1 . $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.71 2010/03/05 16:08:14 nm4 Exp $
3 . /////////////////////////////////////////////////////////////////////////////
4 . This is the primary source of the Exim Manual. It is an xfpt document that is
5 . converted into DocBook XML for subsequent conversion into printing and online
6 . formats. The markup used herein is "standard" xfpt markup, with some extras.
7 . The markup is summarized in a file called Markup.txt.
9 . WARNING: When you use the .new macro, make sure it appears *before* any
10 . adjacent index items; otherwise you get an empty "paragraph" which causes
11 . unwanted vertical space.
12 . /////////////////////////////////////////////////////////////////////////////
17 . /////////////////////////////////////////////////////////////////////////////
18 . This outputs the standard DocBook boilerplate.
19 . /////////////////////////////////////////////////////////////////////////////
23 . /////////////////////////////////////////////////////////////////////////////
24 . These lines are processing instructions for the Simple DocBook Processor that
25 . Philip Hazel has developed as a less cumbersome way of making PostScript and
26 . PDFs than using xmlto and fop. They will be ignored by all other XML
28 . /////////////////////////////////////////////////////////////////////////////
32 foot_right_recto="&chaptertitle; (&chapternumber;)"
33 foot_right_verso="&chaptertitle; (&chapternumber;)"
34 toc_chapter_blanks="yes,yes"
35 table_warn_overflow="overprint"
39 . /////////////////////////////////////////////////////////////////////////////
40 . This generate the outermost <book> element that wraps then entire document.
41 . /////////////////////////////////////////////////////////////////////////////
45 . /////////////////////////////////////////////////////////////////////////////
46 . These definitions set some parameters and save some typing. Remember that
47 . the <bookinfo> element must also be updated for each new edition.
48 . /////////////////////////////////////////////////////////////////////////////
50 .set previousversion "4.69"
53 .set ACL "access control lists (ACLs)"
54 .set I " "
57 . /////////////////////////////////////////////////////////////////////////////
58 . Additional xfpt markup used by this document, over and above the default
59 . provided in the xfpt library.
60 . /////////////////////////////////////////////////////////////////////////////
62 . --- Override the &$ flag to automatically insert a $ with the variable name
64 .flag &$ $& "<varname>$" "</varname>"
66 . --- Short flags for daggers in option headings. They will always be inside
67 . --- an italic string, but we want the daggers to be roman.
69 .flag &!! "</emphasis>†<emphasis>"
70 .flag &!? "</emphasis>‡<emphasis>"
72 . --- A macro for an Exim option definition heading, generating a one-line
73 . --- table with four columns. For cases when the option name is given with
74 . --- a space, so that it can be split, a fifth argument is used for the
84 .itable all 0 0 4 8* left 6* center 6* center 6* right
85 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
89 . --- A macro for the common 2-column tables. The width of the first column
90 . --- is suitable for the many tables at the start of the main options chapter;
91 . --- the small number of other 2-column tables override it.
93 .macro table2 196pt 254pt
94 .itable none 0 0 2 $1 left $2 left
97 . --- A macro that generates .row, but puts &I; at the start of the first
98 . --- argument, thus indenting it. Assume a minimum of two arguments, and
99 . --- allow up to four arguments, which is as many as we'll ever need.
103 .row "&I;$1" "$2" "$3" "$4"
107 .row "&I;$1" "$2" "$3"
115 . --- Macros for option, variable, and concept index entries. For a "range"
116 . --- style of entry, use .scindex for the start and .ecindex for the end. The
117 . --- first argument of .scindex and the only argument of .ecindex must be the
118 . --- ID that ties them together.
121 &<indexterm role="concept">&
122 &<primary>&$1&</primary>&
124 &<secondary>&$2&</secondary>&
130 &<indexterm role="concept" id="$1" class="startofrange">&
131 &<primary>&$2&</primary>&
133 &<secondary>&$3&</secondary>&
139 &<indexterm role="concept" startref="$1" class="endofrange"/>&
143 &<indexterm role="option">&
144 &<primary>&$1&</primary>&
146 &<secondary>&$2&</secondary>&
152 &<indexterm role="variable">&
153 &<primary>&$1&</primary>&
155 &<secondary>&$2&</secondary>&
161 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
163 . ////////////////////////////////////////////////////////////////////////////
166 . ////////////////////////////////////////////////////////////////////////////
167 . The <bookinfo> element is removed from the XML before processing for Ascii
169 . ////////////////////////////////////////////////////////////////////////////
173 <title>Specification of the Exim Mail Transfer Agent</title>
174 <titleabbrev>The Exim MTA</titleabbrev>
175 <date>5 November 2009</date>
176 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
177 <authorinitials>EM</authorinitials>
178 <revhistory><revision>
179 <revnumber>4.71</revnumber>
180 <date>5 November 2009</date>
181 <authorinitials>EM</authorinitials>
182 </revision></revhistory>
183 <copyright><year>2009</year><holder>University of Cambridge</holder></copyright>
188 . /////////////////////////////////////////////////////////////////////////////
189 . This chunk of literal XML implements index entries of the form "x, see y" and
190 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
191 . at the top level, so we have to put the .chapter directive first.
192 . /////////////////////////////////////////////////////////////////////////////
194 .chapter "Introduction" "CHID1"
197 <indexterm role="variable">
198 <primary>$1, $2, etc.</primary>
199 <see><emphasis>numerical variables</emphasis></see>
201 <indexterm role="concept">
202 <primary>address</primary>
203 <secondary>rewriting</secondary>
204 <see><emphasis>rewriting</emphasis></see>
206 <indexterm role="concept">
207 <primary>Bounce Address Tag Validation</primary>
208 <see><emphasis>BATV</emphasis></see>
210 <indexterm role="concept">
211 <primary>Client SMTP Authorization</primary>
212 <see><emphasis>CSA</emphasis></see>
214 <indexterm role="concept">
215 <primary>CR character</primary>
216 <see><emphasis>carriage return</emphasis></see>
218 <indexterm role="concept">
219 <primary>CRL</primary>
220 <see><emphasis>certificate revocation list</emphasis></see>
222 <indexterm role="concept">
223 <primary>delivery</primary>
224 <secondary>failure report</secondary>
225 <see><emphasis>bounce message</emphasis></see>
227 <indexterm role="concept">
228 <primary>dialup</primary>
229 <see><emphasis>intermittently connected hosts</emphasis></see>
231 <indexterm role="concept">
232 <primary>exiscan</primary>
233 <see><emphasis>content scanning</emphasis></see>
235 <indexterm role="concept">
236 <primary>failover</primary>
237 <see><emphasis>fallback</emphasis></see>
239 <indexterm role="concept">
240 <primary>fallover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>filter</primary>
245 <secondary>Sieve</secondary>
246 <see><emphasis>Sieve filter</emphasis></see>
248 <indexterm role="concept">
249 <primary>ident</primary>
250 <see><emphasis>RFC 1413</emphasis></see>
252 <indexterm role="concept">
253 <primary>LF character</primary>
254 <see><emphasis>linefeed</emphasis></see>
256 <indexterm role="concept">
257 <primary>maximum</primary>
258 <seealso><emphasis>limit</emphasis></seealso>
260 <indexterm role="concept">
261 <primary>monitor</primary>
262 <see><emphasis>Exim monitor</emphasis></see>
264 <indexterm role="concept">
265 <primary>no_<emphasis>xxx</emphasis></primary>
266 <see>entry for xxx</see>
268 <indexterm role="concept">
269 <primary>NUL</primary>
270 <see><emphasis>binary zero</emphasis></see>
272 <indexterm role="concept">
273 <primary>passwd file</primary>
274 <see><emphasis>/etc/passwd</emphasis></see>
276 <indexterm role="concept">
277 <primary>process id</primary>
278 <see><emphasis>pid</emphasis></see>
280 <indexterm role="concept">
281 <primary>RBL</primary>
282 <see><emphasis>DNS list</emphasis></see>
284 <indexterm role="concept">
285 <primary>redirection</primary>
286 <see><emphasis>address redirection</emphasis></see>
288 <indexterm role="concept">
289 <primary>return path</primary>
290 <seealso><emphasis>envelope sender</emphasis></seealso>
292 <indexterm role="concept">
293 <primary>scanning</primary>
294 <see><emphasis>content scanning</emphasis></see>
296 <indexterm role="concept">
297 <primary>SSL</primary>
298 <see><emphasis>TLS</emphasis></see>
300 <indexterm role="concept">
301 <primary>string</primary>
302 <secondary>expansion</secondary>
303 <see><emphasis>expansion</emphasis></see>
305 <indexterm role="concept">
306 <primary>top bit</primary>
307 <see><emphasis>8-bit characters</emphasis></see>
309 <indexterm role="concept">
310 <primary>variables</primary>
311 <see><emphasis>expansion, variables</emphasis></see>
313 <indexterm role="concept">
314 <primary>zero, binary</primary>
315 <see><emphasis>binary zero</emphasis></see>
321 . /////////////////////////////////////////////////////////////////////////////
322 . This is the real start of the first chapter. See the comment above as to why
323 . we can't have the .chapter line here.
324 . chapter "Introduction"
325 . /////////////////////////////////////////////////////////////////////////////
327 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
328 Unix-like operating systems. It was designed on the assumption that it would be
329 run on hosts that are permanently connected to the Internet. However, it can be
330 used on intermittently connected hosts with suitable configuration adjustments.
332 Configuration files currently exist for the following operating systems: AIX,
333 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
334 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
335 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
336 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware.
337 Some of these operating systems are no longer current and cannot easily be
338 tested, so the configuration files may no longer work in practice.
340 There are also configuration files for compiling Exim in the Cygwin environment
341 that can be installed on systems running Windows. However, this document does
342 not contain any information about running Exim in the Cygwin environment.
344 The terms and conditions for the use and distribution of Exim are contained in
345 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
346 Public Licence, a copy of which may be found in the file &_LICENCE_&.
348 The use, supply or promotion of Exim for the purpose of sending bulk,
349 unsolicited electronic mail is incompatible with the basic aims of the program,
350 which revolve around the free provision of a service that enhances the quality
351 of personal communications. The author of Exim regards indiscriminate
352 mass-mailing as an antisocial, irresponsible abuse of the Internet.
354 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
355 experience of running and working on the Smail 3 code, I could never have
356 contemplated starting to write a new MTA. Many of the ideas and user interfaces
357 were originally taken from Smail 3, though the actual code of Exim is entirely
358 new, and has developed far beyond the initial concept.
360 Many people, both in Cambridge and around the world, have contributed to the
361 development and the testing of Exim, and to porting it to various operating
362 systems. I am grateful to them all. The distribution now contains a file called
363 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
367 .section "Exim documentation" "SECID1"
368 . Keep this example change bar when updating the documentation!
370 .cindex "documentation"
371 This edition of the Exim specification applies to version &version; of Exim.
372 Substantive changes from the &previousversion; edition are marked in some
373 renditions of the document; this paragraph is so marked if the rendition is
374 capable of showing a change indicator.
377 This document is very much a reference manual; it is not a tutorial. The reader
378 is expected to have some familiarity with the SMTP mail transfer protocol and
379 with general Unix system administration. Although there are some discussions
380 and examples in places, the information is mostly organized in a way that makes
381 it easy to look up, rather than in a natural order for sequential reading.
382 Furthermore, the manual aims to cover every aspect of Exim in detail, including
383 a number of rarely-used, special-purpose features that are unlikely to be of
386 .cindex "books about Exim"
387 An &"easier"& discussion of Exim which provides more in-depth explanatory,
388 introductory, and tutorial material can be found in a book entitled &'The Exim
389 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
390 (&url(http://www.uit.co.uk/exim-book/)).
392 This book also contains a chapter that gives a general introduction to SMTP and
393 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
394 with the latest release of Exim. (Note that the earlier book about Exim,
395 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
397 .cindex "Debian" "information sources"
398 If you are using a Debian distribution of Exim, you will find information about
399 Debian-specific features in the file
400 &_/usr/share/doc/exim4-base/README.Debian_&.
401 The command &(man update-exim.conf)& is another source of Debian-specific
404 .cindex "&_doc/NewStuff_&"
405 .cindex "&_doc/ChangeLog_&"
407 As the program develops, there may be features in newer versions that have not
408 yet made it into this document, which is updated only when the most significant
409 digit of the fractional part of the version number changes. Specifications of
410 new features that are not yet in this manual are placed in the file
411 &_doc/NewStuff_& in the Exim distribution.
413 Some features may be classified as &"experimental"&. These may change
414 incompatibly while they are developing, or even be withdrawn. For this reason,
415 they are not documented in this manual. Information about experimental features
416 can be found in the file &_doc/experimental.txt_&.
418 All changes to the program (whether new features, bug fixes, or other kinds of
419 change) are noted briefly in the file called &_doc/ChangeLog_&.
421 .cindex "&_doc/spec.txt_&"
422 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
423 that it can easily be searched with a text editor. Other files in the &_doc_&
427 .row &_OptionLists.txt_& "list of all options in alphabetical order"
428 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
429 .row &_exim.8_& "a man page of Exim's command line options"
430 .row &_experimental.txt_& "documentation of experimental features"
431 .row &_filter.txt_& "specification of the filter language"
432 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
433 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
436 The main specification and the specification of the filtering language are also
437 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
438 &<<SECTavail>>& below tells you how to get hold of these.
442 .section "FTP and web sites" "SECID2"
445 The primary site for Exim source distributions is currently the University of
446 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
447 distribution'& below. In addition, there is a web site and an FTP site at
448 &%exim.org%&. These are now also hosted at the University of Cambridge. The
449 &%exim.org%& site was previously hosted for a number of years by Energis
450 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
454 As well as Exim distribution tar files, the Exim web site contains a number of
455 differently formatted versions of the documentation. A recent addition to the
456 online information is the Exim wiki (&url(http://wiki.exim.org)),
457 which contains what used to be a separate FAQ, as well as various other
458 examples, tips, and know-how that have been contributed by Exim users.
461 An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
462 this to report bugs, and also to add items to the wish list. Please search
463 first to check that you are not duplicating a previous entry.
467 .section "Mailing lists" "SECID3"
468 .cindex "mailing lists" "for Exim users"
469 The following Exim mailing lists exist:
472 .row &'exim-users@exim.org'& "General discussion list"
473 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
474 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
475 .row &'exim-future@exim.org'& "Discussion of long-term development"
478 You can subscribe to these lists, change your existing subscriptions, and view
479 or search the archives via the mailing lists link on the Exim home page.
480 .cindex "Debian" "mailing list for"
481 If you are using a Debian distribution of Exim, you may wish to subscribe to
482 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
485 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
487 Please ask Debian-specific questions on this list and not on the general Exim
490 .section "Exim training" "SECID4"
491 .cindex "training courses"
492 Training courses in Cambridge (UK) used to be run annually by the author of
493 Exim, before he retired. At the time of writing, there are no plans to run
494 further Exim courses in Cambridge. However, if that changes, relevant
495 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
497 .section "Bug reports" "SECID5"
498 .cindex "bug reports"
499 .cindex "reporting bugs"
500 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
501 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
502 whether some behaviour is a bug or not, the best thing to do is to post a
503 message to the &'exim-dev'& mailing list and have it discussed.
507 .section "Where to find the Exim distribution" "SECTavail"
509 .cindex "distribution" "ftp site"
510 The master ftp site for the Exim distribution is
512 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
516 &*ftp://ftp.exim.org/pub/exim*&
518 The file references that follow are relative to the &_exim_& directories at
519 these sites. There are now quite a number of independent mirror sites around
520 the world. Those that I know about are listed in the file called &_Mirrors_&.
522 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
523 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
524 distributions), and &_Testing_& for testing versions. In the &_exim4_&
525 subdirectory, the current release can always be found in files called
528 &_exim-n.nn.tar.bz2_&
530 where &'n.nn'& is the highest such version number in the directory. The two
531 files contain identical data; the only difference is the type of compression.
532 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
534 .cindex "distribution" "signing details"
535 .cindex "distribution" "public key"
536 .cindex "public key for signed distribution"
537 The distributions are currently signed with Nigel Metheringham's GPG key. The
538 corresponding public key is available from a number of keyservers, and there is
539 also a copy in the file &_nigel-pubkey.asc_&. The signatures for the tar bundles are
542 &_exim-n.nn.tar.gz.asc_&
543 &_exim-n.nn.tar.bz2.asc_&
545 For each released version, the log of changes is made separately available in a
546 separate file in the directory &_ChangeLogs_& so that it is possible to
547 find out what has changed without having to download the entire distribution.
549 .cindex "documentation" "available formats"
550 The main distribution contains ASCII versions of this specification and other
551 documentation; other formats of the documents are available in separate files
552 inside the &_exim4_& directory of the FTP site:
554 &_exim-html-n.nn.tar.gz_&
555 &_exim-pdf-n.nn.tar.gz_&
556 &_exim-postscript-n.nn.tar.gz_&
557 &_exim-texinfo-n.nn.tar.gz_&
559 These tar files contain only the &_doc_& directory, not the complete
560 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
563 .section "Limitations" "SECID6"
565 .cindex "limitations of Exim"
566 .cindex "bang paths" "not handled by Exim"
567 Exim is designed for use as an Internet MTA, and therefore handles addresses in
568 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
569 simple two-component bang paths can be converted by a straightforward rewriting
570 configuration. This restriction does not prevent Exim from being interfaced to
571 UUCP as a transport mechanism, provided that domain addresses are used.
573 .cindex "domainless addresses"
574 .cindex "address" "without domain"
575 Exim insists that every address it handles has a domain attached. For incoming
576 local messages, domainless addresses are automatically qualified with a
577 configured domain value. Configuration options specify from which remote
578 systems unqualified addresses are acceptable. These are then qualified on
581 .cindex "transport" "external"
582 .cindex "external transports"
583 The only external transport mechanisms that are currently implemented are SMTP
584 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
585 transport is available, and there are facilities for writing messages to files
586 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
587 to send messages to other transport mechanisms such as UUCP, provided they can
588 handle domain-style addresses. Batched SMTP input is also catered for.
590 Exim is not designed for storing mail for dial-in hosts. When the volumes of
591 such mail are large, it is better to get the messages &"delivered"& into files
592 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
595 Although Exim does have basic facilities for scanning incoming messages, these
596 are not comprehensive enough to do full virus or spam scanning. Such operations
597 are best carried out using additional specialized software packages. If you
598 compile Exim with the content-scanning extension, straightforward interfaces to
599 a number of common scanners are provided.
603 .section "Run time configuration" "SECID7"
604 Exim's run time configuration is held in a single text file that is divided
605 into a number of sections. The entries in this file consist of keywords and
606 values, in the style of Smail 3 configuration files. A default configuration
607 file which is suitable for simple online installations is provided in the
608 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
611 .section "Calling interface" "SECID8"
612 .cindex "Sendmail compatibility" "command line interface"
613 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
614 can be a straight replacement for &_/usr/lib/sendmail_& or
615 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
616 about Sendmail in order to run Exim. For actions other than sending messages,
617 Sendmail-compatible options also exist, but those that produce output (for
618 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
619 format. There are also some additional options that are compatible with Smail
620 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
621 documents all Exim's command line options. This information is automatically
622 made into the man page that forms part of the Exim distribution.
624 Control of messages on the queue can be done via certain privileged command
625 line options. There is also an optional monitor program called &'eximon'&,
626 which displays current information in an X window, and which contains a menu
627 interface to Exim's command line administration options.
631 .section "Terminology" "SECID9"
632 .cindex "terminology definitions"
633 .cindex "body of message" "definition of"
634 The &'body'& of a message is the actual data that the sender wants to transmit.
635 It is the last part of a message, and is separated from the &'header'& (see
636 below) by a blank line.
638 .cindex "bounce message" "definition of"
639 When a message cannot be delivered, it is normally returned to the sender in a
640 delivery failure message or a &"non-delivery report"& (NDR). The term
641 &'bounce'& is commonly used for this action, and the error reports are often
642 called &'bounce messages'&. This is a convenient shorthand for &"delivery
643 failure error report"&. Such messages have an empty sender address in the
644 message's &'envelope'& (see below) to ensure that they cannot themselves give
645 rise to further bounce messages.
647 The term &'default'& appears frequently in this manual. It is used to qualify a
648 value which is used in the absence of any setting in the configuration. It may
649 also qualify an action which is taken unless a configuration setting specifies
652 The term &'defer'& is used when the delivery of a message to a specific
653 destination cannot immediately take place for some reason (a remote host may be
654 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
657 The word &'domain'& is sometimes used to mean all but the first component of a
658 host's name. It is &'not'& used in that sense here, where it normally refers to
659 the part of an email address following the @ sign.
661 .cindex "envelope, definition of"
662 .cindex "sender" "definition of"
663 A message in transit has an associated &'envelope'&, as well as a header and a
664 body. The envelope contains a sender address (to which bounce messages should
665 be delivered), and any number of recipient addresses. References to the
666 sender or the recipients of a message usually mean the addresses in the
667 envelope. An MTA uses these addresses for delivery, and for returning bounce
668 messages, not the addresses that appear in the header lines.
670 .cindex "message" "header, definition of"
671 .cindex "header section" "definition of"
672 The &'header'& of a message is the first part of a message's text, consisting
673 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
674 &'Subject:'&, etc. Long header lines can be split over several text lines by
675 indenting the continuations. The header is separated from the body by a blank
678 .cindex "local part" "definition of"
679 .cindex "domain" "definition of"
680 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
681 part of an email address that precedes the @ sign. The part that follows the
682 @ sign is called the &'domain'& or &'mail domain'&.
684 .cindex "local delivery" "definition of"
685 .cindex "remote delivery, definition of"
686 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
687 delivery to a file or a pipe on the local host from delivery by SMTP over
688 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
689 host it is running on are &'remote'&.
691 .cindex "return path" "definition of"
692 &'Return path'& is another name that is used for the sender address in a
695 .cindex "queue" "definition of"
696 The term &'queue'& is used to refer to the set of messages awaiting delivery,
697 because this term is in widespread use in the context of MTAs. However, in
698 Exim's case the reality is more like a pool than a queue, because there is
699 normally no ordering of waiting messages.
701 .cindex "queue runner" "definition of"
702 The term &'queue runner'& is used to describe a process that scans the queue
703 and attempts to deliver those messages whose retry times have come. This term
704 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
705 the waiting messages are normally processed in an unpredictable order.
707 .cindex "spool directory" "definition of"
708 The term &'spool directory'& is used for a directory in which Exim keeps the
709 messages on its queue &-- that is, those that it is in the process of
710 delivering. This should not be confused with the directory in which local
711 mailboxes are stored, which is called a &"spool directory"& by some people. In
712 the Exim documentation, &"spool"& is always used in the first sense.
719 . ////////////////////////////////////////////////////////////////////////////
720 . ////////////////////////////////////////////////////////////////////////////
722 .chapter "Incorporated code" "CHID2"
723 .cindex "incorporated code"
724 .cindex "regular expressions" "library"
726 A number of pieces of external code are included in the Exim distribution.
729 Regular expressions are supported in the main Exim program and in the
730 Exim monitor using the freely-distributable PCRE library, copyright
731 © University of Cambridge. The source to PCRE is no longer shipped with
732 Exim, so you will need to use the version of PCRE shipped with your system,
733 or obtain and install the full version of the library from
734 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
736 .cindex "cdb" "acknowledgment"
737 Support for the cdb (Constant DataBase) lookup method is provided by code
738 contributed by Nigel Metheringham of (at the time he contributed it) Planet
739 Online Ltd. The implementation is completely contained within the code of Exim.
740 It does not link against an external cdb library. The code contains the
741 following statements:
744 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
746 This program is free software; you can redistribute it and/or modify it under
747 the terms of the GNU General Public License as published by the Free Software
748 Foundation; either version 2 of the License, or (at your option) any later
750 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
751 the spec and sample code for cdb can be obtained from
752 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
753 some code from Dan Bernstein's implementation (which has no license
754 restrictions applied to it).
757 .cindex "SPA authentication"
758 .cindex "Samba project"
759 .cindex "Microsoft Secure Password Authentication"
760 Client support for Microsoft's &'Secure Password Authentication'& is provided
761 by code contributed by Marc Prud'hommeaux. Server support was contributed by
762 Tom Kistner. This includes code taken from the Samba project, which is released
766 .cindex "&'pwcheck'& daemon"
767 .cindex "&'pwauthd'& daemon"
768 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
769 by code taken from the Cyrus-SASL library and adapted by Alexander S.
770 Sabourenkov. The permission notice appears below, in accordance with the
771 conditions expressed therein.
774 Copyright © 2001 Carnegie Mellon University. All rights reserved.
776 Redistribution and use in source and binary forms, with or without
777 modification, are permitted provided that the following conditions
781 Redistributions of source code must retain the above copyright
782 notice, this list of conditions and the following disclaimer.
784 Redistributions in binary form must reproduce the above copyright
785 notice, this list of conditions and the following disclaimer in
786 the documentation and/or other materials provided with the
789 The name &"Carnegie Mellon University"& must not be used to
790 endorse or promote products derived from this software without
791 prior written permission. For permission or any other legal
792 details, please contact
794 Office of Technology Transfer
795 Carnegie Mellon University
797 Pittsburgh, PA 15213-3890
798 (412) 268-4387, fax: (412) 268-7395
799 tech-transfer@andrew.cmu.edu
802 Redistributions of any form whatsoever must retain the following
805 &"This product includes software developed by Computing Services
806 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
808 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
809 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
810 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
811 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
812 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
813 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
814 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
819 .cindex "Exim monitor" "acknowledgment"
822 The Exim Monitor program, which is an X-Window application, includes
823 modified versions of the Athena StripChart and TextPop widgets.
824 This code is copyright by DEC and MIT, and their permission notice appears
825 below, in accordance with the conditions expressed therein.
828 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
829 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
833 Permission to use, copy, modify, and distribute this software and its
834 documentation for any purpose and without fee is hereby granted,
835 provided that the above copyright notice appear in all copies and that
836 both that copyright notice and this permission notice appear in
837 supporting documentation, and that the names of Digital or MIT not be
838 used in advertising or publicity pertaining to distribution of the
839 software without specific, written prior permission.
841 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
842 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
843 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
844 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
845 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
846 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
851 Many people have contributed code fragments, some large, some small, that were
852 not covered by any specific licence requirements. It is assumed that the
853 contributors are happy to see their code incorporated into Exim under the GPL.
860 . ////////////////////////////////////////////////////////////////////////////
861 . ////////////////////////////////////////////////////////////////////////////
863 .chapter "How Exim receives and delivers mail" "CHID11" &&&
864 "Receiving and delivering mail"
867 .section "Overall philosophy" "SECID10"
868 .cindex "design philosophy"
869 Exim is designed to work efficiently on systems that are permanently connected
870 to the Internet and are handling a general mix of mail. In such circumstances,
871 most messages can be delivered immediately. Consequently, Exim does not
872 maintain independent queues of messages for specific domains or hosts, though
873 it does try to send several messages in a single SMTP connection after a host
874 has been down, and it also maintains per-host retry information.
877 .section "Policy control" "SECID11"
878 .cindex "policy control" "overview"
879 Policy controls are now an important feature of MTAs that are connected to the
880 Internet. Perhaps their most important job is to stop MTAs being abused as
881 &"open relays"& by misguided individuals who send out vast amounts of
882 unsolicited junk, and want to disguise its source. Exim provides flexible
883 facilities for specifying policy controls on incoming mail:
886 .cindex "&ACL;" "introduction"
887 Exim 4 (unlike previous versions of Exim) implements policy controls on
888 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
889 series of statements that may either grant or deny access. ACLs can be used at
890 several places in the SMTP dialogue while receiving a message from a remote
891 host. However, the most common places are after each RCPT command, and at the
892 very end of the message. The sysadmin can specify conditions for accepting or
893 rejecting individual recipients or the entire message, respectively, at these
894 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
897 An ACL is also available for locally generated, non-SMTP messages. In this
898 case, the only available actions are to accept or deny the entire message.
900 When Exim is compiled with the content-scanning extension, facilities are
901 provided in the ACL mechanism for passing the message to external virus and/or
902 spam scanning software. The result of such a scan is passed back to the ACL,
903 which can then use it to decide what to do with the message.
905 When a message has been received, either from a remote host or from the local
906 host, but before the final acknowledgment has been sent, a locally supplied C
907 function called &[local_scan()]& can be run to inspect the message and decide
908 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
909 is accepted, the list of recipients can be modified by the function.
911 Using the &[local_scan()]& mechanism is another way of calling external scanner
912 software. The &%SA-Exim%& add-on package works this way. It does not require
913 Exim to be compiled with the content-scanning extension.
915 After a message has been accepted, a further checking mechanism is available in
916 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
917 runs at the start of every delivery process.
922 .section "User filters" "SECID12"
923 .cindex "filter" "introduction"
924 .cindex "Sieve filter"
925 In a conventional Exim configuration, users are able to run private filters by
926 setting up appropriate &_.forward_& files in their home directories. See
927 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
928 configuration needed to support this, and the separate document entitled
929 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
930 of filtering are available:
933 Sieve filters are written in the standard filtering language that is defined
936 Exim filters are written in a syntax that is unique to Exim, but which is more
937 powerful than Sieve, which it pre-dates.
940 User filters are run as part of the routing process, described below.
944 .section "Message identification" "SECTmessiden"
945 .cindex "message ids" "details of format"
946 .cindex "format" "of message id"
947 .cindex "id of message"
952 Every message handled by Exim is given a &'message id'& which is sixteen
953 characters long. It is divided into three parts, separated by hyphens, for
954 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
955 normally encoding numbers in base 62. However, in the Darwin operating
956 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
957 (avoiding the use of lower case letters) is used instead, because the message
958 id is used to construct file names, and the names of files in those systems are
959 not always case-sensitive.
961 .cindex "pid (process id)" "re-use of"
962 The detail of the contents of the message id have changed as Exim has evolved.
963 Earlier versions relied on the operating system not re-using a process id (pid)
964 within one second. On modern operating systems, this assumption can no longer
965 be made, so the algorithm had to be changed. To retain backward compatibility,
966 the format of the message id was retained, which is why the following rules are
970 The first six characters of the message id are the time at which the message
971 started to be received, to a granularity of one second. That is, this field
972 contains the number of seconds since the start of the epoch (the normal Unix
973 way of representing the date and time of day).
975 After the first hyphen, the next six characters are the id of the process that
976 received the message.
978 There are two different possibilities for the final two characters:
980 .oindex "&%localhost_number%&"
981 If &%localhost_number%& is not set, this value is the fractional part of the
982 time of reception, normally in units of 1/2000 of a second, but for systems
983 that must use base 36 instead of base 62 (because of case-insensitive file
984 systems), the units are 1/1000 of a second.
986 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
987 the fractional part of the time, which in this case is in units of 1/200
992 After a message has been received, Exim waits for the clock to tick at the
993 appropriate resolution before proceeding, so that if another message is
994 received by the same process, or by another process with the same (re-used)
995 pid, it is guaranteed that the time will be different. In most cases, the clock
996 will already have ticked while the message was being received.
999 .section "Receiving mail" "SECID13"
1000 .cindex "receiving mail"
1001 .cindex "message" "reception"
1002 The only way Exim can receive mail from another host is using SMTP over
1003 TCP/IP, in which case the sender and recipient addresses are transferred using
1004 SMTP commands. However, from a locally running process (such as a user's MUA),
1005 there are several possibilities:
1008 If the process runs Exim with the &%-bm%& option, the message is read
1009 non-interactively (usually via a pipe), with the recipients taken from the
1010 command line, or from the body of the message if &%-t%& is also used.
1012 If the process runs Exim with the &%-bS%& option, the message is also read
1013 non-interactively, but in this case the recipients are listed at the start of
1014 the message in a series of SMTP RCPT commands, terminated by a DATA
1015 command. This is so-called &"batch SMTP"& format,
1016 but it isn't really SMTP. The SMTP commands are just another way of passing
1017 envelope addresses in a non-interactive submission.
1019 If the process runs Exim with the &%-bs%& option, the message is read
1020 interactively, using the SMTP protocol. A two-way pipe is normally used for
1021 passing data between the local process and the Exim process.
1022 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1023 example, the ACLs for SMTP commands are used for this form of submission.
1025 A local process may also make a TCP/IP call to the host's loopback address
1026 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1027 does not treat the loopback address specially. It treats all such connections
1028 in the same way as connections from other hosts.
1032 .cindex "message sender, constructed by Exim"
1033 .cindex "sender" "constructed by Exim"
1034 In the three cases that do not involve TCP/IP, the sender address is
1035 constructed from the login name of the user that called Exim and a default
1036 qualification domain (which can be set by the &%qualify_domain%& configuration
1037 option). For local or batch SMTP, a sender address that is passed using the
1038 SMTP MAIL command is ignored. However, the system administrator may allow
1039 certain users (&"trusted users"&) to specify a different sender address
1040 unconditionally, or all users to specify certain forms of different sender
1041 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1042 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1043 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1044 users to change sender addresses.
1046 Messages received by either of the non-interactive mechanisms are subject to
1047 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1048 (either over TCP/IP, or interacting with a local process) can be checked by a
1049 number of ACLs that operate at different times during the SMTP session. Either
1050 individual recipients, or the entire message, can be rejected if local policy
1051 requirements are not met. The &[local_scan()]& function (see chapter
1052 &<<CHAPlocalscan>>&) is run for all incoming messages.
1054 Exim can be configured not to start a delivery process when a message is
1055 received; this can be unconditional, or depend on the number of incoming SMTP
1056 connections or the system load. In these situations, new messages wait on the
1057 queue until a queue runner process picks them up. However, in standard
1058 configurations under normal conditions, delivery is started as soon as a
1059 message is received.
1065 .section "Handling an incoming message" "SECID14"
1066 .cindex "spool directory" "files that hold a message"
1067 .cindex "file" "how a message is held"
1068 When Exim accepts a message, it writes two files in its spool directory. The
1069 first contains the envelope information, the current status of the message, and
1070 the header lines, and the second contains the body of the message. The names of
1071 the two spool files consist of the message id, followed by &`-H`& for the
1072 file containing the envelope and header, and &`-D`& for the data file.
1074 .cindex "spool directory" "&_input_& sub-directory"
1075 By default all these message files are held in a single directory called
1076 &_input_& inside the general Exim spool directory. Some operating systems do
1077 not perform very well if the number of files in a directory gets large; to
1078 improve performance in such cases, the &%split_spool_directory%& option can be
1079 used. This causes Exim to split up the input files into 62 sub-directories
1080 whose names are single letters or digits. When this is done, the queue is
1081 processed one sub-directory at a time instead of all at once, which can improve
1082 overall performance even when there are not enough files in each directory to
1083 affect file system performance.
1085 The envelope information consists of the address of the message's sender and
1086 the addresses of the recipients. This information is entirely separate from
1087 any addresses contained in the header lines. The status of the message includes
1088 a list of recipients who have already received the message. The format of the
1089 first spool file is described in chapter &<<CHAPspool>>&.
1091 .cindex "rewriting" "addresses"
1092 Address rewriting that is specified in the rewrite section of the configuration
1093 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1094 both in the header lines and the envelope, at the time the message is accepted.
1095 If during the course of delivery additional addresses are generated (for
1096 example, via aliasing), these new addresses are rewritten as soon as they are
1097 generated. At the time a message is actually delivered (transported) further
1098 rewriting can take place; because this is a transport option, it can be
1099 different for different forms of delivery. It is also possible to specify the
1100 addition or removal of certain header lines at the time the message is
1101 delivered (see chapters &<<CHAProutergeneric>>& and
1102 &<<CHAPtransportgeneric>>&).
1106 .section "Life of a message" "SECID15"
1107 .cindex "message" "life of"
1108 .cindex "message" "frozen"
1109 A message remains in the spool directory until it is completely delivered to
1110 its recipients or to an error address, or until it is deleted by an
1111 administrator or by the user who originally created it. In cases when delivery
1112 cannot proceed &-- for example, when a message can neither be delivered to its
1113 recipients nor returned to its sender, the message is marked &"frozen"& on the
1114 spool, and no more deliveries are attempted.
1116 .cindex "frozen messages" "thawing"
1117 .cindex "message" "thawing frozen"
1118 An administrator can &"thaw"& such messages when the problem has been
1119 corrected, and can also freeze individual messages by hand if necessary. In
1120 addition, an administrator can force a delivery error, causing a bounce message
1123 .oindex "&%timeout_frozen_after%&"
1124 .oindex "&%ignore_bounce_errors_after%&"
1125 There are options called &%ignore_bounce_errors_after%& and
1126 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1127 The first applies only to frozen bounces, the second to any frozen messages.
1129 .cindex "message" "log file for"
1130 .cindex "log" "file for each message"
1131 While Exim is working on a message, it writes information about each delivery
1132 attempt to its main log file. This includes successful, unsuccessful, and
1133 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1134 lines are also written to a separate &'message log'& file for each message.
1135 These logs are solely for the benefit of the administrator, and are normally
1136 deleted along with the spool files when processing of a message is complete.
1137 The use of individual message logs can be disabled by setting
1138 &%no_message_logs%&; this might give an improvement in performance on very busy
1141 .cindex "journal file"
1142 .cindex "file" "journal"
1143 All the information Exim itself needs to set up a delivery is kept in the first
1144 spool file, along with the header lines. When a successful delivery occurs, the
1145 address is immediately written at the end of a journal file, whose name is the
1146 message id followed by &`-J`&. At the end of a delivery run, if there are some
1147 addresses left to be tried again later, the first spool file (the &`-H`& file)
1148 is updated to indicate which these are, and the journal file is then deleted.
1149 Updating the spool file is done by writing a new file and renaming it, to
1150 minimize the possibility of data loss.
1152 Should the system or the program crash after a successful delivery but before
1153 the spool file has been updated, the journal is left lying around. The next
1154 time Exim attempts to deliver the message, it reads the journal file and
1155 updates the spool file before proceeding. This minimizes the chances of double
1156 deliveries caused by crashes.
1160 .section "Processing an address for delivery" "SECTprocaddress"
1161 .cindex "drivers" "definition of"
1162 .cindex "router" "definition of"
1163 .cindex "transport" "definition of"
1164 The main delivery processing elements of Exim are called &'routers'& and
1165 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1166 number of them is provided in the source distribution, and compile-time options
1167 specify which ones are included in the binary. Run time options specify which
1168 ones are actually used for delivering messages.
1170 .cindex "drivers" "instance definition"
1171 Each driver that is specified in the run time configuration is an &'instance'&
1172 of that particular driver type. Multiple instances are allowed; for example,
1173 you can set up several different &(smtp)& transports, each with different
1174 option values that might specify different ports or different timeouts. Each
1175 instance has its own identifying name. In what follows we will normally use the
1176 instance name when discussing one particular instance (that is, one specific
1177 configuration of the driver), and the generic driver name when discussing
1178 the driver's features in general.
1180 A &'router'& is a driver that operates on an address, either determining how
1181 its delivery should happen, by assigning it to a specific transport, or
1182 converting the address into one or more new addresses (for example, via an
1183 alias file). A router may also explicitly choose to fail an address, causing it
1186 A &'transport'& is a driver that transmits a copy of the message from Exim's
1187 spool to some destination. There are two kinds of transport: for a &'local'&
1188 transport, the destination is a file or a pipe on the local host, whereas for a
1189 &'remote'& transport the destination is some other host. A message is passed
1190 to a specific transport as a result of successful routing. If a message has
1191 several recipients, it may be passed to a number of different transports.
1193 .cindex "preconditions" "definition of"
1194 An address is processed by passing it to each configured router instance in
1195 turn, subject to certain preconditions, until a router accepts the address or
1196 specifies that it should be bounced. We will describe this process in more
1197 detail shortly. First, as a simple example, we consider how each recipient
1198 address in a message is processed in a small configuration of three routers.
1200 To make this a more concrete example, it is described in terms of some actual
1201 routers, but remember, this is only an example. You can configure Exim's
1202 routers in many different ways, and there may be any number of routers in a
1205 The first router that is specified in a configuration is often one that handles
1206 addresses in domains that are not recognized specially by the local host. These
1207 are typically addresses for arbitrary domains on the Internet. A precondition
1208 is set up which looks for the special domains known to the host (for example,
1209 its own domain name), and the router is run for addresses that do &'not'&
1210 match. Typically, this is a router that looks up domains in the DNS in order to
1211 find the hosts to which this address routes. If it succeeds, the address is
1212 assigned to a suitable SMTP transport; if it does not succeed, the router is
1213 configured to fail the address.
1215 The second router is reached only when the domain is recognized as one that
1216 &"belongs"& to the local host. This router does redirection &-- also known as
1217 aliasing and forwarding. When it generates one or more new addresses from the
1218 original, each of them is routed independently from the start. Otherwise, the
1219 router may cause an address to fail, or it may simply decline to handle the
1220 address, in which case the address is passed to the next router.
1222 The final router in many configurations is one that checks to see if the
1223 address belongs to a local mailbox. The precondition may involve a check to
1224 see if the local part is the name of a login account, or it may look up the
1225 local part in a file or a database. If its preconditions are not met, or if
1226 the router declines, we have reached the end of the routers. When this happens,
1227 the address is bounced.
1231 .section "Processing an address for verification" "SECID16"
1232 .cindex "router" "for verification"
1233 .cindex "verifying address" "overview"
1234 As well as being used to decide how to deliver to an address, Exim's routers
1235 are also used for &'address verification'&. Verification can be requested as
1236 one of the checks to be performed in an ACL for incoming messages, on both
1237 sender and recipient addresses, and it can be tested using the &%-bv%& and
1238 &%-bvs%& command line options.
1240 When an address is being verified, the routers are run in &"verify mode"&. This
1241 does not affect the way the routers work, but it is a state that can be
1242 detected. By this means, a router can be skipped or made to behave differently
1243 when verifying. A common example is a configuration in which the first router
1244 sends all messages to a message-scanning program, unless they have been
1245 previously scanned. Thus, the first router accepts all addresses without any
1246 checking, making it useless for verifying. Normally, the &%no_verify%& option
1247 would be set for such a router, causing it to be skipped in verify mode.
1252 .section "Running an individual router" "SECTrunindrou"
1253 .cindex "router" "running details"
1254 .cindex "preconditions" "checking"
1255 .cindex "router" "result of running"
1256 As explained in the example above, a number of preconditions are checked before
1257 running a router. If any are not met, the router is skipped, and the address is
1258 passed to the next router. When all the preconditions on a router &'are'& met,
1259 the router is run. What happens next depends on the outcome, which is one of
1263 &'accept'&: The router accepts the address, and either assigns it to a
1264 transport, or generates one or more &"child"& addresses. Processing the
1265 original address ceases,
1266 .oindex "&%unseen%&"
1267 unless the &%unseen%& option is set on the router. This option
1268 can be used to set up multiple deliveries with different routing (for example,
1269 for keeping archive copies of messages). When &%unseen%& is set, the address is
1270 passed to the next router. Normally, however, an &'accept'& return marks the
1273 Any child addresses generated by the router are processed independently,
1274 starting with the first router by default. It is possible to change this by
1275 setting the &%redirect_router%& option to specify which router to start at for
1276 child addresses. Unlike &%pass_router%& (see below) the router specified by
1277 &%redirect_router%& may be anywhere in the router configuration.
1279 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1280 requests that the address be passed to another router. By default the address
1281 is passed to the next router, but this can be changed by setting the
1282 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1283 must be below the current router (to avoid loops).
1285 &'decline'&: The router declines to accept the address because it does not
1286 recognize it at all. By default, the address is passed to the next router, but
1287 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1288 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1289 &'decline'& into &'fail'&.
1291 &'fail'&: The router determines that the address should fail, and queues it for
1292 the generation of a bounce message. There is no further processing of the
1293 original address unless &%unseen%& is set on the router.
1295 &'defer'&: The router cannot handle the address at the present time. (A
1296 database may be offline, or a DNS lookup may have timed out.) No further
1297 processing of the address happens in this delivery attempt. It is tried again
1298 next time the message is considered for delivery.
1300 &'error'&: There is some error in the router (for example, a syntax error in
1301 its configuration). The action is as for defer.
1304 If an address reaches the end of the routers without having been accepted by
1305 any of them, it is bounced as unrouteable. The default error message in this
1306 situation is &"unrouteable address"&, but you can set your own message by
1307 making use of the &%cannot_route_message%& option. This can be set for any
1308 router; the value from the last router that &"saw"& the address is used.
1310 Sometimes while routing you want to fail a delivery when some conditions are
1311 met but others are not, instead of passing the address on for further routing.
1312 You can do this by having a second router that explicitly fails the delivery
1313 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1314 facility for this purpose.
1317 .section "Duplicate addresses" "SECID17"
1318 .cindex "case of local parts"
1319 .cindex "address duplicate, discarding"
1320 .cindex "duplicate addresses"
1321 Once routing is complete, Exim scans the addresses that are assigned to local
1322 and remote transports, and discards any duplicates that it finds. During this
1323 check, local parts are treated as case-sensitive. This happens only when
1324 actually delivering a message; when testing routers with &%-bt%&, all the
1325 routed addresses are shown.
1329 .section "Router preconditions" "SECTrouprecon"
1330 .cindex "router" "preconditions, order of processing"
1331 .cindex "preconditions" "order of processing"
1332 The preconditions that are tested for each router are listed below, in the
1333 order in which they are tested. The individual configuration options are
1334 described in more detail in chapter &<<CHAProutergeneric>>&.
1337 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1338 the local parts handled by the router may or must have certain prefixes and/or
1339 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1340 skipped. These conditions are tested first. When an affix is present, it is
1341 removed from the local part before further processing, including the evaluation
1342 of any other conditions.
1344 Routers can be designated for use only when not verifying an address, that is,
1345 only when routing it for delivery (or testing its delivery routing). If the
1346 &%verify%& option is set false, the router is skipped when Exim is verifying an
1348 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1349 &%verify_recipient%&, which independently control the use of the router for
1350 sender and recipient verification. You can set these options directly if
1351 you want a router to be used for only one type of verification.
1353 If the &%address_test%& option is set false, the router is skipped when Exim is
1354 run with the &%-bt%& option to test an address routing. This can be helpful
1355 when the first router sends all new messages to a scanner of some sort; it
1356 makes it possible to use &%-bt%& to test subsequent delivery routing without
1357 having to simulate the effect of the scanner.
1359 Routers can be designated for use only when verifying an address, as
1360 opposed to routing it for delivery. The &%verify_only%& option controls this.
1362 Individual routers can be explicitly skipped when running the routers to
1363 check an address given in the SMTP EXPN command (see the &%expn%& option).
1365 If the &%domains%& option is set, the domain of the address must be in the set
1366 of domains that it defines.
1368 .vindex "&$local_part_prefix$&"
1369 .vindex "&$local_part$&"
1370 .vindex "&$local_part_suffix$&"
1371 If the &%local_parts%& option is set, the local part of the address must be in
1372 the set of local parts that it defines. If &%local_part_prefix%& or
1373 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1374 part before this check. If you want to do precondition tests on local parts
1375 that include affixes, you can do so by using a &%condition%& option (see below)
1376 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1377 &$local_part_suffix$& as necessary.
1379 .vindex "&$local_user_uid$&"
1380 .vindex "&$local_user_gid$&"
1382 If the &%check_local_user%& option is set, the local part must be the name of
1383 an account on the local host. If this check succeeds, the uid and gid of the
1384 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1385 user's home directory is placed in &$home$&; these values can be used in the
1386 remaining preconditions.
1388 If the &%router_home_directory%& option is set, it is expanded at this point,
1389 because it overrides the value of &$home$&. If this expansion were left till
1390 later, the value of &$home$& as set by &%check_local_user%& would be used in
1391 subsequent tests. Having two different values of &$home$& in the same router
1392 could lead to confusion.
1394 If the &%senders%& option is set, the envelope sender address must be in the
1395 set of addresses that it defines.
1397 If the &%require_files%& option is set, the existence or non-existence of
1398 specified files is tested.
1400 .cindex "customizing" "precondition"
1401 If the &%condition%& option is set, it is evaluated and tested. This option
1402 uses an expanded string to allow you to set up your own custom preconditions.
1403 Expanded strings are described in chapter &<<CHAPexpand>>&.
1407 Note that &%require_files%& comes near the end of the list, so you cannot use
1408 it to check for the existence of a file in which to lookup up a domain, local
1409 part, or sender. However, as these options are all expanded, you can use the
1410 &%exists%& expansion condition to make such tests within each condition. The
1411 &%require_files%& option is intended for checking files that the router may be
1412 going to use internally, or which are needed by a specific transport (for
1413 example, &_.procmailrc_&).
1417 .section "Delivery in detail" "SECID18"
1418 .cindex "delivery" "in detail"
1419 When a message is to be delivered, the sequence of events is as follows:
1422 If a system-wide filter file is specified, the message is passed to it. The
1423 filter may add recipients to the message, replace the recipients, discard the
1424 message, cause a new message to be generated, or cause the message delivery to
1425 fail. The format of the system filter file is the same as for Exim user filter
1426 files, described in the separate document entitled &'Exim's interfaces to mail
1428 .cindex "Sieve filter" "not available for system filter"
1429 (&*Note*&: Sieve cannot be used for system filter files.)
1431 Some additional features are available in system filters &-- see chapter
1432 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1433 filter only once per delivery attempt, however many recipients it has. However,
1434 if there are several delivery attempts because one or more addresses could not
1435 be immediately delivered, the system filter is run each time. The filter
1436 condition &%first_delivery%& can be used to detect the first run of the system
1439 Each recipient address is offered to each configured router in turn, subject to
1440 its preconditions, until one is able to handle it. If no router can handle the
1441 address, that is, if they all decline, the address is failed. Because routers
1442 can be targeted at particular domains, several locally handled domains can be
1443 processed entirely independently of each other.
1445 .cindex "routing" "loops in"
1446 .cindex "loop" "while routing"
1447 A router that accepts an address may assign it to a local or a remote
1448 transport. However, the transport is not run at this time. Instead, the address
1449 is placed on a list for the particular transport, which will be run later.
1450 Alternatively, the router may generate one or more new addresses (typically
1451 from alias, forward, or filter files). New addresses are fed back into this
1452 process from the top, but in order to avoid loops, a router ignores any address
1453 which has an identically-named ancestor that was processed by itself.
1455 When all the routing has been done, addresses that have been successfully
1456 handled are passed to their assigned transports. When local transports are
1457 doing real local deliveries, they handle only one address at a time, but if a
1458 local transport is being used as a pseudo-remote transport (for example, to
1459 collect batched SMTP messages for transmission by some other means) multiple
1460 addresses can be handled. Remote transports can always handle more than one
1461 address at a time, but can be configured not to do so, or to restrict multiple
1462 addresses to the same domain.
1464 Each local delivery to a file or a pipe runs in a separate process under a
1465 non-privileged uid, and these deliveries are run one at a time. Remote
1466 deliveries also run in separate processes, normally under a uid that is private
1467 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1468 run in parallel. The maximum number of simultaneous remote deliveries for any
1469 one message is set by the &%remote_max_parallel%& option.
1470 The order in which deliveries are done is not defined, except that all local
1471 deliveries happen before any remote deliveries.
1473 .cindex "queue runner"
1474 When it encounters a local delivery during a queue run, Exim checks its retry
1475 database to see if there has been a previous temporary delivery failure for the
1476 address before running the local transport. If there was a previous failure,
1477 Exim does not attempt a new delivery until the retry time for the address is
1478 reached. However, this happens only for delivery attempts that are part of a
1479 queue run. Local deliveries are always attempted when delivery immediately
1480 follows message reception, even if retry times are set for them. This makes for
1481 better behaviour if one particular message is causing problems (for example,
1482 causing quota overflow, or provoking an error in a filter file).
1484 .cindex "delivery" "retry in remote transports"
1485 Remote transports do their own retry handling, since an address may be
1486 deliverable to one of a number of hosts, each of which may have a different
1487 retry time. If there have been previous temporary failures and no host has
1488 reached its retry time, no delivery is attempted, whether in a queue run or
1489 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1491 If there were any permanent errors, a bounce message is returned to an
1492 appropriate address (the sender in the common case), with details of the error
1493 for each failing address. Exim can be configured to send copies of bounce
1494 messages to other addresses.
1496 .cindex "delivery" "deferral"
1497 If one or more addresses suffered a temporary failure, the message is left on
1498 the queue, to be tried again later. Delivery of these addresses is said to be
1501 When all the recipient addresses have either been delivered or bounced,
1502 handling of the message is complete. The spool files and message log are
1503 deleted, though the message log can optionally be preserved if required.
1509 .section "Retry mechanism" "SECID19"
1510 .cindex "delivery" "retry mechanism"
1511 .cindex "retry" "description of mechanism"
1512 .cindex "queue runner"
1513 Exim's mechanism for retrying messages that fail to get delivered at the first
1514 attempt is the queue runner process. You must either run an Exim daemon that
1515 uses the &%-q%& option with a time interval to start queue runners at regular
1516 intervals, or use some other means (such as &'cron'&) to start them. If you do
1517 not arrange for queue runners to be run, messages that fail temporarily at the
1518 first attempt will remain on your queue for ever. A queue runner process works
1519 its way through the queue, one message at a time, trying each delivery that has
1520 passed its retry time.
1521 You can run several queue runners at once.
1523 Exim uses a set of configured rules to determine when next to retry the failing
1524 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1525 should give up trying to deliver to the address, at which point it generates a
1526 bounce message. If no retry rules are set for a particular host, address, and
1527 error combination, no retries are attempted, and temporary errors are treated
1532 .section "Temporary delivery failure" "SECID20"
1533 .cindex "delivery" "temporary failure"
1534 There are many reasons why a message may not be immediately deliverable to a
1535 particular address. Failure to connect to a remote machine (because it, or the
1536 connection to it, is down) is one of the most common. Temporary failures may be
1537 detected during routing as well as during the transport stage of delivery.
1538 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1539 is on a file system where the user is over quota. Exim can be configured to
1540 impose its own quotas on local mailboxes; where system quotas are set they will
1543 If a host is unreachable for a period of time, a number of messages may be
1544 waiting for it by the time it recovers, and sending them in a single SMTP
1545 connection is clearly beneficial. Whenever a delivery to a remote host is
1548 .cindex "hints database"
1549 Exim makes a note in its hints database, and whenever a successful
1550 SMTP delivery has happened, it looks to see if any other messages are waiting
1551 for the same host. If any are found, they are sent over the same SMTP
1552 connection, subject to a configuration limit as to the maximum number in any
1558 .section "Permanent delivery failure" "SECID21"
1559 .cindex "delivery" "permanent failure"
1560 .cindex "bounce message" "when generated"
1561 When a message cannot be delivered to some or all of its intended recipients, a
1562 bounce message is generated. Temporary delivery failures turn into permanent
1563 errors when their timeout expires. All the addresses that fail in a given
1564 delivery attempt are listed in a single message. If the original message has
1565 many recipients, it is possible for some addresses to fail in one delivery
1566 attempt and others to fail subsequently, giving rise to more than one bounce
1567 message. The wording of bounce messages can be customized by the administrator.
1568 See chapter &<<CHAPemsgcust>>& for details.
1570 .cindex "&'X-Failed-Recipients:'& header line"
1571 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1572 failed addresses, for the benefit of programs that try to analyse such messages
1575 .cindex "bounce message" "recipient of"
1576 A bounce message is normally sent to the sender of the original message, as
1577 obtained from the message's envelope. For incoming SMTP messages, this is the
1578 address given in the MAIL command. However, when an address is expanded via a
1579 forward or alias file, an alternative address can be specified for delivery
1580 failures of the generated addresses. For a mailing list expansion (see section
1581 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1586 .section "Failures to deliver bounce messages" "SECID22"
1587 .cindex "bounce message" "failure to deliver"
1588 If a bounce message (either locally generated or received from a remote host)
1589 itself suffers a permanent delivery failure, the message is left on the queue,
1590 but it is frozen, awaiting the attention of an administrator. There are options
1591 that can be used to make Exim discard such failed messages, or to keep them
1592 for only a short time (see &%timeout_frozen_after%& and
1593 &%ignore_bounce_errors_after%&).
1599 . ////////////////////////////////////////////////////////////////////////////
1600 . ////////////////////////////////////////////////////////////////////////////
1602 .chapter "Building and installing Exim" "CHID3"
1603 .scindex IIDbuex "building Exim"
1605 .section "Unpacking" "SECID23"
1606 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1607 creates a directory with the name of the current release (for example,
1608 &_exim-&version;_&) into which the following files are placed:
1611 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1612 .irow &_CHANGES_& "contains a reference to where changes are &&&
1614 .irow &_LICENCE_& "the GNU General Public Licence"
1615 .irow &_Makefile_& "top-level make file"
1616 .irow &_NOTICE_& "conditions for the use of Exim"
1617 .irow &_README_& "list of files, directories and simple build &&&
1621 Other files whose names begin with &_README_& may also be present. The
1622 following subdirectories are created:
1625 .irow &_Local_& "an empty directory for local configuration files"
1626 .irow &_OS_& "OS-specific files"
1627 .irow &_doc_& "documentation files"
1628 .irow &_exim_monitor_& "source files for the Exim monitor"
1629 .irow &_scripts_& "scripts used in the build process"
1630 .irow &_src_& "remaining source files"
1631 .irow &_util_& "independent utilities"
1634 The main utility programs are contained in the &_src_& directory, and are built
1635 with the Exim binary. The &_util_& directory contains a few optional scripts
1636 that may be useful to some sites.
1639 .section "Multiple machine architectures and operating systems" "SECID24"
1640 .cindex "building Exim" "multiple OS/architectures"
1641 The building process for Exim is arranged to make it easy to build binaries for
1642 a number of different architectures and operating systems from the same set of
1643 source files. Compilation does not take place in the &_src_& directory.
1644 Instead, a &'build directory'& is created for each architecture and operating
1646 .cindex "symbolic link" "to build directory"
1647 Symbolic links to the sources are installed in this directory, which is where
1648 the actual building takes place. In most cases, Exim can discover the machine
1649 architecture and operating system for itself, but the defaults can be
1650 overridden if necessary.
1653 .section "PCRE library" "SECTpcre"
1654 .cindex "PCRE library"
1655 Exim no longer has an embedded PCRE library as the vast majority of
1656 modern systems include PCRE as a system library, although you may need
1657 to install the PCRE or PCRE development package for your operating
1658 system. If your system has a normal PCRE installation the Exim build
1659 process will need no further configuration. If the library or the
1660 headers are in an unusual location you will need to set the PCRE_LIBS
1661 and INCLUDE directives appropriately. If your operating system has no
1662 PCRE support then you will need to obtain and build the current PCRE
1663 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1665 .section "DBM libraries" "SECTdb"
1666 .cindex "DBM libraries" "discussion of"
1667 .cindex "hints database" "DBM files used for"
1668 Even if you do not use any DBM files in your configuration, Exim still needs a
1669 DBM library in order to operate, because it uses indexed files for its hints
1670 databases. Unfortunately, there are a number of DBM libraries in existence, and
1671 different operating systems often have different ones installed.
1673 .cindex "Solaris" "DBM library for"
1674 .cindex "IRIX, DBM library for"
1675 .cindex "BSD, DBM library for"
1676 .cindex "Linux, DBM library for"
1677 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1678 Linux distribution, the DBM configuration should happen automatically, and you
1679 may be able to ignore this section. Otherwise, you may have to learn more than
1680 you would like about DBM libraries from what follows.
1682 .cindex "&'ndbm'& DBM library"
1683 Licensed versions of Unix normally contain a library of DBM functions operating
1684 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1685 versions of Unix seem to vary in what they contain as standard. In particular,
1686 some early versions of Linux have no default DBM library, and different
1687 distributors have chosen to bundle different libraries with their packaged
1688 versions. However, the more recent releases seem to have standardized on the
1689 Berkeley DB library.
1691 Different DBM libraries have different conventions for naming the files they
1692 use. When a program opens a file called &_dbmfile_&, there are several
1696 A traditional &'ndbm'& implementation, such as that supplied as part of
1697 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1699 .cindex "&'gdbm'& DBM library"
1700 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1701 compatibility interface it makes two different hard links to it with names
1702 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1703 file name is used unmodified.
1705 .cindex "Berkeley DB library"
1706 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1707 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1708 programmer exactly the same as the traditional &'ndbm'& implementation.
1710 If the Berkeley package is used in its native mode, it operates on a single
1711 file called &_dbmfile_&; the programmer's interface is somewhat different to
1712 the traditional &'ndbm'& interface.
1714 To complicate things further, there are several very different versions of the
1715 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1716 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1717 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1718 versions of Berkeley DB can be obtained from
1719 &url(http://www.sleepycat.com/).
1721 .cindex "&'tdb'& DBM library"
1722 Yet another DBM library, called &'tdb'&, is available from
1723 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1724 operates on a single file.
1728 .cindex "DBM libraries" "configuration for building"
1729 Exim and its utilities can be compiled to use any of these interfaces. In order
1730 to use any version of the Berkeley DB package in native mode, you must set
1731 USE_DB in an appropriate configuration file (typically
1732 &_Local/Makefile_&). For example:
1736 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1737 error is diagnosed if you set more than one of these.
1739 At the lowest level, the build-time configuration sets none of these options,
1740 thereby assuming an interface of type (1). However, some operating system
1741 configuration files (for example, those for the BSD operating systems and
1742 Linux) assume type (4) by setting USE_DB as their default, and the
1743 configuration files for Cygwin set USE_GDBM. Anything you set in
1744 &_Local/Makefile_&, however, overrides these system defaults.
1746 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1747 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1748 in one of these lines:
1753 Settings like that will work if the DBM library is installed in the standard
1754 place. Sometimes it is not, and the library's header file may also not be in
1755 the default path. You may need to set INCLUDE to specify where the header
1756 file is, and to specify the path to the library more fully in DBMLIB, as in
1759 INCLUDE=-I/usr/local/include/db-4.1
1760 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1762 There is further detailed discussion about the various DBM libraries in the
1763 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1767 .section "Pre-building configuration" "SECID25"
1768 .cindex "building Exim" "pre-building configuration"
1769 .cindex "configuration for building Exim"
1770 .cindex "&_Local/Makefile_&"
1771 .cindex "&_src/EDITME_&"
1772 Before building Exim, a local configuration file that specifies options
1773 independent of any operating system has to be created with the name
1774 &_Local/Makefile_&. A template for this file is supplied as the file
1775 &_src/EDITME_&, and it contains full descriptions of all the option settings
1776 therein. These descriptions are therefore not repeated here. If you are
1777 building Exim for the first time, the simplest thing to do is to copy
1778 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1780 There are three settings that you must supply, because Exim will not build
1781 without them. They are the location of the run time configuration file
1782 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1783 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1784 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1785 a colon-separated list of file names; Exim uses the first of them that exists.
1787 There are a few other parameters that can be specified either at build time or
1788 at run time, to enable the same binary to be used on a number of different
1789 machines. However, if the locations of Exim's spool directory and log file
1790 directory (if not within the spool directory) are fixed, it is recommended that
1791 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1792 detected early in Exim's execution (such as a malformed configuration file) can
1795 .cindex "content scanning" "specifying at build time"
1796 Exim's interfaces for calling virus and spam scanning software directly from
1797 access control lists are not compiled by default. If you want to include these
1798 facilities, you need to set
1800 WITH_CONTENT_SCAN=yes
1802 in your &_Local/Makefile_&. For details of the facilities themselves, see
1803 chapter &<<CHAPexiscan>>&.
1806 .cindex "&_Local/eximon.conf_&"
1807 .cindex "&_exim_monitor/EDITME_&"
1808 If you are going to build the Exim monitor, a similar configuration process is
1809 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1810 your installation and saved under the name &_Local/eximon.conf_&. If you are
1811 happy with the default settings described in &_exim_monitor/EDITME_&,
1812 &_Local/eximon.conf_& can be empty, but it must exist.
1814 This is all the configuration that is needed in straightforward cases for known
1815 operating systems. However, the building process is set up so that it is easy
1816 to override options that are set by default or by operating-system-specific
1817 configuration files, for example to change the name of the C compiler, which
1818 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1823 .section "Support for iconv()" "SECID26"
1824 .cindex "&[iconv()]& support"
1826 The contents of header lines in messages may be encoded according to the rules
1827 described RFC 2047. This makes it possible to transmit characters that are not
1828 in the ASCII character set, and to label them as being in a particular
1829 character set. When Exim is inspecting header lines by means of the &%$h_%&
1830 mechanism, it decodes them, and translates them into a specified character set
1831 (default ISO-8859-1). The translation is possible only if the operating system
1832 supports the &[iconv()]& function.
1834 However, some of the operating systems that supply &[iconv()]& do not support
1835 very many conversions. The GNU &%libiconv%& library (available from
1836 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1837 systems to remedy this deficiency, as well as on systems that do not supply
1838 &[iconv()]& at all. After installing &%libiconv%&, you should add
1842 to your &_Local/Makefile_& and rebuild Exim.
1846 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1847 .cindex "TLS" "including support for TLS"
1848 .cindex "encryption" "including support for"
1849 .cindex "SUPPORT_TLS"
1850 .cindex "OpenSSL" "building Exim with"
1851 .cindex "GnuTLS" "building Exim with"
1852 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1853 command as per RFC 2487. It can also support legacy clients that expect to
1854 start a TLS session immediately on connection to a non-standard port (see the
1855 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1858 If you want to build Exim with TLS support, you must first install either the
1859 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1862 If OpenSSL is installed, you should set
1865 TLS_LIBS=-lssl -lcrypto
1867 in &_Local/Makefile_&. You may also need to specify the locations of the
1868 OpenSSL library and include files. For example:
1871 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1872 TLS_INCLUDE=-I/usr/local/openssl/include/
1874 .cindex "USE_GNUTLS"
1875 If GnuTLS is installed, you should set
1879 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1881 in &_Local/Makefile_&, and again you may need to specify the locations of the
1882 library and include files. For example:
1886 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1887 TLS_INCLUDE=-I/usr/gnu/include
1889 You do not need to set TLS_INCLUDE if the relevant directory is already
1890 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1891 given in chapter &<<CHAPTLS>>&.
1896 .section "Use of tcpwrappers" "SECID27"
1897 .cindex "tcpwrappers, building Exim to support"
1898 .cindex "USE_TCP_WRAPPERS"
1899 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1900 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1901 alternative to Exim's own checking facilities for installations that are
1902 already making use of &'tcpwrappers'& for other purposes. To do this, you
1903 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1904 &_tcpd.h_& to be available at compile time, and also ensure that the library
1905 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1906 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1909 USE_TCP_WRAPPERS=yes
1910 CFLAGS=-O -I/usr/local/include
1911 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1913 in &_Local/Makefile_&. The name to use in the &'tcpwrappers'& control files is
1914 &"exim"&. For example, the line
1916 exim : LOCAL 192.168.1. .friendly.domain.example
1918 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1919 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1920 All other connections are denied. Consult the &'tcpwrappers'& documentation for
1925 .section "Including support for IPv6" "SECID28"
1926 .cindex "IPv6" "including support for"
1927 Exim contains code for use on systems that have IPv6 support. Setting
1928 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1929 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1930 where the IPv6 support is not fully integrated into the normal include and
1933 Two different types of DNS record for handling IPv6 addresses have been
1934 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1935 currently seen as the mainstream. Another record type called A6 was proposed
1936 as better than AAAA because it had more flexibility. However, it was felt to be
1937 over-complex, and its status was reduced to &"experimental"&. It is not known
1938 if anyone is actually using A6 records. Exim has support for A6 records, but
1939 this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
1940 support has not been tested for some time.
1944 .section "The building process" "SECID29"
1945 .cindex "build directory"
1946 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
1947 created, run &'make'& at the top level. It determines the architecture and
1948 operating system types, and creates a build directory if one does not exist.
1949 For example, on a Sun system running Solaris 8, the directory
1950 &_build-SunOS5-5.8-sparc_& is created.
1951 .cindex "symbolic link" "to source files"
1952 Symbolic links to relevant source files are installed in the build directory.
1954 &*Warning*&: The &%-j%& (parallel) flag must not be used with &'make'&; the
1955 building process fails if it is set.
1957 If this is the first time &'make'& has been run, it calls a script that builds
1958 a make file inside the build directory, using the configuration files from the
1959 &_Local_& directory. The new make file is then passed to another instance of
1960 &'make'&. This does the real work, building a number of utility scripts, and
1961 then compiling and linking the binaries for the Exim monitor (if configured), a
1962 number of utility programs, and finally Exim itself. The command &`make
1963 makefile`& can be used to force a rebuild of the make file in the build
1964 directory, should this ever be necessary.
1966 If you have problems building Exim, check for any comments there may be in the
1967 &_README_& file concerning your operating system, and also take a look at the
1968 FAQ, where some common problems are covered.
1972 .section 'Output from &"make"&' "SECID283"
1973 The output produced by the &'make'& process for compile lines is often very
1974 unreadable, because these lines can be very long. For this reason, the normal
1975 output is suppressed by default, and instead output similar to that which
1976 appears when compiling the 2.6 Linux kernel is generated: just a short line for
1977 each module that is being compiled or linked. However, it is still possible to
1978 get the full output, by calling &'make'& like this:
1982 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
1983 command reflection in &'make'&. When you ask for the full output, it is
1984 given in addition to the short output.
1988 .section "Overriding build-time options for Exim" "SECToverride"
1989 .cindex "build-time options, overriding"
1990 The main make file that is created at the beginning of the building process
1991 consists of the concatenation of a number of files which set configuration
1992 values, followed by a fixed set of &'make'& instructions. If a value is set
1993 more than once, the last setting overrides any previous ones. This provides a
1994 convenient way of overriding defaults. The files that are concatenated are, in
1997 &_OS/Makefile-Default_&
1998 &_OS/Makefile-_&<&'ostype'&>
2000 &_Local/Makefile-_&<&'ostype'&>
2001 &_Local/Makefile-_&<&'archtype'&>
2002 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2003 &_OS/Makefile-Base_&
2005 .cindex "&_Local/Makefile_&"
2006 .cindex "building Exim" "operating system type"
2007 .cindex "building Exim" "architecture type"
2008 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2009 architecture type. &_Local/Makefile_& is required to exist, and the building
2010 process fails if it is absent. The other three &_Local_& files are optional,
2011 and are often not needed.
2013 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2014 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2015 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2016 values are used, thereby providing a means of forcing particular settings.
2017 Otherwise, the scripts try to get values from the &%uname%& command. If this
2018 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2019 of &'ad hoc'& transformations are then applied, to produce the standard names
2020 that Exim expects. You can run these scripts directly from the shell in order
2021 to find out what values are being used on your system.
2024 &_OS/Makefile-Default_& contains comments about the variables that are set
2025 therein. Some (but not all) are mentioned below. If there is something that
2026 needs changing, review the contents of this file and the contents of the make
2027 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2031 .cindex "building Exim" "overriding default settings"
2032 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2033 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2034 need to change the original files. Instead, you should make the changes by
2035 putting the new values in an appropriate &_Local_& file. For example,
2036 .cindex "Tru64-Unix build-time settings"
2037 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2038 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2039 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2040 called with the option &%-std1%&, to make it recognize some of the features of
2041 Standard C that Exim uses. (Most other compilers recognize Standard C by
2042 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2043 containing the lines
2048 If you are compiling for just one operating system, it may be easier to put
2049 these lines directly into &_Local/Makefile_&.
2051 Keeping all your local configuration settings separate from the distributed
2052 files makes it easy to transfer them to new versions of Exim simply by copying
2053 the contents of the &_Local_& directory.
2056 .cindex "NIS lookup type" "including support for"
2057 .cindex "NIS+ lookup type" "including support for"
2058 .cindex "LDAP" "including support for"
2059 .cindex "lookup" "inclusion in binary"
2060 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2061 lookup, but not all systems have these components installed, so the default is
2062 not to include the relevant code in the binary. All the different kinds of file
2063 and database lookup that Exim supports are implemented as separate code modules
2064 which are included only if the relevant compile-time options are set. In the
2065 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2071 and similar settings apply to the other lookup types. They are all listed in
2072 &_src/EDITME_&. In many cases the relevant include files and interface
2073 libraries need to be installed before compiling Exim.
2074 .cindex "cdb" "including support for"
2075 However, there are some optional lookup types (such as cdb) for which
2076 the code is entirely contained within Exim, and no external include
2077 files or libraries are required. When a lookup type is not included in the
2078 binary, attempts to configure Exim to use it cause run time configuration
2081 .cindex "Perl" "including support for"
2082 Exim can be linked with an embedded Perl interpreter, allowing Perl
2083 subroutines to be called during string expansion. To enable this facility,
2087 must be defined in &_Local/Makefile_&. Details of this facility are given in
2088 chapter &<<CHAPperl>>&.
2090 .cindex "X11 libraries, location of"
2091 The location of the X11 libraries is something that varies a lot between
2092 operating systems, and there may be different versions of X11 to cope
2093 with. Exim itself makes no use of X11, but if you are compiling the Exim
2094 monitor, the X11 libraries must be available.
2095 The following three variables are set in &_OS/Makefile-Default_&:
2098 XINCLUDE=-I$(X11)/include
2099 XLFLAGS=-L$(X11)/lib
2101 These are overridden in some of the operating-system configuration files. For
2102 example, in &_OS/Makefile-SunOS5_& there is
2105 XINCLUDE=-I$(X11)/include
2106 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2108 If you need to override the default setting for your operating system, place a
2109 definition of all three of these variables into your
2110 &_Local/Makefile-<ostype>_& file.
2113 If you need to add any extra libraries to the link steps, these can be put in a
2114 variable called EXTRALIBS, which appears in all the link commands, but by
2115 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2116 command for linking the main Exim binary, and not for any associated utilities.
2118 .cindex "DBM libraries" "configuration for building"
2119 There is also DBMLIB, which appears in the link commands for binaries that
2120 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2121 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2122 binary, and which can be used, for example, to include additional X11
2125 .cindex "configuration file" "editing"
2126 The make file copes with rebuilding Exim correctly if any of the configuration
2127 files are edited. However, if an optional configuration file is deleted, it is
2128 necessary to touch the associated non-optional file (that is,
2129 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2132 .section "OS-specific header files" "SECID30"
2134 .cindex "building Exim" "OS-specific C header files"
2135 The &_OS_& directory contains a number of files with names of the form
2136 &_os.h-<ostype>_&. These are system-specific C header files that should not
2137 normally need to be changed. There is a list of macro settings that are
2138 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2139 are porting Exim to a new operating system.
2143 .section "Overriding build-time options for the monitor" "SECID31"
2144 .cindex "building Eximon"
2145 A similar process is used for overriding things when building the Exim monitor,
2146 where the files that are involved are
2148 &_OS/eximon.conf-Default_&
2149 &_OS/eximon.conf-_&<&'ostype'&>
2150 &_Local/eximon.conf_&
2151 &_Local/eximon.conf-_&<&'ostype'&>
2152 &_Local/eximon.conf-_&<&'archtype'&>
2153 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2155 .cindex "&_Local/eximon.conf_&"
2156 As with Exim itself, the final three files need not exist, and in this case the
2157 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2158 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2159 variables of the same name, preceded by EXIMON_. For example, setting
2160 EXIMON_LOG_DEPTH in the environment overrides the value of
2161 LOG_DEPTH at run time.
2165 .section "Installing Exim binaries and scripts" "SECID32"
2166 .cindex "installing Exim"
2167 .cindex "BIN_DIRECTORY"
2168 The command &`make install`& runs the &(exim_install)& script with no
2169 arguments. The script copies binaries and utility scripts into the directory
2170 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2171 .cindex "setuid" "installing Exim with"
2172 The install script copies files only if they are newer than the files they are
2173 going to replace. The Exim binary is required to be owned by root and have the
2174 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2175 install`& as root so that it can set up the Exim binary in this way. However, in
2176 some special situations (for example, if a host is doing no local deliveries)
2177 it may be possible to run Exim without making the binary setuid root (see
2178 chapter &<<CHAPsecurity>>& for details).
2180 .cindex "CONFIGURE_FILE"
2181 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2182 in &_Local/Makefile_&. If this names a single file, and the file does not
2183 exist, the default configuration file &_src/configure.default_& is copied there
2184 by the installation script. If a run time configuration file already exists, it
2185 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2186 alternative files, no default is installed.
2188 .cindex "system aliases file"
2189 .cindex "&_/etc/aliases_&"
2190 One change is made to the default configuration file when it is installed: the
2191 default configuration contains a router that references a system aliases file.
2192 The path to this file is set to the value specified by
2193 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2194 If the system aliases file does not exist, the installation script creates it,
2195 and outputs a comment to the user.
2197 The created file contains no aliases, but it does contain comments about the
2198 aliases a site should normally have. Mail aliases have traditionally been
2199 kept in &_/etc/aliases_&. However, some operating systems are now using
2200 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2201 Exim's configuration if necessary.
2203 The default configuration uses the local host's name as the only local domain,
2204 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2205 running as the local user. System aliases and &_.forward_& files in users' home
2206 directories are supported, but no NIS or NIS+ support is configured. Domains
2207 other than the name of the local host are routed using the DNS, with delivery
2210 It is possible to install Exim for special purposes (such as building a binary
2211 distribution) in a private part of the file system. You can do this by a
2214 make DESTDIR=/some/directory/ install
2216 This has the effect of pre-pending the specified directory to all the file
2217 paths, except the name of the system aliases file that appears in the default
2218 configuration. (If a default alias file is created, its name &'is'& modified.)
2219 For backwards compatibility, ROOT is used if DESTDIR is not set,
2220 but this usage is deprecated.
2222 .cindex "installing Exim" "what is not installed"
2223 Running &'make install'& does not copy the Exim 4 conversion script
2224 &'convert4r4'&. You will probably run this only once if you are
2225 upgrading from Exim 3. None of the documentation files in the &_doc_&
2226 directory are copied, except for the info files when you have set
2227 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2229 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2230 to their names. The Exim binary itself, however, is handled differently. It is
2231 installed under a name that includes the version number and the compile number,
2232 for example &_exim-&version;-1_&. The script then arranges for a symbolic link
2233 called &_exim_& to point to the binary. If you are updating a previous version
2234 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2235 from the directory (as seen by other processes).
2237 .cindex "installing Exim" "testing the script"
2238 If you want to see what the &'make install'& will do before running it for
2239 real, you can pass the &%-n%& option to the installation script by this
2242 make INSTALL_ARG=-n install
2244 The contents of the variable INSTALL_ARG are passed to the installation
2245 script. You do not need to be root to run this test. Alternatively, you can run
2246 the installation script directly, but this must be from within the build
2247 directory. For example, from the top-level Exim directory you could use this
2250 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2252 .cindex "installing Exim" "install script options"
2253 There are two other options that can be supplied to the installation script.
2256 &%-no_chown%& bypasses the call to change the owner of the installed binary
2257 to root, and the call to make it a setuid binary.
2259 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2263 INSTALL_ARG can be used to pass these options to the script. For example:
2265 make INSTALL_ARG=-no_symlink install
2267 The installation script can also be given arguments specifying which files are
2268 to be copied. For example, to install just the Exim binary, and nothing else,
2269 without creating the symbolic link, you could use:
2271 make INSTALL_ARG='-no_symlink exim' install
2276 .section "Installing info documentation" "SECTinsinfdoc"
2277 .cindex "installing Exim" "&'info'& documentation"
2278 Not all systems use the GNU &'info'& system for documentation, and for this
2279 reason, the Texinfo source of Exim's documentation is not included in the main
2280 distribution. Instead it is available separately from the ftp site (see section
2283 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2284 source of the documentation is found in the source tree, running &`make
2285 install`& automatically builds the info files and installs them.
2289 .section "Setting up the spool directory" "SECID33"
2290 .cindex "spool directory" "creating"
2291 When it starts up, Exim tries to create its spool directory if it does not
2292 exist. The Exim uid and gid are used for the owner and group of the spool
2293 directory. Sub-directories are automatically created in the spool directory as
2299 .section "Testing" "SECID34"
2300 .cindex "testing" "installation"
2301 Having installed Exim, you can check that the run time configuration file is
2302 syntactically valid by running the following command, which assumes that the
2303 Exim binary directory is within your PATH environment variable:
2307 If there are any errors in the configuration file, Exim outputs error messages.
2308 Otherwise it outputs the version number and build date,
2309 the DBM library that is being used, and information about which drivers and
2310 other optional code modules are included in the binary.
2311 Some simple routing tests can be done by using the address testing option. For
2314 &`exim -bt`& <&'local username'&>
2316 should verify that it recognizes a local mailbox, and
2318 &`exim -bt`& <&'remote address'&>
2320 a remote one. Then try getting it to deliver mail, both locally and remotely.
2321 This can be done by passing messages directly to Exim, without going through a
2322 user agent. For example:
2324 exim -v postmaster@your.domain.example
2325 From: user@your.domain.example
2326 To: postmaster@your.domain.example
2327 Subject: Testing Exim
2329 This is a test message.
2332 The &%-v%& option causes Exim to output some verification of what it is doing.
2333 In this case you should see copies of three log lines, one for the message's
2334 arrival, one for its delivery, and one containing &"Completed"&.
2336 .cindex "delivery" "problems with"
2337 If you encounter problems, look at Exim's log files (&'mainlog'& and
2338 &'paniclog'&) to see if there is any relevant information there. Another source
2339 of information is running Exim with debugging turned on, by specifying the
2340 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2341 with debugging turned on by a command of the form
2343 &`exim -d -M`& <&'exim-message-id'&>
2345 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2346 produces rather a lot of output, but you can cut this down to specific areas.
2347 For example, if you use &%-d-all+route%& only the debugging information
2348 relevant to routing is included. (See the &%-d%& option in chapter
2349 &<<CHAPcommandline>>& for more details.)
2351 .cindex '&"sticky"& bit'
2352 .cindex "lock files"
2353 One specific problem that has shown up on some sites is the inability to do
2354 local deliveries into a shared mailbox directory, because it does not have the
2355 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2356 writing to a mailbox file, and if it cannot create the lock file, the delivery
2357 is deferred. You can get round this either by setting the &"sticky bit"& on the
2358 directory, or by setting a specific group for local deliveries and allowing
2359 that group to create files in the directory (see the comments above the
2360 &(local_delivery)& transport in the default configuration file). Another
2361 approach is to configure Exim not to use lock files, but just to rely on
2362 &[fcntl()]& locking instead. However, you should do this only if all user
2363 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2364 see chapter &<<CHAPappendfile>>&.
2366 One thing that cannot be tested on a system that is already running an MTA is
2367 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2368 &%-oX%& option can be used to run an Exim daemon that listens on some other
2369 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2370 &'exim_checkaccess'& utility can be used to check out policy controls on
2373 Testing a new version on a system that is already running Exim can most easily
2374 be done by building a binary with a different CONFIGURE_FILE setting. From
2375 within the run time configuration, all other file and directory names
2376 that Exim uses can be altered, in order to keep it entirely clear of the
2380 .section "Replacing another MTA with Exim" "SECID35"
2381 .cindex "replacing another MTA"
2382 Building and installing Exim for the first time does not of itself put it in
2383 general use. The name by which the system's MTA is called by mail user agents
2384 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2385 operating system), and it is necessary to make this name point to the &'exim'&
2386 binary in order to get the user agents to pass messages to Exim. This is
2387 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2388 or &_/usr/lib/sendmail_&
2389 .cindex "symbolic link" "to &'exim'& binary"
2390 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2391 privilege and executable status from the old MTA. It is then necessary to stop
2392 and restart the mailer daemon, if one is running.
2394 .cindex "FreeBSD, MTA indirection"
2395 .cindex "&_/etc/mail/mailer.conf_&"
2396 Some operating systems have introduced alternative ways of switching MTAs. For
2397 example, if you are running FreeBSD, you need to edit the file
2398 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2399 described. A typical example of the contents of this file for running Exim is
2402 sendmail /usr/exim/bin/exim
2403 send-mail /usr/exim/bin/exim
2404 mailq /usr/exim/bin/exim -bp
2405 newaliases /usr/bin/true
2407 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2408 your Exim installation is &"live"&. Check it by sending a message from your
2409 favourite user agent.
2411 You should consider what to tell your users about the change of MTA. Exim may
2412 have different capabilities to what was previously running, and there are
2413 various operational differences such as the text of messages produced by
2414 command line options and in bounce messages. If you allow your users to make
2415 use of Exim's filtering capabilities, you should make the document entitled
2416 &'Exim's interface to mail filtering'& available to them.
2420 .section "Upgrading Exim" "SECID36"
2421 .cindex "upgrading Exim"
2422 If you are already running Exim on your host, building and installing a new
2423 version automatically makes it available to MUAs, or any other programs that
2424 call the MTA directly. However, if you are running an Exim daemon, you do need
2425 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2426 new binary. You do not need to stop processing mail in order to install a new
2427 version of Exim. The install script does not modify an existing runtime
2433 .section "Stopping the Exim daemon on Solaris" "SECID37"
2434 .cindex "Solaris" "stopping Exim on"
2435 The standard command for stopping the mailer daemon on Solaris is
2437 /etc/init.d/sendmail stop
2439 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2440 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2441 for the text &"sendmail"&; this is not present because the actual program name
2442 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2443 solution is to replace the line that finds the process id with something like
2445 pid=`cat /var/spool/exim/exim-daemon.pid`
2447 to obtain the daemon's pid directly from the file that Exim saves it in.
2449 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2450 still be received from local processes, and if automatic delivery is configured
2451 (the normal case), deliveries will still occur.
2456 . ////////////////////////////////////////////////////////////////////////////
2457 . ////////////////////////////////////////////////////////////////////////////
2459 .chapter "The Exim command line" "CHAPcommandline"
2460 .scindex IIDclo1 "command line" "options"
2461 .scindex IIDclo2 "options" "command line"
2462 Exim's command line takes the standard Unix form of a sequence of options,
2463 each starting with a hyphen character, followed by a number of arguments. The
2464 options are compatible with the main options of Sendmail, and there are also
2465 some additional options, some of which are compatible with Smail 3. Certain
2466 combinations of options do not make sense, and provoke an error if used.
2467 The form of the arguments depends on which options are set.
2470 .section "Setting options by program name" "SECID38"
2472 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2473 were present before any other options.
2474 The &%-bp%& option requests a listing of the contents of the mail queue on the
2476 This feature is for compatibility with some systems that contain a command of
2477 that name in one of the standard libraries, symbolically linked to
2478 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2481 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2482 were present before any other options, for compatibility with Smail. The
2483 &%-bS%& option is used for reading in a number of messages in batched SMTP
2487 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2488 &%-oee%& options were present before any other options, for compatibility with
2489 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2492 .cindex "queue runner"
2493 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2494 were present before any other options, for compatibility with Smail. The &%-q%&
2495 option causes a single queue runner process to be started.
2497 .cindex "&'newaliases'&"
2498 .cindex "alias file" "building"
2499 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2500 If Exim is called under the name &'newaliases'& it behaves as if the option
2501 &%-bi%& were present before any other options, for compatibility with Sendmail.
2502 This option is used for rebuilding Sendmail's alias file. Exim does not have
2503 the concept of a single alias file, but can be configured to run a given
2504 command if called with the &%-bi%& option.
2507 .section "Trusted and admin users" "SECTtrustedadmin"
2508 Some Exim options are available only to &'trusted users'& and others are
2509 available only to &'admin users'&. In the description below, the phrases &"Exim
2510 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2511 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2512 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2515 .cindex "trusted users" "definition of"
2516 .cindex "user" "trusted definition of"
2517 The trusted users are root, the Exim user, any user listed in the
2518 &%trusted_users%& configuration option, and any user whose current group or any
2519 supplementary group is one of those listed in the &%trusted_groups%&
2520 configuration option. Note that the Exim group is not automatically trusted.
2522 .cindex '&"From"& line'
2523 .cindex "envelope sender"
2524 Trusted users are always permitted to use the &%-f%& option or a leading
2525 &"From&~"& line to specify the envelope sender of a message that is passed to
2526 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2527 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2528 users to set envelope senders.
2530 .cindex "&'From:'& header line"
2531 .cindex "&'Sender:'& header line"
2532 For a trusted user, there is never any check on the contents of the &'From:'&
2533 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2534 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2536 Trusted users may also specify a host name, host address, interface address,
2537 protocol name, ident value, and authentication data when submitting a message
2538 locally. Thus, they are able to insert messages into Exim's queue locally that
2539 have the characteristics of messages received from a remote host. Untrusted
2540 users may in some circumstances use &%-f%&, but can never set the other values
2541 that are available to trusted users.
2543 .cindex "user" "admin definition of"
2544 .cindex "admin user" "definition of"
2545 The admin users are root, the Exim user, and any user that is a member of the
2546 Exim group or of any group listed in the &%admin_groups%& configuration option.
2547 The current group does not have to be one of these groups.
2549 Admin users are permitted to list the queue, and to carry out certain
2550 operations on messages, for example, to force delivery failures. It is also
2551 necessary to be an admin user in order to see the full information provided by
2552 the Exim monitor, and full debugging output.
2554 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2555 Exim to attempt delivery of messages on its queue is restricted to admin users.
2556 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2557 option false (that is, specifying &%no_prod_requires_admin%&).
2559 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2560 is restricted to admin users unless &%queue_list_requires_admin%& is set
2565 &*Warning*&: If you configure your system so that admin users are able to
2566 edit Exim's configuration file, you are giving those users an easy way of
2567 getting root. There is further discussion of this issue at the start of chapter
2573 .section "Command line options" "SECID39"
2574 Exim's command line options are described in alphabetical order below. If none
2575 of the options that specifies a specific action (such as starting the daemon or
2576 a queue runner, or testing an address, or receiving a message in a specific
2577 format, or listing the queue) are present, and there is at least one argument
2578 on the command line, &%-bm%& (accept a local message on the standard input,
2579 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2580 outputs a brief message about itself and exits.
2582 . ////////////////////////////////////////////////////////////////////////////
2583 . Insert a stylized XML comment here, to identify the start of the command line
2584 . options. This is for the benefit of the Perl script that automatically
2585 . creates a man page for the options.
2586 . ////////////////////////////////////////////////////////////////////////////
2589 <!-- === Start of command line options === -->
2596 .cindex "options" "command line; terminating"
2597 This is a pseudo-option whose only purpose is to terminate the options and
2598 therefore to cause subsequent command line items to be treated as arguments
2599 rather than options, even if they begin with hyphens.
2602 .oindex "&%--help%&"
2603 This option causes Exim to output a few sentences stating what it is.
2604 The same output is generated if the Exim binary is called with no options and
2607 .vitem &%-B%&<&'type'&>
2609 .cindex "8-bit characters"
2610 .cindex "Sendmail compatibility" "8-bit characters"
2611 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2612 clean; it ignores this option.
2617 .cindex "SMTP" "listener"
2618 .cindex "queue runner"
2619 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2620 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2621 that the daemon should also initiate periodic queue runs.
2623 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2624 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2625 disconnect from the controlling terminal. When running this way, it can be
2626 stopped by pressing ctrl-C.
2628 By default, Exim listens for incoming connections to the standard SMTP port on
2629 all the host's running interfaces. However, it is possible to listen on other
2630 ports, on multiple ports, and only on specific interfaces. Chapter
2631 &<<CHAPinterfaces>>& contains a description of the options that control this.
2633 When a listening daemon
2634 .cindex "daemon" "process id (pid)"
2635 .cindex "pid (process id)" "of daemon"
2636 is started without the use of &%-oX%& (that is, without overriding the normal
2637 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2638 in Exim's spool directory. This location can be overridden by setting
2639 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2642 When &%-oX%& is used on the command line to start a listening daemon, the
2643 process id is not written to the normal pid file path. However, &%-oP%& can be
2644 used to specify a path on the command line if a pid file is required.
2648 .cindex "daemon" "restarting"
2649 can be used to cause the daemon to re-execute itself. This should be done
2650 whenever Exim's configuration file, or any file that is incorporated into it by
2651 means of the &%.include%& facility, is changed, and also whenever a new version
2652 of Exim is installed. It is not necessary to do this when other files that are
2653 referenced from the configuration (for example, alias files) are changed,
2654 because these are reread each time they are used.
2658 This option has the same effect as &%-bd%& except that it never disconnects
2659 from the controlling terminal, even when no debugging is specified.
2663 .cindex "testing" "string expansion"
2664 .cindex "expansion" "testing"
2665 Run Exim in expansion testing mode. Exim discards its root privilege, to
2666 prevent ordinary users from using this mode to read otherwise inaccessible
2667 files. If no arguments are given, Exim runs interactively, prompting for lines
2668 of data. Otherwise, it processes each argument in turn.
2670 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2671 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2672 used without command line arguments. If successful, it uses the &[readline()]&
2673 function, which provides extensive line-editing facilities, for reading the
2674 test data. A line history is supported.
2676 Long expansion expressions can be split over several lines by using backslash
2677 continuations. As in Exim's run time configuration, white space at the start of
2678 continuation lines is ignored. Each argument or data line is passed through the
2679 string expansion mechanism, and the result is output. Variable values from the
2680 configuration file (for example, &$qualify_domain$&) are available, but no
2681 message-specific values (such as &$sender_domain$&) are set, because no message
2682 is being processed (but see &%-bem%& and &%-Mset%&).
2684 &*Note*&: If you use this mechanism to test lookups, and you change the data
2685 files or databases you are using, you must exit and restart Exim before trying
2686 the same lookup again. Otherwise, because each Exim process caches the results
2687 of lookups, you will just get the same result as before.
2689 .vitem &%-bem%&&~<&'filename'&>
2691 .cindex "testing" "string expansion"
2692 .cindex "expansion" "testing"
2693 This option operates like &%-be%& except that it must be followed by the name
2694 of a file. For example:
2696 exim -bem /tmp/testmessage
2698 The file is read as a message (as if receiving a locally-submitted non-SMTP
2699 message) before any of the test expansions are done. Thus, message-specific
2700 variables such as &$message_size$& and &$header_from:$& are available. However,
2701 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2702 recipients are read from the headers in the normal way, and are shown in the
2703 &$recipients$& variable. Note that recipients cannot be given on the command
2704 line, because further arguments are taken as strings to expand (just like
2707 .vitem &%-bF%&&~<&'filename'&>
2709 .cindex "system filter" "testing"
2710 .cindex "testing" "system filter"
2711 This option is the same as &%-bf%& except that it assumes that the filter being
2712 tested is a system filter. The additional commands that are available only in
2713 system filters are recognized.
2715 .vitem &%-bf%&&~<&'filename'&>
2717 .cindex "filter" "testing"
2718 .cindex "testing" "filter file"
2719 .cindex "forward file" "testing"
2720 .cindex "testing" "forward file"
2721 .cindex "Sieve filter" "testing"
2722 This option runs Exim in user filter testing mode; the file is the filter file
2723 to be tested, and a test message must be supplied on the standard input. If
2724 there are no message-dependent tests in the filter, an empty file can be
2727 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2728 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2729 filter and a user filter in the same run. For example:
2731 exim -bF /system/filter -bf /user/filter </test/message
2733 This is helpful when the system filter adds header lines or sets filter
2734 variables that are used by the user filter.
2736 If the test filter file does not begin with one of the special lines
2741 it is taken to be a normal &_.forward_& file, and is tested for validity under
2742 that interpretation. See sections &<<SECTitenonfilred>>& to
2743 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2746 The result of an Exim command that uses &%-bf%&, provided no errors are
2747 detected, is a list of the actions that Exim would try to take if presented
2748 with the message for real. More details of filter testing are given in the
2749 separate document entitled &'Exim's interfaces to mail filtering'&.
2751 When testing a filter file,
2752 .cindex "&""From""& line"
2753 .cindex "envelope sender"
2754 .oindex "&%-f%&" "for filter testing"
2755 the envelope sender can be set by the &%-f%& option,
2756 or by a &"From&~"& line at the start of the test message. Various parameters
2757 that would normally be taken from the envelope recipient address of the message
2758 can be set by means of additional command line options (see the next four
2761 .vitem &%-bfd%&&~<&'domain'&>
2763 .vindex "&$qualify_domain$&"
2764 This sets the domain of the recipient address when a filter file is being
2765 tested by means of the &%-bf%& option. The default is the value of
2768 .vitem &%-bfl%&&~<&'local&~part'&>
2770 This sets the local part of the recipient address when a filter file is being
2771 tested by means of the &%-bf%& option. The default is the username of the
2772 process that calls Exim. A local part should be specified with any prefix or
2773 suffix stripped, because that is how it appears to the filter when a message is
2774 actually being delivered.
2776 .vitem &%-bfp%&&~<&'prefix'&>
2778 This sets the prefix of the local part of the recipient address when a filter
2779 file is being tested by means of the &%-bf%& option. The default is an empty
2782 .vitem &%-bfs%&&~<&'suffix'&>
2784 This sets the suffix of the local part of the recipient address when a filter
2785 file is being tested by means of the &%-bf%& option. The default is an empty
2788 .vitem &%-bh%&&~<&'IP&~address'&>
2790 .cindex "testing" "incoming SMTP"
2791 .cindex "SMTP" "testing incoming"
2792 .cindex "testing" "relay control"
2793 .cindex "relaying" "testing configuration"
2794 .cindex "policy control" "testing"
2795 .cindex "debugging" "&%-bh%& option"
2796 This option runs a fake SMTP session as if from the given IP address, using the
2797 standard input and output. The IP address may include a port number at the end,
2798 after a full stop. For example:
2800 exim -bh 10.9.8.7.1234
2801 exim -bh fe80::a00:20ff:fe86:a061.5678
2803 When an IPv6 address is given, it is converted into canonical form. In the case
2804 of the second example above, the value of &$sender_host_address$& after
2805 conversion to the canonical form is
2806 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2808 Comments as to what is going on are written to the standard error file. These
2809 include lines beginning with &"LOG"& for anything that would have been logged.
2810 This facility is provided for testing configuration options for incoming
2811 messages, to make sure they implement the required policy. For example, you can
2812 test your relay controls using &%-bh%&.
2816 You can test features of the configuration that rely on ident (RFC 1413)
2817 information by using the &%-oMt%& option. However, Exim cannot actually perform
2818 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2821 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2822 are also skipped when testing using &%-bh%&. If you want these callouts to
2823 occur, use &%-bhc%& instead.
2825 Messages supplied during the testing session are discarded, and nothing is
2826 written to any of the real log files. There may be pauses when DNS (and other)
2827 lookups are taking place, and of course these may time out. The &%-oMi%& option
2828 can be used to specify a specific IP interface and port if this is important,
2829 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2830 session were authenticated.
2832 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2833 output just states whether a given recipient address from a given host is
2834 acceptable or not. See section &<<SECTcheckaccess>>&.
2836 Features such as authentication and encryption, where the client input is not
2837 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2838 specialized SMTP test program such as
2839 &url(http://jetmore.org/john/code/#swaks,swaks).
2841 .vitem &%-bhc%&&~<&'IP&~address'&>
2843 This option operates in the same way as &%-bh%&, except that address
2844 verification callouts are performed if required. This includes consulting and
2845 updating the callout cache database.
2849 .cindex "alias file" "building"
2850 .cindex "building alias file"
2851 .cindex "Sendmail compatibility" "&%-bi%& option"
2852 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2853 Exim does not have the concept of a single alias file, and so it cannot mimic
2854 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2855 tend to appear in various scripts such as NIS make files, so the option must be
2858 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2859 configuration option is run, under the uid and gid of the caller of Exim. If
2860 the &%-oA%& option is used, its value is passed to the command as an argument.
2861 The command set by &%bi_command%& may not contain arguments. The command can
2862 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2863 if this is required. If the &%bi_command%& option is not set, calling Exim with
2868 .cindex "local message reception"
2869 This option runs an Exim receiving process that accepts an incoming,
2870 locally-generated message on the current input. The recipients are given as the
2871 command arguments (except when &%-t%& is also present &-- see below). Each
2872 argument can be a comma-separated list of RFC 2822 addresses. This is the
2873 default option for selecting the overall action of an Exim call; it is assumed
2874 if no other conflicting option is present.
2876 If any addresses in the message are unqualified (have no domain), they are
2877 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
2878 options, as appropriate. The &%-bnq%& option (see below) provides a way of
2879 suppressing this for special cases.
2881 Policy checks on the contents of local messages can be enforced by means of
2882 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
2884 .cindex "return code" "for &%-bm%&"
2885 The return code is zero if the message is successfully accepted. Otherwise, the
2886 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
2889 .cindex "message" "format"
2890 .cindex "format" "message"
2891 .cindex "&""From""& line"
2892 .cindex "UUCP" "&""From""& line"
2893 .cindex "Sendmail compatibility" "&""From""& line"
2894 of the message must be as defined in RFC 2822, except that, for
2895 compatibility with Sendmail and Smail, a line in one of the forms
2897 From sender Fri Jan 5 12:55 GMT 1997
2898 From sender Fri, 5 Jan 97 12:55:01
2900 (with the weekday optional, and possibly with additional text after the date)
2901 is permitted to appear at the start of the message. There appears to be no
2902 authoritative specification of the format of this line. Exim recognizes it by
2903 matching against the regular expression defined by the &%uucp_from_pattern%&
2904 option, which can be changed if necessary.
2906 .oindex "&%-f%&" "overriding &""From""& line"
2907 The specified sender is treated as if it were given as the argument to the
2908 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
2909 preference to the address taken from the message. The caller of Exim must be a
2910 trusted user for the sender of a message to be set in this way.
2914 .cindex "address qualification, suppressing"
2915 By default, Exim automatically qualifies unqualified addresses (those
2916 without domains) that appear in messages that are submitted locally (that
2917 is, not over TCP/IP). This qualification applies both to addresses in
2918 envelopes, and addresses in header lines. Sender addresses are qualified using
2919 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
2920 defaults to the value of &%qualify_domain%&).
2922 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
2923 being used to re-submit messages that originally came from remote hosts after
2924 content scanning, you probably do not want to qualify unqualified addresses in
2925 header lines. (Such lines will be present only if you have not enabled a header
2926 syntax check in the appropriate ACL.)
2928 The &%-bnq%& option suppresses all qualification of unqualified addresses in
2929 messages that originate on the local host. When this is used, unqualified
2930 addresses in the envelope provoke errors (causing message rejection) and
2931 unqualified addresses in header lines are left alone.
2936 .cindex "configuration options" "extracting"
2937 .cindex "options" "configuration &-- extracting"
2938 If this option is given with no arguments, it causes the values of all Exim's
2939 main configuration options to be written to the standard output. The values
2940 of one or more specific options can be requested by giving their names as
2941 arguments, for example:
2943 exim -bP qualify_domain hold_domains
2945 .cindex "hiding configuration option values"
2946 .cindex "configuration options" "hiding value of"
2947 .cindex "options" "hiding value of"
2948 However, any option setting that is preceded by the word &"hide"& in the
2949 configuration file is not shown in full, except to an admin user. For other
2950 users, the output is as in this example:
2952 mysql_servers = <value not displayable>
2954 If &%configure_file%& is given as an argument, the name of the run time
2955 configuration file is output.
2956 If a list of configuration files was supplied, the value that is output here
2957 is the name of the file that was actually used.
2959 .cindex "daemon" "process id (pid)"
2960 .cindex "pid (process id)" "of daemon"
2961 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
2962 directories where log files and daemon pid files are written are output,
2963 respectively. If these values are unset, log files are written in a
2964 sub-directory of the spool directory called &%log%&, and the pid file is
2965 written directly into the spool directory.
2967 If &%-bP%& is followed by a name preceded by &`+`&, for example,
2969 exim -bP +local_domains
2971 it searches for a matching named list of any type (domain, host, address, or
2972 local part) and outputs what it finds.
2974 .cindex "options" "router &-- extracting"
2975 .cindex "options" "transport &-- extracting"
2976 .cindex "options" "authenticator &-- extracting"
2977 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
2978 followed by the name of an appropriate driver instance, the option settings for
2979 that driver are output. For example:
2981 exim -bP transport local_delivery
2983 The generic driver options are output first, followed by the driver's private
2984 options. A list of the names of drivers of a particular type can be obtained by
2985 using one of the words &%router_list%&, &%transport_list%&, or
2986 &%authenticator_list%&, and a complete list of all drivers with their option
2987 settings can be obtained by using &%routers%&, &%transports%&, or
2990 .cindex "options" "macro &-- extracting"
2991 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
2992 are available, similarly to the drivers. Because macros are sometimes used
2993 for storing passwords, this option is restricted.
2994 The output format is one item per line.
2998 .cindex "queue" "listing messages on"
2999 .cindex "listing" "messages on the queue"
3000 This option requests a listing of the contents of the mail queue on the
3001 standard output. If the &%-bp%& option is followed by a list of message ids,
3002 just those messages are listed. By default, this option can be used only by an
3003 admin user. However, the &%queue_list_requires_admin%& option can be set false
3004 to allow any user to see the queue.
3006 Each message on the queue is displayed as in the following example:
3008 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3009 red.king@looking-glass.fict.example
3012 .cindex "message" "size in queue listing"
3013 .cindex "size" "of message"
3014 The first line contains the length of time the message has been on the queue
3015 (in this case 25 minutes), the size of the message (2.9K), the unique local
3016 identifier for the message, and the message sender, as contained in the
3017 envelope. For bounce messages, the sender address is empty, and appears as
3018 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3019 the default sender address, the user's login name is shown in parentheses
3020 before the sender address.
3022 .cindex "frozen messages" "in queue listing"
3023 If the message is frozen (attempts to deliver it are suspended) then the text
3024 &"*** frozen ***"& is displayed at the end of this line.
3026 The recipients of the message (taken from the envelope, not the headers) are
3027 displayed on subsequent lines. Those addresses to which the message has already
3028 been delivered are marked with the letter D. If an original address gets
3029 expanded into several addresses via an alias or forward file, the original is
3030 displayed with a D only when deliveries for all of its child addresses are
3036 This option operates like &%-bp%&, but in addition it shows delivered addresses
3037 that were generated from the original top level address(es) in each message by
3038 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3044 .cindex "queue" "count of messages on"
3045 This option counts the number of messages on the queue, and writes the total
3046 to the standard output. It is restricted to admin users, unless
3047 &%queue_list_requires_admin%& is set false.
3052 This option operates like &%-bp%&, but the output is not sorted into
3053 chronological order of message arrival. This can speed it up when there are
3054 lots of messages on the queue, and is particularly useful if the output is
3055 going to be post-processed in a way that doesn't need the sorting.
3059 This option is a combination of &%-bpr%& and &%-bpa%&.
3063 This option is a combination of &%-bpr%& and &%-bpu%&.
3068 This option operates like &%-bp%& but shows only undelivered top-level
3069 addresses for each message displayed. Addresses generated by aliasing or
3070 forwarding are not shown, unless the message was deferred after processing by a
3071 router with the &%one_time%& option set.
3076 .cindex "testing" "retry configuration"
3077 .cindex "retry" "configuration testing"
3078 This option is for testing retry rules, and it must be followed by up to three
3079 arguments. It causes Exim to look for a retry rule that matches the values
3080 and to write it to the standard output. For example:
3082 exim -brt bach.comp.mus.example
3083 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3085 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3086 argument, which is required, can be a complete address in the form
3087 &'local_part@domain'&, or it can be just a domain name. If the second argument
3088 contains a dot, it is interpreted as an optional second domain name; if no
3089 retry rule is found for the first argument, the second is tried. This ties in
3090 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3091 rule is found that matches the host, one that matches the mail domain is
3092 sought. Finally, an argument that is the name of a specific delivery error, as
3093 used in setting up retry rules, can be given. For example:
3095 exim -brt haydn.comp.mus.example quota_3d
3096 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3101 .cindex "testing" "rewriting"
3102 .cindex "rewriting" "testing"
3103 This option is for testing address rewriting rules, and it must be followed by
3104 a single argument, consisting of either a local part without a domain, or a
3105 complete address with a fully qualified domain. Exim outputs how this address
3106 would be rewritten for each possible place it might appear. See chapter
3107 &<<CHAPrewrite>>& for further details.
3111 .cindex "SMTP" "batched incoming"
3112 .cindex "batched SMTP input"
3113 This option is used for batched SMTP input, which is an alternative interface
3114 for non-interactive local message submission. A number of messages can be
3115 submitted in a single run. However, despite its name, this is not really SMTP
3116 input. Exim reads each message's envelope from SMTP commands on the standard
3117 input, but generates no responses. If the caller is trusted, or
3118 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3119 believed; otherwise the sender is always the caller of Exim.
3121 The message itself is read from the standard input, in SMTP format (leading
3122 dots doubled), terminated by a line containing just a single dot. An error is
3123 provoked if the terminating dot is missing. A further message may then follow.
3125 As for other local message submissions, the contents of incoming batch SMTP
3126 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3127 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3128 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3130 Some other SMTP commands are recognized in the input. HELO and EHLO act
3131 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3132 QUIT quits, ignoring the rest of the standard input.
3134 .cindex "return code" "for &%-bS%&"
3135 If any error is encountered, reports are written to the standard output and
3136 error streams, and Exim gives up immediately. The return code is 0 if no error
3137 was detected; it is 1 if one or more messages were accepted before the error
3138 was detected; otherwise it is 2.
3140 More details of input using batched SMTP are given in section
3141 &<<SECTincomingbatchedSMTP>>&.
3145 .cindex "SMTP" "local input"
3146 .cindex "local SMTP input"
3147 This option causes Exim to accept one or more messages by reading SMTP commands
3148 on the standard input, and producing SMTP replies on the standard output. SMTP
3149 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3150 Some user agents use this interface as a way of passing locally-generated
3151 messages to the MTA.
3154 .cindex "sender" "source of"
3155 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3156 set, the senders of messages are taken from the SMTP MAIL commands.
3157 Otherwise the content of these commands is ignored and the sender is set up as
3158 the calling user. Unqualified addresses are automatically qualified using
3159 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3160 &%-bnq%& option is used.
3164 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3165 using a listening daemon. Exim can distinguish the two cases by checking
3166 whether the standard input is a TCP/IP socket. When Exim is called from
3167 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3168 above concerning senders and qualification do not apply. In this situation,
3169 Exim behaves in exactly the same way as it does when receiving a message via
3170 the listening daemon.
3174 .cindex "testing" "addresses"
3175 .cindex "address" "testing"
3176 This option runs Exim in address testing mode, in which each argument is taken
3177 as a recipient address to be tested for deliverability. The results are
3178 written to the standard output. If a test fails, and the caller is not an admin
3179 user, no details of the failure are output, because these might contain
3180 sensitive information such as usernames and passwords for database lookups.
3182 If no arguments are given, Exim runs in an interactive manner, prompting with a
3183 right angle bracket for addresses to be tested.
3185 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3186 &[readline()]& function, because it is running as &'root'& and there are
3189 Each address is handled as if it were the recipient address of a message
3190 (compare the &%-bv%& option). It is passed to the routers and the result is
3191 written to the standard output. However, any router that has
3192 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3193 genuine routing tests if your first router passes everything to a scanner
3196 .cindex "return code" "for &%-bt%&"
3197 The return code is 2 if any address failed outright; it is 1 if no address
3198 failed outright but at least one could not be resolved for some reason. Return
3199 code 0 is given only when all addresses succeed.
3201 .cindex "duplicate addresses"
3202 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3203 addresses after routing is complete, so that only one delivery takes place.
3204 This does not happen when testing with &%-bt%&; the full results of routing are
3207 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3208 routers in the configuration makes any tests on the sender address of a
3210 .oindex "&%-f%&" "for address testing"
3211 you can use the &%-f%& option to set an appropriate sender when running
3212 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3213 default qualifying domain. However, if you have set up (for example) routers
3214 whose behaviour depends on the contents of an incoming message, you cannot test
3215 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3220 .cindex "version number of Exim"
3221 This option causes Exim to write the current version number, compilation
3222 number, and compilation date of the &'exim'& binary to the standard output.
3223 It also lists the DBM library this is being used, the optional modules (such as
3224 specific lookup types), the drivers that are included in the binary, and the
3225 name of the run time configuration file that is in use.
3227 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3228 configuration file. However, this is a static check only. It cannot check
3229 values that are to be expanded. For example, although a misspelt ACL verb is
3230 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3231 alone to discover (for example) all the typos in the configuration; some
3232 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3233 dynamic testing facilities.
3237 .cindex "verifying address" "using &%-bv%&"
3238 .cindex "address" "verification"
3239 This option runs Exim in address verification mode, in which each argument is
3240 taken as a recipient address to be verified by the routers. (This does
3241 not involve any verification callouts). During normal operation, verification
3242 happens mostly as a consequence processing a &%verify%& condition in an ACL
3243 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3244 including callouts, see the &%-bh%& and &%-bhc%& options.
3246 If verification fails, and the caller is not an admin user, no details of the
3247 failure are output, because these might contain sensitive information such as
3248 usernames and passwords for database lookups.
3250 If no arguments are given, Exim runs in an interactive manner, prompting with a
3251 right angle bracket for addresses to be verified.
3253 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3254 &[readline()]& function, because it is running as &'exim'& and there are
3257 Verification differs from address testing (the &%-bt%& option) in that routers
3258 that have &%no_verify%& set are skipped, and if the address is accepted by a
3259 router that has &%fail_verify%& set, verification fails. The address is
3260 verified as a recipient if &%-bv%& is used; to test verification for a sender
3261 address, &%-bvs%& should be used.
3263 If the &%-v%& option is not set, the output consists of a single line for each
3264 address, stating whether it was verified or not, and giving a reason in the
3265 latter case. Without &%-v%&, generating more than one address by redirection
3266 causes verification to end successfully, without considering the generated
3267 addresses. However, if just one address is generated, processing continues,
3268 and the generated address must verify successfully for the overall verification
3271 When &%-v%& is set, more details are given of how the address has been handled,
3272 and in the case of address redirection, all the generated addresses are also
3273 considered. Verification may succeed for some and fail for others.
3276 .cindex "return code" "for &%-bv%&"
3277 return code is 2 if any address failed outright; it is 1 if no address
3278 failed outright but at least one could not be resolved for some reason. Return
3279 code 0 is given only when all addresses succeed.
3281 If any of the routers in the configuration makes any tests on the sender
3282 address of a message, you should use the &%-f%& option to set an appropriate
3283 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3284 calling user at the default qualifying domain.
3288 This option acts like &%-bv%&, but verifies the address as a sender rather
3289 than a recipient address. This affects any rewriting and qualification that
3292 .vitem &%-C%&&~<&'filelist'&>
3294 .cindex "configuration file" "alternate"
3295 .cindex "CONFIGURE_FILE"
3296 .cindex "alternate configuration file"
3297 This option causes Exim to find the run time configuration file from the given
3298 list instead of from the list specified by the CONFIGURE_FILE
3299 compile-time setting. Usually, the list will consist of just a single file
3300 name, but it can be a colon-separated list of names. In this case, the first
3301 file that exists is used. Failure to open an existing file stops Exim from
3302 proceeding any further along the list, and an error is generated.
3304 When this option is used by a caller other than root or the Exim user, and the
3305 list is different from the compiled-in list, Exim gives up its root privilege
3306 immediately, and runs with the real and effective uid and gid set to those of
3307 the caller. However, if ALT_CONFIG_ROOT_ONLY is defined in
3308 &_Local/Makefile_&, root privilege is retained for &%-C%& only if the caller of
3311 That is, the Exim user is no longer privileged in this regard. This build-time
3312 option is not set by default in the Exim source distribution tarbundle.
3313 However, if you are using a &"packaged"& version of Exim (source or binary),
3314 the packagers might have enabled it.
3316 Setting ALT_CONFIG_ROOT_ONLY locks out the possibility of testing a
3317 configuration using &%-C%& right through message reception and delivery, even
3318 if the caller is root. The reception works, but by that time, Exim is running
3319 as the Exim user, so when it re-executes to regain privilege for the delivery,
3320 the use of &%-C%& causes privilege to be lost. However, root can test reception
3321 and delivery using two separate commands (one to put a message on the queue,
3322 using &%-odq%&, and another to do the delivery, using &%-M%&).
3324 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3325 prefix string with which any file named in a &%-C%& command line option
3326 must start. In addition, the file name must not contain the sequence &`/../`&.
3327 However, if the value of the &%-C%& option is identical to the value of
3328 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3329 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3330 unset, any file name can be used with &%-C%&.
3332 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3333 to a directory to which only root has access. This prevents someone who has
3334 broken into the Exim account from running a privileged Exim with an arbitrary
3337 The &%-C%& facility is useful for ensuring that configuration files are
3338 syntactically correct, but cannot be used for test deliveries, unless the
3339 caller is privileged, or unless it is an exotic configuration that does not
3340 require privilege. No check is made on the owner or group of the files
3341 specified by this option.
3343 .vitem &%-D%&<&'macro'&>=<&'value'&>
3345 .cindex "macro" "setting on command line"
3346 This option can be used to override macro definitions in the configuration file
3347 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3348 unprivileged caller, it causes Exim to give up its root privilege.
3349 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3350 completely disabled, and its use causes an immediate error exit.
3352 The entire option (including equals sign if present) must all be within one
3353 command line item. &%-D%& can be used to set the value of a macro to the empty
3354 string, in which case the equals sign is optional. These two commands are
3360 To include spaces in a macro definition item, quotes must be used. If you use
3361 quotes, spaces are permitted around the macro name and the equals sign. For
3364 exim '-D ABC = something' ...
3366 &%-D%& may be repeated up to 10 times on a command line.
3368 .vitem &%-d%&<&'debug&~options'&>
3370 .cindex "debugging" "list of selectors"
3371 .cindex "debugging" "&%-d%& option"
3372 This option causes debugging information to be written to the standard
3373 error stream. It is restricted to admin users because debugging output may show
3374 database queries that contain password information. Also, the details of users'
3375 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3376 writes an error message to the standard error stream and exits with a non-zero
3379 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3380 standard debugging data is output. This can be reduced, or increased to include
3381 some more rarely needed information, by directly following &%-d%& with a string
3382 made up of names preceded by plus or minus characters. These add or remove sets
3383 of debugging data, respectively. For example, &%-d+filter%& adds filter
3384 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3385 no spaces are allowed in the debug setting. The available debugging categories
3388 &`acl `& ACL interpretation
3389 &`auth `& authenticators
3390 &`deliver `& general delivery logic
3391 &`dns `& DNS lookups (see also resolver)
3392 &`dnsbl `& DNS black list (aka RBL) code
3393 &`exec `& arguments for &[execv()]& calls
3394 &`expand `& detailed debugging for string expansions
3395 &`filter `& filter handling
3396 &`hints_lookup `& hints data lookups
3397 &`host_lookup `& all types of name-to-IP address handling
3398 &`ident `& ident lookup
3399 &`interface `& lists of local interfaces
3400 &`lists `& matching things in lists
3401 &`load `& system load checks
3402 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3403 &<<CHAPlocalscan>>&)
3404 &`lookup `& general lookup code and all lookups
3405 &`memory `& memory handling
3406 &`pid `& add pid to debug output lines
3407 &`process_info `& setting info for the process log
3408 &`queue_run `& queue runs
3409 &`receive `& general message reception logic
3410 &`resolver `& turn on the DNS resolver's debugging output
3411 &`retry `& retry handling
3412 &`rewrite `& address rewriting
3413 &`route `& address routing
3414 &`timestamp `& add timestamp to debug output lines
3416 &`transport `& transports
3417 &`uid `& changes of uid/gid and looking up uid/gid
3418 &`verify `& address verification logic
3419 &`all `& almost all of the above (see below), and also &%-v%&
3421 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3422 for &`-all`&. The reason for this is that &`+all`& is something that people
3423 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3424 is included, an awful lot of output that is very rarely of interest is
3425 generated, so it now has to be explicitly requested. However, &`-all`& does
3426 turn everything off.
3428 .cindex "resolver, debugging output"
3429 .cindex "DNS resolver, debugging output"
3430 The &`resolver`& option produces output only if the DNS resolver was compiled
3431 with DEBUG enabled. This is not the case in some operating systems. Also,
3432 unfortunately, debugging output from the DNS resolver is written to stdout
3435 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3436 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3437 However, the &`pid`& selector is forced when debugging is turned on for a
3438 daemon, which then passes it on to any re-executed Exims. Exim also
3439 automatically adds the pid to debug lines when several remote deliveries are
3442 The &`timestamp`& selector causes the current time to be inserted at the start
3443 of all debug output lines. This can be useful when trying to track down delays
3446 If the &%debug_print%& option is set in any driver, it produces output whenever
3447 any debugging is selected, or if &%-v%& is used.
3449 .vitem &%-dd%&<&'debug&~options'&>
3451 This option behaves exactly like &%-d%& except when used on a command that
3452 starts a daemon process. In that case, debugging is turned off for the
3453 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3454 behaviour of the daemon without creating as much output as full debugging does.
3457 .oindex "&%-dropcr%&"
3458 This is an obsolete option that is now a no-op. It used to affect the way Exim
3459 handled CR and LF characters in incoming messages. What happens now is
3460 described in section &<<SECTlineendings>>&.
3464 .cindex "bounce message" "generating"
3465 This option specifies that an incoming message is a locally-generated delivery
3466 failure report. It is used internally by Exim when handling delivery failures
3467 and is not intended for external use. Its only effect is to stop Exim
3468 generating certain messages to the postmaster, as otherwise message cascades
3469 could occur in some situations. As part of the same option, a message id may
3470 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3471 new message contains the id, following &"R="&, as a cross-reference.
3474 .oindex "&%-e%&&'x'&"
3475 There are a number of Sendmail options starting with &%-oe%& which seem to be
3476 called by various programs without the leading &%o%& in the option. For
3477 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3478 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3480 .vitem &%-F%&&~<&'string'&>
3482 .cindex "sender" "name"
3483 .cindex "name" "of sender"
3484 This option sets the sender's full name for use when a locally-generated
3485 message is being accepted. In the absence of this option, the user's &'gecos'&
3486 entry from the password data is used. As users are generally permitted to alter
3487 their &'gecos'& entries, no security considerations are involved. White space
3488 between &%-F%& and the <&'string'&> is optional.
3490 .vitem &%-f%&&~<&'address'&>
3492 .cindex "sender" "address"
3493 .cindex "address" "sender"
3494 .cindex "trusted users"
3495 .cindex "envelope sender"
3496 .cindex "user" "trusted"
3497 This option sets the address of the envelope sender of a locally-generated
3498 message (also known as the return path). The option can normally be used only
3499 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3502 Processes running as root or the Exim user are always trusted. Other
3503 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3504 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3505 of a local message is set to the caller's login name at the default qualify
3508 There is one exception to the restriction on the use of &%-f%&: an empty sender
3509 can be specified by any user, trusted or not, to create a message that can
3510 never provoke a bounce. An empty sender can be specified either as an empty
3511 string, or as a pair of angle brackets with nothing between them, as in these
3512 examples of shell commands:
3514 exim -f '<>' user@domain
3515 exim -f "" user@domain
3517 In addition, the use of &%-f%& is not restricted when testing a filter file
3518 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3521 Allowing untrusted users to change the sender address does not of itself make
3522 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3523 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3524 though this can be overridden by setting &%no_local_from_check%&.
3527 .cindex "&""From""& line"
3528 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3529 given as two arguments or one combined argument). The sender of a
3530 locally-generated message can also be set (when permitted) by an initial
3531 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3532 if &%-f%& is also present, it overrides &"From&~"&.
3536 .cindex "Sendmail compatibility" "&%-G%& option ignored"
3537 This is a Sendmail option which is ignored by Exim.
3539 .vitem &%-h%&&~<&'number'&>
3541 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3542 This option is accepted for compatibility with Sendmail, but has no effect. (In
3543 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3548 .cindex "Solaris" "&'mail'& command"
3549 .cindex "dot" "in incoming non-SMTP message"
3550 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3551 line by itself should not terminate an incoming, non-SMTP message. I can find
3552 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3553 command in Solaris 2.4 uses it. See also &%-ti%&.
3555 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3557 .cindex "forcing delivery"
3558 .cindex "delivery" "forcing attempt"
3559 .cindex "frozen messages" "forcing delivery"
3560 This option requests Exim to run a delivery attempt on each message in turn. If
3561 any of the messages are frozen, they are automatically thawed before the
3562 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3563 and &%hold_domains%& are ignored.
3566 .cindex "hints database" "overriding retry hints"
3567 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3568 the normal retry time has not yet been reached. This option requires the caller
3569 to be an admin user. However, there is an option called &%prod_requires_admin%&
3570 which can be set false to relax this restriction (and also the same requirement
3571 for the &%-q%&, &%-R%&, and &%-S%& options).
3573 The deliveries happen synchronously, that is, the original Exim process does
3574 not terminate until all the delivery attempts have finished. No output is
3575 produced unless there is a serious error. If you want to see what is happening,
3576 use the &%-v%& option as well, or inspect Exim's main log.
3578 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3580 .cindex "message" "adding recipients"
3581 .cindex "recipient" "adding"
3582 This option requests Exim to add the addresses to the list of recipients of the
3583 message (&"ar"& for &"add recipients"&). The first argument must be a message
3584 id, and the remaining ones must be email addresses. However, if the message is
3585 active (in the middle of a delivery attempt), it is not altered. This option
3586 can be used only by an admin user.
3588 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3589 &~<&'message&~id'&>"
3591 .cindex "SMTP" "passed connection"
3592 .cindex "SMTP" "multiple deliveries"
3593 .cindex "multiple SMTP deliveries"
3594 This option is not intended for use by external callers. It is used internally
3595 by Exim to invoke another instance of itself to deliver a waiting message using
3596 an existing SMTP connection, which is passed as the standard input. Details are
3597 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3598 must be root or the Exim user in order to use it.
3602 This option is not intended for use by external callers. It is used internally
3603 by Exim in conjunction with the &%-MC%& option. It signifies that the
3604 connection to the remote host has been authenticated.
3608 This option is not intended for use by external callers. It is used internally
3609 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3610 which Exim is connected supports pipelining.
3612 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3614 This option is not intended for use by external callers. It is used internally
3615 by Exim in conjunction with the &%-MC%& option when the original delivery was
3616 started by a queue runner. It passes on the process id of the queue runner,
3617 together with the file descriptor number of an open pipe. Closure of the pipe
3618 signals the final completion of the sequence of processes that are passing
3619 messages through the same SMTP connection.
3623 This option is not intended for use by external callers. It is used internally
3624 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3625 SMTP SIZE option should be used on messages delivered down the existing
3630 This option is not intended for use by external callers. It is used internally
3631 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3632 host to which Exim is connected supports TLS encryption.
3634 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3636 .cindex "hints database" "not overridden by &%-Mc%&"
3637 .cindex "delivery" "manually started &-- not forced"
3638 This option requests Exim to run a delivery attempt on each message in turn,
3639 but unlike the &%-M%& option, it does check for retry hints, and respects any
3640 that are found. This option is not very useful to external callers. It is
3641 provided mainly for internal use by Exim when it needs to re-invoke itself in
3642 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3643 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3644 respects retry times and other options such as &%hold_domains%& that are
3645 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3646 If you want to run a specific delivery as if in a queue run, you should use
3647 &%-q%& with a message id argument. A distinction between queue run deliveries
3648 and other deliveries is made in one or two places.
3650 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3652 .cindex "message" "changing sender"
3653 .cindex "sender" "changing"
3654 This option requests Exim to change the sender address in the message to the
3655 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3656 &"edit sender"&). There must be exactly two arguments. The first argument must
3657 be a message id, and the second one an email address. However, if the message
3658 is active (in the middle of a delivery attempt), its status is not altered.
3659 This option can be used only by an admin user.
3661 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3663 .cindex "freezing messages"
3664 .cindex "message" "manually freezing"
3665 This option requests Exim to mark each listed message as &"frozen"&. This
3666 prevents any delivery attempts taking place until the message is &"thawed"&,
3667 either manually or as a result of the &%auto_thaw%& configuration option.
3668 However, if any of the messages are active (in the middle of a delivery
3669 attempt), their status is not altered. This option can be used only by an admin
3672 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3674 .cindex "giving up on messages"
3675 .cindex "message" "abandoning delivery attempts"
3676 .cindex "delivery" "abandoning further attempts"
3677 This option requests Exim to give up trying to deliver the listed messages,
3678 including any that are frozen. However, if any of the messages are active,
3679 their status is not altered. For non-bounce messages, a delivery error message
3680 is sent to the sender, containing the text &"cancelled by administrator"&.
3681 Bounce messages are just discarded. This option can be used only by an admin
3684 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3686 .cindex "delivery" "cancelling all"
3687 This option requests Exim to mark all the recipient addresses in the messages
3688 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3689 message is active (in the middle of a delivery attempt), its status is not
3690 altered. This option can be used only by an admin user.
3692 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3694 .cindex "delivery" "cancelling by address"
3695 .cindex "recipient" "removing"
3696 .cindex "removing recipients"
3697 This option requests Exim to mark the given addresses as already delivered
3698 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3699 the remaining ones must be email addresses. These are matched to recipient
3700 addresses in the message in a case-sensitive manner. If the message is active
3701 (in the middle of a delivery attempt), its status is not altered. This option
3702 can be used only by an admin user.
3704 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3706 .cindex "removing messages"
3707 .cindex "abandoning mail"
3708 .cindex "message" "manually discarding"
3709 This option requests Exim to remove the given messages from the queue. No
3710 bounce messages are sent; each message is simply forgotten. However, if any of
3711 the messages are active, their status is not altered. This option can be used
3712 only by an admin user or by the user who originally caused the message to be
3713 placed on the queue.
3715 .vitem &%-Mset%&&~<&'message&~id'&>
3717 .cindex "testing" "string expansion"
3718 .cindex "expansion" "testing"
3719 This option is useful only in conjunction with &%-be%& (that is, when testing
3720 string expansions). Exim loads the given message from its spool before doing
3721 the test expansions, thus setting message-specific variables such as
3722 &$message_size$& and the header variables. The &$recipients$& variable is made
3723 available. This feature is provided to make it easier to test expansions that
3724 make use of these variables. However, this option can be used only by an admin
3725 user. See also &%-bem%&.
3727 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3729 .cindex "thawing messages"
3730 .cindex "unfreezing messages"
3731 .cindex "frozen messages" "thawing"
3732 .cindex "message" "thawing frozen"
3733 This option requests Exim to &"thaw"& any of the listed messages that are
3734 &"frozen"&, so that delivery attempts can resume. However, if any of the
3735 messages are active, their status is not altered. This option can be used only
3738 .vitem &%-Mvb%&&~<&'message&~id'&>
3740 .cindex "listing" "message body"
3741 .cindex "message" "listing body of"
3742 This option causes the contents of the message body (-D) spool file to be
3743 written to the standard output. This option can be used only by an admin user.
3745 .vitem &%-Mvc%&&~<&'message&~id'&>
3747 .cindex "message" "listing in RFC 2822 format"
3748 .cindex "listing" "message in RFC 2922 format"
3749 This option causes a copy of the complete message (header lines plus body) to
3750 be written to the standard output in RFC 2822 format. This option can be used
3751 only by an admin user.
3753 .vitem &%-Mvh%&&~<&'message&~id'&>
3755 .cindex "listing" "message headers"
3756 .cindex "header lines" "listing"
3757 .cindex "message" "listing header lines"
3758 This option causes the contents of the message headers (-H) spool file to be
3759 written to the standard output. This option can be used only by an admin user.
3761 .vitem &%-Mvl%&&~<&'message&~id'&>
3763 .cindex "listing" "message log"
3764 .cindex "message" "listing message log"
3765 This option causes the contents of the message log spool file to be written to
3766 the standard output. This option can be used only by an admin user.
3770 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
3771 treats it that way too.
3775 .cindex "debugging" "&%-N%& option"
3776 .cindex "debugging" "suppressing delivery"
3777 This is a debugging option that inhibits delivery of a message at the transport
3778 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
3779 it just doesn't actually transport the message, but instead behaves as if it
3780 had successfully done so. However, it does not make any updates to the retry
3781 database, and the log entries for deliveries are flagged with &"*>"& rather
3784 Because &%-N%& discards any message to which it applies, only root or the Exim
3785 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
3786 words, an ordinary user can use it only when supplying an incoming message to
3787 which it will apply. Although transportation never fails when &%-N%& is set, an
3788 address may be deferred because of a configuration problem on a transport, or a
3789 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
3790 the message, and applies to any subsequent delivery attempts that may happen
3795 .cindex "Sendmail compatibility" "&%-n%& option ignored"
3796 This option is interpreted by Sendmail to mean &"no aliasing"&. It is ignored
3799 .vitem &%-O%&&~<&'data'&>
3801 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
3804 .vitem &%-oA%&&~<&'file&~name'&>
3806 .cindex "Sendmail compatibility" "&%-oA%& option"
3807 This option is used by Sendmail in conjunction with &%-bi%& to specify an
3808 alternative alias file name. Exim handles &%-bi%& differently; see the
3811 .vitem &%-oB%&&~<&'n'&>
3813 .cindex "SMTP" "passed connection"
3814 .cindex "SMTP" "multiple deliveries"
3815 .cindex "multiple SMTP deliveries"
3816 This is a debugging option which limits the maximum number of messages that can
3817 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
3818 transport. If <&'n'&> is omitted, the limit is set to 1.
3822 .cindex "background delivery"
3823 .cindex "delivery" "in the background"
3824 This option applies to all modes in which Exim accepts incoming messages,
3825 including the listening daemon. It requests &"background"& delivery of such
3826 messages, which means that the accepting process automatically starts a
3827 delivery process for each message received, but does not wait for the delivery
3828 processes to finish.
3830 When all the messages have been received, the reception process exits,
3831 leaving the delivery processes to finish in their own time. The standard output
3832 and error streams are closed at the start of each delivery process.
3833 This is the default action if none of the &%-od%& options are present.
3835 If one of the queueing options in the configuration file
3836 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
3837 overrides it if &%queue_only_override%& is set true, which is the default
3838 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
3842 .cindex "foreground delivery"
3843 .cindex "delivery" "in the foreground"
3844 This option requests &"foreground"& (synchronous) delivery when Exim has
3845 accepted a locally-generated message. (For the daemon it is exactly the same as
3846 &%-odb%&.) A delivery process is automatically started to deliver the message,
3847 and Exim waits for it to complete before proceeding.
3849 The original Exim reception process does not finish until the delivery
3850 process for the final message has ended. The standard error stream is left open
3853 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
3854 false and one of the queueing options in the configuration file is in effect.
3856 If there is a temporary delivery error during foreground delivery, the
3857 message is left on the queue for later delivery, and the original reception
3858 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
3859 restricted configuration that never queues messages.
3864 This option is synonymous with &%-odf%&. It is provided for compatibility with
3869 .cindex "non-immediate delivery"
3870 .cindex "delivery" "suppressing immediate"
3871 .cindex "queueing incoming messages"
3872 This option applies to all modes in which Exim accepts incoming messages,
3873 including the listening daemon. It specifies that the accepting process should
3874 not automatically start a delivery process for each message received. Messages
3875 are placed on the queue, and remain there until a subsequent queue runner
3876 process encounters them. There are several configuration options (such as
3877 &%queue_only%&) that can be used to queue incoming messages under certain
3878 conditions. This option overrides all of them and also &%-odqs%&. It always
3883 .cindex "SMTP" "delaying delivery"
3884 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
3885 However, like &%-odb%& and &%-odi%&, this option has no effect if
3886 &%queue_only_override%& is false and one of the queueing options in the
3887 configuration file is in effect.
3889 When &%-odqs%& does operate, a delivery process is started for each incoming
3890 message, in the background by default, but in the foreground if &%-odi%& is
3891 also present. The recipient addresses are routed, and local deliveries are done
3892 in the normal way. However, if any SMTP deliveries are required, they are not
3893 done at this time, so the message remains on the queue until a subsequent queue
3894 runner process encounters it. Because routing was done, Exim knows which
3895 messages are waiting for which hosts, and so a number of messages for the same
3896 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
3897 configuration option has the same effect for specific domains. See also the
3902 .cindex "error" "reporting"
3903 If an error is detected while a non-SMTP message is being received (for
3904 example, a malformed address), the error is reported to the sender in a mail
3907 .cindex "return code" "for &%-oee%&"
3909 this error message is successfully sent, the Exim receiving process
3910 exits with a return code of zero. If not, the return code is 2 if the problem
3911 is that the original message has no recipients, or 1 any other error. This is
3912 the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
3916 .cindex "error" "reporting"
3917 .cindex "return code" "for &%-oem%&"
3918 This is the same as &%-oee%&, except that Exim always exits with a non-zero
3919 return code, whether or not the error message was successfully sent.
3920 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
3924 .cindex "error" "reporting"
3925 If an error is detected while a non-SMTP message is being received, the
3926 error is reported by writing a message to the standard error file (stderr).
3927 .cindex "return code" "for &%-oep%&"
3928 The return code is 1 for all errors.
3932 .cindex "error" "reporting"
3933 This option is supported for compatibility with Sendmail, but has the same
3938 .cindex "error" "reporting"
3939 This option is supported for compatibility with Sendmail, but has the same
3944 .cindex "dot" "in incoming non-SMTP message"
3945 This option, which has the same effect as &%-i%&, specifies that a dot on a
3946 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
3947 single dot does terminate, though Exim does no special processing for other
3948 lines that start with a dot. This option is set by default if Exim is called as
3949 &'rmail'&. See also &%-ti%&.
3952 .oindex "&%-oitrue%&"
3953 This option is treated as synonymous with &%-oi%&.
3955 .vitem &%-oMa%&&~<&'host&~address'&>
3957 .cindex "sender" "host address, specifying for local message"
3958 A number of options starting with &%-oM%& can be used to set values associated
3959 with remote hosts on locally-submitted messages (that is, messages not received
3960 over TCP/IP). These options can be used by any caller in conjunction with the
3961 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
3962 other circumstances, they are ignored unless the caller is trusted.
3964 The &%-oMa%& option sets the sender host address. This may include a port
3965 number at the end, after a full stop (period). For example:
3967 exim -bs -oMa 10.9.8.7.1234
3969 An alternative syntax is to enclose the IP address in square brackets,
3970 followed by a colon and the port number:
3972 exim -bs -oMa [10.9.8.7]:1234
3974 The IP address is placed in the &$sender_host_address$& variable, and the
3975 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
3976 are present on the command line, the sender host IP address is taken from
3977 whichever one is last.
3979 .vitem &%-oMaa%&&~<&'name'&>
3981 .cindex "authentication" "name, specifying for local message"
3982 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
3983 option sets the value of &$sender_host_authenticated$& (the authenticator
3984 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
3985 This option can be used with &%-bh%& and &%-bs%& to set up an
3986 authenticated SMTP session without actually using the SMTP AUTH command.
3988 .vitem &%-oMai%&&~<&'string'&>
3990 .cindex "authentication" "id, specifying for local message"
3991 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
3992 option sets the value of &$authenticated_id$& (the id that was authenticated).
3993 This overrides the default value (the caller's login id, except with &%-bh%&,
3994 where there is no default) for messages from local sources. See chapter
3995 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
3997 .vitem &%-oMas%&&~<&'address'&>
3999 .cindex "authentication" "sender, specifying for local message"
4000 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4001 option sets the authenticated sender value in &$authenticated_sender$&. It
4002 overrides the sender address that is created from the caller's login id for
4003 messages from local sources, except when &%-bh%& is used, when there is no
4004 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4005 specified on a MAIL command overrides this value. See chapter
4006 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4008 .vitem &%-oMi%&&~<&'interface&~address'&>
4010 .cindex "interface" "address, specifying for local message"
4011 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4012 option sets the IP interface address value. A port number may be included,
4013 using the same syntax as for &%-oMa%&. The interface address is placed in
4014 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4016 .vitem &%-oMr%&&~<&'protocol&~name'&>
4018 .cindex "protocol, specifying for local message"
4019 .vindex "&$received_protocol$&"
4020 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4021 option sets the received protocol value that is stored in
4022 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4023 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4024 SMTP protocol names (see the description of &$received_protocol$& in section
4025 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4026 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4029 .vitem &%-oMs%&&~<&'host&~name'&>
4031 .cindex "sender" "host name, specifying for local message"
4032 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4033 option sets the sender host name in &$sender_host_name$&. When this option is
4034 present, Exim does not attempt to look up a host name from an IP address; it
4035 uses the name it is given.
4037 .vitem &%-oMt%&&~<&'ident&~string'&>
4039 .cindex "sender" "ident string, specifying for local message"
4040 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4041 option sets the sender ident value in &$sender_ident$&. The default setting for
4042 local callers is the login id of the calling process, except when &%-bh%& is
4043 used, when there is no default.
4047 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4048 In Sendmail, this option means &"me too"&, indicating that the sender of a
4049 message should receive a copy of the message if the sender appears in an alias
4050 expansion. Exim always does this, so the option does nothing.
4054 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4055 This option is ignored. In Sendmail it specifies &"old style headers"&,
4056 whatever that means.
4058 .vitem &%-oP%&&~<&'path'&>
4060 .cindex "pid (process id)" "of daemon"
4061 .cindex "daemon" "process id (pid)"
4062 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4063 value. The option specifies the file to which the process id of the daemon is
4064 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4065 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4066 because in those cases, the normal pid file is not used.
4068 .vitem &%-or%&&~<&'time'&>
4070 .cindex "timeout" "for non-SMTP input"
4071 This option sets a timeout value for incoming non-SMTP messages. If it is not
4072 set, Exim will wait forever for the standard input. The value can also be set
4073 by the &%receive_timeout%& option. The format used for specifying times is
4074 described in section &<<SECTtimeformat>>&.
4076 .vitem &%-os%&&~<&'time'&>
4078 .cindex "timeout" "for SMTP input"
4079 .cindex "SMTP" "input timeout"
4080 This option sets a timeout value for incoming SMTP messages. The timeout
4081 applies to each SMTP command and block of data. The value can also be set by
4082 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4083 for specifying times is described in section &<<SECTtimeformat>>&.
4087 This option has exactly the same effect as &%-v%&.
4089 .vitem &%-oX%&&~<&'number&~or&~string'&>
4091 .cindex "TCP/IP" "setting listening ports"
4092 .cindex "TCP/IP" "setting listening interfaces"
4093 .cindex "port" "receiving TCP/IP"
4094 This option is relevant only when the &%-bd%& (start listening daemon) option
4095 is also given. It controls which ports and interfaces the daemon uses. Details
4096 of the syntax, and how it interacts with configuration file options, are given
4097 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4098 file is written unless &%-oP%& is also present to specify a pid file name.
4102 .cindex "Perl" "starting the interpreter"
4103 This option applies when an embedded Perl interpreter is linked with Exim (see
4104 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4105 option, forcing the starting of the interpreter to be delayed until it is
4110 .cindex "Perl" "starting the interpreter"
4111 This option applies when an embedded Perl interpreter is linked with Exim (see
4112 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4113 option, forcing the starting of the interpreter to occur as soon as Exim is
4116 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4118 For compatibility with Sendmail, this option is equivalent to
4120 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4122 It sets the incoming protocol and host name (for trusted callers). The
4123 host name and its colon can be omitted when only the protocol is to be set.
4124 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4125 to embedded Perl. It is therefore impossible to set a protocol value of &`p`&
4126 or &`s`& using this option (but that does not seem a real limitation).
4130 .cindex "queue runner" "starting manually"
4131 This option is normally restricted to admin users. However, there is a
4132 configuration option called &%prod_requires_admin%& which can be set false to
4133 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4134 and &%-S%& options).
4136 .cindex "queue runner" "description of operation"
4137 The &%-q%& option starts one queue runner process. This scans the queue of
4138 waiting messages, and runs a delivery process for each one in turn. It waits
4139 for each delivery process to finish before starting the next one. A delivery
4140 process may not actually do any deliveries if the retry times for the addresses
4141 have not been reached. Use &%-qf%& (see below) if you want to override this.
4144 .cindex "SMTP" "passed connection"
4145 .cindex "SMTP" "multiple deliveries"
4146 .cindex "multiple SMTP deliveries"
4147 the delivery process spawns other processes to deliver other messages down
4148 passed SMTP connections, the queue runner waits for these to finish before
4151 When all the queued messages have been considered, the original queue runner
4152 process terminates. In other words, a single pass is made over the waiting
4153 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4154 this to be repeated periodically.
4156 Exim processes the waiting messages in an unpredictable order. It isn't very
4157 random, but it is likely to be different each time, which is all that matters.
4158 If one particular message screws up a remote MTA, other messages to the same
4159 MTA have a chance of getting through if they get tried first.
4161 It is possible to cause the messages to be processed in lexical message id
4162 order, which is essentially the order in which they arrived, by setting the
4163 &%queue_run_in_order%& option, but this is not recommended for normal use.
4165 .vitem &%-q%&<&'qflags'&>
4166 The &%-q%& option may be followed by one or more flag letters that change its
4167 behaviour. They are all optional, but if more than one is present, they must
4168 appear in the correct order. Each flag is described in a separate item below.
4172 .cindex "queue" "double scanning"
4173 .cindex "queue" "routing"
4174 .cindex "routing" "whole queue before delivery"
4175 An option starting with &%-qq%& requests a two-stage queue run. In the first
4176 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4177 every domain. Addresses are routed, local deliveries happen, but no remote
4180 .cindex "hints database" "remembering routing"
4181 The hints database that remembers which messages are waiting for specific hosts
4182 is updated, as if delivery to those hosts had been deferred. After this is
4183 complete, a second, normal queue scan happens, with routing and delivery taking
4184 place as normal. Messages that are routed to the same host should mostly be
4185 delivered down a single SMTP
4186 .cindex "SMTP" "passed connection"
4187 .cindex "SMTP" "multiple deliveries"
4188 .cindex "multiple SMTP deliveries"
4189 connection because of the hints that were set up during the first queue scan.
4190 This option may be useful for hosts that are connected to the Internet
4193 .vitem &%-q[q]i...%&
4195 .cindex "queue" "initial delivery"
4196 If the &'i'& flag is present, the queue runner runs delivery processes only for
4197 those messages that haven't previously been tried. (&'i'& stands for &"initial
4198 delivery"&.) This can be helpful if you are putting messages on the queue using
4199 &%-odq%& and want a queue runner just to process the new messages.
4201 .vitem &%-q[q][i]f...%&
4203 .cindex "queue" "forcing delivery"
4204 .cindex "delivery" "forcing in queue run"
4205 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4206 message, whereas without &'f'& only those non-frozen addresses that have passed
4207 their retry times are tried.
4209 .vitem &%-q[q][i]ff...%&
4211 .cindex "frozen messages" "forcing delivery"
4212 If &'ff'& is present, a delivery attempt is forced for every message, whether
4215 .vitem &%-q[q][i][f[f]]l%&
4217 .cindex "queue" "local deliveries only"
4218 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4219 be done. If a message requires any remote deliveries, it remains on the queue
4222 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4223 .cindex "queue" "delivering specific messages"
4224 When scanning the queue, Exim can be made to skip over messages whose ids are
4225 lexically less than a given value by following the &%-q%& option with a
4226 starting message id. For example:
4228 exim -q 0t5C6f-0000c8-00
4230 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4231 second message id is given, messages whose ids are lexically greater than it
4232 are also skipped. If the same id is given twice, for example,
4234 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4236 just one delivery process is started, for that message. This differs from
4237 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4238 that it counts as a delivery from a queue run. Note that the selection
4239 mechanism does not affect the order in which the messages are scanned. There
4240 are also other ways of selecting specific sets of messages for delivery in a
4241 queue run &-- see &%-R%& and &%-S%&.
4243 .vitem &%-q%&<&'qflags'&><&'time'&>
4244 .cindex "queue runner" "starting periodically"
4245 .cindex "periodic queue running"
4246 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4247 starting a queue runner process at intervals specified by the given time value
4248 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4249 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4250 single daemon process handles both functions. A common way of starting up a
4251 combined daemon at system boot time is to use a command such as
4253 /usr/exim/bin/exim -bd -q30m
4255 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4256 process every 30 minutes.
4258 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4259 pid file is written unless one is explicitly requested by the &%-oP%& option.
4261 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4263 This option is synonymous with &%-R%&. It is provided for Sendmail
4266 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4268 This option is synonymous with &%-S%&.
4270 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4272 .cindex "queue runner" "for specific recipients"
4273 .cindex "delivery" "to given domain"
4274 .cindex "domain" "delivery to"
4275 The <&'rsflags'&> may be empty, in which case the white space before the string
4276 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4277 which are the possible values for <&'rsflags'&>. White space is required if
4278 <&'rsflags'&> is not empty.
4280 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4281 perform a single queue run, except that, when scanning the messages on the
4282 queue, Exim processes only those that have at least one undelivered recipient
4283 address containing the given string, which is checked in a case-independent
4284 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4285 regular expression; otherwise it is a literal string.
4287 If you want to do periodic queue runs for messages with specific recipients,
4288 you can combine &%-R%& with &%-q%& and a time value. For example:
4290 exim -q25m -R @special.domain.example
4292 This example does a queue run for messages with recipients in the given domain
4293 every 25 minutes. Any additional flags that are specified with &%-q%& are
4294 applied to each queue run.
4296 Once a message is selected for delivery by this mechanism, all its addresses
4297 are processed. For the first selected message, Exim overrides any retry
4298 information and forces a delivery attempt for each undelivered address. This
4299 means that if delivery of any address in the first message is successful, any
4300 existing retry information is deleted, and so delivery attempts for that
4301 address in subsequently selected messages (which are processed without forcing)
4302 will run. However, if delivery of any address does not succeed, the retry
4303 information is updated, and in subsequently selected messages, the failing
4304 address will be skipped.
4306 .cindex "frozen messages" "forcing delivery"
4307 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4308 all selected messages, not just the first; frozen messages are included when
4311 The &%-R%& option makes it straightforward to initiate delivery of all messages
4312 to a given domain after a host has been down for some time. When the SMTP
4313 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4314 effect is to run Exim with the &%-R%& option, but it can be configured to run
4315 an arbitrary command instead.
4319 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4321 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4323 .cindex "delivery" "from given sender"
4324 .cindex "queue runner" "for specific senders"
4325 This option acts like &%-R%& except that it checks the string against each
4326 message's sender instead of against the recipients. If &%-R%& is also set, both
4327 conditions must be met for a message to be selected. If either of the options
4328 has &'f'& or &'ff'& in its flags, the associated action is taken.
4330 .vitem &%-Tqt%&&~<&'times'&>
4332 This an option that is exclusively for use by the Exim testing suite. It is not
4333 recognized when Exim is run normally. It allows for the setting up of explicit
4334 &"queue times"& so that various warning/retry features can be tested.
4338 .cindex "recipient" "extracting from header lines"
4339 .cindex "&'Bcc:'& header line"
4340 .cindex "&'Cc:'& header line"
4341 .cindex "&'To:'& header line"
4342 When Exim is receiving a locally-generated, non-SMTP message on its standard
4343 input, the &%-t%& option causes the recipients of the message to be obtained
4344 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4345 from the command arguments. The addresses are extracted before any rewriting
4346 takes place and the &'Bcc:'& header line, if present, is then removed.
4348 .cindex "Sendmail compatibility" "&%-t%& option"
4349 If the command has any arguments, they specify addresses to which the message
4350 is &'not'& to be delivered. That is, the argument addresses are removed from
4351 the recipients list obtained from the headers. This is compatible with Smail 3
4352 and in accordance with the documented behaviour of several versions of
4353 Sendmail, as described in man pages on a number of operating systems (e.g.
4354 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4355 argument addresses to those obtained from the headers, and the O'Reilly
4356 Sendmail book documents it that way. Exim can be made to add argument addresses
4357 instead of subtracting them by setting the option
4358 &%extract_addresses_remove_arguments%& false.
4360 .cindex "&%Resent-%& header lines" "with &%-t%&"
4361 If there are any &%Resent-%& header lines in the message, Exim extracts
4362 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4363 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4364 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4365 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4367 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4368 message is resent several times). The RFC also specifies that they should be
4369 added at the front of the message, and separated by &'Received:'& lines. It is
4370 not at all clear how &%-t%& should operate in the present of multiple sets,
4371 nor indeed exactly what constitutes a &"set"&.
4372 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4373 are often added at the end of the header, and if a message is resent more than
4374 once, it is common for the original set of &%Resent-%& headers to be renamed as
4375 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4379 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4380 compatibility with Sendmail.
4382 .vitem &%-tls-on-connect%&
4383 .oindex "&%-tls-on-connect%&"
4384 .cindex "TLS" "use without STARTTLS"
4385 .cindex "TLS" "automatic start"
4386 This option is available when Exim is compiled with TLS support. It forces all
4387 incoming SMTP connections to behave as if the incoming port is listed in the
4388 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4389 &<<CHAPTLS>>& for further details.
4394 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4395 Sendmail uses this option for &"initial message submission"&, and its
4396 documentation states that in future releases, it may complain about
4397 syntactically invalid messages rather than fixing them when this flag is not
4398 set. Exim ignores this option.
4402 This option causes Exim to write information to the standard error stream,
4403 describing what it is doing. In particular, it shows the log lines for
4404 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4405 dialogue is shown. Some of the log lines shown may not actually be written to
4406 the log if the setting of &%log_selector%& discards them. Any relevant
4407 selectors are shown with each log line. If none are shown, the logging is
4412 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4413 National Language Support extended characters in the body of the mail item"&).
4414 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4422 . ////////////////////////////////////////////////////////////////////////////
4423 . Insert a stylized DocBook comment here, to identify the end of the command
4424 . line options. This is for the benefit of the Perl script that automatically
4425 . creates a man page for the options.
4426 . ////////////////////////////////////////////////////////////////////////////
4429 <!-- === End of command line options === -->
4436 . ////////////////////////////////////////////////////////////////////////////
4437 . ////////////////////////////////////////////////////////////////////////////
4440 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4441 "The runtime configuration file"
4443 .cindex "run time configuration"
4444 .cindex "configuration file" "general description"
4445 .cindex "CONFIGURE_FILE"
4446 .cindex "configuration file" "errors in"
4447 .cindex "error" "in configuration file"
4448 .cindex "return code" "for bad configuration"
4449 Exim uses a single run time configuration file that is read whenever an Exim
4450 binary is executed. Note that in normal operation, this happens frequently,
4451 because Exim is designed to operate in a distributed manner, without central
4454 If a syntax error is detected while reading the configuration file, Exim
4455 writes a message on the standard error, and exits with a non-zero return code.
4456 The message is also written to the panic log. &*Note*&: Only simple syntax
4457 errors can be detected at this time. The values of any expanded options are
4458 not checked until the expansion happens, even when the expansion does not
4459 actually alter the string.
4461 The name of the configuration file is compiled into the binary for security
4462 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4463 most configurations, this specifies a single file. However, it is permitted to
4464 give a colon-separated list of file names, in which case Exim uses the first
4465 existing file in the list.
4468 .cindex "EXIM_GROUP"
4469 .cindex "CONFIGURE_OWNER"
4470 .cindex "CONFIGURE_GROUP"
4471 .cindex "configuration file" "ownership"
4472 .cindex "ownership" "configuration file"
4473 The run time configuration file must be owned by root or by the user that is
4474 specified at compile time by the EXIM_USER option, or by the user that is
4475 specified at compile time by the CONFIGURE_OWNER option (if set). The
4476 configuration file must not be world-writeable or group-writeable, unless its
4477 group is the one specified at compile time by the EXIM_GROUP option or by the
4478 CONFIGURE_GROUP option.
4480 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4481 to root, anybody who is able to edit the run time configuration file has an
4482 easy way to run commands as root. If you make your mail administrators members
4483 of the Exim group, but do not trust them with root, make sure that the run time
4484 configuration is not group writeable.
4486 A default configuration file, which will work correctly in simple situations,
4487 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4488 defines just one file name, the installation process copies the default
4489 configuration to a new file of that name if it did not previously exist. If
4490 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4491 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4496 .section "Using a different configuration file" "SECID40"
4497 .cindex "configuration file" "alternate"
4498 A one-off alternate configuration can be specified by the &%-C%& command line
4499 option, which may specify a single file or a list of files. However, when
4500 &%-C%& is used, Exim gives up its root privilege, unless called by root or the
4501 Exim user (or unless the argument for &%-C%& is identical to the built-in value
4502 from CONFIGURE_FILE). &%-C%& is useful mainly for checking the syntax of
4503 configuration files before installing them. No owner or group checks are done
4504 on a configuration file specified by &%-C%&.
