3428 acl $t $rm{ACL interpretation}
3429 auth $t $rm{authenticators}
3430 deliver $t $rm{general delivery logic}
3431 dns $t $rm{DNS lookups (see also resolver)}
3432 dnsbl $t $rm{DNS black list (aka RBL) code}
3433 exec $t $rm{arguments for \execv@(@)\ calls}
3434 expand $t $rm{detailed debugging for string expansions}
3435 filter $t $rm{filter handling}
3436 hints@_lookup $t $rm{hints data lookups}
3437 host@_lookup $t $rm{all types of name-to-IP address handling}
3438 ident $t $rm{ident lookup}
3439 interface $t $rm{lists of local interfaces}
3440 lists $t $rm{matching things in lists}
3441 load $t $rm{system load checks}
3442 local@_scan $t $rm{can be used by \*local@_scan()*\ (see chapter ~~CHAPlocalscan)}
3443 lookup $t $rm{general lookup code and all lookups}
3444 memory $t $rm{memory handling}
3445 pid $t $rm{add pid to debug output lines}
3446 process@_info $t $rm{setting info for the process log}
3447 queue@_run $t $rm{queue runs}
3448 receive $t $rm{general message reception logic}
3449 resolver $t $rm{turn on the DNS resolver's debugging output}
3450 retry $t $rm{retry handling}
3451 rewrite $t $rm{address rewriting}
3452 route $t $rm{address routing}
3453 timestamp $t $rm{add timestamp to debug output lines}
3454 tls $t $rm{TLS logic}
3455 transport $t $rm{transports}
3456 uid $t $rm{changes of uid/gid and looking up uid/gid}
3457 verify $t $rm{address verification logic}
3459 all $t $rm{all of the above, and also \-v-\}
3461 .index resolver, debugging output
3462 .index DNS||resolver, debugging output
3463 The \"resolver"\ option produces output only if the DNS resolver was compiled
3464 with \\DEBUG\\ enabled. This is not the case in some operating systems. Also,
3465 unfortunately, debugging output from the DNS resolver is written to stdout
3468 The default (\-d-\ with no argument) omits \"expand"\, \"filter"\,
3469 \"interface"\, \"load"\, \"memory"\, \"pid"\, \"resolver"\, and \"timestamp"\.
3470 However, the \"pid"\ selector is forced when debugging is turned on for a
3471 daemon, which then passes it on to any re-executed Exims. Exim also
3472 automatically adds the pid to debug lines when several remote deliveries are
3475 The \"timestamp"\ selector causes the current time to be inserted at the start
3476 of all debug output lines. This can be useful when trying to track down delays
3479 If the \debug@_print\ option is set in any driver, it produces output whenever
3480 any debugging is selected, or if \-v-\ is used.
3483 .option dd <<debug options>>
3484 This option behaves exactly like \-d-\ except when used on a command that
3485 starts a daemon process. In that case, debugging is turned off for the
3486 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3487 behaviour of the daemon without creating as much output as full debugging does.
3491 This is an obsolete option that is now a no-op. It used to affect the way Exim
3492 handled CR and LF characters in incoming messages. What happens now is
3493 described in section ~~SECTlineendings.
3497 .index bounce message||generating
3498 This option specifies that an incoming message is a locally-generated delivery
3499 failure report. It is used internally by Exim when handling delivery failures
3500 and is not intended for external use. Its only effect is to stop Exim
3501 generating certain messages to the postmaster, as otherwise message cascades
3502 could occur in some situations. As part of the same option, a message id may
3503 follow the characters \-E-\. If it does, the log entry for the receipt of the
3504 new message contains the id, following `R=', as a cross-reference.
3507 There are a number of Sendmail options starting with \-oe-\ which seem to be
3508 called by various programs without the leading \o\ in the option. For example,
3509 the \vacation\ program uses \-eq-\. Exim treats all options of the form
3510 \-e$it{x}-\ as synonymous with the corresponding \-oe$it{x}-\ options.
3512 .option F #<<string>>
3514 .index name||of sender
3515 This option sets the sender's full name for use when a locally-generated
3516 message is being accepted. In the absence of this option, the user's \*gecos*\
3517 entry from the password data is used. As users are generally permitted to alter
3518 their \*gecos*\ entries, no security considerations are involved. White space
3519 between \-F-\ and the <<string>> is optional.
3521 .option f #<<address>>
3522 .index sender||address
3523 .index address||sender
3525 .index envelope sender
3526 .index user||trusted
3527 This option sets the address of the envelope sender of a locally-generated
3528 message (also known as the return path). The option can normally be used only
3529 by a trusted user, but \untrusted@_set@_sender\ can be set to allow untrusted
3532 Processes running as root or the Exim user are always trusted. Other
3533 trusted users are defined by the \trusted@_users\ or \trusted@_groups\ options.
3535 In the absence of \-f-\, or if the caller is not trusted, the sender of a local
3536 message is set to the caller's login name at the default qualify domain.
3538 There is one exception to the restriction on the use of \-f-\: an empty sender
3539 can be specified by any user, trusted or not,
3541 to create a message that can never provoke a bounce. An empty sender can be
3542 specified either as an empty string, or as a pair of angle brackets with
3543 nothing between them, as in these examples of shell commands:
3545 exim -f '<>' user@domain
3546 exim -f "" user@domain
3548 In addition, the use of \-f-\ is not restricted when testing a filter file with
3549 \-bf-\ or when testing or verifying addresses using the \-bt-\ or \-bv-\
3552 Allowing untrusted users to change the sender address does not of itself make
3553 it possible to send anonymous mail. Exim still checks that the ::From:: header
3554 refers to the local user, and if it does not, it adds a ::Sender:: header,
3555 though this can be overridden by setting \no@_local@_from@_check\.
3558 White space between \-f-\ and the <<address>> is optional
3559 (that is, they can be given as two arguments or one combined argument).
3560 The sender of a locally-generated message can also be set (when permitted) by
3561 an initial `From ' line in the message -- see the description of \-bm-\ above
3562 -- but if \-f-\ is also present, it overrides `From'.
3565 .index Sendmail compatibility||\-G-\ option ignored
3566 This is a Sendmail option which is ignored by Exim.
3568 .option h #<<number>>
3569 .index Sendmail compatibility||\-h-\ option ignored
3570 This option is accepted for compatibility with Sendmail, but has no effect. (In
3571 Sendmail it overrides the `hop count' obtained by counting ::Received::
3575 .index Solaris||\*mail*\ command
3576 .index dot||in incoming, non-SMTP message
3577 This option, which has the same effect as \-oi-\, specifies that a dot on a
3578 line by itself should not terminate an incoming, non-SMTP message. I can find
3579 no documentation for this option in Solaris 2.4 Sendmail, but the \*mailx*\
3580 command in Solaris 2.4 uses it. See also \-ti-\.
3582 .option M #<<message id>>#<<message id>> ...
3583 .index forcing delivery
3584 .index delivery||forcing attempt
3585 .index frozen messages||forcing delivery
3586 This option requests Exim to run a delivery attempt on each message in turn. If
3587 any of the messages are frozen, they are automatically thawed before the
3588 delivery attempt. The settings of \queue@_domains\, \queue@_smtp@_domains\, and
3589 \hold@_domains\ are ignored.
3590 .index hints database||overriding retry hints
3591 Retry hints for any of the addresses are
3592 overridden -- Exim tries to deliver even if the normal retry time has not yet
3593 been reached. This option requires the caller to be an admin user. However,
3594 there is an option called \prod@_requires@_admin\ which can be set false to
3595 relax this restriction (and also the same requirement for the \-q-\, \-R-\, and
3599 .option Mar #<<message id>>#<<address>>#<<address>> ...
3600 .index message||adding recipients
3601 .index recipient||adding
3602 This option requests Exim to add the addresses to the list of recipients of the
3603 message (`ar' for `add recipients'). The first argument must be a message id,
3604 and the remaining ones must be email addresses. However, if the message is
3605 active (in the middle of a delivery attempt), it is not altered. This option
3606 can be used only by an admin user.
3608 .index SMTP||passed connection
3609 .index SMTP||multiple deliveries
3610 .index multiple SMTP deliveries
3611 .option MC #<<transport>>#<<hostname>>#<<sequence number>>#<<message id>>
3612 This option is not intended for use by external callers. It is used internally
3613 by Exim to invoke another instance of itself to deliver a waiting message using
3614 an existing SMTP connection, which is passed as the standard input. Details are
3615 given in chapter ~~CHAPSMTP. This must be the final option, and the caller must
3616 be root or the Exim user in order to use it.
3619 This option is not intended for use by external callers. It is used internally
3620 by Exim in conjunction with the \-MC-\ option. It signifies that the connection
3621 to the remote host has been authenticated.
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 server to
3626 which Exim is connected supports pipelining.
3628 .option MCQ #<<process id>> <<pipe fd>>
3629 This option is not intended for use by external callers. It is used internally
3630 by Exim in conjunction with the \-MC-\ option when the original delivery was
3631 started by a queue runner. It passes on the process id of the queue runner,
3632 together with the file descriptor number of an open pipe. Closure of the pipe
3633 signals the final completion of the sequence of processes that are passing
3634 messages through the same SMTP connection.
3637 This option is not intended for use by external callers. It is used internally
3638 by Exim in conjunction with the \-MC-\ option, and passes on the fact that the
3639 SMTP \\SIZE\\ option should be used on messages delivered down the existing
3643 This option is not intended for use by external callers. It is used internally
3644 by Exim in conjunction with the \-MC-\ option, and passes on the fact that the
3645 host to which Exim is connected supports TLS encryption.
3647 .option Mc #<<message id>>#<<message id>> ...
3648 .index hints database||not overridden by \-Mc-\
3649 .index delivery||manually started, not forced
3650 This option requests Exim to run a delivery attempt on each message in turn,
3651 but unlike the \-M-\ option, it does check for retry hints, and respects any
3652 that are found. This option is not very useful to external callers. It is
3653 provided mainly for internal use by Exim when it needs to re-invoke itself in
3654 order to regain root privilege for a delivery (see chapter ~~CHAPsecurity).
3655 However, \-Mc-\ can be useful when testing, in order to run a delivery that
3656 respects retry times and other options such as \hold@_domains\ that are
3657 overridden when \-M-\ is used. Such a delivery does not count as a queue run.
3658 If you want to run a specific delivery as if in a queue run, you should use
3659 \-q-\ with a message id argument. A distinction between queue run deliveries
3660 and other deliveries is made in one or two places.
3662 .option Mes #<<message id>>#<<address>>
3663 .index message||changing sender
3664 .index sender||changing
3665 This option requests Exim to change the sender address in the message to the
3666 given address, which must be a fully qualified address or `<>' (`es' for `edit
3667 sender'). There must be exactly two arguments. The first argument must be a
3668 message id, and the second one an email address. However, if the message is
3669 active (in the middle of a delivery attempt), its status is not altered. This
3670 option can be used only by an admin user.
3672 .option Mf #<<message id>>#<<message id>> ...
3673 .index freezing messages
3674 .index message||manually freezing
3675 This option requests Exim to mark each listed message as `frozen'. This
3676 prevents any delivery attempts taking place until the message is `thawed',
3677 either manually or as a result of the \auto@_thaw\ configuration option.
3678 However, if any of the messages are active (in the middle of a delivery
3679 attempt), their status is not altered. This option can be used only by an admin
3682 .option Mg #<<message id>>#<<message id>> ...
3683 .index giving up on messages
3684 .index message||abandoning delivery attempts
3685 .index delivery||abandoning further attempts
3686 This option requests Exim to give up trying to deliver the listed messages,
3687 including any that are frozen. However, if any of the messages are active,
3688 their status is not altered.
3689 For non-bounce messages, a delivery error message is sent to the sender,
3690 containing the text `cancelled by administrator'. Bounce messages are just
3692 This option can be used only by an admin user.
3694 .option Mmad #<<message id>>#<<message id>> ...
3695 .index delivery||cancelling all
3696 This option requests Exim to mark all the recipient addresses in the messages
3697 as already delivered (`mad' for `mark all delivered'). However, if any message
3698 is active (in the middle of a delivery attempt), its status is not altered.
3699 This option can be used only by an admin user.
3701 .option Mmd #<<message id>>#<<address>>#<<address>> ...
3702 .index delivery||cancelling by address
3703 .index recipient||removing
3704 .index removing recipients
3705 This option requests Exim to mark the given addresses as already delivered
3706 (`md' for `mark delivered'). The first argument must be a message id, and the
3707 remaining ones must be email addresses. These are matched to recipient
3708 addresses in the message in a case-sensitive manner. If the message is active
3709 (in the middle of a delivery attempt), its status is not altered. This option
3710 can be used only by an admin user.
3712 .option Mrm #<<message id>>#<<message id>> ...
3713 .index removing messages
3714 .index abandoning mail
3715 .index message||manually discarding
3716 This option requests Exim to remove the given messages from the queue. No
3717 bounce messages are sent; each message is simply forgotten. However, if any of
3718 the messages are active, their status is not altered. This option can be used
3719 only by an admin user or by the user who originally caused the message to be
3720 placed on the queue.
3722 .option Mt #<<message id>>#<<message id>> ...
3723 .index thawing messages
3724 .index unfreezing messages
3725 .index frozen messages||thawing
3726 .index message||thawing frozen
3727 This option requests Exim to `thaw' any of the listed messages that are
3728 `frozen', so that delivery attempts can resume. However, if any of the messages
3729 are active, their status is not altered. This option can be used only by an
3732 .option Mvb #<<message id>>
3733 .index listing||message body
3734 .index message||listing body of
3735 This option causes the contents of the message body (-D) spool file to be
3736 written to the standard output. This option can be used only by an admin user.
3738 .option Mvh #<<message id>>
3739 .index listing||message headers
3740 .index header lines||listing
3741 .index message||listing header lines
3742 This option causes the contents of the message headers (-H) spool file to be
3743 written to the standard output. This option can be used only by an admin user.
3745 .option Mvl #<<message id>>
3746 .index listing||message log
3747 .index message||listing message log
3748 This option causes the contents of the message log spool file to be written to
3749 the standard output. This option can be used only by an admin user.
3752 This is apparently a synonym for \-om-\ that is accepted by Sendmail, so Exim
3753 treats it that way too.
3756 .index debugging||\-N-\ option
3757 .index debugging||suppressing delivery
3758 This is a debugging option that inhibits delivery of a message at the transport
3759 level. It implies \-v-\. Exim goes through many of the motions of delivery --
3760 it just doesn't actually transport the message, but instead behaves as if it
3761 had successfully done so. However, it does not make any updates to the retry
3762 database, and the log entries for deliveries are flagged with `$*$>' rather
3765 Because \-N-\ discards any message to which it applies, only root or the Exim
3766 user are allowed to use it with \-bd-\, \-q-\, \-R-\ or \-M-\. In other words,
3767 an ordinary user can use it only when supplying an incoming message to which it
3768 will apply. Although transportation never fails when \-N-\ is set, an address
3769 may be deferred because of a configuration problem on a transport, or a routing
3770 problem. Once \-N-\ has been used for a delivery attempt, it sticks to the
3771 message, and applies to any subsequent delivery attempts that may happen for
3775 .index Sendmail compatibility||\-n-\ option ignored
3776 This option is interpreted by Sendmail to mean `no aliasing'. It is ignored by
3780 This option is interpreted by Sendmail to mean `set option`. It is ignored by
3783 .option oA #<<file name>>
3784 .index Sendmail compatibility||\-oA-\ option
3785 This option is used by Sendmail in conjunction with \-bi-\ to specify an
3786 alternative alias file name. Exim handles \-bi-\ differently; see the
3789 .index SMTP||passed connection
3791 .index SMTP||multiple deliveries
3792 .index multiple SMTP deliveries
3793 This is a debugging option which limits the maximum number of messages that can
3794 be delivered down one SMTP connection, overriding the value set in any \%smtp%\
3795 transport. If <<n>> is omitted, the limit is set to 1.
3798 .index background delivery
3799 .index delivery||in the background
3800 This option applies to all modes in which Exim accepts incoming messages,
3801 including the listening daemon. It requests `background' delivery of such
3802 messages, which means that the accepting process automatically starts a
3803 delivery process for each message received, but does not wait for the delivery
3804 processes to finish.
3806 When all the messages have been received, the reception process exits, leaving
3807 the delivery processes to finish in their own time. The standard output and
3808 error streams are closed at the start of each delivery process.
3810 This is the default action if none of the \-od-\ options are present.
3812 If one of the queueing options in the configuration file
3813 (\queue@_only\ or \queue@_only@_file\, for example) is in effect, \-odb-\
3814 overrides it if \queue@_only@_override\ is set true, which is the default
3815 setting. If \queue@_only@_override\ is set false, \-odb-\ has no effect.
3818 .index foreground delivery
3819 .index delivery||in the foreground
3820 This option requests `foreground' (synchronous) delivery when Exim has accepted
3821 a locally-generated message. (For the daemon it is exactly the same as
3822 \-odb-\.) A delivery process is automatically started to deliver the
3823 message, and Exim waits for it to complete before proceeding.
3825 The original Exim reception process does not finish until the delivery
3826 process for the final message has ended. The standard error stream is left open
3829 However, like \-odb-\, this option has no effect if \queue@_only@_override\ is
3830 false and one of the queueing options in the configuration file is in effect.
3833 If there is a temporary delivery error during foreground delivery, the message
3834 is left on the queue for later delivery, and the original reception process
3835 exists. See chapter ~~CHAPnonqueueing for a way of setting up a restricted
3836 configuration that never queues messages.
3840 This option is synonymous with \-odf-\. It is provided for compatibility with
3844 .index non-immediate delivery
3845 .index delivery||suppressing immediate
3846 .index queueing incoming messages
3847 This option applies to all modes in which Exim accepts incoming messages,
3848 including the listening daemon. It specifies that the accepting process should
3849 not automatically start a delivery process for each message received. Messages
3850 are placed on the queue, and remain there until a subsequent queue runner
3851 process encounters them.
3852 There are several configuration options (such as \queue@_only\) that can be
3853 used to queue incoming messages under certain conditions. This option overrides
3854 all of them and also \-odqs-\. It always forces queueing.
3857 .index SMTP||delaying delivery
3858 This option is a hybrid between \-odb-\/\-odi-\ and \-odq-\.
3859 However, like \-odb-\ and \-odi-\, this option has no effect if
3860 \queue@_only@_override\ is false and one of the queueing options in the
3861 configuration file is in effect.
3863 When \-odqs-\ does operate, a delivery process is started for each incoming
3864 message, in the background by default, but in the foreground if \-odi-\ is also
3866 The recipient addresses are routed, and local deliveries are done in the normal
3867 way. However, if any SMTP deliveries are required, they are not done at this
3868 time, so the message remains on the queue until a subsequent queue runner
3869 process encounters it. Because routing was done, Exim knows which messages are
3870 waiting for which hosts, and so a number of messages for the same host can be
3871 sent in a single SMTP connection. The \queue@_smtp@_domains\ configuration
3872 option has the same effect for specific domains. See also the \-qq-\ option.
3875 .index error||reporting
3876 If an error is detected while a non-SMTP message is being received (for
3877 example, a malformed address), the error is reported to the sender in a mail
3879 .index return code||for \-oee-\
3880 Provided this error message is successfully sent, the Exim receiving process
3881 exits with a return code of zero. If not, the return code is 2 if the problem
3882 is that the original message has no recipients, or 1 any other error. This is
3883 the default \-oe$it{x}-\ option if Exim is called as \*rmail*\.
3886 .index error||reporting
3887 .index return code||for \-oem-\
3888 This is the same as \-oee-\, except that Exim always exits with a non-zero
3889 return code, whether or not the error message was successfully sent.
3890 This is the default \-oe$it{x}-\ option, unless Exim is called as \*rmail*\.
3893 .index error||reporting
3894 If an error is detected while a non-SMTP message is being received, the
3895 error is reported by writing a message to the standard error file (stderr).
3896 .index return code||for \-oep-\
3897 The return code is 1 for all errors.
3900 .index error||reporting
3901 This option is supported for compatibility with Sendmail, but has the same
3905 .index error||reporting
3906 This option is supported for compatibility with Sendmail, but has the same
3910 .index dot||in incoming, non-SMTP message
3911 This option, which has the same effect as \-i-\, specifies that a dot on a line
3912 by itself should not terminate an incoming, non-SMTP message.
3913 Otherwise, a single dot does terminate, though Exim does no special processing
3914 for other lines that start with a dot.
3915 This option is set by default if Exim is called as \*rmail*\. See also \-ti-\.
3918 This option is treated as synonymous with \-oi-\.
3920 .option oMa #<<host address>>
3921 .index sender||host address, specifying for local message
3922 A number of options starting with \-oM-\ can be used to set values associated
3923 with remote hosts on locally-submitted messages (that is, messages not received
3924 over TCP/IP). These options can be used by any caller in conjunction with the
3927 \-bf-\, \-bF-\, \-bt-\, or \-bv-\ testing options. In other circumstances, they
3928 are ignored unless the caller is trusted.
3930 The \-oMa-\ option sets the sender host address. This may include a port number
3931 at the end, after a full stop (period). For example:
3933 exim -bs -oMa 10.9.8.7.1234
3935 An alternative syntax is to enclose the IP address in square brackets, followed
3936 by a colon and the port number:
3938 exim -bs -oMa [10.9.8.7]:1234
3940 The IP address is placed in the \$sender@_host@_address$\ variable, and the
3941 port, if present, in \$sender@_host@_port$\.
3943 .option oMaa #<<name>>
3944 .index authentication||name, specifying for local message
3945 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMaa-\
3946 option sets the value of \$sender@_host@_authenticated$\ (the authenticator
3947 name). See chapter ~~CHAPSMTPAUTH for a discussion of SMTP authentication.
3949 .option oMai #<<string>>
3950 .index authentication||id, specifying for local message
3951 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMai-\
3953 value of \$authenticated@_id$\ (the id that was authenticated).
3954 This overrides the default value (the caller's login id) for messages from
3955 local sources. See chapter ~~CHAPSMTPAUTH for a discussion of authenticated
3958 .option oMas #<<address>>
3959 .index authentication||sender, specifying for local message
3960 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMas-\
3961 option sets the authenticated sender value
3962 in \$authenticated@_sender$\.
3963 It overrides the sender address that is created from the caller's login id for
3964 messages from local sources. See chapter ~~CHAPSMTPAUTH for a discussion of
3965 authenticated senders.
3967 .option oMi #<<interface address>>
3968 .index interface||address, specifying for local message
3969 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMi-\
3970 option sets the IP interface address value. A port number may be included,
3971 using the same syntax as for \-oMa-\.
3972 The interface address is placed in \$interface@_address$\ and the port number,
3973 if present, in \$interface@_port$\.
3975 .option oMr #<<protocol name>>
3976 .index protocol||incoming, specifying for local message
3977 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMr-\
3978 option sets the received protocol value that is stored in
3979 \$received@_protocol$\. However, this applies only when \-bs-\ is not used. For
3980 interactive SMTP input (\-bs-\), the protocol is always
3982 `local-' followed by one of the standard SMTP protocol names (see the
3983 description of \$received@_protocol$\ in section ~~SECTexpvar).
3985 For \-bS-\ (batch SMTP) however, the protocol can be set by \-oMr-\.
3987 .option oMs #<<host name>>
3988 .index sender||host name, specifying for local message
3989 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMs-\
3990 option sets the sender host name
3991 in \$sender@_host@_name$\. When this option is present, Exim does not attempt
3992 to look up a host name from an IP address; it uses the name it is given.
3994 .option oMt #<<ident string>>
3995 .index sender||ident string, specifying for local message
3996 See \-oMa-\ above for general remarks about the \-oM-\ options. The \-oMt-\
3997 option sets the sender ident value
3998 in \$sender@_ident$\.
3999 The default setting for local callers is the login id of the calling process.
4002 .index Sendmail compatibility||\-om-\ option ignored
4003 In Sendmail, this option means `me too', indicating that the sender of a
4004 message should receive a copy of the message if the sender appears in an alias
4005 expansion. Exim always does this, so the option does nothing.
4008 .index Sendmail compatibility||\-oo-\ option ignored
4009 This option is ignored. In Sendmail it specifies `old style headers', whatever
4012 .option oP #<<path>>
4013 .index pid (process id)||of daemon
4014 .index daemon||process id (pid)
4015 This option is useful only in conjunction with \-bd-\ or \-q-\ with a time
4016 value. The option specifies the file to which the process id of the daemon is
4017 written. When \-oX-\ is used with \-bd-\, or when \-q-\ with a time is used
4018 without \-bd-\, this is the only way of causing Exim to write a pid file,
4019 because in those cases, the normal pid file is not used.
4021 .option or #<<time>>
4022 .index timeout||for non-SMTP input
4023 This option sets a timeout value for incoming non-SMTP messages. If it is not
4024 set, Exim will wait forever for the standard input. The value can also be set
4025 by the \receive@_timeout\ option. The format used for specifying times is
4026 described in section ~~SECTtimeformat.
4028 .option os #<<time>>
4029 .index timeout||for SMTP input
4030 .index SMTP||timeout, input
4031 This option sets a timeout value for incoming SMTP messages. The timeout
4032 applies to each SMTP command and block of data. The value can also be set by
4033 the \smtp@_receive@_timeout\ option; it defaults to 5 minutes. The format used
4034 for specifying times is described in section ~~SECTtimeformat.
4037 This option has exactly the same effect as \-v-\.
4039 .option oX #<<number or string>>
4040 .index TCP/IP||setting listening ports
4041 .index TCP/IP||setting listening interfaces
4042 .index port||receiving TCP/IP
4043 This option is relevant only when the \-bd-\ (start listening daemon) option is
4044 also given. It controls which ports and interfaces the daemon uses. Details of
4045 the syntax, and how it interacts with configuration file options, are given in
4046 chapter ~~CHAPinterfaces. When \-oX-\ is used to start a daemon, no pid file is
4047 written unless \-oP-\ is also present to specify a pid file name.
4050 .index Perl||starting the interpreter
4051 This option applies when an embedded Perl interpreter is linked with Exim (see
4052 chapter ~~CHAPperl). It overrides the setting of the \perl@_at@_start\ option,
4053 forcing the starting of the interpreter to be delayed until it is needed.
4056 .index Perl||starting the interpreter
4057 This option applies when an embedded Perl interpreter is linked with Exim (see
4058 chapter ~~CHAPperl). It overrides the setting of the \perl@_at@_start\ option,
4059 forcing the starting of the interpreter to occur as soon as Exim is started.
4061 .option p<<rval>>:<<sval>>
4062 For compatibility with Sendmail, this option
4065 -oMr <<rval>> -oMs <<sval>>
4067 It sets the incoming protocol and host name (for trusted callers). The
4068 host name and its colon can be omitted when only the protocol is to be set.
4069 Note the Exim already has two private options, \-pd-\ and \-ps-\, that refer to
4070 embedded Perl. It is therefore impossible to set a protocol value of \"p"\ or
4071 \"s"\ using this option (but that does not seem a real limitation).
4074 .index queue runner||starting manually
4075 This option is normally restricted to admin users. However, there is a
4076 configuration option called \prod@_requires@_admin\ which can be set false to
4077 relax this restriction (and also the same requirement for the \-M-\, \-R-\, and
4080 .index queue runner||description of operation
4081 The \-q-\ option starts one queue runner process. This scans the queue of
4082 waiting messages, and runs a delivery process for each one in turn. It waits
4083 for each delivery process to finish before starting the next one. A delivery
4084 process may not actually do any deliveries if the retry times for the addresses
4085 have not been reached. Use \-qf-\ (see below) if you want to override this.
4086 .index SMTP||passed connection
4087 .index SMTP||multiple deliveries
4088 .index multiple SMTP deliveries
4089 If the delivery process spawns other processes to deliver other messages down
4090 passed SMTP connections, the queue runner waits for these to finish before
4093 When all the queued messages have been considered, the original queue runner
4094 process terminates. In other words, a single pass is made over the waiting
4095 mail, one message at a time. Use \-q-\ with a time (see below) if you want this
4096 to be repeated periodically.
4098 Exim processes the waiting messages in an unpredictable order. It isn't very
4099 random, but it is likely to be different each time, which is all that matters.
4100 If one particular message screws up a remote MTA, other messages to the same
4101 MTA have a chance of getting through if they get tried first.
4103 It is possible to cause the messages to be processed in lexical message id
4104 order, which is essentially the order in which they arrived, by setting the
4105 \queue@_run@_in@_order\ option, but this is not recommended for normal use.
4107 .option q <<qflags>>
4108 The \-q-\ option may be followed by one or more flag letters that change its
4109 behaviour. They are all optional, but if more than one is present, they must
4110 appear in the correct order. Each flag is described in a separate item below.
4113 .index queue||double scanning
4114 .index queue||routing
4115 .index routing||whole queue before delivery
4116 An option starting with \-qq-\ requests a two-stage queue run. In the first
4117 stage, the queue is scanned as if the \queue@_smtp@_domains\ option matched
4118 every domain. Addresses are routed, local deliveries happen, but no remote
4120 .index hints database||remembering routing
4121 The hints database that remembers which messages are
4122 waiting for specific hosts is updated, as if delivery to those hosts had been
4123 deferred. After this is complete, a second, normal queue scan happens, with
4124 routing and delivery taking place as normal. Messages that are routed to the
4125 same host should mostly be delivered down a single SMTP
4126 .index SMTP||passed connection
4127 .index SMTP||multiple deliveries
4128 .index multiple SMTP deliveries
4129 connection because of the hints that were set up during the first queue scan.
4130 This option may be useful for hosts that are connected to the Internet
4134 .index queue||initial delivery
4135 If the \*i*\ flag is present, the queue runner runs delivery processes only for
4136 those messages that haven't previously been tried. (\*i*\ stands for `initial
4137 delivery'.) This can be helpful if you are putting messages on the queue using
4138 \-odq-\ and want a queue runner just to process the new messages.
4141 .index queue||forcing delivery
4142 .index delivery||forcing in queue run
4143 If one \*f*\ flag is present, a delivery attempt is forced for each non-frozen
4144 message, whereas without \f\ only those non-frozen addresses that have passed
4145 their retry times are tried.
4147 .option q[q][i]ff...
4148 .index frozen messages||forcing delivery
4149 If \*ff*\ is present, a delivery attempt is forced for every message, whether
4152 .option q[q][i][f[f]]l
4153 .index queue||local deliveries only
4154 The \*l*\ (the letter `ell') flag specifies that only local deliveries are to be
4155 done. If a message requires any remote deliveries, it remains on the queue for
4158 .option q <<qflags>>#<<start id>>#<<end id>>
4159 .index queue||delivering specific messages
4160 When scanning the queue, Exim can be made to skip over messages whose ids are
4161 lexically less than a given value by following the \-q-\ option with a starting
4162 message id. For example:
4164 exim -q 0t5C6f-0000c8-00
4166 Messages that arrived earlier than \"0t5C6f-0000c8-00"\ are not inspected. If a
4167 second message id is given, messages whose ids are lexically greater than it
4168 are also skipped. If the same id is given twice, for example,
4170 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4172 just one delivery process is started, for that message. This differs from \-M-\
4173 in that retry data is respected, and it also differs from \-Mc-\ in that it
4174 counts as a delivery from a queue run. Note that the selection mechanism does
4175 not affect the order in which the messages are scanned. There are also other
4176 ways of selecting specific sets of messages for delivery in a queue run -- see
4179 .option q <<qflags>><<time>>
4180 .index queue runner||starting periodically
4181 .index periodic queue running
4182 When a time value is present, the \-q-\ option causes Exim to run as a daemon,
4183 starting a queue runner process at intervals specified by the given time value
4184 (whose format is described in section ~~SECTtimeformat). This form of the \-q-\
4185 option is commonly combined with the \-bd-\ option, in which case a single
4186 daemon process handles both functions. A common way of starting up a combined
4187 daemon at system boot time is to use a command such as
4189 /usr/exim/bin/exim -bd -q30m
4191 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4192 process every 30 minutes.
4194 When a daemon is started by \-q-\ with a time value, but without \-bd-\, no pid
4195 file is written unless one is explicitly requested by the \-oP-\ option.
4197 .option qR <<rsflags>>#<<string>>
4198 This option is synonymous with \-R-\. It is provided for Sendmail
4201 .option qS <<rsflags>>#<<string>>
4202 This option is synonymous with \-S-\.
4204 .option R <<rsflags>>#<<string>>
4205 .index queue runner||for specific recipients
4206 .index delivery||to given domain
4207 .index domain||delivery to
4208 The <<rsflags>> may be empty, in which case the white space before the string
4209 is optional, unless the string is \*f*\, \*ff*\, \*r*\, \*rf*\, or \*rff*\,
4210 which are the possible values for <<rsflags>>. White space is required if
4211 <<rsflags>> is not empty.
4213 This option is similar to \-q-\ with no time value, that is, it causes Exim to
4214 perform a single queue run, except that, when scanning the messages on the
4215 queue, Exim processes only those that have at least one undelivered recipient
4216 address containing the given string, which is checked in a case-independent
4217 way. If the <<rsflags>> start with \*r*\, <<string>> is interpreted as a regular
4218 expression; otherwise it is a literal string.
4220 Once a message is selected, all its addresses are processed. For the first
4221 selected message, Exim overrides any retry information and forces a delivery
4222 attempt for each undelivered address. This means that if delivery of any
4223 address in the first message is successful, any existing retry information is
4224 deleted, and so delivery attempts for that address in subsequently selected
4225 messages (which are processed without forcing) will run. However, if delivery
4226 of any address does not succeed, the retry information is updated, and in
4227 subsequently selected messages, the failing address will be skipped.
4229 If the <<rsflags>> contain \*f*\ or \*ff*\, the delivery forcing applies to all
4230 selected messages, not just the first;
4231 .index frozen messages||forcing delivery
4232 frozen messages are included when \*ff*\ is present.
4234 The \-R-\ option makes it straightforward to initiate delivery of all messages
4235 to a given domain after a host has been down for some time. When the SMTP
4236 command \\ETRN\\ is accepted by its ACL (see chapter ~~CHAPACL), its default
4237 effect is to run Exim with the \-R-\ option, but it can be configured to run an
4238 arbitrary command instead.
4241 This is a documented (for Sendmail) obsolete alternative name for \-f-\.
4243 .index delivery||from given sender
4244 .option S <<rsflags>>#<<string>>
4245 .index queue runner||for specific senders
4246 This option acts like \-R-\ except that it checks the string against each
4247 message's sender instead of against the recipients. If \-R-\ is also set, both
4248 conditions must be met for a message to be selected. If either of the options
4249 has \*f*\ or \*ff*\ in its flags, the associated action is taken.
4251 .option Tqt#<<times>>
4252 This an option that is exclusively for use by the Exim testing suite.
4253 It is not recognized when Exim is run normally. It allows for the setting up
4254 of explicit `queue times' so that various warning/retry features can be
4258 .index recipient||extracting from header lines
4259 .index ::Bcc:: header line
4260 .index ::Cc:: header line
4261 .index ::To:: header line
4262 When Exim is receiving a locally-generated, non-SMTP message on its standard
4263 input, the \-t-\ option causes the recipients of the message to be obtained
4264 from the ::To::, ::Cc::, and ::Bcc:: header lines in the message instead of from
4265 the command arguments. The addresses are extracted before any rewriting takes
4268 .index Sendmail compatibility||\-t-\ option
4269 If the command has any arguments, they specify addresses to which the message
4270 is $it{not} to be delivered. That is, the argument addresses are removed from
4271 the recipients list obtained from the headers. This is compatible with Smail 3
4272 and in accordance with the documented behaviour of several versions of
4273 Sendmail, as described in man pages on a number of operating systems (e.g.
4274 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail $it{add}
4275 argument addresses to those obtained from the headers, and the O'Reilly
4276 Sendmail book documents it that way. Exim can be made to add argument addresses
4277 instead of subtracting them by setting the option
4278 \extract__addresses__remove__arguments\ false.
4280 If a ::Bcc:: header line is present, it is removed from the message unless
4281 there is no ::To:: or ::Cc::, in which case a ::Bcc:: line with no data is
4282 created. This is necessary for conformity with the original RFC 822 standard;
4283 the requirement has been removed in RFC 2822, but that is still very new.
4285 .index \Resent@-\ header lines||with \-t-\
4286 If there are any \Resent@-\ header lines in the message, Exim extracts
4287 recipients from all ::Resent-To::, ::Resent-Cc::, and ::Resent-Bcc:: header
4288 lines instead of from ::To::, ::Cc::, and ::Bcc::. This is for compatibility
4289 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4290 \-t-\ was used in conjunction with \Resent@-\ header lines.)
4292 RFC 2822 talks about different sets of \Resent@-\ header lines (for when a
4293 message is resent several times). The RFC also specifies that they should be
4294 added at the front of the message, and separated by ::Received:: lines. It is
4295 not at all clear how \-t-\ should operate in the present of multiple sets,
4296 nor indeed exactly what constitutes a `set'.
4297 In practice, it seems that MUAs do not follow the RFC. The \Resent@-\ lines are
4298 often added at the end of the header, and if a message is resent more than
4299 once, it is common for the original set of \Resent@-\ headers to be renamed as
4300 \X-Resent@-\ when a new set is added. This removes any possible ambiguity.
4303 This option is exactly equivalent to \-t-\ \-i-\. It is provided for
4304 compatibility with Sendmail.
4306 .option tls-on-connect
4307 .index TLS||use without STARTTLS
4308 .index TLS||automatic start
4309 This option is available when Exim is compiled with TLS support.
4311 It forces all incoming SMTP connections to behave as if the incoming port is
4312 listed in the \tls@_on@_connect@_ports\ option. See section ~~SECTsupobssmt and
4313 chapter ~~CHAPTLS for further details.
4317 .index Sendmail compatibility||\-U-\ option ignored
4318 Sendmail uses this option for `initial message submission', and its
4319 documentation states that in future releases, it may complain about
4320 syntactically invalid messages rather than fixing them when this flag is not
4321 set. Exim ignores this option.
4324 This option causes Exim to write information to the standard error stream,
4325 describing what it is doing. In particular, it shows the log lines for
4326 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4327 dialogue is shown. Some of the log lines shown may not actually be written to
4328 the log if the setting of \log@_selector\ discards them. Any relevant selectors
4329 are shown with each log line. If none are shown, the logging is unconditional.
4332 AIX uses \-x-\ for a private purpose (`mail from a local mail program has
4333 National Language Support extended characters in the body of the mail item').
4334 It sets \-x-\ when calling the MTA from its \mail\ command. Exim ignores this
4345 . ============================================================================
4346 .chapter The Exim run time configuration file
4347 .set runningfoot "configuration file"
4348 .rset CHAPconf ~~chapter
4350 .index run time configuration
4351 .index configuration file||general description
4352 .index \\CONFIGURE@_FILE\\
4353 .index configuration file||errors in
4354 .index error||in configuration file
4355 .index return code||for bad configuration
4356 Exim uses a single run time configuration file that is read whenever an Exim
4357 binary is executed. Note that in normal operation, this happens frequently,
4358 because Exim is designed to operate in a distributed manner, without central
4362 If a syntax error is detected while reading the configuration file, Exim
4363 writes a message on the standard error, and exits with a non-zero return code.
4364 The message is also written to the panic log. \**Note**\: only simple syntax
4365 errors can be detected at this time. The values of any expanded options are
4366 not checked until the expansion happens, even when the expansion does not
4367 actually alter the string.
4371 The name of the configuration file is compiled into the binary for security
4372 reasons, and is specified by the \\CONFIGURE@_FILE\\ compilation option. In
4373 most configurations, this specifies a single file. However, it is permitted to
4374 give a colon-separated list of file names, in which case Exim uses the first
4375 existing file in the list.
4377 .index \\EXIM@_USER\\
4378 .index \\EXIM@_GROUP\\
4379 .index \\CONFIGURE@_OWNER\\
4380 .index \\CONFIGURE@_GROUP\\
4381 .index configuration file||ownership
4382 .index ownership||configuration file
4383 The run time configuration file must be owned by root or by the user that is
4384 specified at compile time by the \\EXIM@_USER\\ option, or by the user that is
4385 specified at compile time by the \\CONFIGURE@_OWNER\\ option (if set). The
4386 configuration file must not be world-writeable or group-writeable, unless its
4387 group is the one specified at compile time by the \\EXIM@_GROUP\\ option
4389 or by the \\CONFIGURE@_GROUP\\ option.
4392 \**Warning**\: In a conventional configuration, where the Exim binary is setuid
4393 to root, anybody who is able to edit the run time configuration file has an
4394 easy way to run commands as root. If you make your mail administrators members
4395 of the Exim group, but do not trust them with root, make sure that the run time
4396 configuration is not group writeable.
4398 A default configuration file, which will work correctly in simple situations,
4399 is provided in the file \(src/configure.default)\. If \\CONFIGURE@_FILE\\
4400 defines just one file name, the installation process copies the default
4401 configuration to a new file of that name if it did not previously exist. If
4402 \\CONFIGURE@_FILE\\ is a list, no default is automatically installed. Chapter
4403 ~~CHAPdefconfil is a `walk-through' discussion of the default configuration.
4406 .section Using a different configuration file
4407 .index configuration file||alternate
4408 A one-off alternate configuration can be specified by the \-C-\ command line
4409 option, which may specify a single file or a list of files. However, when \-C-\
4410 is used, Exim gives up its root privilege, unless called by root or the Exim
4411 user (or unless the argument for \-C-\ is identical to the built-in value from
4412 \\CONFIGURE@_FILE\\). \-C-\ is useful mainly for checking the syntax of
4413 configuration files before installing them. No owner or group checks are done
4414 on a configuration file specified by \-C-\.
4416 The privileged use of \-C-\ by the Exim user can be locked out by setting
4417 \\ALT@_CONFIG@_ROOT@_ONLY\\ in \(Local/Makefile)\ when building Exim. However,
4418 if you do this, you also lock out the possibility of testing a
4419 configuration using \-C-\ right through message reception and delivery, even if
4420 the caller is root. The reception works, but by that time, Exim is running as
4421 the Exim user, so when it re-execs to regain privilege for the delivery, the
4422 use of \-C-\ causes privilege to be lost. However, root can test reception and
4423 delivery using two separate commands (one to put a message on the queue, using
4424 \-odq-\, and another to do the delivery, using \-M-\).
4426 If \\ALT@_CONFIG@_PREFIX\\ is defined \(in Local/Makefile)\, it specifies a
4427 prefix string with which any file named in a \-C-\ command line option must
4428 start. In addition, the file name must not contain the sequence \"/../"\. There
4429 is no default setting for \\ALT@_CONFIG@_PREFIX\\; when it is unset, any file
4430 name can be used with \-C-\.
4432 One-off changes to a configuration can be specified by the \-D-\ command line
4433 option, which defines and overrides values for macros used inside the
4434 configuration file. However, like \-C-\, the use of this option by a
4435 non-privileged user causes Exim to discard its root privilege.
4436 If \\DISABLE@_D@_OPTION\\ is defined in \(Local/Makefile)\, the use of \-D-\ is
4437 completely disabled, and its use causes an immediate error exit.
4439 Some sites may wish to use the same Exim binary on different machines that
4440 share a file system, but to use different configuration files on each machine.
4441 If \\CONFIGURE@_FILE@_USE@_NODE\\ is defined in \(Local/Makefile)\, Exim first
4442 looks for a file whose name is the configuration file name followed by a dot
4443 and the machine's node name, as obtained from the \*uname()*\ function. If this
4444 file does not exist, the standard name is tried. This processing occurs for
4445 each file name in the list given by \\CONFIGURE@_FILE\\ or \-C-\.
4447 In some esoteric situations different versions of Exim may be run under
4448 different effective uids and the \\CONFIGURE@_FILE@_USE@_EUID\\ is defined to
4449 help with this. See the comments in \(src/EDITME)\ for details.
4452 .section Configuration file format
4453 .rset SECTconffilfor "~~chapter.~~section"
4454 .index configuration file||format of
4455 .index format||configuration file
4456 Exim's configuration file is divided into a number of different parts. General
4457 option settings must always appear at the start of the file. The other parts
4458 are all optional, and may appear in any order. Each part other than the first
4459 is introduced by the word `begin' followed by the name of the part. The
4463 \*ACL*\: Access control lists for controlling incoming SMTP mail.
4465 .index \\AUTH\\||configuration
4466 \*authenticators*\: Configuration settings for the authenticator drivers. These
4467 are concerned with the SMTP \\AUTH\\ command (see chapter ~~CHAPSMTPAUTH).
4469 \*routers*\: Configuration settings for the router drivers. Routers process
4470 addresses and determine how the message is to be delivered.
4472 \*transports*\: Configuration settings for the transport drivers. Transports
4473 define mechanisms for copying messages to destinations.
4475 \*retry*\: Retry rules, for use when a message cannot be immediately delivered.
4477 \*rewrite*\: Global address rewriting rules, for use when a message arrives and
4478 when new addresses are generated during delivery.
4480 \*local@_scan*\: Private options for the \*local@_scan()*\ function. If you
4481 want to use this feature, you must set
4483 LOCAL_SCAN_HAS_OPTIONS=yes
4485 in \(Local/Makefile)\ before building Exim. Full details of the
4486 \*local@_scan()*\ facility are given in chapter ~~CHAPlocalscan.
4488 .index configuration file||leading whitespace in
4489 .index configuration file||trailing whitespace in
4490 .index whitespace||in configuration file
4492 Leading and trailing whitespace in configuration lines is always ignored.
4494 Blank lines in the file, and lines starting with a @# character (ignoring
4495 leading white space) are treated as comments and are ignored. \**Note**\: a
4496 @# character other than at the beginning of a line is not treated specially,
4497 and does not introduce a comment.
4499 Any non-comment line can be continued by ending it with a backslash.
4501 Note that the general rule for whitespace means that trailing white space after
4502 the backslash is ignored, and leading white space at the start of continuation
4503 lines is also ignored.
4505 Comment lines beginning with @# (but not empty lines) may appear in the middle
4506 of a sequence of continuation lines.
4508 A convenient way to create a configuration file is to start from the
4509 default, which is supplied in \(src/configure.default)\, and add, delete, or
4510 change settings as required.
4512 The ACLs, retry rules, and rewriting rules have their own syntax which is
4513 described in chapters ~~CHAPACL, ~~CHAPretry, and ~~CHAPrewrite, respectively.
4514 The other parts of the configuration file have some syntactic items in common,
4515 and these are described below, from section ~~SECTcos onwards. Before that, the
4516 inclusion, macro, and conditional facilities are described.
4519 .section File inclusions in the configuration file
4520 .index inclusions in configuration file
4521 .index configuration file||including other files
4522 .index .include in configuration file
4523 .index .include@_if@_exists in configuration file
4524 You can include other files inside Exim's run time configuration file by
4527 @.include <<file name>>
4531 @.include@_if@_exists <<file name>>
4533 on a line by itself. Double quotes round the file name are optional. If you use
4534 the first form, a configuration error occurs if the file does not exist; the
4535 second form does nothing for non-existent files.
4537 Includes may be nested to any depth, but remember that Exim reads its
4538 configuration file often, so it is a good idea to keep them to a minimum.
4539 If you change the contents of an included file, you must HUP the daemon,
4540 because an included file is read only when the configuration itself is read.
4542 The processing of inclusions happens early, at a physical line level, so, like
4543 comment lines, an inclusion can be used in the middle of an option setting,
4546 hosts_lookup = a.b.c \
4549 Include processing happens
4551 macro processing (see below). Its effect is to process the lines of the file as
4552 if they occurred inline where the inclusion appears.
4555 .section Macros in the configuration file
4556 .rset SECTmacrodefs "~~chapter.~~section"
4557 .index macro||description of
4558 .index configuration file||macros
4559 If a line in the main part of the configuration (that is, before the first
4560 `begin' line) begins with an upper case letter, it is taken as a macro
4561 definition, and must be of the form
4563 <<name>> = <<rest of line>>
4565 The name must consist of letters, digits, and underscores, and need not all be
4566 in upper case, though that is recommended. The rest of the line, including any
4567 continuations, is the replacement text, and has leading and trailing white
4568 space removed. Quotes are not removed. The replacement text can never end with
4569 a backslash character, but this doesn't seem to be a serious limitation.
4571 Once a macro is defined, all subsequent lines in the file (and any included
4572 files) are scanned for the macro name; if there are several macros, the line is
4573 scanned for each in turn, in the order in which they are defined. The
4574 replacement text is not re-scanned for the current macro, though it is scanned
4575 for subsequently defined macros. For this reason, a macro name may not contain
4576 the name of a previously defined macro as a substring. You could, for example,
4579 ABCD_XYZ = <<something>>
4580 ABCD = <<something else>>
4582 but putting the definitions in the opposite order would provoke a configuration
4585 Macro expansion is applied to individual lines from the file, before checking
4586 for line continuation or file inclusion (see below). If a line consists solely
4587 of a macro name, and the expansion of the macro is empty, the line is ignored.
4588 A macro at the start of a line may turn the line into a comment line or a
4591 As an example of macro usage, consider a configuration where aliases are looked
4592 up in a MySQL database. It helps to keep the file less cluttered if long
4593 strings such as SQL statements are defined separately as macros, for example:
4595 ALIAS_QUERY = select mailbox from user where \
4596 login=${quote_mysql:$local_part};
4598 This can then be used in a \%redirect%\ router setting like this:
4600 data = ${lookup mysql{ALIAS_QUERY}}
4602 In earlier versions of Exim macros were sometimes used for domain, host, or
4603 address lists. In Exim 4 these are handled better by named lists -- see section
4606 Macros in the configuration file can be overridden by the \-D-\ command line
4607 option, but Exim gives up its root privilege when \-D-\ is used, unless called
4608 by root or the Exim user.
4611 .section Conditional skips in the configuration file
4612 .index configuration file||conditional skips
4614 You can use the directives \".ifdef"\, \".ifndef"\, \".elifdef"\,
4615 \".elifndef"\, \".else"\, and \".endif"\ to dynamically include or exclude
4616 portions of the configuration file. The processing happens whenever the file is
4617 read (that is, when an Exim binary starts to run).
4619 The implementation is very simple. Instances of the first four directives must
4620 be followed by text that includes the names of one or macros. The condition
4621 that is tested is whether or not any macro substitution has taken place in the
4625 message@_size@_limit = 50M
4627 message@_size@_limit = 100M
4630 sets a message size limit of 50M if the macro \"AAA"\ is defined, and 100M
4631 otherwise. If there is more than one macro named on the line, the condition
4632 is true if any of them are defined. That is, it is an `or' condition. To
4633 obtain an `and' condition, you need to use nested \".ifdef"\s.
4635 Although you can use a macro expansion to generate one of these directives,
4636 it is not very useful, because the condition `there was a macro substitution
4637 in this line' will always be true.
4639 Text following \".else"\ and \".endif"\ is ignored, and can be used as comment
4640 to clarify complicated nestings.
4643 .section Common option syntax
4644 .rset SECTcos "~~chapter.~~section"
4645 .index common option syntax
4646 .index syntax of common options
4647 .index configuration file||common option syntax
4648 For the main set of options, driver options, and \*local@_scan()*\ options,
4649 each setting is on a line by itself, and starts with a name consisting of
4650 lower-case letters and underscores. Many options require a data value, and in
4651 these cases the name must be followed by an equals sign (with optional white
4652 space) and then the value. For example:
4654 qualify_domain = mydomain.example.com
4656 Some option settings may contain sensitive data, for example, passwords for
4657 accessing databases. To stop non-admin users from using the \-bP-\ command line
4658 option to read these values, you can precede the option settings with the word
4659 `hide'. For example:
4661 hide mysql_servers = localhost/users/admin/secret-password
4663 For non-admin users, such options are displayed like this:
4665 mysql_servers = <value not displayable>
4667 If `hide' is used on a driver option, it hides the value of that option on all
4668 instances of the same driver.
4670 The following sections describe the syntax used for the different data types
4671 that are found in option settings.
4673 .section Boolean options
4674 .index format||boolean
4675 .index boolean configuration values
4676 Options whose type is given as boolean are on/off switches. There are two
4677 different ways of specifying such options: with and without a data value. If
4678 the option name is specified on its own without data, the switch is turned on;
4679 if it is preceded by `no@_' or `not@_' the switch is turned off. However,
4680 boolean options may optionally be followed by an equals sign and one of the
4681 words `true', `false', `yes', or `no', as an alternative syntax. For example,
4682 the following two settings have exactly the same effect:
4687 The following two lines also have the same (opposite) effect:
4692 You can use whichever syntax you prefer.
4696 .section Integer values
4697 .index integer configuration values
4698 .index format||integer
4699 If an integer data item starts with the characters `0x', the remainder of it
4700 is interpreted as a hexadecimal number. Otherwise, it is treated as octal if it
4701 starts with the digit 0, and decimal if not. If an integer value is followed by
4702 the letter K, it is multiplied by 1024; if it is followed by the letter M, it
4703 is multiplied by 1024x1024.
4705 When the values of integer option settings are output, values which are an
4706 exact multiple of 1024 or 1024x1024 are
4707 sometimes, but not always,
4708 printed using the letters K and M. The printing style is independent of the
4709 actual input format that was used.
4711 .section Octal integer values
4712 .index integer format
4713 .index format||octal integer
4714 The value of an option specified as an octal integer is always interpreted in
4715 octal, whether or not it starts with the digit zero. Such options are always
4719 .section Fixed point number values
4720 .index fixed point configuration values
4721 .index format||fixed point
4722 A fixed point number consists of a decimal integer, optionally followed by a
4723 decimal point and up to three further digits.
4726 .section Time interval values
4727 .index time interval||specifying in configuration
4728 .index format||time interval
4729 .rset SECTtimeformat "~~chapter.~~section"
4730 A time interval is specified as a sequence of numbers, each followed by one of
4731 the following letters, with no intervening white space:
4740 For example, `3h50m' specifies 3 hours and 50 minutes. The values of time
4741 intervals are output in the same format.
4742 Exim does not restrict the values; it is perfectly acceptable, for example, to
4743 specify `90m' instead of `1h30m'.
4746 .section String values
4747 .index string||format of configuration values
4748 .index format||string
4749 .rset SECTstrings "~~chapter.~~section"
4750 If a string data item does not start with a double-quote character, it is taken
4751 as consisting of the remainder of the line plus any continuation lines,
4752 starting at the first character after any leading white space, with trailing
4753 white space characters removed, and with no interpretation of the characters in
4754 the string. Because Exim removes comment lines (those beginning with @#) at an
4755 early stage, they can appear in the middle of a multi-line string. The
4756 following settings are therefore equivalent:
4758 trusted_users = uucp:mail
4760 trusted_users = uucp:\
4761 # This comment line is ignored
4764 .index string||quoted
4765 .index escape characters in quoted strings
4766 If a string does start with a double-quote, it must end with a closing
4767 double-quote, and any backslash characters other than those used for line
4768 continuation are interpreted as escape characters, as follows:
4771 @\@\ $t $rm{single backslash}
4773 @\r $t $rm{carriage return}
4775 @\<<octal digits>> $t $rm{up to 3 octal digits specify one character}
4776 @\x<<hex digits>> $t $rm{up to 2 hexadecimal digits specify one character}
4778 If a backslash is followed by some other character, including a double-quote
4779 character, that character replaces the pair.
4781 Quoting is necessary only if you want to make use of the backslash escapes to
4782 insert special characters, or if you need to specify a value with leading or
4783 trailing spaces. These cases are rare, so quoting is almost never needed in
4784 current versions of Exim. In versions of Exim before 3.14, quoting was required
4785 in order to continue lines, so you may come across older configuration files
4786 and examples that apparently quote unnecessarily.
4788 .section Expanded strings
4789 .index string||expansion, definition of
4790 .index expansion||definition of
4791 Some strings in the configuration file are subjected to \*string expansion*\,
4792 by which means various parts of the string may be changed according to the
4793 circumstances (see chapter ~~CHAPexpand). The input syntax for such strings is
4794 as just described; in particular, the handling of backslashes in quoted strings
4795 is done as part of the input process, before expansion takes place. However,
4796 backslash is also an escape character for the expander, so any backslashes that
4797 are required for that reason must be doubled if they are within a quoted
4798 configuration string.
4800 .section User and group names
4801 .index user name||format of
4802 .index format||user name
4803 .index group||name format
4804 .index format||group name
4805 User and group names are specified as strings, using the syntax described
4806 above, but the strings are interpreted specially. A user or group name must
4807 either consist entirely of digits, or be a name that can be looked up using the
4808 \*getpwnam()*\ or \*getgrnam()*\ function, as appropriate.
4810 .section List construction
4811 .index list||syntax of in configuration
4812 .index format||list item in configuration
4813 .index string list, definition
4814 .rset SECTlistconstruct "~~chapter.~~section"
4815 The data for some configuration options is a list of items, with colon as the
4816 default separator. Many of these options are shown with type `string list' in
4817 the descriptions later in this document. Others are listed as `domain list',
4818 `host list', `address list', or `local part list'. Syntactically, they are all
4819 the same; however, those other than `string list' are subject to particular
4820 kinds of interpretation, as described in chapter ~~CHAPdomhosaddlists.
4822 In all these cases, the entire list is treated as a single string as far as the
4823 input syntax is concerned. The \trusted@_users\ setting in section
4824 ~~SECTstrings above is an example. If a colon is actually needed in an item in
4825 a list, it must be entered as two colons. Leading and trailing white space on
4826 each item in a list is ignored. This makes it possible to include items that
4827 start with a colon, and in particular, certain forms of IPv6 address. For
4830 local_interfaces = 127.0.0.1 : ::::1
4832 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address
4834 .index list||separator, changing
4835 .index IPv6||addresses in lists
4836 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
4837 introduced to allow the separator character to be changed. If a list begins
4838 with a left angle bracket, followed by any punctuation character, that
4839 character is used instead of colon as the list separator. For example, the list
4840 above can be rewritten to use a semicolon separator like this:
4842 local_interfaces = <; 127.0.0.1 ; ::1
4844 This facility applies to all lists, with the exception of the list in
4845 \log@_file@_path\. It is recommended that the use of non-colon separators be
4846 confined to circumstances where they really are needed.
4850 .section Empty items in lists
4851 .rset SECTempitelis "~~chapter.~~section"
4852 .index list||empty item in
4853 An empty item at the end of a list is always ignored. In other words, trailing
4854 separator characters are ignored. Thus, the list in
4856 senders = user@domain :
4858 contains only a single item. If you want to include an empty string as one item
4859 in a list, it must not be the last item. For example, this list contains three
4860 items, the second of which is empty:
4862 senders = user1@domain : : user2@domain
4864 \**Note**\: there must be whitespace between the two colons, as otherwise they
4865 are interpreted as representing a single colon data character (and the list
4866 would then contain just one item). If you want to specify a list that contains
4867 just one, empty item, you can do it as in this example:
4871 In this case, the first item is empty, and the second is discarded because it
4872 is at the end of the list.
4876 .section Format of driver configurations
4877 .rset SECTfordricon "~~chapter.~~section"
4878 .index drivers||configuration format
4879 There are separate parts in the configuration for defining routers, transports,
4880 and authenticators. In each part, you are defining a number of driver
4881 instances, each with its own set of options. Each driver instance is defined by
4882 a sequence of lines like this:
4889 In the following example, the instance name is \%localuser%\, and it is
4890 followed by three options settings:
4895 transport = local_delivery
4897 For each driver instance, you specify which Exim code module it uses -- by the
4898 setting of the \driver\ option -- and (optionally) some configuration settings.
4899 For example, in the case of transports, if you want a transport to deliver with
4900 SMTP you would use the \%smtp%\ driver; if you want to deliver to a local file
4901 you would use the \%appendfile%\ driver. Each of the drivers is described in
4902 detail in its own separate chapter later in this manual.
4904 You can have several routers, transports, or authenticators that are based on
4905 the same underlying driver (each must have a different name).
4907 The order in which routers are defined is important, because addresses are
4908 passed to individual routers one by one, in order. The order in which
4909 transports are defined does not matter at all. The order in which
4910 authenticators are defined is used only when Exim, as a client, is searching
4911 them to find one that matches an authentication mechanism offered by the
4914 .index generic options
4915 .index options||generic, definition of
4916 Within a driver instance definition, there are two kinds of option:
4917 $it{generic} and $it{private}. The generic options are those that apply to all
4918 drivers of the same type (that is, all routers, all transports or all
4920 The \driver\ option is a generic option that must appear in every definition.
4921 .index private options
4922 The private options are special for each driver, and none need appear, because
4923 they all have default values.
4925 The options may appear in any order, except that the \driver\ option must
4926 precede any private options, since these depend on the particular driver. For
4927 this reason, it is recommended that \driver\ always be the first option.
4929 Driver instance names, which are used for reference in log entries and
4930 elsewhere, can be any sequence of letters, digits, and underscores (starting
4931 with a letter) and must be unique among drivers of the same type. A router and
4932 a transport (for example) can each have the same name, but no two router
4933 instances can have the same name. The name of a driver instance should not be
4934 confused with the name of the underlying driver module. For example, the
4935 configuration lines:
4940 create an instance of the \%smtp%\ transport driver whose name is
4941 \%remote@_smtp%\. The same driver code can be used more than once, with
4942 different instance names and different option settings each time. A second
4943 instance of the \%smtp%\ transport, with different options, might be defined
4949 command_timeout = 10s
4951 The names \%remote@_smtp%\ and \%special@_smtp%\ would be used to reference
4952 these transport instances from routers, and these names would appear in log
4955 Comment lines may be present in the middle of driver specifications. The full
4956 list of option settings for any particular driver instance, including all the
4957 defaulted values, can be extracted by making use of the \-bP-\ command line
4969 . ============================================================================
4970 .chapter The default configuration file
4971 .set runningfoot "default configuration"
4972 .rset CHAPdefconfil "~~chapter"
4973 .index configuration file||default, `walk through'
4974 .index default||configuration file `walk through'
4975 The default configuration file supplied with Exim as \(src/configure.default)\
4976 is sufficient for a host with simple mail requirements. As an introduction to
4977 the way Exim is configured, this chapter `walks through' the default
4978 configuration, giving brief explanations of the settings. Detailed descriptions
4979 of the options are given in subsequent chapters. The default configuration file
4980 itself contains extensive comments about ways you might want to modify the
4981 initial settings. However, note that there are many options that are not
4982 mentioned at all in the default configuration.
4985 .section Main configuration settings
4986 The main (global) configuration option settings must always come first in the
4987 file. The first thing you'll see in the file, after some initial comments, is
4990 # primary_hostname =
4992 This is a commented-out setting of the \primary@_hostname\ option. Exim needs
4993 to know the official, fully qualified name of your host, and this is where you
4994 can specify it. However, in most cases you do not need to set this option. When
4995 it is unset, Exim uses the \*uname()*\ system function to obtain the host name.
4997 The first three non-comment configuration lines are as follows:
4999 domainlist local_domains = @
5000 domainlist relay_to_domains =
5001 hostlist relay_from_hosts = 127.0.0.1
5003 These are not, in fact, option settings. They are definitions of two named
5004 domain lists and one named host list. Exim allows you to give names to lists of
5005 domains, hosts, and email addresses, in order to make it easier to manage the
5006 configuration file (see section ~~SECTnamedlists).
5008 The first line defines a domain list called \*local@_domains*\; this is used
5009 later in the configuration to identify domains that are to be delivered
5011 .index @@ in a domain list
5012 There is just one item in this list, the string `@@'. This is a special form of
5013 entry which means `the name of the local host'. Thus, if the local host is
5014 called \*a.host.example*\, mail to \*any.user@@a.host.example*\ is expected to
5015 be delivered locally. Because the local host's name is referenced indirectly,
5016 the same configuration file can be used on different hosts.
5018 The second line defines a domain list called \*relay@_to@_domains*\, but the
5019 list itself is empty. Later in the configuration we will come to the part that
5020 controls mail relaying through the local host; it allows relaying to any
5021 domains in this list. By default, therefore, no relaying on the basis of a mail
5022 domain is permitted.
5024 The third line defines a host list called \*relay@_from@_hosts*\. This list is
5025 used later in the configuration to permit relaying from any host or IP address
5026 that matches the list. The default contains just the IP address of the IPv4
5027 loopback interface, which means that processes on the local host are able to
5028 submit mail for relaying by sending it over TCP/IP to that interface. No other
5029 hosts are permitted to submit messages for relaying.
5031 Just to be sure there's no misunderstanding: at this point in the configuration
5032 we aren't actually setting up any controls. We are just defining some domains
5033 and hosts that will be used in the controls that are specified later.
5035 The next configuration line is a genuine option setting:
5037 acl_smtp_rcpt = acl_check_rcpt
5039 This option specifies an \*Access Control List*\ (ACL) which is to be used
5040 during an incoming SMTP session for every recipient of a message (every
5041 \\RCPT\\ command). The name of the list is \*acl@_check@_rcpt*\, and we will
5042 come to its definition below, in the ACL section of the configuration. ACLs
5043 control which recipients are accepted for an incoming message -- if a
5044 configuration does not provide an ACL to check recipients, no SMTP mail can be
5047 Two commented-out options settings are next:
5050 # qualify_recipient =
5052 The first of these specifies a domain that Exim uses when it constructs a
5053 complete email address from a local login name. This is often needed when Exim
5054 receives a message from a local process. If you do not set \qualify@_domain\,
5055 the value of \primary@_hostname\ is used. If you set both of these options, you
5056 can have different qualification domains for sender and recipient addresses. If
5057 you set only the first one, its value is used in both cases.
5059 .index domain literal||recognizing format
5060 The following line must be uncommented if you want Exim to recognize
5061 addresses of the form \*user@@[10.11.12.13]*\ that is, with a `domain literal'
5062 (an IP address) instead of a named domain.
5064 # allow_domain_literals
5066 The RFCs still require this form, but many people think that in the modern
5067 Internet it makes little sense to permit mail to be sent to specific hosts by
5068 quoting their IP addresses. This ancient format has been used by people who
5069 try to abuse hosts by using them for unwanted relaying. However, some
5070 people believe there are circumstances (for example, messages addressed to
5071 \*postmaster*\) where domain literals are still useful.
5073 The next configuration line is a kind of trigger guard:
5077 It specifies that no delivery must ever be run as the root user. The normal
5078 convention is to set up \*root*\ as an alias for the system administrator. This
5079 setting is a guard against slips in the configuration.
5080 The list of users specified by \never@_users\ is not, however, the complete
5081 list; the build-time configuration in \(Local/Makefile)\ has an option called
5082 \\FIXED@_NEVER@_USERS\\ specifying a list that cannot be overridden. The
5083 contents of \never@_users\ are added to this list. By default
5084 \\FIXED@_NEVER@_USERS\\ also specifies root.
5086 When a remote host connects to Exim in order to send mail, the only information
5087 Exim has about the host's identity is its IP address. The next configuration
5092 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5093 in order to get a host name. This improves the quality of the logging
5094 information, but if you feel it is too expensive, you can remove it entirely,
5095 or restrict the lookup to hosts on `nearby' networks.
5096 Note that it is not always possible to find a host name from an IP address,
5097 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5100 The next two lines are concerned with \*ident*\ callbacks, as defined by RFC
5101 1413 (hence their names):
5104 rfc1413_query_timeout = 30s
5106 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5107 You can limit the hosts to which these calls are made, or change the timeout
5108 that is used. If you set the timeout to zero, all ident calls are disabled.
5109 Although they are cheap and can provide useful information for tracing problem
5110 messages, some hosts and firewalls have problems with ident calls. This can
5111 result in a timeout instead of an immediate refused connection, leading to
5112 delays on starting up an incoming SMTP session.
5114 When Exim receives messages over SMTP connections, it expects all addresses to
5115 be fully qualified with a domain, as required by the SMTP definition. However,
5116 if you are running a server to which simple clients submit messages, you may
5117 find that they send unqualified addresses. The two commented-out options:
5119 # sender_unqualified_hosts =
5120 # recipient_unqualified_hosts =
5122 show how you can specify hosts that are permitted to send unqualified sender
5123 and recipient addresses, respectively.
5125 The \percent@_hack@_domains\ option is also commented out:
5127 # percent_hack_domains =
5129 It provides a list of domains for which the `percent hack' is to operate. This
5130 is an almost obsolete form of explicit email routing. If you do not know
5131 anything about it, you can safely ignore this topic.
5133 The last two settings in the main part of the default configuration are
5134 concerned with messages that have been `frozen' on Exim's queue. When a message
5135 is frozen, Exim no longer continues to try to deliver it. Freezing occurs when
5136 a bounce message encounters a permanent failure because the sender address of
5137 the original message that caused the bounce is invalid, so the bounce cannot be
5138 delivered. This is probably the most common case, but there are also other
5139 conditions that cause freezing, and frozen messages are not always bounce
5142 ignore_bounce_errors_after = 2d
5143 timeout_frozen_after = 7d
5145 The first of these options specifies that failing bounce messages are to be
5146 discarded after 2 days on the queue. The second specifies that any frozen
5147 message (whether a bounce message or not) is to be timed out (and discarded)
5148 after a week. In this configuration, the first setting ensures that no failing
5149 bounce message ever lasts a week.
5152 .section ACL configuration
5153 .index default||ACLs
5154 .index ~~ACL||default configuration
5155 In the default configuration, the ACL section follows the main configuration.
5156 It starts with the line
5160 and it contains the definition of one ACL called \*acl@_check@_rcpt*\ that was
5161 referenced in the setting of \acl@_smtp@_rcpt\ above.
5162 .index \\RCPT\\||ACL for
5163 This ACL is used for every \\RCPT\\ command in an incoming SMTP message. Each
5164 \\RCPT\\ command specifies one of the message's recipients. The ACL statements
5165 are considered in order, until the recipient address is either accepted or
5166 rejected. The \\RCPT\\ command is then accepted or rejected, according to the
5167 result of the ACL processing.
5171 This line, consisting of a name terminated by a colon, marks the start of the
5176 This ACL statement accepts the recipient if the sending host matches the list.
5177 But what does that strange list mean? It doesn't actually contain any host
5178 names or IP addresses. The presence of the colon puts an empty item in the
5179 list; Exim matches this only if the incoming message didn't come from a remote
5180 host. The colon is important. Without it, the list itself is empty, and can
5181 never match anything.
5183 What this statement is doing is to accept unconditionally all recipients in
5184 messages that are submitted by SMTP from local processes using the standard
5185 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5188 deny domains = +local_domains
5189 local_parts = ^[.] : ^.*[@%!/|]
5191 deny domains = !+local_domains
5192 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5194 These statements are concerned with local parts that contain any of the
5195 characters `@@', `%', `!', `/', `|', or dots in unusual places. Although these
5196 characters are entirely legal in local parts (in the case of `@@' and leading
5197 dots, only if correctly quoted), they do not commonly occur in Internet mail
5200 The first three have in the past been associated with explicitly routed
5201 addresses (percent is still sometimes used -- see the \percent@_hack@_domains\
5202 option). Addresses containing these characters are regularly tried by spammers
5203 in an attempt to bypass relaying restrictions, and also by open relay testing
5204 programs. Unless you really need them it is safest to reject these characters
5205 at this early stage. This configuration is heavy-handed in rejecting these
5206 characters for all messages it accepts from remote hosts. This is a deliberate
5207 policy of being as safe as possible.
5209 The first rule above is stricter, and is applied to messages that are addressed
5210 to one of the local domains handled by this host. This is implemented by the
5211 first condition, which restricts it to domains that are listed in the
5212 \*local@_domains*\ domain list. The `+' character is used to indicate a
5213 reference to a named list. In this configuration, there is just one domain in
5214 \*local@_domains*\, but in general there may be many.
5216 The second condition on the first statement uses two regular expressions to
5217 block local parts that begin with a dot or contain `@@', `%', `!', `/', or `|'.
5218 If you have local accounts that include these characters, you will have to
5221 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5222 allows them because they have been encountered in practice. (Consider local
5223 parts constructed as `first-initial.second-initial.family-name' when applied to
5224 someone like the author of Exim, who has no second initial.) However, a local
5225 part starting with a dot or containing `/../' can cause trouble if it is used
5226 as part of a file name (for example, for a mailing list). This is also true for
5227 local parts that contain slashes. A pipe symbol can also be troublesome if the
5228 local part is incorporated unthinkingly into a shell command line.
5230 The second rule above applies to all other domains, and is less strict. This
5231 allows your own users to send outgoing messages to sites that use slashes
5232 and vertical bars in their local parts. It blocks local parts that begin
5233 with a dot, slash, or vertical bar, but allows these characters within the
5234 local part. However, the sequence `/../' is barred. The use of `@@', `%', and
5235 `!' is blocked, as before. The motivation here is to prevent your users (or
5236 your users' viruses) from mounting certain kinds of attack on remote sites.
5239 accept local_parts = postmaster
5240 domains = +local_domains
5242 This statement, which has two conditions, accepts an incoming address if the
5243 local part is \*postmaster*\ and the domain is one of those listed in the
5244 \*local@_domains*\ domain list. The `+' character is used to indicate a
5245 reference to a named list. In this configuration, there is just one domain in
5246 \*local@_domains*\, but in general there may be many.
5248 The presence of this statement means that mail to postmaster is never blocked
5249 by any of the subsequent tests. This can be helpful while sorting out problems
5250 in cases where the subsequent tests are incorrectly denying access.
5252 require verify = sender
5254 This statement requires the sender address to be verified before any subsequent
5255 ACL statement can be used. If verification fails, the incoming recipient
5256 address is refused. Verification consists of trying to route the address, to
5259 message could be delivered to it. In the case of remote addresses, basic
5260 verification checks only the domain, but \*callouts*\ can be used for more
5261 verification if required. Section ~~SECTaddressverification discusses the
5262 details of address verification.
5265 # deny message = rejected because $sender_host_address is \
5266 # in a black list at $dnslist_domain\n\
5268 # dnslists = black.list.example
5270 # warn message = X-Warning: $sender_host_address is \
5271 # in a black list at $dnslist_domain
5272 # log_message = found in $dnslist_domain
5273 # dnslists = black.list.example
5275 These commented-out lines are examples of how you could configure Exim to check
5276 sending hosts against a DNS black list. The first statement rejects messages
5277 from blacklisted hosts, whereas the second merely inserts a warning header
5281 accept domains = +local_domains
5283 message = unknown user
5286 This statement accepts the incoming recipient address if its domain is one of
5287 the local domains, but only if the address can be verified. Verification of
5288 local addresses normally checks both the local part and the domain. The
5289 \endpass\ line needs some explanation: if the condition above \endpass\ fails,
5290 that is, if the address is not in a local domain, control is passed to the next
5291 ACL statement. However, if the condition below \endpass\ fails, that is, if a
5292 recipient in a local domain cannot be verified, access is denied and the
5293 recipient is rejected.
5294 .index customizing||ACL failure message
5295 The \message\ modifier provides a customized error message for the failure.
5297 accept domains = +relay_to_domains
5299 message = unrouteable address
5302 This statement accepts the incoming recipient address if its domain is one of
5303 the domains for which this host is a relay, but again, only if the address can
5306 accept hosts = +relay_from_hosts
5308 Control reaches this statement only if the recipient's domain is neither a
5309 local domain, nor a relay domain. The statement accepts the address if the
5310 message is coming from one of the hosts that are defined as being allowed to
5311 relay through this host. Recipient verification is omitted here, because in
5312 many cases the clients are dumb MUAs that do not cope well with SMTP error
5313 responses. If you are actually relaying out from MTAs, you should probably add
5314 recipient verification here.
5316 accept authenticated = *
5318 Control reaches here for attempts to relay to arbitrary domains from arbitrary
5319 hosts. The statement accepts the address only if the client host has
5320 authenticated itself. The default configuration does not define any
5321 authenticators, which means that no client can in fact authenticate. You will
5322 need to add authenticator definitions if you want to make use of this ACL
5325 deny message = relay not permitted
5327 The final statement denies access, giving a specific error message. Reaching
5328 the end of the ACL also causes access to be denied, but with the generic
5329 message `administrative prohibition'.
5332 .section Router configuration
5333 .index default||routers
5334 .index routers||default
5335 The router configuration comes next in the default configuration, introduced
5340 Routers are the modules in Exim that make decisions about where to send
5341 messages. An address is passed to each router in turn, until it is either
5342 accepted, or failed. This means that the order in which you define the routers
5343 matters. Each router is fully described in its own chapter later in this
5344 manual. Here we give only brief overviews.
5346 .index domain literal||default router
5349 # driver = ipliteral
5350 # domains = !+local_domains
5351 # transport = remote_smtp
5353 This router is commented out because the majority of sites do not want to
5354 support domain literal addresses (those of the form \*user@@[10.9.8.7]*\). If
5355 you uncomment this router, you also need to uncomment the setting of
5356 \allow@_domain@_literals\ in the main part of the configuration.
5361 domains = ! +local_domains
5362 transport = remote_smtp
5364 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5368 The first uncommented router handles addresses that do not involve any local
5369 domains. This is specified by the line
5371 domains = ! +local_domains
5373 The \domains\ option lists the domains to which this router applies, but the
5374 exclamation mark is a negation sign, so the router is used only for domains
5375 that are not in the domain list called \*local@_domains*\ (which was defined at
5376 the start of the configuration). The plus sign before \*local@_domains*\
5377 indicates that it is referring to a named list. Addresses in other domains are
5378 passed on to the following routers.
5380 The name of the router driver is \%dnslookup%\,
5381 and is specified by the \driver\ option. Do not be confused by the fact that
5382 the name of this router instance is the same as the name of the driver. The
5383 instance name is arbitrary, but the name set in the \driver\ option must be one
5384 of the driver modules that is in the Exim binary.
5386 The \%dnslookup%\ router routes addresses by looking up their domains in the
5387 DNS in order to obtain a list of hosts to which the address is routed. If the
5388 router succeeds, the address is queued for the \%remote@_smtp%\ transport, as
5389 specified by the \transport\ option. If the router does not find the domain in
5390 the DNS, no further routers are tried because of the \no@_more\ setting, so the
5391 address fails and is bounced.
5393 The \ignore@_target@_hosts\ option specifies a list of IP addresses that are to
5394 be entirely ignored. This option is present because a number of cases have been
5395 encountered where MX records in the DNS point to host names
5396 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5397 Completely ignoring these IP addresses causes Exim to fail to route the
5398 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5399 continue to try to deliver the message periodically until the address timed
5406 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5408 file_transport = address_file
5409 pipe_transport = address_pipe
5411 Control reaches this and subsequent routers only for addresses in the local
5412 domains. This router checks to see whether the local part is defined as an
5413 alias in the \(/etc/aliases)\ file, and if so, redirects it according to the
5414 data that it looks up from that file. If no data is found for the local part,
5415 the value of the \data\ option is empty, causing the address to be passed to
5418 \(/etc/aliases)\ is a conventional name for the system aliases file that is
5419 often used. That is why it is referenced by from the default configuration
5420 file. However, you can change this by setting \\SYSTEM@_ALIASES@_FILE\\ in
5421 \(Local/Makefile)\ before building Exim.
5427 file = $home/.forward
5432 file_transport = address_file
5433 pipe_transport = address_pipe
5434 reply_transport = address_reply
5436 This is the most complicated router in the default configuration. It is another
5437 redirection router, but this time it is looking for forwarding data set up by
5438 individual users. The \check@_local@_user\ setting means that the first thing it
5439 does is to check that the local part of the address is the login name of a
5440 local user. If it is not, the router is skipped. When a local user is found,
5441 the file called \(.forward)\ in the user's home directory is consulted. If it
5442 does not exist, or is empty, the router declines. Otherwise, the contents of
5443 \(.forward)\ are interpreted as redirection data (see chapter ~~CHAPredirect
5446 .index Sieve filter||enabling in default router
5447 Traditional \(.forward)\ files contain just a list of addresses, pipes, or
5448 files. Exim supports this by default. However, if \allow@_filter\ is set (it is
5449 commented out by default), the contents of the file are interpreted as a set of
5450 Exim or Sieve filtering instructions, provided the file begins with `@#Exim
5451 filter' or `@#Sieve filter', respectively. User filtering is discussed in the
5452 separate document entitled \*Exim's interfaces to mail filtering*\.
5454 The \no@_verify\ and \no@_expn\ options mean that this router is skipped when
5455 verifying addresses, or when running as a consequence of an SMTP \\EXPN\\
5457 There are two reasons for doing this:
5459 Whether or not a local user has a \(.forward)\ file is not really relevant when
5460 checking an address for validity; it makes sense not to waste resources doing
5463 More importantly, when Exim is verifying addresses or handling an \\EXPN\\
5464 command during an SMTP session, it is running as the Exim user, not as root.
5465 The group is the Exim group, and no additional groups are set up.
5466 It may therefore not be possible for Exim to read users' \(.forward)\ files at
5470 The setting of \check@_ancestor\ prevents the router from generating a new
5471 address that is the same as any previous address that was redirected. (This
5472 works round a problem concerning a bad interaction between aliasing and
5473 forwarding -- see section ~~SECTredlocmai).
5475 The final three option settings specify the transports that are to be used when
5476 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5477 auto-reply, respectively. For example, if a \(.forward)\ file contains
5479 a.nother@elsewhere.example, /home/spqr/archive
5481 the delivery to \(/home/spqr/archive)\ is done by running the \address@_file\
5487 transport = local_delivery
5489 The final router sets up delivery into local mailboxes, provided that the local
5490 part is the name of a local login, by accepting the address and queuing it for
5491 the \%local@_delivery%\ transport. Otherwise, we have reached the end of the
5492 routers, so the address is bounced.
5495 .section Transport configuration
5496 .index default||transports
5497 .index transports||default
5498 Transports define mechanisms for actually delivering messages. They operate
5499 only when referenced from routers, so the order in which they are defined does
5500 not matter. The transports section of the configuration starts with
5504 One remote transport and four local transports are defined.
5509 This transport is used for delivering messages over SMTP connections. All its
5510 options are defaulted. The list of remote hosts comes from the router.
5514 file = /var/mail/$local_part
5521 This \%appendfile%\ transport is used for local delivery to user mailboxes in
5522 traditional BSD mailbox format. By default it runs under the uid and gid of the
5523 local user, which requires the sticky bit to be set on the \(/var/mail)\
5524 directory. Some systems use the alternative approach of running mail deliveries
5525 under a particular group instead of using the sticky bit. The commented options
5526 show how this can be done.
5528 Exim adds three headers to the message as it delivers it: ::Delivery-date::,
5529 ::Envelope-to:: and ::Return-path::. This action is requested by the three
5530 similarly-named options above.
5536 This transport is used for handling deliveries to pipes that are generated by
5537 redirection (aliasing or users' \(.forward)\ files). The \return@_output\
5538 option specifies that any output generated by the pipe is to be returned to the
5547 This transport is used for handling deliveries to files that are generated by
5548 redirection. The name of the file is not specified in this instance of
5549 \%appendfile%\, because it comes from the \%redirect%\ router.
5554 This transport is used for handling automatic replies generated by users'
5558 .section Default retry rule
5559 .index retry||default rule
5560 .index default||retry rule
5561 The retry section of the configuration file contains rules which affect the way
5562 Exim retries deliveries that cannot be completed at the first attempt. It is
5563 introduced by the line
5567 In the default configuration, there is just one rule, which applies to all
5570 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5572 This causes any temporarily failing address to be retried every 15 minutes for
5573 2 hours, then at intervals starting at one hour and increasing by a factor of
5574 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5575 is not delivered after 4 days of failure, it is bounced.
5578 .section Rewriting configuration
5579 The rewriting section of the configuration, introduced by
5583 contains rules for rewriting addresses in messages as they arrive. There are no
5584 rewriting rules in the default configuration file.
5587 .section Authenticators configuration
5588 .index \\AUTH\\||configuration
5589 The authenticators section of the configuration, introduced by
5591 begin authenticators
5593 defines mechanisms for the use of the SMTP \\AUTH\\ command. No authenticators
5594 are specified in the default configuration file.
5602 . ============================================================================
5603 .chapter Regular expressions
5604 .set runningfoot "regular expressions"
5605 .rset CHAPregexp ~~chapter
5607 .index regular expressions||library
5609 Exim supports the use of regular expressions in many of its options. It
5610 uses the PCRE regular expression library; this provides regular expression
5611 matching that is compatible with Perl 5. The syntax and semantics of
5612 regular expressions is discussed in many Perl reference books, and also in
5615 [(A HREF="http://www.oreilly.com/catalog/regex/")]
5617 $it{Mastering Regular Expressions}
5621 (O'Reilly, ISBN 0-596-00289-0).
5623 The documentation for the syntax and semantics of the regular expressions that
5624 are supported by PCRE is included in plain text in the file
5625 \(doc/pcrepattern.txt)\ in the Exim distribution, and also in the HTML
5626 tarbundle of Exim documentation, and as an appendix to the
5628 [(A HREF="http://www.uit.co.uk/exim-book/")]
5634 It describes in detail the features of the regular expressions that PCRE
5635 supports, so no further description is included here. The PCRE functions are
5636 called from Exim using the default option settings (that is, with no PCRE
5637 options set), except that the \\PCRE@_CASELESS\\ option is set when the
5638 matching is required to be case-insensitive.
5640 In most cases, when a regular expression is required in an Exim configuration,
5641 it has to start with a circumflex, in order to distinguish it from plain text
5642 or an `ends with' wildcard. In this example of a configuration setting, the
5643 second item in the colon-separated list is a regular expression.
5645 domains = a.b.c : ^\\d{3} : *.y.z : ...
5647 The doubling of the backslash is required because of string expansion that
5648 precedes interpretation -- see section ~~SECTlittext for more discussion of
5649 this issue, and a way of avoiding the need for doubling backslashes. The
5650 regular expression that is eventually used in this example contains just one
5651 backslash. The circumflex is included in the regular expression, and has the
5652 normal effect of `anchoring' it to the start of the string that is being
5655 There are, however, two cases where a circumflex is not required for the
5656 recognition of a regular expression: these are the \match\ condition in a
5657 string expansion, and the \matches\ condition in an Exim filter file. In these
5658 cases, the relevant string is always treated as a regular expression; if it
5659 does not start with a circumflex, the expression is not anchored, and can match
5660 anywhere in the subject string.
5662 In all cases, if you want a regular expression to match at the end of a string,
5663 you must code the @$ metacharacter to indicate this. For example:
5665 domains = ^\\d{3}\\.example
5667 matches the domain \*123.example*\, but it also matches \*123.example.com*\.
5670 domains = ^\\d{3}\\.example\$
5672 if you want \*example*\ to be the top-level domain. (The backslash before the
5673 @$ is another artefact of string expansion.)
5676 .section Testing regular expressions
5677 .index testing||regular expressions
5678 .index regular expressions||testing
5680 A program called \*pcretest*\ forms part of the PCRE distribution and is built
5681 with PCRE during the process of building Exim. It is primarily intended for
5682 testing PCRE itself, but it can also be used for experimenting with regular
5683 expressions. After building Exim, the binary can be found in the build
5684 directory (it is not installed anywhere automatically). There is documentation
5685 of various options in \(doc/pcretest.txt)\, but for simple testing, none are
5686 needed. This is the output of a sample run of \*pcretest*\:
5688 re> $cb{/^([^@@]+)@@.+@\.(ac|edu)@\.(?!kr)[a-z]@{2@}@$/}
5689 data> $cb{x@@y.ac.uk}
5693 data> $cb{x@@y.ac.kr}
5695 data> $cb{x@@y.edu.com}
5697 data> $cb{x@@y.edu.co}
5703 Input typed by the user is shown in bold face.
5705 After the `re>' prompt, a regular expression enclosed in delimiters is
5706 expected. If this compiles without error, `data>' prompts are given for strings
5707 against which the expression is matched. An empty data line causes a new
5708 regular expression to be read. If the match is successful, the captured
5709 substring values (that is, what would be in the variables \$0$\, \$1$\, \$2$\,
5710 etc.) are shown. The above example tests for an email address whose domain ends
5711 with either `ac' or `edu' followed by a two-character top-level domain that is
5712 not `kr'. The local part is captured in \$1$\ and the `ac' or `edu' in \$2$\.
5723 . ============================================================================
5724 .chapter File and database lookups
5725 .set runningfoot "file/database lookups"
5726 .rset CHAPfdlookup "~~chapter"
5728 .index database lookups
5729 .index lookup||description of
5730 Exim can be configured to look up data in files or databases as it processes
5731 messages. Two different kinds of syntax are used:
5733 A string that is to be expanded may contain explicit lookup requests. These
5734 cause parts of the string to be replaced by data that is obtained from the
5737 Lists of domains, hosts, and email addresses can contain lookup requests as a
5738 way of avoiding excessively long linear lists. In this case, the data that is
5739 returned by the lookup is often (but not always) discarded; whether the lookup
5740 succeeds or fails is what really counts. These kinds of list are described in
5741 chapter ~~CHAPdomhosaddlists.
5743 It is easy to confuse the two different kinds of lookup, especially as the
5744 lists that may contain the second kind are always expanded before being
5745 processed as lists. Therefore, they may also contain lookups of the first kind.
5746 Be careful to distinguish between the following two examples:
5748 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
5749 domains = lsearch;/some/file
5751 The first uses a string expansion, the result of which must be a domain list.
5752 String expansions are described in detail in chapter ~~CHAPexpand. The
5753 expansion takes place first, and the file that is searched could contain lines
5756 192.168.3.4: domain1 : domain2 : ...
5757 192.168.1.9: domain3 : domain4 : ...
5759 Thus, the result of the expansion is a list of domains (and possibly other
5760 types of item that are allowed in domain lists).
5762 In the second case, the lookup is a single item in a domain list. It causes
5763 Exim to use a lookup to see if the domain that is being processed can be found
5764 in the file. The file could contains lines like this:
5769 Any data that follows the keys is not relevant when checking that the domain
5770 matches the list item.
5772 It is possible to use both kinds of lookup at once. Consider a file containing
5775 192.168.5.6: lsearch;/another/file
5777 If the value of \$sender@_host@_address$\ is 192.168.5.6, expansion of the
5778 first \domains\ setting above generates the second setting, which therefore
5779 causes a second lookup to occur.
5781 The rest of this chapter describes the different lookup types that are
5782 available. Any of them can be used in either of the circumstances described
5783 above. The syntax requirements for the two cases are described in chapters
5784 ~~CHAPexpand and ~~CHAPdomhosaddlists, respectively.
5786 .section Lookup types
5787 .index lookup||types of
5788 .index single-key lookup||definition of
5789 Two different styles of data lookup are implemented:
5791 The \*single-key*\ style requires the specification of a file in which to look,
5792 and a single key to search for.
5794 The key must be a non-empty string for the lookup to succeed.
5796 The lookup type determines how the file is searched.
5798 .index query-style lookup||definition of
5799 The \*query*\ style accepts a generalized database query.
5800 No particular key value is assumed by Exim for query-style lookups. You can
5801 use whichever Exim variable(s) you need to construct the database query.
5803 The code for each lookup type is in a separate source file that is included in
5804 the binary of Exim only if the corresponding compile-time option is set. The
5805 default settings in \(src/EDITME)\ are:
5810 which means that only linear searching and DBM lookups are included by default.
5811 For some types of lookup (e.g. SQL databases), you need to install appropriate
5812 libraries and header files before building Exim.
5816 .section Single-key lookup types
5817 .rset SECTsinglekeylookups "~~chapter.~~section"
5818 .index lookup||single-key types
5819 .index single-key lookup||list of types
5820 The following single-key lookup types are implemented:
5822 .index cdb||description of
5824 .index binary zero||in lookup key
5825 \%cdb%\: The given file is searched as a Constant DataBase file, using the key
5826 string without a terminating binary zero. The cdb format is designed for
5827 indexed files that are read frequently and never updated, except by total
5828 re-creation. As such, it is particulary suitable for large files containing
5829 aliases or other indexed data referenced by an MTA. Information about cdb can
5830 be found in several places:
5832 \?http://www.pobox.com/@~djb/cdb.html?\
5833 \?ftp://ftp.corpit.ru/pub/tinycdb/?\
5834 \?http://packages.debian.org/stable/utils/freecdb.html?\
5836 A cdb distribution is not needed in order to build Exim with cdb support,
5837 because the code for reading cdb files is included directly in Exim itself.
5838 However, no means of building or testing cdb files is provided with Exim, so
5839 you need to obtain a cdb distribution in order to do this.
5841 .index DBM||lookup type
5843 .index binary zero||in lookup key
5844 \%dbm%\: Calls to DBM library functions are used to extract data from the given
5845 DBM file by looking up the record with the given key. A terminating binary
5846 zero is included in the key that is passed to the DBM library. See section
5847 ~~SECTdb for a discussion of DBM libraries.
5848 .index Berkeley DB library||file format
5849 For all versions of Berkeley DB, Exim uses the \\DB@_HASH\\ style of database
5850 when building DBM files using the \exim@_dbmbuild\ utility. However, when using
5851 Berkeley DB versions 3 or 4, it opens existing databases for reading with the
5852 \\DB@_UNKNOWN\\ option. This enables it to handle any of the types of database
5853 that the library supports, and can be useful for accessing DBM files created by
5854 other applications. (For earlier DB versions, \\DB@_HASH\\ is always used.)
5857 .index lookup||dbmnz
5858 .index lookup||dbm, terminating zero
5859 .index binary zero||in lookup key
5861 .index \(/etc/userdbshadow.dat)\
5862 .index dmbnz lookup type
5863 \%dbmnz%\: This is the same as \%dbm%\, except that a terminating binary zero
5864 is not included in the key that is passed to the DBM library. You may need this
5865 if you want to look up data in files that are created by or shared with some
5866 other application that does not use terminating zeros. For example, you need to
5867 use \%dbmnz%\ rather than \%dbm%\ if you want to authenticate incoming SMTP
5868 calls using the passwords from Courier's \(/etc/userdbshadow.dat)\ file. Exim's
5869 utility program for creating DBM files (\*exim@_dbmbuild*\) includes the zeros
5870 by default, but has an option to omit them (see section ~~SECTdbmbuild).
5872 .index lookup||dsearch
5873 .index dsearch lookup type
5874 \%dsearch%\: The given file must be a directory; this is searched for a file
5875 whose name is the key. The key may not contain any forward slash characters.
5876 The result of a successful lookup is the name of the file. An example of how
5877 this lookup can be used to support virtual domains is given in section
5878 ~~SECTvirtualdomains.
5880 .index lookup||iplsearch
5881 .index iplsearch lookup type
5882 \%iplsearch%\: The given file is a text file containing keys and data. A key is
5883 terminated by a colon or white space or the end of the line. The keys in the
5884 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
5885 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
5886 being interpreted as a key terminator. For example:
5888 1.2.3.4: data for 1.2.3.4
5889 192.168.0.0/16 data for 192.168.0.0/16
5890 "abcd::cdab": data for abcd::cdab
5891 "abcd:abcd::/32" data for abcd:abcd::/32
5893 The key for an \%iplsearch%\ lookup must be an IP address (without a mask). The
5894 file is searched linearly, using the CIDR masks where present, until a matching
5895 key is found. The first key that matches is used; there is no attempt to find a
5896 `best' match. Apart from the way the keys are matched, the processing for
5897 \%iplsearch%\ is the same as for \%lsearch%\.
5899 \**Warning 1**\: Unlike most other single-key lookup types, a file of data for
5900 \%iplsearch%\ can \*not*\ be turned into a DBM or cdb file, because those
5901 lookup types support only literal keys.
5903 \**Warning 2**\: In a host list, you must always use \%net-iplsearch%\ so that
5904 the implicit key is the host's IP address rather than its name (see section
5905 ~~SECThoslispatsikey).
5908 .index linear search
5909 .index lookup||lsearch
5910 .index lsearch lookup type
5911 \%lsearch%\: The given file is a text file that is searched linearly for a
5912 line beginning with the search key, terminated by a colon or white space or the
5913 end of the line. The first occurrence that is found in the file is used. White
5914 space between the key and the colon is permitted. The remainder of the line,
5915 with leading and trailing white space removed, is the data. This can be
5916 continued onto subsequent lines by starting them with any amount of white
5917 space, but only a single space character is included in the data at such a
5918 junction. If the data begins with a colon, the key must be terminated by a
5923 Empty lines and lines beginning with @# are ignored, even if they occur in the
5924 middle of an item. This is the traditional textual format of alias files. Note
5925 that the keys in an \%lsearch%\ file are literal strings. There is no
5926 wildcarding of any kind.
5928 .index lookup||lsearch, colons in keys
5929 .index whitespace||in lsearch key
5930 In most \%lsearch%\ files, keys are not required to contain colons or @#
5931 characters, or whitespace. However, if you need this feature, it is available.
5932 If a key begins with a doublequote character, it is terminated only by a
5933 matching quote (or end of line), and the normal escaping rules apply to its
5934 contents (see section ~~SECTstrings). An optional colon is permitted after
5935 quoted keys (exactly as for unquoted keys). There is no special handling of
5936 quotes for the data part of an \%lsearch%\ line.
5938 .index NIS lookup type
5940 .index binary zero||in lookup key
5941 \%nis%\: The given file is the name of a NIS map, and a NIS lookup is done with
5942 the given key, without a terminating binary zero. There is a variant called
5943 \%nis0%\ which does include the terminating binary zero in the key. This is
5944 reportedly needed for Sun-style alias files. Exim does not recognize NIS
5945 aliases; the full map names must be used.
5947 .index wildlsearch lookup type
5948 .index lookup||wildlsearch
5949 .index nwildlsearch lookup type
5950 .index lookup||nwildlsearch
5951 \%wildlsearch%\ or \%nwildlsearch%\: These search a file linearly, like
5952 \%lsearch%\, but instead of being interpreted as a literal string, each key may
5953 be wildcarded. The difference between these two lookup types is that for
5954 \%wildlsearch%\, each key in the file is string-expanded before being used,
5955 whereas for \%nwildlsearch%\, no expansion takes place.
5957 Like \%lsearch%\, the testing is done case-insensitively. The following forms
5958 of wildcard are recognized:
5960 The string may begin with an asterisk to mean `begins with'. For example:
5962 *.a.b.c data for anything.a.b.c
5963 *fish data for anythingfish
5966 The string may begin with a circumflex to indicate a regular expression. For
5967 example, for \%wildlsearch%\:
5969 ^\N\d+\.a\.b\N data for <digits>.a.b
5971 Note the use of \"@\N"\ to disable expansion of the contents of the regular
5972 expression. If you are using \%nwildlsearch%\, where the keys are not
5973 string-expanded, the equivalent entry is:
5975 ^\d+\.a\.b data for <digits>.a.b
5978 If the regular expression contains white space or colon characters, you must
5979 either quote it (see \%lsearch%\ above), or represent these characters in other
5980 ways. For example, \"@\s"\ can be used for white space and \"@\x3A"\ for a
5981 colon. This may be easier than quoting, because if you quote, you have to
5982 escape all the backslashes inside the quotes.
5984 Although I cannot see it being of much use, the general matching function
5985 that is used to implement
5987 means that the string may begin with a lookup name terminated by a semicolon,
5988 and followed by lookup data. For example:
5990 cdb;/some/file data for keys that match the file
5992 The data that is obtained from the nested lookup is discarded.
5994 Keys that do not match any of these patterns are interpreted literally. The
5995 continuation rules for the data are the same as for \%lsearch%\, and keys may
5996 be followed by optional colons.
5998 \**Warning**\: Unlike most other single-key lookup types, a file of data for
5999 \%(n)wildlsearch%\ can \*not*\ be turned into a DBM or cdb file, because those
6000 lookup types support only literal keys.
6003 .section Query-style lookup types
6004 .index lookup||query-style types
6005 .index query-style lookup||list of types
6006 The supported query-style lookup types are listed below. Further details about
6007 many of them are given in later sections.
6009 .index DNS||as a lookup type
6011 \%dnsdb%\: This does a DNS search for
6013 one or more records whose domain names are given in the supplied query. The
6014 resulting data is the contents of the records.
6016 See section ~~SECTdnsdb.
6018 .index Interbase lookup type
6019 .index lookup||Interbase
6020 \%ibase%\: This does a lookup in an Interbase database.
6022 .index LDAP||lookup type
6024 \%ldap%\: This does an LDAP lookup using a query in the form of a URL, and
6025 returns attributes from a single entry. There is a variant called \%ldapm%\
6026 that permits values from multiple entries to be returned. A third variant
6027 called \%ldapdn%\ returns the Distinguished Name of a single entry instead of
6028 any attribute values. See section ~~SECTldap.
6030 .index MySQL||lookup type
6031 .index lookup||MySQL
6032 \%mysql%\: The format of the query is an SQL statement that is passed to a MySQL
6033 database. See section ~~SECTsql.
6035 .index NIS@+ lookup type
6037 \%nisplus%\: This does a NIS+ lookup using a query that can specify the name of
6038 the field to be returned. See section ~~SECTnisplus.
6040 .index Oracle||lookup type
6041 .index lookup||Oracle
6042 \%oracle%\: The format of the query is an SQL statement that is passed to an
6043 Oracle database. See section ~~SECTsql.
6045 .index lookup||passwd
6046 .index passwd lookup type
6047 .index \(/etc/passwd)\
6048 \%passwd%\ is a query-style lookup with queries that are just user names. The
6049 lookup calls \*getpwnam()*\ to interrogate the system password data, and on
6050 success, the result string is the same as you would get from an \%lsearch%\
6051 lookup on a traditional \(/etc/passwd file)\, though with \"*"\ for the
6052 password value. For example:
6054 *:42:42:King Rat:/home/kr:/bin/bash
6057 .index PostgreSQL lookup type
6058 .index lookup||PostgreSQL
6059 \%pgsql%\: The format of the query is an SQL statement that is passed to a
6060 PostgreSQL database. See section ~~SECTsql.
6062 \%testdb%\: This is a lookup type that is used for testing Exim. It is
6063 not likely to be useful in normal operation.
6065 .index whoson lookup type
6066 .index lookup||whoson
6067 \%whoson%\: \*Whoson*\ (\?http://whoson.sourceforge.net?\) is a proposed
6068 Internet protocol that allows Internet server programs to check whether a
6069 particular (dynamically allocated) IP address is currently allocated to a known
6070 (trusted) user and, optionally, to obtain the identity of the said user. In
6071 Exim, this can be used to implement `POP before SMTP' checking using ACL
6074 require condition = \
6075 ${lookup whoson {$sender_host_address}{yes}{no}}
6077 The query consists of a single IP address. The value returned is the name of
6078 the authenticated user.
6081 .section Temporary errors in lookups
6082 .index lookup||temporary error in
6083 Lookup functions can return temporary error codes if the lookup cannot be
6084 completed. For example, a NIS or LDAP database might be unavailable. For this
6085 reason, it is not advisable to use a lookup that might do this for critical
6086 options such as a list of local domains.
6088 When a lookup cannot be completed in a router or transport, delivery
6089 of the message (to the relevant address) is deferred, as for any other
6090 temporary error. In other circumstances Exim may assume the lookup has failed,
6091 or may give up altogether.
6094 .section Default values in single-key lookups
6095 .rset SECTdefaultvaluelookups "~~chapter.~~section"
6096 .index wildcard lookups
6097 .index lookup||default values
6098 .index lookup||wildcard
6099 .index lookup||$*$ added to type
6100 .index default||in single-key lookups
6101 In this context, a `default value' is a value specified by the administrator
6102 that is to be used if a lookup fails.
6104 If `$*$' is added to a single-key lookup type (for example, \lsearch$*$\) and
6105 the initial lookup fails, the key `$*$' is looked up in the file to provide
6106 a default value. See also the section on partial matching below.
6108 .index @*@@ with single-key lookup
6109 .index lookup||$*$@@ added to type
6110 .index alias file||per-domain default
6111 Alternatively, if `$*$@@' is added to a single-key lookup type (for example
6112 \dbm$*$@@\) then, if the initial lookup fails and the key contains an @@
6113 character, a second lookup is done with everything before the last @@ replaced
6114 by $*$. This makes it possible to provide per-domain defaults in alias files
6115 that include the domains in the keys. If the second lookup fails (or doesn't
6116 take place because there is no @@ in the key), `$*$' is looked up.
6117 For example, a \%redirect%\ router might contain:
6119 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mixed-aliases}}
6121 Suppose the address that is being processed is \*jane@@eyre.example*\. Exim
6122 looks up these keys, in this order:
6128 The data is taken from whichever key it finds first. \**Note**\: in an
6129 \%lsearch%\ file, this does not mean the first of these keys in the file. A
6130 complete scan is done for each key, and only if it is not found at all does
6131 Exim move on to try the next key.
6134 .section Partial matching in single-key lookups
6135 .rset SECTpartiallookup "~~chapter.~~section"
6136 .index partial matching
6137 .index wildcard lookups
6138 .index lookup||partial matching
6139 .index lookup||wildcard
6140 .index asterisk||in search type
6141 The normal operation of a single-key lookup is to search the file for an exact
6142 match with the given key. However, in a number of situations where domains are
6143 being looked up, it is useful to be able to do partial matching. In this case,
6144 information in the file that has a key starting with `$*$.' is matched by any
6145 domain that ends with the components that follow the full stop. For example, if
6146 a key in a DBM file is
6148 *.dates.fict.example
6150 then when partial matching is enabled this is matched by (amongst others)
6151 \*2001.dates.fict.example*\ and \*1984.dates.fict.example*\. It is also matched
6152 by \*dates.fict.example*\, if that does not appear as a separate key in the
6155 \**Note**\: Partial matching is not available for query-style lookups. It is
6156 also not available for any lookup items in address lists (see section
6159 Partial matching is implemented by doing a series of separate lookups using
6160 keys constructed by modifying the original subject key. This means that it can
6161 be used with any of the single-key lookup types, provided that
6162 partial matching keys
6163 beginning with a special prefix (default `$*$.') are included in the data file.
6164 Keys in the file that do not begin with the prefix are matched only by
6165 unmodified subject keys when partial matching is in use.
6167 Partial matching is requested by adding the string `partial-' to the front of
6168 the name of a single-key lookup type, for example, \partial-dbm\. When this is
6169 done, the subject key is first looked up unmodified; if that fails, `$*$.'
6170 is added at the start of the subject key, and it is looked up again. If that
6171 fails, further lookups are tried with dot-separated components removed
6172 from the start of the subject key, one-by-one, and `$*$.' added on the front of
6175 A minimum number of two non-$*$ components are required. This can be adjusted
6176 by including a number before the hyphen in the search type. For example,
6177 \partial3-lsearch\ specifies a minimum of three non-$*$ components in the
6178 modified keys. Omitting the number is equivalent to `partial2-'. If the subject
6179 key is \*2250.dates.fict.example*\ then the following keys are looked up when
6180 the minimum number of non-$*$ components is two:
6182 2250.dates.fict.example
6183 *.2250.dates.fict.example
6184 *.dates.fict.example
6187 As soon as one key in the sequence is successfully looked up, the lookup
6190 .index lookup||partial matching, changing prefix
6191 .index prefix||for partial matching
6192 The use of `$*$.' as the partial matching prefix is a default that can be
6193 changed. The motivation for this feature is to allow Exim to operate with file
6194 formats that are used by other MTAs. A different prefix can be supplied in
6195 parentheses instead of the hyphen after `partial'. For example:
6197 domains = partial(.)lsearch;/some/file
6199 In this example, if the domain is \*a.b.c*\, the sequence of lookups is
6200 \"a.b.c"\, \".a.b.c"\, and \".b.c"\ (the default minimum of 2 non-wild
6201 components is unchanged). The prefix may consist of any punctuation characters
6202 other than a closing parenthesis. It may be empty, for example:
6204 domains = partial1()cdb;/some/file
6206 For this example, if the domain is \*a.b.c*\, the sequence of lookups is
6207 \"a.b.c"\, \"b.c"\, and \"c"\.
6209 If `partial0' is specified, what happens at the end (when the lookup with just
6210 one non-wild component has failed, and the original key is shortened right down
6211 to the null string) depends on the prefix:
6213 If the prefix has zero length, the whole lookup fails.
6215 If the prefix has length 1, a lookup for just the prefix is done. For
6216 example, the final lookup for `partial0(.)' is for \"."\ alone.
6218 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6219 remainder is looked up. With the default prefix, therefore, the final lookup is
6220 for `$*$' on its own.
6222 Otherwise, the whole prefix is looked up.
6225 If the search type ends in `$*$' or `$*$@@' (see section
6226 ~~SECTdefaultvaluelookups above), the search for an ultimate default that this
6227 implies happens after all partial lookups have failed. If `partial0' is
6228 specified, adding `$*$' to the search type has no effect with the default
6229 prefix, because the `$*$' key is already included in the sequence of partial
6230 lookups. However, there might be a use for lookup types such as
6231 `partial0(.)lsearch$*$'.
6233 The use of `$*$' in lookup partial matching differs from its use as a wildcard
6234 in domain lists and the like. Partial matching works only in terms of
6235 dot-separated components; a key such as \"*fict.example"\
6236 in a database file is useless, because the asterisk in a partial matching
6237 subject key is always followed by a dot.
6241 .section Lookup caching
6242 .index lookup||caching
6243 .index caching||lookup data
6245 Exim caches all lookup results in order to avoid needless repetition of
6246 lookups. However, because (apart from the daemon) Exim operates as a collection
6247 of independent, short-lived processes, this caching applies only within a
6248 single Exim process. There is no inter-process caching facility.
6250 For single-key lookups, Exim keeps the relevant files open in case there is
6251 another lookup that needs them. In some types of configuration this can lead to
6252 many files being kept open for messages with many recipients. To avoid hitting
6253 the operating system limit on the number of simultaneously open files, Exim
6254 closes the least recently used file when it needs to open more files than its
6255 own internal limit, which can be changed via the \lookup@_open@_max\ option.
6257 The single-key lookup files are closed and the lookup caches are flushed at
6258 strategic points during delivery -- for example, after all routing is complete.
6262 .section Quoting lookup data
6263 .index lookup||quoting
6264 .index quoting||in lookups
6265 When data from an incoming message is included in a query-style lookup, there
6266 is the possibility of special characters in the data messing up the syntax of
6267 the query. For example, a NIS+ query that contains
6271 will be broken if the local part happens to contain a closing square bracket.
6272 For NIS+, data can be enclosed in double quotes like this:
6274 [name="$local_part"]
6276 but this still leaves the problem of a double quote in the data. The rule for
6277 NIS+ is that double quotes must be doubled. Other lookup types have different
6278 rules, and to cope with the differing requirements, an expansion operator
6279 of the following form is provided:
6281 @$@{quote@_<<lookup-type>>:<<string>>@}
6283 For example, the safest way to write the NIS+ query is
6285 [name="${quote_nisplus:$local_part}"]
6287 See chapter ~~CHAPexpand for full coverage of string expansions. The quote
6288 operator can be used for all lookup types, but has no effect for single-key
6289 lookups, since no quoting is ever needed in their key strings.
6293 .section More about dnsdb
6294 .rset SECTdnsdb "~~chapter.~~section"
6296 .index lookup||dnsdb
6297 .index DNS||as a lookup type
6298 The \%dnsdb%\ lookup type uses the DNS as its database. A simple query consists
6299 of a record type and a domain name, separated by an equals sign. For example,
6300 an expansion string could contain:
6302 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6304 The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and,
6305 when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6306 configured). If no type is given, TXT is assumed. When the type is PTR,
6308 the data can be an IP address, written as normal; inversion and the addition of
6309 \in-addr.arpa\ or \ip6.arpa\ happens automatically. For example:
6311 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6313 If the data for a PTR record is not a syntactically valid IP address, it is not
6314 altered and nothing is added.
6316 For any record type, if multiple records are found (or, for A6 lookups, if a
6317 single record leads to multiple addresses), the data is returned as a
6318 concatenation, with newline as the default separator. The order, of course,
6319 depends on the DNS resolver. You can specify a different separator character
6320 between multiple records by putting a right angle-bracket followed immediately
6321 by the new separator at the start of the query. For example:
6323 ${lookup dnsdb{>: a=host1.example}}
6325 It is permitted to specify a space as the separator character. Further
6326 whitespace is ignored.
6328 .index SRV record||in \%dnsdb%\ lookup
6329 For SRV records, the priority, weight, port, and host name are returned for
6330 each record, separated by spaces.
6332 .index MX record||in \%dnsdb%\ lookup
6333 For MX records, both the preference value and the host name are returned for
6334 each record, separated by a space. However, if you want only host names, you
6335 can use the pseudo-type MXH:
6337 ${lookup dnsdb{mxh=a.b.example}}
6339 In this case, the preference values are omitted.
6341 .index name server||for enclosing domain
6342 Another pseudo-type is ZNS (for `zone NS'). It performs a lookup for NS
6343 records on the given domain, but if none are found, it removes the first
6344 component of the domain name, and tries again. This process continues until NS
6345 records are found or there are no more components left (or there is a DNS
6346 error). In other words, it may return the name servers for a top-level domain,
6347 but it never returns the root name servers. If there are no NS records for the
6348 top-level domain, the lookup fails. Consider these examples:
6350 ${lookup dnsdb{zns=xxx.quercite.com}}
6351 ${lookup dnsdb{zns=xxx.edu}}
6353 Assuming that in each case there are no NS records for the full domain name,
6354 the first returns the name servers for \quercite.com\, and the second returns
6355 the name servers for \edu\.
6357 You should be careful about how you use this lookup because, unless the
6358 top-level domain does not exist, the lookup always returns some host names. The
6359 sort of use to which this might be put is for seeing if the name servers for a
6360 given domain are on a blacklist. You can probably assume that the name servers
6361 for the high-level domains such as \com\ or \co.uk\ are not going to be on such
6367 .section Multiple dnsdb lookups
6368 In the previous section, \%dnsdb%\ lookups for a single domain are described.
6369 However, you can specify a list of domains or IP addresses in a single
6370 \%dnsdb%\ lookup. The list is specified in the normal Exim way, with colon as
6371 the default separator, but with the ability to change this. For example:
6373 ${lookup dnsdb{one.domain.com:two.domain.com}}
6374 ${lookup dnsdb{a=one.host.com:two.host.com}}
6375 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6377 In order to retain backwards compatibility, there is one special case: if
6378 the lookup type is PTR and no change of separator is specified, Exim looks
6379 to see if the rest of the string is precisely one IPv6 address. In this
6380 case, it does not treat it as a list.
6382 The data from each lookup is concatenated, with newline separators by default,
6383 in the same way that multiple DNS records for a single item are handled. A
6384 different separator can be specified, as described above.
6386 The \%dnsdb%\ lookup fails only if all the DNS lookups fail. If there is a
6387 temporary DNS error for any of them, the behaviour is controlled by
6388 an optional keyword followed by a comma that may appear before the record
6389 type. The possible keywords are `defer@_strict', `defer@_never', and
6390 `defer@_lax'. With `strict' behaviour, any temporary DNS error causes the
6391 whole lookup to defer. With `never' behaviour, a temporary DNS error is
6392 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6393 With `lax' behaviour, all the queries are attempted, but a temporary DNS
6394 error causes the whole lookup to defer only if none of the other lookups
6395 succeed. The default is `lax', so the following lookups are equivalent:
6397 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6398 ${lookup dnsdb{a=one.host.com:two.host.com}}
6400 Thus, in the default case, as long as at least one of the DNS lookups
6401 yields some data, the lookup succeeds.
6405 .section More about LDAP
6406 .rset SECTldap "~~chapter.~~section"
6409 .index Solaris||LDAP
6410 The original LDAP implementation came from the University of Michigan; this has
6411 become `Open LDAP', and there are now two different releases. Another
6412 implementation comes from Netscape, and Solaris 7 and subsequent releases
6413 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6414 the lookup function level, their error handling is different. For this reason
6415 it is necessary to set a compile-time variable when building Exim with LDAP, to
6416 indicate which LDAP library is in use. One of the following should appear in
6417 your \(Local/Makefile)\:
6419 LDAP_LIB_TYPE=UMICHIGAN
6420 LDAP_LIB_TYPE=OPENLDAP1
6421 LDAP_LIB_TYPE=OPENLDAP2
6422 LDAP_LIB_TYPE=NETSCAPE
6423 LDAP_LIB_TYPE=SOLARIS
6425 If \\LDAP@_LIB@_TYPE\\ is not set, Exim assumes \"OPENLDAP1"\, which has the
6426 same interface as the University of Michigan version.
6428 There are three LDAP lookup types in Exim. These behave slightly differently in
6429 the way they handle the results of a query:
6431 \%ldap%\ requires the result to contain just one entry; if there are more, it
6434 \%ldapdn%\ also requires the result to contain just one entry, but it is the
6435 Distinguished Name that is returned rather than any attribute values.
6437 \%ldapm%\ permits the result to contain more than one entry; the attributes from
6438 all of them are returned.
6441 For \%ldap%\ and \%ldapm%\, if a query finds only entries with no attributes,
6442 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6443 the data returned by a successful lookup is described in the next section.
6444 First we explain how LDAP queries are coded.
6446 .section Format of LDAP queries
6447 .rset SECTforldaque "~~chapter.~~section"
6448 .index LDAP||query format
6449 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6450 the configuration of a \%redirect%\ router one might have this setting:
6452 data = ${lookup ldap \
6453 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6454 c=UK?mailbox?base?}}
6456 .index LDAP||with TLS
6457 The URL may begin with \"ldap"\ or \"ldaps"\ if your LDAP library supports
6458 secure (encrypted) LDAP connections. The second of these ensures that an
6459 encrypted TLS connection is used.
6461 .section LDAP quoting
6462 .index LDAP||quoting
6463 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6464 and the second because the LDAP query is represented as a URL. Furthermore,
6465 within an LDAP query, two different kinds of quoting are required. For this
6466 reason, there are two different LDAP-specific quoting operators.
6468 The \quote@_ldap\ operator is designed for use on strings that are part of
6469 filter specifications. Conceptually, it first does the following conversions on
6477 in accordance with RFC 2254. The resulting string is then quoted according
6478 to the rules for URLs, that is, all characters except
6482 are converted to their hex values, preceded by a percent sign. For example:
6484 ${quote_ldap: a(bc)*, a<yz>; }
6488 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6490 Removing the URL quoting, this is (with a leading and a trailing space):
6492 a\28bc\29\2A, a<yz>;
6495 The \quote@_ldap@_dn\ operator is designed for use on strings that are part of
6496 base DN specifications in queries. Conceptually, it first converts the string
6497 by inserting a backslash in front of any of the following characters:
6501 It also inserts a backslash before any leading spaces or @# characters, and
6502 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6503 is then quoted according to the rules for URLs. For example:
6505 ${quote_ldap_dn: a(bc)*, a<yz>; }
6509 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6511 Removing the URL quoting, this is (with a trailing space):
6513 \ a(bc)*\, a\<yz\>\;\
6515 There are some further comments about quoting in the section on LDAP
6516 authentication below.
6518 .section LDAP connections
6519 .index LDAP||connections
6520 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6521 is in use, via a Unix domain socket. The example given above does not specify
6522 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6525 ldap://<<hostname>>:<<port>>/...
6527 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6528 used. When no server is specified in a query, a list of default servers is
6529 taken from the \ldap@_default@_servers\ configuration option. This supplies a
6530 colon-separated list of servers which are tried in turn until one successfully
6531 handles a query, or there is a serious error. Successful handling either
6532 returns the requested data, or indicates that it does not exist. Serious errors
6533 are syntactical, or multiple values when only a single value is expected.
6534 Errors which cause the next server to be tried are connection failures, bind
6535 failures, and timeouts.
6537 For each server name in the list, a port number can be given. The standard way
6538 of specifing a host and port is to use a colon separator (RFC 1738). Because
6539 \ldap@_default@_servers\ is a colon-separated list, such colons have to be
6540 doubled. For example
6542 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6544 If \ldap@_default@_servers\ is unset, a URL with no server name is passed
6545 to the LDAP library with no server name, and the library's default (normally
6546 the local host) is used.
6548 If you are using the OpenLDAP library, you can connect to an LDAP server using
6549 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6550 \"ldapi"\ instead of \"ldap"\ in LDAP queries. What follows here applies only
6551 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6554 For this type of connection, instead of a host name for the server, a pathname
6555 for the socket is required, and the port number is not relevant. The pathname
6556 can be specified either as an item in \ldap@_default@_servers\, or inline in
6557 the query. In the former case, you can have settings such as
6559 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6561 When the pathname is given in the query, you have to escape the slashes as
6562 \"%2F"\ to fit in with the LDAP URL syntax. For example:
6564 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6566 When Exim processes an LDAP lookup and finds that the `hostname' is really
6567 a pathname, it uses the Unix domain socket code, even if the query actually
6568 specifies \"ldap"\ or \"ldaps"\. In particular, no encryption is used for a
6569 socket connection. This behaviour means that you can use a setting of
6570 \ldap@_default@_servers\ such as in the example above with traditional \"ldap"\
6571 or \"ldaps"\ queries, and it will work. First, Exim tries a connection via
6572 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6575 If an explicit \"ldapi"\ type is given in a query when a host name is
6576 specified, an error is diagnosed. However, if there are more items in
6577 \ldap@_default@_servers\, they are tried. In other words:
6579 Using a pathname with \"ldap"\ or \"ldaps"\ forces the use of the Unix domain
6582 Using \"ldapi"\ with a host name causes an error.
6585 Using \"ldapi"\ with no host or path in the query, and no setting of
6586 \ldap@_default@_servers\, does whatever the library does by default.
6589 .section LDAP authentication and control information
6590 .index LDAP||authentication
6591 The LDAP URL syntax provides no way of passing authentication and other control
6592 information to the server. To make this possible, the URL in an LDAP query may
6593 be preceded by any number of `<<name>>=<<value>>' settings, separated by
6594 spaces. If a value contains spaces it must be enclosed in double quotes, and
6595 when double quotes are used, backslash is interpreted in the usual way inside
6596 them. The following names are recognized:
6598 DEREFERENCE $rm{set the dereferencing parameter}
6601 NETTIME $rm{set a timeout for a network operation}
6604 USER $rm{set the DN, for authenticating the LDAP bind}
6605 PASS $rm{set the password, likewise}
6606 SIZE $rm{set the limit for the number of entries returned}
6607 TIME $rm{set the maximum waiting time for a query}
6609 The value of the \\DEREFERENCE\\ parameter must be one of the words `never',
6610 `searching', `finding', or `always'.
6613 The name \\CONNECT\\ is an obsolete name for \\NETTIME\\, retained for
6614 backwards compatibility. This timeout (specified as a number of seconds) is
6615 enforced from the client end for operations that can be carried out over a
6616 network. Specifically, it applies to network connections and calls to the
6617 \*ldap@_result()*\ function. If the value is greater than zero, it is used if
6618 \\LDAP@_OPT@_NETWORK@_TIMEOUT\\ is defined in the LDAP headers (OpenLDAP), or
6619 if \\LDAP@_X@_OPT@_CONNECT@_TIMEOUT\\ is defined in the LDAP headers (Netscape
6620 SDK 4.1). A value of zero forces an explicit setting of `no timeout' for
6621 Netscape SDK; for OpenLDAP no action is taken.
6623 The \\TIME\\ parameter (also a number of seconds) is passed to the server to
6624 set a server-side limit on the time taken to complete a search.
6627 Here is an example of an LDAP query in an Exim lookup that uses some of these
6628 values. This is a single line, folded for ease of reading:
6632 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6633 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6636 The encoding of spaces as %20 is a URL thing which should not be done for any
6637 of the auxiliary data. Exim configuration settings that include lookups which
6638 contain password information should be preceded by `hide' to prevent non-admin
6639 users from using the \-bP-\ option to see their values.
6641 The auxiliary data items may be given in any order. The default is no
6642 connection timeout (the system timeout is used), no user or password, no limit
6643 on the number of entries returned, and no time limit on queries.
6645 When a DN is quoted in the \\USER=\\ setting for LDAP authentication, Exim
6646 removes any URL quoting that it may contain before passing it LDAP. Apparently
6647 some libraries do this for themselves, but some do not. Removing the URL
6648 quoting has two advantages:
6650 It makes it possible to use the same \quote@_ldap@_dn\ expansion for \\USER=\\
6651 DNs as with DNs inside actual queries.
6653 It permits spaces inside \\USER=\\ DNs.
6655 For example, a setting such as
6657 USER=cn=${quote_ldap_dn:$1}
6659 should work even if \$1$\ contains spaces.
6661 Expanded data for the \\PASS=\\ value should be quoted using the \quote\
6662 expansion operator, rather than the LDAP quote operators. The only reason this
6663 field needs quoting is to ensure that it conforms to the Exim syntax, which
6664 does not allow unquoted spaces. For example:
6669 The LDAP authentication mechanism can be used to check passwords as part of
6670 SMTP authentication. See the \ldapauth\ expansion string condition in chapter
6674 .section Format of data returned by LDAP
6675 .index LDAP||returned data formats
6676 The \%ldapdn%\ lookup type returns the Distinguished Name from a single entry as
6677 a sequence of values, for example
6679 cn=manager, o=University of Cambridge, c=UK
6682 The \%ldap%\ lookup type generates an error if more than one entry matches the
6683 search filter, whereas \%ldapm%\ permits this case, and inserts a newline in
6684 the result between the data from different entries. It is possible for multiple
6685 values to be returned for both \%ldap%\ and \%ldapm%\, but in the former case
6686 you know that whatever values are returned all came from a single entry in the
6689 In the common case where you specify a single attribute in your LDAP query, the
6690 result is not quoted, and does not contain the attribute name. If the attribute
6691 has multiple values, they are separated by commas.
6693 If you specify multiple attributes, the result contains space-separated, quoted
6694 strings, each preceded by the attribute name and an equals sign. Within the
6695 quotes, the quote character, backslash, and newline are escaped with
6696 backslashes, and commas are used to separate multiple values for the attribute.
6697 Apart from the escaping, the string within quotes takes the same form as the
6698 output when a single attribute is requested. Specifying no attributes is the
6699 same as specifying all of an entry's attributes.
6701 Here are some examples of the output format. The first line of each pair is an
6702 LDAP query, and the second is the data that is returned. The attribute called
6703 \attr1\ has two values, whereas \attr2\ has only one value:
6705 ldap:///o=base?attr1?sub?(uid=fred)
6708 ldap:///o=base?attr2?sub?(uid=fred)
6711 ldap:///o=base?attr1,attr2?sub?(uid=fred)
6712 attr1="value1.1, value1.2" attr2="value two"
6714 ldap:///o=base??sub?(uid=fred)
6715 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
6717 The \extract\ operator in string expansions can be used to pick out individual
6718 fields from data that consists of $it{key}=$it{value} pairs. You can make use
6719 of Exim's \-be-\ option to run expansion tests and thereby check the results of
6724 .section More about NIS+
6725 .rset SECTnisplus "~~chapter.~~section"
6726 .index NIS@+ lookup type
6728 NIS+ queries consist of a NIS+ \*indexed name*\ followed by an optional colon
6729 and field name. If this is given, the result of a successful query is the
6730 contents of the named field; otherwise the result consists of a concatenation
6731 of \*field-name=field-value*\ pairs, separated by spaces. Empty values and
6732 values containing spaces are quoted. For example, the query
6734 [name=mg1456],passwd.org_dir
6736 might return the string
6738 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
6739 home=/home/mg1456 shell=/bin/bash shadow=""
6741 (split over two lines here to fit on the page), whereas
6743 [name=mg1456],passwd.org_dir:gcos
6749 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
6750 for the given indexed key. The effect of the \quote@_nisplus\ expansion
6751 operator is to double any quote characters within the text.
6754 .section More about MySQL, PostgreSQL, Oracle, and Interbase
6755 .rset SECTsql "~~chapter.~~section"
6756 .index MySQL||lookup type
6757 .index PostgreSQL lookup type
6758 .index lookup||MySQL
6759 .index lookup||PostgreSQL
6760 .index Oracle||lookup type
6761 .index lookup||Oracle
6762 .index Interbase lookup type
6763 .index lookup||Interbase
6764 If any MySQL, PostgreSQL, Oracle, or Interbase lookups are used, the
6765 \mysql@_servers\, \pgsql@_servers\, \oracle@_servers\, or \ibase@_servers\
6766 option (as appropriate) must be set to a colon-separated list of server
6767 information. Each item in the list is a slash-separated list of four items:
6768 host name, database name, user name, and password. In the case of Oracle, the
6769 host name field is used for the `service name', and the database name field is
6770 not used and should be empty. For example:
6772 hide oracle_servers = oracle.plc.example//ph10/abcdwxyz
6774 Because password data is sensitive, you should always precede the setting with
6775 `hide', to prevent non-admin users from obtaining the setting via the \-bP-\
6776 option. Here is an example where two MySQL servers are listed:
6778 hide mysql_servers = localhost/users/root/secret:\
6779 otherhost/users/root/othersecret
6781 For MySQL and PostgreSQL, a host may be specified as <<name>>:<<port>> but
6782 because this is a colon-separated list, the colon has to be doubled.
6784 For each query, these parameter groups are tried in order until a connection
6785 and a query succeeds. Queries for these databases are SQL statements, so an
6789 ${lookup mysql{select mailbox from users where id='ph10'}{$value}fail}
6791 If the result of the query contains more than one field, the data for
6792 each field in the row is returned, preceded by its name, so the result
6796 ${lookup pgsql{select home,name from users where id='ph10'}{$value}}
6800 home=/home/ph10 name="Philip Hazel"
6802 Values containing spaces and empty values are double quoted, with embedded
6803 quotes escaped by a backslash.
6805 If the result of the query contains just one field, the value is passed back
6806 verbatim, without a field name, for example:
6810 If the result of the query yields more than one row, it is all concatenated,
6811 with a newline between the data for each row.
6813 The \quote@_mysql\, \quote@_pgsql\, and \quote@_oracle\ expansion operators
6814 convert newline, tab, carriage return, and backspace to @\n, @\t, @\r, and @\b
6815 respectively, and the characters single-quote, double-quote, and backslash
6816 itself are escaped with backslashes. The \quote@_pgsql\ expansion operator, in
6817 addition, escapes the percent and underscore characters. This cannot be done
6818 for MySQL because these escapes are not recognized in contexts where these
6819 characters are not special.
6822 .section Special MySQL features
6823 For MySQL, an empty host name or the use of `localhost' in \mysql@_servers\
6824 causes a connection to the server on the local host by means of a Unix domain
6825 socket. An alternate socket can be specified in parentheses. The full syntax of
6826 each item in \mysql@_servers\ is:
6828 <<hostname>>@:@:<<port>>(<<socket name>>)/<<database>>/<<user>>/<<password>>
6830 Any of the three sub-parts of the first field can be omitted. For normal use on
6831 the local host it can be left blank or set to just `localhost'.
6833 No database need be supplied -- but if it is absent here, it must be given in
6836 If a MySQL query is issued that does not request any data (an insert, update,
6837 or delete command), the result of the lookup is the number of rows affected.
6839 \**Warning**\: this can be misleading. If an update does not actually change
6840 anything (for example, setting a field to the value it already has), the result
6841 is zero because no rows are affected.
6845 .section Special PostgreSQL features
6846 PostgreSQL lookups can also use Unix domain socket connections to the database.
6847 This is usually faster and costs less CPU time than a TCP/IP connection.
6848 However it can be used only if the mail server runs on the same machine as the
6849 database server. A configuration line for PostgreSQL via Unix domain sockets
6852 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
6854 In other words, instead of supplying a host name, a path to the socket is
6855 given. The path name is enclosed in parentheses so that its slashes aren't
6856 visually confused with the delimiters for the other server parameters.
6858 If a PostgreSQL query is issued that does not request any data (an insert,
6859 update, or delete command), the result of the lookup is the number of rows
6869 . ============================================================================
6870 .chapter Domain, host, address, and local part lists
6871 .set runningfoot "domain, host, and address lists"
6872 .rset CHAPdomhosaddlists "~~chapter"
6873 .index list||of domains, hosts, etc.
6874 A number of Exim configuration options contain lists of domains, hosts,
6875 email addresses, or local parts. For example, the \hold@_domains\ option
6876 contains a list of domains whose delivery is currently suspended. These lists
6877 are also used as data in ACL statements (see chapter ~~CHAPACL).
6879 Each item in one of these lists is a pattern to be matched against a domain,
6880 host, email address, or local part, respectively. In the sections below, the
6881 different types of pattern for each case are described, but first we cover some
6882 general facilities that apply to all four kinds of list.
6885 .section Expansion of lists
6886 .index expansion||of lists
6888 Each list is expanded as a single string before it is used. The result of
6889 expansion must be a list, possibly containing empty items, which is split up
6890 into separate items for matching. By default, colon is the separator character,
6891 but this can be varied if necessary. See sections ~~SECTlistconstruct and
6892 ~~SECTempitelis for details of the list syntax; the second of these discusses
6893 the way you specify empty list items.
6896 If the string expansion is forced to fail, Exim behaves as if the item it is
6897 testing (domain, host, address, or local part) is not in the list. Other
6898 expansion failures cause temporary errors.
6900 If an item in a list is a regular expression, backslashes, dollars and possibly
6901 other special characters in the expression must be protected against
6902 misinterpretation by the string expander. The easiest way to do this is to use
6903 the \"@\N"\ expansion feature to indicate that the contents of the regular
6904 expression should not be expanded. For example, in an ACL you might have:
6906 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N :
6907 ${lookup{$domain}lsearch{/badsenders/bydomain}}
6909 The first item is a regular expression that is protected from expansion by
6910 \"@\N"\, whereas the second uses the expansion to obtain a list of unwanted
6911 senders based on the receiving domain.
6915 .section Negated items in lists
6916 .index list||negation
6917 .index negation in lists
6918 Items in a list may be positive or negative. Negative items are indicated by a
6919 leading exclamation mark, which may be followed by optional white space. A list
6920 defines a set of items (domains, etc). When Exim processes one of these lists,
6921 it is trying to find out whether a domain, host, address, or local part
6922 (respectively) is in the set that is defined by the list. It works like this:
6924 The list is scanned from left to right. If a positive item is matched, the
6925 subject that is being checked is in the set; if a negative item is matched, the
6926 subject is not in the set. If the end of the list is reached without the
6927 subject having matched any of the patterns, it is in the set if the last item
6928 was a negative one, but not if it was a positive one. For example, the list in
6930 domainlist relay_domains = !a.b.c : *.b.c
6932 matches any domain ending in \*.b.c*\ except for \*a.b.c*\. Domains that match
6933 neither \*a.b.c*\ nor \*@*.b.c*\ do not match, because the last item in the
6934 list is positive. However, if the setting were
6936 domainlist relay_domains = !a.b.c
6938 then all domains other than \*a.b.c*\ would match because the last item in the
6939 list is negative. In other words, a list that ends with a negative item behaves
6940 as if it had an extra item \":*"\ on the end.
6942 Another way of thinking about positive and negative items in lists is to read
6943 the connector as `or' after a positive item and as `and' after a negative
6947 .section File names in lists
6948 .rset SECTfilnamlis "~~chapter.~~section"
6949 .index list||file name in
6950 If an item in a domain, host, address, or local part list is an absolute file
6951 name (beginning with a slash character), each line of the file is read and
6952 processed as if it were an independent item in the list, except that further
6953 file names are not allowed,
6954 and no expansion of the data from the file takes place.
6955 Empty lines in the file are ignored, and the file may also contain comment
6958 For domain and host lists, if a @# character appears anywhere in a line of the
6959 file, it and all following characters are ignored.
6961 Because local parts may legitimately contain @# characters, a comment in an
6962 address list or local part list file is recognized only if @# is preceded by
6963 white space or the start of the line. For example:
6965 not#comment@x.y.z # but this is a comment
6968 Putting a file name in a list has the same effect as inserting each line of the
6969 file as an item in the list (blank lines and comments excepted). However, there
6970 is one important difference: the file is read each time the list is processed,
6971 so if its contents vary over time, Exim's behaviour changes.
6973 If a file name is preceded by an exclamation mark, the sense of any match
6974 within the file is inverted. For example, if
6976 hold_domains = !/etc/nohold-domains
6978 and the file contains the lines
6983 then \*a.b.c*\ is in the set of domains defined by \hold@_domains\, whereas any
6984 domain matching \"*.b.c"\ is not.
6987 .section An lsearch file is not an out-of-line list
6988 As will be described in the sections that follow, lookups can be used in lists
6989 to provide indexed methods of checking list membership. There has been some
6990 confusion about the way \%lsearch%\ lookups work in lists. Because
6991 an \%lsearch%\ file contains plain text and is scanned sequentially, it is
6992 sometimes thought that it is allowed to contain wild cards and other kinds of
6993 non-constant pattern. This is not the case. The keys in an \%lsearch%\ file are
6994 always fixed strings, just as for any other single-key lookup type.
6996 If you want to use a file to contain wild-card patterns that form part of a
6997 list, just give the file name on its own, without a search type, as described
6998 in the previous section.