4506 The privileged use of &%-C%& by the Exim user can be locked out by setting
4507 ALT_CONFIG_ROOT_ONLY in &_Local/Makefile_& when building Exim. However,
4508 if you do this, you also lock out the possibility of testing a
4509 configuration using &%-C%& right through message reception and delivery, even
4510 if the caller is root. The reception works, but by that time, Exim is running
4511 as the Exim user, so when it re-execs to regain privilege for the delivery, the
4512 use of &%-C%& causes privilege to be lost. However, root can test reception and
4513 delivery using two separate commands (one to put a message on the queue, using
4514 &%-odq%&, and another to do the delivery, using &%-M%&).
4516 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4517 prefix string with which any file named in a &%-C%& command line option must
4518 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4519 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4520 name can be used with &%-C%&.
4522 One-off changes to a configuration can be specified by the &%-D%& command line
4523 option, which defines and overrides values for macros used inside the
4524 configuration file. However, like &%-C%&, the use of this option by a
4525 non-privileged user causes Exim to discard its root privilege.
4526 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4527 completely disabled, and its use causes an immediate error exit.
4529 Some sites may wish to use the same Exim binary on different machines that
4530 share a file system, but to use different configuration files on each machine.
4531 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4532 looks for a file whose name is the configuration file name followed by a dot
4533 and the machine's node name, as obtained from the &[uname()]& function. If this
4534 file does not exist, the standard name is tried. This processing occurs for
4535 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4537 In some esoteric situations different versions of Exim may be run under
4538 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4539 help with this. See the comments in &_src/EDITME_& for details.
4543 .section "Configuration file format" "SECTconffilfor"
4544 .cindex "configuration file" "format of"
4545 .cindex "format" "configuration file"
4546 Exim's configuration file is divided into a number of different parts. General
4547 option settings must always appear at the start of the file. The other parts
4548 are all optional, and may appear in any order. Each part other than the first
4549 is introduced by the word &"begin"& followed by the name of the part. The
4553 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4556 .cindex "AUTH" "configuration"
4557 &'authenticators'&: Configuration settings for the authenticator drivers. These
4558 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4560 &'routers'&: Configuration settings for the router drivers. Routers process
4561 addresses and determine how the message is to be delivered (see chapters
4562 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4564 &'transports'&: Configuration settings for the transport drivers. Transports
4565 define mechanisms for copying messages to destinations (see chapters
4566 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4568 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4569 If there is no retry section, or if it is empty (that is, no retry rules are
4570 defined), Exim will not retry deliveries. In this situation, temporary errors
4571 are treated the same as permanent errors. Retry rules are discussed in chapter
4574 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4575 when new addresses are generated during delivery. Rewriting is discussed in
4576 chapter &<<CHAPrewrite>>&.
4578 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4579 want to use this feature, you must set
4581 LOCAL_SCAN_HAS_OPTIONS=yes
4583 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4584 facility are given in chapter &<<CHAPlocalscan>>&.
4587 .cindex "configuration file" "leading white space in"
4588 .cindex "configuration file" "trailing white space in"
4589 .cindex "white space" "in configuration file"
4590 Leading and trailing white space in configuration lines is always ignored.
4592 Blank lines in the file, and lines starting with a # character (ignoring
4593 leading white space) are treated as comments and are ignored. &*Note*&: A
4594 # character other than at the beginning of a line is not treated specially,
4595 and does not introduce a comment.
4597 Any non-comment line can be continued by ending it with a backslash. Note that
4598 the general rule for white space means that trailing white space after the
4599 backslash and leading white space at the start of continuation
4600 lines is ignored. Comment lines beginning with # (but not empty lines) may
4601 appear in the middle of a sequence of continuation lines.
4603 A convenient way to create a configuration file is to start from the
4604 default, which is supplied in &_src/configure.default_&, and add, delete, or
4605 change settings as required.
4607 The ACLs, retry rules, and rewriting rules have their own syntax which is
4608 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4609 respectively. The other parts of the configuration file have some syntactic
4610 items in common, and these are described below, from section &<<SECTcos>>&
4611 onwards. Before that, the inclusion, macro, and conditional facilities are
4616 .section "File inclusions in the configuration file" "SECID41"
4617 .cindex "inclusions in configuration file"
4618 .cindex "configuration file" "including other files"
4619 .cindex "&`.include`& in configuration file"
4620 .cindex "&`.include_if_exists`& in configuration file"
4621 You can include other files inside Exim's run time configuration file by
4624 &`.include`& <&'file name'&>
4625 &`.include_if_exists`& <&'file name'&>
4627 on a line by itself. Double quotes round the file name are optional. If you use
4628 the first form, a configuration error occurs if the file does not exist; the
4629 second form does nothing for non-existent files. In all cases, an absolute file
4632 Includes may be nested to any depth, but remember that Exim reads its
4633 configuration file often, so it is a good idea to keep them to a minimum.
4634 If you change the contents of an included file, you must HUP the daemon,
4635 because an included file is read only when the configuration itself is read.
4637 The processing of inclusions happens early, at a physical line level, so, like
4638 comment lines, an inclusion can be used in the middle of an option setting,
4641 hosts_lookup = a.b.c \
4644 Include processing happens after macro processing (see below). Its effect is to
4645 process the lines of the included file as if they occurred inline where the
4650 .section "Macros in the configuration file" "SECTmacrodefs"
4651 .cindex "macro" "description of"
4652 .cindex "configuration file" "macros"
4653 If a line in the main part of the configuration (that is, before the first
4654 &"begin"& line) begins with an upper case letter, it is taken as a macro
4655 definition, and must be of the form
4657 <&'name'&> = <&'rest of line'&>
4659 The name must consist of letters, digits, and underscores, and need not all be
4660 in upper case, though that is recommended. The rest of the line, including any
4661 continuations, is the replacement text, and has leading and trailing white
4662 space removed. Quotes are not removed. The replacement text can never end with
4663 a backslash character, but this doesn't seem to be a serious limitation.
4665 Macros may also be defined between router, transport, authenticator, or ACL
4666 definitions. They may not, however, be defined within an individual driver or
4667 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4669 .section "Macro substitution" "SECID42"
4670 Once a macro is defined, all subsequent lines in the file (and any included
4671 files) are scanned for the macro name; if there are several macros, the line is
4672 scanned for each in turn, in the order in which the macros are defined. The
4673 replacement text is not re-scanned for the current macro, though it is scanned
4674 for subsequently defined macros. For this reason, a macro name may not contain
4675 the name of a previously defined macro as a substring. You could, for example,
4678 &`ABCD_XYZ = `&<&'something'&>
4679 &`ABCD = `&<&'something else'&>
4681 but putting the definitions in the opposite order would provoke a configuration
4682 error. Macro expansion is applied to individual physical lines from the file,
4683 before checking for line continuation or file inclusion (see above). If a line
4684 consists solely of a macro name, and the expansion of the macro is empty, the
4685 line is ignored. A macro at the start of a line may turn the line into a
4686 comment line or a &`.include`& line.
4689 .section "Redefining macros" "SECID43"
4690 Once defined, the value of a macro can be redefined later in the configuration
4691 (or in an included file). Redefinition is specified by using &'=='& instead of
4696 MAC == updated value
4698 Redefinition does not alter the order in which the macros are applied to the
4699 subsequent lines of the configuration file. It is still the same order in which
4700 the macros were originally defined. All that changes is the macro's value.
4701 Redefinition makes it possible to accumulate values. For example:
4705 MAC == MAC and something added
4707 This can be helpful in situations where the configuration file is built
4708 from a number of other files.
4710 .section "Overriding macro values" "SECID44"
4711 The values set for macros in the configuration file can be overridden by the
4712 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
4713 used, unless called by root or the Exim user. A definition on the command line
4714 using the &%-D%& option causes all definitions and redefinitions within the
4719 .section "Example of macro usage" "SECID45"
4720 As an example of macro usage, consider a configuration where aliases are looked
4721 up in a MySQL database. It helps to keep the file less cluttered if long
4722 strings such as SQL statements are defined separately as macros, for example:
4724 ALIAS_QUERY = select mailbox from user where \
4725 login='${quote_mysql:$local_part}';
4727 This can then be used in a &(redirect)& router setting like this:
4729 data = ${lookup mysql{ALIAS_QUERY}}
4731 In earlier versions of Exim macros were sometimes used for domain, host, or
4732 address lists. In Exim 4 these are handled better by named lists &-- see
4733 section &<<SECTnamedlists>>&.
4736 .section "Conditional skips in the configuration file" "SECID46"
4737 .cindex "configuration file" "conditional skips"
4738 .cindex "&`.ifdef`&"
4739 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
4740 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
4741 portions of the configuration file. The processing happens whenever the file is
4742 read (that is, when an Exim binary starts to run).
4744 The implementation is very simple. Instances of the first four directives must
4745 be followed by text that includes the names of one or macros. The condition
4746 that is tested is whether or not any macro substitution has taken place in the
4750 message_size_limit = 50M
4752 message_size_limit = 100M
4755 sets a message size limit of 50M if the macro &`AAA`& is defined, and 100M
4756 otherwise. If there is more than one macro named on the line, the condition
4757 is true if any of them are defined. That is, it is an &"or"& condition. To
4758 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
4760 Although you can use a macro expansion to generate one of these directives,
4761 it is not very useful, because the condition &"there was a macro substitution
4762 in this line"& will always be true.
4764 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
4765 to clarify complicated nestings.
4769 .section "Common option syntax" "SECTcos"
4770 .cindex "common option syntax"
4771 .cindex "syntax of common options"
4772 .cindex "configuration file" "common option syntax"
4773 For the main set of options, driver options, and &[local_scan()]& options,
4774 each setting is on a line by itself, and starts with a name consisting of
4775 lower-case letters and underscores. Many options require a data value, and in
4776 these cases the name must be followed by an equals sign (with optional white
4777 space) and then the value. For example:
4779 qualify_domain = mydomain.example.com
4781 .cindex "hiding configuration option values"
4782 .cindex "configuration options" "hiding value of"
4783 .cindex "options" "hiding value of"
4784 Some option settings may contain sensitive data, for example, passwords for
4785 accessing databases. To stop non-admin users from using the &%-bP%& command
4786 line option to read these values, you can precede the option settings with the
4787 word &"hide"&. For example:
4789 hide mysql_servers = localhost/users/admin/secret-password
4791 For non-admin users, such options are displayed like this:
4793 mysql_servers = <value not displayable>
4795 If &"hide"& is used on a driver option, it hides the value of that option on
4796 all instances of the same driver.
4798 The following sections describe the syntax used for the different data types
4799 that are found in option settings.
4802 .section "Boolean options" "SECID47"
4803 .cindex "format" "boolean"
4804 .cindex "boolean configuration values"
4805 .oindex "&%no_%&&'xxx'&"
4806 .oindex "&%not_%&&'xxx'&"
4807 Options whose type is given as boolean are on/off switches. There are two
4808 different ways of specifying such options: with and without a data value. If
4809 the option name is specified on its own without data, the switch is turned on;
4810 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
4811 boolean options may be followed by an equals sign and one of the words
4812 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
4813 the following two settings have exactly the same effect:
4818 The following two lines also have the same (opposite) effect:
4823 You can use whichever syntax you prefer.
4828 .section "Integer values" "SECID48"
4829 .cindex "integer configuration values"
4830 .cindex "format" "integer"
4831 If an option's type is given as &"integer"&, the value can be given in decimal,
4832 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
4833 number is assumed. Otherwise, it is treated as an octal number unless it starts
4834 with the characters &"0x"&, in which case the remainder is interpreted as a
4837 If an integer value is followed by the letter K, it is multiplied by 1024; if
4838 it is followed by the letter M, it is multiplied by 1024x1024. When the values
4839 of integer option settings are output, values which are an exact multiple of
4840 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
4841 and M. The printing style is independent of the actual input format that was
4845 .section "Octal integer values" "SECID49"
4846 .cindex "integer format"
4847 .cindex "format" "octal integer"
4848 If an option's type is given as &"octal integer"&, its value is always
4849 interpreted as an octal number, whether or not it starts with the digit zero.
4850 Such options are always output in octal.
4853 .section "Fixed point numbers" "SECID50"
4854 .cindex "fixed point configuration values"
4855 .cindex "format" "fixed point"
4856 If an option's type is given as &"fixed-point"&, its value must be a decimal
4857 integer, optionally followed by a decimal point and up to three further digits.
4861 .section "Time intervals" "SECTtimeformat"
4862 .cindex "time interval" "specifying in configuration"
4863 .cindex "format" "time interval"
4864 A time interval is specified as a sequence of numbers, each followed by one of
4865 the following letters, with no intervening white space:
4875 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
4876 intervals are output in the same format. Exim does not restrict the values; it
4877 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
4881 .section "String values" "SECTstrings"
4882 .cindex "string" "format of configuration values"
4883 .cindex "format" "string"
4884 If an option's type is specified as &"string"&, the value can be specified with
4885 or without double-quotes. If it does not start with a double-quote, the value
4886 consists of the remainder of the line plus any continuation lines, starting at
4887 the first character after any leading white space, with trailing white space
4888 removed, and with no interpretation of the characters in the string. Because
4889 Exim removes comment lines (those beginning with #) at an early stage, they can
4890 appear in the middle of a multi-line string. The following two settings are
4891 therefore equivalent:
4893 trusted_users = uucp:mail
4894 trusted_users = uucp:\
4895 # This comment line is ignored
4898 .cindex "string" "quoted"
4899 .cindex "escape characters in quoted strings"
4900 If a string does start with a double-quote, it must end with a closing
4901 double-quote, and any backslash characters other than those used for line
4902 continuation are interpreted as escape characters, as follows:
4905 .irow &`\\`& "single backslash"
4906 .irow &`\n`& "newline"
4907 .irow &`\r`& "carriage return"
4909 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
4910 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
4914 If a backslash is followed by some other character, including a double-quote
4915 character, that character replaces the pair.
4917 Quoting is necessary only if you want to make use of the backslash escapes to
4918 insert special characters, or if you need to specify a value with leading or
4919 trailing spaces. These cases are rare, so quoting is almost never needed in
4920 current versions of Exim. In versions of Exim before 3.14, quoting was required
4921 in order to continue lines, so you may come across older configuration files
4922 and examples that apparently quote unnecessarily.
4925 .section "Expanded strings" "SECID51"
4926 .cindex "expansion" "definition of"
4927 Some strings in the configuration file are subjected to &'string expansion'&,
4928 by which means various parts of the string may be changed according to the
4929 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
4930 is as just described; in particular, the handling of backslashes in quoted
4931 strings is done as part of the input process, before expansion takes place.
4932 However, backslash is also an escape character for the expander, so any
4933 backslashes that are required for that reason must be doubled if they are
4934 within a quoted configuration string.
4937 .section "User and group names" "SECID52"
4938 .cindex "user name" "format of"
4939 .cindex "format" "user name"
4940 .cindex "groups" "name format"
4941 .cindex "format" "group name"
4942 User and group names are specified as strings, using the syntax described
4943 above, but the strings are interpreted specially. A user or group name must
4944 either consist entirely of digits, or be a name that can be looked up using the
4945 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
4948 .section "List construction" "SECTlistconstruct"
4949 .cindex "list" "syntax of in configuration"
4950 .cindex "format" "list item in configuration"
4951 .cindex "string" "list, definition of"
4952 The data for some configuration options is a list of items, with colon as the
4953 default separator. Many of these options are shown with type &"string list"& in
4954 the descriptions later in this document. Others are listed as &"domain list"&,
4955 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
4956 are all the same; however, those other than &"string list"& are subject to
4957 particular kinds of interpretation, as described in chapter
4958 &<<CHAPdomhosaddlists>>&.
4960 In all these cases, the entire list is treated as a single string as far as the
4961 input syntax is concerned. The &%trusted_users%& setting in section
4962 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
4963 in a list, it must be entered as two colons. Leading and trailing white space
4964 on each item in a list is ignored. This makes it possible to include items that
4965 start with a colon, and in particular, certain forms of IPv6 address. For
4968 local_interfaces = 127.0.0.1 : ::::1
4970 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
4972 &*Note*&: Although leading and trailing white space is ignored in individual
4973 list items, it is not ignored when parsing the list. The space after the first
4974 colon in the example above is necessary. If it were not there, the list would
4975 be interpreted as the two items 127.0.0.1:: and 1.
4977 .section "Changing list separators" "SECID53"
4978 .cindex "list separator" "changing"
4979 .cindex "IPv6" "addresses in lists"
4980 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
4981 introduced to allow the separator character to be changed. If a list begins
4982 with a left angle bracket, followed by any punctuation character, that
4983 character is used instead of colon as the list separator. For example, the list
4984 above can be rewritten to use a semicolon separator like this:
4986 local_interfaces = <; 127.0.0.1 ; ::1
4988 This facility applies to all lists, with the exception of the list in
4989 &%log_file_path%&. It is recommended that the use of non-colon separators be
4990 confined to circumstances where they really are needed.
4992 .cindex "list separator" "newline as"
4993 .cindex "newline" "as list separator"
4994 It is also possible to use newline and other control characters (those with
4995 code values less than 32, plus DEL) as separators in lists. Such separators
4996 must be provided literally at the time the list is processed. For options that
4997 are string-expanded, you can write the separator using a normal escape
4998 sequence. This will be processed by the expander before the string is
4999 interpreted as a list. For example, if a newline-separated list of domains is
5000 generated by a lookup, you can process it directly by a line such as this:
5002 domains = <\n ${lookup mysql{.....}}
5004 This avoids having to change the list separator in such data. You are unlikely
5005 to want to use a control character as a separator in an option that is not
5006 expanded, because the value is literal text. However, it can be done by giving
5007 the value in quotes. For example:
5009 local_interfaces = "<\n 127.0.0.1 \n ::1"
5011 Unlike printing character separators, which can be included in list items by
5012 doubling, it is not possible to include a control character as data when it is
5013 set as the separator. Two such characters in succession are interpreted as
5014 enclosing an empty list item.
5018 .section "Empty items in lists" "SECTempitelis"
5019 .cindex "list" "empty item in"
5020 An empty item at the end of a list is always ignored. In other words, trailing
5021 separator characters are ignored. Thus, the list in
5023 senders = user@domain :
5025 contains only a single item. If you want to include an empty string as one item
5026 in a list, it must not be the last item. For example, this list contains three
5027 items, the second of which is empty:
5029 senders = user1@domain : : user2@domain
5031 &*Note*&: There must be white space between the two colons, as otherwise they
5032 are interpreted as representing a single colon data character (and the list
5033 would then contain just one item). If you want to specify a list that contains
5034 just one, empty item, you can do it as in this example:
5038 In this case, the first item is empty, and the second is discarded because it
5039 is at the end of the list.
5044 .section "Format of driver configurations" "SECTfordricon"
5045 .cindex "drivers" "configuration format"
5046 There are separate parts in the configuration for defining routers, transports,
5047 and authenticators. In each part, you are defining a number of driver
5048 instances, each with its own set of options. Each driver instance is defined by
5049 a sequence of lines like this:
5051 <&'instance name'&>:
5056 In the following example, the instance name is &(localuser)&, and it is
5057 followed by three options settings:
5062 transport = local_delivery
5064 For each driver instance, you specify which Exim code module it uses &-- by the
5065 setting of the &%driver%& option &-- and (optionally) some configuration
5066 settings. For example, in the case of transports, if you want a transport to
5067 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5068 a local file you would use the &(appendfile)& driver. Each of the drivers is
5069 described in detail in its own separate chapter later in this manual.
5071 You can have several routers, transports, or authenticators that are based on
5072 the same underlying driver (each must have a different instance name).
5074 The order in which routers are defined is important, because addresses are
5075 passed to individual routers one by one, in order. The order in which
5076 transports are defined does not matter at all. The order in which
5077 authenticators are defined is used only when Exim, as a client, is searching
5078 them to find one that matches an authentication mechanism offered by the
5081 .cindex "generic options"
5082 .cindex "options" "generic &-- definition of"
5083 Within a driver instance definition, there are two kinds of option: &'generic'&
5084 and &'private'&. The generic options are those that apply to all drivers of the
5085 same type (that is, all routers, all transports or all authenticators). The
5086 &%driver%& option is a generic option that must appear in every definition.
5087 .cindex "private options"
5088 The private options are special for each driver, and none need appear, because
5089 they all have default values.
5091 The options may appear in any order, except that the &%driver%& option must
5092 precede any private options, since these depend on the particular driver. For
5093 this reason, it is recommended that &%driver%& always be the first option.
5095 Driver instance names, which are used for reference in log entries and
5096 elsewhere, can be any sequence of letters, digits, and underscores (starting
5097 with a letter) and must be unique among drivers of the same type. A router and
5098 a transport (for example) can each have the same name, but no two router
5099 instances can have the same name. The name of a driver instance should not be
5100 confused with the name of the underlying driver module. For example, the
5101 configuration lines:
5106 create an instance of the &(smtp)& transport driver whose name is
5107 &(remote_smtp)&. The same driver code can be used more than once, with
5108 different instance names and different option settings each time. A second
5109 instance of the &(smtp)& transport, with different options, might be defined
5115 command_timeout = 10s
5117 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5118 these transport instances from routers, and these names would appear in log
5121 Comment lines may be present in the middle of driver specifications. The full
5122 list of option settings for any particular driver instance, including all the
5123 defaulted values, can be extracted by making use of the &%-bP%& command line
5131 . ////////////////////////////////////////////////////////////////////////////
5132 . ////////////////////////////////////////////////////////////////////////////
5134 .chapter "The default configuration file" "CHAPdefconfil"
5135 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5136 .cindex "default" "configuration file &""walk through""&"
5137 The default configuration file supplied with Exim as &_src/configure.default_&
5138 is sufficient for a host with simple mail requirements. As an introduction to
5139 the way Exim is configured, this chapter &"walks through"& the default
5140 configuration, giving brief explanations of the settings. Detailed descriptions
5141 of the options are given in subsequent chapters. The default configuration file
5142 itself contains extensive comments about ways you might want to modify the
5143 initial settings. However, note that there are many options that are not
5144 mentioned at all in the default configuration.
5148 .section "Main configuration settings" "SECTdefconfmain"
5149 The main (global) configuration option settings must always come first in the
5150 file. The first thing you'll see in the file, after some initial comments, is
5153 # primary_hostname =
5155 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5156 to know the official, fully qualified name of your host, and this is where you
5157 can specify it. However, in most cases you do not need to set this option. When
5158 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5160 The first three non-comment configuration lines are as follows:
5162 domainlist local_domains = @
5163 domainlist relay_to_domains =
5164 hostlist relay_from_hosts = 127.0.0.1
5166 These are not, in fact, option settings. They are definitions of two named
5167 domain lists and one named host list. Exim allows you to give names to lists of
5168 domains, hosts, and email addresses, in order to make it easier to manage the
5169 configuration file (see section &<<SECTnamedlists>>&).
5171 The first line defines a domain list called &'local_domains'&; this is used
5172 later in the configuration to identify domains that are to be delivered
5175 .cindex "@ in a domain list"
5176 There is just one item in this list, the string &"@"&. This is a special form
5177 of entry which means &"the name of the local host"&. Thus, if the local host is
5178 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5179 be delivered locally. Because the local host's name is referenced indirectly,
5180 the same configuration file can be used on different hosts.
5182 The second line defines a domain list called &'relay_to_domains'&, but the
5183 list itself is empty. Later in the configuration we will come to the part that
5184 controls mail relaying through the local host; it allows relaying to any
5185 domains in this list. By default, therefore, no relaying on the basis of a mail
5186 domain is permitted.
5188 The third line defines a host list called &'relay_from_hosts'&. This list is
5189 used later in the configuration to permit relaying from any host or IP address
5190 that matches the list. The default contains just the IP address of the IPv4
5191 loopback interface, which means that processes on the local host are able to
5192 submit mail for relaying by sending it over TCP/IP to that interface. No other
5193 hosts are permitted to submit messages for relaying.
5195 Just to be sure there's no misunderstanding: at this point in the configuration
5196 we aren't actually setting up any controls. We are just defining some domains
5197 and hosts that will be used in the controls that are specified later.
5199 The next two configuration lines are genuine option settings:
5201 acl_smtp_rcpt = acl_check_rcpt
5202 acl_smtp_data = acl_check_data
5204 These options specify &'Access Control Lists'& (ACLs) that are to be used
5205 during an incoming SMTP session for every recipient of a message (every RCPT
5206 command), and after the contents of the message have been received,
5207 respectively. The names of the lists are &'acl_check_rcpt'& and
5208 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5209 section of the configuration. The RCPT ACL controls which recipients are
5210 accepted for an incoming message &-- if a configuration does not provide an ACL
5211 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5212 contents of a message to be checked.
5214 Two commented-out option settings are next:
5216 # av_scanner = clamd:/tmp/clamd
5217 # spamd_address = 127.0.0.1 783
5219 These are example settings that can be used when Exim is compiled with the
5220 content-scanning extension. The first specifies the interface to the virus
5221 scanner, and the second specifies the interface to SpamAssassin. Further
5222 details are given in chapter &<<CHAPexiscan>>&.
5224 Three more commented-out option settings follow:
5226 # tls_advertise_hosts = *
5227 # tls_certificate = /etc/ssl/exim.crt
5228 # tls_privatekey = /etc/ssl/exim.pem
5230 These are example settings that can be used when Exim is compiled with
5231 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5232 first one specifies the list of clients that are allowed to use TLS when
5233 connecting to this server; in this case the wildcard means all clients. The
5234 other options specify where Exim should find its TLS certificate and private
5235 key, which together prove the server's identity to any clients that connect.
5236 More details are given in chapter &<<CHAPTLS>>&.
5238 Another two commented-out option settings follow:
5240 # daemon_smtp_ports = 25 : 465 : 587
5241 # tls_on_connect_ports = 465
5243 .cindex "port" "465 and 587"
5244 .cindex "port" "for message submission"
5245 .cindex "message" "submission, ports for"
5246 .cindex "ssmtp protocol"
5247 .cindex "smtps protocol"
5248 .cindex "SMTP" "ssmtp protocol"
5249 .cindex "SMTP" "smtps protocol"
5250 These options provide better support for roaming users who wish to use this
5251 server for message submission. They are not much use unless you have turned on
5252 TLS (as described in the previous paragraph) and authentication (about which
5253 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5254 on end-user networks, so RFC 4409 specifies that message submission should use
5255 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5256 configured to use port 587 correctly, so these settings also enable the
5257 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5258 &<<SECTsupobssmt>>&).
5260 Two more commented-out options settings follow:
5263 # qualify_recipient =
5265 The first of these specifies a domain that Exim uses when it constructs a
5266 complete email address from a local login name. This is often needed when Exim
5267 receives a message from a local process. If you do not set &%qualify_domain%&,
5268 the value of &%primary_hostname%& is used. If you set both of these options,
5269 you can have different qualification domains for sender and recipient
5270 addresses. If you set only the first one, its value is used in both cases.
5272 .cindex "domain literal" "recognizing format"
5273 The following line must be uncommented if you want Exim to recognize
5274 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5275 (an IP address within square brackets) instead of a named domain.
5277 # allow_domain_literals
5279 The RFCs still require this form, but many people think that in the modern
5280 Internet it makes little sense to permit mail to be sent to specific hosts by
5281 quoting their IP addresses. This ancient format has been used by people who
5282 try to abuse hosts by using them for unwanted relaying. However, some
5283 people believe there are circumstances (for example, messages addressed to
5284 &'postmaster'&) where domain literals are still useful.
5286 The next configuration line is a kind of trigger guard:
5290 It specifies that no delivery must ever be run as the root user. The normal
5291 convention is to set up &'root'& as an alias for the system administrator. This
5292 setting is a guard against slips in the configuration.
5293 The list of users specified by &%never_users%& is not, however, the complete
5294 list; the build-time configuration in &_Local/Makefile_& has an option called
5295 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5296 contents of &%never_users%& are added to this list. By default
5297 FIXED_NEVER_USERS also specifies root.
5299 When a remote host connects to Exim in order to send mail, the only information
5300 Exim has about the host's identity is its IP address. The next configuration
5305 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5306 in order to get a host name. This improves the quality of the logging
5307 information, but if you feel it is too expensive, you can remove it entirely,
5308 or restrict the lookup to hosts on &"nearby"& networks.
5309 Note that it is not always possible to find a host name from an IP address,
5310 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5313 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5314 1413 (hence their names):
5317 rfc1413_query_timeout = 5s
5319 These settings cause Exim to make ident callbacks for all incoming SMTP calls.
5320 You can limit the hosts to which these calls are made, or change the timeout
5321 that is used. If you set the timeout to zero, all ident calls are disabled.
5322 Although they are cheap and can provide useful information for tracing problem
5323 messages, some hosts and firewalls have problems with ident calls. This can
5324 result in a timeout instead of an immediate refused connection, leading to
5325 delays on starting up an incoming SMTP session.
5327 When Exim receives messages over SMTP connections, it expects all addresses to
5328 be fully qualified with a domain, as required by the SMTP definition. However,
5329 if you are running a server to which simple clients submit messages, you may
5330 find that they send unqualified addresses. The two commented-out options:
5332 # sender_unqualified_hosts =
5333 # recipient_unqualified_hosts =
5335 show how you can specify hosts that are permitted to send unqualified sender
5336 and recipient addresses, respectively.
5338 The &%percent_hack_domains%& option is also commented out:
5340 # percent_hack_domains =
5342 It provides a list of domains for which the &"percent hack"& is to operate.
5343 This is an almost obsolete form of explicit email routing. If you do not know
5344 anything about it, you can safely ignore this topic.
5346 The last two settings in the main part of the default configuration are
5347 concerned with messages that have been &"frozen"& on Exim's queue. When a
5348 message is frozen, Exim no longer continues to try to deliver it. Freezing
5349 occurs when a bounce message encounters a permanent failure because the sender
5350 address of the original message that caused the bounce is invalid, so the
5351 bounce cannot be delivered. This is probably the most common case, but there
5352 are also other conditions that cause freezing, and frozen messages are not
5353 always bounce messages.
5355 ignore_bounce_errors_after = 2d
5356 timeout_frozen_after = 7d
5358 The first of these options specifies that failing bounce messages are to be
5359 discarded after 2 days on the queue. The second specifies that any frozen
5360 message (whether a bounce message or not) is to be timed out (and discarded)
5361 after a week. In this configuration, the first setting ensures that no failing
5362 bounce message ever lasts a week.
5366 .section "ACL configuration" "SECID54"
5367 .cindex "default" "ACLs"
5368 .cindex "&ACL;" "default configuration"
5369 In the default configuration, the ACL section follows the main configuration.
5370 It starts with the line
5374 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5375 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5376 and &%acl_smtp_data%& above.
5378 .cindex "RCPT" "ACL for"
5379 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5380 RCPT command specifies one of the message's recipients. The ACL statements
5381 are considered in order, until the recipient address is either accepted or
5382 rejected. The RCPT command is then accepted or rejected, according to the
5383 result of the ACL processing.
5387 This line, consisting of a name terminated by a colon, marks the start of the
5392 This ACL statement accepts the recipient if the sending host matches the list.
5393 But what does that strange list mean? It doesn't actually contain any host
5394 names or IP addresses. The presence of the colon puts an empty item in the
5395 list; Exim matches this only if the incoming message did not come from a remote
5396 host, because in that case, the remote hostname is empty. The colon is
5397 important. Without it, the list itself is empty, and can never match anything.
5399 What this statement is doing is to accept unconditionally all recipients in
5400 messages that are submitted by SMTP from local processes using the standard
5401 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5404 deny message = Restricted characters in address
5405 domains = +local_domains
5406 local_parts = ^[.] : ^.*[@%!/|]
5408 deny message = Restricted characters in address
5409 domains = !+local_domains
5410 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5412 These statements are concerned with local parts that contain any of the
5413 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5414 Although these characters are entirely legal in local parts (in the case of
5415 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5416 in Internet mail addresses.
5418 The first three have in the past been associated with explicitly routed
5419 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5420 option). Addresses containing these characters are regularly tried by spammers
5421 in an attempt to bypass relaying restrictions, and also by open relay testing
5422 programs. Unless you really need them it is safest to reject these characters
5423 at this early stage. This configuration is heavy-handed in rejecting these
5424 characters for all messages it accepts from remote hosts. This is a deliberate
5425 policy of being as safe as possible.
5427 The first rule above is stricter, and is applied to messages that are addressed
5428 to one of the local domains handled by this host. This is implemented by the
5429 first condition, which restricts it to domains that are listed in the
5430 &'local_domains'& domain list. The &"+"& character is used to indicate a
5431 reference to a named list. In this configuration, there is just one domain in
5432 &'local_domains'&, but in general there may be many.
5434 The second condition on the first statement uses two regular expressions to
5435 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5436 or &"|"&. If you have local accounts that include these characters, you will
5437 have to modify this rule.
5439 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5440 allows them because they have been encountered in practice. (Consider the
5441 common convention of local parts constructed as
5442 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5443 the author of Exim, who has no second initial.) However, a local part starting
5444 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5445 file name (for example, for a mailing list). This is also true for local parts
5446 that contain slashes. A pipe symbol can also be troublesome if the local part
5447 is incorporated unthinkingly into a shell command line.
5449 The second rule above applies to all other domains, and is less strict. This
5450 allows your own users to send outgoing messages to sites that use slashes
5451 and vertical bars in their local parts. It blocks local parts that begin
5452 with a dot, slash, or vertical bar, but allows these characters within the
5453 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5454 and &"!"& is blocked, as before. The motivation here is to prevent your users
5455 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5457 accept local_parts = postmaster
5458 domains = +local_domains
5460 This statement, which has two conditions, accepts an incoming address if the
5461 local part is &'postmaster'& and the domain is one of those listed in the
5462 &'local_domains'& domain list. The &"+"& character is used to indicate a
5463 reference to a named list. In this configuration, there is just one domain in
5464 &'local_domains'&, but in general there may be many.
5466 The presence of this statement means that mail to postmaster is never blocked
5467 by any of the subsequent tests. This can be helpful while sorting out problems
5468 in cases where the subsequent tests are incorrectly denying access.
5470 require verify = sender
5472 This statement requires the sender address to be verified before any subsequent
5473 ACL statement can be used. If verification fails, the incoming recipient
5474 address is refused. Verification consists of trying to route the address, to
5475 see if a bounce message could be delivered to it. In the case of remote
5476 addresses, basic verification checks only the domain, but &'callouts'& can be
5477 used for more verification if required. Section &<<SECTaddressverification>>&
5478 discusses the details of address verification.
5480 accept hosts = +relay_from_hosts
5481 control = submission
5483 This statement accepts the address if the message is coming from one of the
5484 hosts that are defined as being allowed to relay through this host. Recipient
5485 verification is omitted here, because in many cases the clients are dumb MUAs
5486 that do not cope well with SMTP error responses. For the same reason, the
5487 second line specifies &"submission mode"& for messages that are accepted. This
5488 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5489 messages that are deficient in some way, for example, because they lack a
5490 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5491 probably add recipient verification here, and disable submission mode.
5493 accept authenticated = *
5494 control = submission
5496 This statement accepts the address if the client host has authenticated itself.
5497 Submission mode is again specified, on the grounds that such messages are most
5498 likely to come from MUAs. The default configuration does not define any
5499 authenticators, though it does include some nearly complete commented-out
5500 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5501 fact authenticate until you complete the authenticator definitions.
5503 require message = relay not permitted
5504 domains = +local_domains : +relay_domains
5506 This statement rejects the address if its domain is neither a local domain nor
5507 one of the domains for which this host is a relay.
5509 require verify = recipient
5511 This statement requires the recipient address to be verified; if verification
5512 fails, the address is rejected.
5514 # deny message = rejected because $sender_host_address \
5515 # is in a black list at $dnslist_domain\n\
5517 # dnslists = black.list.example
5519 # warn dnslists = black.list.example
5520 # add_header = X-Warning: $sender_host_address is in \
5521 # a black list at $dnslist_domain
5522 # log_message = found in $dnslist_domain
5524 These commented-out lines are examples of how you could configure Exim to check
5525 sending hosts against a DNS black list. The first statement rejects messages
5526 from blacklisted hosts, whereas the second just inserts a warning header
5529 # require verify = csa
5531 This commented-out line is an example of how you could turn on client SMTP
5532 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5537 The final statement in the first ACL unconditionally accepts any recipient
5538 address that has successfully passed all the previous tests.
5542 This line marks the start of the second ACL, and names it. Most of the contents
5543 of this ACL are commented out:
5546 # message = This message contains a virus \
5549 These lines are examples of how to arrange for messages to be scanned for
5550 viruses when Exim has been compiled with the content-scanning extension, and a
5551 suitable virus scanner is installed. If the message is found to contain a
5552 virus, it is rejected with the given custom error message.
5554 # warn spam = nobody
5555 # message = X-Spam_score: $spam_score\n\
5556 # X-Spam_score_int: $spam_score_int\n\
5557 # X-Spam_bar: $spam_bar\n\
5558 # X-Spam_report: $spam_report
5560 These lines are an example of how to arrange for messages to be scanned by
5561 SpamAssassin when Exim has been compiled with the content-scanning extension,
5562 and SpamAssassin has been installed. The SpamAssassin check is run with
5563 &`nobody`& as its user parameter, and the results are added to the message as a
5564 series of extra header line. In this case, the message is not rejected,
5565 whatever the spam score.
5569 This final line in the DATA ACL accepts the message unconditionally.
5572 .section "Router configuration" "SECID55"
5573 .cindex "default" "routers"
5574 .cindex "routers" "default"
5575 The router configuration comes next in the default configuration, introduced
5580 Routers are the modules in Exim that make decisions about where to send
5581 messages. An address is passed to each router in turn, until it is either
5582 accepted, or failed. This means that the order in which you define the routers
5583 matters. Each router is fully described in its own chapter later in this
5584 manual. Here we give only brief overviews.
5587 # driver = ipliteral
5588 # domains = !+local_domains
5589 # transport = remote_smtp
5591 .cindex "domain literal" "default router"
5592 This router is commented out because the majority of sites do not want to
5593 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5594 you uncomment this router, you also need to uncomment the setting of
5595 &%allow_domain_literals%& in the main part of the configuration.
5599 domains = ! +local_domains
5600 transport = remote_smtp
5601 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5604 The first uncommented router handles addresses that do not involve any local
5605 domains. This is specified by the line
5607 domains = ! +local_domains
5609 The &%domains%& option lists the domains to which this router applies, but the
5610 exclamation mark is a negation sign, so the router is used only for domains
5611 that are not in the domain list called &'local_domains'& (which was defined at
5612 the start of the configuration). The plus sign before &'local_domains'&
5613 indicates that it is referring to a named list. Addresses in other domains are
5614 passed on to the following routers.
5616 The name of the router driver is &(dnslookup)&,
5617 and is specified by the &%driver%& option. Do not be confused by the fact that
5618 the name of this router instance is the same as the name of the driver. The
5619 instance name is arbitrary, but the name set in the &%driver%& option must be
5620 one of the driver modules that is in the Exim binary.
5622 The &(dnslookup)& router routes addresses by looking up their domains in the
5623 DNS in order to obtain a list of hosts to which the address is routed. If the
5624 router succeeds, the address is queued for the &(remote_smtp)& transport, as
5625 specified by the &%transport%& option. If the router does not find the domain
5626 in the DNS, no further routers are tried because of the &%no_more%& setting, so
5627 the address fails and is bounced.
5629 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
5630 be entirely ignored. This option is present because a number of cases have been
5631 encountered where MX records in the DNS point to host names
5632 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
5633 Completely ignoring these IP addresses causes Exim to fail to route the
5634 email address, so it bounces. Otherwise, Exim would log a routing problem, and
5635 continue to try to deliver the message periodically until the address timed
5642 data = ${lookup{$local_part}lsearch{/etc/aliases}}
5644 file_transport = address_file
5645 pipe_transport = address_pipe
5647 Control reaches this and subsequent routers only for addresses in the local
5648 domains. This router checks to see whether the local part is defined as an
5649 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
5650 data that it looks up from that file. If no data is found for the local part,
5651 the value of the &%data%& option is empty, causing the address to be passed to
5654 &_/etc/aliases_& is a conventional name for the system aliases file that is
5655 often used. That is why it is referenced by from the default configuration
5656 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
5657 &_Local/Makefile_& before building Exim.
5662 # local_part_suffix = +* : -*
5663 # local_part_suffix_optional
5664 file = $home/.forward
5669 file_transport = address_file
5670 pipe_transport = address_pipe
5671 reply_transport = address_reply
5673 This is the most complicated router in the default configuration. It is another
5674 redirection router, but this time it is looking for forwarding data set up by
5675 individual users. The &%check_local_user%& setting specifies a check that the
5676 local part of the address is the login name of a local user. If it is not, the
5677 router is skipped. The two commented options that follow &%check_local_user%&,
5680 # local_part_suffix = +* : -*
5681 # local_part_suffix_optional
5683 .vindex "&$local_part_suffix$&"
5684 show how you can specify the recognition of local part suffixes. If the first
5685 is uncommented, a suffix beginning with either a plus or a minus sign, followed
5686 by any sequence of characters, is removed from the local part and placed in the
5687 variable &$local_part_suffix$&. The second suffix option specifies that the
5688 presence of a suffix in the local part is optional. When a suffix is present,
5689 the check for a local login uses the local part with the suffix removed.
5691 When a local user account is found, the file called &_.forward_& in the user's
5692 home directory is consulted. If it does not exist, or is empty, the router
5693 declines. Otherwise, the contents of &_.forward_& are interpreted as
5694 redirection data (see chapter &<<CHAPredirect>>& for more details).
5696 .cindex "Sieve filter" "enabling in default router"
5697 Traditional &_.forward_& files contain just a list of addresses, pipes, or
5698 files. Exim supports this by default. However, if &%allow_filter%& is set (it
5699 is commented out by default), the contents of the file are interpreted as a set
5700 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
5701 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
5702 separate document entitled &'Exim's interfaces to mail filtering'&.
5704 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
5705 verifying addresses, or when running as a consequence of an SMTP EXPN command.
5706 There are two reasons for doing this:
5709 Whether or not a local user has a &_.forward_& file is not really relevant when
5710 checking an address for validity; it makes sense not to waste resources doing
5713 More importantly, when Exim is verifying addresses or handling an EXPN
5714 command during an SMTP session, it is running as the Exim user, not as root.
5715 The group is the Exim group, and no additional groups are set up.
5716 It may therefore not be possible for Exim to read users' &_.forward_& files at
5720 The setting of &%check_ancestor%& prevents the router from generating a new
5721 address that is the same as any previous address that was redirected. (This
5722 works round a problem concerning a bad interaction between aliasing and
5723 forwarding &-- see section &<<SECTredlocmai>>&).
5725 The final three option settings specify the transports that are to be used when
5726 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
5727 auto-reply, respectively. For example, if a &_.forward_& file contains
5729 a.nother@elsewhere.example, /home/spqr/archive
5731 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
5737 # local_part_suffix = +* : -*
5738 # local_part_suffix_optional
5739 transport = local_delivery
5741 The final router sets up delivery into local mailboxes, provided that the local
5742 part is the name of a local login, by accepting the address and assigning it to
5743 the &(local_delivery)& transport. Otherwise, we have reached the end of the
5744 routers, so the address is bounced. The commented suffix settings fulfil the
5745 same purpose as they do for the &(userforward)& router.
5748 .section "Transport configuration" "SECID56"
5749 .cindex "default" "transports"
5750 .cindex "transports" "default"
5751 Transports define mechanisms for actually delivering messages. They operate
5752 only when referenced from routers, so the order in which they are defined does
5753 not matter. The transports section of the configuration starts with
5757 One remote transport and four local transports are defined.
5762 This transport is used for delivering messages over SMTP connections. All its
5763 options are defaulted. The list of remote hosts comes from the router.
5767 file = /var/mail/$local_part
5774 This &(appendfile)& transport is used for local delivery to user mailboxes in
5775 traditional BSD mailbox format. By default it runs under the uid and gid of the
5776 local user, which requires the sticky bit to be set on the &_/var/mail_&
5777 directory. Some systems use the alternative approach of running mail deliveries
5778 under a particular group instead of using the sticky bit. The commented options
5779 show how this can be done.
5781 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
5782 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
5783 similarly-named options above.
5789 This transport is used for handling deliveries to pipes that are generated by
5790 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
5791 option specifies that any output generated by the pipe is to be returned to the
5800 This transport is used for handling deliveries to files that are generated by
5801 redirection. The name of the file is not specified in this instance of
5802 &(appendfile)&, because it comes from the &(redirect)& router.
5807 This transport is used for handling automatic replies generated by users'
5812 .section "Default retry rule" "SECID57"
5813 .cindex "retry" "default rule"
5814 .cindex "default" "retry rule"
5815 The retry section of the configuration file contains rules which affect the way
5816 Exim retries deliveries that cannot be completed at the first attempt. It is
5817 introduced by the line
5821 In the default configuration, there is just one rule, which applies to all
5824 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
5826 This causes any temporarily failing address to be retried every 15 minutes for
5827 2 hours, then at intervals starting at one hour and increasing by a factor of
5828 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
5829 is not delivered after 4 days of temporary failure, it is bounced.
5831 If the retry section is removed from the configuration, or is empty (that is,
5832 if no retry rules are defined), Exim will not retry deliveries. This turns
5833 temporary errors into permanent errors.
5836 .section "Rewriting configuration" "SECID58"
5837 The rewriting section of the configuration, introduced by
5841 contains rules for rewriting addresses in messages as they arrive. There are no
5842 rewriting rules in the default configuration file.
5846 .section "Authenticators configuration" "SECTdefconfauth"
5847 .cindex "AUTH" "configuration"
5848 The authenticators section of the configuration, introduced by
5850 begin authenticators
5852 defines mechanisms for the use of the SMTP AUTH command. The default
5853 configuration file contains two commented-out example authenticators
5854 which support plaintext username/password authentication using the
5855 standard PLAIN mechanism and the traditional but non-standard LOGIN
5856 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
5857 to support most MUA software.
5859 The example PLAIN authenticator looks like this:
5862 # driver = plaintext
5863 # server_set_id = $auth2
5864 # server_prompts = :
5865 # server_condition = Authentication is not yet configured
5866 # server_advertise_condition = ${if def:tls_cipher }
5868 And the example LOGIN authenticator looks like this:
5871 # driver = plaintext
5872 # server_set_id = $auth1
5873 # server_prompts = <| Username: | Password:
5874 # server_condition = Authentication is not yet configured
5875 # server_advertise_condition = ${if def:tls_cipher }
5878 The &%server_set_id%& option makes Exim remember the authenticated username
5879 in &$authenticated_id$&, which can be used later in ACLs or routers. The
5880 &%server_prompts%& option configures the &(plaintext)& authenticator so
5881 that it implements the details of the specific authentication mechanism,
5882 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
5883 when Exim offers authentication to clients; in the examples, this is only
5884 when TLS or SSL has been started, so to enable the authenticators you also
5885 need to add support for TLS as described in &<<SECTdefconfmain>>&.
5887 The &%server_condition%& setting defines how to verify that the username and
5888 password are correct. In the examples it just produces an error message.
5889 To make the authenticators work, you can use a string expansion
5890 expression like one of the examples in &<<CHAPplaintext>>&.
5892 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
5893 usercode and password are in different positions. &<<CHAPplaintext>>&
5896 .ecindex IIDconfiwal
5900 . ////////////////////////////////////////////////////////////////////////////
5901 . ////////////////////////////////////////////////////////////////////////////
5903 .chapter "Regular expressions" "CHAPregexp"
5905 .cindex "regular expressions" "library"
5907 Exim supports the use of regular expressions in many of its options. It
5908 uses the PCRE regular expression library; this provides regular expression
5909 matching that is compatible with Perl 5. The syntax and semantics of
5910 regular expressions is discussed in many Perl reference books, and also in
5911 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
5912 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
5914 The documentation for the syntax and semantics of the regular expressions that
5915 are supported by PCRE is included in the PCRE distribution, and no further
5916 description is included here. The PCRE functions are called from Exim using
5917 the default option settings (that is, with no PCRE options set), except that
5918 the PCRE_CASELESS option is set when the matching is required to be
5921 In most cases, when a regular expression is required in an Exim configuration,
5922 it has to start with a circumflex, in order to distinguish it from plain text
5923 or an &"ends with"& wildcard. In this example of a configuration setting, the
5924 second item in the colon-separated list is a regular expression.
5926 domains = a.b.c : ^\\d{3} : *.y.z : ...
5928 The doubling of the backslash is required because of string expansion that
5929 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
5930 of this issue, and a way of avoiding the need for doubling backslashes. The
5931 regular expression that is eventually used in this example contains just one
5932 backslash. The circumflex is included in the regular expression, and has the
5933 normal effect of &"anchoring"& it to the start of the string that is being
5936 There are, however, two cases where a circumflex is not required for the
5937 recognition of a regular expression: these are the &%match%& condition in a
5938 string expansion, and the &%matches%& condition in an Exim filter file. In
5939 these cases, the relevant string is always treated as a regular expression; if
5940 it does not start with a circumflex, the expression is not anchored, and can
5941 match anywhere in the subject string.
5943 In all cases, if you want a regular expression to match at the end of a string,
5944 you must code the $ metacharacter to indicate this. For example:
5946 domains = ^\\d{3}\\.example
5948 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
5951 domains = ^\\d{3}\\.example\$
5953 if you want &'example'& to be the top-level domain. The backslash before the
5954 $ is needed because string expansion also interprets dollar characters.
5958 . ////////////////////////////////////////////////////////////////////////////
5959 . ////////////////////////////////////////////////////////////////////////////
5961 .chapter "File and database lookups" "CHAPfdlookup"
5962 .scindex IIDfidalo1 "file" "lookups"
5963 .scindex IIDfidalo2 "database" "lookups"
5964 .cindex "lookup" "description of"
5965 Exim can be configured to look up data in files or databases as it processes
5966 messages. Two different kinds of syntax are used:
5969 A string that is to be expanded may contain explicit lookup requests. These
5970 cause parts of the string to be replaced by data that is obtained from the
5971 lookup. Lookups of this type are conditional expansion items. Different results
5972 can be defined for the cases of lookup success and failure. See chapter
5973 &<<CHAPexpand>>&, where string expansions are described in detail.
5975 Lists of domains, hosts, and email addresses can contain lookup requests as a
5976 way of avoiding excessively long linear lists. In this case, the data that is
5977 returned by the lookup is often (but not always) discarded; whether the lookup
5978 succeeds or fails is what really counts. These kinds of list are described in
5979 chapter &<<CHAPdomhosaddlists>>&.
5982 String expansions, lists, and lookups interact with each other in such a way
5983 that there is no order in which to describe any one of them that does not
5984 involve references to the others. Each of these three chapters makes more sense
5985 if you have read the other two first. If you are reading this for the first
5986 time, be aware that some of it will make a lot more sense after you have read
5987 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
5989 .section "Examples of different lookup syntax" "SECID60"
5990 It is easy to confuse the two different kinds of lookup, especially as the
5991 lists that may contain the second kind are always expanded before being
5992 processed as lists. Therefore, they may also contain lookups of the first kind.
5993 Be careful to distinguish between the following two examples:
5995 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
5996 domains = lsearch;/some/file
5998 The first uses a string expansion, the result of which must be a domain list.
5999 No strings have been specified for a successful or a failing lookup; the
6000 defaults in this case are the looked-up data and an empty string, respectively.
6001 The expansion takes place before the string is processed as a list, and the
6002 file that is searched could contain lines like this:
6004 192.168.3.4: domain1:domain2:...
6005 192.168.1.9: domain3:domain4:...
6007 When the lookup succeeds, the result of the expansion is a list of domains (and
6008 possibly other types of item that are allowed in domain lists).
6010 In the second example, the lookup is a single item in a domain list. It causes
6011 Exim to use a lookup to see if the domain that is being processed can be found
6012 in the file. The file could contains lines like this:
6017 Any data that follows the keys is not relevant when checking that the domain
6018 matches the list item.
6020 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6021 Consider a file containing lines like this:
6023 192.168.5.6: lsearch;/another/file
6025 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6026 first &%domains%& setting above generates the second setting, which therefore
6027 causes a second lookup to occur.
6029 The rest of this chapter describes the different lookup types that are
6030 available. Any of them can be used in any part of the configuration where a
6031 lookup is permitted.
6034 .section "Lookup types" "SECID61"
6035 .cindex "lookup" "types of"
6036 .cindex "single-key lookup" "definition of"
6037 Two different types of data lookup are implemented:
6040 The &'single-key'& type requires the specification of a file in which to look,
6041 and a single key to search for. The key must be a non-empty string for the
6042 lookup to succeed. The lookup type determines how the file is searched.
6044 .cindex "query-style lookup" "definition of"
6045 The &'query-style'& type accepts a generalized database query. No particular
6046 key value is assumed by Exim for query-style lookups. You can use whichever
6047 Exim variables you need to construct the database query.
6050 The code for each lookup type is in a separate source file that is included in
6051 the binary of Exim only if the corresponding compile-time option is set. The
6052 default settings in &_src/EDITME_& are:
6057 which means that only linear searching and DBM lookups are included by default.
6058 For some types of lookup (e.g. SQL databases), you need to install appropriate
6059 libraries and header files before building Exim.
6064 .section "Single-key lookup types" "SECTsinglekeylookups"
6065 .cindex "lookup" "single-key types"
6066 .cindex "single-key lookup" "list of types"
6067 The following single-key lookup types are implemented:
6070 .cindex "cdb" "description of"
6071 .cindex "lookup" "cdb"
6072 .cindex "binary zero" "in lookup key"
6073 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6074 string without a terminating binary zero. The cdb format is designed for
6075 indexed files that are read frequently and never updated, except by total
6076 re-creation. As such, it is particularly suitable for large files containing
6077 aliases or other indexed data referenced by an MTA. Information about cdb can
6078 be found in several places:
6080 &url(http://www.pobox.com/~djb/cdb.html)
6081 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6082 &url(http://packages.debian.org/stable/utils/freecdb.html)
6084 A cdb distribution is not needed in order to build Exim with cdb support,
6085 because the code for reading cdb files is included directly in Exim itself.
6086 However, no means of building or testing cdb files is provided with Exim, so
6087 you need to obtain a cdb distribution in order to do this.
6089 .cindex "DBM" "lookup type"
6090 .cindex "lookup" "dbm"
6091 .cindex "binary zero" "in lookup key"
6092 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6093 DBM file by looking up the record with the given key. A terminating binary
6094 zero is included in the key that is passed to the DBM library. See section
6095 &<<SECTdb>>& for a discussion of DBM libraries.
6097 .cindex "Berkeley DB library" "file format"
6098 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6099 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6100 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6101 the DB_UNKNOWN option. This enables it to handle any of the types of database
6102 that the library supports, and can be useful for accessing DBM files created by
6103 other applications. (For earlier DB versions, DB_HASH is always used.)
6105 .cindex "lookup" "dbmnz"
6106 .cindex "lookup" "dbm &-- terminating zero"
6107 .cindex "binary zero" "in lookup key"
6109 .cindex "&_/etc/userdbshadow.dat_&"
6110 .cindex "dmbnz lookup type"
6111 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6112 is not included in the key that is passed to the DBM library. You may need this
6113 if you want to look up data in files that are created by or shared with some
6114 other application that does not use terminating zeros. For example, you need to
6115 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6116 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6117 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6118 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6120 .cindex "lookup" "dsearch"
6121 .cindex "dsearch lookup type"
6122 &(dsearch)&: The given file must be a directory; this is searched for an entry
6123 whose name is the key by calling the &[lstat()]& function. The key may not
6124 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6125 the lookup is the name of the entry, which may be a file, directory,
6126 symbolic link, or any other kind of directory entry. An example of how this
6127 lookup can be used to support virtual domains is given in section
6128 &<<SECTvirtualdomains>>&.
6130 .cindex "lookup" "iplsearch"
6131 .cindex "iplsearch lookup type"
6132 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6133 terminated by a colon or white space or the end of the line. The keys in the
6134 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6135 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6136 being interpreted as a key terminator. For example:
6138 1.2.3.4: data for 1.2.3.4
6139 192.168.0.0/16: data for 192.168.0.0/16
6140 "abcd::cdab": data for abcd::cdab
6141 "abcd:abcd::/32" data for abcd:abcd::/32
6143 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6144 file is searched linearly, using the CIDR masks where present, until a matching
6145 key is found. The first key that matches is used; there is no attempt to find a
6146 &"best"& match. Apart from the way the keys are matched, the processing for
6147 &(iplsearch)& is the same as for &(lsearch)&.
6149 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6150 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6151 lookup types support only literal keys.
6153 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6154 the implicit key is the host's IP address rather than its name (see section
6155 &<<SECThoslispatsikey>>&).
6157 .cindex "linear search"
6158 .cindex "lookup" "lsearch"
6159 .cindex "lsearch lookup type"
6160 .cindex "case sensitivity" "in lsearch lookup"
6161 &(lsearch)&: The given file is a text file that is searched linearly for a
6162 line beginning with the search key, terminated by a colon or white space or the
6163 end of the line. The search is case-insensitive; that is, upper and lower case
6164 letters are treated as the same. The first occurrence of the key that is found
6165 in the file is used.
6167 White space between the key and the colon is permitted. The remainder of the
6168 line, with leading and trailing white space removed, is the data. This can be
6169 continued onto subsequent lines by starting them with any amount of white
6170 space, but only a single space character is included in the data at such a
6171 junction. If the data begins with a colon, the key must be terminated by a
6176 Empty lines and lines beginning with # are ignored, even if they occur in the
6177 middle of an item. This is the traditional textual format of alias files. Note
6178 that the keys in an &(lsearch)& file are literal strings. There is no
6179 wildcarding of any kind.
6181 .cindex "lookup" "lsearch &-- colons in keys"
6182 .cindex "white space" "in lsearch key"
6183 In most &(lsearch)& files, keys are not required to contain colons or #
6184 characters, or white space. However, if you need this feature, it is available.
6185 If a key begins with a doublequote character, it is terminated only by a
6186 matching quote (or end of line), and the normal escaping rules apply to its
6187 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6188 quoted keys (exactly as for unquoted keys). There is no special handling of
6189 quotes for the data part of an &(lsearch)& line.
6192 .cindex "NIS lookup type"
6193 .cindex "lookup" "NIS"
6194 .cindex "binary zero" "in lookup key"
6195 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6196 the given key, without a terminating binary zero. There is a variant called
6197 &(nis0)& which does include the terminating binary zero in the key. This is
6198 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6199 aliases; the full map names must be used.
6202 .cindex "wildlsearch lookup type"
6203 .cindex "lookup" "wildlsearch"
6204 .cindex "nwildlsearch lookup type"
6205 .cindex "lookup" "nwildlsearch"
6206 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6207 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6208 the file may be wildcarded. The difference between these two lookup types is
6209 that for &(wildlsearch)&, each key in the file is string-expanded before being
6210 used, whereas for &(nwildlsearch)&, no expansion takes place.
6212 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6213 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6214 file that are regular expressions can be made case-sensitive by the use of
6215 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6217 . ==== As this is a nested list, any displays it contains must be indented
6218 . ==== as otherwise they are too far to the left.
6221 The string may begin with an asterisk to mean &"ends with"&. For example:
6223 *.a.b.c data for anything.a.b.c
6224 *fish data for anythingfish
6227 The string may begin with a circumflex to indicate a regular expression. For
6228 example, for &(wildlsearch)&:
6230 ^\N\d+\.a\.b\N data for <digits>.a.b
6232 Note the use of &`\N`& to disable expansion of the contents of the regular
6233 expression. If you are using &(nwildlsearch)&, where the keys are not
6234 string-expanded, the equivalent entry is:
6236 ^\d+\.a\.b data for <digits>.a.b
6238 The case-insensitive flag is set at the start of compiling the regular
6239 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6240 For example, to make the entire pattern case-sensitive:
6242 ^(?-i)\d+\.a\.b data for <digits>.a.b
6245 If the regular expression contains white space or colon characters, you must
6246 either quote it (see &(lsearch)& above), or represent these characters in other
6247 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6248 colon. This may be easier than quoting, because if you quote, you have to
6249 escape all the backslashes inside the quotes.
6251 &*Note*&: It is not possible to capture substrings in a regular expression
6252 match for later use, because the results of all lookups are cached. If a lookup
6253 is repeated, the result is taken from the cache, and no actual pattern matching
6254 takes place. The values of all the numeric variables are unset after a
6255 &((n)wildlsearch)& match.
6258 Although I cannot see it being of much use, the general matching function that
6259 is used to implement &((n)wildlsearch)& means that the string may begin with a
6260 lookup name terminated by a semicolon, and followed by lookup data. For
6263 cdb;/some/file data for keys that match the file
6265 The data that is obtained from the nested lookup is discarded.
6268 Keys that do not match any of these patterns are interpreted literally. The
6269 continuation rules for the data are the same as for &(lsearch)&, and keys may
6270 be followed by optional colons.
6272 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6273 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6274 lookup types support only literal keys.
6278 .section "Query-style lookup types" "SECID62"
6279 .cindex "lookup" "query-style types"
6280 .cindex "query-style lookup" "list of types"
6281 The supported query-style lookup types are listed below. Further details about
6282 many of them are given in later sections.
6285 .cindex "DNS" "as a lookup type"
6286 .cindex "lookup" "DNS"
6287 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6288 are given in the supplied query. The resulting data is the contents of the
6289 records. See section &<<SECTdnsdb>>&.
6291 .cindex "InterBase lookup type"
6292 .cindex "lookup" "InterBase"
6293 &(ibase)&: This does a lookup in an InterBase database.
6295 .cindex "LDAP" "lookup type"
6296 .cindex "lookup" "LDAP"
6297 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6298 returns attributes from a single entry. There is a variant called &(ldapm)&
6299 that permits values from multiple entries to be returned. A third variant
6300 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6301 any attribute values. See section &<<SECTldap>>&.
6303 .cindex "MySQL" "lookup type"
6304 .cindex "lookup" "MySQL"
6305 &(mysql)&: The format of the query is an SQL statement that is passed to a
6306 MySQL database. See section &<<SECTsql>>&.
6308 .cindex "NIS+ lookup type"
6309 .cindex "lookup" "NIS+"
6310 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6311 the field to be returned. See section &<<SECTnisplus>>&.
6313 .cindex "Oracle" "lookup type"
6314 .cindex "lookup" "Oracle"
6315 &(oracle)&: The format of the query is an SQL statement that is passed to an
6316 Oracle database. See section &<<SECTsql>>&.
6318 .cindex "lookup" "passwd"
6319 .cindex "passwd lookup type"
6320 .cindex "&_/etc/passwd_&"
6321 &(passwd)& is a query-style lookup with queries that are just user names. The
6322 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6323 success, the result string is the same as you would get from an &(lsearch)&
6324 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6325 password value. For example:
6327 *:42:42:King Rat:/home/kr:/bin/bash
6330 .cindex "PostgreSQL lookup type"
6331 .cindex "lookup" "PostgreSQL"
6332 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6333 PostgreSQL database. See section &<<SECTsql>>&.
6336 .cindex "sqlite lookup type"
6337 .cindex "lookup" "sqlite"
6338 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6339 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6342 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6343 not likely to be useful in normal operation.
6345 .cindex "whoson lookup type"
6346 .cindex "lookup" "whoson"
6347 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6348 allows a server to check whether a particular (dynamically allocated) IP
6349 address is currently allocated to a known (trusted) user and, optionally, to
6350 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6351 at one time for &"POP before SMTP"& authentication, but that approach has been
6352 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6353 &"POP before SMTP"& checking using ACL statements such as
6355 require condition = \
6356 ${lookup whoson {$sender_host_address}{yes}{no}}
6358 The query consists of a single IP address. The value returned is the name of
6359 the authenticated user, which is stored in the variable &$value$&. However, in
6360 this example, the data in &$value$& is not used; the result of the lookup is
6361 one of the fixed strings &"yes"& or &"no"&.
6366 .section "Temporary errors in lookups" "SECID63"
6367 .cindex "lookup" "temporary error in"
6368 Lookup functions can return temporary error codes if the lookup cannot be
6369 completed. For example, an SQL or LDAP database might be unavailable. For this
6370 reason, it is not advisable to use a lookup that might do this for critical
6371 options such as a list of local domains.
6373 When a lookup cannot be completed in a router or transport, delivery
6374 of the message (to the relevant address) is deferred, as for any other
6375 temporary error. In other circumstances Exim may assume the lookup has failed,
6376 or may give up altogether.
6380 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6381 .cindex "wildcard lookups"
6382 .cindex "lookup" "default values"
6383 .cindex "lookup" "wildcard"
6384 .cindex "lookup" "* added to type"
6385 .cindex "default" "in single-key lookups"
6386 In this context, a &"default value"& is a value specified by the administrator
6387 that is to be used if a lookup fails.
6389 &*Note:*& This section applies only to single-key lookups. For query-style
6390 lookups, the facilities of the query language must be used. An attempt to
6391 specify a default for a query-style lookup provokes an error.
6393 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6394 and the initial lookup fails, the key &"*"& is looked up in the file to
6395 provide a default value. See also the section on partial matching below.
6397 .cindex "*@ with single-key lookup"
6398 .cindex "lookup" "*@ added to type"
6399 .cindex "alias file" "per-domain default"
6400 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6401 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6402 character, a second lookup is done with everything before the last @ replaced
6403 by *. This makes it possible to provide per-domain defaults in alias files
6404 that include the domains in the keys. If the second lookup fails (or doesn't
6405 take place because there is no @ in the key), &"*"& is looked up.
6406 For example, a &(redirect)& router might contain:
6408 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6410 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6411 looks up these keys, in this order:
6417 The data is taken from whichever key it finds first. &*Note*&: In an
6418 &(lsearch)& file, this does not mean the first of these keys in the file. A
6419 complete scan is done for each key, and only if it is not found at all does
6420 Exim move on to try the next key.
6424 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6425 .cindex "partial matching"
6426 .cindex "wildcard lookups"
6427 .cindex "lookup" "partial matching"
6428 .cindex "lookup" "wildcard"
6429 .cindex "asterisk" "in search type"
6430 The normal operation of a single-key lookup is to search the file for an exact
6431 match with the given key. However, in a number of situations where domains are
6432 being looked up, it is useful to be able to do partial matching. In this case,
6433 information in the file that has a key starting with &"*."& is matched by any
6434 domain that ends with the components that follow the full stop. For example, if
6435 a key in a DBM file is
6437 *.dates.fict.example
6439 then when partial matching is enabled this is matched by (amongst others)
6440 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6441 by &'dates.fict.example'&, if that does not appear as a separate key in the
6444 &*Note*&: Partial matching is not available for query-style lookups. It is
6445 also not available for any lookup items in address lists (see section
6446 &<<SECTaddresslist>>&).
6448 Partial matching is implemented by doing a series of separate lookups using
6449 keys constructed by modifying the original subject key. This means that it can
6450 be used with any of the single-key lookup types, provided that
6451 partial matching keys
6452 beginning with a special prefix (default &"*."&) are included in the data file.
6453 Keys in the file that do not begin with the prefix are matched only by
6454 unmodified subject keys when partial matching is in use.
6456 Partial matching is requested by adding the string &"partial-"& to the front of
6457 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6458 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6459 is added at the start of the subject key, and it is looked up again. If that
6460 fails, further lookups are tried with dot-separated components removed from the
6461 start of the subject key, one-by-one, and &"*."& added on the front of what
6464 A minimum number of two non-* components are required. This can be adjusted
6465 by including a number before the hyphen in the search type. For example,
6466 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6467 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6468 subject key is &'2250.dates.fict.example'& then the following keys are looked
6469 up when the minimum number of non-* components is two:
6471 2250.dates.fict.example
6472 *.2250.dates.fict.example
6473 *.dates.fict.example
6476 As soon as one key in the sequence is successfully looked up, the lookup
6479 .cindex "lookup" "partial matching &-- changing prefix"
6480 .cindex "prefix" "for partial matching"
6481 The use of &"*."& as the partial matching prefix is a default that can be
6482 changed. The motivation for this feature is to allow Exim to operate with file
6483 formats that are used by other MTAs. A different prefix can be supplied in
6484 parentheses instead of the hyphen after &"partial"&. For example:
6486 domains = partial(.)lsearch;/some/file
6488 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6489 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6490 components is unchanged). The prefix may consist of any punctuation characters
6491 other than a closing parenthesis. It may be empty, for example:
6493 domains = partial1()cdb;/some/file
6495 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6496 &`a.b.c`&, &`b.c`&, and &`c`&.
6498 If &"partial0"& is specified, what happens at the end (when the lookup with
6499 just one non-wild component has failed, and the original key is shortened right
6500 down to the null string) depends on the prefix:
6503 If the prefix has zero length, the whole lookup fails.
6505 If the prefix has length 1, a lookup for just the prefix is done. For
6506 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6508 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6509 remainder is looked up. With the default prefix, therefore, the final lookup is
6510 for &"*"& on its own.
6512 Otherwise, the whole prefix is looked up.
6516 If the search type ends in &"*"& or &"*@"& (see section
6517 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6518 this implies happens after all partial lookups have failed. If &"partial0"& is
6519 specified, adding &"*"& to the search type has no effect with the default
6520 prefix, because the &"*"& key is already included in the sequence of partial
6521 lookups. However, there might be a use for lookup types such as
6522 &"partial0(.)lsearch*"&.
6524 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6525 in domain lists and the like. Partial matching works only in terms of
6526 dot-separated components; a key such as &`*fict.example`&
6527 in a database file is useless, because the asterisk in a partial matching
6528 subject key is always followed by a dot.
6533 .section "Lookup caching" "SECID64"
6534 .cindex "lookup" "caching"
6535 .cindex "caching" "lookup data"
6536 Exim caches all lookup results in order to avoid needless repetition of
6537 lookups. However, because (apart from the daemon) Exim operates as a collection
6538 of independent, short-lived processes, this caching applies only within a
6539 single Exim process. There is no inter-process lookup caching facility.
6541 For single-key lookups, Exim keeps the relevant files open in case there is
6542 another lookup that needs them. In some types of configuration this can lead to
6543 many files being kept open for messages with many recipients. To avoid hitting
6544 the operating system limit on the number of simultaneously open files, Exim
6545 closes the least recently used file when it needs to open more files than its
6546 own internal limit, which can be changed via the &%lookup_open_max%& option.
6548 The single-key lookup files are closed and the lookup caches are flushed at
6549 strategic points during delivery &-- for example, after all routing is
6555 .section "Quoting lookup data" "SECID65"
6556 .cindex "lookup" "quoting"
6557 .cindex "quoting" "in lookups"
6558 When data from an incoming message is included in a query-style lookup, there
6559 is the possibility of special characters in the data messing up the syntax of
6560 the query. For example, a NIS+ query that contains
6564 will be broken if the local part happens to contain a closing square bracket.
6565 For NIS+, data can be enclosed in double quotes like this:
6567 [name="$local_part"]
6569 but this still leaves the problem of a double quote in the data. The rule for
6570 NIS+ is that double quotes must be doubled. Other lookup types have different
6571 rules, and to cope with the differing requirements, an expansion operator
6572 of the following form is provided:
6574 ${quote_<lookup-type>:<string>}
6576 For example, the safest way to write the NIS+ query is
6578 [name="${quote_nisplus:$local_part}"]
6580 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6581 operator can be used for all lookup types, but has no effect for single-key
6582 lookups, since no quoting is ever needed in their key strings.
6587 .section "More about dnsdb" "SECTdnsdb"
6588 .cindex "dnsdb lookup"
6589 .cindex "lookup" "dnsdb"
6590 .cindex "DNS" "as a lookup type"
6591 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
6592 of a record type and a domain name, separated by an equals sign. For example,
6593 an expansion string could contain:
6595 ${lookup dnsdb{mx=a.b.example}{$value}fail}
6597 If the lookup succeeds, the result is placed in &$value$&, which in this case
6598 is used on its own as the result. If the lookup does not succeed, the
6599 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
6600 &<<SECTforexpfai>>& for an explanation of what this means.
6602 The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and,
6603 when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
6604 configured). If no type is given, TXT is assumed. When the type is PTR,
6605 the data can be an IP address, written as normal; inversion and the addition of
6606 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
6608 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
6610 If the data for a PTR record is not a syntactically valid IP address, it is not
6611 altered and nothing is added.
6613 .cindex "MX record" "in &(dnsdb)& lookup"
6614 .cindex "SRV record" "in &(dnsdb)& lookup"
6615 For an MX lookup, both the preference value and the host name are returned for
6616 each record, separated by a space. For an SRV lookup, the priority, weight,
6617 port, and host name are returned for each record, separated by spaces.
6619 For any record type, if multiple records are found (or, for A6 lookups, if a
6620 single record leads to multiple addresses), the data is returned as a
6621 concatenation, with newline as the default separator. The order, of course,
6622 depends on the DNS resolver. You can specify a different separator character
6623 between multiple records by putting a right angle-bracket followed immediately
6624 by the new separator at the start of the query. For example:
6626 ${lookup dnsdb{>: a=host1.example}}
6628 It is permitted to specify a space as the separator character. Further
6629 white space is ignored.
6631 .section "Pseudo dnsdb record types" "SECID66"
6632 .cindex "MX record" "in &(dnsdb)& lookup"
6633 By default, both the preference value and the host name are returned for
6634 each MX record, separated by a space. If you want only host names, you can use
6635 the pseudo-type MXH:
6637 ${lookup dnsdb{mxh=a.b.example}}
6639 In this case, the preference values are omitted, and just the host names are
6642 .cindex "name server for enclosing domain"
6643 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
6644 records on the given domain, but if none are found, it removes the first
6645 component of the domain name, and tries again. This process continues until NS
6646 records are found or there are no more components left (or there is a DNS
6647 error). In other words, it may return the name servers for a top-level domain,
6648 but it never returns the root name servers. If there are no NS records for the
6649 top-level domain, the lookup fails. Consider these examples:
6651 ${lookup dnsdb{zns=xxx.quercite.com}}
6652 ${lookup dnsdb{zns=xxx.edu}}
6654 Assuming that in each case there are no NS records for the full domain name,
6655 the first returns the name servers for &%quercite.com%&, and the second returns
6656 the name servers for &%edu%&.
6658 You should be careful about how you use this lookup because, unless the
6659 top-level domain does not exist, the lookup always returns some host names. The
6660 sort of use to which this might be put is for seeing if the name servers for a
6661 given domain are on a blacklist. You can probably assume that the name servers
6662 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
6665 .cindex "CSA" "in &(dnsdb)& lookup"
6666 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
6667 records according to the CSA rules, which are described in section
6668 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
6669 not sufficient because of the extra parent domain search behaviour of CSA. The
6670 result of a successful lookup such as:
6672 ${lookup dnsdb {csa=$sender_helo_name}}
6674 has two space-separated fields: an authorization code and a target host name.
6675 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
6676 authorization required but absent, or &"?"& for unknown.
6679 .section "Multiple dnsdb lookups" "SECID67"
6680 In the previous sections, &(dnsdb)& lookups for a single domain are described.
6681 However, you can specify a list of domains or IP addresses in a single
6682 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
6683 the default separator, but with the ability to change this. For example:
6685 ${lookup dnsdb{one.domain.com:two.domain.com}}
6686 ${lookup dnsdb{a=one.host.com:two.host.com}}
6687 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
6689 In order to retain backwards compatibility, there is one special case: if
6690 the lookup type is PTR and no change of separator is specified, Exim looks
6691 to see if the rest of the string is precisely one IPv6 address. In this
6692 case, it does not treat it as a list.
6694 The data from each lookup is concatenated, with newline separators by default,
6695 in the same way that multiple DNS records for a single item are handled. A
6696 different separator can be specified, as described above.
6698 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
6699 temporary DNS error for any of them, the behaviour is controlled by
6700 an optional keyword followed by a comma that may appear before the record
6701 type. The possible keywords are &"defer_strict"&, &"defer_never"&, and
6702 &"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the
6703 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
6704 ignored, and the behaviour is as if the DNS lookup failed to find anything.
6705 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
6706 error causes the whole lookup to defer only if none of the other lookups
6707 succeed. The default is &"lax"&, so the following lookups are equivalent:
6709 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
6710 ${lookup dnsdb{a=one.host.com:two.host.com}}
6712 Thus, in the default case, as long as at least one of the DNS lookups
6713 yields some data, the lookup succeeds.
6718 .section "More about LDAP" "SECTldap"
6719 .cindex "LDAP" "lookup, more about"
6720 .cindex "lookup" "LDAP"
6721 .cindex "Solaris" "LDAP"
6722 The original LDAP implementation came from the University of Michigan; this has
6723 become &"Open LDAP"&, and there are now two different releases. Another
6724 implementation comes from Netscape, and Solaris 7 and subsequent releases
6725 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
6726 the lookup function level, their error handling is different. For this reason
6727 it is necessary to set a compile-time variable when building Exim with LDAP, to
6728 indicate which LDAP library is in use. One of the following should appear in
6729 your &_Local/Makefile_&:
6731 LDAP_LIB_TYPE=UMICHIGAN
6732 LDAP_LIB_TYPE=OPENLDAP1
6733 LDAP_LIB_TYPE=OPENLDAP2
6734 LDAP_LIB_TYPE=NETSCAPE
6735 LDAP_LIB_TYPE=SOLARIS
6737 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
6738 same interface as the University of Michigan version.
6740 There are three LDAP lookup types in Exim. These behave slightly differently in
6741 the way they handle the results of a query:
6744 &(ldap)& requires the result to contain just one entry; if there are more, it
6747 &(ldapdn)& also requires the result to contain just one entry, but it is the
6748 Distinguished Name that is returned rather than any attribute values.
6750 &(ldapm)& permits the result to contain more than one entry; the attributes
6751 from all of them are returned.
6755 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
6756 Exim behaves as if the entry did not exist, and the lookup fails. The format of
6757 the data returned by a successful lookup is described in the next section.
6758 First we explain how LDAP queries are coded.
6761 .section "Format of LDAP queries" "SECTforldaque"
6762 .cindex "LDAP" "query format"
6763 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
6764 the configuration of a &(redirect)& router one might have this setting:
6766 data = ${lookup ldap \
6767 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
6768 c=UK?mailbox?base?}}
6770 .cindex "LDAP" "with TLS"
6771 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
6772 secure (encrypted) LDAP connections. The second of these ensures that an
6773 encrypted TLS connection is used.
6776 .section "LDAP quoting" "SECID68"
6777 .cindex "LDAP" "quoting"
6778 Two levels of quoting are required in LDAP queries, the first for LDAP itself
6779 and the second because the LDAP query is represented as a URL. Furthermore,
6780 within an LDAP query, two different kinds of quoting are required. For this
6781 reason, there are two different LDAP-specific quoting operators.
6783 The &%quote_ldap%& operator is designed for use on strings that are part of
6784 filter specifications. Conceptually, it first does the following conversions on
6792 in accordance with RFC 2254. The resulting string is then quoted according
6793 to the rules for URLs, that is, all non-alphanumeric characters except
6797 are converted to their hex values, preceded by a percent sign. For example:
6799 ${quote_ldap: a(bc)*, a<yz>; }
6803 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
6805 Removing the URL quoting, this is (with a leading and a trailing space):
6807 a\28bc\29\2A, a<yz>;
6809 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
6810 base DN specifications in queries. Conceptually, it first converts the string
6811 by inserting a backslash in front of any of the following characters:
6815 It also inserts a backslash before any leading spaces or # characters, and
6816 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
6817 is then quoted according to the rules for URLs. For example:
6819 ${quote_ldap_dn: a(bc)*, a<yz>; }
6823 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
6825 Removing the URL quoting, this is (with a trailing space):
6827 \ a(bc)*\, a\<yz\>\;\
6829 There are some further comments about quoting in the section on LDAP
6830 authentication below.
6833 .section "LDAP connections" "SECID69"
6834 .cindex "LDAP" "connections"
6835 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
6836 is in use, via a Unix domain socket. The example given above does not specify
6837 an LDAP server. A server that is reached by TCP/IP can be specified in a query
6840 ldap://<hostname>:<port>/...
6842 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
6843 used. When no server is specified in a query, a list of default servers is
6844 taken from the &%ldap_default_servers%& configuration option. This supplies a
6845 colon-separated list of servers which are tried in turn until one successfully
6846 handles a query, or there is a serious error. Successful handling either
6847 returns the requested data, or indicates that it does not exist. Serious errors
6848 are syntactical, or multiple values when only a single value is expected.
6849 Errors which cause the next server to be tried are connection failures, bind
6850 failures, and timeouts.
6852 For each server name in the list, a port number can be given. The standard way
6853 of specifying a host and port is to use a colon separator (RFC 1738). Because
6854 &%ldap_default_servers%& is a colon-separated list, such colons have to be
6855 doubled. For example
6857 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
6859 If &%ldap_default_servers%& is unset, a URL with no server name is passed
6860 to the LDAP library with no server name, and the library's default (normally
6861 the local host) is used.
6863 If you are using the OpenLDAP library, you can connect to an LDAP server using
6864 a Unix domain socket instead of a TCP/IP connection. This is specified by using
6865 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
6866 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
6869 For this type of connection, instead of a host name for the server, a pathname
6870 for the socket is required, and the port number is not relevant. The pathname
6871 can be specified either as an item in &%ldap_default_servers%&, or inline in
6872 the query. In the former case, you can have settings such as
6874 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
6876 When the pathname is given in the query, you have to escape the slashes as
6877 &`%2F`& to fit in with the LDAP URL syntax. For example:
6879 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
6881 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
6882 a pathname, it uses the Unix domain socket code, even if the query actually
6883 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
6884 socket connection. This behaviour means that you can use a setting of
6885 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
6886 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
6887 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
6890 If an explicit &`ldapi`& type is given in a query when a host name is
6891 specified, an error is diagnosed. However, if there are more items in
6892 &%ldap_default_servers%&, they are tried. In other words:
6895 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
6898 Using &`ldapi`& with a host name causes an error.
6902 Using &`ldapi`& with no host or path in the query, and no setting of
6903 &%ldap_default_servers%&, does whatever the library does by default.
6907 .section "LDAP authentication and control information" "SECID70"
6908 .cindex "LDAP" "authentication"
6909 The LDAP URL syntax provides no way of passing authentication and other control
6910 information to the server. To make this possible, the URL in an LDAP query may
6911 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
6912 spaces. If a value contains spaces it must be enclosed in double quotes, and
6913 when double quotes are used, backslash is interpreted in the usual way inside
6914 them. The following names are recognized:
6916 &`DEREFERENCE`& set the dereferencing parameter
6917 &`NETTIME `& set a timeout for a network operation
6918 &`USER `& set the DN, for authenticating the LDAP bind
6919 &`PASS `& set the password, likewise
6920 &`REFERRALS `& set the referrals parameter
6921 &`SIZE `& set the limit for the number of entries returned
6922 &`TIME `& set the maximum waiting time for a query
6924 The value of the DEREFERENCE parameter must be one of the words &"never"&,
6925 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
6926 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
6927 library from trying to follow referrals issued by the LDAP server.
6929 The name CONNECT is an obsolete name for NETTIME, retained for
6930 backwards compatibility. This timeout (specified as a number of seconds) is
6931 enforced from the client end for operations that can be carried out over a
6932 network. Specifically, it applies to network connections and calls to the
6933 &'ldap_result()'& function. If the value is greater than zero, it is used if
6934 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
6935 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
6936 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
6937 Netscape SDK; for OpenLDAP no action is taken.
6939 The TIME parameter (also a number of seconds) is passed to the server to
6940 set a server-side limit on the time taken to complete a search.
6943 Here is an example of an LDAP query in an Exim lookup that uses some of these
6944 values. This is a single line, folded to fit on the page:
6947 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
6948 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
6951 The encoding of spaces as &`%20`& is a URL thing which should not be done for
6952 any of the auxiliary data. Exim configuration settings that include lookups
6953 which contain password information should be preceded by &"hide"& to prevent
6954 non-admin users from using the &%-bP%& option to see their values.
6956 The auxiliary data items may be given in any order. The default is no
6957 connection timeout (the system timeout is used), no user or password, no limit
6958 on the number of entries returned, and no time limit on queries.
6960 When a DN is quoted in the USER= setting for LDAP authentication, Exim
6961 removes any URL quoting that it may contain before passing it LDAP. Apparently
6962 some libraries do this for themselves, but some do not. Removing the URL
6963 quoting has two advantages:
6966 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
6967 DNs as with DNs inside actual queries.
6969 It permits spaces inside USER= DNs.
6972 For example, a setting such as
6974 USER=cn=${quote_ldap_dn:$1}
6976 should work even if &$1$& contains spaces.
6978 Expanded data for the PASS= value should be quoted using the &%quote%&
6979 expansion operator, rather than the LDAP quote operators. The only reason this
6980 field needs quoting is to ensure that it conforms to the Exim syntax, which
6981 does not allow unquoted spaces. For example:
6985 The LDAP authentication mechanism can be used to check passwords as part of
6986 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
6991 .section "Format of data returned by LDAP" "SECID71"
6992 .cindex "LDAP" "returned data formats"
6993 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
6994 as a sequence of values, for example
6996 cn=manager, o=University of Cambridge, c=UK
6998 The &(ldap)& lookup type generates an error if more than one entry matches the
6999 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7000 the result between the data from different entries. It is possible for multiple
7001 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7002 you know that whatever values are returned all came from a single entry in the
7005 In the common case where you specify a single attribute in your LDAP query, the
7006 result is not quoted, and does not contain the attribute name. If the attribute
7007 has multiple values, they are separated by commas.
7009 If you specify multiple attributes, the result contains space-separated, quoted
7010 strings, each preceded by the attribute name and an equals sign. Within the
7011 quotes, the quote character, backslash, and newline are escaped with
7012 backslashes, and commas are used to separate multiple values for the attribute.
7013 Apart from the escaping, the string within quotes takes the same form as the
7014 output when a single attribute is requested. Specifying no attributes is the
7015 same as specifying all of an entry's attributes.
7017 Here are some examples of the output format. The first line of each pair is an
7018 LDAP query, and the second is the data that is returned. The attribute called
7019 &%attr1%& has two values, whereas &%attr2%& has only one value:
7021 ldap:///o=base?attr1?sub?(uid=fred)
7024 ldap:///o=base?attr2?sub?(uid=fred)
7027 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7028 attr1="value1.1, value1.2" attr2="value two"
7030 ldap:///o=base??sub?(uid=fred)
7031 objectClass="top" attr1="value1.1, value1.2" attr2="value two"
7033 The &%extract%& operator in string expansions can be used to pick out
7034 individual fields from data that consists of &'key'&=&'value'& pairs. You can
7035 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7036 results of LDAP lookups.
7041 .section "More about NIS+" "SECTnisplus"
7042 .cindex "NIS+ lookup type"
7043 .cindex "lookup" "NIS+"
7044 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7045 and field name. If this is given, the result of a successful query is the
7046 contents of the named field; otherwise the result consists of a concatenation
7047 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7048 values containing spaces are quoted. For example, the query
7050 [name=mg1456],passwd.org_dir
7052 might return the string
7054 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7055 home=/home/mg1456 shell=/bin/bash shadow=""
7057 (split over two lines here to fit on the page), whereas
7059 [name=mg1456],passwd.org_dir:gcos
7065 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7066 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7067 operator is to double any quote characters within the text.
7071 .section "SQL lookups" "SECTsql"
7072 .cindex "SQL lookup types"
7073 .cindex "MySQL" "lookup type"
7074 .cindex "PostgreSQL lookup type"
7075 .cindex "lookup" "MySQL"
7076 .cindex "lookup" "PostgreSQL"
7077 .cindex "Oracle" "lookup type"
7078 .cindex "lookup" "Oracle"
7079 .cindex "InterBase lookup type"
7080 .cindex "lookup" "InterBase"
7081 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite
7082 databases. Queries for these databases contain SQL statements, so an example
7085 ${lookup mysql{select mailbox from users where id='userx'}\
7088 If the result of the query contains more than one field, the data for each
7089 field in the row is returned, preceded by its name, so the result of
7091 ${lookup pgsql{select home,name from users where id='userx'}\
7096 home=/home/userx name="Mister X"
7098 Empty values and values containing spaces are double quoted, with embedded
7099 quotes escaped by a backslash. If the result of the query contains just one
7100 field, the value is passed back verbatim, without a field name, for example:
7104 If the result of the query yields more than one row, it is all concatenated,
7105 with a newline between the data for each row.
7108 .section "More about MySQL, PostgreSQL, Oracle, and InterBase" "SECID72"
7109 .cindex "MySQL" "lookup type"
7110 .cindex "PostgreSQL lookup type"
7111 .cindex "lookup" "MySQL"
7112 .cindex "lookup" "PostgreSQL"
7113 .cindex "Oracle" "lookup type"
7114 .cindex "lookup" "Oracle"
7115 .cindex "InterBase lookup type"
7116 .cindex "lookup" "InterBase"
7117 If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the
7118 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%&
7119 option (as appropriate) must be set to a colon-separated list of server
7121 (For MySQL and PostgreSQL only, the global option need not be set if all
7122 queries contain their own server information &-- see section
7123 &<<SECTspeserque>>&.) Each item in the list is a slash-separated list of four
7124 items: host name, database name, user name, and password. In the case of
7125 Oracle, the host name field is used for the &"service name"&, and the database
7126 name field is not used and should be empty. For example:
7128 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7130 Because password data is sensitive, you should always precede the setting with
7131 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7132 option. Here is an example where two MySQL servers are listed:
7134 hide mysql_servers = localhost/users/root/secret:\
7135 otherhost/users/root/othersecret
7137 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7138 because this is a colon-separated list, the colon has to be doubled. For each
7139 query, these parameter groups are tried in order until a connection is made and
7140 a query is successfully processed. The result of a query may be that no data is
7141 found, but that is still a successful query. In other words, the list of
7142 servers provides a backup facility, not a list of different places to look.
7144 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7145 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7146 respectively, and the characters single-quote, double-quote, and backslash
7147 itself are escaped with backslashes. The &%quote_pgsql%& expansion operator, in
7148 addition, escapes the percent and underscore characters. This cannot be done
7149 for MySQL because these escapes are not recognized in contexts where these
7150 characters are not special.
7152 .section "Specifying the server in the query" "SECTspeserque"
7153 For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase),
7154 it is possible to specify a list of servers with an individual query. This is
7155 done by starting the query with
7157 &`servers=`&&'server1:server2:server3:...'&&`;`&
7159 Each item in the list may take one of two forms:
7161 If it contains no slashes it is assumed to be just a host name. The appropriate
7162 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7163 of the same name, and the remaining parameters (database, user, password) are
7166 If it contains any slashes, it is taken as a complete parameter set.
7168 The list of servers is used in exactly the same way as the global list.
7169 Once a connection to a server has happened and a query has been
7170 successfully executed, processing of the lookup ceases.
7172 This feature is intended for use in master/slave situations where updates
7173 are occurring and you want to update the master rather than a slave. If the
7174 master is in the list as a backup for reading, you might have a global setting
7177 mysql_servers = slave1/db/name/pw:\
7181 In an updating lookup, you could then write:
7183 ${lookup mysql{servers=master; UPDATE ...} }
7185 That query would then be sent only to the master server. If, on the other hand,
7186 the master is not to be used for reading, and so is not present in the global
7187 option, you can still update it by a query of this form:
7189 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7193 .section "Special MySQL features" "SECID73"
7194 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7195 causes a connection to the server on the local host by means of a Unix domain
7196 socket. An alternate socket can be specified in parentheses. The full syntax of
7197 each item in &%mysql_servers%& is:
7199 <&'hostname'&>::<&'port'&>(<&'socket name'&>)/<&'database'&>/&&&
7200 <&'user'&>/<&'password'&>
7202 Any of the three sub-parts of the first field can be omitted. For normal use on
7203 the local host it can be left blank or set to just &"localhost"&.
7205 No database need be supplied &-- but if it is absent here, it must be given in
7208 If a MySQL query is issued that does not request any data (an insert, update,
7209 or delete command), the result of the lookup is the number of rows affected.
7211 &*Warning*&: This can be misleading. If an update does not actually change
7212 anything (for example, setting a field to the value it already has), the result
7213 is zero because no rows are affected.
7216 .section "Special PostgreSQL features" "SECID74"
7217 PostgreSQL lookups can also use Unix domain socket connections to the database.
7218 This is usually faster and costs less CPU time than a TCP/IP connection.
7219 However it can be used only if the mail server runs on the same machine as the
7220 database server. A configuration line for PostgreSQL via Unix domain sockets
7223 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7225 In other words, instead of supplying a host name, a path to the socket is
7226 given. The path name is enclosed in parentheses so that its slashes aren't
7227 visually confused with the delimiters for the other server parameters.
7229 If a PostgreSQL query is issued that does not request any data (an insert,
7230 update, or delete command), the result of the lookup is the number of rows
7233 .section "More about SQLite" "SECTsqlite"
7234 .cindex "lookup" "SQLite"
7235 .cindex "sqlite lookup type"
7236 SQLite is different to the other SQL lookups because a file name is required in
7237 addition to the SQL query. An SQLite database is a single file, and there is no
7238 daemon as in the other SQL databases. The interface to Exim requires the name
7239 of the file, as an absolute path, to be given at the start of the query. It is
7240 separated from the query by white space. This means that the path name cannot
7241 contain white space. Here is a lookup expansion example:
7243 ${lookup sqlite {/some/thing/sqlitedb \
7244 select name from aliases where id='userx';}}
7246 In a list, the syntax is similar. For example:
7248 domainlist relay_domains = sqlite;/some/thing/sqlitedb \
7249 select * from relays where ip='$sender_host_address';
7251 The only character affected by the &%quote_sqlite%& operator is a single
7252 quote, which it doubles.
7254 The SQLite library handles multiple simultaneous accesses to the database
7255 internally. Multiple readers are permitted, but only one process can
7256 update at once. Attempts to access the database while it is being updated
7257 are rejected after a timeout period, during which the SQLite library
7258 waits for the lock to be released. In Exim, the default timeout is set
7259 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7265 . ////////////////////////////////////////////////////////////////////////////
7266 . ////////////////////////////////////////////////////////////////////////////
7268 .chapter "Domain, host, address, and local part lists" &&&
7269 "CHAPdomhosaddlists" &&&
7270 "Domain, host, and address lists"
7271 .scindex IIDdohoadli "lists of domains; hosts; etc."
7272 A number of Exim configuration options contain lists of domains, hosts,
7273 email addresses, or local parts. For example, the &%hold_domains%& option
7274 contains a list of domains whose delivery is currently suspended. These lists
7275 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7276 arguments to expansion conditions such as &%match_domain%&.
7278 Each item in one of these lists is a pattern to be matched against a domain,
7279 host, email address, or local part, respectively. In the sections below, the
7280 different types of pattern for each case are described, but first we cover some
7281 general facilities that apply to all four kinds of list.
7285 .section "Expansion of lists" "SECID75"
7286 .cindex "expansion" "of lists"
7287 Each list is expanded as a single string before it is used. The result of
7288 expansion must be a list, possibly containing empty items, which is split up
7289 into separate items for matching. By default, colon is the separator character,
7290 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7291 &<<SECTempitelis>>& for details of the list syntax; the second of these
7292 discusses the way to specify empty list items.
7295 If the string expansion is forced to fail, Exim behaves as if the item it is
7296 testing (domain, host, address, or local part) is not in the list. Other
7297 expansion failures cause temporary errors.
7299 If an item in a list is a regular expression, backslashes, dollars and possibly
7300 other special characters in the expression must be protected against
7301 misinterpretation by the string expander. The easiest way to do this is to use
7302 the &`\N`& expansion feature to indicate that the contents of the regular
7303 expression should not be expanded. For example, in an ACL you might have:
7305 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7306 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7308 The first item is a regular expression that is protected from expansion by
7309 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7310 senders based on the receiving domain.
7315 .section "Negated items in lists" "SECID76"
7316 .cindex "list" "negation"
7317 .cindex "negation" "in lists"
7318 Items in a list may be positive or negative. Negative items are indicated by a
7319 leading exclamation mark, which may be followed by optional white space. A list
7320 defines a set of items (domains, etc). When Exim processes one of these lists,
7321 it is trying to find out whether a domain, host, address, or local part
7322 (respectively) is in the set that is defined by the list. It works like this:
7324 The list is scanned from left to right. If a positive item is matched, the
7325 subject that is being checked is in the set; if a negative item is matched, the
7326 subject is not in the set. If the end of the list is reached without the
7327 subject having matched any of the patterns, it is in the set if the last item
7328 was a negative one, but not if it was a positive one. For example, the list in
7330 domainlist relay_domains = !a.b.c : *.b.c
7332 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7333 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7334 list is positive. However, if the setting were
7336 domainlist relay_domains = !a.b.c
7338 then all domains other than &'a.b.c'& would match because the last item in the
7339 list is negative. In other words, a list that ends with a negative item behaves
7340 as if it had an extra item &`:*`& on the end.
7342 Another way of thinking about positive and negative items in lists is to read
7343 the connector as &"or"& after a positive item and as &"and"& after a negative
7348 .section "File names in lists" "SECTfilnamlis"
7349 .cindex "list" "file name in"
7350 If an item in a domain, host, address, or local part list is an absolute file
7351 name (beginning with a slash character), each line of the file is read and
7352 processed as if it were an independent item in the list, except that further
7353 file names are not allowed,
7354 and no expansion of the data from the file takes place.
7355 Empty lines in the file are ignored, and the file may also contain comment
7359 For domain and host lists, if a # character appears anywhere in a line of the
7360 file, it and all following characters are ignored.
7362 Because local parts may legitimately contain # characters, a comment in an
7363 address list or local part list file is recognized only if # is preceded by
7364 white space or the start of the line. For example:
7366 not#comment@x.y.z # but this is a comment
7370 Putting a file name in a list has the same effect as inserting each line of the
7371 file as an item in the list (blank lines and comments excepted). However, there
7372 is one important difference: the file is read each time the list is processed,
7373 so if its contents vary over time, Exim's behaviour changes.
7375 If a file name is preceded by an exclamation mark, the sense of any match
7376 within the file is inverted. For example, if
7378 hold_domains = !/etc/nohold-domains
7380 and the file contains the lines
7385 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7386 any domain matching &`*.b.c`& is not.
7390 .section "An lsearch file is not an out-of-line list" "SECID77"
7391 As will be described in the sections that follow, lookups can be used in lists
7392 to provide indexed methods of checking list membership. There has been some
7393 confusion about the way &(lsearch)& lookups work in lists. Because
7394 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7395 sometimes thought that it is allowed to contain wild cards and other kinds of
7396 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7397 always fixed strings, just as for any other single-key lookup type.
7399 If you want to use a file to contain wild-card patterns that form part of a
7400 list, just give the file name on its own, without a search type, as described
7401 in the previous section. You could also use the &(wildlsearch)& or
7402 &(nwildlsearch)&, but there is no advantage in doing this.
7407 .section "Named lists" "SECTnamedlists"
7408 .cindex "named lists"
7409 .cindex "list" "named"
7410 A list of domains, hosts, email addresses, or local parts can be given a name
7411 which is then used to refer to the list elsewhere in the configuration. This is
7412 particularly convenient if the same list is required in several different
7413 places. It also allows lists to be given meaningful names, which can improve
7414 the readability of the configuration. For example, it is conventional to define
7415 a domain list called &'local_domains'& for all the domains that are handled
7416 locally on a host, using a configuration line such as
7418 domainlist local_domains = localhost:my.dom.example
7420 Named lists are referenced by giving their name preceded by a plus sign, so,
7421 for example, a router that is intended to handle local domains would be
7422 configured with the line
7424 domains = +local_domains
7426 The first router in a configuration is often one that handles all domains
7427 except the local ones, using a configuration with a negated item like this:
7431 domains = ! +local_domains
7432 transport = remote_smtp
7435 The four kinds of named list are created by configuration lines starting with
7436 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
7437 respectively. Then there follows the name that you are defining, followed by an
7438 equals sign and the list itself. For example:
7440 hostlist relay_hosts = 192.168.23.0/24 : my.friend.example
7441 addresslist bad_senders = cdb;/etc/badsenders
7443 A named list may refer to other named lists:
7445 domainlist dom1 = first.example : second.example
7446 domainlist dom2 = +dom1 : third.example
7447 domainlist dom3 = fourth.example : +dom2 : fifth.example
7449 &*Warning*&: If the last item in a referenced list is a negative one, the
7450 effect may not be what you intended, because the negation does not propagate
7451 out to the higher level. For example, consider:
7453 domainlist dom1 = !a.b
7454 domainlist dom2 = +dom1 : *.b
7456 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
7457 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
7458 means it matches the second list as well. The effect is not the same as
7460 domainlist dom2 = !a.b : *.b
7462 where &'x.y'& does not match. It's best to avoid negation altogether in
7463 referenced lists if you can.
7465 Named lists may have a performance advantage. When Exim is routing an
7466 address or checking an incoming message, it caches the result of tests on named
7467 lists. So, if you have a setting such as
7469 domains = +local_domains
7471 on several of your routers
7472 or in several ACL statements,
7473 the actual test is done only for the first one. However, the caching works only
7474 if there are no expansions within the list itself or any sublists that it
7475 references. In other words, caching happens only for lists that are known to be
7476 the same each time they are referenced.
7478 By default, there may be up to 16 named lists of each type. This limit can be
7479 extended by changing a compile-time variable. The use of domain and host lists
7480 is recommended for concepts such as local domains, relay domains, and relay
7481 hosts. The default configuration is set up like this.
7485 .section "Named lists compared with macros" "SECID78"
7486 .cindex "list" "named compared with macro"
7487 .cindex "macro" "compared with named list"
7488 At first sight, named lists might seem to be no different from macros in the
7489 configuration file. However, macros are just textual substitutions. If you
7492 ALIST = host1 : host2
7493 auth_advertise_hosts = !ALIST
7495 it probably won't do what you want, because that is exactly the same as
7497 auth_advertise_hosts = !host1 : host2
7499 Notice that the second host name is not negated. However, if you use a host
7502 hostlist alist = host1 : host2
7503 auth_advertise_hosts = ! +alist
7505 the negation applies to the whole list, and so that is equivalent to
7507 auth_advertise_hosts = !host1 : !host2
7511 .section "Named list caching" "SECID79"
7512 .cindex "list" "caching of named"
7513 .cindex "caching" "named lists"
7514 While processing a message, Exim caches the result of checking a named list if
7515 it is sure that the list is the same each time. In practice, this means that
7516 the cache operates only if the list contains no $ characters, which guarantees
7517 that it will not change when it is expanded. Sometimes, however, you may have
7518 an expanded list that you know will be the same each time within a given
7519 message. For example:
7521 domainlist special_domains = \
7522 ${lookup{$sender_host_address}cdb{/some/file}}
7524 This provides a list of domains that depends only on the sending host's IP
7525 address. If this domain list is referenced a number of times (for example,
7526 in several ACL lines, or in several routers) the result of the check is not
7527 cached by default, because Exim does not know that it is going to be the
7528 same list each time.
7530 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
7531 cache the result anyway. For example:
7533 domainlist_cache special_domains = ${lookup{...
7535 If you do this, you should be absolutely sure that caching is going to do
7536 the right thing in all cases. When in doubt, leave it out.
7540 .section "Domain lists" "SECTdomainlist"
7541 .cindex "domain list" "patterns for"
7542 .cindex "list" "domain list"
7543 Domain lists contain patterns that are to be matched against a mail domain.
7544 The following types of item may appear in domain lists:
7547 .cindex "primary host name"
7548 .cindex "host name" "matched in domain list"
7549 .oindex "&%primary_hostname%&"
7550 .cindex "domain list" "matching primary host name"
7551 .cindex "@ in a domain list"
7552 If a pattern consists of a single @ character, it matches the local host name,
7553 as set by the &%primary_hostname%& option (or defaulted). This makes it
7554 possible to use the same configuration file on several different hosts that
7555 differ only in their names.
7557 .cindex "@[] in a domain list"
7558 .cindex "domain list" "matching local IP interfaces"
7559 .cindex "domain literal"
7560 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
7561 in square brackets (as in an email address that contains a domain literal), but
7562 only if that IP address is recognized as local for email routing purposes. The
7563 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
7564 control which of a host's several IP addresses are treated as local.
7565 In today's Internet, the use of domain literals is controversial.
7568 .cindex "@mx_primary"
7569 .cindex "@mx_secondary"
7570 .cindex "domain list" "matching MX pointers to local host"
7571 If a pattern consists of the string &`@mx_any`& it matches any domain that
7572 has an MX record pointing to the local host or to any host that is listed in
7573 .oindex "&%hosts_treat_as_local%&"
7574 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
7575 are similar, except that the first matches only when a primary MX target is the
7576 local host, and the second only when no primary MX target is the local host,
7577 but a secondary MX target is. &"Primary"& means an MX record with the lowest
7578 preference value &-- there may of course be more than one of them.
7580 The MX lookup that takes place when matching a pattern of this type is
7581 performed with the resolver options for widening names turned off. Thus, for
7582 example, a single-component domain will &'not'& be expanded by adding the
7583 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
7584 options of the &(dnslookup)& router for a discussion of domain widening.
7586 Sometimes you may want to ignore certain IP addresses when using one of these
7587 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
7588 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
7589 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
7590 on a router). For example:
7592 domains = @mx_any/ignore=127.0.0.1
7594 This example matches any domain that has an MX record pointing to one of
7595 the local host's IP addresses other than 127.0.0.1.
7597 The list of IP addresses is in fact processed by the same code that processes
7598 host lists, so it may contain CIDR-coded network specifications and it may also
7599 contain negative items.
7601 Because the list of IP addresses is a sublist within a domain list, you have to
7602 be careful about delimiters if there is more than one address. Like any other
7603 list, the default delimiter can be changed. Thus, you might have:
7605 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
7606 an.other.domain : ...
7608 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
7609 involved, it is easiest to change the delimiter for the main list as well:
7611 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
7612 an.other.domain ? ...
7615 .cindex "asterisk" "in domain list"
7616 .cindex "domain list" "asterisk in"
7617 .cindex "domain list" "matching &""ends with""&"
7618 If a pattern starts with an asterisk, the remaining characters of the pattern
7619 are compared with the terminating characters of the domain. The use of &"*"& in
7620 domain lists differs from its use in partial matching lookups. In a domain
7621 list, the character following the asterisk need not be a dot, whereas partial
7622 matching works only in terms of dot-separated components. For example, a domain
7623 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
7627 .cindex "regular expressions" "in domain list"
7628 .cindex "domain list" "matching regular expression"
7629 If a pattern starts with a circumflex character, it is treated as a regular
7630 expression, and matched against the domain using a regular expression matching
7631 function. The circumflex is treated as part of the regular expression.
7632 Email domains are case-independent, so this regular expression match is by
7633 default case-independent, but you can make it case-dependent by starting it
7634 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
7635 are given in chapter &<<CHAPregexp>>&.
7637 &*Warning*&: Because domain lists are expanded before being processed, you
7638 must escape any backslash and dollar characters in the regular expression, or
7639 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
7640 it is not to be expanded (unless you really do want to build a regular
7641 expression by expansion, of course).
7643 .cindex "lookup" "in domain list"
7644 .cindex "domain list" "matching by lookup"
7645 If a pattern starts with the name of a single-key lookup type followed by a
7646 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
7647 must be a file name in a suitable format for the lookup type. For example, for
7648 &"cdb;"& it must be an absolute path:
7650 domains = cdb;/etc/mail/local_domains.cdb
7652 The appropriate type of lookup is done on the file using the domain name as the
7653 key. In most cases, the data that is looked up is not used; Exim is interested
7654 only in whether or not the key is present in the file. However, when a lookup
7655 is used for the &%domains%& option on a router
7656 or a &%domains%& condition in an ACL statement, the data is preserved in the
7657 &$domain_data$& variable and can be referred to in other router options or
7658 other statements in the same ACL.
7661 Any of the single-key lookup type names may be preceded by
7662 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
7664 domains = partial-dbm;/partial/domains
7666 This causes partial matching logic to be invoked; a description of how this
7667 works is given in section &<<SECTpartiallookup>>&.
7670 .cindex "asterisk" "in lookup type"
7671 Any of the single-key lookup types may be followed by an asterisk. This causes
7672 a default lookup for a key consisting of a single asterisk to be done if the
7673 original lookup fails. This is not a useful feature when using a domain list to
7674 select particular domains (because any domain would match), but it might have
7675 value if the result of the lookup is being used via the &$domain_data$&
7678 If the pattern starts with the name of a query-style lookup type followed by a
7679 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
7680 pattern must be an appropriate query for the lookup type, as described in
7681 chapter &<<CHAPfdlookup>>&. For example:
7683 hold_domains = mysql;select domain from holdlist \
7684 where domain = '$domain';
7686 In most cases, the data that is looked up is not used (so for an SQL query, for
7687 example, it doesn't matter what field you select). Exim is interested only in
7688 whether or not the query succeeds. However, when a lookup is used for the
7689 &%domains%& option on a router, the data is preserved in the &$domain_data$&
7690 variable and can be referred to in other options.
7692 .cindex "domain list" "matching literal domain name"
7693 If none of the above cases apply, a caseless textual comparison is made
7694 between the pattern and the domain.
7697 Here is an example that uses several different kinds of pattern:
7699 domainlist funny_domains = \
7702 *.foundation.fict.example : \
7703 \N^[1-2]\d{3}\.fict\.example$\N : \
7704 partial-dbm;/opt/data/penguin/book : \
7705 nis;domains.byname : \
7706 nisplus;[name=$domain,status=local],domains.org_dir
7708 There are obvious processing trade-offs among the various matching modes. Using
7709 an asterisk is faster than a regular expression, and listing a few names
7710 explicitly probably is too. The use of a file or database lookup is expensive,
7711 but may be the only option if hundreds of names are required. Because the
7712 patterns are tested in order, it makes sense to put the most commonly matched
7717 .section "Host lists" "SECThostlist"
7718 .cindex "host list" "patterns in"
7719 .cindex "list" "host list"
7720 Host lists are used to control what remote hosts are allowed to do. For
7721 example, some hosts may be allowed to use the local host as a relay, and some
7722 may be permitted to use the SMTP ETRN command. Hosts can be identified in
7723 two different ways, by name or by IP address. In a host list, some types of
7724 pattern are matched to a host name, and some are matched to an IP address.
7725 You need to be particularly careful with this when single-key lookups are
7726 involved, to ensure that the right value is being used as the key.
7729 .section "Special host list patterns" "SECID80"
7730 .cindex "empty item in hosts list"
7731 .cindex "host list" "empty string in"
7732 If a host list item is the empty string, it matches only when no remote host is
7733 involved. This is the case when a message is being received from a local
7734 process using SMTP on the standard input, that is, when a TCP/IP connection is
7737 .cindex "asterisk" "in host list"
7738 The special pattern &"*"& in a host list matches any host or no host. Neither
7739 the IP address nor the name is actually inspected.
7743 .section "Host list patterns that match by IP address" "SECThoslispatip"
7744 .cindex "host list" "matching IP addresses"
7745 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
7746 the incoming address actually appears in the IPv6 host as
7747 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
7748 list, it is converted into a traditional IPv4 address first. (Not all operating
7749 systems accept IPv4 calls on IPv6 sockets, as there have been some security
7752 The following types of pattern in a host list check the remote host by
7753 inspecting its IP address:
7756 If the pattern is a plain domain name (not a regular expression, not starting
7757 with *, not a lookup of any kind), Exim calls the operating system function
7758 to find the associated IP address(es). Exim uses the newer
7759 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
7760 This typically causes a forward DNS lookup of the name. The result is compared
7761 with the IP address of the subject host.
7763 If there is a temporary problem (such as a DNS timeout) with the host name
7764 lookup, a temporary error occurs. For example, if the list is being used in an
7765 ACL condition, the ACL gives a &"defer"& response, usually leading to a
7766 temporary SMTP error code. If no IP address can be found for the host name,
7767 what happens is described in section &<<SECTbehipnot>>& below.
7770 .cindex "@ in a host list"
7771 If the pattern is &"@"&, the primary host name is substituted and used as a
7772 domain name, as just described.
7775 If the pattern is an IP address, it is matched against the IP address of the
7776 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
7777 IPv6 addresses can be given in colon-separated format, but the colons have to
7778 be doubled so as not to be taken as item separators when the default list
7779 separator is used. IPv6 addresses are recognized even when Exim is compiled
7780 without IPv6 support. This means that if they appear in a host list on an
7781 IPv4-only host, Exim will not treat them as host names. They are just addresses
7782 that can never match a client host.
7785 .cindex "@[] in a host list"
7786 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
7787 the local host. For example, if the local host is an IPv4 host with one
7788 interface address 10.45.23.56, these two ACL statements have the same effect:
7790 accept hosts = 127.0.0.1 : 10.45.23.56
7794 .cindex "CIDR notation"
7795 If the pattern is an IP address followed by a slash and a mask length (for
7796 example 10.11.42.0/24), it is matched against the IP address of the subject
7797 host under the given mask. This allows, an entire network of hosts to be
7798 included (or excluded) by a single item. The mask uses CIDR notation; it
7799 specifies the number of address bits that must match, starting from the most
7800 significant end of the address.
7802 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
7803 of a range of addresses. It is the number of bits in the network portion of the
7804 address. The above example specifies a 24-bit netmask, so it matches all 256
7805 addresses in the 10.11.42.0 network. An item such as
7809 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
7810 32 for an IPv4 address is the same as no mask at all; just a single address
7813 Here is another example which shows an IPv4 and an IPv6 network:
7815 recipient_unqualified_hosts = 192.168.0.0/16: \
7816 3ffe::ffff::836f::::/48
7818 The doubling of list separator characters applies only when these items
7819 appear inline in a host list. It is not required when indirecting via a file.
7822 recipient_unqualified_hosts = /opt/exim/unqualnets
7824 could make use of a file containing
7829 to have exactly the same effect as the previous example. When listing IPv6
7830 addresses inline, it is usually more convenient to use the facility for
7831 changing separator characters. This list contains the same two networks:
7833 recipient_unqualified_hosts = <; 172.16.0.0/12; \
7836 The separator is changed to semicolon by the leading &"<;"& at the start of the
7842 .section "Host list patterns for single-key lookups by host address" &&&
7843 "SECThoslispatsikey"
7844 .cindex "host list" "lookup of IP address"
7845 When a host is to be identified by a single-key lookup of its complete IP
7846 address, the pattern takes this form:
7848 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7852 hosts_lookup = net-cdb;/hosts-by-ip.db
7854 The text form of the IP address of the subject host is used as the lookup key.
7855 IPv6 addresses are converted to an unabbreviated form, using lower case
7856 letters, with dots as separators because colon is the key terminator in
7857 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
7858 quoting the keys, but this is a facility that was added later.] The data
7859 returned by the lookup is not used.
7861 .cindex "IP address" "masking"
7862 .cindex "host list" "masked IP address"
7863 Single-key lookups can also be performed using masked IP addresses, using
7864 patterns of this form:
7866 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
7870 net24-dbm;/networks.db
7872 The IP address of the subject host is masked using <&'number'&> as the mask
7873 length. A textual string is constructed from the masked value, followed by the
7874 mask, and this is used as the lookup key. For example, if the host's IP address
7875 is 192.168.34.6, the key that is looked up for the above example is
7876 &"192.168.34.0/24"&.
7878 When an IPv6 address is converted to a string, dots are normally used instead
7879 of colons, so that keys in &(lsearch)& files need not contain colons (which
7880 terminate &(lsearch)& keys). This was implemented some time before the ability
7881 to quote keys was made available in &(lsearch)& files. However, the more
7882 recently implemented &(iplsearch)& files do require colons in IPv6 keys
7883 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
7884 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
7885 converted using colons and not dots. In all cases, full, unabbreviated IPv6
7886 addresses are always used.
7888 Ideally, it would be nice to tidy up this anomalous situation by changing to
7889 colons in all cases, given that quoting is now available for &(lsearch)&.
7890 However, this would be an incompatible change that might break some existing
7893 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
7894 IPv6 address) is not the same as specifying just &%net-%& without a number. In
7895 the former case the key strings include the mask value, whereas in the latter
7896 case the IP address is used on its own.
7900 .section "Host list patterns that match by host name" "SECThoslispatnam"
7901 .cindex "host" "lookup failures"
7902 .cindex "unknown host name"
7903 .cindex "host list" "matching host name"
7904 There are several types of pattern that require Exim to know the name of the
7905 remote host. These are either wildcard patterns or lookups by name. (If a
7906 complete hostname is given without any wildcarding, it is used to find an IP
7907 address to match against, as described in the section &<<SECThoslispatip>>&
7910 If the remote host name is not already known when Exim encounters one of these
7911 patterns, it has to be found from the IP address.
7912 Although many sites on the Internet are conscientious about maintaining reverse
7913 DNS data for their hosts, there are also many that do not do this.
7914 Consequently, a name cannot always be found, and this may lead to unwanted
7915 effects. Take care when configuring host lists with wildcarded name patterns.
7916 Consider what will happen if a name cannot be found.
7918 Because of the problems of determining host names from IP addresses, matching
7919 against host names is not as common as matching against IP addresses.
7921 By default, in order to find a host name, Exim first does a reverse DNS lookup;
7922 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
7923 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
7924 are done can be changed by setting the &%host_lookup_order%& option. For
7925 security, once Exim has found one or more names, it looks up the IP addresses
7926 for these names and compares them with the IP address that it started with.
7927 Only those names whose IP addresses match are accepted. Any other names are
7928 discarded. If no names are left, Exim behaves as if the host name cannot be
7929 found. In the most common case there is only one name and one IP address.
7931 There are some options that control what happens if a host name cannot be
7932 found. These are described in section &<<SECTbehipnot>>& below.
7934 .cindex "host" "alias for"
7935 .cindex "alias for host"
7936 As a result of aliasing, hosts may have more than one name. When processing any
7937 of the following types of pattern, all the host's names are checked:
7940 .cindex "asterisk" "in host list"
7941 If a pattern starts with &"*"& the remainder of the item must match the end of
7942 the host name. For example, &`*.b.c`& matches all hosts whose names end in
7943 &'.b.c'&. This special simple form is provided because this is a very common
7944 requirement. Other kinds of wildcarding require the use of a regular
7947 .cindex "regular expressions" "in host list"
7948 .cindex "host list" "regular expression in"
7949 If the item starts with &"^"& it is taken to be a regular expression which is
7950 matched against the host name. Host names are case-independent, so this regular
7951 expression match is by default case-independent, but you can make it
7952 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
7953 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
7958 is a regular expression that matches either of the two hosts &'a.c.d'& or
7959 &'b.c.d'&. When a regular expression is used in a host list, you must take care
7960 that backslash and dollar characters are not misinterpreted as part of the
7961 string expansion. The simplest way to do this is to use &`\N`& to mark that
7962 part of the string as non-expandable. For example:
7964 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
7966 &*Warning*&: If you want to match a complete host name, you must include the
7967 &`$`& terminating metacharacter in the regular expression, as in the above
7968 example. Without it, a match at the start of the host name is all that is
7975 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
7976 .cindex "host" "lookup failures, permanent"
7977 While processing a host list, Exim may need to look up an IP address from a
7978 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
7979 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
7980 behaviour when it fails to find the information it is seeking is the same.
7982 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
7983 apply to temporary DNS errors, whose handling is described in the next section.
7985 .cindex "&`+include_unknown`&"
7986 .cindex "&`+ignore_unknown`&"
7987 By default, Exim behaves as if the host does not match the list. This may not
7988 always be what you want to happen. To change Exim's behaviour, the special
7989 items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at
7990 top level &-- they are not recognized in an indirected file).
7993 If any item that follows &`+include_unknown`& requires information that
7994 cannot found, Exim behaves as if the host does match the list. For example,
7996 host_reject_connection = +include_unknown:*.enemy.ex
7998 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
7999 any hosts whose name it cannot find.
8002 If any item that follows &`+ignore_unknown`& requires information that cannot
8003 be found, Exim ignores that item and proceeds to the rest of the list. For
8006 accept hosts = +ignore_unknown : friend.example : \
8009 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8010 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8011 name can be found for 192.168.4.5, it is rejected.
8014 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8015 list. The effect of each one lasts until the next, or until the end of the
8019 .section "Temporary DNS errors when looking up host information" &&&
8021 .cindex "host" "lookup failures, temporary"
8022 .cindex "&`+include_defer`&"
8023 .cindex "&`+ignore_defer`&"
8024 A temporary DNS lookup failure normally causes a defer action (except when
8025 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8026 host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to
8027 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8028 section. These options should be used with care, probably only in non-critical
8029 host lists such as whitelists.
8033 .section "Host list patterns for single-key lookups by host name" &&&
8034 "SECThoslispatnamsk"
8035 .cindex "unknown host name"
8036 .cindex "host list" "matching host name"
8037 If a pattern is of the form
8039 <&'single-key-search-type'&>;<&'search-data'&>
8043 dbm;/host/accept/list
8045 a single-key lookup is performed, using the host name as its key. If the
8046 lookup succeeds, the host matches the item. The actual data that is looked up
8049 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8050 keys in the file, not IP addresses. If you want to do lookups based on IP
8051 addresses, you must precede the search type with &"net-"& (see section
8052 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8053 two items in the same list, one doing an address lookup and one doing a name
8054 lookup, both using the same file.
8058 .section "Host list patterns for query-style lookups" "SECID81"
8059 If a pattern is of the form
8061 <&'query-style-search-type'&>;<&'query'&>
8063 the query is obeyed, and if it succeeds, the host matches the item. The actual
8064 data that is looked up is not used. The variables &$sender_host_address$& and
8065 &$sender_host_name$& can be used in the query. For example:
8067 hosts_lookup = pgsql;\
8068 select ip from hostlist where ip='$sender_host_address'
8070 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8071 can use the &%sg%& expansion item to change this if you need to. If you want to
8072 use masked IP addresses in database queries, you can use the &%mask%& expansion
8075 If the query contains a reference to &$sender_host_name$&, Exim automatically
8076 looks up the host name if has not already done so. (See section
8077 &<<SECThoslispatnam>>& for comments on finding host names.)
8079 Historical note: prior to release 4.30, Exim would always attempt to find a
8080 host name before running the query, unless the search type was preceded by
8081 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8082 still recognized for query-style lookups, but its presence or absence has no
8083 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8084 See section &<<SECThoslispatsikey>>&.)
8088 .section "Mixing wildcarded host names and addresses in host lists" &&&
8090 .cindex "host list" "mixing names and addresses in"
8091 If you have name lookups or wildcarded host names and IP addresses in the same
8092 host list, you should normally put the IP addresses first. For example, in an
8095 accept hosts = 10.9.8.7 : *.friend.example
8097 The reason for this lies in the left-to-right way that Exim processes lists.
8098 It can test IP addresses without doing any DNS lookups, but when it reaches an
8099 item that requires a host name, it fails if it cannot find a host name to
8100 compare with the pattern. If the above list is given in the opposite order, the
8101 &%accept%& statement fails for a host whose name cannot be found, even if its
8102 IP address is 10.9.8.7.
8104 If you really do want to do the name check first, and still recognize the IP
8105 address, you can rewrite the ACL like this:
8107 accept hosts = *.friend.example
8108 accept hosts = 10.9.8.7
8110 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8111 &<<CHAPACL>>& for details of ACLs.
8117 .section "Address lists" "SECTaddresslist"
8118 .cindex "list" "address list"
8119 .cindex "address list" "empty item"
8120 .cindex "address list" "patterns"
8121 Address lists contain patterns that are matched against mail addresses. There
8122 is one special case to be considered: the sender address of a bounce message is
8123 always empty. You can test for this by providing an empty item in an address
8124 list. For example, you can set up a router to process bounce messages by
8125 using this option setting:
8129 The presence of the colon creates an empty item. If you do not provide any
8130 data, the list is empty and matches nothing. The empty sender can also be
8131 detected by a regular expression that matches an empty string,
8132 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8134 Non-empty items in an address list can be straightforward email addresses. For
8137 senders = jbc@askone.example : hs@anacreon.example
8139 A certain amount of wildcarding is permitted. If a pattern contains an @
8140 character, but is not a regular expression and does not begin with a
8141 semicolon-terminated lookup type (described below), the local part of the
8142 subject address is compared with the local part of the pattern, which may start
8143 with an asterisk. If the local parts match, the domain is checked in exactly
8144 the same way as for a pattern in a domain list. For example, the domain can be
8145 wildcarded, refer to a named list, or be a lookup:
8147 deny senders = *@*.spamming.site:\
8148 *@+hostile_domains:\
8149 bozo@partial-lsearch;/list/of/dodgy/sites:\
8150 *@dbm;/bad/domains.db
8152 .cindex "local part" "starting with !"
8153 .cindex "address list" "local part starting with !"
8154 If a local part that begins with an exclamation mark is required, it has to be
8155 specified using a regular expression, because otherwise the exclamation mark is
8156 treated as a sign of negation, as is standard in lists.
8158 If a non-empty pattern that is not a regular expression or a lookup does not
8159 contain an @ character, it is matched against the domain part of the subject
8160 address. The only two formats that are recognized this way are a literal
8161 domain, or a domain pattern that starts with *. In both these cases, the effect
8162 is the same as if &`*@`& preceded the pattern. For example:
8164 deny senders = enemy.domain : *.enemy.domain
8167 The following kinds of more complicated address list pattern can match any
8168 address, including the empty address that is characteristic of bounce message
8172 .cindex "regular expressions" "in address list"
8173 .cindex "address list" "regular expression in"
8174 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8175 done against the complete address, with the pattern as the regular expression.
8176 You must take care that backslash and dollar characters are not misinterpreted
8177 as part of the string expansion. The simplest way to do this is to use &`\N`&
8178 to mark that part of the string as non-expandable. For example:
8180 deny senders = \N^.*this.*@example\.com$\N : \
8181 \N^\d{8}.+@spamhaus.example$\N : ...
8183 The &`\N`& sequences are removed by the expansion, so these items do indeed
8184 start with &"^"& by the time they are being interpreted as address patterns.
8187 .cindex "address list" "lookup for complete address"
8188 Complete addresses can be looked up by using a pattern that starts with a
8189 lookup type terminated by a semicolon, followed by the data for the lookup. For
8192 deny senders = cdb;/etc/blocked.senders : \
8193 mysql;select address from blocked where \
8194 address='${quote_mysql:$sender_address}'
8196 Both query-style and single-key lookup types can be used. For a single-key
8197 lookup type, Exim uses the complete address as the key. However, empty keys are
8198 not supported for single-key lookups, so a match against the empty address
8199 always fails. This restriction does not apply to query-style lookups.
8201 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8202 cannot be used, and is ignored if specified, with an entry being written to the
8204 .cindex "*@ with single-key lookup"
8205 However, you can configure lookup defaults, as described in section
8206 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8207 default. For example, with this lookup:
8209 accept senders = lsearch*@;/some/file
8211 the file could contains lines like this:
8213 user1@domain1.example
8216 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8219 nimrod@jaeger.example
8223 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8224 would mean that every address matches, thus rendering the test useless.
8226 &*Warning 2*&: Do not confuse these two kinds of item:
8228 deny recipients = dbm*@;/some/file
8229 deny recipients = *@dbm;/some/file
8231 The first does a whole address lookup, with defaulting, as just described,
8232 because it starts with a lookup type. The second matches the local part and
8233 domain independently, as described in a bullet point below.
8237 The following kinds of address list pattern can match only non-empty addresses.
8238 If the subject address is empty, a match against any of these pattern types
8243 .cindex "@@ with single-key lookup"
8244 .cindex "address list" "@@ lookup type"
8245 .cindex "address list" "split local part and domain"
8246 If a pattern starts with &"@@"& followed by a single-key lookup item
8247 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8248 split into a local part and a domain. The domain is looked up in the file. If
8249 it is not found, there is no match. If it is found, the data that is looked up
8250 from the file is treated as a colon-separated list of local part patterns, each
8251 of which is matched against the subject local part in turn.
8253 .cindex "asterisk" "in address list"
8254 The lookup may be a partial one, and/or one involving a search for a default
8255 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8256 patterns that are looked up can be regular expressions or begin with &"*"&, or
8257 even be further lookups. They may also be independently negated. For example,
8260 deny senders = @@dbm;/etc/reject-by-domain
8262 the data from which the DBM file is built could contain lines like
8264 baddomain.com: !postmaster : *
8266 to reject all senders except &%postmaster%& from that domain.
8268 .cindex "local part" "starting with !"
8269 If a local part that actually begins with an exclamation mark is required, it
8270 has to be specified using a regular expression. In &(lsearch)& files, an entry
8271 may be split over several lines by indenting the second and subsequent lines,
8272 but the separating colon must still be included at line breaks. White space
8273 surrounding the colons is ignored. For example:
8275 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8278 As in all colon-separated lists in Exim, a colon can be included in an item by
8281 If the last item in the list starts with a right angle-bracket, the remainder
8282 of the item is taken as a new key to look up in order to obtain a continuation
8283 list of local parts. The new key can be any sequence of characters. Thus one
8284 might have entries like
8286 aol.com: spammer1 : spammer 2 : >*
8287 xyz.com: spammer3 : >*
8290 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8291 local parts for all domains, in addition to the specific local parts listed for
8292 each domain. Of course, using this feature costs another lookup each time a
8293 chain is followed, but the effort needed to maintain the data is reduced.
8295 .cindex "loop" "in lookups"
8296 It is possible to construct loops using this facility, and in order to catch
8297 them, the chains may be no more than fifty items long.
8300 The @@<&'lookup'&> style of item can also be used with a query-style
8301 lookup, but in this case, the chaining facility is not available. The lookup
8302 can only return a single list of local parts.
8305 &*Warning*&: There is an important difference between the address list items
8306 in these two examples:
8309 senders = *@+my_list
8311 In the first one, &`my_list`& is a named address list, whereas in the second
8312 example it is a named domain list.
8317 .section "Case of letters in address lists" "SECTcasletadd"
8318 .cindex "case of local parts"
8319 .cindex "address list" "case forcing"
8320 .cindex "case forcing in address lists"
8321 Domains in email addresses are always handled caselessly, but for local parts
8322 case may be significant on some systems (see &%caseful_local_part%& for how
8323 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8324 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8325 blocking lists should be done in a case-independent manner. Since most address
8326 lists in Exim are used for this kind of control, Exim attempts to do this by
8329 The domain portion of an address is always lowercased before matching it to an
8330 address list. The local part is lowercased by default, and any string
8331 comparisons that take place are done caselessly. This means that the data in
8332 the address list itself, in files included as plain file names, and in any file
8333 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8334 keys in files that are looked up by a search type other than &(lsearch)& (which
8335 works caselessly) must be in lower case, because these lookups are not
8338 .cindex "&`+caseful`&"
8339 To allow for the possibility of caseful address list matching, if an item in
8340 an address list is the string &"+caseful"&, the original case of the local
8341 part is restored for any comparisons that follow, and string comparisons are no
8342 longer case-independent. This does not affect the domain, which remains in
8343 lower case. However, although independent matches on the domain alone are still
8344 performed caselessly, regular expressions that match against an entire address
8345 become case-sensitive after &"+caseful"& has been seen.
8349 .section "Local part lists" "SECTlocparlis"
8350 .cindex "list" "local part list"
8351 .cindex "local part" "list"
8352 Case-sensitivity in local part lists is handled in the same way as for address
8353 lists, as just described. The &"+caseful"& item can be used if required. In a
8354 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8355 set false, the subject is lowercased and the matching is initially
8356 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8357 matching in the local part list, but not elsewhere in the router. If
8358 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8359 option is case-sensitive from the start.
8361 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8362 comments are handled in the same way as address lists &-- they are recognized
8363 only if the # is preceded by white space or the start of the line.
8364 Otherwise, local part lists are matched in the same way as domain lists, except
8365 that the special items that refer to the local host (&`@`&, &`@[]`&,
8366 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8367 Refer to section &<<SECTdomainlist>>& for details of the other available item
8369 .ecindex IIDdohoadli
8374 . ////////////////////////////////////////////////////////////////////////////
8375 . ////////////////////////////////////////////////////////////////////////////
8377 .chapter "String expansions" "CHAPexpand"
8378 .scindex IIDstrexp "expansion" "of strings"
8379 Many strings in Exim's run time configuration are expanded before use. Some of
8380 them are expanded every time they are used; others are expanded only once.
8382 When a string is being expanded it is copied verbatim from left to right except
8383 when a dollar or backslash character is encountered. A dollar specifies the
8384 start of a portion of the string that is interpreted and replaced as described
8385 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8386 escape character, as described in the following section.
8390 .section "Literal text in expanded strings" "SECTlittext"
8391 .cindex "expansion" "including literal text"
8392 An uninterpreted dollar can be included in an expanded string by putting a
8393 backslash in front of it. A backslash can be used to prevent any special
8394 character being treated specially in an expansion, including backslash itself.
8395 If the string appears in quotes in the configuration file, two backslashes are
8396 required because the quotes themselves cause interpretation of backslashes when
8397 the string is read in (see section &<<SECTstrings>>&).
8399 .cindex "expansion" "non-expandable substrings"
8400 A portion of the string can specified as non-expandable by placing it between
8401 two occurrences of &`\N`&. This is particularly useful for protecting regular
8402 expressions, which often contain backslashes and dollar signs. For example:
8404 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8406 On encountering the first &`\N`&, the expander copies subsequent characters
8407 without interpretation until it reaches the next &`\N`& or the end of the
8412 .section "Character escape sequences in expanded strings" "SECID82"
8413 .cindex "expansion" "escape sequences"
8414 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
8415 expanded string is recognized as an escape sequence for the character newline,
8416 carriage return, or tab, respectively. A backslash followed by up to three
8417 octal digits is recognized as an octal encoding for a single character, and a
8418 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
8421 These escape sequences are also recognized in quoted strings when they are read
8422 in. Their interpretation in expansions as well is useful for unquoted strings,
8423 and for other cases such as looked-up strings that are then expanded.
8426 .section "Testing string expansions" "SECID83"
8427 .cindex "expansion" "testing"
8428 .cindex "testing" "string expansion"
8430 Many expansions can be tested by calling Exim with the &%-be%& option. This
8431 takes the command arguments, or lines from the standard input if there are no
8432 arguments, runs them through the string expansion code, and writes the results
8433 to the standard output. Variables based on configuration values are set up, but
8434 since no message is being processed, variables such as &$local_part$& have no
8435 value. Nevertheless the &%-be%& option can be useful for checking out file and
8436 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
8439 Exim gives up its root privilege when it is called with the &%-be%& option, and
8440 instead runs under the uid and gid it was called with, to prevent users from
8441 using &%-be%& for reading files to which they do not have access.
8444 If you want to test expansions that include variables whose values are taken
8445 from a message, there are two other options that can be used. The &%-bem%&
8446 option is like &%-be%& except that it is followed by a file name. The file is
8447 read as a message before doing the test expansions. For example:
8449 exim -bem /tmp/test.message '$h_subject:'
8451 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
8452 Exim message identifier. For example:
8454 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
8456 This loads the message from Exim's spool before doing the test expansions, and
8457 is therefore restricted to admin users.
8460 .section "Forced expansion failure" "SECTforexpfai"
8461 .cindex "expansion" "forced failure"
8462 A number of expansions that are described in the following section have
8463 alternative &"true"& and &"false"& substrings, enclosed in brace characters
8464 (which are sometimes called &"curly brackets"&). Which of the two strings is
8465 used depends on some condition that is evaluated as part of the expansion. If,
8466 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
8467 the entire string expansion fails in a way that can be detected by the code
8468 that requested the expansion. This is called &"forced expansion failure"&, and
8469 its consequences depend on the circumstances. In some cases it is no different
8470 from any other expansion failure, but in others a different action may be
8471 taken. Such variations are mentioned in the documentation of the option that is
8477 .section "Expansion items" "SECTexpansionitems"
8478 The following items are recognized in expanded strings. White space may be used
8479 between sub-items that are keywords or substrings enclosed in braces inside an
8480 outer set of braces, to improve readability. &*Warning*&: Within braces,
8481 white space is significant.
8484 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
8485 .cindex "expansion" "variables"
8486 Substitute the contents of the named variable, for example:
8491 The second form can be used to separate the name from subsequent alphanumeric
8492 characters. This form (using braces) is available only for variables; it does
8493 &'not'& apply to message headers. The names of the variables are given in
8494 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
8495 given, the expansion fails.
8497 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
8498 .cindex "expansion" "operators"
8499 The string is first itself expanded, and then the operation specified by
8500 <&'op'&> is applied to it. For example:
8504 The string starts with the first character after the colon, which may be
8505 leading white space. A list of operators is given in section &<<SECTexpop>>&
8506 below. The operator notation is used for simple expansion items that have just
8507 one argument, because it reduces the number of braces and therefore makes the
8508 string easier to understand.
8510 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
8511 This item inserts &"basic"& header lines. It is described with the &%header%&
8512 expansion item below.
8514 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
8515 {*&<&'arg'&>&*}...}*&"
8517 This expansion dynamically loads and then calls a locally-written C function.
8518 This functionality is available only if Exim is compiled with
8522 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
8523 object so that it doesn't reload the same object file in the same Exim process
8524 (but of course Exim does start new processes frequently).
8526 There may be from zero to eight arguments to the function. When compiling
8527 a local function that is to be called in this way, &_local_scan.h_& should be
8528 included. The Exim variables and functions that are defined by that API
8529 are also available for dynamically loaded functions. The function itself
8530 must have the following type:
8532 int dlfunction(uschar **yield, int argc, uschar *argv[])
8534 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
8535 function should return one of the following values:
8537 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
8538 into the expanded string that is being built.
8540 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
8541 from &'yield'&, if it is set.
8543 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
8544 taken from &'yield'& if it is set.
8546 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
8548 When compiling a function that is to be used in this way with gcc,
8549 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
8550 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
8552 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
8553 {*&<&'string3'&>&*}}*&"
8554 .cindex "expansion" "extracting substrings by key"
8555 .cindex "&%extract%&" "substrings by key"
8556 The key and <&'string1'&> are first expanded separately. Leading and trailing
8557 white space is removed from the key (but not from any of the strings). The key
8558 must not consist entirely of digits. The expanded <&'string1'&> must be of the
8561 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
8564 where the equals signs and spaces (but not both) are optional. If any of the
8565 values contain white space, they must be enclosed in double quotes, and any
8566 values that are enclosed in double quotes are subject to escape processing as
8567 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
8568 for the value that corresponds to the key. The search is case-insensitive. If
8569 the key is found, <&'string2'&> is expanded, and replaces the whole item;
8570 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
8571 variable &$value$& contains the value that has been extracted. Afterwards, it
8572 is restored to any previous value it might have had.
8574 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
8575 key is not found. If {<&'string2'&>} is also omitted, the value that was
8576 extracted is used. Thus, for example, these two expansions are identical, and
8579 ${extract{gid}{uid=1984 gid=2001}}
8580 ${extract{gid}{uid=1984 gid=2001}{$value}}
8582 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
8583 appear, for example:
8585 ${extract{Z}{A=... B=...}{$value} fail }
8587 This forces an expansion failure (see section &<<SECTforexpfai>>&);
8588 {<&'string2'&>} must be present for &"fail"& to be recognized.
8591 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
8592 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
8593 .cindex "expansion" "extracting substrings by number"
8594 .cindex "&%extract%&" "substrings by number"
8595 The <&'number'&> argument must consist entirely of decimal digits,
8596 apart from leading and trailing white space, which is ignored.
8597 This is what distinguishes this form of &%extract%& from the previous kind. It
8598 behaves in the same way, except that, instead of extracting a named field, it
8599 extracts from <&'string1'&> the field whose number is given as the first
8600 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
8601 <&'string3'&> as before.
8603 The fields in the string are separated by any one of the characters in the
8604 separator string. These may include space or tab characters.
8605 The first field is numbered one. If the number is negative, the fields are
8606 counted from the end of the string, with the rightmost one numbered -1. If the
8607 number given is zero, the entire string is returned. If the modulus of the
8608 number is greater than the number of fields in the string, the result is the
8609 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
8610 provided. For example:
8612 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
8616 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
8618 yields &"99"&. Two successive separators mean that the field between them is
8619 empty (for example, the fifth field above).
8622 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
8623 .cindex "list" "selecting by condition"
8624 .cindex "expansion" "selecting from list by condition"
8626 After expansion, <&'string'&> is interpreted as a list, colon-separated by
8627 default, but the separator can be changed in the usual way. For each item
8628 in this list, its value is place in &$item$&, and then the condition is
8629 evaluated. If the condition is true, &$item$& is added to the output as an
8630 item in a new list; if the condition is false, the item is discarded. The
8631 separator used for the output list is the same as the one used for the
8632 input, but a separator setting is not included in the output. For example:
8634 ${filter{a:b:c}{!eq{$item}{b}}
8636 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
8637 to what it was before. See also the &*map*& and &*reduce*& expansion items.
8640 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8641 .cindex "hash function" "textual"
8642 .cindex "expansion" "textual hash"
8643 This is a textual hashing function, and was the first to be implemented in
8644 early versions of Exim. In current releases, there are other hashing functions
8645 (numeric, MD5, and SHA-1), which are described below.
8647 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
8648 <&'n'&>. If you are using fixed values for these numbers, that is, if
8649 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
8650 use the simpler operator notation that avoids some of the braces:
8652 ${hash_<n>_<m>:<string>}
8654 The second number is optional (in both notations). If <&'n'&> is greater than
8655 or equal to the length of the string, the expansion item returns the string.
8656 Otherwise it computes a new string of length <&'n'&> by applying a hashing
8657 function to the string. The new string consists of characters taken from the
8658 first <&'m'&> characters of the string
8660 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
8662 If <&'m'&> is not present the value 26 is used, so that only lower case
8663 letters appear. For example:
8665 &`$hash{3}{monty}} `& yields &`jmg`&
8666 &`$hash{5}{monty}} `& yields &`monty`&
8667 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
8670 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
8671 &*$h_*&<&'header&~name'&>&*:*&" &&&
8672 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8673 &*$bh_*&<&'header&~name'&>&*:*&" &&&
8674 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
8675 &*$rh_*&<&'header&~name'&>&*:*&"
8676 .cindex "expansion" "header insertion"
8677 .vindex "&$header_$&"
8678 .vindex "&$bheader_$&"
8679 .vindex "&$rheader_$&"
8680 .cindex "header lines" "in expansion strings"
8681 .cindex "header lines" "character sets"
8682 .cindex "header lines" "decoding"
8683 Substitute the contents of the named message header line, for example
8687 The newline that terminates a header line is not included in the expansion, but
8688 internal newlines (caused by splitting the header line over several physical
8689 lines) may be present.
8691 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
8692 the data in the header line is interpreted.
8695 .cindex "white space" "in header lines"
8696 &%rheader%& gives the original &"raw"& content of the header line, with no
8697 processing at all, and without the removal of leading and trailing white space.
8700 .cindex "base64 encoding" "in header lines"
8701 &%bheader%& removes leading and trailing white space, and then decodes base64
8702 or quoted-printable MIME &"words"& within the header text, but does no
8703 character set translation. If decoding of what looks superficially like a MIME
8704 &"word"& fails, the raw string is returned. If decoding
8705 .cindex "binary zero" "in header line"
8706 produces a binary zero character, it is replaced by a question mark &-- this is
8707 what Exim does for binary zeros that are actually received in header lines.
8710 &%header%& tries to translate the string as decoded by &%bheader%& to a
8711 standard character set. This is an attempt to produce the same string as would
8712 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
8713 returned. Translation is attempted only on operating systems that support the
8714 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
8715 a system Makefile or in &_Local/Makefile_&.
8718 In a filter file, the target character set for &%header%& can be specified by a
8719 command of the following form:
8721 headers charset "UTF-8"
8723 This command affects all references to &$h_$& (or &$header_$&) expansions in
8724 subsequently obeyed filter commands. In the absence of this command, the target
8725 character set in a filter is taken from the setting of the &%headers_charset%&
8726 option in the runtime configuration. The value of this option defaults to the
8727 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
8730 Header names follow the syntax of RFC 2822, which states that they may contain
8731 any printing characters except space and colon. Consequently, curly brackets
8732 &'do not'& terminate header names, and should not be used to enclose them as
8733 if they were variables. Attempting to do so causes a syntax error.
8735 Only header lines that are common to all copies of a message are visible to
8736 this mechanism. These are the original header lines that are received with the
8737 message, and any that are added by an ACL statement or by a system
8738 filter. Header lines that are added to a particular copy of a message by a
8739 router or transport are not accessible.
8741 For incoming SMTP messages, no header lines are visible in ACLs that are obeyed
8742 before the DATA ACL, because the header structure is not set up until the
8743 message is received. Header lines that are added in a RCPT ACL (for example)
8744 are saved until the message's incoming header lines are available, at which
8745 point they are added. When a DATA ACL is running, however, header lines added
8746 by earlier ACLs are visible.
8748 Upper case and lower case letters are synonymous in header names. If the
8749 following character is white space, the terminating colon may be omitted, but
8750 this is not recommended, because you may then forget it when it is needed. When
8751 white space terminates the header name, it is included in the expanded string.
8752 If the message does not contain the given header, the expansion item is
8753 replaced by an empty string. (See the &%def%& condition in section
8754 &<<SECTexpcond>>& for a means of testing for the existence of a header.)
8756 If there is more than one header with the same name, they are all concatenated
8757 to form the substitution string, up to a maximum length of 64K. Unless
8758 &%rheader%& is being used, leading and trailing white space is removed from
8759 each header before concatenation, and a completely empty header is ignored. A
8760 newline character is then inserted between non-empty headers, but there is no
8761 newline at the very end. For the &%header%& and &%bheader%& expansion, for
8762 those headers that contain lists of addresses, a comma is also inserted at the
8763 junctions between headers. This does not happen for the &%rheader%& expansion.
8766 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
8767 .cindex "expansion" "hmac hashing"
8769 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
8770 shared secret and some text into a message authentication code, as specified in
8771 RFC 2104. This differs from &`${md5:secret_text...}`& or
8772 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
8773 cryptographic hash, allowing for authentication that is not possible with MD5
8774 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
8775 present. For example:
8777 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
8779 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
8782 dd97e3ba5d1a61b5006108f8c8252953
8784 As an example of how this might be used, you might put in the main part of
8785 an Exim configuration:
8787 SPAMSCAN_SECRET=cohgheeLei2thahw
8789 In a router or a transport you could then have:
8792 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
8793 ${hmac{md5}{SPAMSCAN_SECRET}\
8794 {${primary_hostname},${message_exim_id},$h_message-id:}}
8796 Then given a message, you can check where it was scanned by looking at the
8797 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
8798 this header line is authentic by recomputing the authentication code from the
8799 host name, message ID and the &'Message-id:'& header line. This can be done
8800 using Exim's &%-be%& option, or by other means, for example by using the
8801 &'hmac_md5_hex()'& function in Perl.
8804 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8805 .cindex "expansion" "conditional"
8806 .cindex "&%if%&, expansion item"
8807 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
8808 item; otherwise <&'string2'&> is used. The available conditions are described
8809 in section &<<SECTexpcond>>& below. For example:
8811 ${if eq {$local_part}{postmaster} {yes}{no} }
8813 The second string need not be present; if it is not and the condition is not
8814 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
8815 be present instead of the second string (without any curly brackets). In this
8816 case, the expansion is forced to fail if the condition is not true (see section
8817 &<<SECTforexpfai>>&).
8819 If both strings are omitted, the result is the string &`true`& if the condition
8820 is true, and the empty string if the condition is false. This makes it less
8821 cumbersome to write custom ACL and router conditions. For example, instead of
8823 condition = ${if >{$acl_m4}{3}{true}{false}}
8827 condition = ${if >{$acl_m4}{3}}
8830 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8831 .cindex "expansion" "string truncation"
8832 .cindex "&%length%& expansion item"
8833 The &%length%& item is used to extract the initial portion of a string. Both
8834 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
8835 you are using a fixed value for the number, that is, if <&'string1'&> does not
8836 change when expanded, you can use the simpler operator notation that avoids
8839 ${length_<n>:<string>}
8841 The result of this item is either the first <&'n'&> characters or the whole
8842 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
8843 &%strlen%&, which gives the length of a string.
8846 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
8847 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8848 This is the first of one of two different types of lookup item, which are both
8849 described in the next item.
8851 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
8852 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
8853 .cindex "expansion" "lookup in"
8854 .cindex "file" "lookups"
8855 .cindex "lookup" "in expanded string"
8856 The two forms of lookup item specify data lookups in files and databases, as
8857 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
8858 lookups, and the second is used for query-style lookups. The <&'key'&>,
8859 <&'file'&>, and <&'query'&> strings are expanded before use.
8861 If there is any white space in a lookup item which is part of a filter command,
8862 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
8863 other place where white space is significant, the lookup item must be enclosed
8864 in double quotes. The use of data lookups in users' filter files may be locked
8865 out by the system administrator.
8868 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
8869 During its expansion, the variable &$value$& contains the data returned by the
8870 lookup. Afterwards it reverts to the value it had previously (at the outer
8871 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
8872 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
8873 string on failure. If <&'string2'&> is provided, it can itself be a nested
8874 lookup, thus providing a mechanism for looking up a default value when the
8875 original lookup fails.
8877 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
8878 data for the outer lookup while the parameters of the second lookup are
8879 expanded, and also while <&'string2'&> of the second lookup is expanded, should
8880 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
8881 appear, and in this case, if the lookup fails, the entire expansion is forced
8882 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
8883 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
8884 successful lookup, and nothing in the case of failure.
8886 For single-key lookups, the string &"partial"& is permitted to precede the
8887 search type in order to do partial matching, and * or *@ may follow a search
8888 type to request default lookups if the key does not match (see sections
8889 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
8891 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
8892 If a partial search is used, the variables &$1$& and &$2$& contain the wild
8893 and non-wild parts of the key during the expansion of the replacement text.
8894 They return to their previous values at the end of the lookup item.
8896 This example looks up the postmaster alias in the conventional alias file:
8898 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
8900 This example uses NIS+ to look up the full name of the user corresponding to
8901 the local part of an address, forcing the expansion to fail if it is not found:
8903 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
8908 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
8909 .cindex "expansion" "list creation"
8911 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
8912 default, but the separator can be changed in the usual way. For each item
8913 in this list, its value is place in &$item$&, and then <&'string2'&> is
8914 expanded and added to the output as an item in a new list. The separator used
8915 for the output list is the same as the one used for the input, but a separator
8916 setting is not included in the output. For example:
8918 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
8920 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
8921 value of &$item$& is restored to what it was before. See also the &*filter*&
8922 and &*reduce*& expansion items.
8924 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
8925 .cindex "expansion" "numeric hash"
8926 .cindex "hash function" "numeric"
8927 The three strings are expanded; the first two must yield numbers. Call them
8928 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
8929 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
8930 can use the simpler operator notation that avoids some of the braces:
8932 ${nhash_<n>_<m>:<string>}
8934 The second number is optional (in both notations). If there is only one number,
8935 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
8936 processed by a div/mod hash function that returns two numbers, separated by a
8937 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
8940 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
8942 returns the string &"6/33"&.
8946 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
8947 .cindex "Perl" "use in expanded string"
8948 .cindex "expansion" "calling Perl from"
8949 This item is available only if Exim has been built to include an embedded Perl
8950 interpreter. The subroutine name and the arguments are first separately
8951 expanded, and then the Perl subroutine is called with those arguments. No
8952 additional arguments need be given; the maximum number permitted, including the
8953 name of the subroutine, is nine.
8955 The return value of the subroutine is inserted into the expanded string, unless
8956 the return value is &%undef%&. In that case, the expansion fails in the same
8957 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
8958 Whatever you return is evaluated in a scalar context. For example, if you
8959 return the name of a Perl vector, the return value is the size of the vector,
8962 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
8963 with the error message that was passed to &%die%&. More details of the embedded
8964 Perl facility are given in chapter &<<CHAPperl>>&.
8966 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
8967 out the use of this expansion item in filter files.
8970 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
8971 .cindex "&%prvs%& expansion item"
8972 The first argument is a complete email address and the second is secret
8973 keystring. The third argument, specifying a key number, is optional. If absent,
8974 it defaults to 0. The result of the expansion is a prvs-signed email address,
8975 to be typically used with the &%return_path%& option on an &(smtp)& transport
8976 as part of a bounce address tag validation (BATV) scheme. For more discussion
8977 and an example, see section &<<SECTverifyPRVS>>&.
8979 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
8980 {*&<&'string'&>&*}}*&"
8981 .cindex "&%prvscheck%& expansion item"
8982 This expansion item is the complement of the &%prvs%& item. It is used for
8983 checking prvs-signed addresses. If the expansion of the first argument does not
8984 yield a syntactically valid prvs-signed address, the whole item expands to the
8985 empty string. When the first argument does expand to a syntactically valid
8986 prvs-signed address, the second argument is expanded, with the prvs-decoded
8987 version of the address and the key number extracted from the address in the
8988 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
8990 These two variables can be used in the expansion of the second argument to
8991 retrieve the secret. The validity of the prvs-signed address is then checked
8992 against the secret. The result is stored in the variable &$prvscheck_result$&,
8993 which is empty for failure or &"1"& for success.
8995 The third argument is optional; if it is missing, it defaults to an empty
8996 string. This argument is now expanded. If the result is an empty string, the
8997 result of the expansion is the decoded version of the address. This is the case
8998 whether or not the signature was valid. Otherwise, the result of the expansion
8999 is the expansion of the third argument.
9001 All three variables can be used in the expansion of the third argument.
9002 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9003 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9005 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9006 .cindex "expansion" "inserting an entire file"
9007 .cindex "file" "inserting into expansion"
9008 .cindex "&%readfile%& expansion item"
9009 The file name and end-of-line string are first expanded separately. The file is
9010 then read, and its contents replace the entire item. All newline characters in
9011 the file are replaced by the end-of-line string if it is present. Otherwise,
9012 newlines are left in the string.
9013 String expansion is not applied to the contents of the file. If you want this,
9014 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9015 the string expansion fails.
9017 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9018 locks out the use of this expansion item in filter files.
9022 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9023 {*&<&'timeout'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9024 .cindex "expansion" "inserting from a socket"
9025 .cindex "socket, use of in expansion"
9026 .cindex "&%readsocket%& expansion item"
9027 This item inserts data from a Unix domain or Internet socket into the expanded
9028 string. The minimal way of using it uses just two arguments, as in these
9031 ${readsocket{/socket/name}{request string}}
9032 ${readsocket{inet:some.host:1234}{request string}}
9034 For a Unix domain socket, the first substring must be the path to the socket.
9035 For an Internet socket, the first substring must contain &`inet:`& followed by
9036 a host name or IP address, followed by a colon and a port, which can be a
9037 number or the name of a TCP port in &_/etc/services_&. An IP address may
9038 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9041 ${readsocket{inet:[::1]:1234}{request string}}
9043 Only a single host name may be given, but if looking it up yields more than
9044 one IP address, they are each tried in turn until a connection is made. For
9045 both kinds of socket, Exim makes a connection, writes the request string
9046 (unless it is an empty string) and reads from the socket until an end-of-file
9047 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9048 extend what can be done. Firstly, you can vary the timeout. For example:
9050 ${readsocket{/socket/name}{request string}{3s}}
9052 A fourth argument allows you to change any newlines that are in the data
9053 that is read, in the same way as for &%readfile%& (see above). This example
9054 turns them into spaces:
9056 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9058 As with all expansions, the substrings are expanded before the processing
9059 happens. Errors in these sub-expansions cause the expansion to fail. In
9060 addition, the following errors can occur:
9063 Failure to create a socket file descriptor;
9065 Failure to connect the socket;
9067 Failure to write the request string;
9069 Timeout on reading from the socket.
9072 By default, any of these errors causes the expansion to fail. However, if
9073 you supply a fifth substring, it is expanded and used when any of the above
9074 errors occurs. For example:
9076 ${readsocket{/socket/name}{request string}{3s}{\n}\
9079 You can test for the existence of a Unix domain socket by wrapping this
9080 expansion in &`${if exists`&, but there is a race condition between that test
9081 and the actual opening of the socket, so it is safer to use the fifth argument
9082 if you want to be absolutely sure of avoiding an expansion error for a
9083 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9085 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9086 locks out the use of this expansion item in filter files.
9089 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9090 .cindex "expansion" "reducing a list to a scalar"
9091 .cindex "list" "reducing to a scalar"
9094 This operation reduces a list to a single, scalar string. After expansion,
9095 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9096 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9097 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9098 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9099 them. The result of that expansion is assigned to &$value$& before the next
9100 iteration. When the end of the list is reached, the final value of &$value$& is
9101 added to the expansion output. The &*reduce*& expansion item can be used in a
9102 number of ways. For example, to add up a list of numbers:
9104 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9106 The result of that expansion would be &`6`&. The maximum of a list of numbers
9109 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9111 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9112 restored to what they were before. See also the &*filter*& and &*map*&
9115 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9116 This item inserts &"raw"& header lines. It is described with the &%header%&
9117 expansion item above.
9119 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9120 {*&<&'string2'&>&*}}*&"
9121 .cindex "expansion" "running a command"
9122 .cindex "&%run%& expansion item"
9123 The command and its arguments are first expanded separately, and then the
9124 command is run in a separate process, but under the same uid and gid. As in
9125 other command executions from Exim, a shell is not used by default. If you want
9126 a shell, you must explicitly code it.
9128 The standard input for the command exists, but is empty. The standard output
9129 and standard error are set to the same file descriptor.
9130 .cindex "return code" "from &%run%& expansion"
9132 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9133 and replaces the entire item; during this expansion, the standard output/error
9134 from the command is in the variable &$value$&. If the command fails,
9135 <&'string2'&>, if present, is expanded and used. Once again, during the
9136 expansion, the standard output/error from the command is in the variable
9139 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9140 can be the word &"fail"& (not in braces) to force expansion failure if the
9141 command does not succeed. If both strings are omitted, the result is contents
9142 of the standard output/error on success, and nothing on failure.
9145 The return code from the command is put in the variable &$runrc$&, and this
9146 remains set afterwards, so in a filter file you can do things like this:
9148 if "${run{x y z}{}}$runrc" is 1 then ...
9149 elif $runrc is 2 then ...
9153 If execution of the command fails (for example, the command does not exist),
9154 the return code is 127 &-- the same code that shells use for non-existent
9157 &*Warning*&: In a router or transport, you cannot assume the order in which
9158 option values are expanded, except for those preconditions whose order of
9159 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9160 by the expansion of one option, and use it in another.
9162 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9163 out the use of this expansion item in filter files.
9166 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9167 .cindex "expansion" "string substitution"
9168 .cindex "&%sg%& expansion item"
9169 This item works like Perl's substitution operator (s) with the global (/g)
9170 option; hence its name. However, unlike the Perl equivalent, Exim does not
9171 modify the subject string; instead it returns the modified string for insertion
9172 into the overall expansion. The item takes three arguments: the subject string,
9173 a regular expression, and a substitution string. For example:
9175 ${sg{abcdefabcdef}{abc}{xyz}}
9177 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9178 if any $ or \ characters are required in the regular expression or in the
9179 substitution string, they have to be escaped. For example:
9181 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9183 yields &"defabc"&, and
9185 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9187 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9188 the regular expression from string expansion.
9192 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9193 .cindex "&%substr%& expansion item"
9194 .cindex "substring extraction"
9195 .cindex "expansion" "substring extraction"
9196 The three strings are expanded; the first two must yield numbers. Call them
9197 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9198 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9199 can use the simpler operator notation that avoids some of the braces:
9201 ${substr_<n>_<m>:<string>}
9203 The second number is optional (in both notations).
9204 If it is absent in the simpler format, the preceding underscore must also be
9207 The &%substr%& item can be used to extract more general substrings than
9208 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
9209 length required. For example
9211 ${substr{3}{2}{$local_part}}
9213 If the starting offset is greater than the string length the result is the
9214 null string; if the length plus starting offset is greater than the string
9215 length, the result is the right-hand part of the string, starting from the
9216 given offset. The first character in the string has offset zero.
9218 The &%substr%& expansion item can take negative offset values to count
9219 from the right-hand end of its operand. The last character is offset -1, the
9220 second-last is offset -2, and so on. Thus, for example,
9222 ${substr{-5}{2}{1234567}}
9224 yields &"34"&. If the absolute value of a negative offset is greater than the
9225 length of the string, the substring starts at the beginning of the string, and
9226 the length is reduced by the amount of overshoot. Thus, for example,
9228 ${substr{-5}{2}{12}}
9230 yields an empty string, but
9232 ${substr{-3}{2}{12}}
9236 When the second number is omitted from &%substr%&, the remainder of the string
9237 is taken if the offset is positive. If it is negative, all characters in the
9238 string preceding the offset point are taken. For example, an offset of -1 and
9239 no length, as in these semantically identical examples:
9242 ${substr{-1}{abcde}}
9244 yields all but the last character of the string, that is, &"abcd"&.
9248 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
9249 {*&<&'replacements'&>&*}}*&"
9250 .cindex "expansion" "character translation"
9251 .cindex "&%tr%& expansion item"
9252 This item does single-character translation on its subject string. The second
9253 argument is a list of characters to be translated in the subject string. Each
9254 matching character is replaced by the corresponding character from the
9255 replacement list. For example
9257 ${tr{abcdea}{ac}{13}}
9259 yields &`1b3de1`&. If there are duplicates in the second character string, the
9260 last occurrence is used. If the third string is shorter than the second, its
9261 last character is replicated. However, if it is empty, no translation takes
9267 .section "Expansion operators" "SECTexpop"
9268 .cindex "expansion" "operators"
9269 For expansion items that perform transformations on a single argument string,
9270 the &"operator"& notation is used because it is simpler and uses fewer braces.
9271 The substring is first expanded before the operation is applied to it. The
9272 following operations can be performed:
9275 .vitem &*${address:*&<&'string'&>&*}*&
9276 .cindex "expansion" "RFC 2822 address handling"
9277 .cindex "&%address%& expansion item"
9278 The string is interpreted as an RFC 2822 address, as it might appear in a
9279 header line, and the effective address is extracted from it. If the string does
9280 not parse successfully, the result is empty.
9283 .vitem &*${addresses:*&<&'string'&>&*}*&
9284 .cindex "expansion" "RFC 2822 address handling"
9285 .cindex "&%addresses%& expansion item"
9286 The string (after expansion) is interpreted as a list of addresses in RFC
9287 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
9288 operative address (&'local-part@domain'&) is extracted from each item, and the
9289 result of the expansion is a colon-separated list, with appropriate
9290 doubling of colons should any happen to be present in the email addresses.
9291 Syntactically invalid RFC2822 address items are omitted from the output.
9293 It is possible to specify a character other than colon for the output
9294 separator by starting the string with > followed by the new separator
9295 character. For example:
9297 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
9299 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
9300 expansion item, which extracts the working address from a single RFC2822
9301 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
9305 .vitem &*${base62:*&<&'digits'&>&*}*&
9306 .cindex "&%base62%& expansion item"
9307 .cindex "expansion" "conversion to base 62"
9308 The string must consist entirely of decimal digits. The number is converted to
9309 base 62 and output as a string of six characters, including leading zeros. In
9310 the few operating environments where Exim uses base 36 instead of base 62 for
9311 its message identifiers (because those systems do not have case-sensitive file
9312 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
9313 be absolutely clear: this is &'not'& base64 encoding.
9315 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
9316 .cindex "&%base62d%& expansion item"
9317 .cindex "expansion" "conversion to base 62"
9318 The string must consist entirely of base-62 digits, or, in operating
9319 environments where Exim uses base 36 instead of base 62 for its message
9320 identifiers, base-36 digits. The number is converted to decimal and output as a
9323 .vitem &*${domain:*&<&'string'&>&*}*&
9324 .cindex "domain" "extraction"
9325 .cindex "expansion" "domain extraction"
9326 The string is interpreted as an RFC 2822 address and the domain is extracted
9327 from it. If the string does not parse successfully, the result is empty.
9330 .vitem &*${escape:*&<&'string'&>&*}*&
9331 .cindex "expansion" "escaping non-printing characters"
9332 .cindex "&%escape%& expansion item"
9333 If the string contains any non-printing characters, they are converted to
9334 escape sequences starting with a backslash. Whether characters with the most
9335 significant bit set (so-called &"8-bit characters"&) count as printing or not
9336 is controlled by the &%print_topbitchars%& option.
9339 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
9340 .cindex "expansion" "expression evaluation"
9341 .cindex "expansion" "arithmetic expression"
9342 .cindex "&%eval%& expansion item"
9343 These items supports simple arithmetic and bitwise logical operations in
9344 expansion strings. The string (after expansion) must be a conventional
9345 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
9346 logical operators, and parentheses. All operations are carried out using
9347 integer arithmetic. The operator priorities are as follows (the same as in the
9348 C programming language):
9350 .irow &'highest:'& "not (~), negate (-)"
9351 .irow "" "multiply (*), divide (/), remainder (%)"
9352 .irow "" "plus (+), minus (-)"
9353 .irow "" "shift-left (<<), shift-right (>>)"
9356 .irow &'lowest:'& "or (|)"
9358 Binary operators with the same priority are evaluated from left to right. White
9359 space is permitted before or after operators.
9361 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
9362 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
9363 decimal, even if they start with a leading zero; hexadecimal numbers are not
9364 permitted. This can be useful when processing numbers extracted from dates or
9365 times, which often do have leading zeros.
9367 A number may be followed by &"K"& or &"M"& to multiply it by 1024 or 1024*1024,
9368 respectively. Negative numbers are supported. The result of the computation is
9369 a decimal representation of the answer (without &"K"& or &"M"&). For example:
9372 &`${eval:1+1} `& yields 2
9373 &`${eval:1+2*3} `& yields 7
9374 &`${eval:(1+2)*3} `& yields 9
9375 &`${eval:2+42%5} `& yields 4
9376 &`${eval:0xc&5} `& yields 4
9377 &`${eval:0xc|5} `& yields 13
9378 &`${eval:0xc^5} `& yields 9
9379 &`${eval:0xc>>1} `& yields 6
9380 &`${eval:0xc<<1} `& yields 24
9381 &`${eval:~255&0x1234} `& yields 4608
9382 &`${eval:-(~255&0x1234)} `& yields -4608
9385 As a more realistic example, in an ACL you might have
9387 deny message = Too many bad recipients
9390 {>{$rcpt_count}{10}} \
9393 {$recipients_count} \
9394 {${eval:$rcpt_count/2}} \
9398 The condition is true if there have been more than 10 RCPT commands and
9399 fewer than half of them have resulted in a valid recipient.
9402 .vitem &*${expand:*&<&'string'&>&*}*&
9403 .cindex "expansion" "re-expansion of substring"
9404 The &%expand%& operator causes a string to be expanded for a second time. For
9407 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
9409 first looks up a string in a file while expanding the operand for &%expand%&,
9410 and then re-expands what it has found.
9413 .vitem &*${from_utf8:*&<&'string'&>&*}*&
9415 .cindex "UTF-8" "conversion from"
9416 .cindex "expansion" "UTF-8 conversion"
9417 .cindex "&%from_utf8%& expansion item"
9418 The world is slowly moving towards Unicode, although there are no standards for
9419 email yet. However, other applications (including some databases) are starting
9420 to store data in Unicode, using UTF-8 encoding. This operator converts from a
9421 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
9422 converted to underscores. The input must be a valid UTF-8 string. If it is not,
9423 the result is an undefined sequence of bytes.
9425 Unicode code points with values less than 256 are compatible with ASCII and
9426 ISO-8859-1 (also known as Latin-1).
9427 For example, character 169 is the copyright symbol in both cases, though the
9428 way it is encoded is different. In UTF-8, more than one byte is needed for
9429 characters with code values greater than 127, whereas ISO-8859-1 is a
9430 single-byte encoding (but thereby limited to 256 characters). This makes
9431 translation from UTF-8 to ISO-8859-1 straightforward.
9434 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9435 .cindex "hash function" "textual"
9436 .cindex "expansion" "textual hash"
9437 The &%hash%& operator is a simpler interface to the hashing function that can
9438 be used when the two parameters are fixed numbers (as opposed to strings that
9439 change when expanded). The effect is the same as
9441 ${hash{<n>}{<m>}{<string>}}
9443 See the description of the general &%hash%& item above for details. The
9444 abbreviation &%h%& can be used when &%hash%& is used as an operator.
9448 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
9449 .cindex "base64 encoding" "conversion from hex"
9450 .cindex "expansion" "hex to base64"
9451 .cindex "&%hex2b64%& expansion item"
9452 This operator converts a hex string into one that is base64 encoded. This can
9453 be useful for processing the output of the MD5 and SHA-1 hashing functions.
9456 .vitem &*${lc:*&<&'string'&>&*}*&
9457 .cindex "case forcing in strings"
9458 .cindex "string" "case forcing"
9459 .cindex "lower casing"
9460 .cindex "expansion" "case forcing"
9461 .cindex "&%lc%& expansion item"
9462 This forces the letters in the string into lower-case, for example:
9467 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
9468 .cindex "expansion" "string truncation"
9469 .cindex "&%length%& expansion item"
9470 The &%length%& operator is a simpler interface to the &%length%& function that
9471 can be used when the parameter is a fixed number (as opposed to a string that
9472 changes when expanded). The effect is the same as
9474 ${length{<number>}{<string>}}
9476 See the description of the general &%length%& item above for details. Note that
9477 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
9478 when &%length%& is used as an operator.
9481 .vitem &*${local_part:*&<&'string'&>&*}*&
9482 .cindex "expansion" "local part extraction"
9483 .cindex "&%local_part%& expansion item"
9484 The string is interpreted as an RFC 2822 address and the local part is
9485 extracted from it. If the string does not parse successfully, the result is
9489 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
9490 .cindex "masked IP address"
9491 .cindex "IP address" "masking"
9492 .cindex "CIDR notation"
9493 .cindex "expansion" "IP address masking"
9494 .cindex "&%mask%& expansion item"
9495 If the form of the string to be operated on is not an IP address followed by a
9496 slash and an integer (that is, a network address in CIDR notation), the
9497 expansion fails. Otherwise, this operator converts the IP address to binary,
9498 masks off the least significant bits according to the bit count, and converts
9499 the result back to text, with mask appended. For example,
9501 ${mask:10.111.131.206/28}
9503 returns the string &"10.111.131.192/28"&. Since this operation is expected to
9504 be mostly used for looking up masked addresses in files, the result for an IPv6
9505 address uses dots to separate components instead of colons, because colon
9506 terminates a key string in lsearch files. So, for example,
9508 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
9512 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
9514 Letters in IPv6 addresses are always output in lower case.
9517 .vitem &*${md5:*&<&'string'&>&*}*&
9519 .cindex "expansion" "MD5 hash"
9520 .cindex "&%md5%& expansion item"
9521 The &%md5%& operator computes the MD5 hash value of the string, and returns it
9522 as a 32-digit hexadecimal number, in which any letters are in lower case.
9525 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
9526 .cindex "expansion" "numeric hash"
9527 .cindex "hash function" "numeric"
9528 The &%nhash%& operator is a simpler interface to the numeric hashing function
9529 that can be used when the two parameters are fixed numbers (as opposed to
9530 strings that change when expanded). The effect is the same as
9532 ${nhash{<n>}{<m>}{<string>}}
9534 See the description of the general &%nhash%& item above for details.
9537 .vitem &*${quote:*&<&'string'&>&*}*&
9538 .cindex "quoting" "in string expansions"
9539 .cindex "expansion" "quoting"
9540 .cindex "&%quote%& expansion item"
9541 The &%quote%& operator puts its argument into double quotes if it
9542 is an empty string or
9543 contains anything other than letters, digits, underscores, dots, and hyphens.
9544 Any occurrences of double quotes and backslashes are escaped with a backslash.
9545 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
9546 respectively For example,
9554 The place where this is useful is when the argument is a substitution from a
9555 variable or a message header.
9557 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
9558 .cindex "&%quote_local_part%& expansion item"
9559 This operator is like &%quote%&, except that it quotes the string only if
9560 required to do so by the rules of RFC 2822 for quoting local parts. For
9561 example, a plus sign would not cause quoting (but it would for &%quote%&).
9562 If you are creating a new email address from the contents of &$local_part$&
9563 (or any other unknown data), you should always use this operator.
9566 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
9567 .cindex "quoting" "lookup-specific"
9568 This operator applies lookup-specific quoting rules to the string. Each
9569 query-style lookup type has its own quoting rules which are described with
9570 the lookups in chapter &<<CHAPfdlookup>>&. For example,
9572 ${quote_ldap:two * two}
9578 For single-key lookup types, no quoting is ever necessary and this operator
9579 yields an unchanged string.
9582 .vitem &*${randint:*&<&'n'&>&*}*&
9583 .cindex "random number"
9584 This operator returns a somewhat random number which is less than the
9585 supplied number and is at least 0. The quality of this randomness depends
9586 on how Exim was built; the values are not suitable for keying material.
9587 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
9588 Otherwise, the implementation may be arc4random(), random() seeded by
9589 srandomdev() or srandom(), or a custom implementation even weaker than
9593 .vitem &*${rfc2047:*&<&'string'&>&*}*&
9594 .cindex "expansion" "RFC 2047"
9595 .cindex "RFC 2047" "expansion operator"
9596 .cindex "&%rfc2047%& expansion item"
9597 This operator encodes text according to the rules of RFC 2047. This is an
9598 encoding that is used in header lines to encode non-ASCII characters. It is
9599 assumed that the input string is in the encoding specified by the
9600 &%headers_charset%& option, which defaults to ISO-8859-1. If the string
9601 contains only characters in the range 33&--126, and no instances of the
9604 ? = ( ) < > @ , ; : \ " . [ ] _
9606 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
9607 string, using as many &"encoded words"& as necessary to encode all the
9611 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
9612 .cindex "expansion" "RFC 2047"
9613 .cindex "RFC 2047" "decoding"
9614 .cindex "&%rfc2047d%& expansion item"
9615 This operator decodes strings that are encoded as per RFC 2047. Binary zero
9616 bytes are replaced by question marks. Characters are converted into the
9617 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
9618 not recognized unless &%check_rfc2047_length%& is set false.
9620 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
9621 access a header line, RFC 2047 decoding is done automatically. You do not need
9622 to use this operator as well.
9626 .vitem &*${rxquote:*&<&'string'&>&*}*&
9627 .cindex "quoting" "in regular expressions"
9628 .cindex "regular expressions" "quoting"
9629 .cindex "&%rxquote%& expansion item"
9630 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
9631 characters in its argument. This is useful when substituting the values of
9632 variables or headers inside regular expressions.
9635 .vitem &*${sha1:*&<&'string'&>&*}*&
9636 .cindex "SHA-1 hash"
9637 .cindex "expansion" "SHA-1 hashing"
9638 .cindex "&%sha2%& expansion item"
9639 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
9640 it as a 40-digit hexadecimal number, in which any letters are in upper case.
9643 .vitem &*${stat:*&<&'string'&>&*}*&
9644 .cindex "expansion" "statting a file"
9645 .cindex "file" "extracting characteristics"
9646 .cindex "&%stat%& expansion item"
9647 The string, after expansion, must be a file path. A call to the &[stat()]&
9648 function is made for this path. If &[stat()]& fails, an error occurs and the
9649 expansion fails. If it succeeds, the data from the stat replaces the item, as a
9650 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
9651 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
9652 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
9653 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
9654 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
9655 can extract individual fields using the &%extract%& expansion item.
9657 The use of the &%stat%& expansion in users' filter files can be locked out by
9658 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
9659 systems for files larger than 2GB.
9661 .vitem &*${str2b64:*&<&'string'&>&*}*&
9662 .cindex "expansion" "base64 encoding"
9663 .cindex "base64 encoding" "in string expansion"
9664 .cindex "&%str2b64%& expansion item"
9665 This operator converts a string into one that is base64 encoded.
9669 .vitem &*${strlen:*&<&'string'&>&*}*&
9670 .cindex "expansion" "string length"
9671 .cindex "string" "length in expansion"
9672 .cindex "&%strlen%& expansion item"
9673 The item is replace by the length of the expanded string, expressed as a
9674 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
9677 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
9678 .cindex "&%substr%& expansion item"
9679 .cindex "substring extraction"
9680 .cindex "expansion" "substring expansion"
9681 The &%substr%& operator is a simpler interface to the &%substr%& function that
9682 can be used when the two parameters are fixed numbers (as opposed to strings
9683 that change when expanded). The effect is the same as
9685 ${substr{<start>}{<length>}{<string>}}
9687 See the description of the general &%substr%& item above for details. The
9688 abbreviation &%s%& can be used when &%substr%& is used as an operator.
9690 .vitem &*${time_eval:*&<&'string'&>&*}*&
9691 .cindex "&%time_eval%& expansion item"
9692 .cindex "time interval" "decoding"
9693 This item converts an Exim time interval such as &`2d4h5m`& into a number of
9696 .vitem &*${time_interval:*&<&'string'&>&*}*&
9697 .cindex "&%time_interval%& expansion item"
9698 .cindex "time interval" "formatting"
9699 The argument (after sub-expansion) must be a sequence of decimal digits that
9700 represents an interval of time as a number of seconds. It is converted into a
9701 number of larger units and output in Exim's normal time format, for example,
9704 .vitem &*${uc:*&<&'string'&>&*}*&
9705 .cindex "case forcing in strings"
9706 .cindex "string" "case forcing"
9707 .cindex "upper casing"
9708 .cindex "expansion" "case forcing"
9709 .cindex "&%uc%& expansion item"
9710 This forces the letters in the string into upper-case.
9718 .section "Expansion conditions" "SECTexpcond"
9719 .scindex IIDexpcond "expansion" "conditions"
9720 The following conditions are available for testing by the &%${if%& construct
9721 while expanding strings:
9724 .vitem &*!*&<&'condition'&>
9725 .cindex "expansion" "negating a condition"
9726 .cindex "negation" "in expansion condition"
9727 Preceding any condition with an exclamation mark negates the result of the
9730 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9731 .cindex "numeric comparison"
9732 .cindex "expansion" "numeric comparison"
9733 There are a number of symbolic operators for doing numeric comparisons. They
9739 &`>= `& greater or equal
9741 &`<= `& less or equal
9745 ${if >{$message_size}{10M} ...
9747 Note that the general negation operator provides for inequality testing. The
9748 two strings must take the form of optionally signed decimal integers,
9749 optionally followed by one of the letters &"K"& or &"M"& (in either upper or
9750 lower case), signifying multiplication by 1024 or 1024*1024, respectively.
9751 As a special case, the numerical value of an empty string is taken as
9754 .vitem &*bool&~{*&<&'string'&>&*}*&
9755 .cindex "expansion" "boolean parsing"
9756 .cindex "&%bool%& expansion condition"
9757 This condition turns a string holding a true or false representation into
9758 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
9759 (case-insensitively); also positive integer numbers map to true if non-zero,
9760 false if zero. Leading whitespace is ignored.
9761 All other string values will result in expansion failure.
9763 When combined with ACL variables, this expansion condition will let you
9764 make decisions in one place and act on those decisions in another place.
9767 ${if bool{$acl_m_privileged_sender} ...
9770 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9771 .cindex "expansion" "encrypted comparison"
9772 .cindex "encrypted strings, comparing"
9773 .cindex "&%crypteq%& expansion condition"
9774 This condition is included in the Exim binary if it is built to support any
9775 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
9776 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
9777 included in the binary.
9779 The &%crypteq%& condition has two arguments. The first is encrypted and
9780 compared against the second, which is already encrypted. The second string may
9781 be in the LDAP form for storing encrypted strings, which starts with the
9782 encryption type in curly brackets, followed by the data. If the second string
9783 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
9784 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
9785 Typically this will be a field from a password file. An example of an encrypted
9786 string in LDAP form is:
9788 {md5}CY9rzUYh03PK3k6DJie09g==
9790 If such a string appears directly in an expansion, the curly brackets have to
9791 be quoted, because they are part of the expansion syntax. For example:
9793 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
9795 The following encryption types (whose names are matched case-independently) are
9800 .cindex "base64 encoding" "in encrypted password"
9801 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
9802 printable characters to compare with the remainder of the second string. If the
9803 length of the comparison string is 24, Exim assumes that it is base64 encoded
9804 (as in the above example). If the length is 32, Exim assumes that it is a
9805 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
9809 .cindex "SHA-1 hash"
9810 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
9811 printable characters to compare with the remainder of the second string. If the
9812 length of the comparison string is 28, Exim assumes that it is base64 encoded.
9813 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
9814 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
9817 .cindex "&[crypt()]&"
9818 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
9819 only the first eight characters of the password. However, in modern operating
9820 systems this is no longer true, and in many cases the entire password is used,
9821 whatever its length.
9824 .cindex "&[crypt16()]&"
9825 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
9826 use up to 16 characters of the password in some operating systems. Again, in
9827 modern operating systems, more characters may be used.
9829 Exim has its own version of &[crypt16()]&, which is just a double call to
9830 &[crypt()]&. For operating systems that have their own version, setting
9831 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
9832 operating system version instead of its own. This option is set by default in
9833 the OS-dependent &_Makefile_& for those operating systems that are known to
9834 support &[crypt16()]&.
9836 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
9837 it was not using the same algorithm as some operating systems' versions. It
9838 turns out that as well as &[crypt16()]& there is a function called
9839 &[bigcrypt()]& in some operating systems. This may or may not use the same
9840 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
9842 However, since there is now a move away from the traditional &[crypt()]&
9843 functions towards using SHA1 and other algorithms, tidying up this area of
9844 Exim is seen as very low priority.
9846 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
9847 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
9848 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
9849 default is &`{crypt}`&. Whatever the default, you can always use either
9850 function by specifying it explicitly in curly brackets.
9852 .vitem &*def:*&<&'variable&~name'&>
9853 .cindex "expansion" "checking for empty variable"
9854 .cindex "&%def%& expansion condition"
9855 The &%def%& condition must be followed by the name of one of the expansion
9856 variables defined in section &<<SECTexpvar>>&. The condition is true if the
9857 variable does not contain the empty string. For example:
9859 ${if def:sender_ident {from $sender_ident}}
9861 Note that the variable name is given without a leading &%$%& character. If the
9862 variable does not exist, the expansion fails.
9864 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
9865 &~&*def:h_*&<&'header&~name'&>&*:*&"
9866 .cindex "expansion" "checking header line existence"
9867 This condition is true if a message is being processed and the named header
9868 exists in the message. For example,
9870 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
9872 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
9873 the header name must be terminated by a colon if white space does not follow.
9875 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9876 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9877 .cindex "string" "comparison"
9878 .cindex "expansion" "string comparison"
9879 .cindex "&%eq%& expansion condition"
9880 .cindex "&%eqi%& expansion condition"
9881 The two substrings are first expanded. The condition is true if the two
9882 resulting strings are identical. For &%eq%& the comparison includes the case of
9883 letters, whereas for &%eqi%& the comparison is case-independent.
9885 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
9886 .cindex "expansion" "file existence test"
9887 .cindex "file" "existence test"
9888 .cindex "&%exists%&, expansion condition"
9889 The substring is first expanded and then interpreted as an absolute path. The
9890 condition is true if the named file (or directory) exists. The existence test
9891 is done by calling the &[stat()]& function. The use of the &%exists%& test in
9892 users' filter files may be locked out by the system administrator.
9894 .vitem &*first_delivery*&
9895 .cindex "delivery" "first"
9896 .cindex "first delivery"
9897 .cindex "expansion" "first delivery test"
9898 .cindex "&%first_delivery%& expansion condition"
9899 This condition, which has no data, is true during a message's first delivery
9900 attempt. It is false during any subsequent delivery attempts.
9903 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
9904 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
9905 .cindex "list" "iterative conditions"
9906 .cindex "expansion" "&*forall*& condition"
9907 .cindex "expansion" "&*forany*& condition"
9909 These conditions iterate over a list. The first argument is expanded to form
9910 the list. By default, the list separator is a colon, but it can be changed by
9911 the normal method. The second argument is interpreted as a condition that is to
9912 be applied to each item in the list in turn. During the interpretation of the
9913 condition, the current list item is placed in a variable called &$item$&.
9915 For &*forany*&, interpretation stops if the condition is true for any item, and
9916 the result of the whole condition is true. If the condition is false for all
9917 items in the list, the overall condition is false.
9919 For &*forall*&, interpretation stops if the condition is false for any item,
9920 and the result of the whole condition is false. If the condition is true for
9921 all items in the list, the overall condition is true.
9923 Note that negation of &*forany*& means that the condition must be false for all
9924 items for the overall condition to succeed, and negation of &*forall*& means
9925 that the condition must be false for at least one item. In this example, the
9926 list separator is changed to a comma:
9928 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
9930 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
9931 being processed, to enable these expansion items to be nested.
9934 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9935 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9936 .cindex "string" "comparison"
9937 .cindex "expansion" "string comparison"
9938 .cindex "&%ge%& expansion condition"
9939 .cindex "&%gei%& expansion condition"
9940 The two substrings are first expanded. The condition is true if the first
9941 string is lexically greater than or equal to the second string. For &%ge%& the
9942 comparison includes the case of letters, whereas for &%gei%& the comparison is
9945 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
9946 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
9947 .cindex "string" "comparison"
9948 .cindex "expansion" "string comparison"
9949 .cindex "&%gt%& expansion condition"
9950 .cindex "&%gti%& expansion condition"
9951 The two substrings are first expanded. The condition is true if the first
9952 string is lexically greater than the second string. For &%gt%& the comparison
9953 includes the case of letters, whereas for &%gti%& the comparison is
9956 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
9957 &*isip4&~{*&<&'string'&>&*}*& &&&
9958 &*isip6&~{*&<&'string'&>&*}*&
9959 .cindex "IP address" "testing string format"
9960 .cindex "string" "testing for IP address"
9961 .cindex "&%isip%& expansion condition"
9962 .cindex "&%isip4%& expansion condition"
9963 .cindex "&%isip6%& expansion condition"
9964 The substring is first expanded, and then tested to see if it has the form of
9965 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
9966 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
9968 For an IPv4 address, the test is for four dot-separated components, each of
9969 which consists of from one to three digits. For an IPv6 address, up to eight
9970 colon-separated components are permitted, each containing from one to four
9971 hexadecimal digits. There may be fewer than eight components if an empty
9972 component (adjacent colons) is present. Only one empty component is permitted.
9974 &*Note*&: The checks are just on the form of the address; actual numerical
9975 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
9976 check. The main use of these tests is to distinguish between IP addresses and
9977 host names, or between IPv4 and IPv6 addresses. For example, you could use
9979 ${if isip4{$sender_host_address}...
9981 to test which IP version an incoming SMTP connection is using.
9983 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
9984 .cindex "LDAP" "use for authentication"
9985 .cindex "expansion" "LDAP authentication test"
9986 .cindex "&%ldapauth%& expansion condition"
9987 This condition supports user authentication using LDAP. See section
9988 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
9989 queries. For this use, the query must contain a user name and password. The
9990 query itself is not used, and can be empty. The condition is true if the
9991 password is not empty, and the user name and password are accepted by the LDAP
9992 server. An empty password is rejected without calling LDAP because LDAP binds
9993 with an empty password are considered anonymous regardless of the username, and
9994 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
9995 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
9999 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10000 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10001 .cindex "string" "comparison"
10002 .cindex "expansion" "string comparison"
10003 .cindex "&%le%& expansion condition"
10004 .cindex "&%lei%& expansion condition"
10005 The two substrings are first expanded. The condition is true if the first
10006 string is lexically less than or equal to the second string. For &%le%& the
10007 comparison includes the case of letters, whereas for &%lei%& the comparison is
10010 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10011 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10012 .cindex "string" "comparison"
10013 .cindex "expansion" "string comparison"
10014 .cindex "&%lt%& expansion condition"
10015 .cindex "&%lti%& expansion condition"
10016 The two substrings are first expanded. The condition is true if the first
10017 string is lexically less than the second string. For &%lt%& the comparison
10018 includes the case of letters, whereas for &%lti%& the comparison is
10022 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10023 .cindex "expansion" "regular expression comparison"
10024 .cindex "regular expressions" "match in expanded string"
10025 .cindex "&%match%& expansion condition"
10026 The two substrings are first expanded. The second is then treated as a regular
10027 expression and applied to the first. Because of the pre-expansion, if the
10028 regular expression contains dollar, or backslash characters, they must be
10029 escaped. Care must also be taken if the regular expression contains braces
10030 (curly brackets). A closing brace must be escaped so that it is not taken as a
10031 premature termination of <&'string2'&>. The easiest approach is to use the
10032 &`\N`& feature to disable expansion of the regular expression.
10035 ${if match {$local_part}{\N^\d{3}\N} ...
10037 If the whole expansion string is in double quotes, further escaping of
10038 backslashes is also required.
10040 The condition is true if the regular expression match succeeds.
10041 The regular expression is not required to begin with a circumflex
10042 metacharacter, but if there is no circumflex, the expression is not anchored,
10043 and it may match anywhere in the subject, not just at the start. If you want
10044 the pattern to match at the end of the subject, you must include the &`$`&
10045 metacharacter at an appropriate point.
10047 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
10048 At the start of an &%if%& expansion the values of the numeric variable
10049 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
10050 succeeds causes them to be reset to the substrings of that condition and they
10051 will have these values during the expansion of the success string. At the end
10052 of the &%if%& expansion, the previous values are restored. After testing a
10053 combination of conditions using &%or%&, the subsequent values of the numeric
10054 variables are those of the condition that succeeded.
10056 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10057 .cindex "&%match_address%& expansion condition"
10058 See &*match_local_part*&.
10060 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10061 .cindex "&%match_domain%& expansion condition"
10062 See &*match_local_part*&.
10064 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10065 .cindex "&%match_ip%& expansion condition"
10066 This condition matches an IP address to a list of IP address patterns. It must
10067 be followed by two argument strings. The first (after expansion) must be an IP
10068 address or an empty string. The second (after expansion) is a restricted host
10069 list that can match only an IP address, not a host name. For example:
10071 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
10073 The specific types of host list item that are permitted in the list are:
10076 An IP address, optionally with a CIDR mask.
10078 A single asterisk, which matches any IP address.
10080 An empty item, which matches only if the IP address is empty. This could be
10081 useful for testing for a locally submitted message or one from specific hosts
10082 in a single test such as
10083 . ==== As this is a nested list, any displays it contains must be indented
10084 . ==== as otherwise they are too far to the left. This comment applies to
10085 . ==== the use of xmlto plus fop. There's no problem when formatting with
10086 . ==== sdop, with or without the extra indent.
10088 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
10090 where the first item in the list is the empty string.
10092 The item @[] matches any of the local host's interface addresses.
10094 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
10095 even if &`net-`& is not specified. There is never any attempt to turn the IP
10096 address into a host name. The most common type of linear search for
10097 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
10098 masks. For example:
10100 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
10102 It is of course possible to use other kinds of lookup, and in such a case, you
10103 do need to specify the &`net-`& prefix if you want to specify a specific
10104 address mask, for example:
10106 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
10108 However, unless you are combining a &%match_ip%& condition with others, it is
10109 just as easy to use the fact that a lookup is itself a condition, and write:
10111 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
10115 Consult section &<<SECThoslispatip>>& for further details of these patterns.
10117 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10118 .cindex "domain list" "in expansion condition"
10119 .cindex "address list" "in expansion condition"
10120 .cindex "local part" "list, in expansion condition"
10121 .cindex "&%match_local_part%& expansion condition"
10122 This condition, together with &%match_address%& and &%match_domain%&, make it
10123 possible to test domain, address, and local part lists within expansions. Each
10124 condition requires two arguments: an item and a list to match. A trivial
10127 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
10129 In each case, the second argument may contain any of the allowable items for a
10130 list of the appropriate type. Also, because the second argument (after
10131 expansion) is a standard form of list, it is possible to refer to a named list.
10132 Thus, you can use conditions like this:
10134 ${if match_domain{$domain}{+local_domains}{...
10136 .cindex "&`+caseful`&"
10137 For address lists, the matching starts off caselessly, but the &`+caseful`&
10138 item can be used, as in all address lists, to cause subsequent items to
10139 have their local parts matched casefully. Domains are always matched
10142 &*Note*&: Host lists are &'not'& supported in this way. This is because
10143 hosts have two identities: a name and an IP address, and it is not clear
10144 how to specify cleanly how such a test would work. However, IP addresses can be
10145 matched using &%match_ip%&.
10147 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
10148 .cindex "PAM authentication"
10149 .cindex "AUTH" "with PAM"
10150 .cindex "Solaris" "PAM support"
10151 .cindex "expansion" "PAM authentication test"
10152 .cindex "&%pam%& expansion condition"
10153 &'Pluggable Authentication Modules'&
10154 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
10155 available in the latest releases of Solaris and in some GNU/Linux
10156 distributions. The Exim support, which is intended for use in conjunction with
10157 the SMTP AUTH command, is available only if Exim is compiled with
10161 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
10162 in some releases of GNU/Linux &%-ldl%& is also needed.
10164 The argument string is first expanded, and the result must be a
10165 colon-separated list of strings. Leading and trailing white space is ignored.
10166 The PAM module is initialized with the service name &"exim"& and the user name
10167 taken from the first item in the colon-separated data string (<&'string1'&>).
10168 The remaining items in the data string are passed over in response to requests
10169 from the authentication function. In the simple case there will only be one
10170 request, for a password, so the data consists of just two strings.
10172 There can be problems if any of the strings are permitted to contain colon
10173 characters. In the usual way, these have to be doubled to avoid being taken as
10174 separators. If the data is being inserted from a variable, the &%sg%& expansion
10175 item can be used to double any existing colons. For example, the configuration
10176 of a LOGIN authenticator might contain this setting:
10178 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
10180 For a PLAIN authenticator you could use:
10182 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
10184 In some operating systems, PAM authentication can be done only from a process
10185 running as root. Since Exim is running as the Exim user when receiving
10186 messages, this means that PAM cannot be used directly in those systems.
10187 A patched version of the &'pam_unix'& module that comes with the
10188 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
10189 The patched module allows one special uid/gid combination, in addition to root,
10190 to authenticate. If you build the patched module to allow the Exim user and
10191 group, PAM can then be used from an Exim authenticator.
10194 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
10195 .cindex "&'pwcheck'& daemon"
10197 .cindex "expansion" "&'pwcheck'& authentication test"
10198 .cindex "&%pwcheck%& expansion condition"
10199 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
10200 This is one way of making it possible for passwords to be checked by a process
10201 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
10202 deprecated. Its replacement is &'saslauthd'& (see below).
10204 The pwcheck support is not included in Exim by default. You need to specify
10205 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
10206 building Exim. For example:
10208 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
10210 You do not need to install the full Cyrus software suite in order to use
10211 the pwcheck daemon. You can compile and install just the daemon alone
10212 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
10213 access to the &_/var/pwcheck_& directory.
10215 The &%pwcheck%& condition takes one argument, which must be the user name and
10216 password, separated by a colon. For example, in a LOGIN authenticator
10217 configuration, you might have this:
10219 server_condition = ${if pwcheck{$auth1:$auth2}}
10221 Again, for a PLAIN authenticator configuration, this would be:
10223 server_condition = ${if pwcheck{$auth2:$auth3}}
10225 .vitem &*queue_running*&
10226 .cindex "queue runner" "detecting when delivering from"
10227 .cindex "expansion" "queue runner test"
10228 .cindex "&%queue_running%& expansion condition"
10229 This condition, which has no data, is true during delivery attempts that are
10230 initiated by queue runner processes, and false otherwise.
10233 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
10235 .cindex "expansion" "Radius authentication"
10236 .cindex "&%radius%& expansion condition"
10237 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
10238 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
10239 the Radius client configuration file in order to build Exim with Radius
10242 With just that one setting, Exim expects to be linked with the &%radiusclient%&
10243 library, using the original API. If you are using release 0.4.0 or later of
10244 this library, you need to set
10246 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
10248 in &_Local/Makefile_& when building Exim. You can also link Exim with the
10249 &%libradius%& library that comes with FreeBSD. To do this, set
10251 RADIUS_LIB_TYPE=RADLIB
10253 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
10254 You may also have to supply a suitable setting in EXTRALIBS so that the
10255 Radius library can be found when Exim is linked.
10257 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
10258 Radius client library, which calls the Radius server. The condition is true if
10259 the authentication is successful. For example:
10261 server_condition = ${if radius{<arguments>}}
10265 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
10266 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
10267 .cindex "&'saslauthd'& daemon"
10269 .cindex "expansion" "&'saslauthd'& authentication test"
10270 .cindex "&%saslauthd%& expansion condition"
10271 This condition supports user authentication using the Cyrus &'saslauthd'&
10272 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
10273 Using this daemon is one way of making it possible for passwords to be checked
10274 by a process that is not running as root.
10276 The saslauthd support is not included in Exim by default. You need to specify
10277 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
10278 building Exim. For example:
10280 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
10282 You do not need to install the full Cyrus software suite in order to use
10283 the saslauthd daemon. You can compile and install just the daemon alone
10284 from the Cyrus SASL library.
10286 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
10287 two are mandatory. For example:
10289 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
10291 The service and the realm are optional (which is why the arguments are enclosed
10292 in their own set of braces). For details of the meaning of the service and
10293 realm, and how to run the daemon, consult the Cyrus documentation.
10298 .section "Combining expansion conditions" "SECID84"
10299 .cindex "expansion" "combining conditions"
10300 Several conditions can be tested at once by combining them using the &%and%&
10301 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
10302 conditions on their own, and precede their lists of sub-conditions. Each
10303 sub-condition must be enclosed in braces within the overall braces that contain
10304 the list. No repetition of &%if%& is used.
10308 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10309 .cindex "&""or""& expansion condition"
10310 .cindex "expansion" "&""or""& of conditions"
10311 The sub-conditions are evaluated from left to right. The condition is true if
10312 any one of the sub-conditions is true.
10315 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
10317 When a true sub-condition is found, the following ones are parsed but not
10318 evaluated. If there are several &"match"& sub-conditions the values of the
10319 numeric variables afterwards are taken from the first one that succeeds.
10321 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
10322 .cindex "&""and""& expansion condition"
10323 .cindex "expansion" "&""and""& of conditions"
10324 The sub-conditions are evaluated from left to right. The condition is true if
10325 all of the sub-conditions are true. If there are several &"match"&
10326 sub-conditions, the values of the numeric variables afterwards are taken from
10327 the last one. When a false sub-condition is found, the following ones are
10328 parsed but not evaluated.
10330 .ecindex IIDexpcond
10335 .section "Expansion variables" "SECTexpvar"
10336 .cindex "expansion" "variables, list of"
10337 This section contains an alphabetical list of all the expansion variables. Some
10338 of them are available only when Exim is compiled with specific options such as
10339 support for TLS or the content scanning extension.
10342 .vitem "&$0$&, &$1$&, etc"
10343 .cindex "numerical variables (&$1$& &$2$& etc)"
10344 When a &%match%& expansion condition succeeds, these variables contain the
10345 captured substrings identified by the regular expression during subsequent
10346 processing of the success string of the containing &%if%& expansion item.
10347 However, they do not retain their values afterwards; in fact, their previous
10348 values are restored at the end of processing an &%if%& item. The numerical
10349 variables may also be set externally by some other matching process which
10350 precedes the expansion of the string. For example, the commands available in
10351 Exim filter files include an &%if%& command with its own regular expression
10352 matching condition.
10354 .vitem "&$acl_c...$&"
10355 Values can be placed in these variables by the &%set%& modifier in an ACL. They
10356 can be given any name that starts with &$acl_c$& and is at least six characters
10357 long, but the sixth character must be either a digit or an underscore. For
10358 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
10359 variables persist throughout the lifetime of an SMTP connection. They can be
10360 used to pass information between ACLs and between different invocations of the
10361 same ACL. When a message is received, the values of these variables are saved
10362 with the message, and can be accessed by filters, routers, and transports
10363 during subsequent delivery.
10365 .vitem "&$acl_m...$&"
10366 These variables are like the &$acl_c...$& variables, except that their values
10367 are reset after a message has been received. Thus, if several messages are
10368 received in one SMTP connection, &$acl_m...$& values are not passed on from one
10369 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
10370 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
10371 message is received, the values of these variables are saved with the message,
10372 and can be accessed by filters, routers, and transports during subsequent
10375 .vitem &$acl_verify_message$&
10376 .vindex "&$acl_verify_message$&"
10377 After an address verification has failed, this variable contains the failure
10378 message. It retains its value for use in subsequent modifiers. The message can
10379 be preserved by coding like this:
10381 warn !verify = sender
10382 set acl_m0 = $acl_verify_message
10384 You can use &$acl_verify_message$& during the expansion of the &%message%& or
10385 &%log_message%& modifiers, to include information about the verification
10388 .vitem &$address_data$&
10389 .vindex "&$address_data$&"
10390 This variable is set by means of the &%address_data%& option in routers. The
10391 value then remains with the address while it is processed by subsequent routers
10392 and eventually a transport. If the transport is handling multiple addresses,
10393 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
10394 for more details. &*Note*&: The contents of &$address_data$& are visible in
10397 If &$address_data$& is set when the routers are called from an ACL to verify
10398 a recipient address, the final value is still in the variable for subsequent
10399 conditions and modifiers of the ACL statement. If routing the address caused it
10400 to be redirected to just one address, the child address is also routed as part
10401 of the verification, and in this case the final value of &$address_data$& is
10402 from the child's routing.
10404 If &$address_data$& is set when the routers are called from an ACL to verify a
10405 sender address, the final value is also preserved, but this time in
10406 &$sender_address_data$&, to distinguish it from data from a recipient
10409 In both cases (recipient and sender verification), the value does not persist
10410 after the end of the current ACL statement. If you want to preserve
10411 these values for longer, you can save them in ACL variables.
10413 .vitem &$address_file$&
10414 .vindex "&$address_file$&"
10415 When, as a result of aliasing, forwarding, or filtering, a message is directed
10416 to a specific file, this variable holds the name of the file when the transport
10417 is running. At other times, the variable is empty. For example, using the
10418 default configuration, if user &%r2d2%& has a &_.forward_& file containing
10420 /home/r2d2/savemail
10422 then when the &(address_file)& transport is running, &$address_file$&
10423 contains the text string &`/home/r2d2/savemail`&.
10424 .cindex "Sieve filter" "value of &$address_file$&"
10425 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
10426 then up to the transport configuration to generate an appropriate absolute path
10427 to the relevant file.
10429 .vitem &$address_pipe$&
10430 .vindex "&$address_pipe$&"
10431 When, as a result of aliasing or forwarding, a message is directed to a pipe,
10432 this variable holds the pipe command when the transport is running.
10434 .vitem "&$auth1$& &-- &$auth3$&"
10435 .vindex "&$auth1$&, &$auth2$&, etc"
10436 These variables are used in SMTP authenticators (see chapters
10437 &<<CHAPplaintext>>&&--&<<CHAPspa>>&). Elsewhere, they are empty.
10439 .vitem &$authenticated_id$&
10440 .cindex "authentication" "id"
10441 .vindex "&$authenticated_id$&"
10442 When a server successfully authenticates a client it may be configured to
10443 preserve some of the authentication information in the variable
10444 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
10445 user/password authenticator configuration might preserve the user name for use
10446 in the routers. Note that this is not the same information that is saved in
10447 &$sender_host_authenticated$&.
10448 When a message is submitted locally (that is, not over a TCP connection)
10449 the value of &$authenticated_id$& is normally the login name of the calling
10450 process. However, a trusted user can override this by means of the &%-oMai%&
10451 command line option.
10456 .vitem &$authenticated_sender$&
10457 .cindex "sender" "authenticated"
10458 .cindex "authentication" "sender"
10459 .cindex "AUTH" "on MAIL command"
10460 .vindex "&$authenticated_sender$&"
10461 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
10462 SMTP MAIL command if it believes the sender is sufficiently trusted, as
10463 described in section &<<SECTauthparamail>>&. Unless the data is the string
10464 &"<>"&, it is set as the authenticated sender of the message, and the value is
10465 available during delivery in the &$authenticated_sender$& variable. If the
10466 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
10468 .vindex "&$qualify_domain$&"
10469 When a message is submitted locally (that is, not over a TCP connection), the
10470 value of &$authenticated_sender$& is an address constructed from the login
10471 name of the calling process and &$qualify_domain$&, except that a trusted user
10472 can override this by means of the &%-oMas%& command line option.
10475 .vitem &$authentication_failed$&
10476 .cindex "authentication" "failure"
10477 .vindex "&$authentication_failed$&"
10478 This variable is set to &"1"& in an Exim server if a client issues an AUTH
10479 command that does not succeed. Otherwise it is set to &"0"&. This makes it
10480 possible to distinguish between &"did not try to authenticate"&
10481 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
10482 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
10483 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
10484 negative response to an AUTH command, including (for example) an attempt to use
10485 an undefined mechanism.
10487 .vitem &$body_linecount$&
10488 .cindex "message body" "line count"
10489 .cindex "body of message" "line count"
10490 .vindex "&$body_linecount$&"
10491 When a message is being received or delivered, this variable contains the
10492 number of lines in the message's body. See also &$message_linecount$&.
10494 .vitem &$body_zerocount$&
10495 .cindex "message body" "binary zero count"
10496 .cindex "body of message" "binary zero count"
10497 .cindex "binary zero" "in message body"
10498 .vindex "&$body_zerocount$&"
10499 When a message is being received or delivered, this variable contains the
10500 number of binary zero bytes in the message's body.
10502 .vitem &$bounce_recipient$&
10503 .vindex "&$bounce_recipient$&"
10504 This is set to the recipient address of a bounce message while Exim is creating
10505 it. It is useful if a customized bounce message text file is in use (see
10506 chapter &<<CHAPemsgcust>>&).
10508 .vitem &$bounce_return_size_limit$&
10509 .vindex "&$bounce_return_size_limit$&"
10510 This contains the value set in the &%bounce_return_size_limit%& option, rounded
10511 up to a multiple of 1000. It is useful when a customized error message text
10512 file is in use (see chapter &<<CHAPemsgcust>>&).
10514 .vitem &$caller_gid$&
10515 .cindex "gid (group id)" "caller"
10516 .vindex "&$caller_gid$&"
10517 The real group id under which the process that called Exim was running. This is
10518 not the same as the group id of the originator of a message (see
10519 &$originator_gid$&). If Exim re-execs itself, this variable in the new
10520 incarnation normally contains the Exim gid.
10522 .vitem &$caller_uid$&
10523 .cindex "uid (user id)" "caller"
10524 .vindex "&$caller_uid$&"
10525 The real user id under which the process that called Exim was running. This is
10526 not the same as the user id of the originator of a message (see
10527 &$originator_uid$&). If Exim re-execs itself, this variable in the new
10528 incarnation normally contains the Exim uid.
10530 .vitem &$compile_date$&
10531 .vindex "&$compile_date$&"
10532 The date on which the Exim binary was compiled.
10534 .vitem &$compile_number$&
10535 .vindex "&$compile_number$&"
10536 The building process for Exim keeps a count of the number
10537 of times it has been compiled. This serves to distinguish different
10538 compilations of the same version of the program.
10540 .vitem &$demime_errorlevel$&
10541 .vindex "&$demime_errorlevel$&"
10542 This variable is available when Exim is compiled with
10543 the content-scanning extension and the obsolete &%demime%& condition. For
10544 details, see section &<<SECTdemimecond>>&.
10546 .vitem &$demime_reason$&
10547 .vindex "&$demime_reason$&"
10548 This variable is available when Exim is compiled with the
10549 content-scanning extension and the obsolete &%demime%& condition. For details,
10550 see section &<<SECTdemimecond>>&.
10552 .vitem &$dnslist_domain$& &&&
10553 &$dnslist_matched$& &&&
10554 &$dnslist_text$& &&&
10556 .vindex "&$dnslist_domain$&"
10557 .vindex "&$dnslist_matched$&"
10558 .vindex "&$dnslist_text$&"
10559 .vindex "&$dnslist_value$&"
10560 .cindex "black list (DNS)"
10561 When a DNS (black) list lookup succeeds, these variables are set to contain
10562 the following data from the lookup: the list's domain name, the key that was
10563 looked up, the contents of any associated TXT record, and the value from the
10564 main A record. See section &<<SECID204>>& for more details.
10567 .vindex "&$domain$&"
10568 When an address is being routed, or delivered on its own, this variable
10569 contains the domain. Uppercase letters in the domain are converted into lower
10570 case for &$domain$&.
10572 Global address rewriting happens when a message is received, so the value of
10573 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
10574 is set during user filtering, but not during system filtering, because a
10575 message may have many recipients and the system filter is called just once.
10577 When more than one address is being delivered at once (for example, several
10578 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
10579 have the same domain. Transports can be restricted to handling only one domain
10580 at a time if the value of &$domain$& is required at transport time &-- this is
10581 the default for local transports. For further details of the environment in
10582 which local transports are run, see chapter &<<CHAPenvironment>>&.
10584 .oindex "&%delay_warning_condition%&"
10585 At the end of a delivery, if all deferred addresses have the same domain, it is
10586 set in &$domain$& during the expansion of &%delay_warning_condition%&.
10588 The &$domain$& variable is also used in some other circumstances:
10591 When an ACL is running for a RCPT command, &$domain$& contains the domain of
10592 the recipient address. The domain of the &'sender'& address is in
10593 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
10594 normally set during the running of the MAIL ACL. However, if the sender address
10595 is verified with a callout during the MAIL ACL, the sender domain is placed in
10596 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
10597 the &(smtp)& transport.
10600 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10601 &$domain$& contains the domain portion of the address that is being rewritten;
10602 it can be used in the expansion of the replacement address, for example, to
10603 rewrite domains by file lookup.
10606 With one important exception, whenever a domain list is being scanned,
10607 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
10608 a &%sender_domains%& condition in an ACL is being processed, the subject domain
10609 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
10610 that, in a RCPT ACL, the sender domain list can be dependent on the
10611 recipient domain (which is what is in &$domain$& at this time).
10614 .cindex "ETRN" "value of &$domain$&"
10615 .oindex "&%smtp_etrn_command%&"
10616 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
10617 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
10621 .vitem &$domain_data$&
10622 .vindex "&$domain_data$&"
10623 When the &%domains%& option on a router matches a domain by
10624 means of a lookup, the data read by the lookup is available during the running
10625 of the router as &$domain_data$&. In addition, if the driver routes the
10626 address to a transport, the value is available in that transport. If the
10627 transport is handling multiple addresses, the value from the first address is
10630 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
10631 domain by means of a lookup. The data read by the lookup is available during
10632 the rest of the ACL statement. In all other situations, this variable expands
10635 .vitem &$exim_gid$&
10636 .vindex "&$exim_gid$&"
10637 This variable contains the numerical value of the Exim group id.
10639 .vitem &$exim_path$&
10640 .vindex "&$exim_path$&"
10641 This variable contains the path to the Exim binary.
10643 .vitem &$exim_uid$&
10644 .vindex "&$exim_uid$&"
10645 This variable contains the numerical value of the Exim user id.
10647 .vitem &$found_extension$&
10648 .vindex "&$found_extension$&"
10649 This variable is available when Exim is compiled with the
10650 content-scanning extension and the obsolete &%demime%& condition. For details,
10651 see section &<<SECTdemimecond>>&.
10653 .vitem &$header_$&<&'name'&>
10654 This is not strictly an expansion variable. It is expansion syntax for
10655 inserting the message header line with the given name. Note that the name must
10656 be terminated by colon or white space, because it may contain a wide variety of
10657 characters. Note also that braces must &'not'& be used.
10661 When the &%check_local_user%& option is set for a router, the user's home
10662 directory is placed in &$home$& when the check succeeds. In particular, this
10663 means it is set during the running of users' filter files. A router may also
10664 explicitly set a home directory for use by a transport; this can be overridden
10665 by a setting on the transport itself.
10667 When running a filter test via the &%-bf%& option, &$home$& is set to the value
10668 of the environment variable HOME.
10672 If a router assigns an address to a transport (any transport), and passes a
10673 list of hosts with the address, the value of &$host$& when the transport starts
10674 to run is the name of the first host on the list. Note that this applies both
10675 to local and remote transports.
10677 .cindex "transport" "filter"
10678 .cindex "filter" "transport filter"
10679 For the &(smtp)& transport, if there is more than one host, the value of
10680 &$host$& changes as the transport works its way through the list. In
10681 particular, when the &(smtp)& transport is expanding its options for encryption
10682 using TLS, or for specifying a transport filter (see chapter
10683 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
10686 When used in the client part of an authenticator configuration (see chapter
10687 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
10688 client is connected.
10691 .vitem &$host_address$&
10692 .vindex "&$host_address$&"
10693 This variable is set to the remote host's IP address whenever &$host$& is set
10694 for a remote connection. It is also set to the IP address that is being checked
10695 when the &%ignore_target_hosts%& option is being processed.
10697 .vitem &$host_data$&
10698 .vindex "&$host_data$&"
10699 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
10700 result of the lookup is made available in the &$host_data$& variable. This
10701 allows you, for example, to do things like this:
10703 deny hosts = net-lsearch;/some/file
10704 message = $host_data
10706 .vitem &$host_lookup_deferred$&
10707 .cindex "host name" "lookup, failure of"
10708 .vindex "&$host_lookup_deferred$&"
10709 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
10710 message comes from a remote host and there is an attempt to look up the host's
10711 name from its IP address, and the attempt is not successful, one of these
10712 variables is set to &"1"&.
10715 If the lookup receives a definite negative response (for example, a DNS lookup
10716 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
10719 If there is any kind of problem during the lookup, such that Exim cannot
10720 tell whether or not the host name is defined (for example, a timeout for a DNS
10721 lookup), &$host_lookup_deferred$& is set to &"1"&.
10724 Looking up a host's name from its IP address consists of more than just a
10725 single reverse lookup. Exim checks that a forward lookup of at least one of the
10726 names it receives from a reverse lookup yields the original IP address. If this
10727 is not the case, Exim does not accept the looked up name(s), and
10728 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
10729 IP address (for example, the existence of a PTR record in the DNS) is not
10730 sufficient on its own for the success of a host name lookup. If the reverse
10731 lookup succeeds, but there is a lookup problem such as a timeout when checking
10732 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
10733 &"1"&. See also &$sender_host_name$&.
10735 .vitem &$host_lookup_failed$&
10736 .vindex "&$host_lookup_failed$&"
10737 See &$host_lookup_deferred$&.
10741 .vindex "&$inode$&"
10742 The only time this variable is set is while expanding the &%directory_file%&
10743 option in the &(appendfile)& transport. The variable contains the inode number
10744 of the temporary file which is about to be renamed. It can be used to construct
10745 a unique name for the file.
10747 .vitem &$interface_address$&
10748 .vindex "&$interface_address$&"
10749 This is an obsolete name for &$received_ip_address$&.
10751 .vitem &$interface_port$&
10752 .vindex "&$interface_port$&"
10753 This is an obsolete name for &$received_port$&.
10757 This variable is used during the expansion of &*forall*& and &*forany*&
10758 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
10759 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
10763 .vindex "&$ldap_dn$&"
10764 This variable, which is available only when Exim is compiled with LDAP support,
10765 contains the DN from the last entry in the most recently successful LDAP
10768 .vitem &$load_average$&
10769 .vindex "&$load_average$&"
10770 This variable contains the system load average, multiplied by 1000 so that it
10771 is an integer. For example, if the load average is 0.21, the value of the
10772 variable is 210. The value is recomputed every time the variable is referenced.
10774 .vitem &$local_part$&
10775 .vindex "&$local_part$&"
10776 When an address is being routed, or delivered on its own, this
10777 variable contains the local part. When a number of addresses are being
10778 delivered together (for example, multiple RCPT commands in an SMTP
10779 session), &$local_part$& is not set.
10781 Global address rewriting happens when a message is received, so the value of
10782 &$local_part$& during routing and delivery is the value after rewriting.
10783 &$local_part$& is set during user filtering, but not during system filtering,
10784 because a message may have many recipients and the system filter is called just
10787 .vindex "&$local_part_prefix$&"
10788 .vindex "&$local_part_suffix$&"
10789 If a local part prefix or suffix has been recognized, it is not included in the
10790 value of &$local_part$& during routing and subsequent delivery. The values of
10791 any prefix or suffix are in &$local_part_prefix$& and
10792 &$local_part_suffix$&, respectively.
10794 When a message is being delivered to a file, pipe, or autoreply transport as a
10795 result of aliasing or forwarding, &$local_part$& is set to the local part of
10796 the parent address, not to the file name or command (see &$address_file$& and
10799 When an ACL is running for a RCPT command, &$local_part$& contains the
10800 local part of the recipient address.
10802 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
10803 &$local_part$& contains the local part of the address that is being rewritten;
10804 it can be used in the expansion of the replacement address, for example.
10806 In all cases, all quoting is removed from the local part. For example, for both
10809 "abc:xyz"@test.example
10810 abc\:xyz@test.example
10812 the value of &$local_part$& is
10816 If you use &$local_part$& to create another address, you should always wrap it
10817 inside a quoting operator. For example, in a &(redirect)& router you could
10820 data = ${quote_local_part:$local_part}@new.domain.example
10822 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
10823 to process local parts in a case-dependent manner in a router, you can set the
10824 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
10826 .vitem &$local_part_data$&
10827 .vindex "&$local_part_data$&"
10828 When the &%local_parts%& option on a router matches a local part by means of a
10829 lookup, the data read by the lookup is available during the running of the
10830 router as &$local_part_data$&. In addition, if the driver routes the address
10831 to a transport, the value is available in that transport. If the transport is
10832 handling multiple addresses, the value from the first address is used.
10834 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
10835 matches a local part by means of a lookup. The data read by the lookup is
10836 available during the rest of the ACL statement. In all other situations, this
10837 variable expands to nothing.
10839 .vitem &$local_part_prefix$&
10840 .vindex "&$local_part_prefix$&"
10841 When an address is being routed or delivered, and a
10842 specific prefix for the local part was recognized, it is available in this
10843 variable, having been removed from &$local_part$&.
10845 .vitem &$local_part_suffix$&
10846 .vindex "&$local_part_suffix$&"
10847 When an address is being routed or delivered, and a
10848 specific suffix for the local part was recognized, it is available in this
10849 variable, having been removed from &$local_part$&.
10851 .vitem &$local_scan_data$&
10852 .vindex "&$local_scan_data$&"
10853 This variable contains the text returned by the &[local_scan()]& function when
10854 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
10856 .vitem &$local_user_gid$&
10857 .vindex "&$local_user_gid$&"
10858 See &$local_user_uid$&.
10860 .vitem &$local_user_uid$&
10861 .vindex "&$local_user_uid$&"
10862 This variable and &$local_user_gid$& are set to the uid and gid after the
10863 &%check_local_user%& router precondition succeeds. This means that their values
10864 are available for the remaining preconditions (&%senders%&, &%require_files%&,
10865 and &%condition%&), for the &%address_data%& expansion, and for any
10866 router-specific expansions. At all other times, the values in these variables
10867 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
10869 .vitem &$localhost_number$&
10870 .vindex "&$localhost_number$&"
10871 This contains the expanded value of the
10872 &%localhost_number%& option. The expansion happens after the main options have
10875 .vitem &$log_inodes$&
10876 .vindex "&$log_inodes$&"
10877 The number of free inodes in the disk partition where Exim's
10878 log files are being written. The value is recalculated whenever the variable is
10879 referenced. If the relevant file system does not have the concept of inodes,
10880 the value of is -1. See also the &%check_log_inodes%& option.
10882 .vitem &$log_space$&
10883 .vindex "&$log_space$&"
10884 The amount of free space (as a number of kilobytes) in the disk
10885 partition where Exim's log files are being written. The value is recalculated
10886 whenever the variable is referenced. If the operating system does not have the
10887 ability to find the amount of free space (only true for experimental systems),
10888 the space value is -1. See also the &%check_log_space%& option.
10891 .vitem &$mailstore_basename$&
10892 .vindex "&$mailstore_basename$&"
10893 This variable is set only when doing deliveries in &"mailstore"& format in the
10894 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
10895 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
10896 contains the basename of the files that are being written, that is, the name
10897 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
10900 .vitem &$malware_name$&
10901 .vindex "&$malware_name$&"
10902 This variable is available when Exim is compiled with the
10903 content-scanning extension. It is set to the name of the virus that was found
10904 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
10906 .vitem &$max_received_linelength$&
10907 .vindex "&$max_received_linelength$&"
10908 .cindex "maximum" "line length"
10909 .cindex "line length" "maximum"
10910 This variable contains the number of bytes in the longest line that was
10911 received as part of the message, not counting the line termination
10914 .vitem &$message_age$&
10915 .cindex "message" "age of"
10916 .vindex "&$message_age$&"
10917 This variable is set at the start of a delivery attempt to contain the number
10918 of seconds since the message was received. It does not change during a single
10921 .vitem &$message_body$&
10922 .cindex "body of message" "expansion variable"
10923 .cindex "message body" "in expansion"
10924 .cindex "binary zero" "in message body"
10925 .vindex "&$message_body$&"
10926 .oindex "&%message_body_visible%&"
10927 This variable contains the initial portion of a message's body while it is
10928 being delivered, and is intended mainly for use in filter files. The maximum
10929 number of characters of the body that are put into the variable is set by the
10930 &%message_body_visible%& configuration option; the default is 500.
10932 .oindex "&%message_body_newlines%&"
10933 By default, newlines are converted into spaces in &$message_body$&, to make it
10934 easier to search for phrases that might be split over a line break. However,
10935 this can be disabled by setting &%message_body_newlines%& to be true. Binary
10936 zeros are always converted into spaces.
10938 .vitem &$message_body_end$&
10939 .cindex "body of message" "expansion variable"
10940 .cindex "message body" "in expansion"
10941 .vindex "&$message_body_end$&"
10942 This variable contains the final portion of a message's
10943 body while it is being delivered. The format and maximum size are as for
10946 .vitem &$message_body_size$&
10947 .cindex "body of message" "size"
10948 .cindex "message body" "size"
10949 .vindex "&$message_body_size$&"
10950 When a message is being delivered, this variable contains the size of the body
10951 in bytes. The count starts from the character after the blank line that
10952 separates the body from the header. Newlines are included in the count. See
10953 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
10955 .vitem &$message_exim_id$&
10956 .vindex "&$message_exim_id$&"
10957 When a message is being received or delivered, this variable contains the
10958 unique message id that is generated and used by Exim to identify the message.
10959 An id is not created for a message until after its header has been successfully
10960 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
10961 line; it is the local id that Exim assigns to the message, for example:
10962 &`1BXTIK-0001yO-VA`&.
10964 .vitem &$message_headers$&
10965 .vindex &$message_headers$&
10966 This variable contains a concatenation of all the header lines when a message
10967 is being processed, except for lines added by routers or transports. The header
10968 lines are separated by newline characters. Their contents are decoded in the
10969 same way as a header line that is inserted by &%bheader%&.
10971 .vitem &$message_headers_raw$&
10972 .vindex &$message_headers_raw$&
10973 This variable is like &$message_headers$& except that no processing of the
10974 contents of header lines is done.
10976 .vitem &$message_id$&
10977 This is an old name for &$message_exim_id$&, which is now deprecated.
10979 .vitem &$message_linecount$&
10980 .vindex "&$message_linecount$&"
10981 This variable contains the total number of lines in the header and body of the
10982 message. Compare &$body_linecount$&, which is the count for the body only.
10983 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
10984 number of lines received. Before delivery happens (that is, before filters,
10985 routers, and transports run) the count is increased to include the
10986 &'Received:'& header line that Exim standardly adds, and also any other header
10987 lines that are added by ACLs. The blank line that separates the message header
10988 from the body is not counted. Here is an example of the use of this variable in
10991 deny message = Too many lines in message header
10993 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
10995 In the MAIL and RCPT ACLs, the value is zero because at that stage the
10996 message has not yet been received.
10998 .vitem &$message_size$&
10999 .cindex "size" "of message"
11000 .cindex "message" "size"
11001 .vindex "&$message_size$&"
11002 When a message is being processed, this variable contains its size in bytes. In
11003 most cases, the size includes those headers that were received with the
11004 message, but not those (such as &'Envelope-to:'&) that are added to individual
11005 deliveries as they are written. However, there is one special case: during the
11006 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
11007 doing a delivery in maildir format, the value of &$message_size$& is the
11008 precise size of the file that has been written. See also
11009 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
11011 .cindex "RCPT" "value of &$message_size$&"
11012 While running a per message ACL (mail/rcpt/predata), &$message_size$&
11013 contains the size supplied on the MAIL command, or -1 if no size was given. The
11014 value may not, of course, be truthful.
11016 .vitem &$mime_$&&'xxx'&
11017 A number of variables whose names start with &$mime$& are
11018 available when Exim is compiled with the content-scanning extension. For
11019 details, see section &<<SECTscanmimepart>>&.
11021 .vitem "&$n0$& &-- &$n9$&"
11022 These variables are counters that can be incremented by means
11023 of the &%add%& command in filter files.
11025 .vitem &$original_domain$&
11026 .vindex "&$domain$&"
11027 .vindex "&$original_domain$&"
11028 When a top-level address is being processed for delivery, this contains the
11029 same value as &$domain$&. However, if a &"child"& address (for example,
11030 generated by an alias, forward, or filter file) is being processed, this
11031 variable contains the domain of the original address (lower cased). This
11032 differs from &$parent_domain$& only when there is more than one level of
11033 aliasing or forwarding. When more than one address is being delivered in a
11034 single transport run, &$original_domain$& is not set.
11036 If a new address is created by means of a &%deliver%& command in a system
11037 filter, it is set up with an artificial &"parent"& address. This has the local
11038 part &'system-filter'& and the default qualify domain.
11040 .vitem &$original_local_part$&
11041 .vindex "&$local_part$&"
11042 .vindex "&$original_local_part$&"
11043 When a top-level address is being processed for delivery, this contains the
11044 same value as &$local_part$&, unless a prefix or suffix was removed from the
11045 local part, because &$original_local_part$& always contains the full local
11046 part. When a &"child"& address (for example, generated by an alias, forward, or
11047 filter file) is being processed, this variable contains the full local part of
11048 the original address.
11050 If the router that did the redirection processed the local part
11051 case-insensitively, the value in &$original_local_part$& is in lower case.
11052 This variable differs from &$parent_local_part$& only when there is more than
11053 one level of aliasing or forwarding. When more than one address is being
11054 delivered in a single transport run, &$original_local_part$& is not set.
11056 If a new address is created by means of a &%deliver%& command in a system
11057 filter, it is set up with an artificial &"parent"& address. This has the local
11058 part &'system-filter'& and the default qualify domain.
11060 .vitem &$originator_gid$&
11061 .cindex "gid (group id)" "of originating user"
11062 .cindex "sender" "gid"
11063 .vindex "&$caller_gid$&"
11064 .vindex "&$originator_gid$&"
11065 This variable contains the value of &$caller_gid$& that was set when the
11066 message was received. For messages received via the command line, this is the
11067 gid of the sending user. For messages received by SMTP over TCP/IP, this is
11068 normally the gid of the Exim user.
11070 .vitem &$originator_uid$&
11071 .cindex "uid (user id)" "of originating user"
11072 .cindex "sender" "uid"
11073 .vindex "&$caller_uid$&"
11074 .vindex "&$originaltor_uid$&"
11075 The value of &$caller_uid$& that was set when the message was received. For
11076 messages received via the command line, this is the uid of the sending user.
11077 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
11080 .vitem &$parent_domain$&
11081 .vindex "&$parent_domain$&"
11082 This variable is similar to &$original_domain$& (see
11083 above), except that it refers to the immediately preceding parent address.
11085 .vitem &$parent_local_part$&
11086 .vindex "&$parent_local_part$&"
11087 This variable is similar to &$original_local_part$&
11088 (see above), except that it refers to the immediately preceding parent address.
11091 .cindex "pid (process id)" "of current process"
11093 This variable contains the current process id.
11095 .vitem &$pipe_addresses$&
11096 .cindex "filter" "transport filter"
11097 .cindex "transport" "filter"
11098 .vindex "&$pipe_addresses$&"
11099 This is not an expansion variable, but is mentioned here because the string
11100 &`$pipe_addresses`& is handled specially in the command specification for the
11101 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
11102 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
11103 It cannot be used in general expansion strings, and provokes an &"unknown
11104 variable"& error if encountered.
11106 .vitem &$primary_hostname$&
11107 .vindex "&$primary_hostname$&"
11108 This variable contains the value set by &%primary_hostname%& in the
11109 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
11110 a single-component name, Exim calls &[gethostbyname()]& (or
11111 &[getipnodebyname()]& where available) in an attempt to acquire a fully
11112 qualified host name. See also &$smtp_active_hostname$&.
11115 .vitem &$prvscheck_address$&
11116 This variable is used in conjunction with the &%prvscheck%& expansion item,
11117 which is described in sections &<<SECTexpansionitems>>& and
11118 &<<SECTverifyPRVS>>&.
11120 .vitem &$prvscheck_keynum$&
11121 This variable is used in conjunction with the &%prvscheck%& expansion item,
11122 which is described in sections &<<SECTexpansionitems>>& and
11123 &<<SECTverifyPRVS>>&.
11125 .vitem &$prvscheck_result$&
11126 This variable is used in conjunction with the &%prvscheck%& expansion item,
11127 which is described in sections &<<SECTexpansionitems>>& and
11128 &<<SECTverifyPRVS>>&.
11130 .vitem &$qualify_domain$&
11131 .vindex "&$qualify_domain$&"
11132 The value set for the &%qualify_domain%& option in the configuration file.
11134 .vitem &$qualify_recipient$&
11135 .vindex "&$qualify_recipient$&"
11136 The value set for the &%qualify_recipient%& option in the configuration file,
11137 or if not set, the value of &$qualify_domain$&.
11139 .vitem &$rcpt_count$&
11140 .vindex "&$rcpt_count$&"
11141 When a message is being received by SMTP, this variable contains the number of
11142 RCPT commands received for the current message. If this variable is used in a
11143 RCPT ACL, its value includes the current command.
11145 .vitem &$rcpt_defer_count$&
11146 .vindex "&$rcpt_defer_count$&"
11147 .cindex "4&'xx'& responses" "count of"
11148 When a message is being received by SMTP, this variable contains the number of
11149 RCPT commands in the current message that have previously been rejected with a
11150 temporary (4&'xx'&) response.
11152 .vitem &$rcpt_fail_count$&
11153 .vindex "&$rcpt_fail_count$&"
11154 When a message is being received by SMTP, this variable contains the number of
11155 RCPT commands in the current message that have previously been rejected with a
11156 permanent (5&'xx'&) response.
11158 .vitem &$received_count$&
11159 .vindex "&$received_count$&"
11160 This variable contains the number of &'Received:'& header lines in the message,
11161 including the one added by Exim (so its value is always greater than zero). It
11162 is available in the DATA ACL, the non-SMTP ACL, and while routing and
11165 .vitem &$received_for$&
11166 .vindex "&$received_for$&"
11167 If there is only a single recipient address in an incoming message, this
11168 variable contains that address when the &'Received:'& header line is being
11169 built. The value is copied after recipient rewriting has happened, but before
11170 the &[local_scan()]& function is run.
11172 .vitem &$received_ip_address$&
11173 .vindex "&$received_ip_address$&"
11174 As soon as an Exim server starts processing an incoming TCP/IP connection, this
11175 variable is set to the address of the local IP interface, and &$received_port$&
11176 is set to the local port number. (The remote IP address and port are in
11177 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
11178 the port value is -1 unless it has been set using the &%-oMi%& command line
11181 As well as being useful in ACLs (including the &"connect"& ACL), these variable
11182 could be used, for example, to make the file name for a TLS certificate depend
11183 on which interface and/or port is being used for the incoming connection. The
11184 values of &$received_ip_address$& and &$received_port$& are saved with any
11185 messages that are received, thus making these variables available at delivery
11188 &*Note:*& There are no equivalent variables for outgoing connections, because
11189 the values are unknown (unless they are explicitly set by options of the
11190 &(smtp)& transport).
11192 .vitem &$received_port$&
11193 .vindex "&$received_port$&"
11194 See &$received_ip_address$&.
11196 .vitem &$received_protocol$&
11197 .vindex "&$received_protocol$&"
11198 When a message is being processed, this variable contains the name of the
11199 protocol by which it was received. Most of the names used by Exim are defined
11200 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
11201 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
11202 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
11203 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
11204 connection and the client was successfully authenticated.
11206 Exim uses the protocol name &"smtps"& for the case when encryption is
11207 automatically set up on connection without the use of STARTTLS (see
11208 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
11209 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
11210 where the client initially uses EHLO, sets up an encrypted connection using
11211 STARTTLS, and then uses HELO afterwards.
11213 The &%-oMr%& option provides a way of specifying a custom protocol name for
11214 messages that are injected locally by trusted callers. This is commonly used to
11215 identify messages that are being re-injected after some kind of scanning.
11217 .vitem &$received_time$&
11218 .vindex "&$received_time$&"
11219 This variable contains the date and time when the current message was received,
11220 as a number of seconds since the start of the Unix epoch.
11222 .vitem &$recipient_data$&
11223 .vindex "&$recipient_data$&"
11224 This variable is set after an indexing lookup success in an ACL &%recipients%&
11225 condition. It contains the data from the lookup, and the value remains set
11226 until the next &%recipients%& test. Thus, you can do things like this:
11228 &`require recipients = cdb*@;/some/file`&
11229 &`deny `&&'some further test involving'& &`$recipient_data`&
11231 &*Warning*&: This variable is set only when a lookup is used as an indexing
11232 method in the address list, using the semicolon syntax as in the example above.
11233 The variable is not set for a lookup that is used as part of the string
11234 expansion that all such lists undergo before being interpreted.
11236 .vitem &$recipient_verify_failure$&
11237 .vindex "&$recipient_verify_failure$&"
11238 In an ACL, when a recipient verification fails, this variable contains
11239 information about the failure. It is set to one of the following words:
11242 &"qualify"&: The address was unqualified (no domain), and the message
11243 was neither local nor came from an exempted host.
11246 &"route"&: Routing failed.
11249 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
11250 or before the MAIL command (that is, on initial connection, HELO, or
11254 &"recipient"&: The RCPT command in a callout was rejected.
11257 &"postmaster"&: The postmaster check in a callout was rejected.
11260 The main use of this variable is expected to be to distinguish between
11261 rejections of MAIL and rejections of RCPT.
11263 .vitem &$recipients$&
11264 .vindex "&$recipients$&"
11265 This variable contains a list of envelope recipients for a message. A comma and
11266 a space separate the addresses in the replacement text. However, the variable
11267 is not generally available, to prevent exposure of Bcc recipients in
11268 unprivileged users' filter files. You can use &$recipients$& only in these
11272 In a system filter file.
11274 In the ACLs associated with the DATA command and with non-SMTP messages, that
11275 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
11276 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
11277 &%acl_not_smtp_mime%&.
11279 From within a &[local_scan()]& function.
11283 .vitem &$recipients_count$&
11284 .vindex "&$recipients_count$&"
11285 When a message is being processed, this variable contains the number of
11286 envelope recipients that came with the message. Duplicates are not excluded
11287 from the count. While a message is being received over SMTP, the number
11288 increases for each accepted recipient. It can be referenced in an ACL.
11291 .vitem &$regex_match_string$&
11292 .vindex "&$regex_match_string$&"
11293 This variable is set to contain the matching regular expression after a
11294 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
11297 .vitem &$reply_address$&
11298 .vindex "&$reply_address$&"
11299 When a message is being processed, this variable contains the contents of the
11300 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
11301 contents of the &'From:'& header line. Apart from the removal of leading
11302 white space, the value is not processed in any way. In particular, no RFC 2047
11303 decoding or character code translation takes place.
11305 .vitem &$return_path$&
11306 .vindex "&$return_path$&"
11307 When a message is being delivered, this variable contains the return path &--
11308 the sender field that will be sent as part of the envelope. It is not enclosed
11309 in <> characters. At the start of routing an address, &$return_path$& has the
11310 same value as &$sender_address$&, but if, for example, an incoming message to a
11311 mailing list has been expanded by a router which specifies a different address
11312 for bounce messages, &$return_path$& subsequently contains the new bounce
11313 address, whereas &$sender_address$& always contains the original sender address
11314 that was received with the message. In other words, &$sender_address$& contains
11315 the incoming envelope sender, and &$return_path$& contains the outgoing
11318 .vitem &$return_size_limit$&
11319 .vindex "&$return_size_limit$&"
11320 This is an obsolete name for &$bounce_return_size_limit$&.
11323 .cindex "return code" "from &%run%& expansion"
11324 .vindex "&$runrc$&"
11325 This variable contains the return code from a command that is run by the
11326 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
11327 assume the order in which option values are expanded, except for those
11328 preconditions whose order of testing is documented. Therefore, you cannot
11329 reliably expect to set &$runrc$& by the expansion of one option, and use it in
11332 .vitem &$self_hostname$&
11333 .oindex "&%self%&" "value of host name"
11334 .vindex "&$self_hostname$&"
11335 When an address is routed to a supposedly remote host that turns out to be the
11336 local host, what happens is controlled by the &%self%& generic router option.
11337 One of its values causes the address to be passed to another router. When this
11338 happens, &$self_hostname$& is set to the name of the local host that the
11339 original router encountered. In other circumstances its contents are null.
11341 .vitem &$sender_address$&
11342 .vindex "&$sender_address$&"
11343 When a message is being processed, this variable contains the sender's address
11344 that was received in the message's envelope. The case of letters in the address
11345 is retained, in both the local part and the domain. For bounce messages, the
11346 value of this variable is the empty string. See also &$return_path$&.
11348 .vitem &$sender_address_data$&
11349 .vindex "&$address_data$&"
11350 .vindex "&$sender_address_data$&"
11351 If &$address_data$& is set when the routers are called from an ACL to verify a
11352 sender address, the final value is preserved in &$sender_address_data$&, to
11353 distinguish it from data from a recipient address. The value does not persist
11354 after the end of the current ACL statement. If you want to preserve it for
11355 longer, you can save it in an ACL variable.
11357 .vitem &$sender_address_domain$&
11358 .vindex "&$sender_address_domain$&"
11359 The domain portion of &$sender_address$&.
11361 .vitem &$sender_address_local_part$&
11362 .vindex "&$sender_address_local_part$&"
11363 The local part portion of &$sender_address$&.
11365 .vitem &$sender_data$&
11366 .vindex "&$sender_data$&"
11367 This variable is set after a lookup success in an ACL &%senders%& condition or
11368 in a router &%senders%& option. It contains the data from the lookup, and the
11369 value remains set until the next &%senders%& test. Thus, you can do things like
11372 &`require senders = cdb*@;/some/file`&
11373 &`deny `&&'some further test involving'& &`$sender_data`&
11375 &*Warning*&: This variable is set only when a lookup is used as an indexing
11376 method in the address list, using the semicolon syntax as in the example above.
11377 The variable is not set for a lookup that is used as part of the string
11378 expansion that all such lists undergo before being interpreted.
11380 .vitem &$sender_fullhost$&
11381 .vindex "&$sender_fullhost$&"
11382 When a message is received from a remote host, this variable contains the host
11383 name and IP address in a single string. It ends with the IP address in square
11384 brackets, followed by a colon and a port number if the logging of ports is
11385 enabled. The format of the rest of the string depends on whether the host
11386 issued a HELO or EHLO SMTP command, and whether the host name was verified by
11387 looking up its IP address. (Looking up the IP address can be forced by the
11388 &%host_lookup%& option, independent of verification.) A plain host name at the
11389 start of the string is a verified host name; if this is not present,
11390 verification either failed or was not requested. A host name in parentheses is
11391 the argument of a HELO or EHLO command. This is omitted if it is identical to
11392 the verified host name or to the host's IP address in square brackets.
11394 .vitem &$sender_helo_name$&
11395 .vindex "&$sender_helo_name$&"
11396 When a message is received from a remote host that has issued a HELO or EHLO
11397 command, the argument of that command is placed in this variable. It is also
11398 set if HELO or EHLO is used when a message is received using SMTP locally via
11399 the &%-bs%& or &%-bS%& options.
11401 .vitem &$sender_host_address$&
11402 .vindex "&$sender_host_address$&"
11403 When a message is received from a remote host, this variable contains that
11404 host's IP address. For locally submitted messages, it is empty.
11406 .vitem &$sender_host_authenticated$&
11407 .vindex "&$sender_host_authenticated$&"
11408 This variable contains the name (not the public name) of the authenticator
11409 driver that successfully authenticated the client from which the message was
11410 received. It is empty if there was no successful authentication. See also
11411 &$authenticated_id$&.
11413 .vitem &$sender_host_name$&
11414 .vindex "&$sender_host_name$&"
11415 When a message is received from a remote host, this variable contains the
11416 host's name as obtained by looking up its IP address. For messages received by
11417 other means, this variable is empty.
11419 .vindex "&$host_lookup_failed$&"
11420 If the host name has not previously been looked up, a reference to
11421 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
11422 A looked up name is accepted only if it leads back to the original IP address
11423 via a forward lookup. If either the reverse or the forward lookup fails to find
11424 any data, or if the forward lookup does not yield the original IP address,
11425 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
11427 .vindex "&$host_lookup_deferred$&"
11428 However, if either of the lookups cannot be completed (for example, there is a
11429 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
11430 &$host_lookup_failed$& remains set to &"0"&.
11432 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
11433 host name again if there is a subsequent reference to &$sender_host_name$&
11434 in the same Exim process, but it does try again if &$host_lookup_deferred$&
11437 Exim does not automatically look up every calling host's name. If you want
11438 maximum efficiency, you should arrange your configuration so that it avoids
11439 these lookups altogether. The lookup happens only if one or more of the
11440 following are true:
11443 A string containing &$sender_host_name$& is expanded.
11445 The calling host matches the list in &%host_lookup%&. In the default
11446 configuration, this option is set to *, so it must be changed if lookups are
11447 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
11449 Exim needs the host name in order to test an item in a host list. The items
11450 that require this are described in sections &<<SECThoslispatnam>>& and
11451 &<<SECThoslispatnamsk>>&.
11453 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
11454 In this case, the host name is required to compare with the name quoted in any
11455 EHLO or HELO commands that the client issues.
11457 The remote host issues a EHLO or HELO command that quotes one of the
11458 domains in &%helo_lookup_domains%&. The default value of this option is
11459 . ==== As this is a nested list, any displays it contains must be indented
11460 . ==== as otherwise they are too far to the left.
11462 helo_lookup_domains = @ : @[]
11464 which causes a lookup if a remote host (incorrectly) gives the server's name or
11465 IP address in an EHLO or HELO command.
11469 .vitem &$sender_host_port$&
11470 .vindex "&$sender_host_port$&"
11471 When a message is received from a remote host, this variable contains the port
11472 number that was used on the remote host.
11474 .vitem &$sender_ident$&
11475 .vindex "&$sender_ident$&"
11476 When a message is received from a remote host, this variable contains the
11477 identification received in response to an RFC 1413 request. When a message has
11478 been received locally, this variable contains the login name of the user that
11481 .vitem &$sender_rate_$&&'xxx'&
11482 A number of variables whose names begin &$sender_rate_$& are set as part of the
11483 &%ratelimit%& ACL condition. Details are given in section
11484 &<<SECTratelimiting>>&.
11486 .vitem &$sender_rcvhost$&
11487 .cindex "DNS" "reverse lookup"
11488 .cindex "reverse DNS lookup"
11489 .vindex "&$sender_rcvhost$&"
11490 This is provided specifically for use in &'Received:'& headers. It starts with
11491 either the verified host name (as obtained from a reverse DNS lookup) or, if
11492 there is no verified host name, the IP address in square brackets. After that
11493 there may be text in parentheses. When the first item is a verified host name,
11494 the first thing in the parentheses is the IP address in square brackets,
11495 followed by a colon and a port number if port logging is enabled. When the
11496 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
11499 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
11500 was used and its argument was not identical to the real host name or IP
11501 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
11502 all three items are present in the parentheses, a newline and tab are inserted
11503 into the string, to improve the formatting of the &'Received:'& header.
11505 .vitem &$sender_verify_failure$&
11506 .vindex "&$sender_verify_failure$&"
11507 In an ACL, when a sender verification fails, this variable contains information
11508 about the failure. The details are the same as for
11509 &$recipient_verify_failure$&.
11511 .vitem &$sending_ip_address$&
11512 .vindex "&$sending_ip_address$&"
11513 This variable is set whenever an outgoing SMTP connection to another host has
11514 been set up. It contains the IP address of the local interface that is being
11515 used. This is useful if a host that has more than one IP address wants to take
11516 on different personalities depending on which one is being used. For incoming
11517 connections, see &$received_ip_address$&.
11519 .vitem &$sending_port$&
11520 .vindex "&$sending_port$&"
11521 This variable is set whenever an outgoing SMTP connection to another host has
11522 been set up. It contains the local port that is being used. For incoming
11523 connections, see &$received_port$&.
11525 .vitem &$smtp_active_hostname$&
11526 .vindex "&$smtp_active_hostname$&"
11527 During an incoming SMTP session, this variable contains the value of the active
11528 host name, as specified by the &%smtp_active_hostname%& option. The value of
11529 &$smtp_active_hostname$& is saved with any message that is received, so its
11530 value can be consulted during routing and delivery.
11532 .vitem &$smtp_command$&
11533 .vindex "&$smtp_command$&"
11534 During the processing of an incoming SMTP command, this variable contains the
11535 entire command. This makes it possible to distinguish between HELO and EHLO in
11536 the HELO ACL, and also to distinguish between commands such as these:
11541 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
11542 command, the address in &$smtp_command$& is the original address before any
11543 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
11544 the address after SMTP-time rewriting.
11546 .vitem &$smtp_command_argument$&
11547 .cindex "SMTP" "command, argument for"
11548 .vindex "&$smtp_command_argument$&"
11549 While an ACL is running to check an SMTP command, this variable contains the
11550 argument, that is, the text that follows the command name, with leading white
11551 space removed. Following the introduction of &$smtp_command$&, this variable is
11552 somewhat redundant, but is retained for backwards compatibility.
11554 .vitem &$smtp_count_at_connection_start$&
11555 .vindex "&$smtp_count_at_connection_start$&"
11556 This variable is set greater than zero only in processes spawned by the Exim
11557 daemon for handling incoming SMTP connections. The name is deliberately long,
11558 in order to emphasize what the contents are. When the daemon accepts a new
11559 connection, it increments this variable. A copy of the variable is passed to
11560 the child process that handles the connection, but its value is fixed, and
11561 never changes. It is only an approximation of how many incoming connections
11562 there actually are, because many other connections may come and go while a
11563 single connection is being processed. When a child process terminates, the
11564 daemon decrements its copy of the variable.
11566 .vitem "&$sn0$& &-- &$sn9$&"
11567 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
11568 that were current at the end of the system filter file. This allows a system
11569 filter file to set values that can be tested in users' filter files. For
11570 example, a system filter could set a value indicating how likely it is that a
11571 message is junk mail.
11573 .vitem &$spam_$&&'xxx'&
11574 A number of variables whose names start with &$spam$& are available when Exim
11575 is compiled with the content-scanning extension. For details, see section
11576 &<<SECTscanspamass>>&.
11579 .vitem &$spool_directory$&
11580 .vindex "&$spool_directory$&"
11581 The name of Exim's spool directory.
11583 .vitem &$spool_inodes$&
11584 .vindex "&$spool_inodes$&"
11585 The number of free inodes in the disk partition where Exim's spool files are
11586 being written. The value is recalculated whenever the variable is referenced.
11587 If the relevant file system does not have the concept of inodes, the value of
11588 is -1. See also the &%check_spool_inodes%& option.
11590 .vitem &$spool_space$&
11591 .vindex "&$spool_space$&"
11592 The amount of free space (as a number of kilobytes) in the disk partition where
11593 Exim's spool files are being written. The value is recalculated whenever the
11594 variable is referenced. If the operating system does not have the ability to
11595 find the amount of free space (only true for experimental systems), the space
11596 value is -1. For example, to check in an ACL that there is at least 50
11597 megabytes free on the spool, you could write:
11599 condition = ${if > {$spool_space}{50000}}
11601 See also the &%check_spool_space%& option.
11604 .vitem &$thisaddress$&
11605 .vindex "&$thisaddress$&"
11606 This variable is set only during the processing of the &%foranyaddress%&
11607 command in a filter file. Its use is explained in the description of that
11608 command, which can be found in the separate document entitled &'Exim's
11609 interfaces to mail filtering'&.
11611 .vitem &$tls_certificate_verified$&
11612 .vindex "&$tls_certificate_verified$&"
11613 This variable is set to &"1"& if a TLS certificate was verified when the
11614 message was received, and &"0"& otherwise.
11616 .vitem &$tls_cipher$&
11617 .vindex "&$tls_cipher$&"
11618 When a message is received from a remote host over an encrypted SMTP
11619 connection, this variable is set to the cipher suite that was negotiated, for
11620 example DES-CBC3-SHA. In other circumstances, in particular, for message
11621 received over unencrypted connections, the variable is empty. Testing
11622 &$tls_cipher$& for emptiness is one way of distinguishing between encrypted and
11623 non-encrypted connections during ACL processing.
11625 The &$tls_cipher$& variable retains its value during message delivery, except
11626 when an outward SMTP delivery takes place via the &(smtp)& transport. In this
11627 case, &$tls_cipher$& is cleared before any outgoing SMTP connection is made,
11628 and then set to the outgoing cipher suite if one is negotiated. See chapter
11629 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
11630 details of the &(smtp)& transport.
11632 .vitem &$tls_peerdn$&
11633 .vindex "&$tls_peerdn$&"
11634 When a message is received from a remote host over an encrypted SMTP
11635 connection, and Exim is configured to request a certificate from the client,
11636 the value of the Distinguished Name of the certificate is made available in the
11637 &$tls_peerdn$& during subsequent processing. Like &$tls_cipher$&, the
11638 value is retained during message delivery, except during outbound SMTP
11641 .vitem &$tod_bsdinbox$&
11642 .vindex "&$tod_bsdinbox$&"
11643 The time of day and the date, in the format required for BSD-style mailbox
11644 files, for example: Thu Oct 17 17:14:09 1995.
11646 .vitem &$tod_epoch$&
11647 .vindex "&$tod_epoch$&"
11648 The time and date as a number of seconds since the start of the Unix epoch.
11650 .vitem &$tod_full$&
11651 .vindex "&$tod_full$&"
11652 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
11653 +0100. The timezone is always given as a numerical offset from UTC, with
11654 positive values used for timezones that are ahead (east) of UTC, and negative
11655 values for those that are behind (west).
11658 .vindex "&$tod_log$&"
11659 The time and date in the format used for writing Exim's log files, for example:
11660 1995-10-12 15:32:29, but without a timezone.
11662 .vitem &$tod_logfile$&
11663 .vindex "&$tod_logfile$&"
11664 This variable contains the date in the format yyyymmdd. This is the format that
11665 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
11668 .vitem &$tod_zone$&
11669 .vindex "&$tod_zone$&"
11670 This variable contains the numerical value of the local timezone, for example:
11673 .vitem &$tod_zulu$&
11674 .vindex "&$tod_zulu$&"
11675 This variable contains the UTC date and time in &"Zulu"& format, as specified
11676 by ISO 8601, for example: 20030221154023Z.
11679 .vindex "&$value$&"
11680 This variable contains the result of an expansion lookup, extraction operation,
11681 or external command, as described above. It is also used during a
11682 &*reduce*& expansion.
11684 .vitem &$version_number$&
11685 .vindex "&$version_number$&"
11686 The version number of Exim.
11688 .vitem &$warn_message_delay$&
11689 .vindex "&$warn_message_delay$&"
11690 This variable is set only during the creation of a message warning about a
11691 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11693 .vitem &$warn_message_recipients$&
11694 .vindex "&$warn_message_recipients$&"
11695 This variable is set only during the creation of a message warning about a
11696 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
11702 . ////////////////////////////////////////////////////////////////////////////
11703 . ////////////////////////////////////////////////////////////////////////////
11705 .chapter "Embedded Perl" "CHAPperl"
11706 .scindex IIDperl "Perl" "calling from Exim"
11707 Exim can be built to include an embedded Perl interpreter. When this is done,
11708 Perl subroutines can be called as part of the string expansion process. To make
11709 use of the Perl support, you need version 5.004 or later of Perl installed on
11710 your system. To include the embedded interpreter in the Exim binary, include
11715 in your &_Local/Makefile_& and then build Exim in the normal way.
11718 .section "Setting up so Perl can be used" "SECID85"
11719 .oindex "&%perl_startup%&"
11720 Access to Perl subroutines is via a global configuration option called
11721 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
11722 no &%perl_startup%& option in the Exim configuration file then no Perl
11723 interpreter is started and there is almost no overhead for Exim (since none of
11724 the Perl library will be paged in unless used). If there is a &%perl_startup%&
11725 option then the associated value is taken to be Perl code which is executed in
11726 a newly created Perl interpreter.
11728 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
11729 need backslashes before any characters to escape special meanings. The option
11730 should usually be something like
11732 perl_startup = do '/etc/exim.pl'
11734 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
11735 use from Exim. Exim can be configured either to start up a Perl interpreter as
11736 soon as it is entered, or to wait until the first time it is needed. Starting
11737 the interpreter at the beginning ensures that it is done while Exim still has
11738 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
11739 fact used in a particular run. Also, note that this does not mean that Exim is
11740 necessarily running as root when Perl is called at a later time. By default,
11741 the interpreter is started only when it is needed, but this can be changed in
11745 .oindex "&%perl_at_start%&"
11746 Setting &%perl_at_start%& (a boolean option) in the configuration requests
11747 a startup when Exim is entered.
11749 The command line option &%-ps%& also requests a startup when Exim is entered,
11750 overriding the setting of &%perl_at_start%&.
11753 There is also a command line option &%-pd%& (for delay) which suppresses the
11754 initial startup, even if &%perl_at_start%& is set.
11757 .section "Calling Perl subroutines" "SECID86"
11758 When the configuration file includes a &%perl_startup%& option you can make use
11759 of the string expansion item to call the Perl subroutines that are defined
11760 by the &%perl_startup%& code. The operator is used in any of the following
11764 ${perl{foo}{argument}}
11765 ${perl{foo}{argument1}{argument2} ... }
11767 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
11768 arguments may be passed. Passing more than this results in an expansion failure
11769 with an error message of the form
11771 Too many arguments passed to Perl subroutine "foo" (max is 8)
11773 The return value of the Perl subroutine is evaluated in a scalar context before
11774 it is passed back to Exim to be inserted into the expanded string. If the
11775 return value is &'undef'&, the expansion is forced to fail in the same way as
11776 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
11777 by obeying Perl's &%die%& function, the expansion fails with the error message
11778 that was passed to &%die%&.
11781 .section "Calling Exim functions from Perl" "SECID87"
11782 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
11783 is available to call back into Exim's string expansion function. For example,
11786 my $lp = Exim::expand_string('$local_part');
11788 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
11789 Note those are single quotes and not double quotes to protect against
11790 &$local_part$& being interpolated as a Perl variable.
11792 If the string expansion is forced to fail by a &"fail"& item, the result of
11793 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
11794 expansion string, the Perl call from the original expansion string fails with
11795 an appropriate error message, in the same way as if &%die%& were used.
11797 .cindex "debugging" "from embedded Perl"
11798 .cindex "log" "writing from embedded Perl"
11799 Two other Exim functions are available for use from within Perl code.
11800 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
11801 debugging is enabled. If you want a newline at the end, you must supply it.
11802 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
11803 timestamp. In this case, you should not supply a terminating newline.
11806 .section "Use of standard output and error by Perl" "SECID88"
11807 .cindex "Perl" "standard output and error"
11808 You should not write to the standard error or output streams from within your
11809 Perl code, as it is not defined how these are set up. In versions of Exim
11810 before 4.50, it is possible for the standard output or error to refer to the
11811 SMTP connection during message reception via the daemon. Writing to this stream
11812 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
11813 error streams are connected to &_/dev/null_& in the daemon. The chaos is
11814 avoided, but the output is lost.
11816 .cindex "Perl" "use of &%warn%&"
11817 The Perl &%warn%& statement writes to the standard error stream by default.
11818 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
11819 you have no control. When Exim starts up the Perl interpreter, it arranges for
11820 output from the &%warn%& statement to be written to the Exim main log. You can
11821 change this by including appropriate Perl magic somewhere in your Perl code.
11822 For example, to discard &%warn%& output completely, you need this:
11824 $SIG{__WARN__} = sub { };
11826 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
11827 example, the code for the subroutine is empty, so it does nothing, but you can
11828 include any Perl code that you like. The text of the &%warn%& message is passed
11829 as the first subroutine argument.
11833 . ////////////////////////////////////////////////////////////////////////////
11834 . ////////////////////////////////////////////////////////////////////////////
11836 .chapter "Starting the daemon and the use of network interfaces" &&&
11837 "CHAPinterfaces" &&&
11838 "Starting the daemon"
11839 .cindex "daemon" "starting"
11840 .cindex "interface" "listening"
11841 .cindex "network interface"
11842 .cindex "interface" "network"
11843 .cindex "IP address" "for listening"
11844 .cindex "daemon" "listening IP addresses"
11845 .cindex "TCP/IP" "setting listening interfaces"
11846 .cindex "TCP/IP" "setting listening ports"
11847 A host that is connected to a TCP/IP network may have one or more physical
11848 hardware network interfaces. Each of these interfaces may be configured as one
11849 or more &"logical"& interfaces, which are the entities that a program actually
11850 works with. Each of these logical interfaces is associated with an IP address.
11851 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
11852 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
11853 knowledge about the host's interfaces for use in three different circumstances:
11856 When a listening daemon is started, Exim needs to know which interfaces
11857 and ports to listen on.
11859 When Exim is routing an address, it needs to know which IP addresses
11860 are associated with local interfaces. This is required for the correct
11861 processing of MX lists by removing the local host and others with the
11862 same or higher priority values. Also, Exim needs to detect cases
11863 when an address is routed to an IP address that in fact belongs to the
11864 local host. Unless the &%self%& router option or the &%allow_localhost%&
11865 option of the smtp transport is set (as appropriate), this is treated
11866 as an error situation.
11868 When Exim connects to a remote host, it may need to know which interface to use
11869 for the outgoing connection.
11873 Exim's default behaviour is likely to be appropriate in the vast majority
11874 of cases. If your host has only one interface, and you want all its IP
11875 addresses to be treated in the same way, and you are using only the
11876 standard SMTP port, you should not need to take any special action. The
11877 rest of this chapter does not apply to you.
11879 In a more complicated situation you may want to listen only on certain
11880 interfaces, or on different ports, and for this reason there are a number of
11881 options that can be used to influence Exim's behaviour. The rest of this
11882 chapter describes how they operate.
11884 When a message is received over TCP/IP, the interface and port that were
11885 actually used are set in &$received_ip_address$& and &$received_port$&.
11889 .section "Starting a listening daemon" "SECID89"
11890 When a listening daemon is started (by means of the &%-bd%& command line
11891 option), the interfaces and ports on which it listens are controlled by the
11895 &%daemon_smtp_ports%& contains a list of default ports. (For backward
11896 compatibility, this option can also be specified in the singular.)
11898 &%local_interfaces%& contains list of interface IP addresses on which to
11899 listen. Each item may optionally also specify a port.
11902 The default list separator in both cases is a colon, but this can be changed as
11903 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
11904 it is usually best to change the separator to avoid having to double all the
11905 colons. For example:
11907 local_interfaces = <; 127.0.0.1 ; \
11910 3ffe:ffff:836f::fe86:a061
11912 There are two different formats for specifying a port along with an IP address
11913 in &%local_interfaces%&:
11916 The port is added onto the address with a dot separator. For example, to listen
11917 on port 1234 on two different IP addresses:
11919 local_interfaces = <; 192.168.23.65.1234 ; \
11920 3ffe:ffff:836f::fe86:a061.1234
11923 The IP address is enclosed in square brackets, and the port is added
11924 with a colon separator, for example:
11926 local_interfaces = <; [192.168.23.65]:1234 ; \
11927 [3ffe:ffff:836f::fe86:a061]:1234
11931 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
11932 default setting contains just one port:
11934 daemon_smtp_ports = smtp
11936 If more than one port is listed, each interface that does not have its own port
11937 specified listens on all of them. Ports that are listed in
11938 &%daemon_smtp_ports%& can be identified either by name (defined in
11939 &_/etc/services_&) or by number. However, when ports are given with individual
11940 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
11944 .section "Special IP listening addresses" "SECID90"
11945 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
11946 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
11947 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
11948 instead of setting up separate listening sockets for each interface. The
11949 default value of &%local_interfaces%& is
11951 local_interfaces = 0.0.0.0
11953 when Exim is built without IPv6 support; otherwise it is:
11955 local_interfaces = <; ::0 ; 0.0.0.0
11957 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
11961 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
11962 The &%-oX%& command line option can be used to override the values of
11963 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
11964 instance. Another way of doing this would be to use macros and the &%-D%&
11965 option. However, &%-oX%& can be used by any admin user, whereas modification of
11966 the runtime configuration by &%-D%& is allowed only when the caller is root or
11969 The value of &%-oX%& is a list of items. The default colon separator can be
11970 changed in the usual way if required. If there are any items that do not
11971 contain dots or colons (that is, are not IP addresses), the value of
11972 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
11973 items that do contain dots or colons, the value of &%local_interfaces%& is
11974 replaced by those items. Thus, for example,
11978 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
11981 -oX 192.168.34.5.1125
11983 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
11984 (However, since &%local_interfaces%& now contains no items without ports, the
11985 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
11989 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
11990 .cindex "ssmtp protocol"
11991 .cindex "smtps protocol"
11992 .cindex "SMTP" "ssmtp protocol"
11993 .cindex "SMTP" "smtps protocol"
11994 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
11995 before the STARTTLS command was standardized for SMTP. Some legacy clients
11996 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
11997 list of port numbers, connections to those ports must use SSMTP. The most
11998 common use of this option is expected to be
12000 tls_on_connect_ports = 465
12002 because 465 is the usual port number used by the legacy clients. There is also
12003 a command line option &%-tls-on-connect%&, which forces all ports to behave in
12004 this way when a daemon is started.
12006 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
12007 daemon to listen on those ports. You must still specify them in
12008 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
12009 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
12010 connections via the daemon.)
12015 .section "IPv6 address scopes" "SECID92"
12016 .cindex "IPv6" "address scopes"
12017 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
12018 can, in principle, have the same link-local IPv6 address on different
12019 interfaces. Thus, additional information is needed, over and above the IP
12020 address, to distinguish individual interfaces. A convention of using a
12021 percent sign followed by something (often the interface name) has been
12022 adopted in some cases, leading to addresses like this:
12024 fe80::202:b3ff:fe03:45c1%eth0
12026 To accommodate this usage, a percent sign followed by an arbitrary string is
12027 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
12028 to convert a textual IPv6 address for actual use. This function recognizes the
12029 percent convention in operating systems that support it, and it processes the
12030 address appropriately. Unfortunately, some older libraries have problems with
12031 &[getaddrinfo()]&. If
12033 IPV6_USE_INET_PTON=yes
12035 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
12036 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
12037 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
12038 function.) Of course, this means that the additional functionality of
12039 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
12041 .section "Disabling IPv6" "SECID93"
12042 .cindex "IPv6" "disabling"
12043 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
12044 run on a host whose kernel does not support IPv6. The binary will fall back to
12045 using IPv4, but it may waste resources looking up AAAA records, and trying to
12046 connect to IPv6 addresses, causing delays to mail delivery. If you set the
12047 .oindex "&%disable_ipv6%&"
12048 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
12049 activities take place. AAAA records are never looked up, and any IPv6 addresses
12050 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
12051 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
12052 to handle IPv6 literal addresses.
12054 On the other hand, when IPv6 is in use, there may be times when you want to
12055 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
12056 option to globally suppress the lookup of AAAA records for specified domains,
12057 and you can use the &%ignore_target_hosts%& generic router option to ignore
12058 IPv6 addresses in an individual router.
12062 .section "Examples of starting a listening daemon" "SECID94"
12063 The default case in an IPv6 environment is
12065 daemon_smtp_ports = smtp
12066 local_interfaces = <; ::0 ; 0.0.0.0
12068 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
12069 Either one or two sockets may be used, depending on the characteristics of
12070 the TCP/IP stack. (This is complicated and messy; for more information,
12071 read the comments in the &_daemon.c_& source file.)
12073 To specify listening on ports 25 and 26 on all interfaces:
12075 daemon_smtp_ports = 25 : 26
12077 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
12079 local_interfaces = <; ::0.25 ; ::0.26 \
12080 0.0.0.0.25 ; 0.0.0.0.26
12082 To listen on the default port on all IPv4 interfaces, and on port 26 on the
12083 IPv4 loopback address only:
12085 local_interfaces = 0.0.0.0 : 127.0.0.1.26
12087 To specify listening on the default port on specific interfaces only:
12089 local_interfaces = 192.168.34.67 : 192.168.34.67
12091 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
12095 .section "Recognizing the local host" "SECTreclocipadd"
12096 The &%local_interfaces%& option is also used when Exim needs to determine
12097 whether or not an IP address refers to the local host. That is, the IP
12098 addresses of all the interfaces on which a daemon is listening are always
12101 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
12102 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
12103 available interfaces from the operating system, and extracts the relevant
12104 (that is, IPv4 or IPv6) addresses to use for checking.
12106 Some systems set up large numbers of virtual interfaces in order to provide
12107 many virtual web servers. In this situation, you may want to listen for
12108 email on only a few of the available interfaces, but nevertheless treat all
12109 interfaces as local when routing. You can do this by setting
12110 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
12111 &"all"& wildcard values. These addresses are recognized as local, but are not
12112 used for listening. Consider this example:
12114 local_interfaces = <; 127.0.0.1 ; ::1 ; \
12116 3ffe:2101:12:1:a00:20ff:fe86:a061
12118 extra_local_interfaces = <; ::0 ; 0.0.0.0
12120 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
12121 address, but all available interface addresses are treated as local when
12124 In some environments the local host name may be in an MX list, but with an IP
12125 address that is not assigned to any local interface. In other cases it may be
12126 desirable to treat other host names as if they referred to the local host. Both
12127 these cases can be handled by setting the &%hosts_treat_as_local%& option.
12128 This contains host names rather than IP addresses. When a host is referenced
12129 during routing, either via an MX record or directly, it is treated as the local
12130 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
12131 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
12135 .section "Delivering to a remote host" "SECID95"
12136 Delivery to a remote host is handled by the smtp transport. By default, it
12137 allows the system's TCP/IP functions to choose which interface to use (if
12138 there is more than one) when connecting to a remote host. However, the
12139 &%interface%& option can be set to specify which interface is used. See the
12140 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
12146 . ////////////////////////////////////////////////////////////////////////////
12147 . ////////////////////////////////////////////////////////////////////////////
12149 .chapter "Main configuration" "CHAPmainconfig"
12150 .scindex IIDconfima "configuration file" "main section"
12151 .scindex IIDmaiconf "main configuration"
12152 The first part of the run time configuration file contains three types of item:
12155 Macro definitions: These lines start with an upper case letter. See section
12156 &<<SECTmacrodefs>>& for details of macro processing.
12158 Named list definitions: These lines start with one of the words &"domainlist"&,
12159 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
12160 section &<<SECTnamedlists>>&.
12162 Main configuration settings: Each setting occupies one line of the file
12163 (with possible continuations). If any setting is preceded by the word
12164 &"hide"&, the &%-bP%& command line option displays its value to admin users
12165 only. See section &<<SECTcos>>& for a description of the syntax of these option
12169 This chapter specifies all the main configuration options, along with their
12170 types and default values. For ease of finding a particular option, they appear
12171 in alphabetical order in section &<<SECTalomo>>& below. However, because there
12172 are now so many options, they are first listed briefly in functional groups, as
12173 an aid to finding the name of the option you are looking for. Some options are
12174 listed in more than one group.
12176 .section "Miscellaneous" "SECID96"
12178 .row &%bi_command%& "to run for &%-bi%& command line option"
12179 .row &%disable_ipv6%& "do no IPv6 processing"
12180 .row &%keep_malformed%& "for broken files &-- should not happen"
12181 .row &%localhost_number%& "for unique message ids in clusters"
12182 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
12183 .row &%message_body_visible%& "how much to show in &$message_body$&"
12184 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
12185 .row &%print_topbitchars%& "top-bit characters are printing"
12186 .row &%timezone%& "force time zone"
12190 .section "Exim parameters" "SECID97"
12192 .row &%exim_group%& "override compiled-in value"
12193 .row &%exim_path%& "override compiled-in value"
12194 .row &%exim_user%& "override compiled-in value"
12195 .row &%primary_hostname%& "default from &[uname()]&"
12196 .row &%split_spool_directory%& "use multiple directories"
12197 .row &%spool_directory%& "override compiled-in value"
12202 .section "Privilege controls" "SECID98"
12204 .row &%admin_groups%& "groups that are Exim admin users"
12205 .row &%deliver_drop_privilege%& "drop root for delivery processes"
12206 .row &%local_from_check%& "insert &'Sender:'& if necessary"
12207 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
12208 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
12209 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
12210 .row &%never_users%& "do not run deliveries as these"
12211 .row &%prod_requires_admin%& "forced delivery requires admin user"
12212 .row &%queue_list_requires_admin%& "queue listing requires admin user"
12213 .row &%trusted_groups%& "groups that are trusted"
12214 .row &%trusted_users%& "users that are trusted"
12219 .section "Logging" "SECID99"
12221 .row &%hosts_connection_nolog%& "exemption from connect logging"
12222 .row &%log_file_path%& "override compiled-in value"
12223 .row &%log_selector%& "set/unset optional logging"
12224 .row &%log_timezone%& "add timezone to log lines"
12225 .row &%message_logs%& "create per-message logs"
12226 .row &%preserve_message_logs%& "after message completion"
12227 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
12228 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
12229 .row &%syslog_facility%& "set syslog &""facility""& field"
12230 .row &%syslog_processname%& "set syslog &""ident""& field"
12231 .row &%syslog_timestamp%& "timestamp syslog lines"
12232 .row &%write_rejectlog%& "control use of message log"
12237 .section "Frozen messages" "SECID100"
12239 .row &%auto_thaw%& "sets time for retrying frozen messages"
12240 .row &%freeze_tell%& "send message when freezing"
12241 .row &%move_frozen_messages%& "to another directory"
12242 .row &%timeout_frozen_after%& "keep frozen messages only so long"
12247 .section "Data lookups" "SECID101"
12249 .row &%ibase_servers%& "InterBase servers"
12250 .row &%ldap_default_servers%& "used if no server in query"
12251 .row &%ldap_version%& "set protocol version"
12252 .row &%lookup_open_max%& "lookup files held open"
12253 .row &%mysql_servers%& "default MySQL servers"
12254 .row &%oracle_servers%& "Oracle servers"
12255 .row &%pgsql_servers%& "default PostgreSQL servers"
12256 .row &%sqlite_lock_timeout%& "as it says"
12261 .section "Message ids" "SECID102"
12263 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
12264 .row &%message_id_header_text%& "ditto"
12269 .section "Embedded Perl Startup" "SECID103"
12271 .row &%perl_at_start%& "always start the interpreter"
12272 .row &%perl_startup%& "code to obey when starting Perl"
12277 .section "Daemon" "SECID104"
12279 .row &%daemon_smtp_ports%& "default ports"
12280 .row &%daemon_startup_retries%& "number of times to retry"
12281 .row &%daemon_startup_sleep%& "time to sleep between tries"
12282 .row &%extra_local_interfaces%& "not necessarily listened on"
12283 .row &%local_interfaces%& "on which to listen, with optional ports"
12284 .row &%pid_file_path%& "override compiled-in value"
12285 .row &%queue_run_max%& "maximum simultaneous queue runners"
12290 .section "Resource control" "SECID105"
12292 .row &%check_log_inodes%& "before accepting a message"
12293 .row &%check_log_space%& "before accepting a message"
12294 .row &%check_spool_inodes%& "before accepting a message"
12295 .row &%check_spool_space%& "before accepting a message"
12296 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
12297 .row &%queue_only_load%& "queue incoming if load high"
12298 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12299 .row &%queue_run_max%& "maximum simultaneous queue runners"
12300 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12301 .row &%smtp_accept_max%& "simultaneous incoming connections"
12302 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12303 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12304 .row &%smtp_accept_max_per_connection%& "messages per connection"
12305 .row &%smtp_accept_max_per_host%& "connections from one host"
12306 .row &%smtp_accept_queue%& "queue mail if more connections"
12307 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12309 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12310 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12311 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12312 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
12313 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12318 .section "Policy controls" "SECID106"
12320 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
12321 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
12322 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
12323 .row &%acl_smtp_auth%& "ACL for AUTH"
12324 .row &%acl_smtp_connect%& "ACL for connection"
12325 .row &%acl_smtp_data%& "ACL for DATA"
12326 .row &%acl_smtp_etrn%& "ACL for ETRN"
12327 .row &%acl_smtp_expn%& "ACL for EXPN"
12328 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
12329 .row &%acl_smtp_mail%& "ACL for MAIL"
12330 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
12331 .row &%acl_smtp_mime%& "ACL for MIME parts"
12332 .row &%acl_smtp_predata%& "ACL for start of data"
12333 .row &%acl_smtp_quit%& "ACL for QUIT"
12334 .row &%acl_smtp_rcpt%& "ACL for RCPT"
12335 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
12336 .row &%acl_smtp_vrfy%& "ACL for VRFY"
12337 .row &%av_scanner%& "specify virus scanner"
12338 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12340 .row &%dns_csa_search_limit%& "control CSA parent search depth"
12341 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
12342 .row &%header_maxsize%& "total size of message header"
12343 .row &%header_line_maxsize%& "individual header line limit"
12344 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
12345 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
12346 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
12347 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
12348 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
12349 .row &%host_lookup%& "host name looked up for these hosts"
12350 .row &%host_lookup_order%& "order of DNS and local name lookups"
12351 .row &%host_reject_connection%& "reject connection from these hosts"
12352 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
12353 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
12354 .row &%message_size_limit%& "for all messages"
12355 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12356 .row &%spamd_address%& "set interface to SpamAssassin"
12357 .row &%strict_acl_vars%& "object to unset ACL variables"
12362 .section "Callout cache" "SECID107"
12364 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
12366 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
12368 .row &%callout_negative_expire%& "timeout for negative address cache item"
12369 .row &%callout_positive_expire%& "timeout for positive address cache item"
12370 .row &%callout_random_local_part%& "string to use for &""random""& testing"
12375 .section "TLS" "SECID108"
12377 .row &%gnutls_require_kx%& "control GnuTLS key exchanges"
12378 .row &%gnutls_require_mac%& "control GnuTLS MAC algorithms"
12379 .row &%gnutls_require_protocols%& "control GnuTLS protocols"
12380 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
12381 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12382 .row &%tls_certificate%& "location of server certificate"
12383 .row &%tls_crl%& "certificate revocation list"
12384 .row &%tls_dhparam%& "DH parameters for server"
12385 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
12386 .row &%tls_privatekey%& "location of server private key"
12387 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
12388 .row &%tls_require_ciphers%& "specify acceptable ciphers"
12389 .row &%tls_try_verify_hosts%& "try to verify client certificate"
12390 .row &%tls_verify_certificates%& "expected client certificates"
12391 .row &%tls_verify_hosts%& "insist on client certificate verify"
12396 .section "Local user handling" "SECID109"
12398 .row &%finduser_retries%& "useful in NIS environments"
12399 .row &%gecos_name%& "used when creating &'Sender:'&"
12400 .row &%gecos_pattern%& "ditto"
12401 .row &%max_username_length%& "for systems that truncate"
12402 .row &%unknown_login%& "used when no login name found"
12403 .row &%unknown_username%& "ditto"
12404 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
12405 .row &%uucp_from_sender%& "ditto"
12410 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
12412 .row &%header_maxsize%& "total size of message header"
12413 .row &%header_line_maxsize%& "individual header line limit"
12414 .row &%message_size_limit%& "applies to all messages"
12415 .row &%percent_hack_domains%& "recognize %-hack for these domains"
12416 .row &%received_header_text%& "expanded to make &'Received:'&"
12417 .row &%received_headers_max%& "for mail loop detection"
12418 .row &%recipients_max%& "limit per message"
12419 .row &%recipients_max_reject%& "permanently reject excess recipients"
12425 .section "Non-SMTP incoming messages" "SECID111"
12427 .row &%receive_timeout%& "for non-SMTP messages"
12434 .section "Incoming SMTP messages" "SECID112"
12435 See also the &'Policy controls'& section above.
12438 .row &%host_lookup%& "host name looked up for these hosts"
12439 .row &%host_lookup_order%& "order of DNS and local name lookups"
12440 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
12441 .row &%rfc1413_hosts%& "make ident calls to these hosts"
12442 .row &%rfc1413_query_timeout%& "zero disables ident calls"
12443 .row &%sender_unqualified_hosts%& "may send unqualified senders"
12444 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
12445 .row &%smtp_accept_max%& "simultaneous incoming connections"
12446 .row &%smtp_accept_max_nonmail%& "non-mail commands"
12447 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
12448 .row &%smtp_accept_max_per_connection%& "messages per connection"
12449 .row &%smtp_accept_max_per_host%& "connections from one host"
12450 .row &%smtp_accept_queue%& "queue mail if more connections"
12451 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
12453 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
12454 .row &%smtp_active_hostname%& "host name to use in messages"
12455 .row &%smtp_banner%& "text for welcome banner"
12456 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
12457 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
12458 .row &%smtp_enforce_sync%& "of SMTP command/responses"
12459 .row &%smtp_etrn_command%& "what to run for ETRN"
12460 .row &%smtp_etrn_serialize%& "only one at once"
12461 .row &%smtp_load_reserve%& "only reserve hosts if this load"
12462 .row &%smtp_max_unknown_commands%& "before dropping connection"
12463 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
12464 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
12465 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
12466 .row &%smtp_receive_timeout%& "per command or data line"
12467 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
12468 .row &%smtp_return_error_details%& "give detail on rejections"
12473 .section "SMTP extensions" "SECID113"
12475 .row &%accept_8bitmime%& "advertise 8BITMIME"
12476 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
12477 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
12478 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
12479 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
12480 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
12485 .section "Processing messages" "SECID114"
12487 .row &%allow_domain_literals%& "recognize domain literal syntax"
12488 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
12489 .row &%allow_utf8_domains%& "in addresses"
12490 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
12492 .row &%delivery_date_remove%& "from incoming messages"
12493 .row &%envelope_to_remove%& "from incoming messages"
12494 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
12495 .row &%headers_charset%& "default for translations"
12496 .row &%qualify_domain%& "default for senders"
12497 .row &%qualify_recipient%& "default for recipients"
12498 .row &%return_path_remove%& "from incoming messages"
12499 .row &%strip_excess_angle_brackets%& "in addresses"
12500 .row &%strip_trailing_dot%& "at end of addresses"
12501 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
12506 .section "System filter" "SECID115"
12508 .row &%system_filter%& "locate system filter"
12509 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
12511 .row &%system_filter_file_transport%& "transport for delivery to a file"
12512 .row &%system_filter_group%& "group for filter running"
12513 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
12514 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
12515 .row &%system_filter_user%& "user for filter running"
12520 .section "Routing and delivery" "SECID116"
12522 .row &%disable_ipv6%& "do no IPv6 processing"
12523 .row &%dns_again_means_nonexist%& "for broken domains"
12524 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
12525 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
12526 .row &%dns_retrans%& "parameter for resolver"
12527 .row &%dns_retry%& "parameter for resolver"
12528 .row &%hold_domains%& "hold delivery for these domains"
12529 .row &%local_interfaces%& "for routing checks"
12530 .row &%queue_domains%& "no immediate delivery for these"
12531 .row &%queue_only%& "no immediate delivery at all"
12532 .row &%queue_only_file%& "no immediate delivery if file exists"
12533 .row &%queue_only_load%& "no immediate delivery if load is high"
12534 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
12535 .row &%queue_only_override%& "allow command line to override"
12536 .row &%queue_run_in_order%& "order of arrival"
12537 .row &%queue_run_max%& "of simultaneous queue runners"
12538 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
12539 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
12540 .row &%remote_sort_domains%& "order of remote deliveries"
12541 .row &%retry_data_expire%& "timeout for retry data"
12542 .row &%retry_interval_max%& "safety net for retry rules"
12547 .section "Bounce and warning messages" "SECID117"
12549 .row &%bounce_message_file%& "content of bounce"
12550 .row &%bounce_message_text%& "content of bounce"
12551 .row &%bounce_return_body%& "include body if returning message"
12552 .row &%bounce_return_message%& "include original message in bounce"
12553 .row &%bounce_return_size_limit%& "limit on returned message"
12554 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
12555 .row &%dsn_from%& "set &'From:'& contents in bounces"
12556 .row &%errors_copy%& "copy bounce messages"
12557 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
12558 .row &%delay_warning%& "time schedule"
12559 .row &%delay_warning_condition%& "condition for warning messages"
12560 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
12561 .row &%smtp_return_error_details%& "give detail on rejections"
12562 .row &%warn_message_file%& "content of warning message"
12567 .section "Alphabetical list of main options" "SECTalomo"
12568 Those options that undergo string expansion before use are marked with
12571 .option accept_8bitmime main boolean false
12573 .cindex "8-bit characters"
12574 This option causes Exim to send 8BITMIME in its response to an SMTP
12575 EHLO command, and to accept the BODY= parameter on MAIL commands.
12576 However, though Exim is 8-bit clean, it is not a protocol converter, and it
12577 takes no steps to do anything special with messages received by this route.
12578 Consequently, this option is turned off by default.
12580 .option acl_not_smtp main string&!! unset
12581 .cindex "&ACL;" "for non-SMTP messages"
12582 .cindex "non-SMTP messages" "ACLs for"
12583 This option defines the ACL that is run when a non-SMTP message has been
12584 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
12587 .option acl_not_smtp_mime main string&!! unset
12588 This option defines the ACL that is run for individual MIME parts of non-SMTP
12589 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
12592 .option acl_not_smtp_start main string&!! unset
12593 .cindex "&ACL;" "at start of non-SMTP message"
12594 .cindex "non-SMTP messages" "ACLs for"
12595 This option defines the ACL that is run before Exim starts reading a
12596 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
12598 .option acl_smtp_auth main string&!! unset
12599 .cindex "&ACL;" "setting up for SMTP commands"
12600 .cindex "AUTH" "ACL for"
12601 This option defines the ACL that is run when an SMTP AUTH command is
12602 received. See chapter &<<CHAPACL>>& for further details.
12604 .option acl_smtp_connect main string&!! unset
12605 .cindex "&ACL;" "on SMTP connection"
12606 This option defines the ACL that is run when an SMTP connection is received.
12607 See chapter &<<CHAPACL>>& for further details.
12609 .option acl_smtp_data main string&!! unset
12610 .cindex "DATA" "ACL for"
12611 This option defines the ACL that is run after an SMTP DATA command has been
12612 processed and the message itself has been received, but before the final
12613 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
12615 .option acl_smtp_etrn main string&!! unset
12616 .cindex "ETRN" "ACL for"
12617 This option defines the ACL that is run when an SMTP ETRN command is
12618 received. See chapter &<<CHAPACL>>& for further details.
12620 .option acl_smtp_expn main string&!! unset
12621 .cindex "EXPN" "ACL for"
12622 This option defines the ACL that is run when an SMTP EXPN command is
12623 received. See chapter &<<CHAPACL>>& for further details.
12625 .option acl_smtp_helo main string&!! unset
12626 .cindex "EHLO" "ACL for"
12627 .cindex "HELO" "ACL for"
12628 This option defines the ACL that is run when an SMTP EHLO or HELO
12629 command is received. See chapter &<<CHAPACL>>& for further details.
12632 .option acl_smtp_mail main string&!! unset
12633 .cindex "MAIL" "ACL for"
12634 This option defines the ACL that is run when an SMTP MAIL command is
12635 received. See chapter &<<CHAPACL>>& for further details.
12637 .option acl_smtp_mailauth main string&!! unset
12638 .cindex "AUTH" "on MAIL command"
12639 This option defines the ACL that is run when there is an AUTH parameter on
12640 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
12641 &<<CHAPSMTPAUTH>>& for details of authentication.
12643 .option acl_smtp_mime main string&!! unset
12644 .cindex "MIME content scanning" "ACL for"
12645 This option is available when Exim is built with the content-scanning
12646 extension. It defines the ACL that is run for each MIME part in a message. See
12647 section &<<SECTscanmimepart>>& for details.
12649 .option acl_smtp_predata main string&!! unset
12650 This option defines the ACL that is run when an SMTP DATA command is
12651 received, before the message itself is received. See chapter &<<CHAPACL>>& for
12654 .option acl_smtp_quit main string&!! unset
12655 .cindex "QUIT, ACL for"
12656 This option defines the ACL that is run when an SMTP QUIT command is
12657 received. See chapter &<<CHAPACL>>& for further details.
12659 .option acl_smtp_rcpt main string&!! unset
12660 .cindex "RCPT" "ACL for"
12661 This option defines the ACL that is run when an SMTP RCPT command is
12662 received. See chapter &<<CHAPACL>>& for further details.
12664 .option acl_smtp_starttls main string&!! unset
12665 .cindex "STARTTLS, ACL for"
12666 This option defines the ACL that is run when an SMTP STARTTLS command is
12667 received. See chapter &<<CHAPACL>>& for further details.
12669 .option acl_smtp_vrfy main string&!! unset
12670 .cindex "VRFY" "ACL for"
12671 This option defines the ACL that is run when an SMTP VRFY command is
12672 received. See chapter &<<CHAPACL>>& for further details.
12674 .option admin_groups main "string list&!!" unset
12675 .cindex "admin user"
12676 This option is expanded just once, at the start of Exim's processing. If the
12677 current group or any of the supplementary groups of an Exim caller is in this
12678 colon-separated list, the caller has admin privileges. If all your system
12679 programmers are in a specific group, for example, you can give them all Exim
12680 admin privileges by putting that group in &%admin_groups%&. However, this does
12681 not permit them to read Exim's spool files (whose group owner is the Exim gid).
12682 To permit this, you have to add individuals to the Exim group.
12684 .option allow_domain_literals main boolean false
12685 .cindex "domain literal"
12686 If this option is set, the RFC 2822 domain literal format is permitted in
12687 email addresses. The option is not set by default, because the domain literal
12688 format is not normally required these days, and few people know about it. It
12689 has, however, been exploited by mail abusers.
12691 Unfortunately, it seems that some DNS black list maintainers are using this
12692 format to report black listing to postmasters. If you want to accept messages
12693 addressed to your hosts by IP address, you need to set
12694 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
12695 domains (defined in the named domain list &%local_domains%& in the default
12696 configuration). This &"magic string"& matches the domain literal form of all
12697 the local host's IP addresses.
12700 .option allow_mx_to_ip main boolean false
12701 .cindex "MX record" "pointing to IP address"
12702 It appears that more and more DNS zone administrators are breaking the rules
12703 and putting domain names that look like IP addresses on the right hand side of
12704 MX records. Exim follows the rules and rejects this, giving an error message
12705 that explains the mis-configuration. However, some other MTAs support this
12706 practice, so to avoid &"Why can't Exim do this?"& complaints,
12707 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
12708 recommended, except when you have no other choice.
12710 .option allow_utf8_domains main boolean false
12711 .cindex "domain" "UTF-8 characters in"
12712 .cindex "UTF-8" "in domain name"
12713 Lots of discussion is going on about internationalized domain names. One
12714 camp is strongly in favour of just using UTF-8 characters, and it seems
12715 that at least two other MTAs permit this. This option allows Exim users to
12716 experiment if they wish.
12718 If it is set true, Exim's domain parsing function allows valid
12719 UTF-8 multicharacters to appear in domain name components, in addition to
12720 letters, digits, and hyphens. However, just setting this option is not
12721 enough; if you want to look up these domain names in the DNS, you must also
12722 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
12723 suitable setting is:
12725 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
12726 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
12728 Alternatively, you can just disable this feature by setting
12730 dns_check_names_pattern =
12732 That is, set the option to an empty string so that no check is done.
12735 .option auth_advertise_hosts main "host list&!!" *
12736 .cindex "authentication" "advertising"
12737 .cindex "AUTH" "advertising"
12738 If any server authentication mechanisms are configured, Exim advertises them in
12739 response to an EHLO command only if the calling host matches this list.
12740 Otherwise, Exim does not advertise AUTH.
12741 Exim does not accept AUTH commands from clients to which it has not
12742 advertised the availability of AUTH. The advertising of individual
12743 authentication mechanisms can be controlled by the use of the
12744 &%server_advertise_condition%& generic authenticator option on the individual
12745 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
12747 Certain mail clients (for example, Netscape) require the user to provide a name
12748 and password for authentication if AUTH is advertised, even though it may
12749 not be needed (the host may accept messages from hosts on its local LAN without
12750 authentication, for example). The &%auth_advertise_hosts%& option can be used
12751 to make these clients more friendly by excluding them from the set of hosts to
12752 which Exim advertises AUTH.
12754 .cindex "AUTH" "advertising when encrypted"
12755 If you want to advertise the availability of AUTH only when the connection
12756 is encrypted using TLS, you can make use of the fact that the value of this
12757 option is expanded, with a setting like this:
12759 auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}
12761 .vindex "&$tls_cipher$&"
12762 If &$tls_cipher$& is empty, the session is not encrypted, and the result of
12763 the expansion is empty, thus matching no hosts. Otherwise, the result of the
12764 expansion is *, which matches all hosts.
12767 .option auto_thaw main time 0s
12768 .cindex "thawing messages"
12769 .cindex "unfreezing messages"
12770 If this option is set to a time greater than zero, a queue runner will try a
12771 new delivery attempt on any frozen message, other than a bounce message, if
12772 this much time has passed since it was frozen. This may result in the message
12773 being re-frozen if nothing has changed since the last attempt. It is a way of
12774 saying &"keep on trying, even though there are big problems"&.
12776 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
12777 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
12778 thought to be very useful any more, and its use should probably be avoided.
12780 .option av_scanner main string "see below"
12781 This option is available if Exim is built with the content-scanning extension.
12782 It specifies which anti-virus scanner to use. The default value is:
12784 sophie:/var/run/sophie
12786 If the value of &%av_scanner%& starts with dollar character, it is expanded
12787 before use. See section &<<SECTscanvirus>>& for further details.
12791 .option bi_command main string unset
12793 This option supplies the name of a command that is run when Exim is called with
12794 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
12795 just the command name, it is not a complete command line. If an argument is
12796 required, it must come from the &%-oA%& command line option.
12799 .option bounce_message_file main string unset
12800 .cindex "bounce message" "customizing"
12801 .cindex "customizing" "bounce message"
12802 This option defines a template file containing paragraphs of text to be used
12803 for constructing bounce messages. Details of the file's contents are given in
12804 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
12807 .option bounce_message_text main string unset
12808 When this option is set, its contents are included in the default bounce
12809 message immediately after &"This message was created automatically by mail
12810 delivery software."& It is not used if &%bounce_message_file%& is set.
12812 .option bounce_return_body main boolean true
12813 .cindex "bounce message" "including body"
12814 This option controls whether the body of an incoming message is included in a
12815 bounce message when &%bounce_return_message%& is true. The default setting
12816 causes the entire message, both header and body, to be returned (subject to the
12817 value of &%bounce_return_size_limit%&). If this option is false, only the
12818 message header is included. In the case of a non-SMTP message containing an
12819 error that is detected during reception, only those header lines preceding the
12820 point at which the error was detected are returned.
12821 .cindex "bounce message" "including original"
12823 .option bounce_return_message main boolean true
12824 If this option is set false, none of the original message is included in
12825 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
12826 &%bounce_return_body%&.
12829 .option bounce_return_size_limit main integer 100K
12830 .cindex "size" "of bounce, limit"
12831 .cindex "bounce message" "size limit"
12832 .cindex "limit" "bounce message size"
12833 This option sets a limit in bytes on the size of messages that are returned to
12834 senders as part of bounce messages when &%bounce_return_message%& is true. The
12835 limit should be less than the value of the global &%message_size_limit%& and of
12836 any &%message_size_limit%& settings on transports, to allow for the bounce text
12837 that Exim generates. If this option is set to zero there is no limit.
12839 When the body of any message that is to be included in a bounce message is
12840 greater than the limit, it is truncated, and a comment pointing this out is
12841 added at the top. The actual cutoff may be greater than the value given, owing
12842 to the use of buffering for transferring the message in chunks (typically 8K in
12843 size). The idea is to save bandwidth on those undeliverable 15-megabyte
12846 .option bounce_sender_authentication main string unset
12847 .cindex "bounce message" "sender authentication"
12848 .cindex "authentication" "bounce message"
12849 .cindex "AUTH" "on bounce message"
12850 This option provides an authenticated sender address that is sent with any
12851 bounce messages generated by Exim that are sent over an authenticated SMTP
12852 connection. A typical setting might be:
12854 bounce_sender_authentication = mailer-daemon@my.domain.example
12856 which would cause bounce messages to be sent using the SMTP command:
12858 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
12860 The value of &%bounce_sender_authentication%& must always be a complete email
12863 .option callout_domain_negative_expire main time 3h
12864 .cindex "caching" "callout timeouts"
12865 .cindex "callout" "caching timeouts"
12866 This option specifies the expiry time for negative callout cache data for a
12867 domain. See section &<<SECTcallver>>& for details of callout verification, and
12868 section &<<SECTcallvercache>>& for details of the caching.
12871 .option callout_domain_positive_expire main time 7d
12872 This option specifies the expiry time for positive callout cache data for a
12873 domain. See section &<<SECTcallver>>& for details of callout verification, and
12874 section &<<SECTcallvercache>>& for details of the caching.
12877 .option callout_negative_expire main time 2h
12878 This option specifies the expiry time for negative callout cache data for an
12879 address. See section &<<SECTcallver>>& for details of callout verification, and
12880 section &<<SECTcallvercache>>& for details of the caching.
12883 .option callout_positive_expire main time 24h
12884 This option specifies the expiry time for positive callout cache data for an
12885 address. See section &<<SECTcallver>>& for details of callout verification, and
12886 section &<<SECTcallvercache>>& for details of the caching.
12889 .option callout_random_local_part main string&!! "see below"
12890 This option defines the &"random"& local part that can be used as part of
12891 callout verification. The default value is
12893 $primary_host_name-$tod_epoch-testing
12895 See section &<<CALLaddparcall>>& for details of how this value is used.
12898 .option check_log_inodes main integer 0
12899 See &%check_spool_space%& below.
12902 .option check_log_space main integer 0
12903 See &%check_spool_space%& below.
12905 .oindex "&%check_rfc2047_length%&"
12906 .cindex "RFC 2047" "disabling length check"
12907 .option check_rfc2047_length main boolean true
12908 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
12909 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
12910 word; strings to be encoded that exceed this length are supposed to use
12911 multiple encoded words. By default, Exim does not recognize encoded words that
12912 exceed the maximum length. However, it seems that some software, in violation
12913 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
12914 set false, Exim recognizes encoded words of any length.
12917 .option check_spool_inodes main integer 0
12918 See &%check_spool_space%& below.
12921 .option check_spool_space main integer 0
12922 .cindex "checking disk space"
12923 .cindex "disk space, checking"
12924 .cindex "spool directory" "checking space"
12925 The four &%check_...%& options allow for checking of disk resources before a
12926 message is accepted.
12928 .vindex "&$log_inodes$&"
12929 .vindex "&$log_space$&"
12930 .vindex "&$spool_inodes$&"
12931 .vindex "&$spool_space$&"
12932 When any of these options are set, they apply to all incoming messages. If you
12933 want to apply different checks to different kinds of message, you can do so by
12934 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
12935 &$spool_space$& in an ACL with appropriate additional conditions.
12938 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
12939 either value is greater than zero, for example:
12941 check_spool_space = 10M
12942 check_spool_inodes = 100
12944 The spool partition is the one that contains the directory defined by
12945 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
12948 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
12949 files are written if either is greater than zero. These should be set only if
12950 &%log_file_path%& and &%spool_directory%& refer to different partitions.
12952 If there is less space or fewer inodes than requested, Exim refuses to accept
12953 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
12954 error response to the MAIL command. If ESMTP is in use and there was a
12955 SIZE parameter on the MAIL command, its value is added to the
12956 &%check_spool_space%& value, and the check is performed even if
12957 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
12959 The values for &%check_spool_space%& and &%check_log_space%& are held as a
12960 number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up.
12962 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
12963 failure a message is written to stderr and Exim exits with a non-zero code, as
12964 it obviously cannot send an error message of any kind.
12966 .option daemon_smtp_ports main string &`smtp`&
12967 .cindex "port" "for daemon"
12968 .cindex "TCP/IP" "setting listening ports"
12969 This option specifies one or more default SMTP ports on which the Exim daemon
12970 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
12971 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
12973 .option daemon_startup_retries main integer 9
12974 .cindex "daemon startup, retrying"
12975 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
12976 the daemon at startup when it cannot immediately bind a listening socket
12977 (typically because the socket is already in use): &%daemon_startup_retries%&
12978 defines the number of retries after the first failure, and
12979 &%daemon_startup_sleep%& defines the length of time to wait between retries.
12981 .option daemon_startup_sleep main time 30s
12982 See &%daemon_startup_retries%&.
12984 .option delay_warning main "time list" 24h
12985 .cindex "warning of delay"
12986 .cindex "delay warning, specifying"
12987 When a message is delayed, Exim sends a warning message to the sender at
12988 intervals specified by this option. The data is a colon-separated list of times
12989 after which to send warning messages. If the value of the option is an empty
12990 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
12991 message has been on the queue for longer than the last time, the last interval
12992 between the times is used to compute subsequent warning times. For example,
12995 delay_warning = 4h:8h:24h
12997 the first message is sent after 4 hours, the second after 8 hours, and
12998 the third one after 24 hours. After that, messages are sent every 16 hours,
12999 because that is the interval between the last two times on the list. If you set
13000 just one time, it specifies the repeat interval. For example, with:
13004 messages are repeated every six hours. To stop warnings after a given time, set
13005 a very large time at the end of the list. For example:
13007 delay_warning = 2h:12h:99d
13010 .option delay_warning_condition main string&!! "see below"
13011 .vindex "&$domain$&"
13012 The string is expanded at the time a warning message might be sent. If all the
13013 deferred addresses have the same domain, it is set in &$domain$& during the
13014 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
13015 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
13016 &"false"& (the comparison being done caselessly) then the warning message is
13017 not sent. The default is:
13019 delay_warning_condition = ${if or {\
13020 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
13021 { match{$h_precedence:}{(?i)bulk|list|junk} }\
13022 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
13025 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
13026 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
13027 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
13028 &"auto-replied"& in an &'Auto-Submitted:'& header.
13030 .option deliver_drop_privilege main boolean false
13031 .cindex "unprivileged delivery"
13032 .cindex "delivery" "unprivileged"
13033 If this option is set true, Exim drops its root privilege at the start of a
13034 delivery process, and runs as the Exim user throughout. This severely restricts
13035 the kinds of local delivery that are possible, but is viable in certain types
13036 of configuration. There is a discussion about the use of root privilege in
13037 chapter &<<CHAPsecurity>>&.
13039 .option deliver_queue_load_max main fixed-point unset
13040 .cindex "load average"
13041 .cindex "queue runner" "abandoning"
13042 When this option is set, a queue run is abandoned if the system load average
13043 becomes greater than the value of the option. The option has no effect on
13044 ancient operating systems on which Exim cannot determine the load average.
13045 See also &%queue_only_load%& and &%smtp_load_reserve%&.
13048 .option delivery_date_remove main boolean true
13049 .cindex "&'Delivery-date:'& header line"
13050 Exim's transports have an option for adding a &'Delivery-date:'& header to a
13051 message when it is delivered, in exactly the same way as &'Return-path:'& is
13052 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
13053 should not be present in incoming messages, and this option causes them to be
13054 removed at the time the message is received, to avoid any problems that might
13055 occur when a delivered message is subsequently sent on to some other recipient.
13057 .option disable_fsync main boolean false
13058 .cindex "&[fsync()]&, disabling"
13059 This option is available only if Exim was built with the compile-time option
13060 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
13061 a runtime configuration generates an &"unknown option"& error. You should not
13062 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
13063 really, really, really understand what you are doing. &'No pre-compiled
13064 distributions of Exim should ever make this option available.'&
13066 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
13067 updated files' data to be written to disc before continuing. Unexpected events
13068 such as crashes and power outages may cause data to be lost or scrambled.
13069 Here be Dragons. &*Beware.*&
13072 .option disable_ipv6 main boolean false
13073 .cindex "IPv6" "disabling"
13074 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
13075 activities take place. AAAA records are never looked up, and any IPv6 addresses
13076 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
13077 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13078 to handle IPv6 literal addresses.
13081 .option dns_again_means_nonexist main "domain list&!!" unset
13082 .cindex "DNS" "&""try again""& response; overriding"
13083 DNS lookups give a &"try again"& response for the DNS errors
13084 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
13085 keep trying to deliver a message, or to give repeated temporary errors to
13086 incoming mail. Sometimes the effect is caused by a badly set up name server and
13087 may persist for a long time. If a domain which exhibits this problem matches
13088 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
13089 This option should be used with care. You can make it apply to reverse lookups
13090 by a setting such as this:
13092 dns_again_means_nonexist = *.in-addr.arpa
13094 This option applies to all DNS lookups that Exim does. It also applies when the
13095 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
13096 since these are most likely to be caused by DNS lookup problems. The
13097 &(dnslookup)& router has some options of its own for controlling what happens
13098 when lookups for MX or SRV records give temporary errors. These more specific
13099 options are applied after this global option.
13101 .option dns_check_names_pattern main string "see below"
13102 .cindex "DNS" "pre-check of name syntax"
13103 When this option is set to a non-empty string, it causes Exim to check domain
13104 names for characters that are not allowed in host names before handing them to
13105 the DNS resolver, because some resolvers give temporary errors for names that
13106 contain unusual characters. If a domain name contains any unwanted characters,
13107 a &"not found"& result is forced, and the resolver is not called. The check is
13108 done by matching the domain name against a regular expression, which is the
13109 value of this option. The default pattern is
13111 dns_check_names_pattern = \
13112 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
13114 which permits only letters, digits, slashes, and hyphens in components, but
13115 they must start and end with a letter or digit. Slashes are not, in fact,
13116 permitted in host names, but they are found in certain NS records (which can be
13117 accessed in Exim by using a &%dnsdb%& lookup). If you set
13118 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
13121 .option dns_csa_search_limit main integer 5
13122 This option controls the depth of parental searching for CSA SRV records in the
13123 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
13125 .option dns_csa_use_reverse main boolean true
13126 This option controls whether or not an IP address, given as a CSA domain, is
13127 reversed and looked up in the reverse DNS, as described in more detail in
13128 section &<<SECTverifyCSA>>&.
13130 .option dns_ipv4_lookup main "domain list&!!" unset
13131 .cindex "IPv6" "DNS lookup for AAAA records"
13132 .cindex "DNS" "IPv6 lookup for AAAA records"
13133 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
13134 looks for IPv6 address records (AAAA records) as well as IPv4 address records
13135 (A records) when trying to find IP addresses for hosts, unless the host's
13136 domain matches this list.
13138 This is a fudge to help with name servers that give big delays or otherwise do
13139 not work for the AAAA record type. In due course, when the world's name
13140 servers have all been upgraded, there should be no need for this option.
13143 .option dns_retrans main time 0s
13144 .cindex "DNS" "resolver options"
13145 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
13146 retransmission and retry parameters for DNS lookups. Values of zero (the
13147 defaults) leave the system default settings unchanged. The first value is the
13148 time between retries, and the second is the number of retries. It isn't
13149 totally clear exactly how these settings affect the total time a DNS lookup may
13150 take. I haven't found any documentation about timeouts on DNS lookups; these
13151 parameter values are available in the external resolver interface structure,
13152 but nowhere does it seem to describe how they are used or what you might want
13156 .option dns_retry main integer 0
13157 See &%dns_retrans%& above.
13160 .option drop_cr main boolean false
13161 This is an obsolete option that is now a no-op. It used to affect the way Exim
13162 handled CR and LF characters in incoming messages. What happens now is
13163 described in section &<<SECTlineendings>>&.
13165 .option dsn_from main "string&!!" "see below"
13166 .cindex "&'From:'& header line" "in bounces"
13167 .cindex "bounce messages" "&'From:'& line, specifying"
13168 This option can be used to vary the contents of &'From:'& header lines in
13169 bounces and other automatically generated messages (&"Delivery Status
13170 Notifications"& &-- hence the name of the option). The default setting is:
13172 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
13174 The value is expanded every time it is needed. If the expansion fails, a
13175 panic is logged, and the default value is used.
13177 .option envelope_to_remove main boolean true
13178 .cindex "&'Envelope-to:'& header line"
13179 Exim's transports have an option for adding an &'Envelope-to:'& header to a
13180 message when it is delivered, in exactly the same way as &'Return-path:'& is
13181 handled. &'Envelope-to:'& records the original recipient address from the
13182 messages's envelope that caused the delivery to happen. Such headers should not
13183 be present in incoming messages, and this option causes them to be removed at
13184 the time the message is received, to avoid any problems that might occur when a
13185 delivered message is subsequently sent on to some other recipient.
13188 .option errors_copy main "string list&!!" unset
13189 .cindex "bounce message" "copy to other address"
13190 .cindex "copy of bounce message"
13191 Setting this option causes Exim to send bcc copies of bounce messages that it
13192 generates to other addresses. &*Note*&: This does not apply to bounce messages
13193 coming from elsewhere. The value of the option is a colon-separated list of
13194 items. Each item consists of a pattern, terminated by white space, followed by
13195 a comma-separated list of email addresses. If a pattern contains spaces, it
13196 must be enclosed in double quotes.
13198 Each pattern is processed in the same way as a single item in an address list
13199 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
13200 the bounce message, the message is copied to the addresses on the list. The
13201 items are scanned in order, and once a matching one is found, no further items
13202 are examined. For example:
13204 errors_copy = spqr@mydomain postmaster@mydomain.example :\
13205 rqps@mydomain hostmaster@mydomain.example,\
13206 postmaster@mydomain.example
13208 .vindex "&$domain$&"
13209 .vindex "&$local_part$&"
13210 The address list is expanded before use. The expansion variables &$local_part$&
13211 and &$domain$& are set from the original recipient of the error message, and if
13212 there was any wildcard matching in the pattern, the expansion
13213 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
13214 variables &$0$&, &$1$&, etc. are set in the normal way.
13217 .option errors_reply_to main string unset
13218 .cindex "bounce message" "&'Reply-to:'& in"
13219 By default, Exim's bounce and delivery warning messages contain the header line
13221 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
13223 .oindex &%quota_warn_message%&
13224 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
13225 A warning message that is generated by the &%quota_warn_message%& option in an
13226 &(appendfile)& transport may contain its own &'From:'& header line that
13227 overrides the default.
13229 Experience shows that people reply to bounce messages. If the
13230 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
13231 and warning messages. For example:
13233 errors_reply_to = postmaster@my.domain.example
13235 The value of the option is not expanded. It must specify a valid RFC 2822
13236 address. However, if a warning message that is generated by the
13237 &%quota_warn_message%& option in an &(appendfile)& transport contain its
13238 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
13242 .option exim_group main string "compile-time configured"
13243 .cindex "gid (group id)" "Exim's own"
13244 .cindex "Exim group"
13245 This option changes the gid under which Exim runs when it gives up root
13246 privilege. The default value is compiled into the binary. The value of this
13247 option is used only when &%exim_user%& is also set. Unless it consists entirely
13248 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
13249 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
13253 .option exim_path main string "see below"
13254 .cindex "Exim binary, path name"
13255 This option specifies the path name of the Exim binary, which is used when Exim
13256 needs to re-exec itself. The default is set up to point to the file &'exim'& in
13257 the directory configured at compile time by the BIN_DIRECTORY setting. It
13258 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
13260 &*Warning*&: Do not use a macro to define the value of this option, because
13261 you will break those Exim utilities that scan the configuration file to find
13262 where the binary is. (They then use the &%-bP%& option to extract option
13263 settings such as the value of &%spool_directory%&.)
13266 .option exim_user main string "compile-time configured"
13267 .cindex "uid (user id)" "Exim's own"
13268 .cindex "Exim user"
13269 This option changes the uid under which Exim runs when it gives up root
13270 privilege. The default value is compiled into the binary. Ownership of the run
13271 time configuration file and the use of the &%-C%& and &%-D%& command line
13272 options is checked against the values in the binary, not what is set here.
13274 Unless it consists entirely of digits, the string is looked up using
13275 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
13276 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
13277 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
13280 .option extra_local_interfaces main "string list" unset
13281 This option defines network interfaces that are to be considered local when
13282 routing, but which are not used for listening by the daemon. See section
13283 &<<SECTreclocipadd>>& for details.
13286 . Allow this long option name to split; give it unsplit as a fifth argument
13287 . for the automatic .oindex that is generated by .option.
13289 .option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
13290 extract_addresses_remove_arguments
13292 .cindex "command line" "addresses with &%-t%&"
13293 .cindex "Sendmail compatibility" "&%-t%& option"
13294 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
13295 are present on the command line when the &%-t%& option is used to build an
13296 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
13297 line addresses are removed from the recipients list. This is also how Smail
13298 behaves. However, other Sendmail documentation (the O'Reilly book) states that
13299 command line addresses are added to those obtained from the header lines. When
13300 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
13301 argument headers. If it is set false, Exim adds rather than removes argument
13305 .option finduser_retries main integer 0
13306 .cindex "NIS, retrying user lookups"
13307 On systems running NIS or other schemes in which user and group information is
13308 distributed from a remote system, there can be times when &[getpwnam()]& and
13309 related functions fail, even when given valid data, because things time out.
13310 Unfortunately these failures cannot be distinguished from genuine &"not found"&
13311 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
13312 many extra times to find a user or a group, waiting for one second between
13315 .cindex "&_/etc/passwd_&" "multiple reading of"
13316 You should not set this option greater than zero if your user information is in
13317 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
13318 search the file multiple times for non-existent users, and also cause delay.
13322 .option freeze_tell main "string list, comma separated" unset
13323 .cindex "freezing messages" "sending a message when freezing"
13324 On encountering certain errors, or when configured to do so in a system filter,
13325 ACL, or special router, Exim freezes a message. This means that no further
13326 delivery attempts take place until an administrator thaws the message, or the
13327 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
13328 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
13329 warning message whenever it freezes something, unless the message it is
13330 freezing is a locally-generated bounce message. (Without this exception there
13331 is the possibility of looping.) The warning message is sent to the addresses
13332 supplied as the comma-separated value of this option. If several of the
13333 message's addresses cause freezing, only a single message is sent. If the
13334 freezing was automatic, the reason(s) for freezing can be found in the message
13335 log. If you configure freezing in a filter or ACL, you must arrange for any
13336 logging that you require.