7002 .section Named lists
7003 .rset SECTnamedlists "~~chapter.~~section"
7006 A list of domains, hosts, email addresses, or local parts can be given a name
7007 which is then used to refer to the list elsewhere in the configuration. This is
7008 particularly convenient if the same list is required in several different
7009 places. It also allows lists to be given meaningful names, which can improve
7010 the readability of the configuration. For example, it is conventional to define
7011 a domain list called \*local@_domains*\ for all the domains that are handled
7012 locally on a host, using a configuration line such as
7014 domainlist local_domains = localhost:my.dom.example
7016 Named lists are referenced by giving their name preceded by a plus sign, so,
7017 for example, a router that is intended to handle local domains would be
7018 configured with the line
7020 domains = +local_domains
7022 The first router in a configuration is often one that handles all domains
7023 except the local ones, using a configuration with a negated item like this:
7027 domains = ! +local_domains
7028 transport = remote_smtp
7031 The four kinds of named list are created by configuration lines starting with
7032 the words \domainlist\, \hostlist\, \addresslist\, or \localpartlist\,
7033 respectively. Then there follows the name that you are defining, followed by an
7034 equals sign and the list itself. For example:
7036 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7037 addresslist bad_senders = cdb;/etc/badsenders
7039 A named list may refer to other named lists:
7041 domainlist dom1 = first.example : second.example
7042 domainlist dom2 = +dom1 : third.example
7043 domainlist dom3 = fourth.example : +dom2 : fifth.example
7046 \**Warning**\: If the last item in a referenced list is a negative one, the
7047 effect may not be what you intended, because the negation does not propagate
7048 out to the higher level. For example, consider:
7050 domainlist dom1 = !a.b
7051 domainlist dom2 = +dom1 : *.b
7053 The second list specifies `either in the \dom1\ list or \*@*.b*\'. The first
7054 list specifies just `not \*a.b*\', so the domain \*x.y*\ matches it. That means
7055 it matches the second list as well. The effect is not the same as
7057 domainlist dom2 = !a.b : *.b
7059 where \*x.y*\ does not match. It's best to avoid negation altogether in
7060 referenced lists if you can.
7062 Named lists may have a performance advantage. When Exim is routing an
7063 address or checking an incoming message, it caches the result of tests on named
7064 lists. So, if you have a setting such as
7066 domains = +local_domains
7068 on several of your routers
7069 or in several ACL statements,
7070 the actual test is done only for the first one. However, the caching works only
7071 if there are no expansions within the list itself or any sublists that it
7072 references. In other words, caching happens only for lists that are known to be
7073 the same each time they are referenced.
7075 By default, there may be up to 16 named lists of each type. This limit can be
7076 extended by changing a compile-time variable. The use of domain and host lists
7077 is recommended for concepts such as local domains, relay domains, and relay
7078 hosts. The default configuration is set up like this.
7081 .section Named lists compared with macros
7082 .index list||named compared with macro
7083 .index macro||compared with named list
7084 At first sight, named lists might seem to be no different from macros in the
7085 configuration file. However, macros are just textual substitutions. If you
7088 ALIST = host1 : host2
7089 auth_advertise_hosts = !ALIST
7091 it probably won't do what you want, because that is exactly the same as
7093 auth_advertise_hosts = !host1 : host2
7095 Notice that the second host name is not negated. However, if you use a host
7098 hostlist alist = host1 : host2
7099 auth_advertise_hosts = ! +alist
7101 the negation applies to the whole list, and so that is equivalent to
7103 auth_advertise_hosts = !host1 : !host2
7107 .section Named list caching
7108 .index list||caching of named
7109 .index caching||named lists
7110 While processing a message, Exim caches the result of checking a named list if
7111 it is sure that the list is the same each time. In practice, this means that
7112 the cache operates only if the list contains no @$ characters, which guarantees
7113 that it will not change when it is expanded. Sometimes, however, you may have
7114 an expanded list that you know will be the same each time within a given
7115 message. For example:
7117 domainlist special_domains = \
7118 ${lookup{$sender_host_address}cdb{/some/file}}
7120 This provides a list of domains that depends only on the sending host's IP
7121 address. If this domain list is referenced a number of times (for example,
7122 in several ACL lines, or in several routers) the result of the check is not
7123 cached by default, because Exim does not know that it is going to be the
7124 same list each time.
7126 By appending \"@_cache"\ to \"domainlist"\ you can tell Exim to go ahead and
7127 cache the result anyway. For example:
7129 domainlist_cache special_domains = ${lookup{...
7131 If you do this, you should be absolutely sure that caching is going to do
7132 the right thing in all cases. When in doubt, leave it out.
7135 .section Domain lists
7136 .rset SECTdomainlist "~~chapter.~~section"
7137 .index domain list||patterns for
7138 .index list||domain list
7139 Domain lists contain patterns that are to be matched against a mail domain.
7140 The following types of item may appear in domain lists:
7142 .index primary host name
7143 .index host||name, matched in domain list
7144 .index \primary@_hostname\
7145 .index domain list||matching primary host name
7146 .index @@ in a domain list
7147 If a pattern consists of a single @@ character, it matches the local host name,
7148 as set by the \primary@_hostname\ option (or defaulted). This makes it possible
7149 to use the same configuration file on several different hosts that differ only
7152 .index @@[] in a domain list
7153 .index domain list||matching local IP interfaces
7154 .index domain literal
7155 If a pattern consists of the string \"@@[]"\ it matches any local IP interface
7156 address, enclosed in square brackets, as in an email address that contains a
7158 In today's Internet, the use of domain literals is controversial.
7161 .index @@mx@_primary
7162 .index @@mx@_secondary
7163 .index domain list||matching MX pointers to local host
7164 If a pattern consists of the string \"@@mx@_any"\ it matches any domain that
7165 has an MX record pointing to the local host or to any host that is listed in
7166 .index \hosts@_treat@_as@_local\
7167 \hosts@_treat@_as@_local\. The items \"@@mx@_primary"\ and \"@@mx@_secondary"\
7168 are similar, except that the first matches only when a primary MX target is the
7169 local host, and the second only when no primary MX target is the local host,
7170 but a secondary MX target is. `Primary' means an MX record with the lowest
7171 preference value -- there may of course be more than one of them.
7173 The MX lookup that takes place when matching a pattern of this type is
7174 performed with the resolver options for widening names turned off. Thus, for
7175 example, a single-component domain will \*not*\ be expanded by adding the
7176 resolver's default domain. See the \qualify@_single\ and \search@_parents\
7177 options of the \%dnslookup%\ router for a discussion of domain widening.
7179 Sometimes you may want to ignore certain IP addresses when using one of these
7180 patterns. You can specify this by following the pattern with \"/ignore=<<ip
7181 list>>"\, where <<ip list>> is a list of IP addresses. These addresses are
7182 ignored when processing the pattern (compare the \ignore@_target@_hosts\ option
7183 on a router). For example:
7185 domains = @mx_any/ignore=127.0.0.1
7187 This example matches any domain that has an MX record pointing to one of
7188 the local host's IP addresses other than 127.0.0.1.
7190 The list of IP addresses is in fact processed by the same code that processes
7191 host lists, so it may contain CIDR-coded network specifications and it may also
7192 contain negative items.
7194 Because the list of IP addresses is a sublist within a domain list, you have to
7195 be careful about delimiters if there is more than one address. Like any other
7196 list, the default delimiter can be changed. Thus, you might have:
7198 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7199 an.other.domain : ...
7201 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7202 involved, it is easiest to change the delimiter for the main list as well:
7204 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7205 an.other.domain ? ...
7209 .index asterisk||in domain list
7210 .index domain list||asterisk in
7211 .index domain list||matching `ends with'
7212 If a pattern starts with an asterisk, the remaining characters of the pattern
7213 are compared with the terminating characters of the domain. The use of `$*$' in
7214 domain lists differs from its use in partial matching lookups. In a domain
7215 list, the character following the asterisk need not be a dot, whereas partial
7216 matching works only in terms of dot-separated components. For example, a domain
7217 list item such as \"*key.ex"\ matches \*donkey.ex*\ as well as
7220 .index regular expressions||in domain list
7221 .index domain list||matching regular expression
7222 If a pattern starts with a circumflex character, it is treated as a regular
7223 expression, and matched against the domain using a regular expression matching
7224 function. The circumflex is treated as part of the regular expression.
7225 References to descriptions of the syntax of regular expressions are given in
7226 chapter ~~CHAPregexp.
7228 \**Warning**\: Because domain lists are expanded before being processed, you
7229 must escape any backslash and dollar characters in the regular expression, or
7230 use the special \"@\N"\ sequence (see chapter ~~CHAPexpand) to specify that it
7231 is not to be expanded (unless you really do want to build a regular expression
7232 by expansion, of course).
7234 .index lookup||in domain list
7235 .index domain list||matching by lookup
7236 If a pattern starts with the name of a single-key lookup type followed by a
7237 semicolon (for example, `dbm;' or `lsearch;'), the remainder of the pattern
7238 must be a file name in a suitable format for the lookup type. For example, for
7239 `cdb;' it must be an absolute path:
7241 domains = cdb;/etc/mail/local_domains.cdb
7243 The appropriate type of lookup is done on the file using the domain name as the
7244 key. In most cases, the data that is looked up is not used; Exim is interested
7245 only in whether or not the key is present in the file. However, when a lookup
7246 is used for the \domains\ option on a router
7247 or a \domains\ condition in an ACL statement, the data is preserved in the
7248 \$domain@_data$\ variable and can be referred to in other router options or
7249 other statements in the same ACL.
7251 Any of the single-key lookup type names may be preceded by `partial<<n>>-',
7252 where the <<n>> is optional, for example,
7254 domains = partial-dbm;/partial/domains
7256 This causes partial matching logic to be invoked; a description of how this
7257 works is given in section ~~SECTpartiallookup.
7259 .index asterisk||in lookup type
7260 Any of the single-key lookup types may be followed by an asterisk. This causes
7261 a default lookup for a key consisting of a single asterisk to be done if the
7262 original lookup fails. This is not a useful feature when using a domain list to
7263 select particular domains (because any domain would match), but it might have
7264 value if the result of the lookup is being used via the \$domain@_data$\
7267 If the pattern starts with the name of a query-style lookup type followed by a
7268 semicolon (for example, `nisplus;' or `ldap;'), the remainder of the pattern
7269 must be an appropriate query for the lookup type, as described in chapter
7270 ~~CHAPfdlookup. For example:
7272 hold_domains = mysql;select domain from holdlist \
7273 where domain = '$domain';
7275 In most cases, the data that is looked up is not used (so for an SQL query, for
7276 example, it doesn't matter what field you select). Exim is interested only in
7277 whether or not the query succeeds. However, when a lookup is used for the
7278 \domains\ option on a router, the data is preserved in the \$domain@_data$\
7279 variable and can be referred to in other options.
7281 .index domain list||matching literal domain name
7282 If none of the above cases apply, a caseless textual comparison is made between
7283 the pattern and the domain.
7286 Here is an example that uses several different kinds of pattern:
7288 domainlist funny_domains = \
7291 *.foundation.fict.example : \
7292 \N^[1-2]\d{3}\.fict\.example$\N : \
7293 partial-dbm;/opt/data/penguin/book : \
7294 nis;domains.byname : \
7295 nisplus;[name=$domain,status=local],domains.org_dir
7297 There are obvious processing trade-offs among the various matching modes. Using
7298 an asterisk is faster than a regular expression, and listing a few names
7299 explicitly probably is too. The use of a file or database lookup is expensive,
7300 but may be the only option if hundreds of names are required. Because the
7301 patterns are tested in order, it makes sense to put the most commonly matched
7306 .rset SECThostlist "~~chapter.~~section"
7307 .index host list||patterns in
7308 .index list||host list
7309 Host lists are used to control what remote hosts are allowed to do. For
7310 example, some hosts may be allowed to use the local host as a relay, and some
7311 may be permitted to use the SMTP \\ETRN\\ command. Hosts can be identified in
7312 two different ways, by name or by IP address. In a host list, some types of
7313 pattern are matched to a host name, and some are matched to an IP address.
7314 You need to be particularly careful with this when single-key lookups are
7315 involved, to ensure that the right value is being used as the key.
7317 .section Special host list patterns
7318 .index empty item in hosts list
7319 .index host list||empty string in
7320 If a host list item is the empty string, it matches only when no remote host is
7321 involved. This is the case when a message is being received from a local
7322 process using SMTP on the standard input, that is, when a TCP/IP connection is
7325 .index asterisk||in host list
7326 The special pattern `$*$' in a host list matches any host or no host. Neither
7327 the IP address nor the name is actually inspected.
7330 .section Host list patterns that match by IP address
7331 .rset SECThoslispatip "~~chapter.~~section"
7332 .index host list||matching IP addresses
7333 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7334 the incoming address actually appears in the IPv6 host as
7335 `@:@:$tt{ffff}:<<v4address>>'. When such an address is tested against a host
7336 list, it is converted into a traditional IPv4 address first. (Not all operating
7337 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7340 The following types of pattern in a host list check the remote host by
7341 inspecting its IP address:
7343 If the pattern is a plain domain name (not a regular expression, not starting
7344 with $*$, not a lookup of any kind), Exim calls the operating system function
7345 to find the associated IP address(es). Exim uses the newer
7346 \*getipnodebyname()*\ function when available, otherwise \*gethostbyname()*\.
7347 This typically causes a forward DNS lookup of the name. The result is compared
7348 with the IP address of the subject host.
7350 If there is a temporary problem (such as a DNS timeout) with the host name
7351 lookup, a temporary error occurs. For example, if the list is being used in an
7352 ACL condition, the ACL gives a `defer' response, usually leading to a temporary
7353 SMTP error code. If no IP address can be found for the host name, what happens
7354 is described in section ~~SECTbehipnot below.
7357 .index @@ in a host list
7358 If the pattern is `@@', the primary host name is substituted and used as a
7359 domain name, as just described.
7361 If the pattern is an IP address, it is matched against the IP address of the
7362 subject host. IPv4 addresses are given in the normal `dotted-quad' notation.
7363 IPv6 addresses can be given in colon-separated format, but the colons have to
7364 be doubled so as not to be taken as item separators when the default list
7365 separator is used. IPv6 addresses are recognized even when Exim is compiled
7366 without IPv6 support. This means that if they appear in a host list on an
7367 IPv4-only host, Exim will not treat them as host names. They are just addresses
7368 that can never match a client host.
7370 .index @@[] in a host list
7371 If the pattern is `@@[]', it matches the IP address of any IP interface on
7372 the local host. For example, if the local host is an IPv4 host with one
7373 interface address 10.45.23.56, these two ACL statements have the same effect:
7375 accept hosts = 127.0.0.1 : 10.45.23.56
7379 If the pattern is an IP address followed by a slash and a mask length (for
7380 example 10.11.42.0/24), it is matched against the IP address of the subject
7381 host under the given mask.
7382 This allows, an entire network of hosts to be included (or excluded) by a
7384 .index CIDR notation
7385 The mask uses CIDR notation; it specifies the number of address bits that must
7386 match, starting from the most significant end of the address.
7388 \**Note**\: the mask is \*not*\ a count of addresses, nor is it the high number
7389 of a range of addresses. It is the number of bits in the network portion of the
7390 address. The above example specifies a 24-bit netmask, so it matches all 256
7391 addresses in the 10.11.42.0 network. An item such as
7395 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7396 32 for an IPv4 address is the same as no mask at all; just a single address
7399 Here is another example which shows an IPv4 and an IPv6 network:
7401 recipient_unqualified_hosts = 192.168.0.0/16: \
7402 3ffe::ffff::836f::::/48
7404 The doubling of list separator characters applies only when these items
7405 appear inline in a host list. It is not required when indirecting via a file.
7408 recipient_unqualified_hosts = /opt/exim/unqualnets
7410 could make use of a file containing
7415 to have exactly the same effect as the previous example. When listing IPv6
7416 addresses inline, it is usually more convenient to use the facility for
7417 changing separator characters. This list contains the same two networks:
7419 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7422 The separator is changed to semicolon by the leading `<;' at the start of the
7427 .section Host list patterns for single-key lookups by host address
7428 .rset SECThoslispatsikey "~~chapter.~~section"
7429 .index host list||lookup of IP address
7430 When a host is to be identified by a single-key lookup of its complete IP
7431 address, the pattern takes this form:
7433 net-<<single-key-search-type>>;<<search-data>>
7437 hosts_lookup = net-cdb;/hosts-by-ip.db
7439 The text form of the IP address of the subject host is used as the lookup key.
7440 IPv6 addresses are converted to an unabbreviated form, using lower case
7441 letters, with dots as separators because colon is the key terminator in
7442 \%lsearch%\ files. [Colons can in fact be used in keys in \%lsearch%\ files by
7443 quoting the keys, but this is a facility that was added later.] The data
7444 returned by the lookup is not used.
7446 .index IP address||masking
7447 .index host list||masked IP address
7448 Single-key lookups can also be performed using masked IP addresses, using
7449 patterns of this form:
7451 net<<number>>-<<single-key-search-type>>;<<search-data>>
7455 net24-dbm;/networks.db
7457 The IP address of the subject host is masked using <<number>> as the mask
7458 length. A textual string is constructed from the masked value, followed by the
7459 mask, and this is used as the lookup key. For example, if the host's IP address
7460 is 192.168.34.6, the key that is looked up for the above example is
7461 `192.168.34.0/24'. IPv6 addresses are converted to a text value using lower
7462 case letters and dots as separators instead of the more usual colon, because
7463 colon is the key terminator in \%lsearch%\ files. Full, unabbreviated IPv6
7464 addresses are always used.
7466 \**Warning**\: Specifing \net32@-\ (for an IPv4 address) or \net128@-\ (for an
7467 IPv6 address) is not the same as specifing just \net@-\ without a number. In
7468 the former case the key strings include the mask value, whereas in the latter
7469 case the IP address is used on its own.
7472 .section Host list patterns that match by host name
7473 .rset SECThoslispatnam "~~chapter.~~section"
7474 .index host||lookup failures
7475 .index unknown host name
7476 .index host list||matching host name
7477 There are several types of pattern that require Exim to know the name of the
7478 remote host. These are either wildcard patterns or lookups by name. (If a
7479 complete hostname is given without any wildcarding, it is used to find an IP
7480 address to match against, as described in the section ~~SECThoslispatip above.)
7482 If the remote host name is not already known when Exim encounters one of these
7483 patterns, it has to be found from the IP address.
7484 Although many sites on the Internet are conscientious about maintaining reverse
7485 DNS data for their hosts, there are also many that do not do this.
7486 Consequently, a name cannot always be found, and this may lead to unwanted
7487 effects. Take care when configuring host lists with wildcarded name patterns.
7488 Consider what will happen if a name cannot be found.
7490 Because of the problems of determining host names from IP addresses, matching
7491 against host names is not as common as matching against IP addresses.
7493 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7494 if no name is found in the DNS, the system function (\*gethostbyaddr()*\ or
7495 \*getipnodebyaddr()*\ if available) is tried. The order in which these lookups
7496 are done can be changed by setting the \host@_lookup@_order\ option.
7498 There are some options that control what happens if a host name cannot be
7499 found. These are described in section ~~SECTbehipnot below.
7502 .index host||alias for
7503 .index alias for host
7504 As a result of aliasing, hosts may have more than one name. When processing any
7505 of the following types of pattern, all the host's names are checked:
7507 .index asterisk||in host list
7508 If a pattern starts with `$*$' the remainder of the item must match the end of
7509 the host name. For example, \"*.b.c"\ matches all hosts whose names end in
7510 \*.b.c*\. This special simple form is provided because this is a very common
7511 requirement. Other kinds of wildcarding require the use of a regular
7514 .index regular expressions||in host list
7515 .index host list||regular expression in
7516 If the item starts with `@^' it is taken to be a regular expression which is
7517 matched against the host name. For example,
7521 is a regular expression that matches either of the two hosts \*a.c.d*\ or
7522 \*b.c.d*\. When a regular expression is used in a host list, you must take care
7523 that backslash and dollar characters are not misinterpreted as part of the
7524 string expansion. The simplest way to do this is to use \"@\N"\ to mark that
7525 part of the string as non-expandable. For example:
7527 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
7529 \**Warning**\: If you want to match a complete host name, you must include the
7530 \"@$"\ terminating metacharacter in the regular expression, as in the above
7531 example. Without it, a match at the start of the host name is all that is
7536 .section Behaviour when an IP address or name cannot be found
7537 .rset SECTbehipnot "~~chapter.~~section"
7538 .index host||lookup failures
7539 While processing a host list, Exim may need to look up an IP address from a
7540 name (see section ~~SECThoslispatip), or it may need to look up a host name
7541 from an IP address (see section ~~SECThoslispatnam). In either case, the
7542 behaviour when it fails to find the information it is seeking is the same.
7544 .index \"+include@_unknown"\
7545 .index \"+ignore@_unknown"\
7546 By default, Exim behaves as if the host does not match the list. This may not
7547 always be what you want to happen. To change Exim's behaviour, the special
7548 items \"+include@_unknown"\ or \"+ignore@_unknown"\ may appear in the list (at
7549 top level -- they are not recognized in an indirected file).
7551 If any item that follows \"+include@_unknown"\ requires information that
7552 cannot found, Exim behaves as if the host does match the list. For example,
7554 host_reject_connection = +include_unknown:*.enemy.ex
7556 rejects connections from any host whose name matches \"*.enemy.ex"\, and also
7557 any hosts whose name it cannot find.
7559 If any item that follows \"+ignore@_unknown"\ requires information that cannot
7560 be found, Exim ignores that item and proceeds to the rest of the list. For
7563 accept hosts = +ignore_unknown : friend.example : \
7566 accepts from any host whose name is \*friend.example*\ and from 192.168.4.5,
7567 whether or not its host name can be found. Without \"+ignore@_unknown"\, if no
7568 name can be found for 192.168.4.5, it is rejected.
7570 Both \"+include@_unknown"\ and \"+ignore@_unknown"\ may appear in the same
7571 list. The effect of each one lasts until the next, or until the end of the
7574 \**Note**\: This section applies to permanent lookup failures. It does \*not*\
7575 apply to temporary DNS errors. They always cause a defer action.
7578 .section Host list patterns for single-key lookups by host name
7579 .rset SECThoslispatnamsk "~~chapter.~~section"
7580 .index host||lookup failures
7581 .index unknown host name
7582 .index host list||matching host name
7583 If a pattern is of the form
7585 <<single-key-search-type>>;<<search-data>>
7589 dbm;/host/accept/list
7591 a single-key lookup is performend, using the host name as its key. If the
7592 lookup succeeds, the host matches the item. The actual data that is looked up
7595 \**Reminder**\: With this kind of pattern, you must have host $it{names} as
7596 keys in the file, not IP addresses. If you want to do lookups based on IP
7597 addresses, you must precede the search type with `net-' (see section
7598 ~~SECThoslispatsikey). There is, however, no reason why you could not use two
7599 items in the same list, one doing an address lookup and one doing a name
7600 lookup, both using the same file.
7603 .section Host list patterns for query-style lookups
7604 If a pattern is of the form
7606 <<query-style-search-type>>;<<query>>
7608 the query is obeyed, and if it succeeds, the host matches the item. The actual
7609 data that is looked up is not used. The variables \$sender@_host@_address$\ and
7610 \$sender@_host@_name$\ can be used in the query. For example:
7612 hosts_lookup = pgsql;\
7613 select ip from hostlist where ip='$sender_host_address'
7615 The value of \$sender@_host@_address$\ for an IPv6 address contains colons. You
7616 can use the \sg\ expansion item to change this if you need to. If you want to
7617 use masked IP addresses in database queries, you can use the \mask\ expansion
7620 If the query contains a reference to \$sender@_host@_name$\, Exim automatically
7621 looks up the host name if has not already done so. (See section
7622 ~~SECThoslispatnam for comments on finding host names.)
7624 Historical note: prior to release 4.30, Exim would always attempt to find a
7625 host name before running the query, unless the search type was preceded by
7626 \"net-"\. This is no longer the case. For backwards compatibility, \"net-"\ is
7627 still recognized for query-style lookups, but its presence or absence has no
7628 effect. (Of course, for single-key lookups, \"net-"\ $it{is} important.
7629 See section ~~SECThoslispatsikey.)
7632 .section Mixing wildcarded host names and addresses in host lists
7633 .rset SECTmixwilhos "~~chapter.~~section"
7634 .index host list||mixing names and addresses in
7635 If you have name lookups or wildcarded host names and IP addresses in the same
7636 host list, you should normally put the IP addresses first. For example, in an
7639 accept hosts = 10.9.8.7 : *.friend.example
7641 The reason for this lies in the left-to-right way that Exim processes lists.
7642 It can test IP addresses without doing any DNS lookups, but when it reaches an
7643 item that requires a host name, it fails if it cannot find a host name to
7644 compare with the pattern. If the above list is given in the opposite order, the
7645 \accept\ statement fails for a host whose name cannot be found, even if its
7646 IP address is 10.9.8.7.
7648 If you really do want to do the name check first, and still recognize the IP
7649 address, you can rewrite the ACL like this:
7651 accept hosts = *.friend.example
7652 accept hosts = 10.9.8.7
7654 If the first \accept\ fails, Exim goes on to try the second one. See chapter
7655 ~~CHAPACL for details of ACLs.
7660 .section Address lists
7661 .index list||address list
7662 .index address list||empty item
7663 .index address list||patterns
7664 .rset SECTaddresslist "~~chapter.~~section"
7665 Address lists contain patterns that are matched against mail addresses. There
7666 is one special case to be considered: the sender address of a bounce message is
7667 always empty. You can test for this by providing an empty item in an address
7668 list. For example, you can set up a router to process bounce messages by
7669 using this option setting:
7673 The presence of the colon creates an empty item. If you do not provide any
7674 data, the list is empty and matches nothing. The empty sender can also be
7675 detected by a regular expression that matches an empty string,
7677 and by a query-style lookup that succeeds when \$sender@_address$\ is empty.
7679 The following kinds of address list pattern can match any address, including
7680 the empty address that is characteristic of bounce message senders:
7684 As explained above, if a pattern item is empty, it matches the empty address
7688 .index regular expressions||in address list
7689 .index address list||regular expression in
7690 If (after expansion) a pattern starts with `@^', a regular expression match is
7691 done against the complete address, with the pattern as the regular expression.
7692 You must take care that backslash and dollar characters are not misinterpreted
7693 as part of the string expansion. The simplest way to do this is to use \"@\N"\
7694 to mark that part of the string as non-expandable. For example:
7696 deny senders = \N^\d{8}.+@spamhaus.example$\N : ...
7698 The \"@\N"\ sequences are removed by the expansion, so the item does start
7699 with `@^' by the time it is being interpreted as an address pattern.
7701 .index address list||lookup for complete address
7702 Complete addresses can be looked up by using a pattern that starts with a
7703 lookup type terminated by a semicolon, followed by the data for the lookup. For
7706 deny senders = cdb;/etc/blocked.senders : \
7707 mysql;select address from blocked where \
7708 address='${quote_mysql:$sender_address}'
7711 Both query-style and single-key lookup types can be used. For a single-key
7712 lookup type, Exim uses the complete address as the key. However, empty keys are
7713 not supported for single-key lookups, so a match against the empty address
7714 always fails. This restriction does not apply to query-style lookups.
7717 Partial matching for single-key lookups (section ~~SECTpartiallookup) cannot be
7718 used, and is ignored if specified, with an entry being written to the panic
7720 .index @*@@ with single-key lookup
7721 However, you can configure lookup defaults, as described in section
7722 ~~SECTdefaultvaluelookups, but this is useful only for the `$*$@@' type of
7723 default. For example, with this lookup:
7725 accept senders = lsearch*@;/some/file
7727 the file could contains lines like this:
7729 user1@domain1.example
7732 and for the sender address \*nimrod@@jaeger.example*\, the sequence of keys
7735 nimrod@jaeger.example
7739 \**Warning 1**\: Do not include a line keyed by `$*$' in the file, because that
7740 would mean that every address matches, thus rendering the test useless.
7742 \**Warning 2**\: Do not confuse these two kinds of item:
7744 deny recipients = dbm*@;/some/file
7745 deny recipients = *@dbm;/some/file
7747 The first does a whole address lookup, with defaulting, as just described,
7748 because it starts with a lookup type. The second matches the local part and
7749 domain independently, as described in a bullet point below.
7754 The following kinds of address list pattern can match only non-empty addresses.
7755 If the subject address is empty, a match against any of these pattern types
7760 .index @@@@ with single-key lookup
7761 .index address list||@@@@ lookup type
7762 .index address list||split local part and domain
7763 If a pattern starts with `@@@@' followed by a single-key lookup item
7764 (for example, \"@@@@lsearch;/some/file"\), the address that is being checked is
7765 split into a local part and a domain. The domain is looked up in the file. If
7766 it is not found, there is no match. If it is found, the data that is looked up
7767 from the file is treated as a colon-separated list of local part patterns, each
7768 of which is matched against the subject local part in turn.
7770 .index asterisk||in address list
7771 The lookup may be a partial one, and/or one involving a search for a default
7772 keyed by `$*$' (see section ~~SECTdefaultvaluelookups). The local part patterns
7773 that are looked up can be regular expressions or begin with `$*$', or even be
7774 further lookups. They may also be independently negated. For example, with
7776 deny senders = @@dbm;/etc/reject-by-domain
7778 the data from which the DBM file is built could contain lines like
7780 baddomain.com: !postmaster : *
7782 to reject all senders except \postmaster\ from that domain.
7783 .index local part||starting with !
7784 If a local part that actually begins with an exclamation mark is required, it
7785 has to be specified using a regular expression. In \%lsearch%\ files, an entry
7786 may be split over several lines by indenting the second and subsequent lines,
7787 but the separating colon must still be included at line breaks. White space
7788 surrounding the colons is ignored. For example:
7790 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
7793 As in all colon-separated lists in Exim, a colon can be included in an item by
7796 If the last item in the list starts with a right angle-bracket, the remainder
7797 of the item is taken as a new key to look up in order to obtain a continuation
7798 list of local parts. The new key can be any sequence of characters. Thus one
7799 might have entries like
7801 aol.com: spammer1 : spammer 2 : >*
7802 xyz.com: spammer3 : >*
7805 in a file that was searched with \@@@@dbm$*$\, to specify a match for 8-digit
7806 local parts for all domains, in addition to the specific local parts listed for
7807 each domain. Of course, using this feature costs another lookup each time a
7808 chain is followed, but the effort needed to maintain the data is reduced.
7809 .index loop||in lookups
7810 It is possible to construct loops using this facility, and in order to catch
7811 them, the chains may be no more than fifty items long.
7813 The @@@@<<lookup>> style of item can also be used with a query-style
7814 lookup, but in this case, the chaining facility is not available. The lookup
7815 can only return a single list of local parts.
7817 If a pattern contains an @@ character, but is not a regular expression and does
7818 not begin with a lookup type as described above, the local part of the subject
7819 address is compared with the local part of the pattern, which may start with an
7820 asterisk. If the local parts match, the domain is checked in exactly the same
7821 way as for a pattern in a domain list. For example, the domain can be
7822 wildcarded, refer to a named list, or be a lookup:
7824 deny senders = *@*.spamming.site:\
7825 *@+hostile_domains:\
7826 bozo@partial-lsearch;/list/of/dodgy/sites:\
7828 *@dbm;/bad/domains.db
7830 .index local part||starting with !
7831 .index address list||local part starting with !
7832 If a local part that begins with an exclamation mark is required, it has to be
7833 specified using a regular expression, because otherwise the exclamation mark is
7834 treated as a sign of negation.
7836 If a pattern is not one of the above syntax forms, that is, if a
7840 pattern that is not a regular expression or a lookup does not contain an @@
7841 character, it is matched against the domain part of the subject address. The
7842 only two formats that are recognized this way are a literal domain, or a domain
7843 pattern that starts with $*$. In both these cases, the effect is the same as if
7844 \"*@@"\ preceded the pattern.
7847 \**Warning**\: there is an important difference between the address list items
7848 in these two examples:
7851 senders = *@+my_list
7853 In the first one, \"my@_list"\ is a named address list, whereas in the second
7854 example it is a named domain list.
7858 .section Case of letters in address lists
7859 .rset SECTcasletadd "~~chapter.~~section"
7860 .index case of local parts
7861 .index address list||case forcing
7862 .index case forcing in address lists
7863 Domains in email addresses are always handled caselessly, but for local parts
7864 case may be significant on some systems (see \caseful@_local@_part\ for how
7865 Exim deals with this when routing addresses). However, RFC 2505 ($it{Anti-Spam
7866 Recommendations for SMTP MTAs}) suggests that matching of addresses to blocking
7867 lists should be done in a case-independent manner. Since most address lists in
7868 Exim are used for this kind of control, Exim attempts to do this by default.
7870 The domain portion of an address is always lowercased before matching it to an
7871 address list. The local part is lowercased by default, and any string
7872 comparisons that take place are done caselessly. This means that the data in
7873 the address list itself, in files included as plain file names, and in any file
7874 that is looked up using the `@@@@' mechanism, can be in any case. However, the
7875 keys in files that are looked up by a search type other than \%lsearch%\ (which
7876 works caselessly) must be in lower case, because these lookups are not
7880 To allow for the possibility of caseful address list matching, if an item in
7881 an address list is the string `+caseful', the original case of the local
7882 part is restored for any comparisons that follow, and string comparisons are no
7883 longer case-independent. This does not affect the domain, which remains in
7884 lower case. However, although independent matches on the domain alone are still
7885 performed caselessly, regular expressions that match against an entire address
7886 become case-sensitive after `+caseful' has been seen.
7889 .section Local part lists
7890 .rset SECTlocparlis "~~chapter.~~section"
7891 .index list||local part list
7892 .index local part||list
7893 Case-sensitivity in local part lists is handled in the same way as for address
7894 lists, as just described. The `+caseful' item can be used if required. In a
7895 setting of the \local@_parts\ option in a router with \caseful@_local@_part\
7896 set false, the subject is lowercased and the matching is initially
7897 case-insensitive. In this case, `+caseful' will restore case-sensitive matching
7898 in the local part list, but not elsewhere in the router. If
7899 \caseful@_local@_part\ is set true in a router, matching in the \local@_parts\
7900 option is case-sensitive from the start.
7902 If a local part list is indirected to a file (see section ~~SECTfilnamlis),
7903 comments are handled in the same way as address lists -- they are recognized
7904 only if the @# is preceded by white space or the start of the line.
7905 Otherwise, local part lists are matched in the same way as domain lists, except
7906 that the special items that refer to the local host (\"@@"\, \"@@[]"\,
7907 \"@@mx@_any"\, \"@@mx@_primary"\, and \"@@mx@_secondary"\) are not recognized.
7908 Refer to section ~~SECTdomainlist for details of the other available item
7917 . ============================================================================
7918 .chapter String expansions
7919 .set runningfoot "string expansions"
7920 .rset CHAPexpand ~~chapter
7921 .index expansion||of strings
7922 Many strings in Exim's run time configuration are expanded before use. Some of
7923 them are expanded every time they are used; others are expanded only once.
7925 When a string is being expanded it is copied verbatim from left to right except
7926 when a dollar or backslash character is encountered. A dollar specifies the
7927 start of a portion of the string which is interpreted and replaced as described
7928 below in section ~~SECTexpansionitems onwards. Backslash is used as an escape
7929 character, as described in the following section.
7932 .section Literal text in expanded strings
7933 .rset SECTlittext "~~chapter.~~section"
7934 .index expansion||including literal text
7935 An uninterpreted dollar can be included in an expanded string by putting a
7936 backslash in front of it. A backslash can be used to prevent any special
7937 character being treated specially in an expansion, including itself. If the
7938 string appears in quotes in the configuration file, two backslashes are
7939 required because the quotes themselves cause interpretation of backslashes when
7940 the string is read in (see section ~~SECTstrings).
7942 .index expansion||non-expandable substrings
7943 A portion of the string can specified as non-expandable by placing it between
7944 two occurrences of \"@\N"\. This is particularly useful for protecting regular
7945 expressions, which often contain backslashes and dollar signs. For example:
7947 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
7949 On encountering the first \"@\N"\, the expander copies subsequent characters
7950 without interpretation until it reaches the next \"@\N"\ or the end of the
7954 .section Character escape sequences in expanded strings
7955 .index expansion||escape sequences
7956 A backslash followed by one of the letters `n', `r', or `t' in an expanded
7957 string is recognized as an escape sequence for the character newline, carriage
7958 return, or tab, respectively. A backslash followed by up to three octal digits
7959 is recognized as an octal encoding for a single character, and a backslash
7960 followed by `x' and up to two hexadecimal digits is a hexadecimal encoding.
7962 These escape sequences are also recognized in quoted strings when they are read
7963 in. Their interpretation in expansions as well is useful for unquoted strings,
7964 and for other cases such as looked-up strings that are then expanded.
7966 .section Testing string expansions
7967 .index expansion||testing
7968 .index testing||string expansion
7969 .index \-be-\ option
7970 Many expansions can be tested by calling Exim with the \-be-\ option. This takes
7971 the command arguments, or lines from the standard input if there are no
7972 arguments, runs them through the string expansion code, and writes the results
7973 to the standard output. Variables based on configuration values are set up, but
7974 since no message is being processed, variables such as \$local@_part$\ have no
7975 value. Nevertheless the \-be-\ option can be useful for checking out file and
7976 database lookups, and the use of expansion operators such as \sg\, \substr\ and
7979 Exim gives up its root privilege when it is called with the \-be-\ option, and
7980 instead runs under the uid and gid it was called with, to prevent users from
7981 using \-be-\ for reading files to which they do not have access.
7985 .section Forced expansion failure
7986 .rset SECTforexpfai "~~chapter.~~section"
7987 .index expansion||forced failure
7988 A number of expansions that are described in the following section have
7989 alternative `true' and `false' substrings, enclosed in curly brackets. Which
7990 one is used depends on some condition that is evaluated as part of the
7991 expansion. If, instead of a `false' substring, the word `fail' is used (not in
7992 curly brackets), the entire string expansion fails in a way that can be
7993 detected by the code that requested the expansion. This is called `forced
7994 expansion failure', and its consequences depend on the circumstances. In some
7995 cases it is no different from any other expansion failure, but in others a
7996 different action may be taken. Such variations are mentioned in the
7997 documentation of the option that is being expanded.
8001 .section Expansion items
8002 .rset SECTexpansionitems "~~chapter.~~section"
8003 The following items are recognized in expanded strings. White space may be used
8004 between sub-items that are keywords or substrings enclosed in braces inside an
8005 outer set of braces, to improve readability. \**Warning**\: Within braces,
8006 white space is significant.
8010 .item "@$<<variable name>>#$rm{or}#@$@{<<variable name>>@}"
8011 .index expansion||variables
8012 Substitute the contents of the named variable, for example
8017 The second form can be used to separate the name from subsequent alphanumeric
8018 characters. This form (using curly brackets) is available only for variables;
8019 it does $it{not} apply to message headers. The names of the variables are given
8020 in section ~~SECTexpvar below. If the name of a non-existent variable is given,
8021 the expansion fails.
8023 .item "@$@{<<op>>:<<string>>@}"
8024 .index expansion||operators
8025 The string is first itself expanded, and then the operation specified by <<op>>
8026 is applied to it. For example,
8030 The string starts with the first character after the colon, which may be
8031 leading white space. A list of operators is given in section ~~SECTexpop below.
8032 The operator notation is used for simple expansion items that have just one
8033 argument, because it reduces the number of braces and therefore makes the
8034 string easier to understand.
8036 .item "@$@{extract@{<<key>>@}@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8037 .index expansion||extracting substrings by key
8038 The key and <<string1>> are first expanded separately.
8039 Leading and trailing whitespace is removed from the key (but not from any of
8041 The key must not consist entirely of digits. The expanded <<string1>> must be
8044 <<key1>> = <<value1>> <<key2>> = <<value2>> ...
8046 where the equals signs and spaces (but not both) are optional. If any of the
8047 values contain white space, they must be enclosed in double quotes, and any
8048 values that are enclosed in double quotes are subject to escape processing as
8049 described in section ~~SECTstrings. The expanded <<string1>> is searched for
8050 the value that corresponds to the key. The search is case-insensitive. If the
8051 key is found, <<string2>> is expanded, and replaces the whole item; otherwise
8052 <<string3>> is used. During the expansion of <<string2>> the variable \$value$\
8053 contains the value that has been extracted. Afterwards, it is restored to any
8054 previous value it might have had.
8056 If @{<<string3>>@} is omitted, the item is replaced by an empty string if the
8057 key is not found. If @{<<string2>>@} is also omitted, the value that was
8058 extracted is used. Thus, for example, these two expansions are identical, and
8061 @$@{extract@{gid@}{uid=1984 gid=2001@}@}
8062 @$@{extract@{gid@}{uid=1984 gid=2001@}@{@$value@}@}
8064 Instead of @{<<string3>>@} the word `fail' (not in curly brackets) can appear,
8067 @$@{extract@{Z@}@{A=... B=...@}@{@$value@} fail @}
8069 This forces an expansion failure (see section ~~SECTforexpfai); @{<<string2>>@}
8070 must be present for `fail' to be recognized.
8073 .item "@$@{extract@{<<number>>@}@{<<separators>>@}@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8074 .index expansion||extracting substrings by number
8075 The <<number>> argument must consist entirely of decimal digits,
8076 apart from leading and trailing whitespace, which is ignored.
8077 This is what distinguishes this form of \extract\ from the previous kind. It
8078 behaves in the same way, except that, instead of extracting a named field, it
8079 extracts from <<string1>> the field whose number is given as the first
8080 argument. You can use \$value$\ in <<string2>> or \"fail"\ instead of
8081 <<string3>> as before.
8083 The fields in the string are separated by any one of the characters in the
8084 separator string. These may include space or tab characters.
8085 The first field is numbered one. If the number is negative, the fields are
8086 counted from the end of the string, with the rightmost one numbered -1. If the
8087 number given is zero, the entire string is returned. If the modulus of the
8088 number is greater than the number of fields in the string, the result is the
8089 expansion of <<string3>>, or the empty string if <<string3>> is not provided.
8092 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8096 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8098 yields `99'. Two successive separators mean that the field between them is
8099 empty (for example, the fifth field above).
8102 .item "@$@{hash@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8103 .index hash function||textual
8104 .index expansion||textual hash
8105 This is a textual hashing function, and was the first to be implemented in
8106 early versions of Exim. In current releases, there are other hashing functions
8107 (numeric, MD5, and SHA-1), which are described below.
8109 The first two strings, after expansion, must be numbers. Call them <<m>> and
8110 <<n>>. If you are using fixed values for these numbers, that is, if <<string1>>
8111 and <<string2>> do not change when they are expanded, you can use the
8112 simpler operator notation that avoids some of the braces:
8114 @$@{hash@_<<n>>@_<<m>>:<<string>>@}
8116 The second number is optional (in both notations).
8118 If <<n>> is greater than or equal to the length of the string, the expansion
8119 item returns the string. Otherwise it computes a new string of length <<n>> by
8120 applying a hashing function to the string. The new string consists of
8121 characters taken from the first <<m>> characters of the string
8123 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8125 If <<m>> is not present the value 26 is used, so that only lower case
8126 letters appear. For example:
8128 @$@{hash@{3@}@{monty@}@} $rm{yields} \"jmg"\
8129 @$@{hash@{5@}@{monty@}@} $rm{yields} \"monty"\
8130 @$@{hash@{4@}@{62@}@{monty python@}@} $rm{yields} \"fbWx"\
8134 .item "@$header@_<<header name>>:#$rm{or}#@$h@_<<header name>>:"
8135 .item "@$bheader@_<<header name>>:#$rm{or}#@$bh@_<<header name>>:"
8136 .item "@$rheader@_<<header name>>:#$rm{or}#@$rh@_<<header name>>:"
8137 .index expansion||header insertion
8139 .index \$bheader@_$\
8140 .index \$rheader@_$\
8141 .index header lines||in expansion strings
8142 .index header lines||character sets
8143 .index header lines||decoding
8144 Substitute the contents of the named message header line, for example
8148 The newline that terminates a header line is not included in the expansion, but
8149 internal newlines (caused by splitting the header line over several physical
8150 lines) may be present.
8152 The difference between \rheader\, \bheader\, and \header\ is in the way the
8153 data in the header line is interpreted.
8155 .index whitespace||in header lines
8156 \rheader\ gives the original `raw' content of the header line, with no
8157 processing at all, and without the removal of leading and trailing whitespace.
8159 .index base64 encoding||in header lines
8160 \bheader\ removes leading and trailing whitespace, and then decodes base64 or
8161 quoted-printable MIME `words' within the header text, but does no character
8162 set translation. If decoding of what looks superficially like a MIME `word'
8163 fails, the raw string is returned.
8164 .index binary zero||in header line
8165 If decoding produces a binary zero character, it is replaced by a question mark
8166 -- this is what Exim does for binary zeros that are actually received in header
8169 \header\ tries to translate the string as decoded by \bheader\ to a standard
8170 character set. This is an attempt to produce the same string as would be
8171 displayed on a user's MUA. If translation fails, the \bheader\ string is
8172 returned. Translation is attempted only on operating systems that support the
8173 \*iconv()*\ function. This is indicated by the compile-time macro
8174 \\HAVE@_ICONV\\ in a system Makefile or in \(Local/Makefile)\.
8177 In a filter file, the target character set for \header\ can be specified by a
8178 command of the following form:
8180 headers charset "UTF-8"
8182 This command affects all references to \$h@_$\ (or \$header@_$\) expansions in
8183 subsequently obeyed filter commands. In the absence of this command, the target
8184 character set in a filter is taken from the setting of the \headers@_charset\
8185 option in the runtime configuration. The value of this option defaults to the
8186 value of \\HEADERS@_CHARSET\\ in \(Local/Makefile)\. The ultimate default is
8189 Header names follow the syntax of RFC 2822, which states that they may contain
8190 any printing characters except space and colon. Consequently, curly brackets
8191 $it{do not} terminate header names, and should not be used to enclose them as
8192 if they were variables. Attempting to do so causes a syntax error.
8194 Only header lines that are common to all copies of a message are visible to
8195 this mechanism. These are the original header lines that are received with the
8196 message, and any that are added by
8197 an ACL \warn\ statement or by
8198 a system filter. Header lines that are added to a particular copy of a message
8199 by a router or transport are not accessible.
8201 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8202 before the \\DATA\\ ACL, because the header structure is not set up until the
8203 message is received. Header lines that are added by \warn\ statements in a
8204 \\RCPT\\ ACL (for example) are saved until the message's incoming header lines
8205 are available, at which point they are added. When a \\DATA\\ ACL is running,
8206 however, header lines added by earlier ACLs are visible.
8208 Upper case and lower case letters are synonymous in header names. If the
8209 following character is white space, the terminating colon may be omitted, but
8210 this is not recommended, because you may then forget it when it is needed. When
8211 white space terminates the header name, it is included in the expanded string.
8212 If the message does not contain the given header, the expansion item is
8213 replaced by an empty string. (See the \def\ condition in section ~~SECTexpcond
8214 for a means of testing for the existence of a header.)
8216 If there is more than one header with the same name, they are all concatenated
8217 to form the substitution string, up to a maximum length of 64K. A newline
8218 character is inserted between each line.
8219 For the \header\ expansion, for those headers that contain lists of addresses,
8220 a comma is also inserted at the junctions between lines. This does not happen
8221 for the \rheader\ expansion.
8225 .item "@$@{hmac@{<<hashname>>@}@{<<secret>>@}@{<<string>>@}@}"
8226 .index expansion||hmac hashing
8227 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
8228 shared secret and some text into a message authentication code, as specified in
8230 This differs from \"@$@{md5:secret@_text...@}"\ or
8231 \"@$@{sha1:secret@_text...@}"\ in that the hmac step adds a signature to the
8232 cryptographic hash, allowing for authentication that is not possible with MD5
8234 The hash name must expand to either \"md5"\ or \"sha1"\ at present. For
8237 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
8239 For the hostname \*mail.example.com*\ and time 2002-10-17 11:30:59, this
8242 dd97e3ba5d1a61b5006108f8c8252953
8244 As an example of how this might be used, you might put in the main part of
8245 an Exim configuration:
8247 SPAMSCAN_SECRET=cohgheeLei2thahw
8249 In a router or a transport you could then have:
8252 X-Spam-Scanned: ${primary_hostname} ${message_id} \
8253 ${hmac{md5}{SPAMSCAN_SECRET}\
8254 {${primary_hostname},${message_id},$h_message-id:}}
8256 Then given a message, you can check where it was scanned by looking at the
8257 ::X-Spam-Scanned:: header line. If you know the secret, you can check that this
8258 header line is authentic by recomputing the authentication code from the host
8259 name, message ID and the ::Message-id:: header line. This can be done using
8260 Exim's \-be-\ option, or by other means, for example by using the
8261 \*hmac@_md5@_hex()*\ function in Perl.
8264 .item "@${if <<condition>> @{<<string1>>@}@{<<string2>>@}@}"
8265 .index expansion||conditional
8266 If <<condition>> is true, <<string1>> is expanded and replaces the whole item;
8267 otherwise <<string2>> is used. The available conditions are described in
8268 section ~~SECTexpcond below. For example:
8270 ${if eq {$local_part}{postmaster} {yes}{no} }
8272 The second string need not be present; if it is not and the condition is not
8273 true, the item is replaced with nothing. Alternatively, the word `fail' may be
8274 present instead of the second string (without any curly brackets). In this
8275 case, the expansion is forced to fail if the condition is not true (see section
8279 If both strings are omitted, the result is the string \"true"\ if the condition
8280 is true, and the empty string if the condition is false. This makes it less
8281 cumbersome to write custom ACL and router conditions. For example, instead of
8283 condition = ${if >{$acl_m4}{3}{true}{false}}
8287 condition = ${if >{$acl_m4}{3}}
8292 .item "@$@{length@{<<string1>>@}@{<<string2>>@}@}"
8293 .index expansion||string truncation
8294 The \length\ item is used to extract the initial portion of a string. Both
8295 strings are expanded, and the first one must yield a number, <<n>>, say. If you
8296 are using a fixed value for the number, that is, if <<string1>> does not change
8297 when expanded, you can use the simpler operator notation that avoids some of
8300 @$@{length@_<<n>>:<<string>>@}
8302 The result of this item is either the first <<n>> characters or the whole
8303 of <<string2>>, whichever is the shorter. Do not confuse \length\ with
8304 \strlen\, which gives the length of a string.
8307 .item "@${lookup@{<<key>>@} <<search type>> @{<<file>>@} @{<<string1>>@} @{<<string2>>@}@}"
8308 .item "@${lookup <<search type>> @{<<query>>@} @{<<string1>>@} @{<<string2>>@}@}"
8309 .index expansion||lookup in
8311 .index lookup||in expanded string
8312 These items specify data lookups in files and databases, as discussed in
8313 chapter ~~CHAPfdlookup. The first form is used for single-key lookups, and the
8314 second is used for query-style lookups. The <<key>>, <<file>>, and <<query>>
8315 strings are expanded before use.
8317 If there is any white space in a lookup item which is part of a filter command,
8318 a retry or rewrite rule, a routing rule for the \%manualroute%\ router, or any
8319 other place where white space is significant, the lookup item must be enclosed
8320 in double quotes. The use of data lookups in users' filter files may be locked
8321 out by the system administrator.
8324 If the lookup succeeds, <<string1>> is expanded and replaces the entire item.
8325 During its expansion, the variable \$value$\ contains the data returned by the
8326 lookup. Afterwards it reverts to the value it had previously (at the outer
8327 level it is empty). If the lookup fails, <<string2>> is expanded and replaces
8328 the entire item. If @{<<string2>>@} is omitted, the replacement is the empty
8329 string on failure. If <<string2>> is provided, it can itself be a nested
8330 lookup, thus providing a mechanism for looking up a default value when the
8331 original lookup fails.
8333 If a nested lookup is used as part of <<string1>>, \$value$\ contains the data
8334 for the outer lookup while the parameters of the second lookup are expanded,
8335 and also while <<string2>> of the second lookup is expanded, should the second
8338 Instead of @{<<string2>>@} the word `fail' can appear, and in this case, if the
8339 lookup fails, the entire expansion is forced to fail (see section
8340 ~~SECTforexpfai). If both @{<<string1>>@} and @{<<string2>>@} are omitted, the
8341 result is the looked up value in the case of a successful lookup, and nothing
8342 in the case of failure.
8344 For single-key lookups, the string `partial' is permitted to precede the
8345 search type in order to do partial matching, and $*$ or $*$@@ may follow a
8346 search type to request default lookups if the key does not match (see sections
8347 ~~SECTdefaultvaluelookups and ~~SECTpartiallookup for details).
8349 .index numerical variables (\$1$\, \$2$\, etc)||in lookup expansion
8350 If a partial search is used, the variables \$1$\ and \$2$\ contain the wild
8351 and non-wild parts of the key during the expansion of the replacement text.
8352 They return to their previous values at the end of the lookup item.
8354 This example looks up the postmaster alias in the conventional alias file:
8356 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
8358 This example uses NIS+ to look up the full name of the user corresponding to
8359 the local part of an address, forcing the expansion to fail if it is not found:
8361 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8366 .item "@$@{nhash@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8367 .index expansion||numeric hash
8368 .index hash function||numeric
8369 The three strings are expanded; the first two must yield numbers. Call them
8370 <<n>> and <<m>>. If you are using fixed values for these numbers, that is, if
8371 <<string1>> and <<string2>> do not change when they are expanded, you can use
8372 the simpler operator notation that avoids some of the braces:
8374 @$@{nhash@_<<n>>@_<<m>>:<<string>>@}
8376 The second number is optional (in both notations). If there is only one number,
8377 the result is a number in the range 0--<<n>>-1. Otherwise, the string is
8378 processed by a div/mod hash function that returns two numbers, separated by a
8379 slash, in the ranges 0 to <<n>>-1 and 0 to <<m>>-1, respectively. For example,
8381 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8383 returns the string `6/33'.
8387 .item "@$@{perl@{<<subroutine>>@}@{<<arg>>@}@{<<arg>>@}...@}"
8388 .index Perl||use in expanded string
8389 .index expansion||calling Perl from
8390 This item is available only if Exim has been built to include an embedded Perl
8391 interpreter. The subroutine name and the arguments are first separately
8392 expanded, and then the Perl subroutine is called with those arguments. No
8393 additional arguments need be given; the maximum number permitted, including the
8394 name of the subroutine, is nine.
8396 The return value of the subroutine is inserted into the expanded string, unless
8397 the return value is \undef\. In that case, the expansion fails in the same way
8398 as an explicit `fail' on a lookup item.
8399 The return value is a scalar. Whatever you return is evaluated in a scalar
8400 context. For example, if you return the name of a Perl vector, the
8401 return value is the size of the vector, not its contents.
8403 If the subroutine exits by calling Perl's \die\ function, the expansion fails
8404 with the error message that was passed to \die\. More details of the embedded
8405 Perl facility are given in chapter ~~CHAPperl.
8407 The \%redirect%\ router has an option called \forbid@_filter@_perl\ which locks
8408 out the use of this expansion item in filter files.
8411 .item "@$@{readfile@{<<file name>>@}@{<<eol string>>@}@}"
8412 .index expansion||inserting an entire file
8413 .index file||inserting into expansion
8414 The file name and end-of-line string are first expanded separately. The file is
8415 then read, and its contents replace the entire item. All newline characters in
8416 the file are replaced by the end-of-line string if it is present. Otherwise,
8417 newlines are left in the string.
8418 String expansion is not applied to the contents of the file. If you want this,
8419 you must wrap the item in an \expand\ operator. If the file cannot be read, the
8420 string expansion fails.
8422 The \%redirect%\ router has an option called \forbid@_filter@_readfile\ which
8423 locks out the use of this expansion item in filter files.
8427 .item "@$@{readsocket@{<<name>>@}@{<<request>>@}@{<<timeout>>@}@{<<eol string>>@}@{<<fail string>>@}@}"
8428 .index expansion||inserting from a socket
8429 .index socket, use of in expansion
8430 This item inserts data that is read from a Unix domain socket into the expanded
8431 string. The minimal way of using it uses just two arguments:
8433 ${readsocket{/socket/name}{request string}}
8435 Exim connects to the socket, writes the request string (unless it is an
8436 empty string) and reads from the socket until an end-of-file is read. A timeout
8437 of 5 seconds is applied. Additional, optional arguments extend what can be
8438 done. Firstly, you can vary the timeout. For example:
8440 ${readsocket{/socket/name}{request-string}{3s}}
8442 A fourth argument allows you to change any newlines that are in the data
8443 that is read, in the same way as for \readfile\ (see above). This example turns
8446 ${readsocket{/socket/name}{request-string}{3s}{ }}
8448 As with all expansions, the substrings are expanded before the processing
8449 happens. Errors in these sub-expansions cause the expansion to fail. In
8450 addition, the following errors can occur:
8452 Failure to create a socket file descriptor;
8454 Failure to connect the socket;
8456 Failure to write the request-string;
8458 Timeout on reading from the socket.
8460 By default, any of these errors causes the expansion to fail. However, if
8461 you supply a fifth substring, it is expanded and used when any of the above
8462 errors occurs. For example:
8464 ${readsocket{/socket/name}{request-string}{3s}{\n}\
8467 You can test for the existence of the socket by wrapping this expansion in
8468 \"@$@{if exists"\, but there is a race condition between that test and the
8469 actual opening of the socket, so it is safer to use the fifth argument if you
8470 want to be absolutely sure of avoiding an expansion error for a non-existent
8473 The \%redirect%\ router has an option called \forbid@_filter@_readsocket\ which
8474 locks out the use of this expansion item in filter files.
8476 .item "@$rheader@_<<header name>>:#$rm{or}#@$rh@_<<header name>>:"
8477 This item inserts `raw' header lines. It is described with the \header\
8478 expansion item above.
8482 .item "@$@{run@{<<command>> <<args>>@}@{<<string1>>@}@{<<string2>>@}@}"
8483 .index expansion||running a command
8484 The command and its arguments are first expanded separately, and then the
8485 command is run in a separate process, but under the same uid and gid. As in
8486 other command executions from Exim, a shell is not used by default. If you want
8487 a shell, you must explicitly code it.
8488 .index return code||from \run\ expansion
8489 If the command succeeds (gives a zero return code) <<string1>> is expanded and
8490 replaces the entire item; during this expansion, the standard output from the
8491 command is in the variable \$value$\. If the command fails, <<string2>>, if
8492 present, is expanded. If it is absent, the result is empty. Alternatively,
8493 <<string2>> can be the word `fail' (not in braces) to force expansion failure
8494 if the command does not succeed. If both strings are omitted, the result is the
8495 standard output on success, and nothing on failure.
8497 The return code from the command is put in the variable \$runrc$\, and this
8498 remains set afterwards, so in a filter file you can do things like this:
8500 if "${run{x y z}{}}$runrc" is 1 then ...
8501 elif $runrc is 2 then ...
8505 If execution of the command fails (for example, the command does not exist),
8506 the return code is 127 -- the same code that shells use for non-existent
8509 \**Warning**\: In a router or transport, you cannot assume the order in which
8510 option values are expanded, except for those pre-conditions whose order of
8511 testing is documented. Therefore, you cannot reliably expect to set \$runrc$\
8512 by the expansion of one option, and use it in another.
8514 The \%redirect%\ router has an option called \forbid@_filter@_run\ which locks
8515 out the use of this expansion item in filter files.
8518 .item "@$@{sg@{<<subject>>@}@{<<regex>>@}@{<<replacement>>@}@}"
8519 .index expansion||string substitution
8520 This item works like Perl's substitution operator (s) with the global (/g)
8521 option; hence its name. However, unlike the Perl equivalent, Exim does not
8522 modify the subject string; instead it returns the modified string for insertion
8523 into the overall expansion. The item takes three arguments: the subject string,
8524 a regular expression, and a substitution string. For example
8526 ${sg{abcdefabcdef}{abc}{xyz}}
8528 yields `xyzdefxyzdef'. Because all three arguments are expanded before use, if
8529 any @$ or @\ characters are required in the regular expression or in the
8530 substitution string, they have to be escaped. For example
8532 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
8534 yields `defabc', and
8536 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
8538 yields `K1=A K4=D K3=C'.
8539 Note the use of \"@\N"\ to protect the contents of the regular expression from
8544 .item "@$@{substr@{<<string1>>@}@{<<string2>>@}@{<<string3>>@}@}"
8546 .index substring extraction
8547 .index expansion||substring extraction
8548 The three strings are expanded; the first two must yield numbers. Call them
8549 <<n>> and <<m>>. If you are using fixed values for these numbers, that is, if
8550 <<string1>> and <<string2>> do not change when they are expanded, you can use
8551 the simpler operator notation that avoids some of the braces:
8553 @$@{substr@_<<n>>@_<<m>>:<<string>>@}
8555 The second number is optional (in both notations).
8557 If it is absent in the simpler format, the preceding underscore must also be
8561 The \substr\ item can be used to extract more general substrings than \length\.
8562 The first number, <<n>>, is a starting offset, and <<m>> is the length
8563 required. For example
8565 ${substr{3}{2}{$local_part}}
8567 If the starting offset is greater than the string length the result is the null
8568 string; if the length plus starting offset is greater than the string length,
8569 the result is the right-hand part of the string, starting from the given
8570 offset. The first character in the string has offset zero.
8572 The \substr\ expansion item can take negative offset values to count
8573 from the right-hand end of its operand. The last character is offset -1, the
8574 second-last is offset -2, and so on. Thus, for example,
8576 ${substr{-5}{2}{1234567}}
8578 yields `34'. If the absolute value of a negative offset is greater than the
8579 length of the string, the substring starts at the beginning of the string, and
8580 the length is reduced by the amount of overshoot. Thus, for example,
8582 ${substr{-5}{2}{12}}
8584 yields an empty string, but
8586 ${substr{-3}{2}{12}}
8590 When the second number is omitted from \substr\, the remainder of the string is
8591 taken if the offset is positive. If it is negative, all characters in the
8592 string preceding the offset point are taken. For example, an offset of -1 and
8593 no length, as in these semantically identical examples:
8596 ${substr{-1}{abcde}}
8598 yields all but the last character of the string, that is, `abcd'.
8602 .item "@$@{tr@{<<subject>>@}@{<<characters>>@}@{<<replacements>>@}@}"
8603 .index expansion||character translation
8604 This item does single-character translation on its subject string. The second
8605 argument is a list of characters to be translated in the subject string. Each
8606 matching character is replaced by the corresponding character from the
8607 replacement list. For example
8609 ${tr{abcdea}{ac}{13}}
8611 yields `1b3de1'. If there are duplicates in the second character string, the
8612 last occurrence is used. If the third string is shorter than the second, its
8613 last character is replicated. However, if it is empty, no translation takes
8619 .section Expansion operators
8620 .rset SECTexpop "~~chapter.~~section"
8621 .index expansion||operators
8622 For expansion items that perform transformations on a single argument string,
8623 the `operator' notation is used because it is simpler and uses fewer braces.
8624 The substring is first expanded before the operation is applied to it. The
8625 following operations can be performed:
8629 .item "@$@{address:<<string>>@}"
8630 .index expansion||RFC 2822 address handling
8631 The string is interpreted as an RFC 2822 address, as it might appear in a
8632 header line, and the effective address is extracted from it. If the string does
8633 not parse successfully, the result is empty.
8636 .item "@$@{base62:<<digits>>@}"
8638 .index expansion||conversion to base 62
8639 The string must consist entirely of decimal digits. The number is converted to
8640 base 62 (sic) and output as a string of six characters, including leading
8641 zeros. \**Note**\: Just to be absolutely clear: this is \*not*\ base64
8644 .item "@$@{base62d:<<base-62 digits>>@}"
8646 .index expansion||conversion to base 62
8647 The string must consist entirely of base-62 digits. The number is converted to
8648 decimal and output as a string.
8651 .item "@$@{domain:<<string>>@}"
8652 .index domain||extraction
8653 .index expansion||domain extraction
8654 The string is interpreted as an RFC 2822 address and the domain is extracted
8655 from it. If the string does not parse successfully, the result is empty.
8658 .item "@$@{escape:<<string>>@}"
8659 .index expansion||escaping non-printing characters
8660 If the string contains any non-printing characters, they are converted to
8661 escape sequences starting with a backslash. Whether characters with the most
8662 significant bit set (so-called `8-bit characters') count as printing or not is
8663 controlled by the \print@_topbitchars\ option.
8666 .item "@$@{eval:<<string>>@}"
8667 .item "@$@{eval10:<<string>>@}"
8668 .index expansion||expression evaluation
8669 .index expansion||arithmetic expression
8670 These items supports simple arithmetic in expansion strings. The string (after
8671 expansion) must be a conventional arithmetic expression, but it is limited to
8672 the four basic operators (plus, minus, times, divide) and parentheses. All
8673 operations are carried out using integer arithmetic. Plus and minus have a
8674 lower priority than times and divide; operators with the same priority are
8675 evaluated from left to right.
8677 For \eval\, numbers may be decimal, octal (starting with `0') or hexadecimal
8678 (starting with `0x'). For \eval10\, all numbers are taken as decimal, even if
8679 they start with a leading zero. This can be useful when processing numbers
8680 extracted from dates or times, which often do have leading zeros.
8682 A number may be followed by `K' or `M' to multiply it by 1024 or 1024$*$1024,
8683 respectively. Negative numbers are supported. The result of the computation is
8684 a decimal representation of the answer (without `K' or `M'). For example:
8686 @$@{eval:1+1@} $rm{yields} 2
8687 @$@{eval:1+2*3@} $rm{yields} 7
8688 @$@{eval:(1+2)*3@} $rm{yields} 9
8690 As a more realistic example, in an ACL you might have
8692 deny message = Too many bad recipients
8695 {>{$rcpt_count}{10}} \
8698 {$recipients_count} \
8699 {${eval:$rcpt_count/2}} \
8703 The condition is true if there have been more than 10 \\RCPT\\ commands and
8704 fewer than half of them have resulted in a valid recipient.
8707 .item "@$@{expand:<<string>>@}"
8708 .index expansion||re-expansion of substring
8709 The \expand\ operator causes a string to be expanded for a second time. For
8712 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
8714 first looks up a string in a file while expanding the operand for \expand\, and
8715 then re-expands what it has found.
8718 .item "@$@{from@_utf8:<<string>>@}"
8720 .index UTF-8||conversion from
8721 .index expansion||UTF-8 conversion
8722 The world is slowly moving towards Unicode, although there are no standards for
8723 email yet. However, other applications (including some databases) are starting
8724 to store data in Unicode, using UTF-8 encoding. This operator converts from a
8725 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
8726 converted to underscores. The input must be a valid UTF-8 string. If it is not,
8727 the result is an undefined sequence of bytes.
8729 Unicode code points with values less than 256 are compatible with ASCII and
8730 ISO-8859-1 (also known as Latin-1).
8731 For example, character 169 is the copyright symbol in both cases, though the
8732 way it is encoded is different. In UTF-8, more than one byte is needed for
8733 characters with code values greater than 127, whereas ISO-8859-1 is a
8734 single-byte encoding (but thereby limited to 256 characters). This makes
8735 translation from UTF-8 to ISO-8859-1 straightforward.
8738 .item "@$@{hash@_<<n>>@_<<m>>:<<string>>@}"
8739 .index hash function||textual
8740 .index expansion||textual hash
8741 The \hash\ operator is a simpler interface to the hashing function that can be
8742 used when the two parameters are fixed numbers (as opposed to strings that
8743 change when expanded). The effect is the same as
8745 @$@{hash@{<<n>>@}@{<<m>>@}@{<<string>>@}@}
8747 See the description of the general \hash\ item above for details. The
8748 abbreviation \h\ can be used when \hash\ is used as an operator.
8752 .item "@$@{hex2b64:<<hexstring>>@}"
8753 .index base64 encoding||conversion from hex
8754 .index expansion||hex to base64
8755 This operator converts a hex string into one that is base64 encoded. This can
8756 be useful for processing the output of the MD5 and SHA-1 hashing functions.
8759 .item "@$@{lc:<<string>>@}"
8760 .index case forcing in strings
8761 .index string||case forcing
8763 .index expansion||case forcing
8764 This forces the letters in the string into lower-case, for example:
8770 .item "@$@{length@_<<number>>:<<string>>@}"
8771 .index expansion||string truncation
8772 The \length\ operator is a simpler interface to the \length\ function that can
8773 be used when the parameter is a fixed number (as opposed to a string that
8774 changes when expanded). The effect is the same as
8776 @$@{length@{<<number>>@}@{<<string>>@}@}
8778 See the description of the general \length\ item above for details. Note that
8779 \length\ is not the same as \strlen\. The abbreviation \l\ can be used when
8780 \length\ is used as an operator.
8783 .item "@$@{local@_part:<<string>>@}"
8784 .index expansion||local part extraction
8785 The string is interpreted as an RFC 2822 address and the local part is
8786 extracted from it. If the string does not parse successfully, the result is
8790 .item "@$@{mask:<<IP address>>/<<bit count>>@}"
8791 .index masked IP address
8792 .index IP address||masking
8793 .index CIDR notation
8794 .index expansion||IP address masking
8795 If the form of the string to be operated on is not an IP address followed by a
8796 slash and an integer (that is, a network address in CIDR notation), the
8797 expansion fails. Otherwise, this operator converts the IP address to binary,
8798 masks off the least significant bits according to the bit count, and converts
8799 the result back to text, with mask appended. For example,
8801 ${mask:10.111.131.206/28}
8803 returns the string `10.111.131.192/28'. Since this operation is expected to be
8804 mostly used for looking up masked addresses in files, the result for an IPv6
8805 address uses dots to separate components instead of colons, because colon
8806 terminates a key string in lsearch files. So, for example,
8808 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
8812 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
8814 Letters in IPv6 addresses are always output in lower case.
8817 .item "@$@{md5:<<string>>@}"
8819 .index expansion||MD5 hash
8820 The \md5\ operator computes the MD5 hash value of the string, and returns it as
8821 a 32-digit hexadecimal number,
8822 in which any letters are in lower case.
8825 .item "@$@{nhash@_<<n>>@_<<m>>:<<string>>@}"
8826 .index expansion||numeric hash
8827 .index hash function||numeric
8828 The \nhash\ operator is a simpler interface to the numeric hashing function
8829 that can be used when the two parameters are fixed numbers (as opposed to
8830 strings that change when expanded). The effect is the same as
8832 @$@{nhash@{<<n>>@}@{<<m>>@}@{<<string>>@}@}
8834 See the description of the general \nhash\ item above for details.
8837 .item "@$@{quote:<<string>>@}"
8838 .index quoting||in string expansions
8839 .index expansion||quoting
8840 The \quote\ operator puts its argument into double quotes if it
8841 is an empty string or
8842 contains anything other than letters, digits, underscores, dots, and hyphens.
8843 Any occurrences of double quotes and backslashes are escaped with a backslash.
8844 Newlines and carriage returns are converted to \"@\n"\ and \"@\r"\,
8845 respectively For example,
8853 The place where this is useful is when the argument is a substitution from a
8854 variable or a message header.
8856 .item "@$@{quote@_local@_part:<<string>>@}"
8857 This operator is like \quote\, except that it quotes the string only if
8858 required to do so by the rules of RFC 2822 for quoting local parts. For
8859 example, a plus sign would not cause quoting (but it would for \quote\).
8860 If you are creating a new email address from the contents of \$local@_part$\
8861 (or any other unknown data), you should always use this operator.
8864 .item "@$@{quote@_<<lookup-type>>:<<string>>@}"
8865 .index quoting||lookup-specific
8866 This operator applies lookup-specific quoting rules to the string. Each
8867 query-style lookup type has its own quoting rules which are described with
8868 the lookups in chapter ~~CHAPfdlookup. For example,
8870 ${quote_ldap:two * two}
8876 For single-key lookup types, no quoting is ever necessary and this operator
8877 yields an unchanged string.
8880 .item "@$@{rxquote:<<string>>@}"
8881 .index quoting||in regular expressions
8882 .index regular expressions||quoting
8883 The \rxquote\ operator inserts a backslash before any non-alphanumeric
8884 characters in its argument. This is useful when substituting the values of
8885 variables or headers inside regular expressions.
8888 .item "@$@{rfc2047:<<string>>@}"
8889 .index expansion||RFC 2047
8890 This operator encodes text according to the rules of RFC 2047. This is an
8891 encoding that is used in header lines to encode non-ASCII characters. It is
8892 assumed that the input string is in the encoding specified by the
8893 \headers@_charset\ option, which defaults to ISO-8859-1. If the string contains
8894 only characters in the range 33--126, and no instances of the characters
8896 ? = ( ) < > @ , ; : \ " . [ ] _
8898 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
8901 using as many `coded words' as necessary to encode all the characters.
8905 .item "@$@{sha1:<<string>>@}"
8907 .index expansion||SHA-1 hashing
8908 The \sha1\ operator computes the SHA-1 hash value of the string, and returns it
8909 as a 40-digit hexadecimal number, in which any letters are in upper case.
8912 .item "@$@{stat:<<string>>@}"
8913 .index expansion||statting a file
8914 .index file||extracting characteristics
8915 The string, after expansion, must be a file path. A call to the \*stat()*\
8916 function is made for this path. If \*stat()*\ fails, an error occurs and the
8917 expansion fails. If it succeeds, the data from the stat replaces the item, as a
8918 series of <<name>>=<<value>> pairs, where the values are all numerical,
8919 except for the value of `smode'. The names are: `mode' (giving the mode as a
8920 4-digit octal number), `smode' (giving the mode in symbolic format as a
8921 10-character string, as for the \*ls*\ command), `inode', `device', `links',
8922 `uid', `gid', `size', `atime', `mtime', and `ctime'. You can extract individual
8923 fields using the \extract\ expansion item. \**Warning**\: The file size may be
8924 incorrect on 32-bit systems for files larger than 2GB.
8928 .item "@$@{str2b64:<<string>>@}"
8929 .index expansion||base64 encoding
8930 .index base64 encoding||in string expansion
8931 This operator converts a string into one that is base64 encoded.
8935 .item "@$@{strlen:<<string>>@}"
8936 .index expansion||string length
8937 .index string||length in expansion
8938 The item is replace by the length of the expanded string, expressed as a
8939 decimal number. \**Note**\: Do not confuse \strlen\ with \length\.
8942 .item "@$@{substr@_<<start>>@_<<length>>:<<string>>@}"
8944 .index substring extraction
8945 .index expansion||substring expansion
8946 The \substr\ operator is a simpler interface to the \substr\ function that can
8947 be used when the two parameters are fixed numbers (as opposed to strings that
8948 change when expanded). The effect is the same as
8950 @$@{substr@{<<start>>@}@{<<length>>@}@{<<string>>@}@}
8952 See the description of the general \substr\ item above for details. The
8953 abbreviation \s\ can be used when \substr\ is used as an operator.
8955 .item "@$@{time@_interval:<<string>>@}"
8956 .index \time@_interval\
8957 .index time interval||formatting
8958 The argument (after sub-expansion) must be a sequence of decimal digits that
8959 represents an interval of time as a number of seconds. It is converted into a
8960 number of larger units and output in Exim's normal time format, for example,
8963 .item "@$@{uc:<<string>>@}"
8964 .index case forcing in strings
8965 .index string||case forcing
8967 .index expansion||case forcing
8968 This forces the letters in the string into upper-case.
8974 .section Expansion conditions
8975 .rset SECTexpcond "~~chapter.~~section"
8976 .index expansion||conditions
8977 The following conditions are available for testing by the \@$@{if\ construct
8978 while expanding strings:
8982 .item "!<<condition>>"
8983 .index expansion||negating a condition
8984 Preceding any condition with an exclamation mark negates the result of the
8987 .item "<<symbolic operator>> @{<<string1>>@}@{<<string2>>@}"
8988 .index numeric comparison
8989 .index expansion||numeric comparison
8990 There are a number of symbolic operators for doing numeric comparisons. They
8997 >= $t $rm{greater or equal}
8999 <= $t $rm{less or equal}
9003 ${if >{$message_size}{10M} ...
9005 Note that the general negation operator provides for inequality testing. The
9006 two strings must take the form of optionally signed decimal integers,
9007 optionally followed by one of the letters `K' or `M' (in either upper or lower
9008 case), signifying multiplication by 1024 or 1024$*$1024, respectively.
9010 .item "crypteq @{<<string1>>@}@{<<string2>>@}"
9011 .index expansion||encrypted comparison
9012 .index encrypted strings, comparing
9013 This condition is included in the Exim binary if it is built to support any
9014 authentication mechanisms (see chapter ~~CHAPSMTPAUTH). Otherwise, it is
9015 necessary to define \\SUPPORT@_CRYPTEQ\\ in \(Local/Makefile)\ to get \crypteq\
9016 included in the binary.
9018 The \crypteq\ condition has two arguments. The first is encrypted and compared
9019 against the second, which is already encrypted. The second string may be in the
9020 LDAP form for storing encrypted strings, which starts with the encryption type
9021 in curly brackets, followed by the data. If the second string does not begin
9022 with `{' it is assumed to be encrypted with \*crypt()*\
9023 or \*crypt16()*\ (see below),
9024 since such strings cannot begin with `{'. Typically this will be a field from a
9027 An example of an encrypted string in LDAP form is:
9029 {md5}CY9rzUYh03PK3k6DJie09g==
9031 If such a string appears directly in an expansion, the curly brackets have to
9032 be quoted, because they are part of the expansion syntax. For example:
9034 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
9036 The following encryption types
9037 (whose names are matched case-independently)
9041 .index base64 encoding||in encrypted password
9042 \@{md5@}\ computes the MD5 digest of the first string, and expresses this as
9043 printable characters to compare with the remainder of the second string. If the
9044 length of the comparison string is 24, Exim assumes that it is base64 encoded
9045 (as in the above example). If the length is 32, Exim assumes that it is a
9046 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
9050 \@{sha1@}\ computes the SHA-1 digest of the first string, and expresses this as
9051 printable characters to compare with the remainder of the second string. If the
9052 length of the comparison string is 28, Exim assumes that it is base64 encoded.
9053 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
9054 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
9057 \@{crypt@}\ calls the \*crypt()*\ function,
9059 which traditionally used to use only the first eight characters of the
9060 password. However, in modern operating systems this is no longer true, and in
9061 many cases the entire password is used, whatever its length.
9064 .index \*crypt16()*\
9065 \@{crypt16@}\ calls the \*crypt16()*\ function (also known as \*bigcrypt()*\),
9068 was orginally created to use up to 16 characters of the password. Again, in
9069 modern operating systems, more characters may be used.
9072 Exim has its own version of \*crypt16()*\ (which is just a double call to
9073 \*crypt()*\). For operating systems that have their own version, setting
9074 \\HAVE@_CRYPT16\\ in \(Local/Makefile)\ when building Exim causes it to use the
9075 operating system version instead of its own. This option is set by default in
9076 the OS-dependent \(Makefile)\ for those operating systems that are known to
9077 support \*crypt16()*\.
9079 If you do not put any curly bracket encryption type in a \crypteq\ comparison,
9080 the default is either \"@{crypt@}"\ or \"@{crypt16@}"\, as determined by the
9081 setting of \\DEFAULT@_CRYPT\\ in \(Local/Makefile)\. The default default is
9082 \"@{crypt@}"\. Whatever the default, you can always use either function by
9083 specifying it explicitly in curly brackets.
9085 Note that if a password is no longer than 8 characters, the results of
9086 encrypting it with \*crypt()*\ and \*crypt16()*\ are identical. That means that
9087 \*crypt16()*\ is backwards compatible, as long as nobody feeds it a password
9088 longer than 8 characters.
9091 .item "def:<<variable name>>"
9092 .index expansion||checking for empty variable
9093 The \def\ condition must be followed by the name of one of the expansion
9094 variables defined in section ~~SECTexpvar. The condition is true if the named
9095 expansion variable does not contain the empty string, for example
9097 ${if def:sender_ident {from $sender_ident}}
9099 Note that the variable name is given without a leading \@$\ character. If the
9100 variable does not exist, the expansion fails.
9102 .item "def:header@_<<header name>>:##or##def:h@_<<header name>>:"
9103 .index expansion||checking header line existence
9104 This condition is true if a message is being processed and the named header
9105 exists in the message. For example,
9107 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
9109 Note that no \@$\ appears before \header@_\ or \h@_\ in the condition,
9110 and that header names must be terminated by colons if white space does not
9113 .item "eq @{<<string1>>@}@{<<string2>>@}"
9114 .item "eqi @{<<string1>>@}@{<<string2>>@}"
9115 .index string||comparison
9116 .index expansion||string comparison
9117 The two substrings are first expanded. The condition is true if the two
9118 resulting strings are identical: for \eq\ the comparison includes the case of
9119 letters, whereas for \eqi\ the comparison is case-independent.
9121 .item "exists @{<<file name>>@}"
9122 .index expansion||file existence test
9123 .index file||existence test
9124 The substring is first expanded and then interpreted as an absolute path. The
9125 condition is true if the named file (or directory) exists. The existence test
9126 is done by calling the \*stat()*\ function. The use of the \exists\ test in
9127 users' filter files may be locked out by the system administrator.
9129 .item "first@_delivery"
9130 .index delivery||first
9131 .index first delivery
9132 .index expansion||first delivery test
9133 This condition, which has no data, is true during a message's first delivery
9134 attempt. It is false during any subsequent delivery attempts.
9136 .item "ge @{<<string1>>@}@{<<string2>>@}"
9137 .item "gei @{<<string1>>@}@{<<string2>>@}"
9138 .index string||comparison
9139 .index expansion||string comparison
9140 The two substrings are first expanded. The condition is true if the first
9141 string is lexically greater than or equal to the second string: for \ge\ the
9142 comparison includes the case of letters, whereas for \gei\ the comparison is
9145 .item "gt @{<<string1>>@}@{<<string2>>@}"
9146 .item "gti @{<<string1>>@}@{<<string2>>@}"
9147 .index string||comparison
9148 .index expansion||string comparison
9149 The two substrings are first expanded. The condition is true if the first
9150 string is lexically greater than the second string: for \gt\ the comparison
9151 includes the case of letters, whereas for \gti\ the comparison is
9154 .item "isip @{<<string>>@}" 8
9155 .item "isip4 @{<<string>>@}"
9156 .item "isip6 @{<<string>>@}"
9157 .index IP address||testing string format
9158 .index string||testing for IP address
9159 The substring is first expanded, and then tested to see if it has the form of
9160 an IP address. Both IPv4 and IPv6 addresses are valid for \isip\, whereas
9161 \isip4\ and \isip6\ test just for IPv4 or IPv6 addresses, respectively. For
9162 example, you could use
9164 ${if isip4{$sender_host_address}...
9166 to test which version of IP an incoming SMTP connection is using.
9169 .item "ldapauth @{<<ldap query>>@}"
9170 .index LDAP||use for authentication
9171 .index expansion||LDAP authentication test
9172 This condition supports user authentication using LDAP. See section ~~SECTldap
9173 for details of how to use LDAP in lookups and the syntax of queries. For this
9174 use, the query must contain a user name and password. The query itself is not
9175 used, and can be empty. The condition is true if
9176 the password is not empty, and the user name and password are accepted by the
9177 LDAP server. An empty password is rejected without calling LDAP because LDAP
9178 binds with an empty password are considered anonymous regardless of
9179 the username, and will succeed in most configurations.
9180 See chapter ~~CHAPSMTPAUTH for details of SMTP authentication, and chapter
9181 ~~CHAPplaintext for an example of how this can be used.
9184 .item "le @{<<string1>>@}@{<<string2>>@}"
9185 .item "lei @{<<string1>>@}@{<<string2>>@}"
9186 .index string||comparison
9187 .index expansion||string comparison
9188 The two substrings are first expanded. The condition is true if the first
9189 string is lexically less than or equal to the second string: for \le\ the
9190 comparison includes the case of letters, whereas for \lei\ the comparison is
9193 .item "lt @{<<string1>>@}@{<<string2>>@}"
9194 .item "lti @{<<string1>>@}@{<<string2>>@}"
9195 .index string||comparison
9196 .index expansion||string comparison
9197 The two substrings are first expanded. The condition is true if the first
9198 string is lexically less than the second string: for \lt\ the comparison
9199 includes the case of letters, whereas for \lti\ the comparison is
9203 .item "match @{<<string1>>@}@{<<string2>>@}"
9204 .index expansion||regular expression comparison
9205 .index regular expressions||match in expanded string
9206 The two substrings are first expanded. The second is then treated as a regular
9207 expression and applied to the first. Because of the pre-expansion, if the
9208 regular expression contains dollar, or backslash characters, they must be
9209 escaped. Care must also be taken if the regular expression contains braces
9210 (curly brackets). A closing brace must be escaped so that it is not taken as a
9211 premature termination of <<string2>>. The easiest approach is to use the
9212 \"@\N"\ feature to disable expansion of the regular expression.
9215 ${if match {$local_part}{\N^\d{3}\N} ...
9217 If the whole expansion string is in double quotes, further escaping of
9218 backslashes is also required.
9220 The condition is true if the regular expression match succeeds.
9221 The regular expression is not required to begin with a circumflex
9222 metacharacter, but if there is no circumflex, the expression is not anchored,
9223 and it may match anywhere in the subject, not just at the start. If you want
9224 the pattern to match at the end of the subject, you must include the \"@$"\
9225 metacharacter at an appropriate point.
9227 .index numerical variables (\$1$\, \$2$\, etc)||in \if\ expansion
9228 At the start of an \if\ expansion the values of the numeric variable
9229 substitutions \$1$\ etc. are remembered. Obeying a \match\ condition that
9230 succeeds causes them to be reset to the substrings of that condition and they
9231 will have these values during the expansion of the success string. At the end
9232 of the \if\ expansion, the previous values are restored. After testing a
9233 combination of conditions using \or\, the subsequent values of the numeric
9234 variables are those of the condition that succeeded.
9236 .item "match@_domain @{<<string1>>@}@{<<string2>>@}"
9237 .item "match@_address @{<<string1>>@}@{<<string2>>@}"
9238 .item "match@_local@_part @{<<string1>>@}@{<<string2>>@}"
9239 .index domain list||in expansion condition
9240 .index address list||in expansion condition
9241 .index local part list||in expansion condition
9242 These conditions make it possible to test domain, address, and local
9243 part lists within expansions. Each condition requires two arguments: an item
9244 and a list to match. A trivial example is:
9246 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
9248 In each case, the second argument may contain any of the allowable items for a
9249 list of the appropriate type. Also, because the second argument (after
9250 expansion) is a standard form of list, it is possible to refer to a named list.
9251 Thus, you can use conditions like this:
9253 ${if match_domain{$domain}{+local_domains}{...
9256 For address lists, the matching starts off caselessly, but the \"+caseful"\
9257 item can be used, as in all address lists, to cause subsequent items to
9258 have their local parts matched casefully. Domains are always matched
9261 \**Note**\: Host lists are \*not*\ supported in this way. This is because
9262 hosts have two identities: a name and an IP address, and it is not clear
9263 how to specify cleanly how such a test would work. At least, I haven't come
9264 up with anything yet.
9266 .item "pam {<<string1>>:<<string2>>:...@}"
9267 .index PAM authentication
9268 .index \\AUTH\\||with PAM
9269 .index Solaris||PAM support
9270 .index expansion||PAM authentication test
9271 \*Pluggable Authentication Modules*\
9272 (\?http://www.kernel.org/pub/linux/libs/pam/?\)
9273 are a facility which is available in the latest releases of Solaris and in some
9274 GNU/Linux distributions. The Exim support, which is intended for use in
9275 conjunction with the SMTP \\AUTH\\ command, is available only if Exim is
9280 in \(Local/Makefile)\. You probably need to add \-lpam-\ to \\EXTRALIBS\\, and
9281 in some releases of GNU/Linux \-ldl-\ is also needed.
9283 The argument string is first expanded, and the result must be a colon-separated
9285 Leading and trailing whitespace is ignored.
9286 The PAM module is initialized with the service name `exim' and the user name
9287 taken from the first item in the colon-separated data string (<<string1>>). The
9288 remaining items in the data string are passed over in response to requests from
9289 the authentication function. In the simple case there will only be one request,
9290 for a password, so the data consists of just two strings.
9292 There can be problems if any of the strings are permitted to contain colon
9293 characters. In the usual way, these have to be doubled to avoid being taken as
9294 separators. If the data is being inserted from a variable, the \sg\ expansion
9295 item can be used to double any existing colons. For example, the configuration
9296 of a LOGIN authenticator might contain this setting:
9298 server_condition = ${if pam{$1:${sg{$2}{:}{::}}}{yes}{no}}
9300 For a PLAIN authenticator you could use:
9302 server_condition = ${if pam{$2:${sg{$3}{:}{::}}}{yes}{no}}
9304 In some operating systems, PAM authentication can be done only from a process
9305 running as root. Since Exim is running as the Exim user when receiving
9306 messages, this means that PAM cannot be used directly in those systems.
9307 A patched version of the \*pam@_unix*\ module that comes with the
9308 Linux PAM package is available from \?http:@/@/www.e-admin.de/pam@_exim/?\.
9309 The patched module allows one special uid/gid combination, in addition to root,
9310 to authenticate. If you build the patched module to allow the Exim user and
9311 group, PAM can then be used from an Exim authenticator.
9314 .item "pwcheck {<<string1>>:<<string2>>@}"
9315 .index \*pwcheck*\ daemon
9317 .index expansion||\*pwcheck*\ authentication test
9318 This condition supports user authentication using the Cyrus \*pwcheck*\ daemon.
9319 This is one way of making it possible for passwords to be checked by a process
9320 that is not running as root.
9321 \**Note:**\ The use of \*pwcheck*\ is now deprecated. Its replacement is
9322 \*saslauthd*\ (see below).
9324 The pwcheck support is not included in Exim by default. You need to specify
9325 the location of the pwcheck daemon's socket in \(Local/Makefile)\ before
9326 building Exim. For example:
9328 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
9330 You do not need to install the full Cyrus software suite in order to use
9331 the pwcheck daemon. You can compile and install just the daemon alone
9332 from the Cyrus SASL library. Ensure that \*exim*\ is the only user that has
9333 access to the \(/var/pwcheck)\ directory.
9335 The \pwcheck\ condition takes one argument, which must be the user name and
9336 password, separated by a colon. For example, in a LOGIN authenticator
9337 configuration, you might have this:
9339 server_condition = ${if pwcheck{$1:$2}{1}{0}}
9342 .item "queue@_running"
9343 .index queue runner||detecting when delivering from
9344 .index expansion||queue runner test
9345 This condition, which has no data, is true during delivery attempts that are
9346 initiated by queue runner processes, and false otherwise.
9349 .item "radius {<<authentication string>>@}"
9351 .index expansion||Radius authentication
9352 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
9353 set \\RADIUS@_CONFIG@_FILE\\ in \(Local/Makefile)\ to specify the location of
9354 the Radius client configuration file in order to build Exim with Radius
9357 With just that one setting, Exim expects to be linked with the \radiusclient\
9358 library. You can also link Exim with the \libradius\ library that comes with
9359 FreeBSD. To do this, set
9361 RADIUS_LIB_TYPE=RADLIB
9363 in \(Local/Makefile)\, in addition to setting \\RADIUS@_CONFIGURE@_FILE\\.
9365 You may also have to supply a suitable setting in \\EXTRALIBS\\ so that the
9366 Radius library can be found when Exim is linked.
9368 The string specified by \\RADIUS@_CONFIG@_FILE\\ is expanded and passed to the
9369 Radius client library, which calls the Radius server. The condition is true if
9370 the authentication is successful. For example
9372 server@_condition = @$@{if radius@{<<arguments>>@}@{yes@}@{no@}@}
9377 .item "saslauthd @{@{<<user>>@}@{<<password>>@}@{<<service>>@}@{<<realm>>@}@}"
9378 .index \*saslauthd*\ daemon
9380 .index expansion||\*saslauthd*\ authentication test
9381 This condition supports user authentication using the Cyrus \*saslauthd*\
9382 daemon. This replaces the older \*pwcheck*\ daemon, which is now deprecated.
9383 Using this daemon is one way of making it possible for passwords to be checked
9384 by a process that is not running as root.
9386 The saslauthd support is not included in Exim by default. You need to specify
9387 the location of the saslauthd daemon's socket in \(Local/Makefile)\ before
9388 building Exim. For example:
9390 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
9392 You do not need to install the full Cyrus software suite in order to use
9393 the saslauthd daemon. You can compile and install just the daemon alone
9394 from the Cyrus SASL library.
9396 Up to four arguments can be supplied to the \saslauthd\ condition, but only two
9397 are mandatory. For example:
9399 server_condition = ${if saslauthd{{$1}{$2}}{1}{0}}
9401 The service and the realm are optional (which is why the arguments are enclosed
9402 in their own set of braces). For details of the meaning of the service and
9403 realm, and how to run the daemon, consult the Cyrus documentation.
9409 .section Combining expansion conditions
9410 .index expansion||combining conditions
9411 Several conditions can be tested at once by combining them using the \and\ and
9412 \or\ combination conditions. Note that \and\ and \or\ are complete conditions
9413 on their own, and precede their lists of sub-conditions. Each sub-condition
9414 must be enclosed in braces within the overall braces that contain the list. No
9415 repetition of \if\ is used.
9419 .item "or @{@{<<cond1>>@}@{<<cond2>>@}...@}"
9420 .index `or' expansion condition
9421 .index expansion||`or' of conditions
9422 The sub-conditions are evaluated from left to right. The condition is true if
9423 any one of the sub-conditions is true.
9426 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
9428 When a true sub-condition is found, the following ones are parsed but not
9429 evaluated. If there are several `match' sub-conditions the values of the
9430 numeric variables afterwards are taken from the first one that succeeds.
9432 .item "and @{@{<<cond1>>@}@{<<cond2>>@}...@}"
9433 .index `and' expansion condition
9434 .index expansion||`and' of conditions
9435 The sub-conditions are evaluated from left to right. The condition is true if
9436 all of the sub-conditions are true. If there are several `match'
9437 sub-conditions, the values of the numeric variables afterwards are taken from
9438 the last one. When a false sub-condition is found, the following ones are
9439 parsed but not evaluated.
9445 .section Expansion variables
9446 .rset SECTexpvar "~~chapter.~~section"
9447 .index expansion||variables, list of
9450 This section contains an alphabetical list of all the expansion variables. Some
9451 of them are available only when Exim is compiled with specific options such as
9452 support for TLS or the content scanning extension.
9457 .index numerical variables (\$1$\, \$2$\, etc)
9459 \$0$\, \$1$\, etc: When a \match\ expansion condition succeeds, these
9460 variables contain the captured substrings identified by the regular expression
9461 during subsequent processing of the success string of the containing \if\
9462 expansion item. They may also be set externally by some other matching process
9463 which precedes the expansion of the string. For example, the commands available
9464 in Exim filter files include an \if\ command with its own regular expression
9468 \$acl@_c0$\ -- \$acl@_c9$\: Values can be placed in these variables by the
9469 \set\ modifier in an ACL. The values persist throughout the lifetime of an SMTP
9470 connection. They can be used to pass information between ACLs and different
9471 invocations of the same ACL.
9472 When a message is received, the values of these variables are saved with the
9473 message, and can be accessed by filters, routers, and transports during
9474 subsequent delivery.
9477 \$acl@_m0$\ -- \$acl@_m9$\: Values can be placed in these variables by the
9478 \set\ modifier in an ACL. They retain their values while a message is being
9479 received, but are reset afterwards. They are also reset by \\MAIL\\, \\RSET\\,
9480 \\EHLO\\, \\HELO\\, and after starting a TLS session.
9481 When a message is received, the values of these variables are saved with the
9482 message, and can be accessed by filters, routers, and transports during
9483 subsequent delivery.
9487 \$acl@_verify@_message$\: During the expansion of the \message\ and
9488 \log@_message\ modifiers in an ACL statement after an address verification has
9489 failed, this variable contains the original failure message that will be
9490 overridden by the expanded string.
9493 \$address@_data$\: This variable is set by means of the \address@_data\
9494 option in routers. The value then remains with the address while it is
9495 processed by subsequent routers and eventually a transport. If the transport is
9496 handling multiple addresses, the value from the first address is used. See
9497 chapter ~~CHAProutergeneric for more details. \**Note**\: the contents of
9498 \$address@_data$\ are visible in user filter files.
9501 If \$address@_data$\ is set when the routers are called from an ACL to verify
9502 a recipient address, the final value is still in the variable for subsequent
9503 conditions and modifiers of the ACL statement. If routing the address caused it
9504 to be redirected to just one address, the child address is also routed as part
9505 of the verification, and in this case the final value of \$address@_data$\ is
9506 from the child's routing.
9508 If \$address@_data$\ is set when the routers are called from an ACL to verify a
9509 sender address, the final value is also preserved, but this time in
9510 \$sender@_address@_data$\, to distinguish it from data from a recipient
9513 In both cases (recipient and sender verification), the value does not persist
9514 after the end of the current ACL statement. If you want to preserve
9515 these values for longer, you can save them in ACL variables.
9519 \$address@_file$\: When, as a result of aliasing, forwarding, or filtering, a
9520 message is directed to a specific file, this variable holds the name of the
9521 file when the transport is running. At other times, the variable is empty. For
9522 example, using the default configuration, if user \r2d2\ has a \(.forward)\
9527 then when the \%address@_file%\ transport is running, \$address@_file$\
9528 contains `/home/r2d2/savemail'.
9529 .index Sieve filter||value of \$address@_file$\
9530 For Sieve filters, the value may be `inbox' or a relative folder name. It is
9531 then up to the transport configuration to generate an appropriate absolute path
9532 to the relevant file.
9536 \$address@_pipe$\: When, as a result of aliasing or forwarding, a message is
9537 directed to a pipe, this variable holds the pipe command when the transport is
9540 .index authentication||id
9542 \$authenticated@_id$\: When a server successfully authenticates a client it may
9543 be configured to preserve some of the authentication information in the
9544 variable \$authenticated@_id$\ (see chapter ~~CHAPSMTPAUTH). For example, a
9545 user/password authenticator configuration might preserve the user name for use
9546 in the routers. When a message is submitted locally (that is, not over a TCP
9547 connection), the value of \$authenticated@_id$\ is the login name of the
9550 .index sender||authenticated
9551 .index authentication||sender
9552 .index \\AUTH\\||on \\MAIL\\ command
9554 \$authenticated@_sender$\:
9555 When acting as a server, Exim takes note of the \\AUTH=\\ parameter on an
9556 incoming SMTP \\MAIL\\ command
9557 if it believes the sender is sufficiently trusted, as described in section
9558 ~~SECTauthparamail. Unless the data is the string `@<@>', it is set as the
9559 authenticated sender of the message, and the value is available during delivery
9560 in the \$authenticated@_sender$\ variable. If the sender is not trusted, Exim
9561 accepts the syntax of \\AUTH=\\, but ignores the data.
9563 When a message is submitted locally (that is, not over a TCP connection), the
9564 value of \$authenticated@_sender$\ is an address constructed from the login
9565 name of the calling process and \$qualify@_domain$\.
9568 .index authentication||failure
9570 \$authentication@_failed$\:
9571 This variable is set to `1' in an Exim server if a client issues an \\AUTH\\
9572 command that does not succeed. Otherwise it is set to `0'. This makes it
9573 possible to distinguish between `did not try to authenticate'
9574 (\$sender@_host@_authenticated$\ is empty and \$authentication__failed$\ is set
9575 to `0') and `tried to authenticate but failed' (\$sender@_host@_authenticated$\
9576 is empty and \$authentication@_failed$\ is set to `1'). Failure includes any
9577 negative response to an \\AUTH\\ command, including (for example) an attempt to
9578 use an undefined mechanism.
9581 .index message||body, line count
9582 .index body of message||line count
9584 \$body@_linecount$\:
9585 When a message is being received or delivered, this variable contains the
9586 number of lines in the message's body.
9588 .index message||body, binary zero count
9589 .index body of message||binary zero count
9590 .index binary zero||in message body
9592 \$body@_zerocount$\:
9593 When a message is being received or delivered, this variable contains the
9594 number of binary zero bytes in the message's body.
9597 \$bounce@_recipient$\:
9598 This is set to the recipient address of a bounce message while Exim is creating
9599 it. It is useful if a customized bounce message text file is in use (see
9600 chapter ~~CHAPemsgcust).
9603 \$bounce@_return@_size@_limit$\: This contains the value set in the
9604 \bounce@_return@_size@_limit\ option, rounded up to a multiple of 1000. It is
9605 useful when a customized error message text file is in use (see chapter
9608 .index gid (group id)||caller
9610 \$caller@_gid$\: The
9612 group id under which the process that called Exim was
9613 running. This is not the same as the group id of the originator of a message
9614 (see \$originator@_gid$\). If Exim re-execs itself, this variable in the new
9615 incarnation normally contains the Exim gid.
9617 .index uid (user id)||caller
9619 \$caller@_uid$\: The
9621 user id under which the process that called Exim was
9622 running. This is not the same as the user id of the originator of a message
9623 (see \$originator@_uid$\). If Exim re-execs itself, this variable in the new
9624 incarnation normally contains the Exim uid.
9627 \$compile@_date$\: The date on which the Exim binary was compiled.
9630 \$compile@_number$\: The building process for Exim keeps a count of the number
9631 of times it has been compiled. This serves to distinguish different
9632 compilations of the same version of the program.
9636 \$demime@_$\\*xxx*\: Two variables whose names start with \$demime$\ are
9637 available when Exim is compiled with the content-scanning extension and the
9638 obsolete \demime\ condition. For details, see section ~~SECTdemimecond.
9641 .index black list (DNS)
9643 \$dnslist@_domain$\: When a client host is found to be on a DNS (black) list,
9644 the list's domain name is put into this variable so that it can be included in
9645 the rejection message.
9648 \$dnslist@_text$\: When a client host is found to be on a DNS (black) list, the
9649 contents of any associated TXT record are placed in this variable.
9652 \$dnslist@_value$\: When a client host is found to be on a DNS (black) list,
9653 the IP address from the resource record is placed in this variable.
9654 If there are multiple records, all the addresses are included, comma-space
9658 \$domain$\: When an address is being routed, or delivered on its own, this
9659 variable contains the domain. Global address rewriting happens when a message
9660 is received, so the value of \$domain$\ during routing and delivery is the
9661 value after rewriting. \$domain$\ is set during user filtering, but not during
9662 system filtering, because a message may have many recipients and the system
9663 filter is called just once.
9665 When more than one address is being delivered at once (for example, several
9666 \\RCPT\\ commands in one SMTP delivery), \$domain$\ is set only if they all
9667 have the same domain. Transports can be restricted to handling only one domain
9668 at a time if the value of \$domain$\ is required at transport time -- this is
9669 the default for local transports. For further details of the environment in
9670 which local transports are run, see chapter ~~CHAPenvironment.
9672 .index \delay@_warning@_condition\
9673 At the end of a delivery, if all deferred addresses have the same domain, it is
9674 set in \$domain$\ during the expansion of \delay@_warning@_condition\.
9676 The \$domain$\ variable is also used in some other circumstances:
9678 When an ACL is running for a \\RCPT\\ command, \$domain$\ contains the domain
9679 of the recipient address.
9680 \**Note:**\ the domain of the sender address is in \$sender@_address@_domain$\
9681 at \\MAIL\\ time and at \\RCPT\\ time. \$domain$\ is not set for the \\MAIL\\
9684 When a rewrite item is being processed (see chapter ~~CHAPrewrite), \$domain$\
9685 contains the domain portion of the address that is being rewritten; it can be
9686 used in the expansion of the replacement address, for example, to rewrite
9687 domains by file lookup.
9689 With one important exception, whenever a domain list is being scanned,
9690 \$domain$\ contains the subject domain. \**Exception**\: When a domain list in
9691 a \sender@_domains\ condition in an ACL is being processed, the subject domain
9692 is in \$sender@_address@_domain$\ and not in \$domain$\. It works this way so
9693 that, in a \\RCPT\\ ACL, the sender domain list can be dependent on the
9694 recipient domain (which is what is in \$domain$\ at this time).
9696 .index \\ETRN\\||value of \$domain$\
9697 .index \smtp@_etrn@_command\
9698 When the \smtp@_etrn@_command\ option is being expanded, \$domain$\ contains
9699 the complete argument of the \\ETRN\\ command (see section ~~SECTETRN).
9703 \$domain@_data$\: When the \domains\ option on a router matches a domain by
9704 means of a lookup, the data read by the lookup is available during the running
9705 of the router as \$domain@_data$\. In addition, if the driver routes the
9706 address to a transport, the value is available in that transport. If the
9707 transport is handling multiple addresses, the value from the first address is
9710 \$domain@_data$\ is also set when the \domains\ condition in an ACL matches a
9711 domain by means of a lookup. The data read by the lookup is available during
9712 the rest of the ACL statement. In all other situations, this variable expands
9716 \$exim@_gid$\: This variable contains the numerical value of the Exim group id.
9719 \$exim@_path$\: This variable contains the path to the Exim binary.
9722 \$exim@_uid$\: This variable contains the numerical value of the Exim user id.
9726 \$found@_extension$\: This variable is available when Exim is compiled with the
9727 content-scanning extension and the obsolete \demime\ condition. For details,
9728 see section ~~SECTdemimecond.
9732 \$header@_<<name>>$\: This is not strictly an expansion variable. It is
9733 expansion syntax for inserting the message header line with the given name.
9734 Note that the name must be terminated by colon or white space, because it may
9735 contain a wide variety of characters.
9736 Note also that braces must \*not*\ be used.
9740 When the \check@_local@_user\ option is set for a router, the user's home
9741 directory is placed in \$home$\ when the check succeeds. In particular, this
9742 means it is set during the running of users' filter files. A router may also
9743 explicitly set a home directory for use by a transport; this can be overridden
9744 by a setting on the transport itself.
9746 When running a filter test via the \-bf-\ option, \$home$\ is set to the value
9747 of the environment variable \\HOME\\.
9751 When the \%smtp%\ transport is expanding its options for encryption using TLS,
9752 \$host$\ contains the name of the host to which it is connected. Likewise, when
9753 used in the client part of an authenticator configuration (see chapter
9754 ~~CHAPSMTPAUTH), \$host$\ contains the name of the server to which the client
9756 .index transport||filter
9757 .index filter||transport filter
9758 When used in a transport filter (see chapter ~~CHAPtransportgeneric) \$host$\
9759 refers to the host involved in the current connection. When a local transport
9760 is run as a result of a router that sets up a host list, \$host$\ contains the
9761 name of the first host.
9765 This variable is set to the remote host's IP address whenever \$host$\ is set
9766 for a remote connection.
9768 It is also set to the IP address that is being checked when the
9769 \ignore@_target@_hosts\ option is being processed.
9774 If a \hosts\ condition in an ACL is satisfied by means of a lookup, the result
9775 of the lookup is made available in the \$host@_data$\ variable. This
9776 allows you, for example, to do things like this:
9778 deny hosts = net-lsearch;/some/file
9779 message = $host_data
9783 .index host||name lookup, failure of
9785 \$host@_lookup@_deferred$\:
9786 This variable normally contains `0', as does \$host@_lookup@_failed$\. When a
9787 message comes from a remote host and there is an attempt to look up the host's
9788 name from its IP address, and the attempt is not successful, one of these
9789 variables is set to `1'.
9791 If the lookup receives a definite negative response (for example, a DNS lookup
9792 succeeded, but no records were found), \$host@_lookup@_failed$\ is set to `1'.
9794 If there is any kind of problem during the lookup, such that Exim cannot
9795 tell whether or not the host name is defined (for example, a timeout for a DNS
9796 lookup), \$host@_lookup@_deferred$\ is set to `1'.
9798 Looking up a host's name from its IP address consists of more than just a
9799 single reverse lookup. Exim checks that a forward lookup of at least one of the
9800 names it receives from a reverse lookup yields the original IP address. If this
9801 is not the case, Exim does not accept the looked up name(s), and
9802 \$host@_lookup@_failed$\ is set to `1'. Thus, being able to find a name from an
9803 IP address (for example, the existence of a PTR record in the DNS) is not
9804 sufficient on its own for the success of a host name lookup. If the reverse
9805 lookup succeeds, but there is a lookup problem such as a timeout when checking
9806 the result, the name is not accepted, and \$host@_lookup@_deferred$\ is set to
9807 `1'. See also \$sender@_host@_name$\.
9810 \$host@_lookup@_failed$\: See \$host@_lookup@_deferred$\.
9815 The only time this variable is set is while expanding the \directory@_file\
9816 option in the \%appendfile%\ transport. The variable contains the inode number
9817 of the temporary file which is about to be renamed. It can be used to construct
9818 a unique name for the file.
9821 \$interface@_address$\:
9822 When a message is received over a TCP/IP connection, this variable contains the
9823 address of the local IP interface. See also the \-oMi-\ command line option.
9824 This variable can be used in ACLs and also, for example, to make the file name
9825 for a TLS certificate depend on which interface is being used.
9828 \$interface@_port$\:
9829 When a message is received over a TCP/IP connection, this variable contains the
9830 local port number. See also the \-oMi-\ command line option.
9831 This variable can be used in ACLs and also, for example, to make the file name
9832 for a TLS certificate depend on which port is being used.
9836 This variable, which is available only when Exim is compiled with LDAP support,
9837 contains the DN from the last entry in the most recently successful LDAP
9842 This variable contains the system load average, multiplied by 1000 to that it
9843 is an integer. For example, if the load average is 0.21, the value of the
9844 variable is 210. The value is recomputed every time the variable is referenced.
9847 \$local@_part$\: When an address is being routed, or delivered on its own, this
9848 variable contains the local part. When a number of addresses are being
9849 delivered together (for example, multiple \\RCPT\\ commands in an SMTP
9850 session), \$local@_part$\ is not set.
9852 Global address rewriting happens when a message is received, so the value of
9853 \$local@_part$\ during routing and delivery is the value after rewriting.
9854 \$local@_part$\ is set during user filtering, but not during system filtering,
9855 because a message may have many recipients and the system filter is called just
9858 If a local part prefix or suffix has been recognized, it is not included in the
9859 value of \$local@_part$\ during routing and subsequent delivery. The values of
9860 any prefix or suffix are in \$local@_part@_prefix$\ and
9861 \$local@_part@_suffix$\, respectively.
9863 When a message is being delivered to a file, pipe, or autoreply transport as a
9864 result of aliasing or forwarding, \$local@_part$\ is set to the local part of
9865 the parent address, not to the file name or command (see \$address@_file$\ and
9868 When an ACL is running for a \\RCPT\\ command, \$local@_part$\ contains the
9869 local part of the recipient address.
9871 When a rewrite item is being processed (see chapter ~~CHAPrewrite),
9872 \$local@_part$\ contains the local part of the address that is being rewritten;
9873 it can be used in the expansion of the replacement address, for example.
9875 In all cases, all quoting is removed from the local part. For example, for both
9878 "abc:xyz"@test.example
9879 abc\:xyz@test.example
9881 the value of \$local@_part$\ is
9885 If you use \$local@_part$\ to create another address, you should always wrap it
9886 inside a quoting operator. For example, in a \%redirect%\ router you could have:
9888 data = ${quote_local_part:$local_part}@new.domain.example
9890 \**Note**\: The value of \$local@_part$\ is normally lower cased. If you want
9891 to process local parts in a case-dependent manner in a router, you can set the
9892 \caseful@_local@_part\ option (see chapter ~~CHAProutergeneric).
9895 \$local@_part@_data$\:
9896 When the \local@_parts\ option on a router matches a local part by means of a
9897 lookup, the data read by the lookup is available during the running of the
9898 router as \$local@_part@_data$\. In addition, if the driver routes the address
9899 to a transport, the value is available in that transport. If the transport is
9900 handling multiple addresses, the value from the first address is used.
9902 \$local@_part@_data$\ is also set when the \local@_parts\ condition in an ACL
9903 matches a local part by means of a lookup. The data read by the lookup is
9904 available during the rest of the ACL statement. In all other situations, this
9905 variable expands to nothing.
9908 \$local@_part@_prefix$\: When an address is being routed or delivered, and a
9909 specific prefix for the local part was recognized, it is available in this
9910 variable, having been removed from \$local@_part$\.
9913 \$local@_part@_suffix$\: When an address is being routed or delivered, and a
9914 specific suffix for the local part was recognized, it is available in this
9915 variable, having been removed from \$local@_part$\.
9918 \$local@_scan@_data$\: This variable contains the text returned by the
9919 \*local@_scan()*\ function when a message is received. See chapter
9920 ~~CHAPlocalscan for more details.
9923 \$local@_user@_gid$\: See \$local@_user@_uid$\.
9926 \$local@_user@_uid$\: This variable and \$local@_user@_gid$\ are set to
9927 the uid and gid after the \check__local__user\ router precondition succeeds.
9928 This means that their values are available for the remaining preconditions
9929 (\senders\, \require@_files\, and \condition\), for the \address@_data\
9930 expansion, and for any router-specific expansions. At all other times, the
9931 values in these variables are \"(uid@_t)(-1)"\ and \"(gid@_t)(-1)"\,
9935 \$localhost@_number$\: This contains the expanded value of the
9936 \localhost@_number\ option. The expansion happens after the main options have
9941 \$log@_inodes$\: The number of free inodes in the disk partition where Exim's
9942 log files are being written. The value is recalculated whenever the variable is
9943 referenced. If the relevant file system does not have the concept of inodes,
9944 the value of is -1. See also the \check@_log@_inodes\ option.
9947 \$log@_space$\: The amount of free space (as a number of kilobytes) in the disk
9948 partition where Exim's log files are being written. The value is recalculated
9949 whenever the variable is referenced. If the operating system does not have the
9950 ability to find the amount of free space (only true for experimental systems),
9951 the space value is -1. See also the \check@_log@_space\ option.
9955 \$mailstore@_basename$\: This variable is set only when doing deliveries in
9956 `mailstore' format in the \%appendfile%\ transport. During the expansion of the
9957 \mailstore@_prefix\, \mailstore@_suffix\, \message__prefix\, and
9958 \message@_suffix\ options, it contains the basename of the files that are being
9959 written, that is, the name without the `.tmp', `.env', or `.msg' suffix. At all
9960 other times, this variable is empty.
9964 \$malware@_name$\: This variable is available when Exim is compiled with the
9965 content-scanning extension. It is set to the name of the virus that was found
9966 when the ACL \malware\ condition is true (see section ~~SECTscanvirus).
9969 .index message||age of
9971 \$message@_age$\: This variable is set at the start of a delivery attempt to
9972 contain the number of seconds since the message was received. It does not
9973 change during a single delivery attempt.
9975 .index body of message||expansion variable
9976 .index message||body, in expansion
9977 .index binary zero||in message body
9979 \$message@_body$\: This variable contains the initial portion of a message's
9980 body while it is being delivered, and is intended mainly for use in filter
9981 files. The maximum number of characters of the body that are put into the
9982 variable is set by the \message@_body@_visible\ configuration option; the
9983 default is 500. Newlines are converted into spaces to make it easier to search
9984 for phrases that might be split over a line break.
9985 Binary zeros are also converted into spaces.
9987 .index body of message||expansion variable
9988 .index message||body, in expansion
9990 \$message@_body@_end$\: This variable contains the final portion of a message's
9991 body while it is being delivered. The format and maximum size are as for
9994 .index body of message||size
9995 .index message||body, size
9997 \$message@_body@_size$\: When a message is being delivered, this variable
9998 contains the size of the body in bytes. The count starts from the character
9999 after the blank line that separates the body from the header. Newlines are
10000 included in the count. See also \$message@_size$\, \$body@_linecount$\, and
10001 \$body@_zerocount$\.
10004 \$message@_headers$\:
10005 This variable contains a concatenation of all the header lines when a message
10006 is being processed, except for lines added by routers or transports. The header
10007 lines are separated by newline characters.
10011 When a message is being received or delivered, this variable contains the
10012 unique message id that is used by Exim to identify the message.
10013 An id is not created for a message until after its header has been
10014 successfully received.
10015 \**Note**\: This is \*not*\ the contents of the ::Message-ID:: header line; it
10016 is the local id that Exim assigns to the message, for example:
10017 \"1BXTIK-0001yO-VA"\.
10019 .index size||of message
10020 .index message||size
10023 When a message is being processed, this variable contains its size in bytes. In
10024 most cases, the size includes those headers that were received with the
10025 message, but not those (such as ::Envelope-to::) that are added to individual
10026 deliveries as they are written. However, there is one special case: during the
10027 expansion of the \maildir@_tag\ option in the \%appendfile%\ transport while
10028 doing a delivery in maildir format, the value of \$message@_size$\ is the
10029 precise size of the file that has been written. See also
10030 \$message@_body@_size$\, \$body@_linecount$\, and \$body@_zerocount$\.
10032 .index \\RCPT\\||value of \$message@_size$\
10033 While running an ACL at the time of an SMTP \\RCPT\\ command, \$message@_size$\
10034 contains the size supplied on the \\MAIL\\ command, or
10036 if no size was given. The value may not, of course, be truthful.
10041 A number of variables whose names start with \$mime$\ are available when Exim
10042 is compiled with the content-scanning extension. For details, see section
10043 ~~SECTscanmimepart.
10047 \$n0$\ -- \$n9$\: These variables are counters that can be incremented by means
10048 of the \add\ command in filter files.
10051 \$original@_domain$\: When a top-level address is being processed for delivery,
10052 this contains the same value as \$domain$\. However, if a `child' address (for
10053 example, generated by an alias, forward, or filter file) is being processed,
10054 this variable contains the domain of the original address. This differs from
10055 \$parent@_domain$\ only when there is more than one level of aliasing or
10056 forwarding. When more than one address is being delivered in a single transport
10057 run, \$original@_domain$\ is not set.
10059 If new an address is created by means of a \deliver\ command in a system
10060 filter, it is set up with an artificial `parent' address. This has the local
10061 part \*system-filter*\ and the default qualify domain.
10064 \$original@_local@_part$\: When a top-level address is being processed for
10065 delivery, this contains the same value as \$local@_part$\, unless a prefix or
10066 suffix was removed from the local part, because \$original@_local@_part$\
10067 always contains the full local part. When a `child' address (for example,
10068 generated by an alias, forward, or filter file) is being processed, this
10069 variable contains the full local part of the original address.
10071 If the router that did the redirection processed the local part
10072 case-insensitively, the value in \$original@_local@_part$\ is in lower case.
10073 This variable differs from \$parent@_local@_part$\ only when there is more than
10074 one level of aliasing or forwarding. When more than one address is being
10075 delivered in a single transport run, \$original@_local@_part$\ is not set.
10077 If new an address is created by means of a \deliver\ command in a system
10078 filter, it is set up with an artificial `parent' address. This has the local
10079 part \*system-filter*\ and the default qualify domain.
10082 .index gid (group id)||of originating user
10085 \$originator@_gid$\: The value of \$caller@_gid$\ that was set when the message
10086 was received. For messages received via the command line, this is the gid of
10087 the sending user. For messages received by SMTP over TCP/IP, this is normally
10088 the gid of the Exim user.
10090 .index uid (user id)||of originating user
10093 \$originator@_uid$\: The value of \$caller@_uid$\ that was set when the message
10094 was received. For messages received via the command line, this is the uid of
10095 the sending user. For messages received by SMTP over TCP/IP, this is normally
10096 the uid of the Exim user.
10099 \$parent@_domain$\: This variable is similar to \$original@_domain$\ (see
10100 above), except that it refers to the immediately preceding parent address.
10103 \$parent@_local@_part$\: This variable is similar to \$original@_local@_part$\
10104 (see above), except that it refers to the immediately preceding parent address.
10106 .index pid (process id)||of current process
10108 \$pid$\: This variable contains the current process id.
10110 .index filter||transport filter
10111 .index transport||filter
10113 \$pipe@_addresses$\: This is not an expansion variable, but is mentioned here
10114 because the string `@$pipe@_addresses' is handled specially in the command
10115 specification for the \%pipe%\ transport (chapter ~~CHAPpipetransport) and in
10116 transport filters (described under \transport@_filter\ in chapter
10117 ~~CHAPtransportgeneric). It cannot be used in general expansion strings, and
10118 provokes an `unknown variable' error if encountered.
10121 \$primary@_hostname$\: The value set in the configuration file, or read by the
10122 \*uname()*\ function. If \*uname()*\ returns a single-component name, Exim
10123 calls \*gethostbyname()*\ (or \*getipnodebyname()*\ where available) in an
10124 attempt to acquire a fully qualified host name.
10125 See also \$smtp@_active@_hostname$\.
10128 \$qualify@_domain$\: The value set for this option in the configuration file.
10131 \$qualify@_recipient$\: The value set for this option in the configuration file,
10132 or if not set, the value of \$qualify@_domain$\.
10135 \$rcpt@_count$\: When a message is being received by SMTP, this variable
10136 contains the number of \\RCPT\\ commands received for the current message. If
10137 this variable is used in a \\RCPT\\ ACL, its value includes the current
10141 \$rcpt@_defer@_count$\: When a message is being received by SMTP, this variable
10142 contains the number of \\RCPT\\ commands in the current message that have
10143 previously been rejected with a temporary (4\*xx*\) response.
10146 \$rcpt@_fail@_count$\: When a message is being received by SMTP, this variable
10147 contains the number of \\RCPT\\ commands in the current message that have
10148 previously been rejected with a permanent (5\*xx*\) response.
10151 \$received@_count$\: This variable contains the number of ::Received:: header
10152 lines in the message, including the one added by Exim (so its value is always
10153 greater than zero). It is available in the \\DATA\\ ACL, the non-SMTP ACL, and
10154 while routing and delivering.
10157 \$received@_for$\: If there is only a single recipient address in an incoming
10158 message, this variable contains that address when the ::Received:: header line
10160 The value is copied after recipient rewriting has happened, but before the
10161 \*local@_scan()*\ function is run.
10164 \$received@_protocol$\: When a message is being processed, this variable
10165 contains the name of the protocol by which it was received.
10167 Most of the names used by Exim are defined by RFCs 821, 2821, and 3848. They
10168 start with `smtp' (the client used \\HELO\\) or `esmtp' (the client used
10169 \\EHLO\\). This can be followed by `s' for secure (encrypted) and/or `a' for
10170 authenticated. Thus, for example, if the protocol is set to `esmtpsa', the
10171 message was received over an encrypted SMTP connection and the client was
10172 successfully authenticated.
10174 Exim also uses the protocol name `smtps' for the rare situation where the
10175 client initially used \\EHLO\\, set up an encrypted connection using
10176 \\STARTTLS\\, and then used \\HELO\\ afterwards to initiate the encrypted
10179 The \-oMr-\ option provides a way of specifying a custom protocol name for
10180 messages that are injected locally by trusted callers. This is commonly used to
10181 identify messages that are being re-injected after some kind of scanning.
10185 \$recipient@_data$\: This variable is set after an indexing lookup success in
10186 an ACL \recipients\ condition. It contains the data from the lookup, and the
10187 value remains set until the next \recipients\ test. Thus, you can do things
10190 require recipients = cdb*@@;/some/file
10191 deny \*some further test involving*\ @$recipient@_data
10193 \**Warning**\: This variable is set only when a lookup is used as an indexing
10194 method in the address list, using the semicolon syntax as in the example above.
10195 The variable is not set for a lookup that is used as part of the string
10196 expansion that all such lists undergo before being interpreted.
10200 \$recipient@_verify@_failure$\: In an ACL, when a recipient verification fails,
10201 this variable contains information about the failure. It is set to one of the
10204 `qualify': The address was unqualified (no domain), and the message
10205 was neither local nor came from an exempted host.
10207 `route': Routing failed.
10209 `mail': Routing succeeded, and a callout was attempted; rejection occurred at
10210 or before the \\MAIL\\ command (that is, on initial connection, \\HELO\\, or
10213 `recipient': The \\RCPT\\ command in a callout was rejected.
10215 `postmaster': The postmaster check in a callout was rejected.
10217 The main use of this variable is expected to be to distinguish between
10218 rejections of \\MAIL\\ and rejections of \\RCPT\\.
10222 \$recipients$\: This variable contains a list of envelope recipients for a
10223 message. A comma and a space separate the addresses in the replacement text.
10224 However, the variable is not generally available, to prevent exposure of Bcc
10225 recipients in unprivileged users' filter files. You can use \$recipients$\ only
10226 in these two cases:
10228 In a system filter file.
10231 In the ACLs associated with the \\DATA\\ command, that is, the ACLs defined by
10232 \acl@_smtp@_predata\ and \acl@_smtp@_data\.
10237 \$recipients@_count$\: When a message is being processed, this variable
10238 contains the number of envelope recipients that came with the message.
10239 Duplicates are not excluded from the count. While a message is being received
10240 over SMTP, the number increases for each accepted recipient. It can be
10241 referenced in an ACL.
10244 \$reply@_address$\: When a message is being processed, this variable contains
10245 the contents of the ::Reply-To:: header line if one exists
10246 and it is not empty,
10247 or otherwise the contents of the ::From:: header line.
10250 \$return@_path$\: When a message is being delivered, this variable contains the
10251 return path -- the sender field that will be sent as part of the envelope. It
10252 is not enclosed in @<@> characters.
10253 At the start of routing an address,
10254 \$return@_path$\ has the same value as \$sender@_address$\, but if, for
10255 example, an incoming message to a mailing list has been expanded by a router
10256 which specifies a different address for bounce messages, \$return@_path$\
10257 subsequently contains the new bounce address, whereas \$sender@_address$\
10258 always contains the original sender address that was received with the message.
10259 In other words, \$sender@_address$\ contains the incoming envelope sender, and
10260 \$return@_path$\ contains the outgoing envelope sender.
10263 \$return@_size@_limit$\: This is an obsolete name for
10264 \$bounce@_return@_size@_limit$\.
10266 .index return code||from \run\ expansion
10268 \$runrc$\: This variable contains the return code from a command that is run by
10269 the \@$@{run...@}\ expansion item.
10270 \**Warning**\: In a router or transport, you cannot assume the order in which
10271 option values are expanded, except for those pre-conditions whose order of
10272 testing is documented. Therefore, you cannot reliably expect to set \$runrc$\
10273 by the expansion of one option, and use it in another.
10276 \$self@_hostname$\: When an address is routed to a supposedly remote host that
10277 turns out to be the local host, what happens is controlled by the
10278 .index \self\ option||value of host name
10279 \self\ generic router option. One of its values causes the address to be passed
10280 to another router. When this happens, \$self@_hostname$\ is set to the name of
10281 the local host that the original router encountered. In other circumstances its
10285 \$sender@_address$\: When a message is being processed, this variable contains
10286 the sender's address that was received in the message's envelope. For bounce
10287 messages, the value of this variable is the empty string.
10288 See also \$return@_path$\.
10292 \$sender@_address@_data$\: If \$address@_data$\ is set when the routers are
10293 called from an ACL to verify a sender address, the final value is preserved in
10294 \$sender@_address@_data$\, to distinguish it from data from a recipient
10295 address. The value does not persist after the end of the current ACL statement.
10296 If you want to preserve it for longer, you can save it in an ACL variable.
10300 \$sender@_address@_domain$\: The domain portion of \$sender@_address$\.
10303 \$sender@_address@_local@_part$\: The local part portion of \$sender@_address$\.
10306 \$sender@_data$\: This variable is set after a lookup success in an ACL
10307 \senders\ condition or in a router \senders\ option. It contains the data from
10308 the lookup, and the value remains set until the next \senders\ test. Thus, you
10309 can do things like this:
10311 require senders = cdb*@@;/some/file
10312 deny \*some further test involving*\ @$sender@_data
10314 \**Warning**\: This variable is set only when a lookup is used as an indexing
10315 method in the address list, using the semicolon syntax as in the example above.
10316 The variable is not set for a lookup that is used as part of the string
10317 expansion that all such lists undergo before being interpreted.
10320 \$sender@_fullhost$\: When a message is received from a remote host, this
10321 variable contains the host name and IP address in a single string. It ends
10322 with the IP address in square brackets, followed by a colon and a port number
10323 if the logging of ports is enabled. The format of the rest of the string
10324 depends on whether the host issued a \\HELO\\ or \\EHLO\\ SMTP command, and
10325 whether the host name was verified by looking up its IP address. (Looking up
10326 the IP address can be forced by the \host@_lookup\ option, independent of
10327 verification.) A plain host name at the start of the string is a verified host
10328 name; if this is not present, verification either failed or was not requested.
10329 A host name in parentheses is the argument of a \\HELO\\ or \\EHLO\\ command.
10330 This is omitted if it is identical to the verified host name or to the host's
10331 IP address in square brackets.
10334 \$sender@_helo@_name$\: When a message is received from a remote host that has
10335 issued a \\HELO\\ or \\EHLO\\ command, the argument of that command is placed
10336 in this variable. It is also set if \\HELO\\ or \\EHLO\\ is used when a message
10337 is received using SMTP locally via the \-bs-\ or \-bS-\ options.
10340 \$sender@_host@_address$\: When a message is received from a remote host, this
10341 variable contains that host's IP address. For locally submitted messages, it is
10345 \$sender@_host@_authenticated$\: This variable contains the name (not the
10346 public name) of the authenticator driver which successfully authenticated the
10347 client from which the message was received. It is empty if there was no
10348 successful authentication.
10351 \$sender@_host@_name$\: When a message is received from a remote host, this
10352 variable contains the host's name as obtained by looking up its IP address.
10353 For messages received by other means, this variable is empty.
10355 If the host name has not previously been looked up, a reference to
10356 \$sender@_host@_name$\ triggers a lookup (for messages from remote hosts).
10357 A looked up name is accepted only if it leads back to the original IP address
10358 via a forward lookup. If either the reverse or the forward lookup fails
10362 or if the forward lookup does not yield the original IP address,
10363 \$sender@_host@_name$\ remains empty, and \$host@_lookup@_failed$\ is set to
10366 However, if either of the lookups cannot be completed (for example, there is a
10367 DNS timeout), \$host@_lookup@_deferred$\ is set to `1', and
10368 \$host@_lookup@_failed$\ remains set to `0'.
10370 Once \$host@_lookup@_failed$\ is set to `1', Exim does not try to look up the
10371 host name again if there is a subsequent reference to \$sender@_host@_name$\
10372 in the same Exim process, but it does try again if \$sender@_host@_deferred$\
10376 Exim does not automatically look up every calling host's name. If you want
10377 maximum efficiency, you should arrange your configuration so that it avoids
10378 these lookups altogether. The lookup happens only if one or more of the
10379 following are true:
10381 A string containing \$sender@_host@_name$\ is expanded.
10383 The calling host matches the list in \host@_lookup\. In the default
10384 configuration, this option is set to $*$, so it must be changed if lookups are
10385 to be avoided. (In the code, the default for \host@_lookup\ is unset.)
10387 Exim needs the host name in order to test an item in a host list. The items
10388 that require this are described in sections ~~SECThoslispatnam and
10389 ~~SECThoslispatnamsk.
10391 The calling host matches \helo@_try@_verify@_hosts\ or \helo@_verify@_hosts\.
10392 In this case, the host name is required to compare with the name quoted in any
10393 \\EHLO\\ or \\HELO\\ commands that the client issues.
10395 The remote host issues a \\EHLO\\ or \\HELO\\ command that quotes one of the
10396 domains in \helo@_lookup@_domains\. The default value of this option is
10398 helo_lookup_domains = @ : @[]
10400 which causes a lookup if a remote host (incorrectly) gives the server's name or
10401 IP address in an \\EHLO\\ or \\HELO\\ command.
10405 \$sender@_host@_port$\: When a message is received from a remote host, this
10406 variable contains the port number that was used on the remote host.
10409 \$sender@_ident$\: When a message is received from a remote host, this variable
10410 contains the identification received in response to an RFC 1413 request. When a
10411 message has been received locally, this variable contains the login name of the
10412 user that called Exim.
10415 \$sender@_rcvhost$\: This is provided specifically for use in ::Received::
10416 headers. It starts with either the verified host name (as obtained from a
10417 .index DNS||reverse lookup
10418 .index reverse DNS lookup
10419 reverse DNS lookup) or, if there is no verified host name, the IP address in
10420 square brackets. After that there may be text in parentheses. When the first
10421 item is a verified host name, the first thing in the parentheses is the IP
10422 address in square brackets, followed by a colon and a port number if port
10423 logging is enabled. When the first item is an IP address, the port is recorded
10424 as `port=$it{xxxx}' inside the parentheses.
10426 There may also be items of the form `helo=$it{xxxx}' if \\HELO\\ or \\EHLO\\
10427 was used and its argument was not identical to the real host name or IP
10428 address, and `ident=$it{xxxx}' if an RFC 1413 ident string is available. If all
10429 three items are present in the parentheses, a newline and tab are inserted into
10430 the string, to improve the formatting of the ::Received:: header.
10434 \$sender@_verify@_failure$\: In an ACL, when a sender verification fails, this
10435 variable contains information about the failure. The details are the same as
10436 for \$recipient@_verify@_failure$\.
10439 \$smtp@_active@_hostname$\: During an SMTP session, this variable contains the
10440 value of the active host name, as specified by the \smtp@_active@_hostname\
10441 option. The value of \$smtp@_active@_hostname$\ is saved with any message that
10442 is received, so its value can be consulted during routing and delivery.
10445 .index \\AUTH\\||argument
10446 .index \\EXPN\\||argument
10447 .index \\ETRN\\||argument
10448 .index \\VRFY\\||argument
10450 \$smtp@_command@_argument$\: While an ACL is running to check an \\AUTH\\,
10451 \\EHLO\\, \\EXPN\\, \\ETRN\\, \\HELO\\, or \\VRFY\\ command, this variable
10452 contains the argument for the SMTP command.
10455 \$sn0$\ -- \$sn9$\: These variables are copies of the values of the \$n0$\
10456 -- \$n9$\ accumulators that were current at the end of the system filter file.
10457 This allows a system filter file to set values that can be tested in users'
10458 filter files. For example, a system filter could set a value indicating how
10459 likely it is that a message is junk mail.
10463 \$spam@_$\\*xxx*\: A number of variables whose names start with \$spam$\ are
10464 available when Exim is compiled with the content-scanning extension. For
10465 details, see section ~~SECTscanspamass.
10469 \$spool@_directory$\: The name of Exim's spool directory.
10473 \$spool@_inodes$\: The number of free inodes in the disk partition where Exim's
10474 spool files are being written. The value is recalculated whenever the variable
10475 is referenced. If the relevant file system does not have the concept of inodes,
10476 the value of is -1.
10477 See also the \check@_spool@_inodes\ option.
10480 \$spool@_space$\: The amount of free space (as a number of kilobytes) in the
10481 disk partition where Exim's spool files are being written. The value is
10482 recalculated whenever the variable is referenced. If the operating system does
10483 not have the ability to find the amount of free space (only true for
10484 experimental systems), the space value is -1. For example, to check in an ACL
10485 that there is at least 50 megabytes free on the spool, you could write:
10487 condition = ${if > {$spool_space}{50000}}
10489 See also the \check@_spool@_space\ option.
10493 \$thisaddress$\: This variable is set only during the processing of the
10494 \foranyaddress\ command in a filter file. Its use is explained in the
10495 description of that command.
10498 \$tls@_certificate@_verified$\:
10499 This variable is set to `1' if a TLS certificate was verified when the message
10500 was received, and `0' otherwise.
10503 \$tls@_cipher$\: When a message is received from a remote host over an
10504 encrypted SMTP connection, this variable is set to the cipher suite that was
10505 negotiated, for example DES-CBC3-SHA.
10506 In other circumstances, in particular, for message received over unencrypted
10507 connections, the variable is empty.
10508 See chapter ~~CHAPTLS for details of TLS support.
10511 \$tls@_peerdn$\: When a message is received from a remote host over an
10512 encrypted SMTP connection,
10513 and Exim is configured to request a certificate from the client,
10514 the value of the Distinguished Name of the certificate is made available in the
10515 \$tls@_peerdn$\ during subsequent processing.
10518 \$tod@_bsdinbox$\: The time of day and date, in the format required for
10519 BSD-style mailbox files, for example: Thu Oct 17 17:14:09 1995.
10522 \$tod@_epoch$\: The time and date as a number of seconds since the start of the
10526 \$tod@_full$\: A full version of the time and date, for example: Wed, 16 Oct
10527 1995 09:51:40 +0100. The timezone is always given as a numerical offset from
10528 UTC, with positive values used for timezones that are ahead (east) of UTC, and
10529 negative values for those that are behind (west).
10532 \$tod@_log$\: The time and date in the format used for writing Exim's log
10533 files, for example: 1995-10-12 15:32:29,
10534 but without a timezone.
10538 This variable contains the date in the format yyyymmdd. This is the format that
10539 is used for datestamping log files when \log@_file@_path\ contains the \"%D"\
10543 \$tod@_zone$\: This variable contains the numerical value of the local
10544 timezone, for example: -0500.
10548 This variable contains the UTC date and time in `Zulu' format, as specified by
10549 ISO 8601, for example: 20030221154023Z.
10553 \$value$\: This variable contains the result of an expansion lookup, extraction
10554 operation, or external command, as described above.
10557 \$version@_number$\: The version number of Exim.
10560 \$warn@_message@_delay$\: This variable is set only during the creation of a
10561 message warning about a delivery delay. Details of its use are explained in
10562 section ~~SECTcustwarn.
10565 \$warn@_message@_recipients$\: This variable is set only during the creation of
10566 a message warning about a delivery delay. Details of its use are explained in
10567 section ~~SECTcustwarn.
10574 . ============================================================================
10575 .chapter Embedded Perl
10576 .set runningfoot "embedded Perl"
10577 .rset CHAPperl "~~chapter"
10578 .index Perl||calling from Exim
10580 Exim can be built to include an embedded Perl interpreter. When this is done,
10581 Perl subroutines can be called as part of the string expansion process. To make
10582 use of the Perl support, you need version 5.004 or later of Perl installed on
10583 your system. To include the embedded interpreter in the Exim binary, include
10588 in your \(Local/Makefile)\ and then build Exim in the normal way.
10590 .section Setting up so Perl can be used
10591 Access to Perl subroutines is via a global configuration option called
10592 .index \perl@_startup\
10593 \perl@_startup\ and an expansion string operator \@$@{perl ...@}\. If there is
10594 no \perl@_startup\ option in the Exim configuration file then no Perl
10595 interpreter is started and there is almost no overhead for Exim (since none of
10596 the Perl library will be paged in unless used). If there is a \perl@_startup\
10597 option then the associated value is taken to be Perl code which is executed in
10598 a newly created Perl interpreter.
10600 The value of \perl@_startup\ is not expanded in the Exim sense, so you do not
10601 need backslashes before any characters to escape special meanings. The option
10602 should usually be something like
10604 perl_startup = do '/etc/exim.pl'
10606 where \(/etc/exim.pl)\ is Perl code which defines any subroutines you want to
10607 use from Exim. Exim can be configured either to start up a Perl interpreter as
10608 soon as it is entered, or to wait until the first time it is needed. Starting
10609 the interpreter at the beginning ensures that it is done while Exim still has
10610 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
10611 fact used in a particular run. Also, note that this does not mean that Exim is
10612 necessarily running as root when Perl is called at a later time. By default,
10613 the interpreter is started only when it is needed, but this can be changed in
10616 .index \perl@_at@_start\
10617 Setting \perl@_at@_start\ (a boolean option) in the configuration requests
10618 a startup when Exim is entered.
10620 The command line option \-ps-\ also requests a startup when Exim is entered,
10621 overriding the setting of \perl@_at@_start\.
10623 There is also a command line option \-pd-\ (for delay) which suppresses the
10624 initial startup, even if \perl@_at@_start\ is set.
10626 .section Calling Perl subroutines
10627 When the configuration file includes a \perl@_startup\ option you can make use
10628 of the string expansion item to call the Perl subroutines that are defined
10629 by the \perl@_startup\ code. The operator is used in any of the following
10633 ${perl{foo}{argument}}
10634 ${perl{foo}{argument1}{argument2} ... }
10636 which calls the subroutine \foo\ with the given arguments. A maximum of eight
10637 arguments may be passed. Passing more than this results in an expansion failure
10638 with an error message of the form
10640 Too many arguments passed to Perl subroutine "foo" (max is 8)
10642 The return value of the Perl subroutine is evaluated in a scalar context before
10643 it is passed back to Exim to be inserted into the expanded string. If the
10644 return value is \*undef*\, the expansion is forced to fail in the same way as
10645 an explicit `fail' on an \@$@{if ...@}\ or \@$@{lookup...@}\ item. If the
10646 subroutine aborts by obeying Perl's \die\ function, the expansion fails with
10647 the error message that was passed to \die\.
10649 .section Calling Exim functions from Perl
10650 Within any Perl code called from Exim, the function \*Exim@:@:expand@_string*\
10651 is available to call back into Exim's string expansion function. For example,
10654 my $lp = Exim::expand_string('$local_part');
10656 makes the current Exim \$local@_part$\ available in the Perl variable \$lp$\.
10657 Note those are single quotes and not double quotes to protect against
10658 \$local@_part$\ being interpolated as a Perl variable.
10660 If the string expansion is forced to fail by a `fail' item, the result of
10661 \*Exim@:@:expand@_string*\ is \undef\. If there is a syntax error in the
10662 expansion string, the Perl call from the original expansion string fails with
10663 an appropriate error message, in the same way as if \die\ were used.
10665 .index debugging||from embedded Perl
10666 .index log||writing from embedded Perl
10667 Two other Exim functions are available for use from within Perl code.
10668 \*Exim@:@:debug@_write(<<string>>)*\ writes the string to the standard error
10669 stream if Exim's debugging is enabled. If you want a newline at the end, you
10670 must supply it. \*Exim@:@:log@_write(<<string>>)*\ writes the string to Exim's
10671 main log, adding a leading timestamp. In this case, you should not supply a
10672 terminating newline.
10675 .section Use of standard output and error by Perl
10676 .index Perl||standard output and error
10677 You should not write to the standard error or output streams from within your
10678 Perl code, as it is not defined how these are set up. In versions of Exim
10679 before 4.50, it is possible for the standard output or error to refer to the
10680 SMTP connection during message reception via the daemon. Writing to this stream
10681 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
10682 error streams are connected to \(/dev/null)\ in the daemon. The chaos is
10683 avoided, but the output is lost.
10685 .index Perl||\warn\, use of
10686 The Perl \warn\ statement writes to the standard error stream by default. Calls
10687 to \warn\ may be embedded in Perl modules that you use, but over which you have
10688 no control. When Exim starts up the Perl interpreter, it arranges for output
10689 from the \warn\ statement to be written to the Exim main log. You can change
10690 this by including appropriate Perl magic somewhere in your Perl code. For
10691 example, to discard \warn\ output completely, you need this:
10693 $SIG{__WARN__} = sub { };
10695 Whenever a \warn\ is obeyed, the anonymous subroutine is called. In this
10696 example, the code for the subroutine is empty, so it does nothing, but you can
10697 include any Perl code that you like. The text of the \warn\ message is passed
10698 as the first subroutine argument.
10706 . ============================================================================
10707 .chapter Starting the daemon and the use of network interfaces
10708 .set runningfoot "starting the daemon"
10709 .rset CHAPinterfaces "~~chapter"
10710 .index daemon||starting
10711 .index interface||listening
10712 .index network interface
10713 .index interface||network
10714 .index IP address||for listening
10715 .index daemon||listening IP addresses
10716 .index TCP/IP||setting listening interfaces
10717 .index TCP/IP||setting listening ports
10719 A host that is connected to a TCP/IP network may have one or more physical
10720 hardware network interfaces. Each of these interfaces may be configured as one
10721 or more `logical' interfaces, which are the entities that a program actually
10722 works with. Each of these logical interfaces is associated with an IP address.
10723 In addition, TCP/IP software supports `loopback' interfaces (127.0.0.1 in IPv4
10724 and @:@:1 in IPv6), which do not use any physical hardware. Exim requires
10725 knowledge about the host's interfaces for use in three different circumstances:
10727 When a listening daemon is started, Exim needs to know which interfaces
10728 and ports to listen on.
10730 When Exim is routing an address, it needs to know which IP addresses
10731 are associated with local interfaces. This is required for the correct
10732 processing of MX lists by removing the local host and others with the
10733 same or higher priority values. Also, Exim needs to detect cases
10734 when an address is routed to an IP address that in fact belongs to the
10735 local host. Unless the \self\ router option or the \allow@_localhost\
10736 option of the smtp transport is set (as appropriate), this is treated
10737 as an error situation.
10739 When Exim connects to a remote host, it may need to know which interface to use
10740 for the outgoing connection.
10743 Exim's default behaviour is likely to be appropriate in the vast majority
10744 of cases. If your host has only one interface, and you want all its IP
10745 addresses to be treated in the same way, and you are using only the
10746 standard SMTP port, you should not need to take any special action. The
10747 rest of this chapter does not apply to you.
10749 In a more complicated situation you may want to listen only on certain
10750 interfaces, or on different ports, and for this reason there are a number of
10751 options that can be used to influence Exim's behaviour. The rest of this
10752 chapter describes how they operate.
10754 When a message is received over TCP/IP, the interface and port that were
10755 actually used are set in \$interface@_address$\ and \$interface@_port$\.
10758 .section Starting a listening daemon
10759 When a listening daemon is started (by means of the \-bd-\ command line
10760 option), the interfaces and ports on which it listens are controlled by the
10763 \daemon@_smtp@_ports\ contains a list of default ports. (For backward
10764 compatibility, this option can also be specified in the singular.)
10766 \local@_interfaces\ contains list of interface IP addresses on which to
10767 listen. Each item may optionally also specify a port.
10769 The default list separator in both cases is a colon, but this can be changed as
10770 described in section ~~SECTlistconstruct. When IPv6 addresses are involved, it
10771 is usually best to change the separator to avoid having to double all the
10772 colons. For example:
10774 local_interfaces = <; 127.0.0.1 ; \
10777 3ffe:ffff:836f::fe86:a061
10779 There are two different formats for specifying a port along with an IP address
10780 in \local@_interfaces\:
10782 The port is added onto the address with a dot separator. For example, to listen
10783 on port 1234 on two different IP addresses:
10785 local_interfaces = <; 192.168.23.65.1234 ; \
10786 3ffe:ffff:836f::fe86:a061.1234
10789 The IP address is enclosed in square brackets, and the port is added
10790 with a colon separator, for example:
10792 local_interfaces = <; [192.168.23.65]:1234 ; \
10793 [3ffe:ffff:836f::fe86:a061]:1234
10796 When a port is not specified, the value of \daemon@_smtp@_ports\ is used. The
10797 default setting contains just one port:
10799 daemon_smtp_ports = smtp
10801 If more than one port is listed, each interface that does not have its own port
10802 specified listens on all of them. Ports that are listed in
10803 \daemon@_smtp@_ports\ can be identified either by name (defined in
10804 \(/etc/services)\) or by number. However, when ports are given with individual
10805 IP addresses in \local@_interfaces\, only numbers (not names) can be used.
10808 .section Special IP listening addresses
10809 The addresses 0.0.0.0 and @:@:0 are treated specially. They are interpreted
10810 as `all IPv4 interfaces' and `all IPv6 interfaces', respectively. In each
10811 case, Exim tells the TCP/IP stack to `listen on all IPv\*x*\ interfaces'
10812 instead of setting up separate listening sockets for each interface. The
10813 default value of \local@_interfaces\ is
10815 local_interfaces = 0.0.0.0
10817 when Exim is built without IPv6 support; otherwise it is:
10819 local_interfaces = <; ::0 ; 0.0.0.0
10821 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
10824 .section Overriding local@_interfaces and daemon@_smtp@_ports
10825 The \-oX-\ command line option can be used to override the values of
10826 \daemon@_smtp@_ports\ and/or \local@_interfaces\ for a particular daemon
10827 instance. Another way of doing this would be to use macros and the \-D-\
10828 option. However, \-oX-\ can be used by any admin user, whereas modification of
10829 the runtime configuration by \-D-\ is allowed only when the caller is root or
10832 The value of \-oX-\ is a list of items. The default colon separator can be
10833 changed in the usual way if required. If there are any items that do not
10834 contain dots or colons (that is, are not IP addresses), the value of
10835 \daemon@_smtp@_ports\ is replaced by the list of those items. If there are any
10836 items that do contain dots or colons, the value of \local@_interfaces\ is
10837 replaced by those items. Thus, for example,
10841 overrides \daemon@_smtp@_ports\, but leaves \local@_interfaces\ unchanged,
10844 -oX 192.168.34.5.1125
10846 overrides \local@_interfaces\, leaving \daemon@_smtp@_ports\ unchanged.
10847 (However, since \local@_interfaces\ now contains no items without ports, the
10848 value of \daemon@_smtp@_ports\ is no longer relevant in this example.)
10852 .section Support for the obsolete SSMTP protocol
10853 .rset SECTsupobssmt "~~chapter.~~section"
10854 .index ssmtp protocol
10855 .index SMTP||ssmtp protocol
10856 Exim supports the obsolete SSMTP protocol that was used before the \\STARTTLS\\
10857 command was standardized for SMTP. Some legacy clients still use this protocol.
10858 If the \tls@_on@_connect@_ports\ option is set to a list of port numbers,
10859 connections to those ports must use SSMTP. The most common use of this option
10862 tls_on_connect_ports = 465
10864 because 465 is the usual port number used by the legacy clients. There is also
10865 a command line option \-tls-on-connect-\, which forces all ports to behave in
10866 this way when a daemon is started.
10868 \**Warning**\: Setting \tls@_on@_connect@_ports\ does not of itself cause the
10869 daemon to listen on those ports. You must still specify them in
10870 \daemon@_smtp@_ports\, \local@_interfaces\, or the \-oX-\ option. (This is
10871 because \tls@_on@_connect@_ports\ applies to \inetd\ connections as well as to
10872 connections via the daemon.)
10876 .section IPv6 address scopes
10877 IPv6 addresses have `scopes', and a host with multiple hardware interfaces
10878 can, in principle, have the same link-local IPv6 address on different
10879 interfaces. Thus, additional information is needed, over and above the IP
10880 address, to distinguish individual interfaces. A convention of using a
10881 percent sign followed by something (often the interface name) has been
10882 adopted in some cases, leading to addresses like this:
10884 fe80::202:b3ff:fe03:45c1%eth0
10886 To accommodate this usage, a percent sign followed by an arbitrary string is
10887 allowed at the end of an IPv6 address. By default, Exim calls \*getaddrinfo()*\
10888 to convert a textual IPv6 address for actual use. This function recognizes the
10889 percent convention in operating systems that support it, and it processes the
10890 address appropriately. Unfortunately, some older libraries have problems with
10891 \*getaddrinfo()*\. If
10893 IPV6_USE_INET_PTON=yes
10895 is set in \(Local/Makefile)\ (or an OS-dependent Makefile) when Exim is built,
10896 Exim uses \*inet@_pton()*\ to convert a textual IPv6 address for actual use,
10897 instead of \*getaddrinfo()*\. (Before version 4.14, it always used this
10898 function.) Of course, this means that the additional functionality of
10899 \*getaddrinfo()*\ -- recognizing scoped addresses -- is lost.
10902 .section Examples of starting a listening daemon
10903 The default case in an IPv6 environment is
10905 daemon_smtp_ports = smtp
10906 local_interfaces = <; ::0 ; 0.0.0.0
10908 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
10909 Either one or two sockets may be used, depending on the characteristics of
10910 the TCP/IP stack. (This is complicated and messy; for more information,
10911 read the comments in the \(daemon.c)\ source file.)
10913 To specify listening on ports 25 and 26 on all interfaces:
10915 daemon_smtp_ports = 25 : 26
10917 (leaving \local@_interfaces\ at the default setting) or, more explicitly:
10919 local_interfaces = <; ::0.25 ; ::0.26 \
10920 0.0.0.0.25 ; 0.0.0.0.26
10922 To listen on the default port on all IPv4 interfaces, and on port 26 on the
10923 IPv4 loopback address only:
10925 local_interfaces = 0.0.0.0 : 127.0.0.1.26
10927 To specify listening on the default port on specific interfaces only:
10929 local_interfaces = 192.168.34.67 : 192.168.34.67
10931 \**Warning**\: such a setting excludes listening on the loopback interfaces.
10934 .section Recognising the local host
10935 .rset SECTreclocipadd "~~chapter.~~section"
10936 The \local@_interfaces\ option is also used when Exim needs to determine
10937 whether or not an IP address refers to the local host. That is, the IP
10938 addresses of all the interfaces on which a daemon is listening are always
10941 For this usage, port numbers in \local@_interfaces\ are ignored. If either of
10942 the items 0.0.0.0 or @:@:0 are encountered, Exim gets a complete list of
10943 available interfaces from the operating system, and extracts the relevant
10944 (that is, IPv4 or IPv6) addresses to use for checking.
10946 Some systems set up large numbers of virtual interfaces in order to provide
10947 many virtual web servers. In this situation, you may want to listen for
10948 email on only a few of the available interfaces, but nevertheless treat all
10949 interfaces as local when routing. You can do this by setting
10950 \extra@_local@_interfaces\ to a list of IP addresses, possibly including the
10951 `all' wildcard values. These addresses are recognized as local, but are not
10952 used for listening. Consider this example:
10954 local_interfaces = <; 127.0.0.1 ; ::1 ; \
10956 3ffe:2101:12:1:a00:20ff:fe86:a061
10958 extra_local_interfaces = <; ::0 ; 0.0.0.0
10960 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
10961 address, but all available interface addresses are treated as local when
10964 In some environments the local host name may be in an MX list, but with an IP
10965 address that is not assigned to any local interface. In other cases it may be
10966 desirable to treat other host names as if they referred to the local host. Both
10967 these cases can be handled by setting the \hosts@_treat@_as@_local\ option.
10968 This contains host names rather than IP addresses. When a host is referenced
10969 during routing, either via an MX record or directly, it is treated as the local
10970 host if its name matches \hosts@_treat@_as@_local\, or if any of its IP
10971 addresses match \local@_interfaces\ or \extra@_local@_interfaces\.
10974 .section Delivering to a remote host
10975 Delivery to a remote host is handled by the smtp transport. By default, it
10976 allows the system's TCP/IP functions to choose which interface to use (if
10977 there is more than one) when connecting to a remote host. However, the
10978 \interface\ option can be set to specify which interface is used. See the
10979 description of the smtp transport in chapter ~~CHAPsmtptrans for more details.
10988 . ============================================================================
10989 .chapter Main configuration
10990 .set runningfoot "main configuration"
10991 .rset CHAPmainconfig "~~chapter"
10992 .index configuration file||main section
10993 .index main configuration
10994 The first part of the run time configuration file contains three types of item:
10996 Macro definitions: These lines start with an upper case letter. See section
10997 ~~SECTmacrodefs for details of macro processing.
10999 Named list definitions: These lines start with one of the words `domainlist',
11000 `hostlist', `addresslist', or `localpartlist'. Their use is described in
11001 section ~~SECTnamedlists.
11003 Main configuration settings: Each setting occupies one line of the file
11004 (with possible continuations). If any setting is preceded by the word
11005 `hide', the \-bP-\ command line option displays its value to admin users only.
11006 See section ~~SECTcos for a description of the syntax of these option settings.
11008 This chapter specifies all the main configuration options, along with their
11009 types and default values. For ease of finding a particular option, they appear
11010 in alphabetical order in section ~~SECTalomo below. However, because there are
11011 now so many options, they are first listed briefly in functional groups, as an
11012 aid to finding the name of the option you are looking for. Some options are
11013 listed in more than one group.
11015 .set savedisplayflowcheck ~~displayflowcheck
11016 .set displayflowcheck 0
11018 .section Miscellaneous
11021 \bi@_command\ $t$rm{to run for \-bi-\ command line option}
11022 \keep@_malformed\ $t$rm{for broken files -- should not happen}
11023 \localhost@_number\ $t$rm{for unique message ids in clusters}
11024 \message@_body@_visible\ $t$rm{how much to show in \$message@_body$\}
11027 \mua@_wrapper\ $t$rm{run in `MUA wrapper' mode}
11030 \print@_topbitchars\ $t$rm{top-bit characters are printing}
11031 \timezone\ $t$rm{force time zone}
11034 .section Exim parameters
11037 \exim@_group\ $t$rm{override compiled-in value}
11038 \exim@_path\ $t$rm{override compiled-in value}
11039 \exim@_user\ $t$rm{override compiled-in value}
11040 \primary@_hostname\ $t$rm{default from \*uname()*\}
11041 \split@_spool@_directory\ $t$rm{use multiple directories}
11042 \spool@_directory\ $t$rm{override compiled-in value}
11045 .section Privilege controls
11048 \admin@_groups\ $t$rm{groups that are Exim admin users}
11049 \deliver@_drop@_privilege\ $t$rm{drop root for delivery processes}
11050 \local@_from@_check\ $t$rm{insert ::Sender:: if necessary}
11051 \local@_from@_prefix\ $t$rm{for testing ::From:: for local sender}
11052 \local@_from@_suffix\ $t$rm{for testing ::From:: for local sender}
11053 \local@_sender@_retain\ $t$rm{keep ::Sender:: from untrusted user}
11054 \never@_users\ $t$rm{do not run deliveries as these}
11055 \prod@_requires@_admin\ $t$rm{forced delivery requires admin user}
11056 \queue@_list@_requires@_admin\ $t$rm{queue listing requires admin user}
11057 \trusted@_groups\ $t$rm{groups that are trusted}
11058 \trusted@_users\ $t$rm{users that are trusted}
11065 \hosts@_connection@_nolog\ $t$rm{exemption from connect logging}
11068 \log@_file@_path\ $t$rm{override compiled-in value}
11069 \log@_selector\ $t$rm{set/unset optional logging}
11070 \log@_timezone\ $t$rm{add timezone to log lines}
11071 \message@_logs\ $t$rm{create per-message logs}
11072 \preserve@_message@_logs\ $t$rm{after message completion}
11073 \process@_log@_path\ $t$rm{for SIGUSR1 and \*exiwhat*\}
11074 \syslog@_duplication\ $t$rm{controls duplicate log lines on syslog }
11075 \syslog@_facility\ $t$rm{set syslog `facility' field}
11076 \syslog@_processname\ $t$rm{set syslog `ident' field}
11077 \syslog@_timestamp\ $t$rm{timestamp syslog lines}
11079 \write@_rejectlog\ $t$rm{control use of message log}
11083 .section Frozen messages
11086 \auto@_thaw\ $t$rm{sets time for retrying frozen messages}
11087 \freeze@_tell\ $t$rm{send message when freezing}
11088 \move@_frozen@_messages\ $t$rm{to another directory}
11089 \timeout@_frozen@_after\ $t$rm{keep frozen messages only so long}
11092 .section Data lookups
11095 \ldap@_default@_servers\ $t$rm{used if no server in query}
11096 \ldap@_version\ $t$rm{set protocol version}
11097 \lookup@_open@_max\ $t$rm{lookup files held open}
11098 \mysql@_servers\ $t$rm{as it says}
11099 \oracle@_servers\ $t$rm{as it says}
11100 \pgsql@_servers\ $t$rm{as it says}
11103 .section Message ids
11106 \message@_id@_header@_domain\ $t$rm{used to build ::Message-ID:: header}
11107 \message@_id@_header@_text\ $t$rm{ditto}
11110 .section Embedded Perl Startup
11113 \perl@_at@_start\ $t$rm{always start the interpreter}
11114 \perl@_startup\ $t$rm{code to obey when starting Perl}
11120 \daemon@_smtp@_ports\ $t$rm{default ports}
11121 \extra@_local@_interfaces\ $t$rm{not necessarily listened on}
11122 \local@_interfaces\ $t$rm{on which to listen, with optional ports}
11123 \pid@_file@_path\ $t$rm{override compiled-in value}
11124 \queue@_run@_max\ $t$rm{maximum simultaneous queue runners}
11127 .section Resource control
11130 \check@_log@_inodes\ $t$rm{before accepting a message}
11131 \check@_log@_space\ $t$rm{before accepting a message}
11132 \check@_spool@_inodes\ $t$rm{before accepting a message}
11133 \check@_spool@_space\ $t$rm{before accepting a message}
11134 \deliver@_queue@_load@_max\ $t$rm{no queue deliveries if load high}
11135 \queue@_only@_load\ $t$rm{queue incoming if load high}
11136 \queue@_run@_max\ $t$rm{maximum simultaneous queue runners}
11137 \remote@_max@_parallel\ $t$rm{parallel SMTP delivery per message}
11138 \smtp@_accept@_max\ $t$rm{simultaneous incoming connections}
11139 \smtp@_accept@_max@_nommail\ $t$rm{non-mail commands}
11140 \smtp@_accept@_max@_nonmail@_hosts\ $t$rm{hosts to which the limit applies}
11141 \smtp@_accept@_max@_per@_connection\ $t$rm{messages per connection}
11142 \smtp@_accept@_max@_per@_host\ $t$rm{connections from one host}
11143 \smtp@_accept@_queue\ $t$rm{queue mail if more connections}
11144 \smtp@_accept@_queue@_per@_connection\ $t$rm{queue if more messages per connection}
11145 \smtp@_accept@_reserve\ $t$rm{only reserve hosts if more connections}
11146 \smtp@_check@_spool@_space\ $t$rm{from \\SIZE\\ on \\MAIL\\ command}
11147 \smtp@_connect@_backlog\ $t$rm{passed to TCP/IP stack}
11148 \smtp@_load@_reserve\ $t$rm{SMTP from reserved hosts if load high}
11149 \smtp@_reserve@_hosts\ $t$rm{these are the reserve hosts}
11152 .section Policy controls
11155 \acl@_not@_smtp\ $t$rm{set ACL for non-SMTP messages}
11156 \acl@_smtp@_auth\ $t$rm{set ACL for \\AUTH\\}
11157 \acl@_smtp@_connect\ $t$rm{set ACL for connection}
11158 \acl@_smtp@_data\ $t$rm{set ACL for \\DATA\\}
11159 \acl@_smtp@_etrn\ $t$rm{set ACL for \\ETRN\\}
11160 \acl@_smtp@_expn\ $t$rm{set ACL for \\EXPN\\}
11161 \acl@_smtp@_helo\ $t$rm{set ACL for \\EHLO\\ or \\HELO\\}
11162 \acl@_smtp@_mail\ $t$rm{set ACL for \\MAIL\\}
11163 \acl@_smtp@_mailauth\ $t$rm{set ACL for \\AUTH\\ on \\MAIL\\ command}
11166 \acl@_smtp@_mime\ $t$rm{set ACL for MIME parts}
11167 \acl@_smtp@_predata\ $t$rm{set ACL for start of data}
11168 \acl@_smtp@_quit\ $t$rm{set ACL for \\QUIT\\}
11171 \acl@_smtp@_rcpt\ $t$rm{set ACL for \\RCPT\\}
11172 \acl@_smtp@_starttls\ $t$rm{set ACL for \\STARTTLS\\}
11173 \acl@_smtp@_vrfy\ $t$rm{set ACL for \\VRFY\\}
11176 \av@_scanner\ $t$rm{specify virus scanner}
11179 \header@_maxsize\ $t$rm{total size of message header}
11180 \header@_line@_maxsize\ $t$rm{individual header line limit}
11181 \helo@_accept@_junk@_hosts\ $t$rm{allow syntactic junk from these hosts}
11182 \helo@_allow@_chars\ $t$rm{allow illegal chars in \\HELO\\ names}
11183 \helo@_lookup@_domains\ $t$rm{lookup hostname for these \\HELO\\ names}
11184 \helo@_try@_verify@_hosts\ $t$rm{\\HELO\\ soft-checked for these hosts}
11185 \helo@_verify@_hosts\ $t$rm{\\HELO\\ hard-checked for these hosts}
11186 \host@_lookup\ $t$rm{host name looked up for these hosts}
11187 \host@_lookup@_order\ $t$rm{order of DNS and local name lookups}
11188 \host@_reject@_connection\ $t$rm{reject connection from these hosts}
11189 \hosts@_treat@_as@_local\ $t$rm{useful in some cluster configurations}
11190 \local@_scan@_timeout\ $t$rm{timeout for \*local@_scan()*\}
11191 \message@_size@_limit\ $t$rm{for all messages}
11192 \percent@_hack@_domains\ $t$rm{recognize %-hack for these domains}
11195 \spamd@_address\ $t$rm{set interface to SpamAssassin}
11200 .section Callout cache
11203 \callout@_domain@_negative@_expire\ $t$rm{timeout for negative domain cache item}
11204 \callout@_domain@_positive@_expire\ $t$rm{timeout for positive domain cache item}
11205 \callout@_negative@_expire\ $t$rm{timeout for negative address cache item}
11206 \callout@_positive@_expire\ $t$rm{timeout for positive address cache item}
11207 \callout@_random@_local@_part\ $t$rm{string to use for `random' testing}
11213 \tls@_advertise@_hosts\ $t$rm{advertise TLS to these hosts}
11214 \tls@_certificate\ $t$rm{location of server certificate}
11215 \tls@_crl\ $t$rm{certificate revocation list}
11216 \tls@_dhparam\ $t$rm{DH parameters for server}
11219 \tls@_on@_connect@_ports\ $t$rm{specify SSMTP ports}
11222 \tls@_privatekey\ $t$rm{location of server private key}
11223 \tls@_remember@_esmtp\ $t$rm{don't reset after starting TLS}
11224 \tls@_require@_ciphers\ $t$rm{specify acceptable cipers}
11225 \tls@_try@_verify@_hosts\ $t$rm{try to verify client certificate}
11226 \tls@_verify@_certificates\ $t$rm{expected client certificates}
11227 \tls@_verify@_hosts\ $t$rm{insist on client certificate verify}
11230 .section Local user handling
11233 \finduser@_retries\ $t$rm{useful in NIS environments}
11234 \gecos@_name\ $t$rm{used when creating ::Sender::}
11235 \gecos@_pattern\ $t$rm{ditto}
11236 \max@_username@_length\ $t$rm{for systems that truncate}
11237 \unknown@_login\ $t$rm{used when no login name found}
11238 \unknown@_username\ $t$rm{ditto}
11239 \uucp@_from@_pattern\ $t$rm{for recognizing `From ' lines}
11240 \uucp@_from@_sender\ $t$rm{ditto}
11243 .section All incoming messages (SMTP and non-SMTP)
11246 \header@_maxsize\ $t$rm{total size of message header}
11247 \header@_line@_maxsize\ $t$rm{individual header line limit}
11248 \message@_size@_limit\ $t$rm{applies to all messages}
11249 \percent@_hack@_domains\ $t$rm{recognize %-hack for these domains}
11250 \received@_header@_text\ $t$rm{expanded to make ::Received::}
11251 \received@_headers@_max\ $t$rm{for mail loop detection}
11252 \recipients@_max\ $t$rm{limit per message}
11253 \recipients@_max@_reject\ $t$rm{permanently reject excess}
11257 .section Non-SMTP incoming messages
11260 \receive@_timeout\ $t$rm{for non-SMTP messages}
11265 .section Incoming SMTP messages
11266 See also the \*Policy controls*\ section above.
11269 \host@_lookup\ $t$rm{host name looked up for these hosts}
11270 \host@_lookup@_order\ $t$rm{order of DNS and local name lookups}
11271 \recipient@_unqualified@_hosts\ $t$rm{may send unqualified recipients}
11272 \rfc1413@_hosts\ $t$rm{make ident calls to these hosts}
11273 \rfc1413@_query@_timeout\ $t$rm{zero disables ident calls}
11274 \sender@_unqualified@_hosts\ $t$rm{may send unqualified senders}
11275 \smtp@_accept@_keepalive\ $t$rm{some TCP/IP magic}
11276 \smtp@_accept@_max\ $t$rm{simultaneous incoming connections}
11277 \smtp@_accept@_max@_nommail\ $t$rm{non-mail commands}
11278 \smtp@_accept@_max@_nonmail@_hosts\ $t$rm{hosts to which the limit applies}
11279 \smtp@_accept@_max@_per@_connection\ $t$rm{messages per connection}
11280 \smtp@_accept@_max@_per@_host\ $t$rm{connections from one host}
11281 \smtp@_accept@_queue\ $t$rm{queue mail if more connections}
11282 \smtp@_accept@_queue@_per@_connection\ $t$rm{queue if more messages per connection}
11283 \smtp@_accept@_reserve\ $t$rm{only reserve hosts if more connections}
11285 \smtp@_active@_hostname\ $t$rm{host name to use in messages}
11287 \smtp@_banner\ $t$rm{text for welcome banner}
11288 \smtp@_check@_spool@_space\ $t$rm{from \\SIZE\\ on \\MAIL\\ command}
11289 \smtp@_connect@_backlog\ $t$rm{passed to TCP/IP stack}
11290 \smtp@_enforce@_sync\ $t$rm{of SMTP command/responses}
11291 \smtp@_etrn@_command\ $t$rm{what to run for \\ETRN\\}
11292 \smtp@_etrn@_serialize\ $t$rm{only one at once}
11293 \smtp@_load@_reserve\ $t$rm{only reserve hosts if this load}
11294 \smtp@_max@_unknown@_commands\ $t$rm{before dropping connection}
11295 \smtp@_ratelimit@_hosts\ $t$rm{apply ratelimiting to these hosts}
11296 \smtp@_ratelimit@_mail\ $t$rm{ratelimit for \\MAIL\\ commands}
11297 \smtp@_ratelimit@_rcpt\ $t$rm{ratelimit for \\RCPT\\ commands}
11298 \smtp@_receive@_timeout\ $t$rm{per command or data line}
11299 \smtp@_reserve@_hosts\ $t$rm{these are the reserve hosts}
11300 \smtp@_return@_error@_details\ $t$rm{give detail on rejections}
11303 .section SMTP extensions
11306 \accept@_8bitmime\ $t$rm{advertise \\8BITMIME\\}
11307 \auth@_advertise@_hosts\ $t$rm{advertise \\AUTH\\ to these hosts}
11308 \ignore@_fromline@_hosts\ $t$rm{allow `From ' from these hosts}
11309 \ignore@_fromline@_local\ $t$rm{allow `From ' from local SMTP}
11310 \pipelining@_advertise@_hosts\ $t$rm{advertise pipelining to these hosts}
11311 \tls@_advertise@_hosts\ $t$rm{advertise TLS to these hosts}
11314 .section Processing messages
11317 \allow@_domain@_literals\ $t$rm{recognize domain literal syntax}
11318 \allow@_mx@_to@_ip\ $t$rm{allow MX to point to IP address}
11319 \allow@_utf8@_domains\ $t$rm{in addresses}
11320 \delivery@_date@_remove\ $t$rm{from incoming messages}
11321 \envelope@_to@_remote\ $t$rm{from incoming messages}
11322 \extract@_addresses@_remove@_arguments\ $t$rm{affects \-t-\ processing}
11323 \headers@_charset\ $t$rm{default for translations}
11324 \qualify@_domain\ $t$rm{default for senders}
11325 \qualify@_recipient\ $t$rm{default for recipients}
11326 \return@_path@_remove\ $t$rm{from incoming messages}
11327 \strip@_excess@_angle@_brackets\ $t$rm{in addresses}
11328 \strip@_trailing@_dot\ $t$rm{at end of addresses}
11329 \untrusted@_set@_sender\ $t$rm{untrusted can set envelope sender}
11332 .section System filter
11335 \system@_filter\ $t$rm{locate system filter}
11336 \system@_filter@_directory@_transport\ $t$rm{transport for delivery to a directory}
11337 \system@_filter@_file@_transport\ $t$rm{transport for delivery to a file}
11338 \system@_filter@_group\ $t$rm{group for filter running}
11339 \system@_filter@_pipe@_transport\ $t$rm{transport for delivery to a pipe}
11340 \system@_filter@_reply@_transport\ $t$rm{transport for autoreply delivery}
11341 \system@_filter@_user\ $t$rm{user for filter running}
11344 .section Routing and delivery
11347 \dns@_again@_means@_nonexist\ $t$rm{for broken domains}
11348 \dns@_check@_names@_pattern\ $t$rm{pre-DNS syntax check}
11349 \dns@_ipv4@_lookup\ $t$rm{only v4 lookup for these domains}
11350 \dns@_retrans\ $t$rm{parameter for resolver}
11351 \dns@_retry\ $t$rm{parameter for resolver}
11352 \hold@_domains\ $t$rm{hold delivery for these domains}
11353 \local@_interfaces\ $t$rm{for routing checks}
11354 \queue@_domains\ $t$rm{no immediate delivery for these}
11355 \queue@_only\ $t$rm{no immediate delivery at all}
11356 \queue@_only@_file\ $t$rm{no immediate deliveryif file exists}
11357 \queue@_only@_load\ $t$rm{no immediate delivery if load is high}
11358 \queue@_only@_override\ $t$rm{allow command line to override}
11359 \queue@_run@_in@_order\ $t$rm{order of arrival}
11360 \queue@_run@_max\ $t$rm{of simultaneous queue runners}
11361 \queue@_smtp@_domains\ $t$rm{no immediate SMTP delivery for these}
11362 \remote@_max@_parallel\ $t$rm{parallel SMTP delivery per message}
11363 \remote@_sort@_domains\ $t$rm{order of remote deliveries}
11364 \retry@_data@_expire\ $t$rm{timeout for retry data}
11365 \retry@_interval@_max\ $t$rm{safety net for retry rules}
11368 .section Bounce and warning messages
11371 \bounce@_message@_file\ $t$rm{content of bounce}
11372 \bounce@_message@_text\ $t$rm{content of bounce}
11373 \bounce@_return@_body\ $t$rm{include body if returning message}
11374 \bounce@_return@_message\ $t$rm{include original message in bounce}
11375 \bounce@_return@_size@_limit\ $t$rm{limit on returned message}
11376 \bounce@_sender@_authentication\ $t$rm{send authenticated sender with bounce}
11377 \errors@_copy\ $t$rm{copy bounce messages}
11378 \errors@_reply@_to\ $t$rm{::Reply-to:: in bounces}
11379 \delay@_warning\ $t$rm{time schedule}
11380 \delay@_warning@_condition\ $t$rm{condition for warning messages}
11381 \ignore@_bounce@_errors@_after\ $t$rm{discard undeliverable bounces}
11382 \warn@_message@_file\ $t$rm{content of warning message}
11385 .set displayflowcheck ~~savedisplayflowcheck
11387 .section Alphabetical list of main options
11388 .rset SECTalomo "~~chapter.~~section"
11390 Those options that undergo string expansion before use are marked with $**$.
11395 .index \\8BITMIME\\
11396 .index 8-bit characters
11397 .conf accept@_8bitmime boolean false
11398 This option causes Exim to send \\8BITMIME\\ in its response to an SMTP
11399 \\EHLO\\ command, and to accept the \\BODY=\\ parameter on \\MAIL\\ commands.
11400 However, though Exim is 8-bit clean, it is not a protocol converter, and it
11401 takes no steps to do anything special with messages received by this route.
11402 Consequently, this option is turned off by default.
11404 .index ~~ACL||for non-SMTP messages
11405 .index non-SMTP messages, ACL for
11406 .conf acl@_not@_smtp string$**$ unset
11407 This option defines the ACL that is run when a non-SMTP message is on the point
11408 of being accepted. See chapter ~~CHAPACL for further details.
11410 .index ~~ACL||on SMTP connection
11411 .conf acl@_smtp@_connect string$**$ unset
11412 This option defines the ACL that is run when an SMTP connection is received.
11413 See chapter ~~CHAPACL for further details.
11415 .index ~~ACL||setting up for SMTP commands
11416 .index \\AUTH\\||ACL for
11417 .conf acl@_smtp@_auth string$**$ unset
11418 This option defines the ACL that is run when an SMTP \\AUTH\\ command is
11419 received. See chapter ~~CHAPACL for further details.
11421 .index \\DATA\\, ACL for
11422 .conf acl@_smtp@_data string$**$ unset
11423 This option defines the ACL that is run after an SMTP \\DATA\\ command has been
11424 processed and the message itself has been received, but before the final
11425 acknowledgement is sent. See chapter ~~CHAPACL for further details.
11427 .index \\ETRN\\||ACL for
11428 .conf acl@_smtp@_etrn string$**$ unset
11429 This option defines the ACL that is run when an SMTP \\ETRN\\ command is
11430 received. See chapter ~~CHAPACL for further details.
11432 .index \\EXPN\\||ACL for
11433 .conf acl@_smtp@_expn string$**$ unset
11434 This option defines the ACL that is run when an SMTP \\EXPN\\ command is
11435 received. See chapter ~~CHAPACL for further details.
11437 .index \\EHLO\\||ACL for
11438 .index \\HELO\\||ACL for
11439 .conf acl@_smtp@_helo string$**$ unset
11440 This option defines the ACL that is run when an SMTP \\EHLO\\ or \\HELO\\
11441 command is received. See chapter ~~CHAPACL for further details.
11443 .index \\MAIL\\||ACL for
11444 .conf acl@_smtp@_mail string$**$ unset
11445 This option defines the ACL that is run when an SMTP \\MAIL\\ command is
11446 received. See chapter ~~CHAPACL for further details.
11448 .index \\AUTH\\||on \\MAIL\\ command
11449 .conf acl@_smtp@_mailauth string$**$ unset
11450 This option defines the ACL that is run when there is an \\AUTH\\ parameter on
11451 a \\MAIL\\ command. See chapter ~~CHAPACL for details of ACLs, and chapter
11452 ~~CHAPSMTPAUTH for details of authentication.
11455 .index MIME content scanning||ACL for
11456 .conf acl@_smtp@_mime string$**$ unset
11457 This option is available when Exim is built with the content-scanning
11458 extension. It defines the ACL that is run for each MIME part in a message. See
11459 section ~~SECTscanmimepart for details.
11461 .conf acl@_smtp@_predata string$**$ unset
11462 This option defines the ACL that is run when an SMTP \\DATA\\ command is
11463 received, before the message itself is received. See chapter ~~CHAPACL for
11466 .index \\QUIT\\||ACL for
11467 .conf acl@_smtp@_quit string$**$ unset
11468 This option defines the ACL that is run when an SMTP \\QUIT\\ command is
11469 received. See chapter ~~CHAPACL for further details.
11472 .index \\RCPT\\||ACL for
11473 .conf acl@_smtp@_rcpt string$**$ unset
11474 This option defines the ACL that is run when an SMTP \\RCPT\\ command is
11475 received. See chapter ~~CHAPACL for further details.
11477 .index \\STARTTLS\\, ACL for
11478 .conf acl@_smtp@_starttls string$**$ unset
11479 This option defines the ACL that is run when an SMTP \\STARTTLS\\ command is
11480 received. See chapter ~~CHAPACL for further details.
11482 .index \\VRFY\\||ACL for
11483 .conf acl@_smtp@_vrfy string$**$ unset
11484 This option defines the ACL that is run when an SMTP \\VRFY\\ command is
11485 received. See chapter ~~CHAPACL for further details.
11487 .conf admin@_groups "string list" unset
11489 If the current group or any of the supplementary groups of the caller is in
11490 this colon-separated list, the caller has admin privileges. If all your system
11491 programmers are in a specific group, for example, you can give them all Exim
11492 admin privileges by putting that group in \admin@_groups\. However, this does
11493 not permit them to read Exim's spool files (whose group owner is the Exim gid).
11494 To permit this, you have to add individuals to the Exim group.
11496 .conf allow@_domain@_literals boolean false
11497 .index domain literal
11498 If this option is set, the RFC 2822 domain literal format is permitted in
11499 email addresses. The option is not set by default, because the domain literal
11500 format is not normally required these days, and few people know about it. It
11501 has, however, been exploited by mail abusers.
11503 Unfortunately, it seems that some DNS black list maintainers are using this
11504 format to report black listing to postmasters. If you want to accept messages
11505 addressed to your hosts by IP address, you need to set
11506 \allow@_domain@_literals\ true, and also to add \"@@[]"\ to the list of local
11507 domains (defined in the named domain list \local@_domains\ in the default
11508 configuration). This `magic string' matches the domain literal form of all the
11509 local host's IP addresses.
11511 .conf allow@_mx@_to@_ip boolean false
11512 .index MX record||pointing to IP address
11513 It appears that more and more DNS zone administrators are breaking the rules
11514 and putting domain names that look like IP addresses on the right hand side of
11515 MX records. Exim follows the rules and rejects this, giving an error message
11516 that explains the mis-configuration. However, some other MTAs support this
11517 practice, so to avoid `Why can't Exim do this?' complaints, \allow@_mx@_to@_ip\
11518 exists, in order to enable this heinous activity. It is not recommended, except
11519 when you have no other choice.
11521 .index domain||UTF-8 characters in
11522 .index UTF-8||in domain name
11523 .conf allow@_utf8@_domains boolean false
11524 Lots of discussion is going on about internationalized domain names. One
11525 camp is strongly in favour of just using UTF-8 characters, and it seems
11526 that at least two other MTAs permit this. This option allows Exim users to
11527 experiment if they wish.
11529 If it is set true, Exim's domain parsing function allows valid
11530 UTF-8 multicharacters to appear in domain name components, in addition to
11531 letters, digits, and hyphens. However, just setting this option is not
11532 enough; if you want to look up these domain names in the DNS, you must also
11533 adjust the value of \dns@_check@_names@_pattern\ to match the extended form. A
11534 suitable setting is:
11536 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
11537 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
11539 Alternatively, you can just disable this feature by setting
11541 dns_check_names_pattern =
11543 That is, set the option to an empty string so that no check is done.
11545 .conf auth@_advertise@_hosts "host list$**$" $*$
11546 .index authentication||advertising
11547 .index \\AUTH\\||advertising
11548 If any server authentication mechanisms are configured, Exim advertises them in
11549 response to an \\EHLO\\ command only if the calling host matches this list.
11550 Otherwise, Exim does not advertise \\AUTH\\.
11551 Exim does not accept \\AUTH\\ commands from clients to which it has not
11552 advertised the availability of \\AUTH\\. The advertising of individual
11553 authentication mechanisms can be controlled by the use of the
11554 \server@_advertise@_condition\ generic authenticator option on the individual
11555 authenticators. See chapter ~~CHAPSMTPAUTH for further details.
11557 Certain mail clients (for example, Netscape) require the user to provide a name
11558 and password for authentication if \\AUTH\\ is advertised, even though it may
11559 not be needed (the host may accept messages from hosts on its local LAN without
11560 authentication, for example). The \auth@_advertise@_hosts\ option can be used
11561 to make these clients more friendly by excluding them from the set of hosts to
11562 which Exim advertises \\AUTH\\.
11564 .index \\AUTH\\||advertising when encrypted
11565 If you want to advertise the availability of \\AUTH\\ only when the connection
11566 is encrypted using TLS, you can make use of the fact that the value of this
11567 option is expanded, with a setting like this:
11569 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
11571 If \$tls@_cipher$\ is empty, the session is not encrypted, and the result of
11572 the expansion is empty, thus matching no hosts. Otherwise, the result of the
11573 expansion is $*$, which matches all hosts.
11575 .conf auto@_thaw time 0s
11576 .index thawing messages
11577 .index unfreezing messages
11578 If this option is set to a time greater than zero, a queue runner will try a
11579 new delivery attempt on any frozen message if this much time has passed since
11580 it was frozen. This may result in the message being re-frozen if nothing has
11581 changed since the last attempt. It is a way of saying `keep on trying, even
11582 though there are big problems'. See also \timeout@_frozen@_after\ and
11583 \ignore@_bounce@_errors@_after\.
11586 .conf av@_scanner string "see below"
11587 This option is available if Exim is built with the content-scanning extension.
11588 It specifies which anti-virus scanner to use. The default value is:
11590 sophie:/var/run/sophie
11592 If the value of \av@_scanner\ starts with dollar character, it is expanded
11593 before use. See section ~~SECTscanvirus for further details.
11596 .conf bi@_command string unset
11597 .index \-bi-\ option
11598 This option supplies the name of a command that is run when Exim is called with
11599 the \-bi-\ option (see chapter ~~CHAPcommandline). The string value is just the
11600 command name, it is not a complete command line. If an argument is required, it
11601 must come from the \-oA-\ command line option.
11603 .conf bounce@_message@_file string unset
11604 .index bounce message||customizing
11605 .index customizing||bounce message
11606 This option defines a template file containing paragraphs of text to be used
11607 for constructing bounce messages. Details of the file's contents are given in
11608 chapter ~~CHAPemsgcust. See also \warn@_message@_file\.
11610 .conf bounce@_message@_text string unset
11611 When this option is set, its contents are included in the default bounce
11612 message immediately after `This message was created automatically by mail
11613 delivery software.' It is not used if \bounce@_message@_file\ is set.
11615 .index bounce message||including body
11616 .conf bounce@_return@_body boolean true
11617 This option controls whether the body of an incoming message is included in a
11618 bounce message when \bounce@_return@_message\ is true. If it is not set, only
11619 the message header is included.
11621 .index bounce message||including original
11622 .conf bounce@_return@_message boolean true
11623 If this option is set false, the original message is not included in bounce
11624 messages generated by Exim. See also \bounce@_return@_size@_limit\.
11626 .conf bounce@_return@_size@_limit integer 100K
11627 .index size||of bounce, limit
11628 .index bounce message||size limit
11629 .index limit||bounce message size
11630 This option sets a limit in bytes on the size of messages that are returned to
11631 senders as part of bounce messages when \bounce@_return@_message\ is true. The
11632 limit should be less than the value of the global \message@_size@_limit\ and of
11633 any \message@_size@_limit\ settings on transports, to allow for the bounce text
11634 that Exim generates. If this option is set to zero there is no limit.
11636 When the body of any message that is to be included in a bounce message is
11637 greater than the limit, it is truncated, and a comment pointing this out is
11638 added at the top. The actual cutoff may be greater than the value given, owing
11639 to the use of buffering for transferring the message in chunks (typically 8K in
11640 size). The idea is to save bandwidth on those undeliverable 15-megabyte
11643 .index bounce message||sender authentication
11644 .index authentication||bounce message
11645 .index \\AUTH\\||on bounce message
11646 .conf bounce@_sender@_authentication string unset
11647 This option provides an authenticated sender address that is sent with any
11648 bounce messages generated by Exim that are sent over an authenticated SMTP
11649 connection. A typical setting might be:
11651 bounce_sender_authentication = mailer-daemon@my.domain.example
11653 which would cause bounce messages to be sent using the SMTP command:
11655 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
11657 The value of \bounce@_sender@_authentication\ must always be a complete email
11660 .index caching||callout, timeouts
11661 .index callout||caching timeouts
11662 .conf callout@_domain@_negative@_expire time 3h
11663 This option specifies the expiry time for negative callout cache data for a
11664 domain. See section ~~SECTcallver for details of callout verification, and
11665 section ~~SECTcallvercache for details of the caching.
11667 .conf callout@_domain@_positive@_expire time 7d
11668 This option specifies the expiry time for positive callout cache data for a
11669 domain. See section ~~SECTcallver for details of callout verification, and
11670 section ~~SECTcallvercache for details of the caching.
11672 .conf callout@_negative@_expire time 2h
11673 This option specifies the expiry time for negative callout cache data for an
11674 address. See section ~~SECTcallver for details of callout verification, and
11675 section ~~SECTcallvercache for details of the caching.
11677 .conf callout@_positive@_expire time 24h
11678 This option specifies the expiry time for positive callout cache data for an
11679 address. See section ~~SECTcallver for details of callout verification, and
11680 section ~~SECTcallvercache for details of the caching.
11682 .conf callout@_random@_local@_part string$**$ "see below"
11683 This option defines the `random' local part that can be used as part of callout
11684 verification. The default value is
11686 $primary_host_name-$tod_epoch-testing
11688 See section ~~CALLaddparcall for details of how this value is used.
11690 .conf check@_log@_inodes integer 0
11691 See \check@_spool@_space\ below.
11693 .conf check@_log@_space integer 0
11694 See \check@_spool@_space\ below.
11696 .conf check@_spool@_inodes integer 0
11697 See \check@_spool@_space\ below.
11699 .conf check@_spool@_space integer 0
11700 .index checking disk space
11701 .index disk space, checking
11702 .index spool directory||checking space
11703 The four \check@_...\ options allow for checking of disk resources before a
11704 message is accepted.
11706 When any of these options are set, they apply to all incoming messages. If you
11707 want to apply different checks to different kinds of message, you can do so
11708 by testing the the variables \$log@_inodes$\, \$log@_space$\,
11709 \$spool@_inodes$\, and \$spool@_space$\ in an ACL with appropriate additional
11713 \check@_spool@_space\ and \check@_spool@_inodes\ check the spool partition if
11714 either value is greater than zero, for example:
11716 check_spool_space = 10M
11717 check_spool_inodes = 100
11719 The spool partition is the one that contains the directory defined by
11720 \\SPOOL@_DIRECTORY\\ in \(Local/Makefile)\. It is used for holding messages in
11723 \check@_log@_space\ and \check@_log@_inodes\ check the partition in which log
11724 files are written if either is greater than zero. These should be set only if
11725 \log@_file@_path\ and \spool@_directory\ refer to different partitions.
11727 If there is less space or fewer inodes than requested, Exim refuses to accept
11728 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
11729 error response to the \\MAIL\\ command. If ESMTP is in use and there was a
11730 \\SIZE\\ parameter on the \\MAIL\\ command, its value is added to the
11731 \check@_spool@_space\ value, and the check is performed even if
11732 \check@_spool@_space\ is zero, unless \no@_smtp@_check@_spool@_space\ is set.
11734 The values for \check@_spool@_space\ and \check@_log@_space\ are held as a
11735 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
11737 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
11738 failure a message is written to stderr and Exim exits with a non-zero code, as
11739 it obviously cannot send an error message of any kind.
11741 .index port||for daemon
11742 .index TCP/IP||setting listening ports
11743 .conf daemon@_smtp@_ports string "$tt{smtp}"
11744 This option specifies one or more default SMTP ports on which the Exim daemon
11745 listens. See chapter ~~CHAPinterfaces for details of how it is used. For
11746 backward compatibility, \daemon@_smtp@_port\ (singular) is a synonym.
11748 .conf delay@_warning "time list" 24h
11749 .index warning of delay
11750 .index delay warning, specifying
11751 When a message is delayed, Exim sends a warning message to the sender at
11752 intervals specified by this option. The data is a colon-separated list of times
11753 after which to send warning messages.
11755 If the value of the option is an empty string or a zero time, no warnings are
11758 Up to 10 times may be given. If a message has been on the queue for longer than
11759 the last time, the last interval between the times is used to compute
11760 subsequent warning times. For example, with
11762 delay_warning = 4h:8h:24h
11764 the first message is sent after 4 hours, the second after 8 hours, and
11765 the third one after 24 hours. After that, messages are sent every 16 hours,
11766 because that is the interval between the last two times on the list. If you set
11767 just one time, it specifies the repeat interval. For example, with:
11771 messages are repeated every six hours. To stop warnings after a given time, set
11772 a very large time at the end of the list. For example:
11774 delay_warning = 2h:12h:99d
11777 .conf delay@_warning@_condition string$**$ "see below"
11778 The string is expanded at the time a warning message might be sent. If all the
11779 deferred addresses have the same domain, it is set in \$domain$\ during the
11780 expansion. Otherwise \$domain$\ is empty. If the result of the expansion is a
11781 forced failure, an empty string, or a string matching any of `0', `no' or
11782 `false' (the comparison being done caselessly) then the warning message is not
11783 sent. The default is
11785 delay_warning_condition = \
11786 ${if match{$h_precedence:}{(?i)bulk|list|junk}{no}{yes}}
11788 which suppresses the sending of warnings about messages that have `bulk',
11789 `list' or `junk' in a ::Precedence:: header.
11791 .index unprivileged delivery
11792 .index delivery||unprivileged
11793 .conf deliver@_drop@_privilege boolean false
11794 If this option is set true, Exim drops its root privilege at the start of a
11795 delivery process, and runs as the Exim user throughout. This severely restricts
11796 the kinds of local delivery that are possible, but is viable in certain types
11797 of configuration. There is a discussion about the use of root privilege in
11798 chapter ~~CHAPsecurity.
11800 .index load average
11801 .index queue runner||abandoning
11802 .conf deliver@_queue@_load@_max fixed-point unset
11803 When this option is set, a queue run is abandoned if the system load average
11804 becomes greater than the value of the option. The option has no effect on
11805 ancient operating systems on which Exim cannot determine the load average.
11806 See also \queue@_only@_load\ and \smtp@_load@_reserve\.
11808 .conf delivery@_date@_remove boolean true
11809 .index ::Delivery-date:: header line
11810 Exim's transports have an option for adding a ::Delivery-date:: header to a
11811 message when it is delivered -- in exactly the same way as ::Return-path:: is
11812 handled. ::Delivery-date:: records the actual time of delivery. Such headers
11813 should not be present in incoming messages, and this option causes them to be
11814 removed at the time the message is received, to avoid any problems that might
11815 occur when a delivered message is subsequently sent on to some other recipient.
11817 .index DNS||`try again' response, overriding
11818 .conf dns@_again@_means@_nonexist "domain list$**$" unset
11819 DNS lookups give a `try again' response for the DNS errors `non-authoritative
11820 host not found' and `\\SERVERFAIL\\'. This can cause Exim to keep trying to
11821 deliver a message, or to give repeated temporary errors to incoming mail.
11822 Sometimes the effect is caused by a badly set up name server and may persist
11823 for a long time. If a domain which exhibits this problem matches anything in
11824 \dns__again__means__nonexist\, it is treated as if it did not exist. This
11825 option should be used with care.
11826 You can make it apply to reverse lookups by a setting such as this:
11828 dns_again_means_nonexist = *.in-addr.arpa
11831 This option applies to all DNS lookups that Exim does. The \%dnslookup%\ router
11832 has some options of its own for controlling what happens when lookups for MX or
11833 SRV records give temporary errors. These more specific options are applied
11834 after the global option.
11837 .index DNS||pre-check of name syntax
11838 .conf dns@_check@_names@_pattern string "see below"
11839 When this option is set to a non-empty string, it causes Exim to check domain
11840 names for illegal characters before handing them to the DNS resolver, because
11841 some resolvers give temporary errors for malformed names. If a domain name
11842 contains any illegal characters, a `not found' result is forced, and the
11843 resolver is not called. The check is done by matching the domain name against a
11844 regular expression, which is the value of this option. The default pattern is
11846 dns_check_names_pattern = \
11847 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9-]*[^\W_])?)+$
11849 which permits only letters, digits, and hyphens in components, but they may not
11850 start or end with a hyphen.
11851 If you set \allow@_utf8@_domains\, you must modify this pattern, or set the
11852 option to an empty string.
11854 .conf dns@_ipv4@_lookup "domain list$**$" unset
11855 .index IPv6||DNS lookup for AAAA records
11856 .index DNS||IPv6 lookup for AAAA records
11857 When Exim is compiled with IPv6 support, it looks for IPv6 address records
11858 (AAAA and, if configured, A6) as well as IPv4 address records when trying to
11859 find IP addresses for hosts, unless the host's domain matches this list.
11861 This is a fudge to help with name servers that give big delays or otherwise do
11862 not work for the new IPv6 record types. If Exim is handed an IPv6 address
11863 record as a result of an MX lookup, it always recognizes it, and may as a
11864 result make an outgoing IPv6 connection. All this option does is to make Exim
11865 look only for IPv4-style A records when it needs to find an IP address for a
11866 host name. In due course, when the world's name servers have all been upgraded,
11867 there should be no need for this option.
11869 .conf dns@_retrans time 0s
11870 .index DNS||resolver options
11871 The options \dns@_retrans\ and \dns@_retry\ can be used to set the
11872 retransmission and retry parameters for DNS lookups. Values of zero (the
11873 defaults) leave the system default settings unchanged. The first value is the
11874 time between retries, and the second is the number of retries. It isn't
11875 totally clear exactly how these settings affect the total time a DNS lookup may
11876 take. I haven't found any documentation about timeouts on DNS lookups; these
11877 parameter values are available in the external resolver interface structure,
11878 but nowhere does it seem to describe how they are used or what you might want
11881 .conf dns@_retry integer 0
11882 See \dns@_retrans\ above.
11884 .conf drop@_cr boolean false
11885 This is an obsolete option that is now a no-op. It used to affect the way Exim
11886 handled CR and LF characters in incoming messages. What happens now is
11887 described in section ~~SECTlineendings.
11889 .conf envelope@_to@_remove boolean true
11890 .index ::Envelope-to:: header line
11891 Exim's transports have an option for adding an ::Envelope-to:: header to a
11892 message when it is delivered -- in exactly the same way as ::Return-path:: is
11893 handled. ::Envelope-to:: records the original recipient address from the
11894 messages's envelope that caused the delivery to happen. Such headers should not
11895 be present in incoming messages, and this option causes them to be removed at
11896 the time the message is received, to avoid any problems that might occur when a
11897 delivered message is subsequently sent on to some other recipient.
11899 .conf errors@_copy "string list$**$" unset
11900 .index bounce message||copy to other address
11901 .index copy of bounce message
11902 Setting this option causes Exim to send bcc copies of bounce messages that it
11903 generates to other addresses. \**Note**\: this does not apply to bounce messages
11904 coming from elsewhere. The value of the option is a colon-separated list of
11905 items. Each item consists of a pattern, terminated by white space, followed by
11906 a comma-separated list of email addresses. If a pattern contains spaces, it
11907 must be enclosed in double quotes.
11909 Each pattern is processed in the same way as a single item in an address list
11910 (see section ~~SECTaddresslist). When a pattern matches the recipient of the
11911 bounce message, the message is copied to the addresses on the list. The items
11912 are scanned in order, and once a matching one is found, no further items are
11913 examined. For example:
11915 errors_copy = spqr@mydomain postmaster@mydomain.example :\
11916 rqps@mydomain hostmaster@mydomain.example,\
11917 postmaster@mydomain.example
11919 The address list is expanded before use. The expansion variables
11920 \$local@_part$\ and \$domain$\ are set from the original recipient of the error
11921 message, and if there was any wildcard matching in the pattern, the expansion
11922 .index numerical variables (\$1$\, \$2$\, etc)||in \errors@_copy\
11923 variables \$0$\, \$1$\, etc. are set in the normal way.
11925 .conf errors@_reply@_to string unset
11926 .index bounce message||::Reply-to:: in
11927 Exim's bounce and delivery warning messages contain the header line
11929 From: Mail Delivery System @<Mailer-Daemon@@<<qualify-domain>>@>
11931 where <<qualify-domain>> is the value of the \qualify@_domain\ option.
11932 Experience shows that people reply to bounce messages. If the
11933 \errors@_reply@_to\ option is set, a ::Reply-To:: header is added to bounce and
11934 warning messages. For example:
11936 errors_reply_to = postmaster@my.domain.example
11938 The value of the option is not expanded. It must specify a valid RFC 2822
11941 .conf exim@_group string "compile-time configured"
11942 .index gid (group id)||Exim's own
11944 This option changes the gid under which Exim runs when it gives up root
11945 privilege. The default value is compiled into the binary. The value of this
11946 option is used only when \exim@_user\ is also set. Unless it consists entirely
11947 of digits, the string is looked up using \*getgrnam()*\, and failure causes a
11948 configuration error. See chapter ~~CHAPsecurity for a discussion of security
11951 .conf exim@_path string "see below"
11952 .index Exim binary, path name
11953 This option specifies the path name of the Exim binary, which is used when Exim
11954 needs to re-exec itself. The default is set up to point to the file \*exim*\ in
11955 the directory configured at compile time by the \\BIN@_DIRECTORY\\ setting. It
11956 is necessary to change \exim@_path\ if, exceptionally, Exim is run from some
11958 \**Warning**\: Do not use a macro to define the value of this option, because
11959 you will break those Exim utilities that scan the configuration file to find
11960 where the binary is. (They then use the \-bP-\ option to extract option
11961 settings such as the value of \spool@_directory\.)
11963 .conf exim@_user string "compile-time configured"
11964 .index uid (user id)||Exim's own
11966 This option changes the uid under which Exim runs when it gives up root
11967 privilege. The default value is compiled into the binary. Ownership of the run
11968 time configuration file and the use of the \-C-\ and \-D-\ command line options
11969 is checked against the values in the binary, not what is set here.
11971 Unless it consists entirely of digits, the string is looked up using
11972 \*getpwnam()*\, and failure causes a configuration error. If \exim@_group\ is
11973 not also supplied, the gid is taken from the result of \*getpwnam()*\ if it is
11974 used. See chapter ~~CHAPsecurity for a discussion of security issues.
11976 .conf extra@_local@_interfaces "string list" unset
11978 This option defines network interfaces that are to be considered local when
11979 routing, but which are not used for listening by the daemon. See section
11980 ~~SECTreclocipadd for details.
11982 .conf extract@_addresses@_remove@_arguments boolean true
11983 .index \-t-\ option
11984 .index command line||addresses with \-t-\
11985 .index Sendmail compatibility||\-t-\ option
11986 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
11987 are present on the command line when the \-t-\ option is used to build an
11988 envelope from a message's ::To::, ::Cc:: and ::Bcc:: headers, the command line
11989 addresses are removed from the recipients list. This is also how Smail behaves.
11990 However, other Sendmail documentation (the O'Reilly book) states that command
11991 line addresses are added to those obtained from the header lines. When
11992 \extract__addresses__remove__arguments\ is true (the default), Exim subtracts
11993 argument headers. If it is set false, Exim adds rather than removes argument
11996 .conf finduser@_retries integer 0
11997 .index NIS, looking up users, retrying
11998 On systems running NIS or other schemes in which user and group information is
11999 distributed from a remote system, there can be times when \*getpwnam()*\ and
12000 related functions fail, even when given valid data, because things time out.
12001 Unfortunately these failures cannot be distinguished from genuine `not found'
12002 errors. If \finduser@_retries\ is set greater than zero, Exim will try that
12003 many extra times to find a user or a group, waiting for one second between
12006 .index \(/etc/passwd)\, multiple reading of
12008 You should not set this option greater than zero if your user information is in
12009 a traditional \(/etc/passwd)\ file, because it will cause Exim needlessly to
12010 search the file multiple times for non-existent users, and also cause delay.
12013 .conf freeze@_tell "string list, comma separated" unset
12014 .index freezing messages||sending a message when freezing
12015 On encountering certain errors, or when configured to do so in a system filter,
12017 Exim freezes a message. This means that no further delivery attempts take place
12018 until an administrator (or the \auto@_thaw\ feature) thaws the message. If
12019 \freeze@_tell\ is set, Exim generates a warning message whenever it freezes
12020 something, unless the message it is freezing is a
12022 bounce message. (Without this exception there is the possibility of looping.)
12023 The warning message is sent to the addresses supplied as the comma-separated
12024 value of this option. If several of the message's addresses cause freezing,
12025 only a single message is sent.
12026 If the freezing was automatic, the reason(s) for freezing can be found in the
12027 message log. If you configure freezing in a filter or ACL, you must arrange for
12028 any logging that you require.
12030 .conf gecos@_name string$**$ unset
12032 .index `gecos' field, parsing
12033 Some operating systems, notably HP-UX, use the `gecos' field in the system
12034 password file to hold other information in addition to users' real names. Exim
12035 looks up this field for use when it is creating ::Sender:: or ::From:: headers.
12036 If either \gecos@_pattern\ or \gecos@_name\ are unset, the contents of the
12037 field are used unchanged, except that, if an ampersand is encountered, it is
12038 replaced by the user's login name with the first character forced to
12039 upper case, since this is a convention that is observed on many systems.
12041 When these options are set, \gecos@_pattern\ is treated as a regular expression
12042 that is to be applied to the field (again with & replaced by the login name),
12043 and if it matches, \gecos@_name\ is expanded and used as the user's name.
12044 .index numerical variables (\$1$\, \$2$\, etc)||in \gecos@_name\
12045 Numeric variables such as \$1$\, \$2$\, etc. can be used in the expansion to
12046 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
12047 name terminates at the first comma, the following can be used:
12049 gecos_pattern = ([^,]*)
12053 .conf gecos@_pattern string unset
12054 See \gecos@_name\ above.
12056 .conf headers@_charset string "see below"
12057 This option sets a default character set for translating from encoded MIME
12058 `words' in header lines, when referenced by an \$h@_xxx$\ expansion item. The
12059 default is the value of \\HEADERS@_CHARSET\\ in \(Local/Makefile)\. The
12060 ultimate default is ISO-8859-1. For more details see the description of header
12061 insertions in section ~~SECTexpansionitems.
12064 .conf header@_maxsize integer "see below"
12065 .index header section||maximum size of
12066 .index limit||size of message header section
12067 This option controls the overall maximum size of a message's header
12068 section. The default is the value of \\HEADER@_MAXSIZE\\ in
12069 \(Local/Makefile)\; the default for that is 1M. Messages with larger header
12070 sections are rejected.
12072 .conf header@_line@_maxsize integer 0
12073 .index header lines||maximum size of
12074 .index limit||size of one header line
12075 This option limits the length of any individual header line in a message, after
12076 all the continuations have been joined together. Messages with individual
12077 header lines that are longer than the limit are rejected. The default value of
12078 zero means `no limit'.
12082 .conf helo@_accept@_junk@_hosts "host list$**$" unset
12083 .index \\HELO\\||accepting junk data
12084 .index \\EHLO\\||accepting junk data
12085 Exim checks the syntax of \\HELO\\ and \\EHLO\\ commands for incoming SMTP
12086 mail, and gives an error response for invalid data. Unfortunately, there are
12087 some SMTP clients that send syntactic junk. They can be accommodated by setting
12088 this option. Note that this is a syntax check only. See \helo@_verify@_hosts\
12089 if you want to do semantic checking.
12090 See also \helo@_allow@_chars\ for a way of extending the permitted character
12093 .conf helo@_allow@_chars string unset
12094 .index \\HELO\\||underscores in
12095 .index \\EHLO\\||underscores in
12096 .index underscore in \\EHLO\\/\\HELO\\
12097 This option can be set to a string of rogue characters that are permitted in
12098 all \\EHLO\\ and \\HELO\\ names in addition to the standard letters, digits,
12099 hyphens, and dots. If you really must allow underscores, you can set
12101 helo_allow_chars = _
12103 Note that the value is one string, not a list.
12105 .conf helo@_lookup@_domains "domain list$**$" "$tt{@@:@@[]}"
12106 .index \\HELO\\||forcing reverse lookup
12107 .index \\EHLO\\||forcing reverse lookup
12108 If the domain given by a client in a \\HELO\\ or \\EHLO\\ command matches this
12109 list, a reverse lookup is done in order to establish the host's true name. The
12110 default forces a lookup if the client host gives the server's name or any of
12111 its IP addresses (in brackets), something that broken clients have been seen to
12114 .conf helo@_try@_verify@_hosts "host list$**$" unset
12115 .index \\HELO\\||verifying, optional
12116 .index \\EHLO\\||verifying, optional
12117 The RFCs mandate that a server must not reject a message because it doesn't
12118 like the \\HELO\\ or \\EHLO\\ command. By default, Exim just checks the syntax
12119 of these commands (see \helo__accept__junk__hosts\ and \helo@_allow@_chars\
12120 above). However, some sites like to be stricter. If the calling host matches
12121 \helo@_try@_verify@_hosts\, Exim checks that the host name given in the \\HELO\\
12122 or \\EHLO\\ command either:
12124 is an IP literal matching the calling address of the host (the RFCs
12125 specifically allow this), or
12127 .index DNS||reverse lookup
12128 .index reverse DNS lookup
12129 matches the host name that Exim obtains by doing a reverse lookup of the
12130 calling host address, or
12132 when looked up using \*gethostbyname()*\ (or \*getipnodebyname()*\ when
12133 available) yields the calling host address.
12135 However, the \\EHLO\\ or \\HELO\\ command is not rejected if any of the checks
12136 fail. Processing continues, but the result of the check is remembered, and can
12137 be detected later in an ACL by the \"verify = helo"\ condition. If you want
12138 verification failure to cause rejection of \\EHLO\\ or \\HELO\\, use
12139 \helo@_verify@_hosts\ instead.
12142 .conf helo@_verify@_hosts "host list$**$" unset
12143 .index \\HELO\\||verifying, mandatory
12144 .index \\EHLO\\||verifying, mandatory
12145 For hosts that match this option, Exim checks the host name given in the
12146 \\HELO\\ or \\EHLO\\ in the same way as for \helo@_try@_verify@_hosts\. If the
12147 check fails, the \\HELO\\ or \\EHLO\\ command is rejected with a 550 error, and
12148 entries are written to the main and reject logs. If a \\MAIL\\ command is
12149 received before \\EHLO\\ or \\HELO\\, it is rejected with a
12153 .conf hold@_domains "domain list$**$" unset
12154 .index domain||delaying delivery
12155 .index delivery||delaying certain domains
12156 This option allows mail for particular domains to be held on the queue
12157 manually. The option is overridden if a message delivery is forced with the
12158 \-M-\, \-qf-\, \-Rf-\ or \-Sf-\ options, and also while testing or verifying
12159 addresses using \-bt-\ or \-bv-\. Otherwise, if a domain matches an item in
12160 \hold@_domains\, no routing or delivery for that address is done, and it is
12161 deferred every time the message is looked at.
12163 This option is intended as a temporary operational measure for delaying the
12164 delivery of mail while some problem is being sorted out, or some new
12165 configuration tested. If you just want to delay the processing of some
12166 domains until a queue run occurs, you should use \queue@_domains\ or
12167 \queue@_smtp@_domains\, not \hold@_domains\.
12169 A setting of \hold@_domains\ does not override Exim's code for removing
12170 messages from the queue if they have been there longer than the longest retry
12171 time in any retry rule. If you want to hold messages for longer than the normal
12172 retry times, insert a dummy retry rule with a long retry time.
12174 .conf host@_lookup "host list$**$" unset
12175 .index host||name lookup, forcing
12176 Exim does not look up the name of a calling host from its IP address unless it
12177 is required to compare against some host list, or the host matches
12178 \helo@_try@_verify@_hosts\ or \helo@_verify@_hosts\, or the host matches this
12179 option (which normally contains IP addresses rather than host names). The
12180 default configuration file contains
12184 which causes a lookup to happen for all hosts. If the expense of these lookups
12185 is felt to be too great, the setting can be changed or removed.
12187 After a successful reverse lookup, Exim does a forward lookup on the name it
12188 has obtained, to verify that it yields the IP address that it started with. If
12189 this check fails, Exim behaves as if the name lookup failed.
12191 After any kind of failure, the host name (in \$sender@_host@_name$\) remains
12192 unset, and \$host@_lookup@_failed$\ is set to the string `1'. See also
12193 \dns@_again@_means@_nonexist\, \helo__lookup__domains\, and \"verify =
12194 reverse@_host@_lookup"\ in ACLs.
12196 .conf host@_lookup@_order "string list" $tt{bydns:byaddr}
12197 This option specifies the order of different lookup methods when Exim is trying
12198 to find a host name from an IP address. The default is to do a DNS lookup
12199 first, and then to try a local lookup (using \*gethostbyaddr()*\ or equivalent)
12200 if that fails. You can change the order of these lookups, or omit one entirely,
12203 \**Warning**\: the `byaddr' method does not always yield aliases when there are
12204 multiple PTR records in the DNS and the IP address is not listed in
12205 \(/etc/hosts)\. Different operating systems give different results in this
12206 case. That is why the default tries a DNS lookup first.
12209 .conf host@_reject@_connection "host list$**$" unset
12210 .index host||rejecting connections from
12211 If this option is set, incoming SMTP calls from the hosts listed are rejected
12212 as soon as the connection is made.
12213 This option is obsolete, and retained only for backward compatibility, because
12214 nowadays the ACL specified by \acl@_smtp@_connect\ can also reject incoming
12215 connections immediately.
12217 The ability to give an immediate rejection (either by this option or using an
12218 ACL) is provided for use in unusual cases. Many hosts will just try again,
12219 sometimes without much delay. Normally, it is better to use an ACL to reject
12220 incoming messages at a later stage, such as after \\RCPT\\ commands. See
12224 .conf hosts@_connection@_nolog "host list$**$" unset
12225 .index host||not logging connections from
12226 This option defines a list of hosts for which connection logging does not
12227 happen, even though the \smtp@_connection\ log selector is set. For example,
12228 you might want not to log SMTP connections from local processes, or from
12229 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
12230 the daemon; you should therefore strive to restrict its value to a short inline
12231 list of IP addresses and networks. To disable logging SMTP connections from
12232 local processes, you must create a host list with an empty item. For example:
12234 hosts_connection_nolog = :
12236 If the \smtp@_connection\ log selector is not set, this option has no effect.
12239 .conf hosts@_treat@_as@_local "domain list$**$" unset
12240 .index local host||domains treated as
12241 .index host||treated as local
12242 If this option is set, any host names that match the domain list are treated as
12243 if they were the local host when Exim is scanning host lists obtained from MX
12245 or other sources. Note that the value of this option is a domain list, not a
12246 host list, because it is always used to check host names, not IP addresses.
12248 This option also applies when Exim is matching the special items
12249 \"@@mx@_any"\, \"@@mx@_primary"\, and \"@@mx@_secondary"\ in a domain list (see
12250 section ~~SECTdomainlist), and when checking the \hosts\ option in the \%smtp%\
12251 transport for the local host (see the \allow@_localhost\ option in that
12253 See also \local@_interfaces\, \extra@_local@_interfaces\, and chapter
12254 ~~CHAPinterfaces, which contains a discussion about local network interfaces
12255 and recognising the local host.
12257 .conf ignore@_bounce@_errors@_after time 10w
12258 .index bounce message||discarding
12259 .index discarding bounce message
12260 This option affects the processing of bounce messages that cannot be delivered,
12261 that is, those that suffer a permanent delivery failure. (Bounce messages that
12262 suffer temporary delivery failures are of course retried in the usual way.)
12264 After a permanent delivery failure, bounce messages are frozen,
12265 because there is no sender to whom they can be returned. When a frozen bounce
12266 message has been on the queue for more than the given time, it is unfrozen at
12267 the next queue run, and a further delivery is attempted. If delivery fails
12268 again, the bounce message is discarded. This makes it possible to keep failed
12269 bounce messages around for a shorter time than the normal maximum retry time
12270 for frozen messages. For example,
12272 ignore_bounce_errors_after = 12h
12274 retries failed bounce message deliveries after 12 hours, discarding any further
12275 failures. If the value of this option is set to a zero time period, bounce
12276 failures are discarded immediately. Setting a very long time (as in the default
12277 value) has the effect of disabling this option. For ways of automatically
12278 dealing with other kinds of frozen message, see \auto@_thaw\ and
12279 \timeout@_frozen@_after\.
12281 .conf ignore@_fromline@_hosts "host list$**$" unset
12283 .index UUCP||`From' line
12284 Some broken SMTP clients insist on sending a UUCP-like `From' line before the
12285 headers of a message. By default this is treated as the start of the message's
12286 body, which means that any following headers are not recognized as such. Exim
12287 can be made to ignore it by setting \ignore@_fromline@_hosts\ to match those
12288 hosts that insist on sending it. If the sender is actually a local process
12289 rather than a remote host, and is using \-bs-\ to inject the messages,
12290 \ignore__fromline__local\ must be set to achieve this effect.
12292 .conf ignore@_fromline@_local boolean false
12293 See \ignore@_fromline@_hosts\ above.
12295 .conf keep@_malformed time 4d
12296 This option specifies the length of time to keep messages whose spool files
12297 have been corrupted in some way. This should, of course, never happen. At the
12298 next attempt to deliver such a message, it gets removed. The incident is
12301 .conf ldap@_default@_servers "string list" unset
12302 .index LDAP||default servers
12303 This option provides a list of LDAP servers which are tried in turn when an
12304 LDAP query does not contain a server. See section ~~SECTforldaque for details
12305 of LDAP queries. This option is available only when Exim has been built with
12308 .conf ldap@_version integer unset
12309 .index LDAP||protocol version, forcing
12310 This option can be used to force Exim to set a specific protocol version for
12311 LDAP. If it option is unset, it is shown by the \-bP-\ command line option as
12312 -1. When this is the case, the default is 3 if \\LDAP@_VERSION3\\ is defined in
12313 the LDAP headers; otherwise it is 2. This option is available only when Exim
12314 has been built with LDAP support.
12317 .conf local@_from@_check boolean true
12318 .index ::Sender:: header line||disabling addition of
12319 .index ::From:: header line||disabling checking of
12320 When a message is submitted locally (that is, not over a TCP/IP connection) by
12321 an untrusted user, Exim removes any existing ::Sender:: header line, and checks
12322 that the ::From:: header line matches
12324 the login of the calling user and the domain specified by \qualify@_domain\.
12326 \**Note**\: An unqualified address (no domain) in the ::From:: header in a
12327 locally submitted message is automatically qualified by Exim, unless the
12328 \-bnq-\ command line option is used.
12331 You can use \local@_from@_prefix\ and \local@_from@_suffix\ to permit affixes
12332 on the local part. If the ::From:: header line does not match, Exim adds a
12333 ::Sender:: header with an address constructed from the calling user's login and
12334 the default qualify domain.
12336 If \local@_from@_check\ is set false, the ::From:: header check is disabled,
12337 and no ::Sender:: header is ever added. If, in addition, you want to retain
12338 ::Sender:: header lines supplied by untrusted users, you must also set
12339 \local@_sender@_retain\ to be true.
12341 .index envelope sender
12342 These options affect only the header lines in the message. The envelope sender
12343 is still forced to be the login id at the qualify domain unless
12344 \untrusted@_set@_sender\ permits the user to supply an envelope sender.
12347 For messages received over TCP/IP, an ACL can specify `submission mode' to
12348 request similar header line checking. See section ~~SECTthesenhea, which has
12349 more details about ::Sender:: processing.
12353 .conf local@_from@_prefix string unset
12354 When Exim checks the ::From:: header line of locally submitted messages for
12355 matching the login id (see \local@_from@_check\ above), it can be configured to
12356 ignore certain prefixes and suffixes in the local part of the address. This is
12357 done by setting \local@_from@_prefix\ and/or \local@_from@_suffix\ to
12358 appropriate lists, in the same form as the \local@_part@_prefix\ and
12359 \local@_part@_suffix\ router options (see chapter ~~CHAProutergeneric). For
12362 local_from_prefix = *-
12364 is set, a ::From:: line containing
12366 From: anything-user@your.domain.example
12368 will not cause a ::Sender:: header to be added if \*user@@your.domain.example*\
12369 matches the actual sender address that is constructed from the login name and
12372 .conf local@_from@_suffix string unset
12373 See \local@_from@_prefix\ above.
12375 .conf local@_interfaces "string list" "see below"
12376 This option controls which network interfaces are used by the daemon for
12377 listening; they are also used to identify the local host when routing. Chapter
12378 ~~CHAPinterfaces contains a full description of this option and the related
12381 \daemon@_smtp@_ports\, \extra@_local@_interfaces\, \hosts@_treat@_as@_local\,
12382 and \tls@_on@_connect@_ports\.
12384 The default value for \local@_interfaces\ is
12386 local_interfaces = 0.0.0.0
12388 when Exim is built without IPv6 support; otherwise it is
12390 local_interfaces = <; ::0 ; 0.0.0.0
12393 .conf local@_scan@_timeout time 5m
12394 .index timeout||for \*local@_scan()*\ function
12395 .index \*local@_scan()*\ function||timeout
12396 This timeout applies to the \*local@_scan()*\ function (see chapter
12397 ~~CHAPlocalscan). Zero means `no timeout'. If the timeout is exceeded, the
12398 incoming message is rejected with a temporary error if it is an SMTP message.
12399 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
12400 code. The incident is logged on the main and reject logs.
12403 .conf local@_sender@_retain boolean false
12404 .index ::Sender:: header line||retaining from local submission
12405 When a message is submitted locally (that is, not over a TCP/IP connection) by
12406 an untrusted user, Exim removes any existing ::Sender:: header line. If you
12407 do not want this to happen, you must set \local@_sender@_retain\, and you must
12408 also set \local@_from@_check\ to be false (Exim will complain if you do not).
12409 Section ~~SECTthesenhea has more details about ::Sender:: processing.
12413 .conf localhost@_number string$**$ unset
12414 .index host||locally unique number for
12415 .index message||ids, with multiple hosts
12416 Exim's message ids are normally unique only within the local host. If
12417 uniqueness among a set of hosts is required, each host must set a different
12418 value for the \localhost@_number\ option. The string is expanded immediately
12419 after reading the configuration file (so that a number can be computed from the
12420 host name, for example) and the result of the expansion must be a number in the
12421 range 0--16 (or 0--10 on operating systems with case-insensitive file systems).
12422 This is available in subsequent string expansions via the variable
12423 \$localhost@_number$\. When \localhost@_number is set\, the final two
12424 characters of the message id, instead of just being a fractional part of the
12425 time, are computed from the time and the local host number as described in
12426 section ~~SECTmessiden.
12429 .conf log@_file@_path "string list$**$" "set at compile time"
12430 .index log||file path for
12431 This option sets the path which is used to determine the names of Exim's log
12432 files, or indicates that logging is to be to syslog, or both. It is expanded
12433 when Exim is entered, so it can, for example, contain a reference to the host
12434 name. If no specific path is set for the log files at compile or run time, they
12435 are written in a sub-directory called \(log)\ in Exim's spool directory.
12436 Chapter ~~CHAPlog contains further details about Exim's logging, and section
12437 ~~SECTwhelogwri describes how the contents of \log@_file@_path\ are used. If
12438 this string is fixed at your installation (contains no expansion variables) it
12439 is recommended that you do not set this option in the configuration file, but
12440 instead supply the path using \\LOG@_FILE@_PATH\\ in \(Local/Makefile)\ so that
12441 it is available to Exim for logging errors detected early on -- in particular,
12442 failure to read the configuration file.
12444 .conf log@_selector string unset
12445 .index log||selectors
12446 This option can be used to reduce or increase the number of things that Exim
12447 writes to its log files. Its argument is made up of names preceded by plus or
12448 minus characters. For example:
12450 log_selector = +arguments -retry_defer
12452 A list of possible names and what they control is given in the chapter on
12453 logging, in section ~~SECTlogselector.
12455 .conf log@_timezone boolean false
12456 .index log||timezone for entries
12457 By default, the timestamps on log lines are in local time without the
12458 timezone. This means that if your timezone changes twice a year, the timestamps
12459 in log lines are ambiguous for an hour when the clocks go back. One way of
12460 avoiding this problem is to set the timezone to UTC. An alternative is to set
12461 \log@_timezone\ true. This turns on the addition of the timezone offset to
12462 timestamps in log lines. Turning on this option can add quite a lot to the size
12463 of log files because each line is extended by 6 characters. Note that the
12464 \$tod@_log$\ variable contains the log timestamp without the zone, but there is
12465 another variable called \$tod@_zone$\ that contains just the timezone offset.
12467 .conf lookup@_open@_max integer 25
12468 .index too many open files
12469 .index open files, too many
12470 .index file||too many open
12471 .index lookup||maximum open files
12472 .index limit||open files for lookups
12473 This option limits the number of simultaneously open files for single-key
12474 lookups that use regular files (that is, \%lsearch%\, \%dbm%\, and \%cdb%\). Exim
12475 normally keeps these files open during routing, because often the same file is
12476 required several times. If the limit is reached, Exim closes the least recently
12477 used file. Note that if you are using the \*ndbm*\ library, it actually opens
12478 two files for each logical DBM database, though it still counts as one for the
12479 purposes of \lookup@_open@_max\. If you are getting `too many open files'
12480 errors with NDBM, you need to reduce the value of \lookup@_open@_max\.
12482 .conf max@_username@_length integer 0
12483 .index length of login name
12484 .index user name||maximum length
12485 .index limit||user name length
12486 Some operating systems are broken in that they truncate long arguments to
12487 \*getpwnam()*\ to eight characters, instead of returning `no such user'. If
12488 this option is set greater than zero, any attempt to call \*getpwnam()*\ with
12489 an argument that is longer behaves as if \*getpwnam()*\ failed.
12492 .conf message@_body@_visible integer 500
12493 .index body of message||visible size
12494 .index message||body, visible size
12495 This option specifies how much of a message's body is to be included in the
12496 \$message@_body$\ and \$message@_body@_end$\ expansion variables.
12498 .conf message@_id@_header@_domain string$**$ unset
12499 .index ::Message-ID:: header line
12500 If this option is set, the string is expanded and used as the right hand side
12501 (domain) of the ::Message-ID:: header that Exim creates if a
12502 locally-originated incoming message does not have one. `Locally-originated'
12503 means `not received over TCP/IP.'
12504 Otherwise, the primary host name is used.
12505 Only letters, digits, dot and hyphen are accepted; any other characters are
12506 replaced by hyphens. If the expansion is forced to fail, or if the result is an
12507 empty string, the option is ignored.
12509 .conf message@_id@_header@_text string$**$ unset
12510 If this variable is set, the string is expanded and used to augment the text of
12511 the ::Message-id:: header that Exim creates if a
12513 incoming message does not have one. The text of this header is required by RFC
12514 2822 to take the form of an address. By default, Exim uses its internal message
12515 id as the local part, and the primary host name as the domain. If this option
12516 is set, it is expanded, and provided the expansion is not forced to fail, and
12517 does not yield an empty string, the result is inserted into the header
12518 immediately before the @@, separated from the internal message id by a dot. Any
12519 characters that are illegal in an address are automatically converted into
12520 hyphens. This means that variables such as \$tod@_log$\ can be used, because
12521 the spaces and colons will become hyphens.
12523 .conf message@_logs boolean true
12524 .index message||log, disabling
12525 .index log||message log, disabling
12526 If this option is turned off, per-message log files are not created in the
12527 \(msglog)\ spool sub-directory. This reduces the amount of disk I/O required by
12528 Exim, by reducing the number of files involved in handling a message from a
12529 minimum of four (header spool file, body spool file, delivery journal, and
12530 per-message log) to three. The other major I/O activity is Exim's main log,
12531 which is not affected by this option.
12533 .conf message@_size@_limit string$**$ 50M
12534 .index message||size limit
12535 .index limit||message size
12536 .index size||of message, limit
12537 This option limits the maximum size of message that Exim will process. The
12538 value is expanded for each incoming
12539 connection so, for example, it can be made to depend on the IP address of the
12540 remote host for messages arriving via TCP/IP. \**Note**\: This limit cannot be
12541 made to depend on a message's sender or any other properties of an individual
12542 message, because it has to be advertised in the server's response to \\EHLO\\.
12543 String expansion failure causes a temporary error. A value of zero means no
12544 limit, but its use is not recommended. See also \bounce@_return@_size@_limit\.
12546 Incoming SMTP messages are failed with a 552 error if the limit is
12547 exceeded; locally-generated messages either get a stderr message or a delivery
12548 failure message to the sender, depending on the \-oe-\ setting. Rejection of an
12549 oversized message is logged in both the main and the reject logs. See also the
12550 generic transport option \message@_size@_limit\, which limits the size of
12551 message that an individual transport can process.
12553 .conf move@_frozen@_messages boolean false
12554 .index frozen messages||moving
12555 This option, which is available only if Exim has been built with the setting
12557 SUPPORT_MOVE_FROZEN_MESSAGES=yes
12559 in \(Local/Makefile)\, causes frozen messages and their message logs to be
12560 moved from the \(input)\ and \(msglog)\ directories on the spool to \(Finput)\
12561 and \(Fmsglog)\, respectively. There is currently no support in Exim or the
12562 standard utilities for handling such moved messages, and they do not show up in
12563 lists generated by \-bp-\ or by the Exim monitor.
12566 .conf mua@_wrapper boolean false
12567 Setting this option true causes Exim to run in a very restrictive mode in which
12568 it passes messages synchronously to a smart host. Chapter ~~CHAPnonqueueing
12569 contains a full description of this facility.
12572 .conf mysql@_servers "string list" unset
12573 .index MySQL||server list
12574 This option provides a list of MySQL servers and associated connection data, to
12575 be used in conjunction with \%mysql%\ lookups (see section ~~SECTsql). The
12576 option is available only if Exim has been built with MySQL support.
12578 .conf never@_users "string list" unset
12579 Local message deliveries are normally run in processes that are setuid to the
12580 recipient, and remote deliveries are normally run under Exim's own uid and gid.
12581 It is usually desirable to prevent any deliveries from running as root, as a
12584 When Exim is built, an option called \\FIXED@_NEVER@_USERS\\ can be set to a
12585 list of users that must not be used for local deliveries. This list is fixed in
12586 the binary and cannot be overridden by the configuration file. By default, it
12587 contains just the single user name `root'. The \never@_users\ runtime option
12588 can be used to add more users to the fixed list.
12590 If a message is to be delivered as one of the users on the fixed list or the
12591 \never@_users\ list, an error occurs, and delivery is deferred. A common
12594 never@_users = root:daemon:bin
12596 Including root is redundant if it is also on the fixed list, but it does no
12598 This option overrides the \pipe@_as@_creator\ option of the \%pipe%\ transport
12601 .conf oracle@_servers "string list" unset
12602 .index Oracle||server list
12603 This option provides a list of Oracle servers and associated connection data,
12604 to be used in conjunction with \%oracle%\ lookups (see section ~~SECTsql). The
12605 option is available only if Exim has been built with Oracle support.
12607 .conf percent@_hack@_domains "domain list$**$" unset
12608 .index `percent hack'
12609 .index source routing||in email address
12610 .index address||source-routed
12611 The `percent hack' is the convention whereby a local part containing a percent
12612 sign is re-interpreted as a new email address, with the percent replaced by @@.
12613 This is sometimes called `source routing', though that term is also applied to
12614 RFC 2822 addresses that begin with an @@ character. If this option is set, Exim
12615 implements the percent facility for those domains listed, but no others. This
12616 happens before an incoming SMTP address is tested against an ACL.
12618 \**Warning**\: The `percent hack' has often been abused by people who are
12619 trying to get round relaying restrictions. For this reason, it is best avoided
12620 if at all possible. Unfortunately, a number of less security-conscious MTAs
12621 implement it unconditionally. If you are running Exim on a gateway host, and
12622 routing mail through to internal MTAs without processing the local parts, it is
12623 a good idea to reject recipient addresses with percent characters in their
12624 local parts. Exim's default configuration does this.
12626 .conf perl@_at@_start boolean false
12627 This option is available only when Exim is built with an embedded Perl
12628 interpreter. See chapter ~~CHAPperl for details of its use.
12630 .conf perl@_startup string unset
12631 This option is available only when Exim is built with an embedded Perl
12632 interpreter. See chapter ~~CHAPperl for details of its use.
12634 .conf pgsql@_servers "string list" unset
12635 .index PostgreSQL lookup type||server list
12636 This option provides a list of PostgreSQL servers and associated connection
12637 data, to be used in conjunction with \%pgsql%\ lookups (see section ~~SECTsql).
12638 The option is available only if Exim has been built with PostgreSQL support.
12640 .conf pid@_file@_path string$**$ "set at compile time"
12641 .index daemon||pid file path
12642 .index pid file, path for
12643 This option sets the name of the file to which the Exim daemon writes its
12644 process id. The string is expanded, so it can contain, for example, references
12647 pid_file_path = /var/log/$primary_hostname/exim.pid
12649 If no path is set, the pid is written to the file \(exim-daemon.pid)\ in Exim's
12651 The value set by the option can be overridden by the \-oP-\ command line
12652 option. A pid file is not written if a `non-standard' daemon is run by means of
12653 the \-oX-\ option, unless a path is explicitly supplied by \-oP-\.
12655 .conf pipelining@_advertise@_hosts "host list$**$" $*$
12656 .index \\PIPELINING\\||advertising, suppressing
12657 This option can be used to suppress the advertisement of the SMTP
12658 \\PIPELINING\\ extension to specific hosts. When \\PIPELINING\\ is not
12659 advertised and \smtp@_enforce@_sync\ is true, an Exim server enforces strict
12660 synchronization for each SMTP command and response.
12661 When \\PIPELINING\\ is advertised, Exim assumes that clients will use it; `out
12662 of order' commands that are `expected' do not count as protocol errors (see
12663 \smtp@_max@_synprot@_errors\).
12665 .conf preserve@_message@_logs boolean false
12666 .index message logs, preserving
12667 If this option is set, message log files are not deleted when messages are
12668 completed. Instead, they are moved to a sub-directory of the spool directory
12669 called \(msglog.OLD)\, where they remain available for statistical or debugging
12670 purposes. This is a dangerous option to set on systems with any appreciable
12671 volume of mail. Use with care!
12673 .conf primary@_hostname string "see below"
12674 .index name||of local host
12675 .index host||name of local
12676 .index local host||name of
12677 This specifies the name of the current host. It is used in the default \\EHLO\\
12678 or \\HELO\\ command for outgoing SMTP messages (changeable via the \helo@_data\
12679 option in the \%smtp%\ transport),
12680 and as the default for \qualify@_domain\. If it is not set, Exim calls
12681 \*uname()*\ to find it. If this fails, Exim panics and dies. If the name
12682 returned by \*uname()*\ contains only one component, Exim passes it to
12683 \*gethostbyname()*\ (or \*getipnodebyname()*\ when available) in order to
12684 obtain the fully qualified version.
12686 The value of \$primary@_hostname$\ is also used by default in some SMTP
12687 response messages from an Exim server. This can be changed dynamically by
12688 setting \smtp@_active@_hostname\.
12690 .conf print@_topbitchars boolean false
12691 .index printing characters
12692 .index 8-bit characters
12693 By default, Exim considers only those characters whose codes lie in the range
12694 32--126 to be printing characters. In a number of circumstances (for example,
12695 when writing log entries) non-printing characters are converted into escape
12696 sequences, primarily to avoid messing up the layout. If \print@_topbitchars\ is
12697 set, code values of 128 and above are also considered to be printing
12700 .conf process@_log@_path string unset
12701 .index process log path
12702 .index log||process log
12704 This option sets the name of the file to which an Exim process writes its
12705 `process log' when sent a USR1 signal. This is used by the \*exiwhat*\ utility
12706 script. If this option is unset, the file called \(exim-process.info)\ in
12707 Exim's spool directory is used. The ability to specify the name explicitly can
12708 be useful in environments where two different Exims are running, using
12709 different spool directories.
12711 .conf prod@_requires@_admin boolean true
12712 .index \-M-\ option
12713 .index \-R-\ option
12714 .index \-q-\ option
12715 The \-M-\, \-R-\, and \-q-\ command-line options require the caller to be an
12716 admin user unless \prod@_requires@_admin\ is set false. See also
12717 \queue@_list@_requires@_admin\.
12719 .conf qualify@_domain string "see below"
12720 .index domain||for qualifying addresses
12721 .index address||qualification
12722 This option specifies the domain name that is added to any envelope sender
12723 addresses that do not have a domain qualification. It also applies to
12724 recipient addresses if \qualify@_recipient\ is not set.
12726 Unqualified addresses are accepted by default only for locally-generated
12729 Qualification is also applied to addresses in header lines such as ::From:: and
12730 ::To:: for locally-generated messages, unless the \-bnq-\ command line option
12734 Messages from external sources must always contain fully qualified addresses,
12735 unless the sending host matches \sender@_unqualified@_hosts\ or
12736 \recipient@_unqualified@_hosts\ (as appropriate), in which case incoming
12737 addresses are qualified with \qualify@_domain\ or \qualify@_recipient\ as
12738 necessary. Internally, Exim always works with fully qualified envelope
12739 addresses. If \qualify@_domain\ is not set, it defaults to the
12740 \primary@_hostname\ value.
12742 .conf qualify@_recipient string "see below"
12744 This option allows you to specify a different domain for qualifying recipient
12745 addresses to the one that is used for senders. See \qualify@_domain\ above.
12748 .conf queue@_domains "domain list$**$" unset
12749 .index domain||specifying non-immediate delivery
12750 .index queueing incoming messages
12751 .index message||queueing certain domains
12752 This option lists domains for which immediate delivery is not required.
12753 A delivery process is started whenever a message is received, but only those
12754 domains that do not match are processed. All other deliveries wait until the
12755 next queue run. See also \hold@_domains\ and \queue@_smtp@_domains\.
12757 .conf queue@_list@_requires@_admin boolean true
12758 .index \-bp-\ option
12759 The \-bp-\ command-line option, which lists the messages that are on the queue,
12760 requires the caller to be an admin user unless \queue__list__requires__admin\
12761 is set false. See also \prod@_requires@_admin\.
12763 .conf queue@_only boolean false
12764 .index queueing incoming messages
12765 .index message||queueing unconditionally
12766 If \queue@_only\ is set, a delivery process is not automatically started
12767 whenever a message is received. Instead, the message waits on the queue for the
12768 next queue run. Even if \queue@_only\ is false, incoming messages may not get
12769 delivered immediately when certain conditions (such as heavy load) occur.
12771 The \-odq-\ command line has the same effect as \queue@_only\. The \-odb-\ and
12772 \-odi-\ command line options override \queue@_only\ unless
12773 \queue@_only@_override\ is set false. See also \queue@_only@_file\,
12774 \queue@_only@_load\, and \smtp@_accept@_queue\.
12776 .conf queue@_only@_file string unset
12777 .index queueing incoming messages
12778 .index message||queueing by file existence
12779 This option can be set to a colon-separated list of absolute path names, each
12780 one optionally preceded by `smtp'. When Exim is receiving a message,
12781 it tests for the existence of each listed path using a call to \*stat()*\. For
12782 each path that exists, the corresponding queuing option is set.
12783 For paths with no prefix, \queue@_only\ is set; for paths prefixed by `smtp',
12784 \queue@_smtp@_domains\ is set to match all domains. So, for example,
12786 queue_only_file = smtp/some/file
12788 causes Exim to behave as if \queue@_smtp@_domains\ were set to `$*$' whenever
12789 \(/some/file)\ exists.
12791 .conf queue@_only@_load fixed-point unset
12792 .index load average
12793 .index queueing incoming messages
12794 .index message||queueing by load
12795 If the system load average is higher than this value, incoming messages from
12796 all sources are queued, and no automatic deliveries are started. If this
12797 happens during local or remote SMTP input, all subsequent messages on the same
12798 connection are queued. Deliveries will subsequently be performed by queue
12799 runner processes. This option has no effect on ancient operating systems on
12800 which Exim cannot determine the load average. See also
12801 \deliver@_queue@_load@_max\ and \smtp@_load@_reserve\.
12803 .conf queue@_only@_override boolean true
12804 .index queueing incoming messages
12805 When this option is true, the \-od\*x*\-\ command line options override the
12806 setting of \queue@_only\ or \queue@_only@_file\ in the configuration file. If
12807 \queue@_only@_override\ is set false, the \-od\*x*\-\ options cannot be used to
12808 override; they are accepted, but ignored.
12810 .conf queue@_run@_in@_order boolean false
12811 .index queue runner||processing messages in order
12812 If this option is set, queue runs happen in order of message arrival instead of
12813 in an arbitrary order. For this to happen, a complete list of the entire queue
12814 must be set up before the deliveries start. When the queue is all in a single
12815 directory (the default), this happens anyway, but if \split@_spool@_directory\
12816 is set it does not -- for delivery in random order, the sub-directories are
12817 processed one at a time (in random order), to avoid setting up one huge list.
12818 Thus, setting \queue@_run@_in@_order\ with \split@_spool@_directory\ may
12819 degrade performance when the queue is large. In most situations,
12820 \queue@_run@_in@_order\ should not be set.
12822 .conf queue@_run@_max integer 5
12823 .index queue runner||maximum number of
12824 This controls the maximum number of queue runner processes that an Exim daemon
12825 can run simultaneously. This does not mean that it starts them all at once,
12826 but rather that if the maximum number are still running when the time comes to
12827 start another one, it refrains from starting another one. This can happen with
12828 very large queues and/or very sluggish deliveries. This option does not,
12829 however, interlock with other processes, so additional queue runners can be
12830 started by other means, or by killing and restarting the daemon.
12832 .conf queue@_smtp@_domains "domain list$**$" unset
12833 .index queueing incoming messages
12834 .index message||queueing remote deliveries
12835 When this option is set, a delivery process is started whenever a message is
12836 received, routing is performed, and local deliveries take place.
12837 However, if any SMTP deliveries are required for domains that match
12838 \queue@_smtp@_domains\, they are not immediately delivered, but instead the
12839 message waits on the queue for the next queue run. Since routing of the message
12840 has taken place, Exim knows to which remote hosts it must be delivered, and so
12841 when the queue run happens, multiple messages for the same host are delivered
12842 over a single SMTP connection. The \-odqs-\ command line option causes all SMTP
12843 deliveries to be queued in this way, and is equivalent to setting
12844 \queue@_smtp@_domains\ to `$*$'. See also \hold@_domains\ and \queue@_domains\.
12846 .conf receive@_timeout time 0s
12847 .index timeout||for non-SMTP input
12848 This option sets the timeout for accepting a non-SMTP message, that is, the
12849 maximum time that Exim waits when reading a message on the standard input. If
12850 the value is zero, it will wait for ever. This setting is overridden by the
12851 \-or-\ command line option. The timeout for incoming SMTP messages is
12852 controlled by \smtp@_receive@_timeout\.
12854 .index customizing|| ::Received:: header
12855 .index ::Received:: header line||customizing
12856 .conf received@_header@_text string$**$ "see below"
12857 This string defines the contents of the ::Received:: message header that is
12858 added to each message, except for the timestamp, which is automatically added
12859 on at the end (preceded by a semicolon). The string is expanded each time it is
12860 used. If the expansion yields an empty string, no ::Received:: header line is
12861 added to the message. Otherwise, the string should start with the text
12862 `Received:' and conform to the RFC 2822 specification for ::Received:: header
12863 lines. The default setting is:
12865 received_header_text = Received: \
12866 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
12867 {${if def:sender_ident {from $sender_ident }}\
12868 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
12869 by $primary_hostname \
12870 ${if def:received_protocol {with $received_protocol}} \
12871 ${if def:tls_cipher {($tls_cipher)\n\t}}\
12872 (Exim $version_number)\n\t\
12874 ${if def:received_for {\n\tfor $received_for}}
12876 Note the use of quotes, to allow the sequences \"@\n"\ and \"@\t"\ to be used
12877 for newlines and tabs, respectively. The reference to the TLS cipher is omitted
12878 when Exim is built without TLS support. The use of conditional expansions
12879 ensures that this works for both locally generated messages and messages
12880 received from remote hosts, giving header lines such as the following:
12882 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
12883 by marley.carol.example with esmtp (Exim 4.00)
12884 id 16IOWa-00019l-00
12885 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
12886 Received: by scrooge.carol.example with local (Exim 4.00)
12887 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
12889 Until the body of the message has been received, the timestamp is the time when
12890 the message started to be received. Once the body has arrived, and all policy
12891 checks have taken place, the timestamp is updated to the time at which the
12892 message was accepted.
12894 .conf received@_headers@_max integer 30
12895 .index loop||prevention
12896 .index mail loop prevention
12897 .index ::Received:: header line||counting
12898 When a message is to be delivered, the number of ::Received:: headers is
12899 counted, and if it is greater than this parameter, a mail loop is assumed to
12900 have occurred, the delivery is abandoned, and an error message is generated.
12901 This applies to both local and remote deliveries.
12903 .conf recipient@_unqualified@_hosts "host list$**$" unset
12904 .index unqualified addresses
12905 .index host||unqualified addresses from
12906 This option lists those hosts from which Exim is prepared to accept unqualified
12907 recipient addresses in message envelopes. The addresses are made fully
12908 qualified by the addition of the \qualify@_recipient\ value. This option also
12909 affects message header lines. Exim does not reject unqualified recipient
12910 addresses in headers, but it qualifies them only if the message came from a
12911 host that matches \recipient@_unqualified@_hosts\,
12912 or if the message was submitted locally (not using TCP/IP), and the \-bnq-\
12913 option was not set.
12915 .conf recipients@_max integer 0
12916 .index limit||number of recipients
12917 .index recipient||maximum number
12918 If this option is set greater than zero, it specifies the maximum number of
12919 original recipients for any message. Additional recipients that are generated
12920 by aliasing or forwarding do not count. SMTP messages get a 452 response for
12921 all recipients over the limit; earlier recipients are delivered as normal.
12922 Non-SMTP messages with too many recipients are failed, and no deliveries are
12924 .index \\RCPT\\||maximum number of incoming
12925 Note that the RFCs specify that an SMTP server should accept at least 100
12926 \\RCPT\\ commands in a single message.
12928 .conf recipients@_max@_reject boolean false
12929 If this option is set true, Exim rejects SMTP messages containing too many
12930 recipients by giving 552 errors to the surplus \\RCPT\\ commands, and a 554
12931 error to the eventual \\DATA\\ command. Otherwise (the default) it gives a 452
12932 error to the surplus \\RCPT\\ commands and accepts the message on behalf of the
12933 initial set of recipients. The remote server should then re-send the message
12934 for the remaining recipients at a later time.
12936 .conf remote@_max@_parallel integer 2
12937 .index delivery||parallelism for remote
12938 This option controls parallel delivery of one message to a number of remote
12939 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
12940 does all the remote deliveries for a message one by one. Otherwise, if a single
12941 message has to be delivered to more than one remote host, or if several copies
12942 have to be sent to the same remote host, up to \remote@_max@_parallel\
12943 deliveries are done simultaneously. If more than \remote@_max@_parallel\
12944 deliveries are required, the maximum number of processes are started, and as
12945 each one finishes, another is begun. The order of starting processes is the
12946 same as if sequential delivery were being done, and can be controlled by the
12947 \remote@_sort@_domains\ option. If parallel delivery takes place while running
12948 with debugging turned on, the debugging output from each delivery process is
12949 tagged with its process id.
12951 This option controls only the maximum number of parallel deliveries for one
12952 message in one Exim delivery process. Because Exim has no central queue
12953 manager, there is no way of controlling the total number of simultaneous
12954 deliveries if the configuration allows a delivery attempt as soon as a message
12956 .index number of deliveries
12957 .index delivery||maximum number of
12958 If you want to control the total number of deliveries on the system, you
12959 need to set the \queue@_only\ option. This ensures that all incoming messages
12960 are added to the queue without starting a delivery process. Then set up an Exim
12961 daemon to start queue runner processes at appropriate intervals (probably
12962 fairly often, for example, every minute), and limit the total number of queue
12963 runners by setting the \queue__run__max\ parameter. Because each queue runner
12964 delivers only one message at a time, the maximum number of deliveries that can
12965 then take place at once is \queue@_run@_max\ multiplied by
12966 \remote@_max@_parallel\.
12968 If it is purely remote deliveries you want to control, use
12969 \queue@_smtp@_domains\ instead of \queue@_only\. This has the added benefit of
12970 doing the SMTP routing before queuing, so that several messages for the same
12971 host will eventually get delivered down the same connection.
12973 .conf remote@_sort@_domains "domain list$**$" unset
12974 .index sorting remote deliveries
12975 .index delivery||sorting remote
12976 When there are a number of remote deliveries for a message, they are sorted by
12977 domain into the order given by this list. For example,
12979 remote_sort_domains = *.cam.ac.uk:*.uk
12981 would attempt to deliver to all addresses in the \*cam.ac.uk*\ domain first, then
12982 to those in the \uk\ domain, then to any others.
12984 .conf retry@_data@_expire time 7d
12985 .index hints database||data expiry
12986 This option sets a `use before' time on retry information in Exim's hints
12987 database. Any older retry data is ignored. This means that, for example, once a
12988 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
12991 .conf retry@_interval@_max time 24h
12992 .index retry||limit on interval
12993 .index limit||on retry interval
12994 Chapter ~~CHAPretry describes Exim's mechanisms for controlling the intervals
12995 between delivery attempts for messages that cannot be delivered straight away.
12996 This option sets an overall limit to the length of time between retries.
12998 .conf return@_path@_remove boolean true
12999 .index ::Return-path:: header line||removing
13000 RFC 2821, section 4.4, states that an SMTP server must insert a ::Return-path::
13001 header line into a message when it makes a `final delivery'. The ::Return-path::
13002 header preserves the sender address as received in the \\MAIL\\ command. This
13003 description implies that this header should not be present in an incoming
13004 message. If \return@_path@_remove\ is true, any existing ::Return-path::
13005 headers are removed from messages at the time they are received. Exim's
13006 transports have options for adding ::Return-path:: headers at the time of
13007 delivery. They are normally used only for final local deliveries.
13009 .conf return@_size@_limit integer 100K
13010 This option is an obsolete synonym for \bounce@_return@_size@_limit\.
13012 .conf rfc1413@_hosts "host list$**$" $*$
13014 .index host||for RFC 1413 calls
13015 RFC 1413 identification calls are made to any client host which matches an item
13018 .conf rfc1413@_query@_timeout time 30s
13019 .index RFC 1413||query timeout
13020 .index timeout||for RFC 1413 call
13021 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
13022 no RFC 1413 calls are ever made.
13024 .conf sender@_unqualified@_hosts "host list$**$" unset
13025 .index unqualified addresses
13026 .index host||unqualified addresses from
13027 This option lists those hosts from which Exim is prepared to accept unqualified
13028 sender addresses. The addresses are made fully qualified by the addition of
13029 \qualify@_domain\. This option also affects message header lines. Exim does not
13030 reject unqualified addresses in headers that contain sender addresses, but it
13031 qualifies them only if the message came from a host that matches
13032 \sender@_unqualified@_hosts\,
13033 or if the message was submitted locally (not using TCP/IP), and the \-bnq-\
13034 option was not set.
13036 .conf smtp@_accept@_keepalive boolean true
13037 .index keepalive||on incoming connection
13038 This option controls the setting of the \\SO@_KEEPALIVE\\ option on incoming
13039 TCP/IP socket connections. When set, it causes the kernel to probe idle
13040 connections periodically, by sending packets with `old' sequence numbers. The
13041 other end of the connection should send an acknowledgement if the connection is
13042 still okay or a reset if the connection has been aborted. The reason for doing
13043 this is that it has the beneficial effect of freeing up certain types of
13044 connection that can get stuck when the remote host is disconnected without
13045 tidying up the TCP/IP call properly. The keepalive mechanism takes several
13046 hours to detect unreachable hosts.
13049 .conf smtp@_accept@_max integer 20
13050 .index limit||incoming SMTP connections
13051 .index SMTP||incoming connection count
13053 This option specifies the maximum number of simultaneous incoming SMTP calls
13054 that Exim will accept. It applies only to the listening daemon; there is no
13055 control (in Exim) when incoming SMTP is being handled by \*inetd*\. If the value
13056 is set to zero, no limit is applied. However, it is required to be non-zero if
13057 either \smtp@_accept@_max@_per@_host\ or \smtp@_accept@_queue\ is set. See also
13058 \smtp@_accept@_reserve\.
13061 .conf smtp@_accept@_max@_nonmail integer 10
13062 .index limit||non-mail SMTP commands
13063 .index SMTP||limiting non-mail commands
13064 Exim counts the number of `non-mail' commands in an SMTP session, and drops the
13065 connection if there are too many. This option defines `too many'. The check
13066 catches some denial-of-service attacks, repeated failing \\AUTH\\s, or a mad
13067 client looping sending \\EHLO\\, for example. The check is applied only if the
13068 client host matches \smtp@_accept@_max@_nonmail@_hosts\.
13070 When a new message is expected, one occurrence of \\RSET\\ is not counted. This
13071 allows a client to send one \\RSET\\ between messages (this is not necessary,
13072 but some clients do it). Exim also allows one uncounted occurence of \\HELO\\
13073 or \\EHLO\\, and one occurrence of \\STARTTLS\\ between messages. After
13074 starting up a TLS session, another \\EHLO\\ is expected, and so it too is not
13075 counted. The first occurrence of \\AUTH\\ in a connection, or immediately
13076 following \\STARTTLS\\ is not counted. Otherwise, all commands other than
13077 \\MAIL\\, \\RCPT\\, \\DATA\\, and \\QUIT\\ are counted.
13079 .conf smtp@_accept@_max@_nonmail@_hosts "host list$**$" $*$
13080 You can control which hosts are subject to the \smtp@_accept@_max@_nonmail\
13081 check by setting this option. The default value makes it apply to all hosts. By
13082 changing the value, you can exclude any badly-behaved hosts that you have to
13086 .conf smtp@_accept@_max@_per@_connection integer 1000
13087 .index SMTP||incoming message count, limiting
13088 .index limit||messages per SMTP connection
13089 The value of this option limits the number of \\MAIL\\ commands that Exim is
13090 prepared to accept over a single SMTP connection, whether or not each command
13091 results in the transfer of a message. After the limit is reached, a 421
13092 response is given to subsequent \\MAIL\\ commands. This limit is a safety
13093 precaution against a client that goes mad (incidents of this type have been
13096 .conf smtp@_accept@_max@_per@_host string$**$ unset
13097 .index limit||SMTP connections from one host
13098 .index host||limiting SMTP connections from
13099 This option restricts the number of simultaneous IP connections from a single
13100 host (strictly, from a single IP address) to the Exim daemon. The option is
13101 expanded, to enable different limits to be applied to different hosts by
13102 reference to \$sender@_host@_address$\. Once the limit is reached, additional
13103 connection attempts from the same host are rejected with error code 421. The
13104 default value of zero imposes no limit. If this option is set, it is required
13105 that \smtp@_accept@_max\ be non-zero.
13107 \**Warning**\: When setting this option you should not use any expansion
13108 constructions that take an appreciable amount of time. The expansion and test
13109 happen in the main daemon loop, in order to reject additional connections
13110 without forking additional processes (otherwise a denial-of-service attack
13111 could cause a vast number or processes to be created). While the daemon is
13112 doing this processing, it cannot accept any other incoming connections.
13115 .conf smtp@_accept@_queue integer 0
13116 .index SMTP||incoming connection count
13117 .index queueing incoming messages
13118 .index message||queueing by SMTP connection count
13119 If the number of simultaneous incoming SMTP calls handled via the listening
13120 daemon exceeds this value, messages received by SMTP are just placed on the
13121 queue; no delivery processes are started automatically. A value of zero implies
13122 no limit, and clearly any non-zero value is useful only if it is less than the
13123 \smtp@_accept@_max\ value (unless that is zero). See also \queue@_only\,
13124 \queue@_only@_load\, \queue@_smtp@_domains\, and the various \-od-\ command
13127 .conf smtp@_accept@_queue@_per@_connection integer 10
13128 .index queueing incoming messages
13129 .index message||queueing by message count
13130 This option limits the number of delivery processes that Exim starts
13131 automatically when receiving messages via SMTP, whether via the daemon or by
13132 the use of \-bs-\ or \-bS-\. If the value of the option is greater than zero,
13133 and the number of messages received in a single SMTP session exceeds this
13134 number, subsequent messages are placed on the queue, but no delivery processes
13135 are started. This helps to limit the number of Exim processes when a server
13136 restarts after downtime and there is a lot of mail waiting for it on other
13137 systems. On large systems, the default should probably be increased, and on
13138 dial-in client systems it should probably be set to zero (that is, disabled).
13140 .conf smtp@_accept@_reserve integer 0
13141 .index SMTP||incoming call count
13142 .index host||reserved
13143 When \smtp@_accept@_max\ is set greater than zero, this option specifies a
13144 number of SMTP connections that are reserved for connections from the hosts
13145 that are specified in \smtp@_reserve@_hosts\. The value set in
13146 \smtp@_accept@_max\ includes this reserve pool. The specified hosts are not
13147 restricted to this number of connections; the option specifies a minimum number
13148 of connection slots for them, not a maximum. It is a guarantee that that group
13149 of hosts can always get at least \smtp@_accept@_reserve\ connections.
13151 For example, if \smtp@_accept@_max\ is set to 50 and \smtp@_accept@_reserve\ is
13152 set to 5, once there are 45 active connections (from any hosts), new
13153 connections are accepted only from hosts listed in \smtp@_reserve@_hosts\.
13154 See also \smtp@_accept@_max@_per@_host\.
13156 .conf smtp@_active@_hostname string$**$ unset
13157 .index host||name in SMTP responses
13158 .index SMTP||host name in responses
13159 This option is provided for multi-homed servers that want to masquerade as
13160 several different hosts. At the start of an SMTP connection, its value is
13161 expanded and used instead of the value of \$primary@_hostname$\ in SMTP
13162 responses. For example, it is used as domain name in the response to an
13163 incoming \\HELO\\ or \\EHLO\\ command.
13165 The active hostname is placed in the \$smtp__active__hostname$\ variable, which
13166 is saved with any messages that are received. It is therefore available for use
13167 in routers and transports when the message is later delivered.
13170 If this option is unset, or if its expansion is forced to fail, or if the
13171 expansion results in an empty string, the value of \$primary@_hostname$\ is
13172 used. Other expansion failures cause a message to be written to the main and
13173 panic logs, and the SMTP command receives a temporary error. Typically, the
13174 value of \smtp@_active@_hostname\ depends on the incoming interface address.
13177 smtp_active_hostname = ${if eq{$interface_address}{10.0.0.1}\
13178 {cox.mydomain}{box.mydomain}}
13181 .conf smtp@_banner string$**$ "see below"
13182 .index SMTP||welcome banner
13183 .index banner for SMTP
13184 .index welcome banner for SMTP
13185 .index customizing||SMTP banner
13186 This string, which is expanded every time it is used, is output as the initial
13187 positive response to an SMTP connection. The default setting is:
13190 smtp_banner = $smtp_active_hostname ESMTP Exim \
13191 $version_number $tod_full
13194 Failure to expand the string causes a panic error. If you want to create a
13195 multiline response to the initial SMTP connection, use `@\n' in the string at
13196 appropriate points, but not at the end. Note that the 220 code is not included
13197 in this string. Exim adds it automatically (several times in the case of a
13198 multiline response).
13200 .conf smtp@_check@_spool@_space boolean true
13201 .index checking disk space
13202 .index disk space, checking
13203 .index spool directory||checking space
13204 When this option is set, if an incoming SMTP session encounters the \\SIZE\\
13205 option on a \\MAIL\\ command, it checks that there is enough space in the
13206 spool directory's partition to accept a message of that size, while still
13207 leaving free the amount specified by \check@_spool@_space\ (even if that value
13208 is zero). If there isn't enough space, a temporary error code is returned.
13210 .conf smtp@_connect@_backlog integer 20
13211 .index connection backlog
13212 .index SMTP||connection backlog
13213 .index backlog of connections
13214 This option specifies a maximum number of waiting SMTP connections. Exim passes
13215 this value to the TCP/IP system when it sets up its listener. Once this number
13216 of connections are waiting for the daemon's attention, subsequent connection
13217 attempts are refused at the TCP/IP level. At least, that is what the manuals
13218 say; in some circumstances such connection attempts have been observed to time
13219 out instead. For large systems it is probably a good idea to increase the
13220 value (to 50, say). It also gives some protection against denial-of-service
13221 attacks by SYN flooding.
13223 .conf smtp@_enforce@_sync boolean true
13224 .index SMTP||synchronization checking
13225 .index synchronization checking in SMTP
13226 The SMTP protocol specification requires the client to wait for a response from
13227 the server at certain points in the dialogue. Without \\PIPELINING\\ these
13228 synchronization points are after every command; with \\PIPELINING\\ they are
13229 fewer, but they still exist.
13231 Some spamming sites send out a complete set of SMTP commands without waiting
13232 for any response. Exim protects against this by rejecting a message if the
13233 client has sent further input when it should not have. The error response `554
13234 SMTP synchronization error' is sent, and the connection is dropped. Testing for
13235 this error cannot be perfect because of transmission delays (unexpected input
13236 may be on its way but not yet received when Exim checks). However, it does
13237 detect many instances.
13240 The check can be globally disabled by setting \smtp@_enforce@_sync\ false.
13241 If you want to disable the check selectively (for example, only for certain
13242 hosts), you can do so by an appropriate use of a \control\ modifier in an ACL
13243 (see section ~~SECTcontrols). See also \pipelining@_advertise@_hosts\.
13246 .conf smtp@_etrn@_command string$**$ unset
13247 .index \\ETRN\\||command to be run
13248 If this option is set, the given command is run whenever an SMTP \\ETRN\\
13249 command is received from a host that is permitted to issue such commands (see
13250 chapter ~~CHAPACL). The string is split up into separate arguments which are
13251 independently expanded. The expansion variable \$domain$\ is set to the
13252 argument of the \\ETRN\\ command, and no syntax checking is done on it. For
13255 smtp_etrn_command = /etc/etrn_command $domain $sender_host_address
13257 A new process is created to run the command, but Exim does not wait for it to
13258 complete. Consequently, its status cannot be checked. If the command cannot be
13259 run, a line is written to the panic log, but the \\ETRN\\ caller still receives
13260 a 250 success response. Exim is normally running under its own uid when
13261 receiving SMTP, so it is not possible for it to change the uid before running
13264 .conf smtp@_etrn@_serialize boolean true
13265 .index \\ETRN\\||serializing
13266 When this option is set, it prevents the simultaneous execution of more than
13267 one identical command as a result of \\ETRN\\ in an SMTP connection. See
13268 section ~~SECTETRN for details.
13270 .conf smtp@_load@_reserve fixed-point unset
13271 .index load average
13272 If the system load average ever gets higher than this, incoming SMTP calls are
13273 accepted only from those hosts that match an entry in \smtp@_reserve@_hosts\.
13274 If \smtp@_reserve@_hosts\ is not set, no incoming SMTP calls are accepted when
13275 the load is over the limit. The option has no effect on ancient operating
13276 systems on which Exim cannot determine the load average. See also
13277 \deliver@_queue@_load@_max\ and \queue@_only@_load\.
13280 .conf smtp@_max@_synprot@_errors integer 3
13281 .index SMTP||limiting syntax and protocol errors
13282 .index limit||SMTP syntax and protocol errors
13283 Exim rejects SMTP commands that contain syntax or protocol errors. In
13284 particular, a syntactically invalid email address, as in this command:
13286 RCPT TO:<abc xyz@a.b.c>
13288 causes immediate rejection of the command, before any other tests are done.
13289 (The ACL cannot be run if there is no valid address to set up for it.) An
13290 example of a protocol error is receiving \\RCPT\\ before \\MAIL\\. If there are
13291 too many syntax or protocol errors in one SMTP session, the connection is
13292 dropped. The limit is set by this option.
13294 .index \\PIPELINING\\||expected errors
13295 When the \\PIPELINING\\ extension to SMTP is in use, some protocol errors are
13296 `expected', for instance, a \\RCPT\\ command after a rejected \\MAIL\\ command.
13297 Exim assumes that \\PIPELINING\\ will be used if it advertises it (see
13298 \pipelining@_advertise@_hosts\), and in this situation, `expected' errors do
13299 not count towards the limit.
13302 .conf smtp@_max@_unknown@_commands integer 3
13303 .index SMTP||limiting unknown commands
13304 .index limit||unknown SMTP commands
13305 If there are too many unrecognized commands in an incoming SMTP session, an
13306 Exim server drops the connection. This is a defence against some kinds of abuse
13309 into making connections to SMTP ports; in these circumstances, a number of
13310 non-SMTP command lines are sent first.
13313 .conf smtp@_ratelimit@_hosts "host list$**$" unset
13314 .index SMTP||rate limiting
13315 .index limit||rate of message arrival
13316 .index \\RCPT\\||rate limiting
13317 Some sites find it helpful to be able to limit the rate at which certain hosts
13318 can send them messages, and the rate at which an individual message can specify
13319 recipients. When a host matches \smtp@_ratelimit@_hosts\, the values of
13320 \smtp@_ratelimit@_mail\ and \smtp@_ratelimit@_rcpt\ are used to control the
13321 rate of acceptance of \\MAIL\\ and \\RCPT\\ commands in a single SMTP session,
13322 respectively. Each option, if set, must contain a set of four comma-separated
13325 A threshold, before which there is no rate limiting.
13327 An initial time delay. Unlike other times in Exim, numbers with decimal
13328 fractional parts are allowed here.
13330 A factor by which to increase the delay each time.
13332 A maximum value for the delay. This should normally be less than 5 minutes,
13333 because after that time, the client is liable to timeout the SMTP command.
13335 For example, these settings have been used successfully at the site which
13336 first suggested this feature, for controlling mail from their customers:
13338 smtp_ratelimit_mail = 2,0.5s,1.05,4m
13339 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
13341 The first setting specifies delays that are applied to \\MAIL\\ commands after
13342 two have been received over a single connection. The initial delay is 0.5
13343 seconds, increasing by a factor of 1.05 each time. The second setting applies
13344 delays to \\RCPT\\ commands when more than four occur in a single message.
13346 It is also possible to configure delays explicitly in ACLs. See section
13347 ~~SECTACLmodi for details.
13350 .conf smtp@_ratelimit@_mail string unset
13351 See \smtp@_ratelimit@_hosts\ above.
13353 .conf smtp@_ratelimit@_rcpt string unset
13354 See \smtp@_ratelimit@_hosts\ above.
13356 .conf smtp@_receive@_timeout time 5m
13357 .index timeout||for SMTP input
13358 .index SMTP||timeout, input
13359 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
13360 input, including batch SMTP. If a line of input (either an SMTP command or a
13361 data line) is not received within this time, the SMTP connection is dropped and
13362 the message is abandoned.
13363 A line is written to the log containing one of the following messages:
13365 SMTP command timeout on connection from...
13366 SMTP data timeout on connection from...
13368 The former means that Exim was expecting to read an SMTP command; the latter
13369 means that it was in the \\DATA\\ phase, reading the contents of a message.
13372 .index \-os-\ option
13373 The value set by this option can be overridden by the
13374 \-os-\ command-line option. A setting of zero time disables the timeout, but
13375 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
13376 of local input using \-bs-\ or \-bS-\.) For non-SMTP input, the reception
13377 timeout is controlled by \receive@_timeout\ and \-or-\.
13379 .conf smtp@_reserve@_hosts "host list$**$" unset
13380 This option defines hosts for which SMTP connections are reserved; see
13381 \smtp@_accept@_reserve\ and \smtp@_load@_reserve\ above.
13383 .conf smtp@_return@_error@_details boolean false
13384 .index SMTP||details policy failures
13385 .index policy control||rejection, returning details
13386 In the default state, Exim uses bland messages such as
13387 `Administrative prohibition' when it rejects SMTP commands for policy
13388 reasons. Many sysadmins like this because it gives away little information
13389 to spammers. However, some other syadmins who are applying strict checking
13390 policies want to give out much fuller information about failures. Setting
13391 \smtp@_return@_error@_details\ true causes Exim to be more forthcoming. For
13392 example, instead of `Administrative prohibition', it might give:
13394 550-Rejected after DATA: '>' missing at end of address:
13395 550 failing address in "From" header is: <user@dom.ain
13399 .conf spamd@_address string "$tt{127.0.0.1 783}"
13400 This option is available when Exim is compiled with the content-scanning
13401 extension. It specifies how Exim connects to SpamAssassin's \spamd\ daemon. See
13402 section ~~SECTscanspamass for more details.
13405 .conf split@_spool@_directory boolean false
13406 .index multiple spool directories
13407 .index spool directory||split
13408 .index directories, multiple
13409 If this option is set, it causes Exim to split its input directory into 62
13410 subdirectories, each with a single alphanumeric character as its name. The
13411 sixth character of the message id is used to allocate messages to
13412 subdirectories; this is the least significant base-62 digit of the time of
13413 arrival of the message.
13415 Splitting up the spool in this way may provide better performance on systems
13416 where there are long mail queues, by reducing the number of files in any one
13417 directory. The msglog directory is also split up in a similar way to the input
13418 directory; however, if \preserve@_message@_logs\ is set, all old msglog files
13419 are still placed in the single directory \(msglog.OLD)\.
13421 It is not necessary to take any special action for existing messages when
13422 changing \split@_spool@_directory\. Exim notices messages that are in the
13423 `wrong' place, and continues to process them. If the option is turned off after
13424 a period of being on, the subdirectories will eventually empty and be
13425 automatically deleted.
13427 When \split@_spool@_directory\ is set, the behaviour of queue runner processes
13428 changes. Instead of creating a list of all messages in the queue, and then
13429 trying to deliver each one in turn, it constructs a list of those in one
13430 sub-directory and tries to deliver them, before moving on to the next
13431 sub-directory. The sub-directories are processed in a random order. This
13432 spreads out the scanning of the input directories, and uses less memory. It is
13433 particularly beneficial when there are lots of messages on the queue. However,
13434 if \queue@_run@_in@_order\ is set, none of this new processing happens. The
13435 entire queue has to be scanned and sorted before any deliveries can start.
13437 .conf spool@_directory string$**$ "set at compile time"
13438 .index spool directory||path to
13439 This defines the directory in which Exim keeps its spool, that is, the messages
13440 it is waiting to deliver. The default value is taken from the compile-time
13441 configuration setting, if there is one. If not, this option must be set. The
13442 string is expanded, so it can contain, for example, a reference to
13443 \$primary@_hostname$\.
13445 If the spool directory name is fixed on your installation, it is recommended
13446 that you set it at build time rather than from this option, particularly if the
13447 log files are being written to the spool directory (see \log@_file@_path\).
13448 Otherwise log files cannot be used for errors that are detected early on, such
13449 as failures in the configuration file.
13451 By using this option to override the compiled-in path, it is possible to run
13452 tests of Exim without using the standard spool.
13454 .conf strip@_excess@_angle@_brackets boolean false
13455 .index angle brackets, excess
13456 If this option is set, redundant pairs of angle brackets round `route-addr'
13457 items in addresses are stripped. For example, \*@<@<xxx@@a.b.c.d@>@>*\ is treated
13458 as \*@<xxx@@a.b.c.d@>*\. If this is in the envelope and the message is passed on
13459 to another MTA, the excess angle brackets are not passed on. If this option is
13460 not set, multiple pairs of angle brackets cause a syntax error.
13462 .conf strip@_trailing@_dot boolean false
13463 .index trailing dot on domain
13464 .index dot||trailing on domain
13465 If this option is set, a trailing dot at the end of a domain in an address is
13466 ignored. If this is in the envelope and the message is passed on to another
13467 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
13468 domain causes a syntax error.
13469 However, addresses in header lines are checked only when an ACL requests header
13472 .conf syslog@_duplication boolean true
13473 .index syslog||duplicate log lines, suppressing
13474 When Exim is logging to syslog, it writes the log lines for its three
13475 separate logs at different syslog priorities so that they can in principle
13476 be separated on the logging hosts. Some installations do not require this
13477 separation, and in those cases, the duplication of certain log lines is a
13478 nuisance. If \syslog@_duplication\ is set false, only one copy of any
13479 particular log line is written to syslog. For lines that normally go to
13480 both the main log and the reject log, the reject log version (possibly
13481 containing message header lines) is written, at \\LOG@_NOTICE\\ priority.
13482 Lines that normally go to both the main and the panic log are written at
13483 the \\LOG@_ALERT\\ priority.
13485 .conf syslog@_facility string unset
13486 .index syslog||facility, setting
13487 This option sets the syslog `facility' name, used when Exim is logging to
13488 syslog. The value must be one of the strings `mail', `user', `news', `uucp',
13489 `daemon', or `local\*x*\' where \*x*\ is a digit between 0 and 7. If this
13490 option is unset, `mail' is used. See chapter ~~CHAPlog for details of Exim's
13494 .conf syslog@_processname string "$tt{exim}"
13495 .index syslog||process name, setting
13496 This option sets the syslog `ident' name, used when Exim is logging to syslog.
13497 The value must be no longer than 32 characters. See chapter ~~CHAPlog for
13498 details of Exim's logging.
13501 .conf syslog@_timestamp boolean true
13502 .index syslog||timestamps
13503 If \syslog@_timestamp\ is set false, the timestamps on Exim's log lines are
13504 omitted when these lines are sent to syslog. See chapter ~~CHAPlog for
13505 details of Exim's logging.
13507 .conf system@_filter string$**$ unset
13508 .index filter||system filter
13509 .index system filter||specifying
13510 .index Sieve filter||not available for system filter
13511 This option specifies an Exim filter file that is applied to all messages at
13512 the start of each delivery attempt, before any routing is done. System filters
13513 must be Exim filters; they cannot be Sieve filters. If the system filter
13514 generates any deliveries to files or pipes, or any new mail messages, the
13515 appropriate \system@_filter@_...@_transport\ option(s) must be set, to define
13516 which transports are to be used. Details of this facility are given in chapter
13517 ~~CHAPsystemfilter.
13519 .conf system@_filter@_directory@_transport string$**$ unset
13520 This sets the name of the transport driver that is to be used when the
13521 \save\ command in a system message filter specifies a path ending in `/',
13522 implying delivery of each message into a separate file in some directory.
13523 During the delivery, the variable \$address@_file$\ contains the path name.
13525 .conf system@_filter@_file@_transport string$**$ unset
13526 .index file||transport for system filter
13527 This sets the name of the transport driver that is to be used when the \save\
13528 command in a system message filter specifies a path not ending in `/'. During
13529 the delivery, the variable \$address@_file$\ contains the path name.
13531 .index gid (group id)||system filter
13532 .conf system@_filter@_group string unset
13533 This option is used only when \system@_filter@_user\ is also set. It sets the
13534 gid under which the system filter is run, overriding any gid that is associated
13535 with the user. The value may be numerical or symbolic.
13537 .conf system@_filter@_pipe@_transport string$**$ unset 7
13538 .index \%pipe%\ transport||for system filter
13539 This specifies the transport driver that is to be used when a \pipe\ command is
13540 used in a system filter. During the delivery, the variable \$address@_pipe$\
13541 contains the pipe command.
13543 .conf system@_filter@_reply@_transport string$**$ unset
13544 .index \%autoreply%\ transport||for system filter
13545 This specifies the transport driver that is to be used when a \mail\ command is
13546 used in a system filter.
13548 .index uid (user id)||system filter
13549 .conf system@_filter@_user string unset
13550 If this option is not set, the system filter is run in the main Exim delivery
13551 process, as root. When the option is set, the system filter runs in a separate
13552 process, as the given user. Unless the string consists entirely of digits, it
13553 is looked up in the password data. Failure to find the named user causes a
13554 configuration error. The gid is either taken from the password data, or
13555 specified by \system@_filter@_group\. When the uid is specified numerically,
13556 \system@_filter@_group\ is required to be set.
13558 If the system filter generates any pipe, file, or reply deliveries, the uid
13559 under which the filter is run is used when transporting them, unless a
13560 transport option overrides.
13561 Normally you should set \system@_filter@_user\ if your system filter generates
13562 these kinds of delivery.
13564 .conf tcp@_nodelay boolean true
13565 .index daemon||\\TCP@_NODELAY\\ on sockets
13566 .index Nagle algorithm
13567 .index \\TCP@_NODELAY\\ on listening sockets
13568 If this option is set false, it stops the Exim daemon setting the
13569 \\TCP@_NODELAY\\ option on its listening sockets. Setting \\TCP@_NODELAY\\
13570 turns off the `Nagle algorithm', which is a way of improving network
13571 performance in interactive (character-by-character) situations. Turning it off
13572 should improve Exim's performance a bit, so that is what happens by default.