13339 .option gecos_name main string&!! unset
13341 .cindex "&""gecos""& field, parsing"
13342 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
13343 password file to hold other information in addition to users' real names. Exim
13344 looks up this field for use when it is creating &'Sender:'& or &'From:'&
13345 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
13346 of the field are used unchanged, except that, if an ampersand is encountered,
13347 it is replaced by the user's login name with the first character forced to
13348 upper case, since this is a convention that is observed on many systems.
13350 When these options are set, &%gecos_pattern%& is treated as a regular
13351 expression that is to be applied to the field (again with && replaced by the
13352 login name), and if it matches, &%gecos_name%& is expanded and used as the
13355 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
13356 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
13357 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
13358 name terminates at the first comma, the following can be used:
13360 gecos_pattern = ([^,]*)
13364 .option gecos_pattern main string unset
13365 See &%gecos_name%& above.
13368 .option gnutls_require_kx main string unset
13369 This option controls the key exchange mechanisms when GnuTLS is used in an Exim
13370 server. For details, see section &<<SECTreqciphgnu>>&.
13372 .option gnutls_require_mac main string unset
13373 This option controls the MAC algorithms when GnuTLS is used in an Exim
13374 server. For details, see section &<<SECTreqciphgnu>>&.
13376 .option gnutls_require_protocols main string unset
13377 This option controls the protocols when GnuTLS is used in an Exim
13378 server. For details, see section &<<SECTreqciphgnu>>&.
13380 .option gnutls_compat_mode main boolean unset
13381 This option controls whether GnuTLS is used in compatibility mode in an Exim
13382 server. This reduces security slightly, but improves interworking with older
13383 implementations of TLS.
13385 .option headers_charset main string "see below"
13386 This option sets a default character set for translating from encoded MIME
13387 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
13388 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
13389 ultimate default is ISO-8859-1. For more details see the description of header
13390 insertions in section &<<SECTexpansionitems>>&.
13394 .option header_maxsize main integer "see below"
13395 .cindex "header section" "maximum size of"
13396 .cindex "limit" "size of message header section"
13397 This option controls the overall maximum size of a message's header
13398 section. The default is the value of HEADER_MAXSIZE in
13399 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
13400 sections are rejected.
13403 .option header_line_maxsize main integer 0
13404 .cindex "header lines" "maximum size of"
13405 .cindex "limit" "size of one header line"
13406 This option limits the length of any individual header line in a message, after
13407 all the continuations have been joined together. Messages with individual
13408 header lines that are longer than the limit are rejected. The default value of
13409 zero means &"no limit"&.
13414 .option helo_accept_junk_hosts main "host list&!!" unset
13415 .cindex "HELO" "accepting junk data"
13416 .cindex "EHLO" "accepting junk data"
13417 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
13418 mail, and gives an error response for invalid data. Unfortunately, there are
13419 some SMTP clients that send syntactic junk. They can be accommodated by setting
13420 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
13421 if you want to do semantic checking.
13422 See also &%helo_allow_chars%& for a way of extending the permitted character
13426 .option helo_allow_chars main string unset
13427 .cindex "HELO" "underscores in"
13428 .cindex "EHLO" "underscores in"
13429 .cindex "underscore in EHLO/HELO"
13430 This option can be set to a string of rogue characters that are permitted in
13431 all EHLO and HELO names in addition to the standard letters, digits,
13432 hyphens, and dots. If you really must allow underscores, you can set
13434 helo_allow_chars = _
13436 Note that the value is one string, not a list.
13439 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
13440 .cindex "HELO" "forcing reverse lookup"
13441 .cindex "EHLO" "forcing reverse lookup"
13442 If the domain given by a client in a HELO or EHLO command matches this
13443 list, a reverse lookup is done in order to establish the host's true name. The
13444 default forces a lookup if the client host gives the server's name or any of
13445 its IP addresses (in brackets), something that broken clients have been seen to
13449 .option helo_try_verify_hosts main "host list&!!" unset
13450 .cindex "HELO verifying" "optional"
13451 .cindex "EHLO" "verifying, optional"
13452 By default, Exim just checks the syntax of HELO and EHLO commands (see
13453 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
13454 to do more extensive checking of the data supplied by these commands. The ACL
13455 condition &`verify = helo`& is provided to make this possible.
13456 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
13457 to force the check to occur. From release 4.53 onwards, this is no longer
13458 necessary. If the check has not been done before &`verify = helo`& is
13459 encountered, it is done at that time. Consequently, this option is obsolete.
13460 Its specification is retained here for backwards compatibility.
13462 When an EHLO or HELO command is received, if the calling host matches
13463 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
13464 EHLO command either:
13467 is an IP literal matching the calling address of the host, or
13469 .cindex "DNS" "reverse lookup"
13470 .cindex "reverse DNS lookup"
13471 matches the host name that Exim obtains by doing a reverse lookup of the
13472 calling host address, or
13474 when looked up using &[gethostbyname()]& (or &[getipnodebyname()]& when
13475 available) yields the calling host address.
13478 However, the EHLO or HELO command is not rejected if any of the checks
13479 fail. Processing continues, but the result of the check is remembered, and can
13480 be detected later in an ACL by the &`verify = helo`& condition.
13482 .option helo_verify_hosts main "host list&!!" unset
13483 .cindex "HELO verifying" "mandatory"
13484 .cindex "EHLO" "verifying, mandatory"
13485 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
13486 backwards compatibility. For hosts that match this option, Exim checks the host
13487 name given in the HELO or EHLO in the same way as for
13488 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
13489 rejected with a 550 error, and entries are written to the main and reject logs.
13490 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
13493 .option hold_domains main "domain list&!!" unset
13494 .cindex "domain" "delaying delivery"
13495 .cindex "delivery" "delaying certain domains"
13496 This option allows mail for particular domains to be held on the queue
13497 manually. The option is overridden if a message delivery is forced with the
13498 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
13499 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
13500 item in &%hold_domains%&, no routing or delivery for that address is done, and
13501 it is deferred every time the message is looked at.
13503 This option is intended as a temporary operational measure for delaying the
13504 delivery of mail while some problem is being sorted out, or some new
13505 configuration tested. If you just want to delay the processing of some
13506 domains until a queue run occurs, you should use &%queue_domains%& or
13507 &%queue_smtp_domains%&, not &%hold_domains%&.
13509 A setting of &%hold_domains%& does not override Exim's code for removing
13510 messages from the queue if they have been there longer than the longest retry
13511 time in any retry rule. If you want to hold messages for longer than the normal
13512 retry times, insert a dummy retry rule with a long retry time.
13515 .option host_lookup main "host list&!!" unset
13516 .cindex "host name" "lookup, forcing"
13517 Exim does not look up the name of a calling host from its IP address unless it
13518 is required to compare against some host list, or the host matches
13519 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
13520 option (which normally contains IP addresses rather than host names). The
13521 default configuration file contains
13525 which causes a lookup to happen for all hosts. If the expense of these lookups
13526 is felt to be too great, the setting can be changed or removed.
13528 After a successful reverse lookup, Exim does a forward lookup on the name it
13529 has obtained, to verify that it yields the IP address that it started with. If
13530 this check fails, Exim behaves as if the name lookup failed.
13532 .vindex "&$host_lookup_failed$&"
13533 .vindex "&$sender_host_name$&"
13534 After any kind of failure, the host name (in &$sender_host_name$&) remains
13535 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
13536 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
13537 &`verify = reverse_host_lookup`& in ACLs.
13540 .option host_lookup_order main "string list" &`bydns:byaddr`&
13541 This option specifies the order of different lookup methods when Exim is trying
13542 to find a host name from an IP address. The default is to do a DNS lookup
13543 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
13544 if that fails. You can change the order of these lookups, or omit one entirely,
13547 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
13548 multiple PTR records in the DNS and the IP address is not listed in
13549 &_/etc/hosts_&. Different operating systems give different results in this
13550 case. That is why the default tries a DNS lookup first.
13554 .option host_reject_connection main "host list&!!" unset
13555 .cindex "host" "rejecting connections from"
13556 If this option is set, incoming SMTP calls from the hosts listed are rejected
13557 as soon as the connection is made.
13558 This option is obsolete, and retained only for backward compatibility, because
13559 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
13560 connections immediately.
13562 The ability to give an immediate rejection (either by this option or using an
13563 ACL) is provided for use in unusual cases. Many hosts will just try again,
13564 sometimes without much delay. Normally, it is better to use an ACL to reject
13565 incoming messages at a later stage, such as after RCPT commands. See
13566 chapter &<<CHAPACL>>&.
13569 .option hosts_connection_nolog main "host list&!!" unset
13570 .cindex "host" "not logging connections from"
13571 This option defines a list of hosts for which connection logging does not
13572 happen, even though the &%smtp_connection%& log selector is set. For example,
13573 you might want not to log SMTP connections from local processes, or from
13574 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
13575 the daemon; you should therefore strive to restrict its value to a short inline
13576 list of IP addresses and networks. To disable logging SMTP connections from
13577 local processes, you must create a host list with an empty item. For example:
13579 hosts_connection_nolog = :
13581 If the &%smtp_connection%& log selector is not set, this option has no effect.
13585 .option hosts_treat_as_local main "domain list&!!" unset
13586 .cindex "local host" "domains treated as"
13587 .cindex "host" "treated as local"
13588 If this option is set, any host names that match the domain list are treated as
13589 if they were the local host when Exim is scanning host lists obtained from MX
13591 or other sources. Note that the value of this option is a domain list, not a
13592 host list, because it is always used to check host names, not IP addresses.
13594 This option also applies when Exim is matching the special items
13595 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
13596 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
13597 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
13598 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
13599 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
13600 interfaces and recognizing the local host.
13603 .option ibase_servers main "string list" unset
13604 .cindex "InterBase" "server list"
13605 This option provides a list of InterBase servers and associated connection data,
13606 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
13607 The option is available only if Exim has been built with InterBase support.
13611 .option ignore_bounce_errors_after main time 10w
13612 .cindex "bounce message" "discarding"
13613 .cindex "discarding bounce message"
13614 This option affects the processing of bounce messages that cannot be delivered,
13615 that is, those that suffer a permanent delivery failure. (Bounce messages that
13616 suffer temporary delivery failures are of course retried in the usual way.)
13618 After a permanent delivery failure, bounce messages are frozen,
13619 because there is no sender to whom they can be returned. When a frozen bounce
13620 message has been on the queue for more than the given time, it is unfrozen at
13621 the next queue run, and a further delivery is attempted. If delivery fails
13622 again, the bounce message is discarded. This makes it possible to keep failed
13623 bounce messages around for a shorter time than the normal maximum retry time
13624 for frozen messages. For example,
13626 ignore_bounce_errors_after = 12h
13628 retries failed bounce message deliveries after 12 hours, discarding any further
13629 failures. If the value of this option is set to a zero time period, bounce
13630 failures are discarded immediately. Setting a very long time (as in the default
13631 value) has the effect of disabling this option. For ways of automatically
13632 dealing with other kinds of frozen message, see &%auto_thaw%& and
13633 &%timeout_frozen_after%&.
13636 .option ignore_fromline_hosts main "host list&!!" unset
13637 .cindex "&""From""& line"
13638 .cindex "UUCP" "&""From""& line"
13639 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
13640 the headers of a message. By default this is treated as the start of the
13641 message's body, which means that any following headers are not recognized as
13642 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
13643 match those hosts that insist on sending it. If the sender is actually a local
13644 process rather than a remote host, and is using &%-bs%& to inject the messages,
13645 &%ignore_fromline_local%& must be set to achieve this effect.
13648 .option ignore_fromline_local main boolean false
13649 See &%ignore_fromline_hosts%& above.
13652 .option keep_malformed main time 4d
13653 This option specifies the length of time to keep messages whose spool files
13654 have been corrupted in some way. This should, of course, never happen. At the
13655 next attempt to deliver such a message, it gets removed. The incident is
13659 .option ldap_default_servers main "string list" unset
13660 .cindex "LDAP" "default servers"
13661 This option provides a list of LDAP servers which are tried in turn when an
13662 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
13663 details of LDAP queries. This option is available only when Exim has been built
13667 .option ldap_version main integer unset
13668 .cindex "LDAP" "protocol version, forcing"
13669 This option can be used to force Exim to set a specific protocol version for
13670 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
13671 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
13672 the LDAP headers; otherwise it is 2. This option is available only when Exim
13673 has been built with LDAP support.
13677 .option local_from_check main boolean true
13678 .cindex "&'Sender:'& header line" "disabling addition of"
13679 .cindex "&'From:'& header line" "disabling checking of"
13680 When a message is submitted locally (that is, not over a TCP/IP connection) by
13681 an untrusted user, Exim removes any existing &'Sender:'& header line, and
13682 checks that the &'From:'& header line matches the login of the calling user and
13683 the domain specified by &%qualify_domain%&.
13685 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
13686 locally submitted message is automatically qualified by Exim, unless the
13687 &%-bnq%& command line option is used.
13689 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
13690 on the local part. If the &'From:'& header line does not match, Exim adds a
13691 &'Sender:'& header with an address constructed from the calling user's login
13692 and the default qualify domain.
13694 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
13695 and no &'Sender:'& header is ever added. If, in addition, you want to retain
13696 &'Sender:'& header lines supplied by untrusted users, you must also set
13697 &%local_sender_retain%& to be true.
13699 .cindex "envelope sender"
13700 These options affect only the header lines in the message. The envelope sender
13701 is still forced to be the login id at the qualify domain unless
13702 &%untrusted_set_sender%& permits the user to supply an envelope sender.
13704 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
13705 request similar header line checking. See section &<<SECTthesenhea>>&, which
13706 has more details about &'Sender:'& processing.
13711 .option local_from_prefix main string unset
13712 When Exim checks the &'From:'& header line of locally submitted messages for
13713 matching the login id (see &%local_from_check%& above), it can be configured to
13714 ignore certain prefixes and suffixes in the local part of the address. This is
13715 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
13716 appropriate lists, in the same form as the &%local_part_prefix%& and
13717 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
13720 local_from_prefix = *-
13722 is set, a &'From:'& line containing
13724 From: anything-user@your.domain.example
13726 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
13727 matches the actual sender address that is constructed from the login name and
13731 .option local_from_suffix main string unset
13732 See &%local_from_prefix%& above.
13735 .option local_interfaces main "string list" "see below"
13736 This option controls which network interfaces are used by the daemon for
13737 listening; they are also used to identify the local host when routing. Chapter
13738 &<<CHAPinterfaces>>& contains a full description of this option and the related
13739 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
13740 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
13741 &%local_interfaces%& is
13743 local_interfaces = 0.0.0.0
13745 when Exim is built without IPv6 support; otherwise it is
13747 local_interfaces = <; ::0 ; 0.0.0.0
13750 .option local_scan_timeout main time 5m
13751 .cindex "timeout" "for &[local_scan()]& function"
13752 .cindex "&[local_scan()]& function" "timeout"
13753 This timeout applies to the &[local_scan()]& function (see chapter
13754 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
13755 the incoming message is rejected with a temporary error if it is an SMTP
13756 message. For a non-SMTP message, the message is dropped and Exim ends with a
13757 non-zero code. The incident is logged on the main and reject logs.
13761 .option local_sender_retain main boolean false
13762 .cindex "&'Sender:'& header line" "retaining from local submission"
13763 When a message is submitted locally (that is, not over a TCP/IP connection) by
13764 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
13765 do not want this to happen, you must set &%local_sender_retain%&, and you must
13766 also set &%local_from_check%& to be false (Exim will complain if you do not).
13767 See also the ACL modifier &`control = suppress_local_fixups`&. Section
13768 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
13773 .option localhost_number main string&!! unset
13774 .cindex "host" "locally unique number for"
13775 .cindex "message ids" "with multiple hosts"
13776 .vindex "&$localhost_number$&"
13777 Exim's message ids are normally unique only within the local host. If
13778 uniqueness among a set of hosts is required, each host must set a different
13779 value for the &%localhost_number%& option. The string is expanded immediately
13780 after reading the configuration file (so that a number can be computed from the
13781 host name, for example) and the result of the expansion must be a number in the
13782 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
13783 systems). This is available in subsequent string expansions via the variable
13784 &$localhost_number$&. When &%localhost_number is set%&, the final two
13785 characters of the message id, instead of just being a fractional part of the
13786 time, are computed from the time and the local host number as described in
13787 section &<<SECTmessiden>>&.
13791 .option log_file_path main "string list&!!" "set at compile time"
13792 .cindex "log" "file path for"
13793 This option sets the path which is used to determine the names of Exim's log
13794 files, or indicates that logging is to be to syslog, or both. It is expanded
13795 when Exim is entered, so it can, for example, contain a reference to the host
13796 name. If no specific path is set for the log files at compile or run time, they
13797 are written in a sub-directory called &_log_& in Exim's spool directory.
13798 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
13799 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
13800 used. If this string is fixed at your installation (contains no expansion
13801 variables) it is recommended that you do not set this option in the
13802 configuration file, but instead supply the path using LOG_FILE_PATH in
13803 &_Local/Makefile_& so that it is available to Exim for logging errors detected
13804 early on &-- in particular, failure to read the configuration file.
13807 .option log_selector main string unset
13808 .cindex "log" "selectors"
13809 This option can be used to reduce or increase the number of things that Exim
13810 writes to its log files. Its argument is made up of names preceded by plus or
13811 minus characters. For example:
13813 log_selector = +arguments -retry_defer
13815 A list of possible names and what they control is given in the chapter on
13816 logging, in section &<<SECTlogselector>>&.
13819 .option log_timezone main boolean false
13820 .cindex "log" "timezone for entries"
13821 .vindex "&$tod_log$&"
13822 .vindex "&$tod_zone$&"
13823 By default, the timestamps on log lines are in local time without the
13824 timezone. This means that if your timezone changes twice a year, the timestamps
13825 in log lines are ambiguous for an hour when the clocks go back. One way of
13826 avoiding this problem is to set the timezone to UTC. An alternative is to set
13827 &%log_timezone%& true. This turns on the addition of the timezone offset to
13828 timestamps in log lines. Turning on this option can add quite a lot to the size
13829 of log files because each line is extended by 6 characters. Note that the
13830 &$tod_log$& variable contains the log timestamp without the zone, but there is
13831 another variable called &$tod_zone$& that contains just the timezone offset.
13834 .option lookup_open_max main integer 25
13835 .cindex "too many open files"
13836 .cindex "open files, too many"
13837 .cindex "file" "too many open"
13838 .cindex "lookup" "maximum open files"
13839 .cindex "limit" "open files for lookups"
13840 This option limits the number of simultaneously open files for single-key
13841 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
13842 Exim normally keeps these files open during routing, because often the same
13843 file is required several times. If the limit is reached, Exim closes the least
13844 recently used file. Note that if you are using the &'ndbm'& library, it
13845 actually opens two files for each logical DBM database, though it still counts
13846 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
13847 open files"& errors with NDBM, you need to reduce the value of
13848 &%lookup_open_max%&.
13851 .option max_username_length main integer 0
13852 .cindex "length of login name"
13853 .cindex "user name" "maximum length"
13854 .cindex "limit" "user name length"
13855 Some operating systems are broken in that they truncate long arguments to
13856 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
13857 this option is set greater than zero, any attempt to call &[getpwnam()]& with
13858 an argument that is longer behaves as if &[getpwnam()]& failed.
13861 .option message_body_newlines main bool false
13862 .cindex "message body" "newlines in variables"
13863 .cindex "newline" "in message body variables"
13864 .vindex "&$message_body$&"
13865 .vindex "&$message_body_end$&"
13866 By default, newlines in the message body are replaced by spaces when setting
13867 the &$message_body$& and &$message_body_end$& expansion variables. If this
13868 option is set true, this no longer happens.
13871 .option message_body_visible main integer 500
13872 .cindex "body of message" "visible size"
13873 .cindex "message body" "visible size"
13874 .vindex "&$message_body$&"
13875 .vindex "&$message_body_end$&"
13876 This option specifies how much of a message's body is to be included in the
13877 &$message_body$& and &$message_body_end$& expansion variables.
13880 .option message_id_header_domain main string&!! unset
13881 .cindex "&'Message-ID:'& header line"
13882 If this option is set, the string is expanded and used as the right hand side
13883 (domain) of the &'Message-ID:'& header that Exim creates if a
13884 locally-originated incoming message does not have one. &"Locally-originated"&
13885 means &"not received over TCP/IP."&
13886 Otherwise, the primary host name is used.
13887 Only letters, digits, dot and hyphen are accepted; any other characters are
13888 replaced by hyphens. If the expansion is forced to fail, or if the result is an
13889 empty string, the option is ignored.
13892 .option message_id_header_text main string&!! unset
13893 If this variable is set, the string is expanded and used to augment the text of
13894 the &'Message-id:'& header that Exim creates if a locally-originated incoming
13895 message does not have one. The text of this header is required by RFC 2822 to
13896 take the form of an address. By default, Exim uses its internal message id as
13897 the local part, and the primary host name as the domain. If this option is set,
13898 it is expanded, and provided the expansion is not forced to fail, and does not
13899 yield an empty string, the result is inserted into the header immediately
13900 before the @, separated from the internal message id by a dot. Any characters
13901 that are illegal in an address are automatically converted into hyphens. This
13902 means that variables such as &$tod_log$& can be used, because the spaces and
13903 colons will become hyphens.
13906 .option message_logs main boolean true
13907 .cindex "message logs" "disabling"
13908 .cindex "log" "message log; disabling"
13909 If this option is turned off, per-message log files are not created in the
13910 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
13911 Exim, by reducing the number of files involved in handling a message from a
13912 minimum of four (header spool file, body spool file, delivery journal, and
13913 per-message log) to three. The other major I/O activity is Exim's main log,
13914 which is not affected by this option.
13917 .option message_size_limit main string&!! 50M
13918 .cindex "message" "size limit"
13919 .cindex "limit" "message size"
13920 .cindex "size" "of message, limit"
13921 This option limits the maximum size of message that Exim will process. The
13922 value is expanded for each incoming connection so, for example, it can be made
13923 to depend on the IP address of the remote host for messages arriving via
13924 TCP/IP. After expansion, the value must be a sequence of decimal digits,
13925 optionally followed by K or M.
13927 &*Note*&: This limit cannot be made to depend on a message's sender or any
13928 other properties of an individual message, because it has to be advertised in
13929 the server's response to EHLO. String expansion failure causes a temporary
13930 error. A value of zero means no limit, but its use is not recommended. See also
13931 &%bounce_return_size_limit%&.
13933 Incoming SMTP messages are failed with a 552 error if the limit is
13934 exceeded; locally-generated messages either get a stderr message or a delivery
13935 failure message to the sender, depending on the &%-oe%& setting. Rejection of
13936 an oversized message is logged in both the main and the reject logs. See also
13937 the generic transport option &%message_size_limit%&, which limits the size of
13938 message that an individual transport can process.
13941 .option move_frozen_messages main boolean false
13942 .cindex "frozen messages" "moving"
13943 This option, which is available only if Exim has been built with the setting
13945 SUPPORT_MOVE_FROZEN_MESSAGES=yes
13947 in &_Local/Makefile_&, causes frozen messages and their message logs to be
13948 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
13949 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
13950 standard utilities for handling such moved messages, and they do not show up in
13951 lists generated by &%-bp%& or by the Exim monitor.
13954 .option mua_wrapper main boolean false
13955 Setting this option true causes Exim to run in a very restrictive mode in which
13956 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
13957 contains a full description of this facility.
13961 .option mysql_servers main "string list" unset
13962 .cindex "MySQL" "server list"
13963 This option provides a list of MySQL servers and associated connection data, to
13964 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
13965 option is available only if Exim has been built with MySQL support.
13968 .option never_users main "string list&!!" unset
13969 This option is expanded just once, at the start of Exim's processing. Local
13970 message deliveries are normally run in processes that are setuid to the
13971 recipient, and remote deliveries are normally run under Exim's own uid and gid.
13972 It is usually desirable to prevent any deliveries from running as root, as a
13975 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
13976 list of users that must not be used for local deliveries. This list is fixed in
13977 the binary and cannot be overridden by the configuration file. By default, it
13978 contains just the single user name &"root"&. The &%never_users%& runtime option
13979 can be used to add more users to the fixed list.
13981 If a message is to be delivered as one of the users on the fixed list or the
13982 &%never_users%& list, an error occurs, and delivery is deferred. A common
13985 never_users = root:daemon:bin
13987 Including root is redundant if it is also on the fixed list, but it does no
13988 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
13992 .option oracle_servers main "string list" unset
13993 .cindex "Oracle" "server list"
13994 This option provides a list of Oracle servers and associated connection data,
13995 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
13996 The option is available only if Exim has been built with Oracle support.
13999 .option percent_hack_domains main "domain list&!!" unset
14000 .cindex "&""percent hack""&"
14001 .cindex "source routing" "in email address"
14002 .cindex "address" "source-routed"
14003 The &"percent hack"& is the convention whereby a local part containing a
14004 percent sign is re-interpreted as a new email address, with the percent
14005 replaced by @. This is sometimes called &"source routing"&, though that term is
14006 also applied to RFC 2822 addresses that begin with an @ character. If this
14007 option is set, Exim implements the percent facility for those domains listed,
14008 but no others. This happens before an incoming SMTP address is tested against
14011 &*Warning*&: The &"percent hack"& has often been abused by people who are
14012 trying to get round relaying restrictions. For this reason, it is best avoided
14013 if at all possible. Unfortunately, a number of less security-conscious MTAs
14014 implement it unconditionally. If you are running Exim on a gateway host, and
14015 routing mail through to internal MTAs without processing the local parts, it is
14016 a good idea to reject recipient addresses with percent characters in their
14017 local parts. Exim's default configuration does this.
14020 .option perl_at_start main boolean false
14021 This option is available only when Exim is built with an embedded Perl
14022 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14025 .option perl_startup main string unset
14026 This option is available only when Exim is built with an embedded Perl
14027 interpreter. See chapter &<<CHAPperl>>& for details of its use.
14030 .option pgsql_servers main "string list" unset
14031 .cindex "PostgreSQL lookup type" "server list"
14032 This option provides a list of PostgreSQL servers and associated connection
14033 data, to be used in conjunction with &(pgsql)& lookups (see section
14034 &<<SECID72>>&). The option is available only if Exim has been built with
14035 PostgreSQL support.
14038 .option pid_file_path main string&!! "set at compile time"
14039 .cindex "daemon" "pid file path"
14040 .cindex "pid file, path for"
14041 This option sets the name of the file to which the Exim daemon writes its
14042 process id. The string is expanded, so it can contain, for example, references
14045 pid_file_path = /var/log/$primary_hostname/exim.pid
14047 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
14049 The value set by the option can be overridden by the &%-oP%& command line
14050 option. A pid file is not written if a &"non-standard"& daemon is run by means
14051 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
14054 .option pipelining_advertise_hosts main "host list&!!" *
14055 .cindex "PIPELINING" "suppressing advertising"
14056 This option can be used to suppress the advertisement of the SMTP
14057 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
14058 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
14059 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
14060 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
14061 that clients will use it; &"out of order"& commands that are &"expected"& do
14062 not count as protocol errors (see &%smtp_max_synprot_errors%&).
14065 .option preserve_message_logs main boolean false
14066 .cindex "message logs" "preserving"
14067 If this option is set, message log files are not deleted when messages are
14068 completed. Instead, they are moved to a sub-directory of the spool directory
14069 called &_msglog.OLD_&, where they remain available for statistical or debugging
14070 purposes. This is a dangerous option to set on systems with any appreciable
14071 volume of mail. Use with care!
14074 .option primary_hostname main string "see below"
14075 .cindex "name" "of local host"
14076 .cindex "host" "name of local"
14077 .cindex "local host" "name of"
14078 .vindex "&$primary_hostname$&"
14079 This specifies the name of the current host. It is used in the default EHLO or
14080 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
14081 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
14082 The value is also used by default in some SMTP response messages from an Exim
14083 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
14085 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
14086 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
14087 contains only one component, Exim passes it to &[gethostbyname()]& (or
14088 &[getipnodebyname()]& when available) in order to obtain the fully qualified
14089 version. The variable &$primary_hostname$& contains the host name, whether set
14090 explicitly by this option, or defaulted.
14093 .option print_topbitchars main boolean false
14094 .cindex "printing characters"
14095 .cindex "8-bit characters"
14096 By default, Exim considers only those characters whose codes lie in the range
14097 32&--126 to be printing characters. In a number of circumstances (for example,
14098 when writing log entries) non-printing characters are converted into escape
14099 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
14100 is set, code values of 128 and above are also considered to be printing
14103 This option also affects the header syntax checks performed by the
14104 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
14105 the user's full name when constructing From: and Sender: addresses (as
14106 described in section &<<SECTconstr>>&). Setting this option can cause
14107 Exim to generate eight bit message headers that do not conform to the
14111 .option process_log_path main string unset
14112 .cindex "process log path"
14113 .cindex "log" "process log"
14114 .cindex "&'exiwhat'&"
14115 This option sets the name of the file to which an Exim process writes its
14116 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
14117 utility script. If this option is unset, the file called &_exim-process.info_&
14118 in Exim's spool directory is used. The ability to specify the name explicitly
14119 can be useful in environments where two different Exims are running, using
14120 different spool directories.
14123 .option prod_requires_admin main boolean true
14127 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
14128 admin user unless &%prod_requires_admin%& is set false. See also
14129 &%queue_list_requires_admin%&.
14132 .option qualify_domain main string "see below"
14133 .cindex "domain" "for qualifying addresses"
14134 .cindex "address" "qualification"
14135 This option specifies the domain name that is added to any envelope sender
14136 addresses that do not have a domain qualification. It also applies to
14137 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
14138 are accepted by default only for locally-generated messages. Qualification is
14139 also applied to addresses in header lines such as &'From:'& and &'To:'& for
14140 locally-generated messages, unless the &%-bnq%& command line option is used.
14142 Messages from external sources must always contain fully qualified addresses,
14143 unless the sending host matches &%sender_unqualified_hosts%& or
14144 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
14145 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
14146 necessary. Internally, Exim always works with fully qualified envelope
14147 addresses. If &%qualify_domain%& is not set, it defaults to the
14148 &%primary_hostname%& value.
14151 .option qualify_recipient main string "see below"
14152 This option allows you to specify a different domain for qualifying recipient
14153 addresses to the one that is used for senders. See &%qualify_domain%& above.
14157 .option queue_domains main "domain list&!!" unset
14158 .cindex "domain" "specifying non-immediate delivery"
14159 .cindex "queueing incoming messages"
14160 .cindex "message" "queueing certain domains"
14161 This option lists domains for which immediate delivery is not required.
14162 A delivery process is started whenever a message is received, but only those
14163 domains that do not match are processed. All other deliveries wait until the
14164 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
14167 .option queue_list_requires_admin main boolean true
14169 The &%-bp%& command-line option, which lists the messages that are on the
14170 queue, requires the caller to be an admin user unless
14171 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
14174 .option queue_only main boolean false
14175 .cindex "queueing incoming messages"
14176 .cindex "message" "queueing unconditionally"
14177 If &%queue_only%& is set, a delivery process is not automatically started
14178 whenever a message is received. Instead, the message waits on the queue for the
14179 next queue run. Even if &%queue_only%& is false, incoming messages may not get
14180 delivered immediately when certain conditions (such as heavy load) occur.
14182 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
14183 and &%-odi%& command line options override &%queue_only%& unless
14184 &%queue_only_override%& is set false. See also &%queue_only_file%&,
14185 &%queue_only_load%&, and &%smtp_accept_queue%&.
14188 .option queue_only_file main string unset
14189 .cindex "queueing incoming messages"
14190 .cindex "message" "queueing by file existence"
14191 This option can be set to a colon-separated list of absolute path names, each
14192 one optionally preceded by &"smtp"&. When Exim is receiving a message,
14193 it tests for the existence of each listed path using a call to &[stat()]&. For
14194 each path that exists, the corresponding queueing option is set.
14195 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
14196 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
14198 queue_only_file = smtp/some/file
14200 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
14201 &_/some/file_& exists.
14204 .option queue_only_load main fixed-point unset
14205 .cindex "load average"
14206 .cindex "queueing incoming messages"
14207 .cindex "message" "queueing by load"
14208 If the system load average is higher than this value, incoming messages from
14209 all sources are queued, and no automatic deliveries are started. If this
14210 happens during local or remote SMTP input, all subsequent messages received on
14211 the same SMTP connection are queued by default, whatever happens to the load in
14212 the meantime, but this can be changed by setting &%queue_only_load_latch%&
14215 Deliveries will subsequently be performed by queue runner processes. This
14216 option has no effect on ancient operating systems on which Exim cannot
14217 determine the load average. See also &%deliver_queue_load_max%& and
14218 &%smtp_load_reserve%&.
14221 .option queue_only_load_latch main boolean true
14222 .cindex "load average" "re-evaluating per message"
14223 When this option is true (the default), once one message has been queued
14224 because the load average is higher than the value set by &%queue_only_load%&,
14225 all subsequent messages received on the same SMTP connection are also queued.
14226 This is a deliberate choice; even though the load average may fall below the
14227 threshold, it doesn't seem right to deliver later messages on the same
14228 connection when not delivering earlier ones. However, there are special
14229 circumstances such as very long-lived connections from scanning appliances
14230 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
14231 should be set false. This causes the value of the load average to be
14232 re-evaluated for each message.
14235 .option queue_only_override main boolean true
14236 .cindex "queueing incoming messages"
14237 When this option is true, the &%-od%&&'x'& command line options override the
14238 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
14239 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
14240 to override; they are accepted, but ignored.
14243 .option queue_run_in_order main boolean false
14244 .cindex "queue runner" "processing messages in order"
14245 If this option is set, queue runs happen in order of message arrival instead of
14246 in an arbitrary order. For this to happen, a complete list of the entire queue
14247 must be set up before the deliveries start. When the queue is all held in a
14248 single directory (the default), a single list is created for both the ordered
14249 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
14250 single list is not created when &%queue_run_in_order%& is false. In this case,
14251 the sub-directories are processed one at a time (in a random order), and this
14252 avoids setting up one huge list for the whole queue. Thus, setting
14253 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
14254 when the queue is large, because of the extra work in setting up the single,
14255 large list. In most situations, &%queue_run_in_order%& should not be set.
14259 .option queue_run_max main integer 5
14260 .cindex "queue runner" "maximum number of"
14261 This controls the maximum number of queue runner processes that an Exim daemon
14262 can run simultaneously. This does not mean that it starts them all at once,
14263 but rather that if the maximum number are still running when the time comes to
14264 start another one, it refrains from starting another one. This can happen with
14265 very large queues and/or very sluggish deliveries. This option does not,
14266 however, interlock with other processes, so additional queue runners can be
14267 started by other means, or by killing and restarting the daemon.
14269 Setting this option to zero does not suppress queue runs; rather, it disables
14270 the limit, allowing any number of simultaneous queue runner processes to be
14271 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
14272 the daemon's command line.
14274 .option queue_smtp_domains main "domain list&!!" unset
14275 .cindex "queueing incoming messages"
14276 .cindex "message" "queueing remote deliveries"
14277 When this option is set, a delivery process is started whenever a message is
14278 received, routing is performed, and local deliveries take place.
14279 However, if any SMTP deliveries are required for domains that match
14280 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
14281 message waits on the queue for the next queue run. Since routing of the message
14282 has taken place, Exim knows to which remote hosts it must be delivered, and so
14283 when the queue run happens, multiple messages for the same host are delivered
14284 over a single SMTP connection. The &%-odqs%& command line option causes all
14285 SMTP deliveries to be queued in this way, and is equivalent to setting
14286 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
14290 .option receive_timeout main time 0s
14291 .cindex "timeout" "for non-SMTP input"
14292 This option sets the timeout for accepting a non-SMTP message, that is, the
14293 maximum time that Exim waits when reading a message on the standard input. If
14294 the value is zero, it will wait for ever. This setting is overridden by the
14295 &%-or%& command line option. The timeout for incoming SMTP messages is
14296 controlled by &%smtp_receive_timeout%&.
14298 .option received_header_text main string&!! "see below"
14299 .cindex "customizing" "&'Received:'& header"
14300 .cindex "&'Received:'& header line" "customizing"
14301 This string defines the contents of the &'Received:'& message header that is
14302 added to each message, except for the timestamp, which is automatically added
14303 on at the end (preceded by a semicolon). The string is expanded each time it is
14304 used. If the expansion yields an empty string, no &'Received:'& header line is
14305 added to the message. Otherwise, the string should start with the text
14306 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
14307 header lines. The default setting is:
14310 received_header_text = Received: \
14311 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
14312 {${if def:sender_ident \
14313 {from ${quote_local_part:$sender_ident} }}\
14314 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
14315 by $primary_hostname \
14316 ${if def:received_protocol {with $received_protocol}} \
14317 ${if def:tls_cipher {($tls_cipher)\n\t}}\
14318 (Exim $version_number)\n\t\
14319 ${if def:sender_address \
14320 {(envelope-from <$sender_address>)\n\t}}\
14321 id $message_exim_id\
14322 ${if def:received_for {\n\tfor $received_for}}
14325 The reference to the TLS cipher is omitted when Exim is built without TLS
14326 support. The use of conditional expansions ensures that this works for both
14327 locally generated messages and messages received from remote hosts, giving
14328 header lines such as the following:
14330 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
14331 by marley.carol.example with esmtp (Exim 4.00)
14332 (envelope-from <bob@carol.example>)
14333 id 16IOWa-00019l-00
14334 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
14335 Received: by scrooge.carol.example with local (Exim 4.00)
14336 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
14338 Until the body of the message has been received, the timestamp is the time when
14339 the message started to be received. Once the body has arrived, and all policy
14340 checks have taken place, the timestamp is updated to the time at which the
14341 message was accepted.
14344 .option received_headers_max main integer 30
14345 .cindex "loop" "prevention"
14346 .cindex "mail loop prevention"
14347 .cindex "&'Received:'& header line" "counting"
14348 When a message is to be delivered, the number of &'Received:'& headers is
14349 counted, and if it is greater than this parameter, a mail loop is assumed to
14350 have occurred, the delivery is abandoned, and an error message is generated.
14351 This applies to both local and remote deliveries.
14354 .option recipient_unqualified_hosts main "host list&!!" unset
14355 .cindex "unqualified addresses"
14356 .cindex "host" "unqualified addresses from"
14357 This option lists those hosts from which Exim is prepared to accept unqualified
14358 recipient addresses in message envelopes. The addresses are made fully
14359 qualified by the addition of the &%qualify_recipient%& value. This option also
14360 affects message header lines. Exim does not reject unqualified recipient
14361 addresses in headers, but it qualifies them only if the message came from a
14362 host that matches &%recipient_unqualified_hosts%&,
14363 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
14364 option was not set.
14367 .option recipients_max main integer 0
14368 .cindex "limit" "number of recipients"
14369 .cindex "recipient" "maximum number"
14370 If this option is set greater than zero, it specifies the maximum number of
14371 original recipients for any message. Additional recipients that are generated
14372 by aliasing or forwarding do not count. SMTP messages get a 452 response for
14373 all recipients over the limit; earlier recipients are delivered as normal.
14374 Non-SMTP messages with too many recipients are failed, and no deliveries are
14377 .cindex "RCPT" "maximum number of incoming"
14378 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
14379 RCPT commands in a single message.
14382 .option recipients_max_reject main boolean false
14383 If this option is set true, Exim rejects SMTP messages containing too many
14384 recipients by giving 552 errors to the surplus RCPT commands, and a 554
14385 error to the eventual DATA command. Otherwise (the default) it gives a 452
14386 error to the surplus RCPT commands and accepts the message on behalf of the
14387 initial set of recipients. The remote server should then re-send the message
14388 for the remaining recipients at a later time.
14391 .option remote_max_parallel main integer 2
14392 .cindex "delivery" "parallelism for remote"
14393 This option controls parallel delivery of one message to a number of remote
14394 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
14395 does all the remote deliveries for a message one by one. Otherwise, if a single
14396 message has to be delivered to more than one remote host, or if several copies
14397 have to be sent to the same remote host, up to &%remote_max_parallel%&
14398 deliveries are done simultaneously. If more than &%remote_max_parallel%&
14399 deliveries are required, the maximum number of processes are started, and as
14400 each one finishes, another is begun. The order of starting processes is the
14401 same as if sequential delivery were being done, and can be controlled by the
14402 &%remote_sort_domains%& option. If parallel delivery takes place while running
14403 with debugging turned on, the debugging output from each delivery process is
14404 tagged with its process id.
14406 This option controls only the maximum number of parallel deliveries for one
14407 message in one Exim delivery process. Because Exim has no central queue
14408 manager, there is no way of controlling the total number of simultaneous
14409 deliveries if the configuration allows a delivery attempt as soon as a message
14412 .cindex "number of deliveries"
14413 .cindex "delivery" "maximum number of"
14414 If you want to control the total number of deliveries on the system, you
14415 need to set the &%queue_only%& option. This ensures that all incoming messages
14416 are added to the queue without starting a delivery process. Then set up an Exim
14417 daemon to start queue runner processes at appropriate intervals (probably
14418 fairly often, for example, every minute), and limit the total number of queue
14419 runners by setting the &%queue_run_max%& parameter. Because each queue runner
14420 delivers only one message at a time, the maximum number of deliveries that can
14421 then take place at once is &%queue_run_max%& multiplied by
14422 &%remote_max_parallel%&.
14424 If it is purely remote deliveries you want to control, use
14425 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
14426 doing the SMTP routing before queueing, so that several messages for the same
14427 host will eventually get delivered down the same connection.
14430 .option remote_sort_domains main "domain list&!!" unset
14431 .cindex "sorting remote deliveries"
14432 .cindex "delivery" "sorting remote"
14433 When there are a number of remote deliveries for a message, they are sorted by
14434 domain into the order given by this list. For example,
14436 remote_sort_domains = *.cam.ac.uk:*.uk
14438 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
14439 then to those in the &%uk%& domain, then to any others.
14442 .option retry_data_expire main time 7d
14443 .cindex "hints database" "data expiry"
14444 This option sets a &"use before"& time on retry information in Exim's hints
14445 database. Any older retry data is ignored. This means that, for example, once a
14446 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
14450 .option retry_interval_max main time 24h
14451 .cindex "retry" "limit on interval"
14452 .cindex "limit" "on retry interval"
14453 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
14454 intervals between delivery attempts for messages that cannot be delivered
14455 straight away. This option sets an overall limit to the length of time between
14456 retries. It cannot be set greater than 24 hours; any attempt to do so forces
14460 .option return_path_remove main boolean true
14461 .cindex "&'Return-path:'& header line" "removing"
14462 RFC 2821, section 4.4, states that an SMTP server must insert a
14463 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
14464 The &'Return-path:'& header preserves the sender address as received in the
14465 MAIL command. This description implies that this header should not be present
14466 in an incoming message. If &%return_path_remove%& is true, any existing
14467 &'Return-path:'& headers are removed from messages at the time they are
14468 received. Exim's transports have options for adding &'Return-path:'& headers at
14469 the time of delivery. They are normally used only for final local deliveries.
14472 .option return_size_limit main integer 100K
14473 This option is an obsolete synonym for &%bounce_return_size_limit%&.
14476 .option rfc1413_hosts main "host list&!!" *
14478 .cindex "host" "for RFC 1413 calls"
14479 RFC 1413 identification calls are made to any client host which matches an item
14482 .option rfc1413_query_timeout main time 5s
14483 .cindex "RFC 1413" "query timeout"
14484 .cindex "timeout" "for RFC 1413 call"
14485 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
14486 no RFC 1413 calls are ever made.
14489 .option sender_unqualified_hosts main "host list&!!" unset
14490 .cindex "unqualified addresses"
14491 .cindex "host" "unqualified addresses from"
14492 This option lists those hosts from which Exim is prepared to accept unqualified
14493 sender addresses. The addresses are made fully qualified by the addition of
14494 &%qualify_domain%&. This option also affects message header lines. Exim does
14495 not reject unqualified addresses in headers that contain sender addresses, but
14496 it qualifies them only if the message came from a host that matches
14497 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
14498 using TCP/IP), and the &%-bnq%& option was not set.
14501 .option smtp_accept_keepalive main boolean true
14502 .cindex "keepalive" "on incoming connection"
14503 This option controls the setting of the SO_KEEPALIVE option on incoming
14504 TCP/IP socket connections. When set, it causes the kernel to probe idle
14505 connections periodically, by sending packets with &"old"& sequence numbers. The
14506 other end of the connection should send an acknowledgment if the connection is
14507 still okay or a reset if the connection has been aborted. The reason for doing
14508 this is that it has the beneficial effect of freeing up certain types of
14509 connection that can get stuck when the remote host is disconnected without
14510 tidying up the TCP/IP call properly. The keepalive mechanism takes several
14511 hours to detect unreachable hosts.
14515 .option smtp_accept_max main integer 20
14516 .cindex "limit" "incoming SMTP connections"
14517 .cindex "SMTP" "incoming connection count"
14519 This option specifies the maximum number of simultaneous incoming SMTP calls
14520 that Exim will accept. It applies only to the listening daemon; there is no
14521 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
14522 value is set to zero, no limit is applied. However, it is required to be
14523 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
14524 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
14526 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
14527 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
14528 that limit has not been reached for the client host, &%smtp_accept_reserve%&
14529 and &%smtp_load_reserve%& are then checked before accepting the connection.
14532 .option smtp_accept_max_nonmail main integer 10
14533 .cindex "limit" "non-mail SMTP commands"
14534 .cindex "SMTP" "limiting non-mail commands"
14535 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
14536 the connection if there are too many. This option defines &"too many"&. The
14537 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
14538 client looping sending EHLO, for example. The check is applied only if the
14539 client host matches &%smtp_accept_max_nonmail_hosts%&.
14541 When a new message is expected, one occurrence of RSET is not counted. This
14542 allows a client to send one RSET between messages (this is not necessary,
14543 but some clients do it). Exim also allows one uncounted occurrence of HELO
14544 or EHLO, and one occurrence of STARTTLS between messages. After
14545 starting up a TLS session, another EHLO is expected, and so it too is not
14546 counted. The first occurrence of AUTH in a connection, or immediately
14547 following STARTTLS is not counted. Otherwise, all commands other than
14548 MAIL, RCPT, DATA, and QUIT are counted.
14551 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
14552 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
14553 check by setting this option. The default value makes it apply to all hosts. By
14554 changing the value, you can exclude any badly-behaved hosts that you have to
14558 . Allow this long option name to split; give it unsplit as a fifth argument
14559 . for the automatic .oindex that is generated by .option.
14561 .option "smtp_accept_max_per_ &~&~connection" main integer 1000 &&&
14562 smtp_accept_max_per_connection
14563 .cindex "SMTP" "limiting incoming message count"
14564 .cindex "limit" "messages per SMTP connection"
14565 The value of this option limits the number of MAIL commands that Exim is
14566 prepared to accept over a single SMTP connection, whether or not each command
14567 results in the transfer of a message. After the limit is reached, a 421
14568 response is given to subsequent MAIL commands. This limit is a safety
14569 precaution against a client that goes mad (incidents of this type have been
14573 .option smtp_accept_max_per_host main string&!! unset
14574 .cindex "limit" "SMTP connections from one host"
14575 .cindex "host" "limiting SMTP connections from"
14576 This option restricts the number of simultaneous IP connections from a single
14577 host (strictly, from a single IP address) to the Exim daemon. The option is
14578 expanded, to enable different limits to be applied to different hosts by
14579 reference to &$sender_host_address$&. Once the limit is reached, additional
14580 connection attempts from the same host are rejected with error code 421. This
14581 is entirely independent of &%smtp_accept_reserve%&. The option's default value
14582 of zero imposes no limit. If this option is set greater than zero, it is
14583 required that &%smtp_accept_max%& be non-zero.
14585 &*Warning*&: When setting this option you should not use any expansion
14586 constructions that take an appreciable amount of time. The expansion and test
14587 happen in the main daemon loop, in order to reject additional connections
14588 without forking additional processes (otherwise a denial-of-service attack
14589 could cause a vast number or processes to be created). While the daemon is
14590 doing this processing, it cannot accept any other incoming connections.
14594 .option smtp_accept_queue main integer 0
14595 .cindex "SMTP" "incoming connection count"
14596 .cindex "queueing incoming messages"
14597 .cindex "message" "queueing by SMTP connection count"
14598 If the number of simultaneous incoming SMTP connections being handled via the
14599 listening daemon exceeds this value, messages received by SMTP are just placed
14600 on the queue; no delivery processes are started automatically. The count is
14601 fixed at the start of an SMTP connection. It cannot be updated in the
14602 subprocess that receives messages, and so the queueing or not queueing applies
14603 to all messages received in the same connection.
14605 A value of zero implies no limit, and clearly any non-zero value is useful only
14606 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
14607 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
14608 various &%-od%&&'x'& command line options.
14611 . Allow this long option name to split; give it unsplit as a fifth argument
14612 . for the automatic .oindex that is generated by .option.
14614 .option "smtp_accept_queue_per_ &~&~connection" main integer 10 &&&
14615 smtp_accept_queue_per_connection
14616 .cindex "queueing incoming messages"
14617 .cindex "message" "queueing by message count"
14618 This option limits the number of delivery processes that Exim starts
14619 automatically when receiving messages via SMTP, whether via the daemon or by
14620 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
14621 and the number of messages received in a single SMTP session exceeds this
14622 number, subsequent messages are placed on the queue, but no delivery processes
14623 are started. This helps to limit the number of Exim processes when a server
14624 restarts after downtime and there is a lot of mail waiting for it on other
14625 systems. On large systems, the default should probably be increased, and on
14626 dial-in client systems it should probably be set to zero (that is, disabled).
14629 .option smtp_accept_reserve main integer 0
14630 .cindex "SMTP" "incoming call count"
14631 .cindex "host" "reserved"
14632 When &%smtp_accept_max%& is set greater than zero, this option specifies a
14633 number of SMTP connections that are reserved for connections from the hosts
14634 that are specified in &%smtp_reserve_hosts%&. The value set in
14635 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
14636 restricted to this number of connections; the option specifies a minimum number
14637 of connection slots for them, not a maximum. It is a guarantee that this group
14638 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
14639 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
14642 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
14643 set to 5, once there are 45 active connections (from any hosts), new
14644 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
14645 provided the other criteria for acceptance are met.
14648 .option smtp_active_hostname main string&!! unset
14649 .cindex "host" "name in SMTP responses"
14650 .cindex "SMTP" "host name in responses"
14651 .vindex "&$primary_hostname$&"
14652 This option is provided for multi-homed servers that want to masquerade as
14653 several different hosts. At the start of an incoming SMTP connection, its value
14654 is expanded and used instead of the value of &$primary_hostname$& in SMTP
14655 responses. For example, it is used as domain name in the response to an
14656 incoming HELO or EHLO command.
14658 .vindex "&$smtp_active_hostname$&"
14659 The active hostname is placed in the &$smtp_active_hostname$& variable, which
14660 is saved with any messages that are received. It is therefore available for use
14661 in routers and transports when the message is later delivered.
14663 If this option is unset, or if its expansion is forced to fail, or if the
14664 expansion results in an empty string, the value of &$primary_hostname$& is
14665 used. Other expansion failures cause a message to be written to the main and
14666 panic logs, and the SMTP command receives a temporary error. Typically, the
14667 value of &%smtp_active_hostname%& depends on the incoming interface address.
14670 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
14671 {cox.mydomain}{box.mydomain}}
14674 Although &$smtp_active_hostname$& is primarily concerned with incoming
14675 messages, it is also used as the default for HELO commands in callout
14676 verification if there is no remote transport from which to obtain a
14677 &%helo_data%& value.
14679 .option smtp_banner main string&!! "see below"
14680 .cindex "SMTP" "welcome banner"
14681 .cindex "banner for SMTP"
14682 .cindex "welcome banner for SMTP"
14683 .cindex "customizing" "SMTP banner"
14684 This string, which is expanded every time it is used, is output as the initial
14685 positive response to an SMTP connection. The default setting is:
14687 smtp_banner = $smtp_active_hostname ESMTP Exim \
14688 $version_number $tod_full
14690 Failure to expand the string causes a panic error. If you want to create a
14691 multiline response to the initial SMTP connection, use &"\n"& in the string at
14692 appropriate points, but not at the end. Note that the 220 code is not included
14693 in this string. Exim adds it automatically (several times in the case of a
14694 multiline response).
14697 .option smtp_check_spool_space main boolean true
14698 .cindex "checking disk space"
14699 .cindex "disk space, checking"
14700 .cindex "spool directory" "checking space"
14701 When this option is set, if an incoming SMTP session encounters the SIZE
14702 option on a MAIL command, it checks that there is enough space in the
14703 spool directory's partition to accept a message of that size, while still
14704 leaving free the amount specified by &%check_spool_space%& (even if that value
14705 is zero). If there isn't enough space, a temporary error code is returned.
14708 .option smtp_connect_backlog main integer 20
14709 .cindex "connection backlog"
14710 .cindex "SMTP" "connection backlog"
14711 .cindex "backlog of connections"
14712 This option specifies a maximum number of waiting SMTP connections. Exim passes
14713 this value to the TCP/IP system when it sets up its listener. Once this number
14714 of connections are waiting for the daemon's attention, subsequent connection
14715 attempts are refused at the TCP/IP level. At least, that is what the manuals
14716 say; in some circumstances such connection attempts have been observed to time
14717 out instead. For large systems it is probably a good idea to increase the
14718 value (to 50, say). It also gives some protection against denial-of-service
14719 attacks by SYN flooding.
14722 .option smtp_enforce_sync main boolean true
14723 .cindex "SMTP" "synchronization checking"
14724 .cindex "synchronization checking in SMTP"
14725 The SMTP protocol specification requires the client to wait for a response from
14726 the server at certain points in the dialogue. Without PIPELINING these
14727 synchronization points are after every command; with PIPELINING they are
14728 fewer, but they still exist.
14730 Some spamming sites send out a complete set of SMTP commands without waiting
14731 for any response. Exim protects against this by rejecting a message if the
14732 client has sent further input when it should not have. The error response &"554
14733 SMTP synchronization error"& is sent, and the connection is dropped. Testing
14734 for this error cannot be perfect because of transmission delays (unexpected
14735 input may be on its way but not yet received when Exim checks). However, it
14736 does detect many instances.
14738 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
14739 If you want to disable the check selectively (for example, only for certain
14740 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
14741 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
14745 .option smtp_etrn_command main string&!! unset
14746 .cindex "ETRN" "command to be run"
14747 .vindex "&$domain$&"
14748 If this option is set, the given command is run whenever an SMTP ETRN
14749 command is received from a host that is permitted to issue such commands (see
14750 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
14751 are independently expanded. The expansion variable &$domain$& is set to the
14752 argument of the ETRN command, and no syntax checking is done on it. For
14755 smtp_etrn_command = /etc/etrn_command $domain \
14756 $sender_host_address
14758 A new process is created to run the command, but Exim does not wait for it to
14759 complete. Consequently, its status cannot be checked. If the command cannot be
14760 run, a line is written to the panic log, but the ETRN caller still receives
14761 a 250 success response. Exim is normally running under its own uid when
14762 receiving SMTP, so it is not possible for it to change the uid before running
14766 .option smtp_etrn_serialize main boolean true
14767 .cindex "ETRN" "serializing"
14768 When this option is set, it prevents the simultaneous execution of more than
14769 one identical command as a result of ETRN in an SMTP connection. See
14770 section &<<SECTETRN>>& for details.
14773 .option smtp_load_reserve main fixed-point unset
14774 .cindex "load average"
14775 If the system load average ever gets higher than this, incoming SMTP calls are
14776 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
14777 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
14778 the load is over the limit. The option has no effect on ancient operating
14779 systems on which Exim cannot determine the load average. See also
14780 &%deliver_queue_load_max%& and &%queue_only_load%&.
14784 .option smtp_max_synprot_errors main integer 3
14785 .cindex "SMTP" "limiting syntax and protocol errors"
14786 .cindex "limit" "SMTP syntax and protocol errors"
14787 Exim rejects SMTP commands that contain syntax or protocol errors. In
14788 particular, a syntactically invalid email address, as in this command:
14790 RCPT TO:<abc xyz@a.b.c>
14792 causes immediate rejection of the command, before any other tests are done.
14793 (The ACL cannot be run if there is no valid address to set up for it.) An
14794 example of a protocol error is receiving RCPT before MAIL. If there are
14795 too many syntax or protocol errors in one SMTP session, the connection is
14796 dropped. The limit is set by this option.
14798 .cindex "PIPELINING" "expected errors"
14799 When the PIPELINING extension to SMTP is in use, some protocol errors are
14800 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
14801 Exim assumes that PIPELINING will be used if it advertises it (see
14802 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
14803 not count towards the limit.
14807 .option smtp_max_unknown_commands main integer 3
14808 .cindex "SMTP" "limiting unknown commands"
14809 .cindex "limit" "unknown SMTP commands"
14810 If there are too many unrecognized commands in an incoming SMTP session, an
14811 Exim server drops the connection. This is a defence against some kinds of abuse
14814 into making connections to SMTP ports; in these circumstances, a number of
14815 non-SMTP command lines are sent first.
14819 .option smtp_ratelimit_hosts main "host list&!!" unset
14820 .cindex "SMTP" "rate limiting"
14821 .cindex "limit" "rate of message arrival"
14822 .cindex "RCPT" "rate limiting"
14823 Some sites find it helpful to be able to limit the rate at which certain hosts
14824 can send them messages, and the rate at which an individual message can specify
14827 Exim has two rate-limiting facilities. This section describes the older
14828 facility, which can limit rates within a single connection. The newer
14829 &%ratelimit%& ACL condition can limit rates across all connections. See section
14830 &<<SECTratelimiting>>& for details of the newer facility.
14832 When a host matches &%smtp_ratelimit_hosts%&, the values of
14833 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
14834 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
14835 respectively. Each option, if set, must contain a set of four comma-separated
14839 A threshold, before which there is no rate limiting.
14841 An initial time delay. Unlike other times in Exim, numbers with decimal
14842 fractional parts are allowed here.
14844 A factor by which to increase the delay each time.
14846 A maximum value for the delay. This should normally be less than 5 minutes,
14847 because after that time, the client is liable to timeout the SMTP command.
14850 For example, these settings have been used successfully at the site which
14851 first suggested this feature, for controlling mail from their customers:
14853 smtp_ratelimit_mail = 2,0.5s,1.05,4m
14854 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
14856 The first setting specifies delays that are applied to MAIL commands after
14857 two have been received over a single connection. The initial delay is 0.5
14858 seconds, increasing by a factor of 1.05 each time. The second setting applies
14859 delays to RCPT commands when more than four occur in a single message.
14862 .option smtp_ratelimit_mail main string unset
14863 See &%smtp_ratelimit_hosts%& above.
14866 .option smtp_ratelimit_rcpt main string unset
14867 See &%smtp_ratelimit_hosts%& above.
14870 .option smtp_receive_timeout main time 5m
14871 .cindex "timeout" "for SMTP input"
14872 .cindex "SMTP" "input timeout"
14873 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
14874 input, including batch SMTP. If a line of input (either an SMTP command or a
14875 data line) is not received within this time, the SMTP connection is dropped and
14876 the message is abandoned.
14877 A line is written to the log containing one of the following messages:
14879 SMTP command timeout on connection from...
14880 SMTP data timeout on connection from...
14882 The former means that Exim was expecting to read an SMTP command; the latter
14883 means that it was in the DATA phase, reading the contents of a message.
14887 The value set by this option can be overridden by the
14888 &%-os%& command-line option. A setting of zero time disables the timeout, but
14889 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
14890 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
14891 timeout is controlled by &%receive_timeout%& and &%-or%&.
14894 .option smtp_reserve_hosts main "host list&!!" unset
14895 This option defines hosts for which SMTP connections are reserved; see
14896 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
14899 .option smtp_return_error_details main boolean false
14900 .cindex "SMTP" "details policy failures"
14901 .cindex "policy control" "rejection, returning details"
14902 In the default state, Exim uses bland messages such as
14903 &"Administrative prohibition"& when it rejects SMTP commands for policy
14904 reasons. Many sysadmins like this because it gives away little information
14905 to spammers. However, some other sysadmins who are applying strict checking
14906 policies want to give out much fuller information about failures. Setting
14907 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
14908 example, instead of &"Administrative prohibition"&, it might give:
14910 550-Rejected after DATA: '>' missing at end of address:
14911 550 failing address in "From" header is: <user@dom.ain
14914 .option spamd_address main string "see below"
14915 This option is available when Exim is compiled with the content-scanning
14916 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
14917 The default value is
14921 See section &<<SECTscanspamass>>& for more details.
14925 .option split_spool_directory main boolean false
14926 .cindex "multiple spool directories"
14927 .cindex "spool directory" "split"
14928 .cindex "directories, multiple"
14929 If this option is set, it causes Exim to split its input directory into 62
14930 subdirectories, each with a single alphanumeric character as its name. The
14931 sixth character of the message id is used to allocate messages to
14932 subdirectories; this is the least significant base-62 digit of the time of
14933 arrival of the message.
14935 Splitting up the spool in this way may provide better performance on systems
14936 where there are long mail queues, by reducing the number of files in any one
14937 directory. The msglog directory is also split up in a similar way to the input
14938 directory; however, if &%preserve_message_logs%& is set, all old msglog files
14939 are still placed in the single directory &_msglog.OLD_&.
14941 It is not necessary to take any special action for existing messages when
14942 changing &%split_spool_directory%&. Exim notices messages that are in the
14943 &"wrong"& place, and continues to process them. If the option is turned off
14944 after a period of being on, the subdirectories will eventually empty and be
14945 automatically deleted.
14947 When &%split_spool_directory%& is set, the behaviour of queue runner processes
14948 changes. Instead of creating a list of all messages in the queue, and then
14949 trying to deliver each one in turn, it constructs a list of those in one
14950 sub-directory and tries to deliver them, before moving on to the next
14951 sub-directory. The sub-directories are processed in a random order. This
14952 spreads out the scanning of the input directories, and uses less memory. It is
14953 particularly beneficial when there are lots of messages on the queue. However,
14954 if &%queue_run_in_order%& is set, none of this new processing happens. The
14955 entire queue has to be scanned and sorted before any deliveries can start.
14958 .option spool_directory main string&!! "set at compile time"
14959 .cindex "spool directory" "path to"
14960 This defines the directory in which Exim keeps its spool, that is, the messages
14961 it is waiting to deliver. The default value is taken from the compile-time
14962 configuration setting, if there is one. If not, this option must be set. The
14963 string is expanded, so it can contain, for example, a reference to
14964 &$primary_hostname$&.
14966 If the spool directory name is fixed on your installation, it is recommended
14967 that you set it at build time rather than from this option, particularly if the
14968 log files are being written to the spool directory (see &%log_file_path%&).
14969 Otherwise log files cannot be used for errors that are detected early on, such
14970 as failures in the configuration file.
14972 By using this option to override the compiled-in path, it is possible to run
14973 tests of Exim without using the standard spool.
14975 .option sqlite_lock_timeout main time 5s
14976 .cindex "sqlite lookup type" "lock timeout"
14977 This option controls the timeout that the &(sqlite)& lookup uses when trying to
14978 access an SQLite database. See section &<<SECTsqlite>>& for more details.
14980 .option strict_acl_vars main boolean false
14981 .cindex "&ACL;" "variables, handling unset"
14982 This option controls what happens if a syntactically valid but undefined ACL
14983 variable is referenced. If it is false (the default), an empty string
14984 is substituted; if it is true, an error is generated. See section
14985 &<<SECTaclvariables>>& for details of ACL variables.
14987 .option strip_excess_angle_brackets main boolean false
14988 .cindex "angle brackets, excess"
14989 If this option is set, redundant pairs of angle brackets round &"route-addr"&
14990 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
14991 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
14992 passed on to another MTA, the excess angle brackets are not passed on. If this
14993 option is not set, multiple pairs of angle brackets cause a syntax error.
14996 .option strip_trailing_dot main boolean false
14997 .cindex "trailing dot on domain"
14998 .cindex "dot" "trailing on domain"
14999 If this option is set, a trailing dot at the end of a domain in an address is
15000 ignored. If this is in the envelope and the message is passed on to another
15001 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
15002 domain causes a syntax error.
15003 However, addresses in header lines are checked only when an ACL requests header
15007 .option syslog_duplication main boolean true
15008 .cindex "syslog" "duplicate log lines; suppressing"
15009 When Exim is logging to syslog, it writes the log lines for its three
15010 separate logs at different syslog priorities so that they can in principle
15011 be separated on the logging hosts. Some installations do not require this
15012 separation, and in those cases, the duplication of certain log lines is a
15013 nuisance. If &%syslog_duplication%& is set false, only one copy of any
15014 particular log line is written to syslog. For lines that normally go to
15015 both the main log and the reject log, the reject log version (possibly
15016 containing message header lines) is written, at LOG_NOTICE priority.
15017 Lines that normally go to both the main and the panic log are written at
15018 the LOG_ALERT priority.
15021 .option syslog_facility main string unset
15022 .cindex "syslog" "facility; setting"
15023 This option sets the syslog &"facility"& name, used when Exim is logging to
15024 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
15025 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
15026 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
15027 details of Exim's logging.
15031 .option syslog_processname main string &`exim`&
15032 .cindex "syslog" "process name; setting"
15033 This option sets the syslog &"ident"& name, used when Exim is logging to
15034 syslog. The value must be no longer than 32 characters. See chapter
15035 &<<CHAPlog>>& for details of Exim's logging.
15039 .option syslog_timestamp main boolean true
15040 .cindex "syslog" "timestamps"
15041 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
15042 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
15043 details of Exim's logging.
15046 .option system_filter main string&!! unset
15047 .cindex "filter" "system filter"
15048 .cindex "system filter" "specifying"
15049 .cindex "Sieve filter" "not available for system filter"
15050 This option specifies an Exim filter file that is applied to all messages at
15051 the start of each delivery attempt, before any routing is done. System filters
15052 must be Exim filters; they cannot be Sieve filters. If the system filter
15053 generates any deliveries to files or pipes, or any new mail messages, the
15054 appropriate &%system_filter_..._transport%& option(s) must be set, to define
15055 which transports are to be used. Details of this facility are given in chapter
15056 &<<CHAPsystemfilter>>&.
15059 .option system_filter_directory_transport main string&!! unset
15060 .vindex "&$address_file$&"
15061 This sets the name of the transport driver that is to be used when the
15062 &%save%& command in a system message filter specifies a path ending in &"/"&,
15063 implying delivery of each message into a separate file in some directory.
15064 During the delivery, the variable &$address_file$& contains the path name.
15067 .option system_filter_file_transport main string&!! unset
15068 .cindex "file" "transport for system filter"
15069 This sets the name of the transport driver that is to be used when the &%save%&
15070 command in a system message filter specifies a path not ending in &"/"&. During
15071 the delivery, the variable &$address_file$& contains the path name.
15073 .option system_filter_group main string unset
15074 .cindex "gid (group id)" "system filter"
15075 This option is used only when &%system_filter_user%& is also set. It sets the
15076 gid under which the system filter is run, overriding any gid that is associated
15077 with the user. The value may be numerical or symbolic.
15079 .option system_filter_pipe_transport main string&!! unset
15080 .cindex "&(pipe)& transport" "for system filter"
15081 .vindex "&$address_pipe$&"
15082 This specifies the transport driver that is to be used when a &%pipe%& command
15083 is used in a system filter. During the delivery, the variable &$address_pipe$&
15084 contains the pipe command.
15087 .option system_filter_reply_transport main string&!! unset
15088 .cindex "&(autoreply)& transport" "for system filter"
15089 This specifies the transport driver that is to be used when a &%mail%& command
15090 is used in a system filter.
15092 .option system_filter_user main string unset
15093 .cindex "uid (user id)" "system filter"
15094 If this option is not set, the system filter is run in the main Exim delivery
15095 process, as root. When the option is set, the system filter runs in a separate
15096 process, as the given user. Unless the string consists entirely of digits, it
15097 is looked up in the password data. Failure to find the named user causes a
15098 configuration error. The gid is either taken from the password data, or
15099 specified by &%system_filter_group%&. When the uid is specified numerically,
15100 &%system_filter_group%& is required to be set.
15102 If the system filter generates any pipe, file, or reply deliveries, the uid
15103 under which the filter is run is used when transporting them, unless a
15104 transport option overrides. Normally you should set &%system_filter_user%& if
15105 your system filter generates these kinds of delivery.
15108 .option tcp_nodelay main boolean true
15109 .cindex "daemon" "TCP_NODELAY on sockets"
15110 .cindex "Nagle algorithm"
15111 .cindex "TCP_NODELAY on listening sockets"
15112 If this option is set false, it stops the Exim daemon setting the
15113 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
15114 turns off the &"Nagle algorithm"&, which is a way of improving network
15115 performance in interactive (character-by-character) situations. Turning it off
15116 should improve Exim's performance a bit, so that is what happens by default.
15117 However, it appears that some broken clients cannot cope, and time out. Hence
15118 this option. It affects only those sockets that are set up for listening by the
15119 daemon. Sockets created by the smtp transport for delivering mail always set
15123 .option timeout_frozen_after main time 0s
15124 .cindex "frozen messages" "timing out"
15125 .cindex "timeout" "frozen messages"
15126 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
15127 message of any kind that has been on the queue for longer than the given time
15128 is automatically cancelled at the next queue run. If the frozen message is a
15129 bounce message, it is just discarded; otherwise, a bounce is sent to the
15130 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
15131 If you want to timeout frozen bounce messages earlier than other kinds of
15132 frozen message, see &%ignore_bounce_errors_after%&.
15134 &*Note:*& the default value of zero means no timeouts; with this setting,
15135 frozen messages remain on the queue forever (except for any frozen bounce
15136 messages that are released by &%ignore_bounce_errors_after%&).
15139 .option timezone main string unset
15140 .cindex "timezone, setting"
15141 The value of &%timezone%& is used to set the environment variable TZ while
15142 running Exim (if it is different on entry). This ensures that all timestamps
15143 created by Exim are in the required timezone. If you want all your timestamps
15144 to be in UTC (aka GMT) you should set
15148 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
15149 or, if that is not set, from the value of the TZ environment variable when Exim
15150 is built. If &%timezone%& is set to the empty string, either at build or run
15151 time, any existing TZ variable is removed from the environment when Exim
15152 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
15153 unfortunately not all, operating systems.
15156 .option tls_advertise_hosts main "host list&!!" unset
15157 .cindex "TLS" "advertising"
15158 .cindex "encryption" "on SMTP connection"
15159 .cindex "SMTP" "encrypted connection"
15160 When Exim is built with support for TLS encrypted connections, the availability
15161 of the STARTTLS command to set up an encrypted session is advertised in
15162 response to EHLO only to those client hosts that match this option. See
15163 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
15166 .option tls_certificate main string&!! unset
15167 .cindex "TLS" "server certificate; location of"
15168 .cindex "certificate" "server, location of"
15169 The value of this option is expanded, and must then be the absolute path to a
15170 file which contains the server's certificates. The server's private key is also
15171 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
15172 &<<CHAPTLS>>& for further details.
15174 &*Note*&: The certificates defined by this option are used only when Exim is
15175 receiving incoming messages as a server. If you want to supply certificates for
15176 use when sending messages as a client, you must set the &%tls_certificate%&
15177 option in the relevant &(smtp)& transport.
15180 .option tls_crl main string&!! unset
15181 .cindex "TLS" "server certificate revocation list"
15182 .cindex "certificate" "revocation list for server"
15183 This option specifies a certificate revocation list. The expanded value must
15184 be the name of a file that contains a CRL in PEM format.
15187 .option tls_dhparam main string&!! unset
15188 .cindex "TLS" "D-H parameters for server"
15189 The value of this option is expanded, and must then be the absolute path to
15190 a file which contains the server's DH parameter values.
15191 This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
15192 ignored. See section &<<SECTopenvsgnu>>& for further details.
15195 .option tls_on_connect_ports main "string list" unset
15196 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
15197 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
15198 set up without waiting for the client to issue a STARTTLS command. For
15199 further details, see section &<<SECTsupobssmt>>&.
15203 .option tls_privatekey main string&!! unset
15204 .cindex "TLS" "server private key; location of"
15205 The value of this option is expanded, and must then be the absolute path to a
15206 file which contains the server's private key. If this option is unset, or if
15207 the expansion is forced to fail, or the result is an empty string, the private
15208 key is assumed to be in the same file as the server's certificates. See chapter
15209 &<<CHAPTLS>>& for further details.
15212 .option tls_remember_esmtp main boolean false
15213 .cindex "TLS" "esmtp state; remembering"
15214 .cindex "TLS" "broken clients"
15215 If this option is set true, Exim violates the RFCs by remembering that it is in
15216 &"esmtp"& state after successfully negotiating a TLS session. This provides
15217 support for broken clients that fail to send a new EHLO after starting a
15221 .option tls_require_ciphers main string&!! unset
15222 .cindex "TLS" "requiring specific ciphers"
15223 .cindex "cipher" "requiring specific"
15224 This option controls which ciphers can be used for incoming TLS connections.
15225 The &(smtp)& transport has an option of the same name for controlling outgoing
15226 connections. This option is expanded for each connection, so can be varied for
15227 different clients if required. The value of this option must be a list of
15228 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
15229 in somewhat different ways. If GnuTLS is being used, the client controls the
15230 preference order of the available ciphers. Details are given in sections
15231 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
15234 .option tls_try_verify_hosts main "host list&!!" unset
15235 .cindex "TLS" "client certificate verification"
15236 .cindex "certificate" "verification of client"
15237 See &%tls_verify_hosts%& below.
15240 .option tls_verify_certificates main string&!! unset
15241 .cindex "TLS" "client certificate verification"
15242 .cindex "certificate" "verification of client"
15243 The value of this option is expanded, and must then be the absolute path to
15244 a file containing permitted certificates for clients that
15245 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&. Alternatively, if you
15246 are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a
15247 directory containing certificate files. This does not work with GnuTLS; the
15248 option must be set to the name of a single file if you are using GnuTLS.
15251 .option tls_verify_hosts main "host list&!!" unset
15252 .cindex "TLS" "client certificate verification"
15253 .cindex "certificate" "verification of client"
15254 This option, along with &%tls_try_verify_hosts%&, controls the checking of
15255 certificates from clients. The expected certificates are defined by
15256 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
15257 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
15258 &%tls_verify_certificates%& is not set.
15260 Any client that matches &%tls_verify_hosts%& is constrained by
15261 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
15262 present one of the listed certificates. If it does not, the connection is
15263 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
15264 the host to use TLS. It can still send SMTP commands through unencrypted
15265 connections. Forcing a client to use TLS has to be done separately using an
15266 ACL to reject inappropriate commands when the connection is not encrypted.
15268 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
15269 matches this option (but not &%tls_verify_hosts%&), Exim requests a
15270 certificate and checks it against &%tls_verify_certificates%&, but does not
15271 abort the connection if there is no certificate or if it does not match. This
15272 state can be detected in an ACL, which makes it possible to implement policies
15273 such as &"accept for relay only if a verified certificate has been received,
15274 but accept for local delivery if encrypted, even without a verified
15277 Client hosts that match neither of these lists are not asked to present
15281 .option trusted_groups main "string list&!!" unset
15282 .cindex "trusted groups"
15283 .cindex "groups" "trusted"
15284 This option is expanded just once, at the start of Exim's processing. If this
15285 option is set, any process that is running in one of the listed groups, or
15286 which has one of them as a supplementary group, is trusted. The groups can be
15287 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
15288 details of what trusted callers are permitted to do. If neither
15289 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
15292 .option trusted_users main "string list&!!" unset
15293 .cindex "trusted users"
15294 .cindex "user" "trusted"
15295 This option is expanded just once, at the start of Exim's processing. If this
15296 option is set, any process that is running as one of the listed users is
15297 trusted. The users can be specified numerically or by name. See section
15298 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
15299 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
15300 Exim user are trusted.
15302 .option unknown_login main string&!! unset
15303 .cindex "uid (user id)" "unknown caller"
15304 .vindex "&$caller_uid$&"
15305 This is a specialized feature for use in unusual configurations. By default, if
15306 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
15307 gives up. The &%unknown_login%& option can be used to set a login name to be
15308 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
15309 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
15310 is used for the user's real name (gecos field), unless this has been set by the
15313 .option unknown_username main string unset
15314 See &%unknown_login%&.
15316 .option untrusted_set_sender main "address list&!!" unset
15317 .cindex "trusted users"
15318 .cindex "sender" "setting by untrusted user"
15319 .cindex "untrusted user setting sender"
15320 .cindex "user" "untrusted setting sender"
15321 .cindex "envelope sender"
15322 When an untrusted user submits a message to Exim using the standard input, Exim
15323 normally creates an envelope sender address from the user's login and the
15324 default qualification domain. Data from the &%-f%& option (for setting envelope
15325 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
15326 is used) is ignored.
15328 However, untrusted users are permitted to set an empty envelope sender address,
15329 to declare that a message should never generate any bounces. For example:
15331 exim -f '<>' user@domain.example
15333 .vindex "&$sender_ident$&"
15334 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
15335 other envelope sender addresses in a controlled way. When it is set, untrusted
15336 users are allowed to set envelope sender addresses that match any of the
15337 patterns in the list. Like all address lists, the string is expanded. The
15338 identity of the user is in &$sender_ident$&, so you can, for example, restrict
15339 users to setting senders that start with their login ids
15340 followed by a hyphen
15341 by a setting like this:
15343 untrusted_set_sender = ^$sender_ident-
15345 If you want to allow untrusted users to set envelope sender addresses without
15346 restriction, you can use
15348 untrusted_set_sender = *
15350 The &%untrusted_set_sender%& option applies to all forms of local input, but
15351 only to the setting of the envelope sender. It does not permit untrusted users
15352 to use the other options which trusted user can use to override message
15353 parameters. Furthermore, it does not stop Exim from removing an existing
15354 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
15355 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
15356 overriding these actions. The handling of the &'Sender:'& header is also
15357 described in section &<<SECTthesenhea>>&.
15359 The log line for a message's arrival shows the envelope sender following
15360 &"<="&. For local messages, the user's login always follows, after &"U="&. In
15361 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
15362 envelope sender address, the user's login is shown in parentheses after the
15366 .option uucp_from_pattern main string "see below"
15367 .cindex "&""From""& line"
15368 .cindex "UUCP" "&""From""& line"
15369 Some applications that pass messages to an MTA via a command line interface use
15370 an initial line starting with &"From&~"& to pass the envelope sender. In
15371 particular, this is used by UUCP software. Exim recognizes such a line by means
15372 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
15373 matches, the sender address is constructed by expanding the contents of
15374 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
15375 default pattern recognizes lines in the following two forms:
15377 From ph10 Fri Jan 5 12:35 GMT 1996
15378 From ph10 Fri, 7 Jan 97 14:00:00 GMT
15380 The pattern can be seen by running
15382 exim -bP uucp_from_pattern
15384 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
15385 year in the second case. The first word after &"From&~"& is matched in the
15386 regular expression by a parenthesized subpattern. The default value for
15387 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
15388 (&"ph10"& in the example above) as the message's sender. See also
15389 &%ignore_fromline_hosts%&.
15392 .option uucp_from_sender main string&!! &`$1`&
15393 See &%uucp_from_pattern%& above.
15396 .option warn_message_file main string unset
15397 .cindex "warning of delay" "customizing the message"
15398 .cindex "customizing" "warning message"
15399 This option defines a template file containing paragraphs of text to be used
15400 for constructing the warning message which is sent by Exim when a message has
15401 been on the queue for a specified amount of time, as specified by
15402 &%delay_warning%&. Details of the file's contents are given in chapter
15403 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
15406 .option write_rejectlog main boolean true
15407 .cindex "reject log" "disabling"
15408 If this option is set false, Exim no longer writes anything to the reject log.
15409 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
15410 .ecindex IIDconfima
15411 .ecindex IIDmaiconf
15416 . ////////////////////////////////////////////////////////////////////////////
15417 . ////////////////////////////////////////////////////////////////////////////
15419 .chapter "Generic options for routers" "CHAProutergeneric"
15420 .scindex IIDgenoprou1 "options" "generic; for routers"
15421 .scindex IIDgenoprou2 "generic options" "router"
15422 This chapter describes the generic options that apply to all routers.
15423 Those that are preconditions are marked with ‡ in the &"use"& field.
15425 For a general description of how a router operates, see sections
15426 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
15427 which the preconditions are tested. The order of expansion of the options that
15428 provide data for a transport is: &%errors_to%&, &%headers_add%&,
15429 &%headers_remove%&, &%transport%&.
15433 .option address_data routers string&!! unset
15434 .cindex "router" "data attached to address"
15435 The string is expanded just before the router is run, that is, after all the
15436 precondition tests have succeeded. If the expansion is forced to fail, the
15437 router declines, the value of &%address_data%& remains unchanged, and the
15438 &%more%& option controls what happens next. Other expansion failures cause
15439 delivery of the address to be deferred.
15441 .vindex "&$address_data$&"
15442 When the expansion succeeds, the value is retained with the address, and can be
15443 accessed using the variable &$address_data$& in the current router, subsequent
15444 routers, and the eventual transport.
15446 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
15447 that runs a user's filter file, the contents of &$address_data$& are accessible
15448 in the filter. This is not normally a problem, because such data is usually
15449 either not confidential or it &"belongs"& to the current user, but if you do
15450 put confidential data into &$address_data$& you need to remember this point.
15452 Even if the router declines or passes, the value of &$address_data$& remains
15453 with the address, though it can be changed by another &%address_data%& setting
15454 on a subsequent router. If a router generates child addresses, the value of
15455 &$address_data$& propagates to them. This also applies to the special kind of
15456 &"child"& that is generated by a router with the &%unseen%& option.
15458 The idea of &%address_data%& is that you can use it to look up a lot of data
15459 for the address once, and then pick out parts of the data later. For example,
15460 you could use a single LDAP lookup to return a string of the form
15462 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
15464 In the transport you could pick out the mailbox by a setting such as
15466 file = ${extract{mailbox}{$address_data}}
15468 This makes the configuration file less messy, and also reduces the number of
15469 lookups (though Exim does cache lookups).
15471 .vindex "&$sender_address_data$&"
15472 .vindex "&$address_data$&"
15473 The &%address_data%& facility is also useful as a means of passing information
15474 from one router to another, and from a router to a transport. In addition, if
15475 &$address_data$& is set by a router when verifying a recipient address from an
15476 ACL, it remains available for use in the rest of the ACL statement. After
15477 verifying a sender, the value is transferred to &$sender_address_data$&.
15481 .option address_test routers&!? boolean true
15483 .cindex "router" "skipping when address testing"
15484 If this option is set false, the router is skipped when routing is being tested
15485 by means of the &%-bt%& command line option. This can be a convenience when
15486 your first router sends messages to an external scanner, because it saves you
15487 having to set the &"already scanned"& indicator when testing real address
15492 .option cannot_route_message routers string&!! unset
15493 .cindex "router" "customizing &""cannot route""& message"
15494 .cindex "customizing" "&""cannot route""& message"
15495 This option specifies a text message that is used when an address cannot be
15496 routed because Exim has run out of routers. The default message is
15497 &"Unrouteable address"&. This option is useful only on routers that have
15498 &%more%& set false, or on the very last router in a configuration, because the
15499 value that is used is taken from the last router that is considered. This
15500 includes a router that is skipped because its preconditions are not met, as
15501 well as a router that declines. For example, using the default configuration,
15504 cannot_route_message = Remote domain not found in DNS
15506 on the first router, which is a &(dnslookup)& router with &%more%& set false,
15509 cannot_route_message = Unknown local user
15511 on the final router that checks for local users. If string expansion fails for
15512 this option, the default message is used. Unless the expansion failure was
15513 explicitly forced, a message about the failure is written to the main and panic
15514 logs, in addition to the normal message about the routing failure.
15517 .option caseful_local_part routers boolean false
15518 .cindex "case of local parts"
15519 .cindex "router" "case of local parts"
15520 By default, routers handle the local parts of addresses in a case-insensitive
15521 manner, though the actual case is preserved for transmission with the message.
15522 If you want the case of letters to be significant in a router, you must set
15523 this option true. For individual router options that contain address or local
15524 part lists (for example, &%local_parts%&), case-sensitive matching can be
15525 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
15528 .vindex "&$local_part$&"
15529 .vindex "&$original_local_part$&"
15530 .vindex "&$parent_local_part$&"
15531 The value of the &$local_part$& variable is forced to lower case while a
15532 router is running unless &%caseful_local_part%& is set. When a router assigns
15533 an address to a transport, the value of &$local_part$& when the transport runs
15534 is the same as it was in the router. Similarly, when a router generates child
15535 addresses by aliasing or forwarding, the values of &$original_local_part$&
15536 and &$parent_local_part$& are those that were used by the redirecting router.
15538 This option applies to the processing of an address by a router. When a
15539 recipient address is being processed in an ACL, there is a separate &%control%&
15540 modifier that can be used to specify case-sensitive processing within the ACL
15541 (see section &<<SECTcontrols>>&).
15545 .option check_local_user routers&!? boolean false
15546 .cindex "local user, checking in router"
15547 .cindex "router" "checking for local user"
15548 .cindex "&_/etc/passwd_&"
15550 When this option is true, Exim checks that the local part of the recipient
15551 address (with affixes removed if relevant) is the name of an account on the
15552 local system. The check is done by calling the &[getpwnam()]& function rather
15553 than trying to read &_/etc/passwd_& directly. This means that other methods of
15554 holding password data (such as NIS) are supported. If the local part is a local
15555 user, &$home$& is set from the password data, and can be tested in other
15556 preconditions that are evaluated after this one (the order of evaluation is
15557 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
15558 overridden by &%router_home_directory%&. If the local part is not a local user,
15559 the router is skipped.
15561 If you want to check that the local part is either the name of a local user
15562 or matches something else, you cannot combine &%check_local_user%& with a
15563 setting of &%local_parts%&, because that specifies the logical &'and'& of the
15564 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
15565 setting to achieve this. For example:
15567 local_parts = passwd;$local_part : lsearch;/etc/other/users
15569 Note, however, that the side effects of &%check_local_user%& (such as setting
15570 up a home directory) do not occur when a &(passwd)& lookup is used in a
15571 &%local_parts%& (or any other) precondition.
15575 .option condition routers&!? string&!! unset
15576 .cindex "router" "customized precondition"
15577 This option specifies a general precondition test that has to succeed for the
15578 router to be called. The &%condition%& option is the last precondition to be
15579 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
15580 result is a forced failure, or an empty string, or one of the strings &"0"& or
15581 &"no"& or &"false"& (checked without regard to the case of the letters), the
15582 router is skipped, and the address is offered to the next one.
15584 If the result is any other value, the router is run (as this is the last
15585 precondition to be evaluated, all the other preconditions must be true).
15587 The &%condition%& option provides a means of applying custom conditions to the
15588 running of routers. Note that in the case of a simple conditional expansion,
15589 the default expansion values are exactly what is wanted. For example:
15591 condition = ${if >{$message_age}{600}}
15593 Because of the default behaviour of the string expansion, this is equivalent to
15595 condition = ${if >{$message_age}{600}{true}{}}
15597 If the expansion fails (other than forced failure) delivery is deferred. Some
15598 of the other precondition options are common special cases that could in fact
15599 be specified using &%condition%&.
15603 .option debug_print routers string&!! unset
15604 .cindex "testing" "variables in drivers"
15605 If this option is set and debugging is enabled (see the &%-d%& command line
15606 option), the string is expanded and included in the debugging output.
15607 If expansion of the string fails, the error message is written to the debugging
15608 output, and Exim carries on processing.
15609 This option is provided to help with checking out the values of variables and
15610 so on when debugging router configurations. For example, if a &%condition%&
15611 option appears not to be working, &%debug_print%& can be used to output the
15612 variables it references. The output happens after checks for &%domains%&,
15613 &%local_parts%&, and &%check_local_user%& but before any other preconditions
15614 are tested. A newline is added to the text if it does not end with one.
15618 .option disable_logging routers boolean false
15619 If this option is set true, nothing is logged for any routing errors
15620 or for any deliveries caused by this router. You should not set this option
15621 unless you really, really know what you are doing. See also the generic
15622 transport option of the same name.
15625 .option domains routers&!? "domain list&!!" unset
15626 .cindex "router" "restricting to specific domains"
15627 .vindex "&$domain_data$&"
15628 If this option is set, the router is skipped unless the current domain matches
15629 the list. If the match is achieved by means of a file lookup, the data that the
15630 lookup returned for the domain is placed in &$domain_data$& for use in string
15631 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
15632 a list of the order in which preconditions are evaluated.
15636 .option driver routers string unset
15637 This option must always be set. It specifies which of the available routers is
15642 .option errors_to routers string&!! unset
15643 .cindex "envelope sender"
15644 .cindex "router" "changing address for errors"
15645 If a router successfully handles an address, it may assign the address to a
15646 transport for delivery or it may generate child addresses. In both cases, if
15647 there is a delivery problem during later processing, the resulting bounce
15648 message is sent to the address that results from expanding this string,
15649 provided that the address verifies successfully. The &%errors_to%& option is
15650 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
15652 The &%errors_to%& setting associated with an address can be overridden if it
15653 subsequently passes through other routers that have their own &%errors_to%&
15654 settings, or if the message is delivered by a transport with a &%return_path%&
15657 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
15658 the expansion fails to verify, the errors address associated with the incoming
15659 address is used. At top level, this is the envelope sender. A non-forced
15660 expansion failure causes delivery to be deferred.
15662 If an address for which &%errors_to%& has been set ends up being delivered over
15663 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
15664 any bounces that are generated by other MTAs on the delivery route are also
15665 sent there. You can set &%errors_to%& to the empty string by either of these
15671 An expansion item that yields an empty string has the same effect. If you do
15672 this, a locally detected delivery error for addresses processed by this router
15673 no longer gives rise to a bounce message; the error is discarded. If the
15674 address is delivered to a remote host, the return path is set to &`<>`&, unless
15675 overridden by the &%return_path%& option on the transport.
15677 .vindex "&$address_data$&"
15678 If for some reason you want to discard local errors, but use a non-empty
15679 MAIL command for remote delivery, you can preserve the original return
15680 path in &$address_data$& in the router, and reinstate it in the transport by
15681 setting &%return_path%&.
15683 The most common use of &%errors_to%& is to direct mailing list bounces to the
15684 manager of the list, as described in section &<<SECTmailinglists>>&, or to
15685 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
15689 .option expn routers&!? boolean true
15690 .cindex "address" "testing"
15691 .cindex "testing" "addresses"
15692 .cindex "EXPN" "router skipping"
15693 .cindex "router" "skipping for EXPN"
15694 If this option is turned off, the router is skipped when testing an address
15695 as a result of processing an SMTP EXPN command. You might, for example,
15696 want to turn it off on a router for users' &_.forward_& files, while leaving it
15697 on for the system alias file.
15698 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15701 The use of the SMTP EXPN command is controlled by an ACL (see chapter
15702 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
15703 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
15707 .option fail_verify routers boolean false
15708 .cindex "router" "forcing verification failure"
15709 Setting this option has the effect of setting both &%fail_verify_sender%& and
15710 &%fail_verify_recipient%& to the same value.
15714 .option fail_verify_recipient routers boolean false
15715 If this option is true and an address is accepted by this router when
15716 verifying a recipient, verification fails.
15720 .option fail_verify_sender routers boolean false
15721 If this option is true and an address is accepted by this router when
15722 verifying a sender, verification fails.
15726 .option fallback_hosts routers "string list" unset
15727 .cindex "router" "fallback hosts"
15728 .cindex "fallback" "hosts specified on router"
15729 String expansion is not applied to this option. The argument must be a
15730 colon-separated list of host names or IP addresses. The list separator can be
15731 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
15732 each name or address. In fact, the format of each item is exactly the same as
15733 defined for the list of hosts in a &(manualroute)& router (see section
15734 &<<SECTformatonehostitem>>&).
15736 If a router queues an address for a remote transport, this host list is
15737 associated with the address, and used instead of the transport's fallback host
15738 list. If &%hosts_randomize%& is set on the transport, the order of the list is
15739 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
15740 transport for further details.
15743 .option group routers string&!! "see below"
15744 .cindex "gid (group id)" "local delivery"
15745 .cindex "local transports" "uid and gid"
15746 .cindex "transport" "local"
15747 .cindex "router" "setting group"
15748 When a router queues an address for a transport, and the transport does not
15749 specify a group, the group given here is used when running the delivery
15751 The group may be specified numerically or by name. If expansion fails, the
15752 error is logged and delivery is deferred.
15753 The default is unset, unless &%check_local_user%& is set, when the default
15754 is taken from the password information. See also &%initgroups%& and &%user%&
15755 and the discussion in chapter &<<CHAPenvironment>>&.
15759 .option headers_add routers string&!! unset
15760 .cindex "header lines" "adding"
15761 .cindex "router" "adding header lines"
15762 This option specifies a string of text that is expanded at routing time, and
15763 associated with any addresses that are accepted by the router. However, this
15764 option has no effect when an address is just being verified. The way in which
15765 the text is used to add header lines at transport time is described in section
15766 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
15767 message is in the process of being transported. This means that references to
15768 header lines in string expansions in the transport's configuration do not
15769 &"see"& the added header lines.
15771 The &%headers_add%& option is expanded after &%errors_to%&, but before
15772 &%headers_remove%& and &%transport%&. If the expanded string is empty, or if
15773 the expansion is forced to fail, the option has no effect. Other expansion
15774 failures are treated as configuration errors.
15776 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
15777 router that has the &%one_time%& option set.
15779 .cindex "duplicate addresses"
15780 .oindex "&%unseen%&"
15781 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15782 additions are deleted when the address is passed on to subsequent routers.
15783 For a &%redirect%& router, if a generated address is the same as the incoming
15784 address, this can lead to duplicate addresses with different header
15785 modifications. Exim does not do duplicate deliveries (except, in certain
15786 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
15787 which of the duplicates is discarded, so this ambiguous situation should be
15788 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
15792 .option headers_remove routers string&!! unset
15793 .cindex "header lines" "removing"
15794 .cindex "router" "removing header lines"
15795 This option specifies a string of text that is expanded at routing time, and
15796 associated with any addresses that are accepted by the router. However, this
15797 option has no effect when an address is just being verified. The way in which
15798 the text is used to remove header lines at transport time is described in
15799 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
15800 the message is in the process of being transported. This means that references
15801 to header lines in string expansions in the transport's configuration still
15802 &"see"& the original header lines.
15804 The &%headers_remove%& option is expanded after &%errors_to%& and
15805 &%headers_add%&, but before &%transport%&. If the expansion is forced to fail,
15806 the option has no effect. Other expansion failures are treated as configuration
15809 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
15810 router that has the &%one_time%& option set.
15812 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
15813 removal requests are deleted when the address is passed on to subsequent
15814 routers, and this can lead to problems with duplicates -- see the similar
15815 warning for &%headers_add%& above.
15818 .option ignore_target_hosts routers "host list&!!" unset
15819 .cindex "IP address" "discarding"
15820 .cindex "router" "discarding IP addresses"
15821 Although this option is a host list, it should normally contain IP address
15822 entries rather than names. If any host that is looked up by the router has an
15823 IP address that matches an item in this list, Exim behaves as if that IP
15824 address did not exist. This option allows you to cope with rogue DNS entries
15827 remote.domain.example. A 127.0.0.1
15831 ignore_target_hosts = 127.0.0.1
15833 on the relevant router. If all the hosts found by a &(dnslookup)& router are
15834 discarded in this way, the router declines. In a conventional configuration, an
15835 attempt to mail to such a domain would normally provoke the &"unrouteable
15836 domain"& error, and an attempt to verify an address in the domain would fail.
15837 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
15838 router declines if presented with one of the listed addresses.
15840 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
15841 means of the first or the second of the following settings, respectively:
15843 ignore_target_hosts = 0.0.0.0/0
15844 ignore_target_hosts = <; 0::0/0
15846 The pattern in the first line matches all IPv4 addresses, whereas the pattern
15847 in the second line matches all IPv6 addresses.
15849 This option may also be useful for ignoring link-local and site-local IPv6
15850 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
15851 is expanded before use as a list, it is possible to make it dependent on the
15852 domain that is being routed.
15854 .vindex "&$host_address$&"
15855 During its expansion, &$host_address$& is set to the IP address that is being
15858 .option initgroups routers boolean false
15859 .cindex "additional groups"
15860 .cindex "groups" "additional"
15861 .cindex "local transports" "uid and gid"
15862 .cindex "transport" "local"
15863 If the router queues an address for a transport, and this option is true, and
15864 the uid supplied by the router is not overridden by the transport, the
15865 &[initgroups()]& function is called when running the transport to ensure that
15866 any additional groups associated with the uid are set up. See also &%group%&
15867 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
15871 .option local_part_prefix routers&!? "string list" unset
15872 .cindex "router" "prefix for local part"
15873 .cindex "prefix" "for local part, used in router"
15874 If this option is set, the router is skipped unless the local part starts with
15875 one of the given strings, or &%local_part_prefix_optional%& is true. See
15876 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
15879 The list is scanned from left to right, and the first prefix that matches is
15880 used. A limited form of wildcard is available; if the prefix begins with an
15881 asterisk, it matches the longest possible sequence of arbitrary characters at
15882 the start of the local part. An asterisk should therefore always be followed by
15883 some character that does not occur in normal local parts.
15884 .cindex "multiple mailboxes"
15885 .cindex "mailbox" "multiple"
15886 Wildcarding can be used to set up multiple user mailboxes, as described in
15887 section &<<SECTmulbox>>&.
15889 .vindex "&$local_part$&"
15890 .vindex "&$local_part_prefix$&"
15891 During the testing of the &%local_parts%& option, and while the router is
15892 running, the prefix is removed from the local part, and is available in the
15893 expansion variable &$local_part_prefix$&. When a message is being delivered, if
15894 the router accepts the address, this remains true during subsequent delivery by
15895 a transport. In particular, the local part that is transmitted in the RCPT
15896 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
15897 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
15898 the relevant transport.
15900 When an address is being verified, &%local_part_prefix%& affects only the
15901 behaviour of the router. If the callout feature of verification is in use, this
15902 means that the full address, including the prefix, will be used during the
15905 The prefix facility is commonly used to handle local parts of the form
15906 &%owner-something%&. Another common use is to support local parts of the form
15907 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
15908 to tell a user their forwarding is broken &-- by placing a router like this one
15909 immediately before the router that handles &_.forward_& files:
15913 local_part_prefix = real-
15915 transport = local_delivery
15917 For security, it would probably be a good idea to restrict the use of this
15918 router to locally-generated messages, using a condition such as this:
15920 condition = ${if match {$sender_host_address}\
15921 {\N^(|127\.0\.0\.1)$\N}}
15924 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
15925 both conditions must be met if not optional. Care must be taken if wildcards
15926 are used in both a prefix and a suffix on the same router. Different
15927 separator characters must be used to avoid ambiguity.
15930 .option local_part_prefix_optional routers boolean false
15931 See &%local_part_prefix%& above.
15935 .option local_part_suffix routers&!? "string list" unset
15936 .cindex "router" "suffix for local part"
15937 .cindex "suffix for local part" "used in router"
15938 This option operates in the same way as &%local_part_prefix%&, except that the
15939 local part must end (rather than start) with the given string, the
15940 &%local_part_suffix_optional%& option determines whether the suffix is
15941 mandatory, and the wildcard * character, if present, must be the last
15942 character of the suffix. This option facility is commonly used to handle local
15943 parts of the form &%something-request%& and multiple user mailboxes of the form
15947 .option local_part_suffix_optional routers boolean false
15948 See &%local_part_suffix%& above.
15952 .option local_parts routers&!? "local part list&!!" unset
15953 .cindex "router" "restricting to specific local parts"
15954 .cindex "local part" "checking in router"
15955 The router is run only if the local part of the address matches the list.
15956 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
15958 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
15959 string is expanded, it is possible to make it depend on the domain, for
15962 local_parts = dbm;/usr/local/specials/$domain
15964 .vindex "&$local_part_data$&"
15965 If the match is achieved by a lookup, the data that the lookup returned
15966 for the local part is placed in the variable &$local_part_data$& for use in
15967 expansions of the router's private options. You might use this option, for
15968 example, if you have a large number of local virtual domains, and you want to
15969 send all postmaster mail to the same place without having to set up an alias in
15970 each virtual domain:
15974 local_parts = postmaster
15975 data = postmaster@real.domain.example
15979 .option log_as_local routers boolean "see below"
15980 .cindex "log" "delivery line"
15981 .cindex "delivery" "log line format"
15982 Exim has two logging styles for delivery, the idea being to make local
15983 deliveries stand out more visibly from remote ones. In the &"local"& style, the
15984 recipient address is given just as the local part, without a domain. The use of
15985 this style is controlled by this option. It defaults to true for the &(accept)&
15986 router, and false for all the others. This option applies only when a
15987 router assigns an address to a transport. It has no effect on routers that
15988 redirect addresses.
15992 .option more routers boolean&!! true
15993 The result of string expansion for this option must be a valid boolean value,
15994 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
15995 result causes an error, and delivery is deferred. If the expansion is forced to
15996 fail, the default value for the option (true) is used. Other failures cause
15997 delivery to be deferred.
15999 If this option is set false, and the router declines to handle the address, no
16000 further routers are tried, routing fails, and the address is bounced.
16002 However, if the router explicitly passes an address to the following router by
16003 means of the setting
16007 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
16008 does not affect the behaviour if one of the precondition tests fails. In that
16009 case, the address is always passed to the next router.
16011 Note that &%address_data%& is not considered to be a precondition. If its
16012 expansion is forced to fail, the router declines, and the value of &%more%&
16013 controls what happens next.
16016 .option pass_on_timeout routers boolean false
16017 .cindex "timeout" "of router"
16018 .cindex "router" "timeout"
16019 If a router times out during a host lookup, it normally causes deferral of the
16020 address. If &%pass_on_timeout%& is set, the address is passed on to the next
16021 router, overriding &%no_more%&. This may be helpful for systems that are
16022 intermittently connected to the Internet, or those that want to pass to a smart
16023 host any messages that cannot immediately be delivered.
16025 There are occasional other temporary errors that can occur while doing DNS
16026 lookups. They are treated in the same way as a timeout, and this option
16027 applies to all of them.
16031 .option pass_router routers string unset
16032 .cindex "router" "go to after &""pass""&"
16033 Routers that recognize the generic &%self%& option (&(dnslookup)&,
16034 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
16035 routing to continue, and overriding a false setting of &%more%&. When one of
16036 these routers returns &"pass"&, the address is normally handed on to the next
16037 router in sequence. This can be changed by setting &%pass_router%& to the name
16038 of another router. However (unlike &%redirect_router%&) the named router must
16039 be below the current router, to avoid loops. Note that this option applies only
16040 to the special case of &"pass"&. It does not apply when a router returns
16041 &"decline"& because it cannot handle an address.
16045 .option redirect_router routers string unset
16046 .cindex "router" "start at after redirection"
16047 Sometimes an administrator knows that it is pointless to reprocess addresses
16048 generated from alias or forward files with the same router again. For
16049 example, if an alias file translates real names into login ids there is no
16050 point searching the alias file a second time, especially if it is a large file.
16052 The &%redirect_router%& option can be set to the name of any router instance.
16053 It causes the routing of any generated addresses to start at the named router
16054 instead of at the first router. This option has no effect if the router in
16055 which it is set does not generate new addresses.
16059 .option require_files routers&!? "string list&!!" unset
16060 .cindex "file" "requiring for router"
16061 .cindex "router" "requiring file existence"
16062 This option provides a general mechanism for predicating the running of a
16063 router on the existence or non-existence of certain files or directories.
16064 Before running a router, as one of its precondition tests, Exim works its way
16065 through the &%require_files%& list, expanding each item separately.
16067 Because the list is split before expansion, any colons in expansion items must
16068 be doubled, or the facility for using a different list separator must be used.
16069 If any expansion is forced to fail, the item is ignored. Other expansion
16070 failures cause routing of the address to be deferred.
16072 If any expanded string is empty, it is ignored. Otherwise, except as described
16073 below, each string must be a fully qualified file path, optionally preceded by
16074 &"!"&. The paths are passed to the &[stat()]& function to test for the
16075 existence of the files or directories. The router is skipped if any paths not
16076 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
16079 If &[stat()]& cannot determine whether a file exists or not, delivery of
16080 the message is deferred. This can happen when NFS-mounted filesystems are
16083 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
16084 options, so you cannot use it to check for the existence of a file in which to
16085 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
16086 full list of the order in which preconditions are evaluated.) However, as
16087 these options are all expanded, you can use the &%exists%& expansion condition
16088 to make such tests. The &%require_files%& option is intended for checking files
16089 that the router may be going to use internally, or which are needed by a
16090 transport (for example &_.procmailrc_&).
16092 During delivery, the &[stat()]& function is run as root, but there is a
16093 facility for some checking of the accessibility of a file by another user.
16094 This is not a proper permissions check, but just a &"rough"& check that
16095 operates as follows:
16097 If an item in a &%require_files%& list does not contain any forward slash
16098 characters, it is taken to be the user (and optional group, separated by a
16099 comma) to be checked for subsequent files in the list. If no group is specified
16100 but the user is specified symbolically, the gid associated with the uid is
16103 require_files = mail:/some/file
16104 require_files = $local_part:$home/.procmailrc
16106 If a user or group name in a &%require_files%& list does not exist, the
16107 &%require_files%& condition fails.
16109 Exim performs the check by scanning along the components of the file path, and
16110 checking the access for the given uid and gid. It checks for &"x"& access on
16111 directories, and &"r"& access on the final file. Note that this means that file
16112 access control lists, if the operating system has them, are ignored.
16114 &*Warning 1*&: When the router is being run to verify addresses for an
16115 incoming SMTP message, Exim is not running as root, but under its own uid. This
16116 may affect the result of a &%require_files%& check. In particular, &[stat()]&
16117 may yield the error EACCES (&"Permission denied"&). This means that the Exim
16118 user is not permitted to read one of the directories on the file's path.
16120 &*Warning 2*&: Even when Exim is running as root while delivering a message,
16121 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
16122 without root access. In this case, if a check for access by a particular user
16123 is requested, Exim creates a subprocess that runs as that user, and tries the
16124 check again in that process.
16126 The default action for handling an unresolved EACCES is to consider it to
16127 be caused by a configuration error, and routing is deferred because the
16128 existence or non-existence of the file cannot be determined. However, in some
16129 circumstances it may be desirable to treat this condition as if the file did
16130 not exist. If the file name (or the exclamation mark that precedes the file
16131 name for non-existence) is preceded by a plus sign, the EACCES error is treated
16132 as if the file did not exist. For example:
16134 require_files = +/some/file
16136 If the router is not an essential part of verification (for example, it
16137 handles users' &_.forward_& files), another solution is to set the &%verify%&
16138 option false so that the router is skipped when verifying.
16142 .option retry_use_local_part routers boolean "see below"
16143 .cindex "hints database" "retry keys"
16144 .cindex "local part" "in retry keys"
16145 When a delivery suffers a temporary routing failure, a retry record is created
16146 in Exim's hints database. For addresses whose routing depends only on the
16147 domain, the key for the retry record should not involve the local part, but for
16148 other addresses, both the domain and the local part should be included.
16149 Usually, remote routing is of the former kind, and local routing is of the
16152 This option controls whether the local part is used to form the key for retry
16153 hints for addresses that suffer temporary errors while being handled by this
16154 router. The default value is true for any router that has &%check_local_user%&
16155 set, and false otherwise. Note that this option does not apply to hints keys
16156 for transport delays; they are controlled by a generic transport option of the
16159 The setting of &%retry_use_local_part%& applies only to the router on which it
16160 appears. If the router generates child addresses, they are routed
16161 independently; this setting does not become attached to them.
16165 .option router_home_directory routers string&!! unset
16166 .cindex "router" "home directory for"
16167 .cindex "home directory" "for router"
16169 This option sets a home directory for use while the router is running. (Compare
16170 &%transport_home_directory%&, which sets a home directory for later
16171 transporting.) In particular, if used on a &(redirect)& router, this option
16172 sets a value for &$home$& while a filter is running. The value is expanded;
16173 forced expansion failure causes the option to be ignored &-- other failures
16174 cause the router to defer.
16176 Expansion of &%router_home_directory%& happens immediately after the
16177 &%check_local_user%& test (if configured), before any further expansions take
16179 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16181 While the router is running, &%router_home_directory%& overrides the value of
16182 &$home$& that came from &%check_local_user%&.
16184 When a router accepts an address and assigns it to a local transport (including
16185 the cases when a &(redirect)& router generates a pipe, file, or autoreply
16186 delivery), the home directory setting for the transport is taken from the first
16187 of these values that is set:
16190 The &%home_directory%& option on the transport;
16192 The &%transport_home_directory%& option on the router;
16194 The password data if &%check_local_user%& is set on the router;
16196 The &%router_home_directory%& option on the router.
16199 In other words, &%router_home_directory%& overrides the password data for the
16200 router, but not for the transport.
16204 .option self routers string freeze
16205 .cindex "MX record" "pointing to local host"
16206 .cindex "local host" "MX pointing to"
16207 This option applies to those routers that use a recipient address to find a
16208 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
16209 and &(manualroute)& routers.
16210 Certain configurations of the &(queryprogram)& router can also specify a list
16212 Usually such routers are configured to send the message to a remote host via an
16213 &(smtp)& transport. The &%self%& option specifies what happens when the first
16214 host on the list turns out to be the local host.
16215 The way in which Exim checks for the local host is described in section
16216 &<<SECTreclocipadd>>&.
16218 Normally this situation indicates either an error in Exim's configuration (for
16219 example, the router should be configured not to process this domain), or an
16220 error in the DNS (for example, the MX should not point to this host). For this
16221 reason, the default action is to log the incident, defer the address, and
16222 freeze the message. The following alternatives are provided for use in special
16227 Delivery of the message is tried again later, but the message is not frozen.
16229 .vitem "&%reroute%&: <&'domain'&>"
16230 The domain is changed to the given domain, and the address is passed back to
16231 be reprocessed by the routers. No rewriting of headers takes place. This
16232 behaviour is essentially a redirection.
16234 .vitem "&%reroute: rewrite:%& <&'domain'&>"
16235 The domain is changed to the given domain, and the address is passed back to be
16236 reprocessed by the routers. Any headers that contain the original domain are
16241 .vindex "&$self_hostname$&"
16242 The router passes the address to the next router, or to the router named in the
16243 &%pass_router%& option if it is set. This overrides &%no_more%&. During
16244 subsequent routing and delivery, the variable &$self_hostname$& contains the
16245 name of the local host that the router encountered. This can be used to
16246 distinguish between different cases for hosts with multiple names. The
16252 ensures that only those addresses that routed to the local host are passed on.
16253 Without &%no_more%&, addresses that were declined for other reasons would also
16254 be passed to the next router.
16257 Delivery fails and an error report is generated.
16260 .cindex "local host" "sending to"
16261 The anomaly is ignored and the address is queued for the transport. This
16262 setting should be used with extreme caution. For an &(smtp)& transport, it
16263 makes sense only in cases where the program that is listening on the SMTP port
16264 is not this version of Exim. That is, it must be some other MTA, or Exim with a
16265 different configuration file that handles the domain in another way.
16270 .option senders routers&!? "address list&!!" unset
16271 .cindex "router" "checking senders"
16272 If this option is set, the router is skipped unless the message's sender
16273 address matches something on the list.
16274 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16277 There are issues concerning verification when the running of routers is
16278 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
16279 setting, it sets the sender to the null string. When using the &%-bt%& option
16280 to check a configuration file, it is necessary also to use the &%-f%& option to
16281 set an appropriate sender. For incoming mail, the sender is unset when
16282 verifying the sender, but is available when verifying any recipients. If the
16283 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
16287 .option translate_ip_address routers string&!! unset
16288 .cindex "IP address" "translating"
16289 .cindex "packet radio"
16290 .cindex "router" "IP address translation"
16291 There exist some rare networking situations (for example, packet radio) where
16292 it is helpful to be able to translate IP addresses generated by normal routing
16293 mechanisms into other IP addresses, thus performing a kind of manual IP
16294 routing. This should be done only if the normal IP routing of the TCP/IP stack
16295 is inadequate or broken. Because this is an extremely uncommon requirement, the
16296 code to support this option is not included in the Exim binary unless
16297 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
16299 .vindex "&$host_address$&"
16300 The &%translate_ip_address%& string is expanded for every IP address generated
16301 by the router, with the generated address set in &$host_address$&. If the
16302 expansion is forced to fail, no action is taken.
16303 For any other expansion error, delivery of the message is deferred.
16304 If the result of the expansion is an IP address, that replaces the original
16305 address; otherwise the result is assumed to be a host name &-- this is looked
16306 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
16307 produce one or more replacement IP addresses. For example, to subvert all IP
16308 addresses in some specific networks, this could be added to a router:
16310 translate_ip_address = \
16311 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
16314 The file would contain lines like
16316 10.2.3.128/26 some.host
16317 10.8.4.34/26 10.44.8.15
16319 You should not make use of this facility unless you really understand what you
16324 .option transport routers string&!! unset
16325 This option specifies the transport to be used when a router accepts an address
16326 and sets it up for delivery. A transport is never needed if a router is used
16327 only for verification. The value of the option is expanded at routing time,
16328 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
16329 and result must be the name of one of the configured transports. If it is not,
16330 delivery is deferred.
16332 The &%transport%& option is not used by the &(redirect)& router, but it does
16333 have some private options that set up transports for pipe and file deliveries
16334 (see chapter &<<CHAPredirect>>&).
16338 .option transport_current_directory routers string&!! unset
16339 .cindex "current directory for local transport"
16340 This option associates a current directory with any address that is routed
16341 to a local transport. This can happen either because a transport is
16342 explicitly configured for the router, or because it generates a delivery to a
16343 file or a pipe. During the delivery process (that is, at transport time), this
16344 option string is expanded and is set as the current directory, unless
16345 overridden by a setting on the transport.
16346 If the expansion fails for any reason, including forced failure, an error is
16347 logged, and delivery is deferred.
16348 See chapter &<<CHAPenvironment>>& for details of the local delivery
16354 .option transport_home_directory routers string&!! "see below"
16355 .cindex "home directory" "for local transport"
16356 This option associates a home directory with any address that is routed to a
16357 local transport. This can happen either because a transport is explicitly
16358 configured for the router, or because it generates a delivery to a file or a
16359 pipe. During the delivery process (that is, at transport time), the option
16360 string is expanded and is set as the home directory, unless overridden by a
16361 setting of &%home_directory%& on the transport.
16362 If the expansion fails for any reason, including forced failure, an error is
16363 logged, and delivery is deferred.
16365 If the transport does not specify a home directory, and
16366 &%transport_home_directory%& is not set for the router, the home directory for
16367 the transport is taken from the password data if &%check_local_user%& is set for
16368 the router. Otherwise it is taken from &%router_home_directory%& if that option
16369 is set; if not, no home directory is set for the transport.
16371 See chapter &<<CHAPenvironment>>& for further details of the local delivery
16377 .option unseen routers boolean&!! false
16378 .cindex "router" "carrying on after success"
16379 The result of string expansion for this option must be a valid boolean value,
16380 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
16381 result causes an error, and delivery is deferred. If the expansion is forced to
16382 fail, the default value for the option (false) is used. Other failures cause
16383 delivery to be deferred.
16385 When this option is set true, routing does not cease if the router accepts the
16386 address. Instead, a copy of the incoming address is passed to the next router,
16387 overriding a false setting of &%more%&. There is little point in setting
16388 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
16389 the value of &%unseen%& contains expansion items (and therefore, presumably, is
16390 sometimes true and sometimes false).
16392 .cindex "copy of message (&%unseen%& option)"
16393 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
16394 qualifier in filter files. It can be used to cause copies of messages to be
16395 delivered to some other destination, while also carrying out a normal delivery.
16396 In effect, the current address is made into a &"parent"& that has two children
16397 &-- one that is delivered as specified by this router, and a clone that goes on
16398 to be routed further. For this reason, &%unseen%& may not be combined with the
16399 &%one_time%& option in a &(redirect)& router.
16401 &*Warning*&: Header lines added to the address (or specified for removal) by
16402 this router or by previous routers affect the &"unseen"& copy of the message
16403 only. The clone that continues to be processed by further routers starts with
16404 no added headers and none specified for removal. For a &%redirect%& router, if
16405 a generated address is the same as the incoming address, this can lead to
16406 duplicate addresses with different header modifications. Exim does not do
16407 duplicate deliveries (except, in certain circumstances, to pipes -- see section
16408 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
16409 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
16410 &%redirect%& router may be of help.
16412 Unlike the handling of header modifications, any data that was set by the
16413 &%address_data%& option in the current or previous routers &'is'& passed on to
16414 subsequent routers.
16417 .option user routers string&!! "see below"
16418 .cindex "uid (user id)" "local delivery"
16419 .cindex "local transports" "uid and gid"
16420 .cindex "transport" "local"
16421 .cindex "router" "user for filter processing"
16422 .cindex "filter" "user for processing"
16423 When a router queues an address for a transport, and the transport does not
16424 specify a user, the user given here is used when running the delivery process.
16425 The user may be specified numerically or by name. If expansion fails, the
16426 error is logged and delivery is deferred.
16427 This user is also used by the &(redirect)& router when running a filter file.
16428 The default is unset, except when &%check_local_user%& is set. In this case,
16429 the default is taken from the password information. If the user is specified as
16430 a name, and &%group%& is not set, the group associated with the user is used.
16431 See also &%initgroups%& and &%group%& and the discussion in chapter
16432 &<<CHAPenvironment>>&.
16436 .option verify routers&!? boolean true
16437 Setting this option has the effect of setting &%verify_sender%& and
16438 &%verify_recipient%& to the same value.
16441 .option verify_only routers&!? boolean false
16442 .cindex "EXPN" "with &%verify_only%&"
16444 .cindex "router" "used only when verifying"
16445 If this option is set, the router is used only when verifying an address or
16446 testing with the &%-bv%& option, not when actually doing a delivery, testing
16447 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
16448 restricted to verifying only senders or recipients by means of
16449 &%verify_sender%& and &%verify_recipient%&.
16451 &*Warning*&: When the router is being run to verify addresses for an incoming
16452 SMTP message, Exim is not running as root, but under its own uid. If the router
16453 accesses any files, you need to make sure that they are accessible to the Exim
16457 .option verify_recipient routers&!? boolean true
16458 If this option is false, the router is skipped when verifying recipient
16460 or testing recipient verification using &%-bv%&.
16461 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16465 .option verify_sender routers&!? boolean true
16466 If this option is false, the router is skipped when verifying sender addresses
16467 or testing sender verification using &%-bvs%&.
16468 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
16470 .ecindex IIDgenoprou1
16471 .ecindex IIDgenoprou2
16478 . ////////////////////////////////////////////////////////////////////////////
16479 . ////////////////////////////////////////////////////////////////////////////
16481 .chapter "The accept router" "CHID4"
16482 .cindex "&(accept)& router"
16483 .cindex "routers" "&(accept)&"
16484 The &(accept)& router has no private options of its own. Unless it is being
16485 used purely for verification (see &%verify_only%&) a transport is required to
16486 be defined by the generic &%transport%& option. If the preconditions that are
16487 specified by generic options are met, the router accepts the address and queues
16488 it for the given transport. The most common use of this router is for setting
16489 up deliveries to local mailboxes. For example:
16493 domains = mydomain.example
16495 transport = local_delivery
16497 The &%domains%& condition in this example checks the domain of the address, and
16498 &%check_local_user%& checks that the local part is the login of a local user.
16499 When both preconditions are met, the &(accept)& router runs, and queues the
16500 address for the &(local_delivery)& transport.
16507 . ////////////////////////////////////////////////////////////////////////////
16508 . ////////////////////////////////////////////////////////////////////////////
16510 .chapter "The dnslookup router" "CHAPdnslookup"
16511 .scindex IIDdnsrou1 "&(dnslookup)& router"
16512 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
16513 The &(dnslookup)& router looks up the hosts that handle mail for the
16514 recipient's domain in the DNS. A transport must always be set for this router,
16515 unless &%verify_only%& is set.
16517 If SRV support is configured (see &%check_srv%& below), Exim first searches for
16518 SRV records. If none are found, or if SRV support is not configured,
16519 MX records are looked up. If no MX records exist, address records are sought.
16520 However, &%mx_domains%& can be set to disable the direct use of address
16523 MX records of equal priority are sorted by Exim into a random order. Exim then
16524 looks for address records for the host names obtained from MX or SRV records.
16525 When a host has more than one IP address, they are sorted into a random order,
16526 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
16527 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
16528 generic option, the router declines.
16530 Unless they have the highest priority (lowest MX value), MX records that point
16531 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
16532 are discarded, together with any other MX records of equal or lower priority.
16534 .cindex "MX record" "pointing to local host"
16535 .cindex "local host" "MX pointing to"
16536 .oindex "&%self%&" "in &(dnslookup)& router"
16537 If the host pointed to by the highest priority MX record, or looked up as an
16538 address record, is the local host, or matches &%hosts_treat_as_local%&, what
16539 happens is controlled by the generic &%self%& option.
16542 .section "Problems with DNS lookups" "SECTprowitdnsloo"
16543 There have been problems with DNS servers when SRV records are looked up.
16544 Some mis-behaving servers return a DNS error or timeout when a non-existent
16545 SRV record is sought. Similar problems have in the past been reported for
16546 MX records. The global &%dns_again_means_nonexist%& option can help with this
16547 problem, but it is heavy-handed because it is a global option.
16549 For this reason, there are two options, &%srv_fail_domains%& and
16550 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
16551 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
16552 an attempt to look up an SRV or MX record causes one of these results, and the
16553 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
16554 such record"&. In the case of an SRV lookup, this means that the router
16555 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
16556 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
16557 case routing fails.
16562 .section "Private options for dnslookup" "SECID118"
16563 .cindex "options" "&(dnslookup)& router"
16564 The private options for the &(dnslookup)& router are as follows:
16566 .option check_secondary_mx dnslookup boolean false
16567 .cindex "MX record" "checking for secondary"
16568 If this option is set, the router declines unless the local host is found in
16569 (and removed from) the list of hosts obtained by MX lookup. This can be used to
16570 process domains for which the local host is a secondary mail exchanger
16571 differently to other domains. The way in which Exim decides whether a host is
16572 the local host is described in section &<<SECTreclocipadd>>&.
16575 .option check_srv dnslookup string&!! unset
16576 .cindex "SRV record" "enabling use of"
16577 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
16578 addition to MX and address records. The support is disabled by default. To
16579 enable SRV support, set the &%check_srv%& option to the name of the service
16580 required. For example,
16584 looks for SRV records that refer to the normal smtp service. The option is
16585 expanded, so the service name can vary from message to message or address
16586 to address. This might be helpful if SRV records are being used for a
16587 submission service. If the expansion is forced to fail, the &%check_srv%&
16588 option is ignored, and the router proceeds to look for MX records in the
16591 When the expansion succeeds, the router searches first for SRV records for
16592 the given service (it assumes TCP protocol). A single SRV record with a
16593 host name that consists of just a single dot indicates &"no such service for
16594 this domain"&; if this is encountered, the router declines. If other kinds of
16595 SRV record are found, they are used to construct a host list for delivery
16596 according to the rules of RFC 2782. MX records are not sought in this case.
16598 When no SRV records are found, MX records (and address records) are sought in
16599 the traditional way. In other words, SRV records take precedence over MX
16600 records, just as MX records take precedence over address records. Note that
16601 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
16602 defined it. It is apparently believed that MX records are sufficient for email
16603 and that SRV records should not be used for this purpose. However, SRV records
16604 have an additional &"weight"& feature which some people might find useful when
16605 trying to split an SMTP load between hosts of different power.
16607 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
16608 when there is a DNS lookup error.
16612 .option mx_domains dnslookup "domain list&!!" unset
16613 .cindex "MX record" "required to exist"
16614 .cindex "SRV record" "required to exist"
16615 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
16616 record in order to be recognized. (The name of this option could be improved.)
16617 For example, if all the mail hosts in &'fict.example'& are known to have MX
16618 records, except for those in &'discworld.fict.example'&, you could use this
16621 mx_domains = ! *.discworld.fict.example : *.fict.example
16623 This specifies that messages addressed to a domain that matches the list but
16624 has no MX record should be bounced immediately instead of being routed using
16625 the address record.
16628 .option mx_fail_domains dnslookup "domain list&!!" unset
16629 If the DNS lookup for MX records for one of the domains in this list causes a
16630 DNS lookup error, Exim behaves as if no MX records were found. See section
16631 &<<SECTprowitdnsloo>>& for more discussion.
16636 .option qualify_single dnslookup boolean true
16637 .cindex "DNS" "resolver options"
16638 .cindex "DNS" "qualifying single-component names"
16639 When this option is true, the resolver option RES_DEFNAMES is set for DNS
16640 lookups. Typically, but not standardly, this causes the resolver to qualify
16641 single-component names with the default domain. For example, on a machine
16642 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
16643 &'thesaurus.ref.example'& inside the resolver. For details of what your
16644 resolver actually does, consult your man pages for &'resolver'& and
16649 .option rewrite_headers dnslookup boolean true
16650 .cindex "rewriting" "header lines"
16651 .cindex "header lines" "rewriting"
16652 If the domain name in the address that is being processed is not fully
16653 qualified, it may be expanded to its full form by a DNS lookup. For example, if
16654 an address is specified as &'dormouse@teaparty'&, the domain might be
16655 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
16656 occur as a result of setting the &%widen_domains%& option. If
16657 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
16658 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
16659 header lines of the message are rewritten with the full domain name.
16661 This option should be turned off only when it is known that no message is
16662 ever going to be sent outside an environment where the abbreviation makes
16665 When an MX record is looked up in the DNS and matches a wildcard record, name
16666 servers normally return a record containing the name that has been looked up,
16667 making it impossible to detect whether a wildcard was present or not. However,
16668 some name servers have recently been seen to return the wildcard entry. If the
16669 name returned by a DNS lookup begins with an asterisk, it is not used for
16673 .option same_domain_copy_routing dnslookup boolean false
16674 .cindex "address" "copying routing"
16675 Addresses with the same domain are normally routed by the &(dnslookup)& router
16676 to the same list of hosts. However, this cannot be presumed, because the router
16677 options and preconditions may refer to the local part of the address. By
16678 default, therefore, Exim routes each address in a message independently. DNS
16679 servers run caches, so repeated DNS lookups are not normally expensive, and in
16680 any case, personal messages rarely have more than a few recipients.
16682 If you are running mailing lists with large numbers of subscribers at the same
16683 domain, and you are using a &(dnslookup)& router which is independent of the
16684 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
16685 lookups for identical domains in one message. In this case, when &(dnslookup)&
16686 routes an address to a remote transport, any other unrouted addresses in the
16687 message that have the same domain are automatically given the same routing
16688 without processing them independently,
16689 provided the following conditions are met:
16692 No router that processed the address specified &%headers_add%& or
16693 &%headers_remove%&.
16695 The router did not change the address in any way, for example, by &"widening"&
16702 .option search_parents dnslookup boolean false
16703 .cindex "DNS" "resolver options"
16704 When this option is true, the resolver option RES_DNSRCH is set for DNS
16705 lookups. This is different from the &%qualify_single%& option in that it
16706 applies to domains containing dots. Typically, but not standardly, it causes
16707 the resolver to search for the name in the current domain and in parent
16708 domains. For example, on a machine in the &'fict.example'& domain, if looking
16709 up &'teaparty.wonderland'& failed, the resolver would try
16710 &'teaparty.wonderland.fict.example'&. For details of what your resolver
16711 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
16713 Setting this option true can cause problems in domains that have a wildcard MX
16714 record, because any domain that does not have its own MX record matches the
16719 .option srv_fail_domains dnslookup "domain list&!!" unset
16720 If the DNS lookup for SRV records for one of the domains in this list causes a
16721 DNS lookup error, Exim behaves as if no SRV records were found. See section
16722 &<<SECTprowitdnsloo>>& for more discussion.
16727 .option widen_domains dnslookup "string list" unset
16728 .cindex "domain" "partial; widening"
16729 If a DNS lookup fails and this option is set, each of its strings in turn is
16730 added onto the end of the domain, and the lookup is tried again. For example,
16733 widen_domains = fict.example:ref.example
16735 is set and a lookup of &'klingon.dictionary'& fails,
16736 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
16737 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
16738 and &%search_parents%& options can cause some widening to be undertaken inside
16739 the DNS resolver. &%widen_domains%& is not applied to sender addresses
16740 when verifying, unless &%rewrite_headers%& is false (not the default).
16743 .section "Effect of qualify_single and search_parents" "SECID119"
16744 When a domain from an envelope recipient is changed by the resolver as a result
16745 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
16746 corresponding address in the message's header lines unless &%rewrite_headers%&
16747 is set false. Exim then re-routes the address, using the full domain.
16749 These two options affect only the DNS lookup that takes place inside the router
16750 for the domain of the address that is being routed. They do not affect lookups
16751 such as that implied by
16755 that may happen while processing a router precondition before the router is
16756 entered. No widening ever takes place for these lookups.
16757 .ecindex IIDdnsrou1
16758 .ecindex IIDdnsrou2
16768 . ////////////////////////////////////////////////////////////////////////////
16769 . ////////////////////////////////////////////////////////////////////////////
16771 .chapter "The ipliteral router" "CHID5"
16772 .cindex "&(ipliteral)& router"
16773 .cindex "domain literal" "routing"
16774 .cindex "routers" "&(ipliteral)&"
16775 This router has no private options. Unless it is being used purely for
16776 verification (see &%verify_only%&) a transport is required to be defined by the
16777 generic &%transport%& option. The router accepts the address if its domain part
16778 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
16779 router handles the address
16783 by setting up delivery to the host with that IP address. IPv4 domain literals
16784 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
16785 are similar, but the address is preceded by &`ipv6:`&. For example:
16787 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
16789 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
16790 grounds that sooner or later somebody will try it.
16792 .oindex "&%self%&" "in &(ipliteral)& router"
16793 If the IP address matches something in &%ignore_target_hosts%&, the router
16794 declines. If an IP literal turns out to refer to the local host, the generic
16795 &%self%& option determines what happens.
16797 The RFCs require support for domain literals; however, their use is
16798 controversial in today's Internet. If you want to use this router, you must
16799 also set the main configuration option &%allow_domain_literals%&. Otherwise,
16800 Exim will not recognize the domain literal syntax in addresses.
16804 . ////////////////////////////////////////////////////////////////////////////
16805 . ////////////////////////////////////////////////////////////////////////////
16807 .chapter "The iplookup router" "CHID6"
16808 .cindex "&(iplookup)& router"
16809 .cindex "routers" "&(iplookup)&"
16810 The &(iplookup)& router was written to fulfil a specific requirement in
16811 Cambridge University (which in fact no longer exists). For this reason, it is
16812 not included in the binary of Exim by default. If you want to include it, you
16815 ROUTER_IPLOOKUP=yes
16817 in your &_Local/Makefile_& configuration file.
16819 The &(iplookup)& router routes an address by sending it over a TCP or UDP
16820 connection to one or more specific hosts. The host can then return the same or
16821 a different address &-- in effect rewriting the recipient address in the
16822 message's envelope. The new address is then passed on to subsequent routers. If
16823 this process fails, the address can be passed on to other routers, or delivery
16824 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
16825 must not be specified for it.
16827 .cindex "options" "&(iplookup)& router"
16828 .option hosts iplookup string unset
16829 This option must be supplied. Its value is a colon-separated list of host
16830 names. The hosts are looked up using &[gethostbyname()]&
16831 (or &[getipnodebyname()]& when available)
16832 and are tried in order until one responds to the query. If none respond, what
16833 happens is controlled by &%optional%&.
16836 .option optional iplookup boolean false
16837 If &%optional%& is true, if no response is obtained from any host, the address
16838 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
16839 delivery to the address is deferred.
16842 .option port iplookup integer 0
16843 .cindex "port" "&(iplookup)& router"
16844 This option must be supplied. It specifies the port number for the TCP or UDP
16848 .option protocol iplookup string udp
16849 This option can be set to &"udp"& or &"tcp"& to specify which of the two
16850 protocols is to be used.
16853 .option query iplookup string&!! "see below"
16854 This defines the content of the query that is sent to the remote hosts. The
16857 $local_part@$domain $local_part@$domain
16859 The repetition serves as a way of checking that a response is to the correct
16860 query in the default case (see &%response_pattern%& below).
16863 .option reroute iplookup string&!! unset
16864 If this option is not set, the rerouted address is precisely the byte string
16865 returned by the remote host, up to the first white space, if any. If set, the
16866 string is expanded to form the rerouted address. It can include parts matched
16867 in the response by &%response_pattern%& by means of numeric variables such as
16868 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
16869 whether or not a pattern is in use. In all cases, the rerouted address must end
16870 up in the form &'local_part@domain'&.
16873 .option response_pattern iplookup string unset
16874 This option can be set to a regular expression that is applied to the string
16875 returned from the remote host. If the pattern does not match the response, the
16876 router declines. If &%response_pattern%& is not set, no checking of the
16877 response is done, unless the query was defaulted, in which case there is a
16878 check that the text returned after the first white space is the original
16879 address. This checks that the answer that has been received is in response to
16880 the correct question. For example, if the response is just a new domain, the
16881 following could be used:
16883 response_pattern = ^([^@]+)$
16884 reroute = $local_part@$1
16887 .option timeout iplookup time 5s
16888 This specifies the amount of time to wait for a response from the remote
16889 machine. The same timeout is used for the &[connect()]& function for a TCP
16890 call. It does not apply to UDP.
16895 . ////////////////////////////////////////////////////////////////////////////
16896 . ////////////////////////////////////////////////////////////////////////////
16898 .chapter "The manualroute router" "CHID7"
16899 .scindex IIDmanrou1 "&(manualroute)& router"
16900 .scindex IIDmanrou2 "routers" "&(manualroute)&"
16901 .cindex "domain" "manually routing"
16902 The &(manualroute)& router is so-called because it provides a way of manually
16903 routing an address according to its domain. It is mainly used when you want to
16904 route addresses to remote hosts according to your own rules, bypassing the
16905 normal DNS routing that looks up MX records. However, &(manualroute)& can also
16906 route to local transports, a facility that may be useful if you want to save
16907 messages for dial-in hosts in local files.
16909 The &(manualroute)& router compares a list of domain patterns with the domain
16910 it is trying to route. If there is no match, the router declines. Each pattern
16911 has associated with it a list of hosts and some other optional data, which may
16912 include a transport. The combination of a pattern and its data is called a
16913 &"routing rule"&. For patterns that do not have an associated transport, the
16914 generic &%transport%& option must specify a transport, unless the router is
16915 being used purely for verification (see &%verify_only%&).
16918 In the case of verification, matching the domain pattern is sufficient for the
16919 router to accept the address. When actually routing an address for delivery,
16920 an address that matches a domain pattern is queued for the associated
16921 transport. If the transport is not a local one, a host list must be associated
16922 with the pattern; IP addresses are looked up for the hosts, and these are
16923 passed to the transport along with the mail address. For local transports, a
16924 host list is optional. If it is present, it is passed in &$host$& as a single
16927 The list of routing rules can be provided as an inline string in
16928 &%route_list%&, or the data can be obtained by looking up the domain in a file
16929 or database by setting &%route_data%&. Only one of these settings may appear in
16930 any one instance of &(manualroute)&. The format of routing rules is described
16931 below, following the list of private options.
16934 .section "Private options for manualroute" "SECTprioptman"
16936 .cindex "options" "&(manualroute)& router"
16937 The private options for the &(manualroute)& router are as follows:
16939 .option host_all_ignored manualroute string defer
16940 See &%host_find_failed%&.
16942 .option host_find_failed manualroute string freeze
16943 This option controls what happens when &(manualroute)& tries to find an IP
16944 address for a host, and the host does not exist. The option can be set to one
16945 of the following values:
16954 The default (&"freeze"&) assumes that this state is a serious configuration
16955 error. The difference between &"pass"& and &"decline"& is that the former
16956 forces the address to be passed to the next router (or the router defined by
16959 overriding &%no_more%&, whereas the latter passes the address to the next
16960 router only if &%more%& is true.
16962 The value &"ignore"& causes Exim to completely ignore a host whose IP address
16963 cannot be found. If all the hosts in the list are ignored, the behaviour is
16964 controlled by the &%host_all_ignored%& option. This takes the same values
16965 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
16967 The &%host_find_failed%& option applies only to a definite &"does not exist"&
16968 state; if a host lookup gets a temporary error, delivery is deferred unless the
16969 generic &%pass_on_timeout%& option is set.
16972 .option hosts_randomize manualroute boolean false
16973 .cindex "randomized host list"
16974 .cindex "host" "list of; randomized"
16975 If this option is set, the order of the items in a host list in a routing rule
16976 is randomized each time the list is used, unless an option in the routing rule
16977 overrides (see below). Randomizing the order of a host list can be used to do
16978 crude load sharing. However, if more than one mail address is routed by the
16979 same router to the same host list, the host lists are considered to be the same
16980 (even though they may be randomized into different orders) for the purpose of
16981 deciding whether to batch the deliveries into a single SMTP transaction.
16983 When &%hosts_randomize%& is true, a host list may be split
16984 into groups whose order is separately randomized. This makes it possible to
16985 set up MX-like behaviour. The boundaries between groups are indicated by an
16986 item that is just &`+`& in the host list. For example:
16988 route_list = * host1:host2:host3:+:host4:host5
16990 The order of the first three hosts and the order of the last two hosts is
16991 randomized for each use, but the first three always end up before the last two.
16992 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
16993 randomized host list is passed to an &(smtp)& transport that also has
16994 &%hosts_randomize set%&, the list is not re-randomized.
16997 .option route_data manualroute string&!! unset
16998 If this option is set, it must expand to yield the data part of a routing rule.
16999 Typically, the expansion string includes a lookup based on the domain. For
17002 route_data = ${lookup{$domain}dbm{/etc/routes}}
17004 If the expansion is forced to fail, or the result is an empty string, the
17005 router declines. Other kinds of expansion failure cause delivery to be
17009 .option route_list manualroute "string list" unset
17010 This string is a list of routing rules, in the form defined below. Note that,
17011 unlike most string lists, the items are separated by semicolons. This is so
17012 that they may contain colon-separated host lists.
17015 .option same_domain_copy_routing manualroute boolean false
17016 .cindex "address" "copying routing"
17017 Addresses with the same domain are normally routed by the &(manualroute)&
17018 router to the same list of hosts. However, this cannot be presumed, because the
17019 router options and preconditions may refer to the local part of the address. By
17020 default, therefore, Exim routes each address in a message independently. DNS
17021 servers run caches, so repeated DNS lookups are not normally expensive, and in
17022 any case, personal messages rarely have more than a few recipients.
17024 If you are running mailing lists with large numbers of subscribers at the same
17025 domain, and you are using a &(manualroute)& router which is independent of the
17026 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
17027 lookups for identical domains in one message. In this case, when
17028 &(manualroute)& routes an address to a remote transport, any other unrouted
17029 addresses in the message that have the same domain are automatically given the
17030 same routing without processing them independently. However, this is only done
17031 if &%headers_add%& and &%headers_remove%& are unset.
17036 .section "Routing rules in route_list" "SECID120"
17037 The value of &%route_list%& is a string consisting of a sequence of routing
17038 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
17039 entered as two semicolons. Alternatively, the list separator can be changed as
17040 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
17041 Empty rules are ignored. The format of each rule is
17043 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
17045 The following example contains two rules, each with a simple domain pattern and
17049 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
17050 thes.ref.example mail-3.ref.example:mail-4.ref.example
17052 The three parts of a rule are separated by white space. The pattern and the
17053 list of hosts can be enclosed in quotes if necessary, and if they are, the
17054 usual quoting rules apply. Each rule in a &%route_list%& must start with a
17055 single domain pattern, which is the only mandatory item in the rule. The
17056 pattern is in the same format as one item in a domain list (see section
17057 &<<SECTdomainlist>>&),
17058 except that it may not be the name of an interpolated file.
17059 That is, it may be wildcarded, or a regular expression, or a file or database
17060 lookup (with semicolons doubled, because of the use of semicolon as a separator
17061 in a &%route_list%&).
17063 The rules in &%route_list%& are searched in order until one of the patterns
17064 matches the domain that is being routed. The list of hosts and then options are
17065 then used as described below. If there is no match, the router declines. When
17066 &%route_list%& is set, &%route_data%& must not be set.
17070 .section "Routing rules in route_data" "SECID121"
17071 The use of &%route_list%& is convenient when there are only a small number of
17072 routing rules. For larger numbers, it is easier to use a file or database to
17073 hold the routing information, and use the &%route_data%& option instead.
17074 The value of &%route_data%& is a list of hosts, followed by (optional) options.
17075 Most commonly, &%route_data%& is set as a string that contains an
17076 expansion lookup. For example, suppose we place two routing rules in a file
17079 dict.ref.example: mail-1.ref.example:mail-2.ref.example
17080 thes.ref.example: mail-3.ref.example:mail-4.ref.example
17082 This data can be accessed by setting
17084 route_data = ${lookup{$domain}lsearch{/the/file/name}}
17086 Failure of the lookup results in an empty string, causing the router to
17087 decline. However, you do not have to use a lookup in &%route_data%&. The only
17088 requirement is that the result of expanding the string is a list of hosts,
17089 possibly followed by options, separated by white space. The list of hosts must
17090 be enclosed in quotes if it contains white space.
17095 .section "Format of the list of hosts" "SECID122"
17096 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
17097 always separately expanded before use. If the expansion fails, the router
17098 declines. The result of the expansion must be a colon-separated list of names
17099 and/or IP addresses, optionally also including ports. The format of each item
17100 in the list is described in the next section. The list separator can be changed
17101 as described in section &<<SECTlistconstruct>>&.
17103 If the list of hosts was obtained from a &%route_list%& item, the following
17104 variables are set during its expansion:
17107 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
17108 If the domain was matched against a regular expression, the numeric variables
17109 &$1$&, &$2$&, etc. may be set. For example:
17111 route_list = ^domain(\d+) host-$1.text.example
17114 &$0$& is always set to the entire domain.
17116 &$1$& is also set when partial matching is done in a file lookup.
17119 .vindex "&$value$&"
17120 If the pattern that matched the domain was a lookup item, the data that was
17121 looked up is available in the expansion variable &$value$&. For example:
17123 route_list = lsearch;;/some/file.routes $value
17127 Note the doubling of the semicolon in the pattern that is necessary because
17128 semicolon is the default route list separator.
17132 .section "Format of one host item" "SECTformatonehostitem"
17133 Each item in the list of hosts is either a host name or an IP address,
17134 optionally with an attached port number. When no port is given, an IP address
17135 is not enclosed in brackets. When a port is specified, it overrides the port
17136 specification on the transport. The port is separated from the name or address
17137 by a colon. This leads to some complications:
17140 Because colon is the default separator for the list of hosts, either
17141 the colon that specifies a port must be doubled, or the list separator must
17142 be changed. The following two examples have the same effect:
17144 route_list = * "host1.tld::1225 : host2.tld::1226"
17145 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
17148 When IPv6 addresses are involved, it gets worse, because they contain
17149 colons of their own. To make this case easier, it is permitted to
17150 enclose an IP address (either v4 or v6) in square brackets if a port
17151 number follows. For example:
17153 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
17157 .section "How the list of hosts is used" "SECThostshowused"
17158 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
17159 the hosts is tried, in the order specified, when carrying out the SMTP
17160 delivery. However, the order can be changed by setting the &%hosts_randomize%&
17161 option, either on the router (see section &<<SECTprioptman>>& above), or on the
17164 Hosts may be listed by name or by IP address. An unadorned name in the list of
17165 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
17166 interpreted as an indirection to a sublist of hosts obtained by looking up MX
17167 records in the DNS. For example:
17169 route_list = * x.y.z:p.q.r/MX:e.f.g
17171 If this feature is used with a port specifier, the port must come last. For
17174 route_list = * dom1.tld/mx::1225
17176 If the &%hosts_randomize%& option is set, the order of the items in the list is
17177 randomized before any lookups are done. Exim then scans the list; for any name
17178 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
17179 be an interface on the local host and the item is not the first in the list,
17180 Exim discards it and any subsequent items. If it is the first item, what
17181 happens is controlled by the
17182 .oindex "&%self%&" "in &(manualroute)& router"
17183 &%self%& option of the router.
17185 A name on the list that is followed by &`/MX`& is replaced with the list of
17186 hosts obtained by looking up MX records for the name. This is always a DNS
17187 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
17188 below) are not relevant here. The order of these hosts is determined by the
17189 preference values in the MX records, according to the usual rules. Because
17190 randomizing happens before the MX lookup, it does not affect the order that is
17191 defined by MX preferences.
17193 If the local host is present in the sublist obtained from MX records, but is
17194 not the most preferred host in that list, it and any equally or less
17195 preferred hosts are removed before the sublist is inserted into the main list.
17197 If the local host is the most preferred host in the MX list, what happens
17198 depends on where in the original list of hosts the &`/MX`& item appears. If it
17199 is not the first item (that is, there are previous hosts in the main list),
17200 Exim discards this name and any subsequent items in the main list.
17202 If the MX item is first in the list of hosts, and the local host is the
17203 most preferred host, what happens is controlled by the &%self%& option of the
17206 DNS failures when lookup up the MX records are treated in the same way as DNS
17207 failures when looking up IP addresses: &%pass_on_timeout%& and
17208 &%host_find_failed%& are used when relevant.
17210 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
17211 whether obtained from an MX lookup or not.
17215 .section "How the options are used" "SECThowoptused"
17216 The options are a sequence of words; in practice no more than three are ever
17217 present. One of the words can be the name of a transport; this overrides the
17218 &%transport%& option on the router for this particular routing rule only. The
17219 other words (if present) control randomization of the list of hosts on a
17220 per-rule basis, and how the IP addresses of the hosts are to be found when
17221 routing to a remote transport. These options are as follows:
17224 &%randomize%&: randomize the order of the hosts in this list, overriding the
17225 setting of &%hosts_randomize%& for this routing rule only.
17227 &%no_randomize%&: do not randomize the order of the hosts in this list,
17228 overriding the setting of &%hosts_randomize%& for this routing rule only.
17230 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
17231 find IP addresses. This function may ultimately cause a DNS lookup, but it may
17232 also look in &_/etc/hosts_& or other sources of information.
17234 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
17235 no address records are found. If there is a temporary DNS error (such as a
17236 timeout), delivery is deferred.
17241 route_list = domain1 host1:host2:host3 randomize bydns;\
17242 domain2 host4:host5
17244 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
17245 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
17246 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
17247 or &[gethostbyname()]&, and the result of the lookup is the result of that
17250 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
17251 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
17252 instead of TRY_AGAIN. That is why the default action is to try a DNS
17253 lookup first. Only if that gives a definite &"no such host"& is the local
17258 If no IP address for a host can be found, what happens is controlled by the
17259 &%host_find_failed%& option.
17262 When an address is routed to a local transport, IP addresses are not looked up.
17263 The host list is passed to the transport in the &$host$& variable.
17267 .section "Manualroute examples" "SECID123"
17268 In some of the examples that follow, the presence of the &%remote_smtp%&
17269 transport, as defined in the default configuration file, is assumed:
17272 .cindex "smart host" "example router"
17273 The &(manualroute)& router can be used to forward all external mail to a
17274 &'smart host'&. If you have set up, in the main part of the configuration, a
17275 named domain list that contains your local domains, for example:
17277 domainlist local_domains = my.domain.example
17279 You can arrange for all other domains to be routed to a smart host by making
17280 your first router something like this:
17283 driver = manualroute
17284 domains = !+local_domains
17285 transport = remote_smtp
17286 route_list = * smarthost.ref.example
17288 This causes all non-local addresses to be sent to the single host
17289 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
17290 they are tried in order
17291 (but you can use &%hosts_randomize%& to vary the order each time).
17292 Another way of configuring the same thing is this:
17295 driver = manualroute
17296 transport = remote_smtp
17297 route_list = !+local_domains smarthost.ref.example
17299 There is no difference in behaviour between these two routers as they stand.
17300 However, they behave differently if &%no_more%& is added to them. In the first
17301 example, the router is skipped if the domain does not match the &%domains%&
17302 precondition; the following router is always tried. If the router runs, it
17303 always matches the domain and so can never decline. Therefore, &%no_more%&
17304 would have no effect. In the second case, the router is never skipped; it
17305 always runs. However, if it doesn't match the domain, it declines. In this case
17306 &%no_more%& would prevent subsequent routers from running.
17309 .cindex "mail hub example"
17310 A &'mail hub'& is a host which receives mail for a number of domains via MX
17311 records in the DNS and delivers it via its own private routing mechanism. Often
17312 the final destinations are behind a firewall, with the mail hub being the one
17313 machine that can connect to machines both inside and outside the firewall. The
17314 &(manualroute)& router is usually used on a mail hub to route incoming messages
17315 to the correct hosts. For a small number of domains, the routing can be inline,
17316 using the &%route_list%& option, but for a larger number a file or database
17317 lookup is easier to manage.
17319 If the domain names are in fact the names of the machines to which the mail is
17320 to be sent by the mail hub, the configuration can be quite simple. For
17324 driver = manualroute
17325 transport = remote_smtp
17326 route_list = *.rhodes.tvs.example $domain
17328 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
17329 whose names are the same as the mail domains. A similar approach can be taken
17330 if the host name can be obtained from the domain name by a string manipulation
17331 that the expansion facilities can handle. Otherwise, a lookup based on the
17332 domain can be used to find the host:
17335 driver = manualroute
17336 transport = remote_smtp
17337 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
17339 The result of the lookup must be the name or IP address of the host (or
17340 hosts) to which the address is to be routed. If the lookup fails, the route
17341 data is empty, causing the router to decline. The address then passes to the
17345 .cindex "batched SMTP output example"
17346 .cindex "SMTP" "batched outgoing; example"
17347 You can use &(manualroute)& to deliver messages to pipes or files in batched
17348 SMTP format for onward transportation by some other means. This is one way of
17349 storing mail for a dial-up host when it is not connected. The route list entry
17350 can be as simple as a single domain name in a configuration like this:
17353 driver = manualroute
17354 transport = batchsmtp_appendfile
17355 route_list = saved.domain.example
17357 though often a pattern is used to pick up more than one domain. If there are
17358 several domains or groups of domains with different transport requirements,
17359 different transports can be listed in the routing information:
17362 driver = manualroute
17364 *.saved.domain1.example $domain batch_appendfile; \
17365 *.saved.domain2.example \
17366 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
17369 .vindex "&$domain$&"
17371 The first of these just passes the domain in the &$host$& variable, which
17372 doesn't achieve much (since it is also in &$domain$&), but the second does a
17373 file lookup to find a value to pass, causing the router to decline to handle
17374 the address if the lookup fails.
17377 .cindex "UUCP" "example of router for"
17378 Routing mail directly to UUCP software is a specific case of the use of
17379 &(manualroute)& in a gateway to another mail environment. This is an example of
17380 one way it can be done:
17386 command = /usr/local/bin/uux -r - \
17387 ${substr_-5:$host}!rmail ${local_part}
17388 return_fail_output = true
17393 driver = manualroute
17395 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
17397 The file &_/usr/local/exim/uucphosts_& contains entries like
17399 darksite.ethereal.example: darksite.UUCP
17401 It can be set up more simply without adding and removing &".UUCP"& but this way
17402 makes clear the distinction between the domain name
17403 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
17405 .ecindex IIDmanrou1
17406 .ecindex IIDmanrou2
17415 . ////////////////////////////////////////////////////////////////////////////
17416 . ////////////////////////////////////////////////////////////////////////////
17418 .chapter "The queryprogram router" "CHAPdriverlast"
17419 .scindex IIDquerou1 "&(queryprogram)& router"
17420 .scindex IIDquerou2 "routers" "&(queryprogram)&"
17421 .cindex "routing" "by external program"
17422 The &(queryprogram)& router routes an address by running an external command
17423 and acting on its output. This is an expensive way to route, and is intended
17424 mainly for use in lightly-loaded systems, or for performing experiments.
17425 However, if it is possible to use the precondition options (&%domains%&,
17426 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
17427 be used in special cases, even on a busy host. There are the following private
17429 .cindex "options" "&(queryprogram)& router"
17431 .option command queryprogram string&!! unset
17432 This option must be set. It specifies the command that is to be run. The
17433 command is split up into a command name and arguments, and then each is
17434 expanded separately (exactly as for a &(pipe)& transport, described in chapter
17435 &<<CHAPpipetransport>>&).
17438 .option command_group queryprogram string unset
17439 .cindex "gid (group id)" "in &(queryprogram)& router"
17440 This option specifies a gid to be set when running the command while routing an
17441 address for deliver. It must be set if &%command_user%& specifies a numerical
17442 uid. If it begins with a digit, it is interpreted as the numerical value of the
17443 gid. Otherwise it is looked up using &[getgrnam()]&.
17446 .option command_user queryprogram string unset
17447 .cindex "uid (user id)" "for &(queryprogram)&"
17448 This option must be set. It specifies the uid which is set when running the
17449 command while routing an address for delivery. If the value begins with a digit,
17450 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
17451 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
17452 not set, a value for the gid also.
17454 &*Warning:*& Changing uid and gid is possible only when Exim is running as
17455 root, which it does during a normal delivery in a conventional configuration.
17456 However, when an address is being verified during message reception, Exim is
17457 usually running as the Exim user, not as root. If the &(queryprogram)& router
17458 is called from a non-root process, Exim cannot change uid or gid before running
17459 the command. In this circumstance the command runs under the current uid and
17463 .option current_directory queryprogram string /
17464 This option specifies an absolute path which is made the current directory
17465 before running the command.
17468 .option timeout queryprogram time 1h
17469 If the command does not complete within the timeout period, its process group
17470 is killed and the message is frozen. A value of zero time specifies no
17474 The standard output of the command is connected to a pipe, which is read when
17475 the command terminates. It should consist of a single line of output,
17476 containing up to five fields, separated by white space. The maximum length of
17477 the line is 1023 characters. Longer lines are silently truncated. The first
17478 field is one of the following words (case-insensitive):
17481 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
17484 &'Decline'&: the router declines; pass the address to the next router, unless
17485 &%no_more%& is set.
17487 &'Fail'&: routing failed; do not pass the address to any more routers. Any
17488 subsequent text on the line is an error message. If the router is run as part
17489 of address verification during an incoming SMTP message, the message is
17490 included in the SMTP response.
17492 &'Defer'&: routing could not be completed at this time; try again later. Any
17493 subsequent text on the line is an error message which is logged. It is not
17494 included in any SMTP response.
17496 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
17498 &'Pass'&: pass the address to the next router (or the router specified by
17499 &%pass_router%&), overriding &%no_more%&.
17501 &'Redirect'&: the message is redirected. The remainder of the line is a list of
17502 new addresses, which are routed independently, starting with the first router,
17503 or the router specified by &%redirect_router%&, if set.
17506 When the first word is &'accept'&, the remainder of the line consists of a
17507 number of keyed data values, as follows (split into two lines here, to fit on
17510 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
17511 LOOKUP=byname|bydns DATA=<text>
17513 The data items can be given in any order, and all are optional. If no transport
17514 is included, the transport specified by the generic &%transport%& option is
17515 used. The list of hosts and the lookup type are needed only if the transport is
17516 an &(smtp)& transport that does not itself supply a list of hosts.
17518 The format of the list of hosts is the same as for the &(manualroute)& router.
17519 As well as host names and IP addresses with optional port numbers, as described
17520 in section &<<SECTformatonehostitem>>&, it may contain names followed by
17521 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
17522 (see section &<<SECThostshowused>>&).
17524 If the lookup type is not specified, Exim behaves as follows when trying to
17525 find an IP address for each host: First, a DNS lookup is done. If this yields
17526 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
17527 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
17528 result of the lookup is the result of that call.
17530 .vindex "&$address_data$&"
17531 If the DATA field is set, its value is placed in the &$address_data$&
17532 variable. For example, this return line
17534 accept hosts=x1.y.example:x2.y.example data="rule1"
17536 routes the address to the default transport, passing a list of two hosts. When
17537 the transport runs, the string &"rule1"& is in &$address_data$&.
17538 .ecindex IIDquerou1
17539 .ecindex IIDquerou2
17544 . ////////////////////////////////////////////////////////////////////////////
17545 . ////////////////////////////////////////////////////////////////////////////
17547 .chapter "The redirect router" "CHAPredirect"
17548 .scindex IIDredrou1 "&(redirect)& router"
17549 .scindex IIDredrou2 "routers" "&(redirect)&"
17550 .cindex "alias file" "in a &(redirect)& router"
17551 .cindex "address redirection" "&(redirect)& router"
17552 The &(redirect)& router handles several kinds of address redirection. Its most
17553 common uses are for resolving local part aliases from a central alias file
17554 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
17555 files, but it has many other potential uses. The incoming address can be
17556 redirected in several different ways:
17559 It can be replaced by one or more new addresses which are themselves routed
17562 It can be routed to be delivered to a given file or directory.
17564 It can be routed to be delivered to a specified pipe command.
17566 It can cause an automatic reply to be generated.
17568 It can be forced to fail, optionally with a custom error message.
17570 It can be temporarily deferred, optionally with a custom message.
17572 It can be discarded.
17575 The generic &%transport%& option must not be set for &(redirect)& routers.
17576 However, there are some private options which define transports for delivery to
17577 files and pipes, and for generating autoreplies. See the &%file_transport%&,
17578 &%pipe_transport%& and &%reply_transport%& descriptions below.
17582 .section "Redirection data" "SECID124"
17583 The router operates by interpreting a text string which it obtains either by
17584 expanding the contents of the &%data%& option, or by reading the entire
17585 contents of a file whose name is given in the &%file%& option. These two
17586 options are mutually exclusive. The first is commonly used for handling system
17587 aliases, in a configuration like this:
17591 data = ${lookup{$local_part}lsearch{/etc/aliases}}
17593 If the lookup fails, the expanded string in this example is empty. When the
17594 expansion of &%data%& results in an empty string, the router declines. A forced
17595 expansion failure also causes the router to decline; other expansion failures
17596 cause delivery to be deferred.
17598 A configuration using &%file%& is commonly used for handling users'
17599 &_.forward_& files, like this:
17604 file = $home/.forward
17607 If the file does not exist, or causes no action to be taken (for example, it is
17608 empty or consists only of comments), the router declines. &*Warning*&: This
17609 is not the case when the file contains syntactically valid items that happen to
17610 yield empty addresses, for example, items containing only RFC 2822 address
17615 .section "Forward files and address verification" "SECID125"
17616 .cindex "address redirection" "while verifying"
17617 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
17618 &_.forward_& files, as in the example above. There are two reasons for this:
17621 When Exim is receiving an incoming SMTP message from a remote host, it is
17622 running under the Exim uid, not as root. Exim is unable to change uid to read
17623 the file as the user, and it may not be able to read it as the Exim user. So in
17624 practice the router may not be able to operate.
17626 However, even when the router can operate, the existence of a &_.forward_& file
17627 is unimportant when verifying an address. What should be checked is whether the
17628 local part is a valid user name or not. Cutting out the redirection processing
17629 saves some resources.
17637 .section "Interpreting redirection data" "SECID126"
17638 .cindex "Sieve filter" "specifying in redirection data"
17639 .cindex "filter" "specifying in redirection data"
17640 The contents of the data string, whether obtained from &%data%& or &%file%&,
17641 can be interpreted in two different ways:
17644 If the &%allow_filter%& option is set true, and the data begins with the text
17645 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
17646 &'filtering'& instructions in the form of an Exim or Sieve filter file,
17647 respectively. Details of the syntax and semantics of filter files are described
17648 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
17649 document is intended for use by end users.
17651 Otherwise, the data must be a comma-separated list of redirection items, as
17652 described in the next section.
17655 When a message is redirected to a file (a &"mail folder"&), the file name given
17656 in a non-filter redirection list must always be an absolute path. A filter may
17657 generate a relative path &-- how this is handled depends on the transport's
17658 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
17659 for the &(appendfile)& transport.
17663 .section "Items in a non-filter redirection list" "SECTitenonfilred"
17664 .cindex "address redirection" "non-filter list items"
17665 When the redirection data is not an Exim or Sieve filter, for example, if it
17666 comes from a conventional alias or forward file, it consists of a list of
17667 addresses, file names, pipe commands, or certain special items (see section
17668 &<<SECTspecitredli>>& below). The special items can be individually enabled or
17669 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
17670 depending on their default values. The items in the list are separated by
17671 commas or newlines.
17672 If a comma is required in an item, the entire item must be enclosed in double
17675 Lines starting with a # character are comments, and are ignored, and # may
17676 also appear following a comma, in which case everything between the # and the
17677 next newline character is ignored.
17679 If an item is entirely enclosed in double quotes, these are removed. Otherwise
17680 double quotes are retained because some forms of mail address require their use
17681 (but never to enclose the entire address). In the following description,
17682 &"item"& refers to what remains after any surrounding double quotes have been
17685 .vindex "&$local_part$&"
17686 &*Warning*&: If you use an Exim expansion to construct a redirection address,
17687 and the expansion contains a reference to &$local_part$&, you should make use
17688 of the &%quote_local_part%& expansion operator, in case the local part contains
17689 special characters. For example, to redirect all mail for the domain
17690 &'obsolete.example'&, retaining the existing local part, you could use this
17693 data = ${quote_local_part:$local_part}@newdomain.example
17697 .section "Redirecting to a local mailbox" "SECTredlocmai"
17698 .cindex "routing" "loops in"
17699 .cindex "loop" "while routing, avoidance of"
17700 .cindex "address redirection" "to local mailbox"
17701 A redirection item may safely be the same as the address currently under
17702 consideration. This does not cause a routing loop, because a router is
17703 automatically skipped if any ancestor of the address that is being processed
17704 is the same as the current address and was processed by the current router.
17705 Such an address is therefore passed to the following routers, so it is handled
17706 as if there were no redirection. When making this loop-avoidance test, the
17707 complete local part, including any prefix or suffix, is used.
17709 .cindex "address redirection" "local part without domain"
17710 Specifying the same local part without a domain is a common usage in personal
17711 filter files when the user wants to have messages delivered to the local
17712 mailbox and also forwarded elsewhere. For example, the user whose login is
17713 &'cleo'& might have a &_.forward_& file containing this:
17715 cleo, cleopatra@egypt.example
17717 .cindex "backslash in alias file"
17718 .cindex "alias file" "backslash in"
17719 For compatibility with other MTAs, such unqualified local parts may be
17720 preceded by &"\"&, but this is not a requirement for loop prevention. However,
17721 it does make a difference if more than one domain is being handled
17724 If an item begins with &"\"& and the rest of the item parses as a valid RFC
17725 2822 address that does not include a domain, the item is qualified using the
17726 domain of the incoming address. In the absence of a leading &"\"&, unqualified
17727 addresses are qualified using the value in &%qualify_recipient%&, but you can
17728 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
17730 Care must be taken if there are alias names for local users.
17731 Consider an MTA handling a single local domain where the system alias file
17736 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
17737 messages in the local mailbox, and also forward copies elsewhere. He creates
17740 Sam.Reman, spqr@reme.elsewhere.example
17742 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
17743 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
17744 second time round, because it has previously routed it,
17745 and the following routers presumably cannot handle the alias. The forward file
17746 should really contain
17748 spqr, spqr@reme.elsewhere.example
17750 but because this is such a common error, the &%check_ancestor%& option (see
17751 below) exists to provide a way to get round it. This is normally set on a
17752 &(redirect)& router that is handling users' &_.forward_& files.
17756 .section "Special items in redirection lists" "SECTspecitredli"
17757 In addition to addresses, the following types of item may appear in redirection
17758 lists (that is, in non-filter redirection data):
17761 .cindex "pipe" "in redirection list"
17762 .cindex "address redirection" "to pipe"
17763 An item is treated as a pipe command if it begins with &"|"& and does not parse
17764 as a valid RFC 2822 address that includes a domain. A transport for running the
17765 command must be specified by the &%pipe_transport%& option.
17766 Normally, either the router or the transport specifies a user and a group under
17767 which to run the delivery. The default is to use the Exim user and group.
17769 Single or double quotes can be used for enclosing the individual arguments of
17770 the pipe command; no interpretation of escapes is done for single quotes. If
17771 the command contains a comma character, it is necessary to put the whole item
17772 in double quotes, for example:
17774 "|/some/command ready,steady,go"
17776 since items in redirection lists are terminated by commas. Do not, however,
17777 quote just the command. An item such as
17779 |"/some/command ready,steady,go"
17781 is interpreted as a pipe with a rather strange command name, and no arguments.
17784 .cindex "file" "in redirection list"
17785 .cindex "address redirection" "to file"
17786 An item is interpreted as a path name if it begins with &"/"& and does not
17787 parse as a valid RFC 2822 address that includes a domain. For example,
17789 /home/world/minbari
17791 is treated as a file name, but
17793 /s=molari/o=babylon/@x400gate.way
17795 is treated as an address. For a file name, a transport must be specified using
17796 the &%file_transport%& option. However, if the generated path name ends with a
17797 forward slash character, it is interpreted as a directory name rather than a
17798 file name, and &%directory_transport%& is used instead.
17800 Normally, either the router or the transport specifies a user and a group under
17801 which to run the delivery. The default is to use the Exim user and group.
17803 .cindex "&_/dev/null_&"
17804 However, if a redirection item is the path &_/dev/null_&, delivery to it is
17805 bypassed at a high level, and the log entry shows &"**bypassed**"&
17806 instead of a transport name. In this case the user and group are not used.
17809 .cindex "included address list"
17810 .cindex "address redirection" "included external list"
17811 If an item is of the form
17813 :include:<path name>
17815 a list of further items is taken from the given file and included at that
17816 point. &*Note*&: Such a file can not be a filter file; it is just an
17817 out-of-line addition to the list. The items in the included list are separated
17818 by commas or newlines and are not subject to expansion. If this is the first
17819 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
17820 the alias name. This example is incorrect:
17822 list1 :include:/opt/lists/list1
17824 It must be given as
17826 list1: :include:/opt/lists/list1
17829 .cindex "address redirection" "to black hole"
17830 Sometimes you want to throw away mail to a particular local part. Making the
17831 &%data%& option expand to an empty string does not work, because that causes
17832 the router to decline. Instead, the alias item
17833 .cindex "black hole"
17834 .cindex "abandoning mail"
17835 &':blackhole:'& can be used. It does what its name implies. No delivery is
17836 done, and no error message is generated. This has the same effect as specifing
17837 &_/dev/null_& as a destination, but it can be independently disabled.
17839 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
17840 delivery is done for the original local part, even if other redirection items
17841 are present. If you are generating a multi-item list (for example, by reading a
17842 database) and need the ability to provide a no-op item, you must use
17846 .cindex "delivery" "forcing failure"
17847 .cindex "delivery" "forcing deferral"
17848 .cindex "failing delivery" "forcing"
17849 .cindex "deferred delivery, forcing"
17850 .cindex "customizing" "failure message"
17851 An attempt to deliver a particular address can be deferred or forced to fail by
17852 redirection items of the form
17857 respectively. When a redirection list contains such an item, it applies
17858 to the entire redirection; any other items in the list are ignored. Any
17859 text following &':fail:'& or &':defer:'& is placed in the error text
17860 associated with the failure. For example, an alias file might contain:
17862 X.Employee: :fail: Gone away, no forwarding address
17864 In the case of an address that is being verified from an ACL or as the subject
17866 .cindex "VRFY" "error text, display of"
17867 VRFY command, the text is included in the SMTP error response by
17869 .cindex "EXPN" "error text, display of"
17870 The text is not included in the response to an EXPN command. In non-SMTP cases
17871 the text is included in the error message that Exim generates.
17873 .cindex "SMTP" "error codes"
17874 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
17875 &':fail:'&. However, if the message starts with three digits followed by a
17876 space, optionally followed by an extended code of the form &'n.n.n'&, also
17877 followed by a space, and the very first digit is the same as the default error
17878 code, the code from the message is used instead. If the very first digit is
17879 incorrect, a panic error is logged, and the default code is used. You can
17880 suppress the use of the supplied code in a redirect router by setting the
17881 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
17884 .vindex "&$acl_verify_message$&"
17885 In an ACL, an explicitly provided message overrides the default, but the
17886 default message is available in the variable &$acl_verify_message$& and can
17887 therefore be included in a custom message if this is desired.
17889 Normally the error text is the rest of the redirection list &-- a comma does
17890 not terminate it &-- but a newline does act as a terminator. Newlines are not
17891 normally present in alias expansions. In &(lsearch)& lookups they are removed
17892 as part of the continuation process, but they may exist in other kinds of
17893 lookup and in &':include:'& files.
17895 During routing for message delivery (as opposed to verification), a redirection
17896 containing &':fail:'& causes an immediate failure of the incoming address,
17897 whereas &':defer:'& causes the message to remain on the queue so that a
17898 subsequent delivery attempt can happen at a later time. If an address is
17899 deferred for too long, it will ultimately fail, because the normal retry
17903 .cindex "alias file" "exception to default"
17904 Sometimes it is useful to use a single-key search type with a default (see
17905 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
17906 for exceptions to the default. These can be handled by aliasing them to
17907 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
17908 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
17909 results in an empty redirection list has the same effect.
17913 .section "Duplicate addresses" "SECTdupaddr"
17914 .cindex "duplicate addresses"
17915 .cindex "address duplicate, discarding"
17916 .cindex "pipe" "duplicated"
17917 Exim removes duplicate addresses from the list to which it is delivering, so as
17918 to deliver just one copy to each address. This does not apply to deliveries
17919 routed to pipes by different immediate parent addresses, but an indirect
17920 aliasing scheme of the type
17922 pipe: |/some/command $local_part
17926 does not work with a message that is addressed to both local parts, because
17927 when the second is aliased to the intermediate local part &"pipe"& it gets
17928 discarded as being the same as a previously handled address. However, a scheme
17931 localpart1: |/some/command $local_part
17932 localpart2: |/some/command $local_part
17934 does result in two different pipe deliveries, because the immediate parents of
17935 the pipes are distinct.
17939 .section "Repeated redirection expansion" "SECID128"
17940 .cindex "repeated redirection expansion"
17941 .cindex "address redirection" "repeated for each delivery attempt"
17942 When a message cannot be delivered to all of its recipients immediately,
17943 leading to two or more delivery attempts, redirection expansion is carried out
17944 afresh each time for those addresses whose children were not all previously
17945 delivered. If redirection is being used as a mailing list, this can lead to new
17946 members of the list receiving copies of old messages. The &%one_time%& option
17947 can be used to avoid this.
17950 .section "Errors in redirection lists" "SECID129"
17951 .cindex "address redirection" "errors"
17952 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
17953 error is skipped, and an entry is written to the main log. This may be useful
17954 for mailing lists that are automatically managed. Otherwise, if an error is
17955 detected while generating the list of new addresses, the original address is
17956 deferred. See also &%syntax_errors_to%&.
17960 .section "Private options for the redirect router" "SECID130"
17962 .cindex "options" "&(redirect)& router"
17963 The private options for the &(redirect)& router are as follows:
17966 .option allow_defer redirect boolean false
17967 Setting this option allows the use of &':defer:'& in non-filter redirection
17968 data, or the &%defer%& command in an Exim filter file.
17971 .option allow_fail redirect boolean false
17972 .cindex "failing delivery" "from filter"
17973 If this option is true, the &':fail:'& item can be used in a redirection list,
17974 and the &%fail%& command may be used in an Exim filter file.
17977 .option allow_filter redirect boolean false
17978 .cindex "filter" "enabling use of"
17979 .cindex "Sieve filter" "enabling use of"
17980 Setting this option allows Exim to interpret redirection data that starts with
17981 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
17982 are some features of Exim filter files that some administrators may wish to
17983 lock out; see the &%forbid_filter_%&&'xxx'& options below.
17985 It is also possible to lock out Exim filters or Sieve filters while allowing
17986 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
17989 The filter is run using the uid and gid set by the generic &%user%& and
17990 &%group%& options. These take their defaults from the password data if
17991 &%check_local_user%& is set, so in the normal case of users' personal filter
17992 files, the filter is run as the relevant user. When &%allow_filter%& is set
17993 true, Exim insists that either &%check_local_user%& or &%user%& is set.
17997 .option allow_freeze redirect boolean false
17998 .cindex "freezing messages" "allowing in filter"
17999 Setting this option allows the use of the &%freeze%& command in an Exim filter.
18000 This command is more normally encountered in system filters, and is disabled by
18001 default for redirection filters because it isn't something you usually want to
18002 let ordinary users do.
18006 .option check_ancestor redirect boolean false
18007 This option is concerned with handling generated addresses that are the same
18008 as some address in the list of redirection ancestors of the current address.
18009 Although it is turned off by default in the code, it is set in the default
18010 configuration file for handling users' &_.forward_& files. It is recommended
18011 for this use of the &(redirect)& router.
18013 When &%check_ancestor%& is set, if a generated address (including the domain)
18014 is the same as any ancestor of the current address, it is replaced by a copy of
18015 the current address. This helps in the case where local part A is aliased to B,
18016 and B has a &_.forward_& file pointing back to A. For example, within a single
18017 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
18018 &_&~jb/.forward_& contains:
18020 \Joe.Bloggs, <other item(s)>
18022 Without the &%check_ancestor%& setting, either local part (&"jb"& or
18023 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
18024 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
18025 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
18026 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
18027 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
18028 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
18029 original address. See also the &%repeat_use%& option below.
18032 .option check_group redirect boolean "see below"
18033 When the &%file%& option is used, the group owner of the file is checked only
18034 when this option is set. The permitted groups are those listed in the
18035 &%owngroups%& option, together with the user's default group if
18036 &%check_local_user%& is set. If the file has the wrong group, routing is
18037 deferred. The default setting for this option is true if &%check_local_user%&
18038 is set and the &%modemask%& option permits the group write bit, or if the
18039 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
18043 .option check_owner redirect boolean "see below"
18044 When the &%file%& option is used, the owner of the file is checked only when
18045 this option is set. If &%check_local_user%& is set, the local user is
18046 permitted; otherwise the owner must be one of those listed in the &%owners%&
18047 option. The default value for this option is true if &%check_local_user%& or
18048 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
18051 .option data redirect string&!! unset
18052 This option is mutually exclusive with &%file%&. One or other of them must be
18053 set, but not both. The contents of &%data%& are expanded, and then used as the
18054 list of forwarding items, or as a set of filtering instructions. If the
18055 expansion is forced to fail, or the result is an empty string or a string that
18056 has no effect (consists entirely of comments), the router declines.
18058 When filtering instructions are used, the string must begin with &"#Exim
18059 filter"&, and all comments in the string, including this initial one, must be
18060 terminated with newline characters. For example:
18062 data = #Exim filter\n\
18063 if $h_to: contains Exim then save $home/mail/exim endif
18065 If you are reading the data from a database where newlines cannot be included,
18066 you can use the &${sg}$& expansion item to turn the escape string of your
18067 choice into a newline.
18070 .option directory_transport redirect string&!! unset
18071 A &(redirect)& router sets up a direct delivery to a directory when a path name
18072 ending with a slash is specified as a new &"address"&. The transport used is
18073 specified by this option, which, after expansion, must be the name of a
18074 configured transport. This should normally be an &(appendfile)& transport.
18077 .option file redirect string&!! unset
18078 This option specifies the name of a file that contains the redirection data. It
18079 is mutually exclusive with the &%data%& option. The string is expanded before
18080 use; if the expansion is forced to fail, the router declines. Other expansion
18081 failures cause delivery to be deferred. The result of a successful expansion
18082 must be an absolute path. The entire file is read and used as the redirection
18083 data. If the data is an empty string or a string that has no effect (consists
18084 entirely of comments), the router declines.
18086 .cindex "NFS" "checking for file existence"
18087 If the attempt to open the file fails with a &"does not exist"& error, Exim
18088 runs a check on the containing directory,
18089 unless &%ignore_enotdir%& is true (see below).
18090 If the directory does not appear to exist, delivery is deferred. This can
18091 happen when users' &_.forward_& files are in NFS-mounted directories, and there
18092 is a mount problem. If the containing directory does exist, but the file does
18093 not, the router declines.
18096 .option file_transport redirect string&!! unset
18097 .vindex "&$address_file$&"
18098 A &(redirect)& router sets up a direct delivery to a file when a path name not
18099 ending in a slash is specified as a new &"address"&. The transport used is
18100 specified by this option, which, after expansion, must be the name of a
18101 configured transport. This should normally be an &(appendfile)& transport. When
18102 it is running, the file name is in &$address_file$&.
18105 .option filter_prepend_home redirect boolean true
18106 When this option is true, if a &(save)& command in an Exim filter specifies a
18107 relative path, and &$home$& is defined, it is automatically prepended to the
18108 relative path. If this option is set false, this action does not happen. The
18109 relative path is then passed to the transport unmodified.
18112 .option forbid_blackhole redirect boolean false
18113 If this option is true, the &':blackhole:'& item may not appear in a
18117 .option forbid_exim_filter redirect boolean false
18118 If this option is set true, only Sieve filters are permitted when
18119 &%allow_filter%& is true.
18124 .option forbid_file redirect boolean false
18125 .cindex "delivery" "to file; forbidding"
18126 .cindex "Sieve filter" "forbidding delivery to a file"
18127 .cindex "Sieve filter" "&""keep""& facility; disabling"
18128 If this option is true, this router may not generate a new address that
18129 specifies delivery to a local file or directory, either from a filter or from a
18130 conventional forward file. This option is forced to be true if &%one_time%& is
18131 set. It applies to Sieve filters as well as to Exim filters, but if true, it
18132 locks out the Sieve's &"keep"& facility.
18135 .option forbid_filter_dlfunc redirect boolean false
18136 .cindex "filter" "locking out certain features"
18137 If this option is true, string expansions in Exim filters are not allowed to
18138 make use of the &%dlfunc%& expansion facility to run dynamically loaded
18141 .option forbid_filter_existstest redirect boolean false
18142 .cindex "expansion" "statting a file"
18143 If this option is true, string expansions in Exim filters are not allowed to
18144 make use of the &%exists%& condition or the &%stat%& expansion item.
18146 .option forbid_filter_logwrite redirect boolean false
18147 If this option is true, use of the logging facility in Exim filters is not
18148 permitted. Logging is in any case available only if the filter is being run
18149 under some unprivileged uid (which is normally the case for ordinary users'
18150 &_.forward_& files).
18153 .option forbid_filter_lookup redirect boolean false
18154 If this option is true, string expansions in Exim filter files are not allowed
18155 to make use of &%lookup%& items.
18158 .option forbid_filter_perl redirect boolean false
18159 This option has an effect only if Exim is built with embedded Perl support. If
18160 it is true, string expansions in Exim filter files are not allowed to make use
18161 of the embedded Perl support.
18164 .option forbid_filter_readfile redirect boolean false
18165 If this option is true, string expansions in Exim filter files are not allowed
18166 to make use of &%readfile%& items.
18169 .option forbid_filter_readsocket redirect boolean false
18170 If this option is true, string expansions in Exim filter files are not allowed
18171 to make use of &%readsocket%& items.
18174 .option forbid_filter_reply redirect boolean false
18175 If this option is true, this router may not generate an automatic reply
18176 message. Automatic replies can be generated only from Exim or Sieve filter
18177 files, not from traditional forward files. This option is forced to be true if
18178 &%one_time%& is set.
18181 .option forbid_filter_run redirect boolean false
18182 If this option is true, string expansions in Exim filter files are not allowed
18183 to make use of &%run%& items.
18186 .option forbid_include redirect boolean false
18187 If this option is true, items of the form
18189 :include:<path name>
18191 are not permitted in non-filter redirection lists.
18194 .option forbid_pipe redirect boolean false
18195 .cindex "delivery" "to pipe; forbidding"
18196 If this option is true, this router may not generate a new address which
18197 specifies delivery to a pipe, either from an Exim filter or from a conventional
18198 forward file. This option is forced to be true if &%one_time%& is set.
18201 .option forbid_sieve_filter redirect boolean false
18202 If this option is set true, only Exim filters are permitted when
18203 &%allow_filter%& is true.
18206 .cindex "SMTP" "error codes"
18207 .option forbid_smtp_code redirect boolean false
18208 If this option is set true, any SMTP error codes that are present at the start
18209 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
18210 the default codes (451 and 550, respectively) are always used.
18215 .option hide_child_in_errmsg redirect boolean false
18216 .cindex "bounce message" "redirection details; suppressing"
18217 If this option is true, it prevents Exim from quoting a child address if it
18218 generates a bounce or delay message for it. Instead it says &"an address
18219 generated from <&'the top level address'&>"&. Of course, this applies only to
18220 bounces generated locally. If a message is forwarded to another host, &'its'&
18221 bounce may well quote the generated address.
18224 .option ignore_eacces redirect boolean false
18226 If this option is set and an attempt to open a redirection file yields the
18227 EACCES error (permission denied), the &(redirect)& router behaves as if the
18228 file did not exist.
18231 .option ignore_enotdir redirect boolean false
18233 If this option is set and an attempt to open a redirection file yields the
18234 ENOTDIR error (something on the path is not a directory), the &(redirect)&
18235 router behaves as if the file did not exist.
18237 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
18238 router that has the &%file%& option set discovers that the file does not exist
18239 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
18240 against unmounted NFS directories. If the parent can not be statted, delivery
18241 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
18242 is set, because that option tells Exim to ignore &"something on the path is not
18243 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
18244 that some operating systems give ENOENT where others give ENOTDIR.
18248 .option include_directory redirect string unset
18249 If this option is set, the path names of any &':include:'& items in a
18250 redirection list must start with this directory.
18253 .option modemask redirect "octal integer" 022
18254 This specifies mode bits which must not be set for a file specified by the
18255 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
18258 .option one_time redirect boolean false
18259 .cindex "one-time aliasing/forwarding expansion"
18260 .cindex "alias file" "one-time expansion"
18261 .cindex "forward file" "one-time expansion"
18262 .cindex "mailing lists" "one-time expansion"
18263 .cindex "address redirection" "one-time expansion"
18264 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
18265 files each time it tries to deliver a message causes a problem when one or more
18266 of the generated addresses fails be delivered at the first attempt. The problem
18267 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
18268 but of what happens when the redirection list changes during the time that the
18269 message is on Exim's queue. This is particularly true in the case of mailing
18270 lists, where new subscribers might receive copies of messages that were posted
18271 before they subscribed.
18273 If &%one_time%& is set and any addresses generated by the router fail to
18274 deliver at the first attempt, the failing addresses are added to the message as
18275 &"top level"& addresses, and the parent address that generated them is marked
18276 &"delivered"&. Thus, redirection does not happen again at the next delivery
18279 &*Warning 1*&: Any header line addition or removal that is specified by this
18280 router would be lost if delivery did not succeed at the first attempt. For this
18281 reason, the &%headers_add%& and &%headers_remove%& generic options are not
18282 permitted when &%one_time%& is set.
18284 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
18285 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
18286 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
18288 &*Warning 3*&: The &%unseen%& generic router option may not be set with
18291 The original top-level address is remembered with each of the generated
18292 addresses, and is output in any log messages. However, any intermediate parent
18293 addresses are not recorded. This makes a difference to the log only if
18294 &%all_parents%& log selector is set. It is expected that &%one_time%& will
18295 typically be used for mailing lists, where there is normally just one level of
18299 .option owners redirect "string list" unset
18300 .cindex "ownership" "alias file"
18301 .cindex "ownership" "forward file"
18302 .cindex "alias file" "ownership"
18303 .cindex "forward file" "ownership"
18304 This specifies a list of permitted owners for the file specified by &%file%&.
18305 This list is in addition to the local user when &%check_local_user%& is set.
18306 See &%check_owner%& above.
18309 .option owngroups redirect "string list" unset
18310 This specifies a list of permitted groups for the file specified by &%file%&.
18311 The list is in addition to the local user's primary group when
18312 &%check_local_user%& is set. See &%check_group%& above.
18315 .option pipe_transport redirect string&!! unset
18316 .vindex "&$address_pipe$&"
18317 A &(redirect)& router sets up a direct delivery to a pipe when a string
18318 starting with a vertical bar character is specified as a new &"address"&. The
18319 transport used is specified by this option, which, after expansion, must be the
18320 name of a configured transport. This should normally be a &(pipe)& transport.
18321 When the transport is run, the pipe command is in &$address_pipe$&.
18324 .option qualify_domain redirect string&!! unset
18325 .vindex "&$qualify_recipient$&"
18326 If this option is set, and an unqualified address (one without a domain) is
18327 generated, and that address would normally be qualified by the global setting
18328 in &%qualify_recipient%&, it is instead qualified with the domain specified by
18329 expanding this string. If the expansion fails, the router declines. If you want
18330 to revert to the default, you can have the expansion generate
18331 &$qualify_recipient$&.
18333 This option applies to all unqualified addresses generated by Exim filters,
18334 but for traditional &_.forward_& files, it applies only to addresses that are
18335 not preceded by a backslash. Sieve filters cannot generate unqualified
18338 .option qualify_preserve_domain redirect boolean false
18339 .cindex "domain" "in redirection; preserving"
18340 .cindex "preserving domain in redirection"
18341 .cindex "address redirection" "domain; preserving"
18342 If this option is set, the router's local &%qualify_domain%& option must not be
18343 set (a configuration error occurs if it is). If an unqualified address (one
18344 without a domain) is generated, it is qualified with the domain of the parent
18345 address (the immediately preceding ancestor) instead of the global
18346 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
18347 this applies whether or not the address is preceded by a backslash.
18350 .option repeat_use redirect boolean true
18351 If this option is set false, the router is skipped for a child address that has
18352 any ancestor that was routed by this router. This test happens before any of
18353 the other preconditions are tested. Exim's default anti-looping rules skip
18354 only when the ancestor is the same as the current address. See also
18355 &%check_ancestor%& above and the generic &%redirect_router%& option.
18358 .option reply_transport redirect string&!! unset
18359 A &(redirect)& router sets up an automatic reply when a &%mail%& or
18360 &%vacation%& command is used in a filter file. The transport used is specified
18361 by this option, which, after expansion, must be the name of a configured
18362 transport. This should normally be an &(autoreply)& transport. Other transports
18363 are unlikely to do anything sensible or useful.
18366 .option rewrite redirect boolean true
18367 .cindex "address redirection" "disabling rewriting"
18368 If this option is set false, addresses generated by the router are not
18369 subject to address rewriting. Otherwise, they are treated like new addresses
18370 and are rewritten according to the global rewriting rules.
18373 .option sieve_subaddress redirect string&!! unset
18374 The value of this option is passed to a Sieve filter to specify the
18375 :subaddress part of an address.
18377 .option sieve_useraddress redirect string&!! unset
18378 The value of this option is passed to a Sieve filter to specify the :user part
18379 of an address. However, if it is unset, the entire original local part
18380 (including any prefix or suffix) is used for :user.
18383 .option sieve_vacation_directory redirect string&!! unset
18384 .cindex "Sieve filter" "vacation directory"
18385 To enable the &"vacation"& extension for Sieve filters, you must set
18386 &%sieve_vacation_directory%& to the directory where vacation databases are held
18387 (do not put anything else in that directory), and ensure that the
18388 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
18389 needs their own directory; Exim will create it if necessary.
18393 .option skip_syntax_errors redirect boolean false
18394 .cindex "forward file" "broken"
18395 .cindex "address redirection" "broken files"
18396 .cindex "alias file" "broken"
18397 .cindex "broken alias or forward files"
18398 .cindex "ignoring faulty addresses"
18399 .cindex "skipping faulty addresses"
18400 .cindex "error" "skipping bad syntax"
18401 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
18402 non-filter redirection data are skipped, and each failing address is logged. If
18403 &%syntax_errors_to%& is set, a message is sent to the address it defines,
18404 giving details of the failures. If &%syntax_errors_text%& is set, its contents
18405 are expanded and placed at the head of the error message generated by
18406 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
18407 be the same address as the generic &%errors_to%& option. The
18408 &%skip_syntax_errors%& option is often used when handling mailing lists.
18410 If all the addresses in a redirection list are skipped because of syntax
18411 errors, the router declines to handle the original address, and it is passed to
18412 the following routers.
18414 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
18415 error in the filter causes filtering to be abandoned without any action being
18416 taken. The incident is logged, and the router declines to handle the address,
18417 so it is passed to the following routers.
18419 .cindex "Sieve filter" "syntax errors in"
18420 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
18421 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
18422 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
18424 &%skip_syntax_errors%& can be used to specify that errors in users' forward
18425 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
18426 option, used with an address that does not get redirected, can be used to
18427 notify users of these errors, by means of a router like this:
18433 file = $home/.forward
18434 file_transport = address_file
18435 pipe_transport = address_pipe
18436 reply_transport = address_reply
18439 syntax_errors_to = real-$local_part@$domain
18440 syntax_errors_text = \
18441 This is an automatically generated message. An error has\n\
18442 been found in your .forward file. Details of the error are\n\
18443 reported below. While this error persists, you will receive\n\
18444 a copy of this message for every message that is addressed\n\
18445 to you. If your .forward file is a filter file, or if it is\n\
18446 a non-filter file containing no valid forwarding addresses,\n\
18447 a copy of each incoming message will be put in your normal\n\
18448 mailbox. If a non-filter file contains at least one valid\n\
18449 forwarding address, forwarding to the valid addresses will\n\
18450 happen, and those will be the only deliveries that occur.
18452 You also need a router to ensure that local addresses that are prefixed by
18453 &`real-`& are recognized, but not forwarded or filtered. For example, you could
18454 put this immediately before the &(userforward)& router:
18459 local_part_prefix = real-
18460 transport = local_delivery
18462 For security, it would probably be a good idea to restrict the use of this
18463 router to locally-generated messages, using a condition such as this:
18465 condition = ${if match {$sender_host_address}\
18466 {\N^(|127\.0\.0\.1)$\N}}
18470 .option syntax_errors_text redirect string&!! unset
18471 See &%skip_syntax_errors%& above.
18474 .option syntax_errors_to redirect string unset
18475 See &%skip_syntax_errors%& above.
18476 .ecindex IIDredrou1
18477 .ecindex IIDredrou2
18484 . ////////////////////////////////////////////////////////////////////////////
18485 . ////////////////////////////////////////////////////////////////////////////
18487 .chapter "Environment for running local transports" "CHAPenvironment" &&&
18488 "Environment for local transports"
18489 .scindex IIDenvlotra1 "local transports" "environment for"
18490 .scindex IIDenvlotra2 "environment for local transports"
18491 .scindex IIDenvlotra3 "transport" "local; environment for"
18492 Local transports handle deliveries to files and pipes. (The &(autoreply)&
18493 transport can be thought of as similar to a pipe.) Exim always runs transports
18494 in subprocesses, under specified uids and gids. Typical deliveries to local
18495 mailboxes run under the uid and gid of the local user.
18497 Exim also sets a specific current directory while running the transport; for
18498 some transports a home directory setting is also relevant. The &(pipe)&
18499 transport is the only one that sets up environment variables; see section
18500 &<<SECTpipeenv>>& for details.
18502 The values used for the uid, gid, and the directories may come from several
18503 different places. In many cases, the router that handles the address associates
18504 settings with that address as a result of its &%check_local_user%&, &%group%&,
18505 or &%user%& options. However, values may also be given in the transport's own
18506 configuration, and these override anything that comes from the router.
18510 .section "Concurrent deliveries" "SECID131"
18511 .cindex "concurrent deliveries"
18512 .cindex "simultaneous deliveries"
18513 If two different messages for the same local recipient arrive more or less
18514 simultaneously, the two delivery processes are likely to run concurrently. When
18515 the &(appendfile)& transport is used to write to a file, Exim applies locking
18516 rules to stop concurrent processes from writing to the same file at the same
18519 However, when you use a &(pipe)& transport, it is up to you to arrange any
18520 locking that is needed. Here is a silly example:
18524 command = /bin/sh -c 'cat >>/some/file'
18526 This is supposed to write the message at the end of the file. However, if two
18527 messages arrive at the same time, the file will be scrambled. You can use the
18528 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
18529 file using the same algorithm that Exim itself uses.
18534 .section "Uids and gids" "SECTenvuidgid"
18535 .cindex "local transports" "uid and gid"
18536 .cindex "transport" "local; uid and gid"
18537 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
18538 overrides any group that the router set in the address, even if &%user%& is not
18539 set for the transport. This makes it possible, for example, to run local mail
18540 delivery under the uid of the recipient (set by the router), but in a special
18541 group (set by the transport). For example:
18544 # User/group are set by check_local_user in this router
18548 transport = group_delivery
18551 # This transport overrides the group
18553 driver = appendfile
18554 file = /var/spool/mail/$local_part
18557 If &%user%& is set for a transport, its value overrides what is set in the
18558 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
18559 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
18562 .oindex "&%initgroups%&"
18563 When the uid is taken from the transport's configuration, the &[initgroups()]&
18564 function is called for the groups associated with that uid if the
18565 &%initgroups%& option is set for the transport. When the uid is not specified
18566 by the transport, but is associated with the address by a router, the option
18567 for calling &[initgroups()]& is taken from the router configuration.
18569 .cindex "&(pipe)& transport" "uid for"
18570 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
18571 is set and &%user%& is not set, the uid of the process that called Exim to
18572 receive the message is used, and if &%group%& is not set, the corresponding
18573 original gid is also used.
18575 This is the detailed preference order for obtaining a gid; the first of the
18576 following that is set is used:
18579 A &%group%& setting of the transport;
18581 A &%group%& setting of the router;
18583 A gid associated with a user setting of the router, either as a result of
18584 &%check_local_user%& or an explicit non-numeric &%user%& setting;
18586 The group associated with a non-numeric &%user%& setting of the transport;
18588 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
18589 the uid is the creator's uid;
18591 The Exim gid if the Exim uid is being used as a default.
18594 If, for example, the user is specified numerically on the router and there are
18595 no group settings, no gid is available. In this situation, an error occurs.
18596 This is different for the uid, for which there always is an ultimate default.
18597 The first of the following that is set is used:
18600 A &%user%& setting of the transport;
18602 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
18604 A &%user%& setting of the router;
18606 A &%check_local_user%& setting of the router;
18611 Of course, an error will still occur if the uid that is chosen is on the
18612 &%never_users%& list.
18618 .section "Current and home directories" "SECID132"
18619 .cindex "current directory for local transport"
18620 .cindex "home directory" "for local transport"
18621 .cindex "transport" "local; home directory for"
18622 .cindex "transport" "local; current directory for"
18623 Routers may set current and home directories for local transports by means of
18624 the &%transport_current_directory%& and &%transport_home_directory%& options.
18625 However, if the transport's &%current_directory%& or &%home_directory%& options
18626 are set, they override the router's values. In detail, the home directory
18627 for a local transport is taken from the first of these values that is set:
18630 The &%home_directory%& option on the transport;
18632 The &%transport_home_directory%& option on the router;
18634 The password data if &%check_local_user%& is set on the router;
18636 The &%router_home_directory%& option on the router.
18639 The current directory is taken from the first of these values that is set:
18642 The &%current_directory%& option on the transport;
18644 The &%transport_current_directory%& option on the router.
18648 If neither the router nor the transport sets a current directory, Exim uses the
18649 value of the home directory, if it is set. Otherwise it sets the current
18650 directory to &_/_& before running a local transport.
18654 .section "Expansion variables derived from the address" "SECID133"
18655 .vindex "&$domain$&"
18656 .vindex "&$local_part$&"
18657 .vindex "&$original_domain$&"
18658 Normally a local delivery is handling a single address, and in that case the
18659 variables such as &$domain$& and &$local_part$& are set during local
18660 deliveries. However, in some circumstances more than one address may be handled
18661 at once (for example, while writing batch SMTP for onward transmission by some
18662 other means). In this case, the variables associated with the local part are
18663 never set, &$domain$& is set only if all the addresses have the same domain,
18664 and &$original_domain$& is never set.
18665 .ecindex IIDenvlotra1
18666 .ecindex IIDenvlotra2
18667 .ecindex IIDenvlotra3
18675 . ////////////////////////////////////////////////////////////////////////////
18676 . ////////////////////////////////////////////////////////////////////////////
18678 .chapter "Generic options for transports" "CHAPtransportgeneric"
18679 .scindex IIDgenoptra1 "generic options" "transport"
18680 .scindex IIDgenoptra2 "options" "generic; for transports"
18681 .scindex IIDgenoptra3 "transport" "generic options for"
18682 The following generic options apply to all transports:
18685 .option body_only transports boolean false
18686 .cindex "transport" "body only"
18687 .cindex "message" "transporting body only"
18688 .cindex "body of message" "transporting"
18689 If this option is set, the message's headers are not transported. It is
18690 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
18691 or &(pipe)& transports, the settings of &%message_prefix%& and
18692 &%message_suffix%& should be checked, because this option does not
18693 automatically suppress them.
18696 .option current_directory transports string&!! unset
18697 .cindex "transport" "current directory for"
18698 This specifies the current directory that is to be set while running the
18699 transport, overriding any value that may have been set by the router.
18700 If the expansion fails for any reason, including forced failure, an error is
18701 logged, and delivery is deferred.
18704 .option disable_logging transports boolean false
18705 If this option is set true, nothing is logged for any
18706 deliveries by the transport or for any
18707 transport errors. You should not set this option unless you really, really know
18708 what you are doing.
18711 .option debug_print transports string&!! unset
18712 .cindex "testing" "variables in drivers"
18713 If this option is set and debugging is enabled (see the &%-d%& command line
18714 option), the string is expanded and included in the debugging output when the
18716 If expansion of the string fails, the error message is written to the debugging
18717 output, and Exim carries on processing.
18718 This facility is provided to help with checking out the values of variables and
18719 so on when debugging driver configurations. For example, if a &%headers_add%&
18720 option is not working properly, &%debug_print%& could be used to output the
18721 variables it references. A newline is added to the text if it does not end with
18725 .option delivery_date_add transports boolean false
18726 .cindex "&'Delivery-date:'& header line"
18727 If this option is true, a &'Delivery-date:'& header is added to the message.
18728 This gives the actual time the delivery was made. As this is not a standard
18729 header, Exim has a configuration option (&%delivery_date_remove%&) which
18730 requests its removal from incoming messages, so that delivered messages can
18731 safely be resent to other recipients.
18734 .option driver transports string unset
18735 This specifies which of the available transport drivers is to be used.
18736 There is no default, and this option must be set for every transport.
18739 .option envelope_to_add transports boolean false
18740 .cindex "&'Envelope-to:'& header line"
18741 If this option is true, an &'Envelope-to:'& header is added to the message.
18742 This gives the original address(es) in the incoming envelope that caused this
18743 delivery to happen. More than one address may be present if the transport is
18744 configured to handle several addresses at once, or if more than one original
18745 address was redirected to the same final address. As this is not a standard
18746 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
18747 its removal from incoming messages, so that delivered messages can safely be
18748 resent to other recipients.
18751 .option group transports string&!! "Exim group"
18752 .cindex "transport" "group; specifying"
18753 This option specifies a gid for running the transport process, overriding any
18754 value that the router supplies, and also overriding any value associated with
18755 &%user%& (see below).
18758 .option headers_add transports string&!! unset
18759 .cindex "header lines" "adding in transport"
18760 .cindex "transport" "header lines; adding"
18761 This option specifies a string of text that is expanded and added to the header
18762 portion of a message as it is transported, as described in section
18763 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
18764 routers. If the result of the expansion is an empty string, or if the expansion
18765 is forced to fail, no action is taken. Other expansion failures are treated as
18766 errors and cause the delivery to be deferred.
18770 .option headers_only transports boolean false
18771 .cindex "transport" "header lines only"
18772 .cindex "message" "transporting headers only"
18773 .cindex "header lines" "transporting"
18774 If this option is set, the message's body is not transported. It is mutually
18775 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
18776 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
18777 checked, since this option does not automatically suppress them.
18780 .option headers_remove transports string&!! unset
18781 .cindex "header lines" "removing"
18782 .cindex "transport" "header lines; removing"
18783 This option specifies a string that is expanded into a list of header names;
18784 these headers are omitted from the message as it is transported, as described
18785 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
18786 routers. If the result of the expansion is an empty string, or if the expansion
18787 is forced to fail, no action is taken. Other expansion failures are treated as
18788 errors and cause the delivery to be deferred.
18792 .option headers_rewrite transports string unset
18793 .cindex "transport" "header lines; rewriting"
18794 .cindex "rewriting" "at transport time"
18795 This option allows addresses in header lines to be rewritten at transport time,
18796 that is, as the message is being copied to its destination. The contents of the
18797 option are a colon-separated list of rewriting rules. Each rule is in exactly
18798 the same form as one of the general rewriting rules that are applied when a
18799 message is received. These are described in chapter &<<CHAPrewrite>>&. For
18802 headers_rewrite = a@b c@d f : \
18805 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
18806 &'w@z'& in all address-bearing header lines. The rules are applied to the
18807 header lines just before they are written out at transport time, so they affect
18808 only those copies of the message that pass through the transport. However, only
18809 the message's original header lines, and any that were added by a system
18810 filter, are rewritten. If a router or transport adds header lines, they are not
18811 affected by this option. These rewriting rules are &'not'& applied to the
18812 envelope. You can change the return path using &%return_path%&, but you cannot
18813 change envelope recipients at this time.
18816 .option home_directory transports string&!! unset
18817 .cindex "transport" "home directory for"
18819 This option specifies a home directory setting for a local transport,
18820 overriding any value that may be set by the router. The home directory is
18821 placed in &$home$& while expanding the transport's private options. It is also
18822 used as the current directory if no current directory is set by the
18823 &%current_directory%& option on the transport or the
18824 &%transport_current_directory%& option on the router. If the expansion fails
18825 for any reason, including forced failure, an error is logged, and delivery is
18829 .option initgroups transports boolean false
18830 .cindex "additional groups"
18831 .cindex "groups" "additional"
18832 .cindex "transport" "group; additional"
18833 If this option is true and the uid for the delivery process is provided by the
18834 transport, the &[initgroups()]& function is called when running the transport
18835 to ensure that any additional groups associated with the uid are set up.
18838 .option message_size_limit transports string&!! 0
18839 .cindex "limit" "message size per transport"
18840 .cindex "size" "of message, limit"
18841 .cindex "transport" "message size; limiting"
18842 This option controls the size of messages passed through the transport. It is
18843 expanded before use; the result of the expansion must be a sequence of decimal
18844 digits, optionally followed by K or M. If the expansion fails for any reason,
18845 including forced failure, or if the result is not of the required form,
18846 delivery is deferred. If the value is greater than zero and the size of a
18847 message exceeds this limit, the address is failed. If there is any chance that
18848 the resulting bounce message could be routed to the same transport, you should
18849 ensure that &%return_size_limit%& is less than the transport's
18850 &%message_size_limit%&, as otherwise the bounce message will fail to get
18855 .option rcpt_include_affixes transports boolean false
18856 .cindex "prefix" "for local part, including in envelope"
18857 .cindex "suffix for local part" "including in envelope"
18858 .cindex "local part" "prefix"
18859 .cindex "local part" "suffix"
18860 When this option is false (the default), and an address that has had any
18861 affixes (prefixes or suffixes) removed from the local part is delivered by any
18862 form of SMTP or LMTP, the affixes are not included. For example, if a router
18865 local_part_prefix = *-
18867 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
18870 RCPT TO:<xyz@some.domain>
18872 This is also the case when an ACL-time callout is being used to verify a
18873 recipient address. However, if &%rcpt_include_affixes%& is set true, the
18874 whole local part is included in the RCPT command. This option applies to BSMTP
18875 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
18876 &(lmtp)& and &(smtp)& transports.
18879 .option retry_use_local_part transports boolean "see below"
18880 .cindex "hints database" "retry keys"
18881 When a delivery suffers a temporary failure, a retry record is created
18882 in Exim's hints database. For remote deliveries, the key for the retry record
18883 is based on the name and/or IP address of the failing remote host. For local
18884 deliveries, the key is normally the entire address, including both the local
18885 part and the domain. This is suitable for most common cases of local delivery
18886 temporary failure &-- for example, exceeding a mailbox quota should delay only
18887 deliveries to that mailbox, not to the whole domain.
18889 However, in some special cases you may want to treat a temporary local delivery
18890 as a failure associated with the domain, and not with a particular local part.
18891 (For example, if you are storing all mail for some domain in files.) You can do
18892 this by setting &%retry_use_local_part%& false.
18894 For all the local transports, its default value is true. For remote transports,
18895 the default value is false for tidiness, but changing the value has no effect
18896 on a remote transport in the current implementation.
18899 .option return_path transports string&!! unset
18900 .cindex "envelope sender"
18901 .cindex "transport" "return path; changing"
18902 .cindex "return path" "changing in transport"
18903 If this option is set, the string is expanded at transport time and replaces
18904 the existing return path (envelope sender) value in the copy of the message
18905 that is being delivered. An empty return path is permitted. This feature is
18906 designed for remote deliveries, where the value of this option is used in the
18907 SMTP MAIL command. If you set &%return_path%& for a local transport, the
18908 only effect is to change the address that is placed in the &'Return-path:'&
18909 header line, if one is added to the message (see the next option).
18911 &*Note:*& A changed return path is not logged unless you add
18912 &%return_path_on_delivery%& to the log selector.
18914 .vindex "&$return_path$&"
18915 The expansion can refer to the existing value via &$return_path$&. This is
18916 either the message's envelope sender, or an address set by the
18917 &%errors_to%& option on a router. If the expansion is forced to fail, no
18918 replacement occurs; if it fails for another reason, delivery is deferred. This
18919 option can be used to support VERP (Variable Envelope Return Paths) &-- see
18920 section &<<SECTverp>>&.
18922 &*Note*&: If a delivery error is detected locally, including the case when a
18923 remote server rejects a message at SMTP time, the bounce message is not sent to
18924 the value of this option. It is sent to the previously set errors address.
18925 This defaults to the incoming sender address, but can be changed by setting
18926 &%errors_to%& in a router.
18930 .option return_path_add transports boolean false
18931 .cindex "&'Return-path:'& header line"
18932 If this option is true, a &'Return-path:'& header is added to the message.
18933 Although the return path is normally available in the prefix line of BSD
18934 mailboxes, this is commonly not displayed by MUAs, and so the user does not
18935 have easy access to it.
18937 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
18938 the delivery SMTP server makes the final delivery"&. This implies that this
18939 header should not be present in incoming messages. Exim has a configuration
18940 option, &%return_path_remove%&, which requests removal of this header from
18941 incoming messages, so that delivered messages can safely be resent to other
18945 .option shadow_condition transports string&!! unset
18946 See &%shadow_transport%& below.
18949 .option shadow_transport transports string unset
18950 .cindex "shadow transport"
18951 .cindex "transport" "shadow"
18952 A local transport may set the &%shadow_transport%& option to the name of
18953 another local transport. Shadow remote transports are not supported.
18955 Whenever a delivery to the main transport succeeds, and either
18956 &%shadow_condition%& is unset, or its expansion does not result in the empty
18957 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
18958 passed to the shadow transport, with the same delivery address or addresses. If
18959 expansion fails, no action is taken except that non-forced expansion failures
18960 cause a log line to be written.
18962 The result of the shadow transport is discarded and does not affect the
18963 subsequent processing of the message. Only a single level of shadowing is
18964 provided; the &%shadow_transport%& option is ignored on any transport when it
18965 is running as a shadow. Options concerned with output from pipes are also
18966 ignored. The log line for the successful delivery has an item added on the end,
18969 ST=<shadow transport name>
18971 If the shadow transport did not succeed, the error message is put in
18972 parentheses afterwards. Shadow transports can be used for a number of different
18973 purposes, including keeping more detailed log information than Exim normally
18974 provides, and implementing automatic acknowledgment policies based on message
18975 headers that some sites insist on.
18978 .option transport_filter transports string&!! unset
18979 .cindex "transport" "filter"
18980 .cindex "filter" "transport filter"
18981 This option sets up a filtering (in the Unix shell sense) process for messages
18982 at transport time. It should not be confused with mail filtering as set up by
18983 individual users or via a system filter.
18985 When the message is about to be written out, the command specified by
18986 &%transport_filter%& is started up in a separate, parallel process, and
18987 the entire message, including the header lines, is passed to it on its standard
18988 input (this in fact is done from a third process, to avoid deadlock). The
18989 command must be specified as an absolute path.
18991 The lines of the message that are written to the transport filter are
18992 terminated by newline (&"\n"&). The message is passed to the filter before any
18993 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
18994 lines beginning with a dot, and also before any processing implied by the
18995 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
18996 &(pipe)& transports.
18998 The standard error for the filter process is set to the same destination as its
18999 standard output; this is read and written to the message's ultimate
19000 destination. The process that writes the message to the filter, the
19001 filter itself, and the original process that reads the result and delivers it
19002 are all run in parallel, like a shell pipeline.
19004 The filter can perform any transformations it likes, but of course should take
19005 care not to break RFC 2822 syntax. Exim does not check the result, except to
19006 test for a final newline when SMTP is in use. All messages transmitted over
19007 SMTP must end with a newline, so Exim supplies one if it is missing.
19009 .cindex "content scanning" "per user"
19010 A transport filter can be used to provide content-scanning on a per-user basis
19011 at delivery time if the only required effect of the scan is to modify the
19012 message. For example, a content scan could insert a new header line containing
19013 a spam score. This could be interpreted by a filter in the user's MUA. It is
19014 not possible to discard a message at this stage.
19016 .cindex "SMTP" "SIZE"
19017 A problem might arise if the filter increases the size of a message that is
19018 being sent down an SMTP connection. If the receiving SMTP server has indicated
19019 support for the SIZE parameter, Exim will have sent the size of the message
19020 at the start of the SMTP session. If what is actually sent is substantially
19021 more, the server might reject the message. This can be worked round by setting
19022 the &%size_addition%& option on the &(smtp)& transport, either to allow for
19023 additions to the message, or to disable the use of SIZE altogether.
19025 .vindex "&$pipe_addresses$&"
19026 The value of the &%transport_filter%& option is the command string for starting
19027 the filter, which is run directly from Exim, not under a shell. The string is
19028 parsed by Exim in the same way as a command string for the &(pipe)& transport:
19029 Exim breaks it up into arguments and then expands each argument separately (see
19030 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
19031 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
19032 of arguments, one for each address that applies to this delivery. (This isn't
19033 an ideal name for this feature here, but as it was already implemented for the
19034 &(pipe)& transport, it seemed sensible not to change it.)
19037 .vindex "&$host_address$&"
19038 The expansion variables &$host$& and &$host_address$& are available when the
19039 transport is a remote one. They contain the name and IP address of the host to
19040 which the message is being sent. For example:
19042 transport_filter = /some/directory/transport-filter.pl \
19043 $host $host_address $sender_address $pipe_addresses
19046 Two problems arise if you want to use more complicated expansion items to
19047 generate transport filter commands, both of which due to the fact that the
19048 command is split up &'before'& expansion.
19050 If an expansion item contains white space, you must quote it, so that it is all
19051 part of the same command item. If the entire option setting is one such
19052 expansion item, you have to take care what kind of quoting you use. For
19055 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
19057 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
19058 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
19059 stripped by Exim when it read the option's value. When the value is used, if
19060 the single quotes were missing, the line would be split into two items,
19061 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
19062 Exim tried to expand the first one.
19064 Except for the special case of &$pipe_addresses$& that is mentioned above, an
19065 expansion cannot generate multiple arguments, or a command name followed by
19066 arguments. Consider this example:
19068 transport_filter = ${lookup{$host}lsearch{/a/file}\
19069 {$value}{/bin/cat}}
19071 The result of the lookup is interpreted as the name of the command, even
19072 if it contains white space. The simplest way round this is to use a shell:
19074 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
19075 {$value}{/bin/cat}}
19079 The filter process is run under the same uid and gid as the normal delivery.
19080 For remote deliveries this is the Exim uid/gid by default. The command should
19081 normally yield a zero return code. Transport filters are not supposed to fail.
19082 A non-zero code is taken to mean that the transport filter encountered some
19083 serious problem. Delivery of the message is deferred; the message remains on
19084 the queue and is tried again later. It is not possible to cause a message to be
19085 bounced from a transport filter.
19087 If a transport filter is set on an autoreply transport, the original message is
19088 passed through the filter as it is being copied into the newly generated
19089 message, which happens if the &%return_message%& option is set.
19092 .option transport_filter_timeout transports time 5m
19093 .cindex "transport" "filter, timeout"
19094 When Exim is reading the output of a transport filter, it a applies a timeout
19095 that can be set by this option. Exceeding the timeout is normally treated as a
19096 temporary delivery failure. However, if a transport filter is used with a
19097 &(pipe)& transport, a timeout in the transport filter is treated in the same
19098 way as a timeout in the pipe command itself. By default, a timeout is a hard
19099 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
19100 becomes a temporary error.
19103 .option user transports string&!! "Exim user"
19104 .cindex "uid (user id)" "local delivery"
19105 .cindex "transport" "user, specifying"
19106 This option specifies the user under whose uid the delivery process is to be
19107 run, overriding any uid that may have been set by the router. If the user is
19108 given as a name, the uid is looked up from the password data, and the
19109 associated group is taken as the value of the gid to be used if the &%group%&
19112 For deliveries that use local transports, a user and group are normally
19113 specified explicitly or implicitly (for example, as a result of
19114 &%check_local_user%&) by the router or transport.
19116 .cindex "hints database" "access by remote transport"
19117 For remote transports, you should leave this option unset unless you really are
19118 sure you know what you are doing. When a remote transport is running, it needs
19119 to be able to access Exim's hints databases, because each host may have its own
19121 .ecindex IIDgenoptra1
19122 .ecindex IIDgenoptra2
19123 .ecindex IIDgenoptra3
19130 . ////////////////////////////////////////////////////////////////////////////
19131 . ////////////////////////////////////////////////////////////////////////////
19133 .chapter "Address batching in local transports" "CHAPbatching" &&&
19135 .cindex "transport" "local; address batching in"
19136 The only remote transport (&(smtp)&) is normally configured to handle more than
19137 one address at a time, so that when several addresses are routed to the same
19138 remote host, just one copy of the message is sent. Local transports, however,
19139 normally handle one address at a time. That is, a separate instance of the
19140 transport is run for each address that is routed to the transport. A separate
19141 copy of the message is delivered each time.
19143 .cindex "batched local delivery"
19144 .oindex "&%batch_max%&"
19145 .oindex "&%batch_id%&"
19146 In special cases, it may be desirable to handle several addresses at once in a
19147 local transport, for example:
19150 In an &(appendfile)& transport, when storing messages in files for later
19151 delivery by some other means, a single copy of the message with multiple
19152 recipients saves space.
19154 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
19155 a single copy saves time, and is the normal way LMTP is expected to work.
19157 In a &(pipe)& transport, when passing the message
19158 to a scanner program or
19159 to some other delivery mechanism such as UUCP, multiple recipients may be
19163 These three local transports all have the same options for controlling multiple
19164 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
19165 repeating the information for each transport, these options are described here.
19167 The &%batch_max%& option specifies the maximum number of addresses that can be
19168 delivered together in a single run of the transport. Its default value is one
19169 (no batching). When more than one address is routed to a transport that has a
19170 &%batch_max%& value greater than one, the addresses are delivered in a batch
19171 (that is, in a single run of the transport with multiple recipients), subject
19172 to certain conditions:
19175 .vindex "&$local_part$&"
19176 If any of the transport's options contain a reference to &$local_part$&, no
19177 batching is possible.
19179 .vindex "&$domain$&"
19180 If any of the transport's options contain a reference to &$domain$&, only
19181 addresses with the same domain are batched.
19183 .cindex "customizing" "batching condition"
19184 If &%batch_id%& is set, it is expanded for each address, and only those
19185 addresses with the same expanded value are batched. This allows you to specify
19186 customized batching conditions. Failure of the expansion for any reason,
19187 including forced failure, disables batching, but it does not stop the delivery
19190 Batched addresses must also have the same errors address (where to send
19191 delivery errors), the same header additions and removals, the same user and
19192 group for the transport, and if a host list is present, the first host must
19196 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
19197 both when the file or pipe command is specified in the transport, and when it
19198 is specified by a &(redirect)& router, but all the batched addresses must of
19199 course be routed to the same file or pipe command. These two transports have an
19200 option called &%use_bsmtp%&, which causes them to deliver the message in
19201 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
19202 &%check_string%& and &%escape_string%& options are forced to the values
19205 escape_string = ".."
19207 when batched SMTP is in use. A full description of the batch SMTP mechanism is
19208 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
19209 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
19211 .cindex "&'Envelope-to:'& header line"
19212 If the generic &%envelope_to_add%& option is set for a batching transport, the
19213 &'Envelope-to:'& header that is added to the message contains all the addresses
19214 that are being processed together. If you are using a batching &(appendfile)&
19215 transport without &%use_bsmtp%&, the only way to preserve the recipient
19216 addresses is to set the &%envelope_to_add%& option.
19218 .cindex "&(pipe)& transport" "with multiple addresses"
19219 .vindex "&$pipe_addresses$&"
19220 If you are using a &(pipe)& transport without BSMTP, and setting the
19221 transport's &%command%& option, you can include &$pipe_addresses$& as part of
19222 the command. This is not a true variable; it is a bit of magic that causes each
19223 of the recipient addresses to be inserted into the command as a separate
19224 argument. This provides a way of accessing all the addresses that are being
19225 delivered in the batch. &*Note:*& This is not possible for pipe commands that
19226 are specified by a &(redirect)& router.
19231 . ////////////////////////////////////////////////////////////////////////////
19232 . ////////////////////////////////////////////////////////////////////////////
19234 .chapter "The appendfile transport" "CHAPappendfile"
19235 .scindex IIDapptra1 "&(appendfile)& transport"
19236 .scindex IIDapptra2 "transports" "&(appendfile)&"
19237 .cindex "directory creation"
19238 .cindex "creating directories"
19239 The &(appendfile)& transport delivers a message by appending it to an existing
19240 file, or by creating an entirely new file in a specified directory. Single
19241 files to which messages are appended can be in the traditional Unix mailbox
19242 format, or optionally in the MBX format supported by the Pine MUA and
19243 University of Washington IMAP daemon, &'inter alia'&. When each message is
19244 being delivered as a separate file, &"maildir"& format can optionally be used
19245 to give added protection against failures that happen part-way through the
19246 delivery. A third form of separate-file delivery known as &"mailstore"& is also
19247 supported. For all file formats, Exim attempts to create as many levels of
19248 directory as necessary, provided that &%create_directory%& is set.
19250 The code for the optional formats is not included in the Exim binary by
19251 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
19252 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
19255 .cindex "quota" "system"
19256 Exim recognizes system quota errors, and generates an appropriate message. Exim
19257 also supports its own quota control within the transport, for use when the
19258 system facility is unavailable or cannot be used for some reason.
19260 If there is an error while appending to a file (for example, quota exceeded or
19261 partition filled), Exim attempts to reset the file's length and last
19262 modification time back to what they were before. If there is an error while
19263 creating an entirely new file, the new file is removed.
19265 Before appending to a file, a number of security checks are made, and the
19266 file is locked. A detailed description is given below, after the list of
19269 The &(appendfile)& transport is most commonly used for local deliveries to
19270 users' mailboxes. However, it can also be used as a pseudo-remote transport for
19271 putting messages into files for remote delivery by some means other than Exim.
19272 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
19277 .section "The file and directory options" "SECTfildiropt"
19278 The &%file%& option specifies a single file, to which the message is appended;
19279 the &%directory%& option specifies a directory, in which a new file containing
19280 the message is created. Only one of these two options can be set, and for
19281 normal deliveries to mailboxes, one of them &'must'& be set.
19283 .vindex "&$address_file$&"
19284 .vindex "&$local_part$&"
19285 However, &(appendfile)& is also used for delivering messages to files or
19286 directories whose names (or parts of names) are obtained from alias,
19287 forwarding, or filtering operations (for example, a &%save%& command in a
19288 user's Exim filter). When such a transport is running, &$local_part$& contains
19289 the local part that was aliased or forwarded, and &$address_file$& contains the
19290 name (or partial name) of the file or directory generated by the redirection
19291 operation. There are two cases:
19294 If neither &%file%& nor &%directory%& is set, the redirection operation
19295 must specify an absolute path (one that begins with &`/`&). This is the most
19296 common case when users with local accounts use filtering to sort mail into
19297 different folders. See for example, the &(address_file)& transport in the
19298 default configuration. If the path ends with a slash, it is assumed to be the
19299 name of a directory. A delivery to a directory can also be forced by setting
19300 &%maildir_format%& or &%mailstore_format%&.
19302 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
19303 used to determine the file or directory name for the delivery. Normally, the
19304 contents of &$address_file$& are used in some way in the string expansion.
19308 .cindex "Sieve filter" "configuring &(appendfile)&"
19309 .cindex "Sieve filter" "relative mailbox path handling"
19310 As an example of the second case, consider an environment where users do not
19311 have home directories. They may be permitted to use Exim filter commands of the
19316 or Sieve filter commands of the form:
19318 require "fileinto";
19319 fileinto "folder23";
19321 In this situation, the expansion of &%file%& or &%directory%& in the transport
19322 must transform the relative path into an appropriate absolute file name. In the
19323 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
19324 is used as a result of a &"keep"& action in the filter. This example shows one
19325 way of handling this requirement:
19327 file = ${if eq{$address_file}{inbox} \
19328 {/var/mail/$local_part} \
19329 {${if eq{${substr_0_1:$address_file}}{/} \
19331 {$home/mail/$address_file} \
19335 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
19336 location, absolute paths are used without change, and other folders are in the
19337 &_mail_& directory within the home directory.
19339 &*Note 1*&: While processing an Exim filter, a relative path such as
19340 &_folder23_& is turned into an absolute path if a home directory is known to
19341 the router. In particular, this is the case if &%check_local_user%& is set. If
19342 you want to prevent this happening at routing time, you can set
19343 &%router_home_directory%& empty. This forces the router to pass the relative
19344 path to the transport.
19346 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
19347 the &%file%& or &%directory%& option is still used if it is set.
19352 .section "Private options for appendfile" "SECID134"
19353 .cindex "options" "&(appendfile)& transport"
19357 .option allow_fifo appendfile boolean false
19358 .cindex "fifo (named pipe)"
19359 .cindex "named pipe (fifo)"
19360 .cindex "pipe" "named (fifo)"
19361 Setting this option permits delivery to named pipes (FIFOs) as well as to
19362 regular files. If no process is reading the named pipe at delivery time, the
19363 delivery is deferred.
19366 .option allow_symlink appendfile boolean false
19367 .cindex "symbolic link" "to mailbox"
19368 .cindex "mailbox" "symbolic link"
19369 By default, &(appendfile)& will not deliver if the path name for the file is
19370 that of a symbolic link. Setting this option relaxes that constraint, but there
19371 are security issues involved in the use of symbolic links. Be sure you know
19372 what you are doing if you set this. Details of exactly what this option affects
19373 are included in the discussion which follows this list of options.
19376 .option batch_id appendfile string&!! unset
19377 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19378 However, batching is automatically disabled for &(appendfile)& deliveries that
19379 happen as a result of forwarding or aliasing or other redirection directly to a
19383 .option batch_max appendfile integer 1
19384 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
19387 .option check_group appendfile boolean false
19388 When this option is set, the group owner of the file defined by the &%file%&
19389 option is checked to see that it is the same as the group under which the
19390 delivery process is running. The default setting is false because the default
19391 file mode is 0600, which means that the group is irrelevant.
19394 .option check_owner appendfile boolean true
19395 When this option is set, the owner of the file defined by the &%file%& option
19396 is checked to ensure that it is the same as the user under which the delivery
19397 process is running.
19400 .option check_string appendfile string "see below"
19401 .cindex "&""From""& line"
19402 As &(appendfile)& writes the message, the start of each line is tested for
19403 matching &%check_string%&, and if it does, the initial matching characters are
19404 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
19405 a literal string, not a regular expression, and the case of any letters it
19406 contains is significant.
19408 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
19409 are forced to &"."& and &".."& respectively, and any settings in the
19410 configuration are ignored. Otherwise, they default to &"From&~"& and
19411 &">From&~"& when the &%file%& option is set, and unset when any of the
19412 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
19414 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
19415 suitable for traditional &"BSD"& mailboxes, where a line beginning with
19416 &"From&~"& indicates the start of a new message. All four options need changing
19417 if another format is used. For example, to deliver to mailboxes in MMDF format:
19418 .cindex "MMDF format mailbox"
19419 .cindex "mailbox" "MMDF format"
19421 check_string = "\1\1\1\1\n"
19422 escape_string = "\1\1\1\1 \n"
19423 message_prefix = "\1\1\1\1\n"
19424 message_suffix = "\1\1\1\1\n"
19426 .option create_directory appendfile boolean true
19427 .cindex "directory creation"
19428 When this option is true, Exim attempts to create any missing superior
19429 directories for the file that it is about to write. A created directory's mode
19430 is given by the &%directory_mode%& option.
19432 The group ownership of a newly created directory is highly dependent on the
19433 operating system (and possibly the file system) that is being used. For
19434 example, in Solaris, if the parent directory has the setgid bit set, its group
19435 is propagated to the child; if not, the currently set group is used. However,
19436 in FreeBSD, the parent's group is always used.
19440 .option create_file appendfile string anywhere
19441 This option constrains the location of files and directories that are created
19442 by this transport. It applies to files defined by the &%file%& option and
19443 directories defined by the &%directory%& option. In the case of maildir
19444 delivery, it applies to the top level directory, not the maildir directories
19447 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
19448 &"belowhome"&. In the second and third cases, a home directory must have been
19449 set for the transport. This option is not useful when an explicit file name is
19450 given for normal mailbox deliveries. It is intended for the case when file
19451 names are generated from users' &_.forward_& files. These are usually handled
19452 by an &(appendfile)& transport called &%address_file%&. See also
19453 &%file_must_exist%&.
19456 .option directory appendfile string&!! unset
19457 This option is mutually exclusive with the &%file%& option, but one of &%file%&
19458 or &%directory%& must be set, unless the delivery is the direct result of a
19459 redirection (see section &<<SECTfildiropt>>&).
19461 When &%directory%& is set, the string is expanded, and the message is delivered
19462 into a new file or files in or below the given directory, instead of being
19463 appended to a single mailbox file. A number of different formats are provided
19464 (see &%maildir_format%& and &%mailstore_format%&), and see section
19465 &<<SECTopdir>>& for further details of this form of delivery.
19468 .option directory_file appendfile string&!! "see below"
19470 .vindex "&$inode$&"
19471 When &%directory%& is set, but neither &%maildir_format%& nor
19472 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
19473 whose name is obtained by expanding this string. The default value is:
19475 q${base62:$tod_epoch}-$inode
19477 This generates a unique name from the current time, in base 62 form, and the
19478 inode of the file. The variable &$inode$& is available only when expanding this
19482 .option directory_mode appendfile "octal integer" 0700
19483 If &(appendfile)& creates any directories as a result of the
19484 &%create_directory%& option, their mode is specified by this option.
19487 .option escape_string appendfile string "see description"
19488 See &%check_string%& above.
19491 .option file appendfile string&!! unset
19492 This option is mutually exclusive with the &%directory%& option, but one of
19493 &%file%& or &%directory%& must be set, unless the delivery is the direct result
19494 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
19495 specifies a single file, to which the message is appended. One or more of
19496 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
19499 .cindex "NFS" "lock file"
19500 .cindex "locking files"
19501 .cindex "lock files"
19502 If you are using more than one host to deliver over NFS into the same
19503 mailboxes, you should always use lock files.
19505 The string value is expanded for each delivery, and must yield an absolute
19506 path. The most common settings of this option are variations on one of these
19509 file = /var/spool/mail/$local_part
19510 file = /home/$local_part/inbox
19513 .cindex "&""sticky""& bit"
19514 In the first example, all deliveries are done into the same directory. If Exim
19515 is configured to use lock files (see &%use_lockfile%& below) it must be able to
19516 create a file in the directory, so the &"sticky"& bit must be turned on for
19517 deliveries to be possible, or alternatively the &%group%& option can be used to
19518 run the delivery under a group id which has write access to the directory.
19522 .option file_format appendfile string unset
19523 .cindex "file" "mailbox; checking existing format"
19524 This option requests the transport to check the format of an existing file
19525 before adding to it. The check consists of matching a specific string at the
19526 start of the file. The value of the option consists of an even number of
19527 colon-separated strings. The first of each pair is the test string, and the
19528 second is the name of a transport. If the transport associated with a matched
19529 string is not the current transport, control is passed over to the other
19530 transport. For example, suppose the standard &(local_delivery)& transport has
19533 file_format = "From : local_delivery :\
19534 \1\1\1\1\n : local_mmdf_delivery"
19536 Mailboxes that begin with &"From"& are still handled by this transport, but if
19537 a mailbox begins with four binary ones followed by a newline, control is passed
19538 to a transport called &%local_mmdf_delivery%&, which presumably is configured
19539 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
19540 is assumed to match the current transport. If the start of a mailbox doesn't
19541 match any string, or if the transport named for a given string is not defined,
19542 delivery is deferred.
19545 .option file_must_exist appendfile boolean false
19546 If this option is true, the file specified by the &%file%& option must exist.
19547 A temporary error occurs if it does not, causing delivery to be deferred.
19548 If this option is false, the file is created if it does not exist.
19551 .option lock_fcntl_timeout appendfile time 0s
19552 .cindex "timeout" "mailbox locking"
19553 .cindex "mailbox" "locking, blocking and non-blocking"
19554 .cindex "locking files"
19555 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
19556 when locking an open mailbox file. If the call fails, the delivery process
19557 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
19558 Non-blocking calls are used so that the file is not kept open during the wait
19559 for the lock; the reason for this is to make it as safe as possible for
19560 deliveries over NFS in the case when processes might be accessing an NFS
19561 mailbox without using a lock file. This should not be done, but
19562 misunderstandings and hence misconfigurations are not unknown.
19564 On a busy system, however, the performance of a non-blocking lock approach is
19565 not as good as using a blocking lock with a timeout. In this case, the waiting
19566 is done inside the system call, and Exim's delivery process acquires the lock
19567 and can proceed as soon as the previous lock holder releases it.
19569 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
19570 timeout, are used. There may still be some retrying: the maximum number of
19573 (lock_retries * lock_interval) / lock_fcntl_timeout
19575 rounded up to the next whole number. In other words, the total time during
19576 which &(appendfile)& is trying to get a lock is roughly the same, unless
19577 &%lock_fcntl_timeout%& is set very large.
19579 You should consider setting this option if you are getting a lot of delayed
19580 local deliveries because of errors of the form
19582 failed to lock mailbox /some/file (fcntl)
19585 .option lock_flock_timeout appendfile time 0s
19586 This timeout applies to file locking when using &[flock()]& (see
19587 &%use_flock%&); the timeout operates in a similar manner to
19588 &%lock_fcntl_timeout%&.
19591 .option lock_interval appendfile time 3s
19592 This specifies the time to wait between attempts to lock the file. See below
19593 for details of locking.
19596 .option lock_retries appendfile integer 10
19597 This specifies the maximum number of attempts to lock the file. A value of zero
19598 is treated as 1. See below for details of locking.
19601 .option lockfile_mode appendfile "octal integer" 0600
19602 This specifies the mode of the created lock file, when a lock file is being
19603 used (see &%use_lockfile%& and &%use_mbx_lock%&).
19606 .option lockfile_timeout appendfile time 30m
19607 .cindex "timeout" "mailbox locking"
19608 When a lock file is being used (see &%use_lockfile%&), if a lock file already
19609 exists and is older than this value, it is assumed to have been left behind by
19610 accident, and Exim attempts to remove it.
19613 .option mailbox_filecount appendfile string&!! unset
19614 .cindex "mailbox" "specifying size of"
19615 .cindex "size" "of mailbox"
19616 If this option is set, it is expanded, and the result is taken as the current
19617 number of files in the mailbox. It must be a decimal number, optionally
19618 followed by K or M. This provides a way of obtaining this information from an
19619 external source that maintains the data.
19622 .option mailbox_size appendfile string&!! unset
19623 .cindex "mailbox" "specifying size of"
19624 .cindex "size" "of mailbox"
19625 If this option is set, it is expanded, and the result is taken as the current
19626 size the mailbox. It must be a decimal number, optionally followed by K or M.
19627 This provides a way of obtaining this information from an external source that
19628 maintains the data. This is likely to be helpful for maildir deliveries where
19629 it is computationally expensive to compute the size of a mailbox.
19633 .option maildir_format appendfile boolean false
19634 .cindex "maildir format" "specifying"
19635 If this option is set with the &%directory%& option, the delivery is into a new
19636 file, in the &"maildir"& format that is used by other mail software. When the
19637 transport is activated directly from a &(redirect)& router (for example, the
19638 &(address_file)& transport in the default configuration), setting
19639 &%maildir_format%& causes the path received from the router to be treated as a
19640 directory, whether or not it ends with &`/`&. This option is available only if
19641 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
19642 &<<SECTmaildirdelivery>>& below for further details.
19645 .option maildir_quota_directory_regex appendfile string "See below"
19646 .cindex "maildir format" "quota; directories included in"
19647 .cindex "quota" "maildir; directories included in"
19648 This option is relevant only when &%maildir_use_size_file%& is set. It defines
19649 a regular expression for specifying directories, relative to the quota
19650 directory (see &%quota_directory%&), that should be included in the quota
19651 calculation. The default value is:
19653 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
19655 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
19656 (directories whose names begin with a dot). If you want to exclude the
19658 folder from the count (as some sites do), you need to change this setting to
19660 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
19662 This uses a negative lookahead in the regular expression to exclude the
19663 directory whose name is &_.Trash_&. When a directory is excluded from quota
19664 calculations, quota processing is bypassed for any messages that are delivered
19665 directly into that directory.
19668 .option maildir_retries appendfile integer 10
19669 This option specifies the number of times to retry when writing a file in
19670 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
19673 .option maildir_tag appendfile string&!! unset
19674 This option applies only to deliveries in maildir format, and is described in
19675 section &<<SECTmaildirdelivery>>& below.
19678 .option maildir_use_size_file appendfile boolean false
19679 .cindex "maildir format" "&_maildirsize_& file"
19680 Setting this option true enables support for &_maildirsize_& files. Exim
19681 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
19682 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
19683 value is zero. See &%maildir_quota_directory_regex%& above and section
19684 &<<SECTmaildirdelivery>>& below for further details.
19686 .option maildirfolder_create_regex appendfile string unset
19687 .cindex "maildir format" "&_maildirfolder_& file"
19688 .cindex "&_maildirfolder_&, creating"
19689 The value of this option is a regular expression. If it is unset, it has no
19690 effect. Otherwise, before a maildir delivery takes place, the pattern is
19691 matched against the name of the maildir directory, that is, the directory
19692 containing the &_new_& and &_tmp_& subdirectories that will be used for the
19693 delivery. If there is a match, Exim checks for the existence of a file called
19694 &_maildirfolder_& in the directory, and creates it if it does not exist.
19695 See section &<<SECTmaildirdelivery>>& for more details.
19698 .option mailstore_format appendfile boolean false
19699 .cindex "mailstore format" "specifying"
19700 If this option is set with the &%directory%& option, the delivery is into two
19701 new files in &"mailstore"& format. The option is available only if
19702 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
19703 below for further details.
19706 .option mailstore_prefix appendfile string&!! unset
19707 This option applies only to deliveries in mailstore format, and is described in
19708 section &<<SECTopdir>>& below.
19711 .option mailstore_suffix appendfile string&!! unset
19712 This option applies only to deliveries in mailstore format, and is described in
19713 section &<<SECTopdir>>& below.
19716 .option mbx_format appendfile boolean false
19717 .cindex "locking files"
19718 .cindex "file" "locking"
19719 .cindex "file" "MBX format"
19720 .cindex "MBX format, specifying"
19721 This option is available only if Exim has been compiled with SUPPORT_MBX
19722 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
19723 the message is appended to the mailbox file in MBX format instead of
19724 traditional Unix format. This format is supported by Pine4 and its associated
19725 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
19727 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
19728 automatically changed by the use of &%mbx_format%&. They should normally be set
19729 empty when using MBX format, so this option almost always appears in this
19736 If none of the locking options are mentioned in the configuration,
19737 &%use_mbx_lock%& is assumed and the other locking options default to false. It
19738 is possible to specify the other kinds of locking with &%mbx_format%&, but
19739 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
19740 interworks with &'c-client'&, providing for shared access to the mailbox. It
19741 should not be used if any program that does not use this form of locking is
19742 going to access the mailbox, nor should it be used if the mailbox file is NFS
19743 mounted, because it works only when the mailbox is accessed from a single host.
19745 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
19746 the standard version of &'c-client'&, because as long as it has a mailbox open
19747 (this means for the whole of a Pine or IMAP session), Exim will not be able to
19748 append messages to it.
19751 .option message_prefix appendfile string&!! "see below"
19752 .cindex "&""From""& line"
19753 The string specified here is expanded and output at the start of every message.
19754 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
19755 in which case it is:
19757 message_prefix = "From ${if def:return_path{$return_path}\
19758 {MAILER-DAEMON}} $tod_bsdinbox\n"
19760 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
19761 &`\n`& to &`\r\n`& in &%message_prefix%&.
19763 .option message_suffix appendfile string&!! "see below"
19764 The string specified here is expanded and output at the end of every message.
19765 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
19766 in which case it is a single newline character. The suffix can be suppressed by
19771 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
19772 &`\n`& to &`\r\n`& in &%message_suffix%&.
19774 .option mode appendfile "octal integer" 0600
19775 If the output file is created, it is given this mode. If it already exists and
19776 has wider permissions, they are reduced to this mode. If it has narrower
19777 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
19778 if the delivery is the result of a &%save%& command in a filter file specifying
19779 a particular mode, the mode of the output file is always forced to take that
19780 value, and this option is ignored.
19783 .option mode_fail_narrower appendfile boolean true
19784 This option applies in the case when an existing mailbox file has a narrower
19785 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
19786 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
19787 continues with the delivery attempt, using the existing mode of the file.
19790 .option notify_comsat appendfile boolean false
19791 If this option is true, the &'comsat'& daemon is notified after every
19792 successful delivery to a user mailbox. This is the daemon that notifies logged
19793 on users about incoming mail.
19796 .option quota appendfile string&!! unset
19797 .cindex "quota" "imposed by Exim"
19798 This option imposes a limit on the size of the file to which Exim is appending,
19799 or to the total space used in the directory tree when the &%directory%& option
19800 is set. In the latter case, computation of the space used is expensive, because
19801 all the files in the directory (and any sub-directories) have to be
19802 individually inspected and their sizes summed. (See &%quota_size_regex%& and
19803 &%maildir_use_size_file%& for ways to avoid this in environments where users
19804 have no shell access to their mailboxes).
19806 As there is no interlock against two simultaneous deliveries into a
19807 multi-file mailbox, it is possible for the quota to be overrun in this case.
19808 For single-file mailboxes, of course, an interlock is a necessity.
19810 A file's size is taken as its &'used'& value. Because of blocking effects, this
19811 may be a lot less than the actual amount of disk space allocated to the file.
19812 If the sizes of a number of files are being added up, the rounding effect can
19813 become quite noticeable, especially on systems that have large block sizes.
19814 Nevertheless, it seems best to stick to the &'used'& figure, because this is
19815 the obvious value which users understand most easily.
19817 The value of the option is expanded, and must then be a numerical value
19818 (decimal point allowed), optionally followed by one of the letters K, M, or G,
19819 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
19820 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
19823 &*Note*&: A value of zero is interpreted as &"no quota"&.
19825 The expansion happens while Exim is running as root, before it changes uid for
19826 the delivery. This means that files that are inaccessible to the end user can
19827 be used to hold quota values that are looked up in the expansion. When delivery
19828 fails because this quota is exceeded, the handling of the error is as for
19829 system quota failures.
19831 By default, Exim's quota checking mimics system quotas, and restricts the
19832 mailbox to the specified maximum size, though the value is not accurate to the
19833 last byte, owing to separator lines and additional headers that may get added
19834 during message delivery. When a mailbox is nearly full, large messages may get
19835 refused even though small ones are accepted, because the size of the current
19836 message is added to the quota when the check is made. This behaviour can be
19837 changed by setting &%quota_is_inclusive%& false. When this is done, the check
19838 for exceeding the quota does not include the current message. Thus, deliveries
19839 continue until the quota has been exceeded; thereafter, no further messages are
19840 delivered. See also &%quota_warn_threshold%&.
19843 .option quota_directory appendfile string&!! unset
19844 This option defines the directory to check for quota purposes when delivering
19845 into individual files. The default is the delivery directory, or, if a file
19846 called &_maildirfolder_& exists in a maildir directory, the parent of the
19847 delivery directory.
19850 .option quota_filecount appendfile string&!! 0
19851 This option applies when the &%directory%& option is set. It limits the total
19852 number of files in the directory (compare the inode limit in system quotas). It
19853 can only be used if &%quota%& is also set. The value is expanded; an expansion
19854 failure causes delivery to be deferred. A value of zero is interpreted as
19858 .option quota_is_inclusive appendfile boolean true
19859 See &%quota%& above.
19862 .option quota_size_regex appendfile string unset
19863 This option applies when one of the delivery modes that writes a separate file
19864 for each message is being used. When Exim wants to find the size of one of
19865 these files in order to test the quota, it first checks &%quota_size_regex%&.
19866 If this is set to a regular expression that matches the file name, and it
19867 captures one string, that string is interpreted as a representation of the
19868 file's size. The value of &%quota_size_regex%& is not expanded.
19870 This feature is useful only when users have no shell access to their mailboxes
19871 &-- otherwise they could defeat the quota simply by renaming the files. This
19872 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
19873 the file length to the file name. For example:
19875 maildir_tag = ,S=$message_size
19876 quota_size_regex = ,S=(\d+)
19878 An alternative to &$message_size$& is &$message_linecount$&, which contains the
19879 number of lines in the message.
19881 The regular expression should not assume that the length is at the end of the
19882 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
19883 sometimes add other information onto the ends of message file names.
19887 .option quota_warn_message appendfile string&!! "see below"
19888 See below for the use of this option. If it is not set when
19889 &%quota_warn_threshold%& is set, it defaults to
19891 quota_warn_message = "\
19892 To: $local_part@$domain\n\
19893 Subject: Your mailbox\n\n\
19894 This message is automatically created \
19895 by mail delivery software.\n\n\
19896 The size of your mailbox has exceeded \
19897 a warning threshold that is\n\
19898 set by the system administrator.\n"
19902 .option quota_warn_threshold appendfile string&!! 0
19903 .cindex "quota" "warning threshold"
19904 .cindex "mailbox" "size warning"
19905 .cindex "size" "of mailbox"
19906 This option is expanded in the same way as &%quota%& (see above). If the
19907 resulting value is greater than zero, and delivery of the message causes the
19908 size of the file or total space in the directory tree to cross the given
19909 threshold, a warning message is sent. If &%quota%& is also set, the threshold
19910 may be specified as a percentage of it by following the value with a percent
19914 quota_warn_threshold = 75%
19916 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
19917 percent sign is ignored.
19919 The warning message itself is specified by the &%quota_warn_message%& option,
19920 and it must start with a &'To:'& header line containing the recipient(s) of the
19921 warning message. These do not necessarily have to include the recipient(s) of
19922 the original message. A &'Subject:'& line should also normally be supplied. You
19923 can include any other header lines that you want. If you do not include a
19924 &'From:'& line, the default is:
19926 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
19928 .oindex &%errors_reply_to%&
19929 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
19932 The &%quota%& option does not have to be set in order to use this option; they
19933 are independent of one another except when the threshold is specified as a
19937 .option use_bsmtp appendfile boolean false
19938 .cindex "envelope sender"
19939 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
19940 format, with the envelope sender and recipient(s) included as SMTP commands. If
19941 you want to include a leading HELO command with such messages, you can do
19942 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
19943 for details of batch SMTP.
19946 .option use_crlf appendfile boolean false
19947 .cindex "carriage return"
19949 This option causes lines to be terminated with the two-character CRLF sequence
19950 (carriage return, linefeed) instead of just a linefeed character. In the case
19951 of batched SMTP, the byte sequence written to the file is then an exact image
19952 of what would be sent down a real SMTP connection.
19954 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
19955 (which are used to supply the traditional &"From&~"& and blank line separators
19956 in Berkeley-style mailboxes) are written verbatim, so must contain their own
19957 carriage return characters if these are needed. In cases where these options
19958 have non-empty defaults, the values end with a single linefeed, so they must be
19959 changed to end with &`\r\n`& if &%use_crlf%& is set.
19962 .option use_fcntl_lock appendfile boolean "see below"
19963 This option controls the use of the &[fcntl()]& function to lock a file for
19964 exclusive use when a message is being appended. It is set by default unless
19965 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
19966 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
19967 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
19970 .option use_flock_lock appendfile boolean false
19971 This option is provided to support the use of &[flock()]& for file locking, for
19972 the few situations where it is needed. Most modern operating systems support
19973 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
19974 each other. Exim uses &[fcntl()]& locking by default.
19976 This option is required only if you are using an operating system where
19977 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
19978 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
19979 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
19981 .cindex "Solaris" "&[flock()]& support"
19982 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
19983 have it (and some, I think, provide a not quite right version built on top of
19984 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
19985 the ability to use it, and any attempt to do so will cause a configuration
19988 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
19989 is just being mapped onto &[fcntl()]& by the OS).
19992 .option use_lockfile appendfile boolean "see below"
19993 If this option is turned off, Exim does not attempt to create a lock file when
19994 appending to a mailbox file. In this situation, the only locking is by
19995 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
19996 sure that every MUA that is ever going to look at your users' mailboxes uses
19997 &[fcntl()]& rather than a lock file, and even then only when you are not
19998 delivering over NFS from more than one host.
20000 .cindex "NFS" "lock file"
20001 In order to append to an NFS file safely from more than one host, it is
20002 necessary to take out a lock &'before'& opening the file, and the lock file
20003 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
20006 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
20007 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
20008 except when &%mbx_format%& is set.
20011 .option use_mbx_lock appendfile boolean "see below"
20012 This option is available only if Exim has been compiled with SUPPORT_MBX
20013 set in &_Local/Makefile_&. Setting the option specifies that special MBX
20014 locking rules be used. It is set by default if &%mbx_format%& is set and none
20015 of the locking options are mentioned in the configuration. The locking rules
20016 are the same as are used by the &'c-client'& library that underlies Pine and
20017 the IMAP4 and POP daemons that come with it (see the discussion below). The
20018 rules allow for shared access to the mailbox. However, this kind of locking
20019 does not work when the mailbox is NFS mounted.
20021 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
20022 &%use_flock_lock%& to control what kind of locking is used in implementing the
20023 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
20024 without &%use_fcntl_lock%& or &%use_flock_lock%&.
20029 .section "Operational details for appending" "SECTopappend"
20030 .cindex "appending to a file"
20031 .cindex "file" "appending"
20032 Before appending to a file, the following preparations are made:
20035 If the name of the file is &_/dev/null_&, no action is taken, and a success
20039 .cindex "directory creation"
20040 If any directories on the file's path are missing, Exim creates them if the
20041 &%create_directory%& option is set. A created directory's mode is given by the
20042 &%directory_mode%& option.
20045 If &%file_format%& is set, the format of an existing file is checked. If this
20046 indicates that a different transport should be used, control is passed to that
20050 .cindex "file" "locking"
20051 .cindex "locking files"
20052 .cindex "NFS" "lock file"
20053 If &%use_lockfile%& is set, a lock file is built in a way that will work
20054 reliably over NFS, as follows:
20057 Create a &"hitching post"& file whose name is that of the lock file with the
20058 current time, primary host name, and process id added, by opening for writing
20059 as a new file. If this fails with an access error, delivery is deferred.
20061 Close the hitching post file, and hard link it to the lock file name.
20063 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
20064 Unlink the hitching post name.
20066 Otherwise, use &[stat()]& to get information about the hitching post file, and
20067 then unlink hitching post name. If the number of links is exactly two, creation
20068 of the lock file succeeded but something (for example, an NFS server crash and
20069 restart) caused this fact not to be communicated to the &[link()]& call.
20071 If creation of the lock file failed, wait for &%lock_interval%& and try again,
20072 up to &%lock_retries%& times. However, since any program that writes to a
20073 mailbox should complete its task very quickly, it is reasonable to time out old
20074 lock files that are normally the result of user agent and system crashes. If an
20075 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
20076 it before trying again.
20080 A call is made to &[lstat()]& to discover whether the main file exists, and if
20081 so, what its characteristics are. If &[lstat()]& fails for any reason other
20082 than non-existence, delivery is deferred.
20085 .cindex "symbolic link" "to mailbox"
20086 .cindex "mailbox" "symbolic link"
20087 If the file does exist and is a symbolic link, delivery is deferred, unless the
20088 &%allow_symlink%& option is set, in which case the ownership of the link is
20089 checked, and then &[stat()]& is called to find out about the real file, which
20090 is then subjected to the checks below. The check on the top-level link
20091 ownership prevents one user creating a link for another's mailbox in a sticky
20092 directory, though allowing symbolic links in this case is definitely not a good
20093 idea. If there is a chain of symbolic links, the intermediate ones are not
20097 If the file already exists but is not a regular file, or if the file's owner
20098 and group (if the group is being checked &-- see &%check_group%& above) are
20099 different from the user and group under which the delivery is running,
20100 delivery is deferred.
20103 If the file's permissions are more generous than specified, they are reduced.
20104 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
20105 is set false, in which case the delivery is tried using the existing
20109 The file's inode number is saved, and the file is then opened for appending.
20110 If this fails because the file has vanished, &(appendfile)& behaves as if it
20111 hadn't existed (see below). For any other failures, delivery is deferred.
20114 If the file is opened successfully, check that the inode number hasn't
20115 changed, that it is still a regular file, and that the owner and permissions
20116 have not changed. If anything is wrong, defer delivery and freeze the message.
20119 If the file did not exist originally, defer delivery if the &%file_must_exist%&
20120 option is set. Otherwise, check that the file is being created in a permitted
20121 directory if the &%create_file%& option is set (deferring on failure), and then
20122 open for writing as a new file, with the O_EXCL and O_CREAT options,
20123 except when dealing with a symbolic link (the &%allow_symlink%& option must be
20124 set). In this case, which can happen if the link points to a non-existent file,
20125 the file is opened for writing using O_CREAT but not O_EXCL, because
20126 that prevents link following.
20129 .cindex "loop" "while file testing"
20130 If opening fails because the file exists, obey the tests given above for
20131 existing files. However, to avoid looping in a situation where the file is
20132 being continuously created and destroyed, the exists/not-exists loop is broken
20133 after 10 repetitions, and the message is then frozen.
20136 If opening fails with any other error, defer delivery.
20139 .cindex "file" "locking"
20140 .cindex "locking files"
20141 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
20142 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
20143 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
20144 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
20145 file, and an exclusive lock on the file whose name is
20147 /tmp/.<device-number>.<inode-number>
20149 using the device and inode numbers of the open mailbox file, in accordance with
20150 the MBX locking rules. This file is created with a mode that is specified by
20151 the &%lockfile_mode%& option.
20153 If Exim fails to lock the file, there are two possible courses of action,
20154 depending on the value of the locking timeout. This is obtained from
20155 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
20157 If the timeout value is zero, the file is closed, Exim waits for
20158 &%lock_interval%&, and then goes back and re-opens the file as above and tries
20159 to lock it again. This happens up to &%lock_retries%& times, after which the
20160 delivery is deferred.
20162 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
20163 &[flock()]& are used (with the given timeout), so there has already been some
20164 waiting involved by the time locking fails. Nevertheless, Exim does not give up
20165 immediately. It retries up to
20167 (lock_retries * lock_interval) / <timeout>
20169 times (rounded up).
20172 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
20173 and/or &[flock()]& locks) and then deletes the lock file if one was created.
20176 .section "Operational details for delivery to a new file" "SECTopdir"
20177 .cindex "delivery" "to single file"
20178 .cindex "&""From""& line"
20179 When the &%directory%& option is set instead of &%file%&, each message is
20180 delivered into a newly-created file or set of files. When &(appendfile)& is
20181 activated directly from a &(redirect)& router, neither &%file%& nor
20182 &%directory%& is normally set, because the path for delivery is supplied by the
20183 router. (See for example, the &(address_file)& transport in the default
20184 configuration.) In this case, delivery is to a new file if either the path name
20185 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
20187 No locking is required while writing the message to a new file, so the various
20188 locking options of the transport are ignored. The &"From"& line that by default
20189 separates messages in a single file is not normally needed, nor is the escaping
20190 of message lines that start with &"From"&, and there is no need to ensure a
20191 newline at the end of each message. Consequently, the default values for
20192 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
20193 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
20195 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
20196 the files in the delivery directory by default. However, you can specify a
20197 different directory by setting &%quota_directory%&. Also, for maildir
20198 deliveries (see below) the &_maildirfolder_& convention is honoured.
20201 .cindex "maildir format"
20202 .cindex "mailstore format"
20203 There are three different ways in which delivery to individual files can be
20204 done, controlled by the settings of the &%maildir_format%& and
20205 &%mailstore_format%& options. Note that code to support maildir or mailstore
20206 formats is not included in the binary unless SUPPORT_MAILDIR or
20207 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
20209 .cindex "directory creation"
20210 In all three cases an attempt is made to create the directory and any necessary
20211 sub-directories if they do not exist, provided that the &%create_directory%&
20212 option is set (the default). The location of a created directory can be
20213 constrained by setting &%create_file%&. A created directory's mode is given by
20214 the &%directory_mode%& option. If creation fails, or if the
20215 &%create_directory%& option is not set when creation is required, delivery is
20220 .section "Maildir delivery" "SECTmaildirdelivery"
20221 .cindex "maildir format" "description of"
20222 If the &%maildir_format%& option is true, Exim delivers each message by writing
20223 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
20224 directory that is defined by the &%directory%& option (the &"delivery
20225 directory"&). If the delivery is successful, the file is renamed into the
20226 &_new_& subdirectory.
20228 In the file name, <&'stime'&> is the current time of day in seconds, and
20229 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
20230 Exim checks that the time-of-day clock has moved on by at least one microsecond
20231 before terminating the delivery process. This guarantees uniqueness for the
20232 file name. However, as a precaution, Exim calls &[stat()]& for the file before
20233 opening it. If any response other than ENOENT (does not exist) is given,
20234 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
20236 Before Exim carries out a maildir delivery, it ensures that subdirectories
20237 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
20238 do not exist, Exim tries to create them and any superior directories in their
20239 path, subject to the &%create_directory%& and &%create_file%& options. If the
20240 &%maildirfolder_create_regex%& option is set, and the regular expression it
20241 contains matches the delivery directory, Exim also ensures that a file called
20242 &_maildirfolder_& exists in the delivery directory. If a missing directory or
20243 &_maildirfolder_& file cannot be created, delivery is deferred.
20245 These features make it possible to use Exim to create all the necessary files
20246 and directories in a maildir mailbox, including subdirectories for maildir++
20247 folders. Consider this example:
20249 maildir_format = true
20250 directory = /var/mail/$local_part\
20251 ${if eq{$local_part_suffix}{}{}\
20252 {/.${substr_1:$local_part_suffix}}}
20253 maildirfolder_create_regex = /\.[^/]+$
20255 If &$local_part_suffix$& is empty (there was no suffix for the local part),
20256 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
20257 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
20258 not match this name, so Exim will not look for or create the file
20259 &_/var/mail/pimbo/maildirfolder_&, though it will create
20260 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
20262 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
20263 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
20264 does match &%maildirfolder_create_regex%&. In this case, Exim will create
20265 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
20266 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
20268 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
20269 not inadvertently match the toplevel maildir directory, because a
20270 &_maildirfolder_& file at top level would completely break quota calculations.
20272 .cindex "quota" "in maildir delivery"
20273 .cindex "maildir++"
20274 If Exim is required to check a &%quota%& setting before a maildir delivery, and
20275 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
20276 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
20277 Exim assumes the directory is a maildir++ folder directory, which is one level
20278 down from the user's top level mailbox directory. This causes it to start at
20279 the parent directory instead of the current directory when calculating the
20280 amount of space used.
20282 One problem with delivering into a multi-file mailbox is that it is
20283 computationally expensive to compute the size of the mailbox for quota
20284 checking. Various approaches have been taken to reduce the amount of work
20285 needed. The next two sections describe two of them. A third alternative is to
20286 use some external process for maintaining the size data, and use the expansion
20287 of the &%mailbox_size%& option as a way of importing it into Exim.
20292 .section "Using tags to record message sizes" "SECID135"
20293 If &%maildir_tag%& is set, the string is expanded for each delivery.
20294 When the maildir file is renamed into the &_new_& sub-directory, the
20295 tag is added to its name. However, if adding the tag takes the length of the
20296 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
20297 the tag is dropped and the maildir file is created with no tag.
20299 .vindex "&$message_size$&"
20300 Tags can be used to encode the size of files in their names; see
20301 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
20302 happens after the message has been written. The value of the &$message_size$&
20303 variable is set to the number of bytes actually written. If the expansion is
20304 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
20305 be deferred. The expanded tag may contain any printing characters except &"/"&.
20306 Non-printing characters in the string are ignored; if the resulting string is
20307 empty, it is ignored. If it starts with an alphanumeric character, a leading
20312 .section "Using a maildirsize file" "SECID136"
20313 .cindex "quota" "in maildir delivery"
20314 .cindex "maildir format" "&_maildirsize_& file"
20315 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
20316 storing quota and message size information in a file called &_maildirsize_&
20317 within the toplevel maildir directory. If this file does not exist, Exim
20318 creates it, setting the quota from the &%quota%& option of the transport. If
20319 the maildir directory itself does not exist, it is created before any attempt
20320 to write a &_maildirsize_& file.
20322 The &_maildirsize_& file is used to hold information about the sizes of
20323 messages in the maildir, thus speeding up quota calculations. The quota value
20324 in the file is just a cache; if the quota is changed in the transport, the new
20325 value overrides the cached value when the next message is delivered. The cache
20326 is maintained for the benefit of other programs that access the maildir and
20327 need to know the quota.
20329 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
20330 file is maintained (with a zero quota setting), but no quota is imposed.
20332 A regular expression is available for controlling which directories in the
20333 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
20334 See the description of the &%maildir_quota_directory_regex%& option above for
20338 .section "Mailstore delivery" "SECID137"
20339 .cindex "mailstore format" "description of"
20340 If the &%mailstore_format%& option is true, each message is written as two
20341 files in the given directory. A unique base name is constructed from the
20342 message id and the current delivery process, and the files that are written use
20343 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
20344 contains the message's envelope, and the &_.msg_& file contains the message
20345 itself. The base name is placed in the variable &$mailstore_basename$&.
20347 During delivery, the envelope is first written to a file with the suffix
20348 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
20349 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
20350 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
20351 file before accessing either of them. An alternative approach is to wait for
20352 the absence of a &_.tmp_& file.
20354 The envelope file starts with any text defined by the &%mailstore_prefix%&
20355 option, expanded and terminated by a newline if there isn't one. Then follows
20356 the sender address on one line, then all the recipient addresses, one per line.
20357 There can be more than one recipient only if the &%batch_max%& option is set
20358 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
20359 appended to the file, followed by a newline if it does not end with one.
20361 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
20362 failure, it is ignored. Other expansion errors are treated as serious
20363 configuration errors, and delivery is deferred. The variable
20364 &$mailstore_basename$& is available for use during these expansions.
20367 .section "Non-special new file delivery" "SECID138"
20368 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
20369 file is created directly in the named directory. For example, when delivering
20370 messages into files in batched SMTP format for later delivery to some host (see
20371 section &<<SECTbatchSMTP>>&), a setting such as
20373 directory = /var/bsmtp/$host
20375 might be used. A message is written to a file with a temporary name, which is
20376 then renamed when the delivery is complete. The final name is obtained by
20377 expanding the contents of the &%directory_file%& option.
20378 .ecindex IIDapptra1
20379 .ecindex IIDapptra2
20386 . ////////////////////////////////////////////////////////////////////////////
20387 . ////////////////////////////////////////////////////////////////////////////
20389 .chapter "The autoreply transport" "CHID8"
20390 .scindex IIDauttra1 "transports" "&(autoreply)&"
20391 .scindex IIDauttra2 "&(autoreply)& transport"
20392 The &(autoreply)& transport is not a true transport in that it does not cause
20393 the message to be transmitted. Instead, it generates a new mail message as an
20394 automatic reply to the incoming message. &'References:'& and
20395 &'Auto-Submitted:'& header lines are included. These are constructed according
20396 to the rules in RFCs 2822 and 3834, respectively.
20398 If the router that passes the message to this transport does not have the
20399 &%unseen%& option set, the original message (for the current recipient) is not
20400 delivered anywhere. However, when the &%unseen%& option is set on the router
20401 that passes the message to this transport, routing of the address continues, so
20402 another router can set up a normal message delivery.
20405 The &(autoreply)& transport is usually run as the result of mail filtering, a
20406 &"vacation"& message being the standard example. However, it can also be run
20407 directly from a router like any other transport. To reduce the possibility of
20408 message cascades, messages created by the &(autoreply)& transport always have
20409 empty envelope sender addresses, like bounce messages.
20411 The parameters of the message to be sent can be specified in the configuration
20412 by options described below. However, these are used only when the address
20413 passed to the transport does not contain its own reply information. When the
20414 transport is run as a consequence of a
20416 or &%vacation%& command in a filter file, the parameters of the message are
20417 supplied by the filter, and passed with the address. The transport's options
20418 that define the message are then ignored (so they are not usually set in this
20419 case). The message is specified entirely by the filter or by the transport; it
20420 is never built from a mixture of options. However, the &%file_optional%&,
20421 &%mode%&, and &%return_message%& options apply in all cases.
20423 &(Autoreply)& is implemented as a local transport. When used as a result of a
20424 command in a user's filter file, &(autoreply)& normally runs under the uid and
20425 gid of the user, and with appropriate current and home directories (see chapter
20426 &<<CHAPenvironment>>&).
20428 There is a subtle difference between routing a message to a &(pipe)& transport
20429 that generates some text to be returned to the sender, and routing it to an
20430 &(autoreply)& transport. This difference is noticeable only if more than one
20431 address from the same message is so handled. In the case of a pipe, the
20432 separate outputs from the different addresses are gathered up and returned to
20433 the sender in a single message, whereas if &(autoreply)& is used, a separate
20434 message is generated for each address that is passed to it.
20436 Non-printing characters are not permitted in the header lines generated for the
20437 message that &(autoreply)& creates, with the exception of newlines that are
20438 immediately followed by white space. If any non-printing characters are found,
20439 the transport defers.
20440 Whether characters with the top bit set count as printing characters or not is
20441 controlled by the &%print_topbitchars%& global option.
20443 If any of the generic options for manipulating headers (for example,
20444 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
20445 of the original message that is included in the generated message when
20446 &%return_message%& is set. They do not apply to the generated message itself.
20448 .vindex "&$sender_address$&"
20449 If the &(autoreply)& transport receives return code 2 from Exim when it submits
20450 the message, indicating that there were no recipients, it does not treat this
20451 as an error. This means that autoreplies sent to &$sender_address$& when this
20452 is empty (because the incoming message is a bounce message) do not cause
20453 problems. They are just discarded.
20457 .section "Private options for autoreply" "SECID139"
20458 .cindex "options" "&(autoreply)& transport"
20460 .option bcc autoreply string&!! unset
20461 This specifies the addresses that are to receive &"blind carbon copies"& of the
20462 message when the message is specified by the transport.
20465 .option cc autoreply string&!! unset
20466 This specifies recipients of the message and the contents of the &'Cc:'& header
20467 when the message is specified by the transport.
20470 .option file autoreply string&!! unset
20471 The contents of the file are sent as the body of the message when the message
20472 is specified by the transport. If both &%file%& and &%text%& are set, the text
20473 string comes first.
20476 .option file_expand autoreply boolean false
20477 If this is set, the contents of the file named by the &%file%& option are
20478 subjected to string expansion as they are added to the message.
20481 .option file_optional autoreply boolean false
20482 If this option is true, no error is generated if the file named by the &%file%&
20483 option or passed with the address does not exist or cannot be read.
20486 .option from autoreply string&!! unset
20487 This specifies the contents of the &'From:'& header when the message is
20488 specified by the transport.
20491 .option headers autoreply string&!! unset
20492 This specifies additional RFC 2822 headers that are to be added to the message
20493 when the message is specified by the transport. Several can be given by using
20494 &"\n"& to separate them. There is no check on the format.
20497 .option log autoreply string&!! unset
20498 This option names a file in which a record of every message sent is logged when
20499 the message is specified by the transport.
20502 .option mode autoreply "octal integer" 0600
20503 If either the log file or the &"once"& file has to be created, this mode is
20507 .option never_mail autoreply "address list&!!" unset
20508 If any run of the transport creates a message with a recipient that matches any
20509 item in the list, that recipient is quietly discarded. If all recipients are
20510 discarded, no message is created. This applies both when the recipients are
20511 generated by a filter and when they are specified in the transport.
20515 .option once autoreply string&!! unset
20516 This option names a file or DBM database in which a record of each &'To:'&
20517 recipient is kept when the message is specified by the transport. &*Note*&:
20518 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
20520 If &%once%& is unset, or is set to an empty string, the message is always sent.
20521 By default, if &%once%& is set to a non-empty file name, the message
20522 is not sent if a potential recipient is already listed in the database.
20523 However, if the &%once_repeat%& option specifies a time greater than zero, the
20524 message is sent if that much time has elapsed since a message was last sent to
20525 this recipient. A setting of zero time for &%once_repeat%& (the default)
20526 prevents a message from being sent a second time &-- in this case, zero means
20529 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
20530 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
20531 greater than zero, it changes the way Exim implements the &%once%& option.
20532 Instead of using a DBM file to record every recipient it sends to, it uses a
20533 regular file, whose size will never get larger than the given value.
20535 In the file, Exim keeps a linear list of recipient addresses and the times at
20536 which they were sent messages. If the file is full when a new address needs to
20537 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
20538 means that a given recipient may receive multiple messages, but at
20539 unpredictable intervals that depend on the rate of turnover of addresses in the
20540 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
20543 .option once_file_size autoreply integer 0
20544 See &%once%& above.
20547 .option once_repeat autoreply time&!! 0s
20548 See &%once%& above.
20549 After expansion, the value of this option must be a valid time value.
20552 .option reply_to autoreply string&!! unset
20553 This specifies the contents of the &'Reply-To:'& header when the message is
20554 specified by the transport.
20557 .option return_message autoreply boolean false
20558 If this is set, a copy of the original message is returned with the new
20559 message, subject to the maximum size set in the &%return_size_limit%& global
20560 configuration option.
20563 .option subject autoreply string&!! unset
20564 This specifies the contents of the &'Subject:'& header when the message is
20565 specified by the transport. It is tempting to quote the original subject in
20566 automatic responses. For example:
20568 subject = Re: $h_subject:
20570 There is a danger in doing this, however. It may allow a third party to
20571 subscribe your users to an opt-in mailing list, provided that the list accepts
20572 bounce messages as subscription confirmations. Well-managed lists require a
20573 non-bounce message to confirm a subscription, so the danger is relatively
20578 .option text autoreply string&!! unset
20579 This specifies a single string to be used as the body of the message when the
20580 message is specified by the transport. If both &%text%& and &%file%& are set,
20581 the text comes first.
20584 .option to autoreply string&!! unset
20585 This specifies recipients of the message and the contents of the &'To:'& header
20586 when the message is specified by the transport.
20587 .ecindex IIDauttra1
20588 .ecindex IIDauttra2
20593 . ////////////////////////////////////////////////////////////////////////////
20594 . ////////////////////////////////////////////////////////////////////////////
20596 .chapter "The lmtp transport" "CHAPLMTP"
20597 .cindex "transports" "&(lmtp)&"
20598 .cindex "&(lmtp)& transport"
20599 .cindex "LMTP" "over a pipe"
20600 .cindex "LMTP" "over a socket"
20601 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
20603 or by interacting with a Unix domain socket.
20604 This transport is something of a cross between the &(pipe)& and &(smtp)&
20605 transports. Exim also has support for using LMTP over TCP/IP; this is
20606 implemented as an option for the &(smtp)& transport. Because LMTP is expected
20607 to be of minority interest, the default build-time configure in &_src/EDITME_&
20608 has it commented out. You need to ensure that
20612 .cindex "options" "&(lmtp)& transport"
20613 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
20614 included in the Exim binary. The private options of the &(lmtp)& transport are
20617 .option batch_id lmtp string&!! unset
20618 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20621 .option batch_max lmtp integer 1
20622 This limits the number of addresses that can be handled in a single delivery.
20623 Most LMTP servers can handle several addresses at once, so it is normally a
20624 good idea to increase this value. See the description of local delivery
20625 batching in chapter &<<CHAPbatching>>&.
20628 .option command lmtp string&!! unset
20629 This option must be set if &%socket%& is not set. The string is a command which
20630 is run in a separate process. It is split up into a command name and list of
20631 arguments, each of which is separately expanded (so expansion cannot change the
20632 number of arguments). The command is run directly, not via a shell. The message
20633 is passed to the new process using the standard input and output to operate the
20636 .option ignore_quota lmtp boolean false
20637 .cindex "LMTP" "ignoring quota errors"
20638 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
20639 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
20640 in its response to the LHLO command.
20642 .option socket lmtp string&!! unset
20643 This option must be set if &%command%& is not set. The result of expansion must
20644 be the name of a Unix domain socket. The transport connects to the socket and
20645 delivers the message to it using the LMTP protocol.
20648 .option timeout lmtp time 5m
20649 The transport is aborted if the created process or Unix domain socket does not
20650 respond to LMTP commands or message input within this timeout. Delivery
20651 is deferred, and will be tried again later. Here is an example of a typical
20656 command = /some/local/lmtp/delivery/program
20660 This delivers up to 20 addresses at a time, in a mixture of domains if
20661 necessary, running as the user &'exim'&.
20665 . ////////////////////////////////////////////////////////////////////////////
20666 . ////////////////////////////////////////////////////////////////////////////
20668 .chapter "The pipe transport" "CHAPpipetransport"
20669 .scindex IIDpiptra1 "transports" "&(pipe)&"
20670 .scindex IIDpiptra2 "&(pipe)& transport"
20671 The &(pipe)& transport is used to deliver messages via a pipe to a command
20672 running in another process. One example is the use of &(pipe)& as a
20673 pseudo-remote transport for passing messages to some other delivery mechanism
20674 (such as UUCP). Another is the use by individual users to automatically process
20675 their incoming messages. The &(pipe)& transport can be used in one of the
20679 .vindex "&$local_part$&"
20680 A router routes one address to a transport in the normal way, and the
20681 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
20682 contains the local part of the address (as usual), and the command that is run
20683 is specified by the &%command%& option on the transport.
20685 .vindex "&$pipe_addresses$&"
20686 If the &%batch_max%& option is set greater than 1 (the default is 1), the
20687 transport can handle more than one address in a single run. In this case, when
20688 more than one address is routed to the transport, &$local_part$& is not set
20689 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
20690 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
20691 that are routed to the transport.
20693 .vindex "&$address_pipe$&"
20694 A router redirects an address directly to a pipe command (for example, from an
20695 alias or forward file). In this case, &$address_pipe$& contains the text of the
20696 pipe command, and the &%command%& option on the transport is ignored. If only
20697 one address is being transported (&%batch_max%& is not greater than one, or
20698 only one address was redirected to this pipe command), &$local_part$& contains
20699 the local part that was redirected.
20703 The &(pipe)& transport is a non-interactive delivery method. Exim can also
20704 deliver messages over pipes using the LMTP interactive protocol. This is
20705 implemented by the &(lmtp)& transport.
20707 In the case when &(pipe)& is run as a consequence of an entry in a local user's
20708 &_.forward_& file, the command runs under the uid and gid of that user. In
20709 other cases, the uid and gid have to be specified explicitly, either on the
20710 transport or on the router that handles the address. Current and &"home"&
20711 directories are also controllable. See chapter &<<CHAPenvironment>>& for
20712 details of the local delivery environment and chapter &<<CHAPbatching>>&
20713 for a discussion of local delivery batching.
20716 .section "Concurrent delivery" "SECID140"
20717 If two messages arrive at almost the same time, and both are routed to a pipe
20718 delivery, the two pipe transports may be run concurrently. You must ensure that
20719 any pipe commands you set up are robust against this happening. If the commands
20720 write to a file, the &%exim_lock%& utility might be of use.
20725 .section "Returned status and data" "SECID141"
20726 .cindex "&(pipe)& transport" "returned data"
20727 If the command exits with a non-zero return code, the delivery is deemed to
20728 have failed, unless either the &%ignore_status%& option is set (in which case
20729 the return code is treated as zero), or the return code is one of those listed
20730 in the &%temp_errors%& option, which are interpreted as meaning &"try again
20731 later"&. In this case, delivery is deferred. Details of a permanent failure are
20732 logged, but are not included in the bounce message, which merely contains
20733 &"local delivery failed"&.
20735 If the return code is greater than 128 and the command being run is a shell
20736 script, it normally means that the script was terminated by a signal whose
20737 value is the return code minus 128.
20739 If Exim is unable to run the command (that is, if &[execve()]& fails), the
20740 return code is set to 127. This is the value that a shell returns if it is
20741 asked to run a non-existent command. The wording for the log line suggests that
20742 a non-existent command may be the problem.
20744 The &%return_output%& option can affect the result of a pipe delivery. If it is
20745 set and the command produces any output on its standard output or standard
20746 error streams, the command is considered to have failed, even if it gave a zero
20747 return code or if &%ignore_status%& is set. The output from the command is
20748 included as part of the bounce message. The &%return_fail_output%& option is
20749 similar, except that output is returned only when the command exits with a
20750 failure return code, that is, a value other than zero or a code that matches
20755 .section "How the command is run" "SECThowcommandrun"
20756 .cindex "&(pipe)& transport" "path for command"
20757 The command line is (by default) broken down into a command name and arguments
20758 by the &(pipe)& transport itself. The &%allow_commands%& and
20759 &%restrict_to_path%& options can be used to restrict the commands that may be
20762 .cindex "quoting" "in pipe command"
20763 Unquoted arguments are delimited by white space. If an argument appears in
20764 double quotes, backslash is interpreted as an escape character in the usual
20765 way. If an argument appears in single quotes, no escaping is done.
20767 String expansion is applied to the command line except when it comes from a
20768 traditional &_.forward_& file (commands from a filter file are expanded). The
20769 expansion is applied to each argument in turn rather than to the whole line.
20770 For this reason, any string expansion item that contains white space must be
20771 quoted so as to be contained within a single argument. A setting such as
20773 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
20775 will not work, because the expansion item gets split between several
20776 arguments. You have to write
20778 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
20780 to ensure that it is all in one argument. The expansion is done in this way,
20781 argument by argument, so that the number of arguments cannot be changed as a
20782 result of expansion, and quotes or backslashes in inserted variables do not
20783 interact with external quoting. However, this leads to problems if you want to
20784 generate multiple arguments (or the command name plus arguments) from a single
20785 expansion. In this situation, the simplest solution is to use a shell. For
20788 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
20791 .cindex "transport" "filter"
20792 .cindex "filter" "transport filter"
20793 .vindex "&$pipe_addresses$&"
20794 Special handling takes place when an argument consists of precisely the text
20795 &`$pipe_addresses`&. This is not a general expansion variable; the only
20796 place this string is recognized is when it appears as an argument for a pipe or
20797 transport filter command. It causes each address that is being handled to be
20798 inserted in the argument list at that point &'as a separate argument'&. This
20799 avoids any problems with spaces or shell metacharacters, and is of use when a
20800 &(pipe)& transport is handling groups of addresses in a batch.
20802 After splitting up into arguments and expansion, the resulting command is run
20803 in a subprocess directly from the transport, &'not'& under a shell. The
20804 message that is being delivered is supplied on the standard input, and the
20805 standard output and standard error are both connected to a single pipe that is
20806 read by Exim. The &%max_output%& option controls how much output the command
20807 may produce, and the &%return_output%& and &%return_fail_output%& options
20808 control what is done with it.
20810 Not running the command under a shell (by default) lessens the security risks
20811 in cases when a command from a user's filter file is built out of data that was
20812 taken from an incoming message. If a shell is required, it can of course be
20813 explicitly specified as the command to be run. However, there are circumstances
20814 where existing commands (for example, in &_.forward_& files) expect to be run
20815 under a shell and cannot easily be modified. To allow for these cases, there is
20816 an option called &%use_shell%&, which changes the way the &(pipe)& transport
20817 works. Instead of breaking up the command line as just described, it expands it
20818 as a single string and passes the result to &_/bin/sh_&. The
20819 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
20820 with &%use_shell%&, and the whole mechanism is inherently less secure.
20824 .section "Environment variables" "SECTpipeenv"
20825 .cindex "&(pipe)& transport" "environment for command"
20826 .cindex "environment for pipe transport"
20827 The environment variables listed below are set up when the command is invoked.
20828 This list is a compromise for maximum compatibility with other MTAs. Note that
20829 the &%environment%& option can be used to add additional variables to this
20832 &`DOMAIN `& the domain of the address
20833 &`HOME `& the home directory, if set
20834 &`HOST `& the host name when called from a router (see below)
20835 &`LOCAL_PART `& see below
20836 &`LOCAL_PART_PREFIX `& see below
20837 &`LOCAL_PART_SUFFIX `& see below
20838 &`LOGNAME `& see below
20839 &`MESSAGE_ID `& Exim's local ID for the message
20840 &`PATH `& as specified by the &%path%& option below
20841 &`QUALIFY_DOMAIN `& the sender qualification domain
20842 &`RECIPIENT `& the complete recipient address
20843 &`SENDER `& the sender of the message (empty if a bounce)
20844 &`SHELL `& &`/bin/sh`&
20845 &`TZ `& the value of the &%timezone%& option, if set
20846 &`USER `& see below
20848 When a &(pipe)& transport is called directly from (for example) an &(accept)&
20849 router, LOCAL_PART is set to the local part of the address. When it is
20850 called as a result of a forward or alias expansion, LOCAL_PART is set to
20851 the local part of the address that was expanded. In both cases, any affixes are
20852 removed from the local part, and made available in LOCAL_PART_PREFIX and
20853 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
20854 same value as LOCAL_PART for compatibility with other MTAs.
20857 HOST is set only when a &(pipe)& transport is called from a router that
20858 associates hosts with an address, typically when using &(pipe)& as a
20859 pseudo-remote transport. HOST is set to the first host name specified by
20863 If the transport's generic &%home_directory%& option is set, its value is used
20864 for the HOME environment variable. Otherwise, a home directory may be set
20865 by the router's &%transport_home_directory%& option, which defaults to the
20866 user's home directory if &%check_local_user%& is set.
20869 .section "Private options for pipe" "SECID142"
20870 .cindex "options" "&(pipe)& transport"
20874 .option allow_commands pipe "string list&!!" unset
20875 .cindex "&(pipe)& transport" "permitted commands"
20876 The string is expanded, and is then interpreted as a colon-separated list of
20877 permitted commands. If &%restrict_to_path%& is not set, the only commands
20878 permitted are those in the &%allow_commands%& list. They need not be absolute
20879 paths; the &%path%& option is still used for relative paths. If
20880 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
20881 in the &%allow_commands%& list, or a name without any slashes that is found on
20882 the path. In other words, if neither &%allow_commands%& nor
20883 &%restrict_to_path%& is set, there is no restriction on the command, but
20884 otherwise only commands that are permitted by one or the other are allowed. For
20887 allow_commands = /usr/bin/vacation
20889 and &%restrict_to_path%& is not set, the only permitted command is
20890 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
20891 &%use_shell%& is set.
20894 .option batch_id pipe string&!! unset
20895 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20898 .option batch_max pipe integer 1
20899 This limits the number of addresses that can be handled in a single delivery.
20900 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
20903 .option check_string pipe string unset
20904 As &(pipe)& writes the message, the start of each line is tested for matching
20905 &%check_string%&, and if it does, the initial matching characters are replaced
20906 by the contents of &%escape_string%&, provided both are set. The value of
20907 &%check_string%& is a literal string, not a regular expression, and the case of
20908 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
20909 of &%check_string%& and &%escape_string%& are forced to values that implement
20910 the SMTP escaping protocol. Any settings made in the configuration file are
20914 .option command pipe string&!! unset
20915 This option need not be set when &(pipe)& is being used to deliver to pipes
20916 obtained directly from address redirections. In other cases, the option must be
20917 set, to provide a command to be run. It need not yield an absolute path (see
20918 the &%path%& option below). The command is split up into separate arguments by
20919 Exim, and each argument is separately expanded, as described in section
20920 &<<SECThowcommandrun>>& above.
20923 .option environment pipe string&!! unset
20924 .cindex "&(pipe)& transport" "environment for command"
20925 .cindex "environment for &(pipe)& transport"
20926 This option is used to add additional variables to the environment in which the
20927 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
20928 a string which is expanded, and then interpreted as a colon-separated list of
20929 environment settings of the form <&'name'&>=<&'value'&>.
20932 .option escape_string pipe string unset
20933 See &%check_string%& above.
20936 .option freeze_exec_fail pipe boolean false
20937 .cindex "exec failure"
20938 .cindex "failure of exec"
20939 .cindex "&(pipe)& transport" "failure of exec"
20940 Failure to exec the command in a pipe transport is by default treated like
20941 any other failure while running the command. However, if &%freeze_exec_fail%&
20942 is set, failure to exec is treated specially, and causes the message to be
20943 frozen, whatever the setting of &%ignore_status%&.
20946 .option ignore_status pipe boolean false
20947 If this option is true, the status returned by the subprocess that is set up to
20948 run the command is ignored, and Exim behaves as if zero had been returned.
20949 Otherwise, a non-zero status or termination by signal causes an error return
20950 from the transport unless the status value is one of those listed in
20951 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
20953 &*Note*&: This option does not apply to timeouts, which do not return a status.
20954 See the &%timeout_defer%& option for how timeouts are handled.
20956 .option log_defer_output pipe boolean false
20957 .cindex "&(pipe)& transport" "logging output"
20958 If this option is set, and the status returned by the command is
20959 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
20960 and any output was produced, the first line of it is written to the main log.
20963 .option log_fail_output pipe boolean false
20964 If this option is set, and the command returns any output, and also ends with a
20965 return code that is neither zero nor one of the return codes listed in
20966 &%temp_errors%& (that is, the delivery failed), the first line of output is
20967 written to the main log. This option and &%log_output%& are mutually exclusive.
20968 Only one of them may be set.
20972 .option log_output pipe boolean false
20973 If this option is set and the command returns any output, the first line of
20974 output is written to the main log, whatever the return code. This option and
20975 &%log_fail_output%& are mutually exclusive. Only one of them may be set.
20979 .option max_output pipe integer 20K
20980 This specifies the maximum amount of output that the command may produce on its
20981 standard output and standard error file combined. If the limit is exceeded, the
20982 process running the command is killed. This is intended as a safety measure to
20983 catch runaway processes. The limit is applied independently of the settings of
20984 the options that control what is done with such output (for example,
20985 &%return_output%&). Because of buffering effects, the amount of output may
20986 exceed the limit by a small amount before Exim notices.
20989 .option message_prefix pipe string&!! "see below"
20990 The string specified here is expanded and output at the start of every message.
20991 The default is unset if &%use_bsmtp%& is set. Otherwise it is
20994 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
20998 .cindex "&%tmail%&"
20999 .cindex "&""From""& line"
21000 This is required by the commonly used &_/usr/bin/vacation_& program.
21001 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
21002 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
21007 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21008 &`\n`& to &`\r\n`& in &%message_prefix%&.
21011 .option message_suffix pipe string&!! "see below"
21012 The string specified here is expanded and output at the end of every message.
21013 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
21014 The suffix can be suppressed by setting
21018 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21019 &`\n`& to &`\r\n`& in &%message_suffix%&.
21022 .option path pipe string "see below"
21023 This option specifies the string that is set up in the PATH environment
21024 variable of the subprocess. The default is:
21028 If the &%command%& option does not yield an absolute path name, the command is
21029 sought in the PATH directories, in the usual way. &*Warning*&: This does not
21030 apply to a command specified as a transport filter.
21033 .option pipe_as_creator pipe boolean false
21034 .cindex "uid (user id)" "local delivery"
21035 If the generic &%user%& option is not set and this option is true, the delivery
21036 process is run under the uid that was in force when Exim was originally called
21037 to accept the message. If the group id is not otherwise set (via the generic
21038 &%group%& option), the gid that was in force when Exim was originally called to
21039 accept the message is used.
21042 .option restrict_to_path pipe boolean false
21043 When this option is set, any command name not listed in &%allow_commands%& must
21044 contain no slashes. The command is searched for only in the directories listed
21045 in the &%path%& option. This option is intended for use in the case when a pipe
21046 command has been generated from a user's &_.forward_& file. This is usually
21047 handled by a &(pipe)& transport called &%address_pipe%&.
21050 .option return_fail_output pipe boolean false
21051 If this option is true, and the command produced any output and ended with a
21052 return code other than zero or one of the codes listed in &%temp_errors%& (that
21053 is, the delivery failed), the output is returned in the bounce message.
21054 However, if the message has a null sender (that is, it is itself a bounce
21055 message), output from the command is discarded. This option and
21056 &%return_output%& are mutually exclusive. Only one of them may be set.
21060 .option return_output pipe boolean false
21061 If this option is true, and the command produced any output, the delivery is
21062 deemed to have failed whatever the return code from the command, and the output
21063 is returned in the bounce message. Otherwise, the output is just discarded.
21064 However, if the message has a null sender (that is, it is a bounce message),
21065 output from the command is always discarded, whatever the setting of this
21066 option. This option and &%return_fail_output%& are mutually exclusive. Only one
21067 of them may be set.
21071 .option temp_errors pipe "string list" "see below"
21072 .cindex "&(pipe)& transport" "temporary failure"
21073 This option contains either a colon-separated list of numbers, or a single
21074 asterisk. If &%ignore_status%& is false
21075 and &%return_output%& is not set,
21076 and the command exits with a non-zero return code, the failure is treated as
21077 temporary and the delivery is deferred if the return code matches one of the
21078 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
21079 codes are treated as permanent errors. The default setting contains the codes
21080 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
21081 compiled on a system that does not define these macros, it assumes values of 75
21082 and 73, respectively.
21085 .option timeout pipe time 1h
21086 If the command fails to complete within this time, it is killed. This normally
21087 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
21088 specifies no timeout. In order to ensure that any subprocesses created by the
21089 command are also killed, Exim makes the initial process a process group leader,
21090 and kills the whole process group on a timeout. However, this can be defeated
21091 if one of the processes starts a new process group.
21093 .option timeout_defer pipe boolean false
21094 A timeout in a &(pipe)& transport, either in the command that the transport
21095 runs, or in a transport filter that is associated with it, is by default
21096 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
21097 is set true, both kinds of timeout become temporary errors, causing the
21098 delivery to be deferred.
21100 .option umask pipe "octal integer" 022
21101 This specifies the umask setting for the subprocess that runs the command.
21104 .option use_bsmtp pipe boolean false
21105 .cindex "envelope sender"
21106 If this option is set true, the &(pipe)& transport writes messages in &"batch
21107 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
21108 commands. If you want to include a leading HELO command with such messages,
21109 you can do so by setting the &%message_prefix%& option. See section
21110 &<<SECTbatchSMTP>>& for details of batch SMTP.
21112 .option use_classresources pipe boolean false
21113 .cindex "class resources (BSD)"
21114 This option is available only when Exim is running on FreeBSD, NetBSD, or
21115 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
21116 resource limits when a &(pipe)& transport is run to perform a delivery. The
21117 limits for the uid under which the pipe is to run are obtained from the login
21121 .option use_crlf pipe boolean false
21122 .cindex "carriage return"
21124 This option causes lines to be terminated with the two-character CRLF sequence
21125 (carriage return, linefeed) instead of just a linefeed character. In the case
21126 of batched SMTP, the byte sequence written to the pipe is then an exact image
21127 of what would be sent down a real SMTP connection.
21129 The contents of the &%message_prefix%& and &%message_suffix%& options are
21130 written verbatim, so must contain their own carriage return characters if these
21131 are needed. When &%use_bsmtp%& is not set, the default values for both
21132 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
21133 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
21136 .option use_shell pipe boolean false
21137 .vindex "&$pipe_addresses$&"
21138 If this option is set, it causes the command to be passed to &_/bin/sh_&
21139 instead of being run directly from the transport, as described in section
21140 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
21141 where the command is expected to be run under a shell and cannot easily be
21142 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
21143 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
21144 command is expanded as a single string, and handed to &_/bin/sh_& as data for
21149 .section "Using an external local delivery agent" "SECID143"
21150 .cindex "local delivery" "using an external agent"
21151 .cindex "&'procmail'&"
21152 .cindex "external local delivery"
21153 .cindex "delivery" "&'procmail'&"
21154 .cindex "delivery" "by external agent"
21155 The &(pipe)& transport can be used to pass all messages that require local
21156 delivery to a separate local delivery agent such as &%procmail%&. When doing
21157 this, care must be taken to ensure that the pipe is run under an appropriate
21158 uid and gid. In some configurations one wants this to be a uid that is trusted
21159 by the delivery agent to supply the correct sender of the message. It may be
21160 necessary to recompile or reconfigure the delivery agent so that it trusts an
21161 appropriate user. The following is an example transport and router
21162 configuration for &%procmail%&:
21167 command = /usr/local/bin/procmail -d $local_part
21171 check_string = "From "
21172 escape_string = ">From "
21180 transport = procmail_pipe
21182 In this example, the pipe is run as the local user, but with the group set to
21183 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
21184 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
21185 user to supply a correct sender address. If you do not specify either a
21186 &%group%& or a &%user%& option, the pipe command is run as the local user. The
21187 home directory is the user's home directory by default.
21189 &*Note*&: The command that the pipe transport runs does &'not'& begin with
21193 as shown in some &%procmail%& documentation, because Exim does not by default
21194 use a shell to run pipe commands.
21197 The next example shows a transport and a router for a system where local
21198 deliveries are handled by the Cyrus IMAP server.
21201 local_delivery_cyrus:
21203 command = /usr/cyrus/bin/deliver \
21204 -m ${substr_1:$local_part_suffix} -- $local_part
21216 local_part_suffix = .*
21217 transport = local_delivery_cyrus
21219 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
21220 &%return_output%& to cause any text written by Cyrus to be returned to the
21222 .ecindex IIDpiptra1
21223 .ecindex IIDpiptra2
21226 . ////////////////////////////////////////////////////////////////////////////
21227 . ////////////////////////////////////////////////////////////////////////////
21229 .chapter "The smtp transport" "CHAPsmtptrans"
21230 .scindex IIDsmttra1 "transports" "&(smtp)&"
21231 .scindex IIDsmttra2 "&(smtp)& transport"
21232 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
21233 or LMTP protocol. The list of hosts to try can either be taken from the address
21234 that is being processed (having been set up by the router), or specified
21235 explicitly for the transport. Timeout and retry processing (see chapter
21236 &<<CHAPretry>>&) is applied to each IP address independently.
21239 .section "Multiple messages on a single connection" "SECID144"
21240 The sending of multiple messages over a single TCP/IP connection can arise in
21244 If a message contains more than &%max_rcpt%& (see below) addresses that are
21245 routed to the same host, more than one copy of the message has to be sent to
21246 that host. In this situation, multiple copies may be sent in a single run of
21247 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
21248 does when it has too many addresses to send in one message also depends on the
21249 value of the global &%remote_max_parallel%& option. Details are given in
21250 section &<<SECToutSMTPTCP>>&.)
21252 .cindex "hints database" "remembering routing"
21253 When a message has been successfully delivered over a TCP/IP connection, Exim
21254 looks in its hints database to see if there are any other messages awaiting a
21255 connection to the same host. If there are, a new delivery process is started
21256 for one of them, and the current TCP/IP connection is passed on to it. The new
21257 process may in turn send multiple copies and possibly create yet another
21262 For each copy sent over the same TCP/IP connection, a sequence counter is
21263 incremented, and if it ever gets to the value of &%connection_max_messages%&,
21264 no further messages are sent over that connection.
21268 .section "Use of the $host and $host_address variables" "SECID145"
21270 .vindex "&$host_address$&"
21271 At the start of a run of the &(smtp)& transport, the values of &$host$& and
21272 &$host_address$& are the name and IP address of the first host on the host list
21273 passed by the router. However, when the transport is about to connect to a
21274 specific host, and while it is connected to that host, &$host$& and
21275 &$host_address$& are set to the values for that host. These are the values
21276 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
21277 &%serialize_hosts%&, and the various TLS options are expanded.
21280 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
21281 .vindex &$tls_cipher$&
21282 .vindex &$tls_peerdn$&
21283 At the start of a run of the &(smtp)& transport, the values of &$tls_cipher$&
21284 and &$tls_peerdn$& are the values that were set when the message was received.
21285 These are the values that are used for options that are expanded before any
21286 SMTP connections are made. Just before each connection is made, these two
21287 variables are emptied. If TLS is subsequently started, they are set to the
21288 appropriate values for the outgoing connection, and these are the values that
21289 are in force when any authenticators are run and when the
21290 &%authenticated_sender%& option is expanded.
21293 .section "Private options for smtp" "SECID146"
21294 .cindex "options" "&(smtp)& transport"
21295 The private options of the &(smtp)& transport are as follows:
21298 .option address_retry_include_sender smtp boolean true
21299 .cindex "4&'xx'& responses" "retrying after"
21300 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
21301 is the combination of sender and recipient that is delayed in subsequent queue
21302 runs until the retry time is reached. You can delay the recipient without
21303 reference to the sender (which is what earlier versions of Exim did), by
21304 setting &%address_retry_include_sender%& false. However, this can lead to
21305 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
21307 .option allow_localhost smtp boolean false
21308 .cindex "local host" "sending to"
21309 .cindex "fallback" "hosts specified on transport"
21310 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
21311 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
21312 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
21313 the delivery anyway. This should be used only in special cases when the
21314 configuration ensures that no looping will result (for example, a differently
21315 configured Exim is listening on the port to which the message is sent).
21318 .option authenticated_sender smtp string&!! unset
21320 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
21321 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
21322 overriding any existing authenticated sender value. If the string expansion is
21323 forced to fail, the option is ignored. Other expansion failures cause delivery
21324 to be deferred. If the result of expansion is an empty string, that is also
21327 The expansion happens after the outgoing connection has been made and TLS
21328 started, if required. This means that the &$host$&, &$host_address$&,
21329 &$tls_cipher$&, and &$tls_peerdn$& variables are set according to the
21330 particular connection.
21332 If the SMTP session is not authenticated, the expansion of
21333 &%authenticated_sender%& still happens (and can cause the delivery to be
21334 deferred if it fails), but no AUTH= item is added to MAIL commands
21335 unless &%authenticated_sender_force%& is true.
21337 This option allows you to use the &(smtp)& transport in LMTP mode to
21338 deliver mail to Cyrus IMAP and provide the proper local part as the
21339 &"authenticated sender"&, via a setting such as:
21341 authenticated_sender = $local_part
21343 This removes the need for IMAP subfolders to be assigned special ACLs to
21344 allow direct delivery to those subfolders.
21346 Because of expected uses such as that just described for Cyrus (when no
21347 domain is involved), there is no checking on the syntax of the provided
21351 .option authenticated_sender_force smtp boolean false
21352 If this option is set true, the &%authenticated_sender%& option's value
21353 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
21354 authenticated as a client.
21357 .option command_timeout smtp time 5m
21358 This sets a timeout for receiving a response to an SMTP command that has been
21359 sent out. It is also used when waiting for the initial banner line from the
21360 remote host. Its value must not be zero.
21363 .option connect_timeout smtp time 5m
21364 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
21365 to a remote host. A setting of zero allows the system timeout (typically
21366 several minutes) to act. To have any effect, the value of this option must be
21367 less than the system timeout. However, it has been observed that on some
21368 systems there is no system timeout, which is why the default value for this
21369 option is 5 minutes, a value recommended by RFC 1123.
21372 .option connection_max_messages smtp integer 500
21373 .cindex "SMTP" "passed connection"
21374 .cindex "SMTP" "multiple deliveries"
21375 .cindex "multiple SMTP deliveries"
21376 This controls the maximum number of separate message deliveries that are sent
21377 over a single TCP/IP connection. If the value is zero, there is no limit.
21378 For testing purposes, this value can be overridden by the &%-oB%& command line
21382 .option data_timeout smtp time 5m
21383 This sets a timeout for the transmission of each block in the data portion of
21384 the message. As a result, the overall timeout for a message depends on the size
21385 of the message. Its value must not be zero. See also &%final_timeout%&.
21388 .option delay_after_cutoff smtp boolean true
21389 This option controls what happens when all remote IP addresses for a given
21390 domain have been inaccessible for so long that they have passed their retry
21393 In the default state, if the next retry time has not been reached for any of
21394 them, the address is bounced without trying any deliveries. In other words,
21395 Exim delays retrying an IP address after the final cutoff time until a new
21396 retry time is reached, and can therefore bounce an address without ever trying
21397 a delivery, when machines have been down for a long time. Some people are
21398 unhappy at this prospect, so...
21400 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
21401 addresses are past their final cutoff time, Exim tries to deliver to those
21402 IP addresses that have not been tried since the message arrived. If there are
21403 none, of if they all fail, the address is bounced. In other words, it does not
21404 delay when a new message arrives, but immediately tries those expired IP
21405 addresses that haven't been tried since the message arrived. If there is a
21406 continuous stream of messages for the dead hosts, unsetting
21407 &%delay_after_cutoff%& means that there will be many more attempts to deliver
21411 .option dns_qualify_single smtp boolean true
21412 If the &%hosts%& or &%fallback_hosts%& option is being used,
21413 and the &%gethostbyname%& option is false,
21414 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
21415 in chapter &<<CHAPdnslookup>>& for more details.
21418 .option dns_search_parents smtp boolean false
21419 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
21420 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
21421 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
21426 .option fallback_hosts smtp "string list" unset
21427 .cindex "fallback" "hosts specified on transport"
21428 String expansion is not applied to this option. The argument must be a
21429 colon-separated list of host names or IP addresses, optionally also including
21430 port numbers, though the separator can be changed, as described in section
21431 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
21432 item in a &%route_list%& setting for the &(manualroute)& router, as described
21433 in section &<<SECTformatonehostitem>>&.
21435 Fallback hosts can also be specified on routers, which associate them with the
21436 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
21437 &%fallback_hosts%& specified on the transport is used only if the address does
21438 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
21439 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
21440 However, &%hosts_randomize%& does apply to fallback host lists.
21442 If Exim is unable to deliver to any of the hosts for a particular address, and
21443 the errors are not permanent rejections, the address is put on a separate
21444 transport queue with its host list replaced by the fallback hosts, unless the
21445 address was routed via MX records and the current host was in the original MX
21446 list. In that situation, the fallback host list is not used.
21448 Once normal deliveries are complete, the fallback queue is delivered by
21449 re-running the same transports with the new host lists. If several failing
21450 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
21451 copy of the message is sent.
21453 The resolution of the host names on the fallback list is controlled by the
21454 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
21455 both to cases when the host list comes with the address and when it is taken
21456 from &%hosts%&. This option provides a &"use a smart host only if delivery
21460 .option final_timeout smtp time 10m
21461 This is the timeout that applies while waiting for the response to the final
21462 line containing just &"."& that terminates a message. Its value must not be
21465 .option gethostbyname smtp boolean false
21466 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
21467 being used, names are looked up using &[gethostbyname()]&
21468 (or &[getipnodebyname()]& when available)
21469 instead of using the DNS. Of course, that function may in fact use the DNS, but
21470 it may also consult other sources of information such as &_/etc/hosts_&.
21472 .option gnutls_require_kx smtp string unset
21473 This option controls the key exchange mechanisms when GnuTLS is used in an Exim
21474 client. For details, see section &<<SECTreqciphgnu>>&.
21476 .option gnutls_require_mac smtp string unset
21477 This option controls the MAC algorithms when GnuTLS is used in an Exim
21478 client. For details, see section &<<SECTreqciphgnu>>&.
21480 .option gnutls_require_protocols smtp string unset
21481 This option controls the protocols when GnuTLS is used in an Exim
21482 client. For details, see section &<<SECTreqciphgnu>>&.
21484 .option gnutls_compat_mode smtp boolean unset
21485 This option controls whether GnuTLS is used in compatibility mode in an Exim
21486 server. This reduces security slightly, but improves interworking with older
21487 implementations of TLS.
21489 .option helo_data smtp string&!! "see below"
21490 .cindex "HELO" "argument, setting"
21491 .cindex "EHLO" "argument, setting"
21492 .cindex "LHLO argument setting"
21493 The value of this option is expanded after a connection to a another host has
21494 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
21495 command that starts the outgoing SMTP or LMTP session. The default value of the
21500 During the expansion, the variables &$host$& and &$host_address$& are set to
21501 the identity of the remote host, and the variables &$sending_ip_address$& and
21502 &$sending_port$& are set to the local IP address and port number that are being
21503 used. These variables can be used to generate different values for different
21504 servers or different local IP addresses. For example, if you want the string
21505 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
21506 interface address, you could use this:
21508 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
21509 {$primary_hostname}}
21511 The use of &%helo_data%& applies both to sending messages and when doing
21514 .option hosts smtp "string list&!!" unset
21515 Hosts are associated with an address by a router such as &(dnslookup)&, which
21516 finds the hosts by looking up the address domain in the DNS, or by
21517 &(manualroute)&, which has lists of hosts in its configuration. However,
21518 email addresses can be passed to the &(smtp)& transport by any router, and not
21519 all of them can provide an associated list of hosts.
21521 The &%hosts%& option specifies a list of hosts to be used if the address being
21522 processed does not have any hosts associated with it. The hosts specified by
21523 &%hosts%& are also used, whether or not the address has its own hosts, if
21524 &%hosts_override%& is set.
21526 The string is first expanded, before being interpreted as a colon-separated
21527 list of host names or IP addresses, possibly including port numbers. The
21528 separator may be changed to something other than colon, as described in section
21529 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
21530 item in a &%route_list%& setting for the &(manualroute)& router, as described
21531 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
21532 of the &(manualroute)& router is not available here.
21534 If the expansion fails, delivery is deferred. Unless the failure was caused by
21535 the inability to complete a lookup, the error is logged to the panic log as
21536 well as the main log. Host names are looked up either by searching directly for
21537 address records in the DNS or by calling &[gethostbyname()]& (or
21538 &[getipnodebyname()]& when available), depending on the setting of the
21539 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
21540 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
21543 During delivery, the hosts are tried in order, subject to their retry status,
21544 unless &%hosts_randomize%& is set.
21547 .option hosts_avoid_esmtp smtp "host list&!!" unset
21548 .cindex "ESMTP, avoiding use of"
21549 .cindex "HELO" "forcing use of"
21550 .cindex "EHLO" "avoiding use of"
21551 .cindex "PIPELINING" "avoiding the use of"
21552 This option is for use with broken hosts that announce ESMTP facilities (for
21553 example, PIPELINING) and then fail to implement them properly. When a host
21554 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
21555 start of the SMTP session. This means that it cannot use any of the ESMTP
21556 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
21559 .option hosts_avoid_pipelining smtp "host list&!!" unset
21560 .cindex "PIPELINING" "avoiding the use of"
21561 Exim will not use the SMTP PIPELINING extension when delivering to any host
21562 that matches this list, even if the server host advertises PIPELINING support.
21565 .option hosts_avoid_tls smtp "host list&!!" unset
21566 .cindex "TLS" "avoiding for certain hosts"
21567 Exim will not try to start a TLS session when delivering to any host that
21568 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
21571 .option hosts_max_try smtp integer 5
21572 .cindex "host" "maximum number to try"
21573 .cindex "limit" "number of hosts tried"
21574 .cindex "limit" "number of MX tried"
21575 .cindex "MX record" "maximum tried"
21576 This option limits the number of IP addresses that are tried for any one
21577 delivery in cases where there are temporary delivery errors. Section
21578 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
21581 .option hosts_max_try_hardlimit smtp integer 50
21582 This is an additional check on the maximum number of IP addresses that Exim
21583 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
21588 .option hosts_nopass_tls smtp "host list&!!" unset
21589 .cindex "TLS" "passing connection"
21590 .cindex "multiple SMTP deliveries"
21591 .cindex "TLS" "multiple message deliveries"
21592 For any host that matches this list, a connection on which a TLS session has
21593 been started will not be passed to a new delivery process for sending another
21594 message on the same connection. See section &<<SECTmulmessam>>& for an
21595 explanation of when this might be needed.
21598 .option hosts_override smtp boolean false
21599 If this option is set and the &%hosts%& option is also set, any hosts that are
21600 attached to the address are ignored, and instead the hosts specified by the
21601 &%hosts%& option are always used. This option does not apply to
21602 &%fallback_hosts%&.
21605 .option hosts_randomize smtp boolean false
21606 .cindex "randomized host list"
21607 .cindex "host" "list of; randomized"
21608 .cindex "fallback" "randomized hosts"
21609 If this option is set, and either the list of hosts is taken from the
21610 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
21611 were not obtained from MX records (this includes fallback hosts from the
21612 router), and were not randomized by the router, the order of trying the hosts
21613 is randomized each time the transport runs. Randomizing the order of a host
21614 list can be used to do crude load sharing.
21616 When &%hosts_randomize%& is true, a host list may be split into groups whose
21617 order is separately randomized. This makes it possible to set up MX-like
21618 behaviour. The boundaries between groups are indicated by an item that is just
21619 &`+`& in the host list. For example:
21621 hosts = host1:host2:host3:+:host4:host5
21623 The order of the first three hosts and the order of the last two hosts is
21624 randomized for each use, but the first three always end up before the last two.
21625 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
21627 .option hosts_require_auth smtp "host list&!!" unset
21628 .cindex "authentication" "required by client"
21629 This option provides a list of servers for which authentication must succeed
21630 before Exim will try to transfer a message. If authentication fails for
21631 servers which are not in this list, Exim tries to send unauthenticated. If
21632 authentication fails for one of these servers, delivery is deferred. This
21633 temporary error is detectable in the retry rules, so it can be turned into a
21634 hard failure if required. See also &%hosts_try_auth%&, and chapter
21635 &<<CHAPSMTPAUTH>>& for details of authentication.
21638 .option hosts_require_tls smtp "host list&!!" unset
21639 .cindex "TLS" "requiring for certain servers"
21640 Exim will insist on using a TLS session when delivering to any host that
21641 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
21642 &*Note*&: This option affects outgoing mail only. To insist on TLS for
21643 incoming messages, use an appropriate ACL.
21645 .option hosts_try_auth smtp "host list&!!" unset
21646 .cindex "authentication" "optional in client"
21647 This option provides a list of servers to which, provided they announce
21648 authentication support, Exim will attempt to authenticate as a client when it
21649 connects. If authentication fails, Exim will try to transfer the message
21650 unauthenticated. See also &%hosts_require_auth%&, and chapter
21651 &<<CHAPSMTPAUTH>>& for details of authentication.
21653 .option interface smtp "string list&!!" unset
21654 .cindex "bind IP address"
21655 .cindex "IP address" "binding"
21657 .vindex "&$host_address$&"
21658 This option specifies which interface to bind to when making an outgoing SMTP
21659 call. The value is an IP address, not an interface name such as
21660 &`eth0`&. Do not confuse this with the interface address that was used when a
21661 message was received, which is in &$received_ip_address$&, formerly known as
21662 &$interface_address$&. The name was changed to minimize confusion with the
21663 outgoing interface address. There is no variable that contains an outgoing
21664 interface address because, unless it is set by this option, its value is
21667 During the expansion of the &%interface%& option the variables &$host$& and
21668 &$host_address$& refer to the host to which a connection is about to be made
21669 during the expansion of the string. Forced expansion failure, or an empty
21670 string result causes the option to be ignored. Otherwise, after expansion, the
21671 string must be a list of IP addresses, colon-separated by default, but the
21672 separator can be changed in the usual way. For example:
21674 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
21676 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
21677 connection. If none of them are the correct type, the option is ignored. If
21678 &%interface%& is not set, or is ignored, the system's IP functions choose which
21679 interface to use if the host has more than one.
21682 .option keepalive smtp boolean true
21683 .cindex "keepalive" "on outgoing connection"
21684 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
21685 connections. When set, it causes the kernel to probe idle connections
21686 periodically, by sending packets with &"old"& sequence numbers. The other end
21687 of the connection should send a acknowledgment if the connection is still okay
21688 or a reset if the connection has been aborted. The reason for doing this is
21689 that it has the beneficial effect of freeing up certain types of connection
21690 that can get stuck when the remote host is disconnected without tidying up the
21691 TCP/IP call properly. The keepalive mechanism takes several hours to detect
21695 .option lmtp_ignore_quota smtp boolean false
21696 .cindex "LMTP" "ignoring quota errors"
21697 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
21698 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
21699 has advertised support for IGNOREQUOTA in its response to the LHLO command.
21701 .option max_rcpt smtp integer 100
21702 .cindex "RCPT" "maximum number of outgoing"
21703 This option limits the number of RCPT commands that are sent in a single
21704 SMTP message transaction. Each set of addresses is treated independently, and
21705 so can cause parallel connections to the same host if &%remote_max_parallel%&
21709 .option multi_domain smtp boolean true
21710 .vindex "&$domain$&"
21711 When this option is set, the &(smtp)& transport can handle a number of
21712 addresses containing a mixture of different domains provided they all resolve
21713 to the same list of hosts. Turning the option off restricts the transport to
21714 handling only one domain at a time. This is useful if you want to use
21715 &$domain$& in an expansion for the transport, because it is set only when there
21716 is a single domain involved in a remote delivery.
21719 .option port smtp string&!! "see below"
21720 .cindex "port" "sending TCP/IP"
21721 .cindex "TCP/IP" "setting outgoing port"
21722 This option specifies the TCP/IP port on the server to which Exim connects.
21723 &*Note:*& Do not confuse this with the port that was used when a message was
21724 received, which is in &$received_port$&, formerly known as &$interface_port$&.
21725 The name was changed to minimize confusion with the outgoing port. There is no
21726 variable that contains an outgoing port.
21728 If the value of this option begins with a digit it is taken as a port number;
21729 otherwise it is looked up using &[getservbyname()]&. The default value is
21730 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
21731 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
21736 .option protocol smtp string smtp
21737 .cindex "LMTP" "over TCP/IP"
21738 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
21739 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
21740 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
21741 deliveries into closed message stores. Exim also has support for running LMTP
21742 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
21745 .option retry_include_ip_address smtp boolean true
21746 Exim normally includes both the host name and the IP address in the key it
21747 constructs for indexing retry data after a temporary delivery failure. This
21748 means that when one of several IP addresses for a host is failing, it gets
21749 tried periodically (controlled by the retry rules), but use of the other IP
21750 addresses is not affected.