13573 However, it appears that some broken clients cannot cope, and time out. Hence
13574 this option. It affects only those sockets that are set up for listening by the
13575 daemon. Sockets created by the smtp transport for delivering mail always set
13578 .conf timeout@_frozen@_after time 0s
13579 .index frozen messages||timing out
13580 .index timeout||frozen messages
13581 If \timeout@_frozen@_after\ is set to a time greater than zero, a frozen
13582 message of any kind that has been on the queue for longer than the given
13583 time is automatically cancelled at the next queue run. If it is a bounce
13584 message, it is just discarded; otherwise, a bounce is sent to the sender, in a
13585 similar manner to cancellation by the \-Mg-\ command line option. If you want
13586 to timeout frozen bounce messages earlier than other kinds of frozen message,
13587 see \ignore@_bounce@_errors@_after\.
13589 .conf timezone string unset
13590 .index timezone, setting
13591 The value of \timezone\ is used to set the environment variable \\TZ\\ while
13592 running Exim (if it is different on entry). This ensures that all timestamps
13593 created by Exim are in the required timezone. If you want all your timestamps
13594 to be in UTC (aka GMT) you should set
13598 The default value is taken from \\TIMEZONE@_DEFAULT\\ in \(Local/Makefile)\,
13599 or, if that is not set, from the value of the TZ environment variable when Exim
13600 is built. If \timezone\ is set to the empty string, either at build or run
13601 time, any existing \\TZ\\ variable is removed from the environment when Exim
13602 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
13603 unfortunately not all, operating systems.
13605 .conf tls@_advertise@_hosts "host list$**$" unset
13606 .index TLS||advertising
13607 .index encryption||on SMTP connection
13608 .index SMTP||encrypted connection
13609 When Exim is built with support for TLS encrypted connections, the availability
13610 of the \\STARTTLS\\ command to set up an encrypted session is advertised in
13611 response to \\EHLO\\ only to those client hosts that match this option. See
13612 chapter ~~CHAPTLS for details of Exim's support for TLS.
13614 .conf tls@_certificate string$**$ unset
13615 .index TLS||server certificate, location of
13616 .index certificate||for server, location of
13617 The value of this option is expanded, and must then be the absolute path to a
13618 file which contains the server's certificates. The server's private key is also
13619 assumed to be in this file if \tls@_privatekey\ is unset. See chapter ~~CHAPTLS
13620 for further details.
13622 \**Note**\: The certificates defined by this option are used only when Exim is
13623 receiving incoming messages as a server. If you want to supply certificates for
13624 use when sending messages as a client, you must set the \tls@_certificate\
13625 option in the relevant \%smtp%\ transport.
13627 .conf tls@_crl string$**$ unset
13628 .index TLS||server certificate revocation list
13629 .index certificate||revocation list for server
13630 This option specifies a certificate revocation list. The expanded value must
13631 be the name of a file that contains a CRL in PEM format.
13633 .conf tls@_dhparam string$**$ unset
13634 .index TLS||D-H parameters for server
13635 The value of this option is expanded, and must then be the absolute path to
13636 a file which contains the server's DH parameter values.
13637 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
13638 ignored. See section ~~SECTopenvsgnu for further details.
13641 .conf tls@_on@_connect@_ports "string list" unset
13642 This option specifies a list of incoming SSMTP ports that should operate the
13643 obsolete SSMTP protocol, where a TLS session is immediately set up without
13644 waiting for the client to issue a \\STARTTLS\\ command. For further details,
13645 see section ~~SECTsupobssmt.
13648 .conf tls@_privatekey string$**$ unset
13649 .index TLS||server private key, location of
13650 The value of this option is expanded, and must then be the absolute path to a
13651 file which contains the server's private key. If this option is unset, the
13652 private key is assumed to be in the same file as the server's certificates. See
13653 chapter ~~CHAPTLS for further details.
13655 .conf tls@_remember@_esmtp boolean false
13656 .index TLS||esmtp state, remembering
13657 .index TLS||broken clients
13658 If this option is set true, Exim violates the RFCs by remembering that it is in
13659 `esmtp' state after successfully negotiating a TLS session. This provides
13660 support for broken clients that fail to send a new \\EHLO\\ after starting a
13663 .conf tls@_require@_ciphers string$**$ unset
13664 .index TLS||requiring specific ciphers
13665 .index cipher||requiring specific
13666 This option controls which ciphers can be used for incoming TLS connections.
13667 The \%smtp%\ transport has an option of the same name for controlling outgoing
13668 connections. This option is expanded for each connection, so can be varied for
13669 different clients if required. The value of this option must be a list of
13670 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
13671 in somewhat different ways.
13673 If GnuTLS is being used, the client controls the preference order of the
13676 Details are given in sections ~~SECTreqciphssl and ~~SECTreqciphgnu.
13678 .conf tls@_try@_verify@_hosts "host list$**$" unset
13679 .index TLS||client certificate verification
13680 .index certificate||verification of client
13681 See \tls@_verify@_hosts\ below.
13683 .conf tls@_verify@_certificates string$**$ unset
13684 .index TLS||client certificate verification
13685 .index certificate||verification of client
13686 The value of this option is expanded, and must then be the absolute path to
13687 a file containing permitted certificates for clients that
13688 match \tls@_verify@_hosts\ or \tls@_try@_verify@_hosts\. Alternatively, if you
13689 are using OpenSSL, you can set \tls@_verify@_certificates\ to the name of a
13690 directory containing certificate files. This does not work with GnuTLS; the
13691 option must be set to the name of a single file if you are using GnuTLS.
13693 .conf tls@_verify@_hosts "host list$**$" unset
13694 .index TLS||client certificate verification
13695 .index certificate||verification of client
13696 This option, along with \tls@_try@_verify@_hosts\, controls the checking of
13697 certificates from clients.
13698 The expected certificates are defined by \tls@_verify@_certificates\, which
13699 must be set. A configuration error occurs if either \tls@_verify@_hosts\ or
13700 \tls@_try@_verify@_hosts\ is set and \tls@_verify@_certificates\ is not set.
13702 Any client that matches \tls@_verify@_hosts\ is constrained by
13703 \tls@_verify@_certificates\. The client must present one of the listed
13704 certificates. If it does not, the connection is aborted.
13706 A weaker form of checking is provided by \tls@_try@_verify@_hosts\. If a client
13707 matches this option (but not \tls@_verify@_hosts\), Exim requests a
13708 certificate and checks it against \tls@_verify@_certificates\, but does not
13709 abort the connection if there is no certificate or if it does not match. This
13710 state can be detected in an ACL, which makes it possible to implement policies
13711 such as `accept for relay only if a verified certificate has been received, but
13712 accept for local delivery if encrypted, even without a verified certificate'.
13714 Client hosts that match neither of these lists are not asked to present
13717 .conf trusted@_groups "string list" unset
13718 .index trusted group
13719 .index group||trusted
13720 If this option is set, any process that is running in one of the listed groups,
13721 or which has one of them as a supplementary group, is trusted.
13722 The groups can be specified numerically or by name.
13723 See section ~~SECTtrustedadmin for details of what trusted callers are
13724 permitted to do. If neither \trusted@_groups\ nor \trusted@_users\ is set, only
13725 root and the Exim user are trusted.
13727 .conf trusted@_users "string list" unset
13728 .index trusted user
13729 .index user||trusted
13730 If this option is set, any process that is running as one of the listed users
13732 The users can be specified numerically or by name.
13733 See section ~~SECTtrustedadmin for details of what trusted callers are
13734 permitted to do. If neither \trusted@_groups\ nor \trusted@_users\ is set, only
13735 root and the Exim user are trusted.
13737 .index uid (user id)||unknown caller
13738 .conf unknown@_login string$**$ unset
13739 This is a specialized feature for use in unusual configurations. By default, if
13740 the uid of the caller of Exim cannot be looked up using \*getpwuid()*\, Exim
13741 gives up. The \unknown@_login\ option can be used to set a login name to be
13742 used in this circumstance. It is expanded, so values like \user@$caller@_uid\
13743 can be set. When \unknown@_login\ is used, the value of \unknown@_username\ is
13744 used for the user's real name (gecos field), unless this has been set by the
13747 .conf unknown@_username string unset
13748 See \unknown@_login\.
13750 .conf untrusted@_set@_sender "address list$**$" unset
13751 .index trusted user
13752 .index sender||setting by untrusted user
13753 .index untrusted user, setting sender
13754 .index user||untrusted setting sender
13755 .index envelope sender
13756 When an untrusted user submits a message to Exim using the standard input, Exim
13757 normally creates an envelope sender address from the user's login and the
13758 default qualification domain. Data from the \-f-\ option (for setting envelope
13759 senders on non-SMTP messages) or the SMTP \\MAIL\\ command (if \-bs-\ or \-bS-\
13760 is used) is ignored.
13762 However, untrusted users are permitted to set an empty envelope sender address,
13763 to declare that a message should never generate any bounces. For example:
13765 exim -f '<>' user@domain.example
13767 The \untrusted@_set@_sender\ option allows you to permit untrusted users to set
13768 other envelope sender addresses in a controlled way. When it is set, untrusted
13769 users are allowed to set envelope sender addresses that match any of the
13770 patterns in the list. Like all address lists, the string is expanded. The
13771 identity of the user is in \$sender@_ident$\, so you can, for example, restrict
13772 users to setting senders that start with their login ids
13773 followed by a hyphen
13774 by a setting like this:
13776 untrusted_set_sender = ^$sender_ident-
13778 If you want to allow untrusted users to set envelope sender addresses without
13779 restriction, you can use
13781 untrusted_set_sender = *
13783 The \untrusted@_set@_sender\ option applies to all forms of local input, but
13784 only to the setting of the envelope sender. It does not permit untrusted users
13785 to use the other options which trusted user can use to override message
13786 parameters. Furthermore, it does not stop Exim from removing an existing
13787 ::Sender:: header in the message, or from adding a ::Sender:: header if
13788 necessary. See \local__sender__retain\ and \local@_from@_check\ for ways of
13789 overriding these actions. The handling of the ::Sender:: header is also
13790 described in section ~~SECTthesenhea.
13792 The log line for a message's arrival shows the envelope sender following `<='.
13793 For local messages, the user's login always follows, after `U='. In \-bp-\
13794 displays, and in the Exim monitor, if an untrusted user sets an envelope sender
13795 address, the user's login is shown in parentheses after the sender address.
13797 .conf uucp@_from@_pattern string "see below"
13799 .index UUCP||`From' line
13800 Some applications that pass messages to an MTA via a command line interface use
13801 an initial line starting with `From' to pass the envelope sender. In
13802 particular, this is used by UUCP software. Exim recognizes such a line by means
13803 of a regular expression that is set in \uucp@_from@_pattern\. When the pattern
13804 matches, the sender address is constructed by expanding the contents of
13805 \uucp@_from@_sender\, provided that the caller of Exim is a trusted user. The
13806 default pattern recognizes lines in the following two forms:
13808 From ph10 Fri Jan 5 12:35 GMT 1996
13809 From ph10 Fri, 7 Jan 97 14:00:00 GMT
13811 The pattern can be seen by running
13813 exim -bP uucp_from_pattern
13815 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
13816 year in the second case. The first word after `From' is matched in the regular
13817 expression by a parenthesized subpattern. The default value for
13818 \uucp@_from@_sender\ is `$1', which therefore just uses this first word (`ph10'
13819 in the example above) as the message's sender. See also
13820 \ignore@_fromline@_hosts\.
13822 .conf uucp@_from@_sender string$**$ "$tt{@$1}"
13823 See \uucp@_from@_pattern\ above.
13825 .conf warn@_message@_file string unset
13826 .index warning of delay||customizing the message
13827 .index customizing||warning message
13828 This option defines a template file containing paragraphs of text to be used
13829 for constructing the warning message which is sent by Exim when a message has
13830 been on the queue for a specified amount of time, as specified by
13831 \delay@_warning\. Details of the file's contents are given in chapter
13832 ~~CHAPemsgcust. See also \bounce@_message@_file\.
13834 .conf write@_rejectlog boolean true
13835 .index reject log||disabling
13836 If this option is set false, Exim no longer writes anything to the reject log.
13837 See chapter ~~CHAPlog for details of what Exim writes to its logs.
13847 . ============================================================================
13848 .chapter Generic options for routers
13849 .rset CHAProutergeneric "~~chapter"
13850 .set runningfoot "generic router options"
13851 .index options||generic, for routers
13852 .index generic options||router
13854 This chapter describes the generic options that apply to all routers,
13855 identifying those that are preconditions. For a general description of how a
13856 router operates, see sections ~~SECTrunindrou and ~~SECTrouprecon. The latter
13857 specifies the order in which the preconditions are tested. The order of
13858 expansion of the options that provide data for a transport is: \errors@_to\,
13859 \headers@_add\, \headers@_remove\, \transport\.
13863 .conf address@_data string$**$ unset
13864 .index router||data attached to address
13865 The string is expanded just before the router is run, that is, after all the
13866 precondition tests have succeeded. If the expansion is forced to fail, the
13867 router declines. Other expansion failures cause delivery of the address to be
13870 When the expansion succeeds, the value is retained with the address, and can be
13871 accessed using the variable \$address@_data$\ in the current router, subsequent
13872 routers, and the eventual transport.
13874 \**Warning**\: if the current or any subsequent router is a \%redirect%\ router
13875 that runs a user's filter file, the contents of \$address@_data$\ are
13876 accessible in the filter. This is not normally a problem, because such data is
13877 usually either not confidential or it `belongs' to the current user, but if you
13878 do put confidential data into \$address@_data$\ you need to remember this
13881 Even if the router declines or passes, the value of \$address@_data$\ remains
13882 with the address, though it can be changed by another \address@_data\ setting
13883 on a subsequent router. If a router generates child addresses, the value of
13884 \$address@_data$\ propagates to them. This also applies to the special kind of
13885 `child' that is generated by a router with the \unseen\ option.
13887 The idea of \address@_data\ is that you can use it to look up a lot of data for
13888 the address once, and then pick out parts of the data later. For example, you
13889 could use a single LDAP lookup to return a string of the form
13891 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
13893 In the transport you could pick out the mailbox by a setting such as
13895 file = ${extract{mailbox}{$address_data}}
13897 This makes the configuration file less messy, and also reduces the number of
13898 lookups (though Exim does cache lookups).
13900 The \address@_data\ facility is also useful as a means of passing information
13901 from one router to another, and from a router to a transport. In addition, if
13903 \$address@_data$\ is set by a router when verifying a recipient address from an
13904 ACL, it remains available for use in the rest of the ACL statement. After
13905 verifying a sender, the value is transferred to \$sender@_address@_data$\.
13909 .conf address@_test "boolean (precondition)" true
13910 .index \-bt-\ option
13911 .index router||skipping when address testing
13912 If this option is set false, the router is skipped when routing is being tested
13913 by means of the \-bt-\ command line option. This can be a convenience when your
13914 first router sends messages to an external scanner, because it saves you
13915 having to set the `already scanned' indicator when testing real address
13919 .conf cannot@_route@_message string$**$ unset
13920 .index router||customizing `cannot route' message
13921 .index customizing||`cannot route' message
13922 This option specifies a text message that is used when an address cannot be
13923 routed because Exim has run out of routers. The default message is `Unrouteable
13924 address'. This option is useful only on routers that have \more\ set false, or
13925 on the very last router in a configuration, because the value that is used is
13926 taken from the last router that inspects an address. For example, using the
13927 default configuration, you could put:
13929 cannot_route_message = Remote domain not found in DNS
13931 on the first (\%dnslookup%\) router, and
13933 cannot_route_message = Unknown local user
13935 on the final router that checks for local users. If string expansion fails, the
13936 default message is used.
13937 Unless the expansion failure was explicitly forced, a message about the failure
13938 is written to the main and panic logs, in addition to the normal message about
13939 the routing failure.
13941 .conf caseful@_local@_part boolean false
13942 .index case of local parts
13943 .index router||case of local parts
13944 By default, routers handle the local parts of addresses in a case-insensitive
13945 manner, though the actual case is preserved for transmission with the message.
13946 If you want the case of letters to be significant in a router, you must set
13947 this option true. For individual router options that contain address or local
13948 part lists (for example, \local@_parts\), case-sensitive matching can be turned
13949 on by `+caseful' as a list item. See section ~~SECTcasletadd for more details.
13952 The value of the \$local@_part$\ variable is forced to lower case while a
13953 router is running unless \caseful@_local@_part\ is set. When a router assigns
13954 an address to a transport, the value of \$local@_part$\ when the transport runs
13955 is the same as it was in the router. Similarly, when a router generates child
13956 addresses by aliasing or forwarding, the values of \$original@_local@_part$\
13957 and \$parent@_local@_part$\ are those that were used by the redirecting router.
13959 This option applies to the processing of an address by a router. When a
13960 recipient address is being processed in an ACL, there is a separate \control\
13961 modifier that can be used to specify case-sensitive processing within the ACL
13962 (see section ~~SECTcontrols).
13965 .conf check@_local@_user "boolean (precondition)" false
13966 .index local user, checking in router
13967 .index router||checking for local user
13968 .index \(/etc/passwd)\
13969 When this option is true, Exim checks that the local part of the recipient
13970 address (with affixes removed if relevant) is the name of an account on the
13971 local system. The check is done by calling the \*getpwnam()*\ function rather
13972 than trying to read \(/etc/passwd)\ directly. This means that other methods of
13973 holding password data (such as NIS) are supported. If the local part is a local
13974 user, \$home$\ is set from the password data, and can be tested in other
13975 preconditions that are evaluated after this one (the order of evaluation is
13976 given in section ~~SECTrouprecon). However, the value of \$home$\ can be
13977 overridden by \router@_home@_directory\. If the local part is not a local user,
13978 the router is skipped.
13980 If you want to check that the local part is either the name of a local user
13981 or matches something else, you cannot combine \check@_local@_user\ with a
13982 setting of \local@_parts\, because that specifies the logical \*and*\ of the
13983 two conditions. However, you can use a \%passwd%\ lookup in a \local@_parts\
13984 setting to achieve this. For example:
13986 local_parts = passwd;$local_part : lsearch;/etc/other/users
13988 Note, however, that the side effects of \check@_local@_user\ (such as setting
13989 up a home directory) do not occur when a \%passwd%\ lookup is used in a
13990 \local@_parts\ (or any other) precondition.
13993 .conf condition "string$**$ (precondition)" unset
13994 .index router||customized precondition
13995 This option specifies a general precondition test that has to succeed for the
13996 router to be called. The \condition\ option is the last precondition to be
13997 evaluated (see section ~~SECTrouprecon). The string is expanded, and if the
13998 result is a forced failure, or an empty string, or one of the strings `0' or
13999 `no' or `false' (checked without regard to the case of the letters), the router
14000 is skipped, and the address is offered to the next one.
14002 If the result is any other value, the router is run (as this is the last
14003 precondition to be evaluated, all the other preconditions must be true).
14005 The \condition\ option provides a means of applying custom conditions to the
14006 running of routers. Note that in the case of a simple conditional expansion,
14007 the default expansion values are exactly what is wanted. For example:
14009 condition = ${if >{$message_age}{600}}
14011 Because of the default behaviour of the string expansion, this is equivalent to
14013 condition = ${if >{$message_age}{600}{true}{}}
14017 If the expansion fails (other than forced failure) delivery is deferred. Some
14018 of the other precondition options are common special cases that could in fact
14019 be specified using \condition\.
14022 .conf debug@_print string$**$ unset
14023 .index testing||variables in drivers
14024 If this option is set and debugging is enabled (see the \-d-\ command line
14025 option), the string is expanded and included in the debugging output.
14026 If expansion of the string fails, the error message is written to the debugging
14027 output, and Exim carries on processing.
14028 This option is provided to help with checking out the values of variables and
14029 so on when debugging router configurations. For example, if a \condition\
14030 option appears not to be working, \debug@_print\ can be used to output the
14031 variables it references. The output happens after checks for \domains\,
14032 \local@_parts\, and \check@_local@_user\ but before any other preconditions are
14033 tested. A newline is added to the text if it does not end with one.
14036 .conf disable@_logging boolean false
14037 If this option is set true, nothing is logged for any routing errors
14038 or for any deliveries caused by this router. You should not set this option
14039 unless you really, really know what you are doing. See also the generic
14040 transport option of the same name.
14042 .conf domains "domain list$**$ (precondition)" unset
14043 .index router||restricting to specific domains
14044 If this option is set, the router is skipped unless the current domain matches
14045 the list. If the match is achieved by means of a file lookup, the data that the
14046 lookup returned for the domain is placed in \$domain@_data$\ for use in string
14047 expansions of the driver's private options.
14048 See section ~~SECTrouprecon for a list of the order in which preconditions
14052 .conf driver string unset
14053 This option must always be set. It specifies which of the available routers is
14057 .conf errors@_to string$**$ unset
14058 .index envelope sender
14059 .index router||changing address for errors
14060 If a router successfully handles an address, it may queue the address for
14061 delivery or it may generate child addresses. In both cases, if there is a
14062 delivery problem during later processing, the resulting bounce message is sent
14063 to the address that results from expanding this string, provided that the
14064 address verifies successfully.
14065 \errors@_to\ is expanded before \headers@_add\, \headers@_remove\, and
14068 If the option is unset, or the expansion is forced to fail, or the result of
14069 the expansion fails to verify, the errors address associated with the incoming
14070 address is used. At top level, this is the envelope sender. A non-forced
14071 expansion failure causes delivery to be deferred.
14073 If an address for which \errors@_to\ has been set ends up being delivered over
14074 SMTP, the envelope sender for that delivery is the \errors@_to\ value, so that
14075 any bounces that are generated by other MTAs on the delivery route are also
14076 sent there. The most common use of \errors@_to\ is probably to direct mailing
14077 list bounces to the manager of the list, as described in section
14078 ~~SECTmailinglists.
14080 The \errors@_to\ setting associated with an address can be overridden if it
14081 subsequently passes through other routers that have their own \errors@_to\
14083 or if it is delivered by a transport with a \return@_path\ setting.
14085 You can set \errors@_to\ to the empty string by either of these settings:
14090 An expansion item that yields an empty string has the same effect. If you do
14091 this, a locally detected delivery error for addresses processed by this router
14092 no longer gives rise to a bounce message; the error is discarded. If the
14093 address is delivered to a remote host, the return path is set to \"<>"\, unless
14094 overridden by the \return@_path\ option on the transport.
14096 If for some reason you want to discard local errors, but use a non-empty
14097 \\MAIL\\ command for remote delivery, you can preserve the original return
14098 path in \$address@_data$\ in the router, and reinstate it in the transport by
14099 setting \return@_path\.
14102 .conf expn "boolean (precondition)" true
14103 .index address||testing
14104 .index testing||addresses
14105 .index \\EXPN\\||router skipping
14106 .index router||skipping for \\EXPN\\
14107 If this option is turned off, the router is skipped when testing an address
14108 as a result of processing an SMTP \\EXPN\\ command. You might, for example,
14109 want to turn it off on a router for users' \(.forward)\ files, while leaving it
14110 on for the system alias file.
14111 See section ~~SECTrouprecon for a list of the order in which preconditions
14114 The use of the SMTP \\EXPN\\ command is controlled by an ACL (see chapter
14115 ~~CHAPACL). When Exim is running an \\EXPN\\ command, it is similar to testing
14116 an address with \-bt-\. Compare \\VRFY\\, whose counterpart is \-bv-\.
14119 .conf fail@_verify boolean false
14120 .index router||forcing verification failure
14121 Setting this option has the effect of setting both \fail@_verify@_sender\ and
14122 \fail@_verify@_recipient\ to the same value.
14125 .conf fail@_verify@_recipient boolean false
14126 If this option is true and an address is accepted by this router when
14127 verifying a recipient, verification fails.
14130 .conf fail@_verify@_sender boolean false
14131 If this option is true and an address is accepted by this router when
14132 verifying a sender, verification fails.
14135 .conf fallback@_hosts "string list" unset
14136 .index router||fallback hosts
14137 .index fallback||hosts specified on router
14138 String expansion is not applied to this option. The argument must be a
14139 colon-separated list of host names or IP addresses. If a router queues an
14140 address for a remote transport, this host list is associated with the address,
14141 and used instead of the transport's fallback host list. If \hosts@_randomize\
14142 is set on the transport, the order of the list is randomized for each use. See
14143 the \fallback@_hosts\ option of the \%smtp%\ transport for further details.
14145 .conf group string$**$ "see below"
14146 .index gid (group id)||local delivery
14147 .index local transports||uid and gid
14148 .index transport||local
14149 .index router||setting group
14150 When a router queues an address for a transport, and the transport does not
14151 specify a group, the group given here is used when running the delivery
14153 The group may be specified numerically or by name. If expansion fails, the
14154 error is logged and delivery is deferred.
14155 The default is unset, unless \check@_local@_user\ is set, when the default
14156 is taken from the password information. See also \initgroups\ and \user\ and
14157 the discussion in chapter ~~CHAPenvironment.
14160 .conf headers@_add string$**$ unset
14161 .index header lines||adding
14162 .index router||adding header lines
14164 This option specifies a string of text that is expanded at routing time, and
14165 associated with any addresses that are accepted by the router. However, this
14166 option has no effect when an address is just being verified. The way in which
14167 the text is used to add header lines at transport time is described in section
14168 ~~SECTheadersaddrem.
14170 The \headers@_add\ option is expanded after \errors@_to\, but before
14171 \headers@_remove\ and \transport\. If the expanded string is empty, or if the
14172 expansion is forced to fail, the option has no effect. Other expansion failures
14173 are treated as configuration errors.
14175 \**Warning**\: The \headers@_add\ option cannot be used for a \%redirect%\
14176 router that has the \one@_time\ option set.
14180 .conf headers@_remove string$**$ unset
14181 .index header lines||removing
14182 .index router||removing header lines
14184 This option specifies a string of text that is expanded at routing time, and
14185 associated with any addresses that are accepted by the router. However, this
14186 option has no effect when an address is just being verified. The way in which
14187 the text is used to remove header lines at transport time is described in
14188 section ~~SECTheadersaddrem.
14190 The \headers@_remove\ option is expanded after \errors@_to\ and \headers@_add\,
14191 but before \transport\. If the expansion is forced to fail, the option has no
14192 effect. Other expansion failures are treated as configuration errors.
14194 \**Warning**\: The \headers@_remove\ option cannot be used for a \%redirect%\
14195 router that has the \one@_time\ option set.
14199 .conf ignore@_target@_hosts "host list$**$" unset
14200 .index IP address||discarding
14201 .index router||discarding IP addresses
14202 Although this option is a host list, it should normally contain IP address
14203 entries rather than names. If any host that is looked up by the router has an
14204 IP address that matches an item in this list, Exim behaves as if that IP
14205 address did not exist. This option allows you to cope with rogue DNS entries
14208 remote.domain.example. A 127.0.0.1
14212 ignore_target_hosts = 127.0.0.1
14214 on the relevant router. If all the hosts found by a \%dnslookup%\ router are
14215 discarded in this way, the router declines. In a conventional configuration, an
14216 attempt to mail to such a domain would normally provoke the `unrouteable
14217 domain' error, and an attempt to verify an address in the domain would fail.
14219 Similarly, if \ignore@_target@_hosts\ is set on an \%ipliteral%\ router, the
14220 router declines if presented with one of the listed addresses.
14222 This option may also be useful for ignoring link-local and site-local IPv6
14223 addresses. Because, like all host lists, the value of \ignore@_target@_hosts\
14224 is expanded before use as a list, it is possible to make it dependent on the
14225 domain that is being routed.
14227 During its expansion, \$host@_address$\ is set to the IP address that is being
14233 .index additional groups
14234 .index groups, additional
14235 .index local transports||uid and gid
14236 .index transport||local
14237 .conf initgroups boolean false
14238 If the router queues an address for a transport, and this option is true, and
14239 the uid supplied by the router is not overridden by the transport, the
14240 \*initgroups()*\ function is called when running the transport to ensure that
14241 any additional groups associated with the uid are set up. See also \group\ and
14242 \user\ and the discussion in chapter ~~CHAPenvironment.
14245 .conf local@_part@_prefix "string list (precondition)" unset
14246 .index router||prefix for local part
14247 .index prefix||for local part, used in router
14248 If this option is set, the router is skipped unless the local part
14249 starts with one of the given strings, or \local@_part@_prefix@_optional\ is
14251 See section ~~SECTrouprecon for a list of the order in which preconditions
14254 The list is scanned from left to right, and the first prefix that matches is
14255 used. A limited form of wildcard is available; if the prefix begins with an
14256 asterisk, it matches the longest possible sequence of arbitrary characters at
14257 the start of the local part. An asterisk should therefore always be followed by
14258 some character that does not occur in normal local parts.
14259 .index multiple mailboxes
14260 .index mailbox||multiple
14261 Wildcarding can be used to set up multiple user mailboxes, as described in
14262 section ~~SECTmulbox.
14264 During the testing of the \local@_parts\ option, and while the router is
14265 running, the prefix is removed from the local part, and is available in the
14266 expansion variable \$local@_part@_prefix$\. If the router accepts the address,
14267 this remains true during subsequent delivery.
14268 In particular, the local part that is transmitted in the \\RCPT\\ command
14269 for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default. This
14270 behaviour can be overridden by setting \rcpt@_include@_affixes\ true on the
14271 relevant transport.
14273 The prefix facility is commonly used to handle local parts of the form
14274 \owner-something\. Another common use is to support local parts of the form
14275 \real-username\ to bypass a user's \(.forward)\ file -- helpful when trying to
14276 tell a user their forwarding is broken -- by placing a router like this one
14277 immediately before the router that handles \(.forward)\ files:
14281 local_part_prefix = real-
14283 transport = local_delivery
14285 If both \local@_part@_prefix\ and \local@_part@_suffix\ are set for a router,
14286 both conditions must be met if not optional. Care must be taken if wildcards
14287 are used in both a prefix and a suffix on the same router. Different
14288 separator characters must be used to avoid ambiguity.
14290 .conf local@_part@_prefix@_optional boolean false
14291 See \local@_part@_prefix\ above.
14294 .conf local@_part@_suffix "string list (precondition)" unset
14295 .index router||suffix for local part
14296 .index suffix for local part, used in router
14297 This option operates in the same way as \local@_part@_prefix\, except that the
14298 local part must end (rather than start) with the given string, the
14299 \local@_part@_suffix@_optional\ option determines whether the suffix is
14300 mandatory, and the wildcard $*$ character, if present, must be the last
14301 character of the suffix. This option facility is commonly used to handle local
14302 parts of the form \something-request\ and multiple user mailboxes of the form
14305 .conf local@_part@_suffix@_optional boolean false
14306 See \local@_part@_suffix\ above.
14309 .conf local@_parts "local part list$**$ (precondition)" unset
14310 .index router||restricting to specific local parts
14311 .index local part||checking in router
14312 The router is run only if the local part of the address matches the list.
14313 See section ~~SECTrouprecon for a list of the order in which preconditions
14315 section ~~SECTlocparlis for a discussion of local part lists. Because the
14316 string is expanded, it is possible to make it depend on the domain, for
14319 local_parts = dbm;/usr/local/specials/$domain
14321 If the match is achieved by a lookup, the data that the lookup returned
14322 for the local part is placed in the variable \$local@_part@_data$\ for use in
14323 expansions of the router's private options. You might use this option, for
14324 example, if you have a large number of local virtual domains, and you want to
14325 send all postmaster mail to the same place without having to set up an alias in
14326 each virtual domain:
14330 local_parts = postmaster
14331 data = postmaster@real.domain.example
14335 .conf log@_as@_local boolean "see below"
14336 .index log||delivery line
14337 .index delivery||log line format
14338 Exim has two logging styles for delivery, the idea being to make local
14339 deliveries stand out more visibly from remote ones. In the `local' style, the
14340 recipient address is given just as the local part, without a domain. The use of
14341 this style is controlled by this option. It defaults to true for the \%accept%\
14342 router, and false for all the others.
14345 .conf more boolean$**$ true
14346 The result of string expansion for this option must be a valid boolean value,
14347 that is, one of the strings `yes', `no', `true', or `false'. Any other result
14348 causes an error, and delivery is deferred. If the expansion is forced to fail,
14349 the default value for the option (true) is used. Other failures cause delivery
14352 If this option is set false, and the router is run, but declines to handle the
14353 address, no further routers are tried, routing fails, and the address is
14355 .index \self\ option
14356 However, if the router explicitly passes an address to the following router by
14357 means of the setting
14361 or otherwise, the setting of \more\ is ignored. Also, the setting of \more\
14362 does not affect the behaviour if one of the precondition tests fails. In that
14363 case, the address is always passed to the next router.
14366 .conf pass@_on@_timeout boolean false
14367 .index timeout||of router
14368 .index router||timeout
14369 If a router times out during a host lookup, it normally causes deferral of the
14370 address. If \pass@_on@_timeout\ is set, the address is passed on to the next
14371 router, overriding \no@_more\. This may be helpful for systems that are
14372 intermittently connected to the Internet, or those that want to pass to a smart
14373 host any messages that cannot immediately be delivered.
14375 There are occasional other temporary errors that can occur while doing DNS
14376 lookups. They are treated in the same way as a timeout, and this option
14377 applies to all of them.
14380 .conf pass@_router string unset
14381 .index router||go to after `pass'
14382 When a router returns `pass', the address is normally handed on to the next
14383 router in sequence. This can be changed by setting \pass@_router\ to the name
14384 of another router. However (unlike \redirect@_router\) the named router must be
14385 below the current router, to avoid loops. Note that this option applies only to
14386 the special case of `pass'. It does not apply when a router returns `decline'.
14389 .conf redirect@_router string unset
14390 .index router||start at after redirection
14391 Sometimes an administrator knows that it is pointless to reprocess addresses
14392 generated from alias or forward files with the same router again. For
14393 example, if an alias file translates real names into login ids there is no
14394 point searching the alias file a second time, especially if it is a large file.
14396 The \redirect@_router\ option can be set to the name of any router instance. It
14397 causes the routing of any generated addresses to start at the named router
14398 instead of at the first router. This option has no effect if the router in
14399 which it is set does not generate new addresses.
14402 .conf require@_files "string list$**$ (precondition)" unset
14403 .index file||requiring for router
14404 .index router||requiring file existence
14405 This option provides a general mechanism for predicating the running of a
14406 router on the existence or non-existence of certain files or directories.
14407 Before running a router, as one of its precondition tests, Exim works its way
14408 through the \require@_files\ list, expanding each item separately.
14410 Because the list is split before expansion, any colons in expansion items must
14411 be doubled, or the facility for using a different list separator must be used.
14412 If any expansion is forced to fail, the item is ignored. Other expansion
14413 failures cause routing of the address to be deferred.
14415 If any expanded string is empty, it is ignored. Otherwise, except as described
14416 below, each string must be a fully qualified file path, optionally preceded by
14417 `!'. The paths are passed to the \*stat()*\ function to test for the existence
14418 of the files or directories. The router is skipped if any paths not preceded by
14419 `!' do not exist, or if any paths preceded by `!' do exist.
14422 If \*stat()*\ cannot determine whether a file exists or not, delivery of
14423 the message is deferred. This can happen when NFS-mounted filesystems are
14426 This option is checked after the \domains\, \local@_parts\, and \senders\
14427 options, so you cannot use it to check for the existence of a file in which to
14428 look up a domain, local part, or sender. (See section ~~SECTrouprecon for a
14429 full list of the order in which preconditions are evaluated.) However, as
14430 these options are all expanded, you can use the \exists\ expansion condition to
14431 make such tests. The \require@_files\ option is intended for checking files
14432 that the router may be going to use internally, or which are needed by a
14433 transport (for example \(.procmailrc)\).
14435 During delivery, the \*stat()*\ function is run as root, but there is a
14436 facility for some checking of the accessibility of a file by another user.
14437 This is not a proper permissions check, but just a `rough' check that
14438 operates as follows:
14440 If an item in a \require@_files\ list does not contain any forward slash
14441 characters, it is taken to be the user (and optional group, separated by a
14442 comma) to be checked for subsequent files in the list. If no group is specified
14443 but the user is specified symbolically, the gid associated with the uid is
14446 require_files = mail:/some/file
14447 require_files = $local_part:$home/.procmailrc
14449 If a user or group name in a \require@_files\ list does not exist, the
14450 \require@_files\ condition fails.
14452 Exim performs the check by scanning along the components of the file path, and
14453 checking the access for the given uid and gid. It checks for `x' access on
14454 directories, and `r' access on the final file. Note that this means that file
14455 access control lists, if the operating system has them, are ignored.
14457 \**Warning 1**\: When the router is being run to verify addresses for an
14458 incoming SMTP message, Exim is not running as root, but under its own uid. This
14459 may affect the result of a \require@_files\ check. In particular, \*stat()*\
14460 may yield the error \\EACCES\\ (`Permission denied'). This means that the Exim
14461 user is not permitted to read one of the directories on the file's path.
14463 \**Warning 2**\: Even when Exim is running as root while delivering a message,
14464 \*stat()*\ can yield \\EACCES\\ for a file in an NFS directory that is mounted
14465 without root access.
14467 In this case, if a check for access by a particular user is requested, Exim
14468 creates a subprocess that runs as that user, and tries the check again in that
14471 The default action for handling an unresolved \\EACCES\\ is to consider it to
14472 be caused by a configuration error,
14474 and routing is deferred because the existence or non-existence of the file
14475 cannot be determined. However, in some circumstances it may be desirable to
14476 treat this condition as if the file did not exist. If the file name (or the
14477 exclamation mark that precedes the file name for non-existence) is preceded by
14478 a plus sign, the \\EACCES\\ error is treated as if the file did not exist. For
14481 require_files = +/some/file
14483 If the router is not an essential part of verification (for example, it
14484 handles users' \(.forward)\ files), another solution is to set the \verify\
14485 option false so that the router is skipped when verifying.
14488 .conf retry@_use@_local@_part boolean "see below"
14489 .index hints database||retry keys
14490 .index local part||in retry keys
14491 When a delivery suffers a temporary routing failure, a retry record is created
14492 in Exim's hints database. For addresses whose routing depends only on the
14493 domain, the key for the retry record should not involve the local part, but for
14494 other addresses, both the domain and the local part should be included.
14495 Usually, remote routing is of the former kind, and local routing is of the
14498 This option controls whether the local part is used to form the key for retry
14499 hints for addresses that suffer temporary errors while being handled by this
14500 router. The default value is true for any router that has \check@_local@_user\
14501 set, and false otherwise. Note that this option does not apply to hints keys
14502 for transport delays; they are controlled by a generic transport option of the
14505 The setting of \retry@_use@_local@_part\ applies only to the router on which it
14506 appears. If the router generates child addresses, they are routed
14507 independently; this setting does not become attached to them.
14510 .conf router@_home@_directory string$**$ unset
14511 .index router||home directory for
14512 .index home directory||for router
14513 This option sets a home directory for use while the router is running. (Compare
14514 \transport__home@_directory\, which sets a home directory for later
14515 transporting.) In particular, if used on a \%redirect%\ router, this option
14516 sets a value for \$home$\ while a filter is running. The value is expanded;
14517 forced expansion failure causes the option to be ignored -- other failures
14518 cause the router to defer.
14520 Expansion of \router@_home@_directory\ happens immediately after the
14521 \check@_local@_user\ test (if configured), before any further expansions take
14523 (See section ~~SECTrouprecon for a list of the order in which preconditions
14525 While the router is running, \router__home@_directory\ overrides the value of
14526 \$home$\ that came from \check@_local@_user\.
14528 When a router accepts an address and routes it to a transport (including the
14529 cases when a redirect router generates a pipe, file, or autoreply delivery),
14530 the home directory setting for the transport is taken from the first of these
14531 values that is set:
14533 The \home@_directory\ option on the transport;
14535 The \transport@_home@_directory\ option on the router;
14537 The password data if \check@_local@_user\ is set on the router;
14539 The \router@_home@_directory\ option on the router.
14541 In other words, \router@_home@_directory\ overrides the password data for the
14542 router, but not for the transport.
14545 .conf self string "freeze"
14546 .index MX record||pointing to local host
14547 .index local host||MX pointing to
14548 This option applies to those routers that use a recipient address to find a
14549 list of remote hosts. Currently, these are the \%dnslookup%\, \%ipliteral%\,
14550 and \%manualroute%\ routers.
14551 Certain configurations of the \%queryprogram%\ router can also specify a list
14553 Usually such routers are configured to send the message to a remote host via an
14554 \%smtp%\ transport. The \self\ option specifies what happens when the first
14555 host on the list turns out to be the local host.
14556 The way in which Exim checks for the local host is described in section
14559 Normally this situation indicates either an error in Exim's configuration (for
14560 example, the router should be configured not to process this domain), or an
14561 error in the DNS (for example, the MX should not point to this host). For this
14562 reason, the default action is to log the incident, defer the address, and
14563 freeze the message. The following alternatives are provided for use in special
14568 Delivery of the message is tried again later, but the message is not frozen.
14570 \reroute: <<domain>>\
14572 The domain is changed to the given domain, and the address is passed back to
14573 be reprocessed by the routers. No rewriting of headers takes place. This
14574 behaviour is essentially a redirection.
14576 \reroute: rewrite: <<domain>>\
14578 The domain is changed to the given domain, and the address is passed back to be
14579 reprocessed by the routers. Any headers that contain the original domain are
14584 The router passes the address to the next router, or to the router named in the
14585 \pass@_router\ option if it is set.
14586 .index \more\ option
14587 This overrides \no@_more\.
14589 During subsequent routing and delivery, the variable
14590 \$self@_hostname$\ contains the name of the local host that the router
14591 encountered. This can be used to distinguish between different cases for hosts
14592 with multiple names. The combination
14597 ensures that only those addresses that routed to the local host are passed on.
14598 Without \no@_more\, addresses that were declined for other reasons would also
14599 be passed to the next router.
14603 Delivery fails and an error report is generated.
14607 .index local host||sending to
14608 The anomaly is ignored and the address is queued for the transport. This
14609 setting should be used with extreme caution. For an \%smtp%\ transport, it makes
14610 sense only in cases where the program that is listening on the SMTP port is not
14611 this version of Exim. That is, it must be some other MTA, or Exim with a
14612 different configuration file that handles the domain in another way.
14615 .conf senders "address list$**$ (precondition)" unset
14616 .index router||checking senders
14617 If this option is set, the router is skipped unless the message's sender
14618 address matches something on the list.
14619 See section ~~SECTrouprecon for a list of the order in which preconditions
14622 There are issues concerning verification when the running of routers is
14623 dependent on the sender. When Exim is verifying the address in an \errors@_to\
14624 setting, it sets the sender to the null string. When using the \-bt-\ option to
14625 check a configuration file, it is necessary also to use the \-f-\ option to set
14626 an appropriate sender. For incoming mail, the sender is unset when verifying
14627 the sender, but is available when verifying any recipients. If the SMTP
14628 \\VRFY\\ command is enabled, it must be used after \\MAIL\\ if the sender
14631 .conf translate@_ip@_address string$**$ unset
14632 .index IP address||translating
14633 .index packet radio
14634 .index router||IP address translation
14635 There exist some rare networking situations (for example, packet radio) where
14636 it is helpful to be able to translate IP addresses generated by normal routing
14637 mechanisms into other IP addresses, thus performing a kind of manual IP
14638 routing. This should be done only if the normal IP routing of the TCP/IP stack
14639 is inadequate or broken. Because this is an extremely uncommon requirement, the
14640 code to support this option is not included in the Exim binary unless
14641 \\SUPPORT__TRANSLATE__IP__ADDRESS\\=yes is set in \(Local/Makefile)\.
14643 The \translate@_ip@_address\ string is expanded for every IP address generated
14644 by the router, with the generated address set in \$host@_address$\. If the
14645 expansion is forced to fail, no action is taken.
14646 For any other expansion error, delivery of the message is deferred.
14647 If the result of the expansion is an IP address, that replaces the original
14648 address; otherwise the result is assumed to be a host name -- this is looked up
14649 using \*gethostbyname()*\ (or \*getipnodebyname()*\ when available) to produce
14650 one or more replacement IP addresses. For example, to subvert all IP addresses
14651 in some specific networks, this could be added to a router:
14653 $smc{translate@_ip@_address = @\
14654 @$@{lookup@{@$@{mask:@$host@_address/26@}@}lsearch@{/some/file@}@{@$value@}fail@}}
14656 The file would contain lines like
14658 10.2.3.128/26 some.host
14659 10.8.4.34/26 10.44.8.15
14661 You should not make use of this facility unless you really understand what you
14665 .conf transport string$**$ unset
14666 This option specifies the transport to be used when a router accepts an address
14667 and sets it up for delivery. A transport is never needed if a router is used
14668 only for verification. The value of the option is expanded at routing time,
14669 after the expansion of \errors@_to\, \headers@_add\, and \headers@_remove\, and
14670 result must be the name of one of the configured transports. If it is not,
14671 delivery is deferred.
14673 The \transport\ option is not used by the \%redirect%\ router, but it does have
14674 some private options that set up transports for pipe and file deliveries (see
14675 chapter ~~CHAPredirect).
14678 .conf transport@_current@_directory string$**$ unset
14679 .index current directory for local transport
14680 This option associates a current directory with any address that is routed
14681 to a local transport. This can happen either because a transport is
14682 explicitly configured for the router, or because it generates a delivery to a
14683 file or a pipe. During the delivery process (that is, at transport time), this
14684 option string is expanded and is set as the current directory, unless
14685 overridden by a setting on the transport.
14686 If the expansion fails for any reason, including forced failure, an error is
14687 logged, and delivery is deferred.
14688 See chapter ~~CHAPenvironment for details of the local delivery environment.
14692 .conf transport@_home@_directory string$**$ "see below"
14693 .index home directory||for local transport
14694 This option associates a home directory with any address that is routed to a
14695 local transport. This can happen either because a transport is explicitly
14696 configured for the router, or because it generates a delivery to a file or a
14697 pipe. During the delivery process (that is, at transport time), the option
14698 string is expanded and is set as the home directory, unless overridden by a
14699 setting of \home@_directory\ on the transport.
14700 If the expansion fails for any reason, including forced failure, an error is
14701 logged, and delivery is deferred.
14703 If the transport does not specify a home directory, and
14704 \transport@_home@_directory\ is not set for the router, the home directory for
14705 the tranport is taken from the password data if \check@_local@_user\ is set for
14706 the router. Otherwise it is taken from \router@_home@_directory\ if that option
14707 is set; if not, no home directory is set for the transport.
14709 See chapter ~~CHAPenvironment for further details of the local delivery
14714 .conf unseen boolean$**$ false
14715 .index router||carrying on after success
14716 The result of string expansion for this option must be a valid boolean value,
14717 that is, one of the strings `yes', `no', `true', or `false'. Any other result
14718 causes an error, and delivery is deferred. If the expansion is forced to fail,
14719 the default value for the option (false) is used. Other failures cause delivery
14722 When this option is set true, routing does not cease if the router accepts the
14723 address. Instead, a copy of the incoming address is passed to the next router,
14724 overriding a false setting of \more\. There is little point in setting \more\
14725 false if \unseen\ is always true, but it may be useful in cases when the value
14726 of \unseen\ contains expansion items (and therefore, presumably, is sometimes
14727 true and sometimes false).
14729 The \unseen\ option can be used to cause
14730 .index copy of message (\unseen\ option)
14731 copies of messages to be delivered to some other destination, while also
14732 carrying out a normal delivery. In effect, the current address is made into a
14733 `parent' that has two children -- one that is delivered as specified by this
14734 router, and a clone that goes on to be routed further.
14736 Header lines added to the address (or specified for removal) by this router or
14737 by previous routers affect the `unseen' copy of the message only. The clone
14738 that continues to be processed by further routers starts with no added headers
14739 and none specified for removal.
14741 However, any data that was set by the \address@_data\ option in the current or
14742 previous routers is passed on. Setting this option has a similar effect to the
14743 \unseen\ command qualifier in filter files.
14746 .conf user string$**$ "see below"
14747 .index uid (user id)||local delivery
14748 .index local transports||uid and gid
14749 .index transport||local
14750 .index router||user for filter processing
14751 .index filter||user for processing
14752 When a router queues an address for a transport, and the transport does not
14753 specify a user, the user given here is used when running the delivery process.
14754 The user may be specified numerically or by name. If expansion fails, the
14755 error is logged and delivery is deferred.
14756 This user is also used by the \%redirect%\ router when running a filter file.
14757 The default is unset, except when \check@_local@_user\ is set. In this case,
14758 the default is taken from the password information. If the user is specified as
14759 a name, and \group\ is not set, the group associated with the user is used. See
14760 also \initgroups\ and \group\ and the discussion in chapter ~~CHAPenvironment.
14763 .conf verify "boolean (precondition)" true
14764 Setting this option has the effect of setting \verify@_sender\ and
14765 \verify@_recipient\ to the same value.
14767 .conf verify@_only "boolean (precondition)" false
14768 .index \\EXPN\\||with \verify@_only\
14769 .index \-bv-\ option
14770 .index router||used only when verifying
14771 If this option is set, the router is used only when verifying an address or
14772 testing with the \-bv-\ option, not when actually doing a delivery, testing
14773 with the \-bt-\ option, or running the SMTP \\EXPN\\ command. It can be further
14774 restricted to verifying only senders or recipients by means of \verify@_sender\
14775 and \verify@_recipient\.
14777 \**Warning**\: When the router is being run to verify addresses for an incoming
14778 SMTP message, Exim is not running as root, but under its own uid. If the router
14779 accesses any files, you need to make sure that they are accessible to the Exim
14782 .conf verify@_recipient "boolean (precondition)" true
14783 If this option is false, the router is skipped when verifying recipient
14785 or testing recipient verification using \-bv-\.
14786 See section ~~SECTrouprecon for a list of the order in which preconditions
14789 .conf verify@_sender "boolean (precondition)" true
14790 If this option is false, the router is skipped when verifying sender addresses
14791 or testing sender verification using \-bvs-\.
14792 See section ~~SECTrouprecon for a list of the order in which preconditions
14805 . ============================================================================
14806 .chapter The accept router
14807 .set runningfoot "accept router"
14808 .index \%accept%\ router
14809 .index routers||\%accept%\
14810 The \%accept%\ router has no private options of its own. Unless it is being used
14811 purely for verification (see \verify@_only\) a transport is required to be
14812 defined by the generic \transport\ option. If the preconditions that are
14813 specified by generic options are met, the router accepts the address and queues
14814 it for the given transport. The most common use of this router is for setting
14815 up deliveries to local mailboxes. For example:
14819 domains = mydomain.example
14821 transport = local_delivery
14823 The \domains\ condition in this example checks the domain of the address, and
14824 \check@_local@_user\ checks that the local part is the login of a local user.
14825 When both preconditions are met, the \%accept%\ router runs, and queues the
14826 address for the \%local@_delivery%\ transport.
14837 . ============================================================================
14838 .chapter The dnslookup router
14839 .rset CHAPdnslookup "~~chapter"
14840 .set runningfoot "dnslookup router"
14841 .index \%dnslookup%\ router
14842 .index routers||\%dnslookup%\
14843 The \%dnslookup%\ router looks up the hosts that handle mail for the
14844 recipient's domain in the DNS. A transport must always be set for this router,
14845 unless \verify@_only\ is set.
14847 If SRV support is configured (see \check@_srv\ below), Exim first searches for
14848 SRV records. If none are found, or if SRV support is not configured,
14849 MX records are looked up. If no MX records exist, address records are sought.
14850 However, \mx@_domains\ can be set to disable the direct use of address records.
14852 MX records of equal priority are sorted by Exim into a random order. Exim then
14853 looks for address records for the host names obtained from MX or SRV records.
14854 When a host has more than one IP address, they are sorted into a random order,
14855 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
14856 IP addresses found are discarded by a setting of the \ignore@_target@_hosts\
14857 generic option, the router declines.
14859 Unless they have the highest priority (lowest MX value), MX records that point
14860 to the local host, or to any host name that matches \hosts__treat__as__local\,
14861 are discarded, together with any other MX records of equal or lower priority.
14863 .index MX record||pointing to local host
14864 .index local host||MX pointing to
14865 .index \self\ option||in \%dnslookup%\ router
14866 If the host pointed to by the highest priority MX record, or looked up as an
14867 address record, is the local host, or matches \hosts__treat__as__local\, what
14868 happens is controlled by the generic \self\ option.
14871 .section Problems with DNS lookups
14872 .rset SECTprowitdnsloo "~~chapter.~~section"
14873 There have been problems with DNS servers when SRV records are looked up.
14874 Some mis-behaving servers return a DNS error or timeout when a non-existent
14875 SRV record is sought. Similar problems have in the past been reported for
14876 MX records. The global \dns@_again@_means@_nonexist\ option can help with this
14877 problem, but it is heavy-handed because it is a global option.
14879 For this reason, there are two options, \srv@_fail@_domains\ and
14880 \mx@_fail@_domains\, that control what happens when a DNS lookup in a
14881 \%dnslookup%\ router results in a DNS failure or a `try again' response. If an
14882 attempt to look up an SRV or MX record causes one of these results, and the
14883 domain matches the relevant list, Exim behaves as if the DNS had responded `no
14884 such record'. In the case of an SRV lookup, this means that the router proceeds
14885 to look for MX records; in the case of an MX lookup, it proceeds to look for A
14886 or AAAA records, unless the domain matches \mx@_domains\, in which case routing
14891 .section Private options for dnslookup
14892 The private options for the \%dnslookup%\ router are as follows:
14895 .startconf dnslookup
14897 .index options||\%dnslookup%\ router
14898 .conf check@_secondary@_mx boolean false
14899 .index MX record||checking for secondary
14900 If this option is set, the router declines unless the local host is found in
14901 (and removed from) the list of hosts obtained by MX lookup. This can be used to
14902 process domains for which the local host is a secondary mail exchanger
14903 differently to other domains. The way in which Exim decides whether a host is
14904 the local host is described in section ~~SECTreclocipadd.
14906 .conf check@_srv string$**$ unset
14907 .index SRV record||enabling use of
14908 The \%dnslookup%\ router supports the use of SRV records (see RFC 2782) in
14909 addition to MX and address records. The support is disabled by default. To
14910 enable SRV support, set the \check@_srv\ option to the name of the service
14911 required. For example,
14915 looks for SRV records that refer to the normal smtp service. The option is
14916 expanded, so the service name can vary from message to message or address
14917 to address. This might be helpful if SRV records are being used for a
14918 submission service. If the expansion is forced to fail, the \check@_srv\
14919 option is ignored, and the router proceeds to look for MX records in the
14922 When the expansion succeeds, the router searches first for SRV records for
14923 the given service (it assumes TCP protocol). A single SRV record with a
14924 host name that consists of just a single dot indicates `no such service for
14925 this domain'; if this is encountered, the router declines. If other kinds of
14926 SRV record are found, they are used to construct a host list for delivery
14927 according to the rules of RFC 2782. MX records are not sought in this case.
14929 When no SRV records are found, MX records (and address records) are sought in
14930 the traditional way. In other words, SRV records take precedence over MX
14931 records, just as MX records take precedence over address records. Note that
14932 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
14933 defined it. It is apparently believed that MX records are sufficient for email
14934 and that SRV records should not be used for this purpose. However, SRV records
14935 have an additional `weight' feature which some people might find useful when
14936 trying to split an SMTP load between hosts of different power.
14939 See section ~~SECTprowitdnsloo above for a discussion of Exim's behaviour when
14940 there is a DNS lookup error.
14943 .conf mx@_domains "domain list$**$" unset
14944 .index MX record||required to exist
14945 .index SRV record||required to exist
14946 A domain that matches \mx@_domains\ is required to have either an MX or an SRV
14947 record in order to be recognised. (The name of this option could be improved.)
14948 For example, if all the mail hosts in \*fict.example*\ are known to have MX
14949 records, except for those in \*discworld.fict.example*\, you could use this
14952 mx_domains = ! *.discworld.fict.example : *.fict.example
14954 This specifies that messages addressed to a domain that matches the list but
14955 has no MX record should be bounced immediately instead of being routed using
14956 the address record.
14959 .conf mx@_fail@_domains "domain list$**$" unset
14960 If the DNS lookup for MX records for one of the domains in this list causes a
14961 DNS lookup error, Exim behaves as if no MX records were found. See section
14962 ~~SECTprowitdnsloo for more discussion.
14966 .conf qualify@_single boolean true
14967 .index DNS||resolver options
14968 .index DNS||qualifying single-component names
14969 When this option is true, the resolver option \\RES@_DEFNAMES\\ is set for DNS
14970 lookups. Typically, but not standardly, this causes the resolver to qualify
14971 single-component names with the default domain. For example, on a machine
14972 called \*dictionary.ref.example*\, the domain \*thesaurus*\ would be changed to
14973 \*thesaurus.ref.example*\ inside the resolver. For details of what your resolver
14974 actually does, consult your man pages for \*resolver*\ and \*resolv.conf*\.
14977 .conf rewrite@_headers boolean true
14978 .index rewriting||header lines
14979 .index header lines||rewriting
14980 If the domain name in the address that is being processed is not fully
14981 qualified, it may be expanded to its full form by a DNS lookup. For example, if
14982 an address is specified as \*dormouse@@teaparty*\, the domain might be
14983 expanded to \*teaparty.wonderland.fict.example*\. Domain expansion can also
14984 occur as a result of setting the \widen@_domains\ option. If \rewrite@_headers\
14985 is true, all occurrences of the abbreviated domain name in any ::Bcc::, ::Cc::,
14986 ::From::, ::Reply-to::, ::Sender::, and ::To:: header lines of the message are
14987 rewritten with the full domain name.
14989 This option should be turned off only when it is known that no message is
14990 ever going to be sent outside an environment where the abbreviation makes
14993 When an MX record is looked up in the DNS and matches a wildcard record, name
14994 servers normally return a record containing the name that has been looked up,
14995 making it impossible to detect whether a wildcard was present or not. However,
14996 some name servers have recently been seen to return the wildcard entry. If the
14997 name returned by a DNS lookup begins with an asterisk, it is not used for
15000 .conf same@_domain@_copy@_routing boolean false
15001 .index address||copying routing
15002 Addresses with the same domain are normally routed by the \%dnslookup%\ router
15003 to the same list of hosts. However, this cannot be presumed, because the router
15004 options and preconditions may refer to the local part of the address. By
15005 default, therefore, Exim routes each address in a message independently. DNS
15006 servers run caches, so repeated DNS lookups are not normally expensive, and in
15007 any case, personal messages rarely have more than a few recipients.
15009 If you are running mailing lists with large numbers of subscribers at the same
15010 domain, and you are using a \%dnslookup%\ router which is independent of the
15011 local part, you can set \same__domain__copy@_routing\ to bypass repeated DNS
15012 lookups for identical domains in one message. In this case, when \%dnslookup%\
15013 routes an address to a remote transport, any other unrouted addresses in the
15014 message that have the same domain are automatically given the same routing
15015 without processing them independently,
15016 provided the following conditions are met:
15018 No router that processed the address specified \headers@_add\ or
15021 The router did not change the address in any way, for example, by `widening'
15026 .conf search@_parents boolean false
15027 .index DNS||resolver options
15028 When this option is true, the resolver option \\RES@_DNSRCH\\ is set for DNS
15029 lookups. This is different from the \qualify@_single\ option in that it applies
15030 to domains containing dots. Typically, but not standardly, it causes the
15031 resolver to search for the name in the current domain and in parent domains.
15032 For example, on a machine in the \*fict.example*\ domain, if looking up
15033 \*teaparty.wonderland*\ failed, the resolver would try
15034 \*teaparty.wonderland.fict.example*\. For details of what your resolver
15035 actually does, consult your man pages for \*resolver*\ and \*resolv.conf*\.
15037 Setting this option true can cause problems in domains that have a wildcard MX
15038 record, because any domain that does not have its own MX record matches the
15043 .conf srv@_fail@_domains "domain list$**$" unset
15044 If the DNS lookup for SRV records for one of the domains in this list causes a
15045 DNS lookup error, Exim behaves as if no SRV records were found. See section
15046 ~~SECTprowitdnsloo for more discussion.
15050 .conf widen@_domains "string list" unset
15051 .index domain||partial, widening
15052 If a DNS lookup fails and this option is set, each of its strings in turn is
15053 added onto the end of the domain, and the lookup is tried again. For example,
15056 widen_domains = fict.example:ref.example
15058 is set and a lookup of \*klingon.dictionary*\ fails,
15059 \*klingon.dictionary.fict.example*\ is looked up, and if this fails,
15060 \*klingon.dictionary.ref.example*\ is tried. Note that the \qualify@_single\
15061 and \search@_parents\ options can cause some widening to be undertaken inside
15066 .section Effect of qualify@_single and search@_parents
15067 When a domain from an envelope recipient is changed by the resolver as a result
15068 of the \qualify@_single\ or \search@_parents\ options, Exim rewrites the
15069 corresponding address in the message's header lines unless \rewrite@_headers\
15070 is set false. Exim then re-routes the address, using the full domain.
15072 These two options affect only the DNS lookup that takes place inside the router
15073 for the domain of the address that is being routed. They do not affect lookups
15074 such as that implied by
15078 that may happen while processing a router precondition before the router is
15079 entered. No widening ever takes place for these lookups.
15093 . ============================================================================
15094 .chapter The ipliteral router
15095 .set runningfoot "ipliteral router"
15096 .index \%ipliteral%\ router
15097 .index domain literal||routing
15098 .index routers||\%ipliteral%\
15099 This router has no private options. Unless it is being used purely for
15100 verification (see \verify@_only\) a transport is required to be defined by the
15101 generic \transport\ option. The router accepts the address if its domain part
15102 takes the form of an RFC 2822 domain literal, that is, an IP address enclosed
15103 in square brackets. For example, this router handles the address
15107 by setting up delivery to the host with that IP address.
15109 If the IP address matches something in \ignore@_target@_hosts\, the router
15111 .index \self\ option||in \%ipliteral%\ router
15112 If an IP literal turns out to refer to the local host, the generic \self\
15113 option determines what happens.
15115 The RFCs require support for domain literals; however, their use is
15116 controversial in today's Internet. If you want to use this router, you must
15117 also set the main configuration option \allow@_domain@_literals\. Otherwise,
15118 Exim will not recognize the domain literal syntax in addresses.
15126 . ============================================================================
15127 .chapter The iplookup router
15128 .set runningfoot "iplookup router"
15129 .index \%iplookup%\ router
15130 .index routers||\%iplookup%\
15131 The \%iplookup%\ router was written to fulfil a specific requirement in
15132 Cambridge University (which in fact no longer exists). For this reason, it is
15133 not included in the binary of Exim by default. If you want to include it, you
15136 ROUTER_IPLOOKUP=yes
15138 in your \(Local/Makefile)\ configuration file.
15140 The \%iplookup%\ router routes an address by sending it over a TCP or UDP
15141 connection to one or more specific hosts. The host can then return the same or
15142 a different address -- in effect rewriting the recipient address in the
15143 message's envelope. The new address is then passed on to subsequent routers.
15146 If this process fails, the address can be passed on to
15147 other routers, or delivery can be deferred.
15149 Background, for those that are interested: We have an Oracle database of all
15150 Cambridge users, and one of the items of data it maintains for each user is
15151 where to send mail addressed to \*user@@cam.ac.uk*\. The MX records for
15152 \*cam.ac.uk*\ point to a central machine that has a large alias list that is
15153 abstracted from the database. Mail from outside is switched by this system, and
15154 originally internal mail was also done this way. However, this resulted in a
15155 fair number of messages travelling from some of our larger systems to the
15156 switch and back again. The Oracle machine now runs a UDP service that can be
15157 called by the \%iplookup%\ router in Exim to find out where \*user@@cam.ac.uk*\
15158 addresses really have to go; this saves passing through the central switch, and
15159 in many cases saves doing any remote delivery at all.
15161 Since \%iplookup%\ is just a rewriting router, a transport must not be
15164 .startconf iplookup
15165 .index options||\%iplookup%\ router
15167 .conf hosts string unset
15168 This option must be supplied. Its value is a colon-separated list of host
15169 names. The hosts are looked up using \*gethostbyname()*\
15170 (or \*getipnodebyname()*\ when available)
15171 and are tried in order until one responds to the query. If none respond, what
15172 happens is controlled by \optional\.
15174 .conf optional boolean false
15175 If \optional\ is true, if no response is obtained from any host, the address is
15176 passed to the next router, overriding \no@_more\. If \optional\ is false,
15177 delivery to the address is deferred.
15179 .conf port integer 0
15180 .index port||\%iplookup%\ router
15181 This option must be supplied. It specifies the port number for the TCP or UDP
15184 .conf protocol string "udp"
15185 This option can be set to `udp' or `tcp' to specify which of the two protocols
15188 .conf query string$**$ "$tt{@$local@_part@@@$domain @$local@_part@@@$domain}"
15189 This defines the content of the query that is sent to the remote hosts. The
15190 repetition serves as a way of checking that a response is to the correct query
15191 in the default case (see \response@_pattern\ below).
15193 .conf reroute string$**$ unset
15194 If this option is not set, the rerouted address is precisely the byte string
15195 returned by the remote host, up to the first white space, if any. If set, the
15196 string is expanded to form the rerouted address. It can include parts matched
15197 in the response by \response@_pattern\ by means of numeric variables such as
15198 \$1$\, \$2$\, etc. The variable \$0$\ refers to the entire input string,
15199 whether or not a pattern is in use. In all cases, the rerouted address must end
15200 up in the form \*local@_part@@domain*\.
15202 .conf response@_pattern string unset
15203 This option can be set to a regular expression that is applied to the string
15204 returned from the remote host. If the pattern does not match the response, the
15205 router declines. If \response@_pattern\ is not set, no checking of the response
15206 is done, unless the query was defaulted, in which case there is a check that
15207 the text returned after the first white space is the original address. This
15208 checks that the answer that has been received is in response to the correct
15209 question. For example, if the response is just a new domain, the following
15212 response_pattern = ^([^@]+)$
15213 reroute = $local_part@$1
15216 .conf timeout time 5s
15217 This specifies the amount of time to wait for a response from the remote
15218 machine. The same timeout is used for the \*connect()*\ function for a TCP
15219 call. It does not apply to UDP.
15230 . ============================================================================
15231 .chapter The manualroute router
15232 .set runningfoot "manualroute router"
15233 .index \%manualroute%\ router
15234 .index routers||\%manualroute%\
15235 .index domain||manually routing
15236 The \%manualroute%\ router is so-called because it provides a way of manually
15237 routing an address according to its domain. It is mainly used when you want to
15238 route addresses to remote hosts according to your own rules, bypassing the
15239 normal DNS routing that looks up MX records. However, \%manualroute%\ can also
15240 route to local transports, a facility that may be useful if you want to save
15241 messages for dial-in hosts in local files.
15243 The \%manualroute%\ router compares a list of domain patterns with the domain it
15244 is trying to route. If there is no match, the router declines. Each pattern has
15245 associated with it a list of hosts and some other optional data, which may
15246 include a transport. The combination of a pattern and its data is called a
15247 `routing rule'. For patterns that do not have an associated transport, the
15248 generic \transport\ option must specify a transport, unless the router is being
15249 used purely for verification (see \verify@_only\).
15251 In the case of verification, matching the domain pattern is sufficient for the
15252 router to accept the address. When actually routing an address for delivery,
15253 an address that matches a domain pattern is queued for the associated
15254 transport. If the transport is not a local one, a host list must be associated
15255 with the pattern; IP addresses are looked up for the hosts, and these are
15256 passed to the transport along with the mail address. For local transports, a
15257 host list is optional. If it is present, it is passed in \$host$\ as a single
15260 The list of routing rules can be provided as an inline string in \route@_list\,
15261 or the data can be obtained by looking up the domain in a file or database by
15262 setting \route@_data\. Only one of these settings may appear in any one
15263 instance of \%manualroute%\. The format of routing rules is described below,
15264 following the list of private options.
15266 .section Private options for manualroute
15267 .rset SECTprioptman "~~chapter.~~section"
15269 The private options for the \%manualroute%\ router are as follows:
15271 .startconf manualroute
15272 .index options||\%manualroute%\ router
15274 .conf host@_find@_failed string "freeze"
15275 This option controls what happens when \%manualroute%\ tries to find an IP
15276 address for a host, and the host does not exist. The option can be set to one
15285 The default assumes that this state is a serious configuration error. The
15286 difference between `pass' and `decline' is that the former forces the address
15287 to be passed to the next router (or the router defined by \pass@_router\),
15288 .index \more\ option
15289 overriding \no@_more\, whereas the latter passes the address to the next router
15290 only if \more\ is true.
15292 This option applies only to a definite `does not exist' state; if a host lookup
15293 gets a temporary error, delivery is deferred unless the generic
15294 \pass@_on@_timeout\ option is set.
15296 .conf hosts@_randomize boolean false
15297 .index randomized host list
15298 .index host||list of, randomized
15299 If this option is set, the order of the items in a host list in a routing rule
15300 is randomized each time the list is used, unless an option in the routing rule
15301 overrides (see below). Randomizing the order of a host list can be used to do
15302 crude load sharing. However, if more than one mail address is routed by the
15303 same router to the same host list, the host lists are considered to be the same
15304 (even though they may be randomized into different orders) for the purpose of
15305 deciding whether to batch the deliveries into a single SMTP transaction.
15307 When \hosts@_randomize\ is true, a host list may be split
15308 into groups whose order is separately randomized. This makes it possible to
15309 set up MX-like behaviour. The boundaries between groups are indicated by an
15310 item that is just \"+"\ in the host list. For example:
15312 route_list = * host1:host2:host3:+:host4:host5
15314 The order of the first three hosts and the order of the last two hosts is
15315 randomized for each use, but the first three always end up before the last two.
15316 If \hosts@_randomize\ is not set, a \"+"\ item in the list is ignored. If a
15317 randomized host list is passed to an \%smtp%\ transport that also has
15318 \hosts@_randomize set\, the list is not re-randomized.
15320 .conf route@_data string$**$ unset
15321 If this option is set, it must expand to yield the data part of a routing rule.
15322 Typically, the expansion string includes a lookup based on the domain. For
15325 route_data = ${lookup{$domain}dbm{/etc/routes}}
15327 If the expansion is forced to fail, or the result is an empty string, the
15328 router declines. Other kinds of expansion failure cause delivery to be
15331 .conf route@_list "string list, semicolon-separated" unset
15332 This string is a list of routing rules, in the form defined below. Note that,
15333 unlike most string lists, the items are separated by semicolons. This is so
15334 that they may contain colon-separated host lists.
15336 .conf same@_domain@_copy@_routing boolean false
15337 .index address||copying routing
15338 Addresses with the same domain are normally routed by the \%manualroute%\ router
15339 to the same list of hosts. However, this cannot be presumed, because the router
15340 options and preconditions may refer to the local part of the address. By
15341 default, therefore, Exim routes each address in a message independently. DNS
15342 servers run caches, so repeated DNS lookups are not normally expensive, and in
15343 any case, personal messages rarely have more than a few recipients.
15345 If you are running mailing lists with large numbers of subscribers at the same
15346 domain, and you are using a \%manualroute%\ router which is independent of the
15347 local part, you can set \same@_domain@_copy@_routing\ to bypass repeated DNS
15348 lookups for identical domains in one message. In this case, when \%manualroute%\
15349 routes an address to a remote transport, any other unrouted addresses in the
15350 message that have the same domain are automatically given the same routing
15351 without processing them independently. However, this is only done if
15352 \headers@_add\ and \headers@_remove\ are unset.
15357 .section Routing rules in route@_list
15358 The value of \route@_list\ is a string consisting of a sequence of routing
15359 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
15360 entered as two semicolons. Empty rules are ignored. The format of each rule is
15362 <<domain pattern>> <<list of hosts>> <<options>>
15364 The following example contains two rules, each with a simple domain pattern and
15368 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
15369 thes.ref.example mail-3.ref.example:mail-4.ref.example
15371 The three parts of a rule are separated by white space. The pattern and the
15372 list of hosts can be enclosed in quotes if necessary, and if they are, the
15373 usual quoting rules apply. Each rule in a \route@_list\ must start with a
15374 single domain pattern, which is the only mandatory item in the rule. The
15375 pattern is in the same format as one item in a domain list (see section
15377 except that it may not be the name of an interpolated file.
15378 That is, it may be wildcarded, or a regular expression, or a file or database
15379 lookup (with semicolons doubled, because of the use of semicolon as a separator
15380 in a \route@_list\).
15382 The rules in \route@_list\ are searched in order until one of the patterns
15383 matches the domain that is being routed. The list of hosts and then options are
15384 then used as described below. If there is no match, the router declines. When
15385 \route@_list\ is set, \route@_data\ must not be set.
15388 .section Routing rules in route@_data
15389 The use of \route@_list\ is convenient when there are only a small number of
15390 routing rules. For larger numbers, it is easier to use a file or database to
15391 hold the routing information, and use the \route@_data\ option instead.
15392 The value of \route@_data\ is a list of hosts, followed by (optional) options.
15393 Most commonly, \route@_data\ is set as a string that contains an
15394 expansion lookup. For example, suppose we place two routing rules in a file
15397 dict.ref.example: mail-1.ref.example:mail-2.ref.example
15398 thes.ref.example: mail-3.ref.example:mail-4.ref.example
15400 This data can be accessed by setting
15402 route_data = ${lookup{$domain}lsearch{/the/file/name}}
15404 Failure of the lookup results in an empty string, causing the router to
15405 decline. However, you do not have to use a lookup in \route@_data\. The only
15406 requirement is that the result of expanding the string is a list of hosts,
15407 possibly followed by options, separated by white space. The list of hosts must
15408 be enclosed in quotes if it contains white space.
15412 .section Format of the list of hosts
15413 A list of hosts, whether obtained via \route@_data\ or \route@_list\, is always
15414 separately expanded before use. If the expansion fails, the router declines.
15415 The result of the expansion must be a colon-separated list of names and/or
15416 IP addresses. IP addresses are not enclosed in brackets.
15418 If the list of hosts was obtained from a \route@_list\ item, the following
15419 variables are set during its expansion:
15420 .index numerical variables (\$1$\, \$2$\, etc)||in \%manualroute%\ router
15422 If the domain was matched against a regular expression, the numeric variables
15423 \$1$\, \$2$\, etc. may be set.
15425 \$0$\ is always set to the entire domain.
15427 \$1$\ is also set when partial matching is done in a file lookup.
15430 If the pattern that matched the domain was a lookup item, the data that was
15431 looked up is available in the expansion variable \$value$\.
15435 .section How the list of hosts is used
15436 When an address is routed to an \%smtp%\ transport by \%manualroute%\, each of
15437 the hosts is tried, in the order specified, when carrying out the SMTP
15438 delivery. However, the order can be changed by setting the \hosts@_randomize\
15439 option, either on the router (see section ~~SECTprioptman above), or on the
15442 Hosts may be listed by name or by IP address. An unadorned name in the list of
15443 hosts is interpreted as a host name. A name that is followed by \"/MX"\ is
15444 interpreted as an indirection to a sublist of hosts obtained by looking up MX
15445 records in the DNS. For example:
15447 route_list = * x.y.z:p.q.r/MX:e.f.g
15449 If the \hosts@_randomize\ option is set, the order of the items in the list is
15450 randomized before any lookups are done. Exim then scans the list; for any name
15451 that is not followed by \"/MX"\ it looks up an IP address. If this turns out to
15452 be an interface on the local host and the item is not the first in the list,
15453 Exim discards it and any subsequent items. If it is the first item, what
15454 happens is controlled by the
15455 .index \self\ option||in \%manualroute%\ router
15456 \self\ option of the router.
15458 A name on the list that is followed by \"/MX"\ is replaced with the list of
15459 hosts obtained by looking up MX records for the name. This is always a DNS
15460 lookup; the \bydns\ and \byname\ options (see section ~~SECThowoptused below)
15461 are not relevant here. The order of these hosts is determined by the preference
15462 values in the MX records, according to the usual rules. Because randomizing
15463 happens before the MX lookup, it does not affect the order that is defined by
15466 If the local host is present in the sublist obtained from MX records, but is
15467 not the most preferred host in that list, it and any equally or less
15468 preferred hosts are removed before the sublist is inserted into the main list.
15470 If the local host is the most preferred host in the MX list, what happens
15471 depends on where in the original list of hosts the \"/MX"\ item appears. If it
15472 is not the first item (that is, there are previous hosts in the main list),
15473 Exim discards this name and any subsequent items in the main list.
15475 If the MX item is first in the list of hosts, and the local host is the
15476 most preferred host, what happens is controlled by the \self\ option of the
15479 DNS failures when lookup up the MX records are treated in the same way as DNS
15480 failures when looking up IP addresses: \pass@_on@_timeout\ and
15481 \host@_find@_failed\ are used when relevant.
15483 The generic \ignore@_target@_hosts\ option applies to all hosts in the list,
15484 whether obtained from an MX lookup or not.
15487 .section How the options are used
15488 .rset SECThowoptused "~~chapter.~~section"
15489 The options are a sequence of words; in practice no more than three are ever
15490 present. One of the words can be the name of a transport; this overrides the
15491 \transport\ option on the router for this particular routing rule only. The
15492 other words (if present) control randomization of the list of hosts on a
15493 per-rule basis, and how the IP addresses of the hosts are to be found when
15494 routing to a remote transport. These options are as follows:
15496 \randomize\: randomize the order of the hosts in this list, overriding the
15497 setting of \hosts@_randomize\ for this routing rule only.
15499 \no@_randomize\: do not randomize the order of the hosts in this list,
15500 overriding the setting of \hosts@_randomize\ for this routing rule only.
15502 \byname\: use \*getipnodebyname()*\ (\*gethostbyname()*\ on older systems) to
15503 find IP addresses. This function may ultimately cause a DNS lookup, but it may
15504 also look in \(/etc/hosts)\ or other sources of information.
15506 \bydns\: look up address records for the hosts directly in the DNS; fail if
15507 no address records are found. If there is a temporary DNS error (such as a
15508 timeout), delivery is deferred.
15512 route_list = domain1 host1:host2:host3 randomize bydns;\
15513 domain2 host4:host5
15515 If neither \byname\ nor \bydns\ is given, Exim behaves as follows: First, a DNS
15516 lookup is done. If this yields anything other than \\HOST@_NOT@_FOUND\\, that
15517 result is used. Otherwise, Exim goes on to try a call to \*getipnodebyname()*\
15518 or \*gethostbyname()*\, and the result of the lookup is the result of that
15521 \**Warning**\: It has been discovered that on some systems, if a DNS lookup
15522 called via \*getipnodebyname()*\ times out, \\HOST@_NOT@_FOUND\\ is returned
15523 instead of \\TRY@_AGAIN\\. That is why the default action is to try a DNS
15524 lookup first. Only if that gives a definite `no such host' is the local
15529 If no IP address for a host can be found, what happens is controlled by the
15530 \host@_find@_failed\ option.
15532 When an address is routed to a local transport, IP addresses are not looked up.
15533 The host list is passed to the transport in the \$host$\ variable.
15536 .section Manualroute examples
15537 In some of the examples that follow, the presence of the \remote@_smtp\
15538 transport, as defined in the default configuration file, is assumed:
15541 .index smart host||example router
15542 The \%manualroute%\ router can be used to forward all external mail to a
15543 \*smart host*\. If you have set up, in the main part of the configuration, a
15544 named domain list that contains your local domains, for example,
15546 domainlist local_domains = my.domain.example
15548 you can arrange for all other domains to be routed to a smart host by making
15549 your first router something like this:
15552 driver = manualroute
15553 domains = !+local_domains
15554 transport = remote_smtp
15555 route_list = * smarthost.ref.example
15557 This causes all non-local addresses to be sent to the single host
15558 \*smarthost.ref.example*\. If a colon-separated list of smart hosts is given,
15559 they are tried in order
15560 (but you can use \hosts@_randomize\ to vary the order each time).
15561 Another way of configuring the same thing is this:
15564 driver = manualroute
15565 transport = remote_smtp
15566 route_list = !+local_domains smarthost.ref.example
15568 There is no difference in behaviour between these two routers as they stand.
15569 However, they behave differently if \no@_more\ is added to them. In the first
15570 example, the router is skipped if the domain does not match the \domains\
15571 precondition; the following router is always tried. If the router runs, it
15572 always matches the domain and so can never decline. Therefore, \no@_more\ would
15573 have no effect. In the second case, the router is never skipped; it always
15574 runs. However, if it doesn't match the domain, it declines. In this case
15575 \no@_more\ would prevent subsequent routers from running.
15578 .index mail hub example
15579 A \*mail hub*\ is a host which receives mail for a number of domains via MX
15580 records in the DNS and delivers it via its own private routing mechanism. Often
15581 the final destinations are behind a firewall, with the mail hub being the one
15582 machine that can connect to machines both inside and outside the firewall. The
15583 \%manualroute%\ router is usually used on a mail hub to route incoming messages
15584 to the correct hosts. For a small number of domains, the routing can be inline,
15585 using the \route@_list\ option, but for a larger number a file or database
15586 lookup is easier to manage.
15588 If the domain names are in fact the names of the machines to which the mail is
15589 to be sent by the mail hub, the configuration can be quite simple. For
15593 driver = manualroute
15594 transport = remote_smtp
15595 route_list = *.rhodes.tvs.example $domain
15597 This configuration routes domains that match \"*.rhodes.tvs.example"\ to hosts
15598 whose names are the same as the mail domains. A similar approach can be taken
15599 if the host name can be obtained from the domain name by a string manipulation
15600 that the expansion facilities can handle. Otherwise, a lookup based on the
15601 domain can be used to find the host:
15604 driver = manualroute
15605 transport = remote_smtp
15606 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
15608 The result of the lookup must be the name or IP address of the host (or
15609 hosts) to which the address is to be routed. If the lookup fails, the route
15610 data is empty, causing the router to decline. The address then passes to the
15614 .index batched SMTP output example
15615 .index SMTP||batched outgoing, example
15616 You can use \%manualroute%\ to deliver messages to pipes or files in batched
15617 SMTP format for onward transportation by some other means. This is one way of
15618 storing mail for a dial-up host when it is not connected. The route list entry
15619 can be as simple as a single domain name in a configuration like this:
15622 driver = manualroute
15623 transport = batchsmtp_appendfile
15624 route_list = saved.domain.example
15626 though often a pattern is used to pick up more than one domain. If there are
15627 several domains or groups of domains with different transport requirements,
15628 different transports can be listed in the routing information:
15631 driver = manualroute
15633 *.saved.domain1.example $domain batch_appendfile; \
15634 *.saved.domain2.example \
15635 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
15638 The first of these just passes the domain in the \$host$\ variable, which
15639 doesn't achieve much (since it is also in \$domain$\), but the second does a
15640 file lookup to find a value to pass, causing the router to decline to handle
15641 the address if the lookup fails.
15643 .index UUCP||example of router for
15644 Routing mail directly to UUCP software is a specific case of the use of
15645 \%manualroute%\ in a gateway to another mail environment. This is an example of
15646 one way it can be done:
15652 command = /usr/local/bin/uux -r - \
15653 ${substr_-5:$host}!rmail ${local_part}
15654 return_fail_output = true
15660 driver = manualroute
15662 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
15664 The file \(/usr/local/exim/uucphosts)\ contains entries like
15666 darksite.ethereal.example: darksite.UUCP
15668 It can be set up more simply without adding and removing `.UUCP' but this way
15669 makes clear the distinction between the domain name
15670 \*darksite.ethereal.example*\ and the UUCP host name \*darksite*\.
15682 . ============================================================================
15683 .chapter The queryprogram router
15684 .set runningfoot "queryprogram router"
15685 .rset CHAPdriverlast "~~chapter"
15686 .index \%queryprogram%\ router
15687 .index routers||\%queryprogram%\
15688 .index routing||by external program
15689 The \%queryprogram%\ router routes an address by running an external command and
15690 acting on its output. This is an expensive way to route, and is intended mainly
15691 for use in lightly-loaded systems, or for performing experiments. However, if
15692 it is possible to use the precondition options (\domains\, \local@_parts\,
15693 etc) to skip this router for most addresses, it could sensibly be used in
15694 special cases, even on a busy host. There are the following private options:
15696 .startconf queryprogram
15697 .index options||\%queryprogram%\ router
15698 .conf command string$**$ unset
15699 This option must be set. It specifies the command that is to be run. The
15700 command is split up into a command name and arguments, and then each is
15701 expanded separately (exactly as for a \%pipe%\ transport, described in chapter
15702 ~~CHAPpipetransport).
15704 .conf command@_group string unset
15705 .index gid (group id)||in \%queryprogram%\ router
15706 This option specifies a gid to be set when running the command. It must be set
15707 if \command@_user\ specifies a numerical uid. If it begins with a digit, it is
15708 interpreted as the numerical value of the gid. Otherwise it is looked up using
15711 .conf command@_user string unset
15712 .index uid (user id)||for \%queryprogram%\
15713 This option must be set. It specifies the uid which is set when running the
15714 command. If it begins with a digit it is interpreted as the numerical value of
15715 the uid. Otherwise, it is looked up using \*getpwnam()*\ to obtain a value for
15716 the uid and, if \command@_group\ is not set, a value for the gid also.
15718 .conf current@_directory string /
15719 This option specifies an absolute path which is made the current directory
15720 before running the command.
15722 .conf timeout time 1h
15723 If the command does not complete within the timeout period, its process group
15724 is killed and the message is frozen. A value of zero time specifies no
15729 The standard output of the command is connected to a pipe, which is read when
15730 the command terminates. It should consist of a single line of output,
15731 containing up to five fields, separated by white space.
15733 The maximum length of the line is 1023 characters. Longer lines are silently
15736 The first field is one of the following words (case-insensitive):
15738 \*Accept*\: routing succeeded; the remaining fields specify what to do (see
15741 \*Decline*\: the router declines; pass the address to the next router, unless
15744 \*Fail*\: routing failed; do not pass the address to any more routers. Any
15745 subsequent text on the line is an error message. If the router is run as part
15746 of address verification during an incoming SMTP message, the message is
15747 included in the SMTP response.
15749 \*Defer*\: routing could not be completed at this time; try again later. Any
15750 subsequent text on the line is an error message which is logged. It is not
15751 included in any SMTP response.
15753 \*Freeze*\: the same as \*defer*\, except that the message is frozen.
15755 \*Pass*\: pass the address to the next router (or the router specified by
15756 \pass@_router\), overriding \no@_more\.
15758 \*Redirect*\: the message is redirected. The remainder of the line is a list of
15759 new addresses, which are routed independently, starting with the first router,
15760 or the router specified by \redirect@_router\, if set.
15762 When the first word is \*accept*\, the remainder of the line consists of a
15763 number of keyed data values, as follows (split into two lines here, to fit on
15766 ACCEPT TRANSPORT=<<transport>> HOSTS=<<list of hosts>>
15767 LOOKUP=byname|bydns DATA=<<text>>
15769 The data items can be given in any order, and all are optional. If no transport
15770 is included, the transport specified by the generic \transport\ option is used.
15771 The list of hosts and the lookup type are needed only if the transport is an
15772 \%smtp%\ transport that does not itself supply a list of hosts.
15774 The format of the list of hosts is the same as for the \%manualroute%\ router.
15775 As well as host names and IP addresses, it may contain names followed by
15776 \"/MX"\ to specify sublists of hosts that are obtained by looking up MX
15779 If the lookup type is not specified, Exim behaves as follows when trying to
15780 find an IP address for each host: First, a DNS lookup is done. If this yields
15781 anything other than \\HOST@_NOT@_FOUND\\, that result is used. Otherwise, Exim
15782 goes on to try a call to \*getipnodebyname()*\ or \*gethostbyname()*\, and the
15783 result of the lookup is the result of that call.
15785 If the DATA field is set, its value is placed in the \$address@_data$\
15786 variable. For example, this return line
15788 accept hosts=x1.y.example:x2.y.example data="rule1"
15790 routes the address to the default transport, passing a list of two hosts. When
15791 the transport runs, the string `rule1' is in \$address@_data$\.
15799 . ============================================================================
15800 .chapter The redirect router
15801 .set runningfoot "redirect router"
15802 .rset CHAPredirect "~~chapter"
15803 .index \%redirect%\ router
15804 .index routers||\%redirect%\
15805 .index alias file||in a \%redirect%\ router
15806 .index address redirection||\%redirect%\ router
15807 The \%redirect%\ router handles several kinds of address redirection. Its most
15808 common uses are for resolving local part aliases from a central alias file
15809 (usually called \(/etc/aliases)\) and for handling users' personal \(.forward)\
15810 files, but it has many other potential uses. The incoming address can be
15811 redirected in several different ways:
15813 It can be replaced by one or more new addresses which are themselves routed
15816 It can be routed to be delivered to a given file or directory.
15818 It can be routed to be delivered to a specified pipe command.
15820 It can cause an automatic reply to be generated.
15822 It can be forced to fail, with a custom error message.
15824 It can be temporarily deferred.
15826 It can be discarded.
15828 The generic \transport\ option must not be set for \%redirect%\ routers.
15829 However, there are some private options which define transports for delivery to
15830 files and pipes, and for generating autoreplies. See the \file@_transport\,
15831 \pipe@_transport\ and \reply@_transport\ descriptions below.
15834 .section Redirection data
15835 The router operates by interpreting a text string which it obtains either by
15836 expanding the contents of the \data\ option, or by reading the entire contents
15837 of a file whose name is given in the \file\ option. These two options are
15838 mutually exclusive. The first is commonly used for handling system aliases, in
15839 a configuration like this:
15843 data = ${lookup{$local_part}lsearch{/etc/aliases}}
15845 If the lookup fails, the expanded string in this example is empty. When the
15846 expansion of \data\ results in an empty string, the router declines. A forced
15847 expansion failure also causes the router to decline; other expansion failures
15848 cause delivery to be deferred.
15850 A configuration using \file\ is commonly used for handling users' \(.forward)\
15856 file = $home/.forward
15859 If the file does not exist, or causes no action to be taken (for example, it is
15860 empty or consists only of comments), the router declines. \**Warning**\: This
15861 is not the case when the file contains syntactically valid items that happen to
15862 yield empty addresses, for example, items containing only RFC 2822 address
15866 .section Forward files and address verification
15867 .index address redirection||while verifying
15868 It is usual to set \no@_verify\ on \%redirect%\ routers which handle users'
15869 \(.forward)\ files, as in the example above. There are two reasons for this:
15871 When Exim is receiving an incoming SMTP message from a remote host, it is
15872 running under the Exim uid, not as root.
15873 No additional groups are set up, even if the Exim uid is a member of other
15874 groups (that is, the \*initgroups()*\ function is not run).
15875 Exim is unable to change uid to read the file as the user, and it may not be
15876 able to read it as the Exim user. So in practice the router may not be able to
15879 However, even when the router can operate, the existence of a \(.forward)\ file
15880 is unimportant when verifying an address. What should be checked is whether the
15881 local part is a valid user name or not. Cutting out the redirection processing
15882 saves some resources.
15888 .section Interpreting redirection data
15889 .index Sieve filter||specifying in redirection data
15890 .index filter||specifying in redirection data
15891 The contents of the data string, whether obtained from \data\ or \file\, can be
15892 interpreted in two different ways:
15894 If the \allow@_filter\ option is set true, and the data begins with the text
15895 `@#Exim filter' or `@#Sieve filter', it is interpreted as a list of
15896 \*filtering*\ instructions in the form of an Exim or Sieve filter file,
15897 respectively. Details of the syntax and semantics of filter files are described
15898 in a separate document entitled \*Exim's interfaces to mail filtering*\; this
15899 document is intended for use by end users.
15901 Otherwise, the data must be a comma-separated list of redirection items, as
15902 described in the next section.
15904 When a message is redirected to a file (a `mail folder'), the file name given
15905 in a non-filter redirection list must always be an absolute path. A filter may
15906 generate a relative path -- how this is handled depends on the transport's
15907 configuration. See section ~~SECTfildiropt for a discussion of this issue for
15908 the \%appendfile%\ transport.
15911 .section Items in a non-filter redirection list
15912 .rset SECTitenonfilred "~~chapter.~~section"
15913 .index address redirection||non-filter list items
15914 When the redirection data is not an Exim or Sieve filter, for example, if it
15915 comes from a conventional alias or forward file, it consists of a list of
15916 addresses, file names, pipe commands, or certain special items (see section
15917 ~~SECTspecitredli below). The special items can be individually enabled or
15918 disabled by means of options whose names begin with \allow@_\ or \forbid@_\,
15919 depending on their default values. The items in the list are separated by
15920 commas or newlines.
15921 If a comma is required in an item, the entire item must be enclosed in double
15924 Lines starting with a @# character are comments, and are ignored, and @# may
15925 also appear following a comma, in which case everything between the @# and the
15926 next newline character is ignored.
15928 If an item is entirely enclosed in double quotes, these are removed. Otherwise
15929 double quotes are retained because some forms of mail address require their use
15930 (but never to enclose the entire address). In the following description, `item'
15931 refers to what remains after any surrounding double quotes have been removed.
15933 \**Warning**\: If you use an Exim expansion to construct a redirection address,
15934 and the expansion contains a reference to \$local@_part$\, you should make use
15935 of the \quote\ expansion operator, in case the local part contains special
15936 characters. For example, to redirect all mail for the domain
15937 \*obsolete.example*\, retaining the existing local part, you could use this
15940 data = ${quote:$local_part}@newdomain.example
15944 .section Redirecting to a local mailbox
15945 .rset SECTredlocmai "~~chapter.~~section"
15946 .index routing||loops in
15947 .index loop||while routing, avoidance of
15948 .index address redirection||to local mailbox
15949 A redirection item may safely be the same as the address currently under
15950 consideration. This does not cause a routing loop, because a router is
15951 automatically skipped if any ancestor of the address that is being processed
15952 is the same as the current address and was processed by the current router.
15953 Such an address is therefore passed to the following routers, so it is handled
15954 as if there were no redirection. When making this loop-avoidance test, the
15955 complete local part, including any prefix or suffix, is used.
15957 .index address redirection||local part without domain
15958 Specifying the same local part without a domain is a common usage in personal
15959 filter files when the user wants to have messages delivered to the local
15960 mailbox and also forwarded elsewhere. For example, the user whose login is
15961 \*cleo*\ might have a \(.forward)\ file containing this:
15963 cleo, cleopatra@egypt.example
15965 .index backslash in alias file
15966 .index alias file||backslash in
15967 For compatibility with other MTAs, such unqualified local parts may be
15968 preceeded by `@\', but this is not a requirement for loop prevention. However,
15969 it does make a difference if more than one domain is being handled
15972 If an item begins with `@\' and the rest of the item parses as a valid RFC 2822
15973 address that does not include a domain, the item is qualified using the domain
15974 of the incoming address. In the absence of a leading `@\', unqualified
15975 addresses are qualified using the value in \qualify@_recipient\, but you can
15976 force the incoming domain to be used by setting \qualify__preserve@_domain\.
15978 Care must be taken if there are alias names for local users.
15979 Consider an MTA handling a single local domain where the system alias file
15984 Now suppose that Sam (whose login id is \*spqr*\) wants to save copies of
15985 messages in the local mailbox, and also forward copies elsewhere. He creates
15988 Sam.Reman, spqr@reme.elsewhere.example
15990 With these settings, an incoming message addressed to \*Sam.Reman*\ fails. The
15991 \%redirect%\ router for system aliases does not process \*Sam.Reman*\ the
15992 second time round, because it has previously routed it,
15993 and the following routers presumably cannot handle the alias. The forward file
15994 should really contain
15996 spqr, spqr@reme.elsewhere.example
15998 but because this is such a common error, the \check@_ancestor\ option (see
15999 below) exists to provide a way to get round it. This is normally set on a
16000 \%redirect%\ router that is handling users' \(.forward)\ files.
16003 .section Special items in redirection lists
16004 .rset SECTspecitredli "~~chapter.~~section"
16005 In addition to addresses, the following types of item may appear in redirection
16006 lists (that is, in non-filter redirection data):
16009 .index pipe||in redirection list
16010 .index address redirection||to pipe
16011 An item is treated as a pipe command if it begins with `|' and does not parse
16012 as a valid RFC 2822 address that includes a domain. A transport for running the
16013 command must be specified by the \pipe@_transport\ option.
16014 Normally, either the router or the transport specifies a user and a group under
16015 which to run the delivery. The default is to use the Exim user and group.
16017 Single or double quotes can be used for enclosing the individual arguments of
16018 the pipe command; no interpretation of escapes is done for single quotes. If
16019 the command contains a comma character, it is necessary to put the whole item
16020 in double quotes, for example:
16022 "|/some/command ready,steady,go"
16024 since items in redirection lists are terminated by commas. Do not, however,
16025 quote just the command. An item such as
16027 |"/some/command ready,steady,go"
16029 is interpreted as a pipe with a rather strange command name, and no arguments.
16031 .index file||in redirection list
16032 .index address redirection||to file
16033 An item is interpreted as a path name if it begins with `/' and does not parse
16034 as a valid RFC 2822 address that includes a domain. For example,
16036 /home/world/minbari
16038 is treated as a file name, but
16040 /s=molari/o=babylon/@x400gate.way
16042 is treated as an address. For a file name, a transport must be specified using
16043 the \file@_transport\ option. However, if the generated path name ends with a
16044 forward slash character, it is interpreted as a directory name rather than a
16045 file name, and \directory@_transport\ is used instead.
16047 Normally, either the router or the transport specifies a user and a group under
16048 which to run the delivery. The default is to use the Exim user and group.
16049 .index \(/dev/null)\
16050 However, if a redirection item is the path \(/dev/null)\, delivery to it is
16051 bypassed at a high level, and the log entry shows `$*$$*$bypassed$*$$*$'
16052 instead of a transport name. In this case the user and group are not used.
16054 .index included address list
16055 .index address redirection||included external list
16056 If an item is of the form
16058 :include:<<path name>>
16060 a list of further items is taken from the given file and included at that
16062 \**Note**\: such a file can not be a filter file; it is just an out-of-line
16063 addition to the list.
16064 The items in the included list are separated by commas or newlines and are not
16065 subject to expansion. If this is the first item in an alias list in an
16066 \%lsearch%\ file, a colon must be used to terminate the alias name. This
16067 example is incorrect:
16069 list1 :include:/opt/lists/list1
16071 It must be given as
16073 list1: :include:/opt/lists/list1
16076 .index address redirection||to black hole
16077 Sometimes you want to throw away mail to a particular local part. Making the
16078 \data\ option expand to an empty string does not work, because that causes the
16079 router to decline. Instead, the alias item
16081 .index abandoning mail
16085 can be used. It does what its name implies. No delivery is done, and no error
16086 message is generated. This has the same effect as specifing \(/dev/null)\, but
16087 can be independently disabled.
16089 \**Warning**\: If \":blackhole:"\ appears anywhere in a redirection list, no
16090 delivery is done for the original local part, even if other redirection items
16091 are present. If you are generating a multi-item list (for example, by reading a
16092 database) and need the ability to provide a no-op item, you must use
16096 .index delivery||forcing failure
16097 .index delivery||forcing deferral
16098 .index failing delivery||forcing
16099 .index deferred delivery, forcing
16100 .index customizing||failure message
16101 An attempt to deliver a particular address can be deferred or forced to fail by
16102 redirection items of the form
16108 respectively. When a redirection list contains such an item, it applies to the
16109 entire redirection; any other items in the list are ignored (:::blackhole:: is
16110 different). Any text following :::fail:: or :::defer:: is placed in the error
16111 text associated with the failure. For example, an alias file might contain:
16113 X.Employee: :fail: Gone away, no forwarding address
16115 In the case of an address that is being verified from an ACL or as the subject
16116 of a \\VRFY\\ command, the text is included in the SMTP error response by
16117 default. In an ACL, an explicitly provided message overrides the default, but
16118 the default message is available in the variable \$acl@_verify@_message$\ and
16119 can therefore be included in a custom message if this is desired. Exim sends a
16120 451 SMTP code for a :::defer::, and 550 for :::fail::. In non-SMTP cases the
16121 text is included in the error message that Exim generates.
16125 Normally the error text is the rest of the redirection list -- a comma does not
16126 terminate it -- but a newline does act as a terminator. Newlines are not
16127 normally present in alias expansions. In \%lsearch%\ lookups they are removed as
16128 part of the continuation process, but they may exist in other kinds of lookup
16129 and in :::include:: files.
16131 During routing for message delivery (as opposed to verification), a redirection
16132 containing :::fail:: causes an immediate failure of the incoming address,
16133 whereas :::defer:: causes the message to remain on the queue so that a
16134 subsequent delivery attempt can happen at a later time. If an address is
16135 deferred for too long, it will ultimately fail, because the normal retry
16138 .index alias file||exception to default
16139 Sometimes it is useful to use a single-key search type with a default (see
16140 chapter ~~CHAPfdlookup) to look up aliases. However, there may be a need for
16141 exceptions to the default. These can be handled by aliasing them to
16145 This differs from :::fail:: in that it causes the \%redirect%\ router to decline,
16146 whereas :::fail:: forces routing to fail. A lookup which results in an empty
16147 redirection list has the same effect.
16150 .section Duplicate addresses
16151 .index duplicate addresses
16152 .index address||duplicate, discarding
16153 .index pipe||duplicated
16154 Exim removes duplicate addresses from the list to which it is delivering, so as
16155 to deliver just one copy to each address. This does not apply to deliveries
16156 routed to pipes by different immediate parent addresses, but an indirect
16157 aliasing scheme of the type
16159 pipe: |/some/command $local_part
16163 does not work with a message that is addressed to both local parts, because
16164 when the second is aliased to the intermediate local part `pipe' it gets
16165 discarded as being the same as a previously handled address. However, a scheme
16168 localpart1: |/some/command $local_part
16169 localpart2: |/some/command $local_part
16171 does result in two different pipe deliveries, because the immediate parents of
16172 the pipes are distinct.
16175 .section Repeated redirection expansion
16176 .index repeated redirection expansion
16177 .index address redirection||repeated for each delivery attempt
16178 When a message cannot be delivered to all of its recipients immediately,
16179 leading to two or more delivery attempts, redirection expansion is carried out
16180 afresh each time for those addresses whose children were not all previously
16181 delivered. If redirection is being used as a mailing list, this can lead to new
16182 members of the list receiving copies of old messages. The \one@_time\ option
16183 can be used to avoid this.
16185 .section Errors in redirection lists
16186 .index address redirection||errors
16187 If \skip@_syntax@_errors\ is set, a malformed address that causes a parsing
16188 error is skipped, and an entry is written to the main log. This may be useful
16189 for mailing lists that are automatically managed. Otherwise, if an error is
16190 detected while generating the list of new addresses, the original address is
16191 deferred. See also \syntax@_errors@_to\.
16194 .section Private options for the redirect router
16196 The private options for the \%redirect%\ router are as follows:
16198 .startconf redirect
16199 .index options||\%redirect%\ router
16201 .conf allow@_defer boolean false
16202 Setting this option allows the use of :::defer:: in non-filter redirection
16204 or the \defer\ command in an Exim filter file.
16206 .conf allow@_fail boolean false
16207 .index failing delivery||from filter
16208 If this option is true, the :::fail:: item can be used in a redirection list,
16209 and the \fail\ command may be used in a filter file.
16211 .conf allow@_filter boolean false
16212 .index filter||enabling use of
16213 .index Sieve filter||enabling use of
16214 Setting this option allows Exim to interpret redirection data that starts with
16215 `@#Exim filter' or `@#Sieve filter' as a set of filtering instructions. There
16216 are some features of Exim filter files that some administrators may wish to
16217 lock out; see the \forbid@_filter@_xxx\ options below.
16219 It is also possible to lock out Exim filters or Sieve filters while allowing
16220 the other type; see \forbid@_exim@_filter\ and \forbid@_sieve@_filter\.
16223 The filter is run using the uid and gid set by the generic \user\ and \group\
16224 options. These take their defaults from the password data if
16225 \check@_local@_user\ is set, so in the normal case of users' personal filter
16226 files, the filter is run as the relevant user. When \allow@_filter\ is set
16227 true, Exim insists that either \check@_local@_user\ or \user\ is set.
16230 .conf allow@_freeze boolean false
16231 .index freezing messages||allowing in filter
16232 Setting this option allows the use of the \freeze\ command in an Exim filter.
16233 This command is more normally encountered in system filters, and is disabled by
16234 default for redirection filters because it isn't something you usually want to
16235 let ordinary users do.
16238 .conf check@_ancestor boolean false
16239 This option is concerned with handling generated addresses that are the same
16240 as some address in the list of redirection ancestors of the current address.
16241 Although it is turned off by default in the code, it is set in the default
16242 configuration file for handling users' \(.forward)\ files. It is recommended
16243 for this use of the \%redirect%\ router.
16245 When \check@_ancestor\ is set, if a generated address (including the domain) is
16246 the same as any ancestor of the current address, it is replaced by a copy of
16247 the current address. This helps in the case where local part A is aliased to B,
16248 and B has a \(.forward)\ file pointing back to A. For example, within a single
16249 domain, the local part `Joe.Bloggs' is aliased to `jb' and \(@~jb/.forward)\
16252 @\Joe.Bloggs, <<other item(s)>>
16254 Without the \check@_ancestor\ setting, either local part (`jb' or `joe.bloggs')
16255 gets processed once by each router and so ends up as it was originally. If `jb'
16256 is the real mailbox name, mail to `jb' gets delivered (having been turned into
16257 `joe.bloggs' by the \(.forward)\ file and back to `jb' by the alias), but mail
16258 to `joe.bloggs' fails. Setting \check@_ancestor\ on the \%redirect%\ router that
16259 handles the \(.forward)\ file prevents it from turning `jb' back into
16260 `joe.bloggs' when that was the original address. See also the \repeat@_use\
16263 .conf check@_group boolean "see below"
16264 When the \file\ option is used, the group owner of the file is checked only
16265 when this option is set. The permitted groups are those listed in the
16266 \owngroups\ option, together with the user's default group if
16267 \check@_local@_user\ is set. If the file has the wrong group, routing is
16268 deferred. The default setting for this option is true if \check@_local@_user\
16269 is set and the \modemask\ option permits the group write bit, or if the
16270 \owngroups\ option is set. Otherwise it is false, and no group check occurs.
16273 .conf check@_owner boolean "see below"
16274 When the \file\ option is used, the owner of the file is checked only when this
16275 option is set. If \check@_local@_user\ is set, the local user is permitted;
16276 otherwise the owner must be one of those listed in the \owners\ option. The
16277 default value for this option is true if \check@_local@_user\ or \owners\ is
16278 set. Otherwise the default is false, and no owner check occurs.
16280 .conf data string$**$ unset
16281 This option is mutually exclusive with \file\. One or other of them must be
16282 set, but not both. The contents of \data\ are expanded, and then used as the
16283 list of forwarding items, or as a set of filtering instructions. If the
16284 expansion is forced to fail, or the result is an empty string or a string that
16285 has no effect (consists entirely of comments), the router declines.
16287 When filtering instructions are used, the string must begin with `@#Exim
16288 filter', and all comments in the string, including this initial one, must be
16289 terminated with newline characters. For example:
16291 data = #Exim filter\n\
16292 if $h_to: contains Exim then save $home/mail/exim endif
16294 If you are reading the data from a database where newlines cannot be included,
16295 you can use the \$@{sg@}$\ expansion item to turn the escape string of your
16296 choice into a newline.
16298 .conf directory@_transport string$**$ unset
16299 A \%redirect%\ router sets up a direct delivery to a directory when a path name
16300 ending with a slash is specified as a new `address'. The transport used is
16301 specified by this option, which, after expansion, must be the name of a
16302 configured transport. This should normally be an \%appendfile%\ transport.
16304 .conf file string$**$ unset
16305 This option specifies the name of a file that contains the redirection data. It
16306 is mutually exclusive with the \data\ option. The string is expanded before
16307 use; if the expansion is forced to fail, the router declines. Other expansion
16308 failures cause delivery to be deferred. The result of a successful expansion
16309 must be an absolute path. The entire file is read and used as the redirection
16310 data. If the data is an empty string or a string that has no effect (consists
16311 entirely of comments), the router declines.
16313 .index NFS||checking for file existence
16314 If the attempt to open the file fails with a `does not exist' error, Exim
16315 runs a check on the containing directory,
16316 unless \ignore@_enotdir\ is true (see below).
16317 If the directory does not appear to exist, delivery is deferred. This can
16318 happen when users' \(.forward)\ files are in NFS-mounted directories, and there
16319 is a mount problem. If the containing directory does exist, but the file does
16320 not, the router declines.
16322 .conf file@_transport string$**$ unset
16323 A \%redirect%\ router sets up a direct delivery to a file when a path name not
16324 ending in a slash is specified as a new `address'. The transport used is
16325 specified by this option, which, after expansion, must be the name of a
16326 configured transport.
16327 This should normally be an \%appendfile%\ transport.
16328 When it is running, the file name is in \$address@_file$\.
16330 .conf forbid@_blackhole boolean false
16331 If this option is true, the :::blackhole:: item may not appear in a redirection
16335 .conf forbid@_exim@_filter boolean false
16336 If this option is set true, only Sieve filters are permitted when
16337 \allow@_filter\ is true.
16341 .conf forbid@_file boolean false
16342 .index delivery||to file, forbidding
16343 .index Sieve filter||forbidding delivery to a file
16344 .index Sieve filter||`keep' facility, disabling
16345 If this option is true, this router may not generate a new address that
16346 specifies delivery to a local file or directory, either from a filter or from a
16347 conventional forward file. This option is forced to be true if \one@_time\ is
16348 set. It applies to Sieve filters as well as to Exim filters, but if true, it
16349 locks out the Sieve's `keep' facility.
16351 .conf forbid@_filter@_existstest boolean false
16352 .index filter||locking out certain features
16353 If this option is true, string expansions in Exim filters are not allowed to
16354 make use of the \exists\ condition.
16356 .conf forbid@_filter@_logwrite boolean false
16357 If this option is true, use of the logging facility in Exim filters is not
16358 permitted. Logging is in any case available only if the filter is being run
16359 under some unprivileged uid (which is normally the case for ordinary users'
16360 \(.forward)\ files).
16362 .conf forbid@_filter@_lookup boolean false
16363 If this option is true, string expansions in Exim filter files are not allowed
16364 to make use of \lookup\ items.
16366 .conf forbid@_filter@_perl boolean false
16367 This option is available only if Exim is built with embedded Perl support. If
16368 it is true, string expansions in Exim filter files are not allowed to make use
16369 of the embedded Perl support.
16371 .conf forbid@_filter@_readfile boolean false
16372 If this option is true, string expansions in Exim filter files are not allowed
16373 to make use of \readfile\ items.
16375 .conf forbid@_filter@_readsocket boolean false
16376 If this option is true, string expansions in Exim filter files are not allowed
16377 to make use of \readsocket\ items.
16379 .conf forbid@_filter@_reply boolean false
16380 If this option is true, this router may not generate an automatic reply
16381 message. Automatic replies can be generated only from Exim
16383 or Sieve filter files, not from traditional forward files.
16385 This option is forced to be true if \one@_time\ is set.
16387 .conf forbid@_filter@_run boolean false
16388 If this option is true, string expansions in Exim filter files are not allowed
16389 to make use of \run\ items.
16391 .conf forbid@_include boolean false
16392 If this option is true, items of the form
16394 :include:<<path name>>
16396 are not permitted in non-filter redirection lists.
16398 .conf forbid@_pipe boolean false
16399 .index delivery||to pipe, forbidding
16400 If this option is true, this router may not generate a new address which
16401 specifies delivery to a pipe, either from an Exim filter or from a conventional
16402 forward file. This option is forced to be true if \one@_time\ is set.
16405 .conf forbid@_sieve@_filter boolean false
16406 If this option is set true, only Exim filters are permitted when
16407 \allow@_filter\ is true.
16411 .conf hide@_child@_in@_errmsg boolean false
16412 .index bounce message||redirection details, suppressing
16413 If this option is true, it prevents Exim from quoting a child address if it
16414 generates a bounce or delay message for it. Instead it says `an address
16415 generated from <<the top level address>>'. Of course, this applies only to
16416 bounces generated locally. If a message is forwarded to another host, $it{its}
16417 bounce may well quote the generated address.
16419 .conf ignore@_eacces boolean false
16421 If this option is set and an attempt to open a redirection file yields the
16422 \\EACCES\\ error (permission denied), the \%redirect%\ router behaves as if the
16423 file did not exist.
16425 .conf ignore@_enotdir boolean false
16427 If this option is set and an attempt to open a redirection file yields the
16428 \\ENOTDIR\\ error (something on the path is not a directory), the \%redirect%\
16429 router behaves as if the file did not exist.
16431 Setting \ignore@_enotdir\ has another effect as well: When a \%redirect%\
16432 router that has the \file\ option set discovers that the file does not exist
16433 (the \\ENOENT\\ error), it tries to \*stat()*\ the parent directory, as a check
16434 against unmounted NFS directories. If the parent can not be statted, delivery
16435 is deferred. However, it seems wrong to do this check when \ignore@_enotdir\ is
16436 set, because that option tells Exim to ignore `something on the path is not a
16437 directory' (the \\ENOTDIR\\ error). This is a confusing area, because it seems
16438 that some operating systems give \\ENOENT\\ where others give \\ENOTDIR\\.
16441 .conf include@_directory string unset
16442 If this option is set, the path names of any :::include:: items in a redirection
16443 list must start with this directory.
16445 .conf modemask "octal integer" 022
16446 This specifies mode bits which must not be set for a file specified by the
16447 \file\ option. If any of the forbidden bits are set, delivery is deferred.
16449 .conf one@_time boolean false
16450 .index one-time aliasing/forwarding expansion
16451 .index alias file||one-time expansion
16452 .index forward file||one-time expansion
16453 .index mailing lists||one-time expansion
16454 .index address redirection||one-time expansion
16455 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
16456 files each time it tries to deliver a message causes a problem
16457 when one or more of the generated addresses fails be delivered at the first
16458 attempt. The problem is not one of duplicate delivery -- Exim is clever enough
16459 to handle that -- but of what happens when the redirection list changes during
16460 the time that the message is on Exim's queue. This is particularly true in the
16461 case of mailing lists, where new subscribers might receive copies of messages
16462 that were posted before they subscribed.
16464 If \one@_time\ is set and any addresses generated by the router fail to
16465 deliver at the first attempt, the failing addresses are added to the message as
16466 `top level' addresses, and the parent address that generated them is marked
16467 `delivered'. Thus, redirection does not happen again at the next
16470 \**Warning 1**\: This means that any header line addition or removal that is
16471 specified by this router would be lost if delivery did not succeed at the
16472 first attempt. For this reason, the \headers@_add\ and \headers@_remove\
16473 generic options are not permitted when \one@_time\ is set.
16475 \**Warning 2**\: To ensure that the router generates only addresses (as opposed
16476 to pipe or file deliveries or auto-replies) \forbid@_file\, \forbid@_pipe\,
16477 and \forbid@_filter@_reply\ are forced to be true when \one@_time\ is set.
16479 The original top-level address is remembered with each of the generated
16480 addresses, and is output in any log messages. However, any intermediate parent
16481 addresses are not recorded. This makes a difference to the log only if
16482 \all__parents\ log selector is set. It is expected that \one@_time\ will
16483 typically be used for mailing lists, where there is normally just one level of
16486 .conf owners "string list" unset
16487 .index ownership||alias file
16488 .index ownership||forward file
16489 .index alias file||ownership
16490 .index forward file||ownership
16491 This specifies a list of permitted owners for the file specified by \file\.
16492 This list is in addition to the local user when \check@_local@_user\ is set.
16493 See \check@_owner\ above.
16495 .conf owngroups "string list" unset
16496 This specifies a list of permitted groups for the file specified by \file\. The
16497 list is in addition to the local user's primary group when \check@_local@_user\
16498 is set. See \check@_group\ above.
16500 .conf pipe@_transport string$**$ unset
16501 A \%redirect%\ router sets up a direct delivery to a pipe when a string starting
16502 with a vertical bar character is specified as a new `address'. The transport
16503 used is specified by this option, which, after expansion, must be the name of a
16504 configured transport.
16505 This should normally be a \%pipe%\ transport.
16506 When the transport is run, the pipe command is in \$address@_pipe$\.
16508 .conf qualify@_domain string$**$ unset
16509 If this option is set and an unqualified address (one without a domain) is
16510 generated, it is qualified with the domain specified by expanding this string,
16511 instead of the global setting in \qualify@_recipient\. If the expansion fails,
16512 the router declines. If you want to revert to the default, you can have the
16513 expansion generate \$qualify@_recipient$\.
16515 .conf qualify@_preserve@_domain boolean false
16516 .index domain||in redirection, preserving
16517 .index preserving domain in redirection
16518 .index address redirection||domain, preserving
16519 If this is set and an unqualified address (one without a domain) is generated,
16520 it is qualified with the domain of the
16521 parent address (the immediately preceding ancestor) instead of the local
16522 \qualify@_domain\ or global \qualify@_recipient\ value.
16524 .conf repeat@_use boolean true
16525 If this option is set false, the router is skipped for a child address that has
16526 any ancestor that was routed by this router. This test happens before any of
16527 the other preconditions are tested. Exim's default anti-looping rules skip
16528 only when the ancestor is the same as the current address. See also
16529 \check@_ancestor\ above and the generic \redirect@_router\ option.
16531 .conf reply@_transport string$**$ unset
16532 A \%redirect%\ router sets up an automatic reply when a \mail\ or \vacation\
16533 command is used in a filter file. The transport used is specified by this
16534 option, which, after expansion, must be the name of a configured transport.
16535 This should normally be an \%autoreply%\ transport. Other transports are
16536 unlikely to do anything sensible or useful.
16538 .conf rewrite boolean true
16539 .index address redirection||disabling rewriting
16540 If this option is set false, addresses generated by the router are not
16541 subject to address rewriting. Otherwise, they are treated like new addresses
16542 and are rewritten according to the global rewriting rules.
16546 .conf sieve@_vacation@_directory string$**$ unset
16547 .index Sieve filter||vacation directory
16548 To enable the `vacation' extension for Sieve filters, you must set
16549 \sieve@_vacation@_directory\ to the directory where vacation databases are held
16550 (do not put anything else in that directory), and ensure that the
16551 \reply@_transport\ option refers to an \%autoreply%\ transport.
16555 .conf skip@_syntax@_errors boolean false
16556 .index forward file||broken
16557 .index address redirection||broken files
16558 .index alias file||broken
16559 .index broken alias or forward files
16560 .index ignoring faulty addresses
16561 .index skipping faulty addresses
16562 .index error||skipping bad syntax
16563 If \skip@_syntax@_errors\ is set, syntactically malformed addresses in
16564 non-filter redirection data are skipped, and each failing address is logged. If
16565 \syntax@_errors@_to\ is set, a message is sent to the address it defines,
16566 giving details of the failures. If \syntax@_errors@_text\ is set, its contents
16567 are expanded and placed at the head of the error message generated by
16568 \syntax@_errors@_to\. Usually it is appropriate to set \syntax@_errors@_to\ to
16569 be the same address as the generic \errors@_to\ option. The
16570 \skip@_syntax@_errors\ option is often used when handling mailing lists.
16572 If all the addresses in a redirection list are skipped because of syntax
16573 errors, the router declines to handle the original address, and it is passed to
16574 the following routers.
16576 If \skip@_syntax@_errors\ is set when an Exim filter is interpreted, any syntax
16577 error in the filter causes filtering to be abandoned without any action being
16578 taken. The incident is logged, and the router declines to handle the address,
16579 so it is passed to the following routers.
16581 .index Sieve filter||syntax errors in
16583 Syntax errors in a Sieve filter file cause the `keep' action to
16584 occur. This action is specified by RFC 3028.
16586 The values of \skip@_syntax@_errors\, \syntax@_errors@_to\, and
16587 \syntax@_errors@_text\ are not used.
16589 \skip@_syntax@_errors\ can be used to specify that errors in users' forward
16590 lists or filter files should not prevent delivery. The \syntax@_errors@_to\
16591 option, used with an address that does not get redirected, can be used to
16592 notify users of these errors, by means of a router like this:
16598 file = $home/.forward
16599 file_transport = address_file
16600 pipe_transport = address_pipe
16601 reply_transport = address_reply
16604 syntax_errors_to = real-$local_part@$domain
16605 syntax_errors_text = \
16606 This is an automatically generated message. An error has\n\
16607 been found in your .forward file. Details of the error are\n\
16608 reported below. While this error persists, you will receive\n\
16609 a copy of this message for every message that is addressed\n\
16610 to you. If your .forward file is a filter file, or if it is\n\
16611 a non-filter file containing no valid forwarding addresses,\n\
16612 a copy of each incoming message will be put in your normal\n\
16613 mailbox. If a non-filter file contains at least one valid\n\
16614 forwarding address, forwarding to the valid addresses will\n\
16615 happen, and those will be the only deliveries that occur.
16617 You also need a router to ensure that local addresses that are prefixed by
16618 \"real-"\ are recognized, but not forwarded or filtered. For example, you could
16619 put this immediately before the \%userforward%\ router:
16624 local_part_prefix = real-
16625 transport = local_delivery
16628 .conf syntax@_errors@_text string$**$ unset
16629 See \skip@_syntax@_errors\ above.
16631 .conf syntax@_errors@_to string unset
16632 See \skip@_syntax@_errors\ above.
16643 . ============================================================================
16644 .chapter Environment for running local transports
16645 .rset CHAPenvironment "~~chapter"
16646 .set runningfoot "local transport environment"
16647 .index local transports||environment for
16648 .index environment for local transports
16649 .index transport||local, environment for
16650 Local transports handle deliveries to files and pipes. (The \%autoreply%\
16651 transport can be thought of as similar to a pipe.) Exim always runs transports
16652 in subprocesses, under specified uids and gids. Typical deliveries to local
16653 mailboxes run under the uid and gid of the local user.
16655 Exim also sets a specific current directory while running the transport; for
16656 some transports a home directory setting is also relevant. The \%pipe%\
16657 transport is the only one that sets up environment variables; see section
16658 ~~SECTpipeenv for details.
16660 The values used for the uid, gid, and the directories may come from several
16661 different places. In many cases, the router that handles the address associates
16662 settings with that address as a result of its \check@_local@_user\, \group\, or
16663 \user\ options. However, values may also be given in the transport's own
16664 configuration, and these override anything that comes from the router.
16668 .section Concurrent deliveries
16669 .index concurrent deliveries
16670 .index simultaneous deliveries
16671 If two different messages for the same local recpient arrive more or less
16672 simultaneously, the two delivery processes are likely to run concurrently. When
16673 the \%appendfile%\ transport is used to write to a file, Exim applies locking
16674 rules to stop concurrent processes from writing to the same file at the same
16677 However, when you use a \%pipe%\ transport, it is up to you to arrange any
16678 locking that is needed. Here is a silly example:
16682 command = /bin/sh -c 'cat >>/some/file'
16684 This is supposed to write the message at the end of the file. However, if two
16685 messages arrive at the same time, the file will be scrambled. You can use the
16686 \exim@_lock\ utility program (see section ~~SECTmailboxmaint) to lock a file
16687 using the same algorithm that Exim itself uses.
16691 .section Uids and gids
16692 .rset SECTenvuidgid "~~chapter.~~section"
16693 .index local transports||uid and gid
16694 .index transport||local, uid and gid
16695 All transports have the options \group\ and \user\. If \group\ is set, it
16696 overrides any group that the router set in the address, even if \user\ is not
16697 set for the transport. This makes it possible, for example, to run local mail
16698 delivery under the uid of the recipient (set by the router), but in a special
16699 group (set by the transport). For example:
16702 # User/group are set by check_local_user in this router
16706 transport = group_delivery
16709 # This transport overrides the group
16711 driver = appendfile
16712 file = /var/spool/mail/$local_part
16715 If \user\ is set for a transport, its value overrides what is set in the
16716 address. If \user\ is non-numeric and \group\ is not set, the gid associated
16717 with the user is used. If \user\ is numeric, \group\ must be set.
16719 .index \initgroups\ option
16720 When the uid is taken from the transport's configuration, the \*initgroups()*\
16721 function is called for the groups associated with that uid if the \initgroups\
16722 option is set for the transport. When the uid is not specified by the
16723 transport, but is associated with the address by a router, the option for
16724 calling \*initgroups()*\ is taken from the router configuration.
16726 .index \%pipe%\ transport||uid for
16727 The \%pipe%\ transport contains the special option \pipe@_as@_creator\. If this
16728 is set and \user\ is not set, the uid of the process that called Exim to
16729 receive the message is used, and if \group\ is not set, the corresponding
16730 original gid is also used.
16733 .section Current and home directories
16734 .index current directory for local transport
16735 .index home directory||for local transport
16736 .index transport||local, home directory for
16737 .index transport||local, current directory for
16738 Routers may set current and home directories for local transports by means of
16739 the \transport__current@_directory\ and \transport@_home@_directory\ options.
16740 However, if the transport's \current__directory\ or \home@_directory\ options
16741 are set, they override the router's values. In detail, the home directory
16742 for a local transport is taken from the first of these values that is set:
16744 The \home@_directory\ option on the transport;
16746 The \transport@_home@_directory\ option on the router;
16748 The password data if \check@_local@_user\ is set on the router;
16750 The \router@_home@_directory\ option on the router.
16752 The current directory is taken from the first of these values that is set:
16754 The \current@_directory\ option on the transport;
16756 The \transport@_current@_directory\ option on the router.
16759 If neither the router nor the transport sets a current directory, Exim uses the
16760 value of the home directory, if it is set. Otherwise it sets the current
16761 directory to \(/)\ before running a local transport.
16764 .section Expansion variables derived from the address
16765 Normally a local delivery is handling a single address, and in that case the
16766 variables such as \$domain$\ and \$local@_part$\ are set during local
16767 deliveries. However, in some circumstances more than one address may be handled
16768 at once (for example, while writing batch SMTP for onward transmission by some
16769 other means). In this case, the variables associated with the local part are
16770 never set, \$domain$\ is set only if all the addresses have the same
16771 domain, and \$original@_domain$\ is never set.
16782 . ============================================================================
16783 .chapter Generic options for transports
16784 .rset CHAPtransportgeneric "~~chapter"
16785 .set runningfoot "generic transport options"
16787 .index generic options||transport
16788 .index options||generic, for transports
16789 .index transport||generic options for
16790 The following generic options apply to all transports:
16792 .startconf transports
16793 .conf body@_only boolean false
16794 .index transport||body only
16795 .index message||transporting body only
16796 .index body of message||transporting
16797 If this option is set, the message's headers are not transported. It is
16798 mutually exclusive with \headers@_only\. If it is used with the \%appendfile%\ or
16799 \%pipe%\ transports, the settings of \message@_prefix\ and \message@_suffix\
16800 should be checked, because this option does not automatically suppress them.
16802 .conf current@_directory string$**$ unset
16803 .index transport||current directory for
16804 This specifies the current directory that is to be set while running the
16805 transport, overriding any value that may have been set by the router.
16806 If the expansion fails for any reason, including forced failure, an error is
16807 logged, and delivery is deferred.
16809 .conf disable@_logging boolean false
16810 If this option is set true, nothing is logged for any
16811 deliveries by the transport or for any
16812 transport errors. You should not set this option unless you really, really know
16813 what you are doing.
16815 .conf debug@_print string$**$ unset
16816 .index testing||variables in drivers
16817 If this option is set and debugging is enabled (see the \-d-\ command line
16818 option), the string is expanded and included in the debugging output when the
16820 If expansion of the string fails, the error message is written to the debugging
16821 output, and Exim carries on processing.
16822 This facility is provided to help with checking out the values of variables and
16823 so on when debugging driver configurations. For example, if a \headers@_add\
16824 option is not working properly, \debug@_print\ could be used to output the
16825 variables it references. A newline is added to the text if it does not end with
16828 .conf delivery@_date@_add boolean false
16829 .index ::Delivery-date:: header line
16830 If this option is true, a ::Delivery-date:: header is added to the message. This
16831 gives the actual time the delivery was made. As this is not a standard header,
16832 Exim has a configuration option (\delivery@_date@_remove\) which requests its
16833 removal from incoming messages, so that delivered messages can safely be resent
16834 to other recipients.
16836 .conf driver string unset
16837 This specifies which of the available transport drivers is to be used.
16838 There is no default, and this option must be set for every transport.
16840 .conf envelope@_to@_add boolean false
16841 .index ::Envelope-to:: header line
16842 If this option is true, an ::Envelope-to:: header is added to the message. This
16843 gives the original address(es) in the incoming envelope that caused this
16844 delivery to happen. More than one address may be present if the transport is
16845 configured to handle several addresses at once, or if more than one original
16846 address was redirected to the same final address. As this is not a standard
16847 header, Exim has a configuration option (\envelope@_to@_remove\) which requests
16848 its removal from incoming messages, so that delivered messages can safely be
16849 resent to other recipients.
16851 .conf group string$**$ "Exim group"
16852 .index transport||group, specifying
16853 This option specifies a gid for running the transport process, overriding any
16854 value that the router supplies, and also overriding any value associated with
16855 \user\ (see below).
16857 .conf headers@_add string$**$ unset
16858 .index header lines||adding in transport
16859 .index transport||header lines, adding
16861 This option specifies a string of text that is expanded and added to the header
16862 portion of a message as it is transported, as described in section
16863 ~~SECTheadersaddrem. Additional header lines can also be specified by routers.
16864 If the result of the expansion is an empty string, or if the expansion is
16865 forced to fail, no action is taken. Other expansion failures are treated as
16866 errors and cause the delivery to be deferred.
16869 .conf headers@_only boolean false
16870 .index transport||header lines only
16871 .index message||transporting headers only
16872 .index header lines||transporting
16873 If this option is set, the message's body is not transported. It is mutually
16874 exclusive with \body@_only\. If it is used with the \%appendfile%\ or \%pipe%\
16875 transports, the settings of \message@_prefix\ and \message__suffix\ should be
16876 checked, since this option does not automatically suppress them.
16878 .conf headers@_remove string$**$ unset
16879 .index header lines||removing
16880 .index transport||header lines, removing
16882 This option specifies a string that is expanded into a list of header names;
16883 these headers are omitted from the message as it is transported, as described
16884 in section ~~SECTheadersaddrem. Header removal can also be specified by
16885 routers. If the result of the expansion is an empty string, or if the expansion
16886 is forced to fail, no action is taken. Other expansion failures are treated as
16887 errors and cause the delivery to be deferred.
16890 .conf headers@_rewrite string unset
16891 .index transport||header lines, rewriting
16892 .index rewriting||at transport time
16893 This option allows addresses in header lines to be rewritten at transport time,
16894 that is, as the message is being copied to its destination. The contents of the
16895 option are a colon-separated list of rewriting rules. Each rule is in exactly
16896 the same form as one of the general rewriting rules that are applied when a
16897 message is received. These are described in chapter ~~CHAPrewrite. For example,
16899 headers_rewrite = a@b c@d f : \
16902 changes \a@@b\ into \c@@d\ in ::From:: header lines, and \x@@y\ into \w@@z\ in
16903 all address-bearing header lines. The rules are applied to the header lines
16904 just before they are written out at transport time, so they affect only those
16905 copies of the message that pass through the transport. However, only the
16906 message's original header lines, and any that were added by a system filter,
16907 are rewritten. If a router or transport adds header lines, they are
16908 not affected by this option. These rewriting rules are $it{not} applied to the
16909 envelope. You can change the return path using \return@_path\, but you cannot
16910 change envelope recipients at this time.
16912 .conf home@_directory string$**$ unset
16913 .index transport||home directory for
16914 This option specifies a home directory setting for the transport, overriding
16915 any value that may be set by the router. The home directory is placed in
16916 \$home$\ while expanding the transport's private options. It is also used as
16917 the current directory if no current directory is set by the
16918 \current__directory\ option on the transport or the
16919 \transport__current__directory\ option on the router.
16920 If the expansion fails for any reason, including forced failure, an error is
16921 logged, and delivery is deferred.
16924 .index additional groups
16925 .index groups, additional
16926 .index transport||group, additional
16927 .conf initgroups boolean false
16928 If this option is true and the uid for the delivery process is provided by the
16929 transport, the \*initgroups()*\ function is called when running the transport
16930 to ensure that any additional groups associated with the uid are set up.
16932 .conf message@_size@_limit string$**$ 0
16933 .index limit||message size per transport
16934 .index size||of message, limit
16935 .index transport||message size, limiting
16936 This option controls the size of messages passed through the transport. It is
16937 expanded before use; the result of the expansion must be a sequence of digits,
16938 optionally followed by K or M.
16939 If the expansion fails for any reason, including forced failure, or if the
16940 result is not of the required form, delivery is deferred.
16941 If the value is greater than zero and the size of a message exceeds this
16942 limit, the address is failed. If there is any chance that the resulting bounce
16943 message could be routed to the same transport, you should ensure that
16944 \return@_size@_limit\ is less than the transport's \message@_size@_limit\, as
16945 otherwise the bounce message will fail to get delivered.
16948 .conf rcpt@_include@_affixes boolean false
16949 .index prefix||for local part, including in envelope
16950 .index suffix||for local part, including in envelope
16951 .index local part||prefix
16952 .index local part||suffix
16953 When this option is false (the default), and an address that has had any
16954 affixes (prefixes or suffixes) removed from the local part is delivered by any
16955 form of SMTP or LMTP, the affixes are not included. For example, if a router
16958 local_part_prefix = *-
16960 routes the address \*abc-xyz@@some.domain*\ to an SMTP transport, the envelope
16963 RCPT TO:<xyz@some.domain>
16965 If \rcpt@_include@_affixes\ is set true, the whole local part is included in
16966 the \\RCPT\\ command. This option applies to BSMTP deliveries by the
16967 \%appendfile%\ and \%pipe%\ transports as well as to the \%lmtp%\ and \%smtp%\
16970 .conf retry@_use@_local@_part boolean "see below"
16971 .index hints database||retry keys
16972 When a delivery suffers a temporary failure, a retry record is created
16973 in Exim's hints database. For remote deliveries, the key for the retry record
16974 is based on the name and/or IP address of the failing remote host. For local
16975 deliveries, the key is normally the entire address, including both the local
16976 part and the domain. This is suitable for most common cases of local delivery
16977 temporary failure -- for example, exceeding a mailbox quota should delay only
16978 deliveries to that mailbox, not to the whole domain.
16980 However, in some special cases you may want to treat a temporary local delivery
16981 as a failure associated with the domain, and not with a particular local part.
16982 (For example, if you are storing all mail for some domain in files.) You can do
16983 this by setting \retry@_use@_local@_part\ false.
16985 For all the local transports, its default value is true. For remote transports,
16986 the default value is false for tidiness, but changing the value has no effect
16987 on a remote transport in the current implementation.
16989 .conf return@_path string$**$ unset
16990 .index envelope sender
16991 .index transport||return path, changing
16992 .index return path||changing in transport
16993 If this option is set, the string is expanded at transport time and replaces
16994 the existing return path (envelope sender) value in the copy of the message
16995 that is being delivered. An empty return path is permitted. This feature is
16996 designed for remote deliveries, where the value of this option is used in the
16997 SMTP \\MAIL\\ command. If you set \return@_path\ for a local transport, the
16998 only effect is to change the address that is placed in the ::Return-path::
16999 header line, if one is added to the message (see the next option).
17001 The expansion can refer to the existing value via \$return@_path$\. This is
17002 either the message's envelope sender, or an address set by the
17003 \errors@_to\ option on a router. If the expansion is forced to fail, no
17004 replacement occurs; if it fails for another reason, delivery is deferred. This
17005 option can be used to support VERP (Variable Envelope Return Paths) -- see
17006 chapter ~~CHAPSMTP.
17008 \**Note**\: If a delivery error is detected locally,
17009 including the case when a remote server rejects a message at SMTP time,
17010 the bounce message is not sent to the value of this option, but to the
17011 previously set errors address (which defaults to the incoming sender address).
17014 .conf return@_path@_add boolean false
17015 .index ::Return-path:: header line
17016 If this option is true, a ::Return-path:: header is added to the message.
17017 Although the return path is normally available in the prefix line of BSD
17018 mailboxes, this is commonly not displayed by MUAs, and so the user does not
17019 have easy access to it.
17021 RFC 2821 states that the ::Return-path:: header is added to a message `when the
17022 delivery SMTP server makes the final delivery'. This implies that this header
17023 should not be present in incoming messages. Exim has a configuration option,
17024 \return@_path@_remove\, which requests removal of this header from incoming
17025 messages, so that delivered messages can safely be resent to other recipients.
17027 .conf shadow@_condition string$**$ unset
17028 See \shadow@_transport\ below.
17030 .conf shadow@_transport string unset
17031 .index shadow transport
17032 .index transport||shadow
17033 A local transport may set the \shadow@_transport\ option to the name of another
17034 local transport. Shadow remote transports are not supported.
17036 Whenever a delivery to the main transport succeeds, and either
17037 \shadow@_condition\ is unset, or its expansion does not result in the empty
17038 string or one of the strings `0' or `no' or `false', the message is also passed
17039 to the shadow transport, with the same delivery address or addresses.
17040 If expansion fails, no action is taken except that non-forced expansion
17041 failures cause a log line to be written.