21752 However, in some dialup environments hosts are assigned a different IP address
21753 each time they connect. In this situation the use of the IP address as part of
21754 the retry key leads to undesirable behaviour. Setting this option false causes
21755 Exim to use only the host name. This should normally be done on a separate
21756 instance of the &(smtp)& transport, set up specially to handle the dialup
21760 .option serialize_hosts smtp "host list&!!" unset
21761 .cindex "serializing connections"
21762 .cindex "host" "serializing connections"
21763 Because Exim operates in a distributed manner, if several messages for the same
21764 host arrive at around the same time, more than one simultaneous connection to
21765 the remote host can occur. This is not usually a problem except when there is a
21766 slow link between the hosts. In that situation it may be helpful to restrict
21767 Exim to one connection at a time. This can be done by setting
21768 &%serialize_hosts%& to match the relevant hosts.
21770 .cindex "hints database" "serializing deliveries to a host"
21771 Exim implements serialization by means of a hints database in which a record is
21772 written whenever a process connects to one of the restricted hosts. The record
21773 is deleted when the connection is completed. Obviously there is scope for
21774 records to get left lying around if there is a system or program crash. To
21775 guard against this, Exim ignores any records that are more than six hours old.
21777 If you set up this kind of serialization, you should also arrange to delete the
21778 relevant hints database whenever your system reboots. The names of the files
21779 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21780 may be one or two files, depending on the type of DBM in use. The same files
21781 are used for ETRN serialization.
21784 .option size_addition smtp integer 1024
21785 .cindex "SMTP" "SIZE"
21786 .cindex "message" "size issue for transport filter"
21787 .cindex "size" "of message"
21788 .cindex "transport" "filter"
21789 .cindex "filter" "transport filter"
21790 If a remote SMTP server indicates that it supports the SIZE option of the
21791 MAIL command, Exim uses this to pass over the message size at the start of
21792 an SMTP transaction. It adds the value of &%size_addition%& to the value it
21793 sends, to allow for headers and other text that may be added during delivery by
21794 configuration options or in a transport filter. It may be necessary to increase
21795 this if a lot of text is added to messages.
21797 Alternatively, if the value of &%size_addition%& is set negative, it disables
21798 the use of the SIZE option altogether.
21801 .option tls_certificate smtp string&!! unset
21802 .cindex "TLS" "client certificate, location of"
21803 .cindex "certificate" "client, location of"
21805 .vindex "&$host_address$&"
21806 The value of this option must be the absolute path to a file which contains the
21807 client's certificate, for possible use when sending a message over an encrypted
21808 connection. The values of &$host$& and &$host_address$& are set to the name and
21809 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
21812 &*Note*&: This option must be set if you want Exim to be able to use a TLS
21813 certificate when sending messages as a client. The global option of the same
21814 name specifies the certificate for Exim as a server; it is not automatically
21815 assumed that the same certificate should be used when Exim is operating as a
21819 .option tls_crl smtp string&!! unset
21820 .cindex "TLS" "client certificate revocation list"
21821 .cindex "certificate" "revocation list for client"
21822 This option specifies a certificate revocation list. The expanded value must
21823 be the name of a file that contains a CRL in PEM format.
21826 .option tls_privatekey smtp string&!! unset
21827 .cindex "TLS" "client private key, location of"
21829 .vindex "&$host_address$&"
21830 The value of this option must be the absolute path to a file which contains the
21831 client's private key. This is used when sending a message over an encrypted
21832 connection using a client certificate. The values of &$host$& and
21833 &$host_address$& are set to the name and address of the server during the
21834 expansion. If this option is unset, or the expansion is forced to fail, or the
21835 result is an empty string, the private key is assumed to be in the same file as
21836 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
21839 .option tls_require_ciphers smtp string&!! unset
21840 .cindex "TLS" "requiring specific ciphers"
21841 .cindex "cipher" "requiring specific"
21843 .vindex "&$host_address$&"
21844 The value of this option must be a list of permitted cipher suites, for use
21845 when setting up an outgoing encrypted connection. (There is a global option of
21846 the same name for controlling incoming connections.) The values of &$host$& and
21847 &$host_address$& are set to the name and address of the server during the
21848 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
21849 is used in different ways by OpenSSL and GnuTLS (see sections
21850 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
21851 ciphers is a preference order.
21855 .option tls_tempfail_tryclear smtp boolean true
21856 .cindex "4&'xx'& responses" "to STARTTLS"
21857 When the server host is not in &%hosts_require_tls%&, and there is a problem in
21858 setting up a TLS session, this option determines whether or not Exim should try
21859 to deliver the message unencrypted. If it is set false, delivery to the
21860 current host is deferred; if there are other hosts, they are tried. If this
21861 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
21862 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
21863 TLS negotiation fails, Exim closes the current connection (because it is in an
21864 unknown state), opens a new one to the same host, and then tries the delivery
21868 .option tls_verify_certificates smtp string&!! unset
21869 .cindex "TLS" "server certificate verification"
21870 .cindex "certificate" "verification of server"
21872 .vindex "&$host_address$&"
21873 The value of this option must be the absolute path to a file containing
21874 permitted server certificates, for use when setting up an encrypted connection.
21875 Alternatively, if you are using OpenSSL, you can set
21876 &%tls_verify_certificates%& to the name of a directory containing certificate
21877 files. This does not work with GnuTLS; the option must be set to the name of a
21878 single file if you are using GnuTLS. The values of &$host$& and
21879 &$host_address$& are set to the name and address of the server during the
21880 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
21885 .section "How the limits for the number of hosts to try are used" &&&
21887 .cindex "host" "maximum number to try"
21888 .cindex "limit" "hosts; maximum number tried"
21889 There are two options that are concerned with the number of hosts that are
21890 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
21891 &%hosts_max_try_hardlimit%&.
21894 The &%hosts_max_try%& option limits the number of hosts that are tried
21895 for a single delivery. However, despite the term &"host"& in its name, the
21896 option actually applies to each IP address independently. In other words, a
21897 multihomed host is treated as several independent hosts, just as it is for
21900 Many of the larger ISPs have multiple MX records which often point to
21901 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
21902 created as a result of routing one of these domains.
21904 Trying every single IP address on such a long list does not seem sensible; if
21905 several at the top of the list fail, it is reasonable to assume there is some
21906 problem that is likely to affect all of them. Roughly speaking, the value of
21907 &%hosts_max_try%& is the maximum number that are tried before deferring the
21908 delivery. However, the logic cannot be quite that simple.
21910 Firstly, IP addresses that are skipped because their retry times have not
21911 arrived do not count, and in addition, addresses that are past their retry
21912 limits are also not counted, even when they are tried. This means that when
21913 some IP addresses are past their retry limits, more than the value of
21914 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
21915 that all IP addresses are considered before timing out an email address (but
21916 see below for an exception).
21918 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
21919 list to see if there is a subsequent host with a different (higher valued) MX.
21920 If there is, that host is considered next, and the current IP address is used
21921 but not counted. This behaviour helps in the case of a domain with a retry rule
21922 that hardly ever delays any hosts, as is now explained:
21924 Consider the case of a long list of hosts with one MX value, and a few with a
21925 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
21926 hosts at the top of the list are tried at first. With the default retry rule,
21927 which specifies increasing retry times, the higher MX hosts are eventually
21928 tried when those at the top of the list are skipped because they have not
21929 reached their retry times.
21931 However, it is common practice to put a fixed short retry time on domains for
21932 large ISPs, on the grounds that their servers are rarely down for very long.
21933 Unfortunately, these are exactly the domains that tend to resolve to long lists
21934 of hosts. The short retry time means that the lowest MX hosts are tried every
21935 time. The attempts may be in a different order because of random sorting, but
21936 without the special MX check, the higher MX hosts would never be tried until
21937 all the lower MX hosts had timed out (which might be several days), because
21938 there are always some lower MX hosts that have reached their retry times. With
21939 the special check, Exim considers at least one IP address from each MX value at
21940 every delivery attempt, even if the &%hosts_max_try%& limit has already been
21943 The above logic means that &%hosts_max_try%& is not a hard limit, and in
21944 particular, Exim normally eventually tries all the IP addresses before timing
21945 out an email address. When &%hosts_max_try%& was implemented, this seemed a
21946 reasonable thing to do. Recently, however, some lunatic DNS configurations have
21947 been set up with hundreds of IP addresses for some domains. It can
21948 take a very long time indeed for an address to time out in these cases.
21950 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
21951 Exim never tries more than this number of IP addresses; if it hits this limit
21952 and they are all timed out, the email address is bounced, even though not all
21953 possible IP addresses have been tried.
21954 .ecindex IIDsmttra1
21955 .ecindex IIDsmttra2
21961 . ////////////////////////////////////////////////////////////////////////////
21962 . ////////////////////////////////////////////////////////////////////////////
21964 .chapter "Address rewriting" "CHAPrewrite"
21965 .scindex IIDaddrew "rewriting" "addresses"
21966 There are some circumstances in which Exim automatically rewrites domains in
21967 addresses. The two most common are when an address is given without a domain
21968 (referred to as an &"unqualified address"&) or when an address contains an
21969 abbreviated domain that is expanded by DNS lookup.
21971 Unqualified envelope addresses are accepted only for locally submitted
21972 messages, or for messages that are received from hosts matching
21973 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
21974 appropriate. Unqualified addresses in header lines are qualified if they are in
21975 locally submitted messages, or messages from hosts that are permitted to send
21976 unqualified envelope addresses. Otherwise, unqualified addresses in header
21977 lines are neither qualified nor rewritten.
21979 One situation in which Exim does &'not'& automatically rewrite a domain is
21980 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
21981 such a domain should be rewritten using the &"canonical"& name, and some MTAs
21982 do this. The new RFCs do not contain this suggestion.
21985 .section "Explicitly configured address rewriting" "SECID147"
21986 This chapter describes the rewriting rules that can be used in the
21987 main rewrite section of the configuration file, and also in the generic
21988 &%headers_rewrite%& option that can be set on any transport.
21990 Some people believe that configured address rewriting is a Mortal Sin.
21991 Others believe that life is not possible without it. Exim provides the
21992 facility; you do not have to use it.
21994 The main rewriting rules that appear in the &"rewrite"& section of the
21995 configuration file are applied to addresses in incoming messages, both envelope
21996 addresses and addresses in header lines. Each rule specifies the types of
21997 address to which it applies.
21999 Whether or not addresses in header lines are rewritten depends on the origin of
22000 the headers and the type of rewriting. Global rewriting, that is, rewriting
22001 rules from the rewrite section of the configuration file, is applied only to
22002 those headers that were received with the message. Header lines that are added
22003 by ACLs or by a system filter or by individual routers or transports (which
22004 are specific to individual recipient addresses) are not rewritten by the global
22007 Rewriting at transport time, by means of the &%headers_rewrite%& option,
22008 applies all headers except those added by routers and transports. That is, as
22009 well as the headers that were received with the message, it also applies to
22010 headers that were added by an ACL or a system filter.
22013 In general, rewriting addresses from your own system or domain has some
22014 legitimacy. Rewriting other addresses should be done only with great care and
22015 in special circumstances. The author of Exim believes that rewriting should be
22016 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
22017 Although it can sometimes be used as a routing tool, this is very strongly
22020 There are two commonly encountered circumstances where rewriting is used, as
22021 illustrated by these examples:
22024 The company whose domain is &'hitch.fict.example'& has a number of hosts that
22025 exchange mail with each other behind a firewall, but there is only a single
22026 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
22027 &'hitch.fict.example'& when sending mail off-site.
22029 A host rewrites the local parts of its own users so that, for example,
22030 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
22035 .section "When does rewriting happen?" "SECID148"
22036 .cindex "rewriting" "timing of"
22037 .cindex "&ACL;" "rewriting addresses in"
22038 Configured address rewriting can take place at several different stages of a
22039 message's processing.
22041 .vindex "&$sender_address$&"
22042 At the start of an ACL for MAIL, the sender address may have been rewritten
22043 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
22044 ordinary rewrite rules have yet been applied. If, however, the sender address
22045 is verified in the ACL, it is rewritten before verification, and remains
22046 rewritten thereafter. The subsequent value of &$sender_address$& is the
22047 rewritten address. This also applies if sender verification happens in a
22048 RCPT ACL. Otherwise, when the sender address is not verified, it is
22049 rewritten as soon as a message's header lines have been received.
22051 .vindex "&$domain$&"
22052 .vindex "&$local_part$&"
22053 Similarly, at the start of an ACL for RCPT, the current recipient's address
22054 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
22055 rewrite rules have yet been applied to it. However, the behaviour is different
22056 from the sender address when a recipient is verified. The address is rewritten
22057 for the verification, but the rewriting is not remembered at this stage. The
22058 value of &$local_part$& and &$domain$& after verification are always the same
22059 as they were before (that is, they contain the unrewritten &-- except for
22060 SMTP-time rewriting &-- address).
22062 As soon as a message's header lines have been received, all the envelope
22063 recipient addresses are permanently rewritten, and rewriting is also applied to
22064 the addresses in the header lines (if configured). This happens before adding
22065 any header lines that were specified in MAIL or RCPT ACLs, and
22066 .cindex "&[local_scan()]& function" "address rewriting; timing of"
22067 before the DATA ACL and &[local_scan()]& functions are run.
22069 When an address is being routed, either for delivery or for verification,
22070 rewriting is applied immediately to child addresses that are generated by
22071 redirection, unless &%no_rewrite%& is set on the router.
22073 .cindex "envelope sender" "rewriting at transport time"
22074 .cindex "rewriting" "at transport time"
22075 .cindex "header lines" "rewriting at transport time"
22076 At transport time, additional rewriting of addresses in header lines can be
22077 specified by setting the generic &%headers_rewrite%& option on a transport.
22078 This option contains rules that are identical in form to those in the rewrite
22079 section of the configuration file. They are applied to the original message
22080 header lines and any that were added by ACLs or a system filter. They are not
22081 applied to header lines that are added by routers or the transport.
22083 The outgoing envelope sender can be rewritten by means of the &%return_path%&
22084 transport option. However, it is not possible to rewrite envelope recipients at
22090 .section "Testing the rewriting rules that apply on input" "SECID149"
22091 .cindex "rewriting" "testing"
22092 .cindex "testing" "rewriting"
22093 Exim's input rewriting configuration appears in a part of the run time
22094 configuration file headed by &"begin rewrite"&. It can be tested by the
22095 &%-brw%& command line option. This takes an address (which can be a full RFC
22096 2822 address) as its argument. The output is a list of how the address would be
22097 transformed by the rewriting rules for each of the different places it might
22098 appear in an incoming message, that is, for each different header and for the
22099 envelope sender and recipient fields. For example,
22101 exim -brw ph10@exim.workshop.example
22103 might produce the output
22105 sender: Philip.Hazel@exim.workshop.example
22106 from: Philip.Hazel@exim.workshop.example
22107 to: ph10@exim.workshop.example
22108 cc: ph10@exim.workshop.example
22109 bcc: ph10@exim.workshop.example
22110 reply-to: Philip.Hazel@exim.workshop.example
22111 env-from: Philip.Hazel@exim.workshop.example
22112 env-to: ph10@exim.workshop.example
22114 which shows that rewriting has been set up for that address when used in any of
22115 the source fields, but not when it appears as a recipient address. At the
22116 present time, there is no equivalent way of testing rewriting rules that are
22117 set for a particular transport.
22120 .section "Rewriting rules" "SECID150"
22121 .cindex "rewriting" "rules"
22122 The rewrite section of the configuration file consists of lines of rewriting
22125 <&'source pattern'&> <&'replacement'&> <&'flags'&>
22127 Rewriting rules that are specified for the &%headers_rewrite%& generic
22128 transport option are given as a colon-separated list. Each item in the list
22129 takes the same form as a line in the main rewriting configuration (except that
22130 any colons must be doubled, of course).
22132 The formats of source patterns and replacement strings are described below.
22133 Each is terminated by white space, unless enclosed in double quotes, in which
22134 case normal quoting conventions apply inside the quotes. The flags are single
22135 characters which may appear in any order. Spaces and tabs between them are
22138 For each address that could potentially be rewritten, the rules are scanned in
22139 order, and replacements for the address from earlier rules can themselves be
22140 replaced by later rules (but see the &"q"& and &"R"& flags).
22142 The order in which addresses are rewritten is undefined, may change between
22143 releases, and must not be relied on, with one exception: when a message is
22144 received, the envelope sender is always rewritten first, before any header
22145 lines are rewritten. For example, the replacement string for a rewrite of an
22146 address in &'To:'& must not assume that the message's address in &'From:'& has
22147 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
22148 that the envelope sender has already been rewritten.
22150 .vindex "&$domain$&"
22151 .vindex "&$local_part$&"
22152 The variables &$local_part$& and &$domain$& can be used in the replacement
22153 string to refer to the address that is being rewritten. Note that lookup-driven
22154 rewriting can be done by a rule of the form
22158 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
22159 refer to the address that is being rewritten.
22162 .section "Rewriting patterns" "SECID151"
22163 .cindex "rewriting" "patterns"
22164 .cindex "address list" "in a rewriting pattern"
22165 The source pattern in a rewriting rule is any item which may appear in an
22166 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
22167 single-item address list, which means that it is expanded before being tested
22168 against the address. As always, if you use a regular expression as a pattern,
22169 you must take care to escape dollar and backslash characters, or use the &`\N`&
22170 facility to suppress string expansion within the regular expression.
22172 Domains in patterns should be given in lower case. Local parts in patterns are
22173 case-sensitive. If you want to do case-insensitive matching of local parts, you
22174 can use a regular expression that starts with &`^(?i)`&.
22176 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
22177 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
22178 depending on the type of match which occurred. These can be used in the
22179 replacement string to insert portions of the incoming address. &$0$& always
22180 refers to the complete incoming address. When a regular expression is used, the
22181 numerical variables are set from its capturing subexpressions. For other types
22182 of pattern they are set as follows:
22185 If a local part or domain starts with an asterisk, the numerical variables
22186 refer to the character strings matched by asterisks, with &$1$& associated with
22187 the first asterisk, and &$2$& with the second, if present. For example, if the
22190 *queen@*.fict.example
22192 is matched against the address &'hearts-queen@wonderland.fict.example'& then
22194 $0 = hearts-queen@wonderland.fict.example
22198 Note that if the local part does not start with an asterisk, but the domain
22199 does, it is &$1$& that contains the wild part of the domain.
22202 If the domain part of the pattern is a partial lookup, the wild and fixed parts
22203 of the domain are placed in the next available numerical variables. Suppose,
22204 for example, that the address &'foo@bar.baz.example'& is processed by a
22205 rewriting rule of the form
22207 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
22209 and the key in the file that matches the domain is &`*.baz.example`&. Then
22215 If the address &'foo@baz.example'& is looked up, this matches the same
22216 wildcard file entry, and in this case &$2$& is set to the empty string, but
22217 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
22218 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
22219 whole domain. For non-partial domain lookups, no numerical variables are set.
22223 .section "Rewriting replacements" "SECID152"
22224 .cindex "rewriting" "replacements"
22225 If the replacement string for a rule is a single asterisk, addresses that
22226 match the pattern and the flags are &'not'& rewritten, and no subsequent
22227 rewriting rules are scanned. For example,
22229 hatta@lookingglass.fict.example * f
22231 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
22234 .vindex "&$domain$&"
22235 .vindex "&$local_part$&"
22236 If the replacement string is not a single asterisk, it is expanded, and must
22237 yield a fully qualified address. Within the expansion, the variables
22238 &$local_part$& and &$domain$& refer to the address that is being rewritten.
22239 Any letters they contain retain their original case &-- they are not lower
22240 cased. The numerical variables are set up according to the type of pattern that
22241 matched the address, as described above. If the expansion is forced to fail by
22242 the presence of &"fail"& in a conditional or lookup item, rewriting by the
22243 current rule is abandoned, but subsequent rules may take effect. Any other
22244 expansion failure causes the entire rewriting operation to be abandoned, and an
22245 entry written to the panic log.
22249 .section "Rewriting flags" "SECID153"
22250 There are three different kinds of flag that may appear on rewriting rules:
22253 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
22256 A flag that specifies rewriting at SMTP time: S.
22258 Flags that control the rewriting process: Q, q, R, w.
22261 For rules that are part of the &%headers_rewrite%& generic transport option,
22262 E, F, T, and S are not permitted.
22266 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
22268 .cindex "rewriting" "flags"
22269 If none of the following flag letters, nor the &"S"& flag (see section
22270 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
22271 and to both the sender and recipient fields of the envelope, whereas a
22272 transport-time rewriting rule just applies to all headers. Otherwise, the
22273 rewriting rule is skipped unless the relevant addresses are being processed.
22275 &`E`& rewrite all envelope fields
22276 &`F`& rewrite the envelope From field
22277 &`T`& rewrite the envelope To field
22278 &`b`& rewrite the &'Bcc:'& header
22279 &`c`& rewrite the &'Cc:'& header
22280 &`f`& rewrite the &'From:'& header
22281 &`h`& rewrite all headers
22282 &`r`& rewrite the &'Reply-To:'& header
22283 &`s`& rewrite the &'Sender:'& header
22284 &`t`& rewrite the &'To:'& header
22286 "All headers" means all of the headers listed above that can be selected
22287 individually, plus their &'Resent-'& versions. It does not include
22288 other headers such as &'Subject:'& etc.
22290 You should be particularly careful about rewriting &'Sender:'& headers, and
22291 restrict this to special known cases in your own domains.
22294 .section "The SMTP-time rewriting flag" "SECTrewriteS"
22295 .cindex "SMTP" "rewriting malformed addresses"
22296 .cindex "RCPT" "rewriting argument of"
22297 .cindex "MAIL" "rewriting argument of"
22298 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
22299 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
22300 before any other processing; even before syntax checking. The pattern is
22301 required to be a regular expression, and it is matched against the whole of the
22302 data for the command, including any surrounding angle brackets.
22304 .vindex "&$domain$&"
22305 .vindex "&$local_part$&"
22306 This form of rewrite rule allows for the handling of addresses that are not
22307 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
22308 input). Because the input is not required to be a syntactically valid address,
22309 the variables &$local_part$& and &$domain$& are not available during the
22310 expansion of the replacement string. The result of rewriting replaces the
22311 original address in the MAIL or RCPT command.
22314 .section "Flags controlling the rewriting process" "SECID155"
22315 There are four flags which control the way the rewriting process works. These
22316 take effect only when a rule is invoked, that is, when the address is of the
22317 correct type (matches the flags) and matches the pattern:
22320 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
22321 unqualified local part. It is qualified with &%qualify_recipient%&. In the
22322 absence of &"Q"& the rewritten address must always include a domain.
22324 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
22325 even if no rewriting actually takes place because of a &"fail"& in the
22326 expansion. The &"q"& flag is not effective if the address is of the wrong type
22327 (does not match the flags) or does not match the pattern.
22329 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
22330 address, up to ten times. It can be combined with the &"q"& flag, to stop
22331 rewriting once it fails to match (after at least one successful rewrite).
22333 .cindex "rewriting" "whole addresses"
22334 When an address in a header is rewritten, the rewriting normally applies only
22335 to the working part of the address, with any comments and RFC 2822 &"phrase"&
22336 left unchanged. For example, rewriting might change
22338 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
22342 From: Ford Prefect <prefectf@hitch.fict.example>
22345 Sometimes there is a need to replace the whole address item, and this can be
22346 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
22347 causes an address in a header line to be rewritten, the entire address is
22348 replaced, not just the working part. The replacement must be a complete RFC
22349 2822 address, including the angle brackets if necessary. If text outside angle
22350 brackets contains a character whose value is greater than 126 or less than 32
22351 (except for tab), the text is encoded according to RFC 2047. The character set
22352 is taken from &%headers_charset%&, which defaults to ISO-8859-1.
22354 When the &"w"& flag is set on a rule that causes an envelope address to be
22355 rewritten, all but the working part of the replacement address is discarded.
22359 .section "Rewriting examples" "SECID156"
22360 Here is an example of the two common rewriting paradigms:
22362 *@*.hitch.fict.example $1@hitch.fict.example
22363 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
22364 {$value}fail}@hitch.fict.example bctfrF
22366 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
22367 the string expansion to fail if the lookup does not succeed. In this context it
22368 has the effect of leaving the original address unchanged, but Exim goes on to
22369 consider subsequent rewriting rules, if any, because the &"q"& flag is not
22370 present in that rule. An alternative to &"fail"& would be to supply &$1$&
22371 explicitly, which would cause the rewritten address to be the same as before,
22372 at the cost of a small bit of processing. Not supplying either of these is an
22373 error, since the rewritten address would then contain no local part.
22375 The first example above replaces the domain with a superior, more general
22376 domain. This may not be desirable for certain local parts. If the rule
22378 root@*.hitch.fict.example *
22380 were inserted before the first rule, rewriting would be suppressed for the
22381 local part &'root'& at any domain ending in &'hitch.fict.example'&.
22383 Rewriting can be made conditional on a number of tests, by making use of
22384 &${if$& in the expansion item. For example, to apply a rewriting rule only to
22385 messages that originate outside the local host:
22387 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
22388 {$1@hitch.fict.example}fail}"
22390 The replacement string is quoted in this example because it contains white
22393 .cindex "rewriting" "bang paths"
22394 .cindex "bang paths" "rewriting"
22395 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
22396 an address it treats it as an unqualified local part which it qualifies with
22397 the local qualification domain (if the source of the message is local or if the
22398 remote host is permitted to send unqualified addresses). Rewriting can
22399 sometimes be used to handle simple bang paths with a fixed number of
22400 components. For example, the rule
22402 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
22404 rewrites a two-component bang path &'host.name!user'& as the domain address
22405 &'user@host.name'&. However, there is a security implication in using this as
22406 a global rewriting rule for envelope addresses. It can provide a backdoor
22407 method for using your system as a relay, because the incoming addresses appear
22408 to be local. If the bang path addresses are received via SMTP, it is safer to
22409 use the &"S"& flag to rewrite them as they are received, so that relay checking
22410 can be done on the rewritten addresses.
22417 . ////////////////////////////////////////////////////////////////////////////
22418 . ////////////////////////////////////////////////////////////////////////////
22420 .chapter "Retry configuration" "CHAPretry"
22421 .scindex IIDretconf1 "retry" "configuration, description of"
22422 .scindex IIDregconf2 "configuration file" "retry section"
22423 The &"retry"& section of the runtime configuration file contains a list of
22424 retry rules that control how often Exim tries to deliver messages that cannot
22425 be delivered at the first attempt. If there are no retry rules (the section is
22426 empty or not present), there are no retries. In this situation, temporary
22427 errors are treated as permanent. The default configuration contains a single,
22428 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
22429 line option can be used to test which retry rule will be used for a given
22430 address, domain and error.
22432 The most common cause of retries is temporary failure to deliver to a remote
22433 host because the host is down, or inaccessible because of a network problem.
22434 Exim's retry processing in this case is applied on a per-host (strictly, per IP
22435 address) basis, not on a per-message basis. Thus, if one message has recently
22436 been delayed, delivery of a new message to the same host is not immediately
22437 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
22438 log selector is set, the message
22439 .cindex "retry" "time not reached"
22440 &"retry time not reached"& is written to the main log whenever a delivery is
22441 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
22442 the handling of errors during remote deliveries.
22444 Retry processing applies to routing as well as to delivering, except as covered
22445 in the next paragraph. The retry rules do not distinguish between these
22446 actions. It is not possible, for example, to specify different behaviour for
22447 failures to route the domain &'snark.fict.example'& and failures to deliver to
22448 the host &'snark.fict.example'&. I didn't think anyone would ever need this
22449 added complication, so did not implement it. However, although they share the
22450 same retry rule, the actual retry times for routing and transporting a given
22451 domain are maintained independently.
22453 When a delivery is not part of a queue run (typically an immediate delivery on
22454 receipt of a message), the routers are always run, and local deliveries are
22455 always attempted, even if retry times are set for them. This makes for better
22456 behaviour if one particular message is causing problems (for example, causing
22457 quota overflow, or provoking an error in a filter file). If such a delivery
22458 suffers a temporary failure, the retry data is updated as normal, and
22459 subsequent delivery attempts from queue runs occur only when the retry time for
22460 the local address is reached.
22462 .section "Changing retry rules" "SECID157"
22463 If you change the retry rules in your configuration, you should consider
22464 whether or not to delete the retry data that is stored in Exim's spool area in
22465 files with names like &_db/retry_&. Deleting any of Exim's hints files is
22466 always safe; that is why they are called &"hints"&.
22468 The hints retry data contains suggested retry times based on the previous
22469 rules. In the case of a long-running problem with a remote host, it might
22470 record the fact that the host has timed out. If your new rules increase the
22471 timeout time for such a host, you should definitely remove the old retry data
22472 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
22473 messages that it should now be retaining.
22477 .section "Format of retry rules" "SECID158"
22478 .cindex "retry" "rules"
22479 Each retry rule occupies one line and consists of three or four parts,
22480 separated by white space: a pattern, an error name, an optional list of sender
22481 addresses, and a list of retry parameters. The pattern and sender lists must be
22482 enclosed in double quotes if they contain white space. The rules are searched
22483 in order until one is found where the pattern, error name, and sender list (if
22484 present) match the failing host or address, the error that occurred, and the
22485 message's sender, respectively.
22488 The pattern is any single item that may appear in an address list (see section
22489 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
22490 which means that it is expanded before being tested against the address that
22491 has been delayed. A negated address list item is permitted. Address
22492 list processing treats a plain domain name as if it were preceded by &"*@"&,
22493 which makes it possible for many retry rules to start with just a domain. For
22496 lookingglass.fict.example * F,24h,30m;
22498 provides a rule for any address in the &'lookingglass.fict.example'& domain,
22501 alice@lookingglass.fict.example * F,24h,30m;
22503 applies only to temporary failures involving the local part &%alice%&.
22504 In practice, almost all rules start with a domain name pattern without a local
22507 .cindex "regular expressions" "in retry rules"
22508 &*Warning*&: If you use a regular expression in a routing rule pattern, it
22509 must match a complete address, not just a domain, because that is how regular
22510 expressions work in address lists.
22512 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
22513 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
22517 .section "Choosing which retry rule to use for address errors" "SECID159"
22518 When Exim is looking for a retry rule after a routing attempt has failed (for
22519 example, after a DNS timeout), each line in the retry configuration is tested
22520 against the complete address only if &%retry_use_local_part%& is set for the
22521 router. Otherwise, only the domain is used, except when matching against a
22522 regular expression, when the local part of the address is replaced with &"*"&.
22523 A domain on its own can match a domain pattern, or a pattern that starts with
22524 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
22525 &%check_local_user%& is true, and false for other routers.
22527 Similarly, when Exim is looking for a retry rule after a local delivery has
22528 failed (for example, after a mailbox full error), each line in the retry
22529 configuration is tested against the complete address only if
22530 &%retry_use_local_part%& is set for the transport (it defaults true for all
22533 .cindex "4&'xx'& responses" "retry rules for"
22534 However, when Exim is looking for a retry rule after a remote delivery attempt
22535 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
22536 whole address is always used as the key when searching the retry rules. The
22537 rule that is found is used to create a retry time for the combination of the
22538 failing address and the message's sender. It is the combination of sender and
22539 recipient that is delayed in subsequent queue runs until its retry time is
22540 reached. You can delay the recipient without regard to the sender by setting
22541 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
22542 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
22547 .section "Choosing which retry rule to use for host and message errors" &&&
22549 For a temporary error that is not related to an individual address (for
22550 example, a connection timeout), each line in the retry configuration is checked
22551 twice. First, the name of the remote host is used as a domain name (preceded by
22552 &"*@"& when matching a regular expression). If this does not match the line,
22553 the domain from the email address is tried in a similar fashion. For example,
22554 suppose the MX records for &'a.b.c.example'& are
22556 a.b.c.example MX 5 x.y.z.example
22560 and the retry rules are
22562 p.q.r.example * F,24h,30m;
22563 a.b.c.example * F,4d,45m;
22565 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
22566 first rule matches neither the host nor the domain, so Exim looks at the second
22567 rule. This does not match the host, but it does match the domain, so it is used
22568 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
22569 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
22570 first retry rule is used, because it matches the host.
22572 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
22573 first rule to determine retry times, but for all the other hosts for the domain
22574 &'a.b.c.example'&, the second rule is used. The second rule is also used if
22575 routing to &'a.b.c.example'& suffers a temporary failure.
22577 &*Note*&: The host name is used when matching the patterns, not its IP address.
22578 However, if a message is routed directly to an IP address without the use of a
22579 host name, for example, if a &(manualroute)& router contains a setting such as:
22581 route_list = *.a.example 192.168.34.23
22583 then the &"host name"& that is used when searching for a retry rule is the
22584 textual form of the IP address.
22586 .section "Retry rules for specific errors" "SECID161"
22587 .cindex "retry" "specific errors; specifying"
22588 The second field in a retry rule is the name of a particular error, or an
22589 asterisk, which matches any error. The errors that can be tested for are:
22592 .vitem &%auth_failed%&
22593 Authentication failed when trying to send to a host in the
22594 &%hosts_require_auth%& list in an &(smtp)& transport.
22596 .vitem &%data_4xx%&
22597 A 4&'xx'& error was received for an outgoing DATA command, either immediately
22598 after the command, or after sending the message's data.
22600 .vitem &%mail_4xx%&
22601 A 4&'xx'& error was received for an outgoing MAIL command.
22603 .vitem &%rcpt_4xx%&
22604 A 4&'xx'& error was received for an outgoing RCPT command.
22607 For the three 4&'xx'& errors, either the first or both of the x's can be given
22608 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
22609 recognize 452 errors given to RCPT commands for addresses in a certain domain,
22610 and have retries every ten minutes with a one-hour timeout, you could set up a
22611 retry rule of this form:
22613 the.domain.name rcpt_452 F,1h,10m
22615 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
22616 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
22619 .vitem &%lost_connection%&
22620 A server unexpectedly closed the SMTP connection. There may, of course,
22621 legitimate reasons for this (host died, network died), but if it repeats a lot
22622 for the same host, it indicates something odd.
22624 .vitem &%refused_MX%&
22625 A connection to a host obtained from an MX record was refused.
22627 .vitem &%refused_A%&
22628 A connection to a host not obtained from an MX record was refused.
22631 A connection was refused.
22633 .vitem &%timeout_connect_MX%&
22634 A connection attempt to a host obtained from an MX record timed out.
22636 .vitem &%timeout_connect_A%&
22637 A connection attempt to a host not obtained from an MX record timed out.
22639 .vitem &%timeout_connect%&
22640 A connection attempt timed out.
22642 .vitem &%timeout_MX%&
22643 There was a timeout while connecting or during an SMTP session with a host
22644 obtained from an MX record.
22646 .vitem &%timeout_A%&
22647 There was a timeout while connecting or during an SMTP session with a host not
22648 obtained from an MX record.
22651 There was a timeout while connecting or during an SMTP session.
22653 .vitem &%tls_required%&
22654 The server was required to use TLS (it matched &%hosts_require_tls%& in the
22655 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
22656 to STARTTLS, or there was a problem setting up the TLS connection.
22659 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
22662 .vitem &%quota_%&<&'time'&>
22663 .cindex "quota" "error testing in retry rule"
22664 .cindex "retry" "quota error testing"
22665 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
22666 transport, and the mailbox has not been accessed for <&'time'&>. For example,
22667 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
22671 .cindex "mailbox" "time of last read"
22672 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
22673 timeouts when the mailbox is full and is not being read by its owner. Ideally,
22674 it should be based on the last time that the user accessed the mailbox.
22675 However, it is not always possible to determine this. Exim uses the following
22679 If the mailbox is a single file, the time of last access (the &"atime"&) is
22680 used. As no new messages are being delivered (because the mailbox is over
22681 quota), Exim does not access the file, so this is the time of last user access.
22683 .cindex "maildir format" "time of last read"
22684 For a maildir delivery, the time of last modification of the &_new_&
22685 subdirectory is used. As the mailbox is over quota, no new files are created in
22686 the &_new_& subdirectory, because no new messages are being delivered. Any
22687 change to the &_new_& subdirectory is therefore assumed to be the result of an
22688 MUA moving a new message to the &_cur_& directory when it is first read. The
22689 time that is used is therefore the last time that the user read a new message.
22691 For other kinds of multi-file mailbox, the time of last access cannot be
22692 obtained, so a retry rule that uses this type of error field is never matched.
22695 The quota errors apply both to system-enforced quotas and to Exim's own quota
22696 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
22697 when a local delivery is deferred because a partition is full (the ENOSPC
22702 .section "Retry rules for specified senders" "SECID162"
22703 .cindex "retry" "rules; sender-specific"
22704 You can specify retry rules that apply only when the failing message has a
22705 specific sender. In particular, this can be used to define retry rules that
22706 apply only to bounce messages. The third item in a retry rule can be of this
22709 &`senders=`&<&'address list'&>
22711 The retry timings themselves are then the fourth item. For example:
22713 * rcpt_4xx senders=: F,1h,30m
22715 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
22716 host. If the address list contains white space, it must be enclosed in quotes.
22719 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
22721 &*Warning*&: This facility can be unhelpful if it is used for host errors
22722 (which do not depend on the recipient). The reason is that the sender is used
22723 only to match the retry rule. Once the rule has been found for a host error,
22724 its contents are used to set a retry time for the host, and this will apply to
22725 all messages, not just those with specific senders.
22727 When testing retry rules using &%-brt%&, you can supply a sender using the
22728 &%-f%& command line option, like this:
22730 exim -f "" -brt user@dom.ain
22732 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
22733 list is never matched.
22739 .section "Retry parameters" "SECID163"
22740 .cindex "retry" "parameters in rules"
22741 The third (or fourth, if a senders list is present) field in a retry rule is a
22742 sequence of retry parameter sets, separated by semicolons. Each set consists of
22744 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
22746 The letter identifies the algorithm for computing a new retry time; the cutoff
22747 time is the time beyond which this algorithm no longer applies, and the
22748 arguments vary the algorithm's action. The cutoff time is measured from the
22749 time that the first failure for the domain (combined with the local part if
22750 relevant) was detected, not from the time the message was received.
22752 .cindex "retry" "algorithms"
22753 .cindex "retry" "fixed intervals"
22754 .cindex "retry" "increasing intervals"
22755 .cindex "retry" "random intervals"
22756 The available algorithms are:
22759 &'F'&: retry at fixed intervals. There is a single time parameter specifying
22762 &'G'&: retry at geometrically increasing intervals. The first argument
22763 specifies a starting value for the interval, and the second a multiplier, which
22764 is used to increase the size of the interval at each retry.
22766 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
22767 retry, the previous interval is multiplied by the factor in order to get a
22768 maximum for the next interval. The minimum interval is the first argument of
22769 the parameter, and an actual interval is chosen randomly between them. Such a
22770 rule has been found to be helpful in cluster configurations when all the
22771 members of the cluster restart at once, and may therefore synchronize their
22772 queue processing times.
22775 When computing the next retry time, the algorithm definitions are scanned in
22776 order until one whose cutoff time has not yet passed is reached. This is then
22777 used to compute a new retry time that is later than the current time. In the
22778 case of fixed interval retries, this simply means adding the interval to the
22779 current time. For geometrically increasing intervals, retry intervals are
22780 computed from the rule's parameters until one that is greater than the previous
22781 interval is found. The main configuration variable
22782 .cindex "limit" "retry interval"
22783 .cindex "retry" "interval, maximum"
22784 .oindex "&%retry_interval_max%&"
22785 &%retry_interval_max%& limits the maximum interval between retries. It
22786 cannot be set greater than &`24h`&, which is its default value.
22788 A single remote domain may have a number of hosts associated with it, and each
22789 host may have more than one IP address. Retry algorithms are selected on the
22790 basis of the domain name, but are applied to each IP address independently. If,
22791 for example, a host has two IP addresses and one is unusable, Exim will
22792 generate retry times for it and will not try to use it until its next retry
22793 time comes. Thus the good IP address is likely to be tried first most of the
22796 .cindex "hints database" "use for retrying"
22797 Retry times are hints rather than promises. Exim does not make any attempt to
22798 run deliveries exactly at the computed times. Instead, a queue runner process
22799 starts delivery processes for delayed messages periodically, and these attempt
22800 new deliveries only for those addresses that have passed their next retry time.
22801 If a new message arrives for a deferred address, an immediate delivery attempt
22802 occurs only if the address has passed its retry time. In the absence of new
22803 messages, the minimum time between retries is the interval between queue runner
22804 processes. There is not much point in setting retry times of five minutes if
22805 your queue runners happen only once an hour, unless there are a significant
22806 number of incoming messages (which might be the case on a system that is
22807 sending everything to a smart host, for example).
22809 The data in the retry hints database can be inspected by using the
22810 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
22811 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
22812 &'exinext'& utility script can be used to find out what the next retry times
22813 are for the hosts associated with a particular mail domain, and also for local
22814 deliveries that have been deferred.
22817 .section "Retry rule examples" "SECID164"
22818 Here are some example retry rules:
22820 alice@wonderland.fict.example quota_5d F,7d,3h
22821 wonderland.fict.example quota_5d
22822 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
22823 lookingglass.fict.example * F,24h,30m;
22824 * refused_A F,2h,20m;
22825 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
22827 The first rule sets up special handling for mail to
22828 &'alice@wonderland.fict.example'& when there is an over-quota error and the
22829 mailbox has not been read for at least 5 days. Retries continue every three
22830 hours for 7 days. The second rule handles over-quota errors for all other local
22831 parts at &'wonderland.fict.example'&; the absence of a local part has the same
22832 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
22833 fail are bounced immediately if the mailbox has not been read for at least 5
22836 The third rule handles all other errors at &'wonderland.fict.example'&; retries
22837 happen every 15 minutes for an hour, then with geometrically increasing
22838 intervals until two days have passed since a delivery first failed. After the
22839 first hour there is a delay of one hour, then two hours, then four hours, and
22840 so on (this is a rather extreme example).
22842 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
22843 They happen every 30 minutes for 24 hours only. The remaining two rules handle
22844 all other domains, with special action for connection refusal from hosts that
22845 were not obtained from an MX record.
22847 The final rule in a retry configuration should always have asterisks in the
22848 first two fields so as to provide a general catch-all for any addresses that do
22849 not have their own special handling. This example tries every 15 minutes for 2
22850 hours, then with intervals starting at one hour and increasing by a factor of
22851 1.5 up to 16 hours, then every 8 hours up to 5 days.
22855 .section "Timeout of retry data" "SECID165"
22856 .cindex "timeout" "of retry data"
22857 .oindex "&%retry_data_expire%&"
22858 .cindex "hints database" "data expiry"
22859 .cindex "retry" "timeout of data"
22860 Exim timestamps the data that it writes to its retry hints database. When it
22861 consults the data during a delivery it ignores any that is older than the value
22862 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
22863 been tried for 7 days, Exim will try to deliver to it immediately a message
22864 arrives, and if that fails, it will calculate a retry time as if it were
22865 failing for the first time.
22867 This improves the behaviour for messages routed to rarely-used hosts such as MX
22868 backups. If such a host was down at one time, and happens to be down again when
22869 Exim tries a month later, using the old retry data would imply that it had been
22870 down all the time, which is not a justified assumption.
22872 If a host really is permanently dead, this behaviour causes a burst of retries
22873 every now and again, but only if messages routed to it are rare. If there is a
22874 message at least once every 7 days the retry data never expires.
22879 .section "Long-term failures" "SECID166"
22880 .cindex "delivery failure, long-term"
22881 .cindex "retry" "after long-term failure"
22882 Special processing happens when an email address has been failing for so long
22883 that the cutoff time for the last algorithm is reached. For example, using the
22884 default retry rule:
22886 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
22888 the cutoff time is four days. Reaching the retry cutoff is independent of how
22889 long any specific message has been failing; it is the length of continuous
22890 failure for the recipient address that counts.
22892 When the cutoff time is reached for a local delivery, or for all the IP
22893 addresses associated with a remote delivery, a subsequent delivery failure
22894 causes Exim to give up on the address, and a bounce message is generated.
22895 In order to cater for new messages that use the failing address, a next retry
22896 time is still computed from the final algorithm, and is used as follows:
22898 For local deliveries, one delivery attempt is always made for any subsequent
22899 messages. If this delivery fails, the address fails immediately. The
22900 post-cutoff retry time is not used.
22902 If the delivery is remote, there are two possibilities, controlled by the
22903 .oindex "&%delay_after_cutoff%&"
22904 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
22905 default. Until the post-cutoff retry time for one of the IP addresses is
22906 reached, the failing email address is bounced immediately, without a delivery
22907 attempt taking place. After that time, one new delivery attempt is made to
22908 those IP addresses that are past their retry times, and if that still fails,
22909 the address is bounced and new retry times are computed.
22911 In other words, when all the hosts for a given email address have been failing
22912 for a long time, Exim bounces rather then defers until one of the hosts' retry
22913 times is reached. Then it tries once, and bounces if that attempt fails. This
22914 behaviour ensures that few resources are wasted in repeatedly trying to deliver
22915 to a broken destination, but if the host does recover, Exim will eventually
22918 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
22919 addresses are past their final cutoff time, Exim tries to deliver to those IP
22920 addresses that have not been tried since the message arrived. If there are
22921 no suitable IP addresses, or if they all fail, the address is bounced. In other
22922 words, it does not delay when a new message arrives, but tries the expired
22923 addresses immediately, unless they have been tried since the message arrived.
22924 If there is a continuous stream of messages for the failing domains, setting
22925 &%delay_after_cutoff%& false means that there will be many more attempts to
22926 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
22929 .section "Deliveries that work intermittently" "SECID167"
22930 .cindex "retry" "intermittently working deliveries"
22931 Some additional logic is needed to cope with cases where a host is
22932 intermittently available, or when a message has some attribute that prevents
22933 its delivery when others to the same address get through. In this situation,
22934 because some messages are successfully delivered, the &"retry clock"& for the
22935 host or address keeps getting reset by the successful deliveries, and so
22936 failing messages remain on the queue for ever because the cutoff time is never
22939 Two exceptional actions are applied to prevent this happening. The first
22940 applies to errors that are related to a message rather than a remote host.
22941 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
22942 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
22943 commands, and quota failures. For this type of error, if a message's arrival
22944 time is earlier than the &"first failed"& time for the error, the earlier time
22945 is used when scanning the retry rules to decide when to try next and when to
22946 time out the address.
22948 The exceptional second action applies in all cases. If a message has been on
22949 the queue for longer than the cutoff time of any applicable retry rule for a
22950 given address, a delivery is attempted for that address, even if it is not yet
22951 time, and if this delivery fails, the address is timed out. A new retry time is
22952 not computed in this case, so that other messages for the same address are
22953 considered immediately.
22954 .ecindex IIDretconf1
22955 .ecindex IIDregconf2
22962 . ////////////////////////////////////////////////////////////////////////////
22963 . ////////////////////////////////////////////////////////////////////////////
22965 .chapter "SMTP authentication" "CHAPSMTPAUTH"
22966 .scindex IIDauthconf1 "SMTP" "authentication configuration"
22967 .scindex IIDauthconf2 "authentication"
22968 The &"authenticators"& section of Exim's run time configuration is concerned
22969 with SMTP authentication. This facility is an extension to the SMTP protocol,
22970 described in RFC 2554, which allows a client SMTP host to authenticate itself
22971 to a server. This is a common way for a server to recognize clients that are
22972 permitted to use it as a relay. SMTP authentication is not of relevance to the
22973 transfer of mail between servers that have no managerial connection with each
22976 .cindex "AUTH" "description of"
22977 Very briefly, the way SMTP authentication works is as follows:
22980 The server advertises a number of authentication &'mechanisms'& in response to
22981 the client's EHLO command.
22983 The client issues an AUTH command, naming a specific mechanism. The command
22984 may, optionally, contain some authentication data.
22986 The server may issue one or more &'challenges'&, to which the client must send
22987 appropriate responses. In simple authentication mechanisms, the challenges are
22988 just prompts for user names and passwords. The server does not have to issue
22989 any challenges &-- in some mechanisms the relevant data may all be transmitted
22990 with the AUTH command.
22992 The server either accepts or denies authentication.
22994 If authentication succeeds, the client may optionally make use of the AUTH
22995 option on the MAIL command to pass an authenticated sender in subsequent
22996 mail transactions. Authentication lasts for the remainder of the SMTP
22999 If authentication fails, the client may give up, or it may try a different
23000 authentication mechanism, or it may try transferring mail over the
23001 unauthenticated connection.
23004 If you are setting up a client, and want to know which authentication
23005 mechanisms the server supports, you can use Telnet to connect to port 25 (the
23006 SMTP port) on the server, and issue an EHLO command. The response to this
23007 includes the list of supported mechanisms. For example:
23009 &`$ `&&*&`telnet server.example 25`&*&
23010 &`Trying 192.168.34.25...`&
23011 &`Connected to server.example.`&
23012 &`Escape character is '^]'.`&
23013 &`220 server.example ESMTP Exim 4.20 ...`&
23014 &*&`ehlo client.example`&*&
23015 &`250-server.example Hello client.example [10.8.4.5]`&
23016 &`250-SIZE 52428800`&
23021 The second-last line of this example output shows that the server supports
23022 authentication using the PLAIN mechanism. In Exim, the different authentication
23023 mechanisms are configured by specifying &'authenticator'& drivers. Like the
23024 routers and transports, which authenticators are included in the binary is
23025 controlled by build-time definitions. The following are currently available,
23026 included by setting
23029 AUTH_CYRUS_SASL=yes
23033 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
23034 authentication mechanism (RFC 2195), and the second provides an interface to
23035 the Cyrus SASL authentication library. The third can be configured to support
23036 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
23037 not formally documented, but used by several MUAs. The fourth authenticator
23038 supports Microsoft's &'Secure Password Authentication'& mechanism.
23040 The authenticators are configured using the same syntax as other drivers (see
23041 section &<<SECTfordricon>>&). If no authenticators are required, no
23042 authentication section need be present in the configuration file. Each
23043 authenticator can in principle have both server and client functions. When Exim
23044 is receiving SMTP mail, it is acting as a server; when it is sending out
23045 messages over SMTP, it is acting as a client. Authenticator configuration
23046 options are provided for use in both these circumstances.
23048 To make it clear which options apply to which situation, the prefixes
23049 &%server_%& and &%client_%& are used on option names that are specific to
23050 either the server or the client function, respectively. Server and client
23051 functions are disabled if none of their options are set. If an authenticator is
23052 to be used for both server and client functions, a single definition, using
23053 both sets of options, is required. For example:
23057 public_name = CRAM-MD5
23058 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
23060 client_secret = secret2
23062 The &%server_%& option is used when Exim is acting as a server, and the
23063 &%client_%& options when it is acting as a client.
23065 Descriptions of the individual authenticators are given in subsequent chapters.
23066 The remainder of this chapter covers the generic options for the
23067 authenticators, followed by general discussion of the way authentication works
23072 .section "Generic options for authenticators" "SECID168"
23073 .cindex "authentication" "generic options"
23074 .cindex "options" "generic; for authenticators"
23076 .option client_condition authenticators string&!! unset
23077 When Exim is authenticating as a client, it skips any authenticator whose
23078 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
23079 used, for example, to skip plain text authenticators when the connection is not
23080 encrypted by a setting such as:
23082 client_condition = ${if !eq{$tls_cipher}{}}
23084 (Older documentation incorrectly states that &$tls_cipher$& contains the cipher
23085 used for incoming messages. In fact, during SMTP delivery, it contains the
23086 cipher used for the delivery.)
23089 .option driver authenticators string unset
23090 This option must always be set. It specifies which of the available
23091 authenticators is to be used.
23094 .option public_name authenticators string unset
23095 This option specifies the name of the authentication mechanism that the driver
23096 implements, and by which it is known to the outside world. These names should
23097 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
23098 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
23099 defaults to the driver's instance name.
23102 .option server_advertise_condition authenticators string&!! unset
23103 When a server is about to advertise an authentication mechanism, the condition
23104 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
23105 mechanism is not advertised.
23106 If the expansion fails, the mechanism is not advertised. If the failure was not
23107 forced, and was not caused by a lookup defer, the incident is logged.
23108 See section &<<SECTauthexiser>>& below for further discussion.
23111 .option server_condition authenticators string&!! unset
23112 This option must be set for a &%plaintext%& server authenticator, where it
23113 is used directly to control authentication. See section &<<SECTplainserver>>&
23116 For the other authenticators, &%server_condition%& can be used as an additional
23117 authentication or authorization mechanism that is applied after the other
23118 authenticator conditions succeed. If it is set, it is expanded when the
23119 authenticator would otherwise return a success code. If the expansion is forced
23120 to fail, authentication fails. Any other expansion failure causes a temporary
23121 error code to be returned. If the result of a successful expansion is an empty
23122 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23123 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
23124 other result, a temporary error code is returned, with the expanded string as
23128 .option server_debug_print authenticators string&!! unset
23129 If this option is set and authentication debugging is enabled (see the &%-d%&
23130 command line option), the string is expanded and included in the debugging
23131 output when the authenticator is run as a server. This can help with checking
23132 out the values of variables.
23133 If expansion of the string fails, the error message is written to the debugging
23134 output, and Exim carries on processing.
23137 .option server_set_id authenticators string&!! unset
23138 .vindex "&$authenticated_id$&"
23139 When an Exim server successfully authenticates a client, this string is
23140 expanded using data from the authentication, and preserved for any incoming
23141 messages in the variable &$authenticated_id$&. It is also included in the log
23142 lines for incoming messages. For example, a user/password authenticator
23143 configuration might preserve the user name that was used to authenticate, and
23144 refer to it subsequently during delivery of the message.
23145 If expansion fails, the option is ignored.
23148 .option server_mail_auth_condition authenticators string&!! unset
23149 This option allows a server to discard authenticated sender addresses supplied
23150 as part of MAIL commands in SMTP connections that are authenticated by the
23151 driver on which &%server_mail_auth_condition%& is set. The option is not used
23152 as part of the authentication process; instead its (unexpanded) value is
23153 remembered for later use.
23154 How it is used is described in the following section.
23160 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
23161 .cindex "authentication" "sender; authenticated"
23162 .cindex "AUTH" "on MAIL command"
23163 When a client supplied an AUTH= item on a MAIL command, Exim applies
23164 the following checks before accepting it as the authenticated sender of the
23168 If the connection is not using extended SMTP (that is, HELO was used rather
23169 than EHLO), the use of AUTH= is a syntax error.
23171 If the value of the AUTH= parameter is &"<>"&, it is ignored.
23173 .vindex "&$authenticated_sender$&"
23174 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
23175 running, the value of &$authenticated_sender$& is set to the value obtained
23176 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
23177 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
23178 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
23179 given for the MAIL command.
23181 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
23182 is accepted and placed in &$authenticated_sender$& only if the client has
23185 If the AUTH= value was accepted by either of the two previous rules, and
23186 the client has authenticated, and the authenticator has a setting for the
23187 &%server_mail_auth_condition%&, the condition is checked at this point. The
23188 valued that was saved from the authenticator is expanded. If the expansion
23189 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
23190 &$authenticated_sender$& is deleted. If the expansion yields any other value,
23191 the value of &$authenticated_sender$& is retained and passed on with the
23196 When &$authenticated_sender$& is set for a message, it is passed on to other
23197 hosts to which Exim authenticates as a client. Do not confuse this value with
23198 &$authenticated_id$&, which is a string obtained from the authentication
23199 process, and which is not usually a complete email address.
23201 .vindex "&$sender_address$&"
23202 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
23203 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
23204 therefore make use of &$authenticated_sender$&. The converse is not true: the
23205 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
23210 .section "Authentication on an Exim server" "SECTauthexiser"
23211 .cindex "authentication" "on an Exim server"
23212 When Exim receives an EHLO command, it advertises the public names of those
23213 authenticators that are configured as servers, subject to the following
23217 The client host must match &%auth_advertise_hosts%& (default *).
23219 It the &%server_advertise_condition%& option is set, its expansion must not
23220 yield the empty string, &"0"&, &"no"&, or &"false"&.
23223 The order in which the authenticators are defined controls the order in which
23224 the mechanisms are advertised.
23226 Some mail clients (for example, some versions of Netscape) require the user to
23227 provide a name and password for authentication whenever AUTH is advertised,
23228 even though authentication may not in fact be needed (for example, Exim may be
23229 set up to allow unconditional relaying from the client by an IP address check).
23230 You can make such clients more friendly by not advertising AUTH to them.
23231 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
23232 that runs for RCPT) to relay without authentication, you should set
23234 auth_advertise_hosts = ! 10.9.8.0/24
23236 so that no authentication mechanisms are advertised to them.
23238 The &%server_advertise_condition%& controls the advertisement of individual
23239 authentication mechanisms. For example, it can be used to restrict the
23240 advertisement of a particular mechanism to encrypted connections, by a setting
23243 server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}}
23245 .vindex "&$tls_cipher$&"
23246 If the session is encrypted, &$tls_cipher$& is not empty, and so the expansion
23247 yields &"yes"&, which allows the advertisement to happen.
23249 When an Exim server receives an AUTH command from a client, it rejects it
23250 immediately if AUTH was not advertised in response to an earlier EHLO
23251 command. This is the case if
23254 The client host does not match &%auth_advertise_hosts%&; or
23256 No authenticators are configured with server options; or
23258 Expansion of &%server_advertise_condition%& blocked the advertising of all the
23259 server authenticators.
23263 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
23264 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
23265 AUTH is accepted from any client host.
23267 If AUTH is not rejected by the ACL, Exim searches its configuration for a
23268 server authentication mechanism that was advertised in response to EHLO and
23269 that matches the one named in the AUTH command. If it finds one, it runs
23270 the appropriate authentication protocol, and authentication either succeeds or
23271 fails. If there is no matching advertised mechanism, the AUTH command is
23272 rejected with a 504 error.
23274 .vindex "&$received_protocol$&"
23275 .vindex "&$sender_host_authenticated$&"
23276 When a message is received from an authenticated host, the value of
23277 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
23278 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
23279 public name) of the authenticator driver that successfully authenticated the
23280 client from which the message was received. This variable is empty if there was
23281 no successful authentication.
23286 .section "Testing server authentication" "SECID169"
23287 .cindex "authentication" "testing a server"
23288 .cindex "AUTH" "testing a server"
23289 .cindex "base64 encoding" "creating authentication test data"
23290 Exim's &%-bh%& option can be useful for testing server authentication
23291 configurations. The data for the AUTH command has to be sent using base64
23292 encoding. A quick way to produce such data for testing is the following Perl
23296 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
23298 .cindex "binary zero" "in authentication data"
23299 This interprets its argument as a Perl string, and then encodes it. The
23300 interpretation as a Perl string allows binary zeros, which are required for
23301 some kinds of authentication, to be included in the data. For example, a
23302 command line to run this script on such data might be
23304 encode '\0user\0password'
23306 Note the use of single quotes to prevent the shell interpreting the
23307 backslashes, so that they can be interpreted by Perl to specify characters
23308 whose code value is zero.
23310 &*Warning 1*&: If either of the user or password strings starts with an octal
23311 digit, you must use three zeros instead of one after the leading backslash. If
23312 you do not, the octal digit that starts your string will be incorrectly
23313 interpreted as part of the code for the first character.
23315 &*Warning 2*&: If there are characters in the strings that Perl interprets
23316 specially, you must use a Perl escape to prevent them being misinterpreted. For
23317 example, a command such as
23319 encode '\0user@domain.com\0pas$$word'
23321 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
23323 If you have the &%mimencode%& command installed, another way to do produce
23324 base64-encoded strings is to run the command
23326 echo -e -n `\0user\0password' | mimencode
23328 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
23329 in the argument, and the &%-n%& option specifies no newline at the end of its
23330 output. However, not all versions of &%echo%& recognize these options, so you
23331 should check your version before relying on this suggestion.
23335 .section "Authentication by an Exim client" "SECID170"
23336 .cindex "authentication" "on an Exim client"
23337 The &(smtp)& transport has two options called &%hosts_require_auth%& and
23338 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
23339 announces support for authentication, and the host matches an entry in either
23340 of these options, Exim (as a client) tries to authenticate as follows:
23343 For each authenticator that is configured as a client, in the order in which
23344 they are defined in the configuration, it searches the authentication
23345 mechanisms announced by the server for one whose name matches the public name
23346 of the authenticator.
23349 .vindex "&$host_address$&"
23350 When it finds one that matches, it runs the authenticator's client code. The
23351 variables &$host$& and &$host_address$& are available for any string expansions
23352 that the client might do. They are set to the server's name and IP address. If
23353 any expansion is forced to fail, the authentication attempt is abandoned, and
23354 Exim moves on to the next authenticator. Otherwise an expansion failure causes
23355 delivery to be deferred.
23357 If the result of the authentication attempt is a temporary error or a timeout,
23358 Exim abandons trying to send the message to the host for the moment. It will
23359 try again later. If there are any backup hosts available, they are tried in the
23362 If the response to authentication is a permanent error (5&'xx'& code), Exim
23363 carries on searching the list of authenticators and tries another one if
23364 possible. If all authentication attempts give permanent errors, or if there are
23365 no attempts because no mechanisms match (or option expansions force failure),
23366 what happens depends on whether the host matches &%hosts_require_auth%& or
23367 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
23368 delivery is deferred. The error can be detected in the retry rules, and thereby
23369 turned into a permanent error if you wish. In the second case, Exim tries to
23370 deliver the message unauthenticated.
23373 .cindex "AUTH" "on MAIL command"
23374 When Exim has authenticated itself to a remote server, it adds the AUTH
23375 parameter to the MAIL commands it sends, if it has an authenticated sender for
23376 the message. If the message came from a remote host, the authenticated sender
23377 is the one that was receiving on an incoming MAIL command, provided that the
23378 incoming connection was authenticated and the &%server_mail_auth%& condition
23379 allowed the authenticated sender to be retained. If a local process calls Exim
23380 to send a message, the sender address that is built from the login name and
23381 &%qualify_domain%& is treated as authenticated. However, if the
23382 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
23383 the authenticated sender that was received with the message.
23384 .ecindex IIDauthconf1
23385 .ecindex IIDauthconf2
23392 . ////////////////////////////////////////////////////////////////////////////
23393 . ////////////////////////////////////////////////////////////////////////////
23395 .chapter "The plaintext authenticator" "CHAPplaintext"
23396 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
23397 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
23398 The &(plaintext)& authenticator can be configured to support the PLAIN and
23399 LOGIN authentication mechanisms, both of which transfer authentication data as
23400 plain (unencrypted) text (though base64 encoded). The use of plain text is a
23401 security risk; you are strongly advised to insist on the use of SMTP encryption
23402 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
23403 use unencrypted plain text, you should not use the same passwords for SMTP
23404 connections as you do for login accounts.
23406 .section "Plaintext options" "SECID171"
23407 .cindex "options" "&(plaintext)& authenticator (server)"
23408 When configured as a server, &(plaintext)& uses the following options:
23410 .option server_condition authenticators string&!! unset
23411 This is actually a global authentication option, but it must be set in order to
23412 configure the &(plaintext)& driver as a server. Its use is described below.
23414 .option server_prompts plaintext string&!! unset
23415 The contents of this option, after expansion, must be a colon-separated list of
23416 prompt strings. If expansion fails, a temporary authentication rejection is
23419 .section "Using plaintext in a server" "SECTplainserver"
23420 .cindex "AUTH" "in &(plaintext)& authenticator"
23421 .cindex "binary zero" "in &(plaintext)& authenticator"
23422 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
23423 "in &(plaintext)& authenticator"
23424 .vindex "&$auth1$&, &$auth2$&, etc"
23425 .cindex "base64 encoding" "in &(plaintext)& authenticator"
23427 When running as a server, &(plaintext)& performs the authentication test by
23428 expanding a string. The data sent by the client with the AUTH command, or in
23429 response to subsequent prompts, is base64 encoded, and so may contain any byte
23430 values when decoded. If any data is supplied with the command, it is treated as
23431 a list of strings, separated by NULs (binary zeros), the first three of which
23432 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
23433 (neither LOGIN nor PLAIN uses more than three strings).
23435 For compatibility with previous releases of Exim, the values are also placed in
23436 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
23437 variables for this purpose is now deprecated, as it can lead to confusion in
23438 string expansions that also use them for other things.
23440 If there are more strings in &%server_prompts%& than the number of strings
23441 supplied with the AUTH command, the remaining prompts are used to obtain more
23442 data. Each response from the client may be a list of NUL-separated strings.
23444 .vindex "&$authenticated_id$&"
23445 Once a sufficient number of data strings have been received,
23446 &%server_condition%& is expanded. If the expansion is forced to fail,
23447 authentication fails. Any other expansion failure causes a temporary error code
23448 to be returned. If the result of a successful expansion is an empty string,
23449 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
23450 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
23451 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
23452 For any other result, a temporary error code is returned, with the expanded
23453 string as the error text.
23455 &*Warning*&: If you use a lookup in the expansion to find the user's
23456 password, be sure to make the authentication fail if the user is unknown.
23457 There are good and bad examples at the end of the next section.
23461 .section "The PLAIN authentication mechanism" "SECID172"
23462 .cindex "PLAIN authentication mechanism"
23463 .cindex "authentication" "PLAIN mechanism"
23464 .cindex "binary zero" "in &(plaintext)& authenticator"
23465 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
23466 sent as one item of data (that is, one combined string containing two NUL
23467 separators). The data is sent either as part of the AUTH command, or
23468 subsequently in response to an empty prompt from the server.
23470 The second and third strings are a user name and a corresponding password.
23471 Using a single fixed user name and password as an example, this could be
23472 configured as follows:
23476 public_name = PLAIN
23478 server_condition = \
23479 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
23480 server_set_id = $auth2
23482 Note that the default result strings from &%if%& (&"true"& or an empty string)
23483 are exactly what we want here, so they need not be specified. Obviously, if the
23484 password contains expansion-significant characters such as dollar, backslash,
23485 or closing brace, they have to be escaped.
23487 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
23488 the end of a string list are ignored). If all the data comes as part of the
23489 AUTH command, as is commonly the case, the prompt is not used. This
23490 authenticator is advertised in the response to EHLO as
23494 and a client host can authenticate itself by sending the command
23496 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
23498 As this contains three strings (more than the number of prompts), no further
23499 data is required from the client. Alternatively, the client may just send
23503 to initiate authentication, in which case the server replies with an empty
23504 prompt. The client must respond with the combined data string.
23506 The data string is base64 encoded, as required by the RFC. This example,
23507 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
23508 represents a zero byte. This is split up into three strings, the first of which
23509 is empty. The &%server_condition%& option in the authenticator checks that the
23510 second two are &`username`& and &`mysecret`& respectively.
23512 Having just one fixed user name and password, as in this example, is not very
23513 realistic, though for a small organization with only a handful of
23514 authenticating clients it could make sense.
23516 A more sophisticated instance of this authenticator could use the user name in
23517 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
23518 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
23519 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
23520 This is an incorrect example:
23522 server_condition = \
23523 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
23525 The expansion uses the user name (&$auth2$&) as the key to look up a password,
23526 which it then compares to the supplied password (&$auth3$&). Why is this example
23527 incorrect? It works fine for existing users, but consider what happens if a
23528 non-existent user name is given. The lookup fails, but as no success/failure
23529 strings are given for the lookup, it yields an empty string. Thus, to defeat
23530 the authentication, all a client has to do is to supply a non-existent user
23531 name and an empty password. The correct way of writing this test is:
23533 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
23534 {${if eq{$value}{$auth3}}} {false}}
23536 In this case, if the lookup succeeds, the result is checked; if the lookup
23537 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
23538 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
23539 always fails if its second argument is empty. However, the second way of
23540 writing the test makes the logic clearer.
23543 .section "The LOGIN authentication mechanism" "SECID173"
23544 .cindex "LOGIN authentication mechanism"
23545 .cindex "authentication" "LOGIN mechanism"
23546 The LOGIN authentication mechanism is not documented in any RFC, but is in use
23547 in a number of programs. No data is sent with the AUTH command. Instead, a
23548 user name and password are supplied separately, in response to prompts. The
23549 plaintext authenticator can be configured to support this as in this example:
23553 public_name = LOGIN
23554 server_prompts = User Name : Password
23555 server_condition = \
23556 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
23557 server_set_id = $auth1
23559 Because of the way plaintext operates, this authenticator accepts data supplied
23560 with the AUTH command (in contravention of the specification of LOGIN), but
23561 if the client does not supply it (as is the case for LOGIN clients), the prompt
23562 strings are used to obtain two data items.
23564 Some clients are very particular about the precise text of the prompts. For
23565 example, Outlook Express is reported to recognize only &"Username:"& and
23566 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
23567 strings. It uses the &%ldapauth%& expansion condition to check the user
23568 name and password by binding to an LDAP server:
23572 public_name = LOGIN
23573 server_prompts = Username:: : Password::
23574 server_condition = ${if and{{
23576 ldapauth{user="cn=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
23577 pass=${quote:$auth2} \
23578 ldap://ldap.example.org/} }} }
23579 server_set_id = uid=$auth1,ou=people,o=example.org
23581 We have to check that the username is not empty before using it, because LDAP
23582 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
23583 operator to correctly quote the DN for authentication. However, the basic
23584 &%quote%& operator, rather than any of the LDAP quoting operators, is the
23585 correct one to use for the password, because quoting is needed only to make
23586 the password conform to the Exim syntax. At the LDAP level, the password is an
23587 uninterpreted string.
23590 .section "Support for different kinds of authentication" "SECID174"
23591 A number of string expansion features are provided for the purpose of
23592 interfacing to different ways of user authentication. These include checking
23593 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
23594 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
23600 .section "Using plaintext in a client" "SECID175"
23601 .cindex "options" "&(plaintext)& authenticator (client)"
23602 The &(plaintext)& authenticator has two client options:
23604 .option client_ignore_invalid_base64 plaintext boolean false
23605 If the client receives a server prompt that is not a valid base64 string,
23606 authentication is abandoned by default. However, if this option is set true,
23607 the error in the challenge is ignored and the client sends the response as
23610 .option client_send plaintext string&!! unset
23611 The string is a colon-separated list of authentication data strings. Each
23612 string is independently expanded before being sent to the server. The first
23613 string is sent with the AUTH command; any more strings are sent in response
23614 to prompts from the server. Before each string is expanded, the value of the
23615 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
23616 with &$auth1$& for the first prompt. Up to three prompts are stored in this
23617 way. Thus, the prompt that is received in response to sending the first string
23618 (with the AUTH command) can be used in the expansion of the second string, and
23619 so on. If an invalid base64 string is received when
23620 &%client_ignore_invalid_base64%& is set, an empty string is put in the
23621 &$auth$&<&'n'&> variable.
23623 &*Note*&: You cannot use expansion to create multiple strings, because
23624 splitting takes priority and happens first.
23626 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
23627 the data, further processing is applied to each string before it is sent. If
23628 there are any single circumflex characters in the string, they are converted to
23629 NULs. Should an actual circumflex be required as data, it must be doubled in
23632 This is an example of a client configuration that implements the PLAIN
23633 authentication mechanism with a fixed user name and password:
23637 public_name = PLAIN
23638 client_send = ^username^mysecret
23640 The lack of colons means that the entire text is sent with the AUTH
23641 command, with the circumflex characters converted to NULs. A similar example
23642 that uses the LOGIN mechanism is:
23646 public_name = LOGIN
23647 client_send = : username : mysecret
23649 The initial colon means that the first string is empty, so no data is sent with
23650 the AUTH command itself. The remaining strings are sent in response to
23652 .ecindex IIDplaiauth1
23653 .ecindex IIDplaiauth2
23658 . ////////////////////////////////////////////////////////////////////////////
23659 . ////////////////////////////////////////////////////////////////////////////
23661 .chapter "The cram_md5 authenticator" "CHID9"
23662 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
23663 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
23664 .cindex "CRAM-MD5 authentication mechanism"
23665 .cindex "authentication" "CRAM-MD5 mechanism"
23666 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
23667 sends a challenge string to the client, and the response consists of a user
23668 name and the CRAM-MD5 digest of the challenge string combined with a secret
23669 string (password) which is known to both server and client. Thus, the secret
23670 is not sent over the network as plain text, which makes this authenticator more
23671 secure than &(plaintext)&. However, the downside is that the secret has to be
23672 available in plain text at either end.
23675 .section "Using cram_md5 as a server" "SECID176"
23676 .cindex "options" "&(cram_md5)& authenticator (server)"
23677 This authenticator has one server option, which must be set to configure the
23678 authenticator as a server:
23680 .option server_secret cram_md5 string&!! unset
23681 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
23682 When the server receives the client's response, the user name is placed in
23683 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
23684 obtain the password for that user. The server then computes the CRAM-MD5 digest
23685 that the client should have sent, and checks that it received the correct
23686 string. If the expansion of &%server_secret%& is forced to fail, authentication
23687 fails. If the expansion fails for some other reason, a temporary error code is
23688 returned to the client.
23690 For compatibility with previous releases of Exim, the user name is also placed
23691 in &$1$&. However, the use of this variables for this purpose is now
23692 deprecated, as it can lead to confusion in string expansions that also use
23693 numeric variables for other things.
23695 For example, the following authenticator checks that the user name given by the
23696 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
23697 user name, authentication fails.
23701 public_name = CRAM-MD5
23702 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
23703 server_set_id = $auth1
23705 .vindex "&$authenticated_id$&"
23706 If authentication succeeds, the setting of &%server_set_id%& preserves the user
23707 name in &$authenticated_id$&. A more typical configuration might look up the
23708 secret string in a file, using the user name as the key. For example:
23712 public_name = CRAM-MD5
23713 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
23715 server_set_id = $auth1
23717 Note that this expansion explicitly forces failure if the lookup fails
23718 because &$auth1$& contains an unknown user name.
23721 .section "Using cram_md5 as a client" "SECID177"
23722 .cindex "options" "&(cram_md5)& authenticator (client)"
23723 When used as a client, the &(cram_md5)& authenticator has two options:
23727 .option client_name cram_md5 string&!! "the primary host name"
23728 This string is expanded, and the result used as the user name data when
23729 computing the response to the server's challenge.
23732 .option client_secret cram_md5 string&!! unset
23733 This option must be set for the authenticator to work as a client. Its value is
23734 expanded and the result used as the secret string when computing the response.
23738 .vindex "&$host_address$&"
23739 Different user names and secrets can be used for different servers by referring
23740 to &$host$& or &$host_address$& in the options. Forced failure of either
23741 expansion string is treated as an indication that this authenticator is not
23742 prepared to handle this case. Exim moves on to the next configured client
23743 authenticator. Any other expansion failure causes Exim to give up trying to
23744 send the message to the current server.
23746 A simple example configuration of a &(cram_md5)& authenticator, using fixed
23751 public_name = CRAM-MD5
23753 client_secret = secret
23755 .ecindex IIDcramauth1
23756 .ecindex IIDcramauth2
23760 . ////////////////////////////////////////////////////////////////////////////
23761 . ////////////////////////////////////////////////////////////////////////////
23763 .chapter "The cyrus_sasl authenticator" "CHID10"
23764 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
23765 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
23766 .cindex "Cyrus" "SASL library"
23768 The code for this authenticator was provided by Matthew Byng-Maddick of A L
23769 Digital Ltd (&url(http://www.aldigital.co.uk)).
23771 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
23772 library implementation of the RFC 2222 (&"Simple Authentication and Security
23773 Layer"&). This library supports a number of authentication mechanisms,
23774 including PLAIN and LOGIN, but also several others that Exim does not support
23775 directly. In particular, there is support for Kerberos authentication.
23777 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
23778 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
23779 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
23780 name of the driver to determine which mechanism to support.
23782 Where access to some kind of secret file is required, for example in GSSAPI
23783 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
23784 user, and that the Cyrus SASL library has no way of escalating privileges
23785 by default. You may also find you need to set environment variables,
23786 depending on the driver you are using.
23788 The application name provided by Exim is &"exim"&, so various SASL options may
23789 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
23790 Kerberos, note that because of limitations in the GSSAPI interface,
23791 changing the server keytab might need to be communicated down to the Kerberos
23792 layer independently. The mechanism for doing so is dependent upon the Kerberos
23793 implementation. For example, for Heimdal, the environment variable KRB5_KTNAME
23794 may be set to point to an alternative keytab file. Exim will pass this
23795 variable through from its own inherited environment when started as root or the
23796 Exim user. The keytab file needs to be readable by the Exim user.
23799 .section "Using cyrus_sasl as a server" "SECID178"
23800 The &(cyrus_sasl)& authenticator has four private options. It puts the username
23801 (on a successful authentication) into &$auth1$&. For compatibility with
23802 previous releases of Exim, the username is also placed in &$1$&. However, the
23803 use of this variable for this purpose is now deprecated, as it can lead to
23804 confusion in string expansions that also use numeric variables for other
23808 .option server_hostname cyrus_sasl string&!! "see below"
23809 This option selects the hostname that is used when communicating with the
23810 library. The default value is &`$primary_hostname`&. It is up to the underlying
23811 SASL plug-in what it does with this data.
23814 .option server_mech cyrus_sasl string "see below"
23815 This option selects the authentication mechanism this driver should use. The
23816 default is the value of the generic &%public_name%& option. This option allows
23817 you to use a different underlying mechanism from the advertised name. For
23821 driver = cyrus_sasl
23822 public_name = X-ANYTHING
23823 server_mech = CRAM-MD5
23824 server_set_id = $auth1
23827 .option server_realm cyrus_sasl string unset
23828 This specifies the SASL realm that the server claims to be in.
23831 .option server_service cyrus_sasl string &`smtp`&
23832 This is the SASL service that the server claims to implement.
23835 For straightforward cases, you do not need to set any of the authenticator's
23836 private options. All you need to do is to specify an appropriate mechanism as
23837 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
23838 PLAIN, you could have two authenticators as follows:
23841 driver = cyrus_sasl
23842 public_name = CRAM-MD5
23843 server_set_id = $auth1
23846 driver = cyrus_sasl
23847 public_name = PLAIN
23848 server_set_id = $auth2
23850 Cyrus SASL does implement the LOGIN authentication method, even though it is
23851 not a standard method. It is disabled by default in the source distribution,
23852 but it is present in many binary distributions.
23853 .ecindex IIDcyrauth1
23854 .ecindex IIDcyrauth2
23859 . ////////////////////////////////////////////////////////////////////////////
23860 . ////////////////////////////////////////////////////////////////////////////
23861 .chapter "The dovecot authenticator" "CHAPdovecot"
23862 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
23863 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
23864 This authenticator is an interface to the authentication facility of the
23865 Dovecot POP/IMAP server, which can support a number of authentication methods.
23866 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
23867 to use the same mechanisms for SMTP authentication. This is a server
23868 authenticator only. There is only one option:
23870 .option server_socket dovecot string unset
23872 This option must specify the socket that is the interface to Dovecot
23873 authentication. The &%public_name%& option must specify an authentication
23874 mechanism that Dovecot is configured to support. You can have several
23875 authenticators for different mechanisms. For example:
23879 public_name = PLAIN
23880 server_socket = /var/run/dovecot/auth-client
23881 server_set_id = $auth2
23886 server_socket = /var/run/dovecot/auth-client
23887 server_set_id = $auth1
23889 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
23890 &$received_ip_address$& (that is, the connection is local), the &"secured"&
23891 option is passed in the Dovecot authentication command. If, for a TLS
23892 connection, a client certificate has been verified, the &"valid-client-cert"&
23893 option is passed. When authentication succeeds, the identity of the user
23894 who authenticated is placed in &$auth1$&.
23895 .ecindex IIDdcotauth1
23896 .ecindex IIDdcotauth2
23899 . ////////////////////////////////////////////////////////////////////////////
23900 . ////////////////////////////////////////////////////////////////////////////
23902 .chapter "The spa authenticator" "CHAPspa"
23903 .scindex IIDspaauth1 "&(spa)& authenticator"
23904 .scindex IIDspaauth2 "authenticators" "&(spa)&"
23905 .cindex "authentication" "Microsoft Secure Password"
23906 .cindex "authentication" "NTLM"
23907 .cindex "Microsoft Secure Password Authentication"
23908 .cindex "NTLM authentication"
23909 The &(spa)& authenticator provides client support for Microsoft's &'Secure
23910 Password Authentication'& mechanism,
23911 which is also sometimes known as NTLM (NT LanMan). The code for client side of
23912 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
23913 taken from the Samba project (&url(http://www.samba.org)). The code for the
23914 server side was subsequently contributed by Tom Kistner. The mechanism works as
23918 After the AUTH command has been accepted, the client sends an SPA
23919 authentication request based on the user name and optional domain.
23921 The server sends back a challenge.
23923 The client builds a challenge response which makes use of the user's password
23924 and sends it to the server, which then accepts or rejects it.
23927 Encryption is used to protect the password in transit.
23931 .section "Using spa as a server" "SECID179"
23932 .cindex "options" "&(spa)& authenticator (server)"
23933 The &(spa)& authenticator has just one server option:
23935 .option server_password spa string&!! unset
23936 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
23937 This option is expanded, and the result must be the cleartext password for the
23938 authenticating user, whose name is at this point in &$auth1$&. For
23939 compatibility with previous releases of Exim, the user name is also placed in
23940 &$1$&. However, the use of this variable for this purpose is now deprecated, as
23941 it can lead to confusion in string expansions that also use numeric variables
23942 for other things. For example:
23947 server_password = \
23948 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
23950 If the expansion is forced to fail, authentication fails. Any other expansion
23951 failure causes a temporary error code to be returned.
23957 .section "Using spa as a client" "SECID180"
23958 .cindex "options" "&(spa)& authenticator (client)"
23959 The &(spa)& authenticator has the following client options:
23963 .option client_domain spa string&!! unset
23964 This option specifies an optional domain for the authentication.
23967 .option client_password spa string&!! unset
23968 This option specifies the user's password, and must be set.
23971 .option client_username spa string&!! unset
23972 This option specifies the user name, and must be set. Here is an example of a
23973 configuration of this authenticator for use with the mail servers at
23979 client_username = msn/msn_username
23980 client_password = msn_plaintext_password
23981 client_domain = DOMAIN_OR_UNSET
23983 .ecindex IIDspaauth1
23984 .ecindex IIDspaauth2
23990 . ////////////////////////////////////////////////////////////////////////////
23991 . ////////////////////////////////////////////////////////////////////////////
23993 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
23994 "Encrypted SMTP connections"
23995 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
23996 .scindex IIDencsmtp2 "SMTP" "encryption"
23997 .cindex "TLS" "on SMTP connection"
24000 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
24001 Sockets Layer), is implemented by making use of the OpenSSL library or the
24002 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
24003 cryptographic code in the Exim distribution itself for implementing TLS. In
24004 order to use this feature you must install OpenSSL or GnuTLS, and then build a
24005 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
24006 You also need to understand the basic concepts of encryption at a managerial
24007 level, and in particular, the way that public keys, private keys, and
24008 certificates are used.
24010 RFC 3207 defines how SMTP connections can make use of encryption. Once a
24011 connection is established, the client issues a STARTTLS command. If the
24012 server accepts this, the client and the server negotiate an encryption
24013 mechanism. If the negotiation succeeds, the data that subsequently passes
24014 between them is encrypted.
24016 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
24017 and if so, what cipher suite is in use, whether the client supplied a
24018 certificate, and whether or not that certificate was verified. This makes it
24019 possible for an Exim server to deny or accept certain commands based on the
24022 &*Warning*&: Certain types of firewall and certain anti-virus products can
24023 disrupt TLS connections. You need to turn off SMTP scanning for these products
24024 in order to get TLS to work.
24028 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
24030 .cindex "ssmtp protocol"
24031 .cindex "smtps protocol"
24032 .cindex "SMTP" "ssmtp protocol"
24033 .cindex "SMTP" "smtps protocol"
24034 Early implementations of encrypted SMTP used a different TCP port from normal
24035 SMTP, and expected an encryption negotiation to start immediately, instead of
24036 waiting for a STARTTLS command from the client using the standard SMTP
24037 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
24038 allocated for this purpose.
24040 This approach was abandoned when encrypted SMTP was standardized, but there are
24041 still some legacy clients that use it. Exim supports these clients by means of
24042 the &%tls_on_connect_ports%& global option. Its value must be a list of port
24043 numbers; the most common use is expected to be:
24045 tls_on_connect_ports = 465
24047 The port numbers specified by this option apply to all SMTP connections, both
24048 via the daemon and via &'inetd'&. You still need to specify all the ports that
24049 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
24050 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
24051 an extra port &-- rather, it specifies different behaviour on a port that is
24054 There is also a &%-tls-on-connect%& command line option. This overrides
24055 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
24062 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
24063 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
24064 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
24065 followed later, when the first versions of GnuTLS were released. To build Exim
24066 to use GnuTLS, you need to set
24070 in Local/Makefile, in addition to
24074 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
24075 include files and libraries for GnuTLS can be found.
24077 There are some differences in usage when using GnuTLS instead of OpenSSL:
24080 The &%tls_verify_certificates%& option must contain the name of a file, not the
24081 name of a directory (for OpenSSL it can be either).
24083 The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no
24084 facility for varying its Diffie-Hellman parameters. I understand that this has
24085 changed, but Exim has not been updated to provide this facility.
24087 .vindex "&$tls_peerdn$&"
24088 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
24089 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
24090 affects the value of the &$tls_peerdn$& variable.
24092 OpenSSL identifies cipher suites using hyphens as separators, for example:
24093 DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA_ARCFOUR_SHA. What is
24094 more, OpenSSL complains if underscores are present in a cipher list. To make
24095 life simpler, Exim changes underscores to hyphens for OpenSSL and hyphens to
24096 underscores for GnuTLS when processing lists of cipher suites in the
24097 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
24100 The &%tls_require_ciphers%& options operate differently, as described in the
24101 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
24105 .section "GnuTLS parameter computation" "SECID181"
24106 GnuTLS uses D-H parameters that may take a substantial amount of time
24107 to compute. It is unreasonable to re-compute them for every TLS session.
24108 Therefore, Exim keeps this data in a file in its spool directory, called
24109 &_gnutls-params_&. The file is owned by the Exim user and is readable only by
24110 its owner. Every Exim process that start up GnuTLS reads the D-H
24111 parameters from this file. If the file does not exist, the first Exim process
24112 that needs it computes the data and writes it to a temporary file which is
24113 renamed once it is complete. It does not matter if several Exim processes do
24114 this simultaneously (apart from wasting a few resources). Once a file is in
24115 place, new Exim processes immediately start using it.
24117 For maximum security, the parameters that are stored in this file should be
24118 recalculated periodically, the frequency depending on your paranoia level.
24119 Arranging this is easy in principle; just delete the file when you want new
24120 values to be computed. However, there may be a problem. The calculation of new
24121 parameters needs random numbers, and these are obtained from &_/dev/random_&.
24122 If the system is not very active, &_/dev/random_& may delay returning data
24123 until enough randomness (entropy) is available. This may cause Exim to hang for
24124 a substantial amount of time, causing timeouts on incoming connections.
24126 The solution is to generate the parameters externally to Exim. They are stored
24127 in &_gnutls-params_& in PEM format, which means that they can be generated
24128 externally using the &(certtool)& command that is part of GnuTLS.
24130 To replace the parameters with new ones, instead of deleting the file
24131 and letting Exim re-create it, you can generate new parameters using
24132 &(certtool)& and, when this has been done, replace Exim's cache file by
24133 renaming. The relevant commands are something like this:
24137 # chown exim:exim new-params
24138 # chmod 0400 new-params
24139 # certtool --generate-privkey --bits 512 >new-params
24140 # echo "" >>new-params
24141 # certtool --generate-dh-params --bits 1024 >> new-params
24142 # mv new-params gnutls-params
24144 If Exim never has to generate the parameters itself, the possibility of
24145 stalling is removed.
24148 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
24149 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
24150 .oindex "&%tls_require_ciphers%&" "OpenSSL"
24151 There is a function in the OpenSSL library that can be passed a list of cipher
24152 suites before the cipher negotiation takes place. This specifies which ciphers
24153 are acceptable. The list is colon separated and may contain names like
24154 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
24155 directly to this function call. The following quotation from the OpenSSL
24156 documentation specifies what forms of item are allowed in the cipher string:
24159 It can consist of a single cipher suite such as RC4-SHA.
24161 It can represent a list of cipher suites containing a certain algorithm,
24162 or cipher suites of a certain type. For example SHA1 represents all
24163 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
24166 Lists of cipher suites can be combined in a single cipher string using
24167 the + character. This is used as a logical and operation. For example
24168 SHA1+DES represents all cipher suites containing the SHA1 and the DES
24172 Each cipher string can be optionally preceded by one of the characters &`!`&,
24175 If &`!`& is used, the ciphers are permanently deleted from the list. The
24176 ciphers deleted can never reappear in the list even if they are explicitly
24179 If &`-`& is used, the ciphers are deleted from the list, but some or all
24180 of the ciphers can be added again by later options.
24182 If &`+`& is used, the ciphers are moved to the end of the list. This
24183 option does not add any new ciphers; it just moves matching existing ones.
24186 If none of these characters is present, the string is interpreted as
24187 a list of ciphers to be appended to the current preference list. If the list
24188 includes any ciphers already present they will be ignored: that is, they will
24189 not be moved to the end of the list.
24194 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
24196 .cindex "GnuTLS" "specifying parameters for"
24197 .cindex "TLS" "specifying ciphers (GnuTLS)"
24198 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
24199 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
24200 .cindex "TLS" "specifying protocols (GnuTLS)"
24201 .oindex "&%tls_require_ciphers%&" "GnuTLS"
24202 The GnuTLS library allows the caller to specify separate lists of permitted key
24203 exchange methods, main cipher algorithms, MAC algorithms, and protocols.
24204 Unfortunately, these lists are numerical, and the library does not have a
24205 function for turning names into numbers. Consequently, lists of recognized
24206 names have to be built into the application. The permitted key exchange
24207 methods, ciphers, and MAC algorithms may be used in any combination to form a
24208 cipher suite. This is unlike OpenSSL, where complete cipher suite names are
24209 passed to its control function.
24211 For compatibility with OpenSSL, the &%tls_require_ciphers%& option can be set
24212 to complete cipher suite names such as RSA_ARCFOUR_SHA, but for GnuTLS this
24213 option controls only the cipher algorithms. Exim searches each item in the
24214 list for the name of an available algorithm. For example, if the list
24215 contains RSA_AES_SHA, then AES is recognized, and the behaviour is exactly
24216 the same as if just AES were given.
24218 .oindex "&%gnutls_require_kx%&"
24219 .oindex "&%gnutls_require_mac%&"
24220 .oindex "&%gnutls_require_protocols%&"
24221 There are additional options called &%gnutls_require_kx%&,
24222 &%gnutls_require_mac%&, and &%gnutls_require_protocols%& that can be used to
24223 restrict the key exchange methods, MAC algorithms, and protocols, respectively.
24224 These options are ignored if OpenSSL is in use.
24226 All four options are available as global options, controlling how Exim
24227 behaves as a server, and also as options of the &(smtp)& transport, controlling
24228 how Exim behaves as a client. All the values are string expanded. After
24229 expansion, the values must be colon-separated lists, though the separator
24230 can be changed in the usual way.
24232 Each of the four lists starts out with a default set of algorithms. If the
24233 first item in a list does &'not'& start with an exclamation mark, all the
24234 default items are deleted. In this case, only those that are explicitly
24235 specified can be used. If the first item in a list &'does'& start with an
24236 exclamation mark, the defaults are left on the list.
24238 Then, any item that starts with an exclamation mark causes the relevant
24239 entry to be removed from the list, and any item that does not start with an
24240 exclamation mark causes a new entry to be added to the list. Unrecognized
24241 items in the list are ignored. Thus:
24243 tls_require_ciphers = !ARCFOUR
24245 allows all the defaults except ARCFOUR, whereas
24247 tls_require_ciphers = AES : 3DES
24249 allows only cipher suites that use AES or 3DES.
24251 For &%tls_require_ciphers%& the recognized names are AES_256, AES_128, AES
24252 (both of the preceding), 3DES, ARCFOUR_128, ARCFOUR_40, and ARCFOUR (both of
24253 the preceding). The default list does not contain all of these; it just has
24254 AES_256, AES_128, 3DES, and ARCFOUR_128.
24256 For &%gnutls_require_kx%&, the recognized names are DHE_RSA, RSA (which
24257 includes DHE_RSA), DHE_DSS, and DHE (which includes both DHE_RSA and
24258 DHE_DSS). The default list contains RSA, DHE_DSS, DHE_RSA.
24260 For &%gnutls_require_mac%&, the recognized names are SHA (synonym SHA1), and
24261 MD5. The default list contains SHA, MD5.
24263 For &%gnutls_require_protocols%&, the recognized names are TLS1 and SSL3.
24264 The default list contains TLS1, SSL3.
24266 In a server, the order of items in these lists is unimportant. The server
24267 advertises the availability of all the relevant cipher suites. However, in a
24268 client, the order in the &%tls_require_ciphers%& list specifies a preference
24269 order for the cipher algorithms. The first one in the client's list that is
24270 also advertised by the server is tried first. The default order is as listed
24275 .section "Configuring an Exim server to use TLS" "SECID182"
24276 .cindex "TLS" "configuring an Exim server"
24277 When Exim has been built with TLS support, it advertises the availability of
24278 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
24279 but not to any others. The default value of this option is unset, which means
24280 that STARTTLS is not advertised at all. This default is chosen because you
24281 need to set some other options in order to make TLS available, and also it is
24282 sensible for systems that want to use TLS only as a client.
24284 If a client issues a STARTTLS command and there is some configuration
24285 problem in the server, the command is rejected with a 454 error. If the client
24286 persists in trying to issue SMTP commands, all except QUIT are rejected
24289 554 Security failure
24291 If a STARTTLS command is issued within an existing TLS session, it is
24292 rejected with a 554 error code.
24294 To enable TLS operations on a server, you must set &%tls_advertise_hosts%& to
24295 match some hosts. You can, of course, set it to * to match all hosts.
24296 However, this is not all you need to do. TLS sessions to a server won't work
24297 without some further configuration at the server end.
24299 It is rumoured that all existing clients that support TLS/SSL use RSA
24300 encryption. To make this work you need to set, in the server,
24302 tls_certificate = /some/file/name
24303 tls_privatekey = /some/file/name
24305 These options are, in fact, expanded strings, so you can make them depend on
24306 the identity of the client that is connected if you wish. The first file
24307 contains the server's X509 certificate, and the second contains the private key
24308 that goes with it. These files need to be readable by the Exim user, and must
24309 always be given as full path names. They can be the same file if both the
24310 certificate and the key are contained within it. If &%tls_privatekey%& is not
24311 set, or if its expansion is forced to fail or results in an empty string, this
24312 is assumed to be the case. The certificate file may also contain intermediate
24313 certificates that need to be sent to the client to enable it to authenticate
24314 the server's certificate.
24316 If you do not understand about certificates and keys, please try to find a
24317 source of this background information, which is not Exim-specific. (There are a
24318 few comments below in section &<<SECTcerandall>>&.)
24320 &*Note*&: These options do not apply when Exim is operating as a client &--
24321 they apply only in the case of a server. If you need to use a certificate in an
24322 Exim client, you must set the options of the same names in an &(smtp)&
24325 With just these options, an Exim server will be able to use TLS. It does not
24326 require the client to have a certificate (but see below for how to insist on
24327 this). There is one other option that may be needed in other situations. If
24329 tls_dhparam = /some/file/name
24331 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
24332 with the parameters contained in the file. This increases the set of cipher
24333 suites that the server supports. See the command
24337 for a way of generating this data. At present, &%tls_dhparam%& is used only
24338 when Exim is linked with OpenSSL. It is ignored if GnuTLS is being used.
24340 The strings supplied for these three options are expanded every time a client
24341 host connects. It is therefore possible to use different certificates and keys
24342 for different hosts, if you so wish, by making use of the client's IP address
24343 in &$sender_host_address$& to control the expansion. If a string expansion is
24344 forced to fail, Exim behaves as if the option is not set.
24346 .cindex "cipher" "logging"
24347 .cindex "log" "TLS cipher"
24348 .vindex "&$tls_cipher$&"
24349 The variable &$tls_cipher$& is set to the cipher suite that was negotiated for
24350 an incoming TLS connection. It is included in the &'Received:'& header of an
24351 incoming message (by default &-- you can, of course, change this), and it is
24352 also included in the log line that records a message's arrival, keyed by
24353 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
24354 condition can be used to test for specific cipher suites in ACLs.
24355 (For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section
24358 Once TLS has been established, the ACLs that run for subsequent SMTP commands
24359 can check the name of the cipher suite and vary their actions accordingly. The
24360 cipher suite names vary, depending on which TLS library is being used. For
24361 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
24362 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
24363 documentation for more details.
24366 .section "Requesting and verifying client certificates" "SECID183"
24367 .cindex "certificate" "verification of client"
24368 .cindex "TLS" "client certificate verification"
24369 If you want an Exim server to request a certificate when negotiating a TLS
24370 session with a client, you must set either &%tls_verify_hosts%& or
24371 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
24372 apply to all TLS connections. For any host that matches one of these options,
24373 Exim requests a certificate as part of the setup of the TLS session. The
24374 contents of the certificate are verified by comparing it with a list of
24375 expected certificates. These must be available in a file or,
24376 for OpenSSL only (not GnuTLS), a directory, identified by
24377 &%tls_verify_certificates%&.
24379 A file can contain multiple certificates, concatenated end to end. If a
24382 each certificate must be in a separate file, with a name (or a symbolic link)
24383 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
24384 certificate. You can compute the relevant hash by running the command
24386 openssl x509 -hash -noout -in /cert/file
24388 where &_/cert/file_& contains a single certificate.
24390 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
24391 what happens if the client does not supply a certificate, or if the certificate
24392 does not match any of the certificates in the collection named by
24393 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
24394 attempt to set up a TLS session is aborted, and the incoming connection is
24395 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
24396 session continues. ACLs that run for subsequent SMTP commands can detect the
24397 fact that no certificate was verified, and vary their actions accordingly. For
24398 example, you can insist on a certificate before accepting a message for
24399 relaying, but not when the message is destined for local delivery.
24401 .vindex "&$tls_peerdn$&"
24402 When a client supplies a certificate (whether it verifies or not), the value of
24403 the Distinguished Name of the certificate is made available in the variable
24404 &$tls_peerdn$& during subsequent processing of the message.
24406 .cindex "log" "distinguished name"
24407 Because it is often a long text string, it is not included in the log line or
24408 &'Received:'& header by default. You can arrange for it to be logged, keyed by
24409 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
24410 &%received_header_text%& to change the &'Received:'& header. When no
24411 certificate is supplied, &$tls_peerdn$& is empty.
24414 .section "Revoked certificates" "SECID184"
24415 .cindex "TLS" "revoked certificates"
24416 .cindex "revocation list"
24417 .cindex "certificate" "revocation list"
24418 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
24419 certificates are revoked. If you have such a list, you can pass it to an Exim
24420 server using the global option called &%tls_crl%& and to an Exim client using
24421 an identically named option for the &(smtp)& transport. In each case, the value
24422 of the option is expanded and must then be the name of a file that contains a
24426 .section "Configuring an Exim client to use TLS" "SECID185"
24427 .cindex "cipher" "logging"
24428 .cindex "log" "TLS cipher"
24429 .cindex "log" "distinguished name"
24430 .cindex "TLS" "configuring an Exim client"
24431 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
24432 deliveries as well as to incoming, the latter one causing logging of the
24433 server certificate's DN. The remaining client configuration for TLS is all
24434 within the &(smtp)& transport.
24436 It is not necessary to set any options to have TLS work in the &(smtp)&
24437 transport. If Exim is built with TLS support, and TLS is advertised by a
24438 server, the &(smtp)& transport always tries to start a TLS session. However,
24439 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
24440 transport) to a list of server hosts for which TLS should not be used.
24442 If you do not want Exim to attempt to send messages unencrypted when an attempt
24443 to set up an encrypted connection fails in any way, you can set
24444 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
24445 those hosts, delivery is always deferred if an encrypted connection cannot be
24446 set up. If there are any other hosts for the address, they are tried in the
24449 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
24450 the message unencrypted. It always does this if the response to STARTTLS is
24451 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
24452 session after a success response code, what happens is controlled by the
24453 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
24454 delivery to this host is deferred, and other hosts (if available) are tried. If
24455 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
24456 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
24457 negotiation fails, Exim closes the current connection (because it is in an
24458 unknown state), opens a new one to the same host, and then tries the delivery
24461 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
24462 transport provide the client with a certificate, which is passed to the server
24463 if it requests it. If the server is Exim, it will request a certificate only if
24464 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
24466 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
24467 must name a file or,
24468 for OpenSSL only (not GnuTLS), a directory, that contains a collection of
24469 expected server certificates. The client verifies the server's certificate
24470 against this collection, taking into account any revoked certificates that are
24471 in the list defined by &%tls_crl%&.
24474 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
24475 list of permitted cipher suites. If either of these checks fails, delivery to
24476 the current host is abandoned, and the &(smtp)& transport tries to deliver to
24477 alternative hosts, if any.
24480 These options must be set in the &(smtp)& transport for Exim to use TLS when it
24481 is operating as a client. Exim does not assume that a server certificate (set
24482 by the global options of the same name) should also be used when operating as a
24486 .vindex "&$host_address$&"
24487 All the TLS options in the &(smtp)& transport are expanded before use, with
24488 &$host$& and &$host_address$& containing the name and address of the server to
24489 which the client is connected. Forced failure of an expansion causes Exim to
24490 behave as if the relevant option were unset.
24492 .vindex &$tls_cipher$&
24493 .vindex &$tls_peerdn$&
24494 Before an SMTP connection is established, the &$tls_cipher$& and &$tls_peerdn$&
24495 variables are emptied. (Until the first connection, they contain the values
24496 that were set when the message was received.) If STARTTLS is subsequently
24497 successfully obeyed, these variables are set to the relevant values for the
24498 outgoing connection.
24502 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
24504 .cindex "multiple SMTP deliveries with TLS"
24505 .cindex "TLS" "multiple message deliveries"
24506 Exim sends multiple messages down the same TCP/IP connection by starting up
24507 an entirely new delivery process for each message, passing the socket from
24508 one process to the next. This implementation does not fit well with the use
24509 of TLS, because there is quite a lot of state information associated with a TLS
24510 connection, not just a socket identification. Passing all the state information
24511 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
24512 session before passing the socket to a new process. The new process may then
24513 try to start a new TLS session, and if successful, may try to re-authenticate
24514 if AUTH is in use, before sending the next message.
24516 The RFC is not clear as to whether or not an SMTP session continues in clear
24517 after TLS has been shut down, or whether TLS may be restarted again later, as
24518 just described. However, if the server is Exim, this shutdown and
24519 reinitialization works. It is not known which (if any) other servers operate
24520 successfully if the client closes a TLS session and continues with unencrypted
24521 SMTP, but there are certainly some that do not work. For such servers, Exim
24522 should not pass the socket to another process, because the failure of the
24523 subsequent attempt to use it would cause Exim to record a temporary host error,
24524 and delay other deliveries to that host.
24526 To test for this case, Exim sends an EHLO command to the server after
24527 closing down the TLS session. If this fails in any way, the connection is
24528 closed instead of being passed to a new delivery process, but no retry
24529 information is recorded.
24531 There is also a manual override; you can set &%hosts_nopass_tls%& on the
24532 &(smtp)& transport to match those hosts for which Exim should not pass
24533 connections to new processes if TLS has been used.
24538 .section "Certificates and all that" "SECTcerandall"
24539 .cindex "certificate" "references to discussion"
24540 In order to understand fully how TLS works, you need to know about
24541 certificates, certificate signing, and certificate authorities. This is not the
24542 place to give a tutorial, especially as I do not know very much about it
24543 myself. Some helpful introduction can be found in the FAQ for the SSL addition
24544 to Apache, currently at
24546 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
24548 Other parts of the &'modssl'& documentation are also helpful, and have
24549 links to further files.
24550 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
24551 0-201-61598-3), contains both introductory and more in-depth descriptions.
24552 Some sample programs taken from the book are available from
24554 &url(http://www.rtfm.com/openssl-examples/)
24558 .section "Certificate chains" "SECID186"
24559 The file named by &%tls_certificate%& may contain more than one
24560 certificate. This is useful in the case where the certificate that is being
24561 sent is validated by an intermediate certificate which the other end does
24562 not have. Multiple certificates must be in the correct order in the file.
24563 First the host's certificate itself, then the first intermediate
24564 certificate to validate the issuer of the host certificate, then the next
24565 intermediate certificate to validate the issuer of the first intermediate
24566 certificate, and so on, until finally (optionally) the root certificate.
24567 The root certificate must already be trusted by the recipient for
24568 validation to succeed, of course, but if it's not preinstalled, sending the
24569 root certificate along with the rest makes it available for the user to
24570 install if the receiving end is a client MUA that can interact with a user.
24573 .section "Self-signed certificates" "SECID187"
24574 .cindex "certificate" "self-signed"
24575 You can create a self-signed certificate using the &'req'& command provided
24576 with OpenSSL, like this:
24578 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
24581 &_file1_& and &_file2_& can be the same file; the key and the certificate are
24582 delimited and so can be identified independently. The &%-days%& option
24583 specifies a period for which the certificate is valid. The &%-nodes%& option is
24584 important: if you do not set it, the key is encrypted with a passphrase
24585 that you are prompted for, and any use that is made of the key causes more
24586 prompting for the passphrase. This is not helpful if you are going to use
24587 this certificate and key in an MTA, where prompting is not possible.
24589 A self-signed certificate made in this way is sufficient for testing, and
24590 may be adequate for all your requirements if you are mainly interested in
24591 encrypting transfers, and not in secure identification.
24593 However, many clients require that the certificate presented by the server be a
24594 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
24595 certificate. In this situation, the self-signed certificate described above
24596 must be installed on the client host as a trusted root &'certification
24597 authority'& (CA), and the certificate used by Exim must be a user certificate
24598 signed with that self-signed certificate.
24600 For information on creating self-signed CA certificates and using them to sign
24601 user certificates, see the &'General implementation overview'& chapter of the
24602 Open-source PKI book, available online at
24603 &url(http://ospkibook.sourceforge.net/).
24604 .ecindex IIDencsmtp1
24605 .ecindex IIDencsmtp2
24609 . ////////////////////////////////////////////////////////////////////////////
24610 . ////////////////////////////////////////////////////////////////////////////
24612 .chapter "Access control lists" "CHAPACL"
24613 .scindex IIDacl "&ACL;" "description"
24614 .cindex "control of incoming mail"
24615 .cindex "message" "controlling incoming"
24616 .cindex "policy control" "access control lists"
24617 Access Control Lists (ACLs) are defined in a separate section of the run time
24618 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
24619 name, terminated by a colon. Here is a complete ACL section that contains just
24620 one very small ACL:
24624 accept hosts = one.host.only
24626 You can have as many lists as you like in the ACL section, and the order in
24627 which they appear does not matter. The lists are self-terminating.
24629 The majority of ACLs are used to control Exim's behaviour when it receives
24630 certain SMTP commands. This applies both to incoming TCP/IP connections, and
24631 when a local process submits a message using SMTP by specifying the &%-bs%&
24632 option. The most common use is for controlling which recipients are accepted
24633 in incoming messages. In addition, you can define an ACL that is used to check
24634 local non-SMTP messages. The default configuration file contains an example of
24635 a realistic ACL for checking RCPT commands. This is discussed in chapter
24636 &<<CHAPdefconfil>>&.
24639 .section "Testing ACLs" "SECID188"
24640 The &%-bh%& command line option provides a way of testing your ACL
24641 configuration locally by running a fake SMTP session with which you interact.
24642 The host &'relay-test.mail-abuse.org'& provides a service for checking your
24643 relaying configuration (see section &<<SECTcheralcon>>& for more details).
24647 .section "Specifying when ACLs are used" "SECID189"
24648 .cindex "&ACL;" "options for specifying"
24649 In order to cause an ACL to be used, you have to name it in one of the relevant
24650 options in the main part of the configuration. These options are:
24651 .cindex "AUTH" "ACL for"
24652 .cindex "DATA" "ACLs for"
24653 .cindex "ETRN" "ACL for"
24654 .cindex "EXPN" "ACL for"
24655 .cindex "HELO" "ACL for"
24656 .cindex "EHLO" "ACL for"
24657 .cindex "MAIL" "ACL for"
24658 .cindex "QUIT, ACL for"
24659 .cindex "RCPT" "ACL for"
24660 .cindex "STARTTLS, ACL for"
24661 .cindex "VRFY" "ACL for"
24662 .cindex "SMTP" "connection, ACL for"
24663 .cindex "non-SMTP messages" "ACLs for"
24664 .cindex "MIME content scanning" "ACL for"
24667 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
24668 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
24669 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
24670 .irow &%acl_smtp_auth%& "ACL for AUTH"
24671 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
24672 .irow &%acl_smtp_data%& "ACL after DATA is complete"
24673 .irow &%acl_smtp_etrn%& "ACL for ETRN"
24674 .irow &%acl_smtp_expn%& "ACL for EXPN"
24675 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
24676 .irow &%acl_smtp_mail%& "ACL for MAIL"
24677 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
24678 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
24679 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
24680 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
24681 .irow &%acl_smtp_quit%& "ACL for QUIT"
24682 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
24683 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
24684 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
24687 For example, if you set
24689 acl_smtp_rcpt = small_acl
24691 the little ACL defined above is used whenever Exim receives a RCPT command
24692 in an SMTP dialogue. The majority of policy tests on incoming messages can be
24693 done when RCPT commands arrive. A rejection of RCPT should cause the
24694 sending MTA to give up on the recipient address contained in the RCPT
24695 command, whereas rejection at other times may cause the client MTA to keep on
24696 trying to deliver the message. It is therefore recommended that you do as much
24697 testing as possible at RCPT time.
24700 .section "The non-SMTP ACLs" "SECID190"
24701 .cindex "non-SMTP messages" "ACLs for"
24702 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
24703 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
24704 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
24705 the state of the SMTP connection such as encryption and authentication) are not
24706 relevant and are forbidden in these ACLs. However, the sender and recipients
24707 are known, so the &%senders%& and &%sender_domains%& conditions and the
24708 &$sender_address$& and &$recipients$& variables can be used. Variables such as
24709 &$authenticated_sender$& are also available. You can specify added header lines
24710 in any of these ACLs.
24712 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
24713 non-SMTP message, before any of the message has been read. (This is the
24714 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
24715 batched SMTP input, it runs after the DATA command has been reached. The
24716 result of this ACL is ignored; it cannot be used to reject a message. If you
24717 really need to, you could set a value in an ACL variable here and reject based
24718 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
24719 controls, and in particular, it can be used to set
24721 control = suppress_local_fixups
24723 This cannot be used in the other non-SMTP ACLs because by the time they are
24724 run, it is too late.
24726 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
24727 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
24729 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
24730 kind of rejection is treated as permanent, because there is no way of sending a
24731 temporary error for these kinds of message.
24734 .section "The SMTP connect ACL" "SECID191"
24735 .cindex "SMTP" "connection, ACL for"
24736 .oindex &%smtp_banner%&
24737 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
24738 session, after the test specified by &%host_reject_connection%& (which is now
24739 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
24740 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
24741 the message override the banner message that is otherwise specified by the
24742 &%smtp_banner%& option.
24745 .section "The EHLO/HELO ACL" "SECID192"
24746 .cindex "EHLO" "ACL for"
24747 .cindex "HELO" "ACL for"
24748 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
24749 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
24750 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
24751 Note that a client may issue more than one EHLO or HELO command in an SMTP
24752 session, and indeed is required to issue a new EHLO or HELO after successfully
24753 setting up encryption following a STARTTLS command.
24755 If the command is accepted by an &%accept%& verb that has a &%message%&
24756 modifier, the message may not contain more than one line (it will be truncated
24757 at the first newline and a panic logged if it does). Such a message cannot
24758 affect the EHLO options that are listed on the second and subsequent lines of
24762 .section "The DATA ACLs" "SECID193"
24763 .cindex "DATA" "ACLs for"
24764 Two ACLs are associated with the DATA command, because it is two-stage
24765 command, with two responses being sent to the client.
24766 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
24767 is obeyed. This gives you control after all the RCPT commands, but before
24768 the message itself is received. It offers the opportunity to give a negative
24769 response to the DATA command before the data is transmitted. Header lines
24770 added by MAIL or RCPT ACLs are not visible at this time, but any that
24771 are defined here are visible when the &%acl_smtp_data%& ACL is run.
24773 You cannot test the contents of the message, for example, to verify addresses
24774 in the headers, at RCPT time or when the DATA command is received. Such
24775 tests have to appear in the ACL that is run after the message itself has been
24776 received, before the final response to the DATA command is sent. This is
24777 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
24778 associated with the DATA command.
24780 For both of these ACLs, it is not possible to reject individual recipients. An
24781 error response rejects the entire message. Unfortunately, it is known that some
24782 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
24783 before or after the data) correctly &-- they keep the message on their queues
24784 and try again later, but that is their problem, though it does waste some of
24788 .section "The SMTP MIME ACL" "SECID194"
24789 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
24790 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
24793 .section "The QUIT ACL" "SECTQUITACL"
24794 .cindex "QUIT, ACL for"
24795 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
24796 does not affect the response code to QUIT, which is always 221. Thus, the ACL
24797 does not in fact control any access. For this reason, the only verbs that are
24798 permitted are &%accept%& and &%warn%&.
24800 This ACL can be used for tasks such as custom logging at the end of an SMTP
24801 session. For example, you can use ACL variables in other ACLs to count
24802 messages, recipients, etc., and log the totals at QUIT time using one or
24803 more &%logwrite%& modifiers on a &%warn%& verb.
24805 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
24806 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
24808 You do not need to have a final &%accept%&, but if you do, you can use a
24809 &%message%& modifier to specify custom text that is sent as part of the 221
24812 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
24813 failure (for example, failure to open a log file, or when Exim is bombing out
24814 because it has detected an unrecoverable error), all SMTP commands from the
24815 client are given temporary error responses until QUIT is received or the
24816 connection is closed. In these special cases, the QUIT ACL does not run.
24819 .section "The not-QUIT ACL" "SECTNOTQUITACL"
24820 .vindex &$acl_smtp_notquit$&
24821 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
24822 an SMTP session ends without sending QUIT. However, when Exim itself is is bad
24823 trouble, such as being unable to write to its log files, this ACL is not run,
24824 because it might try to do things (such as write to log files) that make the
24825 situation even worse.
24827 Like the QUIT ACL, this ACL is provided to make it possible to do customized
24828 logging or to gather statistics, and its outcome is ignored. The &%delay%&
24829 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
24832 .vindex &$smtp_notquit_reason$&
24833 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
24834 to a string that indicates the reason for the termination of the SMTP
24835 connection. The possible values are:
24837 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
24838 .irow &`bad-commands`& "Too many unknown or non-mail commands"
24839 .irow &`command-timeout`& "Timeout while reading SMTP commands"
24840 .irow &`connection-lost`& "The SMTP connection has been lost"
24841 .irow &`data-timeout`& "Timeout while reading message data"
24842 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
24843 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
24844 .irow &`signal-exit`& "SIGTERM or SIGINT"
24845 .irow &`synchronization-error`& "SMTP synchronization error"
24846 .irow &`tls-failed`& "TLS failed to start"
24848 In most cases when an SMTP connection is closed without having received QUIT,
24849 Exim sends an SMTP response message before actually closing the connection.
24850 With the exception of the &`acl-drop`& case, the default message can be
24851 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
24852 &%drop%& verb in another ACL, it is the message from the other ACL that is
24856 .section "Finding an ACL to use" "SECID195"
24857 .cindex "&ACL;" "finding which to use"
24858 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
24859 you can use different ACLs in different circumstances. For example,
24861 acl_smtp_rcpt = ${if ={25}{$interface_port} \
24862 {acl_check_rcpt} {acl_check_rcpt_submit} }
24864 In the default configuration file there are some example settings for
24865 providing an RFC 4409 message submission service on port 587 and a
24866 non-standard &"smtps"& service on port 465. You can use a string
24867 expansion like this to choose an ACL for MUAs on these ports which is
24868 more appropriate for this purpose than the default ACL on port 25.
24870 The expanded string does not have to be the name of an ACL in the
24871 configuration file; there are other possibilities. Having expanded the
24872 string, Exim searches for an ACL as follows:
24875 If the string begins with a slash, Exim uses it as a file name, and reads its
24876 contents as an ACL. The lines are processed in the same way as lines in the
24877 Exim configuration file. In particular, continuation lines are supported, blank
24878 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
24879 If the file does not exist or cannot be read, an error occurs (typically
24880 causing a temporary failure of whatever caused the ACL to be run). For example:
24882 acl_smtp_data = /etc/acls/\
24883 ${lookup{$sender_host_address}lsearch\
24884 {/etc/acllist}{$value}{default}}
24886 This looks up an ACL file to use on the basis of the host's IP address, falling
24887 back to a default if the lookup fails. If an ACL is successfully read from a
24888 file, it is retained in memory for the duration of the Exim process, so that it
24889 can be re-used without having to re-read the file.
24891 If the string does not start with a slash, and does not contain any spaces,
24892 Exim searches the ACL section of the configuration for an ACL whose name
24893 matches the string.
24895 If no named ACL is found, or if the string contains spaces, Exim parses
24896 the string as an inline ACL. This can save typing in cases where you just
24897 want to have something like
24899 acl_smtp_vrfy = accept
24901 in order to allow free use of the VRFY command. Such a string may contain
24902 newlines; it is processed in the same way as an ACL that is read from a file.
24908 .section "ACL return codes" "SECID196"
24909 .cindex "&ACL;" "return codes"
24910 Except for the QUIT ACL, which does not affect the SMTP return code (see
24911 section &<<SECTQUITACL>>& above), the result of running an ACL is either
24912 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
24913 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
24914 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
24915 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
24916 This also causes a 4&'xx'& return code.
24918 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
24919 &"deny"&, because there is no mechanism for passing temporary errors to the
24920 submitters of non-SMTP messages.
24923 ACLs that are relevant to message reception may also return &"discard"&. This
24924 has the effect of &"accept"&, but causes either the entire message or an
24925 individual recipient address to be discarded. In other words, it is a
24926 blackholing facility. Use it with care.
24928 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
24929 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
24930 RCPT ACL is to discard just the one recipient address. If there are no
24931 recipients left when the message's data is received, the DATA ACL is not
24932 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
24933 remaining recipients. The &"discard"& return is not permitted for the
24934 &%acl_smtp_predata%& ACL.
24937 .cindex "&[local_scan()]& function" "when all recipients discarded"
24938 The &[local_scan()]& function is always run, even if there are no remaining
24939 recipients; it may create new recipients.
24943 .section "Unset ACL options" "SECID197"
24944 .cindex "&ACL;" "unset options"
24945 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
24946 all the same. &*Note*&: These defaults apply only when the relevant ACL is
24947 not defined at all. For any defined ACL, the default action when control
24948 reaches the end of the ACL statements is &"deny"&.
24950 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
24951 these two are ACLs that are used only for their side effects. They cannot be
24952 used to accept or reject anything.
24954 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
24955 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
24956 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
24957 when the ACL is not defined is &"accept"&.
24959 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
24960 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
24961 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
24962 messages over an SMTP connection. For an example, see the ACL in the default
24963 configuration file.
24968 .section "Data for message ACLs" "SECID198"
24969 .cindex "&ACL;" "data for message ACL"
24971 .vindex &$local_part$&
24972 .vindex &$sender_address$&
24973 .vindex &$sender_host_address$&
24974 .vindex &$smtp_command$&
24975 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
24976 that contain information about the host and the message's sender (for example,
24977 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
24978 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
24979 &$local_part$& are set from the argument address. The entire SMTP command
24980 is available in &$smtp_command$&.
24982 When an ACL for the AUTH parameter of MAIL is running, the variables that
24983 contain information about the host are set, but &$sender_address$& is not yet
24984 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
24987 .vindex "&$message_size$&"
24988 The &$message_size$& variable is set to the value of the SIZE parameter on
24989 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
24990 that parameter is not given. The value is updated to the true message size by
24991 the time the final DATA ACL is run (after the message data has been
24994 .vindex "&$rcpt_count$&"
24995 .vindex "&$recipients_count$&"
24996 The &$rcpt_count$& variable increases by one for each RCPT command received.
24997 The &$recipients_count$& variable increases by one each time a RCPT command is
24998 accepted, so while an ACL for RCPT is being processed, it contains the number
24999 of previously accepted recipients. At DATA time (for both the DATA ACLs),
25000 &$rcpt_count$& contains the total number of RCPT commands, and
25001 &$recipients_count$& contains the total number of accepted recipients.
25007 .section "Data for non-message ACLs" "SECTdatfornon"
25008 .cindex "&ACL;" "data for non-message ACL"
25009 .vindex &$smtp_command_argument$&
25010 .vindex &$smtp_command$&
25011 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
25012 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
25013 and the entire SMTP command is available in &$smtp_command$&.
25014 These variables can be tested using a &%condition%& condition. For example,
25015 here is an ACL for use with AUTH, which insists that either the session is
25016 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
25017 does not permit authentication methods that use cleartext passwords on
25018 unencrypted connections.
25021 accept encrypted = *
25022 accept condition = ${if eq{${uc:$smtp_command_argument}}\
25024 deny message = TLS encryption or CRAM-MD5 required
25026 (Another way of applying this restriction is to arrange for the authenticators
25027 that use cleartext passwords not to be advertised when the connection is not
25028 encrypted. You can use the generic &%server_advertise_condition%& authenticator
25029 option to do this.)
25033 .section "Format of an ACL" "SECID199"
25034 .cindex "&ACL;" "format of"
25035 .cindex "&ACL;" "verbs, definition of"
25036 An individual ACL consists of a number of statements. Each statement starts
25037 with a verb, optionally followed by a number of conditions and &"modifiers"&.
25038 Modifiers can change the way the verb operates, define error and log messages,
25039 set variables, insert delays, and vary the processing of accepted messages.
25041 If all the conditions are met, the verb is obeyed. The same condition may be
25042 used (with different arguments) more than once in the same statement. This
25043 provides a means of specifying an &"and"& conjunction between conditions. For
25046 deny dnslists = list1.example
25047 dnslists = list2.example
25049 If there are no conditions, the verb is always obeyed. Exim stops evaluating
25050 the conditions and modifiers when it reaches a condition that fails. What
25051 happens then depends on the verb (and in one case, on a special modifier). Not
25052 all the conditions make sense at every testing point. For example, you cannot
25053 test a sender address in the ACL that is run for a VRFY command.
25056 .section "ACL verbs" "SECID200"
25057 The ACL verbs are as follows:
25060 .cindex "&%accept%& ACL verb"
25061 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
25062 of the conditions are not met, what happens depends on whether &%endpass%&
25063 appears among the conditions (for syntax see below). If the failing condition
25064 is before &%endpass%&, control is passed to the next ACL statement; if it is
25065 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
25066 check a RCPT command:
25068 accept domains = +local_domains
25072 If the recipient domain does not match the &%domains%& condition, control
25073 passes to the next statement. If it does match, the recipient is verified, and
25074 the command is accepted if verification succeeds. However, if verification
25075 fails, the ACL yields &"deny"&, because the failing condition is after
25078 The &%endpass%& feature has turned out to be confusing to many people, so its
25079 use is not recommended nowadays. It is always possible to rewrite an ACL so
25080 that &%endpass%& is not needed, and it is no longer used in the default
25083 .cindex "&%message%& ACL modifier" "with &%accept%&"
25084 If a &%message%& modifier appears on an &%accept%& statement, its action
25085 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
25086 (when an &%accept%& verb either accepts or passes control to the next
25087 statement), &%message%& can be used to vary the message that is sent when an
25088 SMTP command is accepted. For example, in a RCPT ACL you could have:
25090 &`accept `&<&'some conditions'&>
25091 &` message = OK, I will allow you through today`&
25093 You can specify an SMTP response code, optionally followed by an &"extended
25094 response code"& at the start of the message, but the first digit must be the
25095 same as would be sent by default, which is 2 for an &%accept%& verb.
25097 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
25098 an error message that is used when access is denied. This behaviour is retained
25099 for backward compatibility, but current &"best practice"& is to avoid the use
25104 .cindex "&%defer%& ACL verb"
25105 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
25106 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
25107 &%defer%& is the same as &%deny%&, because there is no way of sending a
25108 temporary error. For a RCPT command, &%defer%& is much the same as using a
25109 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
25110 be used in any ACL, and even for a recipient it might be a simpler approach.
25114 .cindex "&%deny%& ACL verb"
25115 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
25116 the conditions are not met, control is passed to the next ACL statement. For
25119 deny dnslists = blackholes.mail-abuse.org
25121 rejects commands from hosts that are on a DNS black list.
25125 .cindex "&%discard%& ACL verb"
25126 &%discard%&: This verb behaves like &%accept%&, except that it returns
25127 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
25128 that are concerned with receiving messages. When all the conditions are true,
25129 the sending entity receives a &"success"& response. However, &%discard%& causes
25130 recipients to be discarded. If it is used in an ACL for RCPT, just the one
25131 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
25132 message's recipients are discarded. Recipients that are discarded before DATA
25133 do not appear in the log line when the &%received_recipients%& log selector is set.
25135 If the &%log_message%& modifier is set when &%discard%& operates,
25136 its contents are added to the line that is automatically written to the log.
25137 The &%message%& modifier operates exactly as it does for &%accept%&.
25141 .cindex "&%drop%& ACL verb"
25142 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
25143 forcibly closed after the 5&'xx'& error message has been sent. For example:
25145 drop message = I don't take more than 20 RCPTs
25146 condition = ${if > {$rcpt_count}{20}}
25148 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
25149 The connection is always dropped after sending a 550 response.
25152 .cindex "&%require%& ACL verb"
25153 &%require%&: If all the conditions are met, control is passed to the next ACL
25154 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
25155 example, when checking a RCPT command,
25157 require message = Sender did not verify
25160 passes control to subsequent statements only if the message's sender can be
25161 verified. Otherwise, it rejects the command. Note the positioning of the
25162 &%message%& modifier, before the &%verify%& condition. The reason for this is
25163 discussed in section &<<SECTcondmodproc>>&.
25166 .cindex "&%warn%& ACL verb"
25167 &%warn%&: If all the conditions are true, a line specified by the
25168 &%log_message%& modifier is written to Exim's main log. Control always passes
25169 to the next ACL statement. If any condition is false, the log line is not
25170 written. If an identical log line is requested several times in the same
25171 message, only one copy is actually written to the log. If you want to force
25172 duplicates to be written, use the &%logwrite%& modifier instead.
25174 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
25175 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
25176 &%logwrite%&, and &%add_header%&) that appear before the first failing
25177 condition. There is more about adding header lines in section
25178 &<<SECTaddheadacl>>&.
25180 If any condition on a &%warn%& statement cannot be completed (that is, there is
25181 some sort of defer), the log line specified by &%log_message%& is not written.
25182 This does not include the case of a forced failure from a lookup, which
25183 is considered to be a successful completion. After a defer, no further
25184 conditions or modifiers in the &%warn%& statement are processed. The incident
25185 is logged, and the ACL continues to be processed, from the next statement
25189 .vindex "&$acl_verify_message$&"
25190 When one of the &%warn%& conditions is an address verification that fails, the
25191 text of the verification failure message is in &$acl_verify_message$&. If you
25192 want this logged, you must set it up explicitly. For example:
25194 warn !verify = sender
25195 log_message = sender verify failed: $acl_verify_message
25199 At the end of each ACL there is an implicit unconditional &%deny%&.
25201 As you can see from the examples above, the conditions and modifiers are
25202 written one to a line, with the first one on the same line as the verb, and
25203 subsequent ones on following lines. If you have a very long condition, you can
25204 continue it onto several physical lines by the usual backslash continuation
25205 mechanism. It is conventional to align the conditions vertically.
25209 .section "ACL variables" "SECTaclvariables"
25210 .cindex "&ACL;" "variables"
25211 There are some special variables that can be set during ACL processing. They
25212 can be used to pass information between different ACLs, different invocations
25213 of the same ACL in the same SMTP connection, and between ACLs and the routers,
25214 transports, and filters that are used to deliver a message. The names of these
25215 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
25216 an underscore, but the remainder of the name can be any sequence of
25217 alphanumeric characters and underscores that you choose. There is no limit on
25218 the number of ACL variables. The two sets act as follows:
25220 The values of those variables whose names begin with &$acl_c$& persist
25221 throughout an SMTP connection. They are never reset. Thus, a value that is set
25222 while receiving one message is still available when receiving the next message
25223 on the same SMTP connection.
25225 The values of those variables whose names begin with &$acl_m$& persist only
25226 while a message is being received. They are reset afterwards. They are also
25227 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
25230 When a message is accepted, the current values of all the ACL variables are
25231 preserved with the message and are subsequently made available at delivery
25232 time. The ACL variables are set by a modifier called &%set%&. For example:
25234 accept hosts = whatever
25235 set acl_m4 = some value
25236 accept authenticated = *
25237 set acl_c_auth = yes
25239 &*Note*&: A leading dollar sign is not used when naming a variable that is to
25240 be set. If you want to set a variable without taking any action, you can use a
25241 &%warn%& verb without any other modifiers or conditions.
25243 .oindex &%strict_acl_vars%&
25244 What happens if a syntactically valid but undefined ACL variable is
25245 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
25246 false (the default), an empty string is substituted; if it is true, an
25247 error is generated.
25249 Versions of Exim before 4.64 have a limited set of numbered variables, but
25250 their names are compatible, so there is no problem with upgrading.
25253 .section "Condition and modifier processing" "SECTcondmodproc"
25254 .cindex "&ACL;" "conditions; processing"
25255 .cindex "&ACL;" "modifiers; processing"
25256 An exclamation mark preceding a condition negates its result. For example:
25258 deny domains = *.dom.example
25259 !verify = recipient
25261 causes the ACL to return &"deny"& if the recipient domain ends in
25262 &'dom.example'& and the recipient address cannot be verified. Sometimes
25263 negation can be used on the right-hand side of a condition. For example, these
25264 two statements are equivalent:
25266 deny hosts = !192.168.3.4
25267 deny !hosts = 192.168.3.4
25269 However, for many conditions (&%verify%& being a good example), only left-hand
25270 side negation of the whole condition is possible.
25272 The arguments of conditions and modifiers are expanded. A forced failure
25273 of an expansion causes a condition to be ignored, that is, it behaves as if the
25274 condition is true. Consider these two statements:
25276 accept senders = ${lookup{$host_name}lsearch\
25277 {/some/file}{$value}fail}
25278 accept senders = ${lookup{$host_name}lsearch\
25279 {/some/file}{$value}{}}
25281 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
25282 the returned list is searched, but if the lookup fails the behaviour is
25283 different in the two cases. The &%fail%& in the first statement causes the
25284 condition to be ignored, leaving no further conditions. The &%accept%& verb
25285 therefore succeeds. The second statement, however, generates an empty list when
25286 the lookup fails. No sender can match an empty list, so the condition fails,
25287 and therefore the &%accept%& also fails.
25289 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
25290 specify actions that are taken as the conditions for a statement are checked;
25291 others specify text for messages that are used when access is denied or a
25292 warning is generated. The &%control%& modifier affects the way an incoming
25293 message is handled.
25295 The positioning of the modifiers in an ACL statement important, because the
25296 processing of a verb ceases as soon as its outcome is known. Only those
25297 modifiers that have already been encountered will take effect. For example,
25298 consider this use of the &%message%& modifier:
25300 require message = Can't verify sender
25302 message = Can't verify recipient
25304 message = This message cannot be used
25306 If sender verification fails, Exim knows that the result of the statement is
25307 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
25308 so its text is used as the error message. If sender verification succeeds, but
25309 recipient verification fails, the second message is used. If recipient
25310 verification succeeds, the third message becomes &"current"&, but is never used
25311 because there are no more conditions to cause failure.
25313 For the &%deny%& verb, on the other hand, it is always the last &%message%&
25314 modifier that is used, because all the conditions must be true for rejection to
25315 happen. Specifying more than one &%message%& modifier does not make sense, and
25316 the message can even be specified after all the conditions. For example:
25319 !senders = *@my.domain.example
25320 message = Invalid sender from client host
25322 The &"deny"& result does not happen until the end of the statement is reached,
25323 by which time Exim has set up the message.
25327 .section "ACL modifiers" "SECTACLmodi"
25328 .cindex "&ACL;" "modifiers; list of"
25329 The ACL modifiers are as follows:
25332 .vitem &*add_header*&&~=&~<&'text'&>
25333 This modifier specifies one or more header lines that are to be added to an
25334 incoming message, assuming, of course, that the message is ultimately
25335 accepted. For details, see section &<<SECTaddheadacl>>&.
25337 .vitem &*continue*&&~=&~<&'text'&>
25338 .cindex "&%continue%& ACL modifier"
25339 .cindex "database" "updating in ACL"
25340 This modifier does nothing of itself, and processing of the ACL always
25341 continues with the next condition or modifier. The value of &%continue%& is in
25342 the side effects of expanding its argument. Typically this could be used to
25343 update a database. It is really just a syntactic tidiness, to avoid having to
25344 write rather ugly lines like this:
25346 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
25348 Instead, all you need is
25350 &`continue = `&<&'some expansion'&>
25353 .vitem &*control*&&~=&~<&'text'&>
25354 .cindex "&%control%& ACL modifier"
25355 This modifier affects the subsequent processing of the SMTP connection or of an
25356 incoming message that is accepted. The effect of the first type of control
25357 lasts for the duration of the connection, whereas the effect of the second type
25358 lasts only until the current message has been received. The message-specific
25359 controls always apply to the whole message, not to individual recipients,
25360 even if the &%control%& modifier appears in a RCPT ACL.
25362 As there are now quite a few controls that can be applied, they are described
25363 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
25364 in several different ways. For example:
25366 . ==== As this is a nested list, any displays it contains must be indented
25367 . ==== as otherwise they are too far to the left. That comment applies only
25368 . ==== when xmlto and fop are used; formatting with sdop gets it right either
25372 It can be at the end of an &%accept%& statement:
25374 accept ...some conditions
25375 control = queue_only
25377 In this case, the control is applied when this statement yields &"accept"&, in
25378 other words, when the conditions are all true.
25381 It can be in the middle of an &%accept%& statement:
25383 accept ...some conditions...
25384 control = queue_only
25385 ...some more conditions...
25387 If the first set of conditions are true, the control is applied, even if the
25388 statement does not accept because one of the second set of conditions is false.
25389 In this case, some subsequent statement must yield &"accept"& for the control
25393 It can be used with &%warn%& to apply the control, leaving the
25394 decision about accepting or denying to a subsequent verb. For
25397 warn ...some conditions...
25401 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
25402 &%logwrite%&, so it does not add anything to the message and does not write a
25406 If you want to apply a control unconditionally, you can use it with a
25407 &%require%& verb. For example:
25409 require control = no_multiline_responses
25413 .vitem &*delay*&&~=&~<&'time'&>
25414 .cindex "&%delay%& ACL modifier"
25416 This modifier may appear in any ACL. It causes Exim to wait for the time
25417 interval before proceeding. However, when testing Exim using the &%-bh%&
25418 option, the delay is not actually imposed (an appropriate message is output
25419 instead). The time is given in the usual Exim notation, and the delay happens
25420 as soon as the modifier is processed. In an SMTP session, pending output is
25421 flushed before the delay is imposed.
25423 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
25426 deny ...some conditions...
25429 The delay happens if all the conditions are true, before the statement returns
25430 &"deny"&. Compare this with:
25433 ...some conditions...
25435 which waits for 30s before processing the conditions. The &%delay%& modifier
25436 can also be used with &%warn%& and together with &%control%&:
25438 warn ...some conditions...
25444 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
25445 responses to several commands are no longer buffered and sent in one packet (as
25446 they would normally be) because all output is flushed before imposing the
25447 delay. This optimization is disabled so that a number of small delays do not
25448 appear to the client as one large aggregated delay that might provoke an
25449 unwanted timeout. You can, however, disable output flushing for &%delay%& by
25450 using a &%control%& modifier to set &%no_delay_flush%&.
25454 .cindex "&%endpass%& ACL modifier"
25455 This modifier, which has no argument, is recognized only in &%accept%& and
25456 &%discard%& statements. It marks the boundary between the conditions whose
25457 failure causes control to pass to the next statement, and the conditions whose
25458 failure causes the ACL to return &"deny"&. This concept has proved to be
25459 confusing to some people, so the use of &%endpass%& is no longer recommended as
25460 &"best practice"&. See the description of &%accept%& above for more details.
25463 .vitem &*log_message*&&~=&~<&'text'&>
25464 .cindex "&%log_message%& ACL modifier"
25465 This modifier sets up a message that is used as part of the log message if the
25466 ACL denies access or a &%warn%& statement's conditions are true. For example:
25468 require log_message = wrong cipher suite $tls_cipher
25469 encrypted = DES-CBC3-SHA
25471 &%log_message%& is also used when recipients are discarded by &%discard%&. For
25474 &`discard `&<&'some conditions'&>
25475 &` log_message = Discarded $local_part@$domain because...`&
25477 When access is denied, &%log_message%& adds to any underlying error message
25478 that may exist because of a condition failure. For example, while verifying a
25479 recipient address, a &':fail:'& redirection might have already set up a
25482 The message may be defined before the conditions to which it applies, because
25483 the string expansion does not happen until Exim decides that access is to be
25484 denied. This means that any variables that are set by the condition are
25485 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
25486 variables are set after a DNS black list lookup succeeds. If the expansion of
25487 &%log_message%& fails, or if the result is an empty string, the modifier is
25490 .vindex "&$acl_verify_message$&"
25491 If you want to use a &%warn%& statement to log the result of an address
25492 verification, you can use &$acl_verify_message$& to include the verification
25495 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
25496 the start of the logged message. If the same warning log message is requested
25497 more than once while receiving a single email message, only one copy is
25498 actually logged. If you want to log multiple copies, use &%logwrite%& instead
25499 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
25500 is logged for a successful &%warn%& statement.
25502 If &%log_message%& is not present and there is no underlying error message (for
25503 example, from the failure of address verification), but &%message%& is present,
25504 the &%message%& text is used for logging rejections. However, if any text for
25505 logging contains newlines, only the first line is logged. In the absence of
25506 both &%log_message%& and &%message%&, a default built-in message is used for
25507 logging rejections.
25510 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
25511 .cindex "&%log_reject_target%& ACL modifier"
25512 .cindex "logging in ACL" "specifying which log"
25513 This modifier makes it possible to specify which logs are used for messages
25514 about ACL rejections. Its argument is a colon-separated list of words that can
25515 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
25516 may be empty, in which case a rejection is not logged at all. For example, this
25517 ACL fragment writes no logging information when access is denied:
25519 &`deny `&<&'some conditions'&>
25520 &` log_reject_target =`&
25522 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
25523 permanent and temporary rejections. Its effect lasts for the rest of the
25527 .vitem &*logwrite*&&~=&~<&'text'&>
25528 .cindex "&%logwrite%& ACL modifier"
25529 .cindex "logging in ACL" "immediate"
25530 This modifier writes a message to a log file as soon as it is encountered when
25531 processing an ACL. (Compare &%log_message%&, which, except in the case of
25532 &%warn%& and &%discard%&, is used only if the ACL statement denies
25533 access.) The &%logwrite%& modifier can be used to log special incidents in
25536 &`accept `&<&'some special conditions'&>
25537 &` control = freeze`&
25538 &` logwrite = froze message because ...`&
25540 By default, the message is written to the main log. However, it may begin
25541 with a colon, followed by a comma-separated list of log names, and then
25542 another colon, to specify exactly which logs are to be written. For
25545 logwrite = :main,reject: text for main and reject logs
25546 logwrite = :panic: text for panic log only
25550 .vitem &*message*&&~=&~<&'text'&>
25551 .cindex "&%message%& ACL modifier"
25552 This modifier sets up a text string that is expanded and used as a response
25553 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
25554 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
25555 there is some complication if &%endpass%& is involved; see the description of
25556 &%accept%& for details.)
25558 The expansion of the message happens at the time Exim decides that the ACL is
25559 to end, not at the time it processes &%message%&. If the expansion fails, or
25560 generates an empty string, the modifier is ignored. Here is an example where
25561 &%message%& must be specified first, because the ACL ends with a rejection if
25562 the &%hosts%& condition fails:
25564 require message = Host not recognized
25567 (Once a condition has failed, no further conditions or modifiers are
25570 .cindex "SMTP" "error codes"
25571 .oindex "&%smtp_banner%&
25572 For ACLs that are triggered by SMTP commands, the message is returned as part
25573 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
25574 is meaningful only for SMTP, as no message is returned when a non-SMTP message
25575 is accepted. In the case of the connect ACL, accepting with a message modifier
25576 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
25577 accept message may not contain more than one line (otherwise it will be
25578 truncated at the first newline and a panic logged), and it cannot affect the
25581 When SMTP is involved, the message may begin with an overriding response code,
25582 consisting of three digits optionally followed by an &"extended response code"&
25583 of the form &'n.n.n'&, each code being followed by a space. For example:
25585 deny message = 599 1.2.3 Host not welcome
25586 hosts = 192.168.34.0/24
25588 The first digit of the supplied response code must be the same as would be sent
25589 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
25590 access, but for the predata ACL, note that the default success code is 354, not
25593 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
25594 the message modifier cannot override the 221 response code.
25596 The text in a &%message%& modifier is literal; any quotes are taken as
25597 literals, but because the string is expanded, backslash escapes are processed
25598 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
25601 .vindex "&$acl_verify_message$&"
25602 If &%message%& is used on a statement that verifies an address, the message
25603 specified overrides any message that is generated by the verification process.
25604 However, the original message is available in the variable
25605 &$acl_verify_message$&, so you can incorporate it into your message if you
25606 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
25607 routers to be passed back as part of the SMTP response, you should either not
25608 use a &%message%& modifier, or make use of &$acl_verify_message$&.
25610 For compatibility with previous releases of Exim, a &%message%& modifier that
25611 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
25612 modifier, but this usage is now deprecated. However, &%message%& acts only when
25613 all the conditions are true, wherever it appears in an ACL command, whereas
25614 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
25615 &%warn%& in an ACL that is not concerned with receiving a message, it has no
25619 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
25620 .cindex "&%set%& ACL modifier"
25621 This modifier puts a value into one of the ACL variables (see section
25622 &<<SECTaclvariables>>&).
25629 .section "Use of the control modifier" "SECTcontrols"
25630 .cindex "&%control%& ACL modifier"
25631 The &%control%& modifier supports the following settings:
25634 .vitem &*control&~=&~allow_auth_unadvertised*&
25635 This modifier allows a client host to use the SMTP AUTH command even when it
25636 has not been advertised in response to EHLO. Furthermore, because there are
25637 apparently some really broken clients that do this, Exim will accept AUTH after
25638 HELO (rather than EHLO) when this control is set. It should be used only if you
25639 really need it, and you should limit its use to those broken clients that do
25640 not work without it. For example:
25642 warn hosts = 192.168.34.25
25643 control = allow_auth_unadvertised
25645 Normally, when an Exim server receives an AUTH command, it checks the name of
25646 the authentication mechanism that is given in the command to ensure that it
25647 matches an advertised mechanism. When this control is set, the check that a
25648 mechanism has been advertised is bypassed. Any configured mechanism can be used
25649 by the client. This control is permitted only in the connection and HELO ACLs.
25652 .vitem &*control&~=&~caseful_local_part*& &&&
25653 &*control&~=&~caselower_local_part*&
25654 .cindex "&ACL;" "case of local part in"
25655 .cindex "case of local parts"
25656 .vindex "&$local_part$&"
25657 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
25658 (that is, during RCPT processing). By default, the contents of &$local_part$&
25659 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
25660 any uppercase letters in the original local part are restored in &$local_part$&
25661 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
25664 These controls affect only the current recipient. Moreover, they apply only to
25665 local part handling that takes place directly in the ACL (for example, as a key
25666 in lookups). If a test to verify the recipient is obeyed, the case-related
25667 handling of the local part during the verification is controlled by the router
25668 configuration (see the &%caseful_local_part%& generic router option).
25670 This facility could be used, for example, to add a spam score to local parts
25671 containing upper case letters. For example, using &$acl_m4$& to accumulate the
25674 warn control = caseful_local_part
25675 set acl_m4 = ${eval:\
25677 ${if match{$local_part}{[A-Z]}{1}{0}}\
25679 control = caselower_local_part
25681 Notice that we put back the lower cased version afterwards, assuming that
25682 is what is wanted for subsequent tests.
25684 .vitem &*control&~=&~enforce_sync*& &&&
25685 &*control&~=&~no_enforce_sync*&
25686 .cindex "SMTP" "synchronization checking"
25687 .cindex "synchronization checking in SMTP"
25688 These controls make it possible to be selective about when SMTP synchronization
25689 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
25690 state of the switch (it is true by default). See the description of this option
25691 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
25693 The effect of these two controls lasts for the remainder of the SMTP
25694 connection. They can appear in any ACL except the one for the non-SMTP
25695 messages. The most straightforward place to put them is in the ACL defined by
25696 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
25697 before the first synchronization check. The expected use is to turn off the
25698 synchronization checks for badly-behaved hosts that you nevertheless need to
25702 .vitem &*control&~=&~fakedefer/*&<&'message'&>
25703 .cindex "fake defer"
25704 .cindex "defer, fake"
25705 This control works in exactly the same way as &%fakereject%& (described below)
25706 except that it causes an SMTP 450 response after the message data instead of a
25707 550 response. You must take care when using &%fakedefer%& because it causes the
25708 messages to be duplicated when the sender retries. Therefore, you should not
25709 use &%fakedefer%& if the message is to be delivered normally.
25711 .vitem &*control&~=&~fakereject/*&<&'message'&>
25712 .cindex "fake rejection"
25713 .cindex "rejection, fake"
25714 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
25715 words, only when an SMTP message is being received. If Exim accepts the
25716 message, instead the final 250 response, a 550 rejection message is sent.
25717 However, Exim proceeds to deliver the message as normal. The control applies
25718 only to the current message, not to any subsequent ones that may be received in
25719 the same SMTP connection.
25721 The text for the 550 response is taken from the &%control%& modifier. If no
25722 message is supplied, the following is used:
25724 550-Your message has been rejected but is being
25725 550-kept for evaluation.
25726 550-If it was a legitimate message, it may still be
25727 550 delivered to the target recipient(s).
25729 This facility should be used with extreme caution.
25731 .vitem &*control&~=&~freeze*&
25732 .cindex "frozen messages" "forcing in ACL"
25733 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
25734 other words, only when a message is being received. If the message is accepted,
25735 it is placed on Exim's queue and frozen. The control applies only to the
25736 current message, not to any subsequent ones that may be received in the same
25739 This modifier can optionally be followed by &`/no_tell`&. If the global option
25740 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
25741 is told about the freezing), provided all the &*control=freeze*& modifiers that
25742 are obeyed for the current message have the &`/no_tell`& option.
25744 .vitem &*control&~=&~no_delay_flush*&
25745 .cindex "SMTP" "output flushing, disabling for delay"
25746 Exim normally flushes SMTP output before implementing a delay in an ACL, to
25747 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
25748 use. This control, as long as it is encountered before the &%delay%& modifier,
25749 disables such output flushing.
25751 .vitem &*control&~=&~no_callout_flush*&
25752 .cindex "SMTP" "output flushing, disabling for callout"
25753 Exim normally flushes SMTP output before performing a callout in an ACL, to
25754 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
25755 use. This control, as long as it is encountered before the &%verify%& condition
25756 that causes the callout, disables such output flushing.
25758 .vitem &*control&~=&~no_mbox_unspool*&
25759 This control is available when Exim is compiled with the content scanning
25760 extension. Content scanning may require a copy of the current message, or parts
25761 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
25762 or spam scanner. Normally, such copies are deleted when they are no longer
25763 needed. If this control is set, the copies are not deleted. The control applies
25764 only to the current message, not to any subsequent ones that may be received in
25765 the same SMTP connection. It is provided for debugging purposes and is unlikely
25766 to be useful in production.
25768 .vitem &*control&~=&~no_multiline_responses*&
25769 .cindex "multiline responses, suppressing"
25770 This control is permitted for any ACL except the one for non-SMTP messages.
25771 It seems that there are broken clients in use that cannot handle multiline
25772 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
25774 If this control is set, multiline SMTP responses from ACL rejections are
25775 suppressed. One way of doing this would have been to put out these responses as
25776 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
25777 (&"use multiline responses for more"& it says &-- ha!), and some of the
25778 responses might get close to that. So this facility, which is after all only a
25779 sop to broken clients, is implemented by doing two very easy things:
25782 Extra information that is normally output as part of a rejection caused by
25783 sender verification failure is omitted. Only the final line (typically &"sender
25784 verification failed"&) is sent.
25786 If a &%message%& modifier supplies a multiline response, only the first
25790 The setting of the switch can, of course, be made conditional on the
25791 calling host. Its effect lasts until the end of the SMTP connection.
25793 .vitem &*control&~=&~no_pipelining*&
25794 .cindex "PIPELINING" "suppressing advertising"
25795 This control turns off the advertising of the PIPELINING extension to SMTP in
25796 the current session. To be useful, it must be obeyed before Exim sends its
25797 response to an EHLO command. Therefore, it should normally appear in an ACL
25798 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
25799 &%pipelining_advertise_hosts%&.
25801 .vitem &*control&~=&~queue_only*&
25802 .oindex "&%queue_only%&"
25803 .cindex "queueing incoming messages"
25804 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
25805 other words, only when a message is being received. If the message is accepted,
25806 it is placed on Exim's queue and left there for delivery by a subsequent queue
25807 runner. No immediate delivery process is started. In other words, it has the
25808 effect as the &%queue_only%& global option. However, the control applies only
25809 to the current message, not to any subsequent ones that may be received in the
25810 same SMTP connection.
25812 .vitem &*control&~=&~submission/*&<&'options'&>
25813 .cindex "message" "submission"
25814 .cindex "submission mode"
25815 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
25816 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
25817 the current message is a submission from a local MUA. In this case, Exim
25818 operates in &"submission mode"&, and applies certain fixups to the message if
25819 necessary. For example, it adds a &'Date:'& header line if one is not present.
25820 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
25821 late (the message has already been created).
25823 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
25824 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
25825 submission mode; the available options for this control are described there.
25826 The control applies only to the current message, not to any subsequent ones
25827 that may be received in the same SMTP connection.
25829 .vitem &*control&~=&~suppress_local_fixups*&
25830 .cindex "submission fixups, suppressing"
25831 This control applies to locally submitted (non TCP/IP) messages, and is the
25832 complement of &`control = submission`&. It disables the fixups that are
25833 normally applied to locally-submitted messages. Specifically:
25836 Any &'Sender:'& header line is left alone (in this respect, it is a
25837 dynamic version of &%local_sender_retain%&).
25839 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
25841 There is no check that &'From:'& corresponds to the actual sender.
25844 This control may be useful when a remotely-originated message is accepted,
25845 passed to some scanning program, and then re-submitted for delivery. It can be
25846 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
25847 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
25850 &*Note:*& This control applies only to the current message, not to any others
25851 that are being submitted at the same time using &%-bs%& or &%-bS%&.
25855 .section "Summary of message fixup control" "SECTsummesfix"
25856 All four possibilities for message fixups can be specified:
25859 Locally submitted, fixups applied: the default.
25861 Locally submitted, no fixups applied: use
25862 &`control = suppress_local_fixups`&.
25864 Remotely submitted, no fixups applied: the default.
25866 Remotely submitted, fixups applied: use &`control = submission`&.
25871 .section "Adding header lines in ACLs" "SECTaddheadacl"
25872 .cindex "header lines" "adding in an ACL"
25873 .cindex "header lines" "position of added lines"
25874 .cindex "&%message%& ACL modifier"
25875 The &%add_header%& modifier can be used to add one or more extra header lines
25876 to an incoming message, as in this example:
25878 warn dnslists = sbl.spamhaus.org : \
25879 dialup.mail-abuse.org
25880 add_header = X-blacklisted-at: $dnslist_domain
25882 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
25883 MIME, and non-SMTP ACLs (in other words, those that are concerned with
25884 receiving a message). The message must ultimately be accepted for
25885 &%add_header%& to have any significant effect. You can use &%add_header%& with
25886 any ACL verb, including &%deny%& (though this is potentially useful only in a
25889 If the data for the &%add_header%& modifier contains one or more newlines that
25890 are not followed by a space or a tab, it is assumed to contain multiple header
25891 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
25892 front of any line that is not a valid header line.
25894 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
25895 They are added to the message before processing the DATA and MIME ACLs.
25896 However, if an identical header line is requested more than once, only one copy
25897 is actually added to the message. Further header lines may be accumulated
25898 during the DATA and MIME ACLs, after which they are added to the message, again
25899 with duplicates suppressed. Thus, it is possible to add two identical header
25900 lines to an SMTP message, but only if one is added before DATA and one after.
25901 In the case of non-SMTP messages, new headers are accumulated during the
25902 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
25903 message is rejected after DATA or by the non-SMTP ACL, all added header lines
25904 are included in the entry that is written to the reject log.
25906 .cindex "header lines" "added; visibility of"
25907 Header lines are not visible in string expansions until they are added to the
25908 message. It follows that header lines defined in the MAIL, RCPT, and predata
25909 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
25910 header lines that are added by the DATA or MIME ACLs are not visible in those
25911 ACLs. Because of this restriction, you cannot use header lines as a way of
25912 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
25913 this, you can use ACL variables, as described in section
25914 &<<SECTaclvariables>>&.
25916 The &%add_header%& modifier acts immediately it is encountered during the
25917 processing of an ACL. Notice the difference between these two cases:
25919 &`accept add_header = ADDED: some text`&
25920 &` `&<&'some condition'&>
25922 &`accept `&<&'some condition'&>
25923 &` add_header = ADDED: some text`&
25925 In the first case, the header line is always added, whether or not the
25926 condition is true. In the second case, the header line is added only if the
25927 condition is true. Multiple occurrences of &%add_header%& may occur in the same
25928 ACL statement. All those that are encountered before a condition fails are
25931 .cindex "&%warn%& ACL verb"
25932 For compatibility with previous versions of Exim, a &%message%& modifier for a
25933 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
25934 effect only if all the conditions are true, even if it appears before some of
25935 them. Furthermore, only the last occurrence of &%message%& is honoured. This
25936 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
25937 are present on a &%warn%& verb, both are processed according to their
25940 By default, new header lines are added to a message at the end of the existing
25941 header lines. However, you can specify that any particular header line should
25942 be added right at the start (before all the &'Received:'& lines), immediately
25943 after the first block of &'Received:'& lines, or immediately before any line
25944 that is not a &'Received:'& or &'Resent-something:'& header.
25946 This is done by specifying &":at_start:"&, &":after_received:"&, or
25947 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
25948 header line, respectively. (Header text cannot start with a colon, as there has
25949 to be a header name first.) For example:
25951 warn add_header = \
25952 :after_received:X-My-Header: something or other...
25954 If more than one header line is supplied in a single &%add_header%& modifier,
25955 each one is treated independently and can therefore be placed differently. If
25956 you add more than one line at the start, or after the Received: block, they end
25957 up in reverse order.
25959 &*Warning*&: This facility currently applies only to header lines that are
25960 added in an ACL. It does NOT work for header lines that are added in a
25961 system filter or in a router or transport.
25966 .section "ACL conditions" "SECTaclconditions"
25967 .cindex "&ACL;" "conditions; list of"
25968 Some of conditions listed in this section are available only when Exim is
25969 compiled with the content-scanning extension. They are included here briefly
25970 for completeness. More detailed descriptions can be found in the discussion on
25971 content scanning in chapter &<<CHAPexiscan>>&.
25973 Not all conditions are relevant in all circumstances. For example, testing
25974 senders and recipients does not make sense in an ACL that is being run as the
25975 result of the arrival of an ETRN command, and checks on message headers can be
25976 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
25977 can use the same condition (with different parameters) more than once in the
25978 same ACL statement. This provides a way of specifying an &"and"& conjunction.