17043 The result of the shadow transport is discarded and does not affect the
17044 subsequent processing of the message. Only a single level of shadowing is
17045 provided; the \shadow@_transport\ option is ignored on any transport when it is
17046 running as a shadow. Options concerned with output from pipes are also ignored.
17048 The log line for the successful delivery has an item added on the end, of the
17051 ST=<<shadow transport name>>
17053 If the shadow transport did not succeed, the error message is put in
17054 parentheses afterwards.
17056 Shadow transports can be used for a number of different purposes, including
17057 keeping more detailed log information than Exim normally provides, and
17058 implementing automatic acknowledgement policies based on message headers that
17059 some sites insist on.
17061 .conf transport@_filter string$**$ unset
17062 .index transport||filter
17063 .index filter||transport filter
17064 This option sets up a filtering (in the Unix shell sense) process for messages
17065 at transport time. It should not be confused with mail filtering as set up by
17066 individual users or via a system filter.
17068 When the message is about to be written out, the command specified by
17069 \transport@_filter\ is started up in a separate process, and the entire
17070 message, including the header lines, is passed to it on its standard input
17071 (this in fact is done from a third process, to avoid deadlock).
17072 The command must be specified as an absolute path.
17075 The lines of the message that are written to the transport filter are
17076 terminated by newline (`@\n').
17078 The message is passed to the filter before any SMTP-specific processing, such
17079 as turning `@\n' into `@\r@\n' and escaping lines beginning with a dot, and
17080 also before any processing implied by the settings of \check@_string\ and
17081 \escape@_string\ in the \%appendfile%\ or \%pipe%\ transports.
17084 The standard error for the filter process is set to the same destination as its
17085 standard output; this is read and written to the message's ultimate
17088 The filter can perform any transformations it likes, but of course should take
17089 care not to break RFC 2822 syntax. A demonstration Perl script is provided in
17090 \(util/transport-filter.pl)\; this makes a few arbitrary modifications just to
17091 show the possibilities. Exim does not check the result, except to test for a
17092 final newline when SMTP is in use. All messages transmitted over SMTP must end
17093 with a newline, so Exim supplies one if it is missing.
17095 .index SMTP||\\SIZE\\
17096 A problem might arise if the filter increases the size of a message that is
17097 being sent down an SMTP connection. If the receiving SMTP server has indicated
17098 support for the \\SIZE\\ parameter, Exim will have sent the size of the message
17099 at the start of the SMTP session. If what is actually sent is substantially
17100 more, the server might reject the message. This can be worked round by setting
17101 the \size@_addition\ option on the \%smtp%\ transport, either to allow for
17102 additions to the message, or to disable the use of \\SIZE\\ altogether.
17104 The value of the \transport@_filter\ option is the command string for starting
17105 the filter, which is run directly from Exim, not under a shell. The string is
17106 parsed by Exim in the same way as a command string for the \%pipe%\ transport:
17107 Exim breaks it up into arguments and then expands each argument separately. The
17108 special argument \$pipe@_addresses$\ is replaced by a number of arguments, one
17109 for each address that applies to this delivery. (This isn't an ideal name for
17110 this feature here, but as it was already implemented for the \%pipe%\
17111 transport, it seemed sensible not to change it.)
17114 .index \$host@_address$\
17115 The expansion variables \$host$\ and \$host@_address$\ are available when the
17116 transport is a remote one. They contain the name and IP address of the host to
17117 which the message is being sent. For example:
17119 transport_filter = /some/directory/transport-filter.pl \
17120 $host $host_address $sender_address $pipe_addresses
17122 The filter process is run under the same uid and gid as the normal delivery.
17123 For remote deliveries this is the Exim uid/gid by default.
17125 The command should normally yield a zero return code. A non-zero code is taken
17126 to mean that the transport filter failed in some way. Delivery of the message
17127 is deferred. It is not possible to cause a message to be bounced from a
17131 If a transport filter is set on an autoreply transport, the original message is
17132 passed through the filter as it is being copied into the newly generated
17133 message, which happens if the \return@_message\ option is set.
17135 .conf transport@_filter@_timeout time 5m
17136 .index transport||filter, timeout
17137 When Exim is reading the output of a transport filter, it a applies a timeout
17138 that can be set by this option. Exceeding the timeout is treated as a
17139 temporary delivery failure.
17142 .conf user string$**$ "Exim user"
17143 .index uid (user id)||local delivery
17144 .index transport||user, specifying
17145 This option specifies the user under whose uid the delivery process is to be
17146 run, overriding any uid that may have been set by the router. If the user is
17147 given as a name, the uid is looked up from the password data, and the
17148 associated group is taken as the value of the gid to be used if the \group\
17151 For deliveries that use local transports, a user and group are normally
17152 specified explicitly or implicitly (for example, as a result of
17153 \check@_local@_user\) by the router or transport.
17155 .index hints database||access by remote transport
17156 For remote transports, you should leave this option unset unless you really are
17157 sure you know what you are doing. When a remote transport is running, it needs
17158 to be able to access Exim's hints databases, because each host may have its own
17170 . ============================================================================
17171 .chapter Address batching in local transports
17172 .set runningfoot "address batching"
17173 .rset CHAPbatching ~~chapter
17174 .index transport||local, address batching in
17175 The only remote transport (\%smtp%\) is normally configured to handle more than
17176 one address at a time, so that when several addresses are routed to the same
17177 remote host, just one copy of the message is sent. Local transports, however,
17178 normally handle one address at a time. That is, a separate instance of the
17179 transport is run for each address that is routed to the transport. A separate
17180 copy of the message is delivered each time.
17182 .index batched local delivery
17183 .index \batch@_max\
17185 In special cases, it may be desirable to handle several addresses at once in a
17186 local transport, for example:
17188 In an \%appendfile%\ transport, when storing messages in files for later
17189 delivery by some other means, a single copy of the message with multiple
17190 recipients saves space.
17192 In an \%lmtp%\ transport, when delivering over `local SMTP' to some process,
17193 a single copy saves time, and is the normal way LMTP is expected to work.
17195 In a \%pipe%\ transport, when passing the message
17196 to a scanner program or
17197 to some other delivery mechanism such as UUCP, multiple recipients may be
17200 The three local transports (\%appendfile%\, \%lmtp%\, and \%pipe%\) all have
17201 the same options for controlling multiple (`batched') deliveries, namely
17202 \batch@_max\ and \batch@_id\. To save repeating the information for each
17203 transport, these options are described here.
17205 The \batch@_max\ option specifies the maximum number of addresses that can be
17206 delivered together in a single run of the transport. Its default value is one.
17207 When more than one address is routed to a transport that has a \batch@_max\
17208 value greater than one, the addresses are delivered in a batch (that is, in a
17209 single run of the transport), subject to certain conditions:
17211 If any of the transport's options contain a reference to \$local@_part$\, no
17212 batching is possible.
17214 If any of the transport's options contain a reference to \$domain$\, only
17215 addresses with the same domain are batched.
17217 .index customizing||batching condition
17218 If \batch@_id\ is set, it is expanded for each address, and only those
17219 addresses with the same expanded value are batched. This allows you to specify
17220 customized batching conditions.
17221 Failure of the expansion for any reason, including forced failure, disables
17222 batching, but it does not stop the delivery from taking place.
17224 Batched addresses must also have the same errors address (where to send
17225 delivery errors), the same header additions and removals, the same user and
17226 group for the transport, and if a host list is present, the first host must
17229 .index ::Envelope-to:: header line
17230 If the generic \envelope@_to@_add\ option is set for the transport, the
17231 ::Envelope-to:: header that is added to the message contains all the addresses
17232 that are batched together.
17234 The \%appendfile%\ and \%pipe%\ transports have an option called \use@_bsmtp\,
17235 which causes them to deliver the message in `batched SMTP' format, with the
17236 envelope represented as SMTP commands. The \check@_string\ and \escape@_string\
17237 options are forced to the values
17240 escape_string = ".."
17242 when batched SMTP is in use. A full description of the batch SMTP mechanism is
17243 given in section ~~SECTbatchSMTP. The \%lmtp%\ transport does not have a
17244 \use@_bsmtp\ option, because it always delivers using the SMTP protocol.
17246 .index \%pipe%\ transport||with multiple addresses
17247 If you are not using BSMTP, but are using a \%pipe%\ transport, you can include
17248 \$pipe@_addresses$\ as part of the command. This is not a true variable; it is
17249 a bit of magic that causes each of the recipient addresses to be inserted into
17250 the command as a separate argument. This provides a way of accessing all the
17251 addresses that are being delivered in the batch.
17253 If you are using a batching \%appendfile%\ transport without \use@_bsmtp\, the
17254 only way to preserve the recipient addresses is to set the \envelope@_to@_add\
17255 option. This causes an ::Envelope-to:: header line to be added to the message,
17256 containing all the recipients.
17263 . ============================================================================
17264 .chapter The appendfile transport
17265 .set runningfoot "appendfile transport"
17266 .rset CHAPappendfile ~~chapter
17267 .index \%appendfile%\ transport
17268 .index transports||\%appendfile%\
17269 .index directory creation
17270 .index creating directories
17271 The \%appendfile%\ transport delivers a message by appending it to an existing
17272 file, or by creating an entirely new file in a specified directory. Single
17273 files to which messages are appended can be in the traditional Unix mailbox
17274 format, or optionally in the MBX format supported by the Pine MUA and
17275 University of Washington IMAP daemon, $it{inter alia}. When each message is
17276 being delivered as a separate file, `maildir' format can optionally be used to
17277 give added protection against failures that happen part-way through the
17278 delivery. A third form of separate-file delivery known as `mailstore' is also
17279 supported. For all file formats, Exim attempts to create as many levels of
17280 directory as necessary, provided that \create@_directory\ is set.
17282 The code for the optional formats is not included in the Exim binary by
17283 default. It is necessary to set \\SUPPORT@_MBX\\, \\SUPPORT@_MAILDIR\\ and/or
17284 \\SUPPORT@_MAILSTORE\\ in \(Local/Makefile)\ to have the appropriate code
17287 .index quota||system
17288 Exim recognises system quota errors, and generates an appropriate message. Exim
17289 also supports its own quota control within the transport, for use when the
17290 system facility is unavailable or cannot be used for some reason.
17292 If there is an error while appending to a file (for example, quota exceeded or
17293 partition filled), Exim attempts to reset the file's length and last
17294 modification time back to what they were before. If there is an error while
17295 creating an entirely new file, the new file is removed.
17297 Before appending to a file, a number of security checks are made, and the
17298 file is locked. A detailed description is given below, after the list of
17301 \%appendfile%\ is most commonly used for local deliveries to users' mailboxes.
17302 However, it can also be used as a pseudo-remote transport for putting messages
17303 into files for remote delivery by some means other than Exim. `Batch SMTP'
17304 format is often used in this case (see the \use@_bsmtp\ option).
17307 .section The file and directory options
17308 .rset SECTfildiropt "~~chapter.~~section"
17309 The \file\ option specifies a single file, to which the message is appended;
17310 the \directory\ option specifies a directory, in which a new file containing
17311 the message is created. Only one of these two options can be set, and for
17312 normal deliveries to mailboxes, one of them \*must*\ be set.
17314 However, \%appendfile%\ is also used for delivering messages to files or
17315 directories whose names (or parts of names) are obtained from alias,
17316 forwarding, or filtering operations (for example, a \save\ command in a user's
17317 Exim filter). When such a transport is running, \$local@_part$\ contains the
17318 local part that was aliased or forwarded, and \$address@_file$\ contains the
17319 name (or partial name) of the file or directory generated by the redirection
17320 operation. There are two cases:
17322 If neither \file\ nor \directory\ is set, the redirection operation
17323 must specify an absolute path (one that begins with \"/"\). This is the most
17324 common case when users with local accounts use filtering to sort mail into
17325 different folders. See for example, the \%address@_file%\ transport in the
17326 default configuration. If the path ends with a slash, it is assumed to be the
17327 name of a directory. A delivery to a directory can also be forced by setting
17328 \maildir@_format\ or \mailstore@_format\.
17330 If \file\ or \directory\ is set for a delivery from a redirection, it is used
17331 to determine the file or directory name for the delivery. Normally, the
17332 contents of \$address@_file$\ are used in some way in the string expansion.
17335 .index Sieve filter||configuring \%appendfile%\
17336 .index Sieve filter||relative mailbox path handling
17337 As an example of the second case, consider an environment where users do not
17338 have home directories. They may be permitted to use Exim filter commands of the
17343 or Sieve filter commands of the form:
17345 require "fileinto";
17346 fileinto "folder23";
17348 In this situation, the expansion of \file\ or \directory\ in the transport must
17349 transform the relative path into an appropriate absolute file name. In the case
17350 of Sieve filters, the name \*inbox*\ must be handled. It is the name that is
17351 used as a result of a `keep' action in the filter. This example shows one way
17352 of handling this requirement:
17354 file = ${if eq{$address_file}{inbox} \
17355 {/var/mail/$local_part} \
17356 {${if eq{${substr_0_1:$address_file}}{/} \
17358 {$home/mail/$address_file} \
17362 With this setting of \file\, \*inbox*\ refers to the standard mailbox location,
17363 absolute paths are used without change, and other folders are in the \(mail)\
17364 directory within the home directory.
17366 \**Note 1**\: While processing an Exim filter, a relative path such as
17367 \(folder23)\ is turned into an absolute path if a home directory is known to
17368 the router. In particular, this is the case if \check@_local@_user\ is set. If
17369 you want to prevent this happening at routing time, you can set
17370 \router@_home@_directory\ empty. This forces the router to pass the relative
17371 path to the transport.
17373 \**Note 2**\: An absolute path in \$address@_file$\ is not treated specially;
17374 the \file\ or \directory\ option is still used if it is set.
17378 .section Private options for appendfile
17379 .index options||\%appendfile%\ transport
17381 .startconf appendfile
17383 .conf allow@_fifo boolean false
17384 .index fifo (named pipe)
17385 .index named pipe (fifo)
17386 .index pipe||named (fifo)
17387 Setting this option permits delivery to named pipes (FIFOs) as well as to
17388 regular files. If no process is reading the named pipe at delivery time, the
17389 delivery is deferred.
17391 .conf allow@_symlink boolean false
17392 .index symbolic link||to mailbox
17393 .index mailbox||symbolic link
17394 By default, \%appendfile%\ will not deliver if the path name for the file is
17395 that of a symbolic link. Setting this option relaxes that constraint, but there
17396 are security issues involved in the use of symbolic links. Be sure you know
17397 what you are doing if you set this. Details of exactly what this option affects
17398 are included in the discussion which follows this list of options.
17400 .conf batch@_id string$**$ unset
17401 See the description of local delivery batching in chapter ~~CHAPbatching.
17402 However, batching is automatically disabled for \%appendfile%\ deliveries that
17403 happen as a result of forwarding or aliasing or other redirection directly to a
17406 .conf batch@_max integer 1
17407 See the description of local delivery batching in chapter ~~CHAPbatching.
17409 .conf check@_group boolean false
17410 When this option is set, the group owner of the file defined by the \file\
17411 option is checked to see that it is the same as the group under which the
17412 delivery process is running. The default setting is false because the default
17413 file mode is 0600, which means that the group is irrelevant.
17415 .conf check@_owner boolean true
17416 When this option is set, the owner of the file defined by the \file\ option is
17417 checked to ensure that it is the same as the user under which the delivery
17418 process is running.
17420 .conf check@_string string "see below"
17422 As \%appendfile%\ writes the message, the start of each line is tested for
17423 matching \check@_string\, and if it does, the initial matching characters are
17424 replaced by the contents of \escape@_string\. The value of \check@_string\ is a
17425 literal string, not a regular expression, and the case of any letters it
17426 contains is significant.
17428 If \use@_bsmtp\ is set the values of \check@_string\ and \escape@_string\ are
17429 forced to `.' and `..' respectively, and any settings in the configuration are
17430 ignored. Otherwise, they default to `From ' and `>From ' when the \file\ option
17431 is set, and unset when
17432 any of the \directory\, \maildir\, or \mailstore\ options are set.
17434 The default settings, along with \message@_prefix\ and \message@_suffix\, are
17435 suitable for traditional `BSD' mailboxes, where a line beginning with `From '
17436 indicates the start of a new message. All four options need changing if another
17437 format is used. For example, to deliver to mailboxes in MMDF format:
17438 .index MMDF format mailbox
17439 .index mailbox||MMDF format
17441 check_string = "\1\1\1\1\n"
17442 escape_string = "\1\1\1\1 \n"
17443 message_prefix = "\1\1\1\1\n"
17444 message_suffix = "\1\1\1\1\n"
17447 .index directory creation
17448 .conf create@_directory boolean true
17449 When this option is true, Exim attempts to create any missing superior
17450 directories for the file that it is about to write. A created directory's mode
17451 is given by the \directory@_mode\ option.
17453 The group ownership of a newly created directory is highly dependent on the
17454 operating system (and possibly the file system) that is being used. For
17455 example, in Solaris, if the parent directory has the setgid bit set, its group
17456 is propagated to the child; if not, the currently set group is used. However,
17457 in FreeBSD, the parent's group is always used.
17460 .conf create@_file string "anywhere"
17461 This option constrains the location of files and directories that are created
17462 by this transport. It applies to files defined by the \file\ option and
17463 directories defined by the \directory\ option. In the case of maildir delivery,
17464 it applies to the top level directory, not the maildir directories beneath.
17466 The option must be set to one of the words `anywhere', `inhome', or
17467 `belowhome'. In the second and third cases, a home directory must have been set
17468 for the transport. This option is not useful when an explicit file name is
17469 given for normal mailbox deliveries. It is intended for the case when file
17470 names are generated from users' \(.forward)\ files. These are usually handled
17471 by an \%appendfile%\ transport called \address@_file\. See also
17472 \file@_must@_exist\.
17474 .conf directory string$**$ unset
17475 This option is mutually exclusive with the \file\ option, but one of \file\ or
17476 \directory\ must be set, unless the delivery is the direct result of a
17477 redirection (see section ~~SECTfildiropt).
17479 When \directory\ is set, the string is expanded, and the message is delivered
17480 into a new file or files in or below the given directory, instead of being
17481 appended to a single mailbox file. A number of different formats are provided
17482 (see \maildir@_format\ and \mailstore@_format\), and see section ~~SECTopdir
17483 for further details of this form of delivery.
17485 .conf directory@_file string$**$ "$tt{q@$@{base62:@$tod@_epoch@}-@$inode}"
17487 When \directory\ is set, but neither \maildir@_format\ nor \mailstore@_format\
17488 is set, \%appendfile%\ delivers each message into a file whose name is obtained
17489 by expanding this string. The default value generates a unique name from the
17490 current time, in base 62 form, and the inode of the file. The variable
17491 \$inode$\ is available only when expanding this option.
17493 .conf directory@_mode "octal integer" 0700
17494 If \%appendfile%\ creates any directories as a result of the \create@_directory\
17495 option, their mode is specified by this option.
17497 .conf escape@_string string "see description"
17498 See \check@_string\ above.
17500 .conf file string$**$ unset
17501 This option is mutually exclusive with the \directory\ option, but one of
17502 \file\ or \directory\ must be set, unless the delivery is the direct result of
17503 a redirection (see section ~~SECTfildiropt). The \file\ option specifies a
17504 single file, to which the message is appended. One or more of
17505 \use@_fcntl@_lock\, \use@_flock@_lock\, or \use@_lockfile\ must be set with
17507 .index NFS||lock file
17508 .index locking files
17510 If you are using more than one host to deliver over NFS into the same
17511 mailboxes, you should always use lock files.
17513 The string value is expanded for each delivery, and must yield an absolute
17514 path. The most common settings of this option are variations on one of these
17517 file = /var/spool/mail/$local_part
17518 file = /home/$local_part/inbox
17521 .index `sticky' bit
17522 In the first example, all deliveries are done into the same directory. If Exim
17523 is configured to use lock files (see \use@_lockfile\ below) it must be able to
17524 create a file in the directory, so the `sticky' bit must be turned on for
17525 deliveries to be possible, or alternatively the \group\ option can be used to
17526 run the delivery under a group id which has write access to the directory.
17529 .conf file@_format string unset
17530 .index file||mailbox, checking existing format
17531 This option requests the transport to check the format of an existing file
17532 before adding to it. The check consists of matching a specific string at the
17533 start of the file. The value of the option consists of an even number of
17534 colon-separated strings. The first of each pair is the test string, and the
17535 second is the name of a transport. If the transport associated with a matched
17536 string is not the current transport, control is passed over to the other
17537 transport. For example, suppose the standard \%local@_delivery%\ transport has
17540 file_format = "From : local_delivery :\
17541 \1\1\1\1\n : local_mmdf_delivery"
17543 Mailboxes that begin with `From' are still handled by this transport, but if a
17544 mailbox begins with four binary ones followed by a newline, control is passed
17545 to a transport called \local__mmdf__delivery\, which presumably is configured
17546 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
17547 is assumed to match the current transport. If the start of a mailbox doesn't
17548 match any string, or if the transport named for a given string is not defined,
17549 delivery is deferred.
17551 .conf file@_must@_exist boolean false
17552 If this option is true, the file specified by the \file\ option must exist, and
17553 an error occurs if it does not. Otherwise, it is created if it does not exist.
17555 .conf lock@_fcntl@_timeout time 0s
17556 .index timeout||mailbox locking
17557 .index mailbox locking||blocking and non-blocking
17558 .index locking files
17559 By default, the \%appendfile%\ transport uses non-blocking calls to \*fcntl()*\
17560 when locking an open mailbox file. If the call fails, the delivery process
17561 sleeps for \lock@_interval\ and tries again, up to \lock@_retries\ times.
17562 Non-blocking calls are used so that the file is not kept open during the wait
17563 for the lock; the reason for this is to make it as safe as possible for
17564 deliveries over NFS in the case when processes might be accessing an NFS
17565 mailbox without using a lock file. This should not be done, but
17566 misunderstandings and hence misconfigurations are not unknown.
17568 On a busy system, however, the performance of a non-blocking lock approach is
17569 not as good as using a blocking lock with a timeout. In this case, the waiting
17570 is done inside the system call, and Exim's delivery process acquires the lock
17571 and can proceed as soon as the previous lock holder releases it.
17573 If \lock@_fcntl@_timeout\ is set to a non-zero time, blocking locks, with that
17574 timeout, are used. There may still be some retrying: the maximum number of
17577 (lock_retries * lock_interval) / lock_fcntl_timeout
17579 rounded up to the next whole number. In other words, the total time during
17580 which \%appendfile%\ is trying to get a lock is roughly the same, unless
17581 \lock@_fcntl@_timeout\ is set very large.
17583 You should consider setting this option if you are getting a lot of delayed
17584 local deliveries because of errors of the form
17586 failed to lock mailbox /some/file (fcntl)
17589 .conf lock@_flock@_timeout time 0s
17590 This timeout applies to file locking when using \*flock()*\ (see \use@_flock\);
17591 the timeout operates in a similar manner to \lock@_fcntl@_timeout\.
17593 .conf lock@_interval time 3s
17594 This specifies the time to wait between attempts to lock the file. See below
17595 for details of locking.
17597 .conf lock@_retries integer 10
17598 This specifies the maximum number of attempts to lock the file. A value of zero
17599 is treated as 1. See below for details of locking.
17601 .conf lockfile@_mode "octal integer" 0600
17602 This specifies the mode of the created lock file, when a lock file is being
17603 used (see \use@_lockfile\).
17605 .conf lockfile@_timeout time 30m
17606 .index timeout||mailbox locking
17607 When a lock file is being used (see \use@_lockfile\), if a lock file already
17608 exists and is older than this value, it is assumed to have been left behind by
17609 accident, and Exim attempts to remove it.
17612 .conf mailbox@_filecount string$**$ unset
17613 .index mailbox||specifying size of
17614 .index size||of mailbox
17615 If this option is set, it is expanded, and the result is taken as the current
17616 number of files in the mailbox. It must be a decimal number, optionally
17617 followed by K or M. This provides a way of obtaining this information from an
17618 external source that maintains the data.
17620 .conf mailbox@_size string$**$ unset
17621 .index mailbox||specifying size of
17622 .index size||of mailbox
17623 If this option is set, it is expanded, and the result is taken as the current
17624 size the mailbox. It must be a decimal number, optionally followed by K or M.
17625 This provides a way of obtaining this information from an external source that
17626 maintains the data. This is likely to be helpful for maildir deliveries where
17627 it is computationally expensive to compute the size of a mailbox.
17630 .conf maildir@_format boolean false
17631 .index maildir format||specifying
17632 If this option is set with the \directory\ option, the delivery is into a new
17633 file, in the `maildir' format that is used by other mail software. When the
17634 transport is activated directly from a \%redirect%\ router (for example, the
17635 \%address@_file%\ transport in the default configuration), setting
17636 \maildir@_format\ causes the path received from the router to be treated as a
17637 directory, whether or not it ends with \"/"\. This option is available only if
17638 \\SUPPORT@_MAILDIR\\ is present in \(Local/Makefile)\. See section
17639 ~~SECTmaildirdelivery below for further details.
17641 .conf maildir@_quota@_directory@_regex string "See below"
17642 .index maildir format||quota, directories included in
17643 .index quota||maildir, directories included in
17644 This option is relevant only when \maildir@_use@_size@_file\ is set. It defines
17645 a regular expression for specifying directories that should be included in the
17646 quota calculation. The default value is
17648 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
17650 which includes the \(cur)\ and \(new)\ directories, and any maildir++ folders
17651 (directories whose names begin with a dot). If you want to exclude the
17653 folder from the count (as some sites do), you need to change this setting to
17655 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
17657 This uses a negative lookahead in the regular expression to exclude the
17658 directory whose name is \(.Trash)\.
17660 .conf maildir@_retries integer 10
17661 This option specifies the number of times to retry when writing a file in
17662 `maildir' format. See section ~~SECTmaildirdelivery below.
17664 .conf maildir@_tag string$**$ unset
17665 This option applies only to deliveries in maildir format, and is described in
17666 section ~~SECTmaildirdelivery below.
17668 .conf maildir@_use@_size@_file boolean false
17669 .index maildir format||\(maildirsize)\ file
17670 Setting this option true enables support for \(maildirsize)\ files. Exim
17671 creates a \(maildirsize)\ file in a maildir if one does not exist, taking the
17672 quota from the \quota\ option of the transport. If \quota\ is unset, the value
17673 is zero. See section ~~SECTmaildirdelivery below for further details.
17675 .conf mailstore@_format boolean false
17676 .index mailstore format||specifying
17677 If this option is set with the \directory\ option, the delivery is into two new
17678 files in `mailstore' format. The option is available only if
17679 \\SUPPORT@_MAILSTORE\\ is present in \(Local/Makefile)\. See section
17680 ~~SECTopdir below for further details.
17682 .conf mailstore@_prefix string$**$ unset
17683 This option applies only to deliveries in mailstore format, and is described in
17684 section ~~SECTopdir below.
17686 .conf mailstore@_suffix string$**$ unset
17687 This option applies only to deliveries in mailstore format, and is described in
17688 section ~~SECTopdir below.
17690 .conf mbx@_format boolean false
17691 .index locking files
17692 .index file||locking
17693 .index file||MBX format
17694 .index MBX format, specifying
17695 This option is available only if Exim has been compiled with \\SUPPORT@_MBX\\
17696 set in \(Local/Makefile)\. If \mbx@_format\ is set with the \file\ option,
17697 the message is appended to the mailbox file in MBX format instead of
17698 traditional Unix format. This format is supported by Pine4 and its associated
17699 IMAP and POP daemons, by means of the \*c-client*\ library that they all use.
17701 \**Note**\: The \message@_prefix\ and \message@_suffix\ options are not
17702 automatically changed by the use of \mbx@_format\. They should normally be set
17703 empty when using MBX format, so this option almost always appears in this
17711 If none of the locking options are mentioned in the configuration,
17712 \use@_mbx@_lock\ is assumed and the other locking options default to false. It
17713 is possible to specify the other kinds of locking with \mbx@_format\, but
17714 \use@_fcntl@_lock\ and \use@_mbx@_lock\ are mutually exclusive. MBX locking
17715 interworks with \*c-client*\, providing for shared access to the mailbox. It
17716 should not be used if any program that does not use this form of locking is
17717 going to access the mailbox, nor should it be used if the mailbox file is NFS
17718 mounted, because it works only when the mailbox is accessed from a single host.
17720 If you set \use@_fcntl@_lock\ with an MBX-format mailbox, you cannot use
17721 the standard version of \*c-client*\, because as long as it has a mailbox open
17722 (this means for the whole of a Pine or IMAP session), Exim will not be able to
17723 append messages to it.
17725 .conf message@_prefix string$**$ "see below"
17727 The string specified here is expanded and output at the start of every message.
17728 The default is unset unless \file\ is specified and \use@_bsmtp\ is not set, in
17731 message_prefix = "From ${if def:return_path{$return_path}\
17732 {MAILER-DAEMON}} $tod_bsdinbox\n"
17735 .conf message@_suffix string$**$ "see below"
17736 The string specified here is expanded and output at the end of every message.
17737 The default is unset unless \file\ is specified and \use@_bsmtp\ is not set, in
17738 which case it is a single newline character. The suffix can be suppressed by
17744 .conf mode "octal integer" 0600
17745 If the output file is created, it is given this mode. If it already exists and
17746 has wider permissions, they are reduced to this mode. If it has narrower
17747 permissions, an error occurs unless \mode__fail__narrower\ is false. However,
17748 if the delivery is the result of a \save\ command in a filter file specifing a
17749 particular mode, the mode of the output file is always forced to take that
17750 value, and this option is ignored.
17752 .conf mode@_fail@_narrower boolean true
17753 This option applies in the case when an existing mailbox file has a narrower
17754 mode than that specified by the \mode\ option. If \mode@_fail@_narrower\ is
17755 true, the delivery is deferred (`mailbox has the wrong mode'); otherwise Exim
17756 continues with the delivery attempt, using the existing mode of the file.
17758 .conf notify@_comsat boolean false
17759 If this option is true, the \*comsat*\ daemon is notified after every successful
17760 delivery to a user mailbox. This is the daemon that notifies logged on users
17761 about incoming mail.
17763 .conf quota string$**$ unset
17764 .index quota||imposed by Exim
17765 This option imposes a limit on the size of the file to which Exim is appending,
17766 or to the total space used in the directory tree when the \directory\ option is
17767 set. In the latter case, computation of the space used is expensive, because
17768 all the files in the directory (and any sub-directories) have to be
17769 individually inspected and their sizes summed.
17770 (See \quota@_size@_regex\ and \maildir@_use@_size@_file\ for ways to avoid this
17771 in environments where users have no shell access to their mailboxes).
17773 As there is no interlock against two simultaneous deliveries into a
17774 multi-file mailbox, it is possible for the quota to be overrun in this case.
17775 For single-file mailboxes, of course, an interlock is a necessity.
17777 A file's size is taken as its \*used*\ value. Because of blocking effects, this
17778 may be a lot less than the actual amount of disk space allocated to the file.
17779 If the sizes of a number of files are being added up, the rounding effect can
17780 become quite noticeable, especially on systems that have large block sizes.
17781 Nevertheless, it seems best to stick to the \*used*\ figure, because this is
17782 the obvious value which users understand most easily.
17784 The value of the option is expanded, and must then be a numerical value
17785 (decimal point allowed), optionally followed by one of the letters K or M. The
17786 expansion happens while Exim is running as root, before it changes uid for the
17787 delivery. This means that files which are inaccessible to the end user can be
17788 used to hold quota values that are looked up in the expansion. When delivery
17789 fails because this quota is exceeded, the handling of the error is as for
17790 system quota failures.
17792 \**Note**\: A value of zero is interpreted as `no quota'.
17794 By default, Exim's quota checking mimics system quotas, and restricts the
17795 mailbox to the specified maximum size, though the value is not accurate to the
17796 last byte, owing to separator lines and additional headers that may get added
17797 during message delivery. When a mailbox is nearly full, large messages may get
17798 refused even though small ones are accepted, because the size of the current
17799 message is added to the quota when the check is made. This behaviour can be
17800 changed by setting \quota@_is@_inclusive\ false. When this is done, the check
17801 for exceeding the quota does not include the current message. Thus, deliveries
17802 continue until the quota has been exceeded; thereafter, no further messages are
17803 delivered. See also \quota@_warn@_threshold\.
17805 .conf quota@_directory string$**$ unset
17806 This option defines the directory to check for quota purposes when delivering
17807 into individual files. The default is the delivery directory, or, if a file
17808 called \(maildirfolder)\ exists in a maildir directory, the parent of the
17809 delivery directory.
17811 .conf quota@_filecount string$**$ 0
17812 This option applies when the \directory\ option is set. It limits the total
17813 number of files in the directory (compare the inode limit in system quotas). It
17814 can only be used if \quota\ is also set. The value is expanded; an expansion
17815 failure causes delivery to be deferred.
17817 .conf quota@_is@_inclusive boolean true
17820 .conf quota@_size@_regex string unset
17821 This option applies when one of the delivery modes that writes a separate file
17822 for each message is being used. When Exim wants to find the size of one of
17823 these files in order to test the quota, it first checks \quota@_size@_regex\.
17824 If this is set to a regular expression that matches the file name, and it
17825 captures one string, that string is interpreted as a representation of the
17826 file's size. The value of \quota@_size@_regex\ is not expanded.
17828 This feature is useful only when users have no shell access to their mailboxes
17829 -- otherwise they could defeat the quota simply by renaming the files. This
17830 facility can be used with maildir deliveries, by setting \maildir@_tag\ to add
17831 the file length to the file name. For example:
17833 maildir_tag = ,S=$message_size
17834 quota_size_regex = ,S=(\d+)
17836 The regular expression should not assume that the length is at the end of the
17837 file name (even though \maildir@_tag\ puts it there) because maildir MUAs
17838 sometimes add other information onto the ends of message file names.
17840 .conf quota@_warn@_message string$**$ "see below"
17841 See below for the use of this option. If it is not set when
17842 \quota@_warn@_threshold\ is set, it defaults to
17844 quota_warn_message = "\
17845 To: $local_part@$domain\n\
17846 Subject: Your mailbox\n\n\
17847 This message is automatically created \
17848 by mail delivery software.\n\n\
17849 The size of your mailbox has exceeded \
17850 a warning threshold that is\n\
17851 set by the system administrator.\n"
17854 .conf quota@_warn@_threshold string$**$ 0
17855 .index quota||warning threshold
17856 .index mailbox||size warning
17857 .index size||of mailbox
17858 This option is expanded in the same way as \quota\ (see above). If the
17859 resulting value is greater than zero, and delivery of the message causes the
17860 size of the file or total space in the directory tree to cross the given
17861 threshold, a warning message is sent. If \quota\ is also set, the threshold may
17862 be specified as a percentage of it by following the value with a percent sign.
17866 quota_warn_threshold = 75%
17868 If \quota\ is not set, a setting of \quota@_warn@_threshold\ that ends with a
17869 percent sign is ignored.
17871 The warning message itself is specified by the \quota@_warn@_message\ option,
17872 and it must start with a ::To:: header line containing the recipient(s). A
17873 ::Subject:: line should also normally be supplied. The \quota\ option does not
17874 have to be set in order to use this option; they are independent of one
17875 another except when the threshold is specified as a percentage.
17877 .conf use@_bsmtp boolean false
17878 .index envelope sender
17879 If this option is set true, \%appendfile%\ writes messages in `batch SMTP'
17880 format, with the envelope sender and recipient(s) included as SMTP commands. If
17881 you want to include a leading \\HELO\\ command with such messages, you can do
17882 so by setting the \message@_prefix\ option. See section ~~SECTbatchSMTP for
17883 details of batch SMTP.
17885 .conf use@_crlf boolean false
17886 .index carriage return
17888 This option causes lines to be terminated with the two-character CRLF sequence
17889 (carriage return, linefeed) instead of just a linefeed character. In the case
17890 of batched SMTP, the byte sequence written to the file is then an exact image
17891 of what would be sent down a real SMTP connection.
17893 The contents of the \message@_prefix\ and \message@_suffix\ options are written
17894 verbatim, so must contain their own carriage return characters if these are
17895 needed. In cases where these options have non-empty defaults, the values end
17896 with a single linefeed, so they
17898 be changed to end with \"@\r@\n"\ if \use@_crlf\ is set.
17900 .conf use@_fcntl@_lock boolean "see below"
17901 This option controls the use of the \*fcntl()*\ function to lock a file for
17902 exclusive use when a message is being appended. It is set by default unless
17903 \use@_flock@_lock\ is set. Otherwise, it should be turned off only if you know
17904 that all your MUAs use lock file locking. When both \use@_fcntl@_lock\ and
17905 \use@_flock@_lock\ are unset, \use@_lockfile\ must be set.
17907 .conf use@_flock@_lock boolean false
17908 This option is provided to support the use of \*flock()*\ for file locking, for
17909 the few situations where it is needed. Most modern operating systems support
17910 \*fcntl()*\ and \*lockf()*\ locking, and these two functions interwork with
17911 each other. Exim uses \*fcntl()*\ locking by default.
17913 This option is required only if you are using an operating system where
17914 \*flock()*\ is used by programs that access mailboxes (typically MUAs), and
17915 where \*flock()*\ does not correctly interwork with \*fcntl()*\. You can use
17916 both \*fcntl()*\ and \*flock()*\ locking simultaneously if you want.
17918 .index Solaris||\*flock()*\ support
17919 Not all operating systems provide \*flock()*\. Some versions of Solaris do not
17920 have it (and some, I think, provide a not quite right version built on top of
17921 \*lockf()*\). If the OS does not have \*flock()*\, Exim will be built without
17922 the ability to use it, and any attempt to do so will cause a configuration
17925 \**Warning**\: \*flock()*\ locks do not work on NFS files (unless \*flock()*\
17926 is just being mapped onto \*fcntl()*\ by the OS).
17928 .conf use@_lockfile boolean "see below"
17929 If this option is turned off, Exim does not attempt to create a lock file when
17930 appending to a mailbox file. In this situation, the only locking is by
17931 \*fcntl()*\. You should only turn \use@_lockfile\ off if you are absolutely
17932 sure that every MUA that is ever going to look at your users' mailboxes uses
17933 \*fcntl()*\ rather than a lock file, and even then only when you are not
17934 delivering over NFS from more than one host.
17936 .index NFS||lock file
17937 In order to append to an NFS file safely from more than one host, it is
17938 necessary to take out a lock $it{before} opening the file, and the lock file
17939 achieves this. Otherwise, even with \*fcntl()*\ locking, there is a risk of
17942 The \use@_lockfile\ option is set by default unless \use@_mbx@_lock\ is set. It
17943 is not possible to turn both \use@_lockfile\ and \use@_fcntl@_lock\ off, except
17944 when \mbx@_format\ is set.
17946 .conf use@_mbx@_lock boolean "see below"
17947 This option is available only if Exim has been compiled with \\SUPPORT@_MBX\\
17948 set in \(Local/Makefile)\. Setting the option specifies that special MBX
17949 locking rules be used. It is set by default if \mbx@_format\ is set and none of
17950 the locking options are mentioned in the configuration. The locking rules are
17951 the same as are used by the \*c-client*\ library that underlies Pine and the
17952 IMAP4 and POP daemons that come with it (see the discussion below). The rules
17953 allow for shared access to the mailbox. However, this kind of locking does not
17954 work when the mailbox is NFS mounted.
17956 You can set \use@_mbx@_lock\ with either (or both) of \use@_fcntl@_lock\ and
17957 \use@_flock@_lock\ to control what kind of locking is used in implementing the
17958 MBX locking rules. The default is to use \*fcntl()*\ if \use@_mbx@_lock\ is set
17959 without \use@_fcntl@_lock\ or \use@_flock@_lock\.
17963 .section Operational details for appending
17964 .rset SECTopappend "~~chapter.~~section"
17965 .index appending to a file
17966 .index file||appending
17967 Before appending to a file, the following preparations are made:
17969 If the name of the file is \(/dev/null)\, no action is taken, and a success
17972 .index directory creation
17973 If any directories on the file's path are missing, Exim creates them if the
17974 \create@_directory\ option is set. A created directory's mode is given by the
17975 \directory@_mode\ option.
17977 If \file@_format\ is set, the format of an existing file is checked. If this
17978 indicates that a different transport should be used, control is passed to that
17981 .index file||locking
17982 .index locking files
17983 .index NFS||lock file
17984 If \use@_lockfile\ is set, a lock file is built in a way that will work
17985 reliably over NFS, as follows:
17987 Create a `hitching post' file whose name is that of the lock file with the
17988 current time, primary host name, and process id added, by opening for writing
17989 as a new file. If this fails with an access error, delivery is deferred.
17991 Close the hitching post file, and hard link it to the lock file name.
17993 If the call to \*link()*\ succeeds, creation of the lock file has succeeded.
17994 Unlink the hitching post name.
17996 Otherwise, use \*stat()*\ to get information about the hitching post file, and
17997 then unlink hitching post name. If the number of links is exactly two, creation
17998 of the lock file succeeded but something (for example, an NFS server crash and
17999 restart) caused this fact not to be communicated to the \*link()*\ call.
18001 If creation of the lock file failed, wait for \lock@_interval\ and try again,
18002 up to \lock@_retries\ times. However, since any program that writes to a
18003 mailbox should complete its task very quickly, it is reasonable to time out old
18004 lock files that are normally the result of user agent and system crashes. If an
18005 existing lock file is older than \lockfile@_timeout\ Exim attempts to unlink it
18006 before trying again.
18009 A call is made to \*lstat()*\ to discover whether the main file exists, and if
18010 so, what its characteristics are. If \*lstat()*\ fails for any reason other
18011 than non-existence, delivery is deferred.
18013 .index symbolic link||to mailbox
18014 .index mailbox||symbolic link
18015 If the file does exist and is a symbolic link, delivery is deferred, unless the
18016 \allow@_symlink\ option is set, in which case the ownership of the link is
18017 checked, and then \*stat()*\ is called to find out about the real file, which
18018 is then subjected to the checks below. The check on the top-level link
18019 ownership prevents one user creating a link for another's mailbox in a sticky
18020 directory, though allowing symbolic links in this case is definitely not a good
18021 idea. If there is a chain of symbolic links, the intermediate ones are not
18024 If the file already exists but is not a regular file, or if the file's owner
18025 and group (if the group is being checked -- see \check@_group\ above) are
18026 different from the user and group under which the delivery is running,
18027 delivery is deferred.
18029 If the file's permissions are more generous than specified, they are reduced.
18030 If they are insufficient, delivery is deferred, unless \mode@_fail@_narrower\
18031 is set false, in which case the delivery is tried using the existing
18034 The file's inode number is saved, and the file is then opened for appending. If
18035 this fails because the file has vanished, \%appendfile%\ behaves as if it hadn't
18036 existed (see below). For any other failures, delivery is deferred.
18038 If the file is opened successfully, check that the inode number hasn't
18039 changed, that it is still a regular file, and that the owner and permissions
18040 have not changed. If anything is wrong, defer delivery and freeze the message.
18042 If the file did not exist originally, defer delivery if the \file@_must@_exist\
18043 option is set. Otherwise, check that the file is being created in a permitted
18044 directory if the \create@_file\ option is set (deferring on failure), and then
18045 open for writing as a new file, with the \\O@_EXCL\\ and \\O@_CREAT\\ options,
18046 except when dealing with a symbolic link (the \allow@_symlink\ option must be
18047 set). In this case, which can happen if the link points to a non-existent file,
18048 the file is opened for writing using \\O@_CREAT\\ but not \\O@_EXCL\\, because
18049 that prevents link following.
18051 .index loop||while file testing
18052 If opening fails because the file exists, obey the tests given above for
18053 existing files. However, to avoid looping in a situation where the file is
18054 being continuously created and destroyed, the exists/not-exists loop is broken
18055 after 10 repetitions, and the message is then frozen.
18057 If opening fails with any other error, defer delivery.
18059 .index file||locking
18060 .index locking files
18061 Once the file is open, unless both \use@_fcntl@_lock\ and \use@_flock@_lock\
18062 are false, it is locked using \*fcntl()*\ or \*flock()*\ or both. If
18063 \use@_mbx@_lock\ is false, an exclusive lock is requested in each case.
18064 However, if \use@_mbx@_lock\ is true,
18065 Exim takes out a shared lock on the open file,
18066 and an exclusive lock on the file whose name is
18068 /tmp/.<<device-number>>.<<inode-number>>
18070 using the device and inode numbers of the open mailbox file, in accordance with
18071 the MBX locking rules.
18073 If Exim fails to lock the file, there are two possible courses of action,
18074 depending on the value of the locking timeout. This is obtained from
18075 \lock@_fcntl@_timeout\ or \lock@_flock@_timeout\, as appropriate.
18077 If the timeout value is zero, the file is closed, Exim waits for
18078 \lock@_interval\, and then goes back and re-opens the file as above and tries
18079 to lock it again. This happens up to \lock@_retries\ times, after which the
18080 delivery is deferred.
18082 If the timeout has a value greater than zero, blocking calls to \*fcntl()*\ or
18083 \*flock()*\ are used (with the given timeout), so there has already been some
18084 waiting involved by the time locking fails. Nevertheless, Exim does not give up
18085 immediately. It retries up to
18087 (lock@_retries * lock@_interval) / <<timeout>>
18089 times (rounded up).
18092 At the end of delivery, Exim closes the file (which releases the \*fcntl()*\
18093 and/or \*flock()*\ locks) and then deletes the lock file if one was created.
18095 .section Operational details for delivery to a new file
18096 .rset SECTopdir "~~chapter.~~section"
18097 .index delivery||to single file
18099 When the \directory\ option is set instead of \file\, each message is delivered
18100 into a newly-created file or set of files. When \%appendfile%\ is activated
18101 directly from a \%redirect%\ router, neither \file\ nor \directory\ is normally
18102 set, because the path for delivery is supplied by the router. (See for example,
18103 the \%address@_file%\ transport in the default configuration.) In this case,
18104 delivery is to a new file if either the path name ends in \"/"\, or the
18105 \maildir@_format\ or \mailstore@_format\ option is set.
18107 No locking is required while writing the message to a new file, so the various
18108 locking options of the transport are ignored. The `From' line that by default
18109 separates messages in a single file is not normally needed, nor is the escaping
18110 of message lines that start with `From', and there is no need to ensure a
18111 newline at the end of each message. Consequently, the default values for
18112 \check@_string\, \message@_prefix\, and \message@_suffix\ are all unset when
18113 any of \directory\, \maildir@_format\, or \mailstore@_format\ is set.
18115 If Exim is required to check a \quota\ setting, it adds up the sizes of all the
18116 files in the delivery directory by default. However, you can specify a
18117 different directory by setting \quota@_directory\. Also, for maildir deliveries
18118 (see below) the \(maildirfolder)\ convention is honoured.
18121 .index maildir format
18122 .index mailstore format
18123 There are three different ways in which delivery to individual files can be
18124 done, controlled by the settings of the \maildir@_format\ and
18125 \mailstore@_format\ options. Note that code to support maildir or mailstore
18126 formats is not included in the binary unless \\SUPPORT@_MAILDIR\\ or
18127 \\SUPPORT@_MAILSTORE\\, respectively, is set in \(Local/Makefile)\.
18129 .index directory creation
18130 In all three cases an attempt is made to create the directory and any necessary
18131 sub-directories if they do not exist, provided that the \create@_directory\
18132 option is set (the default). The location of a created directory can be
18133 constrained by setting \create@_file\. A created directory's mode is given by
18134 the \directory@_mode\ option. If creation fails, or if the \create@_directory\
18135 option is not set when creation is required, delivery is deferred.
18138 .section Maildir delivery
18139 .rset SECTmaildirdelivery "~~chapter.~~section"
18140 .index maildir format||description of
18141 If the \maildir@_format\ option is true, Exim delivers each message by writing
18142 it to a file whose name is \(tmp/<<stime>>.H<<mtime>>P<<pid>>.<<host>>)\ in the
18143 given directory. If the delivery is successful, the file is renamed into the
18144 \(new)\ subdirectory.
18146 In the file name, <<stime>> is the current time of day in seconds, and
18147 <<mtime>> is the microsecond fraction of the time. After a maildir delivery,
18148 Exim checks that the time-of-day clock has moved on by at least one microsecond
18149 before terminating the delivery process. This guarantees uniqueness for the
18150 file name. However, as a precaution, Exim calls \*stat()*\ for the file before
18151 opening it. If any response other than \\ENOENT\\ (does not exist) is given,
18152 Exim waits 2 seconds and tries again, up to \maildir@_retries\ times.
18154 .index quota||in maildir delivery
18156 If Exim is required to check a \quota\ setting before a maildir delivery, and
18157 \quota@_directory\ is not set, it looks for a file called \(maildirfolder)\ in
18158 the maildir directory (alongside \(new)\, \(cur)\, \(tmp)\). If this exists,
18159 Exim assumes the directory is a maildir++ folder directory, which is one level
18160 down from the user's top level mailbox directory. This causes it to start at
18161 the parent directory instead of the current directory when calculating the
18162 amount of space used.
18165 One problem with delivering into a multi-file mailbox is that it is
18166 computationally expensive to compute the size of the mailbox for quota
18167 checking. Various approaches have been taken to reduce the amount of work
18168 needed. The next two sections describe two of them. A third alternative is to
18169 use some external process for maintaining the size data, and use the expansion
18170 of the \mailbox@_size\ option as a way of importing it into Exim.
18174 .section Using tags to record message sizes
18175 If \maildir@_tag\ is set, the string is expanded for each delivery.
18176 When the maildir file is renamed into the \(new)\ sub-directory, the
18177 tag is added to its name. However, if adding the tag takes the length of the
18178 name to the point where the test \*stat()*\ call fails with \\ENAMETOOLONG\\,
18179 the tag is dropped and the maildir file is created with no tag.
18181 Tags can be used to encode the size of files in their names; see
18182 \quota@_size@_regex\ above for an example. The expansion of \maildir@_tag\
18183 happens after the message has been written. The value of the \$message@_size$\
18184 variable is set to the number of bytes actually written. If the expansion is
18185 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
18186 be deferred. The expanded tag may contain any printing characters except `/'.
18187 Non-printing characters in the string are ignored; if the resulting string is
18188 empty, it is ignored. If it starts with an alphanumeric character, a leading
18192 .section Using a maildirsize file
18193 .index quota||in maildir delivery
18194 .index maildir format||\(maildirsize)\ file
18195 If \maildir@_use@_size@_file\ is true, Exim implements the maildir++ rules for
18196 storing quota and message size information in a file called \(maildirsize)\
18197 within the maildir directory. If this file does not exist, Exim creates it,
18198 setting the quota from the \quota\ option of the transport. If the maildir
18199 directory itself does not exist, it is created before any attempt to write a
18200 \(maildirsize)\ file.
18202 The \(maildirsize)\ file is used to hold information about the sizes of
18203 messages in the maildir, thus speeding up quota calculations. The quota value
18204 in the file is just a cache; if the quota is changed in the transport, the new
18205 value overrides the cached value when the next message is delivered. The cache
18206 is maintained for the benefit of other programs that access the maildir and
18207 need to know the quota.
18209 If the \quota\ option in the transport is unset or zero, the \(maildirsize)\
18210 file is maintained (with a zero quota setting), but no quota is imposed.
18212 A regular expression is available for controlling which directories in the
18213 maildir participate in quota calculations. See the description of the
18214 \maildir@_quota@_directory@_regex\ option above for details.
18217 .section Mailstore delivery
18218 .index mailstore format||description of
18219 If the \mailstore@_format\ option is true, each message is written as two files
18220 in the given directory. A unique base name is constructed from the message id
18221 and the current delivery process, and the files that are written use this base
18222 name plus the suffixes \(.env)\ and \(.msg)\. The \(.env)\ file contains the
18223 message's envelope, and the \(.msg)\ file contains the message itself.
18225 During delivery, the envelope is first written to a file with the suffix
18226 \(.tmp)\. The \(.msg)\ file is then written, and when it is complete, the
18227 \(.tmp)\ file is renamed as the \(.env)\ file. Programs that access messages in
18228 mailstore format should wait for the presence of both a \(.msg)\ and a \(.env)\
18229 file before accessing either of them. An alternative approach is to wait for
18230 the absence of a \(.tmp)\ file.
18232 The envelope file starts with any text defined by the \mailstore@_prefix\
18233 option, expanded and terminated by a newline if there isn't one. Then follows
18234 the sender address on one line, then all the recipient addresses, one per line.
18235 There can be more than one recipient only if the \batch@_max\ option is set
18236 greater than one. Finally, \mailstore@_suffix\ is expanded and the result
18237 appended to the file, followed by a newline if it does not end with one.
18239 If expansion of \mailstore@_prefix\ or \mailstore@_suffix\ ends with a forced
18240 failure, it is ignored. Other expansion errors are treated as serious
18241 configuration errors, and delivery is deferred.
18244 .section Non-special new file delivery
18245 If neither \maildir@_format\ nor \mailstore@_format\ is set, a single new file
18246 is created directly in the named directory. For example, when delivering
18247 messages into files in batched SMTP format for later delivery to some host (see
18248 section ~~SECTbatchSMTP), a setting such as
18250 directory = /var/bsmtp/$host
18252 might be used. A message is written to a file with a temporary name, which is
18253 then renamed when the delivery is complete. The final name is obtained by
18254 expanding the contents of the \directory@_file\ option.
18264 . ============================================================================
18265 .chapter The autoreply transport
18266 .set runningfoot "autoreply transport"
18267 .index transports||\%autoreply%\
18268 .index \%autoreply%\ transport
18269 The \%autoreply%\ transport is not a true transport in that it does not cause
18270 the message to be transmitted. Instead, it generates a new mail message.
18272 If the router that passes the message to this transport does not have the
18273 \unseen\ option set, the original message (for the current recipient) is not
18274 delivered anywhere. However, when the \unseen\ option is set on the router that
18275 passes the message to this transport, routing of the address continues, so
18276 another router can set up a normal message delivery.
18279 The \%autoreply%\ transport is usually run as the result of mail filtering, a
18280 `vacation' message being the standard example. However, it can also be run
18281 directly from a router like any other transport. To reduce the possibility of
18282 message cascades, messages created by the \%autoreply%\ transport always have
18283 empty envelope sender addresses, like bounce messages.
18285 The parameters of the message to be sent can be specified in the configuration
18286 by options described below. However, these are used only when the address
18287 passed to the transport does not contain its own reply information. When the
18288 transport is run as a consequence of a
18290 or \vacation\ command in a filter file, the parameters of the message are
18291 supplied by the filter, and passed with the address. The transport's options
18292 that define the message are then ignored (so they are not usually set in this
18293 case). The message is specified entirely by the filter or by the transport; it
18294 is never built from a mixture of options. However, the \file@_optional\,
18295 \mode\, and \return@_message\ options apply in all cases.
18297 \%Autoreply%\ is implemented as a local transport. When used as a result of a
18298 command in a user's filter file, \%autoreply%\ normally runs under the uid and
18299 gid of the user, and with appropriate current and home directories (see chapter
18300 ~~CHAPenvironment).
18302 There is a subtle difference between routing a message to a \%pipe%\ transport
18303 that generates some text to be returned to the sender, and routing it to an
18304 \%autoreply%\ transport. This difference is noticeable only if more than one
18305 address from the same message is so handled. In the case of a pipe, the
18306 separate outputs from the different addresses are gathered up and returned to
18307 the sender in a single message, whereas if \%autoreply%\ is used, a separate
18308 message is generated for each address that is passed to it.
18310 Non-printing characters are not permitted in the header lines generated for the
18311 message that \%autoreply%\ creates, with the exception of newlines that are
18312 immediately followed by whitespace. If any non-printing characters are found,
18313 the transport defers.
18314 Whether characters with the top bit set count as printing characters or not is
18315 controlled by the \print@_topbitchars\ global option.
18317 If any of the generic options for manipulating headers (for example,
18318 \headers@_add\) are set on an \%autoreply%\ transport, they apply to the copy of
18319 the original message that is included in the generated message when
18320 \return@_message\ is set. They do not apply to the generated message itself.
18322 If the \%autoreply%\ transport receives return code 2 from Exim when it submits
18323 the message, indicating that there were no recipients, it does not treat this
18324 as an error. This means that autoreplies sent to \$sender@_address$\ when this
18325 is empty (because the incoming message is a bounce message) do not cause
18326 problems. They are just discarded.
18329 .section Private options for autoreply
18331 .startconf autoreply
18332 .index options||\%autoreply%\ transport
18333 .conf bcc string$**$ unset
18334 This specifies the addresses that are to receive `blind carbon copies' of the
18335 message when the message is specified by the transport.
18337 .conf cc string$**$ unset
18338 This specifies recipients of the message and the contents of the ::Cc:: header
18339 when the message is specified by the transport.
18341 .conf file string$**$ unset
18342 The contents of the file are sent as the body of the message when the message
18343 is specified by the transport. If both \file\ and \text\ are set, the text
18344 string comes first.
18346 .conf file@_expand boolean false
18347 If this is set, the contents of the file named by the \file\ option are
18348 subjected to string expansion as they are added to the message.
18350 .conf file@_optional boolean false
18351 If this option is true, no error is generated if the file named by the \file\
18352 option or passed with the address does not exist or cannot be read.
18354 .conf from string$**$ unset
18355 This specifies the contents of the ::From:: header when the message is specified
18358 .conf headers string$**$ unset
18359 This specifies additional RFC 2822 headers that are to be added to the message when
18360 the message is specified by the transport. Several can be given by using `@\n'
18361 to separate them. There is no check on the format.
18363 .conf log string$**$ unset
18364 This option names a file in which a record of every message sent is logged when
18365 the message is specified by the transport.
18367 .conf mode "octal integer" 0600
18368 If either the log file or the `once' file has to be created, this mode is used.
18371 .conf never@_mail "address list$**$" unset
18372 If any run of the transport creates a message with a recipient that matches any
18373 item in the list, that recipient is quietly discarded. If all recipients are
18374 discarded, no message is created.
18377 .conf once string$**$ unset
18378 This option names a file or DBM database in which a record of each
18379 ::To:: recipient is kept when the message is specified by the transport.
18380 \**Note**\: This does not apply to ::Cc:: or ::Bcc:: recipients.
18381 If \once@_file@_size\ is not set, a DBM database is used, and it is allowed to
18382 grow as large as necessary. If a potential recipient is already in the
18383 database, no message is sent by default. However, if \once@_repeat\ specifies a
18384 time greater than zero, the message is sent if that much time has elapsed since
18385 a message was last sent to this recipient. If \once\ is unset, the message is
18388 If \once@_file@_size\ is set greater than zero, it changes the way Exim
18389 implements the \once\ option. Instead of using a DBM file to record every
18390 recipient it sends to, it uses a regular file, whose size will never get larger
18391 than the given value. In the file, it keeps a linear list of recipient
18392 addresses and times at which they were sent messages. If the file is full when
18393 a new address needs to be added, the oldest address is dropped. If
18394 \once@_repeat\ is not set, this means that a given recipient may receive
18395 multiple messages, but at unpredictable intervals that depend on the rate of
18396 turnover of addresses in the file. If \once@_repeat\ is set, it specifies a
18397 maximum time between repeats.
18399 .conf once@_file@_size integer 0
18402 .conf once@_repeat time$**$ 0s
18404 After expansion, the value of this option must be a valid time value.
18406 .conf reply@_to string$**$ unset
18407 This specifies the contents of the ::Reply-To:: header when the message is
18408 specified by the transport.
18410 .conf return@_message boolean false
18411 If this is set, a copy of the original message is returned with the new
18412 message, subject to the maximum size set in the \return@_size@_limit\ global
18413 configuration option.
18415 .conf subject string$**$ unset
18416 This specifies the contents of the ::Subject:: header when the message is
18417 specified by the transport.
18419 It is tempting to quote the original subject in automatic responses. For
18422 subject = Re: $h_subject:
18424 There is a danger in doing this, however. It may allow a third party to
18425 subscribe your users to an opt-in mailing list, provided that the list accepts
18426 bounce messages as subscription confirmations. Well-managed lists require a
18427 non-bounce message to confirm a subscription, so the danger is relatively
18431 .conf text string$**$ unset
18432 This specifies a single string to be used as the body of the message when the
18433 message is specified by the transport. If both \text\ and \file\ are set, the
18436 .conf to string$**$ unset
18437 This specifies recipients of the message and the contents of the ::To:: header
18438 when the message is specified by the transport.
18448 . ============================================================================
18449 .chapter The lmtp transport
18450 .set runningfoot "lmtp transport"
18451 .index transports||\%lmtp%\
18452 .index \%lmtp%\ transport
18453 .index LMTP||over a pipe
18454 .index LMTP||over a socket
18455 .rset CHAPLMTP "~~chapter"
18456 The \%lmtp%\ transport runs the LMTP protocol (RFC 2033) over a pipe to a
18458 or by interacting with a Unix domain socket.
18459 This transport is something of a cross between the \%pipe%\ and \%smtp%\
18460 transports. Exim also has support for using LMTP over TCP/IP; this is
18461 implemented as an option for the \%smtp%\ transport. Because LMTP is expected
18462 to be of minority interest, the default build-time configure in \(src/EDITME)\
18463 has it commented out. You need to ensure that
18467 is present in your \(Local/Makefile)\ in order to have the \%lmtp%\ transport
18468 included in the Exim binary.
18470 The private options of the \%lmtp%\ transport are as follows:
18473 .index options||\%lmtp%\ transport
18475 .conf batch@_id string$**$ unset
18476 See the description of local delivery batching in chapter ~~CHAPbatching.
18478 .conf batch@_max integer 1
18479 This limits the number of addresses that can be handled in a single delivery.
18480 Most LMTP servers can handle several addresses at once, so it is normally a
18481 good idea to increase this value. See the description of local delivery
18482 batching in chapter ~~CHAPbatching.
18484 .conf command string$**$ unset
18485 This option must be set if \socket\ is not set.
18486 The string is a command which is run in a separate process. It is split up into
18487 a command name and list of arguments, each of which is separately expanded (so
18488 expansion cannot change the number of arguments). The command is run directly,
18489 not via a shell. The message is passed to the new process using the standard
18490 input and output to operate the LMTP protocol.
18492 .conf socket string$**$ unset
18493 This option must be set if \command\ is not set. The result of expansion must
18494 be the name of a Unix domain socket. The transport connects to the socket and
18495 delivers the message to it using the LMTP protocol.
18497 .conf timeout time 5m
18498 The transport is aborted if the created process
18499 or Unix domain socket
18500 does not respond to LMTP commands or message input within this timeout.
18504 Here is an example of a typical LMTP transport:
18508 command = /some/local/lmtp/delivery/program
18512 This delivers up to 20 addresses at a time, in a mixture of domains if
18513 necessary, running as the user \*exim*\.
18521 . ============================================================================
18522 .chapter The pipe transport
18523 .rset CHAPpipetransport "~~chapter"
18524 .set runningfoot "pipe transport"
18525 .index transports||\%pipe%\
18526 .index \%pipe%\ transport
18527 The \%pipe%\ transport is used to deliver messages via a pipe to a command
18528 running in another process.
18531 use of \%pipe%\ as a pseudo-remote transport for passing messages to some other
18532 delivery mechanism (such as UUCP). Another is the use by individual users to
18533 automatically process their incoming messages. The \%pipe%\ transport can be
18534 used in one of the following ways:
18537 A router routes one address to a transport in the normal way, and the transport
18538 is configured as a \%pipe%\ transport. In this case, \$local@_part$\ contains
18539 the local part of the address (as usual), and the command that is run is
18540 specified by the \command\ option on the transport.
18543 If the \batch@_max\ option is set greater than 1 (the default), the transport
18544 can be called upon to handle more than one address in a single run. In this
18545 case, \$local@_part$\ is not set (because it is not unique). However, the
18546 pseudo-variable \$pipe@_addresses$\ (described in section ~~SECThowcommandrun
18547 below) contains all the addresses that are being handled.
18550 A router redirects an address directly to a pipe command (for example, from an
18551 alias or forward file). In this case, \$local@_part$\ contains the local part
18552 that was redirected, and \$address@_pipe$\ contains the text of the pipe
18553 command itself. The \command\ option on the transport is ignored.
18556 The \%pipe%\ transport is a non-interactive delivery method. Exim can also
18557 deliver messages over pipes using the LMTP interactive protocol. This is
18558 implemented by the \%lmtp%\ transport.
18560 In the case when \%pipe%\ is run as a consequence of an entry in a local user's
18561 \(.forward)\ file, the command runs under the uid and gid of that user. In
18562 other cases, the uid and gid have to be specified explicitly, either on the
18563 transport or on the router that handles the address. Current and `home'
18564 directories are also controllable. See chapter ~~CHAPenvironment for details of
18565 the local delivery environment.
18569 .section Concurrent delivery
18570 If two messages arrive at almost the same time, and both are routed to a pipe
18571 delivery, the two pipe transports may be run concurrently. You must ensure that
18572 any pipe commands you set up are robust against this happening. If the commands
18573 write to a file, the \exim@_lock\ utility might be of use.
18577 .section Returned status and data
18578 .index \%pipe%\ transport||returned data
18579 If the command exits with a non-zero return code, the delivery is deemed to
18580 have failed, unless either the \ignore@_status\ option is set (in which case
18581 the return code is treated as zero), or the return code is one of those listed
18582 in the \temp@_errors\ option, which are interpreted as meaning `try again
18583 later'. In this case, delivery is deferred. Details of a permanent failure are
18584 logged, but are not included in the bounce message, which merely contains
18585 `local delivery failed'.
18587 If the return code is greater than 128 and the command being run is a shell
18588 script, it normally means that the script was terminated by a signal whose
18589 value is the return code minus 128.
18591 If Exim is unable to run the command (that is, if \*execve()*\ fails), the
18592 return code is set to 127. This is the value that a shell returns if it is
18593 asked to run a non-existent command. The wording for the log line suggests that
18594 a non-existent command may be the problem.
18596 The \return@_output\ option can affect the result of a pipe delivery. If it is
18597 set and the command produces any output on its standard output or standard
18598 error streams, the command is considered to have failed, even if it gave a zero
18599 return code or if \ignore@_status\ is set. The output from the command is
18600 included as part of the bounce message. The \return@_fail@_output\ option is
18601 similar, except that output is returned only when the command exits with a
18602 failure return code, that is, a value other than zero or a code that matches
18606 .section How the command is run
18607 .rset SECThowcommandrun "~~chapter.~~section"
18608 .index \%pipe%\ transport||path for command
18609 The command line is (by default) broken down into a command name and arguments
18610 by the \%pipe%\ transport itself. The \allow@_commands\ and \restrict@_to@_path\
18611 options can be used to restrict the commands that may be run.
18612 .index quoting||in pipe command
18613 Unquoted arguments are delimited by white space. If an argument appears in
18614 double quotes, backslash is interpreted as an escape character in the usual
18615 way. If an argument appears in single quotes, no escaping is done.
18617 String expansion is applied to the command line except when it comes from a
18618 traditional \(.forward)\ file (commands from a filter file are expanded). The
18619 expansion is applied to each argument in turn rather than to the whole line.
18620 For this reason, any string expansion item that contains white space must be
18621 quoted so as to be contained within a single argument. A setting such as
18623 command = /some/path ${if eq{$local_part}{postmaster}{xxx}{yyy}}
18625 will not work, because the expansion item gets split between several
18626 arguments. You have to write
18628 command = /some/path "${if eq{$local_part}{postmaster}{xxx}{yyy}}"
18630 to ensure that it is all in one argument. The expansion is done in this way,
18631 argument by argument, so that the number of arguments cannot be changed as a
18632 result of expansion, and quotes or backslashes in inserted variables do not
18633 interact with external quoting.
18635 .index transport||filter
18636 .index filter||transport filter
18637 Special handling takes place when an argument consists of precisely the text
18638 `$tt{@$pipe@_addresses}'. This is not a general expansion variable; the only
18639 place this string is recognized is when it appears as an argument for a pipe or
18640 transport filter command. It causes each address that is being handled to be
18641 inserted in the argument list at that point $it{as a separate argument}. This
18642 avoids any problems with spaces or shell metacharacters, and is of use when a
18643 \%pipe%\ transport is handling groups of addresses in a batch.
18645 After splitting up into arguments and expansion, the resulting command is run
18646 in a subprocess directly from the transport, $it{not} under a shell. The
18647 message that is being delivered is supplied on the standard input, and the
18648 standard output and standard error are both connected to a single pipe that is
18649 read by Exim. The \max@_output\ option controls how much output the command may
18650 produce, and the \return@_output\ and \return@_fail@_output\ options control
18651 what is done with it.
18653 Not running the command under a shell (by default) lessens the security risks
18654 in cases when a command from a user's filter file is built out of data that was
18655 taken from an incoming message. If a shell is required, it can of course be
18656 explicitly specified as the command to be run. However, there are circumstances
18657 where existing commands (for example, in \(.forward)\ files) expect to be run
18658 under a shell and cannot easily be modified. To allow for these cases, there is
18659 an option called \use@_shell\, which changes the way the \%pipe%\ transport
18660 works. Instead of breaking up the command line as just described, it expands it
18661 as a single string and passes the result to \(/bin/sh)\. The
18662 \restrict@_to@_path\ option and the \$pipe@_addresses$\ facility cannot be used
18663 with \use@_shell\, and the whole mechanism is inherently less secure.
18666 .section Environment variables
18667 .rset SECTpipeenv "~~chapter.~~section"
18668 .index \%pipe%\ transport||environment for command
18669 .index environment for pipe transport
18670 The environment variables listed below are set up when the command is invoked.
18671 This list is a compromise for maximum compatibility with other MTAs. Note that
18672 the \environment\ option can be used to add additional variables to this
18676 DOMAIN $t $rm{the domain of the address}
18677 HOME $t $rm{the home directory, if set}
18678 HOST $t $rm{the host name when called from a router (see below)}
18679 LOCAL@_PART $t $rm{see below}
18680 LOCAL@_PART@_PREFIX $t $rm{see below}
18681 LOCAL@_PART@_SUFFIX $t $rm{see below}
18682 LOGNAME $t $rm{see below}
18683 MESSAGE@_ID $t $rm{the message's id}
18684 PATH $t $rm{as specified by the \path\ option below}
18685 QUALIFY@_DOMAIN $t $rm{the sender qualification domain}
18686 RECIPIENT $t $rm{the complete recipient address}
18687 SENDER $t $rm{the sender of the message (empty if a bounce)}
18688 SHELL $t `$tt{/bin/sh}'
18689 TZ $t $rm{the value of the \timezone\ option, if set}
18690 USER $t $rm{see below}
18693 When a \%pipe%\ transport is called directly from (for example) an \%accept%\
18694 router, \\LOCAL@_PART\\ is set to the local part of the address. When it is
18695 called as a result of a forward or alias expansion, \\LOCAL@_PART\\ is set to
18696 the local part of the address that was expanded. In both cases, any affixes are
18697 removed from the local part, and made available in \\LOCAL@_PART@_PREFIX\\ and
18698 \\LOCAL@_PART@_SUFFIX\\, respectively. \\LOGNAME\\ and \\USER\\ are set to the
18699 same value as \\LOCAL@_PART\\ for compatibility with other MTAs.
18702 \\HOST\\ is set only when a \%pipe%\ transport is called from a router that
18703 associates hosts with an address, typically when using \%pipe%\ as a
18704 pseudo-remote transport. \\HOST\\ is set to the first host name specified by
18708 If the transport's generic \home@_directory\ option is set, its value is used
18709 for the \\HOME\\ environment variable. Otherwise, a home directory may be set
18710 by the router's \transport@_home@_directory\ option, which defaults to the
18711 user's home directory if \check@_local@_user\ is set.
18713 .section Private options for pipe
18714 .index options||\%pipe%\ transport
18718 .conf allow@_commands "string list$**$" unset
18719 .index \%pipe%\ transport||permitted commands
18720 The string is expanded, and is then interpreted as a colon-separated list of
18721 permitted commands. If \restrict@_to@_path\ is not set, the only commands
18722 permitted are those in the \allow@_commands\ list. They need not be absolute
18723 paths; the \path\ option is still used for relative paths. If
18724 \restrict@_to@_path\ is set with \allow@_commands\, the command must either be
18725 in the \allow@_commands\ list, or a name without any slashes that is found on
18726 the path. In other words, if neither \allow@_commands\ nor \restrict@_to@_path\
18727 is set, there is no restriction on the command, but otherwise only commands
18728 that are permitted by one or the other are allowed. For example, if
18730 allow_commands = /usr/bin/vacation
18732 and \restrict@_to@_path\ is not set, the only permitted command is
18733 \(/usr/bin/vacation)\. The \allow@_commands\ option may not be set if
18734 \use@_shell\ is set.
18736 .conf batch@_id string$**$ unset
18737 See the description of local delivery batching in chapter ~~CHAPbatching.
18739 .conf batch@_max integer 1
18740 This limits the number of addresses that can be handled in a single delivery.
18741 See the description of local delivery batching in chapter ~~CHAPbatching.
18743 .conf check@_string string unset
18744 As \%pipe%\ writes the message, the start of each line is tested for matching
18745 \check@_string\, and if it does, the initial matching characters are replaced
18746 by the contents of \escape@_string\, provided both are set. The value of
18747 \check@_string\ is a literal string, not a regular expression, and the case of
18748 any letters it contains is significant. When \use@_bsmtp\ is set, the contents
18749 of \check@_string\ and \escape@_string\ are forced to values that implement the
18750 SMTP escaping protocol. Any settings made in the configuration file are
18753 .conf command string$**$ unset
18754 This option need not be set when \%pipe%\ is being used to deliver to pipes
18755 obtained directly from address redirections. In other cases, the option must be
18756 set, to provide a command to be run. It need not yield an absolute path (see
18757 the \path\ option below). The command is split up into separate arguments by
18758 Exim, and each argument is separately expanded, as described in section
18759 ~~SECThowcommandrun above.
18761 .conf environment string$**$ unset
18762 .index \%pipe%\ transport||environment for command
18763 .index environment for \%pipe%\ transport
18764 This option is used to add additional variables to the environment in which the
18765 command runs (see section ~~SECTpipeenv for the default list). Its value is a
18766 string which is expanded, and then interpreted as a colon-separated list of
18767 environment settings of the form `<<name>>=<<value>>'.
18769 .conf escape@_string string unset
18770 See \check@_string\ above.
18772 .conf freeze@_exec@_fail boolean false
18773 .index exec failure
18774 .index failure of exec
18775 .index \%pipe%\ transport||failure of exec
18776 Failure to exec the command in a pipe transport is by default treated like
18777 any other failure while running the command. However, if \freeze@_exec@_fail\
18778 is set, failure to exec is treated specially, and causes the message to be
18779 frozen, whatever the setting of \ignore@_status\.
18781 .conf ignore@_status boolean false
18782 If this option is true, the status returned by the subprocess that is set up to
18783 run the command is ignored, and Exim behaves as if zero had been returned.
18784 Otherwise, a non-zero status
18785 or termination by signal
18786 causes an error return from the transport unless the status value is one of
18787 those listed in \temp@_errors\; these cause the delivery to be deferred and
18790 .conf log@_defer@_output boolean false
18791 .index \%pipe%\ transport||logging output
18792 If this option is set, and the status returned by the command is
18793 one of the codes listed in \temp@_errors\ (that is, delivery was deferred),
18794 and any output was produced, the first line of it is written to the main log.
18796 .conf log@_fail@_output boolean false
18797 If this option is set, and the command returns any output, and also ends with a
18798 return code that is neither zero nor one of the return codes listed in
18799 \temp@_errors\ (that is, the delivery failed), the first line of output is
18800 written to the main log.
18802 .conf log@_output boolean false
18803 If this option is set and the command returns any output, the first line of
18804 output is written to the main log, whatever the return code.
18806 .conf max@_output integer 20K
18807 This specifies the maximum amount of output that the command may produce on its
18808 standard output and standard error file combined. If the limit is exceeded, the
18809 process running the command is killed. This is intended as a safety measure to
18810 catch runaway processes. The limit is applied independently of the settings of
18811 the options that control what is done with such output (for example,
18812 \return@_output\). Because of buffering effects, the amount of output may
18813 exceed the limit by a small amount before Exim notices.
18815 .conf message@_prefix string$**$ "see below"
18816 The string specified here is expanded and output at the start of every message.
18817 The default is unset if \use@_bsmtp\ is set. Otherwise it is
18820 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
18826 This is required by the commonly used \(/usr/bin/vacation)\ program.
18827 However, it must $it{not} be present if delivery is to the Cyrus IMAP server,
18828 or to the \tmail\ local delivery agent. The prefix can be suppressed by setting
18833 .conf message@_suffix string$**$ "see below"
18834 The string specified here is expanded and output at the end of every message.
18835 The default is unset if \use@_bsmtp\ is set. Otherwise it is a single newline.
18836 The suffix can be suppressed by setting
18841 .conf path string $tt{/usr/bin}
18842 This option specifies the string that is set up in the \\PATH\\ environment
18843 variable of the subprocess. If the \command\ option does not yield an absolute
18844 path name, the command is sought in the \\PATH\\ directories, in the usual way.
18845 \**Warning**\: This does not apply to a command specified as a transport
18848 .conf pipe@_as@_creator boolean false
18849 .index uid (user id)||local delivery
18850 If the generic \user\ option is not set and this option is true, the delivery
18851 process is run under the uid that was in force when Exim was originally called
18852 to accept the message. If the group id is not otherwise set (via the generic
18853 \group\ option), the gid that was in force when Exim was originally called to
18854 accept the message is used.
18856 .conf restrict@_to@_path boolean false
18857 When this option is set, any command name not listed in \allow@_commands\ must
18858 contain no slashes. The command is searched for only in the directories listed
18859 in the \path\ option. This option is intended for use in the case when a pipe
18860 command has been generated from a user's \(.forward)\ file. This is usually
18861 handled by a \%pipe%\ transport called \address@_pipe\.
18863 .conf return@_fail@_output boolean false
18864 If this option is true, and the command produced any output and ended with a
18865 return code other than zero or one of the codes listed in \temp@_errors\ (that
18866 is, the delivery failed), the output is returned in the bounce message.
18867 However, if the message has a null sender (that is, it is itself a bounce
18868 message), output from the command is discarded.
18870 .conf return@_output boolean false
18871 If this option is true, and the command produced any output, the delivery is
18872 deemed to have failed whatever the return code from the command, and the output
18873 is returned in the bounce message. Otherwise, the output is just discarded.
18874 However, if the message has a null sender (that is, it is a bounce message),
18875 output from the command is always discarded, whatever the setting of this
18878 .conf temp@_errors "string list" "see below"
18879 .index \%pipe%\ transport||temporary failure
18880 This option contains either a colon-separated list of numbers, or a single
18881 asterisk. If \ignore@_status\ is false
18882 and \return@_output\ is not set,
18883 and the command exits with a non-zero return code, the failure is treated as
18884 temporary and the delivery is deferred if the return code matches one of the
18885 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
18886 codes are treated as permanent errors. The default setting contains the codes
18887 defined by \\EX@_TEMPFAIL\\ and \\EX@_CANTCREAT\\ in \(sysexits.h)\. If Exim is
18888 compiled on a system that does not define these macros, it assumes values of 75
18889 and 73, respectively.
18891 .conf timeout time 1h
18892 If the command fails to complete within this time, it is killed. This normally
18893 causes the delivery to fail. A zero time interval specifies no timeout. In
18894 order to ensure that any subprocesses created by the command are also killed,
18895 Exim makes the initial process a process group leader, and kills the whole
18896 process group on a timeout. However, this can be defeated if one of the
18897 processes starts a new process group.
18899 .conf umask "octal integer" 022
18900 This specifies the umask setting for the subprocess that runs the command.
18902 .conf use@_bsmtp boolean false
18903 .index envelope sender
18904 If this option is set true, the \%pipe%\ transport writes messages in `batch
18905 SMTP' format, with the envelope sender and recipient(s) included as SMTP
18906 commands. If you want to include a leading \\HELO\\ command with such messages,
18907 you can do so by setting the \message@_prefix\ option. See section
18908 ~~SECTbatchSMTP for details of batch SMTP.
18910 .conf use@_crlf boolean false
18911 .index carriage return
18913 This option causes lines to be terminated with the two-character CRLF sequence
18914 (carriage return, linefeed) instead of just a linefeed character. In the case
18915 of batched SMTP, the byte sequence written to the pipe is then an exact image
18916 of what would be sent down a real SMTP connection.
18918 The contents of the \message@_prefix\ and \message@_suffix\ options are written
18919 verbatim, so must contain their own carriage return characters if these are
18920 needed. Since the default values for both \message@_prefix\ and
18921 \message@_suffix\ end with a single linefeed, their values
18923 be changed to end with \"@\r@\n"\ if \use@_crlf\ is set.
18925 .conf use@_shell boolean false
18926 If this option is set, it causes the command to be passed to \(/bin/sh)\
18927 instead of being run directly from the transport, as described in section
18928 ~~SECThowcommandrun. This is less secure, but is needed in some situations
18929 where the command is expected to be run under a shell and cannot easily be
18930 modified. The \allow@_commands\ and \restrict@_to@_path\ options, and the
18931 `$tt{@$pipe@_addresses}' facility are incompatible with \use@_shell\. The
18932 command is expanded as a single string, and handed to \(/bin/sh)\ as data for
18937 .section Using an external local delivery agent
18938 .index local delivery||using an external agent
18939 .index \*procmail*\
18940 .index external local delivery
18941 .index delivery||\*procmail*\
18942 .index delivery||by external agent
18943 The \%pipe%\ transport can be used to pass all messages that require local
18944 delivery to a separate local delivery agent such as \procmail\. When doing
18945 this, care must be taken to ensure that the pipe is run under an appropriate
18946 uid and gid. In some configurations one wants this to be a uid that is trusted
18947 by the delivery agent to supply the correct sender of the message. It may be
18948 necessary to recompile or reconfigure the delivery agent so that it trusts an
18949 appropriate user. The following is an example transport and router
18950 configuration for \procmail\:
18955 command = /usr/local/bin/procmail -d $local_part
18959 check_string = "From "
18960 escape_string = ">From "
18969 transport = procmail_pipe
18972 In this example, the pipe is run as the local user, but with the group set to
18973 \*mail*\. An alternative is to run the pipe as a specific user such as \*mail*\
18974 or \*exim*\, but in this case you must arrange for \procmail\ to trust that
18975 user to supply a correct sender address. If you do not specify either a \group\
18976 or a \user\ option, the pipe command is run as the local user. The home
18977 directory is the user's home directory by default.
18979 Note that the command that the pipe transport runs does $it{not} begin with
18983 as shown in the \procmail\ documentation, because Exim does not by default use
18984 a shell to run pipe commands.
18987 The next example shows a transport and a router for a system where local
18988 deliveries are handled by the Cyrus IMAP server.
18991 local_delivery_cyrus:
18993 command = /usr/cyrus/bin/deliver \
18994 -m ${substr_1:$local_part_suffix} -- $local_part
19007 local_part_suffix = .*
19008 transport = local_delivery_cyrus
19010 Note the unsetting of \message@_prefix\ and \message@_suffix\, and the use of
19011 \return@_output\ to cause any text written by Cyrus to be returned to the
19019 . ============================================================================
19020 .chapter The smtp transport
19021 .rset CHAPsmtptrans "~~chapter"
19022 .set runningfoot "smtp transport"
19023 .index transports||\%smtp%\
19024 .index \%smtp%\ transport
19025 The \%smtp%\ transport delivers messages over TCP/IP connections using the SMTP
19026 or LMTP protocol. The list of hosts to try can either be taken from the address
19027 that is being processed (having been set up by the router), or specified
19028 explicitly for the transport. Timeout and retry processing (see chapter
19029 ~~CHAPretry) is applied to each IP address independently.
19031 .section Multiple messages on a single connection
19032 The sending of multiple messages over a single TCP/IP connection can arise in
19035 If a message contains more than \max@_rcpt\ (see below) addresses that are
19036 routed to the same host, more than one copy of the message has to be sent to
19037 that host. In this situation, multiple copies may be sent in a single run of
19038 the \%smtp%\ transport over a single TCP/IP connection. (What Exim actually does
19039 when it has too many addresses to send in one message also depends on the value
19040 of the global \remote@_max@_parallel\ option. Details are given in section
19043 .index hints database||remembering routing
19044 When a message has been successfully delivered over a TCP/IP connection, Exim
19045 looks in its hints database to see if there are any other messages awaiting a
19046 connection to the same host. If there are, a new delivery process is started
19047 for one of them, and the current TCP/IP connection is passed on to it. The new
19048 process may in turn send multiple copies and possibly create yet another
19052 For each copy sent over the same TCP/IP connection, a sequence counter is
19053 incremented, and if it ever gets to the value of \connection@_max@_messages\,
19054 no further messages are sent over that connection.
19057 .section Use of the @$host variable
19059 .index \$host@_address$\
19060 At the start of a run of the \%smtp%\ transport, the values of \$host$\ and
19061 \$host@_address$\ are the name and IP address of the first host on the host list
19062 passed by the router. However, when the transport is about to connect to a
19063 specific host, and while it is connected to that host, \$host$\ and
19064 \$host@_address$\ are set to the values for that host. These are the values
19065 that are in force when the \helo@_data\, \hosts@_try@_auth\, \interface\,
19066 \serialize@_hosts\, and the various TLS options are expanded.
19069 .section Private options for smtp
19070 The private options of the \%smtp%\ transport are as follows:
19072 .index options||\%smtp%\ transport
19074 .conf allow@_localhost boolean false
19075 .index local host||sending to
19076 .index fallback||hosts specified on transport
19077 When a host specified in \hosts\ or \fallback@_hosts\ (see below) turns out to
19078 be the local host, or is listed in \hosts@_treat@_as@_local\, delivery is
19079 deferred by default. However, if \allow@_localhost\ is set, Exim goes on to do
19080 the delivery anyway. This should be used only in special cases when the
19081 configuration ensures that no looping will result (for example, a differently
19082 configured Exim is listening on the port to which the message is sent).
19084 .conf authenticated@_sender string$**$ unset
19086 When Exim has authenticated as a client, this option sets a value for the
19087 \\AUTH=\\ item on outgoing \\MAIL\\ commands, overriding any existing
19088 authenticated sender value. If the string expansion is forced to fail, the
19089 option is ignored. Other expansion failures cause delivery to be deferred. If
19090 the result of expansion is an empty string, that is also ignored.
19092 If the SMTP session is not authenticated, the expansion of
19093 \authenticated@_sender\ still happens (and can cause the delivery to be
19094 deferred if it fails), but no \\AUTH=\\ item is added to \\MAIL\\ commands.
19096 This option allows you to use the \%smtp%\ transport in LMTP mode to
19097 deliver mail to Cyrus IMAP and provide the proper local part as the
19098 `authenticated sender', via a setting such as:
19100 authenticated_sender = $local_part
19102 This removes the need for IMAP subfolders to be assigned special ACLs to
19103 allow direct delivery to those subfolders.
19105 Because of expected uses such as that just described for Cyrus (when no
19106 domain is involved), there is no checking on the syntax of the provided
19109 .conf command@_timeout time 5m
19110 This sets a timeout for receiving a response to an SMTP command that has been
19111 sent out. It is also used when waiting for the initial banner line from the
19112 remote host. Its value must not be zero.
19114 .conf connect@_timeout time 5m
19115 This sets a timeout for the \*connect()*\ function, which sets up a TCP/IP call
19116 to a remote host. A setting of zero allows the system timeout (typically
19117 several minutes) to act. To have any effect, the value of this option must be
19118 less than the system timeout. However, it has been observed that on some
19119 systems there is no system timeout, which is why the default value for this
19120 option is 5 minutes, a value recommended by RFC 1123.
19122 .index SMTP||passed connection
19123 .index SMTP||multiple deliveries
19124 .index multiple SMTP deliveries
19125 .conf connection@_max@_messages integer 500
19126 This controls the maximum number of separate message deliveries that are sent
19127 over a single TCP/IP connection. If the value is zero, there is no limit.
19128 For testing purposes, this value can be overridden by the \-oB-\ command line
19131 .conf data@_timeout time 5m
19132 This sets a timeout for the transmission of each block in the data portion of
19133 the message. As a result, the overall timeout for a message depends on the size
19134 of the message. Its value must not be zero. See also \final@_timeout\.
19136 .conf delay@_after@_cutoff boolean true
19137 This option controls what happens when all remote IP addresses for a given
19138 domain have been inaccessible for so long that they have passed their retry
19141 In the default state, if the next retry time has not been reached for any of
19142 them, the address is bounced without trying any deliveries. In other words,
19143 Exim delays retrying an IP address after the final cutoff time until a new
19144 retry time is reached, and can therefore bounce an address without ever trying
19145 a delivery, when machines have been down for a long time. Some people are
19146 unhappy at this prospect, so...
19148 If \delay@_after@_cutoff\ is set false, Exim behaves differently. If all IP
19149 addresses are past their final cutoff time, Exim tries to deliver to those
19150 IP addresses that have not been tried since the message arrived. If there are
19151 none, of if they all fail, the address is bounced. In other words, it does not
19152 delay when a new message arrives, but immediately tries those expired IP
19153 addresses that haven't been tried since the message arrived. If there is a
19154 continuous stream of messages for the dead hosts, unsetting
19155 \delay@_after@_cutoff\ means that there will be many more attempts to deliver
19158 .conf dns@_qualify@_single boolean true
19159 If the \hosts\ or \fallback@_hosts\ option is being used,
19160 and the \gethostbyname\ option is false,
19161 the \\RES@_DEFNAMES\\ resolver option is set. See the \qualify@_single\ option
19162 in chapter ~~CHAPdnslookup for more details.
19164 .conf dns@_search@_parents boolean false
19165 .index \search@_parents\
19166 If the \hosts\ or \fallback@_hosts\ option is being used, and the
19167 \gethostbyname\ option is false, the \\RES@_DNSRCH\\ resolver option is set.
19168 See the \search@_parents\ option in chapter ~~CHAPdnslookup for more details.
19171 .conf fallback@_hosts "string list" unset
19172 .index fallback||hosts specified on transport
19173 String expansion is not applied to this option. The argument must be a
19174 colon-separated list of host names or IP addresses. Fallback hosts can also be
19175 specified on routers, which associate them with the addresses they process. As
19176 for the \hosts\ option without \hosts@_override\, \fallback@_hosts\ specified
19177 on the transport is used only if the address does not have its own associated
19178 fallback host list. Unlike \hosts\, a setting of \fallback@_hosts\ on an
19179 address is not overridden by \hosts@_override\. However, \hosts@_randomize\
19180 does apply to fallback host lists.
19182 If Exim is unable to deliver to any of the hosts for a particular address, and
19183 the errors are not permanent rejections, the address is put on a separate
19184 transport queue with its host list replaced by the fallback hosts, unless the
19185 address was routed via MX records and the current host was in the original MX
19186 list. In that situation, the fallback host list is not used.
19188 Once normal deliveries are complete, the fallback queue is delivered by
19189 re-running the same transports with the new host lists. If several failing
19190 addresses have the same fallback hosts (and \max@_rcpt\ permits it), a single
19191 copy of the message is sent.
19193 The resolution of the host names on the fallback list is controlled by the
19194 \gethostbyname\ option, as for the \hosts\ option. Fallback hosts apply
19195 both to cases when the host list comes with the address and when it is taken
19196 from \hosts\. This option provides a `use a smart host only if delivery fails'
19199 .conf final@_timeout time 10m
19200 This is the timeout that applies while waiting for the response to the final
19201 line containing just `.' that terminates a message. Its value must not be zero.
19203 .conf gethostbyname boolean false
19204 If this option is true when the \hosts\ and/or \fallback@_hosts\ options are
19205 being used, names are looked up using \*gethostbyname()*\
19206 (or \*getipnodebyname()*\ when available)
19207 instead of using the DNS. Of course, that function may in fact use the DNS, but
19208 it may also consult other sources of information such as \(/etc/hosts)\.
19210 .index \\HELO\\||argument, setting
19211 .index \\EHLO\\||argument, setting
19212 .conf helo@_data string$**$ $tt{@$primary@_hostname}
19213 The value of this option is expanded, and used as the argument for the \\EHLO\\
19214 or \\HELO\\ command that starts the outgoing SMTP session.
19216 .conf hosts "string list$**$" unset
19217 Hosts are associated with an address by a router such as \%dnslookup%\, which
19218 finds the hosts by looking up the address domain in the DNS. However, addresses
19219 can be passed to the \%smtp%\ transport by any router, and not all of them can
19220 provide an associated host list. The \hosts\ option specifies a list of hosts
19221 which are used if the address being processed does not have any hosts
19222 associated with it. The hosts specified by \hosts\ are also used, whether or
19223 not the address has its own hosts, if \hosts@_override\ is set.
19225 The string is first expanded, before being interpreted as a colon-separated
19226 list of host names or IP addresses. If the expansion fails, delivery is
19227 deferred. Unless the failure was caused by the inability to complete a lookup,
19228 the error is logged to the panic log as well as the main log. Host names are
19229 looked up either by searching directly for address records in the DNS or by
19230 calling \*gethostbyname()*\
19231 (or \*getipnodebyname()*\ when available),
19232 depending on the setting of the \gethostbyname\ option. When Exim is compiled
19233 with IPv6 support, if a host that is looked up in the DNS has both IPv4 and
19234 IPv6 addresses, both types of address are used.
19236 During delivery, the hosts are tried in order, subject to their retry status,
19237 unless \hosts@_randomize\ is set.
19239 .conf hosts@_avoid@_esmtp "host list$**$" unset
19240 .index ESMTP, avoiding use of
19241 .index \\HELO\\||forcing use of
19242 .index \\EHLO\\||avoiding use of
19243 .index \\PIPELINING\\||avoiding the use of
19244 This option is for use with broken hosts that announce ESMTP facilities (for
19245 example, \\PIPELINING\\) and then fail to implement them properly. When a host
19246 matches \hosts@_avoid@_esmtp\, Exim sends \\HELO\\ rather than \\EHLO\\ at the
19247 start of the SMTP session. This means that it cannot use any of the ESMTP
19248 facilities such as \\AUTH\\, \\PIPELINING\\, \\SIZE\\, and \\STARTTLS\\.
19250 .conf hosts@_avoid@_tls "host list$**$" unset
19251 .index TLS||avoiding for certain hosts
19252 Exim will not try to start a TLS session when delivering to any host that
19253 matches this list. See chapter ~~CHAPTLS for details of TLS.
19255 .conf hosts@_max@_try integer 5
19256 .index host||maximum number to try
19257 .index limit||number of hosts tried
19258 .index limit||number of MX tried
19259 .index MX record||maximum tried
19260 This option limits the number of IP addresses that are tried for any one
19261 delivery in cases where there are temporary delivery errors. Section
19262 ~~SECTvalhosmax describes in detail how the value of this option is used.
19265 .conf hosts@_max@_try@_hardlimit integer 50
19266 This is an additional check on the maximum number of IP addresses that Exim
19267 tries for any one delivery. Section ~~SECTvalhosmax describes its use and why
19271 .conf hosts@_nopass@_tls "host list$**$" unset
19272 .index TLS||passing connection
19273 .index multiple SMTP deliveries
19274 .index TLS||multiple message deliveries
19275 For any host that matches this list, a connection on which a TLS session has
19276 been started will not be passed to a new delivery process for sending another
19277 message on the same connection. See section ~~SECTmulmessam for an explanation
19278 of when this might be needed.
19280 .conf hosts@_override boolean false
19281 If this option is set and the \hosts\ option is also set, any hosts that are
19282 attached to the address are ignored, and instead the hosts specified by the
19283 \hosts\ option are always used. This option does not apply to
19286 .conf hosts@_randomize boolean false
19287 .index randomized host list
19288 .index host||list of, randomized
19289 .index fallback||randomized hosts
19290 If this option is set, and either the list of hosts is taken from the
19291 \hosts\ or the \fallback@_hosts\ option, or the hosts supplied by the router
19292 were not obtained from MX records (this includes fallback hosts from the
19293 router), and were not randomizied by the router, the order of trying the hosts
19294 is randomized each time the transport runs. Randomizing the order of a host
19295 list can be used to do crude load sharing.
19297 When \hosts@_randomize\ is true, a host list may be split into groups whose
19298 order is separately randomized. This makes it possible to set up MX-like
19299 behaviour. The boundaries between groups are indicated by an item that is just
19300 \"+"\ in the host list. For example:
19302 hosts = host1:host2:host3:+:host4:host5
19304 The order of the first three hosts and the order of the last two hosts is
19305 randomized for each use, but the first three always end up before the last two.
19306 If \hosts@_randomize\ is not set, a \"+"\ item in the list is ignored.
19308 .index authentication||required by client
19309 .conf hosts@_require@_auth "host list$**$" unset
19310 This option provides a list of servers for which authentication must succeed
19311 before Exim will try to transfer a message. If authentication fails for
19312 servers which are not in this list, Exim tries to send unauthenticated. If
19313 authentication fails for one of these servers, delivery is deferred. This
19314 temporary error is detectable in the retry rules, so it can be turned into a
19315 hard failure if required. See also \hosts@_try@_auth\, and chapter
19316 ~~CHAPSMTPAUTH for details of authentication.
19318 .conf hosts@_require@_tls "host list$**$" unset
19319 .index TLS||requiring for certain servers
19320 Exim will insist on using a TLS session when delivering to any host that
19321 matches this list. See chapter ~~CHAPTLS for details of TLS.
19322 \**Note**\: This option affects outgoing mail only. To insist on TLS for
19323 incoming messages, use an appropriate ACL.
19325 .index authentication||optional in client
19326 .conf hosts@_try@_auth "host list$**$" unset
19327 This option provides a list of servers to which, provided they announce
19328 authentication support, Exim will attempt to authenticate as a client when it
19329 connects. If authentication fails, Exim will try to transfer the message
19330 unauthenticated. See also \hosts@_require@_auth\, and chapter ~~CHAPSMTPAUTH
19331 for details of authentication.
19333 .index bind IP address
19334 .index IP address||binding
19335 .conf interface "string list$**$" unset
19336 This option specifies which interface to bind to when making an outgoing SMTP
19337 call. The variables \$host$\ and \$host@_address$\ refer to the host to which a
19338 connection is about to be made during the expansion of the string. Forced
19339 expansion failure, or an empty string result causes the option to be ignored.
19340 Otherwise, after expansion,
19341 the string must be a list of IP addresses, colon-separated by default, but the
19342 separator can be changed in the usual way.
19345 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
19347 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
19348 connection. If none of them are the correct type, the option is ignored. If
19349 \interface\ is not set, or is ignored, the system's IP functions choose which
19350 interface to use if the host has more than one.
19352 .conf keepalive boolean true
19353 .index keepalive||on outgoing connection
19354 This option controls the setting of \\SO@_KEEPALIVE\\ on outgoing TCP/IP socket
19355 connections. When set, it causes the kernel to probe idle connections
19356 periodically, by sending packets with `old' sequence numbers. The other end of
19357 the connection should send a acknowledgement if the connection is still okay or
19358 a reset if the connection has been aborted. The reason for doing this is that
19359 it has the beneficial effect of freeing up certain types of connection that can
19360 get stuck when the remote host is disconnected without tidying up the TCP/IP
19361 call properly. The keepalive mechanism takes several hours to detect
19364 .conf max@_rcpt integer 100
19365 .index \\RCPT\\||maximum number of outgoing
19366 This option limits the number of \\RCPT\\ commands that are sent in a single
19367 SMTP message transaction. Each set of addresses is treated independently, and
19368 so can cause parallel connections to the same host if \remote@_max@_parallel\
19371 .conf multi@_domain boolean true
19372 When this option is set, the \%smtp%\ transport can handle a number of addresses
19373 containing a mixture of different domains provided they all resolve to the same
19374 list of hosts. Turning the option off restricts the transport to handling only
19375 one domain at a time. This is useful if you want to use \$domain$\ in an
19376 expansion for the transport, because it is set only when there is a single
19377 domain involved in a remote delivery.
19379 .conf port string$**$ "see below"
19380 .index port||sending TCP/IP
19381 .index TCP/IP||setting outgoing port
19382 This option specifies the TCP/IP port on the server to which Exim connects. If
19383 it begins with a digit it is taken as a port number; otherwise it is looked up
19384 using \*getservbyname()*\. The default value is normally `smtp', but if
19385 \protocol\ is set to `lmtp', the default is `lmtp'.
19386 If the expansion fails, or if a port number cannot be found, delivery is
19390 .conf protocol string "smtp"
19391 .index LMTP||over TCP/IP
19392 If this option is set to `lmtp' instead of `smtp', the default value for the
19393 \port\ option changes to `lmtp', and the transport operates the LMTP protocol
19394 (RFC 2033) instead of SMTP. This protocol is sometimes used for local
19395 deliveries into closed message stores. Exim also has support for running LMTP
19396 over a pipe to a local process -- see chapter ~~CHAPLMTP.
19398 .conf retry@_include@_ip@_address boolean true
19399 Exim normally includes both the host name and the IP address in the key it
19400 constructs for indexing retry data after a temporary delivery failure. This
19401 means that when one of several IP addresses for a host is failing, it gets
19402 tried periodically (controlled by the retry rules), but use of the other IP
19403 addresses is not affected.
19405 However, in some dialup environments hosts are assigned a different IP address
19406 each time they connect. In this situation the use of the IP address as part of
19407 the retry key leads to undesirable behaviour. Setting this option false causes
19408 Exim to use only the host name. This should normally be done on a separate
19409 instance of the \%smtp%\ transport, set up specially to handle the dialup hosts.
19411 .conf serialize@_hosts "host list$**$" unset
19412 .index serializing connections
19413 .index host||serializing connections
19414 Because Exim operates in a distributed manner, if several messages for the same
19415 host arrive at around the same time, more than one simultaneous connection to
19416 the remote host can occur. This is not usually a problem except when there is a
19417 slow link between the hosts. In that situation it may be helpful to restrict
19418 Exim to one connection at a time. This can be done by setting
19419 \serialize@_hosts\ to match the relevant hosts.
19421 .index hints database||serializing deliveries to a host
19422 Exim implements serialization by means of a hints database in which a record is
19423 written whenever a process connects to one of the restricted hosts. The record
19424 is deleted when the connection is completed. Obviously there is scope for
19425 records to get left lying around if there is a system or program crash. To
19426 guard against this, Exim ignores any records that are more than six hours old.
19428 If you set up this kind of serialization, you should also arrange to delete the
19429 relevant hints database whenever your system reboots. The names of the files
19430 start with \(misc)\ and they are kept in the \(spool/db)\ directory. There
19431 may be one or two files, depending on the type of DBM in use. The same files
19432 are used for ETRN serialization.
19434 .conf size@_addition integer 1024
19435 .index SMTP||\\SIZE\\
19436 .index message||size issue for transport filter
19437 .index size||of message
19438 .index transport||filter
19439 .index filter||transport filter
19440 If a remote SMTP server indicates that it supports the \\SIZE\\ option of the
19441 \\MAIL\\ command, Exim uses this to pass over the message size at the start of
19442 an SMTP transaction. It adds the value of \size@_addition\ to the value it
19443 sends, to allow for headers and other text that may be added during delivery by
19444 configuration options or in a transport filter. It may be necessary to increase
19445 this if a lot of text is added to messages.
19447 Alternatively, if the value of \size@_addition\ is set negative, it disables
19448 the use of the \\SIZE\\ option altogether.
19450 .conf tls@_certificate string$**$ unset
19451 .index TLS||client certificate, location of
19452 .index certificate||for client, location of
19453 The value of this option must be the absolute path to a file which contains the
19454 client's certificate, for use when sending a message over an encrypted
19455 connection. The values of \$host$\ and \$host@_address$\ are set to the name
19456 and address of the server during the expansion. See chapter ~~CHAPTLS for
19459 \**Note**\: This option must be set if you want Exim to use TLS when sending
19460 messages as a client. The global option of the same name specifies the
19461 certificate for Exim as a server; it is not automatically assumed that the same
19462 certificate should be used when Exim is operating as a client.
19464 .conf tls@_crl string$**$ unset
19465 .index TLS||client certificate revocation list
19466 .index certificate||revocation list for client
19467 This option specifies a certificate revocation list. The expanded value must
19468 be the name of a file that contains a CRL in PEM format.
19470 .conf tls@_privatekey string$**$ unset
19471 .index TLS||client private key, location of
19472 The value of this option must be the absolute path to a file which contains the
19473 client's private key, for use when sending a message over an encrypted
19474 connection. The values of \$host$\ and \$host@_address$\ are set to the name
19475 and address of the server during the expansion.
19476 If this option is unset, the private key is assumed to be in the same file as
19478 See chapter ~~CHAPTLS for details of TLS.
19480 .conf tls@_require@_ciphers string$**$ unset
19481 .index TLS||requiring specific ciphers
19482 .index cipher||requiring specific
19483 The value of this option must be a list of permitted cipher suites, for use
19484 when setting up an outgoing encrypted connection. (There is a global option of
19485 the same name for controlling incoming connections.) The values of \$host$\ and
19486 \$host@_address$\ are set to the name and address of the server during the
19487 expansion. See chapter ~~CHAPTLS for details of TLS; note that this option is
19488 used in different ways by OpenSSL and GnuTLS (see sections ~~SECTreqciphssl and
19491 For GnuTLS, the order of the ciphers is a preference order.
19494 .conf tls@_tempfail@_tryclear boolean true
19495 When the server host is not in \hosts@_require@_tls\, and there is a problem in
19496 setting up a TLS session, this option determines whether or not Exim should try
19497 to deliver the message unencrypted. If it is set false, delivery to the
19498 current host is deferred; if there are other hosts, they are tried. If this
19499 option is set true, Exim attempts to deliver unencrypted after a 4\*xx*\
19500 response to \\STARTTLS\\. Also, if \\STARTTLS\\ is accepted, but the subsequent
19501 TLS negotiation fails, Exim closes the current connection (because it is in an
19502 unknown state), opens a new one to the same host, and then tries the delivery
19505 .conf tls@_verify@_certificates string$**$ unset
19506 .index TLS||server certificate verification
19507 .index certificate||verification of server
19508 The value of this option must be the absolute path to a file containing
19509 permitted server certificates, for use when setting up an encrypted connection.
19510 Alternatively, if you are using OpenSSL, you can set
19511 \tls@_verify@_certificates\ to the name of a directory containing certificate
19512 files. This does not work with GnuTLS; the option must be set to the name of a
19513 single file if you are using GnuTLS. The values of \$host$\ and
19514 \$host@_address$\ are set to the name and address of the server during the
19515 expansion of this option. See chapter ~~CHAPTLS for details of TLS.
19520 .section How the limits for the number of hosts to try are used
19521 .rset SECTvalhosmax "~~chapter.~~section"
19522 .index host||maximum number to try
19523 .index limit||hosts, maximum number tried
19525 There are two options that are concerned with the number of hosts that are
19526 tried when an SMTP delivery takes place. They are \hosts@_max@_try\ and
19527 \hosts@_max@_try@_hardlimit\.
19530 The \hosts@_max@_try\ option limits the number of hosts that are tried
19531 for a single delivery. However, despite the term `host' in its name, the option
19532 actually applies to each IP address independently. In other words, a multihomed
19533 host is treated as several independent hosts, just as it is for retrying.
19535 Many of the larger ISPs have multiple MX records which often point to
19536 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
19537 created as a result of routing one of these domains.
19539 Trying every single IP address on such a long list does not seem sensible; if
19540 several at the top of the list fail, it is reasonable to assume there is some
19541 problem that is likely to affect all of them. Roughly speaking, the value of
19542 \hosts@_max@_try\ is the maximum number that are tried before deferring the
19543 delivery. However, the logic cannot be quite that simple.
19545 Firstly, IP addresses that are skipped because their retry times have not
19546 arrived do not count, and in addition, addresses that are past their retry
19547 limits are also not counted, even when they are tried. This means that when
19548 some IP addresses are past their retry limits, more than the value of
19549 \hosts@_max@_retry\ may be tried. The reason for this behaviour is to ensure
19550 that all IP addresses are considered before timing out an email address (but
19551 see below for an exception).
19553 Secondly, when the \hosts@_max@_try\ limit is reached, Exim looks down the host
19554 list to see if there is a subsequent host with a different (higher valued) MX.
19555 If there is, that host is considered next, and the current IP address is used
19556 but not counted. This behaviour helps in the case of a domain with a retry rule
19557 that hardly ever delays any hosts, as is now explained:
19559 Consider the case of a long list of hosts with one MX value, and a few with a
19560 higher MX value. If \hosts@_max@_try\ is small (the default is 5) only a few
19561 hosts at the top of the list are tried at first. With the default retry rule,
19562 which specifies increasing retry times, the higher MX hosts are eventually
19563 tried when those at the top of the list are skipped because they have not
19564 reached their retry times.
19566 However, it is common practice to put a fixed short retry time on domains for
19567 large ISPs, on the grounds that their servers are rarely down for very long.
19568 Unfortunately, these are exactly the domains that tend to resolve to long lists
19569 of hosts. The short retry time means that the lowest MX hosts are tried every
19570 time. The attempts may be in a different order because of random sorting, but
19571 without the special MX check, the higher MX hosts would never be tried
19573 until all the lower MX hosts had timed out (which might be several days),
19574 because there are always some lower MX hosts that have reached their retry
19575 times. With the special check, Exim considers at least one IP address from each
19576 MX value at every delivery attempt, even if the \hosts@_max@_try\ limit has
19577 already been reached.
19579 The above logic means that \hosts@_max@_try\ is not a hard limit, and in
19580 particular, Exim normally eventually tries all the IP addresses before timing
19581 out an email address. When \hosts@_max@_try\ was implemented, this seemed a
19582 reasonable thing to do. Recently, however, some lunatic DNS configurations have
19583 been set up with hundreds of IP addresses for some domains. It can
19584 take a very long time indeed for an address to time out in these cases.
19586 The \hosts@_max@_try@_hardlimit\ option was added to help with this problem.
19587 Exim never tries more than this number of IP addresses; if it hits this limit
19588 and they are all timed out, the email address is bounced, even though not all
19589 possible IP addresses have been tried.
19599 . ============================================================================
19600 .chapter Address rewriting
19601 .set runningfoot "address rewriting"
19602 .rset CHAPrewrite ~~chapter
19603 .index rewriting||addresses
19604 There are some circumstances in which Exim automatically rewrites domains in
19605 addresses. The two most common are when an address is given without a domain
19606 (referred to as an `unqualified address') or when an address contains an
19607 abbreviated domain that is expanded by DNS lookup.
19609 Unqualified envelope addresses are accepted only for locally submitted
19610 messages, or messages from hosts that match \sender@_unqualified@_hosts\ or
19611 \recipient@_unqualified@_hosts\, respectively. Unqualified addresses in header
19612 lines are qualified if they are in locally submitted messages, or messages from
19613 hosts that are permitted to send unqualified envelope addresses. Otherwise,
19614 unqualified addresses in header lines are neither qualified nor rewritten.
19616 One situation in which Exim does $it{not} automatically rewrite a domain is
19617 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
19618 such a domain should be rewritten using the `canonical' name, and some MTAs do
19619 this. The new RFCs do not contain this suggestion.
19621 .section Explicitly configured address rewriting
19622 This chapter describes the rewriting rules that can be used in the
19623 main rewrite section of the configuration file, and also in the generic
19624 \headers@_rewrite\ option that can be set on any transport.
19626 Some people believe that configured address rewriting is a Mortal Sin.
19627 Others believe that life is not possible without it. Exim provides the
19628 facility; you do not have to use it.
19630 The main rewriting rules that appear in the `rewrite' section of the
19631 configuration file are applied to addresses in incoming messages, both envelope
19632 addresses and addresses in header lines. Each rule specifies the types of
19633 address to which it applies.
19635 Rewriting of addresses in header lines applies only to those headers that
19636 were received with the message, and, in the case of transport rewriting, those
19637 that were added by a system filter. That is, it applies only to those headers
19638 that are common to all copies of the message. Header lines that are added by
19639 individual routers or transports (and which are therefore specific to
19640 individual recipient addresses) are not rewritten.
19642 In general, rewriting addresses from your own system or domain has some
19643 legitimacy. Rewriting other addresses should be done only with great care and
19644 in special circumstances. The author of Exim believes that rewriting should be
19645 used sparingly, and mainly for `regularizing' addresses in your own domains.
19646 Although it can sometimes be used as a routing tool, this is very strongly
19649 There are two commonly encountered circumstances where rewriting is used, as
19650 illustrated by these examples:
19652 The company whose domain is \*hitch.fict.example*\ has a number of hosts that
19653 exchange mail with each other behind a firewall, but there is only a single
19654 gateway to the outer world. The gateway rewrites \*@*.hitch.fict.example*\ as
19655 \*hitch.fict.example*\ when sending mail off-site.
19657 A host rewrites the local parts of its own users so that, for example,
19658 \*fp42@@hitch.fict.example*\ becomes \*Ford.Prefect@@hitch.fict.example*\.
19661 .section When does rewriting happen?
19662 .index rewriting||timing of
19663 .index ~~ACL||rewriting addresses in
19664 Configured address rewriting can take place at several different stages of a
19665 message's processing.
19667 At the start of an ACL for \\MAIL\\, the sender address may have been rewritten
19668 by a special SMTP-time rewrite rule (see section ~~SECTrewriteS), but no
19669 ordinary rewrite rules have yet been applied. If, however, the sender address
19670 is verified in the ACL, it is rewritten before verification, and remains
19671 rewritten thereafter. The subsequent value of \$sender@_address$\ is the
19672 rewritten address. This also applies if sender verification happens in a
19673 \\RCPT\\ ACL. Otherwise, when the sender address is not verified, it is
19674 rewritten as soon as a message's header lines have been received.
19676 Similarly, at the start of an ACL for \\RCPT\\, the current recipient's address
19677 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
19678 rewrite rules have yet been applied to it. However, the behaviour is different
19679 from the sender address when a recipient is verified. The address is rewritten
19680 for the verification, but the rewriting is not remembered at this stage. The
19681 value of \$local@_part$\ and \$domain$\ after verification are always the same
19682 as they were before (that is, they contain the unrewritten -- except for
19683 SMTP-time rewriting -- address).
19685 Once a message's header lines have been received, all the envelope recipient
19686 addresses are permanently rewritten, and rewriting is also applied to the
19687 addresses in the header lines (if configured).
19688 .index \*local@_scan()*\ function||address rewriting, timing of
19689 Thus, all the rewriting is completed before the \\DATA\\ ACL and
19690 \*local@_scan()*\ functions are run.
19692 When an address is being routed, either for delivery or for verification,
19693 rewriting is applied immediately to child addresses that are generated by
19694 redirection, unless \no@_rewrite\ is set on the router.
19696 .index envelope sender, rewriting
19697 .index rewriting||at transport time
19698 At transport time, additional rewriting of addresses in header lines can be
19699 specified by setting the generic \headers@_rewrite\ option on a transport. This
19700 option contains rules that are identical in form to those in the rewrite
19701 section of the configuration file. In addition, the outgoing envelope sender
19702 can be rewritten by means of the \return@_path\ transport option. However, it
19703 is not possible to rewrite envelope recipients at transport time.
19707 .section Testing the rewriting rules that apply on input
19708 .index rewriting||testing
19709 .index testing||rewriting
19710 Exim's input rewriting configuration appears in a part of the run time
19711 configuration file headed by `begin rewrite'. It can be tested by the \-brw-\
19712 command line option. This takes an address (which can be a full RFC 2822
19713 address) as its argument. The output is a list of how the address would be
19714 transformed by the rewriting rules for each of the different places it might
19715 appear in an incoming message, that is, for each different header and for the
19716 envelope sender and recipient fields. For example,
19718 exim -brw ph10@exim.workshop.example
19720 might produce the output
19722 sender: Philip.Hazel@exim.workshop.example
19723 from: Philip.Hazel@exim.workshop.example
19724 to: ph10@exim.workshop.example
19725 cc: ph10@exim.workshop.example
19726 bcc: ph10@exim.workshop.example
19727 reply-to: Philip.Hazel@exim.workshop.example
19728 env-from: Philip.Hazel@exim.workshop.example
19729 env-to: ph10@exim.workshop.example
19731 which shows that rewriting has been set up for that address when used in any of
19732 the source fields, but not when it appears as a recipient address. At the
19733 present time, there is no equivalent way of testing rewriting rules that are
19734 set for a particular transport.
19736 .section Rewriting rules
19737 .index rewriting||rules
19738 The rewrite section of the configuration file consists of lines of rewriting
19741 <<source pattern>> <<replacement>> <<flags>>
19743 Rewriting rules that are specified for the \headers@_rewrite\ generic transport
19744 option are given as a colon-separated list. Each item in the list takes the
19745 same form as a line in the main rewriting configuration
19746 (except that any colons must be doubled, of course).
19748 The formats of source patterns and replacement strings are described below.
19749 Each is terminated by white space, unless enclosed in double quotes, in which
19750 case normal quoting conventions apply inside the quotes. The flags are single
19751 characters which may appear in any order. Spaces and tabs between them are
19754 For each address that could potentially be rewritten, the rules are scanned in
19755 order, and replacements for the address from earlier rules can themselves be
19756 replaced by later rules (but see the `q' and `R' flags).
19758 The order in which addresses are rewritten is undefined, may change between
19759 releases, and must not be relied on, with one exception: when a message is
19760 received, the envelope sender is always rewritten first, before any header
19761 lines are rewritten. For example, the replacement string for a rewrite of an
19762 address in ::To:: must not assume that the message's address in ::From:: has (or
19763 has not) already been rewritten. However, a rewrite of ::From:: may assume that
19764 the envelope sender has already been rewritten.
19766 The variables \$local@_part$\ and \$domain$\ can be used in the replacement
19767 string to refer to the address that is being rewritten. Note that lookup-driven
19768 rewriting can be done by a rule of the form
19772 where the lookup key uses \$1$\ and \$2$\ or \$local@_part$\ and \$domain$\ to
19773 refer to the address that is being rewritten.
19775 .section Rewriting patterns
19776 .index rewriting||patterns
19777 .index address list||in a rewriting pattern
19778 The source pattern in a rewriting rule is any item which may appear in an
19779 address list (see section ~~SECTaddresslist). It is in fact processed as a
19780 single-item address list, which means that it is expanded before being tested
19781 against the address.
19783 Domains in patterns should be given in lower case. Local parts in patterns are
19784 case-sensitive. If you want to do case-insensitive matching of local parts, you
19785 can use a regular expression that starts with \"^(?i)"\.
19787 .index numerical variables (\$1$\, \$2$\, etc)||in rewriting rules
19788 After matching, the numerical variables \$1$\, \$2$\, etc. may be set,
19789 depending on the type of match which occurred. These can be used in the
19790 replacement string to insert portions of the incoming address. \$0$\ always
19791 refers to the complete incoming address. When a regular expression is used, the
19792 numerical variables are set from its capturing subexpressions. For other types
19793 of pattern they are set as follows:
19796 If a local part or domain starts with an asterisk, the numerical variables
19797 refer to the character strings matched by asterisks, with \$1$\ associated with
19798 the first asterisk, and \$2$\ with the second, if present. For example, if the
19801 *queen@@*.fict.example
19803 is matched against the address \*hearts-queen@@wonderland.fict.example*\ then
19805 $0 = hearts-queen@wonderland.fict.example
19809 Note that if the local part does not start with an asterisk, but the domain
19810 does, it is \$1$\ that contains the wild part of the domain.
19812 If the domain part of the pattern is a partial lookup, the wild and fixed parts
19813 of the domain are placed in the next available numerical variables. Suppose,
19814 for example, that the address \*foo@@bar.baz.example*\ is processed by a
19815 rewriting rule of the form
19817 *@@partial-dbm;/some/dbm/file <<replacement string>>
19819 and the key in the file that matches the domain is \"*.baz.example"\. Then
19825 If the address \*foo@@baz.example*\ is looked up, this matches the same
19826 wildcard file entry, and in this case \$2$\ is set to the empty string, but
19827 \$3$\ is still set to \*baz.example*\. If a non-wild key is matched in a
19828 partial lookup, \$2$\ is again set to the empty string and \$3$\ is set to the
19829 whole domain. For non-partial domain lookups, no numerical variables are set.
19832 .section Rewriting replacements
19833 .index rewriting||replacements
19834 If the replacement string for a rule is a single asterisk, addresses that
19835 match the pattern and the flags are $it{not} rewritten, and no subsequent
19836 rewriting rules are scanned. For example,
19838 hatta@lookingglass.fict.example * f
19840 specifies that \*hatta@@lookingglass.fict.example*\ is never to be rewritten in
19843 If the replacement string is not a single asterisk, it is expanded, and must
19844 yield a fully qualified address. Within the expansion, the variables
19845 \$local@_part$\ and \$domain$\ refer to the address that is being rewritten.
19846 Any letters they contain retain their original case -- they are not lower
19847 cased. The numerical variables are set up according to the type of pattern that
19848 matched the address, as described above. If the expansion is forced to fail by
19849 the presence of `fail' in a conditional or lookup item, rewriting by the
19850 current rule is abandoned, but subsequent rules may take effect. Any other
19851 expansion failure causes the entire rewriting operation to be abandoned, and an
19852 entry written to the panic log.
19855 .section Rewriting flags
19856 There are three different kinds of flag that may appear on rewriting rules:
19858 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
19861 A flag that specifies rewriting at SMTP time: S.
19863 Flags that control the rewriting process: Q, q, R, w.
19865 For rules that are part of the \headers@_rewrite\ generic transport option,
19866 E, F, T, and S are not permitted.
19869 .section Flags specifying which headers and envelope addresses to rewrite
19870 .index rewriting||flags
19871 If none of the following flag letters, nor the `S' flag (see section
19872 ~~SECTrewriteS) are present, a main rewriting rule applies to all headers and
19873 to both the sender and recipient fields of the envelope, whereas a
19874 transport-time rewriting rule just applies to all headers. Otherwise, the
19875 rewriting rule is skipped unless the relevant addresses are being processed.
19877 E $rm{rewrite all envelope fields}
19878 F $rm{rewrite the envelope From field}
19879 T $rm{rewrite the envelope To field}
19880 b $rm{rewrite the ::Bcc:: header}
19881 c $rm{rewrite the ::Cc:: header}
19882 f $rm{rewrite the ::From:: header}
19883 h $rm{rewrite all headers}
19884 r $rm{rewrite the ::Reply-To:: header}
19885 s $rm{rewrite the ::Sender:: header}
19886 t $rm{rewrite the ::To:: header}
19888 You should be particularly careful about rewriting ::Sender:: headers, and
19889 restrict this to special known cases in your own domains.
19891 .section The SMTP-time rewriting flag
19892 .rset SECTrewriteS "~~chapter.~~section"
19893 .index SMTP||rewriting malformed addresses
19894 .index \\RCPT\\||rewriting argument of
19895 .index \\MAIL\\||rewriting argument of
19896 The rewrite flag `S' specifies a rewrite of incoming envelope addresses at SMTP
19897 time, as soon as an address is received in a \\MAIL\\ or \\RCPT\\ command, and
19898 before any other processing; even before syntax checking. The pattern is
19899 required to be a regular expression, and it is matched against the whole of the
19900 data for the command, including any surrounding angle brackets.
19902 This form of rewrite rule allows for the handling of addresses that are not
19903 compliant with RFCs 2821 and 2822 (for example, `bang paths' in batched SMTP
19904 input). Because the input is not required to be a syntactically valid address,
19905 the variables \$local@_part$\ and \$domain$\ are not available during the
19906 expansion of the replacement string. The result of rewriting replaces the
19907 original address in the \\MAIL\\ or \\RCPT\\ command.
19909 .section Flags controlling the rewriting process
19910 There are four flags which control the way the rewriting process works. These
19911 take effect only when a rule is invoked, that is, when the address is of the
19912 correct type (matches the flags) and matches the pattern:
19914 If the `Q' flag is set on a rule, the rewritten address is permitted to be an
19915 unqualified local part. It is qualified with \qualify@_recipient\. In the
19916 absence of `Q' the rewritten address must always include a domain.
19918 If the `q' flag is set on a rule, no further rewriting rules are considered,
19919 even if no rewriting actually takes place because of a `fail' in the expansion.
19920 The `q' flag is not effective if the address is of the wrong type (does not
19921 match the flags) or does not match the pattern.
19923 The `R' flag causes a successful rewriting rule to be re-applied to the new
19924 address, up to ten times. It can be combined with the `q' flag, to stop
19925 rewriting once it fails to match (after at least one successful rewrite).
19927 .index rewriting||whole addresses
19928 When an address in a header is rewritten, the rewriting normally applies only
19929 to the working part of the address, with any comments and RFC 2822 `phrase'
19930 left unchanged. For example, rewriting might change
19932 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
19936 From: Ford Prefect <prefectf@hitch.fict.example>
19938 Sometimes there is a need to replace the whole address item, and this can be
19939 done by adding the flag letter `w' to a rule. If this is set on a rule that
19940 causes an address in a header line to be rewritten, the entire address is
19941 replaced, not just the working part. The replacement must be a complete RFC
19942 2822 address, including the angle brackets if necessary. If text outside angle
19943 brackets contains a character whose value is greater than 126 or less than 32
19944 (except for tab), the text is encoded according to RFC 2047.
19945 The character set is taken from \headers@_charset\, which defaults to
19948 When the `w' flag is set on a rule that causes an envelope address to be
19949 rewritten, all but the working part of the replacement address is discarded.
19952 .section Rewriting examples
19953 Here is an example of the two common rewriting paradigms:
19955 *@*.hitch.fict.example $1@hitch.fict.example
19956 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
19957 {$value}fail}@hitch.fict.example bctfrF
19959 Note the use of `fail' in the lookup expansion in the second rule, forcing
19960 the string expansion to fail if the lookup does not succeed. In this context it
19961 has the effect of leaving the original address unchanged, but Exim goes on to
19962 consider subsequent rewriting rules, if any, because the `q' flag is not
19963 present in that rule. An alternative to `fail' would be to supply \$1$\
19964 explicitly, which would cause the rewritten address to be the same as before,
19965 at the cost of a small bit of processing. Not supplying either of these is an
19966 error, since the rewritten address would then contain no local part.
19968 The first example above replaces the domain with a superior, more general
19969 domain. This may not be desirable for certain local parts. If the rule
19971 root@*.hitch.fict.example *
19973 were inserted before the first rule, rewriting would be suppressed for the
19974 local part \*root*\ at any domain ending in \*hitch.fict.example*\.
19976 Rewriting can be made conditional on a number of tests, by making use of
19977 \${if$\ in the expansion item. For example, to apply a rewriting rule only to
19978 messages that originate outside the local host:
19980 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
19981 {$1@hitch.fict.example}fail}"
19983 The replacement string is quoted in this example because it contains white
19986 .index rewriting||bang paths
19987 .index bang paths||rewriting
19988 Exim does not handle addresses in the form of `bang paths'. If it sees such an
19989 address it treats it as an unqualified local part which it qualifies with the
19990 local qualification domain (if the source of the message is local or if the
19991 remote host is permitted to send unqualified addresses). Rewriting can
19992 sometimes be used to handle simple bang paths with a fixed number of
19993 components. For example, the rule
19995 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
19997 rewrites a two-component bang path \*host.name!user*\ as the domain address
19998 \*user@@host.name*\. However, there is a security implication in using this as
19999 a global rewriting rule for envelope addresses. It can provide a backdoor
20000 method for using your system as a relay, because the incoming addresses appear
20001 to be local. If the bang path addresses are received via SMTP, it is safer to
20002 use the `S' flag to rewrite them as they are received, so that relay checking
20003 can be done on the rewritten addresses.
20013 . ============================================================================
20014 .chapter Retry configuration
20015 .set runningfoot "retry configuration"
20016 .rset CHAPretry ~~chapter
20017 .index retry||configuration, description of
20018 .index configuration file||retry section
20019 The `retry' section of the run time configuration file contains a list of retry
20020 rules which control how often Exim tries to deliver messages that cannot be
20021 delivered at the first attempt. If there are no retry rules, temporary errors
20022 are treated as permanent. The \-brt-\ command line option can be used to test
20023 which retry rule will be used for a given address or domain.
20025 The most common cause of retries is temporary failure to deliver to a remote
20026 host because the host is down, or inaccessible because of a network problem.
20027 Exim's retry processing in this case is applied on a per-host (strictly, per IP
20028 address) basis, not on a per-message basis. Thus, if one message has recently
20029 been delayed, delivery of a new message to the same host is not immediately
20030 tried, but waits for the host's retry time to arrive. If the \retry@_defer\ log
20031 selector is set, the message
20032 .index retry||time not reached
20033 `retry time not reached' is written to the main log whenever a delivery is
20034 skipped for this reason. Section ~~SECToutSMTPerr contains more details of the
20035 handling of errors during remote deliveries.
20037 Retry processing applies to routing as well as to delivering, except as covered
20038 in the next paragraph. The retry rules do not distinguish between these
20039 actions. It is not possible, for example, to specify different behaviour for
20040 failures to route the domain \*snark.fict.example*\ and failures to deliver to
20041 the host \*snark.fict.example*\. I didn't think anyone would ever need this
20042 added complication, so did not implement it. However, although they share the
20043 same retry rule, the actual retry times for routing and transporting a given
20044 domain are maintained independently.
20046 When a delivery is not part of a queue run (typically an immediate delivery on
20047 receipt of a message), the routers are always run, and local deliveries are
20048 always attempted, even if retry times are set for them. This makes for better
20049 behaviour if one particular message is causing problems (for example, causing
20050 quota overflow, or provoking an error in a filter file). If such a delivery
20051 suffers a temporary failure, the retry data is updated as normal, and
20052 subsequent delivery attempts from queue runs occur only when the retry time for
20053 the local address is reached.
20056 .section Retry rules
20057 .index retry||rules
20059 Each retry rule occupies one line and consists of three or four parts,
20060 separated by white space: a pattern, an error name, an optional list of sender
20061 addresses, and a list of retry parameters. The pattern and sender lists must be
20062 enclosed in double quotes if they contain white space. The rules are searched in
20063 order until one is found where the pattern, error name, and sender list (if
20064 present) match the failing host or address, the error that occurred, and the
20065 message's sender, respectively.
20068 The pattern is any single item that may appear in an address list (see section
20069 ~~SECTaddresslist). It is in fact processed as a one-item address list, which
20070 means that it is expanded before being tested against the address that has
20071 been delayed. Address list processing treats a plain domain name as if it were
20072 preceded by `*@@', which makes it possible for many retry rules to start with
20073 just a domain. For example,
20075 lookingglass.fict.example * F,24h,30m;
20077 provides a rule for any address in the \*lookingglass.fict.example*\ domain,
20080 alice@lookingglass.fict.example * F,24h,30m;
20082 applies only to temporary failures involving the local part \alice\.
20083 In practice, almost all rules start with a domain name pattern without a local
20086 .index regular expressions||in retry rules
20087 \**Warning**\: If you use a regular expression in a routing rule pattern, it
20088 must match a complete address, not just a domain, because that is how regular
20089 expressions work in address lists.
20091 ^@\Nxyz@\d+@\.abc@\.example@$@\N * G,1h,10m,2 \Wrong\
20092 ^@\N[^@@]+@@xyz@\d+@\.abc@\.example@$@\N * G,1h,10m,2 \Right\
20096 .section Choosing which retry rule to use
20097 When Exim is looking for a retry rule after a routing attempt has failed (for
20098 example, after a DNS timeout), each line in the retry configuration is tested
20099 against the complete address only if \retry__use@_local@_part\ is set for the
20100 router. Otherwise, only the domain is used, except when matching against a
20101 regular expression, when the local part of the address is replaced with `*'. A
20102 domain on its own can match a domain pattern, or a pattern that starts with
20103 `*@@'. By default, \retry@_use@_local@_part\ is true for routers where
20104 \check@_local@_user\ is true, and false for other routers.
20106 Similarly, when Exim is looking for a retry rule after a local delivery has
20107 failed (for example, after a mailbox full error), each line in the retry
20108 configuration is tested against the complete address only if
20109 \retry@_use@_local@_part\ is set for the transport (it defaults true for all
20112 When Exim is looking for a retry rule after a remote delivery attempt has
20113 failed, what happens depends on the type of failure. After a 4\*xx*\ SMTP
20114 response for a recipient address, the whole address is used when searching the
20115 retry rules. The rule that is found is used to create a retry time for the
20118 For a temporary error that is not related to an individual address,
20119 (for example, a connection timeout), each line in the retry configuration is
20120 checked twice. First, the name of the remote host is used as a domain name
20121 (preceded by `*@@' when matching a regular expression). If this does not match
20122 the line, the domain from the email address is tried in a similar fashion. For
20123 example, suppose the MX records for \*a.b.c.example*\ are
20125 a.b.c.example MX 5 x.y.z.example
20129 and the retry rules are
20131 p.q.r.example * F,24h,30m;
20132 a.b.c.example * F,4d,45m;
20134 and a delivery to the host \*x.y.z.example*\ fails. The first rule matches
20135 neither the host nor the domain, so Exim looks at the second rule. This does
20136 not match the host, but it does match the domain, so it is used to calculate
20137 the retry time for the host \*x.y.z.example*\. Meanwhile, Exim tries to deliver
20138 to \*p.q.r.example*\. If this fails, the first retry rule is used, because it
20141 In other words, failures to deliver to host \*p.q.r.example*\ use the first
20142 rule to determine retry times, but for all the other hosts for the domain
20143 \*a.b.c.example*\, the second rule is used. The second rule is also used if
20144 routing to \*a.b.c.example*\ suffers a temporary failure.
20146 .section Retry rules for specific errors
20147 .index retry||specific errors, specifying
20148 The second field in a retry rule is the name of a particular error, or an
20149 asterisk, which matches any error. The errors that can be tested for are:
20155 \auth@_failed\: Authentication failed when trying to send to a host in the
20156 \hosts@_require@_auth\ list in an \%smtp%\ transport.
20159 \rcpt@_4xx\: A 4\*xx*\ error was received for an outgoing \\RCPT\\ command.
20160 Either the first or both of the x's can be given as specific digits, for
20161 example: \"rcpt@_45x"\ or \"rcpt@_436"\. For example, to recognize 452 errors
20162 given to \\RCPT\\ commands by a particular host, and have retries every ten
20163 minutes and a one-hour timeout, you could set up a retry rule of this form:
20165 the.host.name rcpt_452 F,1h,10m
20167 These errors apply to both outgoing SMTP (the \%smtp%\ transport) and outgoing
20168 LMTP (either the \%lmtp%\ transport, or the \%smtp%\ transport in LMTP mode).
20169 Note, however, that they apply only to responses to \\RCPT\\ commands.
20172 \refused@_MX\: A connection to a host obtained from an MX record was refused.
20175 \refused@_A\: A connection to a host not obtained from an MX record was
20179 \refused\: A connection was refused.
20182 \timeout@_connect@_MX\: A connection attempt to a host obtained from an MX
20186 \timeout@_connect@_A\: A connection attempt to a host not obtained from an MX
20190 \timeout@_connect\: A connection attempt timed out.
20193 \timeout@_MX\: There was a timeout while connecting or during an SMTP session
20194 with a host obtained from an MX record.
20197 \timeout@_A\: There was a timeout while connecting or during an SMTP session
20198 with a host not obtained from an MX record.
20201 \timeout\: There was a timeout while connecting or during an SMTP session.
20204 \quota\: A mailbox quota was exceeded in a local delivery by the
20205 \%appendfile%\ transport.
20207 .index quota||error testing in retry rule
20208 .index retry||quota error testing
20210 \quota@_\<<time>>: A mailbox quota was exceeded in a local delivery by
20211 the \%appendfile%\ transport, and the mailbox has not been accessed for
20212 <<time>>. For example, \*quota@_4d*\ applies to a quota error when the mailbox
20213 has not been accessed for four days.
20218 .index mailbox||time of last read
20219 The idea of \quota@_\<<time>> is to make it possible to have shorter timeouts
20220 when the mailbox is full and is not being read by its owner. Ideally, it should
20221 be based on the last time that the user accessed the mailbox. However, it is
20222 not always possible to determine this. Exim uses the following heuristic rules:
20224 If the mailbox is a single file, the time of last access (the `atime') is used.
20225 As no new messages are being delivered (because the mailbox is over quota),
20226 Exim does not access the file, so this is the time of last user access.
20228 .index maildir format||time of last read
20229 For a maildir delivery, the time of last modification of the \(new)\
20230 subdirectory is used. As the mailbox is over quota, no new files are created in
20231 the \(new)\ subdirectory, because no new messages are being delivered. Any
20232 change to the \(new)\ subdirectory is therefore assumed to be the result of an
20233 MUA moving a new message to the \(cur)\ directory when it is first read. The
20234 time that is used is therefore the last time that the user read a new message.
20236 For other kinds of multi-file mailbox, the time of last access cannot be
20237 obtained, so a retry rule that uses this type of error field is never matched.