25979 The conditions are as follows:
25983 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
25984 .cindex "&ACL;" "nested"
25985 .cindex "&ACL;" "indirect"
25986 .cindex "&%acl%& ACL condition"
25987 The possible values of the argument are the same as for the
25988 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
25989 &"accept"& the condition is true; if it returns &"deny"& the condition is
25990 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
25991 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
25992 condition false. This means that further processing of the &%warn%& verb
25993 ceases, but processing of the ACL continues.
25995 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
25996 the connection is dropped. If it returns &"discard"&, the verb must be
25997 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
25998 conditions are tested.
26000 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
26001 loops. This condition allows you to use different ACLs in different
26002 circumstances. For example, different ACLs can be used to handle RCPT commands
26003 for different local users or different local domains.
26005 .vitem &*authenticated&~=&~*&<&'string&~list'&>
26006 .cindex "&%authenticated%& ACL condition"
26007 .cindex "authentication" "ACL checking"
26008 .cindex "&ACL;" "testing for authentication"
26009 If the SMTP connection is not authenticated, the condition is false. Otherwise,
26010 the name of the authenticator is tested against the list. To test for
26011 authentication by any authenticator, you can set
26016 .vitem &*condition&~=&~*&<&'string'&>
26017 .cindex "&%condition%& ACL condition"
26018 .cindex "customizing" "ACL condition"
26019 .cindex "&ACL;" "customized test"
26020 .cindex "&ACL;" "testing, customized"
26021 This feature allows you to make up custom conditions. If the result of
26022 expanding the string is an empty string, the number zero, or one of the strings
26023 &"no"& or &"false"&, the condition is false. If the result is any non-zero
26024 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
26025 any other value, some error is assumed to have occurred, and the ACL returns
26026 &"defer"&. However, if the expansion is forced to fail, the condition is
26027 ignored. The effect is to treat it as true, whether it is positive or
26030 .vitem &*decode&~=&~*&<&'location'&>
26031 .cindex "&%decode%& ACL condition"
26032 This condition is available only when Exim is compiled with the
26033 content-scanning extension, and it is allowed only in the ACL defined by
26034 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
26035 If all goes well, the condition is true. It is false only if there are
26036 problems such as a syntax error or a memory shortage. For more details, see
26037 chapter &<<CHAPexiscan>>&.
26039 .vitem &*demime&~=&~*&<&'extension&~list'&>
26040 .cindex "&%demime%& ACL condition"
26041 This condition is available only when Exim is compiled with the
26042 content-scanning extension. Its use is described in section
26043 &<<SECTdemimecond>>&.
26045 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
26046 .cindex "&%dnslists%& ACL condition"
26047 .cindex "DNS list" "in ACL"
26048 .cindex "black list (DNS)"
26049 .cindex "&ACL;" "testing a DNS list"
26050 This condition checks for entries in DNS black lists. These are also known as
26051 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
26052 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
26053 different variants of this condition to describe briefly here. See sections
26054 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
26056 .vitem &*domains&~=&~*&<&'domain&~list'&>
26057 .cindex "&%domains%& ACL condition"
26058 .cindex "domain" "ACL checking"
26059 .cindex "&ACL;" "testing a recipient domain"
26060 .vindex "&$domain_data$&"
26061 This condition is relevant only after a RCPT command. It checks that the domain
26062 of the recipient address is in the domain list. If percent-hack processing is
26063 enabled, it is done before this test is done. If the check succeeds with a
26064 lookup, the result of the lookup is placed in &$domain_data$& until the next
26067 &*Note carefully*& (because many people seem to fall foul of this): you cannot
26068 use &%domains%& in a DATA ACL.
26071 .vitem &*encrypted&~=&~*&<&'string&~list'&>
26072 .cindex "&%encrypted%& ACL condition"
26073 .cindex "encryption" "checking in an ACL"
26074 .cindex "&ACL;" "testing for encryption"
26075 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
26076 name of the cipher suite in use is tested against the list. To test for
26077 encryption without testing for any specific cipher suite(s), set
26083 .vitem &*hosts&~=&~*&<&'&~host&~list'&>
26084 .cindex "&%hosts%& ACL condition"
26085 .cindex "host" "ACL checking"
26086 .cindex "&ACL;" "testing the client host"
26087 This condition tests that the calling host matches the host list. If you have
26088 name lookups or wildcarded host names and IP addresses in the same host list,
26089 you should normally put the IP addresses first. For example, you could have:
26091 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
26093 The lookup in this example uses the host name for its key. This is implied by
26094 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
26095 and it wouldn't matter which way round you had these two items.)
26097 The reason for the problem with host names lies in the left-to-right way that
26098 Exim processes lists. It can test IP addresses without doing any DNS lookups,
26099 but when it reaches an item that requires a host name, it fails if it cannot
26100 find a host name to compare with the pattern. If the above list is given in the
26101 opposite order, the &%accept%& statement fails for a host whose name cannot be
26102 found, even if its IP address is 10.9.8.7.
26104 If you really do want to do the name check first, and still recognize the IP
26105 address even if the name lookup fails, you can rewrite the ACL like this:
26107 accept hosts = dbm;/etc/friendly/hosts
26108 accept hosts = 10.9.8.7
26110 The default action on failing to find the host name is to assume that the host
26111 is not in the list, so the first &%accept%& statement fails. The second
26112 statement can then check the IP address.
26114 .vindex "&$host_data$&"
26115 If a &%hosts%& condition is satisfied by means of a lookup, the result
26116 of the lookup is made available in the &$host_data$& variable. This
26117 allows you, for example, to set up a statement like this:
26119 deny hosts = net-lsearch;/some/file
26120 message = $host_data
26122 which gives a custom error message for each denied host.
26124 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
26125 .cindex "&%local_parts%& ACL condition"
26126 .cindex "local part" "ACL checking"
26127 .cindex "&ACL;" "testing a local part"
26128 .vindex "&$local_part_data$&"
26129 This condition is relevant only after a RCPT command. It checks that the local
26130 part of the recipient address is in the list. If percent-hack processing is
26131 enabled, it is done before this test. If the check succeeds with a lookup, the
26132 result of the lookup is placed in &$local_part_data$&, which remains set until
26133 the next &%local_parts%& test.
26135 .vitem &*malware&~=&~*&<&'option'&>
26136 .cindex "&%malware%& ACL condition"
26137 .cindex "&ACL;" "virus scanning"
26138 .cindex "&ACL;" "scanning for viruses"
26139 This condition is available only when Exim is compiled with the
26140 content-scanning extension. It causes the incoming message to be scanned for
26141 viruses. For details, see chapter &<<CHAPexiscan>>&.
26143 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
26144 .cindex "&%mime_regex%& ACL condition"
26145 .cindex "&ACL;" "testing by regex matching"
26146 This condition is available only when Exim is compiled with the
26147 content-scanning extension, and it is allowed only in the ACL defined by
26148 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
26149 with any of the regular expressions. For details, see chapter
26152 .vitem &*ratelimit&~=&~*&<&'parameters'&>
26153 .cindex "rate limiting"
26154 This condition can be used to limit the rate at which a user or host submits
26155 messages. Details are given in section &<<SECTratelimiting>>&.
26157 .vitem &*recipients&~=&~*&<&'address&~list'&>
26158 .cindex "&%recipients%& ACL condition"
26159 .cindex "recipient" "ACL checking"
26160 .cindex "&ACL;" "testing a recipient"
26161 This condition is relevant only after a RCPT command. It checks the entire
26162 recipient address against a list of recipients.
26164 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
26165 .cindex "&%regex%& ACL condition"
26166 .cindex "&ACL;" "testing by regex matching"
26167 This condition is available only when Exim is compiled with the
26168 content-scanning extension, and is available only in the DATA, MIME, and
26169 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
26170 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
26172 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
26173 .cindex "&%sender_domains%& ACL condition"
26174 .cindex "sender" "ACL checking"
26175 .cindex "&ACL;" "testing a sender domain"
26176 .vindex "&$domain$&"
26177 .vindex "&$sender_address_domain$&"
26178 This condition tests the domain of the sender of the message against the given
26179 domain list. &*Note*&: The domain of the sender address is in
26180 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
26181 of this condition. This is an exception to the general rule for testing domain
26182 lists. It is done this way so that, if this condition is used in an ACL for a
26183 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
26184 influence the sender checking.
26186 &*Warning*&: It is a bad idea to use this condition on its own as a control on
26187 relaying, because sender addresses are easily, and commonly, forged.
26189 .vitem &*senders&~=&~*&<&'address&~list'&>
26190 .cindex "&%senders%& ACL condition"
26191 .cindex "sender" "ACL checking"
26192 .cindex "&ACL;" "testing a sender"
26193 This condition tests the sender of the message against the given list. To test
26194 for a bounce message, which has an empty sender, set
26198 &*Warning*&: It is a bad idea to use this condition on its own as a control on
26199 relaying, because sender addresses are easily, and commonly, forged.
26201 .vitem &*spam&~=&~*&<&'username'&>
26202 .cindex "&%spam%& ACL condition"
26203 .cindex "&ACL;" "scanning for spam"
26204 This condition is available only when Exim is compiled with the
26205 content-scanning extension. It causes the incoming message to be scanned by
26206 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
26208 .vitem &*verify&~=&~certificate*&
26209 .cindex "&%verify%& ACL condition"
26210 .cindex "TLS" "client certificate verification"
26211 .cindex "certificate" "verification of client"
26212 .cindex "&ACL;" "certificate verification"
26213 .cindex "&ACL;" "testing a TLS certificate"
26214 This condition is true in an SMTP session if the session is encrypted, and a
26215 certificate was received from the client, and the certificate was verified. The
26216 server requests a certificate only if the client matches &%tls_verify_hosts%&
26217 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
26219 .vitem &*verify&~=&~csa*&
26220 .cindex "CSA verification"
26221 This condition checks whether the sending host (the client) is authorized to
26222 send email. Details of how this works are given in section
26223 &<<SECTverifyCSA>>&.
26225 .vitem &*verify&~=&~header_sender/*&<&'options'&>
26226 .cindex "&%verify%& ACL condition"
26227 .cindex "&ACL;" "verifying sender in the header"
26228 .cindex "header lines" "verifying the sender in"
26229 .cindex "sender" "verifying in header"
26230 .cindex "verifying" "sender in header"
26231 This condition is relevant only in an ACL that is run after a message has been
26232 received, that is, in an ACL specified by &%acl_smtp_data%& or
26233 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
26234 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
26235 is loosely thought of as a &"sender"& address (hence the name of the test).
26236 However, an address that appears in one of these headers need not be an address
26237 that accepts bounce messages; only sender addresses in envelopes are required
26238 to accept bounces. Therefore, if you use the callout option on this check, you
26239 might want to arrange for a non-empty address in the MAIL command.
26241 Details of address verification and the options are given later, starting at
26242 section &<<SECTaddressverification>>& (callouts are described in section
26243 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
26244 condition to restrict it to bounce messages only:
26247 message = A valid sender header is required for bounces
26248 !verify = header_sender
26251 .vitem &*verify&~=&~header_syntax*&
26252 .cindex "&%verify%& ACL condition"
26253 .cindex "&ACL;" "verifying header syntax"
26254 .cindex "header lines" "verifying syntax"
26255 .cindex "verifying" "header syntax"
26256 This condition is relevant only in an ACL that is run after a message has been
26257 received, that is, in an ACL specified by &%acl_smtp_data%& or
26258 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
26259 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
26260 and &'Bcc:'&). Unqualified addresses (local parts without domains) are
26261 permitted only in locally generated messages and from hosts that match
26262 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26265 Note that this condition is a syntax check only. However, a common spamming
26266 ploy used to be to send syntactically invalid headers such as
26270 and this condition can be used to reject such messages, though they are not as
26271 common as they used to be.
26273 .vitem &*verify&~=&~helo*&
26274 .cindex "&%verify%& ACL condition"
26275 .cindex "&ACL;" "verifying HELO/EHLO"
26276 .cindex "HELO" "verifying"
26277 .cindex "EHLO" "verifying"
26278 .cindex "verifying" "EHLO"
26279 .cindex "verifying" "HELO"
26280 This condition is true if a HELO or EHLO command has been received from the
26281 client host, and its contents have been verified. If there has been no previous
26282 attempt to verify the HELO/EHLO contents, it is carried out when this
26283 condition is encountered. See the description of the &%helo_verify_hosts%& and
26284 &%helo_try_verify_hosts%& options for details of how to request verification
26285 independently of this condition.
26287 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
26288 option), this condition is always true.
26291 .vitem &*verify&~=&~not_blind*&
26292 .cindex "verifying" "not blind"
26293 .cindex "bcc recipients, verifying none"
26294 This condition checks that there are no blind (bcc) recipients in the message.
26295 Every envelope recipient must appear either in a &'To:'& header line or in a
26296 &'Cc:'& header line for this condition to be true. Local parts are checked
26297 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
26298 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
26299 used only in a DATA or non-SMTP ACL.
26301 There are, of course, many legitimate messages that make use of blind (bcc)
26302 recipients. This check should not be used on its own for blocking messages.
26305 .vitem &*verify&~=&~recipient/*&<&'options'&>
26306 .cindex "&%verify%& ACL condition"
26307 .cindex "&ACL;" "verifying recipient"
26308 .cindex "recipient" "verifying"
26309 .cindex "verifying" "recipient"
26310 .vindex "&$address_data$&"
26311 This condition is relevant only after a RCPT command. It verifies the current
26312 recipient. Details of address verification are given later, starting at section
26313 &<<SECTaddressverification>>&. After a recipient has been verified, the value
26314 of &$address_data$& is the last value that was set while routing the address.
26315 This applies even if the verification fails. When an address that is being
26316 verified is redirected to a single address, verification continues with the new
26317 address, and in that case, the subsequent value of &$address_data$& is the
26318 value for the child address.
26320 .vitem &*verify&~=&~reverse_host_lookup*&
26321 .cindex "&%verify%& ACL condition"
26322 .cindex "&ACL;" "verifying host reverse lookup"
26323 .cindex "host" "verifying reverse lookup"
26324 This condition ensures that a verified host name has been looked up from the IP
26325 address of the client host. (This may have happened already if the host name
26326 was needed for checking a host list, or if the host matched &%host_lookup%&.)
26327 Verification ensures that the host name obtained from a reverse DNS lookup, or
26328 one of its aliases, does, when it is itself looked up in the DNS, yield the
26329 original IP address.
26331 If this condition is used for a locally generated message (that is, when there
26332 is no client host involved), it always succeeds.
26334 .vitem &*verify&~=&~sender/*&<&'options'&>
26335 .cindex "&%verify%& ACL condition"
26336 .cindex "&ACL;" "verifying sender"
26337 .cindex "sender" "verifying"
26338 .cindex "verifying" "sender"
26339 This condition is relevant only after a MAIL or RCPT command, or after a
26340 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
26341 the message's sender is empty (that is, this is a bounce message), the
26342 condition is true. Otherwise, the sender address is verified.
26344 .vindex "&$address_data$&"
26345 .vindex "&$sender_address_data$&"
26346 If there is data in the &$address_data$& variable at the end of routing, its
26347 value is placed in &$sender_address_data$& at the end of verification. This
26348 value can be used in subsequent conditions and modifiers in the same ACL
26349 statement. It does not persist after the end of the current statement. If you
26350 want to preserve the value for longer, you can save it in an ACL variable.
26352 Details of verification are given later, starting at section
26353 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
26354 to avoid doing it more than once per message.
26356 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
26357 .cindex "&%verify%& ACL condition"
26358 This is a variation of the previous option, in which a modified address is
26359 verified as a sender.
26364 .section "Using DNS lists" "SECTmorednslists"
26365 .cindex "DNS list" "in ACL"
26366 .cindex "black list (DNS)"
26367 .cindex "&ACL;" "testing a DNS list"
26368 In its simplest form, the &%dnslists%& condition tests whether the calling host
26369 is on at least one of a number of DNS lists by looking up the inverted IP
26370 address in one or more DNS domains. (Note that DNS list domains are not mail
26371 domains, so the &`+`& syntax for named lists doesn't work - it is used for
26372 special options instead.) For example, if the calling host's IP
26373 address is 192.168.62.43, and the ACL statement is
26375 deny dnslists = blackholes.mail-abuse.org : \
26376 dialups.mail-abuse.org
26378 the following records are looked up:
26380 43.62.168.192.blackholes.mail-abuse.org
26381 43.62.168.192.dialups.mail-abuse.org
26383 As soon as Exim finds an existing DNS record, processing of the list stops.
26384 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
26385 to test that a host is on more than one list (an &"and"& conjunction), you can
26386 use two separate conditions:
26388 deny dnslists = blackholes.mail-abuse.org
26389 dnslists = dialups.mail-abuse.org
26391 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
26392 behaves as if the host does not match the list item, that is, as if the DNS
26393 record does not exist. If there are further items in the DNS list, they are
26396 This is usually the required action when &%dnslists%& is used with &%deny%&
26397 (which is the most common usage), because it prevents a DNS failure from
26398 blocking mail. However, you can change this behaviour by putting one of the
26399 following special items in the list:
26401 &`+include_unknown `& behave as if the item is on the list
26402 &`+exclude_unknown `& behave as if the item is not on the list (default)
26403 &`+defer_unknown `& give a temporary error
26405 .cindex "&`+include_unknown`&"
26406 .cindex "&`+exclude_unknown`&"
26407 .cindex "&`+defer_unknown`&"
26408 Each of these applies to any subsequent items on the list. For example:
26410 deny dnslists = +defer_unknown : foo.bar.example
26412 Testing the list of domains stops as soon as a match is found. If you want to
26413 warn for one list and block for another, you can use two different statements:
26415 deny dnslists = blackholes.mail-abuse.org
26416 warn message = X-Warn: sending host is on dialups list
26417 dnslists = dialups.mail-abuse.org
26419 DNS list lookups are cached by Exim for the duration of the SMTP session,
26420 so a lookup based on the IP address is done at most once for any incoming
26421 connection. Exim does not share information between multiple incoming
26422 connections (but your local name server cache should be active).
26426 .section "Specifying the IP address for a DNS list lookup" "SECID201"
26427 .cindex "DNS list" "keyed by explicit IP address"
26428 By default, the IP address that is used in a DNS list lookup is the IP address
26429 of the calling host. However, you can specify another IP address by listing it
26430 after the domain name, introduced by a slash. For example:
26432 deny dnslists = black.list.tld/192.168.1.2
26434 This feature is not very helpful with explicit IP addresses; it is intended for
26435 use with IP addresses that are looked up, for example, the IP addresses of the
26436 MX hosts or nameservers of an email sender address. For an example, see section
26437 &<<SECTmulkeyfor>>& below.
26442 .section "DNS lists keyed on domain names" "SECID202"
26443 .cindex "DNS list" "keyed by domain name"
26444 There are some lists that are keyed on domain names rather than inverted IP
26445 addresses (see for example the &'domain based zones'& link at
26446 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
26447 with these lists. You can change the name that is looked up in a DNS list by
26448 listing it after the domain name, introduced by a slash. For example,
26450 deny message = Sender's domain is listed at $dnslist_domain
26451 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
26453 This particular example is useful only in ACLs that are obeyed after the
26454 RCPT or DATA commands, when a sender address is available. If (for
26455 example) the message's sender is &'user@tld.example'& the name that is looked
26456 up by this example is
26458 tld.example.dsn.rfc-ignorant.org
26460 A single &%dnslists%& condition can contain entries for both names and IP
26461 addresses. For example:
26463 deny dnslists = sbl.spamhaus.org : \
26464 dsn.rfc-ignorant.org/$sender_address_domain
26466 The first item checks the sending host's IP address; the second checks a domain
26467 name. The whole condition is true if either of the DNS lookups succeeds.
26472 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
26473 .cindex "DNS list" "multiple keys for"
26474 The syntax described above for looking up explicitly-defined values (either
26475 names or IP addresses) in a DNS blacklist is a simplification. After the domain
26476 name for the DNS list, what follows the slash can in fact be a list of items.
26477 As with all lists in Exim, the default separator is a colon. However, because
26478 this is a sublist within the list of DNS blacklist domains, it is necessary
26479 either to double the separators like this:
26481 dnslists = black.list.tld/name.1::name.2
26483 or to change the separator character, like this:
26485 dnslists = black.list.tld/<;name.1;name.2
26487 If an item in the list is an IP address, it is inverted before the DNS
26488 blacklist domain is appended. If it is not an IP address, no inversion
26489 occurs. Consider this condition:
26491 dnslists = black.list.tld/<;192.168.1.2;a.domain
26493 The DNS lookups that occur are:
26495 2.1.168.192.black.list.tld
26496 a.domain.black.list.tld
26498 Once a DNS record has been found (that matches a specific IP return
26499 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
26500 are done. If there is a temporary DNS error, the rest of the sublist of domains
26501 or IP addresses is tried. A temporary error for the whole dnslists item occurs
26502 only if no other DNS lookup in this sublist succeeds. In other words, a
26503 successful lookup for any of the items in the sublist overrides a temporary
26504 error for a previous item.
26506 The ability to supply a list of items after the slash is in some sense just a
26507 syntactic convenience. These two examples have the same effect:
26509 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
26510 dnslists = black.list.tld/a.domain::b.domain
26512 However, when the data for the list is obtained from a lookup, the second form
26513 is usually much more convenient. Consider this example:
26515 deny message = The mail servers for the domain \
26516 $sender_address_domain \
26517 are listed at $dnslist_domain ($dnslist_value); \
26519 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
26520 ${lookup dnsdb {>|mxh=\
26521 $sender_address_domain} }} }
26523 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
26524 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
26525 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
26526 of expanding the condition might be something like this:
26528 dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
26530 Thus, this example checks whether or not the IP addresses of the sender
26531 domain's mail servers are on the Spamhaus black list.
26533 The key that was used for a successful DNS list lookup is put into the variable
26534 &$dnslist_matched$& (see section &<<SECID204>>&).
26539 .section "Data returned by DNS lists" "SECID203"
26540 .cindex "DNS list" "data returned from"
26541 DNS lists are constructed using address records in the DNS. The original RBL
26542 just used the address 127.0.0.1 on the right hand side of each record, but the
26543 RBL+ list and some other lists use a number of values with different meanings.
26544 The values used on the RBL+ list are:
26548 127.1.0.3 DUL and RBL
26550 127.1.0.5 RSS and RBL
26551 127.1.0.6 RSS and DUL
26552 127.1.0.7 RSS and DUL and RBL
26554 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
26555 different values. Some DNS lists may return more than one address record;
26556 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
26559 .section "Variables set from DNS lists" "SECID204"
26560 .cindex "expansion" "variables, set from DNS list"
26561 .cindex "DNS list" "variables set from"
26562 .vindex "&$dnslist_domain$&"
26563 .vindex "&$dnslist_matched$&"
26564 .vindex "&$dnslist_text$&"
26565 .vindex "&$dnslist_value$&"
26566 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
26567 the name of the overall domain that matched (for example,
26568 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
26569 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
26570 the DNS record. When the key is an IP address, it is not reversed in
26571 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
26572 cases, for example:
26574 deny dnslists = spamhaus.example
26576 the key is also available in another variable (in this case,
26577 &$sender_host_address$&). In more complicated cases, however, this is not true.
26578 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
26579 might generate a dnslists lookup like this:
26581 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
26583 If this condition succeeds, the value in &$dnslist_matched$& might be
26584 &`192.168.6.7`& (for example).
26586 If more than one address record is returned by the DNS lookup, all the IP
26587 addresses are included in &$dnslist_value$&, separated by commas and spaces.
26588 The variable &$dnslist_text$& contains the contents of any associated TXT
26589 record. For lists such as RBL+ the TXT record for a merged entry is often not
26590 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
26593 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
26594 &-- although these appear before the condition in the ACL, they are not
26595 expanded until after it has failed. For example:
26597 deny hosts = !+local_networks
26598 message = $sender_host_address is listed \
26600 dnslists = rbl-plus.mail-abuse.example
26605 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
26606 .cindex "DNS list" "matching specific returned data"
26607 You can add an equals sign and an IP address after a &%dnslists%& domain name
26608 in order to restrict its action to DNS records with a matching right hand side.
26611 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
26613 rejects only those hosts that yield 127.0.0.2. Without this additional data,
26614 any address record is considered to be a match. For the moment, we assume
26615 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
26616 describes how multiple records are handled.
26618 More than one IP address may be given for checking, using a comma as a
26619 separator. These are alternatives &-- if any one of them matches, the
26620 &%dnslists%& condition is true. For example:
26622 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
26624 If you want to specify a constraining address list and also specify names or IP
26625 addresses to be looked up, the constraining address list must be specified
26626 first. For example:
26628 deny dnslists = dsn.rfc-ignorant.org\
26629 =127.0.0.2/$sender_address_domain
26632 If the character &`&&`& is used instead of &`=`&, the comparison for each
26633 listed IP address is done by a bitwise &"and"& instead of by an equality test.
26634 In other words, the listed addresses are used as bit masks. The comparison is
26635 true if all the bits in the mask are present in the address that is being
26636 tested. For example:
26638 dnslists = a.b.c&0.0.0.3
26640 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
26641 want to test whether one bit or another bit is present (as opposed to both
26642 being present), you must use multiple values. For example:
26644 dnslists = a.b.c&0.0.0.1,0.0.0.2
26646 matches if the final component of the address is an odd number or two times
26651 .section "Negated DNS matching conditions" "SECID205"
26652 You can supply a negative list of IP addresses as part of a &%dnslists%&
26655 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
26657 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
26658 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
26660 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
26662 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
26663 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
26664 words, the result of the test is inverted if an exclamation mark appears before
26665 the &`=`& (or the &`&&`&) sign.
26667 &*Note*&: This kind of negation is not the same as negation in a domain,
26668 host, or address list (which is why the syntax is different).
26670 If you are using just one list, the negation syntax does not gain you much. The
26671 previous example is precisely equivalent to
26673 deny dnslists = a.b.c
26674 !dnslists = a.b.c=127.0.0.2,127.0.0.3
26676 However, if you are using multiple lists, the negation syntax is clearer.
26677 Consider this example:
26679 deny dnslists = sbl.spamhaus.org : \
26681 dnsbl.njabl.org!=127.0.0.3 : \
26684 Using only positive lists, this would have to be:
26686 deny dnslists = sbl.spamhaus.org : \
26688 deny dnslists = dnsbl.njabl.org
26689 !dnslists = dnsbl.njabl.org=127.0.0.3
26690 deny dnslists = relays.ordb.org
26692 which is less clear, and harder to maintain.
26697 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
26698 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
26699 thereby providing more than one IP address. When an item in a &%dnslists%& list
26700 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
26701 the match to specific results from the DNS lookup, there are two ways in which
26702 the checking can be handled. For example, consider the condition:
26704 dnslists = a.b.c=127.0.0.1
26706 What happens if the DNS lookup for the incoming IP address yields both
26707 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
26708 condition true because at least one given value was found, or is it false
26709 because at least one of the found values was not listed? And how does this
26710 affect negated conditions? Both possibilities are provided for with the help of
26711 additional separators &`==`& and &`=&&`&.
26714 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
26715 IP addresses matches one of the listed addresses. For the example above, the
26716 condition is true because 127.0.0.1 matches.
26718 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
26719 looked up IP addresses matches one of the listed addresses. If the condition is
26722 dnslists = a.b.c==127.0.0.1
26724 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26725 false because 127.0.0.2 is not listed. You would need to have:
26727 dnslists = a.b.c==127.0.0.1,127.0.0.2
26729 for the condition to be true.
26732 When &`!`& is used to negate IP address matching, it inverts the result, giving
26733 the precise opposite of the behaviour above. Thus:
26735 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
26736 addresses matches one of the listed addresses. Consider:
26738 dnslists = a.b.c!&0.0.0.1
26740 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26741 false because 127.0.0.1 matches.
26743 If &`!==`& or &`!=&&`& is used, the condition is true there is at least one
26744 looked up IP address that does not match. Consider:
26746 dnslists = a.b.c!=&0.0.0.1
26748 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
26749 true, because 127.0.0.2 does not match. You would need to have:
26751 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
26753 for the condition to be false.
26755 When the DNS lookup yields only a single IP address, there is no difference
26756 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
26761 .section "Detailed information from merged DNS lists" "SECTmordetinf"
26762 .cindex "DNS list" "information from merged"
26763 When the facility for restricting the matching IP values in a DNS list is used,
26764 the text from the TXT record that is set in &$dnslist_text$& may not reflect
26765 the true reason for rejection. This happens when lists are merged and the IP
26766 address in the A record is used to distinguish them; unfortunately there is
26767 only one TXT record. One way round this is not to use merged lists, but that
26768 can be inefficient because it requires multiple DNS lookups where one would do
26769 in the vast majority of cases when the host of interest is not on any of the
26772 A less inefficient way of solving this problem is available. If
26773 two domain names, comma-separated, are given, the second is used first to
26774 do an initial check, making use of any IP value restrictions that are set.
26775 If there is a match, the first domain is used, without any IP value
26776 restrictions, to get the TXT record. As a byproduct of this, there is also
26777 a check that the IP being tested is indeed on the first list. The first
26778 domain is the one that is put in &$dnslist_domain$&. For example:
26781 rejected because $sender_host_address is blacklisted \
26782 at $dnslist_domain\n$dnslist_text
26784 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
26785 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
26787 For the first blacklist item, this starts by doing a lookup in
26788 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
26789 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
26790 value, and as long as something is found, it looks for the corresponding TXT
26791 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
26792 The second blacklist item is processed similarly.
26794 If you are interested in more than one merged list, the same list must be
26795 given several times, but because the results of the DNS lookups are cached,
26796 the DNS calls themselves are not repeated. For example:
26798 reject dnslists = \
26799 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
26800 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
26801 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
26802 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
26804 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
26805 values matches (or if no record is found), this is the only lookup that is
26806 done. Only if there is a match is one of the more specific lists consulted.
26810 .section "DNS lists and IPv6" "SECTmorednslistslast"
26811 .cindex "IPv6" "DNS black lists"
26812 .cindex "DNS list" "IPv6 usage"
26813 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
26814 nibble by nibble. For example, if the calling host's IP address is
26815 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
26817 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
26818 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
26820 (split over two lines here to fit on the page). Unfortunately, some of the DNS
26821 lists contain wildcard records, intended for IPv4, that interact badly with
26822 IPv6. For example, the DNS entry
26824 *.3.some.list.example. A 127.0.0.1
26826 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
26827 Unfortunately, it also matches the entire 3::/4 IPv6 network.
26829 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
26830 &%condition%& condition, as in this example:
26832 deny condition = ${if isip4{$sender_host_address}}
26833 dnslists = some.list.example
26836 .section "Rate limiting incoming messages" "SECTratelimiting"
26837 .cindex "rate limiting" "client sending"
26838 .cindex "limiting client sending rates"
26839 .oindex "&%smtp_ratelimit_*%&"
26840 The &%ratelimit%& ACL condition can be used to measure and control the rate at
26841 which clients can send email. This is more powerful than the
26842 &%smtp_ratelimit_*%& options, because those options control the rate of
26843 commands in a single SMTP session only, whereas the &%ratelimit%& condition
26844 works across all connections (concurrent and sequential) from the same client
26845 host. The syntax of the &%ratelimit%& condition is:
26847 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
26849 If the average client sending rate is less than &'m'& messages per time
26850 period &'p'& then the condition is false; otherwise it is true.
26852 As a side-effect, the &%ratelimit%& condition sets the expansion variable
26853 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
26854 configured value of &'m'&, and &$sender_rate_period$& to the configured value
26857 The parameter &'p'& is the smoothing time constant, in the form of an Exim
26858 time interval, for example, &`8h`& for eight hours. A larger time constant
26859 means that it takes Exim longer to forget a client's past behaviour. The
26860 parameter &'m'& is the maximum number of messages that a client is permitted to
26861 send in each time interval. It also specifies the number of messages permitted
26862 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
26863 constant, you can allow a client to send more messages in a burst without
26864 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
26865 both small, messages must be sent at an even rate.
26867 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
26868 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
26869 when deploying the &%ratelimit%& ACL condition. The script prints usage
26870 instructions when it is run with no arguments.
26872 The key is used to look up the data for calculating the client's average
26873 sending rate. This data is stored in Exim's spool directory, alongside the
26874 retry and other hints databases. The default key is &$sender_host_address$&,
26875 which means Exim computes the sending rate of each client host IP address.
26876 By changing the key you can change how Exim identifies clients for the purpose
26877 of ratelimiting. For example, to limit the sending rate of each authenticated
26878 user, independent of the computer they are sending from, set the key to
26879 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
26880 example, &$authenticated_id$& is only meaningful if the client has
26881 authenticated (which you can check with the &%authenticated%& ACL condition).
26883 The lookup key does not have to identify clients: If you want to limit the
26884 rate at which a recipient receives messages, you can use the key
26885 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
26888 Internally, Exim appends the smoothing constant &'p'& and the options onto the
26889 lookup key because they alter the meaning of the stored data. This is not true
26890 for the limit &'m'&, so you can alter the configured maximum rate and Exim will
26891 still remember clients' past behaviour, but if you alter the other ratelimit
26892 parameters Exim forgets past behaviour.
26894 Each &%ratelimit%& condition can have up to three options. One option
26895 specifies what Exim measures the rate of, and the second specifies how Exim
26896 handles excessively fast clients. The third option can be &`noupdate`&, to
26897 disable updating of the ratelimiting database (see section &<<rearatdat>>&).
26898 The options are separated by a slash, like the other parameters. They may
26899 appear in any order.
26901 .section "Ratelimit options for what is being measured" "ratoptmea"
26902 The &%per_conn%& option limits the client's connection rate.
26904 The &%per_mail%& option limits the client's rate of sending messages. This is
26905 the default if none of the &%per_*%& options is specified.
26907 The &%per_byte%& option limits the sender's email bandwidth. Note that it is
26908 best to use this option in the DATA ACL; if it is used in an earlier ACL it
26909 relies on the SIZE parameter specified by the client in its MAIL command,
26910 which may be inaccurate or completely missing. You can follow the limit &'m'&
26911 in the configuration with K, M, or G to specify limits in kilobytes,
26912 megabytes, or gigabytes, respectively.
26914 The &%per_rcpt%& option causes Exim to limit the rate at which
26915 recipients are accepted. To be effective, it would need to be used in
26916 either the &%acl_smtp_rcpt%& or the &%acl_not_smtp%& ACL. In the
26917 &%acl_smtp_rcpt%& ACL, the number of recipients is incremented by one.
26918 In the case of a locally submitted message in the &%acl_not_smtp%& ACL,
26919 the number of recipients is incremented by the &%$recipients_count%&
26920 for the entire message. Note that in either case the rate limiting
26921 engine will see a message with many recipients as a large high-speed
26924 The &%per_cmd%& option causes Exim to recompute the rate every time the
26925 condition is processed. This can be used to limit the SMTP command rate.
26926 This command is essentially an alias of &%per_rcpt%& to make it clear
26927 that the effect is to limit the rate at which individual commands,
26928 rather than recipients, are accepted.
26930 .section "Ratelimit options for handling fast clients" "ratophanfas"
26931 If a client's average rate is greater than the maximum, the rate limiting
26932 engine can react in two possible ways, depending on the presence of the
26933 &%strict%& or &%leaky%& options. This is independent of the other
26934 counter-measures (such as rejecting the message) that may be specified by the
26935 rest of the ACL. The default mode is leaky, which avoids a sender's
26936 over-aggressive retry rate preventing it from getting any email through.
26938 The &%strict%& option means that the client's recorded rate is always
26939 updated. The effect of this is that Exim measures the client's average rate
26940 of attempts to send email, which can be much higher than the maximum it is
26941 actually allowed. If the client is over the limit it may be subjected to
26942 counter-measures by the ACL until it slows down below the maximum rate. If
26943 the client stops attempting to send email for the time specified in the &'p'&
26944 parameter then its computed rate will decay exponentially to 37% of its peak
26945 value. You can work out the time (the number of smoothing periods) that a
26946 client is subjected to counter-measures after an over-limit burst with this
26949 ln(peakrate/maxrate)
26951 The &%leaky%& (default) option means that the client's recorded rate is not
26952 updated if it is above the limit. The effect of this is that Exim measures the
26953 client's average rate of successfully sent email, which cannot be greater than
26954 the maximum allowed. If the client is over the limit it may suffer some
26955 counter-measures (as specified in the ACL), but it will still be able to send
26956 email at the configured maximum rate, whatever the rate of its attempts. This
26957 is generally the better choice if you have clients that retry automatically.
26959 .section "Using rate limiting" "useratlim"
26960 Exim's other ACL facilities are used to define what counter-measures are taken
26961 when the rate limit is exceeded. This might be anything from logging a warning
26962 (for example, while measuring existing sending rates in order to define
26963 policy), through time delays to slow down fast senders, up to rejecting the
26964 message. For example:
26966 # Log all senders' rates
26967 warn ratelimit = 0 / 1h / strict
26968 log_message = Sender rate $sender_rate / $sender_rate_period
26970 # Slow down fast senders; note the need to truncate $sender_rate
26971 # at the decimal point.
26972 warn ratelimit = 100 / 1h / per_rcpt / strict
26973 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
26974 $sender_rate_limit }s
26976 # Keep authenticated users under control
26977 deny authenticated = *
26978 ratelimit = 100 / 1d / strict / $authenticated_id
26980 # System-wide rate limit
26981 defer message = Sorry, too busy. Try again later.
26982 ratelimit = 10 / 1s / $primary_hostname
26984 # Restrict incoming rate from each host, with a default
26985 # set using a macro and special cases looked up in a table.
26986 defer message = Sender rate exceeds $sender_rate_limit \
26987 messages per $sender_rate_period
26988 ratelimit = ${lookup {$sender_host_address} \
26989 cdb {DB/ratelimits.cdb} \
26990 {$value} {RATELIMIT} }
26992 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
26993 especially with the &%per_rcpt%& option, you may suffer from a performance
26994 bottleneck caused by locking on the ratelimit hints database. Apart from
26995 making your ACLs less complicated, you can reduce the problem by using a
26996 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
26997 this means that Exim will lose its hints data after a reboot (including retry
26998 hints, the callout cache, and ratelimit data).
27001 .section "Reading ratelimit data without updating" "rearatdat"
27002 .cindex "rate limitint" "reading data without updating"
27003 If the &%noupdate%& option is present on a &%ratelimit%& ACL condition, Exim
27004 computes the rate and checks the limit as normal, but it does not update the
27005 saved data. This means that, in relevant ACLs, it is possible to lookup the
27006 existence of a specified (or auto-generated) ratelimit key without incrementing
27007 the ratelimit counter for that key. In order for this to be useful, another ACL
27008 entry must set the rate for the same key (otherwise it will always be zero).
27012 deny ratelimit = 100 / 5m / strict / per_cmd / noupdate
27013 log_message = RATE: $sender_rate/$sender_rate_period \
27014 (max $sender_rate_limit)
27017 &'... some other logic and tests...'&
27021 warn ratelimit = 100 / 5m / strict / per_cmd
27022 condition = ${if le{$sender_rate}{$sender_rate_limit}}
27023 logwrite = RATE UPDATE: $sender_rate/$sender_rate_period \
27024 (max $sender_rate_limit)
27026 In this example, the rate is tested and used to deny access (when it is too
27027 high) in the connect ACL, but the actual computation of the remembered rate
27028 happens later, on a per-command basis, in another ACL.
27032 .section "Address verification" "SECTaddressverification"
27033 .cindex "verifying address" "options for"
27034 .cindex "policy control" "address verification"
27035 Several of the &%verify%& conditions described in section
27036 &<<SECTaclconditions>>& cause addresses to be verified. Section
27037 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
27038 The verification conditions can be followed by options that modify the
27039 verification process. The options are separated from the keyword and from each
27040 other by slashes, and some of them contain parameters. For example:
27042 verify = sender/callout
27043 verify = recipient/defer_ok/callout=10s,defer_ok
27045 The first stage of address verification, which always happens, is to run the
27046 address through the routers, in &"verify mode"&. Routers can detect the
27047 difference between verification and routing for delivery, and their actions can
27048 be varied by a number of generic options such as &%verify%& and &%verify_only%&
27049 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
27050 The available options are as follows:
27053 If the &%callout%& option is specified, successful routing to one or more
27054 remote hosts is followed by a &"callout"& to those hosts as an additional
27055 check. Callouts and their sub-options are discussed in the next section.
27057 If there is a defer error while doing verification routing, the ACL
27058 normally returns &"defer"&. However, if you include &%defer_ok%& in the
27059 options, the condition is forced to be true instead. Note that this is a main
27060 verification option as well as a suboption for callouts.
27062 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
27063 discusses the reporting of sender address verification failures.
27065 The &%success_on_redirect%& option causes verification always to succeed
27066 immediately after a successful redirection. By default, if a redirection
27067 generates just one address, that address is also verified. See further
27068 discussion in section &<<SECTredirwhilveri>>&.
27071 .cindex "verifying address" "differentiating failures"
27072 .vindex "&$recipient_verify_failure$&"
27073 .vindex "&$sender_verify_failure$&"
27074 .vindex "&$acl_verify_message$&"
27075 After an address verification failure, &$acl_verify_message$& contains the
27076 error message that is associated with the failure. It can be preserved by
27079 warn !verify = sender
27080 set acl_m0 = $acl_verify_message
27082 If you are writing your own custom rejection message or log message when
27083 denying access, you can use this variable to include information about the
27084 verification failure.
27086 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
27087 appropriate) contains one of the following words:
27090 &%qualify%&: The address was unqualified (no domain), and the message
27091 was neither local nor came from an exempted host.
27093 &%route%&: Routing failed.
27095 &%mail%&: Routing succeeded, and a callout was attempted; rejection
27096 occurred at or before the MAIL command (that is, on initial
27097 connection, HELO, or MAIL).
27099 &%recipient%&: The RCPT command in a callout was rejected.
27101 &%postmaster%&: The postmaster check in a callout was rejected.
27104 The main use of these variables is expected to be to distinguish between
27105 rejections of MAIL and rejections of RCPT in callouts.
27110 .section "Callout verification" "SECTcallver"
27111 .cindex "verifying address" "by callout"
27112 .cindex "callout" "verification"
27113 .cindex "SMTP" "callout verification"
27114 For non-local addresses, routing verifies the domain, but is unable to do any
27115 checking of the local part. There are situations where some means of verifying
27116 the local part is desirable. One way this can be done is to make an SMTP
27117 &'callback'& to a delivery host for the sender address or a &'callforward'& to
27118 a subsequent host for a recipient address, to see if the host accepts the
27119 address. We use the term &'callout'& to cover both cases. Note that for a
27120 sender address, the callback is not to the client host that is trying to
27121 deliver the message, but to one of the hosts that accepts incoming mail for the
27124 Exim does not do callouts by default. If you want them to happen, you must
27125 request them by setting appropriate options on the &%verify%& condition, as
27126 described below. This facility should be used with care, because it can add a
27127 lot of resource usage to the cost of verifying an address. However, Exim does
27128 cache the results of callouts, which helps to reduce the cost. Details of
27129 caching are in section &<<SECTcallvercache>>&.
27131 Recipient callouts are usually used only between hosts that are controlled by
27132 the same administration. For example, a corporate gateway host could use
27133 callouts to check for valid recipients on an internal mailserver. A successful
27134 callout does not guarantee that a real delivery to the address would succeed;
27135 on the other hand, a failing callout does guarantee that a delivery would fail.
27137 If the &%callout%& option is present on a condition that verifies an address, a
27138 second stage of verification occurs if the address is successfully routed to
27139 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
27140 &(manualroute)& router, where the router specifies the hosts. However, if a
27141 router that does not set up hosts routes to an &(smtp)& transport with a
27142 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
27143 &%hosts_override%& set, its hosts are always used, whether or not the router
27144 supplies a host list.
27146 The port that is used is taken from the transport, if it is specified and is a
27147 remote transport. (For routers that do verification only, no transport need be
27148 specified.) Otherwise, the default SMTP port is used. If a remote transport
27149 specifies an outgoing interface, this is used; otherwise the interface is not
27150 specified. Likewise, the text that is used for the HELO command is taken from
27151 the transport's &%helo_data%& option; if there is no transport, the value of
27152 &$smtp_active_hostname$& is used.
27154 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
27155 test whether a bounce message could be delivered to the sender address. The
27156 following SMTP commands are sent:
27158 &`HELO `&<&'local host name'&>
27160 &`RCPT TO:`&<&'the address to be tested'&>
27163 LHLO is used instead of HELO if the transport's &%protocol%& option is
27166 A recipient callout check is similar. By default, it also uses an empty address
27167 for the sender. This default is chosen because most hosts do not make use of
27168 the sender address when verifying a recipient. Using the same address means
27169 that a single cache entry can be used for each recipient. Some sites, however,
27170 do make use of the sender address when verifying. These are catered for by the
27171 &%use_sender%& and &%use_postmaster%& options, described in the next section.
27173 If the response to the RCPT command is a 2&'xx'& code, the verification
27174 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
27175 Exim tries the next host, if any. If there is a problem with all the remote
27176 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
27177 &%callout%& option is given, in which case the condition is forced to succeed.
27179 .cindex "SMTP" "output flushing, disabling for callout"
27180 A callout may take a little time. For this reason, Exim normally flushes SMTP
27181 output before performing a callout in an ACL, to avoid unexpected timeouts in
27182 clients when the SMTP PIPELINING extension is in use. The flushing can be
27183 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
27188 .section "Additional parameters for callouts" "CALLaddparcall"
27189 .cindex "callout" "additional parameters for"
27190 The &%callout%& option can be followed by an equals sign and a number of
27191 optional parameters, separated by commas. For example:
27193 verify = recipient/callout=10s,defer_ok
27195 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
27196 separate verify options, is retained for backwards compatibility, but is now
27197 deprecated. The additional parameters for &%callout%& are as follows:
27201 .vitem <&'a&~time&~interval'&>
27202 .cindex "callout" "timeout, specifying"
27203 This specifies the timeout that applies for the callout attempt to each host.
27206 verify = sender/callout=5s
27208 The default is 30 seconds. The timeout is used for each response from the
27209 remote host. It is also used for the initial connection, unless overridden by
27210 the &%connect%& parameter.
27213 .vitem &*connect&~=&~*&<&'time&~interval'&>
27214 .cindex "callout" "connection timeout, specifying"
27215 This parameter makes it possible to set a different (usually smaller) timeout
27216 for making the SMTP connection. For example:
27218 verify = sender/callout=5s,connect=1s
27220 If not specified, this timeout defaults to the general timeout value.
27222 .vitem &*defer_ok*&
27223 .cindex "callout" "defer, action on"
27224 When this parameter is present, failure to contact any host, or any other kind
27225 of temporary error, is treated as success by the ACL. However, the cache is not
27226 updated in this circumstance.
27228 .vitem &*fullpostmaster*&
27229 .cindex "callout" "full postmaster check"
27230 This operates like the &%postmaster%& option (see below), but if the check for
27231 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
27232 accordance with the specification in RFC 2821. The RFC states that the
27233 unqualified address &'postmaster'& should be accepted.
27236 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
27237 .cindex "callout" "sender when verifying header"
27238 When verifying addresses in header lines using the &%header_sender%&
27239 verification option, Exim behaves by default as if the addresses are envelope
27240 sender addresses from a message. Callout verification therefore tests to see
27241 whether a bounce message could be delivered, by using an empty address in the
27242 MAIL command. However, it is arguable that these addresses might never be used
27243 as envelope senders, and could therefore justifiably reject bounce messages
27244 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
27245 address to use in the MAIL command. For example:
27247 require verify = header_sender/callout=mailfrom=abcd@x.y.z
27249 This parameter is available only for the &%header_sender%& verification option.
27252 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
27253 .cindex "callout" "overall timeout, specifying"
27254 This parameter sets an overall timeout for performing a callout verification.
27257 verify = sender/callout=5s,maxwait=30s
27259 This timeout defaults to four times the callout timeout for individual SMTP
27260 commands. The overall timeout applies when there is more than one host that can
27261 be tried. The timeout is checked before trying the next host. This prevents
27262 very long delays if there are a large number of hosts and all are timing out
27263 (for example, when network connections are timing out).
27266 .vitem &*no_cache*&
27267 .cindex "callout" "cache, suppressing"
27268 .cindex "caching callout, suppressing"
27269 When this parameter is given, the callout cache is neither read nor updated.
27271 .vitem &*postmaster*&
27272 .cindex "callout" "postmaster; checking"
27273 When this parameter is set, a successful callout check is followed by a similar
27274 check for the local part &'postmaster'& at the same domain. If this address is
27275 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
27276 the postmaster check is recorded in a cache record; if it is a failure, this is
27277 used to fail subsequent callouts for the domain without a connection being
27278 made, until the cache record expires.
27280 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
27281 The postmaster check uses an empty sender in the MAIL command by default.
27282 You can use this parameter to do a postmaster check using a different address.
27285 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
27287 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
27288 one overrides. The &%postmaster%& parameter is equivalent to this example:
27290 require verify = sender/callout=postmaster_mailfrom=
27292 &*Warning*&: The caching arrangements for postmaster checking do not take
27293 account of the sender address. It is assumed that either the empty address or
27294 a fixed non-empty address will be used. All that Exim remembers is that the
27295 postmaster check for the domain succeeded or failed.
27299 .cindex "callout" "&""random""& check"
27300 When this parameter is set, before doing the normal callout check, Exim does a
27301 check for a &"random"& local part at the same domain. The local part is not
27302 really random &-- it is defined by the expansion of the option
27303 &%callout_random_local_part%&, which defaults to
27305 $primary_host_name-$tod_epoch-testing
27307 The idea here is to try to determine whether the remote host accepts all local
27308 parts without checking. If it does, there is no point in doing callouts for
27309 specific local parts. If the &"random"& check succeeds, the result is saved in
27310 a cache record, and used to force the current and subsequent callout checks to
27311 succeed without a connection being made, until the cache record expires.
27313 .vitem &*use_postmaster*&
27314 .cindex "callout" "sender for recipient check"
27315 This parameter applies to recipient callouts only. For example:
27317 deny !verify = recipient/callout=use_postmaster
27319 .vindex "&$qualify_domain$&"
27320 It causes a non-empty postmaster address to be used in the MAIL command when
27321 performing the callout for the recipient, and also for a &"random"& check if
27322 that is configured. The local part of the address is &`postmaster`& and the
27323 domain is the contents of &$qualify_domain$&.
27325 .vitem &*use_sender*&
27326 This option applies to recipient callouts only. For example:
27328 require verify = recipient/callout=use_sender
27330 It causes the message's actual sender address to be used in the MAIL
27331 command when performing the callout, instead of an empty address. There is no
27332 need to use this option unless you know that the called hosts make use of the
27333 sender when checking recipients. If used indiscriminately, it reduces the
27334 usefulness of callout caching.
27337 If you use any of the parameters that set a non-empty sender for the MAIL
27338 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
27339 &%use_sender%&), you should think about possible loops. Recipient checking is
27340 usually done between two hosts that are under the same management, and the host
27341 that receives the callouts is not normally configured to do callouts itself.
27342 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
27343 these circumstances.
27345 However, if you use a non-empty sender address for a callout to an arbitrary
27346 host, there is the likelihood that the remote host will itself initiate a
27347 callout check back to your host. As it is checking what appears to be a message
27348 sender, it is likely to use an empty address in MAIL, thus avoiding a
27349 callout loop. However, to be on the safe side it would be best to set up your
27350 own ACLs so that they do not do sender verification checks when the recipient
27351 is the address you use for header sender or postmaster callout checking.
27353 Another issue to think about when using non-empty senders for callouts is
27354 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
27355 by the sender/recipient combination; thus, for any given recipient, many more
27356 actual callouts are performed than when an empty sender or postmaster is used.
27361 .section "Callout caching" "SECTcallvercache"
27362 .cindex "hints database" "callout cache"
27363 .cindex "callout" "cache, description of"
27364 .cindex "caching" "callout"
27365 Exim caches the results of callouts in order to reduce the amount of resources
27366 used, unless you specify the &%no_cache%& parameter with the &%callout%&
27367 option. A hints database called &"callout"& is used for the cache. Two
27368 different record types are used: one records the result of a callout check for
27369 a specific address, and the other records information that applies to the
27370 entire domain (for example, that it accepts the local part &'postmaster'&).
27372 When an original callout fails, a detailed SMTP error message is given about
27373 the failure. However, for subsequent failures use the cache data, this message
27376 The expiry times for negative and positive address cache records are
27377 independent, and can be set by the global options &%callout_negative_expire%&
27378 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
27380 If a host gives a negative response to an SMTP connection, or rejects any
27381 commands up to and including
27385 (but not including the MAIL command with a non-empty address),
27386 any callout attempt is bound to fail. Exim remembers such failures in a
27387 domain cache record, which it uses to fail callouts for the domain without
27388 making new connections, until the domain record times out. There are two
27389 separate expiry times for domain cache records:
27390 &%callout_domain_negative_expire%& (default 3h) and
27391 &%callout_domain_positive_expire%& (default 7d).
27393 Domain records expire when the negative expiry time is reached if callouts
27394 cannot be made for the domain, or if the postmaster check failed.
27395 Otherwise, they expire when the positive expiry time is reached. This
27396 ensures that, for example, a host that stops accepting &"random"& local parts
27397 will eventually be noticed.
27399 The callout caching mechanism is based on the domain of the address that is
27400 being tested. If the domain routes to several hosts, it is assumed that their
27401 behaviour will be the same.
27405 .section "Sender address verification reporting" "SECTsenaddver"
27406 .cindex "verifying" "suppressing error details"
27407 See section &<<SECTaddressverification>>& for a general discussion of
27408 verification. When sender verification fails in an ACL, the details of the
27409 failure are given as additional output lines before the 550 response to the
27410 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
27413 MAIL FROM:<xyz@abc.example>
27415 RCPT TO:<pqr@def.example>
27416 550-Verification failed for <xyz@abc.example>
27417 550-Called: 192.168.34.43
27418 550-Sent: RCPT TO:<xyz@abc.example>
27419 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
27420 550 Sender verification failed
27422 If more than one RCPT command fails in the same way, the details are given
27423 only for the first of them. However, some administrators do not want to send
27424 out this much information. You can suppress the details by adding
27425 &`/no_details`& to the ACL statement that requests sender verification. For
27428 verify = sender/no_details
27431 .section "Redirection while verifying" "SECTredirwhilveri"
27432 .cindex "verifying" "redirection while"
27433 .cindex "address redirection" "while verifying"
27434 A dilemma arises when a local address is redirected by aliasing or forwarding
27435 during verification: should the generated addresses themselves be verified,
27436 or should the successful expansion of the original address be enough to verify
27437 it? By default, Exim takes the following pragmatic approach:
27440 When an incoming address is redirected to just one child address, verification
27441 continues with the child address, and if that fails to verify, the original
27442 verification also fails.
27444 When an incoming address is redirected to more than one child address,
27445 verification does not continue. A success result is returned.
27448 This seems the most reasonable behaviour for the common use of aliasing as a
27449 way of redirecting different local parts to the same mailbox. It means, for
27450 example, that a pair of alias entries of the form
27453 aw123: :fail: Gone away, no forwarding address
27455 work as expected, with both local parts causing verification failure. When a
27456 redirection generates more than one address, the behaviour is more like a
27457 mailing list, where the existence of the alias itself is sufficient for
27458 verification to succeed.
27460 It is possible, however, to change the default behaviour so that all successful
27461 redirections count as successful verifications, however many new addresses are
27462 generated. This is specified by the &%success_on_redirect%& verification
27463 option. For example:
27465 require verify = recipient/success_on_redirect/callout=10s
27467 In this example, verification succeeds if a router generates a new address, and
27468 the callout does not occur, because no address was routed to a remote host.
27470 When verification is being tested via the &%-bv%& option, the treatment of
27471 redirections is as just described, unless the &%-v%& or any debugging option is
27472 also specified. In that case, full verification is done for every generated
27473 address and a report is output for each of them.
27477 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
27478 .cindex "CSA" "verifying"
27479 Client SMTP Authorization is a system that allows a site to advertise
27480 which machines are and are not permitted to send email. This is done by placing
27481 special SRV records in the DNS; these are looked up using the client's HELO
27482 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
27483 Authorization checks in Exim are performed by the ACL condition:
27487 This fails if the client is not authorized. If there is a DNS problem, or if no
27488 valid CSA SRV record is found, or if the client is authorized, the condition
27489 succeeds. These three cases can be distinguished using the expansion variable
27490 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
27491 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
27492 be likely to cause problems for legitimate email.
27494 The error messages produced by the CSA code include slightly more
27495 detail. If &$csa_status$& is &"defer"&, this may be because of problems
27496 looking up the CSA SRV record, or problems looking up the CSA target
27497 address record. There are four reasons for &$csa_status$& being &"fail"&:
27500 The client's host name is explicitly not authorized.
27502 The client's IP address does not match any of the CSA target IP addresses.
27504 The client's host name is authorized but it has no valid target IP addresses
27505 (for example, the target's addresses are IPv6 and the client is using IPv4).
27507 The client's host name has no CSA SRV record but a parent domain has asserted
27508 that all subdomains must be explicitly authorized.
27511 The &%csa%& verification condition can take an argument which is the domain to
27512 use for the DNS query. The default is:
27514 verify = csa/$sender_helo_name
27516 This implementation includes an extension to CSA. If the query domain
27517 is an address literal such as [192.0.2.95], or if it is a bare IP
27518 address, Exim searches for CSA SRV records in the reverse DNS as if
27519 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
27522 verify = csa/$sender_host_address
27524 In fact, this is the check that Exim performs if the client does not say HELO.
27525 This extension can be turned off by setting the main configuration option
27526 &%dns_csa_use_reverse%& to be false.
27528 If a CSA SRV record is not found for the domain itself, a search
27529 is performed through its parent domains for a record which might be
27530 making assertions about subdomains. The maximum depth of this search is limited
27531 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
27532 default. Exim does not look for CSA SRV records in a top level domain, so the
27533 default settings handle HELO domains as long as seven
27534 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
27535 of legitimate HELO domains.
27537 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
27538 direct SRV lookups, this is not sufficient because of the extra parent domain
27539 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
27540 addresses into lookups in the reverse DNS space. The result of a successful
27543 ${lookup dnsdb {csa=$sender_helo_name}}
27545 has two space-separated fields: an authorization code and a target host name.
27546 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
27547 authorization required but absent, or &"?"& for unknown.
27552 .section "Bounce address tag validation" "SECTverifyPRVS"
27553 .cindex "BATV, verifying"
27554 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
27555 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
27556 Genuine incoming bounce messages should therefore always be addressed to
27557 recipients that have a valid tag. This scheme is a way of detecting unwanted
27558 bounce messages caused by sender address forgeries (often called &"collateral
27559 spam"&), because the recipients of such messages do not include valid tags.
27561 There are two expansion items to help with the implementation of the BATV
27562 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
27563 the original envelope sender address by using a simple key to add a hash of the
27564 address and some time-based randomizing information. The &%prvs%& expansion
27565 item creates a signed address, and the &%prvscheck%& expansion item checks one.
27566 The syntax of these expansion items is described in section
27567 &<<SECTexpansionitems>>&.
27569 As an example, suppose the secret per-address keys are stored in an MySQL
27570 database. A query to look up the key for an address could be defined as a macro
27573 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
27574 WHERE sender='${quote_mysql:$prvscheck_address}'\
27577 Suppose also that the senders who make use of BATV are defined by an address
27578 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
27581 # Bounces: drop unsigned addresses for BATV senders
27582 deny message = This address does not send an unsigned reverse path
27584 recipients = +batv_senders
27586 # Bounces: In case of prvs-signed address, check signature.
27587 deny message = Invalid reverse path signature.
27589 condition = ${prvscheck {$local_part@$domain}\
27590 {PRVSCHECK_SQL}{1}}
27591 !condition = $prvscheck_result
27593 The first statement rejects recipients for bounce messages that are addressed
27594 to plain BATV sender addresses, because it is known that BATV senders do not
27595 send out messages with plain sender addresses. The second statement rejects
27596 recipients that are prvs-signed, but with invalid signatures (either because
27597 the key is wrong, or the signature has timed out).
27599 A non-prvs-signed address is not rejected by the second statement, because the
27600 &%prvscheck%& expansion yields an empty string if its first argument is not a
27601 prvs-signed address, thus causing the &%condition%& condition to be false. If
27602 the first argument is a syntactically valid prvs-signed address, the yield is
27603 the third string (in this case &"1"&), whether or not the cryptographic and
27604 timeout checks succeed. The &$prvscheck_result$& variable contains the result
27605 of the checks (empty for failure, &"1"& for success).
27607 There is one more issue you must consider when implementing prvs-signing:
27608 you have to ensure that the routers accept prvs-signed addresses and
27609 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
27610 router to remove the signature with a configuration along these lines:
27614 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
27616 This works because, if the third argument of &%prvscheck%& is empty, the result
27617 of the expansion of a prvs-signed address is the decoded value of the original
27618 address. This router should probably be the first of your routers that handles
27621 To create BATV-signed addresses in the first place, a transport of this form
27624 external_smtp_batv:
27626 return_path = ${prvs {$return_path} \
27627 {${lookup mysql{SELECT \
27628 secret FROM batv_prvs WHERE \
27629 sender='${quote_mysql:$sender_address}'} \
27632 If no key can be found for the existing return path, no signing takes place.
27636 .section "Using an ACL to control relaying" "SECTrelaycontrol"
27637 .cindex "&ACL;" "relay control"
27638 .cindex "relaying" "control by ACL"
27639 .cindex "policy control" "relay control"
27640 An MTA is said to &'relay'& a message if it receives it from some host and
27641 delivers it directly to another host as a result of a remote address contained
27642 within it. Redirecting a local address via an alias or forward file and then
27643 passing the message on to another host is not relaying,
27644 .cindex "&""percent hack""&"
27645 but a redirection as a result of the &"percent hack"& is.
27647 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
27648 A host which is acting as a gateway or an MX backup is concerned with incoming
27649 relaying from arbitrary hosts to a specific set of domains. On the other hand,
27650 a host which is acting as a smart host for a number of clients is concerned
27651 with outgoing relaying from those clients to the Internet at large. Often the
27652 same host is fulfilling both functions,
27654 . as illustrated in the diagram below,
27656 but in principle these two kinds of relaying are entirely independent. What is
27657 not wanted is the transmission of mail from arbitrary remote hosts through your
27658 system to arbitrary domains.
27661 You can implement relay control by means of suitable statements in the ACL that
27662 runs for each RCPT command. For convenience, it is often easiest to use
27663 Exim's named list facility to define the domains and hosts involved. For
27664 example, suppose you want to do the following:
27667 Deliver a number of domains to mailboxes on the local host (or process them
27668 locally in some other way). Let's say these are &'my.dom1.example'& and
27669 &'my.dom2.example'&.
27671 Relay mail for a number of other domains for which you are the secondary MX.
27672 These might be &'friend1.example'& and &'friend2.example'&.
27674 Relay mail from the hosts on your local LAN, to whatever domains are involved.
27675 Suppose your LAN is 192.168.45.0/24.
27679 In the main part of the configuration, you put the following definitions:
27681 domainlist local_domains = my.dom1.example : my.dom2.example
27682 domainlist relay_domains = friend1.example : friend2.example
27683 hostlist relay_hosts = 192.168.45.0/24
27685 Now you can use these definitions in the ACL that is run for every RCPT
27689 accept domains = +local_domains : +relay_domains
27690 accept hosts = +relay_hosts
27692 The first statement accepts any RCPT command that contains an address in
27693 the local or relay domains. For any other domain, control passes to the second
27694 statement, which accepts the command only if it comes from one of the relay
27695 hosts. In practice, you will probably want to make your ACL more sophisticated
27696 than this, for example, by including sender and recipient verification. The
27697 default configuration includes a more comprehensive example, which is described
27698 in chapter &<<CHAPdefconfil>>&.
27702 .section "Checking a relay configuration" "SECTcheralcon"
27703 .cindex "relaying" "checking control of"
27704 You can check the relay characteristics of your configuration in the same way
27705 that you can test any ACL behaviour for an incoming SMTP connection, by using
27706 the &%-bh%& option to run a fake SMTP session with which you interact.
27708 For specifically testing for unwanted relaying, the host
27709 &'relay-test.mail-abuse.org'& provides a useful service. If you telnet to this
27710 host from the host on which Exim is running, using the normal telnet port, you
27711 will see a normal telnet connection message and then quite a long delay. Be
27712 patient. The remote host is making an SMTP connection back to your host, and
27713 trying a number of common probes to test for open relay vulnerability. The
27714 results of the tests will eventually appear on your terminal.
27719 . ////////////////////////////////////////////////////////////////////////////
27720 . ////////////////////////////////////////////////////////////////////////////
27722 .chapter "Content scanning at ACL time" "CHAPexiscan"
27723 .scindex IIDcosca "content scanning" "at ACL time"
27724 The extension of Exim to include content scanning at ACL time, formerly known
27725 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
27726 was integrated into the main source for Exim release 4.50, and Tom continues to
27727 maintain it. Most of the wording of this chapter is taken from Tom's
27730 It is also possible to scan the content of messages at other times. The
27731 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
27732 scanning after all the ACLs have run. A transport filter can be used to scan
27733 messages at delivery time (see the &%transport_filter%& option, described in
27734 chapter &<<CHAPtransportgeneric>>&).
27736 If you want to include the ACL-time content-scanning features when you compile
27737 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
27738 &_Local/Makefile_&. When you do that, the Exim binary is built with:
27741 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
27742 for all MIME parts for SMTP and non-SMTP messages, respectively.
27744 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
27745 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
27746 run at the end of message reception (the &%acl_smtp_data%& ACL).
27748 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
27749 of messages, or parts of messages, for debugging purposes.
27751 Additional expansion variables that are set in the new ACL and by the new
27754 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
27757 There is another content-scanning configuration option for &_Local/Makefile_&,
27758 called WITH_OLD_DEMIME. If this is set, the old, deprecated &%demime%& ACL
27759 condition is compiled, in addition to all the other content-scanning features.
27761 Content-scanning is continually evolving, and new features are still being
27762 added. While such features are still unstable and liable to incompatible
27763 changes, they are made available in Exim by setting options whose names begin
27764 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
27765 this manual. You can find out about them by reading the file called
27766 &_doc/experimental.txt_&.
27768 All the content-scanning facilities work on a MBOX copy of the message that is
27769 temporarily created in a file called:
27771 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
27773 The &_.eml_& extension is a friendly hint to virus scanners that they can
27774 expect an MBOX-like structure inside that file. The file is created when the
27775 first content scanning facility is called. Subsequent calls to content
27776 scanning conditions open the same file again. The directory is recursively
27777 removed when the &%acl_smtp_data%& ACL has finished running, unless
27779 control = no_mbox_unspool
27781 has been encountered. When the MIME ACL decodes files, they are put into the
27782 same directory by default.
27786 .section "Scanning for viruses" "SECTscanvirus"
27787 .cindex "virus scanning"
27788 .cindex "content scanning" "for viruses"
27789 .cindex "content scanning" "the &%malware%& condition"
27790 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
27791 It supports a &"generic"& interface to scanners called via the shell, and
27792 specialized interfaces for &"daemon"& type virus scanners, which are resident
27793 in memory and thus are much faster.
27795 .oindex "&%av_scanner%&"
27796 You can set the &%av_scanner%& option in first part of the Exim configuration
27797 file to specify which scanner to use, together with any additional options that
27798 are needed. The basic syntax is as follows:
27800 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
27802 If you do not set &%av_scanner%&, it defaults to
27804 av_scanner = sophie:/var/run/sophie
27806 If the value of &%av_scanner%& starts with dollar character, it is expanded
27807 before use. The following scanner types are supported in this release:
27810 .vitem &%aveserver%&
27811 .cindex "virus scanners" "Kaspersky"
27812 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
27813 at &url(http://www.kaspersky.com). This scanner type takes one option,
27814 which is the path to the daemon's UNIX socket. The default is shown in this
27817 av_scanner = aveserver:/var/run/aveserver
27821 .cindex "virus scanners" "clamd"
27822 This daemon-type scanner is GPL and free. You can get it at
27823 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
27824 unpack MIME containers, so it used to be recommended to unpack MIME attachments
27825 in the MIME ACL. This no longer believed to be necessary. One option is
27826 required: either the path and name of a UNIX socket file, or a hostname or IP
27827 number, and a port, separated by space, as in the second of these examples:
27829 av_scanner = clamd:/opt/clamd/socket
27830 av_scanner = clamd:192.168.2.100 1234
27832 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
27833 contributing the code for this scanner.
27836 .cindex "virus scanners" "command line interface"
27837 This is the keyword for the generic command line scanner interface. It can be
27838 used to attach virus scanners that are invoked from the shell. This scanner
27839 type takes 3 mandatory options:
27842 The full path and name of the scanner binary, with all command line options,
27843 and a placeholder (&`%s`&) for the directory to scan.
27846 A regular expression to match against the STDOUT and STDERR output of the
27847 virus scanner. If the expression matches, a virus was found. You must make
27848 absolutely sure that this expression matches on &"virus found"&. This is called
27849 the &"trigger"& expression.
27852 Another regular expression, containing exactly one pair of parentheses, to
27853 match the name of the virus found in the scanners output. This is called the
27854 &"name"& expression.
27857 For example, Sophos Sweep reports a virus on a line like this:
27859 Virus 'W32/Magistr-B' found in file ./those.bat
27861 For the trigger expression, we can match the phrase &"found in file"&. For the
27862 name expression, we want to extract the W32/Magistr-B string, so we can match
27863 for the single quotes left and right of it. Altogether, this makes the
27864 configuration setting:
27866 av_scanner = cmdline:\
27867 /path/to/sweep -ss -all -rec -archive %s:\
27868 found in file:'(.+)'
27871 .cindex "virus scanners" "DrWeb"
27872 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface takes one
27873 argument, either a full path to a UNIX socket, or an IP address and port
27874 separated by white space, as in these examples:
27876 av_scanner = drweb:/var/run/drwebd.sock
27877 av_scanner = drweb:192.168.2.20 31337
27879 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
27880 is used. Thanks to Alex Miller for contributing the code for this scanner.
27883 .cindex "virus scanners" "F-Secure"
27884 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
27885 argument which is the path to a UNIX socket. For example:
27887 av_scanner = fsecure:/path/to/.fsav
27889 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
27890 Thelmen for contributing the code for this scanner.
27892 .vitem &%kavdaemon%&
27893 .cindex "virus scanners" "Kaspersky"
27894 This is the scanner daemon of Kaspersky Version 4. This version of the
27895 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
27896 scanner type takes one option, which is the path to the daemon's UNIX socket.
27899 av_scanner = kavdaemon:/opt/AVP/AvpCtl
27901 The default path is &_/var/run/AvpCtl_&.
27904 .cindex "virus scanners" "mksd"
27905 This is a daemon type scanner that is aimed mainly at Polish users, though some
27906 parts of documentation are now available in English. You can get it at
27907 &url(http://linux.mks.com.pl/). The only option for this scanner type is
27908 the maximum number of processes used simultaneously to scan the attachments,
27909 provided that the demime facility is employed and also provided that mksd has
27910 been run with at least the same number of child processes. For example:
27912 av_scanner = mksd:2
27914 You can safely omit this option (the default value is 1).
27917 .cindex "virus scanners" "Sophos and Sophie"
27918 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
27919 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
27920 for this scanner type is the path to the UNIX socket that Sophie uses for
27921 client communication. For example:
27923 av_scanner = sophie:/tmp/sophie
27925 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
27929 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
27930 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
27933 The &%av_scanner%& option is expanded each time &%malware%& is called. This
27934 makes it possible to use different scanners. See further below for an example.
27935 The &%malware%& condition caches its results, so when you use it multiple times
27936 for the same message, the actual scanning process is only carried out once.
27937 However, using expandable items in &%av_scanner%& disables this caching, in
27938 which case each use of the &%malware%& condition causes a new scan of the
27941 The &%malware%& condition takes a right-hand argument that is expanded before
27942 use. It can then be one of
27945 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
27946 The condition succeeds if a virus was found, and fail otherwise. This is the
27949 &"false"& or &"0"& or an empty string, in which case no scanning is done and
27950 the condition fails immediately.
27952 A regular expression, in which case the message is scanned for viruses. The
27953 condition succeeds if a virus is found and its name matches the regular
27954 expression. This allows you to take special actions on certain types of virus.
27957 You can append &`/defer_ok`& to the &%malware%& condition to accept messages
27958 even if there is a problem with the virus scanner. Otherwise, such a problem
27959 causes the ACL to defer.
27961 .vindex "&$malware_name$&"
27962 When a virus is found, the condition sets up an expansion variable called
27963 &$malware_name$& that contains the name of the virus. You can use it in a
27964 &%message%& modifier that specifies the error returned to the sender, and/or in
27967 If your virus scanner cannot unpack MIME and TNEF containers itself, you should
27968 use the &%demime%& condition (see section &<<SECTdemimecond>>&) before the
27969 &%malware%& condition.
27971 Here is a very simple scanning example:
27973 deny message = This message contains malware ($malware_name)
27977 The next example accepts messages when there is a problem with the scanner:
27979 deny message = This message contains malware ($malware_name)
27981 malware = */defer_ok
27983 The next example shows how to use an ACL variable to scan with both sophie and
27984 aveserver. It assumes you have set:
27986 av_scanner = $acl_m0
27988 in the main Exim configuration.
27990 deny message = This message contains malware ($malware_name)
27991 set acl_m0 = sophie
27994 deny message = This message contains malware ($malware_name)
27995 set acl_m0 = aveserver
28000 .section "Scanning with SpamAssassin" "SECTscanspamass"
28001 .cindex "content scanning" "for spam"
28002 .cindex "spam scanning"
28003 .cindex "SpamAssassin"
28004 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
28005 score and a report for the message. You can get SpamAssassin at
28006 &url(http://www.spamassassin.org), or, if you have a working Perl
28007 installation, you can use CPAN by running:
28009 perl -MCPAN -e 'install Mail::SpamAssassin'
28011 SpamAssassin has its own set of configuration files. Please review its
28012 documentation to see how you can tweak it. The default installation should work
28015 .oindex "&%spamd_address%&"
28016 After having installed and configured SpamAssassin, start the &%spamd%& daemon.
28017 By default, it listens on 127.0.0.1, TCP port 783. If you use another host or
28018 port for &%spamd%&, you must set the &%spamd_address%& option in the global
28019 part of the Exim configuration as follows (example):
28021 spamd_address = 192.168.99.45 387
28023 You do not need to set this option if you use the default. As of version 2.60,
28024 &%spamd%& also supports communication over UNIX sockets. If you want to use
28025 these, supply &%spamd_address%& with an absolute file name instead of a
28028 spamd_address = /var/run/spamd_socket
28030 You can have multiple &%spamd%& servers to improve scalability. These can
28031 reside on other hardware reachable over the network. To specify multiple
28032 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
28033 option, separated with colons:
28035 spamd_address = 192.168.2.10 783 : \
28036 192.168.2.11 783 : \
28039 Up to 32 &%spamd%& servers are supported. The servers are queried in a random
28040 fashion. When a server fails to respond to the connection attempt, all other
28041 servers are tried until one succeeds. If no server responds, the &%spam%&
28044 &*Warning*&: It is not possible to use the UNIX socket connection method with
28045 multiple &%spamd%& servers.
28047 The &%spamd_address%& variable is expanded before use if it starts with
28048 a dollar sign. In this case, the expansion may return a string that is
28049 used as the list so that multiple spamd servers can be the result of an
28052 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
28053 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
28055 deny message = This message was classified as SPAM
28058 The right-hand side of the &%spam%& condition specifies a name. This is
28059 relevant if you have set up multiple SpamAssassin profiles. If you do not want
28060 to scan using a specific profile, but rather use the SpamAssassin system-wide
28061 default profile, you can scan for an unknown name, or simply use &"nobody"&.
28062 However, you must put something on the right-hand side.
28064 The name allows you to use per-domain or per-user antispam profiles in
28065 principle, but this is not straightforward in practice, because a message may
28066 have multiple recipients, not necessarily all in the same domain. Because the
28067 &%spam%& condition has to be called from a DATA ACL in order to be able to
28068 read the contents of the message, the variables &$local_part$& and &$domain$&
28071 The right-hand side of the &%spam%& condition is expanded before being used, so
28072 you can put lookups or conditions there. When the right-hand side evaluates to
28073 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
28076 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
28077 large ones may cause significant performance degradation. As most spam messages
28078 are quite small, it is recommended that you do not scan the big ones. For
28081 deny message = This message was classified as SPAM
28082 condition = ${if < {$message_size}{10K}}
28086 The &%spam%& condition returns true if the threshold specified in the user's
28087 SpamAssassin profile has been matched or exceeded. If you want to use the
28088 &%spam%& condition for its side effects (see the variables below), you can make
28089 it always return &"true"& by appending &`:true`& to the username.
28091 .cindex "spam scanning" "returned variables"
28092 When the &%spam%& condition is run, it sets up a number of expansion
28093 variables. With the exception of &$spam_score_int$&, these are usable only
28094 within ACLs; their values are not retained with the message and so cannot be
28095 used at delivery time.
28098 .vitem &$spam_score$&
28099 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
28100 for inclusion in log or reject messages.
28102 .vitem &$spam_score_int$&
28103 The spam score of the message, multiplied by ten, as an integer value. For
28104 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
28105 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
28106 The integer value is useful for numeric comparisons in
28107 conditions. This variable is special; its value is saved with the message, and
28108 written to Exim's spool file. This means that it can be used during the whole
28109 life of the message on your Exim system, in particular, in routers or
28110 transports during the later delivery phase.
28112 .vitem &$spam_bar$&
28113 A string consisting of a number of &"+"& or &"-"& characters, representing the
28114 integer part of the spam score value. A spam score of 4.4 would have a
28115 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
28116 headers, since MUAs can match on such strings.
28118 .vitem &$spam_report$&
28119 A multiline text table, containing the full SpamAssassin report for the
28120 message. Useful for inclusion in headers or reject messages.
28123 The &%spam%& condition caches its results unless expansion in
28124 spamd_address was used. If you call it again with the same user name, it
28125 does not scan again, but rather returns the same values as before.
28127 The &%spam%& condition returns DEFER if there is any error while running
28128 the message through SpamAssassin or if the expansion of spamd_address
28129 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
28130 statement block), append &`/defer_ok`& to the right-hand side of the
28131 spam condition, like this:
28133 deny message = This message was classified as SPAM
28134 spam = joe/defer_ok
28136 This causes messages to be accepted even if there is a problem with &%spamd%&.
28138 Here is a longer, commented example of the use of the &%spam%&
28141 # put headers in all messages (no matter if spam or not)
28142 warn spam = nobody:true
28143 add_header = X-Spam-Score: $spam_score ($spam_bar)
28144 add_header = X-Spam-Report: $spam_report
28146 # add second subject line with *SPAM* marker when message
28147 # is over threshold
28149 add_header = Subject: *SPAM* $h_Subject:
28151 # reject spam at high scores (> 12)
28152 deny message = This message scored $spam_score spam points.
28154 condition = ${if >{$spam_score_int}{120}{1}{0}}
28159 .section "Scanning MIME parts" "SECTscanmimepart"
28160 .cindex "content scanning" "MIME parts"
28161 .cindex "MIME content scanning"
28162 .oindex "&%acl_smtp_mime%&"
28163 .oindex "&%acl_not_smtp_mime%&"
28164 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
28165 each MIME part of an SMTP message, including multipart types, in the sequence
28166 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
28167 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
28168 options may both refer to the same ACL if you want the same processing in both
28171 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
28172 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
28173 the case of a non-SMTP message. However, a MIME ACL is called only if the
28174 message contains a &'Content-Type:'& header line. When a call to a MIME
28175 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
28176 result code is sent to the client. In the case of an SMTP message, the
28177 &%acl_smtp_data%& ACL is not called when this happens.
28179 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
28180 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
28181 condition to match against the raw MIME part. You can also use the
28182 &%mime_regex%& condition to match against the decoded MIME part (see section
28183 &<<SECTscanregex>>&).
28185 At the start of a MIME ACL, a number of variables are set from the header
28186 information for the relevant MIME part. These are described below. The contents
28187 of the MIME part are not by default decoded into a disk file except for MIME
28188 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
28189 part into a disk file, you can use the &%decode%& condition. The general
28192 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
28194 The right hand side is expanded before use. After expansion,
28198 &"0"& or &"false"&, in which case no decoding is done.
28200 The string &"default"&. In that case, the file is put in the temporary
28201 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
28202 a sequential file name consisting of the message id and a sequence number. The
28203 full path and name is available in &$mime_decoded_filename$& after decoding.
28205 A full path name starting with a slash. If the full name is an existing
28206 directory, it is used as a replacement for the default directory. The filename
28207 is then sequentially assigned. If the path does not exist, it is used as
28208 the full path and file name.
28210 If the string does not start with a slash, it is used as the
28211 filename, and the default path is then used.
28213 The &%decode%& condition normally succeeds. It is only false for syntax
28214 errors or unusual circumstances such as memory shortages. You can easily decode
28215 a file with its original, proposed filename using
28217 decode = $mime_filename
28219 However, you should keep in mind that &$mime_filename$& might contain
28220 anything. If you place files outside of the default path, they are not
28221 automatically unlinked.
28223 For RFC822 attachments (these are messages attached to messages, with a
28224 content-type of &"message/rfc822"&), the ACL is called again in the same manner
28225 as for the primary message, only that the &$mime_is_rfc822$& expansion
28226 variable is set (see below). Attached messages are always decoded to disk
28227 before being checked, and the files are unlinked once the check is done.
28229 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
28230 used to match regular expressions against raw and decoded MIME parts,
28231 respectively. They are described in section &<<SECTscanregex>>&.
28233 .cindex "MIME content scanning" "returned variables"
28234 The following list describes all expansion variables that are
28235 available in the MIME ACL:
28238 .vitem &$mime_boundary$&
28239 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
28240 have a boundary string, which is stored in this variable. If the current part
28241 has no boundary parameter in the &'Content-Type:'& header, this variable
28242 contains the empty string.
28244 .vitem &$mime_charset$&
28245 This variable contains the character set identifier, if one was found in the
28246 &'Content-Type:'& header. Examples for charset identifiers are:
28252 Please note that this value is not normalized, so you should do matches
28253 case-insensitively.
28255 .vitem &$mime_content_description$&
28256 This variable contains the normalized content of the &'Content-Description:'&
28257 header. It can contain a human-readable description of the parts content. Some
28258 implementations repeat the filename for attachments here, but they are usually
28259 only used for display purposes.
28261 .vitem &$mime_content_disposition$&
28262 This variable contains the normalized content of the &'Content-Disposition:'&
28263 header. You can expect strings like &"attachment"& or &"inline"& here.
28265 .vitem &$mime_content_id$&
28266 This variable contains the normalized content of the &'Content-ID:'& header.
28267 This is a unique ID that can be used to reference a part from another part.
28269 .vitem &$mime_content_size$&
28270 This variable is set only after the &%decode%& modifier (see above) has been
28271 successfully run. It contains the size of the decoded part in kilobytes. The
28272 size is always rounded up to full kilobytes, so only a completely empty part
28273 has a &$mime_content_size$& of zero.
28275 .vitem &$mime_content_transfer_encoding$&
28276 This variable contains the normalized content of the
28277 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
28278 type. Typical values are &"base64"& and &"quoted-printable"&.
28280 .vitem &$mime_content_type$&
28281 If the MIME part has a &'Content-Type:'& header, this variable contains its
28282 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
28283 are some examples of popular MIME types, as they may appear in this variable:
28287 application/octet-stream
28291 If the MIME part has no &'Content-Type:'& header, this variable contains the
28294 .vitem &$mime_decoded_filename$&
28295 This variable is set only after the &%decode%& modifier (see above) has been
28296 successfully run. It contains the full path and file name of the file
28297 containing the decoded data.
28302 .vitem &$mime_filename$&
28303 This is perhaps the most important of the MIME variables. It contains a
28304 proposed filename for an attachment, if one was found in either the
28305 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
28306 RFC2047 decoded, but no additional sanity checks are done. If no filename was
28307 found, this variable contains the empty string.
28309 .vitem &$mime_is_coverletter$&
28310 This variable attempts to differentiate the &"cover letter"& of an e-mail from
28311 attached data. It can be used to clamp down on flashy or unnecessarily encoded
28312 content in the cover letter, while not restricting attachments at all.
28314 The variable contains 1 (true) for a MIME part believed to be part of the
28315 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
28319 The outermost MIME part of a message is always a cover letter.
28322 If a multipart/alternative or multipart/related MIME part is a cover letter,
28323 so are all MIME subparts within that multipart.
28326 If any other multipart is a cover letter, the first subpart is a cover letter,
28327 and the rest are attachments.
28330 All parts contained within an attachment multipart are attachments.
28333 As an example, the following will ban &"HTML mail"& (including that sent with
28334 alternative plain text), while allowing HTML files to be attached. HTML
28335 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
28337 deny message = HTML mail is not accepted here
28338 !condition = $mime_is_rfc822
28339 condition = $mime_is_coverletter
28340 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
28342 .vitem &$mime_is_multipart$&
28343 This variable has the value 1 (true) when the current part has the main type
28344 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
28345 Since multipart entities only serve as containers for other parts, you may not
28346 want to carry out specific actions on them.
28348 .vitem &$mime_is_rfc822$&
28349 This variable has the value 1 (true) if the current part is not a part of the
28350 checked message itself, but part of an attached message. Attached message
28351 decoding is fully recursive.
28353 .vitem &$mime_part_count$&
28354 This variable is a counter that is raised for each processed MIME part. It
28355 starts at zero for the very first part (which is usually a multipart). The
28356 counter is per-message, so it is reset when processing RFC822 attachments (see
28357 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
28358 complete, so you can use it in the DATA ACL to determine the number of MIME
28359 parts of a message. For non-MIME messages, this variable contains the value -1.
28364 .section "Scanning with regular expressions" "SECTscanregex"
28365 .cindex "content scanning" "with regular expressions"
28366 .cindex "regular expressions" "content scanning with"
28367 You can specify your own custom regular expression matches on the full body of
28368 the message, or on individual MIME parts.
28370 The &%regex%& condition takes one or more regular expressions as arguments and
28371 matches them against the full message (when called in the DATA ACL) or a raw
28372 MIME part (when called in the MIME ACL). The &%regex%& condition matches
28373 linewise, with a maximum line length of 32K characters. That means you cannot
28374 have multiline matches with the &%regex%& condition.
28376 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
28377 to 32K of decoded content (the whole content at once, not linewise). If the
28378 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
28379 is decoded automatically when &%mime_regex%& is executed (using default path
28380 and filename values). If the decoded data is larger than 32K, only the first
28381 32K characters are checked.
28383 The regular expressions are passed as a colon-separated list. To include a
28384 literal colon, you must double it. Since the whole right-hand side string is
28385 expanded before being used, you must also escape dollar signs and backslashes
28386 with more backslashes, or use the &`\N`& facility to disable expansion.
28387 Here is a simple example that contains two regular expressions:
28389 deny message = contains blacklisted regex ($regex_match_string)
28390 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
28392 The conditions returns true if any one of the regular expressions matches. The
28393 &$regex_match_string$& expansion variable is then set up and contains the
28394 matching regular expression.
28396 &*Warning*&: With large messages, these conditions can be fairly
28402 .section "The demime condition" "SECTdemimecond"
28403 .cindex "content scanning" "MIME checking"
28404 .cindex "MIME content scanning"
28405 The &%demime%& ACL condition provides MIME unpacking, sanity checking and file
28406 extension blocking. It is usable only in the DATA and non-SMTP ACLs. The
28407 &%demime%& condition uses a simpler interface to MIME decoding than the MIME
28408 ACL functionality, but provides no additional facilities. Please note that this
28409 condition is deprecated and kept only for backward compatibility. You must set
28410 the WITH_OLD_DEMIME option in &_Local/Makefile_& at build time to be able to
28411 use the &%demime%& condition.
28413 The &%demime%& condition unpacks MIME containers in the message. It detects
28414 errors in MIME containers and can match file extensions found in the message
28415 against a list. Using this facility produces files containing the unpacked MIME
28416 parts of the message in the temporary scan directory. If you do antivirus
28417 scanning, it is recommended that you use the &%demime%& condition before the
28418 antivirus (&%malware%&) condition.
28420 On the right-hand side of the &%demime%& condition you can pass a
28421 colon-separated list of file extensions that it should match against. For
28424 deny message = Found blacklisted file attachment
28425 demime = vbs:com:bat:pif:prf:lnk
28427 If one of the file extensions is found, the condition is true, otherwise it is
28428 false. If there is a temporary error while demimeing (for example, &"disk
28429 full"&), the condition defers, and the message is temporarily rejected (unless
28430 the condition is on a &%warn%& verb).
28432 The right-hand side is expanded before being treated as a list, so you can have
28433 conditions and lookups there. If it expands to an empty string, &"false"&, or
28434 zero (&"0"&), no demimeing is done and the condition is false.
28436 The &%demime%& condition set the following variables:
28439 .vitem &$demime_errorlevel$&
28440 .vindex "&$demime_errorlevel$&"
28441 When an error is detected in a MIME container, this variable contains the
28442 severity of the error, as an integer number. The higher the value, the more
28443 severe the error (the current maximum value is 3). If this variable is unset or
28444 zero, no error occurred.
28446 .vitem &$demime_reason$&
28447 .vindex "&$demime_reason$&"
28448 When &$demime_errorlevel$& is greater than zero, this variable contains a
28449 human-readable text string describing the MIME error that occurred.
28453 .vitem &$found_extension$&
28454 .vindex "&$found_extension$&"
28455 When the &%demime%& condition is true, this variable contains the file
28456 extension it found.
28459 Both &$demime_errorlevel$& and &$demime_reason$& are set by the first call of
28460 the &%demime%& condition, and are not changed on subsequent calls.
28462 If you do not want to check for file extensions, but rather use the &%demime%&
28463 condition for unpacking or error checking purposes, pass &"*"& as the
28464 right-hand side value. Here is a more elaborate example of how to use this
28467 # Reject messages with serious MIME container errors
28468 deny message = Found MIME error ($demime_reason).
28470 condition = ${if >{$demime_errorlevel}{2}{1}{0}}
28472 # Reject known virus spreading file extensions.
28473 # Accepting these is pretty much braindead.
28474 deny message = contains $found_extension file (blacklisted).
28475 demime = com:vbs:bat:pif:scr
28477 # Freeze .exe and .doc files. Postmaster can
28478 # examine them and eventually thaw them.
28479 deny log_message = Another $found_extension file.
28488 . ////////////////////////////////////////////////////////////////////////////
28489 . ////////////////////////////////////////////////////////////////////////////
28491 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
28492 "Local scan function"
28493 .scindex IIDlosca "&[local_scan()]& function" "description of"
28494 .cindex "customizing" "input scan using C function"
28495 .cindex "policy control" "by local scan function"
28496 In these days of email worms, viruses, and ever-increasing spam, some sites
28497 want to apply a lot of checking to messages before accepting them.
28499 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
28500 passing messages to external virus and spam scanning software. You can also do
28501 a certain amount in Exim itself through string expansions and the &%condition%&
28502 condition in the ACL that runs after the SMTP DATA command or the ACL for
28503 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
28505 To allow for further customization to a site's own requirements, there is the
28506 possibility of linking Exim with a private message scanning function, written
28507 in C. If you want to run code that is written in something other than C, you
28508 can of course use a little C stub to call it.
28510 The local scan function is run once for every incoming message, at the point
28511 when Exim is just about to accept the message.
28512 It can therefore be used to control non-SMTP messages from local processes as
28513 well as messages arriving via SMTP.
28515 Exim applies a timeout to calls of the local scan function, and there is an
28516 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
28517 Zero means &"no timeout"&.
28518 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
28519 before calling the local scan function, so that the most common types of crash
28520 are caught. If the timeout is exceeded or one of those signals is caught, the
28521 incoming message is rejected with a temporary error if it is an SMTP message.
28522 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
28523 code. The incident is logged on the main and reject logs.
28527 .section "Building Exim to use a local scan function" "SECID207"
28528 .cindex "&[local_scan()]& function" "building Exim to use"
28529 To make use of the local scan function feature, you must tell Exim where your
28530 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
28531 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
28532 directory, so you might set
28534 LOCAL_SCAN_SOURCE=Local/local_scan.c
28536 for example. The function must be called &[local_scan()]&. It is called by
28537 Exim after it has received a message, when the success return code is about to
28538 be sent. This is after all the ACLs have been run. The return code from your
28539 function controls whether the message is actually accepted or not. There is a
28540 commented template function (that just accepts the message) in the file
28541 _src/local_scan.c_.
28543 If you want to make use of Exim's run time configuration file to set options
28544 for your &[local_scan()]& function, you must also set
28546 LOCAL_SCAN_HAS_OPTIONS=yes
28548 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
28553 .section "API for local_scan()" "SECTapiforloc"
28554 .cindex "&[local_scan()]& function" "API description"
28555 You must include this line near the start of your code:
28557 #include "local_scan.h"
28559 This header file defines a number of variables and other values, and the
28560 prototype for the function itself. Exim is coded to use unsigned char values
28561 almost exclusively, and one of the things this header defines is a shorthand
28562 for &`unsigned char`& called &`uschar`&.
28563 It also contains the following macro definitions, to simplify casting character
28564 strings and pointers to character strings:
28566 #define CS (char *)
28567 #define CCS (const char *)
28568 #define CSS (char **)
28569 #define US (unsigned char *)
28570 #define CUS (const unsigned char *)
28571 #define USS (unsigned char **)
28573 The function prototype for &[local_scan()]& is:
28575 extern int local_scan(int fd, uschar **return_text);
28577 The arguments are as follows:
28580 &%fd%& is a file descriptor for the file that contains the body of the message
28581 (the -D file). The file is open for reading and writing, but updating it is not
28582 recommended. &*Warning*&: You must &'not'& close this file descriptor.
28584 The descriptor is positioned at character 19 of the file, which is the first
28585 character of the body itself, because the first 19 characters are the message
28586 id followed by &`-D`& and a newline. If you rewind the file, you should use the
28587 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
28588 case this changes in some future version.
28590 &%return_text%& is an address which you can use to return a pointer to a text
28591 string at the end of the function. The value it points to on entry is NULL.
28594 The function must return an &%int%& value which is one of the following macros:
28597 .vitem &`LOCAL_SCAN_ACCEPT`&
28598 .vindex "&$local_scan_data$&"
28599 The message is accepted. If you pass back a string of text, it is saved with
28600 the message, and made available in the variable &$local_scan_data$&. No
28601 newlines are permitted (if there are any, they are turned into spaces) and the
28602 maximum length of text is 1000 characters.
28604 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
28605 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
28606 queued without immediate delivery, and is frozen.
28608 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
28609 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
28610 queued without immediate delivery.
28612 .vitem &`LOCAL_SCAN_REJECT`&
28613 The message is rejected; the returned text is used as an error message which is
28614 passed back to the sender and which is also logged. Newlines are permitted &--
28615 they cause a multiline response for SMTP rejections, but are converted to
28616 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
28619 .vitem &`LOCAL_SCAN_TEMPREJECT`&
28620 The message is temporarily rejected; the returned text is used as an error
28621 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
28624 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
28625 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
28626 message is not written to the reject log. It has the effect of unsetting the
28627 &%rejected_header%& log selector for just this rejection. If
28628 &%rejected_header%& is already unset (see the discussion of the
28629 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
28630 same as LOCAL_SCAN_REJECT.
28632 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
28633 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
28634 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
28637 If the message is not being received by interactive SMTP, rejections are
28638 reported by writing to &%stderr%& or by sending an email, as configured by the
28639 &%-oe%& command line options.
28643 .section "Configuration options for local_scan()" "SECTconoptloc"
28644 .cindex "&[local_scan()]& function" "configuration options"
28645 It is possible to have option settings in the main configuration file
28646 that set values in static variables in the &[local_scan()]& module. If you
28647 want to do this, you must have the line
28649 LOCAL_SCAN_HAS_OPTIONS=yes
28651 in your &_Local/Makefile_& when you build Exim. (This line is in
28652 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
28653 file, you must define static variables to hold the option values, and a table
28656 The table must be a vector called &%local_scan_options%&, of type
28657 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
28658 and a pointer to the variable that holds the value. The entries must appear in
28659 alphabetical order. Following &%local_scan_options%& you must also define a
28660 variable called &%local_scan_options_count%& that contains the number of
28661 entries in the table. Here is a short example, showing two kinds of option:
28663 static int my_integer_option = 42;
28664 static uschar *my_string_option = US"a default string";
28666 optionlist local_scan_options[] = {
28667 { "my_integer", opt_int, &my_integer_option },
28668 { "my_string", opt_stringptr, &my_string_option }
28671 int local_scan_options_count =
28672 sizeof(local_scan_options)/sizeof(optionlist);
28674 The values of the variables can now be changed from Exim's runtime
28675 configuration file by including a local scan section as in this example:
28679 my_string = some string of text...
28681 The available types of option data are as follows:
28684 .vitem &*opt_bool*&
28685 This specifies a boolean (true/false) option. The address should point to a
28686 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
28687 that are defined as &"1"& and &"0"&, respectively. If you want to detect
28688 whether such a variable has been set at all, you can initialize it to
28689 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
28692 .vitem &*opt_fixed*&
28693 This specifies a fixed point number, such as is used for load averages.
28694 The address should point to a variable of type &`int`&. The value is stored
28695 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
28698 This specifies an integer; the address should point to a variable of type
28699 &`int`&. The value may be specified in any of the integer formats accepted by
28702 .vitem &*opt_mkint*&
28703 This is the same as &%opt_int%&, except that when such a value is output in a
28704 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
28705 printed with the suffix K or M.
28707 .vitem &*opt_octint*&
28708 This also specifies an integer, but the value is always interpreted as an
28709 octal integer, whether or not it starts with the digit zero, and it is
28710 always output in octal.
28712 .vitem &*opt_stringptr*&
28713 This specifies a string value; the address must be a pointer to a
28714 variable that points to a string (for example, of type &`uschar *`&).
28716 .vitem &*opt_time*&
28717 This specifies a time interval value. The address must point to a variable of
28718 type &`int`&. The value that is placed there is a number of seconds.
28721 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
28722 out the values of all the &[local_scan()]& options.
28726 .section "Available Exim variables" "SECID208"
28727 .cindex "&[local_scan()]& function" "available Exim variables"
28728 The header &_local_scan.h_& gives you access to a number of C variables. These
28729 are the only ones that are guaranteed to be maintained from release to release.
28730 Note, however, that you can obtain the value of any Exim expansion variable,
28731 including &$recipients$&, by calling &'expand_string()'&. The exported
28732 C variables are as follows:
28735 .vitem &*int&~body_linecount*&
28736 This variable contains the number of lines in the message's body.
28738 .vitem &*int&~body_zerocount*&
28739 This variable contains the number of binary zero bytes in the message's body.
28741 .vitem &*unsigned&~int&~debug_selector*&
28742 This variable is set to zero when no debugging is taking place. Otherwise, it
28743 is a bitmap of debugging selectors. Two bits are identified for use in
28744 &[local_scan()]&; they are defined as macros:
28747 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
28748 testing option that is not privileged &-- any caller may set it. All the
28749 other selector bits can be set only by admin users.
28752 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
28753 by the &`+local_scan`& debug selector. It is not included in the default set
28757 Thus, to write to the debugging output only when &`+local_scan`& has been
28758 selected, you should use code like this:
28760 if ((debug_selector & D_local_scan) != 0)
28761 debug_printf("xxx", ...);
28763 .vitem &*uschar&~*expand_string_message*&
28764 After a failing call to &'expand_string()'& (returned value NULL), the
28765 variable &%expand_string_message%& contains the error message, zero-terminated.
28767 .vitem &*header_line&~*header_list*&
28768 A pointer to a chain of header lines. The &%header_line%& structure is
28771 .vitem &*header_line&~*header_last*&
28772 A pointer to the last of the header lines.
28774 .vitem &*uschar&~*headers_charset*&
28775 The value of the &%headers_charset%& configuration option.
28777 .vitem &*BOOL&~host_checking*&
28778 This variable is TRUE during a host checking session that is initiated by the
28779 &%-bh%& command line option.
28781 .vitem &*uschar&~*interface_address*&
28782 The IP address of the interface that received the message, as a string. This
28783 is NULL for locally submitted messages.
28785 .vitem &*int&~interface_port*&
28786 The port on which this message was received. When testing with the &%-bh%&
28787 command line option, the value of this variable is -1 unless a port has been
28788 specified via the &%-oMi%& option.
28790 .vitem &*uschar&~*message_id*&
28791 This variable contains Exim's message id for the incoming message (the value of
28792 &$message_exim_id$&) as a zero-terminated string.
28794 .vitem &*uschar&~*received_protocol*&
28795 The name of the protocol by which the message was received.
28797 .vitem &*int&~recipients_count*&
28798 The number of accepted recipients.
28800 .vitem &*recipient_item&~*recipients_list*&
28801 .cindex "recipient" "adding in local scan"
28802 .cindex "recipient" "removing in local scan"
28803 The list of accepted recipients, held in a vector of length
28804 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
28805 can add additional recipients by calling &'receive_add_recipient()'& (see
28806 below). You can delete recipients by removing them from the vector and
28807 adjusting the value in &%recipients_count%&. In particular, by setting
28808 &%recipients_count%& to zero you remove all recipients. If you then return the
28809 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
28810 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
28811 and then call &'receive_add_recipient()'& as often as needed.
28813 .vitem &*uschar&~*sender_address*&
28814 The envelope sender address. For bounce messages this is the empty string.
28816 .vitem &*uschar&~*sender_host_address*&
28817 The IP address of the sending host, as a string. This is NULL for
28818 locally-submitted messages.
28820 .vitem &*uschar&~*sender_host_authenticated*&
28821 The name of the authentication mechanism that was used, or NULL if the message
28822 was not received over an authenticated SMTP connection.
28824 .vitem &*uschar&~*sender_host_name*&
28825 The name of the sending host, if known.
28827 .vitem &*int&~sender_host_port*&
28828 The port on the sending host.
28830 .vitem &*BOOL&~smtp_input*&
28831 This variable is TRUE for all SMTP input, including BSMTP.
28833 .vitem &*BOOL&~smtp_batched_input*&
28834 This variable is TRUE for BSMTP input.
28836 .vitem &*int&~store_pool*&
28837 The contents of this variable control which pool of memory is used for new
28838 requests. See section &<<SECTmemhanloc>>& for details.
28842 .section "Structure of header lines" "SECID209"
28843 The &%header_line%& structure contains the members listed below.
28844 You can add additional header lines by calling the &'header_add()'& function
28845 (see below). You can cause header lines to be ignored (deleted) by setting
28850 .vitem &*struct&~header_line&~*next*&
28851 A pointer to the next header line, or NULL for the last line.
28853 .vitem &*int&~type*&
28854 A code identifying certain headers that Exim recognizes. The codes are printing
28855 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
28856 Notice in particular that any header line whose type is * is not transmitted
28857 with the message. This flagging is used for header lines that have been
28858 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
28859 lines.) Effectively, * means &"deleted"&.
28861 .vitem &*int&~slen*&
28862 The number of characters in the header line, including the terminating and any
28865 .vitem &*uschar&~*text*&
28866 A pointer to the text of the header. It always ends with a newline, followed by
28867 a zero byte. Internal newlines are preserved.
28872 .section "Structure of recipient items" "SECID210"
28873 The &%recipient_item%& structure contains these members:
28876 .vitem &*uschar&~*address*&
28877 This is a pointer to the recipient address as it was received.
28879 .vitem &*int&~pno*&
28880 This is used in later Exim processing when top level addresses are created by
28881 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
28882 and must always contain -1 at this stage.
28884 .vitem &*uschar&~*errors_to*&
28885 If this value is not NULL, bounce messages caused by failing to deliver to the
28886 recipient are sent to the address it contains. In other words, it overrides the
28887 envelope sender for this one recipient. (Compare the &%errors_to%& generic
28888 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
28889 an unqualified address, Exim qualifies it using the domain from
28890 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
28891 is NULL for all recipients.
28896 .section "Available Exim functions" "SECID211"
28897 .cindex "&[local_scan()]& function" "available Exim functions"
28898 The header &_local_scan.h_& gives you access to a number of Exim functions.
28899 These are the only ones that are guaranteed to be maintained from release to
28903 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
28904 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
28906 This function creates a child process that runs the command specified by
28907 &%argv%&. The environment for the process is specified by &%envp%&, which can
28908 be NULL if no environment variables are to be passed. A new umask is supplied
28909 for the process in &%newumask%&.
28911 Pipes to the standard input and output of the new process are set up
28912 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
28913 standard error is cloned to the standard output. If there are any file
28914 descriptors &"in the way"& in the new process, they are closed. If the final
28915 argument is TRUE, the new process is made into a process group leader.
28917 The function returns the pid of the new process, or -1 if things go wrong.
28919 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
28920 This function waits for a child process to terminate, or for a timeout (in
28921 seconds) to expire. A timeout value of zero means wait as long as it takes. The
28922 return value is as follows:
28927 The process terminated by a normal exit and the value is the process
28933 The process was terminated by a signal and the value is the negation of the
28939 The process timed out.
28943 The was some other error in wait(); &%errno%& is still set.
28946 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
28947 This function provide you with a means of submitting a new message to
28948 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
28949 want, but this packages it all up for you.) The function creates a pipe,
28950 forks a subprocess that is running
28952 exim -t -oem -oi -f <>
28954 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
28955 that is connected to the standard input. The yield of the function is the PID
28956 of the subprocess. You can then write a message to the file descriptor, with
28957 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
28959 When you have finished, call &'child_close()'& to wait for the process to
28960 finish and to collect its ending status. A timeout value of zero is usually
28961 fine in this circumstance. Unless you have made a mistake with the recipient
28962 addresses, you should get a return code of zero.
28965 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
28966 *sender_authentication)*&
28967 This function is a more sophisticated version of &'child_open()'&. The command
28970 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
28972 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
28975 .vitem &*void&~debug_printf(char&~*,&~...)*&
28976 This is Exim's debugging function, with arguments as for &'(printf()'&. The
28977 output is written to the standard error stream. If no debugging is selected,
28978 calls to &'debug_printf()'& have no effect. Normally, you should make calls
28979 conditional on the &`local_scan`& debug selector by coding like this:
28981 if ((debug_selector & D_local_scan) != 0)
28982 debug_printf("xxx", ...);
28985 .vitem &*uschar&~*expand_string(uschar&~*string)*&
28986 This is an interface to Exim's string expansion code. The return value is the
28987 expanded string, or NULL if there was an expansion failure.
28988 The C variable &%expand_string_message%& contains an error message after an
28989 expansion failure. If expansion does not change the string, the return value is
28990 the pointer to the input string. Otherwise, the return value points to a new
28991 block of memory that was obtained by a call to &'store_get()'&. See section
28992 &<<SECTmemhanloc>>& below for a discussion of memory handling.
28994 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
28995 This function allows you to an add additional header line at the end of the
28996 existing ones. The first argument is the type, and should normally be a space
28997 character. The second argument is a format string and any number of
28998 substitution arguments as for &[sprintf()]&. You may include internal newlines
28999 if you want, and you must ensure that the string ends with a newline.
29001 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
29002 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
29003 This function adds a new header line at a specified point in the header
29004 chain. The header itself is specified as for &'header_add()'&.
29006 If &%name%& is NULL, the new header is added at the end of the chain if
29007 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
29008 NULL, the header lines are searched for the first non-deleted header that
29009 matches the name. If one is found, the new header is added before it if
29010 &%after%& is false. If &%after%& is true, the new header is added after the
29011 found header and any adjacent subsequent ones with the same name (even if
29012 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
29013 option controls where the header is added. If it is true, addition is at the
29014 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
29015 headers, or at the top if there are no &'Received:'& headers, you could use
29017 header_add_at_position(TRUE, US"Received", TRUE,
29018 ' ', "X-xxx: ...");
29020 Normally, there is always at least one non-deleted &'Received:'& header, but
29021 there may not be if &%received_header_text%& expands to an empty string.
29024 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
29025 This function removes header lines. If &%occurrence%& is zero or negative, all
29026 occurrences of the header are removed. If occurrence is greater than zero, that
29027 particular instance of the header is removed. If no header(s) can be found that
29028 match the specification, the function does nothing.
29031 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
29032 int&~length,&~BOOL&~notdel)*&"
29033 This function tests whether the given header has the given name. It is not just
29034 a string comparison, because white space is permitted between the name and the
29035 colon. If the &%notdel%& argument is true, a false return is forced for all
29036 &"deleted"& headers; otherwise they are not treated specially. For example:
29038 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
29040 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
29041 .cindex "base64 encoding" "functions for &[local_scan()]& use"
29042 This function base64-encodes a string, which is passed by address and length.
29043 The text may contain bytes of any value, including zero. The result is passed
29044 back in dynamic memory that is obtained by calling &'store_get()'&. It is
29047 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
29048 This function decodes a base64-encoded string. Its arguments are a
29049 zero-terminated base64-encoded string and the address of a variable that is set
29050 to point to the result, which is in dynamic memory. The length of the decoded
29051 string is the yield of the function. If the input is invalid base64 data, the
29052 yield is -1. A zero byte is added to the end of the output string to make it
29053 easy to interpret as a C string (assuming it contains no zeros of its own). The
29054 added zero byte is not included in the returned count.
29056 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
29057 This function checks for a match in a domain list. Domains are always
29058 matched caselessly. The return value is one of the following:
29060 &`OK `& match succeeded
29061 &`FAIL `& match failed
29062 &`DEFER `& match deferred
29064 DEFER is usually caused by some kind of lookup defer, such as the
29065 inability to contact a database.
29067 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
29069 This function checks for a match in a local part list. The third argument
29070 controls case-sensitivity. The return values are as for
29071 &'lss_match_domain()'&.
29073 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
29075 This function checks for a match in an address list. The third argument
29076 controls the case-sensitivity of the local part match. The domain is always
29077 matched caselessly. The return values are as for &'lss_match_domain()'&.
29079 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
29081 This function checks for a match in a host list. The most common usage is
29084 lss_match_host(sender_host_name, sender_host_address, ...)
29086 .vindex "&$sender_host_address$&"
29087 An empty address field matches an empty item in the host list. If the host name
29088 is NULL, the name corresponding to &$sender_host_address$& is automatically
29089 looked up if a host name is required to match an item in the list. The return
29090 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
29091 returns ERROR in the case when it had to look up a host name, but the lookup
29094 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
29096 This function writes to Exim's log files. The first argument should be zero (it
29097 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
29098 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
29099 them. It specifies to which log or logs the message is written. The remaining
29100 arguments are a format and relevant insertion arguments. The string should not
29101 contain any newlines, not even at the end.
29104 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
29105 This function adds an additional recipient to the message. The first argument
29106 is the recipient address. If it is unqualified (has no domain), it is qualified
29107 with the &%qualify_recipient%& domain. The second argument must always be -1.
29109 This function does not allow you to specify a private &%errors_to%& address (as
29110 described with the structure of &%recipient_item%& above), because it pre-dates
29111 the addition of that field to the structure. However, it is easy to add such a
29112 value afterwards. For example:
29114 receive_add_recipient(US"monitor@mydom.example", -1);
29115 recipients_list[recipients_count-1].errors_to =
29116 US"postmaster@mydom.example";
29119 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
29120 This is a convenience function to remove a named recipient from the list of
29121 recipients. It returns true if a recipient was removed, and false if no
29122 matching recipient could be found. The argument must be a complete email
29129 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
29130 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
29131 This function decodes strings that are encoded according to RFC 2047. Typically
29132 these are the contents of header lines. First, each &"encoded word"& is decoded
29133 from the Q or B encoding into a byte-string. Then, if provided with the name of
29134 a charset encoding, and if the &[iconv()]& function is available, an attempt is
29135 made to translate the result to the named character set. If this fails, the
29136 binary string is returned with an error message.
29138 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
29139 maximum MIME word length is enforced. The third argument is the target
29140 encoding, or NULL if no translation is wanted.
29142 .cindex "binary zero" "in RFC 2047 decoding"
29143 .cindex "RFC 2047" "binary zero in"
29144 If a binary zero is encountered in the decoded string, it is replaced by the
29145 contents of the &%zeroval%& argument. For use with Exim headers, the value must
29146 not be 0 because header lines are handled as zero-terminated strings.
29148 The function returns the result of processing the string, zero-terminated; if
29149 &%lenptr%& is not NULL, the length of the result is set in the variable to
29150 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
29152 If an error is encountered, the function returns NULL and uses the &%error%&
29153 argument to return an error message. The variable pointed to by &%error%& is
29154 set to NULL if there is no error; it may be set non-NULL even when the function
29155 returns a non-NULL value if decoding was successful, but there was a problem
29159 .vitem &*int&~smtp_fflush(void)*&
29160 This function is used in conjunction with &'smtp_printf()'&, as described
29163 .vitem &*void&~smtp_printf(char&~*,&~...)*&
29164 The arguments of this function are like &[printf()]&; it writes to the SMTP
29165 output stream. You should use this function only when there is an SMTP output
29166 stream, that is, when the incoming message is being received via interactive
29167 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
29168 is FALSE. If you want to test for an incoming message from another host (as
29169 opposed to a local process that used the &%-bs%& command line option), you can
29170 test the value of &%sender_host_address%&, which is non-NULL when a remote host
29173 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
29174 output function, so it can be used for all forms of SMTP connection.
29176 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
29177 must start with an appropriate response code: 550 if you are going to return
29178 LOCAL_SCAN_REJECT, 451 if you are going to return
29179 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
29180 initial lines of a multi-line response, the code must be followed by a hyphen
29181 to indicate that the line is not the final response line. You must also ensure
29182 that the lines you write terminate with CRLF. For example:
29184 smtp_printf("550-this is some extra info\r\n");
29185 return LOCAL_SCAN_REJECT;
29187 Note that you can also create multi-line responses by including newlines in
29188 the data returned via the &%return_text%& argument. The added value of using
29189 &'smtp_printf()'& is that, for instance, you could introduce delays between
29190 multiple output lines.
29192 The &'smtp_printf()'& function does not return any error indication, because it
29193 does not automatically flush pending output, and therefore does not test
29194 the state of the stream. (In the main code of Exim, flushing and error
29195 detection is done when Exim is ready for the next SMTP input command.) If
29196 you want to flush the output and check for an error (for example, the
29197 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
29198 arguments. It flushes the output stream, and returns a non-zero value if there
29201 .vitem &*void&~*store_get(int)*&
29202 This function accesses Exim's internal store (memory) manager. It gets a new
29203 chunk of memory whose size is given by the argument. Exim bombs out if it ever
29204 runs out of memory. See the next section for a discussion of memory handling.
29206 .vitem &*void&~*store_get_perm(int)*&
29207 This function is like &'store_get()'&, but it always gets memory from the
29208 permanent pool. See the next section for a discussion of memory handling.
29210 .vitem &*uschar&~*string_copy(uschar&~*string)*&
29213 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
29216 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
29217 These three functions create strings using Exim's dynamic memory facilities.
29218 The first makes a copy of an entire string. The second copies up to a maximum
29219 number of characters, indicated by the second argument. The third uses a format
29220 and insertion arguments to create a new string. In each case, the result is a
29221 pointer to a new string in the current memory pool. See the next section for
29227 .section "More about Exim's memory handling" "SECTmemhanloc"
29228 .cindex "&[local_scan()]& function" "memory handling"
29229 No function is provided for freeing memory, because that is never needed.
29230 The dynamic memory that Exim uses when receiving a message is automatically
29231 recycled if another message is received by the same process (this applies only
29232 to incoming SMTP connections &-- other input methods can supply only one
29233 message at a time). After receiving the last message, a reception process
29236 Because it is recycled, the normal dynamic memory cannot be used for holding
29237 data that must be preserved over a number of incoming messages on the same SMTP
29238 connection. However, Exim in fact uses two pools of dynamic memory; the second
29239 one is not recycled, and can be used for this purpose.
29241 If you want to allocate memory that remains available for subsequent messages
29242 in the same SMTP connection, you should set
29244 store_pool = POOL_PERM
29246 before calling the function that does the allocation. There is no need to
29247 restore the value if you do not need to; however, if you do want to revert to
29248 the normal pool, you can either restore the previous value of &%store_pool%& or
29249 set it explicitly to POOL_MAIN.
29251 The pool setting applies to all functions that get dynamic memory, including
29252 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
29253 There is also a convenience function called &'store_get_perm()'& that gets a
29254 block of memory from the permanent pool while preserving the value of
29261 . ////////////////////////////////////////////////////////////////////////////
29262 . ////////////////////////////////////////////////////////////////////////////
29264 .chapter "System-wide message filtering" "CHAPsystemfilter"
29265 .scindex IIDsysfil1 "filter" "system filter"
29266 .scindex IIDsysfil2 "filtering all mail"
29267 .scindex IIDsysfil3 "system filter"
29268 The previous chapters (on ACLs and the local scan function) describe checks
29269 that can be applied to messages before they are accepted by a host. There is
29270 also a mechanism for checking messages once they have been received, but before
29271 they are delivered. This is called the &'system filter'&.
29273 The system filter operates in a similar manner to users' filter files, but it
29274 is run just once per message (however many recipients the message has).
29275 It should not normally be used as a substitute for routing, because &%deliver%&
29276 commands in a system router provide new envelope recipient addresses.
29277 The system filter must be an Exim filter. It cannot be a Sieve filter.
29279 The system filter is run at the start of a delivery attempt, before any routing
29280 is done. If a message fails to be completely delivered at the first attempt,
29281 the system filter is run again at the start of every retry.
29282 If you want your filter to do something only once per message, you can make use
29283 of the &%first_delivery%& condition in an &%if%& command in the filter to
29284 prevent it happening on retries.
29286 .vindex "&$domain$&"
29287 .vindex "&$local_part$&"
29288 &*Warning*&: Because the system filter runs just once, variables that are
29289 specific to individual recipient addresses, such as &$local_part$& and
29290 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
29291 you want to run a centrally-specified filter for each recipient address
29292 independently, you can do so by setting up a suitable &(redirect)& router, as
29293 described in section &<<SECTperaddfil>>& below.
29296 .section "Specifying a system filter" "SECID212"
29297 .cindex "uid (user id)" "system filter"
29298 .cindex "gid (group id)" "system filter"
29299 The name of the file that contains the system filter must be specified by
29300 setting &%system_filter%&. If you want the filter to run under a uid and gid
29301 other than root, you must also set &%system_filter_user%& and
29302 &%system_filter_group%& as appropriate. For example:
29304 system_filter = /etc/mail/exim.filter
29305 system_filter_user = exim
29307 If a system filter generates any deliveries directly to files or pipes (via the
29308 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
29309 specified by setting &%system_filter_file_transport%& and
29310 &%system_filter_pipe_transport%&, respectively. Similarly,
29311 &%system_filter_reply_transport%& must be set to handle any messages generated
29312 by the &%reply%& command.
29315 .section "Testing a system filter" "SECID213"
29316 You can run simple tests of a system filter in the same way as for a user
29317 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
29318 are permitted only in system filters are recognized.
29320 If you want to test the combined effect of a system filter and a user filter,
29321 you can use both &%-bF%& and &%-bf%& on the same command line.
29325 .section "Contents of a system filter" "SECID214"
29326 The language used to specify system filters is the same as for users' filter
29327 files. It is described in the separate end-user document &'Exim's interface to
29328 mail filtering'&. However, there are some additional features that are
29329 available only in system filters; these are described in subsequent sections.
29330 If they are encountered in a user's filter file or when testing with &%-bf%&,
29333 .cindex "frozen messages" "manual thaw; testing in filter"
29334 There are two special conditions which, though available in users' filter
29335 files, are designed for use in system filters. The condition &%first_delivery%&
29336 is true only for the first attempt at delivering a message, and
29337 &%manually_thawed%& is true only if the message has been frozen, and
29338 subsequently thawed by an admin user. An explicit forced delivery counts as a
29339 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
29341 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
29342 specify an &"unseen"& (non-significant) delivery, and that delivery does not
29343 succeed, it will not be tried again.
29344 If you want Exim to retry an unseen delivery until it succeeds, you should
29345 arrange to set it up every time the filter runs.
29347 When a system filter finishes running, the values of the variables &$n0$& &--
29348 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
29349 users' filter files. Thus a system filter can, for example, set up &"scores"&
29350 to which users' filter files can refer.
29354 .section "Additional variable for system filters" "SECID215"
29355 .vindex "&$recipients$&"
29356 The expansion variable &$recipients$&, containing a list of all the recipients
29357 of the message (separated by commas and white space), is available in system
29358 filters. It is not available in users' filters for privacy reasons.
29362 .section "Defer, freeze, and fail commands for system filters" "SECID216"
29363 .cindex "freezing messages"
29364 .cindex "message" "freezing"
29365 .cindex "message" "forced failure"
29366 .cindex "&%fail%&" "in system filter"
29367 .cindex "&%freeze%& in system filter"
29368 .cindex "&%defer%& in system filter"
29369 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
29370 always available in system filters, but are not normally enabled in users'
29371 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
29372 for the &(redirect)& router.) These commands can optionally be followed by the
29373 word &%text%& and a string containing an error message, for example:
29375 fail text "this message looks like spam to me"
29377 The keyword &%text%& is optional if the next character is a double quote.
29379 The &%defer%& command defers delivery of the original recipients of the
29380 message. The &%fail%& command causes all the original recipients to be failed,
29381 and a bounce message to be created. The &%freeze%& command suspends all
29382 delivery attempts for the original recipients. In all cases, any new deliveries
29383 that are specified by the filter are attempted as normal after the filter has
29386 The &%freeze%& command is ignored if the message has been manually unfrozen and
29387 not manually frozen since. This means that automatic freezing by a system
29388 filter can be used as a way of checking out suspicious messages. If a message
29389 is found to be all right, manually unfreezing it allows it to be delivered.
29391 .cindex "log" "&%fail%& command log line"
29392 .cindex "&%fail%&" "log line; reducing"
29393 The text given with a fail command is used as part of the bounce message as
29394 well as being written to the log. If the message is quite long, this can fill
29395 up a lot of log space when such failures are common. To reduce the size of the
29396 log message, Exim interprets the text in a special way if it starts with the
29397 two characters &`<<`& and contains &`>>`& later. The text between these two
29398 strings is written to the log, and the rest of the text is used in the bounce
29399 message. For example:
29401 fail "<<filter test 1>>Your message is rejected \
29402 because it contains attachments that we are \
29403 not prepared to receive."
29406 .cindex "loop" "caused by &%fail%&"
29407 Take great care with the &%fail%& command when basing the decision to fail on
29408 the contents of the message, because the bounce message will of course include
29409 the contents of the original message and will therefore trigger the &%fail%&
29410 command again (causing a mail loop) unless steps are taken to prevent this.
29411 Testing the &%error_message%& condition is one way to prevent this. You could
29414 if $message_body contains "this is spam" and not error_message
29415 then fail text "spam is not wanted here" endif
29417 though of course that might let through unwanted bounce messages. The
29418 alternative is clever checking of the body and/or headers to detect bounces
29419 generated by the filter.
29421 The interpretation of a system filter file ceases after a
29423 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
29424 set up earlier in the filter file are honoured, so you can use a sequence such
29430 to send a specified message when the system filter is freezing (or deferring or
29431 failing) a message. The normal deliveries for the message do not, of course,
29436 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
29437 .cindex "header lines" "adding; in system filter"
29438 .cindex "header lines" "removing; in system filter"
29439 .cindex "filter" "header lines; adding/removing"
29440 Two filter commands that are available only in system filters are:
29442 headers add <string>
29443 headers remove <string>
29445 The argument for the &%headers add%& is a string that is expanded and then
29446 added to the end of the message's headers. It is the responsibility of the
29447 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
29448 space is ignored, and if the string is otherwise empty, or if the expansion is
29449 forced to fail, the command has no effect.
29451 You can use &"\n"& within the string, followed by white space, to specify
29452 continued header lines. More than one header may be added in one command by
29453 including &"\n"& within the string without any following white space. For
29456 headers add "X-header-1: ....\n \
29457 continuation of X-header-1 ...\n\
29460 Note that the header line continuation white space after the first newline must
29461 be placed before the backslash that continues the input string, because white
29462 space after input continuations is ignored.
29464 The argument for &%headers remove%& is a colon-separated list of header names.
29465 This command applies only to those headers that are stored with the message;
29466 those that are added at delivery time (such as &'Envelope-To:'& and
29467 &'Return-Path:'&) cannot be removed by this means. If there is more than one
29468 header with the same name, they are all removed.
29470 The &%headers%& command in a system filter makes an immediate change to the set
29471 of header lines that was received with the message (with possible additions
29472 from ACL processing). Subsequent commands in the system filter operate on the
29473 modified set, which also forms the basis for subsequent message delivery.
29474 Unless further modified during routing or transporting, this set of headers is
29475 used for all recipients of the message.
29477 During routing and transporting, the variables that refer to the contents of
29478 header lines refer only to those lines that are in this set. Thus, header lines
29479 that are added by a system filter are visible to users' filter files and to all
29480 routers and transports. This contrasts with the manipulation of header lines by
29481 routers and transports, which is not immediate, but which instead is saved up
29482 until the message is actually being written (see section
29483 &<<SECTheadersaddrem>>&).
29485 If the message is not delivered at the first attempt, header lines that were
29486 added by the system filter are stored with the message, and so are still
29487 present at the next delivery attempt. Header lines that were removed are still
29488 present, but marked &"deleted"& so that they are not transported with the
29489 message. For this reason, it is usual to make the &%headers%& command
29490 conditional on &%first_delivery%& so that the set of header lines is not
29491 modified more than once.
29493 Because header modification in a system filter acts immediately, you have to
29494 use an indirect approach if you want to modify the contents of a header line.
29497 headers add "Old-Subject: $h_subject:"
29498 headers remove "Subject"
29499 headers add "Subject: new subject (was: $h_old-subject:)"
29500 headers remove "Old-Subject"
29505 .section "Setting an errors address in a system filter" "SECID217"
29506 .cindex "envelope sender"
29507 In a system filter, if a &%deliver%& command is followed by
29509 errors_to <some address>
29511 in order to change the envelope sender (and hence the error reporting) for that
29512 delivery, any address may be specified. (In a user filter, only the current
29513 user's address can be set.) For example, if some mail is being monitored, you
29516 unseen deliver monitor@spying.example errors_to root@local.example
29518 to take a copy which would not be sent back to the normal error reporting
29519 address if its delivery failed.
29523 .section "Per-address filtering" "SECTperaddfil"
29524 .vindex "&$domain$&"
29525 .vindex "&$local_part$&"
29526 In contrast to the system filter, which is run just once per message for each
29527 delivery attempt, it is also possible to set up a system-wide filtering
29528 operation that runs once for each recipient address. In this case, variables
29529 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
29530 filter file could be made dependent on them. This is an example of a router
29531 which implements such a filter:
29536 domains = +local_domains
29537 file = /central/filters/$local_part
29542 The filter is run in a separate process under its own uid. Therefore, either
29543 &%check_local_user%& must be set (as above), in which case the filter is run as
29544 the local user, or the &%user%& option must be used to specify which user to
29545 use. If both are set, &%user%& overrides.
29547 Care should be taken to ensure that none of the commands in the filter file
29548 specify a significant delivery if the message is to go on to be delivered to
29549 its intended recipient. The router will not then claim to have dealt with the
29550 address, so it will be passed on to subsequent routers to be delivered in the
29552 .ecindex IIDsysfil1
29553 .ecindex IIDsysfil2
29554 .ecindex IIDsysfil3
29561 . ////////////////////////////////////////////////////////////////////////////
29562 . ////////////////////////////////////////////////////////////////////////////
29564 .chapter "Message processing" "CHAPmsgproc"
29565 .scindex IIDmesproc "message" "general processing"
29566 Exim performs various transformations on the sender and recipient addresses of
29567 all messages that it handles, and also on the messages' header lines. Some of
29568 these are optional and configurable, while others always take place. All of
29569 this processing, except rewriting as a result of routing, and the addition or
29570 removal of header lines while delivering, happens when a message is received,
29571 before it is placed on Exim's queue.
29573 Some of the automatic processing takes place by default only for
29574 &"locally-originated"& messages. This adjective is used to describe messages
29575 that are not received over TCP/IP, but instead are passed to an Exim process on
29576 its standard input. This includes the interactive &"local SMTP"& case that is
29577 set up by the &%-bs%& command line option.
29579 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
29580 or ::1) are not considered to be locally-originated. Exim does not treat the
29581 loopback interface specially in any way.
29583 If you want the loopback interface to be treated specially, you must ensure
29584 that there are appropriate entries in your ACLs.
29589 .section "Submission mode for non-local messages" "SECTsubmodnon"
29590 .cindex "message" "submission"
29591 .cindex "submission mode"
29592 Processing that happens automatically for locally-originated messages (unless
29593 &%suppress_local_fixups%& is set) can also be requested for messages that are
29594 received over TCP/IP. The term &"submission mode"& is used to describe this
29595 state. Submission mode is set by the modifier
29597 control = submission
29599 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
29600 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
29601 a local submission, and is normally used when the source of the message is
29602 known to be an MUA running on a client host (as opposed to an MTA). For
29603 example, to set submission mode for messages originating on the IPv4 loopback
29604 interface, you could include the following in the MAIL ACL:
29606 warn hosts = 127.0.0.1
29607 control = submission
29609 .cindex "&%sender_retain%& submission option"
29610 There are some options that can be used when setting submission mode. A slash
29611 is used to separate options. For example:
29613 control = submission/sender_retain
29615 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
29616 true and &%local_from_check%& false for the current incoming message. The first
29617 of these allows an existing &'Sender:'& header in the message to remain, and
29618 the second suppresses the check to ensure that &'From:'& matches the
29619 authenticated sender. With this setting, Exim still fixes up messages by adding
29620 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
29621 attempt to check sender authenticity in header lines.
29623 When &%sender_retain%& is not set, a submission mode setting may specify a
29624 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
29627 control = submission/domain=some.domain
29629 The domain may be empty. How this value is used is described in sections
29630 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
29631 that allows you to specify the user's full name for inclusion in a created
29632 &'Sender:'& or &'From:'& header line. For example:
29634 accept authenticated = *
29635 control = submission/domain=wonderland.example/\
29636 name=${lookup {$authenticated_id} \
29637 lsearch {/etc/exim/namelist}}
29639 Because the name may contain any characters, including slashes, the &%name%&
29640 option must be given last. The remainder of the string is used as the name. For
29641 the example above, if &_/etc/exim/namelist_& contains:
29643 bigegg: Humpty Dumpty
29645 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
29648 Sender: Humpty Dumpty <bigegg@wonderland.example>
29650 .cindex "return path" "in submission mode"
29651 By default, submission mode forces the return path to the same address as is
29652 used to create the &'Sender:'& header. However, if &%sender_retain%& is
29653 specified, the return path is also left unchanged.
29655 &*Note*&: The changes caused by submission mode take effect after the predata
29656 ACL. This means that any sender checks performed before the fix-ups use the
29657 untrusted sender address specified by the user, not the trusted sender address
29658 specified by submission mode. Although this might be slightly unexpected, it
29659 does mean that you can configure ACL checks to spot that a user is trying to
29660 spoof another's address.
29662 .section "Line endings" "SECTlineendings"
29663 .cindex "line endings"
29664 .cindex "carriage return"
29666 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
29667 linefeed) is the line ending for messages transmitted over the Internet using
29668 SMTP over TCP/IP. However, within individual operating systems, different
29669 conventions are used. For example, Unix-like systems use just LF, but others
29670 use CRLF or just CR.
29672 Exim was designed for Unix-like systems, and internally, it stores messages
29673 using the system's convention of a single LF as a line terminator. When
29674 receiving a message, all line endings are translated to this standard format.
29675 Originally, it was thought that programs that passed messages directly to an
29676 MTA within an operating system would use that system's convention. Experience
29677 has shown that this is not the case; for example, there are Unix applications
29678 that use CRLF in this circumstance. For this reason, and for compatibility with
29679 other MTAs, the way Exim handles line endings for all messages is now as
29683 LF not preceded by CR is treated as a line ending.
29685 CR is treated as a line ending; if it is immediately followed by LF, the LF
29688 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
29689 nor a local message in the state where a line containing only a dot is a
29692 If a bare CR is encountered within a header line, an extra space is added after
29693 the line terminator so as not to end the header line. The reasoning behind this
29694 is that bare CRs in header lines are most likely either to be mistakes, or
29695 people trying to play silly games.
29697 If the first header line received in a message ends with CRLF, a subsequent
29698 bare LF in a header line is treated in the same way as a bare CR in a header
29706 .section "Unqualified addresses" "SECID218"
29707 .cindex "unqualified addresses"
29708 .cindex "address" "qualification"
29709 By default, Exim expects every envelope address it receives from an external
29710 host to be fully qualified. Unqualified addresses cause negative responses to
29711 SMTP commands. However, because SMTP is used as a means of transporting
29712 messages from MUAs running on personal workstations, there is sometimes a
29713 requirement to accept unqualified addresses from specific hosts or IP networks.
29715 Exim has two options that separately control which hosts may send unqualified
29716 sender or recipient addresses in SMTP commands, namely
29717 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
29718 cases, if an unqualified address is accepted, it is qualified by adding the
29719 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
29721 .oindex "&%qualify_domain%&"
29722 .oindex "&%qualify_recipient%&"
29723 Unqualified addresses in header lines are automatically qualified for messages
29724 that are locally originated, unless the &%-bnq%& option is given on the command
29725 line. For messages received over SMTP, unqualified addresses in header lines
29726 are qualified only if unqualified addresses are permitted in SMTP commands. In
29727 other words, such qualification is also controlled by
29728 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
29733 .section "The UUCP From line" "SECID219"
29734 .cindex "&""From""& line"
29735 .cindex "UUCP" "&""From""& line"
29736 .cindex "sender" "address"
29737 .oindex "&%uucp_from_pattern%&"
29738 .oindex "&%uucp_from_sender%&"
29739 .cindex "envelope sender"
29740 .cindex "Sendmail compatibility" "&""From""& line"
29741 Messages that have come from UUCP (and some other applications) often begin
29742 with a line containing the envelope sender and a timestamp, following the word
29743 &"From"&. Examples of two common formats are:
29745 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
29746 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
29748 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
29749 Exim recognizes such lines at the start of messages that are submitted to it
29750 via the command line (that is, on the standard input). It does not recognize
29751 such lines in incoming SMTP messages, unless the sending host matches
29752 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
29753 and &%ignore_fromline_local%& is set. The recognition is controlled by a
29754 regular expression that is defined by the &%uucp_from_pattern%& option, whose
29755 default value matches the two common cases shown above and puts the address
29756 that follows &"From"& into &$1$&.
29758 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
29759 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
29760 a trusted user, the message's sender address is constructed by expanding the
29761 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
29762 then parsed as an RFC 2822 address. If there is no domain, the local part is
29763 qualified with &%qualify_domain%& unless it is the empty string. However, if
29764 the command line &%-f%& option is used, it overrides the &"From"& line.
29766 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
29767 sender address is not changed. This is also the case for incoming SMTP messages
29768 that are permitted to contain &"From"& lines.
29770 Only one &"From"& line is recognized. If there is more than one, the second is
29771 treated as a data line that starts the body of the message, as it is not valid
29772 as a header line. This also happens if a &"From"& line is present in an
29773 incoming SMTP message from a source that is not permitted to send them.
29777 .section "Resent- header lines" "SECID220"
29778 .cindex "&%Resent-%& header lines"
29779 RFC 2822 makes provision for sets of header lines starting with the string
29780 &`Resent-`& to be added to a message when it is resent by the original
29781 recipient to somebody else. These headers are &'Resent-Date:'&,
29782 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
29783 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
29786 &'Resent fields are strictly informational. They MUST NOT be used in the normal
29787 processing of replies or other such automatic actions on messages.'&
29790 This leaves things a bit vague as far as other processing actions such as
29791 address rewriting are concerned. Exim treats &%Resent-%& header lines as
29795 A &'Resent-From:'& line that just contains the login id of the submitting user
29796 is automatically rewritten in the same way as &'From:'& (see below).
29798 If there's a rewriting rule for a particular header line, it is also applied to
29799 &%Resent-%& header lines of the same type. For example, a rule that rewrites
29800 &'From:'& also rewrites &'Resent-From:'&.
29802 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
29805 For a locally-submitted message,
29806 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
29807 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
29808 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
29809 included in log lines in this case.
29811 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
29812 &%Resent-%& header lines are present.
29818 .section "The Auto-Submitted: header line" "SECID221"
29819 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
29820 includes the header line:
29822 Auto-Submitted: auto-replied
29825 .section "The Bcc: header line" "SECID222"
29826 .cindex "&'Bcc:'& header line"
29827 If Exim is called with the &%-t%& option, to take recipient addresses from a
29828 message's header, it removes any &'Bcc:'& header line that may exist (after
29829 extracting its addresses). If &%-t%& is not present on the command line, any
29830 existing &'Bcc:'& is not removed.
29833 .section "The Date: header line" "SECID223"
29834 .cindex "&'Date:'& header line"
29835 If a locally-generated or submission-mode message has no &'Date:'& header line,
29836 Exim adds one, using the current date and time, unless the
29837 &%suppress_local_fixups%& control has been specified.
29839 .section "The Delivery-date: header line" "SECID224"
29840 .cindex "&'Delivery-date:'& header line"
29841 .oindex "&%delivery_date_remove%&"
29842 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
29843 set. Exim can be configured to add them to the final delivery of messages. (See
29844 the generic &%delivery_date_add%& transport option.) They should not be present
29845 in messages in transit. If the &%delivery_date_remove%& configuration option is
29846 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
29850 .section "The Envelope-to: header line" "SECID225"
29851 .cindex "&'Envelope-to:'& header line"
29852 .oindex "&%envelope_to_remove%&"
29853 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
29854 Exim can be configured to add them to the final delivery of messages. (See the
29855 generic &%envelope_to_add%& transport option.) They should not be present in
29856 messages in transit. If the &%envelope_to_remove%& configuration option is set
29857 (the default), Exim removes &'Envelope-to:'& header lines from incoming
29861 .section "The From: header line" "SECTthefrohea"
29862 .cindex "&'From:'& header line"
29863 .cindex "Sendmail compatibility" "&""From""& line"
29864 .cindex "message" "submission"
29865 .cindex "submission mode"
29866 If a submission-mode message does not contain a &'From:'& header line, Exim
29867 adds one if either of the following conditions is true:
29870 The envelope sender address is not empty (that is, this is not a bounce
29871 message). The added header line copies the envelope sender address.
29873 .vindex "&$authenticated_id$&"
29874 The SMTP session is authenticated and &$authenticated_id$& is not empty.
29876 .vindex "&$qualify_domain$&"
29877 If no domain is specified by the submission control, the local part is
29878 &$authenticated_id$& and the domain is &$qualify_domain$&.
29880 If a non-empty domain is specified by the submission control, the local
29881 part is &$authenticated_id$&, and the domain is the specified domain.
29883 If an empty domain is specified by the submission control,
29884 &$authenticated_id$& is assumed to be the complete address.
29888 A non-empty envelope sender takes precedence.
29890 If a locally-generated incoming message does not contain a &'From:'& header
29891 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
29892 containing the sender's address. The calling user's login name and full name
29893 are used to construct the address, as described in section &<<SECTconstr>>&.
29894 They are obtained from the password data by calling &[getpwuid()]& (but see the
29895 &%unknown_login%& configuration option). The address is qualified with
29896 &%qualify_domain%&.
29898 For compatibility with Sendmail, if an incoming, non-SMTP message has a
29899 &'From:'& header line containing just the unqualified login name of the calling
29900 user, this is replaced by an address containing the user's login name and full
29901 name as described in section &<<SECTconstr>>&.
29904 .section "The Message-ID: header line" "SECID226"
29905 .cindex "&'Message-ID:'& header line"
29906 .cindex "message" "submission"
29907 .oindex "&%message_id_header_text%&"
29908 If a locally-generated or submission-mode incoming message does not contain a
29909 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
29910 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
29911 to the message. If there are any &'Resent-:'& headers in the message, it
29912 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
29913 message id, preceded by the letter E to ensure it starts with a letter, and
29914 followed by @ and the primary host name. Additional information can be included
29915 in this header line by setting the &%message_id_header_text%& and/or
29916 &%message_id_header_domain%& options.
29919 .section "The Received: header line" "SECID227"
29920 .cindex "&'Received:'& header line"
29921 A &'Received:'& header line is added at the start of every message. The
29922 contents are defined by the &%received_header_text%& configuration option, and
29923 Exim automatically adds a semicolon and a timestamp to the configured string.
29925 The &'Received:'& header is generated as soon as the message's header lines
29926 have been received. At this stage, the timestamp in the &'Received:'& header
29927 line is the time that the message started to be received. This is the value
29928 that is seen by the DATA ACL and by the &[local_scan()]& function.
29930 Once a message is accepted, the timestamp in the &'Received:'& header line is
29931 changed to the time of acceptance, which is (apart from a small delay while the
29932 -H spool file is written) the earliest time at which delivery could start.
29935 .section "The References: header line" "SECID228"
29936 .cindex "&'References:'& header line"
29937 Messages created by the &(autoreply)& transport include a &'References:'&
29938 header line. This is constructed according to the rules that are described in
29939 section 3.64 of RFC 2822 (which states that replies should contain such a
29940 header line), and section 3.14 of RFC 3834 (which states that automatic
29941 responses are not different in this respect). However, because some mail
29942 processing software does not cope well with very long header lines, no more
29943 than 12 message IDs are copied from the &'References:'& header line in the
29944 incoming message. If there are more than 12, the first one and then the final
29945 11 are copied, before adding the message ID of the incoming message.
29949 .section "The Return-path: header line" "SECID229"
29950 .cindex "&'Return-path:'& header line"
29951 .oindex "&%return_path_remove%&"
29952 &'Return-path:'& header lines are defined as something an MTA may insert when
29953 it does the final delivery of messages. (See the generic &%return_path_add%&
29954 transport option.) Therefore, they should not be present in messages in
29955 transit. If the &%return_path_remove%& configuration option is set (the
29956 default), Exim removes &'Return-path:'& header lines from incoming messages.
29960 .section "The Sender: header line" "SECTthesenhea"
29961 .cindex "&'Sender:'& header line"
29962 .cindex "message" "submission"
29963 For a locally-originated message from an untrusted user, Exim may remove an
29964 existing &'Sender:'& header line, and it may add a new one. You can modify
29965 these actions by setting the &%local_sender_retain%& option true, the
29966 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
29969 When a local message is received from an untrusted user and
29970 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
29971 control has not been set, a check is made to see if the address given in the
29972 &'From:'& header line is the correct (local) sender of the message. The address
29973 that is expected has the login name as the local part and the value of
29974 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
29975 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
29976 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
29977 line is added to the message.
29979 If you set &%local_from_check%& false, this checking does not occur. However,
29980 the removal of an existing &'Sender:'& line still happens, unless you also set
29981 &%local_sender_retain%& to be true. It is not possible to set both of these
29982 options true at the same time.
29984 .cindex "submission mode"
29985 By default, no processing of &'Sender:'& header lines is done for messages
29986 received over TCP/IP or for messages submitted by trusted users. However, when
29987 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
29988 not specified on the submission control, the following processing takes place:
29990 .vindex "&$authenticated_id$&"
29991 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
29992 authenticated, and &$authenticated_id$& is not empty, a sender address is
29993 created as follows:
29996 .vindex "&$qualify_domain$&"
29997 If no domain is specified by the submission control, the local part is
29998 &$authenticated_id$& and the domain is &$qualify_domain$&.
30000 If a non-empty domain is specified by the submission control, the local part
30001 is &$authenticated_id$&, and the domain is the specified domain.
30003 If an empty domain is specified by the submission control,
30004 &$authenticated_id$& is assumed to be the complete address.
30007 This address is compared with the address in the &'From:'& header line. If they
30008 are different, a &'Sender:'& header line containing the created address is
30009 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
30010 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
30012 .cindex "return path" "created from &'Sender:'&"
30013 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
30014 the message (the envelope sender address) is changed to be the same address,
30015 except in the case of submission mode when &%sender_retain%& is specified.
30019 .section "Adding and removing header lines in routers and transports" &&&
30020 "SECTheadersaddrem"
30021 .cindex "header lines" "adding; in router or transport"
30022 .cindex "header lines" "removing; in router or transport"
30023 When a message is delivered, the addition and removal of header lines can be
30024 specified in a system filter, or on any of the routers and transports that
30025 process the message. Section &<<SECTaddremheasys>>& contains details about
30026 modifying headers in a system filter. Header lines can also be added in an ACL
30027 as a message is received (see section &<<SECTaddheadacl>>&).
30029 In contrast to what happens in a system filter, header modifications that are
30030 specified on routers and transports apply only to the particular recipient
30031 addresses that are being processed by those routers and transports. These
30032 changes do not actually take place until a copy of the message is being
30033 transported. Therefore, they do not affect the basic set of header lines, and
30034 they do not affect the values of the variables that refer to header lines.
30036 &*Note*&: In particular, this means that any expansions in the configuration of
30037 the transport cannot refer to the modified header lines, because such
30038 expansions all occur before the message is actually transported.
30040 For both routers and transports, the result of expanding a &%headers_add%&
30041 option must be in the form of one or more RFC 2822 header lines, separated by
30042 newlines (coded as &"\n"&). For example:
30044 headers_add = X-added-header: added by $primary_hostname\n\
30045 X-added-second: another added header line
30047 Exim does not check the syntax of these added header lines.
30049 The result of expanding &%headers_remove%& must consist of a colon-separated
30050 list of header names. This is confusing, because header names themselves are
30051 often terminated by colons. In this case, the colons are the list separators,
30052 not part of the names. For example:
30054 headers_remove = return-receipt-to:acknowledge-to
30056 When &%headers_add%& or &%headers_remove%& is specified on a router, its value
30057 is expanded at routing time, and then associated with all addresses that are
30058 accepted by that router, and also with any new addresses that it generates. If
30059 an address passes through several routers as a result of aliasing or
30060 forwarding, the changes are cumulative.
30062 .oindex "&%unseen%&"
30063 However, this does not apply to multiple routers that result from the use of
30064 the &%unseen%& option. Any header modifications that were specified by the
30065 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
30067 Addresses that end up with different &%headers_add%& or &%headers_remove%&
30068 settings cannot be delivered together in a batch, so a transport is always
30069 dealing with a set of addresses that have the same header-processing
30072 The transport starts by writing the original set of header lines that arrived
30073 with the message, possibly modified by the system filter. As it writes out
30074 these lines, it consults the list of header names that were attached to the
30075 recipient address(es) by &%headers_remove%& options in routers, and it also
30076 consults the transport's own &%headers_remove%& option. Header lines whose
30077 names are on either of these lists are not written out. If there are multiple
30078 instances of any listed header, they are all skipped.
30080 After the remaining original header lines have been written, new header
30081 lines that were specified by routers' &%headers_add%& options are written, in
30082 the order in which they were attached to the address. These are followed by any
30083 header lines specified by the transport's &%headers_add%& option.
30085 This way of handling header line modifications in routers and transports has
30086 the following consequences:
30089 The original set of header lines, possibly modified by the system filter,
30090 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
30091 to it, at all times.
30093 Header lines that are added by a router's
30094 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
30095 expansion syntax in subsequent routers or the transport.
30097 Conversely, header lines that are specified for removal by &%headers_remove%&
30098 in a router remain visible to subsequent routers and the transport.
30100 Headers added to an address by &%headers_add%& in a router cannot be removed by
30101 a later router or by a transport.
30103 An added header can refer to the contents of an original header that is to be
30104 removed, even it has the same name as the added header. For example:
30106 headers_remove = subject
30107 headers_add = Subject: new subject (was: $h_subject:)
30111 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
30112 for a &(redirect)& router that has the &%one_time%& option set.
30118 .section "Constructed addresses" "SECTconstr"
30119 .cindex "address" "constructed"
30120 .cindex "constructed address"
30121 When Exim constructs a sender address for a locally-generated message, it uses
30124 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
30128 Zaphod Beeblebrox <zaphod@end.univ.example>
30130 The user name is obtained from the &%-F%& command line option if set, or
30131 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
30132 &"gecos"& field from the password entry. If the &"gecos"& field contains an
30133 ampersand character, this is replaced by the login name with the first letter
30134 upper cased, as is conventional in a number of operating systems. See the
30135 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
30136 The &%unknown_username%& option can be used to specify user names in cases when
30137 there is no password file entry.
30140 In all cases, the user name is made to conform to RFC 2822 by quoting all or
30141 parts of it if necessary. In addition, if it contains any non-printing
30142 characters, it is encoded as described in RFC 2047, which defines a way of
30143 including non-ASCII characters in header lines. The value of the
30144 &%headers_charset%& option specifies the name of the encoding that is used (the
30145 characters are assumed to be in this encoding). The setting of
30146 &%print_topbitchars%& controls whether characters with the top bit set (that
30147 is, with codes greater than 127) count as printing characters or not.
30151 .section "Case of local parts" "SECID230"
30152 .cindex "case of local parts"
30153 .cindex "local part" "case of"
30154 RFC 2822 states that the case of letters in the local parts of addresses cannot
30155 be assumed to be non-significant. Exim preserves the case of local parts of
30156 addresses, but by default it uses a lower-cased form when it is routing,
30157 because on most Unix systems, usernames are in lower case and case-insensitive
30158 routing is required. However, any particular router can be made to use the
30159 original case for local parts by setting the &%caseful_local_part%& generic
30162 .cindex "mixed-case login names"
30163 If you must have mixed-case user names on your system, the best way to proceed,
30164 assuming you want case-independent handling of incoming email, is to set up
30165 your first router to convert incoming local parts in your domains to the
30166 correct case by means of a file lookup. For example:
30170 domains = +local_domains
30171 data = ${lookup{$local_part}cdb\
30172 {/etc/usercased.cdb}{$value}fail}\
30175 For this router, the local part is forced to lower case by the default action
30176 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
30177 up a new local part in the correct case. If you then set &%caseful_local_part%&
30178 on any subsequent routers which process your domains, they will operate on
30179 local parts with the correct case in a case-sensitive manner.
30183 .section "Dots in local parts" "SECID231"
30184 .cindex "dot" "in local part"
30185 .cindex "local part" "dots in"
30186 RFC 2822 forbids empty components in local parts. That is, an unquoted local
30187 part may not begin or end with a dot, nor have two consecutive dots in the
30188 middle. However, it seems that many MTAs do not enforce this, so Exim permits
30189 empty components for compatibility.
30193 .section "Rewriting addresses" "SECID232"
30194 .cindex "rewriting" "addresses"
30195 Rewriting of sender and recipient addresses, and addresses in headers, can
30196 happen automatically, or as the result of configuration options, as described
30197 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
30198 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
30200 Automatic rewriting includes qualification, as mentioned above. The other case
30201 in which it can happen is when an incomplete non-local domain is given. The
30202 routing process may cause this to be expanded into the full domain name. For
30203 example, a header such as
30207 might get rewritten as
30209 To: hare@teaparty.wonderland.fict.example
30211 Rewriting as a result of routing is the one kind of message processing that
30212 does not happen at input time, as it cannot be done until the address has
30215 Strictly, one should not do &'any'& deliveries of a message until all its
30216 addresses have been routed, in case any of the headers get changed as a
30217 result of routing. However, doing this in practice would hold up many
30218 deliveries for unreasonable amounts of time, just because one address could not
30219 immediately be routed. Exim therefore does not delay other deliveries when
30220 routing of one or more addresses is deferred.
30221 .ecindex IIDmesproc
30225 . ////////////////////////////////////////////////////////////////////////////
30226 . ////////////////////////////////////////////////////////////////////////////
30228 .chapter "SMTP processing" "CHAPSMTP"
30229 .scindex IIDsmtpproc1 "SMTP" "processing details"
30230 .scindex IIDsmtpproc2 "LMTP" "processing details"
30231 Exim supports a number of different ways of using the SMTP protocol, and its
30232 LMTP variant, which is an interactive protocol for transferring messages into a
30233 closed mail store application. This chapter contains details of how SMTP is
30234 processed. For incoming mail, the following are available:
30237 SMTP over TCP/IP (Exim daemon or &'inetd'&);
30239 SMTP over the standard input and output (the &%-bs%& option);
30241 Batched SMTP on the standard input (the &%-bS%& option).
30244 For mail delivery, the following are available:
30247 SMTP over TCP/IP (the &(smtp)& transport);
30249 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
30252 LMTP over a pipe to a process running in the local host (the &(lmtp)&
30255 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
30256 the &%use_bsmtp%& option set).
30259 &'Batched SMTP'& is the name for a process in which batches of messages are
30260 stored in or read from files (or pipes), in a format in which SMTP commands are
30261 used to contain the envelope information.
30265 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
30266 .cindex "SMTP" "outgoing over TCP/IP"
30267 .cindex "outgoing SMTP over TCP/IP"
30268 .cindex "LMTP" "over TCP/IP"
30269 .cindex "outgoing LMTP over TCP/IP"
30272 .cindex "SIZE option on MAIL command"
30273 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
30274 The &%protocol%& option selects which protocol is to be used, but the actual
30275 processing is the same in both cases.
30277 If, in response to its EHLO command, Exim is told that the SIZE
30278 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
30279 command. The value of <&'n'&> is the message size plus the value of the
30280 &%size_addition%& option (default 1024) to allow for additions to the message
30281 such as per-transport header lines, or changes made in a
30282 .cindex "transport" "filter"
30283 .cindex "filter" "transport filter"
30284 transport filter. If &%size_addition%& is set negative, the use of SIZE is
30287 If the remote server advertises support for PIPELINING, Exim uses the
30288 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
30289 required for the transaction.
30291 If the remote server advertises support for the STARTTLS command, and Exim
30292 was built to support TLS encryption, it tries to start a TLS session unless the
30293 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
30295 If the remote server advertises support for the AUTH command, Exim scans
30296 the authenticators configuration for any suitable client settings, as described
30297 in chapter &<<CHAPSMTPAUTH>>&.
30299 .cindex "carriage return"
30301 Responses from the remote host are supposed to be terminated by CR followed by
30302 LF. However, there are known to be hosts that do not send CR characters, so in
30303 order to be able to interwork with such hosts, Exim treats LF on its own as a
30306 If a message contains a number of different addresses, all those with the same
30307 characteristics (for example, the same envelope sender) that resolve to the
30308 same set of hosts, in the same order, are sent in a single SMTP transaction,
30309 even if they are for different domains, unless there are more than the setting
30310 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
30311 they are split into groups containing no more than &%max_rcpt%&s addresses
30312 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
30313 in parallel sessions. The order of hosts with identical MX values is not
30314 significant when checking whether addresses can be batched in this way.
30316 When the &(smtp)& transport suffers a temporary failure that is not
30317 message-related, Exim updates its transport-specific database, which contains
30318 records indexed by host name that remember which messages are waiting for each
30319 particular host. It also updates the retry database with new retry times.
30321 .cindex "hints database" "retry keys"
30322 Exim's retry hints are based on host name plus IP address, so if one address of
30323 a multi-homed host is broken, it will soon be skipped most of the time.
30324 See the next section for more detail about error handling.
30326 .cindex "SMTP" "passed connection"
30327 .cindex "SMTP" "batching over TCP/IP"
30328 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
30329 looks in the hints database for the transport to see if there are any queued
30330 messages waiting for the host to which it is connected. If it finds one, it
30331 creates a new Exim process using the &%-MC%& option (which can only be used by
30332 a process running as root or the Exim user) and passes the TCP/IP socket to it
30333 so that it can deliver another message using the same socket. The new process
30334 does only those deliveries that are routed to the connected host, and may in
30335 turn pass the socket on to a third process, and so on.