20240 The quota errors apply both to system-enforced quotas and to Exim's own quota
20241 mechanism in the \%appendfile%\ transport. The \*quota*\ error also applies
20242 when a local delivery is deferred because a partition is full (the \\ENOSPC\\
20247 .section Retry rules for specified senders
20248 .index retry||rules, sender-specific
20249 You can specify retry rules that apply only when the failing message has a
20250 specific sender. In particular, this can be used to define retry rules that
20251 apply only to bounce messages. The third item in a retry rule can be of this
20254 senders=<<address list>>
20256 The retry timings themselves are then the fourth item. For example:
20258 * * senders=: F,1h,30m
20260 matches all temporary errors for bounce messages sent to any host. If the
20261 address list contains white space, it must be enclosed in quotes. For example:
20263 a.domain timeout senders="x@b.dom : y@c.dom" G,8h,10m,1.5
20265 When testing retry rules using \-brt-\, you can supply a sender using the \-f-\
20266 command line option, like this:
20268 exim -f "" -brt user@dom.ain
20270 If you do not set \-f-\ with \-brt-\, a retry rule that contains a senders list
20276 .section Retry parameters
20277 .index retry||parameters in rules
20280 (or fourth, if a senders list is present)
20282 field in a retry rule is a sequence of retry parameter sets, separated by
20283 semicolons. Each set consists of
20285 <<letter>>,<<cutoff time>>,<<arguments>>
20287 The letter identifies the algorithm for computing a new retry time; the cutoff
20288 time is the time beyond which this algorithm no longer applies, and the
20289 arguments vary the algorithm's action. The cutoff time is measured from the
20290 time that the first failure for the domain (combined with the local part if
20291 relevant) was detected, not from the time the message was received.
20292 .index retry||algorithms
20293 The available algorithms are:
20295 \*F*\: retry at fixed intervals. There is a single time parameter specifying
20298 \*G*\: retry at geometrically increasing intervals. The first argument
20299 specifies a starting value for the interval, and the second a multiplier, which
20300 is used to increase the size of the interval at each retry.
20302 When computing the next retry time, the algorithm definitions are scanned in
20303 order until one whose cutoff time has not yet passed is reached. This is then
20304 used to compute a new retry time that is later than the current time. In the
20305 case of fixed interval retries, this simply means adding the interval to the
20306 current time. For geometrically increasing intervals, retry intervals are
20307 computed from the rule's parameters until one that is greater than the previous
20308 interval is found. The main configuration variable
20309 .index limit||retry interval
20310 .index retry||interval, maximum
20311 .index \retry@_interval@_max\
20312 \retry@_interval@_max\ limits the maximum interval between retries.
20314 A single remote domain may have a number of hosts associated with it, and each
20315 host may have more than one IP address. Retry algorithms are selected on the
20316 basis of the domain name, but are applied to each IP address independently. If,
20317 for example, a host has two IP addresses and one is unusable, Exim will
20318 generate retry times for it and will not try to use it until its next retry
20319 time comes. Thus the good IP address is likely to be tried first most of the
20322 .index hints database||use for retrying
20323 Retry times are hints rather than promises. Exim does not make any attempt to
20324 run deliveries exactly at the computed times. Instead, a queue runner process
20325 starts delivery processes for delayed messages periodically, and these attempt
20326 new deliveries only for those addresses that have passed their next retry time.
20327 If a new message arrives for a deferred address, an immediate delivery attempt
20328 occurs only if the address has passed its retry time. In the absence of new
20329 messages, the minimum time between retries is the interval between queue runner
20330 processes. There is not much point in setting retry times of five minutes if
20331 your queue runners happen only once an hour, unless there are a significant
20332 number of incoming messages (which might be the case on a system that is
20333 sending everything to a smart host, for example).
20335 The data in the retry hints database can be inspected by using the
20336 \*exim@_dumpdb*\ or \*exim@_fixdb*\ utility programs (see chapter ~~CHAPutils). The
20337 latter utility can also be used to change the data. The \*exinext*\ utility
20338 script can be used to find out what the next retry times are for the hosts
20339 associated with a particular mail domain, and also for local deliveries that
20340 have been deferred.
20342 .section Retry rule examples
20343 Here are some example retry rules:
20345 alice@wonderland.fict.example quota_5d F,7d,3h
20346 wonderland.fict.example quota_5d
20347 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
20348 lookingglass.fict.example * F,24h,30m;
20349 * refused_A F,2h,20m;
20350 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
20352 The first rule sets up special handling for mail to
20353 \*alice@@wonderland.fict.example*\ when there is an over-quota error and the
20354 mailbox has not been read for at least 5 days. Retries continue every three
20355 hours for 7 days. The second rule handles over-quota errors for all other local
20356 parts at \*wonderland.fict.example*\; the absence of a local part has the same
20357 effect as supplying `$*$@@'. As no retry algorithms are supplied, messages that
20358 fail are bounced immediately if the mailbox has not been read for at least 5
20361 The third rule handles all other errors at \*wonderland.fict.example*\; retries
20362 happen every 15 minutes for an hour, then with geometrically increasing
20363 intervals until two days have passed since a delivery first failed. After the
20364 first hour there is a delay of one hour, then two hours, then four hours, and
20365 so on (this is a rather extreme example).
20367 The fourth rule controls retries for the domain \*lookingglass.fict.example*\.
20368 They happen every 30 minutes for 24 hours only. The remaining two rules handle
20369 all other domains, with special action for connection refusal from hosts that
20370 were not obtained from an MX record.
20372 The final rule in a retry configuration should always have asterisks in the
20373 first two fields so as to provide a general catch-all for any addresses that do
20374 not have their own special handling. This example tries every 15 minutes for 2
20375 hours, then with intervals starting at one hour and increasing by a factor of
20376 1.5 up to 16 hours, then every 8 hours up to 5 days.
20379 .section Timeout of retry data
20380 .index timeout||of retry data
20381 .index \retry@_data@_expire\
20382 .index hints database||data expiry
20383 .index retry||timeout of data
20384 Exim timestamps the data that it writes to its retry hints database. When it
20385 consults the data during a delivery it ignores any that is older than the value
20386 set in \retry@_data@_expire\ (default 7 days). If, for example, a host hasn't
20387 been tried for 7 days, Exim will try to deliver to it immediately a message
20388 arrives, and if that fails, it will calculate a retry time as if it were
20389 failing for the first time.
20391 This improves the behaviour for messages routed to rarely-used hosts such as MX
20392 backups. If such a host was down at one time, and happens to be down again when
20393 Exim tries a month later, using the old retry data would imply that it had been
20394 down all the time, which is not a justified assumption.
20396 If a host really is permanently dead, this behaviour causes a burst of retries
20397 every now and again, but only if messages routed to it are rare. It there is a
20398 message at least once every 7 days the retry data never expires.
20402 .section Long-term failures
20403 .index delivery||failure, long-term
20404 .index retry||after long-term failure
20405 Special processing happens when an email address has been failing for so long
20406 that the cutoff time for the last algorithm is reached. For example, using the
20407 default retry rule:
20409 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
20411 the cutoff time is four days. Reaching the retry cutoff is independent of how
20412 long any specific message has been failing; it is the length of continuous
20413 failure for the recipient address that counts.
20415 When the cutoff time is reached for a local delivery, or for all the IP
20416 addresses associated with a remote delivery, a subsequent delivery failure
20417 causes Exim to give up on the address, and a bounce message is generated.
20418 In order to cater for new messages that use the failing address, a next retry
20419 time is still computed from the final algorithm, and is used as follows:
20421 For local deliveries, one delivery attempt is always made for any subsequent
20422 messages. If this delivery fails, the address fails immediately. The
20423 post-cutoff retry time is not used.
20425 If the delivery is remote, there are two possibilities, controlled by the
20426 .index \delay@_after@_cutoff\
20427 \delay@_after@_cutoff\ option of the \%smtp%\ transport. The option is true by
20428 default and in that case:
20430 Until the post-cutoff retry time for one of the IP addresses is reached,
20431 the failing email address is bounced immediately, without a delivery attempt
20432 taking place. After that time, one new delivery attempt is made to those IP
20433 addresses that are past their retry times, and if that still fails, the address
20434 is bounced and new retry times are computed.
20437 In other words, when all the hosts for a given email address have been failing
20438 for a long time, Exim bounces rather then defers until one of the hosts' retry
20439 times is reached. Then it tries once, and bounces if that attempt fails. This
20440 behaviour ensures that few resources are wasted in repeatedly trying to deliver
20441 to a broken destination, but if the host does recover, Exim will eventually
20444 If \delay@_after@_cutoff\ is set false, Exim behaves differently. If all IP
20445 addresses are past their final cutoff time, Exim tries to deliver to those IP
20446 addresses that have not been tried since the message arrived. If there are
20447 no suitable IP addresses, or if they all fail, the address is bounced. In other
20448 words, it does not delay when a new message arrives, but tries the expired
20449 addresses immediately, unless they have been tried since the message arrived.
20450 If there is a continuous stream of messages for the failing domains, setting
20451 \delay@_after@_cutoff\ false means that there will be many more attempts to
20452 deliver to permanently failing IP addresses than when \delay@_after@_cutoff\ is
20455 .section Ultimate address timeout
20456 .index retry||ultimate address timeout
20457 An additional rule is needed to cope with cases where a host is intermittently
20458 available, or when a message has some attribute that prevents its delivery when
20459 others to the same address get through. In this situation, because some
20460 messages are successfully delivered, the `retry clock' for the address keeps
20461 getting restarted, and so a message could remain on the queue for ever. To
20462 prevent this, if a message has been on the queue for longer than the cutoff
20463 time of any applicable retry rule for a given address, a delivery is attempted
20464 for that address, even if it is not yet time, and if this delivery fails, the
20465 address is timed out. A new retry time is not computed in this case, so that
20466 other messages for the same address are considered immediately.
20476 . ============================================================================
20477 .chapter SMTP authentication
20478 .set runningfoot "SMTP authentication"
20479 .rset CHAPSMTPAUTH "~~chapter"
20480 .index SMTP||authentication configuration
20481 .index authentication
20482 The `authenticators' section of Exim's run time configuration is concerned with
20483 SMTP authentication. This facility is an extension to the SMTP protocol,
20484 described in RFC 2554, which allows a client SMTP host to authenticate itself
20485 to a server. This is a common way for a server to recognize clients that
20486 are permitted to use it as a relay. SMTP authentication is not of relevance to
20487 the transfer of mail between servers that have no managerial connection with
20490 .index \\AUTH\\||description of
20491 Very briefly, the way SMTP authentication works is as follows:
20493 The server advertises a number of authentication \*mechanisms*\ in response to
20494 the client's \\EHLO\\ command.
20496 The client issues an \\AUTH\\ command, naming a specific mechanism. The command
20497 may, optionally, contain some authentication data.
20499 The server may issue one or more \*challenges*\, to which the client must send
20500 appropriate responses. In simple authentication mechanisms, the challenges are
20501 just prompts for user names and passwords. The server does not have to issue
20502 any challenges -- in some mechanisms the relevant data may all be transmitted
20503 with the \\AUTH\\ command.
20505 The server either accepts or denies authentication.
20507 If authentication succeeds, the client may optionally make use of the \\AUTH\\
20508 option on the \\MAIL\\ command to pass an authenticated sender in subsequent
20509 mail transactions. Authentication lasts for the remainder of the SMTP
20512 If authentication fails, the client may give up, or it may try a different
20513 authentication mechanism, or it may try transferring mail over the
20514 unauthenticated connection.
20516 If you are setting up a client, and want to know which authentication
20517 mechanisms the server supports, you can use Telnet to connect to port 25 (the
20518 SMTP port) on the server, and issue an \\EHLO\\ command. The response to this
20519 includes the list of supported mechanisms. For example:
20521 @$ $cb{telnet server.example 25}
20522 Trying 192.168.34.25...
20523 Connected to server.example.
20524 Escape character is '@^]'.
20525 220 server.example ESMTP Exim 4.20 ...
20526 $cb{ehlo client.example}
20527 250-server.example Hello client.example [10.8.4.5]
20533 The second-last line of this example output shows that the server supports
20534 authentication using the PLAIN mechanism. In Exim, the different authentication
20535 mechanisms are configured by specifying \*authenticator*\ drivers. Like the
20536 routers and transports, which authenticators are included in the binary is
20537 controlled by build-time definitions. The following are currently available,
20538 included by setting
20544 in \(Local/Makefile)\, respectively. The first of these supports the CRAM-MD5
20545 authentication mechanism (RFC 2195), and the second can be configured to
20546 support the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism,
20547 which is not formally documented, but used by several MUAs. The third
20548 authenticator supports Microsoft's \*Secure Password Authentication*\
20551 The authenticators are configured using the same syntax as other drivers (see
20552 section ~~SECTfordricon). If no authenticators are required, no authentication
20553 section need be present in the configuration file. Each authenticator can in
20554 principle have both server and client functions. When Exim is receiving SMTP
20555 mail, it is acting as a server; when it is sending out messages over SMTP, it
20556 is acting as a client. Authenticator configuration options are provided for use
20557 in both these circumstances.
20559 To make it clear which options apply to which situation, the prefixes
20560 \server@_\ and \client@_\ are used on option names that are specific to either
20561 the server or the client function, respectively. Server and client functions
20562 are disabled if none of their options are set. If an authenticator is to be
20563 used for both server and client functions, a single definition, using both sets
20564 of options, is required. For example:
20568 public_name = CRAM-MD5
20569 server_secret = ${if eq{$1}{ph10}{secret1}fail}
20571 client_secret = secret2
20573 The \server@_\ option is used when Exim is acting as a server, and the
20574 \client@_\ options when it is acting as a client.
20576 Descriptions of the individual authenticators are given in subsequent chapters.
20577 The remainder of this chapter covers the generic options for the
20578 authenticators, followed by general discussion of the way authentication works
20582 .section Generic options for authenticators
20583 .index authentication||generic options
20585 .startconf authenticators
20586 .index options||generic, for authenticators
20588 .conf driver string unset
20589 This option must always be set. It specifies which of the available
20590 authenticators is to be used.
20592 .conf public@_name string unset
20593 This option specifies the name of the authentication mechanism that the driver
20594 implements, and by which it is known to the outside world. These names should
20595 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
20596 but Exim in fact matches them caselessly. If \public@_name\ is not set, it
20597 defaults to the driver's instance name.
20599 .conf server@_advertise@_condition string$**$ unset
20600 When a server is about to advertise an authentication mechanism, the condition
20601 is expanded. If it yields the empty string, `0', `no', or `false', the
20602 mechanism is not advertised.
20603 If the expansion fails, the mechanism is not advertised. If the failure was not
20604 forced, and was not caused by a lookup defer, the incident is logged.
20605 See section ~~SECTauthexiser below for further discussion.
20607 .conf server@_debug@_print string$**$ unset
20608 If this option is set and authentication debugging is enabled (see the \-d-\
20609 command line option), the string is expanded and included in the debugging
20610 output when the authenticator is run as a server. This can help with checking
20611 out the values of variables.
20612 If expansion of the string fails, the error message is written to the debugging
20613 output, and Exim carries on processing.
20615 .conf server@_set@_id string$**$ unset
20616 When an Exim server successfully authenticates a client, this string is
20617 expanded using data from the authentication, and preserved for any incoming
20618 messages in the variable \$authenticated@_id$\. It is also included in the log
20619 lines for incoming messages. For example, a user/password authenticator
20620 configuration might preserve the user name that was used to authenticate, and
20621 refer to it subsequently during delivery of the message.
20622 If expansion fails, the option is ignored.
20624 .conf server@_mail@_auth@_condition string$**$ unset
20625 This option allows a server to discard authenticated sender addresses supplied
20626 as part of \\MAIL\\ commands in SMTP connections that are authenticated by the
20627 driver on which \server__mail__auth@_condition\ is set. The option is not used
20628 as part of the authentication process; instead its (unexpanded) value is
20629 remembered for later use.
20630 How it is used is described in the following section.
20635 .section The AUTH parameter on MAIL commands
20636 .rset SECTauthparamail "~~chapter.~~section"
20637 .index authentication||sender, authenticated
20638 .index \\AUTH\\||on \\MAIL\\ command
20639 When a client supplied an \\AUTH=\\ item on a \\MAIL\\ command, Exim applies
20640 the following checks before accepting it as the authenticated sender of the
20643 If the connection is not using extended SMTP (that is, \\HELO\\ was used rather
20644 than \\EHLO\\), the use of \\AUTH=\\ is a syntax error.
20646 If the value of the \\AUTH=\\ parameter is `@<@>', it is ignored.
20648 If \acl@_smtp@_mailauth\ is defined, the ACL it specifies is run. While it is
20649 running, the value of \$authenticated@_sender$\ is set to the value obtained
20650 from the \\AUTH=\\ parameter. If the ACL does not yield `accept', the value of
20651 \$authenticated@_sender$\ is deleted. The \acl@_smtp@_mailauth\ ACL may not
20652 return `drop' or `discard'. If it defers, a temporary error code (451) is given
20653 for the \\MAIL\\ command.
20655 If \acl@_smtp@_mailauth\ is not defined, the value of the \\AUTH=\\ parameter
20656 is accepted and placed in \$authenticated@_sender$\ only if the client has
20659 If the \\AUTH=\\ value was accepted by either of the two previous rules, and
20660 the client has authenticated, and the authenticator has a setting for the
20661 \server@_mail@_auth@_condition\, the condition is checked at this point. The
20662 valued that was saved from the authenticator is expanded. If the expansion
20663 fails, or yields an empty string, `0', `no', or `false', the value of
20664 \$authenticated__sender$\ is deleted. If the expansion yields any other value,
20665 the value of \$authenticated@_sender$\ is retained and passed on with the
20669 When \$authenticated@_sender$\ is set for a message, it is passed on to other
20670 hosts to which Exim authenticates as a client. Do not confuse this value with
20671 \$authenticated@_id$\, which is a string obtained from the authentication
20672 process, and which is not usually a complete email address.
20674 Whenever an \\AUTH=\\ value is ignored, the incident is logged. The ACL for
20675 \\MAIL\\, if defined, is run after \\AUTH=\\ is accepted or ignored. It can
20676 therefore make use of \$authenticated@_sender$\. The converse is not true: the
20677 value of \$sender@_address$\ is not yet set up when the \acl@_smtp@_mailauth\
20681 .section Authentication on an Exim server
20682 .rset SECTauthexiser "~~chapter.~~section"
20683 .index authentication||on an Exim server
20684 When Exim receives an \\EHLO\\ command, it advertises the public names of those
20685 authenticators that are configured as servers, subject to the following
20688 The client host must match \auth@_advertise@_hosts\ (default $*$).
20690 It the \server@_advertise@_condition\ option is set, its expansion must not
20691 yield the empty string, `0', `no', or `false'.
20693 The order in which the authenticators are defined controls the order in which
20694 the mechanisms are advertised.
20696 Some mail clients (for example, some versions of Netscape) require the user to
20697 provide a name and password for authentication whenever \\AUTH\\ is advertised,
20698 even though authentication may not in fact be needed (for example, Exim may be
20699 set up to allow unconditional relaying from the client by an IP address check).
20700 You can make such clients more friendly by not advertising \\AUTH\\ to them.
20701 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
20702 that runs for \\RCPT\\) to relay without authentication, you should set
20704 auth_advertise_hosts = ! 10.9.8.0/24
20706 so that no authentication mechanisms are advertised to them.
20708 The \server@_advertise@_condition\ controls the advertisement of individual
20709 authentication mechanisms. For example, it can be used to restrict the
20710 advertisement of a patricular mechanism to encrypted connections, by a setting
20713 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
20715 If the session is encrypted, \$tls@_cipher$\ is not empty, and so the expansion
20716 yields `yes', which allows the advertisement to happen.
20718 When an Exim server receives an \\AUTH\\ command from a client, it rejects it
20719 immediately if \\AUTH\\ was not advertised in response to an earlier \\EHLO\\
20720 command. This is the case if
20722 The client host does not match \auth@_advertise@_hosts\; or
20724 No authenticators are configured with server options; or
20726 Expansion of \server@_advertise@_condition\ blocked the advertising of all the
20727 server authenticators.
20730 Otherwise, Exim runs the ACL specified by \acl@_smtp@_auth\ in order
20731 to decide whether to accept the command. If \acl@_smtp@_auth\ is not set,
20732 \\AUTH\\ is accepted from any client host.
20734 If \\AUTH\\ is not rejected by the ACL, Exim searches its configuration for a
20735 server authentication mechanism that was advertised in response to \\EHLO\\ and
20736 that matches the one named in the \\AUTH\\ command. If it finds one, it runs
20737 the appropriate authentication protocol, and authentication either succeeds or
20738 fails. If there is no matching advertised mechanism, the \\AUTH\\ command is
20739 rejected with a 504 error.
20741 When a message is received from an authenticated host, the value of
20742 \$received@_protocol$\ is set to
20746 instead of `esmtp', and \$sender@_host@_authenticated$\ contains the name (not
20747 the public name) of the authenticator driver that successfully authenticated
20748 the client from which the message was received. This variable is empty if there
20749 was no successful authentication.
20753 .section Testing server authentication
20754 .index authentication||testing a server
20755 .index \\AUTH\\||testing a server
20756 .index base64 encoding||creating authentication test data
20757 Exim's \-bh-\ option can be useful for testing server authentication
20758 configurations. The data for the \\AUTH\\ command has to be sent using base64
20759 encoding. A quick way to produce such data for testing is the following Perl
20763 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
20765 .index binary zero||in authentication data
20766 This interprets its argument as a Perl string, and then encodes it. The
20767 interpretation as a Perl string allows binary zeros, which are required for
20768 some kinds of authentication, to be included in the data. For example, a
20769 command line to run this script on such data might be
20771 encode '\0user\0password'
20773 Note the use of single quotes to prevent the shell interpreting the
20774 backslashes, so that they can be interpreted by Perl to specify characters
20775 whose code value is zero.
20777 \**Warning 1**\: If either of the user or password strings starts with an octal
20778 digit, you must use three zeros instead of one after the leading backslash. If
20779 you do not, the octal digit that starts your string will be incorrectly
20780 interpreted as part of the code for the first character.
20782 \**Warning 2**\: If there are characters in the strings that Perl interprets
20783 specially, you must use a Perl escape to prevent them being misinterpreted. For
20784 example, a command such as
20786 encode '\0user@domain.com\0pas$$word'
20788 gives an incorrect answer because of the unescaped `@@' and `@$' characters.
20790 If you have the \mimencode\ command installed, another way to do produce
20791 base64-encoded strings is to run the command
20793 echo -e -n `\0user\0password' | mimencode
20795 The \-e-\ option of \echo\ enables the interpretation of backslash escapes in
20796 the argument, and the \-n-\ option specifies no newline at the end of its
20797 output. However, not all versions of \echo\ recognize these options, so you
20798 should check your version before relying on this suggestion.
20801 .section Authentication by an Exim client
20802 .index authentication||on an Exim client
20803 The \%smtp%\ transport has two options called \hosts@_require@_auth\ and
20804 \hosts@_try@_auth\. When the \%smtp%\ transport connects to a server that
20805 announces support for authentication, and the host matches an entry in either
20806 of these options, Exim (as a client) tries to authenticate as follows:
20808 For each authenticator that is configured as a client, it searches the
20809 authentication mechanisms announced by the server for one whose name
20810 matches the public name of the authenticator.
20812 When it finds one that matches, it runs the authenticator's client code.
20813 The variables \$host$\ and \$host@_address$\ are available for any string
20814 expansions that the client might do. They are set to the server's name and
20815 IP address. If any expansion is forced to fail, the authentication attempt
20817 and Exim moves on to the next authenticator.
20818 Otherwise an expansion failure causes delivery to be
20821 If the result of the authentication attempt is a temporary error or a timeout,
20822 Exim abandons trying to send the message to the host for the moment. It will
20823 try again later. If there are any backup hosts available, they are tried in the
20826 If the response to authentication is a permanent error (5xx code), Exim carries
20827 on searching the list of authenticators and tries another one if possible. If
20828 all authentication attempts give permanent errors, or if there are no attempts
20829 because no mechanisms match
20830 (or option expansions force failure),
20831 what happens depends on whether the host matches \hosts@_require@_auth\ or
20832 \hosts@_try@_auth\. In the first case, a temporary error is generated, and
20833 delivery is deferred. The error can be detected in the retry rules, and thereby
20834 turned into a permanent error if you wish. In the second case, Exim tries to
20835 deliver the message unauthenticated.
20837 .index \\AUTH\\||on \\MAIL\\ command
20838 When Exim has authenticated itself to a remote server, it adds the \\AUTH\\
20839 parameter to the \\MAIL\\ commands it sends, if it has an authenticated sender
20841 If the message came from a remote host, the authenticated sender is the one
20842 that was receiving on an incoming \\MAIL\\ command, provided that the incoming
20843 connection was authenticated and the \server@_mail@_auth\ condition allowed the
20844 authenticated sender to be retained. If a local process calls Exim to send a
20845 message, the sender address that is built from the login name and
20846 \qualify@_domain\ is treated as authenticated. However, if the
20847 \authenticated@_sender\ option is set on the \%smtp%\ transport, it overrides
20848 the authenticated sender that was received with the message.
20859 . ============================================================================
20860 .chapter The plaintext authenticator
20861 .rset CHAPplaintext "~~chapter"
20862 .set runningfoot "plaintext authenticator"
20863 .index \%plaintext%\ authenticator
20864 .index authenticators||\%plaintext%\
20865 The \%plaintext%\ authenticator can be configured to support the PLAIN and
20866 LOGIN authentication mechanisms, both of which transfer authentication data as
20867 plain (unencrypted) text (though base64 encoded). The use of plain text is a
20868 security risk. If you use one of these mechanisms without also making use of
20869 SMTP encryption (see chapter ~~CHAPTLS) you should not use the same passwords
20870 for SMTP connections as you do for login accounts.
20872 .section Using plaintext in a server
20873 When running as a server, \%plaintext%\ performs the authentication test by
20874 expanding a string. It has the following options:
20876 .startconf plaintext
20877 .index options||\%plaintext%\ authenticator (server)
20879 .conf server@_prompts string$**$ unset
20880 The contents of this option, after expansion, must be a colon-separated list of
20881 prompt strings. If expansion fails, a temporary authentication rejection is
20884 .conf server@_condition string$**$ unset
20885 This option must be set in order to configure the driver as a server. Its use
20886 is described below.
20890 .index \\AUTH\\||in \%plaintext%\ authenticator
20891 .index binary zero||in \%plaintext%\ authenticator
20892 .index numerical variables (\$1$\, \$2$\, etc)||in \%plaintext%\ authenticator
20893 .index base64 encoding||in \%plaintext%\ authenticator
20894 The data sent by the client with the \\AUTH\\ command, or in response to
20895 subsequent prompts, is base64 encoded, and so may contain any byte values
20896 when decoded. If any data is supplied with the command, it is treated as a
20897 list of strings, separated by NULs (binary zeros), which are placed in the
20898 expansion variables \$1$\, \$2$\, etc. If there are more strings in
20899 \server@_prompts\ than the number of strings supplied with the \\AUTH\\
20900 command, the remaining prompts are used to obtain more data. Each response from
20901 the client may be a list of NUL-separated strings.
20903 Once a sufficient number of data strings have been received,
20904 \server@_condition\ is expanded.
20905 If the expansion is forced to fail, authentication fails. Any other expansion
20906 failure causes a temporary error code to be returned.
20907 If the result of a successful expansion is an empty string, `0', `no', or
20908 `false', authentication fails. If the result of the expansion is `1', `yes', or
20909 `true', authentication succeeds and the generic \server@_set@_id\ option is
20910 expanded and saved in \$authenticated@_id$\. For any other result, a temporary
20911 error code is returned, with the expanded string as the error text.
20913 \**Warning**\: If you use a lookup in the expansion to find the user's
20914 password, be sure to make the authentication fail if the user is unknown.
20915 There are good and bad examples at the end of the next section.
20918 .section The PLAIN authentication mechanism
20919 .index PLAIN authentication mechanism
20920 .index authentication||PLAIN mechanism
20921 .index binary zero||in \%plaintext%\ authenticator
20922 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
20923 sent as one item of data (that is, one combined string containing two NUL
20924 separators). The data is sent either as part of the \\AUTH\\ command, or
20925 subsequently in response to an empty prompt from the server.
20927 The second and third strings are a user name and a corresponding password.
20928 Using a single fixed user name and password as an example, this could be
20929 configured as follows:
20933 public_name = PLAIN
20935 server_condition = \
20936 ${if and {{eq{$2}{username}}{eq{$3}{mysecret}}}{yes}{no}}
20939 The \server@_prompts\ setting specifies a single, empty prompt (empty items at
20940 the end of a string list are ignored). If all the data comes as part of the
20941 \\AUTH\\ command, as is commonly the case, the prompt is not used. This
20942 authenticator is advertised in the response to \\EHLO\\ as
20946 and a client host can authenticate itself by sending the command
20948 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
20950 As this contains three strings (more than the number of prompts), no further
20951 data is required from the client. Alternatively, the client may just send
20955 to initiate authentication, in which case the server replies with an empty
20956 prompt. The client must respond with the combined data string.
20958 The data string is base64 encoded, as required by the RFC. This example,
20959 when decoded, is \"<<NUL>>username<<NUL>>mysecret"\, where <<NUL>> represents a
20960 zero byte. This is split up into three strings, the first of which is empty.
20961 The \server@_condition\ option in the authenticator checks that the second two
20962 are \"username"\ and \"mysecret"\ respectively.
20964 Having just one fixed user name and password, as in this example, is not very
20965 realistic, though for a small organization with only a handful of
20966 authenticating clients it could make sense.
20968 A more sophisticated instance of this authenticator could use the user name in
20969 \$2$\ to look up a password in a file or database, and maybe do an encrypted
20970 comparison (see \crypteq\ in chapter ~~CHAPexpand). Here is a example of this
20971 approach, where the passwords are looked up in a DBM file. \**Warning**\: This
20972 is an incorrect example:
20974 server_condition = \
20975 ${if eq{$3}{${lookup{$2}dbm{/etc/authpwd}}}{yes}{no}}
20977 The expansion uses the user name (\$2$\) as the key to look up a password,
20978 which it then compares to the supplied password (\$3$\). Why is this example
20979 incorrect? It works fine for existing users, but consider what happens if a
20980 non-existent user name is given. The lookup fails, but as no success/failure
20981 strings are given for the lookup, it yields an empty string. Thus, to defeat
20982 the authentication, all a client has to do is to supply a non-existent user
20983 name and an empty password. The correct way of writing this test is:
20985 server_condition = ${lookup{$2}dbm{/etc/authpwd}\
20986 {${if eq{$value}{$3}{yes}{no}}}{no}}
20988 In this case, if the lookup succeeds, the result is checked; if the lookup
20989 fails, authentication fails. If \crypteq\ is being used instead of \eq\, the
20990 first example is in fact safe, because \crypteq\ always fails if its second
20991 argument is empty. However, the second way of writing the test makes the logic
20995 .section The LOGIN authentication mechanism
20996 .index LOGIN authentication mechanism
20997 .index authentication||LOGIN mechanism
20998 The LOGIN authentication mechanism is not documented in any RFC, but is in use
20999 in a number of programs. No data is sent with the \\AUTH\\ command. Instead, a
21000 user name and password are supplied separately, in response to prompts. The
21001 plaintext authenticator can be configured to support this as in this example:
21005 public_name = LOGIN
21006 server_prompts = User Name : Password
21007 server_condition = \
21008 ${if and {{eq{$1}{username}}{eq{$2}{mysecret}}}{yes}{no}}
21011 Because of the way plaintext operates, this authenticator accepts data supplied
21012 with the \\AUTH\\ command (in contravention of the specification of LOGIN), but
21013 if the client does not supply it (as is the case for LOGIN clients), the prompt
21014 strings are used to obtain two data items.
21016 Some clients are very particular about the precise text of the prompts. For
21017 example, Outlook Express is reported to recognize only `Username:' and
21018 `Password:'. Here is an example of a LOGIN authenticator which uses those
21019 strings, and which uses the \ldapauth\ expansion condition to check the user
21020 name and password by binding to an LDAP server:
21024 public_name = LOGIN
21025 server_prompts = Username:: : Password::
21026 server_condition = ${if ldapauth \
21028 {user="cn=${quote_ldap_dn:$1},ou=people,o=example.org" \
21031 ldap://ldap.example.org/}{yes}{no}}
21032 server_set_id = uid=$1,ou=people,o=example.org
21034 Note the use of the \quote@_ldap@_dn\ operator to correctly quote the DN for
21035 authentication. However, the basic \quote\ operator, rather than any of the
21036 LDAP quoting operators, is the correct one to use for the password, because
21037 quoting is needed only to make the password conform to the Exim syntax. At the
21038 LDAP level, the password is an uninterpreted string.
21041 .section Support for different kinds of authentication
21042 A number of string expansion features are provided for the purpose of
21043 interfacing to different ways of user authentication. These include checking
21044 traditionally encrypted passwords from \(/etc/passwd)\ (or equivalent), PAM,
21045 Radius, \ldapauth\, and \*pwcheck*\. For details see section ~~SECTexpcond.
21049 .section Using plaintext in a client
21050 The \%plaintext%\ authenticator has just one client option:
21052 .startconf plaintext
21053 .index options||\%plaintext%\ authenticator (client)
21055 .conf client@_send string$**$ unset
21056 The string is a colon-separated list of authentication data strings. Each
21057 string is independently expanded before being sent to the server. The first
21058 string is sent with the \\AUTH\\ command; any more strings are sent in response
21059 to prompts from the server.
21061 \**Note**\: you cannot use expansion to create multiple strings, because
21062 splitting takes priority and happens first.
21064 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
21065 the data, further processing is applied to each string before it is sent. If
21066 there are any single circumflex characters in the string, they are converted to
21067 NULs. Should an actual circumflex be required as data, it must be doubled in
21072 This is an example of a client configuration that implements the PLAIN
21073 authentication mechanism with a fixed user name and password:
21077 public_name = PLAIN
21078 client_send = ^username^mysecret
21080 The lack of colons means that the entire text is sent with the \\AUTH\\
21081 command, with the circumflex characters converted to NULs. A similar example
21082 that uses the LOGIN mechanism is:
21086 public_name = LOGIN
21087 client_send = : username : mysecret
21089 The initial colon means that the first string is empty, so no data is sent with
21090 the \\AUTH\\ command itself. The remaining strings are sent in response to
21100 . ============================================================================
21101 .chapter The cram@_md5 authenticator
21102 .set runningfoot "cram@_md5 authenticator"
21103 .index \%cram@_md5%\ authenticator
21104 .index authenticators||\%cram@_md5%\
21105 .index CRAM-MD5 authentication mechanism
21106 .index authentication||CRAM-MD5 mechanism
21107 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
21108 sends a challenge string to the client, and the response consists of a user
21109 name and the CRAM-MD5 digest of the challenge string combined with a secret
21110 string (password) which is known to both server and client. Thus, the secret
21111 is not sent over the network as plain text, which makes this authenticator more
21112 secure than \%plaintext%\. However, the downside is that the secret has to be
21113 available in plain text at either end.
21115 .section Using cram@_md5 as a server
21116 This authenticator has one server option, which must be set to configure the
21117 authenticator as a server:
21119 .startconf cram@_md5
21120 .index options||\%cram@_md5%\ authenticator (server)
21122 .conf server@_secret string$**$ unset
21123 .index numerical variables (\$1$\, \$2$\, etc)||in \%cram@_md5%\ authenticator
21124 When the server receives the client's response, the user name is placed in
21125 the expansion variable \$1$\, and \server@_secret\ is expanded to obtain the
21126 password for that user. The server then computes the CRAM-MD5 digest that the
21127 client should have sent, and checks that it received the correct string. If the
21128 expansion of \server@_secret\ is forced to fail, authentication fails. If the
21129 expansion fails for some other reason, a temporary error code is returned to
21134 For example, the following authenticator checks that the user name given by the
21135 client is `ph10', and if so, uses `secret' as the password. For any other user
21136 name, authentication fails.
21140 public_name = CRAM-MD5
21141 server_secret = ${if eq{$1}{ph10}{secret}fail}
21144 If authentication succeeds, the setting of \server@_set@_id\ preserves the user
21145 name in \$authenticated@_id$\.
21146 A more tyical configuration might look up the secret string in a file, using
21147 the user name as the key. For example:
21151 public_name = CRAM-MD5
21152 server_secret = ${lookup{$1}lsearch{/etc/authpwd}{$value}fail}
21155 Note that this expansion explicitly forces failure if the lookup fails
21156 because \$1$\ contains an unknown user name.
21158 .section Using cram@_md5 as a client
21159 When used as a client, the \%cram@_md5%\ authenticator has two options:
21161 .startconf cram@_md5
21162 .index options||\%cram@_md5%\ authenticator (client)
21164 .conf client@_name string$**$ "the primary host name"
21165 This string is expanded, and the result used as the user name data when
21166 computing the response to the server's challenge.
21168 .conf client@_secret string$**$ unset
21169 This option must be set for the authenticator to work as a client. Its value is
21170 expanded and the result used as the secret string when computing the response.
21174 Different user names and secrets can be used for different servers by referring
21175 to \$host$\ or \$host@_address$\ in the options.
21177 Forced failure of either expansion string is treated as an indication that this
21178 authenticator is not prepared to handle this case. Exim moves on to the next
21179 configured client authenticator. Any other expansion failure causes Exim to
21180 give up trying to send the message to the current server.
21182 A simple example configuration of a \%cram@_md5%\ authenticator, using fixed
21187 public_name = CRAM-MD5
21189 client_secret = secret
21199 . ============================================================================
21200 .chapter The cyrus@_sasl authenticator
21201 .set runningfoot "cyrus@_sasl authenticator"
21202 .index \%cyrus@_sasl%\ authenticator
21203 .index authenticators||\%cyrus@_sasl%\
21204 .index Cyrus, SASL library
21206 The code for this authenticator was provided by Matthew Byng-Maddick of A L
21207 Digital Ltd (\?http://www.aldigital.co.uk?\).
21209 The \%cyrus@_sasl%\ authenticator provides server support for the Cyrus SASL
21210 library implementation of the RFC 2222 (`Simple Authentication and Security
21211 Layer'). This library supports a number of authentication mechanisms, including
21212 PLAIN and LOGIN, but also several others that Exim does not support directly.
21213 The \%cyrus@_sasl%\ authenticator provides a gatewaying mechanism directly to
21214 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
21215 then so can the \%cyrus@_sasl%\ authenticator. By default it uses the public
21216 name of the driver to determine which mechanism to support.
21218 Where access to some kind of secret file is required, for example in GSSAPI
21219 or CRAM-MD5, it is worth noting that the authenticator runs as the \*exim*\
21220 user, and that the Cyrus SASL library has no way of escalating privileges
21221 by default. You may also find you need to set environment variables,
21222 depending on the driver you are using.
21224 .section Using cyrus@_sasl as a server
21225 The \%cyrus@_sasl%\ authenticator has four private options. It puts the
21226 username (on a successful authentication) into \$1$\.
21228 .startconf cyrus@_sasl
21229 .conf server@_hostname string$**$ $tt{$primary@_hostname}
21230 This option selects the hostname that is used when communicating with
21231 the library. It is up to the underlying SASL plug-in what it does with
21234 .conf server@_mech string $tt{public@_name}
21235 This option selects the authentication mechanism this driver should
21236 use. It allows you to use a different underlying mechanism from the
21237 advertised name. For example:
21240 driver = cyrus_sasl
21241 public_name = X-ANYTHING
21242 server_mech = CRAM-MD5
21246 .conf server@_realm string unset
21247 This specifies the SASL realm that the server claims to be in.
21249 .conf server@_service string $tt{smtp}
21250 This is the SASL service that the server claims to implement.
21254 For straightforward cases, you do not need to set any of the authenticator's
21255 private options. All you need to do is to specify an appropriate mechanism as
21256 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
21257 PLAIN, you could have two authenticators as follows:
21260 driver = cyrus_sasl
21261 public_name = CRAM-MD5
21265 driver = cyrus_sasl
21266 public_name = PLAIN
21270 Cyrus SASL does implement the LOGIN authentication method, even though it is
21271 not a standard method. It is disabled by default in the source distribution,
21272 but it is present in many binary distributions.
21282 . ============================================================================
21283 .chapter The spa authenticator
21284 .set runningfoot "spa authenticator"
21285 .index \%spa%\ authenticator
21286 .index authenticators||\%spa%\
21287 .index authentication||Microsoft Secure Password
21288 .index authentication||NTLM
21289 .index Microsoft Secure Password Authentication
21290 .index NTLM authentication
21291 The \%spa%\ authenticator provides client support for Microsoft's \*Secure
21292 Password Authentication*\ mechanism,
21293 which is also sometimes known as NTLM (NT LanMan). The code for client side of
21294 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
21295 taken from the Samba project (\?http://www.samba.org?\). The code for the
21296 server side was subsequently contributed by Tom Kistner.
21298 The mechanism works as follows:
21300 After the \\AUTH\\ command has been accepted, the client sends an SPA
21301 authentication request based on the user name and optional domain.
21303 The server sends back a challenge.
21305 The client builds a challenge response which makes use of the user's password
21306 and sends it to the server, which then accepts or rejects it.
21308 Encryption is used to protect the password in transit.
21311 .section Using spa as a server
21312 The \%spa%\ authenticator has just one server option:
21315 .index options||\%spa%\ authenticator (server)
21317 .conf server@_password string$**$ unset
21318 .index numerical variables (\$1$\, \$2$\, etc)||in \%spa%\ authenticator
21319 This option is expanded, and the result must be the cleartext password for the
21320 authenticating user, whose name is at this point in \$1$\. For example:
21325 server_password = ${lookup{$1}lsearch{/etc/exim/spa_clearpass}}
21327 If the expansion is forced to fail, authentication fails. Any other expansion
21328 failure causes a temporary error code to be returned.
21334 .section Using spa as a client
21335 The \%spa%\ authenticator has the following client options:
21338 .index options||\%spa%\ authenticator (client)
21340 .conf client@_domain string$**$ unset
21341 This option specifies an optional domain for the authentication.
21343 .conf client@_password string$**$ unset
21344 This option specifies the user's password, and must be set.
21346 .conf client@_username string$**$ unset
21347 This option specifies the user name, and must be set.
21351 Here is an example of a configuration of this authenticator for use with the
21352 mail servers at \*msn.com*\:
21357 client_username = msn/msn_username
21358 client_password = msn_plaintext_password
21359 client_domain = DOMAIN_OR_UNSET
21371 . ============================================================================
21372 .chapter Encrypted SMTP connections using TLS/SSL
21373 .set runningfoot "TLS encryption"
21374 .rset CHAPTLS "~~chapter"
21375 .index encryption||on SMTP connection
21376 .index SMTP||encryption
21377 .index TLS||on SMTP connection
21380 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
21381 Sockets Layer), is implemented by making use of the OpenSSL library or the
21382 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
21383 cryptographic code in the Exim distribution itself for implementing TLS. In
21384 order to use this feature you must install OpenSSL or GnuTLS, and then build a
21385 version of Exim that includes TLS support (see section ~~SECTinctlsssl). You
21386 also need to understand the basic concepts of encryption at a managerial level,
21387 and in particular, the way that public keys, private keys, and certificates are
21390 RFC 2487 defines how SMTP connections can make use of encryption. Once a
21391 connection is established, the client issues a \\STARTTLS\\ command. If the
21392 server accepts this, the client and the server negotiate an encryption
21393 mechanism. If the negotiation succeeds, the data that subsequently passes
21394 between them is encrypted.
21396 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
21397 and if so, what cipher suite is in use, whether the client supplied a
21398 certificate, and whether or not that certificate was verified. This makes it
21399 possible for an Exim server to deny or accept certain commands based on the
21402 \**Warning**\: certain types of firewall and certain anti-virus products can
21403 disrupt TLS connections. You need to turn off SMTP scanning for these products
21404 in order to get TLS to work.
21408 .section Support for the legacy `ssmtp' protocol
21409 .index ssmtp protocol
21410 .index SMTP||ssmtp protocol
21411 Early implementations of encrypted SMTP used a different TCP port from normal
21412 SMTP, and expected an encryption negotiation to start immediately, instead of
21413 waiting for a \\STARTTLS\\ command from the client using the standard SMTP
21414 port. The protocol was called `ssmtp' and port 465 was allocated for this
21417 This approach was abandoned when encrypted SMTP was standardised, but there are
21418 still some legacy clients that use it. Exim supports these clients by means of
21419 the \tls@_on@_connect@_ports\ global option. Its value must be a list of port
21420 numbers; the most common use is expected to be:
21422 tls_on_connect_ports = 465
21424 The port numbers specified by this option apply to all SMTP connections, both
21425 via the daemon and via \*inetd*\. You still need to specify all the ports that
21426 the daemon uses (by setting \daemon@_smtp@_ports\ or \local@_interfaces\ or the
21427 \-oX-\ command line option) because \tls@_on@_connect@_ports\ does not add an
21428 extra port -- rather, it specifies different behaviour on a port that is
21431 There is also a \-tls-on-connect-\ command line option. This overrides
21432 \tls@_on@_connect@_ports\; it forces the legacy behaviour for all ports.
21438 .section OpenSSL vs GnuTLS
21439 .index TLS||OpenSSL \*vs*\ GnuTLS
21440 .rset SECTopenvsgnu "~~chapter.~~section"
21441 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
21442 followed later, when the first versions of GnuTLS were released. To build Exim
21443 to use GnuTLS, you need to set
21447 in Local/Makefile, in addition to
21451 You must also set \\TLS@_LIBS\\ and \\TLS@_INCLUDE\\ appropriately, so that the
21452 include files and libraries for GnuTLS can be found.
21454 There are some differences in usage when using GnuTLS instead of OpenSSL:
21456 The \tls@_verify@_certificates\ option must contain the name of a file, not the
21457 name of a directory (for OpenSSL it can be either).
21459 The \tls@_dhparam\ option is ignored, because early versions of GnuTLS had no
21460 facility for varying its Diffie-Hellman parameters. I understand that this has
21461 changed, but Exim has not been updated to provide this facility.
21463 GnuTLS uses RSA and D-H parameters that take a substantial amount of
21464 time to compute. It is unreasonable to re-compute them for every TLS
21465 session. Therefore, Exim keeps this data in a file in its spool
21466 directory, called \(gnutls-params)\. The file is owned by the Exim user and is
21467 readable only by its owner. Every Exim process that start up GnuTLS reads the
21468 RSA and D-H parameters from this file. If the file does not exist, the first
21469 Exim process that needs it computes the data and writes it to a temporary file
21470 which is renamed once it is complete. It does not matter if several Exim
21471 processes do this simultaneously (apart from wasting a few resources). Once a
21472 file is in place, new Exim processes immediately start using it.
21474 For maximum security, the parameters that are stored in this file should be
21475 recalculated periodically, the frequency depending on your paranoia level.
21476 Arranging this is easy; just delete the file when you want new values to be
21479 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
21480 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
21481 affects the value of the \$tls@_peerdn$\ variable.
21483 OpenSSL identifies cipher suites using hyphens as separators, for example:
21484 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA@_ARCFOUR@_SHA. What is
21485 more, OpenSSL complains if underscores are present in a cipher list. To make
21486 life simpler, Exim changes underscores to hyhens for OpenSSL and hyphens to
21487 underscores for GnuTLS when processing lists of cipher suites in the
21488 \tls@_require@_ciphers\ options (the global option and the \%smtp%\ transport
21491 The \tls@_require@_ciphers\ options operate differently, as described in the
21492 following sections.
21495 .section Requiring specific ciphers in OpenSSL
21496 .rset SECTreqciphssl "~~chapter.~~section"
21497 .index TLS||requiring specific ciphers (OpenSSL)
21498 .index \tls@_require@_ciphers\||OpenSSL
21499 There is a function in the OpenSSL library that can be passed a list of cipher
21500 suites before the cipher negotiation takes place. This specifies which ciphers
21501 are acceptable. The list is colon separated and may contain names like
21502 DES-CBC3-SHA. Exim passes the expanded value of \tls@_require@_ciphers\
21503 directly to this function call. The following quotation from the OpenSSL
21504 documentation specifies what forms of item are allowed in the cipher string:
21506 It can consist of a single cipher suite such as RC4-SHA.
21508 It can represent a list of cipher suites containing a certain algorithm,
21509 or cipher suites of a certain type. For example SHA1 represents all
21510 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
21513 Lists of cipher suites can be combined in a single cipher string using
21514 the + character. This is used as a logical and operation. For example
21515 SHA1+DES represents all cipher suites containing the SHA1 and the DES
21518 Each cipher string can be optionally preceded by the characters \"!"\, \"-"\ or
21521 If \"!"\ is used then the ciphers are permanently deleted from the list. The
21522 ciphers deleted can never reappear in the list even if they are explicitly
21525 If \"-"\ is used then the ciphers are deleted from the list, but some or all
21526 of the ciphers can be added again by later options.
21528 If \"+"\ is used then the ciphers are moved to the end of the list. This
21529 option doesn't add any new ciphers it just moves matching existing ones.
21531 If none of these characters is present then the string is just interpreted as a
21532 list of ciphers to be appended to the current preference list. If the list
21533 includes any ciphers already present they will be ignored: that is, they will
21534 not moved to the end of the list.
21539 .section Requiring specific ciphers in GnuTLS
21540 .rset SECTreqciphgnu "~~chapter.~~section"
21541 .index TLS||requiring specific ciphers (GnuTLS)
21542 .index \tls@_require@_ciphers\||GnuTLS
21543 The GnuTLS library does not have a combined function like OpenSSL. Instead,
21544 it allows the caller to specify separate lists of key-exchange methods,
21545 main cipher algorithms, and MAC algorithms. Unfortunately, these lists are
21546 numerical, and the library does not have a function for turning names into
21547 numbers. Consequently, the list of recognized names has to be built into
21550 At present, Exim permits only the list of main cipher algorithms to be
21551 changed. The \tls@_require@_ciphers\ option is in the same format as for
21552 OpenSSL. Exim searches each item for the name of available algorithm. For
21553 example, if the list contains RSA@_AES@_SHA then AES is recognized.
21555 The cipher algorithms list starts out with a default set of algorithms. If
21556 the first item in \tls@_require@_ciphers\ does \*not*\ start with an
21557 exclamation mark, all the default items are deleted. Thus, only those specified
21558 can be used. If the first item in \tls@_require@_ciphers\ \*does*\ start with
21559 an exclamation mark, the defaults are left on the list.
21561 Then, any item that starts with an exclamation mark causes the relevent
21562 algorithms to be removed from the list, and any item that does not start
21563 with an exclamation mark causes the relevant algorithms to be added to the
21566 tls_require_ciphers = !RSA_ARCFOUR_SHA
21568 allows all the defaults except those that use ARCFOUR, whereas
21570 tls_require_ciphers = AES : 3DES
21572 allows only cipher suites that use AES and 3DES. The currently recognized
21575 AES@_256, AES@_128, AES (both of the preceding), 3DES, and ARCFOUR@_128.
21576 Unrecognized algorithms are ignored. In a server, the order of the list is
21577 unimportant; the server will advertise the availability of all the relevant
21578 cipher suites. However, in a client, the order of the list specifies a
21579 preference order for the algorithms. The first one in the client's list that is
21580 also advertised by the server is tried first. The default order is as listed
21585 .section Configuring an Exim server to use TLS
21586 .index TLS||configuring an Exim server
21587 When Exim has been built with TLS support, it advertises the availability of
21588 the \\STARTTLS\\ command to client hosts that match \tls@_advertise@_hosts\,
21589 but not to any others. The default value of this option is unset, which means
21590 that \\STARTTLS\\ is not advertised at all. This default is chosen because you
21591 need to set some other options in order to make TLS avaliable, and also it is
21592 sensible for systems that want to use TLS only as a client.
21594 If a client issues a \\STARTTLS\\ command and there is some configuration
21595 problem in the server, the command is rejected with a 454 error. If the client
21596 persists in trying to issue SMTP commands, all except \\QUIT\\ are rejected
21599 554 Security failure
21601 If a \\STARTTLS\\ command is issued within an existing TLS session, it is
21602 rejected with a 554 error code.
21604 To enable TLS operations on a server, you must set \tls@_advertise@_hosts\ to
21605 match some hosts. You can, of course, set it to $*$ to match all hosts.
21606 However, this is not all you need to do. TLS sessions to a server won't work
21607 without some further configuration at the server end.
21609 It is rumoured that all existing clients that support TLS/SSL use RSA
21610 encryption. To make this work you need to set, in the server,
21612 tls_certificate = /some/file/name
21613 tls_privatekey = /some/file/name
21615 The first file contains the server's X509 certificate, and the second contains
21616 the private key that goes with it. These files need to be readable by the Exim
21617 user, and must always be given as full path names. They can be the same file if
21618 both the certificate and the key are contained within it. If \tls@_privatekey\
21619 is not set, this is assumed to be the case. The certificate file may also
21620 contain intermediate certificates that need to be sent to the client to enable
21621 it to authenticate the server's certificate.
21623 If you do not understand about certificates and keys, please try to find a
21624 source of this background information, which is not Exim-specific. (There are a
21625 few comments below in section ~~SECTcerandall.)
21627 \**Note**\: These options do not apply when Exim is operating as a client --
21628 they apply only in the case of a server. For a client, you must set the options
21629 of the same name in an \%smtp%\ transport.
21631 With just these options, Exim will work as a server with clients such as
21632 Netscape. It does not require the client to have a certificate (but see below
21633 for how to insist on this). There is one other option that may be needed in
21634 other situations. If
21636 tls_dhparam = /some/file/name
21638 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
21639 with the parameters contained in the file. This increases the set of cipher
21640 suites that the server supports. See the command
21644 for a way of generating this data.
21645 At present, \tls@_dhparam\ is used only when Exim is linked with OpenSSL. It is
21646 ignored if GnuTLS is being used.
21648 The strings supplied for these three options are expanded every time a client
21649 host connects. It is therefore possible to use different certificates and keys
21650 for different hosts, if you so wish, by making use of the client's IP address
21651 in \$sender@_host@_address$\ to control the expansion. If a string expansion is
21652 forced to fail, Exim behaves as if the option is not set.
21654 .index cipher||logging
21655 .index log||TLS cipher
21656 The variable \$tls@_cipher$\ is set to the cipher suite that was negotiated for
21657 an incoming TLS connection. It is included in the ::Received:: header of an
21658 incoming message (by default -- you can, of course, change this), and it is
21659 also included in the log line that records a message's arrival, keyed by `X=',
21660 unless the \tls@_cipher\ log selector is turned off.
21661 The \encrypted\ condition can be used to test for specific cipher suites in
21664 The ACLs that run for subsequent SMTP commands can check the name of the cipher
21665 suite and vary their actions accordingly. The cipher suite names are those used
21666 by OpenSSL. These may differ from the names used elsewhere. For example,
21667 OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts
21668 is known as TLS@_RSA@_WITH@_3DES@_EDE@_CBC@_SHA. Check the OpenSSL
21669 documentation for more details.
21672 .section Requesting and verifying client certificates
21673 .index certificate||verification of client
21674 .index TLS||client certificate verification
21675 If you want an Exim server to request a certificate when negotiating a TLS
21676 session with a client, you must set either \tls@_verify@_hosts\ or
21677 \tls@_try@_verify@_hosts\. You can, of course, set either of them to $*$ to
21678 apply to all TLS connections. For any host that matches one of these options,
21679 Exim requests a certificate as part of the setup of the TLS session. The
21680 contents of the certificate are verified by comparing it with a list of
21681 expected certificates. These must be available in a file or,
21682 for OpenSSL only (not GnuTLS), a directory, identified by
21683 \tls@_verify@_certificates\.
21685 A file can contain multiple certificates, concatenated end to end. If a
21688 each certificate must be in a separate file, with a name (or a symbolic link)
21689 of the form <<hash>>.0, where <<hash>> is a hash value constructed from the
21690 certificate. You can compute the relevant hash by running the command
21692 openssl x509 -hash -noout -in /cert/file
21694 where \(/cert/file)\ contains a single certificate.
21696 The difference between \tls@_verify@_hosts\ and \tls@_try@_verify@_hosts\ is
21697 what happens if the client does not supply a certificate, or if the certificate
21698 does not match any of the certificates in the collection named by
21699 \tls@_verify@_certificates\. If the client matches \tls@_verify@_hosts\, the
21700 attempt to set up a TLS session is aborted, and the incoming connection is
21701 dropped. If the client matches \tls@_try@_verify@_hosts\, the (encrypted) SMTP
21702 session continues. ACLs that run for subsequent SMTP commands can detect the
21703 fact that no certificate was verified, and vary their actions accordingly. For
21704 example, you can insist on a certificate before accepting a message for
21705 relaying, but not when the message is destined for local delivery.
21707 When a client supplies a certificate (whether it verifies or not), the value of
21708 the Distinguished Name of the certificate is made available in the variable
21709 \$tls@_peerdn$\ during subsequent processing of the message.
21710 .index log||distinguished name
21711 Because it is often a long text string, it is not included in the log line or
21712 ::Received:: header by default. You can arrange for it to be logged, keyed by
21713 `DN=', by setting the \tls@_peerdn\ log selector, and you can use
21714 \received@_header@_text\ to change the ::Received:: header. When no certificate
21715 is supplied, \$tls@_peerdn$\ is empty.
21717 .section Revoked certificates
21718 .index TLS||revoked certificates
21719 .index revocation list
21720 .index certificate||revocation list
21721 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
21722 certificates are revoked. If you have such a list, you can pass it to an Exim
21723 server using the global option called \tls@_crl\ and to an Exim client using an
21724 identically named option for the \%smtp%\ transport. In each case, the value of
21725 the option is expanded and must then be the name of a file that contains a CRL
21728 .section Configuring an Exim client to use TLS
21729 .index cipher||logging
21730 .index log||TLS cipher
21731 .index log||distinguished name
21732 .index TLS||configuring an Exim client
21733 The \tls@_cipher\ and \tls@_peerdn\ log selectors apply to outgoing SMTP
21734 deliveries as well as to incoming, the latter one causing logging of the
21735 server certificate's DN. The remaining client configuration for TLS is all
21736 within the \%smtp%\ transport.
21738 It is not necessary to set any options to have TLS work in the \%smtp%\
21739 transport. If Exim is built with TLS support, and TLS is advertised by a
21740 server, the \%smtp%\ transport always tries to start a TLS session. However,
21741 this can be prevented by setting \hosts@_avoid@_tls\ (an option of the
21742 transport) to a list of server hosts for which TLS should not be used.
21744 If you do not want Exim to attempt to send messages unencrypted when an attempt
21745 to set up an encrypted connection fails in any way, you can set
21746 \hosts@_require@_tls\ to a list of hosts for which encryption is mandatory. For
21747 those hosts, delivery is always deferred if an encrypted connection cannot be
21748 set up. If there are any other hosts for the address, they are tried in the
21751 When the server host is not in \hosts@_require@_tls\, Exim may try to deliver
21752 the message unencrypted. It always does this if the response to \\STARTTLS\\ is
21753 a 5\*xx*\ code. For a temporary error code, or for a failure to negotiate a TLS
21754 session after a success response code, what happens is controlled by the
21755 \tls@_tempfail@_tryclear\ option of the \%smtp%\ transport. If it is false,
21756 delivery to this host is deferred, and other hosts (if available) are tried. If
21757 it is true, Exim attempts to deliver unencrypted after a 4\*xx*\ response to
21758 \\STARTTLS\\, and if \\STARTTLS\\ is accepted, but the subsequent TLS
21759 negotiation fails, Exim closes the current connection (because it is in an
21760 unknown state), opens a new one to the same host, and then tries the delivery
21764 The \tls@_certificate\ and \tls@_privatekey\ options of the \%smtp%\ transport
21765 provide the client with a certificate, which is passed to the server if it
21766 requests it. If the server is Exim, it will request a certificate only if
21767 \tls@_verify@_hosts\ or \tls@_try@_verify@_hosts\ matches the client.
21768 \**Note**\: these options must be set in the \%smtp%\ transport for Exim to use
21769 TLS when it is operating as a client. Exim does not assume that a server
21770 certificate (set by the global options of the same name) should also be used
21771 when operating as a client.
21773 If \tls@_verify@_certificates\ is set, it must name a file or,
21774 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
21775 expected server certificates. The client verifies the server's certificate
21776 against this collection, taking into account any revoked certificates that are
21777 in the list defined by \tls@_crl\.
21780 \tls@_require@_ciphers\ is set on the \%smtp%\ transport, it must contain a
21781 list of permitted cipher suites. If either of these checks fails, delivery to
21782 the current host is abandoned, and the \%smtp%\ transport tries to deliver to
21783 alternative hosts, if any.
21785 All the TLS options in the \%smtp%\ transport are expanded before use, with
21786 \$host$\ and \$host@_address$\ containing the name and address of the server to
21787 which the client is connected. Forced failure of an expansion causes Exim to
21788 behave as if the relevant option were unset.
21791 .section Multiple messages on the same encrypted TCP/IP connection
21792 .rset SECTmulmessam "~~chapter.~~section"
21793 .index multiple SMTP deliveries with TLS
21794 .index TLS||multiple message deliveries
21795 Exim sends multiple messages down the same TCP/IP connection by starting up
21796 an entirely new delivery process for each message, passing the socket from
21797 one process to the next. This implementation does not fit well with the use
21798 of TLS, because there is quite a lot of state information associated with a TLS
21799 connection, not just a socket identification. Passing all the state information
21800 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
21801 session before passing the socket to a new process. The new process may then
21802 try to start a new TLS session, and if successful, may try to re-authenticate
21803 if \\AUTH\\ is in use, before sending the next message.
21805 The RFC is not clear as to whether or not an SMTP session continues in clear
21806 after TLS has been shut down, or whether TLS may be restarted again later, as
21807 just described. However, if the server is Exim, this shutdown and
21808 reinitialization works. It is not known which (if any) other servers operate
21809 successfully if the client closes a TLS session and continues with unencrypted
21810 SMTP, but there are certainly some that do not work. For such servers, Exim
21811 should not pass the socket to another process, because the failure of the
21812 subsequent attempt to use it would cause Exim to record a temporary host error,
21813 and delay other deliveries to that host.
21815 To test for this case, Exim sends an \\EHLO\\ command to the server after
21816 closing down the TLS session. If this fails in any way, the connection is
21817 closed instead of being passed to a new delivery process, but no retry
21818 information is recorded.
21820 There is also a manual override; you can set \hosts@_nopass@_tls\ on the
21821 \%smtp%\ transport to match those hosts for which Exim should not pass
21822 connections to new processes if TLS has been used.
21826 .section Certificates and all that
21827 .rset SECTcerandall "~~chapter.~~section"
21828 .index certificate||references to discussion
21829 In order to understand fully how TLS works, you need to know about
21830 certificates, certificate signing, and certificate authorities. This is not the
21831 place to give a tutorial, especially as I do not know very much about it
21832 myself. Some helpful introduction can be found in the FAQ for the SSL addition
21833 to Apache, currently at
21835 \?http://www.modssl.org/docs/2.7/ssl@_faq.html@#ToC24?\
21837 Other parts of the \*modssl*\ documentation are also helpful, and have
21838 links to further files.
21839 Eric Rescorla's book, \*SSL and TLS*\, published by Addison-Wesley (ISBN
21840 0-201-61598-3), contains both introductory and more in-depth descriptions.
21841 Some sample programs taken from the book are available from
21843 \?http://www.rtfm.com/openssl-examples/?\
21846 .section Certificate chains
21847 The file named by \tls@_certificate\ may contain more than one
21848 certificate. This is useful in the case where the certificate that is being
21849 sent is validated by an intermediate certificate which the other end does
21850 not have. Multiple certificates must be in the correct order in the file.
21851 First the host's certificate itself, then the first intermediate
21852 certificate to validate the issuer of the host certificate, then the next
21853 intermediate certificate to validate the issuer of the first intermediate
21854 certificate, and so on, until finally (optionally) the root certificate.
21855 The root certificate must already be trusted by the recipient for
21856 validation to succeed, of course, but if it's not preinstalled, sending the
21857 root certificate along with the rest makes it available for the user to
21858 install if the receiving end is a client MUA that can interact with a user.
21860 .section Self-signed certificates
21861 .index certificate||self-signed
21862 You can create a self-signed certificate using the \*req*\ command provided
21863 with OpenSSL, like this:
21865 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
21868 \(file1)\ and \(file2)\ can be the same file; the key and the certificate are
21869 delimited and so can be identified independently. The \-days-\ option
21870 specifies a period for which the certificate is valid. The \-nodes-\ option is
21871 important: if you do not set it, the key is encrypted with a passphrase
21872 that you are prompted for, and any use that is made of the key causes more
21873 prompting for the passphrase. This is not helpful if you are going to use
21874 this certificate and key in an MTA, where prompting is not possible.
21876 A self-signed certificate made in this way is sufficient for testing, and
21877 may be adequate for all your requirements if you are mainly interested in
21878 encrypting transfers, and not in secure identification.
21880 However, many clients require that the certificate presented by the server be a
21881 user (also called `leaf' or `site') certificate, and not a self-signed
21882 certificate. In this situation, the self-signed certificate described above
21883 must be installed on the client host as a trusted root \*certification
21884 authority*\ (CA), and the certificate used by Exim must be a user certificate
21885 signed with that self-signed certificate.
21887 For information on creating self-signed CA certificates and using them to sign
21888 user certificates, see the \*General implementation overview*\ chapter of the
21889 Open-source PKI book, available online at \?http://ospkibook.sourceforge.net/?\.
21897 . ============================================================================
21898 .chapter Access control lists
21899 .set runningfoot "ACL"
21900 .rset CHAPACL "~~chapter"
21901 .index ~~ACL||description
21902 .index control of incoming mail
21903 .index message||controlling incoming
21904 .index policy control||access control lists
21905 Access Control Lists (ACLs) are defined in a separate section of the run time
21906 configuration file, headed by `begin acl'. Each ACL definition starts with a
21907 name, terminated by a colon. Here is a complete ACL section that contains just
21908 one very small ACL:
21913 accept hosts = one.host.only
21915 You can have as many lists as you like in the ACL section, and the order in
21916 which they appear does not matter. The lists are self-terminating.
21918 The majority of ACLs are used to control Exim's behaviour when it receives
21919 certain SMTP commands. This applies both to incoming TCP/IP connections, and
21920 when a local process submits a message using SMTP by specifying the \-bs-\
21921 option. The most common use is for controlling which recipients are accepted
21922 in incoming messages. In addition, you can define an ACL that is used to check
21923 local non-SMTP messages. The default configuration file contains an example of
21924 a realistic ACL for checking \\RCPT\\ commands. This is discussed in chapter
21927 .section Testing ACLs
21928 The \-bh-\ command line option provides a way of testing your ACL configuration
21929 locally by running a fake SMTP session with which you interact. The host
21930 \*relay-test.mail-abuse.org*\ provides a service for checking your relaying
21931 configuration (see section ~~SECTcheralcon for more details).
21934 .section Specifying when ACLs are used
21935 .index ~~ACL||options for specifying
21936 In order to cause an ACL to be used, you have to name it in one of the relevant
21937 options in the main part of the configuration. These options are:
21938 .index \\AUTH\\||ACL for
21939 .index \\DATA\\, ACLs for
21940 .index \\ETRN\\||ACL for
21941 .index \\EXPN\\||ACL for
21942 .index \\HELO\\||ACL for
21943 .index \\EHLO\\||ACL for
21944 .index \\MAIL\\||ACL for
21945 .index \\QUIT\\, ACL for
21946 .index \\RCPT\\||ACL for
21947 .index \\STARTTLS\\, ACL for
21948 .index \\VRFY\\||ACL for
21949 .index SMTP||connection, ACL for
21950 .index non-smtp message, ACL for
21956 \acl@_not@_smtp\ $t $rm{ACL for non-SMTP messages}
21957 \acl@_smtp@_auth\ $t $rm{ACL for \\AUTH\\}
21958 \acl@_smtp@_connect\ $t $rm{ACL for start of SMTP connection}
21959 \acl@_smtp@_data\ $t $rm{ACL after \\DATA\\ is complete}
21960 \acl@_smtp@_etrn\ $t $rm{ACL for \\ETRN\\}
21961 \acl@_smtp@_expn\ $t $rm{ACL for \\EXPN\\}
21962 \acl@_smtp@_helo\ $t $rm{ACL for \\HELO\\ or \\EHLO\\}
21963 \acl@_smtp@_mail\ $t $rm{ACL for \\MAIL\\}
21964 \acl@_smtp@_mailauth\ $t $rm{ACL for the \\AUTH\\ parameter of \\MAIL\\}
21967 \acl@_smtp@_mime\ $t $rm{ACL for content-scanning MIME parts}
21968 \acl@_smtp@_predata\ $t $rm{ACL at start of \\DATA\\ command}
21969 \acl@_smtp@_quit\ $t $rm{ACL for \\QUIT\\}
21972 \acl@_smtp@_rcpt\ $t $rm{ACL for \\RCPT\\}
21973 \acl@_smtp@_starttls\ $t $rm{ACL for \\STARTTLS\\}
21974 \acl@_smtp@_vrfy\ $t $rm{ACL for \\VRFY\\}
21976 For example, if you set
21978 acl_smtp_rcpt = small_acl
21980 the little ACL defined above is used whenever Exim receives a \\RCPT\\ command
21981 in an SMTP dialogue. The majority of policy tests on incoming messages can be
21982 done when \\RCPT\\ commands arrive. A rejection of \\RCPT\\ should cause the
21983 sending MTA to give up on the recipient address contained in the \\RCPT\\
21984 command, whereas rejection at other times may cause the client MTA to keep on
21985 trying to deliver the message. It is therefore recommended that you do as much
21986 testing as possible at \\RCPT\\ time.
21988 .section The non-SMTP ACL
21989 .index non-smtp message, ACL for
21990 The non-SMTP ACL applies to all non-interactive incoming messages, that is, it
21991 applies to batch SMTP as well as to non-SMTP messages. (Batch SMTP is not
21992 really SMTP.) This ACL is run just before the \*local@_scan()*\ function. Any
21993 kind of rejection is treated as permanent, because there is no way of sending a
21994 temporary error for these kinds of message. Many of the ACL conditions (for
21995 example, host tests, and tests on the state of the SMTP connection such as
21996 encryption and authentication) are not relevant and are forbidden in this ACL.
21998 .section The connect ACL
21999 .index SMTP||connection, ACL for
22000 The ACL test specified by \acl@_smtp@_connect\ happens after the test specified
22001 by \host__reject__connection\ (which is now an anomaly) and any TCP Wrappers
22002 testing (if configured).
22005 .section The DATA ACLs
22006 .index \\DATA\\, ACLs for
22007 Two ACLs are associated with the \\DATA\\ command, because it is two-stage
22008 command, with two responses being sent to the client.
22009 When the \\DATA\\ command is received, the ACL defined by \acl@_smtp@_predata\
22010 is obeyed. This gives you control after all the \\RCPT\\ commands, but before
22011 the message itself is received. It offers the opportunity to give a negative
22012 response to the \\DATA\\ command before the data is transmitted. Header lines
22013 added by \\MAIL\\ or \\RCPT\\ ACLs are not visible at this time, but any that
22014 are defined here are visible when the \acl@_smtp@_data\ ACL is run.
22016 You cannot test the contents of the message, for example, to verify addresses
22017 in the headers, at \\RCPT\\ time or when the \\DATA\\ command is received. Such
22018 tests have to appear in the ACL that is run after the message itself has been
22019 received, before the final response to the \\DATA\\ command is sent. This is
22020 the ACL specified by \acl@_smtp@_data\, which is the second ACL that is
22021 associated with the \\DATA\\ command.
22023 For both of these ACLs, it is not possible to reject individual recipients. An
22024 error response rejects the entire message. Unfortunately, it is known that some
22025 MTAs do not treat hard (5$it{xx}) responses to the \\DATA\\ command (either
22026 before or after the data) correctly -- they keep the message on their queues
22027 and try again later, but that is their problem, though it does waste some of
22030 .section The MIME ACL
22031 The \acl@_smtp@_mime\ option is available only when Exim is compiled with the
22032 content-scanning extension. For details, see chapter ~~CHAPexiscan.
22034 .section The QUIT ACL
22035 .rset SECTQUITACL "~~chapter.~~section"
22036 .index \\QUIT\\, ACL for
22037 The ACL for the SMTP \\QUIT\\ command is anomalous, in that the
22038 outcome of the ACL does not affect the response code to \\QUIT\\,
22039 which is always 221. Thus, the ACL does not in fact control any access.
22040 For this reason, the only verbs that are permitted are \accept\ and \warn\.
22042 This ACL can be used for tasks such as custom logging at the end of an SMTP
22043 session. For example, you can use ACL variables in other ACLs to count
22044 messages, recipients, etc., and log the totals at \\QUIT\\ time using one or
22045 more \logwrite\ modifiers on a \warn\ verb.
22047 You do not need to have a final \accept\, but if you do, you can use a
22048 \message\ modifier to specify custom text that is sent as part of the 221
22049 response to \\QUIT\\.
22051 This ACL is run only for a `normal' \\QUIT\\. For certain kinds of disastrous
22052 failure (for example, failure to open a log file, or when Exim is bombing out
22053 because it has detected an unrecoverable error), all SMTP commands from the
22054 client are given temporary error responses until \\QUIT\\ is received or the
22055 connection is closed. In these special cases, the \\QUIT\\ ACL does not run.
22058 .section Finding an ACL to use
22059 .index ~~ACL||finding which to use
22060 The value of an \acl@_smtp@_$it{xxx}\ option is expanded before use, so you can
22061 use different ACLs in different circumstances. The resulting string does not
22062 have to be the name of an ACL in the configuration file; there are other
22063 possibilities. Having expanded the string, Exim searches for an ACL as follows:
22065 If the string begins with a slash, Exim uses it as a file name, and reads its
22066 contents as an ACL. The lines are processed in the same way as lines in the
22067 Exim configuration file. In particular, continuation lines are supported, blank
22068 lines are ignored, as are lines whose first non-whitespace character is `@#'.
22069 If the file does not exist or cannot be read, an error occurs (typically
22070 causing a temporary failure of whatever caused the ACL to be run). For example:
22072 acl_smtp_data = /etc/acls/\
22073 ${lookup{$sender_host_address}lsearch\
22074 {/etc/acllist}{$value}{default}}
22076 This looks up an ACL file to use on the basis of the host's IP address, falling
22077 back to a default if the lookup fails. If an ACL is successfully read from a
22078 file, it is retained in memory for the duration of the Exim process, so that it
22079 can be re-used without having to re-read the file.
22081 If the string does not start with a slash, and does not contain any spaces,
22082 Exim searches the ACL section of the configuration for an ACL whose name
22083 matches the string.
22085 If no named ACL is found, or if the string contains spaces, Exim parses
22086 the string as an inline ACL. This can save typing in cases where you just
22087 want to have something like
22089 acl_smtp_vrfy = accept
22091 in order to allow free use of the \\VRFY\\ command. Such a string may contain
22092 newlines; it is processed in the same way as an ACL that is read from a file.
22096 .section ACL return codes
22097 .index ~~ACL||return codes
22099 Except for the \\QUIT\\ ACL, which does not affect the SMTP return code (see
22100 section ~~SECTQUITACL above), the
22102 result of running an ACL is either `accept' or `deny', or, if some test
22103 cannot be completed (for example, if a database is down), `defer'. These
22104 results cause 2$it{xx}, 5$it{xx}, and 4$it{xx} return codes, respectively, to
22105 be used in the SMTP dialogue. A fourth return, `error', occurs when there is an
22106 error such as invalid syntax in the ACL. This also causes a 4$it{xx} return
22110 For the non-SMTP ACL, `defer' and `error' are treated in the same way as
22111 `deny', because there is no mechanism for passing temporary errors to the
22112 submitters of non-SMTP messages.
22115 ACLs that are relevant to message reception may also return `discard'. This
22116 has the effect of `accept', but causes either the entire message or an
22117 individual recipient address to be discarded. In other words, it is a
22118 blackholing facility. Use it with care.
22120 If the ACL for \\MAIL\\ returns `discard', all recipients are discarded, and no
22121 ACL is run for subsequent \\RCPT\\ commands. The effect of `discard' in a
22122 \\RCPT\\ ACL is to discard just the one recipient address. If there are no
22123 recipients left when the message's data is received, the \\DATA\\ ACL is not
22124 run. A `discard' return from the \\DATA\\ or the non-SMTP ACL discards all the
22125 remaining recipients.
22127 The `discard' return is not permitted for the \acl@_smtp@_predata\ ACL.
22130 .index \*local@_scan()*\ function||when all recipients discarded
22131 The \*local@_scan()*\ function is always run, even if there are no remaining
22132 recipients; it may create new recipients.
22135 .section Unset ACL options
22136 .index ~~ACL||unset options
22137 The default actions when any of the \acl@_$it{xxx}\ options are unset are not
22138 all the same. \**Note**\: These defaults apply only when the relevant ACL is
22139 not defined at all. For any defined ACL, the default action when control reaches
22140 the end of the ACL statements is `deny'.
22142 For \acl@_not@_smtp\, \acl@_smtp@_auth\, \acl@_smtp@_connect\,
22143 \acl@_smtp@_data\, \acl@_smtp@_helo\, \acl__smtp__mail\, \acl@_smtp@_mailauth\,
22145 \acl@_smtp@_mime\, \acl@_smtp@_predata\, \acl@_smtp@_quit\,
22147 and \acl__smtp__starttls\, the action when the ACL is not defined is `accept'.
22149 For the others (\acl@_smtp@_etrn\, \acl@_smtp@_expn\, \acl@_smtp@_rcpt\, and
22150 \acl@_smtp@_vrfy\), the action when the ACL is not defined is `deny'.
22151 This means that \acl@_smtp@_rcpt\ must be defined in order to receive any
22152 messages over an SMTP connection. For an example, see the ACL in the default
22153 configuration file.
22157 .section Data for message ACLs
22158 .index ~~ACL||data for message ACL
22160 When a \\MAIL\\ or \\RCPT\\ ACL, or either of the \\DATA\\ ACLs, is running,
22161 the variables that contain information about the host and the message's sender
22162 (for example, \$sender@_host@_address$\ and \$sender@_address$\) are set, and
22163 can be used in ACL statements. In the case of \\RCPT\\ (but not \\MAIL\\ or
22164 \\DATA\\), \$domain$\ and \$local@_part$\ are set from the argument address.
22166 When an ACL for the \\AUTH\\ parameter of \\MAIL\\ is running, the variables
22167 that contain information about the host are set, but \$sender@_address$\ is not
22168 yet set. Section ~~SECTauthparamail contains a discussion of this parameter and
22171 The \$message@_size$\ variable is set to the value of the \\SIZE\\ parameter on
22172 the \\MAIL\\ command at \\MAIL\\, \\RCPT\\ and pre-data time, or to -1 if
22173 that parameter is not given. The value is updated to the true message size by
22174 the time the final \\DATA\\ ACL is run (after the message data has been
22177 The \$rcpt@_count$\ variable increases by one for each \\RCPT\\ command
22178 received. The \$recipients@_count$\ variable increases by one each time a
22179 \\RCPT\\ command is accepted, so while an ACL for \\RCPT\\ is being processed,
22180 it contains the number of previously accepted recipients. At \\DATA\\ time (for
22181 both the \\DATA\\ ACLs), \$rcpt@_count$\ contains the total number of \\RCPT\\
22182 commands, and \$recipients@_count$\ contains the total number of accepted
22188 .section Data for non-message ACLs
22189 .rset SECTdatfornon "~~chapter.~~section"
22190 .index ~~ACL||data for non-message ACL
22192 When an ACL is being run for \\AUTH\\, \\EHLO\\, \\ETRN\\, \\EXPN\\, \\HELO\\,
22194 \\STARTTLS\\, or \\VRFY\\, the remainder of the SMTP command line is placed in
22195 \$smtp@_command@_argument$\. This can be tested using a \condition\ condition.
22196 For example, here is an ACL for use with \\AUTH\\, which insists that either
22197 the session is encrypted, or the CRAM-MD5 authentication method is used. In
22198 other words, it does not permit authentication methods that use cleartext
22199 passwords on unencrypted connections.
22202 accept encrypted = *
22205 accept condition = ${if eq{${uc:$smtp_command_argument}}\
22209 deny message = TLS encryption or CRAM-MD5 required
22211 (Another way of applying this restriction is to arrange for the authenticators
22212 that use cleartext passwords not to be advertised when the connection is not
22213 encrypted. You can use the generic \server@_advertise@_condition\ authenticator
22214 option to do this.)
22217 .section Format of an ACL
22218 .index ~~ACL||format of
22219 .index ~~ACL||verbs, definition of
22220 An individual ACL consists of a number of statements. Each statement starts
22221 with a verb, optionally followed by a number of conditions and `modifiers'.
22223 Modifiers can change the way the verb operates, define error and log messages,
22224 set variables, insert delays, and vary the processing of accepted messages.
22227 If all the conditions are met, the verb is obeyed. The same condition may be
22228 used (with different arguments) more than once in the same statement. This
22229 provides a means of specifying an `and' conjunction between conditions. For
22232 deny dnslists = list1.example
22233 dnslists = list2.example
22235 If there are no conditions, the verb is always obeyed.
22237 Exim stops evaluating the conditions and modifiers when it reaches a condition
22238 that fails. What happens then
22240 depends on the verb (and in one case, on a special modifier). Not all the
22241 conditions make sense at every testing point. For example, you cannot test a
22242 sender address in the ACL that is run for a \\VRFY\\ command.
22245 The ACL verbs are as follows:
22247 .index \accept\, ACL verb
22248 \accept\: If all the conditions are met, the ACL returns `accept'. If any of
22249 the conditions are not met, what happens depends on whether \endpass\ appears
22250 among the conditions (for syntax see below). If the failing condition is before
22251 \endpass\, control is passed to the next ACL statement; if it is after
22252 \endpass\, the ACL returns `deny'. Consider this statement, used to check a
22255 accept domains = +local_domains
22259 If the recipient domain does not match the \domains\ condition, control passes
22260 to the next statement. If it does match, the recipient is verified, and the
22261 command is accepted if verification succeeds. However, if verification fails,
22262 the ACL yields `deny', because the failing condition is after \endpass\.
22264 .index \defer\, ACL verb
22265 \defer\: If all the conditions are met, the ACL returns `defer' which, in an
22266 SMTP session, causes a 4\*xx*\ response to be given. For a non-SMTP ACL,
22267 \defer\ is the same as \deny\, because there is no way of sending a temporary
22268 error. For a \\RCPT\\ command, \defer\ is much the same as using a
22269 \%redirect%\ router and \":defer:"\ while verifying, but the \defer\ verb can
22270 be used in any ACL, and even for a recipient it might be a simpler approach.
22272 .index \deny\, ACL verb
22273 \deny\: If all the conditions are met, the ACL returns `deny'. If any of the
22274 conditions are not met, control is passed to the next ACL statement. For
22277 deny dnslists = blackholes.mail-abuse.org
22279 rejects commands from hosts that are on a DNS black list.
22281 .index \discard\, ACL verb
22282 \discard\: This verb behaves like \accept\, except that it returns `discard'
22283 from the ACL instead of `accept'. It is permitted only on ACLs that are
22284 concerned with receiving messages, and it causes recipients to be discarded.
22285 If the \log@_message\ modifier is set when \discard\ operates, its contents are
22286 added to the line that is automatically written to the log.
22288 If \discard\ is used in an ACL for \\RCPT\\, just the one recipient is
22289 discarded; if used for \\MAIL\\, \\DATA\\ or in the non-SMTP ACL, all the
22290 message's recipients are discarded. Recipients that are discarded before
22291 \\DATA\\ do not appear in the log line when the \log@_recipients\ log selector
22294 .index \drop\, ACL verb
22295 \drop\: This verb behaves like \deny\, except that an SMTP connection is
22296 forcibly closed after the 5\*xx*\ error message has been sent. For example:
22298 drop message = I don't take more than 20 RCPTs
22301 condition = ${if > {$rcpt_count}{20}}
22304 There is no difference between \deny\ and \drop\ for the connect-time ACL. The
22305 connection is always dropped after sending a 550 response.
22307 .index \require\, ACL verb
22308 \require\: If all the conditions are met, control is passed to the next ACL
22309 statement. If any of the conditions are not met, the ACL returns `deny'. For
22310 example, when checking a \\RCPT\\ command,
22312 require verify = sender
22314 passes control to subsequent statements only if the message's sender can be
22315 verified. Otherwise, it rejects the command.
22317 .index \warn\, ACL verb
22318 \warn\: If all the conditions are met, a header line is added to an incoming
22319 message and/or a line is written to Exim's main log. In all cases, control
22320 passes to the next ACL statement. The text of the added header line and the log
22321 line are specified by modifiers; if they are not present, a \warn\ verb just
22322 checks its conditions and obeys any `immediate' modifiers such as \set\ and
22325 There is more about adding header lines in section ~~SECTaddheadwarn.
22328 If any condition on a \warn\ statement cannot be completed (that is, there is
22329 some sort of defer), no header lines are added and the configured log line is
22330 not written. No further conditions or modifiers in the \warn\ statement are
22331 processed. The incident is logged, but the ACL continues to be processed, from
22332 the next statement onwards.
22334 If a \message\ modifier is present on a \warn\ verb in an ACL that is not
22335 testing an incoming message, it is ignored, and the incident is logged.
22337 A \warn\ statement may use the \log@_message\ modifier to cause a line to be
22338 written to the main log when the statement's conditions are true.
22339 If an identical log line is requested several times in the same message, only
22340 one copy is actually written to the log. If you want to force duplicates to be
22341 written, use the \logwrite\ modifier instead.
22343 When one of the \warn\ conditions is an address verification that fails, the
22344 text of the verification failure message is in \$acl@_verify@_message$\. If you
22345 want this logged, you must set it up explicitly. For example:
22347 warn !verify = sender
22348 log_message = sender verify failed: $acl_verify_message
22352 At the end of each ACL there is an implicit unconditional \deny\.
22354 As you can see from the examples above, the conditions and modifiers are
22355 written one to a line, with the first one on the same line as the verb, and
22356 subsequent ones on following lines. If you have a very long condition, you can
22357 continue it onto several physical lines by the usual backslash continuation
22358 mechanism. It is conventional to align the conditions vertically.
22361 .section ACL variables
22362 .rset SECTaclvariables "~~chapter.~~section"
22363 .index ~~ACL||variables
22364 There are some special variables that can be set during ACL processing. They
22365 can be used to pass information between different ACLs, different invocations
22366 of the same ACL in the same SMTP connection, and between ACLs and the routers,
22367 transports, and filters that are used to deliver a message. There are two sets
22368 of these variables:
22370 The values of \$acl@_c0$\ to \$acl@_c9$\ persist throughout an SMTP connection.
22371 They are never reset. Thus, a value that is set while receiving one message is
22372 still available when receiving the next message on the same SMTP connection.
22374 The values of \$acl@_m0$\ to \$acl@_m9$\ persist only while a message is being
22375 received. They are reset afterwards. They are also reset by \\MAIL\\, \\RSET\\,
22376 \\EHLO\\, \\HELO\\, and after starting up a TLS session.
22378 When a message is accepted, the current values of all the ACL variables are
22379 preserved with the message and are subsequently made available at delivery
22380 time. The ACL variables are set by modifier called \set\. For example:
22382 accept hosts = whatever
22383 set acl_m4 = some value
22385 \**Note**\: a leading dollar sign is not used when naming a variable that is to
22386 be set. If you want to set a variable without taking any action, you can use a
22387 \warn\ verb without any other modifiers or conditions.
22390 .section Condition and modifier processing
22391 .index ~~ACL||conditions, processing
22392 .index ~~ACL||modifiers, processing
22393 An exclamation mark preceding a condition negates its result. For example,
22395 deny domains = *.dom.example
22396 !verify = recipient
22398 causes the ACL to return `deny' if the recipient domain ends in
22399 \*dom.example*\ and the recipient address cannot be verified.
22401 The arguments of conditions and modifiers are expanded. A forced failure
22402 of an expansion causes a condition to be ignored, that is, it behaves as if the
22403 condition is true. Consider these two statements:
22405 accept senders = ${lookup{$host_name}lsearch\
22406 {/some/file}{$value}fail}
22407 accept senders = ${lookup{$host_name}lsearch\
22408 {/some/file}{$value}{}}
22410 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
22411 the returned list is searched, but if the lookup fails the behaviour is
22412 different in the two cases. The \fail\ in the first statement causes the
22413 condition to be ignored, leaving no further conditions. The \accept\ verb
22414 therefore succeeds. The second statement, however, generates an empty list when
22415 the lookup fails. No sender can match an empty list, so the condition fails,
22416 and therefore the \accept\ also fails.
22418 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
22419 specify actions that are taken as the conditions for a statement are checked;
22420 others specify text for messages that are used when access is denied or a
22421 warning is generated.
22423 The \control\ modifier affects the way an incoming message is handled.
22426 The positioning of the modifiers in an ACL statement important, because the
22427 processing of a verb ceases as soon as its outcome is known. Only those
22428 modifiers that have already been encountered will take effect. For example,
22429 consider this use of the \message\ modifier:
22431 require message = Can't verify sender
22433 message = Can't verify recipient
22435 message = This message cannot be used
22437 If sender verification fails, Exim knows that the result of the statement is
22438 `deny', so it goes no further. The first \message\ modifier has been seen, so
22439 its text is used as the error message. If sender verification succeeds, but
22440 recipient verification fails, the second message is used. If recipient
22441 verification succeeds, the third message becomes `current', but is never used
22442 because there are no more conditions to cause failure.
22444 For the \deny\ verb, on the other hand, it is always the last \message\
22445 modifier that is used, because all the conditions must be true for rejection to
22446 happen. Specifying more than one \message\ modifier does not make sense, and
22447 the message can even be specified after all the conditions. For example:
22450 !senders = *@my.domain.example
22451 message = Invalid sender from client host
22453 The `deny' result does not happen until the end of the statement is reached, by
22454 which time Exim has set up the message.
22457 .section ACL modifiers
22458 .rset SECTACLmodi "~~chapter.~~section"
22459 .index ~~ACL||modifiers, list of
22460 The ACL modifiers are as follows:
22464 .item "control = <<text>>"
22465 .index \control\, ACL modifier
22467 This modifier affects the subsequent processing of the SMTP connection or of an
22468 incoming message that is accepted. The effect of the first type of control
22469 lasts for the duration of the connection, whereas the effect of the second type
22470 lasts only until the current message has been received. The message-specific
22471 controls always apply to the whole message, not to individual recipients,
22472 even if the \control\ modifier appears in a \\RCPT\\ ACL.
22474 As there are now quite a few controls that can be applied, they are described
22475 separately in section ~~SECTcontrols.
22477 The \control\ modifier can be used in several different ways. For example:
22479 It can be at the end of an \accept\ statement:
22481 accept ...some conditions
22482 control = queue_only
22484 In this case, the control is applied when this statement yields `accept', in
22485 other words, when the conditions are all true.
22487 It can be in the middle of an \accept\ statement:
22489 accept ...some conditions...
22490 control = queue_only
22491 ...some more conditions...
22493 If the first set of conditions are true, the control is applied, even if the
22494 statement does not accept because one of the second set of conditions is false.
22495 In this case, some subsequent statement must yield `accept' for the control to
22498 It can be used with \warn\ to apply the control, leaving the
22499 decision about accepting or denying to a subsequent verb. For
22502 warn ...some conditions...
22506 This example of \warn\ does not contain \message\, \log@_message\, or
22507 \logwrite\, so it does not add anything to the message and does not write a log
22511 If you want to apply a control unconditionally, you can use it with a \require\
22514 require control = no_multiline_response
22519 .item "delay = <<time>>"
22520 .index \delay\, ACL modifier
22521 .index \-bh-\ option
22522 This modifier causes Exim to wait for the time interval before proceeding. The
22523 time is given in the usual Exim notation. This modifier may appear in any ACL.
22524 The delay happens as soon as the modifier is processed. However, when testing
22525 Exim using the \-bh-\ option, the delay is not actually imposed (an appropriate
22526 message is output instead).
22528 Like \control\, \delay\ can be used with \accept\ or
22529 \deny\, for example:
22531 deny ...some conditions...
22534 The delay happens if all the conditions are true, before the statement returns
22535 `deny'. Compare this with:
22538 ...some conditions...
22540 which waits for 30s before processing the conditions. The \delay\ modifier can
22541 also be used with \warn\ and together with \control\:
22543 warn ...some conditions...
22550 .index \endpass\, ACL modifier
22551 This modifier, which has no argument, is recognized only in \accept\
22552 statements. It marks the boundary between the conditions whose failure causes
22553 control to pass to the next statement, and the conditions whose failure causes
22554 the ACL to return `deny'. See the description of \accept\ above.
22556 .item "log@_message = <<text>>"
22557 .index \log@_message\, ACL modifier
22558 This modifier sets up a message that is used as part of the log message if the
22559 ACL denies access or a \warn\ statement's conditions are true. For example:
22561 require log_message = wrong cipher suite $tls_cipher
22562 encrypted = DES-CBC3-SHA
22564 \log@_message\ adds to any underlying error message that may exist because of
22565 the condition failure. For example, while verifying a recipient address, a
22566 :::fail:: redirection might have already set up a message. Although the message
22567 is usually defined before the conditions to which it applies, the expansion
22568 does not happen until Exim decides that access is to be denied. This means that
22569 any variables that are set by the condition are available for inclusion in the
22570 message. For example, the \$dnslist@_<<xxx>>$\ variables are set after a DNS
22571 black list lookup succeeds. If the expansion of \log@_message\ fails, or if the
22572 result is an empty string, the modifier is ignored.
22574 If you want to use a \warn\ statement to log the result of an address
22575 verification, you can use \$acl__verify__message$\ to include the verification
22578 If \log@_message\ is used with a \warn\ statement, `Warning:' is added to the
22579 start of the logged message. If the same warning log message is requested more
22580 than once while receiving a single email message, only one copy is actually
22581 logged. If you want to log multiple copies, use \logwrite\ instead of
22582 \log@_message\. In the absence of \log@_message\ and \logwrite\, nothing is
22583 logged for a succesful \warn\ statement.
22585 If \log@_message\ is not present and there is no underlying error message (for
22586 example, from the failure of address verification), but \message\ is present,
22587 the \message\ text is used for logging rejections. However, if any text for
22588 logging contains newlines, only the first line is logged. In the absence of
22589 both \log@_message\ and \message\, a default built-in message is used for
22590 logging rejections.
22592 .item "logwrite = <<text>>"
22593 .index \logwrite\, ACL modifier
22594 .index log||in ACL, immediate
22595 This modifier writes a message to a log file as soon as it is encountered when
22596 processing an ACL. (Compare \log@_message\, which, except in the case of
22597 \warn\, is used only if the ACL statement denies access.) The \logwrite\
22598 modifier can be used to log special incidents in ACLs. For example:
22600 accept <<some special conditions>>
22602 logwrite = froze message because ...
22604 By default, the message is written to the main log. However, it may begin
22605 with a colon, followed by a comma-separated list of log names, and then
22606 another colon, to specify exactly which logs are to be written. For
22609 logwrite = :main,reject: text for main and reject logs
22610 logwrite = :panic: text for panic log only
22613 .item "message = <<text>>"
22614 .index \message\, ACL modifier
22615 This modifier sets up a text string that is expanded and used as an error
22616 message if the current statement causes the ACL to deny access. The expansion
22617 happens at the time Exim decides that access is to be denied, not at the time
22618 it processes \message\. If the expansion fails, or generates an empty string,
22619 the modifier is ignored. For ACLs that are triggered by SMTP commands, the
22620 message is returned as part of the SMTP error response.
22622 The \message\ modifier is also used with the \warn\ verb to specify one or more
22623 header lines to be added to an incoming message when all the conditions are
22624 true. See section ~~SECTaddheadwarn for more details. If \message\ is used with
22625 \warn\ in an ACL that is not concerned with receiving a message, it has no
22628 The text is literal; any quotes are taken as literals, but because the string
22629 is expanded, backslash escapes are processed anyway. If the message contains
22630 newlines, this gives rise to a multi-line SMTP response. Like \log@_message\,
22631 the contents of \message\ are not expanded until after a condition has failed.
22633 If \message\ is used on a statement that verifies an address, the message
22634 specified overrides any message that is generated by the verification process.
22635 However, the original message is available in the variable
22636 \$acl@_verify@_message$\, so you can incorporate it into your message if you
22637 wish. In particular, if you want the text from \:fail:\ items in \%redirect%\
22638 routers to be passed back as part of the SMTP response, you should either not
22639 use a \message\ modifier, or make use of \$acl@_verify@_message$\.
22641 .item "set <<acl@_name>> = <<value>>"
22642 .index \set\, ACL modifier
22643 This modifier puts a value into one of the ACL variables (see section
22644 ~~SECTaclvariables).
22650 .section Use of the control modifier
22651 .rset SECTcontrols "~~chapter.~~section"
22652 .index \control\, ACL modifier
22653 The \control\ modifier supports the following settings:
22657 .item "control = caseful@_local@_part"
22658 .item "control = caselower@_local@_part"
22659 .index ~~ACL||case of local part in
22660 .index case of local parts
22661 These two controls are permitted only in the ACL specified by \acl@_smtp@_rcpt\
22662 (that is, during \\RCPT\\ processing). By default, the contents of
22663 \$local@_part$\ are lower cased before ACL processing. If
22664 `caseful@_local@_part' is specified, any uppercase letters in the original
22665 local part are restored in \$local@_part$\ for the rest of the ACL, or until a
22666 control that sets `caselower@_local@_part' is encountered.
22668 This control affects only the current recipient. Moreover, it applies only to
22669 local part handling that takes place directly in the ACL (for example, as a key
22670 in lookups). If a test to verify the recipient is obeyed, the case-related
22671 handling of the local part during the verification is controlled by the router
22672 configuration (see the \caseful@_local@_part\ generic router option).
22674 This facility could be used, for example, to add a spam score to local parts
22675 containing upper case letters. For example, using \$acl@_m4$\ to accumulate the
22678 warn control = caseful_local_part
22679 set acl_m4 = ${eval:\
22681 ${if match{$local_part}{[A-Z]}{1}{0}}\
22683 control = caselower_local_part
22685 Notice that we put back the lower cased version afterwards, assuming that
22686 is what is wanted for subsequent tests.
22688 .item "control = enforce@_sync"
22689 .item "control = no@_enforce@_sync"
22690 .index SMTP||synchronization checking
22691 .index synchronization checking in SMTP
22692 These controls make it possible to be selective about when SMTP synchronization
22693 is enforced. The global option \smtp@_enforce@_sync\ specifies the initial
22694 state of the switch (it is true by default). See the description of this option
22695 in chapter ~~CHAPmainconfig for details of SMTP synchronization checking.
22697 The effect of these two controls lasts for the remainder of the SMTP
22698 connection. They can appear in any ACL except the one for the non-SMTP
22699 messages. The most straightforward place to put them is in the ACL defined by
22700 \acl@_smtp@_connect\, which is run at the start of an incoming SMTP connection,
22701 before the first synchronization check. The expected use is to turn off the
22702 synchronization checks for badly-behaved hosts that you nevertheless need to
22705 .item "control = fakereject/<<message>>"
22706 .index fake rejection
22707 .index rejection, fake
22708 This control is permitted only for the \\MAIL\\, \\RCPT\\, and \\DATA\\ ACLs,
22709 in other words, only when an SMTP message is being received. If Exim accepts
22710 the message, instead the final 250 response, a 550 rejection message is sent.
22711 However, Exim proceeds to deliver the message as normal. The control applies
22712 only to the current message, not to any subsequent ones that may be received in
22713 the same SMTP connection.
22715 The text for the 550 response is taken from the \control\ modifier. If no
22716 message is supplied, the following is used:
22718 550-Your message has been rejected but is being
22719 550-kept for evaluation.
22720 550-If it was a legitimate message, it may still be
22721 550 delivered to the target recipient(s).
22723 This facilty should be used with extreme caution.
22726 .item "control = freeze"
22727 .index frozen messages||forcing in ACL
22728 This control is permitted only for the \\MAIL\\, \\RCPT\\, \\DATA\\, and
22729 non-SMTP ACLs, in other words, only when a message is being received. If the
22730 message is accepted, it is placed on Exim's queue and frozen. The control
22731 applies only to the current message, not to any subsequent ones that may be
22732 received in the same SMTP connection.
22735 .item "control = no@_mbox@_unspool"
22736 This control is available when Exim is compiled with the content scanning
22737 extension. Content scanning may require a copy of the current message, or parts
22738 of it, to be written in `mbox format' to a spool file, for passing to a virus
22739 or spam scanner. Normally, such copies are deleted when they are no longer
22740 needed. If this control is set, the copies are not deleted. The control
22741 applies only to the current message, not to any subsequent ones that may be
22742 received in the same SMTP connection. It is provided for debugging purposes and
22743 is unlikely to be useful in production.
22746 .item "control = no@_multiline@_response"
22747 .index multiline responses, suppressing
22748 This control is permitted for any ACL except the one for non-SMTP messages.
22749 It seems that there are broken clients in use that cannot handle multiline
22750 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
22752 If this control is set, multiline SMTP responses from ACL rejections are
22753 suppressed. One way of doing this would have been to put out these responses as
22754 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
22755 (`use multiline responses for more' it says -- ha!), and some of the responses
22756 might get close to that. So this facility, which is after all only a sop to
22757 broken clients, is implemented by doing two very easy things:
22759 Extra information that is normally output as part of a rejection caused by
22760 sender verification failure is omitted. Only the final line (typically `sender
22761 verification failed') is sent.
22763 If a \message\ modifier supplies a multiline response, only the first
22766 The setting of the switch can, of course, be made conditional on the
22767 calling host. Its effect lasts until the end of the SMTP connection.
22770 .item "control = queue@_only"
22771 .index \queue@_only\
22772 .index queueing incoming messages
22773 This control is permitted only for the \\MAIL\\, \\RCPT\\, \\DATA\\, and
22774 non-SMTP ACLs, in other words, only when a message is being received. If the
22775 message is accepted, it is placed on Exim's queue and left there for delivery
22776 by a subsequent queue runner. No immediate delivery process is started. In
22777 other words, it has the effect as the \queue@_only\ global option. However, the
22778 control applies only to the current message, not to any subsequent ones that
22779 may be received in the same SMTP connection.
22782 .item "control = submission/<<options>>"
22783 .index message||submission
22784 .index submission mode
22785 This control is permitted only for the \\MAIL\\, \\RCPT\\, and start of data
22786 ACLs (the latter is the one defined by \acl@_smtp@_predata\). Setting it tells
22787 Exim that the current message is a submission from a local MUA. In this case,
22788 Exim operates in `submission mode', and applies certain fixups to the message
22789 if necessary. For example, it add a ::Date:: header line if one is not present.
22790 This control is not permitted in the \acl@_smtp@_data\ ACL, because that is too
22791 late (the message has already been created).
22793 Chapter ~~CHAPmsgproc describes the processing that Exim applies to messages.
22794 Section ~~SECTsubmodnon covers the processing that happens in submission mode;
22795 the available options for this control are described there. The control applies
22796 only to the current message, not to any subsequent ones that may be received in
22797 the same SMTP connection.
22804 .section Adding header lines with the warn verb
22805 .rset SECTaddheadwarn "~~chapter.~~section"
22806 .index header lines||adding in an ACL
22807 .index header lines||position of added lines
22808 .index \warn\, ACL verb
22809 .index \message\, ACL modifier
22810 The \message\ modifier can be used on a \warn\ statement to add an extra header
22811 line to an incoming message, as in this example:
22813 warn message = X-blacklisted-at: $dnslist_domain
22814 dnslists = sbl.spamhaus.org : \
22815 dialup.mail-abuse.org
22817 If an identical header line is requested several times (provoked, for example,
22818 by multiple \\RCPT\\ commands), only one copy is actually added to the message.
22819 If the text of the \message\ modifier contains one or more newlines that are
22820 not followed by a space or a tab, it is assumed to contain multiple header
22821 lines. Each one is checked for valid syntax; \"X-ACL-Warn:"\ is added to the
22822 front of any line that is not a valid header line.
22824 By default, new lines are added at the end of the existing header lines.
22825 However, you can specify that any particular header line should be added right
22826 at the start (before all the ::Received:: lines), immediately after the first
22827 block of ::Received:: lines, or immediately before any line that is not a
22828 ::Received:: or ::Resent-something:: header.
22830 This is done by specifying `:at@_start:', `:after@_received:', or
22831 `:at@_start@_rfc:' (or, for completeness, `:at@_end:') before the text of the
22832 header line, respectively. (Header text cannot start with a colon, as there has
22833 to be a header name first.) For example:
22835 warn message = :after_received:X-My-Header: something or other...
22838 If more than one header is supplied in a single warn statement, each one is
22839 treated independently and can therefore be placed differently. If you add
22840 more than one line at the start, or after the Received: block, they will
22841 end up in reverse order.
22843 \**Warning**\: This facility currently applies only to header lines that are
22844 added in an ACL. It does NOT work for header lines that are added in a
22845 system filter or in a router or transport.
22847 .index header lines||added, visibility of
22848 Header lines that are added by an ACL at \\MAIL\\ or \\RCPT\\ time are not
22849 visible in string expansions in ACLs for subsequent \\RCPT\\ commands or in the
22850 \acl@_smtp@_predata\ ACL. However, they are visible in string expansions in the
22851 ACL that is run after \\DATA\\ is complete (the \acl@_smtp@_data\ ACL). This is
22852 also true for header lines that are added in the \acl@_smtp@_predata\ ACL.
22853 If a message is rejected after \\DATA\\, all added header lines are included in
22854 the entry that is written to the reject log.
22856 If you want to preserve data between \\MAIL\\, \\RCPT\\, and the
22857 \acl@_smtp@_predata\ ACLs, you can use ACL variables, as described in section
22858 ~~SECTaclvariables.
22863 .section ACL conditions
22864 .rset SECTaclconditions "~~chapter.~~section"
22865 .index ~~ACL||conditions, list of
22867 Some of conditions listed in this section are available only when Exim is
22868 compiled with the content-scanning extension. They are included here briefly
22869 for completeness. More detailed descriptions can be found in the discussion on
22870 content scanning in chapter ~~CHAPexiscan.
22873 Not all conditions are relevant in all circumstances. For example, testing
22874 senders and recipients does not make sense in an ACL that is being run as the
22875 result of the arrival of an \\ETRN\\ command, and checks on message headers can
22876 be done only in the ACLs specified by \acl@_smtp@_data\ and \acl__not__smtp\.
22877 You can use the same condition (with different parameters) more than once in
22878 the same ACL statement. This provides a way of specifying an `and' conjunction.
22879 The conditions are as follows:
22883 .item "acl = <<name of acl or ACL string or file name >>"
22884 .index ~~ACL||nested
22885 .index ~~ACL||indirect
22886 .index \acl\, ACL condition
22887 The possible values of the argument are the same as for the
22888 \acl@_smtp@_$it{xxx}\ options. The named or inline ACL is run. If it returns
22889 `accept' the condition is true; if it returns `deny' the condition is false. If
22890 it returns `defer', the current ACL returns `defer'
22892 unless the condition is on a \warn\ verb. In that case, a `defer' return makes
22893 the condition false. This means that further processing of the \warn\ verb
22894 ceases, but processing of the ACL continues.
22897 If the nested \acl\ returns `drop' and the outer condition denies access,
22898 the connection is dropped. If it returns `discard', the verb must be \accept\
22899 or \discard\, and the action is taken immediately -- no further conditions are
22902 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
22903 loops. This condition allows you to use different ACLs in different
22904 circumstances. For example, different ACLs can be used to handle \\RCPT\\
22905 commands for different local users or different local domains.
22907 .item "authenticated = <<string list>>"
22908 .index \authenticated\, ACL condition
22909 .index authentication||ACL checking
22910 .index ~~ACL||testing for authentication
22911 If the SMTP connection is not authenticated, the condition is false. Otherwise,
22912 the name of the authenticator is tested against the list. To test for
22913 authentication by any authenticator, you can set
22918 .item "condition = <<string>>"
22919 .index \condition\, ACL condition
22920 .index customizing||ACL condition
22921 .index ~~ACL||customized test
22922 .index ~~ACL||testing, customized
22923 This feature allows you to make up custom conditions. If the result of
22924 expanding the string is an empty string, the number zero, or one of the strings
22925 `no' or `false', the condition is false. If the result is any non-zero number,
22926 or one of the strings `yes' or `true', the condition is true. For any other
22927 values, some error is assumed to have occured, and the ACL returns `defer'.
22931 .item "decode = <<location>>"
22932 .index \decode\, ACL condition
22933 This condition is available only when Exim is compiled with the
22934 content-scanning extension, and it is allowed only the the ACL defined by
22935 \acl@_smtp@_mime\. It causes the current MIME part to be decoded into a file.
22936 For details, see chapter ~~CHAPexiscan.
22940 .item "dnslists = <<list of domain names and other data>>"
22941 .index \dnslists\, ACL condition
22942 .index DNS list||in ACL
22943 .index black list (DNS)
22944 .index ~~ACL||testing a DNS list
22945 This condition checks for entries in DNS black lists. These are also known as
22946 `RBL lists', after the original Realtime Blackhole List, but note that the use
22947 of the lists at \*mail-abuse.org*\ now carries a charge.
22948 There are too many different variants of this condition to describe briefly
22949 here. See sections ~~SECTmorednslists--~~SECTmorednslistslast for details.
22951 .item "domains = <<domain list>>"
22952 .index \domains\, ACL condition
22953 .index domain||ACL checking
22954 .index ~~ACL||testing a recipient domain
22955 This condition is relevant only after a \\RCPT\\ command. It checks that the
22956 domain of the recipient address is in the domain list. If percent-hack
22957 processing is enabled, it is done before this test is done. If the check
22958 succeeds with a lookup, the result of the lookup is placed in \$domain@_data$\
22959 until the next \domains\ test.
22961 .item "encrypted = <<string list>>"
22962 .index \encrypted\, ACL condition
22963 .index encryption||checking in an ACL
22964 .index ~~ACL||testing for encryption
22965 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
22966 name of the cipher suite in use is tested against the list. To test for
22967 encryption without testing for any specific cipher suite(s), set
22972 .item "hosts = << host list>>"
22973 .index \hosts\, ACL condition
22974 .index host||ACL checking
22975 .index ~~ACL||testing the client host
22976 This condition tests that the calling host matches the host list. If you have
22977 name lookups or wildcarded host names and IP addresses in the same host list,
22978 you should normally put the IP addresses first. For example, you could have:
22980 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
22982 The reason for this lies in the left-to-right way that Exim processes lists.
22983 It can test IP addresses without doing any DNS lookups, but when it reaches an
22984 item that requires a host name, it fails if it cannot find a host name to
22985 compare with the pattern. If the above list is given in the opposite order, the
22986 \accept\ statement fails for a host whose name cannot be found, even if its
22987 IP address is 10.9.8.7.
22989 If you really do want to do the name check first, and still recognize the IP
22990 address even if the name lookup fails, you can rewrite the ACL like this:
22992 accept hosts = dbm;/etc/friendly/hosts
22993 accept hosts = 10.9.8.7
22995 The default action on failing to find the host name is to assume that the host
22996 is not in the list, so the first \accept\ statement fails. The second statement
22997 can then check the IP address.
22999 If a \hosts\ condition is satisfied by means of a lookup, the result
23000 of the lookup is made available in the \$host@_data$\ variable. This
23001 allows you, for example, to set up a statement like this:
23003 deny hosts = net-lsearch;/some/file
23004 message = $host_data
23006 which gives a custom error message for each denied host.
23008 .item "local@_parts = <<local part list>>"
23009 .index \local@_parts\, ACL condition
23010 .index local part||ACL checking
23011 .index ~~ACL||testing a local part
23012 This condition is relevant only after a \\RCPT\\ command. It checks that the
23013 local part of the recipient address is in the list. If percent-hack processing
23014 is enabled, it is done before this test. If the check succeeds with a lookup,
23015 the result of the lookup is placed in \$local@_part@_data$\ until the next
23016 \local@_parts\ test.
23020 .item "malware = <<option>>"
23021 .index \malware\, ACL condition
23022 .index ~~ACL||virus scanning
23023 .index ~~ACL||scanning for viruses
23024 This condition is available only when Exim is compiled with the
23025 content-scanning extension. It causes the incoming message to be scanned for
23026 viruses. For details, see chapter ~~CHAPexiscan.
23031 .item "mime@_regex = <<list of regular expressions>>"
23032 .index \mime@_regex\, ACL condition
23033 .index ~~ACL||testing by regex matching
23034 This condition is available only when Exim is compiled with the
23035 content-scanning extension, and it is allowed only the the ACL defined by
23036 \acl@_smtp@_mime\. It causes the current MIME part to be scanned for a match
23037 with any of the regular expressions. For details, see chapter ~~CHAPexiscan.
23041 .item "recipients = <<address list>>"
23042 .index \recipients\, ACL condition
23043 .index recipient||ACL checking
23044 .index ~~ACL||testing a recipient
23045 This condition is relevant only after a \\RCPT\\ command. It checks the entire
23046 recipient address against a list of recipients.
23050 .item "regex = <<list of regular expressions>>"
23051 .index \regex\, ACL condition
23052 .index ~~ACL||testing by regex matching
23053 This condition is available only when Exim is compiled with the
23054 content-scanning extension. It causes the incoming message to be scanned
23055 for a match with any of the regular expressions. For details, see chapter
23060 .item "sender@_domains = <<domain list>>"
23061 .index \sender@_domains\, ACL condition
23062 .index sender||ACL checking
23063 .index ~~ACL||testing a sender domain
23064 This condition tests the domain of the sender of the message against the given
23066 \**Note**\: the domain of the sender address is in
23067 \$sender@_address@_domain$\. It is \*not*\ put in \$domain$\ during the testing
23068 of this condition. This is an exception to the general rule for testing
23069 domain lists. It is done this way so that, if this condition is used in an
23070 ACL for a \\RCPT\\ command, the recipient's domain (which is in \$domain$\) can
23071 be used to influence the sender checking.
23073 .item "senders = <<address list>>"
23074 .index \senders\, ACL condition
23075 .index sender||ACL checking
23076 .index ~~ACL||testing a sender
23077 This condition tests the sender of the message against the given list. To test
23078 for a bounce message, which has an empty sender, set
23085 .item "spam = <<username>>"
23086 .index \spam\, ACL condition
23087 .index ~~ACL||scanning for spam
23088 This condition is available only when Exim is compiled with the
23089 content-scanning extension. It causes the incoming message to be scanned by
23090 SpamAssassin. For details, see chapter ~~CHAPexiscan.
23094 .item "verify = certificate"
23095 .index \verify\, ACL condition
23096 .index TLS||client certificate verification
23097 .index certificate||verification of client
23098 .index ~~ACL||certificate verification
23099 .index ~~ACL||testing a TLS certificate
23100 This condition is true in an SMTP session if the session is encrypted, and a
23101 certificate was received from the client, and the certificate was verified. The
23102 server requests a certificate only if the client matches \tls@_verify@_hosts\
23103 or \tls@_try@_verify@_hosts\ (see chapter ~~CHAPTLS).
23105 .item "verify = header@_sender/<<options>>"
23106 .index \verify\, ACL condition
23107 .index ~~ACL||verifying sender in the header
23108 .index header lines||verifying the sender in
23109 .index sender||verifying in header
23110 .index verifying||sender in header
23111 This condition is relevant only in an ACL that is run after a message has been
23112 received, that is, in an ACL specified by \acl@_smtp@_data\
23114 or \acl@_not@_smtp\. It checks that there is a verifiable address in at least
23115 one of the ::Sender::, ::Reply-To::, or ::From:: header lines. Such an address
23116 is loosely thought of as a `sender' address (hence the name of the test).
23117 However, an address that appears in one of these headers need not be an address
23118 that accepts bounce messages; only sender addresses in envelopes are required
23119 to accept bounces. Therefore, if you use the callout option on this check, you
23120 might want to arrange for a non-empty address in the \\MAIL\\ command.
23123 Details of address verification and the options are given later, starting at
23124 section ~~SECTaddressverification (callouts are described in section
23125 ~~SECTcallver). You can combine this condition with the \senders\ condition to
23126 restrict it to bounce messages only:
23129 message = A valid sender header is required for bounces
23130 !verify = header_sender
23133 .item "verify = header@_syntax"
23134 .index \verify\, ACL condition
23135 .index ~~ACL||verifying header syntax
23136 .index header lines||verifying syntax
23137 .index verifying||header syntax
23138 This condition is relevant only in an ACL that is run after a message has been
23139 received, that is, in an ACL specified by \acl@_smtp@_data\
23140 or \acl@_not@_smtp\.
23141 It checks the syntax of all header lines that can contain lists of addresses
23142 (::Sender::, ::From::, ::Reply-To::, ::To::, ::Cc::, and ::Bcc::).
23143 Unqualified addresses (local parts without domains) are permitted only in
23144 locally generated messages and from hosts that match
23145 \sender@_unqualified@_hosts\ or \recipient@_unqualified@_hosts\, as
23148 Note that this condition is a syntax check only. However, a common spamming
23149 ploy is to send syntactically invalid headers such as
23153 and this condition can be used to reject such messages.
23155 .item "verify = helo"
23156 .index \verify\, ACL condition
23157 .index ~~ACL||verifying HELO/EHLO
23158 .index \\HELO\\||verifying
23159 .index \\EHLO\\||verifying
23160 .index verifying||\\EHLO\\
23161 .index verifying||\\HELO\\
23162 This condition is true if a \\HELO\\ or \\EHLO\\ command has been received from
23163 the client host, and its contents have been verified. Verification of these
23164 commands does not happen by default. See the description of the
23165 \helo@_verify@_hosts\ and \helo@_try@_verify@_hosts\ options for details of how
23168 .item "verify = recipient/<<options>>"
23169 .index \verify\, ACL condition
23170 .index ~~ACL||verifying recipient
23171 .index recipient||verifying
23172 .index verifying||recipient
23173 This condition is relevant only after a \\RCPT\\ command. It verifies the
23174 current recipient. Details of address verification are given later, starting at
23175 section ~~SECTaddressverification. After a recipient has been verified, the
23176 value of \$address@_data$\ is the last value that was set while routing the
23177 address. This applies even if the verification fails. When an address that is
23178 being verified is redirected to a single address, verification continues with
23179 the new address, and in that case, the subsequent value of \$address@_data$\ is
23180 the value for the child address.
23183 .item "verify = reverse@_host@_lookup"
23184 .index \verify\, ACL condition
23185 .index ~~ACL||verifying host reverse lookup
23186 .index host||verifying reverse lookup
23187 This condition ensures that a verified host name has been looked up from the IP
23188 address of the client host. (This may have happened already if the host name
23189 was needed for checking a host list, or if the host matched \host@_lookup\.)
23190 Verification ensures that the host name obtained from a reverse DNS lookup, or
23191 one of its aliases, does, when it is itself looked up in the DNS, yield the
23192 original IP address.
23194 If this condition is used for a locally generated message (that is, when there
23195 is no client host involved), it always succeeds.
23198 .item "verify = sender/<<options>>"
23199 .index \verify\, ACL condition
23200 .index ~~ACL||verifying sender
23201 .index sender||verifying
23202 .index verifying||sender
23203 This condition is relevant only after a \\MAIL\\ or \\RCPT\\ command, or after
23204 a message has been received (the \acl@_smtp@_data\ or \acl@_not@_smtp\ ACLs).
23205 If the message's sender is empty (that is, this is a bounce message), the
23206 condition is true. Otherwise, the sender address is verified.
23208 If there is data in the \$address@_data$\ variable at the end of routing, its
23209 value is placed in \$sender__address__data$\ at the end of verification. This
23210 value can be used in subsequent conditions and modifiers in the same ACL
23211 statement. It does not persist after the end of the current statement. If you
23212 want to preserve the value for longer, you can save it in an ACL variable.
23214 Details of verification are given later, starting at section
23215 ~~SECTaddressverification. Exim caches the result of sender verification, to
23216 avoid doing it more than once per message.
23218 .item "verify = sender=address/<<options>>"
23219 .index \verify\, ACL condition
23220 This is a variation of the previous option, in which a modified address is
23221 verified as a sender.
23227 .section Using DNS lists
23228 .rset SECTmorednslists "~~chapter.~~section"
23229 .index DNS list||in ACL
23230 .index black list (DNS)
23231 .index ~~ACL||testing a DNS list
23232 In its simplest form, the \dnslists\ condition tests whether the calling host
23233 is on at least one of a number of DNS lists by looking up the inverted IP
23234 address in one or more DNS domains. For example, if the calling host's IP
23235 address is 192.168.62.43, and the ACL statement is
23237 deny dnslists = blackholes.mail-abuse.org : \
23238 dialups.mail-abuse.org
23240 the following records are looked up:
23242 43.62.168.192.blackholes.mail-abuse.org
23243 43.62.168.192.dialups.mail-abuse.org
23246 As soon as Exim finds an existing DNS record, processing of the list stops.
23247 Thus, multiple entries on the list provide an `or' conjunction. If you want to
23248 test that a host is on more than one list (an `and' conjunction), you can use
23249 two separate conditions:
23251 deny dnslists = blackholes.mail-abuse.org
23252 dnslists = dialups.mail-abuse.org
23255 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
23256 behaves as if the host
23258 does not match the list item, that is, as if the DNS record does not exist. If
23259 there are further items in the DNS list, they are processed.
23261 This is usually the required action when \dnslists\ is used with \deny\ (which
23262 is the most common usage), because it prevents a DNS failure from blocking
23263 mail. However, you can change this behaviour by putting one of the following
23264 special items in the list:
23265 .index \"+include@_unknown"\
23266 .index \"+exclude@_unknown"\
23267 .index \"+defer@_unknown"\
23269 +include@_unknown $rm{behave as if the item is on the list}
23270 +exclude@_unknown $rm{behave as if the item is not on the list (default)}
23271 +defer@_unknown $rm{give a temporary error}
23273 Each of these applies to any subsequent items on the list. For example:
23275 deny dnslists = +defer_unknown : foo.bar.example
23278 Testing the list of domains stops as soon as a match is found. If you want to
23279 warn for one list and block for another, you can use two different statements:
23281 deny dnslists = blackholes.mail-abuse.org
23282 warn message = X-Warn: sending host is on dialups list
23283 dnslists = dialups.mail-abuse.org
23286 DNS list lookups are cached by Exim for the duration of the SMTP session,
23287 so a lookup based on the IP address is done at most once for any incoming
23288 connection. Exim does not share information between multiple incoming
23289 connections (but your local name server cache should be active).
23293 .section Specifying the IP address for a DNS list lookup
23294 .index DNS list||keyed by explicit IP address
23295 By default, the IP address that is used in a DNS list lookup is the IP address
23296 of the calling host. However, you can specify another IP address by listing it
23297 after the domain name, introduced by a slash. For example:
23299 deny dnslists = black.list.tls/192.168.1.2
23301 This feature is not very helpful with explicit IP addresses; it is intended for
23302 use with IP addresses that are looked up, for example, the IP addresses of the
23303 MX hosts or nameservers of an email sender address. For an example, see section
23304 ~~SECTmulkeyfor below.
23308 .section DNS lists keyed on domain names
23309 .index DNS list||keyed by domain name
23310 There are some lists that are keyed on domain names rather than inverted IP
23311 addresses (see for example the \*domain based zones*\ link at
23312 \?http://www.rfc-ignorant.org/?\). No reversing of components is used with
23313 these lists. You can change the name that is looked up in a DNS list by listing
23314 it after the domain name, introduced by a slash. For example,
23316 deny message = Sender's domain is listed at $dnslist_domain
23317 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
23319 This particular example is useful only in ACLs that are obeyed after the
23320 \\RCPT\\ or \\DATA\\ commands, when a sender address is available. If (for
23321 example) the message's sender is \*user@@tld.example*\ the name that is looked
23322 up by this example is
23324 tld.example.dsn.rfc-ignorant.org
23327 A single \dnslists\ condition can contain entries for both names and IP
23328 addresses. For example:
23330 deny dnslists = sbl.spamhaus.org : \
23331 dsn.rfc-ignorant.org/$sender_address_domain
23333 The first item checks the sending host's IP address; the second checks a domain
23334 name. The whole condition is true if either of the DNS lookups succeeds.
23339 .section Multiple explicit keys for a DNS list
23340 .rset SECTmulkeyfor "~~chapter.~~section"
23341 .index DNS list||multiple keys for
23342 The syntax described above for looking up explicitly-defined values (either
23343 names or IP addresses) in a DNS blacklist is a simplification. After the domain
23344 name for the DNS list, what follows the slash can in fact be a list of items.
23345 As with all lists in Exim, the default separator is a colon. However, because
23346 this is a sublist within the list of DNS blacklist domains, it is necessary
23347 either to double the separators like this:
23349 dnslists = black.list.tld/name.1::name.2
23351 or to change the separator character, like this:
23353 dnslists = black.list.tld/<;name.1;name.2
23355 If an item in the list is an IP address, it is inverted before the DNS
23356 blacklist domain is appended. If it is not an IP address, no inversion
23357 occurs. Consider this condition:
23359 dnslists = black.list.tld/<;192.168.1.2;a.domain
23361 The DNS lookups that occur are:
23363 2.1.168.192.black.list.tld
23364 a.domain.black.list.tld
23366 Once a DNS record has been found (that matches a specific IP return
23367 address, if specified -- see section ~~SECTaddmatcon), no further lookups are
23368 done. If there is a temporary DNS error, the rest of the sublist of domains or
23369 IP addresses is tried. A temporary error for the whole dnslists item occurs
23370 only if no other DNS lookup in this sublist succeeds. In other words, a
23371 successful lookup for any of the items in the sublist overrides a temporary
23372 error for a previous item.
23374 The ability to supply a list of items after the slash is in some sense just a
23375 syntactic convenience. These two examples have the same effect:
23377 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
23378 dnslists = black.list.tld/a.domain::b.domain
23380 However, when the data for the list is obtained from a lookup, the second form
23381 is usually much more convenient. Consider this example:
23383 deny message = The mail servers for the domain \
23384 $sender_address_domain \
23385 are listed at $dnslist_domain ($dnslist_value); \
23387 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
23388 ${lookup dnsdb {>|mxh=\
23389 $sender_address_domain} }} }
23391 Note the use of \">|"\ in the dnsdb lookup to specify the separator for
23392 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
23393 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
23394 of expanding the condition might be something like this:
23396 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
23398 Thus, this example checks whether or not the IP addresses of the sender
23399 domain's mail servers are on the Spamhaus black list.
23404 .section Data returned by DNS lists
23405 .index DNS list||data returned from
23406 DNS lists are constructed using address records in the DNS. The original RBL
23407 just used the address 127.0.0.1 on the right hand side of each record, but the
23408 RBL+ list and some other lists use a number of values with different meanings.
23409 The values used on the RBL+ list are:
23414 127.1.0.3 $t DUL and RBL
23416 127.1.0.5 $t RSS and RBL
23417 127.1.0.6 $t RSS and DUL
23418 127.1.0.7 $t RSS and DUL and RBL
23420 Some DNS lists may return more than one address record.
23422 .section Variables set from DNS lists
23423 .index DNS list||variables set from
23424 When an entry is found in a DNS list, the variable \$dnslist@_domain$\
23425 contains the name of the domain that matched, \$dnslist@_value$\ contains the
23426 data from the entry, and \$dnslist@_text$\ contains the contents of any
23427 associated TXT record. If more than one address record is returned by the DNS
23428 lookup, all the IP addresses are included in \$dnslist@_value$\, separated by
23431 You can use these variables in \message\ or \log@_message\ modifiers --
23432 although these appear before the condition in the ACL, they are not expanded
23433 until after it has failed. For example:
23435 deny hosts = !+local_networks
23436 message = $sender_host_address is listed \
23438 dnslists = rbl-plus.mail-abuse.example
23442 .section Additional matching conditions for DNS lists
23443 .rset SECTaddmatcon "~~chapter.~~section"
23444 .index DNS list||matching specific returned data
23445 You can add an equals sign and an IP address after a \dnslists\ domain name in
23446 order to restrict its action to DNS records with a matching right hand side.
23449 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
23451 rejects only those hosts that yield 127.0.0.2. Without this additional data,
23452 any address record is considered to be a match. If more than one address record
23453 is found on the list, they are all checked for a matching right-hand side.
23455 More than one IP address may be given for checking, using a comma as a
23456 separator. These are alternatives -- if any one of them matches, the \dnslists\
23457 condition is true. For example:
23459 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
23462 If you want to specify a constraining address list and also specify names or IP
23463 addresses to be looked up, the constraining address list must be specified
23464 first. For example:
23466 deny dnslists = dsn.rfc-ignorant.org\
23467 =127.0.0.2/$sender_address_domain
23470 If the character `&' is used instead of `=', the comparison for each listed
23471 IP address is done by a bitwise `and' instead of by an equality test. In
23472 other words, the listed addresses are used as bit masks. The comparison is
23473 true if all the bits in the mask are present in the address that is being
23474 tested. For example:
23476 dnslists = a.b.c&0.0.0.3
23478 matches if the address is \*x.x.x.*\3, \*x.x.x.*\7, \*x.x.x.*\11, etc. If you
23479 want to test whether one bit or another bit is present (as opposed to both
23480 being present), you must use multiple values. For example:
23482 dnslists = a.b.c&0.0.0.1,0.0.0.2
23484 matches if the final component of the address is an odd number or two times
23488 .section Negated DNS matching conditions
23489 You can supply a negative list of IP addresses as part of a \dnslists\
23492 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
23494 means `deny if the host is in the black list at the domain \*a.b.c*\ and the IP
23495 address yielded by the list is either 127.0.0.2 or 127.0.0.3',
23497 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
23499 means `deny if the host is in the black list at the domain \*a.b.c*\ and the IP
23500 address yielded by the list is not 127.0.0.2 and not 127.0.0.3'. In other
23501 words, the result of the test is inverted if an exclamation mark appears before
23502 the `=' (or the `&') sign.
23504 \**Note**\: this kind of negation is not the same as negation in a domain,
23505 host, or address list (which is why the syntax is different).
23507 If you are using just one list, the negation syntax does not gain you much. The
23508 previous example is precisely equivalent to
23510 deny dnslists = a.b.c
23511 !dnslists = a.b.c=127.0.0.2,127.0.0.3
23513 However, if you are using multiple lists, the negation syntax is clearer.
23514 Consider this example:
23516 deny dnslists = sbl.spamhaus.org : \
23518 dnsbl.njabl.org!=127.0.0.3 : \
23521 Using only positive lists, this would have to be:
23523 deny dnslists = sbl.spamhaus.org : \
23525 deny dnslists = dnsbl.njabl.org
23526 !dnslists = dnsbl.njabl.org=127.0.0.3
23527 deny dnslists = relays.ordb.org
23529 which is less clear, and harder to maintain.
23533 .section DNS lists and IPv6
23534 .rset SECTmorednslistslast "~~chapter.~~section"
23535 .index IPv6||DNS black lists
23536 .index DNS list||IPv6 usage
23537 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
23538 nibble by nibble. For example, if the calling host's IP address is
23539 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
23541 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
23542 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
23544 (split over two lines here to fit on the page). Unfortunately, some of the DNS
23545 lists contain wildcard records, intended for IPv4, that interact badly with
23546 IPv6. For example, the DNS entry
23548 *.3.some.list.example. A 127.0.0.1
23550 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
23551 Unfortunately, it also matches the entire 3@:@:/4 IPv6 network.
23553 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
23554 \condition\ condition, as in this example:
23558 deny condition = ${if isip4{$sender_host_address}}
23561 dnslists = some.list.example
23565 .section Address verification
23566 .rset SECTaddressverification "~~chapter.~~section"
23567 .index verifying||address, options for
23568 .index policy control||address verification
23569 Several of the \verify\ conditions described in section ~~SECTaclconditions
23570 cause addresses to be verified. These conditions can be followed by options
23571 that modify the verification process. The options are separated from the
23572 keyword and from each other by slashes, and some of them contain parameters.
23575 verify = sender/callout
23576 verify = recipient/defer_ok/callout=10s,defer_ok
23579 The first stage of address verification, which always happens, is to run the
23580 address through the routers, in `verify mode'. Routers can detect the
23581 difference between verification and routing for delivery, and their actions can
23582 be varied by a number of generic options such as \verify\ and \verify@_only\
23583 (see chapter ~~CHAProutergeneric). If routing fails, verification fails.
23584 The available options are as follows:
23586 If the \callout\ option is specified, successful routing to one or more remote
23587 hosts is followed by a `callout' to those hosts as an additional check.
23588 Callouts and their sub-options are discussed in the next section.
23590 If there is a defer error while doing verification routing, the ACL
23591 normally returns `defer'. However, if you include \defer@_ok\ in the options,
23592 the condition is forced to be true instead. Note that this is a main
23593 verification option as well as a suboption for callouts.
23595 The \no@_details\ option is covered in section ~~SECTsenaddver, which discusses
23596 the reporting of sender address verification failures.
23599 .index verifying||address, differentiating failures
23600 After an address verification failure, \$sender@_verify@_failure$\ or
23601 \$recipient@_verify@_failure$\ (as appropriate) contains one of the following
23604 \qualify\: The address was unqualified (no domain), and the message
23605 was neither local nor came from an exempted host.
23607 \route\: Routing failed.
23609 \mail\: Routing succeeded, and a callout was attempted; rejection
23610 occurred at or before the \\MAIL\\ command (that is, on initial
23611 connection, \\HELO\\, or \\MAIL\\).
23613 \recipient\: The \\RCPT\\ command in a callout was rejected.
23615 \postmaster\: The postmaster check in a callout was rejected.
23618 The main use of these variables is expected to be to distinguish between
23619 rejections of \\MAIL\\ and rejections of \\RCPT\\ in callouts.
23624 .section Callout verification
23625 .rset SECTcallver "~~chapter.~~section"
23626 .index verifying||address, by callout
23627 .index callout||verification
23628 .index SMTP||callout verification
23629 For non-local addresses, routing verifies the domain, but is unable to do any
23630 checking of the local part. There are situations where some means of verifying
23631 the local part is desirable. One way this can be done is to make an SMTP
23632 \*callback*\ to the sending host (for a sender address) or a \*callforward*\ to
23633 a subsequent host (for a recipient address), to see if the host accepts the
23634 address. We use the term \*callout*\ to cover both cases. This facility should
23635 be used with care, because it can add a lot of resource usage to the cost of
23636 verifying an address. However, Exim does cache the results of callouts, which
23637 helps to reduce the cost. Details of caching are in the next section.
23639 Recipient callouts are usually used only between hosts that are controlled by
23640 the same administration. For example, a corporate gateway host could use
23641 callouts to check for valid recipients on an internal mailserver.
23642 A successful callout does not guarantee that a real delivery to the address
23643 would succeed; on the other hand, a failing callout does guarantee that
23644 a delivery would fail.
23646 If the \callout\ option is present on a condition that verifies an address, a
23647 second stage of verification occurs if the address is successfully routed to
23648 one or more remote hosts. The usual case is routing by a \%dnslookup%\ or a
23649 \%manualroute%\ router, where the router specifies the hosts. However, if a
23650 router that does not set up hosts routes to an \%smtp%\ transport with a
23651 \hosts\ setting, the transport's hosts are used. If an \%smtp%\ transport has
23652 \hosts@_override\ set, its hosts are always used, whether or not the router
23653 supplies a host list.
23655 The port that is used is taken from the transport, if it is specified and is a
23656 remote transport. (For routers that do verification only, no transport need be
23657 specified.) Otherwise, the default SMTP port is used. If a remote transport
23658 specifies an outgoing interface, this is used; otherwise the interface is not
23661 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
23662 test whether a bounce message could be delivered to the sender address. The
23663 following SMTP commands are sent:
23667 HELO <<smtp active host name>>
23671 RCPT TO:<<the address to be tested>>
23674 \\LHLO\\ is used instead of \\HELO\\ if the transport's \protocol\ option is
23677 A recipient callout check is similar. By default, it also uses an empty address
23678 for the sender. This default is chosen because most hosts do not make use of
23679 the sender address when verifying a recipient. Using the same address means
23680 that a single cache entry can be used for each recipient. Some sites, however,
23681 do make use of the sender address when verifying. These are catered for by the
23682 \use@_sender\ and \use@_postmaster\ options, described in the next section.
23684 If the response to the \\RCPT\\ command is a 2$it{xx} code, the verification
23685 succeeds. If it is 5$it{xx}, the verification fails. For any other condition,
23686 Exim tries the next host, if any. If there is a problem with all the remote
23687 hosts, the ACL yields `defer', unless the \defer@_ok\ parameter of the
23688 \callout\ option is given, in which case the condition is forced to succeed.
23693 .section Additional parameters for callouts
23694 .rset CALLaddparcall "~~chapter.~~section"
23695 .index callout||additional parameters for
23696 The \callout\ option can be followed by an equals sign and a number of optional
23697 parameters, separated by commas. For example:
23699 verify = recipient/callout=10s,defer_ok
23701 The old syntax, which had \callout@_defer@_ok\ and \check@_postmaster\ as
23702 separate verify options, is retained for backwards compatibility, but is now
23703 deprecated. The additional parameters for \callout\ are as follows:
23707 .item "<<a time interval>>"
23708 .index callout||timeout, specifying
23709 This specifies the timeout that applies for the callout attempt to each host.
23712 verify = sender/callout=5s
23714 The default is 30 seconds. The timeout is used for each response from the
23717 It is also used for the intial connection, unless overridden by the \connect\
23722 .item "connect = <<time interval>>"
23723 .index callout||connection timeout, specifying
23724 This parameter makes it possible to set a different (usually
23725 smaller) timeout for making the SMTP connection.