30337 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
30338 limit the number of messages sent down a single TCP/IP connection.
30340 .cindex "asterisk" "after IP address"
30341 The second and subsequent messages delivered down an existing connection are
30342 identified in the main log by the addition of an asterisk after the closing
30343 square bracket of the IP address.
30348 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
30349 .cindex "error" "in outgoing SMTP"
30350 .cindex "SMTP" "errors in outgoing"
30351 .cindex "host" "error"
30352 Three different kinds of error are recognized for outgoing SMTP: host errors,
30353 message errors, and recipient errors.
30356 .vitem "&*Host errors*&"
30357 A host error is not associated with a particular message or with a
30358 particular recipient of a message. The host errors are:
30361 Connection refused or timed out,
30363 Any error response code on connection,
30365 Any error response code to EHLO or HELO,
30367 Loss of connection at any time, except after &"."&,
30369 I/O errors at any time,
30371 Timeouts during the session, other than in response to MAIL, RCPT or
30372 the &"."& at the end of the data.
30375 For a host error, a permanent error response on connection, or in response to
30376 EHLO, causes all addresses routed to the host to be failed. Any other host
30377 error causes all addresses to be deferred, and retry data to be created for the
30378 host. It is not tried again, for any message, until its retry time arrives. If
30379 the current set of addresses are not all delivered in this run (to some
30380 alternative host), the message is added to the list of those waiting for this
30381 host, so if it is still undelivered when a subsequent successful delivery is
30382 made to the host, it will be sent down the same SMTP connection.
30384 .vitem "&*Message errors*&"
30385 .cindex "message" "error"
30386 A message error is associated with a particular message when sent to a
30387 particular host, but not with a particular recipient of the message. The
30388 message errors are:
30391 Any error response code to MAIL, DATA, or the &"."& that terminates
30394 Timeout after MAIL,
30396 Timeout or loss of connection after the &"."& that terminates the data. A
30397 timeout after the DATA command itself is treated as a host error, as is loss of
30398 connection at any other time.
30401 For a message error, a permanent error response (5&'xx'&) causes all addresses
30402 to be failed, and a delivery error report to be returned to the sender. A
30403 temporary error response (4&'xx'&), or one of the timeouts, causes all
30404 addresses to be deferred. Retry data is not created for the host, but instead,
30405 a retry record for the combination of host plus message id is created. The
30406 message is not added to the list of those waiting for this host. This ensures
30407 that the failing message will not be sent to this host again until the retry
30408 time arrives. However, other messages that are routed to the host are not
30409 affected, so if it is some property of the message that is causing the error,
30410 it will not stop the delivery of other mail.
30412 If the remote host specified support for the SIZE parameter in its response
30413 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
30414 over-large message will cause a message error because the error arrives as a
30417 .vitem "&*Recipient errors*&"
30418 .cindex "recipient" "error"
30419 A recipient error is associated with a particular recipient of a message. The
30420 recipient errors are:
30423 Any error response to RCPT,
30425 Timeout after RCPT.
30428 For a recipient error, a permanent error response (5&'xx'&) causes the
30429 recipient address to be failed, and a bounce message to be returned to the
30430 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
30431 address to be deferred, and routing retry data to be created for it. This is
30432 used to delay processing of the address in subsequent queue runs, until its
30433 routing retry time arrives. This applies to all messages, but because it
30434 operates only in queue runs, one attempt will be made to deliver a new message
30435 to the failing address before the delay starts to operate. This ensures that,
30436 if the failure is really related to the message rather than the recipient
30437 (&"message too big for this recipient"& is a possible example), other messages
30438 have a chance of getting delivered. If a delivery to the address does succeed,
30439 the retry information gets cleared, so all stuck messages get tried again, and
30440 the retry clock is reset.
30442 The message is not added to the list of those waiting for this host. Use of the
30443 host for other messages is unaffected, and except in the case of a timeout,
30444 other recipients are processed independently, and may be successfully delivered
30445 in the current SMTP session. After a timeout it is of course impossible to
30446 proceed with the session, so all addresses get deferred. However, those other
30447 than the one that failed do not suffer any subsequent retry delays. Therefore,
30448 if one recipient is causing trouble, the others have a chance of getting
30449 through when a subsequent delivery attempt occurs before the failing
30450 recipient's retry time.
30453 In all cases, if there are other hosts (or IP addresses) available for the
30454 current set of addresses (for example, from multiple MX records), they are
30455 tried in this run for any undelivered addresses, subject of course to their
30456 own retry data. In other words, recipient error retry data does not take effect
30457 until the next delivery attempt.
30459 Some hosts have been observed to give temporary error responses to every
30460 MAIL command at certain times (&"insufficient space"& has been seen). It
30461 would be nice if such circumstances could be recognized, and defer data for the
30462 host itself created, but this is not possible within the current Exim design.
30463 What actually happens is that retry data for every (host, message) combination
30466 The reason that timeouts after MAIL and RCPT are treated specially is that
30467 these can sometimes arise as a result of the remote host's verification
30468 procedures. Exim makes this assumption, and treats them as if a temporary error
30469 response had been received. A timeout after &"."& is treated specially because
30470 it is known that some broken implementations fail to recognize the end of the
30471 message if the last character of the last line is a binary zero. Thus, it is
30472 helpful to treat this case as a message error.
30474 Timeouts at other times are treated as host errors, assuming a problem with the
30475 host, or the connection to it. If a timeout after MAIL, RCPT,
30476 or &"."& is really a connection problem, the assumption is that at the next try
30477 the timeout is likely to occur at some other point in the dialogue, causing it
30478 then to be treated as a host error.
30480 There is experimental evidence that some MTAs drop the connection after the
30481 terminating &"."& if they do not like the contents of the message for some
30482 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
30483 should be given. That is why Exim treats this case as a message rather than a
30484 host error, in order not to delay other messages to the same host.
30489 .section "Incoming SMTP messages over TCP/IP" "SECID233"
30490 .cindex "SMTP" "incoming over TCP/IP"
30491 .cindex "incoming SMTP over TCP/IP"
30494 Incoming SMTP messages can be accepted in one of two ways: by running a
30495 listening daemon, or by using &'inetd'&. In the latter case, the entry in
30496 &_/etc/inetd.conf_& should be like this:
30498 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
30500 Exim distinguishes between this case and the case of a locally running user
30501 agent using the &%-bs%& option by checking whether or not the standard input is
30502 a socket. When it is, either the port must be privileged (less than 1024), or
30503 the caller must be root or the Exim user. If any other user passes a socket
30504 with an unprivileged port number, Exim prints a message on the standard error
30505 stream and exits with an error code.
30507 By default, Exim does not make a log entry when a remote host connects or
30508 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
30509 unexpected. It can be made to write such log entries by setting the
30510 &%smtp_connection%& log selector.
30512 .cindex "carriage return"
30514 Commands from the remote host are supposed to be terminated by CR followed by
30515 LF. However, there are known to be hosts that do not send CR characters. In
30516 order to be able to interwork with such hosts, Exim treats LF on its own as a
30518 Furthermore, because common code is used for receiving messages from all
30519 sources, a CR on its own is also interpreted as a line terminator. However, the
30520 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
30522 .cindex "EHLO" "invalid data"
30523 .cindex "HELO" "invalid data"
30524 One area that sometimes gives rise to problems concerns the EHLO or
30525 HELO commands. Some clients send syntactically invalid versions of these
30526 commands, which Exim rejects by default. (This is nothing to do with verifying
30527 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
30528 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
30529 match the broken hosts that send invalid commands.
30531 .cindex "SIZE option on MAIL command"
30532 .cindex "MAIL" "SIZE option"
30533 The amount of disk space available is checked whenever SIZE is received on
30534 a MAIL command, independently of whether &%message_size_limit%& or
30535 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
30536 false. A temporary error is given if there is not enough space. If
30537 &%check_spool_space%& is set, the check is for that amount of space plus the
30538 value given with SIZE, that is, it checks that the addition of the incoming
30539 message will not reduce the space below the threshold.
30541 When a message is successfully received, Exim includes the local message id in
30542 its response to the final &"."& that terminates the data. If the remote host
30543 logs this text it can help with tracing what has happened to a message.
30545 The Exim daemon can limit the number of simultaneous incoming connections it is
30546 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
30547 number of simultaneous incoming connections from a single remote host (see the
30548 &%smtp_accept_max_per_host%& option). Additional connection attempts are
30549 rejected using the SMTP temporary error code 421.
30551 The Exim daemon does not rely on the SIGCHLD signal to detect when a
30552 subprocess has finished, as this can get lost at busy times. Instead, it looks
30553 for completed subprocesses every time it wakes up. Provided there are other
30554 things happening (new incoming calls, starts of queue runs), completed
30555 processes will be noticed and tidied away. On very quiet systems you may
30556 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
30557 it will be noticed when the daemon next wakes up.
30559 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
30560 and can also be set up to reject SMTP calls from non-reserved hosts at times of
30561 high system load &-- for details see the &%smtp_accept_reserve%&,
30562 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
30563 applies in both the daemon and &'inetd'& cases.
30565 Exim normally starts a delivery process for each message received, though this
30566 can be varied by means of the &%-odq%& command line option and the
30567 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
30568 number of simultaneously running delivery processes started in this way from
30569 SMTP input can be limited by the &%smtp_accept_queue%& and
30570 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
30571 subsequently received messages are just put on the input queue without starting
30572 a delivery process.
30574 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
30575 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
30576 started up from the &'inetd'& daemon, because in that case each connection is
30577 handled by an entirely independent Exim process. Control by load average is,
30578 however, available with &'inetd'&.
30580 Exim can be configured to verify addresses in incoming SMTP commands as they
30581 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
30582 to rewrite addresses at this time &-- before any syntax checking is done. See
30583 section &<<SECTrewriteS>>&.
30585 Exim can also be configured to limit the rate at which a client host submits
30586 MAIL and RCPT commands in a single SMTP session. See the
30587 &%smtp_ratelimit_hosts%& option.
30591 .section "Unrecognized SMTP commands" "SECID234"
30592 .cindex "SMTP" "unrecognized commands"
30593 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
30594 commands during a single SMTP connection, it drops the connection after sending
30595 the error response to the last command. The default value for
30596 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
30597 abuse that subvert web servers into making connections to SMTP ports; in these
30598 circumstances, a number of non-SMTP lines are sent first.
30601 .section "Syntax and protocol errors in SMTP commands" "SECID235"
30602 .cindex "SMTP" "syntax errors"
30603 .cindex "SMTP" "protocol errors"
30604 A syntax error is detected if an SMTP command is recognized, but there is
30605 something syntactically wrong with its data, for example, a malformed email
30606 address in a RCPT command. Protocol errors include invalid command
30607 sequencing such as RCPT before MAIL. If Exim receives more than
30608 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
30609 drops the connection after sending the error response to the last command. The
30610 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
30611 broken clients that loop sending bad commands (yes, it has been seen).
30615 .section "Use of non-mail SMTP commands" "SECID236"
30616 .cindex "SMTP" "non-mail commands"
30617 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
30618 DATA. Exim counts such commands, and drops the connection if there are too
30619 many of them in a single SMTP session. This action catches some
30620 denial-of-service attempts and things like repeated failing AUTHs, or a mad
30621 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
30622 defines what &"too many"& means. Its default value is 10.
30624 When a new message is expected, one occurrence of RSET is not counted. This
30625 allows a client to send one RSET between messages (this is not necessary,
30626 but some clients do it). Exim also allows one uncounted occurrence of HELO
30627 or EHLO, and one occurrence of STARTTLS between messages. After
30628 starting up a TLS session, another EHLO is expected, and so it too is not
30631 The first occurrence of AUTH in a connection, or immediately following
30632 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
30633 RCPT, DATA, and QUIT are counted.
30635 You can control which hosts are subject to the limit set by
30636 &%smtp_accept_max_nonmail%& by setting
30637 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
30638 the limit apply to all hosts. This option means that you can exclude any
30639 specific badly-behaved hosts that you have to live with.
30644 .section "The VRFY and EXPN commands" "SECID237"
30645 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
30646 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
30647 appropriate) in order to decide whether the command should be accepted or not.
30648 If no ACL is defined, the command is rejected.
30650 .cindex "VRFY" "processing"
30651 When VRFY is accepted, it runs exactly the same code as when Exim is
30652 called with the &%-bv%& option.
30654 .cindex "EXPN" "processing"
30655 When EXPN is accepted, a single-level expansion of the address is done.
30656 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
30657 than a verification (the &%-bv%& option). If an unqualified local part is given
30658 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
30659 of VRFY and EXPN commands are logged on the main and reject logs, and
30660 VRFY verification failures are logged on the main log for consistency with
30665 .section "The ETRN command" "SECTETRN"
30666 .cindex "ETRN" "processing"
30667 RFC 1985 describes an SMTP command called ETRN that is designed to
30668 overcome the security problems of the TURN command (which has fallen into
30669 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
30670 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
30671 should be accepted or not. If no ACL is defined, the command is rejected.
30673 The ETRN command is concerned with &"releasing"& messages that are awaiting
30674 delivery to certain hosts. As Exim does not organize its message queue by host,
30675 the only form of ETRN that is supported by default is the one where the
30676 text starts with the &"#"& prefix, in which case the remainder of the text is
30677 specific to the SMTP server. A valid ETRN command causes a run of Exim with
30678 the &%-R%& option to happen, with the remainder of the ETRN text as its
30679 argument. For example,
30687 which causes a delivery attempt on all messages with undelivered addresses
30688 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
30689 default), Exim prevents the simultaneous execution of more than one queue run
30690 for the same argument string as a result of an ETRN command. This stops
30691 a misbehaving client from starting more than one queue runner at once.
30693 .cindex "hints database" "ETRN serialization"
30694 Exim implements the serialization by means of a hints database in which a
30695 record is written whenever a process is started by ETRN, and deleted when
30696 the process completes. However, Exim does not keep the SMTP session waiting for
30697 the ETRN process to complete. Once ETRN is accepted, the client is sent
30698 a &"success"& return code. Obviously there is scope for hints records to get
30699 left lying around if there is a system or program crash. To guard against this,
30700 Exim ignores any records that are more than six hours old.
30702 .oindex "&%smtp_etrn_command%&"
30703 For more control over what ETRN does, the &%smtp_etrn_command%& option can
30704 used. This specifies a command that is run whenever ETRN is received,
30705 whatever the form of its argument. For
30708 smtp_etrn_command = /etc/etrn_command $domain \
30709 $sender_host_address
30711 .vindex "&$domain$&"
30712 The string is split up into arguments which are independently expanded. The
30713 expansion variable &$domain$& is set to the argument of the ETRN command,
30714 and no syntax checking is done on the contents of this argument. Exim does not
30715 wait for the command to complete, so its status code is not checked. Exim runs
30716 under its own uid and gid when receiving incoming SMTP, so it is not possible
30717 for it to change them before running the command.
30721 .section "Incoming local SMTP" "SECID238"
30722 .cindex "SMTP" "local incoming"
30723 Some user agents use SMTP to pass messages to their local MTA using the
30724 standard input and output, as opposed to passing the envelope on the command
30725 line and writing the message to the standard input. This is supported by the
30726 &%-bs%& option. This form of SMTP is handled in the same way as incoming
30727 messages over TCP/IP (including the use of ACLs), except that the envelope
30728 sender given in a MAIL command is ignored unless the caller is trusted. In
30729 an ACL you can detect this form of SMTP input by testing for an empty host
30730 identification. It is common to have this as the first line in the ACL that
30731 runs for RCPT commands:
30735 This accepts SMTP messages from local processes without doing any other tests.
30739 .section "Outgoing batched SMTP" "SECTbatchSMTP"
30740 .cindex "SMTP" "batched outgoing"
30741 .cindex "batched SMTP output"
30742 Both the &(appendfile)& and &(pipe)& transports can be used for handling
30743 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
30744 be output in BSMTP format. No SMTP responses are possible for this form of
30745 delivery. All it is doing is using SMTP commands as a way of transmitting the
30746 envelope along with the message.
30748 The message is written to the file or pipe preceded by the SMTP commands
30749 MAIL and RCPT, and followed by a line containing a single dot. Lines in
30750 the message that start with a dot have an extra dot added. The SMTP command
30751 HELO is not normally used. If it is required, the &%message_prefix%& option
30752 can be used to specify it.
30754 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
30755 one recipient address at a time by default. However, you can arrange for them
30756 to handle several addresses at once by setting the &%batch_max%& option. When
30757 this is done for BSMTP, messages may contain multiple RCPT commands. See
30758 chapter &<<CHAPbatching>>& for more details.
30761 When one or more addresses are routed to a BSMTP transport by a router that
30762 sets up a host list, the name of the first host on the list is available to the
30763 transport in the variable &$host$&. Here is an example of such a transport and
30768 driver = manualroute
30769 transport = smtp_appendfile
30770 route_list = domain.example batch.host.example
30774 driver = appendfile
30775 directory = /var/bsmtp/$host
30780 This causes messages addressed to &'domain.example'& to be written in BSMTP
30781 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
30782 message (unless there are more than 1000 recipients).
30786 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
30787 .cindex "SMTP" "batched incoming"
30788 .cindex "batched SMTP input"
30789 The &%-bS%& command line option causes Exim to accept one or more messages by
30790 reading SMTP on the standard input, but to generate no responses. If the caller
30791 is trusted, the senders in the MAIL commands are believed; otherwise the
30792 sender is always the caller of Exim. Unqualified senders and receivers are not
30793 rejected (there seems little point) but instead just get qualified. HELO
30794 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
30795 as NOOP; QUIT quits.
30797 No policy checking is done for BSMTP input. That is, no ACL is run at anytime.
30798 In this respect it is like non-SMTP local input.
30800 If an error is detected while reading a message, including a missing &"."& at
30801 the end, Exim gives up immediately. It writes details of the error to the
30802 standard output in a stylized way that the calling program should be able to
30803 make some use of automatically, for example:
30805 554 Unexpected end of file
30806 Transaction started in line 10
30807 Error detected in line 14
30809 It writes a more verbose version, for human consumption, to the standard error
30812 An error was detected while processing a file of BSMTP input.
30813 The error message was:
30815 501 '>' missing at end of address
30817 The SMTP transaction started in line 10.
30818 The error was detected in line 12.
30819 The SMTP command at fault was:
30821 rcpt to:<malformed@in.com.plete
30823 1 previous message was successfully processed.
30824 The rest of the batch was abandoned.
30826 The return code from Exim is zero only if there were no errors. It is 1 if some
30827 messages were accepted before an error was detected, and 2 if no messages were
30829 .ecindex IIDsmtpproc1
30830 .ecindex IIDsmtpproc2
30834 . ////////////////////////////////////////////////////////////////////////////
30835 . ////////////////////////////////////////////////////////////////////////////
30837 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
30838 "Customizing messages"
30839 When a message fails to be delivered, or remains on the queue for more than a
30840 configured amount of time, Exim sends a message to the original sender, or
30841 to an alternative configured address. The text of these messages is built into
30842 the code of Exim, but it is possible to change it, either by adding a single
30843 string, or by replacing each of the paragraphs by text supplied in a file.
30845 The &'From:'& and &'To:'& header lines are automatically generated; you can
30846 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
30847 option. Exim also adds the line
30849 Auto-Submitted: auto-generated
30851 to all warning and bounce messages,
30854 .section "Customizing bounce messages" "SECID239"
30855 .cindex "customizing" "bounce message"
30856 .cindex "bounce message" "customizing"
30857 If &%bounce_message_text%& is set, its contents are included in the default
30858 message immediately after &"This message was created automatically by mail
30859 delivery software."& The string is not expanded. It is not used if
30860 &%bounce_message_file%& is set.
30862 When &%bounce_message_file%& is set, it must point to a template file for
30863 constructing error messages. The file consists of a series of text items,
30864 separated by lines consisting of exactly four asterisks. If the file cannot be
30865 opened, default text is used and a message is written to the main and panic
30866 logs. If any text item in the file is empty, default text is used for that
30869 .vindex "&$bounce_recipient$&"
30870 .vindex "&$bounce_return_size_limit$&"
30871 Each item of text that is read from the file is expanded, and there are two
30872 expansion variables which can be of use here: &$bounce_recipient$& is set to
30873 the recipient of an error message while it is being created, and
30874 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
30875 option, rounded to a whole number.
30877 The items must appear in the file in the following order:
30880 The first item is included in the headers, and should include at least a
30881 &'Subject:'& header. Exim does not check the syntax of these headers.
30883 The second item forms the start of the error message. After it, Exim lists the
30884 failing addresses with their error messages.
30886 The third item is used to introduce any text from pipe transports that is to be
30887 returned to the sender. It is omitted if there is no such text.
30889 The fourth item is used to introduce the copy of the message that is returned
30890 as part of the error report.
30892 The fifth item is added after the fourth one if the returned message is
30893 truncated because it is bigger than &%return_size_limit%&.
30895 The sixth item is added after the copy of the original message.
30898 The default state (&%bounce_message_file%& unset) is equivalent to the
30899 following file, in which the sixth item is empty. The &'Subject:'& and some
30900 other lines have been split in order to fit them on the page:
30902 Subject: Mail delivery failed
30903 ${if eq{$sender_address}{$bounce_recipient}
30904 {: returning message to sender}}
30906 This message was created automatically by mail delivery software.
30908 A message ${if eq{$sender_address}{$bounce_recipient}
30909 {that you sent }{sent by
30913 }}could not be delivered to all of its recipients.
30914 This is a permanent error. The following address(es) failed:
30916 The following text was generated during the delivery attempt(s):
30918 ------ This is a copy of the message, including all the headers.
30921 ------ The body of the message is $message_size characters long;
30923 ------ $bounce_return_size_limit or so are included here.
30926 .section "Customizing warning messages" "SECTcustwarn"
30927 .cindex "customizing" "warning message"
30928 .cindex "warning of delay" "customizing the message"
30929 The option &%warn_message_file%& can be pointed at a template file for use when
30930 warnings about message delays are created. In this case there are only three
30934 The first item is included in the headers, and should include at least a
30935 &'Subject:'& header. Exim does not check the syntax of these headers.
30937 The second item forms the start of the warning message. After it, Exim lists
30938 the delayed addresses.
30940 The third item then ends the message.
30943 The default state is equivalent to the following file, except that some lines
30944 have been split here, in order to fit them on the page:
30946 Subject: Warning: message $message_exim_id delayed
30947 $warn_message_delay
30949 This message was created automatically by mail delivery software.
30951 A message ${if eq{$sender_address}{$warn_message_recipients}
30952 {that you sent }{sent by
30956 }}has not been delivered to all of its recipients after
30957 more than $warn_message_delay on the queue on $primary_hostname.
30959 The message identifier is: $message_exim_id
30960 The subject of the message is: $h_subject
30961 The date of the message is: $h_date
30963 The following address(es) have not yet been delivered:
30965 No action is required on your part. Delivery attempts will
30966 continue for some time, and this warning may be repeated at
30967 intervals if the message remains undelivered. Eventually the
30968 mail delivery software will give up, and when that happens,
30969 the message will be returned to you.
30971 .vindex "&$warn_message_delay$&"
30972 .vindex "&$warn_message_recipients$&"
30973 However, in the default state the subject and date lines are omitted if no
30974 appropriate headers exist. During the expansion of this file,
30975 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
30976 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
30977 of recipients for the warning message. There may be more than one if there are
30978 multiple addresses with different &%errors_to%& settings on the routers that
30984 . ////////////////////////////////////////////////////////////////////////////
30985 . ////////////////////////////////////////////////////////////////////////////
30987 .chapter "Some common configuration settings" "CHAPcomconreq"
30988 This chapter discusses some configuration settings that seem to be fairly
30989 common. More examples and discussion can be found in the Exim book.
30993 .section "Sending mail to a smart host" "SECID240"
30994 .cindex "smart host" "example router"
30995 If you want to send all mail for non-local domains to a &"smart host"&, you
30996 should replace the default &(dnslookup)& router with a router which does the
30997 routing explicitly:
30999 send_to_smart_host:
31000 driver = manualroute
31001 route_list = !+local_domains smart.host.name
31002 transport = remote_smtp
31004 You can use the smart host's IP address instead of the name if you wish.
31005 If you are using Exim only to submit messages to a smart host, and not for
31006 receiving incoming messages, you can arrange for it to do the submission
31007 synchronously by setting the &%mua_wrapper%& option (see chapter
31008 &<<CHAPnonqueueing>>&).
31013 .section "Using Exim to handle mailing lists" "SECTmailinglists"
31014 .cindex "mailing lists"
31015 Exim can be used to run simple mailing lists, but for large and/or complicated
31016 requirements, the use of additional specialized mailing list software such as
31017 Majordomo or Mailman is recommended.
31019 The &(redirect)& router can be used to handle mailing lists where each list
31020 is maintained in a separate file, which can therefore be managed by an
31021 independent manager. The &%domains%& router option can be used to run these
31022 lists in a separate domain from normal mail. For example:
31026 domains = lists.example
31027 file = /usr/lists/$local_part
31030 errors_to = $local_part-request@lists.example
31033 This router is skipped for domains other than &'lists.example'&. For addresses
31034 in that domain, it looks for a file that matches the local part. If there is no
31035 such file, the router declines, but because &%no_more%& is set, no subsequent
31036 routers are tried, and so the whole delivery fails.
31038 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
31039 expanded into a file name or a pipe delivery, which is usually inappropriate in
31042 .oindex "&%errors_to%&"
31043 The &%errors_to%& option specifies that any delivery errors caused by addresses
31044 taken from a mailing list are to be sent to the given address rather than the
31045 original sender of the message. However, before acting on this, Exim verifies
31046 the error address, and ignores it if verification fails.
31048 For example, using the configuration above, mail sent to
31049 &'dicts@lists.example'& is passed on to those addresses contained in
31050 &_/usr/lists/dicts_&, with error reports directed to
31051 &'dicts-request@lists.example'&, provided that this address can be verified.
31052 There could be a file called &_/usr/lists/dicts-request_& containing
31053 the address(es) of this particular list's manager(s), but other approaches,
31054 such as setting up an earlier router (possibly using the &%local_part_prefix%&
31055 or &%local_part_suffix%& options) to handle addresses of the form
31056 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
31060 .section "Syntax errors in mailing lists" "SECID241"
31061 .cindex "mailing lists" "syntax errors in"
31062 If an entry in redirection data contains a syntax error, Exim normally defers
31063 delivery of the original address. That means that a syntax error in a mailing
31064 list holds up all deliveries to the list. This may not be appropriate when a
31065 list is being maintained automatically from data supplied by users, and the
31066 addresses are not rigorously checked.
31068 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
31069 entries that fail to parse, noting the incident in the log. If in addition
31070 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
31071 whenever a broken address is skipped. It is usually appropriate to set
31072 &%syntax_errors_to%& to the same address as &%errors_to%&.
31076 .section "Re-expansion of mailing lists" "SECID242"
31077 .cindex "mailing lists" "re-expansion of"
31078 Exim remembers every individual address to which a message has been delivered,
31079 in order to avoid duplication, but it normally stores only the original
31080 recipient addresses with a message. If all the deliveries to a mailing list
31081 cannot be done at the first attempt, the mailing list is re-expanded when the
31082 delivery is next tried. This means that alterations to the list are taken into
31083 account at each delivery attempt, so addresses that have been added to
31084 the list since the message arrived will therefore receive a copy of the
31085 message, even though it pre-dates their subscription.
31087 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
31088 on the &(redirect)& router. If this is done, any addresses generated by the
31089 router that fail to deliver at the first attempt are added to the message as
31090 &"top level"& addresses, and the parent address that generated them is marked
31091 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
31092 subsequent delivery attempts. The disadvantage of this is that if any of the
31093 failing addresses are incorrect, correcting them in the file has no effect on
31094 pre-existing messages.
31096 The original top-level address is remembered with each of the generated
31097 addresses, and is output in any log messages. However, any intermediate parent
31098 addresses are not recorded. This makes a difference to the log only if the
31099 &%all_parents%& selector is set, but for mailing lists there is normally only
31100 one level of expansion anyway.
31104 .section "Closed mailing lists" "SECID243"
31105 .cindex "mailing lists" "closed"
31106 The examples so far have assumed open mailing lists, to which anybody may
31107 send mail. It is also possible to set up closed lists, where mail is accepted
31108 from specified senders only. This is done by making use of the generic
31109 &%senders%& option to restrict the router that handles the list.
31111 The following example uses the same file as a list of recipients and as a list
31112 of permitted senders. It requires three routers:
31116 domains = lists.example
31117 local_part_suffix = -request
31118 file = /usr/lists/$local_part$local_part_suffix
31123 domains = lists.example
31124 senders = ${if exists {/usr/lists/$local_part}\
31125 {lsearch;/usr/lists/$local_part}{*}}
31126 file = /usr/lists/$local_part
31129 errors_to = $local_part-request@lists.example
31134 domains = lists.example
31136 data = :fail: $local_part@lists.example is a closed mailing list
31138 All three routers have the same &%domains%& setting, so for any other domains,
31139 they are all skipped. The first router runs only if the local part ends in
31140 &%-request%&. It handles messages to the list manager(s) by means of an open
31143 The second router runs only if the &%senders%& precondition is satisfied. It
31144 checks for the existence of a list that corresponds to the local part, and then
31145 checks that the sender is on the list by means of a linear search. It is
31146 necessary to check for the existence of the file before trying to search it,
31147 because otherwise Exim thinks there is a configuration error. If the file does
31148 not exist, the expansion of &%senders%& is *, which matches all senders. This
31149 means that the router runs, but because there is no list, declines, and
31150 &%no_more%& ensures that no further routers are run. The address fails with an
31151 &"unrouteable address"& error.
31153 The third router runs only if the second router is skipped, which happens when
31154 a mailing list exists, but the sender is not on it. This router forcibly fails
31155 the address, giving a suitable error message.
31160 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
31162 .cindex "Variable Envelope Return Paths"
31163 .cindex "envelope sender"
31164 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
31165 are a way of helping mailing list administrators discover which subscription
31166 address is the cause of a particular delivery failure. The idea is to encode
31167 the original recipient address in the outgoing envelope sender address, so that
31168 if the message is forwarded by another host and then subsequently bounces, the
31169 original recipient can be extracted from the recipient address of the bounce.
31171 .oindex &%errors_to%&
31172 .oindex &%return_path%&
31173 Envelope sender addresses can be modified by Exim using two different
31174 facilities: the &%errors_to%& option on a router (as shown in previous mailing
31175 list examples), or the &%return_path%& option on a transport. The second of
31176 these is effective only if the message is successfully delivered to another
31177 host; it is not used for errors detected on the local host (see the description
31178 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
31179 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
31185 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
31186 {$1-request+$local_part=$domain@your.dom.example}fail}
31188 This has the effect of rewriting the return path (envelope sender) on outgoing
31189 SMTP messages, if the local part of the original return path ends in
31190 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
31191 local part and domain of the recipient into the return path. Suppose, for
31192 example, that a message whose return path has been set to
31193 &'somelist-request@your.dom.example'& is sent to
31194 &'subscriber@other.dom.example'&. In the transport, the return path is
31197 somelist-request+subscriber=other.dom.example@your.dom.example
31199 .vindex "&$local_part$&"
31200 For this to work, you must tell Exim to send multiple copies of messages that
31201 have more than one recipient, so that each copy has just one recipient. This is
31202 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
31203 might be sent to several different recipients in the same domain, in which case
31204 &$local_part$& is not available in the transport, because it is not unique.
31206 Unless your host is doing nothing but mailing list deliveries, you should
31207 probably use a separate transport for the VERP deliveries, so as not to use
31208 extra resources in making one-per-recipient copies for other deliveries. This
31209 can easily be done by expanding the &%transport%& option in the router:
31213 domains = ! +local_domains
31215 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
31216 {verp_smtp}{remote_smtp}}
31219 If you want to change the return path using &%errors_to%& in a router instead
31220 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
31221 routers that handle mailing list addresses. This will ensure that all delivery
31222 errors, including those detected on the local host, are sent to the VERP
31225 On a host that does no local deliveries and has no manual routing, only the
31226 &(dnslookup)& router needs to be changed. A special transport is not needed for
31227 SMTP deliveries. Every mailing list recipient has its own return path value,
31228 and so Exim must hand them to the transport one at a time. Here is an example
31229 of a &(dnslookup)& router that implements VERP:
31233 domains = ! +local_domains
31234 transport = remote_smtp
31236 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
31237 {$1-request+$local_part=$domain@your.dom.example}fail}
31240 Before you start sending out messages with VERPed return paths, you must also
31241 configure Exim to accept the bounce messages that come back to those paths.
31242 Typically this is done by setting a &%local_part_suffix%& option for a
31243 router, and using this to route the messages to wherever you want to handle
31246 The overhead incurred in using VERP depends very much on the size of the
31247 message, the number of recipient addresses that resolve to the same remote
31248 host, and the speed of the connection over which the message is being sent. If
31249 a lot of addresses resolve to the same host and the connection is slow, sending
31250 a separate copy of the message for each address may take substantially longer
31251 than sending a single copy with many recipients (for which VERP cannot be
31259 .section "Virtual domains" "SECTvirtualdomains"
31260 .cindex "virtual domains"
31261 .cindex "domain" "virtual"
31262 The phrase &'virtual domain'& is unfortunately used with two rather different
31266 A domain for which there are no real mailboxes; all valid local parts are
31267 aliases for other email addresses. Common examples are organizational
31268 top-level domains and &"vanity"& domains.
31270 One of a number of independent domains that are all handled by the same host,
31271 with mailboxes on that host, but where the mailbox owners do not necessarily
31272 have login accounts on that host.
31275 The first usage is probably more common, and does seem more &"virtual"& than
31276 the second. This kind of domain can be handled in Exim with a straightforward
31277 aliasing router. One approach is to create a separate alias file for each
31278 virtual domain. Exim can test for the existence of the alias file to determine
31279 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
31280 to a router of this form:
31284 domains = dsearch;/etc/mail/virtual
31285 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
31288 The &%domains%& option specifies that the router is to be skipped, unless there
31289 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
31290 domain that is being processed. When the router runs, it looks up the local
31291 part in the file to find a new address (or list of addresses). The &%no_more%&
31292 setting ensures that if the lookup fails (leading to &%data%& being an empty
31293 string), Exim gives up on the address without trying any subsequent routers.
31295 This one router can handle all the virtual domains because the alias file names
31296 follow a fixed pattern. Permissions can be arranged so that appropriate people
31297 can edit the different alias files. A successful aliasing operation results in
31298 a new envelope recipient address, which is then routed from scratch.
31300 The other kind of &"virtual"& domain can also be handled in a straightforward
31301 way. One approach is to create a file for each domain containing a list of
31302 valid local parts, and use it in a router like this:
31306 domains = dsearch;/etc/mail/domains
31307 local_parts = lsearch;/etc/mail/domains/$domain
31308 transport = my_mailboxes
31310 The address is accepted if there is a file for the domain, and the local part
31311 can be found in the file. The &%domains%& option is used to check for the
31312 file's existence because &%domains%& is tested before the &%local_parts%&
31313 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
31314 because that option is tested after &%local_parts%&. The transport is as
31318 driver = appendfile
31319 file = /var/mail/$domain/$local_part
31322 This uses a directory of mailboxes for each domain. The &%user%& setting is
31323 required, to specify which uid is to be used for writing to the mailboxes.
31325 The configuration shown here is just one example of how you might support this
31326 requirement. There are many other ways this kind of configuration can be set
31327 up, for example, by using a database instead of separate files to hold all the
31328 information about the domains.
31332 .section "Multiple user mailboxes" "SECTmulbox"
31333 .cindex "multiple mailboxes"
31334 .cindex "mailbox" "multiple"
31335 .cindex "local part" "prefix"
31336 .cindex "local part" "suffix"
31337 Heavy email users often want to operate with multiple mailboxes, into which
31338 incoming mail is automatically sorted. A popular way of handling this is to
31339 allow users to use multiple sender addresses, so that replies can easily be
31340 identified. Users are permitted to add prefixes or suffixes to their local
31341 parts for this purpose. The wildcard facility of the generic router options
31342 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
31343 example, consider this router:
31348 file = $home/.forward
31349 local_part_suffix = -*
31350 local_part_suffix_optional
31353 .vindex "&$local_part_suffix$&"
31354 It runs a user's &_.forward_& file for all local parts of the form
31355 &'username-*'&. Within the filter file the user can distinguish different
31356 cases by testing the variable &$local_part_suffix$&. For example:
31358 if $local_part_suffix contains -special then
31359 save /home/$local_part/Mail/special
31362 If the filter file does not exist, or does not deal with such addresses, they
31363 fall through to subsequent routers, and, assuming no subsequent use of the
31364 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
31365 control over which suffixes are valid.
31367 Alternatively, a suffix can be used to trigger the use of a different
31368 &_.forward_& file &-- which is the way a similar facility is implemented in
31374 file = $home/.forward$local_part_suffix
31375 local_part_suffix = -*
31376 local_part_suffix_optional
31379 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
31380 example, &_.forward-special_& is used. Once again, if the appropriate file
31381 does not exist, or does not deal with the address, it is passed on to
31382 subsequent routers, which could, if required, look for an unqualified
31383 &_.forward_& file to use as a default.
31387 .section "Simplified vacation processing" "SECID244"
31388 .cindex "vacation processing"
31389 The traditional way of running the &'vacation'& program is for a user to set up
31390 a pipe command in a &_.forward_& file
31391 (see section &<<SECTspecitredli>>& for syntax details).
31392 This is prone to error by inexperienced users. There are two features of Exim
31393 that can be used to make this process simpler for users:
31396 A local part prefix such as &"vacation-"& can be specified on a router which
31397 can cause the message to be delivered directly to the &'vacation'& program, or
31398 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
31399 &_.forward_& file are then much simpler. For example:
31401 spqr, vacation-spqr
31404 The &%require_files%& generic router option can be used to trigger a
31405 vacation delivery by checking for the existence of a certain file in the
31406 user's home directory. The &%unseen%& generic option should also be used, to
31407 ensure that the original delivery also proceeds. In this case, all the user has
31408 to do is to create a file called, say, &_.vacation_&, containing a vacation
31412 Another advantage of both these methods is that they both work even when the
31413 use of arbitrary pipes by users is locked out.
31417 .section "Taking copies of mail" "SECID245"
31418 .cindex "message" "copying every"
31419 Some installations have policies that require archive copies of all messages to
31420 be made. A single copy of each message can easily be taken by an appropriate
31421 command in a system filter, which could, for example, use a different file for
31422 each day's messages.
31424 There is also a shadow transport mechanism that can be used to take copies of
31425 messages that are successfully delivered by local transports, one copy per
31426 delivery. This could be used, &'inter alia'&, to implement automatic
31427 notification of delivery by sites that insist on doing such things.
31431 .section "Intermittently connected hosts" "SECID246"
31432 .cindex "intermittently connected hosts"
31433 It has become quite common (because it is cheaper) for hosts to connect to the
31434 Internet periodically rather than remain connected all the time. The normal
31435 arrangement is that mail for such hosts accumulates on a system that is
31436 permanently connected.
31438 Exim was designed for use on permanently connected hosts, and so it is not
31439 particularly well-suited to use in an intermittently connected environment.
31440 Nevertheless there are some features that can be used.
31443 .section "Exim on the upstream server host" "SECID247"
31444 It is tempting to arrange for incoming mail for the intermittently connected
31445 host to remain on Exim's queue until the client connects. However, this
31446 approach does not scale very well. Two different kinds of waiting message are
31447 being mixed up in the same queue &-- those that cannot be delivered because of
31448 some temporary problem, and those that are waiting for their destination host
31449 to connect. This makes it hard to manage the queue, as well as wasting
31450 resources, because each queue runner scans the entire queue.
31452 A better approach is to separate off those messages that are waiting for an
31453 intermittently connected host. This can be done by delivering these messages
31454 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
31455 format, from where they are transmitted by other software when their
31456 destination connects. This makes it easy to collect all the mail for one host
31457 in a single directory, and to apply local timeout rules on a per-message basis
31460 On a very small scale, leaving the mail on Exim's queue can be made to work. If
31461 you are doing this, you should configure Exim with a long retry period for the
31462 intermittent host. For example:
31464 cheshire.wonderland.fict.example * F,5d,24h
31466 This stops a lot of failed delivery attempts from occurring, but Exim remembers
31467 which messages it has queued up for that host. Once the intermittent host comes
31468 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
31469 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
31470 causes all the queued up messages to be delivered, often down a single SMTP
31471 connection. While the host remains connected, any new messages get delivered
31474 If the connecting hosts do not have fixed IP addresses, that is, if a host is
31475 issued with a different IP address each time it connects, Exim's retry
31476 mechanisms on the holding host get confused, because the IP address is normally
31477 used as part of the key string for holding retry information. This can be
31478 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
31479 Since this has disadvantages for permanently connected hosts, it is best to
31480 arrange a separate transport for the intermittently connected ones.
31484 .section "Exim on the intermittently connected client host" "SECID248"
31485 The value of &%smtp_accept_queue_per_connection%& should probably be
31486 increased, or even set to zero (that is, disabled) on the intermittently
31487 connected host, so that all incoming messages down a single connection get
31488 delivered immediately.
31490 .cindex "SMTP" "passed connection"
31491 .cindex "SMTP" "multiple deliveries"
31492 .cindex "multiple SMTP deliveries"
31493 Mail waiting to be sent from an intermittently connected host will probably
31494 not have been routed, because without a connection DNS lookups are not
31495 possible. This means that if a normal queue run is done at connection time,
31496 each message is likely to be sent in a separate SMTP session. This can be
31497 avoided by starting the queue run with a command line option beginning with
31498 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
31499 first pass, routing is done but no deliveries take place. The second pass is a
31500 normal queue run; since all the messages have been previously routed, those
31501 destined for the same host are likely to get sent as multiple deliveries in a
31502 single SMTP connection.
31506 . ////////////////////////////////////////////////////////////////////////////
31507 . ////////////////////////////////////////////////////////////////////////////
31509 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
31510 "Exim as a non-queueing client"
31511 .cindex "client, non-queueing"
31512 .cindex "smart host" "suppressing queueing"
31513 On a personal computer, it is a common requirement for all
31514 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
31515 configured to operate that way, for all the popular operating systems.
31516 However, there are some MUAs for Unix-like systems that cannot be so
31517 configured: they submit messages using the command line interface of
31518 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
31521 If the personal computer runs continuously, there is no problem, because it can
31522 run a conventional MTA that handles delivery to the smart host, and deal with
31523 any delays via its queueing mechanism. However, if the computer does not run
31524 continuously or runs different operating systems at different times, queueing
31525 email is not desirable.
31527 There is therefore a requirement for something that can provide the
31528 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
31529 any queueing or retrying facilities. Furthermore, the delivery to the smart
31530 host should be synchronous, so that if it fails, the sending MUA is immediately
31531 informed. In other words, we want something that extends an MUA that submits
31532 to a local MTA via the command line so that it behaves like one that submits
31533 to a remote smart host using TCP/SMTP.
31535 There are a number of applications (for example, there is one called &'ssmtp'&)
31536 that do this job. However, people have found them to be lacking in various
31537 ways. For instance, you might want to allow aliasing and forwarding to be done
31538 before sending a message to the smart host.
31540 Exim already had the necessary infrastructure for doing this job. Just a few
31541 tweaks were needed to make it behave as required, though it is somewhat of an
31542 overkill to use a fully-featured MTA for this purpose.
31544 .oindex "&%mua_wrapper%&"
31545 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
31546 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
31547 assumes that it is being used to &"wrap"& a command-line MUA in the manner
31548 just described. As well as setting &%mua_wrapper%&, you also need to provide a
31549 compatible router and transport configuration. Typically there will be just one
31550 router and one transport, sending everything to a smart host.
31552 When run in MUA wrapping mode, the behaviour of Exim changes in the
31556 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
31557 In other words, the only way to submit messages is via the command line.
31559 Each message is synchronously delivered as soon as it is received (&%-odi%& is
31560 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
31561 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
31562 does not finish until the delivery attempt is complete. If the delivery is
31563 successful, a zero return code is given.
31565 Address redirection is permitted, but the final routing for all addresses must
31566 be to the same remote transport, and to the same list of hosts. Furthermore,
31567 the return address (envelope sender) must be the same for all recipients, as
31568 must any added or deleted header lines. In other words, it must be possible to
31569 deliver the message in a single SMTP transaction, however many recipients there
31572 If these conditions are not met, or if routing any address results in a
31573 failure or defer status, or if Exim is unable to deliver all the recipients
31574 successfully to one of the smart hosts, delivery of the entire message fails.
31576 Because no queueing is allowed, all failures are treated as permanent; there
31577 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
31578 smart host. Furthermore, because only a single yes/no response can be given to
31579 the caller, it is not possible to deliver to some recipients and not others. If
31580 there is an error (temporary or permanent) for any recipient, all are failed.
31582 If more than one smart host is listed, Exim will try another host after a
31583 connection failure or a timeout, in the normal way. However, if this kind of
31584 failure happens for all the hosts, the delivery fails.
31586 When delivery fails, an error message is written to the standard error stream
31587 (as well as to Exim's log), and Exim exits to the caller with a return code
31588 value 1. The message is expunged from Exim's spool files. No bounce messages
31589 are ever generated.
31591 No retry data is maintained, and any retry rules are ignored.
31593 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
31594 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
31595 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
31598 The overall effect is that Exim makes a single synchronous attempt to deliver
31599 the message, failing if there is any kind of problem. Because no local
31600 deliveries are done and no daemon can be run, Exim does not need root
31601 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
31602 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
31603 the advantages and disadvantages of running without root privilege.
31608 . ////////////////////////////////////////////////////////////////////////////
31609 . ////////////////////////////////////////////////////////////////////////////
31611 .chapter "Log files" "CHAPlog"
31612 .scindex IIDloggen "log" "general description"
31613 .cindex "log" "types of"
31614 Exim writes three different logs, referred to as the main log, the reject log,
31619 The main log records the arrival of each message and each delivery in a single
31620 line in each case. The format is as compact as possible, in an attempt to keep
31621 down the size of log files. Two-character flag sequences make it easy to pick
31622 out these lines. A number of other events are recorded in the main log. Some of
31623 them are optional, in which case the &%log_selector%& option controls whether
31624 they are included or not. A Perl script called &'eximstats'&, which does simple
31625 analysis of main log files, is provided in the Exim distribution (see section
31626 &<<SECTmailstat>>&).
31628 .cindex "reject log"
31629 The reject log records information from messages that are rejected as a result
31630 of a configuration option (that is, for policy reasons).
31631 The first line of each rejection is a copy of the line that is also written to
31632 the main log. Then, if the message's header has been read at the time the log
31633 is written, its contents are written to this log. Only the original header
31634 lines are available; header lines added by ACLs are not logged. You can use the
31635 reject log to check that your policy controls are working correctly; on a busy
31636 host this may be easier than scanning the main log for rejection messages. You
31637 can suppress the writing of the reject log by setting &%write_rejectlog%&
31640 .cindex "panic log"
31641 .cindex "system log"
31642 When certain serious errors occur, Exim writes entries to its panic log. If the
31643 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
31644 are usually written to the main log as well, but can get lost amid the mass of
31645 other entries. The panic log should be empty under normal circumstances. It is
31646 therefore a good idea to check it (or to have a &'cron'& script check it)
31647 regularly, in order to become aware of any problems. When Exim cannot open its
31648 panic log, it tries as a last resort to write to the system log (syslog). This
31649 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
31650 message itself is written at priority LOG_CRIT.
31653 Every log line starts with a timestamp, in the format shown in the following
31654 example. Note that many of the examples shown in this chapter are line-wrapped.
31655 In the log file, this would be all on one line:
31657 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
31660 By default, the timestamps are in the local timezone. There are two
31661 ways of changing this:
31664 You can set the &%timezone%& option to a different time zone; in particular, if
31669 the timestamps will be in UTC (aka GMT).
31671 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
31674 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
31678 .cindex "log" "process ids in"
31679 .cindex "pid (process id)" "in log lines"
31680 Exim does not include its process id in log lines by default, but you can
31681 request that it does so by specifying the &`pid`& log selector (see section
31682 &<<SECTlogselector>>&). When this is set, the process id is output, in square
31683 brackets, immediately after the time and date.
31688 .section "Where the logs are written" "SECTwhelogwri"
31689 .cindex "log" "destination"
31690 .cindex "log" "to file"
31691 .cindex "log" "to syslog"
31693 The logs may be written to local files, or to syslog, or both. However, it
31694 should be noted that many syslog implementations use UDP as a transport, and
31695 are therefore unreliable in the sense that messages are not guaranteed to
31696 arrive at the loghost, nor is the ordering of messages necessarily maintained.
31697 It has also been reported that on large log files (tens of megabytes) you may
31698 need to tweak syslog to prevent it syncing the file with each write &-- on
31699 Linux this has been seen to make syslog take 90% plus of CPU time.
31701 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
31702 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
31703 configuration. This latter string is expanded, so it can contain, for example,
31704 references to the host name:
31706 log_file_path = /var/log/$primary_hostname/exim_%slog
31708 It is generally advisable, however, to set the string in &_Local/Makefile_&
31709 rather than at run time, because then the setting is available right from the
31710 start of Exim's execution. Otherwise, if there's something it wants to log
31711 before it has read the configuration file (for example, an error in the
31712 configuration file) it will not use the path you want, and may not be able to
31715 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
31716 list, currently limited to at most two items. This is one option where the
31717 facility for changing a list separator may not be used. The list must always be
31718 colon-separated. If an item in the list is &"syslog"& then syslog is used;
31719 otherwise the item must either be an absolute path, containing &`%s`& at the
31720 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
31721 implying the use of a default path.
31723 When Exim encounters an empty item in the list, it searches the list defined by
31724 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
31725 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
31726 mean &"use the path specified at build time"&. It no such item exists, log
31727 files are written in the &_log_& subdirectory of the spool directory. This is
31728 equivalent to the setting:
31730 log_file_path = $spool_directory/log/%slog
31732 If you do not specify anything at build time or run time, that is where the
31735 A log file path may also contain &`%D`& if datestamped log file names are in
31736 use &-- see section &<<SECTdatlogfil>>& below.
31738 Here are some examples of possible settings:
31740 &`LOG_FILE_PATH=syslog `& syslog only
31741 &`LOG_FILE_PATH=:syslog `& syslog and default path
31742 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
31743 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
31745 If there are more than two paths in the list, the first is used and a panic
31750 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
31751 .cindex "log" "cycling local files"
31752 .cindex "cycling logs"
31753 .cindex "&'exicyclog'&"
31754 .cindex "log" "local files; writing to"
31755 Some operating systems provide centralized and standardized methods for cycling
31756 log files. For those that do not, a utility script called &'exicyclog'& is
31757 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
31758 main and reject logs each time it is called. The maximum number of old logs to
31759 keep can be set. It is suggested this script is run as a daily &'cron'& job.
31761 An Exim delivery process opens the main log when it first needs to write to it,
31762 and it keeps the file open in case subsequent entries are required &-- for
31763 example, if a number of different deliveries are being done for the same
31764 message. However, remote SMTP deliveries can take a long time, and this means
31765 that the file may be kept open long after it is renamed if &'exicyclog'& or
31766 something similar is being used to rename log files on a regular basis. To
31767 ensure that a switch of log files is noticed as soon as possible, Exim calls
31768 &[stat()]& on the main log's name before reusing an open file, and if the file
31769 does not exist, or its inode has changed, the old file is closed and Exim
31770 tries to open the main log from scratch. Thus, an old log file may remain open
31771 for quite some time, but no Exim processes should write to it once it has been
31776 .section "Datestamped log files" "SECTdatlogfil"
31777 .cindex "log" "datestamped files"
31778 Instead of cycling the main and reject log files by renaming them
31779 periodically, some sites like to use files whose names contain a datestamp,
31780 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_&.
31781 Exim has support for this way of working. It is enabled by setting the
31782 &%log_file_path%& option to a path that includes &`%D`& at the point where the
31783 datestamp is required. For example:
31785 log_file_path = /var/spool/exim/log/%slog-%D
31786 log_file_path = /var/log/exim-%s-%D.log
31787 log_file_path = /var/spool/exim/log/%D-%slog
31789 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
31790 examples of names generated by the above examples:
31792 /var/spool/exim/log/mainlog-20021225
31793 /var/log/exim-reject-20021225.log
31794 /var/spool/exim/log/20021225-mainlog
31796 When this form of log file is specified, Exim automatically switches to new
31797 files at midnight. It does not make any attempt to compress old logs; you
31798 will need to write your own script if you require this. You should not
31799 run &'exicyclog'& with this form of logging.
31801 The location of the panic log is also determined by &%log_file_path%&, but it
31802 is not datestamped, because rotation of the panic log does not make sense.
31803 When generating the name of the panic log, &`%D`& is removed from the string.
31804 In addition, if it immediately follows a slash, a following non-alphanumeric
31805 character is removed; otherwise a preceding non-alphanumeric character is
31806 removed. Thus, the three examples above would give these panic log names:
31808 /var/spool/exim/log/paniclog
31809 /var/log/exim-panic.log
31810 /var/spool/exim/log/paniclog
31814 .section "Logging to syslog" "SECID249"
31815 .cindex "log" "syslog; writing to"
31816 The use of syslog does not change what Exim logs or the format of its messages,
31817 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
31818 Exim's log lines are omitted when these lines are sent to syslog. Apart from
31819 that, the same strings are written to syslog as to log files. The syslog
31820 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
31821 by default, but you can change these by setting the &%syslog_facility%& and
31822 &%syslog_processname%& options, respectively. If Exim was compiled with
31823 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
31824 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
31825 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
31826 the time and host name to each line.
31827 The three log streams are mapped onto syslog priorities as follows:
31830 &'mainlog'& is mapped to LOG_INFO
31832 &'rejectlog'& is mapped to LOG_NOTICE
31834 &'paniclog'& is mapped to LOG_ALERT
31837 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
31838 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
31839 these are routed by syslog to the same place. You can suppress this duplication
31840 by setting &%syslog_duplication%& false.
31842 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
31843 entries contain multiple lines when headers are included. To cope with both
31844 these cases, entries written to syslog are split into separate &[syslog()]&
31845 calls at each internal newline, and also after a maximum of
31846 870 data characters. (This allows for a total syslog line length of 1024, when
31847 additions such as timestamps are added.) If you are running a syslog
31848 replacement that can handle lines longer than the 1024 characters allowed by
31849 RFC 3164, you should set
31851 SYSLOG_LONG_LINES=yes
31853 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
31854 lines, but it still splits at internal newlines in &'reject'& log entries.
31856 To make it easy to re-assemble split lines later, each component of a split
31857 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
31858 where <&'n'&> is the component number and <&'m'&> is the total number of
31859 components in the entry. The / delimiter is used when the line was split
31860 because it was too long; if it was split because of an internal newline, the \
31861 delimiter is used. For example, supposing the length limit to be 50 instead of
31862 870, the following would be the result of a typical rejection message to
31863 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
31864 name, and pid as added by syslog:
31866 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
31867 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
31868 [3/5] when scanning for sender: missing or malformed lo
31869 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
31872 The same error might cause the following lines to be written to &"rejectlog"&
31875 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
31876 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
31877 [3/18] er when scanning for sender: missing or malformed
31878 [4/18] local part in "<>" (envelope sender is <ph10@cam
31880 [6\18] Recipients: ph10@some.domain.cam.example
31881 [7\18] P Received: from [127.0.0.1] (ident=ph10)
31882 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
31883 [9\18] id 16RdAL-0006pc-00
31884 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
31885 [11\18] 09:43 +0100
31887 [13\18] Subject: this is a test header
31888 [18\18] X-something: this is another header
31889 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
31892 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
31894 Log lines that are neither too long nor contain newlines are written to syslog
31895 without modification.
31897 If only syslog is being used, the Exim monitor is unable to provide a log tail
31898 display, unless syslog is routing &'mainlog'& to a file on the local host and
31899 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
31904 .section "Log line flags" "SECID250"
31905 One line is written to the main log for each message received, and for each
31906 successful, unsuccessful, and delayed delivery. These lines can readily be
31907 picked out by the distinctive two-character flags that immediately follow the
31908 timestamp. The flags are:
31910 &`<=`& message arrival
31911 &`=>`& normal message delivery
31912 &`->`& additional address in same delivery
31913 &`*>`& delivery suppressed by &%-N%&
31914 &`**`& delivery failed; address bounced
31915 &`==`& delivery deferred; temporary problem
31919 .section "Logging message reception" "SECID251"
31920 .cindex "log" "reception line"
31921 The format of the single-line entry in the main log that is written for every
31922 message received is shown in the basic example below, which is split over
31923 several lines in order to fit it on the page:
31925 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
31926 H=mailer.fict.example [192.168.123.123] U=exim
31927 P=smtp S=5678 id=<incoming message id>
31929 The address immediately following &"<="& is the envelope sender address. A
31930 bounce message is shown with the sender address &"<>"&, and if it is locally
31931 generated, this is followed by an item of the form
31935 which is a reference to the message that caused the bounce to be sent.
31939 For messages from other hosts, the H and U fields identify the remote host and
31940 record the RFC 1413 identity of the user that sent the message, if one was
31941 received. The number given in square brackets is the IP address of the sending
31942 host. If there is a single, unparenthesized host name in the H field, as
31943 above, it has been verified to correspond to the IP address (see the
31944 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
31945 by the remote host in the SMTP HELO or EHLO command, and has not been
31946 verified. If verification yields a different name to that given for HELO or
31947 EHLO, the verified name appears first, followed by the HELO or EHLO
31948 name in parentheses.
31950 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
31951 without brackets, in the HELO or EHLO command, leading to entries in
31952 the log containing text like these examples:
31954 H=(10.21.32.43) [192.168.8.34]
31955 H=([10.21.32.43]) [192.168.8.34]
31957 This can be confusing. Only the final address in square brackets can be relied
31960 For locally generated messages (that is, messages not received over TCP/IP),
31961 the H field is omitted, and the U field contains the login name of the caller
31964 .cindex "authentication" "logging"
31965 .cindex "AUTH" "logging"
31966 For all messages, the P field specifies the protocol used to receive the
31967 message. This is the value that is stored in &$received_protocol$&. In the case
31968 of incoming SMTP messages, the value indicates whether or not any SMTP
31969 extensions (ESMTP), encryption, or authentication were used. If the SMTP
31970 session was encrypted, there is an additional X field that records the cipher
31971 suite that was used.
31973 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
31974 hosts that have authenticated themselves using the SMTP AUTH command. The first
31975 value is used when the SMTP connection was encrypted (&"secure"&). In this case
31976 there is an additional item A= followed by the name of the authenticator that
31977 was used. If an authenticated identification was set up by the authenticator's
31978 &%server_set_id%& option, this is logged too, separated by a colon from the
31979 authenticator name.
31981 .cindex "size" "of message"
31982 The id field records the existing message id, if present. The size of the
31983 received message is given by the S field. When the message is delivered,
31984 headers may be removed or added, so that the size of delivered copies of the
31985 message may not correspond with this value (and indeed may be different to each
31988 The &%log_selector%& option can be used to request the logging of additional
31989 data when a message is received. See section &<<SECTlogselector>>& below.
31993 .section "Logging deliveries" "SECID252"
31994 .cindex "log" "delivery line"
31995 The format of the single-line entry in the main log that is written for every
31996 delivery is shown in one of the examples below, for local and remote
31997 deliveries, respectively. Each example has been split into two lines in order
31998 to fit it on the page:
32000 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
32001 <marv@hitch.fict.example> R=localuser T=local_delivery
32002 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
32003 monk@holistic.fict.example R=dnslookup T=remote_smtp
32004 H=holistic.fict.example [192.168.234.234]
32006 For ordinary local deliveries, the original address is given in angle brackets
32007 after the final delivery address, which might be a pipe or a file. If
32008 intermediate address(es) exist between the original and the final address, the
32009 last of these is given in parentheses after the final address. The R and T
32010 fields record the router and transport that were used to process the address.
32012 If a shadow transport was run after a successful local delivery, the log line
32013 for the successful delivery has an item added on the end, of the form
32015 &`ST=<`&&'shadow transport name'&&`>`&
32017 If the shadow transport did not succeed, the error message is put in
32018 parentheses afterwards.
32020 .cindex "asterisk" "after IP address"
32021 When more than one address is included in a single delivery (for example, two
32022 SMTP RCPT commands in one transaction) the second and subsequent addresses are
32023 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
32024 down a single SMTP connection, an asterisk follows the IP address in the log
32025 lines for the second and subsequent messages.
32027 The generation of a reply message by a filter file gets logged as a
32028 &"delivery"& to the addressee, preceded by &">"&.
32030 The &%log_selector%& option can be used to request the logging of additional
32031 data when a message is delivered. See section &<<SECTlogselector>>& below.
32034 .section "Discarded deliveries" "SECID253"
32035 .cindex "discarded messages"
32036 .cindex "message" "discarded"
32037 .cindex "delivery" "discarded; logging"
32038 When a message is discarded as a result of the command &"seen finish"& being
32039 obeyed in a filter file which generates no deliveries, a log entry of the form
32041 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
32042 <low.club@bridge.example> R=userforward
32044 is written, to record why no deliveries are logged. When a message is discarded
32045 because it is aliased to &":blackhole:"& the log line is like this:
32047 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
32048 <hole@nowhere.example> R=blackhole_router
32052 .section "Deferred deliveries" "SECID254"
32053 When a delivery is deferred, a line of the following form is logged:
32055 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
32056 R=dnslookup T=smtp defer (146): Connection refused
32058 In the case of remote deliveries, the error is the one that was given for the
32059 last IP address that was tried. Details of individual SMTP failures are also
32060 written to the log, so the above line would be preceded by something like
32062 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
32063 mail1.endrest.example [192.168.239.239]: Connection refused
32065 When a deferred address is skipped because its retry time has not been reached,
32066 a message is written to the log, but this can be suppressed by setting an
32067 appropriate value in &%log_selector%&.
32071 .section "Delivery failures" "SECID255"
32072 .cindex "delivery" "failure; logging"
32073 If a delivery fails because an address cannot be routed, a line of the
32074 following form is logged:
32076 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
32077 <jim@trek99.example>: unknown mail domain
32079 If a delivery fails at transport time, the router and transport are shown, and
32080 the response from the remote host is included, as in this example:
32082 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
32083 R=dnslookup T=remote_smtp: SMTP error from remote mailer
32084 after pipelined RCPT TO:<ace400@pb.example>: host
32085 pbmail3.py.example [192.168.63.111]: 553 5.3.0
32086 <ace400@pb.example>...Addressee unknown
32088 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
32089 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
32090 disabling PIPELINING. The log lines for all forms of delivery failure are
32091 flagged with &`**`&.
32095 .section "Fake deliveries" "SECID256"
32096 .cindex "delivery" "fake; logging"
32097 If a delivery does not actually take place because the &%-N%& option has been
32098 used to suppress it, a normal delivery line is written to the log, except that
32099 &"=>"& is replaced by &"*>"&.
32103 .section "Completion" "SECID257"
32106 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
32108 is written to the main log when a message is about to be removed from the spool
32109 at the end of its processing.
32114 .section "Summary of Fields in Log Lines" "SECID258"
32115 .cindex "log" "summary of fields"
32116 A summary of the field identifiers that are used in log lines is shown in
32117 the following table:
32119 &`A `& authenticator name (and optional id)
32120 &`C `& SMTP confirmation on delivery
32121 &` `& command list for &"no mail in SMTP session"&
32122 &`CV `& certificate verification status
32123 &`D `& duration of &"no mail in SMTP session"&
32124 &`DN `& distinguished name from peer certificate
32125 &`DT `& on &`=>`& lines: time taken for a delivery
32126 &`F `& sender address (on delivery lines)
32127 &`H `& host name and IP address
32128 &`I `& local interface used
32129 &`id `& message id for incoming message
32130 &`P `& on &`<=`& lines: protocol used
32131 &` `& on &`=>`& and &`**`& lines: return path
32132 &`QT `& on &`=>`& lines: time spent on queue so far
32133 &` `& on &"Completed"& lines: time spent on queue
32134 &`R `& on &`<=`& lines: reference for local bounce
32135 &` `& on &`=>`& &`**`& and &`==`& lines: router name
32136 &`S `& size of message
32137 &`ST `& shadow transport name
32138 &`T `& on &`<=`& lines: message subject (topic)
32139 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
32140 &`U `& local user or RFC 1413 identity
32141 &`X `& TLS cipher suite
32145 .section "Other log entries" "SECID259"
32146 Various other types of log entry are written from time to time. Most should be
32147 self-explanatory. Among the more common are:
32150 .cindex "retry" "time not reached"
32151 &'retry time not reached'&&~&~An address previously suffered a temporary error
32152 during routing or local delivery, and the time to retry has not yet arrived.
32153 This message is not written to an individual message log file unless it happens
32154 during the first delivery attempt.
32156 &'retry time not reached for any host'&&~&~An address previously suffered
32157 temporary errors during remote delivery, and the retry time has not yet arrived
32158 for any of the hosts to which it is routed.
32160 .cindex "spool directory" "file locked"
32161 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
32162 some other Exim process is already working on the message. This can be quite
32163 common if queue running processes are started at frequent intervals. The
32164 &'exiwhat'& utility script can be used to find out what Exim processes are
32167 .cindex "error" "ignored"
32168 &'error ignored'&&~&~There are several circumstances that give rise to this
32171 Exim failed to deliver a bounce message whose age was greater than
32172 &%ignore_bounce_errors_after%&. The bounce was discarded.
32174 A filter file set up a delivery using the &"noerror"& option, and the delivery
32175 failed. The delivery was discarded.
32177 A delivery set up by a router configured with
32178 . ==== As this is a nested list, any displays it contains must be indented
32179 . ==== as otherwise they are too far to the left.
32183 failed. The delivery was discarded.
32191 .section "Reducing or increasing what is logged" "SECTlogselector"
32192 .cindex "log" "selectors"
32193 By setting the &%log_selector%& global option, you can disable some of Exim's
32194 default logging, or you can request additional logging. The value of
32195 &%log_selector%& is made up of names preceded by plus or minus characters. For
32198 log_selector = +arguments -retry_defer
32200 The list of optional log items is in the following table, with the default
32201 selection marked by asterisks:
32203 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
32204 &` address_rewrite `& address rewriting
32205 &` all_parents `& all parents in => lines
32206 &` arguments `& command line arguments
32207 &`*connection_reject `& connection rejections
32208 &`*delay_delivery `& immediate delivery delayed
32209 &` deliver_time `& time taken to perform delivery
32210 &` delivery_size `& add &`S=`&&'nnn'& to => lines
32211 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
32212 &`*etrn `& ETRN commands
32213 &`*host_lookup_failed `& as it says
32214 &` ident_timeout `& timeout for ident connection
32215 &` incoming_interface `& incoming interface on <= lines
32216 &` incoming_port `& incoming port on <= lines
32217 &`*lost_incoming_connection `& as it says (includes timeouts)
32218 &` outgoing_port `& add remote port to => lines
32219 &`*queue_run `& start and end queue runs
32220 &` queue_time `& time on queue for one recipient
32221 &` queue_time_overall `& time on queue for whole message
32222 &` pid `& Exim process id
32223 &` received_recipients `& recipients on <= lines
32224 &` received_sender `& sender on <= lines
32225 &`*rejected_header `& header contents on reject log
32226 &`*retry_defer `& &"retry time not reached"&
32227 &` return_path_on_delivery `& put return path on => and ** lines
32228 &` sender_on_delivery `& add sender to => lines
32229 &`*sender_verify_fail `& sender verification failures
32230 &`*size_reject `& rejection because too big
32231 &`*skip_delivery `& delivery skipped in a queue run
32232 &` smtp_confirmation `& SMTP confirmation on => lines
32233 &` smtp_connection `& SMTP connections
32234 &` smtp_incomplete_transaction`& incomplete SMTP transactions
32235 &` smtp_no_mail `& session with no MAIL commands
32236 &` smtp_protocol_error `& SMTP protocol errors
32237 &` smtp_syntax_error `& SMTP syntax errors
32238 &` subject `& contents of &'Subject:'& on <= lines
32239 &` tls_certificate_verified `& certificate verification status
32240 &`*tls_cipher `& TLS cipher suite on <= and => lines
32241 &` tls_peerdn `& TLS peer DN on <= and => lines
32242 &` unknown_in_list `& DNS lookup failed in list match
32244 &` all `& all of the above
32246 More details on each of these items follows:
32249 .cindex "&%warn%& ACL verb" "log when skipping"
32250 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
32251 its conditions cannot be evaluated, a log line to this effect is written if
32252 this log selector is set.
32254 .cindex "log" "rewriting"
32255 .cindex "rewriting" "logging"
32256 &%address_rewrite%&: This applies both to global rewrites and per-transport
32257 rewrites, but not to rewrites in filters run as an unprivileged user (because
32258 such users cannot access the log).
32260 .cindex "log" "full parentage"
32261 &%all_parents%&: Normally only the original and final addresses are logged on
32262 delivery lines; with this selector, intermediate parents are given in
32263 parentheses between them.
32265 .cindex "log" "Exim arguments"
32266 .cindex "Exim arguments, logging"
32267 &%arguments%&: This causes Exim to write the arguments with which it was called
32268 to the main log, preceded by the current working directory. This is a debugging
32269 feature, added to make it easier to find out how certain MUAs call
32270 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
32271 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
32272 that are empty or that contain white space are quoted. Non-printing characters
32273 are shown as escape sequences. This facility cannot log unrecognized arguments,
32274 because the arguments are checked before the configuration file is read. The
32275 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
32276 between the caller and Exim.
32278 .cindex "log" "connection rejections"
32279 &%connection_reject%&: A log entry is written whenever an incoming SMTP
32280 connection is rejected, for whatever reason.
32282 .cindex "log" "delayed delivery"
32283 .cindex "delayed delivery, logging"
32284 &%delay_delivery%&: A log entry is written whenever a delivery process is not
32285 started for an incoming message because the load is too high or too many
32286 messages were received on one connection. Logging does not occur if no delivery
32287 process is started because &%queue_only%& is set or &%-odq%& was used.
32289 .cindex "log" "delivery duration"
32290 &%deliver_time%&: For each delivery, the amount of real time it has taken to
32291 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
32293 .cindex "log" "message size on delivery"
32294 .cindex "size" "of message"
32295 &%delivery_size%&: For each delivery, the size of message delivered is added to
32296 the &"=>"& line, tagged with S=.
32298 .cindex "log" "dnslist defer"
32299 .cindex "DNS list" "logging defer"
32300 .cindex "black list (DNS)"
32301 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
32302 DNS black list suffers a temporary error.
32304 .cindex "log" "ETRN commands"
32305 .cindex "ETRN" "logging"
32306 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
32307 is run to determine whether or not it is actually accepted. An invalid ETRN
32308 command, or one received within a message transaction is not logged by this
32309 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
32311 .cindex "log" "host lookup failure"
32312 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
32313 any addresses, or when a lookup of an IP address fails to find a host name, a
32314 log line is written. This logging does not apply to direct DNS lookups when
32315 routing email addresses, but it does apply to &"byname"& lookups.
32317 .cindex "log" "ident timeout"
32318 .cindex "RFC 1413" "logging timeout"
32319 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
32320 client's ident port times out.
32322 .cindex "log" "incoming interface"
32323 .cindex "interface" "logging"
32324 &%incoming_interface%&: The interface on which a message was received is added
32325 to the &"<="& line as an IP address in square brackets, tagged by I= and
32326 followed by a colon and the port number. The local interface and port are also
32327 added to other SMTP log lines, for example &"SMTP connection from"&, and to
32330 .cindex "log" "incoming remote port"
32331 .cindex "port" "logging remote"
32332 .cindex "TCP/IP" "logging incoming remote port"
32333 .vindex "&$sender_fullhost$&"
32334 .vindex "&$sender_rcvhost$&"
32335 &%incoming_port%&: The remote port number from which a message was received is
32336 added to log entries and &'Received:'& header lines, following the IP address
32337 in square brackets, and separated from it by a colon. This is implemented by
32338 changing the value that is put in the &$sender_fullhost$& and
32339 &$sender_rcvhost$& variables. Recording the remote port number has become more
32340 important with the widening use of NAT (see RFC 2505).
32342 .cindex "log" "dropped connection"
32343 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
32344 connection is unexpectedly dropped.
32346 .cindex "log" "outgoing remote port"
32347 .cindex "port" "logging outgoint remote"
32348 .cindex "TCP/IP" "logging ougtoing remote port"
32349 &%outgoing_port%&: The remote port number is added to delivery log lines (those
32350 containing => tags) following the IP address. This option is not included in
32351 the default setting, because for most ordinary configurations, the remote port
32352 number is always 25 (the SMTP port).
32354 .cindex "log" "process ids in"
32355 .cindex "pid (process id)" "in log lines"
32356 &%pid%&: The current process id is added to every log line, in square brackets,
32357 immediately after the time and date.
32359 .cindex "log" "queue run"
32360 .cindex "queue runner" "logging"
32361 &%queue_run%&: The start and end of every queue run are logged.
32363 .cindex "log" "queue time"
32364 &%queue_time%&: The amount of time the message has been in the queue on the
32365 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
32366 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
32367 includes reception time as well as the delivery time for the current address.
32368 This means that it may be longer than the difference between the arrival and
32369 delivery log line times, because the arrival log line is not written until the
32370 message has been successfully received.
32372 &%queue_time_overall%&: The amount of time the message has been in the queue on
32373 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
32374 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
32375 message, so it includes reception time as well as the total delivery time.
32377 .cindex "log" "recipients"
32378 &%received_recipients%&: The recipients of a message are listed in the main log
32379 as soon as the message is received. The list appears at the end of the log line
32380 that is written when a message is received, preceded by the word &"for"&. The
32381 addresses are listed after they have been qualified, but before any rewriting
32383 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
32386 .cindex "log" "sender reception"
32387 &%received_sender%&: The unrewritten original sender of a message is added to
32388 the end of the log line that records the message's arrival, after the word
32389 &"from"& (before the recipients if &%received_recipients%& is also set).
32391 .cindex "log" "header lines for rejection"
32392 &%rejected_header%&: If a message's header has been received at the time a
32393 rejection is written to the reject log, the complete header is added to the
32394 log. Header logging can be turned off individually for messages that are
32395 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
32397 .cindex "log" "retry defer"
32398 &%retry_defer%&: A log line is written if a delivery is deferred because a
32399 retry time has not yet been reached. However, this &"retry time not reached"&
32400 message is always omitted from individual message logs after the first delivery
32403 .cindex "log" "return path"
32404 &%return_path_on_delivery%&: The return path that is being transmitted with
32405 the message is included in delivery and bounce lines, using the tag P=.
32406 This is omitted if no delivery actually happens, for example, if routing fails,
32407 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
32409 .cindex "log" "sender on delivery"
32410 &%sender_on_delivery%&: The message's sender address is added to every delivery
32411 and bounce line, tagged by F= (for &"from"&).
32412 This is the original sender that was received with the message; it is not
32413 necessarily the same as the outgoing return path.
32415 .cindex "log" "sender verify failure"
32416 &%sender_verify_fail%&: If this selector is unset, the separate log line that
32417 gives details of a sender verification failure is not written. Log lines for
32418 the rejection of SMTP commands contain just &"sender verify failed"&, so some
32421 .cindex "log" "size rejection"
32422 &%size_reject%&: A log line is written whenever a message is rejected because
32425 .cindex "log" "frozen messages; skipped"
32426 .cindex "frozen messages" "logging skipping"
32427 &%skip_delivery%&: A log line is written whenever a message is skipped during a
32428 queue run because it is frozen or because another process is already delivering
32430 .cindex "&""spool file is locked""&"
32431 The message that is written is &"spool file is locked"&.
32433 .cindex "log" "smtp confirmation"
32434 .cindex "SMTP" "logging confirmation"
32435 &%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for
32436 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
32437 A number of MTAs (including Exim) return an identifying string in this
32440 .cindex "log" "SMTP connections"
32441 .cindex "SMTP" "logging connections"
32442 &%smtp_connection%&: A log line is written whenever an SMTP connection is
32443 established or closed, unless the connection is from a host that matches
32444 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
32445 only when the closure is unexpected.) This applies to connections from local
32446 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
32447 dropped in the middle of a message, a log line is always written, whether or
32448 not this selector is set, but otherwise nothing is written at the start and end
32449 of connections unless this selector is enabled.
32451 For TCP/IP connections to an Exim daemon, the current number of connections is
32452 included in the log message for each new connection, but note that the count is
32453 reset if the daemon is restarted.
32454 Also, because connections are closed (and the closure is logged) in
32455 subprocesses, the count may not include connections that have been closed but
32456 whose termination the daemon has not yet noticed. Thus, while it is possible to
32457 match up the opening and closing of connections in the log, the value of the
32458 logged counts may not be entirely accurate.
32460 .cindex "log" "SMTP transaction; incomplete"
32461 .cindex "SMTP" "logging incomplete transactions"
32462 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
32463 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
32464 and the message sender plus any accepted recipients are included in the log
32465 line. This can provide evidence of dictionary attacks.
32467 .cindex "log" "non-MAIL SMTP sessions"
32468 .cindex "MAIL" "logging session without"
32469 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
32470 connection terminates without having issued a MAIL command. This includes both
32471 the case when the connection is dropped, and the case when QUIT is used. It
32472 does not include cases where the connection is rejected right at the start (by
32473 an ACL, or because there are too many connections, or whatever). These cases
32474 already have their own log lines.
32476 The log line that is written contains the identity of the client in the usual
32477 way, followed by D= and a time, which records the duration of the connection.
32478 If the connection was authenticated, this fact is logged exactly as it is for
32479 an incoming message, with an A= item. If the connection was encrypted, CV=,
32480 DN=, and X= items may appear as they do for an incoming message, controlled by
32481 the same logging options.
32483 Finally, if any SMTP commands were issued during the connection, a C= item
32484 is added to the line, listing the commands that were used. For example,
32488 shows that the client issued QUIT straight after EHLO. If there were fewer
32489 than 20 commands, they are all listed. If there were more than 20 commands,
32490 the last 20 are listed, preceded by &"..."&. However, with the default
32491 setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case
32492 have been aborted before 20 non-mail commands are processed.
32494 .cindex "log" "SMTP protocol error"
32495 .cindex "SMTP" "logging protocol error"
32496 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
32497 encountered. Exim does not have perfect detection of all protocol errors
32498 because of transmission delays and the use of pipelining. If PIPELINING has
32499 been advertised to a client, an Exim server assumes that the client will use
32500 it, and therefore it does not count &"expected"& errors (for example, RCPT
32501 received after rejecting MAIL) as protocol errors.
32503 .cindex "SMTP" "logging syntax errors"
32504 .cindex "SMTP" "syntax errors; logging"
32505 .cindex "SMTP" "unknown command; logging"
32506 .cindex "log" "unknown SMTP command"
32507 .cindex "log" "SMTP syntax error"
32508 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
32509 encountered. An unrecognized command is treated as a syntax error. For an
32510 external connection, the host identity is given; for an internal connection
32511 using &%-bs%& the sender identification (normally the calling user) is given.
32513 .cindex "log" "subject"
32514 .cindex "subject, logging"
32515 &%subject%&: The subject of the message is added to the arrival log line,
32516 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
32517 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
32518 specifies whether characters with values greater than 127 should be logged
32519 unchanged, or whether they should be rendered as escape sequences.
32521 .cindex "log" "certificate verification"
32522 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
32523 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
32524 verified, and &`CV=no`& if not.
32526 .cindex "log" "TLS cipher"
32527 .cindex "TLS" "logging cipher"
32528 &%tls_cipher%&: When a message is sent or received over an encrypted
32529 connection, the cipher suite used is added to the log line, preceded by X=.
32531 .cindex "log" "TLS peer DN"
32532 .cindex "TLS" "logging peer DN"
32533 &%tls_peerdn%&: When a message is sent or received over an encrypted
32534 connection, and a certificate is supplied by the remote host, the peer DN is
32535 added to the log line, preceded by DN=.
32537 .cindex "log" "DNS failure in list"
32538 &%unknown_in_list%&: This setting causes a log entry to be written when the
32539 result of a list match is failure because a DNS lookup failed.
32543 .section "Message log" "SECID260"
32544 .cindex "message" "log file for"
32545 .cindex "log" "message log; description of"
32546 .cindex "&_msglog_& directory"
32547 .oindex "&%preserve_message_logs%&"
32548 In addition to the general log files, Exim writes a log file for each message
32549 that it handles. The names of these per-message logs are the message ids, and
32550 they are kept in the &_msglog_& sub-directory of the spool directory. Each
32551 message log contains copies of the log lines that apply to the message. This
32552 makes it easier to inspect the status of an individual message without having
32553 to search the main log. A message log is deleted when processing of the message
32554 is complete, unless &%preserve_message_logs%& is set, but this should be used
32555 only with great care because they can fill up your disk very quickly.
32557 On a heavily loaded system, it may be desirable to disable the use of
32558 per-message logs, in order to reduce disk I/O. This can be done by setting the
32559 &%message_logs%& option false.
32565 . ////////////////////////////////////////////////////////////////////////////
32566 . ////////////////////////////////////////////////////////////////////////////
32568 .chapter "Exim utilities" "CHAPutils"
32569 .scindex IIDutils "utilities"
32570 A number of utility scripts and programs are supplied with Exim and are
32571 described in this chapter. There is also the Exim Monitor, which is covered in
32572 the next chapter. The utilities described here are:
32574 .itable none 0 0 3 7* left 15* left 40* left
32575 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
32576 "list what Exim processes are doing"
32577 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
32578 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
32579 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
32580 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
32582 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
32583 .irow &<<SECTmailstat>>& &'eximstats'& &&&
32584 "extract statistics from the log"
32585 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
32586 "check address acceptance from given IP"
32587 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
32588 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
32589 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
32590 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
32591 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
32592 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
32595 Another utility that might be of use to sites with many MTAs is Tom Kistner's
32596 &'exilog'&. It provides log visualizations across multiple Exim servers. See
32597 &url(http://duncanthrax.net/exilog/) for details.
32602 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
32603 .cindex "&'exiwhat'&"
32604 .cindex "process, querying"
32606 On operating systems that can restart a system call after receiving a signal
32607 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
32608 a line describing what it is doing to the file &_exim-process.info_& in the
32609 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
32610 processes it can find, having first emptied the file. It then waits for one
32611 second to allow the Exim processes to react before displaying the results. In
32612 order to run &'exiwhat'& successfully you have to have sufficient privilege to
32613 send the signal to the Exim processes, so it is normally run as root.
32615 &*Warning*&: This is not an efficient process. It is intended for occasional
32616 use by system administrators. It is not sensible, for example, to set up a
32617 script that sends SIGUSR1 signals to Exim processes at short intervals.
32620 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
32621 varies in different operating systems. Not only are different options used,
32622 but the format of the output is different. For this reason, there are some
32623 system configuration options that configure exactly how &'exiwhat'& works. If
32624 it doesn't seem to be working for you, check the following compile-time
32627 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
32628 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
32629 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
32630 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
32632 An example of typical output from &'exiwhat'& is
32634 164 daemon: -q1h, listening on port 25
32635 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
32636 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
32637 [10.19.42.42] (editor@ref.example)
32638 10592 handling incoming call from [192.168.243.242]
32639 10628 accepting a local non-SMTP message
32641 The first number in the output line is the process number. The third line has
32642 been split here, in order to fit it on the page.
32646 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
32647 .cindex "&'exiqgrep'&"
32648 .cindex "queue" "grepping"
32649 This utility is a Perl script contributed by Matt Hubbard. It runs
32653 to obtain a queue listing with undelivered recipients only, and then greps the
32654 output to select messages that match given criteria. The following selection
32655 options are available:
32658 .vitem &*-f*&&~<&'regex'&>
32659 Match the sender address. The field that is tested is enclosed in angle
32660 brackets, so you can test for bounce messages with
32664 .vitem &*-r*&&~<&'regex'&>
32665 Match a recipient address. The field that is tested is not enclosed in angle
32668 .vitem &*-s*&&~<&'regex'&>
32669 Match against the size field.
32671 .vitem &*-y*&&~<&'seconds'&>
32672 Match messages that are younger than the given time.
32674 .vitem &*-o*&&~<&'seconds'&>
32675 Match messages that are older than the given time.
32678 Match only frozen messages.
32681 Match only non-frozen messages.
32684 The following options control the format of the output:
32688 Display only the count of matching messages.
32691 Long format &-- display the full message information as output by Exim. This is
32695 Display message ids only.
32698 Brief format &-- one line per message.
32701 Display messages in reverse order.
32704 There is one more option, &%-h%&, which outputs a list of options.
32708 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
32709 .cindex "&'exiqsumm'&"
32710 .cindex "queue" "summary"
32711 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
32712 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
32713 running a command such as
32715 exim -bp | exiqsumm
32717 The output consists of one line for each domain that has messages waiting for
32718 it, as in the following example:
32720 3 2322 74m 66m msn.com.example
32722 Each line lists the number of pending deliveries for a domain, their total
32723 volume, and the length of time that the oldest and the newest messages have
32724 been waiting. Note that the number of pending deliveries is greater than the
32725 number of messages when messages have more than one recipient.
32727 A summary line is output at the end. By default the output is sorted on the
32728 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
32729 the output to be sorted by oldest message and by count of messages,
32730 respectively. There are also three options that split the messages for each
32731 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
32732 separates frozen messages, and &%-s%& separates messages according to their
32735 The output of &'exim -bp'& contains the original addresses in the message, so
32736 this also applies to the output from &'exiqsumm'&. No domains from addresses
32737 generated by aliasing or forwarding are included (unless the &%one_time%&
32738 option of the &(redirect)& router has been used to convert them into &"top
32739 level"& addresses).
32744 .section "Extracting specific information from the log (exigrep)" &&&
32746 .cindex "&'exigrep'&"
32747 .cindex "log" "extracts; grepping for"
32748 The &'exigrep'& utility is a Perl script that searches one or more main log
32749 files for entries that match a given pattern. When it finds a match, it
32750 extracts all the log entries for the relevant message, not just those that
32751 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
32752 given message, or all mail for a given user, or for a given host, for example.
32753 The input files can be in Exim log format or syslog format.
32754 If a matching log line is not associated with a specific message, it is
32755 included in &'exigrep'&'s output without any additional lines. The usage is:
32757 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
32759 If no log file names are given on the command line, the standard input is read.
32761 The &%-t%& argument specifies a number of seconds. It adds an additional
32762 condition for message selection. Messages that are complete are shown only if
32763 they spent more than <&'n'&> seconds on the queue.
32765 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
32766 makes it case-sensitive. This may give a performance improvement when searching
32767 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
32768 option; with &%-I%& they do not. In both cases it is possible to change the
32769 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
32771 The &%-l%& option means &"literal"&, that is, treat all characters in the
32772 pattern as standing for themselves. Otherwise the pattern must be a Perl
32773 regular expression.
32775 The &%-v%& option inverts the matching condition. That is, a line is selected
32776 if it does &'not'& match the pattern.
32778 If the location of a &'zcat'& command is known from the definition of
32779 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
32780 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
32783 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
32784 .cindex "&'exipick'&"
32785 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
32786 lists messages from the queue according to a variety of criteria. For details
32787 of &'exipick'&'s facilities, visit the web page at
32788 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
32789 the &%--help%& option.
32792 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
32793 .cindex "log" "cycling local files"
32794 .cindex "cycling logs"
32795 .cindex "&'exicyclog'&"
32796 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
32797 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
32798 you are using log files with datestamps in their names (see section
32799 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
32800 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
32801 There are two command line options for &'exicyclog'&:
32803 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
32804 default that is set when Exim is built. The default default is 10.
32806 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
32807 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
32808 overriding the script's default, which is to find the setting from Exim's
32812 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
32813 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
32814 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
32815 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
32816 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
32817 logs are handled similarly.
32819 If the limit is greater than 99, the script uses 3-digit numbers such as
32820 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
32821 to one that is greater, or &'vice versa'&, you will have to fix the names of
32822 any existing log files.
32824 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
32825 the end are deleted. All files with numbers greater than 01 are compressed,
32826 using a compression command which is configured by the COMPRESS_COMMAND
32827 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
32828 root &%crontab%& entry of the form
32830 1 0 * * * su exim -c /usr/exim/bin/exicyclog
32832 assuming you have used the name &"exim"& for the Exim user. You can run
32833 &'exicyclog'& as root if you wish, but there is no need.
32837 .section "Mail statistics (eximstats)" "SECTmailstat"
32838 .cindex "statistics"
32839 .cindex "&'eximstats'&"
32840 A Perl script called &'eximstats'& is provided for extracting statistical
32841 information from log files. The output is either plain text, or HTML.
32842 Exim log files are also supported by the &'Lire'& system produced by the
32843 LogReport Foundation &url(http://www.logreport.org).
32845 The &'eximstats'& script has been hacked about quite a bit over time. The
32846 latest version is the result of some extensive revision by Steve Campbell. A
32847 lot of information is given by default, but there are options for suppressing
32848 various parts of it. Following any options, the arguments to the script are a
32849 list of files, which should be main log files. For example:
32851 eximstats -nr /var/spool/exim/log/mainlog.01
32853 By default, &'eximstats'& extracts information about the number and volume of
32854 messages received from or delivered to various hosts. The information is sorted
32855 both by message count and by volume, and the top fifty hosts in each category
32856 are listed on the standard output. Similar information, based on email
32857 addresses or domains instead of hosts can be requested by means of various
32858 options. For messages delivered and received locally, similar statistics are
32859 also produced per user.
32861 The output also includes total counts and statistics about delivery errors, and
32862 histograms showing the number of messages received and deliveries made in each
32863 hour of the day. A delivery with more than one address in its envelope (for
32864 example, an SMTP transaction with more than one RCPT command) is counted
32865 as a single delivery by &'eximstats'&.
32867 Though normally more deliveries than receipts are reported (as messages may
32868 have multiple recipients), it is possible for &'eximstats'& to report more
32869 messages received than delivered, even though the queue is empty at the start
32870 and end of the period in question. If an incoming message contains no valid
32871 recipients, no deliveries are recorded for it. A bounce message is handled as
32872 an entirely separate message.
32874 &'eximstats'& always outputs a grand total summary giving the volume and number
32875 of messages received and deliveries made, and the number of hosts involved in
32876 each case. It also outputs the number of messages that were delayed (that is,
32877 not completely delivered at the first attempt), and the number that had at
32878 least one address that failed.
32880 The remainder of the output is in sections that can be independently disabled
32881 or modified by various options. It consists of a summary of deliveries by
32882 transport, histograms of messages received and delivered per time interval
32883 (default per hour), information about the time messages spent on the queue,
32884 a list of relayed messages, lists of the top fifty sending hosts, local
32885 senders, destination hosts, and destination local users by count and by volume,
32886 and a list of delivery errors that occurred.
32888 The relay information lists messages that were actually relayed, that is, they
32889 came from a remote host and were directly delivered to some other remote host,
32890 without being processed (for example, for aliasing or forwarding) locally.
32892 There are quite a few options for &'eximstats'& to control exactly what it
32893 outputs. These are documented in the Perl script itself, and can be extracted
32894 by running the command &(perldoc)& on the script. For example:
32896 perldoc /usr/exim/bin/eximstats
32899 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
32900 .cindex "&'exim_checkaccess'&"
32901 .cindex "policy control" "checking access"
32902 .cindex "checking access"
32903 The &%-bh%& command line argument allows you to run a fake SMTP session with
32904 debugging output, in order to check what Exim is doing when it is applying
32905 policy controls to incoming SMTP mail. However, not everybody is sufficiently
32906 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
32907 sometimes you just want to answer the question &"Does this address have
32908 access?"& without bothering with any further details.
32910 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
32911 two arguments, an IP address and an email address:
32913 exim_checkaccess 10.9.8.7 A.User@a.domain.example
32915 The utility runs a call to Exim with the &%-bh%& option, to test whether the
32916 given email address would be accepted in a RCPT command in a TCP/IP
32917 connection from the host with the given IP address. The output of the utility
32918 is either the word &"accepted"&, or the SMTP error response, for example:
32921 550 Relay not permitted
32923 When running this test, the utility uses &`<>`& as the envelope sender address
32924 for the MAIL command, but you can change this by providing additional
32925 options. These are passed directly to the Exim command. For example, to specify
32926 that the test is to be run with the sender address &'himself@there.example'&
32929 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
32930 -f himself@there.example
32932 Note that these additional Exim command line items must be given after the two
32933 mandatory arguments.
32935 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
32936 while running its checks. You can run checks that include callouts by using
32937 &%-bhc%&, but this is not yet available in a &"packaged"& form.
32941 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
32942 .cindex "DBM" "building dbm files"
32943 .cindex "building DBM files"
32944 .cindex "&'exim_dbmbuild'&"
32945 .cindex "lower casing"
32946 .cindex "binary zero" "in lookup key"
32947 The &'exim_dbmbuild'& program reads an input file containing keys and data in
32948 the format used by the &(lsearch)& lookup (see section
32949 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
32950 names as keys and the remainder of the information as data. The lower-casing
32951 can be prevented by calling the program with the &%-nolc%& option.
32953 A terminating zero is included as part of the key string. This is expected by
32954 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
32955 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
32956 strings or the data strings. The &(dbmnz)& lookup type can be used with such
32959 The program requires two arguments: the name of the input file (which can be a
32960 single hyphen to indicate the standard input), and the name of the output file.
32961 It creates the output under a temporary name, and then renames it if all went
32965 If the native DB interface is in use (USE_DB is set in a compile-time
32966 configuration file &-- this is common in free versions of Unix) the two file
32967 names must be different, because in this mode the Berkeley DB functions create
32968 a single output file using exactly the name given. For example,
32970 exim_dbmbuild /etc/aliases /etc/aliases.db
32972 reads the system alias file and creates a DBM version of it in
32973 &_/etc/aliases.db_&.
32975 In systems that use the &'ndbm'& routines (mostly proprietary versions of
32976 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
32977 environment, the suffixes are added to the second argument of
32978 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
32979 when the Berkeley functions are used in compatibility mode (though this is not
32980 recommended), because in that case it adds a &_.db_& suffix to the file name.
32982 If a duplicate key is encountered, the program outputs a warning, and when it
32983 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
32984 option is used. By default, only the first of a set of duplicates is used &--
32985 this makes it compatible with &(lsearch)& lookups. There is an option
32986 &%-lastdup%& which causes it to use the data for the last duplicate instead.
32987 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
32988 &%stderr%&. For other errors, where it doesn't actually make a new file, the
32994 .section "Finding individual retry times (exinext)" "SECTfinindret"
32995 .cindex "retry" "times"
32996 .cindex "&'exinext'&"
32997 A utility called &'exinext'& (mostly a Perl script) provides the ability to
32998 fish specific information out of the retry database. Given a mail domain (or a
32999 complete address), it looks up the hosts for that domain, and outputs any retry
33000 information for the hosts or for the domain. At present, the retry information
33001 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
33002 output. For example:
33004 $ exinext piglet@milne.fict.example
33005 kanga.milne.example:192.168.8.1 error 146: Connection refused
33006 first failed: 21-Feb-1996 14:57:34
33007 last tried: 21-Feb-1996 14:57:34
33008 next try at: 21-Feb-1996 15:02:34
33009 roo.milne.example:192.168.8.3 error 146: Connection refused
33010 first failed: 20-Jan-1996 13:12:08
33011 last tried: 21-Feb-1996 11:42:03
33012 next try at: 21-Feb-1996 19:42:03
33013 past final cutoff time
33015 You can also give &'exinext'& a local part, without a domain, and it
33016 will give any retry information for that local part in your default domain.
33017 A message id can be used to obtain retry information pertaining to a specific
33018 message. This exists only when an attempt to deliver a message to a remote host
33019 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
33020 &'exinext'& is not particularly efficient, but then it is not expected to be
33023 The &'exinext'& utility calls Exim to find out information such as the location
33024 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
33025 passed on to the &'exim'& commands. The first specifies an alternate Exim
33026 configuration file, and the second sets macros for use within the configuration
33027 file. These features are mainly to help in testing, but might also be useful in
33028 environments where more than one configuration file is in use.
33032 .section "Hints database maintenance" "SECThindatmai"
33033 .cindex "hints database" "maintenance"
33034 .cindex "maintaining Exim's hints database"
33035 Three utility programs are provided for maintaining the DBM files that Exim
33036 uses to contain its delivery hint information. Each program requires two
33037 arguments. The first specifies the name of Exim's spool directory, and the
33038 second is the name of the database it is to operate on. These are as follows:
33041 &'retry'&: the database of retry information
33043 &'wait-'&<&'transport name'&>: databases of information about messages waiting
33046 &'callout'&: the callout cache
33048 &'ratelimit'&: the data for implementing the ratelimit ACL condition
33050 &'misc'&: other hints data
33053 The &'misc'& database is used for
33056 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
33058 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
33059 &(smtp)& transport)
33064 .section "exim_dumpdb" "SECID261"
33065 .cindex "&'exim_dumpdb'&"
33066 The entire contents of a database are written to the standard output by the
33067 &'exim_dumpdb'& program, which has no options or arguments other than the
33068 spool and database names. For example, to dump the retry database:
33070 exim_dumpdb /var/spool/exim retry
33072 Two lines of output are produced for each entry:
33074 T:mail.ref.example:192.168.242.242 146 77 Connection refused
33075 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
33077 The first item on the first line is the key of the record. It starts with one
33078 of the letters R, or T, depending on whether it refers to a routing or
33079 transport retry. For a local delivery, the next part is the local address; for
33080 a remote delivery it is the name of the remote host, followed by its failing IP
33081 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
33082 transport). If the remote port is not the standard one (port 25), it is added
33083 to the IP address. Then there follows an error code, an additional error code,
33084 and a textual description of the error.
33086 The three times on the second line are the time of first failure, the time of
33087 the last delivery attempt, and the computed time for the next attempt. The line
33088 ends with an asterisk if the cutoff time for the last retry rule has been
33091 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
33092 consists of a host name followed by a list of ids for messages that are or were
33093 waiting to be delivered to that host. If there are a very large number for any
33094 one host, continuation records, with a sequence number added to the host name,
33095 may be seen. The data in these records is often out of date, because a message
33096 may be routed to several alternative hosts, and Exim makes no effort to keep
33101 .section "exim_tidydb" "SECID262"
33102 .cindex "&'exim_tidydb'&"
33103 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
33104 database. If run with no options, it removes all records that are more than 30
33105 days old. The age is calculated from the date and time that the record was last
33106 updated. Note that, in the case of the retry database, it is &'not'& the time
33107 since the first delivery failure. Information about a host that has been down
33108 for more than 30 days will remain in the database, provided that the record is
33109 updated sufficiently often.
33111 The cutoff date can be altered by means of the &%-t%& option, which must be
33112 followed by a time. For example, to remove all records older than a week from
33113 the retry database:
33115 exim_tidydb -t 7d /var/spool/exim retry
33117 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
33118 message ids. In the former these appear as data in records keyed by host &--
33119 they were messages that were waiting for that host &-- and in the latter they
33120 are the keys for retry information for messages that have suffered certain
33121 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
33122 message ids in database records are those of messages that are still on the
33123 queue. Message ids for messages that no longer exist are removed from
33124 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
33125 For the &'retry'& database, records whose keys are non-existent message ids are
33126 removed. The &'exim_tidydb'& utility outputs comments on the standard output
33127 whenever it removes information from the database.
33129 Certain records are automatically removed by Exim when they are no longer
33130 needed, but others are not. For example, if all the MX hosts for a domain are
33131 down, a retry record is created for each one. If the primary MX host comes back
33132 first, its record is removed when Exim successfully delivers to it, but the
33133 records for the others remain because Exim has not tried to use those hosts.
33135 It is important, therefore, to run &'exim_tidydb'& periodically on all the
33136 hints databases. You should do this at a quiet time of day, because it requires
33137 a database to be locked (and therefore inaccessible to Exim) while it does its
33138 work. Removing records from a DBM file does not normally make the file smaller,
33139 but all the common DBM libraries are able to re-use the space that is released.
33140 After an initial phase of increasing in size, the databases normally reach a
33141 point at which they no longer get any bigger, as long as they are regularly
33144 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
33145 databases is likely to keep on increasing.
33150 .section "exim_fixdb" "SECID263"
33151 .cindex "&'exim_fixdb'&"
33152 The &'exim_fixdb'& program is a utility for interactively modifying databases.
33153 Its main use is for testing Exim, but it might also be occasionally useful for
33154 getting round problems in a live system. It has no options, and its interface
33155 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
33156 key of a database record can then be entered, and the data for that record is
33159 If &"d"& is typed at the next prompt, the entire record is deleted. For all
33160 except the &'retry'& database, that is the only operation that can be carried
33161 out. For the &'retry'& database, each field is output preceded by a number, and
33162 data for individual fields can be changed by typing the field number followed
33163 by new data, for example:
33167 resets the time of the next delivery attempt. Time values are given as a
33168 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
33169 used as optional separators.
33174 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
33175 .cindex "mailbox" "maintenance"
33176 .cindex "&'exim_lock'&"
33177 .cindex "locking mailboxes"
33178 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
33179 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
33180 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
33181 a user agent while investigating a problem. The utility requires the name of
33182 the file as its first argument. If the locking is successful, the second
33183 argument is run as a command (using C's &[system()]& function); if there is no
33184 second argument, the value of the SHELL environment variable is used; if this
33185 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
33186 is unlocked and the utility ends. The following options are available:
33190 Use &[fcntl()]& locking on the open mailbox.
33193 Use &[flock()]& locking on the open mailbox, provided the operating system
33196 .vitem &%-interval%&
33197 This must be followed by a number, which is a number of seconds; it sets the
33198 interval to sleep between retries (default 3).
33200 .vitem &%-lockfile%&
33201 Create a lock file before opening the mailbox.
33204 Lock the mailbox using MBX rules.
33207 Suppress verification output.
33209 .vitem &%-retries%&
33210 This must be followed by a number; it sets the number of times to try to get
33211 the lock (default 10).
33213 .vitem &%-restore_time%&
33214 This option causes &%exim_lock%& to restore the modified and read times to the
33215 locked file before exiting. This allows you to access a locked mailbox (for
33216 example, to take a backup copy) without disturbing the times that the user
33219 .vitem &%-timeout%&
33220 This must be followed by a number, which is a number of seconds; it sets a
33221 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
33222 default), a non-blocking call is used.
33225 Generate verbose output.
33228 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
33229 default is to create a lock file and also to use &[fcntl()]& locking on the
33230 mailbox, which is the same as Exim's default. The use of &%-flock%& or
33231 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
33232 requires that the directory containing the file be writeable. Locking by lock
33233 file does not last for ever; Exim assumes that a lock file is expired if it is
33234 more than 30 minutes old.
33236 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
33237 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
33238 to be taken out on the open mailbox, and an exclusive lock on the file
33239 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
33240 number of the mailbox file. When the locking is released, if an exclusive lock
33241 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
33243 The default output contains verification of the locking that takes place. The
33244 &%-v%& option causes some additional information to be given. The &%-q%& option
33245 suppresses all output except error messages.
33249 exim_lock /var/spool/mail/spqr
33251 runs an interactive shell while the file is locked, whereas
33253 &`exim_lock -q /var/spool/mail/spqr <<End`&
33254 <&'some commands'&>
33257 runs a specific non-interactive sequence of commands while the file is locked,
33258 suppressing all verification output. A single command can be run by a command
33261 exim_lock -q /var/spool/mail/spqr \
33262 "cp /var/spool/mail/spqr /some/where"
33264 Note that if a command is supplied, it must be entirely contained within the
33265 second argument &-- hence the quotes.
33269 . ////////////////////////////////////////////////////////////////////////////
33270 . ////////////////////////////////////////////////////////////////////////////
33272 .chapter "The Exim monitor" "CHAPeximon"
33273 .scindex IIDeximon "Exim monitor" "description"
33274 .cindex "X-windows"
33275 .cindex "&'eximon'&"
33276 .cindex "Local/eximon.conf"
33277 .cindex "&_exim_monitor/EDITME_&"
33278 The Exim monitor is an application which displays in an X window information
33279 about the state of Exim's queue and what Exim is doing. An admin user can
33280 perform certain operations on messages from this GUI interface; however all
33281 such facilities are also available from the command line, and indeed, the
33282 monitor itself makes use of the command line to perform any actions requested.
33286 .section "Running the monitor" "SECID264"
33287 The monitor is started by running the script called &'eximon'&. This is a shell
33288 script that sets up a number of environment variables, and then runs the
33289 binary called &_eximon.bin_&. The default appearance of the monitor window can
33290 be changed by editing the &_Local/eximon.conf_& file created by editing
33291 &_exim_monitor/EDITME_&. Comments in that file describe what the various
33292 parameters are for.
33294 The parameters that get built into the &'eximon'& script can be overridden for
33295 a particular invocation by setting up environment variables of the same names,
33296 preceded by &`EXIMON_`&. For example, a shell command such as
33298 EXIMON_LOG_DEPTH=400 eximon
33300 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
33301 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
33302 overrides the Exim log file configuration. This makes it possible to have
33303 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
33304 syslog messages are routed to a file on the local host.
33306 X resources can be used to change the appearance of the window in the normal
33307 way. For example, a resource setting of the form
33309 Eximon*background: gray94
33311 changes the colour of the background to light grey rather than white. The
33312 stripcharts are drawn with both the data lines and the reference lines in
33313 black. This means that the reference lines are not visible when on top of the
33314 data. However, their colour can be changed by setting a resource called
33315 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
33316 For example, if your X server is running Unix, you could set up lighter
33317 reference lines in the stripcharts by obeying
33320 Eximon*highlight: gray
33323 .cindex "admin user"
33324 In order to see the contents of messages on the queue, and to operate on them,
33325 &'eximon'& must either be run as root or by an admin user.
33327 The monitor's window is divided into three parts. The first contains one or
33328 more stripcharts and two action buttons, the second contains a &"tail"& of the
33329 main log file, and the third is a display of the queue of messages awaiting
33330 delivery, with two more action buttons. The following sections describe these
33331 different parts of the display.
33336 .section "The stripcharts" "SECID265"
33337 .cindex "stripchart"
33338 The first stripchart is always a count of messages on the queue. Its name can
33339 be configured by setting QUEUE_STRIPCHART_NAME in the
33340 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
33341 configuration script by regular expression matches on log file entries, making
33342 it possible to display, for example, counts of messages delivered to certain
33343 hosts or using certain transports. The supplied defaults display counts of
33344 received and delivered messages, and of local and SMTP deliveries. The default
33345 period between stripchart updates is one minute; this can be adjusted by a
33346 parameter in the &_Local/eximon.conf_& file.
33348 The stripchart displays rescale themselves automatically as the value they are
33349 displaying changes. There are always 10 horizontal lines in each chart; the
33350 title string indicates the value of each division when it is greater than one.
33351 For example, &"x2"& means that each division represents a value of 2.
33353 It is also possible to have a stripchart which shows the percentage fullness of
33354 a particular disk partition, which is useful when local deliveries are confined
33355 to a single partition.
33357 .cindex "&%statvfs%& function"
33358 This relies on the availability of the &[statvfs()]& function or equivalent in
33359 the operating system. Most, but not all versions of Unix that support Exim have
33360 this. For this particular stripchart, the top of the chart always represents
33361 100%, and the scale is given as &"x10%"&. This chart is configured by setting
33362 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
33363 &_Local/eximon.conf_& file.
33368 .section "Main action buttons" "SECID266"
33369 .cindex "size" "of monitor window"
33370 .cindex "Exim monitor" "window size"
33371 .cindex "window size"
33372 Below the stripcharts there is an action button for quitting the monitor. Next
33373 to this is another button marked &"Size"&. They are placed here so that
33374 shrinking the window to its default minimum size leaves just the queue count
33375 stripchart and these two buttons visible. Pressing the &"Size"& button causes
33376 the window to expand to its maximum size, unless it is already at the maximum,
33377 in which case it is reduced to its minimum.
33379 When expanding to the maximum, if the window cannot be fully seen where it
33380 currently is, it is moved back to where it was the last time it was at full
33381 size. When it is expanding from its minimum size, the old position is
33382 remembered, and next time it is reduced to the minimum it is moved back there.
33384 The idea is that you can keep a reduced window just showing one or two
33385 stripcharts at a convenient place on your screen, easily expand it to show
33386 the full window when required, and just as easily put it back to what it was.
33387 The idea is copied from what the &'twm'& window manager does for its
33388 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
33389 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
33391 Normally, the monitor starts up with the window at its full size, but it can be
33392 built so that it starts up with the window at its smallest size, by setting
33393 START_SMALL=yes in &_Local/eximon.conf_&.
33397 .section "The log display" "SECID267"
33398 .cindex "log" "tail of; in monitor"
33399 The second section of the window is an area in which a display of the tail of
33400 the main log is maintained.
33401 To save space on the screen, the timestamp on each log line is shortened by
33402 removing the date and, if &%log_timezone%& is set, the timezone.
33403 The log tail is not available when the only destination for logging data is
33404 syslog, unless the syslog lines are routed to a local file whose name is passed
33405 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
33407 The log sub-window has a scroll bar at its lefthand side which can be used to
33408 move back to look at earlier text, and the up and down arrow keys also have a
33409 scrolling effect. The amount of log that is kept depends on the setting of
33410 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
33411 to use. When this is full, the earlier 50% of data is discarded &-- this is
33412 much more efficient than throwing it away line by line. The sub-window also has
33413 a horizontal scroll bar for accessing the ends of long log lines. This is the
33414 only means of horizontal scrolling; the right and left arrow keys are not
33415 available. Text can be cut from this part of the window using the mouse in the
33416 normal way. The size of this subwindow is controlled by parameters in the
33417 configuration file &_Local/eximon.conf_&.
33419 Searches of the text in the log window can be carried out by means of the ^R
33420 and ^S keystrokes, which default to a reverse and a forward search,
33421 respectively. The search covers only the text that is displayed in the window.
33422 It cannot go further back up the log.
33424 The point from which the search starts is indicated by a caret marker. This is
33425 normally at the end of the text in the window, but can be positioned explicitly
33426 by pointing and clicking with the left mouse button, and is moved automatically
33427 by a successful search. If new text arrives in the window when it is scrolled
33428 back, the caret remains where it is, but if the window is not scrolled back,
33429 the caret is moved to the end of the new text.
33431 Pressing ^R or ^S pops up a window into which the search text can be typed.
33432 There are buttons for selecting forward or reverse searching, for carrying out
33433 the search, and for cancelling. If the &"Search"& button is pressed, the search
33434 happens and the window remains so that further searches can be done. If the
33435 &"Return"& key is pressed, a single search is done and the window is closed. If
33436 ^C is typed the search is cancelled.
33438 The searching facility is implemented using the facilities of the Athena text
33439 widget. By default this pops up a window containing both &"search"& and
33440 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
33441 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
33442 However, the linkers in BSDI and HP-UX seem unable to handle an externally
33443 provided version of &%TextPop%& when the remaining parts of the text widget
33444 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
33445 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
33446 on these systems, at the expense of having unwanted items in the search popup
33451 .section "The queue display" "SECID268"
33452 .cindex "queue" "display in monitor"
33453 The bottom section of the monitor window contains a list of all messages that
33454 are on the queue, which includes those currently being received or delivered,
33455 as well as those awaiting delivery. The size of this subwindow is controlled by
33456 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
33457 at which it is updated is controlled by another parameter in the same file &--
33458 the default is 5 minutes, since queue scans can be quite expensive. However,
33459 there is an &"Update"& action button just above the display which can be used
33460 to force an update of the queue display at any time.
33462 When a host is down for some time, a lot of pending mail can build up for it,
33463 and this can make it hard to deal with other messages on the queue. To help
33464 with this situation there is a button next to &"Update"& called &"Hide"&. If
33465 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
33466 type anything in here and press &"Return"&, the text is added to a chain of
33467 such texts, and if every undelivered address in a message matches at least one
33468 of the texts, the message is not displayed.
33470 If there is an address that does not match any of the texts, all the addresses
33471 are displayed as normal. The matching happens on the ends of addresses so, for
33472 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
33473 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
33474 has been set up, a button called &"Unhide"& is displayed. If pressed, it
33475 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
33476 a hide request is automatically cancelled after one hour.
33478 While the dialogue box is displayed, you can't press any buttons or do anything
33479 else to the monitor window. For this reason, if you want to cut text from the
33480 queue display to use in the dialogue box, you have to do the cutting before
33481 pressing the &"Hide"& button.
33483 The queue display contains, for each unhidden queued message, the length of
33484 time it has been on the queue, the size of the message, the message id, the
33485 message sender, and the first undelivered recipient, all on one line. If it is
33486 a bounce message, the sender is shown as &"<>"&. If there is more than one
33487 recipient to which the message has not yet been delivered, subsequent ones are
33488 listed on additional lines, up to a maximum configured number, following which
33489 an ellipsis is displayed. Recipients that have already received the message are
33492 .cindex "frozen messages" "display"
33493 If a message is frozen, an asterisk is displayed at the left-hand side.
33495 The queue display has a vertical scroll bar, and can also be scrolled by means
33496 of the arrow keys. Text can be cut from it using the mouse in the normal way.
33497 The text searching facilities, as described above for the log window, are also
33498 available, but the caret is always moved to the end of the text when the queue
33499 display is updated.
33503 .section "The queue menu" "SECID269"
33504 .cindex "queue" "menu in monitor"
33505 If the &%shift%& key is held down and the left button is clicked when the mouse
33506 pointer is over the text for any message, an action menu pops up, and the first
33507 line of the queue display for the message is highlighted. This does not affect
33510 If you want to use some other event for popping up the menu, you can set the
33511 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
33512 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
33513 value set in this parameter is a standard X event description. For example, to
33514 run eximon using &%ctrl%& rather than &%shift%& you could use
33516 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
33518 The title of the menu is the message id, and it contains entries which act as
33522 &'message log'&: The contents of the message log for the message are displayed
33523 in a new text window.
33525 &'headers'&: Information from the spool file that contains the envelope
33526 information and headers is displayed in a new text window. See chapter
33527 &<<CHAPspool>>& for a description of the format of spool files.
33529 &'body'&: The contents of the spool file containing the body of the message are
33530 displayed in a new text window. There is a default limit of 20,000 bytes to the
33531 amount of data displayed. This can be changed by setting the BODY_MAX
33532 option at compile time, or the EXIMON_BODY_MAX option at run time.
33534 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
33535 delivery of the message. This causes an automatic thaw if the message is
33536 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
33537 a new text window. The delivery is run in a separate process, to avoid holding
33538 up the monitor while the delivery proceeds.
33540 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
33541 that the message be frozen.
33543 .cindex "thawing messages"
33544 .cindex "unfreezing messages"
33545 .cindex "frozen messages" "thawing"
33546 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
33547 that the message be thawed.
33549 .cindex "delivery" "forcing failure"
33550 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
33551 that Exim gives up trying to deliver the message. A bounce message is generated
33552 for any remaining undelivered addresses.
33554 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
33555 that the message be deleted from the system without generating a bounce
33558 &'add recipient'&: A dialog box is displayed into which a recipient address can
33559 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
33560 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
33561 Otherwise it must be entered as a fully qualified address. Pressing RETURN
33562 causes a call to Exim to be made using the &%-Mar%& option to request that an
33563 additional recipient be added to the message, unless the entry box is empty, in
33564 which case no action is taken.
33566 &'mark delivered'&: A dialog box is displayed into which a recipient address
33567 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
33568 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
33569 Otherwise it must be entered as a fully qualified address. Pressing RETURN
33570 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
33571 recipient address as already delivered, unless the entry box is empty, in which
33572 case no action is taken.
33574 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
33575 mark all recipient addresses as already delivered.
33577 &'edit sender'&: A dialog box is displayed initialized with the current
33578 sender's address. Pressing RETURN causes a call to Exim to be made using the
33579 &%-Mes%& option to replace the sender address, unless the entry box is empty,
33580 in which case no action is taken. If you want to set an empty sender (as in
33581 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
33582 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
33583 the address is qualified with that domain.
33586 When a delivery is forced, a window showing the &%-v%& output is displayed. In
33587 other cases when a call to Exim is made, if there is any output from Exim (in
33588 particular, if the command fails) a window containing the command and the
33589 output is displayed. Otherwise, the results of the action are normally apparent
33590 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
33591 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
33592 if no output is generated.
33594 The queue display is automatically updated for actions such as freezing and
33595 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
33596 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
33597 force an update of the display after one of these actions.
33599 In any text window that is displayed as result of a menu action, the normal
33600 cut-and-paste facility is available, and searching can be carried out using ^R
33601 and ^S, as described above for the log tail window.
33608 . ////////////////////////////////////////////////////////////////////////////
33609 . ////////////////////////////////////////////////////////////////////////////
33611 .chapter "Security considerations" "CHAPsecurity"
33612 .scindex IIDsecurcon "security" "discussion of"
33613 This chapter discusses a number of issues concerned with security, some of
33614 which are also covered in other parts of this manual.
33616 For reasons that this author does not understand, some people have promoted
33617 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
33618 existence of this chapter in the documentation. However, the intent of the
33619 chapter is simply to describe the way Exim works in relation to certain
33620 security concerns, not to make any specific claims about the effectiveness of
33621 its security as compared with other MTAs.
33623 What follows is a description of the way Exim is supposed to be. Best efforts
33624 have been made to try to ensure that the code agrees with the theory, but an
33625 absence of bugs can never be guaranteed. Any that are reported will get fixed
33626 as soon as possible.
33629 .section "Building a more &""hardened""& Exim" "SECID286"
33630 .cindex "security" "build-time features"
33631 There are a number of build-time options that can be set in &_Local/Makefile_&
33632 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
33633 Exim administrator who does not have the root password, or by someone who has
33634 penetrated the Exim (but not the root) account. These options are as follows:
33637 ALT_CONFIG_PREFIX can be set to a string that is required to match the
33638 start of any file names used with the &%-C%& option. When it is set, these file
33639 names are also not allowed to contain the sequence &"/../"&. (However, if the
33640 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
33641 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
33642 default setting for &%ALT_CONFIG_PREFIX%&.
33644 If the permitted configuration files are confined to a directory to
33645 which only root has access, this guards against someone who has broken
33646 into the Exim account from running a privileged Exim with an arbitrary
33647 configuration file, and using it to break into other accounts.
33649 If ALT_CONFIG_ROOT_ONLY is defined, root privilege is retained for &%-C%&
33650 and &%-D%& only if the caller of Exim is root. Without it, the Exim user may
33651 also use &%-C%& and &%-D%& and retain privilege. Setting this option locks out
33652 the possibility of testing a configuration using &%-C%& right through message
33653 reception and delivery, even if the caller is root. The reception works, but by
33654 that time, Exim is running as the Exim user, so when it re-execs to regain
33655 privilege for the delivery, the use of &%-C%& causes privilege to be lost.
33656 However, root can test reception and delivery using two separate commands.
33657 ALT_CONFIG_ROOT_ONLY is not set by default.
33659 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
33662 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
33663 never to be used for any deliveries. This is like the &%never_users%& runtime
33664 option, but it cannot be overridden; the runtime option adds additional users
33665 to the list. The default setting is &"root"&; this prevents a non-root user who
33666 is permitted to modify the runtime file from using Exim as a way to get root.
33672 .section "Root privilege" "SECID270"
33674 .cindex "root privilege"
33675 The Exim binary is normally setuid to root, which means that it gains root
33676 privilege (runs as root) when it starts execution. In some special cases (for
33677 example, when the daemon is not in use and there are no local deliveries), it
33678 may be possible to run Exim setuid to some user other than root. This is
33679 discussed in the next section. However, in most installations, root privilege
33680 is required for two things:
33683 To set up a socket connected to the standard SMTP port (25) when initialising
33684 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
33687 To be able to change uid and gid in order to read users' &_.forward_& files and
33688 perform local deliveries as the receiving user or as specified in the
33692 It is not necessary to be root to do any of the other things Exim does, such as
33693 receiving messages and delivering them externally over SMTP, and it is
33694 obviously more secure if Exim does not run as root except when necessary.
33695 For this reason, a user and group for Exim to use must be defined in
33696 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
33697 group"&. Their values can be changed by the run time configuration, though this
33698 is not recommended. Often a user called &'exim'& is used, but some sites use
33699 &'mail'& or another user name altogether.
33701 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
33702 abdication; the process cannot regain root afterwards. Prior to release 4.00,
33703 &[seteuid()]& was used in some circumstances, but this is no longer the case.
33705 After a new Exim process has interpreted its command line options, it changes
33706 uid and gid in the following cases:
33711 If the &%-C%& option is used to specify an alternate configuration file, or if
33712 the &%-D%& option is used to define macro values for the configuration, and the
33713 calling process is not running as root or the Exim user, the uid and gid are
33714 changed to those of the calling process.
33715 However, if ALT_CONFIG_ROOT_ONLY is defined in &_Local/Makefile_&, only
33716 root callers may use &%-C%& and &%-D%& without losing privilege, and if
33717 DISABLE_D_OPTION is set, the &%-D%& option may not be used at all.
33722 If the expansion test option (&%-be%&) or one of the filter testing options
33723 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
33726 If the process is not a daemon process or a queue runner process or a delivery
33727 process or a process for testing address routing (started with &%-bt%&), the
33728 uid and gid are changed to the Exim user and group. This means that Exim always
33729 runs under its own uid and gid when receiving messages. This also applies when
33730 testing address verification
33733 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
33736 For a daemon, queue runner, delivery, or address testing process, the uid
33737 remains as root at this stage, but the gid is changed to the Exim group.
33740 The processes that initially retain root privilege behave as follows:
33743 A daemon process changes the gid to the Exim group and the uid to the Exim
33744 user after setting up one or more listening sockets. The &[initgroups()]&
33745 function is called, so that if the Exim user is in any additional groups, they
33746 will be used during message reception.
33748 A queue runner process retains root privilege throughout its execution. Its
33749 job is to fork a controlled sequence of delivery processes.
33751 A delivery process retains root privilege throughout most of its execution,
33752 but any actual deliveries (that is, the transports themselves) are run in
33753 subprocesses which always change to a non-root uid and gid. For local
33754 deliveries this is typically the uid and gid of the owner of the mailbox; for
33755 remote deliveries, the Exim uid and gid are used. Once all the delivery
33756 subprocesses have been run, a delivery process changes to the Exim uid and gid
33757 while doing post-delivery tidying up such as updating the retry database and
33758 generating bounce and warning messages.
33760 While the recipient addresses in a message are being routed, the delivery
33761 process runs as root. However, if a user's filter file has to be processed,
33762 this is done in a subprocess that runs under the individual user's uid and
33763 gid. A system filter is run as root unless &%system_filter_user%& is set.
33765 A process that is testing addresses (the &%-bt%& option) runs as root so that
33766 the routing is done in the same environment as a message delivery.
33772 .section "Running Exim without privilege" "SECTrunexiwitpri"
33773 .cindex "privilege, running without"
33774 .cindex "unprivileged running"
33775 .cindex "root privilege" "running without"
33776 Some installations like to run Exim in an unprivileged state for more of its
33777 operation, for added security. Support for this mode of operation is provided
33778 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
33779 gid are changed to the Exim user and group at the start of a delivery process
33780 (and also queue runner and address testing processes). This means that address
33781 routing is no longer run as root, and the deliveries themselves cannot change
33785 .cindex "daemon" "restarting"
33786 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
33787 that the daemon can still be started in the usual way, and it can respond
33788 correctly to SIGHUP because the re-invocation regains root privilege.
33790 An alternative approach is to make Exim setuid to the Exim user and also setgid
33791 to the Exim group. If you do this, the daemon must be started from a root
33792 process. (Calling Exim from a root process makes it behave in the way it does
33793 when it is setuid root.) However, the daemon cannot restart itself after a
33794 SIGHUP signal because it cannot regain privilege.
33796 It is still useful to set &%deliver_drop_privilege%& in this case, because it
33797 stops Exim from trying to re-invoke itself to do a delivery after a message has
33798 been received. Such a re-invocation is a waste of resources because it has no
33801 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
33802 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
33803 to the Exim user seems a clean approach, but there is one complication:
33805 In this style of operation, Exim is running with the real uid and gid set to
33806 those of the calling process, and the effective uid/gid set to Exim's values.
33807 Ideally, any association with the calling process' uid/gid should be dropped,
33808 that is, the real uid/gid should be reset to the effective values so as to
33809 discard any privileges that the caller may have. While some operating systems
33810 have a function that permits this action for a non-root effective uid, quite a
33811 number of them do not. Because of this lack of standardization, Exim does not
33812 address this problem at this time.
33814 For this reason, the recommended approach for &"mostly unprivileged"& running
33815 is to keep the Exim binary setuid to root, and to set
33816 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
33817 be used in the most straightforward way.
33819 If you configure Exim not to run delivery processes as root, there are a
33820 number of restrictions on what you can do:
33823 You can deliver only as the Exim user/group. You should explicitly use the
33824 &%user%& and &%group%& options to override routers or local transports that
33825 normally deliver as the recipient. This makes sure that configurations that
33826 work in this mode function the same way in normal mode. Any implicit or
33827 explicit specification of another user causes an error.
33829 Use of &_.forward_& files is severely restricted, such that it is usually
33830 not worthwhile to include them in the configuration.
33832 Users who wish to use &_.forward_& would have to make their home directory and
33833 the file itself accessible to the Exim user. Pipe and append-to-file entries,
33834 and their equivalents in Exim filters, cannot be used. While they could be
33835 enabled in the Exim user's name, that would be insecure and not very useful.
33837 Unless the local user mailboxes are all owned by the Exim user (possible in
33838 some POP3 or IMAP-only environments):
33841 They must be owned by the Exim group and be writeable by that group. This
33842 implies you must set &%mode%& in the appendfile configuration, as well as the
33843 mode of the mailbox files themselves.
33845 You must set &%no_check_owner%&, since most or all of the files will not be
33846 owned by the Exim user.
33848 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
33849 on a newly created mailbox when unprivileged. This also implies that new
33850 mailboxes need to be created manually.
33855 These restrictions severely restrict what can be done in local deliveries.
33856 However, there are no restrictions on remote deliveries. If you are running a
33857 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
33858 gives more security at essentially no cost.
33860 If you are using the &%mua_wrapper%& facility (see chapter
33861 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
33866 .section "Delivering to local files" "SECID271"
33867 Full details of the checks applied by &(appendfile)& before it writes to a file
33868 are given in chapter &<<CHAPappendfile>>&.
33872 .section "IPv4 source routing" "SECID272"
33873 .cindex "source routing" "in IP packets"
33874 .cindex "IP source routing"
33875 Many operating systems suppress IP source-routed packets in the kernel, but
33876 some cannot be made to do this, so Exim does its own check. It logs incoming
33877 IPv4 source-routed TCP calls, and then drops them. Things are all different in
33878 IPv6. No special checking is currently done.
33882 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
33883 Support for these SMTP commands is disabled by default. If required, they can
33884 be enabled by defining suitable ACLs.
33889 .section "Privileged users" "SECID274"
33890 .cindex "trusted users"
33891 .cindex "admin user"
33892 .cindex "privileged user"
33893 .cindex "user" "trusted"
33894 .cindex "user" "admin"
33895 Exim recognizes two sets of users with special privileges. Trusted users are
33896 able to submit new messages to Exim locally, but supply their own sender
33897 addresses and information about a sending host. For other users submitting
33898 local messages, Exim sets up the sender address from the uid, and doesn't
33899 permit a remote host to be specified.
33902 However, an untrusted user is permitted to use the &%-f%& command line option
33903 in the special form &%-f <>%& to indicate that a delivery failure for the
33904 message should not cause an error report. This affects the message's envelope,
33905 but it does not affect the &'Sender:'& header. Untrusted users may also be
33906 permitted to use specific forms of address with the &%-f%& option by setting
33907 the &%untrusted_set_sender%& option.
33909 Trusted users are used to run processes that receive mail messages from some
33910 other mail domain and pass them on to Exim for delivery either locally, or over
33911 the Internet. Exim trusts a caller that is running as root, as the Exim user,
33912 as any user listed in the &%trusted_users%& configuration option, or under any
33913 group listed in the &%trusted_groups%& option.
33915 Admin users are permitted to do things to the messages on Exim's queue. They
33916 can freeze or thaw messages, cause them to be returned to their senders, remove
33917 them entirely, or modify them in various ways. In addition, admin users can run
33918 the Exim monitor and see all the information it is capable of providing, which
33919 includes the contents of files on the spool.
33923 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
33924 delivery of messages on its queue is restricted to admin users. This
33925 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
33926 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
33927 queue is also restricted to admin users. This restriction can be relaxed by
33928 setting &%no_queue_list_requires_admin%&.
33930 Exim recognizes an admin user if the calling process is running as root or as
33931 the Exim user or if any of the groups associated with the calling process is
33932 the Exim group. It is not necessary actually to be running under the Exim
33933 group. However, if admin users who are not root or the Exim user are to access
33934 the contents of files on the spool via the Exim monitor (which runs
33935 unprivileged), Exim must be built to allow group read access to its spool
33940 .section "Spool files" "SECID275"
33941 .cindex "spool directory" "files"
33942 Exim's spool directory and everything it contains is owned by the Exim user and
33943 set to the Exim group. The mode for spool files is defined in the
33944 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
33945 any user who is a member of the Exim group can access these files.
33949 .section "Use of argv[0]" "SECID276"
33950 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
33951 of specific strings, Exim assumes certain options. For example, calling Exim
33952 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
33953 to calling it with the option &%-bS%&. There are no security implications in
33958 .section "Use of %f formatting" "SECID277"
33959 The only use made of &"%f"& by Exim is in formatting load average values. These
33960 are actually stored in integer variables as 1000 times the load average.
33961 Consequently, their range is limited and so therefore is the length of the
33966 .section "Embedded Exim path" "SECID278"
33967 Exim uses its own path name, which is embedded in the code, only when it needs
33968 to re-exec in order to regain root privilege. Therefore, it is not root when it
33969 does so. If some bug allowed the path to get overwritten, it would lead to an
33970 arbitrary program's being run as exim, not as root.
33974 .section "Use of sprintf()" "SECID279"
33975 .cindex "&[sprintf()]&"
33976 A large number of occurrences of &"sprintf"& in the code are actually calls to
33977 &'string_sprintf()'&, a function that returns the result in malloc'd store.
33978 The intermediate formatting is done into a large fixed buffer by a function
33979 that runs through the format string itself, and checks the length of each
33980 conversion before performing it, thus preventing buffer overruns.
33982 The remaining uses of &[sprintf()]& happen in controlled circumstances where
33983 the output buffer is known to be sufficiently long to contain the converted
33988 .section "Use of debug_printf() and log_write()" "SECID280"
33989 Arbitrary strings are passed to both these functions, but they do their
33990 formatting by calling the function &'string_vformat()'&, which runs through
33991 the format string itself, and checks the length of each conversion.
33995 .section "Use of strcat() and strcpy()" "SECID281"
33996 These are used only in cases where the output buffer is known to be large
33997 enough to hold the result.
33998 .ecindex IIDsecurcon
34003 . ////////////////////////////////////////////////////////////////////////////
34004 . ////////////////////////////////////////////////////////////////////////////
34006 .chapter "Format of spool files" "CHAPspool"
34007 .scindex IIDforspo1 "format" "spool files"
34008 .scindex IIDforspo2 "spool directory" "format of files"
34009 .scindex IIDforspo3 "spool files" "format of"
34010 .cindex "spool files" "editing"
34011 A message on Exim's queue consists of two files, whose names are the message id
34012 followed by -D and -H, respectively. The data portion of the message is kept in
34013 the -D file on its own. The message's envelope, status, and headers are all
34014 kept in the -H file, whose format is described in this chapter. Each of these
34015 two files contains the final component of its own name as its first line. This
34016 is insurance against disk crashes where the directory is lost but the files
34017 themselves are recoverable.
34019 Some people are tempted into editing -D files in order to modify messages. You
34020 need to be extremely careful if you do this; it is not recommended and you are
34021 on your own if you do it. Here are some of the pitfalls:
34024 You must ensure that Exim does not try to deliver the message while you are
34025 fiddling with it. The safest way is to take out a write lock on the -D file,
34026 which is what Exim itself does, using &[fcntl()]&. If you update the file in
34027 place, the lock will be retained. If you write a new file and rename it, the
34028 lock will be lost at the instant of rename.
34030 .vindex "&$body_linecount$&"
34031 If you change the number of lines in the file, the value of
34032 &$body_linecount$&, which is stored in the -H file, will be incorrect. At
34033 present, this value is not used by Exim, but there is no guarantee that this
34034 will always be the case.
34036 If the message is in MIME format, you must take care not to break it.
34038 If the message is cryptographically signed, any change will invalidate the
34041 All in all, modifying -D files is fraught with danger.
34043 Files whose names end with -J may also be seen in the &_input_& directory (or
34044 its subdirectories when &%split_spool_directory%& is set). These are journal
34045 files, used to record addresses to which the message has been delivered during
34046 the course of a delivery attempt. If there are still undelivered recipients at
34047 the end, the -H file is updated, and the -J file is deleted. If, however, there
34048 is some kind of crash (for example, a power outage) before this happens, the -J
34049 file remains in existence. When Exim next processes the message, it notices the
34050 -J file and uses it to update the -H file before starting the next delivery
34053 .section "Format of the -H file" "SECID282"
34054 .cindex "uid (user id)" "in spool file"
34055 .cindex "gid (group id)" "in spool file"
34056 The second line of the -H file contains the login name for the uid of the
34057 process that called Exim to read the message, followed by the numerical uid and
34058 gid. For a locally generated message, this is normally the user who sent the
34059 message. For a message received over TCP/IP via the daemon, it is
34060 normally the Exim user.
34062 The third line of the file contains the address of the message's sender as
34063 transmitted in the envelope, contained in angle brackets. The sender address is
34064 empty for bounce messages. For incoming SMTP mail, the sender address is given
34065 in the MAIL command. For locally generated mail, the sender address is
34066 created by Exim from the login name of the current user and the configured
34067 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
34068 leading &"From&~"& line if the caller is trusted, or if the supplied address is
34069 &"<>"& or an address that matches &%untrusted_set_senders%&.
34071 The fourth line contains two numbers. The first is the time that the message
34072 was received, in the conventional Unix form &-- the number of seconds since the
34073 start of the epoch. The second number is a count of the number of messages
34074 warning of delayed delivery that have been sent to the sender.
34076 There follow a number of lines starting with a hyphen. These can appear in any
34077 order, and are omitted when not relevant:
34080 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
34081 This item is obsolete, and is not generated from Exim release 4.61 onwards;
34082 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
34083 recognized, to provide backward compatibility. In the old format, a line of
34084 this form is present for every ACL variable that is not empty. The number
34085 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
34086 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
34087 the data string for the variable. The string itself starts at the beginning of
34088 the next line, and is followed by a newline character. It may contain internal
34091 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
34092 A line of this form is present for every ACL connection variable that is
34093 defined. Note that there is a space between &%-aclc%& and the rest of the name.
34094 The length is the length of the data string for the variable. The string itself
34095 starts at the beginning of the next line, and is followed by a newline
34096 character. It may contain internal newlines.
34098 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
34099 A line of this form is present for every ACL message variable that is defined.
34100 Note that there is a space between &%-aclm%& and the rest of the name. The
34101 length is the length of the data string for the variable. The string itself
34102 starts at the beginning of the next line, and is followed by a newline
34103 character. It may contain internal newlines.
34105 .vitem "&%-active_hostname%&&~<&'hostname'&>"
34106 This is present if, when the message was received over SMTP, the value of
34107 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
34109 .vitem &%-allow_unqualified_recipient%&
34110 This is present if unqualified recipient addresses are permitted in header
34111 lines (to stop such addresses from being qualified if rewriting occurs at
34112 transport time). Local messages that were input using &%-bnq%& and remote
34113 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
34115 .vitem &%-allow_unqualified_sender%&
34116 This is present if unqualified sender addresses are permitted in header lines
34117 (to stop such addresses from being qualified if rewriting occurs at transport
34118 time). Local messages that were input using &%-bnq%& and remote messages from
34119 hosts that match &%sender_unqualified_hosts%& set this flag.
34121 .vitem "&%-auth_id%&&~<&'text'&>"
34122 The id information for a message received on an authenticated SMTP connection
34123 &-- the value of the &$authenticated_id$& variable.
34125 .vitem "&%-auth_sender%&&~<&'address'&>"
34126 The address of an authenticated sender &-- the value of the
34127 &$authenticated_sender$& variable.
34129 .vitem "&%-body_linecount%&&~<&'number'&>"
34130 This records the number of lines in the body of the message, and is always
34133 .vitem "&%-body_zerocount%&&~<&'number'&>"
34134 This records the number of binary zero bytes in the body of the message, and is
34135 present if the number is greater than zero.
34137 .vitem &%-deliver_firsttime%&
34138 This is written when a new message is first added to the spool. When the spool
34139 file is updated after a deferral, it is omitted.
34141 .vitem "&%-frozen%&&~<&'time'&>"
34142 .cindex "frozen messages" "spool data"
34143 The message is frozen, and the freezing happened at <&'time'&>.
34145 .vitem "&%-helo_name%&&~<&'text'&>"
34146 This records the host name as specified by a remote host in a HELO or EHLO
34149 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
34150 This records the IP address of the host from which the message was received and
34151 the remote port number that was used. It is omitted for locally generated
34154 .vitem "&%-host_auth%&&~<&'text'&>"
34155 If the message was received on an authenticated SMTP connection, this records
34156 the name of the authenticator &-- the value of the
34157 &$sender_host_authenticated$& variable.
34159 .vitem &%-host_lookup_failed%&
34160 This is present if an attempt to look up the sending host's name from its IP
34161 address failed. It corresponds to the &$host_lookup_failed$& variable.
34163 .vitem "&%-host_name%&&~<&'text'&>"
34164 .cindex "reverse DNS lookup"
34165 .cindex "DNS" "reverse lookup"
34166 This records the name of the remote host from which the message was received,
34167 if the host name was looked up from the IP address when the message was being
34168 received. It is not present if no reverse lookup was done.
34170 .vitem "&%-ident%&&~<&'text'&>"
34171 For locally submitted messages, this records the login of the originating user,
34172 unless it was a trusted user and the &%-oMt%& option was used to specify an
34173 ident value. For messages received over TCP/IP, this records the ident string
34174 supplied by the remote host, if any.
34176 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
34177 This records the IP address of the local interface and the port number through
34178 which a message was received from a remote host. It is omitted for locally
34179 generated messages.
34182 The message is from a local sender.
34184 .vitem &%-localerror%&
34185 The message is a locally-generated bounce message.
34187 .vitem "&%-local_scan%&&~<&'string'&>"
34188 This records the data string that was returned by the &[local_scan()]& function
34189 when the message was received &-- the value of the &$local_scan_data$&
34190 variable. It is omitted if no data was returned.
34192 .vitem &%-manual_thaw%&
34193 The message was frozen but has been thawed manually, that is, by an explicit
34194 Exim command rather than via the auto-thaw process.
34197 A testing delivery process was started using the &%-N%& option to suppress any
34198 actual deliveries, but delivery was deferred. At any further delivery attempts,
34201 .vitem &%-received_protocol%&
34202 This records the value of the &$received_protocol$& variable, which contains
34203 the name of the protocol by which the message was received.
34205 .vitem &%-sender_set_untrusted%&
34206 The envelope sender of this message was set by an untrusted local caller (used
34207 to ensure that the caller is displayed in queue listings).
34209 .vitem "&%-spam_score_int%&&~<&'number'&>"
34210 If a message was scanned by SpamAssassin, this is present. It records the value
34211 of &$spam_score_int$&.
34213 .vitem &%-tls_certificate_verified%&
34214 A TLS certificate was received from the client that sent this message, and the
34215 certificate was verified by the server.
34217 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
34218 When the message was received over an encrypted connection, this records the
34219 name of the cipher suite that was used.
34221 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
34222 When the message was received over an encrypted connection, and a certificate
34223 was received from the client, this records the Distinguished Name from that
34227 Following the options there is a list of those addresses to which the message
34228 is not to be delivered. This set of addresses is initialized from the command
34229 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
34230 is set; otherwise it starts out empty. Whenever a successful delivery is made,
34231 the address is added to this set. The addresses are kept internally as a
34232 balanced binary tree, and it is a representation of that tree which is written
34233 to the spool file. If an address is expanded via an alias or forward file, the
34234 original address is added to the tree when deliveries to all its child
34235 addresses are complete.
34237 If the tree is empty, there is a single line in the spool file containing just
34238 the text &"XX"&. Otherwise, each line consists of two letters, which are either
34239 Y or N, followed by an address. The address is the value for the node of the
34240 tree, and the letters indicate whether the node has a left branch and/or a
34241 right branch attached to it, respectively. If branches exist, they immediately
34242 follow. Here is an example of a three-node tree:
34244 YY darcy@austen.fict.example
34245 NN alice@wonderland.fict.example
34246 NN editor@thesaurus.ref.example
34248 After the non-recipients tree, there is a list of the message's recipients.
34249 This is a simple list, preceded by a count. It includes all the original
34250 recipients of the message, including those to whom the message has already been
34251 delivered. In the simplest case, the list contains one address per line. For
34255 editor@thesaurus.ref.example
34256 darcy@austen.fict.example
34258 alice@wonderland.fict.example
34260 However, when a child address has been added to the top-level addresses as a
34261 result of the use of the &%one_time%& option on a &(redirect)& router, each
34262 line is of the following form:
34264 <&'top-level address'&> <&'errors_to address'&> &&&
34265 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
34267 The 01 flag bit indicates the presence of the three other fields that follow
34268 the top-level address. Other bits may be used in future to support additional
34269 fields. The <&'parent number'&> is the offset in the recipients list of the
34270 original parent of the &"one time"& address. The first two fields are the
34271 envelope sender that is associated with this address and its length. If the
34272 length is zero, there is no special envelope sender (there are then two space
34273 characters in the line). A non-empty field can arise from a &(redirect)& router
34274 that has an &%errors_to%& setting.
34277 A blank line separates the envelope and status information from the headers
34278 which follow. A header may occupy several lines of the file, and to save effort
34279 when reading it in, each header is preceded by a number and an identifying
34280 character. The number is the number of characters in the header, including any
34281 embedded newlines and the terminating newline. The character is one of the
34285 .row <&'blank'&> "header in which Exim has no special interest"
34286 .row &`B`& "&'Bcc:'& header"
34287 .row &`C`& "&'Cc:'& header"
34288 .row &`F`& "&'From:'& header"
34289 .row &`I`& "&'Message-id:'& header"
34290 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
34291 .row &`R`& "&'Reply-To:'& header"
34292 .row &`S`& "&'Sender:'& header"
34293 .row &`T`& "&'To:'& header"
34294 .row &`*`& "replaced or deleted header"
34297 Deleted or replaced (rewritten) headers remain in the spool file for debugging
34298 purposes. They are not transmitted when the message is delivered. Here is a
34299 typical set of headers:
34301 111P Received: by hobbit.fict.example with local (Exim 4.00)
34302 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
34303 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
34304 038* X-rewrote-sender: bb@hobbit.fict.example
34305 042* From: Bilbo Baggins <bb@hobbit.fict.example>
34306 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
34307 099* To: alice@wonderland.fict.example, rdo@foundation,
34308 darcy@austen.fict.example, editor@thesaurus.ref.example
34309 104T To: alice@wonderland.fict.example, rdo@foundation.example,
34310 darcy@austen.fict.example, editor@thesaurus.ref.example
34311 038 Date: Fri, 11 May 2001 10:28:59 +0100
34313 The asterisked headers indicate that the envelope sender, &'From:'& header, and
34314 &'To:'& header have been rewritten, the last one because routing expanded the
34315 unqualified domain &'foundation'&.
34316 .ecindex IIDforspo1
34317 .ecindex IIDforspo2
34318 .ecindex IIDforspo3
34320 . ////////////////////////////////////////////////////////////////////////////
34321 . ////////////////////////////////////////////////////////////////////////////
34323 .chapter "Support for DKIM (DomainKeys Identified Mail) - RFC4871" "CHID12" &&&
34327 Since version 4.70, DKIM support is compiled into Exim by default. It can be
34328 disabled by setting DISABLE_DKIM=yes in Local/Makefile.
34330 Exim's DKIM implementation allows to
34332 Sign outgoing messages: This function is implemented in the SMTP transport.
34333 It can co-exist with all other Exim features, including transport filters.
34335 Verify signatures in incoming messages: This is implemented by an additional
34336 ACL (acl_smtp_dkim), which can be called several times per message, with
34337 different signature context.
34340 In typical Exim style, the verification implementation does not include any
34341 default "policy". Instead it enables you to build your own policy using
34342 Exim's standard controls.
34344 Please note that verification of DKIM signatures in incoming mail is turned
34345 on by default for logging purposes. For each signature in incoming email,
34346 exim will log a line displaying the most important signature details, and the
34347 signature status. Here is an example:
34349 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM: d=facebookmail.com s=q1-2009b c=relaxed/relaxed a=rsa-sha1 i=@facebookmail.com t=1252484542 [verification succeeded]
34351 You might want to turn off DKIM verification processing entirely for internal
34352 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
34353 control modifier. This should typically be done in the RCPT ACL, at points
34354 where you accept mail from relay sources (internal hosts or authenticated
34358 .section "Signing outgoing messages" "SECID513"
34359 .cindex "DKIM" "signing"
34361 Signing is implemented by setting private options on the SMTP transport.
34362 These options take (expandable) strings as arguments.
34364 .option dkim_domain smtp string&!! unset
34366 The domain you want to sign with. The result of this expanded
34367 option is put into the &%$dkim_domain%& expansion variable.
34369 .option dkim_selector smtp string&!! unset
34371 This sets the key selector string. You can use the &%$dkim_domain%& expansion
34372 variable to look up a matching selector. The result is put in the expansion
34373 variable &%$dkim_selector%& which should be used in the &%dkim_private_key%&
34374 option along with &%$dkim_domain%&.
34376 .option dkim_private_key smtp string&!! unset
34378 This sets the private key to use. You can use the &%$dkim_domain%& and
34379 &%$dkim_selector%& expansion variables to determine the private key to use.
34380 The result can either
34382 be a valid RSA private key in ASCII armor, including line breaks.
34384 start with a slash, in which case it is treated as a file that contains
34387 be "0", "false" or the empty string, in which case the message will not
34388 be signed. This case will not result in an error, even if &%dkim_strict%&
34392 .option dkim_canon smtp string&!! unset
34394 This option sets the canonicalization method used when signing a message.
34395 The DKIM RFC currently supports two methods: "simple" and "relaxed".
34396 The option defaults to "relaxed" when unset. Note: the current implementation
34397 only supports using the same canonicalization method for both headers and body.
34399 .option dkim_strict smtp string&!! unset
34401 This option defines how Exim behaves when signing a message that
34402 should be signed fails for some reason. When the expansion evaluates to
34403 either "1" or "true", Exim will defer. Otherwise Exim will send the message
34404 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
34407 .option dkim_sign_headers smtp string&!! unset
34409 When set, this option must expand to (or be specified as) a colon-separated
34410 list of header names. Headers with these names will be included in the message
34411 signature. When unspecified, the header names recommended in RFC4871 will be
34415 .section "Verifying DKIM signatures in incoming mail" "SECID514"
34416 .cindex "DKIM" "verification"
34418 Verification of DKIM signatures in incoming email is implemented via the
34419 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
34420 syntactically(!) correct signature in the incoming message.
34422 To evaluate the signature in the ACL a large number of expansion variables
34423 containing the signature status and its details are set up during the
34424 runtime of the ACL.
34426 Calling the ACL only for existing signatures is not sufficient to build
34427 more advanced policies. For that reason, the global option
34428 &%dkim_verify_signers%&, and a global expansion variable
34429 &%$dkim_signers%& exist.
34431 The global option &%dkim_verify_signers%& can be set to a colon-separated
34432 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
34433 called. It is expanded when the message has been received. At this point,
34434 the expansion variable &%$dkim_signers%& already contains a colon-
34435 separated list of signer domains and identities for the message. When
34436 &%dkim_verify_signers%& is not specified in the main configuration,
34439 dkim_verify_signers = $dkim_signers
34441 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
34442 DKIM signature in the message. Current DKIM verifiers may want to explicitly
34443 call the ACL for known domains or identities. This would be achieved as follows:
34445 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
34447 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
34448 and "ebay.com", plus all domains and identities that have signatures in the message.
34449 You can also be more creative in constructing your policy. Example:
34451 dkim_verify_signers = $sender_address_domain:$dkim_signers
34454 If a domain or identity is listed several times in the (expanded) value of
34455 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
34458 Inside the &%acl_smtp_dkim%&, the following expansion variables are
34459 available (from most to least important):
34462 .vitem &%$dkim_cur_signer%&
34463 The signer that is being evaluated in this ACL run. This can be domain or
34464 an identity. This is one of the list items from the expanded main option
34465 &%dkim_verify_signers%& (see above).
34466 .vitem &%$dkim_verify_status%&
34467 A string describing the general status of the signature. One of
34469 &%none%&: There is no signature in the message for the current domain or
34470 identity (as reflected by &%$dkim_cur_signer%&).
34472 &%invalid%&: The signature could not be verified due to a processing error.
34473 More detail is available in &%$dkim_verify_reason%&.
34475 &%fail%&: Verification of the signature failed. More detail is
34476 available in &%$dkim_verify_reason%&.
34478 &%pass%&: The signature passed verification. It is valid.
34480 .vitem &%$dkim_verify_reason%&
34481 A string giving a litte bit more detail when &%$dkim_verify_status%& is either
34482 "fail" or "invalid". One of
34484 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
34485 key for the domain could not be retrieved. This may be a temporary problem.
34487 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
34488 record for the domain is syntactically invalid.
34490 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
34491 body hash does not match the one specified in the signature header. This
34492 means that the message body was modified in transit.
34494 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
34495 could not be verified. This may mean that headers were modified,
34496 re-written or otherwise changed in a way which is incompatible with
34497 DKIM verification. It may of course also mean that the signature is forged.
34499 .vitem &%$dkim_domain%&
34500 The signing domain. IMPORTANT: This variable is only populated if there is
34501 an actual signature in the message for the current domain or identity (as
34502 reflected by &%$dkim_cur_signer%&).
34503 .vitem &%$dkim_identity%&
34504 The signing identity, if present. IMPORTANT: This variable is only populated
34505 if there is an actual signature in the message for the current domain or
34506 identity (as reflected by &%$dkim_cur_signer%&).
34507 .vitem &%$dkim_selector%&
34508 The key record selector string
34509 .vitem &%$dkim_algo%&
34510 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
34511 .vitem &%$dkim_canon_body%&
34512 The body canonicalization method. One of 'relaxed' or 'simple'.
34513 .vitem &%dkim_canon_headers%&
34514 The header canonicalization method. One of 'relaxed' or 'simple'.
34515 .vitem &%$dkim_copiedheaders%&
34516 A transcript of headers and their values which are included in the signature
34517 (copied from the 'z=' tag of the signature).
34518 .vitem &%$dkim_bodylength%&
34519 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
34520 limit was set by the signer, "9999999999999" is returned. This makes sure
34521 that this variable always expands to an integer value.
34522 .vitem &%$dkim_created%&
34523 UNIX timestamp reflecting the date and time when the signature was created.
34524 When this was not specified by the signer, "0" is returned.
34525 .vitem &%$dkim_expires%&
34526 UNIX timestamp reflecting the date and time when the signer wants the
34527 signature to be treated as "expired". When this was not specified by the
34528 signer, "9999999999999" is returned. This makes it possible to do useful
34529 integer size comparisons against this value.
34530 .vitem &%$dkim_headernames%&
34531 A colon-separated list of names of headers included in the signature.
34532 .vitem &%$dkim_key_testing%&
34533 "1" if the key record has the "testing" flag set, "0" if not.
34534 .vitem &%$dkim_key_nosubdomaining%&
34535 "1" if the key record forbids subdomaining, "0" otherwise.
34536 .vitem &%$dkim_key_srvtype%&
34537 Service type (tag s=) from the key record. Defaults to "*" if not specified
34539 .vitem &%$dkim_key_granularity%&
34540 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
34542 .vitem &%$dkim_key_notes%&
34543 Notes from the key record (tag n=)
34546 In addition, two ACL conditions are provided:
34549 .vitem &%dkim_signers%&
34550 ACL condition that checks a colon-separated list of domains or identities
34551 for a match against the domain or identity that the ACL is currently verifying
34552 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
34553 verb to a group of domains or identities, like:
34556 # Warn when message apparently from GMail has no signature at all
34557 warn log_message = GMail sender without DKIM signature
34558 sender_domains = gmail.com
34559 dkim_signers = gmail.com
34563 .vitem &%dkim_status%&
34564 ACL condition that checks a colon-separated list of possible DKIM verification
34565 results agains the actual result of verification. This is typically used
34566 to restrict an ACL verb to a list of verification outcomes, like:
34569 deny message = Message from Paypal with invalid or missing signature
34570 sender_domains = paypal.com:paypal.de
34571 dkim_signers = paypal.com:paypal.de
34572 dkim_status = none:invalid:fail
34575 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
34576 see the documentation of the &%$dkim_verify_status%& expansion variable above
34577 for more information of what they mean.
34580 . ////////////////////////////////////////////////////////////////////////////
34581 . ////////////////////////////////////////////////////////////////////////////
34583 .chapter "Adding new drivers or lookup types" "CHID13" &&&
34584 "Adding drivers or lookups"
34585 .cindex "adding drivers"
34586 .cindex "new drivers, adding"
34587 .cindex "drivers" "adding new"
34588 The following actions have to be taken in order to add a new router, transport,
34589 authenticator, or lookup type to Exim:
34592 Choose a name for the driver or lookup type that does not conflict with any
34593 existing name; I will use &"newdriver"& in what follows.
34595 Add to &_src/EDITME_& the line:
34597 <&'type'&>&`_NEWDRIVER=yes`&
34599 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
34600 code is not to be included in the binary by default, comment this line out. You
34601 should also add any relevant comments about the driver or lookup type.
34603 Add to &_src/config.h.defaults_& the line:
34605 #define <type>_NEWDRIVER
34608 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
34609 and create a table entry as is done for all the other drivers and lookup types.
34611 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
34612 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
34613 driver or lookup type and add it to the definition of OBJ.
34615 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
34618 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
34619 as for other drivers and lookups.
34622 Then all you need to do is write the code! A good way to start is to make a
34623 proforma by copying an existing module of the same type, globally changing all
34624 occurrences of the name, and cutting out most of the code. Note that any
34625 options you create must be listed in alphabetical order, because the tables are
34626 searched using a binary chop procedure.
34628 There is a &_README_& file in each of the sub-directories of &_src_& describing
34629 the interface that is expected.
34634 . ////////////////////////////////////////////////////////////////////////////
34635 . ////////////////////////////////////////////////////////////////////////////
34637 . /////////////////////////////////////////////////////////////////////////////
34638 . These lines are processing instructions for the Simple DocBook Processor that
34639 . Philip Hazel has developed as a less cumbersome way of making PostScript and
34640 . PDFs than using xmlto and fop. They will be ignored by all other XML
34642 . /////////////////////////////////////////////////////////////////////////////
34647 foot_right_recto="&chaptertitle;"
34648 foot_right_verso="&chaptertitle;"
34652 .makeindex "Options index" "option"
34653 .makeindex "Variables index" "variable"
34654 .makeindex "Concept index" "concept"
34657 . /////////////////////////////////////////////////////////////////////////////
34658 . /////////////////////////////////////////////////////////////////////////////