23728 verify = sender/callout=5s,connect=1s
23730 If not specified, this timeout defaults to the general timeout value.
23734 .index callout||defer, action on
23735 When this parameter is present, failure to contact any host, or any other kind
23736 of temporary error, is treated as success by the ACL. However, the cache is not
23737 updated in this circumstance.
23740 .item "mailfrom = <<email address>>"
23741 .index callout||sender when verifying header
23742 When verifying addresses in header lines using the \header@_sender\
23743 verification option, Exim behaves by default as if the addresses are envelope
23744 sender addresses from a message. Callout verification therefore tests to see
23745 whether a bounce message could be delivered, by using an empty address in the
23746 \\MAIL\\ command. However, it is arguable that these addresses might never be
23747 used as envelope senders, and could therefore justifiably reject bounce
23748 messages (empty senders). The \mailfrom\ callout parameter allows you to
23749 specify what address to use in the \\MAIL\\ command. For example:
23751 require verify = header_sender/callout=mailfrom=abcd@x.y.z
23753 This parameter is available only for the \header@_sender\ verification option.
23757 .item "maxwait = <<time interval>>"
23758 .index callout||overall timeout, specifying
23759 This parameter sets an overall timeout for performing a callout verification.
23762 verify = sender/callout=5s,maxwait=30s
23764 This timeout defaults to four times the callout timeout for individual SMTP
23765 commands. The overall timeout applies when there is more than one host that can
23766 be tried. The timeout is checked before trying the next host. This prevents
23767 very long delays if there are a large number of hosts and all are timing out
23768 (for example, when network connections are timing out).
23772 .index callout||cache, suppressing
23773 .index caching||callout, suppressing
23774 When this parameter is given, the callout cache is neither read nor updated.
23777 .index callout||postmaster, checking
23778 When this parameter is set, a sucessful callout check is followed by a similar
23779 check for the local part \*postmaster*\ at the same domain. If this address is
23780 rejected, the callout fails. The result of the postmaster check is recorded in
23781 a cache record; if it is a failure, this is used to fail subsequent callouts
23782 for the domain without a connection being made, until the cache record expires.
23785 .item "postmaster@_mailfrom = <<email address>>"
23786 The postmaster check uses an empty sender in the \\MAIL\\ command by default.
23787 You can use this parameter to do a postmaster check using a different address.
23790 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
23792 If both \postmaster\ and \postmaster@_mailfrom\ are present, the rightmost one
23793 overrides. The \postmaster\ parameter is equivalent to this example:
23795 require verify = sender/callout=postmaster_mailfrom=
23797 \**Warning**\: The caching arrangements for postmaster checking do not take
23798 account of the sender address. It is assumed that either the empty address or
23799 a fixed non-empty address will be used. All that Exim remembers is that the
23800 postmaster check for the domain succeeded or failed.
23804 .index callout||`random' check
23805 When this parameter is set, before doing the normal callout check, Exim does a
23806 check for a `random' local part at the same domain. The local part is not
23807 really random -- it is defined by the expansion of the option
23808 \callout@_random@_local@_part\, which defaults to
23810 $primary_host_name-$tod_epoch-testing
23812 The idea here is to try to determine whether the remote host accepts all local
23813 parts without checking. If it does, there is no point in doing callouts for
23814 specific local parts. If the `random' check succeeds, the result is saved in
23815 a cache record, and used to force the current and subsequent callout checks to
23816 succeed without a connection being made, until the cache record expires.
23818 .item "use@_postmaster"
23819 .index callout||sender for recipient check
23820 This parameter applies to recipient callouts only. For example:
23822 deny !verify = recipient/callout=use_postmaster
23824 It causes a non-empty postmaster address to be used in the \\MAIL\\ command
23825 when performing the callout. The local part of the address is \"postmaster"\
23826 and the domain is the contents of \$qualify@_domain$\.
23828 .item "use@_sender"
23829 This option applies to recipient callouts only. For example:
23831 require verify = recipient/callout=use_sender
23833 It causes the message's actual sender address to be used in the \\MAIL\\
23834 command when performing the callout, instead of an empty address. There is no
23835 need to use this option unless you know that the called hosts make use of the
23836 sender when checking recipients. If used indiscriminately, it reduces the
23837 usefulness of callout caching.
23842 If you use any of the parameters that set a non-empty sender for the \\MAIL\\
23843 command (\mailfrom\, \postmaster@_mailfrom\, \use@_postmaster\, or
23844 \use@_sender\), you should think about possible loops. Recipient checking is
23845 usually done between two hosts that are under the same management, and the host
23846 that receives the callouts is not normally configured to do callouts itself.
23847 Therefore, it is normally safe to use \use@_postmaster\ or \use@_sender\ in
23848 these circumstances.
23850 However, if you use a non-empty sender address for a callout to an arbitrary
23851 host, there is the likelihood that the remote host will itself initiate a
23852 callout check back to your host. As it is checking what appears to be a message
23853 sender, it is likely to use an empty address in \\MAIL\\, thus avoiding a
23854 callout loop. However, to be on the safe side it would be best to set up your
23855 own ACLs so that they do not do sender verification checks when the recipient
23856 is the address you use for header sender or postmaster callout checking.
23858 Another issue to think about when using non-empty senders for callouts is
23859 caching. When you set \mailfrom\ or \use@_sender\, the cache record is keyed by
23860 the sender/recipient combination; thus, for any given recipient, many more
23861 actual callouts are performed than when an empty sender or postmaster is used.
23866 .section Callout caching
23867 .rset SECTcallvercache "~~chapter.~~section"
23868 .index hints database||callout cache
23869 .index callout||caching
23870 .index caching||callout
23871 Exim caches the results of callouts in order to reduce the amount of resources
23872 used, unless you specify the \no@_cache\ parameter with the \callout\ option.
23873 A hints database called `callout' is used for the cache. Two different record
23874 types are used: one records the result of a callout check for a specific
23875 address, and the other records information that applies to the entire domain
23876 (for example, that it accepts the local part \*postmaster*\).
23878 When an original callout fails, a detailed SMTP error message is given about
23879 the failure. However, for subsequent failures use the cache data, this message
23882 The expiry times for negative and positive address cache records are
23883 independent, and can be set by the global options \callout@_negative@_expire\
23884 (default 2h) and \callout@_positive@_expire\ (default 24h), respectively.
23886 If a host gives a negative response to an SMTP connection, or rejects any
23887 commands up to and including
23891 (but not including the \\MAIL\\ command with a non-empty address),
23892 any callout attempt is bound to fail. Exim remembers such failures in a
23893 domain cache record, which it uses to fail callouts for the domain without
23894 making new connections, until the domain record times out. There are two
23895 separate expiry times for domain cache records:
23896 \callout@_domain@_negative@_expire\ (default 3h) and
23897 \callout__domain__positive@_expire\ (default 7d).
23899 Domain records expire when the negative expiry time is reached if callouts
23900 cannot be made for the domain, or if the postmaster check failed.
23901 Otherwise, they expire when the positive expiry time is reached. This
23902 ensures that, for example, a host that stops accepting `random' local parts
23903 will eventually be noticed.
23905 The callout caching mechanism is based on the domain of the address that is
23906 being tested. If the domain routes to several hosts, it is assumed that their
23907 behaviour will be the same.
23910 .section Sender address verification reporting
23911 .rset SECTsenaddver "~~chapter.~~section"
23912 .index verifying||suppressing error details
23913 When sender verification fails in an ACL, the details of the failure are
23914 given as additional output lines before the 550 response to the relevant
23915 SMTP command (\\RCPT\\ or \\DATA\\). For example, if sender callout is in use,
23918 MAIL FROM:<xyz@abc.example>
23920 RCPT TO:<pqr@def.example>
23921 550-Verification failed for <xyz@abc.example>
23922 550-Called: 192.168.34.43
23923 550-Sent: RCPT TO:<xyz@abc.example>
23924 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
23925 550 Sender verification failed
23927 If more than one \\RCPT\\ command fails in the same way, the details are given
23928 only for the first of them. However, some administrators do not want to send
23929 out this much information. You can suppress the details by adding
23930 `/no@_details' to the ACL statement that requests sender verification. For
23933 verify = sender/no_details
23937 .section Redirection while verifying
23938 .index verifying||redirection while
23939 .index address redirection||while verifying
23940 A dilemma arises when a local address is redirected by aliasing or forwarding
23941 during verification: should the generated addresses themselves be verified,
23942 or should the successful expansion of the original address be enough to verify
23943 it? Exim takes the following pragmatic approach:
23945 When an incoming address is redirected to just one child address, verification
23946 continues with the child address, and if that fails to verify, the original
23947 verification also fails.
23949 When an incoming address is redirected to more than one child address,
23950 verification does not continue. A success result is returned.
23952 This seems the most reasonable behaviour for the common use of aliasing as a
23953 way of redirecting different local parts to the same mailbox. It means, for
23954 example, that a pair of alias entries of the form
23957 aw123: :fail: Gone away, no forwarding address
23959 work as expected, with both local parts causing verification failure. When a
23960 redirection generates more than one address, the behaviour is more like a
23961 mailing list, where the existence of the alias itself is sufficient for
23962 verification to succeed.
23965 .section Using an ACL to control relaying
23966 .rset SECTrelaycontrol "~~chapter.~~section"
23967 .index ~~ACL||relay control
23968 .index relaying||control by ACL
23969 .index policy control||relay control
23970 An MTA is said to \*relay*\ a message if it receives it from some host and
23971 delivers it directly to another host as a result of a remote address contained
23972 within it. Redirecting a local address via an alias or forward file and then
23973 passing the message on to another host is not relaying,
23974 .index `percent hack'
23975 but a redirection as a result of the `percent hack' is.
23977 Two kinds of relaying exist, which are termed `incoming' and `outgoing'. A host
23978 which is acting as a gateway or an MX backup is concerned with incoming
23979 relaying from arbitrary hosts to a specific set of domains. On the other hand,
23980 a host which is acting as a smart host for a number of clients is concerned
23981 with outgoing relaying from those clients to the Internet at large. Often the
23982 same host is fulfilling both functions, as illustrated in the diagram below,
23983 but in principle these two kinds of relaying are entirely independent. What is
23984 not wanted is the transmission of mail from arbitrary remote hosts through your
23985 system to arbitrary domains.
23987 .figure "Controlled relaying" rm
23989 .call aspic -sgcal -nv
23990 centre ~~sys.linelength;
23996 A: box "Arbitrary" "remote hosts";
23998 D: box "Arbitrary" "domains";
23999 iline down 50 from bottom of C;
24000 H: box width 180 "Local host";
24003 SH: box "Specific" "hosts";
24004 SD: box join right to E "Specific" "domains";
24005 arcarrow clockwise from top of SH to bottom of D plus (-10,-4)
24006 via right of H plus (-20,0);
24007 arcarrow clockwise from bottom of A to top of SD plus (10,4)
24008 via left of H plus (20,0);
24010 ibox join left to right of H "$it{Outgoing}";
24012 ibox join right to left of H "$it{Incoming}";
24014 L: line dashed from right of A to top of H plus (-15,0);
24015 arc dashed to top of H plus (15,0);
24016 arrow dashed to left of D plus (-2,0);
24018 arrow dashed back up 72 right 32 from middle of L plus (8,0);
24019 text at end plus (0, 4) "$it{Not wanted}";
24024 -------------- -----------
24025 | Arbitrary | |Arbitrary|
24026 |remote hosts| | domains |
24027 -------------- -----------
24030 c ---v----------------^--- t
24033 i ---v----------------^--- i
24040 [(IMG SRC="relaying.gif" alt="Controlled relaying")][(br)]
24043 You can implement relay control by means of suitable statements in the ACL that
24044 runs for each \\RCPT\\ command. For convenience, it is often easiest to use
24045 Exim's named list facility to define the domains and hosts involved. For
24046 example, suppose you want to do the following:
24048 Deliver a number of domains to mailboxes on the local host (or process them
24049 locally in some other way). Let's say these are \*my.dom1.example*\ and
24050 \*my.dom2.example*\.
24052 Relay mail for a number of other domains for which you are the secondary MX.
24053 These might be \*friend1.example*\ and \*friend2.example*\.
24055 Relay mail from the hosts on your local LAN, to whatever domains are involved.
24056 Suppose your LAN is 192.168.45.0/24.
24058 In the main part of the configuration, you put the following definitions:
24060 domainlist local_domains = my.dom1.example : my.dom2.example
24061 domainlist relay_domains = friend1.example : friend2.example
24062 hostlist relay_hosts = 192.168.45.0/24
24064 Now you can use these definitions in the ACL that is run for every \\RCPT\\
24068 accept domains = +local_domains : +relay_domains
24069 accept hosts = +relay_hosts
24071 The first statement accepts any \\RCPT\\ command that contains an address in
24072 the local or relay domains. For any other domain, control passes to the second
24073 statement, which accepts the command only if it comes from one of the relay
24074 hosts. In practice, you will probably want to make your ACL more sophisticated
24075 than this, for example, by including sender and recipient verification. The
24076 default configuration includes a more comprehensive example, which is described
24077 in chapter ~~CHAPdefconfil.
24080 .section Checking a relay configuration
24081 .rset SECTcheralcon "~~chapter.~~section"
24082 .index relaying||checking control of
24083 You can check the relay characteristics of your configuration in the same way
24084 that you can test any ACL behaviour for an incoming SMTP connection, by using
24085 the \-bh-\ option to run a fake SMTP session with which you interact.
24087 For specifically testing for unwanted relaying, the host
24088 \*relay-test.mail-abuse.org*\ provides a useful service. If you telnet to this
24089 host from the host on which Exim is running, using the normal telnet port, you
24090 will see a normal telnet connection message and then quite a long delay. Be
24091 patient. The remote host is making an SMTP connection back to your host, and
24092 trying a number of common probes to test for open relay vulnerability. The
24093 results of the tests will eventually appear on your terminal.
24102 . ============================================================================
24103 .chapter Content scanning
24104 .set runningfoot "content scanning"
24105 .rset CHAPexiscan "~~chapter"
24106 .index content scanning
24108 The content-scanning extension of Exim, formerly known as `exiscan', was
24109 originally implemented as a patch by Tom Kistner. The code was integrated into
24110 the main source for Exim release 4.50, and Tom continues to maintain it. Most
24111 of the wording of this chapter is taken from Tom's specification.
24113 If you want to include the content-scanning features when you compile Exim, you
24114 need to arrange for \\WITH@_CONTENT@_SCAN\\ to be defined in your
24115 \(Local/Makefile)\. When you do that, the Exim binary is built with:
24117 An additional ACL (\acl@_smtp@_mime\) that is run for all MIME parts.
24119 Additional ACL conditions and modifiers: \decode\, \malware\, \mime@_regex\,
24120 \regex\, and \spam\. These can be used in the ACL that is run at the end of
24121 message reception (the \acl@_smtp@_data\ ACL).
24123 An additional control feature (`no@_mbox@_unspool') that saves spooled copies
24124 of messages, or parts of messages, for debugging purposes.
24126 Additional expansion variables that are set in the new ACL and by the new
24129 Two new main configuration options: \av@_scanner\ and \spamd@_address\.
24131 There is another content-scanning configuration option for \(Local/Makefile)\,
24132 called \\WITH@_OLD@_DEMIME\\. If this is set, the old, deprecated \demime\ ACL
24133 condition is compiled, in addition to all the other content-scanning features.
24135 Content-scanning is continually evolving, and new features are still being
24136 added. While such features are still unstable and liable to incompatible
24137 changes, they are made available in Exim by setting options whose names begin
24138 \\EXPERIMENTAL@_\\ in \(Local/Makefile)\. Such features are not documented in
24139 this manual. You can find out about them by reading the file called
24140 \(doc/experimental.txt)\.
24142 All the content-scanning facilites work on a MBOX copy of the message that is
24143 temporarily created in a file called:
24145 <<spool@_directory>>/scan/<<message@_id>>/<<message@_id>>.eml
24147 The \(.eml)\ extension is a friendly hint to virus scanners that they can
24148 expect an MBOX-like structure inside that file. The file is created when the
24149 first content scanning facility is called. Subsequent calls to content
24150 scanning conditions open the same file again. The directory is recursively
24151 removed when the \acl@_smtp@_data\ ACL has finished running, unless
24153 control = no_mbox_unspool
24155 has been encountered. When the MIME ACL decodes files, they are put into the
24156 same directory by default.
24159 .section Scanning for viruses
24160 .rset SECTscanvirus "~~chapter.~~section"
24161 .index virus scanning
24162 .index content scanning||for viruses
24163 .index content scanning||the \malware\ condition
24164 The \malware\ ACL condition lets you connect virus scanner software to Exim. It
24165 supports a `generic' interface to scanners called via the shell, and
24166 specialized interfaces for `daemon' type virus scanners, which are resident in
24167 memory and thus are much faster.
24169 .index \av@_scanner\
24170 You can set the \av@_scanner\ option in first part of the Exim configuration
24171 file to specify which scanner to use, together with any additional options that
24172 are needed. The basic syntax is as follows:
24174 av@_scanner = <<scanner-type>>:<<option1>>:<<option2>>:[...]
24176 If you do not set \av@_scanner\, it defaults to
24178 av_scanner = sophie:/var/run/sophie
24180 If the value of \av@_scanner\ starts with dollar character, it is expanded
24183 The following scanner types are supported in this release:
24185 .index virus scanners||Kaspersky
24186 \aveserver\: This is the scanner daemon of Kaspersky Version 5. You can get a
24187 trial version at \?http://www.kaspersky.com?\. This scanner type takes one
24188 option, which is the path to the daemon's UNIX socket. The default is shown in
24191 av_scanner = aveserver:/var/run/aveserver
24195 .index virus scanners||clamd
24196 \clamd\: This daemon-type scanner is GPL and free. You can get it at
24197 \?http://www.clamav.net/?\. Clamd does not seem to unpack MIME containers, so
24198 it is recommended to unpack MIME attachments in the MIME ACL. It takes one
24199 option: either the path and name of a UNIX socket file, or a hostname or IP
24200 number, and a port, separated by space, as in the second of these examples:
24202 av_scanner = clamd:/opt/clamd/socket
24203 av_scanner = clamd:192.168.2.100 1234
24205 If the option is unset, the default is \(/tmp/clamd)\. Thanks to David Saez for
24206 contributing the code for this scanner.
24209 .index virus scanners||command line interface
24210 \cmdline\: This is the keyword for the generic command line scanner interface.
24211 It can be used to attach virus scanners that are invoked from the shell. This
24212 scanner type takes 3 mantadory options:
24214 The full path and name of the scanner binary, with all command line options,
24215 and a placeholder (%s) for the directory to scan.
24217 A regular expression to match against the STDOUT and STDERR output of the virus
24218 scanner. If the expression matches, a virus was found. You must make absolutely
24219 sure that this expression matches on `virus found'. This is called the
24220 `trigger' expression.
24222 Another regular expression, containing exactly one pair of parentheses, to
24223 match the name of the virus found in the scanners output. This is called the
24226 For example, Sophos Sweep reports a virus on a line like this:
24228 Virus 'W32/Magistr-B' found in file ./those.bat
24230 For the trigger expression, we can just match the word `found'. For the name
24231 expression, we want to extract the W32/Magistr-B string, so we can match for
24232 the single quotes left and right of it. Altogether, this makes the
24233 configuration setting:
24235 av_scanner = cmdline:\
24236 /path/to/sweep -all -rec -archive %s:\
24241 .index virus scanners||DrWeb
24242 \drweb\: The DrWeb daemon scanner (\?http://www.sald.com/?\) interface
24243 takes one argument, either a full path to a UNIX socket, or an IP address and
24244 port separated by whitespace, as in these examples:
24246 av_scanner = drweb:/var/run/drwebd.sock
24247 av_scanner = drweb:192.168.2.20 31337
24249 If you omit the argument, the default path \(/usr/local/drweb/run/drwebd.sock)\
24250 is used. Thanks to Alex Miller for contributing the code for this scanner.
24253 .index virus scanners||F-Secure
24254 \fsecure\: The F-Secure daemon scanner (\?http://www.f-secure.com?\) takes one
24255 argument which is the path to a UNIX socket. For example:
24257 av_scanner = fsecure:/path/to/.fsav
24259 If no argument is given, the default is \(/var/run/.fsav)\. Thanks to Johan
24260 Thelmen for contributing the code for this scanner.
24263 .index virus scanners||Kaspersky
24264 \kavdaemon\: This is the scanner daemon of Kaspersky Version 4. This version of
24265 the Kaspersky scanner is outdated. Please upgrade (see \aveserver\ above). This
24266 scanner type takes one option, which is the path to the daemon's UNIX socket.
24269 av_scanner = kavdaemon:/opt/AVP/AvpCtl
24271 The default path is \(/var/run/AvpCtl)\.
24274 .index virus scanners||mksd
24275 \mksd\: This is a daemon type scanner that is aimed mainly at Polish users,
24276 though some parts of documentation are now available in English. You can get it
24277 at \?http://linux.mks.com.pl/?\. The only option for this scanner type is the
24278 maximum number of processes used simultaneously to scan the attachments,
24279 provided that the demime facility is employed and also provided that mksd has
24280 been run with at least the same number of child processes. For example:
24282 av_scanner = mksd:2
24284 You can safely omit this option (the default value is 1).
24287 .index virus scanners||Sophos and Sophie
24288 \sophie\: Sophie is a daemon that uses Sophos' \libsavi\ library to scan for
24289 viruses. You can get Sophie at \?http://www.vanja.com/tools/sophie/?\. The only
24290 option for this scanner type is the path to the UNIX socket that Sophie uses
24291 for client communication. For example:
24293 av_scanner = sophie:/tmp/sophie
24295 The default path is \(/var/run/sophie)\, so if you are using this, you can omit
24299 When \av@_scanner\ is correctly set, you can use the \malware\ condition in the
24300 \\DATA\\ ACL. The \av@_scanner\ option is expanded each time \malware\ is
24301 called. This makes it possible to use different scanners. See further below for
24302 an example. The \malware\ condition caches its results, so when you use it
24303 multiple times for the same message, the actual scanning process is only
24304 carried out once. However, using expandable items in \av@_scanner\ disables
24305 this caching, in which case each use of the \malware\ condition causes a new
24306 scan of the message.
24308 The \malware\ condition takes a right-hand argument that is expanded before
24309 use. It can then be one of
24311 `true', `*', or `1', in which case the message is scanned for viruses. The
24312 condition succeeds if a virus was found, and fail otherwise. This is the
24315 `false' or `0', in which case no scanning is done and the condition fails
24318 A regular expression, in which case the message is scanned for viruses. The
24319 condition succeeds if a virus is found and its name matches the regular
24320 expression. This allows you to take special actions on certain types of virus.
24322 You can append \"/defer@_ok"\ to the \malware\ condition to accept messages even
24323 if there is a problem with the virus scanner.
24325 .index \$malware@_name$\
24326 When a virus is found, the condition sets up an expansion variable called
24327 \$malware@_name$\ that contains the name of the virus. You can use it in a
24328 \message\ modifier that specifies the error returned to the sender, and/or in
24331 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
24332 use the \demime\ condition (see section ~~SECTdemimecond) before the \malware\
24335 Here is a very simple scanning example:
24337 deny message = This message contains malware ($malware_name)
24341 The next example accepts messages when there is a problem with the scanner:
24343 deny message = This message contains malware ($malware_name)
24345 malware = */defer_ok
24347 The next example shows how to use an ACL variable to scan with both sophie and
24348 aveserver. It assumes you have set:
24350 av_scanner = $acl_m0
24352 in the main Exim configuration.
24354 deny message = This message contains malware ($malware_name)
24355 set acl_m0 = sophie
24358 deny message = This message contains malware ($malware_name)
24359 set acl_m0 = aveserver
24364 .section Scanning with SpamAssassin
24365 .rset SECTscanspamass "~~chapter.~~section"
24366 .index content scanning||for spam
24367 .index spam scanning
24368 .index SpamAssassin, scanning with
24369 The \spam\ ACL condition calls SpamAssassin's \spamd\ daemon to get a spam
24370 score and a report for the message. You can get SpamAssassin at
24371 \?http://www.spamassassin.org?\, or, if you have a working Perl installation,
24372 you can use CPAN by running:
24374 perl -MCPAN -e 'install Mail::SpamAssassin'
24376 SpamAssassin has its own set of configuration files. Please review its
24377 documentation to see how you can tweak it. The default installation should work
24380 .index \spamd@_address\
24381 After having installed and configured SpamAssassin, start the \spamd\ daemon.
24382 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
24383 port for \spamd\, you must set the \spamd@_address\ option in the global part
24384 of the Exim configuration as follows (example):
24386 spamd_address = 192.168.99.45 387
24388 You do not need to set this option if you use the default. As of version 2.60,
24389 \spamd\ also supports communication over UNIX sockets. If you want to use
24390 these, supply \spamd@_address\ with an absolute file name instead of a
24393 spamd_address = /var/run/spamd_socket
24396 You can have multiple \spamd\ servers to improve scalability. These can reside
24397 on other hardware reachable over the network. To specify multiple \spamd\
24398 servers, put multiple address/port pairs in the \spamd@_address\ option,
24399 separated with colons:
24401 spamd_address = 192.168.2.10 783 : \
24402 192.168.2.11 783 : \
24405 Up to 32 \spamd\ servers are supported. The servers are
24406 queried in a random fashion. When a server fails to respond
24407 to the connection attempt, all other servers are tried
24408 until one succeeds. If no server responds, the \spam\
24411 \**Warning**\: It is not possible to use the UNIX socket connection method with
24412 multiple \spamd\ servers.
24414 Here is a simple example of the use of the \spam\ condition in a DATA ACL:
24416 deny message = This message was classified as SPAM
24419 The right-hand side of the \spam\ condition specifies the username that
24420 SpamAssassin should scan for. If you do not want to scan for a particular user,
24421 but rather use the SpamAssassin system-wide default profile, you can scan for
24422 an unknown user, or simply use `nobody'. However, you must put something on the
24425 The username allows you to use per-domain or per-user antispam profiles. The
24426 right-hand side is expanded before being used, so you can put lookups or
24427 conditions there. When the right-hand side evaluates to `0' or `false', no
24428 scanning is done and the condition fails immediately.
24430 The \spam\ condition returns true if the threshold specified in the user's
24431 SpamAssassin profile has been matched or exceeded. If you want to use the
24432 \spam\ condition for its side effects (see the variables below), you can make
24433 it always return `true' by appending \":true"\ to the username.
24435 .index spam scanning||returned variables
24436 When the \spam\ condition is run, it sets up the following expansion
24443 \$spam@_score$\: The spam score of the message, for example `3.4' or `30.5'.
24444 This is useful for inclusion in log or reject messages.
24447 \$spam@_score@_int$\: The spam score of the message, multiplied by ten, as an
24448 integer value. For example `34' or `305'. This is useful for numeric
24449 comparisons in conditions. This variable is special; it is saved with the
24450 message, and written to Exim's spool file. This means that it can be used
24451 during the whole life of the message on your Exim system, in particular, in
24452 routers or transports during the later delivery phase.
24455 \$spam@_bar$\: A string consisting of a number of `+' or `@-' characters,
24456 representing the integer part of the spam score value. A spam score of 4.4
24457 would have a \$spam@_bar$\ value of `++++'. This is useful for inclusion in
24458 warning headers, since MUAs can match on such strings.
24461 \$spam@_report$\: A multiline text table, containing the full SpamAssassin
24462 report for the message. Useful for inclusion in headers or reject messages.
24466 The \spam\ condition caches its results. If you call it again with the same user
24467 name, it does not scan again, but rather returns the same values as before.
24469 The \spam\ condition returns DEFER if there is any error while running the
24470 message through SpamAssassin. If you want to treat DEFER as FAIL (to pass on to
24471 the next ACL statement block), append \"/defer@_ok"\ to the right-hand side of
24472 the spam condition, like this:
24474 deny message = This message was classified as SPAM
24475 spam = joe/defer_ok
24477 This causes messages to be accepted even if there is a
24478 problem with \spamd\.
24480 Here is a longer, commented example of the use of the \spam\
24483 # put headers in all messages (no matter if spam or not)
24484 warn message = X-Spam-Score: $spam_score ($spam_bar)
24486 warn message = X-Spam-Report: $spam_report
24489 # add second subject line with *SPAM* marker when message
24490 # is over threshold
24491 warn message = Subject: *SPAM* $h_Subject:
24494 # reject spam at high scores (> 12)
24495 deny message = This message scored $spam_score spam points.
24497 condition = ${if >{$spam_score_int}{120}{1}{0}}
24502 .section Scanning MIME parts
24503 .rset SECTscanmimepart "~~chapter.~~section"
24504 .index content scanning||MIME parts
24505 .index MIME content scanning
24506 .index \acl@_smtp@_mime\
24507 The \acl@_smtp@_mime\ global option defines an ACL that is called once for each
24508 MIME part of a message, including multipart types, in the sequence of their
24509 position in the message.
24511 This ACL is called (possibly many times) just before the \acl@_smtp@_data\ ACL,
24512 but only if the message has a ::MIME-Version:: header. When a call to the MIME
24513 ACL does not yield `accept', ACL processing is aborted and the appropriate
24514 result code is sent to the remote client. The \acl@_smtp@_data\ ACL is not
24515 called in this circumstance.
24517 At the start of the MIME ACL, a number of variables are set from the header
24518 information for the relevant MIME part. These are described below. The contents
24519 of the MIME part are not by default decoded into a disk file except for MIME
24520 parts whose content-type is `message/rfc822'. If you want to decode a MIME part
24521 into a disk file, you can use the \decode\ modifier. The general syntax is:
24523 decode = [/<<path>>/]<<filename>>
24525 The right hand side is expanded before use. After expansion,
24528 `0' or `false', in which case no decoding is done.
24530 The string `default'. In that case, the file is put in the temporary `default'
24531 directory \(<<spool@_directory>>/scan/<<message@_id>>/)\ with a sequential file
24532 name consisting of the message id and a sequence number. The full path and name
24533 is available in \$mime@_decoded@_filename$\ after decoding.
24535 A full path name starting with a slash. If the full name is an existing
24536 directory, it is used as a replacement for the default directory. The filename
24537 is then sequentially assigned. If the path does not exist, it is used as
24538 the full path and file name.
24540 If the string does not start with a slash, it is used as the
24541 filename, and the default path is then used.
24543 You can easily decode a file with its original, proposed
24546 decode = $mime_filename
24548 However, you should keep in mind that \$mime@_filename$\ might contain
24549 anything. If you place files outside of the default path, they are not
24550 automatically unlinked.
24552 For RFC822 attachments (these are messages attached to messages, with a
24553 content-type of `message/rfc822'), the ACL is called again in the same manner
24554 as for the primary message, only that the \$mime@_is@_rfc822$\ expansion
24555 variable is set (see below). Attached messages are always decoded to disk
24556 before being checked, and the files are unlinked once the check is done.
24558 The MIME ACL supports the \regex\ and \mime@_regex\ conditions. These can be
24559 used to match regular expressions against raw and decoded MIME parts,
24560 respectively. They are described in section ~~SECTscanregex.
24562 .index MIME content scanning||returned variables
24563 The following list describes all expansion variables that are
24564 available in the MIME ACL:
24570 \$mime@_boundary$\:
24571 If the current part is a multipart (see \$mime@_is@_multipart$\) below, it
24572 should have a boundary string, which is stored in this variable. If the current
24573 part has no boundary parameter in the ::Content-Type:: header, this variable
24574 contains the empty string.
24578 This variable contains the character set identifier, if one was found in the
24579 ::Content-Type:: header. Examples for charset identifiers are:
24585 Please note that this value is not normalized, so you should do matches
24586 case-insensitively.
24589 \$mime@_content@_description$\:
24590 This variable contains the normalized content of the ::Content-Description::
24591 header. It can contain a human-readable description of the parts content. Some
24592 implementations repeat the filename for attachments here, but they are
24593 usually only used for display purposes.
24596 \$mime@_content@_disposition$\:
24597 This variable contains the normalized content of the ::Content-Disposition::
24598 header. You can expect strings like `attachment' or `inline' here.
24601 \$mime@_content@_id$\:
24602 This variable contains the normalized content of the ::Content-ID:: header.
24603 This is a unique ID that can be used to reference a part from another part.
24606 \$mime@_content@_size$\:
24607 This variable is set only after the \decode\ modifier (see above) has been
24608 successfully run. It contains the size of the decoded part in kilobytes. The
24609 size is always rounded up to full kilobytes, so only a completely empty part
24610 has a \$mime@_content@_size$\ of zero.
24613 \$mime@_content@_transfer@_encoding$\:
24614 This variable contains the normalized content of the
24615 ::Content-transfer-encoding:: header. This is a symbolic name for an encoding
24616 type. Typical values are `base64' and `quoted-printable'.
24619 \$mime@_content@_type$\: If the MIME part has a ::Content-Type:: header, this
24620 variable contains its value, lowercased, and without any options (like `name'
24621 or `charset'). Here are some examples of popular MIME types, as they may appear
24626 application/octet-stream
24630 If the MIME part has no ::Content-Type:: header, this variable contains the
24634 \$mime@_decoded@_filename$\:
24635 This variable is set only after the \decode\ modifier (see above) has been
24636 successfully run. It contains the full path and file name of the file
24637 containing the decoded data.
24640 \$mime@_filename$\: This is perhaps the most important of the MIME variables.
24641 It contains a proposed filename for an attachment, if one was found in either
24642 the ::Content-Type:: or ::Content-Disposition:: headers. The filename will be
24643 RFC2047 decoded, but no additional sanity checks are done. If no filename was
24644 found, this variable contains the empty string.
24647 \$mime@_is@_coverletter$\:
24648 This variable attempts to differentiate the `cover letter' of an e-mail from
24649 attached data. It can be used to clamp down on flashy or unneccessarily encoded
24650 content in the cover letter, while not restricting attachments at all.
24652 The variable contains 1 (true) for a MIME part believed to be part of the
24653 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
24656 The outermost MIME part of a message is always a cover letter.
24658 If a multipart/alternative or multipart/related MIME part is a cover letter, so
24659 are all MIME subparts within that multipart.
24661 If any other multipart is a cover letter, the first subpart is a cover letter,
24662 and the rest are attachments.
24664 All parts contained within an attachment multipart are attachments.
24667 As an example, the following will ban `HTML mail' (including that sent with
24668 alternative plain text), while allowing HTML files to be attached. HTML
24669 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
24671 deny message = HTML mail is not accepted here
24672 !condition = $mime_is_rfc822
24673 condition = $mime_is_coverletter
24674 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
24679 \$mime@_is@_multipart$\:
24680 This variable has the value 1 (true) when the current part has the main type
24681 `multipart', for example `multipart/alternative' or `multipart/mixed'. Since
24682 multipart entities only serve as containers for other parts, you may not want
24683 to carry out specific actions on them.
24686 \$mime@_is@_rfc822$\:
24687 This variable has the value 1 (true) if the current part is not a part of the
24688 checked message itself, but part of an attached message. Attached message
24689 decoding is fully recursive.
24692 \$mime@_part@_count$\:
24693 This variable is a counter that is raised for each processed MIME part. It
24694 starts at zero for the very first part (which is usually a multipart). The
24695 counter is per-message, so it is reset when processing RFC822 attachments (see
24696 \$mime@_is@_rfc822$\). The counter stays set after \acl@_smtp@_mime\ is
24697 complete, so you can use it in the DATA ACL to determine the number of MIME
24698 parts of a message. For non-MIME messages, this variable contains the value -1.
24703 .section Scanning with regular expressions
24704 .rset SECTscanregex "~~chapter.~~section"
24705 .index content scanning||with regular expressions
24706 .index regular expressions||content scanning with
24707 You can specify your own custom regular expression matches on the full body of
24708 the message, or on individual MIME parts.
24710 The \regex\ condition takes one or more regular expressions as arguments and
24711 matches them against the full message (when called in the DATA ACL) or a raw
24712 MIME part (when called in the MIME ACL). The \regex\ condition matches
24713 linewise, with a maximum line length of 32K characters. That means you cannot
24714 have multiline matches with the \regex\ condition.
24716 The \mime@_regex\ condition can be called only in the MIME ACL. It matches up
24717 to 32K of decoded content (the whole content at once, not linewise). If the
24718 part has not been decoded with the \decode\ modifier earlier in the ACL, it is
24719 decoded automatically when \mime@_regex\ is executed (using default path and
24720 filename values). If the decoded data is larger than 32K, only the first 32K
24721 characters are checked.
24723 The regular expressions are passed as a colon-separated list. To include a
24724 literal colon, you must double it. Since the whole right-hand side string is
24725 expanded before being used, you must also escape dollar signs and backslashes
24726 with more backslashes, or use the \"@\N"\ facility to disable expansion.
24727 Here is a simple example that contains two regular expressions:
24729 deny message = contains blacklisted regex ($regex_match_string)
24730 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
24732 The conditions returns true if any one of the regular expressions matches. The
24733 \$regex@_match@_string$\ expansion variable is then set up and contains the
24734 matching regular expression.
24736 \**Warning**\: With large messages, these conditions can be fairly
24741 .section The demime condition
24742 .rset SECTdemimecond "~~chapter.~~section"
24743 .index content scanning||MIME checking
24744 .index MIME content scanning
24745 The \demime\ ACL condition provides MIME unpacking, sanity checking and file
24746 extension blocking. It uses a simpler interface to MIME decoding than the MIME
24747 ACL functionality, but provides no additional facilities. Please note that this
24748 condition is deprecated and kept only for for backward compatibility. You must
24749 set the \\WITH@_OLD@_DEMIME\\ option in \(Local/Makefile)\ at build time to be
24750 able to use the \demime\ condition.
24752 The \demime\ condition unpacks MIME containers in the message. It detects
24753 errors in MIME containers and can match file extensions found in the message
24754 against a list. Using this facility produces files containing the unpacked MIME
24755 parts of the message in the temporary scan directory. If you do antivirus
24756 scanning, it is recommened that you use the \demime\ condition before the
24757 antivirus (\malware\) condition.
24759 On the right-hand side of the \demime\ condition you can pass a colon-separated
24760 list of file extensions that it should match against. For example:
24762 deny message = Found blacklisted file attachment
24763 demime = vbs:com:bat:pif:prf:lnk
24765 If one of the file extensions is found, the condition is true, otherwise it is
24766 false. If there is a temporary error while demimeing (for example, `disk
24767 full'), the condition defers, and the message is temporarily rejected (unless
24768 the condition is on a \warn\ verb).
24770 The right-hand side is expanded before being treated as a list, so you can have
24771 conditions and lookups there. If it expands to an empty string, `false', or
24772 zero (`0'), no demimeing is done and the condition is false.
24774 The \demime\ condition set the following variables:
24780 \$demime@_errorlevel$\: When an error is detected in a MIME container, this
24781 variable contains the severity of the error, as an integer number. The higher
24782 the value, the more severe the error. If this variable is unset or zero, no
24786 \$demime@_reason$\: When \$demime@_errorlevel$\ is greater than zero, this
24787 variable contains a human-readable text string describing the MIME error that
24791 \$found@_extension$\: When the \demime\ condition is true, this variable
24792 contains the file extension it found.
24796 Both \$demime@_errorlevel$\ and \$demime@_reason$\ are set by the first call of
24797 the \demime\ condition, and are not changed on subsequent calls.
24799 If you do not want to check for file extensions, but rather use the \demime\
24800 condition for unpacking or error checking purposes, pass `*' as the
24801 right-hand side value. Here is a more elaborate example of how to use this
24804 # Reject messages with serious MIME container errors
24805 deny message = Found MIME error ($demime_reason).
24807 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
24809 # Reject known virus spreading file extensions.
24810 # Accepting these is pretty much braindead.
24811 deny message = contains $found_extension file (blacklisted).
24812 demime = com:vbs:bat:pif:scr
24814 # Freeze .exe and .doc files. Postmaster can
24815 # examine them and eventually thaw them.
24816 deny log_message = Another $found_extension file.
24830 . ============================================================================
24831 .chapter Adding a local scan function to Exim
24832 .set runningfoot "local scan function"
24833 .rset CHAPlocalscan "~~chapter"
24834 .index \*local@_scan()*\ function||description of
24835 .index customizing||input scan using C function
24836 .index policy control||by local scan function
24838 In these days of email worms, viruses, and ever-increasing spam, some sites
24839 want to apply a lot of checking to messages before accepting them.
24841 The content scanning extension (chapter ~~CHAPexiscan) has facilities for
24842 passing messages to external virus and spam scanning software. You can also do
24844 a certain amount in Exim itself through string expansions and the \condition\
24845 condition in the ACL that runs after the SMTP \\DATA\\ command or the ACL for
24846 non-SMTP messages (see chapter ~~CHAPACL), but this has its limitations.
24848 To allow for further customization to a site's own requirements, there is the
24849 possibility of linking Exim with a private message scanning function, written
24850 in C. If you want to run code that is written in something other than C, you
24851 can of course use a little C stub to call it.
24853 The local scan function is run once for every incoming message, at the point
24854 when Exim is just about to accept the message.
24855 It can therefore be used to control non-SMTP messages from local processes as
24856 well as messages arriving via SMTP.
24858 Exim applies a timeout to calls of the local scan function, and there is an
24859 option called \local@_scan@_timeout\ for setting it. The default is 5 minutes.
24860 Zero means `no timeout'.
24861 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
24862 before calling the local scan function, so that the most common types of crash
24863 are caught. If the timeout is exceeded or one of those signals is caught, the
24864 incoming message is rejected with a temporary error if it is an SMTP message.
24865 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
24866 code. The incident is logged on the main and reject logs.
24869 .section Building Exim to use a local scan function
24870 .index \*local@_scan()*\ function||building Exim to use
24871 To make use of the local scan function feature, you must tell Exim where your
24872 function is before building Exim, by setting \\LOCAL@_SCAN@_SOURCE\\ in your
24873 \(Local/Makefile)\. A recommended place to put it is in the \(Local)\
24874 directory, so you might set
24876 LOCAL_SCAN_SOURCE=Local/local_scan.c
24878 for example. The function must be called \*local@_scan()*\. It is called by
24879 Exim after it has received a message, when the success return code is about to
24880 be sent. This is after all the ACLs have been run. The return code from your
24881 function controls whether the message is actually accepted or not. There is a
24882 commented template function (that just accepts the message) in the file
24883 \(src/local@_scan.c)\.
24885 If you want to make use of Exim's run time configuration file to set options
24886 for your \*local@_scan()*\ function, you must also set
24888 LOCAL_SCAN_HAS_OPTIONS=yes
24890 in \(Local/Makefile)\ (see section ~~SECTconoptloc below).
24894 .section API for local@_scan()
24895 .rset SECTapiforloc "~~chapter.~~section"
24896 .index \*local@_scan()*\ function||API description
24897 You must include this line near the start of your code:
24899 #include "local_scan.h"
24901 This header file defines a number of variables and other values, and the
24902 prototype for the function itself. Exim is coded to use unsigned char values
24903 almost exclusively, and one of the things this header defines is a shorthand
24904 for \"unsigned char"\ called \"uschar"\.
24905 It also contains the following macro definitions, to simplify casting character
24906 strings and pointers to character strings:
24908 #define CS (char *)
24909 #define CCS (const char *)
24910 #define CSS (char **)
24911 #define US (unsigned char *)
24912 #define CUS (const unsigned char *)
24913 #define USS (unsigned char **)
24916 The function prototype for \*local@_scan()*\ is:
24918 extern int local_scan(int fd, uschar **return_text);
24920 The arguments are as follows:
24922 \fd\ is a file descriptor for the file that contains the body of the message
24924 The file is open for reading and writing, but updating it is not recommended.
24925 \**Warning**\: You must \*not*\ close this file descriptor.
24927 The descriptor is positioned at character 19 of the file, which is the first
24928 character of the body itself, because the first 19 characters are the message
24929 id followed by \"-D"\ and a newline. If you rewind the file, you should use the
24930 macro \\SPOOL@_DATA@_START@_OFFSET\\ to reset to the start of the data, just in
24931 case this changes in some future version.
24934 \return@_text\ is an address which you can use to return a pointer to a text
24935 string at the end of the function. The value it points to on entry is NULL.
24937 The function must return an \int\ value which is one of the following macros:
24939 \"LOCAL@_SCAN@_ACCEPT"\
24941 The message is accepted. If you pass back a string of text, it is saved with
24942 the message, and made available in the variable \$local@_scan@_data$\. No
24943 newlines are permitted (if there are any, they are turned into spaces) and the
24944 maximum length of text is 1000 characters.
24946 \"LOCAL@_SCAN@_ACCEPT@_FREEZE"\
24948 This behaves as \\LOCAL@_SCAN@_ACCEPT\\, except that the accepted message is
24949 queued without immediate delivery, and is frozen.
24951 \"LOCAL@_SCAN@_ACCEPT@_QUEUE"\
24953 This behaves as \\LOCAL@_SCAN@_ACCEPT\\, except that the accepted message is
24954 queued without immediate delivery.
24956 \"LOCAL@_SCAN@_REJECT"\
24958 The message is rejected; the returned text is used as an error message which is
24959 passed back to the sender and which is also logged. Newlines are permitted --
24960 they cause a multiline response for SMTP rejections, but are converted to
24961 \"@\n"\ in log lines.
24962 If no message is given, `Administrative prohibition' is used.
24964 \"LOCAL@_SCAN@_TEMPREJECT"\
24966 The message is temporarily rejected; the returned text is used as an error
24967 message as for \\LOCAL@_SCAN@_REJECT\\. If no message is given, `Temporary
24968 local problem' is used.
24970 \"LOCAL@_SCAN@_REJECT@_NOLOGHDR"\
24972 This behaves as \\LOCAL@_SCAN@_REJECT\\, except that the header of the rejected
24973 message is not written to the reject log. It has the effect of unsetting the
24974 \rejected@_header\ log selector for just this rejection. If \rejected@_header\
24975 is already unset (see the discussion of the \log@_selection\ option in section
24976 ~~SECTlogselector), this code is the same as \\LOCAL@_SCAN@_REJECT\\.
24979 \"LOCAL@_SCAN@_TEMPREJECT@_NOLOGHDR"\
24981 This code is a variation of \\LOCAL@_SCAN@_TEMPREJECT\\ in the same way that
24982 \\LOCAL__SCAN__REJECT__NOLOGHDR\\ is a variation of \\LOCAL@_SCAN@_REJECT\\.
24985 If the message is not being received by interactive SMTP, rejections are
24986 reported by writing to \stderr\ or by sending an email, as configured by the
24987 \-oe-\ command line options.
24990 .section Configuration options for local@_scan()
24991 .rset SECTconoptloc "~~chapter.~~section"
24992 .index \*local@_scan()*\ function||configuration options
24993 It is possible to have option settings in the main configuration file
24994 that set values in static variables in the \*local@_scan()*\ module. If you
24995 want to do this, you must have the line
24997 LOCAL_SCAN_HAS_OPTIONS=yes
24999 in your \(Local/Makefile)\ when you build Exim. (This line is in
25000 \(OS/Makefile-Default)\, commented out). Then, in the \*local@_scan()*\ source
25001 file, you must define static variables to hold the option values, and a table to
25004 The table must be a vector called \local@_scan@_options\, of type
25005 \"optionlist"\. Each entry is a triplet, consisting of a name, an option type,
25006 and a pointer to the variable that holds the value. The entries must appear in
25007 alphabetical order. Following \local@_scan@_options\ you must also define a
25008 variable called \local@_scan@_options@_count\ that contains the number of
25009 entries in the table. Here is a short example, showing two kinds of option:
25011 static int my_integer_option = 42;
25012 static uschar *my_string_option = US"a default string";
25014 optionlist local_scan_options[] = {
25015 { "my_integer", opt_int, &my_integer_option },
25016 { "my_string", opt_stringptr, &my_string_option }
25018 int local_scan_options_count =
25019 sizeof(local_scan_options)/sizeof(optionlist);
25021 The values of the variables can now be changed from Exim's runtime
25022 configuration file by including a local scan section as in this example:
25026 my_string = some string of text...
25028 The available types of option data are as follows:
25033 This specifies a boolean (true/false) option. The address should point to
25034 a variable of type \"BOOL"\, which will be set to \\TRUE\\ or \\FALSE\\, which
25035 are macros that are defined as `1' and `0', respectively. If you want to detect
25036 whether such a variable has been set at all, you can initialize it to
25037 \\TRUE@_UNSET\\. (BOOL variables are integers underneath, so can hold more than
25041 This specifies a fixed point number, such as is used for load averages.
25042 The address should point to a variable of type \"int"\. The value is stored
25043 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
25046 This specifies an integer; the address should point to a variable of type
25047 \"int"\. The value may be specified in any of the integer formats accepted by
25051 This is the same as \opt@_int\, except that when such a value is output in a
25052 \-bP-\ listing, if it is an exact number of kilobytes or megabytes, it is
25053 printed with the suffix K or M.
25055 .item "opt@_octint"
25056 This also specifies an integer, but the value is always interpeted as an
25057 octal integer, whether or not it starts with the digit zero, and it is
25058 always output in octal.
25060 .item "opt@_stringptr"
25061 This specifies a string value; the address must be a pointer to a
25062 variable that points to a string (for example, of type \"uschar $*$"\).
25065 This specifies a time interval value. The address must point to a variable of
25066 type \"int"\. The value that is placed there is a number of seconds.
25070 If the \-bP-\ command line option is followed by \"local@_scan"\, Exim prints
25071 out the values of all the \*local@_scan()*\ options.
25074 .section Available Exim variables
25075 .index \*local@_scan()*\ function||available Exim variables
25076 The header \(local@_scan.h)\ gives you access to a number of C variables.
25077 These are the only ones that are guaranteed to be maintained from release to
25078 release. Note, however, that you can obtain the value of any Exim variable by
25079 calling \*expand@_string()*\. The exported variables are as follows:
25083 .item "unsigned int debug@_selector"
25084 This variable is set to zero when no debugging is taking place. Otherwise, it
25085 is a bitmap of debugging selectors. Two bits are identified for use in
25086 \*local@_scan()*\; they are defined as macros:
25088 The \"D@_v"\ bit is set when \-v-\ was present on the command line. This is a
25089 testing option that is not privileged -- any caller may set it. All the
25090 other selector bits can be set only by admin users.
25092 The \"D@_local@_scan"\ bit is provided for use by \*local@_scan()*\; it is set
25093 by the \"+local@_scan"\ debug selector. It is not included in the default set
25096 Thus, to write to the debugging output only when \"+local@_scan"\ has been
25097 selected, you should use code like this:
25099 if ((debug_selector & D_local_scan) != 0)
25100 debug_printf("xxx", ...);
25103 .item "uschar *expand@_string@_message"
25104 After a failing call to \*expand@_string()*\ (returned value NULL), the
25105 variable \expand__string__message\ contains the error message, zero-terminated.
25107 .item "header@_line *header@_list"
25108 A pointer to a chain of header lines. The \header@_line\ structure is discussed
25111 .item "header@_line *header@_last"
25112 A pointer to the last of the header lines.
25114 .item "uschar *headers@_charset"
25115 The value of the \headers@_charset\ configuration option.
25117 .item "BOOL host@_checking"
25118 This variable is TRUE during a host checking session that is initiated by the
25119 \-bh-\ command line option.
25121 .item "uschar *interface@_address"
25122 The IP address of the interface that received the message, as a string. This
25123 is NULL for locally submitted messages.
25125 .item "int interface@_port"
25126 The port on which this message was received.
25128 .item "uschar *message@_id"
25129 This variable contains the message id for the incoming message as a
25130 zero-terminated string.
25133 .item "uschar *received@_protocol"
25134 The name of the protocol by which the message was received.
25136 .item "int recipients@_count"
25137 The number of accepted recipients.
25139 .item "recipient@_item *recipients@_list"
25140 .index recipient||adding in local scan
25141 .index recipient||removing in local scan
25142 The list of accepted recipients, held in a vector of length
25143 \recipients@_count\. The \recipient@_item\ structure is discussed below. You
25144 can add additional recipients by calling \*receive@_add@_recipient()*\ (see
25145 below). You can delete recipients by removing them from the vector and adusting
25146 the value in \recipients@_count\. In particular, by setting \recipients@_count\
25147 to zero you remove all recipients. If you then return the value
25148 \"LOCAL@_SCAN@_ACCEPT"\, the message is accepted, but immediately blackholed.
25149 To replace the recipients, set \recipients@_count\ to zero and then call
25150 \*receive@_add@_recipient()*\ as often as needed.
25152 .item "uschar *sender@_address"
25153 The envelope sender address. For bounce messages this is the empty string.
25155 .item "uschar *sender@_host@_address"
25156 The IP address of the sending host, as a string. This is NULL for
25157 locally-submitted messages.
25159 .item "uschar *sender@_host@_authenticated"
25160 The name of the authentication mechanism that was used, or NULL if the message
25161 was not received over an authenticated SMTP connection.
25163 .item "uschar *sender@_host@_name"
25164 The name of the sending host, if known.
25166 .item "int sender@_host@_port"
25167 The port on the sending host.
25169 .item "BOOL smtp@_input"
25170 This variable is TRUE for all SMTP input, including BSMTP.
25172 .item "BOOL smtp@_batched@_input"
25173 This variable is TRUE for BSMTP input.
25175 .item "int store@_pool"
25176 The contents of this variable control which pool of memory is used for new
25177 requests. See section ~~SECTmemhanloc for details.
25182 .section Structure of header lines
25183 The \header@_line\ structure contains the members listed below.
25184 You can add additional header lines by calling the \*header@_add()*\ function
25185 (see below). You can cause header lines to be ignored (deleted) by setting
25190 .item "struct header@_line *next"
25191 A pointer to the next header line, or NULL for the last line.
25194 A code identifying certain headers that Exim recognizes. The codes are printing
25195 characters, and are documented in chapter ~~CHAPspool of this manual. Notice in
25196 particular that any header line whose type is $*$ is not transmitted with the
25197 message. This flagging is used for header lines that have been rewritten, or
25198 are to be removed (for example, ::Envelope-sender:: header lines.) Effectively,
25199 $*$ means `deleted'.
25202 The number of characters in the header line, including the terminating and any
25205 .item "uschar *text"
25206 A pointer to the text of the header. It always ends with a newline, followed by
25207 a zero byte. Internal newlines are preserved.
25213 .section Structure of recipient items
25214 The \recipient@_item\ structure contains these members:
25218 .item "uschar *address"
25219 This is a pointer to the recipient address as it was received.
25222 This is used in later Exim processing when top level addresses are created
25223 by the \one@_time\ option. It is not relevant at the time \*local@_scan()*\ is
25225 must always contain -1 at this stage.
25227 .item "uschar *errors@_to"
25228 If this value is not NULL, bounce messages caused by failing to deliver to the
25229 recipient are sent to the address it contains. In other words, it overrides the
25230 envelope sender for this one recipient. (Compare the \errors@_to\ generic
25232 If a \*local@_scan()*\ function sets an \errors@_to\ field to an unqualified
25233 address, Exim qualifies it using the domain from \qualify@_recipient\.
25234 When \*local@_scan()*\ is called, the \errors@_to\ field is NULL for all
25239 .section Available Exim functions
25240 .index \*local@_scan()*\ function||available Exim functions
25241 The header \(local@_scan.h)\ gives you access to a number of Exim functions.
25242 These are the only ones that are guaranteed to be maintained from release to
25247 .item "pid@_t child@_open(uschar **argv, uschar **envp, int newumask, int *infdptr, int *outfdptr, BOOL make@_leader)"
25248 This function creates a child process that runs the command specified by
25249 \argv\. The environment for the process is specified by \envp\, which can be
25250 NULL if no environment variables are to be passed. A new umask is supplied for
25251 the process in \newumask\.
25253 Pipes to the standard input and output of the new process are set up
25254 and returned to the caller via the \infdptr\ and \outfdptr\ arguments. The
25255 standard error is cloned to the standard output. If there are any file
25256 descriptors `in the way' in the new process, they are closed. If the final
25257 argument is TRUE, the new process is made into a process group leader.
25259 The function returns the pid of the new process, or -1 if things go wrong.
25262 .item "int child@_close(pid@_t pid, int timeout)"
25263 This function waits for a child process to terminate, or for a timeout (in
25264 seconds) to expire. A timeout value of zero means wait as long as it takes. The
25265 return value is as follows:
25269 The process terminated by a normal exit and the value is the process ending
25274 The process was terminated by a signal and the value is the negation of the
25279 The process timed out.
25283 The was some other error in wait(); \errno\ is still set.
25287 .item "pid@_t child@_open@_exim(int *fd)"
25288 This function provide you with a means of submitting a new message to
25289 Exim. (Of course, you can also call \(/usr/sbin/sendmail)\ yourself if you
25290 want, but this packages it all up for you.) The function creates a pipe,
25291 forks a subprocess that is running
25293 exim -t -oem -oi -f <>
25295 and returns to you (via the \"int *"\ argument) a file descriptor for the pipe
25296 that is connected to the standard input. The yield of the function is the PID
25297 of the subprocess. You can then write a message to the file descriptor, with
25298 recipients in ::To::, ::Cc::, and/or ::Bcc:: header lines.
25300 When you have finished, call \*child@_close()*\ to wait for the process to
25301 finish and to collect its ending status. A timeout value of zero is usually
25302 fine in this circumstance. Unless you have made a mistake with the recipient
25303 addresses, you should get a return code of zero.
25305 .item "void debug@_printf(char *, ...)"
25306 This is Exim's debugging function, with arguments as for \*(printf()*\. The
25307 output is written to the standard error stream. If no debugging is selected,
25308 calls to \*debug@_printf()*\ have no effect. Normally, you should make calls
25309 conditional on the \"local@_scan"\ debug selector by coding like this:
25311 if ((debug_selector & D_local_scan) != 0)
25312 debug_printf("xxx", ...);
25315 .item "uschar *expand@_string(uschar *string)"
25316 This is an interface to Exim's string expansion code. The return value is the
25317 expanded string, or NULL if there was an expansion failure.
25318 The C variable \expand@_string@_message\ contains an error message after an
25319 expansion failure. If expansion does not change the string, the return value is
25320 the pointer to the input string. Otherwise, the return value points to a new
25321 block of memory that was obtained by a call to \*store@_get()*\. See section
25322 ~~SECTmemhanloc below for a discussion of memory handling.
25324 .item "void header@_add(int type, char *format, ...)"
25326 This function allows you to an add additional header line at the end of the
25329 The first argument is the type, and should normally be a space character. The
25330 second argument is a format string and any number of substitution arguments as
25331 for \*sprintf()*\. You may include internal newlines if you want, and you must
25332 ensure that the string ends with a newline.
25335 .item "void header@_add@_at@_position(BOOL after, uschar *name, BOOL topnot, int type, char *$nh{format}, ...)"
25336 This function adds a new header line at a specified point in the header
25337 chain. The header itself is specified as for \*header@_add()*\.
25339 If \name\ is NULL, the new header is added at the end of the chain if \after\
25340 is true, or at the start if \after\ is false. If \name\ is not NULL, the header
25341 lines are searched for the first non-deleted header that matches the name. If
25342 one is found, the new header is added before it if \after\ is false. If \after\
25343 is true, the new header is added after the found header and any adjacent
25344 subsequent ones with the same name (even if marked `deleted'). If no matching
25345 non-deleted header is found, the \topnot\ option controls where the header is
25346 added. If it is true, addition is at the top; otherwise at the bottom. Thus, to
25347 add a header after all the ::Received:: headers, or at the top if there are no
25348 ::Received:: headers, you could use
25350 header_add_at_position(TRUE, US"Received", TRUE,
25351 ' ', "X-xxx: ...");
25353 Normally, there is always at least one non-deleted ::Received:: header, but
25354 there may not be if \received@_header@_text\ expands to an empty string.
25357 .item "void header@_remove(int occurrence, uschar *name)"
25358 This function removes header lines. If \occurrence\ is zero or negative, all
25359 occurrences of the header are removed. If occurrence is greater than zero, that
25360 particular instance of the header is removed. If no header(s) can be found that
25361 match the specification, the function does nothing.
25364 .item "BOOL header@_testname(header@_line *hdr, uschar *name, int length, BOOL notdel)"
25365 This function tests whether the given header has the given name. It is not just
25366 a string comparison, because whitespace is permitted between the name and the
25367 colon. If the \notdel\ argument is true, a false return is forced for all
25368 `deleted' headers; otherwise they are not treated specially. For example:
25370 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
25375 .item "uschar *lss@_b64encode(uschar *cleartext, int length)"
25376 .index base64 encoding||functions for \*local@_scan()*\ use
25377 This function base64-encodes a string, which is passed by address and length.
25378 The text may contain bytes of any value, including zero. The result is passed
25379 back in dynamic memory that is obtained by calling \*store@_get()*\. It is
25382 .item "int lss@_b64decode(uschar *codetext, uschar **cleartext)"
25383 This function decodes a base64-encoded string. Its arguments are a
25384 zero-terminated base64-encoded string and the address of a variable that is set
25385 to point to the result, which is in dynamic memory. The length of the
25386 decoded string is the yield of the function. If the input is invalid base64
25387 data, the yield is -1. A zero byte is added to the end of the output string to
25388 make it easy to interpret as a C string (assuming it contains no zeros of its
25389 own). The added zero byte is not included in the returned count.
25391 .item "int lss@_match@_domain(uschar *domain, uschar *list)"
25392 This function checks for a match in a domain list. Domains are always
25393 matched caselessly. The return value is one of the following:
25395 OK $rm{match succeeded}
25396 FAIL $rm{match failed}
25397 DEFER $rm{match deferred}
25399 DEFER is usually caused by some kind of lookup defer, such as the
25400 inability to contact a database.
25402 .item "int lss@_match@_local@_part(uschar *localpart, uschar *list, BOOL caseless)"
25403 This function checks for a match in a local part list. The third argument
25404 controls case-sensitivity. The return values are as for
25405 \*lss@_match@_domain()*\.
25407 .item "int lss@_match@_address(uschar *address, uschar *list, BOOL caseless)"
25408 This function checks for a match in an address list. The third argument
25409 controls the case-sensitivity of the local part match. The domain is always
25410 matched caselessly. The return values are as for \*lss@_match@_domain()*\.
25412 .item "int lss@_match@_host(uschar *host@_name, uschar *host@_address, uschar *list)"
25413 This function checks for a match in a host list. The most common usage is
25416 lss_match_host(sender_host_name, sender_host_address, ...)
25418 An empty address field matches an empty item in the host list. If the
25419 host name is NULL, the name corresponding to \$sender@_host@_address$\ is
25420 automatically looked up if a host name is required to match an item in the
25421 list. The return values are as for \*lss@_match@_domain()*\, but in addition,
25422 \*lss@_match@_host()*\ returns ERROR in the case when it had to look up a host
25423 name, but the lookup failed.
25425 .item "void log@_write(unsigned int selector, int which, char *format, ...)"
25426 This function writes to Exim's log files. The first argument should be zero (it
25427 is concerned with \log@_selector\). The second argument can be \"LOG@_MAIN"\ or
25429 \"LOG@_PANIC"\ or the inclusive `or' of any combination of them. It specifies
25430 to which log or logs the message is written.
25431 The remaining arguments are a format and relevant insertion arguments. The
25432 string should not contain any newlines, not even at the end.
25435 .item "void receive@_add@_recipient(uschar *address, int pno)"
25436 This function adds an additional recipient to the message. The first argument
25437 is the recipient address. If it is unqualified (has no domain), it is qualified
25438 with the \qualify@_recipient\ domain. The second argument must always be -1.
25440 This function does not allow you to specify a private \errors@_to\ address (as
25441 described with the structure of \recipient@_item\ above), because it pre-dates
25442 the addition of that field to the structure. However, it is easy to add such a
25443 value afterwards. For example:
25445 receive_add_recipient(US"monitor@mydom.example", -1);
25446 recipients_list[recipients_count-1].errors_to =
25447 US"postmaster@mydom.example";
25451 .item "BOOL receive@_remove@_recipient(uschar *recipient)"
25452 This is a convenience function to remove a named recipient from the
25453 list of recipients. It returns true if a recipient was removed, and
25454 false if no matching recipient could be found. The argument must be a
25455 complete email address.
25459 .item "uschar *rfc2047@_decode(uschar *string, BOOL lencheck, uschar *target, int zeroval, int *lenptr, uschar **error)"
25460 This function decodes strings that are encoded according to RFC 2047. Typically
25461 these are the contents of header lines. First, each encoded `word' is decoded
25462 from the Q or B encoding into a byte-string. Then, if provided with the name of
25463 a charset encoding, and if the \*iconv()*\ function is available, an attempt is
25464 made to translate the result to the named character set. If this fails, the
25465 binary string is returned with an error message.
25467 The first argument is the string to be decoded. If \lencheck\ is TRUE, the
25468 maximum MIME word length is enforced. The third argument is the target
25469 encoding, or NULL if no translation is wanted.
25471 .index binary zero||in RFC 2047 decoding
25472 If a binary zero is encountered in the decoded string, it is replaced by the
25473 contents of the \zeroval\ argument. For use with Exim headers, the value must
25474 not be 0 because header lines are handled as zero-terminated strings.
25476 The function returns the result of processing the string, zero-terminated; if
25477 \lenptr\ is not NULL, the length of the result is set in the variable to which
25478 it points. When \zeroval\ is 0, \lenptr\ should not be NULL.
25480 If an error is encountered, the function returns NULL and uses the \error\
25481 argument to return an error message. The variable pointed to by \error\ is set
25482 to NULL if there is no error; it may be set non-NULL even when the function
25483 returns a non-NULL value if decoding was successful, but there was a problem
25487 .item "int smtp@_fflush(void)"
25488 This function is used in conjunction with \*smtp@_printf()*\, as described
25491 .item "void smtp@_printf(char *, ...)"
25492 The arguments of this function are like \*printf()*\; it writes to the SMTP
25493 output stream. You should use this function only when there is an SMTP output
25494 stream, that is, when the incoming message is being received via interactive
25495 SMTP. This is the case when \smtp@_input\ is TRUE and \smtp@_batched@_input\ is
25496 FALSE. If you want to test for an incoming message from another host (as
25497 opposed to a local process that used the \-bs-\ command line option), you can
25498 test the value of \sender@_host@_address\, which is non-NULL when a remote host
25501 If an SMTP TLS connection is established, \*smtp@_printf()*\ uses the TLS
25502 output function, so it can be used for all forms of SMTP connection.
25504 Strings that are written by \*smtp@_printf()*\ from within \*local@_scan()*\
25505 must start with an appropriate response code: 550 if you are going to return
25506 \\LOCAL@_SCAN@_REJECT\\, 451 if you are going to return
25507 \\LOCAL@_SCAN@_TEMPREJECT\\, and 250 otherwise. Because you are writing the
25508 initial lines of a multi-line response, the code must be followed by a hyphen
25509 to indicate that the line is not the final response line. You must also ensure
25510 that the lines you write terminate with CRLF. For example:
25512 smtp_printf("550-this is some extra info\r\n");
25513 return LOCAL_SCAN_REJECT;
25515 Note that you can also create multi-line responses by including newlines in
25516 the data returned via the \return@_text\ argument. The added value of using
25517 \*smtp@_printf()*\ is that, for instance, you could introduce delays between
25518 multiple output lines.
25520 The \*smtp@_printf()*\ function does not return any error indication, because it
25521 does not automatically flush pending output, and therefore does not test
25522 the state of the stream. (In the main code of Exim, flushing and error
25523 detection is done when Exim is ready for the next SMTP input command.) If
25524 you want to flush the output and check for an error (for example, the
25525 dropping of a TCP/IP connection), you can call \*smtp@_fflush()*\, which has no
25526 arguments. It flushes the output stream, and returns a non-zero value if there
25529 .item "void *store@_get(int)"
25530 This function accesses Exim's internal store (memory) manager. It gets a new
25531 chunk of memory whose size is given by the argument. Exim bombs out if it ever
25532 runs out of memory. See the next section for a discussion of memory handling.
25534 .item "void *store@_get@_perm(int)"
25535 This function is like \*store@_get()*\, but it always gets memory from the
25536 permanent pool. See the next section for a discussion of memory handling.
25538 .item "uschar *string@_copy(uschar *string)"
25539 .item "uschar *string@_copyn(uschar *string, int length)" 0
25540 .item "uschar *string@_sprintf(char *format, ...)" 0
25541 These three functions create strings using Exim's dynamic memory facilities.
25542 The first makes a copy of an entire string. The second copies up to a maximum
25543 number of characters, indicated by the second argument. The third uses a format
25544 and insertion arguments to create a new string. In each case, the result is a
25545 pointer to a new string
25546 in the current memory pool. See the next section for more discussion.
25552 .section More about Exim's memory handling
25553 .rset SECTmemhanloc "~~chapter.~~section"
25554 .index \*local@_scan()*\ function||memory handling
25555 No function is provided for freeing memory, because that is never needed.
25556 The dynamic memory that Exim uses when receiving a message is automatically
25557 recycled if another message is received by the same process (this applies only
25558 to incoming SMTP connections -- other input methods can supply only one message
25559 at a time). After receiving the last message, a reception process terminates.
25561 Because it is recycled, the normal dynamic memory cannot be used for holding
25562 data that must be preserved over a number of incoming messages on the same SMTP
25563 connection. However, Exim in fact uses two pools of dynamic memory; the second
25564 one is not recycled, and can be used for this purpose.
25566 If you want to allocate memory that remains available for subsequent messages
25567 in the same SMTP connection, you should set
25569 store_pool = POOL_PERM
25571 before calling the function that does the allocation. There is no need to
25572 restore the value if you do not need to; however, if you do want to revert to
25573 the normal pool, you can either restore the previous value of \store@_pool\ or
25574 set it explicitly to \\POOL@_MAIN\\.
25576 The pool setting applies to all functions that get dynamic memory, including
25577 \*expand@_string()*\, \*store@_get()*\, and the \*string@_xxx()*\ functions.
25578 There is also a convenience function called \*store__get__perm()*\ that gets a
25579 block of memory from the permanent pool while preserving the value of
25590 . ============================================================================
25591 .chapter System-wide message filtering
25592 .set runningfoot "system filtering"
25593 .rset CHAPsystemfilter "~~chapter"
25594 .index filter||system filter
25595 .index filtering all mail
25596 .index system filter
25597 The previous chapters (on ACLs and the local scan function) describe checks
25598 that can be applied to messages before they are accepted by a host. There is
25599 also a mechanism for checking messages once they have been received, but before
25600 they are delivered. This is called the $it{system filter}.
25602 The system filter operates in a similar manner to users' filter files, but it
25603 is run just once per message (however many recipients the message has).
25604 It should not normally be used as a substitute for routing, because \deliver\
25605 commands in a system router provide new envelope recipient addresses.
25606 The system filter must be an Exim filter. It cannot be a Sieve filter.
25608 The system filter is run at the start of a delivery attempt, before any routing
25609 is done. If a message fails to be completely delivered at the first attempt,
25610 the system filter is run again at the start of every retry.
25611 If you want your filter to do something only once per message, you can make use
25612 of the \first@_delivery\ condition in an \if\ command in the filter to prevent
25613 it happening on retries.
25615 \**Warning**\: Because the system filter runs just once, variables that are
25616 specific to individual recipient addresses, such as \$local@_part$\ and
25617 \$domain$\, are not set, and the `personal' condition is not meaningful. If you
25618 want to run a centrally-specified filter for each recipient address
25619 independently, you can do so by setting up a suitable \%redirect%\ router, as
25620 described in section ~~SECTperaddfil below.
25622 .section Specifying a system filter
25623 .index uid (user id)||system filter
25624 .index gid (group id)||system filter
25625 The name of the file that contains the system filter must be specified by
25626 setting \system@_filter\. If you want the filter to run under a uid and gid
25627 other than root, you must also set \system@_filter@_user\ and
25628 \system@_filter@_group\ as appropriate. For example:
25630 system_filter = /etc/mail/exim.filter
25631 system_filter_user = exim
25633 If a system filter generates any deliveries directly to files or pipes (via the
25634 \save\ or \pipe\ commands), transports to handle these deliveries must be
25635 specified by setting \system@_filter@_file@_transport\ and
25636 \system@_filter@_pipe@_transport\, respectively. Similarly,
25637 \system@_filter@_reply@_transport\ must be set to handle any messages generated
25638 by the \reply\ command.
25640 .section Testing a system filter
25641 You can run simple tests of a system filter in the same way as for a user
25642 filter, but you should use \-bF-\ rather than \-bf-\, so that features that
25643 are permitted only in system filters are recognized.
25645 If you want to test the combined effect of a system filter and a user filter,
25646 you can use both \-bF-\ and \-bf-\ on the same command line.
25649 .section Contents of a system filter
25650 The language used to specify system filters is the same as for users' filter
25651 files. It is described in the separate end-user document \*Exim's interface to
25652 mail filtering*\. However, there are some additional features that are
25653 available only in system filters; these are described in subsequent sections.
25654 If they are encountered in a user's filter file or when testing with \-bf-\,
25657 .index frozen messages||manual thaw, testing in filter
25658 There are two special conditions which, though available in users' filter
25659 files, are designed for use in system filters. The condition \first@_delivery\
25660 is true only for the first attempt at delivering a message, and
25661 \manually@_thawed\ is true only if the message has been frozen, and
25662 subsequently thawed by an admin user. An explicit forced delivery counts as a
25663 manual thaw, but thawing as a result of the \auto__thaw\ setting does not.
25665 \**Warning**\: If a system filter uses the \first@_delivery\ condition to
25666 specify an `unseen' (non-significant) delivery, and that delivery does not
25667 succeed, it will not be tried again.
25668 If you want Exim to retry an unseen delivery until it succeeds, you should
25669 arrange to set it up every time the filter runs.
25671 When a system filter finishes running, the values of the variables \$n0$\ --
25672 \$n9$\ are copied into \$sn0$\ -- \$sn9$\ and are thereby made available to
25673 users' filter files. Thus a system filter can, for example, set up `scores' to
25674 which users' filter files can refer.
25677 .section Additional variable for system filters
25678 The expansion variable \$recipients$\, containing a list of all the recipients
25679 of the message (separated by commas and white space), is available in system
25680 filters. It is not available in users' filters for privacy reasons.
25683 .section Defer, freeze, and fail commands for system filters
25684 .index freezing messages
25685 .index message||freezing
25686 .index message||forced failure
25687 .index \fail\||in system filter
25688 .index \freeze\ in system filter
25689 .index \defer\ in system filter
25690 There are three extra commands (\defer\, \freeze\ and \fail\) which are always
25691 available in system filters, but are not normally enabled in users' filters.
25692 (See the \allow@_defer\,
25693 \allow@_freeze\ and \allow@_fail\ options for the \%redirect%\ router.) These
25694 commands can optionally be followed by the word \text\ and a string containing
25695 an error message, for example:
25697 fail text "this message looks like spam to me"
25699 The keyword \text\ is optional if the next character is a double quote.
25701 The \defer\ command defers delivery of the original recipients of the message.
25702 The \fail\ command causes all the original recipients to be failed, and a
25703 bounce message to be created. The \freeze\ command suspends all delivery
25704 attempts for the original recipients. In all cases, any new deliveries that are
25705 specified by the filter are attempted as normal after the filter has run.
25707 The \freeze\ command is ignored if the message has been manually unfrozen and
25708 not manually frozen since. This means that automatic freezing by a system
25709 filter can be used as a way of checking out suspicious messages. If a message
25710 is found to be all right, manually unfreezing it allows it to be delivered.
25712 .index log||\fail\ command log line
25713 .index \fail\||log line, reducing
25714 The text given with a fail command is used as part of the bounce message as
25715 well as being written to the log. If the message is quite long, this can fill
25716 up a lot of log space when such failures are common. To reduce the size of the
25717 log message, Exim interprets the text in a special way if it starts with the
25718 two characters \"@<@<"\ and contains \"@>@>"\ later. The text between these two
25719 strings is written to the log, and the rest of the text is used in the bounce
25720 message. For example:
25722 fail "<<filter test 1>>Your message is rejected \
25723 because it contains attachments that we are \
25724 not prepared to receive."
25727 .index loop||caused by \fail\
25728 Take great care with the \fail\ command when basing the decision to fail on the
25729 contents of the message, because the bounce message will of course include the
25730 contents of the original message and will therefore trigger the \fail\ command
25731 again (causing a mail loop) unless steps are taken to prevent this. Testing the
25732 \error@_message\ condition is one way to prevent this. You could use, for
25735 if $message_body contains "this is spam" and not error_message
25736 then fail text "spam is not wanted here" endif
25738 though of course that might let through unwanted bounce messages. The
25739 alternative is clever checking of the body and/or headers to detect bounces
25740 generated by the filter.
25742 The interpretation of a system filter file ceases after a
25744 \freeze\, or \fail\ command is obeyed. However, any deliveries that were set up
25745 earlier in the filter file are honoured, so you can use a sequence such as
25750 to send a specified message when the system filter is freezing (or deferring or
25751 failing) a message. The normal deliveries for the message do not, of course,
25755 .section Adding and removing headers in a system filter
25756 .rset SECTaddremheasys "~~chapter.~~section"
25757 .index header lines||adding, in system filter
25758 .index header lines||removing, in system filter
25759 .index filter||header lines, adding/removing
25760 Two filter commands that are available only in system filters are:
25762 headers add <<string>>
25763 headers remove <<string>>
25765 The argument for the \headers add\ is a string that is expanded and then added
25766 to the end of the message's headers. It is the responsibility of the filter
25767 maintainer to make sure it conforms to RFC 2822 syntax. Leading white space is
25768 ignored, and if the string is otherwise empty, or if the expansion is forced to
25769 fail, the command has no effect.
25771 You can use `@\n' within the string, followed by white space, to specify
25772 continued header lines. More than one header may be added in one command by
25773 including `@\n' within the string without any following white space. For
25776 headers add "X-header-1: ....\n \
25777 continuation of X-header-1 ...\n\
25780 Note that the header line continuation white space after the first newline must
25781 be placed before the backslash that continues the input string, because white
25782 space after input continuations is ignored.
25784 The argument for \headers remove\ is a colon-separated list of header names.
25785 This command applies only to those headers that are stored with the message;
25786 those that are added at delivery time (such as ::Envelope-To:: and
25787 ::Return-Path::) cannot be removed by this means. If there is more than one
25788 header with the same name, they are all removed.
25791 The \headers\ command in a system filter makes an immediate change to the set
25792 of header lines that was received with the message (with possible additions
25793 from ACL processing). Subsequent commands in the system filter operate on the
25794 modified set, which also forms the basis for subsequent message delivery.
25795 Unless further modified during routing or transporting, this set of headers is
25796 used for all recipients of the message.
25798 During routing and transporting, the variables that refer to the contents of
25799 header lines refer only to those lines that are in this set. Thus, header lines
25800 that are added by a system filter are visible to users' filter files and to all
25801 routers and transports. This contrasts with the manipulation of header lines by
25802 routers and transports, which is not immediate, but which instead is saved up
25803 until the message is actually being written (see section ~~SECTheadersaddrem).
25805 If the message is not delivered at the first attempt, header lines that were
25806 added by the system filter are stored with the message, and so are still
25807 present at the next delivery attempt. Header lines that were removed are still
25808 present, but marked `deleted' so that they are not transported with the
25809 message. For this reason, it is usual to make the \headers\ command conditional
25810 on \first@_delivery\ so that the set of header lines is not modified more than
25813 Because header modification in a system filter acts immediately, you have to
25814 use an indirect approach if you want to modify the contents of a header line.
25817 headers add "Old-Subject: $h_subject:"
25818 headers remove "Subject"
25819 headers add "Subject: new subject (was: $h_old-subject:)"
25820 headers remove "Old-Subject"
25826 .section Setting an errors address in a system filter
25827 .index envelope sender
25828 In a system filter, if a \deliver\ command is followed by
25830 errors@_to <<some address>>
25832 in order to change the envelope sender (and hence the error reporting) for that
25833 delivery, any address may be specified. (In a user filter, only the current
25834 user's address can be set.) For example, if some mail is being monitored, you
25837 unseen deliver monitor@spying.example errors_to root@local.example
25839 to take a copy which would not be sent back to the normal error reporting
25840 address if its delivery failed.
25843 .section Per-address filtering
25844 .rset SECTperaddfil "~~chapter.~~section"
25845 In contrast to the system filter, which is run just once per message for each
25846 delivery attempt, it is also possible to set up a system-wide filtering
25847 operation that runs once for each recipient address. In this case, variables
25848 such as \$local@_part$\ and \$domain$\ can be used, and indeed, the choice of
25849 filter file could be made dependent on them. This is an example of a router
25850 which implements such a filter:
25857 domains = +local_domains
25858 file = /central/filters/$local_part
25863 The filter is run in a separate process under its own uid. Therefore, either
25864 \check@_local@_user\ must be set (as above), in which case the filter is run as
25865 the local user, or the \user\ option must be used to specify which user to use.
25866 If both are set, \user\ overrides.
25868 Care should be taken to ensure that none of the commands in the filter file
25869 specify a significant delivery if the message is to go on to be delivered to
25870 its intended recipient. The router will not then claim to have dealt with the
25871 address, so it will be passed on to subsequent routers to be delivered in the
25883 . ============================================================================
25884 .chapter Message processing
25885 .set runningfoot "message processing"
25886 .rset CHAPmsgproc "~~chapter"
25887 .index message||general processing
25888 Exim performs various transformations on the sender and recipient addresses of
25889 all messages that it handles, and also on the messages' header lines. Some of
25890 these are optional and configurable, while others always take place. All of
25891 this processing, except rewriting as a result of routing, and the addition or
25892 removal of header lines while delivering, happens when a message is received,
25893 before it is placed on Exim's queue.
25895 Some of the automatic processing takes place by default only for
25896 `locally-originated' messages. This adjective is used to describe messages that
25897 are not received over TCP/IP, but instead are passed to an Exim process on its
25898 standard input. This includes the interactive `local SMTP' case that is set up
25899 by the \-bs-\ command line option.
25901 \**Note**\: messages received over TCP/IP on the loopback interface (127.0.0.1
25902 or @:@:1) are not considered to be locally-originated. Exim does not treat the
25903 loopback interface specially in any way.
25905 If you want the loopback interface to be treated specially, you must ensure
25906 that there are appropriate entries in your ACLs.
25910 .section Submission mode for non-local messages
25911 .rset SECTsubmodnon "~~chapter.~~section"
25912 .index message||submission
25913 .index submission mode
25915 Processing that happens automatically for locally-originated messages can also
25916 be requested for other messages. The term `submission mode' is used to describe
25917 this state. Submisssion mode is set by the modifier
25919 control = submission
25921 in a \\MAIL\\, \\RCPT\\, or pre-data ACL for an incoming SMTP message (see
25922 sections ~~SECTACLmodi and ~~SECTcontrols). This makes Exim treat the message
25923 as a local submission, and is normally used when the source of the message is
25924 known to be an MUA running on a client host (as opposed to an MTA). For
25925 example, to set submission mode for messages originating on the IPv4 loopback
25926 interface, you could include the following in the \\MAIL\\ ACL:
25928 warn hosts = 127.0.0.1
25929 control = submission
25931 There are some options that can be used when setting submission mode. A slash
25932 is used to separate options. For example:
25934 control = submission/sender_retain
25936 Specifying \sender@_retain\ has the effect of setting \local@_sender@_retain\
25937 true and \local@_from@_check\ false for the current incoming message. The first
25938 of these allows an existing ::Sender:: header in the message to remain, and the
25939 second suppresses the check to ensure that ::From:: matches the authenticated
25940 sender. With this setting, Exim still fixes up messages by adding ::Date:: and
25941 ::Message-ID:: header lines if they are missing, but makes no attempt to check
25942 sender authenticity in header lines.
25944 A submission mode setting may also specify a domain to be used when generating
25945 a ::From:: or ::Sender:: header. For example:
25947 control = submission/domain=some.domain
25949 The domain may be empty. How this value is used is described in sections
25950 ~~SECTthefrohea and ~~SECTthesenhea.
25955 .section Line endings
25956 .rset SECTlineendings "~~chapter.~~section"
25957 .index line endings
25958 .index carriage return
25960 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
25961 linefeed) is the line ending for messages transmitted over the Internet using
25962 SMTP over TCP/IP. However, within individual operating systems, different
25963 conventions are used. For example, Unix-like systems use just LF, but others
25964 use CRLF or just CR.
25966 Exim was designed for Unix-like systems, and internally, it stores messages
25967 using the system's convention of a single LF as a line terminator. When
25968 receiving a message, all line endings are translated to this standard format.
25969 Originally, it was thought that programs that passed messages directly to an
25970 MTA within an operating system would use that system's convention. Experience
25971 has shown that this is not the case; for example, there are Unix applications
25972 that use CRLF in this circumstance. For this reason, and for compatibility with
25973 other MTAs, the way Exim handles line endings for all messages is now as
25976 LF not preceded by CR is treated as a line ending.
25978 CR is treated as a line ending; if it is immediately followed by LF, the LF
25981 The sequence `CR, dot, CR' does not terminate an incoming SMTP message,
25982 nor a local message in the state where a line containing only a dot is a
25985 If a bare CR is encountered within a header line, an extra space is added after
25986 the line terminator so as not to end the header line. The reasoning behind this
25987 is that bare CRs in header lines are most likely either to be mistakes, or
25988 people trying to play silly games.
25990 If the first header line received in a message ends with CRLF, a subsequent
25991 bare LF in a header line is treated in the same way as a bare CR in a header
25997 .section Unqualified addresses
25998 .index unqualified addresses
25999 .index address||qualification
26000 By default, Exim expects every envelope address it receives from an external
26001 host to be fully qualified. Unqualified addresses cause negative responses to
26002 SMTP commands. However, because SMTP is used as a means of transporting
26003 messages from MUAs running on personal workstations, there is sometimes a
26004 requirement to accept unqualified addresses from specific hosts or IP networks.
26006 Exim has two options that separately control which hosts may send unqualified
26007 sender or receipient addresses in SMTP commands, namely
26008 \sender__unqualified__hosts\ and \recipient__unqualified__hosts\. In both
26009 cases, if an unqualified address is accepted, it is qualified by adding the
26010 value of \qualify__domain\ or \qualify__recipient\, as appropriate.
26011 .index \qualify@_domain\
26012 .index \qualify@_recipient\
26015 Unqualified addresses in header lines are automatically qualified for messages
26016 that are locally originated, unless the \-bnq-\ option is given on the command
26017 line. For messages received over SMTP, unqualified addresses in header lines
26018 are qualified only if unqualified addresses are permitted in SMTP commands. In
26019 other words, such qualification is also controlled by
26020 \sender__unqualified__hosts\ and \recipient__unqualified__hosts\,
26024 .section The UUCP From line
26026 .index UUCP||`From' line
26027 .index sender||address
26028 .index \uucp@_from@_pattern\
26029 .index \uucp@_from@_sender\
26030 .index envelope sender
26031 .index Sendmail compatibility||`From' line
26032 Messages that have come from UUCP (and some other applications) often begin
26033 with a line containing the envelope sender and a timestamp, following the word
26034 `From'. Examples of two common formats are:
26036 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
26037 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
26039 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
26040 Exim recognizes such lines at the start of messages that are submitted to it
26041 via the command line (that is, on the standard input). It does not recognize
26042 such lines in incoming SMTP messages, unless the sending host matches
26043 \ignore@_fromline@_hosts\ or the \-bs-\ option was used for a local message and
26044 \ignore@_fromline@_local\ is set. The recognition is controlled by a regular
26045 expression that is defined by the \uucp@_from@_pattern\ option, whose default
26046 value matches the two common cases shown above and puts the address that
26047 follows `From' into \$1$\.
26049 .index numerical variables (\$1$\, \$2$\, etc)||in `From ' line handling
26050 When the caller of Exim for a non-SMTP message that contains a `From' line is a
26051 trusted user, the message's sender address is constructed by expanding the
26052 contents of \uucp@_sender@_address\, whose default value is `@$1'. This is then
26053 parsed as an RFC 2822 address. If there is no domain, the local part is
26054 qualified with \qualify@_domain\ unless it is the empty string. However, if the
26055 command line \-f-\ option is used, it overrides the `From' line.
26057 If the caller of Exim is not trusted, the `From' line is recognized, but the
26058 sender address is not changed. This is also the case for incoming SMTP messages
26059 that are permitted to contain `From' lines.
26061 Only one `From' line is recognized. If there is more than one, the second is
26062 treated as a data line that starts the body of the message, as it is not valid
26063 as a header line. This also happens if a `From' line is present in an incoming
26064 SMTP message from a source that is not permitted to send them.
26067 .section Resent- header lines
26068 .index \Resent@-\ header lines
26069 RFC 2822 makes provision for sets of header lines starting with the string
26070 \"Resent-"\ to be added to a message when it is resent by the original
26071 recipient to somebody else. These headers are ::Resent-Date::, ::Resent-From::,
26072 ::Resent-Sender::, ::Resent-To::, ::Resent-Cc::, ::Resent-Bcc:: and
26073 ::Resent-Message-ID::. The RFC says:
26075 \*Resent fields are strictly informational. They MUST NOT be used in the normal
26076 processing of replies or other such automatic actions on messages.*\
26078 This leaves things a bit vague as far as other processing actions such as
26079 address rewriting are concerned. Exim treats \Resent@-\ header lines as
26082 A ::Resent-From:: line that just contains the login id of the submitting user
26083 is automatically rewritten in the same way as ::From:: (see below).
26085 If there's a rewriting rule for a particular header line, it is also applied to
26086 \Resent@-\ header lines of the same type. For example, a rule that rewrites
26087 ::From:: also rewrites ::Resent-From::.
26089 For local messages, if ::Sender:: is removed on input, ::Resent-Sender:: is also
26092 For a locally-submitted message,
26093 if there are any \Resent@-\ header lines but no ::Resent-Date::,
26094 ::Resent-From::, or ::Resent-Message-Id::, they are added as necessary. It is
26095 the contents of ::Resent-Message-Id:: (rather than ::Message-Id::) which are
26096 included in log lines in this case.
26098 The logic for adding ::Sender:: is duplicated for ::Resent-Sender:: when any
26099 \Resent@-\ header lines are present.
26103 .section The Auto-Submitted: header line
26104 Whenever Exim generates a bounce or a delay warning message, it includes the
26107 Auto-Submitted: auto-generated
26111 .section The Bcc: header line
26112 .index ::Bcc:: header line
26113 If Exim is called with the \-t-\ option, to take recipient addresses from a
26114 message's header, it removes any ::Bcc:: header line that may exist (after
26115 extracting its addresses). If \-t-\ is not present on the command line, any
26116 existing ::Bcc:: is not removed.
26118 .section The Date: header line
26119 .index ::Date:: header line
26120 If a locally-generated
26122 message has no ::Date:: header line, Exim adds one, using the current date and
26125 .section The Delivery-date: header line
26126 .index ::Delivery-date:: header line
26127 .index \delivery@_date@_remove\
26128 ::Delivery-date:: header lines are not part of the standard RFC 2822 header
26129 set. Exim can be configured to add them to the final delivery of messages. (See
26130 the generic \delivery@_date@_add\ transport option.) They should not be present
26131 in messages in transit. If the \delivery@_date@_remove\ configuration option is
26132 set (the default), Exim removes ::Delivery-date:: header lines from incoming
26135 .section The Envelope-to: header line
26136 .index ::Envelope-to:: header line
26137 .index \envelope@_to@_remove\
26138 ::Envelope-to:: header lines are not part of the standard RFC 2822 header set.
26139 Exim can be configured to add them to the final delivery of messages. (See the
26140 generic \envelope@_to@_add\ transport option.) They should not be present in
26141 messages in transit. If the \envelope@_to@_remove\ configuration option is set
26142 (the default), Exim removes ::Envelope-to:: header lines from incoming
26145 .section The From: header line
26146 .rset SECTthefrohea "~~chapter.~~section"
26147 .index ::From:: header line
26148 .index Sendmail compatibility||`From' line
26149 .index message||submission
26150 .index submission mode
26151 If a submission-mode message does not contain a ::From:: header line, Exim adds
26152 one if either of the following conditions is true:
26154 The envelope sender address is not empty (that is, this is not a bounce
26155 message). The added header line copies the envelope sender address.
26157 The SMTP session is authenticated and \$authenticated@_id$\ is not empty.
26160 If no domain is specified by the submission control, the local part is
26161 \$authenticated@_id$\ and the domain is \$qualify@_domain$\.
26163 If a non-empty domain is specified by the submission control, the local part is
26164 \$authenticated@_id$\, and the the domain is the specified domain.
26166 If an empty domain is specified by the submission control,
26167 \$authenticated@_id$\ is assumed to be the complete address.
26171 A non-empty envelope sender takes precedence.
26173 If a locally-generated incoming message does not contain a ::From:: header
26174 line, Exim adds one containing the sender's address. The calling user's login
26175 name and full name are used to construct the address, as described in section
26176 ~~SECTconstr. They are obtained from the password data by calling
26177 \*getpwuid()*\ (but see the \unknown@_login\ configuration option). The address
26178 is qualified with \qualify@_domain\.
26180 For compatibility with Sendmail, if an incoming, non-SMTP message has a
26181 ::From:: header line containing just the unqualified login name of the calling
26182 user, this is replaced by an address containing the user's login name and full
26183 name as described in section ~~SECTconstr.
26185 .section The Message-ID: header line
26186 .index ::Message-ID:: header line
26187 .index message||submission
26188 If a locally-generated or submission-mode incoming message does not contain a
26189 ::Message-ID:: or ::Resent-Message-ID:: header line, Exim adds one to the
26190 message. If there are any ::Resent-:: headers in the message, it creates
26191 ::Resent-Message-ID::. The id is constructed from Exim's internal message id,
26192 preceded by the letter E to ensure it starts with a letter, and followed by @@
26193 and the primary host name. Additional information can be included in this
26194 header line by setting the
26195 .index \message@_id@_header@_text\
26196 \message@_id@_header@_text\ and/or \message__id__header__domain\ options.
26199 .section The Received: header line
26200 .index ::Received:: header line
26201 A ::Received:: header line is added at the start of every message. The contents
26202 are defined by the \received@_header@_text\ configuration option, and Exim
26203 automatically adds a semicolon and a timestamp to the configured string.
26205 The ::Received:: header is generated as soon as the message's header lines have
26206 been received. At this stage, the timestamp in the ::Received:: header line is
26207 the time that the message started to be received. This is the value that is
26208 seen by the \\DATA\\ ACL and by the \*local@_scan()*\ function.
26210 Once a message is accepted, the timestamp in the ::Received:: header line is
26211 changed to the time of acceptance, which is (apart from a small delay while the
26212 -H spool file is written) the earliest time at which delivery could start.
26215 .section The Return-path: header line
26216 .index ::Return-path:: header line
26217 .index \return@_path@_remove\
26218 ::Return-path:: header lines are defined as something an MTA may insert when
26219 it does the final delivery of messages. (See the generic \return@_path@_add\
26220 transport option.) Therefore, they should not be present in messages in
26221 transit. If the \return@_path@_remove\ configuration option is set (the
26222 default), Exim removes ::Return-path:: header lines from incoming messages.
26225 .section The Sender: header line
26226 .rset SECTthesenhea "~~chapter.~~section"
26227 .index ::Sender:: header line
26228 .index message||submission
26229 For a locally-originated message from an untrusted user, Exim may remove an
26230 existing ::Sender:: header line, and it may add a new one. You can modify these
26231 actions by setting \local@_sender@_retain\ true or \local@_from@_check\ false.
26233 When a local message is received from an untrusted user and
26234 \local@_from@_check\ is true (the default), a check is made to see if the
26235 address given in the ::From:: header line is the correct (local) sender of the
26236 message. The address that is expected has the login name as the local part and
26237 the value of \qualify@_domain\ as the domain. Prefixes and suffixes for the
26238 local part can be permitted by setting \local@_from@_prefix\ and
26239 \local@_from@_suffix\ appropriately. If ::From:: does not contain the correct
26240 sender, a ::Sender:: line is added to the message.
26242 If you set \local@_from@_check\ false, this checking does not occur. However,
26243 the removal of an existing ::Sender:: line still happens, unless you also set
26244 \local@_sender@_retain\ to be true. It is not possible to set both of these
26245 options true at the same time.
26248 .index submission mode
26249 By default, no processing of ::Sender:: header lines is done for messages
26250 received over TCP/IP or for messages submitted by trusted users. However, when
26251 a message is received over TCP/IP in submission mode, and \sender@_retain\ is
26252 not specified on the submission control, the following processing takes place:
26254 First, any existing ::Sender:: lines are removed. Then, if the SMTP session is
26255 authenticated, and \$authenticated@_id$\ is not empty, a sender address is
26256 created as follows:
26258 If no domain is specified by the submission control, the local part is
26259 \$authenticated@_id$\ and the domain is \$qualify@_domain$\.
26261 If a non-empty domain is specified by the submission control, the local part is
26262 \$authenticated@_id$\, and the the domain is the specified domain.
26264 If an empty domain is specified by the submission control,
26265 \$authenticated@_id$\ is assumed to be the complete address.
26267 This address is compared with the address in the ::From:: header line. If they
26268 are different, a ::Sender:: header line containing the created address is
26269 added. Prefixes and suffixes for the local part in ::From:: can be permitted by
26270 setting \local@_from@_prefix\ and \local@_from@_suffix\ appropriately.
26274 .section Adding and removing header lines in routers and transports
26275 .index header lines||adding, in router or transport
26276 .index header lines||removing, in router or transport
26277 .rset SECTheadersaddrem "~~chapter.~~section"
26279 When a message is delivered, the addition and removal of header lines can be
26280 specified in a system filter, or on any of the routers and transports that
26281 process the message. Section ~~SECTaddremheasys contains details about
26282 modifying headers in a system filter.
26284 In contrast to what happens in a system filter, header modifications that are
26285 specified on routers and transports apply only to the particular recipient
26286 addresses that are being processed by those routers and transports. These
26287 changes do not actually take place until a copy of the message is being
26288 transported. Therefore, they do not affect the basic set of header lines, and
26289 they do not affect the values of the variables that refer to header lines.
26291 For both routers and transports, the result of expanding a \headers@_add\
26292 option must be in the form of one or more RFC 2822 header lines, separated by
26293 newlines (coded as `@\n'). For example:
26295 headers_add = X-added-header: added by $primary_hostname\n\
26296 X-added-second: another added header line
26298 Exim does not check the syntax of these added header lines.
26300 The result of expanding \headers@_remove\ must consist of a colon-separated
26301 list of header names. This is confusing, because header names themselves are
26302 often terminated by colons. In this case, the colons are the list separators,
26303 not part of the names. For example:
26305 headers_remove = return-receipt-to:acknowledge-to
26308 When \headers@_add\ or \headers@_remove\ is specified on a router, its value is
26309 expanded at routing time, and then associated with all addresses that are
26310 accepted by that router, and also with any new addresses that it generates. If
26311 an address passes through several routers as a result of aliasing or
26312 forwarding, the changes are cumulative.
26313 .index \unseen\ option
26314 However, this does not apply to multiple routers that result from the use of
26315 the \unseen\ option. Any header modifications that were specified by the
26316 `unseen' router or its predecessors apply only to the `unseen' delivery.
26318 Addresses that end up with different \headers@_add\ or \headers@_remove\
26319 settings cannot be delivered together in a batch, so a transport is always
26320 dealing with a set of addresses that have the same header-processing
26323 The transport starts by writing the original set of header lines that arrived
26324 with the message, possibly modified by the system filter. As it writes out
26325 these lines, it consults the list of header names that were attached to the
26326 recipient address(es) by \headers@_remove\ options in routers, and it also
26327 consults the transport's own \headers@_remove\ option. Header lines whose names
26328 are on either of these lists are not written out. If there are multiple
26329 instances of any listed header, they are all skipped.
26331 After the remaining original header lines have been written, new header
26332 lines that were specified by routers' \headers@_add\ options are written, in
26333 the order in which they were attached to the address. These are followed by any
26334 header lines specified by the transport's \headers@_add\ option.
26336 This way of handling header line modifications in routers and transports has
26337 the following consequences:
26339 The original set of header lines, possibly modified by the system filter,
26340 remains `visible', in the sense that the \$header@_$\\*xxx*\ variables refer to
26343 Header lines that are added by a router's
26344 \headers@_add\ option are not accessible by means of the \$header@_$\\*xxx*\
26345 expansion syntax in subsequent routers or the transport.
26347 Conversely, header lines that are specified for removal by \headers@_remove\ in
26348 a router remain visible to subsequent routers and the transport.
26350 Headers added to an address by \headers@_add\ in a router cannot be removed by
26351 a later router or by a transport.
26353 An added header can refer to the contents of an original header that is to be
26354 removed, even it has the same name as the added header. For example:
26356 headers_remove = subject
26357 headers_add = Subject: new subject (was: $h_subject:)
26361 \**Warning**\: The \headers@_add\ and \headers@_remove\ options cannot be used
26362 for a \%redirect%\ router that has the \one@_time\ option set.
26367 .section Constructed addresses
26368 .rset SECTconstr "~~chapter.~~section"
26369 .index address||constructed
26370 .index constructed address
26371 When Exim constructs a sender address for a locally-generated message, it uses
26374 <<user name>> <$$<<login>>@@<<qualify@_domain>>$$>
26378 Zaphod Beeblebrox <zaphod@end.univ.example>
26380 The user name is obtained from the \-F-\ command line option if set, or
26381 otherwise by looking up the calling user by \*getpwuid()*\ and extracting the
26382 `gecos' field from the password entry. If the `gecos' field contains an
26383 ampersand character, this is replaced by the login name with the first letter
26384 upper cased, as is conventional in a number of operating systems. See the
26385 \gecos@_name\ option for a way to tailor the handling of the `gecos' field. The
26386 \unknown@_username\ option can be used to specify user names in cases when
26387 there is no password file entry.
26389 In all cases, the user name is made to conform to RFC 2822 by quoting all or
26390 parts of it if necessary. In addition, if it contains any non-printing
26391 characters, it is encoded as described in RFC 2047, which defines a way of
26392 including non-ASCII characters in header lines.
26393 The value of the \headers@_charset\ option specifies the name of the encoding
26394 that is used (the characters are assumed to be in this encoding).
26395 The setting of \print@_topbitchars\ controls whether characters with the top
26396 bit set (that is, with codes greater than 127) count as printing characters or
26400 .section Case of local parts
26401 .index case of local parts
26402 .index local part||case of
26403 RFC 2822 states that the case of letters in the local parts of addresses cannot
26404 be assumed to be non-significant. Exim preserves the case of local parts of
26405 addresses, but by default it uses a lower-cased form when it is routing,
26406 because on most Unix systems, usernames are in lower case and case-insensitive
26407 routing is required. However, any particular router can be made to use the
26408 original case for local parts by setting the \caseful@_local@_part\ generic
26411 .index mixed-case login names
26412 If you must have mixed-case user names on your system, the best way to proceed,
26413 assuming you want case-independent handling of incoming email, is to set up
26414 your first router to convert incoming local parts in your domains to the
26415 correct case by means of a file lookup. For example:
26419 domains = +local_domains
26420 data = ${lookup{$local_part}cdb\
26421 {/etc/usercased.cdb}{$value}fail}\
26424 For this router, the local part is forced to lower case by the default action
26425 (\caseful@_local@_part\ is not set). The lower-cased local part is used to look
26426 up a new local part in the correct case. If you then set \caseful@_local@_part\
26427 on any subsequent routers which process your domains, they will operate on
26428 local parts with the correct case in a case-sensitive manner.
26431 .section Dots in local parts
26432 .index dot||in local part
26433 .index local part||dots in
26434 RFC 2822 forbids empty components in local parts. That is, an unquoted local
26435 part may not begin or end with a dot, nor have two consecutive dots in the
26436 middle. However, it seems that many MTAs do not enforce this, so Exim permits
26437 empty components for compatibility.
26440 .section Rewriting addresses
26441 .index rewriting||addresses
26442 Rewriting of sender and recipient addresses, and addresses in headers, can
26443 happen automatically, or as the result of configuration options, as described
26444 in chapter ~~CHAPrewrite. The headers that may be affected by this are ::Bcc::,
26445 ::Cc::, ::From::, ::Reply-To::, ::Sender::, and ::To::.
26447 Automatic rewriting includes qualification, as mentioned above. The other case
26448 in which it can happen is when an incomplete non-local domain is given. The
26449 routing process may cause this to be expanded into the full domain name. For
26450 example, a header such as
26454 might get rewritten as
26456 To: hare@teaparty.wonderland.fict.example
26458 Rewriting as a result of routing is the one kind of message processing that
26459 does not happen at input time, as it cannot be done until the address has
26462 Strictly, one should not do $it{any} deliveries of a message until all its
26463 addresses have been routed, in case any of the headers get changed as a
26464 result of routing. However, doing this in practice would hold up many
26465 deliveries for unreasonable amounts of time, just because one address could not
26466 immediately be routed. Exim therefore does not delay other deliveries when
26467 routing of one or more addresses is deferred.
26474 . ============================================================================
26475 .chapter SMTP processing
26476 .set runningfoot "smtp processing"
26477 .rset CHAPSMTP ~~chapter
26478 .index SMTP||processing details
26479 .index LMTP||processing details
26480 Exim supports a number of different ways of using the SMTP protocol, and its
26481 LMTP variant, which is an interactive protocol for transferring messages into a
26482 closed mail store application. This chapter contains details of how SMTP is
26483 processed. For incoming mail, the following are available:
26485 SMTP over TCP/IP (Exim daemon or \*inetd*\);
26487 SMTP over the standard input and output (the \-bs-\ option);
26489 Batched SMTP on the standard input (the \-bS-\ option).
26491 For mail delivery, the following are available:
26493 SMTP over TCP/IP (the \%smtp%\ transport);
26495 LMTP over TCP/IP (the \%smtp%\ transport with the \protocol\ option set to
26498 LMTP over a pipe to a process running in the local host (the \%lmtp%\
26501 Batched SMTP to a file or pipe (the \%appendfile%\ and \%pipe%\ transports with
26502 the \use@_bsmtp\ option set).
26504 \*Batched SMTP*\ is the name for a process in which batches of messages are
26505 stored in or read from files (or pipes), in a format in which SMTP commands are
26506 used to contain the envelope information.
26509 .section Outgoing SMTP and LMTP over TCP/IP
26510 .rset SECToutSMTPTCP "~~chapter.~~section"
26511 .index SMTP||outgoing over TCP/IP
26512 .index outgoing SMTP over TCP/IP
26513 .index LMTP||over TCP/IP
26514 .index outgoing LMTP over TCP/IP
26517 .index \\SIZE\\ option on \\MAIL\\ command
26518 Outgoing SMTP and LMTP over TCP/IP is implemented by the \%smtp%\ transport.
26519 The \protocol\ option selects which protocol is to be used, but the actual
26520 processing is the same in both cases.
26522 If, in response to its \\EHLO\\ command, Exim is told that the \\SIZE\\
26523 parameter is supported, it adds \\SIZE\\=<<n>> to each subsequent \\MAIL\\
26524 command. The value of <<n>> is the message size plus the value of the
26525 \size@_addition\ option (default 1024) to allow for additions to the message
26526 such as per-transport header lines, or changes made in a
26527 .index transport||filter
26528 .index filter||transport filter
26529 transport filter. If \size@_addition\ is set negative, the use of \\SIZE\\ is
26532 If the remote server advertises support for \\PIPELINING\\, Exim uses the
26533 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
26534 required for the transaction.
26536 If the remote server advertises support for the \\STARTTLS\\ command, and Exim
26537 was built to support TLS encryption, it tries to start a TLS session unless the
26538 server matches \hosts@_avoid@_tls\. See chapter ~~CHAPTLS for more details.
26540 If the remote server advertises support for the \\AUTH\\ command, Exim scans
26541 the authenticators configuration for any suitable client settings, as described
26542 in chapter ~~CHAPSMTPAUTH.
26544 .index carriage return
26546 Responses from the remote host are supposed to be terminated by CR followed by
26547 LF. However, there are known to be hosts that do not send CR characters, so in
26548 order to be able to interwork with such hosts, Exim treats LF on its own as a
26551 If a message contains a number of different addresses, all those with the same
26552 characteristics (for example, the same envelope sender) that resolve to the
26553 same set of hosts, in the same order, are sent in a single SMTP transaction,
26554 even if they are for different domains, unless there are more than the setting
26555 of the \max@_rcpts\ option in the \%smtp%\ transport allows, in which case they
26556 are split into groups containing no more than \max@_rcpts\ addresses each. If
26557 \remote@_max@_parallel\ is greater than one, such groups may be sent in
26558 parallel sessions. The order of hosts with identical MX values is not
26559 significant when checking whether addresses can be batched in this way.
26561 When the \%smtp%\ transport suffers a temporary failure that is not
26562 message-related, Exim updates its transport-specific database, which contains
26563 records indexed by host name that remember which messages are waiting for each
26564 particular host. It also updates the retry database with new retry times.
26565 .index hints database||retry keys
26566 Exim's retry hints are based on host name plus IP address, so if one address of
26567 a multi-homed host is broken, it will soon be skipped most of the time.
26568 See the next section for more detail about error handling.
26570 .index SMTP||passed connection
26571 .index SMTP||batching over TCP/IP
26572 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
26573 looks in the hints database for the transport to see if there are any queued
26574 messages waiting for the host to which it is connected. If it finds one, it
26575 creates a new Exim process using the \-MC-\ option (which can only be used by a
26576 process running as root or the Exim user) and passes the TCP/IP socket to it so
26577 that it can deliver another message using the same socket. The new process does
26578 only those deliveries that are routed to the connected host, and may in turn
26579 pass the socket on to a third process, and so on.
26581 The \connection@_max@_messages\ option of the \%smtp%\ transport can be used to
26582 limit the number of messages sent down a single TCP/IP connection.
26583 .index asterisk||after IP address
26584 The second and subsequent messages delivered down an existing connection are
26585 identified in the main log by the addition of an asterisk after the closing
26586 square bracket of the IP address.
26590 .section Errors in outgoing SMTP
26591 .rset SECToutSMTPerr "~~chapter.~~section"
26592 .index error||in outgoing SMTP
26593 .index SMTP||errors in outgoing
26595 Three different kinds of error are recognized for outgoing SMTP: host errors,
26596 message errors, and recipient errors.
26598 A host error is not associated with a particular message or with a
26599 particular recipient of a message. The host errors are:
26601 Connection refused or timed out,
26603 Any error response code on connection,
26605 Any error response code to \\EHLO\\ or \\HELO\\,
26607 Loss of connection at any time, except after `.',
26609 I/O errors at any time,
26611 Timeouts during the session, other than in response to \\MAIL\\, \\RCPT\\ or
26612 the `.' at the end of the data.
26614 For a host error, a permanent error response on connection, or in response to
26615 \\EHLO\\, causes all addresses routed to the host to be failed. Any other host
26616 error causes all addresses to be deferred, and retry data to be created for the
26617 host. It is not tried again, for any message, until its retry time arrives. If
26618 the current set of addresses are not all delivered in this run (to some
26619 alternative host), the message is added to the list of those waiting for this
26620 host, so if it is still undelivered when a subsequent successful delivery is
26621 made to the host, it will be sent down the same SMTP connection.
26623 .index message||error
26624 A message error is associated with a particular message when sent to a
26625 particular host, but not with a particular recipient of the message. The
26626 message errors are:
26628 Any error response code to \\MAIL\\, \\DATA\\, or the `.' that terminates
26631 Timeout after \\MAIL\\,
26634 or loss of connection after the `.' that terminates the data. A timeout after
26635 the \\DATA\\ command itself is treated as a host error, as is loss of
26636 connection at any other time.
26638 For a message error, a permanent error response (5$it{xx}) causes all addresses
26639 to be failed, and a delivery error report to be returned to the sender. A
26640 temporary error response (4$it{xx}), or one of the timeouts, causes all
26641 addresses to be deferred. Retry data is not created for the host, but instead,
26642 a retry record for the combination of host plus message id is created. The
26643 message is not added to the list of those waiting for this host. This ensures
26644 that the failing message will not be sent to this host again until the retry
26645 time arrives. However, other messages that are routed to the host are not
26646 affected, so if it is some property of the message that is causing the error,
26647 it will not stop the delivery of other mail.
26649 If the remote host specified support for the \\SIZE\\ parameter in its response
26650 to \\EHLO\\, Exim adds SIZE=$it{nnn} to the \\MAIL\\ command, so an
26651 over-large message will cause a message error because the error arrives as a
26652 response to \\MAIL\\.
26654 .index recipient||error
26655 A recipient error is associated with a particular recipient of a message. The
26656 recipient errors are:
26658 Any error response to \\RCPT\\,
26660 Timeout after \\RCPT\\.
26662 For a recipient error, a permanent error response (5$it{xx}) causes the
26663 recipient address to be failed, and a bounce message to be returned to the
26664 sender. A temporary error response (4$it{xx}) or a timeout causes the failing
26665 address to be deferred, and routing retry data to be created for it. This is
26666 used to delay processing of the address in subsequent queue runs, until its
26667 routing retry time arrives. This applies to all messages, but because it
26668 operates only in queue runs, one attempt will be made to deliver a new message
26669 to the failing address before the delay starts to operate. This ensures that,
26670 if the failure is really related to the message rather than the recipient
26671 (`message too big for this recipient' is a possible example), other messages
26672 have a chance of getting delivered. If a delivery to the address does succeed,
26673 the retry information gets cleared, so all stuck messages get tried again, and
26674 the retry clock is reset.
26676 The message is not added to the list of those waiting for this host. Use of the
26677 host for other messages is unaffected, and except in the case of a timeout,
26678 other recipients are processed independently, and may be successfully delivered
26679 in the current SMTP session. After a timeout it is of course impossible to
26680 proceed with the session, so all addresses get deferred. However, those other
26681 than the one that failed do not suffer any subsequent retry delays. Therefore,
26682 if one recipient is causing trouble, the others have a chance of getting
26683 through when a subsequent delivery attempt occurs before the failing
26684 recipient's retry time.
26687 In all cases, if there are other hosts (or IP addresses) available for the
26688 current set of addresses (for example, from multiple MX records), they are
26689 tried in this run for any undelivered addresses, subject of course to their
26690 own retry data. In other words, recipient error retry data does not take effect
26691 until the next delivery attempt.
26693 Some hosts have been observed to give temporary error responses to every
26694 \\MAIL\\ command at certain times (`insufficient space' has been seen). It
26695 would be nice if such circumstances could be recognized, and defer data for the
26696 host itself created, but this is not possible within the current Exim design.
26697 What actually happens is that retry data for every (host, message) combination
26700 The reason that timeouts after \\MAIL\\ and \\RCPT\\ are treated specially is
26701 that these can sometimes arise as a result of the remote host's verification
26702 procedures. Exim makes this assumption, and treats them as if a temporary error
26703 response had been received. A timeout after `.' is treated specially because it
26704 is known that some broken implementations fail to recognize the end of the
26705 message if the last character of the last line is a binary zero. Thus, it is
26706 helpful to treat this case as a message error.
26708 Timeouts at other times are treated as host errors, assuming a problem with the
26709 host, or the connection to it. If a timeout after \\MAIL\\, \\RCPT\\,
26710 or `.' is really a connection problem, the assumption is that at the next try
26711 the timeout is likely to occur at some other point in the dialogue, causing it
26712 then to be treated as a host error.
26714 There is experimental evidence that some MTAs drop the connection after the
26715 terminating `.' if they do not like the contents of the message for some
26716 reason, in contravention of the RFC, which indicates that a 5$it{xx} response
26717 should be given. That is why Exim treats this case as a message rather than a
26718 host error, in order not to delay other messages to the same host.
26723 .section Variable Envelope Return Paths (VERP)
26725 .index Variable Envelope Return Paths
26726 .index envelope sender
26727 Variable Envelope Return Paths -- see
26728 \?ftp://koobera.math.uic.edu/www/proto/verp.txt?\ -- can be supported in Exim
26729 by using the \return@_path\ generic transport option to rewrite the return path
26730 at transport time. For example, the following could be used on an \%smtp%\
26734 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
26735 {$1-request=$local_part%$domain@your.dom.example}fail}
26737 This has the effect of rewriting the return path (envelope sender) on all
26738 outgoing SMTP messages, if the local part of the original return path ends in
26739 `-request', and the domain is \*your.dom.example*\. The rewriting inserts the
26740 local part and domain of the recipient into the return path. Suppose, for
26741 example, that a message whose return path has been set to
26742 \*somelist-request@@your.dom.example*\ is sent to
26743 \*subscriber@@other.dom.example*\. In the transport, the return path is
26746 somelist-request=subscriber%other.dom.example@your.dom.example
26748 For this to work, you must arrange for outgoing messages that have `-request'
26749 in their return paths to have just a single recipient. This can be done by
26754 in the \%smtp%\ transport. Otherwise a single copy of a message might be
26755 addressed to several different recipients in the same domain, in which case
26756 \$local@_part$\ is not available (because it is not unique). Of course, if you
26757 do start sending out messages with this kind of return path, you must also
26758 configure Exim to accept the bounce messages that come back to those paths.
26759 Typically this would be done by setting an \local@_part@_suffix\ option for a
26762 The overhead incurred in using VERP depends very much on the size of the
26763 message, the number of recipient addresses that resolve to the same remote
26764 host, and the speed of the connection over which the message is being sent. If
26765 a lot of addresses resolve to the same host and the connection is slow, sending
26766 a separate copy of the message for each address may take substantially longer
26767 than sending a single copy with many recipients (for which VERP cannot be
26771 .section Incoming SMTP messages over TCP/IP
26772 .index SMTP||incoming over TCP/IP
26773 .index incoming SMTP over TCP/IP
26776 Incoming SMTP messages can be accepted in one of two ways: by running a
26777 listening daemon, or by using \*inetd*\. In the latter case, the entry in
26778 \(/etc/inetd.conf)\ should be like this:
26780 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
26782 Exim distinguishes between this case and the case of a locally running user
26783 agent using the \-bs-\ option by checking whether or not the standard input is
26784 a socket. When it is, either the port must be privileged (less than 1024), or
26785 the caller must be root or the Exim user. If any other user passes a socket
26786 with an unprivileged port number, Exim prints a message on the standard error
26787 stream and exits with an error code.
26789 By default, Exim does not make a log entry when a remote host connects or
26790 disconnects (either via the daemon or \*inetd*\), unless the disconnection is
26791 unexpected. It can be made to write such log entries by setting the
26792 \smtp@_connection\ log selector.
26794 .index carriage return
26796 Commands from the remote host are supposed to be terminated by CR followed by
26797 LF. However, there are known to be hosts that do not send CR characters. In
26798 order to be able to interwork with such hosts, Exim treats LF on its own as a
26800 Furthermore, because common code is used for receiving messages from all
26801 sources, a CR on its own is also interpreted as a line terminator. However, the
26802 sequence `CR, dot, CR' does not terminate incoming SMTP data.
26804 .index \\EHLO\\||invalid data
26805 .index \\HELO\\||invalid data
26806 One area that sometimes gives rise to problems concerns the \\EHLO\\ or
26807 \\HELO\\ commands. Some clients send syntactically invalid versions of these
26808 commands, which Exim rejects by default. (This is nothing to do with verifying
26809 the data that is sent, so \helo@_verify@_hosts\ is not relevant.) You can tell
26810 Exim not to apply a syntax check by setting \helo@_accept@_junk@_hosts\ to
26811 match the broken hosts that send invalid commands.
26813 .index \\SIZE\\ option on \\MAIL\\ command
26814 .index \\MAIL\\||\\SIZE\\ option
26815 The amount of disk space available is checked whenever \\SIZE\\ is received on
26816 a \\MAIL\\ command, independently of whether \message@_size@_limit\ or
26817 \check@_spool@_space\ is configured, unless \smtp__check__spool__space\ is set
26818 false. A temporary error is given if there is not enough space. If
26819 \check@_spool@_space\ is set, the check is for that amount of space plus the
26820 value given with \\SIZE\\, that is, it checks that the addition of the incoming
26821 message will not reduce the space below the threshold.
26823 When a message is successfully received, Exim includes the local message id in
26824 its response to the final `.' that terminates the data. If the remote host logs
26825 this text it can help with tracing what has happened to a message.
26827 The Exim daemon can limit the number of simultaneous incoming connections it is
26828 prepared to handle (see the \smtp@_accept@_max\ option). It can also limit the
26829 number of simultaneous incoming connections from a single remote host (see the
26830 \smtp@_accept@_max@_per@_host\ option). Additional connection attempts are
26831 rejected using the SMTP temporary error code 421.
26833 The Exim daemon does not rely on the \\SIGCHLD\\ signal to detect when a
26834 subprocess has finished, as this can get lost at busy times. Instead, it looks
26835 for completed subprocesses every time it wakes up. Provided there are other
26836 things happening (new incoming calls, starts of queue runs), completed
26837 processes will be noticed and tidied away. On very quiet systems you may
26838 sometimes see a `defunct' Exim process hanging about. This is not a problem; it
26839 will be noticed when the daemon next wakes up.
26841 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
26842 and can also be set up to reject SMTP calls from non-reserved hosts at times of
26843 high system load -- for details see the \smtp@_accept@_reserve\,
26844 \smtp@_load@_reserve\, and \smtp@_reserve@_hosts\ options. The load check
26845 applies in both the daemon and \*inetd*\ cases.
26847 Exim normally starts a delivery process for each message received, though this
26848 can be varied by means of the \-odq-\ command line option and the
26849 \queue@_only\, \queue@_only@_file\, and \queue@_only@_load\ options. The number
26850 of simultaneously running delivery processes started in this way from SMTP
26851 input can be limited by the \smtp__accept__queue\ and
26852 \smtp__accept__queue__per__connection\ options. When either limit is reached,
26853 subsequently received messages are just put on the input queue without starting
26854 a delivery process.
26856 The controls that involve counts of incoming SMTP calls (\smtp@_accept@_max\,
26857 \smtp@_accept@_queue\, \smtp__accept__reserve\) are not available when Exim is
26858 started up from the \*inetd*\ daemon, because in that case each connection is
26859 handled by an entirely independent Exim process. Control by load average is,
26860 however, available with \*inetd*\.
26862 Exim can be configured to verify addresses in incoming SMTP commands as they
26863 are received. See chapter ~~CHAPACL for details. It can also be configured to
26864 rewrite addresses at this time -- before any syntax checking is done. See
26865 section ~~SECTrewriteS.
26867 Exim can also be configured to limit the rate at which a client host submits
26868 \\MAIL\\ and \\RCPT\\ commands in a single SMTP session. See the
26869 \smtp@_ratelimit@_hosts\ option.
26872 .section Unrecognized SMTP commands
26873 .index SMTP||unrecognized commands
26874 If Exim receives more than \smtp@_max@_unknown@_commands\ unrecognized SMTP
26875 commands during a single SMTP connection, it drops the connection after sending
26876 the error response to the last command. The default value for
26877 \smtp@_max@_unknown@_commands\ is 3. This is a defence against some kinds of
26878 abuse that subvert web servers into making connections to SMTP ports; in these
26879 circumstances, a number of non-SMTP lines are sent first.
26881 .section Syntax and protocol errors in SMTP commands
26882 .index SMTP||syntax errors
26883 .index SMTP||protocol errors
26884 A syntax error is detected if an SMTP command is recognized, but there is
26885 something syntactically wrong with its data, for example, a malformed email
26886 address in a \\RCPT\\ command. Protocol errors include invalid command
26887 sequencing such as \\RCPT\\ before \\MAIL\\. If Exim receives more than
26888 \smtp@_max@_synprot@_errors\ such commands during a single SMTP connection, it
26889 drops the connection after sending the error response to the last command. The
26890 default value for \smtp__max__synprot__errors\ is 3. This is a defence against
26891 broken clients that loop sending bad commands (yes, it has been seen).
26894 .section Use of non-mail SMTP commands
26895 .index SMTP||non-mail commands
26896 The `non-mail' SMTP commands are those other than \\MAIL\\, \\RCPT\\, and
26897 \\DATA\\. Exim counts such commands, and drops the connection if there are too
26898 many of them in a single SMTP session. This action catches some
26899 denial-of-service attempts and things like repeated failing \\AUTH\\s, or a mad
26900 client looping sending \\EHLO\\. The global option \smtp@_accept@_max@_nonmail\
26901 defines what `too many' means. Its default value is 10.
26903 When a new message is expected, one occurrence of \\RSET\\ is not counted. This
26904 allows a client to send one \\RSET\\ between messages (this is not necessary,
26905 but some clients do it). Exim also allows one uncounted occurence of \\HELO\\
26906 or \\EHLO\\, and one occurrence of \\STARTTLS\\ between messages. After
26907 starting up a TLS session, another \\EHLO\\ is expected, and so it too is not
26910 The first occurrence of \\AUTH\\ in a connection, or immediately following
26911 \\STARTTLS\\ is also not counted. Otherwise, all commands other than \\MAIL\\,
26912 \\RCPT\\, \\DATA\\, and \\QUIT\\ are counted.
26914 You can control which hosts are subject to the limit set by
26915 \smtp@_accept@_max@_nonmail\ by setting
26916 \smtp@_accept@_max@_nonmail@_hosts\. The default value is \"$*$"\, which makes
26917 the limit apply to all hosts. This option means that you can exclude any
26918 specific badly-behaved hosts that you have to live with.
26922 .section The \\VRFY\\ and \\EXPN\\ commands
26923 When Exim receives a \\VRFY\\ or \\EXPN\\ command on a TCP/IP connection, it
26924 runs the ACL specified by \acl@_smtp@_vrfy\ or \acl@_smtp@_expn\ (as
26925 appropriate) in order to decide whether the command should be accepted or not.
26926 If no ACL is defined, the command is rejected.
26928 .index \\VRFY\\||processing
26929 When \\VRFY\\ is accepted, it runs exactly the same code as when Exim is
26930 called with the \-bv-\ option.
26931 .index \\EXPN\\||processing
26932 When \\EXPN\\ is accepted, a single-level expansion of the address is done.
26933 \\EXPN\\ is treated as an `address test' (similar to the \-bt-\ option) rather
26934 than a verification (the \-bv-\ option). If an unqualified local part is given
26935 as the argument to \\EXPN\\, it is qualified with \qualify@_domain\. Rejections
26936 of \\VRFY\\ and \\EXPN\\ commands are logged on the main and reject logs, and
26937 \\VRFY\\ verification failures are logged on the main log for consistency with
26941 .section The \\ETRN\\ command
26942 .rset SECTETRN "~~chapter.~~section"
26943 .index \\ETRN\\||processing
26944 RFC 1985 describes an SMTP command called \\ETRN\\ that is designed to
26945 overcome the security problems of the \\TURN\\ command (which has fallen into
26946 disuse). When Exim receives an \\ETRN\\ command on a TCP/IP connection, it runs
26947 the ACL specified by \acl@_smtp@_etrn\ in order to decide whether the command
26948 should be accepted or not. If no ACL is defined, the command is rejected.
26950 The \\ETRN\\ command is concerned with `releasing' messages that are awaiting
26951 delivery to certain hosts. As Exim does not organize its message queue by host,
26952 the only form of \\ETRN\\ that is supported by default is the one where the
26953 text starts with the `@#' prefix, in which case the remainder of the text is
26954 specific to the SMTP server. A valid \\ETRN\\ command causes a run of Exim with
26955 the \-R-\ option to happen, with the remainder of the \\ETRN\\ text as its
26956 argument. For example,
26964 which causes a delivery attempt on all messages with undelivered addresses
26965 containing the text `brigadoon'. When \smtp@_etrn@_serialize\ is set (the
26966 default), Exim prevents the simultaneous execution of more than one queue run
26967 for the same argument string as a result of an \\ETRN\\ command. This stops
26968 a misbehaving client from starting more than one queue runner at once.
26970 .index hints database||\\ETRN\\ serialization
26971 Exim implements the serialization by means of a hints database in which a
26972 record is written whenever a process is started by \\ETRN\\, and deleted when
26973 the process completes. However, Exim does not keep the SMTP session waiting for
26974 the \\ETRN\\ process to complete. Once \\ETRN\\ is accepted, the client is sent
26975 a `success' return code. Obviously there is scope for hints records to get left
26976 lying around if there is a system or program crash. To guard against this, Exim
26977 ignores any records that are more than six hours old.
26979 .index \smtp@_etrn@_command\
26980 For more control over what \\ETRN\\ does, the \smtp@_etrn@_command\ option can
26981 used. This specifies a command that is run whenever \\ETRN\\ is received,
26982 whatever the form of its argument. For
26985 smtp_etrn_command = /etc/etrn_command $domain $sender_host_address
26987 The string is split up into arguments which are independently expanded. The
26988 expansion variable \$domain$\ is set to the argument of the \\ETRN\\ command,
26989 and no syntax checking is done on the contents of this argument. Exim does not
26990 wait for the command to complete, so its status code is not checked. Exim runs
26991 under its own uid and gid when receiving incoming SMTP, so it is not possible
26992 for it to change them before running the command.
26995 .section Incoming local SMTP
26996 .index SMTP||local incoming
26997 Some user agents use SMTP to pass messages to their local MTA using the
26998 standard input and output, as opposed to passing the envelope on the command
26999 line and writing the message to the standard input. This is supported by the
27000 \-bs-\ option. This form of SMTP is handled in the same way as incoming
27001 messages over TCP/IP (including the use of ACLs), except that the envelope
27002 sender given in a \\MAIL\\ command is ignored unless the caller is trusted. In
27003 an ACL you can detect this form of SMTP input by testing for an empty host
27004 identification. It is common to have this as the first line in the ACL that
27005 runs for \\RCPT\\ commands:
27009 This accepts SMTP messages from local processes without doing any other tests.
27012 .section Outgoing batched SMTP
27013 .rset SECTbatchSMTP "~~chapter.~~section"
27014 .index SMTP||batched outgoing
27015 .index batched SMTP output
27016 Both the \%appendfile%\ and \%pipe%\ transports can be used for handling batched
27017 SMTP. Each has an option called \use@_bsmtp\ which causes messages to be output
27018 in BSMTP format. No SMTP responses are possible for this form of delivery. All
27019 it is doing is using SMTP commands as a way of transmitting the envelope along
27022 The message is written to the file or pipe preceded by the SMTP commands
27023 \\MAIL\\ and \\RCPT\\, and followed by a line containing a single dot. Lines in
27024 the message that start with a dot have an extra dot added. The SMTP command
27025 \\HELO\\ is not normally used. If it is required, the \message@_prefix\ option
27026 can be used to specify it.
27028 Because \%appendfile%\ and \%pipe%\ are both local transports, they accept only
27029 one recipient address at a time by default. However, you can arrange for them
27030 to handle several addresses at once by setting the \batch@_max\ option. When
27031 this is done for BSMTP, messages may contain multiple \\RCPT\\ commands. See
27032 chapter ~~CHAPbatching for more details.
27034 When one or more addresses are routed to a BSMTP transport by a router that
27035 sets up a host list, the name of the first host on the list is available to the
27036 transport in the variable \$host$\. Here is an example of such a transport and
27041 driver = manualroute
27042 transport = smtp_appendfile
27043 route_list = domain.example batch.host.example
27047 driver = appendfile
27048 directory = /var/bsmtp/$host
27053 This causes messages addressed to \*domain.example*\ to be written in BSMTP
27054 format to \(/var/bsmtp/batch.host.example)\, with only a single copy of each
27055 message (unless there are more than 1000 recipients).
27058 .section Incoming batched SMTP
27059 .rset SECTincomingbatchedSMTP "~~chapter.~~section"
27060 .index SMTP||batched incoming
27061 .index batched SMTP input
27062 The \-bS-\ command line option causes Exim to accept one or more messages by
27063 reading SMTP on the standard input, but to generate no responses. If the caller
27064 is trusted, the senders in the \\MAIL\\ commands are believed; otherwise the
27065 sender is always the caller of Exim. Unqualified senders and receivers are not
27066 rejected (there seems little point) but instead just get qualified. \\HELO\\
27067 and \\EHLO\\ act as \\RSET\\; \\VRFY\\, \\EXPN\\, \\ETRN\\ and \\HELP\\, act
27068 as \\NOOP\\; \\QUIT\\ quits.
27070 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
27071 In this respect it is like non-SMTP local input.
27073 If an error is detected while reading a message, including a missing `.' at
27074 the end, Exim gives up immediately. It writes details of the error to the
27075 standard output in a stylized way that the calling program should be able to
27076 make some use of automatically, for example:
27078 554 Unexpected end of file
27079 Transaction started in line 10
27080 Error detected in line 14
27082 It writes a more verbose version, for human consumption, to the standard error
27085 An error was detected while processing a file of BSMTP input.
27086 The error message was:
27088 501 '>' missing at end of address
27090 The SMTP transaction started in line 10.
27091 The error was detected in line 12.
27092 The SMTP command at fault was:
27094 rcpt to:<malformed@in.com.plete
27096 1 previous message was successfully processed.
27097 The rest of the batch was abandoned.
27099 The return code from Exim is zero only if there were no errors. It is 1 if some
27100 messages were accepted before an error was detected, and 2 if no messages were
27109 . ============================================================================
27110 .chapter Customizing bounce and warning messages
27111 .set runningfoot "customizing messages"
27112 .rset CHAPemsgcust "~~chapter"
27113 When a message fails to be delivered, or remains on the queue for more than a
27114 configured amount of time, Exim sends a message to the original sender, or
27115 to an alternative configured address. The text of these messages is built into
27116 the code of Exim, but it is possible to change it, either by adding a single
27117 string, or by replacing each of the paragraphs by text supplied in a file.
27119 The ::From:: and ::To:: header lines are automatically generated; you can cause
27120 a ::Reply-To:: line to be added by setting the \errors@_reply@_to\ option. Exim
27123 Auto-Submitted: auto-generated
27125 to all warning and bounce messages,
27127 .section Customizing bounce messages
27128 .index customizing||bounce message
27129 .index bounce message||customizing
27130 If \bounce@_message@_text\ is set, its contents are included in the default
27131 message immediately after `This message was created automatically by mail
27132 delivery software.' The string is not expanded. It is not used if
27133 \bounce@_message@_file\ is set.
27135 When \bounce@_message@_file\ is set, it must point to a template file for
27136 constructing error messages. The file consists of a series of text items,
27137 separated by lines consisting of exactly four asterisks. If the file cannot be
27138 opened, default text is used and a message is written to the main and panic
27139 logs. If any text item in the file is empty, default text is used for that
27142 Each item of text that is read from the file is expanded, and there are two
27143 expansion variables which can be of use here: \$bounce@_recipient$\ is set to
27144 the recipient of an error message while it is being created, and
27145 \$return@_size@_limit$\ contains the value of the \return@_size@_limit\ option,
27146 rounded to a whole number.
27148 The items must appear in the file in the following order:
27150 The first item is included in the headers, and should include at least a
27151 ::Subject:: header. Exim does not check the syntax of these headers.
27153 The second item forms the start of the error message. After it, Exim lists the
27154 failing addresses with their error messages.
27156 The third item is used to introduce any text from pipe transports that is to be
27157 returned to the sender. It is omitted if there is no such text.
27159 The fourth item is used to introduce the copy of the message that is returned
27160 as part of the error report.
27162 The fifth item is added after the fourth one if the returned message is
27163 truncated because it is bigger than \return@_size@_limit\.
27165 The sixth item is added after the copy of the original message.
27167 The default state (\bounce@_message@_file\ unset) is equivalent to the
27168 following file, in which the sixth item is empty. The ::Subject:: line has been
27169 split into two here in order to fit it on the page:
27180 Subject: Mail delivery failed
27181 ${if eq{$sender_address}{$bounce_recipient}{: returning message to sender}}
27183 This message was created automatically by mail delivery software.
27185 A message ${if eq{$sender_address}{$bounce_recipient}{that you sent }{sent by
27189 }}could not be delivered to all of its recipients.
27190 The following address(es) failed:
27192 The following text was generated during the delivery attempt(s):
27194 ------ This is a copy of the message, including all the headers. ------
27196 ------ The body of the message is $message_size characters long; only the first
27197 ------ $return_size_limit or so are included here.
27204 .section Customizing warning messages
27205 .rset SECTcustwarn "~~chapter.~~section"
27206 .index customizing||warning message
27207 .index warning of delay||customizing the message
27209 \warn@_message@_file\
27210 can be pointed at a template file for use when
27211 warnings about message delays are created. In this case there are only three
27214 The first item is included in the headers, and should include at least a
27215 ::Subject:: header. Exim does not check the syntax of these headers.
27217 The second item forms the start of the warning message. After it, Exim lists
27218 the delayed addresses.
27220 The third item then ends the message.
27222 The default state is equivalent to the following file, except that the line
27223 starting `A message' has been split here, in order to fit it on the page:
27235 Subject: Warning: message $message_id delayed $warn_message_delay
27237 This message was created automatically by mail delivery software.
27239 A message ${if eq{$sender_address}{$warn_message_recipients}
27240 {that you sent }{sent by
27244 }}has not been delivered to all of its recipients after
27245 more than $warn_message_delay on the queue on $primary_hostname.
27248 The message identifier is: $message_id
27249 The subject of the message is: $h_subject
27250 The date of the message is: $h_date
27252 The following address(es) have not yet been delivered:
27254 No action is required on your part. Delivery attempts will continue for
27255 some time, and this warning may be repeated at intervals if the message
27256 remains undelivered. Eventually the mail delivery software will give up,
27257 and when that happens, the message will be returned to you.
27262 except that in the default state the subject and date lines are omitted if no
27263 appropriate headers exist. During the expansion of this file,
27264 \$warn@_message@_delay$\
27265 is set to the delay time in one of the forms `<<n>> minutes'
27266 or `<<n>> hours', and
27267 \$warn@_message@_recipients$\
27268 contains a list of recipients for the warning message. There may be more than
27269 one if there are multiple addresses with different \errors@_to\ settings on the
27270 routers that handled them.
27278 . ============================================================================
27279 .chapter Some common configuration requirements
27280 .set runningfoot "common configuration requirements"
27281 .rset CHAPcomconreq "~~chapter"
27282 This chapter discusses some configuration requirements that seem to be fairly
27283 common. More examples and discussion can be found in the Exim book.
27286 .section Sending mail to a smart host
27287 .index smart host||example router
27288 If you want to send all mail for non-local domains to a `smart host', you
27289 should replace the default \%dnslookup%\ router with a router which does the
27290 routing explicitly:
27292 send_to_smart_host:
27293 driver = manualroute
27294 route_list = !+local_domains smart.host.name
27295 transport = remote_smtp
27297 You can use the smart host's IP address instead of the name if you wish.
27299 If you are using Exim only to submit messages to a smart host, and not for
27300 receiving incoming messages, you can arrange for it to do the submission
27301 synchronously by setting the \mua@_wrapper\ option (see chapter
27302 ~~CHAPnonqueueing).
27306 .section Using Exim to handle mailing lists
27307 .rset SECTmailinglists "~~chapter.~~section"
27308 .index mailing lists
27309 Exim can be used to run simple mailing lists, but for large and/or complicated
27310 requirements, the use of additional specialized mailing list software such as
27311 Majordomo or Mailman is recommended.
27313 The \%redirect%\ router can be used to handle mailing lists where each list
27314 is maintained in a separate file, which can therefore be managed by an
27315 independent manager. The \domains\ router option can be used to run these
27316 lists in a separate domain from normal mail. For example:
27320 domains = lists.example
27321 file = /usr/lists/$local_part
27324 errors_to = $local_part-request@lists.example
27327 This router is skipped for domains other than \*lists.example*\. For addresses
27328 in that domain, it looks for a file that matches the local part. If there is no
27329 such file, the router declines, but because \no@_more\ is set, no subsequent
27330 routers are tried, and so the whole delivery fails.
27332 The \forbid@_pipe\ and \forbid@_file\ options prevent a local part from being
27333 expanded into a file name or a pipe delivery, which is usually inappropriate in
27336 .index \errors@_to\
27337 The \errors@_to\ option specifies that any delivery errors caused by addresses
27338 taken from a mailing list are to be sent to the given address rather than the
27339 original sender of the message. However, before acting on this, Exim verifies
27340 the error address, and ignores it if verification fails.
27342 For example, using the configuration above, mail sent to
27343 \*dicts@@lists.example*\ is passed on to those addresses contained in
27344 \(/usr/lists/dicts)\, with error reports directed to
27345 \*dicts-request@@lists.example*\, provided that this address can be verified.
27346 There could be a file called \(/usr/lists/dicts-request)\ containing
27347 the address(es) of this particular list's manager(s), but other approaches,
27348 such as setting up an earlier router (possibly using the \local@_part@_prefix\
27349 or \local@_part@_suffix\ options) to handle addresses of the form \owner-xxx\
27350 or \xxx-request\, are also possible.
27353 .section Syntax errors in mailing lists
27354 .index mailing lists||syntax errors in
27355 If an entry in redirection data contains a syntax error, Exim normally defers
27356 delivery of the original address. That means that a syntax error in a mailing
27357 list holds up all deliveries to the list. This may not be appropriate when a
27358 list is being maintained automatically from data supplied by users, and the
27359 addresses are not rigorously checked.
27361 If the \skip@_syntax@_errors\ option is set, the \%redirect%\ router just skips
27362 entries that fail to parse, noting the incident in the log. If in addition
27363 \syntax@_errors@_to\ is set to a verifiable address, a message is sent to it
27364 whenever a broken address is skipped. It is usually appropriate to set
27365 \syntax@_errors@_to\ to the same address as \errors@_to\.
27368 .section Re-expansion of mailing lists
27369 .index mailing lists||re-expansion of
27370 Exim remembers every individual address to which a message has been delivered,
27371 in order to avoid duplication, but it normally stores only the original
27372 recipient addresses with a message. If all the deliveries to a mailing list
27373 cannot be done at the first attempt, the mailing list is re-expanded when the
27374 delivery is next tried. This means that alterations to the list are taken into
27375 account at each delivery attempt, so addresses that have been added to
27376 the list since the message arrived will therefore receive a copy of the
27377 message, even though it pre-dates their subscription.
27379 If this behaviour is felt to be undesirable, the \one@_time\ option can be set
27380 on the \%redirect%\ router. If this is done, any addresses generated by the
27381 router that fail to deliver at the first attempt are added to the message as
27382 `top level' addresses, and the parent address that generated them is marked
27383 `delivered'. Thus, expansion of the mailing list does not happen again at the
27384 subsequent delivery attempts. The disadvantage of this is that if any of the
27385 failing addresses are incorrect, correcting them in the file has no effect on
27386 pre-existing messages.
27388 The original top-level address is remembered with each of the generated
27389 addresses, and is output in any log messages. However, any intermediate parent
27390 addresses are not recorded. This makes a difference to the log only if the
27391 \all@_parents\ selector is set, but for mailing lists there is normally only
27392 one level of expansion anyway.
27395 .section Closed mailing lists
27396 .index mailing lists||closed
27397 The examples so far have assumed open mailing lists, to which anybody may
27398 send mail. It is also possible to set up closed lists, where mail is accepted
27399 from specified senders only. This is done by making use of the generic
27400 \senders\ option to restrict the router that handles the list.
27402 The following example uses the same file as a list of recipients and as a list
27403 of permitted senders. It requires three routers:
27407 domains = lists.example
27408 local_part_suffix = -request
27409 file = /usr/lists/$local_part$local_part_suffix
27414 domains = lists.example
27415 senders = ${if exists {/usr/lists/$local_part}\
27416 {lsearch;/usr/lists/$local_part}{*}}
27417 file = /usr/lists/$local_part
27420 errors_to = $local_part-request@lists.example
27425 domains = lists.example
27427 data = :fail: $local_part@lists.example is a closed mailing list
27429 All three routers have the same \domains\ setting, so for any other domains,
27430 they are all skipped. The first router runs only if the local part ends in
27431 \@-request\. It handles messages to the list manager(s) by means of an open
27434 The second router runs only if the \senders\ precondition is satisfied. It
27435 checks for the existence of a list that corresponds to the local part, and then
27436 checks that the sender is on the list by means of a linear search. It is
27437 necessary to check for the existence of the file before trying to search it,
27438 because otherwise Exim thinks there is a configuration error. If the file does
27439 not exist, the expansion of \senders\ is $*$, which matches all senders. This
27440 means that the router runs, but because there is no list, declines, and
27441 \no@_more\ ensures that no further routers are run. The address fails with an
27442 `unrouteable address' error.
27444 The third router runs only if the second router is skipped, which happens when
27445 a mailing list exists, but the sender is not on it. This router forcibly fails
27446 the address, giving a suitable error message.
27450 .section Virtual domains
27451 .rset SECTvirtualdomains "~~chapter.~~section"
27452 .index virtual domains
27453 .index domain||virtual
27454 The phrase \*virtual domain*\ is unfortunately used with two rather different
27457 A domain for which there are no real mailboxes; all valid local parts are
27458 aliases for other email addresses. Common examples are organizational
27459 top-level domains and `vanity' domains.
27461 One of a number of independent domains that are all handled by the same host,
27462 with mailboxes on that host, but where the mailbox owners do not necessarily
27463 have login accounts on that host.
27465 The first usage is probably more common, and does seem more `virtual' than the
27466 second. This kind of domain can be handled in Exim with a straightforward
27467 aliasing router. One approach is to create a separate alias file for each
27468 virtual domain. Exim can test for the existence of the alias file to determine
27469 whether the domain exists. The \%dsearch%\ lookup type is useful here, leading
27470 to a router of this form:
27474 domains = dsearch;/etc/mail/virtual
27475 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
27478 The \domains\ option specifies that the router is to be skipped, unless there
27479 is a file in the \(/etc/mail/virtual)\ directory whose name is the same as the
27480 domain that is being processed. When the router runs, it looks up the local
27481 part in the file to find a new address (or list of addresses). The \no@_more\
27482 setting ensures that if the lookup fails (leading to \data\ being an empty
27483 string), Exim gives up on the address without trying any subsequent routers.
27485 This one router can handle all the virtual domains because the alias file names
27486 follow a fixed pattern. Permissions can be arranged so that appropriate people
27487 can edit the different alias files. A successful aliasing operation results in
27488 a new envelope recipient address, which is then routed from scratch.
27490 The other kind of `virtual' domain can also be handled in a straightforward
27491 way. One approach is to create a file for each domain containing a list of
27492 valid local parts, and use it in a router like this:
27496 domains = dsearch;/etc/mail/domains
27497 local_parts = lsearch;/etc/mail/domains/$domain
27498 transport = my_mailboxes
27500 The address is accepted if there is a file for the domain, and the local part
27501 can be found in the file. The \domains\ option is used to check for the file's
27502 existence because \domains\ is tested before the \local@_parts\ option (see
27503 section ~~SECTrouprecon). You can't use \require@_files\, because that option
27504 is tested after \local@_parts\. The transport is as follows:
27507 driver = appendfile
27508 file = /var/mail/$domain/$local_part
27511 This uses a directory of mailboxes for each domain. The \user\ setting is
27512 required, to specify which uid is to be used for writing to the mailboxes.
27514 The configuration shown here is just one example of how you might support this
27515 requirement. There are many other ways this kind of configuration can be set
27516 up, for example, by using a database instead of separate files to hold all the
27517 information about the domains.
27520 .section Multiple user mailboxes
27521 .rset SECTmulbox "~~chapter.~~section"
27522 .index multiple mailboxes
27523 .index mailbox||multiple
27524 .index local part||prefix
27525 .index local part||suffix
27526 Heavy email users often want to operate with multiple mailboxes, into which
27527 incoming mail is automatically sorted. A popular way of handling this is to
27528 allow users to use multiple sender addresses, so that replies can easily be
27529 identified. Users are permitted to add prefixes or suffixes to their local
27530 parts for this purpose. The wildcard facility of the generic router options
27531 \local@_part@_prefix\ and \local@_part@_suffix\ can be used for this. For
27532 example, consider this router:
27537 file = $home/.forward
27538 local_part_suffix = -*
27539 local_part_suffix_optional
27542 It runs a user's \(.forward)\ file for all local parts of the form
27543 \*username-$*$*\. Within the filter file the user can distinguish different
27544 cases by testing the variable \$local@_part@_suffix$\. For example:
27546 if $local_part_suffix contains -special then
27547 save /home/$local_part/Mail/special
27550 If the filter file does not exist, or does not deal with such addresses, they
27551 fall through to subsequent routers, and, assuming no subsequent use of the
27552 \local@_part@_suffix\ option is made, they presumably fail. Thus, users have
27553 control over which suffixes are valid.
27555 Alternatively, a suffix can be used to trigger the use of a different
27556 \(.forward)\ file -- which is the way a similar facility is implemented in
27562 file = $home/.forward$local_part_suffix
27563 local_part_suffix = -*
27564 local_part_suffix_optional
27567 If there is no suffix, \(.forward)\ is used; if the suffix is \*-special*\, for
27568 example, \(.forward-special)\ is used. Once again, if the appropriate file
27569 does not exist, or does not deal with the address, it is passed on to
27570 subsequent routers, which could, if required, look for an unqualified
27571 \(.forward)\ file to use as a default.
27574 .section Simplified vacation processing
27575 .index vacation processing
27576 The traditional way of running the \*vacation*\ program is for a user to set up
27577 a pipe command in a \(.forward)\ file
27578 (see section ~~SECTspecitredli for syntax details).
27579 This is prone to error by inexperienced users. There are two features of Exim
27580 that can be used to make this process simpler for users:
27582 A local part prefix such as `vacation-' can be specified on a router which
27583 can cause the message to be delivered directly to the \*vacation*\ program, or
27584 alternatively can use Exim's \%autoreply%\ transport. The contents of a user's
27585 \(.forward)\ file are then much simpler. For example:
27587 spqr, vacation-spqr
27590 The \require@_files\ generic router option can be used to trigger a
27591 vacation delivery by checking for the existence of a certain file in the
27592 user's home directory. The \unseen\ generic option should also be used, to
27593 ensure that the original delivery also proceeds. In this case, all the user has
27594 to do is to create a file called, say, \(.vacation)\, containing a vacation
27597 Another advantage of both these methods is that they both work even when the
27598 use of arbitrary pipes by users is locked out.
27601 .section Taking copies of mail
27602 .index message||copying every
27603 Some installations have policies that require archive copies of all messages to
27604 be made. A single copy of each message can easily be taken by an appropriate
27605 command in a system filter, which could, for example, use a different file for
27606 each day's messages.
27608 There is also a shadow transport mechanism that can be used to take copies of
27609 messages that are successfully delivered by local transports, one copy per
27610 delivery. This could be used, $it{inter alia}, to implement automatic
27611 notification of delivery by sites that insist on doing such things.
27614 .section Intermittently connected hosts
27615 .index intermittently connected hosts
27616 It has become quite common (because it is cheaper) for hosts to connect to the
27617 Internet periodically rather than remain connected all the time. The normal
27618 arrangement is that mail for such hosts accumulates on a system that is
27619 permanently connected.
27621 Exim was designed for use on permanently connected hosts, and so it is not
27622 particularly well-suited to use in an intermittently connected environment.
27623 Nevertheless there are some features that can be used.
27625 .section Exim on the upstream server host
27626 It is tempting to arrange for incoming mail for the intermittently connected
27627 host to remain on Exim's queue until the client connects. However, this
27628 approach does not scale very well. Two different kinds of waiting message are
27629 being mixed up in the same queue -- those that cannot be delivered because of
27630 some temporary problem, and those that are waiting for their destination host
27631 to connect. This makes it hard to manage the queue, as well as wasting
27632 resources, because each queue runner scans the entire queue.
27634 A better approach is to separate off those messages that are waiting for an
27635 intermittently connected host. This can be done by delivering these messages
27636 into local files in batch SMTP, `mailstore', or other envelope-preserving
27637 format, from where they are transmitted by other software when their
27638 destination connects. This makes it easy to collect all the mail for one host
27639 in a single directory, and to apply local timeout rules on a per-message basis
27642 On a very small scale, leaving the mail on Exim's queue can be made to work. If
27643 you are doing this, you should configure Exim with a long retry period for the
27644 intermittent host. For example:
27646 cheshire.wonderland.fict.example * F,5d,24h
27648 This stops a lot of failed delivery attempts from occurring, but Exim remembers
27649 which messages it has queued up for that host. Once the intermittent host comes
27650 online, forcing delivery of one message (either by using the \-M-\ or \-R-\
27651 options, or by using the \\ETRN\\ SMTP command (see section ~~SECTETRN)
27652 causes all the queued up messages to be delivered, often down a single SMTP
27653 connection. While the host remains connected, any new messages get delivered
27656 If the connecting hosts do not have fixed IP addresses, that is, if a host is
27657 issued with a different IP address each time it connects, Exim's retry
27658 mechanisms on the holding host get confused, because the IP address is normally
27659 used as part of the key string for holding retry information. This can be
27660 avoided by unsetting \retry__include__ip__address\ on the \%smtp%\ transport.
27661 Since this has disadvantages for permanently connected hosts, it is best to
27662 arrange a separate transport for the intermittently connected ones.
27665 .section Exim on the intermittently connected client host
27666 The value of \smtp@_accept@_queue@_per@_connection\ should probably be
27667 increased, or even set to zero (that is, disabled) on the intermittently
27668 connected host, so that all incoming messages down a single connection get
27669 delivered immediately.
27671 .index SMTP||passed connection
27672 .index SMTP||multiple deliveries
27673 .index multiple SMTP deliveries
27674 Mail waiting to be sent from an intermittently connected host will probably
27675 not have been routed, because without a connection DNS lookups are not
27676 possible. This means that if a normal queue run is done at connection time,
27677 each message is likely to be sent in a separate SMTP session. This can be
27678 avoided by starting the queue run with a command line option beginning with
27679 \-qq-\ instead of \-q-\. In this case, the queue is scanned twice. In the first
27680 pass, routing is done but no deliveries take place. The second pass is a normal
27681 queue run; since all the messages have been previously routed, those destined
27682 for the same host are likely to get sent as multiple deliveries in a single
27691 . ============================================================================
27692 .chapter Using Exim as a non-queueing client
27693 .set runningfoot "non-queueing client"
27694 .rset CHAPnonqueueing "~~chapter"
27695 .index client, non-queueing
27696 .index smart host||queueing, suppressing
27698 On a personal computer, it is a common requirement for all
27699 email to be sent to a `smart host'. There are plenty of MUAs that can be
27700 configured to operate that way, for all the popular operating systems.
27701 However, there are some MUAs for Unix-like systems that cannot be so
27702 configured: they submit messages using the command line interface of
27703 \(/usr/sbin/sendmail)\. Furthermore, utility programs such as \*cron*\ submit
27706 If the personal computer runs continuously, there is no problem, because it can
27707 run a conventional MTA that handles delivery to the smart host, and deal with
27708 any delays via its queueing mechanism. However, if the computer does not run
27709 continuously or runs different operating systems at different times, queueing
27710 email is not desirable.
27712 There is therefore a requirement for something that can provide the
27713 \(/usr/sbin/sendmail)\ interface but deliver messages to a smart host without
27714 any queueing or retrying facilities. Furthermore, the delivery to the smart
27715 host should be synchronous, so that if it fails, the sending MUA is immediately
27716 informed. In other words, we want something that extends an MUA that submits
27717 to a local MTA via the command line so that it behaves like one that submits
27718 to a remote smart host using TCP/SMTP.
27720 There are a number of applications (for example, there is one called \*ssmtp*\)
27721 that do this job. However, people have found them to be lacking in various
27722 ways. For instance, you might want to allow aliasing and forwarding to be done
27723 before sending a message to the smart host.
27725 Exim already had the necessary infrastructure for doing this job. Just a few
27726 tweaks were needed to make it behave as required, though it is somewhat of an
27727 overkill to use a fully-featured MTA for this purpose.
27729 .index \mua@_wrapper\
27730 There is a Boolean global option called \mua@_wrapper\, defaulting false.
27731 Setting \mua@_wrapper\ true causes Exim to run in a special mode where it
27732 assumes that it is being used to `wrap' a command-line MUA in the manner
27733 just described. As well as setting \mua@_wrapper\, you also need to provide a
27734 compatible router and transport configuration. Typically there will be just one
27735 router and one transport, sending everything to a smart host.
27737 When run in MUA wrapping mode, the behaviour of Exim changes in the
27740 A daemon cannot be run, nor will Exim accept incoming messages from \*inetd*\.
27741 In other words, the only way to submit messages is via the command line.
27743 Each message is synchonously delivered as soon as it is received (\-odi-\ is
27744 assumed). All queueing options (\queue@_only\, \queue@_smtp@_domains\,
27745 \control\ in an ACL, etc.) are quietly ignored. The Exim reception process does
27746 not finish until the delivery attempt is complete. If the delivery is
27747 successful, a zero return code is given.
27749 Address redirection is permitted, but the final routing for all addresses must
27750 be to the same remote transport, and to the same list of hosts. Furthermore,
27751 the return address (envelope sender) must be the same for all recipients, as
27752 must any added or deleted header lines. In other words, it must be possible to
27753 deliver the message in a single SMTP transaction, however many recipients there
27756 If these conditions are not met, or if routing any address results in a failure
27757 or defer status, or if Exim is unable to deliver all the recipients
27758 successfully to one of the smart hosts, delivery of the entire message fails.
27760 Because no queueing is allowed, all failures are treated as permanent; there is
27761 no distinction between 4\*xx*\ and 5\*xx*\ SMTP response codes from the smart
27762 host. Furthermore, because only a single yes/no response can be given to the
27763 caller, it is not possible to deliver to some recipients and not others. If
27764 there is an error (temporary or permanent) for any recipient, all are failed.
27766 If more than one smart host is listed, Exim will try another host after a
27767 connection failure or a timeout, in the normal way. However, if this kind of
27768 failure happens for all the hosts, the delivery fails.
27770 When delivery fails, an error message is written to the standard error stream
27771 (as well as to Exim's log), and Exim exits to the caller with a return code
27772 value 1. The message is expunged from Exim's spool files. No bounce messages
27773 are ever generated.
27775 No retry data is maintained, and any retry rules are ignored.
27777 A number of Exim options are overridden: \deliver@_drop@_privilege\ is forced
27778 true, \max@_rcpt\ in the smtp transport is forced to `unlimited',
27779 \remote@_max@_parallel\ is forced to one, and fallback hosts are ignored.
27781 The overall effect is that Exim makes a single synchronous attempt to deliver
27782 the message, failing if there is any kind of problem. Because no local
27783 deliveries are done and no daemon can be run, Exim does not need root
27784 privilege. It should be possible to run it setuid to \*exim*\ instead of setuid
27785 to \*root*\. See section ~~SECTrunexiwitpri for a general discussion about the
27786 advantages and disadvantages of running without root privilege.
27795 . ============================================================================
27797 .set runningfoot "log files"
27798 .rset CHAPlog "~~chapter"
27799 .index log||types of
27800 .index log||general description
27801 Exim writes three different logs, referred to as the main log, the reject log,
27805 The main log records the arrival of each message and each delivery in a single
27806 line in each case. The format is as compact as possible, in an attempt to keep
27807 down the size of log files. Two-character flag sequences make it easy to pick
27808 out these lines. A number of other events are recorded in the main log. Some of
27809 them are optional, in which case the \log@_selector\ option controls whether
27810 they are included or not. A Perl script called \*eximstats*\, which does simple
27811 analysis of main log files, is provided in the Exim distribution (see section
27815 The reject log records information from messages that are rejected as a result
27816 of a configuration option (that is, for policy reasons).
27817 The first line of each rejection is a copy of the line that is also written to
27818 the main log. Then, if the message's header has been read at the time the log
27819 is written, its contents are written to this log. Only the original header
27820 lines are available; header lines added by ACLs are not logged. You can use the
27821 reject log to check that your policy controls are working correctly; on a busy
27822 host this may be easier than scanning the main log for rejection messages. You
27823 can suppress the writing of the reject log by setting \write@_rejectlog\ false.
27827 When certain serious errors occur, Exim writes entries to its panic log. If the
27828 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
27829 are usually written to the main log as well, but can get lost amid the mass of
27830 other entries. The panic log should be empty under normal circumstances. It is
27831 therefore a good idea to check it (or to have a \*cron*\ script check it)
27832 regularly, in order to become aware of any problems. When Exim cannot open its
27833 panic log, it tries as a last resort to write to the system log (syslog). This
27834 is opened with LOG@_PID+LOG@_CONS and the facility code of LOG@_MAIL. The
27835 message itself is written at priority LOG@_CRIT.
27837 Every log line starts with a timestamp, in the format shown in this example:
27839 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed by QUIT
27841 By default, the timestamps are in the local timezone. There are two
27842 ways of changing this:
27844 You can set the \timezone\ option to a different time zone; in particular, if
27849 the timestamps will be in UTC (aka GMT).
27851 If you set \log@_timezone\ true, the time zone is added to the timestamp, for
27854 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
27860 .section Where the logs are written
27861 .rset SECTwhelogwri "~~chapter.~~section"
27862 .index log||destination
27863 .index log||to file
27864 .index log||to syslog
27866 The logs may be written to local files, or to syslog, or both. However, it
27867 should be noted that many syslog implementations use UDP as a transport, and
27868 are therefore unreliable in the sense that messages are not guaranteed to
27869 arrive at the loghost, nor is the ordering of messages necessarily maintained.
27870 It has also been reported that on large log files (tens of megabytes) you may
27871 need to tweak syslog to prevent it syncing the file with each write -- on Linux
27872 this has been seen to make syslog take 90% plus of CPU time.
27874 The destination for Exim's logs is configured by setting \\LOG@_FILE@_PATH\\ in
27875 \(Local/Makefile)\ or by setting \log@_file@_path\ in the run time
27876 configuration. This latter string is expanded, so it can contain, for example,
27877 references to the host name:
27879 log_file_path = /var/log/$primary_hostname/exim_%slog
27881 It is generally advisable, however, to set the string in \(Local/Makefile)\
27882 rather than at run time, because then the setting is available right from the
27883 start of Exim's execution. Otherwise, if there's something it wants to log
27884 before it has read the configuration file (for example, an error in the
27885 configuration file) it will not use the path you want, and may not be able to
27888 The value of \\LOG@_FILE@_PATH\\ or \log@_file@_path\ is a colon-separated
27889 list, currently limited to at most two items. This is one option where the
27890 facility for changing a list separator may not be used. The list must always be
27891 colon-separated. If an item in the list is `syslog' then syslog is used;
27892 otherwise the item must either be an absolute path, containing \"%s"\ at the
27893 point where `main', `reject', or `panic' is to be inserted, or be empty,
27894 implying the use of a default path.
27896 When Exim encounters an empty item in the list, it searches the list defined by
27897 \\LOG@_FILE@_PATH\\, and uses the first item it finds that is neither empty nor
27898 `syslog'. This means that an empty item in \log@_file@_path\ can be used to
27899 mean `use the path specified at build time'. It no such item exists, log files
27900 are written in the \(log)\ subdirectory of the spool directory. This is
27901 equivalent to the setting:
27903 log_file_path = $spool_directory/log/%slog
27905 If you do not specify anything at build time or run time, that is where the
27908 A log file path may also contain \"%D"\ if datestamped log file names are in
27909 use -- see section ~~SECTdatlogfil below.
27911 Here are some examples of possible settings:
27914 LOG@_FILE@_PATH=syslog $t $rm{syslog only}
27915 LOG@_FILE@_PATH=:syslog $t $rm{syslog and default path}
27916 LOG@_FILE@_PATH=syslog : /usr/log/exim@_%s $t $rm{syslog and specified path}
27917 LOG@_FILE@_PATH=/usr/log/exim@_%s $t $rm{specified path only}
27919 If there are more than two paths in the list, the first is used and a panic
27923 .section Logging to local files that are periodically `cycled'
27924 .index log||cycling local files
27925 .index cycling logs
27926 .index \*exicyclog*\
27927 .index log||local files, writing to
27928 Some operating systems provide centralized and standardised methods for cycling
27929 log files. For those that do not, a utility script called \*exicyclog*\ is
27930 provided (see section ~~SECTcyclogfil). This renames and compresses the main
27931 and reject logs each time it is called. The maximum number of old logs to keep
27932 can be set. It is suggested this script is run as a daily \*cron*\ job.
27934 An Exim delivery process opens the main log when it first needs to write to it,
27935 and it keeps the file open in case subsequent entries are required -- for
27936 example, if a number of different deliveries are being done for the same
27937 message. However, remote SMTP deliveries can take a long time, and this means
27938 that the file may be kept open long after it is renamed if \*exicyclog*\ or
27939 something similar is being used to rename log files on a regular basis. To
27940 ensure that a switch of log files is noticed as soon as possible, Exim calls
27941 \*stat()*\ on the main log's name before reusing an open file, and if the file
27942 does not exist, or its inode has changed, the old file is closed and Exim
27943 tries to open the main log from scratch. Thus, an old log file may remain open
27944 for quite some time, but no Exim processes should write to it once it has been
27948 .section Datestamped log files
27949 .rset SECTdatlogfil "~~chapter.~~section"
27950 .index log||datestamped files
27951 Instead of cycling the main and reject log files by renaming them
27952 periodically, some sites like to use files whose names contain a datestamp,
27953 for example, \(mainlog-20031225)\. The datestamp is in the form \(yyyymmdd)\.
27954 Exim has support for this way of working. It is enabled by setting the
27955 \log@_file@_path\ option to a path that includes \"%D"\ at the point where the
27956 datestamp is required. For example:
27958 log_file_path = /var/spool/exim/log/%slog-%D
27959 log_file_path = /var/log/exim-%s-%D.log
27960 log_file_path = /var/spool/exim/log/%D-%slog
27962 As before, \"%s"\ is replaced by `main' or `reject'; the following are examples
27963 of names generated by the above examples:
27965 /var/spool/exim/log/mainlog-20021225
27966 /var/log/exim-reject-20021225.log
27967 /var/spool/exim/log/20021225-mainlog
27969 When this form of log file is specified, Exim automatically switches to new
27970 files at midnight. It does not make any attempt to compress old logs; you
27971 will need to write your own script if you require this. You should not
27972 run \*exicyclog*\ with this form of logging.
27974 The location of the panic log is also determined by \log@_file@_path\, but it
27975 is not datestamped, because rotation of the panic log does not make sense.
27976 When generating the name of the panic log, \"%D"\ is removed from the string.
27977 In addition, if it immediately follows a slash, a following non-alphanumeric
27978 character is removed; otherwise a preceding non-alphanumeric character is
27979 removed. Thus, the three examples above would give these panic log names:
27981 /var/spool/exim/log/paniclog
27982 /var/log/exim-panic.log
27983 /var/spool/exim/log/paniclog
27987 .section Logging to syslog
27988 .index log||syslog, writing to
27989 The use of syslog does not change what Exim logs or the format of its messages,
27990 except in one respect. If \syslog@_timestamp\ is set false, the timestamps on
27991 Exim's log lines are omitted when these lines are sent to syslog. Apart from
27992 that, the same strings are written to syslog as to log files. The syslog
27993 `facility' is set to \\LOG@_MAIL\\, and the program name to `exim'
27994 by default, but you can change these by setting the \syslog@_facility\ and
27995 \syslog@_processname\ options, respectively. If Exim was compiled with
27996 \\SYSLOG@_LOG@_PID\\ set in \(Local/Makefile)\ (this is the default in
27997 \(src/EDITME)\), then, on systems that permit it (all except ULTRIX), the
27998 \\LOG@_PID\\ flag is set so that the \*syslog()*\ call adds the pid as well as
27999 the time and host name to each line.
28000 The three log streams are mapped onto syslog priorities as follows:
28002 \*mainlog*\ is mapped to \\LOG@_INFO\\
28004 \*rejectlog*\ is mapped to \\LOG@_NOTICE\\
28006 \*paniclog*\ is mapped to \\LOG@_ALERT\\
28008 Many log lines are written to both \*mainlog*\ and \*rejectlog*\, and some are
28009 written to both \*mainlog*\ and \*paniclog*\, so there will be duplicates if
28010 these are routed by syslog to the same place. You can suppress this duplication
28011 by setting \syslog@_duplication\ false.
28013 Exim's log lines can sometimes be very long, and some of its \*rejectlog*\
28014 entries contain multiple lines when headers are included. To cope with both
28015 these cases, entries written to syslog are split into separate \*syslog()*\
28016 calls at each internal newline, and also after a maximum of
28017 870 data characters. (This allows for a total syslog line length of 1024, when
28018 additions such as timestamps are added.) If you are running a syslog
28019 replacement that can handle lines longer than the 1024 characters allowed by
28020 RFC 3164, you should set
28022 SYSLOG_LONG_LINES=yes
28024 in \(Local/Makefile)\ before building Exim. That stops Exim from splitting long
28025 lines, but it still splits at internal newlines in \*reject*\ log entries.
28027 To make it easy to re-assemble split lines later, each component of a split
28028 entry starts with a string of the form `[<<n>>/<<m>>]' or `[<<n>>@\<<m>>]'
28029 where <<n>> is the component number and <<m>> is the total number of components
28030 in the entry. The / delimiter is used when the line was split because it was
28031 too long; if it was split because of an internal newline, the @\ delimiter is
28032 used. For example, supposing the length limit to be 70 instead of 1000, the
28033 following would be the result of a typical rejection message to \*mainlog*\
28034 (LOG@_INFO), each line in addition being preceded by the time, host name, and
28035 pid as added by syslog:
28038 $smc{[1/3] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from [127.0.0.1] (ph10):
28039 [2/3] syntax error in 'From' header when scanning for sender: missing or ma
28040 [3/3] lformed local part in "<>" (envelope sender is <ph10@@cam.example>)}
28042 The same error might cause the following lines to be written to `rejectlog'
28046 $smc{[1/14] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from [127.0.0.1] (ph10):
28047 [2/14] syntax error in 'From' header when scanning for sender: missing or ma
28048 [3@\14] lformed local part in "@<@>" (envelope sender is <ph10@@cam.example>)
28049 [4@\14] Recipients: ph10@@some.domain.cam.example
28050 [5@\14] P Received: from [127.0.0.1] (ident=ph10)
28051 [6@\14] by xxxxx.cam.example with smtp (Exim 4.00)
28052 [7@\14] id 16RdAL-0006pc-00
28053 [8@\14] for ph10@@cam.example; Mon, 16 Sep 2002 16:09:43 +0100
28054 [9@\14] F From: @<@>
28055 [10@\14] Subject: this is a test header
28056 [11@\14] X-something: this is another header
28057 [12@\14] I Message-Id: <E16RdAL-0006pc-00@@xxxxx.cam.example>
28059 [14/14] Date: Mon, 16 Sep 2002 16:09:43 +0100}
28061 Log lines that are neither too long nor contain newlines are written to syslog
28062 without modification.
28064 If only syslog is being used, the Exim monitor is unable to provide a log tail
28065 display, unless syslog is routing \*mainlog*\ to a file on the local host and
28066 the environment variable \\EXIMON@_LOG@_FILE@_PATH\\ is set to tell the monitor
28070 .section Log line flags
28071 One line is written to the main log for each message received, and for each
28072 successful, unsuccessful, and delayed delivery. These lines can readily be
28073 picked out by the distinctive two-character flags that immediately follow the
28074 timestamp. The flags are:
28077 <= $t $rm{message arrival}
28078 => $t $rm{normal message delivery}
28079 -> $t $rm{additional address in same delivery}
28080 *> $t $rm{delivery suppressed by \-N-\}
28081 ** $t $rm{delivery failed; address bounced}
28082 == $t $rm{delivery deferred; temporary problem}
28086 .section Logging message reception
28087 .index log||reception line
28088 The format of the single-line entry in the main log that is written for every
28089 message received is shown in the basic example below, which is split over
28090 several lines in order to fit it on the page:
28093 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@@dwarf.fict.example
28094 H=mailer.fict.example [192.168.123.123] U=exim
28095 P=smtp S=5678 id=<<incoming message id>>
28097 The address immediately following `<=' is the envelope sender address. A bounce
28098 message is shown with the sender address `<>', and if it is locally generated,
28099 this is followed by an item of the form
28103 which is a reference to the message that caused the bounce to be sent.
28107 For messages from other hosts, the H and U fields identify the remote host and
28108 record the RFC 1413 identity of the user that sent the message, if one was
28109 received. The number given in square brackets is the IP address of the sending
28110 host. If there is a single, unparenthesized host name in the H field, as
28111 above, it has been verified to correspond to the IP address (see the
28112 \host@_lookup\ option). If the name is in parentheses, it was the name quoted
28113 by the remote host in the SMTP \\HELO\\ or \\EHLO\\ command, and has not been
28114 verified. If verification yields a different name to that given for \\HELO\\ or
28115 \\EHLO\\, the verified name appears first, followed by the \\HELO\\ or \\EHLO\\
28116 name in parentheses.
28118 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
28119 without brackets, in the \\HELO\\ or \\EHLO\\ command, leading to entries in
28120 the log containing text like these examples:
28122 H=(10.21.32.43) [192.168.8.34]
28123 H=([10.21.32.43]) [192.168.8.34]
28125 This can be confusing. Only the final address in square brackets can be relied
28128 For locally generated messages (that is, messages not received over TCP/IP),
28129 the H field is omitted, and the U field contains the login name of the caller
28132 .index authentication||logging
28133 .index \\AUTH\\||logging
28134 For all messages, the P field specifies the protocol used to receive the
28135 message. This is set to
28139 for messages received from hosts that have authenticated themselves using the
28140 SMTP \\AUTH\\ command. In this case there is an additional item A= followed by
28141 the name of the authenticator that was used. If an authenticated identification
28142 was set up by the authenticator's \server@_set@_id\ option, this is logged too,
28143 separated by a colon from the authenticator name.
28145 The id field records the existing message id, if present.
28146 .index size||of message
28147 The size of the received message is given by the S field. When the message is
28148 delivered, headers may get removed or added, so that the size of delivered
28149 copies of the message may not correspond with this value (and indeed may be
28150 different to each other).
28152 The \log@_selector\ option can be used to request the logging of additional
28153 data when a message is received. See section ~~SECTlogselector below.
28156 .section Logging deliveries
28157 .index log||delivery line
28158 The format of the single-line entry in the main log that is written for every
28159 delivery is shown in one of the examples below, for local and remote deliveries,
28160 respectively. Each example has been split into two lines in order to fit
28164 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv <marv@@hitch.fict.example>
28165 R=localuser T=local@_delivery
28166 2002-10-31 09:00:10 16ZCW1-0005MB-00 => monk@@holistic.fict.example
28167 R=dnslookup T=remote@_smtp H=holistic.fict.example [192.168.234.234]
28169 For ordinary local deliveries, the original address is given in angle brackets
28170 after the final delivery address, which might be a pipe or a file. If
28171 intermediate address(es) exist between the original and the final address, the
28172 last of these is given in parentheses after the final address. The R and T
28173 fields record the router and transport that were used to process the address.
28175 If a shadow transport was run after a successful local delivery, the log line
28176 for the successful delivery has an item added on the end, of the form
28178 ST=<<shadow transport name>>
28180 If the shadow transport did not succeed, the error message is put in
28181 parentheses afterwards.
28183 When more than one address is included in a single delivery (for example, two
28184 SMTP \\RCPT\\ commands in one transaction) the second and subsequent
28185 addresses are flagged with `$tt{@-@>}' instead of `$tt{@=@>}'. When two or more
28186 messages are delivered down a single SMTP connection, an asterisk follows the
28187 IP address in the log lines for the second and subsequent messages.
28189 The generation of a reply message by a filter file gets logged as a `delivery'
28190 to the addressee, preceded by `>'.
28192 The \log@_selector\ option can be used to request the logging of additional
28193 data when a message is delivered. See section ~~SECTlogselector below.
28196 .section Discarded deliveries
28197 .index discarded messages
28198 .index message||discarded
28199 .index delivery||discarded, logging
28200 When a message is discarded as a result of the command `seen finish' being
28201 obeyed in a filter file which generates no deliveries, a log entry of the form
28203 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
28204 <low.club@@bridge.example> R=userforward
28206 is written, to record why no deliveries are logged. When a message is discarded
28207 because it is aliased to `:blackhole:' the log line is like this:
28209 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
28210 <hole@nowhere.example> R=blackhole_router
28214 .section Deferred deliveries
28215 When a delivery is deferred, a line of the following form is logged:
28218 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@@endrest.example
28219 R=dnslookup T=smtp defer (146): Connection refused
28221 In the case of remote deliveries, the error is the one that was given for the
28222 last IP address that was tried. Details of individual SMTP failures are also
28223 written to the log, so the above line would be preceded by something like
28226 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
28227 mail1.endrest.example [192.168.239.239]: Connection refused
28229 When a deferred address is skipped because its retry time has not been reached,
28230 a message is written to the log, but this can be suppressed by setting an
28231 appropriate value in \log@_selector\.
28234 .section Delivery failures
28235 .index delivery||failure, logging
28236 If a delivery fails because an address cannot be routed, a line of the
28237 following form is logged:
28240 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
28241 <jim@trek99.example>: unknown mail domain
28243 If a delivery fails at transport time, the router and transport are shown, and
28244 the response from the remote host is included, as in this example:
28247 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example R=dnslookup
28249 T=remote_smtp: SMTP error from remote mailer after pipelined
28251 RCPT TO:<ace400@pb.example>: host pbmail3.py.example
28252 [192.168.63.111]: 553 5.3.0 <ace400@pb.example>...
28255 The word `pipelined' indicates that the SMTP \\PIPELINING\\ extension was being
28256 used. See \hosts@_avoid@_esmtp\ in the \%smtp%\ transport for a way of
28257 disabling \\PIPELINING\\.
28259 The log lines for all forms of delivery failure are flagged with \"**"\.
28262 .section Fake deliveries
28263 .index delivery||fake, logging
28264 If a delivery does not actually take place because the \-N-\ option has been
28265 used to suppress it, a normal delivery line is written to the log, except that
28266 `=>' is replaced by `$*$>'.
28269 .section Completion
28272 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
28274 is written to the main log when a message is about to be removed from the spool
28275 at the end of its processing.
28279 .section Summary of Fields in Log Lines
28280 .index log||summary of fields
28281 A summary of the field identifiers that are used in log lines is shown in
28282 the following table:
28285 A $t $rm{authenticator name (and optional id)}
28286 C $t $rm{SMTP confirmation on delivery}
28287 CV $t $rm{certificate verification status}
28288 DN $t $rm{distinguished name from peer certificate}
28291 DT $t $rm{on \"=>"\ lines: time taken for a delivery}
28294 F $t $rm{sender address (on delivery lines)}
28295 H $t $rm{host name and IP address}
28296 I $t $rm{local interface used}
28297 id $t $rm{message id for incoming message}
28298 P $t $rm{on \"<="\ lines: protocol used}
28301 $t $rm{on \"=>"\ and \"**"\ lines: return path}
28302 QT $t $rm{on \"=>"\ lines: time spent on queue so far}
28303 $t $rm{on `Completed' lines: time spent on queue}
28306 R $t $rm{on \"<="\ lines: reference for local bounce}
28309 $t $rm{on \"=>"\ \"**"\ and \"=="\ lines: router name}
28312 S $t $rm{size of message}
28313 ST $t $rm{shadow transport name}
28314 T $t $rm{on \"<="\ lines: message subject (topic)}
28317 $t $rm{on \"=>"\ \"**"\ and \"=="\ lines: transport name}
28320 U $t $rm{local user or RFC 1413 identity}
28321 X $t $rm{TLS cipher suite}
28325 .section Other log entries
28326 Various other types of log entry are written from time to time. Most should be
28327 self-explanatory. Among the more common are:
28329 .index retry||time not reached
28330 \*retry time not reached*\##An address previously suffered a temporary error
28331 during routing or local delivery, and the time to retry has not yet arrived.
28332 This message is not written to an individual message log file unless it happens
28333 during the first delivery attempt.
28335 \*retry time not reached for any host*\##An address previously suffered
28336 temporary errors during remote delivery, and the retry time has not yet arrived
28337 for any of the hosts to which it is routed.
28339 .index spool directory||file locked
28340 \*spool file locked*\##An attempt to deliver a message cannot proceed because
28341 some other Exim process is already working on the message. This can be quite
28342 common if queue running processes are started at frequent intervals. The
28343 \*exiwhat*\ utility script can be used to find out what Exim processes are
28346 .index error||ignored
28347 \*error ignored*\##There are several circumstances that give rise to this
28350 Exim failed to deliver a bounce message whose age was greater than
28351 \ignore__bounce__errors__after\. The bounce was discarded.
28353 A filter file set up a delivery using the `noerror' option, and the delivery
28354 failed. The delivery was discarded.
28356 A delivery set up by a router configured with
28360 failed. The delivery was discarded.
28366 .section Reducing or increasing what is logged
28367 .rset SECTlogselector "~~chapter.~~section"
28368 .index log||selectors
28369 By setting the \log@_selector\ global option, you can disable some of Exim's
28370 default logging, or you can request additional logging. The value of
28371 \log@_selector\ is made up of names preceded by plus or minus characters. For
28374 log_selector = +arguments -retry_defer
28376 The list of optional log items is in the following table, with the default
28377 selection marked by asterisks:
28380 address@_rewrite $t $rm{address rewriting}
28381 all@_parents $t $rm{all parents in => lines}
28382 arguments $t $rm{command line arguments}
28383 *connection@_reject $t $rm{connection rejections}
28384 *delay@_delivery $t $rm{immediate delivery delayed}
28385 deliver@_time $t $rm{time taken to perform delivery}
28386 delivery@_size $t $rm{add S=nnn to => lines}
28387 *dnslist@_defer $t $rm{defers of DNS list (aka RBL) lookups}
28388 *etrn $t $rm{ETRN commands}
28389 *host@_lookup@_failed $t $rm{as it says}
28390 ident@_timeout $t $rm{timeout for ident connection}
28391 incoming@_interface $t $rm{incoming interface on <= lines}
28392 incoming@_port $t $rm{incoming port on <= lines}
28393 *lost@_incoming@_connection $t $rm{as it says (includes timeouts)}
28394 outgoing@_port $t $rm{add remote port to => lines}
28395 *queue@_run $t $rm{start and end queue runs}
28398 queue@_time $t $rm{time on queue for one recipient}
28399 queue@_time@_overall $t $rm{time on queue for whole message}
28402 received@_recipients $t $rm{recipients on <= lines}
28403 received@_sender $t $rm{sender on <= lines}
28404 *rejected@_header $t $rm{header contents on reject log}
28405 *retry@_defer $t $rm{`retry time not reached'}
28406 return@_path@_on@_delivery $t $rm{put return path on => and ** lines}
28407 sender@_on@_delivery $t $rm{add sender to => lines}
28408 *size@_reject $t $rm{rejection because too big}
28409 *skip@_delivery $t $rm{delivery skipped in a queue run}
28410 smtp@_confirmation $t $rm{SMTP confirmation on => lines}
28411 smtp@_connection $t $rm{SMTP connections}
28412 smtp@_incomplete@_transaction $t $rm{incomplete SMTP transactions}
28413 smtp@_protocol@_error $t $rm{SMTP protocol errors}
28414 smtp@_syntax@_error $t $rm{SMTP syntax errors}
28415 subject $t $rm{contents of ::Subject:: on <= lines}
28416 tls@_certificate@_verified $t $rm{certificate verification status}
28417 *tls@_cipher $t $rm{TLS cipher suite on <= and => lines}
28418 tls@_peerdn $t $rm{TLS peer DN on <= and => lines}
28420 all $t $rm{all of the above}
28422 More details on each of these items follows:
28424 .index log||rewriting
28425 .index rewriting||logging
28426 \address@_rewrite\: This applies both to global rewrites and per-transport
28428 but not to rewrites in filters run as an unprivileged user (because such users
28429 cannot access the log).
28431 .index log||full parentage
28432 \all@_parents\: Normally only the original and final addresses are logged on
28433 delivery lines; with this selector, intermediate parents are given in
28434 parentheses between them.
28436 .index log||Exim arguments
28437 .index Exim arguments, logging
28438 \arguments\: This causes Exim to write the arguments with which it was called
28440 preceded by the current working directory.
28441 This is a debugging feature, added to make it easier to find out how certain
28442 MUAs call \(/usr/sbin/sendmail)\. The logging does not happen if Exim has given
28443 up root privilege because it was called with the \-C-\ or \-D-\ options.
28444 Arguments that are empty or that contain whitespace are quoted. Non-printing
28445 characters are shown as escape sequences.
28446 This facility cannot log unrecognized arguments, because the arguments are
28447 checked before the configuration file is read. The only way to log such cases
28448 is to interpose a script such as \(util/logargs.sh)\ between the caller and
28451 .index log||connection rejections
28452 \connection@_reject\: A log entry is written whenever an incoming SMTP
28453 connection is rejected, for whatever reason.
28455 .index log||delayed delivery
28456 .index delayed delivery, logging
28457 \delay@_delivery\: A log entry is written whenever a delivery process is not
28458 started for an incoming message because the load is too high or too many
28459 messages were received on one connection. Logging does not occur if no delivery
28460 process is started because \queue@_only\ is set or \-odq-\ was used.
28462 .index log||delivery duration
28463 \deliver@_time\: For each delivery, the amount of real time it has taken to
28464 perform the actual delivery is logged as DT=<<time>>, for example, \"DT=1s"\.
28466 .index log||message size on delivery
28467 .index size||of message
28468 \delivery@_size\: For each delivery, the size of message delivered is added to
28469 the `=>' line, tagged with S=.
28471 .index log||dnslist defer
28472 .index DNS list||logging defer
28473 .index black list (DNS)
28474 \dnslist@_defer\: A log entry is written if an attempt to look up a host in a
28475 DNS black list suffers a temporary error.
28477 .index log||ETRN commands
28478 .index \\ETRN\\||logging
28479 \etrn\: Every legal ETRN command that is received is logged, before the ACL is
28480 run to determine whether or not it is actually accepted. An invalid ETRN
28481 command, or one received within a message transaction is not logged by this
28482 selector (see \smtp@_syntax@_error\ and \smtp@_protocol@_error\).
28484 .index log||host lookup failure
28485 \host@_lookup@_failed\: When a lookup of a host's IP addresses fails to find
28486 any addresses, or when a lookup of an IP address fails to find a host name, a
28487 log line is written. This logging does not apply to direct DNS lookups when
28488 routing email addresses, but it does apply to `byname' lookups.
28490 .index log||ident timeout
28491 .index RFC 1413||logging timeout
28492 \ident@_timeout\: A log line is written whenever an attempt to connect to a
28493 client's ident port times out.
28495 .index log||incoming interface
28496 .index interface||logging
28497 \incoming@_interface\: The interface on which a message was received is added
28498 to the `<=' line as an IP address in square brackets, tagged by I= and followed
28499 by a colon and the port number.
28500 The local interface and port are also added to other SMTP log
28501 lines, for example `SMTP connection from', and to rejection lines.
28503 .index log||incoming remote port
28504 .index port||logging remote
28505 .index TCP/IP||logging incoming remote port
28506 \incoming@_port\: The remote port number from which a message was received is
28507 added to log entries and ::Received:: header lines, following the IP address in
28508 square brackets, and separated from it by a colon. This is implemented by
28509 changing the value that is put in the \$sender@_fullhost$\ and
28510 \$sender@_rcvhost$\ variables. Recording the remote port number has become more
28511 important with the widening use of NAT (see RFC 2505).
28513 .index log||dropped connection
28514 \lost@_incoming@_connection\: A log line is written when an incoming SMTP
28515 connection is unexpectedly dropped.
28517 .index log||outgoing remote port
28518 .index port||logging outgoint remote
28519 .index TCP/IP||logging ougtoing remote port
28520 \outgoing@_port\: The remote port number is added to delivery log lines (those
28521 containing => tags) following the IP address. This option is not included in
28522 the default setting, because for most ordinary configurations, the remote port
28523 number is always 25 (the SMTP port).
28525 .index log||queue run
28526 .index queue runner||logging
28527 \queue@_run\: The start and end of every queue run are logged.
28529 .index log||queue time
28530 \queue@_time\: The amount of time the message has been in the queue on the
28531 local host is logged as QT=<<time>>
28533 on delivery (\"=>"\) lines, for example, \"QT=3m45s"\. The clock starts when
28534 Exim starts to receive the message, so it includes reception time as well as
28535 the delivery time for the current address. This means that it may be longer
28536 than the difference between the arrival and delivery log line times, because
28537 the arrival log line is not written until the message has been successfully
28543 \queue@_time@_overall\: The amount of time the message has been in the queue on
28544 the local host is logged as QT=<<time>> on `Completed' lines, for
28545 example, \"QT=3m45s"\. The clock starts when Exim starts to receive the
28546 message, so it includes reception time as well as the total delivery time.
28549 .index log||recipients
28550 \received@_recipients\: The recipients of a message are listed in the main log
28551 as soon as the message is received. The list appears at the end of the log line
28552 that is written when a message is received, preceded by the word `for'. The
28553 addresses are listed after they have been qualified, but before any rewriting
28555 Recipients that were discarded by an ACL for \\MAIL\\ or \\RCPT\\ do not appear
28558 .index log||sender reception
28559 \received@_sender\: The unrewritten original sender of a message is added to
28560 the end of the log line that records the message's arrival, after the word
28561 `from' (before the recipients if \received@_recipients\ is also set).
28563 .index log||header lines for rejection
28564 \rejected@_header\: If a message's header has been received at the time a
28565 rejection is written to the reject log, the complete header is added to the
28566 log. Header logging can be turned off individually for messages that are
28567 rejected by the \*local@_scan()*\ function (see section ~~SECTapiforloc).
28569 .index log||retry defer
28570 \retry@_defer\: A log line is written if a delivery is deferred because a retry
28571 time has not yet been reached. However, this `retry time not reached' message
28572 is always omitted from individual message logs after the first delivery
28575 .index log||return path
28576 \return@_path@_on@_delivery\: The return path that is being transmitted with
28577 the message is included in delivery and bounce lines, using the tag P=.
28579 This is omitted if no delivery actually happens, for example, if routing fails,
28580 or if delivery is to \(/dev/null)\ or to \":blackhole:"\.
28583 .index log||sender on delivery
28584 \sender@_on@_delivery\: The message's sender address is added to every delivery
28585 and bounce line, tagged by F= (for `from').
28586 This is the original sender that was received with the message; it is not
28587 necessarily the same as the outgoing return path.
28589 .index log||size rejection
28590 \size@_reject\: A log line is written whenever a message is rejected because it
28593 .index log||frozen messages, skipped
28594 .index frozen messages||logging skipping
28595 \skip@_delivery\: A log line is written whenever a message is skipped during a
28596 queue run because it is frozen or because another process is already delivering
28599 .index `spool file is locked'
28600 The message that is written is `spool file is locked'.
28603 .index log||smtp confirmation
28604 .index SMTP||logging confirmation
28605 \smtp@_confirmation\: The response to the final `.' in the SMTP dialogue for
28606 outgoing messages is added to delivery log lines in the form `C="<<text>>"'. A
28607 number of MTAs (including Exim) return an identifying string in this response.
28609 .index log||SMTP connections
28610 .index SMTP||logging connections
28611 \smtp@_connection\: A log line is written whenever an SMTP connection is
28612 established or closed,
28614 unless the connection is from a host that matches \hosts@_connection@_nolog\.
28616 (In contrast, \lost__incoming__connection\ applies only when the closure is
28617 unexpected.) This applies to connections from local processes that use \-bs-\
28618 as well as to TCP/IP connections. If a connection is dropped in the middle of a
28619 message, a log line is always written, whether or not this selector is set, but
28620 otherwise nothing is written at the start and end of connections unless this
28621 selector is enabled.
28623 For TCP/IP connections to an Exim daemon, the current number of connections is
28624 included in the log message for each new connection, but note that the count is
28625 reset if the daemon is restarted.
28626 Also, because connections are closed (and the closure is logged) in
28627 subprocesses, the count may not include connections that have been closed but
28628 whose termination the daemon has not yet noticed. Thus, while it is possible to
28629 match up the opening and closing of connections in the log, the value of the
28630 logged counts may not be entirely accurate.
28632 .index log||SMTP transaction, incomplete
28633 .index SMTP||logging incomplete transactions
28634 \smtp@_incomplete@_transaction\: When a mail transaction is aborted by
28635 \\RSET\\, \\QUIT\\, loss of connection, or otherwise, the incident is logged,
28636 and the message sender plus any accepted recipients are included in the log
28637 line. This can provide evidence of dictionary attacks.
28639 .index log||SMTP protocol error
28640 .index SMTP||logging protocol error
28641 \smtp@_protocol@_error\: A log line is written for every SMTP protocol error
28643 Exim does not have perfect detection of all protocol errors because of
28644 transmission delays and the use of pipelining. If \\PIPELINING\\ has been
28645 advertised to a client, an Exim server assumes that the client will use it, and
28646 therefore it does not count `expected' errors (for example, \\RCPT\\ received
28647 after rejecting \\MAIL\\) as protocol errors.
28649 .index SMTP||logging syntax errors
28650 .index SMTP||syntax errors, logging
28651 .index SMTP||unknown command, logging
28652 .index log||unknown SMTP command
28653 .index log||SMTP syntax error
28654 \smtp@_syntax@_error\: A log line is written for every SMTP syntax error
28655 encountered. An unrecognized command is treated as a syntax error. For an
28656 external connection, the host identity is given; for an internal connection
28657 using \-bs-\ the sender identification (normally the calling user) is given.
28659 .index log||subject
28660 .index subject, logging
28661 \subject\: The subject of the message is added to the arrival log line,
28662 preceded by `T=' (T for `topic', since S is already used for `size').
28663 Any MIME `words' in the subject are decoded. The \print@_topbitchars\ option
28664 specifies whether characters with values greater than 127 should be logged
28665 unchanged, or whether they should be rendered as escape sequences.
28667 .index log||certificate verification
28668 \tls@_certificate@_verified\: An extra item is added to <= and => log lines
28669 when TLS is in use. The item is \"CV=yes"\ if the peer's certificate was
28670 verified, and \"CV=no"\ if not.
28672 .index log||TLS cipher
28673 .index TLS||logging cipher
28674 \tls@_cipher\: When a message is sent or received over an encrypted connection,
28675 the cipher suite used is added to the log line, preceded by X=.
28677 .index log||TLS peer DN
28678 .index TLS||logging peer DN
28679 \tls@_peerdn\: When a message is sent or received over an encrypted connection,
28680 and a certificate is supplied by the remote host, the peer DN is added to the
28681 log line, preceded by DN=.
28684 .section Message log
28685 .index message||log file for
28686 .index log||message log, description of
28687 In addition to the general log files, Exim writes a log file for each message
28688 that it handles. The names of these per-message logs are the message ids, and
28689 .index \(msglog)\ directory
28690 they are kept in the \(msglog)\ sub-directory of the spool directory. Each
28691 message log contains copies of the log lines that apply to the message. This
28692 makes it easier to inspect the status of an individual message without having
28693 to search the main log. A message log is deleted when processing of the message
28695 .index \preserve@_message@_logs\
28696 unless \preserve__message__logs\ is set, but this should be used only with
28697 great care because they can fill up your disk very quickly.
28699 On a heavily loaded system, it may be desirable to disable the use of
28700 per-message logs, in order to reduce disk I/O. This can be done by setting the
28701 \message@_logs\ option false.
28708 . ============================================================================
28709 .chapter Exim utilities
28710 .set runningfoot "utilities"
28711 .rset CHAPutils ~~chapter
28713 A number of utility scripts and programs are supplied with Exim and are
28714 described in this chapter. There is also the Exim Monitor, which is covered in
28715 the next chapter. The utilities described here are:
28717 . This duplication seems to be the only way to arrange that the cross-
28718 . references are omitted in the Texinfo version. They look horribly ugly.
28723 \*exiwhat*\ $t $rm{list what Exim processes are doing}
28725 \*exiqgrep*\ $t $rm{grep the queue}
28727 \*exiqsumm*\ $t $rm{summarize the queue}
28728 \*exigrep*\ $t $rm{search the main log}
28729 \*exipick*\ $t $rm{select messages on various criteria}
28730 \*exicyclog*\ $t $rm{cycle (rotate) log files}
28731 \*eximstats*\ $t $rm{extract statistics from the log}
28732 \*exim@_checkaccess*\ $t $rm{check address acceptance from given IP}
28733 \*exim@_dbmbuild*\ $t $rm{build a DBM file}
28734 \*exinext*\ $t $rm{extract retry information}
28735 \*exim@_dumpdb*\ $t $rm{dump a hints database}
28736 \*exim@_tidydb*\ $t $rm{clean up a hints database}
28737 \*exim@_fixdb*\ $t $rm{patch a hints database}
28738 \*exim@_lock*\ $t $rm{lock a mailbox file}
28745 ~~SECTfinoutwha \*exiwhat*\ $t $rm{list what Exim processes are doing}
28746 ~~SECTgreptheque \*exiqgrep*\ $t $rm{grep the queue}
28747 ~~SECTsumtheque \*exiqsumm*\ $t $rm{summarize the queue}
28748 ~~SECTextspeinf \*exigrep*\ $t $rm{search the main log}
28749 ~~SECTexipick \*exipick*\ $t $rm{select messages on various criteria}
28750 ~~SECTcyclogfil \*exicyclog*\ $t $rm{cycle (rotate) log files}
28751 ~~SECTmailstat \*eximstats*\ $t $rm{extract statistics from the log}
28752 ~~SECTcheckaccess \*exim@_checkaccess*\ $t $rm{check address acceptance from given IP}
28753 ~~SECTdbmbuild \*exim@_dbmbuild*\ $t $rm{build a DBM file}
28754 ~~SECTfinindret \*exinext*\ $t $rm{extract retry information}
28755 ~~SECThindatmai \*exim@_dumpdb*\ $t $rm{dump a hints database}
28756 ~~SECThindatmai \*exim@_tidydb*\ $t $rm{clean up a hints database}
28757 ~~SECThindatmai \*exim@_fixdb*\ $t $rm{patch a hints database}
28758 ~~SECTmailboxmaint \*exim@_lock*\ $t $rm{lock a mailbox file}
28762 .section Finding out what Exim processes are doing (exiwhat)
28763 .rset SECTfinoutwha "~~chapter.~~section"
28765 .index process, querying
28767 On operating systems that can restart a system call after receiving a signal
28768 (most modern OS), an Exim process responds to the \\SIGUSR1\\ signal by writing
28769 a line describing what it is doing to the file \(exim-process.info)\ in the
28770 Exim spool directory. The \*exiwhat*\ script sends the signal to all Exim
28771 processes it can find, having first emptied the file. It then waits for one
28772 second to allow the Exim processes to react before displaying the results. In
28773 order to run \*exiwhat*\ successfully you have to have sufficient privilege to
28774 send the signal to the Exim processes, so it is normally run as root.
28777 \**Warning**\: This is not an efficient process. It is intended for occasional
28778 use by system administrators. It is not sensible, for example, to set up a
28779 script that sends \\SIGUSR1\\ signals to Exim processes at short intervals.
28782 Unfortunately, the \*ps*\ command that \*exiwhat*\ uses to find Exim processes
28783 varies in different operating systems. Not only are different options used,
28784 but the format of the output is different. For this reason, there are some
28785 system configuration options that configure exactly how \*exiwhat*\ works. If it
28786 doesn't seem to be working for you, check the following compile-time options:
28788 EXIWHAT@_PS@_CMD $rm{the command for running \*ps*\}
28789 EXIWHAT@_PS@_ARG $rm{the argument for \*ps*\}
28790 EXIWHAT@_EGREP@_ARG $rm{the argument for \*egrep*\ to select from \*ps*\ output}
28791 EXIWHAT@_KILL@_ARG $rm{the argument for the \*kill*\ command}
28793 An example of typical output from \*exiwhat*\ is
28796 164 daemon: -q1h, listening on port 25
28797 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
28798 10492 delivering 0tAycK-0002ij-00 to mail.ref.example [10.19.42.42]
28799 (editor@@ref.example)
28800 10592 handling incoming call from [192.168.243.242]
28801 10628 accepting a local non-SMTP message
28803 The first number in the output line is the process number. The third line has
28804 been split here, in order to fit it on the page.
28807 .section Selective queue listing (exiqgrep)
28808 .rset SECTgreptheque "~~chapter.~~section"
28809 .index \*exiqgrep*\
28810 .index queue||grepping
28811 This utility is a Perl script contributed by Matt Hubbard. It runs
28815 to obtain a queue listing with undelivered recipients only, and then greps the
28816 output to select messages that match given criteria. The following selection
28817 options are available:
28821 .option f <<regex>>
28822 Match the sender address. The field that is tested is enclosed in angle
28823 brackets, so you can test for bounce messages with
28828 .option r <<regex>>
28829 Match a recipient address. The field that is tested is not enclosed in angle
28832 .option s <<regex>>
28833 Match against the size field.
28835 .option y <<seconds>>
28836 Match messages that are younger than the given time.
28838 .option o <<seconds>>
28839 Match messages that are older than the given time.
28842 Match only frozen messages.
28845 Match only non-frozen messages.
28849 The following options control the format of the output:
28854 Display only the count of matching messages.
28857 Long format -- display the full message information as output by Exim. This is
28861 Display message ids only.
28864 Brief format -- one line per message.
28867 Display messages in reverse order.
28871 There is one more option, \-h-\, which outputs a list of options.
28874 .section Summarising the queue (exiqsumm)
28875 .rset SECTsumtheque "~~chapter.~~section"
28876 .index \*exiqsumm*\
28877 .index queue||summary
28878 The \*exiqsumm*\ utility is a Perl script which reads the output of \*exim
28879 -bp*\ and produces a summary of the messages on the queue. Thus, you use it by
28880 running a command such as
28882 exim -bp | exiqsumm
28884 The output consists of one line for each domain that has messages waiting for
28885 it, as in the following example:
28887 3 2322 74m 66m msn.com.example
28889 Each line lists the number of
28890 pending deliveries for a domain, their total volume, and the length of time
28891 that the oldest and the newest messages have been waiting. Note that the number
28892 of pending deliveries is greater than the number of messages when messages
28893 have more than one recipient.
28895 A summary line is output at the end. By default the output is sorted on the
28896 domain name, but \*exiqsumm*\ has the options \-a-\ and \-c-\, which cause the
28897 output to be sorted by oldest message and by count of messages, respectively.
28899 The output of \*exim -bp*\ contains the original addresses in the message, so
28900 this also applies to the output from \*exiqsumm*\. No domains from addresses
28901 generated by aliasing or forwarding are included (unless the \one@_time\ option
28902 of the \%redirect%\ router has been used to convert them into `top level'
28907 .section Extracting specific information from the log (exigrep)
28908 .rset SECTextspeinf "~~chapter.~~section"
28910 .index log||extracts, grepping for
28911 The \*exigrep*\ utility is a Perl script that searches one or more main log
28912 files for entries that match a given pattern. When it finds a match, it
28913 extracts all the log entries for the relevant message, not just those that
28914 match the pattern. Thus, \*exigrep*\ can extract complete log entries for a
28915 given message, or all mail for a given user, or for a given host, for example.
28917 If a matching log line is not associated with a specific message, it is always
28918 included in \*exigrep*\'s output.
28921 exigrep [-l] [-t<n>] <pattern> [<log file>] ...
28923 The \-t-\ argument specifies a number of seconds. It adds an additional
28924 condition for message selection. Messages that are complete are shown only if
28925 they spent more than <<n>> seconds on the queue.
28927 The \-l-\ flag means `literal', that is, treat all characters in the
28928 pattern as standing for themselves. Otherwise the pattern must be a Perl
28929 regular expression. The pattern match is case-insensitive. If no file names are
28930 given on the command line, the standard input is read.
28932 If the location of a \*zcat*\ command is known from the definition of
28933 \\ZCAT@_COMMAND\\ in \(Local/Makefile)\, \*exigrep*\ automatically passes any
28934 file whose name ends in \\COMPRESS@_SUFFIX\\ through \*zcat*\ as it searches
28937 .section Selecting messages by various criteria (exipick)
28938 .rset SECTexipick "~~chapter.~~section"
28940 John Jetmore's \*exipick*\ utility is included in the Exim distribution. It
28941 lists messages from the queue according to a variety of criteria. For details,
28948 .section Cycling log files (exicyclog)
28949 .rset SECTcyclogfil "~~chapter.~~section"
28950 .index log||cycling local files
28951 .index cycling logs
28952 .index \*exicyclog*\
28953 The \*exicyclog*\ script can be used to cycle (rotate) \*mainlog*\ and
28954 \*rejectlog*\ files. This is not necessary if only syslog is being used, or if
28955 you are using log files with datestamps in their names (see section
28956 ~~SECTdatlogfil). Some operating systems have their own standard mechanisms for
28957 log cycling, and these can be used instead of \*exicyclog*\ if preferred.
28959 Each time \*exicyclog*\ is run the file names get `shuffled down' by one. If
28960 the main log file name is \(mainlog)\ (the default) then when \*exicyclog*\ is
28961 run \(mainlog)\ becomes \(mainlog.01)\, the previous \(mainlog.01)\ becomes
28962 \(mainlog.02)\ and so on, up to a limit which is set in the script, and which
28965 Log files whose numbers exceed the limit are discarded.
28967 Reject logs are handled similarly.
28970 If the limit is greater than 99, the script uses 3-digit numbers such as
28971 \(mainlog.001)\, \(mainlog.002)\, etc. If you change from a number less than 99
28972 to one that is greater, or \*vice versa*\, you will have to fix the names of
28973 any existing log files.
28976 If no \(mainlog)\ file exists, the script does nothing. Files that `drop off'
28977 the end are deleted. All files with numbers greater than 01 are compressed,
28978 using a compression command which is configured by the \\COMPRESS@_COMMAND\\
28979 setting in \(Local/Makefile)\. It is usual to run \*exicyclog*\ daily from a
28980 root \crontab\ entry of the form
28982 1 0 * * * su exim -c /usr/exim/bin/exicyclog
28984 assuming you have used the name `exim' for the Exim user. You can run
28985 \*exicyclog*\ as root if you wish, but there is no need.
28988 .section Mail statistics (eximstats)
28989 .rset SECTmailstat "~~chapter.~~section"
28991 .index \*eximstats*\
28992 A Perl script called \*eximstats*\ is provided for extracting statistical
28993 information from log files. The output is either plain text, or HTML.
28994 Exim log files are also suported by the \*Lire*\ system produced by the
28995 LogReport Foundation (\?http://www.logreport.org?\).
28997 The \*eximstats*\ script has been hacked about quite a bit over time. The
28998 latest version is the result of some extensive revision by Steve Campbell. A
28999 lot of information is given by default, but there are options for suppressing
29000 various parts of it. Following any options, the arguments to the script are a
29001 list of files, which should be main log files. For example:
29003 eximstats -nr /var/spool/exim/log/mainlog.01
29005 By default, \*eximstats*\ extracts information about the number and volume of
29006 messages received from or delivered to various hosts. The information is sorted
29007 both by message count and by volume, and the top fifty hosts in each category
29008 are listed on the standard output. Similar information, based on email
29009 addresses or domains instead of hosts can be requested by means of various
29010 options. For messages delivered and received locally, similar statistics are
29011 also produced per user.
29013 The output also includes total counts and statistics about delivery errors, and
29014 histograms showing the number of messages received and deliveries made in each
29015 hour of the day. A delivery with more than one address in its envelope (for
29016 example, an SMTP transaction with more than one \\RCPT\\ command) is counted
29017 as a single delivery by \*eximstats*\.
29019 Though normally more deliveries than receipts are reported (as messages may
29020 have multiple recipients), it is possible for \*eximstats*\ to report more
29021 messages received than delivered, even though the queue is empty at the start
29022 and end of the period in question. If an incoming message contains no valid
29023 recipients, no deliveries are recorded for it. A bounce message is handled as
29024 an entirely separate message.
29026 \*eximstats*\ always outputs a grand total summary giving the volume and number
29027 of messages received and deliveries made, and the number of hosts involved in
29028 each case. It also outputs the number of messages that were delayed (that is,
29029 not completely delivered at the first attempt), and the number that had at
29030 least one address that failed.
29032 The remainder of the output is in sections that can be independently disabled
29033 or modified by various options. It consists of a summary of deliveries by
29034 transport, histograms of messages received and delivered per time interval
29035 (default per hour), information about the time messages spent on the queue,
29036 a list of relayed messages, lists of the top fifty sending hosts, local
29037 senders, destination hosts, and destination local users by count and by volume,
29038 and a list of delivery errors that occurred.
29040 The relay information lists messages that were actually relayed, that is, they
29041 came from a remote host and were directly delivered to some other remote host,
29042 without being processed (for example, for aliasing or forwarding) locally.
29044 The options for \*eximstats*\ are as follows:
29047 .index \*eximstats*\||options
29049 The `league tables' are computed on the basis of the superior domains of the
29050 sending hosts instead of the sending and receiving hosts. This option may be
29051 combined with \-byhost-\ and/or \-byemail-\.
29054 This is a synonym for \-byemaildomain-\.
29057 The `league tables' are computed on the basis of complete email addresses,
29058 instead of sending and receiving hosts. This option may be combined with
29059 \-byhost-\ and/or \-bydomain-\.
29061 .option byemaildomain
29062 The `league tables' are computed on the basis of the sender's email domain
29063 instead of the sending and receiving hosts. This option may be combined with
29064 \-byhost-\, \-bydomain-\, or \-byemail-\.
29067 The `league tables' are computed on the basis of sending and receiving hosts.
29068 This is the default option. It may be combined with \-bydomain-\ and/or
29072 Cache results of \*timegm()*\ lookups. This results in a significant speedup
29073 when processing hundreds of thousands of messages, at a cost of increasing the
29074 memory utilisation.
29076 .option chartdir <<dir>>
29077 When \-charts-\ is specified, create the charts in the directory <<dir>>.
29079 .option chartrel <<dir>>
29080 When \-charts-\ is specified, this option specifies the relative directory for
29081 the \"img src="\ tags from where to include the charts.
29084 Create graphical charts to be displayed in HTML output. This requires the
29085 \"GD"\, \"GDTextUtil"\, and \"GDGraph"\ Perl modules, which can be obtained
29086 from \?http://www.cpan.org/modules/01modules.index.html?\.
29088 To install these, download and unpack them, then use the normal Perl
29089 installation procedure:
29098 This is a debug flag. It causes \*eximstats*\ to output the \*eval()*\'d parser
29099 to the standard output, which makes it easier to trap errors in the eval
29100 section. Remember to add one to the line numbers to allow for the title.
29104 Show help information about \*eximstats*\' options.
29107 This option controls the histograms of messages received and deliveries per
29108 time interval. By default the time interval is one hour. If \-h0-\ is given,
29109 the histograms are suppressed; otherwise the value of <<n>> gives the number of
29110 divisions per hour. Valid values are 0, 1, 2, 3, 5, 10, 15, 20, 30 or 60, so
29111 \-h2-\ sets an interval of 30 minutes, and the default is equivalent to \-h1-\.
29114 Output the results in HTML instead of plain text.
29117 This option causes \*eximstats*\ to merge old reports into a combined report.
29118 When this option is used, the input files must be outputs from previous calls
29119 to \*eximstats*\, not raw log files. For example, you could produce a set of
29120 daily reports and a weekly report by commands such as
29122 eximstats mainlog.sun > report.sun.txt
29123 eximstats mainlog.mon > report.mon.txt
29124 eximstats mainlog.tue > report.tue.txt
29125 eximstats mainlog.wed > report.wed.txt
29126 eximstats mainlog.thu > report.thu.txt
29127 eximstats mainlog.fri > report.fri.txt
29128 eximstats mainlog.sat > report.sat.txt
29129 eximstats -merge -html report.*.txt > weekly_report.html
29131 You can merge text or html reports and output the results as text or html. You
29132 can use all the normal \*eximstats*\ output options, but only data included in
29133 the original reports can be shown. When merging reports, some loss of accuracy
29134 may occur in the `league tables', towards the ends of the lists. The order of
29135 items in the `league tables' may vary when the data volumes round to the same
29139 Suppress the display of information about failed deliveries (errors).
29142 Suppress information about messages relayed through this host.
29144 .option nr /pattern/
29145 Suppress information about relayed messages that match the pattern, which is
29146 matched against a string of the following form (split over two lines here in
29147 order to fit it on the page):
29149 H=<host> [<ip address>] A=<sender address> =>
29150 H=<host> A=<recipient address>
29154 H=in.host [1.2.3.4] A=from@some.where.example =>
29155 H=out.host A=to@else.where.example
29157 The sending host name appears in parentheses if it has not been verified as
29158 matching the IP address. The mail addresses are taken from the envelope, not
29159 the headers. This option allows you to screen out hosts whom you are happy to
29160 have using your host as a relay.
29163 Suppress the statistics about delivery by transport.
29165 .option nt/<<pattern>>/
29166 Suppress the statistics about delivery by any transport whose name matches the
29167 pattern. If you are using one transport to send all messages to a scanning
29168 mechanism before doing the real delivery, this feature can be used to omit that
29169 transport from your normal statistics (on the grounds that it is of no
29173 .option "pattern" "#<<description>>#/<<pattern>>/"
29174 Count lines matching specified patterns and show them in
29175 the results. For example:
29177 -pattern 'Refused connections' '/refused connection/'
29179 This option can be specified multiple times.
29182 Suppress information about times messages spend on the queue.
29184 .option q <<n1>>...
29185 This option sets an alternative list of time intervals for the queueing
29186 information. The values are separated by commas and are in seconds, but can
29187 involve arithmetic multipliers, so for example you can set 3$*$60 to specify 3
29188 minutes. A setting such as
29192 causes \*eximstats*\ to give counts of messages that stayed on the queue for less
29193 than one minute, less than five minutes, less than ten minutes, and over ten
29197 Sets the `top' count to <<n>>. This controls the listings of the `top <<n>>'
29198 hosts and users by count and volume. The default is 50, and setting 0
29199 suppresses the output altogether.
29202 Omit local information from the `top' listings.
29204 .option t@_remote@_users
29205 Include remote users in the `top' listings.
29210 .section Checking access policy (exim@_checkaccess)
29211 .rset SECTcheckaccess "~~chapter.~~section"
29212 .index \*exim@_checkaccess*\
29213 .index policy control||checking access
29214 .index checking access
29215 The \-bh-\ command line argument allows you to run a fake SMTP session with
29216 debugging output, in order to check what Exim is doing when it is applying
29217 policy controls to incoming SMTP mail. However, not everybody is sufficiently
29218 familiar with the SMTP protocol to be able to make full use of \-bh-\, and
29219 sometimes you just want to answer the question \*Does this address have
29220 access?*\ without bothering with any further details.
29222 The \*exim@_checkaccess*\ utility is a `packaged' version of \-bh-\. It takes
29223 two arguments, an IP address and an email address:
29225 exim_checkaccess 10.9.8.7 A.User@a.domain.example
29227 The utility runs a call to Exim with the \-bh-\ option, to test whether the
29228 given email address would be accepted in a \\RCPT\\ command in a TCP/IP
29229 connection from the host with the given IP address. The output of the utility
29230 is either the word `accepted', or the SMTP error response, for example:
29233 550 Relay not permitted
29235 When running this test, the utility uses \"<>"\ as the envelope sender address
29236 for the \\MAIL\\ command, but you can change this by providing additional
29237 options. These are passed directly to the Exim command. For example, to specify
29238 that the test is to be run with the sender address \*himself@@there.example*\
29241 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
29242 -f himself@there.example
29244 Note that these additional Exim command line items must be given after the two
29245 mandatory arguments.
29247 Because the \exim@_checkaccess\ uses \-bh-\, it does not perform callouts while
29248 running its checks. You can run checks that include callouts by using \-bhc-\,
29249 but this is not yet available in a `packaged' form.
29252 .section Making DBM files (exim@_dbmbuild)
29253 .rset SECTdbmbuild "~~chapter.~~section"
29254 .index DBM||building dbm files
29255 .index building DBM files
29256 .index \*exim@_dbmbuild*\
29257 .index lower casing
29258 .index binary zero||in lookup key
29259 The \*exim@_dbmbuild*\ program reads an input file containing keys and data in
29260 the format used by the \%lsearch%\ lookup (see section ~~SECTsinglekeylookups).
29261 It writes a DBM file using the lower-cased alias names as keys and the
29262 remainder of the information as data. The lower-casing can be prevented by
29263 calling the program with the \-nolc-\ option.
29265 A terminating zero is included as part of the key string. This is expected by
29266 the \%dbm%\ lookup type. However, if the option \-nozero-\ is given,
29267 \*exim@_dbmbuild*\ creates files without terminating zeroes in either the key
29268 strings or the data strings. The \%dbmnz%\ lookup type can be used with such
29271 The program requires two arguments: the name of the input file (which can be a
29272 single hyphen to indicate the standard input), and the name of the output file.
29273 It creates the output under a temporary name, and then renames it if all went
29276 If the native DB interface is in use (\\USE@_DB\\ is set in a compile-time
29277 configuration file -- this is common in free versions of Unix) the two file
29278 names must be different, because in this mode the Berkeley DB functions create
29279 a single output file using exactly the name given. For example,
29281 exim_dbmbuild /etc/aliases /etc/aliases.db
29283 reads the system alias file and creates a DBM version of it in
29284 \(/etc/aliases.db)\.
29286 In systems that use the \*ndbm*\ routines (mostly proprietary versions of Unix),
29287 two files are used, with the suffixes \(.dir)\ and \(.pag)\. In this
29288 environment, the suffixes are added to the second argument of
29289 \*exim@_dbmbuild*\, so it can be the same as the first. This is also the case
29290 when the Berkeley functions are used in compatibility mode (though this is not
29291 recommended), because in that case it adds a \(.db)\ suffix to the file name.
29293 If a duplicate key is encountered, the program outputs a warning, and when it
29294 finishes, its return code is 1 rather than zero, unless the \-noduperr-\ option
29295 is used. By default, only the first of a set of duplicates is used -- this
29296 makes it compatible with \%lsearch%\ lookups. There is an option \-lastdup-\
29297 which causes it to use the data for the last duplicate instead. There is also
29298 an option \-nowarn-\, which stops it listing duplicate keys to \stderr\. For
29299 other errors, where it doesn't actually make a new file, the return code is 2.
29303 .section Finding individual retry times (exinext)
29304 .rset SECTfinindret "~~chapter.~~section"
29305 .index retry||times
29307 A utility called \*exinext*\ (mostly a Perl script) provides the ability to fish
29308 specific information out of the retry database. Given a mail domain (or a
29309 complete address), it looks up the hosts for that domain, and outputs any retry
29310 information for the hosts or for the domain. At present, the retry information
29311 is obtained by running \*exim@_dumpdb*\ (see below) and post-processing the
29312 output. For example:
29314 $ exinext piglet@milne.fict.example
29315 kanga.milne.fict.example:192.168.8.1 error 146: Connection refused
29316 first failed: 21-Feb-1996 14:57:34
29317 last tried: 21-Feb-1996 14:57:34
29318 next try at: 21-Feb-1996 15:02:34
29319 roo.milne.fict.example:192.168.8.3 error 146: Connection refused
29320 first failed: 20-Jan-1996 13:12:08
29321 last tried: 21-Feb-1996 11:42:03
29322 next try at: 21-Feb-1996 19:42:03
29323 past final cutoff time
29325 You can also give \*exinext*\ a local part, without a domain, and it
29326 will give any retry information for that local part in your default domain.
29327 A message id can be used to obtain retry information pertaining to a specific
29328 message. This exists only when an attempt to deliver a message to a remote host
29329 suffers a message-specific error (see section ~~SECToutSMTPerr). \*exinext*\ is
29330 not particularly efficient, but then it isn't expected to be run very often.
29332 The \*exinext*\ utility calls Exim to find out information such as the location
29333 of the spool directory. The utility has \-C-\ and \-D-\ options, which are
29334 passed on to the \*exim*\ commands. The first specifies an alternate Exim
29335 configuration file, and the second sets macros for use within the configuration
29336 file. These features are mainly to help in testing, but might also be useful in
29337 environments where more than one configuration file is in use.
29341 .section Hints database maintenance (exim@_dumpdb, exim@_fixdb, exim@_tidydb)
29342 .rset SECThindatmai "~~chapter.~~section"
29343 .index hints database||maintenance
29344 .index maintaining Exim's hints database
29345 Three utility programs are provided for maintaining the DBM files that Exim
29346 uses to contain its delivery hint information. Each program requires two
29347 arguments. The first specifies the name of Exim's spool directory, and the
29348 second is the name of the database it is to operate on. These are as
29351 \*retry*\: the database of retry information
29353 \*wait-*\<<transport name>>: databases of information about messages waiting
29356 \*callout*\: the callout cache
29358 \*misc*\: other hints data
29360 The \*misc*\ database is used for
29362 Serializing \\ETRN\\ runs (when \smtp@_etrn@_serialize\ is set)
29364 Serializing delivery to a specific host (when \serialize@_hosts\ is set in an
29365 \%smtp%\ transport)
29368 .section exim@_dumpdb
29369 .index \*exim@_dumpdb*\
29370 The entire contents of a database are written to the standard output by the
29371 \*exim@_dumpdb*\ program, which has no options or arguments other than the
29372 spool and database names. For example, to dump the retry database:
29374 exim_dumpdb /var/spool/exim retry
29376 Two lines of output are produced for each entry:
29378 T:mail.ref.example:192.168.242.242 146 77 Connection refused
29379 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
29381 The first item on the first line is the key of the record. It starts with one
29382 of the letters R, or T, depending on whether it refers to a routing or
29383 transport retry. For a local delivery, the next part is the local address; for
29384 a remote delivery it is the name of the remote host, followed by its failing IP
29385 address (unless \no@_retry@_include@_ip@_address\ is set on the \%smtp%\
29386 transport). If the remote port is not the standard one (port 25), it is added
29387 to the IP address. Then there follows an error code, an additional error code,
29388 and a textual description of the error.
29390 The three times on the second line are the time of first failure, the time of
29391 the last delivery attempt, and the computed time for the next attempt. The line
29392 ends with an asterisk if the cutoff time for the last retry rule has been
29395 Each output line from \*exim@_dumpdb*\ for the \*wait-*\$it{xxx} databases
29396 consists of a host name followed by a list of ids for messages that are or were
29397 waiting to be delivered to that host. If there are a very large number for any
29398 one host, continuation records, with a sequence number added to the host name,
29399 may be seen. The data in these records is often out of date, because a message
29400 may be routed to several alternative hosts, and Exim makes no effort to keep
29404 .section exim@_tidydb
29405 .index \*exim@_tidydb*\
29406 The \*exim@_tidydb*\ utility program is used to tidy up the contents of the
29407 hints databases. If run with no options, it removes all records from a database
29408 that are more than 30 days old. The cutoff date can be altered by means of the
29409 \-t-\ option, which must be followed by a time. For example, to remove all
29410 records older than a week from the retry database:
29412 exim_tidydb -t 7d /var/spool/exim retry
29414 Both the \*wait-*\$it{xxx} and \*retry*\ databases contain items that involve
29415 message ids. In the former these appear as data in records keyed by host --
29416 they were messages that were waiting for that host -- and in the latter they
29417 are the keys for retry information for messages that have suffered certain
29418 types of error. When \*exim@_tidydb*\ is run, a check is made to ensure that
29419 message ids in database records are those of messages that are still on the
29420 queue. Message ids for messages that no longer exist are removed from
29421 \*wait-*\$it{xxx} records, and if this leaves any records empty, they are
29422 deleted. For the \*retry*\ database, records whose keys are non-existent
29423 message ids are removed. The \*exim@_tidydb*\ utility outputs comments on the
29424 standard output whenever it removes information from the database.
29427 Certain records are automatically removed by Exim when they are no longer
29428 needed, but others are not. For example, if all the MX hosts for a domain are
29429 down, a retry record is created for each one. If the primary MX host comes back
29430 first, its record is removed when Exim successfully delivers to it, but the
29431 records for the others remain because Exim has not tried to use those hosts.
29433 It is important, therefore, to run \*exim@_tidydb*\ periodically on all the
29434 hints databases. You should do this at a quiet time of day, because it requires
29435 a database to be locked (and therefore inaccessible to Exim) while it does its
29436 work. Removing records from a DBM file does not normally make the file smaller,
29437 but all the common DBM libraries are able to re-use the space that is released.
29438 After an initial phase of increasing in size, the databases normally reach a
29439 point at which they no longer get any bigger, as long as they are regularly
29442 \**Warning**\: If you never run \*exim@_tidydb*\, the space used by the hints
29443 databases is likely to keep on increasing.
29447 .section exim@_fixdb
29448 .index \*exim@_fixdb*\
29449 The \*exim@_fixdb*\ program is a utility for interactively modifying databases.
29450 Its main use is for testing Exim, but it might also be occasionally useful for
29451 getting round problems in a live system. It has no options, and its interface
29452 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
29453 key of a database record can then be entered, and the data for that record is
29456 If `d' is typed at the next prompt, the entire record is deleted. For all
29457 except the \*retry*\ database, that is the only operation that can be carried
29458 out. For the \*retry*\ database, each field is output preceded by a number, and
29459 data for individual fields can be changed by typing the field number followed
29460 by new data, for example:
29464 resets the time of the next delivery attempt. Time values are given as a
29465 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
29466 used as optional separators.
29470 .section Mailbox maintenance (exim@_lock)
29471 .rset SECTmailboxmaint "~~chapter.~~section"
29472 .index mailbox||maintenance
29473 .index \*exim@_lock*\
29474 .index locking mailboxes
29475 The \*exim@_lock*\ utility locks a mailbox file using the same algorithm as
29476 Exim. For a discussion of locking issues, see section ~~SECTopappend.
29477 \*Exim@_lock*\ can be used to prevent any modification of a mailbox by Exim or
29478 a user agent while investigating a problem. The utility requires the name of
29479 the file as its first argument. If the locking is successful, the second
29480 argument is run as a command (using C's \*system()*\ function); if there is no
29481 second argument, the value of the SHELL environment variable is used; if this
29482 is unset or empty, \(/bin/sh)\ is run. When the command finishes, the mailbox
29483 is unlocked and the utility ends. The following options are available:
29488 Use \*fcntl()*\ locking on the open mailbox.
29491 Use \*flock()*\ locking on the open mailbox, provided the operating system
29495 This must be followed by a number, which is a number of seconds; it sets the
29496 interval to sleep between retries (default 3).
29499 Create a lock file before opening the mailbox.
29502 Lock the mailbox using MBX rules.
29505 Suppress verification output.
29508 This must be followed by a number; it sets the number of times to try to get
29509 the lock (default 10).
29511 .option restore@_time
29512 This option causes \exim@_lock\ to restore the modified and read times to the
29513 locked file before exiting. This allows you to access a locked mailbox (for
29514 example, to take a backup copy) without disturbing the times that the user
29518 This must be followed by a number, which is a number of seconds; it sets a
29519 timeout to be used with a blocking \*fcntl()*\ lock. If it is not set (the
29520 default), a non-blocking call is used.
29523 Generate verbose output.
29527 If none of \-fcntl-\,
29529 \-lockfile-\ or \-mbx-\ are given, the default is to create a lock file and
29530 also to use \*fcntl()*\ locking on the mailbox, which is the same as Exim's
29531 default. The use of
29533 or \-fcntl-\ requires that the file be writeable; the use of
29534 \-lockfile-\ requires that the directory containing the file be writeable.
29535 Locking by lock file does not last for ever; Exim assumes that a lock file is
29536 expired if it is more than 30 minutes old.
29538 The \-mbx-\ option can be used with either or both of \-fcntl-\ or \-flock-\.
29539 It assumes \-fcntl-\ by default.
29540 MBX locking causes a shared lock to be taken out on the open mailbox, and an
29541 exclusive lock on the file \(/tmp/.$it{n}.$it{m})\ where $it{n} and $it{m} are
29542 the device number and inode number of the mailbox file. When the locking is
29543 released, if an exclusive lock can be obtained for the mailbox, the file in
29544 \(/tmp)\ is deleted.
29546 The default output contains verification of the locking that takes place. The
29547 \-v-\ option causes some additional information to be given. The \-q-\ option
29548 suppresses all output except error messages.
29552 exim_lock /var/spool/mail/spqr
29554 runs an interactive shell while the file is locked, whereas
29556 exim@_lock -q /var/spool/mail/spqr @<@<End
29560 runs a specific non-interactive sequence of commands while the file is locked,
29561 suppressing all verification output. A single command can be run by a command
29564 exim_lock -q /var/spool/mail/spqr \
29565 "cp /var/spool/mail/spqr /some/where"
29567 Note that if a command is supplied, it must be entirely contained within the
29568 second argument -- hence the quotes.
29576 . ============================================================================
29577 .chapter The Exim monitor
29578 .set runningfoot "monitor"
29579 .rset CHAPeximon ~~chapter
29581 .index Exim monitor
29584 .index Local/eximon.conf
29585 .index \(exim@_monitor/EDITME)\
29586 The Exim monitor is an application which displays in an X window information
29587 about the state of Exim's queue and what Exim is doing. An admin user can
29588 perform certain operations on messages from this GUI interface; however all
29589 such facilities are also available from the command line, and indeed, the
29590 monitor itself makes use of the command line to perform any actions requested.
29593 .section Running the monitor
29594 The monitor is started by running the script called \*eximon*\. This is a shell
29595 script that sets up a number of environment variables, and then runs the
29596 binary called \(eximon.bin)\. The default appearance of the monitor window can
29597 be changed by editing the \(Local/eximon.conf)\ file created by editing
29598 \(exim@_monitor/EDITME)\. Comments in that file describe what the various
29599 parameters are for.
29601 The parameters that get built into the \*eximon*\ script can be overridden for a
29602 particular invocation by setting up environment variables of the same names,
29603 preceded by `$tt{EXIMON@_}'. For example, a shell command such as
29605 EXIMON_LOG_DEPTH=400 eximon
29607 (in a Bourne-compatible shell) runs \*eximon*\ with an overriding setting of the
29608 \\LOG@_DEPTH\\ parameter. If \\EXIMON@_LOG@_FILE@_PATH\\ is set in the
29609 environment, it overrides the Exim log file configuration. This makes it
29610 possible to have \*eximon*\ tailing log data that is written to syslog, provided
29611 that MAIL.INFO syslog messages are routed to a file on the local host.
29613 X resources can be used to change the appearance of the window in the normal
29614 way. For example, a resource setting of the form
29616 Eximon*background: gray94
29618 changes the colour of the background to light grey rather than white. The
29619 stripcharts are drawn with both the data lines and the reference lines in
29620 black. This means that the reference lines are not visible when on top of the
29621 data. However, their colour can be changed by setting a resource called
29622 `highlight' (an odd name, but that's what the Athena stripchart widget uses).
29623 For example, if your X server is running Unix, you could set up lighter
29624 reference lines in the stripcharts by obeying
29627 Eximon*highlight: gray
29632 In order to see the contents of messages on the queue, and to operate on them,
29633 \*eximon*\ must either be run as root or by an admin user.
29635 The monitor's window is divided into three parts. The first contains one or
29636 more stripcharts and two action buttons, the second contains a `tail' of the
29637 main log file, and the third is a display of the queue of messages awaiting
29638 delivery, with two more action buttons. The following sections describe these
29639 different parts of the display.
29643 .section The stripcharts
29645 The first stripchart is always a count of messages on the queue. Its name can
29646 be configured by setting \\QUEUE@_STRIPCHART@_NAME\\ in the
29647 \(Local/eximon.conf)\ file. The remaining stripcharts are defined in the
29648 configuration script by regular expression matches on log file entries, making
29649 it possible to display, for example, counts of messages delivered to certain
29650 hosts or using certain transports. The supplied defaults display counts of
29651 received and delivered messages, and of local and SMTP deliveries. The default
29652 period between stripchart updates is one minute; this can be adjusted by a
29653 parameter in the \(Local/eximon.conf)\ file.
29655 The stripchart displays rescale themselves automatically as the value they are
29656 displaying changes. There are always 10 horizontal lines in each chart; the
29657 title string indicates the value of each division when it is greater than one.
29658 For example, `x2' means that each division represents a value of 2.
29660 It is also possible to have a stripchart which shows the percentage fullness of
29661 a particular disk partition, which is useful when local deliveries are confined
29662 to a single partition.
29663 .index \statvfs\ function
29664 This relies on the availability of the \*statvfs()*\ function or equivalent in
29665 the operating system. Most, but not all versions of Unix that support Exim have
29666 this. For this particular stripchart, the top of the chart always represents
29667 100%, and the scale is given as `x10%'. This chart is configured by setting
29668 \\SIZE@_STRIPCHART\\ and (optionally) \\SIZE@_STRIPCHART@_NAME\\ in the
29669 \(Local/eximon.conf)\ file.
29673 .section Main action buttons
29674 .index size||of monitor window
29675 .index monitor window size
29677 Below the stripcharts there is an action button for quitting the monitor. Next
29678 to this is another button marked `Size'. They are placed here so that shrinking
29679 the window to its default minimum size leaves just the queue count stripchart
29680 and these two buttons visible. Pressing the `Size' button causes the window to
29681 expand to its maximum size, unless it is already at the maximum, in which case
29682 it is reduced to its minimum.
29684 When expanding to the maximum, if the window cannot be fully seen where it
29685 currently is, it is moved back to where it was the last time it was at full
29686 size. When it is expanding from its minimum size, the old position is
29687 remembered, and next time it is reduced to the minimum it is moved back there.
29689 The idea is that you can keep a reduced window just showing one or two
29690 stripcharts at a convenient place on your screen, easily expand it to show
29691 the full window when required, and just as easily put it back to what it was.
29692 The idea is copied from what the \*twm*\ window manager does for its
29693 \*f.fullzoom*\ action. The minimum size of the window can be changed by setting
29694 the \\MIN@_HEIGHT\\ and \\MIN@_WIDTH\\ values in \(Local/eximon.conf)\.
29696 Normally, the monitor starts up with the window at its full size, but it can be
29697 built so that it starts up with the window at its smallest size, by setting
29698 \\START@_SMALL\\=yes in \(Local/eximon.conf)\.
29701 .section The log display
29702 .index log||tail of, in monitor
29703 The second section of the window is an area in which a display of the tail of
29704 the main log is maintained.
29705 To save space on the screen, the timestamp on each log line is shortened by
29706 removing the date and, if \log@_timezone\ is set, the timezone.
29707 The log tail is not available when the only destination for logging data is
29708 syslog, unless the syslog lines are routed to a local file whose name is passed
29709 to \*eximon*\ via the \\EXIMON@_LOG@_FILE@_PATH\\ environment variable.
29711 The log sub-window has a scroll bar at its lefthand side which can be used to
29712 move back to look at earlier text, and the up and down arrow keys also have a
29713 scrolling effect. The amount of log that is kept depends on the setting of
29714 \\LOG@_BUFFER\\ in \(Local/eximon.conf)\, which specifies the amount of memory
29715 to use. When this is full, the earlier 50% of data is discarded -- this is much
29716 more efficient than throwing it away line by line. The sub-window also has a
29717 horizontal scroll bar for accessing the ends of long log lines. This is the
29718 only means of horizontal scrolling; the right and left arrow keys are not
29719 available. Text can be cut from this part of the window using the mouse in the
29720 normal way. The size of this subwindow is controlled by parameters in the
29721 configuration file \(Local/eximon.conf)\.
29723 Searches of the text in the log window can be carried out by means of the ^R
29724 and ^S keystrokes, which default to a reverse and a forward search,
29725 respectively. The search covers only the text that is displayed in the window.
29726 It cannot go further back up the log.
29728 The point from which the search starts is indicated by a caret marker. This is
29729 normally at the end of the text in the window, but can be positioned explicitly
29730 by pointing and clicking with the left mouse button, and is moved automatically
29731 by a successful search. If new text arrives in the window when it is scrolled
29732 back, the caret remains where it is, but if the window is not scrolled back,
29733 the caret is moved to the end of the new text.
29735 Pressing ^R or ^S pops up a window into which the search text can be typed.
29736 There are buttons for selecting forward or reverse searching, for carrying out
29737 the search, and for cancelling. If the `Search' button is pressed, the search
29738 happens and the window remains so that further searches can be done. If the
29739 `Return' key is pressed, a single search is done and the window is closed. If
29740 ^C is typed the search is cancelled.
29742 The searching facility is implemented using the facilities of the Athena text
29743 widget. By default this pops up a window containing both `search' and `replace'
29744 options. In order to suppress the unwanted `replace' portion for eximon, a
29745 modified version of the \TextPop\ widget is distributed with Exim. However, the
29746 linkers in BSDI and HP-UX seem unable to handle an externally provided version
29747 of \TextPop\ when the remaining parts of the text widget come from the standard
29748 libraries. The compile-time option \\EXIMON@_TEXTPOP\\ can be unset to cut out
29749 the modified \TextPop\, making it possible to build Eximon on these systems, at
29750 the expense of having unwanted items in the search popup window.
29753 .section The queue display
29754 .index queue||display in monitor
29755 The bottom section of the monitor window contains a list of all messages that
29756 are on the queue, which includes those currently being received or delivered,
29757 as well as those awaiting delivery. The size of this subwindow is controlled by
29758 parameters in the configuration file \(Local/eximon.conf)\, and the frequency
29759 at which it is updated is controlled by another parameter in the same file --
29760 the default is 5 minutes, since queue scans can be quite expensive. However,
29761 there is an `Update' action button just above the display which can be used to
29762 force an update of the queue display at any time.
29764 When a host is down for some time, a lot of pending mail can build up for it,
29765 and this can make it hard to deal with other messages on the queue. To help
29766 with this situation there is a button next to `Update' called `Hide'. If
29767 pressed, a dialogue box called `Hide addresses ending with' is put up. If you
29768 type anything in here and press `Return', the text is added to a chain of such
29769 texts, and if every undelivered address in a message matches at least one
29770 of the texts, the message is not displayed.
29772 If there is an address that does not match any of the texts, all the addresses
29773 are displayed as normal. The matching happens on the ends of addresses so, for
29774 example, \*cam.ac.uk*\ specifies all addresses in Cambridge, while
29775 \*xxx@@foo.com.example*\ specifies just one specific address. When any hiding
29776 has been set up, a button called `Unhide' is displayed. If pressed, it cancels
29777 all hiding. Also, to ensure that hidden messages do not get forgotten, a hide
29778 request is automatically cancelled after one hour.
29780 While the dialogue box is displayed, you can't press any buttons or do anything
29781 else to the monitor window. For this reason, if you want to cut text from the
29782 queue display to use in the dialogue box, you have to do the cutting before
29783 pressing the `Hide' button.
29785 The queue display contains, for each unhidden queued message, the length of
29786 time it has been on the queue, the size of the message, the message id, the
29787 message sender, and the first undelivered recipient, all on one line. If it is
29788 a bounce message, the sender is shown as `<>'. If there is more than one
29789 recipient to which the message has not yet been delivered, subsequent ones are
29790 listed on additional lines, up to a maximum configured number, following which
29791 an ellipsis is displayed. Recipients that have already received the message are
29793 .index frozen messages||display
29794 If a message is frozen, an asterisk is displayed at the left-hand side.
29796 The queue display has a vertical scroll bar, and can also be scrolled by means
29797 of the arrow keys. Text can be cut from it using the mouse in the normal way.
29798 The text searching facilities, as described above for the log window, are also
29799 available, but the caret is always moved to the end of the text when the queue
29800 display is updated.
29803 .section The queue menu
29804 .index queue||menu in monitor
29805 If the \shift\ key is held down and the left button is clicked when the mouse
29806 pointer is over the text for any message, an action menu pops up, and the first
29807 line of the queue display for the message is highlighted. This does not affect
29810 If you want to use some other event for popping up the menu, you can set the
29811 \\MENU@_EVENT\\ parameter in \(Local/eximon.conf)\ to change the default, or
29812 set \\EXIMON@_MENU@_EVENT\\ in the environment before starting the monitor. The
29813 value set in this parameter is a standard X event description. For example, to
29814 run eximon using \ctrl\ rather than \shift\ you could use
29816 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
29818 The title of the menu is the message id, and it contains entries which act as
29821 \*message log*\: The contents of the message log for the message are displayed in
29824 \*headers*\: Information from the spool file that contains the envelope
29825 information and headers is displayed in a new text window. See chapter
29826 ~~CHAPspool for a description of the format of spool files.
29828 \*body*\: The contents of the spool file containing the body of the message are
29829 displayed in a new text window. There is a default limit of 20,000 bytes to the
29830 amount of data displayed. This can be changed by setting the \\BODY@_MAX\\
29831 option at compile time, or the \\EXIMON@_BODY@_MAX\\ option at run time.
29833 \*deliver message*\: A call to Exim is made using the \-M-\ option to request
29834 delivery of the message. This causes an automatic thaw if the message is
29835 frozen. The \-v-\ option is also set, and the output from Exim is displayed in
29836 a new text window. The delivery is run in a separate process, to avoid holding
29837 up the monitor while the delivery proceeds.
29839 \*freeze message*\: A call to Exim is made using the \-Mf-\ option to request
29840 that the message be frozen.
29842 .index thawing messages
29843 .index unfreezing messages
29844 .index frozen messages||thawing
29845 \*thaw message*\: A call to Exim is made using the \-Mt-\ option to request that
29846 the message be thawed.
29848 .index delivery||forcing failure
29849 \*give up on msg*\: A call to Exim is made using the \-Mg-\ option to request
29850 that Exim gives up trying to deliver the message. A bounce message is generated
29851 for any remaining undelivered addresses.
29853 \*remove message*\: A call to Exim is made using the \-Mrm-\ option to request
29854 that the message be deleted from the system without generating a bounce
29857 \*add recipient*\: A dialog box is displayed into which a recipient address can
29858 be typed. If the address is not qualified and the \\QUALIFY@_DOMAIN\\ parameter
29859 is set in \(Local/eximon.conf)\, the address is qualified with that domain.
29860 Otherwise it must be entered as a fully qualified address. Pressing \\RETURN\\
29861 causes a call to Exim to be made using the \-Mar-\ option to request that an
29862 additional recipient be added to the message, unless the entry box is empty, in
29863 which case no action is taken.
29865 \*mark delivered*\: A dialog box is displayed into which a recipient address can
29866 be typed. If the address is not qualified and the \\QUALIFY@_DOMAIN\\ parameter
29867 is set in \(Local/eximon.conf)\, the address is qualified with that domain.
29868 Otherwise it must be entered as a fully qualified address. Pressing \\RETURN\\
29869 causes a call to Exim to be made using the \-Mmd-\ option to mark the given
29870 recipient address as already delivered, unless the entry box is empty, in which
29871 case no action is taken.
29873 \*mark all delivered*\: A call to Exim is made using the \-Mmad-\ option to mark
29874 all recipient addresses as already delivered.
29876 \*edit sender*\: A dialog box is displayed initialized with the current sender's
29877 address. Pressing \\RETURN\\ causes a call to Exim to be made using the \-Mes-\
29878 option to replace the sender address, unless the entry box is empty, in which
29879 case no action is taken. If you want to set an empty sender (as in bounce
29880 messages), you must specify it as `<>'. Otherwise, if the address is not
29881 qualified and the \\QUALIFY@_DOMAIN\\ parameter is set in
29882 \(Local/eximon.conf)\, the address is qualified with that domain.
29884 When a delivery is forced, a window showing the \-v-\ output is displayed. In
29885 other cases when a call to Exim is made, if there is any output from Exim (in
29886 particular, if the command fails) a window containing the command and the
29887 output is displayed. Otherwise, the results of the action are normally apparent
29888 from the log and queue displays. However, if you set \\ACTION@_OUTPUT\\=yes in
29889 \(Local/eximon.conf)\, a window showing the Exim command is always opened, even
29890 if no output is generated.
29892 The queue display is automatically updated for actions such as freezing and
29893 thawing, unless \\ACTION@_QUEUE@_UPDATE\\=no has been set in
29894 \(Local/eximon.conf)\. In this case the `Update' button has to be used to force
29895 an update of the display after one of these actions.
29897 In any text window that is displayed as result of a menu action, the normal
29898 cut-and-paste facility is available, and searching can be carried out using ^R
29899 and ^S, as described above for the log tail window.
29910 . ============================================================================
29911 .chapter Security considerations
29912 .set runningfoot "security"
29913 .rset CHAPsecurity ~~chapter
29915 This chapter discusses a number of issues concerned with security, some of
29916 which are also covered in other parts of this manual.
29918 For reasons that this author does not understand, some people have promoted
29919 Exim as a `particularly secure' mailer. Perhaps it is because of the existence
29920 of this chapter in the documentation. However, the intent of the chapter is
29921 simply to describe the way Exim works in relation to certain security concerns,
29922 not to make any specific claims about the effectiveness of its security as
29923 compared with other MTAs.
29925 What follows is a description of the way Exim is supposed to be. Best efforts
29926 have been made to try to ensure that the code agrees with the theory, but an
29927 absence of bugs can never be guaranteed. Any that are reported will get fixed
29928 as soon as possible.
29930 .section Building a more `hardened' Exim
29931 .index security||build-time features
29932 There are a number of build-time options that can be set in \(Local/Makefile)\
29933 to create Exim binaries that are `harder' to attack, in particular by a rogue
29934 Exim administrator who does not have the root password, or by someone who has
29935 penetrated the Exim (but not the root) account. These options are as follows:
29937 \\ALT@_CONFIG@_PREFIX\\ can be set to a string that is required to match the
29938 start of any file names used with the \-C-\ option. When it is set, these file
29939 names are also not allowed to contain the sequence `/../'. (However, if the
29940 value of the \-C-\ option is identical to the value of \\CONFIGURE@_FILE\\ in
29941 \(Local/Makefile)\, Exim ignores \-C-\ and proceeds as usual.) There is no
29942 default setting for \ALT@_CONFIG@_PREFIX\.
29944 If the permitted configuration files are confined to a directory to
29945 which only root has access, this guards against someone who has broken
29946 into the Exim account from running a privileged Exim with an arbitrary
29947 configuration file, and using it to break into other accounts.
29949 If \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined, root privilege is retained for \-C-\
29950 and \-D-\ only if the caller of Exim is root. Without it, the Exim user may
29951 also use \-C-\ and \-D-\ and retain privilege. Setting this option locks out
29952 the possibility of testing a configuration using \-C-\ right through message
29953 reception and delivery, even if the caller is root. The reception works, but by
29954 that time, Exim is running as the Exim user, so when it re-execs to regain
29955 privilege for the delivery, the use of \-C-\ causes privilege to be lost.
29956 However, root can test reception and delivery using two separate commands.
29957 \\ALT@_CONFIG@_ROOT@_ONLY\\ is not set by default.
29959 If \\DISABLE@_D@_OPTION\\ is defined, the use of the \-D-\ command line option
29962 \\FIXED@_NEVER@_USERS\\ can be set to a colon-separated list of users that are
29963 never to be used for any deliveries. This is like the \never@_users\ runtime
29964 option, but it cannot be overridden; the runtime option adds additional users
29965 to the list. The default setting is `root'; this prevents a non-root user who
29966 is permitted to modify the runtime file from using Exim as a way to get root.
29970 .section Root privilege
29972 .index root privilege
29973 The Exim binary is normally setuid to root, which means that it gains root
29974 privilege (runs as root) when it starts execution. In some special cases (for
29975 example, when the daemon is not in use and there are no local deliveries), it
29976 may be possible to run Exim setuid to some user other than root. This is
29977 discussed in the next section. However, in most installations, root privilege
29978 is required for two things:
29980 To set up a socket connected to the standard SMTP port (25) when initialising
29981 the listening daemon. If Exim is run from \*inetd*\, this privileged action is
29984 To be able to change uid and gid in order to read users' \(.forward)\ files and
29985 perform local deliveries as the receiving user or as specified in the
29988 It is not necessary to be root to do any of the other things Exim does, such as
29989 receiving messages and delivering them externally over SMTP, and it is
29990 obviously more secure if Exim does not run as root except when necessary.
29991 For this reason, a user and group for Exim to use must be defined in
29992 \(Local/Makefile)\. These are known as `the Exim user' and `the Exim group'.
29993 Their values can be changed by the run time configuration, though this is not
29994 recommended. Often a user called \*exim*\ is used, but some sites use \*mail*\
29995 or another user name altogether.
29997 Exim uses \*setuid()*\ whenever it gives up root privilege. This is a permanent
29998 abdication; the process cannot regain root afterwards. Prior to release 4.00,
29999 \*seteuid()*\ was used in some circumstances, but this is no longer the case.
30001 After a new Exim process has interpreted its command line options, it changes
30002 uid and gid in the following cases:
30004 .index \-C-\ option
30005 .index \-D-\ option
30006 If the \-C-\ option is used to specify an alternate configuration file, or if
30007 the \-D-\ option is used to define macro values for the configuration, and the
30008 calling process is not running as root or the Exim user, the uid and gid are
30009 changed to those of the calling process.
30010 However, if \\ALT@_CONFIG@_ROOT@_ONLY\\ is defined in \(Local/Makefile)\, only
30011 root callers may use \-C-\ and \-D-\ without losing privilege, and if
30012 \\DISABLE@_D@_OPTION\\ is set, the \-D-\ option may not be used at all.
30014 .index \-be-\ option
30015 .index \-bf-\ option
30016 .index \-bF-\ option
30017 If the expansion test option (\-be-\) or one of the filter testing options
30018 (\-bf-\ or \-bF-\) are used, the uid and gid are changed to those of the
30021 If the process is not a daemon process or a queue runner process or a delivery
30022 process or a process for testing address routing (started with \-bt-\), the uid
30023 and gid are changed to the Exim user and group. This means that Exim always
30024 runs under its own uid and gid when receiving messages. This also applies when
30025 testing address verification
30026 .index \-bv-\ option
30027 .index \-bh-\ option
30028 (the \-bv-\ option) and testing incoming message policy controls (the \-bh-\
30031 For a daemon, queue runner, delivery, or address testing process, the uid
30032 remains as root at this stage, but the gid is changed to the Exim group.
30034 The processes that initially retain root privilege behave as follows:
30036 A daemon process changes the gid to the Exim group and the uid to the Exim user
30037 after setting up one or more listening sockets. The \*initgroups()*\ function
30038 is called, so that if the Exim user is in any additional groups, they will be
30039 used during message reception.
30041 A queue runner process retains root privilege throughout its execution. Its job
30042 is to fork a controlled sequence of delivery processes.
30044 A delivery process retains root privilege throughout most of its execution,
30045 but any actual deliveries (that is, the transports themselves) are run in
30046 subprocesses which always change to a non-root uid and gid. For local
30047 deliveries this is typically the uid and gid of the owner of the mailbox; for
30048 remote deliveries, the Exim uid and gid are used. Once all the delivery
30049 subprocesses have been run, a delivery process changes to the Exim uid and gid
30050 while doing post-delivery tidying up such as updating the retry database and
30051 generating bounce and warning messages.
30053 While the recipient addresses in a message are being routed, the delivery
30054 process runs as root. However, if a user's filter file has to be processed,
30055 this is done in a subprocess that runs under the individual user's uid and
30056 gid. A system filter is run as root unless \system@_filter@_user\ is set.
30058 A process that is testing addresses (the \-bt-\ option) runs as root so that
30059 the routing is done in the same environment as a message delivery.
30063 .section Running Exim without privilege
30064 .rset SECTrunexiwitpri "~~chapter.~~section"
30065 .index privilege, running without
30066 .index unprivileged running
30067 .index root privilege||running without
30068 Some installations like to run Exim in an unprivileged state for more of its
30069 operation, for added security. Support for this mode of operation is provided
30070 by the global option \deliver@_drop@_privilege\. When this is set, the uid and
30071 gid are changed to the Exim user and group at the start of a delivery process
30072 (and also queue runner and address testing processes). This means that address
30073 routing is no longer run as root, and the deliveries themselves cannot change
30076 Leaving the binary setuid to root, but setting \deliver@_drop@_privilege\ means
30077 that the daemon can still be started in the usual way, and it can respond
30078 correctly to SIGHUP because the re-invocation regains root privilege.
30080 An alternative approach is to make Exim setuid to the Exim user and also setgid
30082 If you do this, the daemon must be started from a root process. (Calling
30083 Exim from a root process makes it behave in the way it does when it is setuid
30084 root.) However, the daemon cannot restart itself after a SIGHUP signal because
30085 it cannot regain privilege.
30087 It is still useful to set \deliver@_drop@_privilege\ in this case, because it
30088 stops Exim from trying to re-invoke itself to do a delivery after a message has
30089 been received. Such a re-invocation is a waste of resources because it has no
30092 If restarting the daemon is not an issue (for example, if
30094 \mua@_wrapper\ is set, or
30096 \*inetd*\ is being used instead of a daemon), having the binary setuid to the
30097 Exim user seems a clean approach, but there is one complication:
30099 In this style of operation, Exim is running with the real uid and gid set to
30100 those of the calling process, and the effective uid/gid set to Exim's values.
30101 Ideally, any association with the calling process' uid/gid should be dropped,
30102 that is, the real uid/gid should be reset to the effective values so as to
30103 discard any privileges that the caller may have. While some operating systems
30104 have a function that permits this action for a non-root effective uid, quite a
30105 number of them do not. Because of this lack of standardization, Exim does not
30106 address this problem at this time.
30108 For this reason, the recommended approach for `mostly unprivileged' running is
30109 to keep the Exim binary setuid to root, and to set \deliver@_drop@_privilege\.
30110 This also has the advantage of allowing a daemon to be used in the most
30111 straightforward way.
30113 If you configure Exim not to run delivery processes as root, there are a
30114 number of restrictions on what you can do:
30116 You can deliver only as the Exim user/group. You should explicitly use the
30117 \user\ and \group\ options to override routers or local transports that
30118 normally deliver as the recipient. This makes sure that configurations that
30119 work in this mode function the same way in normal mode. Any implicit or
30120 explicit specification of another user causes an error.
30122 Use of \(.forward)\ files is severely restricted, such that it is usually
30123 not worthwhile to include them in the configuration.
30125 Users who wish to use \(.forward)\ would have to make their home directory and
30126 the file itself accessible to the Exim user. Pipe and append-to-file entries,
30127 and their equivalents in Exim filters, cannot be used. While they could be
30128 enabled in the Exim user's name, that would be insecure and not very useful.
30130 Unless the local user mailboxes are all owned by the Exim user (possible in
30131 some POP3 or IMAP-only environments):
30133 They must be owned by the Exim group and be writable by that group. This
30134 implies you must set \mode\ in the appendfile configuration, as well as the
30135 mode of the mailbox files themselves.
30137 You must set \no@_check@_owner\, since most or all of the files will not be
30138 owned by the Exim user.
30140 You must set \file@_must@_exist\, because Exim cannot set the owner correctly
30141 on a newly created mailbox when unprivileged. This also implies that new
30142 mailboxes need to be created manually.
30145 These restrictions severely restrict what can be done in local deliveries.
30146 However, there are no restrictions on remote deliveries. If you are running a
30147 gateway host that does no local deliveries, setting \deliver@_drop@_privilege\
30148 gives more security at essentially no cost.
30150 If you are using the \mua@_wrapper\ facility (see chapter ~~CHAPnonqueueing),
30151 \deliver@_drop@_privilege\ is forced to be true.
30155 .section Delivering to local files
30156 Full details of the checks applied by \%appendfile%\ before it writes to a file
30157 are given in chapter ~~CHAPappendfile.
30160 .section IPv4 source routing
30161 .index source routing||in IP packets
30162 .index IP source routing
30163 Many operating systems suppress IP source-routed packets in the kernel, but
30164 some cannot be made to do this, so Exim does its own check. It logs incoming
30165 IPv4 source-routed TCP calls, and then drops them. Things are all different in
30166 IPv6. No special checking is currently done.
30169 .section The VRFY, EXPN, and ETRN commands in SMTP
30170 Support for these SMTP commands is disabled by default. If required, they can
30171 be enabled by defining suitable ACLs.
30175 .section Privileged users
30176 .index trusted user
30178 .index privileged user
30179 .index user||trusted
30181 Exim recognises two sets of users with special privileges. Trusted users are
30182 able to submit new messages to Exim locally, but supply their own sender
30183 addresses and information about a sending host. For other users submitting
30184 local messages, Exim sets up the sender address from the uid, and doesn't
30185 permit a remote host to be specified.
30187 .index \-f-\ option
30188 However, an untrusted user is permitted to use the \-f-\ command line option in
30189 the special form \-f @<@>-\ to indicate that a delivery failure for the message
30190 should not cause an error report. This affects the message's envelope, but it
30191 does not affect the ::Sender:: header. Untrusted users may also be permitted to
30192 use specific forms of address with the \-f-\ option by setting the
30193 \untrusted@_set@_sender\ option.
30195 Trusted users are used to run processes that receive mail messages from some
30196 other mail domain and pass them on to Exim for delivery either locally, or over
30197 the Internet. Exim trusts a caller that is running as root, as the Exim user,
30198 as any user listed in the \trusted@_users\ configuration option, or under any
30199 group listed in the \trusted@_groups\ option.
30201 Admin users are permitted to do things to the messages on Exim's queue. They
30202 can freeze or thaw messages, cause them to be returned to their senders, remove
30203 them entirely, or modify them in various ways. In addition, admin users can run
30204 the Exim monitor and see all the information it is capable of providing, which
30205 includes the contents of files on the spool.
30207 .index \-M-\ option
30208 .index \-q-\ option
30209 By default, the use of the \-M-\ and \-q-\ options to cause Exim to attempt
30210 delivery of messages on its queue is restricted to admin users. This
30211 restriction can be relaxed by setting the \no@_prod@_requires@_admin\ option.
30212 Similarly, the use of \-bp-\ (and its variants) to list the contents of the
30213 queue is also restricted to admin users. This restriction can be relaxed by
30214 setting \no@_queue@_list@_requires@_admin\.
30216 Exim recognises an admin user if the calling process is running as root or as
30217 the Exim user or if any of the groups associated with the calling process is
30218 the Exim group. It is not necessary actually to be running under the Exim
30219 group. However, if admin users who are not root or the Exim user are to access
30220 the contents of files on the spool via the Exim monitor (which runs
30221 unprivileged), Exim must be built to allow group read access to its spool
30225 .section Spool files
30226 .index spool directory||files
30227 Exim's spool directory and everything it contains is owned by the Exim user and
30228 set to the Exim group. The mode for spool files is defined in the
30229 \(Local/Makefile)\ configuration file, and defaults to 0640. This means that
30230 any user who is a member of the Exim group can access these files.
30233 .section Use of argv[0]
30234 Exim examines the last component of \argv[0]\, and if it matches one of a set
30235 of specific strings, Exim assumes certain options. For example, calling Exim
30236 with the last component of \argv[0]\ set to `rsmtp' is exactly equivalent to
30237 calling it with the option \-bS-\. There are no security implications in this.
30240 .section Use of %f formatting
30241 The only use made of `%f' by Exim is in formatting load average values. These
30242 are actually stored in integer variables as 1000 times the load average.
30243 Consequently, their range is limited and so therefore is the length of the
30247 .section Embedded Exim path
30248 Exim uses its own path name, which is embedded in the code, only when it needs
30249 to re-exec in order to regain root privilege. Therefore, it is not root when it
30250 does so. If some bug allowed the path to get overwritten, it would lead to an
30251 arbitrary program's being run as exim, not as root.
30254 .section Use of sprintf()
30255 .index \*sprintf()*\
30256 A large number of occurrences of `sprintf' in the code are actually calls to
30257 \*string@_sprintf()*\, a function that returns the result in malloc'd store.
30258 The intermediate formatting is done into a large fixed buffer by a function
30259 that runs through the format string itself, and checks the length of each
30260 conversion before performing it, thus preventing buffer overruns.
30262 The remaining uses of \*sprintf()*\ happen in controlled circumstances where
30263 the output buffer is known to be sufficiently long to contain the converted
30267 .section Use of debug@_printf() and log@_write()
30268 Arbitrary strings are passed to both these functions, but they do their
30269 formatting by calling the function \*string@_vformat()*\, which runs through
30270 the format string itself, and checks the length of each conversion.
30273 .section Use of strcat() and strcpy()
30274 These are used only in cases where the output buffer is known to be large
30275 enough to hold the result.
30284 . ============================================================================
30285 .chapter Format of spool files
30286 .set runningfoot "spool file format"
30287 .rset CHAPspool ~~chapter
30288 .index format||spool files
30289 .index spool directory||format of files
30290 .index spool||files, format of
30291 .index spool||files, editing
30292 A message on Exim's queue consists of two files, whose names are the message id
30293 followed by -D and -H, respectively. The data portion of the message is kept in
30294 the -D file on its own. The message's envelope, status, and headers are all
30295 kept in the -H file, whose format is described in this chapter. Each of these
30296 two files contains the final component of its own name as its first line. This
30297 is insurance against disk crashes where the directory is lost but the files
30298 themselves are recoverable.
30300 Some people are tempted into editing -D files in order to modify messages. You
30301 need to be extremely careful if you do this; it is not recommended and you are
30302 on your own if you do it. Here are some of the pitfalls:
30304 You must use the \*exim@_lock*\ utility to ensure that Exim does not try to
30305 deliver the message while you are fiddling with it. The lock is implemented
30306 by opening the -D file and taking out a write lock on it. If you update the
30307 file in place, the lock will be retained. If you write a new file and rename
30308 it, the lock will be lost at the instant of rename.
30310 If you change the number of lines in the file, the value of
30311 \$body@_linecount$\, which is stored in the -H file, will be incorrect.
30313 If the message is in MIME format, you must take care not to break it.
30315 If the message is cryptographically signed, any change will invalidate the
30319 Files whose names end with -J may also be seen in the \(input)\ directory (or
30320 its subdirectories when \split@_spool@_directory\ is set). These are journal
30321 files, used to record addresses to which the message has been delivered during
30322 the course of a delivery run. At the end of the run, the -H file is updated,
30323 and the -J file is deleted.
30325 .section Format of the -H file
30326 .index uid (user id)||in spool file
30327 .index gid (group id)||in spool file
30328 The second line of the -H file contains the login name for the uid of the
30329 process that called Exim to read the message, followed by the numerical uid and
30330 gid. For a locally generated message, this is normally the user who sent the
30331 message. For a message received over TCP/IP, it is normally the Exim user.
30333 The third line of the file contains the address of the message's sender as
30334 transmitted in the envelope, contained in angle brackets. The sender address is
30335 empty for bounce messages. For incoming SMTP mail, the sender address is given
30336 in the \\MAIL\\ command. For locally generated mail, the sender address is
30337 created by Exim from the login name of the current user and the configured
30338 \qualify@_domain\. However, this can be overridden by the \-f-\ option or a
30339 leading `From' line if the caller is trusted, or if the supplied address is
30340 `@<@>' or an address that matches \untrusted@_set@_senders\.
30342 The fourth line contains two numbers. The first is the time that the message
30343 was received, in the conventional Unix form -- the number of seconds since the
30344 start of the epoch. The second number is a count of the number of messages
30345 warning of delayed delivery that have been sent to the sender.
30347 There follow a number of lines starting with a hyphen. These can appear in any
30348 order, and are omitted when not relevant:
30350 \-acl <<number>> <<length>>-\: A line of this form is present for every ACL
30351 variable that is not empty. The number identifies the variable; the
30352 \acl@_c\*x*\$$\ variables are numbered 0--9 and the \acl@_m\*x*\$$\ variables
30353 are numbered 10--19. The length is the length of the data string for the
30354 variable. The string itself starts at the beginning of the next line, and is
30355 followed by a newline character. It may contain internal newlines.
30358 \-active@_hostname <<hostname>>-\: This is present if, when the message was
30359 received over SMTP, the value of \$smtp@_active@_hostname$\ was different to
30360 the value of \$primary@_hostname$\.
30363 \-allow@_unqualified@_recipient-\: This is present if unqualified recipient
30364 addresses are permitted in header lines (to stop such addresses from being
30365 qualified if rewriting occurs at transport time). Local messages that were
30366 input using \-bnq-\ and remote messages from hosts that match
30367 \recipient@_unqualified@_hosts\ set this flag.
30369 \-allow@_unqualified@_sender-\: This is present if unqualified sender
30370 addresses are permitted in header lines (to stop such addresses from being
30371 qualified if rewriting occurs at transport time). Local messages that were
30372 input using \-bnq-\ and remote messages from hosts that match
30373 \sender@_unqualified@_hosts\ set this flag.
30375 \-auth@_id <<text>>-\: The id information for a message received on an
30376 authenticated SMTP connection -- the value of the \$authenticated@_id$\
30379 \-auth@_sender <<address>>-\: The address of an authenticated sender -- the
30380 value of the \$authenticated@_sender$\ variable.
30382 \-body@_linecount <<number>>-\: This records the number of lines in the body of
30383 the message, and is always present.
30386 \-body@_zerocount <<number>>-\: This records the number of binary zero bytes in
30387 the body of the message, and is present if the number is greater than zero.
30390 \-deliver@_firsttime-\: This is written when a new message is first added to
30391 the spool. When the spool file is updated after a deferral, it is omitted.
30393 .index frozen messages||spool data
30394 \-frozen <<time>>-\: The message is frozen, and the freezing happened at
30397 \-helo@_name <<text>>-\: This records the host name as specified by a remote
30398 host in a \\HELO\\ or \\EHLO\\ command.
30400 \-host@_address <<address>>.<<port>>-\: This records the IP address of the host
30401 from which the message was received and the remote port number that was used.
30402 It is omitted for locally generated messages.
30404 \-host@_auth <<text>>-\: If the message was received on an authenticated SMTP
30405 connection, this records the name of the authenticator -- the value of the
30406 \$sender@_host@_authenticated$\ variable.
30408 \-host@_lookup@_failed-\: This is present if an attempt to look up the sending
30409 host's name from its IP address failed. It corresponds to the
30410 \$host@_lookup@_failed$\ variable.
30412 .index DNS||reverse lookup
30413 .index reverse DNS lookup
30414 \-host@_name <<text>>-\: This records the name of the remote host from which
30415 the message was received, if the host name was looked up from the IP address
30416 when the message was being received. It is not present if no reverse lookup was
30419 \-ident <<text>>-\: For locally submitted messages, this records the login of
30420 the originating user, unless it was a trusted user and the \-oMt-\ option was
30421 used to specify an ident value. For messages received over TCP/IP, this records
30422 the ident string supplied by the remote host, if any.
30424 \-interface@_address <<address>>.<<port>>-\: This records the IP address of the
30425 local interface and the port number through which a message was received from a
30426 remote host. It is omitted for locally generated messages.
30428 \-local-\: The message is from a local sender.
30430 \-localerror-\: The message is a locally-generated bounce message.
30432 \-local@_scan <<string>>-\: This records the data string that was
30433 returned by the \*local@_scan()*\ function when the message was received -- the
30434 value of the \$local@_scan@_data$\ variable. It is omitted if no data was
30437 \-manual@_thaw-\: The message was frozen but has been thawed manually, that is,
30438 by an explicit Exim command rather than via the auto-thaw process.
30440 \-N-\: A testing delivery process was started using the \-N-\ option to
30441 suppress any actual deliveries, but delivery was deferred. At any further
30442 delivery attempts, \-N-\ is assumed.
30444 \-received@_protocol-\: This records the value of the \$received@_protocol$\
30445 variable, which contains the name of the protocol by which the message was
30448 \-sender@_set@_untrusted-\: The envelope sender of this message was set by an
30449 untrusted local caller (used to ensure that the caller is displayed in queue
30453 \-spam@_score@_int-\: If a message was scanned by SpamAssassin, this is
30454 present. It records the value of \$spam@_score@_int$\.
30457 \-tls@_certificate@_verified-\: A TLS certificate was received from the client
30458 that sent this message, and the certificate was verified by the server.
30460 \-tls@_cipher <<cipher name>>-\: When the message was received over an
30461 encrypted connection, this records the name of the cipher suite that was used.
30463 \-tls@_peerdn <<peer DN>>-\: When the message was received over an encrypted
30464 connection, and a certificate was received from the client, this records the
30465 Distinguished Name from that certificate.
30468 Following the options there is a list of those addresses to which the message
30469 is not to be delivered. This set of addresses is initialized from the command
30470 line when the \-t-\ option is used and \extract__addresses__remove__arguments\
30471 is set; otherwise it starts out empty. Whenever a successful delivery is made,
30472 the address is added to this set. The addresses are kept internally as a
30473 balanced binary tree, and it is a representation of that tree which is written
30474 to the spool file. If an address is expanded via an alias or forward file, the
30475 original address is added to the tree when deliveries to all its child
30476 addresses are complete.
30478 If the tree is empty, there is a single line in the spool file containing just
30479 the text `XX'. Otherwise, each line consists of two letters, which are either Y
30480 or N, followed by an address. The address is the value for the node of the
30481 tree, and the letters indicate whether the node has a left branch and/or a
30482 right branch attached to it, respectively. If branches exist, they immediately
30483 follow. Here is an example of a three-node tree:
30485 YY darcy@austen.fict.example
30486 NN alice@wonderland.fict.example
30487 NN editor@thesaurus.ref.example
30489 After the non-recipients tree, there is a list of the message's recipients.
30490 This is a simple list, preceded by a count. It includes all the original
30491 recipients of the message, including those to whom the message has already been
30492 delivered. In the simplest case, the list contains one address per line. For
30496 editor@thesaurus.ref.example
30497 darcy@austen.fict.example
30499 alice@wonderland.fict.example
30501 However, when a child address has been added to the top-level addresses as a
30502 result of the use of the \one@_time\ option on a \%redirect%\ router, each line
30503 is of the following form:
30505 <<top-level address>> <<errors@_to address>> <<length>>,<<parent number>>@#<<flag bits>>
30507 The 01 flag bit indicates the presence of the three other fields that follow
30508 the top-level address. Other bits may be used in future to support additional
30509 fields. The <<parent number>> is the offset in the recipients list of the
30510 original parent of the `one time' address. The first two fields are the
30511 envelope sender that is associated with this address and its length. If the
30512 length is zero, there is no special envelope sender (there are then two space
30513 characters in the line). A non-empty field can arise from a \%redirect%\ router
30514 that has an \errors@_to\ setting.
30517 A blank line separates the envelope and status information from the headers
30518 which follow. A header may occupy several lines of the file, and to save effort
30519 when reading it in, each header is preceded by a number and an identifying
30520 character. The number is the number of characters in the header, including any
30521 embedded newlines and the terminating newline. The character is one of the
30525 <<blank>> $t $rm{header in which Exim has no special interest}
30526 #B $t $rm{::Bcc:: header}
30527 #C $t $rm{::Cc:: header}
30528 #F $t $rm{::From:: header}
30529 #I $t $rm{::Message-id:: header}
30530 #P $t $rm{::Received:: header -- P for `postmark'}
30531 #R $t $rm{::Reply-To:: header}
30532 #S $t $rm{::Sender:: header}
30533 #T $t $rm{::To:: header}
30534 #* $t $rm{replaced or deleted header}
30536 Deleted or replaced (rewritten) headers remain in the spool file for debugging
30537 purposes. They are not transmitted when the message is delivered. Here is a
30538 typical set of headers:
30540 111P Received: by hobbit.fict.example with local (Exim 4.00)
30541 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
30542 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
30543 038* X-rewrote-sender: bb@hobbit.fict.example
30544 042* From: Bilbo Baggins <bb@hobbit.fict.example>
30545 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
30546 099* To: alice@wonderland.fict.example, rdo@foundation,
30547 darcy@austen.fict.example, editor@thesaurus.ref.example
30548 109T To: alice@wonderland.fict.example, rdo@foundation.fict.example,
30549 darcy@austen.fict.example, editor@thesaurus.ref.example
30550 038 Date: Fri, 11 May 2001 10:28:59 +0100
30552 The asterisked headers indicate that the envelope sender, ::From:: header, and
30553 ::To:: header have been rewritten, the last one because routing expanded the
30554 unqualified domain \*foundation*\.
30560 . ============================================================================
30561 .chapter Adding new drivers or lookup types
30562 .set runningfoot "adding drivers"
30563 .index adding drivers
30564 .index new drivers, adding
30565 .index drivers||adding new
30566 The following actions have to be taken in order to add a new router, transport,
30567 authenticator, or lookup type to Exim:
30569 Choose a name for the driver or lookup type that does not conflict with any
30570 existing name; I will use `newdriver' in what follows.
30572 Add to \(src/EDITME)\ the line
30574 <<type>>@_NEWDRIVER=yes
30576 where <<type>> is \\ROUTER\\, \\TRANSPORT\\, \\AUTH\\, or \\LOOKUP\\. If the
30577 code is not to be included in the binary by default, comment this line out. You
30578 should also add any relevant comments about the driver or lookup type.
30580 Add to \(src/config.h.defaults)\ the line
30582 @#define <<type>>@_NEWDRIVER
30585 Edit \(src/drtables.c)\, adding conditional code to pull in the private header
30586 and create a table entry as is done for all the other drivers and lookup types.
30588 Edit \(Makefile)\ in the appropriate sub-directory (\(src/routers)\,
30589 \(src/transports)\, \(src/auths)\, or \(src/lookups)\); add a line for the new
30590 driver or lookup type and add it to the definition of OBJ.
30592 Create \(newdriver.h)\ and \(newdriver.c)\ in the appropriate sub-directory of
30595 Edit \(scripts/MakeLinks)\ and add commands to link the \(.h)\ and \(.c)\ files
30596 as for other drivers and lookups.
30598 Then all you need to do is write the code! A good way to start is to make a
30599 proforma by copying an existing module of the same type, globally changing all
30600 occurrences of the name, and cutting out most of the code. Note that any
30601 options you create must be listed in alphabetical order, because the tables are
30602 searched using a binary chop procedure.
30604 There is a \(README)\ file in each of the sub-directories of \(src)\ describing
30605 the interface that is expected.
30611 . ============================================================================
30612 . Fudge for the index page number. We want it to be on a right-hand page.
30614 .set indexpage ~~sys.pagenumber + 1
30615 .if even ~~indexpage
30616 .set indexpage ~~indexpage + 1
30619 .%index Index$e~~indexpage--
30623 . End of Exim specification
git://git.exim.org / exim.git / blob